18,236 research outputs found
Current induced light emission and light induced current in molecular tunneling junctions
The interaction of metal-molecule-metal junctions with light is considered
within a simple generic model. We show, for the first time, that light induced
current in unbiased junctions can take place when the bridging molecule is
characterized by a strong charge-transfer transition. The same model shows
current induced light emission under potential bias that exceeds the molecular
excitation energy. Results based on realistic estimates of molecular-lead
coupling and molecule-radiation field interaction suggest that both effects
should be observable.Comment: 5 pages, 3 figures, RevTeX
Addenda and corrections to work done on the path-integral approach to classical mechanics
In this paper we continue the study of the path-integral formulation of
classical mechanics and in particular we better clarify, with respect to
previous papers, the geometrical meaning of the variables entering this
formulation. With respect to the first paper with the same title, we {\it
correct} here the set of transformations for the auxiliary variables
. We prove that under this new set of transformations the
Hamiltonian , appearing in our path-integral, is an exact
scalar and the same for the Lagrangian. Despite this different transformation,
the variables maintain the same operatorial meaning as before but
on a different functional space. Cleared up this point we then show that the
space spanned by the whole set of variables () of our
path-integral is the cotangent bundle to the {\it reversed-parity} tangent
bundle of the phase space of our system and it is indicated as
. In case the reader feel uneasy with this strange
{\it Grassmannian} double bundle, we show in this paper that it is possible to
build a different path-integral made only of {\it bosonic} variables. These
turn out to be the coordinates of which is the
double cotangent bundle of phase-space.Comment: Title changed, appendix expanded, few misprints fixe
The barriers to and enablers of providing reasonably adjusted health services to people with intellectual disabilities in acute hospitals: evidence from a mixed-methods study.
OBJECTIVE: To identify the factors that promote and compromise the implementation of reasonably adjusted healthcare services for patients with intellectual disabilities in acute National Health Service (NHS) hospitals.
DESIGN: A mixed-methods study involving interviews, questionnaires and participant observation (July 2011-March 2013).
SETTING: Six acute NHS hospital trusts in England.
METHODS: Reasonable adjustments for people with intellectual disabilities were identified through the literature. Data were collected on implementation and staff understanding of these adjustments.
RESULTS: Data collected included staff questionnaires (n=990), staff interviews (n=68), interviews with adults with intellectual disabilities (n=33), questionnaires (n=88) and interviews (n=37) with carers of patients with intellectual disabilities, and expert panel discussions (n=42). Hospital strategies that supported implementation of reasonable adjustments did not reliably translate into consistent provision of such adjustments. Good practice often depended on the knowledge, understanding and flexibility of individual staff and teams, leading to the delivery of reasonable adjustments being haphazard throughout the organisation. Major barriers included: lack of effective systems for identifying and flagging patients with intellectual disabilities, lack of staff understanding of the reasonable adjustments that may be needed, lack of clear lines of responsibility and accountability for implementing reasonable adjustments, and lack of allocation of additional funding and resources. Key enablers were the Intellectual Disability Liaison Nurse and the ward manager.
CONCLUSIONS: The evidence suggests that ward culture, staff attitudes and staff knowledge are crucial in ensuring that hospital services are accessible to vulnerable patients. The authors suggest that flagging the need for specific reasonable adjustments, rather than the vulnerable condition itself, may address some of the barriers. Further research is recommended that describes and quantifies the most frequently needed reasonable adjustments within the hospital pathways of vulnerable patient groups, and the most effective organisational infrastructure required to guarantee their use, together with resource implications
Comparing the Evolution of the Galaxy Disk Sizes with CDM Models: The Hubble Deep Field
The intrinsic sizes of the field galaxies with I<26 in the Hubble and ESO-NTT
Deep Fields are shown as a function of their redshifts and absolute magnitudes
using photometric redshifts derived from the multicolor catalogs and are
compared with the CDM predictions. Extending to lower luminosities and to
higher z our previous analysis performed on the NTT field alone, we find that
the distribution of the galaxy disk sizes at different cosmic epochs is within
the range predicted by typical CDM models. However, the observed size
distribution of faint (M_B>-19) galaxies is skewed with respect to the CDM
predictions and an excess of small-size disks (R_d<2 kpc) is already present at
z~ 0.5. The excess persists up to z~3 and involves brighter galaxies . Such an
excess may be reduced if luminosity-dependent effects, like starburst activity
in interacting galaxies, are included in the physical mechanisms governing the
star formation history in CDM models.Comment: 9 pages, 3 figures, ApJ Letters in pres
An Index Theorem for Domain Walls in Supersymmetric Gauge Theories
The supersymmetric abelian Higgs model with N scalar fields admits multiple
domain wall solutions. We perform a Callias-type index calculation to determine
the number of zero modes of this soliton. We confirm that the most general
domain wall has 2(N-1) zero modes, which can be interpreted as the positions
and phases of (N-1) constituent domain walls. This implies the existence of
moduli for a D-string interpolating between N D5-branes in IIB string theory.Comment: 9 pages, REVTeX4; v2: reference adde
The Pierre Auger Observatory: Results on Ultra-High Energy Cosmic Rays
The focus of this article is on recent results on ultra-high energy cosmic
rays obtained with the Pierre Auger Observatory. The world's largest instrument
of this type and its performance are described. The observations presented here
include the energy spectrum, the primary particle composition, limits on the
fluxes of photons and neutrinos and a discussion of the anisotropic
distribution of the arrival directions of the most energetic particles.
Finally, plans for the construction of a Northern Auger Observatory in
Colorado, USA, are discussed.Comment: Proceedings of the International Workshop on Advances in Cosmic Ray
Science, Waseda University, Shinjuku, Tokyo, Japan, March 2008; to be
published in the Journal of the Physical Society of Japan (JPSJ) supplemen
Emergent Geometry and Quantum Gravity
We explain how quantum gravity can be defined by quantizing spacetime itself.
A pinpoint is that the gravitational constant G = L_P^2 whose physical
dimension is of (length)^2 in natural unit introduces a symplectic structure of
spacetime which causes a noncommutative spacetime at the Planck scale L_P. The
symplectic structure of spacetime M leads to an isomorphism between symplectic
geometry (M, \omega) and Riemannian geometry (M, g) where the deformations of
symplectic structure \omega in terms of electromagnetic fields F=dA are
transformed into those of Riemannian metric g. This approach for quantum
gravity allows a background independent formulation where spacetime as well as
matter fields is equally emergent from a universal vacuum of quantum gravity
which is thus dubbed as the quantum equivalence principle.Comment: Invited Review for Mod. Phys. Lett. A, 17 page
Observational evidence of spin-induced precession in active galactic nuclei
We show that it is possible to explain the physical origin of jet precession
in active galactic nuclei (AGNs) through the misalignment between the rotation
axes of the accretion disk and of the Kerr black hole. We apply this scenario
to quasars, Seyfert galaxies and also to the Galactic Center black hole Sgr A*,
for which signatures of either jet or disk precession have been found. The
formalism adopted is parameterized by the ratio of the precession period to the
black hole mass and can be used to put constraints to the physical properties
of the accretion disk as well as to the black hole spin in those systems.Comment: 10 pages, 1 figure, accepted for publication in ApJ Letter
- …