scientific american - 1994 10 - special issue - life in the universe

... understanding of the laws of nature. T he present gaps in our knowl- edge of the laws of nature stand in the way of explaining the ini- tial conditions of the universe, at 10 Ð12 second after the nominal ... are versions of string theory that predict something like the menu of Þelds in- corporated in the Standard Model. But string theory has had no success- es yet...

Ngày tải lên: 12/05/2014, 14:58

... villainÕs role in other autoimmune diseases: in insulin-dependent diabetes, T lymphocytes destroy insulin-produc- ing cells in the pancreas, and in multiple sclerosis, they direct their fury against the ... near- ly all other genes in the body, those that contain the code for the heavy chains do not preexist in the fertilized egg. In- stead the code resides in fo...

Ngày tải lên: 12/05/2014, 14:50

... a con- ference, Regan suggested that two pro- teins being studied in the lab might just lend themselves to the mod- ern-day alchemy required to win the wager. The two proteins, called B- 1 and ... Net. The current naming system was de- signed in 1983 as a human-friendly in- terface to the dotted clumps of num- bers that routing computers under- stand. Each organization setti...

Ngày tải lên: 12/05/2014, 15:30

... on the vi- ciousness of their anti-Semitism, even though the sites themselves are highly unlikely to include the center’s rating in their Web home pages. Whatever the source of the ratings, they ... mathemat- ics. He majored in the subject at the Uni- versity of Pune, then applied for a mas- ter’s program in math and computer science at the Indian Institute of Tech- nolo...

Ngày tải lên: 12/05/2014, 15:15

... he calls intervention: establish- ing standards and then measuring per- formance against them. Another highly effective technique—having subordi- nates take part in the decision mak- ing—was used ... lying behind the plane of the Milky Way, the gal- axy —named Dwingeloo 1—would be one of the 10 brightest in the sky. Judg- ing from its rate of rotation it has about one third...

Ngày tải lên: 12/05/2014, 15:47

... Meanwhile the floors tie the inner frame to the outer one, bracing the entire edifice. In the case of the World Trade Center, which was a state-of -the- art design in the late 1960s, the steel-mesh ... MYSTERIOUS FLOW COPYRIGHT 2002 SCIENTIFIC AMERICAN, INC. events that were once in the unformed future into the con- crete but fleeting reality of the present, and th...

Ngày tải lên: 12/05/2014, 16:14

... pro- posed second-generation system known as Computer-Assisted Passenger Pre-Screening, or CAPPS II. In terms of the variety of in- formation, the sys- tem goes much fur- ther than the 1.0 ver- sion —and ... another molecule that tricks the cells into taking it up and transferring it into brain tissue or by genetically engineering cells to make FGF and then transplanting those cel...

Ngày tải lên: 12/05/2014, 16:18

... belonged together. For example, if three amino ac- idsÑcall them A, B and CÑare linked together in some order in a chain, the sequence could be determined in the following way. After labeling the chains, they ... the air mass in- land, the inversion layer traps air pol- lutants in the cool air near the ground where people live and breathe. The mountains that surround...

Ngày tải lên: 12/05/2014, 14:50

... of the original miner- als in the peridotite. Some minerals, such as clinopyroxene, melt more easi- ly than do others and hence rapidly de- crease in abundance during the melt- ing. Moreover, the ... FULLER Copyright 1994 Scientific American, Inc. Mayewski hopes better insight into the inconstant nature of the sun will enable researchers to determine whether the present...

Ngày tải lên: 12/05/2014, 14:54

... of the nuclei then spin in opposi- tion to the external Þeld in high-energy orientations. The process is adiabatic, meaning the entropy remains un- changed. The resulting spin distribution is the ... liver failure. Four neurotoxins have been studied in detail. Of these, anatoxin-a and ana- toxin-a(s) seem unique to cyanobacte- ria. The other twoÑsaxitoxin and neo- saxitoxi...

Ngày tải lên: 12/05/2014, 14:50