Injuries of the chest

Click on the link to view

Soft-mode anisotropy in the negative thermal expansion material ReO3

We use a symmetry-motivated approach to analyse neutron pair distribution function data to investigate the character of the soft phonon modes in negative thermal expansion (NTE) material ReO3. This analysis shows that its local structure is dominated by an in-phase octahedral tilting mode and that the octahedral units are far less flexible to scissoring type deformations than in the related NTE compound ScF3. The lack of flexibility in ReO3 restricts the NTE-driving phonons to a smaller region of reciprocal space, limiting the magnitude and temperature range of NTE. These results support the idea that structural flexibility is an important factor in NTE materials. Surprisingly, our results show that the local fluctuations, even at elevated temperatures, respect the symmetry and order parameter direction of the initial pressure induced phase transition in ReO3. The result indicates that the dynamic motions associated with rigid unit modes are highly anisotropic in these systems

Researching trust in the police and trust in justice: a UK perspective

This paper describes the immediate and more distant origins of a programme of comparative research that is examining cross-national variations in public trust in justice and in the police. The programme is built around a module of the fifth European Social Survey, and evolved from a study funded by the European Commission. The paper describes the conceptual framework within which we are operating – developed in large measure from theories of procedural justice. It reviews some of the methodological issues raised by the use of sample surveys to research issues of public trust in the police, public perceptions of institutional legitimacy and compliance with the law. Finally it gives a flavour of some of the early findings emerging from the programme

Expression of soluble, active fragments of the morphogenetic protein SpoIIE from Bacillus subtilis using a library-based construct screen

SpoIIE is a dual function protein that plays important roles during sporulation in Bacillus subtilis. It binds to the tubulin-like protein FtsZ causing the cell division septum to relocate from mid-cell to the cell pole, and it dephosphorylates SpoIIAA phosphate leading to establishment of differential gene expression in the two compartments following the asymmetric septation. Its 872 residue polypeptide contains a multiple-membrane spanning sequence at the N-terminus and a PP2C phosphatase domain at the C-terminus. The central segment that binds to FtsZ is unlike domains of known structure or function, moreover the domain boundaries are poorly defined and this has hampered the expression of soluble fragments of SpoIIE at the levels required for structural studies. Here we have screened over 9000 genetic constructs of spoIIE using a random incremental truncation library approach, ESPRIT, to identify a number of soluble C-terminal fragments of SpoIIE that were aligned with the protein sequence to map putative domains and domain boundaries. The expression and purification of three fragments were optimised, yielding multimilligram quantities of the PP2C phosphatase domain, the putative FtsZ-binding domain and a larger fragment encompassing both these domains. All three fragments are monomeric and the PP2C domain-containing fragments have phosphatase activity

Alternate SlyA and H-NS nucleoprotein complexes control hlyE expression in Escherichia coli K-12

Haemolysin E is a cytolytic pore-forming toxin found in several Escherichia coli and Salmonella enterica strains. Expression of hlyE is repressed by the global regulator H-NS (histone-like nucleoid structuring protein), but can be activated by the regulator SlyA. Expression of a chromosomal hlyE–lacZ fusion in an E. coli slyA mutant was reduced to 60% of the wild-type level confirming a positive role for SlyA. DNase I footprint analysis revealed the presence of two separate SlyA binding sites, one located upstream, the other downstream of the hlyE transcriptional start site. These sites overlap AT-rich H-NS binding sites. Footprint and gel shift data showed that whereas H-NS prevented binding of RNA polymerase (RNAP) at the hlyE promoter (PhlyE), SlyA allowed binding of RNAP, but inhibited binding of H-NS. Accordingly, in vitro transcription analyses showed that addition of SlyA protein relieved H-NS-mediated repression of hlyE. Based on these observations a model for SlyA/H-NS regulation of hlyE expression is proposed in which the relative concentrations of SlyA and H-NS govern the nature of the nucleoprotein complexes formed at PhlyE. When H-NS is dominant RNAP binding is inhibited and hlyE expression is silenced; when SlyA is dominant H-NS binding is inhibited allowing RNAP access to the promoter facilitating hlyE transcription

Time stretched multi hit 3D velocity map imaging of photoelectrons

The 2D photoelectron velocity map imaging VMI technique is commonly employed in gas phase molecular spectroscopy and dynamics investigations due to its ability to efficiently extract photoelectron spectra and angular distributions in a single experiment. However, the standard technique is limited to specific light source polarization geometries. This has led to significant interest in the development of 3D VMI techniques, which are capable of measuring individual electron positions and arrival times, obtaining the full 3D distribution without the need for inversion, forward convolution, or tomographic reconstruction approaches. Here, we present and demonstrate a novel time stretched, 13 lens 3D VMI photoelectron spectrometer, which has sub camera pixel spatial resolution and 210 ps sigma time of flight TOF resolution currently limited by trigger jitter . We employ a kHz CMOS camera to image a standard 40 mm diameter microchannel plate MCP phosphor anode detector providing x and y positions , combined with a digitizer pick off from the MCP anode to obtain the electron TOF. We present a detailed analysis of time space correlation under data acquisition conditions which generate multiple electrons per laser shot, and demonstrate a major advantage of this time stretched 3D VMI approach that the greater spread in electron TOFs permits for an accurate time and position stamping of up to six electrons per laser shot at a 1 kHz repetition rat

Multi-channel electronic and vibrational dynamics in polyatomic resonant high-order harmonic generation

High-order harmonic generation in polyatomic molecules generally involves multiple channels of ionization. Their relative contribution can be strongly influenced by the presence of resonances, whose assignment remains a major challenge for high-harmonic spectroscopy. Here we present a multi-modal approach for the investigation of unaligned polyatomic molecules, using SF6 as an example. We combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Fragment-resolved above-threshold ionization measurements reveal that strong-field ionization opens at least three channels. A shape resonance in one of them is found to dominate the signal in the 20-26 eV range. This resonance induces a phase jump in the harmonic emission, a switch in the polarization state and different dynamical responses to molecular vibrations. This study demonstrates a method for extending high-harmonic spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected

Observational diagnostics of gas in protoplanetary disks

Protoplanetary disks are composed primarily of gas (99% of the mass). Nevertheless, relatively few observational constraints exist for the gas in disks. In this review, I discuss several observational diagnostics in the UV, optical, near-IR, mid-IR, and (sub)-mm wavelengths that have been employed to study the gas in the disks of young stellar objects. I concentrate in diagnostics that probe the inner 20 AU of the disk, the region where planets are expected to form. I discuss the potential and limitations of each gas tracer and present prospects for future research.Comment: Review written for the proceedings of the conference "Origin and Evolution of Planets 2008", Ascona, Switzerland, June 29 - July 4, 2008. Date manuscript: October 2008. 17 Pages, 6 graphics, 134 reference

Quasielastic axial-vector mass from experiments on neutrino-nucleus scattering

We analyze available experimental data on the total and differential charged-current cross sections for quasielastic neutrino and antineutrino scattering off nucleons, measured with a variety of nuclear targets in the accelerator experiments at ANL, BNL, FNAL, CERN, and IHEP, dating from the end of sixties to the present day. The data are used to adjust the poorly known value of the axial-vector mass of the nucleon.Comment: 27 pages, 19 figures. Typos corrected; tables, figures and references added, discussion extended; matches published versio

Mathematically modelling the dynamics of cholesterol metabolism and ageing

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the UK. This conditionbecomes increasingly prevalent during ageing; 34.1% and 29.8% of males and females respectively, over 75years of age have an underlying cardiovascular problem. The dysregulation of cholesterol metabolism isinextricably correlated with cardiovascular health and for this reason low density lipoprotein cholesterol(LDL-C) and high density lipoprotein cholesterol (HDL-C) are routinely used as biomarkers of CVD risk. Theaim of this work was to use mathematical modelling to explore how cholesterol metabolism is affectedby the ageing process. To do this we updated a previously published whole-body mathematical model ofcholesterol metabolism to include an additional 96 mechanisms that are fundamental to this biologicalsystem. Additional mechanisms were added to cholesterol absorption, cholesterol synthesis, reversecholesterol transport (RCT), bile acid synthesis, and their enterohepatic circulation. The sensitivity of themodel was explored by the use of both local and global parameter scans. In addition, acute cholesterolfeeding was used to explore the effectiveness of the regulatory mechanisms which are responsible formaintaining whole-body cholesterol balance. It was found that our model behaves as a hypo-responderto cholesterol feeding, while both the hepatic and intestinal pools of cholesterol increased significantly.The model was also used to explore the effects of ageing in tandem with three different cholesterolester transfer protein (CETP) genotypes. Ageing in the presence of an atheroprotective CETP genotype,conferring low CETP activity, resulted in a 0.6% increase in LDL-C. In comparison, ageing with a genotypereflective of high CETP activity, resulted in a 1.6% increase in LDL-C. Thus, the model has illustrated theimportance of CETP genotypes such as I405V, and their potential role in healthy ageing