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151.
Persistent photoconductivity has been investigated by various models, among which the Macroscopic Barrier model, Large-Lattice-Relaxation model, and Random Local Potential Fluctuations model are mostly well known. Although the three well-known models have played important roles in describing the persistent photoconductivity, they are not the principal cause of persistent photoconductivity. In this paper a classical model originated from
“self-magnetism of electron gas” is proposed to illustrate the persistent
photoconductivity phenomenon. This classical model is based on electron gas
pulsation, which depends on the charge density. Different concentrations of
current carriers create different frequencies in the system, and thus the
system is sensitive to different wave lengths of incident light. Then the
construction of different detectors can be possible for different wave
lengths of incident light. 相似文献
152.
153.
Mohammadreza Estilaei Alex MacKay Clive Roberts John Mayo 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1997,124(2):410-419
Proton-magnetic-resonance measurements have been carried out on juvenile porcine peripheral lung parenchyma. The free-induction-decay signal contained a motionally restricted component which decayed in a few tens of microseconds and a mobile component with aT2time greater than 1 ms. The average second moment,M2, for the motionally restricted signal was found to be 3.42 ± (0.25) × 109s−2. TheT2distribution for the mobile signal consistently showed four resolvable components ofT2range: 2–6, 10–40, 80–110, and 190–400 ms. The 2–6 ms component was present in a fully dehydrated preparation and was therefore assigned to a nonaqueous lung constituent. The motionally restricted FID component had aT1= 0.772 ± 0.11 s and the mobile component had aT1= 0.967 ± 0.02 s. The hydrogen content per unit mass for lung parenchyma and water were estimated in two ways: (1) on the basis of chemical content and (2) on the basis of comparison of restricted and mobile signals to the gravimetric (G) water content for a lung sample studied at a wide range of water contents. Lung wet/dry weight ratios were estimated from the free-induction decays and compared with gravimetric measurement. The ratio of (wet/dry)NMR/(wet/dry)Gwas 1.00 ± 0.08 and 1.00 ± 0.05 for the two methods of estimation. 相似文献
154.
An inventory control problem for deteriorating items with back-ordering and financial considerations
This paper investigates the effects of time value of money and inflation on the optimal ordering policy in an inventory control system. We proposed an economic order quantity model to manage a perishable item over the finite horizon planning under which back-ordering and delayed payment are assumed. The demand and deterioration rates are constant. The present value of total cost during the planning horizon in this inventory system is modeled first, then a three phases solution procedure is proposed to derive the optimal order and shortage quantities, and the number of replenishment during the planning horizon. Finally, the proposed model is illustrated through numerical examples and the sensitivity analysis is reported to find some managerial insights. 相似文献
155.
Yasaman Zamani Mohammad Rabiee Mohammad Ali Shokrgozar Shahin Bonakdar Mohammadreza Tahriri 《Applied biochemistry and biotechnology》2013,171(6):1513-1524
The aim of this study was to obtain a better insight of how nano-fibrous scaffolds can affect human mesenchymal stem cells responses. Therefore, in this study, using electrospinning technique, poly(vinyl alcohol) (PVA) nano-fibers with two different patterns were prepared. In the first structure, PVA nano-fibers were oriented randomly and in the second structure, nano-fibers were electrospun in such a way that a special pattern was obtained. In order to enhance their stability, scaffolds were cross-linked using glutaraldehyde vapor. RGD immobilization was used to improve cell adhesion properties of the scaffolds. SEM micrographs demonstrated that the cell adhesion was effectively enhanced after RGD immobilization and higher cell densities were observed on RGD-modified scaffolds. Randomly oriented nano-fibers showed better cell adhesion compared to patterned structure. Patterned structure also revealed slightly lower cell viability compared to random nano-fibers. Finally, it was assumed that randomly oriented nano-fibers provide a more favorable surface for cells. 相似文献
156.
Mohammadreza Khanmohammadi Amir Bagheri Garmarudi 《Trends in analytical chemistry : TRAC》2011,30(6):864-874
Diagnosis of cancer is one of the most important aspects of medical research and has become the main aim of biomedical investigations. Misdiagnosis is the main drawback in most of the diagnostic routes introduced, while some of these methods are invasive and expensive.Recently, infrared spectroscopy (IR) was proposed as a rapid, accurate and sensitive technique in biomedical research, especially for detection of patterns of illness. We discuss research into cancer detection by IR, the role of data processing in quality assurance of the results obtained and novel proposals, such as bio-fluid analysis for diagnosis. We conclude that IR provides a novel green analytical chemistry approach to clinical oncology and cancer research. 相似文献