The three-dimensional architecture of the mitotic spindle,analyzed by confocal fluorescence and electron microscopy

Fluorescence microscopy techniques have become important tools in mitosis research. The well-known disadvantages of fluorescence microscopy, rapid bleaching, phototoxicity and out-of-focus contributions blurring the in-focus image are obstacles which still need to be overcome. Confocal fluorescence microscopy has the potential to improve our capabilities of analyzing cells, because of its excellent depth-discrimination and image processing power. We have been using a confocal fluorescence microscope for the study of the mechanism of poleward chromosome movement, and report here (1) a cell preparation technique, which allows labeling of fixation sensitive spindle antigens with acceptable microtubule preservation; (2) the use of image processing methods to represent the spatial distribution of various labeled elements in pseudocolour; (3) a novel immunoelectron microscopic labeling method for microtubules, which allows the visualization of their distribution in semithin sections at low magnification; and (4) a first attempt to study microtubule dynamics with a confocal fluorescence microscope in living cells, microinjected with rhodamine labeled tubulin. Our experience indicates that confocal fluorescence microscopy provides real advantages for the study of spatial colocalization of antigens in the mitotic spindle. It does not, however, overcome the basic limits of resolution of the light microscope. Therefore, it has been necessary to use an electron microscopic method. Our preliminary results with living cells show that it is possible to visualize the entire microtubule network in stereo, but that the sensitivity of the instrument is still too low to perform dynamic time studies. It will be worthwhile to further develop this new type of optical instrumentation and explore its usefulness on both fixed and living cells.     

Performance Evaluation of a Multi-Zone Application in Different OpenMP Approaches

We describe a performance study of a multi-zone application benchmark implemented in several OpenMP approaches that exploit multi-level parallelism and deal with unbalanced workload. The multi-zone application was derived from the well-known NAS Parallel Benchmarks (NPB) suite that involves flow solvers on collections of loosely coupled discretization meshes. Parallel versions of this application have been developed using the Subteam concept and Workqueuing model as extensions to the current OpenMP. We examine the performance impact of these extensions to OpenMP and compare with hybrid and nested OpenMP approaches on several large parallel systems.     

Measurements and simulations of transient characteristics of heat pipes

The rejection of heat generated by components and circuits is a very important aspect in design of electronics systems. Heat pipes are very effective, low cost elements, which can be used in cooling systems. This paper presents the modelling and measurements of the heat and mass transfer in heat pipes. The physical model includes the effects of liquid evaporation and condensation inside the heat pipe. The internal vapour flow was fully simulated using computational fluid dynamics. The theory has been compared with experimental measurements using thermographic camera and contact thermometers. The main purpose of this study is to determine the effective heat pipe thermal conductivity in transient state during start up the pipe operation and temperature increase.     

Dynamic electrothermal simulation of integrated resistors at device level

This paper presents the dynamic electrothermal simulation of a rectangular resistor integrated on a semi-conductor substrate. Due to the temperature dependence of the electrical conductivity of the resistive sheet, self-heating provokes a coupling between the electrical and thermal problem and gives rise to nonlinear phenomena. We introduce a time stepping iterative method to perform the calculations. The electrical and thermal solvers are based on FEM and Green's functions techniques, respectively. An extensive dynamic analysis of the device will be presented. The results include heating and cooling curves, Nyquist plot (complex locus) of the thermal impedance, time constant spectrum and structure function. Comparisons with the linear case, i.e. a temperature independent resistor, are made and accompanied by analytical approximations if possible. One key observation is that the nonlinearity may easily be overlooked: its detection is only possible in particular characteristics.     

Analysis of the clover-shaped geometry for a Hall generator

The influence of the contact size on the Hall voltage and its nonlinear behaviour has been investigated for the clover-shaped geometry. The potential problem has been solved by an expansion and an integral-equation technique.     

Characteristics of electro-gas-dynamic wind energy devices

Recently, a new principle has been presented to convert wind energy directly into electric power. The basic idea is that the wind carries charged particles and hence bears an electric current. In this contribution the IV characteristics of such a device will be calculated starting from a conduction model for the charged particles. From the IV characteristics, the maximum attainable power and the influence of several device parameters will be investigated.     

Influence of thermal contact resistance on thermal impedance of microelectronic structures

The thermal impedance Z_th(jω) has been calculated numerically for a silicon chip glued on a ceramic substrate. The non perfect thermal contact is taken into account by modelling the chip-substrate interface as a thermal contact resistance r_c. If Z_th is represented as a Nyquist plot, mainly two circular arcs are observed. The high frequency arc is found to be almost independent from r_c, whereas the low frequency part is largely influenced by r_c. The thermal resistance R_th = Z_th(jω = 0) increases linearly with r_c, as known from the literature. Additionally, our simulations have shown that similar conclusions can be drawn for the real and imaginary part of Z_th at a fixed frequency ω ≠ 0.     

Quality of life before and during antihypertensive treatment: a comparative study of celiprolol and atenolol

BACKGROUND: The well-being of hypertensive patients may be adversely affected by the disease itself, its complications, and other concomitant processes such as anxiety, sedation, and side effects of the prescribed drugs. Some recently developed antihypertensive agents have been suggested to be devoid of these deleterious effects on well-being expressed as quality of life. OBJECT: We compared the effect on quality of life of a standard cardioselective beta-blocker atenolol to the effect of celiprolol as a representative of a new class of selective beta-blockers with vasodilatory properties. One-hundred-thirty-two patients with mild to moderate hypertension were eligible to enter a 28-week double-blind parallel-group study, consisting of a 4-week run-in period on placebo and a 24-week period on dosage-adjusted treatment with either atenolol or celiprolol. RESULTS: Both systolic and diastolic blood pressure were assessed, as was quality of life perception by a selected test battery including the Quality of Life Questionnaire of Bulpitt and Fletcher [1990]. During celiprolol treatment, supine blood pressure fell from 167/101 (range 120-200/95-116) to 150/92 mm Hg (p < 0.0001). This antihypertensive effect was at least as good with celiprolol as with atenolol. Quality of life perception was comparable for the 2 drugs, although some adverse effects were more frequent during atenolol than during celiprolol, particularly after prolonged treatment. Also patient compliance was better for celiprolol than for atenolol. CONCLUSIONS: Our results show that the selective beta-blocker with vasodilatory property celiprolol is at least as effective as atenolol and that it has additional advantage in terms of enhancement of some quality of life variables.