Use text as horizontal labels in Excel scatter plot

Question: I am trying to make a scatter plot in Excel with text as horizontal axis labels.
I have the data

and I want a chart like this

The way I produced this chart was to have a scatter plot with numeric X values and numeric Y values, so instead of Poland I have X=1 and Y=10, Y=11, Y=12, and Y=9. For Germany I chose X=2 and Y=8 and Y=7. I just added some text boxes with the names to hide the numeric X values.

But I want this to be dynamic, so I tried to set the X value labels here:

but I am not able to change the horizontal values.
How can I solve this problem?
Comment: If you only have two or three countries to display, you can use x-values of (say) -1,0 and +1 and a custom format of (say) "Germany";"Poland";"Other" for the x-axis. I haven't offered this as an answer because I don't know a way of extending it to more than 3 x-values. If it is of interest, I can give more details.
Comment: Unfortunately, I need it for a lot of countries, so I had hoped for a solution where I can add a range of country names to be used at certain X values
Comment: I believe you can use custom formatting on the data and then choose 'link to data' for the axis. Will try and work out something more general.
Comment: I don't think it's going to work - you can link to manual formats (at least in my version of Excel 2010) but not to conditional formats.
Answer: You need a helper series. Consider the following screenshot:

The blue dots are plotted from the data in the table on the left. The orange dots are plotted from the helper table. Each orange dot then has a data label assigned. Edit each data label individually, type a <code>=</code> character and click the cell that has the corresponding text.
This process can be automated with the free XY Chart Labeler add-in. Excel 2013 and newer has the option to include "Value from cells" in the data label dialog.
Format the data labels to your preferences and hide the original x axis labels.


Retrieve last entry via ImportXML

Question: Looking for help pulling specific cells from a web site into a Google Spreadsheet. I want to pull "last" price from this page but only a few specific ones. Such as Dow, Nasdaq 100, S&P 500, S&P 400 Mid Cap and Russell 2000. I tried using ImportXMLand managed to import the whole table but can't seem to figure out how to pull just those cells. I also want to be able to do each cell individually so I can move and adjust the spreadsheet to my liking.
Comment: So what's your question?
Answer: You might try:
=index(importhtml("http://bigcharts.marketwatch.com/markets/indexes.asp","Table"),5,4)

for the NASDAQ 100 Index and adjust the 5 to suit for others.
Answer: The following setup will return the last price for NASDAQ 100 Index (NASDAQ Calculation)
A1: http://bigcharts.marketwatch.com/markets/indexes.asp
A2: =//tr[contains(.,'NASDAQ 100 Index (NASDAQ Calculation)')]/td[4]
A3 Formula: =IMPORTXML(A1,A2)
A3 Result: 4,512.54

Retrieve last entry via ImportXML


Publishing Fails

Question: Tool: Microsoft Visual studio 2008
Project Type: WPF Browser application
When after rebuidling all,project is published. it fails with followiung error.
Cannot publish because a project failed to build.
Could not find file 'obj\Release*.exe'.
Clean and rebuild All has been done, no positive signs.
System has been restarted, no positive sign.
Needs help.
Regards,
Shah
Answer: Problem solved by changing machine.
Same project is working on new machine.
Regards,
Shah

Publishing Fails


WorldPay extension

Question: Does anyone know of a working WorldPay extension? I know there was an alpha version developed by MillerTech in 2015 but unsurprisingly this doesn't work.  I would be surprised if a company has not paid for an extension to be developed for themselves.  We can contribute towards this but cannot afford to have this developed ourselves.
Answer: We have one that we've been using for a few clients, we could share it if you needed one?
Comment: That would be wonderful if you could.  Could you contact me at ralph at bis-space.com please?

WorldPay extension


Satellite Images for the Mediterranean Sea Oil Spill

Question: I am looking to obtain free satellite images to detect oil spills in the Mediterranean sea. What sensors would be most appropriate for this task and where can I download this type of data?
Answer: I would recommend Landsat or MODIS for this task.  You can access Landsat or MODIS data through Earth Explorer or Reverb|Echo.  There are a number of publications on the subject to help you along the way:

Brekke, C., & Solberg, A. H. (2005). Oil spill detection by
satellite remote sensing. Remote sensing of environment, 95(1),
1-13.
Hu, C., Li, X., Pichel, W. G., & Muller‐Karger, F. E. (2009).
Detection of natural oil slicks in the NW Gulf of Mexico using MODIS
imagery. Geophysical Research Letters, 36(1).
Comment: @g07kore MODIS has much higher spectral resolution than Landsat and, therefore, is very useful for detecting large scale phenomenon such as oil slicks.  The second paper shows that the researches successfully used MODIS to detect oil slicks even 75m in width.
Comment: With that resolution, you wont be able to see a lot in MODIS and furthermore for analysis i'd recommend LS.
Comment: I am aware of that and did not believe it before i saw your second link. I was more concerned that with the spatial resolution of 250m you'll lose a lot of information. Especially the second figure comparing MODIS and SAR imagery is impressive.


What is the use of both mol and mass representing the same thing i.e. amount of something?

Question: A mol is a unit but also has a magnitude. How can a unit have a magnitude? And if mole is used to measure an amount of substance than what does mass measure?
Comment: If you have 1 mol of O2 and 1 mol of N2, do they have the same mass? No, moles and mass measure 2 different things. At least I think this is what you are asking.
Comment: Maybe the language got a bit complex. I simply want to ask why there is a need of both mol and mass to measure the amount of a substance
Comment: I don't understand what is being asked here. Strictly following your logic, there is no difference between mass and volume, or even between *any extensive properties* whatsoever, which is just wrong.
Answer: Mole itself doesn't have a magnitude, but the value of mole does, in fact it is the magnitude. Any measurement has a magnitude (ie for the mass of 5 kg the magnitude will also be 5).
I think you are confusing it with scalar measurements (ie forces) which also have a direction. For example 5 Newtons 'in that direction'.

Mole is similar to a dozen (just a bit larger). It is used to count how many atoms, molecules, atoms or anything else there are.
If you think about mass as "the amount of stuff there is in an object" you can confuse it with mols
but the actual definition of mass is:

A property of a physical body and a measure of its resistance to acceleration (a change in its state of motion) when a net force is applied.

which is different to mols (which is used to count objects).


How to choose a year end date for your Ontario small business corporation?

Question: While opening a small business corporation in Ontario, how do you select a proper year end date? Is it a random date ?
Or are there guidelines to it?
Answer: There is one edge case that may be of value to you. If you declare a bonus (probably to yourself given a very small company) you can deduct it from your year and then have up to 6 months to actually write the cheque and give it to the person.
Say your year end for the corporation is July 31st. You could declare the bonus July 30th and deduct it from that year, lowering your corporate tax. You could then wait until January 30th to actually write the bonus cheque. The person would then have that taxable income in a later calendar year, deferring paying the tax. Depending on the size of the bonus, this would possibly matter, although if you did large bonuses every year it would only matter the first time.
The other issue is the availability of your bookkeeper or accountant. They are sometimes very busy during personal income tax season. They often like a vacation immediately after that. They may go away in the summer when their kids are out of school. The nice thing about a July 31st year end is that you can probably count on a quick turnaround from your accountant in September. The possible downside is that you won't enjoy reconciling your credit card statements and the like in August as part of getting your year end stuff together. You can avoid that by keeping your books in a decent shape all the time.
Answer: Select the calendar year unless there is a good reason to choose another year end, for example, if your business is really busy at that time of year and you won't have time to do your books.
Comment: This would be a better answer if you listed some of the "good reasons" to choose a non-calendar year end. There may be tax advantages, as indicated in the other answer.


How to remove a tag from deleted files in CVS?

Question: I am trying to maintain a system of tags for my CVS data. One set of tags contains unique tags that never change. They are the nightly-regressed tags. The another type of tag is a  single tag that keep on moving. This is the nightly regress-candidate tag. So, This tag keeps on moving from one version to a newer one for a file. Lets call this tag 'regress_this'. At the time of regression my intention is to checkout this particular tag and run my regression.
My problem is that checking this tag out brings back deleted files too. Since over the course of a day some files get deleted that had the 'regress-this' tag from before. If I can automate that removing a file from CVS will also remove any specific tag on the file then my problem will be solved.
The CVS cvs gets to this the 'rtag -a' but this is not what I am looking for because it also applies the tag to the head revision of all the other files. Also, I dont have a clear-cut list of files that were removed.
The way I apply the tag is by running 'cvs tag -F tagname filenames' so only a few files get tagged at a  time.
I need to filter out the deleted files from my movable tag.
Answer: You could try removing the tag from the repository before applying it:
<code>cvs rtag -d regress_this
</code>


Live Video Streaming with PHP

Question: I have a PHP/AJAX/MYSQL chat application. I want to add video chatting to my application. How can I create live video streaming to be used for live video conferences/chatting in a PHP application. What are the key-terms I need to know if I wanted to build such a system? Is it a good idea in the first place to use PHP? Is there something I'm not thinking about? What other languages can I use, perhaps in conjunction with PHP?
Answer: I am not saying that you have to abandon PHP, but you need different technologies here.
Let's start off simple (without Akamai :-)) and think about the implications here. Video, chat, etc. - it's all client-side in the beginning. The user has a webcam, you want to grab the signal somehow and send it to the server. There is no PHP so far.
I know that Flash supports this though (check this tutorial on webcams and flash) so you could use Flash to transport the content to the server. I think if you'll stay with Flash, then Flex (flex and webcam tutorial) is probably a good idea to look into.
So those are just the basics, maybe it gives you an idea of where you need to research because obviously this won't give you a full video chat inside your app yet. For starters, you will need some sort of way to record the streams and re-publish them so others see other people from the chat, etc..
I'm also not sure how much traffic and bandwidth this is gonna consume though and generally, you will need way more than a Stackoverflow question to solve this issue. Best would be to do a full spec of your app and then hire some people to help you build it.
HTH!
Comment: Great Answer. If I want to transmit live tv what to do. can you suggest me?
Comment: I know its late, but there are things like ReactPHP
Answer:
Please note that the below described service is no longer available as
  it was based on FLV media (Flash)

This project which utilizes the Red5, Flex and PHP for Live Video Streaming and Recording has many features

Stream Live video to the viewers
Record the streams from your cam or other video input devices to the server
Preview the recorded streams and files and thumbnail the frame which you would like to display for the video.
Upload the videos from your computer and convert them to FLV which can be streamed using Red5 .
Choose from any resolutions
Can be plugged to any script
Each website user can have a separate Directory for storing their videos and thumbnails use this link
http://code.google.com/p/red5-flex-streamer/
Answer: PHP will let you build the pages of your site that make up your video conferencing and chat applications, but it won't deliver or stream video for you - PHP runs on the server only and renders out HTML to a client browser.
For the video, the first thing you'll need is a live streaming account with someone like akamai or the numerous others in the field. Using this account gives you an ingress point for your video - ie: the server that you will stream your live video up to.
Next, you want to get your video out to the browsers - windows media player, flash or silverlight will let you achieve this - embedding the appropriate control for your chosen technology into your page (using PHP or whatever) and given the address of your live video feed.
PHP (or other scripting language) would be used to build the chat part of the application and bring the whole thing together (the chat and the embedded video player).
Hope this helps.
Answer: PHP/AJAX/MySQL will not be enough for creating the live video streaming application There is a similar thread here. It primarily suggests using Flex or Silverlight.
Answer: For live video conferencing you can't ignore the need of a streaming server.
Yes, flash will let you display video from a webcam within the local flash control, but that won't let you then send that video over the network - for that you need a streaming server to send it to.
If you're going to build something like this it's prudent to think about how you're going to host the video from a very early stage as it will influence how you build the application. Flash/Flex/Silverlight/Windows Media....etc....
Answer: There are a lot of "off-the-shelf" 'servers' that will run in your environment.
Most of these utilize the aforementioned Flex or Silverlight to implement the actual video itself but I'm pretty sure all will run under LAMP/PHP.
The challenges will picking the best software from everything that's available and getting your hosting-provider to let you stream video (it goes without saying that streaming is heavy on bandwidth).
Answer: Same problem/answer here, quoted below

I'm assuming you mean that you want to run your own private video
  calls, not simply link to Skype calls or similar. You really have 2
  options here: host it yourself, or use a hosted solution and integrate
  it into your product.

Self-Hosted
  ----------------- This is messy. This can all be accomplished with PHP, but that is probably not the most advisable solution, as it is
  not the best tool for the job on all sides. Flash is much more
  efficient at a/v capture and transport on the user end. You can try to
  do this without flash, but you will have headaches. HTML5 may make
  your life easier, but if you're shooting for maximum compatibility,
  flash is the simplest way to go for creating the client. Then, as far
  as the actual server side that will relay the audio/video, you could
  write a chat server in php, but you're better off using an open source
  project, like
  janenz00's mention
  of red5, that's already built and
  interfacing with it through your client (if it doesn't already have
  one). Or you could homebrew a flash client as mentioned before and
  hook it up to a flash streaming server on both sides...either way it
  gets complicated fast, and is beyond my expertise to help you with at
  all.

Hosted Service
  ----------------- All in, my recommendation, unless you want to administer a ridiculous setup of many complex servers and failure
  points is to use a hosted service like
  UserPlane or similar and offload all the
  processing and technical work to people who are good at that, and then
  worry about interfacing with their api and getting their client well
  integrated into your site. You will be a happier developer if you do.

Live Video Streaming with PHP


How to know the data type of constant in arduino IDE?

Question: For example constant of MSBFIRST, It used to as input in SPI.setBitOrder(MSBFIRST). But sadly i don't know the type data of MSBFIRST. This is applied to like SPI_MODE0 and other.
Comment: short and universal answer: look in the .h files of the library for function parameter type
Answer: From SPI.h:
#ifndef LSBFIRST
#define LSBFIRST 0
#endif
#ifndef MSBFIRST
#define MSBFIRST 1
#endif

As you can see, there is no type. The compiler merely substitutes literally "1" for "MSBFIRST". So your code would read, after pre-processing:
 SPI.setBitOrder(1)

To know exactly what type "1" is (I'm not sure why you need to know) then you would look up "C++ integer promotion". In other words, how are literal integers handled by the C++ compiler.

From a comment:

In which case it's better to look at the desired type of the destination function not the type of the macro or const.

Quite right. If you look further into the SPI.h file you see this:
  // This function is deprecated.  New applications should use
  // beginTransaction() to configure SPI settings.
  inline static void setBitOrder(uint8_t bitOrder) {

So, ignoring what type MSBFIRST is, you can see that the function expects uint8_t.
Comment: Maybe he wants to know what the type is so he can use it as a parameter to some form of wrapper function or another form of abstraction layer? In which case it's better to look at the desired type of the destination function not the type of the macro or const.
Comment: @Majenko Indeed. I've amplified my reply to show this.
Comment: @Majenko you are right, i want to know type so i can use it as parameter for my abstraction layer. Nevermind, I already know the data type with using ```Serial.println(MSBFIRST)```,  it was displaying  ```1``` in serial monitor. So i assume the data type is unsigned integer aka byte.


Binaries un-publish themselves?

Question: We are getting some user complaining about component being unpublished from the website. I have check the publishing queue and didn't find any unpublishing jobs for those component.
Is it possible the system can unpublish the component for some reason? Has anybody else seen similar issue?
Comment: Also, does it happen to be a binary (multimedia Component), which don't technically get unpublished, but can be removed from delivery when no longer "in use" (@Frank has a good [write-up on it on TridionWorld].(https://sdltridionworld.com/community/2011_extensions/binaryeventtracker.aspx).
Comment: Is the component actually unpublished? or did the content itself disapear form the website? Is it published embedded on a page or dynamically?
Comment: Interesting to note as well, what action is taken to make the "component" reappear?  Is something being republished again, Component, Template, Page?
Comment: @Puntero The content disappeared from the page. It is just some static content.
Comment: @Elena Just republish the component fixed the issue.
Comment: @Alvin Thanks! I believe it is exactly the issue. The component is just a few static documents. Can you make your comments an answer?
Answer: Frank van Puffelen described how binaries are handled in delivery in his Binary Event Tracker extension.
Basically delivery counts how an image (or binary such as a PDF) is referenced in delivery across presentations. When the items using the image are no longer on the site (or have been updated to no longer reference the image and republished), delivery will remove these items.
To avoid having these binaries from being removed in delivery, you could use a (dynamic) Component Template to explicitly publish them.
Side note: I often see binaries referenced directly by organizations sending links to documentation. In this case, it might be a good practice to reference pages that link to the PDFs. The PDFs wouldn't be automatically unpublished and with a given webpage, you could update the content and files without impacting the shared url.
Edit: noted that you could also remove a reference by republishing.
Comment: I have uploaded the error screen when this happens. It is apparent that the file (the binary image) is missing. We just don't understand why it is gone (why the reference counts going down, I didn't see any unpublish which might impact this.)
Comment: Maybe try a `Where Used` and check publishes as well. If nothing (based on what's published) links to the PDF, the PDF should "go away."
Comment: @charles could it be that there is an error in configuration on the Deployer side, that perhaps a live and staging Deployer are interfearing with eachother?
Answer: Q: Is it possible the system can unpublish the Component for some reason?
A: No not by itself, but there could be event handlers which take care of this.
However in that case you should see the unpublish transaction in the Publish Queue (take a look at all users).
Q: Is it possible to delete an unpublish action after it is done?
A: Yes it is, so you can cover your tracks in that sense.
But when you are talking about a Component being unpublished, is it a Dynamic Component Presentation we are talking about? Or are you referring to a Component Presentation on a Page that is missing? In the last case there could be multiple answers to the question why is has "dissapeared". You should define your question in a bit more detail to get a more detailed answer.
Q: Has anybody else seen similar issue?
A: I've heared similair issues before, and there was always a good explanation as to what happened.
Comment: CP on a page disappearing could be a *publish* (with different CPs) rather than an unpublish.
Comment: Hi Bart, thank you for the answer. a) I have checked all users, there is no unpublish action. b) It is some static content in the page, nothing dynamic. c) Good to know I am not the only one having the issue!
Comment: @charles based on your comment, I'm thinking along the lines which Alvin commented. So indeed you won't be finding a Componet which is unpublished, but a Page which is changed and republished. When you can supply us more detail (edit the question and add it), we can supply a better, more detailed answer
Answer: I don't know if this is related to your problem, but we ran into a something similar a year or two ago.
We kept finding binaries were dissappearing from the file system for no readily apparent reason and eventually tracked the problem down to binaries that had been published in two different ways by mistake.  We have binaries (in this case images) that are used inline within content and placed there by our content editors - this uses the normal PublishBinary method.  We also have images that we, as IT, use that are attached to a page and published using the AddBinary method.
What we found was some of the image components that IT were using had also been use by our content editors inline (we, IT, hadn't stored them in the correct, restricted, place within Tridion).  What this meant was that when the content editors published their pages that used the (shared) images the version used by IT was unpublished.  When we (IT) noticed this and couldn't see why, we just republished the IT pages and the image returned... but was then unpublished from the pages the content editors had created.  This went on for a few iterations, each department blaming the other!!
When we realised the images in question had mistakenly been used by the content editors we created a copy for them to use and moved our copy into the correct restricted area in Tridion and all has been well since. It had never occured to us that Tridion wouldn't allow images (or any binary) to be published via both methods at once because we had never shared our images, but it does make sense: PublishBinary will alwys publish the binary to the location specified in the publication config (eg. /images) with the tcmID suffixed, where as AddBinary will publish the image with its filename unchanged to the location of the page with the AddBinary command.
Hope that helps.

Binaries un-publish themselves?


How were compasses in early interwar planes safeguarded against interference from flight?

Question: I understand during the early days of flight that compasses were regarded as extremely unreliable and unfit for even basic navigation, but I'm unsure as to what caused this unreliability and what the first countermeasures against it were.
Comment: Don't see that as a duplicate, since this question has a historical component to it and asks about not just the solution (the compass swing) but also the causes of the unreliability.  The info in the linked question is a good addition here, but it isn't really a full answer to everything being asked, IMHO.  Voting not to close.
Comment: Does this answer your question? [How do you calibrate the compass of an aircraft on a compass rose?](https://aviation.stackexchange.com/questions/25058/how-do-you-calibrate-the-compass-of-an-aircraft-on-a-compass-rose)
Comment: I do not think magnetic compasses are considered very good navigational aides even these days. The term for the magnetic compass in an airplane in my native language would loose translate into a *"screw compass"*, because if you have to rely on it, you're screwed...
Answer: The unreliability is caused by the nearness of several big bits of magnetic material, chiefly an engine, and some electrical equipment. The countermeasures are something called "swinging the compass". The same fix has been used historically on boats since they started being made of metal.
In essence it involves adjusting "compensators" which are pieces of magnetic material placed near the compass and which cause it to swing by a few degrees. You point the aircraft in all the different compass directions and make the adjustments in order to minimize the deviation of the compass from an accurate reading throughout all directions. This is done in a "standard configuration" of different electrical equipment being on or off.
Once you have minimized the difference between actual directions and what the compass reads you then make up a "deviation card" which is placed near the compass and which the pilot can use to get the correct magnetic heading from the compass reading.
There is an additional unreliability caused by the aircraft's motion. As an aircraft pitches and rolls that movement causes the compass to deviate from an accurate reading. This would happen more in early planes than in more modern ones. This problem was fixed by the invention of the gyro compass or "Direction indicator", which maintains a constant direction and is not subject to the aircraft pitch and roll. However the DI does drift, and so needs to be regularly checked to ensure it aligns with the compass, something you do during level flight to minimize the compass errors.
Both of these mitigations are in use today.
Answer: One common method was to move the guts of the compass out to a wingtip, far away from the engine block and the electrical system, and then electrically link it to a remote reading dial in the cockpit. This was called a flux gate compass, which does not use a swinging needle to detect the direction of the earth's magnetic field and hence does not dance around in rough air.
Comment: The Wikipedia page pointed to [this Aviation Week article,](https://archive.org/details/Aviation_Week_1943-10-18/page/n5/mode/1up) which makes the flux gate compass public knowledge in 1943 (though calls it the result of "seven years' study"). The question specified "early interwar"... was there an earlier version of the fluxgate compass in use?


Stability of the hydrogen atom and positronium

Question: I am trying to get a better understanding of why positronium decays while a hydrigen atom is stable. In the case of positronium, I can write an elementary process were the leptons annihilate into two photons. But for the case of an hydrogen atom, I can not write a similar simple process where quark and electron would annihilate, due to charge conservation. Is it indeed impossible to write such a process at any order?
More speculatively, if we lived in a different world were quarks had integer charge, would a quark/electron bound state be stable?
Comment: Can you better explain the "elementary process"? I'm not sure how two anti-matter particles would annihilate, or how a quark and an electron could annihilate.
Comment: The hydrogen atom is neutral, (electric) charge conservation has nothing to do with this.
Comment: Perhaps I should have said 'simple' process rather : tree-level or one loop order. Positronium annihilation is straightforward to write using simple Feynman diagrams, But I was not able to write one for quark and electron, and I was wondering if one reason was the lack of interaction vertex between up quark  (charge +2/3) and electron (-1).
Answer: The electron is the lightest lepton and the proton is the lightest baryon, so it's hard to see what reaction could occur without violating lepton number or baryon number.
I suppose if proton decay (to a pion and positron) occurs then there could be a reaction to give a pion and two photons.
Comment: $p^{+} + e^{-} \rightarrow n + \mu_{e}$, but that reaction is endothermic
Answer: The symmetries that you're missing are conservation of baryon number $B$ and lepton number $L$.
We strongly suspect that baryon number is not an exact symmetry, because the universe appears to contain very many baryons and very few antibaryons. Actually, a better metric for the baryon asymmetry of the universe is to compare the baryon density to the density of cosmic microwave photons, since that's what the gas of baryons and antibaryons at the Big Bang turned into; by that standard, the universe has a baryon asymmetry of about 10-9. But no process that violates baryon number — starting with a proton, $B=1$, and ending up only with pions, $B=0$, or that sort of thing — has ever been observed in any laboratory.
We also have no evidence for any processes that change lepton number. Weak decays, like $\beta$ decay, always create leptons and antileptons in pairs. I'm not sure whether lepton number violation is required by cosmology in the same way that baryon number violation is: it's possible that the matter electrons are balanced by an equal number of antimatter neutrinos that haven't interacted with anything since the Big Bang. Although the theoretical/phenomenological arguments for $L$-violation are actually stronger than for $B$-violation, since it's possible that the neutrino and antineutrino are actually the same particle.
If you get deep into the literature you'll find discussions of theories that break $B$ and $L$ but conserve the difference $B-L$, predicting, for instance, that the proton should undergo $p\to\pi^0+e^+$. (This was actually the original purpose the giant water tank at Super Kamiokande in Japan: to put lots and lots of hydrogen in view of lots and lots of detectors and to wait for a proton to decay. The mean time before decay for that particular mode is somewhere above 1033 years.) Your hydrogen atom disappearance would have the same Feynman diagram, $e^-+p\to\pi^0$. There are also comparable limits on interactions where $B$ changes by two units, such as $pp\to\pi\pi$ in the confines of a heavy nucleus.
Postironium decay, however, has lepton number zero in the initial state (with one lepton and one antilepton) and lepton number zero in the final state (with zero leptons and two photons), and so is not forbidden by these conservation laws.


My mustang doesn't accelerate. 120000 miles

Question: My car turns on just fine. After a while driving it. The car loses power and it doesn't want to even hit 10 mph. My check engine light is on, but the machine tells me it's the oxygen sensors. Can someone help me?
Comment: Welcome to Motor Vehicle Maintenance & Repair! I'm surprised the mechanic didn't check the cat for function. Sounds like it might be plugged. What is the year/engine of your Mustang?
Comment: 1999, 3.6 I think and my mechanic thought it was overheating. So we changed the fuel filter, and it still with the same problem. I can't use the car for a good 15 minutes before it starts to act up.
Comment: What are the codes?
Answer: The restricted acceleration and low top speed (with accompanying CEL) sounds very much like the car is going into limp mode to me.
Given the error code is pointing to the oxygen sensors I'm surprised the mechanic is leaning towards overheating unless there are more symptoms that aren't in your question. I'd be looking at the oxygen sensors themselves or something else that is restricting the airflow through the engine.
Depending upon the conditions and how you are driving it 10-15 mins sounds very much like the time the engine takes to come up to temperature where the ECU will be attempting to swap from the cold start fueling to using the dynamic figures from the oxygen sensors to tailor AFR, if it's getting no or out of range readings from the sensors this could be enough to trigger limp mode.

My mustang doesn’t accelerate. 120000 miles


Minimum distance between convex Hull: Naive approach

Question: In order to compute minimum distance between convex hulls, can we just use a naive approach like measuring all the points from first convex hull to second convex hull? And take the minimum value?
Comment: Are they disjoint? If not, the minimal distance between two points is zero. If yes, how to understand the distance? As the minimum of distances between two points, or in the Hausdorff sense?
Answer: No !
The hulls are convex polygons, and the closest distance between two convex polygons can occur between two vertices or between a vertex and an edge. (Not counting the overlapping polygons.)

If the hulls have many sides, the total work is proportional to $NM$. You can do a little better as follows:
Try all edges of the polygon that has the less sides, say $N$. For a given edge, the distance of the vertices of the other polygon to the line of support is a function with a single minimum. The minimum can be detected as the vertex of the other polygon that joins a "nearing" edge and a "moving away" edge.
By a process similar to a dichotomic search, this vertex can be detected in $\log_2M$ operations, giving a total workload proportional to $N\log_2M$.


Proof that all real numbers have a rational Cauchy sequence?

Question: I saw in an article that for every real number, there exists a Cauchy sequence of rational numbers that converges to that real number. This was stated without proof, so I'm guessing it is a well-known theorem in analysis, but I have never seen this proof. So could someone give a proof (preferably with a source) for this fact? It can use other theorems from analysis, as long as they aren't too obscure.
Comment: To give a proof, one needs to know what construction of the real numbers you are using. In particlar,, if you are using the construction via Cauchy sequences, then it is true by definition.
Comment: That's obvious: the sequence of successive decimal approximations with $n$ decimal digits, for instance.
Comment: See [this question](https://math.stackexchange.com/questions/209001/for-every-real-number-a-there-exists-a-sequence-r-n-of-rational-numbers-such) for more.
Comment: @celtschk Right, I was talking about the Dedekind cut definition. In fact, the context in which I saw this was an article showing the equivalency between those two definitions. This seemed to be the only hole in it to me.
Answer: Let $\alpha$ be any real number.
Define
$$a_n = \frac{\lfloor n \alpha \rfloor}{n}$$
where $\lfloor , \rfloor $ denotes the floor function.
Then $a_n \in \mathbb Q$. Moreover we have
$$\frac{n \alpha -1}{n} \leq a_n \leq \alpha$$
and hence $a_n \to \alpha$.
Answer: Based on the context gathered from your question and your comments it is clear that you are concerned about the equivalence of construction of reals as Dedekind cuts of rationals and as equivalence classes of Cauchy sequences of rationals.
We can do this in the following manner. First we show that corresponding to a given Dedekind cut of rationals there exists a Cauchy sequence of rationals. To do so in proper manner it is best to explicitly state the definition of a Dedekind cut of rationals.
A Dedekind cut of rationals is a set $A\subseteq\mathbb{Q} $ with the following properties:

$\emptyset\neq A\neq \mathbb{Q} $.
If $p\in A$ and $q\in\mathbb{Q} $ with $q<p$ then $q\in A$.
If $p\in A$ then there exists a $q\in A$ with $p<q$.

The above definition is one provided by Rudin in his Principles of Mathematical Analysis. But the true picture of a Dedekind cut is revealed when one considers not only the set $A$ but also its complement $B=\mathbb{Q} - A$ as done by Dedekind himself.
It is easy to prove that given any positive rational number $\epsilon$ one can find rationals $p, q$ such that $p\in A, q\in B$ such that $0<q-p<\epsilon $. Thus for every positive integer $n$ we can find rationals $a_n, b_n$ such that $a_n\in A, b_n\in B, 0<b_n-a_n<1/n$ and further we can ensure that $b_{n} \geq b_{n+1},a_{n}<a_{n+1}$. Now we can show that $\{a_n\} $ is a Cauchy sequence of rationals. This is how one can find a Cauchy sequence of rationals corresponding to a given Dedekind cut of rationals. Note that the sequence $b_n$ can also be considered here instead of $a_n$.
To do the reverse let us consider a Cauchy sequence of rationals $\{a_n\} $ and we then need to find a Dedekind cut corresponding to it. Consider a rational number $r$. If there is a positive integer $m$ such that $a_n>r$ for all $n\geq m$ then we say that that $r$ is inferior to the sequence $\{a_n\} $. Consider the set $$A=\{p\mid p\in\mathbb {Q}, \exists q\in\mathbb{Q}, q>p, q\text{ is inferior to sequence }\{a_n\} \} $$ Since a Cauchy sequence is bounded it is clear that the set $A$ and its complement $B=\mathbb{Q} - A$ are both non-empty. Also if $p\in A$ then there is some $r\in\mathbb{Q} $ such that $r>p$ and $r$ is inferior to $\{a_n\} $. And if we take a rational $q$ with $q<p$ then $q<r$ and hence $q\in A$. Moreover we also have $(p+r) /2<r$ so that $p<(p+r) /2\in A$. Thus $A$ satisfies all the properties of a Dedekind cut. This is how one finds a Dedekind cut of rationals corresponding to a given Cauchy sequence of rationals.
We still need to show that if $\{b_n\} $ is another Cauchy sequence of rationals which is equivalent to $\{a_n\} $ (ie $a_n-b_n\to 0$) and if we apply the above mentioned procedure to find a Dedekind cut $A'$ corresponding to the sequence $\{b_n\} $ then $A'=A$. This is not difficult to prove and you should try it yourself.

The full equivalence of the construction of reals via Dedekind cuts and via Cauchy sequences of rationals can be done by proving that the correspondence between these approaches described above is an isomorphism which preserves arithmetic as well as order relationship. But carrying out such a proof is boring and lengthy.
Answer: Note that  the set of real numbers is a complete set that is every Cauchy sequence of real numbers is convergent also every convergent sequence is a Cauchy sequence. Therefore once you have a rational sequence converging to a real number the same sequence is a  rational Cauchy sequence converging to the same real number.
Answer: One way to define the real numbers is as equivalence classes of Cauchy sequences (see exercise 3.24 in Princples of Mathematical Analysis by Walter Rudin for the details of the (actually, a more general) construction). Under this construction, it is obvious that every real number has such a Cauchy sequence, since every real number literally is a (set of) Cauchy sequence(s). Once you've done this, it is an easy exercise to prove that $\mathbb{R}$ is the only complete ordered field up to isomorphism, so it doesn't matter which construction you use for $\mathbb{R}$, the Cauchy construction guarantees it.
Comment: Yeah, the article I was reading was about showing that this construction is equivalent to the Dedekind cut construction, so they cited the fact I'm asking about as part of their proof.
Answer: Let $x \in \mathbb R$.
Let $q_i \in \mathbb Q$ so that $x - \frac 1i < q_i < x$.
Claim 1: Such a sequence $\{q_i\}$ exists (because the rationals are dense in the reals)
Claim 2: $q_i \to x$ (by the very definition of limits)
Claim 3: $\{q_i\}$ is cauchy.  (For $n > \frac 2\epsilon; i,j > n$ then $|q_i - x| < \frac 1n < \frac \epsilon 2$ and $|q_i - q_j| < |q_i - x| + |q_j - x| < \epsilon$.)
Basically this is the FUNDAMENTAL principal of the meaning of real numbers.
Real numbers are such that every bounded above sequence has a least upper bound.  That is the fundamental claim of the nature of real numbers.  The means that any sequence in which all the terms get "close together" must have an existent real limit.
A Cauchy sequence is just such a sequence.  To be informal, a Cauchy sequence is a sequence that "ought to" converge although the actual limit point need need be specified (or even be specifiable).
Another way, perhaps without choice is, by the Archmedian principal there exists a unique integer $k_1$ so that $k_1 \le x < k_1 + 1$ and for every integer $n$ there is a unique $k_n$ so that $k_n \le x*n < k_n + 1$ or $\frac {k_n}n \le x < \frac {k_n}n+ \frac 1n$.  Let $q_n = \frac {k_n}n$.  That is a cauchy sequence converging to $x$.
In fact, if $k_n$ is the unique integer so that $k_n \le x*10^n \le k_n +1$ then the sequence $q_n = \frac {k_n}{10^n}$ is nothing more or less then the sequence of $n$th place decimal expansions.  (If $x = \pi$ then $\{q_n\} = \{3, \frac {31}{10}, \frac {314}{100}, \frac {3141}{1000}, ....\}$ etc.)
It is precisely because all reals have cauchy sequences of rationals converging to them, that the concept of decimal numbers even works.


Is there any standard way to refer to college level education?

Question: I'm looking for a way to say college level on the abstract of a paper. In Portuguese we say ensino superior. A direct translation for that would be higher education, but I don't think that fits the language expected on academic writing. Am I right? If so, then what should I say?
Comment: What is the title of the paper whose abstract this reference is to appear in? Do you mean you are writing for an audience of college students? Or that you have been to college? Or that you are now in college? Or that your English is college-level? Really, it's impossible to figure out what you're asking.
Answer: In Australia formal studies pursued after high school are known as tertiary education, in the same vein as primary and secondary education. The term encompasses technical and vocational education in addition to undergraduate university degrees.
Answer: In British-English I would say higher education. In America I think college level would be more common. In formal Bureaucratese "post secondary education" is probably the most correct term
Comment: I'd forgotten that one. Does it make a PhD Quaternary education, I wonder?
Comment: Academe in the UK tends to use the generic 'tertiary education' to cover "formal bureaucratize [sic] post secondary education".


Unable to check in files due to Error"You must fill out all required properties before checking in this document."

Question: I receive this error "You must fill out all required properties before checking in this document." while trying to check in a file. I tried fill up all the properties for the file but still receiving this error. Anybody knows why?
Answer:
Go to the list settings > Advanced settings > change it to No for "Allow management of content types" (don't worry it won't remove any content types).
Then set ALL the columns to non-required in the column settings.
Turn the Allow management of content types back on.
Go into each content type, set each column to require/optional/hidden there.
Comment: Hi, where can I find the setting for step 2? Is it under the column default value setting?
Comment: It is in list settings > columns section, then click the column name.
Answer: These are required columns (the * asterisk indicates a required field).  You will not be able to save unless each required columns has a value, no blanks are allowed.  Or, if you have sufficient permissions, you can edit the columns in the settings to stop columns being required - when it is no longer required it means you can save it with a blank value.


I want to convert 12v DC into 5v DC

Question: I know there are lot of examples are given on internet. I have searched and I found good one. I am not professional in electronics engineering. I am Software Developer and I am trying to create a module that converts 12v into 5v. Actually I want to charge my usb device(mobile/mp3 player) from my motor cycle battery. I have found good tutorial on electroschematics site. but, I am confused in selecting capacitor for C1 and C2 defined in diagram. I dont know what is the voltage for those capacitor?
Comment: If you've found one that uses a 7805 then you haven't found a good one, sorry.
Answer: This is a terrible circuit and will not give you anywhere near the 5V@330mA specified.
Simple envelope calculation to prove this: just use Ohm's law with the full 12V across the input 100 ohm resistor. The maximum current which can flow through this is 120mA. More practically, I'd expect you to get only 60mA max at the output assuming you had a perfect linear regulator, and more likely only 40mA max at the output.
Other things I've noted:

C1 and C2's values are massive. 330mF on the input and 100mF on the output? really? More typical values are in the 100's of microFarads. In theory having large caps doesn't hurt, but ones this large either have very low voltage ratings and/or are much more expensive.
The two resistors really just shouldn't be there.
C3 and C2 are redundant. Get rid of one of them. Note that if you remove the 100 ohm resistor you need to remove the zener diode as well!
Some mobile phones won't charge just because you give them 5V to a USB port. You need to connect the data lines as well. How to do this is beyond the scope of this answer.
This is really pushing a linear regulator to its limit (probably beyond its limit). In the best case you're going to be dissipating 660mW in the regulator, and at the worst you'll be dissipating 3.1W. That's a lot of heat. You'll certainly need some sort of heat sinking in place.

As far as the absolute minimum voltage ratings requires, C1 must have a voltage rating of at least 7.2V in this circuit and C2 must have a minimum voltage rating of 5V. However, you'd have to intentionally go out of your way to find ones rated this low, and it's a bad idea to run caps so close to their max voltage. It's very common to find ones rated at 16V, 25V, 50V, or even higher voltages for pennies. Use these instead.
I would highly suggest you get some pre-made module (preferably one with a DC-DC buck converter rather than a linear regulator). One example is this module. This doesn't solve the data-line issue (4), but it does solve all of the other issues I listed.
Comment: I would read C1 and C2 as 0.33 uF and 0.1 uF, not 0.33 Farad and 0.1 Farad.  It is common to assume uF if no unit is shown, and, if I recall correctly, these are the recommended values from datasheet example circuits.
Comment: True, except the schematic has a mix of components with uF and without. Also, as the OP indicated they aren't experienced with electronics so I was being explicitly clear.
Answer: The Voltage of the C1 and C2 should be at least double of the expected voltage in this circumstance. Typically Capacitors voltages in the range 0.1uf to 0.3uf are around 100 VDC not really too important again as long as it is above the expected Voltage. I do not know why the a 7805 IC will not work. It is rated at 1 amp with a maximum input voltage 35 volts. A heat sink is required to dissipate excess heat. It is very simple, 3 pins Input voltage, ground, and output. The only other components you will need are the R1 and C3. Since their is no AC component to this circuit, the other capacitors really are not necessary.----------
 After reading the above answer you definitly need the R1 to limit the charging current of the phone battery, It would more than likely overheat otherwise.
Answer: I'd go with 25V or more for C1 and 10V or more for C2 and C3. Basically, the capacitor voltage rating is the limit up to which it's guaranteed by the manufacturer to work properly and not leak more than the specified value and, most importantly in your case, not break down. Generally it's a good idea to leave some margin, especially if you expect temperature variations, but it doesn't usually make sense to go higher than twice the expected voltage. It won't hurt, but the part may be more expensive and larger.
Answer: I don't see why a 7805 shouldn't work in the correct setup. This is a long shot and a bit cheap and I don't know whether or not it is helpful. You could consider running a line from the bike's 12 volts to a cigarette lighter socket kit and plugging an automotive USB adapter into it to give you a usb port (or two) with the needed 5 volts. The wire could be run hidden and the socket could be placed in the saddle bag out sight or up front with the speedo/tach. A quick and inexpensive approach. I hope that this is helpful.

I want to convert 12v DC into 5v DC


Is $\mathbb{E}[|X|] \geq |\mathbb{E}[X]|$?

Question: Given a random variable $X$, from the definition of the variance, $\mathbb{E}[X^2] \geq \mathbb{E}[X]^2$. It seems intuitive that $\mathbb{E}[|X|] \geq |\mathbb{E}[X]|$ should be true. Is this the case?
Comment: Apply expectation to $-|X| \leq X \leq |X|$.
Comment: That is almost true : It might be "Equal" too. Change $\gt$ to $\ge$.
Comment: [Expectation inequality involving absolute values](https://math.stackexchange.com/questions/3811554/expectation-inequality-involving-absolute-values) is a duplicate question.
Comment: Try and look up Jensen's Inequality. If your intuition tells you that expectation behaves just like the "integration" operator then that is because it is an integration operator
Comment: I made the change >  to ≥.
Answer: They could be equal, but other than that you're basically right.  The intuition is that $E[X]$ is a sum with both positive and negative terms, some of which cancel each other out, but $E[|X|]$ has the same terms but all made positive.  (This assumes a discrete random variable; if your random variables are continuous, replace sums with integrals.)
More generally: These are both examples of Jensen's inequality, which says that $E(f(X)) \ge f(E(X))$ for a random variable X and a convex function $f$.  When we have $f(x) = x^2$ this becomes $E(X^2) \ge E(X)^2$ (the variance is positive); when we have $f(x) = |x|$ this becomes $E(|X|) \ge |E(X)|$, as you observed.
Answer: If $f(x)$ is the pdf of $X$ you have
$$\mathbb{E}[|X|]=\int_Df(x)|x|\mathrm{d}x$$
and
$$|\mathbb{E}[X]|=\left|\int_D f(x)x\mathrm{d}x\right|$$
Appying the absolute value properties:
$$|\mathbb{E}[X]|=\left|\int_D f(x)x\mathrm{d}x\right|\leq \int_D |f(x)\cdot x|\mathrm{d}x=\int_D |f(x)|\cdot|x|\mathrm{d}x=\int_D f(x)|x|\mathrm{d}x=\mathbb{E}[|X|]$$
So
$$|\mathbb{E}[X]|\leq\mathbb{E}[|X|]$$
Note that a $f(x)$ is always non negative, so $|f(x)|=f(x)$


Is it possible to set up JavaScript to capture when a button is clicked that's from an external site iframe?

Question: Have an iframe on a Visualforce page that's src is from an external site. The iframe has a button that's used to send a recording off via email from that external site. I'm trying to see if it's possible to add some JavaScript to capture the DateTime when that button is clicked. Been getting some unreliable data back from the external site about when users are sending the email, so we want to see if we can capture that on our end instead.
Answer: You can add a listener with JS to the iFrame
ex.
<code>var iframe = document.getElementById('myIFrame');
iframe.contentDocument.body.addEventListener('mouseup', Handler);

function Handler() {
    alert(new Date());
}
</code>
Comment: Rather inaccurate to check on the entire iframe itself for a mouseup event, but an interesting idea. I'll give it more consideration.
Comment: To get the button itself, can also get the contentWindow.document of the iFrame and look for the element itself


IIS7 and Wordpress - Admin has no access to theme directory

Question: After updating my Wordpress site running on IIS7 to version 3.0.3 I tried updating the theme (LightWord) to the latest version. The theme auto upgrade feature failed so I logged into my server and tried to access the directory of the theme via the file system(C:\websites\wordpress_root\wp-content\themes\lightword). To my surprise I was told I did not have access to the directory. I tried viewing the ACL list for the theme folder but again was denied access. I access the Windows 2008 machine (which is actually a VPS) via RDP but I log in as an administrator. Shouldn't I have I have access to ALL files on the server? Has anyone else run into this issue?
Answer: It looks like even the Administrators group was removed from that folder.  It's rare for an app to remove that, but it does occur.  The LightWord theme installer must have a bug in it.
You can get it back again by taking ownership of the folder.  You can do that from the same security tab as you update the permission.  Take ownership, save out, and then add the administrators group back again.
Comment: Thanks for the answer. I tried doing just that, taking back ownership, however I got the access denied message. I even tried to use "takeown" from the command line (running as administrator) but I still received an access denied message. I decided to disable UAC and then rebooted the VPS. After the reboot I found the entire lightword theme directory was gone. very strange.
Comment: Possibly something was stuck in the installer and needed to complete, so the reboot cleared it up.  In regards to the permissions, first you take ownership, then you still need to grant your user (or Administrators) NTFS permissions.  Taking ownership just allows you to grant the NTFS permissions.  In any case, it sounds like the folder has been cleaned up now.


Dashes in "st-vertex-cut" or "st-vertex cut"?

Question: People use "vertex-cut" and "vertex cut" where I am unsure whether it should be with dash or without dash. For me, it looks nicest to have "st-vertex-cut" and then "st-vertex-cut set" without dash, where "st-vertex-cut" specifies the set, but I am unsure. What are the rules for adding the dashes and how to write the set that is defined by vertex cuts disconnecting two terminals called S and T?
Answer: You are forming a compound noun. According to Oxford dictionaries,

In the past, these sorts of compounds were usually hyphenated, but the situation is different today. The tendency is now to write them as either one word or two separate words. However, the most important thing to note is that you should choose one style and stick to it within a piece of writing. Don't refer to a playgroup in one paragraph and a play-group in another.

Your problem is that st-vertex is already hyphenated—and actually not an example of good formatting, I think using capitalized ST or dashed s-t as is done sometimes would be better. Hence, the option of making just one word, * ST-vertexcut, is ruled out. I would go for ST-vertex cut, and ST-vertex cut set (or even ST vertex cut [set]).
Btw, "vertex" is omitted in Wikipedia article, does it mean that you have a variant of what they describe or is it the same?
Comment: The *"st-vertex-cut" is the same as *"s-t cut"* but I deal also with edge cuts so I want to differentiate each cut.
Answer: It all depends on what is modifying what, and how you want to encourage that reading.
You're talking about a set of vertices, which are a cut set and that is a set cutting between a source and target ('st') vertex. So, in order, it should be: st, vertex, cut, and set.
Since the 'st' can't stand alone (it's not a stand alone word), it must be st-vertex, but also it is a cut set of vertices (or vertex cut set).
So based on principles, I'd suggest 'st-vertex cut set'.
But that's logic and not necessarily what people actually do. I've seen both "vertex-cut set" and "vertex cut set"; since, it seems at free variation, it is really now your preference. For readability, I think fewer dashes the better.
Comment: Also, even a better source of an answer: see what other people do (look in algorithms or theoretical cs papers).


How to describe your skill levels in the CV?

Question: What are possible/standard words to describe your skill levels in different programming languages in your CV? I currently use these three:

expert
advanced
beginner

I do not consider myself an expert in any programming language, so I classify all my skills as either beginner or advanced. However, I would like to differentiate more. I am especially looking for something between advanced and expert. Any suggestions? Or should I not even bother to differentiate any more detailed?
Comment: Good question! Is very hard to rate yourself as an expert. What is an expert? What is intermediate?
Comment: Sometimes the best questions are closed :-|
Answer: I would split them into two groups:
Working knowledge
// Here goes a list of the technologies you have worked with and feel comfortable using. You can make use of them right now if asked (with all the help there is of course).
Basic knowledge
// List of the things you have played with or have a basic understanding of their purpose. You can't make practical use of them without studying them in deep first.
That's pretty much the basic dichotomy your employer would understand and would hardly ask for more. Unless an expert level with some technology is asked for specifically.
Comment: But it depends on the job specification- I would not usually show basic knowledge technologies unless they were relevant
Comment: Definitely so. I was just making a point that more than two levels is not really useful.
Comment: I have more than basic knowledge in a certain field, however, I am no longer working with it. What about using different terms? _Active_, _Passive_, _Basic_?
Answer: I don't explicitly indicate my skills and experience with each technology or tool on my resume. Instead, when I provide descriptions of each job and my duties as well as my personal and academic projects, I also mention the core technologies that I've used in support of that position. Every place that I've applied to either asked for a cover letter or provided an application form, which I used to enumerate specific skills that I had (focusing on those relevant to the job description that I was applying to) and described my level of experience with each one.
There are two problems that I see with listing your skills explicitly.
First, you have to tailor your resume even more for each job that you apply to. In order to save space, you are going to want to focus on the skills that are listed in the job description plus anything else that you feel is relevant. You can't possibly list every skill you have - I know that for me, it would take up way too much space. As you gain experience and knowledge, it'll only become harder to choose what to enumerate.
Second, how do you define "expert", "advanced", and "beginner"? Where do you draw the line? Things that I think a beginner should know might be something that you consider to be advanced. Using such ambiguous words doesn't give me any information about you as a candidate for a position. On top of that, languages (or any skill) cover a lot of areas. I could be an expert Java Swing developer, but have no knowledge of Java networking and limited threading knowledge. Am I a beginner, advanced, or expert at Java? Your work experience will let me know what aspects of the language you have used and for how long.
I honestly don't think it's about the skills that you have, but rather what you are capable of learning and contributing to the project, team, and organization. That's the approach I've taken and it appears to have worked quite well for me - I've obtained two six-month co-ops, three summer internships, a TA position, and a full-time job (pending paperwork) with this approach.
Comment: +1 Leaving out "expert" or "advanced". Just don't put down any technology you aren't comfortable with being thrown into the deep end of. Recruiters only look to see if all the right words are there. The technical interview will sort the rest out.
Comment: @Job, don't discriminate based on age, it makes you old farts look like idiots
Comment: Actually, quite a few places I applied to used automated parsing of your resume. This allows them to pick out keywords, like "Java", "Swing", "C++", ".NET" and so on regardless of where they are in your resume. So save the space and make every single word count. Simply listing technologies doesn't tell me anything, but once I identify people who have the knowledge I want, letting me see a story about what you did with that knowledge or technology or tools helps a lot, IMO.
Comment: Dude, you are 23, and your skill list is too long to enumerate on a resume? Actually never mind, for I too leave out my familiarity with Ms Word and Internet Explorer.
Comment: @Job I don't know what's so hard to believe about that. Especially since I've been developing software for 6 years now, and have been employed in the field on-and-off between courses for 5 years, for a total of 2 years of work experience.
Comment: @Shawn, I guess it is not about the age. There are some 19-20 yo heavyweights on SO who are full of doubt (any smart developer should be) rather than inflated sense of accomplishment. Calling names is probably not the smartest route. I am certainly not an old fart. Not too long ago I inflated my own experience based on any random school projects just to get my foot in the door, but I would not openly brag about that stuff.


Slow autofocus from Tamron 150-600 on Canon M6 Mk II

Question: I rented a Tamron 150-600 for birding to use on my Canon M6 Mk II.  It works well but the first shot when I pick it up takes forever to focus.  I carry it over my shoulder turned on  which means it is pointing down at nearby ground when I am not shooting.  I have it set on the 10m-infinity setting and using 1 point AF and one shot AF.  It seems it is so far out of focus there is no contrast at all, then it takes a long time to recover from that.  Once the first focus is achieved it is quick for the next shot.  I will try turning the camera off and see if that helps.
Comment: I think I have the same glass ([`TAMRON SP 150-600mm F/5-6.3 Di VC USD G2 A022`](https://www.tamron.eu/lenses/sp-150-600mm-f5-63-di-vc-usd-g2/) ?) and haven't experienced any issues with it with Canon EOS 2000D. Are you perhaps using `EF-M` + some converting mount? Also, try to set `VC 2` or `VC 3`. If you have another camera, try comparing, I'd bet it's the converter's or camera's fault, especially judging by the notice from Tamron about firmware update.
Comment: I use a Canon EOS M5 and had the same issue with the Sigma 150-600mm. However I was reassured that the issue was happening due to the converter although I was using the Canon Adaptor! Something to do with power and connectivity. In the end, I returned the Sigma. I sometimes get the same issue if I use the Canon 70-300mm L f/5.6! I find that the only lenses that run Hassle free are the EF-M lenses.
Comment: @PeterBadida:  I looked up the firmware update, which claims to provide compatibility with the R series mirrorless but does not say anything about M series (with the APS-C sensor).  Thanks
Comment: Pre-focusing on some far-away object (tree, cloud if border is sharp enough) also helps.
Comment: @PeterBadida:  yes, I am using the Canon EF-M converting mount.  The lens seems to drift toward the near focus when not being used, whether the camera is on or not.  It helps to point it at something 5 meters away or so, then swing up to a farther view.  I suspect my copy is new enough to have the firmware update, but I don't know how to check.  I don't have another camera to check it on.
Comment: @AbdulNQuraishi:  I am planning to try out the Sigma soon.  I have used the old Canon 100-400 with the adapter with no problems.
Answer: Try carrying the lens over your shoulder with the front pointed sideways towards your other shoulder, rather than down. Gravity will pull the focus elements down when you're walking and the lens is pointed down and no power is supplied to the AF motor. It's much like zoom creep.
To feel just how much gravity affects the heavy zoom and focus elements in lenses of this size, try this when you're sitting at home. Point the front of the lens straight up and twist the focus ring or zoom ring in both directions. You'll likely notice greater resistance in one direction than the other for each. Then flip the lens so it is pointing down and repeat the test. You'll likely notice the increased resistance is now when you twist each ring in the opposite direction than before. It's gravity that is the difference!
I really noticed this with a (well used) Sigma 120-300mm f/2.8 Sports I recently used. I had the lens attached to a monopod via the tripod collar. Once I put the monopod over my left shoulder with the lens pointed towards my right shoulder the focus did not creep.
When I first tested the 120-300mm f/2.8 lens I thought it was defective because the focus ring was so much harder to turn in one direction than the other. I was testing it with the lens pointed straight down. Then I thought to point the lens straight up and, lo and behold, it was then equally harder to twist the same ring in the opposite direction. This is even a lens with no extension due to zooming or focusing. It's all internal.
An advantage of putting the monopod over the left shoulder is that the torque acting on the attachment between the monopod and tripod collar will be in the tightening direction, rather than in the loosening direction if you put the monopod over your right shoulder with the lens pointed towards your left shoulder.
Comment: I have used the Canon 100-400 Mk 1 with the adapter and with and without the 1.4x extender with no problems.  Maybe its focus element is lighter.  The Tamron had two tripod sockets on the lens, so I switched the sling to one that pointed the lens up.  It didn't change the direction the focus moved.


Do people need nitrogen from air for health?

Question: Can people breath totally nitrogen-free atmosphere for a long time? I know, nitrogen is essential for life, and in big quantities, but maybe people can take it entirely from food, from proteins, etc?
Comment: Some short comments - Nitrogen gas is pretty much inert and nutritional nitrogen is mainly obtained from the diet. Inhaling pure oxygen will kill you in the longer run. So what exactly is your question? If N2 gas has dietary value, or whether nitrogen-less air where ~79% of some other non-toxic gas substitutes for N2 can sustain life, or whether 100% O2 can possibly sustain life?
Answer:
Do people need nitrogen from air for health?

No. This is well established!

Can people breath totally nitrogen-free atmosphere for a long time?

Yes. Also well established!

I know, nitrogen is essential for life, and in big quantities, but
maybe people can take it entirely from food, from proteins, etc?

As expounded on in the comments by AliceD, nitrogen gas (N2) is entirely taken in by humans from their diet, since atmospheric N2 is pretty inert. It is also not necessary for gas exchange to take place in the lungs.
Some extra questions as an addendum:

Can one substitute N2 in atmospheric air with another gas, and sustain human life?

Yes. All side effects would be attributable to the effects of the substituting gas (e.g. it may be heavier or lighter or equally or more reactive than N2).

Can 100% O2 sustain human life?

No, and such a case has never been recorded. Oxygen toxicity following hyperoxia is very dangerous. Ironically, too much oxygen damages lung tissue and epithelial membranes via oxidation and render the lungs unable to exchange gases correctly; and so death by suffocation follows in such extreme cases such as with 100% O2.
Comment: A pedantic point: dietary nitrogen is ['fixed' nitrogen](https://en.wikipedia.org/wiki/Nitrogen_fixation), not N(2) which (to quote the Wikipedia article) is 'metabolically useless" to all but a few (very important) microorganisms. N(2) is, however, primarily responsible for 'the bends' ([decompression sickness](https://en.wikipedia.org/wiki/Decompression_sickness)). (Nitrogen 'fixation' is why the [Harber process](https://en.wikipedia.org/wiki/Haber_process) is so important)
Comment: Is it known that none of the microbes in the microbiome require nitrogen in the air from inside the intestines for protein synthesis?
Comment: Do they have on ISS nitrogen-based air?
Comment: I think negative effects of oxygen come frm its partial pressure, not from its percentage. Thus, 100% oxygen at 20% atmospheric pressure should be harmless, no?
Comment: Oxygen toxicity depends on partial pressure, sure. That relates to how many O2 molecules there are. Fewer make it less toxic, no doubt. But the act of breathing in low atmospheric pressure is more difficult too, it's another problem entirely. During inhalation, lung volume increases, lung pressure decreases below that of atmospheric pressure. This draws air into the lungs. At lower atmospheric pressure, less total air is drawn in, so breathing is more difficult at lower atmospheric pressures (or at higher altitudes due to the same phenomenon). So you're describing a trade-off.


If $a^k|b^{k+100} $ for every $k$, then show $a|b$.

Question:
If $a^k|b^{k+100} $ for every $k$, then show $a|b$.

Attempt

If $k=1$ it shows that if $p | a$ then $p|b$ too, so $b$ has every prime divisors which $a$ contains. But I don't Know what to do now. Could anyone help?
Answer: Hint:

Use the fact if $d=\gcd(a,b)$, then $a=dx$ and $b=dy$ where $x,y$ are relatively prime.
Use Gauss lemma.

So you got $$d^kx^k\mid d^{k+100}y^{k+100}\implies x^k\mid d^{100}y^{k+100}$$
Now since $x,y$ are relatively prime we have: $$x^k\mid d^{100}$$ which is true for all $k$. So if $x>1$ then $x^k$ is bigger then $d^{100}$ for big enough $k$ which is impossible. So $x=1$.
Answer: Let $p$ be a prime that divides $a$, let $p^m$ be the highest power of $p$ that divides $a$ and let $p^n$ be the highest power of $p$ that divides $b$. We show that $m\leqslant n$.
By hypothesis, we have that $mk\leqslant nk + 100n$ for every $k\geqslant 1$.
Divide by $k$ to obtain that $m\leqslant n + \frac{100n}k$ for every $k\geqslant 1$.
Letting $k\to \infty$, we obtain our result.
Comment: Notice of course that, in the argument above, the $100$ in $k + 100$ could be substituted by any expression that is $o(k)$ as $k\to\infty$.
Comment: There's no need to use primes here - see my answer.
Answer: Hint $\ \forall k\!:\ \color{#c00}{b^{100}} (b/a)^k\in \Bbb Z\,\Rightarrow\, b/a\in \Bbb Z,\,$ since unbounded powers of proper fractions have unbounded denominators, so they can't all be written with $\,\color{#c00}{b^{100}}$ as a denominator. $\ $ QED
Remark $\ $ This is true far more generally. Suppose $ \:D\:$ is any Noetherian integrally closed domain, e.g. any PID. Suppose that $ \:w\:$ is a fraction over $ \:D\:$ such that some unbounded sequence of powers of $ \:w\:$ has a common denominator $ \:0 \ne d\in D,\:$ i.e. $ \:d\!\:w^{n_i}\in D\:$ for all $ \:n_i.\:$ Then $ \:w\in D.$
Proof $\ $ By ACC the sequence of ideals $  (d, dw^{n_1}, dw^{n_2},\ldots)$ eventually stabilizes, which implies that for some $ \:k\:$ we have $ \: dw^{\large n_k}\in (dw^{\large n_{k-1}},\ldots, dw^{\large n_1}, d),\:$ which implies
$$  d\: w^{\large n_k} + c_{\large n_{k-1}} d\: w^{\large n_{k-1}} +\:\! \cdots +\: c_{n_1} d\: w^{\large n_1} + d\: =\: 0$$
Cancelling $ \:d\:$ yields $ \:w\:$ is integral over $ \:D,\:$ hence $ \:w\in D,\:$ since $ \:D\:$ is integrally closed. $\ $ QED
Elements whose powers have such a common denominator are called almost integral. Clearly integral elements are almost integral. By above the converse holds true in Noetherian domains.
Comment: See also [here](https://math.stackexchange.com/a/142786/242)


Proof that free scalar field is conformally invariant

Question: So, under conformal transformations $$x\mapsto x'\\
\phi\mapsto\phi'(x')=\Omega^{(2-D)/2}\phi(x),$$ where $$\eta_{\mu\nu}\frac{\partial x^\mu}{\partial x^{'\alpha}}\frac{\partial x^\nu}{\partial x^{'\beta}}=\Omega^{-2}(x)\eta_{\alpha\beta},$$ the action transforms like
$$S\mapsto\int d^Dx\,\Omega^{D-2}\partial_\mu(\Omega^{(2-D)/2}\phi)\partial^\mu(\Omega^{(2-D)/2}\phi)$$
(A quick way to get to this equations is by instead considering the associated Weyl transformation as described in an answer in Simple conceptual question conformal field theory). It is then obvious that the action is invariant under scale transformations, i.e. when $\Omega$ is constant. However, why is it invariant when $\Omega$ is not constant? What does one do with the terms involving derivatives of $\Omega$?
Comment: The only non-constant $\Omega$ for which this will still be invariant is the one corresponding to special conformal transformations.
Comment: I think this is because $\phi$ is not a primary field. Rather, $\partial\phi$ is a primary field, and the action is invariant under conformal transform. This is true in 2d. For general dimensions, I am not sure.
Comment: $\partial_\mu \phi$ is not primary in $d > 2$.
Comment: So this theory is not Weyl invariant? In any case, let us assume that $\Omega$ is restricted by the equation relating the metrics in the different coordinate systems. This should be enough to proof the invariance of the action since that restriction is already enough to show that $\Omega$ comes from dilations or special conformal transformations (or compositions thereof).
Comment: Oh yeah, for sure. So the general action is Weyl invariant (so the $\Omega$ doesn't have to come from a conformal transformation) if we scale $\partial\phi$ instead of $\phi$. I remember something similar happening in electrodynamics (maybe in a book by Wald?).
Comment: @ConnorBehan I don't think see why it should work for $\Omega$ corresponding to special conformal transformations. The approach I tried was to see if it worked for inversions. The action is not invariant for these, even up to total derivatives because one ends up with an annoying $(D-2)^2x^{-2}\phi^2$ factor
Comment: I can't remember if it's supposed to work for a single inversion. But it looks to fast to say that each $\partial_\mu$ simply picks up the Jacobian to the power of $-\frac{1}{D}$.
Comment: @ConnorBehan It is not that each derivative picks up a factor of $\Omega^{-1}$. It is just that, after contraction with the inverse metric in the kinetic term this is what pops out. In any case, thanks for this conversation. It turns out that everything works out (I should also thank Bruno de Souza Leão Torres for conversations on this). I will try to type it as an answer in case anyone finds it useful in the future.
Answer: As mentioned by @ConnorBehan, the result is only true for Weyl factors coming from conformal transformations. Bruno de Souza Leão Torres stressed to me the importance that said conformal transformations are of the flat metric. Indeed, this proof will only show conformal invariance for the theory coupled to the flat metric.
The conformal transformations of the flat metric are well known: they are generated by translations, rotations, dilations, and special conformal transformations. Invariance under the first three can be checked. This answer will focus on invariance under the last. The key for this is noting that every special conformal transformation is a translation conjugated by inversions $I:x^\mu\mapsto x^\mu/x^2$. Thus, if we check the theory is invariant under inversions then it turns out that the theory will be invariant under special conformal transformations.
Inversions have the conformal factor $\Omega=x^{-2}$. Then, we have
$$\partial_\mu(\Omega^{-\frac{D-2}{2}}\phi)=(D-2)(x^{2})^{\frac{D-4}{2}}x_\mu\phi+(x^2)^{\frac{D-2}{2}}\partial_\mu\phi.$$
We now need to compute the square of this vector and multiply by the remaining factor of $\Omega^{D-2}=(x^2)^{2-D}.$ The resulting term quadratic in derivatives is then clearly the original action. The remaining terms are
$$2(D-2)(x^2)^{-1}x^\mu\phi\partial_\mu\phi+(D-2)^2(x^{2})^{-1}\phi^2.$$
On the first term we can use $2\phi\partial_\mu\phi=\partial_\mu(\phi^2)$. Moreover, note that
$$\partial_\mu((x^2)^{-1}x^\mu)=(x^2)^{-1}(D-2).$$
Then these remaining terms are a total derivative
$$(D-2)\partial_\mu((x^2)^{-1}x^\mu\phi^2).$$
As a final remark, as explained by Bruno in Simple conceptual question conformal field theory, one can modify the scalar field theory so that invariance under any Weyl transformation, even those that can't be undone by diffeomorphisms, is achieved.


Kill Thread in Pthread Library

Question: I use pthread_create(&thread1, &attrs, //... , //...); and need if some condition occured need to kill this thread how to kill this ?
Answer: First store the thread id
pthread_create(&thr, ...)

then later call
pthread_cancel(thr)

However, this not a recommended programming practice! It's better to use an inter-thread communication mechanism like semaphores or messages to communicate to the thread that it should stop execution.
Note that pthread_kill(...) does not actually terminate the receiving thread, but instead delivers a signal to it, and it depends on the signal and signal handlers what happens.
Comment: @Steve: Unfortunately, `pthread_cancel` is the only clean way *in library code* to interrupt a thread that might be blocked on a syscall. The other method is to install an interrupting signal handler and be sure all of your code is prepared to deal with `EINTR`, but library code cannot assume it has a right to change signal handling or impose `EINTR` handling on the caller.
Comment: The problem with pthread_cancel, btw, is that if you use it, then the code running in the thread that's cancelled, has to understand cancellation points, and make sure that (a) it hits one frequently enough that it actually gets cancelled in good time, and (b) it doesn't leak resources when this happens. This is kind of tricky, whereas if you use a message, then it's nicely explicit in your code exactly when the thread can exit.
Answer: There are two approaches to this problem.

Use a signal: The thread installs a signal handler using sigaction() which sets a flag, and the thread periodically checks the flag to see whether it must terminate. When the thread must terminate, issue the signal to it using pthread_kill() and wait for its termination with pthread_join(). This approach requires pre-synchronization between the parent thread and the child thread, to guarantee that the child thread has already installed the signal handler before it is able to handle the termination signal;
Use a cancellation point: The thread terminates whenever a cancellation function is executed. When the thread must terminate, execute pthread_cancel() and wait for its termination with pthread_join(). This approach requires detailed usage of pthread_cleanup_push() and pthread_cleanup_pop() to avoid resource leakage. These last two calls might mess with the lexical scope of the code (since they may be macros yielding { and } tokens) and are very difficult to maintain properly.

(Note that if you have already detached the thread using pthread_detach(), you cannot join it again using pthread_join().)
Both approaches can be very tricky, but either might be specially useful in a given situation.
Answer: I agree with Antti, better practice would be to implement some checkpoint(s) where the thread checks if it should terminate. These checkpoints can be implemented in a number of ways e.g.: a shared variable with lock or an event that the thread checks if it is set (the thread can opt to wait zero time).
Comment: In most general cases this absolutely correct. However, there are many situations in which this is simply not practical. For example, my current project is a minimal text editor, in which I have a dedicated thread for receiving user input. Since `getch()` operates synchronously, my input thread would be unable to detect that it needs to terminate until the user pressed another key. This would be very bad design. Since the user input thread never needs to allocate additional resources, it is far better to kill it with `pthread_cancel()`.
Answer: Take a look at the pthread_kill() function.
Answer: pthread_exit(0)

This will kill the thread.
Comment: This answer is wrong. pthread_exit() is a function used to terminate the thread where this function is called. This is a proper termination. pthread_exit() cannot be used to affect any other thread. Kindly don't mislead.

Kill Thread in Pthread Library


Philippines passport holder transit visa

Question: I bought my e-ticket through an online travel agency PAL- Air Canada. From Manila, layover 3h and 55 mins in Narita Tokyo terminal 2. I will transfer terminals and airlines from terminal 2 to terminal 1 and depart with Air Canada. Do I need to claim my check in luggage in Narita or it will be checked in through to my last destination?
Comment: Title and question (the thing with a question mark) don't match
Answer: Unless your transit is an overnight layover, you do not need a transit visa for Tokyo.
From Timatic:

Visa required, except for holders of onward tickets transiting on the same calendar day.

Narita's transit area closes overnight, so you will have to enter Japan if your departing flight is the next calendar day - however, you should be eligible for a Shore Pass in this instance:

Holders of onward tickets transiting to a third country can obtain a Shore Pass on arrival for a max. stay of 72 hours only if there are no connecting flights on the same calendar day


Where are mailboxes in Gilneas?

Question: I've started a Worgen character and have mailed him a handful of useful bits and pieces (heirlooms and other low level gear).  However I haven't been able to find a mailbox in the Gilneas area since I was Level 1 in Gilneas City.  I've reached Stormglen Village and was wondering when am I next likely to see a mailbox?
Comment: Yes.  The problem is that there appears to be no mailboxes in Gilneas, hence my curiousity.
Comment: You can always set your minimap radar to show mailboxes in your area, but this will only show them in your general vicinity.
Answer: I don't know exactly when this was added (likely patch 4.0.6), but there is now a mailbox in the starting square in Gilnaes.
If you turn around, it should be just past (and to the right of) Gwen Armstead, who gives you the quest Salvage the Supplies.
I'm not sure if any others were added or not.
Comment: I should note that I said 4.0.6 because it was present a month ago when I started a new Worgen.
Comment: That's always been there.  I believe that's the one I was referring to that I saw back in Gilneas City.
Answer: There aren't any. You'll see your first mailboxes (and flight points) when you leave that zone. The reason will make sense when you finish the zone quests...
Comment: I dispute that it makes sense now that I've finished the zone quests.  I can't see why Gilneas has mailboxes and none of the other small towns do.  Any reason that applies to the latter should also apply to the former.  Alas, that's the way it currently is.
Comment: It makes sense from a lore reason, too... after all, the Wall of Gilnaes was erected to prevent anything outside from entering.  What *doesn't* make sense is why Goblins have mailboxes in their second zone (or so I recall).
Answer: There IS a mailbox in Gilneas, near Duskhaven, just outside the Inn.
Answer: I found one. If you run back into the city, in the Merchant Square that was the starting area, the mailbox is still there. Depending at what point in your questing you do this, however, the city might have forsaken crawling in it. For me, I was at the quest where you rescue the miners when I decided I really hated the toon and wanted to send off my looms.
Up until you trigger the forsaken to swarm the city (which I think isn't until you're on the quest to retake it), you can run back into the Merchant Square and use the mailbox.
Comment: If you run back to the Merchant Square it is no longer there. I just did but the town is deserted and you can see nothing. :( I'm forced to finish all the damn quests to delete this toon and get my heirlooms back.

Where are mailboxes in Gilneas?


Can I hide my YouTube link in my Google+ profile and disassociate the two?

Question: Can I hide my YouTube link in my Google+ profile and disassociate the two?
Answer: Google+ Help Official Answer

The only information that is always public is your profile name, your
  profile image and cover photo, and the link to the YouTube channel
  connected to your Google+ profile or page.

Therefore hiding YouTube link from the Google+ Profile is not possible at the moment.
Source: https://plus.google.com/107150983484568200135/posts/ckCoUm2X3Sa
Comment: Please summarize what's at the link within the body of your answer, that way if the link goes stale, the information is still here.
Answer: You have to disconnect your YouTube channel from Google+.

Go to YouTube Settings
Click on "Disconnect channel from Google+" (next to your avatar)
On the next page, tick "I understand that my channel will be renamed."
Click "Rename Channel."

Source:  Why can't I hide my youtube link on my Google+ profile?
Answer:
Go to https://myaccount.google.com/
Account Management → Remove YouTube Content > Hide my profile
Check five boxes

You're good to go!
Took me forever to find this and I can't figure out how to re-enable it just yet—that is, if you wanted to.


Unity Touch problem

Question: Learning from some tutorials.
Made Swipe touch scene.
Have UI(virtual joystick) on canvas screen overlay. The problem is,when I am rotating character by joystick, my camera rotating too. If I've pressed on my UI, swiping script turning my camera around and I can't move the right way.
How can I solve this problem?
@Byte56
So your camera is rotating, when you're trying to steer using your on screen joystick?
Yes
Answer: This is a common problem, a common solution is to use a global flag. Basically, when your UI accepts input, you set a global flag (something like UIConsumingInput) to true. If you have any other inputs, like your camera rotation, you have it test to see if UIConsumingInput is set to true, if UIConsumingInput is true, you don't process input.
Comment: The problem was with my scene... My changes in scripts were not implemented into the build. Don't know why... Anyway, I made changes that you wrote above earlier and I will mark it as the right answer.

Unity Touch problem


Can I get rid of sap stains on my mulberry tree?

Question: My mulberry tree was leaking sap earlier and it left ugly black stains down the trunk. The tree has deeply furrowed bark. Can I remove this?
Answer: First, I can't stress this enough, before considering to remove the sap from the trunk, it would be best to take the time to identify the reason for the leaking sap ie Your tree may very well have bigger problems than just sap stains on the trunk...
Second, I would be very wary of removing sap from a tree trunk, doing so can lead to inflicting even more damage on the tree.
Third, keep in mind it will be almost impossible to remove all the sap from the trunk .
To remove the majority of the sap, use a (very) sharp, large blade (2inch/50mm) woodworking chisel that has been cleaned with something like rubbing alcohol.
Keeping the chisel as near parallel to the trunk as you can, very! carefully slice, pry off the sap. Whatever you do, do not let the chisel cut into the bark, or allow the sap to pull away the bark from the trunk. If the sap is really hard, use a hammer to very! carefully insert the chisel into the sap.
Once you've "very! carefully" finished removing as much of the sap as you can from the trunk with the chisel, take a clean (with rubbing alcohol or similar) woodworkers card scraper or decorators/painters hand scraper and very! carefully (this time keeping the tool perpendicular to the trunk) scrape off as much of the remaining sap as you can without damaging the bark.
I recommend stopping there, don't try to remove anymore sap.
If you felt compelled to try and remove even more sap, the following may work (disclaimer, I've never tried it).
Mix up some eco-friendly "degreasing" cleaning solution (read the label to ensure it is safe to use around plants, etc), then apply directly to the sap via a (new) stiff bristle cleaning brush. Allow the solution to "work into" the sap as per the instructions on the label. Then thoroughly rinse off with cold water.
Comment: Yeah the bigger problem would be bacterial wetwood.
Answer: That leaking sap & stained bark appears to be caused by bacterial wetwood, also known as slime flux. This is a common bacterial infection that creates slightly caustic sap & raises pressure within the wood. The pressure forces the sap out at weak points, staining the bark. The sap smells sort of fermented, right? That's the result of the bacteria having chowed down on the sugars in the sap. You may also notice bugs showing up for a party.
You shouldn't try to remove the bark. You can remove extra sap by infrequent gentle washing with plain water (rain is free, don't buy a hose for this.) Removing the discolored bark or trying to plug/patch will just cause additional spots where sap will leak instead, and may interrupt any compartmenting the tree's done on its own. The best management of the situation is to keep the tree free from additional stress, and living with what it looks (and smells) like.
The good news about slime flux is it can actually prevent other sorts of rot! It also generally does not kill trees. (I've had one infected in this way for 10 years, and it's healthier & larger than ever aside from the flux.)
Comment: Yup! You're the first to answer this right! (And welcome!)
Comment: FWIW my reference tree suffering bacterial wetwood is still growing strong (15 years now), the original leakage area completely healed, with no bark or sap removal, no treatment, and only minimal bark staining remaining there. The tree continues to show symptom (excessive sap leaking, fermentation odor) whenever pruned, however as the tree grows prune points are inevitably higher up, so odor and staining are not as obvious as when the tree was younger.
Answer: Prune the tree at the correct time of the year for that type of tree to avoid the stain from a leaking wound.
Over several years the stain does go away as the wound heals closing the leak. It's not a sick tree, it's just healing the wound!
Comment: What is the correct time of year to prune this type of tree?
Comment: Hint: It is a sick tree (badly infected with slime flux). I posted this as a filler question, still waiting on someone to post the right answer ;)


Does my crawl space need venting

Question: I have a crawl space under my main entrance of the house. It's about 3' tall. I added a heat duct because the floor at the entrance was always cold. So my question is do I need to vent the crawl space because I added the heat vent. Even if I just cut a hole in the door leading to the crawl space and put a vent cover there. Thanks
Comment: What's your climate?
Comment: Is the space enclosed?  Does the heat duct vent into the space?
Comment: I have a full sized door leading into the space. It's in my basement which is fully finished. The heat vent is in the space. There is no insulation on the floor joists.
Answer: Best practice varies with the climate.

If you open up venting between the basement and the dirt crawl, cover the dirt crawl with a moisture barrier.
Consider instead sealing the crawl entrance from the finished basement air, and opening a vent to the outdoors.
In SOME areas you may be allowed to put a fan to the outdoors. Mechanically controlled by humidity, it would offer the best of both cold and warm weather performance.

For research on this topic see,
Moisture Solution Becomes Efficiency Bonanza in Southeastern United States, PDF by Bruce Davis and Cyrus Dastur, AdvancedEnergy.org -Crawl Spaces
Answer: Is there insulation in the floor? There should be. There should be a vent but that has nothing to do with adding a new heat duct.  A vent is going to make the floor even colder.  Vents are normally opened in spring and closed in winter.  So you should add 2 on opposite walls come spring.
Comment: I dont mean add a vent outside. Just wondering if I need to vent in the house to keep air circulating.  Just don't want mould. Thanks
Comment: No you do not want to vent a crawlspace air into the house.  You want to keep that air separate from the house.  If you want to circulate air in crawl space you add vents in the foundation. If you want to circulate air more in the entry you would add a return vent back into furnace.
Comment: @JustinK that isn't strictly true, depending on the type of crawlspace. A crawlspace, like any other space in the house, is either conditioned space or it's not. If it's conditioned space, it's part of the building envelope and should be insulated accordingly (including vapour barrier). If it's not conditioned space, then it should separated accordingly and as far as the rest of the house is concerned treated as if it's "outside" (meaning: there is insulation and vapour barrier between it and the rest of the house).
Answer: Under floor ventilation of wood floors over earth is required by any model code to manage moisture from the earth molding and/or rotting the wood structure. As Justin K indicated, it does make the underfloor area colder, this is why many people block off the vents in the Winter. IMO, if you have adequate floor (and duct) insulation the temperature gained only makes a small difference in energy costs. If the blockage causes moisture issues it will be a false savings.
How serious any moisture problem could be varies greatly by location, climate, soil conditions, and if the earth is covered with a vapor barrier or not. Regardless, you do need vents. Seasonally block the vents if you like, but only if you're sure it will not cause moisture issues.

Does my crawl space need venting


Simultaneity of timelike separated events

Question: It can be easily shown that if we have two time-like separated events which are not simultaneous in one frame then they cannot be made simultaneous by Lorentz transformation. But, if those events are simultaneous in one frame then they can be made non-simultaneous by Lorentz transform, which contradicts the previous statement because we can Lorentz transform back to the original frame making it simultaneous again?
Am I missing something?
Comment: [Understanding the difference between timelike and spacelike separations](https://physics.stackexchange.com/q/449170/37364)
Comment: You have proved by contradiction that distinct timelike-separated events cannot be simultaneous in any frame.
Answer:
if we have two time-like separated events...But, if those events are simultaneous in one frame then they can be made non-simultaneous by Lorentz transform

If two events are both time-like separated and simultaneous then the two events have the same spacetime coordinates and will be simultaneous in all frames.
Furthermore, if the two events are simultaneous in one frame but not in another then the events cannot be time-like separated.
So there is no contradiction. In the second scenario you either have to drop time-like separation or drop that there is a frame where the events are not simultaneous; you can't keep both.
Comment: oh yeah. Thanks a lot. I just realised that simultaneous events at distinct locations have to be spacelike seperated, where it is possible to convert a simultaneous event into non-simultaneous by lorentz transform and vice versa. A S C E N D I N G


Shower is either all hot or all cold

Question: I have new house and one shower is either all hot or all cold. The shower head in the off position is down and when I turn it to the left its all hot. center is off and right is is all cold. I tried adjusting the plastic adjustment ring and that worked a little but is there a way to make is so it goes off to all cold mix then all hot like my other shower is?
Also if this fix can be made by changing the cartage can someone help me identify the brand based on the picture attached.

Answer: It looks like you have an issue with the mixing valve which looks like this -

More specifically it is probably due to an issue in the cartridge which is the front part of the mixing valve and is usually a white plastic cylinder that look like this -

These are in the wall right behind the shower handle.   It is likely that something is either jammed up (sediment) or broken in the cartridge.   If you open things up and take pictures we can help more.
Answer: That's an index button for Moen Faucets

Shower is either all hot or all cold


droid x bluetooth volume too low

Question: Does anyone know how I can get under the hood and modify the db output for my bluetooth media levels? I've read numerous posts of people complaining about this problem but am unable to find a solution.  On previous phones, I was able to access the underlying system settings by inputting some lengthy combination of numbers.  I don't know if this sort of hardware access exists on the droid x. I'm not finding anything on-line as to how to do this.
All ideas welcome.
Answer: Configurations
For most devices, you can only modify the volume of the earpiece, bluetooth, media volume or call volume if you are currently using that feature.
So, the best is to use your device "menu" button when you are using the bluetooth earpiece and check if said option exists. Alternativly, use the volume up/down from your device while with the bluetooth earpiece in use to try and control its volume.
One user at droidxforums mentioned a working solution for him:

Turn off the Bluetooth on the Droid X. Place a phone call like normal. Adjust the call volume to the MAX and then hang up. Turn the Bluetooth on the Droid X back on and activate your voice command. It will work. You can adjust volume up or down in that fashion.

Apps
If to no avail, currently, there are a few apps available from Google Play Store to deal with issues like this:

Recommended for custom ROM:
Volume+ FREE and the donate version Volume+ (Volume Boost)
Gives great results in controlling volume settings separably for each sound output available.

Recommended for Stock ROM
Bluetooth Volume
Worked as promised to control the bluetooth sound output, ideal for boosting in call volume.

This are the ones I have used with excellent results, you can find others at Google Play Store.

droid x bluetooth volume too low