ABSTRACT Big Bang nucleosynthesis (BBN) theory predicts the abundances of the light elements D, 3He, 4He, and 7Li produced in the early universe. The primordial abundances of D and 4He inferred from ...observational data are in good agreement with predictions, however, BBN theory overestimates the primordial 7Li abundance by about a factor of three. This is the so-called "cosmological lithium problem." Solutions to this problem using conventional astrophysics and nuclear physics have not been successful over the past few decades, probably indicating the presence of new physics during the era of BBN. We have investigated the impact on BBN predictions of adopting a generalized distribution to describe the velocities of nucleons in the framework of Tsallis non-extensive statistics. This generalized velocity distribution is characterized by a parameter q, and reduces to the usually assumed Maxwell-Boltzmann distribution for q = 1. We find excellent agreement between predicted and observed primordial abundances of D, 4He, and 7Li for 1.069 ≤ q ≤ 1.082, suggesting a possible new solution to the cosmological lithium problem.
Black carbon (BC) from biomass and fossil fuel combustion alters chemical and physical properties of the atmosphere and snow albedo, yet little is known about its emission or deposition histories. ...Measurements of BC, vanillic acid, and non-sea-salt sulfur in ice cores indicate that sources and concentrations of BC in Greenland precipitation varied greatly since 1788 as a result of boreal forest fires and industrial activities. Beginning about 1850, industrial emissions resulted in a sevenfold increase in ice-core BC concentrations, with most change occurring in winter. BC concentrations after about 1951 were lower but increasing. At its maximum from 1906 to 1910, estimated surface climate forcing in early summer from BC in Arctic snow was about 3 watts per square meter, which is eight times the typical preindustrial forcing value.
Activation of free fatty acid receptor 1 (GPR40) by synthetic partial and full agonists occur via distinct allosteric sites. A crystal structure of GPR40-TAK-875 complex revealed the allosteric site ...for the partial agonist. Here we report the 2.76-Å crystal structure of human GPR40 in complex with a synthetic full agonist, compound 1, bound to the second allosteric site. Unlike TAK-875, which acts as a Gα
-coupled partial agonist, compound 1 is a dual Gα
and Gα
-coupled full agonist. compound 1 binds in the lipid-rich region of the receptor near intracellular loop 2 (ICL2), in which the stabilization of ICL2 by the ligand is likely the primary mechanism for the enhanced G protein activities. The endogenous free fatty acid (FFA), γ-linolenic acid, can be computationally modeled in this site. Both γ-linolenic acid and compound 1 exhibit positive cooperativity with TAK-875, suggesting that this site could also serve as a FFA binding site.
This study establishes connections between day‐to‐day variability of sea level pressure (SLP), surface air temperature (T), and precipitation (PR) and that of fine particulate matter (PM2.5) air ...pollution. In particular, matrix methods were applied to quantify statistical relationships between the daily anomalies of these fields over the continental US, during the 7 year study period. The anomalies were defined as deviations from nonoverlapping 2 week averages to focus on synoptic scales. The main effect of synoptic weather systems on day‐to‐day variability of PM2.5 air pollution consists of formation of a high‐pollution area behind propagating anticyclones and a low‐pollution region in the wake of cyclones. This property is rationalized by the fact that the regions just west of the eastward‐propagating cyclones (or anticyclones) experience the cyclonic (anticyclonic) conditions detrimental to (favorable for) PM2.5 accumulation for the longest period of time. The advection of climatological PM2.5 concentrations by anomalous winds associated with propagating weather systems may also contribute to the formation of the above PM2.5 anomalies, but does not represent a dominant effect. This “synoptically controlled” PM2.5 variability accounts for as much as 30% of the total high‐pass filtered particulate matter (PM) variance in the midwest region throughout the year (irrespective of season), while it is substantially less pronounced along the coasts and in the southern US. The authors argue that the apparent correlations between PM and T, as well as PM and PR anomalies do not imply causality, but rather show that these quantities are commonly related to the external factors associated with the life cycle of midlatitude synoptic storms.
Abstract
The dynamics of a nuclear open quantum system could be revealed in the correlations between the breakup fragments of halo nuclei. The breakup mechanism of a proton halo nuclear system is of ...particular interest as the Coulomb polarization may play an important role, which, however, remains an open question. Here we use a highly efficient silicon detector array and measure the correlations between the breakup fragments of
8
B incident on
120
Sn at near-barrier energies. The energy and angular correlations can be explained by a fully quantum mechanical method based on the state-of-the-art continuum discretized coupled channel calculations. The results indicate that, compared to the neutron halo nucleus
6
He,
8
B presents distinctive reaction dynamics: the dominance of the elastic breakup. This breakup occurs mainly via the short-lived continuum states, almost exhausts the
7
Be yield, indicating the effect of Coulomb polarization on the proton halo state. The correlation information reveals that the prompt breakup mechanism dominates, occurring predominantly on the outgoing trajectory. We also show that, as a large environment, the continuum of
8
B breakup may not significantly influence elastic scattering and complete fusion.
Since 2008, automatic, multiple assessment options have been utilised in selected undergraduate meteorology courses at the University of Wisconsin-Milwaukee. Motivated by a desire to reduce stress ...among students, the assessment methodology includes examination-heavy and homework-heavy alternatives, differing by an adjustable 15% of the overall course grade. Students do not need to commit a priori to one particular assessment option, as the more beneficial of two alternative assessment schemes is automatically chosen at the end of the semester. An analysis of assessment score differences reveals that end-of-semester assessments increased by more than 1% for 48% of the students enrolled, a consequential increase which can improve a student's assessment by a fractional grade. Score differences among the two assessment alternatives tend to be smaller for higher achieving students, and larger for the middle- and lower achieving students. Score differences larger than 3% were rare. Limited survey results indicate that students understand and appreciate the assessment scheme, and feel that it reduces stress and may improve their academic performance. The automatic, multiple assessment methodology presents no risk to either student or instructor, as students can only benefit and virtually no effort is required of the instructor.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
There is significant concern regarding potential impairment of fish reproduction associated with endocrine disrupting chemicals. Aromatase (CYP19) is a steroidogenic enzyme involved in the ...conversion of androgens to estrogens. Inhibition of aromatase by chemicals can result in reduced concentrations of estrogens leading to adverse reproductive effects. These effects have been extensively investigated in a small number of laboratory model fishes, such as fathead minnow (Pimephales promelas), Japanese medaka (Oryzias latipes), and zebrafish (Danio rerio). But, differences in sensitivity among species are largely unknown. Therefore, this study took a first step toward understanding potential differences in sensitivity to aromatase inhibitors among fishes. Specifically, a standard in vitro aromatase inhibition assay using subcellular fractions of whole tissue homogenates was used to evaluate the potential sensitivity of 18 phylogenetically diverse species of freshwater fish to the nonsteroidal aromatase inhibitor fadrozole. Sensitivity to fadrozole ranged by more than 52-fold among these species. Five species were further investigated for sensitivity to up to 4 additional nonsteroidal aromatase inhibitors, letrozole, imazalil, prochloraz, and propiconazole. Potencies of each of these chemicals relative to fadrozole ranged by up to 2 orders of magnitude among the 5 species. Fathead minnow, Japanese medaka, and zebrafish were among the least sensitive to all the investigated chemicals; therefore, ecological risks of aromatase inhibitors derived from these species might not be adequately protective of more sensitive native fishes. This information could guide more objective ecological risk assessments of native fishes to chemicals that inhibit aromatase.
Indicators of environmental policies in force in Mexico, fossil fuels will continue to be used in industrial sectors, especially marine fuels, such as marine diesel oil, in port systems for some ...time. Considering this, we have evaluated several methods corresponding to a top-down system for determining fuel consumption and sulfur dioxide atmospheric emissions for the port of Veracruz in 2020 by type of ship on a daily resolution, considering a sulfur content of 0.5% mass by mass in marine fuel. After analyzing seven methods for determining sulfur dioxide atmospheric emission levels, Goldsworthy’s method was found to be the best option to characterize this port. The port system has two maritime zones, one of which is in expansion, which represented 55.66% of fuel consumption and 23.05% of atmospheric emissions according to the typology of vessels. We found that higher fuel consumption corresponded to container vessels, and tanker vessels represented higher atmospheric emission levels in the berthing position. The main differences that we found in the analysis of the seven methods of the top-down system corresponded to the load factor parameter, main and auxiliary engine power, and estimation of fuel consumption by type of vessel.
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