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91.
Water soluble gold nanoparticles are coated with peptides bearing a dithiol surface active group for studies of lanthanide binding; characteristic red luminescence is observed upon europium binding to the nanoparticles. 相似文献
92.
Marshall CP Marshall AO 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,80(1):133-137
Over the last few decades Raman spectroscopy has been increasingly applied as an analytical tool in geoscience research. Raman spectroscopy is a powerful tool for geologists as it is non-destructive, requires little to no sample preparation, and can be undertaken in situ on various irreplaceable geological samples. Also, this technique is useful in the identification of minerals and geo-organic material. However, despite this ease of application, there are some facets of Raman spectroscopy data that can lead to erroneous interpretations. For instance, there is much confusion in the geological literature distinguishing the difference between the hematite vibrational mode at ca. 1320 cm(-1) and the disordered sp(2) carbonaceous material D band at 1340 cm(-1). Furthermore, geologists will often collect 2 spectra, one in the mineral finger print region (200-800 cm(-1)) and then a spectrum in the carbon first-order region (1000-1800 cm(-1)), rather than performing a full-region scan. This allows the misidentification of the hematite mode at 1320 cm(-1) as the D band from disordered carbonaceous material. Here we show that it is best practice for geologists to collect spectra between 200 and 1800 cm(-1) to better distinguish between hematite and disordered carbonaceous material, materials that often co-occur in geological samples. 相似文献
93.
94.
Reichhardt C Uchida M O'Neil A Li R Prevelige PE Douglas T 《Chemical communications (Cambridge, England)》2011,47(22):6326-6328
Biomimetic chemistry offers new approaches to supramolecular materials synthesis and assembly. We have demonstrated that an assembled viral protein cage, comprising an organic core-shell structure, can be used as a template for the size constrained synthesis of Fe(2)O(3). Particle nucleation is directed by the inner scaffold protein layer, while the size constraints are determined by the outer capsid layer. 相似文献
95.
Sean R. Parkin Edward J. Behrman 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(8):o324-o328
Crystals of 5‐hydroxy‐6‐methyl‐2‐pyridone, (I), grown from a variety of solvents, are invariably trigonal (space group R); these are 5‐hydroxy‐6‐methyl‐2‐pyridone acetone 0.1667‐solvate, C6H7NO2·0.1667C3H6O, (Ia), and 6‐methyl‐5‐hydroxy‐2‐pyridone propan‐2‐ol 0.1667‐solvate, C6H7NO2·0.1667C3H8O, (Ib), and the forms from methanol, (Ic), water, (Id), benzonitrile, (Ie), and benzyl alcohol, (If). They incorporate channels running the length of the c axis that contain extensively disordered solvent molecules. A solvent‐free sublimed powder of 5‐hydroxy‐6‐methyl‐2‐pyridone microcrystals is essentially isostructural. Inversion‐related host molecules interact via pairs of N—H...O hydrogen bonds to form R22(8) dimers. Six of these dimers form large R126(42) puckered rings, in which the O atom of each N—H...O hydrogen bond is also the acceptor in an O—H...O hydrogen bond that involves the 5‐hydroxy group. The large R126(42) rings straddle the axes and form stacked columns viaπ–π interactions between inversion‐related molecules of (I) [mean interplanar spacing = 3.254 Å and ring centroid–centroid distance = 3.688 (2) Å]. The channels are lined by methyl groups, which all point inwards to the centre of the channels. 相似文献
96.
This paper is concerned with the efficient solution of the linear systems of equations that arise from an adaptive space-implicit
time discretisation of the Black-Scholes equation. These nonsymmetric systems are very large and sparse, so an iterative method
will usually be the method of choice. However, such a method may require a large number of iterations to converge, particularly
when the timestep used is large (which is often the case towards the end of a simulation which uses adaptive timestepping).
An appropriate preconditioner is therefore desirable. In this paper we show that a very simple multigrid algorithm with standard
components works well as a preconditioner for these problems. We analyse the eigenvalue spectrum of the multigrid iteration
matrix for uniform grid problems and illustrate the method’s efficiency in practice by considering the results of numerical
experiments on both uniform grids and those which use adaptivity in space. 相似文献
97.
98.
Alison Watts 《International Journal of Game Theory》2007,35(4):505-519
A model of group formation is presented such that the number of groups is fixed, and a person can only join a group if the
group’s members approve the person’s joining. Agents have either local status preferences (each agent wants to be the highest
status agent in his group) or global status preferences (each agent wants to join the highest status group that she can join).
For both preference types, conditions are provided which guarantee the existence of a segregated stable partition such that
similar people are grouped together, and conditions are provided which guarantee the existence of an integrated stable partition
such that dissimilar people are grouped together. Additionally, in a dynamic framework we show that if a new empty group is
added to a segregated stable partition, then integration may occur. 相似文献
99.
Various aspects of our communication are well known to havechanged over time (1-3). This article describes a cross-sectional study that examined the acoustic characteristics of two groups of Australian women aged 18–25 years from recordings made in 1945 and 1993 and investigated the possible changes in the voice across generations. Archival recordings from 1945 which had been used in a longitudinal study (4) were compared to recordings made in 1993. The results of this study show that women in 1993 have significantly deeper voices than women of the same age recorded in 1945. The possible factors influencing this change are discussed. 相似文献
100.
We present a Fourier analysis of multigrid for the two-dimensional discrete convection-diffusion equation. For constant coefficient
problems with grid-aligned flow and semi-periodic boundary conditions, we show that the two-grid iteration matrix can be reduced
via a set of orthogonal transformations to a matrix containing individual 4×4 blocks. This enables a trivial computation of
the norm of the iteration matrix demonstrating rapid convergence in the case of both small and large mesh Peclet numbers,
where the streamline-diffusion discretisation is used in the latter case. We also demonstrate that these results are strongly
correlated with the properties of the iteration matrix arising from Dirichlet boundary conditions.
AMS subject classification (2000) 65F10, 65N22, 65N30, 65N55 相似文献