Spin-gap opening accompanied by a strong magnetoelastic response in the S=1 magnetic dimer system Ba3BiRu2O9

Neutron diffraction, magnetization, resistivity, and heat capacity measurements on the 6H-perovskite Ba3BiRu2O9 reveal simultaneous magnetic and structural dimerization driven by strong magnetoelastic coupling. An isostructural but strongly displacive first-order transition on cooling through T*=176 K is associated with a change in the nature of direct Ru-Ru bonds within Ru2O9 face-sharing octahedra. Above T*, Ba3BiRu2O9 is an S=1 magnetic dimer system with intradimer exchange interactions J0/kB=320 K and interdimer exchange interactions J'/kB=-160 K. Below T*, a spin-gapped state emerges with \Delta\approx220 K. Ab initio calculations confirm antiferromagnetic exchange within dimers, but the transition is not accompanied by long range-magnetic order.Comment: 5 pages, 5 figures, accepted by Physical Review

Fostering purposeful engagement by building staff-student communities

In response to the Covid-19 pandemic, many universities moved to a blended delivery of online and in-person teaching. While necessary for public health, this significant disruption to education risked greater isolation and anxiety for students with the potential for less engagement and, consequently, reduced confidence in their abilities. However, it also presented an opportunity to re-evaluate practice and take steps to create new staff-student communities with potential to shape student engagement.The School of Mathematical Sciences at the University of Nottingham took several approaches to preserve and enhance student engagement, such as induction processes to foster new online communities, initiatives to boost academic and social interaction, development of close partnerships between staff and students in shaping the pandemic response, and the creation of an online staff community to discuss pedagogic practice and share training resources. The effectiveness of these approaches has been evaluated throughout the pandemic via staff-student meetings, module evaluation surveys and staff surveys.More than half the cohort joined an online student forum showing students appreciated online social interaction. However, for studying, students engaged in new one-to-one study-buddy and peer-mentoring schemes which students reported reduced their isolation and anxiety associated with online learning. Students reported online discussion forums to be one of the most useful tools for online learning. They liked being able to ask questions anonymously, in a forum where the lecturer was also present, something they could not do previously with in-person teaching. However, many students reported difficulty with managing their time because of increased asynchronous learning activity indicating a need for students to be trained in how to engage with online studying.Most staff have adopted elements of flipped learning to maximise student-student and student-staff interaction in the limited contact time. Staff engagement in their online community was strong, with most staff attending workshops and training sessions regarding online teaching. Consequently, staff were able to rapidly trial and share approaches that successfully addressed student feedback and promoted interaction

Inhibition of Ral GTPases Using a Stapled Peptide Approach

Aberrant Ras signalling drives numerous cancers and drugs to inhibit this are urgently required. This compelling clinical need, combined with recent innovations in drug discovery including the advent of biologic therapeutic agents, has propelled Ras back to the forefront of targeting efforts. Activated Ras has proved extremely difficult to target directly and the focus has moved to the main downstream Ras-signalling pathways. In particular, the Ras-Raf and Ras-PI3K pathways have provided conspicuous enzyme therapeutic targets, which were more accessible to conventional drug-discovery strategies. The Ras-RalGEF-Ral pathway is a more difficult challenge for traditional medicinal development and there have therefore been few inhibitors reported that disrupt this axis. We have used our structure of a Ral-effector complex as a basis for the design and characterization of α-helical stapled peptides that bind selectively to active, GTP-bound Ral proteins and that compete with downstream effector proteins. The peptides have been thoroughly characterized biophysically. Crucially, the lead peptide enters cells and is biologically active, inhibiting isoform-specific RalB-driven cellular processes. This therefore provides a starting point for therapeutic inhibition of the Ras-RalGEF-Ral pathway.This work was supported by a Cambridge Cancer Centre Pump Priming award to CA, DO and HRM, a BBSRC Studentship to NSC, and a National Institutes for Health grant (CA71443) and the Welch Foundation (grant number I-1414) to MAW.This is the final version of the article. It first appeared from the American Society for Biochemistry and Molecular Biology via https://doi.org/10.1074/jbc.M116.72024

Diffraction in low-energy electron scattering from DNA: bridging gas phase and solid state theory

Using high-quality gas phase electron scattering calculations and multiple scattering theory, we attempt to gain insights on the radiation damage to DNA induced by secondary low-energy electrons in the condensed phase, and to bridge the existing gap with the gas phase theory and experiments. The origin of different resonant features (arising from single molecules or diffraction) is discussed and the calculations are compared to existing experiments in thin films.Comment: 40 pages preprint, 12 figures, submitted to J. Chem. Phy

Fermion scattering by a Schwarzschild black hole

We study the scattering of massive spin-half waves by a Schwarzschild black hole using analytical and numerical methods. We begin by extending a recent perturbation theory calculation to next order to obtain Born series for the differential cross section and Mott polarization, valid at small couplings. We continue by deriving an approximation for glory scattering of massive spinor particles by considering classical timelike geodesics and spin precession. Next, we formulate the Dirac equation on a black hole background, and outline a simple numerical method for finding partial wave series solutions. Finally, we present our numerical calculations of absorption and scattering cross sections and polarization, and compare with theoretical expectations.Comment: Minor changes, 1 figure added. Version to appear in Phys. Rev. D. 36 pages, 13 figure

Inhibition of Ral GTPases Using a Stapled Peptide Approach.

Aberrant Ras signaling drives numerous cancers, and drugs to inhibit this are urgently required. This compelling clinical need combined with recent innovations in drug discovery including the advent of biologic therapeutic agents, has propelled Ras back to the forefront of targeting efforts. Activated Ras has proved extremely difficult to target directly, and the focus has moved to the main downstream Ras-signaling pathways. In particular, the Ras-Raf and Ras-PI3K pathways have provided conspicuous enzyme therapeutic targets that were more accessible to conventional drug-discovery strategies. The Ras-RalGEF-Ral pathway is a more difficult challenge for traditional medicinal development, and there have, therefore, been few inhibitors reported that disrupt this axis. We have used our structure of a Ral-effector complex as a basis for the design and characterization of α-helical-stapled peptides that bind selectively to active, GTP-bound Ral proteins and that compete with downstream effector proteins. The peptides have been thoroughly characterized biophysically. Crucially, the lead peptide enters cells and is biologically active, inhibiting isoform-specific RalB-driven cellular processes. This, therefore, provides a starting point for therapeutic inhibition of the Ras-RalGEF-Ral pathway.This work was supported by a Cambridge Cancer Centre Pump Priming award to CA, DO and HRM, a BBSRC Studentship to NSC, and a National Institutes for Health grant (CA71443) and the Welch Foundation (grant number I-1414) to MAW.This is the final version of the article. It first appeared from the American Society for Biochemistry and Molecular Biology via https://doi.org/10.1074/jbc.M116.72024

Spatially resolved variations in reflectivity across iron oxide thin films

The spin polarising properties of the iron oxide magnetite (Fe3O4) make it attractive for use in spintronic devices, but its sensitivity to compositional and structural variations make it challenging to prepare reli- ably. Infrared microspectroscopy and modelling are used to determine the spatial variation in the chem- ical composition of three thin films of iron oxide; one prepared by pulsed laser deposition (PLD), one by molecular beam epitaxy (MBE) deposition of iron whilst simultaneously flowing oxygen into the chamber and one by flowing oxygen only once deposition is complete. The technique is easily able to distinguish between films which contain metallic iron and different iron oxide phases as well as spatial variations in composition across the films. The film grown by post-oxidising iron is spatially uniform but not fully oxi- dised, the film grown by simultaneously oxidising iron showed spatial variation in oxide composition while the film grown by PLD was spatially uniform magnetite

Enhancing the thermoelectric properties of single and double filled p-type skutterudites synthesized by an up-scaled ball-milling process

The single and double filled p-type skutterudites Ce0.8Fe3CoSb12 and Ce0.5Yb0.5Fe3.25Co0.75Sb12 have been prepared by mechanical alloying. This offers a rapid method for the preparation of skutterudites that could be scaled up for adoption at industrial level. The large-scale samples prepared by ball-milling exhibit enhanced figures of merit ZT, compared with materials prepared by conventional solid-state reaction. At room temperature ZT is increased by ca. 19 % for both single and double filled skutterudites. Maximum figures of merit, ZT = 0.68 and ZT = 0.93 are attained for Ce0.8Fe3CoSb12 at 773 K and Ce0.5Yb0.5Fe3.25Co0.75Sb12 at 823 K respectively. The improvement in thermoelectric values at room temperature may be traced to a reduction in thermal conductivity in the ball-milled samples arising from the reduced grain size. The influence of the microstructure on the thermoelectric properties, together with the stability in air and the performance of the materials after several heating and cooling cycles has been studied and are detailed in this work. The densified samples prepared by ball-milling also show a higher resistance to oxidation, which starts at 694 K for Ce0.8Fe3CoSb12 and at 783 K for Ce0.5Yb0.5Fe3.25Co0.75Sb12

Experimental fragmentation of pipe bombs with varying case thickness

Among all the improvised explosive devices (IEDs) known, pipe bombs are one of the most popular devices used by terrorists. They are simple to use, easy to construct and materials are readily available. For this IED, fragmentation is the primary injury mechanism, which makes them a desirable weapon for terrorists aiming to inflict maximum human casualties. Although the investigation of fragmentation pattern is not novel, there is limited data available on pipe bombs performance in the open literature. Therefore, this research is looking at validating results in current literature, which showed limited repetition and weak experimental design so far; by trial with six pipe bombs with two different thickness (3 of each). The pipe bombs consisted of mild steel casing and aluminised ammonium nitrate as the explosive filler. Fragments were collected, with an average recovery of 72%, and measured regarding mass and velocity. The experiment results show a correlation between the pipe thickness and both the size and velocity of fragments

Infection resilient environments: buildings that keep us healthy and safe - Initial report

The Royal Academy of Engineering and its partners in the National Engineering Policy Centre have been asked by the Government Chief Scientific Adviser to undertake a rapid review of actions to make infrastructure more resilient to infection. This short-turnaround response provides an initial overview of the strategic challenges we as a society face, along with advice on immediate measures that can make a significant difference ahead of winter 2021/2. We have found that the COVID-19 crisis has revealed flaws in the way in which we design, manage and operate buildings that, if left unchecked, will disrupt management of this and other pandemics, impose high financial and health costs on society, and constrain our ability to address other challenges such as climate change. By delivering infection resilient environments we mean to ensure that public and commercial buildings (places of work and leisure, specialist settings such as hospitals and care homes, and potentially transport hubs and carriages) minimise the risk of disease transmission, to support public health during and beyond the current COVID-19 pandemic