Thursday, November 26, 2009

Crime versus subculture: cracker versus hacker

A cracker is a person who gains oneself and/or other people illegal access to computers, most likely to perform some malicious activity. Often such a person is—incorrectly—called a hacker. A hacker's intention is not to damage a computer or to steal data for criminal undertakings. A hacker may detect security gaps and program errors hidden in operating systems, browsers and other software and bring those to public attention; but if so, then for their fixture. Typically, a hacker is a highly creative programmer with a lot of insider knowledge about computers and their inner workings. A hacker's programming style is explorative and unconventional, at least from a non-hacking viewpoint. Hackers are frequently seen (or see themselves) as part of a subculture. Some call it cyber punk.
Terms like password hacker or network hacker should be avoided, if they are meant to refer to malicious programming. Criminal activity is done by crackers—excluding nutcrackers!

Wednesday, November 25, 2009

Metonic cycle named after fifth-century B.C. astronomer Meton of Athens

The Greek astronomer Meton of Athens developed an effective system to adjust lunar calendars to the solar year [1]:
Meton supposedly observed that 19 solar years corresponded almost exactly to 235 lunar months. Since 19 lunar years consist of 228 months, it was thus necessary to add 7 intermediate months into 19 lunar years to put the lunar and solar calendars into phase.
Before Meton, the Babylonians made similar (or the same) observations. Nevertheless, the 19-year, 235-lunar-month cycle is named Metonic cycle or Meton's cycle. It became the basis for the Greek calendar until the Julian calendar was introduced in 46 B.C. [2]. The Metonic cycle was adapted by the Jews in the 4th century A.D., who established a sophisticated lunisolar calendar. The Metonic cycle is still used today to determine the dates of the Jewish festival of Rosh Hashanah and the Christian festival of Easter [3].

Keywords: astronomy, history, calendars, dating

[1] Jacqueline de Bourgoing: The CalendarHistory, Lore, and Legend. Harry N. Abrams, Inc., Publishers, 2001; page 22.
[2] Eric W. Weisstein: Metonic Cycle.
[3] Tony Freeth: Decoding an Ancient Computer. Sci. Am. December 2009, 301 (6), pp. 76-83.

Tuesday, November 24, 2009

Acronym in biochemistry: CALB for Candida antarctica lipase B

CALB stands for the enzyme lipase B specificly isolated from the yeast-like fungus Candida antarctica. CALB exhibits hydrolytic, ester synthesis and transesterification activity. It is a versatile biocatalyst, for example in asymmetric synthesis.
The structure and activity of CALB is currently investigated in various media including water, organic solvents, and ionic liquids as well as in solvent-free processing.

Keywords: organic chemistry, green chemistry, biocatalysis

Selected literature
[1] Kwang-Wook Kim, Boyoung Song, Min-Young Choi and Mahn-Joo Kim: Biocatalysis in Ionic Liquids: Markedly Enhanced Enantioselectivity of Lipase. Org. Lett. 2001, 3 (10), pp. 1507-1509. PDF-version.
[2] Francesco Secundo and Giacomo Carrea: Lipase activity and conformation in neat organic solvents. J. Mol. Catal. B: Enzym. December 2002, 19-20, pp. 93-102.
DOI: 10.1016/S1381-1177(02)00155-8.
[3] Anil Mahapatro, Ajay Kumar, Bhanu Kalra and Richard A. Gross: Solvent-free Adipic Acid/1,8-Octanediol Condensation Polymerizations Catalyzed by Candida antarctica Lipase B. Macromolecules 2004, 37, pp. 35-40. PDF-version.
[4] Hua Zhao, Cecil L. Jones and Janet V. Cowins: Lipase dissolution and stabilization in ether-functionalized ionic liquids. Green Chem. 2009, 11, pp. 1128-1138. DOI: 10.1039/b905388c.

Sunday, November 22, 2009

Physical state of matter and class of particles named after Satyendranath Bose

Satyendranath Bose (also spelled Satyendra Nath Bose) was an Indian Physicist, born in 1894 in Calcutta (West Bengal, India) and later teaching physics at Dacca University in East Bengal (now Bangladesh). In 1924, Bose contacted Albert Einstein in Germany to help him publish a paper on quantum statistics that had been rejected by a British journal. Einstein translated the paper from English into German and submitted it to the journal Zeitschrift für Physik, in which the paper was then published with a note by Einstein. That was the beginning of the history of Bose-Einstein condensates. “Existing” as a predicted state of matter for more than fifty years, in 1989 Eric Cornell and his colleagues demonstrated its real existence by cooling rubidium atoms with laser light to nearly absolute zero temperature.
Bose's significant contributions to science are not only remembered with the terms Bose-Einstein statistics and Bose-Einstein condensate, but also with the name for a class of physical particles, the boson—a story beautifully told by John S. Rigden [2]:
There are various ways that fame comes to a scientist. For Satyendranath Bose it was asking Albert Einstein to run interference for him. Eventually his name was linked with Einstein's in both statistical method of dealing with quantum particles, called Bose-Einstein statistics, as well as the peculiar state of matter known as the Bose-Einstein condensate. In addition, Bose had a class of particles named after him: the boson. […]
Keywords: physics, history, Bose-Einstein statistics, quantum chemistry

[1] Satyendranath Bose (1894-1974) at
[2] John S. Rigden: Hydrogen • The Essential Element. Harvard University Press, Cambridge, Massachusetts and London, England, Third Printing 2003; page 234.

Wednesday, November 18, 2009

Ludolph's number or Ludolphine number: pi

For some time the transcendental number pi (π) was known in Germany as Ludolph's number or Ludolphine number. This name derived from the name of a German mathematician from Hildesheim, who emigrated to the Netherlands, where he taught fencing and mathematics in Delft and Leiden: Ludolph von Ceulen (1540-1610), also known by his latinized name Colonus. Ludolph van Ceulen (note the change from the German von to the Dutch van, meaning of or from in English) evaluated π to over 30 digits—long before the age of digital computing— by using the polygon method of Archimedes.

Keywords: mathematics, geometry, history, circle, radius, circumference, approximation of trancendental number

R. M. Th. E. Oomes, J. J. T. M. Tersteeg and J. Top: Het grafschrift van Ludolph van Ceulen. Nieuw Arch. Wiskd. Juni 2000, 5/1 (nr. 2), pp. 57-62.
Internet: Ludolph's number and Ludolph van Ceulen.

Sunday, November 15, 2009

The unit of silence: a dirac

Several famous physicists have their name attached to a unit. Isaac Newton and his work on classical mechanics is memorized with the SI unit of force: the newton (symbol: N). From newton derives the unit of energy, Nm, which is named the joule (symbol: J) after James Prescott Joule. The list goes on. Paul Dirac, known for his work on the hydrogen atom and the spin of the electron and memorized with the Dirac delta function, also has “his” unit: a dirac (symbol unknown). But this is a unit of a somewhat different kind [1]:
Paul Dirac was a unusual person. Perhaps because Dirac's father demanded that his young son use French rather than his native English to converse with him, the young Dirac adopted the habit of silence during his childhood simply because he could not express his thoughts in French. Whatever the reason, the adult Paul Dirac was a man of silence. Dirac's silence was so intense that it inspired a little levity among physicists. In physics, the units given to physical quantities like time or length are important. Physicists, clearly in jest, have defined the unit of silence as the dirac.
A few diracs—at least microdiracs— would suit everybody well at times!

Keywords: physics, units, history, humans, parents, childhood, solitude, silence, humor

John S. Rigden: Hydrogen • The Essential Element. Harvard University Press, Cambridge, Massachusetts and London, England, Third Printing 2003; p. 88-89.

Friday, November 13, 2009

Acronym in photovoltaics: LFC for laser fired contacts

Laser fired contacts (LFC) are electrically conductive point contacts on the rear of a solar cell, typically a cell based on crystalline silicon in which the silicon surface is separated from a metal layer by a dielectric passivation layer. LFC formation within such a structure is achieved by local laser heating, using a Nd-YAG laser which fires point contacts through the dielectric layer by metal/silicon alloying.
The LFC concept was developed by a team of researchers at the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany [1].

Keywords: photovoltaics, solar cell design, device structure

E. Schneiderlöchner, R. Preu, R. Lüdermann and S. W. Glunz: Laser-fired contacts for crystalline solar cells. Progress in Photovoltaics: Research and Applications 2002, 10, pp. 29-34.
DOI: 10.1002/pip.422.

Thursday, November 12, 2009

Synonyms in polymer chemistry: constitutional repeating unit (CRU) and structural repeating unit (SRU)

A regular single-strand polymer consists of repeating units with two terminal groups at either end. The IUPAC Gold Book [1] defines a constitutional repeating unit (CRU) in a polymer as “the smallest unit the repetition of which constitutes a regular macromolecule, a regular oligomer molecule, a regular block or a regular chain.” The term structural repeating unit (SRU) is used synonymously for CRU [2]. A constitutional unit is an atom or group of atoms (with pendant atoms or groups, if any) comprising a part of the essential structure of a macromolecule, an oligomer molecule, a block or a chain [3].

[2] J. Kahovec, R. B. Fox and K. Hatada (Working Group):
Nomenclature of Regular Single-Stranded Organic Polymers (IUPAC Recommendations 2002). Pure Appl. Chem. 2002, 74 (10), pp. 1921-1956. PDF-version.
[3] A. D. Jenkins, P. Kratochvíl, R. F. T. Stepto and U. W. Suter:
Glossary of basic terms in polymer science (IUPAC Recommendations 1996). Pure Appl. Chem. 1996, 68 (12), pp. 2287-2311. PDF-version.

Tuesday, November 10, 2009

English ‘naked’ and German ‘nackt’ in delicate circumstances

The English adjective naked is translated into German nackt. The words naked and nackt look and sound similar and linguistically have the same root. This suggests plain back-and-forth translation. However, there are notable exceptions as the following examples will illustrate.

The English phrase with the naked eye is typically not translated as mit dem nackten Auge. In German(y), one sees mit dem bloßen Auge (with the bare eye) or mit dem unbewaffneten Auge (with the unequipped eye).

The German term nackte Tatsache does not mean a naked fact, but may be translated as simple fact or brute fact.

In other contexts nackt may be best translated into English by taking adjectives such as nude, bare, plain, blunt or stark.

Keywords: English language, German language, translation, adjectives

Monday, November 9, 2009

LM for living morphine (alive and morphine given)

During the Vietnam War the letters L and M, written on the helmet of an injured soldier, indicated that he was still alive and had received an injection of morphine. In the Norwegian thriller Kakerlakkene (meaning cockroaches in English and Küchenschaben in German) by Jo Nesbø, the Vietnam veteran Ivar Løken has an LM history of its own. This thriller does not take place in Vietnam, but—years after the end of the Vietnam War—in Bangkok,Thailand. A war of a different kind is happening here. This war doesn't include an army, just a few people (and not all of them are Norwegians) connected via sex, gambling, and corruption.

Jo Nesbø:
Kakerlakkene, originally published in Norwegian (Aschehoug, Oslo).
German-language edition: Kakerlaken. Ullstein Taschenbuch, Berlin, Juni 2009.