Progress in Developing Hybrid RPCs: GEM-like Detectors with Resistive Electrodes

We have recently developed an innovative detector of photons and charged particles: a GEM-like gaseous amplification structure with resistive electrodes instead of commonly used metallic ones. This novel detector combines the best property of GEMs- the capability to operate in a cascaded mode and in poorly quenched gases - and of RPC: the protection against sparks. In this paper will shortly review our latest achievements in this direction, however the main focus will be given on a new advanced design that allows to build large area detectors manufactured by a screen printing technology. The proposed detector, depending on the applications, can operate either in a GEM mode (electron multiplications through holes only) or as a hybrid RPC with simultaneous amplifications in the drift region and in the holes. The possible applications of this new detector will be discussed

New results from an extensive aging test on bakelite Resistive Plate Chambers

We present recent results of an extensive aging test, performed at the CERN Gamma Irradiation Facility on two single--gap RPC prototypes, developed for the LHCb Muon System. With a method based on a model describing the behaviour of an RPC under high particle flux conditions, we have periodically measured the electrode resistance R of the two RPC prototypes over three years: we observe a large spontaneous increase of R with time, from the initial value of about 2 MOhm to more than 250 MOhm. A corresponding degradation of the RPC rate capabilities, from more than 3 kHz/cm2 to less than 0.15 kHz/cm2 is also found.Comment: 6 pages, 7 figures, presented at Siena 2002, 8th Topical Seminar on Innovative Particle and Radiation Detectors 21-24 October 2002, Siena, Ital

Fatigue induced changes to kinematic and kinetic gait parameters following six minutes of walking in people with Multiple Sclerosis

This is an Accepted Manuscript of an article published by Taylor & Francis in Disability and Rehabilitation on 20 May 2015, available online: http://www.tandfonline.com/doi/abs/10.3109/09638288.2015.1047969Purpose: The aim of this study was to examine the effect of 6 min of walking on fatigue, exertion and spatiotemporal, kinematic and kinetic gait parameters in people with multiple sclerosis (MS). Methods: Thirty-four people with MS with moderate levels of disability completed measures of fatigue, exertion and instrumented gait analysis before and after 6-min trials of rest and walking (using a modified 6-min walk test, m6MWT). Ten age- and gender-matched healthy controls completed analysis before and after the m6MWT. Results: The MS group had a significant increase in self-reported fatigue following the m6MWT; however, there was no effect on spatiotemporal gait parameters. During stance on the more affected side ankle dorsiflexion at initial contact decreased, while knee and hip flexor moments and hip power absorption increased. On the less affected side ankle and knee power absorption, and hip extensor moment all increased. Healthy controls showed increases in joint kinetics likely due to increased walking speeds following m6MWT. Conclusion: For people with MS, ankle dorsiflexion angle reduces at initial contact following walking induced fatigue, while increased power absorption at the hip, knee and ankle indicate gait inefficiencies that may contribute to higher levels of fatigue and exertion. Implications for Rehabilitation The modified 6-min walk test (m6MWT) leads to significant increases in self-reported fatigue and exertion in people with MS. Following the m6MWT, there is significantly reduced ankle dorsiflexion angle at initial contact in the more affected leg in people with MS. This reveals an important walking-induced kinematic change that should be the target of future orthotic and strengthening interventions. In people with MS, increased power absorption primarily during the stance phase of gait following the m6MWT reveals important walking-induced muscle weakness that should also be monitored in future strengthening and gait retraining interventions

Visual Field Dependence Is Associated with Reduced Postural Sway, Dizziness and Falls in Older People Attending a Falls Clinic.

Moving visual fields can have strong destabilising effects on balance, particularly when visually perceived motion does not correspond to postural movements. This study investigated relationships between visual field dependence (VFD), as assessed using the roll vection test, and reported dizziness, falls and sway under eyes open, eyes closed and optokinetic conditions. Ninety five falls clinic attendees undertook the roll vection test (i.e. attempted to align a rod to the vertical while exposed to a rotating visual field). Sway was assessed under different visual conditions by centre of pressure movement. Participants also completed questionnaires on space and motion discomfort, fear of falling, depression and anxiety. Thirty four (35.8%) participants exhibited VFD, i.e. had an error > 6.5º in the roll vection test. Compared to participants without VFD, participants with VFD demonstrated less movement of the centre of pressure across all visual conditions, were more likely to report space and motion discomfort and to have suffered more multiple falls in the past year. VFD was independent of fear of falling, anxiety and depression. VFD in a falls clinic population is associated with reduced sway possibly due to a stiffening strategy to maintain stance, dizziness symptoms and an increased risk of falls

Enhanced signal of astrophysical tau neutrinos propagating through Earth

Earth absorbs \nue and \numu of energies above about 100 TeV. As is well-known, although \nutau will also disappear through charged-current interactions, the \nutau flux will be regenerated by prompt tau decays. We show that this process also produces relatively large fluxes of secondary \nube and \nubmu, greatly enhancing the detectability of the initial \nutau. This is particularly important because at these energies \nutau is a significant fraction of the expected astrophysical neutrino flux, and only a tiny portion of the atmospheric neutrino flux.Comment: Four pages, two inline figure

Contemporary factors shaping the professional identity of occupational therapy lecturers

Introduction The contemporary factors of neoliberalism and evidence based practice (EBP) have implications for professional autonomy and values, education and training, ways of working and construction of knowledge. Occupational therapy lecturers are at the interface between student education and professional practice and therefore have unique insights into the way in which these factors are shaping their professional identity and that of the profession. Method Nine narrative inquiry focused interviews of occupational therapy lecturers from two universities were carried out. Data was interpreted through a Bourdieusian lens, of professional habitus, and analysed thematically. Findings The main factors influencing occupational therapy lecturer identity were noted to be relationships between professional identity and artistry; the professional body of knowledge and language; evidencing practice, neoliberalism and changes to teaching and learning. Conclusion 2 The structural factors of neoliberalism, EBP and associated policies are influencing the occupational therapy professional habitus and in turn occupational therapy lecturers’ professional identity. An effective critique of these structural factors is required to maintain the profession’s values and artistry and the knowledge upon which occupational therapy lecturers’ identity is formed and their approaches to teaching and learning are based

Study and optimization of RPCs for high rate applications

Due to the low cost, good time resolution and the properties of RPCs with respect to electronics damage protection, they are chosen for many large experiments. These detectors are reliable and stable in their operation with counting rates up to kHz/cm2. The aim of this work is to understand the fundamental rate limits of RPCs in order to find an efficient way for their optimization and hence, extend their applications. Several types of materials have been used and operational parameters have been optimized in this work comprising simulations and experiment. High efficiency, excellent position resolution, low noise and high rate capability is demonstrated. These type of RPCs open new avenues in several applications, for example in crystallography, biology and medicine

The first applications of novel gaseous detectors for UV visualization

We have demonstrated experimentally that recently developed gaseous detectors combined with solid or gaseous photo-cathodes have exceptionally low noise and high quantum efficiency for UV photons while being solar blind. For this reason they can be used for the detection of weak UV sources in daylight conditions. These detectors are extremely robust, can operate in poor gas conditions and are cheap. We present the first results of their applications to hyper-spectroscopy and flame detection in daylight conditions

The Error and Repair Catastrophes: A Two-Dimensional Phase Diagram in the Quasispecies Model

This paper develops a two gene, single fitness peak model for determining the equilibrium distribution of genotypes in a unicellular population which is capable of genetic damage repair. The first gene, denoted by $\sigma_{via}$, yields a viable organism with first order growth rate constant $k > 1$ if it is equal to some target ``master'' sequence $\sigma_{via, 0}$. The second gene, denoted by $\sigma_{rep}$, yields an organism capable of genetic repair if it is equal to some target ``master'' sequence $\sigma_{rep, 0}$. This model is analytically solvable in the limit of infinite sequence length, and gives an equilibrium distribution which depends on \mu \equiv L\eps , the product of sequence length and per base pair replication error probability, and \eps_r , the probability of repair failure per base pair. The equilibrium distribution is shown to exist in one of three possible ``phases.'' In the first phase, the population is localized about the viability and repairing master sequences. As \eps_r exceeds the fraction of deleterious mutations, the population undergoes a ``repair'' catastrophe, in which the equilibrium distribution is still localized about the viability master sequence, but is spread ergodically over the sequence subspace defined by the repair gene. Below the repair catastrophe, the distribution undergoes the error catastrophe when $\mu$ exceeds \ln k/\eps_r , while above the repair catastrophe, the distribution undergoes the error catastrophe when $\mu$ exceeds $\ln k/f_{del}$, where $f_{del}$ denotes the fraction of deleterious mutations.Comment: 14 pages, 3 figures. Submitted to Physical Review

Current cosmological bounds on neutrino masses and relativistic relics

We combine the most recent observations of large-scale structure (2dF and SDSS galaxy surveys) and cosmic microwave anisotropies (WMAP and ACBAR) to put constraints on flat cosmological models where the number of massive neutrinos and of massless relativistic relics are both left arbitrary. We discuss the impact of each dataset and of various priors on our bounds. For the standard case of three thermalized neutrinos, we find an upper bound on the total neutrino mass sum m_nu < 1.0 (resp. 0.6) eV (at 2sigma), using only CMB and LSS data (resp. including priors from supernovae data and the HST Key Project), a bound that is quite insensitive to the splitting of the total mass between the three species. When the total number of neutrinos or relativistic relics N_eff is left free, the upper bound on sum m_nu (at 2sigma, including all priors) ranges from 1.0 to 1.5 eV depending on the mass splitting. We provide an explanation of the parameter degeneracy that allows larger values of the masses when N_eff increases. Finally, we show that the limit on the total neutrino mass is not significantly modified in the presence of primordial gravitational waves, because current data provide a clear distinction between the corresponding effects.Comment: 13 pages, 6 figure