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Limits
Kinds of Limits Terms modified by Limits Selected AbstractsFAITH, PUBLIC POLICY, AND THE LIMITS OF SOCIAL SCIENCE,CRIMINOLOGY AND PUBLIC POLICY, Issue 2 2003PAUL KNEPPER Recent interest on the part of criminologists in the "faith factor" has made possible a contemporary argument for faith-based interventions in crime prevention: if faith "works," then government should support faith-based initiatives because in doing so, government is not endorsing religion, but science. Drawing on the ideas of Karl Popper, Michael Polanyi, and others, this essay reviews this argument within the framework of the philosophy of social science. The discussion reviews such concepts of falsification, structural causality, objectivity, and evidence-based policy making to affirm the place of both faith and science in public life. [source] THE LIMITS OF SOCIAL SCIENCE IN GUIDING POLICYCRIMINOLOGY AND PUBLIC POLICY, Issue 1 2002MARK H. MOORE First page of article [source] THE LIMITS OF SCIENCEADDICTION, Issue 7 2010PETER REUTER No abstract is available for this article. [source] [Commentary] LOW-RISK DRINKING LIMITS: ABSOLUTE VERSUS RELATIVE RISKADDICTION, Issue 8 2009DEBORAH A. DAWSON No abstract is available for this article. [source] COSTS AND LIMITS OF PHENOTYPIC PLASTICITY IN ISLAND POPULATIONS OF THE COMMON FROG RANA TEMPORARIA UNDER DIVERGENT SELECTION PRESSURESEVOLUTION, Issue 6 2009Martin I. Lind Costs and limits are assumed to be the major constraints on the evolution of phenotypic plasticity. However, despite their expected importance, they have been surprisingly hard to find in natural populations. It has therefore been argued that natural selection might have removed high-cost genotypes in all populations. However, if costs of plasticity are linked to the degree of plasticity expressed, then high costs of plasticity would only be present in populations where increased plasticity is under selection. We tested this hypothesis by investigating costs and limits of adaptive phenotypic plasticity in development time in a common garden study of island populations of the common frog Rana temporaria, which have varying levels of development time and phenotypic plasticity. Costs of plasticity were only found in populations with high-plastic genotypes, whereas the populations with the most canalized genotypes instead had a cost of canalization. Moreover, individuals displaying the most extreme phenotypes also were the most plastic ones, which mean we found no limits of plasticity. This suggests that costs of plasticity increase with increased level of plasticity in the populations, and therefore costs of plasticity might be more commonly found in high-plastic populations. [source] GENERATION OF BIOLUMINESCENT MORGANELLA MORGANII AND ITS POTENTIAL USAGE IN DETERMINATION OF GROWTH LIMITS AND HISTAMINE PRODUCTIONJOURNAL OF FOOD SAFETY, Issue 2 2009MEHDI ZAREI ABSTRACT A mini-Tn5 promoter probe carrying the intact lux operon of Photorhabdus luminescens (pUT mini-Tn5 luxCDABE) which allowed measurement of light output without the addition of exogenous substrate was constructed. It was used to create a pool of chromosomally lux -marked strains of Morganella morganii. Also plasmid-mediated expression of bioluminescence in M. morganii was assessed using plasmid pT7-3 luxCDABE. No significant differences in growth and histamine formation characteristics of the lux -marked strains and wild type M. morganii strain were observed. Luminescent strain of M. morganii was used in experiments in which the correlation between light output, viable cell count and histamine formation was assessed. During the exponential growth phase, a positive linear correlation was observed between these three parameters in trypticase soy broth-histidine medium at 37C. It was demonstrated that expression of bioluminescence had not had a significant effect upon both growth rate and histamine production. Thus, the measurement of bioluminescence was found to be a simple, fast and reliable method for determination of viable cell count and histamine content. PRACTICAL APPLICATIONS Constructing predictive models in microbiology requires a large number of data on desired factors. Commonly used traditional methods of counting viable cells and measuring histamine, e.g., to model the growth limits of M. morganii as a function of different intrinsic and extrinsic factors, are time consuming and laborious, and require a lot of laboratory space and materials. According to the results of this research, measurement of bioluminescence is a simple, fast and reliable method for the determination of viable cell count and histamine content during the exponential growth phase. Thus, it can be used as a labor- and material-saving selective data capture method for constructing predictive models in many different areas. [source] A RAPID METHOD OF QUANTIFYING THE RESOLUTION LIMITS OF HEAT-FLOW ESTIMATES IN BASIN MODELSJOURNAL OF PETROLEUM GEOLOGY, Issue 2 2008A. Beha Deterministic forward models are commonly used to quantify the processes accompanying basin evolution. Here, we describe a workflow for the rapid calibration of palaeo heat-flow behaviour. The method determines the heat-flow history which best matches the observed data, such as vitrinite reflectance, which is used to indicate the thermal maturity of a sedimentary rock. A limiting factor in determining the heat-flow history is the ability of the algorithm used in the software for the maturity calculation to resolve information inherent in the measured data. Thermal maturation is controlled by the temperature gradient in the basin over time and is therefore greatly affected by maximum burial depth. Calibration, i.e. finding the thermal history model which best fits the observed data (e.g. vitrinite reflectance), can be a time-consuming exercise. To shorten this process, a simple pseudo-inverse model is used to convert the complex thermal behaviour obtained from a basin simulator into more simple behaviour, using a relatively simple equation. By comparing the calculated "simple" maturation trend with the observed data points using the suggested workflow, it becomes relatively straightforward to evaluate the range within which a best-fit model will be found. Reverse mapping from the simple model to the complex behaviour results in precise values for the heat-flow which can then be applied to the basin model. The goodness-of-fit between the modelled and observed data can be represented by the Mean Squared Residual (MSR) during the calibration process. This parameter shows the mean squared difference between all measured data and the respective predicted maturities. A minimum MSR value indicates the "best fit". Case studies are presented of two wells in the Horn Graben, Danish North Sea. In both wells calibrating the basin model using a constant heat-flow over time is not justified, and a more complex thermal history must be considered. The pseudo-inverse method was therefore applied iteratively to investigate more complex heat-flow histories. Neither in the observed maturity data nor in the recorded stratigraphy was there evidence for erosion which would have influenced the present-day thermal maturity pattern, and heat-flow and time were therefore the only variables investigated. The aim was to determine the simplest "best-fit" heat-flow history which could be resolved at the maximum resolution given by the measured maturity data. The conclusion was that basin models in which the predicted maturity of sedimentary rocks is calibrated solely against observed vitrinite reflectance data cannot provide information on the timing of anomalies in the heat-flow history. The pseudo inverse method, however, allowed the simplest heat-flow history that best fits the observed data to be found. [source] A SIMPLE ALTERNATIVE ANALYSIS FOR THRESHOLD DATA DETERMINED BY ASCENDING FORCED-CHOICE METHODS OF LIMITSJOURNAL OF SENSORY STUDIES, Issue 3 2010HARRY T. LAWLESS ABSTRACT An alternative analysis of forced-choice threshold data sets such as the type generated by ASTM method E-679 involves a simple interpolation of chance-corrected 50% detection. This analysis has several potential advantages. The analysis does not require the ad hoc heuristics for estimating individual thresholds above and below the series. It takes into account the possibility of guessing correctly, which is not considered in the ASTM calculations and produces a downward bias to the estimates. It does not discount correct responses early in the series which may be legitimate detections, but which are discounted by the ASTM method if followed by any incorrect response. Comparisons of the two methods in a large consumer study of odor detection threshold study data set gave comparable values. The interpolation can also be done to determine other levels of detection (e.g. 10, 25%). These values other than 50% can be potentially useful in setting regulatory standards for water or air pollution limits or to food manufacturers who wish to avoid detection of taints by more sensitive individuals. PRACTICAL APPLICATIONS The forced choice methods for threshold estimation have proven practically useful in comparing the potency of various flavor materials and in comparing the sensitivities of individuals. The ASTM method E-679 is one such method. The alternative analysis of results from this procedure which is outlined here provides additional information and does not exhibit the downward bias because of correct guessing. [source] GLOBAL JUSTICE AND THE LIMITS OF HUMAN RIGHTSTHE PHILOSOPHICAL QUARTERLY, Issue 221 2005Dale Dorsey To a great extent, recent discussion of global obligations has been couched in the language of human rights. I argue that this is a mistake. If, as many theorists have supposed, a normative theory applicable to obligations of global justice must also respect the needs of justice internal to recipient nations, any such theory cannot take human rights as an important moral notion. Human rights are inapplicable for the domestic justice of poor nations, and thus cannot form a plausible basis for international justice. Instead, I propose an alternative basis, a form of welfarist maximizing consequentialism. My alternative is superior to rights-based theories in dealing with the special problems of justice found in poor nations. [source] LIMITS TO COMPETITION AND REGULATION IN PRIVATIZED ELECTRICITY MARKETSANNALS OF PUBLIC AND COOPERATIVE ECONOMICS, Issue 4 2009Hulya Dagdeviren ABSTRACT,:,Privatization of electricity has been extensive both in the developed and the developing world. Failures in various areas have led to the emergence of a new consensus which regards competitive pressures and regulation as crucial for utility privatizations to work. This review paper presents a critical evaluation of this newly found wisdom with reference to the developing economies. The experience in the developed world, especially in the USA and the UK, has been used to draw conclusions for the developing economies. Overall, the paper highlights the problems associated with the ,competitive model' both in the developed and developing world and points to the potential instability in private competitive power supply systems. It also examines the degree to which regulation can be a panacea for market failures and structural problems under private provision. [source] RISK DETECTION IN INDIVIDUAL HEALTH CARE: ANY LIMITS?BIOETHICS, Issue 8 2010GER PALMBOOM ABSTRACT Background: Biomedical science is producing an avalanche of data about risk factors, often with a small predictive value, associated with a broad diversity of diseases. Prevention and screening are increasingly moving from public health into the clinic. Therefore, the question of which risk factors to investigate and disclose in the individual patient, becomes ethically increasingly urgent. In line with Wilson and Jungner's public health-related 10 principles for screening, it seems crucial to distinguish important from unimportant health risks. Aim: to explore the ways in which clinicians distinguish important from unimportant health risks. Methods: We interviewed 36 respondents (gastroenterologists and gynaecologists/obstetrics) in 5 focus group interviews and 15 open in-depth interviews on their interpretation of what makes a health risk important. Results: Physicians primarily interpreted importance as the severity of the possible harm, less often its probability. Possibilities of prevention or reassurance strongly influenced their judgment on importance. Discussion: It is not likely that interpreting ,important' as ,severe' will help in differentiating meaningful from meaningless risk knowledge. A more fundamental change in our ways of dealing with risk may be called for. We discuss existing literature on resilience as an alternative way to deal with risk. Balancing prevention and risk reduction with resilience could be a fruitful direction. [source] THE LIMITS OF INTIMATE CITIZENSHIP: REPRODUCTION OF DIFFERENCE IN FLEMISH-ETHIOPIAN ,ADOPTION CULTURES'BIOETHICS, Issue 7 2010KATRIEN DE GRAEVE ABSTRACT The concept of ,intimate citizenship' stresses the right of people to choose how they organize their personal lives and claim identities. Support and interest groups are seen as playing an important role in the pursuit of recognition for these intimate choices, by elaborating visible and positive cultures that invade broader public spheres. Most studies on intimate citizenship take into consideration the exclusions these groups encounter when negotiating their differences with society at large. However, much less attention is paid to the ways in which these groups internalize the surrounding ideologies, identity categories and hierarchies that pervade society and constrain their recognition as full citizens. In contrast, this paper aims to emphasize the reproduction of otherness within alternative spheres of life, and to reveal the ambiguities and complexities involved in their dialectic relationship with society at large. To address this issue, the paper focuses on the role that ,adoption cultures' of Flemish adoptive parents with children from Ethiopia play in the pursuit of being recognized as ,proper' families and full citizens. The ethnographic research among adoptive parents and adoption professionals shows a defensive discourse and action that aims at empowering against potential problems, as well as a tendency to other the adoptive child by pathologizing its non-normativity. By showing the strong embeddedness of adoptive families' practices of familial and cultural construction in larger cultural frames of selfing and othering, characterized by biologism and nativism, one begins to understand the limits of their capacity to realize full citizenship. [source] Simulation Study of the MHD Stability Beta Limit in LHD by TASK3DCONTRIBUTIONS TO PLASMA PHYSICS, Issue 6-7 2010M. Sato Abstract The numerical method for analysis of the "MHD stability beta limit" based on a hierarchy integrated simulation code TASK3D has been developed. The numerical model for the effect of the MHD instabilities is introduced such that the pressure profile is flattened around the rational surface due to the MHD instabilities. The width of the flattening of the pressure gradient is determined from the width of the eigenmode structure of the MHD instabilities (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Improved Detection Limit and Stability of Amperometric Carbon Nanotube-Based Immunosensors by Crosslinking Antibodies with PolylysineELECTROANALYSIS, Issue 2 2008Vito Cataldo Abstract Amperometric immunosensor configurations featuring covalently bound anti-biotin antibodies (Ab) embedded into a polylysine (PLL)-single walled carbon nanotube (SWCNT) composite layer were evaluated. Assemblies were made by first oxidizing pyrolytic graphite (PG) electrodes to form surface carboxylic acid groups, to which PLL, SWCNTs and anti-biotin were covalently linked. Incorporating SWCNT into PLL-antibody assemblies improved the amperometric detection limit for biotin (Ag) labeled with horseradish peroxidase to 10,fmol mL,1. Anti-biotin embedded into the PLL matrix had improved thermal stability and retained its binding ability for biotin after exposure to temperatures of 42,°C for up to 3 hours, while the noncrosslinked antibody was inactivated at this temperature in several minutes. [source] TK/TD dose,response modeling of toxicityENVIRONMETRICS, Issue 5 2007Munni 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] High K Capacitors and OFET Gate Dielectrics from Self-Assembled BaTiO3 and (Ba,Sr)TiO3 Nanocrystals in the Superparaelectric LimitADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Limin Huang Abstract Nanodielectrics is an emerging field with applications in capacitors, gate dielectrics, energy storage, alternatives to Li-ion batteries, and frequency modulation in communications devices. Self-assembly of high k dielectric nanoparticles is a highly attractive means to produce nanostructured films with improved performance,namely dielectric tunability, low leakage, and low loss,as a function of size, composition, and structure. One of the major challenges is conversion of the nanoparticle building block into a reliable thin film device at conditions consistent with integrated device manufacturing or plastic electronics. Here, the development of BaTiO3 and (Ba,Sr)TiO3 superparaelectric uniform nanocrystal (8,12,nm) films prepared at room temperature by evaporative driven assembly with no annealing step is reported. Thin film inorganic and polymer composite capacitors show dielectric constants in the tunable range of 10,30, dependent on composition, and are confirmed to be superparaelectric. Organic thin film transistor (TFT) devices on flexible substrates demonstrate the readiness of nanoparticle-assembled films as gate dielectrics in device fabrication. [source] Use of Observations below Detection Limit for Model CalibrationGROUND WATER, Issue 2 2009Michael LeFrancois Censored (nondetect) values occur when chemical concentrations in water samples are near or below the level that can be measured by an analysis method. It is common to either delete or substitute values for nondetect observations for use in model calibration, but this practice can bias the estimated parameter values and the model predictions. A more realistic representation of the system is obtained from the calibration if we include such observations in a manner reflecting that we know only the value is below the detection limit. Consequently, we propose use of the censored-residual approach to including nondetect values as observations for calibration. In this approach, residuals are calculated as the detection limit minus the simulated value when the simulated value exceeds the detection limit, and the residual is assigned a value of zero when the simulated value is below the detection limit. The new censored-residual approach is particularly advantageous when calibrating transport models to low concentration data. [source] Is One an Upper Limit for Natural Hydraulic Gradients?GROUND WATER, Issue 4 2008D.J. Hart No abstract is available for this article. [source] Label-Free Colorimetric Detection of Lead Ions with a Nanomolar Detection Limit and Tunable Dynamic Range by using Gold Nanoparticles and DNAzyme,ADVANCED MATERIALS, Issue 17 2008Zidong Wang In the presence of Pb2+, a cleaved enzyme,substrate complex releases ssDNA that adsorbs onto and stabilizes gold nanoparticles (AuNPs) against salt-induced aggregation. In the absence of Pb2+, the uncleaved complex can not stabilize the AuNPs, resulting in purple,blue AuNP aggregates (see figure). The sensor has a low detection limit of 3,nM, a high selectivity, and a tunable dynamic range. [source] Control of Glass-Forming Process During Fiber-Drawing to Reduce the Rayleigh Scattering LossJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2006K. Saito Limit of the Rayleigh scattering loss in Ge-doped silica core fiber was estimated from the results of structural relaxation and the Rayleigh scattering measurements, and the most suitable fiber-drawing condition to reduce the Rayleigh scattering loss was determined. An annealing furnace, which could be attached to a fiber-drawing tower, was developed for realizing the optimum fiber-drawing condition. Drawing tests with this furnace confirmed our estimation of the loss. [source] Crack Growth in Soda,Lime,Silicate Glass near the Static Fatigue LimitJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2002Sheldon M. Wiederhorn The atomic force microscope (AFM) was used to explore the nature of features formed on the surfaces of cracks in soda,lime,silicate glass that were held at stress intensity factors below the crack growth threshold. All studies were conducted in water. Cracks were first propagated at a stress intensity factor above the crack growth threshold and then arrested for 16 h at a stress intensity factor below the threshold. The stress intensity factor was then raised to reinitiate crack growth. The cycle was repeated multiple times, varying the hold stress intensity factor, the hold time, and the propagation stress intensity factor. Examination of the fracture surface by optical microscopy showed surface features that marked the points of crack arrest during the hold time. These features were identical to those reported earlier by Michalske in a similar study of crack arrest. A study with the AFM showed these features to be a consequence of a bifurcation of the crack surface. During the hold period, waviness developed along the crack front so that parts of the front propagated out of the original fracture plane, while other parts propagated into the plane. Crack growth changed from the original flat plane to a bifurcated surface with directions of as much as 3° to 5° to the original plane. This modification of crack growth behavior cannot be explained by a variation in the far-field stresses applied to the crack. Nor can the crack growth features be explained by chemical fluctuations within the glass. We speculate that changes in crack growth direction are a consequence of an enhancement in the corrosion rate on the flank of the crack at stresses below the apparent crack growth threshold in a manner described recently by Chuang and Fuller. [source] When is an Individual an Individual Versus a Member of a Group?NUTRITION REVIEWS, Issue 5 2006An Issue in the Application of the Dietary Reference Intakes The Institute of Medicine (IOM) reports on Dietary Reference Intakes (DRIs) present a new paradigm for the description of nutrient requirements. Tradition and the DRI reports themselves have created an erroneous impression that the Recommended Dietary Allowance (RDA) is intended for use with individuals and the Estimated Average Requirement (EAR) is to be used with populations. Two recent IOM committee reports (one on nutrition labeling and one on Women, Infants and Children [WIC] food packages) challenge that interpretation, revealing the critical issues surrounding individuals versus groups or populations. The present paper examines the issues and concludes that the median requirement and Tolerable Upper Limit (UL) are the critical reference values for both individuals and populations. The RDA is both unneeded and lacking a sound scientific basis. [source] IV,Three Moments in the Theory of Definition or Analysis: Its Possibility, Its Aim or Aims, and Its Limit or TerminusPROCEEDINGS OF THE ARISTOTELIAN SOCIETY (HARDBACK), Issue 1pt1 2007David Wiggins The reflections recorded in this paper arise from three moments in the theory of definition and of conceptual analysis. The moments are: (I) Frege's (1894) review of Husserl's Philosophy of Arithmetic (Vol. I), the discussion there of the paradox of analysis, and the division that Frege marks, ensuing upon his distinction of Sinn/sense from Bedeutung/reference, between two different conceptions of definition; (II) Leibniz's still serviceable account (1684, 1704) of a distinction between the clarity and the distinctness of ideas,a distinction that prompts the suggestion that the guiding purpose of lexical definition is Leibnizian clarity whereas that of real definition (as Aristotle has us conceive it) is inseparable from the pursuit of Leibnizian distinctness; (III) Leibniz's speculations (1679) concerning the limit or terminus of analysis. The apparent failure of these speculations, casting doubt as it does upon the aspirations that give rise to them (aspirations not necessarily or entirely alien to the Zeitgeist of our own epoch), points to the long-standing need to reconfigure the philosophical business of enquiry into concepts. [source] Determination of iodoacetic acid using liquid chromatography/electrospray tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2008Benjamin P.-Y. A rapid analytical method based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) using electrospray ionization in negative ion detection mode was developed for the analysis of underivatized iodoacetic acid in water. The method was applied to model reaction mixtures in the study of the formation of iodoacetic acid after chlorinated tap water was boiled in the presence of potassium iodide or iodized table salt. Samples can be directly analyzed by the LC/MS/MS system without extraction or chemical derivatization. Limit of detection was determined to be 0.3,µg/L (or 0.3,ng/mL) and limit of quantitation was about 1,µg/L (1,ng/mL). Copyright © 2008 John Wiley & Sons, Ltd. [source] Development and validation of a rapid and sensitive HPLC method for the quantification of 5-fluorocytosine and its metabolitesBIOMEDICAL CHROMATOGRAPHY, Issue 5 2010Kinta M. Serve Abstract To study the intracellular metabolism of the prodrug 5-fluorocytosine (5FC), we developed a novel reverse-phase high-performance liquid chromatography method to simultaneously detect 5FC and its four major anabolic metabolites: 5-fluorouracil, 5-fluorouridine, 5-fluorouridine-monophosphate and 5-fluoro-2,deoxyuridine-5,-monophosphate. Separation of each compound was accomplished under isocratic conditions using a C18 column and mobile phase of formic acid,water (1,:,99,v/v). The method was validated for both accuracy and reproducibility in cell culture media. Additionally, metabolites were assessed for stability at ambient temperatures and following freeze,thaw cycles. Calibration curves were linear over a range of 1,200,,g/mL. Limit of quantification for four of the five compounds was 1,,g/mL in cell culture media (RSD < 11%). This method was successfully used to monitor intracellular conversion of 5FC to its metabolic products over a 24h period. Copyright © 2009 John Wiley & Sons, Ltd. [source] Validated analysis of fluvastatin in a pharmaceutical capsule formulation and serum by capillary electrophoresisBIOMEDICAL CHROMATOGRAPHY, Issue 6 2001Dilek Do, rukol-Ak The capillary electrophoretic behavior and the determination of fluvastatin (FLU) in capsule and serum is described in this study. Method development was conducted in a fused-silica capillary (L,=,86,cm, Leff,=,58,cm and 75,µm i.d.) and a background electrolyte consisting of 10,mM borate at pH 8 was used. The separation was performed by current-controlled system applying 41,µA, detecting at 239,nm and injecting 0.5,s vacuum injection. A good electropherogram and excellent repeatability was obtained. FLU and phenobarbital sodium (internal standard) migrated (with RSD%) at 4.8 (0.3),min and 5.2 (0.6),min, respectively. Limit of detection (LOD) and limit of quantitation (LOQ) values were found to be 1,×,10,6,M and 2.89,×,10,6,M, respectively. Linearity in the range of 1.03,×,10,5 ,5.15,×,10,5 M was examined employing intra-day and inter-day studies and well-correlated calibration equations were obtained. FLU in a capsule (Lescol® 40,mg declared) was found to be 41.9,±,0.4,mg. Furthermore, FLU was determined in serum applying standard addition technique. Good repeatability and no interference were observed. The method proposed is simple, sensitive, precise and easy to use for the determination of FLU in capsule and serum. Copyright © 2001 John Wiley & Sons, Ltd. Abbreviations used: FLU fluvastatin HMG-CoA hydroxymethylglutaryl coenzyme [source] Youden Index and Optimal Cut-Point Estimated from Observations Affected by a Lower Limit of DetectionBIOMETRICAL JOURNAL, Issue 3 2008Marcus D. Ruopp Abstract The receiver operating characteristic (ROC) curve is used to evaluate a biomarker's ability for classifying disease status. The Youden Index (J), the maximum potential effectiveness of a biomarker, is a common summary measure of the ROC curve. In biomarker development, levels may be unquantifiable below a limit of detection (LOD) and missing from the overall dataset. Disregarding these observations may negatively bias the ROC curve and thus J. Several correction methods have been suggested for mean estimation and testing; however, little has been written about the ROC curve or its summary measures. We adapt non-parametric (empirical) and semi-parametric (ROC-GLM [generalized linear model]) methods and propose parametric methods (maximum likelihood (ML)) to estimate J and the optimal cut-point (c *) for a biomarker affected by a LOD. We develop unbiased estimators of J and c * via ML for normally and gamma distributed biomarkers. Alpha level confidence intervals are proposed using delta and bootstrap methods for the ML, semi-parametric, and non-parametric approaches respectively. Simulation studies are conducted over a range of distributional scenarios and sample sizes evaluating estimators' bias, root-mean square error, and coverage probability; the average bias was less than one percent for ML and GLM methods across scenarios and decreases with increased sample size. An example using polychlorinated biphenyl levels to classify women with and without endometriosis illustrates the potential benefits of these methods. We address the limitations and usefulness of each method in order to give researchers guidance in constructing appropriate estimates of biomarkers' true discriminating capabilities. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A Note on Comparing Exposure Data to a Regulatory Limit in the Presence of Unexposed and a Limit of DetectionBIOMETRICAL JOURNAL, Issue 6 2005Haitao Chu Abstract In some occupational health studies, observations occur in both exposed and unexposed individuals. If the levels of all exposed individuals have been detected, a two-part zero-inflated log-normal model is usually recommended, which assumes that the data has a probability mass at zero for unexposed individuals and a continuous response for values greater than zero for exposed individuals. However, many quantitative exposure measurements are subject to left censoring due to values falling below assay detection limits. A zero-inflated log-normal mixture model is suggested in this situation since unexposed zeros are not distinguishable from those exposed with values below detection limits. In the context of this mixture distribution, the information contributed by values falling below a fixed detection limit is used only to estimate the probability of unexposed. We consider sample size and statistical power calculation when comparing the median of exposed measurements to a regulatory limit. We calculate the required sample size for the data presented in a recent paper comparing the benzene TWA exposure data to a regulatory occupational exposure limit. A simulation study is conducted to investigate the performance of the proposed sample size calculation methods. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A Mixture Model for Occupational Exposure Mean Testing with a Limit of DetectionBIOMETRICS, Issue 3 2001Douglas J. Taylor Summary. Information from detectable exposure measurements randomly sampled from a left-truncated log-normal distribution may be used to evaluate the distribution of nondetectable values that fall below an analytic limit of detection. If the proportion of nondetects is larger than expected under log normality, alternative models to account for these unobserved data should be considered. We discuss one such model that incorporates a mixture of true zero exposures and a log-normal distribution with possible left censoring, previously considered in a different context by Moulton and Halsey (1995, Biometrics51, 1570,1578). A particular relationship is demonstrated between maximum likelihood parameter estimates based on this mixture model and those assuming either left-truncated or left-censored data. These results emphasize the need for caution when choosing a model to fit data involving nondetectable values. A one-sided likelihood ratio test for comparing mean exposure under the mixture model to an occupational exposure limit is then developed and evaluated via simulations. An example demonstrates the potential impact of specifying an incorrect model for the nondetectable values. [source] EPA Re-Establishes Lower Arsenic Limit for Drinking Water; New Standard Fully in Effect by 2006CA: A CANCER JOURNAL FOR CLINICIANS, Issue 1 2002Article first published online: 31 DEC 200 No abstract is available for this article. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||