With the possible exception of plane geometry in high school, most students won't see a proof until linear algebra.
Most Algebra textbooks have a proof or two in them, and sometimes they even require informal proofs in homework: "show that equation 1 is equivalent to equation 2".
Most calculus books also have some proofs, which may be helpful to some students, but are not essential to learning the material.
Excluding geometry, linear algebra is admittedly the first text most students encounter where there are proofs accompanying each new concept.
Geometry as often taught in high school does introduce proofs. That is good, but unfortunately the proofs it uses are fairly rigerous, which is the exception rather than the rule in most of mathematics. The common method of proofs in geometry has one write each assertion on a line on the left side of a table, along with a justification (postulate/axiom 12/using assertions 1 and 5 along with thm 20.5) on the right. Advanced mathematics tends to write more informally skipping many intermediate assertions if they seem obvious, and often making assertions without explicit justification.
What mathematics a programmer needs varies substantially on the work they do. Writing a physics simulation program? Algebra is essential, and calculus may be essential, but may be optional depending on what is being simulated, and the techniques used.
When writing a program to manipulate images, Linear algebra can be very helpful, especially for simple transformations. If you are writing a program to find an optimal schedule of buses for a city, then linear programming is what you need.
On the other hand, if you are writing a basic online store and you can get by with arithmetic (except in so far as Relational Algebra is the basis of the DB being used, etc). Writing a simple (non-physics based) computer game may involve very little math.
Writing a compiler? The important parser techniques etc can be described using math, but a very abstract one, far more abstract than calculus or even set theory.
Engineers, and mathematicians usually do best in law school. People with a strong math education understand logical argument, whether it be in symbols and numbers, or in words.
Very true, but law drives me crazy, because of all cases where caselaw directly contradicts both the literal meaning and the intent of the statute. That can all too easilly happen if the party the literal wording or intent of the statute supported did not give a proper argument for that position, or overlooked some part of the statute. Further, by a similar mechanism existing caselaw that should be considered binding precedent does get inadvertently overlooked all too frequently, resulting in more aggravating inconsistency.
Very true, with the exception of problems that could not be found by any search engine.
That said the results when customized search is disabled is not quite as good as it was when I started using Google. The popularization of Blogs and other self-publishing methods, and especially the spam that went with them, initially caused substantial deterioration of the search results (despite also sometimes having the best answer out there). After a year or so, the quality had recovered most of the way, but has never seemed quite as good as it once was. However, with the customized results, the results are better than they initially were, so I'm not complaining.
Indeed, although I have seen people confused by the horizontal ads that appear at the top of some Google searches, despite the different background color.
Nevertheless at the time Google was started, some of the competitors would accept money for higher placement, or permit ads which were difficult or impossible to distinguish from a regular result.
I would hope they are only using face detection tecnology for street view. They do have actual face recognition technology though, as evidenced by Picassa. (I find it amusing when it tags a face on a photo in the photo, or a face on a t-shirt, etc. It even tagged my Cat's face in one slightly blurry photo. )
I've Seen that go really bad: A zip file that contained a few dozen zip files, inside of each was a single partial rar file.
What happened is that the item in question was originally distributed as split rars. Then one of those "helpful" sites in the warez community that automatically grabs files from some source (perhaps a topsite, or usenet post, or via IRC's DCC feature), and wraps it in a zip along with a copy of the.NFO file, and a file identifying this "helpful" site. Somebody else later came along, downloaded each of those ziped parts, and helpfully combined them inside a new zip file with yet another copy of the.NFO file.
But I have seen packings before that had as many as five layers before you get to the main content. That usually happens when a file like I described gets broken again into pieces to upload somewhere, and somebody else recollects those pieces and puts them in a rar or zip file.
Shampoo is mostly water (as in more than any other single ingredient) . The first ingredient on virtually every bottle of shampoo I have ever seen is "Aqua", which is water.
Granted that it often does contain a whole lot of other ingredients, but certainly enough that it should set off the water detector.
The idea should be that anything that has enough water that it is almost certainly not a bomb making chemical can be immidately ruled safe, letting them examine the others more closely.
Of course high water content does not not rule out the possibility of being a weapon. Saturated solutions of HCL for example are still like 60% water, and yet could easily eat through the aluminum skin of an airplane, or do severe harm to a person.
But nobody's ever tried to hijack an airplane with that yet (as far as I know), so security ignores the possibility.
In my experience, the fun Multiplayer has always been playing against friends. This was a large part of the appeal of games like SSB or Goldeneye.
Unfortunately most Adults don't have many good opportunities to get together with friends and play local multiplayer.
It also turns out that although online multiplayer usually supports playing with friends, it doesn't help much. First of all, it often does not particularly encourage playing with friends, with the option to start a match with complete strangers being usually more prominent. Second, unless you have quite a few friends, the ods of you being on at the same time as your friends tend to not be very good.
You can most definitely have a solid plot of going back in time, as long as the movie does not permit changing the past. The characters might believe they are traveling back and changing the past, but it always was the case that they traveled back in time and did what they did.
There are movies operating on this mechanic that can withstand heavy scrutiny. (They may have minor mistakes, like the continuity mistakes found in non-time-travel movies, but nothing that prevents analyzing the core story). One example of such a movie is _12_Monkeys_.
Philosophers have arguments for permitting backwards time travel (but without permitting changing the past) which appear to be rather sound, more so than most other philosophical arguments. However, permitting such backwards time travel appear to violate free will, since if one were to meet a future self that had traveled back in time, they would not have the option of later choosing not to time travel.
If one allows only forward time travel then one can easily keep free will.
It is easy enough for one card to be connected to both an infrastructure and ad-hoc network. There are however a few minor limitations (such as using the same channel for both). However, many OS's don't have a sufficent API for drivers to allow this, and even when the API is there, not all drivers implement enough to permit this. Indeed sometimes the drivers could not offer such features, because the defined driverchip path is lacking.
Just like pretty much all wifi chips have the hardware to support running in AP mode, but in many cases at least one of the drivers, chip firmware, OS, or driverchip communications path don't support the mode.
Well depending on how you look at third party software, one might claim that much of Darwin is third party, but I will admit that there is extremely little that ships with the latest Macs which Apple is not compiling themselves.
The thing is though that it takes an awfully long time to evolve a creature that even moves randomly, eats food when touching it, and procreate when reasonable.
But until you get to that point, you have no chance of seeing interesting behaviors like using the eye to find food or avoiding predators.
IIRC, about 6 months ago, a post to the critterding mailing list indicated that besides the program creator, only one other person had managed to evolve a creature that would actively look for food.
Lottery can work, but I would think there should be some deterministic algorithm that could be used instead.
It would be nice though if processes that rarely use disk get higher priority than those that are frequently using it, which basically entails combining this information with the ionice priorities to get the actual priorities.
But there is a very easy way to ensure it is not the I/O scheduler making poor decisions. You bring up the CPU scheduler, probably because the OP brought it up, but obviously if the utilization is that low it is not likely the CPU scheduler.[1]
Assuming the I/O scheduler uses ionice values, one could set the io priority of the disk hog to very low. If nothing changes, then it is not the I/O scheduler, and is probably something else like the issue you mentioned. If things return to normal speed then it may well be the I/O scheduler, but still could be other things instead.
Notes:
[1] Although the CPU scheduler does interact with IO. If the scheduler knows that a process is likely to immediately perform a blocking read if scheduled, returning the rest of its timeslice it should schedule that process right away, so that said process will have the opportunity to process said data sooner.
That is very true, with the exception of course being if the author intentionally articulated an idea poorly, for some reason. Perhaps he is writing about different writing styles, and is giving an example of something hard to understand. Perhaps the author wants the sentence to be hard to parse for some other reason, such as part of some sort of riddle.
But in general, You should not need to re-read a sentence more than a time or two to understand it. A good exception, as you point out, is obviously if the author has presumed familiarity with technical terms (be they jargon or not) of which the reader is unfamiliar.
Yeah, I meant to mention the lack of effect form rotation, but forgot. When close, the induced dipoles in the metal will always exactly match the magnet, meaning that the sides closest to each other have opposite poles aligned.
This does mean that the strong magnets would be less dangerous to handle if so encoded, but obviously would only be useful for say lifting metal, or in conjunction with the paired magnet, rather than for attracting a piece of metal from a distance. For many purposes, only a a close effect is desired anyway, so it works out just fine.
The future of TV is invariably going to be basically everything on demand. It really does not matter if this is done over the Internet, or some system like Cable, but it will happen.
But let me clarify. By everything on demand, I mean that all standard shows can be watched on demand including their back catalog, and this for a flat rate fee, not an iTunes-like puchasing of each episode. This will also include shows no longer on the air. This does not mean that there will not be live feeds, although I would expect that a significant portion of TV watching will be non-live, except for live events like sports or American Idol. New episodes of TV shows may well also be watched lived, but only if the timing is convenient.
There will be some exceptions. For example, back episodes of the evening news will likely be kept available for only a few days, perhaps a week. The Weather Channel's weather reporting will likely not be available on demand at all, since it is only really worthwhile live. Headline News may well also be Live only.
The role of networks will be largely diminished. They will likely still be around, but people will not notice which network each show is from very much. They will still help finance production of new shows, and decide which ones are worth keeping, but this will seem like less of a big deal to them, since for regular shows, most people will watch them on demand, and see no advertising, and the network sees only a portion of the flat rate subscription. The real money for networks will be in the live events, where most people will be watching live, and thus will be seeing the advertisements.
Broadcast network affiliates will still be around, but their main role will be providing the local news, and operating the Emergency Alert System. The set-top boxes of the future will receive the emergency Alerts and pause the content being watched to deliver the alert, so that people watching on demand programming will not miss it, and people watching live programming do not need to miss a portion of the programming to hear the Alert, and can skip a few commercials to catch back up with live TV if desired.
If you watch a show from ABC.com, ABC will use geolocation to determine who your local ABC affiate is, and display their logo on the page. Presumably that means they are also sharing advertising income with said affiliate.
LAN = Local Area Network Most common technology: IEEE 802.3 A.K.A. Ethernet
MAN=Metropolitan Area Network A Network that covers a city, or significant portion of a city, or geographical area equivalent in size to a city. (There are also smaller network sizes, including Campus area networks, etc, but they always use either LAN or MAN technologies, so are irrelevant). There was an IEEE 802.6 standard here, but it never caught on. Common technologies here ate ATM, SONET, and increasingly Ethernet and MPLS.
WAN= Wide Area Network The definitions here vary. Some definitions have this include only things larger than a MAN, but others include anything larger than a LAN.
WLAN = Wireless LAN = Wireless Local Area Network The most common technology here is IEEE 802.11 A.K.A wireless Ethernet, A.K.A Wifi
WMAN = Wireless MAN = Wireless Metropolitan Area Network. One such Technology is IEEE 802.16 A.K.A. WirelessMAN (Note: no space) A.K.A. WiMax
The key with phones are that the basic protocols are not fixed sized, or when they are, they permit substantially more digits than we currently use, so we have plenty of room for expansion.
It is entirely possible to change the system to reuire5 digit area codes. After all, there was not much issue when people started needing to dial the area code for local calls, so dialing an extra few digits won't be that big a deal either. The bigger problem would be the way everything format telephone numbers needing to be changed, but we could still handle that.
The main pattern shown in the video is stronger than standard NIB magnets at close range. But die out quickly with distance. That makes them much safer to handle. The strongest NIB magnets could seriously injure you.
I'm curious though about how the pattern used affects how they attract ferrous objects. My hope would be that it has a very similar effect with ferrous objects as with the corresponding magnet, namely that it has greater attraction at short range, but dies out quickly with distance. That also seems logical based on my understanding of induced magnetic dipoles, but I'm no magnetism expert. If so, this also helps to mitigate the other main danger of powerful magnets. (Flying paperclips, etc)
The pattern they show also has minimal net force if one of the magnets is rotated out of alignment, and provides relatively small resistance to such rotation. That has lots of obvious uses for quick- connect quick-disconnect cables, especially those that need to need to withstand high normal forces, but not rotational forces. I'm not clear how the magnets they show handle shearing forces, but either way would have uses for various connectors.
True, except that current theory suggests that some (perhaps most), but not all matter on Luna came from Earth. The problem with water on Luna is obviously that it can only exist trapped below the surface, otherwise it would vaporize and drift away, given Luna's lack of atmosphere.
Slashdot Mirror
With the possible exception of plane geometry in high school, most students won't see a proof until linear algebra.
Most Algebra textbooks have a proof or two in them, and sometimes they even require informal proofs in homework: "show that equation 1 is equivalent to equation 2".
Most calculus books also have some proofs, which may be helpful to some students, but are not essential to learning the material.
Excluding geometry, linear algebra is admittedly the first text most students encounter where there are proofs accompanying each new concept.
Geometry as often taught in high school does introduce proofs. That is good, but unfortunately the proofs it uses are fairly rigerous, which is the exception rather than the rule in most of mathematics. The common method of proofs in geometry has one write each assertion on a line on the left side of a table, along with a justification (postulate/axiom 12/using assertions 1 and 5 along with thm 20.5) on the right. Advanced mathematics tends to write more informally skipping many intermediate assertions if they seem obvious, and often making assertions without explicit justification.
What mathematics a programmer needs varies substantially on the work they do. Writing a physics simulation program? Algebra is essential, and calculus may be essential, but may be optional depending on what is being simulated, and the techniques used.
When writing a program to manipulate images, Linear algebra can be very helpful, especially for simple transformations. If you are writing a program to find an optimal schedule of buses for a city, then linear programming is what you need.
On the other hand, if you are writing a basic online store and you can get by with arithmetic (except in so far as Relational Algebra is the basis of the DB being used, etc). Writing a simple (non-physics based) computer game may involve very little math.
Writing a compiler? The important parser techniques etc can be described using math, but a very abstract one, far more abstract than calculus or even set theory.
Engineers, and mathematicians usually do best in law school. People with a strong math education understand logical argument, whether it be in symbols and numbers, or in words.
Very true, but law drives me crazy, because of all cases where caselaw directly contradicts both the literal meaning and the intent of the statute. That can all too easilly happen if the party the literal wording or intent of the statute supported did not give a proper argument for that position, or overlooked some part of the statute. Further, by a similar mechanism existing caselaw that should be considered binding precedent does get inadvertently overlooked all too frequently, resulting in more aggravating inconsistency.
Very true, with the exception of problems that could not be found by any search engine.
That said the results when customized search is disabled is not quite as good as it was when I started using Google. The popularization of Blogs and other self-publishing methods, and especially the spam that went with them, initially caused substantial deterioration of the search results (despite also sometimes having the best answer out there). After a year or so, the quality had recovered most of the way, but has never seemed quite as good as it once was. However, with the customized results, the results are better than they initially were, so I'm not complaining.
Indeed, although I have seen people confused by the horizontal ads that appear at the top of some Google searches, despite the different background color.
Nevertheless at the time Google was started, some of the competitors would accept money for higher placement, or permit ads which were difficult or impossible to distinguish from a regular result.
I would hope they are only using face detection tecnology for street view. They do have actual face recognition technology though, as evidenced by Picassa. (I find it amusing when it tags a face on a photo in the photo, or a face on a t-shirt, etc. It even tagged my Cat's face in one slightly blurry photo. )
I've Seen that go really bad: A zip file that contained a few dozen zip files, inside of each was a single partial rar file.
What happened is that the item in question was originally distributed as split rars. Then one of those "helpful" sites in the warez community that automatically grabs files from some source (perhaps a topsite, or usenet post, or via IRC's DCC feature), and wraps it in a zip along with a copy of the .NFO file, and a file identifying this "helpful" site. Somebody else later came along, downloaded each of those ziped parts, and helpfully combined them inside a new zip file with yet another copy of the .NFO file.
But I have seen packings before that had as many as five layers before you get to the main content. That usually happens when a file like I described gets broken again into pieces to upload somewhere, and somebody else recollects those pieces and puts them in a rar or zip file.
Shampoo is mostly water (as in more than any other single ingredient) . The first ingredient on virtually every bottle of shampoo I have ever seen is "Aqua", which is water.
Granted that it often does contain a whole lot of other ingredients, but certainly enough that it should set off the water detector.
The idea should be that anything that has enough water that it is almost certainly not a bomb making chemical can be immidately ruled safe, letting them examine the others more closely.
Of course high water content does not not rule out the possibility of being a weapon. Saturated solutions of HCL for example are still like 60% water, and yet could easily eat through the aluminum skin of an airplane, or do severe harm to a person.
But nobody's ever tried to hijack an airplane with that yet (as far as I know), so security ignores the possibility.
In my experience, the fun Multiplayer has always been playing against friends. This was a large part of the appeal of games like SSB or Goldeneye.
Unfortunately most Adults don't have many good opportunities to get together with friends and play local multiplayer.
It also turns out that although online multiplayer usually supports playing with friends, it doesn't help much. First of all, it often does not particularly encourage playing with friends, with the option to start a match with complete strangers being usually more prominent. Second, unless you have quite a few friends, the ods of you being on at the same time as your friends tend to not be very good.
You can most definitely have a solid plot of going back in time, as long as the movie does not permit changing the past. The characters might believe they are traveling back and changing the past, but it always was the case that they traveled back in time and did what they did.
There are movies operating on this mechanic that can withstand heavy scrutiny. (They may have minor mistakes, like the continuity mistakes found in non-time-travel movies, but nothing that prevents analyzing the core story). One example of such a movie is _12_Monkeys_.
Philosophers have arguments for permitting backwards time travel (but without permitting changing the past) which appear to be rather sound, more so than most other philosophical arguments. However, permitting such backwards time travel appear to violate free will, since if one were to meet a future self that had traveled back in time, they would not have the option of later choosing not to time travel.
If one allows only forward time travel then one can easily keep free will.
The TI-89 will do much more than that. It is a full blown computer algebra system, not unlike MAPLE.
You can type "d(sin(x^2))/dx" and get back: "2*x*cos(x^2)" (or an equivalent representation)
You can also type INT(csc(z),z) and get back "ln(tan(z/2))" (or something equivalent).
It is easy enough for one card to be connected to both an infrastructure and ad-hoc network. There are however a few minor limitations (such as using the same channel for both). However, many OS's don't have a sufficent API for drivers to allow this, and even when the API is there, not all drivers implement enough to permit this. Indeed sometimes the drivers could not offer such features, because the defined driverchip path is lacking.
Just like pretty much all wifi chips have the hardware to support running in AP mode, but in many cases at least one of the drivers, chip firmware, OS, or driverchip communications path don't support the mode.
Well depending on how you look at third party software, one might claim that much of Darwin is third party, but I will admit that there is extremely little that ships with the latest Macs which Apple is not compiling themselves.
The thing is though that it takes an awfully long time to evolve a creature that even moves randomly, eats food when touching it, and procreate when reasonable.
But until you get to that point, you have no chance of seeing interesting behaviors like using the eye to find food or avoiding predators.
IIRC, about 6 months ago, a post to the critterding mailing list indicated that besides the program creator, only one other person had managed to evolve a creature that would actively look for food.
For SSD's your requirements are:
Obey ionice priorities.
No starvation.
Lottery can work, but I would think there should be some deterministic algorithm that could be used instead.
It would be nice though if processes that rarely use disk get higher priority than those that are frequently using it, which basically entails combining this information with the ionice priorities to get the actual priorities.
That may be a possibility.
But there is a very easy way to ensure it is not the I/O scheduler making poor decisions. You bring up the CPU scheduler, probably because the OP brought it up, but obviously if the utilization is that low it is not likely the CPU scheduler.[1]
Assuming the I/O scheduler uses ionice values, one could set the io priority of the disk hog to very low. If nothing changes, then it is not the I/O scheduler, and is probably something else like the issue you mentioned. If things return to normal speed then it may well be the I/O scheduler, but still could be other things instead.
Notes:
[1] Although the CPU scheduler does interact with IO. If the scheduler knows that a process is likely to immediately perform a blocking read if scheduled, returning the rest of its timeslice it should schedule that process right away, so that said process will have the opportunity to process said data sooner.
That is very true, with the exception of course being if the author intentionally articulated an idea poorly, for some reason. Perhaps he is writing about different writing styles, and is giving an example of something hard to understand. Perhaps the author wants the sentence to be hard to parse for some other reason, such as part of some sort of riddle.
But in general, You should not need to re-read a sentence more than a time or two to understand it. A good exception, as you point out, is obviously if the author has presumed familiarity with technical terms (be they jargon or not) of which the reader is unfamiliar.
No mention of links, but they do mention its predecessor lynx in the article.
Yeah, I meant to mention the lack of effect form rotation, but forgot. When close, the induced dipoles in the metal will always exactly match the magnet, meaning that the sides closest to each other have opposite poles aligned.
This does mean that the strong magnets would be less dangerous to handle if so encoded, but obviously would only be useful for say lifting metal, or in conjunction with the paired magnet, rather than for attracting a piece of metal from a distance. For many purposes, only a a close effect is desired anyway, so it works out just fine.
The future of TV is invariably going to be basically everything on demand. It really does not matter if this is done over the Internet, or some system like Cable, but it will happen.
But let me clarify. By everything on demand, I mean that all standard shows can be watched on demand including their back catalog, and this for a flat rate fee, not an iTunes-like puchasing of each episode. This will also include shows no longer on the air. This does not mean that there will not be live feeds, although I would expect that a significant portion of TV watching will be non-live, except for live events like sports or American Idol. New episodes of TV shows may well also be watched lived, but only if the timing is convenient.
There will be some exceptions. For example, back episodes of the evening news will likely be kept available for only a few days, perhaps a week. The Weather Channel's weather reporting will likely not be available on demand at all, since it is only really worthwhile live. Headline News may well also be Live only.
The role of networks will be largely diminished. They will likely still be around, but people will not notice which network each show is from very much. They will still help finance production of new shows, and decide which ones are worth keeping, but this will seem like less of a big deal to them, since for regular shows, most people will watch them on demand, and see no advertising, and the network sees only a portion of the flat rate subscription. The real money for networks will be in the live events, where most people will be watching live, and thus will be seeing the advertisements.
Broadcast network affiliates will still be around, but their main role will be providing the local news, and operating the Emergency Alert System. The set-top boxes of the future will receive the emergency Alerts and pause the content being watched to deliver the alert, so that people watching on demand programming will not miss it, and people watching live programming do not need to miss a portion of the programming to hear the Alert, and can skip a few commercials to catch back up with live TV if desired.
If you watch a show from ABC.com, ABC will use geolocation to determine who your local ABC affiate is, and display their logo on the page. Presumably that means they are also sharing advertising income with said affiliate.
LAN = Local Area Network
Most common technology: IEEE 802.3 A.K.A. Ethernet
MAN=Metropolitan Area Network
A Network that covers a city, or significant portion of a city, or geographical area equivalent in size to a city. (There are also smaller network sizes, including Campus area networks, etc, but they always use either LAN or MAN technologies, so are irrelevant). There was an IEEE 802.6 standard here, but it never caught on. Common technologies here ate ATM, SONET, and increasingly Ethernet and MPLS.
WAN= Wide Area Network
The definitions here vary. Some definitions have this include only things larger than a MAN, but others include anything larger than a LAN.
WLAN = Wireless LAN = Wireless Local Area Network
The most common technology here is IEEE 802.11 A.K.A wireless Ethernet, A.K.A Wifi
WMAN = Wireless MAN = Wireless Metropolitan Area Network.
One such Technology is IEEE 802.16 A.K.A. WirelessMAN (Note: no space) A.K.A. WiMax
The key with phones are that the basic protocols are not fixed sized, or when they are, they permit substantially more digits than we currently use, so we have plenty of room for expansion.
It is entirely possible to change the system to reuire5 digit area codes. After all, there was not much issue when people started needing to dial the area code for local calls, so dialing an extra few digits won't be that big a deal either. The bigger problem would be the way everything format telephone numbers needing to be changed, but we could still handle that.
The main pattern shown in the video is stronger than standard NIB magnets at close range. But die out quickly with distance. That makes them much safer to handle. The strongest NIB magnets could seriously injure you.
I'm curious though about how the pattern used affects how they attract ferrous objects. My hope would be that it has a very similar effect with ferrous objects as with the corresponding magnet, namely that it has greater attraction at short range, but dies out quickly with distance. That also seems logical based on my understanding of induced magnetic dipoles, but I'm no magnetism expert. If so, this also helps to mitigate the other main danger of powerful magnets. (Flying paperclips, etc)
The pattern they show also has minimal net force if one of the magnets is rotated out of alignment, and provides relatively small resistance to such rotation. That has lots of obvious uses for quick- connect quick-disconnect cables, especially those that need to need to withstand high normal forces, but not rotational forces. I'm not clear how the magnets they show handle shearing forces, but either way would have uses for various connectors.
True, except that current theory suggests that some (perhaps most), but not all matter on Luna came from Earth. The problem with water on Luna is obviously that it can only exist trapped below the surface, otherwise it would vaporize and drift away, given Luna's lack of atmosphere.