Delta systems under Martin's Axiom

Question: The $\Delta$-system Lemma states that given an uncountable family $\mathcal C$ of sets with finite intersection there exist an uncountable subfamily $\mathcal D$ of $\mathcal C$ and a finite set $\Delta$ such that $d_1 \cap d_2=\Delta$, for all $d_1$ e $d_2$ distinct elements of $\mathcal D$. Does MA($\kappa$) imply that given a family $\mathcal C$ of $\kappa$ sets with finite intersection, there exist a subfamily $\mathcal D$ of $\mathcal C$ with $|\mathcal D|=\kappa$ and a finite set $\Delta$ such that $d_1 \cap d_2=\Delta$, for all $d_1$ e $d_2$ distinct elements of $\mathcal D$?
Answer: Martin's Axiom plays no role here.
This generalization of the Delta System Lemma is true (in ZFC) if and only if  $\kappa$ is a regular uncountable cardinal. This is lemma III.2.6 and exercise III.2.7 in Kunen's book Set Theory (the last edition).
Edit: As Mike pointed out in his answer, there is a missing assumption: one must assume that the family consists of finite sets (both for the usual lemma and its generalization).
There are also generalizations for family of infinite sets. See for instance the answer from Joel David Hamkins to this question.
Answer: Your formulation of delta-system lemma and attempted generalization (under MA) fail because there is an uncountable almost disjoint family of infinite subsets of $\omega$. You must assume that your family consists of finite sets and not just that their pairwise intersections are finite.
I am not sure what Charles' answer was intended to address.
Comment: Yes, I understood it some hours ago ;-)
Comment: Indeed, I overlooked the missing assumption. I will edit my answer. Thanks.

Delta systems under Martin's Axiom


3 lb pork butt roast, started in crockpot on warm instead of low. For 4.5 hours

Question: I placed a 2.89 lb pork butt in crock pot, on warm accidentally instead of low, left to cook for 4.5 hours before I realized it. Internal temp was 122.6 when discovered. Think it's safe to continue cooking on high too at least 165°?
Answer: Unfortunately, no.
122°F is inside the 'danger zone' of 40-140°F, which is where bacteria and such will reproduce well.  4 hours in 'the zone' is risky as even if you heat it to kill off the bacteria, there's still whatever toxins they produced in that time.
I personally like to start my crockpot on high, so I can be sure that it's heating up and get the food out of the danger zone quickly before I switch it to warm.  And it actually saved me about a month ago, when I realized that my crockpot wasn't actually heating… before I had planned an overnight cook.  (So I had a chance to warm it in the oven, then set it on low all night)


Exporting and importing attributes and sets

Question: I'm looking to export all my product attributes and sets into a fresh install. But I'm struggling to find a solution. Any help would be appreciated
Answer: Have you Googled before posting? There is no built-in solution for this, but somebody has done it previously using some scripts. Check out the question below. It involves running scripts writing a file and reading that generated file. Seems pretty simple.
how to export and import all attributes and attribute sets from one magento to other?
Fabian's answer might work as well. That one is more straightforward and involves just exporting and importing tables.
Comment: I tried this solution but it wouldnt update the default attr because they already exist. Such as color.


How to add QT_QPA_PLATFORMTHEME=qt5ct environment variable in Arch Linux?

Question: I am using a standalone tiling window manager QTile. In QTile I want to organize my GTK and QT Themes. For GTK theme I used a program named "lzappearance" and it works perfectly fine. But, for Qt I am using a program named as "qt5ct". On the top it is written this application is not configured correctly and when I click on the information button it says: The QT_QPA_PLATFORMTHEME environment variable is not set(required value: qt5ct).
Please help and guide me on how to set qt5ct and environment variables.
Answer: I'll answer with a full guide to help the ones who have not gotten this far:

Install qt5ct (sudo pacman -S qt5ct)
You might want to install a Qt theme, that can be done by sudo pacman -S breeze for example.
Edit /etc/environment as root by sudo nano /etc/environment and add the line QT_QPA_PLATFORMTHEME=qt5ct and save.
Log out and in (or reboot)
Now in qt5ct you can change your theme and settings

The important part is adding QT_QPA_PLATFORMTHEME=qt5ct to /etc/environment. This makes the Qt theme redirect to qt5ct.
Also, if you want Adwaita for Qt, (as I just did for myselft) you can install adwaita-qt from AUR. (yay install adwaita-qt) It comes with all the variants (light, dark, high contrast and high contrast inverse)
Comment: You're welcome, I just went through the same stuff a month ago with Gnome, the documentation is not very good about this. I'm very glad to help.
Comment: Can you set it locally instead of globally? For example `~/.config/enviroment.d/my-env.conf` works for all the vars expect this one (`QT_QPA_PLATFORMTHEME=qt5ct`).
Comment: Hi, Thanks a lot!! Because of you now I am able to set qt themes in QTile. I digged in the Arch Wiki for qt5ct, environment variables, and the github repo of qt5ct but it did not work.Thanks once again!
Comment: @Scorpion sorry, I have no idea
Answer: tempacc's answer is correct. It works. Thanks for your answer :)
For those interested in a more stable Linux Arch or any other flavors or Linux, I suggest adding this configuration: export QT_QPA_PLATFORMTHEME="qt5ct" into an override configuration file. For example, into this "qt5.conf" override file at: /etc/environment.d/qt5.conf

Below is the same as above. But with details and sources for those interested.
The "environment" file is a core Linux file. Editing any core Linux files is risky to result in an unstable Linux. Simply because, in the future, during Linux periodic updates, any Linux core files may be deleted and replaced. In turn, you risk loosing your valuable configurations. In turn, you risk an increasingly unstable Linux. In turn, you risk spending hours or days searching for the cause of an unstable Linux. To find out that somehow, your configuration was automatically removed.
To resolve this challenge above, I suggest editing a Linux override file. Instead of editing a Linux core file. The main difference between a core file and override file is that, in the future, after the periodic Linux updates, all your override files will likely automatically remain. Thus, a more stable Linux :) Those files are called override because any configuration you add to them will automatically override any core Linux configuration.
According to the Linux community, when possible and when appropriate, it is suggested to always add your configuration to override files
Steps to add the qt5 theme configuration to an override file:

If not already done, create a "environment.d" folder at "/etc/environment.d/qt5.conf". By the way, in the folder name, the ".d" suffix means an override. So double-check that you use the "environment.d" override folder. Not the core "environment" folder.

Inside that "environment.d" folder. Add a "qt5.conf" override file. This "qt5.conf" file could be any other override file name to your liking.

Inside that "qt5.conf" file, add this line: export QT_QPA_PLATFORMTHEME="qt5ct"

Set appropriately the permissions on both the override folder and override file above. If not sure, for your override folder and file, use the exact same permissions as the core folder and file.

For the new configuration to be applied, you might need to reboot your device. Done. Enjoy your more stable Linux :)

Related documentation about Linux configuration overrides at:
• https://jmmv.dev/2020/08/config-files-vs-directories.html
___• https://archive.ph/rcXKV
___• https://web.archive.org/web/20230131035142/https://jmmv.dev/2020/08/config-files-vs-directories.html
• https://manpages.debian.org/apt/sources.list.5.en.html
___• https://archive.ph/cauJe
___• https://web.archive.org/web/20240206050034/https://manpages.debian.org/bookworm/apt/sources.list.5.en.html
• https://www.redhat.com/sysadmin/etc-configuration-directories
___• https://archive.ph/wip/qDg5j
___• https://web.archive.org/web/20240202050823/https://www.redhat.com/sysadmin/etc-configuration-directories
Answer: I know this is an old question, but this is how I was able to set it dynamically on my Arch machine with multiple DE installed (KDE Plasma and i3) running X11 and having qt5ct installed:

Create an executable script within /etc/X11/xinit/xinitrc.d

An example script:

  #!/bin/sh
  if [[ $XDG_SESSION_DESKTOP == "i3" ]]; then
     export QT_QPA_PLATFORMTHEME=qt6ct
  fi

Reboot.
Comment: Thanks for contributing and welcome here. For the sole sake of… grumping… I would observe that you set the variable to qt**6**ct… when… with regards to this not **that** old question… OP appears to be qt**5**… ;-)


Why are my Avocado Leaves turning bright red?

Question: Tree is about 1-2 years old. Some of the leaves are turning bright red, why?
Answer: Looking at your picture, I wouldn't really call that "bright red". I would say it is brown. Those are patches of dead tissue on the leaves. My avocado tree looks like that when the leaves become damaged; they do turn quite a reddish shade of brown.
Dead portions of the leaves aren't necessarily a danger sign if there is some otherwise explainable reason for the leaf damage. For instance: sunburn, mechanical injury while you are maybe pruning or handling the leaves, heat damage from a nearby "outdoor grilling incident",... or some other known cause.
I'm no avocado expert, but the dead patches are so random looking and the rest of the plant looks so vigorous, that (unless someone else comes up with a more educated analysis) I wouldn't worry right now.
Comment: We have another avocado tree, and i've never see the leaves turn that bright. Not sure.


Probability that a component belongs to a giant component

Question: In a configuration model where each node has a degree 2. What is probability that a node belongs to a component of size n.
Answer: I don't know what a "configuration model" is, and this looks more like combinatorial graph theory than statistics.  You also need to know whether multiple edges between nodes are allowed, whether loops are allowed, and how many nodes there are.
Let's suppose there are $v$ nodes and that multiple edges and loops are allowed.  Start at a particular node $A$ and choose one of its edges.  The probability of being a loop (i.e. $A$ belongs to a component of size $1$) is $\frac{1}{v}$.  If not, suppose it attaches to some other node; then the probability of the second edge from the second node goes back to $A$ (i.e. $A$ belongs to a component of size $2$) is $\frac{v-1}{v}\times\frac{1}{v-1} = \frac{1}{v}$. And so on.
So the probability $A$ belongs to a component of size $n$ is $\frac{1}{v}$ (for $1 \le n \le v$).


My Guinness is mixing into my harp and not staying separated, any trouble shooting ideas?

Question: My Guinness is mixing into my harp and not staying seperated! Any trouble shooting ideas? Half and half trouble!
Answer: Here are some troubleshooting tips I've found (source):

Hold your pint glass at an angle, and fill just over halfway with Harp
  or Bass.
Rest the spoon upside down over the center of the glass, and pour the
  Draught Guinness over the spoon which will evenly disperse the flow
  and keep the Guinness from mixing -- the Guinness needs to be on the
  top.
Serve while the nitro is still cascading.

If they're mixing, my guess is that the Guinness is not being poured carefully enough, so that would be where I'd start.
Comment: Drink the Guinness, drink the Harp; jump up and down; next time you see it will be mixed.
Comment: Don't forget: Practice. Practice. Practice.
Answer: If you want you can spend a little bit of money and get a Beer layering Tool I have on of these and it is really helpful almost impossible to mess up


Is EPPlus faster then regular loop logic to map datatable to excel spreadsheet

Question: I'm looking for the way to improve Datatable mapping to Excel spreadsheet.
Current code using looping technique to import data from DataTable to Excel:
<code>for (int i = 0; i < dt.Columns.Count; i++)
{
       thc = new TableHeaderCell();
       thc.BorderWidth = 1;
       thc.BorderStyle = BorderStyle.Solid;
       //thc.Style.Add("backgroundColor", "#cacab5");
       thc.BorderColor = System.Drawing.Color.White;
       thc.BackColor = System.Drawing.Color.BurlyWood;
       thc.Text = dt.Columns[i].ColumnName;
       thr.Cells.Add(thc);
}

tblReport.Rows.Add(thr);

for (int j = 0; j < dt.Rows.Count; j++)
{
     tr = new TableRow();
     tr.BorderStyle = BorderStyle.Solid;
     if (bt == "IE")
         tr.BorderWidth = 1;
     else
         tr.BorderWidth = 2;
     tr.BorderColor = System.Drawing.Color.White;

     long n;

     for (int i = 0; i < dt.Columns.Count; i++)
     {
         td = new TableCell();
         td.BorderWidth = 1;
         td.BorderStyle = BorderStyle.Solid;
         td.BorderColor = System.Drawing.Color.White;
         td.BackColor = System.Drawing.Color.Bisque;
         td.Text = dt.Rows[j][i].ToString();

         n = 0;
         bool isNumeric = long.TryParse(td.Text, out n);
         if (isNumeric && td.Text.Length > 10)
                 td.Attributes.Add("style", @"mso-number-format:\@");

         tr.Cells.Add(td);
     }
     tblReport.Rows.Add(tr);
}
</code>
I found another way to do it through EPPlus.
Which way is faster?
Comment: What is it exactly you are asking? Are you asking if EPPlus is faster than other methods such as .NET InterOp  or COM for creating an Excel document? Or are you asking if there are other ways to map your recordset to the worksheet you want to create?
Comment: I'm looking for the way that is faster then just looping through the whole DataTable. I need to improve the performance of data loading
Answer: EPPlus is very fast and efficient as is. Anything that is going to make it look like it copies your recordset to the workbook in one method is going to internally be looping over columns and rows in one fashion or another. So, the answer is to look at how many things you are doing and how you might optimize them.
From the code snippet you provided, two things I would recommend: First, you do not have to explicitly add rows to the worksheet before inserting values into the cells. This will slow things down quite a lot as your in memory EPPlus object gets bigger. If you are always just writing to the next row, then you never have to explicitly add a row, just reference your next row by index.
Next do not set the display attributes on every cell each time you write a value to the cell. Set it for the whole row (or column) using a range. Or better yet, do it for the whole worksheet at once after you have written out all the data in the cells for all your columns and rows. An example might be like the following which sets a Style setting for the columns A through E in one method call:

using (ExcelRange er = myWorksheet.Cells["A" + lineNo.ToString() + ":E" +
  lineNo.ToString()]) {
                          er.Style.Font.Bold = true;
                      }
Answer: The fastest way I have found is to pass the DataTable into the LoadFromDataTable function for a range of cells.
<code>        _workSheet.Cells[startRow,startColumn,endRow,endColumn].LoadFromDataTable(dataTable);
</code>


Copy and pasting multiple items to the clipboard in IntelliJ IDEA

Question: In IntelliJ IDEA, is it possible to have multiple items in your clipboard and choose which item to paste? What are the keyboard shortcuts?
Answer: Yes, it is possible.
Whilst Ctrl + V is normally used to paste, use Ctrl + Shift + V (IntelliJ Default Key map) which will bring a pop-up of the items in the clipboard to paste.
The default size of the clipboard is 5; it will show the last five things have have been copied. The option to change this is called "Maximum number of contents to keep in clipboard". You can change it quickly by using Ctrl+Shift+A and typing the name of the setting.
Comment: Ctrl + Shift + V is a gem!\
Comment: Unfortunately, that configuration option has disappeared from IntelliJ IDEA 2019.2, at least on Windows. (Exactly which version removed it, I don't know.) Nonetheless, [it remains documented](https://www.jetbrains.com/help/idea/2019.2/working-with-source-code.html#copy_paste). Despite its disappearance from the GUI, the setting remains in effect on one of my machines (to which I do not have access currently). Anyone know where in the various configuration files this setting is stored?
Comment: Just to add that on Mac the shortcut is `Cmd+Shift+V`
Comment: It changed my life!
Answer: On Windows, use CtrlShiftV and on Mac use  ⌘ShiftV to see your clipboard history.
Change Stored History Size
Click ShiftShift, type Maximum number of contents to keep in clipboard, and then edit the value in the dialog.

To manually find the setting, open: Preferences -> Editor -> General and then in the Limits section of the main General page, increase Maximum number of contents to keep in clipboard. I changed mine to 50.

Alternatively, copy and paste multiple lines at once
You can select adjacent line content, random line/positions etc. with multi-caret selection.
Read how to here
Answer: Ctrl + Shift + V will bring up the popup like:
Press shift will help you to choose multiple paste items, then cllick OK.
Answer: to increase clipboard history max item:
shift + shift
search for 'registry'
click on 'Registry...'
search for 'clipboard.history.max.items'
increase it's value


What are estimated magnetic properties of liquid metallic hydrogen?

Question: I understand that liquid metallic hydrogen isn't easy to produce, or keep it stable on Earth, but can be liquid metallic hydrogen magnetised? Does it have magnetic properties at all?
Comment: Btw, does liquid metallic hydrogen considered as exotic matter?
Comment: I presume that your last sentence should read "Does it have magnetic properties at all?" (since metallic hydrogen should indeed have metallic properties). A quick scan of a search on Web of Science shows a variety of articles on magnetic fields of gas giants and liquid metallic hydrogen, but no obvious work on magnetic properties of liquid metallic hydrogen.
Comment: @Ba-Lee - No, liquid metallic hydrogen is not exotic matter. It even has atoms!
Comment: I think it's unlikely that we know for sure given that we can't at present make metallic H without breaking our diamonds... I see one 1986 article reporting a theoretical calculation stating that "a stable antiferromagnetic phase is obtained for metallic H" (PRB **33**, 324) if it helps, then a 1991 article cites it stating that it "undergoes a second transition from a ferromagnetic metal to a ferromagnetic insulator." (PRB **43**, 825), hunting down citations might get you our best guesses, but those might assume a solid form.
Answer: There is no reason to expect metallic hydrogen to be any more magnetic than say metallic sodium, that is, patamagnetic. One caveat is that at sufficiently high pressure and low temperature it may become superconducting.
Apparently, rotating liquid sodium will generate a magnetic field as this experiment aims to prove : https://m.youtube.com/watch?v=OsPyQ4Sv-DA&feature=youtu.be
Comment: I added a link to my answer that will interest you.
Comment: Do you think that "Na" would generate magnetic field around a planet, if it would be in a center of, for example a gas giant?
Comment: Liquid paramagnetic metal will generate a magnetic field if it rotates.
Comment: Cool! Has it been any experiments about this?


How to do the toast message using auto launch flows?

Question: How do we generate a toast message while clicking on a action button where we will be calling the flow.How can we do that using auto launch flows?
Comment: What are you actually doing in autolaunch flow? What have you tried so far? Where did you get stuck?
Comment: If you want any visual feedback, then the simplest option is a one screen visual flow (configuration option)
Comment: We are actually having a button in an object and after clicking on it it will generate a toast message how can we do that using auto launch flows not using screen flows?
Answer: (Non-trigger) auto-launch flows have no ability to present messages since they run in a "headless context" - as the documentation says, they run in the background and are asynchronous. You can initiate them from all sorts of places:

Through the UI
By a standard or custom REST API
By a scheduled job
In async code
etc.

Only the first scenario would have any way to show something on the UI.
I could imagine writing a a custom LWC, e.g. toaster, that polls (or uses the emp API to be notified of creation of) records of a specific type of object, e.g. Toast__c, perhaps associated with the current User, and have this generate toasts from the records' details (deleting the records once the toast is shown). You could then have an auto-launch flow that, when the conditions are met, creates the required record(s) of this custom type Toast__c, setting required properties as needed. As long as you include the custom toaster LWC in your Salesforce UI pages you get toasts appearing from nowhere when the flow generates the records.
You might be able to apply something similar with platform events too.
NB: Trigger-based auto-launch flows also cannot present data for many of the same reasons.
Answer: I had a similar requirement. I used this package. It might help you too: https://unofficialsf.com/show-toast-flow-action/


Where did the 2nd Ooze canister come from?

Question: In Ninja Turtles 2 (1991), we see the foot capture the TGRI professor as he is processing the last canister of Ooze. Shredder forces the professor to use the Ooze to create Tokka and Rahzar, but during the construction site fight scene (before eating the donuts), Shredder holds up a full canister of Ooze. Where did that come from? It was made clear that there was only one left and the amount of Ooze we saw the professor use to create Tokka and Rahzar was significant.
Comment: It's entirely possible that you just stumbled upon the rarest of all commodities: A plot hole in *Ninja Turtles 2*. ;)
Answer: As far as I can tell, it's not a different canister, it's the same canister as earlier in the film. Note that we never actually see it being emptied, only what appears to be 'ooze' traveling down the pipe into the animal enclosures.
Also, there's some bubbling chemicals that the Doc obvious thought were important to the process and some sort of distilling chamber. It's reasonable to assume that he only used a very small amount of the ooze to prime a solution that's less poisonous than simply feeding the animals the raw product, leaving the majority of the original ooze in the canister for later use.


Plane measurable sets and measurable rectangle

Question: Does every measurable set in the plane with positive Lebesgue measure contain a cartesian product of two measurable sets of the real line with positive Lebesgue measures?
Comment: Yes,coudy,you are right.
Comment: though the question is answered (in the negative, by @coudy) it might prompt more questions. If $T$ is a Lebesgue measurable set in the plane of positive measure, is there a suitable affine (not necessarily orthogonal) coordinate system and sets of positive measure on each axis such that their "product" (in the affine system) is contained in $T$? Is there a plane set  $T$ of positive measure such that its projection on every line is nowhere dense (relative to the line)?
Answer: No.
Let $K$ be a Cantor set in the unit interval of positive one-dimensional Lebesgue measure. More generally, we can take any measurable subset of $\bf R$ of positive Lebesgue measure and empty interior. Rotate $K\times K \subset {\bf R}^2$ by a quarter turn (45 degree) in the plane.  The resulting set cannot contain a subset $A\times B$ with $A$ and $B$ of positive measure.
This is shown as follows. Let us project our set on the line of slope -1 through the origin, graduated so that the point $(x,y)$ is sent to the point $x-y$ on the line.
It is a standard fact that if $A$ and $B$ are two subsets in $\bf R$ of positive Lebesgue measure, then the set $A-B=\{x-y \mid x\in A, \ y\in B\}$ contains an interval. This follows from the continuity of $x\mapsto \int {\bf 1}_A(t-x) {\bf 1}_B(t) \ dt$.
So the projection of our set on the line must contain an interval. But this projection is (a translation-rotation of) $K$ which is of empty interior.
Comment: Great idea.  Could we not, instead, take $K$ to be the irrationals and continue in the same way?  The our set in the plane is the set of pairs $(x,y)$ so that $x+y$ and $x-y$ are both irrational.  This contains no measurable rectangle by the same reasoning.
Comment: @Gerald Edgar - Yes, but the deficiency of what you suggest is that it won't give anything in the measure category (in your case $K$ is of full measure).
Comment: @Edgar Yes, indeed. Note that any measurable set $K$ of positive measure and empty interior works here. I edited the answer.
Answer: Here are some variations on your question:
Fact: (Mycielski) Suppose $A$ is a compact subset of plane of positive area. Then there are perfect sets of reals $X, Y$ such that $X$ has positive length and $X \times Y$ is contained in $A$.
Question: Suppose $A$ is a subset of plane of positive area. Must $A$ contain a non null rectangle (a rectangle is a set of the form $X \times Y$)?
Answer: No.
Question: Suppose $A$ is a subset of plane of zero area. Must the complement of $A$ contain a non null rectangle?
Answer: (H. Friedman and (independently) Shelah) Independent of ZFC. True under CH but false in Cohen's model for the negation of CH.
Question: Suppose $A$ is dense $G_{\delta}$ subset of plane. Must $A$ contain a non meager rectangle?
Remark: Yes under CH but I don't know if this is true in ZFC alone.


How do I add a column to a Contribution Summary report which will show the date and amount of the most recent payment/donation?

Question: When running a payment report using the Contribution summary,  along with the columns showing number of payments, payment aggregate and payment average, I would like to be able to see the date and amount of the last/most recent payment. This information can be separately gathered by running a Contribution detail report, but it is a lengthy process going through two separate spreadsheets when, ideally, I would want this information regularly, so having the data within the Contribution summary report who be ideal.
Answer: I recommend the summary fields extension:
https://civicrm.org/extensions/summary-fields
It'll keep a calculated copy of the last contribution amount (and many other useful fields) as custom fields of the contact, making reporting like this much easier.
Because contributions are stored in a separate table, generating fields like 'last contribution' tends to be complicated and mixing it with other values isn't going to be well supported in most reports, but pulling in custom contact field values is almost always supported.
Comment: Thank you, this sounds just right, i will try it


excel - how to enter formula for entire column

Question: I know if I select the entire column and then enter the formula in first column and then press ctrl+enter, it would be taken care of. However, my first row is title row. How else should I do it?
Answer:
Enter your desired formula into the 2nd row of the column you want to fill.

Make sure to use $ for any referenced cells where the row stays the same for all equations.

Select the cell containing the formula, and press Ctrl + Shift + Down.

This should select all cells in that column between the selected cell and the very bottom.

Then press Ctrl + D.

This should fill all the selected cells with the formula you entered into the 2nd row's cell.

Explaining the $ sign a little more.
Example: =VLOOKUP(A2,$B$2:$C$21,2)

Here the value for B2:C21 will be constant for all the cells.
Comment: @pnuts: I don't quite understand what you're getting at; are you pointing out that it's not usually a good thing to have something in every row of the spreadsheet?  If so, then instead of #2 in my answer:

_Select the cell containing the formula, scroll down to the bottom of the area you want to fill, hold SHIFT whilst clicking the bottom-right cell of the area._ (Then do point #3)

Is this what you were referring to?
Answer:
Copy the column
Click anywhere in your data and Format it as Table
Excel 2010 -> Home Tab -> Format as Table
Insert the column, Change the Title to what ever.
Type the formula in the first cell under that
You'll see a lighting icon appear, click it and it will apply it to the entire column.

Update based on a good point by pnuts, no reason to delete the column, copying the column keeps the data!
Comment: @pnuts: I don't know about other Excels, I could only verify this answer for Excel 2010.
Comment: @pnuts : Absolutely, that is a very good point, yes, why delete and lose the data were one can just copy it? Updated the answer. With copy one still has the option to delete, but with delete there is no more options! Keeping and creating more options must be in heart of every solution.
Answer: Go to the first cell in the column that you want to put the formula in, and type in the formula.
Then, after the formula is in that cell, hit Ctrl+Down.
That will select all the cells below the one that you have selected until there is a break in status of the cells (if they are all filled, then an unfilled one shows up in the column, or vice versa)
Comment: @pnuts what do you mean?
Answer: There is another option by using =ARRAYFORMULA()
For example, say you had a header row and 3 columns and wanted your last column to be the product of the first two. In cell C2 you could enter the following:
=ARRAYFORMULA(A2:A*B2:B)

This has three benefits:

Skips the first row completely (your question)
Effectively applies the formula to every row which is useful if you later decide to insert a row
Only one location to modify the formula for every single row

Although, it may not be immediately obvious where how/where the cells are being calculated. (hint: ctrl+~ may help)


what is a "non-derived" environment?

Question: what is the meaning of derived and non-derived environments in phonology?
for example, non derived environment blocking, that does it mean?
I've looked everywhere but I could not find the actual meaning I could only find related theories and effects.
Answer: A derived environment is a phonological context that exists because of a rule or process. For example, the English plural noun "socks" in the sentence "I have white socks" has a final [ks] cluster that results from the plural-forming rule or process which adds [s] to the end of the word, so the [ks] cluster in socks is in a derived environment.
In contrast, the singular English noun "ox" also ends in [ks], but here there is no process or rule that created the consonant cluster. It just existed from the start. So here, the [ks] cluster occurs in a non-derived environment.
Answer: The answer by Brass Tacks is basically correct, but could still be elaborated on for the sake of clarity. The concept was introduced in Kiparsky 1972 in a paper "Abstractness, opacity and global rules" (published by IULC), in an attempt to explain why in Estonian /lugu/ → [loo] "story" but /luu/ "bone" does not undergo vowel lowering. The explanation offered is that the conditions for applying the lowering rule are satisfied in the underlying form (but the rule does not apply), whereas in other cases where the rule does apply, that is because conditions for applying the rule are not present in the underlying form. This notion of "derived environment" and the motivation for empowering grammar with such look-back abilities is discussed in section 1 of that paper.
The concept is relevant because there is a claim that certain rules only apply in a "derived environment". Two things play a role in determining whether a given string is a "derived environment". One is that at least two elements of the structural description are members of different morphological constituents, e.g. plural -s in sock+s. The other is that some property required by the rule only comes about by previously applying some rule, for example in Finnish, t→s/__i which applies to [vesi] ← veti ← /vete/, where final /e/ becomes [i] (thus creating the [i] that triggers the assibilation rule). Assibilation does not apply to /æiti/, because that root is monomorphemic and the potential trigger /i/ does not result from applying a rule.
The evaluation of "in separate morphemes" or "is derived by applying a rule" is carried out with respect to the cycle, therefore the grammar only looks back to morpheme divisions present on the current cycle, or phonological properties in the input of the current cycle – not the properties present in the lexicon.
Comment: Rule-application is not enough to account for Finnish assibilation on its own – cf. _*pyyti/pyysi_ vs _huuti/huusi_ vs _veti/*vesi_. I'm not sure exactly what you mean by 'monomorphemic' here (does applying a rule create a separate morpheme in the current cycle?). To the extent that _vesi_ contains multiple morphemes, so does _äiti_, surely. Assibilation applies in _sinä_, which is definitely monomorphemic as far as the /i/ goes, but doesn't in _veti_, which is unquestionably polymorphemic by any definition (_vetA-_ + _-i_ > _vet-_ + _-i_).
Comment: I don't endorse Kiparsky's claims or the concept "derived form", I'm just explaining the use / of the claim. My own view is simply that some rules have lexical exceptions. I don't know why one would treat /äiti/ as bimorphemic, but that's a discussion for another day.
Comment: I'd suggest moving the mention of Kiparsky up to the start of the answer, then – as it stands, it reads like those are your own examples, not his.

what is a "non-derived" environment?


Is there a way to connect the Monero Core (GUI wallet) to a remote testnet node?

Question: I'm trying to make a liveUSB so people can play with the Monero Core GUI, but I don't want them to download the whole testnet blockchain first just to try it out.
Maybe something like...
monero-core --daemon-address arg
Comment: As this is an old thread, i made a new reddit post with up to date commands [here](https://www.reddit.com/r/Monero/comments/8jtfhx/private_testnet/)
Answer: You can create your own testnet by running two local nodes, and run a miner locally that mines on the local node blockchain. It has been covered in a reddit thread here: https://www.reddit.com/r/Monero/comments/3x5qwo/how_do_i_make_my_own_testnet_network_with_eg_two/
Demon:
/opt/bitmonero/bitmonerod --testnet --testnet-p2p-bind-port 38080 --no-igd --hide-my-port --testnet-data-dir ~/.bitmonero-node2 --p2p-bind-ip 127.0.0.1 --add-exclusive-node 127.0.0.1:38080

Wallet:
/opt/bitmonero/simplewallet --testnet --daemon-port 28081

Then go into the bitmonero node and start mining with the command:
start_mining <your_testnet_address>

I tested them out myself, and the above commands work no problem on a a low powered machine, you'll have your own testnet in less than a minute.
There is also another set of instructions here, https://moneroexamples.github.io/private-testnet/ , they are far more comprehensive, and a bit much to include here, but the above commands work and establishes the absolute basics.
Answer: As this is an old thread, and the monerod commands have evolve in two years, here's the updated how to:
From your working directory, launch the first daemon:
monerod --testnet --no-igd --hide-my-port --data-dir ~/.bitmonero-node1 --p2p-bind-ip 127.0.0.1 --add-exclusive-node 127.0.0.1:38080

Then launch the second daemon:
monerod --testnet --p2p-bind-port 38080 --rpc-bind-port 38081 --zmq-rpc-bind-port 38082 --no-igd --hide-my-port --data-dir ~/.bitmonero-node2 --p2p-bind-ip 127.0.0.1 --add-exclusive-node 127.0.0.1:28080

Those two daemon will be mutually connected.
Launch your favorite monero-wallet-XXX and create a new testnet wallet connected to 127.0.0.1:28081 or 38081
Ensure that your wallet has a starting height of 0 Start mining on one of the two daemon to the public address you created with this wallet.


How to find out the IUPAC names of Alkenes?

Question: While finding out the IUPAC names of organic compounds, should I count the number of the carbon atoms which is attached to the functional group and having the bond in the very same direction in which I counted the former (i.e., the attachment of the functional group)?
I am facing this confusion while solving questions based on the IUPAC nomenclature.
Comment: As it's currently written, it's hard to tell exactly what you're asking. Please clarify your specific problem or add additional details to highlight exactly what you need. It would be best if you would include an example structure that illustrates your problem. You might also want to consider reading our [guidelines on how to ask nomenclature questions](http://meta.chemistry.stackexchange.com/a/3120/7951).
Answer: First of all, alkenes are hydrocarbons. So they do not contain any functional group except the double bond, '='(though i prefer to regard and call it as bond and not functional group). By reading the details of your question, i presume that you are facing difficulties in writing the IUPAC names of organic compounds in general and not only hydrocarbons since you use the word "bond" as well as the phrase "functional group".
To write the IUPAC name for any organic compound in general proceed as below:
1.First, inspect the molecule of the compound for functional groups, multiple bonds and substituent groups.
If more than one type of functional group is present, then, from the seniority table of functional groups find out which of the functional group(s) present in the compound is the located highest in the table. That functional group is known as the primary functional group and the rest are known as secondary functional group(s).
If only one type of functional group is present then that functional group is the primary functional group and there is no secondary functional group.
2.Then, find out the longest carbon atom chain (in the molecule of the organic compound) which contains (if they are present) the maximum number of functional groups (including the primary functional group), multiple bonds and substituent groups.
3.If functional group(s) are present then the carbon atoms are numbered from such an end that the sum of the position numbers of the primary functional group is the least.
If functional group(s) are not present but multiple bonds are present then between the double bond and triple bond whichever multiple bond is nearest to an end, numbering is done from that end. If, different multiple bonds occupy equal position numbers from both ends, then, the double bond gets greater priority over the triple bond and the numbering is done from the end to which the double bond is the nearest.
If both functional group(s) and multiple bond(s) are absent but substituent groups are present, then the numbering is done from an end corresponding to which the sum of the position numbers of the substituent groups is the lowest.
(In this rule, i have used the sum of locants rule which is actually a wrong generalization of the first point of difference rule but it works in most of the cases)
Note that priority(functional group)>priority(bond)>priority(substituent group)
4.Find out the number of carbon atoms in this chain.
5.A typical IUPAC name has the following structure-
$\ce{secondary prefix + primary prefix + word root + primary suffix + secondary suffix}$
SECONDARY PREFIX
The complete secondary prefix consists of the name(s) of the substituent group(s) along with its(their) position numbers and the secondary functional group(s) along with its (their) position numbers arranged in alphabetical order.
PRIMARY PREFIX
The primary prefix indicates whether the compound is cyclic or not. If it is cyclic, the secondary prefix is cyclo otherwise it is left blank.
WORD ROOT
The word root indicates the number of carbon atoms in the longest carbon atom chain.
If it is 1 use meth, if 2 use eth, if 3 use prop, if 4 use but, for 5 or more use greek names for numbers, that is, pent, hex, etc.
PRIMARY SUFFIX
The complete primary suffix consists of ane, if the compound has no multiple bonds.
If multiple bonds are present then it consists of
position number(s) + (di/tri and so on)ene for double bonds and position number(s) + (di/tri and so on) yne for triple bonds.(If the number of double bonds or triple bonds is more than 1 then correspondingly di, tri and so on is added before ene and yne) ( Note that the double bond part is written before the triple bond part)
SECONDARY SUFFIX
The secondary suffix consists of the following :
position number(s) + (di/tri and so on)name used for primary functional group
6.Use '-' to separate a letter and a number and ',' to separate two numbers. If two vowels occur in succession drop the the second vowel.
Here is the seniority table for functional groups.
Answer: To name Organic compound the functional group priority must be followed. For which below is the Priority Table :

Follow the function group priority. Count from the carbon of highest priority such that lowest locant number are given to every carbon. Denote the low priority groups as their corresponding prefixes and the greatest priority group is included in the name of the parent chain.
Comment: [Please give proper credit to the author and site where you found the image, including a direct link to it.](http://chemistry.stackexchange.com/help/referencing) Also note that this image could be misleading since it mixes suffixes, multiple bonds (which are not included in the seniority order of suffixes), and prefixes (which do not have any seniority order).
Comment: @Loong I could not post the link of the original author because I do not have required reputation.


Is Wuala (LaCie) the largest company to accept Bitcoins?

Question: I just found out that you can pay for Wuala with Bitcoins. They are owned by LaCie, who have a revenue of €351.8 million according to Wikipedia. I think this makes them by far the largest company to accept Bitcoin for payment. Is that correct or are there other big players in the economy?
Comment: Just to note that LaCie is now owned by Seagate (http://www.seagate.com/about/newsroom/press-releases/seagate-lacie-completion-acquisition-controlling-interest-master-pr/?paramChannelName=newsroom) meaning that if Wuala is still accepting bitcoins (http://www.wuala.com/en/bitcoin) then this is probably by far the biggest company by market cap. accepting bitcoins in some form.
Answer: It is fantastic to see companies accept Bitcoin, even if it is just an "alpha / trial" like the method Wuala provides.
While Lacie (Wuala) is likely the largest company to accept bitcoins directly as payment, that is a specialized product of interest to a smaller subset of the bitcoin community.  Their volume of bitcoin commerce probably is a fraction of that for other bitcoin businesses which are needed by a wider customer base.  The larger dollar amounts where bitcoins are used directly for purchases might be in categories such as web hosting, dedicated servers, anonymous VPN, etc.
The largest companies to benefit from Bitcoin commerce though are the companies that offer vouchers or e-gift codes that can be used for payment.  These include NewEgg Vouchers (purchased on BTCBuy.info) and Amazon Credit and eBay Gift Codes (purchased on SpendBitcoins.com).   Those are, by far, where the largest amount of Bitcoin commerce is occurring.  Some day these companies will simply cut out the middle man and start accepting bitcoins directly (or through a payment intermediary such as Bit-Pay).


How to capture Opt-in 'Date/Time' on clicking 'Double Opt-in' confirmation link

Question: We are enabling 'Double Opt-in' feature in our Marketing Cloud application and wanted to capture 'Date/time' each subscriber clicks on the confirmation Email in a static field in SFMC. Is it possible to implement this feature completely in Marketing Cloud? Can we use Journey Builder to do that? Suggestions please. (Without using API's?)
Answer: There's two ways to achieve this:

If the link leads to a cloudpage, you can use ampscript to stamp the current date/time
Alternatively, you need to use SQL to update the value

Solving it by ampscript I'm assuming that the subscriber hits a confirmation page. here you could have a script as follows:
<code>%%[
VAR @SubscriberKey, @ConfirmationTime, @SubscriberDE, @UpdateResult

SET @SubscriberKey = _subscriberKey
SET @ConfirmationTime = Now()
SET @SubscriberDE = "DataExensionName"

SET @UpdateResult = UpsertData(@SubscriberDE,1,"SubscriberKey",@SubscriberKey,"OptInTime",@ConfirmationTime)
]%%
</code>
The exact implementation of this, however, depends on your data model. For instance, if you have a static field AND you need to capture an opt in history as well, you need two data extensions.
For the SQL solution, it would be something like this:
<code>SELECT SubscriberKey
EventDate AS OptInDate /* Change name to reflect your field name */

FROM _Click

WHERE LinkName = "OptInConfirmation" /* Change to reflect your link name  */
AND EventDate > DATEADD(hour, -25, GetDate())
</code>
This can be run in automation studio - and let it run once a day, or whatever frequency you choose.
Personally, i would go for the ampscript / cloudpage solution.
Comment: Interesting!! If you could elaborate, it really helps. We do use cloudpage but I am not sure how to use ampscript. Regarding SQL method, where should we write SQL? I mean what could be the triggering point?
Comment: sorry for the slow reply! I'm revising my reply.
Comment: Hi Amulya - did my reply solve your question, or can i do more to help? :) Please mark answer as "best" if it resolved it :)
Comment: Our Business team found some other way to handle this requirement so I din't implement anything. But your approach should work so marking as best answer.


Resources for hoodie design related to theoretical CS

Question: I have to design a hoodie for my computer science batch, and I want it to be related to Theoretical computer science. I don't want to slap on some text with HTML-like angle brackets, but actually want something cool + nerdy that only people with some basic knowledge of CS might understand. I would be grateful, if you could give some suggestion, resources for ideas, or links to similar products.
Thank you.
Answer: I've always found this tattoo pretty daring. Would work on a hoodie.
Comment: This answer could be much improved if it included more than just a link.
Answer: As an undergraduate student, I was a bit mystified by the occurrence of the notion of entropy (from physics) into theoretical computer science (at the time, for the description of the optimal compression of a text with $n_i$ occurrences (summing to $n=\sum_{i\in[1..k]}n_i$) of each symbol $i\in[1..k]$ by prefix free codes, such as the one described by David A. Huffman) and its (at the time to me) occult definition: $${\cal H}(n_1,\ldots,n_k) = \sum_{i\in[1..k]} \frac{n_i}{n} \log_2\frac{n}{n_i}.$$ Since then, I have learned to respect its potency and adequacy in measuring the (des)equilibrium of probability and frequency distributions, and I have used it to measure the spaced used by compressed data structures, the time used by adaptive algorithms (in internal and external memory), sometimes in convoluted ways, and even in instance optimality results.

In 2013, for a colleague's birthday anniversary, I drew quickly a feminine character holding an equation often used in our research, one of the definition of the entropy of a vector of integers. At the time I wrote on my blog "I hope that he will hang it in his office so that it helps his students to memorize it!", and a few years later, a PhD student admitted that he searched on the web for the blog post to find back the formula :).
The definition of the entropy that I used in this drawing, $$n{\cal H}(n_1,\ldots,n_k) = n\log_2 n - \sum_{i\in[1..k]} n_i \log_2 n_i,$$ is a bit atypical (one typically normalizes both sides of the equation by $n$, and combines the two $\log$ terms into one, maybe so that to make it closer to the definition used by statistical physicists). I like this formulation better because it highlights the terms measuring the imbalance of the distribution, and give an intuition into the various analysis which lead to such a formula.
Feel free to use either the formula itself or the drawing: I would be honored! (Do let me know if you do!)


Share data in LAN

Question: I'm building a music library program, and I want to have the ability to share the library in the LAN. How can I discover others who share their library? I'd like to find others' libraries without typing in IPs and stuff.
Answer: Apple uses mdns (they call it Bonjour) to broadcast and discover music shares on the local network without any user configuration.
Many other manufacturers implement UPnP/AV for the same.
Comment: In particular, Apple uses DAAP (http://en.wikipedia.org/wiki/Digital_Audio_Access_Protocol) to share things, using mdns for discovery.
Answer: Probably the easiest way is to use UDP to periodically send a message (containing some info advertising your library's presence) to the broadcast address.  This will be received by all the hosts on your subnet (and perhaps further, depending on your router configuration).  If your app listens for these messages from other hosts, it will over time be able to find all the other instances of your app on the subnet.
Edit:  found this question which has answers that go into more specifics of what I'm talking about.
Comment: Thanks a lot, I think this is the easiest solution. I knew about broadcasts but somehow I had in mind that they weren't forwarded by routers.. -.-
Answer: SNMP
This protocol was designed for what you are looking to do.
There are several libraries that you could use that implement SNMP which would make it easy to send and receive.
Answer: You could get your application to send the fact that the library is shared to a central server - in fact just send the location.
Other instances of your application could then just ask the server for the list of shared libraries.
The advantage of this is that your application isn't constantly broadcasting.
The disadvantage is that you need a central server.

Share data in LAN


RSPEC get ExampleGroup for binding ivars

Question: This one is going to be a tinge interesting. After noting the peculiar behavior of let, I've decided to try and make a direct equivalent of the Lisp Let for RSPEC by binding instance variables to example groups.
Here's the code for this so far:
module RSpec
  module Core
    module MemoizedHelpers
      module ClassMethods

        def let_local(name, &block)
          raise "#let_local called without a block" if block.nil?

          # Binding to string instances, fix
          current_example = caller[0]

          # Attempt to find ivar, if not, make it.
          meth = -> {
            current_example.instance_variable_get("@#{name}") ||
            current_example.instance_variable_set("@#{name}", block.call)
          }

          MemoizedHelpers.module_for(self).send(:define_method, name, meth)

          before(:all) { __send__(name) }
        end
      end
    end
  end
end

Problem being, while it technically works for nested examples, I'm throwing ivars on a string. I know why it currently works but man is that hackish... How can I get a hold of the current example group that that function would be run inside? (ie

This is more of a thought exercise to see if it can be done.
There are definite performance reasons for something like this though, when used correctly (and frozen.) The use case is if you write tests in a functional manner, this let_local will not get in the way of running tests in parallel like the original let, and will not try and rebuild the object repeatedly (think expensive instantiations.)
Granted that this can already be done with a before :all ivar, but this may be a cleaner way about it.
Example test code using it:
describe 'Single local, multiple nested example, same local name' do
  let_local(:a) { Person.new('Doctor', 900) }

  it 'will be 900' do
    expect(a.age).to eq(900)
  end

  it 'will be named Doctor' do
    expect(a.name).to eq('Doctor')
  end

  context 'Doc got old' do
    let_local(:a) { Person.new('Doctor', 1000) }

    it 'should now be 1000' do
      expect(a.age).to eq(1000)
    end

    context 'And older still!' do
      let_local(:a) { Person.new('Doctor', 1100) }

      it 'will now be 1100' do
        expect(a.age).to eq(1100)
      end
    end

    it 'will still be 1000' do
      expect(a.age).to eq(1000)
    end
  end

  it 'will still be 900' do
    expect(a.age).to eq(900)
  end
end

The overall intent is to emulate this type of behavior in Lisp:
(let ((x 1))
  (write-line (write-to-string x))    ; prints 1
  (let ((x 2))
    (write-line (write-to-string x))) ; prints 2
  (write-line (write-to-string x)))   ; prints 1

Any tips or ideas?
Answer: You can already emulate that behavior using standard Ruby. For example,
def let(pr)
  pr.call
end

let->(x=1, y=2) {
  p [x, y]
  let->(x=3, y=4) {
    p [x, y]
  }
  p [x, y]
}

Output:
[1, 2]
[3, 4]
[1, 2]


How to append or join multiple times a video file (single file) to make a 10hour long video of that same file using ffmpeg? is there a way?

Question: I guess i explain what i need in the title but if not i want to make something like this.
Comment: Havent checked, therefore only as a comment, but have a look here: https://trac.ffmpeg.org/wiki/Concatenate and search for this text `This example will loop input.mkv 10 times`
Answer: You can use the Windows command line (DOS or cmd) using copy /b 00001.mts+00001.mts K:\Merged.mts as explained in this step-by-step tutorial, where in your case 00001.mts is the identical file repeated over and over again:

https://photography.tutsplus.com/tutorials/3-free-ways-to-join-spanned-avchd-video-files-into-continuous-clips-on-windows--cms-25830

Connecting the same file 6 times instead of twice, you would just replace in
00001.mts+00001.mts+00001.mts+00001.mts+00001.mts+00001.mts


Prevent local web application from copy

Question: Is there any way to prevent a local web application from being copied to another computer? I searched all over the web and whereas desktop applications have been replaced at a big extend by web application, i haven't find a way to prevent my application from being copied at least without a special effort. Is there any way to achieve this? Something like combine it with a specific mac or something else?
Answer: Once the HTML, css, and JavaScript have been downloaded to a browser, it's out there.
If your code is so amazing that you don't want anyone else even looking at it, you could send the entire page as an image, then every user interaction could send a separate http request and have your server render a new image back after each interaction. This would be a massive headache. It would probably have horrible performance.
Comment: You could obfuscate it so much and include a bunch of execution commands on strings from regexes in it that people are fearful that it's malware and decide not to use it at all. They probably won't copy it then...
Comment: Thank you for your suggestion. For sure it will be a big overhead. My code is not so amazing, but how can i prevent the from copying the www folder from his local computer and install it to another one?

Prevent local web application from copy


Correct use of 惹人心烦: is 然而我不要惹人心烦 a suitable way to say you don't want to be a pain in the neck?

Question: I am not sure if I used the idiom 惹人心烦 correctly. This is the sentence I used:

好啊,然而我不要惹人心烦。

Would that be a good use of it or is there a better way of saying you don't want to be a pain in the neck for someone?
Comment: 惹人心烦 is not an idiom (chengyu). A better phrase would be 我不想整天唠叨[láo dāo] to imply that you don't want to be a constant pain in the neck for someone by nagging whole day.
Answer: Looks fine to me.  But you could say 不好意思麻烦你 = sorry for bothering you.  To me 麻烦你 sounds like a more colloquial way of talking about bothering someone or being a trouble for someone.
Answer: Sounds a little strange to me.
Incidentally, one can get beaten up in school simply by referring to oneself as one. - Sheldon Cooper
Here 人 maps quite well to one as a third person neutral pronoun, but more often than not, is used to refer to oneself, such as me or us (although it can also refer to you, her or them, in most contexts, it points to self).
So 惹 for make, 人 for one, 心 for heart (mood), 烦 for annoyed: 惹人心烦 literally means make one annoyed.
Examples:
这天气真是惹人心烦。(The weather really makes one annoyed. (me or us))
楼上的邻居真是惹人心烦。(The upstairs neighbor really makes one annoyed. (me or us))
对你/她来说,那也许是惹人心烦的吧!(you/her)
--
The correct way to say you don't want to be a pain in the neck for someone is 我不想惹你心烦 (yes, you can substitute 人 directly with 你 if you are talking to that person). On the other hand,  我不想让你麻烦 or 我不想麻烦你 means something different, something similar to I don't want to bother you or I don't want to trouble you). LadyP's interpretation of 麻烦你 is correct.


Bullet holes in game engine?

Question: I've seen questions and videos around the place on how to do these, but all the final products are exactly what I do not need: a plane with the picture of a bullet hole. If I've done that, what would happen if I shoot the very edge of an object? The picture would be sticking out in the middle of the air! Also, if I hit a round object or an object with curves, the same outcome would occur. I need a type of system where the bullet hole that is added can actually "wrap" the object it hits. For example, if I hit a corner of a cube, the bullet hole image should be on both sides of the cube. Also, If I hit an object on an area that has curves, the bullet hole should be curved too. How can I achieve this? Thanks!
Comment: You need some way to adopt the face normal, and a ray that continues afterward, adding holes where needed. there is almost no way for it to "wrap" a corner.
Answer: You need the bullet hole to modify the texture applied to the material. That way it will never stick out!
An interesting approach may be to have multiple U,V vectors per object, and in the fragment shader, detect how close a fragment is to each of the U,V vectors, and if close enough, draw a bullet hole (maybe darken pixels as a function of distance between current U,V, and bullet hole U,V)
I am not sure how this is normally implemented in games however ;)

Bullet holes in game engine?


Interpreting last date of tax submission US

Question: I was wondering if last date of submission of US taxes for 2017 means that tax should reach IRS by April 18 or should be posted to IRS by April 18. Any references would be helpful.
Comment: Today is April 18. This question just occurred to you?
Answer: According to USPS:

Federal Tax Deadlines. If your tax return is postmarked by April 18,
  2017 or October 16, 2017 (extension), the IRS considers it filed on
  time.

Emphasis mine.
Answer: According to the IRS:

Your return is considered filed on time if the envelope is properly
addressed, postmarked, and deposited in the mail by the due date.

So on top of postmarking it, it has to be properly addressed as well. So if it gets returned to you because the address was wrong, then you might be penalized.
Comment: This is a specific (but common) case of the 'postmark rule' https://www.law.cornell.edu/uscode/text/26/7502


How to add/remove text in between string(statement) using js?

Question: How to add/remove text in between string(statement) using js?
For example:
var string =  " "

Now, the string should contain

Comment: If jQuery is new to you, try considering it, it makes such simple & complex tasks quite easy!
Answer: It depends on what you need. You can use regEx in javascript or the plain old string search and replace functions.
Answer: Have a look at the doco for the various string methods.
You can extract pieces of a string using .substr().
You can determine the starting position of a particular substring using .indexOf().
You can replace parts of the string that match a pattern using .replace().
For your specific example it is not clear what criteria you have used to determine where to insert the string with the body tags, e.g., did you want to insert at the string's halfway point, or after the first closing ">", or after the first space, or find an html opening and closing tag pair with nothing but white-space content, or...?
The following would do it after the first closing ">":
var str = " ";

var i = str.indexOf(">");
if (i !== -1)
   str = str.substr(0, i) + " " + str.substr(i + 1);

Note that in most situations you don't want to be using JavaScript to manipulate html markup as a string, much better to use DOM manipulation functions.
Comment: simply we can use replace method to get that.

eg
string.replace("``","``");


Metric space compactness implies sequential compactness - unclear details

Question: I am following through some proofs related to metric spaces - complete, compact and what not.
The book this proposition is taken from is from Royden and Fitzpatrick's Real Analysis.
Here is a proposition:
Proposition: If $X$ is a compact metric space, then it is sequentially compact.
Proof: Let $\{{x_n}\}$ be a sequence in $X$. For each $n$ (integer) let ${F_n}$ be the closure of the set $\{x_k |\ k \ge n\}$. Then $F_n$ is a descending (that is every set is a subset of the ones with smaller indices) sequence of non-empty closed sets. According to the  Cantor Intersection Theorem, $\bigcap_{n=0}^{\infty}{F_n}$ is not empty.
The proof goes on from there, but this was the part that was bothering me.
The Cantor Intersection Theorem: Let $X$ be a metric space. Then $X$ is complete iff whenever ${F_n}$ is a contracting sequence of nonempty closed subsets of X, then $\bigcap_{n=0}^{\infty}{F_n} = \{x\}$ for some $x \in X$.
Here a contracting sequence is such that $F_n \subseteq F_m$ if $m \leq n$, and also $\lim_{n\to0}{diam(F_n)} = 0$.
Cantor's Intersection Theorem is stated for complete spaces. Yet we use it here on a compact space without having proven that compactness implies completeness and totally boundedness ( in fact this proposition is part of a circular proposition of equivalent statements: that completeness + totally boundednes <=> compactness <=> sequential compactness) and so far it was proven that completeness + totally boundedness => compactness. Now this proposition will be used to prove compactness => sequential compactness.
As you see we use an argument which I deem lacks a clear explanation.
Here is my take on trying to prove that this intersection is nonempty.
We have shown that a space is compact iff every collection of closed sets with the finite intersection property has a nonempty intersection.
From here we directly can show that if we take a finite subcollection of the indexed $F_n$, then the intersection will be $F_{n_{max}}$, where $n_{max}$ is the largest index in this finite subcollection, and hence will be nonempty. And since this finite subcollection was arbitrary, then for all finite subcollections this holds and then the whole intersection must be nonempty.
As I am writing this I realize that I am pretty sure of the correctness of my argument, but still would like to know if I am missing something in regards to the books argument with the Cantor Intersection Theorem.
If anyone has an idea if their argument is valid, can you please elaborate?
Comment: [The name _Cantor's intersection theorem_ may refer to different statements.](http://en.wikipedia.org/wiki/Cantor%27s_intersection_theorem) The authors mean the statement for compact spaces and their argument is correct.
Comment: So, in the end, they are referring to the same argument as mine. It is kinda confusing, as they have stated it earlier in the book with  different hypotheses.
Answer: They mean another Cantor intersection theorem: if $F_n$ is a decreasing sequence of non-empty closed sets in a compact space $X$, $\cap_n F_n \neq \emptyset$.
(If the intersection were empty, the complements would  form an open cover of $X$ without a finite subcover).
This is applied correctly here.


Theta's effect for OTM options

Question: How does $\Theta$ change for deep out-of-the money options? Looking at the below graph, it seems the time decay is highest for ATM options and increases rapidly as we approach maturity of the option. From the graph, it seems the deep OTM options have flat $\Theta$ throughout the entire term strucuture. Shouldn't the OTM options experience the most decay?
Comment: The graph would be more instructive if you normalize it by some unit of convexity risk (either gamma or vega). Then you'd actually see what is your theta for similar risk position and be able to judge if it's "high" or "low".
Answer: No because they are worthless in the first place. Theta is in dollar space and therefore, if something is worthless, it is hard for it to lose much more value.
Think about it this way. When you are buying an option, you are really buying gamma from BS PDE. The cost of gamma is theta. Where is gamma highest? ATM
Comment: "The cost of gamma is theta." -- this is by far the best explanation of what it really means to go long an option. Is this the reason why gamma and theta look the opposites of one another? Gammma peaks ATM and decays lower with time, just like the graph above but transposed on the y-axis.
Comment: @Andrew, for correctness sake, may I suggest you update your comment re "worthless" to "almost worthless" or similar terminology. Any option that has not yet expired has time value left, even those without intrinsic value. Just a suggestion.
Comment: what about your promise? : p
Comment: sorry.. haven't had time yet.. at work
Comment: @jessica, that is not an explanation of what it means to go long an option. It simply means that theta is the cost of buying gamma. Hence the inverse albeit still non linear relationship between the two. Andrew provided a very good explanation imho. Upvoted.
Answer: $\Theta$ measures the rate of change of the option value $V$ with time $t$ if the underlying asset $S$ doesn't move. since deep OTM options are almost worthless this change will be small if the asset will not move - they still will be worthless: at least they cannot change much in price since are almost worth 0.
write Black-Scholes equaton as:
$\Theta+\frac12\sigma^2S^2\Gamma+rS\Delta-rV=0$
$\Theta=rV-\frac12\sigma^2S^2\Gamma-rS\Delta=r(V-S\Delta)-\frac12\sigma^2S^2\Gamma$
since $\Gamma$ for OTM call option is close to 0 theta will be higher. and $V$ and $\Delta$ don't change(vary) much, so as the $\Theta$
ofcourse this is just the rule of thumb since formula for $\Theta$ is not so easy to understand at the first glance, or even at 100th
I made a picture which might help to understand this: notice relative stability of hadged portfolio $(V-\Delta S)$, negative (in this case) value of this doesn't vary much with respect to changes in spot when OTM, and vary more when close to ATM (ATM spot strike is 1.5178). this is the change in the second term of equation for $\Theta$ that introduces much to the variation of it, it is $-\frac12\sigma^2S^2\Gamma$. and as said before, since $\Gamma$ converges to 0 for OTM options the shape of this term is as we can see in the picture.
Comment: Comments have been purged.

Theta's effect for OTM options


Can anyone identify this old German bike?

Question: I found this old bike, it comes from Berlin, the brand is ACTIVE, but can't find anything online about the brand. Is this worth putting 500 euro in to restore? Is the bike rare?
Comment: Why exactly 500€? This bike was worth considerably less when it was new.
Answer: I don't know about this particular brand, but I can tell that this is a typical 1980s six-speed bike (the handlebar grips look like a later addition, maybe 90s). In my elementary school half of the students had a bike like this from one or other local brand. They cost less than 500€ adjusted for inflation when new, and before the current shortage 500€ could buy a much better new bike. If this bike does not have documented interesting history, it does not have much monetary value.
On the other hand, it looks like it's in decent shape, so it could be usable right now, or be fixed to usable condition with some adjustment, lubrication and new tires and brake pads.


Group audience versus group content visibility

Question: Can someone explain me what is the difference between group audience and group content visibility?
Answer: The basic concept is if you don't have any access control on the content specifically then the content would inherit the groups access control. But say you had a private group that you wanted some content visible (but not all) then the access control for the content could be set to allow that to happen.
You can read more in the docs here:
Content visibility:
https://www.drupal.org/node/2014755
Group visibility:
https://www.drupal.org/node/2014751
There are even some pretty diagrams listed in the content for more help visualizing these concepts.


Why Earth's crust is max 100 kms wheras Moon and Mars have much thicker ones?

Question: We know that the Earth' mantle and core are hot, whereas the crust has cooled down. The cooling process of the 4,5 billion years of the Earth' exisence resulted  a crust of between 50 and 100 kms. Mars and Moon have a much much thicker crust. Earth has a larger mass consequently a larger surface to lose heat through. Earth' heat is used to move continents around in tectonic moves, and allowing newly formed crust too cool and then sink back into the mantle, using up heat to melt back into it. No such tectonic movement is on the Moon or on the Mars. So why then that Earth' crust is so thin?
Comment: Your figures for the crust thicknesses are off. Earth's crust is 5-10km thick for oceanic crust and 30-50km thick for continental crust. The Moon's crust averages about 50km thick, and the Martian crust is broadly similar.
Comment: Have Mars and the moon cooled more due to lack of atmosphere?
Answer: The moon has cooled faster because it is so small and has less volume per unit of surface area. Lack of an atmosphere might also be a factor. Mars is also small compared to the Earth, has a tenuous atmosphere which makes a very poor blanket, and is about 40 million miles further away from the sun. Small things cool faster than large ones, a fact you can easily test for yourself by filling an egg cup with hot tea at the same time that you fill your normal cup.

Why Earth’s crust is max 100 kms wheras Moon and Mars have much thicker ones?


What is the rationale for the factor of $4$ in the Conics parabola equation?

Question: The Conics form of a parabola equation is $4p(y-k)=(x-h)^2$ where $(h,k)$ is the vertex of the parabola and $p$ is the distance from the vertex to the focus. (Which is also the same distance from the vertex to the directrix).  My question is where does this factor of $4$ come from?
Comment: You have $(x-h)$ where you need $(x-h)^2$.
Answer: If the equation were given as $p(y-k)=(x-h)^2$ rather than as $4p(y-k)=(x-h)^2$, then the distance from the vertex to the focus would be $p/4$ rather than $p$.  In other words, the "$4$" is there in order that $p$ will be that distance.
Consider the case where the vertex is $(h,k)=(0,0)$.  The equation is $4py=x^2$.  According to what you say you've read, the focus should be $(0,p)$.  Let's check that that is indeed the focus.  Remember the basic characterization in terms of focus and directrix: The distance from a point on the curve to the focus is always the same as the distance from that point to the directrix.  Since this parabola has a vertical axis (i.e. the $y$-axis, not the $x$-axis or a line going in some other direction), the directrix should then be the line $y=-p$.
The distance from the point $(x,y)=(x,x^2/(4p))$ on the curve to the directrix is then $y+p$.  The distance from $(x,y)=(x,x^2/(4p))$ to the focus is the distance from $(x,x^2/(4p))$ to $(0,p)$.  That distance is
$$
\sqrt{(y-p)^2+(x-0)^2} =\sqrt{(y-p)^2+4py} = \sqrt{(y^2-2py+p^2)+4py}
$$
$$
=\sqrt{y^2+2py+p^2} = \sqrt{(y+p)^2} = y+p.
$$
So the two distances are indeed equal.
Comment: get my vote in before end of the day :-)
Answer: Precalculus Answer
Let's translate so that the vertex is $(h,k)=(0,0)$ and compute the locus of points equidistant from the directrix $y=-p$ and the focus $(0,p)$.
$$
\begin{align}
x^2+(y-p)^2&=(y+p)^2\\
x^2+y^2-2py+p^2&=y^2+2py+p^2\\
x^2&=4py
\end{align}
$$
Therefore, $4$ is there so that $p$ is the distance from the vertex of the parabola to the focus.

Calculus Answer
Taking a couple of derivatives, we have
$$
\begin{align}
4p(y-k)&=(x-h)^2\\
4py'&=2(x-h)\\
4py''&=2\\
2py''&=1
\end{align}
$$
Since $y''$ at $(h,k)$ is the curvature of the parabola at the vertex, $2p$ is the radius of curvature, and therefore, $p$ is the focal length.
Therefore, $4$ is there so that $p$ is the focal length.
Comment: This answer is very nice, but terrible.  One need not know any calculus to learn an answer to this question.  Under what circumstances is the second derivative equal to the curvature?  Why is the focal length half the radius of curvature?  One who knows nothing about those matters can understand an answer to this question, but cannot understand _this_ answer.
Comment: @MichaelHardy: ah, I missed the [tag:algebra-precalculus] tag. Since you've taken care of the answer from that standpoint, there is not much else for me to do. I don't know if I can come up with anything better than to apply the definition and compute distances.


Command-+ style zooming in iOS Safari

Question: I'd like to be able to zoom in on a web page in iOS Safari the way you can in the Mac OS version using Command-+. Note that this is different than pinch/spread zooming in iOS. If I spread my fingers to zoom a page, everything is magnified but the browser window just gets wider so you can no longer see the whole thing, making side to side panning necessary. On a well-designed web page, if I use Command-+ to zoom in, everything gets larger but the margins don't change. The text gets bigger and re-flows so that it still fits in the same margins. Is there a way to do that in Safari on iOS?
Comment: Either pinching to zoom on your trackpad, double tapping with two fingers on your trackpad, or double tapping with on finger on your magic mouse will do this.
Comment: I'm asking about doing this on an iOS device, not on a Mac. On a Mac, Command-+ does what I want. Pinch zooming on iOS does not do the same thing, as I explained in my original post.
Comment: Ohh sorry I read it wrong, I was thinking you wanted it to happen on your mac as it does in iOS. Unfortunately the only way to really do this is by going into settings>display & brightness>text size and changing it. It's not very elegant and will not work on all sites. I may have a javascript work around though.
Answer: Unfortunately this isn't possible with native iOS controls. A work around is a Javascript bookmarklet. First, bookmark any page and then bookmark another page. Then, choose bookmarks and edit them. For the first one, rename it the minus (-) symbol and change the URL to:
javascript:var p=document.getElementsByTagName('*');for(i=0;i<p.length;i++){if(p[i].style.fontSize){var s=parseInt(p[i].style.fontSize.replace("px",""));}else{var s=12;}s-=2;p[i].style.fontSize=s+"px"}
Do the same for the other bookmark, but rename it the plus symbol (+) and change the URL to:
javascript:var p=document.getElementsByTagName('*');for(i=0;i<p.length;i++){if(p[i].style.fontSize){var s=parseInt(p[i].style.fontSize.replace("px",""));}else{var s=12;}s+=2;p[i].style.fontSize=s+"px"}
Now to increase or decrease the size of text, simply tap the bookmarks.
Comment: Thanks for this. I tried it but it doesn't seem to reliably increase/decrease the font size.

Command-+ style zooming in iOS Safari


Need help for a latin motto - beauty in decay

Question: need som help putting together a few words for a fun motto for a club / small group of friends who have a common interest especially in british vintage motorcycles, but also in vintage stuff in general.  I would like to put into latin that there is beauty in decay degradation and vintage stuff, and was thinking about something like "Ubi tritus, ibi iucunditas" )(where there is decay, there is delight). Is there anyone who can come up with suggestions or corrections on this?
Answer: You can certainly say ubi tritus, ibi iucunditas, but it means "where there is wear, there is enjoyment," which is not really what you are asking for.
As for "beauty in decay," when you say your and your friends' interest is vintage things, I assume you mean old technology, furniture, art, etc. which may show its age, but does presumably, perhaps even thanks to your efforts, not yet rot away. I also assume that you would like to avoid words associated with failing human health like tabes.
With this in mind I would suggest:

Venustas in obsoletis

... which literally means "loveliness, grace, beauty in things that are old, worn out, have fallen into disuse and lost their value." (The verb obsolescere encapsulates all these ideas.) Or one could of course simply translate it as "beauty in the obsolete."


Reasons to carry passport in Korea as a US tourist

Question: Other than having proper identification on hand if stopped by authorities, are there reasons to carry my US passport when I'm outside in Korea? I don't think I would get ID'd for drinks since I am 25 and the drinking culture is not as strict as the US.
Comment: Are there reasons to carry a passport in America?
Comment: @JonathanReez Maybe there is a reason for a tourist in the US to carry their passport, but it may not be the same reason for a tourist in other country to carry their passport outside.
Comment: Are you carrying another form of ID (drivers license) with you? I mean i can understand not wanting to bring a passport, but I would alsways have at least *some* form of ID on me.
Comment: I'll have my state ID but I was just wondering if there would be any reason to carry a high level document on me other than the reasons mentioned in the question.
Comment: General rule is to consult the state department travel website and see if they encourage you to carry passport at all times
Comment: carry a photocopy of your passport with you and keep the original at your hotel (safe?)
Comment: I get ID'd for drinks while traveling and I'm 26. Not often, but it does happen. One time it happened in Scotland, I showed my US driver's license and they asked to see my passport instead.
Answer: The other answer seems good but not specific to South Korea. Here is my 5 years experience as an expat in the country:
Except if you are driving or if you are participating to troublesome situations (fight, illegal activities,...), the police will never check your ID (contrary to the neighborly Japan, where random controls in the street are common).
However, there are situations were you will need your passport:

Banks will ask your passport for some operations like opening an account, international transfers, etc... Note that; as an expat, I have an ARC (Alien Registration Card) and, even though I have been doing the same operations in the same branch with the same agent for some years, they continue to make a copy of my passport.
Not sure of it, but you are likely to need your passport to buy a cellphone or a SIM card.
Some train passes are reserved to foreigners, so you will need your passport to get them. Also, you need to give your passport number when buying train tickets online, and it will be checked when taking your ticket at the counter.
ID controls in bars and restaurants: some bars systematically check IDs of all customers, even if they obviously look adults (I am 32), and bouncers may refuse you to enter if you don't have it. Any ID that looks official and show your age is usually valid though, not only passport.
There are a lot of duty-free shops in big cities. They will check your passport and plane tickets.

Again, all of this is from experience and YMMV. Some people may be flexible and accept any ID (I entered in a ID-checking bar showing my age on FaceBook), other much less. I don't know if a copy of your passport is a valid substitute of your passport.
Answer: From personal experience: I never carried a passport with me on the domestic trips - including the same-day land trips around the country - anywhere I traveled, and I've been to over 50 countries so far. Only two times I was asked by police to show the passports, and both times they let me go after I said the passport is in the hotel safe. They only asked the hotel name, and lost all interest after that. I do carry a photocopy of passport with me, which is often asked by merchants when you purchase something with a credit card.
The could be more reasons, depending on how you spend your days:

If you are in a different part of town, meet someone, have a good time with him/her, and at some later point decide to rent a hotel room - the hotel might not check you in without your passport. In Korea they WILL not check you in, but in other countries like Philippines they would - as long as you look over 18. If you're Caucasian, please mind that in Asia it is difficult for many locals to estimate the age of Caucasian people, so please don't get offended if they assume you're under 18 and ask for ID.
If you decide to purchase something relatively expensive, the merchant might want to see your passport, and might not be happy with photocopy.
In some countries (notably Singapore) you need a passport to buy a SIM card, so if you're walking around and suddenly decide to buy one, you won't be able to. A photocopy will NOT work there (but will work, for example, in Malaysia).
If you want to purchase some duty-free stuff, they usually need your passport as well, to record the passport information as well as ensure your visitor status.
If you got into medical trouble - for example, you broke your leg and need to be admitted to the hospital - the hospital will want your passport too before admitting you.

And of course if you get questioned by the police - and for that being in close proximity of some fighting drunks is enough, or sometime they just raid the whole club - having a passport might make a difference between going home right away, and spending a few hours in a police station/detention cell until they verify your identity and legal status.


What is a Kubernetes Manifest?

Question: I've searched online and most links seem to mention manifests without actually explaining what they are. What are Manifests?
Comment: Manifest is a file (JSON or YAML), containing a description of all the components you want to deploy. Refer the official doc : https://kubernetes.io/docs/concepts/workloads/controllers/deployment/
Answer: It's basically a Kubernetes "API object description". A config file can include one or more of these. (i.e. Deployment, ConfigMap, Secret, DaemonSet, etc)
As per this:

Specification of a Kubernetes API object in JSON or YAML format.
A manifest specifies the desired state of an object that Kubernetes will maintain when you apply the manifest. Each configuration file can contain multiple manifests.

And a previous version of the documentation:

Configuration files - Written in YAML or JSON, these files describe the desired state of your application in terms of Kubernetes API objects. A file can include one or more API object descriptions (manifests).
Comment: can you update the link. The above link is no longer available.
Comment: Updated thanks for pointing out. I can't find what was described initially so I pointed to an updated part of the docs. Docs are in constant flux :-)
Answer: When you are going to deploy to kubernetes , or create a kubernetes resources like a pod , replica-set , configmap , secret , deployment , etc , you need to write a file called manifest that describe that object and its attributes either in yaml or json.
Just like you do in:

puppet manifest
ansible playbook
chef recipe

etc
Ofcourse you can create those objects by using just command line , but the recommended way is to write a file so that you can version control it and use it in a repeatable way.

What is a Kubernetes Manifest?


USB LG Drive Not seen

Question: Have Imac with Maverick and Windows 7 running in Parallels 10. Have a LG USB disk drive that is seen by Win 7 and works with no problems. Spins up, displays and works. It is NOT seen by Imac. Every place I look shows no signs of USB drive. It is plugged in same USB port as when it is used in Win 7. How do I get Imac to see the drive?
Comment: Can you see the drive if you eject it from within Windows, shutdown Windows *and* Parallels and then plug in the disk again?
Answer: I fixed this problem by changing the setting in Parallels under 'Preferences / Devices' to mirror windows-connected devices and then clicking the + button to add all devices that I wanted to access...note, just click the +, and the devices magically appear ;).  Also make sure that the USB drive is formatted as FAT32 or the mac won't see it!

USB LG Drive Not seen


A question related to probability

Question: If I have a coin then chances of getting a $head$ or a $tail$ is $50-50$. But why don't we take in account the case where coin is neither head and tail, where coin is standing upright, or it is making an angle with ground? Some people may object that when we are talking about probability of getting a $head$ or  $tail$, what we mean is that if we are doing experiment in a controlled room, where there is no matter except the coin and that coin is fully uniform, it is $50-50$ chance that I will get a $head$ or  $tail$.
This argument is not a very satisfying one to me, it don't even answer the question:How can we know that only two possible cases are there? Why consider only head and tail? Actually it raises one more question: Why the probability of getting a $head$ or  $tail$ is $50-50$?
Comment: When we speak of things like fair coins in math we are talking about idealized situations, where we can declare the probability as we see fit.  Real world situations may be modeled by such things but it's rare that the modeling is perfect.
Comment: Moreover, it will occur extremely rare that the coin lands upright. If it actually occurs , we just do not count the flip.
Comment: A real coin barely will give the exact probability, only a more or less good approximation. Usually, deviations are so small that we cannot observe it in practice.
Answer: Usually, when mathematicians talk about 'a coin flip' they mean the idea of an ideal coin flip, where the probability of getting 'head' or 'tails' is exactly one half for either of the possibilities. This may or may not be a good model for the outcomes of a real coin flip. But there is nothing stopping you from thinking of a model where the outcome can either be 'head', 'tails' or 'indeterminate', where also 'head' or 'tails' may not have the same probability.
Answer: In real life, as opposed to in a problem in an elementary textbook on probability,  a coin is not a perfect generator of $50$-$50$ odds.
"Probability of a tossed coin landing on edge," Daniel B. Murray and Scott W. Teare,
Phys. Rev. E 48 (Oct. 1993) gives a chance of approximately $1/6000$ that if a U.S. nickel (five-cent coin) is tossed, it will land on edge.
"Dynamical Bias in the Coin Toss," Persi Diaconis, Susan Holmes and Richard Montgomery, SIAM Review Vol. 49, No. 2 (Jun., 2007), pp. 211-235
concluded that with $0.51$ probability, a coin lands with the same side facing up as before it was tossed.
"How random is the toss of a coin?" Matthew P.A. Clark, MBBS and Brian D. Westerberg, MD, CMAJ. 2009 Dec 8; 181(12): E306–E308 found that some people are able to manipulate the toss of a coin.

A question related to probability


Is there a way to watch the Final Fantasy XIII cutscenes a second time?

Question: Is there any way to watch specific Final Fantasy XIII cutscenes after finishing the game?  Some of them are extremely well rendered and I would love to watch them again, but I really don't have the time to replay the game in order to do that.
Answer: In similar fashion to most other Final Fantasy games, there is no way to simply watch the cutscenes on your console after finishing the game. Short of saving before every cutscene, no method exists to replay them without replaying the entire game.
However, many of the cutscenes are posted on YouTube, and are available in 720p (HD) quality.
Comment: Actually, I think you might have been able to in FFX...maybe that was just music though.
Comment: Indeed you can in Final Fantasy X, inside the theatre dome in Luca. However, it's the exception to the rule.
Comment: @Keannu You can only see very few cutscenes(I believe you can see only the pre-rendered ones)


Notification about changes to answers

Question: As per this policy Wouter added information to this answer of mine, but unless I missed it I wasn't notified. I see lots of comments in my mailbox, but do I get notified if someone edits an answer?
Answer: There are no notifications when your posts are edited. Per https://electronics.stackexchange.com/faq#editing

Like Wikipedia, this site is collaboratively edited, and all edits are tracked. If you are not comfortable with the idea of your questions and answers being edited by other trusted users, this may not be the site for you.
Comment: How can I know if I'm (un)comfortable with it if I don't even know about it? That goes especially for older answers, which I don't check regularly anymore.
Comment: I agree.  It seems a simple notification to the author, like you get when someone comments on your post, is a good idea.  When someone else changes the words that appear to be mine, at least I should be notified.  If nothing else, it tells me the kind of things other wish I'd said differently.  So far I haven't objected to or rolled back any edits others have done on my posts (that I know of), but I think it's only fair I have the opportunity to at least inspect them.
Comment: @olin I believe there might be tools at http://stackapps.com that achieve that for you, much like wikipedia has external tools people use to monitor it.
Answer: I remember seeing that and wondering at the time how Wouter did that since he doesn't have enough reputation to edit other people's posts.  I was going to ask about that here, then forgot.
Personally I think that should have been added as a comment or possibly a answer of his own.  Wouter is very new here and his idea of how things are intended to be done is probably still evolving rapidly.  I know it was a bit confusing and overwhelming for me especially in the first week, and I still don't really feel like I understand all that well yet.  My reaction was to avoid doing things until I understood them better.  Other peoples' reaction may be to try various things.
I know Wouter from the PIClist, and he's a smart guy that usually has good things to say.  If this is something he shouldn't have done, I'm sure that's only because he didn't realize that and somebody should politely tell him.  I'd still like to know how someone with his reputation score managed to edit another's post though.
Comment: I think if you don't have enough rep you still can propose an edit, but that it has to be approved by someone more senior. Which I think is what happened here.
Comment: @steve correct, see http://blog.stackoverflow.com/2011/02/suggested-edits-and-edit-review/
Comment: @stevenvh that is correct. It might be beneficial to have a track of who approved what for when something was approved that should not have been.
Comment: @stevenvh, I thought it improved your post without changing its meaning and I was the one that approved it.
Comment: @Kortuk - Yeah, no problem. The reason for my question here is that I'd like to be notified. Not especially about this one, but just any changes.
Comment: @Kellenjb - Personally I don't care that much about who approved it. If I don't agree with it I'd rather talk (in chat) to the one who proposed the change. And I can always rollback, of course.

Notification about changes to answers


My Macbook Air won't update from 10.6.8 to anything

Question: my Macbook Air says it is running the latest version but it is stuck on 10.6.8. When I check for updates it says there are no new updates. I don't want the latest one which seems to be problematic for everyone (is that true??) but I would like to go to 10.9 or the one before the latest one. How do I do this? I have tried through the store but it just says I already have the latest software.
Comment: you can not get 10.9 anymore.
Answer: Unless you have the very earliest (Jan 2008) model you should be able to upgrade to Yosemite. Check your Mac model, click the Apple icon at the top left of your screen, choose About This Mac, then choose More Info.
You can't upgrade to an older version (unless you have a copy of the installer for that version).
Answer: Mavericks / Yosemite are not updates to 10.6, they are new "apps".
In the App Store, search for "Yosemite", it should be the first result. mavericks is no longer offered directly but may be available by less obvious routes.
Also note that if you have an original Macbook Air it may not support the latest operating system.
Comment: what less obvious routes?


Is it possible to color the output of `aafire`?

Question: The program seems cool, but giving it a red color really makes it look like my computer is on fire. I think using grep or similar piping command can do the trick, but I see that it prints ASCII escape codes for colors and removes the special formatting of the output that makes it look like fire.
Answer: cacafire
ASCII fire (aafire) was created with the now dead libaa. That may actually predate terminal color codes (I don't remember). However, the newer varient is the still maintained libcaca which provides cacafire.
Comment: On ubuntu the package is availble in "caca-utils"
Answer: Using command line flags, you can configure the output to display in your terminal rather than a popup window.
aafire -driver stdout -width 80 # match width of your terminal
aafire --help # see available options

Now, the color is controlled using your shell application's preferences. For example, I am using gnome-terminal on Ubuntu, so I just go to the menu Edit>Profile Preferences.
As far as changing the font color and background color itself, this appears to be possible in principle:
aatest

Notice that the first line has a blue background. I imagine this is accomplished with escape characters specifying the background color. You can find lots of discussion about this with people asking about changing their bash prompt color.
In order to insert your escape characters to change the color, I am not sure it would be possible to do this from the shell. Perhaps you could write a custom bash script that accepts input from stdin, pipe the output of aafire into your script, echo the color-changing characters, and finally echo the message from stdin.
Alternatively, you might have to call the library, for instance from a C program.
#include <stdio.h>
#include <aalib.h>
aa_context *context;
void main(int argc, char **argv)
{
  if(!aa_parseoptions(NULL, NULL, &argc, argv) || argc!=1) {
    printf("Usage: %s [options]\n"
           "Options:\n"
           "%s", argv[0], aa_help);
    exit(1);
  }
  context = aa_autoinit(&aa_defparams);
  if(context == NULL) {
    fprintf(stderr,"Cannot initialize AA-lib. Sorry\n");
    exit(2);
  }
  ...
  aa_close(context);
}

Example source code from the aalib documentation.
Answer: Try this
aafire -driver curses


I found an apple IIe without a power supply where can i find one

Question: I found an apple IIe without a power supply where can i find one also any tips on where i can find other parts for it. Btw i know nothing about Retrocomputers.
Answer: The Apple IIe power supply specifications can be found at this link.
The specifications are:

And the connector pinout is:

I can't tell if you are trying to repair an existing power supply brick (if so there are web sites and Youtube links for that) or if you are willing to replace it with something else that meets or exceeds the requirements for the Apple IIe.
But if you are willing to simply find an equivalent power supply that gets you to the right place, and you are willing to adapt such a power supply to the connector you have in hand (cut and paste work, perhaps), then the above specifications should be sufficient. (I have three supplies that meet those specs and I paid exactly US$2 for each one at a shop in the San Francisco area, some years back, when I was visiting.)
Regardless, the above information is all you need to either find someone to help you or else find a power supply that will meet your needs.
You could also consider paying someone to repair your existing power supply. These old supplies are not rocket science. So you should be able to find someone able to achieve that much for you.
Answer: I'm not sure exactly what you mean by "I found an Apple //e". Are you assuming it is a working machine, just in need of a missing PSU?
The best option would be to obtain a known good/working Apple PSU for it. Better yet, an entire working Apple //e would provide a source of swappable parts that you can use to troubleshoot a non-working machine, which is what you may have now.
Without getting into a quagmire of troubleshooting it yourself, you could likely sell it to another collector who has the troubleshooting tools/parts needed to get it working.
If you prefer to tackle the project yourself, I'd recommend one of:

Go online and locate a working Apple II PSU offered by a reputable seller. Beware this may fix the missing PSU but then you have other potential faults to contend with (If luck does not favor you).

Build a bench-top power supply that you can use to power up the motherboard and see if it is working. This will give you confidence to shell out for the working PSU you need.
Answer: ReActive Micro sell new PSUs. The other alternatives if you can source cables is a Q-60B psu from one of the AliExpress vendors, you'll need 12V,-12V,5V and -5V
An original PSU will almost certainly need the RIFA capacitors fixing.
Answer: My Apple II runs fine with an old PC PSU (though this one still had -5V). So you do not need an original one.
Comment: Modern PC PSUs still have -12V. What they miss is -5V but this is easily derived from -12V.