ISSN:0031-9228    

DOI:10.1063/1.2806515

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.881667

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.881669

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.881672

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Dan Shahar, Daniel Tsui and Mansour Shayegan at Princeton University were studying the liquid‐to‐insulator transitions in a quantum Hall system recently when they noticed a surprising symmetry in the plot of longitudinal voltage versus current: For each point close to the phase transition in the liquid phase, they could find a corresponding point in the insulating phase such that the (normalized)I–Vcurve for one fell precisely on theV‐Icurve of the other—that is, the curve with the voltage and current coordinates switched. Such behavior suggests that the underlying dynamics of the liquid and insulator phases must be intimately related, despite their overtly different transport characteristics.

ISSN:0031-9228    

DOI:10.1063/1.881673

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Fifty‐nine years ago, Pierre Auger discovered the extensive air showers generated by high‐energy cosmic rays when he saw that two Geiger counters several hundred meters apart in the Alps were recording coincident counts. Five years from now, if the funding is forthcoming, a pair of3000 km2air‐shower detector arrays bearing his name will begin their concerted assault on the greatest remaining mystery posed by cosmic rays. The Pierre Auger Project, a collaboration of physicists and astronomers from 40 institutions in 19 countries, plans to have one array in Utah monitoring the northern sky while an identical array in the high desert of western Argentina keeps watch over the southern sky.

ISSN:0031-9228    

DOI:10.1063/1.881679

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The first artificial satellite of Earth was placed in orbit almost 40 years ago. That event, in October 1957, had great political and technological significance. Almost overnight, thoughtful people began to discuss the possible uses of Earth satellites. Two great applications of space technology have emerged since then. Communication satellites in synchronous orbit now play a prominent role in our lives. They complement terrestrial links and offer communication services not previously available. Equally profound has been the development of a worldwide navigation service based on the constellation of Global Positioning System satellites.

ISSN:0031-9228    

DOI:10.1063/1.881677

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Polymers—macromolecules composed of many small molecules—are vital to life. For example, proteins provide the cell with structure and carry out its mechanical and enzymatic work. Fatty acids store energy in their bonds, and lipids form the membranes that seal off the cell's aqueous interior from its aqueous exterior. Heredity lies in the very long polymeric strands of deoxyribonucleic acid—DNA.

ISSN:0031-9228    

DOI:10.1063/1.881674

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Suppose we could understand the laws of nature that govern the particles and their interactions, and in addition why the laws are as they are, and also how the universe evolved and perhaps even how it originated—an active research area today That understanding—a theory—would be formulated not in terms of everyday units, but rather units built from constants such as the speed of light, Planck's constant and Newton's constant. From these constants one obtains the natural scales: the Planck length(∼10−33 cm)and the Planck mass(MP∼1019 GeV/c2).I will call this theory the primary theory, a name I like because it suggests that as we go through a hierarchy of effective theories, from macroscopic sizes to atoms to nuclei, we end at a primary one that is not related to another at a deeper level.

ISSN:0031-9228    

DOI:10.1063/1.881680

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2806519

出版商:AIP    

年代:1997

数据来源: AIP