Enthalpy

Neutrons alone are radioactive. As I imagine to understand it, only the density of remaining electrons in a neutron star makes the capture of a an electron by a remaining proton as probable as the emission of an electron by a neutron in a beta minus decay. http://en.wikipedia.org/wiki/Beta_decay http://en.wikipedia.org/wiki/Electron_capture At the fuzzy surface of the star, the density is less, so the proportion of protons and electrons must increase relative to neutrons. --- At the scale of a planet, atomic orbitals are too close to an other in energy, position and momentum, so the effect of quantization can't be felt hence is not interesting. Quantization is still important at the scale of a quantum dots, say 50nm diameter, and this is more or less the upper limit in three dimensions. http://en.wikipedia.org/wiki/Quantum_dot Mono-dimensional items like Squids show quantization at a bigger scale http://en.wikipedia.org/wiki/SQUID

Not all the uncertainty results from the fuzzy nature of waves, alas. Take the EPR so-called "paradox", say with photon polarization. Intricated photons have fully correlated polarizations if you measure them vertically versus horizontally. They are also fully correlated if you measure them right versus left. The experiment tells that the photon pair does not choose its polarization when it is emitted, because a chosen linear polarization would leave no correlation between the circular ones; reciprocally, a chosen circular polarization would leave no correlation between the linear ones; even a chosen elliptic polarization would leave a too small correlation. That is the kind of experiments telling that the property is chosen at the measure, not before. So definite waves lead to uncertain measures, but they don't explain all the weird of QM.

Have you tried to put figures on this uncertainty at the scale of planets? Any reasonable person would qualify by "exact" a solution that would neglect this uncertainty.

There are technological limits. The body must be hot enough to radiate light: light strong enough that the detector measures this instead of ambiant light (including light produced by the surroundings' temperature), light at a wavelength that allows measurement. 300K produces light in the far infra-red, around 10µm, and needs special detectors. Hotter objects are easier: a 3000K filament in a light bulb is nearly white and very brilliant. Colder objects are measured at THz or rather GHz frequencies, but require extremely sensitive receivers that are isolated from ambiant noise: it's done in radioastronomy, but damned hard. Also, the object's emissivity (how easily it radiates as compared to the perfectly emitting black body) must be known, and it depends on wavelength and temperature, so the apparatus uses to work on one material and context only, for instance steel exiting a furnace.

The strong tendency is to consider heat from the compressed gas as a sufficient explanation, especially if the gas is mainly monoatomic. Though, detailed observation is difficult because a part of the light spectrum is stopped by water, so better observations may promote different explanations when available.

A spray flame would already be dangerous (...and fun) enough, BUT... (1) Don't make it from a pressure can, which can blow if heated, and then the explosion of the evolving gas is really serious. (2) Bug sprays are deadly poisons. Only for bugs in their normal condition and cautious concentration if you're lucky, but you can't predict what they produce in a flame. It could have been phosgene, cyanogene, an organo-phosphorus or any compound that tetanizes your lungs or blocks your central nervous system, and then, adios Adventure Helmet. Of course, you knew how to extinguish that particular fire before you lit it, and had the corresponding hardware ready at hand with the procedure in mind, didn't you? I know fire is fun, since I'm a scientist, and have played endlessly with it. I've also survived several such games just by bold luck. As an experimented survivor, the pressure canister and the poison are exactly what I would NOT play with. Please don't. Hope to read you again.

If the propellants pumps were already electric, I wouldn't make a long description nor append my name. Extreme temperatures are not necessary at the electric motor. A quick electric motor is always lighter than a turbine; the accumulator is not, and I provide estimates showing that the extra mass is manageable.

Hydrogen fuel cells would bring big advantages to helicopters. Fly long! Airborne 1t including passengers and fuel takes ~100kW with 78m2 rotor(s), say mean 130kW with the manoeuvres: that's two Honda Clarity fuel cells of <100kg each. 48kg hydrogen keep it in flight for 8h - that's 100kg with the tanks I described there http://www.scienceforums.net/topic/73798-quick-electric-machines/#entry738806 Electric motors save maintenance, expensive and long with gas turbines. Electric motors are easily spread among many rotors, leading naturally to quadtoror-like designs. This is way easier than the pitch of common helicopter blades, which changes over a turn. http://en.wikipedia.org/wiki/Quadrotor Swift start and stop. Important to a businessman who pilots himself. Fuel cells bring range and flight duration that enable the classical missions of gas turbine helicopters, beyond city taxis and sightseeing tours. Electric multi-rotor copters must also be more silent and cleaner, hence better accepted. Marc Schaefer, aka Enthalpy

Of course. Inertia limits their acceleration and speed, a reason why particle accelerators are big, and why metals have a resistivity.

+195°C is unattainable to polypropylene and difficult for a plastic, whose cost follow closely the heat resistance. Silicone would be half-way affordable in small amounts if this rubbery material is acceptable; maybe polyoxophenylene and other technical polymers, up to polyimide, but check the cost... Matweb is a compact source of data, Goodfellow an other one. Could you take a metal or a ceramic? Pyrex for instance would be cheaper.

Vega puts 2300kg in Low-Earth-Orbit with three solid and one toxic stages. Accumulators and electric pumps do it with two stages. The first stage burns 61.5t of Pmdeta and O2 at 100bar and expands to 0.30bar in four D=1m nozzles to achieve 1.23MN & 271s @sl, 1.53MN & 338s @vac. It weighs 6.1t empty including 2.2t accumulators, and brings 4237m/s. The second burns 11.9t at 60bar and expands to 4.6kPa in four D=0.6m nozzles to achieve 358s and excessive 215kN. It weighs 1.43t empty including 0.25t accumulators, and brings 4237m/s. Extruded AA6005 panels make the cylindrical skin, with reinforcing bands welded at the tanks' lower end. The heads are of AA6082; intermediate ones are thicker to resist buckling at 0.5bar difference, and can bear a balsa insulation instead of foam there. ----- An optional third stage starts with 2282kg at Leo to reach the geosynchronous orbit (4328m/s from 30° inclination) or a Mars transfer (3800m/s). It burns 1493kg at 40bar and expands to 62Pa in four D=0.6m nozzles to achieve 405s and 3500N, so the fourth kick from geostationary transfer orbit to Mars transfer lasts 390s. Both tanks are of brazed 100µm steel hold by polymer bands, with foam and multilayer insulation at oxygen. They cumulate 16kg. The truss of D=60mm e=1mm AA7020 tubes that holds them and the payload weighs 42kg. The chambers, nozzles and pumps add 70kg, the accumulators 21kg. Sensors, datacomms, control are heavy, so the empty stage is evaluated at 264kg. ----- Electric pumps ease an affordable Mars access , so this upper stage is also a migration path towards more liquid stages at Vega, while lateral Zefiro-23 can adjust the performance: Marc Schaefer, aka Enthalpy

Galois fields are the foundation of error-correction-codes; more a specialty for electronics engineers but they're made by software and used at computers. Also used for coding. Often used for cryptography. Signal processing is essentially linear. Same remark: electronics/computers. Because non-linear problems are about impossible to solve, the usual first step is to linearize them locally, solve the linearized form, and iterate. Linear and linearized problems use linear algebra heavily, say for finite elements methods. Image processing uses linear transformations as much as it goes. Even compression like Jpeg makes linear operations first: Fourier transforms. Well, linear algebra is used so often, in any field of engineering, that we don't notice it. One has to be fluent with it. We notice when something is not linear.

If you put two neon nuclei really close to an other (but managed to keep their electrons!), the 20 electrons would see the equivalent of a calcium nucleus and arrange themselves accordingly, that is 1s2.2s2.2p6.3s2.3p6.4s2. The binding energy of these electrons is 1786MJ/mol or 18,5keV while the narrowing energy of the pair of neon nuclei is >21MeV (inferred from >200MeV for uranium, more charged but bigger). So electrons can't keep nuclei that close, only the strong interaction can (and muons to some extent). http://www.webelements.com/neon/atoms.html http://www.webelements.com/calcium/atoms.html Then if the nuclei were close but not that much, atomic orbitals would interfere to create bonding and antibonding molecular orbitals. If the number of protons hence electrons just fills the bonding orbitals as in N2, you get a very stable molecule and an inert gas. Have few electrons more like in O2, then some must go to anti-bonding orbitals. These "anti-bonding" molecular orbitals are still more favourable to the electrons than far from the charged nucleus, but less than the atomic orbitals of the separated atoms. O2 is stable but very reactive. http://en.wikipedia.org/wiki/Antibonding http://en.wikipedia.org/wiki/Triplet_oxygen Neon is a simple nobe gas where two sets of 2p6 electrons would fill three bonding and three antibonding molecular orbitals resulting from 2p, the result being less favourable to the electrons than the separated neon atoms. Same for 2s and 1s electrons, if getting even closer. Though, Ar, Kr, Xe can form "excimers" as atom pairs (or with Cl and F) which are stable for minutes and are used in UV lasers and now UV lamps. I imagine excimers could build under high pressure in sonoluminescence and explain the non-thermal radiation - provided this one is real, which is difficult to observe and is debated. Pressure would in fact compact more than two nuclei, for instance in a star, so the electrons would be shared among many nuclei, resulting in a pasma or a metal (cold hydrogen does). The resulting electron energies are strongly anti-bonding and this prevents matter from collapsing, in our usual matter as well as in white dwarves, up to a limit of electron density where electron capture by protons gets more probable than beta emission, resulting in a neutron star.

Drill bits are commonly used for D=0.4mm at printed circuit boards; the main difficulty is to stop all translations, since the bits are fragile. I doubt they exist at D=0.1mm. 0.1mm should be no big worry for a laser. But don't expect nice walls nor accurate dimensions. The material's thickness is also limited by the cut's conical angle. Smaller diameters are possible in thin materials. With optical, UV or electron beam patterning followed by plasma etching, you can go down to 22nm presently... Or stop before if you don't make microchips. An electron beam can also evaporate a hole directly. More exotic possibilities exist. For instance radioactivity can destroy a thin polymer on the path of alpha particles, at many random places, which are then etched hollow by a corrosive liquid. Nice sieve.

Please forgive my ignorance... I had expected most poly-chloro-something and poly-ol to make a polycondensate easily, just like a diacid makes a polycondensate easily with a diamine or a diol. Why is the produced HCl important to sustain the reaction? Even if SiCl4 is added dropwise, it is concentrated in or near the drops. To get it consumed by fresh diol rather than by the oligocondensate, I'd have thought to dilute SiCl4 before dropping it in the concentrated diol, so the diol overwhelms the tetrachloro right from the beginning and eats it up before the concentration of product can increase. Could you react them in gas phase? Butane-diol has some vapour pressure while the product has intuitively a very low one so the product will rain away from the reaction phase, avoiding the polycondensation. In fact, it should rain away at the di- or tri-thing step, but if this step rains into liquid diol you've won. N2, Ar... can dilute SiCl4 and are easily separated from the excess diol for being much more volatile. The diol can even stay liquid, as a mist. Or contact or bubble the diluted tetrachloro at the upper part of liquid diol, as your denser product will sink below the diol, thus escaping the tetrachloro. The density ratio between the liquid and the gas is to provide the overwhelming abundance of diol. Did I miss something, like the diol being much more reactive than the resulting mono-ol? And: why does the diol react only at its primary alcohol, instead of giving many isomers?

An accelerometer may suffice, with proper signal processing, as the duration of the rebound is caracteristic, and its correlation with the rebound impulse even more. Or cover the target with many contact sensors, maybe similar to a keyboard where foam gets conductive when compressed. The many contacts will tell if the object is round. The contact area can be correlated with the rebound duration, or even the are as a function of time during the rebound. Better: this discriminates simultaneous hits by a ball and a different object or a player.

I don't think it's too simple, no... Turns: you should first make your plane more symmetrical, and this needs a clean work. Then, look at your plane, especially the tips of the wing's trailing edge. Try to curve then gently upwards and downwards unsymmetrically; observe how, as a result, the plane rolls then turns. Once you've understood the effect, you can act on these tips to achieve a straigt flight. Observe that all parts of a paper aeroplane, not just the wing tips, have an influence. Worse, paper foldings have a significant thickness which does influence all aerodynamic moments, so if you fold the paper to the wing's upper side instead of lower, you get a plane that behaves a completely different way - often unmanageable. Or for instance, if you close the fuselage's folding with glue, you get a different design with different flight properties - usually it flies badly. Much more difficult is the pitch stability. By curving both tips of the wing's trailing edge upwards or downwards, you pull the plane's nose up or down, which defines the equilibrium speed - but the plane has to have an equilibrium, which is difficult for pitch. In short, the yaw stability of a plane is like an arrow, the pitch is not. When a plane flies exaggeratedly downwards, it accelerates, and the higher speed must achieve a pitch moment that pulls the nose. This is achieved by putting the mass forward and, when aeroplanes have several wings, using a bigger angle of attack at the forward wing - be this one smaller or bigger than the aft wing. Then, stability also needs damping, and this is very far from obvious... For having only one wing, most paper planes are difficult to stabilize in pitch, and tend to oscilate in the vertical plane, or even diverge without oscilation. One design much sounder in this respect is that one: http://www.zurqui.com/crinfocus/paper/airplane.html - the tail is sometimes omitted but must be present. It is one major advantage of this model. - extra flourish at the tail's end is not needed - but may have advantages - bending the wingtips is not needed. It can be done downwards as well; observe the slower flight then. It may look less easy to fold, but I very strongly recommend to start (...and finish) with this model as you'll get something usable in a finite time - which isn't the case with a random model. Once you've understood flight mechanics, you can try your own model... I'd say: change as little as you're allowed to. Like: bend the tips downward and observe the difference, or glue the fuselage closed (little glue!) and try to let it fly properly. If some day you have completely understood what makes a good paper plane (which I haven't after thousands of trials) just tell us... There is more physics in it that you can study in months.

Maybe I had a wrong figure in memory with 10-9 torr: websites cite rather 10-6 torr for aluminium deposition. I suspect this isn't linked with purity, since silicon isn't sensitive to hydrogen, oxygen, nitrogen, argon, carbon (it's more gold, sodium and a few more which are unwanted) but with the spontaneous oxidation of aluminium during the deposition. Getter: if it's a filament I don't worry about the needed temperature, which a current achieves easily. What about household aluminium foil as a getter? At least it's inexpensive, large (wide access is necessary at low pressure), and some mechanism can move it between two rolls. A flat coil could be supplied with power at a reasonable impedance and induce the heating current in the foil.

Yes, and this effect is used in thrusters. Search for "hall effect thruster". Wiki has also an article on electric propulsion.

Rice for instance does not burn in normal condition, but the thin layer of starch it deposits in a pan during cooking burns easily. It's a matter of thickness mainly.

I don't know (or remember) in detail why we needed such a pressure for integrated circuits. I do remember that the substrates had to be warm to obtain uniform, smooth, well-connected aluminium. Possibly the layer would oxidize in real time if it grew in a moderate vacuum. 5*10-4 torr is definitely easier to achieve. Titanium was considered a good getter back then, as it also adsorbs hydrogen, in addition to its reaction with oxygen and nitrogen. A flame at low pressure would be difficult, but a filament or foil of getter metal can be heated by electric current. As well, evaporation of the coating metal looks easiest in the shape of a filament heated by a current. This enables more refractory metals: gold. Liquid nitrogen tends to be pure because many compounds are solid at that temperature, so it's more a question of circuit cleanliness after the nitrogen evaporates. Is there a known easy process (wet chemical, like for silver) to deposit gold? Gold is the best mirror silver, if I dare to say.

Hi Ron, nice to see you here! A ball with top spin drags air to be slower at the top, the pressure increases there, and the ball is pushed down. Notice that Bernouilli's law should not have been applied here... Because the variation of pressure results from friction, at least in part.

Sending power by light in an accurate direction is a means to transfer power. 98% quantum efficiency is normal at the receiver. The receivers's power efficiency is less good but can be reasonable if light is monochromatic well tuned to the material's wide bandgap. Imagine 2eV gap and photons, and 1.3V output voltage, this term is 65%. If made properly, targeting can be very efficient over a reasonable distance and by good weather. Light sources are bad. Laser diodes less so. Forget the 90%. You won't transmit by light the real-time power needed by a car, will you? This transmission is NOT what you suggested by "unless iron barrier". Are you really trying to understand a friend's work? Or do you want us to give ideas for your own work instead, and try to conceal this goal?

To go from 10-3 torr to 10-10 torr, the kind of vacuum needed for aluminium deposition, argon must be removed as well, and worse, hydrogen. Flushing with nitrogen is done, but traditionally it doesn't suffice to get the amount of hydrogen low enough. I see two "oil diffusion pump" (search word) at eBay.com for 500 usd.

CPU have gained no serious speed since the Code 2. Then 3.3GHz, now 3.6GHz with 20% more cycle efficiency, in so many years. The AVX hardware will perform in one cycle instead of two at the coming Core generation, which will improve the software that uses the AVX instructions. No lab has made a quantum computer, nor even has a research path towards a demonstrator.