Triggered Star Formation in the Environment of Young Massive Stars

Recent observations with the Spitzer Space Telescope show clear evidence that star formation takes place in the surrounding of young massive O-type stars, which are shaping their environment due to their powerful radiation and stellar winds. In this work we investigate the effect of ionising radiation of massive stars on the ambient interstellar medium (ISM): In particular we want to examine whether the UV-radiation of O-type stars can lead to the observed pillar-like structures and can trigger star formation. We developed a new implementation, based on a parallel Smooth Particle Hydrodynamics code (called IVINE), that allows an efficient treatment of the effect of ionising radiation from massive stars on their turbulent gaseous environment. Here we present first results at very high resolution. We show that ionising radiation can trigger the collapse of an otherwise stable molecular cloud. The arising structures resemble observed structures (e.g. the pillars of creation in the Eagle Nebula (M16) or the Horsehead Nebula B33). Including the effect of gravitation we find small regions that can be identified as formation places of individual stars. We conclude that ionising radiation from massive stars alone can trigger substantial star formation in molecular clouds.Comment: 4 pages, 2 figures. To appear in: "Triggered Star Formation in a Turbulent ISM", IAU Symposium 237, Prague, Czech Republic, August 2006; eds. B.G.Elmegreen & J. Palou

22467 CONTAINMENT FIRE SIMULATION BY A CFD CODE

ABSTRACT In the frame of an international collaborative project to evaluate fire models a code benchmark was initiated to better quantify the strengths and weaknesses of the codes involved. CFX has been applied to simulate selected cases of both parts of the benchmark. These simulations are presented and discussed in this paper. In the first part of the benchmark a pool fire just represented by a heat release table is considered. Consequently, the physical fire model within CFX is simple. Radiative heat exchange together with turbulent mixing are involved. Two cases with and without venting of the fire room are compared. The second part of the benchmark requires a more detailed fire model in order to inspect the availability of oxygen locally and to control the fire intensity. Under unvented conditions oxygen starvation is encountered and the fire oscillates. Mechanical ventilation changes this behavior and provides enough oxygen all over the simulation time. The predefined damage criteria to characterize, if a target cable in the fire room would be damaged, are not met. However, surface temperatures predicted are well above the assumed threshold temperatures

Prioritisation of Research and Development for modelling the safe production, storage, delivery and use of hydrogen.

Hydrogen is expected to play an important role in the energy mix of a future low carbon society, (the European Strategic Energy Technology Plan of the European Commission (COM 2007 - 723) and in the Hydrogen, Fuel Cells & Infrastructure Technologies Program-Multi-Year Research, Development, and Demonstration Plan of the USA Department of Energy (DoE 2007). Hydrogen safety issues must be addressed in order to ensure that the wide spread deployment and use of hydrogen and fuel cell technologies can occur with the same or lower level of hazards and associated risk compared to the conventional fossil fuel technologies. Hydrogen safety is a EU Policy relevant issue as it is stated in the priority 3 Action 2 (Continuous improvement in safety and security) of the EU “Energy 2020 A strategy for competitive, sustainable and secure energy”: “The same security and safety considerations will also be upheld in the development and deployment of new energy technologies (hydrogen safety, safety of CO2 transportation network, CO2 storage, etc…)” Computational Fluid Dynamics (CFD) is one of the tools to investigate safety issues related to the production, storage, delivery and use of hydrogen. CFD techniques can provide a wealthy amount of information on the dynamics of hypothetical hydrogen accident and its consequences. The CFD-based consequence analysis is then used in risk assessments. This report describes the output of a workshop organised at the Institute for Energy and Transport (JRC) in Petten, Netherlands to identify the gaps and issues in CFD modelling of hydrogen release and combustion. A hydrogen accident usually follows a typical sequence of events: an unintended release, the mixing of hydrogen with air to form a flammable mixture, the ignition of the flammable cloud and depending on the conditions, and a fire or an explosion (deflagration or/and detonation). For each stage of the accident, the critical CFD issues have been identified and prioritised. Beyond the specific issues of CFD modelling that are described for each accident stage in the report, some general modelling issues can be found in all stages: • lack of an extensive validation of CFD codes/models that covers all the relevant range of conditions that can be found in hypothetical accident scenarios e.g. in terms of geometrical lay-out, leak flow rates. • lack of a CFD validation protocol for hydrogen like it exists for Liquefied Natural Gas (LNG): the Model Evaluation Protocols (MEP) for assessment of models for accident consequences, with guidance on evaluating models in terms of scientific assessment, verification and validation. • lack of a database of experiments for validation of hydrogen models. • in some cases, lack of complete and accurate experimental data for the CFD validation. The goals of this work were to perform a state of the art review in CFD modelling of hypothetical accidents scenarios related to hydrogen technologies and identify and prioritise the gaps in the field. The report is based on a dedicated workshop organised in Petten with the participation of external experts an extensive literature review performed by experts in the field and the direct expertise and experience of the experts. The experts were carefully selected according to their experience/expertise, number of scientific publications and participations to International Conferences, seminars, workshops and to international and/or European co-funded projects such as HySafe (Hydrogen Safety), HyApproval (Approval of Hydrogen Re-fuelling Stations), European Integrated Hydrogen Projects. By performing a state of the art review of CFD modelling for hydrogen safety issues, a consensus was reached among the scientific experts as to the main gaps in the field and on the priority of the research needs.JRC.F.2-Cleaner energ

Gap Analysis of CFD Modelling of Accidental Hydrogen Release and Combustion

The report describes the findings of a workshop that was held at the Institute for Energy (JRC) in Petten Netherlands, on the topic "Gap analysis of CFD modelling of hydrogen release and combustion". The main topic was divided in 6 sub-topics: release and dispersion, auto-ignition, fires, deflagrations, detonations and DDT, and accident consequences. For each sub-topic, the main gaps in CFD modelling were identified and prioritised.JRC.DDG.F.2-Cleaner energ

Driving Turbulence and Triggering Star Formation by Ionizing Radiation

We present high resolution simulations on the impact of ionizing radiation of massive O-stars on the surrounding turbulent interstellar medium (ISM). The simulations are performed with the newly developed software iVINE which combines ionization with smoothed particle hydrodynamics (SPH) and gravitational forces. We show that radiation from hot stars penetrates the ISM, efficiently heats cold low density gas and amplifies over-densities seeded by the initial turbulence. The formation of observed pillar-like structures in star forming regions (e.g. in M16) can be explained by this scenario. At the tip of the pillars gravitational collapse can be induced, eventually leading to the formation of low mass stars. Detailed analysis of the evolution of the turbulent spectra shows that UV-radiation of O-stars indeed provides an excellent mechanism to sustain and even drive turbulence in the parental molecular cloud.Comment: 5 pages, 2 figures, accepted by ApJ Letter

COMPORTAMIENTO DE INCUBACIÓN DE CHORORÓ (TARABA MAJOR) Y CHOCA COMÚN (THAMNOPHILUS CAERULESCENS) EN ARGENTINA

RESUMEN ∙ La familia Thamnophilidae agrupa unas doscientas especies de aves paseriformes. Si bien en los últimos años se ha avanzado en el conocimiento de la biología reproductiva de muchas de estas especies, todavía hay algunas para las que ciertos parámetros reproductivos son aún desconocidos. Con el presente trabajo contribuimos al conocimiento de la biología reproductiva del Chororó (Taraba major) y la Choca Común (Thamnophilus caerulescens), aportando principalmente datos sobre su comportamiento de incubación en la provincia de Córdoba, Argentina, en el extremo sur de su distribución. Registramos tamaño de la puesta, duración del período de incubación y otras variables asociadas al comportamiento de incubación utilizando sensores remotos y observaciones directas, y medimos crecimiento de pichones en el nido. En las dos especies los adultos compartieron tareas de incubación, y el porcentaje de atención diario al nido fue elevado en ambas (T. major: 91,46%; T. caerulescens: 92,52%). El patrón de incubación durante las horas de luz resultó diferente entre las especies. Para T. major, con el transcurso del día aumento la duración y disminuyó la cantidad de los eventos de incubación y recesos. En contraposición, para T. caerulescens ambas variables se mantuvieron constantes a lo largo del día. Los datos aportados por este trabajo enriquecen el conocimiento de la biología reproductiva de especies de tamnofílidos poco estudiadas, y sirven de base para investigar respecto a los factores que moldean los comportamientos de cuidado parental en estas aves.  ABSTRACT ∙ Incubation behavior of Great Antshrike (Taraba major) and Variable Antshrike (Thamnophilus caerulescens) in Argentina The Thamnophilidae family comprises approximately 200 species of passeriforme birds. Even though in the last years there has been advancement in the knowledge of the reproductive biology of many of those species, there are still species for which several reproductive parameters are unknown. With this work we contribute to the knowledge of the reproductive biology of the Great Antshrike (Taraba major) and the Variable Antshrike (Thamnophilus caerulescens) mainly providing data on their incubation behavior in the province of Córdoba, Argentina, corresponding to their southernmost distribution. We recorded clutch size, total duration of the incubation period, and other variables associated with incubation behavior by means of remote sensors and direct observations. In both species, adults shared incubation duties and nest attentiveness was high (T. major: 91.46%; T. caerulescens: 92.52%). The pattern of incubation for daylight hours was different between the species. In the case of T. major, the duration of on and off bouts increased during the course of the day, and the number of bouts decreased. In contrast, for T. caerulescens both variables remained constant throughout the day. The data provided in this study enriches our knowledge of the reproductive biology of understudied Thamnophilidae species, and are useful as baseline information to investigate the factors that shape parental care behaviors in these birds.

Stroke genetics informs drug discovery and risk prediction across ancestries

Previous genome-wide association studies (GWASs) of stroke - the second leading cause of death worldwide - were conducted predominantly in populations of European ancestry(1,2). Here, in cross-ancestry GWAS meta-analyses of 110,182 patients who have had a stroke (five ancestries, 33% non-European) and 1,503,898 control individuals, we identify association signals for stroke and its subtypes at 89 (61 new) independent loci: 60 in primary inverse-variance-weighted analyses and 29 in secondary meta-regression and multitrait analyses. On the basis of internal cross-ancestry validation and an independent follow-up in 89,084 additional cases of stroke (30% non-European) and 1,013,843 control individuals, 87% of the primary stroke risk loci and 60% of the secondary stroke risk loci were replicated (P < 0.05). Effect sizes were highly correlated across ancestries. Cross-ancestry fine-mapping, in silico mutagenesis analysis(3), and transcriptome-wide and proteome-wide association analyses revealed putative causal genes (such as SH3PXD2A and FURIN) and variants (such as at GRK5 and NOS3). Using a three-pronged approach(4), we provide genetic evidence for putative drug effects, highlighting F11, KLKB1, PROC, GP1BA, LAMC2 and VCAM1 as possible targets, with drugs already under investigation for stroke for F11 and PROC. A polygenic score integrating cross-ancestry and ancestry-specific stroke GWASs with vascular-risk factor GWASs (integrative polygenic scores) strongly predicted ischaemic stroke in populations of European, East Asian and African ancestry(5). Stroke genetic risk scores were predictive of ischaemic stroke independent of clinical risk factors in 52,600 clinical-trial participants with cardiometabolic disease. Our results provide insights to inform biology, reveal potential drug targets and derive genetic risk prediction tools across ancestries.</p

Stroke genetics informs drug discovery and risk prediction across ancestries

Previous genome-wide association studies (GWASs) of stroke — the second leading cause of death worldwide — were conducted predominantly in populations of European ancestry1,2. Here, in cross-ancestry GWAS meta-analyses of 110,182 patients who have had a stroke (five ancestries, 33% non-European) and 1,503,898 control individuals, we identify association signals for stroke and its subtypes at 89 (61 new) independent loci: 60 in primary inverse-variance-weighted analyses and 29 in secondary meta-regression and multitrait analyses. On the basis of internal cross-ancestry validation and an independent follow-up in 89,084 additional cases of stroke (30% non-European) and 1,013,843 control individuals, 87% of the primary stroke risk loci and 60% of the secondary stroke risk loci were replicated (P < 0.05). Effect sizes were highly correlated across ancestries. Cross-ancestry fine-mapping, in silico mutagenesis analysis3, and transcriptome-wide and proteome-wide association analyses revealed putative causal genes (such as SH3PXD2A and FURIN) and variants (such as at GRK5 and NOS3). Using a three-pronged approach4, we provide genetic evidence for putative drug effects, highlighting F11, KLKB1, PROC, GP1BA, LAMC2 and VCAM1 as possible targets, with drugs already under investigation for stroke for F11 and PROC. A polygenic score integrating cross-ancestry and ancestry-specific stroke GWASs with vascular-risk factor GWASs (integrative polygenic scores) strongly predicted ischaemic stroke in populations of European, East Asian and African ancestry5. Stroke genetic risk scores were predictive of ischaemic stroke independent of clinical risk factors in 52,600 clinical-trial participants with cardiometabolic disease. Our results provide insights to inform biology, reveal potential drug targets and derive genetic risk prediction tools across ancestries