Correlation of shock initiated and thermally initiated chemical reactions in a 1:1 atomic ratio nickel-silicon mixture

Shock initiated chemical reaction experiments have been performed on a 1:1 atomic ratio mixture of 20- to 45-µm nickel and –325 mesh crystalline silicon powders. It has been observed that no detectable or only minor surface reactions occur between the constituents until a thermal energy threshold is reached, above which the reaction goes to completion. The experiments show the energy difference between virtually no and full reaction is on the order of 5 percent. Differential scanning calorimetery (DSC) of statically pressed powders shows an exothermic reaction beginning at a temperature which decreases with decreasing porosity. Powder, shock compressed to just below the threshold energy, starts to react in the DSC at 621 °C while powder statically pressed to 23% porosity starts to react at about 30 °C higher. Tap density powder starts to react at 891 °C. The DSC reaction initiation temperature of the shock compressed but unreacted powder corresponds to a thermal energy in the powder of 382 J/g which agrees well with the thermal energy produced by a shock wave with the threshold energy (between 384 and 396 J/g). (Thermal energies referenced to 20 °C.) A sharp energy threshold and a direct correlation with DSC results indicates that the mean thermal energy determines whether or not the reaction will propagate in the elemental Ni+Si powder mixture rather than local, particle level conditions. From this it may be concluded that the reaction occurs on a time scale greater than the time constant for thermal diffusion into the particle interiors

Efficacy and acceptability of non-invasive brain stimulation for the treatment of adult unipolar and bipolar depression: A systematic review and meta-analysis of randomised sham-controlled trials

We examined the efficacy and acceptability of non-invasive brain stimulation in adult unipolar and bipolar depression. Randomised sham-controlled trials of transcranial direct current stimulation (tDCS), transcranial magnetic stimulation (TMS) and theta-burst stimulation (TBS), without co-initiation of another treatment, were included. We analysed effects on response, remission, all-cause discontinuation rates and continuous depression severity measures. Fifty-six studies met our criteria for inclusion (N = 3,058, mean age = 44.96 years, 61.73% female). Response rates demonstrated efficacy of high-frequency rTMS over the left DLPFC (OR = 3.75, 95% CI [2.44; 5.75]), right-sided low-frequency rTMS (OR = 7.44, 95%CI [2.06; 26.83]) bilateral rTMS (OR = 3.68,95%CI [1.66; 8.13]), deep TMS (OR = 1.69, 95%CI [1.003; 2.85]), intermittent TBS (OR = 4.70, 95%CI [1.14; 19.38]) and tDCS (OR = 4.17, 95% CI [2.25; 7.74]); but not for continuous TBS, bilateral TBS or synchronised TMS. There were no differences in all-cause discontinuation rates. The strongest evidence was for high-frequency rTMS over the left DLPFC. Intermittent TBS provides an advance in terms of reduced treatment duration. tDCS is a potential treatment for non-treatment resistant depression. To date, there is not sufficient published data available to draw firm conclusions about the efficacy and acceptability of TBS and sTMS

Cross-disciplinary research: What configurations of fields of science are found in grant proposals today?

Considering the complexity of the world problems, it seems evident that they do not fit straightforwardly into a disciplinary framework. In this context, the question arises as to whether and how frequently several disciplines cooperate on research projects. Cross-disciplinary cooperation in research might be difficult for two reasons. On one hand, many researchers feel that efforts to achieve methodological rigour, exactness, and control are only possible in the circumscribed area of a discipline. On the other hand, it is claimed that funding organizations, with their rigid disciplinary classification systems, impede cross-disciplinary research in the context of their selection and evaluation procedures. For a total of N = 8,496 grant proposals submitted to the Austrian Science Fund (FWF) from 1999 to 2009, detailed codings of the subdisciplines involved were available for the statistical analysis. Latent class analysis produced 12 latent classes or configurations of fields of science. Mono-disciplinary projects are very well represented in physics/astronomy/mechanics, geosciences, and clinical medicine. Cross-disciplinarity is found particularly in research project proposals of fields of science with clearly overlapping content (e.g. preclinical and clinical medicine) and mainly in research proposals submitted by fields of science within the humanities and social science

New Criticality of 1D Fermions

One-dimensional massive quantum particles (or 1+1-dimensional random walks) with short-ranged multi-particle interactions are studied by exact renormalization group methods. With repulsive pair forces, such particles are known to scale as free fermions. With finite $m$-body forces (m = 3,4,...), a critical instability is found, indicating the transition to a fermionic bound state. These unbinding transitions represent new universality classes of interacting fermions relevant to polymer and membrane systems. Implications for massless fermions, e.g. in the Hubbard model, are also noted. (to appear in Phys. Rev. Lett.)Comment: 10 pages (latex), with 2 figures (not included

Fluctuations and differential contraction during regeneration of Hydra vulgaris tissue toroids

We studied regenerating bilayered tissue toroids dissected from Hydra vulgaris polyps and relate our macroscopic observations to the dynamics of force-generating mesoscopic cytoskeletal structures. Tissue fragments undergo a specific toroid-spheroid folding process leading to complete regeneration towards a new organism. The time scale of folding is too fast for biochemical signalling or morphogenetic gradients which forced us to assume purely mechanical self-organization. The initial pattern selection dynamics was studied by embedding toroids into hydro-gels allowing us to observe the deformation modes over longer periods of time. We found increasing mechanical fluctuations which break the toroidal symmetry and discuss the evolution of their power spectra for various gel stiffnesses. Our observations are related to single cell studies which explain the mechanical feasibility of the folding process. In addition, we observed switching of cells from a tissue bound to a migrating state after folding failure as well as in tissue injury. We found a supra-cellular actin ring assembled along the toroid's inner edge. Its contraction can lead to the observed folding dynamics as we could confirm by finite element simulations. This actin ring in the inner cell layer is assembled by myosin- driven length fluctuations of supra-cellular {\alpha}-actin structures (myonemes) in the outer cell-layer.Comment: 19 pages and 8 figures, submitted to New Journal of Physic

Doing what others do: norms, science, and collective action on global warming

Does rhetoric highlighting social norms or mentioning science in a communication affect individuals’ beliefs about global warming and/or willingness to take action? We draw from framing theory and collective-interest models of action to motivate hypotheses that are tested in two large web-based survey-experiments using convenience samples. Our results show that attitudes about global warming, support for policies that would reduce carbon emissions, and behavioral intentions to take voluntary action are strongly affected by norm- and science-based interventions. This has implications for information campaigns targeting voluntary efforts to promote lifestyle changes that would reduce greenhouse gas emissions

Numerical observation of non-axisymmetric vesicles in fluid membranes

By means of Surface Evolver (Exp. Math,1,141 1992), a software package of brute-force energy minimization over a triangulated surface developed by the geometry center of University of Minnesota, we have numerically searched the non-axisymmetric shapes under the Helfrich spontaneous curvature (SC) energy model. We show for the first time there are abundant mechanically stable non-axisymmetric vesicles in SC model, including regular ones with intrinsic geometric symmetry and complex irregular ones. We report in this paper several interesting shapes including a corniculate shape with six corns, a quadri-concave shape, a shape resembling sickle cells, and a shape resembling acanthocytes. As far as we know, these shapes have not been theoretically obtained by any curvature model before. In addition, the role of the spontaneous curvature in the formation of irregular crenated vesicles has been studied. The results shows a positive spontaneous curvature may be a necessary condition to keep an irregular crenated shape being mechanically stable.Comment: RevTex, 14 pages. A hard copy of 8 figures is available on reques

Diversification of stream invertebrate communities by large wood

This work was carried out within the SMART Joint Doctorate (Science for the MAnagement of Rivers and their Tidal systems) funded with the support of the Erasmus Mundus programme of the European Union