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Hi. I think learning long ago, that a flame cannot be smaller than a certain limit. How is the theory -or fact-? Perhaps that is the principle of operation of flame arresters, which are a bunch of small holes. If an explosion happens at the end of a hose carrying -say gasoline- vapors, would the flame propagate inside the hose towards the source of vapors and blowup everything; or if the hose is small enough it won't happen ? Is a burning explosive wavefront also prevented to propagate trough a flame arrester, of that is only for flames ? -if they are not the same- What prevents the flame of a bunsen burner to ignite the vapors in the hose all the way back to its butane tank and... kaboom ? Yes, no oxygen in there.... What if a mixture of combustible vapors and air are flowing in the hose ? Miguel

Yes, superb teaching ability together with knowledge, rare to find both in a person! Miguel

Excellent explanation; thanks, Glider. This bring more questions; the core of the trunk being dead still functions 'pumping' nutrients to the branch tips ? Interesting. And the only few live cells on the trunk are just under the bark; would that be a reason that a tree mostly dies on a forest fire, as there is high exposure to flames ? And what about the roots, is there a dead portion there too, and the outer layers are the only ones extracting nutrients ? If so, at the transition from roots to trunk, there is nutrients ducting connection from the roots exterior to the trunk center ? The trunk center 'pumps' vertically and the body 'pumps' horizontally towards the live cells ? It has to be a very interesting mechanism if performed by dead tissue. Capillarity related ?

The water bridge article is here: http://eloah.at/waterbridge/Water_Bridge_JOPDAP.pdf The video is here: http://www.tendencias21.net/Descubren-que-el-agua-puede-formar-puentes_a2004.html?voir_commentaire=oui Enjoy, and ...do it? The anode conection from a CRT television or monitor can be borrowed to try. Just discharge before handling.

Hello all. A sawed off section of a tree shows the seasonal rings, age, and some environmental characteristics, but my question is about growth alone; the addition of material to the trunk. Is the younger material at the center or at the bark ? Or, in other words, the diameter of a tree increases as new wood cells form at the core and migrate outward or the new cells accumulate under the bark ?

Hello. As our lives are highly ruled by 24 hour periods, meals at mostly regular intervals and sitting on the throne is also periodical, the intestinal transit should be a multiple of 24 hours; if am thinking well. How long does it take a 'normal' routine meal to evacuate ? Miguel

A video camera in an air filled underwater housing is ballasted to be neutrally buoyant. Does not sink, does not float. Will removing a 200 grams (dry) ballast weight from inside the housing result in a more, less or equal amount of flotation if the same 200 grams weight is removed from ballast attached outside (wet) ? Miguel

Hi all. At a store, I found framed between two glasses, a bunch of tree leaves missing its 'green' tissue, and nicely dyed and impregnated in several colors, and gold? powder. Yes, bought it. Too nice (or unique) to pass. It may be a common practice among people that does manual art and that type of adorns, drying plants, etc. but I never saw such thing before. The question is; how is it done? What chemical can erode tree leaves, leaving only its fibrous skeleton, looking as a 'gauze', with only the natural pattern of the tiny leaf veins. Hope the image inserts. It may seem double exposure, but it actually is the fibers shadow on a blank paper placed behind the frame. Miguel:-)

That is way wrong ! Since when an electric vehicle is rated that way as mpg ? ¿ 300 miles per gallon of ... volts ? The reporter even mentions "...when I step on the gas" Yes, sure, gas... Even a hybrid would have to de-rate the figures for the strict time it runs on gasoline. Miguel

The drop descending earlier goes faster than the ones after it because has been traveling a longer time under gravity acceleration. If a drop goes faster, it will be further ahead between it and the next one. There is an asimptote as at a certain point the speed will not increase beyond the air drag. So, the drops will be more apart the longer they have been falling.

Well, the misconcept is the water does NOT evaporate at 100 Celsius. The water evaporates at ANY temperature. What happens at 100 Celsius is NOT evaporation, is change of state to STEAM, which is NOT vapor. The misuse of the word vapor -even in text books- under and over 100 Celsius produces the misconception. If vapor meant being over 100 Celsius, clouds would have to be hot, and they are not. They are vapor, not steam. Miguel

Hi alan2. Enjoy: http://www.sciencenews.org/articles/20020105/fob2.asp Is not a new article, but lately there is very little noise about the technology. Miguel Edit-added: http://www.scirus.com/srsapp/search?q=magnetocaloric+metals&ds=jnl&ds=nom&ds=web&g=s&t=all

OK. A sort of a blender at melting temperature, the size of the wanted batch. In the mentioned alloy example, what trick is needed to prevent the phosphor to stop existing by becoming smoke when gets to ignition temperature way before iron melts? There should be dozens of elements that will refuse to stay 'alive' at high furnace temperatures... how is that controlled ? Simply such alloys are impossible to achieve; or engineering strategies/processes get into play ?

Hi. When a magnetocaloric compound is exposed to a magnetic field it heats up; Until when? For how long ? As long as the field increases? If the material heats up -say 10ºC- ; starts cooling back by radiation/convection/other or maintains:eek: a delta t ? Miguel

If you want an alloy of say iron, manganese, phosphor, and germanium; do you melt them with desired proportions in a very, very hot 'blender' and push the 'on' button for a while ? Or is it more rocket science than that ?

Hi. Too many years ago, a knowledgeable chemist engineer told me that an iron object would hardly rust ever again if treated with caustic soda. What is the treatment? dipping in a solution? media blasting? burying the metal in it? what concentration, or else ? Miguel

Hi all. The basics are simple, the currents produced by dissimilar metals in seawater, the erosion and deposition of material depending on the electronegativity... I see it as a simple galvanic cell, a 'battery', but I have a void somewhere in all this. If an iron barge floats on seawater, and no other metals are part of its hull, will still need (Zn, Al) sacrificial anodes attached ? If an aluminium boat hull has a bronze propeller I can understand the migration of charges and erosion of metals; but what if the hull is only aluminium and no other metals, will it still deteriorate and need protection ? Now, an aluminium hull has good electrical connection with its stainless steel shaft and bronze propeller, as they are all attached to each other... how does the corrosion/electric currrents work there ? If a boat with aluminium hull is 20 metres away from an iron one; will there be electrical / ionic / metal migration / currents in the seawater and between the boats ? Any clear light is welcome. I believe am mixing battery reactions, electrolysis and electroplating... Miguel

You can form your own opinions... http://www.youtube.com/watch?v=_9ak7iiYwVQ http://www.fdp.nu/perendev/default.asp

It is in video: http://www.metacafe.com/watch/718152/how_to_turn_water_into_ice_in_seconds/ Thanks.

DrDNA: Precipitation in the sense of some ions being in higher concentration near the bottom of the container. To say it simpler, a solution of a teaspoon of salt in a litre of water, steady temperature, capped, undisturbed for a year. Which ions will sink because of their greater specific weight; Na or Cl ? Miguel

Hi all. In a plain solution of table salt, left for years undisturbed in a closed jar; which ions will be more abundant (precipitate) at the bottom - Cl or Na ? Miguel

Thanks, Rocket and Pioneer. I did not think of those variables; the air pressure to be watched; and the viscosity being lower can result in smaller bubbles. Yes, the smaller the better for my application. Thanks

Am back with my bubbles ; would like opinions on what would happen if very fine air bubbles are released from aquarium type stones under a fluid as viscous as honey. The actual test will happen in a few days as am waiting for some supplies but will apreciate your opinion before. I believe large bubbles would surface and eventually pop, but small ones (smaller than ~1mmØ) would stay trapped at least several hours. The question is; if the supply of bubbles does not stop from the bottom of the container; how will the mix behave; will there be a limit of expansion ? Will tunneling to release the air develop ? I find it hard to visualize. Help please. Miguel

This is not my field of expertise, obviously... I believe boron phosphate dissolves in water ; would it cause the bubbles in soapy water to harden ? Or what would you do to harden bubbles ? Miguel feparetz

Hi. Do not know about your radiotron CRT , but I may be of help. Is there a particular number for such tube? ----> Look trough the glass to the connections of the four pins, the filament should be entering into the center of a small metal tube, and you already identified them as it glows. The other two may be cathode, a connection to the small metal tube. The last may be a grid, there is a chance you can see trough the glass the actual grid of ultrafine wire. Applying 300V instead of the full rated 500V should produce some indication of the tube being functional. I do not know what you mean with PD. Miguel