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Dominant Cause (dominant + cause)
Selected AbstractsTransient climate simulation forced by natural and anthropogenic climate forcingsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 6 2002Cédric Bertrand Abstract Numerical experiments have been carried out with a two-dimensional sector-averaged global climate model coupled to a diffusive ocean in order to assess the potential impact of four hypothesized mechanisms of decadal to century-scale climate variability, both natural and anthropogenically induced: (1) solar variability; (2) variability in volcanic aerosol loading of the atmosphere; (3) anthropogenic increase of sulphate aerosols' concentration; (4) anthropogenic increase of greenhouse gas concentrations. Our results suggest that neither the individual responses nor the combined natural or anthropogenic forcings allow one to reproduce all of the recorded major temperature fluctuations since the latter half of the 19th century. They show that these temperature variations are the result of both naturally driven climate fluctuations and the effects of industrialization. By contrast, the dominant cause of decade-to-century-scale variability of the 21st century is likely to be changes in atmospheric trace-gas concentrations. Indeed, when the solar, volcanic, and tropospheric aerosols forcings used in our experiments are extended into the future, they are unable to counter the expected greenhouse warming. Copyright © 2002 Royal Meteorological Society. [source] Should we use proportional sampling for species,area studies?JOURNAL OF BIOGEOGRAPHY, Issue 8 2004José H. Schoereder Abstract Aim, In this paper we aim to show that proportional sampling can detect species,area relationships (SARs) more effectively than uniform sampling. We tested the contribution of alpha and beta diversity in ant communities as explanations for the SAR. Location, Tropical forest remnants in Viçosa, Minas Gerais, Brazil (20 °45, S, 42 °50, W). Methods, We sampled 17 forest remnants with proportional sampling. To disentangle sampling effects from other mechanisms, species richness was fitted in a model with remnant size, number of samples (sampling effects) and an interaction term. Results, A SAR was observed independent of the number of samples, discarding sampling effects. Alpha diversity was not influenced by remnant size, and beta diversity increased with remnant size; evidence to the fact that habitat diversity within remnants could be the dominant cause of the SAR. Such a relationship between beta diversity and remnant area may have also arisen due to the combined effects of territoriality and aggregation of ant species. Main conclusions, The proposed model, together with proportional sampling, allowed the distinction between sampling effects and other mechanisms. [source] Computational assessment of the effect of polyethylene wear rate, mantle thickness, and porosity on the mechanical failure of the acetabular cement mantleJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2010Oliver J. Coultrup Abstract Clinical studies have revealed that aseptic loosening is the dominant cause of failure in total hip arthroplasty, particularly for the acetabular component. For a cemented polyethylene cup, failure is generally accompanied by the formation of fibrous tissue at the cement,bone interface. A variety of reasons for the formation of this tissue have been suggested, including osteolysis and mechanical overload at the cement,bone interface. In this study, a computational cement damage accumulation method was used to investigate the effect of polyethylene cup penetration, cement mantle thickness, and cement porosity on the number of cycles required to achieve mechanical fatigue failure of the cement mantle. Cup penetration was found to increase cement mantle stresses, resulting in a reduction in cement mantle fatigue life of 9% to 11% for a high cup penetration rate. The effect of using a thin (2 mm) over a thick (4 mm) cement mantle also reduced cement mantle fatigue life between 9% and 11%, and greatly raised cancellous bone stresses. Cement porosity was found to have very little effect on cement mantle fatigue life. Failure modes and cement stresses involved suggest that only extreme combinations of a thin cement mantle and high cup penetration may lead to mechanical failure of the cement mantle, thereby allowing wear debris access to the cement,bone interface. A thin cement mantle may also lead to the mechanical overload of the cement,bone interface. In this manner, the authors suggest that the mechanical factors may contribute to the failure mode of cemented polyethylene cups. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:565,570, 2010 [source] Epidemiological and mycological data of onychomycosis in Goiania, BrazilMYCOSES, Issue 1 2010L. K. H. Souza Summary Onychomycosis defined as fungal infection of the nail represents more than 50% of all onychopathies. Epidemiological studies have shown that this mycosis is worldwide in occurrence, but with geographical variation in distribution. The direct microscopy and culture of the nail samples were performed to identify the causative agent. Out of 2273 patients with nail infection examined between January 2000 and December 2004 in Goiania, state of Goias, Brazil, diagnosis of onychomycosis was confirmed in 1282 cases, with dermatophytes and Candida species being the most common aetiological agents isolated. Dermatophyte onychomycosis was more common in toenails than in fingernails, while onychomycosis caused by yeast had a similar frequency in both toenails and fingernails. Among the species identified, Candida albicans was responsible for 492 cases (38.4%) of onychomycosis, Trichophyton rubrum was found in 327 cases (25.6%) and Trichophyton mentagrophytes in 258 cases (20.1%). Other fungi isolated from nail infections included Aspergillus sp., Trichosporon sp., Geotrichum sp. and Fusarium sp. In our study, yeast of the genus Candida were the dominant cause of onychomycosis in women and dermatophytes were the principal cause of this condition in men. [source] Evidence from Amazonian forests is consistent with isohydric control of leaf water potentialPLANT CELL & ENVIRONMENT, Issue 2 2006ROSIE A. FISHER ABSTRACT Climate modelling studies predict that the rain forests of the Eastern Amazon basin are likely to experience reductions in rainfall of up to 50% over the next 50,100 years. Efforts to predict the effects of changing climate, especially drought stress, on forest gas exchange are currently limited by uncertainty about the mechanism that controls stomatal closure in response to low soil moisture. At a through-fall exclusion experiment in Eastern Amazonia where water was experimentally excluded from the soil, we tested the hypothesis that plants are isohydric, that is, when water is scarce, the stomata act to prevent leaf water potential from dropping below a critical threshold level. We made diurnal measurements of leaf water potential (,l), stomatal conductance (gs), sap flow and stem water potential (,stem) in the wet and dry seasons. We compared the data with the predictions of the soil,plant,atmosphere (SPA) model, which embeds the isohydric hypothesis within its stomatal conductance algorithm. The model inputs for meteorology, leaf area index (LAI), soil water potential and soil-to-leaf hydraulic resistance (R) were altered between seasons in accordance with measured values. No optimization parameters were used to adjust the model. This ,mechanistic' model of stomatal function was able to explain the individual tree-level seasonal changes in water relations (r2 = 0.85, 0.90 and 0.58 for ,l, sap flow and gs, respectively). The model indicated that the measured increase in R was the dominant cause of restricted water use during the dry season, resulting in a modelled restriction of sap flow four times greater than that caused by reduced soil water potential. Higher resistance during the dry season resulted from an increase in below-ground resistance (including root and soil-to-root resistance) to water flow. [source] THE DECLINE IN THE VOLATILITY OF THE BUSINESS CYCLES IN THE UKTHE MANCHESTER SCHOOL, Issue 2008CHRISTINA V. ATANASOVA We analyse the sources of the decline of business cycle volatility in the UK using a dynamic factor model that allows for the presence of a structural break in the conditional mean and variance of output, sales, income and unemployment. We augment the factor model with an economic component to investigate the role of structural changes and improved monetary policy in the volatility decline of the series. Our results suggest that the dominant cause for the observed volatility decline is the reduced variability of shocks. [source] Early cortical lens opacities: a short overviewACTA OPHTHALMOLOGICA, Issue 6 2009Gijs F.J.M. Vrensen Abstract. Cataract is still the dominant cause of blindness worldwide. Cortical cataract is the most prevalent of the age-related changes in the human lenses that require surgical intervention to restore vision. The absence of adequate cataract surgery in most developing countries is the main cause of the high prevalence of cataract blindness worldwide. Lens ageing is accompanied by dramatic increases in stiffness, light scattering and coloration of the lens nucleus. These changes start to become manifest as early as the fourth or fifth decade of life and lead to nuclear cataract in old age. In the same period the equatorial deep lens cortex starts to show small opaque shades, which eventually grow out to segmental and annular opacities. These opaque shades are filled with small vesicles and contain abnormal amounts of cross-linked proteins, cholesterol and phospholipids. They are bordered by membranes that are rich in square arrays, have ,degenerate' gap junctions and have few intramembranous particles. It has been shown that the opaque shades represent cohorts of locally affected fibres segregated from unaffected neighbouring fibres by ,non-leaky' membranes. This segregation is an effective mechanism delaying the outgrowth of these opacities to cuneiform cataracts entering the pupillary space and thus leading to blinding cortical cataracts. Although cataract formation is mostly considered to be a multi-factorial disease, oxidative stress might be one of the leading causes for both nuclear and cortical cataract. In cortical cataracts shear stress between cortex and nucleus during accommodation may also play a significant role. [source] | |||||||||||||