1,543 research outputs found
Non-equilibrium two-phase coexistence in a confined granular layer
We report the observation of the homogenous nucleation of crystals in a dense
layer of steel spheres confined between two horizontal plates vibrated
vertically. Above a critical vibration amplitude, two-layer crystals with
square symmetry were found to coexist in steady state with a surrounding
granular liquid. By analogy to equilibrium hard sphere systems, the phase
behavior can be explained through entropy maximization. However, dramatic
non-equilibrium effects are present, including a significant difference in the
granular temperatures of the two phases.Comment: 4 pages, 3 figures, RevTex4 forma
Statistical Properties of Contact Maps
A contact map is a simple representation of the structure of proteins and
other chain-like macromolecules. This representation is quite amenable to
numerical studies of folding. We show that the number of contact maps
corresponding to the possible configurations of a polypeptide chain of N amino
acids, represented by (N-1)-step self avoiding walks on a lattice, grows
exponentially with N for all dimensions D>1. We carry out exact enumerations in
D=2 on the square and triangular lattices for walks of up to 20 steps and
investigate various statistical properties of contact maps corresponding to
such walks. We also study the exact statistics of contact maps generated by
walks on a ladder.Comment: Latex file, 15 pages, 12 eps figures. To appear on Phys. Rev.
Prevalence of and associations with agitation in residents with dementia living in care homes: MARQUE cross-sectional study
BACKGROUND: Agitation is reportedly the most common neuropsychiatric symptom in care home residents with dementia. AIMS: To report, in a large care home survey, prevalence and determinants of agitation in residents with dementia. METHOD: We interviewed staff from 86 care homes between 13 January 2014 and 12 November 2015 about residents with dementia with respect to agitation (Cohen-Mansfield Agitation Inventory (CMAI)), quality of life (DEMQOL-proxy) and dementia severity (Clinical Dementia Rating). We also interviewed residents and their relatives. We used random effects models adjusted for resident age, gender, dementia severity and care home type with CMAI as a continuous score. RESULTS: Out of 3053 (86.2%) residents who had dementia, 1489 (52.7%) eligible residents participated. Fifteen per cent of residents with very mild dementia had clinically significant agitation compared with 33% with mild (odds ratios (ORs)=4.49 95% confidence interval (CI)=2.30) and 45% with moderate or severe dementia (OR=6.95 95% CI=3.63, 13.31 and OR=6.23 95% CI=3.25, 11.94, respectively). More agitation was associated with lower quality of life (regression coefficient (rc)=-0.53; 95% CI=-0.61, -0.46) but not with staffing or resident ratio (rc=0.03; 95% CI=-0.04, 0.11), level of residents' engagement in home activities (rc=3.21; 95% CI=-0.82, 7.21) or family visit numbers (rc=-0.03; 95% CI=-0.15, 0.08). It was correlated with antipsychotic use (rc=6.45; 95% CI=3.98, 8.91). CONCLUSIONS: Care home residents with dementia and agitation have lower quality of life. More staffing time and activities as currently provided are not associated with lower agitation levels. New approaches to develop staff skills in understanding and responding to the underlying reasons for individual resident's agitation require development and testing. DECLARATION OF INTEREST: None. COPYRIGHT AND USAGE: © The Royal College of Psychiatrists 2017. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) license
Splitting of the Dipole and Spin-Dipole Resonances
Cross sections for the 90,92,94Zr(p,n) reactions were measured at energies of
79.2 and 119.4 MeV. A phenomenological model was developed to describe the
variation with bombarding energy of the position of the L=1 peak observed in
these and other (p,n) reactions. The model yields the splitting between the
giant dipole and giant spin dipole resonances. Values of these splittings are
obtained for isotopes of Zr and Sn and for 208Pb.Comment: 14 pages, 4 figure
Effect of bond lifetime on the dynamics of a short-range attractive colloidal system
We perform molecular dynamics simulations of short-range attractive colloid
particles modeled by a narrow (3% of the hard sphere diameter) square well
potential of unit depth. We compare the dynamics of systems with the same
thermodynamics but different bond lifetimes, by adding to the square well
potential a thin barrier at the edge of the attractive well. For permanent
bonds, the relaxation time diverges as the packing fraction
approaches a threshold related to percolation, while for short-lived bonds, the
-dependence of is more typical of a glassy system. At intermediate
bond lifetimes, the -dependence of is driven by percolation at low
, but then crosses over to glassy behavior at higher . We also
study the wavevector dependence of the percolation dynamics.Comment: Revised; 9 pages, 9 figure
Static and Dynamic Anomalies in a Repulsive Spherical Ramp Liquid: Theory and Simulation
We compare theoretical and simulation results for static and dynamic
properties for a model of particles interacting via a spherically symmetric
repulsive ramp potential. The model displays anomalies similar to those found
in liquid water, namely, expansion upon cooling and an increase of diffusivity
upon compression. In particular, we calculate the phase diagram from the
simulation and successfully compare it with the phase diagram obtained using
the Rogers-Young (RY) closure for the Ornstein-Zernike equation. Both the
theoretical and the numerical calculations confirm the presence of a line of
isobaric density maxima, and lines of compressibility minima and maxima.
Indirect evidence of a liquid-liquid critical point is found. Dynamic
properties also show anomalies. Along constant temperature paths, as the
density increases, the dynamics alternates several times between slowing down
and speeding up, and we associate this behavior with the progressive
structuring and de-structuring of the liquid. Finally we confirm that mode
coupling theory successfully predicts the non-monotonic behavior of dynamics
and the presence of multiple glass phases, providing strong evidence that
structure (the only input of mode coupling theory) controls dynamics.Comment: Static and Dynamic Anomalies in a Repulsive Spherical Ramp Liquid:
Theory and Simulatio
Homozygous NLRP1 gain-of-function mutation in siblings with a syndromic form of recurrent respiratory papillomatosis
© 2019 National Academy of Sciences. All rights reserved. Juvenile-onset recurrent respiratory papillomatosis (JRRP) is a rare and debilitating childhood disease that presents with recurrent growth of papillomas in the upper airway. Two common human papillomaviruses (HPVs), HPV-6 and -11, are implicated in most cases, but it is still not understood why only a small proportion of children develop JRRP following exposure to these common viruses. We report 2 siblings with a syndromic form of JRRP associated with mild dermatologic abnormalities. Whole-exome sequencing of the patients revealed a private homozygous mutation in NLRP1, encoding Nucleotide-Binding Domain Leucine-Rich Repeat Family Pyrin Domain-Containing 1. We find the NLRP1 mutant allele to be gain of function (GOF) for inflammasome activation, as demonstrated by the induction of inflammasome complex oligomerization and IL-1β secretion in an overexpression system. Moreover, patient-derived keratinocytes secrete elevated levels of IL-1β at baseline. Finally, both patients displayed elevated levels of inflammasome-induced cytokines in the serum. Six NLRP1 GOF mutations have previously been described to underlie 3 allelic Mendelian diseases with differing phenotypes and modes of inheritance. Our results demonstrate that an autosomal recessive, syndromic form of JRRP can be associated with an NLRP1 GOF mutation
Do Hadronic Charge Exchange Reactions Measure Electroweak L = 1 Strength?
An eikonal model has been used to assess the relationship between calculated
strengths for first forbidden beta decay and calculated cross sections for
(p,n) charge exchange reactions. It is found that these are proportional for
strong transitions, suggesting that hadronic charge exchange reactions may be
useful in determining the spin-dipole matrix elements for astrophysically
interesting leptonic transitions.Comment: 14 pages, 5 figures, Submitted to Physical Review
Mesoscopic modeling of a two-phase flow in the presence of boundaries: the Contact Angle
We present a mesoscopic model, based on the Boltzmann Equation, for the
interaction between a solid wall and a non-ideal fluid. We present an analytic
derivation of the contact angle in terms of the surface tension between the
liquid-gas, the liquid-solid and the gas-solid phases. We study the dependency
of the contact angle on the two free parameters of the model, which determine
the interaction between the fluid and the boundaries, i.e. the equivalent of
the wall density and of the wall-fluid potential in Molecular Dynamics studies.
We compare the analytical results obtained in the hydrodynamical limit for
the density profile and for the surface tension expression with the numerical
simulations. We compare also our two-phase approach with some exact results for
a pure hydrodynamical incompressible fluid based on Navier-Stokes equations
with boundary conditions made up of alternating slip and no-slip strips.
Finally, we show how to overcome some theoretical limitations connected with a
discretized Boltzmann scheme and we discuss the equivalence between the surface
tension defined in terms of the mechanical equilibrium and in terms of the
Maxwell construction.Comment: 29 pages, 12 figure
Hydrogen Bond Dynamics Near A Micellar Surface: Origin of the Universal Slow Relaxation at Complex Aqueous Interfaces
The dynamics of hydrogen bonds among water molecules themselves and with the
polar head groups (PHG) at a micellar surface have been investigated by long
molecular dynamics simulations. The lifetime of the hydrogen bond between a PHG
and a water molecule is found to be much longer than that between any two water
molecules, and is likely to be a general feature of hydrophilic surfaces of
organized assemblies. Analyses of individual water trajectories suggest that
water molecules can remain bound to the micellar surface for more than a
hundred picosecond. The activation energy for such a transition from the bound
to a free state for the water molecules is estimated to be about 3.5kcal/mole.Comment: 12 pages. Phys. Rev. Lett. (Accepted) (2002
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