Spatially resolving light detectors allow, with proper calibration, quantitative analysis of the variations in two-dimensional intensity distributions over time. An ultra-sensitive microfluorometer ...was assembled by using as a detector a microchannel plate-intensified video camera. The camera was interfaced with a software-based digital video analysis system to digitize, average, and process images and to directly control the timing of the experiments to minimize exposure of the specimen to light. The detector system has been characterized to allow its use as a photometer. A major application has been to perform fluorescence recovery after photobleaching measurements by using the camera in place of a photomultiplier tube (video-FRAP) with the goal of detecting possible anisotropic diffusion or convective flow. Analysis of the data on macromolecular diffusion in homogenous aqueous glycol solutions yielded diffusion constants in agreement with previous measurements. Results on lipid probe diffusion in dimyristoyl-phosphatidylcholine multibilayers indicated that at temperatures above the gel-to-liquid crystalline phase transition diffusion is isotropic, and analysis of video-FRAP data yielded diffusion coefficients consistent with those measured previously by using spot photobleaching. However, lipid probes in these multibilayers held just below the main phase transition temperature exhibited markedly anisotropic diffusive fluxes when the bleaching beam was positioned proximate to domain boundaries in the P β ′ phase. Lipid probes and lectin receptor complexes diffused isotropically in fibroblast surface membranes with little evidence for diffusion channeled parallel to stress fibers. A second application was to trace the time evolution of cell surface reactions such as patching. The feasibility of following, on the optical scale, the growth of individual receptor clusters induced by the ligand wheat germ agglutinin was demonstrated.
Grounding for EMC at the European XFEL Kapitza, H.; Eckoldt, H.; Faesing, M.
International Symposium on Electromagnetic Compatibility - EMC EUROPE,
2012-Sept.
Conference Proceeding
Odprti dostop
The European X-Ray Free Electron Laser (XFEL) research facility is currently being built at Deutsches Elektronensynchrotron (DESY) in Hamburg, Germany. In this large underground facility high power ...RF stations are operated next to high precision diagnostics instruments. This made electromagnetic compatibility (EMC) an important issue from the very beginning of the project. A well-designed grounding system with a hierarchical structure is an essential ingredient for safety and EMC. Important parts of the facility ground were implemented in the course of the civil construction work. The specialties of tunnel boring and building far below the ground water level had to be taken into account. Some aspects of facility grounding were investigated at the free electron laser facility FLASH which operates for users at DESY for some years.
Broad-band dielectric spectroscopy (10 exp --1 -10 exp 7 Hz) was used to analyze the molecular dynamics of a set of combined main-chain side-group liquid-crystalline polymers. By varying the chemical ...structure, a detailed assignment of the observed relaxational processes was possible. Three relaxational processes were found: (i) an alpha -relaxation, which is assigned to the dynamic glass process of the polymeric main chain and through spacer coupled side-group movements, (ii) a beta sub s -relaxation, which is assigned to the rotation of the mesogenic side group around its long axis; (iii) a beta sub m -relaxation, which is assigned to the rotation of the mesogenic group in the main chain around its long axis. Graphs. 24 ref.--AA
The lateral mobility of the lipid analog N-4-nitrobenzo-2-oxa-1,3 diazole phosphatidylethanolamine and of the integral protein glycophorin in giant dimyristoylphosphatidylcholine vesicles was studied ...by the photobleaching technique. Above the temperature of the chain-melting transition (Tm = 23 degrees C), the diffusion coefficient, Dp, of the protein Dp = (4 +/- 2) X 10(-8) cm2/s at 30 degrees C was within the experimental errors equal to the corresponding values DL of the lipid analog. In the P beta 1 phase the diffusion of lipid and glycophorin was studied as a function of the probe and the protein concentration. (a) At low lipid-probe content (cL less than 5 mmol/mol of total lipid), approximately 20% of the probe diffuses fast (D approximately equal to 10(-8) - 10(-9) cm2/s), while the mobility of the rest is strongly reduced (D less than 10(-10) cm2/s). At a higher concentration (cp approximately 20 mmol), all probe is immobilized (D less than 10(-10) cm2/s). (b) Incorporation of glycophorin up to cp = 0.4 mmol/mol of total lipid leads to a gradual increase of the fraction of mobile lipid probe due to the lateral-phase separation into a pure P beta 1 phase and a fraction of lipid that is fluidized by strong hydrophilic lipid-protein interaction. (c) The diffusion of the glycophorin molecules is characterized by a slow and a fast fraction. The latter increases with increasing protein content, which is again due to the lateral-phase separation caused by the hydrophilic lipid-protein interaction. The results are interpreted in terms of a fast transport along linear defects in the P beta 1 phase, which form quasi-fluid paths for a nearly one dimensional and thus very effective transport. Evidence for this interpretation of the diffusion measurements is provided by freeze-fracture electron microscopy.
Abstract
In order to meet international standards, printed circuit board (PCB) base materials have to be flame‐retardant according to the UL 94V specification. Up to now this has been achieved with ...FR4 materials by using brominated aromatic components. FR4 materials are glass epoxy based and are by far most prevalent in PCB production. Unfortunately, in the case of fire or smoldering, these materials evolve highly corrosive, and, under unfavorable conditions, even highly toxic decomposition products. In the search for flame retardancy without the use of bromine, the effect of different structural elements on the burning behavior of cured resins has been investigated. As a result of these investigations an epoxy resin was developed that contains tailor‐made N‐ and P‐containing constituents that form flame‐retardant structures during processing and curing of the material. The new material meets all requirements for printed circuit boards and can be processed without any need to modify established technologies. Analytical and ecotoxicological investigations of the combustion products of the new material show that they are comparable with those of wood from the beech tree. PCBs and electronic assemblies manufactured therefrom successfully passed all functional tests. The base materials recently became commercially available.
The lateral diffusion coefficients (D) of the molecular fluorescence probe 3,3'-dioctadecylindocarbocyanine iodide (DII) in the membrane of discoiderythrocyte ghosts has been measured with the ...photobleaching technique between 7 degrees C and 40 degrees C. A fluorescence microscope which allows bleaching experiments within small local fields (approx. 1 micron m2) at high magnification (X1600) has been used for these measurements. The diffusion coefficient increases from D = 9 - 10-10 cm2/s to D = 7.5 - 10-9 cm2/s from 7 to 40 degrees C. An increase in membrane fluidity between 12 degrees C and 17 degrees C indicates a conformational change of the lipid bilayer moiety in this temperature region. The diffusion coefficient measured in the regions between the spicules of echinocytes is appreciably smaller than in the untransformed discoid ghosts. In the myelin tubes originating from cells, the lateral diffusion is somewhat larger (about a factor of 2) than in the non-transformed ghosts. With the fluorescence probe technique the rate of growth of myelin tubes of 0.3 micronm diameter has been estimated.
The implementation of the GESIMA mesoscale atmospheric model on message passing, distributed memory parallel computers is presented. Particular emphasis is given to the parallelization of the ...conjugate gradient solver using pre-conditioning by an incomplete LU factorization. Performance results are presented for the Cray T3D and Cray T3E systems, which show good scalability over a range of problem sizes and numbers of processors.
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