An unexpected cooling effect in Saturn's upper atmosphere

The upper atmospheres of the four Solar System giant planets exhibit high temperatures that cannot be explained by the absorption of sunlight. In the case of Saturn the temperatures predicted by models of solar heating are approximately 200 K, compared to temperatures of approximately 400 K observed independently in the polar regions and at 30 degrees latitude. This unexplained 'energy crisis' represents a major gap in our understanding of these planets' atmospheres. An important candidate for the source of the missing energy is the magnetosphere, which injects energy mostly in the polar regions of the planet. This polar energy input is believed to be sufficient to explain the observed temperatures, provided that it is efficiently redistributed globally by winds, a process that is not well understood. Here we show, using a numerical model, that the net effect of the winds driven by the polar energy inputs is not to heat but to cool the low-latitude thermosphere. This surprising result allows us to rule out known polar energy inputs as the solution to the energy crisis at Saturn. There is either an unknown--and large--source of polar energy, or, more probably, some other process heats low latitudes directly.     

An unexpected specialization for horizontal disparity in primate primary visual cortex

The horizontal separation of the eyes means that objects nearer or farther than the fixation point project to different locations on the two retinae, differing principally in their horizontal coordinates (horizontal binocular disparity). Disparity-selective neurons have generally been studied with disparities applied in only one direction (often horizontal), which cannot determine whether the encoding is specialized for processing disparities along the horizontal axis. It is therefore unclear if disparity selectivity represents a specialization for naturally occurring disparities. I used random dot stereograms to study disparity-selective neurons from the primary visual cortex (V1) of awake fixating monkeys. Many combinations of vertical and horizontal disparity were used, characterizing the surface of responses as a function of two-dimensional disparity. Here I report that the response surface usually showed elongation along the horizontal disparity axis, despite the isotropic stimulus. Thus these neurons modulated their firing rate over a wider range of horizontal disparity than vertical disparity. This demonstrates that disparity-selective cells are specialized for processing horizontal disparity, and that existing models of disparity selectivity require substantial revision.     

S波段微波癌症诊断仪

70年代,微波辐射计量开始应用于生物医学领域。Leroy等人用微波热像仪诊断乳腺癌、脑血管疾病及脑膜肿瘤,但都没有解决深部肿瘤的探测问题。为此,本文报道S波段微波癌症诊断仪的研制。1.微波热辐射的接收生物组织中自发微波热辐射波矢量图实际上为椭球面,若所用天线是线偏振的,则探头仅能探测辐射到天线口面的总功率的一半。846型S波段微波诊断仪采用了圆极化探头,检测到的生物热辐射功率较前人的大一倍。检测辐射功率较测量亮温方便,但辐射功率的特征值为亮度温度T_B。在实际应用中常用T_B作为被测值,只要微波辐射计能分别提取亮度温度信息T_(Bi)及各层媒质的发射率e_i,各层媒质的实际物理温度T_i便可唯一确定。对于分层媒质有T_B=sum from i=1 to n(T_(Bi))=sum from i=1 to n(e_iT_i),当不计层间散射时,可改写成T_B=sum from i=1 to n(η_iT_B)。设皮肤组织对T_B的贡献的百分比为η_s,同样设     

Thin films: unexpected magnetism in a dielectric oxide

It is generally accepted that magnetic order in an insulator requires the cation to have partially filled shells of d or f electrons. Here we show that thin films of hafnium dioxide (HfO2), an insulating oxide better known as a dielectric layer for nanoscale electronic devices, can be ferromagnetic even without doping. This discovery challenges our understanding of magnetism in insulators, because neither Hf4+ nor O2- are magnetic ions and the d and f shells of the Hf4+ ion are either empty or full.     

DCE-MRM对乳腺癌的循证诊断:Meta分析

目的:用Meta分析评价DCE-MRM对乳腺癌诊断价值.材料和方法:全面收集DCE-MRM乳腺癌诊断的文献,并用定量方法进行合并.采用Excell 2007和Metadisc1.4软件.结果:文献56篇,病人总数8048例;合并敏感性和特异性分别为80.9%(CI:79.6%-82.1%)和80.7.9%(CI79.4-81.9%),合并阳性拟然比为3.508(CI:.2.965-4.150),合并阴性拟然比为0.194(CI0.143-0.264),合并比数比为21.672(CI:15.811-29.706),SROC面积0.8901.结论:DCE-MRM对乳腺癌的诊断敏感性和特异性稍高.     

胶质细胞与药物成瘾

药物成瘾是一种慢性和复发性脑病.传统的观念认为胶质细胞在药物成瘾中仅起辅助作用.目前发现胶质细胞上存在众多的神经递质受体和转运体,且能分泌多种氨基酸、多肽、神经营养因子及炎症因子,对神经递质的代谢、神经冲动的传导以及突触的调节等起着重要的作用；且胶质细胞在药物成瘾中发生极大变化.对中枢神经系统中的星形胶质细胞、小胶质细...     

感知校园氛围对大学生手机依赖的影响:有调节的中介

以匿名方式对821名大学生进行校园氛围、手机依赖、社交焦虑以及自我控制的问卷调查。结果显示:感知校园氛围负向预测大学生的手机依赖(β=-0.353,P0.001),其中社交焦虑在两者中起部分中介作用;学校氛围对社交焦虑以及社交焦虑对手机依赖的预测作用均受个体自我控制高低水平的调节作用(β=0.533,β=-0.362,P均小于0.001)。     

Learning about addiction from the genome

Drug addiction can be defined as the compulsive seeking and taking of a drug despite adverse consequences. Although addiction involves many psychological and social factors, it also represents a biological process: the effects of repeated drug exposure on a vulnerable brain. The sequencing of the human and other mammalian genomes will help us to understand the biology of addiction by enabling us to identify both genes that contribute to individual risk for addiction and those through which drugs cause addiction. We illustrate this potential impact by searching a draft sequence of the human genome for genes related to desensitization of receptors that mediate the actions of drugs of abuse on the nervous system.