An IR Search for Extinguished Supernovae in Starburst Galaxies

IR and Radio band observations of heavily extinguished regions in starburst galaxies suggest a very high SN rate associated with such regions. Optically measured supernova (SN) rates may therefore underestimate the total SN rate by factors of up to 10, due to the high extinction to SNe in starburst regions. The IR/radio SN rates come from a variety of indirect means, however, which suffer from model dependence and other problems. We describe a direct measurement of the SN rate from a regular patrol of starburst galaxies done with K' band imaging to minimize the effects of extinction. A collection of K' measurements of core-collapse SNe near maximum light is presented. Results of a preliminary SN search using the MIRC camera at the Wyoming IR Observatory (WIRO), and an improved search using the ORCA optics are described. A monthly patrol of starburst galaxies within 25 Mpc should yield 1.6 - 9.6 SNe/year. Our MIRC search with low-resolution (2.2" pixels) failed to find extinguished SNe, limiting the SN rate outside the nucleus (at > 15" radius) to less than 3.8 Supernova Rate Units (SRU or SNe/century/10^10 L(solar); 90% confidence). The MIRC camera had insufficient resolution to search nuclear starburst regions, where SN activity is concentrated, explaining why we found no heavily obscured SNe. We conclude that high-resolution, small field SN searches in starburst nuclei are more productive than low resolution, large-field searches, even for our large galaxies. With our ORCA high-resolution optics, we could limit the total SN rate to < 1.3 SRU at 90% confidence in 3 years of observations, lower than the most pessimistic estimate.Comment: AJ Submitted 1998 Dec. 13. View figures and download all as one file at http://panisse.lbl.gov/public/bruce/irs

Human rights violations in organ procurement practice in China

Over 90% of the organs transplanted in China before 2010 were procured from prisoners. Although Chinese officials announced in December 2014 that the country would completely cease using organs harvested from prisoners, no regulatory adjustments or changes in China’s organ donation laws followed. As a result, the use of prisoner organs remains legal in China if consent is obtained

Cross‐valley vortices in the Inn valley, Austria: Structure, evolution and governing force imbalances

Exchange of momentum and scalars in the mountain boundary layer is achieved through an interaction of meso-to-microscale motions, occurring to varying extents depending on the combined effect of thermally driven as well as dynamically driven forcings. One such motion, known as a secondary circulation, results from a horizontal force imbalance across a curved valley segment, wherein the centrifugal force towards the outside of the valley bend can create a pressure gradient force in the opposite direction. The lack of adequate measurement strategies capable of sampling such motions in curved mountain valleys explains the near-absence of any observational evidence of secondary circulations there. The goal of the CROSSINN (Cross-valley flow in the Inn valley investigated by dual-Doppler lidar measurements) campaign, conducted in a curved segment of the Inn valley, Austria, was to determine the character of the cross-valley flow by means of a coplanar retrieval applied to a multi-Doppler wind lidar configuration. A signature of a secondary circulation, hereafter referred to as a cross-valley vortex, stood out particularly during intense daytime upvalley flow episodes. Vortices were detected on 23 upvalley wind days, with a declining frequency of occurrence from August to October. Nearly all identified vortices were marked by a low-level upvalley jet, a clockwise wind direction turning with height, and a cessation of upvalley flow at the local ridgeline level. The routinely sampled coplanar-retrieved cross-valley wind field enabled the quantification of more advanced parameters based on vorticity, revealing a faster spin rate of the vortex around its streamwise axis given a stronger upvalley flow, and a period of revolution on the order of several tens of minutes. A detailed inspection of the lateral momentum budget and associated uncertainties confirmed the importance of the relationship between the centrifugal and the pressure gradient force for the cross-valley vortex occurrence in a curved valley

Effect of atomic transfer on the decay of a Bose-Einstein condensate

We present a model describing the decay of a Bose-Einstein condensate, which assumes the system to remain in thermal equilibrium during the decay. We show that under this assumption transfer of atoms occurs from the condensate to the thermal cloud enhancing the condensate decay rate

Fusion pore expansion is a slow, discontinuous, and Ca2+-dependent process regulating secretion from alveolar type II cells

In alveolar type II cells, the release of surfactant is considerably delayed after the formation of exocytotic fusion pores, suggesting that content dispersal may be limited by fusion pore diameter and subject to regulation at a postfusion level. To address this issue, we used confocal FRAP and N-(3-triethylammoniumpropyl)-4-(4-[dibutylamino]styryl) pyridinium dibromide (FM 1-43), a dye yielding intense localized fluorescence of surfactant when entering the vesicle lumen through the fusion pore (Haller, T., J. Ortmayr, F. Friedrich, H. Volkl, and P. Dietl. 1998. Proc. Natl. Acad. Sci. USA. 95:1579–1584). Thus, we have been able to monitor the dynamics of individual fusion pores up to hours in intact cells, and to calculate pore diameters using a diffusion model derived from Fick's law. After formation, fusion pores were arrested in a state impeding the release of vesicle contents, and expanded at irregular times thereafter. The expansion rate of initial pores and the probability of late expansions were increased by elevation of the cytoplasmic Ca2+ concentration. Consistently, content release correlated with the occurrence of Ca2+ oscillations in ATP-treated cells, and expanded fusion pores were detectable by EM. This study supports a new concept in exocytosis, implicating fusion pores in the regulation of content release for extended periods after initial formation

M e t hylsi lyl hyd roxylami nes: Preparative, Spectroscopic and Ab initio Studiest

Methylsilylhydroxylamines [ (MeH,Si),NOMe, (MeH,Si) MeNOMe, Me,NOSiH,Me] have been prepared from bromo(methy1)silane and the corresponding methylhydroxylamines in the presence of an auxiliary base (triethylamine or N,N,N&apos;,N&apos;-tetramethylethylenediamine). The compounds were studied by N M R spectroscopy of all elements present ( l H , 13C, 15N, 170, 29Si). The magnitude of the one-bond coupling constants 1J(&apos;5N29Si) is interpreted in terms of the hybridization associated with the pyramidal co-ordination of nitrogen, a unique structural feature in Si/N chemistry. Ab initiu studies confirmed these structural predictions. Singly silylated hydroxylamines have been shown to be more strongly pyramidal than doubly silylated ones. Calculations on the model compound (H,Si),NOMe gave a barrier to inversion at nitrogen of 9.7 kcal mol-&apos;. This inversion is accompanied by a partial rotation around the N-0 bond. The has a planar co-ordination at the nitrogen atom, has been maintained ever since, and during the last 40 years the structures of a large number of silylamines have been determined.2 As a general rule it was derived from these results that all compounds with doubly and triply silylated nitrogen atoms exhibit a planar geometry at n i t r~g e n .~ Only for a few monosilylated amines deviations from a planar arrangement of the nitrogen substituents occur, but with significant variations for the gas phase and the solid state. p,d, B~n d i n g ,~ formerly the most widespread hypothesis to explain this and other unique properties of silylamines, like low basicity at nitrogen and short Si-N bonds, was shown to be rather insignificant, and p,. interactions (negative hyperconjugation, anomeric effect) and an electrostatic repulsion model &apos; have since been introduced as more meaningful approaches. Compounds with a wide variety of substituents at the silicon part of the molecules have been structurally studied, but the variations of nitrogen substituents have been limited to silylated hydrazines some of which were presented in previous papers from this laboratory.8 For this class of Si/N compounds with nitrogen in its oxidation state -11, planarity at nitrogen induced by silyl substituents appears to be also well established.&apos; As a continuation of these studies we have now investigated silylated hydroxylamines bearing oxygen as a very electronegative substituent at nitrogen in its oxidation state -I. In this context we recently reported the unique structure of 0-methyl-N,N-bis(ptolylsily1)hydroxylamine 1, oneofonly a few doubly N-silylated compounds with a pyramidal co-ordination sphere at nitrogen. &apos; &apos; t Non-SI unit employed: cal = 4.184 J. 1 As a follow-up to this work, and as a part of our current search for new single-source feedstock precursors for chemical vapour deposition &apos; (CVD) of silicon nitride and oxynitride films, &apos; we are now examining low-molecular-weight silylhydroxylamines with low carbon contents and high volatilities. These small molecules should also allow a direct comparison of experimental data with the results of more sophisticated theoretical calculations of structure and bonding. Results and Discussion Preparation of Methylsilylhydroxy1amines.-Since compounds with silyl groups H,Si are generally pyrophoric, methylsilyl groups, the organosilyl groups with the lowest carbon content, were chosen for this study. Bromo(methy1)silane is a powerful silylating agent for N H and OH functions and reacts with 0-methyl, N,O-dimethyl-and N,N-dimethylhydroxylamine in the presence of triethylamine to give the silylated hydroxylamines 2,3 and 4, respectively (Scheme 1). The compounds have low boiling points (97, 61 and 58 &quot;C, respectively), and separation from the solvents and from the excess of triethylamine is difficult. These complications can be overcome by a solvent-free reaction mode and by using N,N,N&apos;,N&apos;-tetramethylethylenediamine (tmen) as the dehydrohalogenating agent. The advantage of tmen is its dibasic nature. Since both di-and mono-protonated tmen salts are non-volatile

Inverse Problems in a Bayesian Setting

In a Bayesian setting, inverse problems and uncertainty quantification (UQ) --- the propagation of uncertainty through a computational (forward) model --- are strongly connected. In the form of conditional expectation the Bayesian update becomes computationally attractive. We give a detailed account of this approach via conditional approximation, various approximations, and the construction of filters. Together with a functional or spectral approach for the forward UQ there is no need for time-consuming and slowly convergent Monte Carlo sampling. The developed sampling-free non-linear Bayesian update in form of a filter is derived from the variational problem associated with conditional expectation. This formulation in general calls for further discretisation to make the computation possible, and we choose a polynomial approximation. After giving details on the actual computation in the framework of functional or spectral approximations, we demonstrate the workings of the algorithm on a number of examples of increasing complexity. At last, we compare the linear and nonlinear Bayesian update in form of a filter on some examples.Comment: arXiv admin note: substantial text overlap with arXiv:1312.504

Cooperative underwater acoustic communications

This article presents a contemporary overview of underwater acoustic communication (UWAC) and investigates physical layer aspects on cooperative transmission techniques for future UWAC systems. Taking advantage of the broadcast nature of wireless transmission, cooperative communication realizes spatial diversity advantages in a distributed manner. The current literature on cooperative communication focuses on terrestrial wireless systems at radio frequencies with sporadic results on cooperative UWAC. In this article, we summarize initial results on cooperative UWAC and investigate the performance of a multicarrier cooperative UWAC considering the inherent unique characteristics of the underwater channel. Our simulation results demonstrate the superiority of cooperative UWAC systems over their point-to-point counterparts. © 1979-2012 IEEE

Influence of Antipodally Coupled Iodine and Carbon Atoms on the Cage Structure of 9,12-I2-closo-1,2-C2B10H10 : An Electron Diffraction and Computational Study

Because of the comparable electron scattering abilities of carbon and boron, the electron diffraction structure of the C2v-symmetric molecule closo-1,2-C2B10H12 (1), one of the building blocks of boron cluster chemistry, is not as accurate as it could be. On that basis, we have prepared the known diiodo derivative of 1, 9,12-I2-closo-1,2-C2B10H10 (2), which has the same point-group symmetry as 1 but in which the presence of iodine atoms, with their much stronger ability to scatter electrons, ensures much better structural characterization of the C2B10 icosahedral core. Furthermore, the influence on the C2B10 geometry in 2 of the antipodally positioned iodine substituents with respect to both carbon atoms has been examined using the concerted application of gas electron diffraction and quantum chemical calculations at the MP2 and density functional theory (DFT) levels. The experimental and computed molecular geometries are in good overall agreement. Molecular dynamics simulations used to obtain vibrational parameters, which are needed for analyzing the electron diffraction data, have been performed for the first time for this class of compound. According to DFT calculations at the ZORA-SO/BP86 level, the 11B chemical shifts of the boron atoms to which the iodine substituents are bonded are dominated by spin-orbit coupling. Magnetically induced currents within 2 have been calculated and compared to those for [B12H12]2-, the latter adopting a regular icosahedral structure with Ih point-group symmetry. Similar total current strengths are found but with a certain anisotropy, suggesting that spherical aromaticity is present; electron delocalization in the plane of the hetero atoms in 2 is slightly hindered compared to that for [B12H12]2-, presumably because of the departure from ideal icosahedral symmetry