角倍蚜优良冬寄主侧枝匐灯藓的繁育研究

侧枝匐灯藓是角倍蚜的优良冬寄主,其生长状况直接关系到角倍蚜越冬蚜的成活率,进而影响五倍子的产量,但目前关于侧枝匐灯藓培植方法的研究较少。本研究采用直接移栽、撕碎繁殖、切碎繁殖3种繁殖方式,结合垄床、塑料毡、泡沫箱3种不同载体进行试验处理,结果表明,采用1∶1比例直接移栽垄床植藓处理,藓的总鲜重、盖度、藓块厚度等指标值均最大,能够在较短的时间内提供释放秋迁蚜的冬寄主藓;采用比例为1∶1撕碎繁殖方式以垄床或泡沫箱载体植藓均能获得最大的藓新枝数和藓茎高度,可以作为角倍蚜种虫生产中冬寄主藓的主要繁殖方式;采用1∶4或1∶8比例进行切碎繁殖藓萌发的新枝最多,可以作为优良冬寄主藓的种藓繁殖的主要方式。通过主成分分析法进行分析,结果表明,3个主成分累积贡献率为86.573%,可以较好地反映出24个处理10个测试指标的综合信息。综合评价结果以A1B1C1、A1B1C2、A2B4C1、A2B5C1、A2B3C2、A2B5C2、A2B4C3处理的综合性状最佳。     

Global dynamics of an epidemiological model with age of infection and disease relapse

In this paper, an epidemiological model with age of infection and disease relapse is investigated. The basic reproduction number for the model is identified, and it is shown to be a sharp threshold to completely determine the global dynamics of the model. By analysing the corresponding characteristic equations, the local stability of a disease-free steady state and an endemic steady state of the model is established. By means of suitable Lyapunov functionals and LaSalle's invariance principle, it is verified that if the basic reproduction number is less than unity, the disease-free steady state is globally asymptotically stable, and hence the disease dies out; if the basic reproduction number is greater than unity, the endemic steady state is globally asymptotically stable and the disease becomes endemic.     

An age-structured within-host HIV-1 infection model with virus-to-cell and cell-to-cell transmissions

In this paper, a within-host HIV-1 infection model with virus-to-cell and direct cell-to-cell transmission and explicit age-since-infection structure for infected cells is investigated. It is shown that the model demonstrates a global threshold dynamics, fully described by the basic reproduction number. By analysing the corresponding characteristic equations, the local stability of an infection-free steady state and a chronic-infection steady state of the model is established. By using the persistence theory in infinite dimensional system, the uniform persistence of the system is established when the basic reproduction number is greater than unity. By means of suitable Lyapunov functionals and LaSalle's invariance principle, it is shown that if the basic reproduction number is less than unity, the infection-free steady state is globally asymptotically stable; if the basic reproduction number is greater than unity, the chronic-infection steady state is globally asymptotically stable. Numerical simulations are carried out to illustrate the feasibility of the theoretical results.     

Cortical pattern formation during visual hallucinations

We theoretically investigate pattern formation during simple visual hallucinations caused by epileptic activity. To this end we analyze the activator-inhibitor model of Ermentrout and Cowan [1]. In contrast to these authors we focus on a different disease mechanism: According to experimental findings (cf. [2]) we decrease the influence of the inhibitor on the activator. This causes spontaneous pattern formation due to a bifurcation. The model parameters determine whether one or two or four modes become unstable. By means of the center manifold theorem, in all cases the order parameter equation is derived, the stability of the solution is proofed, and the bifurcating activity pattern is calculated explicitely in lowest order. Taking into account terms up to third order in all cases the order parameter equation has a potential. For the two-modes and the four-modes instability this potential causes a winner-takes all dynamics. We integrate the order parameter equation numerically and plot the visual hallucinations which result from the bifurcating cortical activity. The theoretically derived hallucinations correspond to clinically observed visual hallucinations (cf. [3, 4]), which are, for instance, well-known from petit mal epilepsy [5].Finally we investigate the influence of noise on the activity patterns as well as the visual hallucinations.     

Comparison of coulter volumes with radiometrically determined intracellular water volumes for cultured cells

Summary During methotrexate-induced differentiation of cultured human choriocarcinoma (BeWo) cells, proliferation is inhibited, morphologic and biochemical changes occur, and giant, often multinucleated, cells form. We have used the increase in cell volume as a marker of the mature syncytiotrophoblastlike phenotype. Uninduced and differentiated BeWo cells are not spherical, and theoretical considerations suggested that deviations in shape could result in significant errors in Coulter volume. To determine if the values obtained by electrical pulse sizing reflected the actual mass of BeWo cells, we have evaluated the relationship between Coulter volumes and intracellular water volumes obtained using a shape-independent estimate for eight cell types. A close correlation (r ²=0.97) was found, indicating that cell volume changes in populations of irregularly shaped cells can be accurately measured using a Coulter instrument. Supported by an operating grant from the National Cancer Institute of Canada. N.S.B. was a recipient of a studentship award from the Alberta Heritage Foundation for Medical Research. C.E.C. is a Senior Research Scientist of the National Cancer Institute of Canada. The McEachern Laboratory is a research facility of the Faculty of Medicine, University of Alberta, and the Cross Cancer Institute, Edmonton, Alberta.     

Redox-linked proton translocation by direct-coupled ligand conduction

The term direct-coupled is considered in the context of redox-linked proton translocation mechanisms, and the origins of this concept, its philosophical implications, applications, and contributions to the development of bioenergetics, are discussed.     

暗视条件下鲫鱼视网膜电图的单变量分析

本工作研究了暗视条件下鲫鱼视网膜电图(ERG)的特性。ERG 波形没有波长特异性。不同波长的 b 波振幅-强度曲线平行性良好。b 波不同时相(上升相、峰值、下降相)的光谱敏感性甚为一致。进而,对颜色混合刺激的 b 波幅值与基于单变量原理所作的预测几乎完全一致。基于这些结果,我们的结论是:在暗视条件下,鲤属鱼 ERG b 波仅反映了杆细胞系统的活动,并非象有些研究所认为的也有明视系统的贡献。     

Avoiding the Trust Deficit: Public Engagement, Values, the Precautionary Principle and the Future of Nanotechnology

Debates about the regulatory requirements surrounding the introduction of nanotechnology products have, at least in Australia, remained largely within disciplinary boundaries and industry and academic circles. This paper argues for a more interdisciplinary and inclusive upstream debate about the introduction of ethical, regulatory and legal frameworks that may avoid the loss of public trust that has characterised the introduction of many new technologies in the past. Insights from risk-perception theory and research are used to introduce the notion of risk as narrative as a framework for action. This paper suggests three main strategies for moving forward; drawing insights from the “trust gap” experiences of other new technologies; the application of the active form of the precautionary principle; and, the creation of nano-futures that meet both community and industry values through effective public engagement.