1,051 research outputs found

    Aerosol chemical composition and distribution during the Pacific Exploratory Mission (PEM) Tropics

    Get PDF
    Distributions of aerosol-associated soluble ions over much of the South Pacific were determined by sampling from the NASA DC-8 as part of the Pacific Exploratory Mission (PEM) Tropics campaign. The mixing ratios of all ionic species were surprisingly low throughout the free troposphere (2-12 km), despite the pervasive influence from biomass burning plumes advecting over the South Pacific from the west during PEM-Tropics. At the same time, the specific activity of 7Be frequently exceeded 1000 fCi m-3 through much of the depth of the troposphere. These distributions indicate that the plumes must have been efficiently scavenged by precipitation (removing the soluble ions), but that the scavenging must have occurred far upwind of the DC-8 sampling regions (otherwise 7Be activities would also have been low). This inference is supported by large enhancements of HNO3 and carboxylic acids in many of the plumes, as these soluble acidic gases would also be readily scavenged in any precipitation events. Decreasing mixing ratios of NH4 + with altitude in all South Pacific regions sampled provide support for recent suggestions that oceanic emissions of NH3 constitute a significant source far from continents. Our sampling below 2 km reaffirms the latitudinal pattern in the methylsulfonate/non-sea-salt sulfate (MSA/nss SO4 =) molar ratio established through surface-based and shipboard sampling, with values increasing from \u3c0.05 in the tropics to nearly 0.6 at 70°S. However, we also found very high values of this ratio (0.2-0.5) at 10 km altitude above the intertropical convergence zone near 10°N. It appears that wet convective pumping of dimethylsulfide from the tropical marine boundary layer is responsible for the high values of the MSA/nss SO4 = ratio in the tropical upper troposphere. This finding complicates use of this ratio to infer the zonal origin of biogenic S transported long distances. Copyright 1999 by the American Geophysical Union

    Acquisition of sensorimotor fMRI under general anaesthesia: Assessment of feasibility, the BOLD response and clinical utility

    Get PDF
    We evaluated whether task-related fMRI (functional magnetic resonance imaging) BOLD (blood oxygenation level dependent) activation could be acquired under conventional anaesthesia at a depth enabling neurosurgery in five patients with supratentorial gliomas. Within a 1.5 T MRI operating room immediately prior to neurosurgery, a passive finger flexion sensorimotor paradigm was performed on each hand with the patients awake, and then immediately after the induction and maintenance of combined sevoflurane and propofol general anaesthesia. The depth of surgical anaesthesia was measured and confirmed with an EEG-derived technique, the Bispectral Index (BIS). The magnitude of the task-related BOLD response and BOLD sensitivity under anaesthesia were determined. The fMRI data were assessed by three fMRI expert observers who rated each activation map for somatotopy and usefulness for radiological neurosurgical guidance. The mean magnitudes of the task-related BOLD response under a BIS measured depth of surgical general anaesthesia were 25% (tumour affected hemisphere) and 22% (tumour free hemisphere) of the respective awake values. BOLD sensitivity under anaesthesia ranged from 7% to 83% compared to the awake state. Despite these reductions, somatotopic BOLD activation was observed in the sensorimotor cortex in all ten data acquisitions surpassing statistical thresholds of at least p < 0.001uncorr. All ten fMRI activation datasets were scored to be useful for radiological neurosurgical guidance. Passive task-related sensorimotor fMRI acquired in neurosurgical patients under multi-pharmacological general anaesthesia is reproducible and yields clinically useful activation maps. These results demonstrate the feasibility of the technique and its potential value if applied intra-operatively. Additionally these methods may enable fMRI investigations in patients unable to perform or lie still for awake paradigms, such as young children, claustrophobic patients and those with movement disorders

    "How do pilates trained physiotherapists utilize and value pilates exercise for MSK conditions? A qualitative study"

    Get PDF
    Background Pilates is a popular exercise therapy approach offering numerous benefits, including muscular strength, flexibility, control, and core stability. Pilates has been widely utilized in the prevention and rehabilitation of a variety of musculoskeletal disorders. Objectives The aim of this study was to explore the experiences and opinions of Pilates trained NHS and private practice physiotherapists in the UK, regarding the perceived benefits, risks, delivery and rationale for this exercise method. Methods This qualitative study used a self‐designed electronic survey to retrieve the views of 30 physiotherapists, who had undertaken formal Pilates Instruction training, recruited by a purposive and snowball sampling method. Questions were either multiple choice or open‐ended, examined via thematic analysis. Results Physiotherapists identified the most important benefits of Pilates as reduction in fear‐avoidance, improving bodily awareness and increasing muscular strength. Exercises that promote general movement were highlighted as being particularly useful, with a majority recommending daily practice for optimum benefit. Participants recognized lack of core strength as a key indicator, whereas others criticized excessive focus on this principle. Conclusions Physiotherapists identified a range of inter‐linked benefits and recognized that Pilates is hugely modifiable. Individualizing exercises can further encourage participation and negate the restriction of some health conditions. NHS and Private Practice Therapists utilize Pilates in a similar way, although rationales for its use may differ, as the justification for Pilates exercise may be evolving. Pilates appears a valuable methodology in the NHS, which can help patients engage with activity

    SIMULATION AND PERFORMANCE ANALYSIS OF A HYBRID ROCKET ENGINE WITH SELF-PRESSURIZING OXIDIZER

    Get PDF
    There are many challenges to simulate and design a hybrid engine, such as the dimensioning of the feed lines and tanks, propulsive performance calculations, and simulations of the expected behavior in the combustion chamber and the oxidizer tank during the engine operation. In this work, methods are assembled in a concise and complete analysis of the Gluon hybrid rocket engine, developed by PION Labs, with a blowdown pressurization system, using N2O as oxidizer and a paraffin-based fuel. For that, a study will be presented on the peculiar characteristics of the oxidizer and its behavior during the phases of operation of the rocket engine. Then, the main equations that describe the operation of the rocket engine, including the combustion chamber, injection plate, feed lines, and the oxidizer tank are presented, and the performance indicators calculations of the engine are shown and discussed. Finally, simulation results of the combustion chamber and the oxidizer tank during engine firing will be presented, leading to the concluding remarks on the data obtained

    Perceived benefits, rationale and preferences of exercises utilized within Pilates group exercise programmes for people with chronic musculoskeletal conditions : a questionnaire of Pilates‐trained physiotherapists

    Get PDF
    Introduction: An estimated 29% of the population, around 17.8 million people, live with a musculoskeletal condition in the UK. Pilates exercise has positive benefits, including reducing pain and disability for people with musculoskeletal conditions. The aim of the present study was to explore the views of Pilates ‐ trained physiother- apists in relation to the perceived benefits of, and clinical reasoning for, exercise prescription in Pilates classes. Methods: A qualitative approach was taken to both data collection and analysis, using a thematic framework. Data were collected via electronic questionnaires using open ‐ ended questions. Participants included 15 Pilates ‐ trained physiotherapists who regularly ran Pilates exercise classes within seven private physiotherapy clinics for people with a range of chronic musculoskeletal conditions. Results: The results were organized into six main themes: Perceived benefits 1: Improved function and increased levels of activity. Perceived benefits 2: Improved ability to manage their musculoskeletal condition autonomously; Efficacy of group Pilates exercise; Optimum combination of exercises used within a class; Physiothera- pist rationale for the most effective exercises; Precautions with specific exercises. Conclusions: The study was the first to investigate perceived benefits, rationale and preference for choice of exercise among Pilates ‐ trained physiotherapists. Physiotherapists felt that the Pilates classes facilitated an active lifestyle and self ‐ management approach. They used a combination of exercises in each class to address all the main muscle groups, but some had specific exercise preferences related to the patients' needs. Exercises were linked to evidence around neuromuscular control, direction preference and biomechanical principles

    On the origin of the Boson peak in globular proteins

    Full text link
    We study the Boson Peak phenomenology experimentally observed in globular proteins by means of elastic network models. These models are suitable for an analytic treatment in the framework of Euclidean Random Matrix theory, whose predictions can be numerically tested on real proteins structures. We find that the emergence of the Boson Peak is strictly related to an intrinsic mechanical instability of the protein, in close similarity to what is thought to happen in glasses. The biological implications of this conclusion are also discussed by focusing on a representative case study.Comment: Proceedings of the X International Workshop on Disordered Systems, Molveno (2006
    corecore