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151.
Yang VX Munce N Pekar J Gordon ML Lo S Marcon NE Wilson BC Vitkin IA 《Optics letters》2004,29(15):1754-1756
High-resolution optical coherence tomography demands a large detector bandwidth and a high numerical aperture for real-time imaging, which is difficult to achieve over a large imaging depth. To resolve these conflicting requirements we propose a novel multifocus fiber-based optical coherence tomography system with a micromachined array tip. We demonstrate the fabrication of a prototype four-channel tip that maintains a 9-14-microm spot diameter with more than 500 microm of imaging depth. Images of a resolution target and a human tooth were obtained with this tip by use of a four-channel cascaded Michelson fiber-optic interferometer, scanned simultaneously at 8 kHz with geometric power distribution across the four channels. 相似文献
152.
An integrated fluidic adaptive zoom lens is demonstrated for what is believed to be the first time. A zoom lens was fabricated using an UV lithographic-galvanic-like process involving soft lithography and wafer bonding. The zooming capability of such a lens was achieved by varying the focal length instead of the distance between the lenses. A zoom ratio of greater than 2 was obtained for devices that are 8 mm thick and have a 20-mm lens diameter. Including the 30-mm image distance, the total physical length of the fluidic zoom lens was less than 43 mm. More-compact systems with a higher zoom ratio can be obtained by reduction of the aperture size. 相似文献
153.
Protonation and bromination of an osmabenzyne: reactions leading to the formation of new metallabenzynes 总被引:1,自引:0,他引:1
Wen TB Ng SM Hung WY Zhou ZY Lo MF Shek LY Williams ID Lin Z Jia G 《Journal of the American Chemical Society》2003,125(4):884-885
The reactivities of benzynes and metal-carbyne complexes are normally associated with the triple bond units. However, we have now found that electrophiles do not attack the formal osmium-carbon triple bond of osmabenzyne complex 1. Instead, 1 undergoes electrophilic substitution reactions-the typical reactions of aromatic systems. 相似文献
154.
Grotjahn DB Collins LS Wolpert M Bikzhanova GA Lo HC Combs D Hubbard JL 《Journal of the American Chemical Society》2001,123(34):8260-8270
Using a series of Ir(I) and Rh(I) ketene complexes, conclusions about the structure and bonding of complexes of the fundamentally important ketene ligand class are reached. In a unique comparison of X-ray structures of the same metal fragment to ketenes in both the eta(2)-(C,C) and the eta(2)-(C,O) binding mode, the Ir-Cl bond distances in complexes of trans-Cl(Ir)[P(i-Pr)(3)](2) to phenylketene [4, eta(2)-(C,C)] and diphenylketene [2a, eta(2)-(C,O)] are 2.371(3) and 2.285(2) A, respectively. This would be consistent with greater trans influence of a ketene ligand bound to a metal through its C=C bond than one connected by its C=O bond. Back-bonding of Ir(I) and Rh(I) to diphenylketene was assessed using trans-Cl(M)[P(i-Pr)(3)](2)[eta(2)-(C,O)-diphenylketene] (2a and 2d). Most bond lengths and angles are identical, but slightly greater back-bonding by Ir(I) is suggested by the somewhat greater deformation of the ketene C=C=O system [C-C-O angles are 136.6(4) and 138.9(4) in the Ir and Rh cases 2a and 2d, respectively]. Syntheses of new labeled ketenes Ph(2)C=(13)C=O and Ph(2)C=C=(18)O and their Ir(I) and Rh(I) complexes are reported, along with the generation of an Ir(I) complex of PhCH=(13)C=O. The effects of isotopic substitution on infrared absorption data for ketene complexes are presented for the first time. Preliminary normal coordinate mode analysis allowed definitive assignment of absorptions ascribed to the C-O stretching frequencies of coordinated ketenes, which are near the absorptions for aromatic ring systems commonly found as substituents on ketenes. For free diphenylketene and four of its complexes and a phenylketene complex characterized by X-ray diffraction, the magnitude of the (13)C-(13)C coupling between the two ketene carbons is correlated to carbon-carbon bond distance. 相似文献
155.
The paper is concerned with finding sufficient smoothness conditionson the diffusion and drift coefficient of a one-dimensionalstochastic diffusion to imply the existence and smoothness ofa taboo density. 相似文献
156.
Flight parameter estimation methods for an airborne acoustic source can be divided into two categories, depending on whether the narrow-band lines or the broadband component of the received signal spectrum is processed to estimate the flight parameters. This paper provides a common framework for the formulation and test of two flight parameter estimation methods: one narrow band, the other broadband. The performances of the two methods are evaluated by applying them to the same acoustic data set, which is recorded by a planar array of passive acoustic sensors during multiple transits of a turboprop fixed-wing aircraft and two types of rotary-wing aircraft. The narrow-band method, which is based on a kinematic model that assumes the source travels in a straight line at constant speed and altitude, requires time-frequency analysis of the acoustic signal received by a single sensor during each aircraft transit. The broadband method is based on the same kinematic model, but requires observing the temporal variation of the differential time of arrival of the acoustic signal at each pair of sensors that comprises the planar array. Generalized cross correlation of each pair of sensor outputs using a cross-spectral phase transform prefilter provides instantaneous estimates of the differential times of arrival of the signal as the acoustic wavefront traverses the array. 相似文献
157.
A tensorial formalism adapted to the case of XY(5)Z symmetric tops has been developed as an extension of the usual one for the octahedral molecules. We use the O(3) superset O(h) superset C(4&v) group chain. All the coupling coefficients and formulas for the computation of matrix elements are given for this chain. Such relations are also deduced in the C(4v) group itself. Copyright 2000 Academic Press. 相似文献
158.
J.-M. Chauveau C. Morhain B. Lo B. Vinter P. Vennéguès M. Laügt D. Buell M. Tesseire-Doninelli G. Neu 《Applied Physics A: Materials Science & Processing》2007,88(1):65-69
Non polar ZnO and (Zn, Co)O layers were successfully grown on (11̄02) sapphire (R-plane sapphire). The growth process was
shown to directly influence the surface morphology as well as the strain state in (112̄0) ZnO (A-plane ZnO). The dominant
defect lines seen in photoluminescence were due to basal stacking faults as demonstrated by means of selective photoluminescence
and transmission electron microscopy. We present a novel method for growing high quality A-plane ZnO by inserting a (Zn, Co)O
thin buffer layer, which strongly reduced the surface roughness. Finally (Zn, Mg)O/ZnO quantum well structures were grown
on such a buffer layer. These quantum wells exhibited no intrinsic quantum confined Stark effect.
PACS 81.05.Dz; 81.15.Hi; 78.67.Hc; 68.65.Fg 相似文献
159.
Salvatore Giuffrida Guglielmo G. Condorelli Lucia L. Costanzo Giorgio Ventimiglia Raffaella Lo Nigro Maria Favazza Enrico Votrico Corrado Bongiorno Ignazio L. Fragalà 《Journal of nanoparticle research》2007,9(4):611-619
Liquid Phase Photo-Deposition (LPPD) technique has been used to obtain both colloidal particles and thin films of metallic
and chloride nickel from solutions of only precursor Ni(acac)2 (acac=2,4-pentandionato). Metallic nickel was obtained from ethanol solutions by direct nickel(II) photoreduction at 254 nm
and by acetone sensitised reaction at 300 nm. In this latter process the rate was higher than in the first one. NiCl2 was formed from CCl4 solution by a solvent-initiated reaction. TEM analysis, performed on colloidal particles of nickel, showed that their dimensions
are in the range 2–4 nm. The films did not present carbon contamination and were characterized by AFM, XPS and GIXRD. Metallic
films consisted of particles of 20–40 nm that are the result of the aggregation of smaller crystallites (4–5 nm). Larger agglomerations
(around 200 nm) have been observed for NiCl2 films. 相似文献
160.
Entangled two-photon generalized binomial states of the electromagnetic field in two separate cavities are considered. The
nonlocal properties of this entangled field state are analyzed by studying the electric field correlations between the two
cavities. A Bell’s inequality violation is obtained using an appropriate dichotomic cavity operator that is, in principle,
measurable.
The text was submitted by the authors in English. 相似文献