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271.
S. J. Parry 《Journal of Radioanalytical and Nuclear Chemistry》1984,81(1):143-151
The value of boron, in addition to cadmium, as a thermal neutron filter for the epithermal neutron activation of short-lived radionuclides is shown to depend on sample matrix. Activation ratios of fifty nuclides are measured and the improvement in sensitivity is calculated for geological and biological matrices. The addition of boron, in the case of geological samples where the major interference is Al, improved detection for only F, Y, Sn, Ba, Er, W and Pt. In biological samples where Na is a problem the detection limits for F, Br, Rb, Y, Mo, Pd, Sn, Sb, I, Ba, Nd, Sm, Gd, Er, Hf, W, Re, Pt, Au, Th and U are all theoretically improved. 相似文献
272.
273.
We show that continuous filling transitions are possible in 3D wedge geometries made from substrates exhibiting first-order wetting transitions, and develop a fluctuation theory yielding a complete classification of the critical behavior. Our fluctuation theory is based on the derivation of a Ginzburg criterion for filling and also on an exact transfer-matrix analysis of a novel effective Hamiltonian that we propose as a model for wedge fluctuation effects. The influence of interfacial fluctuations is very strong and, in particular, leads to a remarkable universal divergence of the interfacial roughness xi( perpendicular) approximately (T(F)-T)(-1/4) on approaching the filling temperature T(F), valid for all possible types of intermolecular forces. 相似文献
274.
A novel method for the quantitative assessment of the membrane partitioning of a ligand from the aqueous phase is described,
demonstrated here with the thoroughly studied antipsychotic chlorpromazine (CPZ). More specifically, collisional quenching
of the fluorescence of a pyrene labeled fluorescent lipid analog 1-palmitoyl-2[10-(pyren-1-yl)]decanoyl-sn-glycero-3-phosphocholine (PPDPC) by CPZ was utilized, using 1-palmitoyl-2-oleyl-sn-glycero-3-phosphocholine and -serine (POPC and POPS) liposomes as model membranes. The molar partition coefficient is obtained
from two series of titrations, one with constant [phospholipid] and increasing [drug] and the other with constant [drug] and
varying total [phospholipid], the latter further comprising of large unilamellar vesicles (LUVs) of POPC/POPS/PPDPC at a constant
concentration of 10 μM and indicated concentrations of POPC/POPS LUVs. Notably, the approach described is generic and can
be employed in screening for the membrane partitioning of compounds, providing that a suitable fluorescence parameter can
be incorporated into one population of liposomes utilized as model membranes. 相似文献
275.
Hunt DM Carvalho LS Cowing JA Parry JW Wilkie SE Davies WL Bowmaker JK 《Photochemistry and photobiology》2007,83(2):303-310
Of the four classes of vertebrate cone visual pigments, the shortwave-sensitive SWS1 class shows some of the largest shifts in lambda(max), with values ranging in different species from 390-435 nm in the violet region of the spectrum to < 360 nm in the ultraviolet. Phylogenetic evidence indicates that the ancestral pigment most probably had a lambda(max) in the UV and that shifts between violet and UV have occurred many times during evolution. In violet-sensitive (VS) pigments, the Schiff base is protonated whereas in UV-sensitive (UVS) pigments, it is almost certainly unprotonated. The generation of VS pigments in amphibia, birds and mammals from ancestral UVS pigments must involve therefore the stabilization of protonation. Similarly, stabilization must be lost in the evolution of avian UVS pigments from a VS ancestral pigment. The key residues in the opsin protein for these shifts are at sites 86 and 90, both adjacent to the Schiff base and the counterion at Glu113. In this review, the various molecular mechanisms for the UV and violet shifts in the different vertebrate groups are presented and the changes in the opsin protein that are responsible for the spectral shifts are discussed in the context of the structural model of bovine rhodopsin. 相似文献
276.
Hughes KH Parry SM Parlant G Burghardt I 《The journal of physical chemistry. A》2007,111(41):10269-10283
The hybrid quantum-classical approach of Burghardt and Parlant [Burghardt, I.; Parlant, G. J. Chem. Phys. 2004, 120, 3055], referred to here as the quantum-classical moment (QCM) approach, is demonstrated for the dynamics of a quantum double well coupled to a classical harmonic coordinate. The approach combines the quantum hydrodynamic and classical Liouvillian representations by the construction of a particular type of moments (that is, partial hydrodynamic moments) whose evolution is determined by a hierarchy of coupled equations. For pure states, which are at the center of the present study, this hierarchy terminates at the first order. In the Lagrangian picture, the deterministic trajectories result in dynamics which is Hamiltonian in the classical subspace, while the projection onto the quantum subspace evolves under a generalized hydrodynamic force. Importantly, this force also depends upon the classical (Q, P) variables. The present application demonstrates the tunneling dynamics in both the Eulerian and Lagrangian representations. The method is exact if the classical subspace is harmonic, as is the case for the systems studied here. 相似文献
277.
R. Mitchell Parry Asiri S. Galhena Chaminda M. Gamage Rachel V. Bennett May D. Wang Facundo M. Fernández 《Journal of the American Society for Mass Spectrometry》2013,24(4):646-649
We present omniSpect, an open source web- and MATLAB-based software tool for both desorption electrospray ionization (DESI) and matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI) that performs computationally intensive functions on a remote server. These functions include converting data from a variety of file formats into a common format easily manipulated in MATLAB, transforming time-series mass spectra into mass spectrometry images based on a probe spatial raster path, and multivariate analysis. OmniSpect provides an extensible suite of tools to meet the computational requirements needed for visualizing open and proprietary format MSI data. 相似文献
278.
Esa A. Jaatinen Matthew P. Adams Alison Chou Nick McKay Parry Peter M. Fredericks 《Journal of Raman spectroscopy : JRS》2014,45(8):636-641
The surface enhanced Raman scattering effect has shown immense potential for detecting trace amounts of explosive vapor molecules. To date, efforts to produce a commercially available, reliable SERS sensor have been impeded by an inability to separate the electromagnetic enhancement produced by the metallic nanostructure from other signal enhancing effects. Here, we show a new Raman sensor that uses surface acoustic waves (SAWs) to produce controllable surface structures on gold films deposited on LiNbO3 substrates that modulate the Raman signal of a target compound (thiophenol) adsorbed on the films. We demonstrate that this sensor can dynamically control the Raman signal simply by changing the SAW's amplitude, allowing the Raman signal enhancement factor to be directly measured with no variation in the concentration of the target compound. The physically adsorbed molecules can be removed from the sensor without physical cleaning or damage, making it possible to reuse it for real‐time Raman detection. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
279.
280.
Ryhänen SJ Säily VM Parry MJ Luciani P Mancini G Alakoskela JM Kinnunen PK 《Journal of the American Chemical Society》2006,128(26):8659-8663
While much is known about the self-assembly of lipids on nanoscale, our understanding of their biologically relevant mesoscale organization remains incomplete. Here, we show for a cationic gemini lipid a sharp and reversible transition from small vesicles with an average diameter of approximately 40 nm to giant vesicles (GVs) with an average diameter of approximately 11 microm. This transition is dependent on proper [NaCl] and specific temperature. Below this transition and in the vicinity of the air/water interface, a series of mesoscale morphological transitions was observed, revealing complex structures resembling biological membranes. On the basis of microscopy experiments, a tentative [NaCl] versus temperature shape/size phase diagram was constructed. To explain this unprecedented transition, we propose a novel mechanism whereby a specific interaction of Cl(-) counterion with the cationic gemini surfactant initiates the formation of a commensurate solute counterion lattice with low spontaneous curvature. In keeping with the high bending rigidity of NaCl crystal, this tightly associated ionic lattice enslaves membrane curvature and the mesoscale 3-D organization of this lipid. 相似文献