COPROLITES FROM CALVERT CLIFFS: MIOCENE FECAL PELLETS AND BURROWED CROCODILIAN DROPPINGS FROM THE CHESAPEAKE GROUP OF MARYLAND, U.S.A.

New finds of remarkable coprolites (fossilized feces) are here reported from the famous Miocene marine sediments of the Chesapeake Group exposed along Calvert Cliffs (Maryland, U.S.A.). Although vertebrate coprolites have been described from these deposits, here we provide the first description of tiny invertebrate fecal pellets. Thus far, these fecal pellets have only been found in the upper Miocene (Tortonian) St. Marys Formation. The micro-coprolites represent the coprulid ichnospecies Coprulus oblongus. The fecal pellets are found in small clusters or strings of dozens to masses of many hundreds. Pellets range in size from approximately 0.4 – 2.0 mm wide by 1.0 – 5.0 mm long, and range in color from gray to brownish black. Their length/diameter ratio is always very nearly 2. These coprulids have been found in a variety of Miocene fossils/concretions including a uranoscopid neurocranium, naticid gastropod, bivalve shells, barnacle tests, and in pellet-backfilled sinuous burrows through sediment. Because the fecal pellets are often found in tiny spaces or spaces thought to be inaccessible to shelled invertebrates, the coprulids are attributed to small and soft-bodied polychaetes or other annelids. Some coprolites attributed to crocodilians from the lower-middle Miocene Calvert Formation were tunneled into, presumably the result of coprophagy, by some unknown kind of organism(s). These compound trace fossils are in the form of burrows that excavate the coprolites, the sides of which are sculptured by scratch/gouge marks.

Theoretical studies on the two-photon absorption of II–VI semiconductor nano clusters

Semiconductor clusters, ZnnOn, ZnnSn, and CdnSn (n = 2–8), were optimized and the corresponding stable structures were acquired. The symmetry, bond length, bond angle, and energy gap between HOMO and LUMO were analyzed. According to reasonable calculation and comparative analysis for small clusters Zn2O2, Zn2S2, and Cd2S2, an effective method based on density function theory (DFT) and basis set which lay the foundation for the calculation of the large clusters have been obtained. The two-photon absorption (TPA) results show that for the nano clusters with planar configuration, sizes play important role on the TPA cross section, while symmetries determine the TPA cross section under circumstance of 3D stable structures. All our conclusions provide theoretical support for the development of related experiments.

A DFT study of SenTenclusters

First principle calculations have been performed to study the characteristic properties of SenTen (n=5-10) clusters. Present study reveals that the properties of these small clusters are consistent with the properties...

Solvent-Induced Assembly of One-Patch Silica Nanoparticles into Robust Clusters, Wormlike Chains and Bilayers

We report the synthesis and solvent-induced assembly of one-patch silica nanoparticles in the size range of 100–150 nm. They consisted, as a first approximation, of silica half-spheres of which the truncated face was itself concave and carried in its center a polymeric patch made of grafted polystyrene chains. The multistage synthesis led to 98% pure batches and allowed a fine control of the patch-to-particle size ratio from 0.69 to 1.54. The self-assembly was performed in equivolume mixtures of tetrahydrofuran and ethanol, making the polymeric patches sticky and ready to coalesce together. The assembly kinetics was monitored by collecting samples over time and analyzing statistically their TEM images. Small clusters, such as dimers, trimers, and tetramers, were formed initially and then evolved in part into micelles. Accordingly to previous simulation studies, more or less branched wormlike chains and planar bilayers were observed in the long term, when the patch-to-particle size ratio was high enough. We focused also on the experimental conditions that could allow preparing small clusters in a good morphology yield.

The role of geographical factor in the formation and development of human potential

This article summarizes the results of the study on development and analysis of the typology of Russian regions according to criteria for the quality of human potential. Prior to this, ten clusters of this typology were studied separately, exceptions from the typical entry into clusters with neighboring regions were considered. Although among the qualitative characteristics of human potential there was not a single one, reflecting the territorial location of the regions, but in the typology they were distributed precisely on the basis of geography. Unobserved factors, whose effects on human potential are mediated by study-driven indicators, played a crucial role in clustering regions. Such a result naturally brought us to the works of L.N. Gumilev, which were studied in terms of the role played by geography of territories, landscapes and climate in the formation of human potential. In many ways, geographical conditions also determine the nature of economic activities, which form the abilities and skills of the population that characterize human potential. It was concluded that the typology of regions obtained on the characteristics of human potential corresponds to the composition of federal districts, with the exception of four small clusters, three of which — with a pronounced raw material specialization and one — with the financial advantages of two capital cities. Accordingly, this implies the expediency of using the administrations of federal districts to solve the problem of improving the quality of human potential. The protracted process of giving administrative status to federal districts can be completed by setting them the important social task of developing and implementing a strategy for improving the qualitative characteristic of population.

Statewide Longitudinal Trends in Transmitted HIV-1 Drug Resistance in Rhode Island, USA

Background HIV-1 transmitted drug resistance (TDR) remains a global challenge that can impact care, yet its comprehensive assessment is limited and heterogenous. We longitudinally characterized statewide TDR in Rhode Island. Methods Demographic and clinical data from treatment-naïve individuals were linked to protease, reverse transcriptase and integrase sequences, routinely obtained over 2004–2020. TDR extent, trends, impact on 1 st-line regimens, and association with transmission networks were assessed using Stanford Database, Mann-Kendall statistic, and phylogenetic tools. Results In 1,123 individuals, TDR to any antiretroviral increased from 8% (2004) to 26% (2020), driven by NNRTI (5-18%), and less NRTI TDR (2-8%). Dual- and triple-class TDR were low and major InSTI resistance was absent. Predicted intermediate-high resistance was in 77% of those with TDR, with differential suppression patterns. Among all individuals, 34% were in molecular clusters, some only with members with TDR who shared mutations. Among clustered individuals, people with TDR were more likely in small clusters. Conclusions In a unique (statewide) assessment over 2004–2020, TDR increased, primarily, but not solely, driven by NNRTIs, impacting antiretroviral regimens. Limited TDR to multi-class regimens and PrEP are encouraging, however, surveillance and its integration with molecular epidemiology should continue, to potentially improve care and prevention interventions.

Quantification of CH₄ coal mining emissions in Upper Silesia by passive airborne remote sensing observations with the Methane Airborne MAPper (MAMAP) instrument during the CO₂ and Methane (CoMet) campaign

Methane (CH4) is the second most important anthropogenic greenhouse gas, whose atmospheric concentration is modulated by human-induced activities, and it has a larger global warming potential than carbon dioxide (CO2). Because of its short atmospheric lifetime relative to that of CO2, the reduction of the atmospheric abundance of CH4 is an attractive target for short-term climate mitigation strategies. However, reducing the atmospheric CH4 concentration requires a reduction of its emissions and, therefore, knowledge of its sources. For this reason, the CO2 and Methane (CoMet) campaign in May and June 2018 assessed emissions of one of the largest CH4 emission hot spots in Europe, the Upper Silesian Coal Basin (USCB) in southern Poland, using top-down approaches and inventory data. In this study, we will focus on CH4 column anomalies retrieved from spectral radiance observations, which were acquired by the 1D nadir-looking passive remote sensing Methane Airborne MAPper (MAMAP) instrument, using the weighting-function-modified differential optical absorption spectroscopy (WFM-DOAS) method. The column anomalies, combined with wind lidar measurements, are inverted to cross-sectional fluxes using a mass balance approach. With the help of these fluxes, reported emissions of small clusters of coal mine ventilation shafts are then assessed. The MAMAP CH4 column observations enable an accurate assignment of observed fluxes to small clusters of ventilation shafts. CH4 fluxes are estimated for four clusters with a total of 23 ventilation shafts, which are responsible for about 40 % of the total CH4 mining emissions in the target area. The observations were made during several overflights on different days. The final average CH4 fluxes for the single clusters (or sub-clusters) range from about 1 to 9 t CH4 h−1 at the time of the campaign. The fluxes observed at one cluster during different overflights vary by as much as 50 % of the average value. Associated errors (1σ) are usually between 15 % and 59 % of the average flux, depending mainly on the prevailing wind conditions, the number of flight tracks, and the magnitude of the flux itself. Comparison to known hourly emissions, where available, shows good agreement within the uncertainties. If only emissions reported annually are available for comparison with the observations, caution is advised due to possible fluctuations in emissions during a year or even within hours. To measure emissions even more precisely and to break them down further for allocation to individual shafts in a complex source region such as the USCB, imaging remote sensing instruments are recommended.

Modelling the Melting of Gallium Clusters: A Path to Understanding Molecular Solids

<p>Gallium is a molecular solid with many unique properties. Comprised of Ga2 dimers but exhibiting metal-like electronic characteristics, gallium may be deemed a molecular metal. The role of this dual covalent-metallic nature may explain gallium’s fascinating thermodynamic behaviour. While bulk gallium melts at 303 K, clusters with only 10’s of atoms melt at temperatures between 500 and 800 K, according to experiment. The measured specific heat curves exhibit a strong size-sensitivity, where the addition of a single atom can alter the melting temperature by up to 100 K. This research addresses the relationship of electronic structure to the melting behaviour in small gallium clusters through a parallel tempering implementation of first-principles molecular dynamics simulations. These simulations cover 11 cluster sizes and two charge states, including neutral clusters sized 7-12 atoms and cationic clusters sized 32-35 atoms. The modelling of small clusters sets a lower size limit for melting and illustrates that greater-than-bulk melting is not universal for small gallium clusters. The larger cluster sizes allow for a direct comparison to experimental data. Each simulation reveals that the clusters have a non-covalent nature more similar to the metallic surface structure of bulk gallium than its covalently bonded interior. The dramatic lowering of melting temperatures and cluster stabilities with single atom additions supports the conclusion that the difference in the nature of bonding between bulk and clusters accounts for the melting temperature discrepancy. Finally, in order to gain additional insight into the nature of bonding in molecular solids, the cohesive energies of the solid halogens are calculated by the method of increments. These calculations investigate the relative N-body correlation energy contributions to the total cohesive energy for solid Cl2, Br2 and I2.</p>

Modelling the Melting of Gallium Clusters: A Path to Understanding Molecular Solids

<p>Gallium is a molecular solid with many unique properties. Comprised of Ga2 dimers but exhibiting metal-like electronic characteristics, gallium may be deemed a molecular metal. The role of this dual covalent-metallic nature may explain gallium’s fascinating thermodynamic behaviour. While bulk gallium melts at 303 K, clusters with only 10’s of atoms melt at temperatures between 500 and 800 K, according to experiment. The measured specific heat curves exhibit a strong size-sensitivity, where the addition of a single atom can alter the melting temperature by up to 100 K. This research addresses the relationship of electronic structure to the melting behaviour in small gallium clusters through a parallel tempering implementation of first-principles molecular dynamics simulations. These simulations cover 11 cluster sizes and two charge states, including neutral clusters sized 7-12 atoms and cationic clusters sized 32-35 atoms. The modelling of small clusters sets a lower size limit for melting and illustrates that greater-than-bulk melting is not universal for small gallium clusters. The larger cluster sizes allow for a direct comparison to experimental data. Each simulation reveals that the clusters have a non-covalent nature more similar to the metallic surface structure of bulk gallium than its covalently bonded interior. The dramatic lowering of melting temperatures and cluster stabilities with single atom additions supports the conclusion that the difference in the nature of bonding between bulk and clusters accounts for the melting temperature discrepancy. Finally, in order to gain additional insight into the nature of bonding in molecular solids, the cohesive energies of the solid halogens are calculated by the method of increments. These calculations investigate the relative N-body correlation energy contributions to the total cohesive energy for solid Cl2, Br2 and I2.</p>