bluuebunny/crossref_metadata_2025 huggingface dataset:
An Evaluation of Nonresponse Bias in Peer, Self, and Teacher Ratings of Children's Psychosocial Adjustment
Authors: Gerrits Marleen H. , Van Den Oord Edwin J. C. G. , Voogt Robert
Published: October 2003

The last decades have shown a rapid increase in nonresponse rates. For this reason it is important to study nonresponse and think about it critically. In this article we investigated whether nonresponse affected estimates of the levels of adjustment problems in children and the correlations between these outcomes. The nonresponse was caused by parents who refused permission to interview their children at school, parents who did not return a questionnaire, teachers who did not complete the questionnaire, and parents who refused to participate in an in‐depth study, with nonresponse rates of 9%, 69%, 25%, and 46% respectively. The sample consisted of 1282 children aged 4–5 years and the dependent measures were peer‐rated sociometric status, self‐rated wellbeing at school, and teacher‐rated behaviour problems. Despite considerable nonresponse in some conditions our results showed hardly any evidence for bias. This suggested that bias cannot simply be inferred from the amount of nonresponse and that standard rules such as “nonresponse rates higher than 50% are not acceptable” lack a scientific basis. Instead, we argue that to assess non‐response bias the specific conditions and analyses of the study will need to be considered and special measures may be required.
Ten‐year Follow‐up of Adolescent‐onset Anorexia Nervosa: Psychiatric Disorders and Overall Functioning Scales
Authors: Wentz Elisabet , Gillberg Christopher , Gillberg I. Carina , Råstam Maria
Published: October 2003

The aim of this study was to assess prospectively the long‐term outcome in a representative sample of teenage‐onset anorexia nervosa (AN) in respect of psychiatric disorders and overall outcome. Fifty‐one AN cases, recruited by community screening, with a mean age of onset of 14 years, was contrasted with 51 matched comparison cases at a mean age of 24 years (10 years after AN onset). All 102 cases had been examined at ages 16 and 21 years. At 24 years all probands were interviewed regarding psychiatric disorders (SCID‐I) and overall outcome (Morgan‐Russell assessment schedule, the GAF). There were no deaths at 10‐year follow‐up. One in four in the AN group had a persisting eating disorder (ED), including three who still had anorexia nervosa. Lifetime diagnoses of affective disorders and obsessive‐compulsive disorder were over‐represented in the AN group. Outcome according to Morgan‐Russell was poor in 27%, intermediate in 29%, and good in 43%. According to the GAF, half the AN group had a poor psychosocial functioning. These were subjects with either a persisting ED or lifelong problems with social interaction or obsessive‐compulsive behaviour. Ten‐year outcome of teenage‐onset AN is favourable in the majority of cases; most individuals have recovered from their ED and have no other axis I disorder. However, half the AN group reported poor psychosocial outcome, in most cases explained by a persisting ED or chronic obsessive‐compulsive behaviour/social interaction problems.
Rethinking Maternal Sensitivity: Mothers’ Comments on Infants’ Mental Processes Predict Security of Attachment at 12 Months
Authors: Meins Elizabeth , Fernyhough Charles , Fradley Emma , Tuckey Michelle
Published: October 2003

This study investigated predictors of attachment security in a play context using a sample of 71 mothers and their 6‐month‐old infants. We sought to rethink the concept of maternal sensitivity by focusing on mothers’ ability accurately to read the mental states governing infant behaviour. Five categories were devised to assess this ability, four of which were dependent on maternal responses to infant behaviours, such as object‐directed activity. The fifth, mothers’Appropriate mind‐related comments, assessed individual differences in mothers’ proclivity to comment appropriately on their infants’ mental states and processes. Higher scores in this fifth category related to a secure attachment relationship at 12 months. Maternal sensitivity and Appropriate mind‐related comments were independent predictors of attachment security at 12 months, respectively accounting for 6.5% and 12.7% of its variance. We suggest that these findings are in line with current theorising on internal working models of attachment, and may help to explain security‐related differences in mentalising abilities.
Longitudinal Change in Parenting Associated with Developmental Delay and Catch‐up
Authors: Croft Carla , O'Connor Thomas G. , Keaveney Lisa , Groothues Christine , Rutter Michael
Published: October 2003

The current study examined the predictors of parent‐child relationship quality and developmental change in a sample of children adopted into the U.K. following severe early privation, and in a comparison sample of nondeprived, within‐country adoptees. One hundred and fifty‐eight children adopted from Romania and 52 U.K. adoptees were assessed at age 6 years; longitudinal data (age 4 and 6 years) were available on the 110 Romanian adoptees placed into U.K. homes before 24 months of age and all U.K. adoptees. Ratings of parent‐child positivity and negativity during a semistructured interaction task were obtained from coders who were blind to the child's background. Results indicated that adoptive parent‐child relationship quality was related to duration of deprivation and that cognitive/developmental delay mediated this association. The magnitude of this effect was modest and diminished over time. Longitudinal analyses revealed that positive change in parent‐child relationship quality was most marked among children who exhibited cognitive catch‐up between assessments. The direction of effects appeared to be primarily child to parent. The findings underscore the need for further research on the long‐term impact of early experiences on psychosocial development.
Preschool Developmental Pathways to Preadolescent Internalizing and Externalizing Problems
Authors: Mesman Judi , Bongers Ilja L. , Koot Hans M.
Published: October 2003

The present study investigated longitudinal pathways from specific early preschool behavioral problems (ages 2–3 years) to internalizing and externalizing problems in pre‐adolescence (ages 10–11 years), and the role of social problems at school entry (ages 4–5 years) in such pathways. Path analyses were performed using both parent and teacher reports in a sample of 251 to 346 children from the general population, depending on the availability of parent and teacher data at each time of assessment. Structural equation modeling revealed homotypic internalizing and externalizing pathways, predictions from early preschool externalizing problems to later internalizing problems, and negative predictive paths from early internalizing problems to externalizing problems in preadolescence. Cross‐informant predictions spanning 8 years were found between parent‐reported aggression and overactivity at ages 2–3 years and teacher‐reported externalizing problems at ages 10–11 years. Further, results showed that boys’ pathways were more complex and showed greater predictive validity than pathways for girls, and that social problems at school entry played a significant role in pathways to internalizing problems, but only for boys. The results are discussed from a developmental psychopathology perspective.
Block Design Performance in the Williams Syndrome Phenotype: A Problem with Mental Imagery?
Authors: Farran Emily K. , Jarrold Christopher , Gathercole Susan E.
Published: October 2003

Williams syndrome (WS) is a rare genetic disorder which, among other characteristics, has a distinctive cognitive profile. Nonverbal abilities are generally poor in relation to verbal abilities, but also show varying levels of ability in relation to each other. Performance on block construction tasks represents arguably the weakest nonverbal ability in WS. In this study we examined two requirements of block construction tasks in 21 individuals with WS and 21 typically developing (TD) control individuals. The Squares tasks, a novel twodimensional block construction task, manipulated patterns by segmentation and perceptual cohesiveness to investigate the first factor, processing preference (local or global), and by obliqueness to examine the second factor, the ability to use mental imagery. These two factors were investigated directly by the Children's Embeded Figures Test (CEFT; Witkin, Oltman, Raskin, & Karp, 1971) and a mental rotation task respectively. Results showed that individuals with WS did not differ from the TD group in their processing style. However, the ability to use mental imagery was significantly poorer in the WS group than the TD group. This suggests that weak performance on the block construction tasks in WS may relate to an inability to use mental imagery.
Handedness in Boys with Gender Identity Disorder
Authors: Zucker Kenneth J. , Beaulieu Nicole , Bradley Susan J. , Grimshaw Gina M. , Wilcox Anne
Published: October 2003

Handedness preference was assessed in 205 boys with gender identity disorder and 205 clinical control boys referred for other reasons. Boys with gender identity disorder were significantly more likely to be left‐handed than the clinical control boys (19.5% vs. 8.3%, respectively). The boys with gender identity disorder, but not the clinical control boys, also had a significantly higher rate of left‐handedness compared to three independent, general population studies of nonreferred boys (11.8%; N= 14,253) by Hardyck, Goldman, and Petrinovich (1975), Calnan and Richardson (1976), and Eaton, Chipperfield, Ritchot, and Kostiuk (1996). Left‐handedness appears to be a behavioral marker of an underlying neurobiological process associated with gender identity disorder in boys.
Predicting Early Fatherhood and Whether Young Fathers Live with Their Children: Prospective Findings and Policy Reconsiderations
Authors: Jaffee Sara R. , Caspi Avshalom , Moffitt Terrie E. , Taylor Alan , Dickson Nigel
Published: October 2003

This prospective study of a birth cohort addressed three questions. Which individual and family‐of‐origin characteristics predict the age at which young men make the transition to fatherhood? Do these same characteristics predict how long young men live with their child? Are individual differences in the amount of time fathers spend living with their child associated with the father's psychosocial characteristics in young adulthood? In this unique study, it was found that by age 26, 19% of the 499 study men had become fathers. Individual and family‐of‐origin characteristics were assessed from birth until age 15 and contemporaneous characteristics were assessed at age 26. Young men who experienced a stressful rearing environment and a history of conduct problems were more likely to become fathers at an early age and to spend less time living with their child. Of those who experienced none of the risk factors, fewer than 10% had become fathers by age 26 compared to more than 60% of those who experienced five risk factors. Fathers who lived apart from their child reported the most social and psychological difficulties in young adulthood. These findings point to individual and family‐of‐origin characteristics that might be targeted in order to delay fatherhood and increase levels of paternal involvement. However, given their troubled life histories and poor social‐psychological adjustment in young adulthood, some absent fathers might have difficulties providing positive parenting and partnering unless policy initiatives to promote intact families also support young fathers.
Practitioner Review: The Role of Direct Observation in the Assessment of Young Children
Authors: Pellegrini A. D.
Published: October 2003

In this review I examine the role of play and assessment in the lives of young children. These two seemingly opposing constructs are first defined. Next, I address a particularly important form of assessment, “high stakes” assessment, and argue that if it must be used, we should use a variety of assessment methods. One such method that I discuss in great detail is the use of direct observations of children's play. Examples of reliable and valid inferences about children's social cognitive functioning made with this family of methods are provided. Two specific observational instruments (one for observing play in the classroom and one for observing play in the playground) are presented. Recommendations for their use by practitioners are made.
Intellectual Problems Shown by 11‐year‐old Children Whose Mothers Had Postnatal Depression
Authors: Hay Dale F. , Pawlby Susan , Sharp Deborah , Asten Paul , Mills Alice , Kumar R.
Published: October 2003

The aim of the study was to examine long‐term sequelae in the children of mothers who were depressed at 3 months postpartum. In a community sample from two general practices in South London, 149 women were given psychiatric interviews at 3 months postpartum and 132 of their children (89%) were tested at 11 years of age. The children of women who were depressed at 3 months postpartum had significantly lower IQ scores. They also had attentional problems and difficulties in mathematical reasoning, and were more likely than other children to have special educational needs. Boys were more severely affected than girls, with the sex difference most pronounced on Performance IQ. The links between postnatal depression and the children's intellectual problems were not mediated by parental IQ and were not accounted for by measures of social disadvantage nor by the mother's later mental health problems. Breastfeeding did not remove the effect of the mother's illness on Full Scale IQ, but exerted its own influence on Verbal IQ and appeared to mediate the link with mathematical ability. The findings show that adverse experiences in infancy predict cognitive ability and academic performance a decade later.
Cognitive Vulnerability to Depression in 5‐year‐old Children of Depressed Mothers
Authors: Murray Lynne , Woolgar Matt , Cooper Peter , Hipwell Alison
Published: October 2003

Studies of cognitive vulnerability to depression in young children have, in the main, relied on self‐report questionnaires (e.g. of self‐esteem, attributional style). They have failed to produce convincing evidence of a cognitive vulnerability to depression in children under 8 years. In the current study latent depressive cognitions were investigated in the 5‐year‐old children (N= 94) of depressed and well mothers in a situation of mild stress, that is, the threat of losing a card deal in a modified version of the competitive children's card game “Snap”. In the context of “losing”, but not “winning”, deals, children who had been exposed to maternal depression, either in the previous 12 months or at any other time during their lifetime, were more likely than nonexposed children to express depressive cognitions (hopelessness, pessimism, and low self‐worth). The association between depressive cognitions and recent exposure to maternal depression was in part accounted for by current maternal hostility to the child. The results of this study stand in contrast to those of studies which have used questionnaire methods to assess vulnerability to depressive cognitions in this age group. They suggest that it might be important to employ ecologically realistic situations to access latent self‐cognitions in young children; and they underscore the importance, increasingly evident in research with adults and older children, of employing methods that involve the induction of low mood in order to elicit cognitions relevant to depression.
Development of the Children's Eating Behaviour Questionnaire
Authors: Wardle Jane , Guthrie Carol Ann , Sanderson Saskia , Rapoport Lorna
Published: October 2003

Individual differences in several aspects of eating style have been implicated in the development of weight problems in children and adults, but there are presently no reliable and valid scales that assess a range of dimensions of eating style. This paper describes the development and preliminary validation of a parent‐rated instrument to assess eight dimensions of eating style in children; the Children's Eating Behaviour Questionnaire (CEBQ). Constructs for inclusion were derived both from the existing literature on eating behaviour in children and adults, and from interviews with parents. They included reponsiveness to food, enjoyment of food, satiety responsiveness, slowness in eating, fussiness, emotional overeating, emotional undereating, and desire for drinks. A large pool of items covering each of these constructs was developed. The number of items was then successively culled through analysis of responses from three samples of families of young children (N= 131; N= 187; N= 218), to produce a 35‐item instrument with eight scales which were internally valid and had good test‐retest reliability. Investigation of variations by gender and age revealed only minimal gender differences in any aspect of eating style. Satiety responsiveness and slowness in eating diminished from age 3 to 8. Enjoyment of food and food responsiveness increased over this age range. The CEBQ should provide a useful measure of eating style for research into the early precursors of obesity or eating disorders. This is especially important in relation to the growing evidence for the heritability of obesity, where good measurement of the associated behavioural phenotype will be crucial in investigating the contribution of inherited variations in eating behaviour to the process of weight gain.
Feeding Behaviour in the Weaning Period
Authors: Parkinson Kathryn N. , Drewett Robert F.
Published: October 2003

Feeding behaviour in the weaning period is important theoretically and practically. The aim of the study was to develop appropriate observational codes for its description, to assess their reliability, and to examine the relationships between feeding behaviour, meal duration, and food intake. One hundred children aged 12–14 months were visited in their own homes, and two of each child's usual meals video‐recorded and analysed using direct observation. Codes were developed that distinguished between the mother feeding her child directly and assisting her child's self‐feeding, and between the child's behaviour when responding to being fed by the mother and when feeding themselves. All‐occurrence sampling was used to record counts of these feeding acts during the meals. Two observers replicated coding of 40 randomly chosen meals to determine the reliability of these counts. Except for three codes which were used very infrequently (median counts of zero over the 200 meals), reliability was high with p > .80. There was wide variation in the extent to which individual children fed themselves during meals, with only moderate consistency from meal to meal. Food intake was uncorrelated with meal duration, but correlated with the number of bites of food taken. Adjusted for the number of bites, longer meals were associated with a lower intake. When fed by the mother the child's food intake was greater than when they fed themselves, but the duration of the meals was little affected. The coding scheme is simple to use and generally reliable, and provides a means for relating more global measures of emotional or other characteristics of mealtime behaviour to feeding behaviour and nutritional intake.
Predicting Pathways of Specific Language Impairment: What Differentiates Good and Poor Outcome?
Authors: Botting Nicola , Faragher Brian , Simkin Zoë , Knox Emma , Conti‐Ramsden Gina
Published: October 2003

A group of 117 children who met criteria for Specific Language Impairment (SLI) at 7 years of age were reassessed at 11 years of age. The data gathered from both stages were used to identify predictors of good and poor outcome from earlier test assessments. Results of logistic regressions indicated that measures of narrative retelling skills and expressive syntax were the strongest predictors of overall prognosis. This finding persisted when a nonverbal measure was included as a predictor alongside language measures in the regression model. There was found to be a lack of independent predictive contribution of early measures of articulation to later overall prognosis. Demographic factors (maternal education and family income) were not differently distributed across outcome groups. The theoretical and practical implications of the findings are discussed.
Child Abuse and Performance Task Assessments of Executive Functions in Boys
Authors: Mezzacappa Enrico , Kindlon Dan , Earls Felton
Published: October 2003

We examined executive functions using performance tasks in 126 boys aged 6 to 16 years, who attended public schools and therapeutic schools for children with emotional and behavioral problems. Children were further grouped based on the presence or absence of substantiated abuse histories. Based on their abuse histories and schools of origin, children were classified as Therapeutic, Abused (TA, N= 25), Therapeutic, Nonabused (TN, N= 52), and Public School (PS, N= 48). Controlling IQ and medication status, we compared children in the three groups on teacher ratings of behavior, on experimenter observations of behavior during testing, and on performance tasks challenging the capacities to inhibit an act in progress, and to passively avoid responses associated with adverse consequences. We examined mean group differences in symptoms, behaviors, and task performance, as well as differential age‐dependent changes in these dimensions. Independent of abuse history, therapeutic school children demonstrated comparable levels of internalizing and externalizing symptoms, and comparable levels of redirections to task during testing sessions, that were significantly higher than those of the public school children. Both groups of therapeutic school children also showed comparable overall performance on the capacities to inhibit an act in progress, and to passively avoid responses associated with adverse consequences that were poorer than the performance of children from the public school. Children with histories of substantiated abuse showed diminished improvement with increasing age in the capacity to passively avoid responses associated with adverse consequences when compared not only to the public school children, but also to the children from the therapeutic schools without histories of abuse. Our findings complement reports of behavioral observations of abused children, and reports associating child abuse with altered cognitive development in other areas of competence. They suggest that child abuse may negatively influence the expected developmental progression of competence in certain executive functions. This in turn could have implications for the nature and the persistence of certain forms of psychopathology associated with abuse and poor self‐control. Given the cross‐sectional nature of our data, however, longitudinal developmental studies of the relations between child abuse and executive functions are needed to elucidate the influence of abuse on the growth and development of such organizing principles of behavioral self‐regulation.
Social Understanding in Autism: Eye Gaze as a Measure of Core Insights
Authors: Ruffman Ted , Garnham Wendy , Rideout Paul
Published: October 2003

Twenty‐eight children with autism and 33 MLD children were given two tasks tapping social understanding and a control task tapping probability understanding. For each task there was a measure of eye gaze (where children looked when anticipating the return of a story character or an object) and a verbal measure (a direct question). We found that eye gaze was better than verbal performance at differentiating children with autism from children with MLD. Children with autism did not look to the correct location in anticipation of the story character's return in the social tasks, but they did look to the correct location in the nonsocial probability task. We also found that within the autistic group, children who looked least to the correct location were rated as having the most severe autistic characteristics. Further, we found that whereas verbal performance correlated with general language ability in the autistic group, eye gaze did not. We argue that: (a) eye gaze probably taps unconscious but core insights into social behavior and as such is better than verbal measures at differentiating children with autism from mentally handicapped controls, (b) eye gaze taps either spontaneous processes of simulation or rudimentary pattern recognition, both of which are less based in language, and (c) the social understanding of children with autism is probably based mostly on verbally mediated theories whereas control children also possess more spontaneous insights indexed by eye gaze.
Implementing a Multi‐Agency Needs Assessment in a Secure Adolescent Unit
Authors: Hindley Nick , James Anthony C. , Gurney‐Smith Ben
Published: October 2003

Background:  Process issues in relation to the introduction of standardised needs assessments have traditionally received little attention.

Method:  Descriptive approach to the theoretical and practical aspects of the development of an assessment process using a structured instrument, the clinical version of the Salford Needs Assessment Schedule for Adolescents (SNASA). The context for this was child and adolescent mental health liaison with a social services secure unit for adolescent boys.

Results:  The use of a structured process model facilitated the implementation process enormously. Positive outcomes were experienced by participating staff at different levels within agency hierarchies and by the wider professional network.

Conclusions:  Successful implementation and continuing use of structured assessments and other instruments in multi‐agency settings requires attention to process issues. Such attention needs to be concerted and ongoing. Within child and adolescent mental health settings such an approach may be helpful beyond the field of secure adolescent care.
Honeymoons and Liabilities: The Relationship between Age and Performance in Research and Development Alliances
Authors: Deeds David L. , Rothaermel Frank T.
Published: October 2003

The use of strategic alliances by technology ventures has increased dramatically over the last 20 years. During this period companies not only have increased the use of alliances but also have used them in more strategically important areas, particularly in research and development (R&D) and new product development. Thus, successful management of strategic alliances in high‐technology industries has become critical to a firm's new product development and ultimately to firm performance. Yet little is known about what determines the performance of individual alliances. This article examines the relationship between the age of an alliance and the performance of the alliance.

Two competing hypotheses regarding the form of the functional relationship between alliance age and alliance performance are developed and are tested. First, a liability of newness hypothesis, which posits that alliance performance increases in a linear fashion over time, is tested. Then a honeymoon hypothesis, which posits that the relationship between age and alliance performance is nonlinear with alliance performance decreasing initially but increasing over time, is tested. It is proposed further here that alliances that are more important to the focal firm exhibit longer honeymoon periods.

A measure of individual alliance performance is developed based on our field study in the biotechnology industry. The competing hypotheses are tested using regression analysis on the sample of 115 R&D alliances. Then the analysis is extended by splitting the sample into high‐ and low‐importance alliances to enhance the robustness of the findings. Further, such a split‐sample approach enables testing for a potential moderating effect of alliance importance on the hypothesized relationship between alliance age and alliance performance.

The results suggest that the relationship between age and alliance performance seems to be U‐shaped curvilinear rather than linear, with the minimum point of alliance performance occurring after approximately four and one‐half years. Thus, the results indicate that strategic alliances appear to face a liability of adolescence rather than a liability of newness. Contrary to expectations, it also is found that important alliances exhibit generally shorter honeymoons.
Does an Industry Effect Exist for Initial Public Offerings?
Authors: Akhigbe Aigbe , Borde Stephen F. , Whyte Ann Marie
Published: October 2003

We examine the impact of initial public offerings (IPOs) on rival firms and find that the valuation effects are insignificant. This insignificant reaction can be explained by offsetting information and competitive effects. Significant positive information effects are associated with IPOs in regulated industries and the first IPO in an industry following a period of dormancy. Significant negative competitive effects are associated with larger IPOs in competitive industries, those in relatively risky industries, those in high‐performing industries, and those in the technology sector. IPO firms that use the proceeds for debt repayment appear to represent a more significant competitive threat to rival firms relative to IPO firms that use their proceeds for other purposes.
Motives in the Acquisitions of NASDAQ Targets during the Aftermath of the 1987 Crash
Authors: Gondhalekar Vijay , Bhagwat Yatin
Published: October 2003

After the crash of 1987, the Nasdaq composite index stayed below the precrash level for nearly two years. Takeover activity surged in this after‐crash period. We compare the motives in the acquisitions of Nasdaq targets during the after‐crash period with those in the ten‐year period before the crash. We find that the announcement period return to acquirers and the proportion of acquirers with positive gains declines in the after‐crash period. For both the periods, agency is the motive for takeovers that have negative total gains (acquirer + target), but synergy and hubris are comotives for takeovers that have positive total gains. The proportion of takeovers in which the managers of acquirers act against the interest of the shareholders increases after the crash.
SUBORBITS IN INFINITE PRIMITIVE PERMUTATION GROUPS
Authors: EVANS DAVID M.
Published: October 2003

For every infinite cardinal κ, we construct a primitive permutation group which has a finite suborbit
paired with a suborbit of size κ. This answers a question of Peter M. Neumann.
COMPLETE INTERSECTIONS IN RELATION TO A PAPER
OF B. J. BIRCH
Authors: ALEKSANDROV A. G. , MOROZ B. Z.
Published: October 2003

A new property of a complete intersection in a graded Noetherian ring is proved; this result, in conjunction
with the Jacobian criterion, is then applied to the description of the loci of singularities in a family of
affine varieties introduced in a well-known paper on forms of many variables.
ON ALGEBRAIC AND GEOMETRIC DIMENSIONS FOR GROUPS WITH TORSION
Authors: BRADY NOEL , LEARY IAN J. , NUCINKIS BRITA E. A.
Published: October 2003

Various notions of dimension for discrete groups are compared. A group is exhibited that acts with finite
stabilizers on an acyclic 2-complex in such a way that the fixed point subcomplex for any non-trivial
finite subgroup is contractible, but such that the group does not admit any such action on a contractible
2-complex. This group affords a counterexample to a natural generalization of the Eilenberg–Ganea
conjecture.
Effects of Ischaemia on Subsequent Exercise‐Induced Oxygen Uptake Kinetics in Healthy Adult Humans
Authors: Walsh Michael L. , Takahashi Aya , Endo Masako , Miura Akira , Fukuba Yoshiyuki
Published: October 2003

Leg muscles were occluded (33 kPa) prior to exercise to determine whether the induced metabolic changes, and reactive hyperaemia upon occlusion release just prior to the exercise, would accelerate the subsequent oxygen consumption (V̇O2) response. Eight subjects performed double bouts (6 min duration, 6 min rest in‐between) of square wave leg cycle ergometry both below and above their lactate threshold (LT). Prior to exercise, large blood pressure cuffs were put around the upper thighs. Occlusion durations were 0 min (control), 5 min and 10 min. Ischaemia was terminated within 5 s prior to exercise onset. Heart rate, V̇O2, ventilatory rate (V̇E), electromyogram (EMG) and haemoglobin/myoglobin (Hb/Mb) saturation were recorded continuously. Single exponential modelling demonstrated that, compared to control (time constant = 53.9 ± 13.9 s), ischaemia quickened the V̇O2 response (P < 0.05) for the first bout of exercise above LT (time constant = 48.3 ± 14.5 s) but not to any other exercise bout below or above LT. The 3‐6 min integrated EMG (iEMG) slope was correlated to the 3‐6 min V̇O2 slope (r = 0.73). Hb/Mb saturation verified the ischaemia but did not show a consistent relation to the V̇O2 time course. Reactive hyperaemia induced a faster V̇O2 response for work rates above LT. The effect, while significant, was not large considering the expected favourable metabolic and circulatory changes induced by ischaemia.
Nitric Oxide Facilitates Vagal Control of Heart Rate Via Actions in the Cardiac Parasympathetic Ganglia of the Anaesthetised Dog
Authors: Markos F. , Snow H. M. , Kidd C. , Conlon K.
Published: October 2003

The effects of neuronal inhibition of nitric oxide (NO) production on the bradycardia resulting from stimulation of preganglionic and postganglionic parasympathetic fibres were investigated in an anaesthetised dog preparation following transection of the cervical vagi and in the presence of a β‐adrenoreceptor antagonist. Injection of 1‐(2‐trifluoromethylphenyl) imidazole (TRIM), an inhibitor of neuronally released NO, into the sinus node artery reduced the bradycardia evoked by right cervical vagal stimulation. In contrast, when the response to preganglionic stimulation had been abolished by hexamethonium (10 mg kg−1), the bradycardia following stimulation of postganglionic parasympathetic fibres on the atrial epicardium was unaffected by TRIM. First, these results confirm the facilitatory actions of neuronally released NO on vagal heart responses in the dog. Second, they indicate that this modulatory and facilitatory role of NO is likely to be exerted at vagal preganglionic‐postganglionic synaptic mechanisms in the cardiac parasympathetic ganglia and not at the postganglionic‐sinoatrial node synapse.
C‐Nociceptor Activation of Hypothalamic Neurones and the Columnar Organisation of Their Projections to the Periaqueductal Grey in the Rat
Authors: Lumb B. M. , Parry D. M. , Semenenko F. M. , McMullan S. , Simpson D. A. A.
Published: October 2003

The induction of Fos protein was used to localise hypothalamic neurones activated by ramps of noxious skin heating delivered at a rate of 2.5 °C s−1 to preferentially activate C‐nociceptors. This was combined with retrograde transport of cholera toxin subunit B from identified ‘pressor’ and ‘depressor’ sites in the dorsolateral/lateral or the ventrolateral columns of the periaqueductal grey. Fos‐positive neurones were found throughout the rostral hypothalamus. Despite this wide distribution, those neurones double labelled retrogradely from the periaqueductal grey were focused in the lateral area of the anterior hypothalamus. More than 20% of Fos‐positive neurones in this region projected to depressor sites in the ventrolateral periaqueductal grey, and 10% projected to its dorsolateral/lateral sector. These results are discussed in relation to the peripheral inputs to hypothalamic‐midbrain pathways and their role in the cardiovascular responses to different components of the pain signal.
Tetrodotoxin Block of A‐Fibre Conduction and its Effect on Reflex Responses Evoked by Electrical Stimulation of the Sural Nerve in the Decerebrated Rabbit
Authors: Clarke R. W. , Brown‐Reid K. , Kasher P. , Harris J.
Published: October 2003

In the present study, we have investigated the viability of using tetrodotoxin (TTX) to induce selective blockade of myelinated fibre conduction in rabbit sural nerve, and explored some aspects of reflexes evoked by non‐myelinated sural nerve afferents before and after application of TTX. In rabbits decerebrated under halothane‐nitrous oxide anaesthesia, application of 30 nM TTX to the desheathed sural nerve completely blocked Aβ and Aδ waves of the compound action potential evoked by electrical stimulation of the nerve at 95 times threshold. The amplitude of C‐fibre volleys evoked by these stimuli was reduced to a mean of 60% of pre‐treatment values. Reflexes evoked in medial gastrocnemius motoneurones by sural nerve stimulation showed corresponding changes after TTX treatment, with activation latency increasing from 5‐7 ms in the control state to > 100 ms after TTX application. Temporal summation (wind up) in long latency reflexes (> 100 ms) was significantly enhanced after application of TTX. These data show that low concentrations of TTX can selectively block conduction in rabbit sural nerve A‐fibres, providing a method for studying the central actions of non‐myelinated C‐fibres in isolation.
The Influence of Initial Elastic Surface Stresses on Instrumented Sharp Indentation
Authors: Giannakopoulos A. E.
Published: October 2003

The present work examines the influence of pre-existing, elastic surface stresses on instrumented sharp indentation. The surface is modeled as a homogeneous and isotropic elastoplastic solid in the context of linear elasticity and Mises plasticity with isotropic strain hardening and associative flow rule. Prior to indentation, a homogeneous, biaxial, elastic stress state may exist in the substrate. The influence of the initial elastic surface stresses on the force-depth response of instrumented sharp indentation tests, such as Vickers and Berkovich, was analyzed. The unique connection of the indentation loading response and the average initial stress is based on a relation of the stresses right under the indenter, which holds universally for nearly incompressible materials.
Instability Boundary for Rotor-Hydrodynamic Bearing Systems, Part 1: Jeffcott Rotor With External Damping
Authors: Guo Zenglin , Kirk R. Gordon
Published: October 2003

The instability of rotor-hydrodynamic bearing systems has been a major concern in high-speed rotating machine design. The threshold speed is usually considered to be a barrier that cannot be driven through. However, if some kind of external damping is introduced, the situation may be different. The study is first conducted on the Jeffcott rotor with external damping for both vertical and horizontal configurations. For the vertical system, it has been shown by both analytical and numerical study that there is a threshold speed at which the rotor will get into an upper stable region from the previous unstable region. For the horizontal system, an extended Lund Stability Method is presented which proves that the system may have two threshold speeds. This results in a stability pattern which has one region of instability sandwiched between two regions of stability. Then, the study is expanded to the extended Jeffcott rotor. With the introduction of equivalent journal mass, another threshold speed appears which forms a top and final boundary to the stable operation of the rotor. The results of a numerical study show that with the external damping increased, the first several unstable regions can be reduced or eradicated. The external damping has little effect on the last top threshold which is mainly dependent on the value of journal mass. It has also been shown that a certain value of external damping and small journal mass would be very beneficial to improve the stability characteristics of the system over the entire speed range.
Instability Boundary for Rotor-Hydrodynamic Bearing Systems, Part 2: Rotor With External Flexible Damped Support
Authors: Guo Zenglin , Kirk R. Gordon
Published: October 2003

A rotor-hydrodynamic bearing system having external flexible damped bearing supports is more complicated than that discussed in Part 1 but it can provide a means to improve the stability of the rotor system. A model for both vertical and horizontal analysis is developed first. Then, the analytical study on the vertical rotor is conducted. The results show that there can be up to four threshold speeds in this configuration that form a consecutive regional pattern, taking turns by stable or unstable regions. Furthermore, the numerical calculation by MATLAB is carried out to obtain the results for the horizontal system. The stability maps for various parametric configurations are presented. It has been shown that the value of support damping has a strong effect on the first several lower threshold speeds. But it has little effect on the last top threshold speed which is mainly determined by the portion of journal mass. Within a certain range of external damping value, the first several regions of instability can be reduced or eradicated. As far as the entire stability map is concerned, there is an optimum range of support damping that can make the rotor have only one top threshold speed over the entire running speed range. When the support stiffness is increased, the system stability map becomes narrow which means a small support stiffness is good for broadening the range of optimum external damping.
Air Entrainment Processes in a Circular Plunging Jet: Void-Fraction and Acoustic Measurements
Authors: Chanson H. , Manasseh R.
Published: October 2003

Circular plunging jets were studied by both void fraction and acoustic techniques. There were two aims: to measure the structure of the jet flow and its regimes as a function of jet speed and free-jet length; and to develop and validate the acoustic measurement technique in the developing flow. Void fractions and bubble count rates were measured in the developing shear layer of a large-size plunging jet d1=25 mm. The data compared well with a solution of an advective diffusion equation and showed an increased air entrainment rate with increasing free-jet length for x1/d1⩽12. The acoustic data were processed by a novel technique to extract both bubble count and bubble size data. Three plunging jet flow regimes were noted. Near inception, acoustic pulses are isolated and indicate individual bubble entrainment as observable visually. Above a characteristic jet velocity, the number of the bubble pulses increases sharply although bubbles are still produced intermittently. At higher velocities, bubble production becomes quasi-continuous. The study suggests that an acoustic technique calibrated through detailed laboratory measurements can provide useful, absolute data in high-void fraction flows. The robust acoustic sensor can then be used in hostile industrial or environmental flows where more delicate instruments are impractical.
On the Mechanical Modeling of Functionally Graded Interfacial Zone With a Griffith Crack: Anti-Plane Deformation
Authors: Wang Y.-S. , Huang G.-Y. , Dross D.
Published: October 2003

An analytical model is developed for a functionally graded interfacial zone between two dissimilar elastic solids. Based on the fact that an arbitrary curve can be approached by a continuous broken line, the interfacial zone with material properties varying continuously in an arbitrary manner is modeled as a multilayered medium with the elastic modulus varying linearly in each sublayer and continuous on the interfaces between sublayers. With this new multilayered model, we analyze the problem of a Griffith crack in the interfacial zone. The transfer matrix method and Fourier integral transform technique are used to reduce the mixed boundary-value problem to a Cauchy singular integral equation. The stress intensity factors are calculated. The paper compares the new model to other models and discusses its advantages.
Turbulent Boundary Layers Over Surfaces Smoothed by Sanding
Authors: Schultz Michael P. , Flack Karen A.
Published: October 2003

Flat-plate turbulent boundary layer measurements have been made on painted surfaces, smoothed by sanding. The measurements were conducted in a closed return water tunnel, over a momentum thickness Reynolds number Reθ range of 3000 to 16,000, using a two-component laser Doppler velocimeter (LDV). The mean velocity and Reynolds stress profiles are compared with those for smooth and sandgrain rough walls. The results indicate an increase in the boundary layer thickness (δ) and the integral length scales for the unsanded, painted surface compared to a smooth wall. More significant increases in these parameters, as well as the skin-friction coefficient Cf were observed for the sandgrain surfaces. The sanded surfaces behave similarly to the smooth wall for these boundary layer parameters. The roughness functions ΔU+ for the sanded surfaces measured in this study agree within their uncertainty with previous results obtained using towing tank tests and similarity law analysis. The present results indicate that the mean profiles for all of the surfaces collapse well in velocity defect form. The Reynolds stresses also show good collapse in the overlap and outer regions of the boundary layer when normalized with the wall shear stress.
A Displacement Equivalence-Based Damage Model for Brittle Materials—Part II: Verification
Authors: Liu Y. , Soh C. K. , Dong Y. , Yang Y.
Published: October 2003

This paper focuses on the application of the damage model for brittle materials proposed in the preceding paper on theory. The evolution rule of damage derived using the Onsager relations is specified according to the experimental observation. The loading-unloading condition is discussed and the tangent modulus is derived. Then, the determination of the modal parameters is presented. For verification, the proposed model is applied to concrete under uniaxial and biaxial loading, and the numerical results are compared with those of other researchers and with the experimental results. The results are generally in good agreement and the proposed model is considered worthy for further research work.
Stroh-Like Complex Variable Formalism for the Bending Theory of Anisotropic Plates
Authors: Hwu C.
Published: October 2003

Based upon the knowledge of the Stroh formalism and the Lekhnitskii formalism for two-dimensional anisotropic elasticity as well as the complex variable formalism developed by Lekhnitskii for plate bending problems, in this paper a Stroh-like formalism for the bending theory of anisotropic plates is established. The key feature that makes the Stroh formalism more attractive than the Lekhnitskii formalism is that the former possesses the eigenrelation that relates the eigenmodes of stress functions and displacements to the material properties. To retain this special feature, the associated eigenrelation and orthogonality relation have also been obtained for the present formalism. By intentional rearrangement, this new formalism and its associated relations look almost the same as those for the two-dimensional problems. Therefore, almost all the techniques developed for the two-dimensional problems can now be applied to the plate bending problems. Thus, many unsolved plate bending problems can now be solved if their corresponding two-dimensional problems have been solved successfully. To illustrate this benefit, two simple examples are shown in this paper. They are anisotropic plates containing elliptic holes or inclusions subjected to out-of-plane bending moments. The results are simple, exact and general. Note that the anisotropic plates treated in this paper consider only the homogeneous anisotropic plates. If a composite laminate is considered, it should be a symmetric laminate to avoid the coupling between stretching and bending behaviors.