How many bits are addressed through one CAS command in DRAM?

Question: From what I understand one column and row pairing corresponds to 64 bits from the DRAM chip, but this makes me think that one would then incur the CAS Latency (~18 clock cycles in DDR4) for EVERY transfer. I feel like this is obviously not the case or else DRAM would be severely limited by the CAS delay and not the available bandwidth. Thanks for the help!
Comment: Isn't it totally up to the specific chip?
Comment: With the right device (one that has page-mode support) you can get 256 bits from a CAS access.
Comment: Don't forget that DDR chips have multiple banks internally, which means that you can interleave operations on individual banks to keep the I/O bandwidth filled up, even if any single bank can't do it on its own. This is what we normally do in high-bandwidth video systems, where the problem is somewhat simplified because nearly all of the accesses are sequential anyway.
Comment: Great point Dave. Can you expand upon what you mean by multiple "banks"? I am familiar with the concept of ranks in memory systems. Are they the same?
Comment: I don't know what a "rank" is in this context. A typical DDR chip has 4 banks that operate essentially independently of each other, except that they share a common set of input (address and command) and I/O (data) buses. They can usually transfer up to 8 words of data in a DDR burst. You can initiate a burst transfer on bank 0, and while that is happening internally and on the data bus, you can initiate a burst on bank 1 using the command and address buses, and so on. By the time the burst on bank 3 has been started, bank 0 is now ready for a new operation.
Comment: ... 32 words of data get transferred in each "super burst" across all four banks. You can typically achieve >90% bus utilization, even with a mix of reads and writes.
Answer: How many bits depends upon the width of the memory chip, you can always put more in parallel to get more data at the same time. So each access cycle is whatever the width of the chip is.
It can vary but generally you can access multiple row addresses without having to set the column again as long as it's the same.
If the rows are all in a block then you can be even faster and do a burst where the chip itself auto increments the row address internally.
In a PC (my knowledge here is out of date here so apologies if it's changed since) the DRAM is always accessed in bursts of 4 cycles, each burst has a fully qualified address with both CAS and RAS set.
However other memory controllers can act very differently and can make better use of the potential speed benefits depending upon their application.
Comment: Thanks for the responses. Does anyone know of any good reading material that might have this same information or simply lots of basic things about SDRAM? Preferably something reputable that I could cite in an informal presentation.
Comment: In a x86_64 PC the L2 cache line size is 64bytes so this is the natural size in which you want to access (reading) any higher level ram (plus maybe ECC bits)
Comment: DDR4 is 64 bits wide which would imply that if you are required to fit the memory in pairs one read is 128 bits and it would take a burst of 4 cycles to fill a cache line. So that seems to tie up nicely.


Shakespeare's omission of 'as' before 'single' in 'When sorrows come, they come not single spies...'

Question: When Shakespeare wrote: "When sorrows come, they come not single spies, but in battalions", why didn't he put an "as" before "single spies"?
Comment: Because that's how he wanted it.
Comment: It's a much better title now. Why not tell us where the line is from?
Comment: it's for the syllable count, a nice 466
Comment: @HotLicks - don't bother commenting if you've nothing useful to say.
Answer: Mainly to maintain metre, but perhaps also to make it a metaphor rather than a simile. The metaphor sounds more arrogant, more assertive, which matches Claudius' character.
Comment: I can't agree with this. (1) *As* in this context would not make this a simile--it plays the same role as *in* in *in battalions*; (2) metaphors are not inherently more "arrogant" or "assertive" than similes; (3) Claudius is not particularly "arrogant" or "assertive" in this passage: he is rather shaken by recent events and the current atmosphere.
Comment: I did say 'perhaps' indicating what follows is my interpretation. (1) I do understand that 'as' is a preposition too, but my understanding is C is comparing 'sorrows' to 'spies' in an analogy.  Regarding (2) I made no such generalisation. (3) Open to interpretation. At least we agree that this is for metrical purposes - which is the correct answer. +1 on your response for staying on topic: I've clearly muddied the waters!
Answer: In this sort of context, where the nominal is a secondary subject complement, EME did not require as with nominals, just as we still don't require it with adjectivals:

He came galumphing back.
  He came home defeated.

Here's a non-Shakespearean example:

Firſt, [God] comes a Little-One : to ſshew, that hee is food for Little-Ones ; [...] A little One hee comes, from the leaſt of the cities ; Little, of Accompt : Little, in Appearance ; that we might not be afraid to come neere him. [...] And laſtly, he comes a Little-One to us, to ſhew, we muſt come, as Little-Ones, to him. —Austin, Devotionis Augustinianae Flamma, 1635

So Shakespeare might include as or omit it; and the meter here calls for omission.
Comment: " ... where the nominal is a secondary subject complement" - what does that mean? And what is EME?
Comment: EME = Early Modern English
Comment: @Peter4075 A "secondary complement" is a non-obligatory complement to the verb. An object complement describes the object of the clause--*He drinks his coffee **black***, where *black* describes *coffee*--and a subject complement describes the subject of the clause--*He drinks his coffee **naked***, where *naked* describes *He*.


Doubt in Field Calculator

Question: I am working in an project.I have a point Shapefile its projection is NAD83(HARN)Pennslyvaniasouth(ftUS)*EPSG3365* when I measure its distance(between two points) it gives me the answer in feet .yes its acceptable for me.I also calculated its x-coordinate and y-coordinate for the points in field Calculator it displays me the answer in feet.This is the problem.In my company they are insisting me to show the LAT-LONG value in Decimal Degrees.Is it possible to show the Lat-long in Decimal degrees in QGIS?
Comment: For that, you need to project your layer to a geographic coordinate system first: Select the layer, click "Layer / Save as", then choose a geographic CRS such as EPSG:4326. Then use the field calculator on this new layer to get the coordinates in latitude/longitude.
Comment: It's not really clear what exactly you're trying to do. What do you mean by "calculated its lat-long"? What expression did you use in the field calculator? Do you simply want the geographic coordinates (latitude/longitude) for all the points in your layer?
Comment: @Jake let me properly explain "calculated its lat-long" means i calculated X-coordinate($X) and y-coordinate($Y) in field calculator. I am getting ($X ,$y) in feet but I want this in Decimal Degree.Is it possible to get in QGIS  I am asking?
Answer: I think transform() function was not available when the question was posted (Y2013).
Now we can solve this CRS issue, just by the Field Calculator!
For Longitude: ......  x(transform($geometry, 'EPSG:3365', 'EPSG:4326'))
For Latitude: .........   y(transform($geometry, 'EPSG:3365', 'EPSG:4326'))
I created three random points near Philadelphia, and the transform() worked as expected. (Imported to GoogleEarth as KML and made a visual check).

Doubt in Field Calculator


charging a lead acid battery

Question: (n00b question) I have a small (6 cell regular bike) leadacid battery and want to charge it via solar sheet of 15V - 0.3A. the voltage solar sheet changes and in cloudy day goes below 10V. does the battery keep charging that those levels (though very slowly?)
Answer: What you asked about:
No, a nominally 12v lead acid battery will not charge at 10V unless it is essentially fully discharged.
What you didn't ask about :-) :
You MUST have a diode* between the panel and battery to prevent the battery discharging into the battery when the panel voltage is below battery voltage.
 (* diode or functional equivalent - there are alternatives but a diode is simplest and cheapest and good enough.
To see if your panel is losing much energy.
The complete answer re the adequacy of your panel to charge your battery in a range of light conditions is given in the paragraph labelled ==> below BUT all the rest gives you a much better feel for your system.
Use a current meter (multimeter or other) that is able to read the maximum current the PV panel will produce.
Described below  are several measurements which you can make under various conditions. Here I'll just use the terms Isc, Voc, Ichg and Vdiode. How to measure these and what they mean is detail below under "measurements".

Isc - warning: Note that I say below that Isc must be measured with battery disconnected. In fact, as long as you do the right thing you can measure Isc by shorting the panel with an ammeter at any point. BUT short on the wrong side of the ammeter and you  will get magic smoke. Ammeter may die, Battery may die. Wiring may die. For extra points on a big system (bigger than this) you may die doing that BUT common sense should stop you shorting in the wrong place.

SO

Under various sun conditions measure Isc, Voc, Ichg, Vchg, Vdiode
Record all figures including assessment of light level. If a lux meter is available so much the better.
==> Note the sun conditions when Ichg is hardly more than zero.
If Isc under those conditions is a significant portion of Isc_bright_sun then you are wasting energy and your panel would benefit from more cells and thus a higher Voc.

-

MEASUREMENTS:
(a) Isc = panel short circuit current.
Made WITHOUT battery connected **.
 Expose the panel to sunlight and connect the meter probes across the panel (Without the battery connected !!!).  This essentially short circuits the panel and gives an idea of its maximum realistic output = Isc at the given light conditions.
(b) Voc = panel open circuit voltage.
(C) Ichg. Connect panel to battery via a diode and via a current meter which has low voltage drop.   Measure charge current into battery.

Using a multimeter set to the 10 amp range will usually be OK.
You may only be able to resolve current to 10 mA in this mode but low voltage drop is more important than accuracy.
Measuring the voltage across the meter when it is measuring peak current in bright sunlight will be useful. You'll need a secind meter to do this.
Vdrop across the meter will ideally be only 0.1V or les and not more than ay 0.3V max.
You may be able to use ag a 500 mA or 200 mA range but thse will usually have too much voltage drop.

(d) Vchg = Panel voltage when charging
(e) Vdiode = diode forward voltage drop
A "magic" measurement - ie far more can be told from this one reading than may be expected.
Place a volt-meter across the diode and measure the voltage. When the battery is being charged the diode will forward conduct, & panel voltage will be above battery voltage by a diode drop = 0.6 - 0.8V for silicon and 0.3 - 0.5 V for Schottky diodes.
When the battery is not charging Vdiode will change polarity and will tell you how low panel voltage is compared to battery voltage.
Monitoring Vdiode will tell you quite a lot from a single reading about how a system is performing.

High Vdiode conducting = heavy charge.
Vdiode starting to drop off peak value but still > say 0.5V for silicon = charging at lower rates.

Vdiode +ve but 0 - 0.5V = trying to charg but only just - as the diode conducts the battery voltage will rise due to the tickle of current nd hold Vbattery just below Vpanel over a moderate range. This shows you that the panel is about at its starting to charge point but only just.

Vdiode is negative. Panel voltage is below battery voltage. How much below shows how far off charge you are.

Made without battery connected **.
  Measure the panel voltage when exposed unloaded to sunlight.
. Also measure the panel voltage "open circuit" in full sunlight = Voc.
Now repeat in various cloudy conditions. Note Isc at various Voc's for varying degrees of cloud.
Now connect the panel to the battery with the battery reasonably well charged from another source. Battery Voc should be well above 12V.

Blocking Diode
Using a Schottky diode rather than a silicon diode will give you a very small gain in charging capability - not liable to be worthwhile in most cases.
Using a 1N400x diode will work fine (x = 1...7 and indicates breakdown voltage. as 1N4001 = 50V any will work for you.
 ie anything from here
Datasheet for 1N4001 ... 1N4007 here
If using a Schottky diode then a 1 amp rated one at 20V or better should be used. These are somewhat more sensitive to static electricity damage than silicon diodes.   I'd probably use a 30V diode here rather than 20V to reduce the chances of unfortunate happenings.
 Anything from here rated at 20V or higher should work .
eg a 1N5817 - 1N5818 - 1N5819 rated at 20 / 30 / 40 Volt respectively will work well.
Comment: Thanks for answering more than I asked. I needed that info. :) I had been taking readings from battery terminals but without d/c the panels. now i take two readings. Its sunshine and so panel is reading 15.4V and battery V has changed for original 8V to 10.1V. Also setup a IN4007 blocking diode.
Answer: The 6 cell Lead Acid battery should ideally be charged at 13.8V to 14.7V
Any lower and you wouldn't be able to reach full charge and any higher and the battery might get heated up and might get damaged .
If the battery voltage is higher than your charging voltage current will start flowing in the opposite direction and thus discharging the battery.
Think of the battery as an overhead tank of water in a building or home.
The voltage of the battery is like the pressure in the tap below.
To fill the overhead tank using that tap, you'll need to put higher pressure into the tap than the pressure of water coming out of the tap. Only then the water will start flowing upwards into the tank.
The charging current is like the rate of the the flow in the tap. The slower the rate of filling it the longer it will take to fill up the tank.
And similarly the volume of the tank is like the capacity of the tank, for e.g. 7Ah for a small battery and 150Ah for a larger battery. Larger the tank and longer it will take to charge it at the same current or flow rate.
Actually after giving that example, i just figured that even the battery characteristics can be understood the same way, but I'll leave that out for now so not to confuse you.
Adding a diode ensures that even when you don't have enough voltage to charge the battery, it doesn't start discharging, even though it will not charge at all at lower voltage.

charging a lead acid battery


How can I change the post order after filtering in WordPress?

Question: After filtering the post list in the admin dashboard, how can I change the order of posts after filtering and it will display in the same order at the front end too?
Answer: Hello Radheeka Chopda and welcome to our lovely community.
I would highly suggest you first read How to ask good questions before making more questions.
But since I can assume what you are looking for, let me know if this code below helps you with your problem.
CODE:
<code>// Change the order of posts on the front end
function custom_frontend_posts_order($query) {
    if (!is_admin() && $query->is_main_query() && $query->get('post_type') == 'post') {
        $query->set('orderby', 'your_custom_order_field'); // Replace 'your_custom_order_field' with the same order field used in the admin dashboard
        $query->set('order', 'ASC'); // Set the same order as used in the admin dashboard
    }
}
add_action('pre_get_posts', 'custom_frontend_posts_order');
</code>
Incase this is not what you're looking for, make sure to provide more information and the piece of code you are using to filter the post list in the admin dashboard, for us to help you figure things out!


Slang word or term for WWII food ration stamps?

Question: Does anyone know of a slang word or term that was used for food ration stamps in WWII?
Comment: You may need to indicate a particular country. Rationing was widespread and different cultures would have different slang.
Answer: My mom always refers to them as "coupons", "ration coupons", or "ration tickets". She lived in New England, US.
Incidentally, (for those of you who feel like society is going to hell in a handbasket) in those days it was common for people to take in foster children (from families who could not support them) in order to steal their rations.
Ration coupons were distributed to each citizen - adults and children, alike - so the children's tickets were simply taken from them by greedy "benefactors". The children were forced to subsist on gruel, while the adults ate their rations of meat and butter.
Comment: I recall reading that, by the end of the war, over 90% of the population had somehow managed to get their ration quotas raised.  IIRC, becoming a minister was a popular way to get a larger gasoline ration.  (I recall seeing several articles on the topic of rationing ca 1970, but nothing recently.)


How is BAB calculated for a Fused being?

Question: How do you calculate the BAB on the fused being created by the fusion power? If you fuse together two half bab characters does it make a full bab character?
Answer: You get the best bonus.
Relevant clauses:
1.

class features are pooled

2.

this effectively means the fused being uses the better...attack bonus...of either member

The pattern is that bonuses of the same type do not stack, they overlap, and you get the best bonus available to you.  If you have a Psion 20 and a Wilder 20, you get 10 BAB.  If you have a Psion 20 and another Psion 18, you get 10 BAB.  If you have a Psion 20 and a Fighter 14, you get 14 BAB.
Comment: @Cellheim the power explicitly calls that distinction out:  "For each of the six ability scores, the fused being's score is the higher of yours and the other creature's".  If the Fused Being's Strength is X, that's what he uses on attack rolls with Melee weapons(unless there's an exception, like weapon finesse)
Comment: The power is unclear on Size modifier.  My personal ruling as an experienced 3.5 DM is that the fused creature is the size of the largest base creature, and would have adjustments for size accordingly.  So, if they were the same size, it'd be Better_of_2_BABs + Better_of_2_Strengths.  If they were different sizes, it'd be Better_of_2_BABs + Better_of_2_Strengths + Larger_Size_Modifier
Comment: But attack bonus isn't the same as base attack bonus if I understand correctly. So can you use one character's BAB and another character's strength modifier when determining attack bonus or are you restricted to choosing the better attack bonus of the component characters?
Comment: So then does the hypothetical creature use the better of the two BABs +  the better of the two strength modifiers + the size modifier to determine attack bonus or is it just the better of the two attack bonuses of the individual creatures?


How to upload an image programmatically from URL

Question: I have a task to upload an image into Sitecore's media library programmatically given the url to the image. How would I make this possible?
Answer: There are a couple of steps involved.

Download the image from the url via a WebRequest
Copy the download stream to a MemoryStream
Set up a MediaCreator
Configure MediaCreatorOptions
Create the MediaItem

Optionally you also need to consider the context Database and permissions. In this example I am just uploading to "web" and ignoring security. You will probably want to change this a bit.
        var webRequest = WebRequest.Create("http://your-domain/logo.png");
        using (var webResponse = webRequest.GetResponse())
        {
            using (var stream = webResponse.GetResponseStream())
            {
                if (stream != null)
                {
                    using (var memoryStream = new MemoryStream())
                    {
                        stream.CopyTo(memoryStream);

                        var mediaCreator = new MediaCreator();
                        var options = new MediaCreatorOptions
                        {
                            Versioned = false,
                            IncludeExtensionInItemName = false,
                            Database = Factory.GetDatabase("web"),
                            Destination = "/sitecore/media library/Files/logo"
                        };

                        using(new SecurityDisabler())
                            mediaCreator.CreateFromStream(memoryStream, "logo.png", options);
                    }
                }
            }
        }

Note: Copying the stream to a MemoryStream is required because the MediaCreator will issue .Seek() operations on the stream, something which is not supported on a stream you get from a WebRequest directly.
Answer: You need to download the image and use MediaManager.Creator.CreateFromStream method.
Sitecore.Resources.Media.MediaManager.Creator.CreateFromStream(ms, fileName, options);

Here is a nice blog post explaining how to create media item programmatically:
Adding a file to the Sitecore Media Library programatically
Scroll to the bottom to see creating media item from stream.
Answer: There are many great approaches to this as seen by the list of responses to this question. I would however recommend a solution that is very repeatable and perhaps more automated.
Sitecore PowerShell Extensions
This approach offers a set of PowerShell commands bundled with the SPE Remoting module.
Script
# Source : https://github.com/SitecorePowerShell/Console/tree/master/Modules
Import-Module -Name SPE -Force

$props = @{
    Session = (New-ScriptSession -Username "admin" -Password "b" -ConnectionUri "http://console")
    Verbose = $true
}

# Upload single file
Get-Item -Path C:\temp\data.xml | Send-RemoteItem @props -RootPath App
Get-Item -Path C:\temp\data.xml | Send-RemoteItem @props -RootPath Package -Destination "\"
Get-Item -Path C:\temp\largeimage.jpg | Send-RemoteItem @props -RootPath App -Destination "\upload\images\"
Get-Item -Path C:\temp\image.png | Send-RemoteItem @props -RootPath Media -Destination "Images/"
Get-Item -Path C:\temp\image.png | Send-RemoteItem @props -RootPath Media -Destination "/sitecore/media library/Images/image2.png"
Get-Item -Path C:\temp\cover.jpg | Send-RemoteItem @props -Destination "{04DAD0FD-DB66-4070-881F-17264CA257E1}"

# Upload single file using full qualified path
Send-RemoteItem @props -Path "C:\temp\data.xml" -Destination "C:\inetpub\wwwroot\Console\Website\upload\data1.xml"

Get-Item -Path C:\temp\data.zip | Send-RemoteItem @props -RootPath App -Destination "\upload"

# Upload multiple files in a flat structure
Get-ChildItem -Path "C:\temp\" -Filter "*.xml" | Send-RemoteItem -Session $session -RootPath Media -Destination "Files/" -Verbose

# Upload multiple files in a compressed zip to maintain directory structure
Get-Item -Path C:\temp\Kittens.zip | Send-RemoteItem @props -RootPath Media -Destination "Images/" -SkipExisting

# Close out the existing session
Stop-ScriptSession -Session $props.Session

Setup
Check out this page in the Gitbook for SPE to see how to get setup and running.
Answer: Also note that if you want to update a media stream for an existing media item (the equivalent of an author using detach/attach using the Sitecore UI). Obtain a reference to the MediaItem and then call:
var media = MediaManager.GetMedia(mediaItem);

media.SetStream(stream, "YourFileExtension");

This can be useful if there are content items linking to the media item and you don't want to break existing links but you do want to modify the content of the media item.


How to set color levels (or white point level) on all layers of an image using gimp?

Question: I have an image with multiple layers, and I have to set the same white point on all pf them. how can I do it without selecting each layer at once?
Answer: Doing the layers one by one, most tools in Gimp can save their settings. You can save them explicitly by giving them names,  but they are also saved automatically (see the Presets selector at the top of the Curves or Levels tools).

So you would just do one layer and then reuse the settings on the others.
Another method is to load them as tiles and make one single big layer, make the change on that layer, and then split it again to tiles (but I don't know a script that does that directly, there are however scripts that can do this after saving the tiles to individual files).
Answer: The menu bar has commands to repeat the most recent filter operation, Filters -> Repeat "<previous filter>".  It has the shortcut Ctrl+F, so you can easily repeat it after selecting each layer.

Colors -> Levels... will also show up in Filters -> Repeat "<previous filter>" after you use it, even though it lives under the Colors menu.


Are RAID 5 systems suitable for larger disk sizes?

Question: Why is it generally considered that RAID 5 systems are not suitable for larger disk sizes? Is the same true for RAID 6?
Answer: RAID5 is unsuitable full stop
A good explanation (from 5 years ago) is here:
http://storagemojo.com/2010/02/27/does-raid-6-stops-working-in-2019/
Comment: I understand the risk of multiple drives failing, before the rebuild is complete, increases.
But RAID6 can deal with 2 disk failures. Is RAID6 suitable for large disk sizes?
Comment: @Anthony sure, if you don't care much about performance.
Comment: You only pay a performance penalty with RAID-5/6 if you don't know how to build a RAID array and/or don't know how to align IO operations. If you go and build a 14+2 RAID-6 arrays, sure you'll have performance problems. But, for example, if you build 8+2 RAID-6 arrays and know to select proper segment sizes and partition alignments so that the file system you build on top of the arrays(s) writes full RAID stripes that are aligned, you won't see any performance issues. 14+2 arrays are like buying a Ferrari, putting it in 6th gear while stopped, popping the clutch, and then saying it's slow.
Comment: @Anthony Even with 2 parity drives, you have to remember you have disks that are all the same age. One has failed and all of a sudden you massively increase the load on the others to rebuild. This increases the chance of another one failing, or even 2 (which would be a bad thing).


potato and carrot dumpling,how would you make it diabetic frendly?

Question: not sure how to put this recipe up for others to cross-reference but it's on food.com if anyone wants to find it. the recipes name is carrot and potato dumplings and my question is how would you make it diabetic friendly? I'm honestly not sure myself, thussly my question here.  Also I'm diabetic myself, so ANY advice as to how to make it diabetic friendly would be nice! I'm not sure how to make it better for diabetics in anyone's interested.
Comment: Not sure why this question is closed. Come on guys, there are regularly questions asking for low carb substitutes, why close this one? But to the question you can finely grate them and wash off most of the starch and see how it goes. Maybe add some binder e.g. egg or thickener e.g. xanthan to keep it together. Good luck.
Comment: I'd recommend a diabetic tag for questions like this.
Comment: You might alter it slightly, substituting cauliflower, mashed, and add a beaten egg white to bind before steaming.
Comment: acturally that does make some sense @Dorothy
Comment: We are not a health site, which is why this question was closed. Medical issues should be discussed in places that are designed for that subject.
Answer: I referenced the recipe which has only the two ingredients, grated potatoes and carrots, and seasoning. For the potato, substitute cauliflower, cooked until very soft, mashed. Fold in the carrots and a beaten egg white to bind the mixture before steaming, rather than the boiling option.


What's the difference between 'ignorant' and 'silly'?

Question:
while an ignorant person will flounder and encounter difficulty
Comment: In Hiberno-English, *ignorant* has another meaning: angry, quick-tempered.
Answer: Ignorance is lack of knowledge.

lack of knowledge or information : he acted in ignorance of basic procedures.

Silly is behaving in a foolish manner, or showing poor judgment.

having or showing a lack of common sense or judgment; absurd and foolish : another of his silly jokes | "Don't be silly!" she said

[Both definitions from NOAD]
Comment: @tenfour: I don't think ignorant is always pejorative. Often, yes, but not always.
Comment: I'd add that "ignorant" is always pejorative, and "silly" is often used as a more positive synonym, even though the underlying meaning is still the same. "What an ignorant decision" comes from someone who's just angry. "What a silly decision" comes from more light-hearted conversation or someone not willing to be so blunt about the point.
Comment: Just to add, look at the etymology of *nice*. http://www.etymonline.com/index.php?search=nice&searchmode=none
Comment: I agree with shiny & new: "ignorant" is often used as if it meant "willfully ignorant" and in that sense it is pejorative, but it is not pejorative in and of itself.
Answer: "Ignorant" is (at least on the surface) factual, while "silly" is purely an expression of opinion.  For example, my manager makes decisions I consider silly (and sometimes downright stupid), while he thinks them wise (if not brilliant).  But we agree they aren't ignorant decisions: he has all the necessary information before deciding, including my sage advice.
Answer: A possible approach to shed some light on the difference between ignorant and silly is to adopt an etymological point of view.
Whereas the origin of ignorant is pretty straightforward ("deprived of knowledge" in Latin), that of silly is more complex.
The word silly has its root in Old English and probably beyond in Proto Indo European.  It comes from Old Germanic sâlîg and the associated meanings shifted gradually from...

"happy, blissful" (OE) to
"blessed" (c.1200) to
"pious, innocent" (late 13c) to
"simple-minded, lacking in reason" (late 16c)
and today even "foolish".

So that as others have already mentioned, ignorance is a lack of knowledge and silliness a lack of common sense.


Do we take gravity = 9.8 m/s² for all heights when solving problems? Why or why not?

Question: Do we take gravity = 9.8 m/s² for all heights when solving problems?
Comment: I take it as 10 - it makes doing the approximation head-doable
Answer: No, the value $9.8\frac{\mathrm{m}}{\mathrm{s}^2}$ is an approximation that is only valid at or near the Earth's surface. You can go a few miles up or down and it'll still be good enough, but once you get any significant distance away from the surface of Earth, you would need to use a different value for gravitational acceleration. You can calculate the value from Newton's law of gravitation, $F = Gm_1m_2/r^2$, and you'll get
$$g = \frac{GM}{r^2} = \frac{3.99\times 10^{14}\ \mathrm{m^3/s^2}}{r^2}$$
where $M$ is the mass of the Earth and $r$ is the distance from the Earth's center to the point for which you are doing the calculation.
Comment: It's strange that you would measure the height in miles when the value for gravity is in meters per second squared.
Comment: Maybe if you are a geologist, but for most scientist, we rarely use anything but SI units.
Comment: @LDC3 _some_ scientists rarely use anything but SI units, I'm sure, but many branches of science have their own conventional unit systems. In particle physics we use natural units ($c$ and $\hbar$ set to 1), in condensed matter they often use some lattice spacing as a length unit, in cosmology they use megaparsecs or the Hubble radius, and so on. The point is, a qualified scientist is capable of understanding the science regardless of what units are used.
Comment: Not really; miles are a common unit for height. And it's trivial to convert when needed.
Comment: Maybe you could cite that $g = \frac{GM}{r^2} \approx \frac{4 \cdot 10^{14}}{r^2}$ (error: 0.3%). r in meters, g in m/s²
Comment: [Relevant meta](http://meta.physics.stackexchange.com/questions/15/shall-we-force-to-use-si). Consensus seems to be SI good, natural too (where appropriate), CGS is edge case.
Answer: To expand a little on David's point assume we move from the nominal "surface" where $g$ is $9.8\text{ m}/\text{s}^2$ to another point at radius $r + \Delta r$. How much does the acceleration of gravity change?
$$
g = \frac{GM}{(r+\Delta r)^2} = \frac{GM}{r^2(1 + \Delta r/r)^2}
$$
and as long as $\Delta r$ is small compared to $r$ we can reasonably approximate this as
$$
g \approx \frac{GM}{r^2}\left(1 - 2\frac{\Delta r}{r}\right) .
$$
Well, the radius of the Earth is about $6000 \text{ km}$ so the approximation is good at less than 1% error for around $30\text{ km}$ up or down from the nominal surface, which is all the land and sea floor, and a bit up and down from there.
It is also worth noticing that due to variations in the local mass density of the Earth the measured value of $g$ even at the surface can vary by several tenth of a percent.
Comment: In fact, the measured variations in $g$ are very useful to geophysicists, oil prospectors, etc.
Comment: I was reading an [article on the use of optical lattice clocks](http://spectrum.ieee.org/aerospace/satellites/introducing-the-worlds-most-precise-clock) today which explained how such clocks allow an even more precise measurement of these changes - useful to evaluate height of water table, prospect for oil and gas, etc.
Answer: $g$ becomes $ g \approx 9.7 \frac{m}{s^2}$ at a height of about 35km, so it would be ok to use the value $9.81$ for "down to earth" problems.
The relevant wikipedia article has lots of useful information, like for example the following approximation formula for different heights:   $$  g_h=g_0\left(\frac{r_e}{r_e+h}\right)^2 $$
Where $g_h$, is the gravity measure at height $h$ above sea level; $r_e$, is the Earth's mean radius and $g_0$, is the standard gravity.
Comment: @Tobias: It's an approximation in the sense that it treats earth 1) as a point or a perfect sphere 2) not rotating, etc...
Comment: that's not an approximation, it's exact (as long as you assume earth as a point mass...)
Answer: It might also be worth mentioning that $g$ isn't even constant over the earth's surface at sea level. Depending on the mass distribution and the shape (not perfectly spherical!) of the earth, different parts of the world have different $g$.
Answer: The approximation of 9.81 m/s^2 is a generalisation.  The exact value is most likely different at a specific location, due to the distance from the centre of the earth to the point being evaluated.
The reference to "surface of the earth" is also a relative since the earth is known not to be perfectly round due to centrifugal forces making the radius greater at the equator.
Also, since the earth is spinning the same centrifugal forces have a slight influence on object mass at the evaluation point.
In metrology laboratories, the exact value for g is displayed for that exact location.
Answer: Acceleration due to gravity, g is not a universal constant like G. Its calculated by formula mentioned in previous answers. So, for a constant mass system, g depends only on r (distance between center of earth & object in problem). As r = R + h (R is radius of earth & h is height of object from surface) & R is constant, g depends mainly on height.
The relation: Increase the height, g will become less (as per formula)
The value 9.8 m/s² is valid for the object at the surface of earth (at sea level). When height is small (with respect to radius of earth), the value is slightly less than 9.8 m/s². So, this variation can be neglected for a high school etc problems. When accuracy is important (due to scientific reasons etc), the value of g can't be 9.8 m/s².
Once again, This consideration is valid only for constant mass system. Plus, for relativistic systems, the formula isn't valid with constant space & time scale.
Answer: As we go above or below the surface of earth the value of g decreases since g is inversely proportional to height


Show application on second screen even when logged off

Question: I have second screen attached to my computer and I would like to use the screen to be showing something permanently. Actually I want just one special application to be running there in full screen. The application does not require any input from neigther keyboard nor mouse.
I know I can extend the screen and move any window there. But I would like to be also able to log off and let some other user (family member) to log to that computer withot affecting what is being displayed on second screen.
I don't know if this is a good way to go but this is what I tried:
I did go under C:\Windows\system32. I removed sethc.exe (after changing nececcary file permisions). I copied cmd.exe and set the name of the copy to be sethc.exe. Now anytime the shift is pressed 5 times command prompt appears insted of Ease of access window. From that command I am able to run any aplication even when I am logged off or when the computer is locked. I can use mouse to move new windows to second screen.
The problems with this approch is that the windows on second screen are hidden with desktop background when a user logs in. They reaper when the user locks the computer again and it disapers when swiching user.
So what is the right way to do what I want? How can I make the contents of second screen permanent?
Note that I don't mind security issues, risk of breaking the computer and I even don't mind writeng c++ code and calling Win API functions or anything what will be neccecary. The application I want to run there is open source ... so in case if it is realy neccecary I would be willing to look in to its source codes and try to modify it.
Comment: The application running on second screen is VirtualBox it filters USB with second keyboard and second mouse and it appears as if we have second computer where second family member can work. That is why we don't want user swiching on first computer affect second screen with virtual computer.
Answer: It looks like your problem is: You want to run two desktops/logins concurrently on the same physical machine.
This is referred to as Multiseat desktop virtualization and has been answered here:
Dedicated mouse and keyboard for a virtual machine, is it possible?


Is there an English word meaning "the use of uncommon words"?

Question: Is there an English word meaning "the use of uncommon words" or similar?
Answer: It depends on what you mean by "uncommon". Lexiphanicism is the use of excessive terminology, while patavinity is the use of local or provincial words.
(I hope you are not just looking for slang or jargon.)
Comment: Thank you, thank you for telling me about lexiphanicism.  What a beautiful word.  I'll keep it on my desktop, and wait for an opportunity to use it.
Answer: In the category of similar words, there's sesquipedalian, meaning prone to using long words.
Answer: If the uncommon words are being used specifically to obscure meaning, then "obfuscation" might apply.
Comment: Obfuscation could be achieved with uncommon use of common words as well.
Answer: Obscurantist is related to the 'obfuscation' direction of your question.
Answer: If you mean use of words or meanings that are outdated, you might be looking for archaic.
Answer: Depending on how and why you want to use it, logorrhea (also spelled logorrhoea) might do the trick. It doesn't specifically mean using uncommon words but either a. excessive verbosity generally or b. a psychological disorder resulting in incoherent talkativeness.
As an added bonus it conjures up a little hint of a certain other word ending -rrhea.
Answer: Esoteric Writing
Esoteric (merriam-webster)
1 a : designed for or understood by the specially initiated alone
a body of esoteric legal doctrine — B. N. Cardozo
b : requiring or exhibiting knowledge that is restricted to a small group
esoteric terminology;
broadly : difficult to understand esoteric subjects
esoteric (wiktionary)
1. Understood only by a chosen few or an enlightened inner circle.
The writing in this manual is very esoteric; I need a degree in engineering just to understand it!
Answer: Perhaps you mean using uncommon words in a pompous way: pontification. To express your opinion in a pompous or dogmatic way.
Comment: Welcome to English Language & Usage! This answer would be improved by citing an external source with the definition of this word.
Answer: The prior answers appertain to the question more precisely, but I think in the right context, a word such as "ponderous," meaning laborious, dull, and excessively detailed, might be suitable;  It also carries a more literary connotation than loquacious or garrulous, which describe speaking with superabundant wordiness, droning on, or talking in a roundabout manner.


Moving on in candy crush level 35 in a laptop

Question: How can I get past level 35 without paying on a laptop please?  I have read the way of doing it on a tablet or phone, but I play via Facebook on my laptop.
Answer: It doesn't matter where you play. If you are playing with Facebook and you reach a block level, you need three of your Facebook friends help.
Ask people sending them requests to unlock your way to the next section in order to cotinue playing.
Comment: Yeah, pay, ask friends or wait till you get the option to unlock the level by playing. Not sure when this option rises but i had it several times. However you need to clear 3 levels and between these levels you have a cooldown time of 24 hours.
Answer: You would have to ask 3 friends to help you. 3 friends shouldn't be too much and the fact that Candy Crush is quite a bit popular.
Also, I heard that there is this thing called "Mystery Quests" where you do a quest every 24 hours. You'll need to do this like 3 times in total if you don't want to ask. However, this only works on iOS version I believe.
http://candy-crush-saga.wikia.com/wiki/Mystery_Quests


When did Indo-European descendants stop speaking Old English? What were the influencing factors in the shift from Old English to Modern English?

Question: There is Old English, and there is the English we speak now. When did exactly did the British (or Americans) change from speaking Old English to speaking the current form of English?
Comment: Remember there was no sudden, exact time when people "stopped speaking Old English" or any other form. Terms such as these are simply labels attached arbitrarily, a posteori, for the pure convenience of those studying the history of the language. So in this specific case, "Old English" is usually used to label a period when English had an overt case system and various other features (including several key morphological features). But there was no single point in time when these features suddenly disappeared, nor did they all evolve at the same rate at the same time.
Comment: There is a Wikipedia page on this. That's pretty general reference. The first hit on Googling "old English" is a wiki page on it. Wfaulk quoted Wikipedia--if you don't trust the internet, why choose his answer? I'm saying that you could come up with much better questions by putting in at least *some* effort.
Answer: I am just adding some dates for those not familiar with English history.
Old English (before 1066AD) is almost unreadable, with a different grammar and a few extra characters. It is closer to Danish or Dutch.

Fæder úre, ðú ðe eart on heofonum,
  Sí ðín nama gehálgod.
  Tó becume ðín rice.
  Gewurde ðín willa
  On eorþan swá swá on heofonum.
  Urne dægwhamlícan hlaf syle ús tódæg.
  And forgyf ús úre gyltas,
  Swá swá wé forgyfaþ úrum gyltendum.
  And ne gelæd ðu ús on costnunge,
  Ac álýs ús of yfele. Sóþlice.

Middle English (1100-1500AD) is almost readable, but the pronunciation is very different.

Oure fadir that art in heuenes,
  halewid be thi name;
  thi kyngdoom come to;
  be thi wille don, in erthe as in heuene.
  Yyue to vs this dai oure breed ouer othir substaunce,
  and foryyue to vs oure dettis, as we foryyuen to oure dettouris;
  and lede vs not in to temptacioun, but delyuere vs fro yuel. Amen.

Then, Early Modern English starts around 1600; this still sounds old fashioned, but is recognisable if you read the King James bible or Shakespeare.

Our Father which art in heaven,
  Hallowed be thy name.
  Thy kingdom come,
  Thy will be done in earth, as it is in heaven.
  Give us this day our daily bread.
  And forgive us our debts, as we forgive our debtors.
  And lead us not into temptation, but deliver us from evil:
  For thine is the kingdom, and the power, and the glory, for ever. Amen.
Comment: They don't seem to be translation of each other, for example there is no bit about "thine is the kingdom" in the second text.
Comment: @Louis Rhys : The last line is an addition used in some English speaking churches but not part of the original biblical text.  The other texts here don't have it.
Comment: I assumed all three were translated from a Latin original. Is that not true?
Comment: Or Greek (at least for the king James), but all are from sources written in 'English' at the time. The extra line in the KJB is in protestant bible translations but not Catholic ones, there weren't official catholic bibles in English at the time
Comment: And of course, postmodern English: "Yo big daddy in da sky yo namez like totes kewl, ya gots da richez, we gon do what u want up n down, mang, but like gimme some food", and so on.
Comment: @JanusBahsJacquet Lol
Answer: There are considered to be three major eras of English: Old English, Middle English, and Modern English.  Old English is a very different language, complete with a different alphabet.  Middle English emerged after the Norman conquest of England with influence from French and other continental languages.  Modern English emerged a few hundred years later with the Great Vowel Shift.  The first few hundred years of Modern English are referred to as Early Modern English, which is well represented in the works of Shakespeare.  The current version of English started to coalesce around 1700.
I could go on, but: http://en.wikipedia.org/wiki/History_of_the_English_language
Comment: Old English didn't always have a different alphabet. They switched from runes to the Roman alphabet (with the additional letters æ, ð, þ, ƿ) some time in the 9th century.
Comment: I didn't mean that the Old English alphabet and the Modern English alphabet don't share any letters, just that the set of letters is different.
Comment: They kept using some of the Old English letters for a while in Middle English.
Comment: I didn't say they didn't.


iPhone support Multiple Languages

Question: In my project, I need to support the Korean language. How is it possible - can anyone explain briefly with example, whether it is possible or not?
Comment: Duplicate: http://stackoverflow.com/questions/898308/how-simplify-iphone-localization
Comment: Also why not just do this? Plenty of information: http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=iphone+localization
Answer: It's certainly possible.
You just tell Xcode to add a Korean localization to any of your application's localizable resources that need to change for that language.  (Localizable resources include strings files, xib files, and potentially any images containing text.)  Xcode will create a copy of your existing English resource, which you can modify and replace with a Korean-language equivalent.
Then when your application is run on a device with Korean set as its preferred language, iOS will automatically use the Korean resources intead of the English ones to present the application's user interface.  If you have used good localization code practices (such as using NSLocalizedString to reference strings you present in the user interface) you shouldn't have to change any of your code to support different languages.
Answer: Check this guide on how to localize your apps for iPhone: http://www.icanlocalize.com/site/tutorials/iphone-applications-localization-guide/

iPhone support Multiple Languages


Corner Radius for Hover Rectangle

Question: How can I set something like corner radius for the default rectangle which appears when an item is hovered?
Answer: Your question is a bit non-specific, which is why people are down voting you.
If you're talking about a Flex Button; the rounded corners on roll-over are part of an FXG asset; which is not changed by use of the cornerRadius style.  At least in the mobile skin; I imagine the desktop skin is similar.
We put together a mobile skin that will create a square button; and something that should have been trivial took a few days.  It's available as part of the Flextras Mobile Flex Components Package and usable for free.
Here is a sample we put together to show the button differences.
You can use in a non-mobile project at your own risk, though.
Answer: Trival in Flex3.
You did not specify what you are styling so this is how I would style a button
<code><mx:Style>
  .roundedbtn{
    cornerRadius: 10;
  }
</mx:Style>

<mx:Button id='btn' styleName='mybtnnormal />

// or in ActionScript
btn.styleName = 'roundedbtn';

// or without the styles
<mx:Button cornerRadius="10" />
</code>

Corner Radius for Hover Rectangle


"How many" separation axioms are there?

Question: In my topology class, we've covered a number of separation axioms; specifically, we've covered the chain normal $\implies$ completely regular $\implies$ regular $\implies$ Hausdorff $\implies$ $T_1$. I also know that these axioms weren't discovered in order, resulting in situations like having $T_{2\frac12}$ or $T_{3\frac12}$. My question is, are the axioms I've listed (and the other common ones) the "only" separation axioms, or are there more that aren't as useful, and so aren't as commonly mentioned? Do we know how many axioms could exist, or do we know if we've found all of them?
Comment: Counterexamples in Topology is a great book that spends time on these.
Comment: https://en.wikipedia.org/wiki/Separation_axiom?wprov=sfti1 The Wikipedia page on separation axioms is a good start.
Answer: "Separation axiom" is an informal notion, not something that's precisely defined. One could write down arbitrarily many logical conditions that distinguish topologies into finer and finer classes (until each class is not provably larger than a single homeomorphism class), but we probably wouldn't consider all these conditions to be "about separation" or to be useful in proving other properties of interest.
Answer: I would say there is ton of separation axioms, but most of them are not important. Also, they do not form a mere collection or a chain of properties – they can be organized in various meaningful ways. Let me illustrate this on some examples.
One can build a preliminary version of a "periodic table" of separation axioms by considering two aspects: what we are separating (points, points and closed sets, closed sets) and how we are separating (by disjoint neighborhoods, by neighborhoods with disjoint closure, by function, …). I personally call the groups of axioms corresponding to what we are separationg by "tier 2, tier 3, tier 4" axioms. Tier 2 includes $T_2$/Hausdorff, $T_{2\frac{1}{2}}$/Urysohn, functionally Hausdorff. The corresponding axioms in tier 3 are $T_3$/regular and $T_{3\frac{1}{2}}$/completely regular. Note that the separation by neighborhoods and the separation by closed neighborhoods collapsed here. Tier 4 includes $T_4$/normal – here the three ways of separation collapsed.
Let's come back to $T_0$ and $T_1$. I put them to tier 1. Note that applying $T_0$ or $T_1$ separation to closed sets and $T_0$ separation to a point and a closed set is trivial. But the $T_1$ separation applied to a point and a closed set reads as follows: for every $x ∉ F$ there is $U$ such that $x ∉ U ⊇ F$, or equivalently $x ∈ \overline{\{y\}}$ iff $y ∈ \overline{\{x\}}$. This axiom is called symmetry, and one may observe that $T_1$ is exactly the conjunction of $T_0$ and symmetry. Let's put it to tier 1 as well.
Note that the "bare" axioms from tier 3 do not imply the corresponding axioms in tier 2 since tier 2 implies $T_1$. But since tier 3 implies symmetry, it is enough to add $T_0$ to have the implication. So every axiom in tier 3 has the bare and the $T_0$ variant. This is the distinction between regular and $T_3$ (but both competing conventions of how to assign the names to the properties are used). Similarly for the implication from tier 4 to tier 3, it is enough to add symmetry, and for tier 4 $\implies$ tier 2 we need to add $T_1$. (Note that this means that there are four variants of normality: bare normality, symmetric normality, $T_0$ normality, and $T_1$ normality. But practically this is not of much importance.)
There are more ways how to enrich our table of separation axioms.
Essentially, all separation axioms are stable under sums and none are stable under quotients. Tiers 1, 2, 3 are also stable under subspaces and products, but this is not the case for tier 4. So we may consider productively normal and heredirily normal (also called completely normal or $T_5$).
Or we may consider more means of separation, e.g. the perfect separation: sets $A, B ⊆ X$ are perfectly separated if there is a continuous map $f: X \to [0, 1]$ such that $A = f^{-1}(0)$ and $B = f^{-1}(1)$. The tier 4 variant is called perfect normality or $T_6$ (as it turns out, the property is hereditary, and so implies $T_5$). One may also consider perfectly Hausdorff and pefectly regular (although in the latter case, one has to be careful: if we demand perfectness on the closed set, we already obtain $T_6$, and if we demand it on the point, we obtain "just" the conjunction of complete normality and perfect Hausdorffness). Another mean is separation by a clopen set (stronger than functional separation, but incomparable with perfect separation) – we obtain totally separated, zero-dimensional, and strongly zero-dimensional/ultranormal. I think I've even once seen called them $D_2$, $D_3$, $D_4$. $D_1$ would be hereditarily disconnected, even though it doesn't exactly fit the scheme (but it implies $T_1$). Also note that totally disconnected is inconsitently used both for $D_1$ and $D_2$.
To answer your question, note that picking a space $S$ and its subsets $S_0, S_1$, we may define the corresponding mean of separation: $A, B ⊆ X$ are $(S, S_0, S_1)$-separated is there is a continuous map $f:X \to S$ such that $f[A] ⊆ S_0$ and $f[B] ⊆ S_1$. So in theory, you can pick your favourite space and sets and make your own separation axiom. Note that the standard axioms (but using perfect separation) are of this form.
There are much more things I didn't mention: collectionwise Hausdorffness and normality related to paracompactness, axioms relative to other axioms (preregularity is $T_2/T_0$, you can substract $T_0$ from any property), relative axioms for subspaces (two points in $X ⊆ Y$ separated by disjoint neighborhoods in $Y$), very weak axioms like $T_{\frac{1}{2}}$ and $T_D$, point-free axioms like subfitness, etc.

"How many" separation axioms are there?


usage of "is" and "do"

Question: Why do you say, "A bus doesn't travel on water"  but you then say, "Garbage collection isn't a profession."  What are the rules for when to use "do" (doesn't) and when to use "is" (isn't)?
Answer: I'll answer for the verbs on their own.  For verb phrases, that can become pretty complicated and seems to be beyond what you are asking.
The verb is usually acts to declare existence or (perhaps partial) equivalence:

They said it wasn't there, but it is!
He is just like his father.

The verb do usually specifies an action.

He did it!
I do pottery; my girlfriend does calligraphy.

Thus:

A bus doesn't travel on water. [action]
Garbage collection isn't a profession. [equivalence]
The bus is traveling on water! [sigh, why I'm avoiding verb phrases  One could argue that "traveling on water" is a state of being, but I don't want to go there.]
Answer: In Early Modern English, all verbs formed negatives by simply postposing "not":

A coach goes not on water.
Waste collection is not a profession.

In modern English, only auxiliaries (have, be, can, may, will, etc) form it in this way:

I will not (won't) go.
You can not (cannot/can't) go.
He has not (hasn't) gone.

If there is no auxiliary, then except for 'be' and sometimes 'have', you need to add the otherwise optional auxiliary 'do'.
So

A bus travels on water = A bus does travel on water.

In the positive, the "do/does" is optional, and we only use it for contrast or emphasis; but in the negative

A bus does not travel on water.

it is required.
The exception is "be":

Garbage collection is a profession.
Garbed collection is not (isn't) a profession.

In most varieties of English "doesn't be" is not grammatical.
The other partial exception is "have":
When it is an auxiliary itself, it cannot take "do":

I have seen him.
I haven't seen him (not "I don't have seen him").

When it is a full verb, both are possible:

I have a car.

In the negative:

I haven't a car.

or

I don't have a car.

Many people would regard the first form as old-fashioned, especially American speakers. It's more common in British English, but even here, it is usually augmented by "got": "I haven't got a car".

usage of "is" and "do"


How much does a legal license cost?

Question: The Core rulebook covers buying fake licenses but is there any mention in RAW on how much a legal license costs?
Answer: No, there's no RAW mention of cost.
This isn't surprising though: Shadowrunners generally don't use legal licenses because of the overbearing bureaucratic requirements they place on the character, as well as the ease with which they allow authorities to track you. Page 68 of the core book, for example, mentions that magic licenses give permission for authorities to search the character's home at any time. This is compounded with the fact that this license will be tied to the character's fake SIN, which will likely draw scrutiny from the authorities.
Answer: The only reference I could see to legal licenses said "pay a small fee".  It seems to me that this is an arbitrary GM decisions for the various locations if you want to force them to pay for something that only matters once in however many in game years it's required for renewal.  If you want, you can say that this sort of thing would be factored into their Lifestyle costs, since it's on the up and up
Answer: The cost of a legal license should be covered by your lifestyle, as that includes stuff like rent and taxes.
Besides that, you can obviously come up with something cool as a GM to get it into the game. Something like: "You need to do this run to delete the tax requirements of your license."
Answer: There is no given cost in Raw as far as I'm aware. The only thing that you could do to get close would be to take the "Buying The Basics" (p.252) section out of Run Faster and then do your research how much such a license would cost today and then try to convert with the help of the tables out of said section. Of course that does not work for cyberware or magic but it might give you a direction. DocRattie has a good point that most legal licenses would be out of your lifestyle or your past so you would not need to pay for it at all. But i would be careful for just handing out licenses without a good justification. In my games for example everyone who has a real sin also has a real driving license since I would assume most people would have one. But I wouldn't give licenses for things like weapons, cyberware or magic without a very good reason. For Example: I had a player who asked if he could have a real magic license with his sin to which I asked him how he avoided being, possibly forcefully, hired by a corporation since they are always looking for new mages and a full mage with magic 6 is a promising asset. Which was basically asking "I can give you your magic license but why don't you take the wanted quality for that?". Always keep the old Shadowrun Slogan in your head: "Everything has a price."
Answer: Both lifestyles and licenses are attached to a SIN (System Identification Number, your personal ID), fake or not. The core rulebook (p. 367) defines Licenses like this:

Licenses
A basic SIN allows a person to function within the most basic parameters of the law. If a person wants to operate outside these very confining strictures, they need special permission in the form of a license. What actions or items require a license vary widely with the laws of the country, but there are some common similarities shown in the Common Licenses Table below. Acquiring a license (legally) is, again, dependent on the laws of the country. For the most part, acquiring a license involves making an application, paying some sort of fee, a SIN check, and possibly passing one or more certification, testing, or training programs. The exact details of acquiring a license are left up to the gamemaster, but government bureaucracies are notoriously slow and frustrating.

And later in the book we are told the differences between legal and illegal licenses and permits:

Licenses and permits can be obtained through legal channels, as long as you're a solid citizen with a legal SIN—of course, that goes for shadowrunners with fake SINs acquiring fake licenses, too. A fake license is connected to a fake SIN, and if one of them is exposed, the other becomes worthless.

This means that a license, fake or not, is as good as the SIN that it is connected to. So the cost of such an illegal license shouldn't be very different from a legal license because it really doesn't matter if your SIN has a bad rating that can easily be verified by the cops.
You do not want a legal SIN or licenses if you are a shadowrunner
Ultimately, you do not want to buy legal licenses if you are going to use it for illegal actions, you are bound to get caught sooner or later and you won't be able to discard your SIN, you will have to hack into government security and burn your legal SIN from the system, which could be extremely difficult.
If you use your real SIN when you meet with a Mr. Johnson, there's a good chance that he now knows exactly who you are and where to find you if things go badly or he decides to double cross you (something that never happens in shadowrun). If you practice any illegal actions and they research on the public grid for camera feed or traffic, they will eventually trace it back to you. If you leave a drop of your blood on a run, they might be able to trace your SIN through your DNA.
If you happen to pay for your apartment's rent using your legal SIN and do something illegal that puts your face on Knight Errant's database of wanted criminals, eventually their investigators will cross the data and find someone who looks a lot like you, and guess what, they are the same person!
So, even if you wanted to use a legal SIN to do legal stuff, like take a cab, buy food, go to a cafe, you do not want to have your DNA, fingerprints, retina, and especially your face registered on official government databases. It's a security flaw beyond imagination to your character and you are bound to get caught sooner or later if you do that.
Answer: I struck a deal with my GM for my concealed Tiffani Needlers, 500 nuyen for the gun license, 500 for concealed carry and 200 for the license to buy munitions for it. Everything is restricted about the gun, they did cost me around 2600 nuyens and 2200 for legal papers, for both. The reason we struck that deal is that I am playing a face with a "day job" for Horizon and a legal life, so I can't just risk going around with illegal things.
Comment: Hi, welcome to the site. Unfortunately, your answer has attracted some downvotes—we're pretty strict about answering the question that was asked. This question is specifically asking about the rules of the game, so the agreement that you and your GM came to doesn't quite answer the question. If your answer is that there *are no* rules for this, so people must come to a deal with the GM and you want to suggest the one you went with, that's fine—then you have answered the question (there are no rules) *and* provided extra useful information. But you can't skip the first part.

How much does a legal license cost?


Taking care of mint with bent stems

Question: A few of my mint plant's stems are bent, some by almost 90 degrees (this isn't from disease, it came about as a result of rough treatment). I tried bending the stems back, but they go back to being bent in a few seconds. Should I leave the plant be and allow it to heal? Or is this a more serious condition, and should I cut off the stem below the bend with a scissor?
Comment: Pictures, please?
Comment: Is it in a pot or in the ground? And as requested, yes, photo please
Answer: Most of the mint plant will recover.
Strong wind and footfall is common, so they are evolved to recover. It will take few days.

Taking care of mint with bent stems


How OpenGL stores commands internally?

Question: It is said ihat OpenGl driver stores OpenGL commands in some fifo queue
buffer then it executes it. I am urging to know how it is stored. It is some array containing data records and offsets, enums as command ty;pes or something different? I know that probably this is not standarized so it can be (maybe) done in different ways but I am courious about at least some, one real implementation. How it is/can be done?
Answer: If you really wanted to know, you'd have to go into nVidia or ATI driver code, and that's proprietary. But you can always check the Mesa GL source code.

How OpenGL stores commands internally?


How come I got last month's field research breakthrough encounter?

Question: This morning (September 1st) I completed my 7th field research task and I was expecting to get an Entei. Instead I got a Raikou. I thought that at the beginning of each month the pokemons switched to the new one. How come this happened?
Answer: According to https://www.eurogamer.net/articles/2018-08-21-pokemon-go-field-research-special-research-quests-research-breakthroughs-5392

So, you can complete the task, but just don't claim the reward for that task before 1pm PST / 9pm UK time of the first of the month, as doing so will activate the arrival of the Special Research reward at the top of the screen.
If it's before then, it'll be the reward for the month before (so in April, this was Moltres). Wait until after, it'll be the next month's (so in May, this was Zapdos).
To clarify further, this is when you complete the task, not open it. Even if you then open it after the change, it'll be the prior month's Pokémon. To be safe, wait until it's the new month if you want to get the latest creature.

So effectively, you completed your 7th task too soon. If you wanted an Entei, you should have waited until after the rollover moment.
Comment: That explains it.  I took the reward at 7:00 AM EST.  I should have waited until later in the afternoon.
Answer: If you read the news post announcing the new encounter, it has a date and time that the new pokemon will be available. In this case, it starts at 1pm Pacific Time.


Lasso equivalent estimator with differenziable penalty function

Question: The lasso estimator is define as $argmin_{\beta}~ MSE +\lambda \parallel \beta\parallel_1$ I am wondering if there is an alternative penalty function that is $C^\infty$ and that preserves the sparsity of the lasso estimator.
Comment: $C$ is the regularity. It means that the penalty function can be derived infinite time.  http://mathworld.wolfram.com/C-InfinityFunction.html
Comment: The problem is not the minimization. I want to train a neural network with the extreme learning machine method. In order to do that I need a $C^\infty$  functions on the nodes. And I want to use a lasso like function on the nodes.
Answer: This is not possible. It's exactly the nondifferentiability at zero that induces sparsity.
Indeed, by the KKT conditions, we see that any $\hat\beta = \arg\min_\beta \mathrm{MSE} + \lambda \mathrm{pen}(\beta)$ maybe rewritten as $$\hat\beta = \arg\min_{\beta \, : \, \mathrm{pen}(\beta) \leq C} \mathrm{MSE}$$ for some constant $C$. (Note that this direction holds even if the penalty $\mathrm{pen}$ is nonconvex.) Since sparsity is induced by the level sets $\{\beta \, : \, \mathrm{pen}(\beta) = C\}$ having "corners" on the coordinate axes, all we need to do is determine whether a differentiable function can have "corners" in its level sets. However, by the implicit function theorem, we know that this isn't possible.


Old pulp sci-fi series from the seventies with many books

Question: Back in the late seventies I began collecting a sci-fi series. There were just a ton of them, and they were all pretty standard pulp sci-fi hero stuff, all about the same hero and, I believe, by the same author... someone who later became famous and wrote these under a pseudonym. My mom chucked the books while I was overseas, and I can't remember what they were. I thought it was the Lucky Star series by Asimov, but those were only six books.
Comment: Hi, we could really do with a bit more detail. Can you describe the plots of any books? Appearance of central characters, bad guys? There are a lot of series to choose from. That said I'd suggest starting by taking a look at the Perry Rhodan series. Long running pulp fiction as you describe... also take a look at the guidelines on how to write a clear question... https://scifi.stackexchange.com/tour  good luck, hope you find what you re after.
Comment: @vaugnOhlman Nice!  Glad you got an answer.  Deleting my Doc Savage suggestion.
Comment: Hi, welcome to SF&F!  This is a bit thin on detail; do you recall any of the covers, any names or plot details?  From what you've said here I can think of 2 possibilities off the top of my head:  E.C. Tubb's *Dumarest* series ran over 30 books from the 60s through the 80s and Perry Rhodan ran to over 100 issues in English translation through the 70s.
Comment: Well, for all of those questions, I still got my answer! Thanks!! It was the Perry Rhodan series!!!
Answer: I suggested this in the comments as wild guess as the description was "pulp fiction, long-running from the 1970's" which put in my mind the Perry Rhodan series. Turned out to be correct as mentioned by the person asking, even though this series started in the 1960's.
Comment: Thanks. I really didn't have much to go on, but your answer was perfect.
Comment: Well, my comment 'there were just a ton of them' definitely fits, as it is the largest series in existence per the wikipedia.
Comment: Most recent release - 2019 - This series is still going?  That has to be some kind of record...
Comment: @DarrelHoffman: It definitely is. Most recent issue is #3071, "Xirashos Tiefen", released 2020-06-26. The next one is due tomorrow. One per week. Since 1961. It *is* pulp SciFi, mind you, some of the issues are pretty crap to be honest and continuity was not always perfect, but the length of the run makes it special in its very own way. If you pick up a current issue and just start reading, you will have *no* idea what they are talking about, as the in-universe story had been built continuously...
Comment: glad to be of service. Have to admit it was simply dumb luck on my part!
Answer: As confirmed by the OP in comments, this was the Perry Rhodan series.
Wikipedia says of the series:

The first 126 novels (plus five novels of the spinoff series Atlan) were translated into English and published by Ace Books between 1969 and 1978

And describes the basic plot as:

The story line starts in 1971 with the first manned moon landing by U.S. Space Force Major Perry Rhodan and his crew, who discover a marooned extraterrestrial space ship from the (fictional) planet Arkon in the (real) M13 cluster. Appropriating the Arkonide technology, they proceed to unify Terra and carve out a place for humanity in the galaxy and the cosmos. (The concepts for two of the technical accomplishments that enable them to do so—positronic brains and starship drives for near-instantaneous hyperspatial translation—are direct adoptions from Isaac Asimov's science fiction universe.)
As the series progresses, major characters, including the title character, are granted relative immortality. It is relative in the sense that they are immune to age and disease, but could suffer a violent death. The story continues over the course of millennia, including flashbacks thousands and even millions of years into the past, and the scope widens to encompass other galaxies, extremely remote parts of space, parallel universes and weirder cosmic structures, time travel, paranormal powers, weird/cute/aggressive aliens and bodyless entities (some with sheer god-like powers).

The first few English translations appeared with these covers:
Comment: That's another series where I would go to the bookstore, and all they'd have was like #5, #17, #23... so I never bought any.
Comment: I was lucky in my book store. It was money I lacked.


brakes have been bled still go to floor

Question: I have already bled brakes and changed the master cylinder. What would be the next step to try to fix the brakes. The brakes still go to the floor.
Comment: What year/make/model of vehicle is this? *How* did you go about bleeding the brakes (step-by-step)? Did you bench bleed the master?
Comment: If you pump the master cylinder does the fluid level drop?
Comment: When you say it goes to the floor, does it do that without pressing the brake pedal, or only when you press it?
Comment: Are you losing fluid?  What was the original symptom that caused you to need to change the master and bleed the system?
Comment: Does the vehicle have ABS?  If so, did you bleed the ABS pump?
Comment: Does the car come to a stop when you press the brakes?
Answer: Turn the car on and press the brake to the floor.  When you release the brake-- listen for a kind of hollow wind sucking in from under the dash.  If you hear a hollow sucking noise it means your Power Brake Booster is failed and you need to replace your Power Brake Booster.  The noise can be faint  or close to none at all but if your pedal is still going to floor after changing the Master Cylinder then it is likely that the Power Booster is gone.
Comment: I don't think that would cause the brakes to "go to the floor." The brake booster simply assists in pressing the pedal by using a vacuum line to increase the driver's effective force against the pedal. If the booster broke, it would increase the effort required to brake, but not cause a loss of pedal response. Then again, I could be wrong. Less experience here.
Comment: A vacuum leak in one of the hoses can cause the brake booster to not function properly. Inspect all vacuum lines for leaks and replace them if they are defective. My old Mercury Mystique had an issue with the vacuum line. It was constantly rubbing against the firewall and wore a hole right through it.

brakes have been bled still go to floor


Magento 1.9 multiple users in admin

Question: I have a few questions about Magento admin/backoffice performance.
How well does Magento handle multiple users in the backoffice editing, removing and inserting products? What about multiple users uploading images to different products?
In such a scenario, is it acceptable to set reindexing on automatic?
My guess is "Of course not!" but I'd like to hear somebody with more experience than me.
Answer: All your indexes should be on "Manual", especially if you are processing major changes on your catalogue. Only the "save" action on a product or a category can be very resource intensive, but you will notice a huge improvement by having your indexes on Manual.
Also, check all your third party extensions. Some of them could have observers on product/category saves that could cause issues for your store.
Answer: If you could post more details about your hosting environment it could help answer the question. Generally speaking, Magento can handle multiple users just fine. As mentioned you'll probably want to set all indexes to manual then only update them manually, on a cron, or with a 3rd party indexing extension.
If you're concerned or notice it will affect traffic for your visitors you can actually put the admin on a separate server so it doesn't affect anything else. Basically you just need to copy all the files to another server (or share the files using NFS or something) and be sure your local.xml uses the IP for the database server (if you leave it as localhost the admin server will look for the DB on its server rather than the primary server).
With Magento your performance bottleneck will almost always come from PHP. The actual queries to the database for updating or deleting products etc. are minimal. There are a few things you can do to optimize your primary server to try and reduce the load of admin activity and thus handle more traffic. There is a LOT of material available on this throughout the inter-webs but here are some easy ones:

Use the Magento compiler (about Magento compilation)
Have your host setup an opcode cache (APC, eAccelerator, etc.)
Increase the number of cores or threads on your server.
Install a full page cache (this won't speed up the back end but could reduce the load on the server on the front-end thus freeing up resources for admin activities)

Again, your primary bottleneck is PHP. So you either need to make it more efficient through caching, better hardware, etc. or be lazy and add more hardware to handle the increased workload.

Magento 1.9 multiple users in admin


Imitate CSS3 transition in IE?

Question: I'm using a combination of rules to achieve the CSS3 transition rule in as cross-browser compatible a way as possible: I'm using transition, -webkit-transition, -moz-transition, and -o-transition.
Is there a similar -ms-transition property for any version of Internet Explorer? Is there a proprietary filter for older versions of IE, similar to how the following rules work for opacity in IE 6-8?
/* IE 8 */
-ms-filter: "progid:DXImageTransform.Microsoft. Alpha(Opacity=50)";
/* IE 5-7 */
filter: alpha(opacity=50);

Comment: Short answer, no. You'll have to use javascript in some form to achieve the same effect in IE9. My understanding is IE10 will have CSS3 transitions.
Answer: There isn't any kind of transition effect in older versions of IE.
The only way that I know of to get anything close to it is to use JQuery's fadeIn() and fadeOut() methods, which do actually work in all versions of IE.
However, I should caution that they still fall foul of IE's notoriously poor opacity handling. JQuery's fade effects can have some weird glitches when used with IE6-8, especially if you're fading a block which contains graphics.
If you decide to try it, the code is dead simple. Simply include JQuery in your headers, and then:
$('#myelement').fadeIn();

in the appropriate place.
See the JQuery FadeIn manual page for further information.
Of course, this would be instead of any CSS transition effect; it's all done through Javascript, and you'd probably need to throw away your CSS3 transitions, or it'll clash with the JQuery effects. But if you want it to work with IE, that's the price you'll pay.
And as I say, watch out for the glitches. Test it, and see how it looks for you.
It's the only way to do it, so if you really need a transition effect in IE, that's what you'll need to do, but be prepared to accept that it may not look all that good.
Other Javascript libraries such as Mootools or Dojo may have similar effects which you could also try, but I would imagine if they do have it, they'd suffer from the same issues.
Comment: Thanks for this. I think I'm going to stick with CSS3 transitions as a progressive enhancement tool - they're not crucial to the site.
Answer: I ran into this while researching the same question: http://www.useragentman.com/blog/csssandpaper-a-css3-javascript-library/
I also found a library called move.js, which can be used alongside CSS3 transitions: https://github.com/visionmedia/move.js
Hope this helps.
Answer: IE10 will have CSS3 transitions, until then you will have to use javascript.
Answer: CSS3 transition rule and other CSS3 rules works fine in IE 10. Prefix "-ms-" is no longer required, but will still be recognized. To ensure compatibility in the future, applications using the Microsoft vendor prefix with transition properties should be updated accordingly. So, update your CSS code, add line with rule, without any prefix.
Answer: for IE < 10 you can try either one of those
I have not tried personally but they look promising
http://www.useragentman.com/blog/csssandpaper-a-css3-javascript-library/ or
http://addyosmani.com/blog/css3transitions-jquery/ (broken link)
Comment: it's not good practice to just paste the link - visit http://meta.stackoverflow.com/tags/link-only-answers/info

Imitate CSS3 transition in IE?


Can a person benefit from damaging terrorists?

Question: A few months ago Islamic Revolutionary Guard Corps (Sepaah Pasdaran) of Iran was designated as a terrorist organization by USA. As a person who lives in Iran I was wondering if I damage Islamic Revolutionary Guard Corps in anyway, say damaging their personnel or their properties, can I be protected by USA? For example can I come to USA as a refugee.
Comment: The Kurdish translators embedded with the US Forces in Iraq weren't given any refugee clearance to come to the US. Don't stick your head out.
Comment: I think this would be a question for the consulate, but I'm pretty sure that the answer is "no", personal fighting against the IRGC isn't an "in" to refugee immigration, probably quite the opposite.
Comment: https://www.nbcnews.com/news/world/only-2-iraqi-translators-who-worked-u-s-troops-got-n1035661
Answer: The basic requirement for being granted refugee status is demonstrating that you have been persecuted or have a well-founded fear that you will be persecuted, and is connected to race, religion, nationality, social group membership or political opinion (there are other grounds such as reunification with close family in the US). What you describe doesn't clearly fill the bill (was this just youthful vandalism?). A pattern of public politically dangerous statements would probably be necessary – there isn't a clear objective legal statement of what constitutes evidence that you have a reasonable fear of persecution.
A prerequisite is a referral from the U.S. Refugee Admissions Program. The usual first step is apply at the US embassy, but that may be a bit difficult (but you might exit to another country).


PHP: Best way to iterate two parallel arrays?

Question: As seen in this other answer, there are several ways to iterate two same-sized arrays simultaneously; however, all of the methods have a rather significant pitfall.  Here are some of the caveats with the methods suggested:

You can't use FALSE values in one of the arrays.
You can only use scalar values in one of the arrays.
You must use numerically indexed arrays.
Both arrays must share the same keys.
Etc.

My question is - is there a method for doing this which doesn't suffer from any of these (or other) significant caveats?
Bear in mind that I'm simply asking this out of curiosity; I have no use-case in mind, nor do I even know if such a case actually exists or would be useful/practical in a real-world scenario.  However, here is some example data:
$arr1 = [ 'a' => 1, 'b' => FALSE, 'c' => new DateTime() ];
$arr2 = [ 'foo', TRUE, 7 ];

Comment: What's wrong with beefsack's answer to that question? Seems like it would work regardless of the content or structure of the arrays.
Comment: it would not work with because  `'b' => FALSE` @nickb
Comment: @Baba - No, [it works with `'b' => false`](http://codepad.viper-7.com/nNZuNj).
Answer: You can use a MultipleIterator:
$iterator = new MultipleIterator;
$iterator->attachIterator(new ArrayIterator($array1));
$iterator->attachIterator(new ArrayIterator($array2));

foreach ($iterator as $values) {
    var_dump($values[0], $values[1]);
}

You can find more examples concerning the various options in the docs.
Answer: As of PHP 5.5 you can do this:
foreach (array_map(null, $array1, $array2) as list($item1, $item2))
{
    var_dump($item1);
    var_dump($item2);
}

https://www.php.net/manual/en/control-structures.foreach.php#control-structures.foreach.list
Answer: <?php

$arr1 = array( 'a' => 1, 'b' => FALSE, 'c' => new DateTime() );
$arr2 = array( 'foo', TRUE, 7, 5 );

reset($arr1);
reset($arr2);

while ( (list($key, $val) = each($arr1))
    && (list($key2, $val2) = each($arr2))
) {
    var_dump($val,$val2);
    // or whatever you wanted to do with them
}

http://www.php.net/manual/en/function.each.php
Comment: your script has error and would not work if total arrays in `$arr2` > `$arr1` ... correct it before they start voting you down
Comment: @Baba I had find a server to test, because I didn't really test it the first go. It wasn't a problem with the length of the arrays (from what I could tell), but there were problems (like I don't have 5.4 on the server I tested on), so thanks for pointing that out.


Key Distribution vs Key Management?

Question: What exactly is the difference between "Key Distribution" and "Key Management"?
Answer: Key Distribution. Key distribution is, well, the process of distributing (cryptographic) keys to different parties. Usually this involves mechanisms which are considered "out-of-band", i.e. mechanisms that don't use the later communication channel for the transport of keys. Alternatively key distribution can be done by relying the distribution of new keys upon the safe distribution of old keys, that's what a KDC is doing.

Key management. Key management is, well, the process of managing (cryptographic) keys, the usual meaning implies management over the whole lifetime of the key. Key distribution is a part of key management, but it also includes key generation, key escrow (for backup purposes), key deletion, key revokation, key usage and key trust management. If you want to learn more about key management, the Handbook of Applied Cryptography has an entire chapter devoted to it (PDF).
Comment: Please note: These definitions are mine and may not 100% align with other definitions you may come across.

Key Distribution vs Key Management?


Can I use an external JSP tag library with XPages?

Question: I would like to use a JSP tag library supplied by a different (not IBM) software company with XPages. Is this possible? If you can, how can I associate the new jar file to the tag library namespace so it would be recognized?
Answer: I highly doubt it. In all likelihood, the library would have to be converted to a JSF component library. There are some similarities between the syntax used to define each, but the primary difference is that JSP uses a single Java class known as a tag handler to both define the nature of an object (i.e. its properties) and to send markup to the browser that is representative of the object state. In contrast, JSF uses two: the component and the renderer. The component is just the identity of the object; the renderer handles the markup generation. A subtler difference is that JSP tag libraries are by convention stored as .tld files, which are then referenced from within the JSP page; XPages expect components to be defined in .xsp-config files and renderers to be defined in faces-config.xml files. If a component is properly defined (even if its corresponding renderer is not), Designer will recognize the prefix:tag syntax on any page at build time and generate the appropriate Java code. Otherwise, Designer rejects the tag as invalid and refuses to build the project.
In summary, JSP tag libraries are, to my knowledge, not natively consumable in XPage apps, but can be used as a basis for creating JSF component libraries that can be consumed in any XPage app.
Comment: The interesting question: There are [several JSF libraries](http://www.jsfmatrix.net/) out there. Could we use those?


How to install packages onto a flash drive

Question: I have a computer with Ubuntu Linux, and I have no more room on PC, so I have a flash drive that I want to install packages onto, is there any way to install a package onto a flash drive?
Answer: Most pre-built packages (particularly in Debian-based systems) are not relocatable.  You could build your own packages to suit your choice of directory layout.  Lacking that, you have what's built.  Those go into a limited set of directories.
You could mount the flash drive in your filesystem where the machine expects to own those files, e.g., /usr/bin, but that would confuse things when you took the drive out.  It's best not to do that.
Conceivably you could have packages which install completely under /opt, and mount the flash drive there.  It all depends on what packages you have (or build).
When you mount a filesystem on a mountpoint, the existing contents of the directory on the mountpoint are hidden.

You might find that expedient, e.g., if you wanted to make /var much larger by mounting a large filesystem there, it would be inconvenient to delete all of the existing files under /var before preparing to reboot with the large filesystem mounted.
In the case of /opt (or other useful places to put programs), you might decide to use rsync to copy the existing files from the mountpoint to the new filesystem and leave a copy of those intact, e.g., for system maintenance.
Doing that does have the drawback that the hidden files would not be updated when you upgrade your system.  Also, library upgrades may cause those hidden files to stop working properly—making them less useful in system maintenance.
For that reason, it is usually preferable to install your add-on files in a directory which is not used for packages managed by the system.
Comment: So, If i want to mount a drive elsewhere, do I just use `mount` in the directory that I want it to mount in?


Is there a theoretical size limit by ferromagnetic materials?

Question: Hemoglobin contains 4 iron atoms and oxidized hemoglobin is diamagnetic.1 On the other hand iron-oxide nano particles can be ferromagnetic.2 I did not manage to find any reference about the size limit where this property disappears but obviously at some point it does. By nanoparticles my impression that there is a size limit due to the production technology and not because the particle size reaches a theoretical limit. Can somebody explain why this property disappears and in theory what is the minimum size where it is present? A hemoglobin contains 4 iron atoms one in each heme ring. Would it be ferromagnetic if these iron atoms were closer to each other?
Answer: Iron is not ferromagnetic in oxyhemoglobin because of its bonding which ends up giving it a filled shell. This has nothing to do with number of iron atoms.
You can see ferromagnetism in very small nanoparticles of iron, but eventually if you look at a small enough nanoparticle you start to see the iron sit in a superposition of spin up and spin down due to quantum/thermal finite size effects.
Comment: Thanks! Can you elaborate your answer on how big the "small enough" is?
Comment: Take a look at Kthaxt's answer for that
Comment: Iron atoms do not have a filled shell. And as I remember, in at least one of its forms (oxygenated or deoxygenated, I do not remember now), the heme group has a magnetic moment. Pauling measured it long ago.
Comment: Yes the atoms on their own do not have filled shells of course. You are right that unoxygenated hemoglobin have magnetic moments, but oxyhemoglobin as mentioned in the question does not. The point is that just having iron atoms does not give you ferromagnetism.
Answer: In tiny particles of ferromagnetic substances, the magnetization direction will fluctuate spontaneously under the action of thermal energies. There is a transition temperature to a blocked state (a frozen state, permanent moment). At high temperatures, the substance will display superparamagnetism.
It is difficult to say something about sizes and/or temperatures. It depends primarily on the magnetocrystalline anisotropy, etc.
Answer: Many magnetic nano particles (MNPs) are actually superparamagnetic, not ferromagnetic. This is often a desired quality in many applications. So some MNPs that are 1 um large are actually made out of 50 nm beads, giving the entire particle a super paramagnetic property. It is certainly possible to manufacture beads this small.
A ferromagnetic material starts acting superparamagnetic once it is small enough to contain only one magnetic domain. This occurs below the Curie temperature of the material. How big this is depends on the temperature. So "small enough" is typically given by this expression:
$$ T_B = \frac{KV}{k_B \log{ \frac{\tau_m}{\tau_0}} }$$
Where K is the nanoparticle's magnetic anisotropy energy density, V its volume, $k_B$ the Boltzmann constant, $\tau_0$ the "attempt time" which is material dependent (usually 10^-9 seconds), and $\tau_m$ is the measurement time. So by setting the blocking temperature to room temperature, you can solve for V for a particular material and estimate the minimum size to be superparamagnetic.
Physically, what this means is the particle has enough thermal energy that it "flips" many times during the measurement, thus the material's magnetization averages to zero, as opposed to having a fixed remnant magnetization, like a ferromagnetic material.