The collaborative effect of ram pressure and merging on star formation and stripping fraction

Aims: We investigate the effect of ram pressure stripping (RPS) on simulations of merging pairs of gas-rich spiral galaxies. Our goal is to provide an estimate of the combined effect of merging and RPS on stripping efficiency and star formation rate. Methods: We make use of the combined N-body/hydrodynamic code GADGET-2. In our simulations, we vary mass ratios between 1:4 and 1:8 in a binary merger. We sample different geometric configurations of the merging systems (edge-on and face-on mergers, different impact parameters). Furthermore, we vary the properties of the intracluster medium (ICM) in rough steps: The speed of the merging system relative to the ICM between 500 and 1000 km/s, the ICM density between $10^{-29}$ and $10^{-27}$ g/cm$^3$, and the ICM direction relative to the mergers' orbital plane. Ram pressure is kept constant within a simulation time period, as is the ICM temperature of $10^7$ K. Each simulation in the ICM is compared to simulations of the merger in vacuum and the non-merging galaxies with acting ram pressure. Results: Averaged over the simulation time (1 Gyr) the merging pairs show a negligible 5% enhancement in SFR, when compared to single galaxies under the same environmental conditions. The SFRs peak at the time of the galaxies first fly-through. There, our simulations show SFRs of up to 20 M$_{\odot}$/yr (compared to 3 M$_{\odot}$/yr of the non-merging galaxies in vacuum). In the most extreme case, this constitutes a short-term ($<50$ Myr) SFR increase of 50% over the non-merging galaxies experiencing ram pressure. The wake of merging galaxies in the ICM typically has a third to half the star mass seen in the non-merging galaxies and 5% to 10 % less gas mass. The joint effect of RPS and merging, according to our simulations, is not significantly different from pure ram pressure effects.Comment: 12 pages, 13 figures, 3 tables, A&

Semantic 3D Reconstruction with Finite Element Bases

We propose a novel framework for the discretisation of multi-label problems on arbitrary, continuous domains. Our work bridges the gap between general FEM discretisations, and labeling problems that arise in a variety of computer vision tasks, including for instance those derived from the generalised Potts model. Starting from the popular formulation of labeling as a convex relaxation by functional lifting, we show that FEM discretisation is valid for the most general case, where the regulariser is anisotropic and non-metric. While our findings are generic and applicable to different vision problems, we demonstrate their practical implementation in the context of semantic 3D reconstruction, where such regularisers have proved particularly beneficial. The proposed FEM approach leads to a smaller memory footprint as well as faster computation, and it constitutes a very simple way to enable variable, adaptive resolution within the same model

Impulse Purchases, Gun Ownership and Homicides:Evidence from a Firearm Demand Shock

Do firearm purchase delay laws reduce aggregate homicide levels? Using quasi-experimental evidence from a 6-month countrywide gun demand shock starting in late 2012, we show that U.S. states with legislation preventing immediate handgun purchases experienced smaller increases in handgun sales. Our findings are hard to reconcile with entirely rational consumers, but suggest that gun buyers behave time-inconsistently. In a second step, we demonstrate that states with purchase delays also witnessed 3% lower homicide rates during the same period compared to states allowing instant handgun access. We report suggestive evidence that lower handgun sales primarily reduced impulsive assaults and domestic violence

Impulse Purchases, Gun Ownership and Homicides:Evidence from a Firearm Demand Shock

Do firearm purchase delay laws reduce aggregate homicide levels? Using variation from a 6-month countrywide gun demand shock in 2012/2013, we show that U.S. states with legislation preventing immediate handgun purchases experienced smaller increases in handgun sales. Our findings indicate that this is likely driven by comparatively lower purchases among impulsive consumers. We then demonstrate that states with purchase delays also witnessed comparatively 2% lower homicide rates during the same period. Further evidence shows that lower handgun sales coincided primarily with fewer impulsive assaults and points towards reduced acts of domestic violence

Gamma-rays from dark matter annihilations strongly constrain the substructure in halos

Recently, it has been shown that electrons and positrons from dark matter (DM) annihilations provide an excellent fit to the Fermi, PAMELA, and HESS data. Using this DM model, which requires an enhancement of the annihilation cross section over its standard value to match the observations, we show that it immediately implies an observable level of gamma-ray emission for the Fermi telescope from nearby galaxy clusters such as Virgo and Fornax. We show that this DM model implies a peculiar feature from final state radiation that is a distinctive signature of DM. Using the EGRET upper limit on the gamma-ray emission from Virgo, we constrain the minimum mass of substructures within DM halos to be > 5x10^-3 M_sun -- about four orders of magnitudes larger than the expectation for cold dark matter. This limits the cutoff scale in the linear matter power spectrum to k < 35/kpc which can be explained by e.g., warm dark matter. Very near future Fermi observations will strongly constrain the minimum mass to be > 10^3 M_sun: if the true substructure cutoff is much smaller than this, the DM interpretation of the Fermi/PAMELA/HESS data must be wrong. To address the problem of astrophysical foregrounds, we performed high-resolution, cosmological simulations of galaxy clusters that include realistic cosmic ray (CR) physics. We compute the dominating gamma-ray emission signal resulting from hadronic CR interactions and find that it follows a universal spectrum and spatial distribution. If we neglect the anomalous enhancement factor and assume standard values for the cross section and minimum subhalo mass, the same model of DM predicts comparable levels of the gamma-ray emission from DM annihilations and CR interactions. This suggests that spectral subtraction techniques could be applied to detect the annihilation signal.Comment: 5 pages, 2 figures (published version; minor corrections to figures and result, equation added

Ein architektonisches Periodisierungsmodell anhand fertigungstechnischer Kriterien, dargestellt am Beispiel des Holzbaus.: Dissertation ETH Nr. 18605

Zeitgenössische Fertigungstechnik ist im Begriff, einen Einfluss auf die Architekturentwicklung auszuüben wie zuletzt in der Industrialisierung des 19. Jahrhunderts. Während neue computergestützte Möglichkeiten auf breiter Basis diskutiert und erprobt werden, bleiben ihre Wurzeln und ihr Verhältnis zu früheren Fertigungstechniken im Dunkeln. Christoph Schindler betrachtet Architektur aus der Perspektive der Fertigungstechnik. Sein Ziel ist es, die von aktueller Informationstechnik getriebene gegenwärtige Forschung im Bauwesen historisch zu kontextualisieren und als Teil einer kontinuierlichen Entwicklung zu identifizieren. Im Zentrum der Arbeit steht als These das Schema eines allgemeinen technikgeschichtlichen Periodisierungsmodells, das handwerkliche, industrielle und informationstechnische Fertigung zu integrieren versucht. Grundlage dieses Periodisierungsmodells ist das Verhältnis der drei Kategorien Stoff, Energie und Information in der jeweiligen fertigungstechnischen Periode. Die Stichhaltigkeit des Modells wird anhand der Geschichte des Holzbaus überprüft, da der Holzbau wie keine andere Konstruktionsweise die Beziehungen zwischen Fertigungstechnik und Bauen umfassender über einen vergleichbar langen Zeitraum illustriert. Es wird untersucht, ob das vorgeschlagene Modell sich anhand von historischen Fakten belegen lässt – \u2028wie grundlegende Veränderungen in der Fertigungstechnik die Holzverarbeitung beeinflusst und wie diese jeweils Konstruktion und Erscheinungsbild der Holzarchitektur geprägt haben.Contemporary production technology is about to exert an influence on the development of architecture as fundamentally as experienced during Industrialization in the 19th century. While new computer-aided methods are widely discussed and applied, their roots and relation to previous production technology remain obscure. Christoph Schindler analyzes architecture from the perspective of production technology. It aims to contextualize contemporary research in the building industry—driven by information technology—and identify it as part of a continuous development in history of technology. The thesis is built around the scheme of a periodization model, which intends to integrate fabrication within manual, industrial and information technology. It is based on the relation between the three categories matter, energy, and information in each respective period. The validity of the model is proven with help of history of timber architecture, as no other construction method illustrates the relation between processing technology, fabrication methods and architecture more comprehensively over a comparable period of time. It will be studied whether the proposed model can be circumstantiated with historical facts— how constitutive changes in process technology influenced wood processing and how they respectively coined construction and appearance of timber architecture

Establishing semantic research graphs in humanities\u27 research practice

This paper presents approaches and challenges to developing research software for qualitative humanities and social sciences research. While these methods so far lack a digital enhancement, we realized a range of research environments based on semantic graph technologies in research practice. In order to understand the researchers\u27 needs and take the existing research practice seriously, a participatory and agile design approach was used by which several researchers were involved in realizing concrete research projects. A user-centered agile approach with fast prototyping was included. To materialize the needed interaction at an early stage of the research life cycle, this was accompanied by trainings, workshops, and joint paper publications in the different research communities. (DIPF/Orig.