A Dense Packing of Regular Tetrahedra

We construct a dense packing of regular tetrahedra, with packing density $D > >.7786157$.Comment: full color versio

OSTRACISM AND INTEREST IN EXTREME GROUPS

Drawing from the temporal need-threat theory of ostracism (Williams, 2009), and uncertainty-identity theory (Hogg, 2007), I tested the hypothesis that ostracism increases interest in extreme groups. In a cross-sectional survey, Study 1 showed that chronic ostracism positively predicts interest in the Westboro Baptist Church, Mormonism, Scientology, and Alcoholics Anonymous. Study 2 established causal direction; relative to included participants, ostracized participants expressed greater willingness to attend a meeting of an extreme group following a recruitment attempt. Expressing a desire to attend meetings facilitated recovery of basic need satisfaction. Ostracism also induced self-uncertainty, but this did not mediate the effect. In an attempted replication involving no interpersonal contact, Study 3 failed to show differences in group interest as a function of ostracism. Studies 1 and 2 suggest that ostracism increases vulnerability to extreme group recruitment, and Study 3\u27s failed results suggest that prior contact with a group member is a boundary condition

In search of dying radio sources in the local universe

Up till now very few dying sources were known, presumably because the dying phase is short at centimeter wavelengths. We therefore have tried to improve the statistics on sources that have ceased to be active, or are intermittently active. The latter sources would partly consist of a fossil radio plasma left over from an earlier phase of activity, plus a recently restarted core and radio jets. Improving the statistics of dying sources will give us a better handle on the evolution of radio sources, in particular the frequency and time scales of radio activity. We have used the WENSS and NVSS surveys, in order to find sources with steep spectral indices, associated with nearby elliptical galaxies. In the cross correlation we presently used only unresolved sources, with flux densities at 1.4 GHz larger than 10 mJy. The eleven candidates thus obtained were observed with the VLA in various configurations, in order to confirm the steepness of the spectra, and to check whether active structures like flat-spectrum cores and jets are present, perhaps at low levels. We estimated the duration of the active and relic phases by modelling the integrated radio spectra using the standard models of spectral evolution. We have found six dying sources and three restarted sources, while the remaining two candidates remain unresolved also with the new VLA data and may be Compact Steep Spectrum sources, with an unusually steep spectrum. The typical age of the active phase, as derived by spectral fits, is in the range 10^7 - 10^8 years. For our sample of dying sources, the age of the relic phase is on average shorter by an order of magnitude than the active phase.Comment: 21 pages, 17 figures, accepted by A&A. For a version with high quality figures, see http://erg.ca.astro.it/preprints/dying2007

Regulation of de Novo Synthesis of Cytochrome P-450 17Α in Mouse LeydigCell Cultures a

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73047/1/j.1749-6632.1987.tb25049.x.pd

Relative effects on global warming of halogenated methanes and ethanes of social and industrial interest

The relative potential global warming effects for several halocarbons (chlorofluorocarbons (CFC's)-11, 12, 113, 114, and 115; hydrochlorofluorocarbons (HCFC's) 22, 123, 124, 141b, and 142b; and hydrofluorocarbons (HFC's) 125, 134a, 143a, and 152a; carbon tetrachloride; and methyl chloroform) were calculated by two atmospheric modeling groups. These calculations were based on atmospheric chemistry and radiative convective models to determine the chemical profiles and the radiative processes. The resulting relative greenhouse warming when normalized to the effect of CFC-11 agree reasonably well as long as we account for differences between modeled lifetimes. Differences among results are discussed. Sensitivity of relative warming values is determined with respect to trace gas levels assumed. Transient relative global warming effects are analyzed

Certification of Bounds of Non-linear Functions: the Templates Method

The aim of this work is to certify lower bounds for real-valued multivariate functions, defined by semialgebraic or transcendental expressions. The certificate must be, eventually, formally provable in a proof system such as Coq. The application range for such a tool is widespread; for instance Hales' proof of Kepler's conjecture yields thousands of inequalities. We introduce an approximation algorithm, which combines ideas of the max-plus basis method (in optimal control) and of the linear templates method developed by Manna et al. (in static analysis). This algorithm consists in bounding some of the constituents of the function by suprema of quadratic forms with a well chosen curvature. This leads to semialgebraic optimization problems, solved by sum-of-squares relaxations. Templates limit the blow up of these relaxations at the price of coarsening the approximation. We illustrate the efficiency of our framework with various examples from the literature and discuss the interfacing with Coq.Comment: 16 pages, 3 figures, 2 table