Show user 'Access denied' page or redirect to landing page

Question: When authenticated user in a particular role  is trying to access a page (by manually typing URL) to which the user's role does not have permission: It is better to show an access denied page or redirect the user to the landing page ? Need answers from UX and security perspective.
Answer: There's a 3rd option for security concerns: denying a page exists
Working on enterprise software, I've come across feature request for customers who used our platform:

Customers who do not want to show or hint to an unauthenticated (or forbidden) user that a certain type of content even exists for those who do not have permission.

So instead of a '403 Forbidden' page, the solution was to give a 404. We kept the wording vague, with a link to the homepage, login form upper right, and a search field.
Here's an example from a Github 404 page (although it's cheeky, which might not be appropriate for your site).

You may not have the same security or intellectual property concerns, so in that case a 403 page would at least let them know that further permissions are needed (But they know there's content that exists).

Directing users to the homepage will not inform them of their insufficient permissions and they may mistake this for content that's not found, or make them think they have the wrong URL, when in actuality it's a permissions issue.

Due to our (and our customers) security concerns we concluded that a 404 is a better solution.
Comment: Is giving false information a good idea?
Comment: @ShreyasTripathy Sometimes, yes. It's a bit like the "_I can neither confirm nor deny..._" (when clearly the speaker _could_ confirm one way or the other if they chose to). Sometimes for business/security reasons, you don't want to give out too much information, even if that means technically lying.


A question about Julia set for quadratic family

Question: Let $P_{c}(z)=z^2+c$. It seems from the software that the map between the parameter $c$ and the Julia set $J(P_c)$ is an injective map. Is there some reference about it?  Any comments and reference will be appreciated.
Answer: I expect that you will find the answer (and a lot more) in the following paper, since it's easy to figure out which quadratic polynomials (if any) commute with one another:
Commuting polynomials and polynomials with same Julia set,
Pau Atela, Jun Hu,
 Int. J. Bifurcation Chaos 06, 2427 (1996). DOI: http://dx.doi.org/10.1142/S0218127496001570
Abstract: It has been known since Julia that polynomials commuting under composition have the same Julia set. More recently in the works of Baker and Eremenko, Fern\'andez, and Beardon, results were given on the converse question: When do two polynomials have the same Julia set? We give a complete answer to this question and show the exact relation between the two problems of polynomials with the same Julia set and commuting pairs.
The paper is also available on the ArXiv
https://arxiv.org/abs/math/9504210
Comment: Thank you, professor. Very nice paper. This is first time I know Fernandez's result, which claims that if f and g has the same degree and the same leading coefficient, then  $J(f)=J(g)$ implies $f=g$.
Answer: Joe's answer and the cited paper are, indeed, quite nice. I think the basic idea is fairly self-contained and probably easier than the reference.
Two complex polynomials $f$ and $g$ of the same degree have geometrically similar Julia sets precisely when there is an affine function $\varphi(z)=mz+b$ with $m\neq0$ such that
$$\varphi(f(z)) = g(\varphi(z)).$$
The function $\varphi$ is called a conjugacy and it's easy to see why this should work. By induction,
$$\varphi(f^n(z)) = g^n(\varphi(z)).$$
As a result, $\varphi$ maps an orbit of $f$ containing the point $z_0$ onto an orbit of $g$ containing the point $\varphi(z_0)$ so we expect the dynamics of $f$ and $g$ to be closely related; the nicer the function $\varphi$. The nicer the relationship and our $\varphi$ is about as nice as it could be.
Now the question is, when is there an affine conjugacy between
$$f(z)=z^2+c_1\: \text{ and } \: g(z)=z^2+c_2?$$
If you simply expand the conjugation equation or
$$m(z^2+c_1)+b = (mz+b)^2+c_2$$
and collect terms you find the system
\begin{align}
  m^2-m &= 0 \\
  2bm &= 0 \\
  mc_1-c_2-b^2+b &= 0.
\end{align}
Recalling that $m$ can't be zero for $\varphi$ to be an affine function, we see that the first equation implies that $m=1$ so that the second equation implies $b=0$. Plugging those into the last equation we see that $c_1=c_2$.
Comment: But isn't the hard part proving that if $J(f)=J(g)$, then there is an affine conjugacy? Once you know that, then rest, as you've indicated, is straightforward.
Answer: For $z^2+c$ it is really easy: the answer is yes. In general, if Julia sets of polynomials coincide, these polynomials are equal unless their common Julia set has a rotation symmetry, or polynomials are permutable.
(Baker, Eremenko, Ann. Acad. Sci. Fenn., 12 (1987) 229-236.)
http://www.acadsci.fi/mathematica/Vol12/vol12pp229-236.pdf
For $z^2+c$ we never have rotational symmetry and never have permutable polynomials. The result cited above was reproved and generalized by many other people. For rational functions, the question in full generality is still open.
Comment: Thanks for your comment and reference, professor. Would you think it may be too optimistic  to guess that $\lambda\rightarrow J(\lambda*\exp)$ be injective map for the paramters $\lambda$  for which $J(\lambda*exp)\neq \mathbb{C}$.
Comment: @yaoxiao: I don't know how to prove or disprove this.


Ground influence on 434 MHz radio signal

Question: I have read in a paper that ground acts as reflector for radio signals in 434 MHz band. Why is that the case?
Comment: Ground acts as a RF reflector is true but I have never heard anything unique about 434 MHz.  So, can you quote the context of this statement or include a link to the paper?
Comment: Well, the author said 'At these frequencies the ground acts as a reflector.'. This implys that at some frequencies ground doesn't act as a reflector.
Comment: I think that ground acts like a reflector (from poor to worse) at frequencies from about 2 MHz up to VHF.  This is why a simple Dipole antenna in free space (no ground at all) usually has far less gain then a Dipole about 1/4 wave above average ground.  Free space gain for a dipole is about 2.1 dBi whereas a 40-meter dipole up about 40 to 50 feet above ground has lobes with gain up to 5, 6, or even 7 dBi.  The ground reflections interfere constructively and destructively with the antenna radiations to produce gain (and nulls of negative dB gain).
Answer: Radio waves reflect from the ground because the ground is a big, flat surface that's conductive enough. It reflects for the same reason that a mirror reflects light.
For a simplified explanation, let's assume the ground is an infinite, flat, perfectly conductive plane. As a wave approaches the ground, the conductivity of the ground constrains the electric field to 0 (you can't develop a voltage if there's no resistance to work against).
The mechanism is identical to a wave reflecting off a short at the end of a transmission line, except the wave is free to move in all three dimensions.
For illustration, I'm going to borrow an animation from Dan Russel's excellent page on wave reflection:

An analogous system which might be more intuitive is a string incident upon a free boundary, like a massless ring sliding without friction on a rod. The lack of friction or mass is analogous to the lack of resistance or inductance in an electrical material. Dan Russel says it better than I can:

The animation [...] shows a wave train moving toward the right, incident upon a free boundary. A free boundary means that there is no force to limit the displacement. Mathematically, this results in the string having zero slope at the boundary.

This limit means the wave can't penetrate the material, nor can the material absorb the wave. The energy must go somewhere, and the only solution given these constraints is reflection.
Now, this shows a wave orthogonal to a plane, reflecting back in the same direction from which it came, forming a standing wave. But if the wave is at an oblique angle (as is more usually the case with radio waves and the ground), then we can think of the wave as separate and independent horizontal and vertical components. Only the vertical component is reflected, because it is perpendicular to the ground. The horizontal component continues unchanged. Just like an ordinary mirror, which works the same way, but at a much higher frequency.
And of course, the ground isn't perfectly conductive, so some fraction of the radio wave will be absorbed. And the ground is also not perfectly flat, so the reflection is distorted to some degree.
Still, it's reflective enough at most radio frequencies to significantly alter propagation. See for example the two-ray ground reflection model and image antennas.


Moving a SharePoint sub-site up a level and making it the new top-level site

Question: Have a Sub-Site that's not being used.  However, there is a Sub-Site underneath it that is heavily used.  Now the site owner wants to make the Sub of the Sub a new Top level Sub-site.  Is it possible for someone who doesn't have site admin level permissions?  If not, then I will just submit it up the chain in my environment.  Thanks.
Answer: The easiest way to do this is using the powershell export-spweb command on the sub site you wish to move, and then import it , using import-spweb, at the url of the new site collection.
Comment: From my experience this is best approach.
Answer: You can try the input and output operations mentioned by Mangler but this requires the permissions of the site admin .
Here is the guide source:
Import and export: Stsadm operations
And here are some tips you should note:
1.Make sure you have deployed the same features and customizations  to the destination site.
2.Before you import the sites, please create a new top site with the same site template with the site to be imported, and use this site path as the URL parameter in the IMPORTE command line.
Comment: Thanks.  I don't have Site Admin, but will make sure I add some parts of all the answers into our internal ticketing systems
Answer: With out using powershell, you can actually save the site as template, (it would be hard for sites with a lot of default features activated / deactivated)
On SharePoint admin, go to classic features then create the site from there, select the tempalate to 'select tempalte later',
When the site got created you will be prompted on what template you will use on that site, select the site template solution you uploaded then you're good to go.
Hope the concept shed some light! Happy Learning!


Wigner Rotation

Question: I'm trying to show that the composition of two Lorentz boosts produces a boost and a rotation using the generators from the Lorentz Group. If $\vec{K}$ denotes the Lorentz Boost generators and $\vec{S}$ denotes the rotation generators then two successive Lorentz Boosts in the $x$- and then $y$-directions is given by $$e^{-\xi_yK_y}e^{-\xi_xK_x}$$ How do I go on from here to prove the result is another boost and a rotation? I know I have to make use of the commutator $$[K_i,K_j]=-\epsilon_{ijk}S_k$$ but I'm not sure how to proceed.
Comment: Related : [General matrix Lorentz transformation](https://physics.stackexchange.com/q/361227/)
Comment: [related](https://physics.stackexchange.com/questions/395036/composition-of-lorentz-transformations-using-generators?rq=1).
Answer: Well, you are meant to compose the two exponentials of the noncommuting boost generators, possibly by the CBH expansion identity, or else by simply expanding each exponential to a few low orders in the ξ rapidity parameters, as the WP article suggests, and utilize the commutators. In your case, you need $[K_y,K_x]=S_z$, $[K_y,S_z]=-K_x$, and $[K_x,S_z]=K_y$, which happen to close to an SU(2)!
That is, to say,
$$ e^{-\xi_yK_y}e^{-\xi_xK_x}\\ = \Large e^{-\xi_yK_y-\xi_xK_x +\frac{\xi_y\xi_x}{2} [K_y,K_x]- \frac{\xi_y\xi_x}{12}(\xi_y [K_y,[K_y,K_x]] + \xi_x [K_x,[K_x,K_y]]  )+... }\\= \Large e^{-\xi_yK_y-\xi_xK_x +\frac{\xi_y\xi_x}{2} S_z+ \frac{\xi_y\xi_x}{12}(\xi_y  K_x + \xi_x K_y  )+... }
~~.$$
In point of fact, the $O(\xi^4)$ term in the exponent vanishes in this particular case, and the leading non-vanishing one is $O(\xi^5)$, which you could easily compute.
There is a closed form for such an SU(2) expression, (or, better, the Gibbs composition formula), so a linear combination of the three generators with coefficients to all orders in ξ. The complete expression is a product of a boost and a Wigner rotation, $\exp(\theta S_z)\exp(a K_y +b  K_x)   $, with   $\tan \theta= (\sinh \xi_x \sinh \xi_y )/(\cosh \xi_x +\cosh \xi_y)$, and $a(\xi_y, \xi_x)$ and $b(\xi_x, \xi_y)$ messy Gibbs parameters, and amounts to an SU(2) group identity. (Observe this ordering elements, when combined as above, yields the composite single element found above, to this order in the ξs, $\exp(\xi_x\xi_y S_Z/2+...) =\exp (\xi_y K_y/3 -\xi_x K_x/3+...) $,  where the lagging new composite boost is asymmetric in x and y, as it should be!)
To sum up, combining two boosts along different axes x and y produces a Lorentz transformation which is not just a pure boost, the $O(\xi)$ sum of boosts, but also an $O(\xi^2)$ rotation, the Wigner rotation underlying the Thomas precession.
You may also observe that, if you undid these two boosts in the same order, you would get a doubled Wigner rotation as the leading, $O(\xi^2)$, remnant,
$$
e^{-\xi_yK_y}e^{-\xi_xK_x}  e^{\xi_yK_y}e^{\xi_xK_x} \\ =   e^{
  \xi_y\xi_x [K_y,K_x]  +  O(\xi^3) +... }=  e^{
  \xi_y\xi_x  S_z  +  O(\xi^3) +... } ~~.
$$
This is called the group commutator, whose logarithm is the corrected Lie algebra commutator, a  double Wigner rotation.

Wigner Rotation


Is it considered proper (normal) to post the same question on askubuntu and at the same time on Unix&Linux?

Question: Some questions that are fit to ask on http://unix.stackexchange.com are not fit here, but the other way around should always be ok. But is it? - (from askubuntu's point of view, of course)
Comment: Related MSO Q: [Is cross-posting a question on multiple Stack Exchange sites permitted if the question is on-topic for each site?](http://meta.stackexchange.com/q/64068/195914) says NO.
Answer: My answer on the other question may sound favourable but it is really talking about the wider community (outside of Stack Exchange). There is one reason why the answer to your question is a decided no:
Unix&Linux.SE does not allow cross posting.
It doesn't matter what we say, posting something to both here and there will break their rules so please avoid doing it.
Comment: @cipricus That should be fine, since that question *is not the same as this one*: even if they are worded the same, this question is about whether or not something is considered proper on Ask Ubuntu and by its community; that question is about whether or not something is considered proper on Unix.SE and by its community.
Comment: meanwhile i already posted *this* question on their meta site :)


what is the best way to acquire hops for exporting

Question: Here recently me and my have been discussing going into selling hops over seas where there is a demand for them. That being said would it be better to buy land and grow,or buy from local farmers? we have a hops commissioner here in which im going into this coming week i just came across this forum, so i thought i would ask...... thanks
Answer: Unless you have millions of dollars, you don't want to buy land and grow hops.  It's simply not as easy as just "growing hops".  You also have to have processing facilities.  You should contact a major wholesaler like Hopunion or S.S. Steiner.
Answer: In addition to Denny's points, you could see if your own region has something similar to the Northeast Hop Alliance or whether any nearby agricultural colleges have programs like UVM's Vermont Hops Project (to use examples local to me). You may be able to find a good deal of up-to-date research and information on breeding, growing, processing, marketing and selling hops.
Answer: Also bear in mind that exporting means that you have to adhere to the rules and regulations of the country that you are exporting to. This means providing certificates to ensure that the product meets their safety requirements. For instance: America has a type of mite that can kill all of South Africa's hops, so if you want to being hops from USA into SA, you have to provide them with proper documentation that the hops does not carry that mite.
To add a bit to Denny's points: If you plant hops, your first year will have very low yield, so expect at least one year of low/no income.
Have you been to a hop farm? There is a surprising amount of construction required for the hops to GROW! Trellises and irrigation is critical. And then there is harvesting, cleaning, processing, packaging, storing!
Just be aware of the whole process. There might be some unexpected, very expensive lessons if you do not do all your research.
Good luck with your venture.


NDA/non-compete disclosure to new employer

Question: I'm pretty naive and new to all of this legal stuff and it seems like I'm learning the hard way about all of it. I signed a confidentiality/non-compete/non-solicitation at a previous employer, and was recently offered an internship (not done school yet) at a large tech company. I disclosed those previous agreements to them and they seemed pretty sketched out about it. They wanted copies of said agreements and to know generally what I did at previous employer. Is this standard procedure for big companies? Is there any chance that this could ruin my job offer? The two jobs are totally unrelated. I just want to make sure that these previous agreements aren't going to mess up my opportunity in anyway, as it is super important.
Comment: You may not need to pay for a lawyer's time. Check with your university; many have legal services available to students.
Comment: "Is there any chance that this could ruin my job offer?" Whatever you are claiming the hard way doesn't extend to reading the NDAs you signed. The HR of your prospective employer is doing its due diligence and is doing what you should have done all along, which is to read your own NDAs. And you think anyone can answer your question about your NDAs without reading your NDAs and without knowing what the activities of the job entails? Voting to close.
Comment: They could completely ruin your chances at getting the internship, have no effect whatsoever, or anything in between, depending on what they say and when they expire.  You need to figure out how to pay for an hour or two (or more maybe) of an employment lawyer's time and meet with them, bring all the documents you signed and any formal communication from your potential new place you want to intern at.  Those non competes etc may have already expired or they might let you out of them if they are binding and applicable, but you need to find out from a professional.
Comment: Would be great to tell us what country you are talking about.
Comment: I am in Canada.
Comment: How easy or difficult is it for you to obtain a copy of the agreement that you signed at your previous employer?
Comment: I have my own copies of the agreement.
Comment: @user2880415 Well, then to start with, just read it and see if you find anything problematic. Most NDAs contain standard stuff like you should not disclose any company confidential information to a competitor, etc. so switching a job usually works out okay. I have myself switched jobs a couple of times, and the NDA was not even discussed. (I had even forgotten about them.) Moreover, I am not a citizen of the country that the employers were based in, so I had to sign a somewhat "stricter" NDA, but it still caused no problems.
Answer: No one can give you a definitive answer without reading the full text of the documents you signed. If this became a big enough issue you might want to talk to a lawyer.
That said: In general, an NDA should not stop you from getting a new job. When you signed the NDA you promised not to disclose certain types of information about the company. So it shouldn't matter where you go to work after that, as long as you don't disclose this information. Unless your new employer is hiring you with the thought that you will tell them all this secret information about a competitor, it should be a non-issue.
A non-compete agreement is a different thing. By definition it limits where you can go to work after leaving the company you signed the agreement with. I once had an employer ask me to sign a non-compete agreement that said I would not take a job with any company that had "anything to do with computers of any sort whatsoever" for two years. That's pretty broad to begin with, probably eliminating about 90% of the companies in the country. Considering that my profession is software development, that basically said that I wasn't allowed to have a job for 2 years after leaving them. I talked to my boss and got them to change "of any sort whatsoever" to "relevant to the business of" that company. But I'm sure lots of people take jobs without even think about the non-compete agreement, then on their first day they're given this form to sign and what are they going to do? Refuse to sign and maybe be told, "Oh well then, I guess we have to withdraw the job offer." And you've already quit your previous job, maybe turned down other offers, and you're in the street.
Anyway, my point is, you should ask to see any non-compete agreement before you take a job. But given that you either didn't do that or found it acceptable, now the issue is to analyze whether the terms of that agreement prevent you from working for this new company. If they do, then you're pretty much out of luck. Find a job that you can take without breaking a contract. If they don't, then no problem.
In real life, I don't recall a company ever asking me if I had signed a non-compete agreement that would prevent me from working for them. I think that generally companies don't worry about this sort of thing unless you really cause them trouble, like stealing clients from the former company, or starting up a project that directly competes with a project you were involved in at the former company.
Comment: Non-compete clauses are typically governed by state law, and in many states (in the US at least) overly broad non-compete clauses are unenforceable. A quick search for Canadian related non-compete appears that it is pretty much the same. Unfortunately, a company may choose not to risk the lawsuit to hire someone under a strict non-compete agreement, even if it is likely unenforceable.
Answer: This is perfectly normal.  If you signed an agreement with Burger King, and then went off to work for MacDonald's - it's possible that your new employer could face legal repercussions.
The new company wants to make sure that they're not going to get sued for hiring you.  If the two companies are completely unrelated, you don't have anything to worry about.  The company is just doing due diligence.
Comment: enforceability of nda/non competes does depend on the level of employee.
Answer: NDAs are important.  They can bring both you and the company you work for into serious legal trouble if you are hired in violation of one.
It was good to bring it up ahead of time, since it's not necessarily easy to trace down, and it's much better for the company to research it first, than for you to be terminated abruptly some number of years or months from now when the company figures out they are in violation and tries to fix the problem as quickly as possible.
As to what happens in this particular situation - this falls into the realm of "get a lawyer for advice" - the writing of this particular NDA and the way it's interpreted by the new company's lawyers is the key to the likely outcome.  Some NDAs have been ruled unenforceable by courts, and some have led to years of legal battles.  Some companies are super cautious, some are not.


Changing (alternating non linear) screw motion

Question: I'm looking to put gradual pressure on a syringe.
Comment: I don't think you understand the difference. If the syringe moves as the contents are pressed out you will lose pressure. If the syringe is blocked and you turn the screw you will get very high pressure and something will break. I think you are trying to control the motion, not the pressure.
Comment: Are you saying "pressure" when you mean "displacement"?
Comment: I mean put pressure to move that part
Comment: If you are willing, it would be better to explain what you are trying to accomplish, rather than what you think is the solution. What is the syringe being used for?
Comment: I have rolled back your question to the previous edit as you seem to have accidentally deleted almost all the content and making the answers below look very strange.
Comment: Actually I need to delete this post.
Answer: Cams offer a simple way to make a variable motion profile.

Figure 1. A simple cam-operated contraption can be built out of wood.

Syringe.
Syringe holder. This really needs a slot from one edge to allow easy changing of the syringe.
Drive-rod guide lower.
Drive-rod guide upper.
Drive rod. This and the two guides ensure that the syringe only sees vertical motion on its plugner.
The drive cam. The radius on this changes to give the motion profile you require for a constant velocity rotation of the cam.
Cam axle.
Cam handle.
Assembly supports.

Instructions for use:

Rotate cam handle anti-clockwise to the horizontal position (9 o'clock).
Lift the drive-rod and insert the syringe.
Rotate cam handle clockwise at even speed to 3 o'clock position.

Design:

Get out your protractor, some paper and a pencil.
Measure the stroke of your syringe. This is the difference between the cam's minimum and maximum radius.
Draw a semicircle on the paper with a radius of, say 50 mm.
Draw radii every 10° from the centre out past the semi-circle.
On each 10° line mark a point as many mm away from the semi-circle as you want the syringe depressed at that angle. So, for an even dispense on a 90 mm syringe you would have a point at 50, 55, 60, ... 135, 140 mm giving you a stroke of 90 mm in 180°. Draw that first as your reference and then you should be able to work out how to get the profile you want. Your profile just has to:

start on the same 0° start point as we've constructed above.
be always increasing.
finish on the 180° point we've constructed above.

Have fun.
The image was created with OnShape which is an online, in-your-browser 3D CAD package. Use is free if you are prepared to make your designs public. It's all rather amazing!
Comment: There are only two moving parts, 5 and 6. Everything else can be fixed.
Comment: An impressively simple yet elegant solution. The cam profile is easily modified for different pressure rates, just as the OP requested.
Answer: Just a basic crude idea.
you can have the piston screw threads installed on a hexagonal shaft in 6 sections (not a continuous tooth but 6 individual teeth or spikes) around a  shaft that has 6 separate faces and is flexible so it can change its diameter by letting these faces move in/out.
And the female thread in the syringe shaped like a cone, a funnel, getting wider as it gets deeper, but with the same pitch.
Then the slope of the thread pitch will be less as it gets deeper and the piston will move less/ a full rotation.
my apologies for the poor quality sketch.


What database app is best for including in a distributable app?

Question: MySQL versus SQLite, for example?  I understand that MySQL is harder to setup and configure...  Would SQLite or another db be better suited in this regard?
Comment: The question seems a bit more, ah, StackOverflow-ish.  Have you looked there? http://stackoverflow.com/questions/3630/sqlite-vs-mysql
Answer: If you want high portability, SQLite is the best. However, for operating with large data amounts, MySQL wins.
MySQL
- needs setup
- needs creating the schema while installing
- very fast
- many storage engines
- has many useful things that are missing in SQLite
SQLite
- only library needed (and language bindings in some cases, sqlite3-ruby for ex.)
- portability
- you can redistribute the database along with application
- needs regular optimisation (VACUUM)
- not too fast
- almost unusable with many (100.000.000+) records
Answer: One key element to keep in mind: the license.
If you're going the commercial route with your application, bear in mind that either you need to distribute it under GPL2 (in which case you need to make the source available, among other things) or you need to get a license from Oracle (presumable against hard-earned, cold cash).
On the contrary SQLite is in the public domain so you're free to do whatever you want with it.
That being said sqlite is very easy to embed so it's likely to be the easiest route assuming its feature set and performance profile works for you.


Mushy Aglaonema stem with browning leaf tips. Answer asap please

Question: Recently I've been watering my Aglaonema Silver Bay a little too much (due to the scorching heat of summer in India). I've noticed that the stem has gotten pretty mushy and dark brownish. The plant cannot stand erect when I move it. It dangles. The tips of all the leaves have started browning too. The pups around the plant seem unaffected by the excessive watering. How can I save my plant? Please answer asap.
Answer: The stem is dying due to over watering which has led to root rot.
You can cut the stem above the dying area and root the top of the cutting in water.  Then cut the stem below the dying area and provide more sun and less water.  It may bud out and regrow.
Comment: Thanks for the answer. Is there any way that the plant could dry out the mushy area and replenish overtime? What about the pups surrounding it? Is it better to replant them in dry and fresh soil rather than letting them sit in the wet soil? Will doing so disturb the root ball?
Comment: @FariyalAjrad The plant is already stressed so splitting the root ball will only add more stress.  I would not recommend this.  The mushy area will not "heal" as plants do not recover from injuries in the same way that people do.  Move the plant to more light and that will do wonders


How can I get readers to like a character they've never met?

Question: Okay, so in my story, a character goes missing, however you never actually meet them. How can I get readers to like them even though they're never even introduced to them?
Comment: See: Julie Mao from The Expanse.
Comment: Have your characters tell (likable) stories about the missing person?
Comment: As an example of an absent character the reader grows to *dislike*, Emma, by Jane Austen does this with both Frank Churchill and Jane Fairfax, although they do pitch up in the last half of the book.
Comment: @Harabeck Poor example, you start the story from Julie's perspective!
Comment: Dumbledore was pretty absent and everyone loved him ;-)
Answer: Warning: This answer contains a link to TV Tropes. Please be careful accordingly, or you will fall into a vortex and never return.
This literary trope is called "Posthumous Character," and although your character isn't actually dead (presumably), the same idea applies. You are trying to get your audience to like, understand and see a character who is not actually present in your narrative.
Therefore, this absent character will probably be developed entirely through flashbacks. This is hard to do properly, of course, and it has a big drawback - it has already happened, after all, so it can't really affect anything in your present-day plot. But if you're trying to develop a missing character, this is really the only tool for the job. Other, related options could be parallel story structure, where you tell both the current-day story and the past story of this missing character's adventures.
Movies do this "developing dead/absent characters through flashbacks" kind of thing all the time. When a character has a tragic backstory, i.e. a missing wife or deceased children, the movie will flash back to a time when those characters were alive, showing us how kind and loving the wife was or how wonderful the children were. You can mirror this kind of nostalgic flashing-back in your story, if you want to develop absent characters without actually having them be present.
However, are you sure doing this is a good idea?
Why you shouldn't always develop absent characters
Developing characters who a) aren't actually important to your narrative, b) will never show up, or c) are dead, is often, to put it bluntly, a waste of your time. Why spend your valuable word count developing a character who we will never get to meet? Why should your reader care about somebody who never appears except for flashbacks, doesn't help the protagonist in any way, and basically never affects the plot? I'm guessing that you could cut this character out of the story entirely and not affect anything at all, and that's never what you want.
(For reference, consider the Sexy Lamp Test. Could you replace your character with a lamp and have literally nothing change?)
To make the exploration of absent characters count, then, tie it to a character who is present. A dead wife isn't important to the story unless we learn how much her living husband misses her. A missing son isn't important to the story unless we know he makes our motherly protagonist cry at night. And so on.
In short: You can absolutely develop absent characters, using flashbacks and other tropes. However, be warned: without having a solid, strong narrative reason for why developing this absent character is important, all you will do by developing them is waste your time and word count. Your effort is probably better spent on your actual characters and protagonists, not one that the reader will never meet.
Comment: Nice answer. +1 (if I could give you another +1 for the disclaimer, I would)
Comment: Just be careful not to devolve into a *"Whenever Poochie's not on screen,
all the other characters should be asking, 'Where's Poochie?'"* scenario.
Comment: Granny Aching is one of Pratchett's best characters, although we never see her. +1
Comment: +1 Twin peaks built the largely absent character of Laura Palmer up of the series.  I don't know if the character was necessarily likeable but the character was built into a demi-god over the series despite just being primarily referenced by others.
Answer: Show how they matter to people:
I have a major character in my novel who is dead, and appears only as a spiritual entity. The ghost interacts with people by sending dreams and visions. She is also one of the most sympathetic characters in the story. Sendings and visions are not a material way of showing up, but can work. Dream sendings operate like a flashback, introducing the character with things that happened long ago.
Sometimes you have someone who will show up later in the story and play a prominent part. You want your readers to know them and to know their importance. Relate the character by the actions of the other characters. Have them talk about the missing character, remember the things they did together. Have the things they do center around helping the missing character, or have them say how the missing character changed their life.
Try to imagine The Lord of the Rings with Gandalf as an unseen presence. The characters talk about him, refer to the things he is doing and has done, how he changed their lives and fought evils. Without actually seeing him, you can see how you can set him up as a great hero and savior. If/when he shows up, you wouldn't need to develop his personality unless you wanted it to clash with the vision you had created.
Answer: The absent character makes itself felt through their material or spiritual connection to the protagonists. For example, a missing senior hunter or warrior would always be in the minds of their junior friends because of all the techniques and valuable survival skills they taught them. When stuck, they would brainstorm "what would X do here?" which enables them to shed light from a different perspective and helps them to prevail.
If the absent person was good at crafting the protagonists would wear clothes and gear that helps them on a daily basis in their adventures.
There may also be an exclusively spiritual bond: A love or deep friendship, an oath of loyalty, something they achieved together — any and all of these can be a source of mental strength which keeps them going in the face of adversary and makes clear why the missing character is important to them and why they revere them.
Answer: If your POV character has a lot of affection for the missing character, that will tend to shape the way your reader feels about that character. But it needs to be organic, and not too heavy handed. Otherwise it will backfire. Showing the ways the missing character leaves a hole in the POV character's life is likely your best bet.
There's a great example in the movie Stand By Me. The POV character's older brother is deceased. He only appears in one brief flashback, but that demonstrates clearly how he shows the love for the POV character that the rest of the family doesn't. He's also referred to frequently by other characters in ways that highlight how much they liked and respected him.

How can I get readers to like a character they’ve never met?


Mathematica notebook opening off the screen

Question: I have an issue with opening Mathematica notebook. I'm using Student version of Mathematica 12.0 on Windows 10. When I initiate the Mathematica or create a new document from the start page, it opens without any problems. But when I click to open the already existing notebook, it seems to be opening off the screen with only a little bit of it visible on the far right edge (attached screenshot). I can't move it at all. Have you ever encountered this problem?
Comment: While not a Wolfram Language solution, you can use the menu Window > Arrange Windows > (I like Stack)
Comment: "I can't move it at all." You can press Alt+Space to open the window's system menu. Then simply press the underlined character of the "Move" menu item. Then you can move it using the keyboard (and then the mouse). Or use Win+arrow keys.
Answer: Yes, I have encountered this problem very often. For me, the reason is that I have 2 screens on my desktop pc and when I save a notebook which is on the second screen and open this notebook later, e.g. on my MacBook, then it happens that the notebook window has coordinates outside my Mac screen-area.
The solution is simple: Assuming testme.nb is your notebook (you need to include the path as well), then you can do:
nb = NotebookOpen["testme.nb"];
SetOptions[nb, WindowMargins -> {{0, 0}, {0, 0}}]

and it should jump to the upper left corner of your screen.
Answer: In Windows, it is simpler to right-click the Mathematica icon on the taskbar, select the notebook, which is still off-screen, then hit Win-LeftArrow (or similar combinations) which will dock the notebook on the left of the visible screen.


How to deal with stubborn players?

Question: Okay, so my problem is that one of the people I have in my party (my brother) is VERY stubborn when it comes to playing a session of D&D, everything from getting on his tablet and getting distracted to the point where when it's his turn he has no clue what is even happening, saying things like "I punch the monster" when it is 50 feet away from him. I tried to incite a tabletop rule of "No electronics" but everytime I tell him to put his tablet away, he labels me a "Tight-ass DM" and tells me its my fault no one is having fun. What can I do about this? Is he right? Should I make changes to adhere to his rules? I have contemplated removing him from the game, but I really don't want to as he is my brother.
Comment: Closing as duplicate for the time being.  Is your problem really different, or just that you don't like the existing answers? The solution to that is to go bump that question (I know you don't have enough rep to bounty it yet) to get better answers there...  If it's different you'll need to explain why more.
Comment: Welcome to rpg.se! If your question is different enough from [this one](http://rpg.stackexchange.com/q/33948/4398) that its answers can't help you, please edit this question to highlight the details of your particular situation that you need addressed.
Comment: I'm not sure why, but when he's angry he constantly talks about how he doesn't like the game as it is "Unrealistic and stupid", but strangely enough, he doesn't want to stop playing. I've told him he will have to stop playing until he can straighten himself out, so maybe that will change his mind. Otherwise, someone else will have to take on his character, as well as theirs. @BESW I have already looked there for an answer, but thanks for helping anyway.
Comment: Don't answer in comments.
Answer: Is no one having fun, like he says, or is it just him?
If he's not having fun, why is he still playing?
You need to talk to him about whether or not he is really interested in playing in your game or not. Maybe he just wants to be there to hang out with friends, and could just spectate.
Comment: They usually are frustrated that he is bringing the game down and they wish they could continue, but as I said, he just doesn't seem to be cooperative. I'm going to remove him from the game and see if that makes the game any more fun for everyone, and honestly, I think most it likely will as there would be only players who actually try then.

How to deal with stubborn players?


Formal test for heteroscedasticity

Question: Are there any formal tests for heteroscedasticity for non-normal data? I want to run the test on time series logged returns, so would it be okay to assume a linear relationship? To me it makes intuitive sense that the greater the return (rise or fall in price) the greater the variance.
Answer: With financial data, the question you raised was first addressed in the 1980s by Robert Engle who later got a Nobel Prize for his contributions to econometrics, as well as Tim Bollerslev. They formalized exactly what you think makes sense: the greater the change in the asset price, the more volatility will endure. Models of these type are called autoregressive conditional heteroskedastity models, or ARCH for short, and they say that variance at time $t$ is a function of the magnitudes of shocks in prior periods:
$$
\sigma_t^2 = \alpha_0 + \alpha_1 \epsilon_{t-1}^2 + \alpha_2 \epsilon_{t-2}^2 + \ldots + \nu_t
$$
with understanding that coefficients in this model are positive. There's been an unimaginable number of extensions this model has received, including all soft of transforms, putting lags of $\sigma_t^2$ into the model, treating positive and negative shocks differently, specifying thresholds, etc. These are reduced form models, in the sense that they may not provide a clear message about the mechanism, but they fit financial data very well, and in particular generate the desirable heavy tail distributions even with $\epsilon_t$ are conditionally $N(0,\sigma_t^2)$.
The heteroskedasticity test in this context would of course be the test that $\alpha_1 = \alpha_2 = \ldots = 0$.
Answer: One such test is the Brown-Forsythe test, which is derived from ANOVA.
The basic idea is that you pick a way to partition your data and then compare the mean absolute deviations from the median of each group. One common way is to put observations whose time is before the half-way point in one group, and those whose time is at/after the half-way point in another.
Answer: For time series data, you can also examine the ACF and PACF of squared residuals of your model that assumes a constant variance.  Formally, you could run a Ljung-Box or McLeod-Li test.

Formal test for heteroscedasticity


EQ and Filters in music

Question: Earlier today I asked a question about EQ and got back some helpful information which actually clarified equalization completely for me. However I'm confused on what's the difference between equalization and filters. Is there a difference or are the terms used interchangeably?  If there's a difference what is it ? Below I posted the link to the question I asked about equalization earlier.
Answer: A filter is usually a particular kind of EQ where volumes at certain frequencies are only cut and not boosted. Most of the time a filter cuts everything above a certain frequency (low-pass filter) or everything below it (high-pass filter). There are others like notch and bandpass filters that either filter or "let pass" adjustable bands of frequencies somewhere in the middle.
But the point is that a filter uses EQ to "filter out" frequencies rather than boost them whereas EQ usually refers to the ability to cut or boost.
Comment: I guess. Maybe we're using different definitions. Filters (in the electronics sense) are used to implement EQs, so it's pretty strange to say that a filter is a kind of EQ.
Comment: Isn't it more correct to say that an EQ is a particular type (or use of) a filter (filters, to be specific)?
Comment: No, not in my opinion. You could stretch the common meaning of filter and apply it to a different context such as calling a compressor a filter that filters out dynamic ranges. Or by saying an EQ filters frequencies whereas as an air filter filters particulates. But in the common meaning of "filter" in relation to EQ, it's a subset of what EQ is. It's cut-only EQ.
Answer: EQ is a type of filter. The difference in naming is mainly because of the different ways different types of filters can be used.
Typically, EQ is adjusted for individual instruments to improve the mix (to avoid two instruments "competing" for the same range of audio frequencies, etc) and remains constant for the duration of the piece. The EQ controls usually show a display of amplitude against frequency, calibrated in well defined units like Hertz and decibels.
On the other hand many musical instruments have "built-in filters" which affect the sound - for example a wah-wah mute on a trumpet, the una corda pedal on a piano, the bowing position on a string instrument (sul ponticello / sul tasto), the many types of effects pedals on electric guitars, etc. These can be varied from note to note, or sometimes within a single note, as the performer wishes.
Similar filter effects can be created after recording the audio, or on audio that is generated entirely by electronics. Filters used this way usually have controls that don't show an "objective" measurement of what they do to the sound like an EQ filter display, but are designed to be easy to use in real time.
Answer: A "filter" is not a well-defined term: basically it is used for any kind of sound processing intended to leave information in place.  A low-cut filter is used for removing rumble noises and attenuates the signal increasingly with lower frequencies.  It is a special form of a high-pass filter: there are also "shelving" high pass filters which have a frequency response ending on a "shelf", meaning that they don't attenuate more than a given amount even as frequencies get lower.  A graphical EQ typically has shelving filters as its first and last control.
A notch filter cuts out a certain frequency.
All of those filters are "linear" and "time-invariant", meaning that you cannot distinguish running through signals through separate (identical) filters and then summing the results from summing the original signals and running them through a single filter, and if you send a delayed signal in, the result will be the response for the undelayed signal, just appropriately delayed.
A graphical EQ is a whole filter bank typically arranged with logarithmic frequency steps designed in a manner where the output will be identical to the input (apart from scaling) as long as all controls are at the same height.  So basically all individual filters in a graphical EQ tend to have a "shelf", for all but the first and the last in the middle of their range.  It is either that, or the overlap of the individual filter ranges is so much that the total frequency response comes out flat nevertheless.
Now all of that are linear filters, but there is also non-linear filtering like the one used for noise suppression or echo compensation (both of which tend to be done by piece-wise linear filtering but with the filter being constantly adapted to the signal, making the end result non-linear with regard to the overall input).
I don't really know a rigid definition of "filter" that would apply to everything commonly called a "filter" but excluding intentional distortion (various kinds of vacuum tube sound simulation including "clean", tape drive simulation, plain old overdrive and so on).
So basically it's more or less convention when some input-derived signal processing is labelled "filter" and when not.  There is no hard and sticky rule people would agree on.

EQ and Filters in music


What does "Nothing like anything" mean?

Question: What does the phrase "Nothing like anything" mean? Literally it doesn't make sense to me and also I do not know its figurative meaning either.
Answer: To be nothing like means it is completely different and has nothing in common. Nothing like anything means incomparable; completely different from all other things. This is the literal meaning of the term, no figurative or idiom involved.
There are three examples of nothing like anything in the Corpus of Contemporary American English (COCA):

it was just an unbelievable event and nothing like anything the country had ever gone through before

Here the speaker means the event was completely unlike any event previously experienced in the country.

" It seems like I've always had some type of adversity, " Bobby says. " My freshman year at Duke, we lost the title game by 30 to UNLV.... But this is big adversity, nothing like anything else. # "

Here the speaker is referring to some type of adversity that this time has a magnitude never before seen, incomparable to any previous adversity.

" She spun around, drinking in the scenery, marveling at its almost palpable presence. " But... this is nothing like anything I've ever seen on the' net! "

Here, whatever it is the speaker is experiencing is unlike any experience she has had in the same environment.
Comment: Note that in all of these examples, the "anything" is qualified. I wonder if it is in the instance you are asking about.
Answer: "Nothing like X" is a common phrase that is a more emphatic way of saying "not like X".  It means that X has nothing in common with the thing you are comparing it with.

I am not like my father. (we do some/many things differently)
I am nothing like my father! (we are totally different)

So, "nothing like anything" would be used to say that something is completely unique, and would be more emphatic than "not like anything".
On a general style note, the phrase "nothing like anything" sounds fairly informal/colloquial, so you would probably want to avoid it in situations where that matters.
Answer: It is a way of saying that there are no common characteristics.
X is not like Y. (could share some characteristics)
X is nothing like Y. (absolutely no common

What does "Nothing like anything" mean?


how do i navigate blender on a vaio z canvas

Question: I recently acquired a Vaio Z Canvas which has a very useful shortcut key menu that I can display on the left of my screen as can be seen in the image. Up to this point I've been using these shortcuts to help navigate with the use of "emulate 3 button mouse" setting with alt allowing me to orbit, ctlr+alt to zoom and shift+alt to pan. The problem I'e experienced is that these navigation functions have just stopped working...All the other shortcuts I on the panel still work and the navigation is still possible when i use an actual keyboard. if anyone knows how i can fix this problem or even better, show me a way to navigate with the use of like non-pen touches i will be eternally grateful
Answer: I'm not familiar with the Vaio Z, but if it supports multi-touch, try dragging/pinching with two fingers. (This is how it works on a Mac OS X trackpad.)


How "add" could be implemented in only bitshift operations

Question: Typically, add/subtract/multiply/divide are primitive operations in an Instruction Set Architecture (ISA). I am interested to know if they can instead be implemented efficiently using only bitshift operators. I'm interested to know what sequence of bitshift operations can reproduce the addition operation.
Comment: This is covered in courses and textbooks on digital logic. A circuit which adds two numbers is known as an *adder*.
Answer: This is impossible, a shift does not combine two operands.
Answer: You can partly perform an addition, but the practical interest is definitely null.
A logic circuit can be described as a thruth table.
Consider for instance the truth table of a full adder (sum)
a b c | sum=a xor b xor c
0 0 0 | 0
0 0 1 | 1
0 1 0 | 1
0 1 1 | 0
1 0 0 | 1
1 0 1 | 0
1 1 0 | 0
1 1 1 | 1

Shifting can somehow be considered as a way to perform a table lookup.
If we build v=4*a+2*b+c and T=0b10010110, we can see that the LSB of T>>v equals the corresponding entry.
So, to get only the corresponding bit, we can do
unsigned fulladd_sum(unsigned a,b,c) {
  // note a,b,c must only have their LSB eventually set
  unsigned int as, bs, cs;
  unsigned int T=0b10010110;
  unsigned int sum;
  as=a<<2; bs=b<<1; cs=c<<0;
  sum = ((T >> as) >> bs) >> cs ;
  return (sum <<31) >> 31 ; // to get rid of useless bits
}

And we have the sum bit. We can do the same for the carry and process this way successive bits.
The only problem, as already spotted, is that we have no way to combine bits and the result will be spread over several variables representing the successive logic weights of the result.
Concerning the operands, we can have normal operands and extract individual bits by shifting and cleaning (with ((op >> i) <<31) >>31 to get the ith bit).


Honey-fermented garlic left open overnight

Question: I am a five days or so into the process of honey-fermenting a batch of garlic. Took the can out to let it burp last night but then left it open on the kitchen counter and only realised in the morning. Do I have to throw it all away now? Particularly concerned about botulism...
Comment: I didn't know that was a thing, can you edit with details of what you are trying to do and what the normal steps are?
Answer: As far as I can tell, with lots of googling, recipes for honey-fermented garlic have the process happening at room temperature, with fermentation occurring for up to a month. I have found some questions on the internet about safety, though this seems to be a fairly common ferment.   The process of fermentation itself creates an inhospitable environment for the growth of botulism, because of the formation of alcohol and acidity.  Ideally, you are looking for a pH below 4.6.  The best way to determine the safety of your ferment would be to measure the pH.


Vipassana meditation with samadhi

Question: In vipassana meditation either samadhi or insight  comes as the  vehicle .When samadhi comes as a vehicle it's called Samanthayanika vipassana .In Samanthayanika meditation how yogi see the impermanence suffering and no self?
Comment: Think about it. How can one see anicca, dukkha, anatta when observing concepts that are stable, satisfying and experienced as self?
Comment: @user13579 Samanthayanika meditation can not be the samadhi used in satipatthana that cultivates  vipassana?
Answer: I think it is wrong to say that either insight (panna) or concetration (samadhi) comes through Vipassana. They both come through Vipassana, they both aid each other in their "coming through" and further growth. Of course, it is relativly easier to develop samadhi as compared to panna; nonetheless samadhi is perfected only when one has panna and panna cannot be perfected without having perfected samadhi.
It is unclear what you mean when you say 'comes as a vehicle'. But if I were to take vehicle as that which carries you over the river of samsar- then 'vehicle' is vipassana. Concentration and Insight both go in hand in hand. A yogi who has perfected samadhi has more chances of perfecting panna, and therefore, is closer to Nirvana; than a yogi who is yet to perfect samadhi (for perfection of panna without perfection of samadhi is not possible).
DO note that these are not the only two things to be perfected. These are only two Paramitas. There are more.
Since the vehicle is Vipasssana only, one 'sees' the three marks of existence (anicca (impermanence), anatta (no-self), dukhha(suffering)) as anyone else would see-through insight build on a foundation of samadhi and other perfections (paramitas).
Comment: Great answer! I believe the questioner was referring to the two vehicles model that posits one vehicle as being A) one who practices first Samatha and then Vipassana, and B) one who practices Vipassana and then Samatha. I agree that they arise and assist each other on the Path, and must both be developed in tandem for true progress. Some modes of practice however might stress one or the other. For example, first gaining Ekagatta and then using this calm, wizened mind to look at the Three Characteristics.
Comment: @SunWuKong Yes! I very much agree that there are traditions that stress one over the other. That is good, because everyone begins at a different point. Thus, for people who think they need to work on samadhi, can go for vehicle A. Likewise, people who think they need to work on panna[pali] (prajna[sanskrit]), can go for school B.

Vipassana meditation with samadhi


What is the AXA Schengen Insurance office phone number?

Question: I made the payment for a Schengen (Europe Travel) visa at the AXA-Schengen website, but haven't yet got (it has been five hours) any insurance documents by email. How long should I wait? They don't have any phone numbers listed on their website, and say that we should email them first. This is pretty ridiculous. If I made a payment, I should get my documents immediately. Please, does anyone have a phone number I can call?
Comment: Your lucky.in my case is they have not send me the refund for almost 4 months now. I called the number you provided and they said they only have do assistant but thwy dont hav number or cant contact the axa for refund! I feel so much that this is a scam. They already email me back that they will refund me in september since august flight was cancelled but its november now! :(
Answer:
How long should I wait?

According to the FAQs on their website, you should have received the insurance certificate immediately after payment:

Q: How do you send the proof/certificate of insurance?
  A: The mandatory insurance certificate is sent by e-mail immediately after payment. You just need to print it.

Since it's not uncommon for auto-generated emails to end up in some sort of spam folder, be sure to check there too. Your mail provider may have flagged the email as 'suspicious'.

Please, does anyone have a phone number I can call?

It looks like the AXA Schengen travel insurance is mainly an online-only business, as it can only be purchased the website. Hence, it's no surprise all customer service related queries are routed through email@example.com. There is a mention of an emergency contact number, but apparently only listed on the actual certificate.
That being said, I see two obvious options if you still want to try and phone the company:

AXA Assistance is represented by Inter Partner Assistance. You can grab their phone number from their website (sorry, in Dutch, but I'm sure you'll be able to figure out the phone numbers). You'll see that the address mentioned there matches the one listed on the AXA Assistance contact page. As a matter of fact: http://www.ip-assistance.com/ basically just redirects to http://www.axa-assistance.com/.  You may contact Inter Partner Assistance on +3225500400.
Try one of the many AXA offices in Europe. Not sure which one would be best to call though. Anything Schengen related is probably out of scope for the local offices and I wouldn't be surprised if they'll just refer you to the aforementoned email address (that is, if they refer you at all).

Last but not least, and perhaps handy for future readers:

Any communication with AXA Schengen (written, verbal or electronic) may be in French, Dutch, English or Spanish.
Comment: Oh my gosh, YOU NAILED IT! :) The website link you provided (http://www.ip-assistance.com/) is what I went to, and got this number: + 32 2 550 04 00. The automated response is in (I think) French, which I do not understand, so I just pressed 1 until I got a person on the line :) She sent me my documents right away. Thank you so much! This was a fantastic answer.
Comment: @user1096863: Glad to hear that worked out for you and that you're all sorted out. :) You phoned a Belgium number (Brussels, to be precise), so there's a good chance the automated response was in French. It's either that or Dutch, but that would sound quite differently. Happy travels!
Answer: In case this helps anyone in the future, you can access your documents from the AXA Schengen website at any time.
For "name of beneficiary" put your last name, and for "policy number" put the order reference (it begins with SCHE....) in the email that you got when you paid. If you didn't get the order email immediately then your payment either didn't go through or the email got caught in a spam filter!


what is this marine creature?

Question: I found this creature floating in the Mediterranean Sea, probably dead.
I tried looking it up in the Marine Species Identification Portal but I couldn't find anything like that. It looks like some kind of jellyfish or hydrozoan.
Answer: This is a blue button jellyfish! they eat zooplankton and are usually found drifting along on currents
they aren't true jellyfish and just like a jellyfish have no blood, brain or nervous system. they aren't usually toxic enough to hurt but can cause irritation to the skin.
they live in warm waters off of Europe and in the golf of Mexico and the Mediterranean.
they are hermaphrodites and have both male and female reproductive parts. they lay eggs which turn into polyps
here is a website I found all about them as I'm not extremely knowledgeable on this species.
https://www.thoughtco.com/blue-button-jelly-porpita-porpita-2291819
Comment: Welcome to Biology.SE! While your answer seems reasonable, you are more likely to get a positive response if you explain why your identification is correct. Specifically, please [edit] your answer to add discussion of key features that led you to this conclusion and supporting references or at least validated images. Without this your answer is indistinguishable from opinion and (contrary to best practices) requires users to follow a link. ——— Thank you for taking the [tour], but please also consult the help pages for additional advice on [Answer] effectively on this site. Thank you!

what is this marine creature?


Reclassify raster based on Z-values in Arcmap 10.4.1

Question: I have a raster which has a Z-value applied to each pixel. I want to reclassify the raster so that any pixels with values below 1 are removed. Is there an ArcMap tool which can perform this task?
Answer: Answered this myself, the Reclassify tool under 3D Analyst tools - Raster Reclass allows you to redefine the values of a range of pixels. I set one of the classes as 0-1 and set the new values to 'NoData'. The resulting output created the raster without any pixel values below 1.
Comment: That will work, there are other solutions as well. FYI, this operation isn't a 'clip', clipping usually means erasing everything outside of a certain 2D boundary from your original layer.
Answer: I would suggest you look at the "Set Null" tool if you are hoping to keep all other raster values intact but remove those < 1.


How does image reconstruction take place in neural network?

Question: I am reading through and thinking about how neural network works and have been reading about convolutional neural networks (CNN). I am particularly interested in image filtering (or enhancing) using CNN. The thing that confuses me is, how exactly does CNN produce the output, filtered/enhanced image? From what I understand each layer convolves the previous input into more distinctive features, so aren't we essentially losing details? How would the network then know that, for example, this noisy image A, should be cleaned up here and there as such trained to produce a clean image B?
Answer: A plain CNN normally isn't used to produce an image as output; but if you combine it with deconvolution layers, then you can produce an image as output.


Notation for quotient ring

Question: I'm wondering where the notation for the quotient of a ring by an ideal comes from.  I.e., why do we write $R/I$ to denote a ring structure on the set $\{r+I: r\in I\}$, wouldn't $R+I$ be more natural?
Comment: $R+I$ would usually be interpreted as $\{r+i\mid r\in R, i\in I\}$, so that is likely to cause confusion.
Answer: When $A,B\subseteq R$, with $R$ a ring, it is common to write
$$A+B=\{a+b:a\in A,b\in B\}$$
This is particularly useful when $A$ and $B$ are ideals, in which case $A+B$ is also an ideal. So $R+I$ already has an interpretation (although it would just be $R$).
On the other hand, if $R$ is finite, then the number of elements of $R/I$ is $|R|/|I|$. I believe this is the origin of the corresponding notation for groups (and then it makes sense to use the same notation for quotients of all types of algebraic object).
Comment: I find the "order" argument for the notation especially compelling. I wonder if the slash notation has its roots in equivalence relations. @martin Rubey It's common practice to write $X/\sim$ for the classes of an equivalence relation $\sim$ on $X$, and since there's no operation involved the question about using $+$ becomes kind of moot.
Comment: @rschwieb I suppose one could also backwards engineer a possible root of the notation that way as well, with each $I$ defining an equivalence relation on $R$ by $x\sim y$ iff $x-y\in I$, so that $R/I=R/{\sim}$.
Comment: That's what my question was: "does the use of the notation in equivalence relations predate the special-case use here?"
Comment: @rschwieb Ha, sorry, missed that. I read your whole comment once, and then when I wanted to remind myself what you said about equivalence relations I started again from the @. Oops.
Answer: We do so because in general what we are doing is arranging the object $R$ into equivalence classes (in such a way that the set of equivalence classes has a structure analogous to that of $R$), in a manner very similar to what happens when one takes one integer modulo another (in fact this can be reconceptualized as the quotient of the ring $\mathbb Z$ by one of its ideals $n\mathbb Z$). This is a very general operation done in many objects in mathematics, and it is almost always referred to as a quotient. Further $R + I$ in most contexts refers to something like the set of all $r + i$, where $i \in R, i \in I$, whereas $R/I$ refers to the set of equivalence classes $\hat{r}$, where $r, s \in \hat{r}$ if $r - s \in I$. This can be understood as simply $r + I$ but it is not the same as the set of ALL $r + I$ as above, because (with notation as before) $r + I$ and $s + I$ are the same thing. There is more structure there than just taking sums of things.
Comment: I don't mean to necromance here but this post does occasionally get upvotes still so I feel I should make myself clearer. My main point is that arranging objects into equivalence classes is very similar to the process of taking quotients. In particular if one wants to figure out how many dollars one has if one has 100 quarters, one divides by four. In doing so one "bundles" or "packages" the set of 100 quarters into 25 packs of 4. I feel that this process is very similar to packaging a ring into packs of $I$, which one does in taking a quotient by an ideal. This is how I think about it anyway.

Notation for quotient ring


How to fire a Pentax AF 360 FGZ flash with a canon 7D camera

Question: I have a Pentax AF 360 FGZ flash and a Canon 7D camera. Different hardware I know. But I want to be able to fire the flash, possibly using a remote trigger that would allow me to remotely take the shot and fire the flash as well.
Comment: Since you can not take advantage of all the built-in automation of that pentax flash, I would sell it and buy a cheaper, more powerful, manual flash like the Yongnuo YN-560.
Comment: Is it possible to use the wireless mode and fire it as slave?
Comment: I would love to be able to use the wireless mode. As far as I remember, AF360 is wireless
Answer: Aside from the wireless P-TTL "smart" optical triggering with Pentax gear, the AF 360 FGZ has a "dumb" optical slave mode (Slave 2) built-in that works with any simple flash burst (read: will work with any brand camera gear). Set the 7D's pop-up flash into M mode (to avoid sending out an eTTL pre-flash), and it should trigger the AF 360 to fire in sync. You will, of course, have all the range/line of sight issues that optical slaving does.  But you don't have to buy radio triggers to use this flash off-camera with your 7D.
From this pentaxforums post, to place the flash into the "dumb" optical slave mode:

Set the switch on the right side in the upper position.
Hold "light" button down for 2 seconds.
Press the "S" (select) button to toggle between Slave 1 (Wireless P-TTL) mode and Slave 2 (Optical dumb slave) mode.
Press "light" button to accept and exit.

Any flash burst (even one from a P&S) should trigger the flash remotely.
To get the camera shutter to operate remotely, however, you do need a shutter remote of some kind (cable release, radio triggers, or an infrared remote) as a separate signal. You can only trip the camera shutter via the camera hotshoe with Canon RT remote-flash gear (e.g., 600EX-RTs).
See also: What should I look for in a wireless flash trigger for a home studio?
Comment: Be aware that the AF360FGZ will go back to TTL mode when it powers off. This will be annoying if you want to use it in dumb-slave mode all the time.
Answer: You could pick up a set of cheap radio triggers, or you could take David Hobby's advice and use some 1/8" adapters and a long cable with male 1/8" connectors on each end.
Comment: Will the radio trigger be able to fire the camera as well? or it is just a way of firing the flash when the camera's button is pressed
Comment: The ones I linked just makes the flash fire at an appropriate time, but there are triggers that can work as remote shutter releases too -- they just cost more. Here's a description of [how to use PocketWizard triggers to do that](http://wiki.pocketwizard.com/index.php?title=Remote_Camera_Triggering).


Can I fingering my husband anal?

Question: I am a married women. During physical intercourse I have fingering my husband anal. Is it permissable? And also can I put sex toy in my husband anal?
Comment: I have no knowledge about this very situation. However, it is clear that you and your husband are allowed to enjoy your sexual intimacy in every way possible. Except, sex during a period or anal sex. Since fingering doesn't constitute anal sex...I don't think it's going to be a problem. Although don't take my word for it...
Answer: Assalamu'alaykum wa rahmatullahi wa barakatuh.
I will try to answer this question to the best of my knowledge insha'Allah.
Firstly, it is established by the consensus that anal sex is haram; the definition of "anal sex" may be inferred as the penetration of the penis (or equivalent) into the anal passage. Thus, although it may be suggested that a finger is not a penis, however, the overall effect [of insertion] can be deduced as equivalent; the same can be said for any other foreign objects (such as "sex toys").
Overall, from my research, as well as some deduction: in the same way that penetration in the anus is unlawful, sticking any other foreign objects into the anus [as an alternative] is also impermissible.
However, although I am confident about this legislation, I would like to highlight that I am no scholar.
Nonetheless, this is something that should definitely be avoided.
Jazak'Allak Khayrun.

Can I fingering my husband anal?


The acceleration of gyroscopic precession

Question: If we take the movement of a rotating gyroscope held horizontally at one end with a rope, then the rotational momentum of the gyroscope's spin exists, as well as the rotational momentum caused by torque applied by gravity over time. This would lead to a linear combination of those rotational momenta, which would require the gyroscope to rotate around the Y (vertical) axis. The question is: If the torque is applied constantly, shouldn't it cause the rotational momentum to get constantly larger, and thus increase the rate of precession, or in simpler terms, shouldn't the gyroscope accelerate while precessing?
Comment: You are asking about how an applied torque is affecting the spinning gyroscope. That question already has an answer. Note that the applied torque can either come from an external weight or from the weight of the gyro wheel itself; there's no real difference there See: [Precession of a gyroscope](https://physics.stackexchange.com/a/47645/17198)
Comment: I understand that it is spinning, but I do not understand why it is not accelerating in that direction while spinning.
Answer: The torque vector (or moment) produced by gravity is equal to the rate of change of the angular momentum vector. In the case of a horizontal gyroscope, both vectors are horizontal and at right angles.  The momentum vector changes in direction but not in magnitude.
Comment: did you mean "but **not** in magnitude"?
Comment: yes I understand that, but shouldn't the angular momentum vector caused by gravitational torque increase in magnitude over time?
Comment: You are correct. It should be  "but not in magnitude". I have made the correction.  The torque from gravity causes a constant horizontal rate of change for the angular momentum of the gyroscope, so the vertical angular momentum vector associated with the motion of the center of mass around the point of support does not change. Friction with the air or at the point of support does cause a vertical torque which  causes the angular momentum vector for the gyroscope to slowly swing downward.


How should airline pilots find out about military activity along their route?

Question: What sources of information should a commercial pilot review before takeoff to become aware of military activity that might pose a risk to their flight?
Comment: I'm not sure what you're asking. Are you asking about awareness of routine military training within a country (which one?), or international conflicts, or something else?
Comment: Your title asks about military but your question is commercial.
Comment: @Pondlife  Thanks for the feedback: an attempt to clarify is provided.
Answer: Military operations are conducted in certain airspace blocks that should be well marked on your charts.  If you are IFR your route should avoid such areas, if you are VFR, hope you know what you are doing.
Answer: All countries chart Special Use Airspace (with various classifications such as Prohibited, Restricted, Danger, Warning, Alert, etc.) designated for military training, defense or other national security purposes, along with the hours it is active (if not full time). Many national and international authorities also publish lists/maps of conflict zones and risk levels.
When planning a flight, airline dispatchers will generally avoid SUA and conflict zones. This includes even SUA expected to be inactive at flight time because delays before departure or en route could change that, so it's simpler to just use a route that is valid at all times, which is generally easy to do by following charted airways. However, special routes to avoid severe weather, which are inherently time-sensitive anyway, may go through inactive SUA.
Different airlines will have different policies on conflict zones and how much risk is too much; some knowingly fly into conflict zones to cash in on desperate travelers with no other options, though they usually stop doing that after one or two of their planes get shot down.
The pilot will review the flight plan before departure and contact the dispatcher with any questions, which a route through SUA or a conflict zone would likely generate, and won't accept it until they are satisfied. However, since they spend all day flying planes rather than staying up to date on military conflicts around the world, they are often at the mercy of dispatchers (and airline policy) when it comes to rapidly changing conflict zones.


Mailing list and privacy

Question: I'm going to start a mailing list for my website and I'm concerned about my users' privacy (regarding their addresses, contents not allowed, etc.. I'm kind of new to these things). Is there any document/policy I can read about this topic?
Answer: The laws and acts that governs data protection and emailing various from country to country, while a lot of them change from country to country most say among the same thing and you will need to learn the key points of these and its far to many to list but for example. Not keeping peoples data on file for more than 2 years, you are responsible for safe keeping of their data and may be liable for leaked/hacked information if your not taking responsible measures.
Google is your best friend for learning the various laws and acts in various countries on this subject and there's just to many results to list them here.
Links regarding Data Protection and Emailing
Marketing Laws and Acts UK
Data Protection Act UK
Wikipedia on the Spam Laws
Can-ACT SPAM US
Data Protection Acts and Privacy US and UK
Comment: Also to add to this. If you use a reputable mailing list company (such as Mailchimp or Constant Contact) they will help you with the guidelines. The other important point that I think often gets overlooked is that in general you can only use the persons details for purpose for which it was given. So if someone signs up for one reason that is the only reason you can use their information.
Answer: It's rather challenging to learn about so many laws just to write a privacy policy.  Plus, many matters are not required by law, but are considered best practices.  In the US, regulators are known to crack down on practices that were never illegal, but that after the fact, seemed to be unfair or deceptive to the consumer.  I don't think it's wise to rely on Google for legal advice.  Not even Wikipedia.  However, some law firm websites have good resources.
Why don't you take advantage of the work that others have done and look at some reputable websites' privacy policies.  Look at the biggest sites, then look at sites comparable to yours.  One of my favorites is the news website, New York Magazine.  It's got good headings
http://nymag.com/newyork/privacy/
Here is a sample from the retail world: The Body Shop.  It also has a good example of a Cookie Notification, which is important in the UK.
http://www.thebodyshop.com/services/aboutus_privacypolicy.aspx
Best wishes!

Mailing list and privacy


Distributing my own sexual photographs as a child?

Question: Would it be illegal to distribute sexual photographs of myself as a child for free or in exchange for money given that I am an adult now?
Comment: If you actually plan to do this, you might want to consult a psychiatrist before you consult a lawyer.
Comment: @gnasher729 haha. No I don't. But just wondering if it's myself I am doing it to it shouldn't be illegal. Plus it can also be argued that it might help reduce child pornography.
Comment: Consider that whoever held these pictures while you were a child (or afterwards) will also be in serious trouble.
Answer: The US child porn law is Chapter 110 of Title 18. It refers to a "minor", defined as anyone under 18. Sexually explicit conduct is defined, which you can read about. Regarding distribution (not production), 18 USC 2252 (A)(1) identifies as an offender anyone who

knowingly transports or ships using any means or facility of
  interstate or foreign commerce or in or affecting interstate or
  foreign commerce by any means including by computer or mails, any
  visual depiction, if—
(A) the producing of such visual depiction involves the use of a minor
  engaging in sexually explicit conduct; and
(B) such visual depiction is of such conduct;

"Affecting interstate commerce" is a term of legal art that means "doing, at all", which relates the law to the Commerce Clause and givers the federal government jurisdiction. There is a big interstate trade in child porn, and absolutely restricting distribution of child porn is part of what's necessary to regulate this form of interstate commerce (see Wickard v. Filburn, 317 U.S. 111 (1942): "affecting interstate commerce" can be found even when a farmer grown wheat for home consumption).
There is no overriding of the law in case the minor is now an adult, and there is no overriding of the law if the producer, purchaser or distributor is the child in the porno.
The core prohibition is 18 USC 2251, and distribution is covered in (d)(1), which defines the person to be punished as one who

knowingly makes, prints, or publishes, or causes to be made, printed,
  or published, any notice or advertisement seeking or offering—
(A) to receive, exchange, buy, produce, display, distribute, or
  reproduce, any visual depiction, if the production of such visual
  depiction involves the use of a minor engaging in sexually explicit
  conduct and such visual depiction is of such conduct; or
(B) participation in any act of sexually explicit conduct by or with
  any minor for the purpose of producing a visual depiction of such
  conduct;
Answer: In New South Wales, Australia this would make you a sex offender and, if convicted, put you on the sex offender's register for life. It doesn't matter if the child pornography is of you and it doesn't matter that you are now an adult and can give consent - the fact is that it is child pornography and the distribution of that is a crime under the Crimes Act 1900.


Identification and advice required for pretty but aggressive ground cover

Question: We have a plant spreading across a gravel covered bed.  It is my intention to plant ground cover here and wonder if I can keep this plant.  My neighbour says it is very aggressive and will grow into brick work (the bed is along side our house), could you help with identification and advice, please?  We are in the East Midlands, UK.
Comment: Any chance of another photo, taken from further away,. or a bit further back - at first glance, this could be Ground Ivy (Glechoma hederachea) but the leaves don't have enough scallops at the edges. so a pic of its general appearance could be helpful. When was this pic taken - in spring?
Comment: What shape are the stems? I want to say this looks something like creeping Charlie, but it's just not quite right. Are the stems squarish like a mint stem?
Comment: Could you detach a plant and see if the flower and leaves are from the same plant? The flower doesn't seems a Glechoma.  I would go for a Schrophulariaceae.
Comment: It doesn't appear to be Creeping Charlie, but this plant reminds me a lot of it, including the flowers. Does it smell minty at all, by chance? I'm guessing it's in the mint family, whatever it is (maybe even a cross-species hybrid).
Answer: It is a Cymbalaria, maybe a Cymbalaria muralis: https://en.wikipedia.org/wiki/Cymbalaria
For the second part (advice), assuming it is a Cymbalaria muralis. AFAIK she is not a competitive plant, but she can live in dry places (muralis = walls) where few other plants could live, so she will not invade other places.  I have her in many walls, but it seems she is not to causing any problems with roots.
EDITED: added second paragraph.
Answer: The flower looks very much like skullcap, which has a distinctive oddball insect looking form like your plant. Its also a member of the mint family which would make it an agressive spreader. However most all scullcaps have very matte leaves, not shiny at all, and covered with a lacework of veins. I looked around at various skullcaps though and the plant and its leaf forms is pretty variable and there were a couple shiny varietes. Its the flower that makes me think its a skullcap, but this is little more than a guess. Maybe this will lead someone else here to the right species of skullcap.


Stealing minerals with single scout worker

Question: What is the point to lots of the higher league players taking their scouting worker and mining from the enemy field? Is this just for BM? What is the purpose of this?
Answer: This is to disrupt mineral syncing. Experienced players will try to line up two of their workers to alternate mining from each of the closest mineral patches. So if they have 12 workers, 8 will be mining from close mineral patches and 4 from far mineral patches.
With your scouting worker, you can disrupt this by jumping on these close patches with good timing. This causes your opponent's workers to desycn from the patch and move to another, often starting a chain reaction. This can slow income heavily.
The goal isn't actually to steal minerals, it's to disrupt mining.
Comment: Old post I know. But another point which is important is the mineral walk. If the ramp is blocked by a Zealot inbetween a core and GW, the worker will walk through the Zealot and into the base. It is also imporantant to have the scouting worker mineral walk out of the base again!
Comment: "This can slow income heavily" - any ideas by how much?
Comment: @PiotrMigdal Wouldn't be too hard to test, but no I don't know how much unfortunately. I do know that with tight build orders it's more than enough to mess up timings.
Answer: I've seen pro-level players use their scouting worker to try and disrupt the efficiency of the enemy's mining.  Since only one worker at a time can mine any mineral patch, they will try to time their scouting mining so that it makes an enemy worker's AI believe that that patch is occupied or oversaturated, causing it to run off to mine somewhere else.  They will usually do this on one of the closer mineral patches, as these are mined slightly faster.
It's unlikely that this tactic makes a significant impact on the game, even if executed perfectly.  I think it mainly boils down to (1) the psychological effect or (2) just something to do with your extra APM in the very early game.
Answer: It's not only to disrupt syncing as the others have said but to completely prevent mining from one of the mineral fields.
While there is a worker mining a mineral patch no other workers can mine from it. So if you use your worker to mine from one of the mineral patches then they are losing 1/8 of their income (assuming they have at least 8 workers), which is quite a considerable effect.
To ensure that you stop them from using the patch as long as possible players will make sure that their harassing worker never finishes mining, they will click away to cancel mining and then right away click back onto the patch to continue mining. This means there is a very short amount of time for another worker to start mining, if left to the AI, it would never be able to mine from this patch.
In order to combat this the player getting harassed by this method will need to get one of their workers and spam click on the field that is being mined by the enemy so that there is a chance that they start mining when their opponent cancels for a moment.
Note you cannot use your workers to try to kill it because if they are doing it properly they will be behind your mineral patches, if it's an SCV it may be worth sending one worker to keep hitting it but if they have the APM to use this tactic they will likely be paying enough attention to not take much damage. Drones and probes will recover their hp so it's not worth it at all. It is best to just chase it off with your first military unit.
These sort of tactics are great for a slight early game advantage but it also helps to put your opponent off tilt, they may become flustered and start making silly mistakes that could cost them the game in the long run.


Slowing the day down

Question: I have been told that if I slow down today from 24 hours to 30, I'd end up getting hotter days, colder nights and more intense weather.  That's fine, except that Earth's diverse climate makes that statement broad.  So what would the SPECIFIC consequences be?
Comment: lots of wind...
Comment: @bilbo_pinguin: Rotation has no effect on gravitation. The centrifugal force counteracts the gravitation a bit, meaning you weigh less on the equator than on the poles (there you have no centrifugal force). But the effect lessens your weight by 0.3% - so it is of no significance: http://en.wikipedia.org/wiki/Gravity_of_Earth#Latitude
Comment: "No one knows." Is probably the answer to your question. Climate is complex and difficult to predict.
Comment: If you intend to achieve that by slowing the Earth spin, then you have to consider the effect on gravity. And this [question](https://worldbuilding.stackexchange.com/questions/8408/could-we-still-live-if-earths-spin-speed-slowed-down-by-90) is related (if not dupe?).
Comment: Also, similar question here:  http://worldbuilding.stackexchange.com/questions/2527/day-and-night-temperature-on-an-earthlike-planet-with-longer-rotational-period?rq=1
Answer: The extended solar heating duration at the equatorial region may drive that edge of the Hadley Cell to higher altitudes.  This would probably move the northern edge of this cell farther north, moving the 'desert formation' region with it. The ITCZ (The Inter Tropical Convergence Zone) would vary farther North over landmasses as well, causing the tropical rainforest and wet/dry or savanna regions to expand as well.
The storm belts should see more activity as well, with longer heating times driving formation of higher and hence larger/stronger hurricanes.  The midwest's tornado alley may slide farther north as well, causing tornadoes to become more common in the northern U.S.
The longer days of course come with longer nights, so inland areas, due to continentalty, will see more extreme variation in temperatures.
I'm not sure about the mechanics on the formation of the Polar cell, but intuitively if the extra daytime drives the Hadley cell North, the extra darkness should drive the Polar cell south?  This might effectively 'tighten' the temperate climate zone farther then it already is.
All guesswork of course, since even our climatologists with supercomputer driven models seem to be struggling over the effects of changing the temperature a few degrees.
Comment: I think (but I'm by no means an expert) that the oceanic effects could be the opposite.   Longer days, more equatorial warming in the ocean (er, I think), slight increase in ocean currents.    Land in the path of the warm ocean currents might stay temperate and a stronger ocean current might melt more of the arctic sea ice, warming the polar region.   But, I agree 100% - lots of guess work with this one.   It would likely need to be modeled and run on a super computer to have a good answer.
Answer: If you just slow down the planet like Earth, then yes. More action of the Sun will increase the overall planet temperature. There will be more water with less ice on the poles. More water heated by the sun results in more clouds and more rain and very little clear sky above you. The atmosphere will be very hot because of the greenhouse effect. In the end, we will get something akin to Venus, but much colder. There will no Sun in the sky, because clouds will cover it all; there will be a hot and wet climate. But you can avoid all this trouble by moving the planet a little far away from the star, and, maybe, expand it diameter a little. Then you can get an Earth-like climate with a 30 hours day cycle.
Answer: The changes will depend where you stand. If your close to the oceans, the changes will be minimized. The reason is that water takes more time to absorb the heat and takes more time to dissipate it. Also, oceans currents are better to distribute the energy than the winds overland. Overall, It would not be hotter : the days are longer but so does the nights. it just give more time to build up the heat but over the oceans the process is slower than overland.
Over the land, the change will increase the diurnal temperature range. Days will be hotter but night will be colder too. This problem would be exacerbated (like in the real world) by a low humidity. Meaning the deserts would have the biggest temperature range. Oceanic climates like Western Europe on the other hand, would be less affected since the dominant winds are pushing the humidity form the Atlantic ocean inland.
Thus all this would make the interior of the continents less pleasant places to live: increase in heat waves and freezing temperatures. It also means more extreme weather conditions as the difference in temperature between the oceans and the land increases. When the land is hot it will pull the air from the ocean further inland. When it's cold, the winds will blow toward the sea, like the Siberian highs. This could make winter drier and colder but summers wetter and could lessen the heating if there is a sufficient cloud cover and enough precipitations from the sea to cool off the land.
The major temperature swing overland could make weather systems like the Jet steam, subtropical stream, more unstable and erratic (less predictable). They change following the difference of temperature (this influences the air pressure that drives them). Generally, higher temperature range means more winds and stronger Jets. As North America and Asia would heat up faster than the oceans surrounding them, it will increase the pressure difference and thus increase the strength of the (polar) Jet stream.
This is my answer. It's probably incomplete but as the other mentioned, it would require some serious climate model to answer the question with more details.

Slowing the day down


information about tubes?

Question: okay, so i ride 20 x 2.4 tires that have a max psi of 110. last night my tire EXPLODED! the shop i buy my stuff from is closed for the rest of tonight and tomorrow and im going to the bmx park tomorrow. i have a old tire that is a 20 x 2.1 that has a tube in it i could use but im worried that it might be to much of a size difference and i don't what it to blow while im riding tomorrow. what do you guys think?
Comment: You ride a 2.4 at 110 psi.  That is a LOT of pressure for a big tire.
Comment: Should work just fine.  If it's not OK you will notice a flat spot in the inflated tire, near the valve, due to the rubber being over-tight in that area.  (Most tubes are built for a range of tire widths, eg 2.1 to 2.5 inches.)
Comment: OP wrote that the tires have a max psi of 110. But hopefully he/she is not inflating them to the max pressure. That would be foolish for such a large tire.
Answer: Unless you are particularly heavy, I would not worry about size - not that much difference in load carrying between a 2.1 and 2.4 that it will cause a blowout. Blowouts are caused by a tire failure of some description (bead failure, not seated on rim properly or cut to tire are the most common causes). You say "old tire and tube" - how old and what condition?
If your choice is ride on the 2.1 or not ride - I know what I would do.

information about tubes?


How do I get Swift working on my Pi 3b

Question: I am a longtime iOS OS X developer who's switched most of his work to Swift.
Now that Swift is open source, it has been offered for non-Apple ARM devices like the Pi.
Based on my reading, it looks like you need to install Ubuntu on your Pi in order to get the Swift compiler up and running, so that's what I've done.
I then downloaded the latest Swift package for Pi and installed it, following the instructions on this page: http://dev.iachieved.it/iachievedit/swift-3-0-on-raspberry-pi-2-and-3/
However, when I try to create an run a simple hello world Swift app with the command "swift hello.swift" I get an error I don't understand:
<code>/home/build/workspace/Swift-3.0-Pi3-ARM-Incremental/swift/lib/Serialization/ModuleFile.cpp:1031: swift::serialization::Status swift::ModuleFile::associateWithFileContext(swift::FileUnilt *, swift::SourceLoc): Assertion `getStatus() == Status::Valid && "Invalid module file"' failed.
</code>
And:
<code>Stack Dump:
0.    Program Arguments: /home/ubuntu/swift-3.0/usr/bin/swift -frontend -interpret hello.swift -target arm7--linux-gnueabihf -disable-objc-interop -color-diagnostics -module-name hello
1.    While reading from /home/ubuntu/swift-3.0/usr/lib/swift/linux/arm7/Swift.swiftmodule
</code>
Can anybody tell me what's going wrong? I'm not super-strong with the UNIX command line I'm afraid. Conversant, but not fluent.
Answer: Swift does work out of the box on Ubuntu but only on Intel devices, so not on ARM. However, Uraimo has made some scripts to easily build the swift compiler on a raspberry with Raspbian.
https://github.com/uraimo/buildSwiftOnARM#building-swift-on-arm

How do I get Swift working on my Pi 3b


Vauxhall corsa diesel leaking oil

Question: I was driving to work this morning & my engine oil warning light appeared on my dash. I assumed it needed a top up. When Parking up at work I noticed that oily black water was pouring out under neath the car I opened the bonnet & it appears to be overflowing out of a yellow cap located near the coolant chamber, can someone please help as to why this is happening. The car doesn't appear any different when driving sounds & drives as usual? Thanks
Comment: If it is water, you shouldn't drive it - as that water is used to help cool the engine. If it is boiling out, your engine may overheat and fail. Expensively.
Answer: You could be really lucky and it could be that the rubber seal within the cap has deteriorated and is no longer holding the pressure in the expansion tank.
** CAUTION ** - Do NOT remove this cap whilst the car is warm, you risk scalding from both super heated water and escaping steam.
Once the car has cooled, remove this cap.  If it appears to be loose then it may just need refitted tightly.  If it was tight but the inside of the cap looks like it's deteriorated or checked, order a replacement.
Now the bad news; typically this behavior is caused by a failed head gasket where cylinder pressure is escaping into the coolant system.
I suspect it is water / coolant you are seeing under the car and it may be black because the route its taken to get to the ground has seen it wash across various grimy, oily bits under the bonnet.
Your best bet is to get a compression test done.  A garage won't change very much for this and it will tell you for certain if any cylinder pressure is escaping.  If it is you have three realistic choices; rebuild the engine, replace the engine or change your car.
There are numerous products online which claim you can add them to the coolant and they solve the problem, I have yet to find any which work.
Answer: An 'end of its life' head gasket might cause the problem. But before that you be sure about the liquid- is it oil or water or whatever.

Vauxhall corsa diesel leaking oil