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121.
The development of the Lanczos algorithm for finding eigenvalues of large sparse symmetric matrices was followed by that of block forms of the algorithm. In this paper, similar extensions are carried out for a relative of the Lanczos method, the conjugate gradient algorithm. The resulting block algorithms are useful for simultaneously solving multiple linear systems or for solving a single linear system in which the matrix has several separated eigenvalues or is not easily accessed on a computer. We develop a block biconjugate gradient algorithm for general matrices, and develop block conjugate gradient, minimum residual, and minimum error algorithms for symmetric semidefinite matrices. Bounds on the rate of convergence of the block conjugate gradient algorithm are presented, and issues related to computational implementation are discussed. Variants of the block conjugate gradient algorithm applicable to symmetric indefinite matrices are also developed. 相似文献
122.
Dianne Pham Upamanyu Basu Ivanna Pohorilets Claudette M. St Croix Simon C. Watkins Kazunori Koide 《Angewandte Chemie (International ed. in English)》2020,59(40):17435-17441
Hydrogen peroxide (H2O2) mediates the biology of wound healing, apoptosis, inflammation, etc. H2O2 has been fluorometrically imaged with protein‐ or small‐molecule‐based probes. However, only protein‐based probes have afforded temporal insights within seconds. Small‐molecule‐based electrophilic probes for H2O2 require many minutes for a sufficient response in biological systems. Here, we report a fluorogenic probe that selectively undergoes a [2,3]‐sigmatropic rearrangement (seleno‐Mislow‐Evans rearrangement) with H2O2, followed by acetal hydrolysis, to produce a green fluorescent molecule in seconds. Unlike other electrophilic probes, the current probe acts as a nucleophile. The fast kinetics enabled real‐time imaging of H2O2 produced in endothelial cells in 8 seconds (much earlier than previously shown) and H2O2 in a zebrafish wound healing model. This work may provide a platform for endogenous H2O2 detection in real time with chemical probes. 相似文献
123.
Ana Ramón‐Laca Adrian M. T. Linacre Dianne M. Gleeson Shanan S. Tobe 《Electrophoresis》2013,34(24):3370-3376
An identification assay has been developed that allows accurate detection of 19 of the most common terrestrial mammals present in New Zealand (cow, red deer, goat, dog, horse, hedgehog, cat, tammar wallaby, mouse, weasel, ferret, stoat, sheep, rabbit, Pacific rat, Norway rat, ship rat, pig, and brushtail possum). This technique utilizes species‐specific primers that, combined in a multiplex PCR, target small fragments of the mitochondrial cytochrome b gene. Each species, except hedgehog, produces two distinctive species‐specific fragments, making the assay self‐confirmatory and enabling the identification of multiple species simultaneously in DNA mixtures. The multiplex assay detects as little as 100 copies of mitochondrial DNA, which makes it a very reliable tool for degraded and trace samples. Reliability, accuracy, reproducibility, and sensitivity tests to validate the technique were performed. The technique featured here enabled a prompt response in a predation specific event, but can also be useful for wildlife management and conservation, pest incursions detection, forensic, and industrial purposes in a very simple and cost‐effective manner. 相似文献
124.
This study investigated several knowledge gaps with respect to the diffusive gradients in thin films (DGT) technique for measurement of oxyanions (As(III), As(V), Se(IV), Se(VI), PO43−, and V(V)) using the ferrihydrite and Metsorb™ binding layers. Elution efficiencies for each binding layer were higher with 1:20 dilutions, as analytical interferences for ICP-MS were minimised. Diffusion coefficients measured by diffusion cell and by DGT time-series experiments were found to agree well and generally agreed with previously reported values, although a range of diffusion coefficients have been reported for inorganic As and Se species. The relative binding affinity for both ferrihydrite and Metsorb™ was PO43− ≈ As(V) > V(V) ≈ As(III) > Se(IV) ? Se(VI) and effective binding capacities were measured in single ion solutions, and spiked synthetic freshwater and seawater, advising practical decisions about DGT monitoring. Under the conditions tested the performance of both ferrihydrite and Metsorb™ binding layers was directly comparable for As(V), As(III) Se(IV), V(V) and PO43− over a deployment spanning ≤2 days for both freshwater and seawater. In order to return quantitative data for several analytes we recommend that the DGT method using either ferrihydrite or Metsorb™ be deployed for a maximum of 2 days in marine waters likely to contain high levels of the most strongly adsorbing oxyanions contaminants. The high pH, the competitive ions present in seawater and the identity of co-adsorbing ions affect the capacity of each binding layer for the analytes of interest. In freshwaters, longer deployment times can be considered but the concentration and identity of co-adsorbing ions may impact on quantitative uptake of Se(IV). This study found ferrihydrite-DGT outperformed Metsorb-DGT while previous studies have found the opposite, with variation in binding materials masses used being a likely reason. Clearly, preparation of both binding layers should always be optimised to produce the highest capacity possible, especially for seawater deployments. 相似文献
125.
Quantification of water compartmentation in cell suspensions by diffusion-weighted and T(2)-weighted MRI 总被引:1,自引:0,他引:1
Roth Y Ocherashvilli A Daniels D Ruiz-Cabello J Maier SE Orenstein A Mardor Y 《Magnetic resonance imaging》2008,26(1):88-102
When studying water diffusion in biological systems, any specific signal attenuation curve may be reproduced by a broad range of mathematical functions. Our goals were to quantify the diffusion and T2 relaxation properties of water in a simple biological system and to study the changes that occur in osmotically stressed cells. 相似文献
126.
Marijke WA de Backer Maike AD Brans Mieneke CM Luijendijk Keith M Garner Dianne MA van den Heuvel R Jeroen Pasterkamp Roger AH Adan 《BMC neuroscience》2010,11(1):94