3,267 research outputs found
Escobar's Conjecture on a sharp lower bound for the first nonzero Steklov eigenvalue
It was conjectured by Escobar [J. Funct. Anal. 165 (1999), 101-116] that for
an -dimensional () smooth compact Riemannian manifold with
boundary, which has nonnegative Ricci curvature and boundary principal
curvatures bounded below by , the first nonzero Steklov eigenvalue is
greater than or equal to with equality holding only on isometrically
Euclidean balls with radius . In this paper, we confirm this conjecture in
the case of nonnegative sectional curvature. The proof is based on a
combination of Qiu-Xia's weighted Reilly type formula with a special choice of
the weight function depending on the distance function to the boundary, as well
as a generalized Pohozaev type identity.Comment: 18 pages, 0 figures; all comments are welcome. In v2, we revised the
statement in Section 1.2 on the comparison of Theorem 3 and the known
results, and added three reference
J/\psi polarization in photo-production up-to the next-to-leading order of QCD
We investigate the J/psi polarization in photoproduction at the Hadron
Electron Ring Accelerator(HERA) up to the next-to-leading order of QCD. The
results show that the transverse momentum p_t and energy fraction z
distributions of J/psi production do not agree with the observed ones very
well. The theoretical uncertainties for the z distributions of the J/psi
polarization parameters with respect to various choices of the renormalization
and factorization scales are too large to give an accurate prediction. The
uncertainties for the p_t distributions of these parameters are small when
p_t>3GeV and the obtained p_t distributions can not describe the experimental
data even in this region.Comment: 5 pages, 3 figures. Discussion on the theoretical uncertainties from
the choice of renormalization scale was adde
Microbiomes in agroecosystem : diversity, function and assembly mechanisms
Soils are a main repository of biodiversity harbouring immense diversity of microbial species that plays a central role in fundamental ecological processes and acts as the seed bank for emergence of the plant microbiome in cropland ecosystems. Crop-associated microbiomes play an important role in shaping plant performance, which includes but not limited to nutrient uptake, disease resistance, and abiotic stress tolerance. Although our understanding of structure and function of soil and plant microbiomes has been rapidly advancing, most of our knowledge comes from ecosystems in natural environment. In this review, we present an overview of the current knowledge of diversity and function of microbial communities along the soil–plant continuum in agroecosystems. To characterize the ecological mechanisms for community assembly of soil and crop microbiomes, we explore how crop host and environmental factors such as plant species and developmental stage, pathogen invasion, and land management shape microbiome structure, microbial co-occurrence patterns, and crop-microbiome interactions. Particularly, the relative importance of deterministic and stochastic processes in microbial community assembly is illustrated under different environmental conditions, and potential sources and keystone taxa of the crop microbiome are described. Finally, we highlight a few important questions and perspectives in future crop microbiome research
The effects of anti-sense interleukin-5 gene transferred by recombinant adeno-associated virus in allergic rats
The accumulation and infiltration of eosinophils in airways is one of the most important characteristics of asthma, and is mediated partly by secretion of IL-5 from Th2 lymphocytes. It is well known that interleukin-5 (IL-5) played an important role in the regulation of eosinophils. In this study, an anti-sense IL-5 gene transferred by recombinant adeno-associated virus (rAAV-ASIL-5) was prepared to transfect allergic rats. It was found that the expression of IL-5 protein in plasma and BALF were inhibited significantly. The rAAV-ASIL-5-mediated suppression of total cell counts in peripheral blood and BALF were also observed. Moreover, rAAV-ASIL-5 remarkably reduced the eosinophil counts in peripheral blood and BALF, as well as the expression of ECP protein in plasma and BALF. The inflammation in lungs of rAAV-ASIL-5 pretreated rats also became slighter when compared with allergic rats. Otherwise, no apparent pathological damage to vital organs of rats was found. In conclusion, recombinant adeno-associated virus-mediated delivery of anti-sense IL-5 gene inhibited the accumulation of eosinophils and the airways inflammation in rat model of allergic asthma via suppressing IL-5 expression. It suggested the feasibility of rAAV-ASIL-5 in the gene therapy for allergic asthma and other eosinophilic diseases
- …