Is it a good idea to scan external HDD with Ubuntu?
Do I need to have antivirus software installed?
How many physical degrees of freedom does the $\mathrm{SU(N)}$ Yang-Mills theory have? Why doesn't a bike/bicycle fall if going with a high speed? Why does a bike/bicycle fall when its speed is very low or close to zero and is balanced when going with a high speed? Prove $n-m \mid n^r - m^r\,$ [Factor Theorem, monomial case] In respect to a larger proof I need to prove that $(n-m) \mid (n^r - m^r) $ (where $\mid$ means divides, i.e., $a \mid b$ means that $b$ modulus $a$ = $0$). I have played around with this for a while now but to no avail and would be grateful if you could help me. How can I know what speed card to get for my camera? Field that is a subfield of own of its subfields Let $K$ and $L$ be fields. We have homomorphisms $f: K \to L$ and $g: L \to K$. Are $K$ and $L$ necessarily isomorphic? A two way String hash function What makes a good tag separator? I'm building an application to allow technical people to enter configuration changes.  I'd like to add tags to each change.  Right now I'm using spaces, commas and semicolons.  It appears SO uses spaces and requires hyphens to make multiple words.  I read something that leads me to believe that WordPress uses commas and that a space isn't a separator.  Is there any best practice out there?  Has anyone had any good or bad experiences? Getting a black screen when installing or Live booting Ubuntu (any version) in my laptop I have an ACER Aspire laptop. Model number is E5-573G-56RG. I bought it only 15 days back. There is no DVD drive in it. I have tried various versions of Ubuntu- 14.04.2, 14.04.3, 15.10, 12.04.5. Tried disabling secure boot, fast startup. I current have Windows 10 Home and Windows 10 PRO (not-activated) installed with GPT partition in UEFI bios. I actually want only the Home edition and Ubuntu 14.04.3 (preferably because of LTS) or 15.10. In case more information is required, kindly ask me..  I tried installing through Wubi, when booting if I choose Ubuntu it automatically restarts and goes into Windows 10 Home! (I didn't have Windows 10 PRO at that time)  NONE OF THE SOLUTIONS I REFERRED HELPED ME.  I have spent 5 days (literally at least 20 hours reading all of them and trying out all kinds of editing in the grub command line, like removing quiet splash, adding and replacing with nomodeset, no splash, acpi_osi=off, acpi_osi=Linux, acpi_backlight=vendor,  acpi_backlight=legacy, noveau.modeset=0, i915.i915_enable_rc6=1 and such things! But I was not able to succeed installing which is why I doubt if there is some more thing to be done or know exactly what has to be done. What is the rationale for all comparisons returning false for IEEE754 NaN values? Sharing a Bluetooth Keyboard and Mouse sequentially between two Macs I work out of my house where I have two computers: a mid-2010 Macbook Pro (for my day job) and a mid-2010 iMac (personal). During the workday, my iMac acts as a second display for my Macbook Pro via Mini Displayport.  Currently, I use a USB keyboard and mouse for my work computer and a Bluetooth keyboard and Magic Mouse + Magic Trackpad for use with my personal computer. I'd like to get rid of the wired keyboard and mouse and just use the Bluetooth stuff for both machines (but never simultaneously).   Is it possible to easily share the single set of input devices without having to repeatedly break and reestablish the pairing of the input device to the correct computer? I'm not opposed to buying some type of additional hardware to accomplish this, provided it's not prohibitively costly or cumbersome to use or configure.  It's not clear to me how I would tell the MacBook Pro to leave the devices alone so the iMac can have them for the evening. I want to avoid de-pairing and re-pairing the devices each time I want to shift them back or forth.  Basically is there software or hardware that works as a Bluetooth KVM switch? Story with multiple 'third planet' races Is it possible to upgrade a BGA 1224 CPU? I want to upgrade the CPU of my T430s laptop from i7-3520M to i7-3632QM. I'm sure i7-3632QM is supported (same socket (BGA1224), same TDP (35W) and microcode found in BIOS (306A9.PAT)).  So my question is: 1) is it possible to de-solder the current CPU without damaging it, and to solder the new CPU without damaging it and the motherboard ? 2) if so, what tools are necessary? who can do that at a reasonnable cost?  Until now, I was unable to find anyone able (or willing) to do that (I'm located in France, and I have tried a local fablab, electronics shops, TV repair shops, ...). Any hint would be appreciated. How to read the following Itinerary What do the abbreviations mean in the following itinerary:     2  EK 641 L 29NOV 2 KBLDXB HK1       I  1630 1905   *1A/E*                      3  EK 344 L 29NOV 2 DXBKUL HK1       3  2140 0835+1 *1A/E*                      4  MH 704 V 30NOV 3 KULMNL HK1       M  1245 1630   *1A/E*                      5  UA 184 Y 01DEC 4 MNLGUM HK1       1  2255 0440+1 *1A/E*                      6  UA 155 Y 02DEC 5 GUMTKK HK1          0820 1008   especially, the numbers (2,2,3,4,5) before KBLDXB, KULMNL.... The letters and numbers before time (I, 3, M, 1) *1A/E*? Vertical component of moving weight at a 45 degree angle Here's an easier one. I use the leg press machine at the gym so I don't have to worrying about hurting myself while lifting heavier weight.  The weight glides on a track that looks to be 45 degrees.  What's the equation to figure out how much weight I would be able to squat normally.  IE the vertical component of moving 400lbs at a 45 degree angle. What does a two overlapping circles symbol mean in an electrical schematic/diagram? In my D&amp;D 5e campaign one of the PCs who's a wood elf started dating a dark elf, and as a result she got pregnant and she is about to give birth. One of the other players had their PC die and he is considering playing as the child of the couple.  My question is, which race is the child going to be? What are the left and right ideals of matrix ring? How about the two sided ideals? Facebook: Ways to preserve image quality of uploaded images? After uploading an image, Facebook converts it to a new image.  Their conversion process introduces artifacts and mottling to the magenta-ish parts of the image.  Original image:   Facebook's conversion:   Are there ways to preserve the original quality of this image and have the image appearance on Facebook reflect more of the original quality? Where does the question mark go — inside or outside the parentheses? I know that when brackets enclose part of a sentence, the full stop goes outside.     I tripped over this morning. I was distracted by a plane (which turned out to be Superman).   If it's a full sentence, the full stop goes inside.     I tripped over. (I was distracted by a plane that turned out to be Superman.)   What happens when there's a question mark and only part of the sentence is a question?     I tripped over this morning. I was distracted by a plane (or was it Superman?)      (or was it Superman?).      (or was it Superman)?   What happens to the full stop that belongs to the rest of the sentence, and why? How can there be animals on the surface in Zion's world? It is apparently canon that  in Neo's day.  However, in the first movie, The Matrix, Morpheus tells Neo that one of the things known for certain is that humans "burned the sky" in order to deny solar engery to the machines, which in turn led to the humans who survived the War being plugged into the Matrix to provide bioelectric energy to supply the machines.  If there's not enough sunlight for solar power, how can there be enough to grow plants to serve as food for animals?  Low levels I can understand -- house plants, at least, thrive in conditions too dim for solar panels to produce cost-effective power -- but every surface scene we see in the trilogy is as dark as a cloudy night; light coming only from the machines.  That wouldn't begin to support photosynthesis, which means all animal life would starve in, at most, a matter of a few years.