16,452 research outputs found
Riggs on strong justification
In 'The Weakness of Strong Justification' Wayne Riggs claims that the requirement that justified beliefs be truth conducive (likely to be true) is not always compatible with the requirement that they be epistemically responsible (arrived at in an epistemically responsible manner)1. He supports this claim by criticising Alvin Goldman's view that if a belief is strongly justified, it is also epistemically responsible. In light of this, Riggs recommends that we develop two independent conceptions of justification, one that insists upon the requirement that beliefs be truth conducive and another that insists that they be epistemically responsible. It will then, on his view, be possible to properly evaluate beliefs with regard to each conception of justification. Riggs, however, is mistaken in supposing that the two epistemic requirements are independent. If a belief is responsibly arrived at, it is therefore likely to be true. He is thus also mistaken in supposing that the two epistemic requirements are incompatible. This mistake arises because Riggs assumes that justification is possible or, at least, that it involves standards that are akin to our own. Moreover, once this assumption is made explicit, we can see why a notion of justification that connects epistemic practice with likely truth is significant
Anomalous Parallel Field Negative Magnetoresistance in Ultrathin Films Near the Superconductor-Insulator Transition
A parallel field negative magnetoresistance has been found in
quench-condensed ultrathin films of amorphous bismuth in the immediate vicinity
of the thickness-tuned superconductor-insulator transition. The effect appears
to be a signature of quantum fluctuations of the order parameter associated
with the quantum critical point.Comment: Revised content includes revised argument and new figures 3 and 4.
Totals: 4 pages, 4 figure
Thermally stable electrolytes for rechargeable lithium batteries, phase 2
During the second year of research under NASA SBIR Contract NAS7-967, Covalent Associates and NASA contract monitors at the Jet Propulsion Laboratory agreed to perform an evaluation of the three best electrolytes developed during Phase 2. Due to the extensive period of time required to collect meaningful cycling data, we realized the study would extend well beyond the original formal end of the Phase 2 program (August 31, 1988). The substitution of this effort in lieu of an earlier proposed 20-cell final deliverable is formally documented in Modification No. 1 of Contract NAS7-967 as task 7. This Addendum contains the results of the cycling studies performed at Covalent Associates. In addition, sealed ampoules of each of these three electrolytes were delivered to the Jet Propulsion Laboratory Electrochemical Power Group. Their concurrent evaluation in a different test vehicle has also been recently concluded and their results are also summarized herein
A computer program for the calculation of laminar and turbulent boundary layer flows
The results are presented of a study to produce a computer program to calculate laminar and turbulent boundary layer flows. The program is capable of calculating the following types of flow: (1) incompressible or compressible, (2) two dimensional or axisymmetric, and (3) flows with significant transverse curvature. Also, the program can handle a large variety of boundary conditions, such as blowing or suction, arbitrary temperature distributions and arbitrary wall heat fluxes. The program has been specialized to the calculation of equilibrium air flows and all of the thermodynamic and transport properties used are for air. For the turbulent transport properties, the eddy viscosity approach has been used. Although the eddy viscosity models are semi-empirical, the model employed in the program has corrections for pressure gradients, suction and blowing and compressibility. The basic method of approach is to put the equations of motion into a finite difference form and then solve them by use of a digital computer. The program is written in FORTRAN 4 and requires small amounts of computer time on most scientific machines. For example, most laminar flows can be calculated in less than one minute of machine time, while turbulent flows usually require three or four minutes
Valence Quark Distribution in A=3 Nuclei
We calculate the quark distribution function for 3He/3H in a relativistic
quark model of nuclear structure which adequately reproduces the nucleon
approximation, nuclear binding energies, and nuclear sizes for small nuclei.
The results show a clear distortion from the quark distribution function for
individual nucleons (EMC effect) arising dominantly from a combination of
recoil and quark tunneling effects. Antisymmetrization (Pauli) effects are
found to be small due to limited spatial overlaps. We compare our predictions
with a published parameterization of the nuclear valence quark distributions
and find significant agreement.Comment: 18pp., revtex4, 4 fig
Bottom-loading dilution refrigerator with ultra-high vacuum deposition capability
A Kelvinox 400 dilution refrigerator with the ability to load samples onto
the mixing chamber from the bottom of the cryostat has been combined with an
ultrahigh-vacuum (UHV) deposition chamber equipped with molecular beam sources.
The liquid helium cooled sample transfer mechanism is used in a manner that
allows films to be grown on substrates which are kept at temperatures of order
8K with chamber pressures in the 10^-9 to 10^-10 Torr range. This system
facilitates the growth of quench-condensed ultrathin films which must always be
kept below ~ 12K in a UHV environment during and after growth. Measurements can
be made on the films down to millikelvin temperatures and in magnetic fields up
to 15 T.Comment: 10 pages text, 1figur
Observation of discrete energy levels in a quantum confined system
Low temperature scanning tunneling microscope images and spectroscopic data
have been obtained on subnanometer size Pb clusters fabricated using the
technique of buffer layer assisted growth. Discrete energy levels were resolved
in current-voltage characteristics as current peaks rather than current steps.
Distributions of peak voltage spacings and peak current heights were consistent
with Wigner-Dyson and Porter-Thomas distributions respectively, suggesting the
relevance of random matrix theory to the description of the electronic
eigenstates of the clusters. The observation of peaks rather than steps in the
current-voltage characteristics is attributed to a resonant tunneling process
involving the discrete energy levels of the cluster, the tip, and the states at
the interface between the cluster and the substrate surface.Comment: 4 pages, 4 figure
Characterizing the Hofstadter butterfly's outline with Chern numbers
In this work, we report original properties inherent to independent particles
subjected to a magnetic field by emphasizing the existence of regular
structures in the energy spectrum's outline. We show that this fractal curve,
the well-known Hofstadter butterfly's outline, is associated to a specific
sequence of Chern numbers that correspond to the quantized transverse
conductivity. Indeed the topological invariant that characterizes the
fundamental energy band depicts successive stairways as the magnetic flux
varies. Moreover each stairway is shown to be labeled by another Chern number
which measures the charge transported under displacement of the periodic
potential. We put forward the universal character of these properties by
comparing the results obtained for the square and the honeycomb geometries.Comment: Accepted for publication in J. Phys. B (Jan 2009
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