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In 2011 the collinear laser spectroscopy programme at the University of Jyväskylä Accelerator Laboratory (JYFL), Finland, will move to the new IGISOL 4 facility. With its own dedicated cyclotron, this new laboratory will offer unparalleled access to beam time for both technique development and exploitation. Production of sub-millisecond states is available, including elements of a refractory nature. 相似文献
23.
The convenient preparation of chiral tetrahydrothiophenes (THTs) in high enantiopurity via phosphorothioic acids and related compounds is reported. We consider these to be safer alternatives to the use of H(2)S which is a highly toxic gas. Each of the THTs is derived from a common intermediate, thereby greatly enhancing the flexibility of the synthesis. The key transformation is a base-promoted, intramolecular, carbon-sulfur bond-forming event. These reactions are highly stereospecific as they operate through a double S(N)2 displacement mechanism. The methodology is amenable to a broad array of functional groups and heterocycles. The tetrahydrothiophene motif is important because it is present in a number of bioactive natural products. They have also been utilized to promote various asymmetric transformations including hydrogenation, epoxidation, cyclopropanation, and aziridination reactions. 相似文献
24.
Emily C. Corcoran William Forest Robert Horton David G. Kelly Kristine Mattson Curtis McDonld Kathy S. Nielsen Kristin Topping Ron D. Weir Andre Yonkeu 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(1):251-256
Commercial radio-opaque combat (CRC) fabrics, for incorporation into personal protective equipment used by first responders
and armed forces, are marketed as having the ability to provide a level of protection against specific types of radiation.
For a CRC material, a standard combat uniform and a multi-layered chemical, biological, radiological, nuclear (CBRN) protective
material, the present work examines chemical composition and radiation protection against gamma-rays and neutron fluxes. Significant
reduction in gamma-ray transmittance occurs only for the CRC fabric (46–514 keV) with gamma-ray attenuation coefficients of
3.10 to <0.10 cm2 g−1. Reduction in neutron transmittance, for all three fabrics, could not be assessed with certainty as the measured transmittance
was obscured by large statistical uncertainties. 相似文献
25.
We extend previous work on the linear viscoelastic moduli of heterogeneous nematic polymers in a small-amplitude oscillatory
shear flow, focusing on the role of the orientational anchoring conditions at the plates. When tangential or normal anchoring
conditions are applied, the Doi–Marrucci–Greco orientation tensor-flow model effectively reduces to the Leslie–Ericksen director-flow
model, predicting that director distortions control the dynamic moduli with negligible contributions from tensor-order parameters.
In this paper, we examine oblique anchoring angles. We use a combination of analysis and numerical simulation on the generalized
tensor-flow system for arbitrary anchoring conditions to show that any oblique anchoring condition induces a nontrivial order
parameter contribution to the dynamic moduli, which vanishes only in the limit of tangential or normal anchoring. Our approach
reveals that the storage and loss moduli admit an approximate decomposition in terms of two reduced problems that are exactly
solvable: the heterogeneous director–flow response plus the monodomain tensor response to an imposed shear. The importance
of this result is that we gain scaling properties of the moduli with respect to material parameters and experimental conditions
without having to compute and assimilate across the full parameter space. These results provide insight into the relative
importance of the distortional vs bulk nematic elastic stress in determining the viscoelastic moduli, predicting that anchoring
conditions tune the relative contributions. 相似文献
26.
Y. Gangrsky K. Marinova S. Zemlyanoi M. Avgoulea J. Billowes P. Campbell B. Cheal B. Tordoff M. Bissell D. H. Forest M. Gardner G. Tungate J. Huikari H. Penttilä J. Äystö 《Hyperfine Interactions》2006,171(1-3):209-215
Collinear laser spectroscopy experiments on the ScII transition 3d4s
3D2→3d4p
3F3 at λ ≈ 363.1 nm were performed on the 42–46Sc isotopic chain using an ion guide isotope separator with a cooler–buncher. Isotope and isomer shifts and hyperfine structures
of five ground states and two isomers were measured. Preliminary results on the nuclear moments and charge radii changes deduced
from these measurements are reported. 相似文献
27.
M. Gregory Forest Sebastian Heidenreich Siegfried Hess Xiaofeng Yang Ruhai Zhou 《ournal of non Newtonian Fluid Mechanics》2008
Nano-rod dispersions in steady shear exhibit persistent transient responses both in experiments and simulations. The rotational contribution from shear flow couples with orientational diffusion, excluded-volume interactions, and distortional elasticity to yield complex dynamics and gradient morphology of the rod ensemble. The classification of sheared responses has mostly focused on “nematodynamics” of the collective particle response known as tumbling, wagging and kayaking; in heterogeneous simulations, one monitors the variability in nematodynamics across the domain. In this paper, we focus on flow coupling and non-Newtonian feedback in transient heterogeneous simulations, and in particular on a remarkable effect: the formation of localized, pulsating jet layers in the shear gap. We solve the Navier–Stokes momentum equations coupled through an orientation-dependent stress to three different orientational models (a kinetic Smoluchowski equation and two tensor models, one from kinetic closure and another from irreversible thermodynamics). A similar spurt phenomenon was reported in 1D simulations of a model for planar nematic liquids by Kupferman et al. [R. Kupferman, M. Kawaguchi, M.M. Denn, Emergence of structure in models of liquid crystalline polymers with elasticity, J. Non-Newt. Fluid Mech. 91 (2000) 255–271], which we extend to full orientational configuration space. We show: the pulsating jet layers correlate, in space and time, with the formation of a non-topological “oblate defect phase” in which the principal axis of orientation spreads from a unique direction to a circle; the jet-defect layers form where the local nematodynamics transitions from finite oscillation (wagging) to continuous rotation (tumbling), and when neighboring directors lose phase coherence; and, a negative first normal stress difference develops in the pulsating jet-defect layers. Finally, we extend one model algorithm to two space dimensions and show numerical stability of the jet-defect phenomenon to 2D perturbations. 相似文献
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<正>Two new oleanane-type saponins,crotalarioside A(1) and crotalarioside B(2),were isolated from the roots of Polygala crotalarioides.Their structures were elucidated on the basis of spectroscopic and chemical evidence. 相似文献