bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiple imputation for threshold‐crossing data with interval censoring
Authors: Dorey Frederick J. , Little Roderick J. A. , Schenker Nathaniel 
Published: April 2007

AbstractMedical statistics often involve measurements of the time when a variable crosses a threshold value. The time to threshold crossing may be the outcome variable in a survival analysis, or a time‐dependent covariate in the analysis of a subsequent event. This paper presents new methods for analysing threshold‐crossing data that are interval censored in that the time of threshold crossing is known only within a specified interval. Such data typically arise in event‐history studies when the threshold is crossed at some time between data‐collection points, such as visits to a clinic. We propose methods based on multiple imputation of the threshold‐crossing time with use of models that take into account values recorded at the times of visits. We apply the methods to two real data sets, one involving hip replacements and the other on the prostate specific antigen )PSA( assay for prostate cancer. In addition, we compare our methods with the common practice of imputing the threshold‐crossing time as the right endpoint of the interval. The two examples require different imputation models, but both lead to simple analyses of the multiply imputed data that automatically take into account variability due to imputation.
Estimating the causal effect of smoking cessation in the presence of confounding factors using a rank preserving structural failure time model
Authors: Mark Steven D. , Robins James M. 
Published: April 2007

AbstractEstimating the causal effect of quitting smoking on time to death or first myocardial infarction requires that one control for the differences in risk factors between individuals who elect to quite at each timetversus those who elect to continue smoking at timet. In this paper we examine the limitations of standard time varying Cox proportional hazards models to yield tests and estimates of this effect. Implementing the method of G‐estimation proposed by Robins, we perform an observational analysis of data from the Multiple Risk Factor Intervention Trial )MRFIT( and estimate the causal effect of cigarette cessation while controlling for such time varying confounders as angina. We reject the null hypothesis of no effect of quitting on time to failure, and estimate that by quitting smoking, an individual increases by 50 per cent his time to death or first myocardial infarction )MI(.
Incomplete factorial designs for randomized clinical trials
Authors: Byar David P. , Herzberg Agnes M. , Tan Wai‐Yuan 
Published: April 2007

AbstractRecently there has been increased interest in considering factorial designs for randomized clinical trials when one wishes to study two or more treatments. Such designs may offer impressive gains in efficiency compared with a series of trials studying one treatment at a time. This is especially true when the treatments do not interact with one another. If interactions are of special interest, factorial designs provide one sensible approach for studying them, but larger sample sizes would be required because tests for interactions have lower power than those for main effects. In trials designed to test putative agents for preventing cancer, interactions may be of less interest so that fractions of higher‐order factorial designs might be appropriate. Sometimes it may not be reasonable, interesting, feasible, or ethical to study all treatment combinations required in a complete or fractional factorial design, yet one may want to preserve some of the factorial structure to increase efficiency and to aid understanding. For such situations, incomplete factorial designs are proposed. Although not all of the advantages of full factorial designs are preserved, such designs may provide reasonable compromises for certain situations.
Reporting bayesian analyses of clinical trials
Authors: Hughes Michael D. 
Published: April 2007

AbstractMany clinicians wrongly interpretp‐values as probabilities that treatment has an adverse effect and confidence intervals as probability intervals. Such inferences can be validly drawn from Bayesian analyses of trial results. These analyses use the data to update the prior )or pre‐trial( beliefs to give posterior )or post‐trial( beliefs about the magnitude of a treatment effect. However, for these methods to gain acceptance in the medical literature, understanding between statisticians and clinicians of the issues involved in choosing appropriate prior distributions for trial reporting needs to be reached. I focus on two types of prior that deserve consideration. The first is the non‐informative prior giving standardized likelihood distributions as post‐trial probability distributions. Their use is unlikely to be controversial among statisticians whilst being intuitively appealing to clinicians. The second type of prior has a spike of probability mass at the point of no treatment effect. Varying the magnitude of the spike illustrates the sensitivity of the conclusions drawn to the degree of prior scepticism in a treatment effect. With both, graphical displays provide clinical readers with the opportunity to explore the results more fully. An example of how a clinical trial might be reported in the medical literature using these methods is given.
Trees and tracking
Authors: Segal Mark Robert , Tager Ira B. 
Published: April 2007

AbstractEpidemiologists have used the term ‘tracking’ to connote an individual's maintenance of relative rank of some longitudinally measured characteristic over a given time span. To assess the extent to which an attribute tracks we have first to summarize individual growth curves, and second to quantify the notion of maintenance of relative rank, both in the face of random error. A sequence of papers appearing in 1981 provided differing methodologies for appraising tracking. Here we take a different approach to tracking by using regression trees for longitudinal data. The above two concerns are simultaneously addressed in that the procedure identifies subgroups. defined in terms of covariates, within which the collection of growth curves is homogeneous. After reviewing the existing approaches to tracking we describe the tree‐structured methodology, and present an illustrative example pertaining to lung function growth in children.
HOW reliable are change‐corrected measures of agreement?
Authors: Guggenmoos‐Holzmann Irene 
Published: April 2007

AbstractChance‐corrected measures of agreement are prone to exhibit paradoxical and counter‐intuitive results when used as measures of reliability. It is demonstrated that these problems arise with Cohen's kappa as well as with Aickin's alpha. They are the consequence of an analogy to Simpson's paradox in mixed populations. It is further shown that chance‐corrected measures of agreement may yield misleading values for binary ratings. It is concluded that improvements in the design and the analysis of reliability studies are a pre‐requisite for valid and pertinent results.
Sample size calculations for ordered categorical data
Authors: Whitehead John 
Published: April 2007

AbstractMany clinical trials yield data on an ordered categorical scale such asvery good, good, moderate, poor. Under the assumption of proportional odds, such data can be analysed using techniques of logistic regression. In simple comparisons of two treatments this approach becomes equivalent to the Mann–Whitney test. In this paper sample size formulae consistent with an eventual logistic regression analysis are derived. The influence on efficiency of the number and breadth of categories will be examined. Effects of misclassification and of stratification are discussed, and examples of the calculations are given.
Cross‐validation in survival analysis
Authors: Verweij Pierre J. M. , Van Houwelingen Hans C. 
Published: April 2007

AbstractThe predictive value of a statistical model is conceptually different from the explained variation. In this paper we construct a measure of the predictive value of the Cox proportional hazards model, computed from the leave‐one‐out regression coefficients. These coefficients can also be used to calculate a shrinkage factor which can be applied to improve the predictions and that can be used inR2‐type measures of the proportion of explained variation. Our methods are illustrated by a study of chemotherapy for advanced ovarian cancer.
Alert systems for post‐marketing surveillance of adverse drug reactions
Authors: Praus Michaela , Schindel Fritz , Fescharek Reinhard , Schwarz Sabine 
Published: April 2007

AbstractWhen monitoring spontaneous reports of adverse reactions to registered drugs, it is important to detect any change in the number of reported adverse reactions in the course of time. Sales adjusted adverse drug reaction rates are usually compared in order to be able to take drug exposure into account. Here we review the so‐called arithmetic and some statistical procedures which could form the basis for an alert system. The advantages and disadvantages of each of these methods are discussed. The importance of data requirements and the problems which arise when using an alert system are pointed out and then clarified with the help of the example of diphtheria/tetanus vaccine.
An efficient MAC protocol for cooperative diversity in mobile ad hoc networks
Authors: Islam Md. Rajibul , Hamouda Walaa 
Published: April 2007

AbstractCooperative diversity is proposed to combat the detrimental effects of channel fading. In this paper, we investigate the effectiveness of cooperative diversity in interference limited ad hoc networks. The negative effects due to relay blocking on the network throughput are investigated. We show that the relay blocking problem is mainly dependent on the relay selection criterion. To overcome this problem, we propose a new cooperative diversity technique based on a modified IEEE 802.11 Medium Access Control (MAC) protocol. The throughput performance of the proposed MAC protocol is analyzed using a random structured network where nodes are assumed to be equipped with multiple antennas. In our simulations, we consider both single‐ and multiple‐relay scenarios over fading channels. Copyright © 2007 John Wiley & Sons, Ltd.
MAC protocols using directional antennas in IEEE 802.11 based ad hoc networks
Authors: Ko Young‐Bae , Choi Jong‐Mu , Vaidya Nitin H. 
Published: April 2007

AbstractUsing directional antennas can be beneficial for wireless ad hoc networks consisting of a collection of wireless hosts. The most important benefit includes a reduction of the radio interference. Thus, it can significantly increase the spatial reuse, thereby improving the network throughput. To best utilize directional antennas, a suitable Medium Access Control (MAC) protocol must be designed. Current MAC protocols, such as the IEEE 802.11 standard, do not benefit when using directional antennas, because these protocols have been designed for omnidirectional antennas. In this paper, we present modified MAC protocols suitable for 802.11 based ad hoc networks using directional antennas. Our comprehensive simulation results demonstrate the performance improvement obtained with the proposed protocols. Copyright © 2007 John Wiley & Sons, Ltd.
Sucrose inversion monitored by x‐ray scattering and chemometrics
Authors: Goraieb Karen , Alexandre Thais L. , Bueno Maria Izabel M. S. 
Published: April 2007

AbstractThe present work proposes a reliable method to monitor the acid‐induced inversion of sucrose (a disaccharide) into β‐fructose and α‐glucose (both monosaccharides) by x‐ray spectrometry (XRS) coupled with chemometrics. A conventional energy dispersive x‐ray fluorescence (EDXRF) equipment is used to obtain the spectra during the inversion process, and the multivariate method of partial least squares (PLS) is used to correlate them with the respective rotation angles obtained by the traditional polarimetric method. It is shown that it is possible to monitor sucrose inversion by XRS with a good correlation coefficient (∼0.97) for calibration with rotation angles. The root‐mean‐square error of cross validation (RMSECV) value of 1.81 is also adequate. Copyright © 2007 John Wiley & Sons, Ltd.
Seminal and endocrine characteristics of male Pallas' Cats (Otocolobus manul) maintained under artificial lighting with simulated natural photoperiods
Authors: Newell‐Fugate Annie , Kennedy‐Stoskopf Suzanne , Brown Janine L. , Levine Jay F. , Swanson William F. 
Published: April 2007

AbstractPallas' cats (Otocolobus manul) have a pronounced reproductive seasonality controlled by photoperiod. Previous studies of reproduction in captive Pallas' cats exposed to natural light showed a breeding season of December–April. This study evaluated the impact of artificial lighting timed to simulate natural photoperiods on male reproductive seasonality of four Pallas' cats housed indoors. Semen evaluation, blood collection, and body weight measurements were conducted every 1–2 months from November 2000–June 2001. Fecal samples were collected from each male twice weekly to assess testosterone and corticoid concentrations. Mean values for reproductive traits (sperm attributes, testicular volume) were highest from February–April, the defined breeding season. Fecal testosterone concentrations were highest from mid‐January to mid‐March. Male Pallas' cats managed indoors under simulated photoperiods experienced a delayed onset of the breeding season by 1–2 months and a decreased length of the breeding season. Over the course of the study, fecal corticoid concentrations did not seem to differ among seasons. Although mating attempts during this study were unsuccessful, subsequent pairings of male and female Pallas' cats in the same research colony during the 2002 and 2003 breeding seasons produced viable offspring. These results suggest that male Pallas' cats, housed indoors under simulated photoperiods, exhibit distinct reproductive cyclic patterns, characterized by a delayed and truncated breeding season. Adrenocortical activity varied among individuals, but did not adversely affect reproductive parameters. Housing Pallas' cats indoors under simulated photoperiods may represent a viable strategy for maintaining breeding success while limiting disease exposure. Zoo Biol 0:1–13, 2007. © 2007 Wiley‐Liss, Inc.
World supply and demand situation for oilseeds, oils, and meals
Authors: Mielke Siegfried 
Published: April 2007

AbstractIn recent years, the demand for meal has been relatively stronger than for vegetable oils. Thus, we have to get the meal demand if we want to determine the extent of oil production and the requirements of oilseeds. This is true although the average annual increase in world meal consumption has declined from 5.5% during the five seasons ended 1970–71 to probably 3.8% in the following five seasons. The share of soybean meal is predominating and ever increasing from 49% ten years ago to as much as 61% this season.In most seasons, including the current one, soybean oil output is determined by the more rapidly increasing meal demand. It is thus often in surplus supply, specifically at present. The marketing of soybean oil is becoming even more difficult as world supplies of low‐cost palm oil and lauric oils are increasing more and more sharply.World supplies of oilseeds are developing in cycles of ca. seven years—three years buildup stocks and four years liquidation. The present expansion period, which ends this season, has been more pronounced owing to last season's severe economic recession which also affected the consumption of meals and oils/fats.Present prospects for the next five seasons point to a slowing‐down of the increase in world production of soybeans, soybean oil, and meal owing to a continuing sharp expansion of supplies of palm oil and lauric oils. This assumes that the general economic activity will more or less stagnate or show only a small expansion during this period.
Referee chemists and official methods
Authors: Link William E. 
Published: April 2007

AbstractThe need for Referee Chemists was recognized more than 50 years ago. Currently the Examination Board of the American Oil Chemists’ Society issues certificates to commercial laboratories in the name of qualified representatives who are members of the AOCS. A total of 79 chemists presently hold Referee Certificates in categories of cottonseed, soybeans, peanuts, cottonseed oil and other cup refined oils, soybean oil and other neutral oil loss oils, tallow and grease, protein concentrates, and cellulose yields. Referee Certificates have also been issued to a few chemists in Japan and Canada. The National Cottonseed Products Association, National Soybean Processors Association, etc., publish listings of their Official Chemists, who must first obtain AOCS referee certificates.Laboratories holding certificates must use Official Methods of the AOCS wherever applicable. The AOCSOfficial and Tentative Methods is one of the leading sources of standard methods for the fat and oil industries in the world. The origin of the present edition of AOCSMethods is described, and the roles of the Uniform Methods Committee, various technical committees, and the editor in the development, publication, and distribution of the methods are discussed.
Characteristics and composition of vegetable oil‐bearing materials
Authors: Langstraat A. 
Published: April 2007

AbstractA survey of the commercially most important oil‐bearing fruits and seeds is presented. Their place in the nutrition of the world's population is sketched, both as a source of fat and as a potential source of protein. Origin and occurrence of a number of oil fruits and seeds are treated, and their relative importance is discussed. Characteristics of the vegetable oils are described in the light of their fatty acid compositions. Nutritional aspects of polyunsaturated fatty acids are discussed briefly, as well as the antinutritional properties of erucic acid. Oilseed proteins are discussed from the point of view of their growing importance as a source of food for man, and compositions of their essential amino acids are discussed in relation to their nutritive value.
Current equipment for mechanical oil extraction
Authors: Tindale L. H. , Hill‐Haas S. R. 
Published: April 2007

AbstractThis paper describes the range of screw presses available to processors and lists technical features which have been brought to the authors’ attention. The range of equipment is discussed manufacturer by manufacturer, starting with the smallest available equipment and progressing to the largest. The manufacturer's rated capacity is used as the measure of size. As most manufacturers prepare their information in a variety of ways, this paper, in an attempt to compare machines on a uniform basis, has based all throughputs on 2,000 lb/ton, with meats from “whole cottonseed” (with an assumed hull content of 8–10%) at 24 hr/day. For this reason, the figures given in this paper will not always agree with figures published by manufactures. Throughputs on other material should be discussed with the equipment manufacturers, who generally have available data on most commercially processed oil‐bearing seeds.
Energy conservation in solvent extraction plants
Authors: Jongeneelen H. P. J. 
Published: April 2007

AbstractSolvent extraction plants have been designed for a long time at low capital cost, often at the expense of higher operating costs. Due to rising energy prices, the processing cost structure is changing to such an extent that the designs should be reconsidered. Conservation of steam, on the liquid side (distillation and condensation) and on the solid side (desolventizing, toasting, drying, and cooling), is discussed for existing plant designs.
Safety in solvent extraction plants—USA
Authors: Heilman John E. 
Published: April 2007

AbstractThe history of the National Fire Protection Association, Solvent Extraction Committee, is discussed with particular emphasis on the impact of the Occupational Safety and Health Act of 1971. A review of the important features standardized in NFPA No. 36, “Solvent Extraction Plants,” is discussed, with particular emphasis on their relevance to construction of new plants and expansion of existing plants.
Protein products and hulls for animal foods
Authors: Roberts R. 
Published: April 2007

AbstractThe acceptability of a raw material to the animal feed industry is based on two parameters—it must be both safe and economical. Approximately 90% of the world production of oilseeds is supplied by five materials—soy, cotton, groundnut, sunflower, and rape—and it is interesting that three of these materials contain significant antinutrients. The large use of soy in animal feeds is indicative of the part played by the seed processor in improving the value of a product, and work with both chicks and calves will be discussed in this area. The use of cottonseed in the U.K. is virtually restricted to ruminant feeds because of their tolerance to gossypol, but the significance of the processing in minimizing the level of free toxin and the antidote effect of soluble iron will be considered. Rapeseed is taking on a major role in the EEC. While the geneticist has made significant contributions in recent years and the processor still has his part to play, problems with the oilseed are not all solved, and this complex of activity will be discussed. The economic value of a commodity is a sum of the value of its individual nutrients and the rightness of dehulling, and the overall effect of processing conditions, both good and bad, can offer an optimum compromise. This optimum compromise is still our goal.
Oilseed vegetable protein concentrates
Authors: Johnson Dale W. 
Published: April 2007

AbstractSoy protein concentrates are articles of commerce in the U.S. and other areas of the world. The procedures for producing these products involve processes where the protein is “immobilized” by various procedures, whereby soluble materials such as carbohydrates, mineral matter, and other water or alcohol soluble constituents are removed. There have been four general procedures which have been used commercially, but recently a fifth procedure involving what might be referred to as a “triple” solvent procedure has been developed. While the commercial products available, at least in the U.S., are from soy, development work has been carried out to produce concentrate products from peanut, sunflower, sesame, and rapeseed. However, there are no commercial installations for producing protein concentrates from these oilseeds. A brief discussion of the various processes is presented.
Bleaching practices in the U.S.
Authors: Goebel Ernst H. 
Published: April 2007

AbstractThe differences between European and U.S. vegetable oils with respect to their influence on bleaching requirements are discussed. Based on the information supplied by over 50 refiners, a summary gives an insight into bleaching conditions with earth and heat. These data are condensed in a chart relative to most used oils and fats. General information on pre‐and post‐bleach is also indicated.
Miscella refining
Authors: Cavanagh G. C. 
Published: April 2007

AbstractMiscella refining can be practiced as a batch process or, preferably, as a continuous process with oil concentrations through the range of 30–70% by wt of oil. Miscella refining is preferably practiced at the oilseed solvent extraction plant for the economic reason of single solvent recovery system. Three immediate benefits are lower refining loss, lighter colored refined oil, and elimination of water washing. Various types of chemical conditioning, mechanical conditioning, and combinations of both are discussed for miscella refining certain oils. Blends of compatible crude oils can be advantageously miscella refined and, if desired, winterized or hydrogenated to produce oils with unique properties.