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Physical Unit. Like, as opposed to a Logical Unit (LU). The terminology of computing really brings home the difference between physics and logic. It's practically a new Cartesian duality.

Plutonium. Atomic number Z = 94. An actinide. The fissionable material in Fat Man, the atomic bomb dropped over Nagasaki, was Plutonium-239. Plutonium is an unusual metal. At the time of its discovery (or creation, if you prefer) it was the only element known to have five allotropic solid phases. (It may still be unique in this respect; I don't know.) The delta phase, stable between about 300°C and 475°C, has a negative coefficient of thermal expansion. The linear contraction coefficient (you just gotta use terms like that whenever the opportunity arises) averages 2.1×10-5/K in that range.

Other solids that shrink on heating over some range of temperatures include various zeolites and zirconium tungstate (ZrW2O8). Liquid water is well-known to contract up to about 3.984°C), but the stable low-pressure allotrope of ice (ice Ih -- hexagonal phase I) has a positive thermal expansivity at high temperatures (i.e., temperatures not far below freezing). Ice Ih does have a negative thermal expansivity from 73K down to 10K or below. (The expansivity and its temperature derivative must vanish at 0K, so polynomial have the expansivity varying quadratically near zero. So far as it is possible to tell by extrapolation from data above 10K, the expansivity is negative between 0K and 10K.)

Learn more at its entry in WebElements and its entry at Chemicool.

Police/Umbrella. It's not anything to do with a police cordon. It has to do with a pattern in English accentuation. There is a tendency in English for nouns to have initial stress and verbs not to. In P/U dialects, this tendency is strengthened. (This is especially noticeable in <-tion> homographs, with noun and verb distinguished by their different stress.)

Typically in P/U dialects, nouns like police and umbrella are pronounced with stress on the initial syllable. The term ``PU dialect'' is used in at least two slightly different ways. It may refer to dialects in which only some polysyllabic nouns that don't normally have initial stress receive initial stress, or it may refer to dialects in which initial stress for nouns is regularized, and nouns without initial stress are exceptional.

PolyUrethane. Also called PolyUrea.

There's an informative polyurethane entry in the Macrogalleria.

Princeton University. Actually, ``PU'' is rarely used because it's already an expression of disgust at a bad odor. There's no other obvious acronym, though.

Spanish noun for various hard things that come to a point. The spines or quills of a hedgehog (erizo) or porcupine (porcu espín) can be called either espinas or púas. The teeth of a comb (peine) can be called dientes (literally `teeth') or púas.

The word is also applied to some sharp things that are not necessarily pin-shaped. For example, a guitar pick (or ``plectrum,'' if you want to be that way) is a púa. Regardless of shape, the barbs on barbed wire and the (normally metal) hooks or points of a carding brush (carda) are called púas.

A sewing or knitting needle is normally called an aguja in Spanish, as is the sharp end of a syringe.

For some reason (or perhaps for no reason), the word púa seems to have caught the fancy of bonaerenses: A phonograph needle is called a púa, although I may have the wrong tense on the copula, and there are colloquial expressions like ``darle la púa a algien'' (`to needle someone'; literally `to give someone the needle') and ``meter la púa'' (`stir up trouble, intrigue'; literally `stick in the needle').

PUBlic house. A house where the general public can come in and drink beer. In the US until the 1970's, bar was the common word and pub was a British affectation. (In a bar, anything you say that I don't get is a personal affront, unnerstan!?) Then people noticed that commercial beer tasted like soda, and microbreweries spread across the land -- a movement! The bars attached to these breweries were called pubs, and the combined establishments were called brewpubs. Eventually the word pub came into more general use as the equivalent of bar.

Disclaimer: the assertions in this entry are not based on any particular research, just my impressions over the years.

When adjectives ending in -ic form -ly adverbs, they usually get a bonus -al: -ically.

I don't know why public becomes publicly. A much less common example is anticly, which appears to be about as common as antically. Cholericly seems to be six or seven times more common than its longer form. It may be significant that public, antic, and choleric all function as nouns as well as adjectives, and that the -ical adjectives of these words are rare. (``What corpus?'' What ``corpus''? All ratios have been determined by ``googling the web.'')

All other such exception forms that I can track down are less common than the corresponding regularly constructed -ically forms. Phlegmaticly seems to be about four times less common phegmatically. A few other terms have -icly frequencies on the order of one tenth those of their -ically forms. These tend to be technical terms like metalicly and cubicly. Other instances of -icly are typically 100 times less common than the corresponding -ically forms.

Someone who keeps a pub. I guess a republican is someone who keeps a pub again.

public art
Oh! You said ``art''? I thought you said ``fart''! So you wanted something that inspires or maybe looks good, instead of something that stinks? But we'll have to tear down the whole sculpture and start all over again!

See Priestley for an uplifting anecdote. Well, an anecdote. See Pulitzer Prize entry for the uplift, or get a push-up bra if that don't suitcha.

Faraday's maxim was ``Work. Finish. Publish.'' James Clerk Maxwell noted that

[Faraday] ... shews us his unsuccessful as well as his successful experiments, and his crude ideas as well as his developed ones.

Franklin had a maxim similar to Faraday's, but he was a printer by trade, after all. Franklin cautiously withheld publication of some experiments he had not at first properly interpreted. [But by sending them to his contact P. Collinson at the Royal Society, he assured himself priority in case they were correct. Franklin wasn't born yesterday, you know. He was born in 1706 (New Style; i.e. Gregorian calendar).]

public key encryption
Encryption system probably based on computational-complexity results of Rivest, Shamir and Adleman (some public-key systems are known as RSA-algorithm systems.) PGP is such a system, and the evil Clipper chip which the US government encourages private industry to use is also such a system.

The general idea is: you issue a ``public key'' and maintain a private key known only by yourself and by the untrustworthy ``friends'' you've been fool enough to trust, and all the people they told. Anyone who knows your public key can encrypt a message for you. However, only someone with your private key can decrypt a message thus encrypted. In principle, no public key system is safe against code-breaking. Someone with the public key can just encode a moderately long message and test enough candidate private keys until the right one is found -- the one that decrypts the known encrypted message correctly. By making the decryption depend on a sufficiently long private key, however, one can make this approach impractical. This is not the whole story, however. In any real private key system, a great deal is known about the encryption/decryption code, and so one can imagine that someone could find shortcuts to discover the private key. Crudely, one could imagine that only the first twenty bits of a long private key affected decryption of the first five characters, so one could quickly test the 2^20 or about one million possibilities on the first five characters, and with odds of 26^5 or about 12 million to one, chances are good that only the correct combination of the first 20 bits would be able to correctly recover the first five characters. No one would design an encryption system quite this stupid, but one might accidentally design a system in which a subset of the decryption task depended only on a subset of the private key in some way. This would enable someone to break the code by small steps.

The essence of the problem of designing a safe public-key code, therefore, is to make sure that the decryption algorithm is a sufficiently complicated function of all of the private key. What RSA did was to find a class of algorithms which were in a sense as complicated as prime factorization. That is, they were able to show that the task of breaking the code was equivalent in difficulty to that of finding the prime factors of a large composite number. That is a quite difficult problem, even with all the short-cuts that have been developed in the more than two thousand years since Eratosthenes came up with a sieve algorithm for quickly determining if a particular number was the factor of another. It is by that thread -- the difficulty of factoring numbers -- that much of the privacy people believe they have hangs.

public library
An echo chamber for bawling babies and screaming children.

The PUBlic PATent Foundation. ``The Public Patent Foundation protects civil liberties and free markets from wrongly issued patents and unsound patent policy by providing those persons and businesses otherwise economically, politically, and socially deprived of access to the system governing patents with representation, advocacy and education.''


``PubPat works against wrongly issued patents and unsound patent policy through several activities.''

Percutaneous Umbilical Blood Sampling. More accurate than the alternative methods of fetal genetic testing (amnio and CVS) but with a higher risk of miscarriage. Not normally performed until the eighteenth week of pregnancy, and then very often to confirm amnio results.

Public Utilities Commission.

A dark reddish color, maybe purplish or brownish or grayish or some combination of these. The word comes from French, where couleur puce means `flea color.' I suppose the precise shade of red depends on just how blood-engorged it is when squashed. Yuck. The word puce is derived from the Old French word pulce < Latin pulex, pulic-. In Spanish, a flea is una pulga (and el pulgar and una pulgada are `the thumb' and `an inch,' resp.).

Pontificia Universidad Católica del Ecuador.

PolyUrethane (PU) Dispersion. A suspension of polyurethane in water. Used as an adhesive or as a veneer. See the LMA's downloadable glossary.

Potior, utor, fungor, fruor. Four of the most important Latin verbs that govern an object in the ablative case. Another such is vescor. Yeah, they're all deponents. Believe me, fifteen years ago, if you had told me that one day I'd be writing ``of the most important Latin verbs,'' I'd have answered ``what are you smoking? Let me have a puff.''

Patriotic Union of Kurdistan.

Princeton University Library.

Pulitzer Prize
Joseph Pulitzer was a tabloid-newspaper publisher. Like Henry Ford, Alfred Nobel, Cecil Rhodes and Cecil Rhodes, he was able to use the money he made in life to purchase a sterling name in death. He endowed what is now the Graduate School of Journalism at Columbia University, and the Pulitzer Prizes. There was a nasty article about the Columbia School of Journalism in TNR in 1995. It made some telling points about the school's lack of candor or of anything useful to impart. Look, everybody's beating up on journalists nowadays, but this is meta-beating-up. The fault is not in the journalists but in their star professors. This is really hip; blame the J-schools. Then again, the article had no good news on the students' basic news sense, either.

Anyway, back on-topic: Joe's prize is given in fourteen different journalism categories:

There are six ``Letters & Drama'' categories: and there's a music prize.

Prestigious prizes like this are a lot like speeding tickets. The speeding ticket may be $100, but you'll pay many times that in increased insurance premiums.

Visit the homepage, apparently set up by CJR, for further information, including copies of the actual winning articles, photographs, etc. that won a Pulitzer in journalism.

Edible seed. Examples mentioned in this glossary include lentils, mung, and peas. The standard for ``edible'' is a little higher than ``ingestible in moderate quantities without ill effect.'' One might say that pulse is not-just-incidentally edible seed. I mean, grape pits are not pulses. As is common with foods, the distinction between singular and plural is not carefully observed, and the plural of pulse can be pulse or pulses.

If you want to puff up your erudition without conveying or even expressing any additional information, you can say that a pulse is the esculent seed of a leguminous plant. By extension (say ``metonymically''), the word pulse is also used to refer to the plant that yields the pulse (i.e., to the legume).

[Phone icon]

pulse dialing
Old-style phone number signaling. A typical pulse is a 40 msec connect and 60 msec break (``60% break''). The pulse is the break (contacts open) interval. Interdigit time (interval between last pulse of one number and first pulse of next) should be greater than about 700 msec. Vide normally-on, normally-off.

pulsed CO2 laser
Here's a bibliography assembled to understand some details.


Cougar. The cougar's binomial monicker is Puma concolor. It is said to have over 40 names in English; other names are mountain screamer and catamount, and more commonly mountain lion and panther. The last is shared with other species: The name panther (or painter -- probably a variant) in North America is applied to the cougar. A panther elsewhere is a member of a different genus: Panthera. The panther of Central and South America is the jaguar (P. onca); the panther of the Old World is the leopard (P. pardus). (For more on the etymology of the latter, see the pardo entry.)

They're all more or less beautiful animals. They should all have the opportunity to become more beautiful through taxidermy.

The name puma is originally from the Quechua language of Peru, and entered English via Spanish. The word cougar is originally from Tupi (or at least from one of the Tupi languages of South America). The name was apparently first borrowed into Portuguese as çuçuarana, and went from there into the French of Buffon's zoological work, and thence eventually into English. The principal Tupi language today, and the best-documented, is Guaraní (one of the official languages of Paraguay). Guaraní is reported in some references as the specific source of the the word cougar, but at least one reference I have seen gives contradictory information.

I'd like to nail down some of the ulterior etymology, but it will have to wait. Frustratingly, one promising sources available to me for this language, a bidirectional Spanish-Guaraní dictionary, has a printing defect at a critical place (an incorrect fascicle is inserted, leaving out the fascicle where puma ought to be). (And the dictionary I reference in the next paragraph has a number of pages printed blank.) I think my library will repair the problems by ordering or scrounging replacement pages; I'm putting in the problem reports on September 1, 2008, and will get back to this entry later.

For now let me say that it seems that cougar (and possibly jaguar also) is a compound noun based on ara or (possibly just modern Guaraní) eira. The latter is ``lince o gato montés; animal carnivoro, feroz y sanguinario'' according to an abridged 2005 edition of a dictionary by Félix Giménez Gómez (``Félix de Guaranía''). [`Lynx or mountain cat; animal that is carnivorous, fierce, and sanguinary.'] Cougar in this book is eira guasu, where guasu probably means `large.'

Party Unity My Ass. Originally a D.C.-based group of die-hard supporters of Hillary Clinton for the Democratic Party presidential nomination that urged her to fight for the nomination all the way to the party's Denver convention in August. PUMA was founded on June 1, 2008. The final primaries were held on June 3, Obama claimed that he had clinched the nomination (an assertion based critically on a count of superdelegates declaring for him) on June 4, and Clinton conceded the Democratic contest and endorsed Barack Obama on June 9. By the time of the convention, PUMA was being used primarily to mean a die-hard backer of Hillary, without reference to the formal organization.

Public Use Microdata Area. That's the expansion according to the US Census Bureau; literate people write the expansion of PUMA with a hyphen between public and use.

Young cougar, where ``cougar'' is understood in the slang sense explained at the cougar entry.

Public Use Microdata Samples. US Census Bureau usage. A literate person would expand that with a hyphen between the first two words.

The comment ``the cliché `hope springs eternal' springs eternal'' springs eternal.

Since C is free-format, you have the opportunity to develop your own distinctive style:

The comment

the cliché
springs eternal
springs eternal
springs eternal;

I just received the following email message. (It's from someone known by no one reading this entry, so why should I name him and embarrass him in front of all his friends?)

> I understand completely.  I've passed up many come-ons
> from women due to poor punctuation.  It's a real turnoff.

(After all -- isn't that the point, really?)

(Very sorry couldnt resist)

punitive and compensatory
Damages awarded by a jury. Mostly punitive, or it wouldn't have been big enough to make the news. The judge will probably set aside or reduce the eye-popping punitive damages, but that news will be buried in the back of the business pages in a week or two.

punto de quiebre
Spanish for `breaking point.' This idiom and more generally the use of quiebre as a noun are widespread, but appear to be recent innovations.

PARC Universal Packet Protocol.

Princeton University Press.

Progressive Unionist Party. A left-wing unionist (q.v.) party of Northern Ireland. PUP supported the Good Friday Agreement. PUP is the political ally of the Ulster Volunteer Force (UVF).

I don't know much about Northern Ireland -- I need this scorecard just to keep track of who some of the players are. Here's something possibly relevant from another former part of the British Empire that was partitioned.

One of my friends who was disappeared during the dirty war in Argentina lived. She was bribed out and fled to Israel the day she was released. (That evening, a different part of the state apparatus came by to try to take her.) She had been a typical nonviolent leftist in Argentina -- a socialist. She told me that after she arrived in Israel, she realized how completely irrelevant the usual left-right distinctions were there.

PUP is firmly unionist, but also declares itself dedicated to ``bettering the lot of the ordinary person.'' PUP won two seats in the first Northern Ireland Assembly elections.

Puppis. Official IAU abbreviation for the constellation.

Potentially Unwanted ProgramS. That's the prohibitively standard expansion, but I would have expanded the first P as Probably. Is there a singular form? No, the litter is large, but there is an uncountable form: crapware.

This is usually some kind of error for ``population,'' but ``Zero Pupulation'' seems to be the slogan and part of the name of a program associated with Spay Houston and similar organizations. ``Spay Houston'' sounds overzealous to me. Look, it may be public-spirited and all, but outright enthusiasm is uncalled for.


PURCHase. Airline fare abbreviation. Not much abbreviated. I guess they like that word pretty much as it is. I notice that this list of travel-industry abbreviations doesn't have anything for refun.

(You can't use BUY as an abbreviation for purchase, because buy is not an abbreviation. See?)

Another meaning of purchase is grip or hold. I suspect that is its original meaning. It's irresponsible of me to just mention it like that, but I'm tired and no one is paying me to look it up. In the 1980's, Russian language purists used to bemoan the fact that the Russian word for `get' was replacing that which originally meant `buy,' and there was speculation that the peculiarities of the centrally controlled economy (controlled prices and controlled supply, both low for consumer goods, and gee: shortages) were driving this semantic shift. The idea was that whether one bought was not the question; whether one found to buy was. Soviets never left home without a mesh bag, just in case they ran across anything to buy. Here's a joke from the good old Soviet days:

An inventor has just been awarded an Order of Lenin for designing a new small plane. Soon every Soviet citizen will have his own personal plane. He is being interviewed (I mean the inventor, not Lenin) on State TV, and the interviewer wants to know what practical good it does to have a personal plane. The inventor explains: ``Suppose you're in Moscow, and you hear that there's cheese in Minsk. You can fly to Minsk and get cheese!''

A variant of the surname Purdue (q.v.).

A variant of the surname Purdue (q.v.).

A Scots variant of the surname Purdue (q.v.).

A cat's allowance, I suppose.

A variant of the surname Purdue (q.v.).

Long ago, I was taught that this surname represented the French word perdu, meaning `lost,' and that the name was given to some orphans. A Dictionary of Surnames, by Patrick Hanks and Flavia Hodges (1988), apparently does not consider this theory worth mentioning. It explains this as well as the English surnames Purday, Purdey, Purdye, and Purdu, and the Scots surname Purdie, in terms of the Anglo-Norman French oath pur die, from the Old French p(o)ur Dieu (`by God,' ultimately from Latin pro Deo). There's also a French surname Pourdieu, which would appear to clinch it. The idea is that Purdy or something similar became the nickname of anyone who used the oath frequently, and eventually became the surname of his descendants. It reminds me of the Spanish word coño, which in its plain sense names the external portion of the female genitalia, and which was widely used as a coarse interjection by Spanish conquistadores. It is still used this way to indicate anger or surprise. Ironically, in some South American Indian languages, it became the word for Spaniard.

A similar class of surnames, which includes Perdue, is described at the Depardieu entry.

Purdue University
The original Purdue University was established by an act of the Indiana State legislature in 1869, to be located near Lafayette (now West Lafayette). More details at this page.

Purdy, Purdye
A variant of the surname Purdue (q.v.).

The name of a particular nitrogen-containing double-ring organic compound, and also of derivatives obtained by substitution of one or more hydrogens. In nucleic acids, by far the most common purines are guanine (G) and adenine (A).

A breakdown product of purines is uric acid. Uric acid crystals cause the inflammation associated with the famous disease gout and certain kinds of kidney stones. The trademark Purina I presume is intended to suggest purity and is unrelated to purines. Like humans, however, Dalmatians and some other dog species form urinary stones -- ``urate'' or ``purine'' stones. Those animals should not consume too much organ meat (``beef by-products''). Other foods which are high in purines, and which you should therefore avoid feeding that ``stone-forming dog'' dog, include caviar, anchovies, clams, sardines and herring.

Persistent Uniform Resource Locator. Developed by OCLC: a PURL is a kind of logical name or alias for a URL. A location given as a PURL is interpreted by an intermediate resolution service which maintains a database linking the PURL to its current URL and returns that URL to the user client, similar to the use of email aliases. References expressed as PURL's are intended to remain viable even as documents change their physical locations.

OCLC operates its own PURL resolution service but is distributing the source code to promote the use of the system.

pursuing other opportunities
Collecting unemployment.

Public Understanding of Science. Really! I saw it in that well-known quarterly of erudite nonsense, Social Text. The European Union funded a related entity called OPUS.

Now if they could come up with an acronym that suggested something that wouldn't be worth bending over to examine more closely...

Public Understanding of Science (not abbreviated PUS, that I have seen yet) is also the title of a quarterly journal (vol. 1 in January 1992) originally published by the IOP and now by Sage Publications.

push parenting
Never mind a definition. Suffice it to say that I first encountered the term in Ralph Schoenstein's book My Kid's an Honor Student, Your Kid's a Loser: The Pushy Parent's Guide to Raising the Perfect Child (2002). A book I haven't read, but which seems to be the cause of many of the ghits for this term, is No More Push Parenting: How to Find Success and Balance in a Hypercompetitive World (2003), by Elisabeth Guthrie, M.D., and Kathy Matthews.

Schoenstein (p. xvi): ``...America is now crawling with parents who are driving their darlings toward acceptances at both Harvard and the Menninger Clinic, parents who will sacrifice anything to make their children superior. They will even sacrifice the children.''

A Japanese term for female push parents is kyoiku-mama.

push present
A gift a husband gives to his wife for popping out an offspring unit. Usually jewelry. Perhaps especially if labor or morning sickness was prolonged. I first encountered the phenomenon of the push present in the year 2000, but a reader of this glossary reports that in New York City at the end of 1998, a horrified colleague of her husband couldn't believe he'd never heard of it.

Pontificia Università San Tommaso d'Aquino. `Pontifical University of Saint Thomas Aquinas.' (Also has the Latin moniker Pontificiae Universitatis a Sancto Thoma Aquinate in Urbe and what I guess is the nickname Angelicum.) It was founded and is run by the Dominicans, and is located near the Lateran basilica in Rome. (Italians, and particularly Romans, often refer to the city of Rome somewhat elliptically as la cità -- `the city,' urbe in Latin. What nerve!)

Pope John Paul II received his doctorate in Philosophy from PUST. (Thesis: ``The Problems of Faith in the Works of St. John of the Cross.'' Philosophy? Whatever.) He went back to Poland and got another degree there afterwards.

John Paul I got his doctorate from the Gregorian University in Rome, in Sacred Theology. (Thesis: ``The origin of the human soul according to Antonio Rosmini.'' Whatever.) The Greg is a Jesuit institution. John Paul I died only a month after being elected pope. I don't think it was after-effects of the white smoke. Draw your own conclusions.

The academic press of PUST, called Angelicum University Press instead of something stupid like PUSTSA (ess for stampa), publishes Angelicum, a quarterly journal of theology, philosophy, social science, and canon law. Articles are published in the principal European (scholarly) languages -- mainly Italian, English, French, German, and Spanish. Well, there seems to be some controversy about this. According to my local library catalog entry, they only publish articles in English, French, German, Italian or Latin. I promise to have look-see some day if I remember. I want to see if they publish in Polish.

Are-a you stupid-a sumthin? See PUST.

An option to sell (stock) at a certain price during a certain time. If the price of the stock falls, you can buy the stock at a reduced price and exercise the option for a profit. If the stock goes up, you don't exercise the option, but you're out the price of buying the option itself. Nowadays, this time-honored kind of trading goes by the fancy new name of ``derivative trading.''

Programmable Unijunction Transistor.

Power-Up 3-State. Logic device that goes into high-impedance state (vide tri-state) during power-up and power-down, to protect devices that are inserted in live circuits.


PhotoVoltaic. The photovoltaic effect -- an electric current flow or potential difference induced by the absorption of light -- was first discovered by Alexandre Edmond Becquerel in 1839. Selenium photovoltaic cells, originally with energy conversion efficiencies of no more than 0.5%, have been used since the 1880's as light meters for photography.

It should be noted that historically, the better-known effect associated with selenium (Se) is photoconductivity: conductivity different (higher, in this case) under illumination than in the dark. Photoconductivity was discovered by Willoughby Smith in 1873, as he was investigating the tetchy behavior of a selenium resistor he had in a box....

Currently, the noun use of the term photovoltaic or PV designates photovoltaic devices used as power supplies, a/k/a ``solar cells.'' As a practical matter, these are mostly silicon-based.

Principal Value.

PolyVinyl Alcohol.

PolyVinyl Acetate. To avoid confusion with polyvinyl alcohol (supra), you can use the abbreviation PVAc (q.v.).

PolyVinyl ACetate. This was once used for flexible transparent films. I still have a few twenty-year-old books wrapped in vinyl acetate book covers, and they're all still pretty flexible. Unfortunately, they're also sticky on the outside: the PVA has sweat some of its plasticizer. That's why it's not used for that any more. Vinyl chloride is also used for thin flexible films (vide PVC infra) but it eventually hardens up and cracks.

It may be called ``acetate'' for short, and under that name San Diego Plastics, Inc. has a short page of information.

Vinyl acetate-alcohol copolymers are used in acrylic latex paints to hold hydrophobic acrylic monomer in suspension, as explained in the PVA entry of the Macrogalleria.

The Roberts & Etherington Dictionary of Descriptive Terminology for Bookbinding and the Conservation of Books is entirely too sanguine about this stuff in its entry.

PolyVinyl Butyral.

Permanent Virtual Circuit.

Permanent Virtual Connection.

Poly n-Vinyl Carbazole. Has some application in microelectronics. Production negligible compared to polyvinyl chloride (next entry).

PolyVinyl Chloride. Invented at a B. F. Goodrich laboratory in 1926; originally used in adhesives and sheets.

Code 3 in PCS. May be indicated by `V' embossed on surface.

San Diego Plastics, Inc. serves a short page of application-oriented information on PVC. There's an informative PVC entry in the Macrogalleria. It's popular in applications that require a cheap flexible barrier between the wet and the the dry (garden hoses, raincoats, floortile). Related comments at PVA entry.

``Exotic'' clothing is available from clothiers with no apparent awareness of the utility--nay, the necessity--of the apostrophe in forming the English genitive case, in Nylon and PVC as well as Leather and Rubber. The traditional considerations of comfort and warmth do not appear to have played an important rôle in the design of this bas couture. Link dead? There's always more.

There are other kinds of good, also possibly not clean, fun that you can have with PVC. Apparently polymer clay is PVC that one finishes polymerizing--crosslinking, I guess--in the oven.

See as well the acrylic acid entry.

Private Virtual Circuit. Mocked up by a communications protocol called Frame Relay.

Permanent Virtual Channel Connection.

Peak-to-Valley Current Ratio.

Physical Vapor Deposition. [Deposition by beams.]

Most epitaxial deposition methods fall into one of the two broad categories PVD and CVD. As explained in more detail at the CVD entry, PVD is the relatively low-pressure situation: the term is applied when molecules of the material to be deposited are unlikely to suffer a collision in going from source to deposition surface. (Hence the material moves in a straight line, hence ``beams.'')

* Plasma Vapor Deposition. This usage is completely disapproved. This disapproval is completely unenforceable.

Poly(VinyliDene Fluoride). (Elf Atochem North America: Kynar ®.)

Parallel Virtual Machine. A software package that permits a number of Unix computers to work together like a single parallel computer.

Here's a tutorial introduction served by the Maui High Performance Computing Center. Here's one from Paul Marcelin at NERSC and LLNL. Here's some more.

Another such package is MPI (Message Passing Interface).

Parallel Virtual Machine (PVM, entry above) message-passing library from and for IBM.

Private Voluntary Organization. A kind of NGO, q.v.


PolyVinylPurolidone. Novel material for breast implant gel. See the AA entry.

Permanent Virtual Path Connection.

Perpetual Vice-President--Member Pickwick Club. That would be Joseph Smiggers, Esq. Cf. G.C.M.P.

PhotoVoltage Spectroscopy.

Passaic Valley Sewerage Commissioners. ``In order to protect and preserve local streams and rivers from water pollution, the Passaic Valley Sewerage Commissioners (PVSC) operate one of the country's largest treatment plants for the wastewaters of northern New Jersey. With many expansions, and recent upgrading to secondary treatment, the facility has been striving, since its initial operation in 1924, to improve local water quality in accordance with federal and state water quality legislation.''

Pennsylvania Vintage Snowmobile Club. ``Vintage'' in this context seems to mean twenty or so years old at minimum. There's been a Vintage Snowmobile Webring since 1998.

IEEE PhotoVoltaic Specialists Conference. (Sic: no apostrophe.) This is one of the three major PV conferences. PVSC is the American conference, EU-PSEC is the European, and PVSEC is the Asian. Each of these conferences is held every year-and-a-half. The EU-PSEC is held a half year before (or one year after) the PVSC.

Grafted uneasily onto this schedule since 1994, there is a world conference (called ``World Conference on Photovoltaic Energy Conversion'' two out of the first three times) every four years or so.

  1. 1990 May 21-25 (Kissimmee, Florida)
  2. 1991 October 7-11 (Las Vegas, Nevada)
  3. 1993 May 10-14 (Galt House Hotel in Louisville, Kentucky)
  4. 1994 December 5-9 (Hilton Waikoloa Village Waikoloa, Hawaii)
    (Billed as the ``First World Conference on Photovoltaic Energy Conversion'')
  5. 1996 May 13-17 (Washington, D.C.)
  6. 1997 September 29 to October 3 (Anaheim Marriott Hotel, Anaheim, California)
  7. 1998 July 6-10 (Vienna, Austria)
    ``Second World Conference and Exhibition on Photovoltaic Solar Energy Conversion''
  8. 2000 September 15-22 (Anchorage Hilton Anchorage, Alaska)
  9. 2002 May 20-24 (Hyatt Regency New Orleans, New Orleans, Louisiana)
  10. 2003 May 11-15 (Osaka, Japan)
    ``Third World Conference on Photovoltaic Energy Conversion''

The fourteenth PVSC organizing committtee established an award to recognize persons who have made ``outstanding contributions to the advancement of photovoltaic science and technology,'' named in memory of one of the founders of the photovoltaic field, William R. Cherry. The award is given to one person (generally a different person) at each PVSC. You're probably wondering why I would bother to mention this. I mention this because Charles E. Backus was the recipient in May 1987, and I know Chuck, and I wanted to name-drop.

Pittsburgh Vintage Scooter Club.

Pocatello Valley Soccer Club.

Potomac Valley Samoyed Club.

PV Science and Engineering Conference. Name is prefixed with ``Asian,'' ``Asia/Pacific,'' or ``International'' according to the whim of the writer. By any name it's one of the big-three PV conferences. This one is usually thin-film-dominated (i.e., has a materials focus), with most of the presentations coming from Japan.

  1. 1990 November 26-30, Kyoto, Japan
  2. 1999 September 20-24, Sapporo City, Japan
  3. 2001 June 11-15, Cheju Island, Korea
  4. 2004 January 20-30, Bankok, Thailand


Physical Vapor Transport.


PW, .pw
Palau. USPS abbreviation and top-level domain name.

Pratt & Whitney. ``Pratt'' ``is the world's leading designer, developer and manufacturer of gas turbine engines for commercial, military and general aviation aircraft.'' A subsidiary of UTC.

Public Works.

Publishers Weekly. Industry magazine. From the same people who publish Bowker's Annual.

Pacific Weightlifting Association. ``Northern California's Local Weightlifting Committee (LWC) of USA Weightlifting'' (USAW). That LWC ``covers California from South of Fresno to the Oregon Border and includes ten Western Counties of Nevada.''

Anther weightlifting PWA is the Philippine.

Permittivity and Wave Analyzer.

Person With AIDS. I'm not aware of any other diseases whose victims are known as PWX's, with any X. On the other hand, there's EDP -- Emotionally Disturbed Person.

Philip W. Anderson. Nobel laureate in Physics.

Philippine Weightlifting Association. Aren't the Philippines in the Pacific?

Printed Wiring Assembly.

Progressive Writers Association.

Public Works { Administration | Authority }.

FDR was elected US president in 1932 to end the Great Depression. (That's right, it was a time when everyone was bummed out. At least there were a lot of bums out. You know -- farmers, industrial workers, craftsmen, and other out-of-work riff-raff.) FDR's recovery plan, if trying anything that might work can be called a plan, was entitled the New Deal. One of the best-known New Deal programs was the PWA (Public Works Administration; officially the Federal Administration of Public Works), established by the National Industrial Recovery Act of 1933. Man did they spend money. Man did they build a lot of public works. They also loaned money to states and cities so they could spend a lot of money.

The PWA was headed by Harold L. Ickes from 1933 to 1939, when a reorganization made it a division of the Federal Works Agency. As war approached, industrial production became more important, and the PWA was abolished in June 1941.

People With AIDS. It's not surprising that PWA (in the sense of Person With AIDS) often occurs in the plural at places in text where it must be expanded. The gloss in these cases typically avoids the awkward ``persons'' in favor of ``people.'' It's a positive sign, a healthy sign. A positive sign of lexical health, anyway.

Where treatment is available, PWA's are a large proportion of HIV positives. However, the vast majority of HIV+'s live in Africa, where treatment is available to very few. Without drugs, PWA's tend to survive only 18 to 24 months after the onset of full-blown AIDS.

The country with the largest number of HIV+'s is South Africa, which is also the richest country in Africa for now. As of Spring 2004, the South African government's effort against AIDS consisted almost entirely of encouraging condom use. (Condom use soared to the 5-10% level by 2002. Whoopee. Congratulations all around.) Another large portion of national AIDS-prevention expenditures appears to go to the production of overpriced plays about AIDS by Prime Minister Thabo Mbeki's wife. (Also, some provinces are distributing antiretroviral drugs.) Mr. Mbeki, an economist by training, made a name for himself (more precisely an eponym, as in ``some crazy mbeki'') by questioning whether AIDS was really just HIV infection. South Africa held its third post-Apartheid national elections in April 2004, and as expected the ANC won again handily, with over two-thirds of the vote. (It's a parliamentary system with at-large, list-only voting.) As Mbeki began his second term that month, 5.3 million of South Africa's population of 45 million were estimated to be infected with HIV.

Accurate statistics are hard to gather for most of Africa, and are quickly out of date. Indeed, HIV+'s are asymptomatic for as long as a decade after infection (and contagious for most of that time), so in the absence of systematic testing, most victims are unaware or uncertain of their own status. A major source of information is sampling of pregnant women. Their rates of infection, even when already at high (a few percent) levels, have exhibited alarming doubling times of as little as a year. Among the most horrifying statistics, it seems well agreed that in Botswana in 2003 over 35% of the population was HIV+. Almost all of these people will die young. Namibia may be worse, but data are virtually nonexistent. Across southern and western Africa, AIDS is a holocaust. In thirty to forty countries, with a total population of 800 million or so, it is or is becoming the leading cause of death. Life expectancy is declining rapidly; infant and adult mortality rates are rising. The population of South Africa at least has already begun to shrink. In some countries a quarter of all children are orphans, and significant numbers of these are homeless and alone. The most productive age segment of the population is dying off so rapidly that it is creating labor shortages. Resources are shifting toward care of the weak and sick, and away from food and education. Up next: India.

Printed Wiring Board. A rigid support, like G-10 fiberglass, with connections in the form of flat metal strips. Typically the connections are ``printed'' as a pattern of lines of etch-resist ink over a uniform metal coating on the board. Etching removes the unmasked regions, leaving the interconnect lines. The etch-resist is then also washed off, leaving the wires exposed and available for connection.

At the ends of the lines, holes may be drilled to allow the leads of surface components or sockets to be passed through. Discrete components like resistors and power transistors are inserted directly. Chips, and long ago transistors and even longer ago tubes, were not usually soldered on directly. Instead, sockets were soldered onto the board and these active components were inserted. This served two purposes: (1) Since hot solder and iron didn't touch the active components, there was no need for careful heat-sinking and shorting of sensitive leads when the board was assembled. (2) Tubes and transistors could be replaced easily.

Actually, tube circuits tended to have the sockets on a hard metal chassis, and then later some separate circuit boards that might be printed. I've decided to take a little trip down vacuum tube memory lane, so you may want to skip down.

Tubes especially had lifetimes much shorter than other components. When your old (black and white) TV started malfunctioning, you'd take off the back panel and, if there was nothing obviously toasted, you'd look at the circuit diagram pasted on the inside for clues. The tubes on the diagram, or the circuit blocks they were part of, had labels indicating their function. Thus, if your sound crapped out, you looked to see what tubes were part of the audio amp block. (I should say that some of this worked in reverse: if the blocks weren't labeled, you'd recognize them, or maybe identify them from familiar tubes with very standard functions. The more you looked, the more clues you'd find.) After doing all this intellectual heavy lifting, you'd rip out all the tubes and take them to Radio Shack or even a good drug store -- why risk wasting a trip? The old jalopy could break down any time.

Down at the store, there was a tube tester with a slanted top surface and a shallow lip at the edge. One of the tubes you placed there would roll off and could be replaced without further testing. The rest you would look up in alphabetical order in a binder attached to the tester. The binder would tell you what settings to use on the tester (these corresponded to pin pattern, plate and filament voltages with corresponding meter settings, etc.) and tell you what number to expect on the meter. (The meter face was on the top surface of the testing station. That's the reason the top surface had to be slanted, see?) Sometimes there'd be two sets of settings for two separate tests, but let's face it: it was a pretty crude test. Mostly you found out if the tube was working approximately right as a diode. However, when tubes go down the tubes, they tend to go big time, so crude tests are fine. When you found a bad tube, you said: ``Yup, it was obvious from the circuit diagram.'' If the TV didn't have a circuit diagram, you said ``Ahh, these 6AU8's, they don't make'em like they used to.''

If you were a professional, of course, you used professional methods. The first method was checking that the tube filaments got hot. You could do this a number of ways. One way was to

That's not a method. There's no ``CONTINUE'' method in professional tube testing. ``CONTINUE'' is just a note the glossarist left to himself, that he should add stuff to this entry later.

Printed Wiring Board Assembly.

Personal WaterCraft. ``Personal'' like a ``personal pan pizza'' at Pizza Hut: large enough only for one person. Actually, some PWC's can now carry as many as four riders. Popular PWC's include the Kawasaki Jet Ski, Yamaha WaveRunner, and Bombardier Sea-Doo. Basically riding lawn-mowers for the waves, but faster.

p-w.c., pwc
PieceWise Constant.

PricewaterhouseCoopers, LLP. One of the Big Four accounting firms.

Person infected With HIV.

Predominantly White Institution. I've only seen this in reference to US or North American colleges and universities. PWI is often used as a contrast to HBCU, but of course it isn't. Among other things, HBCU is an official designation.

Public Windows Interface. An emulator planned as part of COSE, that will allow Microsoft Windows codes to run within an X window. That's Windows 3.1 emulation, as far as I know, I don't know of any Windows 95 emulation by Unix machines.

Personal Watercraft Industry Association. Founded in 1987 as an affiliate of the National Marine Manufacturers Association, it represents all (as of 2008) four U.S. PWC manufacturers: Kawasaki, Yamaha, Honda, and BRP.

PWL, p-w.l., p.-w.-l, pwl
PieceWise Linear.

Pulse-Width Modulation.

Particles per Wafer Pass.

The expansion seems to be some kind of secret, but anyway they publish Math, Engineering, and Computer Science Pedagogy. As it happens, they've apparently been swallowed up by Brooks/Cole Publishing Company.

Person Who Stutters. (Except in the UK, where the person stammers instead.) I suppose this is another of those supposed euphemisms.

Public Water System.

Post eXchange. The general store on a military base.

PXA lamp
Pulsed Xenon Arc. A kind of lamp used in graphic arts applications requiring instant-start, high-stability light output, and daylight-quality color temperature (6000 K is typical of xenon).

Portable X-Ray Fluorescence (spectromet{er|ry}).

Low-resolution video compression for teleconferencing.

(Domain code for) Paraguay.

The major event in Paraguayan history since independence was the war of 1864-1870, known as la Guerra de la Triple Alianza in Spanish and a Guerra da Tríplice Aliança in Portuguese, `the War of the Triple Alliance.' It was easily the bloodiest conflict in Latin-American history. Fighting began in December 1864, when Paraguay, with a population of half a million, invaded Brazil, which had a population of 11 million (all numbers approximate). In response, that triple alliance was formed between Argentina, Brazil, and Uruguay, and declared war on Paraguay on May 1, 1865. At the end of the war, Paraguay's population was about 200,000 and mostly female.

Percus-Yevick (equation). An approximate, closed nonlinear integral equation for the pair distribution.

Per Year. Often in percentage growth rates as in ``24%py.''

Program Year.

PYrimidine. The name of a particular six-membered nitrogen-containing organic ring...
       H         H
        \       /
        //     \\
       //       \\
      N           C---H         pyrimidine
       \         /
        \ _____ /
... and also of derivatives obtained by substitution of one or more hydrogens. In nucleic acids, by far the most common pyrimidines are cytosine (C), thymine (T), and uracil (U).

Presidential Young Investigator.

Iron sulfide (FeS2). Mineral with shiny metallic crystals that sometimes look like gold sometimes does in its naturally-occurring state. Thus, pyrite is also called fool's gold. Interestingly, gold typically is found in association with pyrite or (more often) quartz.

[column] There is another connection between quartz and pyrite, apart from the association with gold: the name pyrite is evolved from the Latin word for flint [ultimately from Greek for fire (pyr-) stone], and flint itself is made of finely divided quartz. Perhaps this is not a coincidence. See the explanation of how quartz, pyrites, and gold all happen to be found together under the pluton entry.

The word pyrite is also used in indefinite singular and plural forms (i.e., ``a pyrite,'' ``pyrites'') to refer to metal sulfides in general. This is most often for metal-sulfide compounds that include iron stoichiometrically, like chalcopyrite, CuFeS2. Another well-known sulfide is galena (lead sulfide: PbS).

Flipping channels the other day, I found an elegant lady (so far as I could tell) explaining to a select audience of QVC insiders like me about the precious but affordable jewelry made with ``iron pyrite.'' It turns out that this is found underground in Southern France and Switzerland (she didn't mention other sources, such as New Jersey), so it's a mineral. The pyrite is surrounded by ``silver,'' so it's precious. Oh, brother. All that glitters ain't copper either (see Cu for related story).

This attribute is perhaps best expressed by an equation:
	pyrophoric substance + air (at STP) = Kaboom.
Sometimes a nasty look is required to initiate the reaction of marginally pyrophoric substances. A very useful concept to be aware of: silane is pyrophoric.

Pretty Young Thing. As you get older, you realize that ``pretty'' might be an adverb.

Pythagorean triple
Three positive integers a, b, c which could be the lengths of the sides of a right triangle:
a² + b² = c².

It is clear that the 3,4,5 triple was used to generate right angles in the Middle East in times when it is not clear that the Pythagorean theorem was known. Leonardo Pisano (Fibonacci) devoted seven of the twenty-four propositions in his Liber quadratorum (`Book of Squares') to finding different kinds of Pythagorean triples.

There are a few equivalent construction methods for Pythagorean triples. Here's one that essentially defines one Pythagorean triple for every fraction u/v: if u and v are integers, then a = u² + 2uv, b = 2v² + 2uv, and c = u² + 2uv + 2v² are a Pythagorean triple.

The usual approach takes q = v and p = u + v, so a = p² - q², b = 2pq, and c = p² + q² are a Pythagorean triple. It's worth noting that in looking for inequivalent triples, only p and q of opposite parity need be considered: if p and q are both odd or both even, then a, b and c will all be even and the triple will simply be a multiple of a smaller one.

The inbounds region of a US football field is a rectangular region 300 feet long and 160 feet wide. These dimensions are the legs of a Pythagorean triple (proportional to an 8, 15, 17 triangle), so the diagonal of the rectangle is 340 feet long. I suppose this could be useful if your mensuration technology is four zebras and ten yards of chain. Note that all boundary markers (pylons and lines) are outside the playing field; measurements are taken to the inside of the boundary markers. Hence, a player who steps on the sideline is out of bounds.

The inbounds region of a Canadian football field is 110 yards long by 65 yards wide (330 by 195 feet). This does not yield a Pythagorean triple, so the diagonal is irrational. (But it's only an algebraic irrational -- it's not transcendental. There's no crying in baseball, and there's no transcendence in football.) Since practical conversion factors are normally defined to be rational, the diagonal is also irrational in unreasonable international units that will remain unnamed. Frankly, there's no particular rational reason for sending the ball precisely along the diagonal, either. On the other hand, at 127.8 yards, it would be a mighty, impressive pass (read the comma at your discretion).

The playing-field aspect ratios above are 1.875 and 1.692 (US and Canada, resp.), or 2.25 and 2.308, resp., when you add in the end zones (ten and twenty yards deep, resp.). As long as we're on the subject of rectangles with aspect ratios that vary by nationality, let's consider paper. In the US, by far the most common size of paper sold in sheets is 8.5 by 11 inches, with an aspect ratio of 1.294. Less common, but also a standard, is ``legal paper,'' 8.5 by 14 (ratio 1.647). Nearest half-centimeter approximations to these standard sizes are used in any country that uses the metric system but which has an economy closely integrated with that of any large country that does not, much. Otherwise, they use a boring system of paper sizes which have aspect ratio equal to the square root of two (i.e., about 1.4142), because it's such a clever-seeming idea. Here's a thoroughly informative (though typically biased) page on irrational ISO paper sizes. Here's a proposal to convert Canadian football to metric dimensions.

Pyxis. Official IAU abbreviation for the constellation.

Lead Zirconate Titanate: Pb(Zr,Ti)O3. Popular piezoelectric material for generation of ultrasound up to 5 MHz.

Power at 1 DeciBel of gain compression.

Power at 1 DeciBel of gain compression, referenced to the input.

Power at 1 DeciBel of gain compression, referenced to the output.

Plug and Play. I've seen this abbreviation in a military RFP. I guess ``PnP'' doesn't seem serious enough. But hey, if you want a laugh, check out how the missile-shield tests are rigged.


Platform for Privacy Preferences Project. Yes, that's four P's altogether.

The 5 Permanent members of the UN Security Council.

An ad hoc group comprising the P5 plus another country. The designation P5+1 was used in 2006 for talks on what to do about Iran's nuclear program. Germany, which had been part of the E3, was the one non-P5 member engaged in the discussions.

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