Asymptotically anti-de Sitter space-times: symmetries and conservation laws revisited

In this short note, we verify explicitly in static coordinates that the non trivial asymptotic Killing vectors at spatial infinity for anti-de Sitter space-times correspond one to one to the conformal Killing vectors of the conformally flat metric induced on the boundary. The fall-off conditions for the metric perturbations that guarantee finiteness of the associated conserved charges are derived.Comment: 6 pages Latex file, Proceedings for the conference "Renormalization Group and Anomalies in Gravity and Cosmology", Ouro Preto, Brazil, 17 - 23 March, 200

Downregulation of genes with a function in axon outgrowth and synapse formation in motor neurones of the VEGF(delta/delta) mouse model of amyotrophic lateral sclerosis

Background: Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen that stimulates vasculogenesis. It has also been shown to act as a neurotrophic factor in vitro and in vivo. Deletion of the hypoxia response element of the promoter region of the gene encoding VEGF in mice causes a reduction in neural VEGF expression, and results in adult-onset motor neurone degeneration that resembles amyotrophic lateral sclerosis (ALS). Investigating the molecular pathways to neurodegeneration in the VEGF(delta/delta) mouse model of ALS may improve understanding of the mechanisms of motor neurone death in the human disease. Results: Microarray analysis was used to determine the transcriptional profile of laser captured spinal motor neurones of transgenic and wild-type littermates at 3 time points of disease. 324 genes were significantly differentially expressed in motor neurones of presymptomatic VEGF(delta/delta) mice, 382 at disease onset, and 689 at late stage disease. Massive transcriptional downregulation occurred with disease progression, associated with downregulation of genes involved in RNA processing at late stage disease. VEGF(delta/delta) mice showed reduction in expression, from symptom onset, of the cholesterol synthesis pathway, and genes involved in nervous system development, including axonogenesis, synapse formation, growth factor signalling pathways, cell adhesion and microtubule-based processes. These changes may reflect a reduced capacity of VEGF(delta/delta) mice for maintenance and remodelling of neuronal processes in the face of demands of neural plasticity. The findings are supported by the demonstration that in primary motor neurone cultures from VEGF(delta/delta) mice, axon outgrowth is significantly reduced compared to wild-type littermates. Conclusions: Downregulation of these genes involved in axon outgrowth and synapse formation in adult mice suggests a hitherto unrecognized role of VEGF in the maintenance of neuronal circuitry. Dysregulation of VEGF may lead to neurodegeneration through synaptic regression and dying-back axonopathy

Homoclinic chaos and energy condition violation

In this letter we discuss the connection between so-called homoclinic chaos and the violation of energy conditions in locally rotationally symmetric Bianchi type IX models, where the matter is assumed to be non-tilted dust and a positive cosmological constant. We show that homoclinic chaos in these models is an artifact of unphysical assumptions: it requires that there exist solutions with positive matter energy density $\rho>0$ that evolve through the singularity and beyond as solutions with negative matter energy density $\rho<0$. Homoclinic chaos is absent when it is assumed that the dust particles always retain their positive mass.In addition, we discuss more general models: for solutions that are not locally rotionally symmetric we demonstrate that the construction of extensions through the singularity, which is required for homoclinic chaos, is not possible in general.Comment: 4 pages, RevTe

How Advanced Change Patterns Impact the Process of Process Modeling

Process model quality has been an area of considerable research efforts. In this context, correctness-by-construction as enabled by change patterns provides promising perspectives. While the process of process modeling (PPM) based on change primitives has been thoroughly investigated, only little is known about the PPM based on change patterns. In particular, it is unclear what set of change patterns should be provided and how the available change pattern set impacts the PPM. To obtain a better understanding of the latter as well as the (subjective) perceptions of process modelers, the arising challenges, and the pros and cons of different change pattern sets we conduct a controlled experiment. Our results indicate that process modelers face similar challenges irrespective of the used change pattern set (core pattern set versus extended pattern set, which adds two advanced change patterns to the core patterns set). An extended change pattern set, however, is perceived as more difficult to use, yielding a higher mental effort. Moreover, our results indicate that more advanced patterns were only used to a limited extent and frequently applied incorrectly, thus, lowering the potential benefits of an extended pattern set

Integrability of irrotational silent cosmological models

We revisit the issue of integrability conditions for the irrotational silent cosmological models. We formulate the problem both in 1+3 covariant and 1+3 orthonormal frame notation, and show there exists a series of constraint equations that need to be satisfied. These conditions hold identically for FLRW-linearised silent models, but not in the general exact non-linear case. Thus there is a linearisation instability, and it is highly unlikely that there is a large class of silent models. We conjecture that there are no spatially inhomogeneous solutions with Weyl curvature of Petrov type I, and indicate further issues that await clarification.Comment: Minor corrections and improvements; 1 new reference; to appear Class. Quantum Grav.; 16 pages Ioplpp

Characteristics and content of intrusive images in patients with eating disorders

Contains fulltext : 206049.pdf (publisher's version ) (Open Access)The aim of this study was to examine the characteristics and content of intrusive images in patients with different subtypes of eating disorders (EDs). Data were collected from 74 ED patients, 22 dieting and 29 non-dieting controls. Participants completed a set of self-report questionnaires. Intrusive images of ED patients were significantly more repetitive, detailed, vivid and distressing than intrusive images of dieting and/or non-dieting controls. Most of the intrusive images were the same for the ED subtypes, however patients with AN were more likely to report an observer vantage perspective than patients with BN, who were more likely to report a field vantage perspective. As expected, intrusive images' content was related to body-checking (weight and shape) or negative self (evaluated by themselves or others). Finally, there were significant associations between intrusive images' vividness and weight and shape concerns. These findings indicate that intrusive images may be a core element of EDs and targeting intrusive images in therapy may be helpful.12 p

Estudios sobre la credibilidad de Wikipedia: una revisión

La evaluación de la credibilidad de Wikipedia ha sido objeto de atención en los estudios sobre credibilidad de la información. Este trabajo presenta un estado de la cuestión, que ha sido elaborado siguiendo la técnica de revisión sistematizada de bibliografía. Se han diferenciado tres tipos de estudios: estudios generales, del ámbito de la salud y del ámbito educativo. Los datos obtenidos permiten afirmar que se aplican diferentes modelos y técnicas de análisis para este tipo de estudios, que los principios heurísticos de evaluación de los usuarios desempeñan un papel fundamental, y que las evaluaciones de credibilidad están influenciados por los contextos sociales y educativos e los usuarios, y por el tipo de necesidad de información. Finalmente, se afirma que evaluar la credibilidad se enmarca en proceso continuo de cambio e interacción. The evaluation of the credibility of Wikipedia has received special attention in studies on the credibility of information on the web. This paper presents a state of the art, which has been carried out following the systematized literature review technique. Three types of studies have been differentiated: general studies, the health field and the educational field. The data support the conclusion that different models and analysis techniques for such studies are applied; that the heuristic principles of user evaluation play a key role; and that assessments of credibility are influenced by user''s social and educational contexts, and by the type of information needed. Finally, it is stated that credibility is part of a continuous process of change and interaction

Hubble Space Telescope WFPC2 Imaging of SN 1979C and Its Environment

The locations of supernovae in the local stellar and gaseous environment in galaxies contain important clues to their progenitor stars. As part of a program to study the environments of supernovae using Hubble Space Telescope (HST) imaging data, we have examined the environment of the Type II-L SN 1979C in NGC 4321 (M100). We place more rigorous constraints on the mass of the SN progenitor, which may have had a mass M \approx 17--18 M_sun. Moreover, we have recovered and measured the brightness of SN 1979C, m=23.37 in F439W (~B; m_B(max) = 11.6), 17 years after explosion. .Comment: 18 pages, 8 figures, submitted to PAS

Gamma-Ray Burst Spectral Correlations: Photospheric and Injection Effects

We present a physical framework that can account for most of the observed spectral properties of the prompt gamma-ray burst emission. This includes the variety of spectral shapes, shape evolutions, and spectral correlations between flux and spectral peak, within bursts described by Borgonovo & Ryde, and among bursts described by Amati/Ghirlanda. In our proposed model the spectral peak is given by the photospheric emission from a relativistic outflow for which the horizon length is much smaller than the radial width. The observed duration of the thermal flash will be given by the radial light-crossing time. This then gives that the typical emission site is at ~10e11 cm from the center, with a Lorentz factor of ~300. This emission is accompanied by non-thermal emission from dissipation locations outside the photosphere. The relative strength of these two components depend on injection effects at the central engine leading to varying relative location of the saturation and photospheric radii. The total emission can then reproduce the observed variety. The spectral correlations are found by assuming that the amount of energy dissipated depends non-linearly on the averaged particle density. Beside the spectral correlations this also gives a description of how the relative strength of the thermal component varies with temperature within a burst.Comment: ApJ accepted, acknowledgement adde