Relevant Parameters (relevant + parameter)

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


Hypomethylation of PRAME is responsible for its aberrant overexpression in human malignancies

GENES, CHROMOSOMES AND CANCER, Issue 9 2007
Tino Schenk
The preferentially expressed antigen of melanoma (PRAME) is expressed at high levels in large fractions of human malignancies, e.g., acute myeloid leukemia. Therefore, PRAME is an important marker for diagnosis of various malignant diseases and a relevant parameter for monitoring minimal residual disease. It is supposed to be involved in tumorigenic processes. Because of these important aspects we investigated its transcriptional regulation in detail. Most relevant was a detailed DNA methylation analysis of the PRAME 5, region by genomic sequencing in correlation with PRAME expression in various human patient samples and cell lines. In combination with DNA-truncation/transfection experiments with respect to DNA methylation, we show that changes in the methylation pattern in defined parts of the regulatory regions of PRAME are sufficient for its upregulation in cells usually not expressing the gene. © 2007 Wiley-Liss, Inc. [source]


Controllable Soluble Protein Concentration Gradients in Hydrogel Networks,

ADVANCED FUNCTIONAL MATERIALS, Issue 21 2008
Brian J. Peret
Abstract Here, controlled formation of sustained, soluble protein concentration gradients within hydrated polymer networks is reported. The approach involves spatially localizing proteins or biodegradable, protein-loaded microspheres within hydrogels to form a protein-releasing "depot." Soluble protein concentration gradients are then formed as the released protein diffuses away from the localized source. Control over key gradient parameters, including maximum concentration, gradient magnitude, slope, and time dynamics, is achieved by controlling the release of protein from the depot and subsequent transport through the hydrogel. Results demonstrate a direct relationship between the amount of protein released from the depot and the source concentration, gradient magnitude, and slope of the concentration gradient. In addition, an inverse relationship exists between the diffusion coefficient of protein within the hydrogel and the slope of the concentration gradient. The time dynamics of the concentration gradient profile can be directly correlated to protein release from the localized source, providing a mechanism for temporarily controlling gradient characteristics. Therefore, each key biologically relevant parameter associated with the protein concentration gradient can be controlled by defining protein release and diffusion. It is anticipated that the resulting materials may be useful in 3D cell culture systems, and in emerging tissue engineering approaches that aim to regenerate complex, functional tissues. [source]


The Salty Dog: Serum Sodium and Potassium Effects on Modern Pacing Electrodes

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2007
RICK McVENES
Background: This study was conducted to characterize the behavior of chronic modern endocardial electrodes with capacitively coupled constant voltage pulse generators in canines. Methods: Five animals were studied with chronic paired unipolar microporous platinum, and porous steroid-eluting electrodes in the ventricle. Screw-in and passive fixation electrodes were also implanted in the atrium. IV infusions of 500,800 mL of 50 meq KCl in 500 mL Ringer's solution, and 3% NaCl were given over periods of 120 and 80 minutes, respectively, during separate anesthetized monitors. Results: Mean maximum Na+ and K+ achieved was 158 and 8.3 meq/L, respectively. During KCl infusion, ventricular threshold, current, and energy decreased. In the atrium, half the leads went to exit block at ,7.0 meq/L K+. Others continued to perform acceptably. The atrial electrogram decreased 70% with no change in the ventricular signal. No change in impedance occurred. During NaCl infusion, no changes in atrial or ventricular threshold occurred while current increased 21%,32%. This resulted in a 40%,55% increase in energy due to a 20% decrease in impedance. The atrial electrogram decreased 32%,36% while the ventricular amplitude decreased 25%. Slew rate decreased 19%,27%. Control studies for effects of heart rate, fluid volume, and anesthesia duration did not cause any changes. Conclusion: These data support the conclusion that threshold is a voltage mediated response. Thus, voltage thresholds, not energy, current or pulse duration is the most relevant parameter for safety margin determination. Atrial parameters should be followed during electrolyte imbalances. Correlation in humans is needed. [source]


On surface deformation of melt-intercalated polyethylene,clay nanocomposites during scratching

POLYMER ENGINEERING & SCIENCE, Issue 11 2006
A. Mudaliar
Electron microscopy has been used to examine the mechanically-induced surface damage introduced during scratching of polyethylene(PE),clay nanocomposites. The determining role of clay in reducing the susceptibility to surface deformation is predicted from the characteristics of surface morphology and the scratch deformation parameters. The reinforcement of PE with nanoclay reduces the susceptibility to scratch damage and stress whitening. Microcracks and surface deformation features namely wrinkles/ridges are the primary source of light scattering resulting in stress whitening. The scratch deformation behavior is discussed in terms of tensile modulus, percentage crystallinity, elastic recovery, and scratch hardness. Scratch hardness is a relevant parameter that can be appropriately used to determine resistance to scratch deformation. POLYM. ENG. SCI. 46:1625,1634, 2006. © 2006 Society of Plastics Engineers [source]


The Evaluation Method of Smoothing Algorithms in Voltammetry

ELECTROANALYSIS, Issue 22 2003
Malgorzata Jakubowska
Abstract The criterion for testing the influence of smoothing algorithms for the relevant parameters considered in analytical experiment is presented. The proposed approach assumes that the improvement of the whole set of measured curves should be considered. The calibration curve parameters with confidence intervals, correlation coefficient, detection limit, signal to noise ratio and parameters of recovery function are utilized for the evaluation. Performance of evaluation method is presented for several kinds of experimental noises. [source]


TK/TD dose,response modeling of toxicity

ENVIRONMETRICS, Issue 5 2007
Munni Begum
Abstract In environmental cancer risk assessment of a toxic chemical, the main focus is in understanding induced target organ toxicity that may in turn lead to carcinogenicity. Mathematical models based on systems of ordinary differential equations with biologically relevant parameters are tenable methods for describing the disposition of chemicals in target organs. In evaluation of a toxic chemical, dose,response assessment often addresses only toxicodynamics (TD) of the chemical, while its toxicokinetics (TK) do not enter into consideration. The primary objective of this research is to integrate both TK and TD in evaluation of toxic chemicals while performing dose,response assessment. Population models, with hierarchical setup and nonlinear predictors, for TK concentration and TD effect measures are considered. A one-compartment model with biologically relevant parameters, such as organ volume, uptake rate and excretion rate, or clearance, is used to derive the TK predictor while a two parameter Emax model is used as a predictor for TD measures. Inference of the model parameters with nonnegative and assay's Limit of Detection (LOD) constraints was carried out by Bayesian approaches using Markov Chain Monte Carlo (MCMC) techniques. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Single End-to-End Azidocopper(II) Chain Based on an Electroactive Ligand: A Structural, Electrochemical, Magnetic and Ab Initio Study

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 31 2009
Guillaume Pilet
Abstract By combining azide and the (Z)-1,1,1-trifluoro-4-(quinolin-8-ylamino)but-3-en-2-one enaminone ligand, HL, an azido-bridged copper(II) one dimensional polymer was synthesized in a one-pot reaction. The solved and refined crystal structure evidenced the unusual single and asymmetric end-to-end coordination mode of the azide ion. The redox properties of this complex were studied by cyclic voltammetry, andoxidation of the azido bridge was evidenced. Magneticmeasurements, combined with magnetostructural-driven analysis revealed a weak ferromagnetic interaction between the copper(II) ions within the N3, -bridged chains, complemented by an antiferromagnetic interaction between the chains mediated by ,,, interactions. A survey of the scarce literature of single end-to-end azido bridges, associated with quantum chemical ab initio calculations, was carried out to tentatively identify the relevant parameters driving the weak intrachain exchange interaction.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


Tests and calculations of short-circuit forces and displacements in high-voltage substations with strained conductors and droppers

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2000
N. Stein
Forschungsgemeinschaft für Elektrische Anlagen und Stromwirtschaft FCH and DKE UK 121.2 have recently completed an extensive systematic programme of short-circuit tests on substation bus bars of stranded conductors with and without droppers. The present test series, in continuation of the former studies, comprises 100-kV and 400-kV arrangements, applying the relevant parameters of the former. Apart from other variations, different current paths were studied for the arrangements with droppers. The present paper is confined to giving a survey of the 100-kV arrangements, parameter variations, measurements and test results, as far as they presently relate to the calculation procedure oflEC, CENELEC and D/V/VDE. It is further reported on studies with the Finite-Element Method (FEM) which show a remarkable comparative accuracy. Finally, the standardized method of IEC 60865-1 and EN 60865-1 for the calculation of short-circuit tensile forces is extended onto arrangements with droppers. [source]


FIXATION OF NEW ALLELES AND THE EXTINCTION OF SMALL POPULATIONS: DRIFT LOAD, BENEFICIAL ALLELES, AND SEXUAL SELECTION

EVOLUTION, Issue 6 2000
Michael C. Whitlock
Abstract With a small effective population size, random genetic drift is more important than selection in determining the fate of new alleles. Small populations therefore accumulate deleterious mutations. Left unchecked, the effect of these fixed alleles is to reduce the reproductive capacity of a species, eventually to the point of extinction. New beneficial mutations, if fixed by selection, can restore some of this lost fitness. This paper derives the overall change in fitness due to fixation of new deleterious and beneficial alleles, as a function of the distribution of effects of new mutations and the effective population size. There is a critical effective size below which a population will on average decline in fitness, but above which beneficial mutations allow the population to persist. With reasonable estimates of the relevant parameters, this critical effective size is likely to be a few hundred. Furthermore, sexual selection can act to reduce the fixation probability of deleterious new mutations and increase the probability of fixing new beneficial mutations. Sexual selection can therefore reduce the risk of extinction of small populations. [source]


VARIATION OF SHELL SHAPE IN THE CLONAL SNAIL MELANOIDES TUBERCULATA AND ITS CONSEQUENCES FOR THE INTERPRETATION OF FOSSIL SERIES

EVOLUTION, Issue 2 2000
Sarah Samadi
Abstract., Interpreting paleontological data is difficult because the genetic nature of observed morphological variation is generally unknown. Indeed, it is hardly possible to distinguish among several sources of morphological variation including phenotypic plasticity, sexual dimorphism, within-species genetic variation or differences among species. This can be addressed using fossil organisms with recent representatives. The freshwater snail Melanoides tuberculata ranks in this category. A fossil series of this and other species have been studied in the Turkana Basin (Kenya) and is presented as one of the best examples illustrating the punctuated pattern of evolution by the tenants of this theory. Melanoides tuberculata today occupies most of the tropics. We studied variation of shell shape in natural populations of this parthenogenetic snail using Raup's model of shell coiling. We considered different sources of variation on estimates of three relevant parameters of Raup's model: (1) variation in shell shape was detected among clones, and had both genetic and environmental bases; (2) sexual dimorphism, in those clones in which males occur, appeared as an additional source of shell variation; and (3) ecophenotypic variation was detected by comparing samples from different sites and years within two clones. We then tested the performance of discriminant function analyses, a classical tool in paleontological studies, using several datasets. Although the three sources of variation cited above contributed significantly to the observed morphological variance, they could not be detected without a priori knowledge of the biological entities studied. However, it was possible to distinguish between M. tuberculata and a related thiarid species using these analyses. Overall, this suggests that the tools classically used in paleontological studies are poorly efficient when distinguishing between important sources of within-species variation. Our study also gives some empirical bases to the doubts cast on the interpretation of the molluscan series of the Turkana Basin. [source]


Flammability ranking of foliage species by factor analysis of physical and chemical pyric properties

FIRE AND MATERIALS, Issue 6 2008
Yanlong Shan
Abstract In this paper, factor analysis is introduced to evaluate the flammability of 55 foliage species that may be used in China for construction of the fuel break network of forest strips with lower flammability. Six pyric parameters, i.e. air dry moisture content, absolute dry moisture content, ignition point, ash content, caloric value and extractive content, are measured and used as variables for factor analysis. The covariance analysis shows that four principal factors can be extracted to reflect the flammability in different physical and chemical senses. In terms of the contributions of the four factors to the variances and the physical significance of the relevant parameters, the four factors are, respectively, termed as ,flaming factor,' ,air dry factor,' ,ash factor' and ,absolute dry factor.' The stability of the factor analysis method is examined by a different number of samples considered, and the variation degrees of the orderings indicate that the method has high reliability to measure the total flammability of foliage species. The results of the flammability evaluation are verified by comparison with the recommended tree species in the Chinese technology standard. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Effects of Solvent Mixtures on the Nanoscale Phase Separation in Polymer Solar Cells,

ADVANCED FUNCTIONAL MATERIALS, Issue 12 2008
Yan Yao
Abstract The mixed solvent approach has been demonstrated as a promising method to modify nanomorphology in polymer solar cells. This work aims to understand the unique role of the additive in the mixture solvent and how the optimized nanoscale phase separation develops laterally and vertically during the non-equilibrium spin-coating process. We found the donor/acceptor components in the active layer can phase separate into an optimum morphology with the additive. Supported by AFM, TEM and XPS results, we proposed a model and identified relevant parameters for the additive such as solubility and vapor pressures. Other additives are discovered to show the ability to improve polymer solar cell performance as well. [source]


Neural Signal Manager: a collection of classical and innovative tools for multi-channel spike train analysis

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 11 2009
Antonio Novellino
Abstract Recent developments in the neuroengineering field and the widespread use of the micro electrode arrays (MEAs) for electrophysiological investigations made available new approaches for studying the dynamics of dissociated neuronal networks as well as acute/organotypic slices maintained ex vivo. Importantly, the extraction of relevant parameters from these neural populations is likely to involve long-term measurements, lasting from a few hours to entire days. The processing of huge amounts of electrophysiological data, in terms of computational time and automation of the procedures, is actually one of the major bottlenecks for both in vivo and in vitro recordings. In this paper we present a collection of algorithms implemented within a new software package, named the Neural Signal Manager (NSM), aimed at analyzing a huge quantity of data recorded by means of MEAs in a fast and efficient way. The NSM offers different approaches for both spike and burst analysis, and integrates state-of-the-art statistical algorithms, such as the inter-spike interval histogram or the post stimulus time histogram, with some recent ones, such as the burst detection and its related statistics. In order to show the potentialities of the software, the application of the developed algorithms to a set of spontaneous activity recordings from dissociated cultures at different ages is presented in the Results section. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Synergistic, antagonistic and additive effects of multiple stressors: predation threat, parasitism and pesticide exposure in Daphnia magna

JOURNAL OF APPLIED ECOLOGY, Issue 6 2008
Anja Coors
Summary 1Predation and parasitism are important factors in the ecology and evolution of natural populations and may, along with other environmental factors, interact with the impact of anthropogenic pollutants. 2Our study aimed at identifying potential interactions between three stressors (predation threat, parasitism and pesticide exposure) and at exploring the predictability of their joint effects by using the model of independent action. We assessed in a full-factorial design the impacts of these stressors on key life-history traits and population growth rate of the water flea Daphnia magna. 3When applied as single stressors, predation threat and parasite challenge induced varying stressor-specific adaptive responses. The pesticide carbaryl was applied at a generally sublethal concentration, which caused low mortality only in first-brood offspring. 4Pesticide exposure interacted synergistically with parasite challenge regarding survival, which suggests immunomodulatory activity of the pesticide. Predation threat by phantom midge larvae showed antagonistic interactions for amount of first-brood offspring with both parasite challenge and carbaryl exposure. All stressors additively affected age and size at maturity, which added up to a considerable delay in the onset of reproduction in the three-stressor combination. The intrinsic rate of natural increase, r, reflected the non-additive and additive effects on single endpoints and showed significant synergistic interactions for all two-stressor combinations. The combination of all stressors resulted in a dramatic reduction of r compared to the stressor-free control. 5The model of independent action proved useful in quantitatively predicting effects of additively acting stressors, and in visualizing the occurrence and magnitude of non-additive effects in accordance with results of analysis of variances. 6Synthesis and applications. Cumulative additive effects and non-additive interactions of natural antagonists and pollutants are shown to result in considerable impacts on ecologically relevant parameters. As a starting point for an environmentally more realistic risk assessment of chemicals, it may be a valuable strategy to screen for non-additive effects among many stress factors simultaneously in simplified experimental designs by using the model of independent action. [source]


Reproductive skew in birds: models, problems and prospects

JOURNAL OF AVIAN BIOLOGY, Issue 2 2000
Robert D. Magrath
In recent years there has been a resurgence of interest in models to explain the partitioning of direct reproduction (,reproductive skew') among members of one sex within social groups. We review models of skew, identify problems of testing models, and consider how to make progress. One series of models assumes that dominants have complete control of subordinate reproduction, but may allow subordinates some reproduction as a way of enticing them to help or getting them to share the cost of reproduction. Another series of models assume that dominants have limited control of subordinate reproduction. Reproductive skew may also be affected by incest avoidance or control by the opposite sex. Models are largely untested because no study of birds has quantified all relevant parameters, and we see no prospect of this happening soon. A common simplifying approach is to test qualitative predictions about the effect on skew of relatedness among group members. However, these data alone cannot distinguish among models because models do not make unique predictions, partly because skew is also affected by other factors. A major problem in cooperatively-breeding birds is that any effect of relatedness will often be confounded by covariation with relatedness asymmetry and subordinate competitiveness. Progress can be made with the development of theory, controlling confounding variables through the choice of study species or types of social group, and, most importantly, testing assumptions underlying hypotheses. [source]


Towards a more general species,area relationship: diversity on all islands, great and small

JOURNAL OF BIOGEOGRAPHY, Issue 4 2001
Lomolino
Aim To demonstrate a new and more general model of the species,area relationship that builds on traditional models, but includes the provision that richness may vary independently of island area on relatively small islands (the small island effect). Location We analysed species,area patterns for a broad diversity of insular biotas from aquatic and terrestrial archipelagoes. Methods We used breakpoint or piecewise regression methods by adding an additional term (the breakpoint transformation) to traditional species,area models. The resultant, more general, species,area model has three readily interpretable, biologically relevant parameters: (1) the upper limit of the small island effect (SIE), (2) an estimate of richness for relatively small islands and (3) the slope of the species,area relationship (in semi-log or log,log space) for relatively large islands. Results The SIE, albeit of varying magnitude depending on the biotas in question, appeared to be a relatively common feature of the data sets we studied. The upper limit of the SIE tended to be highest for species groups with relatively high resource requirements and low dispersal abilities, and for biotas of more isolated archipelagoes. Main conclusions The breakpoint species,area model can be used to test for the significance, and to explore patterns of variation in small island effects, and to estimate slopes of the species,area (semi-log or log,log) relationship after adjusting for SIE. Moreover, the breakpoint species,area model can be expanded to investigate three fundamentally different realms of the species,area relationship: (1) small islands where species richness varies independent of area, but with idiosyncratic differences among islands and with catastrophic events such as hurricanes, (2) islands beyond the upper limit of SIE where richness varies in a more deterministic and predictable manner with island area and associated, ecological factors and (3) islands large enough to provide the internal geographical isolation (large rivers, mountains and other barriers within islands) necessary for in situ speciation. [source]


Treatment of textile dye wastewater by using an electrochemical bipolar disc stack reactor

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2004
Karuppan Muthukumar
Abstract Textile dye house wastewater from a reactive dye processing unit was treated by using an electrochemical oxidation technique. The experiments were carried out in an electrochemical bipolar disc reactor using RuO2 coated on titanium as anode and titanium as cathode. The sodium chloride present in the effluent was used as supporting electrolyte. Operating parameters such as current density, reservoir hold-up and electrolysis time were studied for maximum Chemical Oxygen Demand (COD) reduction and other relevant parameters such as current efficiency and power consumption per kg of COD removal were calculated. The higher flow rate and lower reservoir hold-up resulted in improved COD removal. The applied current density was also found to significantly influence the reduction of COD. A suitable mathematical model is also proposed to illustrate the relationship between the basic parameters. Pseudo mass transfer coefficients were also evaluated for different experimental conditions. Copyright © 2004 Society of Chemical Industry [source]


Fountain flow revisited: The effect of various fluid mechanics parameters

AICHE JOURNAL, Issue 5 2010
Evan Mitsoulis
Abstract Numerical simulations have been undertaken for the benchmark problem of fountain flow present in injection-mold filling. The finite element method (FEM) is used to provide numerical results for both cases of planar and axisymmetric domains under laminar, isothermal, steady-state conditions for Newtonian fluids. The effects of inertia, gravity, surface tension, compressibility, slip at the wall, and pressure dependence of the viscosity are all considered individually in parametric studies covering a wide range of the relevant parameters. These results extend previous ones regarding the shape of the front, and in particular the centerline front position, as a function of the dimensionless parameters. The pressures from the simulations have been used to compute the excess pressure losses in the system (front pressure correction or exit correction). Inertia leads to highly extended front positions relative to the inertialess Newtonian values, which are 0.895 for the planar case and 0.835 for the axisymmetric one. Gravity acting in the direction of flow shows the same effect, while gravity opposing the flow gives a reduced bulge of the fountain. Surface tension, slip at the wall, and compressibility, all decrease the shape of the front. Pressure-dependence of the viscosity leads to increased front position as a corresponding dimensionless parameter goes from zero (no effect) to higher values of the pressure-shift factor. The exit correction increases monotonically with inertia, compressibility, and gravity, while it decreases monotonically with slip and pressure-dependence of the viscosity. Contour plots of the primary variables (velocity-pressure) show interesting trends compared with the base case (zero values of the dimensionless parameters and of surface tension). © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]


Selectivity for patch-distributed reactive spherical surfaces

AICHE JOURNAL, Issue 2 2007
Jui-Chuang Wu
Abstract The selectivity of reactions on active patches over those on a partially active carrier surface is investigated for patch-covered spheres. The effects of relevant parameters including patch and carrier reactivities, patch coverage, patch size, and patch separation state are studied. The selectivity is found to increase with increasing relative dominance of the patch reactivity over the carrier reactivity and patch coverage, as expected. Interestingly, it also increases with decreasing patch size and increasing patch separations. Decrease in patch size creates more patch,carrier interfaces and thus enhances the competition effectiveness of the patches against the carrier surface. With respect to the patch separation state, more complete utilization of the patches is achieved for well-separated patches and thus enhances the selectivity toward the patches. © 2007 American Institute of Chemical Engineers AIChE J 2007 [source]


Raman scattering determination of the depth of cure of light-activated composites: influence of different clinically relevant parameters

JOURNAL OF ORAL REHABILITATION, Issue 6 2002
G. Leloup
The purpose of this research was to determine the depth of cure of light-activated composites in relation with different clinically relevant parameters. A Raman spectroscopic method has been used. The measurement of cure is made on a relative basis by comparing the vibration band of the residual unpolymerized methacrylate C=C bond at 1640 cm,1 against the aromatic C=C stretching band at 1610 cm,1 used as an internal standard. The information gained draw attention to the importance of light transmission during the exposure. The influence of sample's thickness on the depth of cure is illustrated by a second order polynomial regression. The shade and translucency of the resin composite also modify the light transmission and thus have a significant influence on the degree of conversion. Moreover the light-source intensity and the distance from the curing tip are important parameters of influence. A significant reduction of the depth of cure is observed for all sample thickness of resin composite tested when using a light device with an intensity of 300 mW cm,2 as well as using a distance from the curing tip higher than 20 mm. [source]


Mechanics of column beds: I. Acquisition of the relevant parameters

AICHE JOURNAL, Issue 3 2003
Bee Gaik Yew
The efficiency of chromatographic columns is adversely affected by large-scale radial variations of the packing density or void ratio of the material used to prepare the bed. This heterogeneity is due to wall friction effects that take place during the preparation of the column and to seepage effects operating during the packing process and the subsequent operation of the column. The dependence of the bed's void fraction on the stress applied during its consolidation was determined, as well as its permeability at various stages of the consolidation process and the coefficient of friction between typical packing materials and the stainless steel wall of chromatographic columns. These results are required to develop and use numerical models of the volumetric response to axial compression of the bed and models of the coupled mechanical-seepage rheology of particulate materials. [source]


Surface modification of polyvinylidene fluoride pervaporation membranes

AICHE JOURNAL, Issue 12 2002
Mohamed Khayet
Polyvinylidene fluoride (PVDF) membranes were surface-modified using fluorinated surface-modifying macromolecules (SMMs) additives. The membranes were prepared using the phase-inversion method. Two novel SMM formulations were used. The effect of some relevant parameters, such as the solvent evaporation time, evaporation temperature, and concentration of SMM in the PVDF casting solution, was considered. The prepared membranes were characterized in terms of the contact angle analysis, the liquid entry pressure of water measurements, and the scanning electron microscopy. Pervaporation experiments were conducted for dilute chloroform/water binary mixtures. Based on the contact angle analysis, the incorporation of SMM into the PVDF casting solution produced membranes with higher surface hydrophobicity. The pervaporative performance of the prepared membranes was investigated, and the relationship between the surface characteristics of the modified PVDF membranes and the chloroform separation discussed. [source]


Bayesian analysis of single-molecule experimental data

JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 3 2005
S. C. Kou
Summary., Recent advances in experimental technologies allow scientists to follow biochemical processes on a single-molecule basis, which provides much richer information about chemical dynamics than traditional ensemble-averaged experiments but also raises many new statistical challenges. The paper provides the first likelihood-based statistical analysis of the single-molecule fluorescence lifetime experiment designed to probe the conformational dynamics of a single deoxyribonucleic acid (DNA) hairpin molecule. The conformational change is initially treated as a continuous time two-state Markov chain, which is not observable and must be inferred from changes in photon emissions. This model is further complicated by unobserved molecular Brownian diffusions. Beyond the simple two-state model, a competing model that models the energy barrier between the two states of the DNA hairpin as an Ornstein,Uhlenbeck process has been suggested in the literature. We first derive the likelihood function of the simple two-state model and then generalize the method to handle complications such as unobserved molecular diffusions and the fluctuating energy barrier. The data augmentation technique and Markov chain Monte Carlo methods are developed to sample from the posterior distribution desired. The Bayes factor calculation and posterior estimates of relevant parameters indicate that the fluctuating barrier model fits the data better than the simple two-state model. [source]


Serum osmolality and outcome in intensive care unit patients

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 8 2006
B. Holtfreter
Background:, The aim of the present study was to compare 16 routine clinical and laboratory parameters, acute physiologic and chronic health evaluation (APACHE) and sequential organ failure assessment (SOFA) score for their value in predicting mortality during hospital stay in patients admitted to a general intensive care unit (ICU). Methods:, A retrospective observational clinical study was carried out in a 15-bed ICU in a university hospital. Nine hundred and thirty-three consecutive patients with ICU stay > 24 h (36.2% surgical, 29.1% medical and 34.7% trauma) were observed. Blood sampling, patient surveillance and data collection were performed. The primary outcome was mortality in the hospital. We used receiver operating characteristic (ROC) analyses and logistic regression to compare the 16 relevant parameters, APACHE II and SOFA scores. Results:, Two hundred and thirty-three out of the 933 patients died (mortality 25.0%). One laboratory parameter, serum osmolality [area under the curve (AUC) 0.732] had a predictive value for mortality which lay between that of APACHE II (AUC 0.784) and SOFA (AUC 0.720) scores. When outcome prediction was restricted to long-term patients (ICU stay > 5 days), serum osmolality (AUC 0.711) performed better than either of the standard scores (APACHE AUC 0.655, SOFA AUC 0.636). Using logistic regression analysis, the association of clinical parameters, age and diagnosis group with mortality was determined. Conclusion:, Elevated serum osmolality at ICU admission is associated with an increased mortality risk in critically ill patients. Serum osmolality is cheaper and more rapid to determine than the scoring systems. However, further studies are needed to evaluate the predictive value of serum osmolality in different patient populations. [source]


An improved experimental and regression methodology for sorption isotherms

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 2 2005
Elisabeth J Quirijns
Abstract Sorption isotherms of corn and starch cylinders with immobilised catalase are experimentally determined at different temperatures for use in drying models in optimal control studies. This application of the sorption isotherm requires an accurate prediction of the sorption data at different temperatures for the low water activity range. The GAB equation is used for the prediction of the sorption isotherms. Two major problems are encountered by employing standard procedures, ie prediction of sorption at aw < 0.11 and sensitivity of the GAB parameters to the applied data range. An improved methodology is developed, consisting of extending the standard experimental procedure with additional data points in the low water activity range and changing the criterion in the regression procedure in the sum of squares, which is weighed by the variance of the experimental data. The new methodology leads to accurate, consistent and physically relevant parameters of the GAB equation, which are independent of the applied data range in the regression analysis and which result in accurate predictions of the sorption behaviour at low water activity. The sorption data at different temperatures at low water activity can be predicted in the best way with parameters obtained after direct regression based on weighed SSQ. Copyright © 2004 Society of Chemical Industry [source]


Influence of extraction temperature on the final quality of espresso coffee,

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2003
Susana Andueza
Abstract The final quality of espresso coffee (EC) depends upon certain technical conditions, such as the extraction temperature used in preparing it. The aim of this work was to investigate the effects of water temperature (88, 92, 96 and 98,°C) on the final quality of three types of EC (Arabica, Robusta Natural blend and Robusta Torrefacto blend) in order to select the optimal temperature. Volatile compound (analysed by Static headspace gas chromatography/mass spectrometry) and sensory flavour profiles were the most relevant parameters, whereas physicochemical, taste and mouthfeel parameters were not very useful for selecting the water temperature. For Arabica and Robusta Natural blend ECs, 92,°C was the optimal water temperature. For Robusta Torrefacto blend EC the overall acceptability might lead to the selection of 88,°C as the ideal water temperature, but the high percentages of key odorants related to roasty and earthy/musty flavours and the ,not hot enough' perception dictated the selection of 92,°C in this case as well. © 2003 Society of Chemical Industry [source]


Unemployment May Be Lower if Unions Bargain over Wages and Employment

LABOUR, Issue 1 2002
Hartmut Egger
This paper addresses the question under which circumstances unemployment can be lower if unions bargain over wages and employment in a general equilibrium framework. Thereby, it turns out that the unemployment rate may negatively depend on the wage rate, if the unemployment compensation scheme contains a constant real term in addition to the replacement ratio component. This is, compared with a pure replacement ratio scheme, the more plausible formalization of the real world's compensation systems, at least for European countries. Besides the theoretical analysis, the paper also derives political implications by identifying the relevant parameters for the decision on whether weakening unions will be a good strategy for an economy to overcome its unemployment problem. [source]


Laser ablation-inductively coupled plasma mass spectrometry in archaeometric research

MASS SPECTROMETRY REVIEWS, Issue 1 2010
Martín Resano
Abstract Laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) is a solid sampling technique in continuous expansion in all types of research fields in which direct multi-elemental or isotopic analysis is required. In particular, this technique shows unique characteristics that made its use recommended in many archaeometric applications, where valuable solid artifacts are often the target samples, because it offers flexibility to achieve spatially resolved information with high detection power and a wide linear range, in a fast and straightforward way, and with minimal sample damage. The current review provides a systematic survey of publications that reported the use of LA-ICPMS in an archaeological context, highlights its main capabilities and limitations and discusses the most relevant parameters that influence the performance of this technique for this type of application. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 29:55,78, 2010 [source]


Numerical optimization study of multiple-pass aeroassisted orbital transfer

OPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 4 2002
Anil V. Rao
Abstract A direct transcription method is applied to the problem of multiple-pass aeroassisted orbital transfer from geostationary orbit to low Earth orbit with a large inclination change. The objective is to provide minimum-impulse requirements and corresponding optimal trajectories for a gliding vehicle with a high lift-to-drag ratio subject to constraints on heating rate, angle of attack, and transfer time. The multiple-pass aeroassisted orbital transfer problem is set up as a multi-phase optimal control problem. All relevant parameters, including de-orbiting, intermediate, and circularizing impulses, are optimized. Copyright © 2002 John Wiley & Sons, Ltd. [source]


Investigation of ZnTe thin films grown by Pulsed Laser Deposition method

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007
B. Kotlyarchuk
Abstract This paper is devoted to optimization of the Pulsed Laser Deposition (PLD) growth condition of ZnTe films on various substrates and subsequent investigation of relevant parameters of growth process, structural, optical and electrical properties of grown films. Studies of the effect of growth parameters on the structural quality and properties of grown films were carried out. X-ray diffraction measurements showed that the ZnTe films, which have been deposited at optimal substrate temperatures, were characterized by a (111) preferred orientation with large average grain size. The optical transmission and reflectance in the energy range 1.5,5.5 eV for films grown at various substrate temperatures were measured. We calculated the variation in the absorption coefficient with the photon energy from the transmittance spectrum for samples grown at various substrate temperatures. Obtained data were analyzed and the value of the absorption coefficient, for allowed direct transitions, has been determined as a function of photon energy. We found that the undoped ZnTe films, which were grown by the PLD method, are typically p-type and possess resistivity in the range of 103 , cm at room temperature. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]