3,670 research outputs found
Variants of the human PPARG locus and the susceptibility to chronic periodontitis
Apart from its regulatory function in lipid and glucose metabolism, peroxisome proliferator-activated receptor (PPAR)γ has impact on the regulation of inflammation and bone metabolism. The aim of the study was to investigate the association of five polymorphisms (rs10865710, rs2067819, rs3892175, rs1801282, rs3856806) within the PPARG gene with chronic periodontitis. The study population comprised 402 periodontitis patients and 793 healthy individuals. Genotyping of the PPARG gene polymorphisms was performed by PCR and melting curve analysis. Comparison of frequency distribution of genotypes between individuals with periodontal disease and healthy controls for the polymorphism rs3856806 showed a P-value of 0.04 but failed to reach significance after correction for multiple testing (P 0.90). A 3-site analysis (rs2067819-rs1801282-rs3856860) revealed five haplotypes with a frequency of ≥1% among cases and controls. Following adjustment for age, gender and smoking, none of the haplotypes was significantly different between periodontitis and healthy controls after Bonferroni correction. This study could not show a significant association between PPARG gene variants and chronic periodontitis
Reconstructing the geometric structure of a Riemannian symmetric space from its Satake diagram
The local geometry of a Riemannian symmetric space is described completely by
the Riemannian metric and the Riemannian curvature tensor of the space. In the
present article I describe how to compute these tensors for any Riemannian
symmetric space from the Satake diagram, in a way that is suited for the use
with computer algebra systems. As an example application, the totally geodesic
submanifolds of the Riemannian symmetric space SU(3)/SO(3) are classified.
The submission also contains an example implementation of the algorithms and
formulas of the paper as a package for Maple 10, the technical documentation
for this implementation, and a worksheet carrying out the computations for the
space SU(3)/SO(3) used in the proof of Proposition 6.1 of the paper.Comment: 23 pages, also contains two Maple worksheets and technical
documentatio
Phonon-affected steady-state transport through molecular quantum dots
We consider transport through a vibrating molecular quantum dot contacted to
macroscopic leads acting as charge reservoirs. In the equilibrium and
nonequilibrium regime, we study the formation of a polaron-like transient state
at the quantum dot for all ratios of the dot-lead coupling to the energy of the
local phonon mode. We show that the polaronic renormalization of the dot-lead
coupling is a possible mechanism for negative differential conductance.
Moreover, the effective dot level follows one of the lead chemical potentials
to enhance resonant transport, causing novel features in the inelastic
tunneling signal. In the linear response regime, we investigate the impact of
the electron-phonon interaction on the thermoelectrical properties of the
quantum dot device.Comment: 11 pages, 7 figures, FQMT11 Proceeding
Division, adjoints, and dualities of bilinear maps
The distributive property can be studied through bilinear maps and various
morphisms between these maps. The adjoint-morphisms between bilinear maps
establish a complete abelian category with projectives and admits a duality.
Thus the adjoint category is not a module category but nevertheless it is
suitably familiar. The universal properties have geometric perspectives. For
example, products are orthogonal sums. The bilinear division maps are the
simple bimaps with respect to nondegenerate adjoint-morphisms. That formalizes
the understanding that the atoms of linear geometries are algebraic objects
with no zero-divisors. Adjoint-isomorphism coincides with principal isotopism;
hence, nonassociative division rings can be studied within this framework.
This also corrects an error in an earlier pre-print; see Remark 2.11
Uniform electron gases
We show that the traditional concept of the uniform electron gas (UEG) --- a
homogeneous system of finite density, consisting of an infinite number of
electrons in an infinite volume --- is inadequate to model the UEGs that arise
in finite systems. We argue that, in general, a UEG is characterized by at
least two parameters, \textit{viz.} the usual one-electron density parameter
and a new two-electron parameter . We outline a systematic
strategy to determine a new density functional across the
spectrum of possible and values.Comment: 8 pages, 2 figures, 5 table
Phonon affected transport through molecular quantum dots
To describe the interaction of molecular vibrations with electrons at a
quantum dot contacted to metallic leads, we extend an analytical approach that
we previously developed for the many-polaron problem. Our scheme is based on an
incomplete variational Lang-Firsov transformation, combined with a perturbative
calculation of the electron-phonon self-energy in the framework of generalised
Matsubara functions. This allows us to describe the system at weak to strong
coupling and intermediate to large phonon frequencies. We present results for
the quantum dot spectral function and for the kinetic coefficient that
characterises the electron transport through the dot. With these results we
critically examine the strengths and limitations of our approach, and discuss
the properties of the molecular quantum dot in the context of polaron physics.
We place particular emphasis on the importance of corrections to the concept of
an antiadiabatic dot polaron suggested by the complete Lang-Firsov
transformation.Comment: 30 pages, 15 figures, revised version including new figure
Compression of sub-relativistic space-charge-dominated electron bunches for single-shot femtosecond electron diffraction
We demonstrate compression of 95 keV, space-charge-dominated electron bunches
to sub-100 fs durations. These bunches have sufficient charge (200 fC) and are
of sufficient quality to capture a diffraction pattern with a single shot,
which we demonstrate by a diffraction experiment on a polycrystalline gold
foil. Compression is realized by means of velocity bunching as a result of a
velocity chirp, induced by the oscillatory longitudinal electric field of a 3
GHz radio-frequency cavity. The arrival time jitter is measured to be 80 fs
Tunable wettability of polymer films by partial engulfment of nanoparticles
A series of poly(methyl methacrylate) (PMMA) surfaces decorated by Cu nanoparticles (NP) with gradually varied morphology were prepared by high-pressure CO2 treatment at various time spans. Combining the characterizations of transmission electron microscopy (TEM) and atomic force microscopy (AFM), an accurate three-dimensional view of the morphology of the surfaces was presented. Subsequently, the wettability of the surfaces decreases near linearly with the increase of the apparent height of the decorating NPs in both static (static contact angle) and dynamic (contact angle hysteresis) aspects. The observed tendency contradicts to the Wenzel or Cassie-Baxter model and is explained by the contribution of nanomeniscus formed between the decorating NP and the flat substrate. The capillary pressure from this meniscus is negative and results in the increase of the contact angle with the apparent height (H-N) of the Cu NPs decorating the PMMA surface. In addition, the effect of the coverage (C-N) by NPs on the wettability can be explained on the same basis. Our experiment demonstrates the important influence of the nanomeniscus on the wettability, which is usually not taken into account. The results in this work provide a comprehensive understanding of how nanostructure affects the wettability of the decorated surfaces and shed light on how to obtain certain wettability through nanostructuring of the surface morphology
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