Detection of a Novel, and Likely Ancestral, Tn916-Like Element from a Human Saliva Metagenomic Library

Tn916 is a conjugative transposon (CTn) and the first reported and most well characterised of the Tn916/Tn1545 family of CTns. Tn916-like elements have a characteristic modular structure and different members of this family have been identified based on similarities and variations in these modules. In addition to carrying genes encoding proteins required for their conjugation, Tn916-like elements also carry accessory, antimicrobial resistance genes; most commonly the tetracycline resistance gene, tet(M). Our study aimed to identify and characterise tetracycline resistance genes from the human saliva metagenome using a functional metagenomic approach. We identified a tetracycline-resistant clone, TT31, the sequencing of which revealed it to encode both tet(M) and tet(L). Comparison of the TT31 sequence with the accessory, regulation, and recombination modules of other Tn916-like elements indicated that a partial Tn916-like element encoding a truncated orf9 was cloned in TT31. Analysis indicated that a previous insertion within the truncated orf9 created the full length orf9 found in most Tn916-like transposons; demonstrating that orf9 is, in fact, the result of a gene fusion event. Thus, we hypothesise that the Tn916-like element cloned in TT31 likely represents an ancestral Tn916

Interactions at metal-GaAs(100) interfaces

The interaction of reactive and unreactive metals with clean, oxidised and sulphur passivated GaAs(lOO) surfaces has been investigated using a range of experimental techniques. The deposition of both gold and iron on chemically cleaned and oxidised GaAs(lOO) surfaces has revealed a correlation between the magnitude of the ideality parameter determined by current-voltage measurements and the presence of interface states as detected by the deep level transient spectroscopy (DLTS) technique. Schottky barrier diodes exhibiting near-ideal behaviour were fabricated by deposition of both gold and iron on GaAs surfaces immediately after chemical etch in H2S 0 4:H20 2:H20 (5:1:1). No interface states were detected on these diodes. However, metals deposited on oxidised surfaces gave rise to highly non-ideal IV characteristics. In addition, DLTS studies revealed the presence of interface states, caused by defects induced during the oxidation of the GaAs surfaces prior to metal deposition. The passivating effects of sulphur in the forms of hydrogen sulphide. H2S and molecular sulphur, S2 on the GaAs surface have also been investigated. In particular, the adsorption of molecular sulphur on the As decapped GaAs surface has been studied using surface sensitive synchrotron radiation. Clean GaAs (100) surfaces with different As to Ga surface atom ratios were prepared by the thermal decapping of a protective As overlayer deposited on MBE grown GaAs. Studies have shown that the uptake of sulphur by the As and Ga surface atoms depends strongly on the As to Ga ratio of the clean decapped surface. Such sulphur treatments result in the adsorption of a monolayer of sulphur w hich is bonded to both the Ga and As surface atoms. As a complement to sulphur passivation, which has the effect of slowing down and/or preventing oxidation of GaAs surfaces, the reduction and removal of oxides by the deposition of ultrathin layers of titanium has been investigated. By exposing clean GaAs surfaces to air at atmosphere, a monolayer of oxides was grown. The subsequent deposition of titanium resulted in the complete removal of the As and Ga oxides and the formation of an extremely abrupt Ti-TiOx-GaAs (x~l) interface

Design and fabrication of highly efficient non-linear optical devices for implementing high-speed optical processing

We present the design and fabrication of micro-cavity semiconductor devices for enhanced Two-Photon-Absorption response, and demonstrate the use of these devices for implementing sensitive autocorrelation measurements on pico-second optical pulses

High-sensitivity two-photon absorption microcavity autocorrelator

A GaAs-AlAs microcavity device has been used as a photodetector in an autocorrelator for measuring the temporal pulsewidth of 1.5-/spl mu/m optical pulses. Enhancement of the two-photon absorption photocurrent due to the microcavity structure results in an autocorrelation (average power times peak power) sensitivity of 9.3/spl times/10/sup -4/ (mW)/sup 2/, which represents two orders of magnitude improvement when compared with conventional autocorrelators

Two-photon absorption in microcavities for optical autocorrelation and sampling

We have designed novel semiconductor microcavity structures for the enhancement of the two-photon absorption (TPA) photocurrent. We report a TPA autocorrelation technique for short optical pulses that uses the microcavity structure instead of a second harmonic generation crystal. Knowledge of these characteristics is important for implementation in applications such as optical switching and sampling in optical time division multiplexed (OTDM) communications systems

A novel approach towards two-photon absorption based detectors

Summary: We have demonstrated that the inherent inefficiency of the TPA process in semiconductors can be overcome by incorporating the semiconductor in a microcavity structure. Proof of concept devices with a 0.27μm Ga0.7Al0.3As active region and two Bragg reflectors with the cavity resonance of 890 nm were fabricated. We measured the TPA photocurrent of these devices and have demonstrated a factor of 12000 enhancement over a nonmicrocavity device at 890 nm. Our active length of 0.27 nm is as efficient as 5.4 mm without a microcavity, overcoming the very long detector lengths limiting the use of TPA in practical autocorrelators, optical switches and sampling devices for real telecommunication systems. The effect of the cavity is to enhance the intra-cavity optical intensity, which leads to an increase in the nonlinear response of the active region. We studied, theoretically and experimentally, the impact of the cavity on the temporal response and the sensitivity of the device, which are critical considerations for commercial applications. This cavity design has a 3 pico-second response time and the autocorrelation trace is comparable with the BBO crystal response for an input 1.6 ps pulse. Devices designed for 1550 nm have also been realised and our measurements indicate these two-photon absorption based detectors are potential candidates for optical autocorrelation of short optical pulses, and for optical switching and sampling in optical time division multiplexed (OTDM) communications systems

Achieving Carbon Neutrality at Bridgestone Nature Reserve at Chestnut Mountain

We examined options to achieve carbon neutrality at The Nature Conservancy‘s Bridgestone Nature Reserve at Chestnut Mountain. We conducted a basic energy audit for the primary structure (office), as well as secondary structures, vehicles and power equipment, to determine needed energy efficiency improvements. We concluded that small enhancements, such as adding insulation and replacing appliances, can maximize energy efficiency and reduce carbon footprint. We also contacted outside entities to conduct formal commercial energy audits and provide cost estimates for installing a wind turbine and solar panels. Our final proposal includes estimated cost and timeline of transitioning all facilities and equipment from commercial energy production and fossil fuel use to renewable energy. The use of carbon offsets with forested land is a potential temporary measure to achieve carbon neutrality. Full carbon neutrality can be achieved at this facility through a combination of energy use reduction, renewable energy generation, and allocation of a small piece of forested land for carbon sequestration

Simvastatin inhibits L-type Ca2+-channel activity through impairment of mitochondrial function

© The Author(s) 2019. Published by Oxford University Press on behalf of the Society of Toxicology. Plasma membrane ion channels and mitochondrial electron transport complexes (mETC) are recognized "off targets" for certain drugs. Simvastatin is one such drug, a lipophilic statin used to treat hypercholesterolemia, but which is also associated with adverse effects like myopathy and increased risk of glucose intolerance. Such myopathy is thought to arise through adverse actions of simvastatin on skeletal muscle mETC and mitochondrial respiration. In this study, we investigated whether the glucose intolerance associated with simvastatin is also mediated via adverse effects on mETC in pancreatic beta-cells because mitochondrial respiration underlies insulin secretion from these cells, an effect in part mediated by promotion of Ca2+ influx via opening of voltage-gated Ca2+ channels (VGCCs). We used murine pancreatic beta-cells to investigate these ideas. Mitochondrial membrane potential, oxygen consumption, and ATP-sensitive-K+- channel activity were monitored as markers of mETC activity, respiration, and cellular ATP/ADP ratio respectively; Ca2+ channel activity and Ca2+ influx were also measured. In intact beta-cells, simvastatin inhibited oxidative respiration (IC50 approximately 3 mM) and mETC (1 0.1 mM reversed activation of VGCCs by glucose but had no significant effect in the sugar s absence. The VGCC effects were mimicked by rotenone which also decreased respiration and ATP/ADP. This study demonstrates modulation of beta-cell VGCC activity by mitochondrial respiration and their sensitivity to mETC inhibitors. This reveals a novel outcome for the action of drugs like simvastatin for which mETC is an "off target"

Mental Toughness and Associated Personality Characteristics of Marathon des Sables Athletes

Mental toughness (MT) is commonly referred to as an important prerequisite for sustained athletic achievement. The increased research focus on MT has led to the development of a consistent debate centered around whether the construct is a unidimensional or multidimensional trait, and whether it can be differentiated from similar constructs such as hardiness. In order to move toward more clarity of MT, the present study is exploratory in nature, using athletes who have competed in the Marathon des Sables (MdS) ultra-endurance event. The MdS is a timed 250 km race in the Sahara Desert that takes place over 6 days in temperatures exceeding 40°C. Forty two British MdS competitors were recruited via the United Kingdom organizing company. Each participant completed the NEO PI-R as a measure of the five major domains of personality, as well as the six traits or facets that define each domain. Additionally, they completed the Sport Mental Toughness Questionnaire (SMTQ). The MdS sample’s NEO PI-R results were compared against general population norms, and results showed a distinct ultra-endurance athlete profile characterized by significantly higher levels of extraversion and openness to experience. Additionally, the MdS sample’s SMTQ scores were higher than the normed sample consisting of a collection of athletes representing multiple sports. Finally, linear regression analyses indicated a convergence between the two measures, supporting the argument that MT may in fact be measured by a general personality questionnaire such as the NEO PI-R