989 research outputs found
Communication:Two measures of isochronal superposition
A liquid obeys isochronal superposition if its dynamics is invariant along
the isochrones in the thermodynamic phase diagram (the curves of constant
relaxation time). This paper introduces two quantitative measures of isochronal
superposition. The measures are used to test the following six liquids for
isochronal superposition: 1,2,6 hexanetriol, glycerol, polyphenyl ether,
diethyl phthalate, tetramethyl tetraphenyl trisiloxane, and dibutyl phthalate.
The latter four van der Waals liquids obey isochronal superposition to a higher
degree than the two hydrogen-bonded liquids. This is a predic- tion of the
isomorph theory, and it confirms findings by other groups.Comment: 14 pages (article 4 pages, supplementary 10 pages), 42 figure
Long-Term Mortality in Patients with Tuberculous Meningitis: A Danish Nationwide Cohort Study
Background: With high short-term mortality and substantial excess morbidity among survivors, tuberculous meningitis (TBM) is the most severe manifestation of extra-pulmonary tuberculosis (TB). The objective of this study was to assess the long-term mortality and causes of death in a TBM patient population compared to the background population. Methods: A nationwide cohort study was conducted enrolling patients notified with TBM in Denmark from 1972–2008 and alive one year after TBM diagnosis. Data was extracted from national registries. From the background population we identified a control cohort of individuals matched on gender and date of birth. Kaplan-Meier survival curves and Cox regression analysis were used to estimate mortality rate ratios (MRR) and analyse causes of death. Findings: A total of 55 TBM patients and 550 individuals from the background population were included in the study. Eighteen patients (32.7%) and 107 population controls (19.5%) died during the observation period. The overall MRR was 1.79 (95%CI: 1.09–2.95) for TBM patients compared to the population control cohort. TBM patients in the age group 31–60 years at time of diagnosis had the highest relative risk of death (MRR 2.68; 95%CI 1.34–5.34). The TBM patients had a higher risk of death due to infectious disease, but not from other causes of death. Conclusion: Adult TBM patients have an almost two-fold increased long-term mortality and the excess mortality stems fro
Aspects of harmonisation of individual monitoring for external radiation in Europe: Conclusions of a EURADOS action
Following the publication of the EU Council Directive 96/29, EURADOS coordinated two working groups (WGs) for promoting the process of harmonisation on individual monitoring of occupationally exposed persons in Europe. An overview of the major findings of the second WG is presented. Information on the technical and quality standards and on the accreditation and approval procedures has been compiled. The catalogue of dosimetric services has been updated and extended. An overview of national regulations and standards for protection from radon and other natural sources in workplaces has been made, attempting to combine the results from individual monitoring for external, internal and workplace monitoring. A first status description of the active personal dosemeters, including legislative and technical information, and their implementation has been made. The importance of practical factors on the uncertainty in the dose measurement has been estimated. Even if a big progress has been made towards harmonisation, there is still work to be don
Effective Rheology of Bubbles Moving in a Capillary Tube
We calculate the average volumetric flux versus pressure drop of bubbles
moving in a single capillary tube with varying diameter, finding a square-root
relation from mapping the flow equations onto that of a driven overdamped
pendulum. The calculation is based on a derivation of the equation of motion of
a bubble train from considering the capillary forces and the entropy production
associated with the viscous flow. We also calculate the configurational
probability of the positions of the bubbles.Comment: 4 pages, 1 figur
Molecular Characterisation of Small Molecule Agonists Effect on the Human Glucagon Like Peptide-1 Receptor Internalisation
The glucagon-like peptide receptor (GLP-1R), which is a G-protein coupled receptor (GPCR), signals through both Gαs and Gαq coupled pathways and ERK phosphorylation to stimulate insulin secretion. The aim of this study was to determine molecular details of the effect of small molecule agonists, compounds 2 and B, on GLP-1R mediated cAMP production, intracellular Ca2+ accumulation, ERK phosphorylation and its internalisation. In human GLP-1R (hGLP-1R) expressing cells, compounds 2 and B induced cAMP production but caused no intracellular Ca2+ accumulation, ERK phosphorylation or hGLP-1R internalisation. GLP-1 antagonists Ex(9-39) and JANT-4 and the orthosteric binding site mutation (V36A) in hGLP-1R failed to inhibit compounds 2 and B induced cAMP production, confirming that their binding site distinct from the GLP-1 binding site on GLP-1R. However, K334A mutation of hGLP-1R, which affects Gαs coupling, inhibited GLP-1 as well as compounds 2 and B induced cAMP production, indicating that GLP-1, compounds 2 and B binding induce similar conformational changes in the GLP-1R for Gαs coupling. Additionally, compound 2 or B binding to the hGLP-1R had significantly reduced GLP-1 induced intracellular Ca2+ accumulation, ERK phosphorylation and hGLP-1R internalisation. This study illustrates pharmacology of differential activation of GLP-1R by GLP-1 and compounds 2 and B
Freezing and melting line invariants of the Lennard-Jones system
The invariance of several structural and dynamical properties of the
Lennard-Jones (LJ) system along the freezing and melting lines is interpreted
in terms of the isomorph theory. First the freezing/melting lines for LJ system
are shown to be approximated by isomorphs. Then we show that the invariants
observed along the freezing and melting isomorphs are also observed on other
isomorphs in the liquid and crystalline phase. Structure is probed by the
radial distribution function and the structure factor and dynamics is probed by
the mean-square displacement, the intermediate scattering function, and the
shear viscosity. Studying these properties by reference to the isomorph theory
explains why known single-phase melting criteria holds, e.g., the Hansen-Verlet
and the Lindemann criterion, and why the Andrade equation for the viscosity at
freezing applies, e.g., for most liquid metals. Our conclusion is that these
empirical rules and invariants can all be understood from the isomorph theory
and that the invariants are not peculiar to the freezing and melting lines, but
hold along all isomorphs.Comment: 21 pg, 12 figures Accepted from PCCP (Physical Chemistry Chemical
Physics
The impact range for smooth wall–liquid interactions in nanoconfined liquids
Bulk and nanoconfined liquids have initially very different physics; for
instance, nanoconfined liquids show stratification and position-dependent
relaxation processes. A number of similarities between bulk and nanoconfined
liquids have nevertheless been reported in computer simulations during the last
decade. Inspired by these observations, we present results from molecular
dynamics computer simulations of three nanoconfined liquids (i.e.,
single-component Lennard-Jones (LJ) liquid, Kob-Andersen binary LJ mixture, and
an asymmetric dumbbell model) demonstrating also a microscopic similarity
between bulk and nanoconfined liquids. The results show that the interaction
range for the wall-liquid and liquid-liquid interactions of the nanoconfined
liquid are identical to the bulk liquid as long as the liquid remains "Roskilde
simple" in nanoconfinement, i.e., the liquid has strong correlations between
virial and potential energy equilibrium fluctuations in the NVT ensemble.Comment: 8 page
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