628 research outputs found
Measuring functional renormalization group fixed-point functions for pinned manifolds
Exact numerical minimization of interface energies is used to test the
functional renormalization group (FRG) analysis for interfaces pinned by
quenched disorder. The fixed-point function R(u) (the correlator of the
coarse-grained disorder) is computed. In dimensions D=d+1, a linear cusp in
R''(u) is confirmed for random bond (d=1,2,3), random field (d=0,2,3), and
periodic (d=2,3) disorders. The functional shocks that lead to this cusp are
seen. Small, but significant, deviations from 1-loop FRG results are compared
to 2-loop corrections. The cross-correlation for two copies of disorder is
compared with a recent FRG study of chaos.Comment: 4 pages, 4 figure
Test of Sum Rules in Nucleon Transfer Reactions
The quantitative consistency of nucleon transfer reactions as a probe of the occupancy of valence orbits in nuclei is tested. Neutron-adding, neutron-removal, and proton-adding transfer reactions were measured on the four stable even Ni isotopes, with particular attention to the cross section determinations. The data were analyzed consistently in terms of the distorted wave Born approximation to yield spectroscopic factors. Valence-orbit occupancies were extracted, utilizing the Macfarlane-French sum rules. The deduced occupancies are consistent with the changing number of valence neutrons, as are the vacancies for protons, both at the level of <5%. While there has been some debate regarding the true “observability” of spectroscopic factors, the present results indicate that empirically they yield self-consistent results
Stability of growing vesicles
We investigate the stability of growing vesicles using the formalism of
nonequilibrium thermodynamics. The vesicles are growing due to the accretion of
lipids to the bilayer which forms the vesicle membrane. The thermodynamic
description is based on the hydrodynamics of a water{/}lipid mixture together
with a model of the vesicle as a discontinuous system in the sense of linear
nonequilibrium thermodynamics. This formulation allows the forces and fluxes
relevant to the dynamic stability of the vesicle to be identified. The method
is used to analyze the stability of a spherical vesicle against arbitrary
axisymmetric perturbations. It is found that there are generically two critical
radii at which changes of stability occur. In the case where the perturbation
takes the form of a single zonal harmonic, only one of these radii is physical
and is given by the ratio , where is the hydraulic
conductivity and is the Onsager coefficient related to changes in
membrane area due to lipid accretion. The stability of such perturbations is
related to the value of corresponding to the particular zonal harmonic:
those with lower are more unstable than those with higher . Possible
extensions of the current work and the need for experimental input are
discussed.Comment: 17 pages, 3 figure
Valence nucleon populations in the Ni isotopes
Measurements of neutron-adding, neutron-removing, and proton-adding reactions were carried out for the four stable even Ni isotopes. Particular attention was paid to obtaining precise values of the cross sections at the peaks of the angular distributions. Tests with sum rules for the neutron data indicate that the results are self-consistent at the level of a few tenths of a nucleon. Data on proton-adding reactions were also obtained and analyzed with a slightly different method—while these data are also consistent, the ambiguities are larger. The occupancies of the neutron orbits derived from the data, the proton vacancies, and the energy centroids of the neutron, neutron-hole, and proton single-particle excitations are obtained. The data also provide some estimate about the closure of the 0f7/2 shell. The results are compared to shell-model calculations and may serve as a reference point for future exploration
What makes you not a Sikh? : a preliminary mapping of values
This study sets out to establish which Sikh values contrasted with or were shared by non-Sikh adolescents. A survey of attitude toward a variety of Sikh values was fielded in a sample of 364 non-Sikh schoolchildren aged between 13 and 15 in London. Values where attitudes were least positive concerned Sikh duties/code of conduct, festivals, rituals, prayer Gurdwara attendance, listening to scripture recitation, the amrit initiation. Sikh values empathized with by non-Sikhs concerned family pride, charity, easy access to ordination and Gurdwaras, maintaining the five Ks, seeing God in all things, abstaining from meat and alcohol and belief in the stories of Guru Nanak. Further significant differences of attitude toward Sikhism were found in comparisons by sex, age and religious affiliation. Findings are applied to teaching Sikhism to pupils of no faith adherence. The study recommends the extension of values mapping to specifically Sikh populations
Caveolin 1 is overexpressed and amplified in a subset of basal-like and metaplastic breast carcinomas: a morphologic, ultrastructural, immunohistochemical, and in situ hybridization analysis
The distribution and significance of caveolin 1 (CAV1) expression in different breast cell types and role in breast carcinogenesis remain poorly understood. Both tumor-suppressive and oncogenic roles have been proposed for this protein. The aims of this study were to characterize the distribution of CAV1 in normal breast, benign breast lesions, breast cancer precursors, and metaplastic breast carcinomas; to assess the prognostic significance of CAV1 expression in invasive breast carcinomas; and to define whether CAV1 gene amplification is the underlying genetic mechanism driving CAV1 overexpression in breast carcinomas. Purpose: The distribution and significance of caveolin 1 (CAV1) expression in different breast cell types and role in breast carcinogenesis remain poorly understood. Both tumor-suppressive and oncogenic roles have been proposed for this protein. The aims of this study were to characterize the distribution of CAV1 in normal breast, benign breast lesions, breast cancer precursors, and metaplastic breast carcinomas; to assess the prognostic significance of CAV1 expression in invasive breast carcinomas; and to define whether CAV1 gene amplification is the underlying genetic mechanism driving CAV1 overexpression in breast carcinomas.
Experimental Design: CAV1 distribution in frozen and paraffin-embedded whole tissue sections of normal breast was evaluated using immunohistochemistry, immunofluorescence, and immunoelectron microscopy. CAV1 expression was immunohistochemically analyzed in benign lesions, breast cancer precursors, and metaplastic breast carcinomas and in a cohort of 245 invasive breast carcinomas from patients treated with surgery followed by anthracycline-based chemotherapy. In 25 cases, CAV1 gene amplification was assessed by chromogenic in situ hybridization.
Results: In normal breast, CAV1 was expressed in myoepithelial cells, endothelial cells, and a subset of fibroblasts. Luminal epithelial cells showed negligible staining. CAV1 was expressed in 90% of 39 metaplastic breast carcinomas and in 9.4% of 245 invasive breast cancers. In the later cohort, CAV1 expression was significantly associated with ‘basal-like’ immunophenotype and with shorter disease-free and overall survival on univariate analysis. CAV1 gene amplification was found in 13% of cases with strong CAV1 expression.
Conclusions: The concurrent CAV1 amplification and overexpression call into question its tumor-suppressive effects in basal-like breast carcinomas
A regioselective three component reaction of pyridine N-oxides, acyl chlorides and cyclic ethers
A novel 3-component reaction of pyridine N-oxides, acyl chlorides and cyclic ethers is described. Treatment of an electron defi-cient pyridine N-oxide with an acyl chloride in the presence of a cyclic ether at 25–50 °C leads to a substituted pyridine as a single regioisomer in up to 58% isolated yield. Isotopic labelling experiments and substrate scope support the reaction proceeding through a carbene intermediate
Notes on Notebooks: Is Jupyter the Bringer of Jollity?
As the interactive computational notebook becomes a more prominent code development medium, we examine advantages and disadvantages of this particular source code format. We specify the structure of a coding notebook layout. We describe complexities in notebook programming; some of these are incidental whereas others may be inherent complexities. We outline how we envisage research and development might proceed to advance the cause of notebook programming
Impact of baryon physics on dark matter structures: a detailed simulation study of halo density profiles
The back-reaction of baryons on the dark matter halo density profile is of
great interest, not least because it is an important systematic uncertainty
when attempting to detect the dark matter. Here, we draw on a large suite of
high resolution cosmological hydrodynamical simulations, to systematically
investigate this process and its dependence on the baryonic physics associated
with galaxy formation. The inclusion of baryons results in significantly more
concentrated density profiles if radiative cooling is efficient and feedback is
weak. The dark matter halo concentration can in that case increase by as much
as 30 (10) per cent on galaxy (cluster) scales. The most significant effects
occur in galaxies at high redshift, where there is a strong anti-correlation
between the baryon fraction in the halo centre and the inner slope of both the
total and the dark matter density profiles. If feedback is weak, isothermal
inner profiles form, in agreement with observations of massive, early-type
galaxies. However, we find that AGN feedback, or extremely efficient feedback
from massive stars, is necessary to match observed stellar fractions in groups
and clusters, as well as to keep the maximum circular velocity similar to the
virial velocity as observed for disk galaxies. These strong feedback models
reduce the baryon fraction in galaxies by a factor of 3 relative to the case
with no feedback. The AGN is even capable of reducing the baryon fraction by a
factor of 2 in the inner region of group and cluster haloes. This in turn
results in inner density profiles which are typically shallower than isothermal
and the halo concentrations tend to be lower than in the absence of baryons.Comment: 20 pages, 14 figures, 1 table. MNRAS in press. Version 2: added a few
references
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