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排序方式: 共有348条查询结果,搜索用时 890 毫秒
341.
An unexpected synthesis of symmetrical hydroxybiphenylmethanes involving the reaction of 2-hydroxyphenyl benzyl ketones with ethoxymethyl chloride has been observed. Some new interesting observations of Labat test on colorimetric detection of bichalconyloxy, bichalconyl and biflavonylmethanes having oxygenated ortho positions are presented. 相似文献
342.
Ian P. Martines Hristo V. Kojouharov James P. Grover 《Applied mathematics and computation》2009,215(2):573-582
Presented is a chemostat model in which one microbial population excretes a poison that increases the mortality of another, with toxin production increasing as the growth rate of the toxic species decreases. The model is intended to explore the role of allelopathy in blooms of harmful algae, such as red tide (Karenia brevis) and golden algae (Prymnesium parvum). This study introduces the model and its biological basis, and proceeds to the analysis of its asymptotic states. All theoretical results are supported by a set of numerical simulations. A discussion of biological conclusions and similarities to other mathematical models is also presented. 相似文献
343.
Garret Moddel Zixu Zhu Sachit Grover Saumil Joshi 《Solid State Communications》2012,152(19):1842-1845
The ability to tune the carrier-type concentration ratio with applied field along with a mean-free path length approaching 1 μm in graphene enables a new diode in which the diode polarity can be reversed. The diode consists of a thin graphene film with a geometric asymmetry that determines a preferred direction for charge-carrier transport, independent of whether the carriers are electrons or holes. We fabricated submicron geometric diodes by patterning and etching exfoliated graphene. Applying field-effect voltages to the substrate, we reversed the carrier type and demonstrated reversal of the diode polarity. The graphene geometric diodes exhibited rectification at 28 THz, opening the way to ultrahigh speed applications for these versatile devices. 相似文献
344.
Rakhi Grover Ritu Srivastava Omwati Rana A.K. Srivastava K.K. Maurya K.N. Sood D.S. Mehta M.N. Kamalasanan 《Journal of luminescence》2012,132(2):330-336
Hybrid organic–inorganic light emitting devices combine the color purity and durability of inorganic light emitting diodes (LEDs) with high efficiency, flexibility and low processing cost of organic LEDs (OLEDs). A significant challenge is to incorporate inorganic nanocrystals inside the OLED structure. In the present work, thin films of CdS were successfully incorporated inside standard OLED structure using vacuum thermal evaporation technique. For the characterization of these films, they were deposited on plain glass plates at room temperature and studied using structural (XRD and TEM), morphological (SEM and AFM) and optical (UV and PL) techniques. The films were found to be composed of nanocrystals of CdS in which the size of the crystals increased with the increase in film thickness. The hybrid organic–inorganic LEDs showed improved luminance and efficiency as compared to the organic LED without CdS layers. 相似文献
345.
Michael J. Casciato Galit Levitin Dennis W. Hess Martha A. Grover 《Journal of nanoparticle research》2012,14(5):836
Silver nanoparticles (AgNPs) have been deposited on silicon and glass surfaces via a supercritical carbon dioxide (sc-CO2) synthesis route for application in surface-enhanced Raman spectroscopy (SERS). Arrhenius plots revealed that nucleation
and growth processes in this system depend on both temperature and surface chemistry. Results also demonstrated that temperature
and surface chemistry could be varied to control nanoparticle properties, such as the mean nanoparticle size, density, and
surface coverage, providing two useful variables for manipulating the properties of AgNPs deposited on surfaces in this system.
These data also provide scientific insight into the underlying mechanisms governing heterogeneous AgNP deposition on a substrate
in a sc-CO2 system in addition to engineering insight into the variables that can be used to manipulate AgNP characteristics. The mean
particle size could be tuned over the range 20–200 nm, the interparticle distance could be tuned over the range 70 nm–1 μm,
and the surface coverage could be tuned over the range 0.035–0.58. Products were analyzed by scanning electron microscopy
with image analysis, transmission electron microscopy, X-ray diffraction, and SERS. The silver nanoparticle-coated substrates
were successfully applied in SERS, detecting the model analyte Rhodamine 6G at a concentration of 1 μM, a three orders of
magnitude improvement over SERS surfaces previously fabricated in sc-CO2 systems. Such surfaces can find use in trace concentration analyte detection in biomedical, chemical, and environmental applications. 相似文献
346.
Lov K Grover 《Pramana》2001,56(2-3):333-348
The quantum search algorithm is a technique for searching N possibilities in only O(√N) steps. Although the algorithm itself is widely known, not so well known is the series of steps that first led to it, these are quite different from any of the generally known forms of the algorithm. This paper describes these steps, which start by discretizing Schrödinger’s equation. This paper also provides a self contained introduction to quantum computing algorithms from a new perspective. 相似文献
347.
A mathematical model describing the coupling of electrical,optical and thermal effects in semiconductor lasers is introduced.Numerical and asymptotic solutions are derived, including expressionsfor key physical quantities such as the initial time delay,the frequency of spike oscillation and the temperature rise,together with its influence on the photon density, the electronconcentration and the threshold current. The consequences ofthermal effects in reducing efficiency are thus quantified. 相似文献
348.