The effect of recent fire history on the abundance and viability of large seeds in the soil of sclerophyll forest in Tasmania, Australia

There are few data on the effects of recent fire history on the composition of soil seed banks in sclerophyll forest communities. We predicted that the abundance and viability of soil-stored seeds would vary with fire history. Soils were sampled from areas with six different fire histories on Mt Nelson, Tasmania, Australia. Large seeds were extracted by hand separation and tested for viability. Responses to at least one of the two strongly-correlated components of fire history were detected in several taxa and for native and exotic seed. Native seeds, exotic seeds, Astroloma humifusum seed and Exocarpos cupressiformis seed were all more abundant in the soils of areas with one or less fires in the last 60 years than in the soils of areas burnt five times over the last 60 years. The viability of A. humifusum seeds decreased with fire frequency. These results support the hypothesis that frequent and recent fire can deplete the soil seed bank, and reduce soil seed viability, at least for some large-seeded species and species groups

Template-Stripped Multifunctional Wedge and Pyramid Arrays for Magnetic Nanofocusing and Optical Sensing

We present large-scale reproducible fabrication of multifunctional ultrasharp metallic structures on planar substrates with capabilities including magnetic field nanofocusing and plasmonic sensing. Objects with sharp tips such as wedges and pyramids made with noble metals have been extensively used for enhancing local electric fields via the lightning-rod effect or plasmonic nanofocusing. However, analogous nanofocusing of magnetic fields using sharp tips made with magnetic materials has not been widely realized. Reproducible fabrication of sharp tips with magnetic as well as noble metal layers on planar substrates can enable straightforward application of their material and shape-derived functionalities. We use a template-stripping method to produce plasmonic-shell-coated nickel wedge and pyramid arrays at the wafer-scale with tip radius of curvature close to 10 nm. We further explore the magnetic nanofocusing capabilities of these ultrasharp substrates, deriving analytical formulas and comparing the results with computer simulations. These structures exhibit nanoscale spatial control over the trapping of magnetic microbeads and nanoparticles in solution. Additionally, enhanced optical sensing of analytes by these plasmonic-shell-coated substrates is demonstrated using surface-enhanced Raman spectroscopy. These methods can guide the design and fabrication of novel devices with applications including nanoparticle manipulation, biosensing, and magnetoplasmonics

Brain enlargement and dental reduction were not linked in hominin evolution

The large brain and small postcanine teeth of modern humans are among our most distinctive features, and trends in their evolution are well studied within the hominin clade. Classic accounts hypothesize that larger brains and smaller teeth coevolved because behavioral changes associated with increased brain size allowed a subsequent dental reduction. However, recent studies have found mismatches between trends in brain enlargement and posterior tooth size reduction in some hominin species. We use a multiple-variance Brownian motion approach in association with evolutionary simulations to measure the tempo and mode of the evolution of endocranial and dental size and shape within the hominin clade. We show that hominin postcanine teeth have evolved at a relatively consistent neutral rate, whereas brain size evolved at comparatively more heterogeneous rates that cannot be explained by a neutral model, with rapid pulses in the branches leading to later Homo species. Brain reorganization shows evidence of elevated rates only much later in hominin evolution, suggesting that fast-evolving traits such as the acquisition of a globular shape may be the result of direct or indirect selection for functional or structural traits typical of modern humans

Computational study of human head response to primary blast waves of five levels from three directions

Human exposure to blast waves without any fragment impacts can still result in primary blast-induced traumatic brain injury (bTBI). To investigate the mechanical response of human brain to primary blast waves and to identify the injury mechanisms of bTBI, a three-dimensional finite element head model consisting of the scalp, skull, cerebrospinal fluid, nasal cavity, and brain was developed from the imaging data set of a human female. The finite element head model was partially validated and was subjected to the blast waves of five blast intensities from the anterior, right lateral, and posterior directions at a stand-off distance of one meter from the detonation center. Simulation results show that the blast wave directly transmits into the head and causes a pressure wave propagating through the brain tissue. Intracranial pressure (ICP) is predicted to have the highest magnitude from a posterior blast wave in comparison with a blast wave from any of the other two directions with same blast intensity. The brain model predicts higher positive pressure at the site proximal to blast wave than that at the distal site. The intracranial pressure wave invariably travels into the posterior fossa and vertebral column, causing high pressures in these regions. The severities of cerebral contusions at different cerebral locations are estimated using an ICP based injury criterion. Von Mises stress prevails in the cortex with a much higher magnitude than in the internal parenchyma. According to an axonal injury criterion based on von Mises stress, axonal injury is not predicted to be a cause of primary brain injury from blasts. Copyright

Structure and function of the thermostable L-asparaginase from Thermococcus kodakarensis.

L-Asparaginases catalyse the hydrolysis of asparagine to aspartic acid and ammonia. In addition, L-asparaginase is involved in the biosynthesis of amino acids such as lysine, methionine and threonine. These enzymes have been used as chemotherapeutic agents for the treatment of acute lymphoblastic leukaemia and other haematopoietic malignancies since the tumour cells cannot synthesize sufficient L-asparagine and are thus killed by deprivation of this amino acid. L-Asparaginases are also used in the food industry and have potential in the development of biosensors, for example for asparagine levels in leukaemia. The thermostable type I L-asparaginase from Thermococcus kodakarensis (TkA) is composed of 328 amino acids and forms homodimers in solution, with the highest catalytic activity being observed at pH 9.5 and 85°C. It has a Km value of 5.5 mM for L-asparagine, with no glutaminase activity being observed. The crystal structure of TkA has been determined at 2.18 Å resolution, confirming the presence of two α/β domains connected by a short linker region. The N-terminal domain contains a highly flexible β-hairpin which adopts `open' and `closed' conformations in different subunits of the solved TkA structure. In previously solved L-asparaginase structures this β-hairpin was only visible when in the `closed' conformation, whilst it is characterized with good electron density in all of the subunits of the TkA structure. A phosphate anion resides at the active site, which is formed by residues from both of the neighbouring monomers in the dimer. The high thermostability of TkA is attributed to the high arginine and salt-bridge content when compared with related mesophilic enzymes

Developing performance using rational emotive behavior therapy (REBT): A case study with an elite archer

© 2017 Human Kinetics, Inc. Rational emotive behavior therapy (REBT; Ellis, 1957) is a psychotherapeutic approach receiving increasing interest within sport. REBT is focused on identifying, disputing, and replacing irrational beliefs (IBs) with rational beliefs (RBs) to promote emotional well-being and goal achievement. This study provides a detailed case outlining the application and effect of seven one-to-one REBT sessions with an elite level archer who was experiencing performance-related anxiety, before and during competition. The case also offers an insight into common misconceptions, challenges, and guidance for those who may consider applying REBT within their practice. Data revealed meaningful short and long-term (6-months) reductions in IBs and improvements in RBs, self-efficacy, perception of control and archery performance. The case supports the effective application of REBT as an intervention with athletic performers, promoting lasting changes in an athlete's ability to manage their cognitions, emotions and behaviors in the pursuit of performance excellence

Structure of the 2,4'-dihydroxyacetophenone dioxygenase from Alcaligenes sp. 4HAP.

The enzyme 2,4'-dihydroxyacetophenone dioxygenase (DAD) catalyses the conversion of 2,4'-dihydroxyacetophenone to 4-hydroxybenzoic acid and formic acid with the incorporation of molecular oxygen. Whilst the vast majority of dioxygenases cleave within the aromatic ring of the substrate, DAD is very unusual in that it is involved in C-C bond cleavage in a substituent of the aromatic ring. There is evidence that the enzyme is a homotetramer of 20.3 kDa subunits, each containing nonhaem iron, and its sequence suggests that it belongs to the cupin family of dioxygenases. In this paper, the first X-ray structure of a DAD enzyme from the Gram-negative bacterium Alcaligenes sp. 4HAP is reported, at a resolution of 2.2 Å. The structure establishes that the enzyme adopts a cupin fold, forming dimers with a pronounced hydrophobic interface between the monomers. The catalytic iron is coordinated by three histidine residues (76, 78 and 114) within a buried active-site cavity. The iron also appears to be tightly coordinated by an additional ligand which was putatively assigned as a carbonate dianion since this fits the electron density optimally, although it might also be the product formate. The modelled carbonate is located in a position which is highly likely to be occupied by the α-hydroxyketone group of the bound substrate during catalysis. Modelling of a substrate molecule in this position indicates that it will interact with many conserved amino acids in the predominantly hydrophobic active-site pocket where it undergoes peroxide radical-mediated heterolysis

Fostering the healthcare workforce during the COVID‐19 pandemic: Shared leadership, social capital, and contagion among health professionals

Health professionals managing patients with COVID-19 disease are at high risk of contagion. All medical personnel involved in caring for patients need coordination, knowledge and trust. Empirical work on human resources has tended to focus on the effects of human resource practices on performance, whereas leadership and social interactions have been overlooked. Based upon interviews with medical staff working in specialised medical units, this study uses the social capital theory to examine relationships among shared leadership, social capital, and contagion rates. First, shared leadership was found to positively affect COVID-19 contagion among health professionals. Second, by sharing information and a common language, and showing high levels of trust, namely social capital, medical units seem to reduce contagion rates of COVID-19. In other words, shared leadership plays a fundamental role in improving performance in healthcare by means of social capital

Distinguishing Social from Nonsocial Navigation in Moving Animal Groups

Many animals, such as migrating shoals of fish, navigate in groups. Knowing the mechanisms involved in animal navigation is important when it comes to explaining navigation accuracy, dispersal patterns, population and evolutionary dynamics, and consequently, the design of conservation strategies. When navigating toward a common target, animals could interact socially by sharing available information directly or indirectly, or each individual could navigate by itself and aggregations may not disperse because all animals are moving toward the same target. Here we present an analysis technique that uses individual movement trajectories to determine the extent to which individuals in navigating groups interact socially, given knowledge of their target. The basic idea of our approach is that the movement directions of individuals arise from a combination of responses to the environment and to other individuals. We estimate the relative importance of these responses, distinguishing between social and nonsocial interactions. We develop and test our method, using simulated groups, and we demonstrate its applicability to empirical data in a case study on groups of guppies moving toward shelter in a tank. Our approach is generic and can be extended to different scenarios of animal group movement. © 2012 by The University of Chicago

Structural evidence for the partially oxidized dipyrromethene and dipyrromethanone forms of the cofactor of porphobilinogen deaminase: structures of the Bacillus megaterium enzyme at near-atomic resolution.

The enzyme porphobilinogen deaminase (PBGD; hydroxymethylbilane synthase; EC 2.5.1.61) catalyses an early step of the tetrapyrrole-biosynthesis pathway in which four molecules of the monopyrrole porphobilinogen are condensed to form a linear tetrapyrrole. The enzyme possesses a dipyrromethane cofactor, which is covalently linked by a thioether bridge to an invariant cysteine residue (Cys241 in the Bacillus megaterium enzyme). The cofactor is extended during the reaction by the sequential addition of the four substrate molecules, which are released as a linear tetrapyrrole product. Expression in Escherichia coli of a His-tagged form of B. megaterium PBGD has permitted the X-ray analysis of the enzyme from this species at high resolution, showing that the cofactor becomes progressively oxidized to the dipyrromethene and dipyrromethanone forms. In previously solved PBGD structures, the oxidized cofactor is in the dipyromethenone form, in which both pyrrole rings are approximately coplanar. In contrast, the oxidized cofactor in the B. megaterium enzyme appears to be in the dipyrromethanone form, in which the C atom at the bridging α-position of the outer pyrrole ring is very clearly in a tetrahedral configuration. It is suggested that the pink colour of the freshly purified protein is owing to the presence of the dipyrromethene form of the cofactor which, in the structure reported here, adopts the same conformation as the fully reduced dipyrromethane form