Development of Improved Torsional Potentials in Classical Force Field Models of Poly (Lactic Acid)

In this work, existing force field descriptions of poly (lactic acid), or PLA, were improved by modifying the torsional potential energy terms to more accurately model the bond rotational behavior of PLA. Extensive calculations were carried out using density functional theory (DFT), for small PLA molecules in vacuo, and also using DFT with a continuum model to approximate the electronic structure of PLA in its condensed phase. From these results, improved force field parameters were developed using a combination of the OPLS and CHARMM force fields. The new force field, PLAFF2, is an update to the previously developed PLAFF model developed in David Bruce\u27s group, and results in more realistic conformational distributions during simulation of bulk amorphous PLA. It is demonstrated that the PLAFF2 model retains the accuracy of the original PLAFF in simulating the crystalline α polymorph of PLA. The PLAFF2 model has superior performance to any other publicly available force field for use with PLA; hence, we recommend its use in future modeling studies on the material, whether in its crystalline or amorphous form

A Computational Approach for the Rational Design of Bimetallic Clusters for Ethanol Formation from Syn-gas

A major challenge associated with the synthesis of ethanol from syn-gas is an inability to find a low-cost catalyst that promotes the proper combination of CO dissociation and CO insertion steps, so as to yield ethanol as the primary reaction product and inhibit the formation of methane, methanol, longer chain alkanes, and other coking reaction products. We used quantum mechanical simulations for the rational design of bimetallic catalysts. Several promising 13-atom bimetallic clusters were selected by the identification of key reaction descriptors for ethanol formation reaction. Density Functional Theory (DFT) simulations and Bronsted-Evans-Polanyi (BEP) relations were used to map out the full reaction mechanism from syn-gas to ethanol. Selectivity analysis was conducted including hydrocarbons, methanol, acetaldehyde and ethanol as products. Microkinetic models were built, considering all necessary adsorption and reaction steps as well as the diffusion of intermediate species between different metal surface sites. More general selectivity trends were identified by altering the surface concentrations of various metal sites. These simulations indicate the nature and stability of the various bimetallic nanocatalysts and more importantly identify specific metal combinations that are ideally suited for ethanol production

Mindfulness Training for Judges: Mind Wandering and the Development of Cognitive Resilience

The benefits of mindfulness practices for lawyers have been the subject of broad discussion within the profession for a number of years. Increasingly, this discussion has expanded to include judges and the work of the judiciary. In this article we explore more deeply the relevance of mindfulness to judges, and in particular, how it can support their resilience, health, and well-being, as well as their cognitive functioning. We hope to educate and support judges who would like to gain greater mastery over their cognitive capacity and emotional well-being. Recognizing that the full breadth of this subject is beyond an article of this length, we focus on a primary vulnerability to which we are all susceptible but which can be especially consequential for judges in their high-stakes world of decision making: mind wandering. We consider some ways this vulnerability may limit judges’ performance and well-being and review a growing body of scientific research, which examines the benefits of mindfulness training to mitigate this vulnerability by helping to bolster attention and working memory capacity. We then offer simple mindfulness practices, which have been found to be useful in developing attention and working memory capacity, which we term “skills” as they may be developed through ongoing mindfulness practice

Agricultural contamination impacts antibiotic resistance gene abundances in river bed sediment temporally

Kewaunee County, Wisconsin is an agricultural area dominated by concentrated animal feeding operations and manure fertilized cropland. The objective of this study was to characterize chemical and antibiotic resistance gene (ARG) profiles of 20 surface water locations in Kewaunee County to better understand relationships between agricultural contamination and ARG abundance over one year. Surface water (n = 101) and bed sediment (n = 93) were collected from 20 sites during five timepoints between July 2016 and May 2017. Samples were analyzed for six genes (erm(B), tet(W), sul1, qnrA, intI1 and 16S rRNA) and water chemistry and pollution indicators. qnrA, intI1 and sul1 genes in surface water were significantly higher than erm(B) and tet(W); however, no difference was present in sediment samples. Redundancy analysis identified positive correlations of nitrate, Escherichia coli, and coliforms with tet(W) and intI1 genes in sediment and intI1, sul1 and tet(W) genes in water. Temporal patterns of ARG abundance were identified with significantly higher gene abundances found in sediment during Kewaunee County\u27s manure fertilization period; however, surface water patterns were not distinct. Together, these results suggest Kewaunee County sediments serve as a site of accumulation for non-point source agricultural pollution and ARGs on a temporal scale associated with manure fertilization

Insights into the Ecology and Evolutionary Success of Crocodilians Revealed through Bite-Force and Tooth-Pressure Experimentation

BackgroundCrocodilians have dominated predatory niches at the water-land interface for over 85 million years. Like their ancestors, living species show substantial variation in their jaw proportions, dental form and body size. These differences are often assumed to reflect anatomical specialization related to feeding and niche occupation, but quantified data are scant. How these factors relate to biomechanical performance during feeding and their relevance to crocodilian evolutionary success are not known.Methodology/Principal FindingsWe measured adult bite forces and tooth pressures in all 23 extant crocodilian species and analyzed the results in ecological and phylogenetic contexts. We demonstrate that these reptiles generate the highest bite forces and tooth pressures known for any living animals. Bite forces strongly correlate with body size, and size changes are a major mechanism of feeding evolution in this group. Jaw shape demonstrates surprisingly little correlation to bite force and pressures. Bite forces can now be predicted in fossil crocodilians using the regression equations generated in this research.Conclusions/SignificanceCritical to crocodilian long-term success was the evolution of a high bite-force generating musculo-skeletal architecture. Once achieved, the relative force capacities of this system went essentially unmodified throughout subsequent diversification. Rampant changes in body size and concurrent changes in bite force served as a mechanism to allow access to differing prey types and sizes. Further access to the diversity of near-shore prey was gained primarily through changes in tooth pressure via the evolution of dental form and distributions of the teeth within the jaws. Rostral proportions changed substantially throughout crocodilian evolution, but not in correspondence with bite forces. The biomechanical and ecological ramifications of such changes need further examination

A New Horned Crocodile from the Plio-Pleistocene Hominid Sites at Olduvai Gorge, Tanzania

BACKGROUND: The fossil record reveals surprising crocodile diversity in the Neogene of Africa, but relationships with their living relatives and the biogeographic origins of the modern African crocodylian fauna are poorly understood. A Plio-Pleistocene crocodile from Olduvai Gorge, Tanzania, represents a new extinct species and shows that high crocodylian diversity in Africa persisted after the Miocene. It had prominent triangular "horns" over the ears and a relatively deep snout, these resemble those of the recently extinct Malagasy crocodile Voay robustus, but the new species lacks features found among osteolaemines and shares derived similarities with living species of Crocodylus. METHODOLOGY/PRINCIPAL FINDINGS: The holotype consists of a partial skull and skeleton and was collected on the surface between two tuffs dated to approximately 1.84 million years (Ma), in the same interval near the type localities for the hominids Homo habilis and Australopithecus boisei. It was compared with previously-collected material from Olduvai Gorge referable to the same species. Phylogenetic analysis places the new form within or adjacent to crown Crocodylus. CONCLUSIONS/SIGNIFICANCE: The new crocodile species was the largest predator encountered by our ancestors at Olduvai Gorge, as indicated by hominid specimens preserving crocodile bite marks from these sites. The new species also reinforces the emerging view of high crocodylian diversity throughout the Neogene, and it represents one of the few extinct species referable to crown genus Crocodylus

Geographic Distribution, Habitat, Reproduction, and Conservation Status of Crocodilians in the Americas

The chapter gives an introductory overview on the biology of the 11 species of crocodilians inhabiting the Americas. Geographical distribution is broadly discussed in the light of biogeographical and evolutionary origins. As a broad generalization, crocodilians are morphologically, genetically, and ecologically conservative and show a high dispersal ability, which together complicate the delimitation of species boundaries. Furthermore, distinct clades of crocodilians are a result of environmental selection for different adaptive characteristics. Gene flow occurs between clades, but distinct morphological varieties are sometimes a result of environmental filters. Thus, many taxa of crocodilians can be considered ecological species. Reproductive characteristics, such as nest-site choice and female reproductive output, influence reproductive success and thus population trends, so we discuss reproductive and habitat characteristics in the light of conservation genetics. Finally, the status of crocodilians is discussed both in terms of past hunting pressure and current conservation and management initiatives. In general, crocodilians can look after themselves if they have sufficient habitat, but some species are critically endangered by hunting, even though much of their original habitat remains intact. Conservation actions must be applied locally, taking into account threats and dispersal between source and sink populations. Given the difficulty of studying the dispersal of crocodilians by direct observation in most places in Latin America, the definition of effective management units will depend on genetic studies that can be linked to economic or conservation goals