What does it mean to have 'half' spin? I have looked on Wikipedia and a few youtube videos on spin but they don't explain what it means to have $1/2$ spin. I am 18 and only starting to learning about quantum mechanics not so long ago, so please keep the vocabulary to a minimal.
I often hear about subatomic particles having a property called "spin" but also that it doesn't actually relate to spinning about an axis like you would think. Which particles have spin? What does spin mean if not an actual spinning motion?
We have this large database (>1TB) that we intend to "shrink".  The database revolves around one main entity, let's call it "Visit".  For discussion, let's say it is a database for a medical practice.  There are a total of 30 visit "types", such as procedure, annual, follow-up, immunisation etc, each of which is a subsidary table to "Visit", e.g. "visit_immuno".  The database has accummulated some 12 years of data since 2000.  Someone has proposed that we keep about 3 years of data in the "live" version and have the rest live in an "old_data" database.  The date is ONLY stored in the "Visit" table since it is normalised.  The Visit table also contains a ROWVERSION column and a BIGINT pseudo-identity (clustered) column.  For all intents and purposes, let's say the clustering key is populated by a SEQUENCE (SQL Server 2012 Enterprise) - we shall name it cid.  The visit.date is not always in the same order as the clustering key, for example when a doctor goes on extended visitations and returns with his "briefcase" of data, it gets merged into the main table.  There are also some updates to the "visit" table that will cause the ROWVERSION column to be out of sync with both the cid and date columns - to put it simply, neither ROWVERSION nor cid would make suitable partition keys for this reason.  The business rule for removing data from the "live" is that the visit.date must be greater than 36 months and a child visit_payment record must exist.  Also, the "old_data" database does not contain any of the base tables except visit%.  So we end up with:  Live DB (daily use) - All tables Old-Data DB - older data for the visit% tables  The proposal calls for a Combined DB that is a shell containing Synonyms to ALL the base tables in the Live DB (except visit%) plus Views that UNION ALL across the visit% tables in the two databases.  Assuming the same indexes are created in the Old-Data DB, will the queries perform well on the UNION-ALL Views?  What type of query patterns might trip up the execution plan for the UNION-ALL Views? How to iterate over arguments in a Bash script Stack Overflow reputation in CV Should I mention my Stack Overflow (and other Stack Exchange sites) reputation in my CV while applying for a post-graduate position? What resolution should a large format artwork for print be? For wall-sized graphics and large banners (e.g. 3m × 5m), what is an acceptable PPI for print? As I understand it 300 ppi is the typical for 'small' artworks (esp. for clean text resolution). However, for small artworks, the audience usually engages at a much closer distance. Therefore, in the interests of keeping a bitmap file down to a reasonable size, can you get away with a much-reduced PPI for a large format/banner print? Is doing two PhDs a good path? I am studying a combined bachelor of engineering (electrical) and bachelor of mathematics; I just started this year and will graduate in 2018. The reason why I am doing double degrees and not a single degree is because I love both electrical engineering and mathematics and I could not ignore any of them. So with this in mind, I am thinking of doing two PhDs when I graduate (one in electrical engineering and one in mathematics). Is this a good path or I should concentrate on only one of them? The trigonometric ratios of an angle greater than $90^\circ$ are equal to the supplementary angle's ratios.  I'm just clarifying this, but the ratios don't actually exist for angles greater than $90^\circ$ right? (since by definition these ratios are of a right angle triangle). Is it just mathematical custom to assume the ratios of an angle greater than $90^\circ$ to be equivalent to its supplementary angle's ratios? For convenience? Is it a wise-decision to buy full-frame lenses for use on an APS-C body? I have a Canon 550D which I've been using for around a year now. I really love it and have learned a great deal with this and the 18 - 135mm kit lens. But now with experience I feel the need to get some better glass. I won't be buying a new body any time soon because I figure investing in some good glass is more important.   As I have looked around, I see quite a few good used L lenses I can get in ebay for good bargain prices. But I know that the EF lenses don't have the same focal length in the cropped sensors. Is it a wise decision to buy these EF lenses or buy the cropped sensor alternatives?  I have the following lenses in mind that I am looking to buy down the line from the canon range over the next several months.  16-35mm f/2.8L, 24-70mm f/2.8L, 70-200 f/4L.  Are these apt choices for cropped sensors? I know most pros with FFs use these but I am a bit skeptic that they will serve the same purpose for me. If so what are the alternatives for this that have almost as good image quality? What is the difference between const_iterator and non-const iterator in the C++ STL? What is the difference between a const_iterator and an iterator and where would you use one over the other? Hard disk file system is shown as Raw file system; how can I access it? biblatex: separator for citing multiple sources, some of them with page, some not I'm using biblatex for my references.  Normally, if I use \cite{source1, source2, source3}, I get a citation like  [3, 45, 98]   If I now want to give a page number for one of them, it looks confusing imho, as I should get (did not try it out up to now, honestly)   [3, 45, 78, p. 23f, 98]   So imho it would make sense to change one of the separator from a comma to e. g. a semicolon like:  [3; 45; 78, p. 23f; 98]   Question 1: Does that make sense, or are there other conventions for citing sources with and without page numbers together?  (Up to now I collected the citations without page number in one cite command and added singular \cite[][p. xy]{} commands for those with page numbers., so I'd get:   [3, 45, 98][78, p. 23f]   )  the \cites[]{}[]{}[]{} could also do that, but it also uses the same separators for entries and postnotes.  Question 2: How could I change the separator globally for those number-citations from comma to semicolon in biblatex? I have a datetime column in MySQL.   How can I convert it to the display as mm/dd/yy H:M (AM/PM) using PHP? I don't know if it's the right place to ask but can somebody advise me for buying a ram memory for my computer.  I have a Dell Vostro 200 with 1GB of RAM and 667MHz. (2 x 512MB)  I want to buy raise the amount of RAM but I'm confused whether to buy 1 x 2GB or 2 x 1GB  I know it's the same for the available amount of memory but is ther a difference maybe in the clock speed so that 2 x 667MHz will be better than 1 x 667MHz. or maybe accessing one single memory slot will be faster and better than accessing two slots.  Please anyone helps. What is the name of the package for R? I tried aptitude search r, but (unsurprisingly), there are waaaay too many results to sift through. Separate labels in cases As much as I have tried, it doesn't seem possible to use separate labels when using a casesconstruction (from the amsmath package).  Ideally, I would like to be able to write something like  \documentclass{article} \usepackage{amsmath} \begin{document} \begin{equation} f(x)=\begin{cases}   1&amp;x\geq0\label{positive}\\   0&amp;x&lt;0\label{negative} \end{cases} \end{equation} \end{document}   and later refer to both cases at different places. What would be the best way to achieve this result? Is it safe to check floating point values for equality to 0? I know you can't rely on equality between double or decimal type values normally, but I'm wondering if 0 is a special case.  While I can understand imprecisions between 0.00000000000001 and 0.00000000000002, 0 itself seems pretty hard to mess up since it's just nothing.  If you're imprecise on nothing, it's not nothing anymore.  But I don't know much about this topic so it's not for me to say.  double x = 0.0; return (x == 0.0) ? true : false;   Will that always return true? Possible pitfalls of using this (extension method based) shorthand In a simple battery + resistor circuit, what form of energy is lost from the electrons upon exiting the resistor? I will give this question a little context. Firstly, as I understand it, as soon as I "close the switch" on a circuit, electric current pretty quickly establishes a steady state where, at any given cross section along a wire, the average kinetic energy of that slice is both constant and equal anywhere along the wire. (Please correct me if I am misunderstanding).   If the average kinetic energy is constant anywhere throughout the wire in the circuit (which confuses me, as I would think that the electrons should all accelerate after exiting the resistor since they are no longer being impeded as much), that means that the average velocity is constant. So, in the example of a simple circuit with a battery of v Volts and a resistor of o Ohms, my question is the following:  Because a 'voltage drop' is known to occur across the resistor, what type energy is being "traded" to generate the heat that radiates from the resistor? I would think that the reflexive answer is "electrical energy"...hence the VOLTAGE drop (the sacrificed energy is clearly not kinetic, as the velocity is constant everywhere). However, I find this confusing. Does this mean that if I had a positive test charge, it would be easier for me to bring it to the beginning of the resistor as compared to bringing it to the end of the resister?     Further, if the correct answer IS "electrical energy", why exactly DOES electrical energy get "dissipated" as the electrons pass through the resistor? I always here the comment Oh! It's because all the electrons are running into densely packed crap which impedes their flow but that to me sounds like a reason for their KINETIC energy to be reduced. However, clearly that's not the case. So, ultimately, I guess the real question is:  **What goes on in the resistor that is literally removing electrical energy **. I am sure that this is a quantum mechanics question, but my quantum mechanics knowledge is not terribly strong. If I could get an answer that is devoid of crazy wave function equations, I would greatly appreciate it. Thanks! Showing OSM source acknowledgment on the map in QGIS? I am using OpenStreetMap as a base layer via XYZ tiles in QGIS 3.01.  I can't seem to find a way of having source acknowledgement appear on the lower right corner of the map.  Can somebody point me in the right direction? For some special purpose, I want to prevent non-root users of the Linux Server from changing or renaming the filenames. However, they can modify and write to the contents of the file. How to do this from command line. Im not familiar with Ubuntu or Linux in general but have succesfully installed dual-boot windows7/Ubuntu on a single harddisk on my private PC. I used the "Install Ubuntu alongside them"-option.   On my work PC I have an existing windows 7 64-bit installation that boots from BIOS firmware on a SSD drive (C:), and have my working data (documents etc) on a partition on a separate disk (D:). I now want to install Ubuntu (v 14.04.3) on the remaining unformatted space on D:\ using with the option of choosing system using GRUB. There are of cause fine descriptions around (e.g.  and ). My question is how to setup the partitions in the "something else"- option during the Ubuntu installation.   In  tutorial they assume that all partitions on the D-drive can be deleted; however I only obviously want to keep the working data on the existing D-partition, and place Ubuntu on the residual space (or part of it) on the D:-drive.  A) How is this ensured ? B) how many partitions should I make (boot, root, home, swap ?)  C) and should boot be made primary, and the others logical ? D) Should I set Device for boot loader installation as/dev/sdb - will this not erase the existing D-partion ?