220 research outputs found
Characterizing the entanglement of bipartite quantum systems
We derive a separability criterion for bipartite quantum systems which
generalizes the already known criteria. It is based on observables having
generic commutation relations. We then discuss in detail the relation among
these criteria.Comment: 5 pages, 2 figures. Revised versio
The OD,D geometry of string theory
We construct an action for double field theory using a metric connection that
is compatible with both the generalised metric and the O_{D,D} structure. The
connection is simultaneously torsionful and flat. Using this connection one may
construct a proper covariant derivative for double field theory. We then write
the doubled action in terms of the generalised torsion of this connection. This
action then exactly reproduces that required for doubled field theory and
gauged supergravity.Comment: 26 pages, latex, v2 typos corrected and references adde
Amnion as a surrogate tissue reporter of the effects of maternal preeclampsia on the fetus
We described the study design, detailed analytical methods, and verification results in the supporting information file. (DOCX 21.2 MB
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Can Physicians Identify Inappropriate Nuclear Stress Tests? An Examination of Inter-Rater Reliability for the 2009 Appropriate Use Criteria for Radionuclide Imaging
Background—We sought to determine inter-rater reliability of the 2009 Appropriate Use Criteria for radionuclide imaging and whether physicians at various levels of training can effectively identify nuclear stress tests with inappropriate indications.
Methods and Results—Four hundred patients were randomly selected from a consecutive cohort of patients undergoing nuclear stress testing at an academic medical center. Raters with different levels of training (including cardiology attending physicians, cardiology fellows, internal medicine hospitalists, and internal medicine interns) classified individual nuclear stress tests using the 2009 Appropriate Use Criteria. Consensus classification by 2 cardiologists was considered the operational gold standard, and sensitivity and specificity of individual raters for identifying inappropriate tests were calculated. Inter-rater reliability of the Appropriate Use Criteria was assessed using Cohen κ statistics for pairs of different raters. The mean age of patients was 61.5 years; 214 (54%) were female. The cardiologists rated 256 (64%) of 400 nuclear stress tests as appropriate, 68 (18%) as uncertain, 55 (14%) as inappropriate; 21 (5%) tests were unable to be classified. Inter-rater reliability for noncardiologist raters was modest (unweighted Cohen κ, 0.51, 95% confidence interval, 0.45–0.55). Sensitivity of individual raters for identifying inappropriate tests ranged from 47% to 82%, while specificity ranged from 85% to 97%.
Conclusions—Inter-rater reliability for the 2009 Appropriate Use Criteria for radionuclide imaging is modest, and there is considerable variation in the ability of raters at different levels of training to identify inappropriate tests
Time-Dependent Vacuum Energy Induced by D-Particle Recoil
We consider cosmology in the framework of a `material reference system' of D
particles, including the effects of quantum recoil induced by closed-string
probe particles. We find a time-dependent contribution to the cosmological
vacuum energy, which relaxes to zero as for large times . If
this energy density is dominant, the Universe expands with a scale factor . We show that this possibility is compatible with recent
observational constraints from high-redshift supernovae, and may also respect
other phenomenological bounds on time variation in the vacuum energy imposed by
early cosmology.Comment: 14 pages LATEX, no figure
Phase IIA trial of 1% topical cidofovir for treatment of high-grade perianal squamous intraepithelial neoplasia in HIV-infected men and women (AMC046)
Phenomenology of the Gowdy Universe on
Numerical studies of the plane symmetric, vacuum Gowdy universe on yield strong support for the conjectured asymptotically velocity term
dominated (AVTD) behavior of its evolution toward the singularity except,
perhaps, at isolated spatial points. A generic solution is characterized by
spiky features and apparent ``discontinuities'' in the wave amplitudes. It is
shown that the nonlinear terms in the wave equations drive the system
generically to the ``small velocity'' AVTD regime and that the spiky features
are caused by the absence of these terms at isolated spatial points.Comment: 19 pages, 21 figures, uses Revtex, psfi
Meaning, Truth, and Physics
A physical theory is a partially interpreted axiomatic formal system (L,S), where L is a formal language with some logical, mathematical and physical axioms, and with some derivation rules, and the semantics S is a relationship between the formulas of L and some states of affairs in the physical world. In our ordinary discourse, the formal system L is regarded as an abstract object or structure, the semantics S as something which involves the mental/conceptual realm. This view is of course incompatible with physicalism. How can physical theory be accommodated in a purely physical ontology? The aim of this paper is to outline an account for meaning and truth of physical theory, within the philosophical framework spanned by three doctrines: physicalism, empiricism, and the formalist philosophy of mathematics
Thermal conductivity of amorphous carbon thin films
Thermal conductivities of amorphous carbon thin films are measured
in the temperatures range 80--400 K using the method. Sample films
range from soft a-C:H prepared by remote-plasma deposition ( W
m K at room temperature) to amorphous diamond with a large
fraction of bonded carbon deposited from a filtered-arc source ( W m K). Effective-medium theory provides a
phenomenological description of the variation of conductivity with mass
density. The thermal conductivities are in good agreement with the minimum
thermal conductivity calculated from the measured atomic density and
longitudinal speed of sound.Comment: 4 pages, 4 figure
Entangling macroscopic oscillators exploiting radiation pressure
It is shown that radiation pressure can be profitably used to entangle {\it
macroscopic} oscillators like movable mirrors, using present technology. We
prove a new sufficient criterion for entanglement and show that the achievable
entanglement is robust against thermal noise. Its signature can be revealed
using common optomechanical readout apparatus.Comment: 4 pages, 2 eps figures, new separability criterion added, new figure
2, authors list change
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