Enthalpy

The direction of natural evolution is to spread energy as evenly as possible among the accessible means of energy storage. (That's approximately the meaning of entropy). If you consider the electronic states in most small molecules, they are well separated, by several eV. Other means to store energy offer a cheaper entry ticket: rotations are ine the meV range or less, vibrations a bit under 1eV. Our usual room temperature is 26meV; at equilibrium, each means of energy storage receives about as much. It implies that rotations store 26meV each, vibrations can store heat in some molecules (especially solids), but higher electronic states are not populated. QM modifies a bit the statistics, but the result stands that at 26meV temperature, electronic states at 5eV over the ground state are empty. Their probability of occupation resembles exp(-5/0.026) which is zero for practical purposes. In fact, the "entry ticket" make these means store far less energy than 26meV each, so what spread evenly is the temperature, better than the energy. "Disorder" is misleading; even spreading of energy is easier to understand, even temperature (or Fermi level, or Gibbs energy) more accurate.

It's not a matter of OpenGL... And believe it or not, molecular modelling software does use OpenGL, DirectX and the like, efficiently. Molecular modelling tries to compute the structure of a molecule (bond distances, angles, and with some models, electron distribution) from the atoms and bonds given by the user. This is the difficult part of the task, not image rendering.

There was such a Stirling in the small industry park where I worked years ago. We were in a forest, and wood chips (bark, sawdust, chopped small branches) heated a Stirling to make electricity, so it does work. I ignore how bad the economics of the project are. What I don't grasp at all is the fuss in ecological circles about the Stirling engine. It's nothing more than a converter from external heat to movement, and any vapour machine does that far better: smaller, cheaper, more efficient. Especially a vapour turbine is so much smaller. In a farm, you might also consider the production of methane, for local use or for sale - it's essentially the same as natural gas. A farm may also produce vegetable oil to run engines, either at cars or electricity generators. Though, this one doesn't use waste products. Petrol from vegetable waste would be very nice but isn't operational up to now; science in progress.

The materials are nothing special; it's a matter of cold essentially. Polystyrene foam can provide insulation. Weather stations launch two balloons a day (12 and 24 gmt). Excellent quality.We went to such a station and got the envelope, the helium, the launch service, the radio tracking from the weather station, for free or for little money. A balloon must integrate in the air traffic: radar echo, parachute, maybe notification to air men, hardware digestible by a fan, and so on. It must also integrate in the radiocomm traffic; again, weather stations have their proper frequency bands which we could use outside their usual flight window, this helps a lot. Finding a balloon fallen somewhere on the ground is very difficult, even with radar tracking that happened to work, so transmit the data in flight, don't rely on data storage. A balloon commonly flies 200km away, so transmission isn't obvious even if high above the horizon, and you lose the link far before touchdown, say at 10km altitude. People finding a fallen balloon tend to keep it for themselves, so writing "danger - radioactivity" on it is better than "I'm a science experiment, please call my owners". You have to decide if the equipment must work at ambient temperature (like -70°C, very difficult for batteries) or if you provide it more comfort. Don't forget condensation on optics. Experiments on stratospheric balloons by amateurs have been done thousands of times, so just check the literature. Would you prefer something more original than taking pictures? Measure the disruptive voltage as a function of the air pressure? Collect micrometeorites? Detect cosmic rays?

Wow, nice toy! Dna: the modelling algorithms used by Arguslab (every programme uses the same ones more or less) take a computation time that increases faster than the number of atoms, possibly as the square. 10 atoms run, 30 atoms are slow, 100 atoms are already too much. Faster methods should check first which atoms interfere or not, but most programmes don't, alas. An other option models atoms as mechanical balls that can stick; far less accurate, this has the capacity to model poteins and their interactions.

If there's a physical limit, it exceeds by far the technology's capability. We can produce photons in colliders, supposedly of a few TeV. Cosmic rays contain much bigger energies; whether each one has been a photon or something else is hard to determine, but they do result partially in photons in a shower. One limit on the propagation over big distances could be the interaction with other photons making the cosmic background. It's not a limit on the existence of photons. An other limit would be a minimum length predicted by unification theories. Very far both from technology limits and from observed photon energies.

I'd say: no upper limit. And even worse: independent particles are only an approximation necessary to our understanding, but normally they're entangled. In the artificial case of experiments, the goal is usually to get simple situations, which involves reducing the number of entangled particles. I haven't read "symphony" before in this context. Translation gone inaccurate?

Looks good to me up to the rotational energy. ---------- The "usual" kinetic energy is just an alternative way to compute the same rotational energy. Your estimate is less accurate because it would put all the spoke mass at the rim, hence attribute it too much speed. Sicne the spokes are rather light, you get approximately the same result, which is a way to double-check it. The kinetic energy is properly computed in your line inertia-spoke. The factor 1/3 results from the mean value of the squared speed: it's an integral of the squared speed, taken from zero radius hence zero speed up to the maximum radius. Both approaches, by the angular speed and the linear speed, should have given the same result (and they do approximately here). There is no reason to add both results. ---------- No torque nor force can be deduced can be deduced from the kinetic energy the way you did, which apparently comes from falling objects. One need for torque is to accelerate the wheel up to 0.55m/s or 0.1turn/hour. You have to decide how much time you accept for the acceleration. The way passengers embark may decide that. The time to achieve the angular speed (rad/s) gives an angular acceleration (rad/s2) which, multiplied by the inertia (kg*m2), tells a torque (N*m). The torque multiplied by the angular speed (rad/s) is a mechanical power (W) obtained after some losses. Just like the kinetic energy can be computed, approximately or exactly, through the angula speed (rad/s) or the linear speed (m/s), one could also compute the force (N) needed to accelerate (m/s2) the wheel (kg) to a certain speed (for instance 0.55m/s) within a desired time (s). This force multiplied by the speed is a mechanical power (W). Both methods (torque times angular speed, versus force times linear speed) should give the same power, because the radius multiplies the force to define the torque, but divides the linear speed to define the angular speed. ---------- The other need for torque is because the wheel isn't balanced. You have to estimate by how much it's unbalanced through its construction and assembling (not obvious), and more easily, by how much the passengers unbalance the wheel. This depends on how the passengers board and unboard; if this happens to be the main contribution, and if this contribution is considered big, you might put constraints on the wheel operation. I'd try to avoid such constraints.

No, technology has evolved since. Telecom rules even demand accurate transmission frequencies and explicitly prohibit the use of damped oscillations.

You may want to have a molecule modeling software as well. Less a hand pleasure than plastic balls, but it has advantages as well, provided you don't overtrust it. This one is decently easy to use and is free: http://www.arguslab.com/arguslab.com/ArgusLab.html many more exist.

The wave versus particle debate is (1) outdated (2) philosophy, not physics (3) counter-productive. The useful way of understanding is whether objects interfere, can concentrate some attributes in a smaller volume than previously in some situations, and so on. The superposition of states is routinely observed.

Radioactive half-lives span from very long (238U) to extremely short, without a clear lower limit. No worry with Sensei's example of a half-life equal to 1, even less so because he didn't tell the unit. Here's an example of a chart of the nuclides, where the colours indicate the half-life between 10+15s and 10-15s: http://www.nndc.bnl.gov/chart/

On May 01, 2014, I proposed to recompose mainly ethylenediamine in a gas generator (good for a staged combustion as well) with some dissolved ammonia to avoid soot. Ethylenediamine is a bit volatile and corrosive, so I checked if 1,2,3-triamino-propane (a ligand known as Trap) could replace it. It can, but needs 2-3 times more ammonia than ethylenediamine does, so I doubt the triaminopropane mixture improves the vapour. Though, triaminopropane in smaller proportion could serve as an antifreeze in ethylenediamine.

While neither Wiki nor Nasa claim the hole at Glenn facility was previously a mine shaft, it's clear that water leaks are the same difficulty, whatever the bore was initially intended for. At Nasa's Glenn center, the hole is fully cemented - and within the concrete walls, a steel tube is airtight. I'm not convinced that mine shafts are cemented: since the mines themselves are not, miners have to pump the water out anyway, so I suppose they leave the shaft naked as well where the materials are sound enough. Reusing a mine shaft would imply to dry it first, and then either continue to pump water out permanently, or cement the walls and the bottom. Nothing tragic, but it's a cost. For me, the true benefit would be the bigger depth if available, as 600m depth double the fall time over 150m height. Both a tower and a bore can host the vacuum bubble option, which can retrofit an existing drop tube.

That's a bit of metal, some polymer straps, and a stack of plastic films.

I have no opinion about electrochemistry. I'm just pointing out that the very companies that produce rechargeable batteries call "cathode" the negative electrode whatever the current direction, that's why they say "cathode material" for a rechargeable battery. Sony use "cathode" and "anode" the same way as Saft http://www.sony.com.cn/products/ed/battery/download.pdf for instance on pages 9 to 11, on figure 1 and in the text. Panasonic also call "anode" and "cathode" some components of their rechargeable cells http://datasheet.octopart.com/VL2330-1VC-Panasonic-datasheet-9706278.pdf on the drawing titled "construction". So does the academic "Journal of power sources" http://adsabs.harvard.edu/abs/2014JPS...247..412W

Depending on what support and interconnects you use, and what kind of circuits... breadboards are inadequate for many electronic functions because of electromagnetic interferences. But a Veroboard with a ground plane works in many cases. It looks like the blue boards there http://en.wikipedia.org/wiki/Perfboard Has someone here tried pot soldering for single units? I fear random results and long learning time. Up to now, I've seen individuals and companies solder by hand even for 20 identical circuits, and jump to wave soldering for >20 circuits, often at subcontractors then. Yes, from the EU, and I say lead-free solder is nonsense because it solders nothing. Since users don't chew their electronic gadgets, which are later recycled because of gold, I don't care about solid lead in them. And at the same time, the EU accepts fluorescent light-bulbs that contain gaseous mercury, which users inhale when the bulb breaks - as toxic, and with a path to the organism.

Despite their low relative speed, the experiment needs vacuum in the bubble to achieve a good microgravity. Not air drag makes parasitic forces here, but buoyancy. I give here illustrative figures with the usual 1Pa residual pressure and a 4m*D1m experiment shell in a 5m*D2m vacuum bubble. The drag compensation engine can apply 300N briefly on the 100kg vacuum bubble. The resulting air pressure gradient, 37µPa/m, exerts 0.1mN on the 200kg experiment, or 0.06*10-6g. The bungees bring 54m/s within 10m, that's over 15g at the peak - nobody expects microgravity then - and buoyancy pushes with 6mN. The pressure gradient then oscillates with 30ms period. One acoustic damping time (0.1s?) reduces the effect to 1*10-6g. Each opposing pair of guiding rolls needs a viscoelastic damper: polyurethane, Viton... If the suspension oscillates at 5Hz and the track is straight within 5mm peak, the resulting 5m/s2 produces 0.07mN or 0.1*10-6g. The same side movements result in 0.2m/s air speed, in which Cx=0.4 creates only 0.3µN. The vacuum bubble operates hence at a residual pressure similar to a vacuum tube, but is much smaller, so the vacuum is achieved faster, more easily, and can improve further for better microgravity. A thought for my father. Marc Schaefer, aka Enthalpy

If you plan to use your equipment often, as a future professional or a regular hobbyist, buy quality right from the beginning: - If not right now, you'll invest in it later, and abandon your first buy - Bad equipment is more difficult to use hence discouraging. Where I live, professionals consider only Weller, though other manufacturers can be good, and meanwhile Weller also sells a few bad irons. The one on Davidivad's picture looks good, of for instance item 131338672317 on eBay (paste the number in their "search" area, observe the picture, buy where you want). Pay attention that the tip is pressed axially and not by a radial (=at the side) screw: fundamental for the heat transfer. I got mine from Conrad for 60€, not really cheap, but still a bargain. A set of interchangeable tips is not really necessary. Any decent tip must be covered with a layer that resists corrosion: I suppose it's nickel. For a printed circuit, 30W is a common choice. The regulation is comfortable because the iron is ready quickly, but it's not vital; 60W keeps then good for printed circuits and more capable elsewhere. A tip fine enough is paramount for electronics. A holder where the iron aims downwards saves time but isn't vital and can be purchased separately later. A sponge is necessary and can be any natural sponge, absolutely not the plastic things used for dish washing, silicone things are less good. I see no reason for low voltage (24V) at a soldering iron. If you put this together, you arrive naturally to the suggested soldering station, but this isn't a necessity. ---------- Do not use a desoldering pump nor a desoldering iron, gun, station... They destroy the printed circuits. The proper way is a desoldering braid - not exactly cheap, but some sources are less expensive. The ones covered with a white metal (I suppose tin) are far better than the usual ones of bare red copper. http://en.wikipedia.org/wiki/Desoldering The EU forbids Sn-Pb solder in professional equipment (RoHS directive). That's nonsense because the present stuff solders nothing. Stick to Sn-Pb and nothing else. 63%Sn is slightly better than 60%; additional 2%Ag is too expensive; soldering flux in the solder wire is absolutely necessary; for printed circuits, have a small diameter. You'll probably need wire cutters (side cutters for electronics). The good ones are expensive from renown manufacturers, pity. Look for short and sturdy blades. To remove the insulation from wires, I've already had all options... Do not take any automatic thing. The ones that work look like scissors, have zero adjustment nor mecanism, and bear a few dents of varied depths that you select for the present wire. It's also the cheapest construction, nice. These ones (need 2 series of diameters) (the ones I have) are excellent: items 361075372407 and 201212686986 on eCreek, while less good grips make it cheaper: 270959890315.A slightly different construction like item 141183498487 on eCreek could be good as well, but I haven't tried it.

This document confirms my impression that manufacturers of rechargeable batteries also call "cathode" the negative electrode whatever the current direction: http://www.saftbatteries.com/force_download/Defense_Systems_Brochure_0.pdf on page 4 of 6 (or search "cathode") about LiNiCoAlO2. Looks like the claim at Wiki and the common use of several professions differ widely.

If the dipole consists of two finite charges with finite separation, each feels a force as 1/R2 from a distant one. In that sense, Coulomb's law still applies.

Better definition indeed. But I'm still surprised that the cathode gets an anode when the current direction changes. This is not the vocabulary in use in electrical engineering - definitely not for diodes, nor did I hear it for accumulators.

This understanding would suffice more or less for a double-slit experiment using a detector. It does not for other behaviours of quantum objects. You might have a browse at orbital pictures of "pentacene" made by "atomic force microscope": the same pair of electrons is observed all the way to image the shape of the wavefunction, which then isn't just a statistics over many point events. That's why one shouldn't restrict his interest to the double slit. The object is a wave and a particle all the time. It's a wave in that it diffracts, and so on, as was previouslt known from light. It's a particle in that some properties (charge, energy, angular momentum) don't spread over the wave's extension. If one pixel of a detector gets a photon, the energy is all there and nowhere else. Also, to compute the extension and shape of the wave, we take the complete charge, mass etc. of the particle at each possible position. When a photon gets absorbed in a CCD camera, it still behaves as a wave. It keeps an extension, for instance one thousand atoms, because the absorbing electron had such an extension before and has it after. Rather, the photon has adapted its extension to the electron that happened to absorb it; in that sense, it's a particle if you wish: it didn't need to reduce its extension to a point for it, but adapted its extension while keeping the other attributes, especially the energy transferred to the electron. Wave and particle at the same time is abstract, but the good aspect is that you don't have to tell when it would be one or the other. Interferences were produced with photons, then electrons, and more recently with atoms and molecules. These heavier objects use to have a delocalization that is smaller than their mechanical dimensions, so it takes difficult conditions to observe interferences - typically produce fringes wide enough.

O yes. Maybe "both sides" is "both ends"? If the masses ar imperfectly balanced, I don't wee why one should use two instead of a single lighter one, and if they are, one gets no vibration. With unbalanced masses, the motor's bearing will work under very unsound conditions. I would be worth checking if they can survive it.

It's still valid for each charge of the dipole. Only the net effect, as the difference between two forces in 1/R2, changes as 1/R3.