Enthalpy

Can the hydrogen have a chemical bond with any kind of atom to build a hydrogen bond with a third atom? Can the third atom be of any nature to receive a hydrogen bond? Then, are there conditions on distance? With that, you can count the possible bonds by looking the molecule. In more complicated shapes, a 3D model may be necessary.

Welcome! Gas sensors, no, sorry... But in case this helps, the fantastic website at Ioffe: http://www.ioffe.rssi.ru/SVA/NSM/Semicond/ has data about indium nitride. The searchwords give 10,000 hits, so it's a fairly common subject: "Indium nitride" "gas sensor" looks like usual thin-film methods, amorphous and 10nm thick. I've just seen a response time in hours in one paper, less nice.

You miss one point. The emission mechanism of photons already defines a duration. It's called a decay lifetime (for the excited state), a transition time... If the emitting object is undisturbed, this defines the coherence time and the resulting linewidth. External influences can change the lifetime, for instance shocks among gas particles, or a resonant cavity, or neighbour emitting objects that influence an other. This lifetime can be 1ns or far less, and in some occasions more (neutral hydrogen, extremely dilute in space, emitting at 21cm). Even if you don't observe in a day an excited atom with 1ns state lifetime, it will de-excite in 1ns. The photon will be emitted immediately, will have this duration, and after that, coherence is as much lost as light is: obscurity. Only within the 1ns is uncertainty. Yous "photon-wave" and "photon-particle" have no sense, that's why nobody uses them.

Radiowave propagation through plasma Section VII C of [Anderson 2002] caps the effect to 1/400th the anomaly. More arguments here indicate a negligible effect. Over the propagation path, the plasma's density can change with time. The plasma amount gives a delay, its change rate a speed error, the acceleration of the rate an acceleration error. In case an acceleration of the amount change rate, nicely constant over one half Solar cycle, were any credible, millisecond pulsars would disprove it. Their signal measured over a similar time span at similar frequency passes through about the same amount of plasma to reach Earth, and once their spindown and geometric and relativistic effects are compensated, they can show 10-16 stability, much more accurate that Pioneer's unexpected speed of 10-9c. The steady part of the plasma density at the spacecraft decreases faster than R-2 (distance to the Sun) and influences the Doppler speed measure. The substantially constant craft speed through varying density results in an acceleration error decreasing faster than R-3 - faster than Sunlight recoil as R-2 which makes 10% of the anomaly at 48AU (see future section). If plasma were to explain 20% of the anomaly there, its resulting error would outweigh Sunlight recoil tens of times near 1AU, which knowingly doesn't happen. Marc Schaefer, aka Enthalpy

Hello everybody! The Pioneer anomaly is or was a possibly anormal small deceleration best observed at Pioneer-10. http://en.wikipedia.org/wiki/Pioneer_10 http://en.wikipedia.org/wiki/Pioneer_anomaly It was reported by Anderson et al (arXiv gr-qc/9808081v2), Turyshev et al (arXiv gr-qc/9903024v2), and in detail in 2002 by Anderson et al: http://arxiv.org/abs/gr-qc/0104064 This latter paper studies and rejects possible explanations: everyone should read its sections VII and VIII before suggesting residual gas, dust, Sunlight and heat recoil, leaks, unknown planets, dark matter and many many more. The 2002 paper explicitly discarded the infrared recoil by Pioneer's central body as too weak, and decaying too much over time to explain the constant deceleration (VIII D) the infrared recoil by the RTG (radioisotope thermoelectric generators) asymmetry (VIII C) the influence of interplanetary plasma on radiowave propagation (VII C) for being tiny to conclude that the deceleration wasn't explained. But in 2012, Turyshev et al modelled Pioneer's heat transfers with finite elements: http://arxiv.org/abs/1204.2507v1 and claimed that infrared recoil by Pioneer's central body plus the RTG (and some radio propagation through plasma) sufficed. So here's how I tried to make my own opinion - and I agree with Turyshev, that is, with the 2002 paper he co-authored. Anomaly, rather. Method choices I have no spacecraft data, no means to model the heat transfers within Pioneer - and no desire neither, because this gives "believe me" styled results not open to scientific discussion. Instead, I adjust a fraction of the produced heat radiated forward; at the Sun distances I consider, the louvers are closed, external sources are small, temperatures vary little, and the forward fraction even less so. I fit the speed curve instead of the acceleration. Speeds being cleaner than accelerations, visual impression can already convince. Error bars on the acceleration accept tolerances regularly of the same sign, but these tolerances cumulate on a speed curve to show a misfit. Or equivalently, the integration reduces the passband available for noise. All important to see if the curvatures of two functions fit. The speed curve I have starts at 40AU. Sunlight pressure is small there, and model details get negligible. The speed curve I pinched it from Anderson et al (arXiv gr-qc/9808081v2, bigger there) and added Sun distances on it, which I only found on a Pioneer "artwork" AC97-0036-3 at Nasa's website. Science would deserve better, yes. (click the picture for full size) The orange straight line is fit by my eyes through my mouse. Oscillations at the end have 1 terrestrial year period, so I'm confident they can be modelled out. And in case anybody believes the far-off isolated points are valid, he's welcome to explain this bigger anomaly. Sunlight pressure, radiocom recoil, heaters I did it as usual, and took also 252kg craft mass. The RTG add 5% area to the 2.74m antenna which reflects ~80% of Sunlight. The absorbed ~20% are emitted as IR by the read side (e~0,90) and the front side (e~0.03 for cold naked aluminium). I take 2/3 of the reflected and radiated power for their recoil, as in a cosine pattern. Since the incoming Sunlight is 5.2W at 40.4UA, Anderson's factor of 1.77 instead of my 1.66 would change only 0.6W, and a different aluminium emissivity nothing. The transmitter shall send 8W permanently rearwards. But maybe 0.5W from the source radiation pattern don't reach the primary mirror, which would make 1W difference. Twelve 238Pu heaters (Turyshev takes eleven) shall deliver 1W at launch and decay with 87.7 years half-life. Pioneer's bus is to radiate forward the same proportion of their heat as for equipment heat. More to come. Marc Schaefer, aka Enthalpy

Very nice for data centers, Juniper's dense interconnect for Ethernet, since data centers treat independent requests. For a supercomputer, their 5µs latency is unbearable. 50ns would be a strong programming constraint, 5ns a reasonable one, 500ps excellent. The silicon chip suggested in message #22 would be in the 5ns to 50ns range.

Electrolyte conductivity depends on the charge count of the ions and their mobility. The mobility depends on anything, so it's eperimental. At low concentrations, the mobility depends little on the concentration. Ions separate in a polar solvent because solvent molecules surround them to bring the adequate charge (from their ends) near the ions. Consequently, ions don't move alone in an electrolyte: they move with many solvent molecules together. That's why so simple relation exists between ion mobility or the mass or size of the ion - different number of solvent (water) molecules moving with the ion make it more or less heavy and bulky.

Just remember to wear gloves when using any solvent, especially if regularly. - We need our fat on our skin - Some solvents let unwanted compounds permeate the skin - Some minor components of white spirit, kerosene, Diesel oil are not innocent.

In the Hall effect, as well as the Lorentz force, the effect is at 90° from both the speed and the induction - not opposite. The Lorentz force is a Hall effect, just discovered by different people bearing different names. Charge carriers deflected to the side of the wire are a little bit more concentrated there, and the resulting electrostatic force appears as a Lorentz force. About the direction of current, induction, speed, induced voltage... It's good to know the rules to answer exams. In real life, you have 50% risk to be wrong using them, so everyone tries and, if not the desired polarity, swaps the terminals.

I have my doubts about that. The coherence time of a laser is hugely shorter than a day, which means that photons arrive well separated at the detector. A laser emitting photons one at a time must also have a much shorter coherence time than with many photons simultaneously. What's still possible is make interferences from a single laser emitting a single photon at a time. About interferences among non coherent, or just among non synchronized sources: the resulting pattern wobbles quickly. It holds during one coherence time of the source, which is unobservable with thermal radiation, and seriously short with lasers even good. If the observation time clearly exceeds the coherence time, the interferences patterns sum at random, giving a uniform result, undistinguishable from the absence of interference. One gets interferences with thermal radiation, but then each photon must interfere with itself, which requires a single light source, and paths length closely matched so the offset is less than the coherence length (or time).

You can detect a particle once (... recent experiments did better, but let's forget that). So "the energy or charge distribution" is not measurable, hence a theory doesn't need to answer it. If using many particles, if needed successively, then the probability distribution can be observed, and QM does predict it. Please read again my previous answer. The particle spreads more and more, there is still one (1) particle. Every serious physicist has QM, because this is what works, and damned well. If you wish to have something else, that's your problem. For several years, we see the shape of wavefunctions for atoms and molecules, using atomic force microscopes and the like. QM not only predicts spectra with fantastic accuracy, using no free fitting parameter - in itself an absolute proof of correctness. It also explains why matter has a volume, as an immediate and concrete consequence. This depends on how much momentum the photon loses upon reflection. And if it loses equally much at both mirrors, no worry at all - which looks like the proper answer. The photon is reflected by both mirrors. Simple descriptions like "know through which slit" usually involve a detector that destroys the photon, and then interference is lost. With only a small modification of the photon (mirror recoil reduces the photon's frequency a little bit), one would have to check how much recoil is necessary to make a detection, how much it changes the photon, and whether interference is still possible then. An interaction is not always as binary as an absorption by a camera pixel. When electrons are diffracted by a crystal, they interfere with many atoms without being absorbed.

As the LHC seems to discover nothing beyond Higg's boson, newspaper put titles like "the end of physics". But hey, physics doesn't limit to particles! Few examples at random: Superconductors. Understand them, find better materials, make better coils, invent machines that use them. For electricity storage, everything remains to be done, and this is uuuuuuurgent! If finally we have good storage for hydrogen, then we must produce it - preferably not through electricity - and transport it properly. Dark matter. Earth. Solar system.

(1) The outputs can be made coherent, sometimes, with a significant technological effort to synchronize the oscillations (2) I didn't understand the question.

It's worse than that: we know the photon has taken both paths. That's why interferences are built. If you try to imagine a point-like photon (or electron, or any particle) propagating, you'll make wrong conclusions. They are waves and propagate as such. These waves are also particles in the sense that they're absorbed once, as locally as is necessary. (1) yes (2) no (3) It doesn't even need a prism. A single atom emits light very broadly, because an atom is small. Farther from the emitter, the energy spreads in more volume. Accordingly, the number of photons is constant, but the probability to detect the photon in a give small volume element diminishes. For instance, a distant star emits many photons, but the chances to detect one in a camera pixel are faint. We need a big telescope mirror to concentrate light in the pixel and improve the chances.

You can forget the noise cancellation adapted to radar. It works only in one direction, and anyway, it demands too much accuracy to attenuate the reflection by a significant factor. As on difficulty more, every part of the aeroplane reflects the radar wave: shall we cover the whole craft with antennas? In headsets, sound is cancelled at one location only, and 20dB is a good result: not the same difficulty at all. "One direction only" is worse than it looks, because the craft receives many signals from many sources, not only the radar. As it tries to cancel out the echo from a TV transmitter, the active echo cancellation would reveal itself to a passive radar. The signal of Over-The-Horizon radars also propagates over several paths. It's an annoyance for signal processing, but makes them immune against signal cancellation. The aircraft sending a signal cancelling the first propagation path reveals itself through the other paths, as much as a perfect reflector would - nothing stealth then. About LED: this one is really fiction. They emit light fully uncontrolled, neither in phase nor amplitude. Plus, their wavelength isn't agile. Zero chance to cancel anything. IRST and other optronics: from the ground, you want to detect arriving planes, but these emit little infrared from the front. Worse, passive IR detectors don't measure the distance. Provided two aircraft will again fight in flight some day (it did happen in 1991, but the conflict was so unequal that new technology wasn't required), passive IR won't do all the job. And missiles have their own radar, about impossible to replace. The disadvantage of the radar receiver over the target is much worse than a quarter. It's easily like 80dB.

Yes, the damage added by human pollution may be small (or not) as compared with the natural radioactivity. But linearity is important, as it tells that the amount of added damage does not depend on the dilution. The added damage becomes only difficult to attribute to the added pollution. Most people live outside the Ocean but many eat products obtained from the Ocean. There are also some differences between natural and man-made radioactivity. Most natural activity in the Ocean is from 40K, which we don't concentrate. We eat fish containing it, but excrete it. As opposed, we concentrate 131I (no more a worry now from Fukushima) in thyroid, 90Sr in our bones.

Yes. It's done for instance at nuclear fusion experiments, where many lasers add their power to compress the target. In this case; one master oscillator laser provides reference light split among the many amplifier lasers, whose powerful outputs are merged. Which isn't simple, because the phase must be coherent despite the long paths. Other people use fibre lasers as amplifiers and merge the light. Fibre lasers are easier to cool. Some consider it could be the next candidate as a light source for laser nuclear fusion. You can also synchronize several oscillator lasers, "just" by letting them share their light... it needs matched caracteristics, sure. In a more general view, one laser is just several synchronized sources of light like individual molecules or dopants or charge carriers. Merging the light of several lasers means only that these lasing elements belong to several entities, for instance are in different cavities, but with enough coupling.

In a supercomputer, interconnection IS the limiting factor. Very different from a file server where the tasks are nearly independent from an other. In that sense, the optical interconnects described in teh linked papers, which limit the number of nodes and put constraints on simultaneous communications, are inferior to a silicon chip as I suggest in message #22.

The magnetosphere stops mainly the Solar wind. Many cosmic rays have a higher energy and pass the magnetosphere without even a significant deviation.

The radioactivity presently released isn't that huge, but the one released during the accident was, it has rained down on the Pacific mainly, and it must easily exceed one year of releases by Sellafield or La Hague. Dilution is not the ultimate answer - except for the nuclear industry. Because the risk associated with small concentrations of radiation is proportional to it, dilution means that more animals and humans are exposed to a smaller increase in the risk. By the "linear-no-threshold" model, which is the norm and is reaffirmed regularly, but is fought by propaganda organizations of the nuclear industry, the smaller individual risk shared by more persons means the same increase of illness in the global population. The most commonly accepted report: dep.state.pa.us/brp/radon_division/BEIR%20VII%20Preliminary%20Report.pdf first paragraph: "A comprehensive review of available biological and biophysical data supports a “linear-no-threshold” (LNT) risk model" of which nuclear propagandists take "effects of low dose can't be proven". The big difficulty is that a small risk in a big population is impossible or very difficult to measure (or even to prove in a trial). The position of scientist is then to extrapolate it linearly, because for each single cell, there is no "small dose": one absorbed ray is devastating to it - so one considers that more rays just increase the number of cells that present a risk to become a cancer, hence the linearity. The position of the nuclear industry is that the small risk isn't measured hence it doesn't exist - or even, I've read "they won't be able to prove his cancer is our fault". These two positions explain the huge discrepancy in the fatalities estimates after a catastrophe - like 10 or 1000 or >10,000 for Chernobyl. ---------- Electrolysis: not the good method. Filters are already installed, more are arriving, Tepco will solve it - it's the reason why the government tells "we take action". However, filters as well as electrolysis would leave tritium. This one will be diluted and released in the Ocean, it's already planned like this.

To my limited understanding, we say "collapse" when the receiving object, for instance an atom or a camera pixel, can interact with the incoming particle (here the photon) only if this particle is in a special state, more restrictive than the set of states the particle can have. So for instance if the photon can have any polarization but the mirror reflects only the horizontal one, we'd say "collapse". Possibly even if it leaves many states allowed to the reflected photon. Or if the photon can have varied energies but the mirror is selective. If the mirror is big enough and reflects all energies, polarizations... I would not say "collapse" because the reflected photon can be as diverse as when arriving. Special mention to the size. A photon arriving from a distant star is extremely wide and gets detected a one camera pixel. In this case, where again the detector has constrained the wide diversity of behaviours available to the particle, we don't say "collapse". I suppose this wording is because the photon concentrated in one pixel after light-years travel is not an eigenstate of light's equation, so the event is not the choice of one eigenstates among several available. But below the question of wording, an interesting part is that the particle determines its behaviour only when needed (at the detector), not before - this was an open question long ago, and the experimental answer is "no hidden parameter". The particle IS undetermined until it must "choose". An other interesting part is that the particle determines itself at the interaction, but only as much as is needed. Say, if the detector allows for some tolerance on the position, then the momentum will keep some precision. Or imagine a screen with two slits: a photon must first "choose" if it hits the screen or not, but if passing through, it does not "choose" through which slit, and this allows interferences downstream the slits. As long as you treat photons like waves, they propagate as expected, most often... Until you detect them, and then they're granular, hence particles. It's most often the same for any particle. If you consider propagation like a wave and interactions like a particle, with choice ("collapse") at the interaction, you're often right - the true worries come with entanglement. From such considerations, that particles restrict they behaviour only when needed, and only as much as needed, I take my integrist wording about particles, for instance: - "A valence electron in an atom has the size of the atom". The electron can be smaller, but only if the experiment can force it so. It can be as small as needed for all our existing experiments, hence "point-like". But only if the measure needs it. When the electron is an orbital, we have no reason to allege it's smaller. - "The size of a photon is the extension of the wave packet", because we have no other means to determine the size. Once detected, the photon can be 3µm*3µm. Prior to that, the wave packet is the only thing that defines a size; if emitted at 21cm by neutral hydrogen, the wave packet is several million light-years long, and I say this is the size of the photon. Take with caution.

Instead of part wave reflectors, one can spread the reflection continously, if possible as a Gaussian distribution. This works over a wide frequency range. The true worry of stealth aeroplanes is that over-the-horizon radars (OTH, see Wiki) use low frequencies, with about half a wavelength fitting in the target's size. Facets and all shapes do nothing against that, and paints neither.

I've seen some ropes of small diameter made with carbon fibres and a matrix, for instance a Cousin, but they are stiff! http://www.cousin-trestec.com/en/cousin-trestec-en/sports-loisirsen/ Could they conceivably work for a cable car? If flexible enough, they would bring a lower thermal expansion, more stiffness... And a doubtful reliability. Sorry, I just trust steel. Dmitry91, so nice to see you here! Marc

Alcohol is always distilled. If not, it won't burn at all: it's as concentrated as in wine. Alcohol is always mass-produced by fermentation of organic material: corn, sugar cane, sugar beet... Never from crude oil, which contains essentially hydrocarbons. If the question is alcohol versus gasoline, the answer is "Brazilians use ethanol everyday in their cars". About as good, but the injector needs a specific adjustment. It's excellent for the Brazilian cane producers, and also for the inhabitants, as the exhaust gas is much cleaner - I testify from first-nose observation.

What material deposits? - Air is dirty in cities. You see that when arriving by plane. When mines and steelmaking was active here, we got a dust layer on cars everyday. - Flowers, trees... produce dust (pollen and so on) as well, and not little. Main source of dust in homes. Depends much on the season. - Dust separated from the road surface, from concrete, and more Cleaning: at least for the chain, a grease solvent will do. - White spirit - Turpentine Observe if you develop allergies, and check the cost of renewing the grease. Maybe grease dissolved in clean solvent (jar+tap) is a quick way to lubricate the chain after cleaning. At other bike parts, especially painted ones, these two solvents can have drawbacks. Other, chlorinated solvents may promote corrosion.