Classical percolation fingerprints in the high-temperature regime of the integer quantum Hall effect

We have performed magnetotransport experiments in the high-temperature regime (up to 50 K) of the integer quantum Hall effect for two-dimensional electron gases in semiconducting heterostructures. While the magnetic field dependence of the classical Hall law presents no anomaly at high temperatures, we find a breakdown of the Drude-Lorentz law for the longitudinal conductance beyond a crossover magnetic field B_c ~ 1 T, which turns out to be correlated with the onset of the integer quantum Hall effect at low temperatures. We show that the high magnetic field regime at B > B_c can be understood in terms of classical percolative transport in a smooth disordered potential. From the temperature dependence of the peak longitudinal conductance, we extract scaling exponents which are in good agreement with the theoretically expected values. We also prove that inelastic scattering on phonons is responsible for dissipation in a wide temperature range going from 1 to 50 K at high magnetic fields.Comment: 14 pages + 8 Figure

Serial measurements of phosphorylated neurofilament-heavy in the serum of subjects with amyotrophic lateral sclerosis

There is a need for a blood biomarker of disease activity in ALS. This marker needs to measure the loss of motor neurones. Phosphorylated neurofilament heavy chain (pNfH) in the serum is a biomarker of axonal injury. Previous studies have found that levels of pNfH are elevated in ALS. We have performed a serial study of pNfH levels in 98 subjects from our ALS clinic. There was significant elevation of levels of pNfH in subjects with ALS compared to controls, although there was considerable variability. In studies of individuals who had two or more serial samples, we found that the levels of pNfH increased over time in the early stage of disease. Levels were low in subjects with long survival. The rate of rise of pNfH was inversely correlated with survival. We suggest that the initial level of pNfH is a marker of disease severity and that changes in pNfH levels are markers of disease progression

Fatigue resistance: is it possible having a unique response?

The mechanical characterisation of the asphalt concrete in terms of both the fatigue resistance and the stiffness modulus is necessary to use any design method of the flexible road pavements. Different kinds of test are usually used in experimental work such as bending tests, uniaxial tests, etc., but sometimes they do not give the same answer. In this paper mechanical characterization was carried out by means of fatigue tests undertaken with two most used testing machines for asphalt material: two point bending (2PB) test at IFSTTAR in Nantes (France) and four point bending (4PB) test at University of Palermo, in Palermo (Italy). Different strain controlled tests were undertaken for the same material under the same loading conditions, frequency and temperature (15 Hz and 20˚C), according to the European standard 12697 part 24 and 26. The first results of this interlaboratory activity are showed in this paper

A Rapid and Reliable Method of Counting Neurons and Other Cells in Brain Tissue: A Comparison of Flow Cytometry and Manual Counting Methods

It is of critical importance to understand the numbers and distributions of neurons and non-neurons in the cerebral cortex because cell numbers are reduced with normal aging and by diseases of the CNS. The isotropic fractionator method provides a faster way of estimating numbers of total cells and neurons in whole brains and dissected brain parts. Several comparative studies have illustrated the accuracy and utility of the isotropic fractionator method, yet it is a relatively new methodology, and there is opportunity to adjust procedures to optimize its efficiency and minimize error. In the present study, we use 142 samples from a dissected baboon cortical hemisphere to evaluate if isotropic fractionator counts using a Neubauer counting chamber and fluorescence microscopy could be accurately reproduced using flow cytometry methods. We find greater repeatability in flow cytometry counts, and no evidence of constant or proportional bias when comparing microscopy to flow cytometry counts. We conclude that cell number estimation using a flow cytometer is more efficient and more precise than comparable counts using a Neubauer chamber on a fluorescence microscope. This method for higher throughput, precise estimation of cell numbers has the potential to rapidly advance research in post-mortem human brains and vastly improve our understanding of cortical and subcortical structures in normal, injured, aged, and diseased brains

Geometric morphometrics defines shape differences in the cortical area map of C57BL/6J and DBA/2J inbred mice

BACKGROUND: We previously described planar areal differences in adult mouse visual, somatosensory, and neocortex that collectively discriminated C57BL/6J and DBA/2J inbred strain identity. Here we use a novel application of established methods of two-dimensional geometric morphometrics to examine shape differences in the cortical area maps of these inbred strains. RESULTS: We used Procrustes superimposition to align a reliable set of landmarks in the plane of the cortical sheet from tangential sections stained for the cytochrome oxidase enzyme. Procrustes superimposition translates landmark configurations to a common origin, scales them to a common size, and rotates them to minimize an estimate of error. Remaining variation represents shape differences. We compared the variation in shape between C57BL/6J and DBA/2J relative to that within each strain using a permutation test of Goodall's F statistic. Significant differences in shape in the posterior medial barrel subfield (PMBSF), as well as differences in shape across primary sensory areas, characterize the cortical area maps of these common inbred, isogenic strains. CONCLUSION: C57BL/6J and DBA/2J have markedly different cortical area maps, in both size and shape. These differences suggest polymorphism in genetic factors underlying cortical specification, even between common isogenic strains. Comparing cortical phenotypes between normally varying inbred mice or between genetically modified mice can identify genetic contributions to cortical specification. Geometric morphometric analysis of shape represents an additional quantitative tool for the study of cortical development, regardless of whether it is studied from phenotype to gene or gene to phenotype

Disability in young adults following major trauma: 5 year follow up of survivors

BACKGROUND: Injuries are a major cause of mortality and morbidity in young people. Despite this, the long-term consequences for young survivors of severe injury are relatively unexplored. METHODS: Population based cohort study involving 5 year post injury structured interview of all cases of major trauma (Injury Severity Score > 15) identified retrospectively for 12 month period (1988 to 1989) within former Yorkshire Health Authority area of the United Kingdom. RESULTS: 125 individuals aged 11–24 years at time of injury were identified. Of these, 109 (87%) were interviewed. Only 20% (95% CI 14–29%) of those interviewed reported no disability. Mean Office of Population Census and Surveys (OPCS) disability score of the remainder was 7.5 (median 5.8, range 0.5 to 19.4). The most commonly encountered areas of disability were behaviour (54%, 95% CI 45–63%), intellectual functioning (39%, 95% CI 31–49%) and locomotion (29%, 95% CI 22–39%). Many respondents reported that their daily lives were adversely affected by their health problems for example, causing problems with work, 54% (95% CI 45–63%), or looking after the home, 28% (95% CI 21–38%). Higher OPCS scores were usually but not always associated with greater impact on daily activities. The burden of caring responsibilities fell largely on informal carers. 51% (95% CI 42–61%) of those interviewed would have liked additional help to cope with their injury and disability. CONCLUSION: The study has revealed significant disability amongst a cohort of young people 5 years post severe injury. Whilst many of these young people were coping well with the consequences of their injuries, others reported continuing problems with the activities of daily life. The factors underpinning the young people's differing experiences and social outcome should be explored

Care during the third stage of labour: A postal survey of UK midwives and obstetricians

<p>Abstract</p> <p>Background</p> <p>There are two approaches to care during the third stage of labour: Active management includes three components: administration of a prophylactic uterotonic drug, cord clamping and controlled cord traction. For physiological care, intervention occurs only if there is clinical need. Evidence to guide care during the third stage is limited and there is variation in recommendations which may contribute to differences in practice. This paper describes current UK practice during the third stage of labour.</p> <p>Methods</p> <p>A postal survey of 2230 fellows and members of the Royal College of Obstetricians and Gynaecologists (RCOG) and 2400 members of the Royal College of Midwives was undertaken. Respondents were asked about care during the third stage of labour, for vaginal and caesarean births and their views on the need for more evidence to guide care in the third stage. The data were analysed in Excel and presented as descriptive statistics.</p> <p>Results</p> <p>1189 (53%) fellows and members of the RCOG and 1702 (71%) midwives responded, of whom 926 (78%) and 1297 (76%) respectively had conducted or supervised births in the last year. 93% (863/926) of obstetricians and 73% (942/1297) of midwives report 'always or usually' using active management. 66% (611/926) of obstetricians and 33% (430/1297) of midwives give the uterotonic drug with delivery of the anterior shoulder; this was intramuscular Syntometrine^®for 79% (728/926) and 86% (1118/1293) respectively. For term births, 74% (682/926) of obstetricians and 41% (526/1297) of midwives clamp the cord within 20 seconds, as do 57% (523/926) and 55% (707/1297) for preterm births. Controlled cord traction was used by 94% of both obstetricians and midwives. For caesarean births, intravenous oxytocin was the uterotonic used by 90% (837/926) of obstetricians; 79% (726/926) clamp the cord within 20 seconds for term births as do 63% (576/926) for preterm births.</p> <p>Physiological management was used 'always or usually' by 2% (21/926) of obstetricians and 9% (121/1297) of midwives. 81% (747/926) of obstetricians and 89% (1151/1297) of midwives thought more evidence from randomised trials was needed; the most popular question was when is best to clamp the cord.</p> <p>Conclusions</p> <p>Active management of the third stage of labour is widely used by both obstetricians and midwives in the UK. Syntometrine^®is usually used for vaginal births and oxytocin for caesarean births; when this is given and when the cord is clamped varies.</p

Time dependent viscoelastic rheological response of pure, modified and synthetic bituminous binders

Bitumen is a viscoelastic material that exhibits both elastic and viscous components of response and displays both a temperature and time dependent relationship between applied stresses and resultant strains. In addition, as bitumen is responsible for the viscoelastic behaviour of all bituminous materials, it plays a dominant role in defining many of the aspects of asphalt road performance, such as strength and stiffness, permanent deformation and cracking. Although conventional bituminous materials perform satisfactorily in most highway pavement applications, there are situations that require the modification of the binder to enhance the properties of existing asphalt material. The best known form of modification is by means of polymer modification, traditionally used to improve the temperature and time susceptibility of bitumen. Tyre rubber modification is another form using recycled crumb tyre rubber to alter the properties of conventional bitumen. In addition, alternative binders (synthetic polymeric binders as well as renewable, environmental-friendly bio-binders) have entered the bitumen market over the last few years due to concerns over the continued availability of bitumen from current crudes and refinery processes. This paper provides a detailed rheological assessment, under both temperature and time regimes, of a range of conventional, modified and alternative binders in terms of the materials dynamic (oscillatory) viscoelastic response. The rheological results show the improved viscoelastic properties of polymer- and rubber-modified binders in terms of increased complex shear modulus and elastic response, particularly at high temperatures and low frequencies. The synthetic binders were found to demonstrate complex rheological behaviour relative to that seen for conventional bituminous binders

Moisture-induced strength degradation of aggregate–asphalt mastic bonds

A common manifestation of moisture-induced damage in asphalt mixtures is the loss of adhesion at the aggregate–asphalt mastic interface and/or cohesion within the bulk mastic. This paper investigates the effects of moisture on the aggregate–mastic interfacial adhesive strength as well as the bulk mastic cohesive strength. Physical adsorption concepts were used to characterise the thermodynamic work of adhesion and debonding of the aggregate–mastic bonds using dynamic vapour sorption and contact angle measurements. Moisture diffusion in the aggregate substrates and in the bulk mastics was determined using gravimetric techniques. Mineral composition of the aggregates was characterised by a technique based on the combination of a scanning electron microscope and multiple energy dispersive X-ray detectors. Aggregate–mastic bond strength was determined using moisture-conditioned butt-jointed tensile test specimens, while mastic cohesive strength was determined using dog bone-shaped tensile specimens. Aggregate–mastic bonds comprising granite mastics performed worse in terms of moisture resistance than limestone mastic bonds. The effect of moisture on the aggregate–mastic interfacial bond appears to be more detrimental than the effect of moisture on the bulk mastic