Discovery of a family of γ-aminobutyrate ureas via rational derepression of a silent bacterial gene cluster

Gaburedins, a family of γ-aminobutyrate (GABA)-derived ureas, have been discovered by deletion of gbnR, an arpA-like putative transcriptional repressor in Streptomyces venezuelae ATCC 10712. Comparison of metabolite profiles in the wild type and mutant strains revealed six metabolites in the mutant that are lacking from the wild type. The structure of gaburedin A was established by HRMS combined with 1- and 2-D NMR spectroscopy and was confirmed by total synthesis. The other metabolites were confirmed as congeners using HRMS, MS/MS and feeding of putative biosynthetic precursors. Two genes, gbnA and gbnB, are proposed to be involved in gaburedin biosynthesis. Consistent with this hypothesis, deletion of gbnB in the gbnR mutant abolished gaburedin production. This is the first report to disclose the discovery of novel natural products via rational deletion of a putative pathway-specific regulatory gene

Field-effect mobility enhanced by tuning the Fermi level into the band gap of Bi2Se3

By eliminating normal fabrication processes, we preserve the bulk insulating state of calcium-doped Bi2Se3 single crystals in suspended nanodevices, as indicated by the activated temperature dependence of the resistivity at low temperatures. We perform low-energy electron beam irradiation (<16 keV) and electrostatic gating to control the carrier density and therefore the Fermi level position in the nanodevices. In slightly p-doped Bi2-xCaxSe3 devices, continuous tuning of the Fermi level from the bulk valence band to the band-gap reveals dramatic enhancement (> a factor of 10) in the field-effect mobility, which suggests suppressed backscattering expected for the Dirac fermion surface states in the gap of topological insulators

Temperature-dependent magnetospectroscopy of HgTe quantum wells

We report on magnetospectroscopy of HgTe quantum wells in magnetic fields up to 45 T in temperature range from 4.2 K up to 185 K. We observe intra- and inter-band transitions from zero-mode Landau levels, which split from the bottom conduction and upper valence subbands, and merge under the applied magnetic field. To describe experimental results, realistic temperature-dependent calculations of Landau levels have been performed. We show that although our samples are topological insulators at low temperatures only, the signature of such phase persists in optical transitions at high temperatures and high magnetic fields. Our results demonstrate that temperature-dependent magnetospectroscopy is a powerful tool to discriminate trivial and topological insulator phases in HgTe quantum wells

Sex-specific differences in fit between two different types of body armour: A pilot study

Aim: to assess sex-specific differences in wearability and comfort when wearing body armour.Design: A randomized counter-balanced study.Method: Ten participants (females n = 6, mean height = 167.97 ± 3.67 cm, mean mass = 65.30 ± 10.57 kg: males n = 4, mean height = 82.15 ± 6.98 cm, mean weight = 85.55 ± 9.96 kg) were included following eligibility criteria and assessed against occupational tasks for which they gave subjective feedback when wearing a law enforcement (2.1 kg) and military (6.4 kg) body armour system. Subjective feedback was provided on mannequin sketches and compared between sexes and body armour types. Bond University Human Research Ethics Committee provided ethics approval (RO15803).Results: Greater negative feedback was received, subjectively, from both sexes regarding the military body armour. Female participants recorded areas of most discomfort to include the neck, shoulder, chest, and hip, whilst males recorded areas to be the neck, shoulder, and abdomen. Females reported greater subjective concerns than males regarding body armour fit.Conclusion: With levels of discomfort associated with injury in police officers wearing body armour, the comfort and fit of body armour and differences between sexes must be considered. These differences require consideration when returning injured officers back to work, especially following brachial plexus palsy and meralgia paresthetica injuries.</div