bluuebunny/crossref_metadata_2025 huggingface dataset:
Ambipolar light-emitting organic field-effect transistor
Authors: Rost Constance , Karg Siegfried , Riess Walter , Loi Maria Antonietta , Murgia Mauro , Muccini Michele
Published: August 2004

We demonstrate a light-emitting organic field-effect transistor (OFET) with pronounced ambipolar current characteristics. The ambipolar transport layer is a coevaporated thin film of α-quinquethiophene (α-5T) as hole-transport material and N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13) as electron-transport material. The light intensity is controlled by both the drain–source voltage VDS and the gate voltage VG. Moreover, the latter can be used to adjust the charge-carrier balance. The device structure serves as a model system for ambipolar light-emitting OFETs and demonstrates the general concept of adjusting electron and hole mobilities by coevaporation of two different organic semiconductors.
Effect of nitrogen containing plasmas on interface stability of hafnium oxide ultrathin films on Si(100)
Authors: Chen P. , Bhandari H. B. , Klein T. M.
Published: August 2004

Hafnium oxide dielectric thin films were deposited by metalorganic chemical vapor deposition with Hf (IV) t-butoxide and either an O2, N2, or N2O plasma in a 1:1 ratio with helium. Films approximately 5nm thick were analyzed using angle-resolved x-ray photoelectron spectroscopy (XPS) and variable angle ellipsometry before and after heat treatment in an ultrahigh vacuum up to 470°C. Interdiffusion and/or reaction of the film with the silicon substrate, as measured by an increase in thickness and an increase in Si-O type bonding at the interface was most apparent with O2 plasma deposited films and least observed with N2 plasma deposited films. Also, the Hf(4f) XPS peak shifts toward higher binding energy after anneals for the N2 and N2O plasma deposited films indicates further oxidation of the film. In contrast, oxygen plasma deposited films do not exhibit a Hf(4f) peak shift. These results provide evidence that high-κ film∕substrate stability may be controlled by applying appropriate plasma chemistry.
Pyrolysis of complex organics following high-energy proton irradiationof a simple inorganic gas mixture
Authors: Takano Yoshinori , Marumo Katsumi , Yabashi Suguru , Kaneko Takeo , Kobayashi Kensei
Published: August 2004

Complex organics formed by 3MeV proton irradiation of a simple inorganic gas mixture with a composition representative of the primitive earth atmosphere (carbon monoxide, nitrogen, and water) were characterized by application of Curie-point pyrolysis. Pyrolysis products consisted of a wide variety of organic compounds including amide compounds, heterocyclic, and polycyclic aromatic hydrocarbons. The present data showed that primary and primitive organic matter serving as “precursors” to fundamental building blocks associated with life might have been formed in a gaseous mixture of a similar composition to that of the primitive earth atmosphere. Large numbers of endogenous organic compounds and protocatalysis components produced by cosmic rays may have contributed significantly to the early stages of chemical evolution on the primitive earth.
Effect of lattice-misfit strain on the process-induced imprint behavior in epitaxial Pb(Zr0.52Ti0.48)O3 thin films
Authors: Wu Wenbin , Wang Y. , Pang G. K. H. , Wong K. H. , Choy C. L.
Published: August 2004

The effect of lattice-misfit strain on the process-induced imprint behavior in Pb(Zr0.52Ti0.48)O3 (PZT) capacitors with Pt (top), and SrRuO3, La0.7Sr0.3MnO3 or LaNiO3 (bottom) electrodes has been studied. With the different oxide electrodes and by changing the deposition oxygen pressure, various lattice-misfit strains in the epitaxial PZT films have been produced. It was found that after in situ annealing at reduced oxygen pressures, the capacitors showed an increased voltage offset in the polarization-electric field hysteresis loops with increasing the misfit strain, irrelevant to the oxide electrodes employed, while lattice disorder at the bottom interface can effectively eliminate the voltage shift. Our results suggest that the imprint behavior is caused by oxygen loss via dislocations generated by the misfit strain relaxation at the growth temperature.
Detecting domain-wall trapping and motion at a constriction in narrow ferromagnetic wires using perpendicular-current giant magnetoresistance
Authors: Zambano A. J. , Pratt W. P.
Published: August 2004

We present a versatile method for detecting the presence and motion of a trapped domain wall in a narrow ferromagnetic layer using current-perpendicular-to-plane (CPP) giant magnetoresistance (MR). The CPP-MR response to small motions of the trapped domain wall is enhanced because the CPP current is restricted to the region of wall trapping. We use a Permalloy∕Cu∕Permalloy spin valve in the shape of a long, ∼500-nm-wide wire with a constriction (notch) near its middle that acts as a trapping site for a head-to-head domain wall. Two different notch shapes were studied, mostly at 4.2K but also at 295K.
Nature of persistent photoconductivity in GaAs0.7Sb0.3∕GaAs multiple quantum wells
Authors: Chen T. T. , Su W. S. , Chen Y. F. , Liu P. W. , Lin H. H.
Published: August 2004

The optoelectronic properties of undoped type-II GaAs0.7Sb0.3∕GaAs (100) multiple quantum wells have been investigated by photoluminescence (PL), and photoconductivity measurements. Quite interestingly, persistent photoconductivity (PPC) has been discovered in this material. The decay kinetics of the PPC effect can be well described by the stretched-exponential function IPPC(t)=IPPC(0)exp[−(t∕τ)β], (0<β<1), which is similar to the behavior observed in many disorder systems. Through the study of the PPC effect under various conditions, and combining with the characteristics of the PL spectra, we identify that the origin of the PPC effect arises from the spatial separation of photoexcited electrons and holes. Here, the photoexcited electrons fall into the GaAs layer, and holes are trapped by local potential minima due to alloy fluctuations in the GaAsSb layer. This process prevents the recombination of electrons and holes, and thus the PPC occurs. In order to return to the initial states, photoexcited electrons have to overcome the energy barrier caused by the conduction band offset.
Experimental measurement of water wave band gaps
Authors: Jeong Taek Seong , Kim Jae-Eun , Park Hae Yong , Lee In-Won
Published: August 2004

We experimentally demonstrate the existence of water wave band gaps in finite two-dimensional periodic graphitic and triangular structures composed of vertical cylinders which stand on the bottom of the water tank and project out of the water surface. The experimental data agree fairly well with the numerical simulations obtained from the multiple scattering method. The experimental evidence of water wave band gaps suggests that two-dimensional periodic structures of vertically oriented solid cylinders constitute a much better solution for the problem of coastal erosion.
Excitonic signature in gain and carrier induced change of refractive index spectra of (In,Al)GaN quantum well lasers
Authors: Schwarz Ulrich T. , Sturm E. , Wegscheider W. , Kümmler V. , Lell A. , Härle V.
Published: August 2004

The exciton is observed in (In,Al)GaN laser diodes as resonance in the optical gain spectra and in the spectra of the carrier induced change of the refractive index. The observed instability of the exciton with respect to the free electron-hole plasma with increasing carrier densities is accompanied by a blueshift of the exciton resonance due to the quantum confined Stark shift. The experiments confirm central points of many-body simulations of InGaN∕GaN quantum wells. The exciton becomes unstable near threshold and so lasing occurs from the electron–hole plasma.
Colossal kinetic isotope effects in proton-coupled electron transfer
Authors: Huynh My Hang V. , Meyer Thomas J.
Published: August 2004

The kinetics of reduction of benzoquinone (Q) to hydroquinone (H
2
Q) by the Os(IV) hydrazido (
trans
-[Os
IV
(tpy)(Cl)
2
(N(H)N(CH
2
)
4
O)]-PF
6
= [1]PF
6
, tpy = 2,2′:6′,2″-terpyridine), sulfilimido (
trans
-[Os
IV
-(tpy)(Cl)
2
(NS(H)-4-C
6
H
4
Me)]PF
6
= [2]PF
6
), and phosphoraniminato (
trans
-[Os
IV
(Tp)(Cl)
2
(NP(H)(Et)
2
)] = [3], Tp
–
= tris(pyrazolyl)-borate) complexes have been studied in 1:1 (vol/vol) CH
3
CN/H
2
O and CH
3
CN/D
2
O (1.0 M in NH
4
PF
6
/KNO
3
at 25.0 ± 0.1°C). The reactions are first order in both [Q] and Os(IV) complex and occur by parallel pH-independent (
k
1
) and pH-dependent (
k
2
) pathways that can be separated by pH-dependent measurements. Saturation kinetics are observed for the acid-independent pathway, consistent with formation of a H-bonded intermediate (
K
A
) followed by a redox step (
k
red
). For the pH-independent pathway,
k
1
(H
2
O)/
k
1
(D
2
O) kinetic isotope effects are 455 ± 8 for [1
+
], 198 ± 6 for [2
+
], and 178 ± 5 for [3]. These results provide an example of colossal kinetic isotope effects for proton-coupled electron transfer reactions involving nitrogen, sulfur, and phosphorus as proton-donor atoms.
Nascent blood vessels in the skin arise from nestin-expressing hair-follicle cells
Authors: Amoh Yasuyuki , Li Lingna , Yang Meng , Moossa A. R. , Katsuoka Kensei , Penman Sheldon , Hoffman Robert M.
Published: August 2004

Besides forming hair shafts, the highly organized, metabolically vigorous hair follicle plays several crucial roles in skin architecture. The follicle contains a distinct population of presumptive follicular stem cells that express nestin, also a marker for neural stem cells. These nestin-expressing follicle cells are located principally in the follicular bulge region. Nestin-driven GFP (ND-GFP), transfected into mice, principally labels cells in the bulge region, which is consistent with the cells' being the stem cells of the hair follicle. We report here that ND-GFP also labels developing skin blood vessels that appear to originate from hair follicles and form a follicle-linking network. This is seen most clearly by transplanting ND-GFP-labeled vibrissa (whisker) hair follicles to unlabeled nude mice. New vessels grow from the transplanted follicle, and these vessels increase when the local recipient skin is wounded. The ND-GFP-expressing structures are blood vessels, because they display the characteristic endothelial-cell-specific markers CD31 and von Willebrand factor. This model displays very early events in skin angiogenesis and can serve for rapid antiangiogenesis drug screening.
Blood pressure responses in healthy older people to 50 g carbohydrate drinks with differing glycaemic effects
Authors: Visvanathan Renuka , Chen Richard , Horowitz Michael , Chapman Ian
Published: August 2004

The aim of the present study was to determine the effects on blood pressure response of 50 g carbohydrate drinks with differing glycaemic effects in ten healthy elderly subjects (age >65 years; randomized crossover design). Systolic (SBP), diastolic (DBP) and mean arterial (MAP) blood pressure, heart rate and plasma glucose levels were determined following ingestion of equal volumes (379 ml) of water and 50 g carbohydrate drinks with differing reported glycaemic indices (GI) (surrogate marker for glycaemic effect): (1) low-GI: Apple & Cherry Juice; (2) intermediate-GI: Fanta Orange; (3) high-glucose. Glucose (SBP and DBP P<0·001; MAP P=0·005) and Fanta Orange (SBP P=0·005; DBP and MAP P<0·001) ingestion caused a significant decrease in BP whilst blood pressure increased (SBP P=0·008; MAP P=0·005) from baseline following Apple & Cherry Juice ingestion. Water had no significant effect on postprandial blood pressure. Fanta Orange and Apple & Cherry Juice caused similar (P=0·679) glycaemic effects, which were significantly greater than water, but lower than glucose (P<0·001). There was no significant correlation between the glycaemic effect of the carbohydrate drinks and there was no change in blood pressure from baseline (SBP r −0·123, P=0·509; DBP r −0·051, P=0·784; MAP r −0·069, P=0·712). Apple & Cherry Juice and Fanta Orange had similar glycaemic effects, but differing effects on blood pressure. Therefore, it is unlikely that the glycaemic effect of a drink can be used to predict the subsequent cardiovascular response.
Qualitative and Quantitative Histomorphologic Assessment of Fathead Minnow Pimephales promelas Gonads as an Endpoint for Evaluating Endocrine-Active Compounds: A Pilot Methodology Study
Authors: Wolf Jeffrey C. , Dietrich Daniel R. , Friederich Urs , Caunter John , Brown Andrew R.
Published: August 2004

Although histopathology is routinely employed as a tool for the detection and assessment of xenobiotic-mediated effects in mammals, it is less frequently applied to fish. In part, this is due to a lack of method standardization regarding study design, tissue preservation, tissue sectioning, histopathological evaluation, reporting, and statistical analysis. The objectives of the present study were: (1) to test and refine a method for the microsurgical excision of fathead minnow (FHM) Pimephales promelas gonads for the purpose of histopathologic examination; (2) to determine the optimal combination of fixation and embedding procedures for the histopathologic and morphometric analysis of FHM gonads following exposure to a known estrogenic compound, 17 β-estradiol (E2); and (3) to provide a method for the categorization and quantification of cell types in FHM gonads by manually counting cells in digitized images using image analysis software. The light microscopic evaluation of individual gametogenic cells was greatly facilitated by specimen preparation techniques that included the excision of gonads via microdissection and by optimized fixation and embedding procedures.
Can drug injectors be encouraged to adopt non‐injecting routes of administration (NIROA) for drugs?
Authors: DOLAN KATE , CLEMENT NICOLE , ROUEN DAVID , REES VAUGHAN , SHEARER JAMES , WODAK ALEX
Published: August 2004

Drug use by injection can cause problems specific to this form of administration. Problems include an increased risk of drug overdose, drug dependence, the transmission of HIV, hepatitis B and hepatitis C and vein damage. Shifting drug injectors from injecting to another route of administration may minimize these problems. The aims of the study were to develop and trial an intervention to assist willing injecting drug users (IDUs) to shift to non‐injecting routes of administration (NIROA) and to explore the acceptability and practicality of facilitating NIROA. IDUs were assessed and suitable subjects entered a cognitive behavioural trial consisting of five 1‐hour sessions of individual therapy with a registered psychologist. Forty‐two subjects were assessed (22 males and 20 females). Thirty subjects entered treatment. The mean age was 36 years. Twenty‐one subjects were followed‐up at 3 months and 10 subjects at 6 months. At 3 and 6 months, the proportion of subjects who had commenced using NIROA was 30% and 50%, respectively. This pilot study showed that it was possible to assist a minority of drug injectors to move from injecting to the non‐injecting administration of drugs. However, many of these appeared to be already motivated to cease using drugs and adopting NIROA was one way of assisting this. Poor follow‐up rate, lack of control group, questions about cost‐effectiveness and the impact of market factors which possibly constrain shifting to NIROA suggest that further research is needed before it could be said that NIROA should be recommended as a viable harm reduction strategy in the Australian context.
A review of drug use and driving: epidemiology, impairment, risk factors and risk perceptions
Authors: KELLY ERIN , DARKE SHANE , ROSS JOANNE
Published: August 2004

The existing literature on the prevalence of drug driving, the effects of drugs on driving performance, risk factors and risk perceptions associated with drug driving was reviewed. The 12‐month prevalence of drug driving among the general population is approximately 4%. Drugs are detected commonly among those involved in motor vehicle accidents, with studies reporting up to 25% of accident‐involved drivers positive for drugs. Cannabis is generally the most common drug detected in accident‐involved drivers, followed by benzodiazepines, cocaine, amphetamines and opioids. Polydrug use is common among accident‐involved drivers. Studies of impairment indicate an undeniable association between alcohol and driving impairment. There is also evidence that cannabis and benzodiazepines increase accident risk. The most equivocal evidence surrounds opioids and stimulants. It is apparent that drugs in combination with alcohol, and multiple drugs, present an even greater risk. Demographically, young males are over‐represented among drug drivers. Although there is an association between alcohol use problems and drink driving, it is unclear whether such an association exists between drug use problems and drug driving. Evidence surrounding psychosocial factors and driving behaviour is also equivocal at this stage. While most drivers perceive drug driving to be dangerous and unacceptable, there is less concern about impaired driving among drug drivers and drink drivers than from those who have not engaged in impaired driving. Risk perceptions differ according to drug type, with certain drugs (e.g. cannabis) seen as producing less impairment than others (e.g. alcohol). It is concluded that drug driving is a significant problem, both in terms of a general public health issue and as a specific concern for drug users.
A Bayesian Approach to DNA Sequence Segmentation
Authors: Boys Richard J. , Henderson Daniel A.
Published: August 2004

SummaryMany deoxyribonucleic acid (DNA) sequences display compositional heterogeneity in the form of segments of similar structure. This article describes a Bayesian method that identifies such segments by using a Markov chain governed by a hidden Markov model. Markov chain Monte Carlo (MCMC) techniques are employed to compute all posterior quantities of interest and, in particular, allow inferences to be made regarding the number of segment types and the order of Markov dependence in the DNA sequence. The method is applied to the segmentation of the bacteriophagelambdagenome, a common benchmark sequence used for the comparison of statistical segmentation algorithms.
An Extended General Location Model for Causal Inferences from Data Subject to Noncompliance and Missing Values
Authors: Peng Yahong , Little Roderick J. A. , Raghunathan Trivellore E.
Published: August 2004

SummaryNoncompliance is a common problem in experiments involving randomized assignment of treatments, and standard analyses based on intention‐to‐treat or treatment received have limitations. An attractive alternative is to estimate the Complier‐Average Causal Effect (CACE), which is the average treatment effect for the subpopulation of subjects who would comply under either treatment (Angrist, Imbens, and Rubin, 1996,Journal of American Statistical Association91,444–472). We propose an extended general location model to estimate the CACE from data with noncompliance and missing data in the outcome and in baseline covariates. Models for both continuous and categorical outcomes and ignorable and latent ignorable (Frangakis and Rubin, 1999,Biometrika86,365–379) missing‐data mechanisms are developed. Inferences for the models are based on the EM algorithm and Bayesian MCMC methods. We present results from simulations that investigate sensitivity to model assumptions and the influence of missing‐data mechanism. We also apply the method to the data from a job search intervention for unemployed workers.
Maximum Likelihood Analysis of a General Latent Variable Model with Hierarchically Mixed Data
Authors: Lee Sik‐Yum , Song Xin‐Yuan
Published: August 2004

SummaryA general two‐level latent variable model is developed to provide a comprehensive framework for model comparison of various submodels. Nonlinear relationships among the latent variables in the structural equations at both levels, as well as the effects of fixed covariates in the measurement and structural equations at both levels, can be analyzed within the framework. Moreover, the methodology can be applied to hierarchically mixed continuous, dichotomous, and polytomous data. A Monte Carlo EM algorithm is implemented to produce the maximum likelihood estimate. The E‐step is completed by approximating the conditional expectations through observations that are simulated by Markov chain Monte Carlo methods, while the M‐step is completed by conditional maximization. A procedure is proposed for computing the complicated observed‐data log likelihood and the BIC for model comparison. The methods are illustrated by using a real data set.
A Semiparametric Method for Analyzing Matched Case–Control Family Studies with a Continuous Outcome and Proband Sampling
Authors: Wang Molin , Williamson John M. , Redline Susan
Published: August 2004

Summary We consider matched case–control familial studies which match a group of patients, called “case probands,” with a group of disease‐free subjects, called “control probands,” using a set of family‐level matching variables. Family members of each proband are then recruited into the study. Of interest here is the familial aggregation of the response variable and the effects of subject‐specific covariates on the response. We propose an estimating equation approach to jointly estimate the main effects and intrafamilial correlations for matched family studies with a continuous outcome. Only knowledge of the first two joint moments of the response variable is required. The induced estimators for the main effects and intrafamilial correlations are consistent and asymptotically normally distributed. We apply the proposed method to sleep apnea data. A simulation study demonstrates the usefulness of our approach.
Dose‐Finding Based on Efficacy–Toxicity Trade‐Offs
Authors: Thall Peter F. , Cook John D.
Published: August 2004

SummaryWe present an adaptive Bayesian method for dose‐finding in phase I/II clinical trials based on trade‐offs between the probabilities of treatment efficacy and toxicity. The method accommodates either trinary or bivariate binary outcomes, as well as efficacy probabilities that possibly are nonmonotone in dose. Doses are selected for successive patient cohorts based on a set of efficacy–toxicity trade‐off contours that partition the two‐dimensional outcome probability domain. Priors are established by solving for hyperparameters that optimize the fit of the model to elicited mean outcome probabilities. For trinary outcomes, the new algorithm is compared to the method ofThall and Russell(1998,Biometrics54,251–264) by application to a trial of rapid treatment for ischemic stroke. The bivariate binary outcome case is illustrated by a trial of graft‐versus‐host disease treatment in allogeneic bone marrow transplantation. Computer simulations show that, under a wide rage of dose‐outcome scenarios, the new method has high probabilities of making correct decisions and treats most patients at doses with desirable efficacy–toxicity trade‐offs.
Applications of a Parametric Model for Informative Censoring
Authors: Siannis Fotios
Published: August 2004

SummaryIn this article, we explore the use of a parametric model (for analyzing survival data) which is defined to allow sensitivity analysis for the presence of informative censoring. The dependence between the failure and the censoring processes is expressed through a parameter δ and a general bias functionB(t, θ). We calculate the expectation of the potential bias due to informative censoring, which is an overall measure of how misleading our results might be if censoring is actually nonignorable. Bounds are also calculated for quantities of interest, e.g., parameter of the distribution of the failure process, which do not depend on the choice of the bias function for fixed δ. An application that relates to systematic lupus erythematosus data illustrates how additional information can result in reducing the uncertainty on estimates of the location parameter. Sensitivity analysis on a relative risk parameter is also explored.
Functional Mapping of Quantitative Trait Loci Underlying Growth Trajectories Using a Transform‐Both‐Sides Logistic Model
Authors: Wu Rongling , Ma Chang‐Xing , Lin Min , Wang Zuoheng , Casella George
Published: August 2004

SummaryThe incorporation of developmental control mechanisms of growth has proven to be a powerful tool in mapping quantitative trait loci (QTL) underlying growth trajectories. A theoretical framework for implementing a QTL mapping strategy with growth laws has been established. This framework can be generalized to an arbitrary number of time points, where growth is measured, and becomes computationally more tractable, when the assumption of variance stationarity is made. In practice, however, this assumption is likely to be violated for age‐specific growth traits due to a scale effect. In this article, we present a new statistical model for mapping growth QTL, which also addresses the problem of variance stationarity, by using a transform‐both‐sides (TBS) model advocated byCarroll and Ruppert(1984,Journal of the American Statistical Association79,321–328). The TBS‐based model for mapping growth QTL cannot only maintain the original biological properties of a growth model, but also can increase the accuracy and precision of parameter estimation and the power to detect a QTL responsible for growth differentiation. Using the TBS‐based model, we successfully map a QTL governing growth trajectories to a linkage group in an example of forest trees. The statistical and biological properties of the estimates of this growth QTL position and effect are investigated using Monte Carlo simulation studies. The implications of our model for understanding the genetic architecture of growth are discussed.
Predicting and Correcting Bias Caused by Measurement Error in Line Transect Sampling Using Multiplicative Error Models
Authors: Marques Tiago A.
Published: August 2004

SummaryLine transect sampling is one of the most widely used methods for animal abundance assessment. Standard estimation methods assume certain detection on the transect, no animal movement, and no measurement errors. Failure of the assumptions can cause substantial bias. In this work, the effect of error measurement on line transect estimators is investigated. Based on considerations of the process generating the errors, a multiplicative error model is presented and a simple way of correcting estimates based on knowledge of the error distribution is proposed. Using beta models for the error distribution, the effect of errors and of the proposed correction is assessed by simulation. Adequate confidence intervals for the corrected estimates are obtained using a bootstrap variance estimate for the correction and the delta method. As noted byChen(1998,Biometrics54,899–908), even unbiased estimators of the distances might lead to biased density estimators, depending on the actual error distribution. In contrast with the findings of Chen, who used an additive model, unbiased estimation of distances, given a multiplicative model, lead to overestimation of density. Some error distributions result in observed distance distributions that make efficient estimation impossible, by removing the shoulder present in the original detection function. This indicates the need to improve field methods to reduce measurement error. An application of the new methods to a real data set is presented.
Calculation of Sample Size in Survival Trials: The Impact of Informative Noncompliance
Authors: Jiang Qi , Snapinn Steven , Iglewicz Boris
Published: August 2004

Summary Sample size calculations for survival trials typically include an adjustment to account for the expected rate of noncompliance, or discontinuation from study medication. Existing sample size methods assume that when patients discontinue, they do so independently of their risk of an endpoint; that is, that noncompliance is noninformative. However, this assumption is not always true, as we illustrate using results from a published clinical trial database. In this article, we introduce a modified version of the method proposed by Lakatos (1988, Biometrics44, 229–241) that can be used to calculate sample size under informative noncompliance. This method is based on the concept of two subpopulations: one with high rates of endpoint and discontinuation and another with low rates. Using this new method, we show that failure to consider the impact of informative noncompliance can lead to a considerably underpowered study.
Confidence Interval Estimation of the Intraclass Correlation Coefficient for Binary Outcome Data
Authors: Zou Guangyong , Donner Allan
Published: August 2004

SummaryWe obtain closed‐form asymptotic variance formulae for three point estimators of the intraclass correlation coefficient that may be applied to binary outcome data arising in clusters of variable size. Our results include as special cases those that have previously appeared in the literature (Fleiss and Cuzick, 1979,Applied Psychological Measurement3,537–542;Bloch and Kraemer, 1989,Biometrics45,269–287;Altaye, Donner, and Klar, 2001,Biometrics57,584–588). Simulation results indicate that confidence intervals based on the estimator proposed by Fleiss and Cuzick provide coverage levels close to nominal over a wide range of parameter combinations. Two examples are presented.
Some Unexamined Aspects of Analysis of Covariance in Pretest–Posttest Studies
Authors: Ganju Jitendra
Published: August 2004

Summary The use of an analysis of covariance (ANCOVA) model in a pretest–posttest setting deserves to be studied separately from its use in other (non‐pretest–posttest) settings. For pretest–posttest studies, the following points are made in this article: (a) If the familiar change from baseline model accurately describes the data‐generating mechanism for a randomized study then it is impossible for unequal slopes to exist. Conversely, if unequal slopes exist, then it implies that the change from baseline model as a data‐generating mechanism is inappropriate. An alternative data‐generating model should be identified and the validity of the ANCOVA model should be demonstrated. (b) Under the usual assumptions of equal pretest and posttest within‐subject error variances, the ratio of the standard error of a treatment contrast from a change from baseline analysis to that from ANCOVA is less than 21/2. (c) For an observational study it is possible for unequal slopes to exist even if the change from baseline model describes the data‐generating mechanism. (d) Adjusting for the pretest variable in observational studies may actually introduce bias where none previously existed.
Is rigor mortis the cause of post‐mortem shrinkage in juvenile Pagrus auratus?
Authors: Morison A. K.
Published: August 2004

An experiment demonstrated that post‐mortem shrinkage in fork length of juvenile pink snapper Pagrus auratus(179–262 mm) was the same in fish in which rigor mortis was surgically inhibited, as in intact fish, and averaged 5·5 ± 0·2 mm (mean ± s.e., range 2–9 mm) after 168 h.
Energetics and morphology of sockeye salmon: effects of upriver migratory distance and elevation
Authors: Crossin G. T. , Hinch S. G. , Farrell A. P. , Higgs D. A. , Lotto A. G. , Oakes J. D. , Healey M. C.
Published: August 2004

Depending on population, wild Fraser River sockeye salmon Oncorhynchus nerka travel distances of <100 km to >1100 km and ascend elevations ranging from near sea‐level to 1200 m to reach spawning areas. Populations embarking on distant, high elevation migrations (i.e. Early Stuart, Chilko and Horsefly populations) began their upriver spawning migrations with higher densities of somatic energy (c. 9·2 to 9·8 MJ kg−1) and fewer eggs (c. 3200 to 3800) than populations making shorter, low elevation migrations (i.e. Weaver and Adams; c. 7·1 to 8·3 MJ kg−1 gross somatic energy and c. 4300 to 4700 eggs). Populations making difficult upriver migrations also had morphologies that were smaller and more fusiform than populations making less difficult migrations, traits that may facilitate somatic energy conservation by reducing transport costs. Indeed, fish travelling long distances expended less somatic energy per unit of migratory difficulty than those travelling shorter distances (2·8 to 3·8 kJ v. 10–1400 kJ). Consistent with evolutionary theory, difficult migrations appear to select for energy efficiency but ultimately fish making more difficult migrations produce fewer eggs, even when differences in body length have been accounted for. Despite large among‐population differences in somatic energy at the start of upriver migration, all populations completed migration and spawning, and subsequently died, with c. 4 MJ kg−1 of energy remaining, a level which may reflect a threshold to sustain life.
Physiological responses in Nile tilapia exposed to different photoperiod regimes
Authors: Biswas A. K. , Maita M. , Yoshizaki G. , Takeuchi T.
Published: August 2004

After conditioning Nile tilapia Oreochromis niloticus for 2 weeks, the photoperiod regime of 12 tanks of fish was changed to a 6L : 6D photoperiod while 12 further tanks were retained on the conditioning photoperiod regime (12L : 12D). Blood samples were collected 3 days (first sampling) and 3 months (second sampling) after changing the photoperiod regime. Blood was collected at 6 h intervals from both photoperiod regimes (1000, 1600, 2200 and 0400 hours). At the first sampling time, fish in the 6L : 6D had significantly higher cortisol both in the light and dark phases than levels in fish in the 12L : 12D photoperiod. At the second sampling time, the levels were significantly higher only in the light phase. The levels of cortisol, glucose and Cl− in fish exposed to the 6L : 6D photoperiod, however, were far lower than those of acute stress‐induced levels observed in fish exposed to a stress experiment. Furthermore, there were no significant differences in overall values of all the variables between the photoperiod regimes at the second sampling time. This indicated that the fish exposed to the 6L : 6D photoperiod were not chronically stressed. Significantly higher blood lymphocyte counts were observed in fish exposed to the 6L : 6D compared to those of the 12L : 12D photoperiod during the light phase at the second sampling time. Other variables (glucose, Cl−, haematocrit and neutrophil) did not show a significant difference between the treatments at either sampling time. These results demonstrated that the artificial photoperiod regime did not cause a significant acute or chronic stress response in Nile tilapia.
Climate variables and spawning migrations of the striped mullet and white mullet in the north‐western area of the Gulf of Mexico
Authors: Ibáñez A. L. , Gutiérrez Benítez O.
Published: August 2004

The ‘smoothed’(4253e HT smoother) 6 year time series with a monthly periodicity of catches (where the increases of the catches reflect the spawning migration) of Mugil cephalus and Mugil curema, were correlated (Pearson correlation index) against the ‘smoothed’ data on rainfall, water temperature, daylight and tide monthly averages. Water temperature and M. curema spawning migrations had a negative correlation (r = −0·77), while tide monthly averages and M. cephalus spawning migrations were positively correlated (r = 0·84). The two environmental variables that showed highly significant correlations were water temperature and daylight (r = 0·85, P < 0·05). Meteorological tides were used as a reflection of the effect of the north winds from the Gulf of Mexico which produce an average tide rise from September to November. The relationship of these variables with spawning migrations is discussed, and it is suggested, in particular, that meteorological tides, as a reflection of the north winds, are the trigger (zeitgebers) for M. cephalus spawning in the ocean.
Fish larvae assemblages in the Gulf of California
Authors: Aceves‐Medina G. , Jiménez‐Rosenberg S. P. A. , Hinojosa‐Medina A. , Funes‐Rodríguez R. , Saldierna‐Martínez R. J. , Smith P. E.
Published: August 2004

The distributional diversity and assemblages of fish larvae in the Gulf of California indicated two main seasonal stages and two transitional periods: in winter, the tropical water mass is confined to the south‐east portion of the mouth of the Gulf and larval fish assemblages are dominated by subtropical and temperate‐subarctic species; in summer; tropical water invades the Gulf and assemblages are dominated by tropical species. Both seasonal stages are separated by transitional periods coinciding with strong latitudinal temperature gradients. During the autumn and spring transitional periods, the Gulf of California splits into three regions: a northern region where temperate and subarctic species spawn from autumn to spring, a southern region dominated by tropical and subtropical species year round and a central region where tropical and temperate assemblages merge. Seasonal changes in the location of the regions, as well as the borders between them, show expansion and contraction of the northern and southern faunas related to the general oceanic circulation patterns during the year.
Genetic exchange between anchialine cave populations by means of larval dispersal: the case of a new gastropod species Neritilia cavernicola
Authors: Kano Yasunori , Kase Tomoki
Published: August 2004

Despite being limited to caves, many anchialine taxa have disjunct insular distributions, which raises questions about their origins and colonization history. This study deals with the new gastropod Neritilia cavernicola sp. n. (Neritopsina: Neritiliidae) from anchialine caves on two islands in the Philippines that are separated by the deep Bohol Strait and situated 200 km apart along the coastline of Cebu Island. Neritilia cavernicola is an obligate stygobiont and most closely resembles Neritilia littoralis, which lives in interstitial waters of the Nansei‐shoto Islands, Japan. Its eggs and larval shells are identical to those of other Neritilia species, despite their different adult habitats. This suggests a marine planktotrophic phase (as occurs in amphidromous riverine species of Neritilia), and consequent migration between islands via ocean currents. Here we present the first genetic structure for anchialine cave organisms; comparisons of 1276 bp sequences from mitochondrial cytochrome oxidase I show no evidence of genetic isolation between the islands. All individuals evidently are part of a panmictic population and the low vagility of adults and their seemingly isolated cave habitats do not limit gene flow in N. cavernicola. This migration model, based on marine larval dispersal, may be widely applicable to anchialine stygobites with insular distributions, as many such organisms (including shrimps, crabs and fishes) are phylogenetically allied to amphidromous species.
Systematic Review of the Literature on Postpartum Care: Methodology and Literature Search Results
Authors: Levitt Cheryl , Shaw Elizabeth , Wong Sharon , Kaczorowski Janusz , Springate Russ , Sellors John , Enkin Murray
Published: August 2004

Abstract:  Background: The postpartum period is a time for multiple clinical interventions. To date, no critical review of these interventions exists. This systematic review examined evidence for the effectiveness of postpartum interventions that have been reported in the literature. Methods: MEDLINE, Cinahl, PsycINFO, and the Cochrane Library were searched for randomized controlled trials of interventions initiated from immediately after birth to 1 year in postnatal women that were conducted in North America, Europe, Australia, or New Zealand. The initial literature search was done in 1999, using postpartum content search terms, and was enhanced in 2003. In both years, bibliographic databases were searched from their inception. Studies were categorized into key topic areas. Data extraction forms were developed and completed for each study, and the quality of each study was systematically reviewed. Groups of studies in a topic area were reviewed together, and clinically relevant questions emanating from the studies were identified to determine whether the studies, alone or together, provided evidence to support the clinical intervention. Results: In the 1999 search, of 671 studies identified, 140 studies were randomized controlled trials that met the selection criteria: 41 studies related to breastfeeding, 33 to postpartum perineal pain management, and 63 to 11 other key topic areas (Papanicolaou test, rubella immunization, contraception, postpartum support, early discharge, postpartum depression and anxiety, postpartum medical disorders, smoking cessation, nutrition supplements other than breastfeeding, effects of pelvic floor exercise, and effects of early newborn contact).The results of the systematic review of each topic will be summarized in separate papers as they are completed. Conclusions: This systematic search has identified key topic areas in postpartum care for which randomized controlled trials have been conducted. Our ultimate goal is to provide evidence‐based guidelines on the use of routine postpartum interventions.
Content and Processes of Postpartum Counseling After a Distressing Birth Experience: A Review
Authors: Gamble Jenny , Creedy Debra
Published: August 2004

Abstract:  Background: A distressing birth experience can produce debilitating symptoms of psychological trauma; however, little is known about the content and processes of counseling interventions to relieve trauma symptoms. This review identifies and examines common content and processes of postpartum counseling interventions to address trauma symptoms following childbirth. Method: A search of major databases (Cinahl 1982–2003; Cochrane 2003; Embase; Proquest; Psychlit; Pubmed/Medline 1966–2003; Sociofile) was conducted, using combinations of the key words of “childbirth,”“postpartum,”“posttraumatic stress disorder,”“anxiety,”“trauma,”“stress,”“debriefing,” and “counselling” or “counseling.” Identified content and processes were clustered through a thematic analysis. Results: Nineteen publications were retrieved. Counseling strategies provided women with opportunities to talk about their birth experience, express feelings about what happened, have questions answered, address gaps in knowledge or understanding of events, connect the event with emotions and behavior, talk about future pregnancies, and explore existential issues. Conclusions: Descriptions of postpartum counseling and debriefing are generalized and nonspecific; they provide minimal direction for postpartum counseling models, lack necessary detail for replication, may require psychotherapeutic training and therefore be unsuitable for use by caregivers, and are often based on opinion with little empirical evaluation. Few studies have tested specific counseling interventions on a range of maternal outcomes. Further research is needed to develop counseling models for use by health professionals with women who report a distressing birth experience.
Outcomes of Free‐Standing, Midwife‐Led Birth Centers: A Structured Review
Authors: Walsh Denis , Downe Soo M.
Published: August 2004

Abstract:  Background: Over the last two decades, childbirth worldwide has been increasingly concentrated in large centralized hospitals, with a parallel trend toward more birth interventions. At the same time in several countries, interest in midwife‐led care and free‐standing birth centers has steadily increased. The objective of this review is to establish the current evidence base for free‐standing, midwife‐led birth centers. Methods: A structured review, based on Cochrane guidelines, was conducted that included nonrandomized studies. The comparative outcomes measured were rates of normal vaginal birth; cesarean section; intact perineum; episiotomy; transfers; and babies remaining with their mothers. Results: Of the 5 controlled studies that met the review criteria, all except one was a single site study. Since no study was randomized, meta‐analysis was not performed. The included studies all raised quality concerns, and significant heterogeneity was observed among them. For the outcomes measured, every study reported a benefit for women intending to give birth in the free‐standing, midwife‐led unit. Conclusions: The benefits shown for women recruited into the included studies who intended to give birth in a free‐standing, midwife‐led unit suggest a question about the efficacy of consultant unit care for low‐risk women. However, the findings cannot be generalized beyond the individual studies. Good quality controlled studies are needed to investigate these issues in the future.
Characterization of Ets‐binding sequence of human transglutaminase 3 gene promoter
Authors: Kim Chang Deok , Seo Eun‐Young , Sung Yeul‐Hoon , Kim Hyun‐Woong , Seo Young‐Joon , Park Jang‐Kyu , Lee Jeung‐Hoon
Published: August 2004

Abstract:  The Ets‐ and Sp1‐transcription factors have been implicated in the epithelial specific expression of transglutaminase 3 gene (TGM3) in vitro. By electrophoretic mobility shift assay (EMSA), the core motif of Ets‐binding sequence of TGM3 was determined as ACAGGAAT (−118 to −111 bp from transcriptional start site). However, a sequence extending from −120 to +10 of TGM3 proximal promoter region failed to induce the expression of CAT reporter in transfected normal human epidermal keratinocytes (NHEKs). In contrast, a construct extending from −126 to +10 bp showed the highest expression of CAT gene, indicating the presence of an important element(s) between −126 and −120 bp that affects TGM3 expression in NHEKs. To find the critical sequences in this promoter region, we performed EMSA analysis with competitor oligonucleotides, in which the upstream nucleotides of Ets core motif were mutated. The results showed that the mutation of A at −125 dramatically reduced the binding of Ets to its recognition sequence. Transient transfection assay revealed that the mutation in this nucleotide greatly diminished the expression of CAT reporter gene in NHEKs. Together, these results suggest that the upstream sequence of Ets core motif is critical for the expression of TGM3 in NHEKs cultured in vitro.
Topical β‐carotene is converted to retinyl esters in human skin ex vivo and mouse skin in vivo
Authors: Antille Christophe , Tran Christian , Sorg Olivier , Saurat Jean‐Hilaire
Published: August 2004

Abstract:  Human epidermis contains endogenous retinoids (retinol and retinyl esters) and carotenoids (mostly β‐carotene). Previous studies have shown that the enzymes involved in retinoid metabolism are present in human epidermis. There is still a controversy about the presence in the skin of the enzymes able to convert β‐carotene into vitamin A (retinol), although a recent study demonstrated the conversion of β‐carotene into retinol in human cultured epidermal cells. In this study, we addressed the question of the possible bioconversion of topical β‐carotene into vitamin A or derivatives by human and mouse skin. Surgically excised human abdominal skin was mounted on Franz perfusion chambers to assess the cutaneous penetration of topical β‐carotene as well as its metabolism, after a 24‐h incubation period, whereas hairless mice received topical β‐carotene 24 h before assaying epidermal β‐carotene and retinoid concentrations. Epidermal retinoid and β‐carotene concentrations were determined by high‐pressure liquid chromatography. Topical β‐carotene penetrated well into human and mouse epidermis and induced a 10‐fold (human) and a threefold (mouse) increase of epidermal retinyl esters, which demonstrates that topical β‐carotene is converted into retinyl esters by human and mouse epidermis and thus appears as a precursor of epidermal vitamin A.