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121.
R. J. Gillespie 《Angewandte Chemie (International ed. in English)》1967,6(10):819-830
The theory described in this article emphasizes the importance of interactions between the electron pairs in the valence shell of a central atom in determining stereochemistry and it assumes that interactions between the ligands are generally of lesser importance although sufficiently bulky groups, or chelate ligands, may play an important role in determining the stereochemistry. If lone-pair electrons are present in the valence shell of the central atom then the two theories (the theory of interaction of electron pairs and the theory of interaction between ligands) predict different structures. In the great majority of cases the determined structures are those expected if it is assumed that lone pairs are stereochemically active, i.e. if repulsions between electron pairs in the valence shell determine stereochemistry. 相似文献
122.
Christina L. Randall Aubri Gillespie Siddarth Singh Timothy G. Leong David H. Gracias 《Analytical and bioanalytical chemistry》2009,393(4):1217-1224
We describe the fabrication of 3D membranes with precisely patterned surface nanoporosity and their utilization in size selective
sampling. The membranes were self-assembled as porous cubes from lithographically fabricated 2D templates (Leong et al., Langmuir 23:8747–8751, 2007) with face dimensions of 200 μm, volumes of 8 nL, and monodisperse pores ranging in size from approximately 10 μm to 100 nm.
As opposed to conventional sampling and filtration schemes where fluid is moved across a static membrane, we demonstrate sampling
by instead moving the 3D nanoporous membrane through the fluid. This new scheme allows for straightforward sampling in small
volumes, with little to no loss. Membranes with five porous faces and one open face were moved through fluids to sample and
retain nanoscale beads and cells based on pore size. Additionally, cells retained within the membranes were subsequently cultured
and multiplied using standard cell culture protocols upon retrieval.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
123.
124.
Capacitively coupled contactless conductivity is presented as a simple non-invasive tool for the visualisation and evaluation of the axial homogeneity of packing density in capillary LC columns. Irregularities in frit structure and gross column voids were readily identified, the latter of which was confirmed with digital photography. Relative homogeneity of packing density was compared for two packed columns by measuring the variation in conductive response per unit length and varied from 1.1 to 4.2%. The on-column scanning methodology was applied to real-time visualisation of in-situ buffering effects arising from a packed poly-iminodiacetic acid bonded resin. Finally, the scanning detection technique was applied to the pre-elution visualisation of on-column band broadening. 相似文献
125.
The weighted stochastic simulation algorithm (wSSA) was developed by Kuwahara and Mura [J. Chem. Phys. 129, 165101 (2008)] to efficiently estimate the probabilities of rare events in discrete stochastic systems. The wSSA uses importance sampling to enhance the statistical accuracy in the estimation of the probability of the rare event. The original algorithm biases the reaction selection step with a fixed importance sampling parameter. In this paper, we introduce a novel method where the biasing parameter is state-dependent. The new method features improved accuracy, efficiency, and robustness. 相似文献
126.
Jayalakshmi Somuramasami Brian E. Winger Todd A. Gillespie Hilkka I. Kenttämaa 《Journal of the American Society for Mass Spectrometry》2010,21(5):773-784
A mass spectrometric method has been developed for the identification of carbonyl and hydroxyl functional groups, as well
as for counting the functional groups, in previously unknown protonated bifunctional oxygen-containing analytes. This method
utilizes solution reduction before mass spectrometric analysis to convert the carbonyl groups to hydroxyl groups. Gas-phase
ion-molecule reactions of the protonated reduced analytes with neutral trimethylborate (TMB) in a FT-ICR mass spectrometer
give diagnostic product ions. The reaction sequence likely involves three consecutive steps, proton abstraction from the protonated
analyte by TMB, addition of the neutral analyte to the boron reagent, and elimination of a neutral methanol molecule. The
number of methanol molecules eliminated upon reactions with TMB reveals the number of hydroxyl groups in the analyte. Comparison
of the reactions of the original and reduced analytes reveals the presence and number of carbonyl and hydroxyl groups in the
analyte. 相似文献
127.
Doo S. J. Roblin P. Jessen G. H. Fitch R. C. Gillespie J. K. Moser N. A. Crespo A. Simpson G. King J. 《Microwave and Wireless Components Letters, IEEE》2006,16(12):681-683
IV knee walk-out in AlGaN/GaN high electron mobility transistors (HEMTs) on a Sapphire substrate is analyzed using dynamic radio frequency (RF) load-lines acquired with a large signal network analyzer (LSNA) for both continuous-wave (CW) and pulsed-IV/RF excitations. When thermal effects and traps are bypassed using pulsed-IV biasing and pulsed-RF excitations, the IV knee walk-out observed in CW load-lines is found to be effectively suppressed and the device delivers the maximum output power expected for class A operation. It is also demonstrated using pulsed-IV/RF measurements at various substrate temperatures that the IV knee walk-out primarily arises from thermal effects at high bias rather than trapping in the on-wafer devices characterized 相似文献
128.
In silicate sol-gel glass doped with trivalent terbium, the intensity of violet and blue fluorescence from the 5D3 level is highly dependent on terbium concentration, on the presence of Al3+ co-dopant, and on annealing conditions. Evidence is presented that aluminum co-doping prevents rare earth clusters from forming, and also modifies the coupling of rare earth ions to the local environment. 5D3 emission is observed in glasses annealed at 750 °C, and increases in intensity with increasing annealing time and with higher temperature. This behavior is shown to be due to the removal of residual hydroxyl ions. 相似文献
129.
D. Yu. Akimov A. Bewick M. V. Danilov D. C. R. Davidge J. V. Dawson V. A. Ditlov J. R. Gillespie A. S. Howard W. G. Jones M. K. Joshi A. G. Kovalenko D. A. Kovalenko V. N. Lebedenko T. J. Sumner J. J. Quenby 《Physics of Atomic Nuclei》2003,66(3):497-499
The current status of the development study focused on building a novel two-phase xenon detector for dark matter search is described. Discrimination of the radioactive background is based on particle identification that comes from the analysis of the scintillation-to-ionization ratio. Electroluminescence (proportional scintillation) is used for “amplification” of the ionization signal. 相似文献
130.
The design of a head-mounted display with a field of view of 40 degrees and suitable for use with a micro display of 17.5 mm diagonal is presented. It is a combination of a diffractive-refractive eyepiece with an appropriate reflective relay system. The eyepiece design is based on a Kellner eyepiece. By replacing the cemented-doublet of the traditional eyepiece with a diffractive-refractive element (a plano-convex lens with the plane surface as the diffractive surface) an improved eyepiece is obtained. The proposed eyepiece shows a considerable reduction in physical size (which is particularly important for binocular systems) and weight, and exhibits superior performance compared to the traditional refractive type. It is emphasized that the proposed design has a performance that is well matched to a micro display with SXGA resolution. 相似文献