Effect of ausforming temperature and strain on the bainitic transformation kinetics of a low carbon boron steel

The effect of ausforming temperature and strain on the bainitic transformation kinetics was investigated in a low carbon boron steel. A new mechanism, which is based on the competition between the increase in nucleation rate and the decrease in average volume of bainite sheaf after deformation, is proposed. The increase in nucleation rate is due to the decrease in boron concentration at the grain boundaries after small deformation and the formation of sub-grain boundaries at the grain interior after large deformation. The decrease in average volume of bainite sheaf is ascribed to the frequent impingement of bainite sub-units after deformation. The increase in nucleation rate after deformation results in the decrease in incubation time, which is confirmed from the experiment. The increase in nucleation rate overcomes the decrease in average volume of bainite sheaf, resulting in the increase in transformation velocity and volume fraction after small deformation. On the contrary, the decrease in the average volume of bainite sheaf overcomes the increase in nucleation rate after large deformation, leading to the decrease in transformation velocity and volume fraction of bainite.     

Waveguide modes of 1D photonic crystals in a transverse magnetic field

We analyze waveguide modes in 1D photonic crystals containing layers magnetized in the plane. It is shown that the magnetooptical nonreciprocity effect emerges in such structures during the propagation of waveguide modes along the layers and perpendicularly to the magnetization. This effect involves a change in the phase velocity of the mode upon reversal of the direction of magnetization. Comparison of the effects in a nonmagnetic photonic crystal with an additional magnetic layer and in a photonic crystal with magnetic layers shows that the magnitude of this effect is several times larger in the former case in spite of the fact that the electromagnetic field of the modes in the latter case is localized in magnetic regions more strongly. This is associated with asymmetry of the dielectric layers contacting with the magnetic layer in the former case. This effect is important for controlling waveguide structure modes with the help of an external magnetic field.     

CPL技术在空间飞行器上的应用

本文对ＣＰＬ技术进行了简要概述,介绍了其工作原理与工作特性,并讨论了ＣＰＬ技术在空间飞行器上的可能应用方式。其中,对ＣＰＬ技术应用于空间设备的散热进行了全面阐述,并给予理论分析;此外,对ＣＰＬ技术应用于空间设备的主动热控制,也作了简要介绍;对ＣＰＬ技术未来有发展前景的应用方式进行了展望。     

Influence of X-ray on the autophagic-lysosomal system in rat pancreatic acini

Lysosomes have an important role in radiation injury of cells and tissues. Activation of autophagy is frequently observed in different types of pathological tissue degeneration. In radiation response it increases in some cases, and lysosomes are responsible for regulated degradation of the autophagic vacuoles. Lysosomes are also involved in ionizing radiation induced cell death. In apoptosis lysosomes degrade content of the phagocytotic vacuoles derived from engulfed apoptotic blebs. On the other hand lysosomal enzymes discharged from disintegrated cells have a key role in induction of necrotic changes. In this work we investigate autophagy and lysosomal protein degradation in the relatively radiation insensitive exocrine pancreatic acini in vivo and in vitro. Type of cell death induced by X-ray was also examined in relation to the changes of the lysosomal processes. In 5h after 16 Gy in vivo whole body irradiation we observed significant increase in the cytoplasmic volume fraction of autophagic vacuoles and in the number of apoptotic cells in vivo. But in the acini isolated from irradiated rats we could not detect a change in the lysosomal degradation of intracellular proteins. Therefore irradiation probably influences the autophagy in an earlier step than lysosomal degradation. Extended necrotic lesions were not observed in vivo as long as 48 h. Isolated pancreatic acini usually contain more autophagic vacuoles than in vivo, but we could not observe additional increase in autophagy after 8 Gy, in vitro irradiation. Lysosomal degradation of intracellular proteins was also unaltered after 8 Gy, in vitro irradiation. Other biochemical functional parameters of the isolated pancreatic acini, like protein synthesis and amylase secretion were not changed either after 8 Gy, in vitro X-ray treatment. These results indicate that pancreatic acinar cells in vitro have a high tolerance to irradiation. The observed in vivo radiation induced changes of the exocrine pancreas are possibly indirectly induced by injuries of more sensitive mechanisms.     

降雨对无线激光通信的影响

通过激光信号在雨介质中传输的实验发现,在大雨环境下,激光信号透射率要比在小雨或微雨的情况下大。这说明光信号在小雨时衰减较大,在大雨时衰减较小。这一现象与人们通常所认为的有所不同。针对降雨对激光信号的影响,根据Mie散射理论和Weibull雨滴尺寸分布模型,分析了不同尺寸的粒子对光的散射作用以及对衰减效率因子的影响,推导出单球粒子对光波的衰减公式,得到了衰减与降雨率的确定关系。通过数值计算发现,与小粒子相比大粒子的前向散射光强更大且更加集中;激光信号在雨介质中传输时,衰减系数在小雨时较大,中雨、大雨时较小,暴雨时不断增大。这一结果与实际情况较吻合,为激光在通信系统中的应用提供了一定的理论依据。     

Thermodynamically equilibrium roton states of nanoparticles in molten and vapour phases

We show a possibility for a thermodynamically equilibrium nanocrystalline structure consisting of nanosized solid inclusions to appear in a melt just beyond the melting curve. Thermodynamic stability of the nanocrystalline structure in the melt results from the free energy lowering due to rotational motion of nanoparticles. The main contribution to the reduction of the free energy of the system is due to an increase in the rotational entropy and change in formation energy of nanocrystals, i.e. the nanocrystalline structure in the melt, like vacancies in a crystal, is an equilibrium defect structure of the melt. It is demonstrated that similar nanocrystalline structures can also appear in the vapour phase in the form of liquid nanodrops and in liquid solutions, e.g. in He II.     

Certain general questions of fast-electron transport II. Kinetic equations and conditions governing the accelerated motion of fast electrons in dielectrics in an electric field

A general kinetic equation for the differential density of fast particles moving in a medium in an external field is derived on the basis of the continuity equation in phase space. An equation is written for the differential flux in the case of fixed target particles. This equation is used to derive equations for fast electrons; account is taken of the coupling of energy-loss and scattering events in an electric field for various particular problems analogous to those studied in the theory of electron transport in the absence of a field. The kinetic equations are used to analyze the conditions governing accelerated motion of electrons in a dielectric in an external electric field in the continuous-deceleration approximation. Account is taken of fluctuations in the energy loss and of multiple scattering. There are two energy ranges of particles moving in a dielectric in which accelerated motion can occur; in the case of an electron beam with a continuous energy spectrum, this acceleration would be accompanied by monochromatization of the beam.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 7–12, February, 1972.     

Photostability of a C<Subscript>60</Subscript> fullerene coating as a solid-phase photosensitizer of singlet oxygen

The stability of the optical properties and the generation efficiency of singlet oxygen of a solidphase photosensitizer based on fullerene in an aqueous suspension subjected to prolonged intense irradiation with visible light are studied in comparison with a photosensitizer based on methylene blue in an aqueous solution. Changes in the absorption spectra show that, as a result of 20-min irradiation, the content of fullerene decreases by 2% from its initial value, while that of methylene blue decreases by 19%. In both cases, the dynamics of the decrease in the photosensitizing ability of the photosensitizers in the course of their irradiation correlates with the changes in their spectra, but the magnitude of this decrease in the case of the solid-phase photosensitizer is greater than the magnitude of its spectral changes because of the surface nature of the photosensitization process. The study of the absorption spectra of fullerene coatings shows that their irradiation in water or in air causes the same photodegradation of fullerene. At the same time, studies with the help of the electron spin resonance (ESR) technique reveal differences in the nature of processes undergone by fullerene in water and in air.     

Technological applications of Mössbauer spectroscopy

A brief review is given of some recent industrial applications of Mossbauer spectroscopy. One of the most desirable futures of the Mossbauer effect is the feasibility of performing in situ measurements. Such measurements are extremely important especially in the upgrading of coal derived liquids. Such applications have been very successful in understanding the role of iron sulfides stoichiometries in direct coal liquefaction. The use of in situ techniques in invaluable in the investigation of the metal support interaction and their relation to carburization processes in Fischer-Tropsch reactions. Some examples of such applications will be presented in this paper. In this paper, emphasis will be placed in the use of a multiple technique approach to elucidate scientific problems of industrial importance.     

Changes in ADC caused by tensile loading of rabbit achilles tendon: evidence for water transport

Water diffusion measurements were performed on rabbit Achilles tendons during static tensile loading and tendons in an unloaded state. The apparent diffusion coefficient (ADC) was measured along two directions: parallel and perpendicular to the long axis of the tendon. Tendons were studied after being prepared in two ways: (a) after being stored frozen in phosphate-buffered saline (PBS) and (b) freshly isolated. Statistically significant directional anisotropy was observed in the ADC in all tendons. The ADC was significantly greater in the direction parallel to the long axis of the tendon than in the perpendicular direction. The anisotropy is attributed to the greater restrictions seen by the water molecules in the perpendicular direction and is consistent with the known geometry of the tendon. Storage in PBS caused tendons to swell. This increased the ADC measured along both directions and reduced the anisotropy. The existence of anisotropy in the ADC was not related to the orientation of the specimen in the magnet. The ADC increased along both directions following the application of a 5-N tensile load; the increase was greatest along the perpendicular axis of the tendon. In order to determine whether load-related changes in the ADC reflected changes in interfibrilar spacing, we used electron microscopy to measure load-related changes in fibril spacing. Load-related changes in fiber spacing could not account for the observed changes in the ADC. The increase in ADC caused by loading was attributed to the extrusion of tendon water into a bulk phase along the outside surface of the tendon. In PBS-stored samples, enough fluid was extruded that it could be visualized. The transient response of the ADC to a 5-N tensile load was also studied. The absolute ADC in both directions increased with loading and recovered to baseline upon unloading. The transient changes in ADC, for both loading and unloading, had a mean time constant of approximately 15 min. The magnitude of the load-induced transient ADC changes was comparable to that seen in the static-loading experiments.     

Dispersion behavior of electromagnetic wave near the resonance in 1D magnetized ferrite photonic crystals

In the present article, we have analyzed the dispersion of electromagnetic wave in the one dimensional magnetized ferrite photonic crystals near the resonance in the permeability of the constituent materials for transverse magnetization in the transverse electric mode. The dispersion relation is obtained by transfer matrix method. It is observed that in the vicinity of resonant frequency, large numbers of oscillations occur in the normalized Bloch wave number. These oscillations in the Bloch wave number are strongly dependent on external magnetic fields, filling factor, and damping constant. The frequency regime of these oscillations is found to be shifted in higher frequency range with increase in the magnitude of the magnetic fields. With increase in the filling factor keeping length of periods fixed, number of oscillations is found to be increased. Near the resonance, effect of incident angle is negligible. It is demonstrated that these nearly equidistant oscillations occurring in the vicinity of resonance may be used for making filter in micro wave frequency range.     

Self-assembled monolayer resists and nanoscale lithography of silicon dioxide thin films by chemically enhanced vapor etching (CEVE)

We report on the use of electron-beam exposed monolayers of undecylenic acid in the etch rate enhancement of silicon dioxide films in HF vapor for the formation of nanoscale features in the oxide. Variations of the etching characteristics with electron beam parameters are examined and the results analyzed in terms of proposed models of the etching mechanism. Apparent variations in the relative concentrations of etch initiator with the thermal history of the samples prior to etching provides support for the dominant etch initiator within this system as the carboxylic acid moiety bound at the oxide surface. Other variations in the etching characteristics are discussed in terms of differences in localized concentrations of hydrocarbon crosslinks and the effect that this has upon the etch initiation. The process has been employed in the production of features in silicon dioxide surface masks with sizes down to 50 nm.     

微波消解-ICP-AES测定鄱阳湖流域沉积物中微量元素

为了研究鄱阳湖沉积物中微量元素近几年来随季节、年度及沿程的变化情况,对2003年和2005年不同季节采集的鄱阳湖流域各采样点底泥进行了ICP-AES测定.结果表明,鄱阳湖沉积物中各元素的含量随着季节和年度变化而发生一定改变,枯水期普遍大于丰水期;南矶山2005年Cu和Pb含量较2003年有所降低;蔡家湾则与南矶山相反;姚公渡2005年Cu含量也较2003年低,Pb含量则高于2003年;与鄱阳湖流域底泥背景值相比,所测几个样点的Cu,Pb,Cr和Zn含量均在一定程度上超标;除大坞河外,其余各样点As含量均在背景值范围内;从饶河到鄱阳湖入湖口处,各元素含量呈逐渐降低趋势.文章提出的研究方法操作简便,效率高,劳动强度低.     

Vortices in Low-Dimensional Magnetic Systems

Vortices are objects that are important to describe several physical phenomena. There are many examples of such objects in nature as in a large variety of physical situations like in fluid dynamics, superconductivity, magnetism, and biology. Historically, the interest in magnetic vortex-like excitations begun in the 1960s. That interest was mainly associated with an unusual phase-transition phenomenon in two-dimensional magnetic systems. More recently, direct experimental evidence for the existence of magnetic vortex states in nano-disks was found. The interest in such model was renewed due to the possibility of the use of magnetic nano-disks as bit elements in nano-scale memory devices. The goal of this study is to review some key points for the understanding of the vortex behavior and the progress that have been done in the study of vortices in low-dimensional magnetic systems.     

梯度磁场作用下光纤中磁流体光透射特性研究的建模与分析

对光纤中磁流体在梯度磁场作用下的光透射特性进行了研究,提出光纤中磁流体的光透射率变化主要来源于梯度磁场引起的磁流体密度分布变化。根据郎之万函数和流体理论,推导了光纤中磁流体在梯度磁场作用下的密度分布,并根据Beer-Lambert定律,得到磁流体光功率透射衰减和纳米粒子局部密度的关系,从而建立光纤中磁流体在梯度磁场作用下光透射特性的理论模型。进而对光纤中磁流体在不同梯度磁场作用下的光透射功率进行数值分析,得到不同磁场强度和磁场梯度下光纤中磁流体透射功率的变化规律。最后将数值分析的结果和实验数据进行对比,验证了模型的合理性, 同时也验证了梯度磁场作用下磁流体光透射功率的变化主要来源于磁流体密度分布变化的推论。     

忽地笑鳞茎中总生物碱含量的月动态变化

采用紫外分光光度法测定了不同月份忽地笑鳞茎中总生物碱含量,为确定适宜的采收时间提供实验依据。结果表明,忽地笑鳞茎中总生物碱含量随生长发育时期或月份不同存在一定差异,其中11月的最高,12月次之,1月的最低,最高值与最低值相比,约为2.6倍,差异达极显著水平(P<0.01)。精密度、稳定性实验及回收率等方法学考察表明,紫外分光光度法测定忽地笑鳞茎中总生物碱含量效果好,稳定性强,方法可靠。综合忽地笑鳞茎中总生物碱含量、中药材产量和土地利用率等因素考虑,以11月底前后采收比较适宜。     

Influence of the type of light polarization on photoinduced processes

We investigate the influence of the type of light polarization (linear or circular) on the efficiency of non-linear optical processes in photoanisotropic materials. A theoretical model of photoprocesses in materials in which optical non-linearity is related to absorbing centres with intrinsic linear anisotropy is constructed. Theoretical calculations show that the photostationary concentration of the photoproducts (and the mean values of the non-linear changes in optical constants) in these materials is higher if the exciting light is circularly polarized. Experimental results on non-linear processes in samples of fluorescein incorporated in orthoboric acid and in azodye/polymer layers are in good agreement with the theory. This revised version was published online in November 2006 with corrections to the Cover Date.     

Spectral luminescence properties of indotricarbocyanine dye in biological tissues

We have established that the shape and position of the maximum in the fluorescence spectrum of an indotricarbocyanine dye in tumor and normal tissues in vivo change over time after intravenous injection of the dye. Based on analysis of the spectral properties of the dye in vivo and in blood plasma, the dependence of the properties on the time since injection has shown that in the living body, the environment of the dye molecule changes as the photosensitizer goes from the skin into the tissue. We have established that in tissues in vivo, the dye molecules are localized in a region with low dielectric constant of the medium. We have shown that the change in the ratio of the concentrations of the different forms of hemoglobin in the blood has an effect on the absorption and shape of the fluorescence spectrum of the dye in tissues in vivo.     

Ultrastructural study on dynamics of plastids and mitochondria during microgametogenesis in watermelon

Dynamics of plastids and mitochondria during microgametogenesis in watermelon were examined by means of transmission electron microscopy. Plastids are present as proplastids in the microspore and as amyloplasts in the vegetative cell of the bicellular pollen grain, whereas the generative cell is completely devoid of plastids, suggesting that microspore plastids are excluded from the generative cell during the microspore mitotic division. Therefore, watermelon is classified as Lycopersicon type, where plastids exclusion from the generative cell leads to purely maternal plastid inheritance. Mitochondria in the generative cell show noticeable alterations in size and cristae during microgametogenesis. The diameter of mitochondria is about 0.5 μm in the newly born generative cell, while only about 0.16 μm in the spindle-shaped generative cell. Numerous cristae are present in mitochondria in the spherical generative cell, but, in contrast, mere two or three cristae retain in the spindle-shaped generative cell in the mature pollen grain. In conclusion, the size and cristae number of mitochondria in the generative cell are reduced significantly during microgametogenesis in watermelon.     

Electrostatic field and charge distribution in small charged dielectric droplets

The charge distribution in small dielectric droplets is calculated on the basis of continuum medium approximation. There are considered charged liquid spherical droplets of methanol in the range of nanometer sizes. The problem is solved by the following way. We find the free energy of some ion in dielectric droplet, which is a function of distribution of other ions in the droplet. The probability of location of the ion in some element of volume in the droplet is a function of its free energy in this element of volume. The same approach can be applied to other ions in the droplet. The obtained charge distribution differs considerably from the surface distribution. The curve of the charge distribution in the droplet as a function of radius has maximum near the surface. Relative concentration of charges in the vicinity of the center of the droplet does not equal to zero, and it is the higher, the less is the total charge of the droplet. According to the estimates the model is applicable if the droplet radius is larger than 10 nm.