1000 resultados para Obturation material


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Experiments have been carried out to investigate the polar distribution of atomic material ablated during the pulsed laser deposition of Cu in vacuum. Data were obtained as functions of focused laser spot size and power density. Thin films were deposited onto flat glass substrates and thickness profiles were transformed into polar atomic flux distributions of the form f(theta)=cos(n) theta. At constant focused laser power density on target, I=4.7+/-0.3X10(8) W/cm(2), polar distributions were found to broaden with a reduction in the focused laser spot size. The polar distribution exponent n varied from 15+/-2 to 7+/-1 for focused laser spot diameter variation from 2.5 to 1.4 mm, respectively, with the laser beam exhibiting a circular aspect on target. With the focused laser spot size held constant at phi=1.8 mm, polar distributions were observed to broaden with a reduction in the focused laser power density on target, with the associated polar distribution exponent n varying from 13+/-1.5 to 8+/-1 for focused laser power density variation from 8.3+/-0.3X10(8) to 2.2+/-0.1X10(8) W/cm(2) respectively. Data were compared with an analytical model available within the literature, which correctly predicts broadening of the polar distribution with a reduction in focused laser spot size and with a reduction in focused laser power density, although the experimentally observed magnitude was greater than that predicted in both cases. (C) 1996 American Institute of Physics.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The taxonomic importance of uninucleate vs. multinucleate vegetative cells in the Ceramiaceae is emphasized. It has been possible to make visible nuclei in old material, including type specimens, using aceto-carmine and aceto-iron-haematoxylin stains. The holotypes of Ceramium roseum and Callithamnion fasciculatum (currently known as Callithamnion roseum and Pleonosporium borreri var. fasciculatum) have uninucleate cells and belong to Aglaothamnion. In contrast, the holotype of Callithamnion decompositum, a name that has been applied to collections of at least two uninucleate taxa, has multinucleate cells; its morphological and cytological details agree with those of specimens collected in France and Ireland that were previously thought to represent an undescribed species. Female reproductive morphology (described from a thallus with gametangia in addition to tetrasporangia), in conjunction with habit and vegetative features, indicates that this species belongs to Compsothamnion (Compsothamnieae), as a third species, being distinguished from C. thuyoides and C. gracillimum by its sessile, lateral tetrasporangia. The required new combinations under Aglaothamnion and Compsothamnion are made.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The aim of this paper is to identify the various managerial issues encountered by UK/Irish contractors in the management of materials in confined urban construction sites. Through extensive literature review, detailed interviews, case studies, cognitive mapping, causal loop diagrams, questionnaire survey and documenting severity indices, a comprehensive insight into the materials management concerns within a confined construction site environment is envisaged and portrayed. The leading issues highlighted are: that contractors’ material spatial requirements exceed available space, it is difficult to coordinate the storage of materials in line with the programme, location of the site entrance makes delivery of materials particularly difficult, it is difficult to store materials on-site due to the lack of space, and difficult to coordinate the storage requirements of the various sub-contractors. With the continued development of confined urban centres and the increasing high cost of materials, any marginal savings made on-site would translate into significant monetary savings at project completion. Such savings would give developers a distinct competitive advantage in this challenging economic climate. As on-site management professionals successfully identify, acknowledge and counteract the numerous issues illustrated, the successful management of materials on a confined urban construction site becomes attainable.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

A study of the components of the fruits of Kigelia pinnata was undertaken to identify compounds with potential growth inhibitory activity against human melanoma cells, since extracts from the fruits of this plant have been described in traditional medicine to have application in the treatment of skin cancer and other skin ailments. A bioactivity-guided fractionation process yielded a number of crude fractions, which demonstrated cytotoxicity in vitro against human melanoma cells. Compounds isolated and identified included the isocoumarins, demethylkigelin (1) and kigelin 2), fatty acids, oleic (3) and heneicosanoic acids (4), the furonaphthoquinone, 2-(1-hydroxyethyl)-naphtho[2,3-b]furan-4,9-dione (5), and ferulic acid (6). A number of structurally related synthetic compounds were also tested using the MTT assay. The most potent series of these compounds, the furonaphthoquinones, also demonstrated a cytotoxic effect in two human breast cancer cell lines tested.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In many situations, the number of data points is fixed, and the asymptotic convergence results of popular model selection tools may not be useful. A new algorithm for model selection, RIVAL (removing irrelevant variables amidst Lasso iterations), is presented and shown to be particularly effective for a large but fixed number of data points. The algorithm is motivated by an application of nuclear material detection where all unknown parameters are to be non-negative. Thus, positive Lasso and its variants are analyzed. Then, RIVAL is proposed and is shown to have some desirable properties, namely the number of data points needed to have convergence is smaller than existing methods.

Relevância:

20.00% 20.00%

Publicador:

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This paper aims to contribute to the ongoing debate on the use of resource accounting tools in regional policy making. The Northern Limits project applied Material Flow Analysis and Ecological Footprinting to regional policy making in Northern Ireland over a number of years. The early phase of the research informed the regions first sustainable development strategy which was published in 2006 with key targets relating to the Ecological Footprint and improving the resource efficiency of the economy. Phase II identified the next steps required to address data availability and quality and the use of MFA and EF in providing a measurement and monitoring framework for the strategy and in the development of the strategy implementation plan. The use of MFA and Ecological Footprinting in sustainable regional policy making and the monitoring of its implementation is an ongoing process which has raised a number of research issues which can inform the ongoing application and development of these and other resource accounting tools to within Northern Ireland, provide insights for their use in other regions and help set out the priorities for research to support this important policy area.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Chemoenzymatic dynamic kinetic resolution (DKR) of rac-1-phenyl ethanol into R-1-phenylethanol acetate was investigated with emphasis on the minimization of side reactions. The organometallic hydrogen transfer (racemization) catalyst was varied, and this was observed to alter the rate and extent of oxidation of the alcohol to form ketone side products. The performance of highly active catalyst [(pentamethylcyclopentadienyl) IrCl2(1-benzyl,3-methyl-imidazol-2-ylidene)] was found to depend on the batch of lipase B used. The interaction between the bio- and chemo-catalysts was reduced by employing physical entrapment of the enzyme in silica using a sol-gel process. The nature of the gelation method was found to be important, with an alkaline method preferred, as an acidic method was found to initiate a further side reaction, the acid catalyzed dehydration of the secondary alcohol. The acidic gel was found to be a heterogeneous solid acid.

Relevância:

20.00% 20.00%

Publicador:

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In this article, we take advantage of the recent availability of data from the special module on material deprivation in the 2009 European Union Statistics on Income and Living Conditions to develop a more comprehensive understanding of the relationship between material deprivation and economic stress, the mediating and moderating roles played by cross-national differences in levels of income and income inequality, and the implications for competing perspectives on the nature of reference groups in Europe. The article establishes the critical role of basic deprivation, relating to inability to enjoy customary standards of living, in influencing economic stress levels. National income levels and inequality had no direct influence on economic stress. However, the impact of basic deprivation was stronger in countries with higher levels of income, indicating the crucial role of national reference groups. An interaction between basic deprivation and income inequality was also observed. However, contrary to the expectation that experiencing basic deprivation in a national context of high income inequality is likely to be particularly stressful, the consequences of such deprivation were most negative in low inequality countries. Experiencing basic deprivation where high income levels and lower inequality would lead to the expectation that such deprivation is eminently avoidable exacerbates its impact. © The Author 2013.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In this paper, taking advantage of the inclusion of a special module on material deprivation in EU-SILC 2009. we provide a comparative analysis of patterns of deprivation. Our analysis identifies six relatively distinct dimensions of deprivation with generally satisfactory overall levels of reliability and mean levels of reliability across countries. Multi-level analysis based on 28 European countries reveals systematic variation in the importance of within and between country variation for a range of deprivation dimensions. The basic deprivation dimension is the sole dimension to display a graduated pattern of variation across countries. It also reveals the highest correlations with national and household income, the remaining deprivation dimensions and economic stress. It comes closest to capturing an underlying dimension of generalized deprivation that can provide the basis for a comparative European analysis of exclusion from customary standards of living. A multilevel analysis revealed that a range of household characteristics and household reference person socio-economic factors were related to basic deprivation and controlling for contextual differences in such factors allowed us to account for substantial proportions of both within and between country variance. The addition of macro-economic factors relating to average levels of disposable income and income inequality contributed relatively little further in the way of explanatory power. Further analysis revealed the existence of a set of significant interactions between micro socioeconomic attributes and country level gross national disposable income per capita. The impact of socio-economic differentiation was significantly greater where average income levels were lower. Or, in other words, the impact of the latter was greater for more disadvantaged socio-economic groups. Our analysis supports the suggestion that an emphasis on the primary role of income inequality to the neglect of differences in absolute levels of income may be misleading in important respects. (C) 2012 International Sociological Association Research Committee 28 on Social Stratification and Mobility. Published by Elsevier Ltd. All rights reserved.