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Understanding effective diameter and its application to terrestrial radiation in ice clouds
D. L. Mitchell, R. P. Lawson,B. Baker
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2011,
Abstract: The cloud property known as "effective diameter" or "effective radius", which in essence is the cloud particle size distribution (PSD) volume at bulk density divided by its projected area, is used extensively in atmospheric radiation transfer, climate modeling and remote sensing. This derives from the assumption that PSD optical properties can be uniquely described in terms of their effective diameter, De, and their cloud water content (CWC), henceforth referred to as the De-CWC assumption. This study challenges this assumption, showing that while the De-CWC assumption appears generally valid for liquid water clouds, it appears less valid for ice clouds in regions where (1) absorption is not primarily a function of either the PSD ice water content (IWC) or the PSD projected area, and (2) where wave resonance (i.e. photon tunneling) contributes significantly to absorption. These two regions often strongly coincide at terrestrial wavelengths when De<~60 μm, which is where this De-CWC assumption appears poorest. Treating optical properties solely in terms of De and IWC may lead to errors up to 24%, 26% and 20% for terrestrial radiation in the window region regarding the absorption and extinction coefficients and the single scattering albedo, respectively. Outside the window region, errors may reach 33% and 42% regarding absorption and extinction. The magnitude and sign of these errors can change rapidly with wavelength, which may produce significant errors in climate modeling, remote sensing and other applications concerned with the wavelength dependence of radiation. Where the De-CWC assumption breaks down, ice cloud optical properties appear to depend on De, IWC and the PSD shape. Optical property parameterizations in climate models and remote sensing algorithms based on historical PSD measurements may exhibit errors due to previously unknown PSD errors (i.e. the presence of ice artifacts due to the shattering of larger ice particles on the probe inlet tube during sampling). More recently developed cloud probes are designed to mitigate this shattering problem. Using realistic PSD shapes for a given temperature (and/or IWC) and cloud type may minimize errors associated with PSD shape in ice optics parameterizations and remote sensing algorithms. While this topic was investigated using two ice optics schemes (the Yang et al., 2005 database and the modified anomalous diffraction approximation, or MADA), a physical understanding of the limitations of the De-IWC assumption was made possible by using MADA. MADA allows one to approximate the contribution of photon tunneling to absorption relative to other optical processes, which reveals that part of the error regarding the De-IWC assumption can be associated with tunneling. By relating the remaining error to the radiation penetration depth in bulk ice (ΔL) due to absorption, the domain where the De-IWC assumption is weakest was described in terms of De and ΔL.
Pilot study on multidrug resistant tuberculosis in Nigeria
Lawson L,Habib A,Okobi M,Idiong D
Annals of African Medicine , 2010,
Abstract: Background: Drug resistant tuberculosis (TB) has lately emerged and it represents a serious public health problem. We set out to determine drug resistance among TB patients. Methods: Using automated BACTEC cultures, multidrug resistant-tuberculosis (MDR-TB) was investigated in 117 diagnosed cases in Abuja, Nigeria. Results: Ten (31%) of 32 culture-positive patients were resistant to at least one and four (13%) to all of the four drugs tested. No association between drug resistance and human immunodeficiency virus (HIV) infection was found. Conclusions: MDR-TB is present in Nigeria and larger studies are urgently required. TB clinical management and control efforts should be improved.
Formation of large ( 100 μm) ice crystals near the tropical tropopause
E. J. Jensen,L. Pfister,T. V. Bui,P. Lawson
Atmospheric Chemistry and Physics Discussions , 2007,
Abstract: Recent high-altitude aircraft measurements with in situ imaging instruments indicated the presence of relatively large ( 100 μm length), thin (aspect ratios of 6:1 or larger) hexagonal plate ice crystals near the tropical tropopause in very low concentrations (<0.01 L 1). These crystals were not produced by deep convection or aggregation. We use simple growth-sedimentation calculations as well as detailed cloud simulations to evaluate the conditions required to grow the large crystals. Uncertainties in crystal aspect ratio leave a range of possibilities, which could be constrained by knowledge of the water vapor concentration in the air where the crystal growth occurred. Unfortunately, water vapor measurements made in the cloud formation region near the tropopause ranged from <2 ppmv to 3.5 ppmv. The higher water vapor concentrations correspond to very large ice supersaturations (relative humidities with respect to ice of about 200%). If the aspect ratios of the hexagonal plate crystals are as small as the image analysis suggests (6:1, see companion paper Lawson et al., 2007) then growth of the large crystals before they sediment out of the supersaturated layer would only be possible if the water vapor concentration were on the high end of the range indicated by the different measurements (>3 ppmv). On the other hand, if the crystal aspect ratios are quite a bit larger ( 14), then H2O concentrations toward the low of the measurement range ( 2–2.3 ppmv) would suffice to grow the large crystals. Gravity-wave driven temperature and vertical wind perturbations only slightly modify the H2O concentrations needed to grow the crystals. We find that it would not be possible to grow the large crystals with water concentrations less than 2 ppmv, even with assumptions of a very high aspect ratio of 15 and steady upward motion of 2 cm s 1 to loft the crystals in the tropopause region. These calculations would seem to imply that the measurements indicating water vapor concentrations less than 2 ppmv are implausible, but we cannot rule out the possibility that higher humidity prevailed upstream of the aircraft measurements and the air was dehydrated by the cloud formation. Simulations of the cloud formation with a detailed model indicate that the large crystals probably nucleated on very effective ice nuclei. Also, growth of the large crystals would not have been possible if homogeneous freezing of aqueous aerosols and subsequent ice crystal growth had rapidly depleted vapor in excess of saturation, implying either very slow cooling during cloud formation or that th
Reexamination of the Species Assignment of Diacavolinia Pteropods Using DNA Barcoding
Amy E. Maas, Leocadio Blanco-Bercial, Gareth L. Lawson
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0053889
Abstract: Thecosome pteropods (Mollusca, Gastropoda) are an ecologically important, diverse, and ubiquitous group of holoplanktonic animals that are the focus of intense research interest due to their external aragonite shell and vulnerability to ocean acidification. Characterizing the response of these animals to low pH and other environmental stressors has been hampered by continued uncertainty in their taxonomic identification. An example of this confusion in species assignment is found in the genus Diacavolinia. All members of this genus were originally indentified as a single species, Cavolinia longirostris, but over the past fifty years the taxonomy has been revisited multiple times; currently the genus comprises 22 different species. This study examines five species of Diacavolinia, including four sampled in the Northeast Atlantic (78 individuals) and one from the Eastern tropical North Pacific (15 individuals). Diacavolina were identified to species based on morphological characteristics according to the current taxonomy, photographed, and then used to determine the sequence of the “DNA barcoding” region of the cytochrome c oxidase subunit I (COI). Specimens from the Atlantic, despite distinct differences in shell morphology, showed polyphyly and a genetic divergence of <3% (K2P distance) whereas the Pacific and Atlantic samples were more distant (~19%). Comparisons of Diacavolinia spp. with other Cavolinia spp. reveal larger distances (~24%). These results indicate that specimens from the Atlantic comprise a single monophyletic species and suggest possible species-level divergence between Atlantic and Pacific populations. The findings support the maintenance of Diacavolinia as a separate genus, yet emphasize the inadequacy of our current taxonomic understanding of pteropods. They highlight the need for accurate species identifications to support estimates of biodiversity, range extent and natural exposure of these planktonic calcifiers to environmental variability; furthermore, the apparent variation of the pteropods shell may have implications for our understanding of the species’ sensitivity to ocean acidification.
Human Immunodeficiency Virus, Syphilis Prevalence and Risk Factors among Migrant Workers in Konongo, Ghana  [PDF]
Andrew A. Adjei, James Brandful, Mark Lurie, Margaret Lartey, Francis Krampa, Awewura Kwara, Theophilus K. Adiku, Yao Tettey, Richard K. Gyasi, Aaron L. Lawson, Timothy Flanigan
Advances in Infectious Diseases (AID) , 2014, DOI: 10.4236/aid.2014.43020
Abstract: Migrant workers, particularly gold mining workers, have been identified as a group at risk for HIV and sexually transmitted infections (STI). A cross-sectional study was undertaken on the correlates of human immunodeficiency virus (HIV) and syphilis infections in a sample of migrants (Ghanaian citizens [156] and non-Ghanaian citizens [8]) working in a gold mining centres in Konongo, Ghana. The study was conducted between the months of January 2013 to December 2013. Of a total of 600 eligible migrant workers, only 164 (27.33%; males 114, females 50) of the eligible migrants took part in the study. Subjects voluntarily completed a risk-factor questionnaire and provided blood specimen for testing for the presence of antibodies to HIV and Treponema pallidum, the causative agent of syphilis. These data were analyzed using both univariate and multivariate techniques. The median age of the participants was 29.0 years (range 18 - 62 years). Of the 164 migrant workers tested, HIV and syphilis seroprevalence were 6.7% and 3.7% respectively. On multivariate analysis, the independent determinants for HIV infection were being female [odds ratio (OR) 2.94; 95% confidence interval (95% CI 0.86 - 10.0); unmarried (OR 10.13; 95% CI 1.2 - 81.09); drug use (OR 3.76; 95% CI 0.38 - 36.3); and blood transfusion (OR 2.45; 95% CI 0.27 - 22.37). Similarly, on multivariate analysis, the independent determinants for syphilis infection were having concurrent sexual partners (OR 2.16; 95% CI 0.38 - 12.12); and blood transfusion (OR 5.07; 95% CI 0.51 - 50.37). Consistent with similar studies worldwide, our results suggest high prevalence of HIV and syphilis infections among migrant workers who work in gold mining centres in Ghana.
La imaginación sociológica desde la perspectiva histórica.
George LAWSON
Relaciones Internacionales , 2007,
Abstract: El autor se ala como los orígenes dispares de las disciplinas de Sociología y de Relaciones Internacionales no ha sido óbice para que en las últimas dos décadas se hayan acercado de forma muy intensa. Esto se debe al doble giro en las Relaciones Internacionales hacia la Historia (Escuela Inglesa) y hacia la Sociología (constructivismo). Tras hacer un repaso de los autores que han transitado en este lugar de encuentro que es la Sociología Histórica, se concluye con los potenciales beneficios que ofrece este nuevo enfoque: el rechazo a las categorías eternas y universales; la posibilidad de una efectiva periodización en las Relaciones Internacionales; y la capacidad que la Sociología Histórica de las Relaciones Internacionales concede para acabar con las suposiciones dadas sobre algunos conceptos y mitos centrales. This article explains how the origins of Sociology and International Relations have become closely related over the last twenty years. This new phenomenon is explained by the double approach in International Relations to History (English School) on the one hand, and to Sociology (Constructivism) on the other. After a brief look at the essential literature on Historic Sociology, Lawson presents the potential main results of such new approach to IR: the rejection of eternal and universal categories; the possibility to establish periods in International Relations; and the capacity that International Relations Historic Sociology could provide in order to eliminate given suppositions related to some central concepts and myths.
Treatment options and patient perspectives in the management of fibromyalgia: future trends
Kim Lawson
Neuropsychiatric Disease and Treatment , 2008,
Abstract: Kim LawsonBiomedical Research Centre, Sheffield Hallam University, Faculty of Health and Wellbeing, Sheffield, UKAbstract: Fibromyalgia (FM) is a common, complex, and difficult to treat chronic widespread pain disorder, which usually requires a multidisciplinary approach using both pharmacological and non-pharmacological (education and exercise) interventions. It is a condition of heightened generalized sensitization to sensory input presenting as a complex of symptoms including pain, sleep dysfunction, and fatigue, where the pathophysiology could include dysfunction of the central nervous system pain modulatory systems, dysfunction of the neuroendocrine system, and dysautonomia. A cyclic model of the pathophysiological processes is compatible with the interrelationship of primary symptoms and the array of postulated triggers associated with FM. Many of the molecular targets of current and emerging drugs used to treat FM have been focused to the management of discrete symptoms rather than the condition. Recently, drugs (eg, pregabalin, duloxetine, milnacipran, sodium oxybate) have been identified that demonstrate a multidimensional efficacy in this condition. Although the complexity of FM suggests that monotherapy, non-pharmacological or pharmacological, will not adequately address the condition, the outcomes from recent clinical trials are providing important clues for treatment guidelines, improved diagnosis, and condition-focused therapies.Keywords: fibromyalgia, pain, sleep dysfunction, fatigue, exercise, pharmacological treatments
Beneficial treatment of fibromyalgia
Lawson K
Journal of Postgraduate Medicine , 2009,
Abstract:
The Role of Assets: Insights into How The Chronically Poor Cope with HIV/AIDS
D. Lawson
Field Actions Science Reports , 2010,
Abstract: The paper extends the combined research methods literature with an investigation of the impact of ill health on assets and consumption behaviour of the chronically poor. Focusing on Uganda, and using national household panel data for 1992-99, the study extends the survey by visiting the same households and collecting both life history and further quantitative data. By adopting such an approach we are able to further explain a number of important issues that underly the role ill health plays in the lives of the chronically poor. In particular we find a clear association between sickness and descents into poverty. Asset smoothing seems to be very common amongst households that encounter general sickness, with food consumption almost always reduced, for a period of time, before selling assets. In contrast households suffering from HIV/AIDS, or at least severely physically debilitating sickness, often consumption smooth. Cet article complète la littérature utilisant différentes méthodes de recherche avec une étude de l’impact d’un mauvais état de santé sur les biens et le comportement de consommation des chroniquement pauvres. Ciblée sur l’Ouganda et se basant sur les données d’enquêtes nationales menées sur un échantillon représentatif de ménages en 1992 et en 1999, cette étude a porté sur les mêmes ménages et a collecté des données sur la vie des personnes interrogées et d’autres données quantitatives. Cette approche nous permet de mieux expliquer un certain nombre de points importants qui sous-tendent le r le qu’un mauvais état de santé joue dans la vie des chroniquement pauvres. Nous avons notamment identifié un lien clair entre la maladie et le basculement dans la pauvreté. Le lissage des biens semble être très fréquent chez les ménages confrontés à la maladie ; ils commencent presque toujours par réduire leur consommation alimentaire, pendant une certaine période, avant de vendre leurs biens. En revanche, les ménages atteints du VIH/SIDA, ou d’une autre maladie physiquement très invalidante, lissent souvent leur consommation. El artículo amplía la documentación existente sobre métodos de investigación combinados con una investigación sobre el impacto de la mala salud en los bienes y en el comportamiento del consumo de los pobres crónicos. Centrándose en Uganda, y utilizando datos del panel de hogares nacionales para 1992-1999, el estudio amplía la investigación visitando las mismas casas y recopilando datos sobre vidas y datos cuantitativos adicionales. Adoptando este enfoque podemos explicar además varias cuestiones importantes subyacentes al papel q
SAS Macros for Analysis of Unreplicated 2^k and 2^(k-p) Designs with a Possible Outlier
John Lawson
Journal of Statistical Software , 2008,
Abstract: Many techniques have been proposed for judging the significance of effects in unreplicated 2^k and 2^(k-p) designs. However, relatively few methods have been proposed for analyzing unreplicated designs with possible outliers. Outliers can be a major impediment to valid interpretation of data from unreplicated designs. This paper presents SAS macros which automate a manual method for detecting an outlier and performing an analysis of data from an unreplicated 2^k and 2^(k-p) design when an outlier is present. This method was originally suggested by Cuthbert Daniel and is based on the normal or half normal plot of effects. This automated version was shown in simulation studies to perform better than other procedures proposed to do the same thing.
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