Quantitative Terms (quantitative + term)

Distribution by Scientific Domains

Selected Abstracts

Is contact allergy in man lifelong?

An overview of patch test follow-ups
In contradistinction from certain strains of mice, contact allergy in man is hypothesized to be either lifelong or at least to last for years. We examined follow-up studies on contact allergy, as evaluated by patch testing, attempting to quantify its natural history. The allergens include colophonium, gold sodium thiosulfate, nickel, and cobalt. At present, due to technical limitations, we cannot state in quantitative terms whether contact allergy in man is lifelong and whether its clinical manifestations change. Thus, we list some criteria for future studies which may help resolve the above question. [source]

Solution of the linear diffusion equation for modelling erosion processes with a time varying diffusion coefficient

Georgios Aim.
Abstract In the present paper the differential equation of the temporal development of a landform (mountain) with a time dependent diffusion coefficient is solved. It is shown that the shape and dimensions of the landform at time t are independent of the specific variation of the diffusion coefficient with time; they only depend on the mean value of the diffusion coefficient in the time interval where the erosion process takes place. Studying the behaviour of the solution of the differential equation in the wave number domain, it is concluded that Fourier analysis may help in estimating, in quantitative terms, the initial dimensions, the age or, alternatively, the value of the diffusion coefficient of the landform. The theoretical predictions are tested on a hill of the southern part of the Ural mountainous region, in order to show how the results of the mathematical analysis can be used in describing, in quantitative terms, the morphological development of landforms due to erosion processes. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Precautions to improve the accuracy of quantitative determinations of biomarkers in clinical diagnostics

Nasim Ghasemzadeh
Abstract Although protein biomarkers have a great potential as biomarkers for diagnosis of diseases, they are seldom used in hospitals. There are many reasons for this, for instance, the difficulties to (i) find a biomarker for which the concentration in body fluids clearly differs between patients and healthy subjects, (ii) attain purification of the biomarker close to 100%, which is required for production of conventional protein antibodies as well as artificial gel antibodies for selective capture of a biomarker, (iii) design a standard curve for rapid and accurate determination of the concentration of the biomarker in the body fluid because of adsorption of the biomarker onto vials, pipettes, etc., (iv) determine accurately the sample volume delivered by a pipette, (v) avoid polymerization of the biomarker upon storage and to decide whether it is in the form not only of monomers, but also of dimers, trimers, etc., in the native state, (vi) determine the degree of possible glycosylation and amidation of the biomarker and (vii) decide whether glycosylation and amidation positively or negatively affects the possibilit to use the protein as a biomarker. In this article, we discuss in quantitative terms the difficulties (iii,vii) and how to overcome them, which also may help to overcome the difficulty (ii), which in turn minimizes difficulty (i). [source]

The ttgGHI solvent efflux pump operon of Pseudomonas putida DOT-T1E is located on a large self-transmissible plasmid

José J. Rodríguez-Herva
Summary Pseudomonas putida DOT-T1E is a solvent-tolerant strain able to grow in the presence of > 1% (v/v) toluene in the culture medium. A set of multidrug efflux pumps have been found to play a major role in the tolerance of this bacterium to organic solvents (Rojas et al., J Bacteriol 183: 3967,3973). In the course of studies of the mechanisms underlying solvent tolerance in DOT-T1E, we isolated a spontaneous solvent-sensitive mutant derivative which had lost the genes encoding the TtgGHI efflux pump, the most important extrusion element in quantitative terms. Genomic comparisons between the mutant and its parental strain by microarray analysis revealed that in addition to the ttgVW-ttgGHI gene cluster, another group of genes, highly similar to those found in the Tn4653A and ISPpu12 transposable elements of the TOL plasmid pWW0 from P. putida mt-2, were also absent from this strain. Further analysis demonstrated that strain DOT-T1E harboured a large plasmid (named pGRT1) that was lost from the solvent-sensitive mutant. Mapping analysis revealed that the ttgVW-ttgGHI genes and the Tn4653A -like transposon are borne by the pGRT1 plasmid. Plasmid pGRT1 is highly stable and its frequency of loss is below 10,8 per cell per generation under a variety of growth conditions, including nutritional and physical stresses. The pGRT1 plasmid is self-transmissible, and its acquisition by the toluene-sensitive P. putida KT2440 and Pseudomonas aeruginosa PAO1 increased the recipient's tolerance to toluene up to levels similar to those exhibited by P. putida DOT-T1E. We discuss the importance and potential benefits of this plasmid for the development of bacteria with enhanced solvent tolerance, and its potential impact for bioremediation and whole-cell biotransformations. [source]

On the Ekberg, Kabo and Andersson calculation of the Dang Van high cycle fatigue limit for rolling contact fatigue

ABSTRACT Recently, various methods have been proposed to assess the risk of rolling contact fatigue failure by Ekberg, Kabo and Andersson, and in particular, the Dang Van multiaxial fatigue criterion has been suggested in a simple approximate formulation. In this note, it is found that the approximation implied can be very significant; the calculation is improved and corrected, and focused on the study of plane problems but for a complete range of possible friction coefficients. It is found that predicted fatigue limit could be much higher than that under standard uniaxial tension/compression for ,hard materials' than for ,ductile materials.' This is in qualitative agreement, for example, with gears' design standards, but in quantitative terms, particularly for frictionless condition, the predicted limit seems possibly too high, indicating the need for careful comparison with experimental results. Some comments are devoted to the interplay of shakedown and fatigue. [source]

Plant species richness of nature reserves: the interplay of area, climate and habitat in a central European landscape

GLOBAL ECOLOGY, Issue 4 2002
Petr Py
Abstract Aim To detect regional patterns of plant species richness in temperate nature reserves and determine the unbiased effects of environmental variables by mutual correlation with operating factors. Location The Czech Republic. Methods Plant species richness in 302 nature reserves was studied by using 14 explanatory variables reflecting the reserve area, altitude, climate, habitat diversity and prevailing vegetation type. Backward elimination of explanatory variables was used to analyse the data, taking into account their interactive nature, until the model contained only significant terms. Results A minimal adequate model with reserve area, mean altitude, prevailing vegetation type and habitat diversity (expressed as the number of major habitat types in the reserve) accounted for 53.9% of the variance in species number. After removing the area effect, habitat diversity explained 15.6% of variance, while prevailing vegetation type explained 29.6%. After removing the effect of both area and vegetation type, the resulting model explained 10.3% of the variance, indicating that species richness further increased with habitat diversity, and most obviously towards warm districts. After removing the effects of area, habitat diversity and climatic district, the model still explained 9.4% of the variance, and showed that species richness (i) significantly decreased with increasing mean altitude and annual precipitation, and with decreasing January temperature in the region of the mountain flora, and (ii) increased with altitudinal range in regions of temperate and thermophilous flora. Main conclusions We described, in quantitative terms, the effects of the main factors that might be considered to be determining plant species richness in temperate nature reserves, and evaluated their relative importance. The direct habitat effect on species richness was roughly equal to the direct area effect, but the total direct and indirect effects of area slightly exceeded that of habitat. It was shown that the overall effect of composite variables such as altitude or climatic district can be separated into particular climatic variables, which influence the richness of flora in a context-specific manner. The statistical explanation of richness variation at the level of families yielded similar results to that for species, indicating that the system of nature conservation provides similar degrees of protection at different taxonomic levels. [source]

Measuring the quantitative performance of surgical operating lists: theoretical modelling of ,productive potential' and ,efficiency'

ANAESTHESIA, Issue 5 2009
J. J. Pandit
Summary We previously defined surgical list ,efficiency' as: maximising theatre utilisation, minimising over-running, and minimising cancellations. ,Efficiency' maximises output for input; ,productivity' emphasises total output. We define six criteria that any measure of productivity (better termed ,quantitative performance') needs to satisfy. We then present a theoretical analysis that fulfils these by incorporating: ,speed' of surgery (with reference to average speeds), ,patient contact' (synonymous with minimising gaps between cases), and ,efficiency' (as previously defined). ,Speed' and ,patient contact' together constitute a ,productive potential'. Our formula satisfies the pre-set criteria and yields plausible results in both hypothetical and real data sets, To be productive in these quantitative terms, teams in any specialty need to achieve minimum quality standards defined by their sub-specialty; to plan their lists to utilise the time available with no cancellations or over-runs and to work at least as fast as average with minimal gaps between cases. ,Productive potential' combined with ,efficiency' yielding ,actual productivity' in our theoretical analysis more completely describes quantitative surgical list performance than any other single measure. [source]

Incorporating Physiological and Biochemical Mechanisms into Pharmacokinetic,Pharmacodynamic Models: A Conceptual Framework,

Svein G. Dahl
In general, modelling of data has the purpose (1) to describe experimental data, (2a) to reduce the amount of data resulting from an experiment, e.g. a clinical trial and (2b) to obtain the most relevant parameters, (3) to test hypotheses and (4) to make predictions within the boundaries of experimental conditions, e.g. range of doses tested (interpolation) and out of the boundaries of the experimental conditions, e.g. to extrapolate from animal data to the situation in man. Describing the drug/xenobiotic-target interaction and the chain of biological events following the interaction is the first step to build a biologically based model. This is an approach to represent the underlying biological mechanisms in qualitative and also quantitative terms, thus being inherently connected in many aspects to systems biology. As the systems biology models may contain variables in the order of hundreds connected with differential equations, it is obvious that it is in most cases not possible to assign values to the variables resulting from experimental data. Reduction techniques may be used to create a manageable model which, however, captures the biologically meaningful events in qualitative and quantitative terms. Until now, some success has been obtained by applying empirical pharmacokinetic/pharmacodynamic models which describe direct and indirect relationships between the xenobiotic molecule and the effect, including tolerance. Some of the models may have physiological components built in the structure of the model and use parameter estimates from published data. In recent years, some progress toward semi-mechanistic models has been made, examples being chemotherapy-induced myelosuppression and glucose-endogenous insulin-antidiabetic drug interactions. We see a way forward by employing approaches to bridge the gap between systems biology and physiologically based kinetic and dynamic models. To be useful for decision making, the ,bridging' model should have a well founded mechanistic basis, but being reduced to the extent that its parameters can be deduced from experimental data, however capturing the biological/clinical essential details so that meaningful predictions and extrapolations can be made. [source]

Landslides and Their Contribution to Land-cover Change in the Mountains of Mexico and Central America,

BIOTROPICA, Issue 4 2006
Carla Restrepo
ABSTRACT Landsliding is a natural process influencing montane ecosystems, particularly in areas with elevated rainfall and seismic activity. Yet, to date, little effort has been made to quantify the contribution of this process to land-cover change. Focusing on the mountains of Mexico and Central America (M-CA), we estimated the contribution of landsliding to land-cover change at two scales. At the scale of M-CA, we classified the terrain into major landforms and entered in a GIS historical data on earthquake- and rainfall-triggered landslides. At the scale of the Sierra de Las Minas of Guatemala, we investigated Landsat TM data to map rainfall-triggered landslides. During the past 110 yr, >136,200 ha of land in the mountains of M-CA have been affected by landslides, which translates into disturbance rates exceeding 0.317 percent/century. In Sierra de Las Minas, rainfall associated with hurricane Mitch affected 1765 ha of forest, or equivalently, landslides triggered by storms of this magnitude transformed between 0.196 (return time of 500 yr) and 1.290 (return time of 75 yr) percent of forest/century. Although landsliding results in smaller rates of land-cover change than deforestation, we hypothesize that it has a stronger impact on ecosystems, both in qualitative and quantitative terms, given its influence on vegetation and soil. Moreover, interactions between landsliding and deforestation may be altering the expression of this complex process such that the few protected areas in the mountains of M-CA may represent the only possibility for the conservation of this process. RESUMEN Los deslizamientos de tierra representan un fenómeno natural que afecta a todos los ecosistemas montañosos, particularmente aquellos que se encuentran en áreas de elevadas precipitaciones y actividad sísmica. Sin embargo, hasta el presente los esfuerzos por cuantificar la contribución de este proceso a cambios de cobertura de suelo han sido limitados. Enfocados en las montañas de México y Centro America (M-OA) estimamos que la contribución de los deslizamientos de tierra con cambios de cobertura de suelo a dos escalas. A la escala de M-CA, clasificamos el terreno basado en clases mayores de relieve e incluímos datos históricos de sismos y tormentas que han provocado deslizamientos de tierra en un SIG. A la escala de la Sierra de Las Minas en Guatemala, investigamos datos Landsat TM para identificar y localizar deslizamientos de tierra disperados por lluvia. Durante los últimos 110 años >136,200 ha de tierra han sido transformados por deslizamientos de tierra en las montañas de M-CA, lo que se traduce en tasas de perturbación >0.317 por ciento/siglo. En la Sierra de Las Minas, las lluvias asociadas con el huracán Mitch transformaron 1765 ha de bosque, lo que es equivalente a tasas de perturbación por deslizamientos de tierra entre 0.196 (tasa de retorno de 500 años) y 1.290 por ciento/siglo (tasa de retorno de 75 años). A pesar de que las tasas de cambio de cobertura vegetal por deslizamientos son menores que las causadas por deforestación, hipotetizamos que tienen un mayor impacto en estos ecosistemas tanto en términos cualitativos como cuantitativos por su influencia sobre la vegetación y el suelo. Además, interacciones entre los deslizamientos de tierra y la deforestación podrían estar afectando la expresión de este complejo proceso de tal forma que las pocas áreas montañosas de México y Centro América que están protegidas representan la única posibilidad para la conservación de este proceso. [source]