环境样品中痕量铝的现代光度分析研究新进展

论文综述和评论了近年来环境样品中痕量铝的光度分析研究新进展。重点论述了现代光度分析法测定环境样品中铝的研究新进展 ,内容包括 :胶束增溶分光光度法、双波长分光光度法、导数分光光度法、催化光度法、固相光度法、流动注射光度法。对普通光度法和胶束增溶光度法的反应体系、测定条件、摩尔吸收系数 (ε)或检出限、线性范围及其应用进行了归纳总结 ,评述了各种光度法测定的优劣 ,展望了光度法测定痕量铝的发展前景     

钛光度分析的某些进展

综述了光度法测定钛近 5年来研究的某些进展 ,涉及经典光度法、动力学光度法、计算光度法及流动注射光度法测钛 ,引文 6 0篇。     

国内光度法测定亚硝酸根进展

对国内近年来(2000—2009年)亚硝酸根的光度法测定进展作了回顾,主要涉及亚硝酸根的光度测定中应用普通分光光度法、流动注射光度法、催化光度法和荧光光度法等内容,引用文献88篇。     

催化动力学光度法测定痕量Fe(Ⅲ)的研究进展

论文探讨和论述了近年来催化动力学光度法测定痕量铁的研究进展。具体探讨和评述内容包括:比较催化光度法与原子吸收法、萃取光度法的优缺点;介绍催化动力学光度法的原理;评述催化褪色动力学光度法研究进展、催化显色动力学光度法研究进展、阻抑显色催化动力学光度法研究进展、阻抑褪色催化动力学光度法研究进展;包括指示反应及其条件、方法的检出限、干扰情况、测定范围、应用等。论文还探讨和展望了催化动力学光度法未来的研究方向和发展前景。内容包括:①对传统显色剂改性或合成新的高灵敏度、高选择性显色剂;②活性剂增敏研究;③加强相关催化机理的研究和探讨;④开展酶催化动力学光度法研究。     

杂多酸(蓝)分光光度法在测定痕量元素中的研究进展

杂多酸能被还原为有颜色的杂多蓝,结合分光光度法,可对痕量元素进行准确的分析。目前,杂多酸分光光度法作为一种分析技术,具有精度高、操作简便、分析速度快等优点,在痕量分析领域得到了迅速发展。文章综述了杂多酸在测定痕量元素P, As, Si和V中的应用及研究进展。方法主要包括钼蓝法、杂多酸-碱性染料法、荧光分光光度法、流动注射分光光度法、原子吸收分光光度法、激光热透镜分光光度法等,并对这些方法进行了比较分析。     

催化动力学光度法测定痕量锰的研究进展

评述了近年来催化动力学光度法测定痕量锰的研究进展。具体内容包括: 催化褪色动力学光度法测定痕量锰的研究进展;催化显色动力学光度法测定痕量锰的研究进展。在研究方法方面,内容包括指示反应及其条件、方法的检出限、测定范围、应用等。展望了催化动力学光度法未来的研究方向和发展前景;如加强活性剂增敏的研究、方法的选择性研究、相关催化机理的研究和酶催化动力学光度法的研究。     

国内动力学光度法测定碘研究的某些进展

本文综述了国内光度法测定碘研究的某些进展,分别从催化氧化动力学,阻抑动力学、非动力学光度法和催化荧光光度法等几个类别进行归纳,并从反应介质、检出限、线性范围和应用等方面进行叙述.     

蛋白质光度法定量分析研究现状

本文综述了吸光光度法、荧光光度法、共振散射光度法定量分析蛋白质的研究现状,参考文献86篇。     

催化动力学光度法测定痕量铜的研究进展

本文探讨和论述了近年来催化动力学光度法测定痕量铜的研究进展，比较了催化光度法与原子吸收法、萃取光度法的优缺点；介绍了催化动力学光度法的原理；评述了催化褪色光度法、催化显色光度法、催化荧光光度法等的研究进展，探讨和展望了催化动力学光度法未来的研究方向和发展前景，包括：1．对传统显色剂改性或合成新的高灵敏度、高选择性显色剂；2．活性剂增敏研究；3．加强相关催化机理的研究和探讨。全文参考文献29篇。     

DAN荧光法等3种测定蛹虫草菌丝体中硒含量的方法比较

通过DAN荧光法,3,3-二氨基联苯胺分光光度法和邻苯二胺紫外分光光度法测定蛹虫草菌丝体中硒的含量,对测得结果进行统计分析,并对其检出限、回收率进行比较研究.研究结果表明,DAN荧光法、3,3-二氨基联苯胺分光光度法和邻苯二胺紫外分光光度法中,硒含量相对标准偏差分别是2.5%,9.2%和6.1%;线性回归系数都大于0....     

Quantum corrections to the electrical conduction in an AlGaN/GaN heterostructure

A new method for magneto-transport characterisation of semiconductor heterostructures is presented. The classical model of mixed conduction, modified by corrections resulting from quantum effects, has been used in the analysis of the conductivity-tensor components, magnetoresistance, and Hall coefficient in n-type Al_0.85Ga_0.15N/GaN in magnetic fields up to 12 T, in the temperature range from 2 to 295 K. The mixed conduction is due to high-mobility carriers in the conduction band in the interface and to low-mobility carriers in the conduction band in the GaN layer and in an impurity band. The corrections to the conduction of high-mobility carriers result from quantum effects: negative magnetoresistance, extraordinary Hall effect, and freeze-out of electrons. Negative magnetoresistance is due to localisation of electrons and to increasing tunnel coupling between electron states in different minima of a random potential, due to interface roughness. The extraordinary Hall effect has been explained by interaction of electrons with magnetic moments of dislocations in the interface. Decreasing concentration of electrons is probably due to Landau quantisation of the conduction band in the interface of the heterostructure. Received: 27 November 2000 / Accepted: 18 December 2000 / Published online: 3 April 2001     

A new method for quantitation of spin concentration by EPR spectroscopy: application to methemoglobin and metmyoglobin

A new method of EPR spectral analysis is developed to quantitate overlapping signals. The method requires double integration of a number of spectra containing the signals in different proportions and the subsequent solution of a system of linear equations. The result gives the double integral values of the individual lines, which can then be further used to find the concentrations of all the paramagnetic species present. There is no requirement to deconvolute the whole spectrum into its individual components. The method is employed to quantify different heme species in methemoglobin and metmyoglobin preparations. A significantly greater intensity of the high-spin signal in metmyoglobin, compared to methemoglobin at the same heme concentration, is shown to be due to larger amounts of low-spin forms in methemoglobin. Three low-spin types in methemoglobin and two in metmyoglobin are present in these samples. When their calculated concentrations are added to those of the high-spin forms, the results correspond to the total heme concentrations obtained by optical spectroscopy.     

Improved in vivo human carotid artery wall T2 estimation

T₂^? quantification has been shown to noninvasively and accurately estimate tissue iron content in the liver and heart; applying this to thin-walled carotid arteries introduces a new challenge to the estimation process. With most imaging voxels in a vessel being along its boundaries, errors in parameter estimation may result from partial volume mixing and misregistration due to motion in addition to noise and other common error sources. To minimize these errors, we propose a novel technique to reliably estimate T₂^? in thin regions of vessel wall. The technique weights data points to reduce the influence of expected error sources. It uses neighborhoods of data to increase the number of points for fitting and to assess lack of fit for automated outlier detection and deletion. The performance of this method was observed in simulations, phantom and in vivo patient studies and compared to results obtained using a pixelwise linear least squares estimation of T₂^?. The new proposed method showed a closer match to the expected results, and a 4.2-fold decrease in interobserver variability for in vivo studies. This increased confidence in estimation should improve the ability to reliably quantify iron noninvasively in the arterial wall.     

近红外光谱检测技术及其在林业中的应用

近红外光谱是20 世纪80 年代以来发展最快、最引人注目的光谱分析技术。文章介绍了近红外光谱技术的发展历程和在国外的应用概况,重点列举了近红外光谱在林业中的成功应用实例。资料表明, 近红外光谱以其快速、无损伤、操作简单、稳定性好、效率高等特点,在国外的水果品质检测、木材性质检测和林业育种中的应用已成为一个活跃的研究领域。而近红外光谱技术在我国林业上的研究和应用则刚刚起步,因此本文对国内外利用近红外光谱技术在林业上的应用作一综述,并对近红外检测技术在林业上的应用进行了展望,以推动近红外光谱技术在我国林业科技和生产中的应用。     

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.     

Brain mechanisms involved in the control of vocalization

This article reviews recent experimental and clinical literature on the central neural mechanisms involved in vocalization. Various parts of the cerebral cortex, limbic system, basal ganglia, and extrapyramidal system have been shown in human and animal studies to be important in vocalization, but the exact function of these areas with regard to vocal control is unclear. The limbic system and diencephalon project to the midbrain periaqueductal gray (PAG), which may be important for coordination of various muscle groups involved in vocalization. The PAG neurons project to the reticular formation, nucleus retroambiguus, and nucleus ambiguus. Neurons in the nucleus retroambiguus seem to be involved in control of neurons related to the respiratory or laryngeal systems. Different types of motoneurons of the laryngeal muscles in the nucleus ambiguus are related to various functions such as vocalization, swallowing, and respiration.     

Information Theory for Agents in Artificial Intelligence,Psychology, and Economics

This review looks at some of the central relationships between artificial intelligence, psychology, and economics through the lens of information theory, specifically focusing on formal models of decision-theory. In doing so we look at a particular approach that each field has adopted and how information theory has informed the development of the ideas of each field. A key theme is expected utility theory, its connection to information theory, the Bayesian approach to decision-making and forms of (bounded) rationality. What emerges from this review is a broadly unified formal perspective derived from three very different starting points that reflect the unique principles of each field. Each of the three approaches reviewed can, in principle at least, be implemented in a computational model in such a way that, with sufficient computational power, they could be compared with human abilities in complex tasks. However, a central critique that can be applied to all three approaches was first put forward by Savage in The Foundations of Statistics and recently brought to the fore by the economist Binmore: Bayesian approaches to decision-making work in what Savage called ‘small worlds’ but cannot work in ‘large worlds’. This point, in various different guises, is central to some of the current debates about the power of artificial intelligence and its relationship to human-like learning and decision-making. Recent work on artificial intelligence has gone some way to bridging this gap but significant questions remain to be answered in all three fields in order to make progress in producing realistic models of human decision-making in the real world in which we live in.     

Immunodetection of type I acidic keratins associated to periderm granules during the transition of cornification from embryonic to definitive chick epidermis

The change in the modality of cornification from embryonic to definitive epidermis in the chick has been studied using immunocytochemistry and electron microscopy to show that the initial soft cornification based on an acidic type I alpha-keratin transits to a definitive hard cornification based on beta-proteins in the claw, scales and feathers. The first two periderm layers contain acidic keratins associated with periderm granules and participate in a mild form of cornification before shedding of the periderm. The transition from embryonic to adult cornification is best seen in the transitional layers of the claw where numerous periderm granules merge with packets or bundles of corneous beta-proteins. This process is hardly seen in scale and feathers where periderm granules remain most in the periderm or in the feather sheath. Periderm granules disappear in corneocytes generated underneath the periderm in scales or in the transitional layer in claws and are replaced by beta-proteins associated to other types of acidic alpha-keratins. This process produces a mechanically resistant corneous material underneath the softer periderm, adapted to terrestrial demand for mechanical protection in scales and in the dorsal part of the claw, the unguis. In the ventral part of the claw, the sub-unguis, scarce or no beta-proteins are accumulated resulting in a softer corneous layer. The study indicates that specific alpha-keratins form the cytoskeletal framework of definitive corneocytes in claws, scales and feathers, and that specialized corneous beta-proteins are deposited over this framework to produce epidermal layers with higher mechanical resistance.     

Noise emitted by water supply installations

This work deals with the problem of noise generated by water supply systems in homes. Measurements were made in situ to determine normal conditions of installations and noise levels generated in different rooms in the home. In order to determine the sources of noise and the best construction methods to minimise noise generation, a laboratory was also built to reproduce the conditions of this type of installation in homes. Tests were carried out in this laboratory on different configurations of type of tap, installation material, walling and fastening of the installation, to allow quantitative determination of the differences in noise generation between the various configurations used in households.     

Self‐Collimation in Photonic Crystals: Applications and Opportunities

A comprehensive review considering recent advances in self‐collimation and its applications in optical integration is covered in the current article. Self‐collimation is compared to the conventional technique of photonic bandgap engineering to control the light propagation in photonic crystal‐based structures. It is fully discussed how the self‐collimation phenomenon can be tailored to be independent of the incident angle and polarization. This adds substantial flexibility to the structure to overcome light coupling challenges and simultaneously aids in the omission of bulk and challenging elements, including polarizers and lenses from optical integrated circuits. Additionally, designed structures have the potential to be rescaled to operate in any desired frequency range thanks to the scalability rule in the field of electromagnetics. Moreover, it is shown that one can boost the coupling efficiency by applying an anti‐reflection property to the structure, which provides not only efficient index matching but also the matching between external waves with uniform amplitude and Bloch waves with periodic amplitude.