Physical conditions in the primitive solar nebula

Physical conditions for model of primitive solar nebul

Explosive Nucleosynthesis: What we learned and what we still do not understand

This review touches on historical aspects, going back to the early days of nuclear astrophysics, initiated by B$^2$FH and Cameron, discusses (i) the required nuclear input from reaction rates and decay properties up to the nuclear equation of state, continues (ii) with the tools to perform nucleosynthesis calculations and (iii) early parametrized nucleosynthesis studies, before (iv) reliable stellar models became available for the late stages of stellar evolution. It passes then through (v) explosive environments from core-collapse supernovae to explosive events in binary systems (including type Ia supernovae and compact binary mergers), and finally (vi) discusses the role of all these nucleosynthesis production sites in the evolution of galaxies. The focus is put on the comparison of early ideas and present, very recent, understanding.Comment: 11 pages, to appear in Springer Proceedings in Physics (Proc. of Intl. Conf. "Nuclei in the Cosmos XV", LNGS Assergi, Italy, June 2018

Impact Factor: outdated artefact or stepping-stone to journal certification?

A review of Garfield's journal impact factor and its specific implementation as the Thomson Reuters Impact Factor reveals several weaknesses in this commonly-used indicator of journal standing. Key limitations include the mismatch between citing and cited documents, the deceptive display of three decimals that belies the real precision, and the absence of confidence intervals. These are minor issues that are easily amended and should be corrected, but more substantive improvements are needed. There are indications that the scientific community seeks and needs better certification of journal procedures to improve the quality of published science. Comprehensive certification of editorial and review procedures could help ensure adequate procedures to detect duplicate and fraudulent submissions.Comment: 25 pages, 12 figures, 6 table

Effect of bio-engineering on size, shape, composition and rigidity of bacterial microcompartments

Bacterial microcompartments (BMCs) are proteinaceous organelles that are found in a broad range of bacteria and are composed of an outer shell that encases an enzyme cargo representing a specific metabolic process. The outer shell is made from a number of different proteins that form hexameric and pentameric tiles, which interact to allow the formation of a polyhedral edifice. We have previously shown that the Citrobacter freundii BMC associated with 1,2-propanediol utilization can be transferred into Escherichia coli to generate a recombinant BMC and that empty BMCs can be formed from just the shell proteins alone. Herein, a detailed structural and proteomic characterization of the wild type BMC is compared to the recombinant BMC and a number of empty BMC variants by 2D-gel electrophoresis, mass spectrometry, transmission electron microscopy (TEM) and atomic force microscopy (AFM). Specifically, it is shown that the wild type BMC and the recombinant BMC are similar in terms of composition, size, shape and mechanical properties, whereas the empty BMC variants are shown to be smaller, hollow and less malleable

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

Terrestrial implications for the maritime geoarchaeological resource: A view from the Lower Palaeolithic

Stone tools and faunal remains have been recovered from the English Channel and the North Sea through trawling, dredging for aggregates, channel clearance, and coring. These finds highlight the potential for a maritime Lower Palaeolithic archaeological resource. It is proposed here that any Lower Palaeolithic artefacts, faunal remains, and sediments deposited in the maritime zone during dry, low-stand phases were once (and may still be) contextually similar to their counterparts in the terrestrial Lower Palaeolithic records of north-western Europe. Given these similarities, can interpretive models and analytical frameworks developed for terrestrial archaeology be profitably applied to an assessment of the potential value of any maritime resource? The terrestrial geoarchaeological resource for the Lower Palaeolithic is dominated by artefacts and ecofacts that have been fluvially reworked. The spatio-temporal resolution of these data varies from entire river valleys and marine isotope stages to river channel gravel bar surfaces and decadal timescales, thus supporting a variety of questions and approaches. However, the structure of the terrestrial resource also highlights two fundamental limitations in current maritime knowledge that can restrict the application of terrestrial approaches to any potential maritime resource: (i) how have the repetitive transgressions and regressions of the Middle and Late Pleistocene modified the terrace landforms and sediments associated with the river systems of the English Channel and southern North Sea basins?; and (ii) do the surviving submerged terrace landforms and fluvial sedimentary deposits support robust geochronological models, as is the case with the classical terrestrial terrace sequences? This paper highlights potential approaches to these questions, and concludes that the fluvial palaeogeography, Pleistocene fossils, and potential Lower Palaeolithic artefacts of the maritime geoarchaeological resource can be profitably investigated in future as derived, low-resolution data sets, facilitating questions of colonisation, occupation, demography, and material culture

Effect of promoter architecture on the cell-to-cell variability in gene expression

According to recent experimental evidence, the architecture of a promoter, defined as the number, strength and regulatory role of the operators that control the promoter, plays a major role in determining the level of cell-to-cell variability in gene expression. These quantitative experiments call for a corresponding modeling effort that addresses the question of how changes in promoter architecture affect noise in gene expression in a systematic rather than case-by-case fashion. In this article, we make such a systematic investigation, based on a simple microscopic model of gene regulation that incorporates stochastic effects. In particular, we show how operator strength and operator multiplicity affect this variability. We examine different modes of transcription factor binding to complex promoters (cooperative, independent, simultaneous) and how each of these affects the level of variability in transcription product from cell-to-cell. We propose that direct comparison between in vivo single-cell experiments and theoretical predictions for the moments of the probability distribution of mRNA number per cell can discriminate between different kinetic models of gene regulation.Comment: 35 pages, 6 figures, Submitte

Diffusion of Subsidized ACTs in Accredited Drug Shops in Tanzania: Determinants of Stocking and Characteristics of Early and Late Adopters.

Many households in sub-Saharan Africa utilize the private sector as a primary source of treatment for malaria episodes. Expanding access to effective treatment in private drug shops may help reduce incidence of severe disease and mortality. This research leveraged a longitudinal survey of stocking of subsidized artemisinin combination therapies (ACTs), an effective anti-malarial, in Accredited Drug Dispensing Outlets (ADDOs) in two regions of Tanzania. This provided a unique opportunity to explore shop and market level determinants of product diffusion in a developing country retail market. 356 ADDOs in the Rukwa and Mtwara regions of Tanzania were surveyed at seven points between Feb 2011 and May 2012. Shop level audits were used to measure the availability of subsidized ACTs at each shop. Data on market and shop level factors were collected during the survey and also extracted from GIS layers. Regression and network based methodologies were used. Shops classified as early and late adopters, following Rogers' model of product diffusion, were compared. The Bass model of product diffusion was applied to determine whether shops stocked ACTs out of a need to imitate market competitors or a desire to satisfy customer needs. Following the introduction of a subsidy for ACTs, stocking increased from 12% to nearly 80% over the seven survey rounds. Stocking was influenced by higher numbers of proximal shops and clinics, larger customer traffic and the presence of a licensed pharmacist. Early adopters were characterized by a larger percentage of customers seeking care for malaria, a larger catchment and sourcing from specific wholesalers/suppliers. The Bass model of product diffusion indicated that shops were adopting products in response to competitor behavior, rather than customer demand. Decisions to stock new pharmaceutical products in Tanzanian ADDOs are influenced by a combination of factors related to both market competition and customer demand, but are particularly influenced by the behavior of competing shops. Efforts to expand access to new pharmaceutical products in developing country markets could benefit from initial targeting of high profile shops in competitive markets and wholesale suppliers to encourage faster product diffusion across all drug retailers

The deuteron: structure and form factors

A brief review of the history of the discovery of the deuteron in provided. The current status of both experiment and theory for the elastic electron scattering is then presented.Comment: 80 pages, 33 figures, submited to Advances in Nuclear Physic