bluuebunny/crossref_metadata_2025 huggingface dataset:
Multivariate Elliptically Contoured Distributions for Repeated Measurements
Authors: Lindsey J. K.
Published: May 2004

Summary. The multivariate power exponential distribution, a member of the multivariate elliptically contoured family, provides a useful generalization of the multivariate normal distribution for the modeling of repeated measurements. Both light and heavy tailed distributions are included. The covariance matrix retains its interpretation so that it can easily be structured for serial dependence and several levels of variance components. A crossover trial on insulin applied to rabbits, with a series of repeated measurements within each period, is analyzed by means of this distribution using autocorrelation and two levels of variance components.
Model Choice and Influential Cases for Survival Studies
Authors: Wei Wen Hsiang , Su Ju Shiang
Published: May 2004

Summary.Deletion diagnostics are developed for identifying observations that influence the estimates of regression parameters and the mixture parameter in the families of relative risk functions for failure time data. The diagnostic for the regression parameters is a generalization of Cain and Lange's (1984,Biometrics40, 493–499) measure of individual influence. The generalizations of martingale residuals, Schoenfeld's partial residuals (1982,Biometrika69, 239–241), and score residuals by Therneau, Grambsch, and Fleming (1990,Biometrika77, 147–160) are also obtained. The influence of some observations on regression parameters can be drastically modified as the mixture parameter changes, even for a very small change. In addition, adding or deleting some observations might result in choosing different models. The diagnostics are applied to a family proposed by Guerrero and Johnson (1982,Biometrika69, 309–314). One illustrative example is presented.
A Hierarchical Bayesian Model to Predict the Duration of Immunity toHaemophilus InfluenzasType B
Authors: Auranen Kari , Eichner Martin , Käyhty Helena , Takala Aino K. , Arjas Elja
Published: May 2004

Summary.A hierarchical Bayesian regression model is fitted to longitudinal data onHaemophilus influenzaetype b (Hib) serum antibodies. To estimate the decline rate of the antibody concentration, the model accommodates the possibility of unobserved subclinical infections with Hib bacteria that cause increasing concentrations during the study period. The computations rely on Markov chain Monte Carlo simulation of the joint posterior distribution of the model parameters. The model is used to predict the duration of immunity to subclinical Hib infection and to a serious invasive Hib disease.
Methodology for Estimating the Abundance of Rare Animals: Seabird Nesting on North East Herald Cay
Authors: Welsh A. H. , Cunningham R. B. , Chambers R. L.
Published: May 2004

Summary. We discuss the problem of estimating the number of nests of different species of seabirds on North East Herald Cay based on the data from a 1996 survey of quadrats along transects and data from similar past surveys. We consider three approaches based on different plausible models, namely a conditional negative binomial model that allows for additional zeros in the data, a weighting approach (based on a heteroscedastic regression model), and a transform‐both‐sides regression approach. We find that the conditional negative binomial approach and a linear regression approach work well but that the transform‐both‐sides approach should not be used. We apply the conditional negative binomial and linear regression approaches with poststratification based on data quality and availability to estimate the number of frigatebird nests on North East Herald Cay.
Weighted Normality‐Based Estimator in Correcting Correlation Coefficient Estimation Between Incomplete Nutrient Measurements
Authors: Wang C. Y.
Published: May 2004

Summary. Consider the problem of estimating the correlation between two nutrient measurements, such as the percent energy from fat obtained from a food frequency questionnaire (FFQ) and that from repeated food records or 24‐hour recalls. Under a classical additive model for repeated food records, it is known that there is an attenuation effect on the correlation estimation if the sample average of repeated food records for each subject is used to estimate the underlying long‐term average. This paper considers the case in which the selection probability of a subject for participation in the calibration study, in which repeated food records are measured, depends on the corresponding FFQ value, and the repeated longitudinal measurement errors have an autoregressive structure. This paper investigates a normality‐based estimator and compares it with a simple method of moments. Both methods are consistent if the first two moments of nutrient measurements exist. Furthermore, joint estimating equations are applied to estimate the correlation coefficient and related nuisance parameters simultaneously. This approach provides a simple sandwich formula for the covariance estimation of the estimator. Finite sample performance is examined via a simulation study, and the proposed weighted normality‐based estimator performs well under various distributional assumptions. The methods are applied to real data from a dietary assessment study.
Testing for Differences in Survival with Delayed Ascertainment
Authors: Fine Jason P. , Tsiatis Anastasios A.
Published: May 2004

Summary. During the interim stages of most large‐scale clinical trials, knowledge that a patient is alive or dead is usually not up‐to‐date. This is due to the pattern of patient visits to hospitals as well as the administrative set‐up used by the study to obtain information on vital status. On a two‐armed study, if the process of ascertaining vital status is not the same in both treatment groups, then the standard method of testing based on the logrank statistic may not be applicable. Instead, an ad hoc modification to the logrank test, which artificially truncates follow‐up prior to the time of analysis, is often used. These approaches have not been formally addressed in the literature. In the early stages of a clinical trial, severe bias or loss of power may result. For this situation, we propose a class of test statistics that extends the usual class of U statistics. Asymptotic normality is derived by reformulating the statistics in terms of counting processes and employing the theory of U statistics along with martingale techniques. For early interim analyses, a numerical study indicates that the new tests can be more powerful than the current practice when differential ascertainment is present. To illustrate the potential loss of information when lagging follow‐up to control for ascertainment delays, we reanalyze an AIDS clinical trial with the truncated logrank and the new statistics.
A Two‐Sample Comparison for Multiple Ordered Event Data
Authors: Chang Shu‐Hui
Published: May 2004

Summary. A longitudinal study is conducted to compare the process of a particular disease between two groups. The process of the disease is monitored according to which of several ordered events occur. In the paper, the sojourn time between two successive events is considered as the outcome of interest. The group effects on the sojourn times of the multiple events are parameterized by scale changes in a semiparametric accelerated failure time model where the dependence structure among the multivariate sojourn times is unspecified. Suppose that the sojourn times are subject to dependent censoring and the censoring times are observed for all subjects. A log‐rank‐type estimating approach by rescaling the sojourn times and the dependent censoring times into the same distribution is constructed to estimate the group effects and the corresponding estimators are consistent and asymptotically normal. Without the dependent censoring, the independent censoring times in general are not available for the uncensored data. In order to complete the censoring information, pseudo‐censoring times are generated from the corresponding nonparametrically estimated survival function in each group, and we can still obtained unbiased estimating functions for the group effects. A real application and a simulation study are conducted to illustrate the proposed methods.
Estimation in a Cox Proportional Hazards Cure Model
Authors: Sy Judy P. , Taylor Jeremy M. G.
Published: May 2004

Summary.Some failure time data come from a population that consists of some subjects who are susceptible to and others who are nonsusceptible to the event of interest. The data typically have heavy censoring at the end of the follow‐up period, and a standard survival analysis would not always be appropriate. In such situations where there is good scientific or empirical evidence of a nonsusceptible population, the mixture or cure model can be used (Farewell, 1982,Biometrics38, 1041–1046). It assumes a binary distribution to model the incidence probability and a parametric failure time distribution to model the latency. Kuk and Chen (1992,Biometrika79, 531–541) extended the model by using Cox's proportional hazards regression for the latency. We develop maximum likelihood techniques for the joint estimation of the incidence and latency regression parameters in this model using the nonparametric form of the likelihood and an EM algorithm. A zero‐tail constraint is used to reduce the near nonidentifiability of the problem. The inverse of the observed information matrix is used to compute the standard errors. A simulation study shows that the methods are competitive to the parametric methods under ideal conditions and are generally better when censoring from loss to follow‐up is heavy. The methods are applied to a data set of tonsil cancer patients treated with radiation therapy.
A Comparison Study of Models and Fitting Procedures for Biphasic Viral Dynamics in HIV‐1 Infected Patients Treated with Antiviral Therapies
Authors: Ding A. Adam , Wu Hulin
Published: May 2004

Summary. The study of HIV dynamics is one of the most important developments in recent AIDS research. It has led to a new understanding of the pathogenesis of HIV infection. But, although important findings in HIV dynamics have been published in prestigious scientific journals in the last 5 years, the model‐fitting procedures used in these publications have not been studied in any detail. In this paper, we evaluate the performance of four model‐fitting procedures proposed and used in biphasic HIV dynamic data analysis via extensive Monte Carlo simulations. We propose some guidelines for practitioners to select an appropriate method for their own data analysis. Real data examples from an AIDS clinical trial are provided as illustrations.
Lymphatics at the crossroads of angiogenesis and lymphangiogenesis
Authors: Scavelli Claudio , Weber Elisabetta , Aglianò Margherita , Cirulli Teresa , Nico Beatrice , Vacca Angelo , Ribatti Domenico
Published: May 2004

The lymphatic system is implicated in interstitial fluid balance regulation, immune cell trafficking, oedema and cancer metastasis. However, the sequence of events that initiate and coordinate lymphatic vessel development (lymphangiogenesis) remains obscure. In effect, the understanding of physiological regulation of lymphatic vasculature has been overshadowed by the greater emphasis focused on angiogenesis, and delayed by a lack of specific markers, thereby limiting this field to no more than a descriptive characterization. Recently, new insights into lymphangiogenesis research have been due to the discovery of lymphatic‐specific markers and growth factors of vascular endothelial growth factor (VEGF) family, such as VEGF‐C and VEGF‐D. Studies using transgenic mice overexpressing VEGF‐C and VEGF‐D have demonstrated a crucial role for these factors in tumour lymphangiogenesis. Knowledge of lymphatic development has now been redefined at the molecular level, providing an interesting target for innovative therapies. This review highlights the recent insights and advances into the field of lymphatic vascular research, outlining the most important aspects of the embryo development, structure, specific markers and methods applied for studying lymphangiogenesis. Finally, molecular mechanisms involved in the regulation of lymphangiogenesis are described.
Constructivity, Computability and Computers in Economic Theory: Some Cautionary Notes
Authors: Velupillai K. Vela
Published: May 2004

An overview of the varieties of mathematics that underpin the functioning of a computer is attempted in this paper. Against the backdrop of such an overview, the question is posed whether, and to what extent, the economist has respected these varieties of mathematics in posing economic questions and seeking answers via it, i.e. the computer. The answers are not particularly edifying for the economist.
Does maternal condition or predation risk influence small mammal population dynamics?
Authors: Banks Peter B. , Powell Fiona
Published: May 2004

There is strong debate over whether the intrinsic traits of individuals or the extrinsic environment exert the greater influence on small mammal population dynamics. We test the roles of maternal effects (an intrinsic factor) and predation risk (an extrinsic factor) in the population dynamics of wild strain house mice using a 2‐factor enclosure experiment. Pre‐release supplemental feeding with a high‐fat diet created female treatment founders that were 6–10% heavier than controls, a condition that we predicted would be passed on as a maternal effect. Predation risk was enhanced using regular application of predator (red fox Vulpes vulpes) scats. Founder populations of six females and six males released into eight, 15×15 m enclosures showed near exponential population growth over 17 weeks (maximum 3 generations). But there were no responses to either treatment in terms of survival, inherited body weights, fecundity or population size. We suggest that elevated maternal condition may have only minor and transient intergenerational effects with little long‐term consequence. We also suggest that the general significance of predator scats as a cue to predation risk to alter prey behaviour may have been overestimated. Hence our results question the role of either factor in causing long‐term responses that influence condition to affect population processes.
Competition between Eurasian otterLutra lutraand American minkMustela visonprobed by niche shift
Authors: Bonesi Laura , Chanin Paul , Macdonald David W.
Published: May 2004

Interspecific competition is one of several constraints that might prevent an individual from maximising its energy intake. When an interspecific competitor is introduced, an individual is often forced to shift its diet according to the intensity of the competitive pressure. In this paper, we explore whether the introduced American mink (Mustela visonSchreber) shifts its diet when the density of its potential competitor, the Eurasian otter (Lutra lutraL.), is increased. We compared the diets of otter and mink at the same location but at two moments in time when the relative densities of these two species were different while controlling for the abundance of aquatic prey. Mink and otters are semi‐aquatic mammals belonging to the same guild of mustelids and otters are expected to be the dominant competitor because they are larger and better at hunting underwater. The diets of otters and mink overlap to a great extent but while otters specialise mainly on aquatic prey, mink are able to exploit both aquatic and terrestrial prey. These observations prompted the hypothesis investigated in this work that at higher otter densities the diet of mink should change to include a higher proportion of terrestrial items. This hypothesis was supported by the data and at higher otter densities mink diet was observed to consist of a higher proportion of mammals and birds while fewer fish were present, although this pattern was present only in winter while no changes were observed in spring. Meanwhile the diet of otters remained basically unchanged. In the second part of the study, we investigated whether niche breadth and niche overlap between otter and mink changed at different otter densities. We found that niche overlap declined as the density of otters increased, in agreement with the prediction of habitat selection theory.
Reproduction now or later: optimal host‐handling strategies in the whitefly parasitoidEncarsia formosa
Authors: Burger Joep M. S. , Hemerik Lia , Lenteren Joop C. van , Vet Louise E. M.
Published: May 2004

We developed a dynamic state variable model for studying optimal host‐handling strategies in the whitefly parasitoidEncarsia formosaGahan (Hymenoptera: Aphelinidae). We assumed that (a) the function of host feeding is to gain nutrients that can be matured into eggs, (b) oögenesis is continuous and egg load dependent, (c) parasitoid survival is exponentially distributed and (d) parasitoids encounter hosts randomly, are autogenous and have unlimited access to non‐host food sources to obtain energy for maintenance and activity. The most important prediction of the model is that host feeding is maladaptive under field conditions of low host density (0.015 cm−2) and short parasitoid life expectancy (maximum reproductive period of 7 d). Nutrients from the immature stage that can be matured into eggs are sufficient to prevent egg limitation. Both host density and parasitoid life expectancy have a positive effect on the optimal host‐feeding ratio. Parasitoids that make random decisions gain on average only 35% (0.015 hosts cm−2) to 60% (1.5 hosts cm−2) of the lifetime reproductive success of parasitoids that make optimal decisions, independent of their life expectancy. Parameters that have a large impact on lifetime reproductive success and therefore drive natural selection are parasitoid life expectancy and the survival probability of deposited eggs (independent of host density), the number of host encounters per day (when host density is low) and the egg maturation rate and number of host types (when host density is high). Explaining the evolution of host‐feeding behaviour under field conditions requires field data showing that life expectancy in the field is not as short as we assumed, or may require incorporation of variation in host density. Incorporating variation in walking speed, parasitised host types or egg resorption is not expected to provide an explanation for the evolution of host‐feeding behaviour under field conditions.
Population and community variability in randomly fluctuating environments
Authors: Gonzalez A. , Descamps‐Julien B.
Published: May 2004

The prediction that environmental fluctuations may destabilise populations and yet stabilise aggregate community properties has remained largely untested. We examined population and community stability under constant and fluctuating temperatures in simple planktonic assemblages of differing algal richness. Temperature dependent resource competition produced a highly asymmetric community structure where algal community biomass was dominated by one species. For a given level of species richness, temperature fluctuations induced lower community covariance and thus stabilised community biomass. However, increasing algal species richness increased the variability of population abundance and growth rates, as well as population and community variability. Consumer dynamics were directly destabilised by environmental fluctuations. These results confirm recent theoretical studies suggesting a stabilising effect of environmental fluctuations at the community level. However, they also support the theoretical prediction that increasing species richness may be of limited value for community stability, most especially in asymmetric communities, when competition directly affects population variability.
Rapidly changing life history during invasion
Authors: Bøhn Thomas , Terje Sandlund Odd , Amundsen Per‐Arne , Primicerio Raul
Published: May 2004

The fish species vendace (Coregonus albula) invaded the sub‐arctic Pasvik watercourse during the second half of the 1980s, and became the dominant pelagic species in the upstream part of the watercourse within a few years. Life history traits of the pioneer population of vendace in Pasvik were recorded from 1991–2000. A rapid increase in population density in the upstream part of the watercourse was accompanied by decreased growth rates, decreased fecundity and a reduced size at first maturation. The downstream part of the watercourse showed a similar, but delayed, change in life history traits compared to the upstream part. The study documents great life history variability of a non‐native fish species entering a new environment. We discuss two co‐acting explanations for the observed patterns: (i) a density dependent response mediated by food depletion; and (ii) a pioneer strategy that allocates resources to favour reproduction at early developmental stages with a high number of offspring, trading off growth and size of offspring.
Effects of macrograzers and light on periphyton stoichiometry
Authors: Hillebrand Helmut , De Montpellier Geraldine , Liess Antonia
Published: May 2004

Ecological stoichiometry describes the biochemical constraints of trophic interactions emerging from the different nutrient content and nutrient demand of producers and consumers, respectively. Most research on this topic originates from well‐mixed pelagic food webs, whereas the idea has received far less attention in spatially structured habitats. Here, we test how light as well as grazing and nutrient regeneration by consumers affects growth and biomass of benthic primary producers. In the first laboratory experiment, we manipulated grazer presence (two different snail species plus ungrazed control), in the second experiment we factorially combined manipulation of grazer presence and light intensity. We monitored snail and periphyton biomass as well as dissolved and particulate nutrients (nitrogen and phosphorus) over time. Grazers significantly reduced algal biomass in both experiments. Grazers affected periphyton nutrient content depending on the prevailing nutrient limitation and their own body stoichiometry. In the nitrogen (N‐) limited first experiment, grazers increased N both in the periphyton and in the water column. The effect was stronger for grazers with lower N‐content. In the phosphorus (P‐) limited second experiment, grazers increased the P‐content of the periphyton, but the grazer with lower N‐content had additionally positive effects on algal N. Light reduction did not affect periphyton biomass, but increased chlorophyll‐, N‐ and P‐content of the periphyton. These experiments revealed that the indirect effects of grazers on periphyton were bound by stoichiometric constraints of nutrient incorporation and excretion.
Funding the bud bank: a review of the costs of buds
Authors: Vesk Peter A. , Westoby Mark
Published: May 2004

Retaining a reserve of buds or meristems for recovery from occasional damage is widespread among plants. Yet possession of a bud bank is not ubiquitous. Presumably there are costs to maintaining buds and for some species these costs outweigh the benefits. This paper has two themes. We estimate carbon costs of constructing and maintaining buds, and review other costs and benefits of buds in different situations. Second, we develop a framework for thinking quantitatively about the costs and benefits. Given available data and some reasonable assumptions, the absolute carbon costs of buds seem small. So the fact that many species do not maintain bud banks suggests that the benefits of buds may be negligible for them. Alternatively, buds may carry other costs. Costs of bud protection or of reserves that are coordinated with buds seem likely candidates.
Our Didcot: an inclusive arts project devised by a Learning Support Unit
Authors: Pignéguy Sarah
Published: May 2004

Sarah Pignéguy here describes a creative art s project set up to support the acquisition of social skills and to offer students the chance to experience a different style of teaching and learning. Her down‐to‐earth account shows what can be achieved on a relatively low budget in a single term.
Transgenic Bt maize and Rhopalosiphum padi (Hom., Aphididae) performance
Authors: Lumbierres Belén , Albajes Ramon , Pons Xavier
Published: May 2004

Abstract.  1. The population abundance and age structure of Rhopalosiphum padi, one of the most common maize aphid species, on transgenic Bt (expressing the Cry1Ab protein) and non‐Bt isogenic maize was studied in commercial plots during three crop seasons.

2. A higher density of aphids, particularly alates and young nymphs, occurred in Bt plots at very young maize development stages, corresponding to the settlement period, in the 3 years studied. Possible causes are discussed. After this period, there were no differences between Bt and non‐Bt maize.

3. Mortality, development, and reproduction of the offspring of alate forms of R. padi and the offspring of different generations of apterous forms fed with Bt maize were evaluated in the laboratory under controlled conditions.

4. The developmental and pre‐reproductive times of the offspring of the first generation of alatae were shorter and the intrinsic rate of natural increase (rm) higher when aphids fed on Bt maize. The opposite occurs with the offspring of the first generation of apterous mothers, which have lower nymphal and adult mortality, shorter developmental and pre‐reproductive times, a higher effective fecundity rate, and greater rm, when fed on non‐Bt maize. The differences in aphid development on the two cultivars may be linked to changes in host‐plant quality due to pleiotropic effects of the genetic modification.

5. No differences on aphid mortality, developmental and pre‐reproductive times, fecundity, and rm were found between the offspring of apterous aphids maintained on Bt or non‐Bt maize for several generations.
Optimal foraging shapes host preference of a polyphagous leafminer
Authors: Scheirs Jan , Zoebisch Tomas G. , Schuster David J. , De Bruyn Luc
Published: May 2004

Abstract.  1. Most research on host selection by arthropods is based on optimal oviposition theory. This theory, also called the oviposition preference–offspring performance hypothesis, predicts that a female will choose those hosts for oviposition on which larvae perform best. Recent studies suggested, however, that optimal foraging by adults, or the quality of the host for adult performance, might also influence host choice.

2. This study investigated whether host preference of the polyphagous leafminer Liriomyza trifolii is determined by optimal foraging and/or optimal oviposition.

3. Female realised fecundity correlated nearly perfectly with feeding and oviposition preference of L. trifolii. The relationships between host preference and the offspring performance measures were always weaker. Hosts optimal for adult nutrition were also optimal for offspring performance but not vice versa. Hence, it was concluded that optimal foraging shapes feeding and oviposition preference of L. trifolii as this is the best strategy in order to maximise female fitness.
Leaf ties as colonization sites for forest arthropods: an experimental study
Authors: Lill John T. , Marquis Robert J.
Published: May 2004

Abstract.  1. Secondary colonization of leaf shelters constructed by caterpillars has been reported from a number of systems. Both the mechanism (larval or adult movement vs. oviposition) and the cues used by arthropods in locating leaf shelters, however, have received little attention.

2. Artificial leaf shelters (i.e. leaf ties or pairs of leaves clipped together to form sandwiches) were constructed on understorey white oak (Quercus alba L.) trees and the abundance and species composition of arthropods colonizing and ovipositing on leaf pairs was examined in three treatments: occupied leaf ties (containing a leaf‐tying caterpillar), unoccupied leaf ties, and non‐tied control leaves.

3. The density of arthropods present in the occupied and unoccupied leaf ties after two weeks was seven and four times greater respectively, than non‐tied controls. The guild composition of these early colonists differed among treatments, with the highest densities of leaf chewers, scavengers, and predators in occupied ties and the lowest densities in non‐tied controls.

4. The densities of all arthropods ovipositing on leaf pairs in the occupied and unoccupied leaf tie treatments were four and three times greater than non‐tied controls. Leaf‐chewing insects (including leaf‐tiers and non‐tying inquiline species) and scavengers showed strong oviposition preferences for tied leaves. However, most species of leaf‐tying caterpillars and the psocids (Psocoptera) did not distinguish between occupied and unoccupied ties, suggesting that these groups do not use occupancy‐related cues in selecting oviposition sites.
Effects of eugregarine parasites on adult longevity in the polymorphic damselfly Mnais costalis Selys
Authors: Tsubaki Yoshitaka , Hooper Rowan E.
Published: May 2004

Abstract.  1. The relationship between the abundance of midgut parasites (eugregarine trophozooites) and the survival of hosts (field‐collected damselflies, Mnais costalis) was investigated under laboratory conditions.

2. Males of M. costalis are morphologically and behaviourally polymorphic, typically existing as clear‐winged non‐territorial sneaks and orange‐winged territorial fighters (the latter are larger in size). The survival cost of eugregarine infection for the two morphs was compared.

3. Orange‐winged males showed shorter longevity compared to clear‐winged males when they were fed at levels lower than the natural feeding rate, or when they were deprived of food. In contrast, morph longevity did not differ when they were fed until satiation every day.

4. Within each morph, the survival of damselflies was negatively correlated with the parasite abundance except when damselflies were fed until satiation.

5. The results suggest that the abundance of eugregarine parasites exerts a substantial cost, which is associated with the maintenance of alternative mating strategies, together with the higher developmental cost and energy expenditure of the fighter morph.
The effects of nutritional imbalance on compensatory feeding for cellulose‐mediated dietary dilution in a generalist caterpillar
Authors: Lee Kwang Pum , Raubenheimer David , Simpson Stephen J.
Published: May 2004

Abstract.The interactive effects of macronutrient balance [protein (P) : carbohydrate (C) ratio] and dietary dilution by cellulose on nutritional regulation and performance were investigated in the generalist caterpillarSpodoptera littoralis(Boisduval). Caterpillars were reared through the final stadium on one of 20 foods varying factorially in macronutrient content (P + C%: 42, 33.6. 25.2 or 16.8%) and P : C ratio (5 : 1, 2 : 1, 1 : 1, 1 : 2 or 1 : 5). The animals compensate by eating more of diluted foods, but suffer reduced nutrient intake in proportion to the degree of dilution. Increase in food intake with dilution is greater on balanced than imbalanced foods and this is reflected in greater reduction of dry pupal mass with dilution in the latter. Whereas dilution results in a reduction in the amount of whichever macronutrient is in excess in the food, by contrast, the ability to compensate for the deficient macronutrient in the food is unaffected by nutrient imbalance. Excess protein intake due to nutritional imbalance (diets with high P : C ratios) results in a regulatory decrease in the efficiency of retention of ingested nitrogen relative to restricted protein intake on oppositely imbalanced foods (low P : C ratios). By contrast, decreased protein intake due to dietary dilution is associated with a non‐regulatory reduction in the efficiency of retention, irrespective of P : C ratio. Dilution is similarly associated with reduced utilization efficiency of ingested carbohydrate. The ecological implications of these results are discussed.
The importance of fluctuating thermal regimes for repairing chill injuries in the tropical beetle Alphitobius diaperinus (Coleoptera: Tenebrionidae) during exposure to low temperature
Authors: Renault D. , Nedved O. , Hervant F. , Vernon P.
Published: May 2004

Abstract.  In this study, the impact of acclimation (1 month at 15 °C vs. breeding at 30 °C) and fluctuating thermal regimes (daily transfers from low temperatures to various higher temperatures for 2 h) on the cold tolerance of the tropical beetle, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae) was examined. Acclimation increased significantly the duration of survival (Lt50) at a constant 5 °C (7.7 ± 0.3 days to 9.7 ± 0.5 days). Survival of acclimated and nonacclimated beetles increased slightly at alternating temperatures of 5 °C/10 °C or 5 °C/15 °C. When daily transfer to 20 °C was applied, survival (Lt50) was improved markedly (nonacclimated: 15.5 ± 0.7 days, acclimated: 19.6 ± 0.6 days). The higher temperatures may allow progressive repair of injuries, and the effects of chilling may be repaired completely at 25 and 30 °C, a phenomenon recorded here for the first time. It is estimated that the theoretical upper threshold of chill injury (Th) of nonacclimated beetles is 15.1 °C whereas it is shifted down to 11.2 °C in acclimated beetles, which might enable this temperature to allow effective repair of injury.
Healthy Behaviors and Sources of Health Information Among Low‐Income Pregnant Women
Authors: Lewallen Lynne Porter
Published: May 2004

Abstract  This article addresses responses from two open‐ended questions, describing the healthy behaviors and sources of health information in 150 low‐income pregnant women. Data for this exploratory study were collected as part of a larger descriptive correlational study. Qualitative content analysis was used in the analysis. One hundred fifty English‐speaking pregnant women aged 18 and over were interviewed at a public prenatal clinic in the Southeastern United States at their first prenatal visit.

Health behaviors were placed into seven mutually exclusive categories: food‐related behaviors, substance‐related behavior, exercise/rest/activity, self‐awareness/appearance, learning, focus on baby, and no specific behaviors. Sources of information questions were placed into seven mutually exclusive categories: family, health personnel, reading, hearing, other people, self‐intuitive, and no response.

Low‐income pregnant women are aware of healthy behaviors and report practicing them during their pregnancies. Because family members are a common source of information for health practices, they should be included in health education efforts.
Reliability and Validity of the Chinese Version of the Worry Scale
Authors: Shiu Ann Tak‐Ying , Wong Rebecca Yee‐Man
Published: May 2004

Abstract  This article presents the findings on the development and validation of a Chinese version of the Worry Scale (WS), a measure of worry about hypoglycemia. A previously developed 16‐item WS was back‐translated and applied to 117 Chinese diabetic patients living in Hong Kong. An iterative process of factor and item analyses identified a unidimensional 10‐item Chinese WS (WS‐10), which accounted for 57.15% of the total variance. Cronbach's alpha was 0.91. Strong correlation was demonstrated between the WS‐10 and WS with 16 items (r = 0.97, p = 0.000). Comparing the level of worry about hypoglycemia between Type 1 and Type 2 diabetic patients established a contrast‐group validity of the WS‐10 (p = 0.002). Criterion validity was established by correlating the WS‐10 with the respondents' glycosylated hemoglobin (r = −0.29, p = 0.002). Test‐retest reliability using intraclass correlation (ICC) was established, ICC(1, 1) = 0.68. As the clinical administration of this scale takes less than 5 min, the Chinese WS‐10 offers a useful instrument to identify patients with high levels of worry about hypoglycemia for clinical and education interventions. It also provides public health nurses with a reliable and valid prepost measure of intervention effectiveness. The Chinese WS‐10 will facilitate further research about the effects of worry concerning hypoglycemia on self‐care behaviors with the Chinese populations.
Interview: Paul C Reilly
Authors: Crainer Stuart
Published: May 2004

With growing media scrutiny and increasing pressure for results, who'd be a CEO? A unique perspective comes from Paul C Reilly, chairman and CEO of the world's leading recruitment firm, Korn/Ferry International. Before taking over in 2001, Reilly was CEO of KPMG International. Having led two of the world's most successful service firms, Reilly shares his thoughts about being a CEO and the state of the executive job market. Interview by Stuart Crainer.
Interview: Arie de Geus
Authors: Dearlove Des
Published: May 2004

After a 38‐year career at Royal/Dutch Shell including heading the company's highly influential Group Planning department and overseeing pioneering work on scenario planning, decision making and the management of change, Arie de Geus is one of the few management practitioners to blaze a trail in the academic world. Widely credited with originating the concept of the “Learning Organisation”, de Geus is the author of the best‐selling 1997 book The Living Company and the influential Harvard Business Review article “Planning as Learning”. Interview by Des Dearlove.
Neural Synergy Between Kinetic Vision and Touch
Authors: Blake Randolph , Sobel Kenith V. , James Thomas W.
Published: May 2004

Ambiguous visual information often produces unstable visual perception. In four psychophysical experiments, we found that unambiguous tactile information about the direction of rotation of a globe whose three-dimensional structure is ambiguous significantly influences visual perception of the globe. This disambiguation of vision by touch occurs only when the two modalities are stimulated concurrently, however. Using functional magnetic resonance imaging, we discovered that touching the rotating globe, even when not looking at it, reliably activates the middle temporal visual area (MT+), a brain region commonly thought to be crucially involved in registering structure from motion. Considered together, our results show that the brain draws on somatosensory information to resolve visual conflict.
Divide and Conquer
Authors: Mitroff Stephen R. , Scholl Brian J. , Wynn Karen
Published: May 2004

Coherent visual experience requires not only segmenting incoming visual input into a structured scene of objects, but also binding discrete views of objects into dynamic representations that persist across time and motion. However, surprisingly little work has explored the principles that guide the construction and maintenance of such persisting object representations. What causes a part of the visual field to be treated as the same object over time? In the cognitive development literature, a key principle of object persistence is cohesion: An object must always maintain a single bounded contour. Here we demonstrate for the first time that mechanisms of adult midlevel vision are affected by cohesion violations. Using the object-file framework, we tested whether object-specific preview benefits—a hallmark of persisting object representations—are obtained for dynamic objects that split into two during their motion. We found that these preview benefits do not fully persist through such cohesion violations without incurring significant performance costs. These results illustrate how cohesion is employed as a constraint that guides the maintenance of object representations in adult midlevel vision.
Is the emerging non‐farm market economy the route out of poverty in Vietnam?
Authors: Van De Walle Dominique , Cratty Dorothyjean
Published: May 2004

Are the household characteristics that are good for the transition to a more diversified market‐oriented economy in Vietnam also important for reducing poverty? Or are there trade‐offs? The determinants of both poverty incidence and participation in rural off‐farm activities are modeled as functions of household and community characteristics using comprehensive national household surveys for 1993 and 1998. While there are some common causative factors, such as education and region of residence, the processes determining poverty and inhibiting diversification are clearly not the same. Participation in the emerging rural non‐farm market economy will be the route out of poverty for some, but certainly not all, of Vietnam's poor.
Firm ownership and internal labour practices in a transition economy
Authors: Friedman Jed
Published: May 2004

One feature common to many post‐socialist transition economies is a relatively compressed wage structure in the state‐owned sector. We conjecture that this compressed wage structure creates weak incentives for work effort and worker skill acquisition and thus presents adverse consequences for the entire transition economy if a substantial portion of the labour force works in the state sector. We explore firm wage incentives and worker training, as well as other labour practices and outcomes, in a transition setting with matched firm and worker data collected in one of the largest provinces of Vietnam – Ho Chi Minh City. The Vietnamese state sector exhibits a compressed wage distribution in relation to privately owned firms with foreign ownership. State wage practices stress tenure over worker productivity and their wage policies result in flatter wage–experience profiles and lower returns to education. The state work force is in greater need of formal training, a need that is in part met through direct government financing. In spite of the opportunities for government financed training and at least partly due to inefficient worker incentives, state firms, by certain measures, exhibit lower levels of labour productivity. The private sector comparison group to state firms for all of these findings is foreign owned firms. The internal labour practices of foreign firms are more consistent with a view of profit‐maximizing firms operating with no political constraints. This is not the case for Vietnamese de novo private firms that exhibit much more idiosyncratic behaviour and whose labour practices are often indistinguishable from state firms. The exact reasons for this remain a topic of on‐going research yet we conjecture that various private sector constraints, including limited access to formal capital, play an important role.
Character‐state space versus rate of evolution in phylogenetic inference
Authors: Simmons Mark P. , Reeves Aaron , Davis Jerrold I.
Published: May 2004

With only four alternative character states, parallelisms and reversals are expected to occur frequently when using nucleotide characters for phylogenetic inference. Greater available character‐state space has been described as one of the advantages of third codon positions relative to first and second codon positions, as well as amino acids relative to nucleotides. We used simulations to quantify how character‐state space and rate of evolution relate to one another, and how this relationship is affected by differences in: tree topology, branch lengths, rate heterogeneity among sites, probability of change among states, and frequency of character states. Specifically, we examined how inferred tree lengths, consistency and retention indices, and accuracy of phylogenetic inference are affected. Our results indicate that the relatively small increases in the character‐state space evident in empirical data matrices can provide enormous benefits for the accuracy of phylogenetic inference. This advantage may become more pronounced with unequal probabilities of change among states. Although increased character‐state space greatly improved the accuracy of topology inference, improvements in the estimation of the correct tree length were less apparent. Accuracy and inferred tree length improved most when character‐state space increased initially; further increases provided more modest improvements. © The Willi Hennig Society 2004.
Investigation of a peroxisome proliferator‐activated receptor gamma haplotype effect on meat quality and carcass traits in pigs
Authors: Grindflek E. , Hoen N. , Sundvold H. , Rothschild M. F. , Plastow G. , Lien S.
Published: May 2004

Peroxisome proliferator‐activated receptor gamma (PPARG) is a key transcription factor that controls adipocyte differentiation and fat deposition in mammals. The primary goal of this study was to investigate PPARG as a candidate gene for meat quality and carcass traits in swine. Part of the PPARG promoter, along with the most 5′‐proximal exon of the gene, was amplified by PCR and subsequently screened for polymorphisms by sequencing. A Met59Val substitution was detected in the porcine PPARG gene along with four polymorphisms in the promoter region of the adipose‐specific PPARG2. Three of these polymorphisms were chosen for genotyping and tested for association with meat quality, carcass and growth traits, according to the candidate gene approach. More than 1500 animals from different lines and populations were used in the study with records for meat quality and carcass traits. No convincing associations were found between the traits investigated and the PPARG genotypes. It does not appear that variation at the PPARG locus is affecting meat quality, carcass or growth traits in the pig populations studied.
Characterization of open reading frame‐expressed sequence tags generated from Bos indicus and B. taurus mammary gland cDNA libraries
Authors: da Mota A. F. , Sonstegard T. S. , Van Tassell C. P. , Shade L. L. , Matukumalli L. K. , Wood D. L. , Capuco A. V. , Brito M. A. P. , Connor E. E. , Martinez M. L. , Coutinho L. L.
Published: May 2004

Sequence‐based gene expression data are used to interpret results from functional genomic and proteomics studies. Although more than 300 000 bovine‐expressed sequence tags (ESTs) are available in public databases, a more thorough and directed sampling of the expressed genome is needed to identify new transcripts and improve assembly and annotation of existing transcript sequences. Accordingly, we examined the utility of constructing cDNA libraries synthesized by arbitrarily primed RT‐PCR of mRNA from tissues not well represented in the publicly available bovine EST database. A total of 33 cDNA libraries were constructed from healthy and infected mammary gland tissues of Brazilian Gir and Holstein cattle. This series of libraries was used to generate 6481 open reading frame‐expressed sequence tags (ORESTES) that assembled into 1798 unique sequence elements of which, 1157 did not significantly match sequence assemblies available in the Bos taurus gene index. However, a total of 264 of these 1157 sequence elements aligned with mouse and human expressed sequences demonstrating that ORESTES is an effective resource for discovery of novel expressed sequences in cattle. Furthermore, comparison of the alignment position of bovine ORESTES‐derived sequence elements to human gene reference sequences suggested that the priming events for cDNA synthesis more often occurred at the central portion of a transcript, which may have contributed to the relatively high rate of novel sequence discovery.