Generation of Adaptive Streak Surfaces Using Moving Least Squares

We introduce a novel method for the generation of fully adaptive streak surfaces in time-varying flow fields based on particle advection and adaptive mesh refinement. Moving least squares approximation plays an important role in multiple stages of the proposed algorithm, which adaptively refines the surface based on curvature approximation and circumradius properties of the underlying Delaunay mesh. We utilize the grid-less Moving Least Squares approximation method for both curvature and surface estimation as well as vector field evaluation during particle advection. Delaunay properties of the surface triangulation are guaranteed by edge flipping operations on the progressive surface mesh. The results of this work illustrate the benefit of adaptivity techniques to streak surface generation and provide the means for a qualitative analysis of the presented approach

On Moving Least Squares Based Flow Visualization

Modern simulation and measurement methods tend to produce meshfree data sets if modeling of processes or objects with free surfaces or boundaries is desired. In Computational Fluid Dynamics (CFD), such data sets are described by particle-based vector fields. This paper presents a summary of a selection of methods for the extraction of geometric features of such point-based vector fields while pointing out its challenges, limitations, and applications

Mudança climática e adaptação no Brasil: uma análise crítica

Semi-arid areas are considered to be strongly susceptible to the adverse impacts of climate change. In this context, the Brazilian Government has started a series of actions to reduce the vulnerability of those groups least prepared to cope with future changes, particularly family farmers. Based on the analysis of the current climate change legislation and other published official documents we find five reasons for concern regarding the current approach that may impede a sustainable reduction in vulnerability in the semi-arid Northeast. Given that large shares of family farmers are already strongly impacted in the context of current climate variability we find that actions that reduce their vulnerability do not necessarily depend on the certainty of future impacts. Therefore, actions that aim to reduce existing socioeconomic and environmental vulnerabilities can be more useful to turn family farmers in the Northeast more resilient to change.Regiões semiáridas são consideradas altamente suscetíveis aos impactos adversos da mudança climática. Nesse contexto, o governo federal começou a implementar uma série de medidas para reduzir a vulnerabilidade de grupos menos preparados, como a agricultura familiar, para lidar com futuras mudanças. Baseado numa análise da legislação vigente sobre mudanças climáticas e dos principais documentos oficiais publicados, o presente trabalho identifica cinco fatores de preocupação referentes à atual abordagem que podem impedir uma redução sustentável de vulnerabilidade em áreas de risco no sertão brasileiro. Dado que grande parte da agricultura familiar já está fortemente impactada no contexto da variabilidade climática atual, isso implica que ações que reduzem a sua vulnerabilidade não dependem necessariamente da certeza de futuros impactos climáticos. Assim, medidas que tentam reduzir as existentes vulnerabilidades socioeconômicas e ambientais podem ser mais úteis para tornar a agricultura familiar do Nordeste mais resiliente às mudanças previstas

Extending an Open-Source Federated Identity Management System for Enhanced HPC Security

Strengthening the security infrastructure around HPC systems has become an urgent and important task, driven especially by the impact of a recent large-scale attack on the world-wide HPC community by a yet unknown party. Multiple European HPC systems had to be shut down for several weeks in mid-May of 2020 after backdoors were found on the systems. In the aftermath of the attack, two core security issues were identified: the absence of strong authentication, and a wide-spread practice of insecure handling of SSH key pairs. We present our approach for extending an existing, open source, federated identity management system with user-friendly two-factor authentication (2FA) using Time-Based One-Time Password (TOTP) and centralized, secure SSH key management. A special focus will be put on how we integrated scientific workflows and automation with the new security measures by combining 2FA, SSH key management and security policies in an elegant, secure and user-friendly way

Dryland adaptation in Northeast Brazil: Lessons from a community-based pilot project

Family farmers in Brazil’s semi-arid region (the Sertão) are highly vulnerable to climate change. In this context, the community-based Adapta Sertão (“adapt Sertão” or “adapt the Sertão”) pilot project aims to strengthen the adaptive capacity of such families in the region of Pintadas, State of Bahia, through integration of immediate livelihood needs with community empowerment and market-based incentives. This short paper discusses the project’s main components, its results and constraints since implementation in 2006. The project is found to have contributed to rural livelihood improvement of its beneficiaries, especially where related to local capacity building. However, the impacts of the strongest drought recorded in the last 50 years continue to affect beneficiaries. CBA in semiarid Brazil may thus need to interact more broadly with those public policies, plans and programs help reduce vulnerability to climatic, social, environmental and economic stressors in general, in order to help family farmers better to sustainably adapt to future climate change.Los agricultores familiares en la región semiárida de Brasil (Sertão) son muy vulnerables al cambio climático. En este contexto, el proyecto piloto basado en la comunidad Adapta Sertão («adaptar Sertão» o «adaptar la región de Sertão») está dirigido a fortalecer la capacidad de adaptación de dichas familias en la región de Pintadas, Estado de Bahía, a través de la integración de las necesidades de subsistencia inmediatas mediante capacitación de la comunidad e iniciativas basadas en el mercado. Este informe breve aborda los principales elementos del proyecto, sus resultados y limitaciones desde su implementación en 2006. Se ha descubierto que el proyecto ha contribuido a la mejora de las condiciones de subsistencia de sus beneficiarios en regiones rurales, en especial, en relación con la construcción de capacidades locales. No obstante, el impacto de la sequía más importante registrada en los últimos 50 años sigue afectando a los beneficiarios. De este modo, la CBA en la región semiárida de Brasil tendrá que interactuar en mayor profundidad con políticas, planes y programas para la reducción de la vulnerabilidad a factores de estrés climáticos, sociales, medioambientales y económicos en general, a fin de ayudar a los agricultores familiares a adaptarse de una forma más sostenible al cambio climático futuro.Les familles d'exploitants agricoles du Sertão, région semi-aride du Brésil, sont très vulnérables au changement climatique. Dans ce contexte, le projet pilote communautaire Adapta Sertão ("adapter le Sertão") vise à renforcer la capacité d'adaptation de ces familles dans la région de Pintadas, dans l'Etat de Bahia, par l'intégration des besoins de moyens de subsistance immédiats via l'autonomisation des communautés et des incitations commerciales. Ce court article expose les principaux éléments du projet, ses résultats et ses contraintes depuis sa mise en oeuvre en 2006. Ce projet a contribué à améliorer la vie rurale de ses bénéficiaires, en particulier concernant le développement des capacités locales. Toutefois, les conséquences de la plus forte sécheresse qu'ait connu le Brésil au cours de ces 50 dernières années, continuent d'affecter les bénéficiaires. L'adaptation communautaire dans les régions semi-arides du Brésil peut ainsi passer par une interaction à plus grande échelle avec ces politiques, plans et programmes publics visant à réduire la vulnérabilité aux facteurs de stress climatiques, sociaux, environnementaux et économiques en général, afin de faciliter l'adaptation des familles d'exploitants agricoles au changement climatique futur de manière durable

Ambient and substrate energy influence decomposer diversity differentially across trophic levels

The species-energy hypothesis predicts increasing biodiversity with increasing energy in ecosystems. Proxies for energy availability are often grouped into ambient energy (i.e., solar radiation) and substrate energy (i.e., non-structural carbohydrates or nutritional content). The relative importance of substrate energy is thought to decrease with increasing trophic level from primary consumers to predators, with reciprocal effects of ambient energy. Yet, empirical tests are lacking. We compiled data on 332,557 deadwood-inhabiting beetles of 901 species reared from wood of 49 tree species across Europe. Using host-phylogeny-controlled models, we show that the relative importance of substrate energy versus ambient energy decreases with increasing trophic levels: the diversity of zoophagous and mycetophagous beetles was determined by ambient energy, while non-structural carbohydrate content in woody tissues determined that of xylophagous beetles. Our study thus overall supports the species-energy hypothesis and specifies that the relative importance of ambient temperature increases with increasing trophic level with opposite effects for substrate energy

Ambient and substrate energy influence decomposer diversity differentially across trophic levels.

The species-energy hypothesis predicts increasing biodiversity with increasing energy in ecosystems. Proxies for energy availability are often grouped into ambient energy (i.e., solar radiation) and substrate energy (i.e., non-structural carbohydrates or nutritional content). The relative importance of substrate energy is thought to decrease with increasing trophic level from primary consumers to predators, with reciprocal effects of ambient energy. Yet, empirical tests are lacking. We compiled data on 332,557 deadwood-inhabiting beetles of 901 species reared from wood of 49 tree species across Europe. Using host-phylogeny-controlled models, we show that the relative importance of substrate energy versus ambient energy decreases with increasing trophic levels: the diversity of zoophagous and mycetophagous beetles was determined by ambient energy, while non-structural carbohydrate content in woody tissues determined that of xylophagous beetles. Our study thus overall supports the species-energy hypothesis and specifies that the relative importance of ambient temperature increases with increasing trophic level with opposite effects for substrate energy

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters