1,018 research outputs found

    Time-Fractional KdV Equation for the plasma in auroral zone using Variational Methods

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    The reductive perturbation method has been employed to derive the Korteweg-de Vries (KdV) equation for small but finite amplitude electrostatic waves. The Lagrangian of the time fractional KdV equation is used in similar form to the Lagrangian of the regular KdV equation. The variation of the functional of this Lagrangian leads to the Euler-Lagrange equation that leads to the time fractional KdV equation. The Riemann-Liouvulle definition of the fractional derivative is used to describe the time fractional operator in the fractional KdV equation. The variational-iteration method given by He is used to solve the derived time fractional KdV equation. The calculations of the solution with initial condition A0*sech(cx)^2 are carried out. Numerical studies have been made using plasma parameters close to those values corresponding to the dayside auroral zone. The effects of the time fractional parameter on the electrostatic solitary structures are presented.Comment: 1 tex file + 5 eps figure

    The tension between fire risk and carbon storage: evaluating U.S. carbon and fire management strategies through ecosystem models

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    Fire risk and carbon storage are related environmental issues because fire reduction results in carbon storage through the buildup of woody vegetation, and stored carbon is a fuel for fires. The sustainability of the U.S. carbon sink and the extent of fire activity in the next 100 yr depend in part on the type and effectiveness of fire reduction employed. Previous studies have bracketed the range of dynamics from continued fire reduction to the complete failure of fire reduction activities. To improve these estimates, it is necessary to explicitly account for fire reduction in terrestrial models. A new fire reduction submodel that estimates the spatiotemporal pattern of reduction across the United States was developed using gridded data on biomass, climate, land-use, population, and economic factors. To the authors’ knowledge, it is the first large-scale, gridded fire model that explicitly accounts for fire reduction. The model was calibrated to 1° × 1° burned area statistics [Global Burnt Area 2000 Project (GBA-2000)] and compared favorably to three important diagnostics. The model was then implemented in a spatially explicit ecosystem model and used to analyze 1620 scenarios of future fire risk and fire reduction strategies. Under scenarios of climate change and urbanization, burned area and carbon emissions both increased in scenarios where fire reduction efforts were not adjusted to match new patterns of fire risk. Fuel reducing management strategies reduced burned area and fire risk, but also limited carbon storage. These results suggest that to promote carbon storage and minimize fire risk in the future, fire reduction efforts will need to be increased and spatially adjusted and will need to employ a mixture of fuel-reducing and non-fuel-reducing strategies

    An unusual case of spontaneous bladder perforation with associated autodialysis of the ensuing urinary ascites

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    Spontaneous rupture of the urinary bladder is a rare occurrence, and when encountered it is a diagnostic challenge. We present an unusual case of urinary bladder rupture in a patient with severe cerebral palsy who initially presented with localized abdominal pain and during admission developed generalized peritonitis caused by bladder rupture. In this case, the patient had none of risk factors associated with urinary bladder

    The Challenges of Processing Kite Aerial Photography Imagery with Modern Photogrammetry Techniques

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    Kite Aerial Photography (KAP) is a traditional method of collecting small-format aerial photography used for work in a variety of fields. This research explored techniques for processing KAP imagery with a focus on some of the challenges specific to photo processing. The performance of multiple automated image compositing programs was compared using a common set of 29 images. Those packages that were based on a photogrammetry approach outperformed the non-photogrammetric software, and generated similar levels of quality to one another. While all three photogrammetric packages produced satisfactory output, each had unique challenges

    DIRECT ESTIMATION OF ABOVEGROUND FOREST PRODUCTIVITY THROUGH HYPERSPECTRAL REMOTE SENSING OF CANOPY NITROGEN

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    The concentration of nitrogen in foliage has been related to rates of net photosynthesis across a wide range of plant species and functional groups and thus represents a simple and biologically meaningful link between terrestrial cycles of carbon and nitrogen. Although foliar N is used by ecosystem models to predict rates of leaf‐level photosynthesis, it has rarely been examined as a direct scalar to stand‐level carbon gain. Establishment of such relationships would greatly simplify the nature of forest C and N linkages, enhancing our ability to derive estimates of forest productivity at landscape to regional scales. Here, we report on a highly predictive relationship between whole‐canopy nitrogen concentration and aboveground forest productivity in diverse forested stands of varying age and species composition across the 360 000‐ha White Mountain National Forest, New Hampshire, USA. We also demonstrate that hyperspectral remote sensing can be used to estimate foliar N concentration, and hence forest production across a large number of contiguous images. Together these data suggest that canopy‐level N concentration is an important correlate of productivity in these forested systems, and that imaging spectrometry of canopy N can provide direct estimates of forest productivity across large landscapes

    The relationship between regional variations in blood flow and histology in a transplanted rat fibrosarcoma

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    The regional distribution of blood flow to the LBDS1 fibrosarcoma, transplanted into the subcutaneous site in rats, was investigated using the readily diffusible compound 14C-iodo-antipyrine (14C-IAP). Quantitative autoradiography was used to establish absolute values of specific blood flow F for 100 X 100 X 20 microns adjacent tissue volumes of the unperturbed tumour. Mean blood flow to whole tumours was found to decrease with increase in tumour size. This relationship was abolished if blood flow was only measured in sections cut from the periphery of the tumours. Detailed analysis of a sub-group of tumours showed that blood flow to individual tumours was heterogeneous. The range of blood flow was large, indicating that mean blood flow to a whole tumour is a poor reflection of the blood perfusion pattern of that tumour. Necrotic tumour regions were usually very poorly perfused. With the exception of the smallest tumours studied, blood flow was lower in the centre of tumours than in the periphery. Necrosis also tended to develop centrally. However, the peripheral to central gradient of blood flow was apparent even when densely cellular, viable tumour regions and necrotic regions were analysed separately. The decrease in blood flow with tumour size was also apparent in densely cellular, viable tumour regions when analysed separately. Qualitative comparison of tumour histology and regional blood flow showed that there were areas of very low blood flow associated with viable tumour regions. Less common were areas of rather high blood flow associated with necrotic tumour regions. A complicated relationship exists between tumour histology and blood flow. The quantitative autoradiography technique is suitable for investigating the most poorly perfused and the most well perfused viable fractions of animal tumours which may limit the efficacy of different types of therapy

    Benign Cystic Mesothelioma: A Rare Cause for Scrotal Swelling

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    Benign cystic mesothelioma of the tunica vaginalis is a rare occurrence. It usually presents with painless gradual swelling in the scrotum. These types of benign mesotheliomas typically occur in the peritoneum and usually affect young to middle-aged patients. We present in this case an unusual case of benign cystic mesothelioma of the tunica vaginalis in a 77-year-old male patient

    Organisational interventions for improving wellbeing and reducing work-related stress in teachers [Review].

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    Background: The teaching profession is an occupation with a high prevalence of work-related stress. This may lead to sustained physical and mental health problems in teachers. It can also negatively affect the health, wellbeing and educational attainment of children, and impose a financial burden on the public budget in terms of teacher turnover and sickness absence. Most evaluated interventions for the wellbeing of teachers are directed at the individual level, and so do not tackle the causes of stress in the workplace. Organisational-level interventions are a potential avenue in this regard. Objectives: To evaluate the effectiveness of organisational interventions for improving wellbeing and reducing work-related stress in teachers. Search methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, PsycINFO, ASSIA, AEI, BEI, BiblioMap, DARE, DER, ERIC, IBSS, SSCI, Sociological Abstracts, a number of specialist occupational health databases, and a number of trial registers and grey literature sources from the inception of each database until January 2015. Selection criteria: Randomised controlled trials (RCTs), cluster-RCTs, and controlled before-and-after studies of organisational-level interventions for the wellbeing of teachers. Data collection and analysis: We used standard methodological procedures expected by Cochrane. Main results: Four studies met the inclusion criteria. They were three cluster-randomised controlled trials and one with a stepped-wedge design. Changing task characteristics One study with 961 teachers in eight schools compared a task-based organisational change intervention along with stress management training to no intervention. It found a small reduction at 12 months in 10 out of 14 of the subscales in the Occupational Stress Inventory, with a mean difference (MD) varying from -3.84 to 0.13, and a small increase in the Work Ability Index (MD 2.27; 95% confidence interval (CI) 1.64 to 2.90; 708 participants, low-quality evidence). Changing organisational characteristics@ Two studies compared teacher training combined with school-wide coaching support to no intervention. One study with 59 teachers in 43 schools found no significant effects on job-related anxiety (MD -0.25 95% CI -0.61 to 0.11, very low-quality evidence) or depression (MD -0.26 95% CI -0.57 to 0.05, very low-quality evidence) after 24 months. The other study with 77 teachers in 18 schools found no significant effects on the Maslach Burnout Inventory subscales (e.g. emotional exhaustion subscale: MD -0.05 95% CI -0.52 to 0.42, low-quality evidence) or the Teacher Perceived Emotional Ability subscales (e.g. regulating emotions subscale: MD 0.11 95% CI -0.11 to 0.33, low-quality evidence) after six months. Multi-component intervention: One study with 1102 teachers in 34 schools compared a multi-component intervention containing performance bonus, job promotion opportunities and mentoring support to a matched-comparison group consisting of 300 schools. It found moderately higher teacher retention rates (MD 11.50 95% CI 3.25 to 19.75 at 36 months follow-up, very low-quality evidence). However, the authors reported results only from one cohort out of four (eight schools), demonstrating a high risk of reporting bias. Authors’ conclusions: We found low-quality evidence that organisational interventions lead to improvements in teacher wellbeing and retention rates. We need further evaluation of the effects of organisational interventions for teacher wellbeing. These studies should follow a complex- interventions framework, use a cluster-rando
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