CompizConfig 3D windows don't work - Ubuntu 14.04 LTS

Question: I've recently been experimenting with CompizConfig Settings Manager. I almost have my desktop configured, the way that suits my preferences. I'm trying to add the final touch by enabling 3D windows for my desktop cube. The cube itself runs great but when I go to enable 3D windows and spin the cube it goes black, and doesn't appear to be there. You can see the windows but they are glitchy.
I spent the past five day trying to configure compiz so this would not happen. Unfortunately all I can come up with is... that this only happens when viewing the 3D cube, and if you adjust the minimum cube  size and window space setting to maximum or to minimum then this does not happen. But when you do this the windows do not hover off of the cube and the windows are still 2D.
This is my processor and graphics card.

Processor: Intel® Celeron(R) CPU N2840 @ 2.16GHz × 2
Graphics : Intel® Bay Trail

Here is my unity 3d compatibility test
<code> ~$ /usr/lib/nux/unity_support_test -p
OpenGL vendor string:   Intel Open Source Technology Center
OpenGL renderer string: Mesa DRI Intel(R) Bay Trail
OpenGL version string:  3.0 Mesa 10.1.3

Not software rendered:    yes
Not blacklisted:          yes
GLX fbconfig:             yes
GLX texture from pixmap:  yes
GL npot or rect textures: yes
GL vertex program:        yes
GL fragment program:      yes
GL vertex buffer object:  yes
GL framebuffer object:    yes
GL version is 1.4+:       yes

Unity 3D supported:       yes
</code>
I hope I have provided enough information for a good answer. Here are some screenshots (click for more)
Comment: Note you can use http://imgur.com for a screenshot
Comment: Upload to imgur using their website, and post the given link
Answer: There is nothing you can do, the plugin is broken. It's still available because it could be fixed,  but someone would need to actually do that. If you search in Launchpad there may be a bug report, if not file one.
(- Not that a bug on this  has a great chance of being fixed.
Comment: Darn.:/ thanks for the help though doug much appreciated


Stop Windows %tmp% environment variable using short file name

Question: I have a C++ application that is using the %tmp% variable (from the GetTempPath() function). Unfortunately there is a bug where it can't handle the tidle that may appear in the user's local temp directory path if it is generated using short file names.
What I would like to do is make it so that the %tmp% environment variable does not include a short file name, if this is possible.
In my research I came across the following commands:
fsutil.exe 8dot3name set C: 1
fsutil.exe 8dot3name strip /s /v C:\

I have ran both of these and the first command successfully disabled short file names. The second command, however, failed for approximately 2000 existing short file names as they are already referenced in the registry. That's fine, but I really only care about that one environment variable, so was wondering if there was a way I could either force remove that short file name, or if, as I have a feeling it would be, this is not advised, if there is a way I can force the environment variable to use the long file name? I understand that the %tmp% variable uses the %userprofile% variable, and that the latter is actually the offending variable, so I take it it is that one I will need to look at ..?
Any help would be greatly advised.
Cheers!
Answer: Maybe I'm too late for you, but perhaps it helps somone else:
the GetLongPathName() function should convert the short name to a long one.


What does the band structure of a SSH topological insulator mean?

Question:
I'd like to know what the band structure (or gap) of a SSH topological insulator means. In particular, what does the K mean in the x-axis? I've seen different points from the Brillouin Zone from other topological insulators, but why does a SSH topological insulator only have K? Thanks.
Comment: I'm not an expert, but I'm guessing it is because it is a one-dimensional structure. Other points in the Brillouin Zone define symmetries in a 3D crystal.
Comment: Do you mean the $k$, indicated in (a) as the wavenumber?
Comment: For non-experts like me who want to learn more about this, the figure shown in the OP appears to be from "A short course on topological insulators" (https://arxiv.org/abs/1509.02295)
Answer: In this case, k is the crystal momentum which is a good quantum number that labels the eigenstates of the  Hamiltonian in the independent-particle approximation. You may be confusing it with K, the symmetry point in the band structure of higher-dimensional lattices. For those lattices its more complicated to plot the energy as a function of the crystal momentum and so one chooses special paths in the first Brillouin zone that go along high-symmetry points to sample the band structure of the material. In this case, because its only a one dimensional system, the dispersion relation only depends upon a single number (instead of three for a 3D lattice) so one can plot the dispersion relation as a function of crystal momentum without the need of sampling special points in the first Brillouin zone.
For this topological insulator, the closing of the gap at the zone boundary is a hallmark of the topological phase transition. In changing the parameters of the Hamiltonian (v and w in the plot), you can eventually close the gap which will generate zero energy modes that are localized at the edges of the SSH chain.


modal box login form ajax jquery php

Question: I am looking for login / register using a form in modal box which appears as a pop up, ajax and jQuery to post data and php/mysql to update data in database. Please could you point me in right direction?
I have written code which opens a separate page when "login" is clicked. I am looking for functionality like
http://www.krizna.com/jquery/jquery-ajax-form-submit-using-twitter-bootstrap-modal/?demo
Also, let me know if twitter bootstrap is better or if should i use my own designs.
Answer: For nice looking Modal Window you can use - BootStrap
And BootStrap is better :)
Answer: Bootstrap would make this easier. Check out http://bootsnipp.com/snippets/featured/modal-with-tabbed-content for an example of how to make a login modal.

modal box login form ajax jquery php


Holonomic constraints and degrees of freedom?

Question: Can we say that a constraint decreases the degrees of freedom of a system if and only if it is holonomic. Either way please can you explain why?
Answer: A constraint condition can reduce the DOF of the system if it can be used to express a coordinate in terms of the others. This can always be done in case of holonomic constraints which are basically just algebraic functions of the coordinates and time. This means that you just have to manipulate the constraint equation in such a way that one of the coordinates is on the left side and all others on the right and then eliminate. Look at the example below.
Holonomic Constraint
Say the holonomic constraint is $f(q_1,q_2,q_3,...,t)=0$, then you just have to bring it in the form $q_1 = g(q_2,q_3,...,t)$ and then substitute the value of $q_1$ thus obtained in all the equations of motion. This would reduce the DOF by 1.
Non-holonomic Constraint
But if the constraint is non-holonomic you might not be able to perform this manipulation.

Suppose your constraint is non-holonomic because it is an inequality of the form $f(q_1,q_2,q_3,...,t) \ge 0$ then the best you can do is get a relation like $q_1 \ge g(q_2,q_3,...,t)$. Obviously you cannot use this to eliminate the coordinate $q_1$ from the equation of motion.
For another example, consider if the constraint was in the form of $f(q_1, q_2, q_3,...,\dot q_1,\dot q_2,\dot q_3,...,t) = 0$. This constraint will not be considered holonomic unless you could integrate it and get it to the form $f(q_1,q_2,q_3,...,t)=0$. There may be problems where this integration cannot be performed without solving the equations of motion first(look at Herbert Goldstein's pure rolling example in the first chapter). In this case too you will not be able to eliminate any coordinates from the equations of motion. In general, constraints involving velocities are of this type

So only holonomic constraints guarantee a reduction in the number of DOF of the system.
Comment: you say that "$f(q_1,q_2,q_3,...,t)=0$, then you just have to bring it in the form $q_1 = g(q_2,q_3,...,t)$". How is it obvious that you can always do that? What about functions that are not injective?
Comment: @Numrok probably we also need to be able to differentiate $f$ by $q_1$
Answer: yes constraints whether holonomic or non holonomic it must have  reduce the degree of freedom As if the system of pendulam then it is holonomic it has two constraint  the first one is they can't move freely in x y coordinate and other is z=0 so it reduce the degree of freedom
Answer: If a constraint can be expressed as f(r1,r2,...t) =0 .
position vectors are connected with time then the constraints are called holonomic ,but if they can not be expressed as above then the constraints are non-holonomic
Comment: How does this address the reduction in degrees of freedom?


Is it OK to edit Python questions to make them PEP 8 compliant?

Question: I've seen a couple of edits changing the style of the code with an edit summary stating that the code is now PEP 8 compliant. Most of the time it makes the code easier to read but I also see some Meta discussions suggesting that changing the style of someone else's code is not welcomed. Does PEP 8 have a special standing since it is an official guide?
Comment: Can you show us some examples of this?
Answer: Please don't edit code in questions.
There are several reasons for this. The most important being that you might well edit out the problem.
Beyond that, people have to work with old systems, and can't use the latest and greatest versions of compilers, IDEs etc so their question is using the code they have to deal with.
By all means suggest an answer using the latest versions, styles and guidelines but don't expect it to be accepted as there's little chance that it'll help the OP (unless they are able to upgrade).
Comment: @Braiam - Yes, by all means edit **answers** to update and refresh them, but the code in **questions** is a statement of the problem. Updating it **changes the problem**.
Comment: @colidyre formatting code is a grey area - especially in Python where you can change the behaviour with a misplaced tab, so it *is* better to err on the side of caution and not change it.
Comment: I don't quite understand the argument. I like to edit posts (also code!), if it is not PEP-8 compliant (Python). **I will of course make sure that I do not make any changes to the content**. Most of the time it is just a distance after a comma or between operators. IMO, this helps enormously to see the code better at a glance. In my opinion, code that is not written according to recognized guidelines is sloppy code and I generally don't trust it as much as I do for code respecting coding guidelines. Applying PEP-8 leads simply to better readabilty, **"Readability counts." -- Zen Of Python**
Comment: I understand the risks, especially by changing indentation. But I do not agree on things like adding spaces between operators and similar changes that doesn't change any behaviour. If its a grey zone, there must be some acceptable things and some better to avoid in most circumstances. Don't you agree? I mean what could be wrong e. g. on adding a space between operators?
Comment: @colidyre I agree with you in theory, but experience has taught me that having a blanket "ban" is much easier to explain. While you may be conscientious enough to get it right, not everyone is. There's nothing stopping you suggesting such edits but please don't be surprised or upset when your suggestion is rejected.
Comment: Just to add, especially with python, editing code will likely mess up code since it depends on white space and all that stuff.
Comment: @ChrisF agree. It's much more easier to handle that with a strict "don't ever touch code" message. But I'm also not 100% satisfied. ;) As you said, maybe its a good way in the middle just trying to improve code by applying some PEP-8 and hoping that it will be accepted, without being upset if not! :)


Hide site contents from visitors

Question: I have a communication site. I want to hide site content from a few visitors. Just want to provide them access to view home pages only. For this I used Restricted Read permission. But user with Restricted Read permission is able to see site contents and other pages also. It is behaving like normal Read permission.
Anyone having idea about it ?
Answer: To achieve your requirement, you could copy the Read permission level and then remove the "View Application Pages" from the copied Read permission level.
Grant the copied Read permission level to the user, then the user cannot access the site contents.
Comment: The permission level I created had only view page and open permissions selected. It is the least permission required to open the website. Still user is able to access site content. It always used to work in on premise. But not working in online.

Hide site contents from visitors


Change Background Image in Itext to watermark or alter opacity c# ASP.net

Question: I want to make my background image in iText transparent
here is my code for the image:
    string root = Server.MapPath("~");
    string parent = Path.GetDirectoryName(root);
    string grandParent = Path.GetDirectoryName(parent);
    string imageFilePath = parent + "/Images/logo.png";
    iTextSharp.text.Image jpg = iTextSharp.text.Image.GetInstance(imageFilePath);
    jpg.ScaleToFit(1700, 800);
    jpg.Alignment = iTextSharp.text.Image.UNDERLYING;
    jpg.SetAbsolutePosition(100, 250);
    jpg.ScaleAbsoluteHeight(500);
    jpg.ScaleAbsoluteWidth(500);

Any idea?
Answer: Please take a look at the BackgroundTransparant example. It is a variation on the BackgroundImage example.
In your code, you're adding the Image to the Document instance. That's OK, but if you want to make such an image transparent, you need to introduce a soft mask. That's not difficult, but there's an easier way to make your background transparent: add the image to the direct content, and introduce a PdfGState defining the opacity:
PdfContentByte canvas = writer.getDirectContentUnder();
Image image = Image.getInstance(IMAGE);
image.SetAbsolutePosition(0, 0);
canvas.SaveState();
PdfGState state = new PdfGState();
state.setFillOpacity(0.6f);
canvas.setGState(state);
canvas.addImage(image);
canvas.restoreState();

Compare background_image.pdf with background_transparent.pdf to see the difference.
My example is written in Java, but it's very easy to port this to C#:
PdfContentByte canvas = writer.DirectContentUnder;
Image image = Image.GetInstance(IMAGE);
image.SetAbsolutePosition(0, 0);
canvas.SaveState();
PdfGState state = new PdfGState();
state.FillOpacity = 0.6f;
canvas.SetGState(state);
canvas.AddImage(image);
canvas.RestoreState();


I am a member of a facebook group but members cannot tag me in a post

Question: How can I fix that so I can be tagged in the post?
Answer: Are you under 18? If so, you can only be tagged by friends or friends of friends.
According to Facebook Help Center's Who can tag me?

Anyone can tag you in photos and other posts. Tags from people you're
  not friends with may appear in your timeline review where you can
  decide if you want to allow them on your timeline. Remember, posts you
  choose not to allow on your timeline may appear in News Feed and
  elsewhere on Facebook.
If you don't like something you're tagged in, you can remove the tag
  or ask the person who tagged you to remove the post.
Note: Minors can only be tagged by friends and friends of friends.


setTint() on half image

Question: I'm developing a game where I need to paint half of a image when the user is either wrong or right. To paint the image, I'm using setTint() to paint the image the color I need, but it paints the whole image, is there any way I can paint only half, using setTint or another method?
Answer: I'm unfamiliar with phaser, but a general way to achieve this is to create two Image objects, each one having half of the picture, and position the second below the first, so it looks like one complete image.
At the moment the user answers, you can use setTint() to change only half of the picture.
This method has its limitations, as you can't dynamically split an image to more parts this way, but it is a simple method that gets the desired result.
Comment: Yean, I was trying to avoid this, because i have a lot of images to apply this, but I think i'll have to use this method.
But I'll keep looking for something else, if I find I'll post here!
Thanks so much man, have a really nice day!
Comment: @ArthurOliveira You can also do the same thing by using shaders, which can be more automated, but I'm not familiar enough with `phaser` to know how it handles them.
Comment: I don't know much about shaders, but for sure I'll look for and try to use it. Thanks so much man!!

setTint() on half image


Main character reincarnated in a forest and fights a giant ant-like creature, saved by a mysterious girl

Question: From the plot I remember the main character getting reincarnated in a forest. While he fights with some kind of giant ant-like creature he gets saved by a mysterious knight-like girl. So she sleeps with him to save this refugee village because of his unique over-powered system abilities. I remember her being a former princess or something of the sort
Answer: This sounds like a misremembering of Isekai Apocalypse Mynoghra - The Conquest of the World Starts With the Civilization of Ruin.
From Baka-Updates:

I reincarnated as an evil god.
Ira Takuto succumbed to illness at a young age and ended up reincarnating in a world that resembled the strategy simulation game, 『Eternal Nations』, of which he loved playing when alive. What appeared in front of him was Atou, a girl belonging to the evil civilization that he used to play as, 「Mynoghra」. The two of them decided to create a new country in this world once again.

The protagonist, Ira Takuto, dies in bed from illness at the age of 18, and then suddenly finds himself sitting on a stone throne in a forest. It turns out that he's inside a country management simulation game called 'Eternal Nations', which he was the top-ranked player in before he died.
He's also greeted by a female hero called 'Atou', who addresses him as her king and master, and remembers everything they did 'together' when he played the game in the real world. In fact, she's keen for them to start the game over, and build a new country like they did before, and he agrees.
One of the first things they do is summon a 'scout unit', which resembles a giant ant, to scout the area around them. The scout unit discovers a settlement of dark elves nearby. It turns out that the elves are refugees from another land, where they'd been persecuted and chased out. They're also starving, so Ira uses his powers to conjure up food for them.
This last part isn't relevant to your description, but the elves also perceive Ira as a dark shadowy being, rather than the normal-looking person the reader sees him as. As a result of this perception, they're reluctant to trust him initially, but their leader feels forced to beg for his aid out of desperation.
Answer: Another possibility is "Survival in Another World with My Mistress!" (Goshujin-sama to Yuku Isekai Survival!).
While it is a cricket rather than an ant monster and she doesn't save him, the two lead characters do sleep together and he uses his Minecraft-like abilities to save a refugee village and she is a former princess.


Why are imaginary numbers called imaginary numbers

Question: Why do we call imaginary numbers "imaginary numbers"? As far as I can tell, there's nothing really imaginary about them. They exist. They're used all the time. What makes them so "imaginary"?
Comment: Because "irrational numbers" was already in use.
Comment: You might want to read [this](http://www.cut-the-knot.org/arithmetic/algebra/HistoricalRemarks.shtml). As Ted says, it's really unfortunate terminology, just as with our use of the adjective *complex*...
Comment: The term is historical. When they were originally invented, people thought there might be something wrong with them. Now we know there's nothing wrong with them, but the term has stuck.
Comment: Follow this link: http://www.purplemath.com/modules/complex.htm
Comment: @ J.M. That was an informative article too.
Comment: Because the word 'unreal' was yet to come...
Answer: Those numbers were once poorly understood and regarded by some as fictitious.The use of imaginary numbers was not widely accepted by many. It was left to Euler and others to use them. Euler, in his Introduction to Algebra, wrote the following:

Because all conceivable numbers are either greater than zero or less than 0 or equal to 0, then it is clear that the square roots of negative numbers cannot be included among the possible numbers [real numbers]. Consequently we must say that these are impossible numbers. And this circumstance leads us to the concept of such number, which by their nature are impossible, and ordinarily are called imaginary or fancied numbers, because they exist only in imagination.

In short, it is a matter of acceptance of or the lack of it which gave them the name.
Comment: +1 for the reference and an `imaginary` +1 for *fancied numbers*.
Answer: Mathematicians thought up an answer to the square root of -1, and they simply "imagined" a soultion, hence imaginary numbers. they found out it could be very useful, and kept it that way. the name, however, has stuck.


How does speaker's power output affect sonar's detection limit and it's resolution?

Question: I am planning to make a sonar application using smart-phone speaker and microphone, and it is given that speaker's power output is 3 watts and sound frequency is 20 kHz. I wanted to understand how will the quality of detected signal decrease with increased distance and at what distance limit the received signal would be too weak for the readings. I made some research and my assumption according to it is that reliable maximum range would be between 10-25 meters, yet I am unsure. But it is still unclear for me how the range is being calculated and how does it relate to the properties(size and shape mainly) of the objects that are going to be detected. And I wanted to know if knowledge of power output and frequency is sufficient to answer the above question? I would appreciate if you can bring some clarification to the topic or maybe if you can share some reference material for better understanding. Thank you very much.
Comment: In dry air at 20 °C (68 °F), the speed of sound is 343.2 metres per second (varies with temperature and humidity). With a target at 25m the pulse covers twice that - you do the maths for timing the return pulse to the microphone. It is unlikely that the speaker will be outputting full power at 20kHz which is the limit of human hearing (unless you're a child). The magnitude of the return signal will depend upon the size, material and shape of the target.
Comment: Thanks for your comment. I actually know these details, what you wrote is the working principle of sonar. I understand it, but I don't understand why it is stated 25 meters, not 50. How do people calculate effective distances, and how can I calculate it for my specifications?
Comment: As with radar, the 4th power law applies.
Answer:
how the range is being calculated and how does it relate to the
  properties(size and shape mainly) of the objects that are going to be
  detected

I'm going to make an answer based on what I think you should concentrate on.
Output power increases range for sure. If 3 watts is being outputted to the speaker maybe, due to speaker defficiencies only 10% of 3 watts is actually converted to sound energy. If we stick with 300 mW output power (rather like you would make calculations in radio wave transmission) then that power can be roughly said to emit in all directions in a hemisphere.
You can then talk sensibly about watts per square metre and, at say 10m the area of a sphere is \$4\pi r^2\$ = 1257 sq metres. Half that area is infiltrated by the speaker output power so power density at 10m is 300 mW / 628 = 0.48 mW/sq m.
So, if a 1 sq metre object at 10m totally reflects all the incident power then it regenerates 0.48 mW. This is also subject to the same rule as before i.e. all that power is distributed as watts per sq metre on a hemi sphere and, at 10m distance the power per sq metre is 0.76 uW / sq metre.
The microphone receiving that incident power might only be 1 cm square so the power it actually receives is 10,000 times lower i.e. 76 pico watts. If the microphone is 10% efficient at converting that to electrical power then you should see an electrical signal of 7.6 pico watts.
Converting that power to voltage calls for a leap of faith in terms of impedance presented to the microphone and sensitivity of the JFET inside the capsule but maybe you can assume that power is amplified a 1000 times by the JFET and dumped across a 2k2 resistor (pretty standard circuit but could be as high as 10 kohm).
So 7.6 pico watts becomes 7.6 nano watts due to the JFET inside the capsule and this power produces a voltage across the 2k2 resistor. So the output voltage = \$\sqrt{P \times R}\$ = 4.1 mV RMS. A pretty good signal really.
Of course, this assumes 100% reflection of power and is 100% unlikely - at best/typical you might see 1% reflected power so that 4.1 mV RMS is probably going to be more like 0.13 mV RMS.
Bottom line is that the numbers are guesswork given that you don't know how much output power can be transmitted in a pulse and that the microphone size and internals are guesswork too. Efficiencies of both speaker and microphone may be way off the mark too.
Just to try and put things in perspective, a signal from a pretty average electret capsule of a few mV RMS is typical of 92 dB SPL.
Comment: Then it seems that the trick is to look for minimum requirements of the receiver signal, and calculate max. distance that could provide that minimum(reverse calculation). Thanks a lot for your help.


Regarding log-normal specification

Question: I'm working with a log-normal regression model. However, some of the dependent variable equal zero (not missing). Can I use an alternative specification like $log(y+1)$ ~ $X$ (most $y$s are really large)? Or should I just omit those observations? Do I have to do balance check every time I drop some observations and report all the result in appendix?
Comment: Some zeros are not a problem with generalized linear models and logarithmic link. These work on the assumption that the mean is positive and do not use direct logarithmic transformation of the response.
Comment: Unless those observations are clearly erroneous (as determined by independent information), removing them would be mistake.  The results would be biased.
Comment: Very similar questions have extensive discussions at http://stats.stackexchange.com/questions/30728 and http://stats.stackexchange.com/questions/41361.
Answer: The answer to this question really depends on the meaning of $y=0$ in your application. You've said most $y$ are really large -- this means that those $y$'s that are zero are quite different from the other $y$'s. Are they really likely to be generated by the same process that generates the large $y$'s?
If $y=0$ is truly comparable with $y\gg0$ then you could use the approach you suggest of taking $\log(y+1)$. This would equate to a functional form of
$$
y_i = e ^ {\beta_0} e^ {\beta_1 x_i,1} ... e^{\beta_n x_i,n}e^{\epsilon_i}+1
$$
Note that the errors $\epsilon_i$ are exponential, not additive using this transformation.
If most $y$'s are really large, then $\log(y+1)$ will also be much larger when $y\neq0$, so including those observations for which $y=0$ will increase the error in your regression significantly. The distribution of error terms will be non-normal (and may effectively be a mixture of two different distributions). Coefficient estimates will potentially be biased if the process generating the $y=0$ terms is different to that generating the $y>0$ terms.
You could ignore the cases where $y=0$ entirely, if you considered that the aim of your model is to understand the relationship between the $y$'s and the $x$'s conditional of $y>0$.
Alternatively, and perhaps more satisfactorily if $y=0$ has meaning in your context, you could explicitly model the probability of $y=0$ vs $y>0$ using a binary model (ie a logitistic regression)and then have a sub-model that only considered the case where $y>0$. This would avoid omitting any data points, at the cost of having to consider what explanatory variables are suitable for explaining the probability of $y=0$.
Rob Hyndman's blog has some further discussion on transforming data with zeroes in it.
Comment: Your characterization of leverage is erroneous. You also need to consider the effects of the $\log(y)+1$ transformation on the error terms, which have been neglected.
Comment: @whuber I've removed the erroneous leverage point, and added the error terms to the function.
Comment: Thanks for your answer. I think I will just omit those observations. Actually $ y=0 $ cases are quite unusual. Maybe there're some mistakes in the records.
I also appreciate your solution of running two regressions. This will definitely be a useful method in some other cases.

Regarding log-normal specification


Why is homology not (co)representable?

Question: This is in the same vein as my previous question on the representability of the cohomology ring. Why are the homology groups not corepresentable in the homotopy category of spaces?
Answer: Corepresentable functors preserve products; homology does not.
One replacement is the following.  Let X be a CW-complex with basepoint.  Then the spaces {K(Z,n)} represent reduced integral homology in the sense that for sufficiently large n, the reduced homology Hk(X) coincides with the homotopy groups of the smash product:
pin+k(X ^ K(Z,n)) = [Sn+k, X ^ K(Z,n)]
This is some kind of "stabilization", and it factors through taking the n-fold suspension of X.  Taking suspensions makes wedges more and more closely related to products.  This doesn't make homology representable, but provides some alternative description that's more workable than simply an abstract functor.
Comment: That's still not what "representable" means for a functor.  Representable means that there is an object D such that Hom(D,X) is the functor.  Homology is not representable, even in the stable case.  That's why no-one ever talks about homology operations.  Also, I'm not sure about your formula for the stabilisation.  The equivalence between a spectrum and its Omega-spectrum holds in the category of spectra, not in the category of spaces. So you ought to have Sigma^n X wedge K(Z,k) and while this maps to X wedge K(Z,k+n) it isn't an equivalence.
Comment: Yes.  It's not representable; I was just trying to give the closest thing I know.

Also, the formula only works for n roughly larger than twice k, not all k simultaneously.
Comment: I see. But your last sentence is slightly misleading as it seems to imply that stably, homology is representable (say, for spectra). This isn't the case so, in the interest of clarity, I'd prefer it if it were edited. Technically, a generalised homology theory is defined for spaces by E_k(X) = {S,Sigma^infty X wedge E}^{-k}. Due to Freudental's suspension theorem, we can compute that by taking a sufficiently high limit, as you say (though I'm still not sure about your forumla - I'll need to write it out in full to be sure and these comment boxes are just that little bit too shor
Comment: I've edited it slightly and I hope it's more palatable.  For the formula you use Freudenthal suspension twice to pass from X ^ K(Z,n) to X ^ S^1 ^ K(Z,n) to X ^ K(Z,n+1).
Answer: While it's true that there are lots of internal things that a corepresentable homology functor wouldn't support, I think it's also enlightening to see that you wouldn't get the nice sorts of dualities that homology and cohomology theories have.  After all, we've already agreed that cohomology theories ought to be somehow representable, so maybe we should start there.  Instead of using stable maps $X \to E_n$ to produce $n$-degree $E$-cohomology classes of $X$, you can think of these instead as elements in the stable homotopy groups $\pi_{-*}^S F(X, E)$, where $F(X, E)$ denotes the function spectrum of maps $X \to E$.  This presentation makes the right choice for defining $E$-homology somehow much more obvious: the functor $F(X, -)$ has an adjoint, called the smash product (this is the whole point of the smash product -- it plays the role of "tensor product" for spaces!), and so for homology we think about maps $S^n \to E \wedge X$ instead.  That homology and cohomology are not (usually) exact duals in a linear algebraic sense is somehow measuring the twist introduced by this adjunction.  This does actually turn out to be the right definition for homology; (extraordinary) homology theories in the traditional sense are in fact modeled by functors of the form $\pi_*^S (E \wedge -)$.
This construction has a number of attractive features -- for instance, it means that we can (under some flatness and ringy conditions) think about "homology cooperations" associated to a spectrum, and they look like $E_* E$, a pleasant mirror of cohomology operations living in $E^* E$.  We also always get a pairing $E^* X \times E_* X \to E_* E$ of cohomology and homology classes that lands in homology operations, by composing as $S^n \to E \wedge X \to E \wedge E$.  (This pairing even gets used occasionally, though I'd be hard-pressed to come up with an obvious citation.)
For the most familiar homology theory, singular homology with $\mathbb{Z}/p$-coefficients, this flatness business does hold, the operations and cooperations even turn out to be $\mathbb{Z}/p$-vector space duals, and the coaction and action line up in the way you'd expect from Milnor's work.
(This belongs as a comment on Lawson's answer, I think, but it looks like I'm too new here to make that happen.)
Comment: Upvoted for clarity and depth.
Answer: The dual to cohomology in the functorial sense turns out to be not homology, but homotopy (as described here).
For instance ordinary homotopy groups are the homotopy theory co-represented by spheres.
Comment: The duality to which you refer is called Eckmann-Hilton duality, and is also intimately tied in with Koszul duality of operads.

Why is homology not (co)representable?


Biometrics for a second UK partner visa

Question: I had a partner visa back in 2014 for the UK. We stayed there for 10 months and then returned back to Australia. We would like to move back to the UK, but I'm not sure if I need to do biometrics again. I would need to fly from my home in from Cairns to Brisbane for these biometric scans, and I don't want to this unless I really need to.
Answer: Yes, you will need to provide biometrics again.
Following the Apply online from outside the UK link in https://www.gov.uk/uk-family-visa/partner-spouse takes you to a page where it states "To complete your application, you must make arrangements to provide your biometrics".

Biometrics for a second UK partner visa


Gammu: run on receive exit status 1

Question: I'm trying to use gammu and gammu-smsd to send and receive sms with my raspberry pi using a Huawei intrnet key.
My problem is that when I send an sms from my phone to raspberry pi, it read the sms, it try to start the program linked at RunOnReceive = in /etc/gammu-smsdrcn file but then, it says: Process failed with exit status 1.
I tried any kind of solution but I'm not capable to solve this problem by my self; I've set each permission on the script.
Can someone help me?
Thank you a lot.
Comment: Same problem here. I have set all the permisions to the gammu user (the one that runs the daemon), and I keep on getting that error. If you have found a solution, can you post it? Thanks :-)
Answer: You no doubt have this sorted by now, but I have just been through the same trip, tore out a lot of hair and finally made it out the back .... :-)
I'm using a ZTE stick with wvdial for internet connection. The stick appears as modems on /dev/USBtty0, 1 and 2. wvdial uses USBtty2, so gammu (I think) has to use a different one.
So I installed gammu/gammu-smsd on USBtty1 in gammu-config and /etc/gammu-smsdrc.  The receive daemon gammu-smsd fires up automatically on boot.
First trap for young players - if you want to send an SMS with
   echo "whatever" | gammu sendsms TEXT xxxyyyzzzz (where the last is the phone  no) - you need to kill the receive daemon for that to work ie
 service gammu-smsd stop     # kill receive daemon
 echo etc etc gammu etc etc  # send the SMS
 service gammu-smsd start    # revive the receive daemon

Now for the RunOnReceive thing ...
start with sudovi - gives some config file to edit. There's a line in there about pi BLAH-BLAH-BLAH as a sudoer. Duplicate it with gammu BLAH-BLAH-BLAH. Same BLAHs. Save it.
It's something to do with permissions - I'm not an expert here :-)
So my RunOnReceive line is { sudo /home/pi/procSMS.sh $SMS_1_TEXT }
The script didn't seem to know what $SMS_1_TEXT was, so I passed it through as a parameter - inside the script it's treated as $1.  It works.
While testing I ran a process in another window - just tail -f /var/log/syslog which lets you watch it all in real time ...
Comment: Why don't send SMS using SMSD instead of stopping it? See http://wammu.eu/docs/manual/smsd/inject.html
Answer: I was getting the same error on Raspberry Pi in combination with Huawei E3131 (Process failed with exit status 1) but I solved it.

make sure you have file permissions set well. Gammu runs deamon under "gammu" user by default. So you can change it (/etc/init.d/gammu-smsd) to user who is already located in your system and has rights for executing the script. Or change script permissions by following: chmod 755 script.sh. It means you give execute rights to other users too.
In fact there is additional option. Run gammu deamon with parameter -U username. Unfortunatelly it did not work for me when I used root user.
PS: I would recommend to not to place the script inside /etc directory. Use /home directory instead.
turn on debuging in /etc/gammu-smsdrc. Use parameters: logformat and debuglevel in section smsd. Default log is located in /var/log/syslog. May be it helps you deeply localize the problem.
And the best at the end... I found that gammu returns the error even if it runs the script well! You have to write exit code inside you bash script. If you do not specify an exit code, gammu represents it as error 1. Add exit 0 in case of success in the end of the script and error message disappears.

Gammu: run on receive exit status 1


In Gmail, how to a delete an email and view the next email?

Question: Often when I am reading a set of emails, I wish to delete (or archive) the email I am reading and move to the next email in the list (inbox or search result).  However, when I press "archive", etc., it does the action and moves back to the list.
Answer: First turn on keyboard shortcuts in settings.
Now you can use [ and ] to archive and move to the previous/next conversation.
Comment: thanks, do you know how to **Delete** and move to the previous/next conversation?
Comment: Ok... I'll just delete my answer!! How did I miss these shortcuts..! +2 if I could :D
Comment: Sorry, I don't know of a way to do that.
Answer: There is a new 'labs' feature called 'Auto-advance' that looks like it will do what you want.
You can access the labs settings by clicking on the small green icon next to your email address on the top-right of the page.
Hope this helps.


Can I continue to travel within the US on an expired visa?

Question: I am an EU citizen, and I don't need a visa for the United States. But there is an issue, as my visa is expired. If I continue to travel within the US, will they check my visa?
Comment: I'm confused. If you don't need a visa, what has expired? Your passport, or some unnecessary visa you got accidentally?
Answer: In general, no, your immigration status will not be checked whilst you are within the US.
However various organisations - most notably the Police - can check your immigration status at any time, and if they find your visa status is expired they can take steps up to and including detaining you and handing you to DHS (the Department of Homeland Security).  This is very unlikely to occur unless you come to the attention of the police for other reasons, but it can happen.
By overstaying the time you are allowed to be in the US you are putting your chances of being allowed back into the US at any time in the future at risk.  Once you've overstayed at all you are no longer able to use the Visa Waiver Program to re-enter the US in future, and will be required to obtain a visa.  Depending on the length of time you overstay, you will likely be denied a visa for several years - the longer you overstay, the longer until you will be allowed back into the US again.
Comment: When you depart by air the airline passes the details of when you depart to USCIS ("Immigration"). When you depart by land (to Canada/Mexico) you pass through immigration at the border. So whilst they don't necessarily "check" upon exit, they do record electronically when you entered/exited the country.
Comment: Do they systematically check upon exit?
Comment: people have been detained on trying to exit the US with expired visa and ended up in jail before being declared persona non grata and evicted with a blacklist entry denying them the right to return for a set period or even permanently.


How to clean up Sent Mail

Question: I want to keep my Sent Mail folder (label would be more correct) clean, i.e. move done messages to some archive and keep only a few that remind me of something.
In the inbox I can do this by archiving an email. It is gone from the inbox but not deleted altogether. In the Sent Mail folder this doesn't work: when I archive a sent email the Sent Mail folder keeps listing it.
Comment: I think I might have figured it out! Please check out my post on the GMail Support Forums:
https://support.google.com/mail/thread/9578278?msgid=9578278 I have also posted this on Apple Support Forums:
https://discussions.apple.com/thread/250474579 Let me know if this works!
Answer: Actually, Sent mail in Gmail isn't a folder nor a label. It's a system view similar to "All Mail".
The only way to remove messages from there is by deleting them.

Remarks  (Update)
As @user829755 found some web pages suggests the use of IMAP client to remove messages from the Sent. According to bkc56 in Managing Sent Mail this could work temporarily but once Gmail refreshes the user mailbox index, the removed messages will appear in Sent again.

References
How can I clear Sent Folder. I have assigned emails to Labels. If I delete them out of Sent Mail it will delete all. - Gmail Help Forum
Answer: Rubén's answer sounds reasonable but then I found
this URL which describes how to solve the problem via the imap interface with external email client. I tried it out and it seems to work. I have now emails that I wrote myself and they appear in All Mail and under some label I gave to them but no longer in the Sent Mail folder.
But: see Rubén's comment
Comment: According to http://gmail-tips.blogspot.mx/2013/05/managing-sent-mail.html using IMAP to remove messages from Sent isn't permanent.
Answer: For many years I have been using a desktop IMAP client (Microsoft Outlook) to move messages out of the Sent pseudo-folder to the Inbox.
From there I move them to the folder(s) I want them to be in. They have never re-appeared under Sent.
Answer: Here is a creative solution I have just started using.  I created labels sent2016, sent2015, sent2014, etc.  Then I applied the labels, for example search for sent emails before:2016/01/01 after:2014/12/31, select all, then click on "Select all messages that match this search", then apply the label "sent2015".  After doing this for each completed year, I then labeled all the current year's sent messages too (sent2016).
The next step, for me, since I read my email in Thunderbird, was to unsubscribe the Sent folder, and to subscribe to sent2016 instead.  Now when I look at messages in sent2016, I'm only looking at the current year, not 8 years worth of messages!
I think this would also be somewhat helpful if I were reading my gmail in the browser, too, because instead of checking the "Sent" box, I could look in the "sent2016" label.
(I did select all the old sent messages labeled "sent2015", for example, and hit "archive"; but I don't know that that was particularly helpful....)
P.S. I also unchecked IMAP for the old labels.
Comment: Bad idea, apparently.  Thunderbird keeps spinning around and around, trying to put a copy of every recently sent message.
Comment: Found http://gmail-tips.blogspot.com/2013/05/managing-sent-mail.html, have applied these suggestions: (1) hide "sent" in imap (gmail settings - > labels); show "sent2016" instead; (2) go into account settings in thunderbird, uncheck "when sending messages, automatically".

How to clean up Sent Mail


Inspection of 'Regexp.union'

Question: Regexp.union returns the following inspection:
Regexp.union(/dogs/, /cats/i) #=> /(?-mix:dogs)|(?i-mx:cats)/

What does ?-mix: mean?
Answer: They are flag switches inside the regexp. /cats/i means "use flag i across the whole regexp". You can turn flags on and off inside a regexp, so the above is equivalent to /(?i:cats)/. There are two other flags that can be manipulated this way: m and x. Since by default all flags are disabled unless specified otherwise, it is equivalent to /(?i-mx:cats)/ ("enable i and disable m and x inside the regular expression cats").
When you combine regular expressions, they explicitly disable the disabled flags so that they would not inherit them from an outer context. For example:
tiny = /tiny/             # case sensitive
tina = /#{tiny} tina/i    # case insensitive
# => /(?-mix:tiny) tina/i

This will match "tiny tina" or "tiny Tina", but not "Tiny Tina". If the embedded regexp for tiny did not explicitly turn off case sensitivity, and just yielded /tiny tina/i, everything would be case insensitive.
Answer: What you're seeing is a representation of options on sub-regexes. The options to the left of the hyphen are on, and the options to the right of the hyphen are off. It's smart to explicitly set each option as on or off to ensure the right behavior if this regex ever became part of a larger one.
In your example, (?-mix:dogs) means that the m, i, and x options are all off whereas in (?i-mx:cats), the i option is on and thus that subexpression is case-insensitive.
See the Ruby docs on Regexp Options:

The end delimiter for a regexp can be followed by one or more single-letter options which control how the pattern can match.

/pat/i - Ignore case
/pat/m - Treat a newline as a character matched by .
/pat/x - Ignore whitespace and comments in the pattern
/pat/o - Perform #{} interpolation only once

i, m, and x can also be applied on the subexpression level with the (?on-off) construct, which enables options on, and disables options off for the expression enclosed by the parentheses.

Inspection of 'Regexp.union'


What's the difference between *.duckduckgo.com and duckduckgo.com?

Question: What's the difference between *.duckduckgo.com and duckduckgo.com? On the SSL certificate it shows the two at the bottom as valid DNS for DuckDuckGo. I understand the asterisk is a wildcard in code, but before a lot of domains I see the same thing. Can someone briefly answer this question?
Answer: In computer networking, a wildcard certificate is a public key certificate which can be used with multiple sub-domains of a domain.
A single wildcard certificate for https://*.example.com will secure all these subdomains on the https://*.example.com domain:
                 payment.example.com
                 contact.example.com
                 login-secure.example.com
                 www.example.com
Instead of getting separate certificates for subdomains, you can use a single certificate for all main domains and subdomains and reduce cost and complexity.
Source: Wikipedia Wildcard certificate

What’s the difference between *.duckduckgo.com and duckduckgo.com?


Can I pack a razor in a carry-on on planes leaving Toronto Pearson airport?

Question: Can I?  Never carried a razor before.  The women's Gillete safety razor?  Now, I'm pretty sure the TSA are good with it but I read on the Transport Canada  site which was updated on 2011 that razors aren't allowed?
By the way, are Europeans okay with razors in general?
Edit:  Safety razor!
Comment: Do you mean [old-school safety razors with disposable double-edged blades](http://upload.wikimedia.org/wikipedia/commons/a/a4/Chrome-Safety-Razor.jpg) or [modern-day disposable razors](http://krikor.info/wp-content/uploads/2009/08/venus-line.png) which are sometimes called safety razors ([wikipedia for example includes them in its dedicated article](https://en.wikipedia.org/wiki/Safety_razor#Recent_changes)).
Comment: I did once carry a one-use-only razor for shaving. They made me trash it :)
Answer: Canada
The Canadian TSA website says that you can indeed pack disposable razors and cartridges in your carry-on:

Disposable (safety) razors and blade cartridges

Carry On Baggage: Yes
Checked Baggage: Yes

European Union
Whereas the website of the European TSA-equivalent organisation mentions razors (without mentioning disposable or not) and the fact that they are prohibited in carry-on luggage:

LIST OF PROHIBITED ARTICLES IN YOUR CABIN BAGGAGE:
[...]
c. objects with a sharp point or sharp edge (objects with a sharp point or sharp edge capable of being used to cause serious injury), including:

[...]
razor blades,

For future reference, here is the list of prohibited items on flights originatin within the EU.
UK
As @chx correctly points out, UK is also in Europe. According to the governmental authorities, disposable razors are allowed in both carry-ons and hold luggage:
Comment: +1 Thanks for the future reference. I'm really saddened that I can't take a catapult with me though..
Comment: The UK is part of the EU so it's also within the same framework, no reason to single it out. But the EU commission Directorate General for Mobility and Transport is nothing like the TSA, it enacts rules that are implemented by national authorities (hence the potential discrepancies or possibly additional rules) and has many other roles but does not train or hire screeners or operate security checkpoints.
Comment: @JoErNanO since your link does not distinct between disposable blades and straight razors. See https://www.gov.uk/hand-luggage-restrictions/personal-items for UK which is the strictest, http://www.frankfurt-airport.com/content/frankfurt_airport/en/misc/container/airport-guide/english/jcr:content.file/2014-01-06-airportguide_en-fro.pdf for Germany and if you want I can dig more but disposable is good anywhere.
Comment: @chx Yes I often forget that UK is in Europe. Thanks. :)
Comment: @Flimzy That's what I thought too. However I was unable to discern if that was the case from the way the question in phrased. Therefore, I went by the assumption that the [gillette woman safety razor](http://krikor.info/wp-content/uploads/2009/08/venus-line.png) is the disposable one.
Comment: I would think "razor blade" refers to [this](http://reprap.org/mediawiki/images/8/85/Razor_blade_rec.jpg) rather than [that](http://globe-views.com/dcim/dreams/razor/razor-05.jpg).
Comment: Once again: your answer is incorrect / misleading . The link you provided does not discern between the two kind of razors. I've already given you UK and Germany. Please remove yours.


Why are there metal shavings in my brake pads?

Question: I have several brake pads on my cantilever brakes that have several small metal shavings embedded in the pad.  Is this normal?  What should I do about it?
Comment: I had a real bad problem with this using Yokozuna pink pads on Velocity Synergy rims. I switched to Kool Stop dual compound pads and it is way less noticeable.
Answer: This is normal to some extent - brake pads have to be made of soft material which wears down on the rims (and conversely, the rims wear down into the brake pads to some extent) in order to stop you. This means the pads pick up grime and bits of metal from the rims and road and stuff which embed into the pads and in turn wear down your rims / reduce braking efficiency. If they're eating large portions of metal, then you should probably switch the pads to ones made of different material (anecdotal evidence suggests the pads which come with most cheaper brakes belong in the trash).
I'd start with a high quality pad (e.g. Koolstop Salmon pads), and making sure the rims are clean (use citrus degreaser/rubbing alcohol). Mavic and some others make special blocks for cleaning and (slightly) sanding your rims as well, which you can use (but definitely not necessary).
If you do get metal or other contaminants in your pads though, you can pick it out with tweezers and buff the pads with some fine sandpaper (remove the grit afterwards!). Make sure the pads have sufficient material leftover after this - if the metal backing comes through, your rims are going to take damage.
Also, make sure your brakes are properly adjusted: http://sheldonbrown.com/canti-trad.html
http://www.parktool.com/blog/repair-help/cantilever-brake-service is a good link to look at as well (Specifically see the "Pad Wear" section). If your brakes are rubbing on the brake tracks, you'll pick up more cruft (and wear out your rims), for example.
Also, check your rim wear indicators (if you have them - they're reasonably common on modern rims) to make sure that you're not too worn on the rims as well (this is typically a little groove which should be there on the rims, but can appear in other forms such as something that appears when the rim is too worn out). If you don't have them, you can try a procedure like http://archive.ctc.org.uk/resources/Magazine/20011163.pdf. If the rims get too worn, they break and you end up hurt (probably).
Comment: I use a wire brush on my brake pads once in a while and it works quite well in removing any metal shavings or similar from the pads. Also, not all rims have wear indicators. My old Campa Moskva just exploded on me. Luckily, my bike was tied to a lamppost at that point and only the tire and tube were done for.
Comment: @arne - good point, updated with a technique for measuring rim wear without the indicators.
Answer: It is unlikely, but remotely possible that some brake pads might even contain some metal, which is the case with car brake pads.
Comment: You're thinking of [sintered disc brake pads](http://www.pinkbike.com/news/brake-pad-information-2009.html). They're quite normal on bicycle disc brakes, but this question is about cantilevers :)
Comment: Theres a metal backing plate in most pads, but if your pads are worn to this point, your rims will quickly be eaten up (and your brakes won't exactly work). Some pads have things like iron oxide in them (Kool Stop Salmon's have this, and hence their color). However, metal shavings shouldn't be designed into pads (unless you're getting your brakes from an ACME villain or something), since they'll wear down rims more and won't stop you as well as the brake compound.
Answer: I have found that they are contaminated at manufacture, not collected as from road debris or the rim wearing away. I saw a chunk about a quarter of an inch long and 16th of an inch wide buried, actually held fast in the brake block and it gouged a groove in the rim of the front wheel in short order. There were many other pieces of shiny metal in the blocks and other blocks I had as spares.
Comment: The "chucnk about a quater of an inch long and 16th of an inch wide buried" is actually the supporting structure that allows the whole pad to press against rim and keeps the rubber from tearing away from the bolt. Otherwise, nice rant but not really based on reality.
Comment: Welcome to Bicycles SE.  This post was flagged as "rude or abusive." I have removed the portion that discussed the perceived status of the bike industry as a whole and left the portion that answered the OPs question.


Export and Import settings of Plasma5

Question: Is there a way of exporting and importing Plasma5 settings like settings for the taskbar, dophlin, shortcuts and so on and import them for a new user or on a new installation?
Answer: Configuration files are stored in ~/.config and ~/.kde/share (for KDE apps). If you want to get the configuration for a specific program, look for a file containing the program's name and ending in rc or .conf. Some examples are

~/.config/dolphinrc
~/.kde/share/config/amarokrc
~/.config/kde.org/plasmashell.conf

Be careful, though, as some programs may store their configurations in unexpected places. Some configurations also may not work if the new user has a different name from the old one (for example, one line in my amarokrc is 1=./home/andrew/Music - this would be different depending on the username) or if they are a different person than the old user (~/.config/emaildefaults stores the user's preferred email address).
Some programs may even have several configuration files containing different data! Picmi, for example, uses ~/.config/picmirc to store high scores, and ~/.config/picmi/picmi.conf to store the previous window position.
If this is just to transfer a single user's settings to the new computer, you could likely get away without changing anything (I copied my entire user folder over when I switched computers, because I had the same username on both machines), but otherwise you'll need to be careful about what files you keep and what files you leave behind.

Export and Import settings of Plasma5


rpm without root

Question: Is is possible to use rpm without root access?
Answer: There are lots of answers suggesting relocatable packages.  The relocation option is for administrators to choose the destination (making destination be /opt instead of /usr/local for example) and is not really for user permissions.
While it may be possible to get around some permissions issues using this method, the MAJOR problem is that when you perform rpm operations, it is modifying the /var/lib/rpm/__db.* databases that are owned root:root.  So as JPerkSter said "short answer = no".  Setting up sudo to allow the specific needs would probably be the best bet.
Answer: Considering all of the above, regarding relocatable builds, you could try following the instructions listed here.
rpm --initdb --root /home/username/local --dbpath /home/username/local/lib/rpm
rpm --root /home/username/local --dbpath /home/username/local/lib/rpm \
 --relocate /usr=/home/username/local --nodeps -ivh package.rpm

Answer: Depending on the contents of the package you could simply extract the contents of the rpm and use it from somewhere withing your home directory.  Even if it isn't flagged as relocatable.  If binaries in the package have hard-coded paths, or if the application requires root access then it may not be possible.
Comment: this is actually incorrect, you can't actually run the `rpm` command without sudo/root access.
Comment: extract the contents gets my vote (from 2023): ```rpm2cpio httpd-2.4.51-7.el9_0.x86_64.rpm | cpio -idmv```
Answer: Some packages are relocatable so they may work fine without root, just specify prefix when installing it:
rpm -i my.rpm --prefix=/my/home/folder
If package is not relocatable you may still extract the files from RPM and try to run it. You can extract RPM files using for example:

rpm2cpio
or midnight commander

Copy the files into your ~/ folder, add any additional dependency libraries and hope for the best. Not guaranteed but you may get some non-relocatable packages working this way.
Answer: The RPM spec contains an option called 'relocatable'.  If the rpm is built with relocatability turned on then it can be installed in a user specified directory using the '--prefix' option.  So presumably an rpm could be installed locally without superuser access as long as two conditions are met:

The package was originally built to be relocatable
The 'rpm' binary does not attempt to add the package to the global system catalog

But, in general, no, you need superuser access to install an RPM.  While the relocatable option exists, I have nearly never seen a package that has been built to support it.
Answer: You can force it to install under a different directory using a different dbpath. Also you should probably not run any scripts directly without checking them out.
This will put an rpm under the current directory and extract the scripts so you can edit and run them if necessary.
rpm --install --badreloc --relocate /=`pwd` -dbpath `pwd`/rpm_db --nodeps --noscripts package.rpm

rpm --query --scripts -p package.rpm > scripts.txt

Answer: Yes, but you may not want to. I have used custom puppet manifests and rpm packages to maintain software on compute clusters on which I did not have root access. In theory it is as simple as
rpm --inittb --root /foo
rpm --dbpath /foo -i bar.rpm

However, there are quirks in how this behaves across EL4, EL5, and EL6, so you'll need a different set of steps and options for each one. I don't have that information handy anymore. Those quirks, as well as frequent RPM database issues (perhaps due to NFS), made me regret using rpm.
Answer: You can build RPM's without root access, just do so inside your homedirectory.  As far as installing RPM's, I would say the short answer = no.
Answer: Expanding Zoredache's link about extracting the files from an RPM without installing:
If you have a package file called foo.rpm, you can extract its files under the current directory path using:
rpm2cpio foo.rpm | cpio -idmv

For example, if you do this in /home/myself and the package contains files /lib/foo.so and /usr/bin/foo, these files will be extracted into /home/myself/lib/foo.so and /home/myself/usr/bin/foo.
Answer: no its not possible rpm with out root,su or sudo access

rpm without root


How to remove roots in sewage drain

Question: I have a root growing in my sewage drain and I'm wondering what is the best way to remove it and what are the implications of having an apparently cracked main sewage line.  Backstory:  a few months ago my toilet stopped up and while investigating I took the toilet off and discovered a pinky finger sized root growing all the way up to the toilet wax ring and forming a thick mat of roots around the wax ring area. I was able to run a cheap auger I bought at Lowe's and clear the line of solids that had backed up. However, I have not been able to clear the roots from the drain.  I did buy this powder root inhibitor chemical at Lowe's which I guess stops future growth. I have not been able to remove the actual root system. I live in a concrete slab suburban house that is about 60 feet feet from the main sewage line at the cul de sac. There is a large silver maple tree growing in my front yard which I suspect the roots came from.  How do I best deal with this problem without breaking the bank??
Comment: Rent a properly sized auger with enough cable to get all the way out to the main.
Answer: There at different styles of augger heads on larger units. Most folks are familiar with the cork screw style end that will grab chunks of hair and roots but there are also several styles of cutting heads the one I have the best luck with for clearing roots is a head that has 2 flat loops that are about 3" long and then 2 more flat loops that are a bit shorter but are the same diameter as the longer ones the loops are a flat stainless material that is fairly thin. These won't cut through a plug very well but they scrape the walls and cut the roots. I have found once roots get in the pipe it becomes an annual event until the pipe is replaced (even using chemical inhibitor). The large augger I purchased came with 3 or 4 heads , I found the best thing was to the head that looked like a hunting arrow to punch a hole in the mess then use the one with the loops. My unit has a power feed lever I go forward until I notice some back pressure then let it spin at that location for a little while move forward very slowly so the bands or loops cut the roots loose I do run water when doing this so everything is flushed as it is cut loose. The first time I did this I did not run water and all the chopped up root pieces plugged at the entrance to the main line and I had to run the cork screw head in to pull the roots out. I have had this happen in 2 homes 1 got so bad I replaced the line the other I just ran the snake every spring and never had and more problems until the next spring.
Comment: Spring?  If the line is problematic due too root growth and needs an annual cleaning, I'd do it in the fall, as soon as the leaves have turned and the growing season has ended.
Comment: For me that's when I or the renters had problems with both houses it may have worked to do it in the fall but who wants to play with poop if they don't have to.
Comment: My first house was a piece of crap, and I owned it 6 years.  I called roto-rooter the first time, the guy that came said he'd been there before (for previous owner) and told me to just get on the annual program at a discount and that I should have it cleaned every year in the fall as soon as the leaves turned.  In all honesty if I was doing it myself, I'd rather prevention on a nice warm day, as opposed to playing in poop on a cold, rainy, winter night.
Answer:
How do I best deal with this problem without breaking the bank?

Your long-term lowest cost solution might be to hire a root removal specialist to come out twice a year and proactively clean the line. At approx. $125 per service (avg. depending on access), you could do this for many years before you would reach the cost of line replacement. There would still be the potential for inconvenient surprise stoppages because using a root cutter does not clear the entire line of roots (the heavy cable and cutter lie on the bottom of the pipe, leaving a "curtain" of roots untouched) nor does it prevent growth.
The most effective and reliable options (also the most expensive) are to either replace the line or have it hydro-blasted and "shot" with a liner to prevent future root intrusion.

How to remove roots in sewage drain


Putting a one year old in the crib and shutting door

Question: Will it hurt a one year olds development if the crib is used as a place to play with toys, turn cartoons on and shut the door as a way to keep them from under foot several times a day?  My grandbaby's daddy does this and I don't like it. I never put my babies in their crib unless ut was bedtime or naptime.  This bothers me and worries me at the same time.  Am I wrong to feel this way?
Comment: +1: Would be interested to see any studies on this. Informally, our one-year old goes to war even when we put her down for a regularly scheduled nap, so this technique is never really an option for us, but all the reading I've done suggests she's fine to be left if playing happily. The issue for me would be the TV.
Comment: I can think anecdotally of information about how it is valuable for babies to explore and so even playpens as containers over a long period of time are looked down on today.  I am also a big, big proponent of good sleep associations, so for us the crib is exclusively for sleep times.  Plus the issue that TV is at best neutral and at worst harmful for the under 2 set.  But I don't have any solid data to back up the sleep association thing and the contained space thing.
Answer: The real worry for me would be the television. The American Academy of Pediatrics states that "young children learn best by interacting with people, not screens" -- meaning toddlers should be around people. Putting a toddler in an enclosed space (crib, playpen, baby-fenced-off room) isn't harmful per se, and I often will put my toddler in his playpen while I'm trying to do something else: cleaning, cooking, homework, or just taking a break from Mom Time. But leaving him alone there for long periods of time means he isn't getting time to socialize -- that's extremely important for a one year old, and he flips out if he's caged up and lonely.
Since this is not your child, though, you should probably approach it diplomatically -- mention the scientific basis for avoiding TV for babies, acknowledge that a parent gets exhausted by their child sometimes and needs a break, and then see if everybody together can find a solution that's better for your grandchild.
Comment: Erica, Yes the interaction with others is my concern and social development.  They put videos in like Bambi, Cinderella etc, which we all grew up watching.  And the  concern I have, you mentioned, feeling lonely.  I too, put my babies in playpens, but they were in the room with me, never alone.  Thanks, and I do want to be diplomatic as well.  I take my Grandbaby every chance I get!  It is a special time for me! :-)  Thanks for your response!
Answer: Every child is different and has different needs.  Ditto that of parents.
My son did not like being left in his crib, and would cry and fuss if he was in it and not ready to sleep.  He needed socialization quite desperately so even when he had to be penned up we kept him near someone.
My daughter, who was born when my son was nearly 2, is more introverted, and we find the toys-alone-in-the-crib to be enjoyable for her; she is unhappy if she goes straight to bed without some personal time with some favorite toys.  She gets ample "social time" with her brother, and in fact when she starts getting towards nap time she gets very aggravated by him, so some crib time helps everyone's nerves.
Answer: Crib time is just as important as socialization. Isolated playtime allows 5 month to 16 month old children time for their own thoughts.  Learning to entertain themselves is necessary for learning how to play.  Private playtime teaches them independence.  Babies need to know that they are separate individuals from others.  Make sure the toys are age appropriate and interesting to the child.  Fun children's music played in a CD player is better than TV for children.   Socialization should include direct eye contact, hugging, speaking directly to the child and caring for their many needs.  Reading to them encourages language development.  Alternate crib playtime (twenty minutes to a half hour)with family socialization (most of the day time) to prevent loneliness.
Comment: Looking back at my children, this is far too generalized. I have one child, that always enjoyed some solitude - from day one, actually, one child, that needed company and was desperate to be left alone for even very short time spans.


How did Voyager catch up to the Equinox?

Question: In the Equinox episodes of Star Trek: Voyager the rationale for sacrificing the eel-like aliens was in order to attain higher warp speed and thus arrive to the Alpha quadrant faster, but in the finale the Voyager crew manages to catch up to the Equinox.  How was Voyager able to catch up?  If the Equinox ends up not being faster than Voyager even after sacrificing the eel-like aliens, what is the rationale for the Equinox crew to abandon Voyager and strike out on its own?
Answer: The first part of lucasbachmann's answer covers the main point, but I thought I'd add a bit more detail.
Toward the end of the first episode of the two-part story, Janeway ordered Seven of Nine to go to the USS Equinox's engine room and take its warp core modifications offline.

JANEWAY: (to Seven) Go to their engine room. Take those warp core modifications offline.
Star Trek: Voyager - S05E26 - "Equinox"

Seven carried out this order, so when the Equinox made its escape, it only did so at regular warp speeds.

CHAKOTAY: Chakotay to Seven of Nine. What's your status?
SEVEN: I've dismantled the antimatter injectors, but I'll need several minutes to neutralise the dilithium matrix.
CHAKOTAY: We don't have much time.
SEVEN: Understood.
Star Trek: Voyager - S05E26 - "Equinox"

When Ransom's crew reinstated the warp core modifications in the second episode, they learned that they still couldn't get them to work, because Seven had also encoded the power relays to keep them offline. As a result, the Equinox was limited to regular warp speeds throughout that episode.

RANSOM: Infuse the enhanced warp drive with twenty isograms of the compound.
LESSING: Aye, sir. Warp drive ready.
RANSOM: Engage.
(Shudder then a jolt.)
RANSOM: What happened?
GILMORE: The power relays are offline. They've been encoded.
Star Trek: Voyager - S06E01 - "Equinox, Part II"

For reference, in the Voyager pilot, the USS Voyager was stated to be an Intrepid-class vessel with a sustainable cruise velocity of warp 9.975.

STADI: That's our ship. That's Voyager. Intrepid class. Sustainable cruise velocity of warp factor nine point nine seven five.
Star Trek: Voyager - S01E01 - "Caretaker"

Whereas, according to this article from StarTrek.com, the USS Equinox was a Nova-class vessel with a top speed of warp 8.

The U.S.S. Equinox NCC-72381 was a top-of-the-line Nova-class science vessel. The Nova-class replaced the aging Oberth-class starship used for the past century. At a length of around 222 meters long, 8 decks, and a crew of 78, the ship was relatively small compared to other ships of the time.
It had a top speed of warp 8, which was efficient for general scientific missions. Two shuttlecraft and an optional "wave rider" shuttle, located on the bottom of the "saucer" section, made for a decent auxiliary craft complement. Armaments included 11 Type X phaser arrays and 3 photon torpedo launchers, giving the ship the ability to defend itself decently during its voyages.
Inside the U.S.S. Equinox NCC-72381

In fact, at one point, Janeway stated that without its enhanced drive, the Equinox was only capable of warp 6. It's unclear if this was a mistake by the writers, or if the Equinox's top speed was reduced by the damage the ship had taken. Either way, it was significantly slower than Voyager, which explains why Voyager repeatedly caught up to it.

JANEWAY: Our first priority is to find Ransom. Still no sign of nucleogenic particles?
CHAKOTAY: Not yet.
JANEWAY: Then he couldn't have gotten far. Without his enhanced drive, his ship's only capable of warp six.
Star Trek: Voyager - S06E01 - "Equinox, Part II"

With it's enhanced drive fully operational, the Equinox was apparently capable of travelling over 10,000 light years in under two weeks.

RANSOM: We examined the remains and discovered it could be converted to enhance our propulsion systems. It was already dead. What would you have done? We travelled over ten thousand light years in less than two weeks. We'd found our salvation. How could we ignore it?
Star Trek: Voyager - S05E26 - "Equinox"

By comparison,  Janeway stated that even at maximum speeds, it'd take the Voyager 75 years to travel the roughly 70,000-light-year distance between the Caretaker's array and Federation space. Doing a very rough calculation, that'd make the Equinox somewhere in the region of 250 times faster than Voyager, when utilising its enhanced warp drive.

KIM: Captain, if these sensors are working, we're over seventy thousand light years from where we were. We're on the other side of the galaxy.
[...]
JANEWAY: We're alone in an uncharted part of the galaxy. We have already made some friends here, and some enemies. We have no idea of the dangers we're going to face, but one thing is clear. Both crews are going to have to work together if we're to survive. That's why Commander Chakotay and I have agreed that this should be one crew. A Starfleet crew. And as the only Starfleet vessel assigned to the Delta Quadrant, we'll continue to follow our directive to seek out new worlds and explore space. But our primary goal is clear. Even at maximum speeds, it would take seventy five years to reach the Federation, but I'm not willing to settle for that. There's another entity like the Caretaker out there somewhere who has the ability to get us there a lot faster. We'll be looking for her, and we'll be looking for wormholes, spatial rifts, or new technologies to help us. Somewhere along this journey, we'll find a way back. Mister Paris, set a course for home.
Star Trek: Voyager - S01E01 - "Caretaker"
Comment: @Acccumulation - If you assume that the top speed of the Equinox (when in full working order) was warp 6, then sure, the two statements are wholly compatible. However, according to [this article](https://intl.startrek.com/article/inside-the-u-s-s-equinox-ncc-72381) from startrek.com, the Equinox's top speed is warp 8. The two statements can still be reconciled by by assuming that the Equinox's top speed was reduced by the damage it'd taken, but that wasn't clarified, so the latter statement could simply have been a writing error.
Comment: Literally speaking, it's not a discrepancy. "Its top speed is warp 6" is consistent with "It can't travel faster than warp 8".
Answer: Edit: I misread the question.  In the scope of the chase within the episode the answer is the Equinox is a very damaged ship using regular warp.
Transcript from http://www.chakoteya.net/Voyager/525.htm

KIM: Casualty reports are coming in. Two dead, thirteen wounded. We took heavy damage to the engines.

JANEWAY: The Equinox?

KIM: They've gone to warp.

JANEWAY: Any sign of nucleogenic particles?

KIM: No.

JANEWAY: Then they haven't engaged their enhanced warp drive yet. Keep looking for
(The sound of new fissures opening.)

While it is not the same question so I'm not going to consider it a duplicate - Voyager's large distance jumps are well documented.  See Did Voyager "shave off" more years than were necessary?
Note "Equinox" comes before "Dragon's Teeth" and "The Voyager Conspiracy".
The Equinox crew knew what they were doing was unethical but it was also consistently faster.
Voyager just gets lucky hits for large jumps. (Of course so did Equinox in its own way.)
Traveling with Voyager would be a loss of independence and legal consequences. Though I suspect a good lawyer could get them acquitted for not knowing those creatures were intelligent - which I recall Voyager figured out. The Federation no doubt has stronger animal rights than we do - but people still need to eat.
Odds are there was some other shady stuff done on their trip too.
Comment: Probably worth editing out all of the unneeded stuff in this answer.


Confusion with the Lorentz transformation

Question: I want to show that ,for me at rest on earth, one clock in movement with speed V ticks slower.
The proper time is the time of the clock at movement, so i do:
$\Delta t=\gamma\Delta t'+\frac {V}{c^2}\gamma \Delta x' $ but $\Delta x'=0$  so its done...
My question is:
Why cant i convert from $\Delta t'=\gamma \Delta t -\frac{V}{c^2}\gamma \Delta x$ like this.
In my conception the transformations work both ways.
Comment: I'm not sure I understand your question.  Are $\Delta t$ and $\Delta x$ supposed to be in your frame, while $\Delta t'$ and $\Delta x'$ are in the rest frame of the clock?
Answer: I cannot comment because of my low reputation hence I am writing this as an answer  I must say that in the latter transformation
$$\Delta t'=\gamma \Delta t -\frac{V}{c^2}\gamma \Delta x$$
where $\Delta x=V \Delta t$ (The event describing the presence of observer in motion at time = $\Delta t$) this implies

$$\Delta t'=\gamma \Delta t -\frac{V^2}{c^2}\gamma \Delta t \implies \Delta t'=\gamma(1-\frac{V^2}{c^2}) \Delta t \implies \Delta t'=\frac{\Delta t}{\gamma} $$ which yields the same result
Comment: I assume these were the notations you meant to use


Attirbutable risk from competing risks

Question: There are a number of ways to estimate attributable risk fractions from Cox regression and logistic regression. Does anyone know how to estimate attributable risk from a competing risks regression using subdistribution hazard ratios, with 95% confidence intervals?
Answer: This page provides quick summary of the Fine-Gray subdistribution hazard approach to competing risks, with a link to further information. As @AdamO put it on that page:

The intepretation of this subdistributional hazard function is the instantaneous risk of death from cause 1 given you are either still alive, or you've already died of something else. In effect, it averages across these two possibilities in such a way that a high risk of dying previously from other causes lowers your hazard for that specific failure.

According to the vignette on competing risks provided with the R survival package, this approach to modeling competing risks:

can be done as a two stage process: the first stage creates a special data set while the second fits a weighted coxph or survfit model to the data.

The special data set is a collection of data sets, one for each endpoint, formulated to meet the requirements of the Fine-Gray analysis. That package has a finegray() function to produce the data sets from the original survival data. Cox regressions with weights assigned by the finegray() function then provide the basis for hazard ratios, confidence intervals, and so forth for each endpoint. There is also a cmprsk package for such analyses.
Before you proceed, however, make sure that you understand the limitations of this approach. As the competing risks vignette puts it on page 24:

A weakness of the Fine-Gray approach is that since the two endpoints are modeled separately, the results do not have to be consistent.

And on page 25:

The primary strength of the Fine-Gray model with respect to the Cox model approach is that if lifetime risk is a primary question, then the model has given us a simple and digestible answer to that question ... . This simplicity is not without a price, however, and these authors are not proponents of the approach. There are five issues.

Of which the first and perhaps most important is:

The attempt to capture a complex process as a single value is grasping for a simplicity that does not exist for many (perhaps most) data sets. The necessary assumptions in a multivariate Cox model of proportional hazards, linearity of continuous variables, and no interactions are strong ones. For the FG model these need to hold for a combined process — the mixture of transition rates to each endpoint — which turns out to be a more difficult barrier.
Comment: Thank you but attributable risk cannot be calculated directly from cmprsk package
Comment: @bvowe it might help for you to edit your question to provide more details and an example of the type of attributable risk calculation that you wish to perform for a Fine-Gray analysis. Do you mean risk of each type of event as a function of some type of exposure, or some relative risk of the two types of events?
Comment: thanks for your note i am hoping to estimate the percentage of the outcome that is attributable to a specific risk factor in the context of the competing risks models
Comment: @bvowe I don't use `cmprsk` and only included it as it seemed potentially useful. The `survival` package method for Fine-Gray produces separate datasets for each competing outcome, suitable for Cox regressions. So any method "to estimate attributable risk fractions from Cox regression" would seem to apply to that competing-risks approach. See pages 19-20 of the vignette linked in my answer for an example of such Cox regressions based on Fine-Gray analysis of a data set having 2 competing risks.

Attirbutable risk from competing risks


How does lending "create" money?

Question: I keep hearing that when banks loan money, it creates money and increases the money supply. But this confuses me. Wouldn't the money have to have already been created in order for them to lend it in the first place? I don't see why lending money that already exists would "create" new money?
Comment: another possible duplicate: https://economics.stackexchange.com/q/45858/28068 or https://economics.stackexchange.com/questions/6219/how-is-money-created-on-net. This question was already asked here several times
Answer: In a fractional reserve system, banks increase the money supply because loans are backed by demand deposits. In other words, banks will give out loans using the bank deposits of customers. The customer whose money is being lent is nonetheless still able to withdraw or transfer their bank balance, which means the money supply has expanded. For example, if a bank has 10 dollars in customer deposits, and lends out 9 dollars, 9 dollars has now been added to the money supply, because the customer retains the ability to use and spend their 10 dollars balance and the recipient of the loan now also has 9 dollars to spend.
It may seem that fractional reserve banking is self-contradicting, because evidently the bank could not honor a withdrawal request on demand by the customer for their whole 10 dollar balance after having lent out 9 dollars. This problem is somewhat reduced because in the real world, it is generally unlikely that all customers would demand all their deposits all at once, so a bank only needs to hold a certain percentage of deposits on hand to satisfy demand for withdrawals, which is the reserves of a bank. Also note that if a customer just wants to transfer money from one account to another within the banking system, that doesn't draw on bank reserves at all (and in fact, one of the early tactics banks used in times of crisis before the Federal Reserve system was to temporarily ban cash withdrawals, while allowing transfers between bank accounts).
Of course, sometimes the assumption that there will not be a sudden demand by all depositors for their money fails, which causes a bank run. Bank runs often will result in bank failure, since the bank only has part of depositors' deposits in ready money, while the rest is tied up in loans, which can't necessarily be immediately called in.
In contrast, in a full reserve system, which maybe is a more "intuitive" system of banking, banks only lend from time deposits. For example, if a bank makes a loan of 10 dollars in a full reserve system, it will make the loan from certificate of deposits or other long-term instruments, where the customer has deposited their money for a fixed period and cannot withdraw it before then. In this system, no money is created because the creation of new money by a loan is offset by the temporary "freezing" of the customer's deposit in a time deposit.

How does lending “create” money?


Running once or twice a week for 1 hour duration each, risk of injury excluding shorter runs?

Question: I don't have too much time to dedicate to shorter runs but I'd like to keep my jogging consistent. Am I at risk of anything if I just keep a weekly/biweekly running schedule for longer duration instead of shorter runs spaced more freuqently?
Answer: Your risk of injury doesn't come from the length of your run, but from its intensity and from external factors like proper recovery.
If you fear injuries or knees problems, you should definitively try with minimalist shoes (you can see brands like Merell, Vibram for Vivo Barefoot for this). This allows to have a natural biomecanic movement, and thus, not letting all the power of your steps traumatizing your knees.
Indeed, you will have shorter, easier, lighter footsteps. The impact will be absorbed by your calves muscles. Your ankles will be free to play their roles (stabilizing). Your feelings and feeback will be much more pleasant.
But beware ! This is a very different effort and your calves will be very sollicitated. You need to re-learn to run with them. Begin very low and go progressively. If you are interested, I strongly advise you to follow this guide : https://us.vibram.com/on/demandware.static/-/Sites-VibramUS-Library/default/dw5f33655e/natural-training-guide.pdf
And stretching is a must if you want to maintain or develop good quality muscles and a good recovery.
Comment: I think this got downvoted for not answering the question, but the advice seems interesting nonetheless, and the first sentence does in fact (at least partly) answer the question.


Threats due to a stolen password db file (e.g. keepass)

Question: If someonelse could get your password db file (e.g. .kdbx file for keepass), maybe due to a hacking attack, how threaten is your security in fact?
Of course this is a problem and you should change all your passwords, but how "dangerous" is this really? Is there any value without having the master password?
Answer: If you've picked a strong master password, they've effectively got an encrypted blob of data which they can try brute force your password from, but may never succeed (Assuming that the password DB format is free from errors).
However, unlike with a website password or other online service (Chat/ssh/etc), there are no limits on how many times they can try different passwords, or on what speed the password comparison runs at - they can send copies of the file to thousands of machines and try to brute force starting from different places to minimise the time to find the password. With a website, the web server is the limiting factor - even with thousands of source machines, it will only do comparisons at a rate it can support, or it'll fall over.
For a really good password, this doesn't matter - the number of potential passwords is far too high to try them all in a useful time (assuming for the purpose of argument that whatever data you have is probably not very useful to anyone in a few thousand/million years). Picking and remembering a really good password is harder though, so it's possible that it is actually a quote from a book or common phrase, which might be tried sooner than pure brute force would suggest.
If, on the other hand, you have a weak master password, they've got an easy to decrypt list of passwords and sites, and it probably won't take them long to get access.
Additional - based on @André's comment:
As André says, if the hack occurred on a device where the database is used, as opposed to one where it is just stored (main PC vs. backup server), there is a chance of a keylogger being used to find the master password. As a result, it would be recommended not to open any password databases on machines which are suspect until they have been completely rebuilt from a clean state. Most password managers try to prevent passwords being read from memory, although this is not 100% perfect, but again, this can be avoided by not opening the database on suspect devices (or ones which you don't have control over).
Comment: If they got his pass DB via hacking there's a good chance they can also leave a little present (keylogger) on the machine, saving them from bruteforcing the pass. In this case it's extremely dangerous as the password no longer protects the DB.
Comment: @AndréBorie Of course hacking a persons PC and leaving a key logger behind will compromise almost all password managers. In fact KeyPass, with its lock to user account and optional key file security might be more resistant then online password managers in respect to PC hacks.
Comment: @AstroDan I doubt it - if you've got a keylogger installed this means you can execute arbitrary code on the machine, and at that point what prevents you from either stealing the keyfile (and the user account's UUID or whatever is used to lock the Keepass DB) or just waiting for the user to unlock the DB and harvesting all passwords from memory?
Comment: @AndréBorie I didn't say completely safe I said more resistant. All you need to steal the passwords from an online system is the master password. Stealing the UUID (environment fingerprint) is hard and the key file can be stored in hardware, for example a Yubikey.


Why are mass shooters in America so much more likely to be male than female?

Question: Is there any scientific research on why this is so? I got this statistic from an article titled "Why Are Almost All Mass Shooters Men?" on The Violence Project.
However, their reasoning for the "why" is, in my opinion, not at all concrete.
Comment: Males ae more likely to commit violent crime in general. by almost 3:1 and Homicide are overwhelmingly commited by males, https://www.statista.com/statistics/251886/murder-offenders-in-the-us-by-gender/ why do you think mass homicide should be any different?
Comment: It would be useful to check if the same gender pattern holds true for other countries, as well.
Answer: The Violence Project does hold statistics on this, as you found. If you search for why most shooters are men, you'd get something like this:

"Men just are generally more violent," said the group's president, Jillian Peterson, a forensic psychologist and professor of criminology and criminal justice at Hamline University. "There are many theories as to why that is."

As NPR has reported, researchers say that men, more than women, tend to externalize their problems and look for others to blame, which can translate into anger and violence. And when women do choose violence, guns are not typically their weapon of choice.

Therefore, to investigate why this is so, you will find research on male socialization useful, specifically on its effect on how anger is expressed, and so on. I found a few related research papers: [1], [2], [3]. Basically, what you want to find is the research that backs up the above statement.
Comment: Hey Troy, apologies for this unrelated comment, but may I know what does your pfp says?  It's a really nice picture.
Comment: Hi @GedankenExperimentalist, it says "Lamp Gensou" or "Lamp Phantasmagoria/Fantasty." Gensou is an album by Lamp. Enjoy the music!
Answer: Here is another possibly helpful answer.  If you look at shame research the situations that cause one to feel shame and the negative responses to shame differ largely by gender.  My sources on shame are Brene Brown ("Men, Women and Worthiness: The experience of shame and the power of being enough" should suffice).  Men feel shame when we feel weak, useless, or ineffective; while for women the emotion comes about when one is unable to meet a large net of mutually competing expectations.  Moreover, when men feel shame and do not display resilience we largely react with aggression.  Women are more likely to react by withdrawling or people pleasing.  These types of negative reactions are referred to by Brene Brown as "shame screens".
One of the major demographics in shootings are "incels", and the other are domestic terrorists (see https://womenspolicy.sccgov.org/sites/g/files/exjcpb1076/files/Ruth%20Darlene_Presentation%20Slides.pdf for information about the incel threat, along with stories like https://www.nytimes.com/2019/08/10/us/mass-shootings-misogyny-dayton.html from the Times and https://www.washingtonpost.com/health/2022/06/03/why-so-many-mass-shooters-young-angry-men/ in the Post).  Incels are primarily men who are having trouble with their romantic relationships and react with a large violent shame screen of a shooting.  Because the constructs around the emotion of shame primarily evoke aggression in men, we make up almost all of these individuals.
Moreover, gender constructs around aggression and anger disincentivize women from acting aggressively while they incentivize men to.  As a result, most domestic terrorists are also male.
I want to be clear in saying that neither domestic terrorism or incel violence are the work of mental illness.  Even in schizophrenia, which has been heavily demonized, violence only increases 1% when one normalizes for other factors influencing violence in collecting statistics (this was in a Harvard study that I cannot find).  However, mentally ill people are 10 times more likely to be victims of violence rather than perpetrators (see https://www.mentalhealth.gov/basics/mental-health-myths-facts).  Also, while the Secret Service report linked above displays that 2/3 of individuals have "mental health symptoms" that does not mean that they have a diagnosis in the DSMIV or DSMV or that a psychiatric professional would diagnose them with a diagnosis after observing them.
In short, when it comes to shooting and violence, many culture's gender norms make it so primarily men are the perpetrators.
Answer: I think you have to look at the larger picture of gender and violence. Men appear more competitive than women.  It seems that just about anything can become a competition. They seem more concerned with pride and proving themselves, and seem to have more of a tendency towards dominance
They start almost all the wars. They are the rapists. Even in junior high, you don't see girls dunking each other's heads in the toilets. Males have quite a range of violent behavior and need for dominance.
You do see women verbally arguing with each other, and on rare occasions fighting which rarely ends in serious physical danger or murder. You do see women caring for children and their elderly relatives, and very aware of their needs more than you see this in men. Carol Gilligan, a Harvard professor wrote about the gender difference as justice versus care, where men seek justice. So each has a role in preserving and protecting society, Ironically, men may seek justice through the violence of war.
Men's violence is more excused. Concepts like boys will be boys, football, wrestling, and "taking it outside" allow men sanctioned violence. It seems when we say our society is or has become more violent, we tend to blame that violence on all of society, rather than noting that it is men who take assault weapons into crowds and murder large numbers of people in malls, schools and churches. The serial killers seem to be men. It looks like there is a genetic component, a socialization component, and a society willing to attribute men's violence to the whole society, rather than focusing on that specific group, so it might be more properly addressed. The same genetics that lead men to be destructive, seem to often lead them to be heroic. There are many men who rush into burning buildings and hostage situations. Maybe women have fewer opportunities, as they are not often firefighters or police officers,
Comment: There seems to be a little over-generalisation going on and some gender bias here. Most men don't arm up and commit mass shootings. Most men don't rape, and some women are known to be sexually violent. Even Carol Gilligan, who you referred to, points out that men and women use both moral orientations https://www.jstor.org/stable/23086381. Where men can seem more physically violent, women are known, quite often, to be extremely violent verbally, which can be just as damaging through mental pathways leading to suicidal ideation in their victims (see e.g. https://doi.org/10.1136/adc.2008.143156)
Comment: *"Sticks and stone will break our bones"*, but words, too, can damage and hurt. They can kill the spirit, doing far more harm than sticks and stones ever could. Have you also considered the social contract with men that they must protect women and girls being that they are "the weaker sex"?