环境化合物联合作用及其研究方法评价

化合物的联合毒性作用是一个极具挑战性但又有很强现实意义的课题.介绍了环境化合物联合作用方式和机制,并对主要的联合作用方法进行了评价.强调从实验室对动物的高剂量到现实中人所接受的低剂量的外推是关键问题.     

浅议毒物兴奋效应

剂量反应关系的本质是毒理学的重要特征,并且它在大多数的毒理学教材中都有详细阐述[1]。对环境污染物的危险度评价是毒理学的重要任务之一。目前危险度评价所面临的主要挑战是数据的外推。管理者将从动物实验得到的结果外推到人,不仅要从老鼠到人,还要从实验动物的高剂量接触外推到人的低剂量暴露。这两种外推都存在着很大的不确定性[2]。为了解决这种外推的不确定性,一种新的剂量反应关系模型——毒物兴奋效应——引起了一些科学学的注意。在环境毒理学和医学毒理学领域,毒物兴奋效应是一个很有争议的概念[3-4]。本综述的主要目的是讨论毒物兴奋效应的定义、发展、重要特征、机制、应用和为何未被广泛接受等一系列问题。     

由深度和灰度重建三维物体表面的新方法

提出一种由特征点深度与灰度重建三维物体可视表面的新方法。文中把已知深度和图像灰度结合起来,实现了一个递归外推算法,以唯一确定整个物体表面的深度。实验结果说明了重建方法的正确性和可行性。     

多维平稳序列对线性系统的外推问题

<正> 一、问题的陈述工程技术中提出的多维平稳过程输入下对线性固定补偿系统的外推、滤波问题具有广泛的实际意义。从数学上看,这类问题是经典的外推问题的推广。然而却提出了若干新的问题(如在多维场合下与空间的可分离性有关等)。一维平稳序列在正则条件下已经有一些结果。本文就多维平稳序列在更一般的条件下进行讨论。设列向量     

基于双向预测插值的多维矢量鬼成像视频

为了进一步提升运动物体鬼成像视频的质量,根据视频中每帧都具有相关性的特点,提出了一种基于双向预测插值的多维矢量鬼成像视频的实时成像算法.即运用具有能量集中特点的多维矢量Walsh变换,将总数一定的Walsh基图样分成更少的组,使每组的有效基图样翻倍,再分别作用于目标物体,重构后得到数量少但成像质量更好的隔帧图像,再通过双向预测插值得到中间帧.使用该算法作用于像素为64×64的目标物体,可在实时状态下实现运动物体鬼成像的视频.在采样数量和采样时间不变的情况下,可实现高质量重构,得到了品质更好的鬼成像视频.     

运动物体的双基地图象重建的几个定理

用图象重建的方法研究运动物体的双基地雷达成象．在改进模型的基础上，把成象归结为解析函数的外推和函数沿一簇椭圆曲线Ｒａｄｏｎ变换的反演，阐明了运动距离和物体可完全成象的关系，给出了唯一性定理．     

多维资源的多元优化处理应用研究

多维资源的多元优化处理问题是一个典型NP-Hard问题,一般通过多种算法进行解决.在禁忌算法和遗传算法的基础上构建了一个基于多策略算法的多维资源多元优化处理模型,该模型通过优化资源分配的初始结果,避免用单一算法所得结果误差大和资源分配的两极分化现象,使资源利用更加合理化和人性化,且可平衡实际分配结果与期待值之间的关系,更大程度上满足用户需求.     

低能N~+注入蒙古黄芪种子的生物学效应

以蒙古黄芪种子为材料,研究了不同剂量的N+注入对蒙古黄芪种子发芽势、发芽率、成苗率和幼苗叶片中叶绿素含量、过氧化物酶(POD)、过氧化氢酶(CAT)、超氧化物歧化酶(SOD)活性、丙二醛含量的影响.结果表明:随着N+注入剂量的增加发芽势和发芽率的变化趋势为先降低后升高再降低,表现为"马鞍型"曲线,成苗率在低剂量时与发芽率相接近,在高剂量时成苗率明显降低.对叶片叶绿素含量以及过氧化物酶(POD)、过氧化氢酶(CAT)、超氧化物歧化酶(SOD)的活性,在低剂量上表现为激活效应,高剂量上表现为抑制效应;丙二醛含量在低剂量时明显低于对照,高剂量时含量升高,因此低剂量的N+注入蒙古黄芪种子能够提高幼苗的抗逆性,能够为育种提供一种有效的诱变方法.     

紫梅消银洗液作用于豚鼠的急毒实验研究

目的:验证紫梅消银洗液用于银屑病治疗的安全性.方法:将豚鼠随机分为完整空白对照组、破损空白对照组、低剂量紫梅消银洗液完整皮肤组、低剂量紫梅消银洗液破损皮肤组、高剂量紫梅消银洗液完整皮肤组、高剂量紫梅消银洗液破损皮肤组,每组10只,进行豚鼠的急毒实验.结果:空白对照组、高剂量与低剂量紫梅消银洗液完整与破损皮肤组的豚鼠皮肤毛发、眼和粘膜、呼吸、中枢神经系统、四肢活动及体重均无任何差异,先后观察14 d内无豚鼠死亡.结论:高、低浓度的紫梅消银洗液与空白对照组比较未出现任何急性毒性反应,且安全范围较大.     

毒物兴奋效应与神经保护

 毒物兴奋效应(hormesis)指有毒物质或处理因素在低剂量或低水平时对生物体表现为有利作用,但在高剂量或高水平时表现出其相反作用的双相剂量效应,可视为细胞或机体在不利环境中的一种适应机制。最近,研究人员将hormesis 理论应用到神经保护中,增强神经细胞自适应能力,这将为神经疾病预防治疗提供新思路和新方法。一些低剂量的有利刺激能够明显增强神经细胞对于更剧烈刺激的抵抗能力,这种现象被称为神经毒物兴奋作用(neurohormesis)。综述了hormesis 的研究现状、低剂量化学物质、辐射与热量限制等通过引起神经细胞适应性反应而起神经保护作用及机制。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the