1,140 research outputs found
Cavity optomechanics with Si3N4 membranes at cryogenic temperatures
We describe a cryogenic cavity-optomechanical system that combines Si3N4
membranes with a mechanically-rigid Fabry-Perot cavity. The extremely high
quality-factor frequency products of the membranes allow us to cool a MHz
mechanical mode to a phonon occupation of less than 10, starting at a bath
temperature of 5 kelvin. We show that even at cold temperatures
thermally-occupied mechanical modes of the cavity elements can be a limitation,
and we discuss methods to reduce these effects sufficiently to achieve ground
state cooling. This promising new platform should have versatile uses for
hybrid devices and searches for radiation pressure shot noise.Comment: 19 pages, 5 figures, submitted to New Journal of Physic
One-loop divergences in the two-dimensional non-anticommutative supersymmetric sigma-model
We discuss the structure of the non-anticommutative N=2 non-linear
sigma-model in two dimensions, constructing differential operators which
implement the deformed supersymmetry generators and using them to reproduce the
classical action. We then compute the one-loop quantum corrections and express
them in a more compact form using the differential operators.Comment: 20pp, 8 figures, uses LaTeX. Title expanded to clarify conten
Research shapes policy: but the dynamics are subtle
Major policy initiatives such as the Quality and Outcomes Framework (QOF) in the national contract for UK general practitioners might variably be informed by evidence at their inception, implementation and subsequent evolution. But what evidence gets admitted into these policy debates—and what is left out? Using QOF as an example, this article demonstrates what an analysis of the relationship between policy and the associated research can tell us about the underlying policy assumptions and about the role of evidence in policy debates
Isotropic-nematic phase transition in suspensions of filamentous virus and the neutral polymer Dextran
We present an experimental study of the isotropic-nematic phase transition in
an aqueous mixture of charged semi-flexible rods (fd virus) and neutral polymer
(Dextran). A complete phase diagram is measured as a function of ionic strength
and polymer molecular weight. At high ionic strength we find that adding
polymer widens the isotropic-nematic coexistence region with polymers
preferentially partitioning into the isotropic phase, while at low ionic
strength the added polymer has no effect on the phase transition. The nematic
order parameter is determined from birefringence measurements and is found to
be independent of polymer concentration (or equivalently the strength of
attraction). The experimental results are compared with the existing
theoretical predictions for the isotropic-nematic transition in rods with
attractive interactions.Comment: 8 Figures. To be published in Phys. Rev. E. For more information see
http://www.elsie.brandeis.ed
A system of relational syllogistic incorporating full Boolean reasoning
We present a system of relational syllogistic, based on classical
propositional logic, having primitives of the following form:
Some A are R-related to some B;
Some A are R-related to all B;
All A are R-related to some B;
All A are R-related to all B.
Such primitives formalize sentences from natural language like `All students
read some textbooks'. Here A and B denote arbitrary sets (of objects), and R
denotes an arbitrary binary relation between objects. The language of the logic
contains only variables denoting sets, determining the class of set terms, and
variables denoting binary relations between objects, determining the class of
relational terms. Both classes of terms are closed under the standard Boolean
operations. The set of relational terms is also closed under taking the
converse of a relation. The results of the paper are the completeness theorem
with respect to the intended semantics and the computational complexity of the
satisfiability problem.Comment: Available at
http://link.springer.com/article/10.1007/s10849-012-9165-
Persistent inequalities in unplanned hospitalisation among colon cancer patients across critical phases of their care pathway, England, 2011-13.
BACKGROUND: Reducing hospital emergency admissions is a key target for all modern health systems. METHODS: We analysed colon cancer patients diagnosed in 2011-13 in England. We screened their individual Hospital Episode Statistics records in the 90 days pre-diagnosis, the 90 days post-diagnosis, and the 90 days pre-death (in the year following diagnosis), for the occurrence of hospital emergency admissions (HEAs). RESULTS: Between a quarter and two thirds of patients experience HEA in the three 90-day periods examined: pre-diagnosis, post-diagnosis and before death. Patients with tumour stage I-III from more deprived backgrounds had higher proportions of HEAs than less deprived patients during all studied periods. This remains even after adjusting for differing distributions of risk factors such as age, sex, comorbidity and stage at diagnosis. CONCLUSIONS: Although in some cases HEAs might be unavoidable or even appropriate, the proportion of HEAs varies by socioeconomic status, even after controlling for the usual patient factors, suggestive of remediable causes of excess emergency healthcare utilisation in patients belonging to higher deprivation groups. Future inquiries should address the potential role of clinical complications, sub-optimal healthcare administration, premature discharge or a lack of social support as potential explanations for these patterns of inequality
The non-anticommutative supersymmetric Wess-Zumino model
We discuss the non-anticommutative (N=1/2) supersymmetric Wess-Zumino model
in four dimensions. Firstly we introduce differential operators which implement
the non-anticommutative supersymmetry algebra acting on the component fields
and action. Then we perform the renormalisation of the model up to two-loop
order, including the complete set of terms necessary for renormalisability. We
show that (at least up to this order) the results obtained when we eliminate
the auxiliary field after renormalisation are equivalent to those obtained when
we eliminate the auxiliary fields before quantisation.Comment: 28 pages, 7 figures, uses LaTe
The Underestimation Of Egocentric Distance: Evidence From Frontal Matching Tasks
There is controversy over the existence, nature, and cause of error in egocentric distance judgments. One proposal is that the systematic biases often found in explicit judgments of egocentric distance along the ground may be related to recently observed biases in the perceived declination of gaze (Durgin & Li, Attention, Perception, & Psychophysics, in press), To measure perceived egocentric distance nonverbally, observers in a field were asked to position themselves so that their distance from one of two experimenters was equal to the frontal distance between the experimenters. Observers placed themselves too far away, consistent with egocentric distance underestimation. A similar experiment was conducted with vertical frontal extents. Both experiments were replicated in panoramic virtual reality. Perceived egocentric distance was quantitatively consistent with angular bias in perceived gaze declination (1.5 gain). Finally, an exocentric distance-matching task was contrasted with a variant of the egocentric matching task. The egocentric matching data approximate a constant compression of perceived egocentric distance with a power function exponent of nearly 1; exocentric matches had an exponent of about 0.67. The divergent pattern between egocentric and exocentric matches suggests that they depend on different visual cues
A renormalisable non-anticommutative SU(N)xU(1) gauge theory in components
We discuss the non-anticommutative (N=1/2) supersymmetric SU(N)\otimes U(1)
gauge theory including a superpotential. We show how recent proposals for
obtaining a renormalisable version of the theory may be implemented in the
component formalism at the one-loop level.Comment: 25pp, 14 figures, LaTeX; minor typo fixed, reference added, notation
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