184 research outputs found
Frictional Behavior and Surface Failure of Acrylic Denture Teeth
The wear characteristics of acrylic denture teeth were investigated under single- and double-pass sliding. The response of acrylic teeth to sliding was that of a relatively ductile material. The wear characteristics were affected similarly by environments of water and saliva. The "enamel" surfaces showed more resistance to penetration and were less susceptible to surface damage than the "dentin" surfaces. The effect of the second pass was to increase track width and cause a more severe mode of surface failure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67388/2/10.1177_00220345810600051001.pd
Moisture Absorption of Graphite-Epoxy Composites Immersed in Liquids and in Humid Air
Moisture absorption of graphite-epoxy composites immersed in liquids and in himid air were investigated. The moisture content as a function of time and temperature was measured for three materials: Fiberite T300/1034, Hercules AS/3501-5 and Narmco T300/5208. Tests were per formed a) with the materials immersed in No. 2 diesel fuel, in jet A fuel, in aviation oil, in saturated salt water, and in distilled water (in the range of 300 to 322 K) and b)with the materials exposed to humid air (in the range 322 to 366 K). The results obtained were compared to available composite and neat resin data.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68153/2/10.1177_002199837901300205.pd
Small Fermi surface in the one-dimensional Kondo lattice model
We study the one-dimensional Kondo lattice model through the density matrix
renormalization group (DMRG). Our results for the spin correlation function
indicate the presence of a small Fermi surface in large portions of the phase
diagram, in contrast to some previous studies that used the same technique. We
argue that the discrepancy is due to the open boundary conditions, which
introduce strong charge perturbations that strongly affect the spin Friedel
oscillations.Comment: 5 pages, 7 figure
Linear Field Dependence of the Normal-State In-Plane Magnetoresistance of Sr2RuO4
The transverse and longitudinal in-plane magnetoresistances in the normal
state of superconducting Sr2RuO4 single crystals have been measured. At low
temperatures, both of them were found to be positive with a linear
magnetic-field dependence above a threshold field, a result not expected from
electronic band theory. We argue that such behavior is a manifestation of a
novel coherent state characterized by a spin pseudo gap in the quasi-particle
excitation spectrum in Sr2RuO4.Comment: 4 pages + 5 figure
Disordered Bosons: Condensate and Excitations
The disordered Bose Hubbard model is studied numerically within the
Bogoliubov approximation. First, the spatially varying condensate wavefunction
in the presence of disorder is found by solving a nonlinear Schrodinger
equation. Using the Bogoliubov approximation to find the excitations above this
condensate, we calculate the condensate fraction, superfluid density, and
density of states for a two-dimensional disordered system. These results are
compared with experiments done with adsorbed in porous media.Comment: RevTeX, 26 pages and 10 postscript figures appended (Figure 9 has
three separate plots, so 12 postcript files altogether
Crossover from two- to three-dimensional critical behavior for nearly antiferromagnetic itinerant electrons
The crossover from two- to three-dimensional critical behavior of nearly
antiferromagnetic itinerant electrons is studied in a regime where the
inter-plane single-particle motion of electrons is quantum-mechanically
incoherent because of thermal fluctuations. This is a relevant regime for very
anisotropic materials like the cuprates. The problem is studied within the
Two-Particle Self-Consistent approach (TPSC), that has been previously shown to
give a quantitative description of Monte Carlo data for the Hubbard model. It
is shown that TPSC belongs to the limit of the universality class. However, contrary to the usual approaches,
cutoffs appear naturally in the microscopic TPSC theory so that parameter-free
calculations can be done for Hubbard models with arbitrary band structure. A
general discussion of universality in the renormalized-classical crossover from
to is also given.Comment: Revtex, 23 pages + 6 postcript figures (with epsfile
Properties and units in the clinical laboratory sciences part XXIV. Properties and units in clinical molecular genetics (IUPAC Technical Report)
Molecular Technology and Informatics for Personalised Medicine and Healt
Onset of Superfluidity in 4He Films Adsorbed on Disordered Substrates
We have studied 4He films adsorbed in two porous glasses, aerogel and Vycor,
using high precision torsional oscillator and DC calorimetry techniques. Our
investigation focused on the onset of superfluidity at low temperatures as the
4He coverage is increased. Torsional oscillator measurements of the 4He-aerogel
system were used to determine the superfluid density of films with transition
temperatures as low as 20 mK. Heat capacity measurements of the 4He-Vycor
system probed the excitation spectrum of both non-superfluid and superfluid
films for temperatures down to 10 mK. Both sets of measurements suggest that
the critical coverage for the onset of superfluidity corresponds to a mobility
edge in the chemical potential, so that the onset transition is the bosonic
analog of a superconductor-insulator transition. The superfluid density
measurements, however, are not in agreement with the scaling theory of an onset
transition from a gapless, Bose glass phase to a superfluid. The heat capacity
measurements show that the non-superfluid phase is better characterized as an
insulator with a gap.Comment: 15 pages (RevTex), 21 figures (postscript
Quantum Criticality via Magnetic Branes
Holographic methods are used to investigate the low temperature limit,
including quantum critical behavior, of strongly coupled 4-dimensional gauge
theories in the presence of an external magnetic field, and finite charge
density. In addition to the metric, the dual gravity theory contains a Maxwell
field with Chern-Simons coupling. In the absence of charge, the magnetic field
induces an RG flow to an infrared AdS geometry, which is
dual to a 2-dimensional CFT representing strongly interacting fermions in the
lowest Landau level. Two asymptotic Virasoro algebras and one chiral Kac-Moody
algebra arise as {\sl emergent symmetries} in the IR. Including a nonzero
charge density reveals a quantum critical point when the magnetic field reaches
a critical value whose scale is set by the charge density. The critical theory
is probed by the study of long-distance correlation functions of the boundary
stress tensor and current. All quantities of major physical interest in this
system, such as critical exponents and scaling functions, can be computed
analytically. We also study an asymptotically AdS system whose magnetic
field induced quantum critical point is governed by a IR Lifshitz geometry,
holographically dual to a D=2+1 field theory. The behavior of these holographic
theories shares important similarities with that of real world quantum critical
systems obtained by tuning a magnetic field, and may be relevant to materials
such as Strontium Ruthenates.Comment: To appear in Lect. Notes Phys. "Strongly interacting matter in
magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A.
Schmitt, H.-U. Ye
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