2,031 research outputs found

    Estimation of geopotential from satellite-to-satellite range rate data: Numerical results

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    A technique for high-resolution geopotential field estimation by recovering the harmonic coefficients from satellite-to-satellite range rate data is presented and tested against both a controlled analytical simulation of a one-day satellite mission (maximum degree and order 8) and then against a Cowell method simulation of a 32-day mission (maximum degree and order 180). Innovations include: (1) a new frequency-domain observation equation based on kinetic energy perturbations which avoids much of the complication of the usual Keplerian element perturbation approaches; (2) a new method for computing the normalized inclination functions which unlike previous methods is both efficient and numerically stable even for large harmonic degrees and orders; (3) the application of a mass storage FFT to the entire mission range rate history; (4) the exploitation of newly discovered symmetries in the block diagonal observation matrix which reduce each block to the product of (a) a real diagonal matrix factor, (b) a real trapezoidal factor with half the number of rows as before, and (c) a complex diagonal factor; (5) a block-by-block least-squares solution of the observation equation by means of a custom-designed Givens orthogonal rotation method which is both numerically stable and tailored to the trapezoidal matrix structure for fast execution

    Creating Modern Community Conservation Organizations and Institutions to Effect Successful Forest Conservation Change

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    Despite increased investment, current conservation strategies have failed to stop environmental degradation and loss of biodiversity of the earth’s ecosystems with consequent climate change. Community Conservation’s (CC) 30 years of experience has produced a successful, cost-effective, field-tested flexible formula to catalyze communities to stop deforestation and biodiversity loss. Our method focuses on four concepts: 1) catalyzing projects, leaving ownership to on-site community-based organizations (CBOs) or local nongovernmental organizations (NGOs); 2) encouraging creation of CBOs; 3) helping build complex federations or networks for a stronger community voice; and 4) creating conservation contagion for regional change. Based on trust, we initially make the community aware of their special forests and wildlife and ask their help in protecting them. Then we help them create CBOs and build federations of conservation activists to strengthen and empower them to manage their projects and their natural resources. By bringing community members to interact together from within a large region, we strive to create conservation contagion. Case histories from Assam, India; northern Peru; the Huon Peninsula in Papua New Guinea; Madagascar; Belize; and Wisconsin, USA demonstrate successes based on the formation of CBOs and community federations, allowing communities to play a powerful role in protecting and restoring forests

    Exploiting species differences to understand the CFTR Cl<sup>-</sup> channel

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    The anion channel cystic fibrosis transmembrane conductance regulator (CFTR) is a unique ATP-binding cassette (ABC) transporter. CFTR plays a pivotal role in transepithelial ion transport as its dysfunction in the genetic disease cystic fibrosis (CF) dramatically demonstrates. Phylogenetic analysis suggests that CFTR first appeared in aquatic vertebrates fulfilling important roles in osmosensing and organ development. Here, we review selectively, knowledge of CFTR structure, function and pharmacology, gleaned from cross-species comparative studies of recombinant CFTR proteins, including CFTR chimeras. The data argue that subtle changes in CFTR structure can affect strongly channel function and the action of CF mutations.</jats:p

    Airway obstruction by extrinsic tracheal compression during spinal surgery under prone position -A case report-

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    Tracheal compression by vascular anomalies in adults is uncommon and most related reports are of children. A 79-year-old woman without any respiratory history underwent a lumbar spine surgery under general anesthesia. She suddenly developed airway obstruction after a position change from supine to prone. A fiberoptic bronchoscopy showed the obstruction of endotracheal tube. The obstruction was relieved after we changed the depth of endotracheal tube and supported the patient's neck with a cotton roll. The surgery ended without any other event and the patient recovered safely. A computed tomography revealed the rightward tracheal deviation and tortuous innominate artery contact with trachea. The patient didn't manifest any respiratory related symptoms during postoperative period, and she was discharged without any treatment

    The Importance of Poisoning vs. Road Traffic Injuries as a Cause of Death in Rural Sri Lanka

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    Road traffic crashes are considered by the WHO to be the most important global cause of death from injury. However, this may not be true for large areas of rural Asia where road vehicles are uncommon. The issue is important, since emphasising the importance of road traffic crashes risks switching resources to urban areas, away from already underfunded rural regions. In this study, we compared the importance of road traffic crashes with other forms of injury in a poor rural region of South Asia.We collected data on all deaths from injury in the North Central Province of Sri Lanka (NCP; population 1,105,198 at 2001 census) over 18 months using coronial, hospital, and police data. We calculated the incidence of death from all forms of intentional and unintentional injury in the province. The annual incidence of death from injury in the province was high: 84.2 per 100,000 population. Half of the deaths were from self-harm (41.3/100,000). Poisoning (35.7/100,000)-in particular, pesticide self-poisoning (23.7/100,000)-was the most common cause of death, being 3.9-fold more common than road traffic crashes (9.1/100,000).In poor rural regions of South Asia, fatal self-harm and pesticide self-poisoning in particular are significantly more important than road traffic injuries as a cause of death. It is possible that the data used by the WHO to calculate global injury estimates are biased towards urban areas with better data collection but little pesticide poisoning. More studies are required to inform a debate about the importance of different forms of injury and how avoidable deaths from any cause can be prevented. In the meantime, marked improvements in the effectiveness of therapy for pesticide poisoning, safer storage, reduced pesticide use, or reductions in pesticide toxicity are required urgently to reduce the number of deaths from self-poisoning in rural Asia

    Complement is activated in progressive multiple sclerosis cortical grey matter lesions

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    The symptoms of multiple sclerosis (MS) are caused by damage to myelin and nerve cells in the brain and spinal cord. Inflammation is tightly linked with neurodegeneration, and it is the accumulation of neurodegeneration that underlies increasing neurological disability in progressive MS. Determining pathological mechanisms at play in MS grey matter is therefore a key to our understanding of disease progression

    Singularity in polarization:rewiring yeast cells to make two buds

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    SummaryFor budding yeast to ensure formation of only one bud, cells must polarize toward one, and only one, site. Polarity establishment involves the Rho family GTPase Cdc42, which concentrates at polarization sites via a positive feedback loop. To assess whether singularity is linked to the specific Cdc42 feedback loop, we disabled the yeast cell's endogenous amplification mechanism and synthetically rewired the cells to employ a different positive feedback loop. Rewired cells violated singularity, occasionally making two buds. Even cells that made only one bud sometimes initiated two clusters of Cdc42, but then one cluster became dominant. Mathematical modeling indicated that, given sufficient time, competition between clusters would promote singularity. In rewired cells, competition occurred slowly and sometimes failed to develop a single “winning” cluster before budding. Slowing competition in normal cells also allowed occasional formation of two buds, suggesting that singularity is enforced by rapid competition between Cdc42 clusters
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