Three-dimensional shape variation of talar surface morphology in hominoid primates.

The hominoid foot is of particular interest to biological anthropologists, as changes in its anatomy through time reflect the adoption of terrestrial locomotion, particularly in species of Australopithecus and Homo. Understanding the osteological morphology associated with changes in whole foot function and the development of the plantar medial longitudinal foot arch are key to understanding the transition through habitual bipedalism in australopithecines to obligate bipedalism and long-distance running in Homo. The talus is ideal for studying relationships between morphology and function in this context, as it is a major contributor to the adduction-abduction, plantar-dorsal flexion and inversion-eversion of the foot, and transmits all forces encountered from the foot to the leg. The talar surface is predominantly covered by articular facets, which have different quantifiable morphological characters, including surface area, surface curvature and orientation. The talus also presents challenges to the investigator, as its globular shape is very difficult to quantify accurately and reproducibly. Here we apply a three-dimensional approach using type 3 landmarks (slid semilandmarks) that are geometrically homologous to determine overall talar shape variations in a range of living and fossil hominoid taxa. Additionally, we use novel approaches to quantify the relative orientations and curvatures of talar articular facets by determining the principal vectors of facet orientation and fitting spheres to articular facets. The resulting metrics are analysed using phylogenetic regressions and principal components analyses. Our results suggest that articular surface curvatures reflect locomotor specialisations with, in particular, orangutans having more highly curved facets in all but the calcaneal facet. Similarly, our approach to quantifying articular facet orientation appears to be effective in discriminating between extant hominoid species, and may therefore provide a sound basis for the study of fossil taxa and evolution of bipedalism in Australopithecus and Homo.

Finite element micro-modelling of a human ankle bone reveals the importance of the trabecular network to mechanical performance: new methods for the generation and comparison of 3D models.

Most modelling of whole bones does not incorporate trabecular geometry and treats bone as a solid non-porous structure. Some studies have modelled trabecular networks in isolation. One study has modelled the performance of whole human bones incorporating trabeculae, although this required considerable computer resources and purpose-written code. The difference between mechanical behaviour in models that incorporate trabecular geometry and non-porous models has not been explored. The ability to easily model trabecular networks may shed light on the mechanical consequences of bone loss in osteoporosis and remodelling after implant insertion. Here we present a Finite Element Analysis (FEA) of a human ankle bone that includes trabecular network geometry. We compare results from this model with results from non-porous models and introduce protocols achievable on desktop computers using widely available softwares. Our findings show that models including trabecular geometry are considerably stiffer than non-porous whole bone models wherein the non-cortical component has the same mass as the trabecular network, suggesting inclusion of trabecular geometry is desirable. We further present new methods for the construction and analysis of 3D models permitting: (1) construction of multi-property, non-porous models wherein cortical layer thickness can be manipulated; (2) maintenance of the same triangle network for the outer cortical bone surface in both 3D reconstruction and non-porous models allowing exact replication of load and restraint cases; and (3) creation of an internal landmark point grid allowing direct comparison between 3D FE Models (FEMs).

Finite element analysis of a micromechanical model of bone and a new 3D approach to validation.

Finite Element Analysis (FEA) is now widely used to analyse the mechanical behaviour of bone structures. Ideally, simulations are validated against experimental data. To date, validation of Finite Element Models (FEMs) has been 2 Dimensional (2D) only, being based on comparison with surface-mounted strain gauge readings. In this study we present a novel 3-Dimensional (3D) approach to validation that allows comparison of modelled with experimental results between any two points in 3D space throughout the structure, providing magnitude and direction data for comparison, internally and externally. Specifically, we validate a FEM of a rat tibia, including trabecular network geometry, using a material testing stage housed within a microCT scanner. We further apply novel landmark based morphometric approaches to more effectively compare modelled and experimental results. 542 landmark points on the cortical and trabecular bone surfaces of the model were selected and validated in 3D against experimental data. This approach may hold considerable potential in fields wherein a better understanding of the mechanical behaviour of trabecular networks is important, e.g., the studies of osteoporosis and trabecular loss after orthopaedic implant insertion.

Toward integration of geometric morphometrics and computational biomechanics: new methods for 3D virtual reconstruction and quantitative analysis of Finite Element Models.

The ability to warp three-dimensional (3D) meshes from known biological morphology to fit other known, predicted or hypothetical morphologies has a range of potential applications in functional morphology and biomechanics. One of the most challenging of these applications is Finite Element Analysis (FEA), a potentially powerful non-destructive tool in the prediction of mechanical behaviour. Geometric morphometrics is another typically computer-based approach commonly applied in morphological studies that allows for shape differences between specimens to be quantified and analysed. There has been some integration of these two fields in recent years. Although a number of shape warping approaches have been developed previously, none are easily accessible. Here we present an easily accessed method for warping meshes based on freely available software and test the effectiveness of the approach in FEA using the varanoid lizard mandible as a model. We further present new statistical approaches, strain frequency plots and landmark point strains, to analyse FEA results quantitatively and further integrate FEA with geometric morphometrics. Using strain frequency plots, strain field, bending displacements and landmark point strain data we demonstrate that the mechanical behaviour of warped specimens reproduces that of targets without significant error. The influence of including internal cavity morphology in FEA models was also examined and shown to increase bending displacements and strain magnitudes in FE models. The warping approaches presented here will be useful in a range of applications including the generation and analysis of virtual reconstructions, generic models that approximate species means, hypothetical morphologies and evolutionary intermediaries.

Calculating the axes of rotation for the subtalar and talocrural joints using 3D bone reconstructions.

Orientation of the subtalar joint axis dictates inversion and eversion movements of the foot and has been the focus of evolutionary and clinical studies for a number of years. Previous studies have measured the subtalar joint axis against the axis of the whole foot, the talocrural joint axis and, recently, the principal axes of the talus. The present study introduces a new method for estimating average joint axes from 3D reconstructions of bones and applies the method to the talus to calculate the subtalar and talocrural joint axes. The study also assesses the validity of the principal axes as a reference coordinate system against which to measure the subtalar joint axis. In order to define the angle of the subtalar joint axis relative to that of another axis in the talus, we suggest measuring the subtalar joint axis against the talocrural joint axis. We present corresponding 3D vector angles calculated from a modern human skeletal sample. This method is applicable to virtual 3D models acquired through surface-scanning of disarticulated 'dry' osteological samples, as well as to 3D models created from CT or MRI scans.

Allometric shape vector projection: a new method for the identification of allometric shape characters and trajectories applied to the human astragalus (talus).

The surface morphology of the human astragalus (talus) is difficult to represent accurately using landmarks as it is essentially globular in shape. Advances in laser scanning technology allow fast and accurate capture of bone surface morphology. However, methodologies to utilise these new accurate 3D data have not been fully developed. The present study uses canonical sampling of whole surface morphology attained through laser scanning and for the first time applies the technique to analysis of bone morphology. We introduce a new technique for identifying allometric shape characters in whole bone surface morphology. In a sample of adult human astragalus the new technique is successful in identifying and isolating intra-specific allometric shape characters in a bone which typically lacks landmarks and has, consequently, proved difficult to analyse using traditional 3D morphometric methods.

Set-size and frequency-of-occurrence judgements in young and older adults: the role of the availability heuristic.

Two experiments examined the cognitive processes underlying judgements of set size and judgements of frequency of occurrence in young (Experiments 1 and 2) and older (Experiment 2) adults. Previous research has implicated the availability heuristic in set-size judgements, whereas an automatic processing mechanism has been implicated in judgements of frequency of occurrence. In the current experiments, path analysis was employed to investigate the role of an availability bias in performance on the judgement tasks. In Experiments 1 and 2, both types of judgement were influenced by repetition frequency of words independent of the availability (recall) of specific exemplars. Experiment 2 extended the investigation to include age differences. Although older adults' recall performance was poorer overall, the availability bias was age invariant, and there were no age differences in either set-size or frequency-of-occurrence judgements. Our results indicate that both set-size and frequency-of-occurrence judgements are independent of the availability bias evident in recall, and they support the notion that an automatic processing mechanism underlies both types of judgement.

Evaluation of a smoking cessation programme that uses behaviour modification.

AIM: To obtain an up-to-date measure of the end-of-course success rate of the Isis Stop Smoking Programme and to determine which demographic, socioeconomic and behavioural factors were predictors of success in the programme. METHOD: Data from a questionnaire completed at the outset of course participation were available for 1016 Isis participants. The data were statistically analysed. RESULTS: "Success" was defined as having consumed no cigarettes during the final 24 hours of participation on the Isis Programme. The overall success rate at completion of the programme was 69% of participants. For both males and females, the number of cigarettes consumed on beginning the programme was the strongest predictor of success. Other predictors were commitment to quitting, nicotine yield of the usual cigarette, number of years of smoking and age. Young females had a particularly good success rate. Participants were categorised according to the New Zealand Socioeconomic Index of Occupational Status. Professional and technical workers were the most successful quitters and the unemployed, self-employed and students had particularly low success rates. CONCLUSION: Assuming proportionality of recent end-of-course success rates with comparable figures from the late 1970s, the proportion of Isis participants who continue to be non-smokers one year from completing the course would be approximately 33%. Further investigation to confirm this is warranted.

Sample frequency and sample duration as sources of stimulus control in delayed matching to sample.

Three experiments examined sample duration and sample presentation frequency (SPF) on choice in a two-alternative, delayed matching-to-sample task. In Experiment 1, using a behavioural-detection approach, we demonstrated bias toward the more frequent sample, despite the conditional probability of reinforcement for a correct match on any particular trial remaining at 1.0 for both stimuli. Although retention-interval duration influenced both discriminability and bias in Experiment 1, bias was independent of retention interval in two subsequent experiments. Experiments 2 and 3 replicated the effects of SPF on bias, and demonstrated that discriminability of the stimuli was not influenced by the SPF manipulation. Experiment 2 also investigated the effect of a within-session variation in sample duration on discriminability and bias measures, both with and without unequal SPFs. Discriminability was enhanced to both the short and long samples of the unequal sample-durations' condition relative to discrimination in conditions where samples were presented for equal durations. Bias generated by varying SPF was independent of sample-duration effects and of retention-interval duration. Taken together, these data suggest independent and qualitatively different effects of sample frequency and sample duration on matching behaviour: Sample frequency has its effect on bias measures, while sample duration influences discriminability. We suggest that sample frequency is a global task factor influencing reference memory, and sample duration is a trial-specific, conditional discrimination factor, involving short-term or working memory processing.

Adult age differences in on-line contingency judgements.

This research was designed to further our understanding of age differences in contingency judgements and to consider the role of working memory in such judgements. Experiment 1 examined age differences in contingency judgement accuracy when information processing requirements were manipulated. Young and older adults estimated the degree of contingency between two categorical variables. Contingencies, amount of information, and speed of execution were varied. Participants discriminated the contingencies well. Judgement accuracy declined with smaller numbers of trials and shorter intertrial intervals. The judgement deterioration was more severe for older adults. In Experiment 2, speed interfered again more with the judgements made by older adults. Modulations of this effect occurred as a function of stimulus duration and distribution of event frequencies. Overall, the judgement deterioration is consistent with Wagner's (1981) model of automatic memory processing.

Adults' conceptions of everyday memory failures in others: factors that mediate the effects of target age.

This study investigated young and older adults' conceptions of memory failure in others. One hundred young and 100 older adults rated memory failures in targets of 20, 40, 60, and 80 years of age as to how likely the memory failures were due to lack of effort or lack of ability. With increasing age, targets' forgetful episodes were rated as less likely to be caused by lack of effort and more likely to be due to lack of ability. A Subject Age x Target Age interaction on ability ratings showed age to be more salient for older subjects. Memory content, type of memory, subject sex, and target sex all influenced judgment of memory failure. The results support Erber's (1989) notion of a double standard in memory-failure appraisal; they demonstrated that adults' conceptions of memory include a decremental view of memorial ability with increasing age that is differentially sensitive to subject, target, and memorial variables.

Responses of broiler chicks to dietary copra cake of high lipid content.

1. Broiler chicks fed on a diet containing 500 g/kg expeller copra cake of high residual oil content not only retained less dry matter and gained less weight than those fed on a control diet with no copra, they also experienced difficulty in achieving similar food intakes. 2. Chicks given the 500 g/kg copra ration initially displayed an excited behaviour pattern, which may have developed out of frustration as they could neither derive adequate nourishment from their food nor increase food intakes sufficiently to allow them to achieve their genetic potential for growth. 3. Chicks however showed considerable adaptation in that efficiency of food utilisation and intakes were increased gradually; the latter appeared to be partly regulated by an increased intake of water that was associated with copra feeding. The surface area of the intestines was also increased in order to facilitate the absorption of nutrients, and greater proportions of the nutrients absorbed were converted into body weight. 4. There were no significant differences in 7-week body weights of chicks fed the control, 125 g/kg and 250 g/kg copra diets. Although weight gains at the 500 g/kg inclusion rate were lower, the carcases of these chicks had less abdominal fat and were consequently leaner.

Optical isomers of 2,3-dimercapto-1-propanesulfonate: antidotal activity, in vitro and in vivo, against sodium arsenite.

DMPS (2,3-dimercapto-1-propanesulfonate, Na salt) is an important water soluble analog of dimercaprol. All investigations of this antidote for heavy metal intoxication have dealt only with the racemic mixture. In the present report, the optical isomers of DMPS have been separated and the arsenic-antidote activity of the levo-rotatory (-)-isomer, the dextro-rotatory (+)-isomer and the racemic mixture of DMPS have been investigated in vivo and in vitro. The individual optical isomers and the racemic mixture of DMPS are effective equally, in vitro, in preventing the inhibition by sodium arsenite of the activity of mouse kidney pyruvate dehydrogenase complex. In addition, when pyruvate dehydrogenase is inhibited, in vitro, by sodium arsenite, any of the three DMPS preparations will reverse the inhibition equally well. The in vitro evidence suggests that two molecules of DMPS are required to prevent the effects of one molecule of sodium arsenite. Neither the LD50 nor the ED50 values of each of the three forms of DMPS differ significantly when measured i.p. in mice. In addition, there is no striking difference between the effectiveness of the levo- or dextro-rotatory DMPS when given orally to mice challenged with sodium arsenite. Thus, the use of the individual optical isomers of DMPS does not appear to have any advantage over the racemic mixture as an arsenic antidote under these conditions.

Cross-validation of a heroin addiction (He) scale in a treatment setting.

An He (Heroin addiction) scale has been developed from the MMPI for differentiating incarcerated addicts from nonaddicts. Its clinical utility has not been tested among addicts seeking treatment in hospital-based treatment programs. In this cross-validation study, the He scale did not differentiate heroin users (n = 336) from polydrug users (n = 179). Further, White heroin users scored significantly higher than Black heroin users. Findings were similar in both analysis of variance and co-variance designs, both when potentially-confounding covariates were controlled and uncontrolled (i.e., the covariates age, education, socioeconomic status, and admission status). Although the scale showed promise for differentiating compulsive users of proscribed drugs categorized generally (but not heroin users specifically), nevertheless additional refinement of the scale is needed before it can be applied in hospital settings. Race, age, and admission status emerged as subject background characteristics meriting systematic attention in scale refinement.