702 research outputs found
Equivalence of the (generalised) Hadamard and microlocal spectrum condition for (generalised) free fields in curved spacetime
We prove that the singularity structure of all n-point distributions of a
state of a generalised real free scalar field in curved spacetime can be
estimated if the two-point distribution is of Hadamard form. In particular this
applies to the real free scalar field and the result has applications in
perturbative quantum field theory, showing that the class of all Hadamard
states is the state space of interest. In our proof we assume that the field is
a generalised free field, i.e. that it satisies scalar (c-number) commutation
relations, but it need not satisfy an equation of motion. The same argument
also works for anti-commutation relations and it can be generalised to
vector-valued fields. To indicate the strengths and limitations of our
assumption we also prove the analogues of a theorem by Borchers and Zimmermann
on the self-adjointness of field operators and of a very weak form of the
Jost-Schroer theorem. The original proofs of these results in the Wightman
framework make use of analytic continuation arguments. In our case no
analyticity is assumed, but to some extent the scalar commutation relations can
take its place.Comment: 18 page
Absence of a dose-rate effect in the transformation of C3H 10T1/2 cells by α-particles
The findings of Hill et al. (1984) on the greatly enhanced transformation frequencies at very low dose rates of fission neutrons induced us to perform an analogous study with -particles at comparable dose rates. Transformation frequencies were determined with γ-rays at high dose rate (0·5 Gy/min), and with -particles at high (0·2 Gy/min) and at low dose rates (0·83-2·5 mGy/min) in the C3H 10T1/2 cell system.
α-particles were substantially more effective than γ-rays, both for cell inactivation and for neoplastic transformation at high and low dose rates. The relative biological effectiveness (RBE) for cell inactivation and for neoplastic transformation was of similar magnitude, and ranged from about 3 at an -particle dose of 2 Gy to values of the order of 10 at 0·25 Gy. In contrast to the experiments of Hill et al. (1984) with fission neutrons, no increased transformation frequencies were observed when the -particle dose was protracted over several hours
More Model-Independent Analysis of b->s Processes
We study model-independently the implications of non-standard scalar and
pseudoscalar interactions for the decays b ->s gamma, b -> s g, b -> s l^+l^-
(l=e,mu) and B_s -> mu^+ mu^-. We find sizeable renormalization effects from
scalar and pseudoscalar four-quark operators in the radiative decays and at
O(alpha_s) in hadronic b decays. Constraints on the Wilson coefficients of an
extended operator basis are worked out. Further, the ratios R_H = BR(B -> H
mu^+ mu^-)/BR(B -> H e^+ e^-), for H=K^(*), X_s, and their correlations with
B_s -> mu^+ mu^- decay are investigated. We show that the Standard Model
prediction for these ratios defined with the same cut on the dilepton mass for
electron and muon modes, R_H= 1 + O(m^2_mu/m^2_b), has a much smaller
theoretical uncertainty (<1%) than the one for the individual branching
fractions. The present experimental limit R_K < 1.2 puts constraints on scalar
and pseudoscalar couplings, which are similar to the ones from current data on
BR(B_s -> mu^+ mu^-). We find that new physics corrections to R_{K*} and
R_{X_s} can reach 13% and 10%, respectively.Comment: 28 pages, 6 figures; Table 1 updated, two refs added (to appear in
PRD
Anaemia in schoolchildren in eight countries in Africa and Asia
Objective: To report on the haemoglobin concentrations and prevalence of anaemia in schoolchildren in eight countries in Africa and Asia.
Design: Blood samples were collected during surveys of the health of schoolchildren as a part of programmes to develop school-based health services.
Setting: Rural schools in Ghana, Indonesia, Kenya, Malawi, Mali, Mozambique, Tanzania and Vietnam.
Subjects: Nearly 14 000 children enrolled in basic education in three age ranges (7-11 years, 12-14 years and >/= 15 years) which reflect the new UNICEF/WHO
thresholds to define anaemia.
Results: Anaemia was found to be a severe public health problem (defined as >40% anaemic) in five African countries for children aged 7-11 years and in four of the same countries for children aged 12-14 years. Anaemia was not a public health problem in the children studied in the two Asian countries. More boys than girls were anaemic, and children who enrolled late in school were more likely to be
anaemic than children who enrolled closer to the correct age. The implications of the four new thresholds defining anaemia for school-age children are examined.
Conclusions: Anaemia is a significant problem in schoolchildren in sub-Saharan Africa. School-based health services which provide treatments for simple conditions
that cause blood loss, such as worms, followed by multiple micronutrient supplements including iron, have the potential to provide relief from a large burden of anaemia
Low Complexity Regularization of Linear Inverse Problems
Inverse problems and regularization theory is a central theme in contemporary
signal processing, where the goal is to reconstruct an unknown signal from
partial indirect, and possibly noisy, measurements of it. A now standard method
for recovering the unknown signal is to solve a convex optimization problem
that enforces some prior knowledge about its structure. This has proved
efficient in many problems routinely encountered in imaging sciences,
statistics and machine learning. This chapter delivers a review of recent
advances in the field where the regularization prior promotes solutions
conforming to some notion of simplicity/low-complexity. These priors encompass
as popular examples sparsity and group sparsity (to capture the compressibility
of natural signals and images), total variation and analysis sparsity (to
promote piecewise regularity), and low-rank (as natural extension of sparsity
to matrix-valued data). Our aim is to provide a unified treatment of all these
regularizations under a single umbrella, namely the theory of partial
smoothness. This framework is very general and accommodates all low-complexity
regularizers just mentioned, as well as many others. Partial smoothness turns
out to be the canonical way to encode low-dimensional models that can be linear
spaces or more general smooth manifolds. This review is intended to serve as a
one stop shop toward the understanding of the theoretical properties of the
so-regularized solutions. It covers a large spectrum including: (i) recovery
guarantees and stability to noise, both in terms of -stability and
model (manifold) identification; (ii) sensitivity analysis to perturbations of
the parameters involved (in particular the observations), with applications to
unbiased risk estimation ; (iii) convergence properties of the forward-backward
proximal splitting scheme, that is particularly well suited to solve the
corresponding large-scale regularized optimization problem
A Model for the Development of the Rhizobial and Arbuscular Mycorrhizal Symbioses in Legumes and Its Use to Understand the Roles of Ethylene in the Establishment of these two Symbioses
We propose a model depicting the development of nodulation and arbuscular mycorrhizae. Both processes are dissected into many steps, using Pisum sativum L. nodulation mutants as a guideline. For nodulation, we distinguish two main developmental programs, one epidermal and one cortical. Whereas Nod factors alone affect the cortical program, bacteria are required to trigger the epidermal events. We propose that the two programs of the rhizobial symbiosis evolved separately and that, over time, they came to function together. The distinction between these two programs does not exist for arbuscular mycorrhizae development despite events occurring in both root tissues. Mutations that affect both symbioses are restricted to the epidermal program. We propose here sites of action and potential roles for ethylene during the formation of the two symbioses with a specific hypothesis for nodule organogenesis. Assuming the epidermis does not make ethylene, the microsymbionts probably first encounter a regulatory level of ethylene at the epidermis–outermost cortical cell layer interface. Depending on the hormone concentrations there, infection will either progress or be blocked. In the former case, ethylene affects the cortex cytoskeleton, allowing reorganization that facilitates infection; in the latter case, ethylene acts on several enzymes that interfere with infection thread growth, causing it to abort. Throughout this review, the difficulty of generalizing the roles of ethylene is emphasized and numerous examples are given to demonstrate the diversity that exists in plants
Multivariate proteomic profiling identifies novel accessory proteins of coated vesicles.
Despite recent advances in mass spectrometry, proteomic characterization of transport vesicles remains challenging. Here, we describe a multivariate proteomics approach to analyzing clathrin-coated vesicles (CCVs) from HeLa cells. siRNA knockdown of coat components and different fractionation protocols were used to obtain modified coated vesicle-enriched fractions, which were compared by stable isotope labeling of amino acids in cell culture (SILAC)-based quantitative mass spectrometry. 10 datasets were combined through principal component analysis into a "profiling" cluster analysis. Overall, 136 CCV-associated proteins were predicted, including 36 new proteins. The method identified >93% of established CCV coat proteins and assigned >91% correctly to intracellular or endocytic CCVs. Furthermore, the profiling analysis extends to less well characterized types of coated vesicles, and we identify and characterize the first AP-4 accessory protein, which we have named tepsin. Finally, our data explain how sequestration of TACC3 in cytosolic clathrin cages causes the severe mitotic defects observed in auxilin-depleted cells. The profiling approach can be adapted to address related cell and systems biological questions
Has the evolution of complexity in the amphibian papilla influenced anuran speciation rates?
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72375/1/j.1420-9101.2006.01079.x.pd
Caste development and reproduction: a genome-wide analysis of hallmarks of insect eusociality
The honey bee queen and worker castes are a model system for developmental plasticity. We used established expressed sequence tag information for a Gene Ontology based annotation of genes that are differentially expressed during caste development. Metabolic regulation emerged as a major theme, with a caste-specific difference in the expression of oxidoreductases vs. hydrolases. Motif searches in upstream regions revealed group-specific motifs, providing an entry point to cis-regulatory network studies on caste genes. For genes putatively involved in reproduction, meiosis-associated factors came out as highly conserved, whereas some determinants of embryonic axes either do not have clear orthologs (bag of marbles, gurken, torso), or appear to be lacking (trunk) in the bee genome. Our results are the outcome of a first genome-based initiative to provide an annotated framework for trends in gene regulation during female caste differentiation (representing developmental plasticity) and reproduction
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
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