淡水生态系统中的TOP—DOWN效应与生物多样性保护

淡水生态系统中高营养级类群可以对低营养级类群产生强烈的影响,最终导致整个生态环境的改变,这一现象被称作下行（ｔｏｐｄｏｗｎ）效应。本文对ｔｏｐｄｏｗｎ的含义特别是鱼类所产生ｔｏｐｄｏｗｎ效应的结果进行了阐述,提出了ｔｏｐｄｏｗｎ效应还表现在当原来生态系统中的高营养级类群缺少时,也会造成生态系统结构与功能发生变化的观点。最后,根据淡水生态系统ｔｏｐｄｏｗｎ效应的特点,认为在淡水生态系统的生物多样性保护中,应注意高营养级类群的保护和谨慎地对待引种问题     

云杉蚜虫-天敌-杀虫剂相互作用控制模型的动态特性

使用微分方程与控制理论研究了使用杀虫剂对一类云杉蚜虫与其天敌相互作用模型的动态特性的影响．其中包括云杉蚜虫-天敌-杀虫剂相互作用控制模型正平衡点存在个数及正平衡点的稳定性与杀虫剂使用量的关系．研究结果表明：适当地使用杀虫剂可以在天敌数量不足的情况下控制害虫爆发的事件．     

Magnetosonic oscillations of thin plasma columns

Oscillations of a plasma column in a longitudinal magnetic field are considered. It is found that eigenmodes with frequencies close to the ion cyclotron frequency can be excited in columns the radii of which are smaller than the characteristic wavelength of magnetosonic oscillations predicted by the theory of homogeneous plasma. The eigenmodes have the form of waves running around the column axis in the direction of electron gyration in the magnetic field. Magnetosonic oscillations can be excited as a side effect when using helical antennas for ion cyclotron resonance heating of plasma. These oscillations should enhance electron heating in the plasma core, as well as both electron and ion heating at the periphery of the plasma column. The spectrum of eigenmodes of inhomogeneous plasma columns includes oscillations of different nature. Comparative analysis of their properties performed in the present paper is useful for understanding the full picture of the physical processes occurring during ion cyclotron resonance heating and clarifying the characteristic features of the magnetosonic oscillations under study.     

影像基因组学分析方法研究进展

在生物医学大数据背景下,精准医学的研究重点之一是基因型数据和表型数据的融合及关联分析,通过数据融合及关联分析,认识疾病表型特征与基因多态性及基因活动之间的关系。影像基因组学作为一个新兴研究领域,它将疾病影像数据和基因组数据整合,并挖掘两者之间的联系,从而发现能够反映基因多态或表达的影像特征,在此基础上建立基于影像特征的非侵入式疾病诊断方法,是目前生物医学最有前景的研究领域之一。综述了影像基因组学领域的研究方法,包括基因组数据分析、影像数据分析以及基因组数据-影像数据融合分析方法。在此基础上,介绍了影像基因组学目前在临床上的典型应用,包括疾病的辅助诊断、预后预测和疗效评估。最后,对影像基因组学的未来发展进行了展望。     

Effect of the magnetic field curvature on magnetic islands in tokamaks

The effect of the magnetic field curvature on magnetic islands in a tokamak is analyzed. It is demonstrated that the original investigation of this effect by Kotschenreuther et al. (1985) is inconsistent: on the one hand, the authors made the correct assumption that this is an ideal effect and, on the other hand, they described it in terms of the parameters characteristic of the “resistive ordering” approach, which is incompatible with the ideal approximation. More recent studies of the magnetic curvature effect have produced further ambiguities; as a result, a branch of the theory of magnetic islands has arisen that is based on the supposition that the effect under discussion can be described in terms of the Glasser-Greene-Johnson parameter D_R. This branch is shown to be erroneous, because the parameter D_R describes the plasma response to magnetic field perturbations on spatial scales of about the dimension of the linear resistive layer, while the characteristic spatial scale of the magnetic islands is much longer. It is concluded that the correct theory developed here for the magnetic curvature effect makes more optimistic predictions about its stabilizing role.     

Heat-induced changes in the finite strain viscoelastic behavioir of a collaagenous tissue

Supra-physiological temperatures are increasingly being used to treat many different soft need for injuries. To identify improved clinical treatments, however, there is a need for better information on the effect of the mechanics on the thermal damage process as well as the effect of the incurred damage on the subsequent mechanical properties. In this paper we report the first biaxial data on the stress relaxation behavior of a collagenous tissue before and after thermal damage. Based on a two-dimensional finite strain viscoelastic model, which incorporates an exponential elastic response, it is shown that the thermal damage can significantly decrease the characteristic time for stress relaxation and the stress residual.     

The role of plasma noradrenaline in health and disease

This paper proposes that plasma noradrenaline plays a central role in the physiology and pathophysiology of the macrocirculation, the heart, veins and arteries. The proposal stems, in the final analysis, from the finding that noradrenaline dilates the canine lateral saphenous vein when it is released from its microcirculation, the vasa venarum. The concentration threshold of the effect is estimated to be at least eight times lower than the threshold of the constrictor effect of intralumenal noradrenaline. Combined with other evidence, the finding indicates that, contrary to opinion, plasma noradrenaline has an effective β₁-agonist hormonal effect on the macrocirculation, at normal concentrations. It also indicates that noradrenaline has a bi-polar effect. The reason it has that effect is that noradrenaline is a primary biological stimulus and like all primary stimuli investigated to date, it can be expected to have two cross-inhibitory components, commonly referred to as excitor and lateral inhibitory. When examined, neuronal noradrenaline shows the features characteristic of excitor components in general and plasma noradrenaline shows those characteristic of inhibitory components. The most significant of the latter is that inhibitory components are the most potent physiological modulators of excitor components. A striking example of that modulation effect occurs in smooth muscle contraction where muscles contracted by neuronal noradrenaline stimulation appear to be incapable of relaxing without stimulation by plasma noradrenaline-hence the proposition that vascular stenosis and cardiospasm are caused by a pathological loss of plasma noradrenaline stimulation. By triggering turbulence, cholesterol plaques increase the arterial microcirculatory flow and so increase the β₁-agonist effect of plasma noradrenaline. This paper proposes that this cholesterol driven increase in the microcirculatory effect of plasma noradrenaline is the cause of the arteriosclerotic syndrome, a proposition that is consistent with the success of beta-blockade in treating manifestations of the syndrome. The paper concludes by examining a variety of conditions, including dissecting aneurysms, dilator cardiac failure, angina, myocardial infarction, hypertension, eclampsia and cirrhosis and pointing out that all of them, like varicose veins, show evidence consistent with having been caused by a turbulence induced increase in a β₁-agonist stimulatory effect of microcirculatory plasma noradrenaline.     

Fluctuations in the Size of Isolated Single-Species Populations and Natural Selection

This paper discusses the basic types of dynamical behavior of populations obtained in discrete models, such as monotonous dynamics, stable limited cycles, and chaotic variations. All these modes are shown to have possibly arisen in the evolution of limited populations under the effect of density-independent selection. This effect together with that of density-dependent non-selective factors has been termed F-selection, which is characterized by independence of relative fitnesses from population density, whereas populations may be ecologically limited; in other words, absolute fitnesses prove to be a function of population size. The characteristic of F-selection is to be not sensitive to changes in population size but to lead to fluctuations, that create conditions for achieving density-dependent selection.     

Vibration arthrometry in assessment of knee disorders: the problem of angular velocity

A knee joint that has sustained a painful injury will typically require skillful examination, by an orthopaedic surgeon, for signs of internal damage. These signs include characteristic sounds and vibrations, which are produced by the knee when it is stressed. The technique of vibration arthrometry is being developed to assist the clinical examiner in identifying these vibrations and to improve diagnostic accuracy. To detect and record the knee vibrations, small lightweight accelerometers are positioned on various bony prominences around the knee. These produce electronic signals which permit objective analysis of the vibration characteristics. It has been found that varying the investigative procedure can affect the magnitude of some parameters of the vibration signal. If these parameters are to be used in evidence of knee pathology, the effect of the investigative procedure must be normalized. The effect of speed of joint movement has been quantified in a pilot study involving 24 patients with internal knee damage. Custom-designed hardware was used to measure joint speed as the rate of change of joint angle, which was measured by an electrogoniometer. It was found that the energy content of the vibration, reflected by the peak amplitude and root mean square value was strongly affected by joint speed. However, the characteristic shape of the vibration, reflected by the peak frequency in the harmonic spectrum of the signal, remained similar for the range of joint speed in the investigation.     

Modelling modification of chemical mutagenesis in human cells. III. Linear index of protection as the standardized criterion of modification]

The effect of substances with radioprotective activity, APAETP 2,3 (aminopropylaminoethylthiophosphoric acid 2,3), APAETP 3,3 and cystaphos, on chromosome aberrations, induced by thioTEPA in the culture of human lymphocytes was investigated. It is shown that the obtained curves "concentration -- effect" for thioTEPA can be described by equations rho = 1 -- e-(KC + alpha)2 and X = E -(KC + alpha)2 --1 for aberrant cells and for chromosome breaks in the presence of the investigated substances. On the basis of comparison of angle coefficients of regression the unificated characteristic of the efficiency of chemical mutagenesis is proposed: the linear protection index (LPI), with generalizes the effect of modificators in chemical mutagenesis.     

胡萝卜吸附式低温干燥特性的研究

对胡萝卜吸附式低温干燥过程的干燥特性进行了试验研究。考察了干燥气体 (空气 )的湿度和风量以及物料粒度对胡萝卜干燥特性和复水比的影响 ,得到形状相似的干燥曲线 ,用自定义最小二乘法拟合均能获得较好的结果。结果表明 :吸附式低温干燥过程可使被干燥物料达到超干水平 (含水率 <5 % ) ;增加干燥气体流量对干燥过程进行有利 ,当气体流量从 2 0 0L/h增加到 4 0 0L/h时 ,胡萝卜含水率从 4 1 13%降低到 34 93% ;被干燥物料颗粒大小和形状对干燥过程有显著影响 ;经过吸附式干燥后的胡萝卜色泽鲜艳 ,无褐变 ,外表品质优于热风干燥。吸附式低温干燥后胡萝卜的复水比 (6 5 2 )显著高于热风干燥 (1 78)。     

Characterization of prompt gamma-ray emission with respect to the Bragg peak for proton beam range verification: A Monte Carlo study

In this paper we report a Geant4 simulation study to investigate the characteristic prompt gamma (PG) emission in a water phantom for real-time monitoring of the Bragg peak (BP) during proton beam irradiation. The PG production, emission spatial correlation with the BP, and position preference for detection with respect to the BP have been quantified in different PG energy windows as a function of proton pencil-beam energy from 100 to 200 MeV. The PG response to small BP shifts was evaluated using a 2 cm-thick slab with different human body materials embedded in a water phantom. Our results show that the prominent characteristic PG emissions of 4.44, 5.21 and 6.13 MeV exhibit distinctive correlation with the dose deposition curve. The accuracy in BP position identification using these characteristic PG rays is highly consistent as the beam energy increases from 100 to 200 MeV. There exists a position preference for PG detection with respect to the BP position, which has a strong dependence on the proton beam energy and PG energies. It was also observed that a submillimeter shift of the BP position can be realized by using PG signals. These results indicate that the characteristic PG signal is sensitive and reliable for BP tracking. Although the maximization of the PG measurement associated with the BP is difficult, it can be optimized with energy and detection position preferences.     

《农业植物病理学》课程网站的建设

在进行区级精品教材—《农业植物病理学》(华南本)的编著工作的同时,开展了《农业植物病理学》课程网站的开发设计,提出了网站的设计思路及网站建设的方法,并就其测试效果及性能进行了分析。     

Quantification of the effect of electrical and thermal parameters on radiofrequency ablation for concentric tumour model of different sizes

Radiofrequency ablation (RFA) has been increasingly used in treating cancer for multitude of situations in various tissue types. To perform the therapy safely and reliably, the effect of critical parameters needs to be known beforehand. Temperature plays an important role in the outcome of the therapy and any uncertainties in temperature assessment can be lethal. This study presents the RFA case of fixed tip temperature where we’ve analysed the effect of electrical conductivity, thermal conductivity and blood perfusion rate of the tumour and surrounding normal tissue on the radiofrequency ablation. Ablation volume was chosen as the characteristic to be optimised and temperature control was achieved via PID controller. The effect of all 6 parameters each having 3 levels was quantified with minimum number of experiments harnessing the fractional factorial characteristic of Taguchi’s orthogonal arrays. It was observed that as the blood perfusion increases the ablation volume decreases. Increasing electrical conductivity of the tumour results in increase of ablation volume whereas increase in normal tissue conductivity tends to decrease the ablation volume and vice versa. Likewise, increasing thermal conductivity of the tumour results in enhanced ablation volume whereas an increase in thermal conductivity of the surrounding normal tissue has a debilitating effect on the ablation volume and vice versa. With increase in the size of the tumour (i.e., 2–3 cm) the effect of each parameter is not linear. The parameter effect varies with change in size of the tumour that is manifested by the different gradient observed in ablation volume. Most important is the relative insensitivity of ablation volume to blood perfusion rate for smaller tumour size (2 cm) that is also in accordance with the previous results presented in literature. These findings will provide initial insight for safe, reliable and improved treatment planning perceptively.     

Atherosclerosis in Japanese quail and the effect of lipoic acid

The Japanese quail (Coturnix coturnix japonica) is a useful laboratory animal for the study of atherosclerosis. It is small, omnivorous, easy to maintain, and susceptible to either spontaneous or cholesterol-induced atherosclerosis, and it has a low feed consumption and short life cycle. It develops atheromatous lesions with the characteristic lipid deposition and myofibroblastic proliferation in the aorta and sometimes in the coronary artery. Japanese quail can be genetically bred into lines highly susceptible and resistant to atherosclerosis. A nutritional study has indicated that a high intake of soy protein prevents the disease in the quail. Contradictory results of studies with rabbits were reported in the early literature on the prevention of atherosclerosis by lipoic acid. Recently the effect of lipoic acid on atherosclerosis was reevaluated in the quail. A preventive effect of this compound was demonstrated when it was implanted s.c. and slowly released in the animal.     

The species-area relation I. A model for discrete sampling

A simple mathematical model describing the species-area relation was developed. This paper dealt with the case that discrete random samples are combined. Modelling was made on the assumption that the occurrence probability of a species in a quadrat has a continuous density distribution. The model, given by the equation (6), holds only for a particular size of quadrat (i.e. the characteristic area). More general form applicable to the quadrats the size of which is near to the characteristic area was represented by the equation (9). Validity of the model was examined for the data of plant and insect communities, and it was concluded that the observation can be predicted by the model unless the size of sampling unit considerably differs from the characteristic area. The uniformity of specific density (i. e. the number of species per quadrat) and the size of characteristic area were discussed as being important in an understanding of community structure.     

污染河道治理技术研究进展

河道综合整治已引起人们广泛关注。综述了国内外河道治理常用的物理、化学和生物等方法的原理和工艺。物理法介绍了调水、机械除藻、底泥疏浚等,该法治标不治本;化学法有混凝沉淀,它易造成产生二次污染;生态-生物法是国外近年来发展很快的,借助自然界自身的水体自净能力治理受污水体的一类新技术,包括河道曝气法、生物膜法、生物修复技术,土地处理法等。同时也介绍了目前发展起来的最新河道治理工艺,如悬浮填料移动床、曝气生态净化系统和底泥生物氧化等多种方法,这类工艺是将生物法与其他工艺相结合,具有多功能、高效率等特点。     

How applicable is the general adaptation syndrome to the unicellular Tetrahymena?

Hormone receptors, hormones and signal transduction pathways characteristic of higher vertebrates can be observed also in the unicellular Tetrahymena. Previous work showed that stress conditions (starvation, high temperature, high salt concentration, formaldehyde or alcohol treatment) elevated the intracellular level of four hormones (ACTH, endorphin, serotonin and T₃). Here, the effect of other stressors (CuSO4 poisoning, tryptophan hydroxylase inhibitor parachlorphenylalanine (PCPA) treatment) on the same and other hormones (epinephrine, insulin, histamine) was studied, using immunocytochemistry and flow cytometric analysis. It was found, that each effect increased the intracellular hormone contents, but some hormones (histamine, T₃) were less reactive. Insulin—which is a life‐saving factor for Tetrahymena—itself provoked elevation of hormone amounts in association with a stressor, further increased the level of hormones. It was concluded that the ancestor of Selye's General Adaptation Syndrome (GAS) can be found already at unicellular level, and this possibly has a life saving function. Copyright © 2008 John Wiley & Sons, Ltd.