838 research outputs found
Reconstruction of Black Hole Metric Perturbations from Weyl Curvature
Perturbation theory of rotating black holes is usually described in terms of
Weyl scalars and , which each satisfy Teukolsky's complex
master wave equation and respectively represent outgoing and ingoing radiation.
On the other hand metric perturbations of a Kerr hole can be described in terms
of (Hertz-like) potentials in outgoing or ingoing {\it radiation
gauges}. In this paper we relate these potentials to what one actually computes
in perturbation theory, i.e and . We explicitly construct
these relations in the nonrotating limit, preparatory to devising a
corresponding approach for building up the perturbed spacetime of a rotating
black hole. We discuss the application of our procedure to second order
perturbation theory and to the study of radiation reaction effects for a
particle orbiting a massive black hole.Comment: 6 Pages, Revtex
Kombucha Tea-associated microbes remodel host metabolic pathways to suppress lipid accumulation
The popularity of the ancient, probiotic-rich beverage Kombucha Tea (KT) has surged in part due to its purported health benefits, which include protection against metabolic diseases; however, these claims have not been rigorously tested and the mechanisms underlying host response to the probiotics in KT are unknown. Here, we establish a reproducible method to maintain C. elegans on a diet exclusively consisting of Kombucha Tea-associated microbes (KTM), which mirrors the microbial community found in the fermenting culture. KT microbes robustly colonize the gut of KTM-fed animals and confer normal development and fecundity. Intriguingly, animals consuming KTMs display a marked reduction in total lipid stores and lipid droplet size. We find that the reduced fat accumulation phenotype is not due to impaired nutrient absorption, but rather it is sustained by a programed metabolic response in the intestine of the host. KTM consumption triggers widespread transcriptional changes within core lipid metabolism pathways, including upregulation of a suite of lysosomal lipase genes that are induced during lipophagy. The elevated lysosomal lipase activity, coupled with a decrease in lipid droplet biogenesis, is partially required for the reduction in host lipid content. We propose that KTM consumption stimulates a fasting-like response in the C. elegans intestine by rewiring transcriptional programs to promote lipid utilization. Our results provide mechanistic insight into how the probiotics in Kombucha Tea reshape host metabolism and how this popular beverage may impact human metabolism
Integrating Maternal Depression Screening Into an Early Intervention Program: An Implementation Evaluation
Background: In all 50 states, early intervention (EI) services to improve long-term child cognitive and academic outcomes are provided to infants and toddlers with suspected or diagnosed developmental delays. When mothers of EI-enrolled children experience depressive symptoms, uptake of EI services can be compromised. Aims: The purpose of the article is to present a depressive symptom screening intervention for mothers consisting of toolkit development for EI staff and families, symptom screening for mothers and follow-up protocol. To formally evaluate the implementation of the intervention, our research team followed the consolidated framework for implementation research (CFIR). Methods: Participants were 12 EI service coordinators across two offices. Focus groups and individual interviews were used to develop the toolkit and education module. Through the five CFIR domains, we evaluated the implemented intervention in order to allow other teams to learn from our experiences. Results: Our team successfully partnered with SCs to develop the intended deliverables. Still, the SCs found it challenging to conduct the screenings and reported mixed success. Conclusions: Preparation of EI SCs to integrate mental health screenings into their existing skillsets requires a high level of support from the research team, resulting in a rich understanding of the barriers-and potential rewards-for staff and families
Hydrography and circulation near the crest of the East Pacific Rise between 9° and 10°N
Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 58 (2011): 365-376, doi:10.1016/j.dsr.2011.01.009.Topography has a strong effect on the physical oceanography over the flanks and crests of
the global mid-ocean ridge system. Here, we present an analysis of the hydrography and circulation near
the crest of the East Pacific Rise (EPR) between 9â—¦ and 10â—¦N, which coincides with an integrated study site
(ISS) of the RIDGE2000 program. The analysis is based primarily on survey and mooring data collected
during the LADDER project, which aimed to investigate oceanographic and topographic influences on larval
retention and dispersal in hydrothermal vent communities. Results indicate that the yearly averaged regional
mean circulation is characterized by a westward drift of 0.5–1 cm·s−1 across the EPR axis and by north- and
southward flows along the western and eastern upper ridge flanks, respectively. The westward drift is part
of a basin-scale zonal flow that extends across most of the Pacific ocean near 10â—¦N, whereas the meridional
currents near the ridge crest are a topographic effect. In spite of considerable mesoscale variability, which
dominates the regional circulation and dispersal on weekly to monthly time scales, quasi-synoptic surveys
carried out during the mooring deployment and recovery cruises indicate subinertial circulations that are
qualitatively similar to the yearly averaged flow but associated with significantly stronger velocities. Weekly
averaged mooring data indicate that the anticyclonically sheared along-flank flows are associated with core
speeds as high as 10 cm·s−1 and extend ≈10 km off axis and 200m above the ridge-crest topography. Near the
northern limit of the study region, the Lamont Seamount Chain rises from the western ridge flank and restricts
along-EPR flow to five narrow passages, where peak velocities in excess of 20 cm·s−1 were observed. Outside
the region of the ridge-crest boundary currents the density field over the EPR near 10â—¦N is characterized by
isopycnals dipping into the ridge flanks. Directly above the EPR axis the ridge-crest boundary currents give
rise to an isopycnal dome. During times of strong westward cross-EPR flow isopycnal uplift over the eastern
flank causes the cross-ridge density field below the doming isopycnals to be asymmetric, with higher densities
over the eastern than over the western flank. The data collected during the LADDER project indicate that
dispersal of hydrothermal products from the EPR ISS on long time scales is predominantly to the west,
whereas mesoscale variability dominates dispersal on weekly to monthly time scales, which are particularly
important in the context of larval dispersal.Co-funding of the LADDER project by the biological and physical oceanography
divisions of the National Science Foundation under grants OCE-0425361 and OCE-0424953 is gratefully
acknowledged, as is support of J.W. Lavelle by NOAA’s Pacific Marine Environmental Laboratory and by the
NOAA Vents Program
Universal features of the order-parameter fluctuations : reversible and irreversible aggregation
We discuss the universal scaling laws of order parameter fluctuations in any
system in which the second-order critical behaviour can be identified. These
scaling laws can be derived rigorously for equilibrium systems when combined
with the finite-size scaling analysis. The relation between order parameter,
criticality and scaling law of fluctuations has been established and the
connexion between the scaling function and the critical exponents has been
found. We give examples in out-of-equilibrium aggregation models such as the
Smoluchowski kinetic equations, or of at-equilibrium Ising and percolation
models.Comment: 19 pages, 10 figure
Second order gauge invariant gravitational perturbations of a Kerr black hole
We investigate higher than the first order gravitational perturbations in the
Newman-Penrose formalism. Equations for the Weyl scalar representing
outgoing gravitational radiation, can be uncoupled into a single wave equation
to any perturbative order. For second order perturbations about a Kerr black
hole, we prove the existence of a first and second order gauge (coordinates)
and tetrad invariant waveform, , by explicit construction. This
waveform is formed by the second order piece of plus a term, quadratic
in first order perturbations, chosen to make totally invariant and to
have the appropriate behavior in an asymptotically flat gauge.
fulfills a single wave equation of the form where is the same wave operator as for first order perturbations and is a
source term build up out of (known to this level) first order perturbations. We
discuss the issues of imposition of initial data to this equation, computation
of the energy and momentum radiated and wave extraction for direct comparison
with full numerical approaches to solve Einstein equations.Comment: 19 pages, REVTEX. Some misprints corrected and changes to improve
presentation. Version to appear in PR
The influence of gene expression time delays on Gierer-Meinhardt pattern formation systems
There are numerous examples of morphogen gradients controlling long range signalling in developmental and cellular systems. The prospect of two such interacting morphogens instigating long range self-organisation in biological systems via a Turing bifurcation has been explored, postulated, or implicated in the context of numerous developmental processes. However, modelling investigations of cellular systems typically neglect the influence of gene expression on such dynamics, even though transcription and translation are observed to be important in morphogenetic systems. In particular, the influence of gene expression on a large class of Turing bifurcation models, namely those with pure kinetics such as the Gierer–Meinhardt system, is unexplored. Our investigations demonstrate that the behaviour of the Gierer–Meinhardt model profoundly changes on the inclusion of gene expression dynamics and is sensitive to the sub-cellular details of gene expression. Features such as concentration blow up, morphogen oscillations and radical sensitivities to the duration of gene expression are observed and, at best, severely restrict the possible parameter spaces for feasible biological behaviour. These results also indicate that the behaviour of Turing pattern formation systems on the inclusion of gene expression time delays may provide a means of distinguishing between possible forms of interaction kinetics. Finally, this study also emphasises that sub-cellular and gene expression dynamics should not be simply neglected in models of long range biological pattern formation via morphogens
Pre-clinical evaluation of novel mucoadhesive bilayer patches for local delivery of clobetasol-17-propionate to the oral mucosa
Oral lichen planus (OLP) and recurrent aphthous stomatitis (RAS) are chronic inflammatory conditions often characterised by erosive and/or painful oral lesions that have a considerable impact on quality of life. Current treatment often necessitates the use of steroids in the form of mouthwashes, creams or ointments, but these are often ineffective due to inadequate drug contact times with the lesion. Here we evaluate the performance of novel mucoadhesive patches for targeted drug delivery. Electrospun polymeric mucoadhesive patches were produced and characterised for their physical properties and cytotoxicity before evaluation of residence time and acceptability in a human feasibility study. Clobetasol-17-propionate incorporated into the patches was released in a sustained manner in both tissue-engineered oral mucosa and ex vivo porcine mucosa. Clobetasol-17 propionate-loaded patches were further evaluated for residence time and drug release in an in vivo animal model and demonstrated prolonged adhesion and drug release at therapeutic-relevant doses and time points. These data show that electrospun patches are adherent to mucosal tissue without causing tissue damage, and can be successfully loaded with and release clinically active drugs. These patches hold great promise for the treatment of oral conditions such as OLP and RAS, and potentially many other oral lesions
Confining QCD Strings, Casimir Scaling, and a Euclidean Approach to High-Energy Scattering
We compute the chromo-field distributions of static color-dipoles in the
fundamental and adjoint representation of SU(Nc) in the loop-loop correlation
model and find Casimir scaling in agreement with recent lattice results. Our
model combines perturbative gluon exchange with the non-perturbative stochastic
vacuum model which leads to confinement of the color-charges in the dipole via
a string of color-fields. We compute the energy stored in the confining string
and use low-energy theorems to show consistency with the static quark-antiquark
potential. We generalize Meggiolaro's analytic continuation from parton-parton
to gauge-invariant dipole-dipole scattering and obtain a Euclidean approach to
high-energy scattering that allows us in principle to calculate S-matrix
elements directly in lattice simulations of QCD. We apply this approach and
compute the S-matrix element for high-energy dipole-dipole scattering with the
presented Euclidean loop-loop correlation model. The result confirms the
analytic continuation of the gluon field strength correlator used in all
earlier applications of the stochastic vacuum model to high-energy scattering.Comment: 65 pages, 13 figures, extended and revised version to be published in
Phys. Rev. D (results unchanged, 2 new figures, 1 new table, additional
discussions in Sec.2.3 and Sec.5, new appendix on the non-Abelian Stokes
theorem, old Appendix A -> Sec.3, several references added
Machine Learning in Automated Text Categorization
The automated categorization (or classification) of texts into predefined
categories has witnessed a booming interest in the last ten years, due to the
increased availability of documents in digital form and the ensuing need to
organize them. In the research community the dominant approach to this problem
is based on machine learning techniques: a general inductive process
automatically builds a classifier by learning, from a set of preclassified
documents, the characteristics of the categories. The advantages of this
approach over the knowledge engineering approach (consisting in the manual
definition of a classifier by domain experts) are a very good effectiveness,
considerable savings in terms of expert manpower, and straightforward
portability to different domains. This survey discusses the main approaches to
text categorization that fall within the machine learning paradigm. We will
discuss in detail issues pertaining to three different problems, namely
document representation, classifier construction, and classifier evaluation.Comment: Accepted for publication on ACM Computing Survey
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