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排序方式: 共有272条查询结果,搜索用时 15 毫秒
1.
Vladimir Rozenshtein Alexander Berg Haim Levanon Uwe Krueger Dietmar Stehlik Yuri Kandrashkin Art Van Der Est 《Israel journal of chemistry》2003,43(3-4):373-381
Light-induced spin-polarized transient EPR spectra are reported for several water-soluble copper porphyrins. The spectra are assigned to the doublet ground state, with emissive spin polarization resulting from photoexcitation and subsequent electronic relaxation. In contrast to other systems for which polarization of a doublet ground state has been observed, the exchange interactions in the copper porphyrins are strong and the geometry is fixed. It is proposed that intersystem crossing from the photoexcited trip-doublet to the trip-quartet state can lead to net polarization of the spin system and that this polarization is maintained during electronic decay, possibly via charge-transfer and exciplex states. The intensity of the observed spin polarization is essentially independent of the molecular orientation in the external field, but is strongly dependent on the nature of the charged peripheral groups. Possible reasons for this behavior are discussed. 相似文献
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Bituminous coal piles stored in the open air can undergo autocatalytic heating accompanied by the emission of small but appreciable amounts of molecular hydrogen. When the coal is contained in a confined space and the temperature reaches 40°C, accumulation of hydrogen is expected. This process has been observed for a wide variety of bituminous coals. The amount of hydrogen gas expected to accumulate in the air pocket above the coal cargo in ship holds (assuming that the coal's temperature approaches 40°C during the voyage) has been calculated. The results clearly indicate that in most cases the hydrogen concentration will be appreciably above the lower explosion limit in air. Hence when bituminous coals are stored in a confined space (e.g. a ship hold), the explosive risk of hydrogen should be taken into account. 相似文献
4.
Avner Adini Irit Adini Etty Grad Yuval Tal Haim D. Danenberg Peter M. Kang Benjamin D. Matthews Robert J. DAmato 《International journal of molecular sciences》2021,22(10)
Myocardial infarction (MI) remains the leading cause of death in the western world. Despite advancements in interventional revascularization technologies, many patients are not candidates for them due to comorbidities or lack of local resources. Non-invasive approaches to accelerate revascularization within ischemic tissues through angiogenesis by providing Vascular Endothelial Growth Factor (VEGF) in protein or gene form has been effective in animal models but not in humans likely due to its short half-life and systemic toxicity. Here, we tested the hypothesis that PR1P, a small VEGF binding peptide that we developed, which stabilizes and upregulates endogenous VEGF, could be used to improve outcome from MI in rodents. To test this hypothesis, we induced MI in mice and rats via left coronary artery ligation and then treated animals with every other day intraperitoneal PR1P or scrambled peptide for 14 days. Hemodynamic monitoring and echocardiography in mice and echocardiography in rats at 14 days showed PR1P significantly improved multiple functional markers of heart function, including stroke volume and cardiac output. Furthermore, molecular biology and histological analyses of tissue samples showed that systemic PR1P targeted, stabilized and upregulated endogenous VEGF within ischemic myocardium. We conclude that PR1P is a potential non-invasive candidate therapeutic for MI. 相似文献
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This work presents experimental results on pickup velocity (critical velocity) measurements for a variety of particulate solids. The present experiments together with previously published experiments of a number of researchers encompass about 100 measurements of 24 materials for a wide range of particle sizes, shapes and densities. Based on the experimental results, three zones are defined by establishing simple relationships between the Reynolds and Archimedes numbers. The empirical relationships were further modified by taking into account the pipe diameter and particle shape (sphericity). The three-zone model was shown to reasonably correlate to Geldart's classification groups. 相似文献
6.
Changchun?Liu Michael?G.?Mauk Haim?H.?BauEmail author 《Microfluidics and nanofluidics》2011,11(2):209-220
An inexpensive, disposable, integrated, polymer-based cassette for loop-mediated isothermal amplification (LAMP) of target
nucleic acids was designed, fabricated, and tested. The LAMP chamber was equipped with single-use, thermally actuated valves
made with a composite consisting of a mixture of PDMS and expandable microspheres. The effect of the composite composition
on its expansion was investigated, and the valve’s performance was evaluated. In its closed state, the valve can hold pressures
as high as 200 kPa without any significant leakage. Both the LAMP chamber and the valves were actuated with thin film heaters.
The utility of the cassette was demonstrated by carrying out LAMP of Escherichia coli DNA target and reverse transcribed loop meditated isothermal amplification (RT-LAMP) of RNA targets. The amplicons were detected
in real time with a portable, compact detector. The system was capable of detecting as few as 10 target molecules per sample
in well under 1 h. The portable, integrated cassette system described here is particularly suited for applications at the
point of care and in resource-poor countries, where funds and trained personnel are in short supply. 相似文献
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Color scales are commonly used to represent numerical information visually. Most scales are derived from some physical or mathematical behavior; even worse, sometimes they are selected based solely on hardware capabilities. In most known cases, no consideration is made to the perceptual capabilities of the human observer, who is ultimately the “consumer” of the information to be delivered by the scale. This article presents a method and an algorithm for the derivation of color scales, such that their perceptual properties—in particular, the perceptual steps between colors along the scale—can be controlled by the scale designer. This approach has been used for the design of the linearized gray scale and the linearized optimized color scale (LOCS). These scales are demonstrated and are also compared to the linearized heated-object scale. © 1996 John Wiley & Sons, Inc. 相似文献
9.
The problem of defining vector space operations on fuzzy and probability vectors is discussed. It is shown that such a definition is equivalent to choosing a 1-1 and onto mapping from the unit interval into the real axis. Although such a mapping cannot be continuous, it is suggested that under certain approximations a continuous mapping can be chosen. A characterization of some useful mappings with applications to image processing is also given. 相似文献
10.
Haim Gershoni 《IIE Transactions》1969,1(3):244-251
Experienced time study analysts in the United Kingdom and Israel analyzed a series of motion pictures of a simple manual task. Comparison of the analyses of the two groups showed no significant differences between results. Furthermore, none of these men was able to detect partially trained workers or variations in the micro-method. Variations between observers were minimal where the observations concerned a very specific task situation. 相似文献