Wikipedia:Reference desk/Archives/Science/2014 May 1
Science desk | ||
---|---|---|
< April 30 | << Apr | May | Jun >> | May 2 > |
Welcome to the Wikipedia Science Reference Desk Archives |
---|
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
May 1
[edit]If I can smell something is it losing mass?
[edit]If I can smell something I suppose it means that thing is being dissolved into the air. Is it therefore losing mass? Hayttom 11:10, 1 May 2014 (UTC) — Preceding unsigned comment added by Hayttom (talk • contribs)
- Yes. --Jayron32 12:13, 1 May 2014 (UTC)
- Odor implies such. It says "low concentrations", i.e. you're only inhaling a very small quantity of whatever is being emanated, but obviously if you're sensing it then it's no longer "attached to" its source, hence its source is losing some small quantity of mass. ←Baseball Bugs What's up, Doc? carrots→ 12:26, 1 May 2014 (UTC)
- I suppose an exception is if the item modifies existing air in some way, so as to make it have an odor. Air purifiers which create ozone and space heaters which burn dust in the air might qualify. StuRat (talk) 13:55, 1 May 2014 (UTC)
- Also, when you can no longer smell it, that implies that the volatile compounds have all evaporated/sublimated into the air. Of course, grinding off the surface may expose more volatiles. StuRat (talk) 13:59, 1 May 2014 (UTC)
- Supposing you had an open container of a common substance such as rubbing alcohol. Once it "totally" evaporates, isn't there still some residual scent in the container? ←Baseball Bugs What's up, Doc? carrots→ 15:12, 1 May 2014 (UTC)
- In that case, it's highly likely that there are some impurities in the alcohol that are still producing smell - and that some of the alcohol has been absorbed into the container somehow. But if it's literally all gone - then of course there can be no smell.
- Smell is only possible if some of the molecules of the substance made it into your nose somehow...if there are literally no molecules left - then there obviously isn't going to be any smell. But even humans - with our relatively poor sense of smell - can detect quite low concentrations of some substances...so there may not have to be very much left for us to detect it.
- To answer the question though - it may be that the substance is emitting some chemical but absorbing something else. So you could imagine something absorbing water from the air while emitting something else. In that case, the bulk of the material could increase while the smell is being emitted. If there was some kind of chemical reaction with something in the air that produced the smell - then it's quite possible that the result is an increased mass. Imagine something which reacts with air to make nitrous oxide. That stuff smells slightly sweet - but we might imagine some solid that absorbs oxygen and produces nitrous oxide as a byproduct...it would gain mass as time goes on and continue to generate that slightly sweet smell until the reaction is complete and the mass has increased.
- SteveBaker (talk) 15:36, 1 May 2014 (UTC)
- Good point. For example, what about the bloated blue whales discussed in this (fairly gross) story?[1] Could they be gaining mass as they decompose? Or is the decomposition merely re-arranging molecules already existing within the carcass? ←Baseball Bugs What's up, Doc? carrots→ 15:43, 1 May 2014 (UTC)
- I guess mass might be passing from the air to the solid (or semi-solid) parts of the carcass. But the fact that the body is capable of inflating like that suggests that any gases involved in that reaction were wholly contained by the carcass all along. I can't say the same for any decomposition at the outer edge - some substances might be oxidising, in which case they'd be gaining mass from the wider atmosphere, but they might also give off odour and other things at the same time, resulting in mass loss. AlexTiefling (talk) 15:48, 1 May 2014 (UTC)
- I very much doubt that the bloated whales are gaining mass. They are getting bigger - but that's just gasses as a decomposition byproduct. I don't think they are getting any heavier. SteveBaker (talk) 16:36, 1 May 2014 (UTC)
- I guess mass might be passing from the air to the solid (or semi-solid) parts of the carcass. But the fact that the body is capable of inflating like that suggests that any gases involved in that reaction were wholly contained by the carcass all along. I can't say the same for any decomposition at the outer edge - some substances might be oxidising, in which case they'd be gaining mass from the wider atmosphere, but they might also give off odour and other things at the same time, resulting in mass loss. AlexTiefling (talk) 15:48, 1 May 2014 (UTC)
- Good point. For example, what about the bloated blue whales discussed in this (fairly gross) story?[1] Could they be gaining mass as they decompose? Or is the decomposition merely re-arranging molecules already existing within the carcass? ←Baseball Bugs What's up, Doc? carrots→ 15:43, 1 May 2014 (UTC)
- SteveBaker (talk) 15:36, 1 May 2014 (UTC)
Thanks, everybody. Hayttom 08:31, 6 May 2014 (UTC)
![](http://upload.wikimedia.org/wikipedia/en/thumb/f/fb/Yes_check.svg/20px-Yes_check.svg.png)
Mr Frosty (is such fun; he makes treats for everyone)
[edit]Did Nalgene have to make a deal with the toy manufacturer to call their cryogenic storage containers "Mr Frosty"? --129.215.47.59 (talk) 12:48, 1 May 2014 (UTC)
- There's no reference to a "Mr Frosty" in the Nalgene article. Do you have more details you could share with us? ←Baseball Bugs What's up, Doc? carrots→ 13:58, 1 May 2014 (UTC)
- With trade names like that, there are generally only legal problems if the public are likely to confuse the two products. It's a legal minefield though - and these things often end up in court even when the layman would say there was clearly no confusion. For example, I recall a legal battle in the UK between Digital Equipment Corp (DEC) and the company that begat the Dyson vacuum cleaner. DEC had a computer called "VAX" and there was a vacuum cleaner called "Vax". You'd think it was obvious that there was no conflict - but it didn't stop them from winding up in court. In that case, it was ruled that nobody had infinged on anyone's trade name because there was no possibility of confusing a gigantic minicomputer with a domestic vacuum cleaner - so nobody had to rename anything and no money had to change hands. However, such battles do often end up in bloodbaths - the Apple record company (which was owned by the Beatles) wound up in court with Apple computers (the fact that their logos were almost identical didn't help!). But it was ruled to be OK so long as Apple Computers didn't make or sell music...which they didn't back in the era of the Apple 2 computer. Well, you can imagine what went wrong when Apple produced the iPod and started selling music on iTunes...which clearly COULD result in confusion between the record label and the music sales service. The resulting bloody re-run of that legal mess explains why, for the longest time, you couldn't buy Beatles music on iTunes.
- According to Trademark247, "Mr. Frosty" is a registered trademark of Nalge Nunc International Corporation. According to this page, it is also a trademark for Sea Watch International Corporation, for use in labeling seafood. I can't find any information on the use of the name as a trademark for toys. Looie496 (talk) 01:00, 2 May 2014 (UTC)
Using napalm in a car instead of gasoline
[edit]What would happen if you used napalm in a car's gasoline tank instead of gasoline? Would it blow up or would the engine just fail to start? ScienceApe (talk) 13:42, 1 May 2014 (UTC)
- Napalm is gasoline - with the addition of substances to make it into a thick gel. The modern form of it is only about 33% gasoline, the rest is polystyrene and benzene. So even if you could somehow get it into the cylinder, there isn't enough gasoline in there to run your engine. Another problem (aside from whether your fuel pump could pump it) is that the fuel injectors in a car engine are designed to spray the fuel as very fine droplets. I doubt that it could do that with something as gelatinous as napalm.
- I strongly disagree with the assertion that gasoline is "highly explosive" - as a liquid, it's really quite hard to even set on fire. Only the vapor from it will burn at all. So you need it sprayed in fine droplets with a large surface area to evaporate from to get it to burn quickly enough. If you toss a lighted match into a bucket of gasoline, the match goes out...there is no exciting "Kaboom!". I'd also argue strongly against the assertion that a car engine is a controlled explosion. Fuel burns in the cylinders - it doesn't explode.
- The significant difference is that most explosives contain their own oxygen. For example - when nitroglycerin explodes:
- 4 C3H5N3O9 ==> 12 CO2 + 10 H2O + 6 N2+O2
- Everything that's needed to make it go "boom!" is right there inside the nitroglycerin molecule...so it's easily able to explode.
- Gasoline, on the other hand, requires LOTS of oxygen to make it burn. Gasoline is a complicated mix of chemicals - but one of the main ones is octane. Here is how octane burns:
- 2 C8H18 + 25 O2 ==> 16 CO2 + 18 H2O
- As you can see, you need 25 oxygen molecules for every two molecules of octane. Octane itself contains no oxygen whatever - so it can't even burn by itself, so it certainly won't explode. You've got to mix it with LOTS of oxygen to get it to combust - every molecule of the octane needs to be close enough to 25 oxygen molecules to react - and that's why it has to be in vapor form. Once that happens, the reaction goes quite quickly - and lots of byproduct means that the volume increases rapidly. You can call that an "explosion" - but it's no different than how wheat flour or sawdust will burn so rapidly that the effect is explosive if you get it in a fine dust up in the air. However, a grain of wheat or a lump of wood isn't "an explosive" - and neither is gasoline.
- That's why people who want their cars to go faster get fixated on turbo-chargers and super-chargers and big air scoops - getting more air into the engine is needed to get more gasoline to burn in order to make the car go faster. If you had a car that ran on nitroglycerin, you wouldn't need an air intake at all.
- SteveBaker (talk) 15:10, 1 May 2014 (UTC)
- If you google "automobile engine controlled explosion" you will find plenty of references, so if you don't like that characterization of the process, go complain to those individual writers, not to me who merely quoted them. Also, what's the answer to the OP's question, "...would the engine just fail to start?" I'm guessing it would indeed fail to start, but you're the expert, so we'll defer to you an that one. ←Baseball Bugs What's up, Doc? carrots→ 15:35, 1 May 2014 (UTC)
- If you google "magnets cure rheumatism" or "obama not US citizen", you'll get lots of hits too...doesn't make it true. SteveBaker (talk) 16:34, 1 May 2014 (UTC)
- One of the links that turns up is this, from the "How Stuff Works" department of the Discovery Channel. Feel free to contact that fringe group and tell them why you're right and they're wrong. ←Baseball Bugs What's up, Doc? carrots→ 18:07, 1 May 2014 (UTC)
- To be somewhat fair to Bugs, sometimes "combustive expansion of gases" is sometimes referred to as a low explosive while those that truly detonate are sometimes referred to as a high explosive. Low explosives occur when any combustible material is confined in a tight space; i.e. what happens in a piston chamber of a car engine. It just depends on what terminology you use. Some people prefer to not use the term "low explosive" because it confuses the very chemically different processes of "deflagration" and detonation. --Jayron32 16:52, 1 May 2014 (UTC)
- As far as I'm aware, a detonation is just an explosion that propagates through the explosive medium at supersonic speeds. That tends to create a much sharper and more damaging shock wave. I don't often disagree with Steve, but I think it's not unreasonable to describe what happens in a combustion engine as a controlled series of fuel-air explosions. --Stephan Schulz (talk) 09:40, 2 May 2014 (UTC)
- To add (not sure if it's helpful), there is a technical difference between a rapid burning and a detonation. This was vividly shown in a safety video for silane which will usually readily burn in air (violently). And sometimes it will mix and detonate. I don't know if engines burn or detonate gasoline but the video was cool for silane. --DHeyward (talk) 02:41, 4 May 2014 (UTC)
- As far as I'm aware, a detonation is just an explosion that propagates through the explosive medium at supersonic speeds. That tends to create a much sharper and more damaging shock wave. I don't often disagree with Steve, but I think it's not unreasonable to describe what happens in a combustion engine as a controlled series of fuel-air explosions. --Stephan Schulz (talk) 09:40, 2 May 2014 (UTC)
- If you google "magnets cure rheumatism" or "obama not US citizen", you'll get lots of hits too...doesn't make it true. SteveBaker (talk) 16:34, 1 May 2014 (UTC)
- If you google "automobile engine controlled explosion" you will find plenty of references, so if you don't like that characterization of the process, go complain to those individual writers, not to me who merely quoted them. Also, what's the answer to the OP's question, "...would the engine just fail to start?" I'm guessing it would indeed fail to start, but you're the expert, so we'll defer to you an that one. ←Baseball Bugs What's up, Doc? carrots→ 15:35, 1 May 2014 (UTC)
- SteveBaker (talk) 15:10, 1 May 2014 (UTC)
- In direct answer to your direct question – it is a hydro-carbon, so a compression ignition engine (one that runs on diesel fuel) would run just like it was fueled by any other hydrocarbonous fuel. Don't have any reference to hand but I think you'll find that the naphthoic acid component of napalm is a corrosive by-product of the petroleum industry. It is a very cheap by-product. In modern fuel injected engines, this I think, would cause less problems. However, I it think it corrodes steel pipe lines as well. The combination of naphthoic acid and palmitic acid might also jell, causing the fuel delivery system to gum up. It is slow to vaporize, so a carbureted engine is unlikely to run without with out carb-heat.--Aspro (talk) 19:48, 1 May 2014 (UTC)
vitreous humor
[edit]Where does vitreous humor come from? If it's already present at birth, what organ (or other source) secretes it during gestation? Babies' eyeballs are smaller than adults, so as a person grows, where does the extra humor come from? 2001:18E8:2:28CA:F000:0:0:2B89 (talk) 14:00, 1 May 2014 (UTC)
Never mind, the page explains it, and I didn't see it until re-reading. "It is produced by cells in the non-pigmented portion of the ciliary body deriven from embryonic mesenchyme cells which then degenerate after birth." But could you help me understand what this means? I saw ciliary body, but I don't understand what a mesenchyme cell is. 2001:18E8:2:28CA:F000:0:0:2B89 (talk) 14:03, 1 May 2014 (UTC)
- In 1879, Charles Sedgwick Minot, an anatomist based out of Harvard Medical School in Boston, Massachusetts, first described what he termed mesamoeboids, the cellular portion of what would soon come to be recognized as mesenchyme. Minot found these cells in the context of histological studies of mesoderm. He understood the loose, mobile cells of mesenchyme as primitive representatives of the mesoderm, but did not consider these cells as a type of tissue. Two years after Minot’s recognition of mesamoeboids, Oscar and Richard Hertwig, two brothers and doctoral students of Ernst Haeckel at the University of Jena in Jena, Germany, coined the term mesenchyma in their publication Die Coelomtheorie. Versucheiner Erklärung des mittleren Keimblattes (Coelom Theory: An attempt to explain the middle germ layer), and they used it to describe the type of tissue that was comprised of the amoeboid cells that Minot had portrayed. The Hertwig brothers established that mesenchyme originates from mesoderm, and they situated this relationship in the broader context of the development of the coelom, a fluid-filled body cavity. Their Die Coelomtheorie also advanced the idea that the three germ layers maintain separate identities and develop distinct tissues and organs, a concept known as germ-layer theory. (Source: http://embryo.asu.edu/pages/mesenchyme) Basically, mesenchymal cells are the precursors of cells of the mesoderm, which will later become your blood and muscles. 140.254.227.117 (talk) 14:28, 1 May 2014 (UTC)
- Hmmm, come to think of it... it is not commonly, but nonetheless repeatedly has been observed that a choristoma of the lacrimal gland can occur in the ciliary body and/or connected iris tissue. Now embryologically, the brain (from which the eyes branch out) is a folded in layer of the outer epidermis. Assuming this indicates some real affinity between the cell types, does that make the ciliary body with its aqueous and vitreous humor production a sort of a sweat gland, and vitreous humor a sort of "mucus"? (To be clear this is outrageous speculation, and I'm not sure how I'd go about trying to prove such thing) Wnt (talk) 16:16, 2 May 2014 (UTC)
Andromeda...
[edit]The nearest Galaxy to the Earth is Andromeda...
You nead 2,5 Years if you travel in Space with 1.000.000 * c !!!!!!...
(c = 300.000 km/sec)Light speed
I cannot imagine that!!!...
You???...
SPYROU Kosta - Greece - Honeycomp (talk) 14:32, 1 May 2014 (UTC)
- I have more difficulty imagining a plausible faster-than-light propulsion method than I do contemplating how far away the Andromeda galaxy is. For what it's worth, there are several nearer galaxies (apart from the Milky Way) such as the Large Magellanic Cloud However, this 'question' appears to be a request for opinions rather than anything a reference desk can help with - it's best not to ask that sort of question here, as the header explains. AlexTiefling (talk) 14:40, 1 May 2014 (UTC)
- There is, if I got this right, another galaxy which is even closer than the Magellanic clouds. They are hard to detect because they are on the "wrong" side of the Milky way. - ¡Ouch! (hurt me / more pain) 08:28, 6 May 2014 (UTC)
- If you mean the cognitive processes that run in the brain when you use the term "imagination", I suppose you - assuming that you are human and have your prefrontal cortex and other areas in tact and normally functioning - can in fact imagine it like any other concept. This may be of interest to you. Source: http://scienceblogs.com/developingintelligence/2007/05/31/the-neuroscience-of-imaginatio-1/ 140.254.227.117 (talk) 14:47, 1 May 2014 (UTC)
SPYROU Kosta: I wanted to point only that IF we could travel faster than Light... faster * 1.000.000 is enormous!!!... Honeycomp (talk) 14:50, 1 May 2014 (UTC)
SPYROU Kosta: THANK you 140.254.227.117 about your consern for my Brain Health!!!... You are so "kind" and "childish"... :-) Honeycomp (talk) 15:04, 1 May 2014 (UTC)
- I think we're coming to the point where this joke isn't funny any more. RomanSpa (talk) 05:53, 2 May 2014 (UTC)
- ...and please (I've seen that one a lot, not just on the ref desk or on the internet) do not call the galaxy "Andromeda." Andromeda is a constellation; the galaxy is called the Andromeda nebula or the Andromeda galaxy. - ¡Ouch! (hurt me / more pain) 08:28, 6 May 2014 (UTC)
Comets and Aristotle
[edit]If Aristotle thought the heavens were unchanging and perfect, how did he account for comets? Looking around on Google produced the sublunary sphere article but nothing else, really. The article notes that Tycho's observation of a nova undermined the Aristotelian position, but it also says that comets likewise undermined it, and I don't understand why, since comets have been well known and rather common throughout human history. 2001:18E8:2:28CA:F000:0:0:2B89 (talk) 14:49, 1 May 2014 (UTC)
- He figured gases rose from Earth to high in the atmosphere, where they ignited and burned either quickly (meteor) or slowly (comet). Meteorology (Aristotle) has a link to the English text to the book; Book I deals with these "fiery exhalations". 88.112.50.121 (talk) 16:14, 1 May 2014 (UTC)
Impedance matching between transmission lines
[edit]I have a project that requires good broadband (upto 1GHz say) matching between a 50 ohm parallel plate line and a 350 ohm parallel plate line. Im wondering what would be the better method: a) straight tapered matching section or b) exponential tapered section. Also, what length of section should I use for each of the above methods to get a better than -20dB match upto 1GHz? --109.151.101.168 (talk) 14:53, 1 May 2014 (UTC)
- One issue is that different wavelengths will require different transition lengths. So at 1 MHz it would be 1000 times longer than at 1 GHz. Have you got a lower limit on frequency or do you need to go to DC? Are your two parallel plates sections the same separation and only differ in width? Exponentiation transition will be better. I ran an optimization for you with 4 fixed sections, which gives 73.8 108.9 160.7 and 237.1 Ohms, (values should be at fifth root of 350/50 powers) but this still only gives you 82% power transfer, no-where near the 99% you want.[2] Graeme Bartlett (talk) 23:01, 1 May 2014 (UTC)
- As suggested here, it is the lower end of the matching band that will be the difficult end. Without that specification the problem is ill-defined (or impossible, if you require down to DC). Wouldn't it be great if we could build DC transformers that are 99% efficient out of a simple shaped transmission line? —Quondum 00:07, 2 May 2014 (UTC)
- The problem is most certainly incompletely specified. Power level? Does it need to be bidirectional or are you interested in power flow in only one direction? If you don't need bidirectionality, the simplest, most boardband approach is to use a transistor - if matching from low Z to High Z use a common base circuit. That can go down to DC if necessary. If bidirectionality over a very board band is required, you can use a gyrator. What is important - low return loss and flat response (eg an intrumention problem) or efficient power transfer (eg a transmitter or radio reciever front end)? Most truely boardband applications are instrumentation/measurement applications, so power loss doesn't matter so much, but low reflection is critical. In such cases, use a resistive matching pad - which inherently goes down to DC as well as as high as you need when carefully constructed with chip resistors. Matching with intermediate matching steps and stubs is inherently narrowband as has already been said. 1.122.161.156 (talk) 10:49, 2 May 2014 (UTC)
- In reply to Graeme's posting and helpful calculation of reflection coefficient etc, no, I dont need a dc response as I am sending fast pulses from a low impedance charge line into the high impedance line by means of avalanche switches. To give an indication of the low end response: I can stand, say, about 10% droop on the top of my pulses. What this means as a lower frequency limit of the matching section, I am uncertain.
- In reply to 161.156: Power is pulsed but average is only likely to be milliwatts. I do need biderectionallity as the switches are in the low impedance line. Transistors in normal operation modes are unlikely to work at the sub nanosecond rise times I need. My basic need is to get maximum power transfer from the low Z line to the hiZ line.
- Any more thoughts greatly appreciated.109.151.101.168 (talk) 13:22, 2 May 2014 (UTC)
- PS: parallel plates are same width but different spacings.109.151.101.168 (talk) 13:24, 2 May 2014 (UTC)
- You stated an upper frequency limit of 1 GHz, which will approximately reproduce a step taking no less than 0.5 nS. Transistors are readily available that will give that sort of bandwidth. In any case, at the power level you specified, quite ordinary silicon NPN RF transistors can be used in avalanche mode to provide sub-nanosecond pulse rise times. This technique has been common in sampling oscilloscopes since the 1960's when transistors could barely work to 200 MHz in linear mode. To find the low frequency cutoff required, you need the pulse repetition frequency, unless some sort of DC restoration phenomenum is operational, in which case you need to know the pulse width and calculate on that. Why does the switch need to be in the low impedance line if you actually want the pulses in the high impedance line? It will be a lot simpler to switch in the hi-Z line. 1.122.161.156 (talk) 14:39, 2 May 2014 (UTC)
- The "frequence response" near DC is puzzling. If I apply a very slowly changing voltage to the two conductors why would the output not mirror the input faithfully? Even if I had a length of lamp cord spliced to coax spliced to twinlead? (It's been a long time since the "fields and waves class.) Edison (talk) 13:43, 2 May 2014 (UTC)
- Well, yes, but the OP specified a return loss (reflection) better than 20 dB. And we must presume that the response over the frequency range needs to be flat. Using intermediate impedance sections or matching stubs will result in reflected impedance changing with frequency and thus the return loss and power level must change with frequency. Putting it another way, yes, at low frequencies, the voltage on the high impedance line must faithfully copy the input, but it is the wrong voltage, as required voltage for a given power rises with impedance. 1.122.161.156 (talk) 14:39, 2 May 2014 (UTC)
- A Time-domain reflectometer would give Edison educational insight into their series connected lamp cord/coax/twinlead. By "mirror faithfully" they presumably expect their input change to produce an output at the speed of light. They will be disapointed because 1) with dielectric insulations between the conductors of the lamp cord, etc. the propagation speed is slower than c, and 2) at each point where they splice leads there is an impedance mismatch that reflects part of any signal (i.e. transient voltage change) back towards the source. It will take considerably longer than the time for one traversal of the cables for transient forward and reflected pulses to die down. Eventually the conductors settle at the same DC voltage throughout but now there is no AC power transmission and Transmission line effect is irrelevant at DC. 84.209.89.214 (talk) 17:30, 2 May 2014 (UTC)
- Well, yes, but the OP specified a return loss (reflection) better than 20 dB. And we must presume that the response over the frequency range needs to be flat. Using intermediate impedance sections or matching stubs will result in reflected impedance changing with frequency and thus the return loss and power level must change with frequency. Putting it another way, yes, at low frequencies, the voltage on the high impedance line must faithfully copy the input, but it is the wrong voltage, as required voltage for a given power rises with impedance. 1.122.161.156 (talk) 14:39, 2 May 2014 (UTC)
- In general, the matching will be good over some frequency if the geometry of the line changes slowly relative to the associated wavelength. This is an optimization problem, so you need to specify what must be optimized. In particular, is it the length of the match? you have already given the acceptable return loss, though that probably is not rigid. My guess is that a smooth exponential taper will be a good start if length of the matching section is to be minimized, but I have no direct experience and will have to defer to others with hands-on experience. —Quondum 15:46, 2 May 2014 (UTC)
The OP requires a passive matching line length L with tapered impedance z(t) ohms where:
- z(0) = 50
- z(TL) = 350
- t = distance/(speed of light) if the plates are airpaced
A 1V impulse on the 50 ohm input causes a reflected voltage waveform
- ø(t) = (z( TL - t) - 50 ) / (z( TL - t) + 50 )
Reflected power is maximum at frequency = 2 / TL so if this must be below -20 dB
- integral from t=0 to TL of ø(t) cos (π /TL - TL/2) dt < 0.1
Adjusting the length L and having a non-linear impedance taper could allow the VSWR (a measure of Impedance matching) to be minimised for a limited range of frequencies.
I recommend this venerable application note about applications of Step recovery diodes in pulse generators.
- "Pulse and Waveform Generation with Step Recovery Diodes" (PDF), Application note AN 918, Palo Alto: Hewlett-Packard, October 1984
{{citation}}
: Missing or empty|title=
(help). Available at Hewlett-Packard HPRFhelp.
84.209.89.214 (talk) 17:51, 2 May 2014 (UTC)
Male and female bell peppers?
[edit]According to a perhaps unreliable source, some bell pepper fruits (aka sweet peppers) are male and some are female. Moreover, the "sex" of each pepper can be determined by counting the lobes: 4 lobes = female, 3 lobes = male.
Further, female peppers = sweeter and better for eating raw, male peppers = firmer and better for cooking.
Is there any truth to this? Either the part about two sexes of pepper fruits or the part about the shape of peppers being related to their sweetness and consistency.
I suspect it is pure nonsense but... how does one know for sure? Thanks, CBHA (talk) 19:33, 1 May 2014 (UTC)
- I am not a botanist, but I found a knowledgeable-looking blog post that debunks the idea. Capsicum annuum should be relevant, but it doesn't have much information on the morphology of the plant. AndrewWTaylor (talk) 20:09, 1 May 2014 (UTC)
- This claim is total nonsense. A bell pepper is the fruit of the plant. All botanical fruits (of which bell peppers are an example) are developed from the plants ovary- making them as definitively female as I can imagine. The whole complex of female plant parts, including the ovary, is called the Gynoecium. Most fruits that we eat come from "perfect" flowers, meaning each flower has male and female parts. Fruit_anatomy also has some good descriptions. It is true that some plants come in male and female versions, but in that case, the male bears no fruit. Holly is a well-known example of such a Dioecious plant (other popular examples of dioecy are ginko and cannabis). Finally, some plants, like birch have both sex organs on a plant, but each individual flower can be male or female. If you want to get more into the details of how all this works, see plant reproductive morphology. SemanticMantis (talk) 20:24, 1 May 2014 (UTC)
- I will add that in my WP:OR experience, smaller peppers tend to have fewer lobes, and tend to be firmer. SemanticMantis (talk) 20:25, 1 May 2014 (UTC)
- More WP:OR - in my experience, it seems that the number of lobes varies by the colour (green, red, and yellow ones have four, orange ones have three), which suggests that it varies by cultivar or variety. It wouldn't surprise me if peppers from another farm or another country would break down differently. Matt Deres (talk) 16:43, 2 May 2014 (UTC)