Utilization Of B-Mode Ultrasound As A Body Fat Estimate In Collegiate Football Players

The purpose of the present study was to validate a 7-site ultrasound imaging protocol to predict percent body fat (%BF) in a Division I football team. Body composition was estimated by ultrasound, seven site skinfolds (SKINFOLD), and the three compartment-water (3C-W) model of Siri (1961), using Bioimpedance spectroscopy (BIS) to estimate total body water (TBW) and air-displacement plethysmography (BODPOD®) to determine body density (Db). Pearson’s product-moment correlation analyses were run to determine between ΣUltrasound and the criterion 3C-W, and between the ΣSkinfold and ΣUltrasound. Strong positive correlations were observed between ΣSkinfold and ΣUltrasound (r=.984; pUltrasound and %BF from 3C-W (r=0.878, pUltrasound, (%BF= 6.194+(.096* ΣUltrasound); standard error of the estimate [SEE]=2.97%). Cross validation analyses were performed using an independent sample of 29 players. Mean observed %BF and mean predicted %BF were 18.32 ± 6.26% and 18.78 ± 6.22%, respectively. The constant error (CE), SEE and validity coefficient (r) were 0.004%, 2.64%, and 0.91, respectively. The total error (TEE) was 2.87%. Conclusion: The positive relationship between ultrasound measurements and the 3C-W model suggests the B-mode ultrasound may be a practical alternative of predicting %BF in Division I football players

A fast and portable Re-Implementation of Piskunov and Valenti's Optimal-Extraction Algorithm with improved Cosmic-Ray Removal and Optimal Sky Subtraction

We present a fast and portable re-implementation of Piskunov and Valenti's optimal-extraction algorithm (Piskunov & Valenti, 2002} in C/C++ together with full uncertainty propagation, improved cosmic-ray removal, and an optimal background-subtraction algorithm. This re-implementation can be used with IRAF and most existing data-reduction packages and leads to signal-to-noise ratios close to the Poisson limit. The algorithm is very stable, operates on spectra from a wide range of instruments (slit spectra and fibre feeds), and has been extensively tested for VLT/UVES, ESO/CES, ESO/FEROS, NTT/EMMI, NOT/ALFOSC, STELLA/SES, SSO/WiFeS, and finally, P60/SEDM-IFU data.Comment: 23 pages, 12 figure

The psychological distress of the young driver: a brief report

Objective: To explore the role of psychological distress in the self-reported risky driving of young novice drivers. Design: Cross-sectional online survey of 761 tertiary students aged 17-25 years with an intermediate (Provisional) driving licence who completed Kessler’s Psychological Distress Scale and the Behaviour of Young Novice Drivers Scale. Setting: Queensland, Australia, August-October 2009. Main outcome measures: Psychological distress, risky driving. Results: Regression analyses revealed that psychological distress uniquely explained 8.5% of the variance in young novice’s risky driving, with adolescents experiencing psychological distress also reporting higher levels of risky driving. Psychological distress uniquely explained a significant 6.7% and 9.5% of variance in risky driving for males and females respectively. Conclusions: Medical practitioners treating adolescents who have been injured through risky behaviour need to aware of the potential contribution of psychological distress, whilst mental health professionals working with adolescents experiencing psychological distress need to be aware of this additional source of potential harm. The nature of the causal relationships linking psychological distress and risky driving behaviour are not yet fully understood, indicating a need for further research so that strategies such as screening can be investigated

Theoretical basis and practical aspects of small specimen creep testing

Interest in and the application of small specimen creep test techniques are increasing. This is because it is only possible to obtain small samples of material in some situations, for example, the scoop samples that are removed from in-service components, the heat-affected zones that are created when welds are used to join components and the desire to produce only small amounts of material in alloy development programmes. It is therefore important to review and compare the theoretical basis and practical aspects of each of the small specimen creep testing methods, in order to clearly understand which of the methods is the best for any specific application. This article provides the theoretical basis for each commonly used test method

Small two-bar specimen creep testing of Grade P91 steel at 650oC

Commonly used small creep specimen types, such as ring and impression creep specimens, are capable of providing minimum creep strain rate data from small volumes of material. However, these test types are unable to provide the creep rupture data. In this paper the recently developed two-bar specimen type, which can be used to obtain minimum creep strain rate and creep rupture creep data from small volumes of material, is described. Conversion relationships are used to convert (i) the applied load to the equivalent uniaxial stress, and (ii) the load line deformation rate to the equivalent uniaxial creep strain rate. The effects of the specimen dimension ratios on the conversion factors are also discussed in this paper. This paper also shows comparisons between two-bar specimen creep test data and the corresponding uniaxial creep test data, for grade P91 steel at 650°C

Modelling of a Grade 91 power plant pressurised header weldment under ultra super-critical creep conditions

This paper is concerned with the creep-damage modelling of a Grade 91 pressurised header, which was observed to undergo in-service cracking in the weldments. A multi-axial creep damage model of Kachanov type, with a single state damage variable, has been implemented into finite element analysis to study the creep damage responses of weldments and the sub-zones i.e. the base metal (BM), weld metal (WM) and heat-affected zone (HAZ). Material properties for each weld constituent were obtained from the results of accelerated creep tests on materials extracted from the header. Predictions of crack initiation were made for sections of the stub to header welds. This analysis was also used to estimate creep failure life of the header weldment under ultra-super-critical conditions. Further, creep crack growth behaviour was predicted based on time-dependent critical damage growth. The predicted damage distributions and failure mode of the cross-weld creep test specimens were in good agreement with the reported experimental observations. The predicted damage distributions and cracking in the header correlate reasonably well with the reported industrial observations

Use of small specimen creep data in component life management: a review

Small specimen creep testing techniques are novel mechanical test techniques that have been developed over the past 25 years. They mainly include the sub-size uniaxial test, the small punch creep test, the impression creep test, the small ring creep test and the two-bar creep test. This paper outlines the current methods in practice for data interpretation as well as the state-of-the-art procedures for conducting the tests. Case studies for the use of impression creep testing and material strength ranking of creep resistant steels are reviewed along with the requirement for the standardisation of the impression creep test method. A database of small specimen creep testing is required to prove the validity of the tests

Language skills, peer rejection, and the development of externalizing behavior from kindergarten to fourth grade

Background: Children with poorer language skills are more likely to show externalizing behavior problems, as well as to become rejected by their peers. Peer rejection has also been found to affect the development of externalizing behavior. This study explored the role of peer rejection in the link between language skills and the development of externalizing behavior. Methods: Six hundred and fifteen (615) children were followed from kindergarten to grade 4. Receptive language skills were measured with the Peabody Picture Vocabulary Test in grade 2. Teachers reported externalizing behavior and peer reports of social rejection were measured annually. Results: Children with poorer receptive language skills showed increasing externalizing behavior, while children with better receptive language skills showed decreases in externalizing behavior. Children with poorer receptive language skills experienced peer rejection most frequently. The link between receptive language skills and the development of externalizing behavior was mediated by the development of peer rejection. Findings suggested that this mediational link applied mostly to boys. Conclusion: Children with poorer language skills are at increased risk of becoming rejected by mainstream peers, which adds to the development of externalizing behavior. © 2010 The Authors. Journal of Child Psychology and Psychiatry. © 2010 Association for Child and Adolescent Mental Health

Formation Control for a Fleet of Autonomous Ground Vehicles: A Survey

Autonomous/unmanned driving is the major state-of-the-art step that has a potential to fundamentally transform the mobility of individuals and goods. At present, most of the developments target standalone autonomous vehicles, which can sense the surroundings and control the vehicle based on this perception, with limited or no driver intervention. This paper focuses on the next step in autonomous vehicle research, which is the collaboration between autonomous vehicles, mainly vehicle formation control or vehicle platooning. To gain a deeper understanding in this area, a large number of the existing published papers have been reviewed systemically. In other words, many distributed and decentralized approaches of vehicle formation control are studied and their implementations are discussed. Finally, both technical and implementation challenges for formation control are summarized