1,701 research outputs found
New holomorphically closed subalgebras of -algebras of hyperbolic groups
We construct dense, unconditional subalgebras of the reduced group
-algebra of a word-hyperbolic group, which are closed under holomorphic
functional calculus and possess many bounded traces. Applications to the cyclic
cohomology of group -algebras and to delocalized -invariants of
negatively curved manifolds are given
Calculus and heat flow in metric measure spaces and applications to spaces with Ricci bounds from below
This paper is devoted to a deeper understanding of the heat flow and to the
refinement of calculus tools on metric measure spaces (X,d,m). Our main results
are:
- A general study of the relations between the Hopf-Lax semigroup and
Hamilton-Jacobi equation in metric spaces (X,d).
- The equivalence of the heat flow in L^2(X,m) generated by a suitable
Dirichlet energy and the Wasserstein gradient flow of the relative entropy
functional in the space of probability measures P(X).
- The proof of density in energy of Lipschitz functions in the Sobolev space
W^{1,2}(X,d,m).
- A fine and very general analysis of the differentiability properties of a
large class of Kantorovich potentials, in connection with the optimal transport
problem.
Our results apply in particular to spaces satisfying Ricci curvature bounds
in the sense of Lott & Villani [30] and Sturm [39,40], and require neither the
doubling property nor the validity of the local Poincar\'e inequality.Comment: Minor typos corrected and many small improvements added. Lemma 2.4,
Lemma 2.10, Prop. 5.7, Rem. 5.8, Thm. 6.3 added. Rem. 4.7, Prop. 4.8, Prop.
4.15 and Thm 4.16 augmented/reenforced. Proof of Thm. 4.16 and Lemma 9.6
simplified. Thm. 8.6 corrected. A simpler axiomatization of weak gradients,
still equivalent to all other ones, has been propose
Photon trains and lasing : The periodically pumped quantum dot
We propose to pump semiconductor quantum dots with surface acoustic waves
which deliver an alternating periodic sequence of electrons and holes. In
combination with a good optical cavity such regular pumping could entail
anti-bunching and sub-Poissonian photon statistics. In the bad-cavity limit a
train of equally spaced photons would arise.Comment: RevTex, 5 pages, 1 figur
The Dirac operator on generalized Taub-NUT spaces
We find sufficient conditions for the absence of harmonic spinors on
spin manifolds constructed as cone bundles over a compact K\"ahler base. These
conditions are fulfilled for certain perturbations of the Euclidean metric, and
also for the generalized Taub-NUT metrics of Iwai-Katayama, thus proving a
conjecture of Vi\csinescu and the second author.Comment: Final version, 16 page
Transcriptomic and proteomic insights into innate immunity and adaptations to a symbiotic lifestyle in the gutless marine worm Olavius algarvensis
Background: The gutless marine worm Olavius algarvensis has a completely reduced digestive and excretory system, and lives in an obligate nutritional symbiosis with bacterial symbionts. While considerable knowledge has been gained of the symbionts, the host has remained largely unstudied. Here, we generated transcriptomes and proteomes of O. algarvensis to better understand how this annelid worm gains nutrition from its symbionts, how it adapted physiologically to a symbiotic lifestyle, and how its innate immune system recognizes and responds to its symbiotic microbiota. Results: Key adaptations to the symbiosis include (i) the expression of gut-specific digestive enzymes despite the absence of a gut, most likely for the digestion of symbionts in the host's epidermal cells; (ii) a modified hemoglobin that may bind hydrogen sulfide produced by two of the worm's symbionts; and (iii) the expression of a very abundant protein for oxygen storage, hemerythrin, that could provide oxygen to the symbionts and the host under anoxic conditions. Additionally, we identified a large repertoire of proteins involved in interactions between the worm's innate immune system and its symbiotic microbiota, such as peptidoglycan recognition proteins, lectins, fibrinogen-related proteins, Toll and scavenger receptors, and antimicrobial proteins. Conclusions: We show how this worm, over the course of evolutionary time, has modified widely-used proteins and changed their expression patterns in adaptation to its symbiotic lifestyle and describe expressed components of the innate immune system in a marine oligochaete. Our results provide further support for the recent realization that animals have evolved within the context of their associations with microbes and that their adaptive responses to symbiotic microbiota have led to biological innovations
Practical Methods for Identification of Rice Endosperm Protein Bodies and Fecal Protein Particles in Light Microscopy
Indigestible 1-3 ~m protein \u27cores\u27, particles that originate from protein bodies of rice endosperm, were examined in bright-field and fluorescence microscopy, using a variety of histological and histochemical procedures. Our application of histological, histochemical and chemical approaches to a study of the feces of aoimals fed rice-containing diets has resulted in the development of methods for routine identification of insoluble rice fecal protein particles. For the specific identification of rice endosperm storage protein, whether protein bodies, cores or fecal protein particles, aqueous eosin Y stain in conjunction with fluorescence microscopy, and a combination of orange G + aniline blue in bright-field microscopy appear to be reliable methods when used in conjunction with each other
Upgrade of the HadGEM3-A based attribution system to high resolution and a new validation framework for probabilistic event attribution
We present a substantial upgrade of the Met Office system for the probabilistic attribution of extreme weather and climate events with higher horizontal and vertical resolution (60 km mid-latitudes and 85 vertical levels), the latest Hadley Centre atmospheric and land model (ENDGame dynamics with GA6.0 science and JULES at GL6.0) as well as an updated forcings set. A new set of experiments designed for the evaluation and implementation of an operational attribution service are described which consist of pairs of multi-decadal stochastic physics ensembles continued on a season by season basis by large ensembles that are able to sample extreme at- mospheric states possible in the recent past. Diagnostics from these experiments form the HadGEM3-A contribution to the international Climate of the 20th Century Plus (C20CĂŸ) project and were analysed under the European Climate and Weather Events: Interpretation and Attribution (EUCLEIA) event attribution project as well as contributing to the Climate Science for Service Partnership (CSSP)-China programme. After discussing the framing issues surrounding questions that can be asked with our system we construct a novel approach to the evaluation of atmosphere-only ensembles intended for event attribution, in the process highlighting and clarifying the distinction between hindcast skill and model performance. A framework based around assessing model representation of predictable components and ensuring exchangeability of model and real world statistics leads to a form of detection and attribution to boundary condition forcing as a means of quantifying one degree of freedom of potential model error and allowing for the bias correction of event probabilities and resulting probability ratios. This method is then applied systematically across the globe to assess contributions from anthropogenic influence and specific boundary conditions to the changing probability of observed and record seasonal mean temperatures of four recent 3-month seasons from March 2016âFebruary 2017
Human influence on the record-breaking cold event in January of 2016 in Eastern China
Anthropogenic influences are estimated to have reduced the likelihood of an extreme cold event in midwinter with the intensity equal to or stronger than the record of 2016 in eastern China by about twoâthirds
The challenges facing public libraries in the Big Society: The role of volunteers, and the issues that surround their use in England
The use of volunteers in English public libraries is nothing new, however their use is becoming ever greater and one may argue that we are increasingly seeing a mixed economy of public library provision, in the wider arena of the Big Society. This paper presents the findings of a Delphi Study of 15 library managers undertaken as part of a Professional Doctorate exploring the challenges facing public libraries in England today, particularly focusing on volunteer use. An overview of relevant supporting literature is provided to help contextualize the research, particularly focusing on concepts such as the political background surrounding policy development, community engagement, the Big Society, and volunteering. Explanation of how the Delphi Study was conducted is given, together with a discussion of the key findings. Results show that opinions of library managers cover a broad spectrum. Although volunteer use is generally viewed by the respondents as a good thing, with potential to further enhance a service and aid community engagement, there are also a number of concerns. These concerns particularly relate to the idea of the volunteer as a replacement to paid staff rather than an enhancement to the service. Other key concerns relate to the quality of service provision, the rationale behind volunteer use, and the capacity of communities to deliver. Volunteer use in public libraries on this scale is a new phenomenon, and the longevity of such a development is largely unknown. This raises the question as to whether this is simply a large scale ideological experiment, or a move to even greater community engagement
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