There are a lot of different types of quantum dots. Some are colloidal (dots in a liquid) - others are buried or built into materials. The fluorescent dots that you are familiar with are the colloidal ones; some are made of CdSe, ZnSe, etc, and being in a liquid medium, of course they are injectable and can be used as biological fluorescent markers. In terms of color of light emitted, the bulk material emits at some characteristic color. With QDs, as you change their size, the light emitted changes color, even though you're using the same material. Larger dots emit at a longer wavelength (redder), smaller dots at higher wavelengths (bluer).
The other type of quantum dots, the ones with photovoltaic/electronic applications, tend to be dots that are buried or grown into another solid material. The "dots" that this researcher has created are of this type - basically it seems he's managed to create individual silicon atoms on a surface that have dangling bonds in a sea of non-dangling-bond Si. The fact that the dangling bond Si atoms are far-separated from each other makes them maintain their atomic energy levels instead of having their energy levels develop into bands, as what happens in typical crystalline material. It seems like these dots were developed for quantum computing purposes and are concerned with the wave functions of the electrons, as opposed to light emission and band gap energies.
As someone who works with typical quantum dots, I find Wolkow's research interesting, but I wouldn't necessarily call what he's created a "quantum dot." Usually we are concerned with the bandgap shifting that is possible by changing the size of the dot. As I interpret his paper, it seems he's managed to create individual dangling-bond Si atoms surrounded by Si terminated by H. These dangling-bond states *handwaving explanation* seem to remain with quantized energy states instead of acting like the bulk material they're surrounded by, which have energy bands. It seems like he's interested more in electron tunneling effects for quantum computing rather than bandgap size manipulation. Maybe I'm just old-fashioned in how I think about quantum dots:p
Off-topic: Damn! I just used my last mod point! I would mod you Overrated just to prove that I really DON'T have a penis:p
Truthfully, I totally agree with you on the marijuana culture issue - at least within the sphere of universities, which is where most of us Slashdotters probably encounter it. However, it does depend on where you are - sometimes the people selling marijuana DO also sell harder drugs, too (my boyfriend worked in Hawaii for a while, the latter was the case there).
This is news? I thought that this idea has been around for a while, or at least it was the logical conclusion of having a multiverse. A livable universe doesn't exist "just for us," it just so happens that out of all of them, at least one of them would end up hospitable. Kind of like planets and solar systems.
I dated a guy who had two teenage boys (he was divorced with half-time custody). He works at a national lab, so it's not like he doesn't know what high-speed internet access is like, AND he certainly has the money to shell out for it. The reason he kept dial-up at home was 2-fold. 1) He could get all the large-size content at work (videos, pictures, etc) and 2) he could control his children's online time a lot better and not be tube addicts. The younger one especially is a bit of a gamer, and the father didn't want him to play for hours and hours. He was of the opinion that his kids should be doing more real-world activity, and if they wanted/needed high-speed, they could easily get it at their mom's house.
First of all, the title of the summary is misleading - the elements that are called "rare earth elements", a.k.a. the lanthanides, are NOT the ones mentioned. Those are elements such as neodymium, erbium, thulium, dysprosium, and so forth. They're relatively common, actually. In addition, all of the "-iums" are NECESSARY for the optical transmission system. I have done a bit of work in the area, and it is doping with these elements that basically allows it all to work - lanthanides for optical fibers and lasers, gallium, indium, etc for semiconductor devices....
And, if you think about it, pretty much any element is toxic if you are around large enough quantities of it.
The idea in the article is interesting, but I personally feel it's totally bogus. Yes, crunching data with mathematical formulas can help extract something useful, but...
Strictly speaking, isn't a mathematical formula a model? All of the theories (models) we use in materials science to explain things (quantum mechanics, stress/strain relations of materials, etc) are all mathematical. Qualitative understanding doesn't give you a numerical prediction.
Perhaps the above is a bit of a logical flaw, but you still need the maths to get information out of all the data. You need to know what to look for and make the necessesary algorithm (low-level model?). AFTERWARDS, though, you need to understand that data. Otherwise, you have not done much to advance your understanding. I did RTFA, and the person mentioned who "discovered a new species" but doesn't know anything about it...neat. What, really, has he done? Just thrown out some meta-data for someone else to analyze, model, and study. Google is not the end of scientific method. To the contrary, I think it will only help.
Yes, dear. I know that. However, there's some weird shit with the glass transition, in that it looks like a second-order thermodynamic transition, but it isn't. The volume and enthalpy of glass goes from that of it's kindred solid to that of a liquid, with the smooth glass transition joining the two regions. I think a big issue that needs to be discussed is, what exactly is a solid? The glass guys have an easy way of determining a solid: viscosity. If it has enough resistance to flow, they define it as a solid.
First of all, we've known about metallic glasses for years. There's a melt-spinner in the basement of my matsci building that we use to make metallic glasses. Their properties have been fairly well-studied.
Second of all, I don't really like the experiment that these people conducted. They simulated atoms during solidification, but they used microspheres within ANOTHER medium. With glasses, during there is no matrix material within which other molecules are moving. I find their model and extrapolation to be questionable. We are still trying to thermodynamically understand the glass transition and the solid amorphous state compared to the solid crystalline state.
That's a good point that it is probably not the best to be able to check out everyone's DNA without them knowing. If that were done, it would be a severe violation of privacy.
However, it is ridiculous that the state feels that it must be involved to the point that it (by way of doctors) is the one that can tell you/allows you when you can and cannot get your own DNA tested. It's your personal, defining data and you have a right to know what's in it, no ifs, ands, or buts. What next, they tell you when you are allowed to gift some sperm to your wife?
The situation with nanomaterials is the same as the situation with radioactive materials when that field was new. Having worked at Los Alamos National Laboratory, I can say that there used to be practices that were normal that are now regulated to hell, with respect to materials handling, dust generation/cleanliness, etc. Currently, I work somewhere else, and I work with nanomaterials all day long - and when I say nano, I mean powders with individual particles of about 5-20 nm diameter. All the personal protective equipment I usually don is nitrile gloves and safety goggles, and try to work with the material under a fume hood. We try to have safe work practices, but I have the feeling that in 40 years regulations will make you do all your work with them in gloveboxes/cleanrooms/respirators.
Nothing that we've had to work with so far emits coherent and narrow-band T-rays. These wavelengths lie between those that can be understood by quantum mechanics, and those of classical physics.
Having worked at a national lab for a bit, I can attest that accountability of items is FUBAR. They're pretty good at some things, like chemical inventory (can't let the terrorists steal our stuff...our 10 grams of stuff...and blow us up with it!) They are pretty horrible at some other things, though. The lab I was at actually undertook a program of reducing "extraneous" laptops and other electronic storage devices that were no longer necessary. The reason a lot of things go unaccounted for is that getting rid of them is such a PITA that no one ever does... and it slinks off to a dark corner of the office, never to be found again, or something else of that nature. For example, my boss gave me an ancient laptop to use that he should have gotten rid of, but there was no paperwork to say that it was actually loaned to me - it was still in his name. Considering the size of governmet organizations, that type of thing can multiply quickly into thousands of misaccounted items.
I'm a materials scientist, so hopefully I can explain this quickly for you all:)
The images that are given (before and after) are some scanning electron microscope images. Think optical microscope except with electrons. Anyway, there is a serious improvement in the structure - the edges are a lot cleaner and more defined. This is a really simple and beautiful way of letting Nature do the hard work for us. What this is doing is liquifing the material and letting surface tension pull it into the lowest-energy configuration (least amount of surface area locally).
It's really a neat way of doing it, because fabrication is really tough - uses either chemical etching or some method of particle bombardment to remove atoms. There's a big trend in matsci to build down, and build up, at the same time at the nanoscale. Think of this as the "error-correction" process after fabrication.
--This is not the same as annealing - annealing is a solid-state process, putting energy into the material to enable atoms to move and remove stress and other small defects from the material.
When I was growing up (which wasn't that long ago, really), my parents got me a Ranger Rick subscription as a very little kid. Then they got me Kids Discover which I read until I was 9 or so, I think. National Geographic is also really good, and Scientific American, for when she gets a little older. In addition, the public library should have some nice glossy picture books about the planets and other things. I would recommend that she read as opposed to watching TV; she'll become a better reader and you can really get lost in books, stare at the pictures and let your mind turn on all of it - take your time as opposed to being rushed along as films too often do. But films are good too:)
I think an easy solution to this problem (new-user aid vs experienced user non-irritation) would be to offer an option during the install - "what's your level of Ubuntu usage? a) First-time user, b) middle-of-the-road smart person who might need a little help, c) power user." That way you could avoid all of the annoying dialog boxes if you wanted to, while still allowing the OS to aid people who want it for their new adoption.
Slashdot Mirror
What's going to be the next scare over -- the radioactive americium in smoke detectors?
Yes. Yes, it is. In fact, it occurred at Los Alamos National Lab a few years back (I was there when it happened).
There are a lot of different types of quantum dots. Some are colloidal (dots in a liquid) - others are buried or built into materials. The fluorescent dots that you are familiar with are the colloidal ones; some are made of CdSe, ZnSe, etc, and being in a liquid medium, of course they are injectable and can be used as biological fluorescent markers. In terms of color of light emitted, the bulk material emits at some characteristic color. With QDs, as you change their size, the light emitted changes color, even though you're using the same material. Larger dots emit at a longer wavelength (redder), smaller dots at higher wavelengths (bluer).
The other type of quantum dots, the ones with photovoltaic/electronic applications, tend to be dots that are buried or grown into another solid material. The "dots" that this researcher has created are of this type - basically it seems he's managed to create individual silicon atoms on a surface that have dangling bonds in a sea of non-dangling-bond Si. The fact that the dangling bond Si atoms are far-separated from each other makes them maintain their atomic energy levels instead of having their energy levels develop into bands, as what happens in typical crystalline material. It seems like these dots were developed for quantum computing purposes and are concerned with the wave functions of the electrons, as opposed to light emission and band gap energies.
As someone who works with typical quantum dots, I find Wolkow's research interesting, but I wouldn't necessarily call what he's created a "quantum dot." Usually we are concerned with the bandgap shifting that is possible by changing the size of the dot. As I interpret his paper, it seems he's managed to create individual dangling-bond Si atoms surrounded by Si terminated by H. These dangling-bond states *handwaving explanation* seem to remain with quantized energy states instead of acting like the bulk material they're surrounded by, which have energy bands. It seems like he's interested more in electron tunneling effects for quantum computing rather than bandgap size manipulation. Maybe I'm just old-fashioned in how I think about quantum dots :p
Off-topic: Damn! I just used my last mod point! I would mod you Overrated just to prove that I really DON'T have a penis :p
Truthfully, I totally agree with you on the marijuana culture issue - at least within the sphere of universities, which is where most of us Slashdotters probably encounter it. However, it does depend on where you are - sometimes the people selling marijuana DO also sell harder drugs, too (my boyfriend worked in Hawaii for a while, the latter was the case there).
In my case, I think it's the Strong Myopic Principle. I'd look for the other life-forms, but...where are my glasses?!
This is news? I thought that this idea has been around for a while, or at least it was the logical conclusion of having a multiverse. A livable universe doesn't exist "just for us," it just so happens that out of all of them, at least one of them would end up hospitable. Kind of like planets and solar systems.
I dated a guy who had two teenage boys (he was divorced with half-time custody). He works at a national lab, so it's not like he doesn't know what high-speed internet access is like, AND he certainly has the money to shell out for it. The reason he kept dial-up at home was 2-fold. 1) He could get all the large-size content at work (videos, pictures, etc) and 2) he could control his children's online time a lot better and not be tube addicts. The younger one especially is a bit of a gamer, and the father didn't want him to play for hours and hours. He was of the opinion that his kids should be doing more real-world activity, and if they wanted/needed high-speed, they could easily get it at their mom's house.
First of all, the title of the summary is misleading - the elements that are called "rare earth elements", a.k.a. the lanthanides, are NOT the ones mentioned. Those are elements such as neodymium, erbium, thulium, dysprosium, and so forth. They're relatively common, actually. In addition, all of the "-iums" are NECESSARY for the optical transmission system. I have done a bit of work in the area, and it is doping with these elements that basically allows it all to work - lanthanides for optical fibers and lasers, gallium, indium, etc for semiconductor devices....
And, if you think about it, pretty much any element is toxic if you are around large enough quantities of it.
The idea in the article is interesting, but I personally feel it's totally bogus. Yes, crunching data with mathematical formulas can help extract something useful, but...
Strictly speaking, isn't a mathematical formula a model? All of the theories (models) we use in materials science to explain things (quantum mechanics, stress/strain relations of materials, etc) are all mathematical. Qualitative understanding doesn't give you a numerical prediction.
Perhaps the above is a bit of a logical flaw, but you still need the maths to get information out of all the data. You need to know what to look for and make the necessesary algorithm (low-level model?). AFTERWARDS, though, you need to understand that data. Otherwise, you have not done much to advance your understanding. I did RTFA, and the person mentioned who "discovered a new species" but doesn't know anything about it...neat. What, really, has he done? Just thrown out some meta-data for someone else to analyze, model, and study. Google is not the end of scientific method. To the contrary, I think it will only help.
Yes, dear. I know that. However, there's some weird shit with the glass transition, in that it looks like a second-order thermodynamic transition, but it isn't. The volume and enthalpy of glass goes from that of it's kindred solid to that of a liquid, with the smooth glass transition joining the two regions. I think a big issue that needs to be discussed is, what exactly is a solid? The glass guys have an easy way of determining a solid: viscosity. If it has enough resistance to flow, they define it as a solid.
First of all, we've known about metallic glasses for years. There's a melt-spinner in the basement of my matsci building that we use to make metallic glasses. Their properties have been fairly well-studied.
Second of all, I don't really like the experiment that these people conducted. They simulated atoms during solidification, but they used microspheres within ANOTHER medium. With glasses, during there is no matrix material within which other molecules are moving. I find their model and extrapolation to be questionable. We are still trying to thermodynamically understand the glass transition and the solid amorphous state compared to the solid crystalline state.
That's a good point that it is probably not the best to be able to check out everyone's DNA without them knowing. If that were done, it would be a severe violation of privacy. However, it is ridiculous that the state feels that it must be involved to the point that it (by way of doctors) is the one that can tell you/allows you when you can and cannot get your own DNA tested. It's your personal, defining data and you have a right to know what's in it, no ifs, ands, or buts. What next, they tell you when you are allowed to gift some sperm to your wife?
The situation with nanomaterials is the same as the situation with radioactive materials when that field was new. Having worked at Los Alamos National Laboratory, I can say that there used to be practices that were normal that are now regulated to hell, with respect to materials handling, dust generation/cleanliness, etc. Currently, I work somewhere else, and I work with nanomaterials all day long - and when I say nano, I mean powders with individual particles of about 5-20 nm diameter. All the personal protective equipment I usually don is nitrile gloves and safety goggles, and try to work with the material under a fume hood. We try to have safe work practices, but I have the feeling that in 40 years regulations will make you do all your work with them in gloveboxes/cleanrooms/respirators.
Nothing that we've had to work with so far emits coherent and narrow-band T-rays. These wavelengths lie between those that can be understood by quantum mechanics, and those of classical physics.
Having worked at a national lab for a bit, I can attest that accountability of items is FUBAR. They're pretty good at some things, like chemical inventory (can't let the terrorists steal our stuff...our 10 grams of stuff...and blow us up with it!) They are pretty horrible at some other things, though. The lab I was at actually undertook a program of reducing "extraneous" laptops and other electronic storage devices that were no longer necessary. The reason a lot of things go unaccounted for is that getting rid of them is such a PITA that no one ever does... and it slinks off to a dark corner of the office, never to be found again, or something else of that nature. For example, my boss gave me an ancient laptop to use that he should have gotten rid of, but there was no paperwork to say that it was actually loaned to me - it was still in his name. Considering the size of governmet organizations, that type of thing can multiply quickly into thousands of misaccounted items.
I'm a materials scientist, so hopefully I can explain this quickly for you all :)
:)
The images that are given (before and after) are some scanning electron microscope images. Think optical microscope except with electrons. Anyway, there is a serious improvement in the structure - the edges are a lot cleaner and more defined. This is a really simple and beautiful way of letting Nature do the hard work for us. What this is doing is liquifing the material and letting surface tension pull it into the lowest-energy configuration (least amount of surface area locally).
It's really a neat way of doing it, because fabrication is really tough - uses either chemical etching or some method of particle bombardment to remove atoms. There's a big trend in matsci to build down, and build up, at the same time at the nanoscale. Think of this as the "error-correction" process after fabrication.
--This is not the same as annealing - annealing is a solid-state process, putting energy into the material to enable atoms to move and remove stress and other small defects from the material.
Hope that helps
When I was growing up (which wasn't that long ago, really), my parents got me a Ranger Rick subscription as a very little kid. Then they got me Kids Discover which I read until I was 9 or so, I think. National Geographic is also really good, and Scientific American, for when she gets a little older. In addition, the public library should have some nice glossy picture books about the planets and other things. I would recommend that she read as opposed to watching TV; she'll become a better reader and you can really get lost in books, stare at the pictures and let your mind turn on all of it - take your time as opposed to being rushed along as films too often do. But films are good too :)
I think an easy solution to this problem (new-user aid vs experienced user non-irritation) would be to offer an option during the install - "what's your level of Ubuntu usage? a) First-time user, b) middle-of-the-road smart person who might need a little help, c) power user." That way you could avoid all of the annoying dialog boxes if you wanted to, while still allowing the OS to aid people who want it for their new adoption.