Polygon with cylindrical edges

Question: I am trying to model regular polygons (triangle, square, pentagon, hexagon, etc.) with the edges made up of cylindrical rods, kind of like the bonds in a molecule. I can get the basic shape by working with a circle mesh and changing to the appropriate number of vertices, but would appreciate some help in changing the edges to cylindrical "bonds." An example of a folded hexagon that I am trying to model is shown below. Thank you!
Comment: Hello, I'm not sure to understand what it should look like. Have you tried to add a skin modifier then a subdivision modifier ?
Comment: Sorry for not being very clear. Just added an image of a folded hexagon.
Answer: I think the easiest way to do this is to bevel a curve object.
Go to Blender Preferences > Add-ons. Type "extra" in the search bar, and activate the Add Curve: Extra Objects add-on by checking the box next to it.

Then in the 3D Viewport press Shift + a, choose Curve > Polygon and set the sides to 6.
In the Properties window, go to Object Data Properties > Bevel, and change the Depth value to give the curve thickness.

Then move and rotate the vertexes in Edit Mode to get the desired result.

If you want the corners to be less sharp and more rounded you can change the handle type of the selected vertices (from the original Vector) to Aligned. You can also use Vector and Aligned vertices together in one curve to get a more precise result.

EDIT:
Alternatively (which I quite stupidly didn't realize before) you can place Spheres to represent the atoms at the corners of the curve. If you would use a Hook modifier the curve would follow the position of the atom object.
Select the curve. Go into Edit Mode. Select a corner Vertex. Press Ctrl + S and choose Cursor to Selected. Go to object mode and Press Shift + A and choose a spherical object like Mesh > UV Sphere. (Press S to scale it down)
Now select the the sphere and Shift select the curve (in that order) so both are selected. Go into Edit model and select the curve vertex and press Ctrl + H and choose Hook to Selected object.

However if you choose to do this, you might want to parent the curve and all its atoms to an empty object, to be able to move the molecule (by moving the empty) without issues. (Add an empty, move it in the center of your molecule, select al the parts of the molecule, Shift select the empty, press Ctrl + P and choose Object(keep Transform). )
Comment: Ooops, you just beat me to it!  I'll eave mine in, just for the differences.
Comment: I didn't even realise the object should have spheres, but since it is about a scientific model of a molecule it makes sense of course. Also I think instancing the spheres is the easiest way to go. So +1 : ) Though the Hook modifier would allow different atoms to move with the curve vertices (I might edit my answer accordingly.)
Comment: Hooking! Good idea :) All depends on what OP needs to do with these models .. maybe we've both gone OTT
Comment: Quite possibly, yes : )
Comment: This is "super" helpful. Especially because I can now do this with or without the spheres for atoms depending on the model I am trying to make. I'll need the corners to be sharp rather than rounded but thank you for letting me know how to do either one. What a great community!
Answer: One route would be via Curves (make them 2D, if your polygons are planar.)

Enable the shipped add-on 'Add Curve: Extra Objects' This will give you a polygonal curve option.
Create your polygon of choice, and (for the optional next part,) Shift D make  a copy of it, and Header > Object menu > Convert that to a mesh.
In its geometry panel, ensure  the original (if 2D) curve-polygon has no fill, and give it a bevel, of whatever resolution and thickness suits.

For the second part, you could take some of the tedium out of placing atoms on your polygons by:

In the Mesh copy, Object Properties tab > Relations panel > Instancing, set instancing to Vertex.
Create a sphere at the origin (pivot) of the original Curve-polygon You can hide that one, eventually.
Parent the sphere to the mesh copy. Duplicates should appear on the corners of the curve.
You can CtrlA the dupliverts, > Make Instances Real. Then you can scale them independently in Object mode.
You can give them independent materials by associating the materials with the Objects, rather than their Data, just under the materials list panel in the  Materials tab.

Eventually, you could parent the atoms to their polygons / various polygons to one another so they move about together, or convert the whole lot to joined? meshes if you're going in that kind of direction.
Answer: Try using the Skin Modifier and the Subdivision surface modifier.

If you need more precise control over it, you can select all the vertices, hit E to extrude and then S to scale it a little bigger, and then select everything again, hit E, and extrude upward.  You can then use the subdivision surface modifier to make the edges round, and select any edges you want to be sharp, press Shit+E and then drag the mouse out to create a sharp edge.
Comment: I don't know much about the skin modifier and never used it before. So this is a good chance to try it out. Looks like this is a useful one to know for some of my other projects as well. Thanks for suggesting this different approach.

Polygon with cylindrical edges


How is income earned on a J1 student visa taxed?

Question: So I am an Irish J1 student doing an internship in Minnesota and have been since july 5th of this year. I have been getting paid a monthly paycheck of $2,000 for the 6 months I have been here and thus was expecting my taxable income to be $12,000. However I got a nasty shock to discover that the apartment the company has been renting for me and the car and any other expense paid to me has been put down as income to be and i am not considered an employee but a separate entity. I was told, and I calculated my tax based on the cash I received to only be a couple of hundred dollars and I budgeted for that, Now however my tax has become $4,300 due to the way they have classified me. Is there any way I can be exempt from this or reduce this as I have not budgeted for this amount, also all of the money I have been paid has gone into living expenses so I have not had the chance to save up this amount of money. Any help would be greatly appreciated
Comment: Talk to the company and review any contract document you have with them and see how they proposed your pay and bonuses would be calculated. Depending on how they worded their offer, you may very well be screwed, but if you are lucky and they left the wording open to interpretation, you can ask an IRS advocate for recalculation and they tend to be pretty good at working things out. They might at the very least lower your liability by settling on a smaller number.
Answer: On what basis are you not employee? You should probably get some tax/legal advice, but generally J1 internship is by definition employment.
You should also check the tax treaty between the US and Ireland, if there's one, and check what it says about training related income. You may find a pleasant surprise there.
Most universities have support for international students/visiting scholars, check the international students' office at your school.
Answer: J-1 students are considered to be nonresidents for taxation purposes during their first five years of presence in the US. J-1 scholars are considered to be non-residents for taxation purposes during their first two years of presence in the US.
Comment: While correct, how is it addressing the question?


Is conduit required when running a short distance to an adjacent 60 amp subpanel?

Question: I am installing a surface mounted 60 amp subpanel 5 inches to the right of my current surface mounted main panel. For the short run, can I use 6/3 non-metallic cable w/ground between the two panels using two clamp connectors and staple it to the plywood or do I have to run individual #6 THHN conductors and #10 THHN ground in conduit instead? I only have smaller size holes available on the side of my main panel, which makes attaching larger conduit to accommodate the 4 wires more difficult.
Answer: If you use cable, you are limited to the 60°C rating, so 6/3 isn't big enough for 60A - you'd have to go with 4/3
If you use conduit, and the terminations are rated for 75C, 6 (THHN) is fine. Also, if you use metal conduit, you don't need a grounding wire. The metal conduit is the grounding conductor.
Since it's less than 24 inches long, (a "nipple") you can fill to 60%, so 1/2" EMT, or IMC, or RMC will fit the 3x 6 AWG THHN wires you need (since you don't need a grounding wire, the conduit does that) - no large hole required. 75°C terminations are normal on service equipment, but do verify that yours are so marked - otherwise you are limited to 60°C ratings, in whch case you'll need the "larger of the small size holes" to take 3/4" conduit for 4AWG.
Comment: Also if using cable the the code requires "protection from physical damage", which is poorly defined in the code. Many jurisdictions have adopted local ordinances to define and as a result further restrict.
Comment: 2 locknuts each end - one inside the panel, one outside the panel.
Comment: when using a short nipple to connect the 2 panels is a locknut on both ends sufficient or do you recommend a short piece of threaded conduit with chase nipples in each panel?
Answer: You can do it any way you want.
I would run several EMT short conduits.
What I would do, however, is run 3-4 short EMT conduits between the 2 panels.  "Gee, that would require learning a new craft and buying $6 worth of fittings, why would I do that?"

The EMT conduit takes care of all grounding.  No ground wires at all needed.
It makes it EASY to reroute circuits into the new panel.

It is perfectly legit to bring a circuit into the old panel, terminate its ground wire there, then extend only hot and neutral wires into the new panel.  The several EMT conduits I mention make this easy.
I have installations with 2 panels next to each other like this, and having those conduit pipes really works nice.
1 near the bottom and 1 near the top for routing convenience.  The third is for the feeder.  Since the conduit is <24 inches,  you can disregard thermal derates, so you only need to worry about conduit fill.
1" would be a much better choice if available (at least for the feeder).  However a 3/4" pipe will support

3x #6 THHN, plus 6x #12 ...or...
3x #6 THHN plus 8x #14.

So you can bring #6 feeder + 3 circuits over in one pipe; 4 if they are all 15A.  1" would be a better choice as it'd let you run bigger feeder. I'm not sure what you are doing, but you may find 60A to be stifling.
And there's no earthly reason to be stifled. Spaces are CHEAP.
Think BIG on subpanels.  Really. Really. Big.
We're talking breaker spaces... though bus capacity is connected.
I've been helping people for a long time here. The #1 mistake I see is people scrimping on the size of their subpanel, getting just enough spaces for today, and getting into a serious jam later because they've run out of spaces.  Then they realize they could've avoided this by spending a measly $20 more on a bigger panel then. Suddenly scrimping doesn't seem so clever.
Or people think they must "match up" subpanel amps to feeder amps. That's not true at any level. Panel rating is a "redline" max rating like a tire rating.  If you regularly drive 85 mph you want better than 85 mph tires.  "Main breaker" size for a subpanel is also irrelevant.
Also, if you have any future aspiration for a generator, having a nice big subpanel is a great idea. Now you don't need a messy expensive transfer switch; you can simply get a panel interlock ($30-65) and switch the whole subpanel.  Any circuit you want on generator, just migrate it to the subpanel.  No limit to number of circuits - except for the size of the subpanel, of course.
Almost all panel knThree #6 Cu feeder wires can share the pipe with 6 #12 wireswill take can have as many wires as will fit.  In practicality this means 1 conduit near top, 1 conduit near bottom, both for convenience of routing... and 1 conduit for the feeder.
Comment: thanks for the idea! if i want to move a few circuits from the main to the sub panel is it ok to extend circuit conductors in the main panel by splicing them and then routing new wire into the sub panel? or should the wire be completely removed from the main panel and run into sub panel?
Comment: Yes, it's perfectly fine to use the main panel as a junction box to the sub @johns. You only need to extend hot(s) and neutral.  That's why I recommend the multiple conduits, which allow you to use individual wires, called THHN in the conduit.  Most places sell 'em by the foot for 20 cents a foot or something.  You can keep ground in the original panel that the cable lands in.


Combining a Multiwire Branch Circuit on a single breaker

Question: I have a Multiwire Branch Circuit connected to two 15A Breakers (Handle tied together). Each circuit only has 2 duplex receptacles on it that are seldomly  used. Is it acceptable to combine both the HOTs together and pigtail to only 1 of the 15A breakers? I would than remove the Handle Tie and use the renamed 15A Breaker for a new circuit.
Comment: I work with MWBCs quite a lot, and I can't really see a problem with that.  That's been proposed to me as a method for validating that an MWBC is not cross-connected with any other circuits.  (by using a GFCI to detect cross-connect leakage).
Answer: Since

the two hot conductors do not rejoin at any point (we know this because you'd have a 240V short on your hands otherwise), making it so that the rules about wires in parallel don't apply
the two hot conductors are being protected by the same breaker in the new configuration (i.e. two 14AWG hots on the same 15A breaker, returning via a 14AWG neutral), eliminating the possibility of an overloaded neutral, and
this is all on one breaker, making it all part of one branch circuit and avoiding a violation of 200.4(A) regarding shared neutrals

you can go ahead and do this safely by wirenutting both hots to a pigtail from the chosen breaker in the panel.  (312.8 allows splicing in the panel provided you aren't overflowing the gutter space.)
I would put a tag on the wires in the cable saying "Same Leg" at the various boxes this feeds though to avoid confusion between this (admittedly somewhat odd) configuration and an actual multi-wire branch circuit.
Comment: Some breakers are designed to accept two hots. They typically have a mount with channels on each side of the screw. In that case it's not necessary to pigtail.
Answer: My only concern comes from the IAEI (International Association of Electrical Inspectors).
*Question:
Can a UL Listed product be modified in the field if the manufacturer indicates that the revision is ok and sends out new parts?
Answer:
The UL Mark applies to products as they were originally manufactured. UL does not know the effect modifications in the field will have on a product. Therefore, unless the modifications are specifically tested and evaluated by UL, UL cannot say that the modifications void the UL Mark, or that the product continues to comply with UL's safety requirements. The exception would be when the product has specific replacement markings.*
So why not just replace the breakers, cost is not relevant and everyone is happy.
Comment: In effect, isn't it the same as having a spare breaker with a handle tie?
Comment: Have you checked with UL to see if that modification cause that equipment to lose its UL listing.
Answer: Short answer: No, not like that.
You have to remove one of the wires in the panel and cap it off.
Then go to each receptacle that was on that wire and rewire it to the remaining hot wire instead of the disconnected one. Cap off the disconnected wire at each receptacle.
Then you are good.
Good luck and stay safe!
Comment: I'm not the OP and not a sparky but I'm curious as to why this is required. No wires will be subject to overcurrent as would be if the two hots were to be connected to two breakers on the same leg. Thanks
Comment: I'm not seeing how this is "paralleling" if the two never come back together. How is it different than a pigtail in the panel?
Comment: He's not paralleling because each hot serves differeent loads.
Comment: Agreed, but the Electrical Code does not allow paralleling of conductors less than 1/0 with a few exceptions for elevators. And, IMHO, it is better form to have only one wire per breaker.
Comment: Hmmmm good point if they are separate receptacles are not joined in the field then they would not be considered paralleled. One of them should still be re-identified (if they are red and black) so that the next person doesn't think they are different legs of the 240 volt system. They will now be on the same leg. Both wires on the same breaker seems like bad form and may be confusing.


SharePoint hide files and folders

Question: Is there any way to hide certain files and folders from certain people, but make it so the people with the correct permissions can see and access the files
Answer: If you remove the permission on the item level, only people with at least read permission can see the item.
If we're talking about documents and libraries I strongly recomment using folders and change the permission on the folders. All documents in the folders will then inherit the folder permission.
Considering two users (A & B) and one library with two folders (Public & Secret) user A has read permission to both folders and can read all documents in the library. User B on the other hand only has read permission to the folder called Public. For user B it would seem the library only contains one folder called Public.
Using the permission approach is the only true way in terms of security. You can do a "security by obscurity" approach by using views and hiding the documents/items, but any half-smart end user would be able to figure out a way to get to see all items.
Answer: Yes, it is possible.
I would suggest to get familiar with the SharePoint permission model - You might find usefull this official documentation by Microsoft and how to break role inheritance
Answer: Just as Morten and Kristaps said. It is possible to do so with break permission inheritance.
For files, go to the properties of the file, find the shared with button in the view ribbon. Click on it and then select stop sharing in the pop up window. Make sure you have select all the required users to be shared with the file.
For subfolder, also to the shared with button. This time you shall select advanced button in the pop up. Break permission inheritance and then customize the permission level on different groups according to your requirements.

SharePoint hide files and folders


What exactly do Wrinklers do?

Question: I have entered the Grandmapocalypse, and these things called 'Wrinklers' are spawning on my main cookie. Are they positive or negative, and what do they do?
Answer:
 (Yes, note the Christmas Hat)

Wrinklers are leech-like creatures which has a 0.0003% chance to spawn, per frame, and the chances increase as you go through each stage of the Grandmapocalypse.
When spawned, they will appear in the Big Cookie Window, where it'll move towards your cookie.

When a Wrinkler is attached to your cookie, you gain a 5% debuff to your Cookie Per Second, and this stacks as multiple Wrinklers attaches to it (up to a maximum of 10, thus 50% debuff).
To remove one, simply click on it (multiple times) and they'll pop, returning 1.1 times the cookies it leeched.
In the long run, although they appear to be a debuff - They actually return more than lost, since none of the cookies they leech are actually destroyed.
Comment: Ok, thanks. I just started the **Grandmapocalypse**, and I'm getting lots of the Wrinklers. I leave them there a bit, then kill them.
Answer: You should not kill them after a small amount of time they are a long term game mechanic that you can get loads of cookies from if you leave them for a long time.

What exactly do Wrinklers do?


Stainless steel pan

Question: It's stainless steel pan. After using it for steaming chicken, fish, the pan has got brown/stains (pls see picture). Cannot be removed with baking soda and stains are smooth. Should I continue to use? Am concerned about chemicals coming out from stains when pan is heated (even though used for steaming only). Pls advise. Thanks.
Comment: Its hard to tell from the image but that looks like a mixing bowl not a pan. Can you provide more(better) images.
Answer: If you are in the USA, Bar Keepers Friend is a useful product that we've had success using to clean stainless steel kitchen bowls, pots, etc. If you are not in the USA, find a cleaner with oxalic acid as the active ingredient.

Stainless steel pan


Design a FPGA based Oscilloscope

Question: I want to design a little oscilloscope that is able to analyze signals up to 1 MHz using a Xilinx FPGA. I want use the VGA interface in order to display the signals. Is it possible obtain a good result using only FPGA and an external RAM for signal elaboration? Or is it necessary to use an external microprocessor? With the Xilinx ISE Webpack license I can't use the MicroBlaze softcore processor, but only the PicoBlaze. What is the better way to obtain a good result with a simple and cheap design?
Comment: One thing that will improve the usability of your instrument a lot is to implement a configurable decimation filter, so that you can capture at lower time/division settings without the aliasing which would result if you simply sampled at a low rate.  Many of the first-generation cheapy digital scopes are lacking this, and it means they often give highly misleading displays which require skill to interpret.  You'll probably also find it easy to get an ADC several times faster than you mention, with a filter this will work better than the 2 MSPS device that would be the minimum for your needs.
Comment: Some not-so-cheap scopes fell prey to this, too.
Comment: Thanks for the advice, I think it's a good idea but before I do that I would decide the main architecture of the device.
Answer: 1 MHz is slow enough that this should be doable without a FPGA.  Perhaps you may want to use a external A/D or sample memory, but orchestrating all that should be possible with just a decently fast microcontroller.
Some of the dsPIC 33F have built-in A/Ds that can sample at 1 MHz, if I remember right.  You don't typically need lots of bits for a oscilloscope, since the user will adjust the gain and offset to zoom in on what they want to see.  Entry level scopes don't have more than 256 pixels vertically anyway, so obviously aren't showing more than 8 bit of information per sample.  The 10 bits the internal A/D of a dsPIC can do should be sufficient.
Comment: The main problem of using a microcontrollers is the VGA interface, that uses a good part of the microcontroller resources. For that reason I decided to use an FPGA. The 1 MHz sample rate isn't enought in order to view a 1 MHz signal (I want a sample rate that is 10 times the signal frequency). I prefer an external ADC because in future I can replace it with a faster one.
Comment: Good idea; there appear to be lots of people who've done this e.g.: http://www.instructables.com/id/DPScope-Build-Your-Own-USBPC-Based-Oscilloscope/
Comment: If you want to do it as an FPGA project, then do so - at a minimum it will be a different direction of learning, and the basic idea will be extensible up to a hundred megasmples or more.  Olin does have a point though - at the specific performance range you mention, something can be built using on-chip resources of a modern microcontroller.  Most would also be looking at LCD displays in this day and age, rather than VGA output, and there are both micros with such support on-chip, and also serial interface displays which simpler micros can use.
Comment: I prefer an FPGA because the possible improvements are more than what can offer a microcontroller. I want to use VGA because the device must be little and cheap and it can't have an onboard display.
Answer: I think this is quite doable. I'll assume you've selected a part with a built in ADC per channel that you want.
The architecture depends on whether you want to have a framebuffer or not; it will consume RAM but make it easier to debug. Non-framebuffer designs would probably have a character generator ROM approach instead for numbers in the UI.
Either way, the key to getting it working nicely is not to involve the microprocessor in putting the trace on screen. Each ADC should be connected to a ring buffer of the N most recent samples, where N is the number of samples across the width of the screen. On the VGA vertical blanking interval, capture this to another buffer which will represent the set of samples to display. You can then either translate them into pixels in the framebuffer; or generate a one-line framebuffer for each line of the display by scanning the sample buffer for any situation where there is a sample below the scanline next to one above the scanline.
(This might involve two different RAMs, one being written to by the ADCs and one being the display one, swapping roles every frame).
Comment: I'd actually argue that it is more straightforward not to have a framebuffer, but run a comparison to the desired volts vs time graph as the display is generated rather than to run the same comparison only to write to a framebuffer.  This saves a lot of memory, meaning the whole design can be implemented in on chip block ram in a low end FPGA, and there's enough for a substantial storage buffer.  A character mapped display can also be overlayed, provided a single text size is acceptable.
Comment: I think that is a good idea use a separate buffer for the ADC samples, that simplify the work but I want to save the samples in memory and allow the user to "STOP" the signal and zoom it. My problem is how interface all this parts together. The only PicoBlaze ins't enought for that task. I think that the signal sample must be controller by hardware to avoid performance problems.
Comment: The key to building zoom will be to realize that you don't have much ability to zoom in, only ability to zoom out from the native resolution by downsampling, and to change the offset into the buffer where your visible display starts.  Incidentally, you'll probably want a circular buffer so that you can preserve things which happened *before* your trigger condition.  If you are really uncertain where to start, consider writing a software simulation to test algorithms first, and feeding it with wav files.
Comment: For that reason I want to have a big circular buffer and I want to sample at the max speed in order to have the possibility of zoom in. Before test algorithms I would like to made an idea of what could be a good block diagram of the device.
Answer: An oscilloscope is comprised of many parts, but what truly defines an oscilloscope's performance and utility is it's trigger circuits.  Being able to define when to start a sample, the conditions that are needed to capture an event beyond just sampling and displaying really define/extend the usefulness of the instrument.
I would argue that if you truly wanted to build something special and useful that you really only have the choice of implementing an 'Scope of that sort of bandwidth in a FPGA.  With line buffers and decision logic you can implement some non-causal filters and signal processing that can isolate out those certain events that truly help you debug.  It is after all those intermittent (perhaps even singular) events that make debugging very difficult.
While a sound card like (Sample and then display) system is where you should start at that should not be the end goal.
Comment: I believe that there are a lot of features that make an oscilloscope good. For start I want to define a basic architecture that, in future, can be extended. When I have a basic architecture (That takes and prints samples on the screen) that works good I start to add new functions and improve it.
Comment: Yes, you need to be able to capture and display, that's obvious.  But if you want to do something really useful you're on the right track designing a system that can extract meaning out of the signals.
Comment: Sure, but before do this I want to have a good base of the device.
Answer: Basically, I think it is doable with pure hardware. We need more information to tell You if You need microprocessor or not. If You want to display one waveform at fixed frequency and fixed amplitude, I would say it is easy to do in hardware, but remember, that You'll have to configure ADC and other peripherals, probably using SPI, so at least picoblaze will be needed.
Comment: I want to realize a "complete" device that has adjustable Time and Volts division and a basic user interface. I would to get a device that has the main functions of a standard oscilloscope but has a limitated frequency range (0 to 1 Mhz) and that can be used with every VGA monitor. I started to write some code for the Programmable Gain Amplifier and the ADC on the PicoBlaze and I designed a basic VGA controller. My problem is that the PicoBlaze isn't powerful enough in order to elaborate the signal and drive the VGA controller. I would like an advice on how merge all the parts.
Comment: Keep the processor out of the realtime operation.  If you want to use one for configuration, it's relatively easy to put SPI-like configuration registers in your FPGA, and set them from a microcontroller or even by twiddling bits from a PC.
Comment: @socrates - at 2 MSPS SPI may barely still be an option, but most oscilloscope designs would use a parallel interface ADC, at least until you get to the gigasample range where various ultra high performance semi-serialized interfaces might be used.

Design a FPGA based Oscilloscope


What does the ‡ symbol in the Chart Supplement (A/FD) designate?

Question: In the Chart Supplement there is occasionally a <code>‡</code> symbol after the operating hours for control towers (and other time information) like what's shown below.

What does the ‡ symbol represent?
Comment: I'm pretty sure the `‡` is what you're talking about - if not let me know & revert my edit :-)
Answer: The ‡ symbol in the A/FD specifies that the location observes daylight savings time.
This is from the A/FD legend, which can be found online by going to the online digital A/FD and searching for an airport.  The A/FD Legend link will then be at the top of the search results (unfortunately the link changes every cycle so I can't include an exact link).

6 TIME CONVERSION
Hours of operation of all facilities are expressed
  in Coordinated Universal Time (UTC) and shown as ''Z'' time. The
  directory indicates the number of hours to be subtracted from UTC to
  obtain local standard time and local daylight saving time UTC–5(–4DT).
  The symbol ‡ indicates that during periods of Daylight Saving Time
  effective hours will be one hour earlier than shown. In those areas
  where daylight saving time is not observed the (–4DT) and ‡ will not
  be shown. Daylight saving time is in effect from 0200 local time the
  second Sunday in March to 0200 local time the first Sunday in
  November. Canada and all U.S. Conterminous States observe daylight
  saving time except Arizona and Puerto Rico, and the Virgin Islands. If
  the state observes daylight saving time and the operating times are
  other than daylight saving times, the operating hours will include the
  dates, times and no ‡ symbol will be shown, i.e., April 15–Aug 31
  0630–1700Z, Sep 1–Apr 14 0600–1700Z.
Comment: @JanHudec While that is true, it isn't really important here since this is an FAA publication that only covers US airports.  That quote is directly from the legend.  :-)
Comment: It is important to note that the period of daylight saving time is different in different countries. In Europe daylight saving time starts 0200L last Sunday in March too, but ends _last_ Sunday in _October_. And on southern hemisphere it's the other half of the year.
Answer: Or, alternatively, the answer is that the tower has the same (local) operating hours no matter if it's DST or not, i.e., it's always 9-5 local.  However, since all hours are written in Zulu and the conversion to Zulu and local can change depending on if it's DST or not, this provides a quick shortcut to duplicating every entry's times.
More than anything else, this is a cautionary note that one should never speak 'x Standard time' unless you mean it - just say 'x time' instead.


Can stem cells from male convert to cells of female-only organs, and vice versa?

Question: As we know, stem cells can convert to different cells of other organs, can male use their own stem cells to convert it into cells of female-only organs(and vice versa)?
Comment: Well a stem cell is what every cell comes from, they go through differentiation to become any cell in the body. So theoretically, yeah that kind of differentiation could occur, you'd just need the correct stimulation.
Comment: @user19270 no, you are **completely** incorrect. There is no "stimulation" to change an X chromosome into a Y, or vice versa.
Answer: I am assuming you are talking about embryological stem cells and embryological development of genitalia.
The answer is no.
Male stem cells have XY chromosomes. Y chromosome is the sex determining chromosome with SRY gene that determines testes development. Absence of the Y chromosome leads to female development by default. That is why XX forms women and there are people with only one X chromosome which are women. (Turner's syndrome)
It might be possible that SRY gene undergoes a mutation and the gene isn't expressed. There are Y chromosome linked diseases.
You should read up about Y chromosome and development of genitalia.
https://en.wikipedia.org/wiki/Y_chromosome
https://en.wikipedia.org/wiki/Development_of_the_reproductive_system


How to implement rel=author on a page with multiple authors?

Question: I have a forum, and I would like to add rel=author to my pages. However, each page has multiple authors, and I'm not sure how I should implement rel=author if I have multiple authors.
Does anyone have any advice?
Answer: I used the instructions on the article How To Implement Rel=Author for creating my page. The only difference is that I had two rel=author links instead of one. I then tested the page with Google's rich snippets testing tool, and the first author that was linked was displayed as if it were the only author. The second author was not displayed at all.
Multiple rel=author links is something that I think Google should recognize, as pages like forums and wikis usually have more than one author.
Comment: Pages like forums and wikis can have dozens of authors on a single page, which Google would be unable to display in any useful form. I would argue that `rel=author` is inappropriate for pages with THAT many authors.
Answer: I couldn't find any author-specific information, but the HTML specs do allow you to define more than one link with the same relationship, e.g.
<link rel="alternate" hreflang="de" href="//de.example.com/my/page.htm">
<link rel="alternate" hreflang="en-gb" href="//uk.example.com/my/page.htm">
<link rel="alternate" type="application/rss+xml" href="/my/page.rss">
<link rel="alternate" type="application/atom+xml" href="/my/page.xml">
<link rel="alternate" type="application/pdf" href="/my/page.pdf">
<link rel="alternate" type="application/pdf" media="print" href="/my/print-page.pdf">
<link rel="alternate" media="handheld" href="/my/mobile/page.htm">

I would assume that the same could be done with the author relationship.
Comment: I'll try it then, and I'll let you know how it goes...
Comment: Result of my experiment: http://webmasters.stackexchange.com/a/25185/6901
Comment: do you know if Google will recognize it, though?
Comment: @Christofian: That, I do not know. Maybe you can try it and let us know? =P
Answer: According to the HTML5 Working Draft:

The author keyword may be used with link, a, and area elements. This
  keyword creates a hyperlink.
For a and area elements, the author keyword indicates that the
  referenced document provides further information about the author of
  the nearest article element ancestor of the element defining the
  hyperlink, if there is one, or of the page as a whole, otherwise.

While the specification does not indicate a resolution for multiple authors specified at the HTML5 document level, the element level does provide support for multiple authors within a single HTML5 document (which should cover your forum's needs).
Answer: Testing a page on the testing tool i saw this:

Note: The testing tool currently only checks the first rel=author link listed on a webpage for a link to a Google+ profile [...]. It's possible that authorship may in fact be working for this page because of other rel=author links on the page. To verify that authorship is working on this page, please ensure the first profile listed on the site links to the appropriate Google+ profile.
Answer: Maybe someone is still seeing this question, so it could be useful to point out that Google no more supports Google Authorship
https://plus.google.com/u/0/+JohnMueller/posts/HZf3KDP1Dm8
https://support.google.com/webmasters/answer/6083347?hl=en
And it encourages the use of structured data.
So, no more need to add rel=author for Google. It still exists as microformat and could be used by other applications.
You can still add where you are author through Google+ for social purposes.
But that doesn't mean Google no more recognizes author of a post. It analyzes structured data, bylines, citations, as always it did.


Constructing a stock market index using PCA

Question: Let's say that I've got a final component and its score derived from n number of stock returns (time-series data). I want to construct a stock market index using this component (having negative and positive values). There is a good approach to to this? Also, I want that this index to have a starting value of 1,000.
Thank you.
Comment: This is on-topic here, so this is a perfectly reasonable place to ask about it. At the same time, [quant.SE] specializes in quantitative finance, so perhaps they would be able to provide a more illuminating answer. I only mention this to improve the chances that you get a helpful response.
Comment: Thank you, @Sycorax. I'm new here... Can I move the post to the Quantitative Finance area, or should I delete the post here and repost there? Thanks.
Comment: If you believe this question would be more appropriate for QF (and you should make that determination based on your reading of the description in the help center for QF), you can click "flag" below your question and write a note asking the moderators to move it. On all of StackOverflow, we discourage cross-positing/re-posting questions. But please I'm not trying to *tell* you to move it, since it is on-topic here.
Answer: I was able to recreate a simple example of creating an index from made up stock returns using the R tidyverse. Check and see what you think.

options(tidyverse.quiet = TRUE)
library(tidyverse)
library(broom)
set.seed(42)
stocks <- tibble(
  time = as.Date('2009-01-01') + 0:99,
  X = rnorm(100, 0, 1),
  Y = rnorm(100, 0, 2),
  Z = rnorm(100, 0, 4))

This was what the fake returns looks like.
stocks %>%
  gather(stock, return, -time) %>%
  ggplot(aes(time, return)) +
  geom_line(aes(group = stock, color = stock))

stocks %>%
  gather(stock, return, -time) %>%
  group_by(time) %>%
  summarise(avg_ret = mean(return)) -> avg_return
avg_return %>%
  ggplot(aes(time, avg_ret)) +
  geom_line()

And this is the average return looks like.

Now, this is how one can create an index from the PCA, treating each stock as a different variable.
stocks %>%
  select(-time) %>%
  as.matrix() %>%
  prcomp(.) -> pca
pca_index <-
augment(pca, data = stocks) %>%
  mutate(
    time,
    base_1000_index = (.fittedPC1*1000)/first(.fittedPC1))
pca_index %>%
  as.tibble() %>%
ggplot(data = ., aes(x = time, y = base_1000_index )) +
  geom_line()

And this would be the base 1000 index. You can see how I built it from in the second line of the mutate block.

Now, to interpret such index is a bit difficult. The classical idea of a principal component is to to change the data such as you reduce the variability of it, by only having the directions of greater variance.
Using the first component projection o each data point, means that you are capturing the most variability of the stocks. I can't really wrap my head around what that could mean in the form of an index.
Comment: Thank you for your answer. Based on what I have found out regarding the topic, I do not use only the PC1, but I select all components based on Kaiser rule, i.e., with the eigenvalues >1. After this, I get the scores of each components and weight them with their explained variance as a % of the total cumulative explained variance. In the end, I get a single component and based on it I want to construct the index.
Your index takes also negative values, and I do not want this because I will work with logarithmic returns based on this index.
Comment: @Niqx In classic PCA, a principal component can have positive or negative loadings on the original basis vectors. In this context, this corresponds to positive or negative portfolio weights (where a negative weight corresponds to shorting an asset). Are you looking for some kind of restricted PCA where loadings cannot be ngative?
Comment: @Guilherme Marthe In securities markets, there's huge cross-sectional correlation and the first principal component (depending on the set of securities you're working with...) often ends up looking similar to the return on the market portfolio. In your example, the first PC looks pretty similar to $z$, which makes sense since it has so much more variance.
Comment: @Matthew I just want to derive an index from these loadings, and being a stock market index, it cannot have negative values.
I found somewhere a sort of normalization of the loadings (putting the index in the range of, let's say, 0 and 1,000), but this is not suitable for my case as the index may exceed the cap value (1,000). I'm still struggling to find a way to derive an index from these loadings. I need the index returns to work with some VaR and systemic risk models.


Where can I follow the latest intellectual and academic developments in Kant research?

Question: By this, I mean specifically the academic research, and since I am primarily interested in Kant, so on Kant too.
Answer: Not that I'm an expert on this, but here's a couple suggestions:

Wikipedia has an article with a list of philosophy journals. While I'm sure many journals include articles about Kant, there is a journal dedicated to talking about Kant. These obviously can be very expensive, so if you have access to a college library, it is probably better to go through that then buying yourself.
Another approach is instead of trying to follow all of academic development in philosophy (or even within a specific topic), you can do the opposite: find a few people who write about topics you are interested in, and read their books, see if they have videos on YouTube, subscribe to their blog, etc.
Answer: If your top interest is Kant and you truly want to get involved in the academic literature, then the top journal is Kant Studien.
Also, you should look at the work of Henry Allison, Marcia Baron, Thomas Hill, Christine Korsgaard, Nora O'Neill, and Allen Wood. (I'm sure I'm missing some important people there, but this is a good place to start to learn about contemporary Kantianism).


QGIS 3.4 : Add points to exact locations?

Question: I would like to add several coordinates at specific British National Grid Easting and Northing values. I know this can be done by bringing in a .csv, but I want to know is there a way to manually enter the numbers in QGIS 3.4, and then the point moves to that location ? I've read that in QGIS 2.x there was a plugin called Numerical Vertex Editor that doesn't seem to exist for 3.x ?
Answer: In QGIS 3.x, create a point, choose the node tool, right-click on a snapped point and select Vertex editor.
A new panel appear and you can enter the true coordinates.
Answer: The node tool has been mentioned. If you are in projected coordinate system, you can also use the "Advanced Digitizing panel" and lock the X and Y fields. Use the second button to lock continuously. Then your point will go to these coordinates.
Comment: The only restriction for this tool is to work with a projected coordinate system. It's no use with WGS 84 for example. In this case, the British National Grid is a projected SCR, it will work.
Comment: Indeed, I added your note.
Answer: There is a neat plugin that does a fantastic one-dialog job, Lat Lon Tools. Would be great if it was Core.


Isn't online anonymity compromised by any SSL connection?

Question: When using a vpn, proxy etc to hide your IP, if you, as an example, login securely to a bank website, they will (or can) obtain your real IP contained in the encrypted data. Likewise, any SSL secured webpage has access to your real IP don't they.
To me this apparent universal oversight, seems worrying for those attempting anonymity online. Is this correct?
Comment: Security and Anonymity are two different things. Security often depends highly on not having anonymity between the two communicating parties. It's what authentication is about.
Comment: Thanks everyone for your comments. One of my concerns is that recently almost all browsers have removed the user's ability to switch Ssl/Tls off. And again almost all search engines require ssl.
I read specifically that a bank stored the clients IP at the user end for authentication which was then encrypted safely, sent to them, and they could access the IP their end.
So I assumed this was the usual practice with SSL communication.
My interest is anonymity both through network sniffing and from sites visited. As far as I can tell it seems a fairly unknown risk for anonymity online, as using pl
Answer: No. Online anonymity is compromised by a lot of other things.
SSL is there to prevent people from snooping on the contents of your connection, and to verify you're connecting to the correct host.
While a man-in-the-middle attack may still be performed, the attacker will not typically be able to read the contents.
SSL is not there to make you anonymous when visiting a website. It's there to encrypt the contents of your connection. Example:

No SSL

Dovid is talking to Simon, but someone is snooping on their connection.
Dovid: Hi, Simon!
Simon sees: Hi, Simon!
Attacker sees: Hi, Simon!

With SSL

Dovid is talking to Simon, but someone is snooping on their connection.
Dovid: Hi, Simon!
Simon sees: Hi, Simon!
Attacker sees: vdO2KVfFbvPuK30YxZ7luUDORbJdwGc9uXp (fake string as an example)

Furthermore, having your IP address attached to any connection is required to get a response back. How will the person you're contacting know who to reply to if they don't know where you're coming from?
Better yet, if you receive a letter in the mail without a return address on it, how will you respond? The same concept applies with the internet protocol.
Answer: HTTPS is not a tool to hide who you are, it is a tool to hide what you are saying. The purpose of SSL is to establish a secure means of communication between a client and a server. If you want anonymity then you need to use something like Tor with HTTPS.
The EFF has a neat site that explains how you can hide who you are, as well as what you are saying. It also shows what happens if you only use Tor or HTTPS without the other.
To get a really easy example of what things are like without SSL, run wireshark and then try logging into something over HTTP (home routers are notorious for this). When you inspect the HTTP packet you will see your credentials in plaintext. If SSL is used then this isnt possible unless you had established a MITM before the client and server formed their secure communication!
Your browser also leaks a lot of data while you are browsing so the fact that someone can see your IP is the least of your worries. In fact these methods are so powerful you can use them to fingerprint users even if they are on Tor.
Answer:
When using a vpn, proxy etc to hide your IP, ... they will (or can) obtain your real IP contained in the encrypted data.

It is not true that SSL will contain your real IP address in the encrypted data. SSL will only contain the data sent by the browser and the real IP is usually not one of them. The IP will be contained in the unencrypted data though but only in the connection to the VPN. This is needed to get data back from the VPN. But the server you access through VPN will only see the IP address of the VPN, not yours.
That does not mean that it is impossible for a server to get knowledge of your real IP address. There are techniques like WebRTC which can be helpful to get this IP address and therefore these techniques are disabled in the Tor browser bundle where they care about anonymity. But this is completely unrelated to SSL.

To me this apparent universal oversight, seems worrying for those attempting anonymity online. Is this correct?

SSL is intended to secure the connection against sniffing and tampering and insofar provides a bit more privacy. But privacy is not the main aspect of SSL, encryption and tamper resistance is. Please don't assume that anything which provides some security also increases privacy because often it does not. In lots of cases more security even can have a negative impact to privacy, just look at all the data collection they do to find terrorists.
Answer: No. SSL/TLS increases the privacy of your data through encryption. The encryption technology is not responsible for disclosure of your IP address.
Specifically, SSL/TLS exists at the application layer of the OSI model whereas IP addresses are disclosed at the network layer. Thus, the disclosure of your IP address is common across all applications communicating via the IP protocol.
Other methods exist to prevent disclosure of your IP address to certain parties. Onion routing is an especially good example of this.
Answer: For those attempting anonymity online the only "safe" way to do it is to be paranoid.  Here's how the "pros" do it.
First you have to build a completely fake persona, and memorize it.  Then you have to obtain some laptop from some cash-and-go place like a pawnshop or a craigslist transaction because if they get a 'bot on your laptop when your using it they can get the serial number and go back to the manufacturer and trace it to the retailer and subpoena to get your name.  Then you have to nuke and repave the laptop and use your fake persona.  Then you have to take the laptop to some "public access wifi" place and use it there.  Once you have used it, keep it powered off unless you are at your wifi signal place.  Oh and don't drive your car there because they might have security cameras going that will record your license plate.  And go to a different wifi place each time because once you post your manifesto they will put a plainclothes detective in a car watching the wifi place.  And don't forget to construct a hat out of aluminum foil to block the brainwave scanners.
Comment: A tin foil hat block a lot of things, including job offers and marriage proposals, but one thing it does not block is a brainwave reader, assuming such a thing existed; [this paraphrased from Physics.SE.](http://physics.stackexchange.com/questions/208516/can-tin-foil-hats-block-anything)
Comment: I dont think it is tinfoil hat of the OP to wonder why SSL is showing the source IP at the destination. Its a common misconception if you are not familiar with networking. It also doesnt help that SSL is sometimes sold as a magic, fix all your security problems technology by some people/organizations where it simply is not that.
Comment: This is cute, but it won't work in the USA. ;)
Comment: Even if the OP did what you suggest, you still don't address concerns about SSL and privacy.


Patent details changed without consent

Question: I am the inventor of a live patent application which has been altered by the owner of the patent against my wishes. If I withdraw my name from the patent application will this stop the patent going forward?
Answer: Unfortunately, there is likely nothing you can do.
An inventor has no influence over a patent application, once they have assigned away their rights.  Moreover, there is no facility for an inventor to withdraw their name, except on the grounds that they are not actually an inventor.
Answer: The answer you are looking for is not straightforward. Where was this patent application filed? Countries (and regional treaties, like the EPO or WIPO) have different rules for that.
For patents filed with the EPO, the consent of the wrongly designated person is required for corrections, except for the case where another inventor is added. The applicant must consent too, in all cases. See Guidelines for Examination, EPO, 2016, Part A, Chapter III/5.6 at
http://www.epo.org/law-practice/legal-texts/html/guidelines/e/index.htm
I am not familiar with US rules. If you refer to a US patent application put a relevant tag to your question, maybe someone US-based will pick it up.

Patent details changed without consent


How exactly are molecules detected in space?

Question: Recently the sugar glycoaldehyde was detected in a star system 400 light years from Earth. How exactly are molecules detected in space? I am aware that spectroscopy is used to detect them, but I don't know the details.
Comment: This is a very interesting question. My basic understanding that the molecule has a spectral line within the electromagnetic spectrum that identifies it, like a thumbprint. When a telescope is directed at such star you will receive the spectral line but at a different frequency due to the phenomena of redshift.
Comment: You may ask this on the astronomy stack exchange and get an answer!
Comment: yeah, try astronomy or physics stackexchange
Comment: I'm not an astrochemist, but the key technology apparently is *infrared spectroscopy*. One instrument currently in use is the **HIFI** (Heterodyne Instrument for the Far Infrared) aboard the **Herschel** probe. Please have a look at the site of [ESA](http://www.esa.int/Our_Activities/Space_Science/Herschel) and the [JPL](https://herschel.jpl.nasa.gov/hifiInstrument.shtml) for further information.
Answer: The research article corresponding to the observation to which the question is referring is Detection of the simplest sugar, glycolaldehyde, in a solar-type protostar with ALMA. Note that the molecule is glycolaldehyde rather than glycoaldehyde.
ALMA is the Atacama Large Millimeter/submillimeter Array, a radio telescope array in the Atacama desert.  The extremely low humidity of the Atacama desert minimizes water vapor interference.
This observation of glycolaldehyde in space is not the first.  It was earlier observed by Greenbank radio telescope, in West Virginia, USA, for example.  The Greenbank observation is reported in INTERSTELLAR GLYCOLALDEHYDE: THE FIRST SUGAR.  Glycolaldehyde was detected through radio signals in the 71-103 GHz range that are photons emitted when the molecule transitions from an excited rotation state to a lower energy rotational state.
In the ALMA observation, the molecule was detected based upon radio signals near 220 GHz and 690 GHz.  These correspond to photons emitted by the molecule when transitioning from an excited rotational state to a lower energy rotational state, but are a different set of transitions from those observed at Greenbank, including some for excited vibrational states.
I'll try to add more information later, there are a wide variety of spectroscopic techniques: absorbance vs. emission; rotation, vibration and electronics transitions, and many different frequency ranges.
Comment: How does rotation and vibration lead to emission. How do you map the frequency of light received uniquely to a molecule. How do you know this frequency of light comes from a molecule and not some energy from a star or other source. I guess I'm concerned with how the actual spectroscopy works.
Comment: The rotational states are quantized.  Quantum mechanics dictates that a molecule can not rotate arbitrarily, but only in discreet energy amounts.  See http://en.wikipedia.org/wiki/Rotational_spectroscopy  On Earth in laboratories libraries of spectra of molecules are compiled such as: http://spec.jpl.nasa.gov/ftp/pub/catalog/catdir.html  Then a comparison is made between the signal from space and the library of spectra


Applying to a psychology PhD with only neuroscience research experience

Question: I am currently unsure whether I want to do my PhD in psychology or neuroscience so I'm applying to both programs. The issue is that all of my previous research experience is exclusively in neuroscience. Within my psychology applications, do I need to explain why I only have neuroscience experience in my statement of purpose? If so, how should I go about doing this? I was a psychology major and I became interested in neuroscience during my second year, so that's why how I chose my first experience. I chose my second experience because they hired me due to my initial experience so I didn't have a lot of leeway with this one. I am still unsure which subject I prefer however.
Answer: You ask how you should go about applying. Just do it. The evaluation of whether your background is lacking or not will be made be any a committee at any institution you apply to. We can't judge that here. And, your record is what it is.
But the committee will e looking for indicators of success so make sure that your materials and statements indicate a high likelihood of success, not the possibility of failure. In particular use positive terms in describing your background. Don't say "Sorry, I only studied neuroscience...". Say, "I have a strong research background in neuroscience". That is to say, leave out words like "only".
I don't know the fields at all, but on the face of it I would think that (a) any research experience at all is a plus and (b) neuroscience gives you pretty good insight into some of the problems in psychology.
In some places there is an opportunity in doctoral studies to take additional courswork to fill in any gaps. This would be true in the US, for example.
Keep it positive. Knock 'em dead.
Answer: There are many fields in psychology that have a close relationship with neurosciences such as cognitive psychology, pharmacology, rehabilitative psychology etc. So it is worth exploring and explaining how your previous experience in neuroscience will enrich and support your future ambition in psychology.
You have done some psychology subjects by the sounds of it, so you do have some relevant experience. Just remember though, for most countries, there are strict regulation around clinical practice and becoming a registered psychologist. A research psychology PhD would not meet those requirements, so do your research.


How physically small can human intelligence get?

Question: A common trope in science fiction is the idea that a human's consciousness and intelligence can be downloaded onto a computer.  I recently had the idea that maybe in some apocalyptic scenario, millions of people could download their brains onto computers to be stored for later.  They would still be able to think and have awareness during this time and maybe even communicate with each other.  So, I got to wondering: how small can that computer reasonably get?  Could you have a computer storing the information of a brain be the size of, say, a flash drive, or could it be done with nanotechnology? How far down could you go?
Comment: This question does NOT have an answer at the link, at best it is a non-answer (as small as you want). This question should be re-opened.
Comment: [My design](https://worldbuilding.stackexchange.com/questions/20622/ways-to-make-contact-with-aliens-on-a-much-larger-size-scale) is about a micogram for the quantum computer proper, 10× that with necessary isolation shielding.  I had to really try to come up with a way to do that many operations in a small enough package, and lowball estimates of data storage.
Answer: From Here:
"The average human brain has about 100 billion neurons (or nerve cells) and many more neuroglia (or glial cells) which serve to support and protect the neurons (although see the end of this page for more information on glial cells). Each neuron may be connected to up to 10,000 other neurons, passing signals to each other via as many as 1,000 trillion synaptic connections."
From Here: "Today's transistors are about 70 silicon atoms wide, so the possibility of making them even smaller is itself shrinking. We're getting very close to the limit of how small we can make a transistor."
I will tackle this by first considering just how much space it would take to store such a brain; without processing: a pure "download". The minimum requirement would be to store every one of these connections, so that other future (much larger) machinery could reproduce the function of a given human brain. Just like we store a computer program in bits on a hard drive, but it cannot execute there, it must be loaded into memory, have hardware and power to translate the bits into activating circuits that accomplish instructions, and so on.
A single silicon atom is approximately spherical about 0.2 nm wide; presume a binary bit (0 or 1) could plausibly be stored in a cube about 0.3 nm on a side in some crystal-like matrix (in some future technology; but we can already manipulate individual atoms; so not entirely implausible).
How many bits do we need to store
Naively; Each of 100 billion neurons $(10^{11})$ can be connected to any other neuron; so we could store 100B bits per neuron with a 1/0 to indicate connected or not.
However, the average is only 7000 connections per neuron, but we don't know which 7000, so we need to store neuron numbers instead. It takes 37 bits to store a number up to 100B, so assuming the average holds for our quick estimate, about 49000 bits per neuron to store all the connections in the brain. We need $4.9\times 10^{15}$ bits to store the brain.
How large is the Crystal
We take the cube root of that to determine the number of elements per side in our crystal cube. The result is about 170,000 atoms per side. Multiplied by 0.3nm, our cube is 0.000051 meters per side; or 0.051 millimeters. If you prefer inches: 0.0020079, about 1/498 of an inch (larger than 1/500).
For comparison; human hair varies from about 0.002 to 0.006 in width; so this is in the range of the thinnest human hair. Given two such hairs crossing each other, the size of just their intersection can contain enough atoms to store all the connections in the brain. To store 1 billion people on such cubes would require 1000 times as much space on each side: So a 2-inch per side cube per billion people.
To Execute
Now you require transistors and support circuitry and power. Here is some information on that front. In that project, they require 100 elements per neuron and 20 per synapse (connection). Since we have 7000 connections per neuron, 20x7000 = 140,000 transistors for the synapses per neuron, versus 100 for the neuron itself: Plus we need both input and output; so figure about 250,000 transistors per neuron. On top of that, actual transistors extant today are 70 silicon atoms. Perhaps 24 is plausible; but I think we push credibility to get down to molecule size. Add cooling requirements (this would be blazing hot). So our problem is for execution we must scale up to 24 x 250,000 per neuron (a factor of 6 million). To get our storage cube to 6M times the volume; it scales up to 0.365 inches per side.
Now if you want to store a billion people; you need 365 inches per side, about 28,141 cubic feet. Presuming a processor 10 feet tall, you need a footprint 54 feet on a side; this could fit in a small warehouse. Or more likely a spaceship. Chances are you need a nuclear power plant to supply power, and need to run it cooled by empty space to about 3K, or -270C, shaded from the sun and well away from Earth (a heat source).
But those are engineering details!
Comment: One very important thing that you have overlooked here is that the state of synapses &c is analog, not binary, so you need at minimum several floats to represent the state, not just a bit.  For a reference, about a decade ago simulating a few cortical columns (of which there are about 10^8 in the human brain) took a BlueGene supercomputer, which occupied a few dozen refrigerator-sized cabinets.
Comment: Storage bits: you considered addressing links, but did not discuss the *weights* associated with them, or the current state of the cell.  But your figure for addressing is too high because most connections are local, and in fact a cortical column is a standard part that can be repeated from a template.
Comment: @jamesq: The **operation** is analog; whether there is a connection is not. For **storage** purposes I think a single bit per pair is sufficient. As for operation: Transistors are actually analog! Recall they replaced amplifiers and have a graduated response map (or ramp) from fully closed to fully open. I wouldn't assume that how IBM did it is the best way of all time to get the job done. I am just trying to compute a minimum which may not be realizable; e.g. you can't hide this in a garage: But it might fit in the space of an existing large mall or factory; you don't need a square mile.
Comment: @Amadeus: The action potential firing by one neuron and propagating to the connected neurons is a binary event.  The cumulative state that determines whether the firing will or will not take place is very much an analog process, though.  I do realize you're trying to guess at a minimum: what I'm trying to say is that that minimum is probably much larger than you think.
Comment: Definitely worth noting that 1 bit per atom on each atom in a crystal matrix would be an *absolute physical laws* minimum on size. This avoids the messy issue of "how the hell do you read it?" But we can scale up easily enough by multiplying the number of atoms needed by the current scale of electronics and adding some padding and bussing space. So starting at a grain of sand and adding all that in...yeah, you might end up with a crystal the size of a current flash drive.
Answer: I think this is one of those questions that ultimately boils down to "whatever size you need it to for your story", depending on how far into the future it's set.  On the one hand, while we're not able to model the human mind, we've made a lot of recent advances in neural networking and artificial intelligences, and many of the cutting edge tools that have been developed can be run on a high-end desktop (just be sure to get the best graphics card you can afford).  On the other hand, computer hardware is constantly both increasing in performance and shrinking in size.  The smartphone in your pocket has more computing power than all of the computers that put mankind on the moon back in the 60s.
At some point in the future, we'll be able to model neural nets complex enough to replicate a human mind, and figure out a way to "upload" ourselves.  None of us know exactly when we'll reach that point.  It may happen in ten years, it may take a hundred, it may take a thousand.  And of course, your apocalypse doesn't have to happen immediately after we've reached that point.  Brain-uploading technology could be well-developed and centuries old by the time of your story.
And similarly, no one knows how small or how powerful computers will have become by then.  If we've managed to get quantum or optical computing working by then, the computers capable of doing this might be desktop-sized, or even smaller.  You might be able to run a human brain-model on your supersmartphone.  You could even dream up some sort of "hyperspace" computer that is the size of a grain of rice and yet more powerful than the entirety of modern-day computing.
So, having said all of this, you are asking about uploading millions of people into an environment where they're all networked with one another.  I would expect that would require at least some sort of significant size, if you're trying to stay within the bounds of physics as we know it.  I'm picturing something data-center-sized, unless you're bringing hyper-advanced tech into play.
Comment: I don't find «some sort of significant size» to be a useful answer.
Comment: Which is why the next sentence specifies "something data-center-sized". :-p
Comment: The question that needs to be asked here is whether neural nets or "artificial intelligence", however useful they may be for automating certain tasks, actually replicate the actual mind (human or animal) in any meaningful way.
Answer: My design is about a micogram for the quantum computer proper, 10× that with necessary isolation shielding.  I had to really try to come up with a convinsing way to do that many operations in a small enough package, and lowball estimates of data storage.
In this post I go over the needed resources.  The smallest is of course a direct program not an emulation of our own physical layers:

you already knew how the brain worked to produce intelligence, writing that program fairly directly would require 1015 FLOPS (Blue Gene/P circa 2007) and 100 Terabytes.

The size requirement is driven by the data storage.  Figure 1 atom per bit?  Figure the needed volume for that.
Some other answers go over the connectivity, having more wiring than processing.  But real hardware already avoids that problem: 1 core simulates many nurons, and data transfer is over network links, not point to point between every pair of cores!  With a program (not a simulation) the concept is clearer — each op needs its own argument data, and as long as the store can keep up with the mill, a normal memory back attached to the processor will suffice.
In my quantum computer description from my story (in the linked post) it avoids all wiring by having waves of interference patterns play over the storage matrix.  More generally, you can imagine a 3D crystal being addressed by lasers that find the crystal transparent to individual beams and non-linear where they intersect.  So no wiresv the probe light passes through the storage itself without problems.
A quantum computer can perform a lot of operations.  In fiction they are just ridiculously fast, and that may hold for you.  In reality they can solve or search certain classes of problems using superposition as parallelism to find the right one; the program would have to be written to use that kind of operation to get that kind of exponential speedup.  But even classical computation is fast if the parts are very tiny.  If you do logic usingbspin states of single atoms, the speed would be limited to lightspeed getting information through it.  In my fictional treatment, I try to minimise the volume used for most common calculations, to boost the speed imposed by this limit.
If you have multiple nano-sized cores, unlike my design, you can have a lot of them in what we consider a small space.  So you might consider a design that's a cube of 1000 to a side or a billion nano-cores, each having simple processing capability and some local memory.  Look up how many gates a CPU needs — say, 12000 for the ARM M0 — and say each gate is made from just a few atoms.
A billion × 12000 × 10 is about 1014 atoms, which is about 2 nanograms of carbon if I figured that right.  Add 1014 bits of storage at about the same size for single-atom memory.  If memory takes up several atoms, or is stored in multiple copies, multiply that out.
Give the whole thing an extra order of magnitude for measure, and that's 50 nanograms.  At 3.5 g/cm³ that's about 25µm cube. (Somebody check my calculations please.)
Answer: Very small.
We have only applied serious resources to research in neural nets and quantum computing since the 80's. Assume some hefty developments in those areas, and a building the size of a large shopping mall might house the equipment for storing a planetary population.
This makes the reasonable assumption that there would be similar geometric progressions to Moore's law in those technologies.
https://en.wikipedia.org/wiki/Moore%27s_law
A great example of this is that discrete parts were used to emulate neurons in the 80's to wire up neural nets that had no more than a cockroaches nervous system. Today you can buy for $4000 a credit card board that has 4096 neurons.
http://www.general-vision.com/hardware/neurostack/
Comment: Do you think you could **quantify** better than "very small"?
Comment: Sure I could. I could even post calculations to back up my statements that are wrong by two orders of magnitude and ask somebody else to check my calculations. I made a very conservative statement that a large building could hold a planetary populations consciousness and dispensed with making any calculations that would require making possibly invalid assumptions.


What does ぴろーん mean?

Question: This appears to be some kind of adult slang term, or maybe it's internet slang, whatever the case may be I can't find a definition in any dictionary. Is it an onomatopoeia?
Comment: I know exactly what it means but I don't know whether or not it is ok to explain it here.
Comment: @TokyoNagoya:  Just explain it as objectively as possible.  After all, this topic exists.  http://japanese.stackexchange.com/q/1129/78
Comment: It's okay to discuss taboo language (although it's understandable if some users want to avoid doing so).  After all, taboo language is still language.  One caveat: we should try to keep question titles "safe for work" in case they're promoted on other Stack Exchange sites, which people may be using from work.  (The question istrasci links to would have to have its title censored if it were asked today.)
Comment: That's what I thought, because I even asked on Yahoo answers in Japan and no one's answering. There must be some way you can explain it without having to be explicit.
Comment: All I get so far is that it might have something to do with "penis" and it might have something to do with stretching, but it still isn't clear.
Answer: It is an onomatopoeia, not the name for an object unless the author/speaker uses it as such for his own aesthetic purposes but this would be fairly rare.
It describes the way a long object dangles, stretches, lies down, etc. in a lazy manner.  The long object coud actually be anything from linguini to a cat stretching its body, from hair to stretching cheese, etc.
If OP saw/heard the word in adult content, it would probably be about a male organ.
Comment: Thanks for that explanation. Does the first part, the "P," stand for an English word that also starts with "P," and is perhaps, 5 letters long?
Comment: Is it the second "P" in the women's version of O.P.P.?
Answer: ぴろーん is an onomatopoeia to describe a long thin rolled object extends and runs like a tonge of a chameleon. It's nothing to do with adult slang terms.
Comment: I think user4092 is right. It has nothing to do with those mystic funny connotation.
Answer: maybe its a "loooooong" penis?
Comment: That's what I would have guessed.
Comment: @istrasci なんでぇ~~www

What does ぴろーん mean?


What can I do to get my car to stop surging?

Question: 2001 Chevy Malibu has been surging for the past 2 years. The transmission has been checked, I had just replaced the catalitic converter around the same time the car started surging. I took off the MAF and the car stopped surging but it rode rough. I replaced the MAF and the car still surges. It starts to surge after a right turn, after it goes over a speed bump, after it goes over a dip. It surges going up hill, it starts to surge when the car comes to a sudden stop or after I slam on the brakes. And now it even starts to surge when I'm just driving straight down the road and I excelerate. I put the OBD2 machine on it but it does not have any codes(DTC'S) on it. Please help, I don't know what to do.
Comment: Check your motor mounts. I'm not sure about your car, but would assume it is drive by cable. If so, the engine could be tilting when doing any of these actions, pulling slightly on the cable, which could cause the surge.
Comment: Most Surges are due to IACV valve either clogged or bad. If that is not the case check fuel pressure as it may go up and down.
Answer: I had a Chevy van do that same thing and after several pricey mechanics looked at it a "good ole local boy" mechanic found the issue. My main computer was mounted under my drivers seat and was loose. Going around corners, up hills, stopping ect.... Would break connection and cause surging that drove me crazy for months! He bolted it back down and fixed several wires that we're loose from all the movement. Problem solved!


If two features are highly correlated to each other and giving same impact on target variable in this case, which feature we need to select?

Question: in my dataset, I am having plenty of features and two features are highly correlated to each other and giving same impact on target variable, in this case which feature we need to select  in order to build model  and what strategy  we have to use to select any one of the features
Comment: Why not pick both?
Comment: Its not a good way to take both features which are highly correlated to each other ,because each features has to be independent to each other not dependent .
Comment: According to what? The Gauss-Markov theorem makes no such assumption, for instance.
Answer: First let me answer your specific question:
If you want to decide which feature of two highly correlated, high impact features I would look at the following additional attributes of your features:

How is the data quality or amount of data? Is one better or higher than the other? Choose this one.
Is it in any way harmful to remove one of the features? If yes, keep the one with lees harm (for example accuracy drops, other calculations become complicated or maybe you need one of the features for your output)

However I want to ask you to consider the following before removing any of those features:

Is having both features in any way harmful to your accuracy?  For example if your features correlate with each other but each also correlates with your target it might still be fine to use both. Also depending on your algorithm it is not harmful at all to use both. Some algorithms are more sensitive to multicolinearity than others.
Do you safe considerable time when training if you remove one of your features? If so than go ahead and remove the one by looking at the example attributes I listed above
What is important for you? Coefficients/p-values or prediction accuracy? Multicolinearity can be harmful for coefficients and the interpretability of your model but still yield good prediction accuracy. Multicolinearity between features doesn't necessarily mean that you have bad predictions.
Do you have a problem of high dimensionality? If so removing high-correlation features reduces your number of dimensions and is therefor beneficial for your algorithm


Is using a hair dryer on my M3D build plate safe?

Question: I often have trouble with prints being especially difficult to remove from the build plate on my Micro3D printer.  My wife suggested using a hair dryer on the underside of the plate.  I was initially appalled at the idea, but now I think she may be on to something.  Is this safe?  Good idea? Bad idea?  Heresay?
Comment: Do you get the build plate out of the printer for the procedure? I realized that I do not know whether this is even possible when I finished my answer, and it will need to be revisited depending on this ;)
Answer: Typically, people cool down their build plates to get parts to release, rather than heat them up. That said, I doubt a hair drier will get hot enough to do any damage to the build plate. You could try it with no harm done.
Comment: I've definitely tried it, and it seems to work pretty well in getting the parts to loosen up. I'm just worried about damage to the plate.
Answer: That was a problem for me too. My M3d printer was getting stuck to the plate. However, I now print on painters tape, and I put down painters take on the bed. Then I glue stick the tape, and when I am done, I just pull it up.
You should try it, because it will allow you to print with other then the m3d plastic.
Comment: Thanks for the answer. I have considered using painters tape, but I thought the purpose of the coating on the build plate was to eliminate the need for that.

Regardless, this doesn't really answer my question about whether it's safe to use a hair dryer to lightly heat up the build plate so my prints come off easier.
Answer: It's what i do. Painters tape. are you using the m3d plastic? that's why. the coating is to make sure it sticks their only plan to get it off is to bend the plate a little bit. Hair drier won't end the world. don't hold the plate and hair dry it, that might hurt. But M3D sells spare plates it you destroy it. Try it out, tell us what happens.
Comment: Yeah, I use their "3D Ink" and I haven't been using painters tape, and I do flex the plate a little (which also worries me that I'm going to damage it), but the hair dryer trick seems to work ok, though I've only done it a few times.
Comment: cool, thanks for the tip. but also, you should look into hatchbox plastic on amazon. its 4 times the amount of plastic for a little more than the m3d plastic. i use it with tape and its awesome and i have so much of it. i think its 20\$ for 1lb roll where m3d is 15\$ for 1.5 lb roll. Logic is there somewhere.
Answer: I agree to Tom's first part of the answer, usually you'd cool down the plate to loosen the print. This is reasoned by the shrinkage of the builplate while the print stays extended. The strain put into the interface helps to get the print of. Warming the plate could essentially do the same, but since you deposit a warm filament, one would assume that by warming up you will reduce the strain that has been built up by the regular cooling of the filament already.
I guess an uneven heating with a hairdryer will probably introduce uneven strain or evan some kind of warping of the buildplate that puts more strain to the interface which makes your approach work. If you want to test whether you have some local deformation you could characterize this by reflecting a laserpointer from the heatbed and marking the reflection on a rather far away wall for some controlled positions you can get the laser in (by say putting it on a photography tripod). The change of this reflections towards each other could tell you about the deformation.
I also agree that most of the hairdryers around would not be hot enough to be a worry, but since most of the Micro3D is made from plastic I would put twice the time into figuring out if that is really true.
Just for the fun of it, you could put an ice cube next to your finished print if you make sure that molten water will not go anywhere it is not supposed to be. Maybe this lifts off the print as well. However, I do not recommend doing this, of course.
Answer: Before I got an aftermarket heated print bed for my M3D, I regularly used a hair dryer to pre-heat the build plate up to 60-70 °C before printing with no ill effects.
Answer: cold wind can help to acceleratory cool down and dry the build plates to make it easy to part them.


Create a Select by Attributes subquery from a locational selection in ArcGIS with multiple variables

Question: I have a large shapefile of GPS points. Each point has a unique point ID number, but they are all part of different clusters, where each cluster has a unique cluster ID number (there is no overlap between clusters). For example, points 1, 2, and 3 are part of Cluster 100 and points 4, 5, and 6 are part of Cluster 200. I have done a Select by Location query of these points based on their proximity to a road feature class, and now have about 1400 points selected. I would now like to select any additional points that share a common Cluster ID to the already selected points. For example, say I captured points 1 and 2 of Cluster 100 with the locational selection query, how would I capture point 3 of Cluster 100 as well, in an efficient query? Or is there a way to have a subquery in the Select by Location query that would look at the cluster ID attribute?
Answer: Sounds like you can use the 'Select by Attributes' tool with the selection method set to 'Add to Current Selection'

Then just build your query to select all the points with a Cluster ID for the group that you're interested in.  That will add any that got missed by the spatial query.
Comment: Is there a query that can efficiently identify 100+ unique cluster IDs?
Comment: I'm afraid I don't understand your question.  If you just want to see all the unique values present in a field just select the field in the dialog box and click the "Get Unique Values" button.  If you need to do things automatically - as in get the computer to do this for you - then you're looking at using a python script or maybe a model.  That is a whole other ball of wax.
Answer: Here's what I ended up doing:
After doing my Select by Location query, I made a selectional layer of those points within the defined proximity of the road. I then ran a Frequency tool with the Cluster ID as the only frequency field and saved the table. I then joined this frequency table to the full set of points based on the Cluster ID, keeping only matching records. I then started an editing session and deleted all the points indicated in the joined table.


Strange permission behaviour

Question: We have a SP 2010 system. We recently discovered that users with no permissions to a library are able to open documents in a library if provided with a direct url link to the document, thereby appearing to bypass  any permissions that have been set in the library. But if the users are supplied with a document id link to the same document  their lack of permissions are respected and they will get access denied as one would expect. Has anyone come across this kind of behaviour before?  Any help would be greatly appreciated as this is a major security hole.
Answer: If you've already checked the following my apologies for suggesting it:
For the document (or documents) in question, can you verify that they have not had permissions broken off from the library ? If they are in a folder, also check that the folder hasn't had it's permissions broken off.
I've seen what you are describing when the document had broken permissions off from the library. User could go straight to the document (in my case a word document) but obviously could not go to the library and browse. As for the document id link: This probably tries to open up other assets in the library or site to which the user doesn't have permission (the document ID link is probably trying to open up a display page for the properties of the document which might pull images, scripts, etc. to which the user doesn't have access).
Answer: Problem solved. It turns out a previous developer who had developed for us a library provisioning tool for some inexplicable reason decided to set the alloweveryoneviewitems property to true in the code. This meant every library we have provisioned in our system had this value set to true. Easy to fix with powershell script changing the value to false - problem no more.

Strange permission behaviour


Birthday notifications for a select group of friends on Facebook

Question: I don't want to be notified about every friend's birthday on Facebook. There are only several birthdays that I want to be notified of. Is there any way to filter these messages somehow (e.g. by adding the friends to a list) and have it only remind me of these birthdays (via email)?
Comment: So I am guessing you do not want to use any of those shady facebook applications ;)  ?
Comment: I ended up just looking at the list of all birthdays and adding the ones I wanted to my Google Calendar... not a great solution!
Comment: @phwd: haha exactly
Comment: @x3ja: This is probably the best way to do this today.
Answer: If you use Yahoo mail there is a way of doing this. In Yahoo Contacts you can import your Face Book Contacts. Once they are imported you will will have to go to each individual that you would like your birthday updates from and choose to "Get Updates"  They will get a request to allow you to get the updates. once this is done you will get the updaes from a group of friends into your yahoo mailbox. If you don't use yahoo then you can set up a forwarding rule to forward the updates to your Email Address.
Comment: Is it a one-time import or can it sync the contacts? Doesn't that mean that my Contacts would need to be using Yahoo so that I can get their updates? What kind of request will they be getting... is it an email?
Comment: Yes I just tried it. It sends an email invitation to the user. So the user would have to know before hand. Also you would have to set your profile picture otherwise it looks like a spam-ish email. Also the user needs to sign in to make the connection.
In addition, once the user confirms you as a Connection, you will get to share more, including birthday reminders and Contact Information updates. I have not tested if it does only birthday reminders though ,not putting the test subject through that trouble.


Should I emphasize certain traits in my CV for master's application?

Question: Should I modify my CV to emphasize certain traits before including it in my application for a master's degree or just include my usual professional CV?
Answer: An academic CV typically contains items you wouldn't want to list in a professional resume, such as a complete publishing history. Your resume may list as a bullet point that you are published, but they don't want 20 pages listing each publication, for instance. So, yes, your academic CV should be different.
Comment: Of course, a master's candidate isn't likely to have 20 pages of publications. . . .
Comment: @aeismail certainly, but it illustrates the point.
Answer: Yes, it's a good idea.
It's a good idea to tailor your CV and/or resume to each position you apply for. Keep two copies of your CV:

comprehensive (academic) version that has everything you've accomplished in academia and your profession, and
short version that only contains pertinent information.

Some applications require you to submit a short (2 page or less CV). You might consider submitting both a long and short CV to your program.
Answer: A CV is very different from a professional resume. Your CV should emphasize those elements that pertain to the Master's program that you are applying to. For example, if you've been working in a biotech lab and are applying to a bio MS, then filter that up to the top.
Academic publications should also rank very highly -- but deprecate most non-academic publications such as novels, unless you are applying to an arts or literature related MA>
Answer: You should always modify your CV to emphasize certain traits.  If a decision maker is sorting CVs, you want yours to be noticed. Citing specific and credible experience directly related to the program (or company for a general CV) to which you are applying, gives you a much better chance of getting noticed.
I personally re-work my CV for each opportunity I ever applying for. It takes 15 minutes, and can make a huge difference between where you will spend the next few years of your life.
Take the 15 minutes to rework your CV and make it specific to the desired opportunity.


How is all this bitcoin theft happening?

Question: When reading many stories about bitcoin theft, what is the usual gist? Dont most of these hackers get digital wallets that are encrypted? How do they make use of it, crack it...or its not encrypted at all?
Comment: Bitcoin-related thefts seem get a lot of attention compare to the much more common banking-related or payment service theft.  http://mashable.com/2012/10/24/barnes-noble-pin-pad-hack/
Comment: Speaking of Shamir's Secret Sharing method, there's excellent implementation, [Passbin](https://itunes.apple.com/us/app/passbin/id718617728?lmt=8) @ AppStore
Comment: I would NEVER trust an app to split my secrets. Only use an open source library, and make sure you download the code and run it yourself on a computer that's disconnected from the internet (ideally never been connected to the internet). Try this python implementation: https://github.com/halfmoonlabs/secretsharing.
Answer: There are many ways theft can occur.
Even though the cases where hackers have stolen from exchanges or from individuals, in terms of the number of bitcoins lost that amount is chump change compared to the amount of coins lost to scammers such as PirateAt40 and other scams, including loans not being repaid or currency trades that go bad.
But as far as bitcoins lost to hackings, yes -- the thefts have been due to poor security practices being implemented by exchange operators and other businesses where an attacker takes advantage of that to steal funds.
The list of the top thefts in which these hackings includes some of the details for various incidents.
Security is difficult and expensive, and Bitcoin startups generally don't have the revenue and profits sufficient to attract the capital that would allow top-notch security to be implemented.  As a result, they become juicy targets for the attackers.
Even following the recommendations for securing online services does not ensure that there is no risk of theft, but most losses from theft thus far were because those recommendations weren't followed.
As far as the term "cracking" ... that generally refers to discovering passwords.  In June 2011 when an attacker obtained the list of accounts and password hashes from Mt. Gox, cracking was able to discover passwords for many accounts due to there having been poor security on the password hashing method implemented by Mt. Gox at the time.  Most Bitcoin-related service operators are smarter than that but that incident has helped any that weren't to become a little more aware of proper password security methods (e.g., BCrypt).
Password cracking might also be used by an attacker to gain access to a system which which may hold coins in an unecrypted wallet, or that breach may lead to credential that provide access to additional systems which hold coins in an unencrypted wallet.
The reason hackers are successful when compromising these server systems used by exchanges and other bitcoin businesses is because if software needs the ability to send outgoing payments then the attacker who has compromised the system then gains that same capability.  Even if the wallet is encrypted, the software would use the passphrase to unencrypt it so either the Bitcoin client is responding to requests after the passphrase has already been provided or the passphrase is avaialble to the software to make such requests.  And thus if that system is compromised there is no protection possible for those coins in the wallet on that system.
For this reason, any exchange or bitcoin business using hosting for their systems where the hosting service has any access to the hosted service whatsoever, those coins are at risk.  But most Bitcoin businesses are not at the scale necessary to justify proper security at data centers (e.g., using their own hardware colocated in locked cages in highly secure facilities).
Even with that, that is just the security for the hot wallet containing a fraction of the service's bitcoins needed for daily operations.  Security for the offline wallet might involve using paper wallets stored in bank vaults, or access protected with Shamir's Secret Sharing method even.
Much more common than breaches of security at Bitcoin exchanges and services are compromises of individual EWallet accounts at these online services.   This often happens when an individual shares a username and password for their exchange account with another service.  For instance, after the Mt. Gox passwords were leaked, other exchanges went on lockdown because so many accountholders had common login credentials on both services.  A protection against that is for the exchange to offer multi-factor authentication.
Individual users of the Bitcoin.org client can protect their wallets with passphrase encryption.  This still leaves them vulnerable to a replay attack should their system be compromised with a keylogger or similar malware.  For this reason, offline/cold wallet and "air gap" systems are recommended when the amount of bitcoins held are significant.  A similar recommendation exists for online banking, so compromised systems aren't specific to Bitcoin users.
Comment: Shamir Secret Sharing is great. If you're looking for a straightforward, easy-to-read python implementation, I'd check out secretsharing: https://github.com/halfmoonlabs/secretsharing.