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Hi. Hair turns gray or grows grey? I have not seen dark hair at the older top end and grey at the newer bottom; or does it happen? If grey hair never has a dark top section; does it mean that it grows grey from the 'new' start ? Then, if it grows from the scalp as grey, it has to be from a follicle that previously lost its dark hair to the root, right ?

Thanks for the responses... Do you know of any oil type with a low amount of reacting oxygen / moisture that you can recommend, please? or process to de-oxygenate it ? Heating it up to evaporate moisture ?

Hi. Can the surface oxide layer be permanently removed if a piece of the metal is scraped while submerged in oil -and kept in it- ?

What should be expected from vinegar + baking soda? And a pool chlorine tablet + alcohol ?

Trying to find how to put together one deflated 'party' balloon with a few grams of water in it and a chamber or packet with some compound also inside, that due to mechanical jerk they mix and produce a gas, perhaps CO2, so in less than a minute would inflate to something like 5 to 10 litres. What household or simple compounds could achieve this ? Would baking soda or baking powder or a more energetic something work ? Ideas ?

Thanks !

Hi. Would polar coordinates be preferred for calculations on a heliostat mirror aiming? Get about a metre long piece of string, anchor one end to anything, call that T 'target' and also anchor about the middle of the string to anything else, higher or lower, being that point M -mirror- Grabbing the end of the string point S -sun- , a solar ray path can be visualized by moving the string along a plane. Now, what are convenient reference axis to use for calculating the azimuth and elevation the mirror M should aim so S always illuminates T ? Or, any other suggestions on how is it done ?

What is voltage produced by a galvanic cell made with carbon and magnesium electrodes, on a ClNa electrolyte; ? If the Mg is replaced with aluminium, what would be then the voltage generated ? What atomic data of the Mg, C, Al elements is used to determine/calculate the voltage generated ?

Hi all. Looking how to calculate the power developed by an undershot water wheel spun by a laminar flowing river in function of -Flat paddles submerged area, -Speed of river ignoring friction losses. http://commons.wikimedia.org/wiki/Image:Undershot_water_wheel_schematic.svg Thanks.

Thanks !

How is it called? It is shown usually in the Pacific ocean -for available space-, I believe has something to do with (solar?) declination trough seasons, it is an elongated "8" What does it mean ?

Hi. 1.- Go to a "Home depot" type of store and buy one. If you can beat by far their less than $2 price TO THE PUBLIC for a sprinkler, then keep thinking. 2.- A patent is highly likely to drive you nuts waiting never less than 2 years until issued IF granted or any other sprinkler manufacturer does not bite you. 3.- The ONLY thing a patent gives you is the right to sue. To sue, you need a lot of money to feed lawyers. Probably more than the amount you need to start production with no patent. 4.- If after years of sweat and tears you start production protected by a patent, the chinese will copy it for a fifth of the price if the idea is truly brilliant. Then, just MAKE them and sell them to all related stores at your reach -now-. Good luck. Miguel The same thing happens to me often. After typing a response, and "Logged in" showing, the submitted message dissapears unretrievable. Just highlight the text and copy it before clicking "Submit reply" Then you can retry pasting.

Hi all. A young fellow started work as an electronics technician a couple of years ago in a factory and by whatever reason management did not train him on the products, by his own means slowly learned and found out the innerworkings of the products he handles, meanwhile struggling and appearing unfit for the job. Another technician to do similar activity was hired. Should the now experienced technician on his own train/teach/share/guide the new one with all the knowledge management did not care to supply ? If yes, the new guy will appear more competent for the job. If no, the company suffers. And other implications depending the point of views of each technician and management. Suggestions ?

If the audio signals from two microphones are fed to a differential amplifier, its output will be only the audio which is sensed in real time by one microphone more than by the other. That way, equal sounds reaching simultaneously to both microphones will not be amplified by canceling each other due to phase inversion of one by the differential amplifier. Success depends much of microphone placement and directional characteristics. In open environment, sounds sources headings play a role in the success of the cancellation. A "voice canceling schematic diagram" or "vocal remover..." search could yield further details. Miguel

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