Laser beams: knotted threads of darkness

Destructive interference may lead to complete cancellation when light waves travelling in different directions cross, and in three-dimensional space this occurs along lines that are vortices of electromagnetic energy flow. Here we confirm theoretical predictions by experimentally creating combinations of optical laser beams in which these dark threads form stable loops that are linked and knotted.     

金属－氧化物－金属隧道结的光发射

报道通过改进制作工艺，将Ａｌ－Ａｌ２Ｏ３－Ａｕ隧道结的耐压增强到５．３Ｖ，发光外量子效率增强到８．２×１０（－４）均高过迄今见到的关于该类结的最高耐压和最高效率的报道。我们观测到了该发光结上的Ａｕ膜厚度对发射光谱形状的影响，观测到了该光谱的截止频率≈３．２６ｅＶ，峰值≈２．１ｅＶ，并提出了理论解释；特别是利用对该结表面所拍得的ＳＴＭ照片，首次将Ｌａｋｓ－Ｍｉｌｌｓ近似模型用于该光谱峰位的解释。     

水中高压脉冲放电的光辐射研究

目的 研究水中高压脉冲放电的光辐射性质。方法 通过高温计－示波器系统,测量放电的光谱辐射亮度;采用灰体辐射模型,计算放电通道的温度和发射率;结合放电的电特性,分析这一过程中等离子体的光辐射特性。结果 在电容器储能为３１２．５Ｊ、最大峰值电流为５０ｋＡ的条件下,计算得到的最高温度约为５×１０＾４Ｋ。光辐射能量的绝大部分分布在远紫外的范围（１０￣２００ｎｍ）。结论 水中放电的光辐射特性对应于放电的电特     

空间目标的光散射特性研究

利用Modtran大气传输模型计算了不同高度的太阳辐射和傍晚不同时刘的背景辐射．利用基尔霍夫近似法求出雷达散射截面。进而求出双向反射分布函数．通过双向反射分布函数将光辐射的入射照度和目标的散射亮度联系起来．结合目标的几何建模，计算了空中目标在不同位置以及在不同观测站观测时的光谱分布，并与傍晚时刘观测站的背景辐射进行比较。从而确定卫星的最佳观测时间．     

眼点拟微绿球藻在黑暗胁迫下的超补偿生长响应

采用LRH—GⅡ型光照培养箱培养试验藻种,设置了持续黑暗胁迫（分6个强度处理）和间断黑暗胁迫（分4个模式处理）两项试验,研究了眼点拟微绿球藻（Nannochloropsis oculata）在不同环境胁迫下的生理生态变化和该藻种在黑暗胁迫下的超补偿生长响应情况．两个试验的结果均显示,眼点拟微绿球藻在持续黑暗胁迫和间断胁迫后,均表现出明显的超补偿作用现象．黑暗对眼点拟微绿球藻的生长造成显著抑制,但是适当进行黑暗胁迫以后恢复生长,微藻具有更强的生长繁殖能力,细胞净增率最大可达123％．经SSR测验,不同的胁迫方式、胁迫持续时间和胁迫模式与超补偿现象发生时间及强度密切相关。     

Constant darkness is a circadian metabolic signal in mammals

Environmental light is the 'zeitgeber' (time-giver) of circadian behaviour. Constant darkness is considered a 'free-running' circadian state. Mammals encounter constant darkness during hibernation. Ablation of the master clock synchronizer, the suprachiasmatic nucleus, abolishes torpor, a hibernation-like state, implicating the circadian clock in this phenomenon. Here we report a mechanism by which constant darkness regulates the gene expression of fat catabolic enzymes in mice. Genes for murine procolipase (mClps) and pancreatic lipase-related protein 2 (mPlrp2) are activated in a circadian manner in peripheral organs during 12 h dark:12 h dark (DD) but not light-dark (LD) cycles. This mechanism is deregulated in circadian-deficient mPer1-/-/mPer2m/m mice. We identified circadian-regulated 5'-AMP, which is elevated in the blood of DD mice, as a key mediator of this response. Synthetic 5'-AMP induced torpor and mClps expression in LD animals. Torpor induced by metabolic stress was associated with elevated 5'-AMP levels in DD mice. Levels of glucose and non-esterified fatty acid in the blood are reversed in DD and LD mice. Induction of mClps expression by 5'-AMP in LD mice was reciprocally linked to blood glucose levels. Our findings uncover a circadian metabolic rhythm in mammals.     

试从创造意义上谈理解教育

从根本上说，教育就是针对人进行的，而当今的教育视野中“人”正在逐渐消失，缺少了灵性和感悟，缺少了理解，从创造的意义上讲，实行理解教育，能够使人处于一种不断更新的状态中，能够提高人们的意识水平从而使人的个性得到张扬和扩展。     

二维光子晶体波导输出端的能量分布

利用惠更斯原理计算了光通过光子晶体波导入射到真空中的能量分布情况.采用的具体模型是二维正方格子旋转正方空气散射子光子晶体波导(PCW),发现传导模在PCW与真空的分界线上能量分布越发散,在真空中能量传播的越远.而加大线缺陷的宽度可以使能量衰减较为缓慢,所以也可以加大能量传播范围.     

Light interference from single atoms and their mirror images

A single atom emitting single photons is a fundamental source of light. But the characteristics of this light depend strongly on the environment of the atom. For example, if an atom is placed between two mirrors, both the total rate and the spectral composition of the spontaneous emission can be modified. Such effects have been observed using various systems: molecules deposited on mirrors, dye molecules in an optical cavity, an atom beam traversing a two-mirror optical resonator, single atoms traversing a microwave cavity and a single trapped electron. A related and equally fundamental phenomenon is the optical interaction between two atoms of the same kind when their separation is comparable to their emission wavelength. In this situation, light emitted by one atom may be reabsorbed by the other, leading to cooperative processes in the emission. Here we observe these phenomena with high visibility by using one or two single atom(s), a collimating lens and a mirror, and by recording the individual photons scattered by the atom(s). Our experiments highlight the intimate connection between one-atom and two-atom effects, and allow their continuous observation using the same apparatus.     

松根轻油—苯酚—甲醛共聚合的研究

研究了松根轻油—苯酚—甲醛的共聚合过程,合成出性能优良的松根轻油酚醛树脂。利用红外光谱、核磁共振、质谱分析与元素分析等对松根轻油酚醛树脂的分子结构及基本性能进行测试,并探讨了共聚反应的机理。测试结果表明:松根轻油酚醛树脂具有高软化点、高油溶性等优良性能,可溶于多种有机溶剂;其生产工艺简便,原料成本低廉,具有较高的实际应用价值。     

生物组织对偏振光背向散射Mueller矩阵的分布

用Stokes矢量描述光的偏振状态,光学器件对光的作用,用相应的Mueller矩阵表示,根据散射介质的对称性,从理论上推导出了生物组织背向散射Mueller矩阵的分布,对球形粒子组成的散射介质,画出了各Mueller矩阵元随方位角的分布图,与相应的实验结果进行了比较,结果表明,由球形散射粒子组成的不同粒子直径、不同浓度的散射介质,其背向散射Mueller矩阵的分布花样具有相似性,要区分各散射介质中散射粒子的大小、浓度等特征,必须细致的研究散射介质背向散射Mueller矩阵分布花样强度随径向的变化.     

持续黑暗状态下对大鼠松果体细胞分泌松果体素的昼夜节律研究

为研究体外培养的大鼠松果体细胞分泌的松果体素是否具有内在节律,收集体外培养的大鼠松果体细胞在白天6∶00,8∶00,10∶00,12∶00,15∶00,和夜晚18∶00,20∶00,22∶00,1∶00,4∶00各个时间点的培养上清,并用放射免疫方法(RIA)检测各个时间点松果体细胞培养上清中的松果体素水平.CCF(complex cosine function)统计分析结果表明,在持续黑暗的环境下,体外培养的大鼠松果体细胞分泌的松果体素在培养3,6,9天后仍然表现出内在节律.然而,这种内在节律在培养12天后消失.上述结果提示体外培养的大鼠松果体细胞可以作为一个有用的体外模型来分析节律系统的生理基础.     

松根轻油—苯乙烯阳离子共聚合的研究

本文对精制松根轻油—苯乙烯的阳离子共聚合进行研究,系统地考察了该共聚合体系的各个主要影响因素,优选出适宜的共聚合条件。该共聚树脂的产率可达82％,其中,固态树脂的产率可达67％。通过对主原料(松根轻油,沸点110～200℃)的色谱—质谱联用分析和对松根轻油—苯乙烯共聚树脂的红外光谱分析,可确认该树脂为萜烯—苯乙烯共聚树脂,进而可推测出其分子结构。该共聚树脂为芳香族改性萜烯树脂,可用作热熔胶的增粘树脂在胶粘剂工业中推广应用。     

Light echoes from ancient supernovae in the Large Magellanic Cloud

The light from historical supernovae could in principle still be visible as scattered-light echoes centuries after the explosion. The detection of light echoes could allow us to pinpoint the supernova event both in position and age and, most importantly, permit the acquisition of spectra to determine the 'type' of the supernova centuries after the direct light from the explosion first reached Earth. Although echoes have been discovered around some nearby extragalactic supernovae, targeted searches have not found any echoes in the regions of historical Galactic supernovae. Here we report three faint variable-surface-brightness complexes with high apparent proper motions pointing back to three of the six smallest (and probably youngest) previously catalogued supernova remnants in the Large Magellanic Cloud, which are believed to have been thermonuclear (type Ia) supernovae. Using the distance and apparent proper motions of these echo arcs, we estimate ages of 610 and 410 years for two of them.     

液化天然气中轻烃分离工艺的优化设计

根据液化天然气(LNG)冷量的特性,按照冷量梯级利用的原则,设计了一种新的LNG轻烃分离流程,其特征在于轻烃分离过程不需要使用压缩机,能耗较低,而且可利用LNG的冷量将一部分分离完轻烃的甲烷再液化过冷并低压液相储存,使轻烃分离流程具有供气调峰功能,同时使分离获得的轻烃产品保持低压液相,方便产品的储运和销售.文中还以深圳项目进口的3.7×106t/a澳大利亚LNG为例,利用此流程进行轻烃分离的模拟计算.结果表明:相对现有工艺,新流程功耗降低47.3%,脱甲烷塔的热负荷降低27.3%,且能够将20%左右的甲烷低压储存用于供气调峰,经济效益明显;如将获得的C2 轻烃替代石脑油用于裂解制乙烯,可以降低乙烯装置的投资、生产能耗及成本.     

平班水电站运用"黑启动"的可行性

“黑启动”是在电网崩溃的时候，机纽能在第一时间反应，迅速启动，使整个电网恢复供电，弥补电力系统的损失．平班水电站有运用“黑启动”的诸多优越性。