65,197 research outputs found
The Complete Jamming Landscape of Confined Hard Discs
An exact description of the complete jamming landscape is developed for a
system of hard discs of diameter , confined between two lines separated
by a distance . By considering all possible local
packing arrangements, the generalized ensemble partition function of jammed
states is obtained using the transfer matrix method, which allows us to
calculate the configurational entropy and the equation of state for the
packings. Exploring the relationship between structural order and packing
density, we find that the geometric frustration between local packing
environments plays an important role in determining the density distribution of
jammed states and that structural "randomness" is a non-monotonic function of
packing density. Molecular dynamics simulations show that the properties of the
equilibrium liquid are closely related to those of the landscape.Comment: 5 Pages, 4 figure
Evaluation of high temperature structural adhesives for extended service
The preliminary evaluation of crosslinked polyphenyl quinoxaline (X-PPQ), LARC-TPI, ethyl terminated polysulfone (ETPS), and crosslinked polyimide (X-PI) as adhesives is presented. Lap shear strength stability under thermal, combined thermal/humidity, and stressed and unstressed Skydrol exposure was determined. The X-PPQ, LARC-TPI, and X-PI exhibited good adhesive performance at 505K (450 F) after 1000 hours at 505K. These three polymers also performed well after exposure to combined elevated temperature/high humidity, as well as, to Skydrol while under stress. The ETPS exhibited good ambient temperature adhesive properties, but performed poorly under all other exposure conditions, presumably due to inadequate chain extension and crosslinking
Two hard spheres in a pore: Exact Statistical Mechanics for different shaped cavities
The Partition function of two Hard Spheres in a Hard Wall Pore is studied
appealing to a graph representation. The exact evaluation of the canonical
partition function, and the one-body distribution function, in three different
shaped pores are achieved. The analyzed simple geometries are the cuboidal,
cylindrical and ellipsoidal cavities. Results have been compared with two
previously studied geometries, the spherical pore and the spherical pore with a
hard core. The search of common features in the analytic structure of the
partition functions in terms of their length parameters and their volumes,
surface area, edges length and curvatures is addressed too. A general framework
for the exact thermodynamic analysis of systems with few and many particles in
terms of a set of thermodynamic measures is discussed. We found that an exact
thermodynamic description is feasible based in the adoption of an adequate set
of measures and the search of the free energy dependence on the adopted measure
set. A relation similar to the Laplace equation for the fluid-vapor interface
is obtained which express the equilibrium between magnitudes that in extended
systems are intensive variables. This exact description is applied to study the
thermodynamic behavior of the two Hard Spheres in a Hard Wall Pore for the
analyzed different geometries. We obtain analytically the external work, the
pressure on the wall, the pressure in the homogeneous zone, the wall-fluid
surface tension, the line tension and other similar properties
Anomaly mediated neutrino-photon interactions at finite baryon density
We propose new physical processes based on the axial vector anomaly and
described by the Wess-Zumino-Witten term that couples the photon, Z-boson, and
the omega-meson. The interaction takes the form of a pseudo-Chern-Simons term,
. This term
induces neutrino-photon interactions at finite baryon density via the coupling
of the Z-boson to neutrinos. These interactions may be detectable in various
laboratory and astrophysical arenas. The new interactions may account for the
MiniBooNE excess. They also produce a competitive contribution to neutron star
cooling at temperatures >10^9 K. These processes and related axion--photon
interactions at finite baryon density appear to be relevant in many
astrophysical regimes.Comment: 4 pages, 2 figures; references adde
On Superalgebras of Matrices with Symmetry Properties
It is known that semi-magic square matrices form a 2-graded algebra or
superalgebra with the even and odd subspaces under centre-point reflection
symmetry as the two components. We show that other symmetries which have been
studied for square matrices give rise to similar superalgebra structures,
pointing to novel symmetry types in their complementary parts. In particular,
this provides a unifying framework for the composite `most perfect square'
symmetry and the related class of `reversible squares'; moreover, the
semi-magic square algebra is identified as part of a 2-gradation of the general
square matrix algebra. We derive explicit representation formulae for matrices
of all symmetry types considered, which can be used to construct all such
matrices.Comment: 25 page
Development of ductile claddings for dispersion-strengthened nickel-base alloys Final report
Development of ductile oxidation-resistant cladding alloys for thoria dispersion, strengthened nickel and nickel-chromiu
Validity of the second law in nonextensive quantum thermodynamics
The second law of thermodynamics in nonextensive statistical mechanics is
discussed in the quantum regime. Making use of the convexity property of the
generalized relative entropy associated with the Tsallis entropy indexed by q,
Clausius' inequality is shown to hold in the range of q between zero and two.
This restriction on the range of the entropic index, q, is purely quantum
mechanical and there exists no upper bound of q for validity of the second law
in classical theory.Comment: 12 pages, no figure
Preferences for Prenatal Tests for Cystic Fibrosis: A Discrete Choice Experiment to Compare the Views of Adult Patients, Carriers of Cystic Fibrosis and Health Professionals
As new technologies enable the development of non-invasive prenatal diagnosis (NIPD) for cystic fibrosis (CF), research examining stakeholder views is essential for the preparation of implementation strategies. Here, we compare the views of potential service users with those of health professionals who provide counselling for prenatal tests. A questionnaire incorporating a discrete choice experiment examined preferences for key attributes of NIPD and explored views on NIPD for CF. Adult patients (n = 92) and carriers of CF (n = 50) were recruited from one children’s and one adult NHS specialist CF centre. Health professionals (n = 70) were recruited via an e-mail invitation to relevant professional bodies. The key attribute affecting service user testing preferences was no miscarriage risk, while for health professionals, accuracy and early testing were important. The uptake of NIPD by service users was predicted to be high and includes couples that would currently decline invasive testing. Many service users (47%) and health professionals (55.2%) thought the availability of NIPD for CF would increase the pressure to undergo prenatal testing. Most service users (68.5%) thought NIPD for CF should be offered to all pregnant women, whereas more health professionals (68.2%) thought NIPD should be reserved for known carrier couples. The implications for clinical practice are discussed
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