385 research outputs found
Spatial Structure of Ion Beams in an Expanding Plasma
We report spatially resolved perpendicular and parallel, to the magnetic field, ion velocity distribution function (IVDF) measurements in an expanding argon helicon plasma. The parallel IVDFs, obtained through laser induced fluorescence (LIF), show an ion beam with vâââ8000âm/s flowing downstream and confined to the center of the discharge. The ion beam is measurable for tens of centimeters along the expansion axis before the LIF signal fades, likely a result of metastable quenching of the beam ions. The parallel ion beam velocity slows in agreement with expectations for the measured parallel electric field. The perpendicular IVDFs show an ion population with a radially outward flow that increases with distance from the plasma axis. Structures aligned to the expanding magnetic field appear in the DC electric field, the electron temperature, and the plasma density in the plasma plume. These measurements demonstrate that at least two-dimensional and perhaps fully three-dimensional models are needed to accurately describe the spontaneous acceleration of ion beams in expanding plasmas
The Shapovalov determinant for the Poisson superalgebras
Among simple Z-graded Lie superalgebras of polynomial growth, there are
several which have no Cartan matrix but, nevertheless, have a quadratic even
Casimir element C_{2}: these are the Lie superalgebra k^L(1|6) of vector fields
on the (1|6)-dimensional supercircle preserving the contact form, and the
series: the finite dimensional Lie superalgebra sh(0|2k) of special Hamiltonian
fields in 2k odd indeterminates, and the Kac--Moody version of sh(0|2k). Using
C_{2} we compute N. Shapovalov determinant for k^L(1|6) and sh(0|2k), and for
the Poisson superalgebras po(0|2k) associated with sh(0|2k). A. Shapovalov
described irreducible finite dimensional representations of po(0|n) and
sh(0|n); we generalize his result for Verma modules: give criteria for
irreducibility of the Verma modules over po(0|2k) and sh(0|2k)
Centre and Representations of U_q(sl(2|1)) at Roots of Unity
Quantum groups at roots of unity have the property that their centre is
enlarged. Polynomial equations relate the standard deformed Casimir operators
and the new central elements. These relations are important from a physical
point of view since they correspond to relations among quantum expectation
values of observables that have to be satisfied on all physical states. In this
paper, we establish these relations in the case of the quantum Lie superalgebra
U_q(sl(2|1)). In the course of the argument, we find and use a set of
representations such that any relation satisfied on all the representations of
the set is true in U_q(sl(2|1)). This set is a subset of the set of all the
finite dimensional irreducible representations of U_q(sl(2|1)), that we
classify and describe explicitly.Comment: Minor corrections, References added. LaTeX2e, 18 pages, also
available at http://lapphp0.in2p3.fr/preplapp/psth/ENSLAPP583.ps.gz . To
appear in J. Phys. A: Math. Ge
A systematic review to determine use of the Endometriosis Health Profiles to measure quality of life outcomes in women with endometriosis
BACKGROUND The Endometriosis Health Profiles (EHPs), the EHP-30 and EHP-5, are patient-reported outcome measures that were developed to measure the health-related quality of life (HRQoL) of women living with endometriosis. Prior to their development, a systematic review was undertaken which identified that the HRQoL of women living with endometriosis was poorly understood, with only three medical and one surgical study identified. OBJECTIVE AND RATIONALE The 20-year anniversary of the EHP-30 provided a timely opportunity to assess how the tools have been used and explore what the findings tell us about the impact of endometriosis and its associated treatments upon womenâs QoL. Applying robust systematic review methodology, following PRISMA guidelines, we sought to answer: How many studies have used the EHP and for what purpose?; What are the demographic characteristics and international context of the studies?; What is the methodological nature and quality of the studies?; Which interventions have been assessed and what are the reported EHP outcomes?; and Can the EHP outcomes of these interventions be analysed using a meta-analysis and, if so, what do the results show? SEARCH METHODS The electronic databases MEDLINE, CINAHL, PsycINFO, PubMed, and Google Scholar were searched from the year the EHP was first published, in 2001 to 26 February 2020 using the search terms âEHP30â, âEHP5â, âEHP-30â, âEHP-5â, âendometriosis health profile 30â, and âendometriosis health profile 5â. We updated the searches on 9 April 2021. All included studies were quality assessed using the Mixed Methods Appraisal Tool (MMAT). OUTCOMES The review included 139 papers. In clinical intervention studies, the EHPs were deployed most frequently to measure the outcomes of medical (nâ=â35) and surgical (nâ=â21) treatment. The EHPs were also used in 13 other intervention studies, 29 non-interventional studies, 32 psychometric/cross cultural validation studies; six diagnostic studies, and in three other studies to measure outcomes in related conditions. They were mainly deployed in studies undertaken in Europe and North America. Overall, regardless of the nature of the intervention, most women reported improvements in HRQoL after treatment. Surgical interventions generally resulted in significant improvements for the longest amount of time. There was also evidence that when participants stopped taking medication their EHP scores worsened, perhaps reinforcing the temporary impact of medical treatment. Younger patients reported more negative impact upon their HRQoL. Further evidence using classical test theory to support the EHPsâ robust psychometric properties, including acceptability, dimensionality, reliability, validity (including cross-cultural), and responsiveness, was demonstrated, particularly for the EHP-30. Strikingly, using anchor-based methods, EHP-30 responsiveness studies demonstrate the largest mean changes in the âcontrol and powerlessnessâ domain post-intervention, followed by âpainâ. MMAT outcomes indicated the quality of the papers was good, with the exception of five studies. A meta-analysis was not undertaken owing to the heterogeneity of the interventions and papers included in this review. WIDER IMPLICATIONS Women with endometriosis face a lifetime of surgical and/or medical interventions to keep the condition under control. Less invasive treatments that can lead to improved longer term physical and psycho-social outcomes are needed. The EHPs are reliable, valid, acceptable, and responsive tools, but more assessment of EHP outcomes using modern psychometric methods and in the context of women from ethnically diverse backgrounds and in routine clinical care would be beneficial. Given the brevity of the EHP-5, it may be the most appropriate version to use in routine clinical practice, whereas the longer EHP-30, which provides more granularity, is more appropriate for research
The G0 Experiment: Apparatus for Parity-Violating Electron Scattering Measurements at Forward and Backward Angles
In the G0 experiment, performed at Jefferson Lab, the parity-violating
elastic scattering of electrons from protons and quasi-elastic scattering from
deuterons is measured in order to determine the neutral weak currents of the
nucleon. Asymmetries as small as 1 part per million in the scattering of a
polarized electron beam are determined using a dedicated apparatus. It consists
of specialized beam-monitoring and control systems, a cryogenic hydrogen (or
deuterium) target, and a superconducting, toroidal magnetic spectrometer
equipped with plastic scintillation and aerogel Cerenkov detectors, as well as
fast readout electronics for the measurement of individual events. The overall
design and performance of this experimental system is discussed.Comment: Submitted to Nuclear Instruments and Method
Measuring Servitization Progress and Outcome:The Case of âAdvanced Servicesâ
The purpose of this paper is to establish a framework for assessing the progress and outcome of a manufacturerâs transformation towards becoming a provider of âadvanced servicesâ â a complex bundling of products and services, whereby manufacturers offer capabilities and outcomes instead of products alone. âAdvanced servicesâ represent the most complex offering in the current servitization trend among manufacturers. However, current performance measures lack the breadth and focus to assess progress or outcomes, and so support research and practice of organisational transformation efforts required. To address this gap the paper investigates how a manufacturerâs efforts to become an âadvanced servicesâ provider can be comprehensively measured, and develops a framework for assessing the transformation journey towards becoming an âadvanced servicesâ provider. The research method is based on (1) a systematic literature review process to create a comprehensive set of service-related performance measures that are available to assess a manufacturerâs servitization efforts, followed by (2) an engagement with an expert panel to synthesise the identified measures and create a set of âadvanced servicesâ performance measures. The proposed framework is presented as a scorecard that can be used in practice to assess the progress and outcome of a manufacturerâs transformation towards becoming a provider of âadvanced servicesâ
Delivery of non-invasive ventilation to people living with motor neuron disease in the UK
Objective Non-invasive ventilation (NIV) improves survival and quality of life in motor neuron disease (MND), but many patients fail to receive effective ventilation. This study aimed to map the respiratory clinical care for MND patients at a service and individual healthcare professional (HCP) level to understand where attention may be needed to ensure all patients receive optimal care.
Methods Two online surveys of HCPs working with MND patients in the UK were conducted. Survey 1 targeted HCPs providing specialist MND care. Survey 2 targeted HCPs working in respiratory/ventilation services and community teams. Data were analysed using descriptive and inferential statistics.
Results Responses from 55 HCPs providing specialist MND care who worked at 21 MND care centres and networks and 13 Scotland Health Boards were analysed from Survey 1. Responses from 85 HCPs from respiratory/ventilation services and 73 HCPs from community teams, representing 97 services were analysed from Survey 2.
Significant differences in practice were identified at each stage of the respiratory care pathway as well as evidence of the need for improvement. This included when patients were referred to respiratory services, the time taken waiting to commence NIV, the availability of sufficient NIV equipment and provision of services, particularly out of hours.
Conclusion We have highlighted significant disparity in MND respiratory care practices. Increased awareness of the factors that influence NIV success and the performance of individuals and services is important for optimal practice
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