科学思想的火花照亮人类智慧的星空

 当暴风雨即将来临的时候,满天阴霾,空气沉闷,正所谓"山雨欲来风满楼,黑云压城城欲摧"。突然,一声霹雳,一道强光划破长空,照得天空和大地无比灿烂。天上的云层,地上的山水,像水洗过一样,尽收眼底。这就是闪电,是云层与云层之间,云层与大地之间由火花放电产生的巨大的电火花。     

暴涨——宇宙年少时

热大爆炸宇宙学的成功：宇宙学的标准模型 工业上一种产品的成功,莫过于成为业界的标准。同样地,科学中一个理论的成功,莫过于被誉为标准模型。热大爆炸宇宙学,正是这样一个标准模型。在介绍今天故事的重点——暴涨之前,让我们回顾一下,作为现代宇宙学的标准模型,热大爆炸宇宙学,如何描述宇宙的现状、过去和未来。我们的宇宙,从诞生至今,已经有137亿岁了。这相当于人类几千年文明史的几百万倍。宇宙浩瀚无垠,当今科学尚不能确定整个宇宙空间的大小,是有限还是无限。然而,我们能观测到的宇宙总是有限的。     

光:你是诗情,你是画意

 对于光,我的感情最深。每天清晨起床后,我的第一件事,就是掀开窗帘,看看阳光怎么样。如果是艳阳东升,我会很兴奋;如果是蓝天白云,我会高兴得手舞足蹈,把大家叫起来观天,让全家人分享这快乐。对光的痴情,来自我的爱好--风光摄影,它是光与影的艺术。在我心里,光,最有诗情,也最有画意。     

酒引发超导电性

 在谈论酗酒时,酒常常与物理学有关。但现在酒似乎对某些超导体有直接作用。日本筑波的国家材料科学研究所的Keita Deguchi 与他的同事表明,热的酒精饮料对硫化碲铁(Iron Tellurium Sulphide)材料能引发超导电性。
啤酒,传统的日本的低度和高度米酒,威士忌酒和白葡萄酒都有效应,但用红葡萄酒加热24 小时,获得最好的效果。有关的机制尚不得而知。也许,酒对材料提供了氧原子,但纯的乙醇与水的混合以及普通饮料则不起作用。把材料曝露在空气中几个月,也有效应。这与酒精饮料处理材料十分不同。由于今年是超导电性发现100 周年纪念,所以,值得用香槟酒作进一步研究。     

电磁辐射与电磁污染

 1831年,英国物理学家法拉第发现了电磁感应现象。到了19世纪80年代,人们利用电磁感应原理,建立起世界上第一座发电站。从此,人类便大步迈进了电磁辐射的应用时代。现在我们已经知道,电磁作用力是自然界四种基本相互作用力之一。地球上生命的起源与繁殖,完全依赖于太阳辐射的能量。我们不仅依靠阳光中的红外线获得温暖,而且还以可见光提供照明,方便生活,体味五彩斑斓的世界。从科学角度来讲,没有阳光,就没有人类所需要的各种食物,人类就难以生存。当前,电视、电话、手机、电脑、因特网及绿色能源等科技成果,已深入到我们工作和生活的方方面面。     

和风细雨 润物无声EI北大核心CSCD

桃李不言,下自成蹊。谨以此文纪念徐叙瑢先生逝世一周年。谨此记录我与先生的一段师生情缘,怀念先生传道授业解惑的和风细雨,感悟先生勉励后学的润物无声。我与先生结缘于1992年,在春暖花开的4月,刚刚通过了长春物理所研究生复试之后。当时身为中学物理教师的我对研究生这个概念心存神秘,心向往之。心目中的院士,简直深不可测、更是高山仰止。     

穷酸的西南联大与3位诺贝尔奖得主——真正意义上的世界一流大学

西南联大的历史,前后不过8年半（1937年9月至1946年5月）。当年的物质条件可够穷酸的：学生宿舍无一砖一瓦,全是夯黄土为墙,堆茅草为顶,窗户没有一块玻璃,仅有几根树枝聊以象征。绝大多数师生经常是食不果腹,衣不蔽体,不时还要在敌机轰炸下逃生。在校学生不超过2000。可是当年的西南联大,在三不管的地方,坚守大学理想。主张“教授是大学的灵魂”,实行“不妄用一钱,     

捕捉引力波

 一、足够精确的牛顿引力理论在宏观物理世界中,引力是一种主要的作用。太阳东升西坠,地球四季交替,海水潮涨潮落,众多自然现象都受到引力的支配。1687年,牛顿在前人的研究基础上,导出了万有引力定律。利用万有引力定律可以圆满地解释哥白尼的学说和开普勒的行星运动三定律。牛顿引力理论的精彩之处还有准确地预言了海王星和冥王星的存在,指导天文学家成功地发现了这两颗太阳行星。按牛顿的引力理论,两物体间的引力作用是瞬间完成的。但爱因斯坦认为,光速是任何作用的极限速度,因此引力作用不可能在瞬间实现。1905年,爱因斯坦发表著名的历史文献《论动体的电动力学》,建立了狭义相对论。在以后     

伟大变革呼唤科普

 科学技术是推动人类社会前进的最高意义上的革命力量。中国正面临伟大的变革,中国的伟大变革呼唤着科学技术,更呼唤着科学技术的普及。科学是现代技术的发源地,现代科学是推动高技术产生的基础。发展科学事业是科学家的职责。他们从事科学研究,探索自然界的规律,推动人类的文明与进步。同样,科技普及工作也是科学家的职责。     

激光诱导击穿光谱技术快速探测煤灰中的重金属锌

煤灰的成分指的是煤中矿物质的完全燃烧,产生各种金属和非金属氧化物和盐,这是使用煤时的重要参数。煤被广泛用于生产和人民生活,作为重要的能源物质。大量来自燃煤燃烧的煤尘（煤灰）被释放到大气中并与大气中的各种物质相互作用而形成雾霾。煤灰中的金属氧化物和空气中的小液滴之间发生一系列物理化学反应,这导致了雾霾的形成。在实验中,采用激光诱导击穿光谱（LIBS）分析煤灰中的元素。实验样品由某钢铁公司提供,分为七个样品,并标上序号。样品分别加入蒸馏水和0.1‰,0.2‰,0.2％,0.4％,0.8％,1％硫酸锌溶液,分别用1～7号标记。为了获得更好的LIBS信号,样品被研磨为粉末状,并使用蒸馏水使硫酸锌与煤灰充分混合。通过使用压片机将煤灰压制成10 mm直径和10 mm厚的煤灰块。为获得准确的元素结果,X射线荧光光谱也被用作参考,并且原始样品不含锌元素。由于光谱分析和波长漂移现象的不确定性,因此实验中,分别选择了铁,钙,钛和铝四种高纯单质。在相同的实验条件下,将四条测量的元素谱线与NIST原子光谱数据库中相应的谱图比较。实验中的所有光谱根据波长差或偏移进行校正。此时,纯单质的元素谱线可以与样品的光谱对齐。当元素谱中的特征线与样品中的谱线对齐时,样品就可以被识别和确认。由于铝元素与目标元素具有相似的化学和物理性质,铝元素是煤灰和地壳中的主要元素之一,具有中等的光谱强度。因此将铝元素作为内标元素,运用内标校准方法来确定样品中锌的浓度。模拟含锌大气气溶胶是通过向煤灰中添加含锌元素来实现的。还有一些其他的金属元素,包括铁,钙,锰,钛和铝也被用来加入煤灰中,用以模拟大气气溶胶。两种方法的相对差异分别为1.78％,3.39％,5.17％,0.20％。造成差异的原因可能是由于光谱仪缺乏分辨率或背景噪声的影响,这是可能导致测量误差的原因之一。由于实验室条件的限制,无法确定基底是否会影响实验结果,这将在未来的实验中得到进一步的证实。实验拟合曲线测得煤灰中锌的线性相关系数为0.995 72,这表明可以通过粗略估算锌的激光强度来估计煤灰中的锌含量的实现。实验结果证明LIBS技术可用于煤灰中金属元素的快速检测,为基于锌含量的大气环境检测提供了一种新方法。在建立元素的校准曲线后,LIBS技术将来可以用来进行更快速,更准确的定量分析。     

Dynamics of a waveguide pulsed-periodic CO2 laser with loss modulation

The nonlinear dynamics of a waveguide CO₂ laser with combined periodic loss and pumping modulation is investigated theoretically and experimentally. The possibilities of controlling time and energy parameters of the output radiation using the corresponding selection of the detuning of the cavity's longitudinal mode from the center of the amplification line, the amplitude, and the frequency of loss modulation are demonstrated. The observed asymmetric dependence of the lasing-radiation density on the detuning of the cavity frequency is explained by the attendant modulation of the refractive index of the loss modulator. To whom correspondence should be addressed. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 471–478, July–August, 1999.     

Hardware and software for the automating atomic-absorption spectrometers AAS, S115, and saturn

We describe a modified GELIOS System intended to automate the atomic-absorption spectrometers AAS, S115, SATURN, and Perkin-Elmer 503. Software is prepared in the visual environment of programming DELFI-3 and functions under the control of Windows 95. A distinguishing feature of the GELIOS System is simultaneous search for the peak and area of the absorption signal, correction of the errors of measurements, automatic digital filtration of data, control of the time of operation of hollow-cathode lamps, measurement of spectra and the statistical resource of the service life of hollow-cathode lamps, use of different methods to construct a calibrating graph, the possibility of memorizing the data of the analysis in an archived file, and a formation of the report for printing. The system contains an electrovic data directory on atomicabsorption analysis in five volumes for 67 elements of the Mendeleev system. To whom correspondence should be addressed. “University” Science and Production Center, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 734–737, September–October, 1999.     

基于高光谱技术的酸奶中常见致病菌的快速鉴别及计数

酸奶是一种发酵型乳制品饮料,因其特殊的功能性和良好的口感而广受欢迎。但由于商业链的不正当运行,如奶源非法获取、灭菌不充分等原因,导致酸奶中致病菌大量滋生,酸奶中毒事件频繁发生。酸奶中常见的致病菌主要有大肠杆菌、金黄色葡萄球菌和沙门氏菌,这三种致病菌由人体摄入并达到一定的数量时会产生腹痛、腹泻等严重的消化道疾病,并且会破坏人体肠道内的正常菌群平衡,因此国标对奶制品中这三种致病菌的数量已有明确的限量规定。由于酸奶的主要消费对象为老人和小孩,故其潜在危害不容小觑。传统菌落检测方法虽具有简单,灵敏、可操作性强等优点,但当不同菌落混杂在一起时无法同时进行定性定量的检测,且具有试剂成本高,检测周期长,人为因素影响较大等缺点。因此开发一种快速、简单、准确的混合鉴定计数方法为避免致病菌对酸奶的潜在危害提供了有效的途径。高光谱技术同时包含样本的光谱信息与图像信息,既能够根据化学组分的微小变化进行精确识别（光谱信息）,又能够反映出菌株在外部多层次的变化（图像信息）。因此该研究尝试对比高光谱图像技术和光谱技术,采用模式识别的方法,对比不同的模型识别结果,优选出最佳识别率的识别模型作为计数模型,最后通过最佳鉴别计数模型的识别分类结果来达到对酸奶中常见致病菌鉴定计数的目的。首先,购买酸奶中常见的乳酸菌种（保加利亚乳杆菌、嗜热链球菌、嗜酸乳杆菌、干酪乳杆菌、植物乳杆菌）和潜在污染的致病菌种（金黄色葡萄球菌、大肠杆菌、沙门氏菌）等标准菌株进行培养,提取经过48 h培养后的菌落图像信息和光谱信息。采用几种不同的预处理方式（SNV,MC,MSC,1stDER,2ndDER）对所提取的光谱数据进行预处理,并应用遗传算法筛除光谱数据中冗余的波段,保留有效波段。利用图像处理技术对图像信息中的菌株与培养基背景进行去除,然后采用主成分分析法从每幅图中优选出3个特征波长,并运用图像处理技术从特征波长所对应图像中提取菌株的18个基于GLCM的纹理特征信息。挑选合适的主成分分别建立不同的鉴别模型（LDA,KNN,BP-ANN,LS-SVM）,通过其最终的鉴别模型的识别率来确定最佳鉴别计数模型。最后从标准菌株中分别挑选出30株进行计数测试,通过比较模式识别的分类数量结果与菌株的实际数量来验证模式识别效果的准确率。研究表明,运用SNV预处理后光谱数据在提高信噪比效果上明显优于其他几种预处理方式。745.790 8,773.098 4和779.207 0 nm为图像信息中方差贡献率最大的三个波长,运用从特征波长所对应的图像中所提取的纹理特征信息建立图像识别模型。通过对比图像信息和光谱信息的模式识别结果发现,光谱特征鉴别模型普遍优于图像纹理特征鉴别模型,且当主成分数为9时,运用光谱特征所建立的LS-SVM模型的校正集识别率为96.25%,预测集的识别率为91.88%,为最优模型。采用优选的最优模型对菌株进行识别计数,大肠杆菌计数的相对误差为3.33%,金黄色葡萄球菌和沙门氏菌计数的相对误差均为0,验证了高光谱技术应用于酸奶中常见致病菌的鉴别计数的可行性。     

Fluorescence of free complex molecules

A number of phenomena that determine the nature of the fluorescence of free complex molecules and the possibility of its analytical application are considered. Attention is specially paid to the specific features of the energetics of radiationless transitions, the role of statistical factors in the formation of spectral properties and the interrelationship among the luminescence-spectrum characteristics of rarefied vapors of complicated molecules, and the processes of energy transfer in collisions. The properties of polarized fluorescence of hot and jet-cooled vapors, the processes of relaxation of anisotropy in time and during collision reorientation, and transfer of anisotropy in photodisintegration are analyzed. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 5, pp. 620–634, September–October, 1998.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Influence of nonplanar distortions of the tetrapyrrole macroring on the electronic states of porphyrin dications

Quantum-chemical calculations of the excited electronic states of a porphyrin dication have been performed by the CNDO/S method for different angles determining the saddle-like and ruffled distortions of the porphyrin macroring. It is shown that saddle-like distortions arising as a result of a tilt of the pyrrole rings have a significant influence on the energies of the molecular orbitals and energies of the excited electronic states of porphyrin molecules, especially on the oscillator strength of the G→Q transition. The results of the calculations performed are in good agreement with the experimental spectra of porphyrin dications. To whom correspondence should be addressed. Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 559–562, July–August, 1999.     

Ice internal friction: Standard theoretical perspectives on friction codified,adapted for the unusual rheology of ice,and unified

Sea ice contains flaws including frictional contacts. We aim to describe quantitatively the mechanics of those contacts, providing local physics for geophysical models. With a focus on the internal friction of ice, we review standard micro-mechanical models of friction. The solid's deformation under normal load may be ductile or elastic. The shear failure of the contact may be by ductile flow, brittle fracture, or melting and hydrodynamic lubrication. Combinations of these give a total of six rheological models. When the material under study is ice, several of the rheological parameters in the standard models are not constant, but depend on the temperature of the bulk, on the normal stress under which samples are pressed together, or on the sliding velocity and acceleration. This has the effect of making the shear stress required for sliding dependent on sliding velocity, acceleration, and temperature. In some cases, it also perturbs the exponent in the normal-stress dependence of that shear stress away from the value that applies to most materials.

We unify the models by a principle of maximum displacement for normal deformation, and of minimum stress for shear failure, reducing the controversy over the mechanism of internal friction in ice to the choice of values of four parameters in a single model. The four parameters represent, for a typical asperity contact, the sliding distance required to expel melt-water, the sliding distance required to break contact, the normal strain in the asperity, and the thickness of any ductile shear zone.     

光谱法锌离子检测系统的研究

采取标准锌显色剂与锌发生显色反应，生成不溶于水的絮状络合物。用光谱仪测它的吸光度，研究其特征谱与吸光度的特点，建立其浓度与特征波长吸光度间的数学模型。本文所采用的显色剂主要与锌、铜、镉、镍四种离子发生络合反应。因此分别探索了四种离子高浓度以及低浓度时显色反应的吸光度，最终通过得到锌离子浓度与吸光度的关系式以及锌离子浓度与四波长下四种离子混合溶液显色后的吸光度的关系式，给出了锌离子的吸光度与总吸光度的关系式。显色反应能否满足分光光度法的要求，主要与显色剂的性质有关，同时显色反应的条件也至关重要。因为在显色反应过程中，主要是锌离子与锌显色剂发生络合反应形成络离子，进而形成絮状络合物。络离子一般比较稳定，但在水溶液中也存在着电离平衡，也就是说当显色条件发生变化时，既有可能形成络离子，也有可能发生络离子的分解，从而影响络合反应的程度。显色条件包括显色剂用量、pH值、反应温度、显色时间、待测溶液的盐度以及浊度等。重点研究待测溶液的盐度对锌离子浓度测量值的影响，并通过实验给出影响规律以及校正模型。     

Silicon Porosification: State of the Art

This review is devoted to the analysis of the problems related to fabrication of the Si porous layers. The review was motivated by a great interest to Si-based porous materials from nano- to macro-scale for various applications in electronics, optoelectronics, photonics, chemical sensors, biosensors, etc. The peculiarities of the silicon porosification and the principles of preparing porous layers are considered in the present article. Various methods used for Si porosification such as chemical stain etching, chemical vapor etching, laser-induced etching, metal-assisted etching, spark processing and reactive ion (plasma) etching were analyzed. However, the main attention was focused on electrochemical porosification of Si. The review discusses in detail the influence of parameters such as electrolyte composition and pH, current density, etching time, temperature, wafer doping and orientation, lighting, magnetic field, and ultrasonic agitation on the process of Si porosification. It was shown that the structure of porous silicon strongly depends on both technological parameters of electrochemical etching and the parameters of the semiconductor subject to treatment. This review also addresses the main properties of porous silicon, porous multilayer and 3D structure formation, oxidation of porous Si, release of the porous layer, drying, storage, etching, filling and surface functionalizing of porous Si. Features of III-V compound porosification are also briefly analyzed.     

ICP-AES测定铜电解液中的Fe、Ni、Pb、Bi、Sb、Zn和As

利用ICP-AES分析技术,通过对样品处理、元素分析谱线、酸度等因素进行试验研究,综合确定了分析条件,对铜电解液中杂质元素（Fe、Ni、Pb、Bi、Sb、Zn、As）进行了ICP-AES测定。结果表明,ICP-AES测定铜电解液中Fe、Ni、Pb、Bi、Sb、Zn和As,可以满足铜电解生产的需要,为高纯阴极铜的生产起了指导作用。