bluuebunny/crossref_metadata_2025 huggingface dataset:
A Proportional Hazards Model for Incidence and Induced Remission of Disease
Authors: Dunson David B. , Baird Donna D.
Published: May 2004

Summary. To assess the protective effects of a time‐varying covariate, we develop a stochastic model based on tumor biology. The model assumes that individuals have a Poisson‐distributed pool of initiated clones, which progress through predetectable, detectable mortal and detectable immortal stages. Time‐independent covariates are incorporated through a log‐linear model for the expected number of clones, resulting in a proportional hazards model for disease onset. By allowing time‐dependent covariates to induce clone death, with rate dependent on a clone's state, the model is flexible enough to accommodate delayed disease onset and remission or cure of preexisting disease. Inference uses Bayesian methods via Markov chain Monte Carlo. Theoretical properties are derived, and the approach is illustrated through analysis of the effects of childbirth on uterine leiomyoma (fibroids).
Functional Mixed Effects Models
Authors: Guo Wensheng
Published: May 2004

Summary.In this article, a new class of functional models in which smoothing splines are used to model fixed effects as well as random effects is introduced. The linear mixed effects models are extended to non‐parametric mixed effects models by introducing functional random effects, which are modeled as realizations of zero‐mean stochastic processes. The fixed functional effects and the random functional effects are modeled in the same functional space, which guarantee the population‐average and subject‐specific curves have the same smoothness property. These models inherit the flexibility of the linear mixed effects models in handling complex designs and correlation structures, can include continuous covariates as well as dummy factors in both the fixed or random design matrices, and include the nested curves models as special cases. Two estimation procedures are proposed. The first estimation procedure exploits the connection between linear mixed effects models and smoothing splines and can be fitted using existing software. The second procedure is a sequential estimation procedure using Kalman filtering. This algorithm avoids inversion of large dimensional matrices and therefore can be applied to large data sets. A generalized maximum likelihood (GML) ratio test is proposed for inference and model selection. An application to comparison of cortisol profiles is used as an illustration.
Two‐Stage Designs for Gene–Disease Association Studies
Authors: Satagopan Jaya M. , Verbel David A. , Venkatraman E. S. , Offit Kenneth E. , Begg Colin B.
Published: May 2004

Summary. The goal of this article is to describe a two‐stage design that maximizes the power to detect gene‐disease associations when the principal design constraint is the total cost, represented by the total number of gene evaluations rather than the total number of individuals. In the first stage, all genes of interest are evaluated on a subset of individuals. The most promising genes are then evaluated on additional subjects in the second stage. This will eliminate wastage of resources on genes unlikely to be associated with disease based on the results of the first stage. We consider the case where the genes are correlated and the case where the genes are independent. Using simulation results, it is shown that, as a general guideline when the genes are independent or when the correlation is small, utilizing 75% of the resources in stage 1 to screen all the markers and evaluating the most promising 10% of the markers with the remaining resources provides near‐optimal power for a broad range of parametric configurations. This translates to screening all the markers on approximately one quarter of the required sample size in stage 1.
Dose Finding Using the Biased Coin Up‐and‐Down Design and Isotonic Regression
Authors: Stylianou Mario , Flournoy Nancy
Published: May 2004

Summary.We are interested in finding a dose that has a prespecified toxicity rate in the target population. In this article, we investigate five estimators of the target dose to be used with the up‐and‐down biased coin design (BCD) Introduced By Durham and Flournoy (1994,Statistical Decision Theory and Related Topics).These estimators are derived using maximum likelihood, weighted least squares, sample averages, and isotonic regression. A linearly interpolated isotonic regression estimate is shown to be simple to derive and to perform as well as or better than the other target dose estimators in terms of mean square error and average number of subjects needed for convergence in most scenarios studied.
Modeling and Real‐Time Prediction of Classical Swine Fever Epidemics
Authors: Meester Ronald , de Koning Jan , de Jong Mart C. M. , Diekmann Odo
Published: May 2004

Summary. We propose a new method to analyze outbreak data of an infectious disease such as classical swine fever. The underlying model is a two‐type branching process. It is used to deduce information concerning the epidemic from detected cases. In particular, the method leads to prediction of the future course of the epidemic and hence can be used as a basis for control policy decisions. We test the model with data from the large 1997‐1998 classical swine fever epidemic in The Netherlands. It turns out that our results are in good agreement with the data.
Testing for Conditional Multiple Marginal Independence
Authors: Bilder Christopher R. , Loughin Thomas M.
Published: May 2004

Summary. Survey respondents are often prompted to pick any number of responses from a set of possible responses. Categorical variables that summarize this kind of data are called pick any/c variables. Counts from surveys that contain a pick any/c variable along with a group variable (r levels) and stratification variable (q levels) can be marginally summarized into an r×c×q contingency table. A question that may naturally arise from this setup is to determine if the group and pick any/c variable are marginally independent given the stratification variable. A test for conditional multiple marginal independence (CMMI) can be used to answer this question. Since subjects may pick any number out of c possible responses, the Cochran (1954, Biometrics10, 417–451) and Mantel and Haenszel (1959, Journal of the National Cancer Institute22, 719–748) tests cannot be used directly because they assume that units in the contingency table are independent of each other. Therefore, new testing methods are developed. Cochran's test statistic is extended to r×2×q tables, and a modified version of this statistic is proposed to test CMMI. Its sampling distribution can be approximated through bootstrapping. Other CMMI testing methods discussed are bootstrap p‐value combination methods and Bonferroni adjustments. Simulation findings suggest that the proposed bootstrap procedures and the Bonferroni adjustments consistently hold the correct size and provide power against various alternatives.
Interval Estimation for a Difference Between Intraclass Kappa Statistics
Authors: Dormer Allan , Zou Guangyong
Published: May 2004

Summary. Model‐based inference procedures for the kappa statistic have developed rapidly over the last decade. However, no method has yet been developed for constructing a confidence interval about a difference between independent kappa statistics that is valid in samples of small to moderate size. In this article, we propose and evaluate two such methods based on an idea proposed by Newcombe (1998, Statistics in Medicine, 17, 873–890) for constructing a confidence interval for a difference between independent proportions. The methods are shown to provide very satisfactory results in sample sizes as small as 25 subjects per group. Sample size requirements that achieve a prespecified expected width for a confidence interval about a difference of kappa statistic are also presented.
Dynamic Conditionally Linear Mixed Models for Longitudinal Data
Authors: Pourahmadi M. , Daniels M. J.
Published: May 2004

Summary.We develop a new class of models, dynamic conditionally linear mixed models, for longitudinal data by decomposing the within‐subject covariance matrix using a special Cholesky decomposition. Here ‘dynamic’ means using past responses as covariates and ‘conditional linearity’ means that parameters entering the model linearly may be random, but nonlinear parameters are nonrandom. This setup offers several advantages and is surprisingly similar to models obtained from the first‐order linearization method applied to nonlinear mixed models. First, it allows for flexible and computationally tractable models that include a wide array of covariance structures; these structures may depend on covariates and hence may differ across subjects. This class of models includes, e.g., all standard linear mixed models, antedependence models, and Vonesh‐Carter models. Second, it guarantees the fitted marginal covariance matrix of the data is positive definite. We develop methods for Bayesian inference and motivate the usefulness of these models using a series of longitudinal depression studies for which the features of these new models are well suited.
On the Use of Nonparametric Curves in Phase I Trials with Low Toxicity Tolerance
Authors: Cheung Ying Kuen
Published: May 2004

Summary. Gasparini and Eisele (2000, Biometrics56, 609–615) propose a design for phase I clinical trials during which dose allocation is governed by a Bayesian nonparametric estimate of the dose‐response curve. The authors also suggest an elicitation algorithm to establish vague priors. However, in situations where a low percentile is targeted, priors thus obtained can lead to undesirable rigidity given certain trial outcomes that can occur with a nonnegligible probability. Interestingly, improvement can be achieved by prescribing slightly more informative priors. Some guidelines for prior elicitation are established using a connection between this curve‐free method and the continual reassessment method.
Curve‐Free and Model‐Based Continual Reassessment Method Designs
Authors: O'Quigley John
Published: May 2004

Summary. Gasparini and Eisele (2000, Biometrics56, 609‐615) present a development of the continual reassessment method of O'Quigley, Pepe, and Fisher (1990, Biometrics46, 33–48). They call their development a curve‐free method for Phase I clinical trials. However, unless we are dealing with informative prior information, then the curve‐free method coincides with the usual model‐based continual reassessment method. Both methods are subject to arbitrary specification parameters, and we provide some discussion on this. Whatever choices are made for one method, there exists equivalent choices for the other method, where “equivalent” means that the operating characteristics (sequential dose allocation and final recommendation) are the same. The insightful development of Gasparini and Eisele provides clarification on some of the basic ideas behind the continual reassessment method, particularly when viewed from a Bayesian perspective. But their development does not lead to a new class of designs and the comparative results in their article, indicating some preference for curve‐free designs over model‐based designs, are simply reflecting a more fortunate choice of arbitrary specification parameters. Other choices could equally well have inversed their conclusion. A correct conclusion should be one of operational equivalence. The story is different for the case of informative priors, a situation that is inherently much more difficult. We discuss this. We also mention the important idea of two‐stage designs (Moller, 1995, Statistics in Medicine14, 911–922; O'Quigley and Shen, 1996, Biometrics52, 163–174), arguing, via a simple comparison with the results of Gasparini and Eisele (2000), that there is room for notable gains here. Two‐stage designs also have an advantage of avoiding the issue of prior specification altogether.
Book reviews
Authors: Ridout M. S.
Published: May 2004

HASTIE, T., TIBSHIRANI, R. and FRIEDMAN, J. The Elements of Statistical Learning: Data Mining, Inference, and Prediction.

ATKINSON, A. and RIANI, M. Robust Diagnostic Regression Analysis.

CHRISTENSEN, R. Advanced Linear Modelling, 2nd edition.

MILLARD, S.P. and KRAUSE, A. (editors). Applied Statistics in the Pharmaceutical Industry with Case Studies using s‐PLUS.

EVERITT, B. S. and DUNN, G. Applied Multivariate Data Analysis, 2nd edition.

COX, T. F. and COX, M. A. A. Multidimensional Scaling, 2nd edition.

FREUND, R. J. and LITTELL, R. C. SAS® System for Regression, 3rd edition.

LIU, J. S. Monte Carlo Strategies in Scientific Computing.

LUNNEBORG, C. E. Data Analysis by Resampling: Concepts and Applications.

HOUGAARD, P. Analysis of Multivariate Survival Data.

EGGERMONT, P. P. B. and LARICCIA, V. N. Maximum Penalized Likelihood Estimation, Volume 1: Density Estimation.

KOT, M. Elements of Mathematical Ecology.

Brief Reports by the Editor

GRIMMETT, G. and STIRZAKER, D. Probability and Random Processes.

GRIMMETT, G. and STIRZAKER, D. One Thousand Exercises in Probability.

CONDRA, L. W. Reliability Improvement with Design of Experiments, 2nd edition.

VOIT, E. O. Computational Analysis of Biochemical Systems.

TITTERINGTON, D. M. and COX, D. R. (editors). Biometrika: One Hundred Years.
Sub‐cellular localization of Ni in the hyperaccumulator, Hybanthus floribundus (Lindley) F. Muell
Authors: BIDWELL S. D. , CRAWFORD S. A. , WOODROW I. E. , SOMMER‐KNUDSEN J. , MARSHALL A. T.
Published: May 2004

The cellular and subcellular distribution of Ni within leaves of Hybanthus floribundus (Lindley) F. Muell, a hyperaccumulator of Ni, was investigated at relatively high spatial resolution using energy‐dispersive X‐ray microanalysis (EDAX). Elemental distribution maps showed that Ni was predominantly localized in the vacuoles of epidermal cells in the leaves. Quantification of Ni revealed concentrations up to 275 mmol kg−1 (embedded tissue) in some epidermal vacuoles. The accumulation of Ni in these cells was associated with a decrease in the concentration of Na and K. There was no indication that Ni was associated with P, S or Cl in the vacuoles. Ni was also concentrated on the outside of cell walls throughout the leaves, indicating that apoplastic compartmentation is also involved in Ni tolerance and accumulation in this plant.
Bipedal animals, and their differences from humans
Authors: Alexander R. McN.
Published: May 2004

Humans, birds and (occasionally) apes walk bipedally. Humans, birds, many lizards and (at their highest speeds) cockroaches run bipedally. Kangaroos, some rodents and many birds hop bipedally, and jerboas and crows use a skipping gait. This paper deals only with walking and running bipeds. Chimpanzees walk with their knees bent and their backs sloping forward. Most birds walk and run with their backs and femurs sloping at small angles to the horizontal, and with their knees bent. These differences from humans make meaningful comparisons of stride length, duty factor, etc., difficult, even with the aid of dimensionless parameters that would take account of size differences, if dynamic similarity were preserved. Lizards and cockroaches use wide trackways. Humans exert a two‐peaked pattern of force on the ground when walking, and an essentially single‐peaked pattern when running. The patterns of force exerted by apes and birds are never as markedly two‐peaked as in fast human walking. Comparisons with quadrupedal mammals of the same body mass show that human walking is relatively economical of metabolic energy, and human running is expensive. Bipedal locomotion is remarkably economical for wading birds, and expensive for geese and penguins.
Acquisition of bipedalism: the Miocene hominoid record and modern analogues for bipedal protohominids
Authors: Nakatsukasa Masato
Published: May 2004

The well‐known fossil hominoid Proconsul from the Early Miocene of Kenya was a non‐specialized arboreal quadruped with strong pollicial/hallucial assisted grasping capability. It lacked most of the suspensory specializations acquired in living hominoids. Nacholapithecus, however, from the Middle Miocene of Kenya, although in part sharing with Proconsul the common primitive anatomical body design, was more specialized for orthograde climbing, ‘hoisting’ and bridging, with the glenoid fossae of the scapula probably being cranially orientated, the forelimbs proportionally large, and very long toes. Its tail loss suggests relatively slow movement, although tail loss may already have occurred in Proconsul. Nacholapithecus‐like positional behaviour might thus have been a basis for development of more suspensory specialized positional behaviour in later hominoids. Unfortunately, after 13 Ma, there is a gap in the hominoid postcranial record in Africa until 6 Ma. Due to this gap, a scenario for later locomotor evolution prior to the divergence of Homo and Pan cannot be determined with certainty. The time gap also causes difficulties when we seek to determine polarities of morphological traits in very early hominids. Interpretation of the form–function relationships of postcranial features in incipient hominids will be difficult because it is predicted that they had incorporated bipedalism only moderately into their total positional repertoires. However, Japanese macaques, which are trained in traditional bipedal performance, may provide useful hints about bipedal adaptation in the protohominids. Kinematic analyses revealed that these macaques walked bipedally with a longer stride and lower stride frequency than used by ordinary macaques, owing to a more extended posture of the hindlimb joints. The body centre of gravity rises during the single‐support phase of stance. Energetic studies of locomotion in these bipedal macaques revealed that energetic expenditure was 20–30% higher in bipedalism than in quadrupedalism, regardless of walking velocity.
Fossils, feet and the evolution of human bipedal locomotion
Authors: Harcourt‐Smith W. E. H. , Aiello L. C.
Published: May 2004

We review the evolution of human bipedal locomotion with a particular emphasis on the evolution of the foot. We begin in the early twentieth century and focus particularly on hypotheses of an ape‐like ancestor for humans and human bipedal locomotion put forward by a succession of Gregory, Keith, Morton and Schultz. We give consideration to Morton's (1935) synthesis of foot evolution, in which he argues that the foot of the common ancestor of modern humans and the African apes would be intermediate between the foot of Pan and Hylobates whereas the foot of a hypothetical early hominin would be intermediate between that of a gorilla and a modern human. From this base rooted in comparative anatomy of living primates we trace changing ideas about the evolution of human bipedalism as increasing amounts of postcranial fossil material were discovered. Attention is given to the work of John Napier and John Robinson who were pioneers in the interpretation of Plio‐Pleistocene hominin skeletons in the 1960s. This is the period when the wealth of evidence from the southern African australopithecine sites was beginning to be appreciated and Olduvai Gorge was revealing its first evidence for Homo habilis. In more recent years, the discovery of the Laetoli footprint trail, the AL 288‐1 (A. afarensis) skeleton, the wealth of postcranial material from Koobi Fora, the Nariokotome Homo ergaster skeleton, Little Foot (Stw 573) from Sterkfontein in South Africa, and more recently tantalizing material assigned to the new and very early taxa Orrorin tugenensis, Ardipithecus ramidus and Sahelanthropus tchadensis has fuelled debate and speculation. The varying interpretations based on this material, together with changing theoretical insights and analytical approaches, is discussed and assessed in the context of new three‐dimensional morphometric analyses of australopithecine and Homo foot bones, suggesting that there may have been greater diversity in human bipedalism in the earlier phases of our evolutionary history than previously suspected.
Transmission electron microscopy of fluorapatite–gelatine composite particles prepared using focused ion beam milling
Authors: VOLKERT C. A. , BUSCH S. , HEILAND B. , DEHM G.
Published: May 2004

In this paper, synthetic fluorapatite–gelatine composite particles are prepared for transmission electron microscopy (TEM) studies using two methods based on focused ion beam (FIB) milling. TEM studies on the FIB‐prepared specimens are compared with TEM observations on samples prepared using an ultramicrotome. The results show that ultramicrotome slicing causes significant cracking of the apatite, whereas the ion beam can be used to make high‐quality, crack‐free specimens with no apparent ion beam‐induced damage. The TEM observations on the FIB‐prepared samples confirm that the fluorapatite composite particles are composed of elongated, preferentially orientated grains and reveal that the grain boundaries contain many small interstices filled with an amorphous phase.
Giving up on Modern Foreign Languages? Students' Perceptions of Learning French
Authors: Graham Suzanne J.
Published: May 2004

This article reports on the findings of an investigation into the attitudes of English students aged 16 to 19 years towards French and how they view the reasons behind their level of achievement. Those students who attributed success to effort, high ability, and effective learning strategies had higher levels of achievement, and students intending to continue French after age 16 were more likely than noncontinuers to attribute success to these factors. Low ability and task difficulty were the main reasons cited for lack of achievement in French, whereas the possible role of learning strategies tended to be overlooked by students. It is argued that learners' self‐concept and motivation might be enhanced through approaches that encourage learners to explore the causal links between the strategies they employ and their academic performance, thereby changing the attributions they make for success or failure.
The Effects of Teaching Spoken Arabic on Students'Attitudes and Motivation in Israel
Authors: Donitsa‐Schmidt Smadar , Inbar Ofra , Shohamy Elana
Published: May 2004

The study investigated whether changes in the educational context of teaching Arabic as a second language in Israeli schools affect students' attitudes towards the language, its speakers and culture, and motivation to study the language. These changes included teaching spoken Arabic rather than Modern Standard Arabic and lowering the starting age of instruction. Self‐report questionnaires were distributed to 692 students (4th–6th grade) and 362 parents from 14 elementary schools. The findings revealed that students who study spoken Arabic (experimental group), as opposed to those who do not (control group), report holding more positive attitudes towards the Arabic language, its culture, and speakers, and also claim to be more motivated to study the language. Findings also confirm the important role that parents have over their children's behavior because parents' attitudes constituted one of the predictors of students' motivation to study Arabic. Yet, the variable that best predicted students' motivation was their satisfaction with their Arabic study program.
Fast Capitalism, School Reform, and Second Language Literacy Practices
Authors: Gebhard Meg
Published: May 2004

This 2‐year qualitative study explores the ironies of educational reform in the United States as experienced by three second language learners attending a school attempting to transform itself into a high‐performance elementary school in California's Silicon Valley. Drawing on the concept of “fast capitalism” in a globalized economic work order (Gee, Hull, & Lankshear, 1996) and the tools of critical discourse analysis (Fairclough, 1989), the findings from this investigation reveal that the discourses of school reform in the United States visibly and invisibly placed second language learners in new highly vulnerable positions. In what follows I provide an analysis of this vulnerability by relating the experiences of three families and their attempts to enrol and stay enrolled in the school of their choice. Next, I provide a critical analysis of the discourses of reading and writing instruction and of a text produced by a focal student named Alma in this context. This analysis highlights the ways in which classroom literacy practices inadvertently constrained the efforts of second language learners to acquire academic literacies and ultimately legitimated the school's decision to declare Alma “not Web material.” The implications of this study relate to better understanding classroom SLA from a historical, institutional perspective and to supporting teachers and policy makers in addressing the needs of second language learners in a time of rapid social and economic change.
What Factors in Early Pregnancy Indicate that the Mother Will Be Hit by Her Partner during the Year after Childbirth? A Nationwide Swedish Survey
Authors: Rådestad Ingela , Rubertsson Christine , Ebeling Marie , Hildingsson Ingegerd
Published: May 2004

Abstract: Background:To be hit by one's intimate partner during the first year after childbirth may affect a woman's health and ability to take care of her newborn. The purpose of this study was to document the prevalence and indicators in early pregnancy of a woman being hit by her partner during the year after childbirth.Method:Information was collected by a postal questionnaire in early pregnancy and 12 months after childbirth from the approximately 5,550 women in Sweden who visited an antenatal care clinic for the first time during one of three chosen weeks in 1999 and 2000.Results:Of the 3,266 recruited women, 2,563 returned the follow‐up questionnaire. Being hit during the first year after childbirth was reported by 52 of the 2,563 (2%) women: 32 (61%) had been hit by their partner once, 12 (23%) twice, and 8 (15%) three or more times. Risk increased in women who were age 24 years or younger (3.9% had been hit), unmarried (7.1%), born in countries outside Europe (6.8%), with a partner born outside Europe (5.4%), had a low level of education (8.9%), and were unemployed (5.0%). In early pregnancy, women with back pain (4.0%), a chronic illness (4.1%), coital pain (6.1%), frequent depression‐related symptoms (8.1%), stomach pain (3.8%), or a urinary tract problem (6.3%) were hit more often than others after childbirth.Conclusions:At least 2 percent of Swedish women giving birth in 2000 were hit by their partner during the year after childbirth. Using identified predictors during antenatal care may increase the likelihood of finding women at risk, thereby enhancing the possibility of interventions to prevent this crime and health hazard.
Why Do Some Women Change Their Opinion About Childbirth Over Time?
Authors: Waldenström Ulla
Published: May 2004

Abstract:  Background: The current investigation is a follow‐up of a study on women's memory of childbirth, which showed that 60 percent made the same assessment of their overall birth experience at 1 year after delivery as they did at 2 months postpartum, and 24 percent had became more negative and 16 percent more positive. The study purpose was to gain some understanding of what factors make some women change their assessment over time. Methods: Data from a longitudinal cohort study of 2,428 women who completed questionnaires in early pregnancy, at 2 months, and at 1 year after birth were analyzed. Two subsamples were studied: 1,451 women who said childbirth was a positive experience at 2 months and 151 who said it was a negative experience. Comparisons were made, within each sample, between those who made the same assessment at 1 year and those who had changed their view, with respect to psychosocial background, labor outcomes, infant health outcomes during first year, and experiences of intrapartum care. Results: Changing the assessment from positive to less positive, mostly to “mixed feelings,” was associated with difficult childbirth, such as painful labor and cesarean section; dissatisfaction with intrapartum care; and psychosocial problems, such as single status, depressive symptoms, and worry about the birth in early pregnancy. Changing the assessment from negative to less negative was associated with less worry about the birth in early pregnancy and a more positive experience of support by the birth‐attending midwife. Conclusions: This study supported the view that measures of satisfaction with childbirth soon after delivery may be colored by relief that labor is over and the happy birth of a baby. More negative aspects may take longer to integrate. Supportive care may have long‐term effects and may protect some women from a long‐lasting negative experience.
Women's Attitudes Toward Mode of Delivery in South Korea—a Society with High Cesarean Section Rates
Authors: Lee Sang‐Il , Khang Young‐Ho , Lee Moo‐Song
Published: May 2004

Abstract:  Background: In South Korea, cesarean section rates (i.e., the proportion of all live births delivered by cesarean section) approached 40 percent in 2000. The relative contribution of physicians and women to this high rate has been a source of debate. This study explored attitudes toward mode of delivery among South Korean women. Methods: A nationwide cross‐sectional telephone survey of 505 Korean women aged 20 to 49 years was conducted using a proportionate quota and systematic random sampling method. The response rate was 57.3 percent. Data were collected using a structured questionnaire consisting of 7 questions about vaginal and cesarean delivery. Results: Over 95 percent of women preferred vaginal delivery during pregnancy and were willing to recommend this method to others. Of the women who delivered by cesarean section, 10.6 percent stated that they had requested a cesarean birth. Attitudes toward vaginal or cesarean delivery differed significantly according to a woman's education level. Conclusions: Most study participants showed more favorable attitudes toward vaginal delivery than cesarean delivery. This result does not support the assumption that the upsurge of cesarean section rates in South Korea is associated with women's positive attitudes toward cesarean section. The main cause of the rapid rise of cesarean section rates in South Korea during the past two decades have its origins in health care practitioners and the health care system in which they work.
Parental Attitudes Toward Breastfeeding: Their Association with Feeding Outcome at Hospital Discharge
Authors: Scott Jane A. , Shaker Iolanda , Reid Margaret
Published: May 2004

Abstract:  Background: A woman chooses to breastfeed for many reasons. Recent research, however, suggests that parental attitudes toward breastfeeding are stronger predictors of infant feeding choice than commonly cited sociodemographic factors. The objective of the current study was to compare the infant feeding attitudes of expectant couples, and to determine to what degree their individual attitudes during early pregnancy were predictive of the method of infant feeding at discharge from hospital. Methods: A convenience sample of pregnant women (gestational age 8–12 weeks), who were attending maternity clinics in Glasgow, Scotland, in 2000, completed the 17‐item Iowa Infant Feeding Attitude Scale (IIFAS), together with their partners. Results: The IIFAS was completed by 108 expectant couples. At discharge from hospital 49.1 percent of women were exclusively breastfeeding, and 50.9 percent were exclusively formula‐feeding. A woman's total infant feeding attitude score was significantly correlated with her partner's score(r = 0.67, p < 0.001). There was no difference in the infant feeding attitudes of formula‐feeding couples(p = 0.987), but breastfeeding women tended to be more supportive of breastfeeding than their partners(p = 0.022). Maternal, but not paternal, infant feeding attitude was a significant predictor of the choice of feeding method (OR = 1.16 95% CI = 1.09–1.24). Conclusions: Infant feeding attitudes tended to be shared by expectant couples. Maternal infant feeding attitude was a better predictor of feeding choice than were demographic factors. Paternal attitudes were not found to be independently associated with feeding choice. Identification of women with neutral infant feeding attitudes using the IIFAS may be an effective way of targeting interventions at those women who are most likely to be receptive to such programs.
Electron transport is the functional limitation of photosynthesis in field‐grown Pima cotton plants at high temperature
Authors: WISE R. R. , OLSON A. J. , SCHRADER S. M. , SHARKEY T. D.
Published: May 2004

Restrictions to photosynthesis can limit plant growth at high temperature in a variety of ways. In addition to increasing photorespiration, moderately high temperatures (35–42 °C) can cause direct injury to the photosynthetic apparatus. Both carbon metabolism and thylakoid reactions have been suggested as the primary site of injury at these temperatures. In the present study this issue was addressed by first characterizing leaf temperature dynamics in Pima cotton (Gossypium barbadense) grown under irrigation in the US desert south‐west. It was found that cotton leaves repeatedly reached temperatures above 40 °C and could fluctuate as much as 8 or 10 °C in a matter of seconds. Laboratory studies revealed a maximum photosynthetic rate at 30–33 °C that declined by 22% at 45 °C. The majority of the inhibition persisted upon return to 30 °C. The mechanism of this limitation was assessed by measuring the response of photosynthesis to CO2 in the laboratory. The first time a cotton leaf (grown at 30 °C) was exposed to 45 °C, photosynthetic electron transport was stimulated (at high CO2) because of an increased flux through the photorespiratory pathway. However, upon cooling back to 30 °C, photosynthetic electron transport was inhibited and fell substantially below the level measured before the heat treatment. In the field, the response of assimilation (A) to various internal levels of CO2 (Ci) revealed that photosynthesis was limited by ribulose‐1,5‐bisphosphate (RuBP) regeneration at normal levels of CO2 (presumably because of limitations in thylakoid reactions needed to support RuBP regeneration). There was no evidence of a ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) limitation at air levels of CO2 and at no point on any of 30 A–Ci curves measured on leaves at temperatures from 28 to 39 °C was RuBP regeneration capacity measured to be in substantial excess of the capacity of Rubisco to use RuBP. It is therefore concluded that photosynthesis in field‐grown Pima cotton leaves is functionally limited by photosynthetic electron transport and RuBP regeneration capacity, not Rubisco activity.
Thylakoid membrane responses to moderately high leaf temperature in Pima cotton
Authors: SCHRADER S. M. , WISE R. R. , WACHOLTZ W. F. , ORT D. R. , SHARKEY T. D.
Published: May 2004

Photosynthesis is inhibited by high temperatures that plants are likely to experience under natural conditions. Both  increased  thylakoid  membrane  ionic  conductance and ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) deactivation have been suggested as the primary cause. The moderately heat‐tolerant crop Pima S‐6 cotton (Gossypium barbadense) was used to examine heat stress‐induced inhibition of photosynthesis. Previous field‐work indicated that moderate heat stress (T = 35–45 °C) is associated with very rapid leaf temperature changes. Therefore, a system was devised for rapidly heating intact, attached leaves to mimic natural field heat‐stress conditions and monitored Rubisco activation, carbon‐cycle metabolites, thylakoid ionic conductance, and photosystem I activity. As a proxy for NADPH and stromal redox status the activation state of NADP‐malate dehydrogenase (NADP‐MDH) was measured. In dark‐adapted cotton leaves, heating caused an increase in thylakoid permeability at temperatures as low as 36 °C. The increased permeability did not cause a decline in adenosine 5′‐triphosphate (ATP) levels during steady‐state or transient heating. Rapid heating caused a transient decline in ribulose 1,5‐bisphosphate without a decrease in Rubisco activation. Sustained heating caused a decline in Rubisco activation and also oxidized the stroma as judged by NADP‐MDH activation and this is hypothesized to result from increased cyclic photophosphorylation, explaining the maintenance of ATP content in the face of increased thylakoid membrane ion leakiness.
Summer frost resistance and freezing patterns measuredin situin leaves of major alpine plant growth forms in relation to their upper distribution boundary
Authors: TASCHLER D. , NEUNER G.
Published: May 2004

Summer frost resistance and ice nucleation temperatures for 33 alpine plant species were measuredin situto avoid the shortcomings of laboratory tests. Species were selected to investigate the relationship between plant stature and upper distribution boundary, and frost resistance and freezing patterns. The species testedin situwere on average 1.1 K (± 0.2, SE) frost hardier than in laboratory tests. Frost resistance (LT50) ranged from −4.5 to −14.6 °C and appeared insufficient to protect against air temperature minima, corroborating reports of natural frost damage. All species tolerated extracellular ice formation (recorded at −1.9 ± 0.2 °C; E1). Initial frost damage occurred at average temperatures 4.9 K below E1. In 64% of the species a second exotherm (E2) and frost damage were recorded between −3.7 and −9.4 °C. In the highest ranging species E2 was not detectable. Frost resistance increased with increasing upper distribution boundary (0.4 K per 100 m), corresponding well with the altitudinal decrease in air temperature minima. No relationship between plant stature and frost resistance was found. Graminoids were significantly frost hardier than other growth forms. Frost survival at high altitudes will depend not only on altitudinal increase in frost resistance but also on freezing avoidance strategies, snow cover protection and a high recuperation capacity.
Stress‐induced changes in carbon sources for isoprene production in Populus deltoides
Authors: FUNK J. L. , MAK J. E. , LERDAU M. T.
Published: May 2004

Isoprene is emitted from leaves of numerous plant species and has important implications for plant metabolism and atmospheric chemistry. The ability to use stored carbon (alternative carbon sources), as opposed to recently assimilated photosynthate, for isoprene production may be important as plants routinely experience photosynthetic depression in response to environmental stress. A CO2‐labelling study was performed and stable isotopes of carbon were used to examine the role of alternative carbon sources in isoprene production in Populus deltoides during conditions of water stress and high leaf temperature. Isotopic fractionation during isoprene production was higher in heat‐ and water‐stressed leaves (−8.5 and −9.3‰, respectively) than in unstressed controls (−2.5 to −3.2‰). In unstressed plants, 84–88% of the carbon in isoprene was derived from recently assimilated photosynthate. A significant shift in the isoprene carbon composition from photosynthate to alternative carbon sources was observed only under severe photosynthetic limitation (stomatal conductance < 0.05 mol m−2 s−1). The contribution of photosynthate to isoprene production decreased to 77 and 61% in heat‐ and water‐stressed leaves, respectively. Across water‐ and heat‐stress experiments, allocation of photosynthate was negatively correlated to the ratio of isoprene emission to photosynthesis. In water‐stressed plants, the use of alternative carbon was also related to stomatal conductance. It has been proposed that isoprene emission may be regulated by substrate availability. Thus, understanding carbon partitioning to isoprene production from multiple sources is essential for building predictive models of isoprene emission.
Evolution and deposits of a gravelly braid bar, Sagavanirktok River, Alaska
Authors: Lunt I. A. , Bridge J. S.
Published: May 2004

The evolution, migration and deposits of a gravelly braid bar in the Sagavanirktok River, northern Alaska, are described in unprecedented detail using annual aerial photographs, ground‐penetrating radar (GPR) profiles, trenches and cores. Compound braid bars in the Sagavanirktok River form by chute cut‐off of point bars and by growth of mid‐channel unit bars. Subsequent growth is primarily by accretion of unit bars onto their lateral and downstream margins. The upstream ends of braid bars may be sites of erosion or unit bar deposition. Compound braid bar deposits vary in thickness laterally and are thickest in medial sections and near cut banks. Compound bar deposits are typically composed of three to seven sets of simple large‐scale inclined strata, each simple set formed by a unit bar. The simple large‐scale strata contain medium‐scale cross‐strata (from dune migration) and planar strata (from migration of bedload sheets). The upstream and medial parts of compound braid bar deposits show very little vertical variation in grain size, but downstream and lateral margins tend to fine upwards. The deposits are mostly poorly sorted sands and gravels, although sands tend to be deposited at the top of the braid bar, and open‐framework gravels preferentially occur near the top and base of the braid bar. The patterns of braid bar growth and migration, and the nature of the deposits, described from the Sagavanirktok River are generally similar to other sandy and gravelly braided rivers, and consistent with the theoretical braid bar model of Bridge (1993).
Mudstones of the Tanqua Basin, South Africa: an analysis of lateral and stratigraphic variations within mudstones, and a comparison of mudstones within and between turbidite fans
Authors: Andersson P. O. D. , Worden R. H.
Published: May 2004

Permian deep‐water mudstones in the Tanqua Basin, South Africa, have been studied using geochemical and spectral gamma ray techniques. The mudstones occur as thick sequences between sand‐rich submarine fans, but also occur as thinner mud‐rich units within each fan. The interfan mudstones are interpreted to have accumulated during transgression and the consequent period of relatively high sea‐level, while the submarine fans and their intrafan mudstones were deposited during regression and relatively low sea‐level. Geochemical analyses revealed systematic differences between interfan and intrafan mudstones because the two types of mudstones have slightly different source lithologies. Differences between the two types of mudstone suggest that changes in relative sea‐level played a role in controlling exposure of sediment source areas. There are geochemical signals that display systematic stratigraphic trends within both interfan and intrafan mudstones. These are best explained by gradual denudation, exposure and weathering of different lithologies within a single sediment source area. Both interfan and intrafan mudstones have uniform geochemical signals along the flow direction except for the relative amount of uranium. It is most likely that the basinward increase in uranium in the mudstones is the result of reduced clastic dilution of uranium‐bearing pelagic fallout.
High‐arctic fan delta recording deglaciation and environment disequilibrium
Authors: Lønne Ida , Nemec W.
Published: May 2004

Study of a Holocene fan delta in Adventfjorden, Spitsbergen, provides new insight into the nature of high‐arctic coastal sedimentation and deglaciation dynamics. The fjord‐side, gravelly Gilbert‐type fan delta began to form at the local marine limitc. 10 ka BP, supplied seasonally with sediment by meltwater from a cirque glacier left behind by the retreating Late Weichselian ice sheet. Relative sea level had fallen by 63 m, and the fan delta reached a radius ofc. 1 km by 6 ka BP, when the relic glacier eventually melted down and fluvial activity declined. A strong influence of marine processes is recorded by the fan‐delta foreset facies, overlain by alluvium. Supplied with sediment by longshore drift, the fan‐delta front continued to advance at a lower rate, while relative sea level fell further by 5 m and ceased to fall around 5·4 ka BP. The following transgression was countered by longshore sediment supply until 4·7 ka BP, when the delta‐front beach aggraded and a spit platform began to climb onto the delta plain, recording a relative sea‐level rise of 4 m. The subsequent regression was initially non‐depositional, with the relative sea level falling by > 4 m in 200 years, outpacing fluvial supply, and the re‐emerging fan delta being swept by longshore currents. A regressive beach began to formc. 4·3 ka BP, while relative sea level gradually reached its present‐day position. The feeder braided stream was wandering across the delta plain during this time, but incised once the fan‐delta shoreline began to retreat by wave erosion and turned into a receding modern escarpment. The stream has since been adjusting its profile by gradually eroding the pre‐existing alluvium and distributing the coarse sediment supplied from catchment slopes by debrisflows and snow avalanches. Modern snowflows have also spread debris onto the abandoned fan surface. The erosional retreat of the fan delta has been accompanied by lateral shoreline accretion on both its sides. The study has important regional implications and demonstrates that Holocene fan deltas can provide a valuable record of the deglaciation history in high‐arctic terrains, where glacial deposits are scarcely preserved on land.
Physical and chemical growth conditions of Ordovician organogenic deep‐water dolomite concretions: implications for the δ18O of Early Palaeozoic sea water
Authors: Hesse Reinhard , Shah Jehangir , Islam Shafiul
Published: May 2004

The estimated depth of formation of authigenic dolomite concretions in the Middle Ordovician Cloridorme Formation, Quebec, ranges from < 1 m to 150–200 m below sea floor (mbsf) (mostly between < 1 and 25 mbsf), based on centre‐to‐margin variations in minus‐cement porosity (80–90% to 45–75%). Formation depths are > 350 mbsf (25–17% porosity) in the Lower Ordovician Levis Formation. Outward‐decreasing δ13CVPDB values (10·2–0·8‰) suggest precipitation in the methane generation zone with an increasing contribution of light carbonate derived by advection from thermocatalytic reactions at depth. Anomalously low δ18OVPDB values (centre‐to‐margin variations of −0·4 to −7·5‰) give reasonable temperatures for the concretion centres only if the δ18O of Ordovician sea water was negative (−6‰) and the bottom water was warm (> 15 °C). The 3–5‰ lower values for the concretion margins compared with the centres can be explained if, in addition, volcanic‐ash alteration, organic‐matter decomposition and/or advection of 18O‐depleted water lowered the δ18O of the pore water further by 2·0–4·0‰ during the first 25–200 m of burial. Reasonable growth temperatures for the margins of 17–20 °C are compatible with a lowering of the isotopic ratios by 1 to < 1·3‰ as a temperature effect. The systematic concentric isotope zonation of the concretions suggests that the well‐ordered near‐stoichiometric dolomite is a primary feature and not the result of recrystallization. Diagenetic dolomite beds of the Cloridorme Formation appear to have formed by coalescence of concretions, as shown by randomly sampled traverses that indicate formation at different subsurface depths. Growth of the Cloridorme dolomites was probably limited by calcium availability, at least 50% of which was derived from connate water, and the remainder by diffusion from sea water. Dolomite precipitation was favoured over calcite by very high sedimentation rates, the abundance of marine organic matter in the host sediment and a correspondingly thin sulphate reduction zone. Deep‐seated concretion growth in the Levis Formation required either internal sources for the participating ions (carbonate dissolution event) or porewater advection along faults.