转小鼠金属硫蛋白(MT)基因烟草不同器官中金属离子铅和锌的分布

转金属硫蛋白(MT)基因植物具有清除重金属污染的能力,但是金属离子在植物体内的分布研究较少。文章以多代培育纯合的转MT烟草为材料,研究了转MT基因烟草积累铅和锌以及铅和锌在不同器官的分布情况。结果表明转基因植株的老叶、茎部和根部铅和锌积累量显著高于普通烟草植株,整株的铅和锌含量分别提高了21.8%和27.2%。铅和锌在植物体内的分布也发生了变化,转基因植株老叶和根中的铅含量分别高出普通烟草同位置的30.2%和47.8%,锌在转基因植株老叶、茎和根中的含量分别高出普通烟草同位置的44.7%,29.2%和21.6%,说明铅更容易在转基因植株老叶和根中积累,而锌更容易在转基因植株的老叶和茎中积累。     

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.     

石墨狭缝中甲烷吸附的分子动力学模拟

用分子动力学模拟研究石墨狭缝中甲烷的吸附,考察狭缝宽度和温度对甲烷吸附的影响.模拟发现甲烷在石墨狭缝中出现分层现象,吸附层中甲烷具有类液特征,第一吸附层内甲烷中总有两个氢原子的连线与另外两个氢原子的连线分别位于平行于狭缝壁的两个平面内,游离层中甲烷呈现气体的特征;碳原子间的平均作用势说明吸附层中甲烷分子间结合能力大于游离层,吸附态是甲烷在石墨狭缝中的主要赋存形式之一;伦敦力以及由吸附层净电荷产生的电场力是甲烷吸附和分层的主要原因;甲烷的吸附量随狭缝宽度增大或温度升高而减少,当狭缝宽度小于16.46Å时,甲烷仅以吸附形态存在.甲烷在第一吸附层中的扩散能力最弱、游离层中最强,甲烷扩散系数随狭缝宽度的增大或温度的升高而增大.     

火焰原子吸收光谱法测定鸭粪中铜和锌的含量

采用火焰原子吸收光谱法测定白洋淀生态养鸭场中饲料及鸭粪中的铜和锌含量,测定结果为饲料中的铜含量范围在9.7-61.55mg/kg,锌含量范围在63.14-149.07mg/kg,在禽类饲料中铜、锌含量属于较低的类型;鸭粪中铜含量范围在13.71-94.74mg/kg,锌含量范围在156.98-346.31mg/kg,参...     

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.     

水溶液中微量Cu元素的激光诱导光谱检测

采用普通打印纸作为基底置于含有痕量重金属离子的水溶液中,用于富集溶液中的重金属Cu元素,烘干后用激光诱导击穿光谱进行定量分析。该方法克服了用激光诱导击穿光谱方法直接分析液相样品中重金属含量时存在水的溅射和灵敏度低等不足。实验中选用324.7 nm的光谱线作为分析线,研究了光谱强度与富集时间的关系,建立了用于溶液中Cu元素定量测量的校正曲线,检测限达到0.023 mg·L-1。为水体中重金属检测提供了一个可行的具有良好灵敏度分析技术。     

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.     

Preparation of the Speech-LanguagePathologist Specializing in Voice: An Educational Survey

This study investigates the academic and clinical preparation a speech-language pathologist receives in the area of voice. The purpose is to determine how to structure continuing education and specialty training in vocology, defined as the science and practice of voice habilitation. Surveys were sent to the graduate programs in speech-language pathology accredited by the American Speech-Language-Hearing Association (ASHA) in 1994, and again in 1999. Results from the 1994 survey indicated that students received limited information and clinical experience in handling typical voice cases. Although most programs required a voice disorders course, fewer mandated coursework in normal voice production or clinical experience with voice patients. The follow-up survey showed that the educational environment in 1999 is similar to that in 1994. It is evident that the programs are in compliance with the Educational Training Board model developed by ASHA for basic clinical competence, but no structure for specialty training has yet emerged.     

‘Phase transitions’ in bacteria – From structural transitions in free living bacteria to phenotypic transitions in bacteria within biofilms

Phase transitions are common in inanimate systems and have been studied extensively in natural sciences. Less explored are the rich transitions that take place at the micro- and nano-scales in biological systems. In conventional phase transitions, large-scale properties of the media change discontinuously in response to continuous changes in external conditions. Such changes play a significant role in the dynamic behaviours of organisms. In this review, we focus on some transitions in both free-living and biofilms of bacteria. Particular attention is paid to the transitions in the flagellar motors and filaments of free-living bacteria, in cellular gene expression during the biofilm growth, in the biofilm morphology transitions during biofilm expansion, and in the cell motion pattern transitions during the biofilm formation. We analyse the dynamic characteristics and biophysical mechanisms of these phase transition phenomena and point out the parallels between these transitions and conventional phase transitions. We also discuss the applications of some theoretical and numerical methods, established for conventional phase transitions in inanimate systems, in bacterial biofilms.     

Spin-1/2 relativistic particle in a magnetic field in NC phase space

This work provides an accurate study of the spin-l/2 relativistic particle in a magnetic field in NC phase space. By detailed calculation we find that the Dirac equation of the relativistic particle in a magnetic field in noncommutative space has similar behaviour to what happens in the Landau problem in commutative space even if an exact map does not exist. By solving the Dirac equation in NC phase space, we not only obtain the energy level of the spin-1/2 relativistic particle in a magnetic field in NC phase space but also explicitly offer some additional terms related to the momentum-momentum non-commutativity.     

污染土壤对脐橙叶片镉含量影响的光谱预测

近年来可见-近红外光谱技术在农业污染监测中应用越来越广泛,但在果树的重金属污染研究中应用较少。本文以纽荷尔脐橙(Citrus sinensis[L.]Osbeck cv. Newhall)为研究对象,采用盆栽方法,通过添加镉（Cd）形成不同污染程度的土壤,然后定期监测叶片中Cd含量及其光谱,分别建立了基于光谱指数的线性回归预测模型,以及基于偏最小二乘回归（PLSR）的Cd含量高光谱预测模型。结果表明：Cd更容易向新叶迁移和聚集,在高Cd污染的土壤中这种现象更加明显;新叶光谱在700～730 nm之间反射率升高,发生红边蓝移现象,老叶光谱没有显著变化;基于光谱指数建立的线性回归模型的R2达到0.8左右,而利用PLSR方法建立的预测模型精度普遍高于线性回归模型,其R2达到0.9左右,并且标准归一化（SNV）的光谱预处理方法可以显著提高PLSR模型的预测精度。研究显示,可见-近红外光谱技术在脐橙重金属污染监测上有很好的潜力。     

An fMRI study of magnitude comparison and exact addition in children

By contrast to the adult literature, in which a consistent parietofrontal network for number processing has been identified, the data from studies of number processing in children have been less consistent, probably due to differences in study design and control conditions. Number processing was examined using functional magnetic resonance imaging in 18 right-handed children (8–12 years) from the Cape Coloured community in Cape Town, South Africa, using Proximity Judgment and Exact Addition (EA) tasks. The findings were consistent with the hypothesis that, as in adults, the anterior horizontal intraparietal sulcus (HIPS) plays a major role in the representation and manipulation of quantity in children. The posterior medial frontal cortex, believed to be involved in performance monitoring in more complex arithmetic manipulations in adults, was extensively activated even for relatively simple symbolic number processing in the children. Other areas activated to a greater degree in the children included the left precentral sulcus, which may mediate number knowledge and, for EA, the head of the caudate nucleus, which is part of a fronto-subcortical circuit involved in the behavioral execution of sequences. Two regions that have been linked to number processing in adults — the angular gyrus and posterior superior parietal lobule — were not activated in the children. The data are consistent with the inference that although the functional specialization of the anterior HIPS may increase as symbolic number processing becomes increasingly automatic, this region and other elements of the parietofrontal network identified in adults are already reliably and robustly activated by middle childhood.     

Spectral Properties of Single BODIPY Dyes in Polystyrene Microspheres and in Solutions

The absorption, fluorescence, fluorescence quantum yield, and photostability of five BODIPY dyes are characterized and compared as single dyes in two environments, in 40-nm polystyrene spheres and in solution. The absorption and fluorescence spectra of the dyes in spheres are similar in profile but shifted to lower energies compared to those in solution. All the dyes are highly fluorescent, with three having fluorescence quantum yields of 1.0. For three of the five dyes, the yields were the same in spheres as in solution (1.00, 1.00, and 0.73). The high concentration of these dyes in spheres does not quench their fluorescence. For two other dyes the yields dropped, from 1.00 to 0.55 in one case and 0.83 to 0.50 in another, comparing the dyes in solution versus in spheres. The photodegradation of the dyes decreases in spheres compared to in solution in all but one case. For one dye, it decreases as much as 800-fold. Dyes overlooked because of low fluorescence or stability in solution could become useful fluorescent materials in the microsphere environment.     

X-ray scattering and polarization in wavelength-dispersive spectrometers

Background suppression is discussed in wavelength-dispersive polarization X-ray spectrometer (WDPXRS), in which the goniometer scans in plane perpendicular to primary and secondary beams. Background suppression coefficients in WDPXRS and energy-dispersive polarization X-ray spectrometer are determined by different expressions (in “The scattering suppression of X-rays with energy of 20–200 keV in spectrometers with Barkla polarizers,” doi: 10.1002/xrs.3046 ). It is proposed to install silicon drift detectors in WDPXRS and implement energy-dispersive and wavelength-dispersive modes in one channel.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Raman and fluorescence investigations on retrieved Biolox® delta femoral heads

Since the introduction of ceramic‐on‐ceramic couplings in total hip arthroplasty, continuous efforts have been performed to improve the performance of the prosthetic components. To expand the applications of ceramics, in 2000 an innovative alumina–zirconia composite was introduced in the market. The present study represents the first investigation aimed at characterising at the molecular level Biolox® delta retrievals implanted between 1999 and 2009. Fluorescence and Raman results showed that a progressive improvement of the material properties has occurred in the period between 1999 and 2009. Raman spectroscopy showed that wear was the main cause of the in vivo tetragonal‐to‐monoclinic zirconia transformation. Our findings validated the in vitro accelerated ageing protocols proposed in the literature to simulate the effects of the in vivo wear, because the mechanism operating in vivo was found to be the same active in vitro. The in vitro fracture of a new femoral head appeared to be an extreme wear condition that determined the most significant changes in the residual stress state and monoclinic content both in the section of the fragments and on their surface. The micro‐Raman mapping of the fractured articulating surface showed that the tetragonal‐to‐monoclinic transformation involved a region much more extended than as reported in the literature. Copyright © 2012 John Wiley & Sons, Ltd.     

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。     

XPS and SIMS investigation on the role of nitrogen in Si nanocrystals formation

Since the demonstration of optical gain in silicon nanocrystals, in the last few years several papers appeared in the literature reporting gain measurements in silicon nanocrystals embedded in a silica matrix produced by different techniques. However, it is still unclear which are the structural, physical and chemical factors that contribute to enhance photoluminescence and gain in this type of samples. In particular, the presence and the role of nitrogen in the SiO₂ matrix are in fact supposed to be essential factors in understanding the gain mechanism.In fact it is possible to obtain similar samples with very different nitrogen content in the silica matrix changing one of the precursor gases used in the deposition process, thus evidencing the structural and chemical differences introduced by the presence of nitrogen. In this paper SIMS and XPS analysis of two series of similar samples, but with a very different nitrogen content, will be presented and compared. The data collected at different annealing temperatures, together with ellipsometric measurements, give important information on the role played by the nitrogen present in the matrix in the process of silicon nanocrystal formation. Moreover, we demonstrate that the annealing process causes always some oxidation of the sample surface and that nitrogen is incorporated in the material from the annealing atmosphere in nitrogen free samples.