Simple mechanism combines positive locking and quick-release features

For secure locking and quick release of two objects, this device uses a spring-loaded slotted bolt, locked in position by two retainer arms. When these retainer arms are freed from contact, the bolt is ejected and the objects released

Nuclear Reactions Rates Governing the Nucleosynthesis of Ti44

Large excesses of Ca44 in certain presolar graphite and silicon carbide grains give strong evidence for Ti44 production in supernovae. Furthermore, recent detection of the Ti44 gamma-line from the Cas A SNR by CGRO/COMPTEL shows that radioactive Ti44 is produced in supernovae. These make the Ti44 abundance an observable diagnostic of supernovae. Through use of a nuclear reaction network, we have systematically varied reaction rates and groups of reaction rates to experimentally identify those that govern Ti44 abundance in core-collapse supernova nucleosynthesis. We survey the nuclear-rate dependence by repeated calculations of the identical adiabatic expansion, with peak temperature and density chosen to be 5.5xE9 K and 1E7 g/cc, respectively, to approximate the conditions in detailed supernova models. We find that, for equal total numbers of neutrons and protons (eta=0), Ti44 production is most sensitive to the following reaction rates: Ti44(alpha,p)V47, alpha(2alpha,gamma)C12, Ti44(alpha,gamma)Cr48, V45(p,gamma)Cr46. We tabulate the most sensitive reactions in order of their importance to the Ti44 production near the standard values of currently accepted cross-sections, at both reduced reaction rate (0.01X) and at increased reaction rate (100X) relative to their standard values. Although most reactions retain their importance for eta > 0, that of V45(p,gamma)Cr46 drops rapidly for eta >= 0.0004. Other reactions assume greater significance at greater neutron excess: C12(alpha,gamma)O16, Ca40(alpha,gamma)Ti44, Al27(alpha,n)P30, Si30(alpha,n)S33. Because many of these rates are unknown experimentally, our results suggest the most important targets for future cross section measurements governing the value of this observable abundance.Comment: 37 pages, LaTex, 17 figures, 8 table

PVLAS experiment, star cooling and BBN constraints: Possible interpretation with temperature dependent gauge symmetry breaking

It is known that the kinetic mixing of photon and another U(1)_ex gauge boson can introduce millicharged particles. Millicharged particles $f$ of mass 0.1 eV can explain the PVLAS experiment. We suggest a temperature dependent gauge symmetry breaking of U(1)_ex for this idea to be consistent with astrophysical and cosmological constraints.Comment: 9 pages, 3 figue

Mitigating the risk of Zika virus contamination of raw materials and cell lines in the manufacture of biologicals

Ensuring the virological safety of biologicals is challenging due to the risk of viral contamination of raw materials and cell banks, and exposure during in-process handling to known and/or emerging viral pathogens. Viruses may contaminate raw materials and biologicals intended for human or veterinary use and remain undetected until appropriate testing measures are employed. The outbreak and expansive spread of the mosquito-borne flavivirus Zika virus (ZIKV) poses challenges to screening human- and animal -derived products used in the manufacture of biologicals. Here, we report the results of an in vitro study where detector cell lines were challenged with African and Asian lineages of ZIKV. We demonstrate that this pathogen is robustly detectable by in vitro assay, thereby providing assurance of detection of ZIKV, and in turn underpinning the robustness of in vitro virology assays in safety testing of biologicals

Description strategies to make an interactive science simulation accessible

Interactive simulations are increasingly important in science education, yet most are inaccessible to blind learners. In developing an accessible prototype of a PhET interactive science simulation, we encountered significant challenges in providing screen reader access, including the need to: 1) describe unpredictable event sequences, 2) cue productive interactions, and 3) to simultaneously convey multiple changes. To address these challenges, we extended existing practices for verbal description of visual interactive content, and we created new strategies for developing rich description for accessible interactive science simulations

Direct imaging of a massive dust cloud around R Coronae Borealis

We present recent polarimetric images of the highly variable star R CrB using ExPo and archival WFPC2 images from the HST. We observed R CrB during its current dramatic minimum where it decreased more than 9 mag due to the formation of an obscuring dust cloud. Since the dust cloud is only in the line-of-sight, it mimics a coronograph allowing the imaging of the star's circumstellar environment. Our polarimetric observations surprisingly show another scattering dust cloud at approximately 1.3" or 2000 AU from the star. We find that to obtain a decrease in the stellar light of 9 mag and with 30% of the light being reemitted at infrared wavelengths (from R CrB's SED) the grains in R CrB's circumstellar environment must have a very low albedo of approximately 0.07%. We show that the properties of the dust clouds formed around R CrB are best fitted using a combination of two distinct populations of grains size. The first are the extremely small 5 nm grains, formed in the low density continuous wind, and the second population of large grains (~0.14 {\mu}m) which are found in the ejected dust clouds. The observed scattering cloud, not only contains such large grains, but is exceptionally massive compared to the average cloud.Comment: 8 pages, 7 figures published in A&

Molybdenum Isotopes from a Neutron Burst

The molybdenum isotopes in two silicon carbide X grains have been studied with resonant-ionization mass spectrometry (1). The resulting isotopic patterns are anomalous and quite puzzling. In particular, the grains show large excesses in 95Mo and 97Mo. Such an isotopic signature is distinctly different from the s-process pattern seen in the mainstream SiC grains in which 96Mo and 98Mo excesses pre-vail. It is also different from the expected r-process pattern for which the largest expected excess would be at 100Mo. The X grain Mo isotopic patterns suggest a different origin for these isotopes than the classical s- and r-processes

The ongoing pursuit of R Coronae Borealis stars: the ASAS-3 survey strikes again

CONTEXT: R Coronae Borealis stars( RCBs) are rare, hydrogen-deficient, carbon rich super giant variable stars that are likely the evolved merger products of pairs of CO and He white dwarfs. Only 55 RCB stars have been found in our galaxy and their distribution on the sky is weighted heavily by microlensing survey field positions. A less biased wide-area survey would enable us to test competing evolutionary scenarios, understand the population or populations that produce RCBs, and constrain their formation rate. AIMS: The ASAS-3 survey monitored the sky south of declination +28deg between 2000 and 2010 to a limiting magnitude of V = 14. We searched ASAS-3 for RCB variables using several different methods to ensure that the probability of RCB detection was as high as possible and to reduce selection biases based on luminosity, temperature, dust production activity and shell brightness. METHODS: Candidates whose light curves were visually inspected were pre-selected based on their infrared (IR) excesses due to warm dust in their circumstellar shells using the WISE and/or 2MASS catalogues. Criteria on light curve variability were also applied when necessary to minimise the number of objects. Initially, we searched for RCB stars among the ASAS-3 ACVS1.1 variable star catalogue, then among the entire ASAS-3 south source catalogue, and finally directly interrogated the light curve database for objects that were not catalogued in either of those. We then acquired spectra of 104 stars to determine their real nature using the SSO/WiFeS spectrograph. RESULTS: We report 21 newly discovered RCB stars and 2 new DY Per stars. Two previously suspected RCB candidates were also spectroscopically confirmed. Our methods allowed us to extend our detection efficiency to fainter magnitudes that would not have been easily accessible to discovery techniques based onlight curve variability. The overall detection efficiencyis about 90% for RCBs with maximum light brighter than V ∼13. CONCLUSIONS: With these new discoveries, 76 RCBs are now known in our Galaxy and 22 in the Magellanic Clouds. This growing sample is of great value to constrain the peculiar and disparate atmosphere composition of RCBs. Most importantly, we show that the spatial distribution and apparent magnitudes of Galactic RCB stars is consistent with RCBs being part of the Galactic bulge population.Department of HE and Training approved lis

Abundances of Linear Carbon-Chain Molecules in Supernovae

This paper continues our effort to under-stand the condensation of carbon solids in a gas of pure C and O atoms when these exist within the interior of an expanding young supernova. This setting has a sufficiently large number of energetic electrons that the CO molecule is disrupted with a lifetime of a few months, causing the abundance of CO to be no greater than 1% or so of the C abundance. As a consequence, the CO molecule cannot consume the available C atoms, even when the O abundance exceeds that of