No, he's saying that hydrogen and fluorine could be used as a propellant system, and that they'd make a darn good combination, at least in comparison with other chemical propellants. It all boils down to producing an intensely exothermic redox reaction. Fluorine is the most electronegative element, and thus rapidly oxidizes most substances- you can "burn" asbestos in a fluorine atmosphere. The more energetic the redox reaction, the more energy you get from the same amount of fuel (higher specific impulse).
It's great in theory, but I believe you've already grasped why this system is not used in practice, at least by anyone I've ever heard of- the clouds of hydrofluoric acid. Plus, it's not like elemental fluorine is inexpensive, or easy to handle, or anything like that- there isn't enough of a performance advantage to choose it over liquid hydrogen/LOX or hydrazine/dinitrogen tetroxide, and the prospect of producing acid rain that can etch glass and melt bones pretty much strikes it from the list.
the difference is quite possibly the poly-exclusion principle. I have only casual knowledge in the topic
Indeed. It's the Pauli exclusion principle, named after Wolfgang Pauli. It does prohibit fermions from existing in the same quantum state, though, as you describe. However, the previous poster is also correct in stating that there are bosons which do not carry a fundamental force, and most bosons are actually quite massive. The key characteristic of a boson is integer spin- fermions possess half-integer spin. There are certain situations in which normally fermionic matter becomes bosonic matter, which is no doubt what the above poster was referring to with the Rb-80 example. Perhaps the best known examples of this sort of transition are Cooper pairs in superconductors. Below a critical temperature, crystal lattice vibrations (phonons) in type I superconductive materials induce electrons, which normally repel each other and normally follow the PEP, to pair up in weak, loose arrangements called Cooper pairs. Essentially, two half integer particles (electrons) form one integer spin particle (Cooper pair), which makes it a boson. Similarly, certain atomic nuclei with particular numbers and arrangements of neutrons and protons can act as bosons. This has long been known with simple atoms- this is what makes helium-4 superfluid at 2.17K, and has recently been demonstrated in much larger nuclei.
Freeman Dyson is a well-known physicist. You can no doubt find many reviews of Prey that focus exclusively on its merits as a work of literature. Personally, however, if I were to read a book review by Freeman Dyson, well-known physicist, I would hope that he would inject some of his professional expertise into the review. He's a physicist- if I wanted a discussion of its prose, I would find a review from a professional in that area. I don't think the purpose of a book review is just to mention the key elements of the plot and how much the reviewer liked it or disliked it- a third grader can do that.
This book wasn't written in a vacuum (well, probably not). It's supposed to be creative fiction, yes, but it's also a classic Michael Crichton cautionary tale of "TECHNOLOGY GONE HORRIBLY WRONG!!" Remember when Jurassic Park came out, and news organizations had scientist-type persons assessing the likelihood that humans could genetically engineer dinosaurs? This is the same sort of thing. Professor Dyson is the scientist-type person, and the question posed is whether nanotech von Neumann machines could destroy the human race. He provides reasons why the scenario presented in the novel is not completely realistic, but I think that Dyson's review of the science and his review of the fiction are independent of each other.
I haven't read Prey yet, but I have read nearly everything else by Crichton, and I've enjoyed most of them. I think a key factor in my enjoyment of many of them has been their sheer plausibility, and the way Crichton combines emerging technologies and scientific discoveries in unusual ways to produce a highly original story, like the combination of chaos theory and genetics in Jurassic Park. His works are generally rather heavy in the science component of science fiction- they're all set in the present or near future, take place on Earth, etc. I hardly think an examination of the science involved is unfair.
Well, the big advantage to this sort of attack is that you don't do most of the work out in the open. While in many situations it would indeed appear suspicious, it's not totally obvious what your intent is if you've removed the lock to a door that you have the key to open anyway. Assuming you do it with some measure of discreetness, it's likely no one would even know. You can then perform this master key making operation in secret, and then replace your lock. You now have a master key. At this point, entering the door of your choice could scarcely qualify as an "attack"- it's a simple measure of unlocking the door with the master. Depending on the particular door and what's behind it, you may be able to do this in broad daylight with hundreds of people around- if people see you confidently walk up with a key and open a door marked "Authorized Personnel Only" or similar with the key, they're going to be much more likely to assume that you're Authorized Personnel than a clever criminal who cut a master. You could probably even do this in full view of security staff, depending on circumstances. Given that you have come to possess a regular key somehow, you probably have been legitimately granted access rights to part of the same building anyway, so your presence probably won't be taken as unusual. Pretty much the only people you'd have to worry about are maintenance personnel/building supervisors- i.e., people who may know exactly who is supposed to have a master key.
I don't think this paper is going to set off a rash of burglaries and attacks, however. This method is still a lot of work given that most locks out there can be forced open with simple tools in seconds- getting regular access and then making a key is too much effort for the smash-and-grab crowd. For the doors that contain really nice stuff behind them, I'm going to guess that many are protected by more than just one lock that is part of a master key system. They may have their own key at least, and obviously for higher security doors, you're looking at the personal identification and trained men with guns approach to security, which is generally quite successful.
The venue where this becomes most applicable is probably in academia, where, for better or for worse, academic freedom tends to mean lax security. At the university physics department where I work, I have both a building entry key and a room key. I'm fairly certain that my room key is part of a master key system- if I had a master key, I would have access to the entire physics building, where a good quanitity of dangerous and expensive materials and equipment reside. Having a master would allow you access to every room in most dormitories, as well- I expect if this paper circulates on college campuses, it will no doubt lead to some hilarious pranks, but perhaps a few thefts as well.
You got things backwards there. Paraffins are saturated compounds with empirical formula C(n)H(2n+2). For example, octane has formula C8H18. As the carbon chain increases in length for a paraffin (I prefer the modern term alkane- the name paraffin also describes a solid unsaturated hydrocarbon, C25H52), the melting and boiling points increase. In other words, simple alkanes like methane (CH4) and ethane (C2H6) are gases at room temperature. Butane (C4H10) and pentane (C5H12) boil right around room temperature. The alkane series consists of steadily thickening liquids- compare the viscosities of gasoline (mostly octane) and diesel fuel (mostly hexadecane aka cetane,C16H34). Around 20 carbons, the alkanes start to become solid around room temperature. When they mention a fuel similar to paraffin, I'm guessing they mean something similar to the candle paraffin then, around 23-27 carbons.
Olefins (better name: alkenes) are the ones with double bonds in them, and are so named because they tend to produce oily liquids at room temperature. A simple comparision is availble in your kitchen- saturated fats, mostly from animals, tend to be solid at room temperature, whereas unsaturated vegetable fats tend to be liquids (like corn or canola oil) When you see a solid vegetable fat, like in margarine, chances are it has been partially hydrogenated, which converts some of the double bonds to single bonds, increasing the melting point.
It is generally going to be alkanes and not alkenes that you would see used as fuel, due to the combustion properties. Alkenes are much more reactive compounds generally- instead of complete combustion, you'd likely get a ton of nasty side reactions- polymerizations, epoxidations. These reactions make alkenes much more valuable as a starting point in synthesis of plastics and other materials. So, examining alkanes as fuels, it becomes apparent that the longer the chain, the more energy can be extracted from complete combustion. However, the longer the chain, the more oxygen will be needed to produce complete combustion. If complete combustion fails to occur, then the end products will include carbon monoxide and soot.
In a rocket engine, the rocket supplies its own oxidizer, as there isn't much oxygen in space. As such, I'm less interested in the fuel this hybrid rocket will use, and more in the liquid oxidizer (which is not described in the article). IIRC, the space shuttle uses liquid oxygen from the big red external tank (along with liquid hydrogen from the same place) to power it early on, but the main engine of the orbiter is also equipped to burn (once the external tank runs dry) hydrazine (N2H4, one of the most thoroughly awesome substances in the universe) with dinitrogen tetroxide (N2O4) as an oxidizer. These fuels work very well as rocket fuel, as they are storable at room temperature as liquids, unlike the cryogens used in the external tank, and they are hypergolic, meaning that they spontaneously explode when placed in contact with each other. This is actually a really good thing for a rocket, since you don't need some sort of complex igniter system, and you can easily turn the rocket on and off by opening and closing the fuel valves (unlike the current solid rocket boosters on the sides, which burn continously like fireworks rockets). If you were to use some sot of solid alkane fuel in the boosters, then you'd want to find an oxidizer, preferably not a cyrogenic one, that was able to deliver a large amount of oxygen very quckly to the fuel. In the current SRB, this is conveniently done by aluminum perchlorate- essentially, you get the fuel and oxidizer in one compound. However, it seems for environemntal and control (like I said, burns like a fireworks rocket) reasons, NASA wants to phase this out. Dinitrogen tetroxide is a possibility for an oxidizer, but when nitrogen compunds are involved in combustion, NOx nitrogen oxides are often formed, which are also pollutants. Also, one can only guess the side reactions of a nitrogen oxide with a hydrocarbon in very high energy combustion- isocyanates, cyanides- poisonous stuff. Thus, choosing an alkane as a rocket fuel isn't really as intriguing as what they would choose as an oxidizer.
Dark matter doesn't necessarily need to be completely invisible, just rather hard to detect. Its exact properties depend on the sort of dark matter candidate you are considering. The two general types of dark matter candidates are MACHOs- MAssive Compact Halo Objects, which are relatively large (but very small on a galactic scale), dim objects such as gas giant planets, brown dwarfs, and black holes. Many of these object emit faint radiation, but are completely washed out by brighter objects nearby, or are merely too dim and too far away. The major method for searching for MACHOs is gravitational microlensing- if a MACHO passes between us and a faraway star, its gravity should bend the star's light like a lens, making it appear temporarily brighter, with the intensity chance and duration being indicative of the mass and velocity of the MACHO.
The other major candidate is that an invisible cloud of massive particles surrounds our galaxy. These particles would have to have a gravitational field (i.e., nonzero mass), but must be extremely nonreactive- dark matter seems to have effects on a galactic scale,
but seems to be undetectable or nearly undetectable on earth. Some physicists think that no known particle meets this description, and are looking for WIMPs (Weakly Interacting Massive Particles) I believe these were named before the MACHOs, btw. As their name implies, they interact with normal matter very weakly- they can pass though many miles of solid matter (like the entire earth) and emerge unscathed. Detection efforts usually involve sensitive experiments carried out deep underground. There are other physicists who believe the dark matter has been located already- in the humble neutrino. Results from the Super Kamiokande neutrino detector strongly suggests that the neutrino, long believed to be massless, has a very small but finite mass. The exact mass is unknown, but should exist because neutrinos oscillate freely among its 3 varieties (electron, muon, and tau), which could only occur if the neutrino had a mass. This mass is very, very small- much smaller than that of an electron, even, but there are so many neutrinos that even a tiny mass would mean that neutrinos make up the vast majority of matter in the universe.
Re:Chemistry is fun-damental
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Uncle Tungsten
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· Score: 4, Insightful
Hmmm. Even as a biochem major, I don't think I'd agree that chemistry is the fundamental science- I have no problem with the physicists claiming that one, actually. Well, really, I'd like to see the mathematicians fight it out with the physicists over this issue. Anyway, I've always liked the term "the central science" for chemistry. Sitting in between physics and biology gives chemistry a broad spectrum of topics to work with. Last semester I took physical chemistry and biochem classes concurrently, and it was fascinating to study similar chemical reactions from two wildly different perspectives- using molecular orbital theory to explain how and why a reaction takes place, for example, and then seeing a similar reaction pop up in biochem, and studying its role in a metabolic pathway.
Frankly, the lines between the sciences get blurry in many places. The example that the parent poster gave with computers is a perfect case in point. The semiconductors used in computers can be looked at from a chemical perspective- dopant agents and valence shells and whatnot- or from a physical basis- free electrons and holes and energy gaps and such. Chemistry traditionally describes the actions of electrons in materials, since such behavior is the basis for chemical bonding- but the movements of electrons can also be considered in terms of electromagnetic and even quantum mechanical effects, which are traditionally in the domain of der physik. I know people in research groups who call themselves chemists, and others who consider themselves to be physicists, but they study the same things, and use many of the same tools- and then there are people who also research in the same areas, but call it materials science.
There are gray areas on the other end of the spectrum, too. I consider myself to be a biochem major, but how does biochemistry differ from molecular biology (which is a separate major offered here)? There is also considerable overlap with organic chemistry- my o chem prof from last year, for instance, studies how various RNAs fold. You can look at something like evolution from a biochemical standpoint- genes, operons, mutations, etc, or from a biological standpoint- equilibria, populations, selection.
This has led to all sorts of interesting combinations of disciplines with chemistry- my roommate is part of a research group that uses computer models (with Linux!) to study protein folding. Is this computational physical biochemistry? Or chemical computational biophysics?
This ties in with a/. article that was posted a few days ago about a possible modification to the Special Theory of Relativity to include the Planck energy, which can be found here . When you start to talk about the very beginnings of the universe, the various Planck dimensions come into play, and set an upper limit to what can actually ever be known about the conditions at the start. These dimensions are described by combinations of Planck's constant h, the speed of light c, and the universal gravitational constant G- for instance, Planck length is (Gh/c^3)^1/2, which equals roughly
10^-33 cm. This was roughly the size of the entire universe at the Planck time, Gh/c^5)^1/2, which is about 10^-43 seconds. From these arise other scales such as the Planck energy, 1.2 x 10^19 GeV and the Planck temperature, 1.4 x 10^32 K. At these conditions, the laws of physics as we know them did not apply. There are a variety of ways to explain why this should be the case. In many Grand Unified Theories, the four fundamental forces (gravity, electromagnetic, strong, weak) are considered to be aspects of a unified superforce. There is evidence to back this up- at energies that can be achieved in particle acclerators, the weak and electromagnetic forces merge to form an electroweak force. The strong force is expected to join in at about 10^14 GeV, well beyond our present reach, unfortunately. Gravity, oddly enough the weakest of the forces (but with infinite range) holds out until the Planck energy. A universe at these conditions cannot be described by known physical laws- it is pure chaos. The universe is too hot, too dense for particles as we understand them to exist.
Another way of looking at the universe at Planck time arises from the equations for the dimensions themselves. The relationships among the equations are no accident- there are Heisenberg Uncertainty relations that exist between many of the quantities involved. As such, you can imagine the universe at Planck time to have the interesting property that completely random quantum fluctuations will occur, and will occur on the order of the Planck length. The thing is, the Planck length is also the size of the universe at this instant. So in essence, we're talking about a period where the universe is completely undefined, and it becomes meaningless to talk of things like particles and forces and even space and time itself. Now, clearly, the universe exited this phase somehow- else the universe as we know it could not exist. Why did this occur? Well, since an experiment at such energies is not likely to be possible, this question is perhaps best relegated to the realm of metaphysics. As to what happened prior to this period, there really was no "prior." The four dimensions (3 space, 1 time) that we know and love are a part of the whole universe package- the universe is not just expanding its space, but its spacetime. In fact, there are some theories (like supersymmetry) which predict the existence of many more dimensions, like 10 or 26 (they make the math work out nicely). As to why we cannot see them now, the idea is that extremely early in the history of our universe, the rest (meaning those other than the 4 we notice) folded up on themselves, and are currently sized (which brings us back to) on the order of the Planck length.
IAAB too (not the same one as above), and I have to say, sorry, you're wrong. Yes, adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C), but bases are not restricted to one strand of a double stranded DNA- A and T or G and C can be found in the same strand. In fact, there are some regions where sequences consisting of A's and T's or C's and G's together play a critical role, like a sequence of TATAAT (or similar) called the TATA box, which is recognized by RNA polymerase, and leads to initiation of transcription. Usually, all 4 bases are present in each of the two strands, and since there are three bases in each codon, 4^3, or 64, possible different amino acids can be coded for from a single codon. Now, there are only actually 20 amino acids that are coded for (there are a few exceptions to this that depend on specific context), so a few of the possible codons can be used to code for a stop in protein translation, and there is a redundancy built in called "wobble" that allows correct translation despite certain slight mutations.
Now, although there are two strands in most DNA molecules, only one actually codes for proteins- the two strands are sometimes referred to as sense and nonsense (or antisense) strands. Both are involved in replication, however- a DNA helicase splits the two strands, each acts as a template for a new complementary strand. And both can and usually do contain all four bases, with the concentration of each base in either strand being totally independent. Since the two strands in a double helix are complementary, the amount of adenine must equal the amount of thymine and the amount of cytosine must equal the amount of guanine in both strands . In fact, recognizing this relationship led to the realization that complementary base-pairing occurs. The original IAAB is correct though- the genetic code is indeed base 4- although nature has chosen to not use it to its full potential (i.e. code for 64 different amino acids) in favor of building in some redundancy.
Actually, proton flow occurs regularly in nearly every cell of your body- mitochondria use the energy of electrons from glycolysis and the Krebs cycle in the electron transport chain to pump protons across the inner membrane of the mitochondrion using transport proteins. This creates an electrochemical proton gradient- since the concentration of protons outside is greater than inside, osmotic pressure is created, and since protons are charged particles, a voltage across the membrane also exists. These protons, which have high potential energy, want to "fall" back to a lower potential energy state inside the membrane, but they need a transport protein to let them get back across. ATP synthase fills this role nicely, and as its name suggests, also serves another purpose. ATP synthase is like an electric motor, using the energy of the flowing protons to power conversion of ADP to ATP, which can then be used to power cell activities.
Come to think of it (no pun intended- you'll see what I mean), in neurons, a voltage gradient is set up not using electrons or protons, but rather large (relatively) ions, specifically Na+ and K+. The activity of these pumps, along with the net charge associated with proteins in the neurons, produces a neuron resting potential of about -70 millivolts relative to the outside of the cell. Nerve impulses travel up and down the long thin neurons by a carefully choreographed operation of ion channels and pumps in the cell- the ion channels are voltage gated, so a nearby chnnge in potential results in ion channel opening, allowing a flood of positive sodium ions back into the neuron, causing the cell to become depolarized. Since a nearby depolarization triggers further depolarization along the length of the neuron, the changing electrical potential in the neuron can be seen as a wave racing down its length. At gaps between neurons (synapses) the electrical signal causes the release of a chemical neurotransmitter like acetylcholine or GABA, which diffuses to the terminus of another neuron, triggering the electrical signal again. In this way, the flow of ions leads to nerve impulses, and thus, even thoughts.
My vote for the worst edit ever is "Die Hard With A Vengeance." Fot those of you who haven't seen it, at the very start of the movie, the villain threatens to blow up buildings unless John McClane (Bruce Willis) follows his instructions. His first instruction is to go to a street corner in Harlem with a sandwich-board with the message in huge red letters, "I HATE N*GG*RS" Obviously, since it's Harlem, and John McClane is white, and most of the residents of Harlem are not, there looks to be trouble. However, in the cable TV edit, the words on the sign have been altered to read, "I HATE EVERYBODY" Not quite the same effect. I mean, I've watched plenty of movies where dialogue has been edited, but that was probably the only one I've seen so far where written text was altered.
But that's not what the original poster is saying. It's one thing to say that Telstar was more important than Sputnik. Fine, everyone's entitled to their own opinion on such matters. However, the controversy here is that Forbes had posted 1954 as the launch date of Telstar, three years before Sputnik, when in fact it was launched in 1962. It's a silly mistake to make, since the Sputnik launch in 1957 is a well-known date. Anyway, Forbes has taken note, and changed the date. Controversy over.
Because fast clocks run slow. For an operation like Global Positioning, the GPS receiver needs to know how long it took a signal from the satellites to arrive. A GPS receiver needs several satellites in order to pinpoint a location through triangulation. Given the distance that the signal has to travel, if the time calculated for the signal is inaccurate, the postion could be off by several kilometers. In order to maintain accuracy, each satellite contains an atomic clock (which employs QM- hyperfine transitions are definitely not a classical effect). All well and good- the expensive atomic clocks on the satellites keep time for much less expensive GPS recievers (which contain a quartz clock) by resetting them with a radio signal. However, orbital satellites move at a relativistically significant velocity. Left uncorrected, the atomic clocks on the GPS sats will lose about a microsecond a day. Without Einsteinian relativity, we'd have no idea why this occurred, and thus going about correcting it would be a shot in the dark. Since do we know what the time dilation equations are, we can just redefine the number of Cs-133 transitions that make up a second for the atomic clocks on the sats, so that seconds effectively tick away faster, and thus keep excellent time with ground clocks, and allow GPS to determine positions with a very high level of accuracy. Relativity has a number of other uses- gravitational lenses have allowed astronomers to see objects are too distant to be seen even with the most powerful telescopes.
As for the contributions of Quantum Mechanics on daily life, well, theory helps lead to invention. The idea of a "laser" becomes a lot more obvious if a theory of stimulated emission exists. The idea of using atoms to tell time becomes a lot more reasonable if you know that their behavior is quantized. It became a lot easier to develop new superconductive alloys once the BCS theory took scientists past the "guess and check" approach. Nuclear Magnetic Resonance and its well-known cousin MRI depend on quantized nuclei spins. Throw most other forms of spectroscopy in with that- the Raman effect, for instance is quantum mechanical. Scanning tunneling microscopes depend on the tunneling properties of electrons- and those couldn't have possibly have been developed without knowledge of QM. And really, QM is just starting to take center stage- in the next few years, you'll start to see quantum computing, molecular machines that take advantage (or are plagued by) quantum effects, and no doubt a bunch of stuff that hasn't been thought of yet.
This mixture of recycled paper and the cheap mineral gypsum is cheap, to boot: Industry insiders say this is the only business where you can sandwich dirt between two layers of garbage and get money for it.
Apparently industry insiders don't watch much television.
Well, the reason it sits so high with respect to the ecliptic once again traces back to the Russians, who need to be able to launch Soyuz and Proton missions from Baikonur way up in the frosty northlands. Florida is just a smidge closer to the Equator than Kazakhstan. Of course, ideally, the ISS would maintain a spot on the ecliptic, and everyone would launch their rockets/shuttles from Kourou in French Guiana. Unfortunately, that seems wildly impractical given the 5 decades of infrastructure sunk into the American and Russian programs.
Personally, I'd rather see the ISS boosted up to geostationary orbit (a herculean task, I realize) and used as a staging area for construction of a space elevator. That way some good might come of that orbiting albatross.
I'm not certain I follow the reasoning as to why 64-bit computing is ideal for genomics. I mean, it's generally going to be faster and more efficient than 32-bit computing, but that really has little to do with codons. I don't know why you would need to assign a 64-bit number to an element in a set of 64 elements- as other posters have pointed out, you'd only need a 6-bit set of numbers to label 64 things. Besides, saying there are 64 codons is a tad naive, since it doesn't account for things like post-translational modifications to amino acids and nonstandard tRNA anticodons. I hope no one has tried to study the translation of something like collagen (full of modified amino acid hydroxyproline) thinking that the codons were the last word in the formation of the protein. I don't see why 64 bits is optimal as far as the crunching is concerned- are you saying that a 128-bit computer program would for some reason not be as suitable to the task?
You make an excellent point, especially since it has been discovered that in the case of many of the cell's chemical pathways, one enzyme pretty much just hands off the substrate to the next enzyme in the chain, as opposed to letting it float around in the cytosol and find the next enzyme. So yes, protein-protein interactions are going to be a very important consideration for proteomics researchers. Unfortunately, we do have to walk before we can run. The current state of things is such that we have trouble figuring out how a simple oligopeptide will fold. We must figure that out, then more complicated peptides, then multi-subunit proteins like hemoglobin or rubisco, then we can hit up the protein-protein interactions. I'd imagine this sort of computation is going to require massively parallel computing on a scale that puts today's state of the art to shame, and probably some new ideas in applying pertubation theory. All that figures to keep computational chemists nicely employed for a long time to come.
Interesting you should say that, since the foundation of molecular biology owes a lot to noted physicist Erwin Schrodinger, and his little book, "What Is Life?" Most of his speculations were incorrect- he believed that proteins, not nucleic acids, were the information carriers of the cell, for example, but as is often the case, sometimes asking the right questions can be even more important than finding answers. However, it's more than a case of a genius coming in with a bold new idea- by the late 1940s, molecular biology was an idea whose time had come. If "What is Life?" had been written in say, 1890, it would have probably been quickly forgotten- in order to make molecular biology a reality, a critical mass of organic and physical chemistry knowledge was needed, and a variety of chemical and biological techniques like X-ray diffraction, mass spec, chromatography, and cell fractionation needed to be developed.
In my opinion, the "What Is Life?" of the bioinformatics age is J. Craig Venter's whole genome shotgun sequencing method. Once again, a totally different way of doing things, and once again, from an outsider- not as much from the field of study as from every one else engaged in that field. I've had the honor of meeting Dr. Venter and listening to him lecture- he's staggeringly brilliant. He also may be the most arrogant man I've ever met. (And I've also met Stephen Wolfram.) I think often a maverick or an outsider is needed to shake things up and move things forward- either an ingenue who doesn't know the "conventional wisdom" or the hardnosed type who simply doesn't care what everyone else thinks.
Of course, once again, the new idea would have gone nowhere without thre requisite advances, this time in computing, not just in technology, but in computer science (fast algorithms so very important), and also in the development of the miracle that is the Polymerase Chain Reaction. Oh, and with regard to the title of this thread, noted biochemistry student reverseengineer is decidedly more upbeat about the idea of a bunch of "damn biologists drving Ferraris." He wants a 360 Modena, a red one.
Heh, the first time I loaded the STUMPY page, it asked me, "What are these pictures of?" In place of each of the six gifs was a >. Needless to say, I was confused. I was going to answer , "Greater than symbols," but then I had the good sense to reload, which caused me to get gifs that loaded properly.
"Power out of Thin Air." And, um, also hydrogen. These fuel cells are neat, but Coleman (according to the website) maintains that they're only meant for industrial applications at the present. Looking at the hydrogen canisters they currently have available, they are industrial-size jobs, several feet tall, filled with H2 gas at 2000 psi, and can provide hours of power. These types of cylinders are pretty dangerous no matter what is stored in them. I work at my university's physics department helium/nitrogen facility, and I'd consider the pressurized helium gas cylinders at room temp to be far more dangerous than the liquid nitrogen and liquid helium we also vend, because a damaged 2000 psi gas cylinder is essentially a 150 lb. steel missile. Still, if properly handled and stored, they aren't too much of a worry. The types of customers who would use the AirGen in its current state are the types who probably have some high-pressure cylinders of various gases in use at the worksite anyway- the hydrogen cylinders are certainly no more dangerous than the oxygen canisters used all the time in oxyacetylene welding.
What seems to be lost in all of the bickering over the explosiveness of hydrogen is the recognition of the real potential breakthrough of this product- the AirGen canister, the one that stores hydrogen as metal hydride. If it is as good as it sounds, it's a major step towards solving the fuel storage problems that have held fuel cells back for so long. Unfortunately, they don't give much in the way of specs- I'd be very interested to know how much uptime that 15 lb. canister produces in comparison to the pressurized cylinders, and what the uptime/price ratio is. (It generally costs about 20-30 bucks to fill one of the large hydrogen cylinders, which suggests that it'd only cost about 2-3 dollars an hour to provide clean emergency power. I can see why people are interested.) I'd also like to know more about the metal hydride it uses- lithium, or is it something else, like nickel or palladium? Storing hydrogen as a metal hydride is a good way to make it a lot safer and more convenient, but most metal hydrides are still extraordinarily reactive- I can remember all the reactions from organic chemistry that used lithium aluminum hydride to carry out heavy-duty reductions. Eschewing the huge steel cylinder/bomb to provide hydrogen fuel is a great idea, but I'd rather not have to keep a Type D fire extinguisher handy near my computer. Unfortunately, I get the feeling that specs are minimal because the AirGen canister is not quite ready for prime time- which is a familiar story for fuel cells.
The way I've heard it explained, vodka martinis should be shaken, rather than stirred, as shaking ends up producing a colder beverage, and vodka is more palatable cold. This is in contrast to gin, which tastes like crap no matter how it is served. (Just kidding.) While confirming the veracity of my answer, I found that the Straight Dope has a nice explanation of this subject, as they often do.
Yeah, yeah, the above poster isn't refuting that prime factorization is hard- just that it's not the same as "factoring primes." To say "factoring primes" to many people implies that it is a prime number you are factoring, which is of course easy, since the factors of a prime are 1 and the number itself. You speak of finding the prime factorization of a number, which is ideally a composite, so you break it down into a product of primes. The composite numbers used in public-key cryptography are a little unusual, since they generally have precisely 3 factors- 1, a very large prime, and another very large prime.
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Yeah, but you can find them in great condition, I bet, since the roughest duty they get is usually in a parade. The pants might be soiled, however.
No, he's saying that hydrogen and fluorine could be used as a propellant system, and that they'd make a darn good combination, at least in comparison with other chemical propellants. It all boils down to producing an intensely exothermic redox reaction. Fluorine is the most electronegative element, and thus rapidly oxidizes most substances- you can "burn" asbestos in a fluorine atmosphere. The more energetic the redox reaction, the more energy you get from the same amount of fuel (higher specific impulse).
It's great in theory, but I believe you've already grasped why this system is not used in practice, at least by anyone I've ever heard of- the clouds of hydrofluoric acid. Plus, it's not like elemental fluorine is inexpensive, or easy to handle, or anything like that- there isn't enough of a performance advantage to choose it over liquid hydrogen/LOX or hydrazine/dinitrogen tetroxide, and the prospect of producing acid rain that can etch glass and melt bones pretty much strikes it from the list.
the difference is quite possibly the poly-exclusion principle. I have only casual knowledge in the topic Indeed. It's the Pauli exclusion principle, named after Wolfgang Pauli. It does prohibit fermions from existing in the same quantum state, though, as you describe. However, the previous poster is also correct in stating that there are bosons which do not carry a fundamental force, and most bosons are actually quite massive. The key characteristic of a boson is integer spin- fermions possess half-integer spin. There are certain situations in which normally fermionic matter becomes bosonic matter, which is no doubt what the above poster was referring to with the Rb-80 example. Perhaps the best known examples of this sort of transition are Cooper pairs in superconductors. Below a critical temperature, crystal lattice vibrations (phonons) in type I superconductive materials induce electrons, which normally repel each other and normally follow the PEP, to pair up in weak, loose arrangements called Cooper pairs. Essentially, two half integer particles (electrons) form one integer spin particle (Cooper pair), which makes it a boson. Similarly, certain atomic nuclei with particular numbers and arrangements of neutrons and protons can act as bosons. This has long been known with simple atoms- this is what makes helium-4 superfluid at 2.17K, and has recently been demonstrated in much larger nuclei.
Freeman Dyson is a well-known physicist. You can no doubt find many reviews of Prey that focus exclusively on its merits as a work of literature. Personally, however, if I were to read a book review by Freeman Dyson, well-known physicist, I would hope that he would inject some of his professional expertise into the review. He's a physicist- if I wanted a discussion of its prose, I would find a review from a professional in that area. I don't think the purpose of a book review is just to mention the key elements of the plot and how much the reviewer liked it or disliked it- a third grader can do that.
This book wasn't written in a vacuum (well, probably not). It's supposed to be creative fiction, yes, but it's also a classic Michael Crichton cautionary tale of "TECHNOLOGY GONE HORRIBLY WRONG!!" Remember when Jurassic Park came out, and news organizations had scientist-type persons assessing the likelihood that humans could genetically engineer dinosaurs? This is the same sort of thing. Professor Dyson is the scientist-type person, and the question posed is whether nanotech von Neumann machines could destroy the human race. He provides reasons why the scenario presented in the novel is not completely realistic, but I think that Dyson's review of the science and his review of the fiction are independent of each other. I haven't read Prey yet, but I have read nearly everything else by Crichton, and I've enjoyed most of them. I think a key factor in my enjoyment of many of them has been their sheer plausibility, and the way Crichton combines emerging technologies and scientific discoveries in unusual ways to produce a highly original story, like the combination of chaos theory and genetics in Jurassic Park. His works are generally rather heavy in the science component of science fiction- they're all set in the present or near future, take place on Earth, etc. I hardly think an examination of the science involved is unfair.
Well, the big advantage to this sort of attack is that you don't do most of the work out in the open. While in many situations it would indeed appear suspicious, it's not totally obvious what your intent is if you've removed the lock to a door that you have the key to open anyway. Assuming you do it with some measure of discreetness, it's likely no one would even know. You can then perform this master key making operation in secret, and then replace your lock. You now have a master key. At this point, entering the door of your choice could scarcely qualify as an "attack"- it's a simple measure of unlocking the door with the master. Depending on the particular door and what's behind it, you may be able to do this in broad daylight with hundreds of people around- if people see you confidently walk up with a key and open a door marked "Authorized Personnel Only" or similar with the key, they're going to be much more likely to assume that you're Authorized Personnel than a clever criminal who cut a master. You could probably even do this in full view of security staff, depending on circumstances. Given that you have come to possess a regular key somehow, you probably have been legitimately granted access rights to part of the same building anyway, so your presence probably won't be taken as unusual. Pretty much the only people you'd have to worry about are maintenance personnel/building supervisors- i.e., people who may know exactly who is supposed to have a master key.
I don't think this paper is going to set off a rash of burglaries and attacks, however. This method is still a lot of work given that most locks out there can be forced open with simple tools in seconds- getting regular access and then making a key is too much effort for the smash-and-grab crowd. For the doors that contain really nice stuff behind them, I'm going to guess that many are protected by more than just one lock that is part of a master key system. They may have their own key at least, and obviously for higher security doors, you're looking at the personal identification and trained men with guns approach to security, which is generally quite successful.
The venue where this becomes most applicable is probably in academia, where, for better or for worse, academic freedom tends to mean lax security. At the university physics department where I work, I have both a building entry key and a room key. I'm fairly certain that my room key is part of a master key system- if I had a master key, I would have access to the entire physics building, where a good quanitity of dangerous and expensive materials and equipment reside. Having a master would allow you access to every room in most dormitories, as well- I expect if this paper circulates on college campuses, it will no doubt lead to some hilarious pranks, but perhaps a few thefts as well.
You got things backwards there. Paraffins are saturated compounds with empirical formula C(n)H(2n+2). For example, octane has formula C8H18. As the carbon chain increases in length for a paraffin (I prefer the modern term alkane- the name paraffin also describes a solid unsaturated hydrocarbon, C25H52), the melting and boiling points increase. In other words, simple alkanes like methane (CH4) and ethane (C2H6) are gases at room temperature. Butane (C4H10) and pentane (C5H12) boil right around room temperature. The alkane series consists of steadily thickening liquids- compare the viscosities of gasoline (mostly octane) and diesel fuel (mostly hexadecane aka cetane,C16H34). Around 20 carbons, the alkanes start to become solid around room temperature. When they mention a fuel similar to paraffin, I'm guessing they mean something similar to the candle paraffin then, around 23-27 carbons. Olefins (better name: alkenes) are the ones with double bonds in them, and are so named because they tend to produce oily liquids at room temperature. A simple comparision is availble in your kitchen- saturated fats, mostly from animals, tend to be solid at room temperature, whereas unsaturated vegetable fats tend to be liquids (like corn or canola oil) When you see a solid vegetable fat, like in margarine, chances are it has been partially hydrogenated, which converts some of the double bonds to single bonds, increasing the melting point.
It is generally going to be alkanes and not alkenes that you would see used as fuel, due to the combustion properties. Alkenes are much more reactive compounds generally- instead of complete combustion, you'd likely get a ton of nasty side reactions- polymerizations, epoxidations. These reactions make alkenes much more valuable as a starting point in synthesis of plastics and other materials. So, examining alkanes as fuels, it becomes apparent that the longer the chain, the more energy can be extracted from complete combustion. However, the longer the chain, the more oxygen will be needed to produce complete combustion. If complete combustion fails to occur, then the end products will include carbon monoxide and soot.
In a rocket engine, the rocket supplies its own oxidizer, as there isn't much oxygen in space. As such, I'm less interested in the fuel this hybrid rocket will use, and more in the liquid oxidizer (which is not described in the article). IIRC, the space shuttle uses liquid oxygen from the big red external tank (along with liquid hydrogen from the same place) to power it early on, but the main engine of the orbiter is also equipped to burn (once the external tank runs dry) hydrazine (N2H4, one of the most thoroughly awesome substances in the universe) with dinitrogen tetroxide (N2O4) as an oxidizer. These fuels work very well as rocket fuel, as they are storable at room temperature as liquids, unlike the cryogens used in the external tank, and they are hypergolic, meaning that they spontaneously explode when placed in contact with each other. This is actually a really good thing for a rocket, since you don't need some sort of complex igniter system, and you can easily turn the rocket on and off by opening and closing the fuel valves (unlike the current solid rocket boosters on the sides, which burn continously like fireworks rockets). If you were to use some sot of solid alkane fuel in the boosters, then you'd want to find an oxidizer, preferably not a cyrogenic one, that was able to deliver a large amount of oxygen very quckly to the fuel. In the current SRB, this is conveniently done by aluminum perchlorate- essentially, you get the fuel and oxidizer in one compound. However, it seems for environemntal and control (like I said, burns like a fireworks rocket) reasons, NASA wants to phase this out. Dinitrogen tetroxide is a possibility for an oxidizer, but when nitrogen compunds are involved in combustion, NOx nitrogen oxides are often formed, which are also pollutants. Also, one can only guess the side reactions of a nitrogen oxide with a hydrocarbon in very high energy combustion- isocyanates, cyanides- poisonous stuff. Thus, choosing an alkane as a rocket fuel isn't really as intriguing as what they would choose as an oxidizer.
Great, now I can finally do away with that glucose/ephedrine IV!
Dark matter doesn't necessarily need to be completely invisible, just rather hard to detect. Its exact properties depend on the sort of dark matter candidate you are considering. The two general types of dark matter candidates are MACHOs- MAssive Compact Halo Objects, which are relatively large (but very small on a galactic scale), dim objects such as gas giant planets, brown dwarfs, and black holes. Many of these object emit faint radiation, but are completely washed out by brighter objects nearby, or are merely too dim and too far away. The major method for searching for MACHOs is gravitational microlensing- if a MACHO passes between us and a faraway star, its gravity should bend the star's light like a lens, making it appear temporarily brighter, with the intensity chance and duration being indicative of the mass and velocity of the MACHO. The other major candidate is that an invisible cloud of massive particles surrounds our galaxy. These particles would have to have a gravitational field (i.e., nonzero mass), but must be extremely nonreactive- dark matter seems to have effects on a galactic scale, but seems to be undetectable or nearly undetectable on earth. Some physicists think that no known particle meets this description, and are looking for WIMPs (Weakly Interacting Massive Particles) I believe these were named before the MACHOs, btw. As their name implies, they interact with normal matter very weakly- they can pass though many miles of solid matter (like the entire earth) and emerge unscathed. Detection efforts usually involve sensitive experiments carried out deep underground. There are other physicists who believe the dark matter has been located already- in the humble neutrino. Results from the Super Kamiokande neutrino detector strongly suggests that the neutrino, long believed to be massless, has a very small but finite mass. The exact mass is unknown, but should exist because neutrinos oscillate freely among its 3 varieties (electron, muon, and tau), which could only occur if the neutrino had a mass. This mass is very, very small- much smaller than that of an electron, even, but there are so many neutrinos that even a tiny mass would mean that neutrinos make up the vast majority of matter in the universe.
Hmmm. Even as a biochem major, I don't think I'd agree that chemistry is the fundamental science- I have no problem with the physicists claiming that one, actually. Well, really, I'd like to see the mathematicians fight it out with the physicists over this issue. Anyway, I've always liked the term "the central science" for chemistry. Sitting in between physics and biology gives chemistry a broad spectrum of topics to work with. Last semester I took physical chemistry and biochem classes concurrently, and it was fascinating to study similar chemical reactions from two wildly different perspectives- using molecular orbital theory to explain how and why a reaction takes place, for example, and then seeing a similar reaction pop up in biochem, and studying its role in a metabolic pathway.
Frankly, the lines between the sciences get blurry in many places. The example that the parent poster gave with computers is a perfect case in point. The semiconductors used in computers can be looked at from a chemical perspective- dopant agents and valence shells and whatnot- or from a physical basis- free electrons and holes and energy gaps and such. Chemistry traditionally describes the actions of electrons in materials, since such behavior is the basis for chemical bonding- but the movements of electrons can also be considered in terms of electromagnetic and even quantum mechanical effects, which are traditionally in the domain of der physik. I know people in research groups who call themselves chemists, and others who consider themselves to be physicists, but they study the same things, and use many of the same tools- and then there are people who also research in the same areas, but call it materials science. There are gray areas on the other end of the spectrum, too. I consider myself to be a biochem major, but how does biochemistry differ from molecular biology (which is a separate major offered here)? There is also considerable overlap with organic chemistry- my o chem prof from last year, for instance, studies how various RNAs fold. You can look at something like evolution from a biochemical standpoint- genes, operons, mutations, etc, or from a biological standpoint- equilibria, populations, selection.
This has led to all sorts of interesting combinations of disciplines with chemistry- my roommate is part of a research group that uses computer models (with Linux!) to study protein folding. Is this computational physical biochemistry? Or chemical computational biophysics?
This ties in with a /. article that was posted a few days ago about a possible modification to the Special Theory of Relativity to include the Planck energy, which can be found here . When you start to talk about the very beginnings of the universe, the various Planck dimensions come into play, and set an upper limit to what can actually ever be known about the conditions at the start. These dimensions are described by combinations of Planck's constant h, the speed of light c, and the universal gravitational constant G- for instance, Planck length is (Gh/c^3)^1/2, which equals roughly
10^-33 cm. This was roughly the size of the entire universe at the Planck time, Gh/c^5)^1/2, which is about 10^-43 seconds. From these arise other scales such as the Planck energy, 1.2 x 10^19 GeV and the Planck temperature, 1.4 x 10^32 K. At these conditions, the laws of physics as we know them did not apply. There are a variety of ways to explain why this should be the case. In many Grand Unified Theories, the four fundamental forces (gravity, electromagnetic, strong, weak) are considered to be aspects of a unified superforce. There is evidence to back this up- at energies that can be achieved in particle acclerators, the weak and electromagnetic forces merge to form an electroweak force. The strong force is expected to join in at about 10^14 GeV, well beyond our present reach, unfortunately. Gravity, oddly enough the weakest of the forces (but with infinite range) holds out until the Planck energy. A universe at these conditions cannot be described by known physical laws- it is pure chaos. The universe is too hot, too dense for particles as we understand them to exist.
Another way of looking at the universe at Planck time arises from the equations for the dimensions themselves. The relationships among the equations are no accident- there are Heisenberg Uncertainty relations that exist between many of the quantities involved. As such, you can imagine the universe at Planck time to have the interesting property that completely random quantum fluctuations will occur, and will occur on the order of the Planck length. The thing is, the Planck length is also the size of the universe at this instant. So in essence, we're talking about a period where the universe is completely undefined, and it becomes meaningless to talk of things like particles and forces and even space and time itself. Now, clearly, the universe exited this phase somehow- else the universe as we know it could not exist. Why did this occur? Well, since an experiment at such energies is not likely to be possible, this question is perhaps best relegated to the realm of metaphysics. As to what happened prior to this period, there really was no "prior." The four dimensions (3 space, 1 time) that we know and love are a part of the whole universe package- the universe is not just expanding its space, but its spacetime. In fact, there are some theories (like supersymmetry) which predict the existence of many more dimensions, like 10 or 26 (they make the math work out nicely). As to why we cannot see them now, the idea is that extremely early in the history of our universe, the rest (meaning those other than the 4 we notice) folded up on themselves, and are currently sized (which brings us back to) on the order of the Planck length.
IAAB too (not the same one as above), and I have to say, sorry, you're wrong. Yes, adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C), but bases are not restricted to one strand of a double stranded DNA- A and T or G and C can be found in the same strand. In fact, there are some regions where sequences consisting of A's and T's or C's and G's together play a critical role, like a sequence of TATAAT (or similar) called the TATA box, which is recognized by RNA polymerase, and leads to initiation of transcription. Usually, all 4 bases are present in each of the two strands, and since there are three bases in each codon, 4^3, or 64, possible different amino acids can be coded for from a single codon. Now, there are only actually 20 amino acids that are coded for (there are a few exceptions to this that depend on specific context), so a few of the possible codons can be used to code for a stop in protein translation, and there is a redundancy built in called "wobble" that allows correct translation despite certain slight mutations.
Now, although there are two strands in most DNA molecules, only one actually codes for proteins- the two strands are sometimes referred to as sense and nonsense (or antisense) strands. Both are involved in replication, however- a DNA helicase splits the two strands, each acts as a template for a new complementary strand. And both can and usually do contain all four bases, with the concentration of each base in either strand being totally independent. Since the two strands in a double helix are complementary, the amount of adenine must equal the amount of thymine and the amount of cytosine must equal the amount of guanine in both strands . In fact, recognizing this relationship led to the realization that complementary base-pairing occurs. The original IAAB is correct though- the genetic code is indeed base 4- although nature has chosen to not use it to its full potential (i.e. code for 64 different amino acids) in favor of building in some redundancy.
Actually, proton flow occurs regularly in nearly every cell of your body- mitochondria use the energy of electrons from glycolysis and the Krebs cycle in the electron transport chain to pump protons across the inner membrane of the mitochondrion using transport proteins. This creates an electrochemical proton gradient- since the concentration of protons outside is greater than inside, osmotic pressure is created, and since protons are charged particles, a voltage across the membrane also exists. These protons, which have high potential energy, want to "fall" back to a lower potential energy state inside the membrane, but they need a transport protein to let them get back across. ATP synthase fills this role nicely, and as its name suggests, also serves another purpose. ATP synthase is like an electric motor, using the energy of the flowing protons to power conversion of ADP to ATP, which can then be used to power cell activities.
Come to think of it (no pun intended- you'll see what I mean), in neurons, a voltage gradient is set up not using electrons or protons, but rather large (relatively) ions, specifically Na+ and K+. The activity of these pumps, along with the net charge associated with proteins in the neurons, produces a neuron resting potential of about -70 millivolts relative to the outside of the cell. Nerve impulses travel up and down the long thin neurons by a carefully choreographed operation of ion channels and pumps in the cell- the ion channels are voltage gated, so a nearby chnnge in potential results in ion channel opening, allowing a flood of positive sodium ions back into the neuron, causing the cell to become depolarized. Since a nearby depolarization triggers further depolarization along the length of the neuron, the changing electrical potential in the neuron can be seen as a wave racing down its length. At gaps between neurons (synapses) the electrical signal causes the release of a chemical neurotransmitter like acetylcholine or GABA, which diffuses to the terminus of another neuron, triggering the electrical signal again. In this way, the flow of ions leads to nerve impulses, and thus, even thoughts.
My vote for the worst edit ever is "Die Hard With A Vengeance." Fot those of you who haven't seen it, at the very start of the movie, the villain threatens to blow up buildings unless John McClane (Bruce Willis) follows his instructions. His first instruction is to go to a street corner in Harlem with a sandwich-board with the message in huge red letters, "I HATE N*GG*RS" Obviously, since it's Harlem, and John McClane is white, and most of the residents of Harlem are not, there looks to be trouble. However, in the cable TV edit, the words on the sign have been altered to read, "I HATE EVERYBODY" Not quite the same effect. I mean, I've watched plenty of movies where dialogue has been edited, but that was probably the only one I've seen so far where written text was altered.
But that's not what the original poster is saying. It's one thing to say that Telstar was more important than Sputnik. Fine, everyone's entitled to their own opinion on such matters. However, the controversy here is that Forbes had posted 1954 as the launch date of Telstar, three years before Sputnik, when in fact it was launched in 1962. It's a silly mistake to make, since the Sputnik launch in 1957 is a well-known date. Anyway, Forbes has taken note, and changed the date. Controversy over.
Because fast clocks run slow. For an operation like Global Positioning, the GPS receiver needs to know how long it took a signal from the satellites to arrive. A GPS receiver needs several satellites in order to pinpoint a location through triangulation. Given the distance that the signal has to travel, if the time calculated for the signal is inaccurate, the postion could be off by several kilometers. In order to maintain accuracy, each satellite contains an atomic clock (which employs QM- hyperfine transitions are definitely not a classical effect). All well and good- the expensive atomic clocks on the satellites keep time for much less expensive GPS recievers (which contain a quartz clock) by resetting them with a radio signal. However, orbital satellites move at a relativistically significant velocity. Left uncorrected, the atomic clocks on the GPS sats will lose about a microsecond a day. Without Einsteinian relativity, we'd have no idea why this occurred, and thus going about correcting it would be a shot in the dark. Since do we know what the time dilation equations are, we can just redefine the number of Cs-133 transitions that make up a second for the atomic clocks on the sats, so that seconds effectively tick away faster, and thus keep excellent time with ground clocks, and allow GPS to determine positions with a very high level of accuracy. Relativity has a number of other uses- gravitational lenses have allowed astronomers to see objects are too distant to be seen even with the most powerful telescopes.
As for the contributions of Quantum Mechanics on daily life, well, theory helps lead to invention. The idea of a "laser" becomes a lot more obvious if a theory of stimulated emission exists. The idea of using atoms to tell time becomes a lot more reasonable if you know that their behavior is quantized. It became a lot easier to develop new superconductive alloys once the BCS theory took scientists past the "guess and check" approach. Nuclear Magnetic Resonance and its well-known cousin MRI depend on quantized nuclei spins. Throw most other forms of spectroscopy in with that- the Raman effect, for instance is quantum mechanical. Scanning tunneling microscopes depend on the tunneling properties of electrons- and those couldn't have possibly have been developed without knowledge of QM. And really, QM is just starting to take center stage- in the next few years, you'll start to see quantum computing, molecular machines that take advantage (or are plagued by) quantum effects, and no doubt a bunch of stuff that hasn't been thought of yet.
This mixture of recycled paper and the cheap mineral gypsum is cheap, to boot: Industry insiders say this is the only business where you can sandwich dirt between two layers of garbage and get money for it. Apparently industry insiders don't watch much television.
Well, the reason it sits so high with respect to the ecliptic once again traces back to the Russians, who need to be able to launch Soyuz and Proton missions from Baikonur way up in the frosty northlands. Florida is just a smidge closer to the Equator than Kazakhstan. Of course, ideally, the ISS would maintain a spot on the ecliptic, and everyone would launch their rockets/shuttles from Kourou in French Guiana. Unfortunately, that seems wildly impractical given the 5 decades of infrastructure sunk into the American and Russian programs.
Personally, I'd rather see the ISS boosted up to geostationary orbit (a herculean task, I realize) and used as a staging area for construction of a space elevator. That way some good might come of that orbiting albatross.
I'm not certain I follow the reasoning as to why 64-bit computing is ideal for genomics. I mean, it's generally going to be faster and more efficient than 32-bit computing, but that really has little to do with codons. I don't know why you would need to assign a 64-bit number to an element in a set of 64 elements- as other posters have pointed out, you'd only need a 6-bit set of numbers to label 64 things. Besides, saying there are 64 codons is a tad naive, since it doesn't account for things like post-translational modifications to amino acids and nonstandard tRNA anticodons. I hope no one has tried to study the translation of something like collagen (full of modified amino acid hydroxyproline) thinking that the codons were the last word in the formation of the protein. I don't see why 64 bits is optimal as far as the crunching is concerned- are you saying that a 128-bit computer program would for some reason not be as suitable to the task?
You make an excellent point, especially since it has been discovered that in the case of many of the cell's chemical pathways, one enzyme pretty much just hands off the substrate to the next enzyme in the chain, as opposed to letting it float around in the cytosol and find the next enzyme. So yes, protein-protein interactions are going to be a very important consideration for proteomics researchers. Unfortunately, we do have to walk before we can run. The current state of things is such that we have trouble figuring out how a simple oligopeptide will fold. We must figure that out, then more complicated peptides, then multi-subunit proteins like hemoglobin or rubisco, then we can hit up the protein-protein interactions. I'd imagine this sort of computation is going to require massively parallel computing on a scale that puts today's state of the art to shame, and probably some new ideas in applying pertubation theory. All that figures to keep computational chemists nicely employed for a long time to come.
Interesting you should say that, since the foundation of molecular biology owes a lot to noted physicist Erwin Schrodinger, and his little book, "What Is Life?" Most of his speculations were incorrect- he believed that proteins, not nucleic acids, were the information carriers of the cell, for example, but as is often the case, sometimes asking the right questions can be even more important than finding answers. However, it's more than a case of a genius coming in with a bold new idea- by the late 1940s, molecular biology was an idea whose time had come. If "What is Life?" had been written in say, 1890, it would have probably been quickly forgotten- in order to make molecular biology a reality, a critical mass of organic and physical chemistry knowledge was needed, and a variety of chemical and biological techniques like X-ray diffraction, mass spec, chromatography, and cell fractionation needed to be developed.
In my opinion, the "What Is Life?" of the bioinformatics age is J. Craig Venter's whole genome shotgun sequencing method. Once again, a totally different way of doing things, and once again, from an outsider- not as much from the field of study as from every one else engaged in that field. I've had the honor of meeting Dr. Venter and listening to him lecture- he's staggeringly brilliant. He also may be the most arrogant man I've ever met. (And I've also met Stephen Wolfram.) I think often a maverick or an outsider is needed to shake things up and move things forward- either an ingenue who doesn't know the "conventional wisdom" or the hardnosed type who simply doesn't care what everyone else thinks.
Of course, once again, the new idea would have gone nowhere without thre requisite advances, this time in computing, not just in technology, but in computer science (fast algorithms so very important), and also in the development of the miracle that is the Polymerase Chain Reaction. Oh, and with regard to the title of this thread, noted biochemistry student reverseengineer is decidedly more upbeat about the idea of a bunch of "damn biologists drving Ferraris." He wants a 360 Modena, a red one.
Ah,United Devices- you guys rock, what with the helping me help cure cancer and all.
Heh, the first time I loaded the STUMPY page, it asked me, "What are these pictures of?" In place of each of the six gifs was a >. Needless to say, I was confused. I was going to answer , "Greater than symbols," but then I had the good sense to reload, which caused me to get gifs that loaded properly.
"Power out of Thin Air." And, um, also hydrogen. These fuel cells are neat, but Coleman (according to the website) maintains that they're only meant for industrial applications at the present. Looking at the hydrogen canisters they currently have available, they are industrial-size jobs, several feet tall, filled with H2 gas at 2000 psi, and can provide hours of power. These types of cylinders are pretty dangerous no matter what is stored in them. I work at my university's physics department helium/nitrogen facility, and I'd consider the pressurized helium gas cylinders at room temp to be far more dangerous than the liquid nitrogen and liquid helium we also vend, because a damaged 2000 psi gas cylinder is essentially a 150 lb. steel missile. Still, if properly handled and stored, they aren't too much of a worry. The types of customers who would use the AirGen in its current state are the types who probably have some high-pressure cylinders of various gases in use at the worksite anyway- the hydrogen cylinders are certainly no more dangerous than the oxygen canisters used all the time in oxyacetylene welding.
What seems to be lost in all of the bickering over the explosiveness of hydrogen is the recognition of the real potential breakthrough of this product- the AirGen canister, the one that stores hydrogen as metal hydride. If it is as good as it sounds, it's a major step towards solving the fuel storage problems that have held fuel cells back for so long. Unfortunately, they don't give much in the way of specs- I'd be very interested to know how much uptime that 15 lb. canister produces in comparison to the pressurized cylinders, and what the uptime/price ratio is. (It generally costs about 20-30 bucks to fill one of the large hydrogen cylinders, which suggests that it'd only cost about 2-3 dollars an hour to provide clean emergency power. I can see why people are interested.) I'd also like to know more about the metal hydride it uses- lithium, or is it something else, like nickel or palladium? Storing hydrogen as a metal hydride is a good way to make it a lot safer and more convenient, but most metal hydrides are still extraordinarily reactive- I can remember all the reactions from organic chemistry that used lithium aluminum hydride to carry out heavy-duty reductions. Eschewing the huge steel cylinder/bomb to provide hydrogen fuel is a great idea, but I'd rather not have to keep a Type D fire extinguisher handy near my computer. Unfortunately, I get the feeling that specs are minimal because the AirGen canister is not quite ready for prime time- which is a familiar story for fuel cells.
The way I've heard it explained, vodka martinis should be shaken, rather than stirred, as shaking ends up producing a colder beverage, and vodka is more palatable cold. This is in contrast to gin, which tastes like crap no matter how it is served. (Just kidding.) While confirming the veracity of my answer, I found that the Straight Dope has a nice explanation of this subject, as they often do.
Yeah, yeah, the above poster isn't refuting that prime factorization is hard- just that it's not the same as "factoring primes." To say "factoring primes" to many people implies that it is a prime number you are factoring, which is of course easy, since the factors of a prime are 1 and the number itself. You speak of finding the prime factorization of a number, which is ideally a composite, so you break it down into a product of primes. The composite numbers used in public-key cryptography are a little unusual, since they generally have precisely 3 factors- 1, a very large prime, and another very large prime.