Energy Sources for Triton's Geyser-Like Plumes

Four geyser-like plumes were discovered near Triton's south pole in areas now in permanent sunlight. Because Triton's southern hemisphere is nearing a maximum summer solstice, insolation as a driver or a trigger for Triton's geyser-like plumes is an attractive hypothesis. Trapping of solar radiation in a translucent, low-conductivity surface layer (in a solid-state greenhouse), which is subsequently released in the form of latent heat of sublimation, could provide the required energy. Both the classical solid-state greenhouse consisting of exponentially absorbed insolation in a gray, translucent layer of solid nitrogen, and the "super" greenhouse consisting of a relatively transparent solid-nitrogen layer over an opaque, absorbing layer are plausible candidates. Geothermal heat may also play a part if assisted by the added energy input of seasonal cycles of insolation.     

Triton's Plumes: The Dust Devil Hypothesis

Triton's plumes are narrow columns 10 kilometers in height, with tails extending horizontally for distances over 100 kilometers. This structure suggests that the plumes are an atmospheric rather than a surface phenomenon. The closest terrestrial analogs may be dust devils, which are atmospheric vortices originating in the unstable layer close to the ground. Since Triton has such a low surface pressure, extremely unstable layers could develop during the day. Patches of unfrosted ground near the subsolar point could act as sites for dust devil formation because they heat up relative to the surrounding nitrogen frost. The resulting convection would warm the atmosphere to temperatures of 48 kelvin or higher, as observed by the Voyager radio science team. Assuming that velocity scales as the square root of temperature difference times the height of the mixed layer, a velocity of 20 meters per second is derived for the strongest dust devils on Triton. Winds of this speed could raise particles provided they are a factor of 103 to 104 less cohesive than those on Earth.     

Scatterers in Triton's Atmosphere: Implications for the Seasonal Volatile Cycle

Nitrogen and methane ices on the surface of Triton, Neptune's largest satellite, are exchanged between the summer and winter hemispheres on a seasonal time scale. Images of the satellite's sky obtained by the Voyager 2 spacecraft show the presence of several types of scattering materials that provide insights into this seasonal cycle of volatiles. Discrete clouds, probably composed of N(2) ice particles, arise in regions of active sublimation. They are found chiefly poleward of 30 degrees S in the southern, summer hemisphere. Haze particles, probably made of hydrocarbon ices, are present above most, but not all places. Recent snowfall may have occurred at low southern latitudes in places where they are absent. The latent heat released in the formation of the discrete clouds may have a major impact on the thermal balance of the lower atmosphere. Triton may have been less red at the time of the Voyager flyby than 12 years earlier due to recent N(2) snowfall at a wide range of latitudes.     

Jupiter's Clouds: Equatorial Plumes and Other Cloud Forms in the Pioneer 10 Images

Pioneer 10 images of Jupiter show bright nuclei in the equatorial zone that appear to be thermally driven sources of cloud plume formations.     

十字花科植物中低芥酸野生种的发掘和FAE1基因的功能验证

 【目的】发掘低芥酸野生种,并探明这些野生种的低芥酸遗传机理。【方法】本研究采用同源序列法从野生种和甘蓝型油菜中分离FAE1序列。用酵母系统异源表达野生种的FAE1。用气相色谱法分析脂肪酸组成。【结果】比较FAE1序列发现5个野生种的FAE1序列与甘蓝型油菜的FAE1同源性高于85%。分析它们编码的蛋白质序列,发现5个野生种在第282位氨基酸残基处都是丝氨酸,而且与酶活性相关的氨基酸残基（Cys223、His302、His387、His391和His420）都没有发生突变,这些特征与报道的高芥酸油菜品种相同,不同于低芥酸油菜。Western Blot分析发现野生种的FAE1都在酵母系统中获得了表达,转化诸葛菜和荠菜FAE1的酵母并未合成长链脂肪酸,而转化新疆野芥、新疆白芥和菘蓝的FAE1的酵母都有微量长链脂肪酸的合成。【结论】诸葛菜和芥菜确为低芥酸野生种,而且其低芥酸性状源于FAE1编码产物的失活。     

Trace Gas Analysis of Power Plant Plumes Via Aircraft Measurement: O3, NOx, and SO2 Chemistry

The gaseouis plume from an isolated 1000-megawatt power plant was systematically examined from a single engine aircraft to determine the extent to which NO(x) and SO(2), chemistry occurs as a function of distance. The concentrations of ambient ozone, water vapor, and hydroxyl free radicals are indicated to be of major importance in defining the chemistry of power plant plumes during summertime conditions.     

Lead and Helium Isotope Evidence from Oceanic Basalts for a Common Deep Source of Mantle Plumes

Linear arrays in lead isotope space for mid-ocean ridge basalts (MORBs) converge on a single end-member component that has intermediate lead, strontium, and neodymium isotope ratios compared with the total database for oceanic island basalts (OIBs) and MORBs. The MORB data are consistent with the presence of a common mantle source region for OIBs that is sampled by mantle plumes. 3He/4He ratios for MORBs show both positive and negative correlation with the 206Pb/204Pb ratios, depending on the MORB suite. These data suggest that the common mantle source is located in the transition zone region. This region contains recycled, oceanic crustal protoliths that incorporated some continental lead before their subduction during the past 300 to 2000 million years.     

A、H股的协整关系与价格发现功能

南宋初期的士大夫张九成是著名禅师大慧宗杲的居士弟子,他本人的佛禅知见,契合于大乘经论与诸禅师的论道,卓然深刻,受到宗杲的称赞和肯定。可见张九成在佛法修证上下了一番工夫,佛法在他心中具有相当的地位和影响。     

Data transfer: Basic concepts

Experimental methods often utilize computers to acquire, then transfer data to more convenient facilities for storage, processing, and analysis. Knowledge of the basic concepts of digital data transmission is often essential in the proper set up and operation of microprocessor-based instrumentation. This paper discusses methods of electronically transferring data from laboratory or field facilities to a central computer.     

情爱意象:沈从文的民俗审美发现

从民俗学角度看,沈从文小说中出现的审美意象显示出与民间情爱主题的某种关联:风、云、雨、水是天地造化的结果,也是具有情爱内涵的意象;自然界许多动植物被赋予了情爱和子嗣繁衍的内涵;民俗节日也是民间男欢女爱的时节。小说中民俗风物的意象化是作者叙事建构的结果。     

发现法教学与素质教育

发现法教学强调学生的主体性、创造性,是素质教育的体现。教学中应遵循赞美鼓励原则、建构主义原则、全面发展原则。     

景观题名的作用、归属及基本技法

景观题名是园林规划设计不可缺少的一环,其权限和职责,应归于规划设计人员。景观题名有其自身的规律。成功的景观题名必须符合“切”、“雅”、“精”、“新”的要求。题名的基本技法有直观写实法和意境传神法两大类。     

DNA干扰现象及其作用机理研究进展

与体内某一基因相同的DNA序列可特异性抑制细胞内靶标基因的表达,这种现象称之为DNA干扰(DNAi)。DNAi是随着转录后基因沉默现象而在烟草属植物上被发现,之后在一些动植物及其细胞上也被发现。在原核生物中也存在DNAi现象,且原核生物的Ago在体外也能实现DNAi。原核生物DNAi的机理主要是Ago以DNA为向导切割DNA或RNA,而真核生物可能是基因转录后抑制、基因组甲基化和启动子结合的转录抑制等。本文还对DNAi的进一步研究和应用进行了讨论和展望。     

Basic research and economic health: the coming challenge

The United States faces an international economic challenge that can best be met with a renewed emphasis on the basic science and engineering that underlies new technology. For 20 years, however, the nation has not invested adequately in the science and engineering base, with the result that we have too few young people entering science and engineering programs and inadequate facilities and equipment in the nation's universities. We need a fresh infusion of resources into the universities, together with a new emphasis on cooperative efforts between universities and industry. The engineering research centers recently established by the National Science Foundation are an example of how we should proceed.