现代技术中的微量级热现象

近年来，在制造具有新颖结构的微型器件和材料（例如微电子器件、微机电系统和各种先进材料）方面取得了巨大的进展。这种发展使得热科学领域中的热现象。从发生在大量级结构中转移到发生在级结构中。对于更好地理解和控制能量传递而言，这种转移既提出了挑战又提供了机遇。本文从微尺寸、微结构和微时间三方面说明了上述微量级热现象。     

Evolutionary genetics. Clonal inheritance of avian mitochondrial DNA.

We have taken a new approach to test the commonly accepted, but recently questioned, principle of clonal inheritance of vertebrate mitochondrial DNA (mtDNA) by relating its inheritance to a female-specific marker of nuclear DNA. Whereas this is impossible in organisms with male heterogamy (such as mammals), we show here that genealogies of mtDNA and the female-specific W chromosome of a bird species are completely concordant. Our results indicate that inheritance of mtDNA is free of detectable recombination effects over an evolutionary timescale.     

South-polar features on Venus similar to those near the north pole

Venus has no seasons, slow rotation and a very massive atmosphere, which is mainly carbon dioxide with clouds primarily of sulphuric acid droplets. Infrared observations by previous missions to Venus revealed a bright 'dipole' feature surrounded by a cold 'collar' at its north pole. The polar dipole is a 'double-eye' feature at the centre of a vast vortex that rotates around the pole, and is possibly associated with rapid downwelling. The polar cold collar is a wide, shallow river of cold air that circulates around the polar vortex. One outstanding question has been whether the global circulation was symmetric, such that a dipole feature existed at the south pole. Here we report observations of Venus' south-polar region, where we have seen clouds with morphology much like those around the north pole, but rotating somewhat faster than the northern dipole. The vortex may extend down to the lower cloud layers that lie at about 50 km height and perhaps deeper. The spectroscopic properties of the clouds around the south pole are compatible with a sulphuric acid composition.     

Prostaglandin-like substances inPropionibacterium acnes. IV. Effect on isolated human vessels

Summary The present study demonstrates a powerful vasoconstrictor activity of prostaglandin-like substances (PLS), extracted fromP. acnes, on human blood vessels. PLS is about equipotent to PGE₂ in its effect on human umbilical vessels, but the contractile response pattern is different. PLS therefore seems to have specific and different physiological characteristics.     

A pump for use in measuring arteriovenous differences in concentration

Zusammenfassung Eine Pumpe wurde konstruiert, welche das Blut durch zwei Kanäle der Zirkulation entzieht bzw. wieder zuführt. Der Vorgang erfolgt mit konstanter Geschwindigkeit, unabhängig von Druckschwankungen an der Entnahme- bzw. Zuführungsstelle.Die Pumpe erwies sich als geeignet für die Aufrechterhaltung einer extracorporellen Zirkulation während der kontinuierlichen Messung arteriovenöser Konzentrations-differenzen von radioaktiv markierten Substanzen.

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A grant from Reservationsauslaget of the Karolinska Institutet is gratefully acknowledged.     

Transmembrane potential of J774.2 mouse macrophage cells measured by microelectrode and ion distribution methods

The transmembrane potential (Em) of J774.2 macrophage cells measured by microelectrodes was -24.1 +/- 0.7 mV (mean +/- SEM). Em measured by lipophilic ion distribution was -35 +/- 2 mV or -40 +/- 2 mV, using a cation or anion, respectively. By any method, colchicine reduced Em by approximately 3 mV.