4,418 research outputs found
Open-closed field algebras
We introduce the notions of open-closed field algebra and open-closed field
algebra over a vertex operator algebra V. In the case that V satisfies certain
finiteness and reductivity conditions, we show that an open-closed field
algebra over V canonically gives an algebra over a \C-extension of the
Swiss-cheese partial operad. We also give a tensor categorical formulation and
categorical constructions of open-closed field algebras over V.Comment: 55 pages, largely revised, an old subsection is deleted, a few
references are adde
Operator Ordering in Quantum Radiative Processes
In this work we reexamine quantum electrodynamics of atomic eletrons in the
Coulomb gauge in the dipole approximation and calculate the shift of atomic
energy levels in the context of Dalibard, Dupont-Roc and Cohen-Tannoudji (DDC)
formalism by considering the variation rates of physical observables. We then
analyze the physical interpretation of the ordering of operators in the dipole
approximation interaction Hamiltonian in terms of field fluctuations and
self-reaction of atomic eletrons, discussing the arbitrariness in the
statistical functions in second order bound-state perturbation theory.Comment: Latex file, 12 pages, no figures, includes PACS numbers and minor
changes in the text with the addition of a new sectio
Quark Effects in the Gluon Condensate Contribution to the Scalar Glueball Correlation Function
One-loop quark contributions to the dimension-four gluon condensate term in
the operator product expansion (OPE) of the scalar glueball correlation
function are calculated in the MS-bar scheme in the chiral limit of quark
flavours. The presence of quark effects is shown not to alter the cancellation
of infrared (IR) singularities in the gluon condensate OPE coefficients. The
dimension-four gluonic condensate term represents the leading power corrections
to the scalar glueball correlator and, therein, the one-loop logarithmic
contributions provide the most important condensate contribution to those QCD
sum-rules independent of the low-energy theorem (the subtracted sum-rules).Comment: latex2e, 6 pages, 7 figures embedded in latex fil
Minimal immersions of closed surfaces in hyperbolic three-manifolds
We study minimal immersions of closed surfaces (of genus ) in
hyperbolic 3-manifolds, with prescribed data , where
is a conformal structure on a topological surface , and is a holomorphic quadratic differential on the surface . We
show that, for each for some , depending only on
, there are at least two minimal immersions of closed surface
of prescribed second fundamental form in the conformal structure
. Moreover, for sufficiently large, there exists no such minimal
immersion. Asymptotically, as , the principal curvatures of one
minimal immersion tend to zero, while the intrinsic curvatures of the other
blow up in magnitude.Comment: 16 page
Consumption strategies and motivations of Chinese consumers: The case of UK sustainable luxury fashion
Purpose: The purpose of this paper is to explore Chinese consumersâ motivations to purchase luxury fashion products in the UK and how far sustainability plays a role in the decision-making process, by extending the consumer typology of translators, exceptors, selectors. The authors further add an additional dimension to defining âluxuryâ. Design/methodology/approach: An exploratory design utilising multiple qualitative research tools (semi-structured interviews, focus groups) provides the basis for this research. A grounded analysis was applied. Findings: Findings map motivational drivers to purchasing luxury products and establish a fourth consumer type âindulgersâ. Well-being further emerged as a key characteristic that defines âluxuryâ. Research limitations/implications: The sample size is limited to Chinese consumers purchasing luxury fashion in the UK, and thus may not be generalised. Practical implications: This research helps managers to understand the consumer types and underlying motivations of Chinese consumers purchasing luxury fashion in the UK. As one of the largest target groups, this research informs managers on how to further capitalise on this market. Originality/value: This paper creates a new consumer typology that not only categorises consumers according to their consumption aspects, but further identifies their underlying motivations to do so
Risk factors for recurrent C lostridium difficile infection in hematopoietic stem cell transplant recipients
Background Recurrent C lostridium difficile infection ( CDI ) represents a significant burden on the healthcare system and is associated with poor outcomes in hematopoietic stem cell transplant ( HSCT ) patients. Data are limited evaluating recurrence rates and risk factors for recurrence in HSCT patients. Methods HSCT patients who developed CDI between January 2010 and December 2012 were divided into 2 groups: nonârecurrent CDI (nr CDI ) and recurrent CDI ( rCDI ). Risk factors for rCDI were compared between groups. Rate of recurrence in HSCT patients was compared to that in other hospitalized patients. Results CDI was diagnosed in 95 of 711 HSCT patients (22 rCDI and 73 nr CDI ). Recurrence rates were similar in HSCT patients compared with other hospitalized patients (23.2% vs. 22.9%, P Â >Â 0.99). Patients in the rCDI group developed the index case of CDI significantly earlier than the nr CDI group (3.5Â days vs. 7.0Â days after transplant, P Â =Â 0.05). On univariate analysis, patients with rCDI were more likely to have prior history of CDI and neutropenia at the time of the index CDI case. Neutropenia at the time of the index CDI case was the only independent predictor of rCDI (78.8 vs. 34.8%, P Â =Â 0.006) on multivariate analysis. Conclusions The rate of rCDI was similar between HSCT and other hospitalized patients, and the majority of patients developed the index case of CDI within a week of transplantation. Neutropenia at the index CDI case may be associated with increased rates of rCDI .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109272/1/tid12267.pd
Wealth redistribution with finite resources
We present a simplified model for the exploitation of finite resources by
interacting agents, where each agent receives a random fraction of the
available resources. An extremal dynamics ensures that the poorest agent has a
chance to change its economic welfare. After a long transient, the system
self-organizes into a critical state that maximizes the average performance of
each participant. Our model exhibits a new kind of wealth condensation, where
very few extremely rich agents are stable in time and the rest stays in the
middle class.Comment: 4 pages, 3 figures, RevTeX 4 styl
Effect of selective post-aging treatment on subsurface damage of quasicrystal reinforced Al composite manufactured by selective laser melting
In this work, Al-Fe-Cr quasicrystal reinforced Al matrix composite was in-situ prepared by using selective laser melting from powder mixture of Al-Cu-Fe-Cr quasicrystal and pure Al. The effect of selective post-aging treatment on microstructure and mechanical properties were determined with focus on the metastable phases. The microstructural analysis, which was determined by X-ray diffraction and scanning electron microscopy, indicates that the Al-based intermetallic is precipitated from supersaturated α-Al after the aging process. Moreover, the compression tests were performed on the samples in form of dense and lattice structures (50% porosity). The elastic modules of dense and lattice structural samples reduce from 21.3âŻGPa and 4.4â14.6âŻGPa and 3.6âŻGPa by using a low cooling-rated aging process. After aging process, the compressive deformation behavior of dense part changes from elastic-plastic-fracture mode to elastic-plastic-densification mode. On the other hand, the failure mechanism of lattice structural sample changes from rapid-single-stage to slow-double-stage with an improvement of the strain at failure
Prokaryotic expression, purification and immunogenicity analysis of CpsD protein from Streptococcus iniae
Streptococcus iniae is a major cause of serious bacterial infections in both fish and human beings. Capsular polysaccharide (CPS) of S. iniae is vital to evade phagocytic clearance of the host and serves as an important protective antigen of S. iniae infection in aquatic animals. The CpsD gene was determined to be highly conservative in capsule polysaccharide operon. Prokaryotic expression of the CpsD gene of a clinical isolate of S. iniae from channel catfish and immunogenic examination of the recombinant protein were first described in this essay. The recombinant protein was expressed in the form of inclusion bodies (IBs). Induction conditions in Escherichia coli were optimized with 0.6mM Isopropyl ÎČ-D-1-Thiogalactopyranoside at 37°C for 5h after the culture mid-log phase in Luria Bertani (LB) medium. The recombinant protein CpsD was thus expressed and purified by immobilized metal affinity chromatography (IMAC), yielding approximate 582.47 mg the protein per liter culture. Western blot analysis showed that the purified CpsD had reactogenicity. It will possibly reveal more details of capsule synthesis and capsule regulation during various stages of the S. iniae infectious process
Running of the Spectral Index and Violation of the Consistency Relation Between Tensor and Scalar Spectra from trans-Planckian Physics
One of the firm predictions of inflationary cosmology is the consistency
relation between scalar and tensor spectra. It has been argued that such a
relation -if experimentally confirmed- would offer strong support for the idea
of inflation. We examine the possibility that trans-Planckian physics violates
the consistency relation in the framework of inflation with a cut-off proposed
in astro-ph/0009209. We find that despite the ambiguity that exists in choosing
the action, Planck scale physics modifies the consistency relation
considerably. It also leads to the running of the spectral index. For modes
that are larger than our current horizon, the tensor spectral index is
positive. For a window of k values with amplitudes of the same order of the
modes which are the precursor to structure formation, the behavior of tensor
spectral index is oscillatory about the standard Quantum Field theory result,
taking both positive and negative values. There is a hope that in the light of
future experiments, one can verify this scenario of short distance physics.Comment: v1: 18 pages, 8 figures; v4: matched with the NPB versio
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