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21.
A. P. Knights J. J. Ackert D. F. Logan E. Huante-Ceron P. E. Jessop 《Optical and Quantum Electronics》2012,44(12-13):575-580
In this paper we outline two recent results which demonstrate the utility of deep-level engineering in silicon photonics. We describe the integration of silicon waveguide p-i-n photo-detectors in a ring (or race-track) resonator structure. The detectors are made sensitive to wavelengths around 1,550?nm via the introduction of deep-levels into the intrinsic volume of the waveguide detector. By exploiting the multiple-pass of the optical signal through the detector, we are able to significantly decrease the size of the detector structure (relative to straight waveguide detectors) while maintaining excellent responsivity on resonance. We also describe the use of deep-levels for optical modulation. Preliminary results show that thallium doped silicon waveguides may be switched between a dark and transparent condition through the variation of phosphorus doping. It is suggested that active devices may be fabricated in such a way as to vary the occupancy of the thallium level through field mediated modulation. The straightforward fabrication methods described lend themselves to a high-volume, high yield manufacturing process which should find general applicability in wavelength division multiplexing systems. 相似文献
22.
David J. Kennedy Paul Todd Sam Logan Matthew Becker Klearchos K. Papas Lee R. Moore 《Journal of magnetism and magnetic materials》2007
Quadrupole magnetic flow sorting (QMS) is being adapted from the separation of suspensions of single cells (<15 μm) to the isolation of pancreatic islets (150–350 μm) for transplant. To achieve this goal, the critical QMS components have been modeled and engineered to optimize the separation process. A flow channel has been designed, manufactured, and tested. The quadrupole magnet assembly has been designed and verified by finite element analysis. Pumps have been selected and verified by test. Test data generated from the pumps and flow channel demonstrate that the fabricated channel and peristaltic pumps fulfill the requirements of successful QMS separation. 相似文献
23.
Elizabeth K. Heaney S.R. Logan William E. Watts 《Journal of organometallic chemistry》1978,153(2):229-237
In aqueous solution (pH 9) containing N2O, the unsaturated acids -FcCHCH(CH2)nCO2H (n = 0 and 1) and FcCCCO2H each undergo photo-oxidation, upon illumination with u.v. light of wavelength 240-250 nm, giving dipolar ferricenium species which may be chemically reduced back to the original acids. The mechanism of photo-oxidation, which is inhibited by ethanol, appears to be similar to that previously proposed for saturated ω-ferrocenylalkanoic acids. 相似文献
24.
Elizabeth K. Heaney S.R. Logan William E. Watts 《Journal of organometallic chemistry》1978,150(2):309-319
The anions of 4-([3]ferrocenophanyl)butanoic acids (Id and IId), when excited by light of around 240 nm wavelength in aqueous solution in the presence of N2O, undergo photo-oxidation to zwitterions (III and IV respectively) in a manner completely analogous to the reaction of 4-ferrocenylbutanoate anion. The differences in the kinetic parameters of the reactions are thought to be attributable in part to slight tilting of the cyclopentadienyl rings caused by the connecting trimethylene bridge. 相似文献
25.
Importance of molecular details in predicting bacterial adhesion to hydrophobic surfaces 总被引:2,自引:0,他引:2
Salerno MB Logan BE Velegol D 《Langmuir : the ACS journal of surfaces and colloids》2004,20(24):10625-10629
Electrostatic and hydrophobic forces are generally recognized as important in bacterial adhesion. Current continuum models for these forces often wrongly predict measurements of bacterial adhesion forces. The hypothesis tested here is that even qualitative guides to bacterial adhesion often require more than continuum information about hydrophobic forces; they require knowledge about molecular details of the bacteria and substrate surface. In this study, four different strains of bacteria were adsorbed to silica surfaces hydrophobized with alkylsilanes. The thickness of the lipopolysaccharide layers varied on the different bacteria, and the lengths of the alkylsilane molecules were varied from experiment to experiment. Bacterial adhesion was assessed using column experiments and atomic force microscopy (AFM) experiments. Results show that hydrophobized surfaces have higher bacterial sticking coefficients and stronger adhesion forces than bare silica surfaces, as expected. However, adhesion decreased as the solution Debye length became longer than the alkylsilane, perhaps since the silane molecules could not "reach" the bacterial surface. Similarly, those bacteria with a long o-antigen layer had decreased adhesion, perhaps since the silane molecules could not reach surface-bound proteins on the bacteria. This study reveals that macroscopic measurements such as contact angle are not able to fully describe bacterial adhesion; rather, additional details such as the molecular length are required to predict adhesion. 相似文献
26.
A theory is presented for propagation of waves in bounded media near the mobility edge, based on the self-consistent theory for localization. It predicts a spatially inhomogeneous diffusion constant that leads to scale dependence in enhanced backscattering and transmission. 相似文献
27.
本文应用MUSIG模型[1]和均一直径模型对某溶液堆台架模型堆芯内气液流动传热进行了数值模拟.在MUSIG模型中堆芯内离散相气泡被分为5组不同直径的气泡,用于分析堆芯内气泡的流动变化和大小分布,采用Luo and Svendsen[2]和Prince and Blanch[3]模型描述不同直径气泡组间的破裂和聚合.在均一直径模型中,堆芯内的气体被考虑为同一直径的组分,并且不考虑其破裂与聚合现象.计算得到采用两个模型的模拟结果并且对其进行了对比研究.结果显示应用MUSIG模型的计算结果与台架实验结果吻合更好. 相似文献
28.
With all driving fields on Raman resonance, a tripod-type atomic system quickly evolves into a dark state decoupled from the lossy excited level. The dark state depends strongly on field Rabi frequencies, spontaneous decay rates, and the initial atomic population in a complicated way. Analytical results reveal that it is a sixfold degenerate dark state with its three components superposed both coherently and incoherently due to population redistribution from spontaneous emission. 相似文献
29.
Mark J. Logan 《代数通讯》2013,41(8):3739-3742
This note points out a factor of the Poincaré polynomial of the λ-isotypic component of the exterior algebra λL, where L is a complex semisimple Lie algebra and λ is a dominant weight. Although these polynomials have been studied with regard to their factorizations, this particular factor seems to have gone unstated. 相似文献
30.
Tarun Gheyi Logan Rodgers Richard Romero J. Michael Sauder Stephen K. Burley 《Journal of the American Society for Mass Spectrometry》2010,21(10):1795-1801
A strategy for increasing the efficiency of protein crystallization/structure determination with mass spectrometry has been
developed. This approach combines insights from limited proteolysis/mass spectrometry and crystallization via in situ proteolysis.
The procedure seeks to identify protease-resistant polypeptide chain segments from purified proteins on the time-scale of
crystal formation, and subsequently crystallizing the target protein in the presence of the optimal protease at the right
relative concentration. We report our experience with 10 proteins of unknown structure, two of which yielded high-resolution
X-ray structures. The advantage of this approach comes from its ability to select only those structure determination candidates
that are likely to benefit from application of in situ proteolysis, using conditions most likely to result in formation of
a stable proteolytic digestion product suitable for crystallization. 相似文献