bluuebunny/crossref_metadata_2025_split huggingface dataset:
ANALYSIS OF DOUBLY CENSORED DATA AND THE HIV INCUBATION PERIOD DISTRIBUTION IN WESTERN AUSTRALIA
Authors: James Ian R. , Hogan Stephen J. , Mallal Simon A. 
Published: February 2008

SummaryThe paper analyses the distribution of times from HIV seroconversion to the first AIDS defining illness for a subcohort of the Western Australian HIV Cohort Study for whom the seroconversion date is known to fall within a calendar time window. The analysis is based on a generalised gamma model for the incubation times and a piecewise constant distribution for the conditional times of seroconversion given the seroconversion windows. This allows flexible hazard shapes and also allows comparison of goodness of fit of the gamma and Weibull distributions which are often used for modelling incubation times. Computational issues are discussed. In these data, neither age at seroconversion, nor calendar time of seroconversion, nor the identification of a seroconversion illness appears to afFect incubation distributions. The Weibull distribution appears to provide a reasonable fit. The distribution of times from seroconversion to an HIV‐related death is also briefly considered.
ROBUST TESTS BASED ON THE SAMPLE CHARACTERISTIC FUNCTION
Authors: Lenth R.V. , Markatou M. , Tsimikas J. 
Published: February 2008

SummaryA new method is described for robust analysis of variance in the balanced fixed effects case. The method uses the empirical characteristic function of the treatment samples, and has an interpretation in terms of S‐estimators. The test statistic, under the null hypothesis, asymptotically follows a central chi‐square distribution, and under contiguous alternatives a noncentral chi‐square distribution. A Monte Carlo study suggests that, for finite samples, this is reasonably well approximated by the usual F distribution used in analysis of variance. The test statistic has a bounded influence function. The new procedure competes well with Huber's and a Wald‐type procedure except in very heavy‐tailed cases.
ON A SHARED ALLELE TEST OF RANDOM MATING
Authors: Zhou S. , Maller R.A. , Speed T.P. 
Published: February 2008

SummaryA simple random sample is observed from a population with a large number‘K’ of alleles, to test for random mating. Of n couples, nijkl have female genotype ij and male genotype kl (i, j, k, l{1,…, A‘}). The large contingency table is collapsed into three counts, n0, n1 and n2 where np is the number of couples with s alleles in common (s = 0,1, 2). The counts are estimated by np̂o where n0, is the estimated probability of a couple having s alleles in common under the hypothesis of random mating. The usual chi‐square goodness of fit statistic X2 compares observed (ns) with expected (np̂) over the three categories, s = 0,1,2. An empirical observation has suggested that X2 is close to having a chi‐square distribution with two degrees of freedom (X) despite a large number of parameters implicitly estimated in e. This paper gives two theorems which show that x is indeed the approximate distribution of X2 for large n and K1“, provided that no allele type over‐dominates the others.
CHARACTERISATIONS OF SOME INCOME DISTRIBUTIONS BASED ON MULTIPLICATIVE DAMAGE MODELS
Authors: Fosam E.B. , Sapatinas T. 
Published: February 2008

SummaryThis paper characterises the Pareto and scaled beta distributions within the context of multiplicative damage and generating models. The results obtained allow the destructive or generating mechanism to have more general distributions on (0,1) than the beta(e, l) distribution considered by several authors, thus generalising some recent results. Errors in earlier work are mentioned.
A TWO‐STAGE UNRELATED RANDOMISED RESPONSE PROCEDURE
Authors: JinhChang Horng , HsinLiang Der 
Published: February 2008

SUMMARYIn a sample survey, questions requiring personal or controversial assertions often give rise to resistance. A randomised response procedure can be used to help the researcher gather accurate data in this case. This paper describes a new two‐stage unrelated randomised response procedure that combines the use of two randomisation devices (Mangat & Singh, 1990) and an unrelated question (Horwitz et al. 1967). It examines the situation where the respondents are not completely truthful in their answers. The efficiency of this new method is compared with the original one‐stage procedure proposed by Horwitz et al. (1967), and guidelines for choosing the values of different parameters for the procedures are provided. Results from an empirical study which examines the efficiency and feasibility of the proposed method are given.
SURVIVAL ANALYSIS WITH TIME DEPENDENT FRAILTY USING A LONGITUDINAL MODEL
Authors: McGilchrist C.A. , Yau K.K.W. 
Published: February 2008

SUMMARYA method of estimation for generalised mixed models is applied to the estimation of regression parameters in a proportional hazards model with time dependent frailty. A parameter representing change over time is introduced and is modelled in turn into a fixed effect, a normally distributed random effect and a longitudinal effect in which the random component relates to the patient characteristics. Both maximum likelihood and residual maximum likelihood estimators are given.
PROPERLY RESCALED COMPONENTS OF SMOOTH TESTS OF FIT ARE DIAGNOSTIC
Authors: Henze Norbert , Klar Bernhard 
Published: February 2008

SUMMARYThe paper illustrates a typical pitfall associated with a conventional interpretation of components of smooth tests of fit, for example the first nonzero components of the smooth tests for Poissonity, exponentiality, normality and the geometric distribution. In order to achieve a directed diagnosis concerning the kind of departure from a hypothesised model, an appropriate rescaling of components is necessary.
VALID RANDOMISATION FOR THE FIRST‐DIFFERENCE ANALYSIS
Authors: Monod H. , Azaïs J‐M. , Bailey R.A. 
Published: February 2008

SUMMARYA general method is presented for randomising a block design while preserving the neighbour relationships between treatments. The randomisation possesses validity properties for the first‐difference analysis introduced by Besag & Kempton (1986). The estimators of treatment differences are unbiased, and the paper shows how to calculate quadratic estimators of their variance, which are unbiased if treatment effects and plot effects are additive. Simplifications, which appear when the design is neighbour‐balanced, are described and illustrated.
√n‐CONSISTENT ESTIMATION IN A RANDOM COEFFICIENT AUTOREGRESSIVE MODEL
Authors: Schick Anton 
Published: February 2008

SummaryThis paper deals with √n‐consistent estimation of the parameter μ in the RCAR(l) model defined by the difference equation Xj=(μ+Uj)Xj‐l+ej (jε Z),where {ej: jε Z} and {Uj: jε Z} are two independent sets of i.i.d. random variables with zero means, positive finite variances and E[(μ+U1)2] < 1. A class of asymptotically normal estimators of μ indexed by a family of bounded measurable functions is introduced. Then an estimator is constructed which is asymptotically equivalent to the best estimator in that class. This estimator, asymptotically equivalent to the quasi‐maximum likelihood estimator derived in Nicholls & Quinn (1982), is much simpler to calculate and is asymptotically normal without the additional moment conditions those authors impose.
EMPIRICAL INFLUENCE FOR ROBUST SMOOTHING
Authors: Manchester Lise 
Published: February 2008

SummaryA simple graphical method is presented to display the sensitivity of a scatter plot smoother (e.g. loess, kernel smoothers) to perturbations in the data. This enables the robustness of smoothers which have been designed to be robust to be examined directly in particular examples. Graphs are shown of various robust smoothers on several standard datasets, so that the robustness of the smoothers can be compared. The method is found to be useful in revealing features of the smoothers. Related graphs for displaying the sensitivity of a smoother tok> 1 outliers are also presented.
GLOBAL LOG‐CONCAVITY OF THE LIKELIHOOD IN MODELS WITH GROUPED DISCRETE DATA
Authors: Moffatt Peter G. 
Published: February 2008

summaryThe paper considers the property of global log‐concavity of the likelihood function in discrete data models in which the data are observed in ‘grouped’ form, meaning that for some observations, while the actual value is unknown, the realisation of the discrete random variable is known to fall within a certain range of values. A typical likelihood contribution in this type of model is a sum of probabilities over a range of realisations. An important issue is whether the property of log‐concavity in the ungrouped case carries over to the grouped counterpart; the paper finds, by way of a simple but relevant counter‐example, that this is not always the case. However, in two cases of practical interest, namely the Poisson and geometric models, the property of log‐concavity is preserved under grouping.
SOME SECOND ORDER ASYMPTOTICS IN EXPONENTIAL FAMILY NON‐LINEAR REGRESSION MODELS (A GEOMETRIC APPROACH)
Authors: Wei Bo‐Cheng , Zhu Hong‐Tu 
Published: February 2008

summaryThe differential geometric framework of Amari (1982a, 1985) is applied to the study of some second order asymptotics related to the curvatures for exponential family nonlinear regression models, in which the observations are independent but not necessarily identically distributed. This paper presents a set of reasonable regularity conditions which are needed to study asymptotics from a geometric point of view in regression models. A new stochastic expansion of a first order efficient estimator is derived and used to study several asymptotic problems related to Fisher information in terms of curvatures. The bias and the covariance of the first order efficient estimator are also calculated according to the expansion.
TWO‐WAY CHANGE‐POINT MODEL AND ITS APPLICATION
Authors: Hirotsu Chihiro 
Published: February 2008

summaryExact null and alternative distributions of the two‐way maximally selected x2 for interaction between the ordered rows and columns are derived for each of the normal and Poisson models, respectively. The method is one of the multiple comparison procedures for ordered parameters and is useful for defining a block interaction or a two‐way change‐point model as a simple alternative to the two‐way additive model. The construction of a confidence region for the two‐way change‐point is then described. An important application is found in a dose‐response clinical trial with ordered categorical responses, where detecting the dose level which gives significantly higher responses than the lower doses can be formulated as a problem of detecting a change in the interaction effects.
CORRECTED SCORE FUNCTIONS IN CLASSICAL ERROR‐IN‐VARIABLES AND INCIDENTAL PARAMETER MODELS
Authors: Gimenez Patricia , Bolfarine Heleno 
Published: February 2008

SummaryNakamura (1990) introduced an approach to estimation in measurement error models based on a corrected score function, and claimed that the estimators obtained are consistent for functional models. Proof of the claim essentially assumed the existence of a corrected log‐likelihood for which differentiation with respect to model parameters can be interchanged with conditional expectation taken with respect to the measurement error distributions, given the response variables and true covariates. This paper deals with simple yet practical models for which the above assumption is false, i.e. a corrected score function for the model may not be obtained through differentiating a corrected log‐likelihood although it exists. Alternative regularity conditions with no reference to log‐likelihood are given, under which the corrected score functions yield consistent and asymptotically normal estimators. Application to functional comparative calibration yields interesting results.
CASE‐DELETION DIAGNOSTICS FOR TEST STATISTICS IN MULTIVARIATE REGRESSION
Authors: Tang M.K. , Fung Wing K. 
Published: February 2008

SummaryInfluence measures in multivariate regression analysis have been widely developed, especially through use of the case‐deletion approach. However, there seem to be few accounts of the influence of observations on test statistics in hypothesis testing. This paper examines four common multivariate tests, namely the Wilks' ratio, Lawley‐Hotelling trace, Pillai's trace and Roy's greatest root for testing a general linear hypothesis of the regression coefficients in multivariate regression. The influence of observations is measured using the case‐deletion approach. The proposed diagnostic measures, except that of Roy's greatest root, can be expressed in terms of statistics without involving the actual deletion of observations. An illustrative example is given with satisfactory results.
The Relationship between Farm Succession and Farm Assets on Belgian Farms
Authors: Calus Mieke , Van Huylenbroeck Guido , Van Lierde Dirk 
Published: February 2008

AbstractA major bottleneck in the farm life cycle is intergenerational farm transfer. At the end of the farm life cycle only a limited number of family farms is transferred to the next generation. The average economic farm size increases and this can entail a high financial burden for the successor. This article explores total farm assets as a potential tool to identify farms with a higher probability of transfer. The theory of asset fixity and transaction cost theory are used to explain why higher total farm assets should result in a higher intention to transfer the farm to the next generation, independent of farm type. Empirical results support this theory and show that lower total farm assets often result in farm discontinuation because the total farm value approaches the value of liquidation. Furthermore, our results show that farmers anticipate farm succession possibilities by adapting their farm management. The proposed indicator could therefore be a useful tool for targeting succession or retirement policies.
Crossed cerebral lateralization for verbal and visuo‐spatial function in a pair of handedness discordant monozygotic twins: MRI and fMRI brain imaging
Authors: Lux Silke , Keller Simon , Mackay Clare , Ebers George , Marshall John C. , Cherkas Lynne , Rezaie Roozbeh , Roberts Neil , Fink Gereon R. , Gurd Jennifer M. 
Published: February 2008

AbstractTo examine the nature of hemispheric lateralization for neural processes underlying verbal fluency and visuo‐spatial attention, we investigated a single pair of handedness discordant monozygotic (MzHd) twins. Imaging of the brain was undertaken using magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI) in combination with manual performance tasks. The twins were discordant for MRI anatomical asymmetries of the pars triangularis and planum temporale, whose asymmetry was consistent with verbal laterality on fMRI. Thus, the right‐handed twin had left lateralized verbal with right lateralized visuo‐spatial attention, while the left‐handed twin had right lateralized verbal with left lateralized visuo‐spatial activation; these data lend further support for to the conclusions of Sommer et al.
Regional structural characteristics of bovine periodontal ligament samples and their suitability for biomechanical tests
Authors: Bosshardt Dieter D. , Bergomi Marzio , Vaglio Giovanna , Wiskott Anselm 
Published: February 2008

AbstractMechanical testing of the periodontal ligament requires a practical experimental model. Bovine teeth are advantageous in terms of size and availability, but information is lacking as to the anatomy and histology of their periodontium. The aim of this study, therefore, was to characterize the anatomy and histology of the attachment apparatus in fully erupted bovine mandibular first molars. A total of 13 teeth were processed for the production of undecalcified ground sections and decalcified semi‐thin sections, for NaOH maceration, and for polarized light microscopy. Histomorphometric measurements relevant to the mechanical behavior of the periodontal ligament included width, number, size and area fraction of blood vessels and fractal analysis of the two hard–soft tissue interfaces. The histological and histomorphometric analyses were performed at four different root depths and at six circumferential locations around the distal and mesial roots. The variety of techniques applied provided a comprehensive view of the tissue architecture of the bovine periodontal ligament. Marked regional variations were observed in width, surface geometry of the two bordering hard tissues (cementum and alveolar bone), structural organization of the principal periodontal ligament connective tissue fibers, size, number and numerical density of blood vessels in the periodontal ligament. No predictable pattern was observed, except for a statistically significant increase in the area fraction of blood vessels from apical to coronal. The periodontal ligament width was up to three times wider in bovine teeth than in human teeth. The fractal analyses were in agreement with the histological observations showing frequent signs of remodeling activity in the alveolar bone – a finding which may be related to the magnitude and direction of occlusal forces in ruminants. Although samples from the apical root portion are not suitable for biomechanical testing, all other levels in the buccal and lingual aspects of the mesial and distal roots may be considered. The bucco‐mesial aspect of the distal root appears to be the most suitable location.
Unique features of spermiogenesis in the Musky Rat‐kangaroo: reflection of a basal lineage or a distinct fertilization process?
Authors: Lloyd Shan , Carrick Frank , Hall Les 
Published: February 2008

AbstractPrevious research has found the mature spermatozoon of the Musky Rat‐kangaroo to share many characteristics with other macopodoids, some phalangeroids and even the dasyurids. While there have been several studies published on the ultrastructure of the mature marsupial spermatozoon, there are only a few detailed studies on marsupial spermatogenesis. Furthermore, there have been no studies undertaken which combine the staging of the epithelial cell cycle with transmission electron microscopy to describe the ultrastructural changes in the developing spermatozoon during these stages. Such studies have the potential to be used in determining the required time taken for certain components of the spermatozoa to develop. During this study, eight stages of the seminiferous epithelium were observed and the ultrastructure of spermatogenesis was divided into nine phases. Maturational processes in the epididymides are also described. Among the features reported are: the formation of a unique acrosomal granule different from those reported in any other marsupial, the absence of contraction of the nuclear ring, a conspicuous acrosomal compaction process despite the almost 100% coverage of the dorsal nuclear surface and the retention of late spermatids within the seminiferous tubules until the early spermatids have developed to the nuclear protrusion phase.
Structure‐function relationships in tendons: a review
Authors: Benjamin M. , Kaiser E. , Milz S. 
Published: February 2008

AbstractThe purpose of the current review is to highlight the structure‐function relationship of tendons and related structures to provide an overview for readers whose interest in tendons needs to be underpinned by anatomy. Because of the availability of several recent reviews on tendon development and entheses, the focus of the current work is primarily directed towards what can best be described as the ‘tendon proper’ or the ‘mid‐substance’ of tendons. The review covers all levels of tendon structure from the molecular to the gross and deals both with the extracellular matrix and with tendon cells. The latter are often called ‘tenocytes’ and are increasingly recognized as a defined cell population that is functionally and phenotypically distinct from other fibroblast‐like cells. This is illustrated by their response to different types of mechanical stress. However, it is not only tendon cells, but tendons as a whole that exhibit distinct structure‐function relationships geared to the changing mechanical stresses to which they are subject. This aspect of tendon biology is considered in some detail. Attention is briefly directed to the blood and nerve supply of tendons, for this is an important issue that relates to the intrinsic healing capacity of tendons. Structures closely related to tendons (joint capsules, tendon sheaths, pulleys, retinacula, fat pads and bursae) are also covered and the concept of a ‘supertendon’ is introduced to describe a collection of tendons in which the function of the whole complex exceeds that of its individual members. Finally, attention is drawn to the important relationship between tendons and fascia, highlighted by Wood Jones in his concept of an ‘ectoskeleton’ over half a century ago – work that is often forgotten today.
Lizards with rhythm? Multi‐day patterns in total daily movement
Authors: Kerr G. D. , Bottema M. J. , Bull C. M. 
Published: February 2008

AbstractIrregular and unpredictable day‐to‐day patterns in locomotor activity are often observed in animal movement patterns. While ecological processes may drive some variability in activity, underlying rhythms may modulate activity patterns independently of exogenous factors. We investigated multiple day (infradian) locomotor activity rhythms, in long‐term continuous records of individual daily step counts, in a natural population of the Australian sleepy lizard Tiliqua rugosa. We examined temporal periodicity in locomotor activity using spectral analysis of sequential, overlapping 12‐day windows of activity data. Lizards were inactive on average 1 day in 6, independent of ambient temperature, and showed infradian locomotor activity rhythms. In a drought year, 2002/2003, rhythms did not exceed randomized activity patterns. In an average rainfall year, 2003/2004, 6 and 2‐day cycles occurred significantly more often than by chance. Individuals normally moved independently of conspecifics, although there was some short‐term synchrony of activity rhythms. Rainfall did not consistently produce a synchronized pulse of activity in the population. We propose individually based rhythms, associated with differing optimal thermoregulatory requirements for foraging and digestion. In studies of population ecology, individual activity rhythms may explain day‐to‐day variation in encounter rates.