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Search Results: 1 - 10 of 32754 matches for " John Freund "
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Direct Estimation of Sizes of Higher-Order Graphs
John C. Collins,Andreas Freund
Physics , 1997, DOI: 10.1016/S0550-3213(97)00445-8
Abstract: With the aid of simple examples we show how to make simple estimates of the sizes of higher-order Feynman graphs. Our methods enable appropriate values of renormalization and factorization scales to be made. They allow the diagnosis of the source of unusually large corrections that are in need of resummation.
Proof of Factorization for Deeply Virtual Compton Scattering in QCD
John C. Collins,Andreas Freund
Physics , 1998, DOI: 10.1103/PhysRevD.59.074009
Abstract: We show that factorization holds for the deeply virtual Compton scattering amplitude in QCD, up to power suppressed terms, to all orders in perturbation theory. Furthermore, we show that the virtuality of the produced photon does not influence the general theorem.
A Distributed Magnetometer Network
John Scoville,John Spritzer,Friedemann Freund
Physics , 2014,
Abstract: Various possiblities for a distributed magnetometer network are considered. We discuss strategies such as croudsourcing smartphone magnetometer data, the use of trees as magnetometers, and performing interferometry using magnetometer arrays to synthesize the magnetometers into a large-scale low-frequency radio telescope. Geophysical and other applications of such a network are discussed.
Pre-earthquake Magnetic Pulses
John Scoville,Jorge Heraud,Friedemann Freund
Physics , 2014,
Abstract: A semiconductor model of rocks is shown to describe unipolar magnetic pulses, a phenomenon that has been observed prior to earthquakes. These pulses are observable because their extremely long wavelength allows them to pass through the Earth's crust. Interestingly, the source of these pulses may be triangulated to pinpoint locations where stress is building deep within the crust. We couple a semiconductor drift-diffusion model to a magnetic field in order to describe the electromagnetic effects associated with electrical currents flowing within rocks. The resulting system of equations is solved numerically and it is seen that a volume of rock may act as a diode that produces transient currents when it switches bias. These unidirectional currents are expected to produce transient unipolar magnetic pulses similar in form, amplitude, and duration to those observed before earthquakes, and this suggests that the pulses could be the result of geophysical semiconductor processes.
Paradox of Peroxy Defects and Positive Holes in Rocks Part II: Outflow of Electric Currents from Stressed Rocks
John Scoville,Jaufray Sornette,Friedemann Freund
Physics , 2015,
Abstract: Understanding the electrical properties of rocks is of fundamental interest. We report on currents generated when stresses are applied. Loading the center of gabbro tiles, 30x30x0.9 cm$^3$, across a 5 cm diameter piston, leads to positive currents flowing from the center to the unstressed edges. Changing the constant rate of loading over 5 orders of magnitude from 0.2 kPa/s to 20 MPa/s produces positive currents, which start to flow already at low stress levels, <5 MPa. The currents increase as long as stresses increase. At constant load they flow for hours, days, even weeks and months, slowly decreasing with time. When stresses are removed, they rapidly disappear but can be made to reappear upon reloading. These currents are consistent with the stress-activation of peroxy defects, such as O$_3$Si-OO-SiO$_3$, in the matrix of rock-forming minerals. The peroxy break-up leads to positive holes h$^{\bullet}$, i.e. electronic states associated with O$^-$ in a matrix of O$^{2-}$, plus electrons, e'. Propagating along the upper edge of the valence band, the holes are able to flow from stressed to unstressed rock, traveling fast and far by way of a phonon-assisted electron hopping mechanism using energy levels at the upper edge of the valence band. Impacting the tile center leads to h$^{\bullet}$ pulses, 4-6 ms long, flowing outward at ~100 m/sec at a current equivalent to 1-2 x 10$^9$ A/km$^3$. Electrons, trapped in the broken peroxy bonds, are also mobile, but only within the stressed volume.
From Where Did the Water Come That Filled the Earth’s Oceans? A Widely Overlooked Redox Reaction  [PDF]
Friedemann T. Freund, Minoru M. Freund
American Journal of Analytical Chemistry (AJAC) , 2015, DOI: 10.4236/ajac.2015.64033
Abstract: Though two-thirds of Earth’s surface is covered by oceans, measurements of hydroxyl concentrations in upper mantle minerals, specifically in olivine, reportedly provide surprisingly low values. This has been interpreted to mean that there is little dissolved H2O in the Earth’s mantle. By inference, when Earth formed, there might not have been able enough water to fill the oceans through volcanic degassing. It has therefore been proposed that the missing water was delivered to Earth from space, through comets and other impacting bodies. However, the reported low hydroxyl concentrations in olivine and similar mineralsis probably based on a profound misunderstanding of a solid state reaction that converts hydroxyls into something more difficult to detect. There is indeed a redox reaction that converts, during cooling, solute hydroxyls in the matrix of minerals into peroxy plus H2. This widely overlooked redox conversion takes place under thermodynamic non-equilibrium conditions. Its significance is that any mineral and any rock available for collection at the Earth surface has gone through a process that causes hydroxyls, the telltale sign of dissolved H2O, to change into peroxyplusH2. The H2 molecules are diffusively mobile and may leave even structurally dense mineral grains. The remaining peroxy thus become the memory of the “true” solute H2O content, besides a few residual hydroxyls. Though first described over 30 years ago, this redox conversion has been largely ignored. As a result it is unknown how much H2O is contained in the Earth’s upper mantle but it is certainly much more than has been assumed until now on the basis of analysis of residual hydroxyls.
Association between Magnetic Resonance Imaging and the Result of Medial Branch Blocks  [PDF]
Stephan Klessinger, Wolfgang Freund
Pain Studies and Treatment (PST) , 2017, DOI: 10.4236/pst.2017.51001
Abstract: The aim of this retrospective practice audit was to assess the correlation between painful zygapophysial joints and changes seen in magnetic resonance imaging (MRI). Patients with unilateral pain were tested with controlled medial branch blocks. The MRI scans of patients with a positive response were compared blinded with normal MRI scans. The dimensions of the joint were assessed and osteoarthritis was graded. Fifteen symptomatic patients and 15 asymptomatic patients were included and evaluated. Comparison of the joints showed that the maximum diameter of symptomatic joints was significantly larger, and the grading of osteoarthritis was significantly higher for symptomatic joints. No healthy patient was assigned a grade 3. Grades 2 and 3 were found significantly more often in symptomatic patients. Only one symptomatic joint was assigned grade 0. Grade 0 was found significantly more often in asympto-matic patients. The presented MRI technique has limited value as a diagnostic test for lumbar zygapophysial joint pain. It is not possible to detect a single symptomatic joint. However, the osteoarthritis grading for the lumbar zyg-apophysial joints might be helpful for finding predictors for negative response if the results of the rating are grade zero. Therefore, unnecessary medial branch blocks might be avoided.
A cross-sectional survey of the prevalence of environmental tobacco smoke preventive care provision by child health services in Australia
Todd R Heard, Justine B Daly, Jennifer A Bowman, Megan AG Freund, John H Wiggers
BMC Public Health , 2011, DOI: 10.1186/1471-2458-11-324
Abstract: One-hundred and fifty-one (83%) child health service managers within New South Wales, Australia completed a questionnaire in 2002 regarding the: assessment of parental smoking and child ETS exposure; the provision of parental smoking cessation and ETS-exposure reduction advice; and strategies used to support the provision of such care. Child health services were categorised based on their size and case-mix, and a chi-square analysis was performed to compare the prevalence of ETS risk assessment and ETS prevention advice between service types. Logistic regression analysis was used to examine associations between the existence of care support strategies and the provision of ETS risk assessment and ETS exposure prevention advice.A significant proportion of services reported that they did not assess parental smoking status (26%), and reported that they did not assess the ETS exposure (78%) of any child. Forty four percent of services reported that they did not provide smoking cessation advice and 20% reported they did not provide ETS exposure prevention advice. Community based child and family health services reported a greater prevalence of ETS preventive care compared to other hospital based units. Less than half of the services reported having strategies to support the provision of ETS preventive care. The existence of such support strategies was associated with greater odds of care provision.The existence of major gaps in recommended ETS preventive care provision suggests a need for additional initiatives to increase such care delivery. The low prevalence of strategies that support such care delivery suggests a potential avenue to achieve this outcome.Children are particularly vulnerable to the harmful effects of environmental tobacco smoke (ETS) because of their relatively underdeveloped immune and pulmonary systems, their small body size, and their higher rates of ventilation [1,2]. Exposure to ETS increases a child's risk of developing diseases of the respiratory
A cluster randomised trial to evaluate a physical activity intervention among 3-5 year old children attending long day care services: study protocol
Meghan Finch, Luke Wolfenden, Philip J Morgan, Megan Freund, Rebecca Wyse, John Wiggers
BMC Public Health , 2010, DOI: 10.1186/1471-2458-10-534
Abstract: The study will employ a cluster randomised controlled trial design. Three hundred children aged between 3-5 years from twenty randomly selected long day care services in the Hunter Region of New South Wales, Australia will be invited to participate in the trial. Ten of the 20 long day care services will be randomly allocated to deliver the intervention with the remaining ten services allocated to a wait list control group. The physical activity intervention will consist of a number of strategies including: delivering structured fundamental movement skill activities, increasing physical activity opportunities, increasing staff role modelling, providing children with a physical activity promoting indoor and outdoor environment and limiting children's small screen recreation and sedentary behaviours. Intervention effectiveness will be measured via child physical activity levels during attendance at long day care. The study also seeks to determine the acceptability and extent of implementation of the intervention by services and their staff participating in the study.The trial will address current gaps in the research evidence base and contribute to the design and delivery of future interventions promoting physical activity for young children in long day care settings.Australian New Zealand Clinical Trials Registry ACTRN12610000087055Regular physical activity among young children can contribute to social, psychological and fundamental motor skill development, maintain bone health and prevent obesity [1-6]. Despite these benefits, research suggests that preschool aged children are not adequately physically active [3,7,8]. For example, a recent study found that 44% and 21% of Australian preschool aged children are not sufficiently active on weekdays and weekends respectively [8].For a variety of reasons, childcare services (centre based care including long day care services and pre-school) have been identified as a promising setting for the delivery of interventions to in
A school-based resilience intervention to decrease tobacco, alcohol and marijuana use in high school students
Rebecca K Hodder, Justine Daly, Megan Freund, Jenny Bowman, Trevor Hazell, John Wiggers
BMC Public Health , 2011, DOI: 10.1186/1471-2458-11-722
Abstract: A non-controlled before and after study was undertaken. Data regarding student resilience and protective factors, and measures of tobacco, alcohol and marijuana use were collected from grade 7 to 10 students at baseline (n = 1449) and one year following a three year intervention (n = 1205).Significantly higher resilience and protective factors scores, and significantly lower prevalence of substance use were evident at follow up.The results suggest that the intervention has the potential to increase resilience and protective factors, and to decrease the use of tobacco, alcohol and marijuana by adolescents. Further more rigorous research is required to confirm this potential.Tobacco, alcohol and other drug use contribute significantly to mortality and morbidity in many countries [1,2]. Tobacco use generally commences in early adolescence [3], with earlier uptake associated with heavier smoking [4], rapid establishment of nicotine dependence even after brief intermittent use [5] and greater difficulty in quitting in adulthood [4]. Similar to tobacco, initiation of alcohol use generally occurs in adolescence [6], and earlier drinking experiences have been linked to alcohol dependence in adulthood [7]. The patterns of illicit substance misuse developed in youth are similarly associated with continued use into adult life [8]. World wide, a significant proportion of adolescents use tobacco, alcohol and marijuana, with such use being greater in older adolescent age groups [9-13].Schools are considered an ideal setting for programs aimed at decreasing the prevalence of health risk behaviours as: they provide access to young people at a time when they are vulnerable to emotional problems and risk taking behaviour [14]; young people spend half their waking hours at school; and the quality of experiences with teachers and peers can have a positive impact on young people's health and emotional well-being [15]. Despite such potential, reviews of school-based programs designed to
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