When to use Student's or Normal distribution in linear regression?

Question: I am looking at some problems, and in some, to test the coefficients, sometimes I see people using Student's distribution, and sometimes I see Normal distribution. What is the rule?
Comment: This is not an answer, but do note that the $t$-distribution approaches the normal distribution as the degrees-of-freedom parameter $\nu$ grows larger. Past $\nu \geq 30$, there is no appreciable difference, particularly in most hypothesis-testing frameworks. The limiting behavior is "from above" in the sense that the if $T \sim t_{\nu}$ and $Z \sim \mathcal{N}(0,1)$, then $|T|$ is [stochastically larger](http://en.wikipedia.org/wiki/Stochastic_ordering) than $|Z|$.
Answer: The normal distribution is the large sample distribution in many meaningful statistical problems that involve some version of the Central Limit Theorem: you have (approximately) independent pieces of information that are being added up to arrive at the answer. If parameter estimates are asymptotically normal, their functions will also be asymptotically normal (in regular cases).
On the other hand, the Student $t$ distribution is derived under more restrictive conditions of i.i.d. normal regression errors. If you can buy this assumption, you can buy the $t$-distribution being used for testing hypothesis in linear regression. The use of this distribution provides wider confidence intervals than the use of the normal distribution. The substantive meaning of that is that in small samples, you need to estimate your measure of uncertainty, the regression mean squared error, or the standard deviation of residuals, $\sigma$. (In large samples, you kinda have as much information as if you knew it, so the $t$-distribution degenerates to the normal distribution.)
There are some occasions in linear regression, even with finite samples, where the Student distribution cannot be justified. They are related to violations of the second order conditions on regression errors; namely, that they are (1) constant variance, and (2) independent. If these assumptions are violated, and you correct your standard errors using Eicker/White estimator for heteroskedastic, but independent residuals; or Newey-West estimator for serially correlated errors, or clustered standard errors for cluster-correlated data, there is no way you can pull a reasonable justification for Student distribution. However, by employing an appropriate version of asymptotic normality argument (traingular arrays and such), you can justify the normal approximation (although you should have in mind that your confidence intervals would very likely be too narrow).
Comment: (+1) I love the implication, in the opening of the third paragraph, that linear regression is done with infinite (non-"finite") samples!
Comment: @whuber: :) In my books, if it is normal, it must be relying on CLT or something asymptotic. Otherwise, it makes as much sense as [this](http://stats.stackexchange.com/questions/726/famous-statistician-quotes/4301#4301).
Answer: I like the representation of the student t distribution as a mixture of a normal distribution and a gamma distribution:
$$Student(x|\mu,\sigma^2,\nu)=\int_{0}^{\infty}Normal\left(x|\mu,\frac{\sigma^2}{\rho}\right)Gamma\left(\rho|\frac{\nu}{2},\frac{\nu}{2}\right)d\rho$$
Note that the mean of the gamma distribution is $E[\rho|\nu]=1$ and the variance of this distribution is $V[\rho|\nu]=\frac{2}{\nu}$.  So we can view the t-distribution as generalising the constant variance assumption to a "similar" variance assumption.  $\nu$ basically controls how similar we allow the variances to be.  You also view this as "random weighted" regression, for we can use the above integral as a "hidden variable" representation as follows:
$$y_i=\mu_i+\frac{e_i}{\sqrt{\rho_i}}$$
Where $e_i\sim N(0,\sigma^2)$ and $\rho_i\sim Gamma\left(\frac{\nu}{2},\frac{\nu}{2}\right)$ all variables independent.  In fact this is basically just the definition of the t-distribution, as $Gamma\left(\frac{\nu}{2},\frac{\nu}{2}\right)\sim \frac{1}{\nu}\chi^2_\nu$
You can see why this result makes the student t distribution "robust" compared to the normal because a large error $y_i-\mu_i$ can occur due to a large value of $\sigma^2$ or due to a small value of $\rho_i$.  Now becuase $\sigma^2$ is common to all observations, but $\rho_i$ is specific to the ith one, the general "common sense" thing to conclude is that outliers give evidence for small $\rho_i$.  Additionally, if you were to do linear regression $\mu_i=x_i^T\beta$, you will find that $\rho_i$ is the weight for the ith observation, assuming that $\rho_i$ is known.:
$$\hat{\beta}=(\sum_i\rho_ix_ix_i^T)^{-1}(\sum_i\rho_ix_iy_i)$$
So an outlier constitutes evidence for small $\rho_i$ which means the ith observation gets less weight.  Additionally, an small "outlier" - an observation which is predicted/fitted much better than the rest - constitutes evidence for large $\rho_i$.  Hence this observation will be given more weight in the regression.  This is in line with what one would intuitively do with an outlier or a good data point.
Note that there is no "rule" for deciding these things, although mine and others response to this question may be useful for finding some tests you can do along the finite variance path (student t is infinite variance for degrees of freedom less than or equal to two).
Comment: +1: this looks right, but I don't think you should say a mixture of a normal and a gamma distribution, but rather a normal-gamma–normal compound distribution and motivate this construction by saying that the normal-gamma distribution is the conjugate prior of the normal distribution (parametrized by mean and precision).
Comment: Yeah, point taken about the mixture - although I can't think of a non-clumsy way to correct it right now.  Note that this form is not unique to conjugate distributions - for example if we replace the gamma pdf with an inverted exponential pdf, we get the laplace distribution.  This leads to "least absolute deviations" instead of least squares as a form of robustifying the normal distribution.  Other distributions would lead to other "robustifications" - perhaps not as analytically pretty as student t though.
Comment: If X is a standard normal random variable and U is a chi-squared random variable with ν degrees of freedom, then ${\displaystyle {\frac {X}{\sqrt {(U/\nu )}}}}$ is a Student's t (ν) random variable. [here](https://en.wikipedia.org/wiki/Relationships_among_probability_distributions).


Printing on Hahnemühle Photo Rag 308 and 500 gsm with Canon PIXMA PRO-100

Question: I am considering to purchase the Canon PIXMA PRO-100 and would like to use the Hahnemühle Photo Rag 308 and 500 gsm for my primary media.  I've read a few reviews where users claim that this particular printer tends to jam up when really thick media is used.  Has anyone used the Photo Rag 308 and 500 gsm or a similar art paper with this printer?
Answer: Haven't used them, but the Canon user manual for the Pro-100 states:

Paper Weight / Thickness
You can use paper in the following weight ranges.
rear tray: From 17 to 28 lb (64 to 105 g /m2) (plain paper except for Canon genuine paper)

You can use non-Canon genuine specialty paper that is up to 53 lb (200 g /m2).

Do not use heavier or lighter paper (except for Canon genuine paper), as it could jam in the printer.
manual feed tray: From 4 to 23.6 mil (0.1 to 0.6 mm) (up to 93 lb (350 g /m2))
Do not use paper thicker or heavier than this, as it could jam in the printer.

So, the Pro-100's rear tray can only take up to 200 gsm, and the manual feed slot can take from 0.1 to 0.6mm thickness and up to 350 gsm.
Hahnemühle's website gives the following thicknesses for their Photo Rag paper:

308 gsm: thickness: 0,48mm  (18 mil)
500 gsm: thickness: 0,80mm  (31 mil)

So, it looks like, from the specs, that the 308 gsm Photo Rag is within specs for use with the Pro-100's manual feed tray (but not the rear tray), and that the 500 gsm is too thick and too heavy and could cause a jam.
Practical experience may be different.


Allow users to upload the same document to multiple folders

Question: We have a sharepoint site with multiple external organisations who each have access to one folder only. On some occasions, our users will want to share the same document with all organisations. Is there a way they can do this with one upload rather than multiple? In other words almost a drop down menu where they can select the multiple organisation folders they want to share these documents with.
Answer: Just at the top of my head, this can probably be achieved via a custom column in the Document Library and also Power Automate to do the file copying.
SharePoint changes
Document Library changes: Add a new column to store list of organization values
Power Automate Flow

Trigger - When a file is created
Get custom file property that you created earlier which is the list of organization values
Loop through the values in the custom file property
For each value, "Copy File" to respective document library.

Something like below:
Answer: You can upload the same document in multiple folders using the PnP Powershell below.
PnP Powershell code:
<code>#Config Variables
$SiteURL = "https://yourdomain.sharepoint.com/sites/xyzax-version1/"
$SourceFilePath ="C:\PnP powershell.txt"
$DestinationPath = Import-CSV -path "C:\test.csv" -Header("DestinationPath") #Site Relative Path of the Library

#Get Credentials to connect
$Cred = Get-Credential

#Connect to PnP Online
Connect-PnPOnline -Url $SiteURL -Credentials $Cred

#powershell pnp to upload file to sharepoint online
foreach ($Url in $DestinationPath )
{
Add-PnPFile -Path $SourceFilePath -Folder $Url.DestinationPath
}
</code>
Here are steps:
1.Enter all individual employee folders URL in a .csv file.
2.Form URL as table(Title is "DestinationPath")

3.Replace code: $SiteURL, $SourceFilePath, $DestinationPath

If the answer is helpful, please click "√" on the left panel of the answer and kindly upvote it.


Downloading things

Question: How do I download things to my computer with Ubuntu?  Every time I go online to download something like Adobe flashplayer or Java, it goes into my download folder.  I don't know what to do with it after that.  I can't activate whatever it is I want to download!  Is there an equivalent to an exe file?
Comment: I think that you are confusing *download* with *install*, isn't?
Comment: and also remember 1 thing: do NOT download the Windows version. Things you are talking about (java and flash) can be installed from Ubuntu Software Center or from a PPA. There is not really a need to download the software itself.
Answer: You may be confusing "downloading" something with "installing" software.
Most normal software you would want to install is available in the ubuntu Software Centre which can be easily searched. If you want to install software that isn't in the Software Centre, your best bet is to try to find a "repository" from the software developer that is compatible with the version of ubuntu you have installed and add then add it to your system as a location for Software Centre to look.
While ubuntu does have the equivalent of an install file (exe or msi) in Windows, you should use them as a last resort. The file you're looking for is a .deb file and you will need to make sure it's compatible with your ubuntu version and system architecture before you use it.
This is really quite a big topic and there's a whole lot more I haven't covered. Here's some things to read:
https://help.ubuntu.com/community/InstallingSoftware
https://help.ubuntu.com/community/Repositories/Ubuntu

Downloading things


Is this a conditional promise?

Question: Assalamualaikum may Allah SWT bless you for helping me out because I am in great confusion. Once when I was being very guilty about my actions ( I was addicted to some sort of p***) I said to Allah that please don't let anyone see the phone's history (it was a family phone ) and I said I will never repeat this action again please don't let anybody get to know about it I promise I will never do that again. So does this statement make it a conditional vow or promise? Does it mean if Allah will listen my dua then I cannot return to the same sin again? meaning will I be breaking a promise or vow?
Answer: From the nature of this scenario, it probably is a promise / agreement between you and Allah. However, if Allah decides that leaking this information is for your best, then he will do it. Only Allah knows best.
P.S.: You should also ask an Imam or another scholar about this as well, I am not that knowledgeable. And also, make dua and ask for forgiveness from this sin.

Is this a conditional promise?


How to transition between running along joists to running perpendicular

Question: Referring to picture provided, what is the best way to transition my SER cable from running with the ceiling joists to running perpendicular? I can't drill through every joist due to all the existing pipes, HVAC and wires. This 2-2-2-4 cable is feeding a sub panel in my attached garage, and where the cable is perpendicular through the last joist, it feeds directly straight into the garage.
Answer: The picture provided does not need a hole in "every joist" it needed one more hole in one more joist.
The best way to treat that problem is to drill that hole, missing the one visible or possibly more pipes invisible there. For instance, run left along the face of the joist-with-hole until past the pipe, then drill through joist-with-awkwardly-attached-cable where the pipe is not in the way.
If you have a long run (not pictured) where you need to run through many joists and have too many obstacles, transitioning to conduit or a conduit protective sleeve attached to the bottom of the joists is one of many methods, or building a lumber protective structure under the joists (ultimately a soffit, if you finish the basement ceiling) is another.
However 334.15(c) permits direct attachment to the joists for that cable size without additional protective measures. It might not be best, but it's adequate for code purposes.
Comment: That may be easiest if you run the cable on the invisible face of *joist-with-awkwardly-attached-cable* rather than the visible face of *joist-with-hole* allowing you to use the full width of the joist bay to make the turn.
Comment: I mean, clearly one hole was drilled, seems like it'd be facile to drill another one!, right?
Comment: If I don't go crazy with the 90 degree direction change, I guess I could just run it along the joist in the picture that already has the hole drilled in it.
Comment: 334.17(B) specifies that minimum bend radius (not diameter) shall be 5 times the cable diameter so that's exactly how crazy you can go with the 90 degree bend.
Comment: Attaching cables such as that to the bottom of joists is not permitted by code where I live, because they are clearly "subject to damage".
Comment: Is there anything that says the cable has to penetrate the joist at 90º?  You could drill your hole at 45º (as long as the length of the hole is less than the 1/3 joist height), offset to the left of the 90º hole in the joist by the wall.


Subscribe to changes of an arbitrary web page

Question: There is a plain (html) web page, which occasionally gets updated with text information. Is there any way to get notified (by any means) if this particular web page content is changed whereas website doesn't provide any subscription mechanism?
Comment: periodically programatically scrape the site, record the MD5/SHA sum, compare to previous invocation and send an alert/email when it changes.    In Linux you can use curl or wget or a number of other tools, and wrap it in a trivial bash script.
Answer: Linux (and WSL)
You should be able to use the following even in the  Windows Subsystem for Linux (WSL)
Under Linux you can use wget with the -N option (timestamp) from the directory in which you have previously downloaded the page.
wget -N  https://example.com/your_page.html

It will download only a new version of the file, asking to the server the timestamp. wget will give a different output in case the download succeed or not.

File downloaded

HTTP request sent, awaiting response... 200 OK

Not downloaded because it has the same timestamp

HTTP request sent, awaiting response... 304 Not Modified

So at the end you can build your command-line or a script similar to
wget -N https://example.com/your_page.html 2>&1 \
      | grep "304 Not Modified" >/dev/null \
      && echo "Not downloaded, old one" \
      || echo "There is a new file"

Notes:

-N activate the timestamp usage
2>&1 redirect the standard error to the standard output, needed for the following grep
| grep "304 Not Modified" pipe the output of the previous command (wget) as input of grep that selects the line with "304 Not Modified". It exit with status 0 (true) if it founds a match.
&& logic and (aka then) execute the following command if the previous exit status is 0. You can omit this part.
|| logic or (aka else) execute the following command if the exit status is not 0.
each \ is used in the shell to go to a new line and  it must be the last character of the line
change echo this or that with your command...

Final remarks
With wget -O - | md5sum you can create a checksum to reuse the next time without the need to keep a local copy...


How to allow only one mode of resonance in a cantilever beam

Question: So I am designing a MEMS structure consisting of cantilever arrays.
For my problem, I want the cantilevers to vibrate only at their 1st mode of resonance and reject all the other modes of resonance passively.
Is there anyway I can achieve this mechanically, that is by modulating the cantilever structure?
Comment: What reading have you already done on the fundamentals of cantilever resonance? What analysis have you already done on the significance of the factors that control it? I ask because structure, material, and driving power can be equally important to consider. Showing what you already understand of this yet why you only want to consider structure will help generate a better answer.
Answer: It is physically impossible to make a real-world structure with only one mode of vibration, though it may be possible to design something with only one mode in the frequency range that you are interested in.
But if you are designing a MEMS system, this is probably irrelevant, because you can easily filter out the response from the unwanted modes. Any MEMS system is likely to have enough computing power to do some real-time digital filtering of the signal from the MEMS transducer.


Can a conference paper with all weak reject get accepted at the end?

Question: Those who have experience in setting in conference program committees: can a paper with all "weak reject" reviews get accepted for publication at the end?
Comment: If they don't have enough papers, then yes. This is more typical of some workshops. Good conferences mostly have much more papers submitted than time slots for talks. This is what defines the acceptance rate and why it is an important metric.
Comment: In case you refer to a proceeding it would be better no to publish. Better go through what caused the weak rejection. I add this because in my field submitters are never aware of the referee procedure for their work to get a slot as talk or poster.  This is just after conference, for the corresponding proceeding manuscript.
Answer: If nobody wants to accept the paper, it shouldn't get accepted.  This holds even for workshops and symposia with very loose standards, as the reviewers should be making their judgements based on those standards (e.g., "this paper is pretty half-baked and poorly written, but we're just looking for interesting ideas to discuss, so it's a weak accept").
Thus, the answer ought to be no, it cannot be accepted (except in certain unusual cases, such as the organizers deciding there is a hidden nugget with value enough for shepherding to improve the paper).
A struggling, eccentric, or fraudulent organization, however might just not care, and accept it anyway. If you have this happen to a paper of yours, you may wish to reconsider whether you really want to publish it in that venue.


Are triangulated equivalence detected at compact level?

Question: Suppose that $D$ and $E$ are compactly generated triangulated categories, even algebraic (i.e. equivalent to derived categories of small dg categories) if we want, and asume that their subcategories $D^c$ and $E^c$ of compact objects are triangle equivalent. Are $D$ and $E$ triangle equivalent?. By Theorem 9.2 of Keller's 'Deriving dg categories', we know that the answer is 'yes' when either $D$ or $E$ is the derived category of (the category of modules over) a small $k$-linear category, but I do not know the general answer.
Any help would be highly appreciated.
Comment: Welcome to MathOverflow, Manuel. The site supports basic LaTeX formatting ("MathJax", technically). I've added formatting to your question to make it a little easier to read: I hope you don't mind.
Comment: I fear that you cannot really write down a functor $D \to E$ because homotopy colimits are not functorial on the level of triangulated category. If you have instead an equivalence between stable infinity categories of compact object, you obtain an equivalence between $Ind(D^c)$ and $Ind(E^c)$, which agree with $D$ and $E$ when the latter are compactly generated stable infinity categories.
Comment: Dear Jeremy,  Thank you very mucy for adding TeX formatting to my question.
Comment: Thank you Lennart. Your comment is very helpful for me. I had the impression that going to the context of infinity categories or that of (Grothendieck) derivators, the answer might be 'yes'. But still, without adding further structure, I would like to find  examples beyond the derived categories of rings (with several objects), for which the answer to my question is positive.
Answer: Consider the case where $D$ is the ordinary stable homotopy category of spectra, and $E$ is assumed to have all coproducts (which is clearly a necessary condition), and we also assume that $D^c\simeq E^c$ as tensor triangulated categories.  It is an old conjecture of Margolis that this forces $D$ to be equivalent to $E$, and I believe that this is still open in full generality.  In both $D$ and $E$ one can define a square-zero ideal of phantom maps.  Hovey, Palmieri and I proved that $D/\text{Ph}_D\simeq E/\text{Ph}_E$ and that $\text{Ph}_D\simeq\text{Ph}_E$ as a module over this quotient.  Schwede and Shipley proved in https://arxiv.org/abs/math/0108143 that $D\simeq E$ provided that $E\simeq\text{Ho}(E_0)$ for some Quillen model category $E_0$.
Comment: Thanks Neil. Although my interest is more on  algebraic triangulated categories, your information should be helpful. Hopefully, some of the proofs on the two references that you mention  admit some adaptation.


During jailbreaking iPhone 4 shuts down and can't start again

Question: I have an iPhone 4 which I tried to install Cydia on, and everything worked well. However, when I tried to put it in DFU mode, it shuts down. I attempt to power it back up but nothing happens. What could be causing this problem?
Answer: Try plugging in to computer then press the home and power button, it usually worked for me.
Comment: I agree, on this newest Evasi0n jailbreak I noticed that recovery mode works best if its already plugged in to the computer. Home and power button, release power when apple logo comes up and hold home button for another 8-10 seconds. It should connect then!
Answer: It hasn't shut down - DFU mode displays a black screen, so you might think it has shut down. Go ahead and do whatever thing you wanted to do in DFU mode.


Turning off specific hard drives due to inactivity

Question: Is there a built-in tool in Windows 7 (or perhaps any software out there) that can turn off SPECIFIC hard drives due to inactivity? I have a few backup hard drives that I don't want spinning when they are not being backed up to. I know that there's a general setting in Windows 7 that affects all hard drives, but I want to be able to apply this setting to only specific ones. Thanks
Answer: If your drives use the SATA interface, try USB Safely Remote.


Custom Authorization Attribute

Question: I am implementing a CustomAuthorizeAttribute. I need to get the name of the action being executed. How can i get the name of current action name getting executed in the AuthorizeCore function which i am overriding ?
Comment: Why do you need the name of the action? One of the points of implementing a custom authorization attribute is so that it can be done independently of which action is being executed.
Comment: @Daniel you might want to create Authorization based on a action name convention. Altough this might be better achieved using some kind of IFilterProvider.
Comment: @Daniel, Hi, I want to map certain actions to a Role. Hence the requirement. I am basically mapping users to roles and roles to actions and i validate if the user has rights to execute an action based on his role.
Answer: If you're using cache (or have plans to), then overriding AuthorizeCore, like Darin Dimitrov shows in this answer is a much safer bet:
protected override bool AuthorizeCore(HttpContextBase httpContext)
{
    var routeData = httpContext.Request.RequestContext.RouteData;
    var controller = routeData.GetRequiredString("controller");
    var action = routeData.GetRequiredString("action");
    ...
}

The reason for this is documented in the MVC source code itself:
AuthorizeAttribute.cs (lines 72-101)
public virtual void OnAuthorization(AuthorizationContext filterContext) {
    if (filterContext == null) {
        throw new ArgumentNullException("filterContext");
    }

    if (OutputCacheAttribute.IsChildActionCacheActive(filterContext)) {
        // If a child action cache block is active, we need to fail immediately, even if authorization
        // would have succeeded. The reason is that there's no way to hook a callback to rerun
        // authorization before the fragment is served from the cache, so we can't guarantee that this
        // filter will be re-run on subsequent requests.
        throw new InvalidOperationException(MvcResources.AuthorizeAttribute_CannotUseWithinChildActionCache);
    }

    if (AuthorizeCore(filterContext.HttpContext)) {
        // ** IMPORTANT **
        // Since we're performing authorization at the action level, the authorization code runs
        // after the output caching module. In the worst case this could allow an authorized user
        // to cause the page to be cached, then an unauthorized user would later be served the
        // cached page. We work around this by telling proxies not to cache the sensitive page,
        // then we hook our custom authorization code into the caching mechanism so that we have
        // the final say on whether a page should be served from the cache.

        HttpCachePolicyBase cachePolicy = filterContext.HttpContext.Response.Cache;
        cachePolicy.SetProxyMaxAge(new TimeSpan(0));
        cachePolicy.AddValidationCallback(CacheValidateHandler, null /* data */);
    }
    else {
        HandleUnauthorizedRequest(filterContext);
    }
}

Even if you didn't plan on using cache, those two magic strings seem a small price to pay for the peace of mind you get in return (and the potential headaches you save yourself.) If you still want to override OnAuthorization instead, you should at least make sure the request isn't cached. See this post by Levi for more context.
Answer: You can get the Action Name like this:
public class CustomAuthFilter : IAuthorizationFilter
    {
        public void OnAuthorization(AuthorizationContext filterContext)
        {
            filterContext.ActionDescriptor.ActionName;
        }
    }

EDIT:
If you want to inherit from the AuthorizationAttribute you'll need to override the OnAuthorization method.
public class CustomAuthAttribute : AuthorizeAttribute
{
    public override void OnAuthorization(AuthorizationContext filterContext)
    {
        base.OnAuthorization(filterContext);
    }
}

Comment: Magic strings !!  yes you are right. I will go with filterContext.ActionDescriptor.ActionName;
Comment: Thanks. I guess i could also use var controllerName = filterContext.RouteData.Values["controller"];
            var actionName = filterContext.RouteData.Values["action"];
Comment: You could. You're using magic string which is ALWAYS more error prone and I'm also sure what would happen when calling ChildActions from a view...

Custom Authorization Attribute


Possible up-vote abuse?

Question: The question I came across in New Question queue, looked so horrific I didn't dare rate it; I just put in my rash opinion as a comment.  I glanced at it later, and it had 2 up-votes.  Knowing a bit about folks perusing new questions, I'm kind of surprised it got up-voted twice in a day.  Did the poster have some friends up-vote it perhaps?
Post: Optimizing queries using indexes
Answer:
The question I came across in New Question queue, looked so horrific...

Horrific? In my estimation, that question is above average for its type.
It explains the problem clearly, admits it is coursework, provides DDL and sample data, shows what they have tried, and why it seems inadequate. Given that we allow 'homework' style questions, what more could we ask of the querent here?

...I didn't dare rate it

Why ever not? The voting system exists for many reasons. One is to give feedback to the writer - a down vote suggests something ought to be improved in someone's opinion. Voting on questions is also free. I am honestly at a loss to comprehend the source of your fear here.

I just put in my rash opinion as a comment.

Yeah, well please don't do that. It's counterproductive for many reasons, see Is the comment-only answer acceptable? in the FAQ.
Your 'comment' would be better as an answer (of the frame-challenge variety), which people could then vote on as they feel it deserves (up or down).

Did the poster have some friends up-vote it perhaps?

Not that I can see. It seems two other people disagreed with your assessment and found it to be worthy of an upvote.

Returning to the question of the quality of the question, or its suitability for the site. As far as I can discern from your comment, it seems you disagree with the question they have been set, or the way it ought to be answered.
You might have a point there, but it's one the asker is unlikely to be able to 'fix'. The question they have been set is what it is. You might not like it, or think it is relevant given your particular real-world experience. Well, fair enough.
Comment: Very helpful.  This will help me in reviews. Thanks!
Answer: I, too, often wonder why people upvote questions that to me seem to be of low quality. But then I remind myself: It's the internets; people upvote junk all the time for whatever reasons. If you don't like the question, downvote and move along. Or just move along. Your time is not worth somebody's two extra unicorn points.
Comment: I upvoted this answer even though I hate it. I just really love mustaches.
Comment: Question up votes award 10 points these days. It used to be 5.

Possible up-vote abuse?


Send a Push Notification from a device to another device

Question: I have setup Firebase authentication in my game for Android. I need to implement a feature in my Android game, where a user can challenge another player. I need to implement it this way: The user is shown the list of all users registered on Firebase on the Game. To any user, he can tap on a button for respective user to send a challenge. When, he taps, a push notification is to be recieved by that user. When he taps on the notification, he is redirected to a specific part of the game. Maybe a specific scene for now and he is shown there the Challenger's name.
I have explored the Firebase documentation, but it does not provide information for client-client push notifications.
Maybe there are other options available like GameSparks and OneSignal. But I don't know if there is a requirement of own Server for implementing it.
Comment: Have you considered the potential griefing implications of allowing any user to cause push notifications to be sent to any other user, even if they have no pre-existing relationship (such as being on each others' friends lists or being in a match together currently)?
Comment: @DMGregory I know this is not the ideal way. I'm just working to implement this feature. When I'm done with it, I'll be restricting to only friends.
Comment: Note that every push notification is ultimately initiated server-side. Your user can send a message to a server asking it to trigger a push notification to another user, without the notification ever travelling client-to-client per se.
Comment: Alright... Then my question would be how to implement this 'server' functionality on Firebase. You are welcome to guide me about that in Answer.
I've read somewhere I need to write 'function' on firebase. But what will be exactly the way to do it. Or what prequisites I need to know before jumping into it.
Note: I'm sorry if my terms disturb you. I'm totally noob with Firebase.
Answer: Don't send the notification directly. That isn't possible. However, you can deal with the notifications like this:
One user sends the challenge to the other. I'd assume it could be as simple as a string saying that it is a challenge and a couple of strings with information about the sender. Then, all you have to do is tell the receiving end to notify the user every time it receives a challenge. This way, all the code is local, and the information being sent is nice and simple.
In short, send the other device the challenge, which then prompts the user with a notification. The rest is all handled locally. Hope this helps!
Comment: This answer would be better if it described or showed code explaining how to send such a challenge to a specific user, and how to receive and act on such a challenge. How would the app be able to respond to the challenge if it's not currently running? (Since that's what push notifications do: they notify you of something even when you're not in the app).


Leaf too long? Honey mango

Question: The seedling is not even 3 inches tall and has a leaf bigger than itself. This is a polyembryonic honey mango seed. It gets 1 hour of sunlight daily and the pot has no drainage holes. I also am probably overwatering it. I water it once a day.
Comment: Good question; if could include length of the leaf, overall height, current watering amount, current nutrient type, amount & frequency, size of container, hours of diffuse light per day, age of the seedling, average daytime temperature, and average night time temperature, could also be helpful. We encourage you to take the [Tour], and browse through the [Help] to learn more about how the site works! Thank you! Welcome to the site!
Answer: I wouldn't be concerned about the size of that one leaf, it looks healthy, but it is a concern that you have it in a pot without drainage holes. Since you mention it yourself, you probably already know it shouldn't be in something that doesn't have drainage holes, so I'd recommend you move it into a pot with holes; the difficulty is deciding when to do that so as not to cause damage to fragile new roots. You may need to wait until it grows on a bit more, unless it starts to show problems related with poor drainage.
Information here about growing mango from seed - you will need to scroll down a fair way to get past the 'how to germinate' section https://empressofdirt.net/grow-mango-seed/
Comment: I just put it in a pot with drainage holes, I broke the the tip of the longest root but it was just the very very tip but it was still hanging on by a thread.
Comment: fingers crossed then!

Leaf too long? Honey mango


Baking after rising

Question: I have risen my dinner rolls a second time. Now they have plumped up in their baking pan. How quickly do I need to bake the bread once the bread has risen a second time?
Comment: Do you mean how long must they bake, or how long can you wait until you begin to bake?
Comment: It depends on the size of the rolls, and the temperature of the oven. You are usually looking at around 25-30 mins at 400F
Answer: Once you have gotten the bread to rise a second time, you want to get it in the oven ASAP after it has risen to the level you want.  You could always deflate it, and let it rerise, if you've gone past what you wanted, but your yeast may not have enough energy to go a third time.

Baking after rising


weird symbols when opening a file written in arabic

Question: When I open a TeX file containing arabic letters, I only see weird letters. I tried WinEdt, Emacs, TeXMaker. But when I open the same file using Notepad, it looks OK.  What shoud I do?
Comment: Make sure that the encoding that is used by the editors are inline with the encoding that the one used by Notepad. TeXnicCenter still doesn't support Unicode in a convenient way.
Comment: Instead of the "thank you", which is nice of course, upvote a correct answer and, especially if it solved your problem, accept it please, thanks!
Answer: You need to use an editor that can handle and display Unicode-encoded characters. The ones you mention -- other than notepad -- are probably not Unicode-aware. Actually, the very latest version of Texmaker is Unicode-aware; you may be using a somewhat obsolete version of that program.
Try opening your file with TeXworks, TeXshop (if you use a Mac), or any other editor that's Unicode-aware, and you should be in business.


Converting Chinese spouse visa to work visa

Question: I am a Pakistani passport holder. I'm currently in China on a spouse visa. I want to apply for a work visa now. Can I go to Hong Kong to apply for this visa or do I need to go back to Pakistan and apply for a work visa from there?
Answer: If you have all the paperwork for your Z visa, you can go to Hong Kong, and apply either directly, at the China Resources Building in Wanchai, or through a travel agency. Note that you won't be converting your spousal visa. You will ce cancelling it, and applying for a new visa, the Z visa.
However, as a Pakistani, you need a visa to go to Hong Kong. So I'm not sure it is worth the effort.
I have heard of travel agencies in Shenzhen, with partners/branches in HK, that can take your passport and documents, send it to HK, process the application, and return the passport with the visa and stamp. Not sure if that still works. Worth enquiring though.


If oxygen were pumped into space where would it go?

Question: If an astronaut went into space with a sealed container of oxygen and opened it up in space and let all the oxygen go, what would happen to it? would it all just dissipate into some other particle or matter or would it just stay there until something consumed it
Comment: I'm voting to close this question as off-topic because this is not about astronomy as defined in the help centre.
Answer: Gases tries to occupy all the volume of the container in which they are encased in equilibrated pressure. This happens because the gas molecules are always colliding and kicking each other in a 3D high velocity brownian motion. The result is that the gas molecules occupies all the container's volume homogeneously.
So, if the sealed container is opened up in space, the oxygen would quickly leak out, because the molecules near the vacuum edge would be instantaneosuly kicked out by the gas innermost molecules. This would happen rather quickly and in a chained manner, but is dependent on the size of the open hole. Macroscopically, the result would be that all the gas would be running out in a form of a wind/jet out of the open hole into outer space. This would only stop when all the molecules becomes too far apart from each other to have any further intermolecular interaction.
This means that the oxygen (or any other gas) would be dissipated into outer space. The gas molecules would initially be spread out by the intermolecular collisions and then would go outwardly due to the momentum acquired from each individual gas molecule.
When freed in outer space, each molecule would eventually reach something else to interact, so they could be attracted and retained by some gravity well (most likely from a planet or moon), or interact with some magnetosphere (if near a planet) or interact with some other molecule wandering around, or with a cosmic ray or be catched by the solar wind particles (or any of the equivalent if this happens near some other star).
If this happens in intergalactic space where there is no body with appreciable gravity or magnetic field nearby, no stellar wind and the cosmic rays are very sparse and rare and the very few that exists are randomly directed, then the molecules would just spread out in virtually linear trajectories and travel the intergalactic space lonely, quietly and virtually undisturbed for some billions or trillions of years. In their journey, each molecule would only very occasionally interact with some other molecule (likely to be hydrogen) or some other lost particle wandering around.
Comment: If your sealed container is big enough and under enough pressure, at some point the gas will become self-gravitating. It's been some years since I did the calc, but IIRC, if you were to fill the solar system with gas at 1 atmosphere pressure out to the distance of Pluto, you'd end up with a black hole.
Comment: What we consider "breathable" air has an average individual molecular velocity of about 700 MPH.   Rapid expansion of gas can have a cooling effect, but it would still likely fly apart at some 400 miles per hour as a very rough guess.   in 1 second, your gas would have spread out to a radius of over 500 feet, so it tends towards a near vacuum very quickly.   Curiously, if you were to release a container of gas and you had a fellow astronaut near by, you might watch him get blown away from you, not at super high speed, but visibly pushed.
Comment: @WayfaringStranger Yes, I am talking about everyday containers, not something big and massive enough to have any non-negligible self-gravity.
Answer: It's sort of like a pool and water: a big empty pool is space, and water is air; if you pour one drop of water in the pool, that's not going to fill it up. Instead, the water tries to fill the pool evenly. Hope this helps/helped!


How do I enable horizontal two-finger scrolling on Deepin?

Question: I have a touchpad on my laptop that supports two-finger scrolling. I checked the Deepin control center for the setting but I can only find natural scrolling. Can I enable horizontal two-finger scrolling in Deepin?
Comment: I'm using Ubuntu 17.10 official. I just installed Deepin alongside the Gnome desktop environment.
Answer: These settings are not in the control center by default. The solution is to edit the setting in the Dconf Editor program. Run the following command:
sudo apt install dconf-editor

Ender your password and hit Enter or Return on your keyboard.
Next, open Dconf Editor either by running dconf-editor in the terminal or opening it in the application menu.
Now you need to navigate to com>deepin>dde>touchpad and enable the option that says "horiz-scroll-enabled." It should look like this:
Image of Dconf Editor settings
Now you can use horizontal scrolling!
Comment: @Maxwells.c you can use: ``gsettings set com.deepin.dde.touchpad horiz-scroll-enabled true``
Comment: It worked thank you! Is there an command to disable/enable touchpad on terminal?
Comment: can not find `deepin` under `com` or anywhere else


I want to find similarity for 20 organisms on 25 parameters? How to do this ? Any software is available for this?

Question: How to find similarity  for 20 organisms on 25 parameters? How to do this ? Any software available for this?
Answer: There is not a specific software available which calculates "similarity of organisms".
Yet the tag you provided leads to right direction. You are looking for measures of dissimilarity which are synonymously called distance measures.
(They are called measures of dissimilarity because a value of 0 signifies no difference.)
As you did not provide information about the scales of your parameters, you can not expect any concrete advise but a general answer.
The distance measures applicability is strongly restricted to certain scales. Whereas Euclidean Distance is widely used as a distance measure of numerical vectors, LCCS (Longest Common Subsequence) is used for string similarity and DTW (Dynamic Time Warping) is used for time-series.
You can find a good overview here, but you will have to provide more information about your parameters to get any concrete advice.
For implementation of any distance measure, you can mostly calculate it (such as Euclidean Distance) in Excel or will use a statistics tool like SPSS or - most recommended - you learn programming with R or with python, where a lot of libraries offer functions that do the work for you.


Fuzzy search in Asset Library

Question: Has anyone out there found a way to do a fuzzy search in the Asset Library? Currently, search only seems to return results that match the exact search query. Any help or plugin link is greatly apprecitated!
Answer: You can do a fuzzy search using the <code>*</code> character.  See here for a list of supported syntaxes.
Update:
As of Craft 2.5, you can enable fuzzy searching by default.
Comment: Not perfect, since it requires some client training...but good enough!

Fuzzy search in Asset Library


GUI doesn't start in Ubuntu server 16.04

Question: I had a VPS running Ubuntu server 18.04. When I installed the Ubuntu desktop, it worked fine. For a reason, I have to change the server to Ubuntu 16.04. When I try to install any desktop environment, Ubuntu, mate, kubuntu using the tasksel, it gets installed fine. After rebooting the server, the GUI doesn't start and only the command prompt is shown. Why is this happening and how could I fix this?
Answer: If you installed the GUI properly, then it should be an error at the lightdm.
Simple restart the lightdm service with the following command line:
<code>$ sudo service lightdm restart
</code>
If this keeps happening, you can try to reinstall your GUI or add a simple script at init.d that performs this action.


Choosing a Change Point Detection Algorithm

Question: I am currently working on a dataset that belongs to the restaurant and food delivery domain. After completing sentiment analysis and quantification, I now need to select a Change Point Detection Algorithm and detect a shift in the sentiment signal in the reviews on each category of restaurant. The signal will be a score that is the difference between the positivity and negativity of the reviews in a certain time frame.
I have considered 3 sentiments that are positive, neutral and negative and am thus contemplating the use of a multivariate time series. Since, I have the complete dataset at hand, I will be conducting an offline change point detection algorithm to detect a shift in the sentiment of the reviews in the pre-covid and post-covid time.
Please provide me some help as to how do I select an algorithm. I am very confused and a few factors to consider with links to resources are welcome.
Answer: The problem with Change point detection (or positive/negative trend detection), is that it depends on many things, including noise and sensitivity through time.
For instance, you cannot send an alert when the scores just started being negative in one day. You have to wait a few days to see if the trend is actually bad or not.
Consequently, you have to tune your model to define the "few days" and the "criticality".
That's why I would recommend to visualize every category trends by using a general score system (ex: sum of positive +1, neutral 0 and negative -1) and applying a smoothing function (ex: Kalman filter, with different noise reduction values). In this way, you should be able to detect the required sensitivity to detect when the situation is becoming critical or better.
For the smoothing function, you can use pykalman. After evaluating the right noise reduction and the right quantity of days N, you can apply the diff function to measure the difference of the filtered curve in the last N days.
Comment: Thankyou @Nicolas M so much for this. I really appreciate the time you took to help me on this. May I know if this is the criterion based approach? If yes, where do the other approaches like the Bayesian appear in your structure of thinking about it.
Comment: You are totally right to choose a mathematical criterion approach like Bayesian. But I would recommend first to observe the resulting curves and set a quantity of days that would "make sense" to you (could be more or less one week or two in your case).
Comment: Thankyou @Nicolas M so much for this.
Answer: You haven't specified the programming language you are using,so I'll provide different options.
The "ruptures" package in python would be a good option that would allow you to try out several different change point detection methods to your data. Before using it maybe it would be helpful to read this review, where the rupture methods are further explained - understanding the methods better will help you on the method selection.Another review paper that summarises and explains change point detection methods is "A Survey of Methods for Time Series Change Point Detection".
Alternatively if you are using R you could use the "changepoint" package (reference manual here)
Finally, from the description of the task I believe simpler change point detection methods could also work e.g. I would start with trying CUSUM method (available in R here and it is also integrated in the signal processing library in matlab)


Why does google play music conceal music files from the user on an android but not on a desktop computer?

Question: It seems inconsistent to me. I can do anything I want with files I bought from the play store as long as I'm on my computer. What's the point of restricting access on phones?
Answer: Google Music tries its best to hide the music files everywhere, but some cases (like connecting your phone to a computer) cannot be prevented. If you have rooted your phone you actually can access the files using the right tools.
It's part of fighting piracy: Google can't prevent piracy but they can make it as hard and inconvenient as possible so users will pay for their music.
Comment: Yeah but take phones out of the picture(I know this is an android forum). I can use a Mac to buy play store music. The files are right where I keep all my music on my mac. I was able to attach a google-purchased song to an email. So why different rules for different devices? Just wondering if anyone thinks that makes sense.
Comment: I think it's because Google is trying to push its music on de mand ("Spotify") service. If you can access the downloaded files, you can play all your favourite songs in the trial and keep the high quality audio files. It might also be a attempt at forcing users to use their music app, because you're less likely to switch to a competitor if it's hard to play your music in another app.


Can you build 10.7 applications with xcode 3?

Question: Can you build Mac SDK 10.7 applications without having Mac SDK 10.7? Such as with an old Xcode?
Or do you need a new one? And what's the earliest 10.7 SDK was included in Xcode?
Answer: No you can't.  In order to build apps for 10.7 you need the 10.7 library, which is only available in Xcode 4
Answer: You can build applications that run on 10.7, but in order to use 10.7 specific API calls you need to build with Xcode on 10.7 or later.
The earliest Xcode that included the 10.7 SDK was Xcode 4.2 for Lion. Note that the Snow Leopard version of Xcode 4.2 does not include the 10.7 SDK.
You can Drag and Drop older SDKs into newer versions of Xcode and usually get them to work, you can't go the other way.


How can I print the entire email message without Google chopping off some of the text?

Question: How can I print the entire email message without Google chopping off some of the text?  Usually less than all of the text is available for printing.
Answer: To print an email (or an entire conversation), you have to use Gmail buttons.
On the top right corner of the mail, there is this icon:
Click on the down arrow, then you will get a menu, just choose Print.
If you want to print the entire conversation, click on the printer icon  on the top right of the conversation (at the right edge of the title/label line).
You can find official documentation here.
If this is how you proceed, I can't help you, I haven't seen Gmail chopping my printed emails, even in case of (very) long emails.
Comment: This answer no longer answers the question as it is out of date.
Answer: This worked for me:

Click on the Icon for 'New Window' (upper right corner).  This reduces the space wasted on GMail headers.
In that new window, click on the "Print All" Icon (upper right corner).  This pops up a Preview with Print controls.
It may now say 'n sheets of paper' for an n-page email. If so you can print now.
If not, pulldown 'Pages' where it says 'All' and select 'Custom'.
Fill in the Custom range.  e.g 1-2.
Print.
Answer: I  select Shrink to 50% and the whole message is printed but obvious a lot smaller but very readable,
Answer: Click on print preview and select Shrink to fit under scale.  That solved the problem for me
Comment: This does not seem to be the problem. The asker is saying that Google is cutting the text, so that is not available to the printing software.


Controlling z-axis / bring-to-front at runtime (Delphi)

Question: In Delphi, how do you control a visual control's z-axis position at runtime?  e.g. How, programmatically and at runtime, do you accomplish the equivalent of (from the IDE main menu) "Edit -> Bring to Front" at designtime?
Comment: Not sure why no one else voted this up.  If it's worth answering, and not a duplicate on SO, it's worth voting up, isn't it?
Answer: TControl.BringToFront;  will usually do it.
Comment: You can look at their index in the Controls collection of their parent.
Comment: One of those "duh" moments here, apparently!  Thanks!
Comment: I was wondering if part of the question was missing or something {-:
Comment: Well, actually there is a small (much less important to the task at hand) "other half" -- on a "stack" of multiple controls, how does one determine what order they are in, without moving moving them / changing their order?
Answer: Just to add some information.
Controls are created in order (in the dfm file). The last control overlaps the first if they share part of the window. You can change the order by changing the order of the controls in the dfm file.
At runtime, you can change the order in the control list. But BringToFront will do this for you.


Accessing preexisting files in the mount point after mounting a filesystem

Question: Consider i have files in /mnt
i am mounting an nfs share to /mnt. After that i can find the nfs share contents in /mnt. But the preexisted files are missing. Is there any way to access both the preexisting and mounted files simultaneously?
Answer: Strictly speaking: No you cannot see Filesystem contents for lower mounted filesystems.
Nevertheless there are some solutions to the problems. The few that spring to mind being:

unionfs - takes few FS and presents a merged view of them
aufs - same thing as unionfs but more mature

Best practice is NOT to mount multiple filesystems on one mountpoint. If it is required to be accessible under a single tree either make directories inside the mountpoint and mount it there or mount them one under the other e.g. /mnt/nfs/< nfs share files >
Answer: I don't think you can. (see EDIT) The easiest way to do this is to create a subdirectory in /mnt and then mount the nfs share in the subdirectory. If, for example, you have the file1.txt and file2.txt in /mnt and you have file3.txt and file4.txt in the nfs share.
<code># mkdir /mnt/nfs
# mount <nfs-share> /mnt/nfs
</code>
Then
<code># ls /mnt
file1.txt file2.txt nfs
# ls /mnt/nfs
file3.txt file4.txt
</code>
EDIT: This was the closest thing I could find
What does Linux do with existing files in a mount point?
The general idea is to bind mount the parent directory of /mnt (i.e. /) so that the actual contents of /mnt can be accessed.
<code># mkdir /fakeroot
# mount --bind / /fakeroot
# mount <nfs-share> /mnt
</code>
Now:
<code># ls /mnt
file3.txt file4.txt
# ls /fakeroot/mnt
file1.txt file2.txt
</code>
If you want to see both the files in /mnt and the files in the nfs share in /mnt you will probably need a union filesystem.


Is it possible to manually change Network position of Network Analyst Stop without moving the stop?

Question: Network Analyst does not always choose the street I need.
When I get a new .mxd file, the Route territories have been defined and the Network Analyst Stops placed centered at the nearest network street (within the county parcel shape) or where the position has been marked from a previous visit.
When I Solve, the solution does not always take me to the correct road.
The Network Analyst Stop graphically represents the target, but sometimes the house and driveway are not on the same street. Sometimes the Property and Parcel are landlocked with no network street associated.
Without moving the stop from the house (target) to the driveway, how can I manually change the position on the network?
This is difficult in rural areas where the roads and driveways are thousands of feet apart, but also in downtown areas. A house at 101 5th Avenue will be routed around the corner to Baker Street.  Since there is a sidewalk easement on the front of the parcel, the Stop is closer to the side street than to its address.
Answer: I found the answer.
With the stop still located near Baker Street at the back of the parcel, add a stop at the desired location (Driveway at 5th Avenue).
With stop Selected, press 1 to show the Position on the Network street layer, adjust until best position is located.
Select Properties of NEW STOP and copy Source OID and PosAlong.
Source OID is the Network Street and PosAlong is a percentage of the stop's position from 0 to 1.
Enter these values into the Original Stop Properties and Network Analyst will Route to the Driveway on 5th Avenue instead of to Baker Street on the back of the parcel.


Speak with you later

Question: As far as I know, it is not common. However, I heard saying "speak with you later" instead of "talk to you later or bye" sounds rather formal and suits business conversations? Is it correct?
Answer: I don't think people only use talk to you later in informal speeches, I think people use it because it's the most proper way to say it.
Speak is used in sentences such as:

Do you speak English?
How many languages can he speak?
Does he know how to speak politely?

It may be understood as one hability, or capacity of talking in a specific way: Do you speak informally? - It's an hability of speaking informally.
All what is referred to a language will probably use the verb Speak -

He speaks very well
He likes to speak English as a beginner so that people will find him funny
He speaks the blind people-language
He speaks formally when delivering a speech.

Maybe "Speak to you later" may also be used in a high degree of formality.
Comment: You say "it's the most proper way to say it" - why? according to who? There's no indication as to whether Q or your answer is about American, British, or other form of English. At least in southern BrE, *Speak to you* later is not uncommon - either in person or over the 'phone. I would certainly use it sometimes, but couldn't give any firm explanation as to when I would use either form. I might be more likely to use *Speak ...* if I were intending to, say, confirm an arrangement or follow-up on the current discussion; and use *Talk ...* if the future occasion was merely to be a 'chat', etc..
Comment: @TrevorD - I'm afraid I can't look for any sources in Internet now, as I'm through the mobile app, it would be pretty hard to select some, cut and paste.. I will look for some sources and examples of sentences containing the words Speak and Talk.
Comment: And your answer to my comment that "There's no indication as to whether Q or your answer is about American, British, or other form of English." is what?
Answer: It can be somewhat formal and threatening given the context.
If a parent is called into school because their child has misbehaved, the parent may say upon leaving the principal's office

I will speak with your later young man!
I will deal with you when we get home!

Usually in a business situation, one may want to sound more informal or friendly, so instead of

Speak to you later.

One might use

Let's chat later.
  Let's catchup later.
  Let's talk later.

though "Speak to you later" is perfectly acceptable, similar to "Sincerely yours" at the end of a letter.
"Speak" may carry a heavier feeling than other  descriptions of conversing.  If someone has done something wrong, one might say

He has been spoken to about that.
  Should I speak to him about that?  (AmE)
  Should I have a word with him about that? (BrE)

If someone says

Can I speak with/to you?

it's often portrayed as something serious in the movies, like when a doctor informs a family member of a serious diagnosis.
Another example is, we rarely say

he speaks to himself.
he talks to himself
He talks to himself.
  He's always chatting with himself.

since we're usually on less formal terms with ourselves.

Speak with you later


What time of year is the cheapest to travel to Canada from Europe?

Question: I live in Ireland and I want to visit some relatives in Canada. Some of them live in Kelowna, BC and some in Langley, BC.
Which time of year is the cheapest and which is the most expensive? Also, are there any travel days that are the cheapest?
Answer: This is a surprisingly complex question and impossible to give an absolute answer to. You are right that the price of flights vary through the year and some times are more expensive than others. However, the price of flights is also greatly influenced by when you purchase plus other market dynamics such as popular events.
That being said, Canada is a very seasonal country with huge variations in weather which also affect volumes of tourists. The high season when flights are expected to be quite expensive is summer when schools are closed. This occurs from the last week of June until labor day which is on the first Monday of September.
There is another right season from the week before Christmas to the Monday that follows new year. Schools are closed also during the period and so anyone who wants to escape the cold winter with their kids travels during that week which causes prices to peak even higher than summer prices.
Outside of those two high seasons prices are generally much lower, particular to and from Europe because it includes many popular destinations. Flights can cost less than half price! The lowest prices often occur during the months of October and November, than again around April or May which are almost as cheap.
The general advice is to book international travel 6 months ahead of time to secure low prices and good flights. As the date gets closer, prices tend to increase steadily but then at the last minute, when spots are available, it is possible for prices to drop again, although those flights can be pretty tough with long layovers, many connections and even change of airports.
Answer: Flights are priced on supply and demand and vary a lot. Currently the cheapest round trip from Dublin to Vancouver in February is about 350 Euro. In August this will be at least twice as much.
Prices are lower if demand is lower. This typically means

No school holidays at either country
Undesirable weather in the destination
No major holidays, business, sports or other events
Weekdays that are not good for business travelers (mid-week or Saturday)
Crummy connections with long layovers

Most of these factors are hard to know so I wouldn't try to optimize any of these factors other than season. There are many search engines that allow you to look for the cheapest flight over a significant time range which makes this much easier than guessing.
Keep in mind that flight cost is not the only expense and sometimes spending a little extra money on a better flight option can make the trip much more enjoyable and may also save you money overall.
Answer: Travel to Canada is very seasonal. The peak tourist season is summer, and specifically from Victoria Day (or May two-four, the last Monday before 25th May) to Labour Day, the first Monday of September. Expect flights in that time to be more expensive.
The other peak season is ski season, but whether that affects you is going to be dependent on where you are going. Calgary and Vancouver airports, and to a lesser extent Montreal, will have higher prices at that time, but not as high as summer.
The couple of weeks around Christmas will be expensive, like almost everywhere else in the world.


Taking the garbage disposal switch off an outlet

Question: I am taking the switch for the garbage disposal off of an outlet, to make the outlet always hot.  The wiring has a red, black, white and ground.  Do I wire nut the black and red (hot) wires together then pigtail it into the new outlet?
Comment: How will you operate the disposal? Removing the disposal? As someone said, easiest is to remove the switch rather than mess with the outlet wires.
Comment: Unclear -- is the garbage disposal plugged into a switched outlet?
Comment: A bit unclear what you are trying to do, plus the specifics depend on the current configuration. Where are these black/red/white wires? At the switch or at the outlet? Do you know whether power goes from the panel to the outlet to the switch? or is from the panel to the switch to the outlet? Is the outlet currently 1/2 switched, 1/2 always hot? Or is it all switched?
Comment: Can you post photos of what's going on here?
Answer: Probably the red wire is switched hot and the black wire is always hot. You should not use both, just select one, probably the black. Assuming you're using a new outlet without the tab broken, just connect the black, white and ground; cap off the red wire with a wirenut (add electrical tape if desired). If the result is that both receptacles are switched, use the red wire instead and cap the black instead.
You don't want to connect both the red and black since if they don't originate with the same breaker, you have a Multi-Wire Branch Circuit (MWBC) where the red and black are actually opposite legs for your 240V house feed. In this case, connecting them together will trip your breakers (best case) or cause a fire (worst case).
Are you actually removing the switch (putting on a blank plate)? In this case, instead of changing out the outlet, you could simply remove the switch and connect together the wires that went to the switch (not the ground wire).


smoothness of multivariable functions

Question: What does it mean for a function $\mathbb{R}^n \to \mathbb{R}^m$ to be smooth? I see this in books, but typically we only talk about smoothness when the target set is $\mathbb{R}$.
Answer: Short answer: $f$ is smooth if and only if all of its components are.
Long answer: Observe that you can define partial derivatives for your vector valued $f$ exactly in the same way as you did for scalar valued functions. Indeed the only operations you used on the target space were sums and multiplication by a scalar. So you can just rephrase the "scalar-valued" definition to adapt it to the present case.
Answer: It usually means a $C^{\infty}$ function, or equivalently, a funtion which has partial derivatives for all order.
Another useful fat is that a function $f:\mathbb{R}^n \to \mathbb{R}^m$ is smooth iff every coordinate function $f_i:\mathbb{R} \to \mathbb{R}^m$ is smooth.

smoothness of multivariable functions


Company phone number on contact page

Question: It would be great if somehow it would be possible to show the account phone number for each contact (on their contact sheet). Is this possible somehow? Since entering the account phone number for each contact would seem a but redundant to me.
Answer: The best possible way to achieve this is using a Cross-object formula field. Since Account is a master of Contact, you can access Account fields in contact Formulas.
You can use this document to help writing the formula. There is a formula to display Accounts website on Contact, use it to display Account contact.
Do mark this answer as 'Solved' if it solves your problem.
Comment: Thx, is there some reference to the names of the fields in the accounts object?
Answer: Like what Sforce.Ninja suggested, your best bet would be using a cross-object formula field. There's a formula you can use to display the accounts' website on contact then use it to display the account contact. I think this documentation should help.

Company phone number on contact page


IP spoofing behind Meraki NAT

Question: I am using Meraki MX80 for NAT. There are a bunch of internal subnets, and the NAT works as expected. A colleague raised the question, what happens if a packet spoofs its source IP to something that's not in those internal subnets. Will such packets be dropped?
Comment: Depending on how you have the device configured, the traffic not matching an address range for NAT could be routed normally. You will need to provide the configuration (sanitize any public addresses).
Answer: Agree with Ron Maupin.  More details would need to be provided.
With that being said, the default behavior would be to drop the packet if it doesn't hold the route for the IP address.  Your packets would send out but the firewall wouldn't be able to return the ingress packets over the same session, thus your route would break.  If your device that was spoofing the IP was also configured to respond to the same spoofed IP, then it may work.  Of course, none of the spoofed traffic would work if your Meraki wasn't set to NAT the said spoofed subnet/IP in the first place.

IP spoofing behind Meraki NAT


array holding reference to extinct object

Question: I thought that if a C# array held reference types it would simply hold references to each of the objects, however the code below tells me otherwise.  It appears as if the array is holding a reference to an object of which I thought was set to be garbage collected.  I feel like i'm missing something fundamental here.  Can anyone tell me why the array reference does not change when foo is reassigned?
    abstract class AbstractBaseClass
    {
        protected int _someProperty;

        public virtual int SomeProperty
        {
            get
            {
                return _someProperty;
            }
            set
            {
                _someProperty = value;
            }
        }
    }

    class DerrivedClass1 : AbstractBaseClass
    {

    }

    class DerrivedClass2 : AbstractBaseClass
    {
        public override int SomeProperty
        {
            get
            {
                return _someProperty + 1;
            }
            set
            {
                _someProperty = value;
            }
        }
    }

    static void Main()
    {
        AbstractBaseClass foo;
        AbstractBaseClass bar;
        AbstractBaseClass[] array = new AbstractBaseClass [1];

        foo = new DerrivedClass1();
        foo.SomeProperty = 99;
        array[0] = foo;
        Console.WriteLine("Value of foo.SomeProperty: " + foo.SomeProperty.ToString());

        bar = new DerrivedClass2();
        bar.SomeProperty = 99;
        Console.WriteLine("Value of bar.SomeProperty: " + bar.SomeProperty.ToString());

        foo = bar;
        Console.WriteLine("Value of foo.SomeProperty after assignment: " + foo.SomeProperty.ToString());

        Console.WriteLine("Value of array[0] after assignment: " + array[0].SomeProperty.ToString());

    }

Answer: When you set:
array[0] = foo;

You're actually doing a by-value copy of the reference to the object pointed to by foo, and copying that reference into "array[0]".
Later, when you do:
foo = bar;

You're doing the same thing - copying, by value, the reference to the object pointed to by bar, into the variable foo.  This has no effect on array[0], since the reference was copied by value originally.  In order to make the first DerivedClass1 instance (foo's original reference) a candidate for GC, you need to explicitly set array[0] to some other reference (or null).
Answer: You changed the reference of the variable foo, not of array[0].
In your mind, you are thinking that array[0] points to foo, where they actually both point to the same memory location within the heap.
When you assign bar to foo, you are changing the place to which foo points.  You haven't touched array[0], so it still points to the same memory location it always pointed to--the original foo.
Comment: Also, this has nothing to do with garbage collection.  I'd suggest grabbing a copy of CLR Via C# by Jeffrey Richter.  Great book for someone at your level.
Answer: You are not thinking about reference assignment properly. array[0] = foo; causes the memory location array[0] to hold a reference to the same object that the memory location foo was referencing. It does not cause array[0] to reference the memory location foo itself. Therefore, changing which object foo references does not affect which object array[0] references.
Answer: The array element is storing the reference to the object that is initially referenced by foo. The array element is not tied to foo directly. When you modify what object foo references, the array element is unaffected.
Foo foo = new Foo();
foo.Name = "Andy";
Foo anotherFoo = foo;
foo.Name = "Bart";
Console.WriteLine(anotherFoo.Name); // writes Bart
foo = new Foo();
foo.Name = "Claire";
Console.WriteLine(anotherFoo.Name); // writes Bart

While you're modifying the properties of the object referenced by foo, other variables referencing that same object will "see" those updates, because they're looking at the same object. However, when I say foo = new Foo() (or you say foo = bar), you're changing foo to reference another object.
Your array element does not know or care about foo, it only knows about the object foo was referencing at the time of the assignment.
Answer: foo only references the object, which is stored in memory.
array[0] = foo will copy the reference to the array, so both the array and foo now point to the same object.
foo = bar will copy the bar reference to foo, so both foo and bar point to the second object. But the array will still point to the first object, because you haven't changed the reference in the array.
You should think of it as a home address. If two of your friends know your old address, but you only tell friend A your new address, friend B will visit your old address and find your old house. In your example, the array is friend B and only knows the in-memory location of the first object.
Answer: You have two references to the DerrivedClass1 instance:

The local foo variable, although foo ceases being a reference to the first object as soon as you assign bar to it
The array item at array[0]. This reference remains intact until the end of the method.

The assignment to the foo variable will never affect the contents of the array -- only making a change to array[0] will do that.
The object isn't eligible for garbage collection until all the references to it are cleared. This means that the DerrivedClass1 object won't be garbage collected before the array is garbage collected.
Answer: You create a new DerivedClass1 object and store its reference in foo, then you copy that reference to array[0], you copy it, that is, at that point you have two references to the same object.
When you do foo = bar; you overwrite the first copy of the reference from the foo variable, not the reference itself, so now foo simply points to another object, the same that bar is pointing, but array[0] still points to the first one, so it should not be garbage collected, and the object is unchanged.


Configuring routing in Juniper router

Question: I have a Juniper SRX220 (junos) router where I have configured vlan.1 and vlan.2 with IP 10.0.1.1/24 and 10.0.2.1/24.
Now I want to route between these networks. How do I configure that in Junos? I can't figure that out from the manual and it does not work out of the box.
Answer: Because this is an SRX, there are a number of requirements here.
Step 1:
Define VLANS (think layer 2)
set vlans vlan1 description desktops vlan-id 1 l3-interface vlan.1

set vlans vlan2 description servers vlan-id 2 l3-interface vlan.2

Step 2:
Define L3 interfaces bound to those vlans...
set interfaces vlan unit 1 family inet address 10.0.1.1/24

set interfaces vlan unit 2 family inet addresses 10.0.2.1/24

Step 3:
Place those L3 interfaces into a zone
set security zones security-zone trust interfaces vlan.1

set security zones security-zone trust interfaces vlan.2

Step 4:
Since this is an SRX, you must create a policy permitting intra-zone traffic
set security policies from-zone trust to-zone trust policy trust-to-trust match source-address any destination-address any application any then permit

Step 5:
Set physical interfaces onto that VLAN
set interfaces ge-0/0/0 unit 0 family ethernet switching port-mode access vlan members vlan1

set interfaces ge-0/0/1 unit 0 family ethernet switching port-mode access vlan members vlan2

Step 6:
Plug devices in. Once any interface assigned to that VLAN is physically up, the VLAN interface for that VLAN will come up.
Comment: Thanks a million! It was step 4 and step 5 that was missing in my configuration.
Comment: If you are going to use this device as just a router, you can change the default action to permit instead of drop, FYI.

Configuring routing in Juniper router


What is actually meant by "parallel paths" in a simplex progressive lap winding of a DC Generator?

Question: Many of my textbooks mention "parallel path" term, but I am unable to actually understand it. Also along with this it would be quite helpful to know, how the polarity of brushes is determined?
Comment: A specific reference on some inspectable website that you can link is necessary. Do not assume we are about to guess which ref book you refer to or which page.
Answer: Since the ends of each winding are bend inwards ( the beginning of a winding is placed at one lamella and the end of the same winding is placed at the next adjacent lamella this type of winding is called lap winding.
If you follow the windings you will find two parallel branches of windings for a 2 pole dc generator. For a four pole generator you will find 4 parallel branches of windings. From brush to brush you can consider each winding as a dc source and they are all in series so you will find Brush (lamella)- winding- lammela - winding -lammela - winding - brusch (lamella). This in two paths for a 2 pole machine and 4 paths for a 4 pole machine and so on.
Explanation of a wave winding and more in depth information you can find in
http://www.electrical4u.com/armature-winding-pole-pitch-coil-span-commutator-pitch/


Verb with UP in the meaning "will be soon"

Question: Here's my question)
Which verb can I use with UP to say that something will be soon? For example "Christmas's coming!" What can I put instead of "is coming"? Is it possible to use "keep up"?
Comment: "Christmas's coming **up**!", probably. (0:
Comment: FYI, I think it's easier to pronounce *Christmas is* than *Christmas's* and in my experience the uncontracted form is preferred, even when writing.
Answer: You can say "Christmas is coming up" to mean that Christmas is approaching soon.
In this instance the apostrophe is incorrect in my view.
If you were to say "Christmas's celebrations are coming up" that would be appropriate, as there is a possessive relationship (I'm not sure of the correct grammatical terminology, but I'm sure others can clarify/correct me on this) between Christmas and celebrations, i.e. we are referring to the celebrations of Christmas.
It is not appropriate to use "keep up" which has a different meaning, as in "Keep up the good work".


How can I turn on Wobbly Windows on Ubuntu Mate 18.04?

Question: I tried turn on in compizconfig but I does not work.
Any solution or it is possible?
Answer: First of all you need to switch window decorator to Compiz in mate-tweak.

Then install CompizConfig Settings Manager
sudo apt install compizconfig-settings-manager

and launch it with ccsm, confirm usage, enter wobbly in search bar, click checkbox near it and confirm disable of Snapping Windows plugin:

and enjoy:
Answer: You do not need compizconfig or mate-tweak.
Just Open Ubuntu Software Center, then search for 'Wobbly Windows' and install it. Click on 'Extension Settings' scrool down to Wobbly WIndows and keep it ON.
There you go !
It works for me.


Dropping off your resume in person for a job that does not exist

Question: In another question titled "Personally Handing a Resume to an Employer", the consensus was follow the correct procedure which normally means do it online. If however the job does not exist there is no clear procedure to follow. In this situation is handing a resume in person an effective way of making your case for future employment, if not, what other methods could be more effective and why?
Comment: Out of interest why was this on-hold yet the original question is almost identical in spirit and is not on-hold, indeed has great support from the community. The reason given for being on-hold is a bit vague, almost all questions on this SE can be classified as "advice on what to do".
Comment: Cold-calling for jobs (except maybe restaurants and retail) was over 25 years ago. Figure out who might be hiring and get an introduction on Linked-In or otherwise.
Answer: No, this is also not advisable. Because there is no telling whether anyone you would need to talk to about this would even be available you might make the trip in vein and even if you can talk to someone, you might come at a very inconvenient time four them. That does not leave a good impression, which is what you are trying to accomplish.
Instead, write an email conveying your enthusiasm and idea (and how this would benefit them and not just you) , attach your resume and let them deal with your inquiry at their own convenience. Add that you'd be happy to discuss this on the phone or in person, if you want.
Yes, they might never answer, but this at least won't leave them with a bad impression.
Comment: This is not actually about me, detailing how it would benefit the company is a great suggestion which I shall pass along.
Answer: Catching people by surprise, putting them on the spot and getting in their faces as a way to make friends and influence people so that you can get hired - that's definitely inadvisable unless you have a persona as a sales person who excels at cold calling. Or you want to learn how to be a sales person who excels at cold calling.
I look at sales people who excel at cold calling me with a mixture of fear, admiration and loathing :) - fear because I don't know them and I don't expect them and here they are, right in my face. Admiration for having the sheer guts to get in my home ground as uninvited, total strangers who know that the first three words they say to the receptionist could send them packing. And loathing because even if they got shot through the head, they WILL be back. I don't think that there too many of these sales people any more.
If you show up uninvited, there is a 95+% probability that you will be treated as an interloper. And that's assuming that you make it to the receptionist's desk. More likely, you won't make it past building security if they have building security, so you won't even get to the receptionist's desk.
Comment: The person is quite friendly, I would imagine their approach would be to chat to HR and ask what they are looking for in engineering graduates. Which is to say the tone would be similar to a university careers expo. Then ask if they have any unskilled positions so he could start contributing to the company / better understand engineering work environments. Sounds like email would be the way to go however, or perhaps a university careers day maybe?
Comment: @User university careers days, online and off-line job fairs, in my case - sideline and off-line conversations at computer meetups, conferences - I love Pycon, etc. Meet people, talk to them long enough to get their contact info, pick their brains after the event is over. The more informal the setting, the better the chances for the new professional to network successfully.
Answer: Dropping off your resume when a job doesn't exist will not generally work for many companies because they need a job opening to attach the resume to. Many times they flush all the old resumes from there system after a few months under the assumption they are outdated or out of the market, though some do keep electronic ones longer a a source of contact information.
Unless the company is small there is no way to know that HR or the relevant hiring manger will be at that location. If that isn't the right place it is unlikely that the resume will end up in the right place.
You will have better luck with a contact that works there or somebody you meet at a university event.


Camera path contraints

Question: I am creating a path for the camera in a scene. I need the camera to follow a NurbsPath, and then half way through the path, it needs to track a certain standing object. In order to do that, I am using two different camera constrains. One is "follow track" that applies for the entire clip. The other one, is  "Track to" which take place in the later part of the clip. The problem is I can't figure a way to do that smoothly. So far… I created two different clips (one with one constrain and the other with both) then created a third track between the camera position between the two. However, the results were not smooth and the camera swerved a lot in the middle clip
I wonder if you can come up with a better way of doing this.
Comment: Animate the "influence" values.
Answer: Make sure the Track To constraint is below the Follow Path, this way if you enabled Follow curve in the Follow Path constraint, the Track To will override it, and you will be able to animate its influence:
Comment: Thank you so much! I have been working on this for weeks. You made my day!..

Camera path contraints


'How many people came to your party?' or 'How many people did come to your party?' is correct

Question: I don't understand why question 'How many people came to your party?' is correct instead of 'How many people did come to your party?'. Is it any grammar rule?
Comment: Why do you think it is incorrect?
Comment: Because I did some excercise in workbook and key answer suggested that.
Answer: Either may be correct. *How many people did come?* is contrastive: it would be appropriate if your hearer had been talking about the people who didn't come. But without some such context, do support is unnecessary because the interrogative phrase, how many people, acts as the subject of the question: when that is the case, there is no inversion or do support.

Who came?, not Who did come?, except in contrastive contexts, but
Who(m) did you invite?, not Who(m) you invited?, because here who is the object of invite.
Answer: Either sentence would be grammatically correct, but it is more common to hear "How many people came to your party?"


XNA - debugging

Question: I know how to debug step by step in XNA however when I do that the screen is gray and the console does not give out any output. This is a problem because it greatly limits my ability to find problems. Is there anyway around this?
Answer: Ideally, what you want to do is set a breakpoint in visual studio, run your game as normal, and then start stepping through when you reach the breakpoint. You can then hit "continue" when you want the game to run again. There is no way to simultaneously step through step by step and also have the game running as normal.
Another option is to print out debugging information to a log file, and read the file later (for instance, when you want to collect broad statistics about what's going on in the game) -- or drawing debugging information onscreen.
Answer: Running game "normally" is not possible, while stepping in debugger. However, game should continue normally, when you press continue, if it does not, then you have a bug.
You can output text to visual studio output window using
<code>System.Diagnostics.Debug.WriteLine("It's me, Bugxor!");
</code>
If your output window is not open, you can open it from top menu "VIEW->Output" or keyboard shortcut "CTRL+W,O"

XNA - debugging


Best way to see multiple Microsoft Word windows?

Question: I just made the switch from Windows to Mac, and one thing that's been bothering me is that on a Mac, I can't see multiple Word documents that I have open.  On Windows, they all appear in the taskbar (after checking the option to not collapse instances of the same program) and I can quickly switch between them, which is useful for a variety of reasons.  On a mac, I can't do that.  The best way I've discovered so far is to go into mission control, but then I still have to make two gestures instead of one, and it's hard to see which window is which.  What's the best way to do this?
Answer: App Exposé
Trigger using swipe gesture:

System Preferences → Trackpad → More Gestures → App Exposé

Trigger using keys or mouse:

System Preferences → Mission Control

Dock Icon:

You can trigger App Exposé by right-clicking the Word icon in the Dock and choosing the option Show All Windows.

Alternatively you can cycle all Windows of the same application using:

⌘+~ (US keyboard layout)
Comment: Isn't this the option the OP was talking about? The way I read it, he was looking for a better way than using App Exposé.
Comment: I like this option, but isn't there some way to show multiple instances of the same program in the dock?  Or to show the different documents currently open?  It really seems like there should be.
Comment: @MathiasBynens He is only talking about Mission Control.
Comment: @gentmatt Whoops, my bad!
Comment: @AndrewLatham I've come up with a way to trigger App Exposé using one key.
Answer:
Hyperdock will give you window previews of each open window
belonging to an application by hovering over the dock icon, which you
can then click to activate.

Witch has a popup panel that displays the open
windows belonging to an application and also gives you a preview if
you hover over it.

Fantasktik probably offers the most
similar functionality to the Windows taskbar. However, the original
developer seems to have disappeared and this hasn't been updated in a
while (and therefore probably won't ever be). The new
"owner" claims it works on Lion, so it might be worth a try.
Comment: That's still more clicks than I would like =/

Basically that's like Windows, but without the "don't collapse" option selected.
Comment: @AndrewLatham Fair enough. Just for interest, I've also added [Fantasktik](http://dj50.ro/fantasktik/) to the answer, which although its not been updated in a while, offers the most similar functionality to the Windows taskbar IMHO. Indeed, I used to use this when I first switched...
Answer: You can use ⌘ + ~ to toggle between multiple windows of the same app.
This is an OS X-wide keyboard shortcut, so it works in Word for Mac 2011, too.
Answer: In system preferences you can turn on the gesture for Application Exposè which is essentially Mission Control but only for either the current application or the one your cursor was hovering over in the dock at the time.
This should make it easier to see what it what, but overall it's simply not realistic to force Windows methods of UI interaction onto a Mac desktop.  For every person switcher wanting to see a Dock icon per document window are a probably more non-switchers who want to use the Mac method of seeing an icon for the app, and one for each minimised windows - unless even this is switched off and the document minimise to the app icon.
It's one of the fundamental difference between the Doc and the Task Bar.  The Dock is an application launcher/switcher, and a minimised window holder.  The Task Bar is essentially an area for any and all running Windows.


Boot up error prohibitory sign flashing folder with question mark

Question: 3 weeks ago my hard drive failed so I bought a new one. (Macbook pro late 2011)
5 days ago, the new one flashed prohibitory sign, flashing folder with question mark. Every once in a while I could get it to desktop, but I would reboot, and back into the error. I reinstalled the OS through a USB, but still get the error. Is there a good chance it's the sata cable that needs to be replaced?
Answer: Try an erase and install, instead of just reinstalling OS X.

Back up your files and boot into an external install media (not the Recovery HD).
Open Disk Utility, select the internal disk and repartition it to 1 partition.
Install OS X normally, then restore your files.
Answer: Flashing folder with question mark means that your mac can not find OS to boot. It's either it can not find some files needed in the early stages of boot up process, or can't find boot volume, or can't find the hard drive.
Before destroying all your data try reassigning your boot partition in Startup Disk preferences.
If that doesn't help check your cables. You simply might have not plugged them in firmly enough or there might be some dust in there that prevents good connection.
Check an article on the Apple KB for more options: A flashing question mark appears when you start your Mac.
Comment: Which _files needed in the early stages of boot up process_ are you referring to?
Comment: @okiharaherbst Usually files on the UEFI boot volume but also might be a kernel.
Answer: First, you need to isolate the problem. Put the internal hardrive in a casing and connect it to your laptop through USB. Then boot up the OS X in this configuration by holding down OPTION key. If everything is smooth after a couple of hours, the problem is definitely SATA cable.
I have a 2011 13' MBP (A1278) and the cable broke a year ago. From what I read, the cable from this year (Parts No. 821-1226-A) is particularly faulty. You can replace it with the next iteration (821-1480-A). The latter is wider and longer, but it fits into older machines.
Comment: I have a related problem, but I want to clarify one point to make sure it's not something different. If the SATA cable is bad, is it possible that the OS will run correctly? In my case, the system has the boot problem 9/10 times, but once I get it to boot then all seems good until the next reboot. (I guess I would normally expect a failing SATA cable to cause some sort of problems during normal usage.)


How are bioremediation microbes removed from the environment once they perform their function?

Question: In the case of bioaugmentation, microbes are introduced into the environment to clean up and absorb a certain pollutant. My question is how is that microbe then removed from the environment once it performs its function?
Comment: A bit broad.  Sometimes it will die off when food supply is too small to support the population; sometimes it will need to be removed with poisons or predators; sometimes it doesn't need to be removed as it is relatively benign to the environment.  What case of bioaugmentation are you referring to specifically?
Comment: Heavy metal bioaugmentation.
Answer: Usually you have to introduce conditions which hinder multiplication of the microbe such as altering the pH and emperature. This is hard to achieve in a large environment, alternatively, you can introduce a recombinant of that microbe which posses a survivability threat to the initial microbe.
Comment: Could you add some sources describing these steps actually being performed?