How much could I safely heat a content-less cast-iron pan?

Question: To which temperature could I safely heat my cast-iron pan on the stove, without any contents? I don't want to re-season it afterwards. Afterwards, I'd just let the pan cool off in room temperature. The base is ~0.5 cm thick.
Comment: I put cast iron pans inside a wood fire until red hot to strip down all the coating (nothing else will do). They survive perfectly.
Answer: If it is completely empty, you probably can't reach dangerous temperatures with your stove. The iron itself melts at 1500°C. The seasoning can be burnt off at much lower temperatures, a self-cleaning cycle in the oven is enough for it (500°C). I have taken an iron pan to above 400°C without damaging the seasoning. (I don't know exactly how high it was, my thermometer doesn't go above 400°C). This was on an induction stove set at maximum, I doubt that any other kind of stove can produce such temperatures.
Edit I just heard an example showing that you can take a pan on a resistive stove to above 500°C with prolonged heating, so you should be measuring it if you plan to go that high. (and if you have a thermometer in this range, you can post your findings to further limit the range of 400° to 500°C, because I'm curious).
But if you say "no contents", be careful that it is actually just the pan. You cannot oil it, because the self-ignition temperature (of flash point) of vegetable oil is low, Wikipedia gives it at 327°C. It could just smoke terribly and throw a spark or two when you reach it, but it can also flame up and then you are holding a small brand in your hand.
Answer: I bring my cast-iron to 500C regularly for steaks. I preheat the skillet in a 525F oven (as hot as it will go), then I put it on my hottest burner (electric coil stove) for 5 minutes. Checked with an IR thermometer, that does in fact get the pan to 500C. Once I answered the phone and let it go for longer than 5 minutes (8 maybe?). It made an audible poof and burnt all the seasoning in the bottom of the pan to ash. So, I'd say 500C for a short amount of time is your absolute upper limit if you want to preserve your seasoning.
Answer: Over 720°C you run the risk of changing the hardness and other properties. A domestic stove should not be able to get anywhere near this temperature
This is best done outside on a standalone gas burner. Do not have any liquids near by
Where are you going to get a suitable thermometer from :-)
Comment: @TimN: It's *perfectly normal* to preheat pans before adding food, and to preheat them completely empty (except for Teflon, where you add the oil cold, to make sure that the oil smoking gives you warning before the Teflon overheats).
Comment: My planned range was up to 250°C, but I'll see what I can find at the local faculty for material physics :)
Comment: @TimN: 250°C/482°F? I heat mine hotter than that for normal cooking applications. That temperature is only a concern for Teflon and similar; iron, stainless, even aluminum should be fine.
Comment: @derobert I just wanted to be careful since I normally don't cook without pan contents, and maybe it could hurt the seasoning.


How do you figure out the pronunciation of unknown characters without copying and pasting, on a computer?

Question: With Chinese there is an awesome keyboard setting on iOS where you can draw a character, so if you see one you don't know you just draw it into a dictionary to identify it.
Obviously you can just copy and paste unknown characters but I would be surprised if there were no way on an iPad to draw a Japanese character for input. Is this true? Do Japanese people have any way for inputting kanji apart from typing the pronunciation?
Comment: iOS can use different types of 3rd-party developed keyboards. I'm almost certain you want the one called "手書きキーボード" which can be purchased for 490-yen. I do not use that one, but I do use a different 3rd party keyboard (which makes English easier to type) with no problem.
Answer: The same feature is part of many Japanese dictionary apps these days. I use an app called 'Midori' and it has that feature. You just draw the kanji you want to find and it will offer candidates which resemble your drawing. You can also do this online and draw the kanji with a mouse (check it out here).
If you don't have the option of using a drawing recognition tool, you can use pop-up tools such as 'rikaikun' (for Chrome here) or other versions for different browsers. When you hover the mouse over the unfamiliar kanji, a pop-up appears that gives you information which includes the readings.
Recently, advances in technology have led to the development of Optical Character Recognition (OCR) technology, allowing you to use your phone's camera to recognise kanji characters. A Google app with that feature can be seen here.
If you have no access to digital apps such as the above, you have to go with one of the older systems devised to categorise kanji. These include systems which organize kanji variously by radicals, by stroke number (if known), the SKIP method see here, and some others.


draining sauna into crawlspace

Question: I'm thinking of setting up a drain from my sauna through the floor of my house into my crawlspace.  Practically speaking, would this damage the house?
Answer: Yes, it could lead to wood rot and a severe mold problem.  Don't do it.
Answer: Put the drain down through the floor like you were planning. Add a j-trap (like under your kitchen sink).Add more pvc to reach the floor of the crawl space. Add a 90 degree turn,then add horizontal pvc to the outside of your house. When you come to the outside stop. Dig a trench about 6 inches or less (enough to cover the 1 1/2 or 2"pvc). Make sure it goes far enough from the house so it won't drain back through the ground into you basement (or back under you house into the crawl space usally 6-7 feet). Where the pvc stopped at the outside of your house add a 45 degree coupling,then a short piece of pcv (2"), then another 45 degree coupling then enough pvc to the end of your trench. Cover the pvc. Leave the end open(or put an unglued cap on the end to keep rodents out). now when you want to drain the sauna go out take the plug out, pull the plug on the sauna and drain. After draining, put the plug back in. It doesn't take long for the sauna to drain.You really don't have to cuver the pvc outside the house, but if you do you can mow over it without having to move it all the time. This is exactly how I did the baptistry drain for our church when we were finally able to purchase and install our baptistry. If you were to simply drain the water into your crawl space eventually there would be so much mold you woud have to abandon your house.
Comment: Interesting.  Do you think it'd be worthwhile to cut a hole in the subfloor and install a sump pump directly under the drain?
Comment: He would have to buy a sump pump and then run piping to a drain. This seems more excessive.

draining sauna into crawlspace


why feed section in social networking sites are similar?

Question: Why is that every social networking sites have feeds page similar. Most of them use card structure for their feeds page. I just want to know the reason behind such use case. I thought every Social networking sites had mobile in their mind before they started building for the web ( it will be easier for the users to switch between mobile and web ) Can anyone help?
Answer: All of the sites look similar because designs that catch on tend to get copied.  There are a couple of main reasons:

When something new and trendy appears and becomes popular, other companies try to "keep up" by doing something similar.
Once something becomes an established paradigm, it also becomes easy for users to understand and use.

But there is no inherent reason why a card-based feed, or even the concept of a feed had to exist.  This is one possible way of structuring information among many.  If some early pioneering social networking site had invented something else, we might all be using that now.
Comment: Did mobile view have any impact on this feed design structure?
Comment: I'd say that the reason is because people (actually, read: business-oriented world, among which social networks are perceived as a cash-cow - whether it's an objective truth or not) are obsessed over having a social network, not of inventing something new, in particular such "unimportant" thing as UI.
Comment: @GunaSeelan Facebook's activity feed was launched in 2006, before mobile web really took off.  Probably not a big consideration then.  Surely mobile was a factor in subsequent development of the concept.  But why do you ask about mobile with this specific feature?  It's not clear to me.
Comment: @dan1111 Because we are building something similar( for Mobile and Web ) . So before we take a different approach( on Feeds page design ) so I wanted some clear thought.  Can the feeds design be different in Mobile and Web. I thought design should be similar so that people won't have any difficulty navigating it. Correct me If I am wrong


Is there a 'tag-less' tag?

Question: Is there a tag that we can use for games which we don't already have tags for? While we do have an extensive library of tags, there is no way we have a tag for every single game available on steam, in other countries (not America, I mean), for arcade, for mobiles, for consoles and handhelds and PCs, there are just too many. If there isn't already a tag for these, is it worth creating one? And how should we make the etiquette? Should we have a way to request a tag to be added if you don't have to reputation handy for it?
Answer: Yes, it is always worth creating a tag for a game that doesn't yet have a tag, provided it's done as part of the process of asking a question about that game. Don't start creating tags for games that have no questions.
In the event a tag doesn't exist, and you do not have the required reputation level to create the tag in question, you can put a small note on the bottom of your question stating that you tried to create the tag and this will be edited out and the question will be retagged by a higher rep user when the question is reviewed.
Since you can't raise a question without a tag, you can use a 'similar' tag (for example, for a prequel if the game is a sequel) or the 'untagged' tag if the former isn't appropriate (use of the untagged tag will certainly draw attention to the question and get it retagged asap).
Comment: Pretty sure [untagged] cannot be manually set. It's applied automatically by the system when the final tag of a question is pruned. Could, of course, be different on Arqade what with the thing about tags not actually being removed from the system here.
Comment: Last time I tried it could, although it looks like we have no questions against it (that aren't undeleted) in which case probably not. At the end of the day, setting the wrong tag and highlighting it to somebody (which is the general gist of my post) will result in the tag being edited in by somebody
Comment: I believe Anna Lear made it so we couldn't use [tag:untagged] anymore as a result of our tag cleanup today!
Answer: There's no reason to create tags when there is no question about that tag.  Otherwise we'd have way too many tags for every game in existence for no particular reason.  If you don't have the reputation to make a tag, you can either request a tag to be made on the meta or just let someone with the reputation to edit your question to put the right tag on.
As a side note, there used to be an untagged tag but we've done our best to burninate it.
Comment: untagged is fine for low rep users, since it draws attention to have the question retagged pretty quickly if the game tag doesn't exist.

Is there a 'tag-less' tag?


What can Blood Stone Shards be used for?

Question: I have about 40 Blood Stone Shards right now. They seem to drop like nobodies business. Do they have a use besides fortifying weapons that I need to save them up for? Or is their drop rate just really high in general?
Answer: Blood Stone Shards are only used for upgrading weapons up to +3. You need 3 for +1, 5 for +2 and 8 for +3. That means you need a total of 16 shards per weapon to get to the next upgrade material tier.
The further you advance in the game, the more Blood Stone Shards you will come across. The same goes for the Blood Stone of higher tier (Twin Shards and Chunks). If you have an excess of materials, you can use them to upgrade weapons you don't use so often or sell it to the messengers in the Hunter's Dream for 200 blood echoes each.
If you try to upgrade all weapons you come across, you shouldn't have too many left though. I recently had reached my inventory limit for shards and still didn't have enough to upgrade all my weapons. There is no other use for Blood Stone materials that I know of.
Comment: I neglected to mention the +3, +5, +7 in my answer. It hadn't occurred to me that the OP may have missed that. Nice spot! +1
Answer: It sounds to me like you only have a couple of weapons that you use.
If you only have a couple of weapons, and they're fully fortified until the point where you need Twin Blood Stone Shards; then use the money to buy the other weapons.
Some of them are useful for different things, e.g. the Cleaver. Other weapons like your firearm and torch can be fortified too.
If you haven't got much spare money yet, don't worry you will have soon enough.

Either that or the total opposite extreme is true, and you've bought all of the different weapons, and fortified all of them; after replaying a lot of the levels over and amassing a lot of Blood Stone Shards.


What is the recommended CIDR when creating VPC on AWS?

Question: I have been creating AWS VPCs and I am wondering if there is a recommended CIDR value when creating VPCs. What are the factors that I must consider when choosing a CIDR and does the CIDR value affect the performance of the network?
Answer: I would recommend the following considerations:
If you creating an IPSEC connection between your corporate LAN and your VPC, use a CIDR that is different than that on your corporate LAN. This will prevent routing overlaps and create an identity distinction for reference.
For very large networks, use at least different 16-bit masks in different regions eg
eu-west-1 10.1.0.0/16
us-east-1 10.2.0.0/16
us-west-1 10.3.0.0/16

For smaller networks, use a 24-bit mask in different regions eg
eu-west-1 10.0.1.0/24
us-east-1 10.0.2.0/24
us-west-1 10.0.3.0/24

Consider making a distinction between private and public subnets, eg
private 10.0.1.0/24 (3rd byte < 129)
public 10.0.129.0/24 (3rd byte > 128)

Don't over-allocate address space to subnets, eg
eu-west-1 10.0.1.0/26
eu-west-1 10.0.1.64/26
eu-west-1 10.0.1.128/26
eu-west-1 10.0.1.192/26

(62 hosts per subnet)

Don't under-allocate either. If you use a load of Elastic Load Balancers, remember that they will also consume available ip addresses on your subnets. This is a particularly true if you use ElasticBeanstalk.
Comment: I found this article from AWS on VPC Subnet layout quite helpful: https://medium.com/aws-activate-startup-blog/practical-vpc-design-8412e1a18dcc#.bmeh8m3si
Answer: Some things I considered the last time I created a new VPC:

Make sure the IP ranges from different regions don't overlap. You shouldn't have a 172.31.0.0/16 in us-west eu-ireland, for example. It will make VPN between those two regions a problem requiring double-NAT to solve. No thanks.
Make sure the IP range is large enough to hold all the instances you think you'll need x.x.x.x/24 will accommodate 254 different addresses. There are probably hundreds of CIDR calculators out there to help you figure this out.
I create a lot of different subnets in a single VPC, rather than creating multiple VPCs. The subnets can talk to each other - I can have private vs. public subnets to keeps some instances shielded from the open internet. Use a NAT instance so that the private subnet can talk to the public subnet. Use security groups to isolate groups of instances from one another.
Answer: Amazon doesn't appear to recommend any particular network size for your VPC (see the VPC network administrator's guide and note the use of /16s), but in general there are two reasons to consider the performance effects of CIDR:

Routing. A smaller prefix (larger network) is frequently used for route aggregation and can actually improve performance.
Broadcast and multicast traffic, which is more relevant to your situation and can result in decreased performance on smaller prefixes. You can mitigate the effects of this traffic by further subnetting the VPC as shown in the network admin guide.

Consider the initial number of nodes in your VPC and projected growth for the anticipated project lifetime and you should have a good starting point for prefix size. Remember that there is no harm in starting with a small prefix such as /16 because you can always create subnets.
Comment: I just want to point out for future readers that AWS VPC does _not_ support broadcast or multicast, so the second bullet point isn't relevant.

https://aws.amazon.com/vpc/faqs/
Answer: Another consideration is whether you will need to use AWS ClassicLink to allow access to the VPC from EC2 instances outside of the VPC. From the AWS documentation:

VPCs with routes that conflict with the EC2-Classic private IP address range of 10/8 cannot be enabled for ClassicLink. This does not include VPCs with 10.0.0.0/16 and 10.1.0.0/16 IP address ranges that already have local routes in their route tables. For more information, see Routing for ClassicLink.

from http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/vpc-classiclink.html#classiclink-routing
Answer: In case someone may find this question and would be interested in setting a CIDR-based specification of just a single ip address (such as if you are setting the RDP IP allowed in a new AWS stack), you would do that with the ip address and then /32 (which means "one ip address), so if your address were 184.108.40.2067 you'd specify:
18.104.22.1687/32
Comment: Except that an IP address could never be `220.127.116.117` (255 being the largest allowed octet).
Answer: The recommended CIDR for VPC depends on requirement. The largest block size for VPC Ipv4 CIDR is a /16 netmask with 65,536 IP addresses and Smallest is a /28 netmask with 16 IP addresses.


Are transitions strips necessary from room to room if installing luxury vinyl planks throughout house?

Question: I would like to replace our carpet and tile with the locking/floating luxury vinyl planks throughout most of the house. Our house runs long and think it would look so much nicer without transition strips from room to room where there will be lvp only, such as between the living room and kitchen/family room as shown in this photo taken from the entry way. Is this possible or do you recommend transition strips to avoid buckling, etc.?
Comment: You need to read the instructions for your product. Some have maximum room lengths, beyond which an expansion channel must be installed.
Comment: Can you add the identity of the planks you plan to use?  Also, dimensions and layout of the area and the direction you plan to run the planks.
Comment: Thank you so much for your response! We like a Coretec product because of the color. The planks are 5"x4ft and we'd like to run the planks parallel to the length of the house (the right wall).
Answer: Transitions strips are generally to provide a transition from one flooring surface to another; oftentimes because of a height difference. Sometimes they provide a threshold from one room to another where the flooring is the same but a limit barrier is desired, like from the living room to the kitchen/dining room.
Transitions give visual cues and can change the design dynamics visually to a space—make it look bigger or more cozy, etc.
If you're using a single kind of flooring throughout and there are no height differences or underlayment/stability issues, you don't have to install transitions.
You do need to install base of some kind where the flooring meets the walls. Doorways, around corners and curved spaces require base and sometimes transitions, depending on the flooring and installation layout.
Be sure to do a "dry" layout and determine where you need to make cuts, keeping in mind, the cuts should be made at the least visible part of the floor. For example, in a small bathroom, you generally want to use a full tile coming out from the wall or tub and make cuts at the threshold of the door.
Comment: Thank you very much for your response! By "base", do you mean quarter-round or shoe molding? If so, I'm hoping the baseboards will cover up the gap between flooring and walls and try to minimize quarter-round or shoe as much as possible.
Comment: Quarter round is usual but you can be creative with your choice. Check youtube for alternative ideas on base/baseboards.  Depending on the thickness or depth of the baseboard you're using, it may cover to the edge of the flooring (be certain to remove existing base for best results). Follow manufacturer's installation instructions.


The transition function of the union of regular languages

Question: I follow Michael Sipser's book, "Introduction to the Theory of Computation".
To be specific, I am trying to understand the proof about the union of regular languages. However, I have a problem grasping how exactly the transition function is defined.
The book says that for each $(r_1, r_2) \in Q$ and each $a \in\sum$, let
$\delta((r_1, r_2),a) = (\delta_1(r_1, a), \delta_2(r_2,a))$. The problem is that I cannot understand what happens if, for example, $\delta_2(r_2,a) = \emptyset$ and $\delta_1(r_1, a) = q_1$ and I get $\delta((r_1, r_2),a) = (q_1, \emptyset)$, which does not belong to the set of all pairs of states.
Comment: What do you mean by $\delta(r,a)=\emptyset$ ? does it mean lack of transition from state $r$ upon reading the character $a$?
Comment: @Ariel Yes, that what is meant by $\emptyset$. At least that is how I see it.
Comment: is $\emptyset$ a state? If $\emptyset$ is a state, then you have no problem. If $\emptyset$ is not a state, then $\delta_1(r_2,a) = \emptyset$ is impossible because the range of $\delta_1$ is (a subset of) the set of states.
Answer: In the definition of a deterministic finite automaton, we require that the transition function $\delta$ is well defined on all of $Q\times\Sigma$, i.e. $\delta: Q\times \Sigma\rightarrow Q$. Sometimes we allow omitting transitions, and say that the automaton is "stuck" if it stumbles upon this transition, however in Sipser's book he defines the transition function as above (defined on all of $Q\times\Sigma$).
If you insist on allowing the the automaton to get stuck, then this results in a slight modification of the proof. Instead of looking at $Q_1\times Q_2$ (where $Q_i$ is the state set of the $i'th$ automaton), consider the state space
$\left(Q_1\cup\left\{\widehat{q_1}\right\}\right)\times\left(Q_1\cup\left\{\widehat{q_2}\right\}\right)$, where $\widehat{q_1},\widehat{q_2}$ are special states designed to deal with lack of transition. You can now complete the details yourself.
Comment: Thank you for your answer. If I want to construct an automaton that recognizes only ${0}$ over the alphabet ${0,1}$, then I have to include transitions for $1$ somehow. Is that correct? Do transitions for $1$ have to lead to some state from which there is no escape?
Comment: If you define DFA as above, then yes.
Answer: The transition function of a DFA gets a state and a symbol and outputs a state. It cannot output the empty set. That would be a type mismatch. In other words, in a DFA, every state has an outgoing transition for every symbol – exactly one, in fact.
You can define an "extended" DFA in which some transitions are allowed to be missing, but you would then need to modify the definition of the product DFA. It is a good exercise to see what the appropriate modification would be.


How to design gunshots

Question: I'm not native English speaker, apology for not being fluent. Right now I am trying to design gunshots. From what I've found out on internet, gunshots sfx are made up of attack(low), body(mid), punch(low), mechanism. I tried to grab different layers from library. But the main problem I am facing is running out of headroom. I know most people are talking about compression and limiting. So what is usual setting of attack, release, ratio? Should I use multi compression? Are there any plugins good for gunshots design? Right now I start lowering every layer level first to create more headroom. To use Req, H-comp, and mostly Flux Solera, which have clipper effect, to gain up gunshots sfx. I hope others would like to give me some ideas and share their experiences. Thanks all.
Comment: I've even come across people mimicking gunshots by slapping a flip flop on the floor
Answer: Great question, let's hope there are some equally great answers to follow.
Gunshots come in many different shapes and sizes (single shot, automatic, small caliber, large caliber, suppressed, silenced), as well as different environments (interior, exterior, small spaces, large spaces) and flavors (antique, modern, and futuristic weaponry). Each one has its own characteristic, and by the way, there are no rules. :) That's the good news.
You have the basic breakdown correct: Attack, body, punch and mechanic. (There are more, arguably, but I think those four cover the food groups pretty well). So, knowing the pieces, you just have to start arranging them to make your particular puzzle complete.
Not knowing what kind of gunshot you are trying to design, it's difficult to go into much detail about what will/won't work. What I do recommend is to put away your plugins and put on your listening ears. If you have a shooting range nearby, get a day pass and learn what real guns sound like (better yet, do some shooting yourself - personal experience can be an extremely valuable education, regardless of the subject matter). If you have a film/TV show/game that you are trying to emulate, play those scenes over and over and dissect what makes the guns sound so good.
If I had to recommend some plugins, I would say that a compressor/limiter is a useful tool to increase the apparant loudness of the shot (Waves MV2, L2, etc), while a tranient enhancer of some kind will restore the bite or attack (Waves TransX, SPL, etc). For low end enhancement you can go to Waves RBass or MaxxBass (I promise I'm not a sales rep for Waves :)).
Lastly, just sit down and start experimenting with different elements. Slight timing adjustments can make a HUGE difference, as can short/long reverbs and delays.
Have fun!
Comment: I think all the plugins you mention are on heavy sale right now, fyi.
Comment: Thank you. I tried today but still having no success. So I extracted the 5.1 audio from the blurry of John Wick2 and 13 Hours.Since I am doing a 5.1 movie mixing project and I studied their gun design from my Protools. I noticed that most of their gunshots are spreaded to LCR. And obviously, both L and R have the same layer which is usually high-frequency, the attack part. And the center one, I think that is body. And the most punchy sound is coming from LFE. Is this an usual practice for designing gunshot in movie mixing?

How to design gunshots


Does taking graduate course as an undergraduate increase chances of getting into graduate school?

Question: I would like to know does it help if I take a graduate course related to my major in engineering as an undergraduate and do very well in it? will it increase my chance of getting to graduate school in case if graduate school committee sees the graduate course in my transcript?
Comment: Yes, it will help!  In fact, you can repeat the procedure and expect it to help even more.
Answer: Yes, I think most admissions committees would see this as good evidence of your preparation for graduate study.
Answer: There are two specific reasons why it will help:

It shows that you can work at a high level;
If the course is in the area where you are applying to study, it shows that you have investigated that specific area and have some level of commitment to it.

However, in my experience the graduate level course may not compensate for poor or patchy performance on the undergraduate programme that you're meant to be completing at the time (not saying that this is the case, but I've seen some try). Some recruiters see patchy UG performance with additional courses that you didn't need to take as an indication that you can't focus on the most important, immediate task. In either case, I'd expect detailed questions on why you took additional graduate courses, and how you balanced your workload, at interview.
Answer: It really depends on the student and the graduate course(s). Consider two students.
Graduate courses are unlikely to help a student with a strong academic record and a near perfect GPA, but no previous research experience and recommendation letters that only speak about classroom abilities. There will be little doubt from the admissions committee about the ability of this student to learn advanced concepts and the weakness of the application is the limited evidence to evaluate research potential.
Graduate courses may help an applicant with a good record of relevant research experience and recommendation letters that focus on the research, but a weak academic record. The weak part of this type of applicant is fear over the ability to learn advanced concepts. The ability of a graduate course to sway the decision of the admissions committee will depend on both the grade and the content of the course. Anything less than a B in a graduate course is likely a disaster and it may take an A to sway an admissions committee. Similarly, taking a course that is unrelated to your research interests or is viewed as a "soft" topic will likely decrease the value of the course.
Answer: I would say overall, yes.
My school offers what's called a "project course" and it's intended to get senior students aiming for their masters experience with research and writing a thesis. You speak to a professor in your faculty who's research revolves around a topic that interests you and you will write an honours thesis related to that under their supervision throughout the year. I study Computer Science, so my project courses also contained an application aspect. If I want to get into grad school, they will see that I have built a large program, written a thesis, and worked under the supervision of a professor at my institution. All desirable traits in a grad student.
It is very, very common for students who take these courses to get their position as a masters student under the same professor the very next year. Definitely something an academic advisor will recommend you do.
Comment: It is not clear to me that this is a graduate course if it is aimed at "senior students". Further, I think this is a relatively unique course that it is difficult to draw inferences from it.
Comment: We have multiple course offerings across several faculties, and from my own network of friends at a variety of different schools across the country, they have the same opportunities. Although it may not be a graduate course, it is a course where you can prepare a thesis and application on graduate level content. This serves the purpose of preparing senior students for their masters degree by giving them experience working with a professor. Hope this clears it up a bit.


Showing coercivity condition for an energy functional

Question: Consider the energy functional $e(\cdot)$
\begin{align*}
e(f,Q)&=\int_a^b \bigg\{f^4\bigg[1+\|\frac{d}{dr}Q\|^2+f^2\dot f^2\bigg]\bigg\} \,dr,
\end{align*}
over the space of
\begin{equation*}
{\mathcal E}:=\left\{ (Q, f) :
\begin{array}{l}
Q \in W^{1,4}([a,b],{\bf SO}(n)),\\
Q(a)=Q(b)=I,\\
f \in W^{1,4}[a,b],\\
\dot f>0 \mbox{ ${\cal L}^1$-a.e. on $(a,b)$},\\
f(a)=a, f(b)=b.
\end{array}
\right\}
\end{equation*}
It is easy to show that, energy functional $e(\cdot)$ is coercive when $Q\in W^{1,2}$ and $f\in W^{1,2}$, in another words, there exists $d=d(n, a, b)>0$ such that
\begin{equation*}
e(f, Q) \ge d ( \|Q\|^2_{W^{1,2}} + \|f\|^2_{W^{1,2}}).
\end{equation*}
Now my question is:
The energy functional $e(\cdot)$ is coercive on the space $\mathcal E$ or not? In another words could we find $\gamma=\gamma(n, a, b)>0$ such that
\begin{equation*}
e(f, Q) \ge \gamma ( \|Q\|^4_{W^{1,4}} + \|f\|^4_{W^{1,4}}).
\end{equation*}
for all $(f, Q)\in \mathcal E$.
Answer: No. The reason is that
$$e(f,Q)=\int_a^b \bigg\{f^4\bigg[1+\|\frac{d}{dr}Q\|^2+f^2\dot f^2\bigg]\bigg\} \,dr,
$$
with $b\geq f\geq a$ (since $f$ is continuous and monotonous) gives
$$
e(f,Q) \leq \left(1+\frac{b^4}{2}\right)\left(\|f\|^4_{W^{1,4}} + \|Q\|^2_{W^{1,2}}\right)
$$
So your inequality would imply that there exists $C_1,C_2>0$ such that for all $f,Q\in\mathcal{E}$
$$
C_1\|Q\|^2_{W^{1,2}} + C_2\|f\|^4_{W^{1,4}} \geq  \|Q\|^4_{W^{1,4}}.
$$
Now, fix $f=a+b\frac{t-a}{b-a}$, and it becomes for all $Q\in\mathcal{E}$
$$
C_3(\|Q\|^2_{W^{1,2}} + 1) \geq  \|Q\|^4_{W^{1,4}},
$$
if you cook-up a sequence $Q_n$  with $\|Q_n\|_{W^{1,2}}=1$ and  $\|Q_n\|_{W^{1,4}}>n$  you have a contradiction.
Note that $W^{1,4}$ is not natural, since you can also obtain a bound from above of the form
$$
e(f,Q) \leq C(a,b)\left(\|f\|^2_{W^{1,2}} + \|Q\|^2_{W^{1,2}}\right).
$$
--- edited after the comment to the first part of the answer--
If you are looking for a minimizer, it is immediate to note that
$$
e(f,Q)\geq e(f,I)
$$
for any $f$ since it is a sum of squares, and $(f,I)\in \mathcal{E}$. Therefore you just want to solve
$$
\min_{f\in \mathcal{X}} \int_a^b \left( f^4 +f^6 \left(\frac{df}{dt}\right)^2\right) \,dt,
$$
with $\mathcal{X}=\{f \in W^{1,2}(a,b)~:~f(a)=a,f(b)=b, f^\prime>0~a.e.\}$, a convex set. A calculus of variation problem in one dimension with a monotone integrand-> textbook question. The infimum will be in $\bar{\mathcal{X}}$ in general, and $f$ satisfies either the Euler-Lagrange equation, or is constant.
To find a simple answer, let us assume that $0<a<b$. Then $f>0$ in $\mathcal{X}$, and if you set $g=f^4$, you find that your problem is also
$$
\min_{g\in \mathcal{Y}} \int_a^b \left( g + \frac{1}{16} \left(\frac{dg}{dt}\right)^2\right) \,dt,
$$
with $\mathcal{Y}=\{f \in W^{1,2}(a,b)~:~g(a)=a^4,g(b)=b^4, g^\prime>0~a.e.\}$, a convex, open set.
Now, the Euler-Lagrange equation is simply $$1+\frac{1}{8}g^{\prime\prime}=0.$$ You can solve it by hand, and playing with it, you find for example that when $$a>
\frac{\sqrt{6}}{8}\frac{\left(3554+2(33)^{3/2}\right)^{1/3}}{\sqrt{7}\left(3554+2(33)^{3/2}\right)^{2/3}+(33)^{3/2}+116\left(3554+2(33)^{3/2}\right)^{1/3}+1777)},$$
the solution with $g(a)=a^4$ and $g(b)=b^4$ is strictly increasing and therefore is in $\mathcal{Y}$, whereas otherwise the positivity of the gradient constraint comes into play for suitable $b$s.
Comment: Indeed what I'm trying to do is to show that the energy functional $e(f, Q)$ admit local minimizers. I would be grateful if you let me know yours ideas.
Comment: @MSSHD see updated answer
Comment: What about $W^{1,4}$, Actually I would like to prove we have the minimizer in $W^{1,4}$ not in $W^{1,2}$.
Answer: that is a good idea !
i guess that your conjecture may has a counter-example !
see : http://www.stanford.edu/class/math220b/handouts/calcvar.pdf
that is because :
$e(f, Q) \ge d ( \|Q\|^2_{W^{1,2}} + \|f\|^2_{W^{1,2}})$$\Longrightarrow$$f^4(1+\vert{\nabla{Q}}\vert^2+f^2\vert{\nabla{f}}^2\vert)$$\ge$$d(Q^2+\vert{\nabla{Q}}\vert^2+f^2+\vert{\nabla{f}}^2\vert)$
we select $d=f^4$  to get :
$1+\vert{\nabla{Q}}\vert^2+f^2\vert{\nabla{f}}^2\vert$$\ge$$Q^2+\vert{\nabla{Q}}\vert^2+f^2+\vert{\nabla{f}}^2\vert$$\ge$$4Q\nabla{Q}+4f\nabla{f}$$\Longrightarrow$$f\nabla{f}(4-f\nabla{f})+Q\nabla{Q}(4-\frac{\nabla{Q}}{Q})\le1$
on the other hand ,
$f^4(1+\vert{\nabla{Q}}\vert^2+f^2\vert{\nabla{f}}^2\vert)$$-\gamma(Q^4+\nabla{Q}^4+f^4+\nabla{f}^4)\ge0$$\Longrightarrow$$1+\vert{\nabla{Q}}\vert^2+f^2\vert{\nabla{f}}^2\vert$$\ge$$4Q^2\nabla{Q}^2+4f^2\nabla{f}^2$$\Longrightarrow$$3f^2\nabla{f}^2+Q^2\nabla{Q}^2(4-\frac{1}{Q^2})\le1$
by comparing the two inequality above, we have :
$3f^2\nabla{f}^2+Q^2\nabla{Q}^2(4-\frac{1}{Q^2})\le$$f\nabla{f}(4-f\nabla{f})+Q\nabla{Q}(4-\frac{\nabla{Q}}{Q})$
$\Longrightarrow$$4f\nabla{f}(f\nabla{f}-1)+4Q\nabla{Q}(Q\nabla{Q}-1)\le0$
now, it is clear that your problem is related with the convexity and the concavity of the function you defined on $[a,b]$  !
Answer: The Euler-Lagrange Equations of the $e(f, Q)$ over the admissible space $\mathcal E$ arise as the following system
\begin{align*}
\left \{ \begin {array}{ll}
(i)\ \ \frac{d}{dr} \bigg[ f^4 Q^t \frac{d}{dr} Q \bigg] ={\bf 0},\\
\\
(ii)\ \frac{d}{dr} \bigg[ f^2 \dot f \bigg] =
2f^3 +3f^5 \dot f^2 + 2f^3 |dQ|^2,
\end{array} \right.
\end{align*}
Now as the functional $e(\cdot, \cdot)$ is coercive on $\mathcal E$ when we choose the $f, Q$ in $W^{1,2}$ instead of $W^{1,4}$ and an application of direct methods shows the system has a solution. Well, could we claim this result in $\mathcal E$ by $f, Q$ in $W^{1,4}$?
Comment: you just need to show that the minimiser you obtain is in $W^{1,4}$. Note that $\mathcal{E}$ is not closed, so it is an infimum and not a minimum in general, cf. detailed answer above.
Answer: It is evident that your functional $e(f, Q)$ has minimizer in the space $W^{1,2}$ since you have coercivity in this space and an application of direct method of calculus of variation givee you the required result in $W^{1,2}$. So the system of Euler-Lagrange equation you wrote in below, has solution in $W^{1,2}$. Now from the first equation (equation (i) you can compute $\dot{Q}$ and $Q$, in fact we have
$$ \dot{Q} = \frac{1}{f^4}Q C$$
in which $C$ is a (skew symmetric) constant matrix. therefore $|\dot{Q}|^4 < \infty$ and hence $Q \in W^{1,4}$ (in fact by this argument you can show that the solution $Q$ is smooth).  Similarly form the equation (ii) you can compute $f''$ in terms of $f$ and $f'$ and $|\dot{Q}|$ which shows that $f''$ exists (note that $f$ is bounded on [a,b]) so $f'$ is continuous and consequently for the solution $f\in W^{1,2}$ of the above system we have  $f\in W^{1,4}$.  In fact by the above argument one can show that the solution $f$ of the above system is also smooth (similar to the solution $Q$).  Therefore the solution (Q,f) which first was proved to be in the space $W^{1,2}$ is in the space $W^{1,4}$ and moreover by applying the system of equation (i) and (ii) similarly we could prove that this solution $(Q, f)$is a $C^{\infty}$ solution.


How do Canon's EF 35mm ƒ/2 and EF 35mm ƒ/2 IS USM lenses differ?

Question: What's the difference between the Canon EF 35mm f/2 lens that was available in 2008, and the EF 35mm f/2 IS USM lens now available, apart from the £200 extra price difference?
Comment: Don't you suspect IS and USM mean something?
Comment: @osullic To be fair to the OP, I edited the question title and body to refer to the correct lens model names. OP didn't include "IS" as originally written (although, I think they did include "USM").
Answer: The lenses are two totally different designs for the Canon EOS EF mount that have the same focal length and maximum aperture. They share little else in common.
EF 35mm f/2:

Introduced in 1990 shortly after the introduction of the EOS system in 1987.
7 lens elements in 5 groups.
5 blade aperture diaphragm.
0.25 meter minimum focusing distance with 0.23X maximum magnification
67.4mm wide x 42.5mm long weighing 210 grams.
Arc form micro-AF motor with no full-time manual focus. (Turning the MF ring while the lens is set to AF can damage the AF motor or gearing)
Fewer internal lens surfaces have anti-reflective coatings.

EF 35mm f/2 IS USM:

Introduced in 2012, 22 years after the EF 35mm f/2.
10 lens elements in 8 groups including a glass mold aspherical lens that effectively corrects for various aberrations, including curvature of field, making possible higher image quality than its predecessor.
8 blade circular aperture diaphragm.
0.24mm MFD with a 0.24X MM.
77.9mm wide x 62.6mm long weighing 335 grams.
Ring type Ultrasonic Motor AF with full-time manual focus.
Multi coatings on most internal lens elements to reduce flare and ghosting.
Image Stabilization rated at four stops.

The newer EF 35mm f/2 IS USM is a modern lens design created for use with digital cameras. The EF 35mm f/2 was a film era lens that, while a good value and performer for its time, shows its age a bit when used with digital cameras and held up to the higher level of scrutiny expected by most photographers today.
There's also the newer (2015) and more expensive EF 35mm f/1.4 L II USM that is a significant improvement over the legendary EF 35mm f/1.4 L USM introduced in 1998.


Filtering home-rendered lard

Question: I recently rendered some lard at home from some pork fat I bought from a nearby Mexican grocery store (Mi Pueblo in San Jose). The lard is delicious and I'm glad I made it, but I wish I knew how best to make it "cleaner". It's not very light-colored now that it's chilled, and I can see some burnt pork solids left it it. What's the best and easiest way to get my lard nice and clear?
Comment: Are you using cheesecloth, and worried because the finer particles get through and settle out? Or are you just running it through a sieve and seeing small cracklings still floating in it...?
Comment: I'm seeing tiny dark pork particles and I want nice clean clear creamy lard.
Comment: If you have burnt pork solids, that suggests to me that you rendered over heat that was too high.  You might have better luck with extremely low heat
Answer: For applications such as these where I really want a fine strain, much more than any of my strainers can handle, I line a larger-hole strainer with cheesecloth (if I have trouble with the cheesecloth staying I use a rubber band to hold it in place).
Although I have not tried it with rendered lard, I have used it in a lot of other places (stock immediately comes to mind) where I have a lot of little particles that make it through my finest of strainers.  A quick search for a lard/cheesecloth/strainer keyword combination shows that a lot of recipes for home-rendered lard seem to suggest this so I think it would work.
You can find a picture of a cheesecloth-lined strainer here or just Google image search it if the link dies.
Oh, and as an aside, I find that purchasing the cheesecloth in bulk at a fabric store (such as Jo-Ann Fabrics in the USA) is much, much cheaper than buying small packages in a kitchen store (such as Williams-Sonoma).
Comment: I've never seen cheesecloth at fabric stores (but admit, I haven't been looking) ... but I know you can get muslin, which will work as a decent substitute (but because of the tighter weave, it won't drain through quite as quickly ... but it'll stain out the small bits really well)  In a pinch, I've also been known to line a strainer with paper towel, you just have to be patient, and careful to make sure you don't tear it or you have to start over.
Answer: At Asian grocery stores you can find a variety of very fine-mesh sieves and strainers. I have a couple that are fairly broad and shallow, and in my meat-eating and fat-rendering days I used to use those to get the fat pretty "clean".
Restaurant supply places sell bigger strainers (generally under the uncomfortable name "China cap") with very fine mesh, and that might work. Thing is however that you don't necessarily want a lot of volume in the strainer, as the fat has to stay hot and liquid or else you're in trouble.

Filtering home-rendered lard


How are large prime numbers found?

Question: So I've found multiple ways of determining if a number is prime but I was wondering how they pick a number in the first place. For example the GIMPS project I assume is just trying different numbers to square 2 by but what about other methods? Or is it just a process of testing each and every unknown number?
Comment: The general approach to find large prime numbers is to sieve out small factors to get candidates (numbers that might be prime) before testing whether they are actually prime. This is rather time consuming for very large numbers and the chance to be successful is small even if we sieve out the prime factors upto $10^9$ or so. In short, finding (new) very large primes remains difficult.
Comment: In general they are picked because they are the result of a closed formula. Look [here](https://en.wikipedia.org/wiki/Formula_for_primes) or [here](https://en.wikipedia.org/wiki/Generating_primes).
Comment: Primes of many other types of numbers have been found (factorial primes ; form $n!\pm 1$ , primorial primes ; form $p$#$\pm1$, where $p$#$=2\cdot 3\cdot 5\cdots\cdot p$ , fibonacci primes (fibonacci numbers that are prime) , repunit primes ; form $\frac{10^n-1}{9}$, the decimal expansion just contains of $n$ ones, and many more) , but as pointed out in the answers below the largest known primes are Mersenne-primes. Which numbers are chosen depends on what kind of primes are wanted.
Answer: GIMPS just considers Mersenne primes, so there is a fixed formula.
However if you are looking for a "biggish" prime, say 1024-bits well suited for cryptography, that is a prime $p$ with $2^{1024} < p < 2^{1025}$. Out of the $2^{1024}$ numbers in the range, approximately
$$\frac{2^{1025}}{\log 2^{1025}} - \frac{2^{1024}}{\log 2^{1024}}$$
are prime. So the fraction which are prime is
$$\frac{2}{\log 2^{1025}} - \frac{1}{\log 2^{1024}}=
\frac{2}{1025\log 2} - \frac{1}{1024\log 2} = 0.001406$$
Since you can test as many as you want, that's not such bad odds.
Comment: See https://en.wikipedia.org/wiki/Prime_number_theorem for more information on the density of the primes.
Answer: By the frivolous theorem of arithmetic, the large primes that have been found are quite small. Let's say $p$ is the largest known prime. Then between $p$ and $p^p$ there are roughly $$\frac{p^p}{\log p^p} - \frac{p}{\log p}$$ primes that are bigger than $p$, and of course $p^p$ still falls quite short of infinity. This is quite a large number (to us) when we plug in something like $p = 2^{74207281} - 1$, the largest known prime number right now according to the Prime Pages.
It's not surprising that this largest known prime is a Mersenne prime, a number of the form $2^n - 1$ (and $n$ is also prime). The other answerers have already mentioned the Lucas-Lehmer test. Just for fun try it on $2^{31} - 1$, you might find it to be quite faster than trial division up to $\sqrt{2^{31} - 1} \approx 46340$.
But it's still time-consuming. Take note of these remarks from Chris Caldwell regarding $2^{74207281} - 1$:

This prime was first detected by a machine on September 17, 2015, but was not notice[d] by a human until January 7th at 22:30 UTC--so this becomes the official discovery date.
The primality proof took 31 days of non-stop computing on a PC with an Intel I7-4790 CPU. To prove there were no errors in the prime discovery process, the new prime was independently verified using both different software and hardware. Andreas Hoglund and David Stanfill each verified the prime using the CUDALucas software running on NVidia Titan Black GPUs in 2.3 days. David Stanfill verified it using ClLucas on an AMD Fury X GPU in 3.5 days. Serge Batalov also verified it using Ernst Mayer's MLucas software on two Intel Xeon 18-core Amazon EC2 servers in 3.5 days.

The largest known non-Mersenne prime as of today is $10223 \times 2^{31172165} + 1$. This prime is special because it pertains to the problem of Sierpinski numbers, which I'm not going to go into detail here.
So what projects like GIMPS and Seventeen or Bust do is look for primes that can be expressed in a certain compact way. But they are limited in how far they can go. For example, is $2^{2^{127} - 1} - 1$ prime? Some say there aren't enough resources in the universe to answer that question.
There was a related question a few months ago, something like what is the largest prime number $p$ such that the value of $\pi(p)$ is known exactly? (e.g., $\pi(7) = 4$, $\pi(11) = 5$, etc.) Obviously $\pi(2^{74207281} - 1)$ can at present only be estimated.
But, if we define $\pi_M(n)$ to tell us how many Mersenne primes there are less than or equal to $n$, it turns out that $\pi_M(2^{74207281} - 1)$ is also unknown. It's believed to be 49, but could just as easily be 50 or 51 (I suppose it could also be 52 or higher, but I'd wager money against that).
I suppose I could talk about this for hours. Perhaps the most useful thing I could tell you to do is to play around with Wolfram Alpha. Type NextPrime[ then some "random" 20-digit number, ], press Enter. You might get a prime number that is too small for practical applications in cryptography, but is too large and unlikely to come up in casual everyday conversation.
Comment: http://mathworld.wolfram.com/FrivolousTheoremofArithmetic.html
Answer: One can generate prime numbers using Fermat's little theorem. This theorem states that if $p$ is prime and $a\neq 0 \bmod p$ then:
$$a^{p-1} = 1 \bmod p$$
Suppose then that for some number $n$ and some $a\neq 0 \bmod n$ the above equation would hold when taking $p$ equal to $n$. Then that doesn't prove that $n$ is prime. To get to a rigorous primality test, more tests need to be done, see. e.g. here. But the reverse of Fermat's little theorem is true if $n$ is of the form $h p + 1$ or $h p^2 + 1$ and $h < p$ for some known prime $p$. So, this then allows you to generate ever larger primes using just Fermat's little theorem as the primality test.
Here is a simple example using my HP calculator that allows integer computation with a maximum of 12 digits. I'm then restricted to finding primes smaller than $10^6$ due to having to repeatedly compute the square modulo $n$ to compute large powers. If I start with $p = 13$, then $n_1 = 10\times p + 1 = 131$ passes the Fermat test, therefore $n_1$ is prime. Then $n_2 = 50\times n_1 + 1 = 6551$ passes the test, therefore $n_2$ is prime. Then I find that $n_3 = 122\times n_2 + 1 = 799,223$ passes the test, so $n_3$ is prime. So, within minutes I could find this large prime using only my antique HP calculator.
Answer: By using the power of distributed computing to test potential prime numbers of specific forms.
The most famous is of course the search for Mersenne primes, which are of the form $2^p - 1$, where $p$ is also prime. That right there helps to narrow the search. For example, we immediately know that $2^{91} - 1$ is not prime, because it's divisible by $2^7 - 1$ and $2^{13} - 1$.
But not all primes give primes as Mersenne exponents. For example, $2^{23} - 1 = 47 \times 178481$. There are ways to detect a lot of primes like $23$, further narrowing down the search. According to the Great Internet Mersenne Prime Search (GIMPS), the slower computers in the network are assigned the task of ferreting out primes like $23$, so that the faster computers can concentrate on testing primes likelier to be Mersenne prime exponents.
Once in a while, however, large prime numbers are found almost by accident. For instance, if $a_0 = 20615674205555510$ and $a_1 = 3794765361567513$, the sequence defined by $a_n = a_{n - 2} + a_{n - 1}$ for $n > 1$ contains no primes. However, if you swap $a_0$ and $a_1$, then $a_{138} = 439351292910452432574786963588089477522344721$ is prime.
On November $9$, $2005$, Eric W. Weisstein announced that $a_{156075}$ is also prime. See Mathworld for more details. These are small numbers compared to the largest known Mersenne prime, and even smaller compared to prime numbers large beyond our comprehension.
Answer: Most recent record-breaking large primes have been Mersenne numbers, i.e. of the form $2^p-1$ (which can only be prime for prime $p$), because they have an especially easy test: https://en.wikipedia.org/wiki/Lucas-Lehmer_primality_test So we just keep trying successively larger $p$ in the tens of millions. Sometimes, this is used instead: https://en.wikipedia.org/wiki/Lucas-Lehmer-Riesel_test

How are large prime numbers found?


Hydrogen cloud at the universe's beginning?

Question: What prevented all of the hydrogen at the universe's start from coalescing into one gigantic star?
Comment: You may be interested to learn that the vast majority of the hydrogen in the universe *still* hasn't collapsed into stars. Just as steam cannot condense into water droplets above the boiling point, hot gas cannot clump into a star without cooling sufficiently.
Comment: The "bang" part of the big bang?
Comment: @AsphirDom: *It is not known. There are only theories stating that it was expanding (postulating expansion without knowing the force behind it).* Not true. No force is required in order to explain or maintain cosmological expansion. *According to current knowledge nothing can expand after it collapsed into black whole.* This is true in classical GR, but irrelevant, since we're not discussing black holes. See http://physics.stackexchange.com/questions/3294/big-bang-snuffed-by-a-black-hole
Comment: It is not known. There are only theories stating that it was expanding (postulating expansion without knowing the force behind it). If you will step by one million years later we might know the answer. According to current knowledge nothing can expand after it collapsed into black whole.
Answer: There are two reasons:
First, the expansion of space, which was rapid in the early universe, separated the initial density fluctuations into isolated potential wells. Dark matter and ordinary matter then accumulated into these local potential wells, which eventually become galaxy clusters.
Second, the temperature of the early universe was very high, so that hydrogen and helium atoms were ionized. These ionized atoms and free electrons interacted with photons; basically, the early universe was like a plasma. But these photons exerted a radiation pressure on the matter: as matter falls into the potential wells, it heats up, and the radiation prevents it from compressing further. In fact, the radiation reverses the motion, and the matter recoils.
As the universe expanded, the photons lost energy, and matter could fall back in, etc. This 'tug of war' between matter and radiation caused oscillations, and continued until the universe had cooled sufficiently for the ions and electrons to combine into neutral atoms. The photons then decoupled from the atoms, and we can still observe them today as the Cosmic Microwave Background. The oscillations are imprinted in this CMB as temperature fluctuations.
For a detailed overview of the processes in the early universe, see this source: http://background.uchicago.edu/~whu/intermediate/intermediate.html
Comment: @user12811: You have the entropy argument backwards. In a gravitating system, entropy is maximized by clumping of the matter degrees of freedom. It's essentially the opposite of an ideal gas. The early universe was in fact in a very low-entropy state, because the gravitational-wave degrees of freedom were not activated, and there is currently no explanation for this.
Comment: To the first, doesn't this assume that the matter was NOT evenly distributed to begin with? What explains this?
Comment: On large scales, matter was evenly distributed. But locally, there were very small perturbations in the density. The leading theory is that these perturbations were caused by quantum fluctuations at the end of the [inflationary era](http://en.wikipedia.org/wiki/Inflation_%28cosmology%29#Effects_of_asymmetries).
Comment: Yes. Would say it is an additional reason that indeed utter uniformity would be required to create such a single star. That is the least likely of all states given it requires perfect order to impose on a random background. Why would one expect such uniformity, that implies much lower entropy than any other prior state. THere is no reason for that.
Answer: Pulsar and Chris White have given nice explanations of why the dynamics of the early universe would not lead to the formation of one big starlike object. There is also another, much more generic argument against such a process, which boils down to the existence of cosmological horizons. At any given time in the evolution of the universe, there have been parts of the universe far enough apart that they could never have had any causal relationship -- no signal could have propagated between them, even at the speed of light, even if the signal was emitted immediately after the big bang. If matter in region A and matter in region B are separated in this way, then it's not possible for them to have collapsed into the same object, simply because relativity prevents the matter at A and B from even coming together that fast.


What does the term "second mortgage" mean? Can I easily get one?

Question: Are these loans easy to get if you have enough equity in your current home?  Is there any negative connotation associated with getting a second mortgage
Answer: Answering the first part, it is basically a home equity loan.  You are taking a loan out against available equity in your house.  It generally is at a higher interest rate than what you would get on your first mortgage.
Answer: I took a second mortgage when I moved house because I had a long-term fixed rate mortgage that would have incurred punitive fees if I had cancelled it. Rather than doing that I took a second mortgage over the same term for the difference. As my second mortgage was with the same lender, they still had "First Charge" on the property (This means that in the event of default they have first call on the property to recoup their losses), so the interest rate was not higher (actually it was slightly less than my first mortgage).
My case is not that usual, normally a 'second mortgage' is with a separate provider that takes a "Second Charge" on the property. The interest rates are normally higher as a result as there is more chance that the lender will not recoup their money in case of a default as the first charge has priority. The second mortgage may still be cheaper than an unsecured loan, as the second charge provides some collateral, this might make it attractive if a sudden expense needs to be covered.
Answer: A second mortgage is a loan taken out on your house while you still have another mortgage secured by your house. They are a secured loan as they use the borrower's home as security.
Some advantages of Second Mortgages:

They allow you to borrow a large amount as the loan is secured
against your home.
They have lower interest rates than other types of
debt.
Unlike unsecured personal loans like credit cards, second
mortgage interest rates are commonly in the single digits.

Some important points to consider when you take a second mortgage

If you stop making payments, your lender will be able to take your home through foreclosure, which can cause serious problems for you and your family.
Second mortgages can be expensive. You'll need to pay numerous costs for things like credit checks, appraisals, origination fees, and more.
The mortgage rates are typically lower than credit card interest rates, but they're often slightly higher than your first loan's rate.
Comment: Re: "They allow you to borrow a large amount" -- maybe. If your house is worth $200,000 and you owe $200,000 on an outstanding mortgage you won't be able to get a second mortgage. A second mortgage is secured by the **equity** in your house, that is, the difference between what it's worth and what you owe; that puts an effective upper limit on the amount you can borrow.
Comment: Welcome to Money.SE! Thanks for the good first answer.
Comment: @PeteBecker - the question does say "if you have enough equity in your current home."
Answer: Second mortgages were also a popular way for home buyers without a down payment to borrow 100% of the money, but avoid certain extra fees if they borrowed all the money from a single lender.
For example, to borrow $100,000 on a house would incur something called PMI (private mortgage insurance).  So to borrow $100,000 to buy my house, my payment might be $800/month, but I would have an additional $100/month of PMI to pay.  (These numbers are totally made up and not based in math in any way)
So instead of that, borrows might get a first mortgage for $80,000 so they don't have to pay the PMI and get a second mortgage for the difference.  This can be beneficial if the second mortgage payment is less than the PMI for borrowing 100%.
As far as I know they aren't as easy to get these days, like any loan you need to be qualified and I think 100% financing is probably harder to come by.  The negative connotation is no worse than any other loan.  I am personally against borrowing money, but if you had big medical expenses, major home repairs or some other emergency I could see it justified.  Probably not for a big vacation or for new car though.
Comment: A key reason they are harder to get is that a major factor in the qualification is how much equity you have in the house (what its worth versus what you owe). With plummeting house prices, a lot of people are finding their equity has vanished.


What is SDS PAGE gel polymerization time?

Question: I am working on 20% SDS PAGE. I want to know optimum polymerization time for 20% resolving gel and 6% stacking gel. If I increase the time then would it affect the band pattern?
Comment: it depends on many factors such as APS concentration, TEMED concentration and ambient temperature
Answer: There is nothing like a general polymerization time, as this is a chemical reaction which depends on many factors. The most important are:
APS: Concentration and and the age of the chemical are important. APS decomposes over time when it is not stored completely dry (which it is not on most benches) and also with freezing thawing cycles in storage. APS provides the free radicals necessary for the reaction; without it no polymerization will happen. In my experience APS is the most critical part of the reaction, with old solutions making the polymerization really slow. I would make a stock solution, freeze it in aliquots. For making gels I thaw on aliquot and keep it in the fridge afterwards for a week and then discard it.
TEMED: Is the catalyst for the reaction, too much of it will start the reaction very fast.
Temperature: The warmer it is, the faster the polymerization will be. In the cold room you will not get complete reaction, if any.
What you can do is to store the remaining acrylamide in the beaker and wait until it is polymerized. Then your gel should also be ok to use. A longer polymerization time (assuming that your gel was completely polymerized before) will not change the resolving capacity of your gel.
Comment: "*with old solutions making the polymerization really fast*"... I guess you meant fresh solutions. Old solutions are bad.
Comment: -1 For having to scrape acrylamide out of the beaker! (I didn't actually down vote)
Comment: @canadianer You can do the mixing in a plastic tube if you want and discard it when the polymerization is finished. Makes more trash though.
Answer: Others have already explained the effect of different factors on polymerization time. This answer is mostly about:

If I increase the time then would it affect the band pattern?

It may.
Some tips:

Make a little extra mix so that you can leave some in the beaker to know if polymerization has happened.
Always layer the poured resolving gel with water so that the gel doesn't get dried up.
Don't leave the gel for long time after polymerization. Not only it wastes time, it also may cause the gel to dry up and SDS/Urea to precipitate/crystallize.
Wash the gels with the running buffer after removing the comb/before loading the sample. You can use a fine needled (high gauge) to do that.
Pre-run the gel to equilibriate it; this not generally necessary and as Nick Sandor said, would destroy stacking gel. However it is important for big urea gels and somewhat important for continuous SDS-gels if you have left it for a quite some time post polymerization. So it is better to not leave the gel for a long time
Comment: In theory, pre-running SDS-PAGE discontinuous gels will destroy the stacking gel, because glycine, which doesn't belong there, will go in. In practice, I see a lot of people recommending it, regardless of theory, and in the absence of any empirical evidence. "To remove unpolymerized acrylamide", some say, to which I reply that it will take just as much as passing bromophenol blue and glycine through the gel.
Comment: @NickSandor For usual SDS-PAGE it is not necessary- I agree and thanks for the point; it would change the pH and composition of stacking gel. I edited the answer. But for urea gels (continuous) it is always recommended.
Answer: The polymerization time is strongly dependent on APS and TEMED concentrations. I do not think that the increased time for polymerization would somehow influence the division of the proteins in negative way. Actually the time varies from 20 min to 1 h, but I personally leave the gel to polymerize longer. Unpolymerized Acrylamide could build adducts with some proteins which could result in multiple bands. In addition acrymamide itself is toxic, so I always give it additional time to polymerize. Good luck!
Answer: APS and TEMED concentrations matter a lot. Even with that standardized, your polyacrylamide on the shelf is losing reactive groups as we speak. Who know how long it sat in the warehouse? It all adds up to the fact that the minimum required time is practically impossible to predict.
On the other hand, once polymerized, a gel is stable for days without apparent loss of quality. Overnight polymerization will be "optimal" in the sense that the gel won't get any better with longer or shorter polymerization. But so will be a two-days old gel. People used to cast gels every Friday, and leave them in wet paper towels in the cold room for the next week.


How to fix dark themes on Kali Linux running XFCE desktop environment?

Question: I am still new in running desktop environments on xRDP. When I first installed XFCE and applied arc-dark theme, it worked fine and similar to the screenshot shown here.
Then I decided to change to KDE Plasma. So, I purged kali-desktop-xfce by using
<code>    apt purge kali-desktop-xfce
    apt install kde-plasma-desktop
    echo "startkde" > ~/.xsession
</code>
But, KDE Plasma was lagging. So, I decided to purge KDE Plasma and switch back to XFCE.
<code>    apt purge kde-plasma-desktop
    apt install kali-desktop-xfce
    echo "xfce4-session" > ~/.xsession
</code>
To my surprise, the configuration that I did was still there when I ran XFCE again, and that includes the arc-dark theme being applied. But, I faced a new problem that I never faced previously. The theme is broken, and I've spent hours searching for solutions, but found none that had something to do with what I am facing in the screenshot.

I tried changing to other dark themes, but the white parts wouldn't change according to the themes. The top panel is also broken as in the font is dark color instead of white (or any other light colors). I suspected that this is happening because of GTK, but still couldn't figure out the real issue.
Please help!
Answer: I see that this question is old but still I faced the same problem and the issue was in overriden <code>~/.gtkrc-2.0</code> that was created by kde installation somehow. So this issue is fixed by removing this file.


How to run script on interface state change in Windows?

Question: I basically want to shutdown/start some services based on Network name and type I connect, so even better to run script when the network is automatically detected is it possible? Thanks.
Answer: You can also use the Windows Task Scheduler for listening on the WMI event.
Comment: You are the best, don't know to which answer to put now the green check :x
Comment: +1 - Didn't know that trick.  Looks a little tricky to configure but with enough playing looks like it would be pretty cool.
Answer: There may be some tool out there, but you can roll your own with some work.
See this link about working with WMI events: http://trevorsullivan.net/2009/11/16/powershell-getting-started-with-wmi-events/
Basically you'd be writing a powershell script or c# program to listen for WMI events, which can be something like a dhcp lease being renewed or the connection coming online.  But you'd have to do some more digging for the specific event you want if it's not a the dhcp lease event (which it sounds like it's not.)  Then your script can do whatever you want when that event comes up - like starting services etc.
The link should provide you with some direction to keep looking in, or punt because it's kind of a pain.
You'd want to use some kinda of query like this in wbemtest to drill down and see which event you are interested in (like the article spells out).  Then you'd do the necessary register-wmi event stuff in powershell once you're happy with your query.
<code>SELECT * FROM __InstanceModificationEvent WITHIN 3 WHERE TargetInstance ISA 'Win32_NetworkAdapterConfiguration'
</code>
Comment: Thank you very much for such an brief answer, down there is also additional answer how to make it even simpler with Windows Task Scheduler which I was looking for.
Answer: That sounds like the problem that the Network Location Awareness service tries to solve.  I bet PowerShell could be employed to use whatever .NET plumbing exists to listen for NLA service events.
Answer: You could set up a permanent WMI event consumer, using either the CommandLineEventConsumer or ActiveScriptEventConsumer.
http://msdn.microsoft.com/en-us/library/aa384749(v=VS.85).aspx - Active Script Event Consumer
http://msdn.microsoft.com/en-us/library/aa393249(v=VS.85).aspx - Command Line Event Consumer
Cheers


Who was Richard Thompson?

Question: There is family of famous groups with unusual group-theoretic properties due to a mathematician called Richard Thompson that are widely studied in group theory. The papers on these groups and the Wikipedia entry simply say that these were written down in some unpublished hand-written notes of Thompson in the 1960's. A search on Google / Wikipedia / MathSciNet has not revealed anything about who Richard Thompson was, except a possible implication that Thompson was motivated by questions coming from logic. Does anyone have any information?
Comment: Not the same as J.G.Thompson, of the Feit-Thompson theorem.
Comment: R. Thompson is a former graduate student of Ralph McKenzie in UC Berkeley
Comment: Seeing that there are still actively working mathematicians that have collaborated with him, cross posting on mathoverflow might be worthwhile, hoping for the non trivial chance of an answer from firsthand experience.
Comment: When I was a graduate student at Berkeley 2010-2016, Richard Thompson was a regular attendee of the Berkeley Logic Colloquium. I assume he still attends (when the pandemic situation allows).
Comment: @njuffa :  thanks for all the info. This is very interesting. I really appreciate the effort.
Answer: I was only able to find fragmentary information on Thompson. A good starting point is his PhD thesis, which gives us his full name:

Richard Joseph Thompson, Transformational Structure of Algebraic Logics. PhD thesis, University of California, Berkeley, 1979

A partial scan of the thesis is publicly available free of cost. From this we learn that Thompson received an A.B. degree from San Jose State in 1965, that he was accepted into the PhD program at Berkeley in 1973, and that his degree was conferred on June 16, 1979. His thesis advisor was Ralph McKenzie. This agrees with the entry for McKenzie at the Mathematics Genealogy Project. Curiously, there is no mention of R. J. Thompson in the La Torre college yearbooks of San Jose State from the years 1964 and 1965.
Thompson's handwritten notes are inconsistently referenced in the literature, with some dating them to 1965 (e.g. David Matthew Robertson, Conjugacy and centralisers
in Thompson's group $T$, PhD thesis, Newcastle University, 2018), while others date them to 1973 (e.g. John Donnelly, "Ruinous subsets of Richard Thompson's group $F$," Journal of Pure and Applied Algebra 208 (2007) 733–737). In many instances the notes are referred to as "widely circulated". What are claimed to be scans of Thompson's original hand-written notes can be found here: part 1, part 2.
The first proper publication of the material appears to be in R. McKenzie and R. J. Thompson, "An elementary construction of unsolvable word problems in group theory", in Word Problems, Proc. Conf. Irvine 1969 (edited by W. W. Boone, F. B. Cannonito, and R. C. Lyndon), Studies in Logic and the Foundations of Mathematics, vol. 71, North-Holland, Amsterdam, 1973, pp. 457–478.
There are only a few other papers by R. J. Thompson, some of which appeared in somewhat obscure Eastern European publications. Thompson did a brief stint  at the Institute for Advanced Studies in Princeton in 1974-1975. Membership lists of the Association for Symbolic Logic published in The Journal of Symbolic Logic, Vol. 45, No. 4, Dec. 1980 and The Journal of Symbolic Logic, Vol. 47, No. 4, Dec. 1982 show him as a member of that organization. Publications in 1988 and 1993 indicate that Thompson was affiliated with the Mathematical Institute of the Hungarian Academy of Sciences, Budapest:

Richard J. Thompson, "Noncommutative cylindric algebras and relativizations of cylindrical algebras", Bulletin of the Section of Logic 17 (2):75-81 (1988) (scan online)

H. Andréka and R. J. Thompson, "A Stone type representation theorem for algebras of relations of higher rank", Transactions of the American Mathematical Society, Vol. 309, No. 2, October 1988, pp. 671-682 (scan online)

Richard J. Thompson, "Complete description of substitutions in cylindric algebras and other algebraic methods." Algebraic Methods in Logic and in Computer Science, Banach Center Publications, Institute of Mathematics, Polish Academy of Sciences, Vol. 28, 1993, pp. 327-342. (scan online)

The last professional trace of R. J. Thompson coincides with the last known year of publication, when he was listed as a participant, but not presenter, at a workshop/conference: Universal Algebra and Category Theory Conference, Berkeley, July 12-23, 1993.
Comment: @RBarryYoung: Most likely, McKenzie was spending a sabbatical year at IAS and took his PhD student (Thompson) with him to Princeton, to continue advising. This is completely normal.
Comment: Wait, he was admitted to the Berkley PhD program in 1973, *then* did a stint at the IAS in Princeton in 1974-1975, and then *went back* to Berkley to finish his PhD in 1979?  Doesn't this all seem a bit odd and out of order?
Answer: To add to njuffa's answer.
Thompson contributed to group theory, and algebraic logic.  The original motivation for his calculations/constructs was algebraic logic.  His thesis and all but two of his papers were on sets of laws that characterized certain types of algebraic logics with an eye to finding such sets that are finite.
The first setting was a system of expression manipulations (duplication or elimination of a symbol, shifting parentheses, permuting symbols) which gave a monoid whose group of units was the group now known as V.  He proved the group infinite and finitely presented and when advised to find normal subgroups was able to show there are none.  This is the subject of his handwritten notes and is his most well known result in group theory.  In those notes Thompson establishes the basics of the three groups now known as F, T, and V.  The first part of the expository paper of Cannon, Floyd and Parry on the Thompson groups is a detailed expansion of those notes.
His two papers not in algebraic logic are the one mentioned by njuffa and one paper by himself extending an embedding theorem of Boone and Higman.
Embeddings into finitely generated simple groups which preserve the word problem, in Word Problems, II, (S. I. Adian, W. W. Boone, G. Higman, eds.), North-Holland (1980) 401-441.
That last paper is also quite well known.  Both papers in group theory contain pieces of the basic information about the groups F and V.
His work in algebraic logic is highly regarded by the algebraic logic community.  For most of his life Thompson worked through an agency for K-12 students with reading and math difficulties in the bay area around San Jose, CA.
By the way, the scanned notes in njuffa's response contains a common, often propogated error.  The third page of Part 1 (it starts with $C_n^m$) should actually be the fifth page.  No other rearrangement is necessary.
Richard Thompson is alive and retired in California.
Comment: Has anyone made a LaTeX version of the handwritten notes? Seems quite an easy thing to do...
Comment: @Carl-FredrikNybergBrodda: The Thompson notes are complete in parts and are very sketchy in others.  The (1996) Cannon-Floyd-Parry article in Enseignement fills in all the gaps, gives a good history in the first couple of pages, and adds material, with attributions where needed.  Of course if it is deemed of historical interest ...
Comment: Thanks @MattBrin for this info. I appreciate the texture that all of this provides. Maybe I should have added that my initial reason for being interested in Richard Thompson is that I was watching a 2018 ICM lecture of Andres Navas, who referred to the groups of Richard Thompson. I was already aware of the group theorist John Thompson, and was interested in trying to understand if this could have been the same person. When I tried to use basic search methods to find out about R. Thompson, I didn't come up with much at all.
Answer: Richard is a distant cousin of mine.
He was living in Sunnyvale, CA when I met him about 15 years ago.
He owns a house there, but he's pretty elderly and doesn't keep it up much.
He's a bit eccentric.

Who was Richard Thompson?


Theodor name for a baby

Question: We are expecting to have our first baby and my husband really likes the name Theodor (after Theodor Herzl) but I read it is not a Jewish name (it is Greek). Is it appropriate to name a child after a Jew when the name originates from another culture?
Comment: Welcome to MY! As it stands, your question seems a bit personal. Perhaps you could edit your question to address this? (Perhaps "is it appropriate to name a child after a Jew when the name originates from another culture?") Hope you enjoy your stay!
Comment: Do note that Alexander is a popular Jewish name that dates back to the times of the second Temple, originally after Alexander the Great.
Comment: Possible dupe: https://judaism.stackexchange.com/q/78/8775, https://judaism.stackexchange.com/q/45248/8775. Also arguably related: https://judaism.stackexchange.com/q/73/8775.
Comment: Ivanka trumps son is named theodore so i guess then its a Jewish name
Comment: Why not let him be Theodore in English, but Benyamin Ze'ev in Hebrew? https://en.wikipedia.org/wiki/Theodor_Herzl
Comment: I have two good friends, who are fromm, named Theodore. Although neither has Theodore as a Jewish name, rather as secular names.
Answer: Many great Jewish names have non-Jewish roots.

Moshe was given a non-Jewish name by his adopted Egyptian parents. (I know plenty of people will get upset at me for making a claim based on scientific evidence and not halachic evidence, but Moshe is actually a common ancient Egyptian name - we have archaeological evidence of many people with that name).
Avraham was named by his non-Jewish parents, and since there were no Jews around at the time, it seems impossible for this to have been a Jewish name.
Shifra was trusted by Pharaoh because she has an Egyptian name.
Tzipora (Moshe's wife) was Midianite.
Hadassah tried to hide her Jewish identity by taking on the more locally acceptable name of Esther.
Yael - Technically there's a Machloket on whether or not she was Jewish, and the possibility that the name's origins are non-Jewish and that doesn't seem to bother anyone. (Seventh most popular Jewish girl's name in Israel according to JPost)
Naamah was a descendant of Cain

Many last names that we think of as stereotypically Jewish are actually just common surnames. See this article for a good rundown of where many common Jewish surnames come from. Many of them have secular origins derived from the surrounding culture.
We sometimes adopt names from local culture and if we use it long enough, it becomes Jewish in people's minds. What counts as  "Jewish" name comes and goes based on the environment, language, and culture. Adolf was once a Jewish name. So was Ishmael.
In summary, name your kid whatever you want and don't worry about what other people think. B'sha'a tova.
Comment: Shouldn't your summary be: "don't worry if a Jewish name appears to have non-Jewish roots"? Because that's what you seem to show here. Not "name your kid whatever you want and don't worry about what other people think"
Comment: Avraham was named "Avram" by his parents
Comment: All but the last three were from before the giving of the Torah, when *everyone* was a non-Jew (at least according to some).
Comment: @ShmuelBrin Even if there as no Torah, it seems obvious from both Pshat and various commentaries and midrashim that there was a unique culture. That's why for example I didn't include Miriam and Aharon in the list. Names are a product of culture. (And in the case of the Jews in Egypt, one that is specifically called out as a piece of their culture they kept).
Answer: It seems to me that the medrashim praising the Jews for their use of Jewish names should make one wonder what constitutes a Jewish name and why the use of Jewish names is praiseworthy; among the Biblical generations the concept seems less obvious than it is for us.
Perhaps a name is Jewish because it makes it's bearer recognizable as a Jew, or because it expresses a Jewish worldview (such as by praising G-d). Perhaps this is praiseworthy because of some practical consequence of these qualities: discouraging assimilation, making Jews feel the weight of our other praiseworthy (or disgraceful) behavior, or simply helping Jews find one another.
It seems to me that the name Theodor might "read" as Jewish because of Hertzl, and that a somewhat corresponding Hebrew name like Nassaniel/Nathaniel (which, like Theodor, means "G-d has given") would do so even more strongly. (Other possible references to Hertzl would include Binyomin Ze'ev, Hertzl's Hebrew name, which rosends suggested; and Hershel or Hirsh, perhaps related to Hertzl in etymology.)
Comment: Hertzl is dim. of G. Hertz, heart.  Hershel is dim of G. Hirsch, deer
Comment: @Nissim Nanach I think that Hertz is not heart, the internal organ, but hart, the male deer.  This is a cognate of the names Hershel or Hirsch.
Comment: Then what's heart in Yiddish? Isn't it harts, with dim. hertzl? https://www.cs.uky.edu/~raphael/yiddish/dictionary.cgi has hertsl as dim. of root herts, heart
Comment: @Nissim Nanach My point was that if OP wanted to give her (now 4-year-old) child a Jewish name that recalls Theodor Hertzl, she could choose a Yiddish name close to Hertzl in sound and meaning. So I'm afraid I don't see what the Yiddish word for the bodily organ has to do with it. To confirm the meanings of the words or names I suggested, you could could try a translation site or dictionary.

Theodor name for a baby


Changing the spelling of "G-d" and Halachic erasure

Question: Is there a problem of "erasing the name of HaShem" if you erase the English word spelled G-o-d, and if so, is there then a problem of erasing it in order to spell it in a more acceptable way (such as G-d), and if so, is there a problem of simply changing the spelling by erasing the 'o' and replacing it with a '-'?
Comment: If erasing the whole word "God" to change it is forbidden, then erasing any letter of it is forbidden.
Answer: No. There isn't really an issue in writing or erasing 'God'
See: http://doseofhalacha.blogspot.co.uk/2014/07/god-or-g-d.html

There is no issue in writing or printing Hashem's name properly, providing one knows that it won't be destroyed.
Rambam (Yesodei Hatorah 6:1) writes that there are 7 sheimos (names of Hashem) that mustn't be erased. There is no issur in erasing a kinui (moniker) such as chanun or rachum, etc. R' Akiva Eiger (YD 276:9 quoting the Tashbetz) writes that as translations of sheimos have the status of kinuim, there is no issur in erasing them either.
The Shach (YD 179:11) writes that Hashem's name in a foreign language is not considered sheimos and thus may be erased. Likewise, the Mishna Berura (85:10) writes that the issur only applies to erasing sheimos in Hebrew (See Minchas Chinuch 437:5).
Nonetheless, the Aruch Hashulchan (CM 27:3) urges people to be extra particular when writing letters with sheimos even in a foreign language.
Thus, while it is not strictly forbidden to write or erase the word 'God', it is good practice to write 'G-d' and such writings must still be treated with respect. Thus, rather than thrown in the bin, a paper containing the word 'God' should be recycled with other documents, or wrapped before disposal (See Igros Moshe OC 4:39).


Using links from link lists in content editor webpart

Question: Is there any way to use link item from link list in CEWP.
I have some link which appear on different web part pages in CEWP.
URL will change some times in the future.
I would like to have it as link in links-list and change URL just once in this item instead of changing manualy on every page.
Answer: I'm not sure what your CEWP is doing but a content editor is typically just a blob of HTML and won't be globally updated.  If you items are in a list, you can drop the list on other pages and when you update your core list, the results will distribute down to the list view web parts on the pages.
Or if you want to manipulate the way your links appear, you can use the new Content Search Web Part, which is similar to a CQWP from 2010 but better!  :)
Comment: Yes, I have plain html in CEWP, linking to some graphics and pages in same sharepoint site.

I was hoping I can use something like:

/sites/some_site/Lists/Links/AllItems.aspx?ID=1&colum=URL

to get a value of LinkItem URL column.
Comment: I'm confused to what your end goal is. Are you saying you just want to extract a single link from your link's list and reference it in plain HTML?


How do you stop an update on an Xbox One Game?

Question: I have recently bought an xbox one. I also bought the game Doom for my xbox one.
After it has installed itself, it wanted to install 58 gigabytes of updates over my network.
How can I stop it updating, and just play the game, how it was on the disk?
Comment: If all else fails you could pull out the ethernet cord (or cut power to your wifi router) and thus disrupt the internet connection and stop the download.  Then, you can take your time going through the XBox settings to disable internet connectivity entirely, and away you go.
Comment: I thought there was an option to not update the game when it prompts you for the update.  What happens if you try that?
Comment: Somebody else accidentally clicked it, and I can't stop the update
Answer: To stop an update:

Go to your My games and Apps section on your Xbox
Navigate to the Queue section on the left and find the game being updated on the right (Doom in this case).
Press the Menu button on your controller and select Cancel.  This will stop the update process.

Source: Xbox Support Page, as well as experience.
Note that I am unsure if you will be able to play the game offline.  I'm not sure how physical disc copies of games work, but I believe that in order to play any digitally owned game, they must be kept up to date (I could be wrong).
Answer: Don't try to cancel an update. If you cancel an update that has started, it will delete the whole game and its data. Found out the hard way today.
Answer: You can't stop a game update for any title, you can pause an update and that's about it. I found it to be a pain myself, I started the update not knowing what size it was and thinking maybe a couple of gigs at most and then seen it was 58gig when my monthly allowance is 50gig lol. I paused it and had to take it to my sisters as she lives in the city and has unlimited allowance and update it there. So all you can do is pause it really but you wont be able to play the game until you do the update. Also I have found the loading times to be much longer since the update to the point were i'am not even arsed playing the game anymore. If I had the option to go back I would just uninstall the game instead of updating tbh. Nice work Bethesda!
Answer: For doing exactly what you want, install the game from disc, but try installing it after you have toggled the option "Go offline" in Network.
Comment: As the OP clearly states, however, he already installed the game, but just wants to stop the updating.


What do you call when people are crushing each other

Question: When human stampedes occur a person can trip and fall and then another person falls on him and then another person blah bla, or in football when everyone jumps onto each other on the ground to get the ball away from the one on the bottom
How would you call that? Human clump
Answer: OK, so there are many, many ways to describe human "stampedes", one can say that the players fall down in a heap.
In rugby, this is called a pile. But in regular football (soccer), this doesn't exist. Two or three players may bump into each other but there is no real pile-up. In American football, it's called a pile-up or pile and occurs when players fall over each other in a heap over the player with the ball.
They are squashing each other when on the ground. The rules are different in rugby and American football, but I think pile and pile-up answers your question.
bottom of the pile
Answer: By "football" I assume you mean "American football" since what we Americans call "soccer" doesn't usually involve a lot of clumping (at least, when played by adults)
In addition to the suggestions in Lambie's answer, there are a number of other terms that depend on the context.  With football, we call this situation a dogpile, which can be used as a verb to dogpile.

The defense dogpiled the running back to keep him from moving across the goal line.

On a more somber note, when too people people are trying to move in a particular direction, often in a panic, this is called a crush, a human stampede, or a crowd collapse.  Unfortunate people can be crushed or trampled by the crowd.

Dr Fruin explained that virtually all crowd deaths are the result of compressive asphyxia and not the "trampling" that is often reported in the media.


Accidentally deleted steam download files

Question: I am currently downloading a game on Steam. I accidentally deleted some files in the downloading folder under steamapps but the download ran normally. Would the missing downloading folder files have any effect on the outcome of the game once it has finished downloading? If so, what could happen?
Comment: How did you even delete this accidentally lol. Anyways, steam should normally check the game before launching it so it would download the missing files.
Answer: It depends on the game, but essentially anything can happen - the game might run normally, the game might not launch at all, or the game might crash unexpectedly. It's not really worth finding out, so your best bet is to have Steam verify that all the game's files are present and accounted for.
What you should do is right-click on the game in your Steam library, then go Properties -> Local Files -> Verify Integrity of Game Cache.
This will make Steam double check that all of the files it expects to be present are there, and it'll download stuff if anything is missing. Once it's done, the game is definitely ok to play.


Is it OK to list a previous subordinate\employee as a reference?

Question: When filling out my reference list on a job application, would it be acceptable to list a previous subordinate as a professional reference (when applying to another company)?  I managed this person for 5 years, they have since left (in good standing) to another department and have moved to a higher position (same title as mine).  We still maintain a good professional relationship and they've been in their new department for 1 year.
Comment: What is the type of role you are applying for ? If it is a managerial role, your ex subordinate can vouch for your management skills but if it is technical or something which they have not seen about you, then they will not be a good reference
Comment: Anecdotal: I hopped on a call with the hiring head of a company as a reference for my former manager last month. Similarly to yourself, we maintain a good professional relationship, and it's been about 18 months since he left our company. Was I the only reference? Probably not.
Comment: It is a higher managerial role in the same field
Answer:
Is it OK to list a previous subordinate\employee as a reference?

Certainly.
It's fine to have a group of references with different relationships to you - some bosses, some peers, some subordinates.
But in general, folks doing reference checks would prefer to check with your former bosses. They are the ones who could answer the typical "How was OP as a worker?" and "Would you hire OP again?" questions.
If you include previous subordinates/employees as references, make sure there are enough bosses as well.
Answer: This is acceptable, but it may not be sufficient.
When potential employers are talking to references, they are looking for a few simple things:

Can they verify you worked at Company A?
Can they verify you worked in the role you put on your resume?
Can they verify the dates you were in that role?

Other than these points, and a couple of fairly vague questions about you, the employer shouldn't be asking much more - and your reference should be saying less (unless they can giving a glowing reference).
The verification part ends up putting the employer into a Catch-22 - they also have to verify that the referee is qualified to answer the questions. The easiest thing is to talk to the HR at Company A, or someone else that is easy to confirm is at Company A by calling the company's main number and asking for that person.
Of course, it is great to have a referee that is going to help sell you to a potential employer so, by all means, include this person as a reference - but you should have already sold yourself in the interview, and remember the new company is seeking confirmation of details you've provided, which means you need to have a verifiable contact at your old company, too.

disclaimer: it isn't always possible, especially if your previous company was toxic and you know you can't rely on using them as a reference.
Comment: Is a reference supposed to directly verify your work history? I was under the impression that they're there purely to provide information on your work performance and character traits.
Comment: @dukeling that kind of thing is tricky - a referee is either going to "stick to the facts", or exaggerate... Really, you should get an idea on character from the interview(s)
Comment: @Dukeling If it's a background check, yes. But I agree, I've never had an actual reference need to verify history beyond that I worked there and was good to work with, have mad skills, etc. Interestingly, for my last BGC (at a Fortune 10 company), *anyone* who could verify that I worked there was sufficient. Oddly, they couldn't verify themselves that I had worked at that company 8 years prior, I had to have a former coworker do it. I even have the same user id, but they still couldn't tell I'd ever worked there.


How magento 1.7 creates new shipment from admin area?

Question: I have the following problem with magento 188.8.131.52 - shipment and invoice emails are not sent to the customer who placed the order. However, these emails are sent to the email addresses that are set in magento area in Send Invoice Email Copy To and Send Shipment Email Copy To. I've managed to track the process of sending these emails in magento core files but I cannot find where and how magento admin area calls a function to create a new shipment when the button submit shipment is clicked. If you have any suggestions please help.
Answer: The shipment is saved in Mage_Adminhtml_Sales_Order_ShipmentController::saveAction().
The e-mail is sent from Mage_Sales_Model_Order_Shipment::sendEmail().
If you don't have any extensions or custom code that changes the behavior of sending e-mails, the e-mail should be sent without any issues. If the e-mail arrives to one of the store e-mail addresses then it might be an issue with the customer's e-mail address (maybe it ends up in spam).
Comment: Thank you for your quick response.I had a look at sendEmail and it has 2 parameters.If $notifyCustomer = true(the default value)then the shipment email is sent both to the customer and the store emails,if not the shipment email is sent only to the store emails set in the Send Shipment Email Copy To field.That is why I would like to see the instance of the function when it is called and its 1st parameter.I suppose that when this sendEmail function is called its first parameter $notifyCustomer is set to false and hence the result is-sending the sipment email only to store emails,not to customer.
Comment: However, if you add manually the customer email in the Send Shipment Email Copy To field, then the shipment email is sent correctly, which means that it's not an issue with the customer's e-mail address.