bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement error in dietary assessment: An investigation using covariance structure models. Part I
Authors: Plummer Martyn , Clayton David 
Published: April 2007

AbstractRepeated measures of diet are analysed in an attempt to discover the measurement error properties of various dietary assessment methods. It is customary in such studies to assume that one reference measurement is ‘valid’ (without error) but this assumption is not tenable. An alternative approach, widely used in social science, is to model the covariance matrix of the repeated measures. We apply this methodology to assessments of nitrogen intake, which is essentially equivalent to protein intake.
Modelling lactation using an inverse polynomial in a multilevel statistical model
Authors: Drewett R. F. , Goldstein H. 
Published: April 2007

AbstractA method is outlined for modelling the relationship between breast‐milk production and time from delivery, suitable for data collected longitudinally. The relationship is described using inverse polynomials. In a two‐level model the coefficients are specified as random variables across subjects, allowing within‐ and between‐subject variation to be separately estimated. In a three‐level model, day‐to‐day variation can also be separately estimated. The model is illustrated using data from the Chiang Mai Lactation Project. It allows the use of covariates that vary over time, and provides a method of analysis that is compatible with the practical constraints on the timing of data collection that are inherent in longitudinal studies.
On population and individual bioequivalence
Authors: Schall Robert , Luus Herman G. 
Published: April 2007

AbstractIn a traditional assessment of the bioequivalence of two formulations of a drug one compares the average bioavailability from the two formulations. Anderson and Hauck argued that in some situations it is not sufficient to demonstrate average bioequivalence, and they proposed a method for the assessment of what they called individual bioequivalence, which essentially is the comparison of the individual responses to the two drug formulations within subjects. In this paper we propose a unified strategy for the assessment of bioequivalence that encompasses new approaches to the assessment of both population bioequivalence, which is the comparison of the marginal or population distributions of bioavailabilities, and individual bioequivalence, which is the comparison of the conditional or within‐subject distributions of bioavailabilities. The general idea is to use a comparison of the reference formulation to itself as the basis for the comparison of the test with the reference formulation. The new approaches overcome the main weakness of the current methods for the assessment of bioequivalence by considering the variability of bioavailabilities in addition to their means. The current methods for the assessment of bioequivalence, namely the conventional assessment of average bioequivalence and the proposal by Anderson and Hauck for the assessment of individual bioequivalence, emerge as special cases. One can evaluate the new bioequivalence criteria statistically by use of bootstrap confidence intervals.
An index of disease activity in rheumatoid arthritis
Authors: Jones P. W. , Ziade M. F. M. , Davis M. J. , Dawes P. T. 
Published: April 2007

AbstractThis paper describes the Stoke Index which has been designed to give a global measure of disease activity in rheumatoid arthritis. The index is based on two objective laboratory measurements, one subjective and two semi‐objective clinical measurements, chosen from 13 measurements using clinical judgement. Variable selection routines in principal components analysis are used to demonstrate that the index measures clinically defined disease activity. Its sensitivity and reversibility are also considered. A comparison is carried out with another index (Mallya‐Mace) and a modification is suggested.
Influence of model‐building strategies on the results of a case‐control study
Authors: Blettner Maria , Sauerbrei Willi 
Published: April 2007

AbstractWe evaluate the analysis of a case‐control study in which many variables were investigated simultaneously. The purpose of the study was to explore some rather unspecific hypotheses about potential risk factors for adult brain tumour. Our aim is to show that in the analysis of case‐control studies many decisions are necessary which are usually not published in detail. As in most studies these decisions are made during analysis and are data dependent. We demonstrate that the data allow sensible alternative decisions which influence the final results. A sensitivity analysis of several aspects of the analysis such as different measurement scales, variable selection, handling of missing values and interactions was performed, and demonstrated variation in the results based on the strategy for analysis. We conclude that details of the final analysis should be decided in the planning phase of a case‐control study, and that more details of model‐building strategies must be published. Results from a study where the analysis is highly data dependent must be interpreted with caution and validation of the results with new studies is essential.
Comparison of methods for the analysis of longitudinal interval count data
Authors: Stukel Thérèse A. 
Published: April 2007

AbstractLongitudinal studies are often concerned with estimating the recurrence rate of a non‐fatal event. In many cases, only the total number of events occurring during successive time intervals is known. We compared a mixed Poisson‐gamma regression method proposed by Thall and a quasi‐likelihood method proposed by Zeger and Liang for the analysis of such data, in the case where the mean was correctly specified, using simulation techniques with large samples. Both methods produced similar standard errors in most situations, except in the case of time‐dependent covariates with non‐Poisson‐gamma data where they were seriously underestimated by the Thall method. A simple method for discriminating between the variance forms of the two methods is described. The findings are applied to the analyses of clinical trials of non‐melanoma skin cancer and familial polyposis. This study extends the findings of Breslow concerning variance misspecification in overdispersed Poisson and quasi‐likelihood models to the longitudinal setting.
A case for bayesianism in clinical trials
Authors: Berry Donald A. 
Published: April 2007

AbstractThis paper describes a Bayesian approach to the design and analysis of clinical trials, and compares it with the frequentist approach. Both approaches address learning under uncertainty. But they are different in a variety of ways. The Bayesian approach is more flexible. For example, accumulating data from a clinical trial can be used to update Bayesian measures, independent of the design of the trial. Frequentist measures are tied to the design, and interim analyses must be planned for frequentist measures to have meaning. Its flexibility makes the Bayesian approach ideal for analysing data from clinical trials. In carrying out a Bayesian analysis for inferring treatment effect, information from the clinical trial and other sources can be combined and used explicitly in drawing conclusions. Bayesians and frequentists address making decisions very differently. For example, when choosing or modifying the design of a clinical trial, Bayesians use all available information, including that which comes from the trial itself. The ability to calculate predictive probabilities for future observations is a distinct advantage of the Bayesian approach to designing clinical trials and other decisions. An important difference between Bayesian and frequentist thinking is the role of randomization.
Statistical and ethical issues in monitoring clinical trials
Authors: Pocock Stuart J. 
Published: April 2007

AbstractMost randomized clinical trials require periodic monitoring of the accumulating data. While the efficiency of trial management is enhanced by data monitoring, ethical reasons should primarily dictate the need to terminate or change a trial in response to interim findings.This article focuses on the ethical dilemma of when to stop a clinical trial and places statistical stopping rules in the context of such ethical decision making. Other issues include the organization of data monitoring committees and the problems of premature publication and exaggerated estimation in trials that stop early. Several topical examples are used to convey the relevance of these issues to current practice.
Applying Bayesian ideas in drug development and clinical trials
Authors: Spiegelhalter David J. , Freedman Laurence S. , Parmar Mahesh K. B. 
Published: April 2007

AbstractThe Bayesian paradigm emphasizes that studies are not performed in isolation, and that external evidence can be used formally in the design, monitoring and reporting of clinical trials. A variety of tools for assessing the current evidence for treatment efficacy are presented, making use of graphical display to provide insight into ethical and efficiency issues in starting and stopping trials – these are illustrated with a trial in osteosarcoma that is currently taking place. Finally we recommend that an additional ‘interpretation’ section is placed in clinical reports to provide a bridge between ‘results’ and ‘discussion’ – it is this section that would contain the Bayesian perspective.
The application of large gaussian mixed models to the analysis of 24 hour ambulatory blood pressure monitoring data in clinical trials
Authors: Selwyn Murray R. , Difranco Donna M. 
Published: April 2007

AbstractWe propose the use of Gaussian mixed models to analyse statistically 24 hour ambulatory blood pressure data from clinical trials. We develop specific models and apply them to data from a clinical study that compares two angiotensin‐converting enzyme inhibitors. We investigate and discuss computing issues related to the implementation of such methods. We conclude that this methodology provides a sophisticated but practical approach to the analysis of such data.
A strategy for assembling samples of adult twin pairs in the United States
Authors: Goldberg Jack , Henderson William G. , Eisen Seth A. , True William , Ramakrishnan Viswanathan , Lyons Michael J. , Tsuang Ming T. 
Published: April 2007

AbstractIn this paper we develop a methodology for the identification of large numbers of U.S. adult twin pairs. Data for this study derive from the U.S. Department of Defense and the Vietnam Era Twin )VET( Registry. The Department of Defense identified potential male twins )n = 10,002( using a computerized record linkage algorithm based on the same last name, same date of birth, and the same first five digits of the Social Security number. Twinship was confirmed by comparison with the Vietnam Era Twin Registry. We developed a logistic regression model that predicts the probability that a paired record identifies twins based on the absolute difference in the last four digits in the Social Security number, the age of issuance of the Social Security number, and the frequency of occurrence of the last name. We used the estimated coefficients derived from this regression model to assign predicted probabilities of being a twin to each matched record. There is a close correspondence between the observed and expected number of twins when evaluated across deciles of predicted probabilities of being a twin; the value of the Harrell's c index )c = 0·68 ∓ 0·0004( indicates the overall predictive accuracy of the regression equation. The results from this study demonstrate the feasibility of identifying adult male–male twin pairs from any large computerized database that contains name, date of birth and Social Security number. However, the selection criteria used in the creation of the computer database must be clearly specified to avoid constructing a biased sample of twins.
Risk ratio and rate ratio estimation in case‐cohort designs: Hypertension and cardiovascular mortality
Authors: Schouten Evert G. , Dekker Jacqueline M. , Kok Frans J. , Cessie Saskia Le , Van Houwelingen Hans C. , Pool Jan , Vandnbroucke Jan P. 
Published: April 2007

AbstractMultivariate analysis in case‐base designs depends on approximate methods. In the present study, new pseudo‐likelihood methods are developed for this design. With these methods, the case‐cohort risk ratio and rate ratio as well as their standard errors are easily estimated using logistic regression and Poisson regression, respectively. This is illustrated by the association between hypertension and cardiovascular mortality in a cohort, estimated by case‐cohort analysis, using samples of several sizes. The estimates are compared with those obtained in full‐cohort and nested case‐control designs. The results indicate that these methods, which require nothing but widely available computer software, are valid. The case‐cohort design, therefore, is a good, sometimes even advantageous alternative to the nested case‐control design, in studying a disease that is not very rare. Application of the risk ratio method to the full cohort, using a ‘sample’ of 100 per cent follows logically; whenever the true risk ratio is desired instead of the odds ratio, a multivariate model for its estimation is therefore available.
Tracking of markers and onset of disease among HIV‐1 seroconverters
Authors: Galai Noya , Muñoz Alvaro , Chen Kan , Carey Vincent J. , Chmiel Joan , Zhou Susan Y. J. 
Published: April 2007

AbstractRepeated measurements on persons infected with HIV‐1 indicate that infection has a dynamic impact on several markers of immune suppression and activation. The objectives of this report are: )a( to provide a statistical model for the correlation structure of serial measurements of immunological markers, and )b( to identify features of marker profiles associated with the timing of AIDS diagnoses. We analyse data obtained from 328 seroconverters participating in the Multicenter AIDS Cohort Study on whom the date of HIV‐1 seroconversion is known within ∓ 4·5 months. Immunological markers considered here are CD4 cell counts, serum β2‐microglobulin and serum neopterin. The statistical model for HIV‐related changes in markers consists of )1( a piecewise linear regression model for the trajectories of markers over time and )2( a two‐parameter autocorrelation function that generalizes Markovian and simple random effects autocorrelation structures. Application of this model for marker measurements revealed a high degree of tracking, as the estimated autocorrelation function exhibited sub‐exponential decay over time. Though current marker levels are most informative on future values, there is substantial information )memory( in previous measurements. A feature suggested by the analysis of groups formed according to the length of the AIDS‐free period, is the sequential divergence of the CD4 trajectories where steeper declines occurred with a two‐year lag prior to AIDS onset. For AIDS cases diagnosed 3–5 and 5–7 years after seroconversion, the rates of decline compared with those free of AIDS for at least 4 years were steeper by 95 and 46 per cent respectively at two years prior to AIDS.
A technique for summarizing longitudinal data
Authors: Hathaway Dale K. , D'agostino Ralph B. 
Published: April 2007

AbstractMany studies collect longitudinal data but do not use them efficiently. We propose a technique for reducing a set of longitudinal data into four common summary statistics together with time. These statistics can be used in place of the raw data in further analyses, for example in a regression analysis. Instead of arbitrarily choosing the summary statistics, we derive them mathematically, thus justifying their use. This simplifies the subsequent analyses, and also improves the interpretation of the results. An example from the Framingham Heart Study illustrates the procedure.
Bayesian analysis of binary data from an audit of cervical smears
Authors: Raab Gillian M. , Elton Robert A. 
Published: April 2007

AbstractA large data set of unsatisfactory smear rates from 629 different cervical smear takers is used to illustrate a Bayesian approach to the analysis of medical audit data with a binary outcome. It is shown that this gives more relevant results in terms of characterizing individual smear takers than frequentist methods, and that the full Bayesian analysis is preferable to an empirical Bayes approximation when the number of different smear takers is small and at least one individual smear taker has contributed only a few smears. Plots of Bayesian posterior distributions with 95 per cent confidence sets are suggested as a useful way of feeding back the results to individual clinicians.
Inherent difficulties with active control equivalence studies
Authors: Senn Stephen 
Published: April 2007

AbstractA simple model is used to investigate the relevance of ‘competence’ to active control equivalence studies )ACES(. It is shown that to the extent that such trials are successful the results of such trials must raise doubts regarding their competence. ACES are thus more problematic than classical clinical trials and the problems with such studies cannot be solved simply by exchanging the usual roles of null and alternative hypotheses.
Effect of shipping on quality of seeds, meals, fats, and oils
Authors: Spencer Max R. 
Published: April 2007

AbstractAlthough few studies have been conducted relative to quality preservation of oilseeds and their products while in transportation containers, there are known causative factors of quality degradation which are applicable from long experience of storage in ordinary land‐based containers. Often the success of quality retention is a function of the basic level of quality negotiated by the buyer and seller and the inherent idiosyncrasies of the commodity when handled and when exposed to the ambient conditions of the air and container.
Continuous processing of palm fruit
Authors: de Ramecourt Bernard 
Published: April 2007

AbstractIn the last few years we have seen a remarkable breakthrough of palm oil products into the oilseed world. The old extraction techniques, often inherited from artisan methods, have been modernized to give birth to a veritable “palm oilworks” industry. Present equipment and methods permit obtaining, under optinum yield conditions, high quality products responding well to the requirements of the manufacturers of oil and vegetable fat products.
Batch and continuous solvent extraction
Authors: Bernardini Ernesto 
Published: April 2007

AbstractTwo physical processes are used for the removal of oil from oilseeds, one called “solution extraction” and the other “diffusion extraction.” In batch type solvent extraction plants, a diffusion process takes place. Due to their high steam and labor requirements, such plants are being steadily replaced with continuous solvent extraction plants, whose main component is the extractor which can be either of the immersion or percolation type. The combined use of these two types of extractor makes it possible to extract oil directly from oilseeds, even if they have a high oil content, with no need for continuous screw presses or expellers. Comparative data on the processes in most common use are given.
Standards for protein based foods in developing countries
Authors: Achaya K. T. 
Published: April 2007

AbstractLegal specifications in India are issued by the Central Committee for Food Standards and are limited in number. Specifications issued by the Indian Standards Institution (ISI), which are discussed in this paper, are optional but prestigious and much more numerous. Foods based on milk proteins emphasize minimal protein damage, estimated by solubility measurement, and high sanitary quality. The latter is common to all other ISI food specifications as well. Edible oilseed proteins for use as food ingredients are formulated in various types or grades and carry such criteria as protein level, fiber content, and appropriate antinutrient level. Proteins from various sources may enter products such as protein mixes, weaning and toddler foods, biscuits, “vegetable” milks, and offspring of the latter like yogurt, ice cream, and reconstitutable powders. In certain products, protein level may be varied inversely with protein quality. To define the latter, the protein efficiency ratio has been adopted and a working methodology for India evolved through collaborative experimentation. The level of any added vitamins and minerals in these protein foods is such that an expected daily consumption of the food would carry 1/3 the Indian recommended daily allowance. Concentrate protein foods stand in a class apart in their very high levels of the nutrients present. Enriched staples like wheat flours could carry proteins, vitamins, and minerals or omit proteins if found functionally disadvantageous. Codes of practice are being developed by ISI in related fields, such as food advertising, in which one clause enjoins that sound established foods or food practices should not be denigrated; food labeling, in which the problem is to ensure a label meaningful to consumers; and date marking, which could hinge on certain and expected shelf life of the food.
Texturized protein products
Authors: Brain Ross 
Published: April 2007

AbstractTexture is changed in oilseed protein fractions by mechanical and chemical means in specialized equipment. Processing conditions are closely controlled to ensure end product forms wanted. The arrangement of equipment used in the production of textured proteins is discussed as it relates to a commercial plant design. The nature of feed materials and details of processing conditions required to produce texture in soy protein are presented. Other forms of textured oilseed protein are discussed.
New technology in oilseed proteins
Authors: Becker Kenneth W. , Tiernan Eugene A. 
Published: April 2007

AbstractThe protein industry is in a technical improvement revolution that will lead to tastier and flatulence free products. They will have longer shelf life, allow higher product yields, and be more efficient in energy conservation. The improved processes discussed include methods for making superior quality flours and grits, better extruded products, and higher quality concentrates and isolates. The new products will have high protein efficiency ratio ratings and a broad range of nitrogen solubility index. Some of the decision‐making information that processors should have before appropriating capital are described.
Bleaching practices in Europe
Authors: Patterson H. B. W. 
Published: April 2007

AbstractAdsorption onto porous solids is used to remove from oils not only pigments but also several other minor components. Now that long established process steps such as degumming, neutralization, and washing have become even more effective, the technique of adsorption is being continually evaluated to ensure that no unjustified expenditure is allowed to continue. Practical advice is offered on bleaching procedures and the subsequent separation of the adsorbent from the oil.
Degumming, refining, bleaching, and deodorization theory
Authors: Cowan John C. 
Published: April 2007

AbstractBasic theory and principles of degumming, refining, bleaching, and deodorization are reviewed. Composition of crude oils, hydration of ions and molecules, neutralization of organic acid, and separation and modification of products by centrifugation, adsorption, and vacuum steam distillation are briefly summarized. Reactions of vegetable oils include hydration, neutralization, and oxidation.
Degumming and refining practices in the U.S.
Authors: Carr Roy A. 
Published: April 2007

AbstractThe “state of the art” of degumming and refining crude vegetable oils in the U.S. is discussed with reference to (a) production volumes and significant quality characteristics of oils processed; (b) processes and equipment for degumming, refining, and waterwashing the oils, illustrated by diagrams and flow charts; and (c) key process controls and analytical testing requirements for each unit operation.