Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

闪电电场变化波形时域特征分析及放电类型识别

对闪电电场变化波形进行时域特征分析,研究闪电放电类型识别方法,是闪电探测系统研制工作的重要组成部分.利用闪电快电场变化资料,研究分析闪电波形的时域特征,分别统计负地闪回击和双极性窄脉冲波形的上升时间、下降时间、脉冲宽度等多个特征参数,得出负地闪回击波形上升时间平均值为2.9μs、下降时间平均值为89μs、脉冲宽度平均值为15.4μs,而双极性窄脉冲波形的上升时间平均值为1.7μs、下降时间平均值为2.1μs、脉冲宽度平均值为2.4μs.通过对闪电波形参数的统计分析,给出了不同放电过程的识别判据,实现了对地闪回击、双极性窄脉冲的自动识别,并利用实测数据进行了验证.结果表明,制定的波形识别判据对负地闪回击的识别效率可达到90%,对正地闪回击与双极性窄脉冲事件也有较高的识别率.     

可持续气象信息中心的双极PROMETHEE动态评价方法

随着电子设备、计算机等大量的使用,全国气象信息中心的环境污染问题逐渐呈现出来.本文首次将可持续发展的概念引入到气象信息中心管理中.作为可持续发展的三大支柱,经济、环境、社会之间不可避免地存在冲突,双极模糊集对这类冲突信息具有强大的描述能力.考虑到可持续发展评价是一个多年的动态过程,本文提出了一种双极PROMETHEE可持续气象信息中心的动态评价方法.实例验证了新方法的有效性和可行性.     

Mechanism on bipolar distribution of Permian brachiopods

By reasearch on geographic distribution, nine genera in bipolar distribution are selected from Permian brachiopods. These taxa originated from middle-high latitude areas in the boreal realm, of which five genera were derived from Late Carboniferous, and other four genera originated from Permian. They were all in bipolar distribution during some different stages in Permian. Specific diversity for each genus was high in the boreal realm, whereas in the Gondwana realm was very low. Perdurability was long in the boreal realm, and short in the Gondwana realm. It was the time when these nine genera came to their maximum diversity that these genera appeared in the Gondwana and formed bipolar distribution; while they also migrated to the low latitude from high latitude. This shows very close relationship between several main cooling events in Permian and the migration of genera from the boreal realm to the Gondwana reahn through the Tethys. Therefore, the cooling events might be the main drive which caused these cold-water-type brachiopods migrated to the Gondwana realm and being bipolar distribution. In this process, the planula tolerance to warm water would be another important factor.     

LATE‐GLACIAL GLACIER EVENTS IN SOUTHERNMOST SOUTH AMERICA: A BLEND OF ‘NORTHERN’ AND 'SOUTHERN’ HEMISPHERIC CLIMATIC SIGNALS?

ABSTRACT. This paper examines new geomorphological, chronological and modelling data on glacier fluctuations in southernmost South America in latitudes 46–55°S during the last glacial–interglacial transition. Establishing leads and lags between the northern and southern hemispheres and between southern mid‐latitudes and Antarctica is key to an appreciation of the mechanisms and resilience of global climate. This is particularly important in the southern hemisphere where there is a paucity of empirical data. The overall structure of the last glacial cycle in Patagonia has a northern hemisphere signal. Glaciers reached or approached their Last Glacial Maxima on two or more occasions at 25–23 ka (calendar) and there was a third less extensive advance at 17.5 ka. Deglaciation occurred in two steps at 17.5 ka and at 11.4 ka. This structure is the same as that recognized in the northern hemisphere and taking place in spite of glacier advances occurring at a time of high southern hemisphere summer insolation and deglaciation at a time of decreasing summer insolation. The implication is that at orbital time scales the‘northern’ signal dominates any southern hemisphere signal. During deglaciation, at a millennial scale, the glacier fluctuations mirror an antiphase 'southern’ climatic signal as revealed in Antarctic ice cores. There is a glacier advance coincident with the Antarctic Cold Reversal at 15.3–12.2 ka. Furthermore, deglaciation begins in the middle of the Younger Dryas. The implication is that, during the last glacial–interglacial transition, southernmost South America was under the influence of sea surface temperatures, sea ice and southern westerlies responding to conditions in the 'southern’ Antarctic domain. Such asynchrony may reflect a situation whereby, during deglaciation, the world is more sensitized to fluctuations in the oceanic thermohaline circulation, perhaps related to the bipolar seesaw, than at orbital timescales.     

磁尾地向传播等离子体团的模拟研究

卫星观测证实了磁尾等离子体团与亚暴活动的相关性,除了具有北-南双极特征的尾向传播等离子体团外,还发现地向传播等离子体团,它们表现为南-北双极中性片事件和南-北双极瓣区讯号. 资料分析表明:南-北双极讯号的出现几率远低于北-南双极讯号,并且南-北双极事件主要发生于行星际磁场北向和地磁宁静条件,它们往往与小的孤立的地磁亚暴相关. 本文根据地磁宁静时期(IMF Bz北向且By≥Bz)越尾电场Ey分量的分布特点,对地向传播等离子体团作模拟研究. 两类算例的数值结果展示了通量绳磁结构及具有复杂闭合磁力线位形的等离子体团的基本特征,上述特征与尾向传播的等离子体团类似,与IMP 8卫星关于地向传播南-北中性片事件的观测特征大致相符. 数值结果还展示了与Schindler示意图相类似的磁力线拓扑位形,在一定程度上为南-北事件出现几率低作出了解释;并且揭示了磁尾中性片内越尾磁场分量By对磁重联发展的抑制作用. 本文的模拟研究说明:无论磁尾处于活动时期(IMF Bz为南向),还是宁静时期(IMF Bz为北向且By≥Bz),磁场重联均是磁尾等离子体加速和加热的通用机制.     

Optical spectrum of the bipolar nebula AFGL 2688

Based on echelle spectra obtained at the prime focus of the 6-m telescope, we have determined for the first time the detailed chemical composition of one of the components of the bipolar nebula identified with the intense infrared source AFGL 2688 by the model-atmosphere method. The iron abundance [Fe/H]=?0.59 dex derived for AFGL 2688 suggests that the object probably belongs to an intermediate population of the Galaxy. The stellar atmosphere exhibits high carbon and nitrogen abundances, [C/Fe]=+0.73 and [N/Fe]=+2.00, and C/O>1, confirming that the object is at the post-AGB stage. However, the detected overabundance of s-process elements (yttrium and barium) relative to iron is modest: [X/Fe]=+0.55. The lanthanides are even less enhanced: for La, Ce, Pr, and Nd, the mean abundance relative to iron is [la/Fe]=+0.26. This behavior of the heavy metals is consistent with the low intensity of the 21-μm band in the infrared spectrum of AFGL 2688; the intensity of this emission band is great in the spectra of all the studied PPN with large overabundances of s-process elements. An analysis of the radial velocities measured from spectral features originating in the atmosphere and in the circumstellar shell has revealed a high-velocity (～60 km s^?1) component of the stellar wind from AFGL 2688.     

基于电离层反射的袖珍云闪(CID)三维定位研究

袖珍云闪是一类区别于常规闪电放电过程的特殊放电现象,能够同时产生极强的高频和低频辐射信号,其低频辐射信号在电离层与地面之间反射后能够在电场变化波形上形成电离层反射脉冲对.电离层反射信号与原信号的时间差包含着放电三维位置和电离层高度的信息,而借助于多站闪电探测网络的同步观测就能够反演这些信息.基于这一规律,本文发展了一种对袖珍云闪实现三维定位的新方法.这种方法不仅能够对大范围内的袖珍云闪实现准确的三维定位,同时还能够反演电离层的高度,是一种潜在的研究电离层相关性质的有效手段.通过将定位结果与雷达回波比较,证明这种方法具有较高的精度.利用这种方法,计算了5489例正极性袖珍云闪和1400例负极性袖珍云闪的放电高度,发现正极性袖珍云闪主要集中在7~14 km,而负极性袖珍云闪达到了15~18 km.负极性袖珍云闪的放电高度总体上与对流层顶高度相当,其数量相比于正极性袖珍云闪明显偏少,因此很可能产生于较为罕见的极旺盛的雷暴过程中.     

The onset of axial symmetry in protoplanetary nebulae

We have obtained resolved IR images, at wavelengths from 1.2µm to 12.5µm, of a small sample of protoplanetary nebulae. The results suggest that all PPNe are axially, not spherically, symmetric, that spherical symmetry ends at the tip of the AGB, and that AGB evolution terminates with a burst of remarkably rapid, equatorially concentrated mass-loss.     

Atlantic ocean heat piracy and the bipolar climate see‐saw during Heinrich and Dansgaard–Oeschger events

The millennial‐scale asynchrony of Antarctic and Greenland climate records during the last glacial period implies that the global climate system acts as a bipolar see‐saw driven by either high‐latitudinal and/or near‐equatorial sea‐surface perturbations. Based on the results of recent modelling of generic Heinrich and Dansgaard–Oeschger scenarios, we discuss the possibility that oscillations of the deep‐ocean conveyor may have been sufficient to cause this bipolar see‐saw. The bipolar climate asynchrony in our scenarios is caused by the toggle between North Atlantic heat piracy and South Atlantic counter heat piracy. Ocean circulation has an enhanced sensitivity to the northern deep‐water source as the North Atlantic Deep Water (NADW) cannot enter the Southern Ocean at depths shallower than the bottom of the Drake Passage. Any shoaling of the NADW can, therefore, increase the northward incursion of Antarctic Bottom Water (AABW), and trigger an interhemispheric climate oscillation. As hundreds of years are required to warm the respective high latitudes, the observed climate lead and lags between the two hemispheres can be explained entirely by the variability of the meridional overturning and by the corresponding change in the oceanic heat transport. Accordingly, it is entirely feasible for the global climate to work like a pendulum, which theoretically could be controlled by pushing at either of the deep‐water sources. Our model scenarios suggest that it is entirely feasible for the bipolar climate see‐saw to be controlled solely by variations in NADW formation. Copyright © 2001 John Wiley & Sons, Ltd.