ISSN:0031-9228    

DOI:10.1063/1.2218522

出版商:AIP    

年代:1906

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2218523

出版商:AIP    

年代:1906

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2218526

出版商:AIP    

年代:1906

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2218530

出版商:AIP    

年代:1906

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2218533

出版商:AIP    

年代:1906

数据来源: AIP

摘要:

When chemically reactiveatoms or molecules combine, their valence electrons snap into new, energy‐minimizing configurations. But suppose you want to steer the reaction toward a particular configuration—an unfavored oxidation state, say, or a specific isomer. Somehow, you'd have to reach into the nascent molecule and, at just the right moment, divert the valence electrons from their habitual target.

ISSN:0031-9228    

DOI:10.1063/1.2218534

出版商:AIP    

年代:1906

数据来源: AIP

摘要:

A material's propertiesdepend not only on its constituents but also on how the constituents are arranged in space. Diamond, for example, shares the same atomic constituents as graphite and the same tetrahedral structure as silicon, yet it resembles neither black flaky graphite nor gray brittle silicon.

ISSN:0031-9228    

DOI:10.1063/1.2218535

出版商:AIP    

年代:1906

数据来源: AIP

摘要:

The self‐winding wristwatchprovides a familiar example of a ratchet. An internal mechanism that's asymmetric with respect to clockwise and counterclockwise converts the energy imparted by random wrist motion into purposeful winding of the clockwork. More generally a ratchet is a kind of rectifier—macroscopic or microscopic—that forces the otherwise random thermal or mechanical motion of a system that's out of equilibrium into a specific direction by means of an asymmetric potential. Microscopic ratchets called Brownian motors are thought to be important for motion in biological systems (see the article by Dean Astumian and Peter Ha¨nggi in PHYSICSTODAY, November 2002, page 33).

ISSN:0031-9228    

DOI:10.1063/1.2218536

出版商:AIP    

年代:1906

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2218537

出版商:AIP    

年代:1906

数据来源: AIP

摘要:

The Isotope Separationand Acceleration (ISAC) facility at TRIUMF, Canada's national nuclear‐ and particle‐physics laboratory in Vancouver, began flexing its new muscles in April after a Can$48 million ($43 million) upgrade. ISAC‐II, as the new part of the facility is known, revs radioactive isotopes to at least 4.5 MeV per nucleon, a three‐fold increase; a further boost to 6.5 MeV per nucleon is planned in the next few years, and a move to heavier species will start next year. ISAC‐II will be used for studies of nuclear structure, nuclear reactions, and nuclear astrophysics.

ISSN:0031-9228    

DOI:10.1063/1.2218542

出版商:AIP    

年代:1906

数据来源: AIP