223 research outputs found
A New Symmetry for QED
We demonstrate that QED exhibits a previously unobserved symmetry. Some
consequences are discussed.Comment: 9 pages, MZ-TH/93-02, DIAS-STP-93-0
How do HMOs Achieve Savings? The Effectiveness of One Organization\u27s Strategies.
To examine how a group practice used organizational strategies rather than provider-level incentives to achieve savings for health maintenance organization (HMO) compared to fee-for-service (FFS) patients. A large group practice with a group model HMO also treating FFS patients. Data sources were all patient encounter records, demographic files, and clinic records covering 3.5 years (1986-1989). The clinic\u27s procedures to record services and charges were identical for FFS and HMO patients. All FFS and HMO patients under age 65 who received any outpatient services during approximately 100,000 episodes of the seven study illnesses were eligible
Topological Field Theory and Rational Curves
We analyze the superstring propagating on a Calabi-Yau threefold. This theory
naturally leads to the consideration of Witten's topological non-linear
sigma-model and the structure of rational curves on the Calabi-Yau manifold. We
study in detail the case of the world-sheet of the string being mapped to a
multiple cover of an isolated rational curve and we show that a natural
compactification of the moduli space of such a multiple cover leads to a
formula in agreement with a conjecture by Candelas, de la Ossa, Green and
Parkes.Comment: 20 page
Charges and fluxes in Maxwell theory on compact manifolds with boundary
We investigate the charges and fluxes that can occur in higher-order Abelian
gauge theories defined on compact space-time manifolds with boundary. The
boundary is necessary to supply a destination to the electric lines of force
emanating from brane sources, thus allowing non-zero net electric charges, but
it also introduces new types of electric and magnetic flux. The resulting
structure of currents, charges, and fluxes is studied and expressed in the
language of relative homology and de Rham cohomology and the corresponding
abelian groups. These can be organised in terms of a pair of exact sequences
related by the Poincar\'e-Lefschetz isomorphism and by a weaker flip symmetry
exchanging the ends of the sequences. It is shown how all this structure is
brought into play by the imposition of the appropriately generalised Maxwell's
equations. The requirement that these equations be integrable restricts the
world-volume of a permitted brane (assumed closed) to be homologous to a cycle
on the boundary of space-time. All electric charges and magnetic fluxes are
quantised and satisfy the Dirac quantisation condition. But through some
boundary cycles there may be unquantised electric fluxes associated with
quantised magnetic fluxes and so dyonic in nature.Comment: 28 pages, plain Te
Entropy of random coverings and 4D quantum gravity
We discuss the counting of minimal geodesic ball coverings of -dimensional
riemannian manifolds of bounded geometry, fixed Euler characteristic and
Reidemeister torsion in a given representation of the fundamental group. This
counting bears relevance to the analysis of the continuum limit of discrete
models of quantum gravity. We establish the conditions under which the number
of coverings grows exponentially with the volume, thus allowing for the search
of a continuum limit of the corresponding discretized models. The resulting
entropy estimates depend on representations of the fundamental group of the
manifold through the corresponding Reidemeister torsion. We discuss the sum
over inequivalent representations both in the two-dimensional and in the
four-dimensional case. Explicit entropy functions as well as significant bounds
on the associated critical exponents are obtained in both cases.Comment: 54 pages, latex, no figure
BRST Analysis of Physical States for 2D (Super) Gravity Coupled to (Super) Conformal Matter
We summarize some recent results on the BRST analysis of physical states of
2D gravity coupled to c<=1 conformal matter and the supersymmetric
generalization.Comment: 11 page
Geometric phases in adiabatic Floquet theory, abelian gerbes and Cheon's anholonomy
We study the geometric phase phenomenon in the context of the adiabatic
Floquet theory (the so-called the Floquet theory). A double
integration appears in the geometric phase formula because of the presence of
two time variables within the theory. We show that the geometric phases are
then identified with horizontal lifts of surfaces in an abelian gerbe with
connection, rather than with horizontal lifts of curves in an abelian principal
bundle. This higher degree in the geometric phase gauge theory is related to
the appearance of changes in the Floquet blocks at the transitions between two
local charts of the parameter manifold. We present the physical example of a
kicked two-level system where these changes are involved via a Cheon's
anholonomy. In this context, the analogy between the usual geometric phase
theory and the classical field theory also provides an analogy with the
classical string theory.Comment: This new version presents a more complete geometric structure which
is topologically non trivia
Molecular Detection of Invasive Species in Heterogeneous Mixtures Using a Microfluidic Carbon Nanotube Platform
Screening methods to prevent introductions of invasive species are critical for the protection of environmental and economic benefits provided by native species and uninvaded ecosystems. Coastal ecosystems worldwide remain vulnerable to damage from aquatic species introductions, particularly via ballast water discharge from ships. Because current ballast management practices are not completely effective, rapid and sensitive screening methods are needed for on-site testing of ships in transit. Here, we describe a detection technology based on a microfluidic chip containing DNA oligonucleotide functionalized carbon nanotubes. We demonstrate the efficacy of the chip using three ballast-transported species either established (Dreissena bugensis) or of potential threat (Eriocheir sinensis and Limnoperna fortuneii) to the Laurentian Great Lakes. With further refinement for on-board application, the technology could lead to real-time ballast water screening to improve ship-specific management and control decisions
Why less may be more: a mixed methods study of the work and relatedness of 'weak ties' in supporting long-term condition self-management
Background: The distribution of the roles and responsibilities of long-term condition management (LTCM) outside of formal health services implicates a wide set of relationships and activities of involvement. Yet, compared to studies of professional implementation, patient systems of implementation remain under-investigated. The aim of this paper is to explore the work, meaning and function attributed to ‘weaker’ ties relative to other more bonding relationships in order to identify the place of these within a context of systems of support for long-term conditions.
Methods: This is a mixed methods survey with nested qualitative study. A total of 300 people from deprived areas in the North West of England with chronic illnesses took part in a survey conducted in 2010 to 2011. A concentric circles diagram was used as a research tool with which participants identified 2,544 network members who contributed to illness management. Notions of ‘work’ were used to describe activities associated with chronic illness and to identify how weaker ties are included and perceived to be involved through social network members (SNM) contributions.
Results: The results provide an articulation of how SNMs are substantially involved in weak tie illness management. Weaker ties constituted 16.1% of network membership involved in illness work. The amount of work undertaken was similar but less than that of stronger ties. Weaker ties appeared more durable and less liable to loss over time than stronger ties. The qualitative accounts suggested that weak ties enabled the moral positioning of the self-managing ‘self’ and acted on the basis of a strong sense of reciprocity.
Conclusions: Weak ties act as an acceptable bridge between a sense of personal agency and control and the need for external support because it is possible to construct a sense of moral acceptability through reciprocal exchange. Access to weak tie resources needs to be taken into account when considering the ways in which systems of health implementation for chronic illness are designed and delivered
Supporting self-management after attending a structured education programme: a qualitative longitudinal investigation of type 1 diabetes patients’ experiences and views
Background: Structured education programmes for patients with diabetes and other chronic conditions are being widely adopted. However, follow-up studies suggest that course graduates may struggle to sustain the self-care practices taught on their courses over time. This study explored the support needs of patients with type 1 diabetes after attending a structured education programme promoting an empowerment approach and training in use of flexible intensive insulin therapy, a regimen now widely advocated and used to manage this condition. The objective was to inform future support offered to course graduates.
Methods: Repeat, in-depth interviews with 30 type 1 diabetes patients after attending Dose Adjustment for Normal Eating (DAFNE) courses in the UK, and six and 12 months later. Data were analysed using an inductive, thematic approach.
Results: While the flexible intensive insulin treatment approach taught on DAFNE courses was seen as a logical and effective way of managing one’s diabetes, it was also considered more technically complex than other insulin regimens. To sustain effective disease self-management using flexible intensive insulin treatment over time, patients often expected, and needed, on-going input and support from health care professionals trained in the approach. This included: help determining insulin dose adjustments; reassurance; and, opportunities to trouble-shoot issues of concern. While some benefits were identified to receiving follow-up support in a group setting, most patients stated a preference or need for tailored and individualised support from appropriately-trained clinicians, accessible on an ‘as and when needed’ basis.
Conclusions: Our findings highlight potential limitations to group-based forms of follow-up support for sustaining diabetes self-management. To maintain the clinical benefits of structured education for patients with type 1 diabetes over time, course graduates may benefit from and prefer ongoing, one-to-one support from health care professionals trained in the programme’s practices and principles. This support should be tailored and personalised to reflect patients’ specific and unique experiences of applying their education and training in the context of their everyday lives, and could be the subject of future research
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