268 research outputs found
an extensible tuplespace as XML-middleware
XMLSpaces.NET implements the Linda concept as a middleware for XML documents.
It introduces an extended matching flexibility on nested tuples and richer
data types for fields, including objects and XML documents. It is completely
XML-based since data, tuples and tuplespaces are seen as trees represented as
XML documents. XMLSpaces.NET is extensible in that it supports a hierarchy of
matching relations on tuples and an open set of matching amongst data,
documents and objects. It is currently being implemented on the .NET platform
Sharp estimates on the first eigenvalue of the p-Laplacian with negative Ricci lower bound
We complete the picture of sharp eigenvalue estimates for the p-Laplacian on
a compact manifold by providing sharp estimates on the first nonzero eigenvalue
of the nonlinear operator when the Ricci curvature is bounded from
below by a negative constant. We assume that the boundary of the manifold is
convex, and put Neumann boundary conditions on it. The proof is based on a
refined gradient comparison technique and a careful analysis of the underlying
model spaces.Comment: Sign mistake fixed in the proof of the gradient comparison theorem
(theorem 5.1 pag 10), and some minor improvements aroun
Z_2-Bi-Gradings, Majorana Modules and the Standard Model Action
The action functional of the Standard Model of particle physics is intimately
related to a specific class of first order differential operators called Dirac
operators of Pauli type ("Pauli-Dirac operators"). The aim of this article is
to carefully analyze the geometrical structure of this class of Dirac operators
on the basis of real Dirac operators of simple type. On the basis of simple
type Dirac operators, it is shown how the Standard Model action (STM action)
may be viewed as generalizing the Einstein-Hilbert action in a similar way the
Einstein-Hilbert action is generalized by a cosmological constant. Furthermore,
we demonstrate how the geometrical scheme presented allows to naturally
incorporate also Majorana mass terms within the Standard Model. For reasons of
consistency these Majorana mass terms are shown to dynamically contribute to
the Einstein-Hilbert action by a "true" cosmological constant. Due to its
specific form, this cosmological constant can be very small. Nonetheless, this
cosmological constant may provide a significant contribution to dark
matter/energy. In the geometrical description presented this possibility arises
from a subtle interplay between Dirac and Majorana masses
Existence of blow-up solutions for a non-linear equation with gradient term in RN
AbstractIn this paper we study the existence of positive large solutions for the equation Δpu+λ|∇u|p−1=ρ(x)f(u) in RN, where f is a non-negative non-decreasing function and ρ is a non-negative continuous function. We show under some hypotheses detailed below the existence of positive solutions which blow up at infinity
A remark on an overdetermined problem in Riemannian Geometry
Let be a Riemannian manifold with a distinguished point and
assume that the geodesic distance from is an isoparametric function.
Let be a bounded domain, with , and consider
the problem in with on ,
where is the -Laplacian of . We prove that if the normal
derivative of along the boundary of is a
function of satisfying suitable conditions, then must be a
geodesic ball. In particular, our result applies to open balls of
equipped with a rotationally symmetric metric of the form
, where is the standard metric of the sphere.Comment: 8 pages. This paper has been written for possible publication in a
special volume dedicated to the conference "Geometric Properties for
Parabolic and Elliptic PDE's. 4th Italian-Japanese Workshop", organized in
Palinuro in May 201
Monochromatization of femtosecond XUV light pulses with the use of reflection zone plates
We report on a newly built laser based tabletop setup which enables generation of femtosecond light pulses in the XUV range via employing the process of high order harmonic generation HHG in a gas medium. The spatial, spectral, and temporal characteristics of the XUV beam are presented. Monochromatization of XUV light with minimum temporal pulse distortion is the central issue of this work. Off center reflection zone plates are shown to be superior to gratings when selection of a desired harmonic is carried out with the use of a single optical element. A cross correlation technique was applied to characterize the performance of zone plates in the time domain. By using laser pulses of 25 fs length to pump the HHG process, a pulse duration of 45 fs for monochromatized harmonics was achieved in the present setu
Inhibition of SARS-CoV-2 Replication by a Small Interfering RNA Targeting the Leader Sequence
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected almost 200 million people worldwide and led to approximately 4 million deaths as of August 2021. Despite successful vaccine development, treatment options are limited. A promising strategy to specifically target viral infections is to suppress viral replication through RNA interference (RNAi). Hence, we designed eight small interfering RNAs (siRNAs) targeting the highly conserved 5′-untranslated region (5′-UTR) of SARS-CoV-2. The most promising candidate identified in initial reporter assays, termed siCoV6, targets the leader sequence of the virus, which is present in the genomic as well as in all subgenomic RNAs. In assays with infectious SARS-CoV-2, it reduced replication by two orders of magnitude and prevented the development of a cytopathic effect. Moreover, it retained its activity against the SARS-CoV-2 alpha variant and has perfect homology against all sequences of the delta variant that were analyzed by bioinformatic means. Interestingly, the siRNA was even highly active in virus replication assays with the SARS-CoV-1 family member. This work thus identified a very potent siRNA with a broad activity against various SARS-CoV viruses that represents a promising candidate for the development of new treatment options
Nonlinear massive spin-two field generated by higher derivative gravity
We present a systematic exposition of the Lagrangian field theory for the
massive spin-two field generated in higher-derivative gravity. It has been
noticed by various authors that this nonlinear field overcomes the well known
inconsistency of the theory for a linear massive spin-two field interacting
with Einstein's gravity. Starting from a Lagrangian quadratically depending on
the Ricci tensor of the metric, we explore the two possible second-order
pictures usually called "(Helmholtz-)Jordan frame" and "Einstein frame". In
spite of their mathematical equivalence, the two frames have different
structural properties: in Einstein frame, the spin-two field is minimally
coupled to gravity, while in the other frame it is necessarily coupled to the
curvature, without a separate kinetic term. We prove that the theory admits a
unique and linearly stable ground state solution, and that the equations of
motion are consistent, showing that these results can be obtained independently
in either frame. The full equations of motion and the energy-momentum tensor
for the spin--two field in Einstein frame are given, and a simple but
nontrivial exact solution to these equations is found. The comparison of the
energy-momentum tensors for the spin-two field in the two frames suggests that
the Einstein frame is physically more acceptable. We point out that the
energy-momentum tensor generated by the Lagrangian of the linearized theory is
unrelated to the corresponding tensor of the full theory. It is then argued
that the ghost-like nature of the nonlinear spin-two field, found long ago in
the linear approximation, may not be so harmful to classical stability issues,
as has been expected
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