5,093 research outputs found
Algorithms for Kullback-Leibler Approximation of Probability Measures in Infinite Dimensions
In this paper we study algorithms to find a Gaussian approximation to a
target measure defined on a Hilbert space of functions; the target measure
itself is defined via its density with respect to a reference Gaussian measure.
We employ the Kullback-Leibler divergence as a distance and find the best
Gaussian approximation by minimizing this distance. It then follows that the
approximate Gaussian must be equivalent to the Gaussian reference measure,
defining a natural function space setting for the underlying calculus of
variations problem. We introduce a computational algorithm which is
well-adapted to the required minimization, seeking to find the mean as a
function, and parameterizing the covariance in two different ways: through low
rank perturbations of the reference covariance; and through Schr\"odinger
potential perturbations of the inverse reference covariance. Two applications
are shown: to a nonlinear inverse problem in elliptic PDEs, and to a
conditioned diffusion process. We also show how the Gaussian approximations we
obtain may be used to produce improved pCN-MCMC methods which are not only
well-adapted to the high-dimensional setting, but also behave well with respect
to small observational noise (resp. small temperatures) in the inverse problem
(resp. conditioned diffusion).Comment: 28 page
Nonlinearities and Parametric Amplification in Superconducting Coplanar Waveguide Resonators
Experimental investigations of the nonlinear properties of superconducting
niobium coplanar waveguide resonators are reported. The nonlinearity due to a
current dependent kinetic inductance of the center conductor is strong enough
to realize bifurcation of the nonlinear oscillator. When driven with two
frequencies near the threshold for bifurcation, parametric amplification with a
gain of +22.4 dB is observed.Comment: 4 pages, 5 figures, 1 table. In version 2: Added appendix with model
description and fits to measurements. Minor corrections and rephrasin
Antifouling bastadin congeners target blue mussel phenoloxidase and complex copper(II) ions
Synthetically prepared congeners of spongederived bastadin derivatives such as 5,5'-dibromohemibastadin- 1 (DBHB) that suppress the settling of barnacle larvae were identified in this study as strong inhibitors of blue mussel phenoloxidase that is involved in the firm attachment of mussels to a given substrate. The IC50 value of DBHB as the most active enzyme inhibitor encountered in this study amounts to 0.84 mu M. Inhibition of phenoloxidase by DBHB is likely due to complexation of copper(II) ions from the catalytic centre of the enzyme by the a-oxo-oxime moiety of the compound as shown here for the first time by structure activity studies and by X-ray structure determination of a copper(II) complex of DBHB.Biotechnology & Applied MicrobiologyMarine & Freshwater BiologySCI(E)EI0ARTICLE61148-11581
A long and complex enhancer activates transcription of the gene coding for the highly abundant immediate early mRNA in murine cytomegalovirus
Using the simian virus 40 "enhancer trap"
approach, we have identified a transcription enhancer located
just upstream of the major immediate early gene of murine
cytomegalovirus. This enhancer has several striking properties.
(.) Together with the enhancer ofhuman cytomegalovirus,
it is the strongest transcription enhancer found to date. (ö) It
is an extremely long enhancer, spanning >700 base pairs. (ĂI)
It consists of a rather complex pattern of sequence repeats, the
longest of which is 181 base pairs. Also, several types of short
sequence motifs are scattered throughout the enhancer in
monomeric, heterodimeric, or homodimeric (palindromic)
form. These motifs have been identified to be components of
other enhancers and promoters, and they are presumably
binding sites for specific nuclear factors. Our analysis suggests
that enhancers are composed of a modular arrangement of
short conserved sequence motifs and that enhancer strength is
correlated with the redundancy of these motifs
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Motherhood, Moral Authority and the Charismatic Matriarch in the Aftermath of Lethal Violence
Images of maternal suffering are an evocative and powerful means of communication in a world where the private grief of victims has increasingly become subject to commodification and public consumption. This article looks at the influence of bereaved mothers as symbols of respect, peace and dignity in the aftermath of violence, and as a result their persuasive presence in family activism. Drawing upon two case studies, this article explores the importance of victimsâ stories in public life and, in particular, the presence of the charismatic matriarch in creating communities of solidarity, raising awareness of harms that have previously gone unheard and prompting policy change. It considers the âcanonicalâ story of the mother in public life and concludes by arguing that more attention should be paid to victimsâ stories and their influence on policy-making, politics and eventually in becoming public grievances
Elective affinities of the Protestant ethic : Weber and the chemistry of capitalism
Peer reviewedPostprin
Maternal and Paternal Risk Factors for Cryptorchidism and Hypospadias: A CaseâControl Study in Newborn Boys
Little is known on environmental risk factors for cryptorchidism and hypospadias, which are among the most frequent congenital abnormalities. The aim of our study was to identify risk factors for cryptorchidism and hypospadias, with a focus on potential endocrine disruptors in parental diet and occupation. In a caseâcontrol study nested within a cohort of 8,698 male births, we compared 78 cryptorchidism cases and 56 hypospadias cases with 313 controls. The participation rate was 85% for cases and 68% for controls. Through interviews, information was collected on pregnancy aspects and personal characteristics, lifestyle, occupation, and dietary phytoestrogen intake of both parents. Occupational exposure to potential endocrine disruptors was classified based on self-reported exposure and ratings of occupational hygienists based on job descriptions. Our findings indicate that paternal pesticide exposure was associated with cryptorchidism [odds ratio (OR) = 3.8; 95% confidence interval (95% CI), 1.1â13.4]. Smoking of the father was associated with hypospadias (OR = 3.8; 95% CI, 1.8â8.2). Maternal occupational, dietary, and lifestyle exposures were not associated with either abnormality. Both abnormalities were associated with suboptimal maternal health, a lower maternal education, and a Turkish origin of the parents. Being small for gestational age was a risk factor for hypospadias, and preterm birth was a risk factor for cryptorchidism. Because paternal pesticide exposure was significantly associated with cryptorchidism and paternal smoking was associated with hypospadias in male offspring, paternal exposure should be included in further studies on cryptorchidism and hypospadias risk factors
A Log File Analysis on the Validity of Partial Solutions in Figural Matrices Tests
As a component of many intelligence test batteries, figural matrices tests are an effective
way to assess reasoning, which is considered a core ability of intelligence. Traditionally, the sum
of correct items is used as a performance indicator (total solution procedure). However, recent
advances in the development of computer-based figural matrices tests allow additional indicators
to be considered for scoring. In two studies, we focused on the added value of a partial solution
procedure employing log file analyses from a computer-based figural matrices test. In the first study
(n = 198), we explored the internal validity of this procedure by applying both an exploratory bottomup approach (using sequence analyses) and a complementary top-down approach (using rule jumps,
an indicator taken from relevant studies). Both approaches confirmed that higher scores in the partial
solution procedure were associated with higher structuredness in participantsâ response behavior.
In the second study (n = 169), we examined the external validity by correlating the partial solution
procedure in addition to the total solution procedure with a Grade Point Average (GPA) criterion.
The partial solution procedure showed an advantage over the total solution procedure in predicting
GPA, especially at lower ability levels. The implications of the results and their applicability to other
tests are discussed
Stress Induces the Danger-Associated Molecular Pattern HMGB-1 in the Hippocampus of Male Sprague Dawley Rats: A Priming Stimulus of Microglia and the NLRP3 Inflammasome
Exposure to acute and chronic stressors sensitizes the proinflammatory response of microglia to a subsequent immune challenge. However, the proximal signal by which stressors prime microglia remains unclear. Here, high mobility group box-1 (HMGB-1) protein was explored as a potential mediator of stress-induced microglial priming and whether HMGB-1 does so via the nucleotide-binding domain, leucine-rich repeat, pyrin domain containing protein 3 (NLRP3) inflammasome. Exposure to 100 inescapable tail shocks (ISs) increased HMGB-1 and NLRP3 protein in the hippocampus and led isolated microglia to release HMGB-1 ex vivo. To determine whether HMGB-1 signaling is necessary for stress-induced sensitization of microglia, the HMGB-1 antagonist BoxA was injected into the cisterna magnabefore IS. Hippocampal microglia were isolated 24 h later and stimulated with LPS ex vivo to probe for stress-induced sensitization of proinflammatory responses. Previous IS potentiated gene expression of NLRP3 and proinflammatory cytokines to LPS, that is, microglia were sensitized. Treatment with BoxA abolished this effect. To determine whether HMGB-1 is sufficient to prime microglia, IS was replaced with intracerebral administration of disulfide or fully reduced HMGB-1. Intracerebral disulfide HMGB-1 mimicked the effect of the stressor, because microglia isolated from HMGB-1-treated rats expressed exaggerated NLRP3 and proinflammatory cytokine expression after LPS treatment, whereas fully reduced HMGB-1 had no effect. The present results suggest that the CNS innate immune system can respond to an acute stressor as if it were cellular damage, thereby releasing the danger signal HMGB-1 in the brain to prime microglia by acting on the NLRP3 inflammasome, in preparation for a later immune challenge
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