14,459 research outputs found
Quantum integrability of quadratic Killing tensors
Quantum integrability of classical integrable systems given by quadratic
Killing tensors on curved configuration spaces is investigated. It is proven
that, using a "minimal" quantization scheme, quantum integrability is insured
for a large class of classic examples.Comment: LaTeX 2e, no figure, 35 p., references added, minor modifications. To
appear in the J. Math. Phy
Nuclear medium effects in -nucleus deep inelastic scattering
We study the nuclear medium effects in the weak structure functions
and in the deep inelastic neutrino/antineutrino
reactions in nuclei.
We use a theoretical model for the nuclear spectral functions which
incorporates the conventional nuclear effects, such as Fermi motion, binding
and nucleon correlations.
We also consider the pion and rho meson cloud contributions calculated from a
microscopic model for meson-nucleus self-energies. The calculations have been
performed using relativistic nuclear spectral functions which include nucleon
correlations. Our results are compared with the experimental data of NuTeV and
CDHSW.Comment: 24 pages, 14 figure
A systematic review of practices to promote vegetable acceptance in the first three years of life.
Background: Although most children do not meet vegetable intake recommendations no clear universal guidelines exist on the best method of introducing and promoting vegetables in infants.
Objective: To identify strategies to promote vegetable acceptance in children from the start of complementary feeding until 3 years of age.
Design: A comprehensive search strategy was performed using the databases Scopus and Pubmed. Articles published before March 2018 measuring vegetable intake and/or liking were included.
Results: 46 papers, 25 experimental (intervention) studies, and 21 observational studies were included. Intervention studies revealed that repeated exposure increased acceptance of the target vegetable, whereas exposure to variety was found to be particularly effective in increasing acceptance of a new vegetable. Starting complementary feeding with vegetables increased vegetable acceptance, whereas starting with fruits did not. Visual exposure to an unfamiliar vegetable increased the acceptance of that vegetable even without consuming it, while visual exposure to a familiar vegetable did not. A stepwise introduction of vegetables resulted in better initial acceptance of vegetables than introducing vegetables directly. Observational studies showed that vegetable consumption was associated with frequency of exposure, exposure to variety, and modelling. A majority of studies found a positive association between breastfeeding and vegetable acceptance, but only two out of seven studies found an association between age of vegetable introduction and their acceptance.
Conclusions: Based on the papers reviewed, we conclude that introducing vegetables at the beginning of complementary feeding, giving a different type of vegetable every day and ensuring repeated exposure to the same vegetable following an interval of a few days are the most promising strategies to promote vegetable intake in children starting complementary feeding until they are 3 years of age
Pair Correlations, Short Range Order and Dispersive Excitations in the Quasi-Kagome Quantum Magnet Volborthite
We present spatial and dynamic information on the s=1/2 distorted kagome
antiferromagnet volborthite, Cu3V2O7(OD)2.2D2O, obtained by polarized and
inelastic neutron scattering. The instantaneous structure factor, S(Q), is
dominated by nearest neighbor pair correlations, with short range order at wave
vectors Q1=0.65(3) {\AA}^-1 and Q2=1.15(5) {\AA}^-1 emerging below 5 K. The
excitation spectrum, S(Q,{\omega}), reveals two steep branches dispersing from
Q1 and Q2, and a flat mode at {\omega}=5.0(2) meV. The results allow us to
identify the cross-over at T*=1 K in 51V NMR and specific heat measurements as
the build-up of correlations at Q_1. We compare our data to theoretical models
proposed for volborthite, and demonstrate that the excitation spectrum can be
explained by spin-wave-like excitations with anisotropic exchange parameters,
as also suggested by recent local density calculations.Comment: Rewritten article resubmitted to Phys. Rev. Lett. 021
Inclusion of non-spherical components of the Pauli blocking operator in (p,p') reactions
We present the first calculations of proton elastic and inelastic scattering
in which the Pauli blocking operator contains the leading non-spherical
components as well as the usual spherical (angle-averaged) part. We develop a
formalism for including the contributions to the effective nucleon-nucleon
interaction from the resulting new G-matrix elements that extend the usual
two-nucleon spin structure and may not conserve angular momentum. We explore
the consequences of parity conservation, time reversal invariance, and
nucleon-nucleon antisymmetrization for the new effective interaction. Changes
to the calculated cross section and spin observables are small in the energy
range from 100 to 200 MeV.Comment: 24 pages, 4 figures, to be published in Physical Review
Molecular Line Profile Fitting with Analytic Radiative Transfer Models
We present a study of analytic models of starless cores whose line profiles
have ``infall asymmetry,'' or blue-skewed shapes indicative of contracting
motions. We compare the ability of two types of analytical radiative transfer
models to reproduce the line profiles and infall speeds of centrally condensed
starless cores whose infall speeds are spatially constant and range between 0
and 0.2 km s-1. The model line profiles of HCO+ (J=1-0) and HCO+ (J=3-2) are
produced by a self-consistent Monte Carlo radiative transfer code. The analytic
models assume that the excitation temperature in the front of the cloud is
either constant (``two-layer'' model) or increases inward as a linear function
of optical depth (``hill'' model). Each analytic model is matched to the line
profile by rapid least-squares fitting.
The blue-asymmetric line profiles with two peaks, or with a blue shifted peak
and a red shifted shoulder, can be well fit by the ``HILL5'' model (a five
parameter version of the hill model), with an RMS error of 0.02 km s-1. A peak
signal to noise ratio of at least 30 in the molecular line observations is
required for performing these analytic radiative transfer fits to the line
profiles.Comment: 48 pages, 20 figures, accepted for publication in Ap
Direct and Regioselective Di-alpha-fucosylation on the Secondary Rim of beta-Cyclodextrin
A straightforward glycosylation method is described to regio- and stereoselectively introduce two alpha-L-fucose moieties directly to the secondary rim of beta-cyclodextrin. Using NMR and MS fragmentation studies, the nonasaccharide structure was determined, which was also visualized using molecular dynamics simulations. The reported glycosylation method proved to be robust on gram-scale, and may be generally applied to directly glycosylate beta-cyclodextrins to make well-defined multivalent glycoclusters.</p
Inheritance of physico-chemical properties and ROS generation by carbon quantum dots derived from pyrolytically carbonized bacterial sources
Bacteria are frequently used in industrial processes and nutrient supplementation to restore a healthy human microflora, but use of live bacteria is often troublesome. Here, we hypothesize that bacterially-derived carbon-quantum-dots obtained through pyrolytic carbonization inherit physico-chemical properties from probiotic and pathogenic source-bacteria. Carbon-quantum-dots carbonized at reaction-temperatures below 200 ​°C had negligible quantum-yields, while temperatures above 220 ​°C yielded poor water-suspendability. Fourier-transform infrared-spectroscopy demonstrated preservation of amide absorption bands in carbon-quantum-dots derived at intermediate temperatures. X-ray photoelectron-spectroscopy indicated that the at%N in carbon-quantum-dots increased with increasing amounts of protein in source-bacterial surfaces. Carbonization transformed hydrocarbon-like bacterial surface compounds into heterocyclic aromatic-carbon structures, evidenced by a broad infrared absorption band (920-900 ​cm−1) and the presence of carbon in C–C functionalities of carbon-quantum-dots. The chemical composition of bacterially-derived carbon-quantum-dots could be explained by the degradation temperatures of main bacterial cell surface compounds. All carbon-quantum-dots generated reactive-oxygen-species, most notably those derived from probiotic lactobacilli, carrying a high amount of surface protein. Concluding, amide functionalities in carbon-quantum-dots are inherited from surface proteins of source-bacteria, controlling reactive-oxygen-species generation. This paves the way for applications of bacterially-derived carbon-quantum-dots in which reactive-oxygen-species generation is essential, instead of hard-to-use live bacteria, such as in food supplementation or probiotic-assisted antibiotic therapy
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