Improving data analysis in herpetology: Using Akaike's information criterion (AIC) to assess the strength of biological hypotheses

USGS Publications Warehouse

Mazerolle, M.J.

2006-01-01

In ecology, researchers frequently use observational studies to explain a given pattern, such as the number of individuals in a habitat patch, with a large number of explanatory (i.e., independent) variables. To elucidate such relationships, ecologists have long relied on hypothesis testing to include or exclude variables in regression models, although the conclusions often depend on the approach used (e.g., forward, backward, stepwise selection). Though better tools have surfaced in the mid 1970's, they are still underutilized in certain fields, particularly in herpetology. This is the case of the Akaike information criterion (AIC) which is remarkably superior in model selection (i.e., variable selection) than hypothesis-based approaches. It is simple to compute and easy to understand, but more importantly, for a given data set, it provides a measure of the strength of evidence for each model that represents a plausible biological hypothesis relative to the entire set of models considered. Using this approach, one can then compute a weighted average of the estimate and standard error for any given variable of interest across all the models considered. This procedure, termed model-averaging or multimodel inference, yields precise and robust estimates. In this paper, I illustrate the use of the AIC in model selection and inference, as well as the interpretation of results analysed in this framework with two real herpetological data sets. The AIC and measures derived from it is should be routinely adopted by herpetologists. ?? Koninklijke Brill NV 2006.

A new model of selection in women's handball.

PubMed

Srhoj, Vatromir; Rogulj, Nenad; Zagorac, Nebojsa; Katić, Ratko

2006-09-01

The aim of the study was to assess the basic motor abilities that determine top performance in women's handball, and to identify test panel for primary selection at handball school. The study included 155 female attendants of the Split Handball School, mean age 12.5 years. Differences in the basic motor abilities between the subjects that developed into elite handball players after 7-year training process and those that abandoned handball for being unable to meet the competition criteria were evaluated by use of discriminative analysis. The former were found to have also been superior initially in all variables analyzed, and in arm coordination, overall body coordination, throw and jump explosive strength, arm movement frequency and repetitive trunk strength in particular. Motor superiority based on the abilities of coordination, explosive strength and speed determines performance in women's handball, qualifying these abilities as reliable selection criteria. Based on this study results, a new model of selection in women's handball, with fine arm coordination as the major limiting factor of performance, has been proposed.

Extinction risk and eco-evolutionary dynamics in a variable environment with increasing frequency of extreme events

PubMed Central

Vincenzi, Simone

2014-01-01

One of the most dramatic consequences of climate change will be the intensification and increased frequency of extreme events. I used numerical simulations to understand and predict the consequences of directional trend (i.e. mean state) and increased variability of a climate variable (e.g. temperature), increased probability of occurrence of point extreme events (e.g. floods), selection pressure and effect size of mutations on a quantitative trait determining individual fitness, as well as the their effects on the population and genetic dynamics of a population of moderate size. The interaction among climate trend, variability and probability of point extremes had a minor effect on risk of extinction, time to extinction and distribution of the trait after accounting for their independent effects. The survival chances of a population strongly and linearly decreased with increasing strength of selection, as well as with increasing climate trend and variability. Mutation amplitude had no effects on extinction risk, time to extinction or genetic adaptation to the new climate. Climate trend and strength of selection largely determined the shift of the mean phenotype in the population. The extinction or persistence of the populations in an ‘extinction window’ of 10 years was well predicted by a simple model including mean population size and mean genetic variance over a 10-year time frame preceding the ‘extinction window’, although genetic variance had a smaller role than population size in predicting contemporary risk of extinction. PMID:24920116

A Systematic Review of Isometric Lingual Strength-Training Programs in Adults With and Without Dysphagia.

PubMed

McKenna, Victoria S; Zhang, Bin; Haines, Morgan B; Kelchner, Lisa N

2017-05-17

This systematic review summarizes the effects of isometric lingual strength training on lingual strength and swallow function in adult populations. Furthermore, it evaluates the designs of the reviewed studies and identifies areas of future research in isometric lingual strength training for dysphagia remediation. A comprehensive literature search of 3 databases and additional backward citation search identified 10 studies for inclusion in the review. The review reports and discusses the isometric-exercise intervention protocols, pre- and postintervention lingual-pressure data (maximum peak pressures and lingual-palatal pressures during swallowing), and oropharyngeal swallowing measures such as penetration-aspiration scales, oropharyngeal residue and duration, lingual volumes, and quality-of-life assessments. Studies reported gains in maximum peak lingual pressures following isometric lingual strength training for both healthy adults and select groups of individuals with dysphagia. However, due to the variability in study designs, it remains unclear whether strength gains generalize to swallow function. Although isometric lingual strength training is a promising intervention for oropharyngeal dysphagia, the current literature is too variable to confidently report specific therapeutic benefits. Future investigations should target homogenous patient populations and use randomized controlled trials to determine the efficacy of this treatment for individuals with dysphagia.

Fecundity selection on ornamental plumage colour differs between ages and sexes and varies over small spatial scales.

PubMed

Parker, T H; Wilkin, T A; Barr, I R; Sheldon, B C; Rowe, L; Griffith, S C

2011-07-01

Avian plumage colours are some of the most conspicuous sexual ornaments, and yet standardized selection gradients for plumage colour have rarely been quantified. We examined patterns of fecundity selection on plumage colour in blue tits (Cyanistes caeruleus L.). When not accounting for environmental heterogeneity, we detected relatively few cases of selection. We found significant disruptive selection on adult male crown colour and yearling female chest colour and marginally nonsignificant positive linear selection on adult female crown colour. We discovered no new significant selection gradients with canonical rotation of the matrix of nonlinear selection. Next, using a long-term data set, we identified territory-level environmental variables that predicted fecundity to determine whether these variables influenced patterns of plumage selection. The first of these variables, the density of oaks within 50 m of the nest, influenced selection gradients only for yearling males. The second variable, an inverse function of nesting density, interacted with a subset of plumage selection gradients for yearling males and adult females, although the strength and direction of selection did not vary predictably with population density across these analyses. Overall, fecundity selection on plumage colour in blue tits appeared rare and inconsistent among sexes and age classes. © 2011 The Authors. Journal of Evolutionary Biology © 2011 European Society For Evolutionary Biology.

Maintenance of Genetic Variability under Strong Stabilizing Selection: A Two-Locus Model

PubMed Central

Gavrilets, S.; Hastings, A.

1993-01-01

We study a two locus model with additive contributions to the phenotype to explore the relationship between stabilizing selection and recombination. We show that if the double heterozygote has the optimum phenotype and the contributions of the loci to the trait are different, then any symmetric stabilizing selection fitness function can maintain genetic variability provided selection is sufficiently strong relative to linkage. We present results of a detailed analysis of the quadratic fitness function which show that selection need not be extremely strong relative to recombination for the polymorphic equilibria to be stable. At these polymorphic equilibria the mean value of the trait, in general, is not equal to the optimum phenotype, there exists a large level of negative linkage disequilibrium which ``hides'' additive genetic variance, and different equilibria can be stable simultaneously. We analyze dependence of different characteristics of these equilibria on the location of optimum phenotype, on the difference in allelic effect, and on the strength of selection relative to recombination. Our overall result that stabilizing selection does not necessarily eliminate genetic variability is compatible with some experimental results where the lines subject to strong stabilizing selection did not have significant reductions in genetic variability. PMID:8514145

The Effect of Weld Penetration on Blast Performance of Welded Panels

DTIC Science & Technology

2014-08-01

requirements of blast and ballistic protection, structural strength, fatigue resistance, unit mass and production cost. The testing described in this report...UNCLASSIFIED 7 TETRA S 20 9 3-G is an austenitic filler material often selected for welding high strength armour steels to control hydrogen induced...repeatability, lower cost, faster test turnaround and a reduced number of variables to control . Figure 30 is an illustration of the simplifications made

Extinction risk and eco-evolutionary dynamics in a variable environment with increasing frequency of extreme events.

PubMed

Vincenzi, Simone

2014-08-06

One of the most dramatic consequences of climate change will be the intensification and increased frequency of extreme events. I used numerical simulations to understand and predict the consequences of directional trend (i.e. mean state) and increased variability of a climate variable (e.g. temperature), increased probability of occurrence of point extreme events (e.g. floods), selection pressure and effect size of mutations on a quantitative trait determining individual fitness, as well as the their effects on the population and genetic dynamics of a population of moderate size. The interaction among climate trend, variability and probability of point extremes had a minor effect on risk of extinction, time to extinction and distribution of the trait after accounting for their independent effects. The survival chances of a population strongly and linearly decreased with increasing strength of selection, as well as with increasing climate trend and variability. Mutation amplitude had no effects on extinction risk, time to extinction or genetic adaptation to the new climate. Climate trend and strength of selection largely determined the shift of the mean phenotype in the population. The extinction or persistence of the populations in an 'extinction window' of 10 years was well predicted by a simple model including mean population size and mean genetic variance over a 10-year time frame preceding the 'extinction window', although genetic variance had a smaller role than population size in predicting contemporary risk of extinction. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

A Systematic Review of Isometric Lingual Strength-Training Programs in Adults With and Without Dysphagia

PubMed Central

Zhang, Bin; Haines, Morgan B.; Kelchner, Lisa N.

2017-01-01

Purpose This systematic review summarizes the effects of isometric lingual strength training on lingual strength and swallow function in adult populations. Furthermore, it evaluates the designs of the reviewed studies and identifies areas of future research in isometric lingual strength training for dysphagia remediation. Method A comprehensive literature search of 3 databases and additional backward citation search identified 10 studies for inclusion in the review. The review reports and discusses the isometric-exercise intervention protocols, pre- and postintervention lingual-pressure data (maximum peak pressures and lingual-palatal pressures during swallowing), and oropharyngeal swallowing measures such as penetration-aspiration scales, oropharyngeal residue and duration, lingual volumes, and quality-of-life assessments. Results Studies reported gains in maximum peak lingual pressures following isometric lingual strength training for both healthy adults and select groups of individuals with dysphagia. However, due to the variability in study designs, it remains unclear whether strength gains generalize to swallow function. Conclusion Although isometric lingual strength training is a promising intervention for oropharyngeal dysphagia, the current literature is too variable to confidently report specific therapeutic benefits. Future investigations should target homogenous patient populations and use randomized controlled trials to determine the efficacy of this treatment for individuals with dysphagia. PMID:28282484

Genes under weaker stabilizing selection increase network evolvability and rapid regulatory adaptation to an environmental shift.

PubMed

Laarits, T; Bordalo, P; Lemos, B

2016-08-01

Regulatory networks play a central role in the modulation of gene expression, the control of cellular differentiation, and the emergence of complex phenotypes. Regulatory networks could constrain or facilitate evolutionary adaptation in gene expression levels. Here, we model the adaptation of regulatory networks and gene expression levels to a shift in the environment that alters the optimal expression level of a single gene. Our analyses show signatures of natural selection on regulatory networks that both constrain and facilitate rapid evolution of gene expression level towards new optima. The analyses are interpreted from the standpoint of neutral expectations and illustrate the challenge to making inferences about network adaptation. Furthermore, we examine the consequence of variable stabilizing selection across genes on the strength and direction of interactions in regulatory networks and in their subsequent adaptation. We observe that directional selection on a highly constrained gene previously under strong stabilizing selection was more efficient when the gene was embedded within a network of partners under relaxed stabilizing selection pressure. The observation leads to the expectation that evolutionarily resilient regulatory networks will contain optimal ratios of genes whose expression is under weak and strong stabilizing selection. Altogether, our results suggest that the variable strengths of stabilizing selection across genes within regulatory networks might itself contribute to the long-term adaptation of complex phenotypes. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Heart Rate Dynamics after Combined Strength and Endurance Training in Middle-Aged Women: Heterogeneity of Responses

PubMed Central

Goldberger, Ary L.; Tulppo, Mikko P.; Laaksonen, David E.; Nyman, Kai; Keskitalo, Marko; Häkkinen, Arja; Häkkinen, Keijo

2013-01-01

The loss of complexity in physiological systems may be a dynamical biomarker of aging and disease. In this study the effects of combined strength and endurance training compared with those of endurance training or strength training alone on heart rate (HR) complexity and traditional HR variability indices were examined in middle-aged women. 90 previously untrained female volunteers between the age of 40 and 65 years completed a 21 week progressive training period of either strength training, endurance training or their combination, or served as controls. Continuous HR time series were obtained during supine rest and submaximal steady state exercise. The complexity of HR dynamics was assessed using multiscale entropy analysis. In addition, standard time and frequency domain measures were also computed. Endurance training led to increases in HR complexity and selected time and frequency domain measures of HR variability (P<0.01) when measured during exercise. Combined strength and endurance training or strength training alone did not produce significant changes in HR dynamics. Inter-subject heterogeneity of responses was particularly noticeable in the combined training group. At supine rest, no training-induced changes in HR parameters were observed in any of the groups. The present findings emphasize the potential utility of endurance training in increasing the complex variability of HR in middle-aged women. Further studies are needed to explore the combined endurance and strength training adaptations and possible gender and age related factors, as well as other mechanisms, that may mediate the effects of different training regimens on HR dynamics. PMID:24013586

Biomotor structures in elite female handball players.

PubMed

Katić, Ratko; Cavala, Marijana; Srhoj, Vatromir

2007-09-01

In order to identify biomotor structures in elite female handball players, factor structures of morphological characteristics and basic motor abilities of elite female handball players (N = 53) were determined first, followed by determination of relations between the morphological-motor space factors obtained and the set of criterion variables evaluating situation motor abilities in handball. Factor analysis of 14 morphological measures produced three morphological factors, i.e. factor of absolute voluminosity (mesoendomorph), factor of longitudinal skeleton dimensionality, and factor of transverse hand dimensionality. Factor analysis of 15 motor variables yielded five basic motor dimensions, i.e. factor of agility, factor of jumping explosive strength, factor of throwing explosive strength, factor of movement frequency rate, and factor of running explosive strength (sprint). Four significant canonic correlations, i.e. linear combinations, explained the correlation between the set of eight latent variables of the morphological and basic motor space and five variables of situation motoricity. First canonic linear combination is based on the positive effect of the factors of agility/coordination on the ability of fast movement without ball. Second linear combination is based on the effect of jumping explosive strength and transverse hand dimensionality on ball manipulation, throw precision, and speed of movement with ball. Third linear combination is based on the running explosive strength determination by the speed of movement with ball, whereas fourth combination is determined by throwing and jumping explosive strength, and agility on ball pass. The results obtained were consistent with the model of selection in female handball proposed (Srhoj et al., 2006), showing the speed of movement without ball and the ability of ball manipulation to be the predominant specific abilities, as indicated by the first and second linear combination.

Pleiotropic Models of Polygenic Variation, Stabilizing Selection, and Epistasis

PubMed Central

Gavrilets, S.; de-Jong, G.

1993-01-01

We show that in polymorphic populations many polygenic traits pleiotropically related to fitness are expected to be under apparent ``stabilizing selection'' independently of the real selection acting on the population. This occurs, for example, if the genetic system is at a stable polymorphic equilibrium determined by selection and the nonadditive contributions of the loci to the trait value either are absent, or are random and independent of those to fitness. Stabilizing selection is also observed if the polygenic system is at an equilibrium determined by a balance between selection and mutation (or migration) when both additive and nonadditive contributions of the loci to the trait value are random and independent of those to fitness. We also compare different viability models that can maintain genetic variability at many loci with respect to their ability to account for the strong stabilizing selection on an additive trait. Let V(m) be the genetic variance supplied by mutation (or migration) each generation, V(g) be the genotypic variance maintained in the population, and n be the number of the loci influencing fitness. We demonstrate that in mutation (migration)-selection balance models the strength of apparent stabilizing selection is order V(m)/V(g). In the overdominant model and in the symmetric viability model the strength of apparent stabilizing selection is approximately 1/(2n) that of total selection on the whole phenotype. We show that a selection system that involves pairwise additive by additive epistasis in maintaining variability can lead to a lower genetic load and genetic variance in fitness (approximately 1/(2n) times) than an equivalent selection system that involves overdominance. We show that, in the epistatic model, the apparent stabilizing selection on an additive trait can be as strong as the total selection on the whole phenotype. PMID:8325491

A public dataset of running biomechanics and the effects of running speed on lower extremity kinematics and kinetics

PubMed Central

Fukuchi, Claudiane A.; Duarte, Marcos

2017-01-01

Background The goals of this study were (1) to present the set of data evaluating running biomechanics (kinematics and kinetics), including data on running habits, demographics, and levels of muscle strength and flexibility made available at Figshare (DOI: 10.6084/m9.figshare.4543435); and (2) to examine the effect of running speed on selected gait-biomechanics variables related to both running injuries and running economy. Methods The lower-extremity kinematics and kinetics data of 28 regular runners were collected using a three-dimensional (3D) motion-capture system and an instrumented treadmill while the subjects ran at 2.5 m/s, 3.5 m/s, and 4.5 m/s wearing standard neutral shoes. Results A dataset comprising raw and processed kinematics and kinetics signals pertaining to this experiment is available in various file formats. In addition, a file of metadata, including demographics, running characteristics, foot-strike patterns, and muscle strength and flexibility measurements is provided. Overall, there was an effect of running speed on most of the gait-biomechanics variables selected for this study. However, the foot-strike patterns were not affected by running speed. Discussion Several applications of this dataset can be anticipated, including testing new methods of data reduction and variable selection; for educational purposes; and answering specific research questions. This last application was exemplified in the study’s second objective. PMID:28503379

A public dataset of running biomechanics and the effects of running speed on lower extremity kinematics and kinetics.

PubMed

Fukuchi, Reginaldo K; Fukuchi, Claudiane A; Duarte, Marcos

2017-01-01

The goals of this study were (1) to present the set of data evaluating running biomechanics (kinematics and kinetics), including data on running habits, demographics, and levels of muscle strength and flexibility made available at Figshare (DOI: 10.6084/m9.figshare.4543435); and (2) to examine the effect of running speed on selected gait-biomechanics variables related to both running injuries and running economy. The lower-extremity kinematics and kinetics data of 28 regular runners were collected using a three-dimensional (3D) motion-capture system and an instrumented treadmill while the subjects ran at 2.5 m/s, 3.5 m/s, and 4.5 m/s wearing standard neutral shoes. A dataset comprising raw and processed kinematics and kinetics signals pertaining to this experiment is available in various file formats. In addition, a file of metadata, including demographics, running characteristics, foot-strike patterns, and muscle strength and flexibility measurements is provided. Overall, there was an effect of running speed on most of the gait-biomechanics variables selected for this study. However, the foot-strike patterns were not affected by running speed. Several applications of this dataset can be anticipated, including testing new methods of data reduction and variable selection; for educational purposes; and answering specific research questions. This last application was exemplified in the study's second objective.

Effect of isometric quadriceps exercise on muscle strength, pain, and function in patients with knee osteoarthritis: a randomized controlled study.

PubMed

Anwer, Shahnawaz; Alghadir, Ahmad

2014-05-01

[Purpose] The aim of present study was to investigate the effects of isometric quadriceps exercise on muscle strength, pain, and function in knee osteoarthritis. [Subjects and Methods] Outpatients (N=42, 21 per group; age range 40-65 years; 13 men and 29 women) with osteoarthritis of the knee participated in the study. The experimental group performed isometric exercises including isometric quadriceps, straight leg raising, and isometric hip adduction exercise 5 days a week for 5 weeks, whereas the control group did not performed any exercise program. The outcome measures or dependent variables selected for this study were pain intensity, isometric quadriceps strength, and knee function. These variables were measured using the Numerical Rating Scale (NRS), strength gauge device, and reduced WOMAC index, respectively. All the measurements were taken at baseline (week 0) and at the end of the trial at week 5. [Results] In between-group comparisons, the maximum isometric quadriceps strength, reduction in pain intensity, and improvement in function in the isometric exercise group at the end of the 5th week were significantly greater than those of the control group (p<0.05). [Conclusion] The 5-week isometric quadriceps exercise program showed beneficial effects on quadriceps muscle strength, pain, and functional disability in patients with osteoarthritis of the knee.

Credibility Elements of eWOM Messages in the Context of Health Care Services. A Romanian Perspective

PubMed Central

Purcarea, VL; Gheorghe, IR; Petrescu, CM

2013-01-01

The purpose of this paper is to investigate the Romanian consumers’ determinants of eWOM messages’ perceived credibility in the context of health care services. We selected a sample of 127 women and we administered a questionnaire. We used the partial least squares to uncover the established relationships between the variables of the model, namely the argument strength and the source credibility of a eWOM message and the intention to purchase a health care service based on the information embedded in the eWOM messages. The results revealed that all variables had positive direct correlations with each other but the argument strength of a message has the highest impact on the intention. PMID:24146683

Credibility elements of eWOM messages in the context of health care services. A Romanian perspective.

PubMed

Purcarea, V L; Gheorghe, I R; Petrescu, C M

2013-09-15

The purpose of this paper is to investigate the Romanian consumers' determinants of eWOM messages' perceived credibility in the context of health care services. We selected a sample of 127 women and we administered a questionnaire. We used the partial least squares to uncover the established relationships between the variables of the model, namely the argument strength and the source credibility of a eWOM message and the intention to purchase a health care service based on the information embedded in the eWOM messages. The results revealed that all variables had positive direct correlations with each other but the argument strength of a message has the highest impact on the intention.

Effects of age, gender and educational background on strength of motivation for medical school.

PubMed

Kusurkar, Rashmi; Kruitwagen, Cas; ten Cate, Olle; Croiset, Gerda

2010-08-01

The aim of this study was to determine the effects of selection, educational background, age and gender on strength of motivation to attend and pursue medical school. Graduate entry (GE) medical students (having Bachelor's degree in Life Sciences or related field) and Non-Graduate Entry (NGE) medical students (having only completed high school), were asked to fill out the Strength of Motivation for Medical School (SMMS) questionnaire at the start of medical school. The questionnaire measures the willingness of the medical students to pursue medical education even in the face of difficulty and sacrifice. GE students (59.64 ± 7.30) had higher strength of motivation as compared to NGE students (55.26 ± 8.33), so did females (57.05 ± 8.28) as compared to males (54.30 ± 8.08). 7.9% of the variance in the SMMS scores could be explained with the help of a linear regression model with age, gender and educational background/selection as predictor variables. Age was the single largest predictor. Maturity, taking developmental differences between sexes into account, was used as a predictor to correct for differences in the maturation of males and females. Still, the gender differences prevailed, though they were reduced. Pre-entrance educational background and selection also predicted the strength of motivation, but the effect of the two was confounded. Strength of motivation appears to be a dynamic entity, changing primarily with age and maturity and to a small extent with gender and experience.

THE PEDIATRIC RHEUMATOLOGY INTERNATIONAL TRIALS ORGANIZATION PROVISIONAL CRITERIA FOR THE EVALUATION OF RESPONSE TO THERAPY IN JUVENILE DERMATOMYOSITIS

PubMed Central

Ruperto, Nicolino; Pistorio, Angela; Ravelli, Angelo; Rider, Lisa G.; Pilkington, Clarissa; Oliveira, Sheila; Wulffraat, Nico; Espada, Graciela; Garay, Stella; Cuttica, Ruben; Hofer, Michael; Quartier, Pierre; Melo-Gomes, Jose; Reed, Ann M.; Wierzbowska, Malgorzata; Feldman, Brian M.; Harjacek, Miroslav; Huppertz, Hans-Iko; Nielsen, Susan; Flato, Berit; Lahdenne, Pekka; Michels, Harmut; Murray, Kevin J.; Punaro, Lynn; Rennebohm, Robert; Russo, Ricardo; Balogh, Zsolt; Rooney, Madeleine; Pachman, Lauren M.; Wallace, Carol; Hashkes, Philip; Lovell, Daniel J.; Giannini, Edward H.; Martini, Alberto

2010-01-01

Objective To develop a provisional definition for the evaluation of response to therapy in juvenile dermatomyositis (JDM) based on the PRINTO JDM core set of variables. Methods Thirty-seven experienced pediatric rheumatologists from 27 countries, achieved consensus on 128 difficult patient profiles as clinically improved or not improved using a stepwise approach (patients rating, statistical analysis, definition selection). Using the physicians’ consensus ratings as the “gold-standard measure”, chi-square, sensitivity, specificity, false positive and negative rate, area under the ROC, and kappa agreement for candidate definitions of improvement were calculated. Definitions with kappa >0.8 were multiplied with the face validity score to select the top definitions. Results The top definition of improvement was: at least 20% improvement from baseline in 3/6 core set variables with no more than 1 of the remaining worsening by more than 30%, which cannot be muscle strength. The second highest scoring definition was at least 20% improvement from baseline in 3/6 core set variables with no more than 2 of the remaining worsening by more than 25%, which cannot be muscle strength which is definition P1 selected by the IMACS group. The third is similar to the second with the maximum amount of worsening set to 30%. This indicates convergent validity of the process. Conclusion we proposes a provisional data driven definition of improvement that reflects well the consensus rating of experienced clinicians, which incorporates clinically meaningful change in core set variables in a composite endpoint for the evaluation of global response to therapy in JDM. PMID:20583105

Cholinergic enhancement reduces functional connectivity and BOLD variability in visual extrastriate cortex during selective attention.

PubMed

Ricciardi, Emiliano; Handjaras, Giacomo; Bernardi, Giulio; Pietrini, Pietro; Furey, Maura L

2013-01-01

Enhancing cholinergic function improves performance on various cognitive tasks and alters neural responses in task specific brain regions. We have hypothesized that the changes in neural activity observed during increased cholinergic function reflect an increase in neural efficiency that leads to improved task performance. The current study tested this hypothesis by assessing neural efficiency based on cholinergically-mediated effects on regional brain connectivity and BOLD signal variability. Nine subjects participated in a double-blind, placebo-controlled crossover fMRI study. Following an infusion of physostigmine (1 mg/h) or placebo, echo-planar imaging (EPI) was conducted as participants performed a selective attention task. During the task, two images comprised of superimposed pictures of faces and houses were presented. Subjects were instructed periodically to shift their attention from one stimulus component to the other and to perform a matching task using hand held response buttons. A control condition included phase-scrambled images of superimposed faces and houses that were presented in the same temporal and spatial manner as the attention task; participants were instructed to perform a matching task. Cholinergic enhancement improved performance during the selective attention task, with no change during the control task. Functional connectivity analyses showed that the strength of connectivity between ventral visual processing areas and task-related occipital, parietal and prefrontal regions reduced significantly during cholinergic enhancement, exclusively during the selective attention task. Physostigmine administration also reduced BOLD signal temporal variability relative to placebo throughout temporal and occipital visual processing areas, again during the selective attention task only. Together with the observed behavioral improvement, the decreases in connectivity strength throughout task-relevant regions and BOLD variability within stimulus processing regions support the hypothesis that cholinergic augmentation results in enhanced neural efficiency. This article is part of a Special Issue entitled 'Cognitive Enhancers'. Copyright © 2012 Elsevier Ltd. All rights reserved.

Cholinergic enhancement reduces functional connectivity and BOLD variability in visual extrastriate cortex during selective attention

PubMed Central

Ricciardi, Emiliano; Handjaras, Giacomo; Bernardi, Giulio; Pietrini, Pietro; Furey, Maura L.

2012-01-01

Enhancing cholinergic function improves performance on various cognitive tasks and alters neural responses in task specific brain regions. Previous findings by our group strongly suggested that the changes in neural activity observed during increased cholinergic function may reflect an increase in neural efficiency that leads to improved task performance. The current study was designed to assess the effects of cholinergic enhancement on regional brain connectivity and BOLD signal variability. Nine subjects participated in a double-blind, placebo-controlled crossover functional magnetic resonance imaging (fMRI) study. Following an infusion of physostigmine (1mg/hr) or placebo, echo-planar imaging (EPI) was conducted as participants performed a selective attention task. During the task, two images comprised of superimposed pictures of faces and houses were presented. Subjects were instructed periodically to shift their attention from one stimulus component to the other and to perform a matching task using hand held response buttons. A control condition included phase-scrambled images of superimposed faces and houses that were presented in the same temporal and spatial manner as the attention task; participants were instructed to perform a matching task. Cholinergic enhancement improved performance during the selective attention task, with no change during the control task. Functional connectivity analyses showed that the strength of connectivity between ventral visual processing areas and task-related occipital, parietal and prefrontal regions was reduced significantly during cholinergic enhancement, exclusively during the selective attention task. Cholinergic enhancement also reduced BOLD signal temporal variability relative to placebo throughout temporal and occipital visual processing areas, again during the selective attention task only. Together with the observed behavioral improvement, the decreases in connectivity strength throughout task-relevant regions and BOLD variability within stimulus processing regions provide further support to the hypothesis that cholinergic augmentation results in enhanced neural efficiency. PMID:22906685

A Study of Behavior and Body Type in Troubled Youth

ERIC Educational Resources Information Center

Shasby, Gregory; Kingsley, Ronald F.

1978-01-01

This study explored the relationship of selected physiological and morphological variables of male youth experiencing persistent and inappropriate behaviors in the home, school, and/or community, and a control group. The results tend to support differences between the groups in body type, percent of body fat, and strength. (Author)

Effects of glovebox gloves on grip and key pinch strength and contact forces for simulated manual operations with three commonly used hand tools.

PubMed

Sung, Peng-Cheng

2014-01-01

This study examined the effects of glovebox gloves for 11 females on maximum grip and key pinch strength and on contact forces generated from simulated tasks of a roller, a pair of tweezers and a crescent wrench. The independent variables were gloves fabricated of butyl, CSM/hypalon and neoprene materials; two glove thicknesses; and layers of gloves worn including single, double and triple gloving. CSM/hypalon and butyl gloves produced greater grip strength than the neoprene gloves. CSM/hypalon gloves also lowered contact forces for roller and wrench tasks. Single gloving and thin gloves improved hand strength performances. However, triple layers lowered contact forces for all tasks. Based on the evaluating results, selection and design recommendations of gloves for three hand tools were provided to minimise the effects on hand strength and optimise protection of the palmar hand in glovebox environments. To improve safety and health in the glovebox environments where gloves usage is a necessity, this study provides recommendations for selection and design of glovebox gloves for three hand tools including a roller, a pair of tweezers and a crescent wrench based on the results discovered in the experiments.

Does sexual selection explain human sex differences in aggression?

PubMed

Archer, John

2009-08-01

I argue that the magnitude and nature of sex differences in aggression, their development, causation, and variability, can be better explained by sexual selection than by the alternative biosocial version of social role theory. Thus, sex differences in physical aggression increase with the degree of risk, occur early in life, peak in young adulthood, and are likely to be mediated by greater male impulsiveness, and greater female fear of physical danger. Male variability in physical aggression is consistent with an alternative life history perspective, and context-dependent variability with responses to reproductive competition, although some variability follows the internal and external influences of social roles. Other sex differences, in variance in reproductive output, threat displays, size and strength, maturation rates, and mortality and conception rates, all indicate that male aggression is part of a sexually selected adaptive complex. Physical aggression between partners can be explained using different evolutionary principles, arising from the conflicts of interest between males and females entering a reproductive alliance, combined with variability following differences in societal gender roles. In this case, social roles are particularly important since they enable both the relatively equality in physical aggression between partners from Western nations, and the considerable cross-national variability, to be explained.

Biomotor status and kinesiological education of girls aged 10 to 12 years--example: volleyball.

PubMed

Milić, Mirjana; Grgantov, Zoran; Katić, Ratko

2012-09-01

The aim of this study was to define processes of orientation and/or selection towards sports game of volleyball in schoolgirls of Kastela, aged 10-12, by examining the relations between regular classes of physical education (PE) and extracurricular sport activities. For this purpose, two morphological measures were used (body height and body mass) and a set of 11 motor tests (6 basic motor abilities tests and 5 motor achievement tests) on a sample of 242 girls aged 10-12 was used, divided into a subsample of 42 girls participating in volleyball training (Volleyball players) and a subsample of 200 girls who do not participate in volleyball training (volleyball non-players). Based on the comparison of test results of schoolgirls from Kastela and Croatian norms, factor analysis of applied variables and discriminant analysis of these variables between volleyball players and non-players, processes and/or phases of selection in forming quality volleyball players were defined. Selection processes are preceded by orientation processes in physical education classes, i.e. choosing those sport activities which are in accordance with the biomotor status of students. Results have shown that orientation and initial selection in female volleyball needs to be executed based on the motor set of psychomotor speed, repetitive strength of the trunk and flexibility (muscle tone regulation), and body height. Volleyball training has affected the muscle mass development and the development of strength factors, so that explosive strength of jumping and/or takeoff along with body height, has predominantly differentiated female volleyball players from non-players, aged 10 to 12, and serve and spike quality will have dominant influence on the match outcome.

Effects of two classification strategies on a Benthic Community Index for streams in the Northern Lakes and Forests Ecoregion

USGS Publications Warehouse

Butcher, Jason T.; Stewart, Paul M.; Simon, Thomas P.

2003-01-01

Ninety-four sites were used to analyze the effects of two different classification strategies on the Benthic Community Index (BCI). The first, a priori classification, reflected the wetland status of the streams; the second, a posteriori classification, used a bio-environmental analysis to select classification variables. Both classifications were examined by measuring classification strength and testing differences in metric values with respect to group membership. The a priori (wetland) classification strength (83.3%) was greater than the a posteriori (bio-environmental) classification strength (76.8%). Both classifications found one metric that had significant differences between groups. The original index was modified to reflect the wetland classification by re-calibrating the scoring criteria for percent Crustacea and Mollusca. A proposed refinement to the original Benthic Community Index is suggested. This study shows the importance of using hypothesis-driven classifications, as well as exploratory statistical analysis, to evaluate alternative ways to reveal environmental variability in biological assessment tools.

Development, refinement, and testing of a short term solar flare prediction algorithm

NASA Technical Reports Server (NTRS)

Smith, Jesse B., Jr.

1993-01-01

During the period included in this report, the expenditure of time and effort, and progress toward performance of the tasks and accomplishing the goals set forth in the two year research grant proposal, consisted primarily of calibration and analysis of selected data sets. The heliographic limits of 30 degrees from central meridian were continued. As previously reported, all analyses are interactive and are performed by the Principal Investigator. It should also be noted that the analysis time involved by the Principal Investigator during this reporting period was limited, partially due to illness and partially resulting from other uncontrollable factors. The calibration technique (as developed by MSFC solar scientists), incorporates sets of constants which vary according to the wave length of the observation data set. One input constant is then varied interactively to correct for observing conditions, etc., to result in a maximum magnetic field strength (in the calibrated data), based on a separate analysis. There is some insecurity in the methodology and the selection of variables to yield the most self-consistent results for variable maximum field strengths and for variable observing/atmospheric conditions. Several data sets were analyzed using differing constant sets, and separate analyses to differing maximum field strength - toward standardizing methodology and technique for the most self-consistent results for the large number of cases. It may be necessary to recalibrate some of the analyses, but the sc analyses are retained on the optical disks and can still be used with recalibration where necessary. Only the extracted parameters will be changed.

Poor correlation between handgrip strength and isokinetic performance of knee flexor and extensor muscles in community-dwelling elderly women.

PubMed

Felicio, Diogo Carvalho; Pereira, Daniele Sirineu; Assumpção, Alexandra Miranda; de Jesus-Moraleida, Fabianna Resende; de Queiroz, Barbara Zille; da Silva, Juscelio Pereira; de Brito Rosa, Naysa Maciel; Dias, João Marcos Domingues; Pereira, Leani Souza Máximo

2014-01-01

To investigate the correlation between handgrip strength and performance of knee flexor and extensor muscles determined using an isokinetic dynamometer in community-dwelling elderly women. This was a cross-sectional study. Sample selection for the study was made by convenience, and 221 (71.07 ± 4.93 years) community-dwelling elderly women were included. Knee flexor and extensor muscle performance was measured using an isokinetic dynamometer Biodex System 3 Pro. The isokinetic variables chosen for analysis were peak torque, peak torque/bodyweight, total work/bodyweight, total work, average power, and agonist/antagonist ratio at the angular velocities of 60°/s and 180°/s. Assessment of handgrip strength was carried out using the Jamar dynamometer. Spearman's correlation coefficient was calculated to identify intervariable correlations. Only knee flexor peak torque (60°/s) and average power (60°/s), and knee extensor peak torque (180°/s) and total work (180°/s) were significantly (P < 0.05), yet poorly, correlated with handgrip strength (r < 0.30). The majority of analyses did not show any correlation between variables assessed by isokinetic dynamometer and handgrip dynamometer. Caution is required when generalizing handgrip strength as a predictor of global muscle strength in community-dwelling elderly women. © 2013 Japan Geriatrics Society.

Expression level, cellular compartment and metabolic network position all influence the average selective constraint on mammalian enzymes

PubMed Central

2011-01-01

Background A gene's position in regulatory, protein interaction or metabolic networks can be predictive of the strength of purifying selection acting on it, but these relationships are neither universal nor invariably strong. Following work in bacteria, fungi and invertebrate animals, we explore the relationship between selective constraint and metabolic function in mammals. Results We measure the association between selective constraint, estimated by the ratio of nonsynonymous (Ka) to synonymous (Ks) substitutions, and several, primarily metabolic, measures of gene function. We find significant differences between the selective constraints acting on enzyme-coding genes from different cellular compartments, with the nucleus showing higher constraint than genes from either the cytoplasm or the mitochondria. Among metabolic genes, the centrality of an enzyme in the metabolic network is significantly correlated with Ka/Ks. In contrast to yeasts, gene expression magnitude does not appear to be the primary predictor of selective constraint in these organisms. Conclusions Our results imply that the relationship between selective constraint and enzyme centrality is complex: the strength of selective constraint acting on mammalian genes is quite variable and does not appear to exclusively follow patterns seen in other organisms. PMID:21470417

Pelvic-floor strength in women with incontinence as assessed by the brink scale.

PubMed

FitzGerald, Mary P; Burgio, Kathryn L; Borello-France, Diane F; Menefee, Shawn A; Schaffer, Joseph; Kraus, Stephen; Mallett, Veronica T; Xu, Yan

2007-10-01

The purpose of this study was to describe how clinical pelvic-floor muscle (PFM) strength (force-generating capacity) is related to patient characteristics, lower urinary tract symptoms, and fecal incontinence symptoms. Data were obtained from 643 women who were participating in a randomized surgical trial for treatment of stress urinary incontinence. Patient demographic variables, baseline urinary and fecal incontinence symptom questionnaires, urodynamic data and urinary diary data, pad test results, and standardized assessment of pelvic organ support were compared with PFM strength as described by the Brink scoring system. Bivariate analysis of factors associated with the Brink scale score was done using analysis of variance and linear regression. Multivariate analysis included patient variables that were significant on bivariate analysis. The mean Brink scale score was 9 (SD=2) and did not vary widely in this large, but highly select, patient sample. We found a weak, but statistically strong, relationship between age and Brink score. Brink scores were not related to diary and pad test measures of incontinence severity. Overall, PFM strength was good in this sample of women with stress incontinence. Scores tended to be similar, and it is possible that the Brink scale does not reflect real clinical differences in PFM strength.

Effects of age, gender and educational background on strength of motivation for medical school

PubMed Central

Kruitwagen, Cas; ten Cate, Olle; Croiset, Gerda

2009-01-01

The aim of this study was to determine the effects of selection, educational background, age and gender on strength of motivation to attend and pursue medical school. Graduate entry (GE) medical students (having Bachelor’s degree in Life Sciences or related field) and Non-Graduate Entry (NGE) medical students (having only completed high school), were asked to fill out the Strength of Motivation for Medical School (SMMS) questionnaire at the start of medical school. The questionnaire measures the willingness of the medical students to pursue medical education even in the face of difficulty and sacrifice. GE students (59.64 ± 7.30) had higher strength of motivation as compared to NGE students (55.26 ± 8.33), so did females (57.05 ± 8.28) as compared to males (54.30 ± 8.08). 7.9% of the variance in the SMMS scores could be explained with the help of a linear regression model with age, gender and educational background/selection as predictor variables. Age was the single largest predictor. Maturity, taking developmental differences between sexes into account, was used as a predictor to correct for differences in the maturation of males and females. Still, the gender differences prevailed, though they were reduced. Pre-entrance educational background and selection also predicted the strength of motivation, but the effect of the two was confounded. Strength of motivation appears to be a dynamic entity, changing primarily with age and maturity and to a small extent with gender and experience. PMID:19774476

Correlations and path analysis among agronomic and technological traits of upland cotton.

PubMed

Farias, F J C; Carvalho, L P; Silva Filho, J L; Teodoro, P E

2016-08-12

To date, path analysis has been used with the aim of breeding different cultures. However, for cotton, there have been few studies using this analysis, and all of these have used fiber productivity as the primary dependent variable. Therefore, the aim of the present study was to identify agronomic and technological properties that can be used as criteria for direct and indirect phenotypes in selecting cotton genotypes with better fibers. We evaluated 16 upland cotton genotypes in eight trials conducted during the harvest 2008/2009 in the State of Mato Grosso, using a randomized block design with four replicates. The evaluated traits were: plant height, average boll weight, percentage of fiber, cotton seed yield, fiber length, uniformity of fiber, short fiber index, fiber strength, elongation, maturity of the fibers, micronaire, reflectance, and the degree of yellowing. Phenotypic correlations between the traits and cotton fiber yield (main dependent variable) were unfolded in direct and indirect effects through path analysis. Fiber strength, uniformity of fiber, and reflectance were found to influence fiber length, and therefore, these traits are recommended for both direct and indirect selection of cotton genotypes.

The Paediatric Rheumatology International Trials Organisation provisional criteria for the evaluation of response to therapy in juvenile dermatomyositis.

PubMed

Ruperto, Nicolino; Pistorio, Angela; Ravelli, Angelo; Rider, Lisa G; Pilkington, Clarissa; Oliveira, Sheila; Wulffraat, Nico; Espada, Graciela; Garay, Stella; Cuttica, Ruben; Hofer, Michael; Quartier, Pierre; Melo-Gomes, Jose; Reed, Ann M; Wierzbowska, Malgorzata; Feldman, Brian M; Harjacek, Miroslav; Huppertz, Hans-Iko; Nielsen, Susan; Flato, Berit; Lahdenne, Pekka; Michels, Harmut; Murray, Kevin J; Punaro, Lynn; Rennebohm, Robert; Russo, Ricardo; Balogh, Zsolt; Rooney, Madeleine; Pachman, Lauren M; Wallace, Carol; Hashkes, Philip; Lovell, Daniel J; Giannini, Edward H; Gare, Boel Andersson; Martini, Alberto

2010-11-01

To develop a provisional definition for the evaluation of response to therapy in juvenile dermatomyositis (DM) based on the Paediatric Rheumatology International Trials Organisation juvenile DM core set of variables. Thirty-seven experienced pediatric rheumatologists from 27 countries achieved consensus on 128 difficult patient profiles as clinically improved or not improved using a stepwise approach (patient's rating, statistical analysis, definition selection). Using the physicians' consensus ratings as the "gold standard measure," chi-square, sensitivity, specificity, false-positive and-negative rates, area under the receiver operating characteristic curve, and kappa agreement for candidate definitions of improvement were calculated. Definitions with kappa values >0.8 were multiplied by the face validity score to select the top definitions. The top definition of improvement was at least 20% improvement from baseline in 3 of 6 core set variables with no more than 1 of the remaining worsening by more than 30%, which cannot be muscle strength. The second-highest scoring definition was at least 20% improvement from baseline in 3 of 6 core set variables with no more than 2 of the remaining worsening by more than 25%, which cannot be muscle strength (definition P1 selected by the International Myositis Assessment and Clinical Studies group). The third is similar to the second with the maximum amount of worsening set to 30%. This indicates convergent validity of the process. We propose a provisional data-driven definition of improvement that reflects well the consensus rating of experienced clinicians, which incorporates clinically meaningful change in core set variables in a composite end point for the evaluation of global response to therapy in juvenile DM. Copyright © 2010 by the American College of Rheumatology.

A variant of sparse partial least squares for variable selection and data exploration.

PubMed

Olson Hunt, Megan J; Weissfeld, Lisa; Boudreau, Robert M; Aizenstein, Howard; Newman, Anne B; Simonsick, Eleanor M; Van Domelen, Dane R; Thomas, Fridtjof; Yaffe, Kristine; Rosano, Caterina

2014-01-01

When data are sparse and/or predictors multicollinear, current implementation of sparse partial least squares (SPLS) does not give estimates for non-selected predictors nor provide a measure of inference. In response, an approach termed "all-possible" SPLS is proposed, which fits a SPLS model for all tuning parameter values across a set grid. Noted is the percentage of time a given predictor is chosen, as well as the average non-zero parameter estimate. Using a "large" number of multicollinear predictors, simulation confirmed variables not associated with the outcome were least likely to be chosen as sparsity increased across the grid of tuning parameters, while the opposite was true for those strongly associated. Lastly, variables with a weak association were chosen more often than those with no association, but less often than those with a strong relationship to the outcome. Similarly, predictors most strongly related to the outcome had the largest average parameter estimate magnitude, followed by those with a weak relationship, followed by those with no relationship. Across two independent studies regarding the relationship between volumetric MRI measures and a cognitive test score, this method confirmed a priori hypotheses about which brain regions would be selected most often and have the largest average parameter estimates. In conclusion, the percentage of time a predictor is chosen is a useful measure for ordering the strength of the relationship between the independent and dependent variables, serving as a form of inference. The average parameter estimates give further insight regarding the direction and strength of association. As a result, all-possible SPLS gives more information than the dichotomous output of traditional SPLS, making it useful when undertaking data exploration and hypothesis generation for a large number of potential predictors.

Spiritual Well-Being and Dyadic Adjustment: Mediator Effects for Family Strengths

PubMed Central

Ghaffari, Majid

2016-01-01

Objectives The aim of the present study was to test a structural model of hypothesized relationships between spiritual well-being, intervening variables of personal worth of self and others, commitment to relationship stability, commitment to relationship growth, positive interaction/appreciation, communication/conflict resolution, time spent together, and, the dependent variable, dyadic adjustment. Materials and Methods Two hundred and sixty eight (171 females and 97 males) married parent subjects were selected by convenience sampling from three universities in Mazandaran, Iran, to take part in this study. They were all volunteers and were not paid and their age range was 23 to 47 (31.07 ± 4.37 years). All participants were asked to complete the spiritual well-being scale (SWBS), family strengths scale (FSS) and revised dyadic adjustment scale (RDAS). Results The results from structural equation modeling confirmed a hierarchy for the development of family strengths, and indicated that spiritual well-being and strength in most characteristics affected dyadic adjustment, positively (P <0.05). Conclusions Couples’ level of dyadic adjustment is increased when they have higher spiritual well-being, value each other, have commitment to each other, communicate well, enjoy being with each other, and spend time together. PMID:27822273

Spiritual Well-Being and Dyadic Adjustment: Mediator Effects for Family Strengths.

PubMed

Ghaffari, Majid

2016-09-01

The aim of the present study was to test a structural model of hypothesized relationships between spiritual well-being, intervening variables of personal worth of self and others, commitment to relationship stability, commitment to relationship growth, positive interaction/appreciation, communication/conflict resolution, time spent together, and, the dependent variable, dyadic adjustment. Two hundred and sixty eight (171 females and 97 males) married parent subjects were selected by convenience sampling from three universities in Mazandaran, Iran, to take part in this study. They were all volunteers and were not paid and their age range was 23 to 47 (31.07 ± 4.37 years). All participants were asked to complete the spiritual well-being scale (SWBS), family strengths scale (FSS) and revised dyadic adjustment scale (RDAS). The results from structural equation modeling confirmed a hierarchy for the development of family strengths, and indicated that spiritual well-being and strength in most characteristics affected dyadic adjustment, positively (P <0.05). Couples' level of dyadic adjustment is increased when they have higher spiritual well-being, value each other, have commitment to each other, communicate well, enjoy being with each other, and spend time together.

Aeroelastic Tailoring Study of N+2 Low Boom Supersonic Commerical Transport Aircraft

NASA Technical Reports Server (NTRS)

Pak, Chan-Gi

2015-01-01

The Lockheed Martin N+2 Low - boom Supersonic Commercial Transport (LSCT) aircraft was optimized in this study through the use of a multidisciplinary design optimization tool developed at the National Aeronautics and S pace Administration Armstrong Flight Research Center. A total of 111 design variables we re used in the first optimization run. Total structural weight was the objective function in this optimization run. Design requirements for strength, buckling, and flutter we re selected as constraint functions during the first optimization run. The MSC Nastran code was used to obtain the modal, strength, and buckling characteristics. Flutter and trim analyses we re based on ZAERO code, and landing and ground control loads were computed using an in - house code. The w eight penalty to satisfy all the design requirement s during the first optimization run was 31,367 lb, a 9.4% increase from the baseline configuration. The second optimization run was prepared and based on the big-bang big-crunch algorithm. Six composite ply angles for the second and fourth composite layers were selected as discrete design variables for the second optimization run. Composite ply angle changes can't improve the weight configuration of the N+2 LSCT aircraft. However, this second optimization run can create more tolerance for the active and near active strength constraint values for future weight optimization runs.

Family strengths, motivation, and resources as predictors of health promotion behavior in single-parent and two-parent families.

PubMed

Ford-Gilboe, M

1997-06-01

The extent to which selected aspects of family health potential (strengths, motivation, and resources) predicted health work (health-related problem-solving and goal attainment behaviors) was examined in a Canadian sample of 138 female-headed single-parent families and two-parent families. The mother and one child (age 10-14) each completed mailed self-report instruments to assess the independent variables of family cohesion, family pride, mother's non-traditional sex role orientation, general self-efficacy, internal health locus of control, network support, community support, and family income, as well as the dependent variable, health work. With the effects of mothers' education held constant, the independent variables predicted 22 to 27% of the variance in health work in the total sample and each family type. Family cohesion was the most consistent predictor of health work, accounting for 8 to 13% of the variance. The findings challenge existing problem-oriented views of single-parent families by focusing on their potential to engage in health promotion behavior.

Latent mnemonic strengths are latent: a comment on Mickes, Wixted, and Wais (2007).

PubMed

Rouder, Jeffrey N; Pratte, Michael S; Morey, Richard D

2010-06-01

Mickes, Wixted, and Wais (2007) proposed a simple test of latent strength variability in recognition memory. They asked participants to rate their confidence using either a 20-point or a 99-point strength scale and plotted distributions of the resulting ratings. They found 25% more variability in ratings for studied than for new items, which they interpreted as providing evidence that latent mnemonic strength distributions are 25% more variable for studied than for new items. We show here that this conclusion is critically dependent on assumptions--so much so that these assumptions determine the conclusions. In fact, opposite conclusions, such that study does not affect the variability of latent strength, may be reached by making different but equally plausible assumptions. Because all measurements of mnemonic strength variability are critically dependent on untestable assumptions, all are arbitrary. Hence, there is no principled method for assessing the relative variability of latent mnemonic strength distributions.

Water quality parameter measurement using spectral signatures

NASA Technical Reports Server (NTRS)

White, P. E.

1973-01-01

Regression analysis is applied to the problem of measuring water quality parameters from remote sensing spectral signature data. The equations necessary to perform regression analysis are presented and methods of testing the strength and reliability of a regression are described. An efficient algorithm for selecting an optimal subset of the independent variables available for a regression is also presented.

Multi scale habitat relationships of Martes americana in northern Idaho, U.S.A.

Treesearch

Tzeidle N. Wasserman; Samuel A. Cushman; David O. Wallin; Jim Hayden

2012-01-01

We used bivariate scaling and logistic regression to investigate multiple-scale habitat selection by American marten (Martes americana). Bivariate scaling reveals dramatic differences in the apparent nature and strength of relationships between marten occupancy and a number of habitat variables across a range of spatial scales. These differences include reversals in...

Interspecific competition alters nonlinear selection on offspring size in the field.

PubMed

Marshall, Dustin J; Monro, Keyne

2013-02-01

Offspring size is one of the most important life-history traits with consequences for both the ecology and evolution of most organisms. Surprisingly, formal estimates of selection on offspring size are rare, and the degree to which selection (particularly nonlinear selection) varies among environments remains poorly explored. We estimate linear and nonlinear selection on offspring size, module size, and senescence rate for a sessile marine invertebrate in the field under three different intensities of interspecific competition. The intensity of competition strongly modified the strength and form of selection acting on offspring size. We found evidence for differences in nonlinear selection across the three environments. Our results suggest that the fitness returns of a given offspring size depend simultaneously on their environmental context, and on the context of other offspring traits. Offspring size effects can be more pervasive with regards to their influence on the fitness returns of other traits than previously recognized, and we suggest that the evolution of offspring size cannot be understood in isolation from other traits. Overall, variability in the form and strength of selection on offspring size in nature may reduce the efficacy of selection on offspring size and maintain variation in this trait. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

Selection criteria for internal medicine residency applicants and professionalism ratings during internship.

PubMed

Cullen, Michael W; Reed, Darcy A; Halvorsen, Andrew J; Wittich, Christopher M; Kreuziger, Lisa M Baumann; Keddis, Mira T; McDonald, Furman S; Beckman, Thomas J

2011-03-01

To determine whether standardized admissions data in residents' Electronic Residency Application Service (ERAS) submissions were associated with multisource assessments of professionalism during internship. ERAS applications for all internal medicine interns (N=191) at Mayo Clinic entering training between July 1, 2005, and July 1, 2008, were reviewed by 6 raters. Extracted data included United States Medical Licensing Examination scores, medicine clerkship grades, class rank, Alpha Omega Alpha membership, advanced degrees, awards, volunteer activities, research experiences, first author publications, career choice, and red flags in performance evaluations. Medical school reputation was quantified using U.S. News & World Report rankings. Strength of comparative statements in recommendation letters (0 = no comparative statement, 1 = equal to peers, 2 = top 20%, 3 = top 10% or "best") were also recorded. Validated multisource professionalism scores (5-point scales) were obtained for each intern. Associations between application variables and professionalism scores were examined using linear regression. The mean ± SD (minimum-maximum) professionalism score was 4.09 ± 0.31 (2.13-4.56). In multivariate analysis, professionalism scores were positively associated with mean strength of comparative statements in recommendation letters (β = 0.13; P = .002). No other associations between ERAS application variables and professionalism scores were found. Comparative statements in recommendation letters for internal medicine residency applicants were associated with professionalism scores during internship. Other variables traditionally examined when selecting residents were not associated with professionalism. These findings suggest that faculty physicians' direct observations, as reflected in letters of recommendation, are useful indicators of what constitutes a best student. Residency selection committees should scrutinize applicants' letters for strongly favorable comparative statements.

Chronic low back pain in patients with systemic lupus erythematosus: prevalence and predictors of back muscle strength and its correlation with disability.

PubMed

Cezarino, Raíssa Sudré; Cardoso, Jefferson Rosa; Rodrigues, Kedma Neves; Magalhães, Yasmin Santana; Souza, Talita Yokoy de; Mota, Lícia Maria Henrique da; Bonini-Rocha, Ana Clara; McVeigh, Joseph; Martins, Wagner Rodrigues

To determine the prevalence of Chronic Low Back Pain and predictors of Back Muscle Strength in patients with Systemic Lupus Erythematosus. Cross-sectional study. Ninety-six ambulatory patients with lupus were selected by non-probability sampling and interviewed and tested during medical consultation. The outcomes measurements were: Point prevalence of chronic low back pain, Oswestry Disability Index, Tampa Scale of Kinesiophobia, Fatigue Severity Scale and maximal voluntary isometric contractions of handgrip and of the back muscles. Correlation coefficient and multiple linear regression were used in statistical analysis. Of the 96 individuals interviewed, 25 had chronic low back pain, indicating a point prevalence of 26% (92% women). The correlation between the Oswestry Index and maximal voluntary isometric contraction of the back muscles was r=-0.4, 95% CI [-0.68; -0.01] and between the maximal voluntary isometric contraction of handgrip and of the back muscles was r=0.72, 95% CI [0.51; 0.88]. The regression model presented the highest value of R 2 being observed when maximal voluntary isometric contraction of the back muscles was tested with five independent variables (63%). In this model handgrip strength was the only predictive variable (β=0.61, p=0.001). The prevalence of chronic low back pain in individuals with systemic lupus erythematosus was 26%. The maximal voluntary isometric contraction of the back muscles was 63% predicted by five variables of interest, however, only the handgrip strength was a statistically significant predictive variable. The maximal voluntary isometric contraction of the back muscles presented a linear relation directly proportional to handgrip and inversely proportional to Oswestry Index i.e. stronger back muscles are associated with lower disability scores. Copyright © 2017. Published by Elsevier Editora Ltda.

Fluctuating selection across years and phenotypic variation in food-deceptive orchids.

PubMed

Scopece, Giovanni; Juillet, Nicolas; Lexer, Christian; Cozzolino, Salvatore

2017-01-01

Nectarless flowers that deceive pollinators offer an opportunity to study asymmetric plant-insect interactions. Orchids are a widely used model for studying these interactions because they encompass several thousand species adopting deceptive pollination systems. High levels of intra-specific phenotypic variation have been reported in deceptive orchids, suggesting a reduced consistency of pollinator-mediated selection on their floral traits. Nevertheless, several studies report on widespread directional selection mediated by pollinators even in these deceptive orchids. In this study we test the hypothesis that the observed selection can fluctuate across years in strength and direction thus likely contributing to the phenotypic variability of this orchid group. We performed a three-year study estimating selection differentials and selection gradients for nine phenotypic traits involved in insect attraction in two Mediterranean orchid species, namely Orchis mascula and O. pauciflora , both relying on a well-described food-deceptive pollination strategy. We found weak directional selection and marginally significant selection gradients in the two investigated species with significant intra-specific differences in selection differentials across years. Our data do not link this variation with a specific environmental cause, but our results suggest that pollinator-mediated selection in food-deceptive orchids can change in strength and in direction over time. In perennial plants, such as orchids, different selection differentials in the same populations in different flowering seasons can contribute to the maintenance of phenotypic variation often reported in deceptive orchids.

Locomotor-respiratory coupling patterns and oxygen consumption during walking above and below preferred stride frequency.

PubMed

O'Halloran, Joseph; Hamill, Joseph; McDermott, William J; Remelius, Jebb G; Van Emmerik, Richard E A

2012-03-01

Locomotor respiratory coupling patterns in humans have been assessed on the basis of the interaction between different physiological and motor subsystems; these interactions have implications for movement economy. A complex and dynamical systems framework may provide more insight than entrainment into the variability and adaptability of these rhythms and their coupling. The purpose of this study was to investigate the relationship between steady state locomotor-respiratory coordination dynamics and oxygen consumption [Formula: see text] of the movement by varying walking stride frequency from preferred. Twelve male participants walked on a treadmill at a self-selected speed. Stride frequency was varied from -20 to +20% of preferred stride frequency (PSF) while respiratory airflow, gas exchange variables, and stride kinematics were recorded. Discrete relative phase and return map techniques were used to evaluate the strength, stability, and variability of both frequency and phase couplings. Analysis of [Formula: see text] during steady-state walking showed a U-shaped response (P = 0.002) with a minimum at PSF and PSF - 10%. Locomotor-respiratory frequency coupling strength was not greater (P = 0.375) at PSF than any other stride frequency condition. The dominant coupling across all conditions was 2:1 with greater occurrences at the lower stride frequencies. Variability in coupling was the greatest during PSF, indicating an exploration of coupling strategies to search for the coupling frequency strategy with the least oxygen consumption. Contrary to the belief that increased strength of frequency coupling would decrease oxygen consumption; these results conclude that it is the increased variability of frequency coupling that results in lower oxygen consumption.

Testing biomechanical models of human lumbar lordosis variability.

PubMed

Castillo, Eric R; Hsu, Connie; Mair, Ross W; Lieberman, Daniel E

2017-05-01

Lumbar lordosis (LL) is a key adaptation for bipedalism, but factors underlying curvature variations remain unclear. This study tests three biomechanical models to explain LL variability. Thirty adults (15 male, 15 female) were scanned using magnetic resonance imaging (MRI), a standing posture analysis was conducted, and lumbar range of motion (ROM) was assessed. Three measures of LL were compared. The trunk's center of mass was estimated from external markers to calculate hip moments (M hip ) and lumbar flexion moments. Cross-sectional areas of lumbar vertebral bodies and trunk muscles were measured from scans. Regression models tested associations between LL and the M hip moment arm, a beam bending model, and an interaction between relative trunk strength (RTS) and ROM. Hip moments were not associated with LL. Beam bending was moderately predictive of standing but not supine LL (R 2  = 0.25). Stronger backs and increased ROM were associated with greater LL, especially when standing (R 2  = 0.65). The strength-flexibility model demonstrates the differential influence of RTS depending on ROM: individuals with high ROM exhibited the most LL variation with RTS, while those with low ROM showed reduced LL regardless of RTS. Hip moments appear constrained suggesting the possibility of selection, and the beam model explains some LL variability due to variations in trunk geometry. The strength-flexibility interaction best predicted LL, suggesting a tradeoff in which ROM limits the effects of back strength on LL. The strength-flexibility model may have clinical relevance for spinal alignment and pathology. This model may also suggest that straight-backed Neanderthals had reduced lumbar mobility. © 2017 Wiley Periodicals, Inc.

Strength reduction in slash pine (Pinus elliotii) wood caused by decay fungi

Treesearch

Zhong Yang; Zhehui Jiang; Chung Y. Hse; Todd F. Shupe

2009-01-01

Small wood specimens selected from slash pine (Pinus elliotii )trees at three growth rates (fast, medium, and slow) were inoculated with brown-rot and white-rot fungi and then evaluated for work to maximum load (WML), modulus of rupture (MOR), and modulus of elasticity (MOE). The experimental variables studied included a brown-rot fungus (Gloeophyllum trabeum...

Design Optimization and In Vitro-In Vivo Evaluation of Orally Dissolving Strips of Clobazam

PubMed Central

Bala, Rajni; Khanna, Sushil; Pawar, Pravin

2014-01-01

Clobazam orally dissolving strips were prepared by solvent casting method. A full 32 factorial design was applied for optimization using different concentration of film forming polymer and disintegrating agent as independent variable and disintegration time, % cumulative drug release, and tensile strength as dependent variable. In addition the prepared films were also evaluated for surface pH, folding endurance, and content uniformity. The optimized film formulation showing the maximum in vitro drug release, satisfactory in vitro disintegration time, and tensile strength was selected for bioavailability study and compared with a reference marketed product (frisium5 tablets) in rabbits. Formulation (F6) was selected by the Design-expert software which exhibited DT (24 sec), TS (2.85 N/cm2), and in vitro drug release (96.6%). Statistical evaluation revealed no significant difference between the bioavailability parameters of the test film (F6) and the reference product. The mean ratio values (test/reference) of C max (95.87%), t max (71.42%), AUC0−t (98.125%), and AUC0−∞ (99.213%) indicated that the two formulae exhibited comparable plasma level-time profiles. PMID:25328709

The transfer of strength and power into the stroke biomechanics of young swimmers over a 34-week period.

PubMed

Morais, Jorge E; Silva, António J; Garrido, Nuno D; Marinho, Daniel A; Barbosa, Tiago M

2018-03-24

The purpose of this study was to learn the interplay between dry-land strength and conditioning, and stroke biomechanics in young swimmers, during a 34-week training programme. Twenty-seven swimmers (overall: 13.33 ± 0.85 years old; 11 boys: 13.5 ± 0.75 years old; 16 girls: 13.2 ± 0.92 years old) competing at regional- and national-level competitions were evaluated. The swimmers were submitted to a specific in-water and dry-land strength training over 34 weeks (and evaluated at three time points: pre-, mid-, and post-test; M1, M2, and M3, respectively). The 100-m freestyle performance was chosen as the main outcome (i.e. dependent variable). The arm span (AS; anthropometrics), throwing velocity (TV; strength), stroke length (SL), and stroke frequency (SF; kinematics) were selected as independent variables. There was a performance enhancement over time (M1 vs. M3: 68.72 ± 5.57 s, 66.23 ± 5.23 s; Δ = -3.77%; 95% CI: -3.98;-3.56) and an overall improvement of the remaining variables. At M1 and M2, all links between variables presented significant effects (p < .001), except the TV-SL and the TV-SF path. At M3, all links between variables presented significant effects (p ≤ .05). Between M1 and M3, the direct effect of the TV to the stroke biomechanics parameters (SL and SF) increased. The model predicted 89%, 88%, and 92% of the performance at M1, M2, and M3, respectively, with a reasonable adjustment (i.e. goodness-of-fit M1: χ 2 /df = 3.82; M2: χ 2 /df = 3.08; M3: χ 2 /df = 4.94). These findings show that strength and conditioning parameters have a direct effect on the stroke biomechanics, and the latter one on the swimming performance.

A search for cataclysmic binaries containing strongly magnetic white dwarfs

NASA Technical Reports Server (NTRS)

Bond, H. E.; Chanmugam, G.

1982-01-01

The AM Herculis type binaries which contain accreting white dwarfs with surface magnetic fields of a few times 10 to the seventh power gauss were studied. If white dwarfs in cataclysmic binaries have a range of field strengths similar to that among single white dwarfs. AM Her like systems should exist with fields as high as 3 x 10 to the eighth power gauss. It is suggested that such objects will not have the strong optical polarization of the AM Her variables; however, they exhibit high harmonic cyclotron emission, making them spectacular UV sources. We made IUE observations of seven candidate cataclysmic variables selected for optical similarity to AM Her binaries. Although all seven objects were detected in the UV, none display unusually strong UV continua. It is suggested that the distribution of magnetic field strengths among single white dwarfs may be different from that among binaries.

False recognition production indexes in forward associative strength (FAS) lists with three critical words.

PubMed

Beato, María Soledad; Arndt, Jason

2014-01-01

False memory illusions have been widely studied using the Deese/Roediger-McDermott paradigm (DRM). In this paradigm, participants study words semantically related to a single nonpresented critical word. In a memory test critical words are often falsely recalled and recognized. The present study was conducted to measure the levels of false recognition for seventy-five Spanish DRM word lists that have multiple critical words per list. Lists included three critical words (e.g., HELL, LUCEFER, and SATAN) simultaneously associated with six studied words (e.g., devil, demon, fire, red, bad, and evil). Different levels of forward associative strength (FAS) between the critical words and their studied associates were used in the construction of the lists. Specifically, we selected lists with the highest FAS values possible and FAS was continuously decreased in order to obtain the 75 lists. Six words per list, simultaneously associated with three critical words, were sufficient to produce false recognition. Furthermore, there was wide variability in rates of false recognition (e.g., 53% for DUNGEON, PRISON, and GRATES; 1% for BRACKETS, GARMENT, and CLOTHING). Finally, there was no correlation between false recognition and associative strength. False recognition variability could not be attributed to differences in the forward associative strength.

Laser-Aided Ceramic Bracket Debonding: A Comprehensive Review

PubMed Central

Ghazanfari, Rezvaneh; Nokhbatolfoghahaei, Hanieh; Alikhasi, Marzieh

2016-01-01

Different techniques have been introduced for the removal of ceramic brackets. Since the early 1990s, lasers have been used experimentally for debonding ceramic brackets. The goal of this study is to give a comprehensive literature review on laser-aided ceramic bracket debonding. PubMed and Google Scholar databases were used to identify dental articles with the following combination of key words: Ceramic brackets, Debonding, and Laser. Sixteen English articles from 2004 to 2015 were selected. The selected studies were categorized according to the variables investigated including the intrapulpal temperature, shear bond strength, debonding time, enamel damage and bracket failure. Most articles reported decreased shear bond strength and debonding time following laser irradiation without any critical and irritating increase in pulpal temperature. There were no reports of bracket failure or enamel damage. Laser irradiation is an efficient way to reduce shear bond strength of ceramic bracket and debonding time. This technique is a safe way for removing ceramic bracket with minimal impact on intrapulpal temperature and enamel surface and it reduces ceramic bracket failure. PMID:27330690

Effects of Reduced Strength on Self-Selected Pacing for Long-Duration Activities

NASA Technical Reports Server (NTRS)

Buxton, Roxanne E.; Ryder, Jeffrey W.; English, Kirk E.; Guined, Jamie R.; Ploutz-Snyder, Lori L.

2015-01-01

Strength and aerobic capacity are predictors of astronaut performance for extravehicular activities (EVA) during exploration missions. It is expected that astronauts will self-select a pace below their ventilatory threshold (VT). PURPOSE: To determine the percentage of VT that subjects self-select for prolonged occupational tasks. METHODS: Maximal aerobic capacity and a variety of lower-body strength and power variables were assessed in 17 subjects who climbed 480 rungs on a ladder ergometer and then completed 10 km on a treadmill as quickly as possible using a self-selected pace. The tasks were performed on 4 days, with a weighted suit providing 0% (suit fabric only), 40%, 60%, and 80% of additional bodyweight (BW), thereby altering the strength to BW ratio. Oxygen consumption and heart rate were continuously measured. Repeated measures ANOVA and post-hoc comparisons were performed on the percent of VT values under each suited condition. RESULTS: Subjects consistently self-paced at or below VT for both tasks and the pace was related to suit weight. At the midpoint for the ladder climb the 80% BW condition elicited the lowest metabolic cost (-19+/-14% below VT), significantly different than the 0% BW (-3+/-16%, P=0.002) and the 40% BW conditions (-5+/-22%, P=0.023). The 60% BW condition (-13+/-19%) was different than the 40% BW condition (P=0.034). Upon completion of the ladder task there were no differences among the conditions (0%BW: 3+/-18%; 40%BW: 3+/-21%; 60%BW: - 8+/-25%; 80%BW: -10+/-18%). All subjects failed to complete 5km at 80%BW. At the midpoint of the treadmill test the three remaining conditions were all significantly different (0%BW: -20+/-15%; 40%BW: - 33+/-15%; 60%BW: -41+/-19%). Upon completion of the treadmill test the 60% BW condition (-38+/-12%) was significantly different than the 40% BW (-28+/-15%, P=0.024). CONCLUSIONS: Decreasing relative strength results in progressive and disproportionate decreases (relative to VT) in self-selected pacing during long-duration activities. Thus, during prolonged, endurance-type activities, large reductions in strength cause notable performance decrements despite no changes in aerobic capacity. These data highlight the importance of both aerobic capacity and muscle strength to the performance of prolonged EVA in exploration mission scenarios.

Selection Criteria for Internal Medicine Residency Applicants and Professionalism Ratings During Internship

PubMed Central

Cullen, Michael W.; Reed, Darcy A.; Halvorsen, Andrew J.; Wittich, Christopher M.; Kreuziger, Lisa M. Baumann; Keddis, Mira T.; McDonald, Furman S.; Beckman, Thomas J.

2011-01-01

OBJECTIVE: To determine whether standardized admissions data in residents' Electronic Residency Application Service (ERAS) submissions were associated with multisource assessments of professionalism during internship. PARTICIPANTS AND METHODS: ERAS applications for all internal medicine interns (N=191) at Mayo Clinic entering training between July 1, 2005, and July 1, 2008, were reviewed by 6 raters. Extracted data included United States Medical Licensing Examination scores, medicine clerkship grades, class rank, Alpha Omega Alpha membership, advanced degrees, awards, volunteer activities, research experiences, first author publications, career choice, and red flags in performance evaluations. Medical school reputation was quantified using U.S. News & World Report rankings. Strength of comparative statements in recommendation letters (0 = no comparative statement, 1 = equal to peers, 2 = top 20%, 3 = top 10% or “best”) were also recorded. Validated multisource professionalism scores (5-point scales) were obtained for each intern. Associations between application variables and professionalism scores were examined using linear regression. RESULTS: The mean ± SD (minimum-maximum) professionalism score was 4.09±0.31 (2.13-4.56). In multivariate analysis, professionalism scores were positively associated with mean strength of comparative statements in recommendation letters (β=0.13; P=.002). No other associations between ERAS application variables and professionalism scores were found. CONCLUSION: Comparative statements in recommendation letters for internal medicine residency applicants were associated with professionalism scores during internship. Other variables traditionally examined when selecting residents were not associated with professionalism. These findings suggest that faculty physicians' direct observations, as reflected in letters of recommendation, are useful indicators of what constitutes a best student. Residency selection committees should scrutinize applicants' letters for strongly favorable comparative statements. PMID:21364111

Sex steroids, sexual behavior, and selection attention for erotic stimuli in women using oral contraceptives.

PubMed

Alexander, G M; Sherwin, B B

1993-01-01

The relationship between sex steroids and sexual behavior was examined in 19 oral contraceptive users. Retrospective assessment of sexual attitudes were obtained and women completed daily ratings of sexual behavior and well-being for 28 days. Plasma levels of free testosterone (T), estradiol, and progesterone were measured at weekly intervals. In addition, women performed a novel selective attention task designed to measure the strength of the tendency to be distracted by sexual stimuli. Multiple regression analyses using average sexual behavior variables as dependent variables, and hormone levels sexual attitudes and well-being as predictor variables, showed that free T was strongly and positively associated with sexual desire, sexual thoughts, and anticipation of sexual activity. A role for T in attention to sexual stimuli was also supported by the positive correlation between free T and the bias for sexual stimuli in a subgroup of women. These results are consistent with the hypothesis that T may enhance cognitive aspects of women's sexual behavior.

Comparison of climate envelope models developed using expert-selected variables versus statistical selection

USGS Publications Warehouse

Brandt, Laura A.; Benscoter, Allison; Harvey, Rebecca G.; Speroterra, Carolina; Bucklin, David N.; Romañach, Stephanie; Watling, James I.; Mazzotti, Frank J.

2017-01-01

Climate envelope models are widely used to describe potential future distribution of species under different climate change scenarios. It is broadly recognized that there are both strengths and limitations to using climate envelope models and that outcomes are sensitive to initial assumptions, inputs, and modeling methods Selection of predictor variables, a central step in modeling, is one of the areas where different techniques can yield varying results. Selection of climate variables to use as predictors is often done using statistical approaches that develop correlations between occurrences and climate data. These approaches have received criticism in that they rely on the statistical properties of the data rather than directly incorporating biological information about species responses to temperature and precipitation. We evaluated and compared models and prediction maps for 15 threatened or endangered species in Florida based on two variable selection techniques: expert opinion and a statistical method. We compared model performance between these two approaches for contemporary predictions, and the spatial correlation, spatial overlap and area predicted for contemporary and future climate predictions. In general, experts identified more variables as being important than the statistical method and there was low overlap in the variable sets (<40%) between the two methods Despite these differences in variable sets (expert versus statistical), models had high performance metrics (>0.9 for area under the curve (AUC) and >0.7 for true skill statistic (TSS). Spatial overlap, which compares the spatial configuration between maps constructed using the different variable selection techniques, was only moderate overall (about 60%), with a great deal of variability across species. Difference in spatial overlap was even greater under future climate projections, indicating additional divergence of model outputs from different variable selection techniques. Our work is in agreement with other studies which have found that for broad-scale species distribution modeling, using statistical methods of variable selection is a useful first step, especially when there is a need to model a large number of species or expert knowledge of the species is limited. Expert input can then be used to refine models that seem unrealistic or for species that experts believe are particularly sensitive to change. It also emphasizes the importance of using multiple models to reduce uncertainty and improve map outputs for conservation planning. Where outputs overlap or show the same direction of change there is greater certainty in the predictions. Areas of disagreement can be used for learning by asking why the models do not agree, and may highlight areas where additional on-the-ground data collection could improve the models.

Analysis of Tests Evaluating Sport Climbers’ Strength and Isometric Endurance

PubMed Central

Ozimek, Mariusz; Staszkiewicz, Robert; Rokowski, Robert

2016-01-01

Abstract The present study was designed to determine which types of specific tests provide an effective evaluation of strength and endurance in highly trained competitive sport climbers. The research process consisted of three basic components: the measurement of selected somatic characteristics of the climbers, the assessment of their physical conditioning, and a search for correlations between the anthropometric and “conditioning” variables on the one hand, and climber’s performance on the other. The sample of subjects consisted of 14 experienced volunteer climbers capable of handling 7a- 8a+/b on-sight rock climbing grades. The strongest correlations (Spearman’s rank) were found between climber’s competence and the relative results of the finger strength test (r = 0.7); much lower, but still statistically significant coefficients were found between the level of competence and the results of the muscle endurance tests (r = 0.53 – 0.57). Climbers aspiring to attain an elite level must have strong finger and forearm muscles, but most of all, they must be capable of releasing their potential during specific motor capability tests engaging these parts of the body. The forearm muscles of elite climbers must also be very resistant to fatigue. Since highly trained athletes vary only slightly in body mass, this variable does not have a major effect on their performance during strength and endurance tests. PMID:28149428

Flexible categorization of relative stimulus strength by the optic tectum

PubMed Central

Mysore, Shreesh P.; Knudsen, Eric I.

2011-01-01

Categorization is the process by which the brain segregates continuously variable stimuli into discrete groups. We report that patterns of neural population activity in the owl optic tectum (OT) categorize stimuli based on their relative strengths into “strongest” versus “other”. The category boundary shifts adaptively to track changes in the absolute strength of the strongest stimulus. This population-wide categorization is mediated by the responses of a small subset of neurons. Our data constitute the first direct demonstration of an explicit categorization of stimuli by a neural network based on relative stimulus strength or salience. The finding of categorization by the population code relaxes constraints on the properties of downstream decoders that might read out the location of the strongest stimulus. These results indicate that the ensemble neural code in the OT could mediate bottom-up stimulus selection for gaze and attention, a form of stimulus categorization in which the category boundary often shifts within hundreds of milliseconds. PMID:21613487

Bearing Strengths of Some Wrought-aluminum Alloys

NASA Technical Reports Server (NTRS)

Moore, R L; Wescoat, C

1943-01-01

Although a number of investigations of the bearing strength of aluminum alloys have been made, the problem remains one of considerable interest to the aircraft industry. For this reason it has seemed advisable to make additional tests of the commonly used aircraft alloys in an effort to establish a better basis for the selection of allowable bearing values. Current design practice does not recognize the effect of edge distance upon bearing strengths, and for this reason edge distance was one of the principal variables considered in this investigation. The increasing emphasis being placed upon permanent set limitations makes it essential that more information on bearing yield phenomena be obtained. The object of this investigation was to determine bearing yield and ultimate strengths of the following aluminum alloy products: 17S-T, 24S-T, Alclad 24S-T, 24S-RT, 52S-0, 52S-1/2H, 52S-H, 53S-T, and 61S-T extrusions. Ratios of these bearing properties to tensile properties were also determined.

Fluctuating environments, sexual selection and the evolution of flexible mate choice in birds.

PubMed

Botero, Carlos A; Rubenstein, Dustin R

2012-01-01

Environmentally-induced fluctuation in the form and strength of natural selection can drive the evolution of morphology, physiology, and behavior. Here we test the idea that fluctuating climatic conditions may also influence the process of sexual selection by inducing unexpected reversals in the relative quality or sexual attractiveness of potential breeding partners. Although this phenomenon, known as 'ecological cross-over', has been documented in a variety of species, it remains unclear the extent to which it has driven the evolution of major interspecific differences in reproductive behavior. We show that after controlling for potentially influential life history and demographic variables, there are significant positive associations between the variability and predictability of annual climatic cycles and the prevalence of infidelity and divorce within populations of a taxonomically diverse array of socially monogamous birds. Our results are consistent with the hypothesis that environmental factors have shaped the evolution of reproductive flexibility and suggest that in the absence of severe time constraints, secondary mate choice behaviors can help prevent, correct, or minimize the negative consequences of ecological cross-overs. Our findings also illustrate how a basic evolutionary process like sexual selection is susceptible to the increasing variability and unpredictability of climatic conditions that is resulting from climate change.

Aeroelastic Tailoring Study of N+2 Low-Boom Supersonic Commercial Transport Aircraft

NASA Technical Reports Server (NTRS)

Pak, Chan-gi

2015-01-01

The Lockheed Martins N+2 Low-boom Supersonic Commercial Transport (LSCT) aircraft is optimized in this study through the use of a multidisciplinary design optimization tool developed at the NASA Armstrong Flight Research Center. A total of 111 design variables are used in the first optimization run. Total structural weight is the objective function in this optimization run. Design requirements for strength, buckling, and flutter are selected as constraint functions during the first optimization run. The MSC Nastran code is used to obtain the modal, strength, and buckling characteristics. Flutter and trim analyses are based on ZAERO code and landing and ground control loads are computed using an in-house code.

Associations between neighbourhood and household environmental variables and fruit consumption: exploration of mediation by individual cognitions and habit strength in the GLOBE study.

PubMed

Tak, Nannah I; te Velde, Saskia J; Kamphuis, Carlijn Bm; Ball, Kylie; Crawford, David; Brug, Johannes; van Lenthe, Frank J

2013-03-01

The present study examined associations of several home and neighbourhood environmental variables with fruit consumption and explored whether these associations were mediated by variables derived from the Theory of Planned Behaviour (TPB) and by habit strength. Data of the Dutch GLOBE study on household and neighbourhood environment, fruit intake and related factors were used, obtained by self-administered questionnaires (cross-sectional), face-to-face interviews and audits. The city of Eindhoven in the Netherlands Adults (n 333; mean age 58 years, 54% female). Multiple mediation analyses were conducted using regression analyses to assess the association between environmental variables and fruit consumption, as well as mediation of these associations by TPB variables and by habit strength. Intention, perceived behaviour control, subjective norm and habit strength were associated with fruit intake. None of the neighbourhood environmental variables was directly or indirectly associated with fruit intake. The home environmental variable 'modelling behaviour by family members' was indirectly, but not directly, associated with fruit intake. Habit strength and perceived behaviour control explained most of the mediated effect (71.9%). Modelling behaviour by family members was indirectly associated with fruit intake through habit strength and perceived behaviour control. None of the neighbourhood variables was directly or indirectly, through any of the proposed mediators, associated with adult fruit intake. These findings suggest that future interventions promoting fruit intake should address a combination of the home environment (especially modelling behaviour by family members), TPB variables and habit strength for fruit intake.

Formulation and optimisation of raft-forming chewable tablets containing H2 antagonist

PubMed Central

Prajapati, Shailesh T; Mehta, Anant P; Modhia, Ishan P; Patel, Chhagan N

2012-01-01

Purpose: The purpose of this research work was to formulate raft-forming chewable tablets of H2 antagonist (Famotidine) using a raft-forming agent along with an antacid- and gas-generating agent. Materials and Methods: Tablets were prepared by wet granulation and evaluated for raft strength, acid neutralisation capacity, weight variation, % drug content, thickness, hardness, friability and in vitro drug release. Various raft-forming agents were used in preliminary screening. A 23 full-factorial design was used in the present study for optimisation. The amount of sodium alginate, amount of calcium carbonate and amount sodium bicarbonate were selected as independent variables. Raft strength, acid neutralisation capacity and drug release at 30 min were selected as responses. Results: Tablets containing sodium alginate were having maximum raft strength as compared with other raft-forming agents. Acid neutralisation capacity and in vitro drug release of all factorial batches were found to be satisfactory. The F5 batch was optimised based on maximum raft strength and good acid neutralisation capacity. Drug–excipient compatibility study showed no interaction between the drug and excipients. Stability study of the optimised formulation showed that the tablets were stable at accelerated environmental conditions. Conclusion: It was concluded that raft-forming chewable tablets prepared using an optimum amount of sodium alginate, calcium carbonate and sodium bicarbonate could be an efficient dosage form in the treatment of gastro oesophageal reflux disease. PMID:23580933

Formulation and optimisation of raft-forming chewable tablets containing H2 antagonist.

PubMed

Prajapati, Shailesh T; Mehta, Anant P; Modhia, Ishan P; Patel, Chhagan N

2012-10-01

The purpose of this research work was to formulate raft-forming chewable tablets of H2 antagonist (Famotidine) using a raft-forming agent along with an antacid- and gas-generating agent. Tablets were prepared by wet granulation and evaluated for raft strength, acid neutralisation capacity, weight variation, % drug content, thickness, hardness, friability and in vitro drug release. Various raft-forming agents were used in preliminary screening. A 2(3) full-factorial design was used in the present study for optimisation. The amount of sodium alginate, amount of calcium carbonate and amount sodium bicarbonate were selected as independent variables. Raft strength, acid neutralisation capacity and drug release at 30 min were selected as responses. Tablets containing sodium alginate were having maximum raft strength as compared with other raft-forming agents. Acid neutralisation capacity and in vitro drug release of all factorial batches were found to be satisfactory. The F5 batch was optimised based on maximum raft strength and good acid neutralisation capacity. Drug-excipient compatibility study showed no interaction between the drug and excipients. Stability study of the optimised formulation showed that the tablets were stable at accelerated environmental conditions. It was concluded that raft-forming chewable tablets prepared using an optimum amount of sodium alginate, calcium carbonate and sodium bicarbonate could be an efficient dosage form in the treatment of gastro oesophageal reflux disease.

The association between home environmental variables and soft drink consumption among adolescents. Exploration of mediation by individual cognitions and habit strength.

PubMed

Tak, N I; Te Velde, S J; Oenema, A; Van der Horst, K; Timperio, A; Crawford, D; Brug, J

2011-04-01

Soft-drink consumption is one of the important target behaviours for the prevention of excessive weight gain among adolescents. To be able to modify these behaviours in obesity prevention interventions, further understanding of the underlying factors and mediational pathways is required. The present study aimed to explore associations between home environment variables and adolescent soft drink consumption and potential mediation of these associations by individual cognitions derived from the Theory of Planned Behaviour and habit strength. The ENDORSE study (N=1005) provided data on soft drink consumption and on home environment variables related to soft drink consumption (availability, accessibility, parental modelling, and parental rules), cognitive variables (intention, attitude, perceived behaviour control, and parental norm) and habit strength. Multiple mediation analyses were conducted using regression analyses according to the steps described by MacKinnon to assess the association between home environment variables and soft drink consumption and mediation of these associations by cognitive variables and habit strength. The bootstrapping method was used to calculate the confidence intervals. There were significant associations between the home environment variables and soft drink consumption. After inclusion of the mediators the strength of these associations was reduced. In the multiple mediator models, habit strength (39.4-62.6%) and intention (19.1-36.6%) were the strongest mediators. Intention and habit strength partly mediate the associations between home environment factors and soft drink consumption, suggesting that home environment variables influence soft drink consumption both indirectly and directly. Copyright © 2011 Elsevier Ltd. All rights reserved.

Genetic improvement of fiber length and coarseness based on paper product performance and material variability - a review

Treesearch

Brian K. Via; Michael Stine; Todd F. Shupe; Chi-Leung So; Leslie Groom

2004-01-01

Improvement of specific gravity through tree breeding was an early choice made in the mid 20th century due to its ease of measurement and impact on pulp yield and lumber strength and stiffness. This was often the first, and in many cases, the only wood quality trait selected for. However, from a product standpoint, increased specific gravity has shown to lower many...

The AGT Gene M235T Polymorphism and Response of Power-Related Variables to Aerobic Training.

PubMed

Aleksandra, Zarębska; Zbigniew, Jastrzębski; Waldemar, Moska; Agata, Leońska-Duniec; Mariusz, Kaczmarczyk; Marek, Sawczuk; Agnieszka, Maciejewska-Skrendo; Piotr, Żmijewski; Krzysztof, Ficek; Grzegorz, Trybek; Ewelina, Lulińska-Kuklik; Semenova, Ekaterina A; Ahmetov, Ildus I; Paweł, Cięszczyk

2016-12-01

The C allele of the M235T (rs699) polymorphism of the AGT gene correlates with higher levels of angiotensin II and has been associated with power and strength sport performance. The aim of the study was to investigate whether or not selected power-related variables and their response to a 12-week program of aerobic dance training are modulated by the AGT M235T genotype in healthy participants. Two hundred and one Polish Caucasian women aged 21 ± 1 years met the inclusion criteria and were included in the study. All women completed a 12-week program of low and high impact aerobics. Wingate peak power and total work capacity, 5 m, 10 m, and 30 m running times and jump height and jump power were determined before and after the training programme. All power-related variables improved significantly in response to aerobic dance training. We found a significant association between the M235T polymorphism and jump-based variables (squat jump (SJ) height, p = 0.005; SJ power, p = 0.015; countermovement jump height, p = 0.025; average of 10 countermovement jumps with arm swing (ACMJ) height, p = 0.001; ACMJ power, p = 0.035). Specifically, greater improvements were observed in the C allele carriers in comparison with TT homozygotes. In conclusion, aerobic dance, one of the most commonly practiced adult fitness activities in the world, provides sufficient training stimuli for augmenting the explosive strength necessary to increase vertical jump performance. The AGT gene M235T polymorphism seems to be not only a candidate gene variant for power/strength related phenotypes, but also a genetic marker for predicting response to training.

Investigating the Spectroscopic Variability of Magentically Active M Dwarfs In SDSS.

NASA Astrophysics Data System (ADS)

Ventura, Jean-Paul; Schmidt, Sarah J.; Cruz, Kelle; Rice, Emily; Cid, Aurora

2018-01-01

Magnetic activity, a wide range of observable phenomena produced in the outer atmospheres of stars is, currently, not well understood for M dwarfs. In higher mass stars, magnetic activity is powered by a dynamo process involving the differential rotation of a star’s inner regions. This process generates a magnetic field, heats up regions in the chromosphere and produces Hα emission line radiation from collisional excitation. Using spectroscopic data from the Sloan Digital Sky Survey (SDSS), I compare Hα emission line strengths for a subsample of 12,000 photometric variability selected M dwarfs from Pan-STARRS1 with those of a known non-variable sample. Presumably, the photometric variability originates from the occurrence of star spots at the stellar surface, which are the result of an intense magnetic field and associated chromospheric heating. We proceed with this work in order to test whether the photometric variability of the sample correlates with chromospheric Hα emission features. If not, we explore alternate reasons for that photometric variability (e.g. binarity or transiting planetary companions)

Environment-dependent variation in selection on life history across small spatial scales.

PubMed

Lange, Rolanda; Monro, Keyne; J Marshall, Dustin

2016-10-01

Variation in life-history traits is ubiquitous, even though genetic variation is thought to be depleted by selection. One potential mechanism for the maintenance of trait variation is spatially variable selection. We explored spatial variation in selection in the field for a colonial marine invertebrate that shows phenotypic differences across a depth gradient of only 3 m. Our analysis included life-history traits relating to module size, colony growth, and phenology. Directional selection on colony growth varied in strength across depths, while module size was under directional selection at one depth but not the other. Differences in selection may explain some of the observed phenotypic differentiation among depths for one trait but not another: instead, selection should actually erode the differences observed for this trait. Our results suggest selection is not acting alone to maintain trait variation within and across environments in this system. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Examining the Causes of Memory Strength Variability: Recollection, Attention Failure, or Encoding Variability?

ERIC Educational Resources Information Center

Koen, Joshua D.; Aly, Mariam; Wang, Wei-Chun; Yonelinas, Andrew P.

2013-01-01

A prominent finding in recognition memory is that studied items are associated with more variability in memory strength than new items. Here, we test 3 competing theories for why this occurs--the "encoding variability," "attention failure", and "recollection" accounts. Distinguishing among these theories is critical…

Optimal Design of General Stiffened Composite Circular Cylinders for Global Buckling with Strength Constraints

NASA Technical Reports Server (NTRS)

Jaunky, N.; Ambur, D. R.; Knight, N. F., Jr.

1998-01-01

A design strategy for optimal design of composite grid-stiffened cylinders subjected to global and local buckling constraints and strength constraints was developed using a discrete optimizer based on a genetic algorithm. An improved smeared stiffener theory was used for the global analysis. Local buckling of skin segments were assessed using a Rayleigh-Ritz method that accounts for material anisotropy. The local buckling of stiffener segments were also assessed. Constraints on the axial membrane strain in the skin and stiffener segments were imposed to include strength criteria in the grid-stiffened cylinder design. Design variables used in this study were the axial and transverse stiffener spacings, stiffener height and thickness, skin laminate stacking sequence and stiffening configuration, where stiffening configuration is a design variable that indicates the combination of axial, transverse and diagonal stiffener in the grid-stiffened cylinder. The design optimization process was adapted to identify the best suited stiffening configurations and stiffener spacings for grid-stiffened composite cylinder with the length and radius of the cylinder, the design in-plane loads and material properties as inputs. The effect of having axial membrane strain constraints in the skin and stiffener segments in the optimization process is also studied for selected stiffening configurations.

Optimal Design of General Stiffened Composite Circular Cylinders for Global Buckling with Strength Constraints

NASA Technical Reports Server (NTRS)

Jaunky, Navin; Knight, Norman F., Jr.; Ambur, Damodar R.

1998-01-01

A design strategy for optimal design of composite grid-stiffened cylinders subjected to global and local buckling constraints and, strength constraints is developed using a discrete optimizer based on a genetic algorithm. An improved smeared stiffener theory is used for the global analysis. Local buckling of skin segments are assessed using a Rayleigh-Ritz method that accounts for material anisotropy. The local buckling of stiffener segments are also assessed. Constraints on the axial membrane strain in the skin and stiffener segments are imposed to include strength criteria in the grid-stiffened cylinder design. Design variables used in this study are the axial and transverse stiffener spacings, stiffener height and thickness, skin laminate stacking sequence, and stiffening configuration, where herein stiffening configuration is a design variable that indicates the combination of axial, transverse, and diagonal stiffener in the grid-stiffened cylinder. The design optimization process is adapted to identify the best suited stiffening configurations and stiffener spacings for grid-stiffened composite cylinder with the length and radius of the cylinder, the design in-plane loads, and material properties as inputs. The effect of having axial membrane strain constraints in the skin and stiffener segments in the optimization process is also studied for selected stiffening configuration.

Effects of dancing on the risk of falling related factors of healthy older adults: a systematic review.

PubMed

Fernández-Argüelles, Esther López; Rodríguez-Mansilla, Juan; Antunez, Luis Espejo; Garrido-Ardila, Elisa María; Muñoz, Rafael Perez

2015-01-01

Deficits of balance or postural control in persons of advanced age are one of the factors that influence the risk of falling. The most appropriate treatment approaches and their benefits are still unknown. The aim of this article is to systematically review the scientific literature to identify the therapeutic effects of dancing as a physical exercise modality on balance, flexibility, gait, muscle strength and physical performance in older adults. A systematic search of Pubmed, Cochrane Library Plus, PEDro, Science Direct, Dialnet and Academic Search Complete using the search terms "dance", "older", "dance therapy", "elderly", "balance", "gait" and "motor skills". The eligibility criteria were: studies written in English and Spanish, published from January 2000 to January 2013, studies which analyzed the effects of dance (ballroom dance and/or dance based exercise) in older adults over 60 years of age with no disabling disease and included the following variables of study: balance, gait, risk of falls, strength, functionality, flexibility and quality of life. 123 articles were found in the literature. A final selection of seven articles was used for the present manuscript. Although the selected studies showed positive effects on the risk of falling related to factors (balance, gait and dynamic mobility, strength and physical performance), there were some aspects of the studies such as the methodological quality, the small sample size, the lack of homogeneity in relation to the variables and the measurement tools, and the existing diversity regarding the study design and the type of dance, that do not enable us to confirm that dance has significant benefits on these factors based on the scientific evidence. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Lumbar kinematic variability during gait in chronic low back pain and associations with pain, disability and isolated lumbar extension strength.

PubMed

Steele, James; Bruce-Low, Stewart; Smith, Dave; Jessop, David; Osborne, Neil

2014-12-01

Chronic low back pain is a multifactorial condition with many dysfunctions including gait variability. The lumbar spine and its musculature are involved during gait and in chronic low back pain the lumbar extensors are often deconditioned. It was therefore of interest to examine relationships between lumbar kinematic variability during gait, with pain, disability and isolated lumbar extension strength in participants with chronic low back pain. Twenty four participants with chronic low back pain were assessed for lumbar kinematics during gait, isolated lumbar extension strength, pain, and disability. Angular displacement and kinematic waveform pattern and offset variability were examined. Angular displacement and kinematic waveform pattern and offset variability differed across movement planes; displacement was highest and similar in frontal and transverse planes, and pattern variability and offset variability higher in the sagittal plane compared to frontal and transverse planes which were similar. Spearman's correlations showed significant correlations between transverse plane pattern variability and isolated lumbar extension strength (r=-.411) and disability (r=.401). However, pain was not correlated with pattern variability in any plane. The r(2) values suggested 80.5% to 86.3% of variance was accounted for by other variables. Considering the lumbar extensors role in gait, the relationship between both isolated lumbar extension strength and disability with transverse plane pattern variability suggests that gait variability may result in consequence of lumbar extensor deconditioning or disability accompanying chronic low back pain. However, further study should examine the temporality of these relationships and other variables might account for the unexplained variance. Copyright © 2014 Elsevier Ltd. All rights reserved.

An Evidence-Based Framework for Strengthening Exercises to Prevent Hamstring Injury.

PubMed

Bourne, Matthew N; Timmins, Ryan G; Opar, David A; Pizzari, Tania; Ruddy, Joshua D; Sims, Casey; Williams, Morgan D; Shield, Anthony J

2018-02-01

Strength training is a valuable component of hamstring strain injury prevention programmes; however, in recent years a significant body of work has emerged to suggest that the acute responses and chronic adaptations to training with different exercises are heterogeneous. Unfortunately, these research findings do not appear to have uniformly influenced clinical guidelines for exercise selection in hamstring injury prevention or rehabilitation programmes. The purpose of this review was to provide the practitioner with an evidence-base from which to prescribe strengthening exercises to mitigate the risk of hamstring injury. Several studies have established that eccentric knee flexor conditioning reduces the risk of hamstring strain injury when compliance is adequate. The benefits of this type of training are likely to be at least partly mediated by increases in biceps femoris long head fascicle length and improvements in eccentric knee flexor strength. Therefore, selecting exercises with a proven benefit on these variables should form the basis of effective injury prevention protocols. In addition, a growing body of work suggests that the patterns of hamstring muscle activation diverge significantly between different exercises. Typically, relatively higher levels of biceps femoris long head and semimembranosus activity have been observed during hip extension-oriented movements, whereas preferential semitendinosus and biceps femoris short head activation have been reported during knee flexion-oriented movements. These findings may have implications for targeting specific muscles in injury prevention programmes. An evidence-based approach to strength training for the prevention of hamstring strain injury should consider the impact of exercise selection on muscle activation, and the effect of training interventions on hamstring muscle architecture, morphology and function. Most importantly, practitioners should consider the effect of a strength training programme on known or proposed risk factors for hamstring injury.

Orthodontic bracket bonding without previous adhesive priming: A meta-regression analysis.

PubMed

Altmann, Aline Segatto Pires; Degrazia, Felipe Weidenbach; Celeste, Roger Keller; Leitune, Vicente Castelo Branco; Samuel, Susana Maria Werner; Collares, Fabrício Mezzomo

2016-05-01

To determine the consensus among studies that adhesive resin application improves the bond strength of orthodontic brackets and the association of methodological variables on the influence of bond strength outcome. In vitro studies were selected to answer whether adhesive resin application increases the immediate shear bond strength of metal orthodontic brackets bonded with a photo-cured orthodontic adhesive. Studies included were those comparing a group having adhesive resin to a group without adhesive resin with the primary outcome measurement shear bond strength in MPa. A systematic electronic search was performed in PubMed and Scopus databases. Nine studies were included in the analysis. Based on the pooled data and due to a high heterogeneity among studies (I(2)  =  93.3), a meta-regression analysis was conducted. The analysis demonstrated that five experimental conditions explained 86.1% of heterogeneity and four of them had significantly affected in vitro shear bond testing. The shear bond strength of metal brackets was not significantly affected when bonded with adhesive resin, when compared to those without adhesive resin. The adhesive resin application can be set aside during metal bracket bonding to enamel regardless of the type of orthodontic adhesive used.

Tensile properties of nicalon fiber-reinforced carbon following aerospace turbine engine testing

NASA Astrophysics Data System (ADS)

Pierce, J. L.; Zawada, L. P.; Srinivasan, R.

2003-06-01

The durability of coated Nicalon silicon carbide fiber-reinforced carbon (SiC/C) as the flap and seal exhaust nozzle components in a military aerospace turbine engine was studied. Test specimens machined from both a flap and a seal component were tested for residual strength following extended ground engine testing on a General Electric F414 afterburning turbofan engine. Although small amounts of damage to the protective exterior coating were identified on each component following engine testing, the tensile strengths were equal to the as-fabricated tensile strength of the material. Differences in strength between the two components and variability within the data sets could be traced back to the fabrication process using witness coupon test data from the manufacturer. It was also observed that test specimens machined transversely across the flap and seal components were stronger than those machined along the length. The excellent retained strength of the coated SiC/C material after extended exposure to the severe environment in the afterburner exhaust section of an aerospace turbofan engine has resulted in this material being selected as the baseline material for the F414 exhaust nozzle system.

Parametric studies on tensile strength in joining AA6061- T6 and AA7075-T6 by gas metal arc welding process

NASA Astrophysics Data System (ADS)

Ishak, M.; Noordin, N. F. M.; Shah, L. H.

2015-12-01

Proper selection of the welding parameters can result in better joining. In this study, the effects of various welding parameters on tensile strength in joining dissimilar aluminum alloys AA6061-T6 and AA7075-T6 were investigated. 2 mm thick samples of both base metals were welded by semi-automatic gas metal arc welding (GMAW) using filler wire ER5356. The welding current, arc voltage and welding speed were chosen as variables parameters. The strength of each specimen after the welding operations were tested and the effects of these parameters on tensile strength were identified by using Taguchi method. The range of parameter for welding current were chosen from 100 to 115 A, arc voltage from 17 to 20 V and welding speed from 2 to 5 mm/s. L16 orthogonal array was used to obtained 16 runs of experiments. It was found that the highest tensile strength (194.34 MPa) was obtained with the combination of a welding current of 115 A, welding voltage of 18 V and welding speed of 4 mm/s. Through analysis of variance (ANOVA), the welding voltage was the most effected parameter on tensile strength with percentage of contribution at 41.30%.

Liquid Chromatographic Analysis of Nitrocellulose-Base Propellants

DTIC Science & Technology

1983-03-28

18 radial PkC column using 10 micron silica coated with octadecyl silane. The detector was a LC 85 variable wavelength UV detector from Perkin-Elmer...Snyder, L. R. J Chrom Scd i6, (1978), 223. i •2 Glatch, J. L., Kirkland, J. J., Squire, K. M., and Miner, J. M.; J. Chromatgography, 199, (1980), 57. 4...assuming non retained peaks elute at 1 minute). This produces 3 solvents of approximately the same strengths bnt greatly differing selectivities. Once

Mechanical Properties of Nonwoven Reinforced Thermoplastic Polyurethane Composites

PubMed Central

Tausif, Muhammad; Pliakas, Achilles; O’Haire, Tom; Goswami, Parikshit; Russell, Stephen J.

2017-01-01

Reinforcement of flexible fibre reinforced plastic (FRP) composites with standard textile fibres is a potential low cost solution to less critical loading applications. The mechanical behaviour of FRPs based on mechanically bonded nonwoven preforms composed of either low or high modulus fibres in a thermoplastic polyurethane (TPU) matrix were compared following compression moulding. Nonwoven preform fibre compositions were selected from lyocell, polyethylene terephthalate (PET), polyamide (PA) as well as para-aramid fibres (polyphenylene terephthalamide; PPTA). Reinforcement with standard fibres manifold improved the tensile modulus and strength of the reinforced composites and the relationship between fibre, fabric and composite’s mechanical properties was studied. The linear density of fibres and the punch density, a key process variable used to consolidate the nonwoven preform, were varied to study the influence on resulting FRP mechanical properties. In summary, increasing the strength and degree of consolidation of nonwoven preforms did not translate to an increase in the strength of resulting fibre reinforced TPU-composites. The TPU composite strength was mainly dependent upon constituent fibre stress-strain behaviour and fibre segment orientation distribution. PMID:28772977

How well can body size represent effects of the environment on demographic rates? Disentangling correlated explanatory variables.

PubMed

Brooks, Mollie E; Mugabo, Marianne; Rodgers, Gwendolen M; Benton, Timothy G; Ozgul, Arpat

2016-03-01

Demographic rates are shaped by the interaction of past and current environments that individuals in a population experience. Past environments shape individual states via selection and plasticity, and fitness-related traits (e.g. individual size) are commonly used in demographic analyses to represent the effect of past environments on demographic rates. We quantified how well the size of individuals captures the effects of a population's past and current environments on demographic rates in a well-studied experimental system of soil mites. We decomposed these interrelated sources of variation with a novel method of multiple regression that is useful for understanding nonlinear relationships between responses and multicollinear explanatory variables. We graphically present the results using area-proportional Venn diagrams. Our novel method was developed by combining existing methods and expanding upon them. We showed that the strength of size as a proxy for the past environment varied widely among vital rates. For instance, in this organism with an income breeding life history, the environment had more effect on reproduction than individual size, but with substantial overlap indicating that size encompassed some of the effects of the past environment on fecundity. This demonstrates that the strength of size as a proxy for the past environment can vary widely among life-history processes within a species, and this variation should be taken into consideration in trait-based demographic or individual-based approaches that focus on phenotypic traits as state variables. Furthermore, the strength of a proxy will depend on what state variable(s) and what demographic rate is being examined; that is, different measures of body size (e.g. length, volume, mass, fat stores) will be better or worse proxies for various life-history processes. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

Ti-6Al-4V Additively Manufactured by Selective Laser Melting with Superior Mechanical Properties

NASA Astrophysics Data System (ADS)

Xu, W.; Sun, S.; Elambasseril, J.; Liu, Q.; Brandt, M.; Qian, M.

2015-03-01

The Achilles' heel of additively manufactured Ti-6Al-4V by selective laser melting (SLM) is its inferior mechanical properties compared with its wrought (forged) counterparts. Acicular α' martensite resulted from rapid cooling by SLM is primarily responsible for high strength but inadequate tensile ductility achieved in the as-fabricated state. This study presents a solution to eliminating the adverse effect of the nonequilibrium α' martensite. This is achieved by enabling in situ martensite decomposition into a novel ultrafine (200-300 nm) lamellar ( α + β) microstructure via the selection of an array of processing variables including the layer thickness, energy density, and focal offset distance. The resulting tensile elongation reached 11.4% while the yield strength was kept above 1100 MPa. These properties compare favorably with those of mill-annealed Ti-6Al-4V consisting of globular α and β. The fatigue life of SLM-fabricated Ti-6Al-4V with an ultrafine lamellar ( α + β) structure has approached that of the mill-annealed counterparts and is much superior to that of SLM-fabricated Ti-6Al-4V with α' martensite.

Relationship between physical fitness at the end of pre-season and the in-season game performance in Japanese female professional baseball players.

PubMed

Watanabe, Yuya; Yamada, Yosuke; Yoshida, Tsukasa; Matsui, Tomoyuki; Seo, Kazuya; Azuma, Yoshikazu; Hiramoto, Machiko; Miura, Yuichiro; Fukushima, Hideaki; Shimazu, Akito; Eto, Toshiaki; Saotome, Homare; Kida, Noriyuki; Morihara, Toru

2017-10-30

This study examined anthropometric and fitness profiles of Japanese female professional baseball players and investigated the relationship between players' physical fitness and in-season game performance. Fifty-seven players who were registered in the Japan Women's Baseball League (JWBL) participated. Height, weight, grip strength, back strength, knee-extension and -flexion strength, hamstring extensibility, vertical jump height, and horizontal jump distance were measured at pre-season (February and March) in 2013. Game performance during the 2013 season (March to November) was obtained from official JWBL statistics. Vertical jump height showed significant positive correlations with individual performance records [e.g., total bases (r = 0.551), slugging percentage (r = 0.459), and stolen bases (r = 0.442)]. Similar relationships were observed between horizontal jump distance and performance statistics in most cases. In contrast, grip, back, and lower-limb strength, and hamstring extensibility were not significantly correlated with game performance. Stepwise regression analysis selected vertical jump height as an independent variable, significantly correlating with several game performance measures (e.g., total bases: adjusted R = 0.257). Also, vertical jump height and body mass index were identified as independent variables significantly associated with stolen bases (adjusted R = 0.251). Maximal jump performance, rather than simple isometric muscle strength or flexibility, is a good performance test that can be used at the end of pre-season to predict in-season batting and stolen base performance. Our findings demonstrate the importance of constructing pre-season training programs to enhance lower-limb muscular power that is linked to successful in-season performance in female baseball players.

Energy density and variability in abundance of pigeon guillemot prey: Support for the quality-variability trade-off hypothesis

USGS Publications Warehouse

Litzow, Michael A.; Piatt, John F.; Abookire, Alisa A.; Robards, Martin D.

2004-01-01

1. The quality-variability trade-off hypothesis predicts that (i) energy density (kJ g-1) and spatial-temporal variability in abundance are positively correlated in nearshore marine fishes; and (ii) prey selection by a nearshore piscivore, the pigeon guillemot (Cepphus columba Pallas), is negatively affected by variability in abundance. 2. We tested these predictions with data from a 4-year study that measured fish abundance with beach seines and pigeon guillemot prey utilization with visual identification of chick meals. 3. The first prediction was supported. Pearson's correlation showed that fishes with higher energy density were more variable on seasonal (r = 0.71) and annual (r = 0.66) time scales. Higher energy density fishes were also more abundant overall (r = 0.85) and more patchy at a scale of 10s of km (r = 0.77). 4. Prey utilization by pigeon guillemots was strongly non-random. Relative preference, defined as the difference between log-ratio transformed proportions of individual prey taxa in chick diets and beach seine catches, was significantly different from zero for seven of the eight main prey categories. 5. The second prediction was also supported. We used principal component analysis (PCA) to summarize variability in correlated prey characteristics (energy density, availability and variability in abundance). Two PCA scores explained 32% of observed variability in pigeon guillemot prey utilization. Seasonal variability in abundance was negatively weighted by these PCA scores, providing evidence of risk-averse selection. Prey availability, energy density and km-scale variability in abundance were positively weighted. 6. Trophic interactions are known to create variability in resource distribution in other systems. We propose that links between resource quality and the strength of trophic interactions may produce resource quality-variability trade-offs.

Knee-Extension Torque Variability and Subjective Knee Function in Patients with a History of Anterior Cruciate Ligament Reconstruction.

PubMed

Goetschius, John; Hart, Joseph M

2016-01-01

When returning to physical activity, patients with a history of anterior cruciate ligament reconstruction (ACL-R) often experience limitations in knee-joint function that may be due to chronic impairments in quadriceps motor control. Assessment of knee-extension torque variability may demonstrate underlying impairments in quadriceps motor control in patients with a history of ACL-R. To identify differences in maximal isometric knee-extension torque variability between knees that have undergone ACL-R and healthy knees and to determine the relationship between knee-extension torque variability and self-reported knee function in patients with a history of ACL-R. Descriptive laboratory study. Laboratory. A total of 53 individuals with primary, unilateral ACL-R (age = 23.4 ± 4.9 years, height = 1.7 ± 0.1 m, mass = 74.6 ± 14.8 kg) and 50 individuals with no history of substantial lower extremity injury or surgery who served as controls (age = 23.3 ± 4.4 years, height = 1.7 ± 0.1 m, mass = 67.4 ± 13.2 kg). Torque variability, strength, and central activation ratio (CAR) were calculated from 3-second maximal knee-extension contraction trials (90° of flexion) with a superimposed electrical stimulus. All participants completed the International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, and we determined the number of months after surgery. Group differences were assessed using independent-samples t tests. Correlation coefficients were calculated among torque variability, strength, CAR, months after surgery, and IKDC scores. Torque variability, strength, CAR, and months after surgery were regressed on IKDC scores using stepwise, multiple linear regression. Torque variability was greater and strength, CAR, and IKDC scores were lower in the ACL-R group than in the control group (P < .05). Torque variability and strength were correlated with IKDC scores (P < .05). Torque variability, strength, and CAR were correlated with each other (P < .05). Torque variability alone accounted for 14.3% of the variance in IKDC scores. The combination of torque variability and number of months after surgery accounted for 21% of the variance in IKDC scores. Strength and CAR were excluded from the regression model. Knee-extension torque variability was moderately associated with IKDC scores in patients with a history of ACL-R. Torque variability combined with months after surgery predicted 21% of the variance in IKDC scores in these patients.

The accumulation of reproductive isolation in early stages of divergence supports a role for sexual selection.

PubMed

Martin, M D; Mendelson, T C

2016-04-01

Models of speciation by sexual selection propose that male-female coevolution leads to the rapid evolution of behavioural reproductive isolation. Here, we compare the strength of behavioural isolation to ecological isolation, gametic incompatibility and hybrid inviability in a group of dichromatic stream fishes. In addition, we examine whether any of these individual barriers, or a combined measure of total isolation, is predicted by body shape differences, male colour differences, environmental differences or genetic distance. Behavioural isolation reaches the highest values of any barrier and is significantly greater than ecological isolation. No individual reproductive barrier is associated with any of the predictor variables. However, marginally significant relationships between male colour and body shape differences with ecological and behavioural isolation are discussed. Differences in male colour and body shape predict total reproductive isolation between species; hierarchical partitioning of these two variables' effects suggests a stronger role for male colour differences. Together, these results suggest an important role for divergent sexual selection in darter speciation but raise new questions about the mechanisms of sexual selection at play and the role of male nuptial ornaments. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

Fatigue testing of weldable high strength steels under simulated service conditions

NASA Astrophysics Data System (ADS)

Tantbirojn, Natee

There have been concerns over the effect of Cathodic Protection (CP) on weldable high strength steels employed in Jack-up production platform. The guidance provided by the Department of Energy HSE on higher strength steels, based on previous work, was to avoid overprotection as this could cause hydrogen embrittlement. However, the tests conducted so far at UCL for the SE702 type high strength steels (yields strength around 690 MPa) have shown that the effect of over protection on high strength steels may not be as severe as previously thought. For this thesis, SE702 high strength steels have been investigated in more detail. Thick (85mm) parent and ground welded plates were tested under constant amplitude in air and seawater with CP. Tests were also conducted on Thick (40mm) T-butt welded plates under variable amplitude loading in air and seawater with two CP levels (-800mV and -1050mV). Different backing materials (ceramic and metallic) for the welding process of the T-butt plates were also investigated. The variable amplitude sequences employed were generated using the Jack-up Offshore Standard load History (JOSH). The fatigue results are presented as crack growth and S/N curves. They were compared to the conventional offshore steel (BS 4360 50D). The results suggested that the fatigue life of the high strength steels was comparable to the BS 4360 50D steels. The effect of increasing the CP was found to be detrimental to the fatigue life but the effect was not large. The effect of CP was less noticeable in T-butt welded plates. However, in general, the effect of overprotection is not as detrimental to the Jack-up steels as previously thought. The load histories generated by JOSH were found to have some unfavourable characteristics. The framework is based on Markov Chain method and pseudo-random number generator for selecting sea-states. A study was carried out on the sequence generated by JOSH. The generated sequences were analysed for their validity for fatigue testing. This has resulted in recommendations on the methods for generating standard load histories.

Computational simulation of coupled material degradation processes for probabilistic lifetime strength of aerospace materials

NASA Technical Reports Server (NTRS)

Boyce, Lola; Bast, Callie C.

1992-01-01

The research included ongoing development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subjected to a number of effects or primative variables. These primative variable may include high temperature, fatigue or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation has been randomized and is included in the computer program, PROMISS. Also included in the research is the development of methodology to calibrate the above described constitutive equation using actual experimental materials data together with linear regression of that data, thereby predicting values for the empirical material constraints for each effect or primative variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from the open literature for materials typically of interest to those studying aerospace propulsion system components. Material data for Inconel 718 was analyzed using the developed methodology.

Lower limb muscle impairment in myotonic dystrophy type 1: the need for better guidelines.

PubMed

Petitclerc, Émilie; Hébert, Luc J; Desrosiers, Johanne; Gagnon, Cynthia

2015-04-01

In myotonic dystrophy type 1 (DM1), leg muscle weakness is a major impairment. There are challenges to obtaining a clear portrait of muscle strength impairment. A systematic literature review was conducted on lower limb strength impairment in late-onset and adult phenotypes to document variables which affect strength measurement. Thirty-two articles were reviewed using the COSMIN guidelines. Only a third of the studies described a reproducible protocol. Only 2 muscle groups have documented reliability for quantitative muscle testing and only 1 total score for manual muscle testing. Variables affecting muscle strength impairment are not described in most studies. This review illustrates the variability in muscle strength assessment in relation to DM1 characteristics and the questionable validity of the results with regard to undocumented methodological properties. There is therefore a clear need to adopt a consensus on the use of a standardized muscle strength assessment protocol. © 2015 Wiley Periodicals, Inc.

Quiet Clean Short-haul Experimental Engine (QCSEE) Under-The-Wing (UTW) composite nacelle subsystem test report. [to verify strength of selected composite materials

NASA Technical Reports Server (NTRS)

Stotler, C. L., Jr.; Johnston, E. A.; Freeman, D. S.

1977-01-01

The element and subcomponent testing conducted to verify the under the wing composite nacelle design is reported. This composite nacelle consists of an inlet, outer cowl doors, inner cowl doors, and a variable fan nozzle. The element tests provided the mechanical properties used in the nacelle design. The subcomponent tests verified that the critical panel and joint areas of the nacelle had adequate structural integrity.

A reliability-based cost effective fail-safe design procedure

NASA Technical Reports Server (NTRS)

Hanagud, S.; Uppaluri, B.

1976-01-01

The authors have developed a methodology for cost-effective fatigue design of structures subject to random fatigue loading. A stochastic model for fatigue crack propagation under random loading has been discussed. Fracture mechanics is then used to estimate the parameters of the model and the residual strength of structures with cracks. The stochastic model and residual strength variations have been used to develop procedures for estimating the probability of failure and its changes with inspection frequency. This information on reliability is then used to construct an objective function in terms of either a total weight function or cost function. A procedure for selecting the design variables, subject to constraints, by optimizing the objective function has been illustrated by examples. In particular, optimum design of stiffened panel has been discussed.

Weldability of AA 5052 H32 aluminium alloy by TIG welding and FSW process - A comparative study

NASA Astrophysics Data System (ADS)

Shanavas, S.; Raja Dhas, J. Edwin

2017-10-01

Aluminium 5xxx series alloys are the strongest non-heat treatable aluminium alloy. Its application found in automotive components and body structures due to its good formability, good strength, high corrosion resistance, and weight savings. In the present work, the influence of Tungsten Inert Gas (TIG) welding parameters on the quality of weld on AA 5052 H32 aluminium alloy plates were analyzed and the mechanical characterization of the joint so produced was compared with Friction stir (FS) welded joint. The selected input variable parameters are welding current and inert gas flow rate. Other parameters such as welding speed and arc voltage were kept constant throughout the study, based on the response from several trial runs conducted. The quality of the weld is measured in terms of ultimate tensile strength. A double side V-butt joints were fabricated by double pass on one side to ensure maximum strength of TIG welded joints. Macro and microstructural examination were conducted for both welding process.

Relationship Between Selected Strength and Power Assessments to Peak and Average Velocity of the Drive Block in Offensive Line Play.

PubMed

Jacobson, Bert H; Conchola, Eric C; Smith, Doug B; Akehi, Kazuma; Glass, Rob G

2016-08-01

Jacobson, BH, Conchola, EC, Smith, DB, Akehi, K, and Glass, RG. Relationship between selected strength and power assessments to peak and average velocity of the drive block in offensive line play. J Strength Cond Res 30(8): 2202-2205, 2016-Typical strength training for football includes the squat and power clean (PC) and routinely measured variables include 1 repetition maximum (1RM) squat and 1RM PC along with the vertical jump (VJ) for power. However, little research exists regarding the association between the strength exercises and velocity of an actual on-the-field performance. The purpose of this study was to investigate the relationship of peak velocity (PV) and average velocity (AV) of the offensive line drive block to 1RM squat, 1RM PC, the VJ, body mass (BM), and body composition. One repetition maximum assessments for the squat and PC were recorded along with VJ height, BM, and percent body fat. These data were correlated with PV and AV while performing the drive block. Peal velocity and AV were assessed using a Tendo Power and Speed Analyzer as the linemen fired, from a 3-point stance into a stationary blocking dummy. Pearson product analysis yielded significant (p ≤ 0.05) correlations between PV and AV and the VJ, the squat, and the PC. A significant inverse association was found for both PV and AV and body fat. These data help to confirm that the typical exercises recommended for American football linemen is positively associated with both PV and AV needed for the drive block effectiveness. It is recommended that these exercises remain the focus of a weight room protocol and that ancillary exercises be built around these exercises. Additionally, efforts to reduce body fat are recommended.

Physical Exercise Improves Heart Rate Variability in Patients with Type 2 Diabetes: A Systematic Review.

PubMed

Villafaina, Santos; Collado-Mateo, Daniel; Fuentes, Juan Pedro; Merellano-Navarro, Eugenio; Gusi, Narcis

2017-09-23

The aim of the present systematic review is to provide an up-to-date analysis of the research on the effects of exercise programs on heart rate variability (HRV) in individuals with type 2 diabetes mellitus (T2DM). An electronic search of the literature (PubMed, PEDro and Web of Science) was performed. "HRV", "heart rate variability", "exercise", "physical" and "diabetes" were the terms used for article retrieval. Lastly, 15 articles were selected. PRISMA methodology was employed and data were extracted according to the PICOS approach. Although HRV is not routinely measured in the management of T2DM, it is an important measure due to its relation with mortality and diabetic neuropathy. Physical exercise has become a therapy for T2DM, because it improves physical fitness and functional capacity, enhances metabolic control and insulin sensitivity, reduces inflammatory markers and neuropathy symptoms and can increase the regenerative capacity of cutaneous axons, slowing or preventing neuropathy progression. However, it is not clear to what extent physical exercise can improve HRV in this population. Participation in the 15 selected studies was similar in men and women (48.01% men and 51.99% women). All the intervention programs included aerobic training, and it was complemented by strength training in four studies. Duration of physical exercise sessions ranged between 30 and 75 min, the frequency being between 2 and 7 days/week. Statistically significant improvements in groups with diabetes, relative to baseline, were observed in nine studies. More than 3 days per week of aerobic training, complemented by strength training, during at least 3 months seems to improve HRV in T2DM. Weekly frequency might be the most important factor to improve HRV. These aspects could help to design better programs based in scientific evidence, incorporating HRV as an important variable associated with diabetic neuropathy and mortality.

[Anthropometry, body composition and functional limitations in the elderly].

PubMed

Arroyo, Patricia; Lera, Lydia; Sánchez, Hugo; Bunout, Daniel; Santos, José Luis; Albala, Cecilia

2007-07-01

Functional limitations limit the independence and jeopardize the quality of life of elderly subjects. To assess the association between anthropometric measures and body composition with functional limitations in community-living older people. Cross-sectional survey of 377 people > or = 6 5 years old (238 women), randomly selected from the SABE/Chile project. Complete anthropometric measurements were done. Handgrip muscle strength was measured using dynamometers. Body composition was determined using Dual-Energy X-Ray Absorptiometry. Functional limitations were assessed using self reported and observed activities. Body mass index was strongly associated with fat mass (men r =0.87; women r =0.91) and with lean mass (men r =0.55; women r =0.62). Males had significantly greater lean mass (48.9 kg vs 34.9 kg), and bone mass than females (2.6 kg vs 1.8 kg) and women had higher fat mass than men (26.3 kg vs 22.9 kg). The prevalence of functional limitations was high, affecting more women than men (63.7% vs 37.5%, p <0.01). Functional limitations were associated with lower handgrip strength in both sexes. In the multiple regression models, with functional limitations as dependent variable and anthropometric measures as contributing variables, only hand grip strength had a significant association (negative) with functional limitations in both genders. Age was also a significant risk factor for functional limitations among women. Hand grip strength was strongly and inversely associated with functional limitations. Handgrip dynamometry is an easy, cheap and low time-consuming indicator for the assessment of functional limitations and the evaluation of geriatric interventions aimed to improve functional ability.

Turkish College Students' Subjective Wellbeing in Regard to Psychological Strengths and Demographic Variables: Implications for College Counseling

ERIC Educational Resources Information Center

Sivis-Cetinkaya, Rahsan

2013-01-01

This study investigated Turkish college students' subjective wellbeing in regard to psychological strength and demographic variables. A sample of Turkish college students (N?=?1,052) aged 17-32 (mean age = 21, SD = 1.79) was administered various psychological strength instruments--the Gratitude Scale, the Rosenberg Self Esteem Inventory, the…

Evaluating the strength of the land$-$atmosphere moisture feedback in Earth system models using satellite observations

DOE PAGES

Levine, Paul A.; Randerson, James T.; Swenson, Sean C.; ...

2016-12-09

The relationship between terrestrial water storage (TWS) and atmospheric processes has important implications for predictability of climatic extremes and projection of future climate change. In places where moisture availability limits evapotranspiration (ET), variability in TWS has the potential to influence surface energy fluxes and atmospheric conditions. Where atmospheric conditions, in turn, influence moisture availability, a full feedback loop exists. Here we developed a novel approach for measuring the strength of both components of this feedback loop, i.e., the forcing of the atmosphere by variability in TWS and the response of TWS to atmospheric variability, using satellite observations of TWS, precipitation,more » solar radiation, and vapor pressure deficit during 2002–2014. Our approach defines metrics to quantify the relationship between TWS anomalies and climate globally on a seasonal to interannual timescale. Metrics derived from the satellite data were used to evaluate the strength of the feedback loop in 38 members of the Community Earth System Model (CESM) Large Ensemble (LENS) and in six models that contributed simulations to phase 5 of the Coupled Model Intercomparison Project (CMIP5). We found that both forcing and response limbs of the feedback loop in LENS were stronger than in the satellite observations in tropical and temperate regions. Feedbacks in the selected CMIP5 models were not as strong as those found in LENS, but were still generally stronger than those estimated from the satellite measurements. Consistent with previous studies conducted across different spatial and temporal scales, our analysis suggests that models may overestimate the strength of the feedbacks between the land surface and the atmosphere. Lastly, we describe several possible mechanisms that may contribute to this bias, and discuss pathways through which models may overestimate ET or overestimate the sensitivity of ET to TWS.« less

Predicting Bobsled Pushing Ability from Various Combine Testing Events.

PubMed

Tomasevicz, Curtis L; Ransone, Jack W; Bach, Christopher W

2018-03-12

The requisite combination of speed, power, and strength necessary for a bobsled push athlete coupled with the difficulty in directly measuring pushing ability makes selecting effective push crews challenging. Current practices by USA Bobsled and Skeleton (USABS) utilize field combine testing to assess and identify specifically selected performance variables in an attempt to best predict push performance abilities. Combine data consisting of 11 physical performance variables were collected from 75 subjects across two winter Olympic qualification years (2009 and 2013). These variables were sprints of 15-, 30-, and 60 m, a flying 30 m sprint, a standing broad jump, a shot toss, squat, power clean, body mass, and dry-land brake and side bobsled pushes. Discriminant Analysis (DA) in addition to Principle Component Analysis (PCA) was used to investigate two cases (Case 1: Olympians vs. non-Olympians; Case 2: National Team vs. non-National Team). Using these 11 variables, DA led to a classification rule that proved capable of identifying Olympians from non-Olympians and National Team members from non-National Team members with 9.33% and 14.67% misclassification rates, respectively. The PCA was used to find similar test variables within the combine that provided redundant or useless data. After eliminating the unnecessary variables, DA on the new combinations showed that 8 (Case 1) and 20 (Case 2) other combinations with fewer performance variables yielded misclassification rates as low as 6.67% and 13.33% respectively. Utilizing fewer performance variables can allow governing bodies in many other sports to create more appropriate combine testing that maximize accuracy, while minimizing irrelevant and redundant strategies.

Designing nacre-like materials for simultaneous stiffness, strength and toughness: Optimum materials, composition, microstructure and size

NASA Astrophysics Data System (ADS)

Barthelat, Francois

2014-12-01

Nacre, bone and spider silk are staggered composites where inclusions of high aspect ratio reinforce a softer matrix. Such staggered composites have emerged through natural selection as the best configuration to produce stiffness, strength and toughness simultaneously. As a result, these remarkable materials are increasingly serving as model for synthetic composites with unusual and attractive performance. While several models have been developed to predict basic properties for biological and bio-inspired staggered composites, the designer is still left to struggle with finding optimum parameters. Unresolved issues include choosing optimum properties for inclusions and matrix, and resolving the contradictory effects of certain design variables. Here we overcome these difficulties with a multi-objective optimization for simultaneous high stiffness, strength and energy absorption in staggered composites. Our optimization scheme includes material properties for inclusions and matrix as design variables. This process reveals new guidelines, for example the staggered microstructure is only advantageous if the tablets are at least five times stronger than the interfaces, and only if high volume concentrations of tablets are used. We finally compile the results into a step-by-step optimization procedure which can be applied for the design of any type of high-performance staggered composite and at any length scale. The procedure produces optimum designs which are consistent with the materials and microstructure of natural nacre, confirming that this natural material is indeed optimized for mechanical performance.

Memory Variability Is Due to the Contribution of Recollection and Familiarity, Not to Encoding Variability

ERIC Educational Resources Information Center

Koen, Joshua D.; Yonelinas, Andrew P.

2010-01-01

It is well established that the memory strength of studied items is more variable than the strength of new items on tests of recognition memory, but the reason why this occurs is poorly understood. One account for this old "item variance effect" is based on single-process theory, which proposes that this effect is due to variability in how well…

A Systematic Review of the Effect of Cognitive Strategies on Strength Performance.

PubMed

Tod, David; Edwards, Christian; McGuigan, Mike; Lovell, Geoff

2015-11-01

Researchers have tested the beliefs of sportspeople and sports medicine specialists that cognitive strategies influence strength performance. Few investigators have synthesised the literature. The specific objectives were to review evidence regarding (a) the cognitive strategy-strength performance relationship; (b) participant skill level as a moderator; and (c) cognitive, motivational, biomechanical/physiological, and emotional mediators. Studies were sourced via electronic databases, reference lists of retrieved articles, and manual searches of relevant journals. Studies had to be randomised or counterbalanced experiments with a control group or condition, repeated measures, and a quality control score above 0.5 (out of 1). Cognitive strategies included goal setting, imagery, self-talk, preparatory arousal, and free choice. Dependent variables included maximal strength, local muscular endurance, or muscular power. Globally, cognitive strategies were reliability associated with increased strength performance (results ranged from 61 to 65 %). Results were mixed when examining the effects of specific strategies on particular dependent variables, although no intervention had an overall negative influence. Indeterminate relationships emerged regarding hypothesised mediators (except cognitive variables) and participant skill level as a moderator. Although cognitive strategies influence strength performance, there are knowledge gaps regarding specific types of strength, especially muscular power. Cognitive variables, such as concentration, show promise as possible mediators.

Interseason variability in isokinetic strength and poor correlation with Nordic hamstring eccentric strength in football players.

PubMed

van Dyk, N; Witvrouw, E; Bahr, R

2018-04-25

In elite sport, the use of strength testing to establish muscle function and performance is common. Traditionally, isokinetic strength tests have been used, measuring torque during concentric and eccentric muscle action. A device that measures eccentric hamstring muscle strength while performing the Nordic hamstring exercise is now also frequently used. The study aimed to investigate the variability of isokinetic muscle strength over time, for example, between seasons, and the relationship between isokinetic testing and the new Nordic hamstring exercise device. All teams (n = 18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Qatar. Isokinetic strength was investigated for measurement error, and correlated to Nordic hamstring exercise strength. Of the 529 players included, 288 players had repeated tests with 1/2 seasons between test occasions. Variability (measurement error) between test occasions was substantial, as demonstrated by the measurement error (approximately 25 Nm, 15%), whether separated by 1 or 2 seasons. Considering hamstring injuries, the same pattern was observed among injured (n = 60) and uninjured (n = 228) players. A poor correlation (r = .35) was observed between peak isokinetic hamstring eccentric torque and Nordic hamstring exercise peak force. The strength imbalance between limbs calculated for both test modes was not correlated (r = .037). There is substantial intraindividual variability in all isokinetic test measures, whether separated by 1 or 2 seasons, irrespective of injury. Also, eccentric hamstring strength and limb-to-limb imbalance were poorly correlated between the isokinetic and Nordic hamstring exercise tests. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Physical characteristics of experienced and junior open-wheel car drivers.

PubMed

Raschner, Christian; Platzer, Hans-Peter; Patterson, Carson

2013-01-01

Despite the popularity of open-wheel car racing, scientific literature about the physical characteristics of competitive race car drivers is scarce. The purpose of this study was to compare selected fitness parameters of experienced and junior open-wheel race car drivers. The experienced drivers consisted of five Formula One, two GP2 and two Formula 3 drivers, and the nine junior drivers drove in the Formula Master, Koenig, BMW and Renault series. The following fitness parameters were tested: multiple reactions, multiple anticipation, postural stability, isometric upper body strength, isometric leg extension strength, isometric grip strength, cyclic foot speed and jump height. The group differences were calculated using the Mann-Whitney U-test. Because of the multiple testing strategy used, the statistical significance was Bonferroni corrected and set at P < 0.004. Significant differences between the experienced and junior drivers were found only for the jump height parameter (P = 0.002). The experienced drivers tended to perform better in leg strength (P = 0.009), cyclic foot speed (P = 0.024) and grip strength (P = 0.058). None of the other variables differed between the groups. The results suggested that the experienced drivers were significantly more powerful than the junior drivers: they tended to be quicker and stronger (18% to 25%) but without statistical significance. The experienced drivers demonstrated excellent strength and power compared with other high-performance athletes.

Multiobjective Optimization of Atmospheric Plasma Spray Process Parameters to Deposit Yttria-Stabilized Zirconia Coatings Using Response Surface Methodology

NASA Astrophysics Data System (ADS)

Ramachandran, C. S.; Balasubramanian, V.; Ananthapadmanabhan, P. V.

2011-03-01

Atmospheric plasma spraying is used extensively to make Thermal Barrier Coatings of 7-8% yttria-stabilized zirconia powders. The main problem faced in the manufacture of yttria-stabilized zirconia coatings by the atmospheric plasma spraying process is the selection of the optimum combination of input variables for achieving the required qualities of coating. This problem can be solved by the development of empirical relationships between the process parameters (input power, primary gas flow rate, stand-off distance, powder feed rate, and carrier gas flow rate) and the coating quality characteristics (deposition efficiency, tensile bond strength, lap shear bond strength, porosity, and hardness) through effective and strategic planning and the execution of experiments by response surface methodology. This article highlights the use of response surface methodology by designing a five-factor five-level central composite rotatable design matrix with full replication for planning, conduction, execution, and development of empirical relationships. Further, response surface methodology was used for the selection of optimum process parameters to achieve desired quality of yttria-stabilized zirconia coating deposits.

Central and Peripheral Fatigue During Resistance Exercise - A Critical Review.

PubMed

Zając, Adam; Chalimoniuk, Małgorzata; Maszczyk, Adam; Gołaś, Artur; Lngfort, Józef

2015-12-22

Resistance exercise is a popular form of conditioning for numerous sport disciplines, and recently different modes of strength training are being evaluated for health benefits. Resistance exercise differs significantly in nature, and several variables determine the direction and range of adaptive changes that occur in the muscular and skeletal system of the body. Some modes of resistance training can also be effective in stimulating the cardiovascular system. These variables include exercise selection (general, specific, single or multi joint, dynamic, explosive), type of resistance (free weights, variable resistance, isokinetics), order of exercise (upper and lower body or push and pull exercises), and most of all the training load which includes intensity expressed as % of 1RM, number of repetitions, number of sets and the rest interval between sets. Manipulating these variables allows for specific adaptive changes which may include gains in muscle mass, muscle strength or muscle endurance. It has been well established that during resistance exercise fatigue occurs, regardless of the volume and intensity of work applied. The peripheral mechanisms of fatigue have been studied and explained in more detail than those related to the CNS. This review is an attempt to bring together the latest knowledge regarding fatigue, both peripheral and central, during resistance exercise. The authors of this review concentrated on physiological and biochemical mechanisms underlying fatigue in exercises performed with maximal intensity, as well as those performed to exhaustion with numerous repetitions and submaximal load.

Elastic Bands as a Component of Periodized Resistance Training.

PubMed

Joy, Jordan M; Lowery, Ryan P; Oliveira de Souza, Eduardo; Wilson, Jacob M

2016-08-01

Joy, JM, Lowery, RP, Oliveira de Souza, E, and Wilson, JM. Elastic bands as a component of periodized resistance training. J Strength Cond Res 30(8): 2100-2106, 2016-Variable resistance training (VRT) has recently become a component of strength and conditioning programs. Prior research has demonstrated increases in power and/or strength using low loads of variable resistance. However, no study has examined using high loads of variable resistance as a part of a periodized training protocol to examine VRT within the context of a periodized training program and to examine a greater load of variable resistance than has been examined in prior research. Fourteen National Collegiate Athletic Association division II male basketball players were recruited for this study. Athletes were divided equally into either a variable resistance or control group. The variable resistance group added 30% of their 1 repetition maximum (1RM) as band tension to their prescribed weight 1 session per week. Rate of power development (RPD), peak power, strength, body composition, and vertical jump height were measured pretreatment and posttreatment. No baseline differences were observed between groups for any measurement of strength, power, or body composition. A significant group by time interaction was observed for RPD, in which RPD was greater in VRT posttraining than in the control group. Significant time effects were observed for all other variables including squat 1RM, bench press 1RM, deadlift 1RM, clean 3RM, vertical jump, and lean mass. Although there were no significant group ×-time interactions, the VRT group's percent changes and effect sizes indicate a larger treatment effect in the squat and bench press 1RM values and the vertical jump performed on the force plate and vertec. These results suggest that when using variable resistance as a component of a periodized training program, power and strength can be enhanced. Therefore, athletes who add variable resistance to 1 training session per week may enhance their athletic performance.

Analysis of the independent power of age-related, anthropometric and mechanical factors as determinants of the structure of radius and tibia in normal adults. A pQCT study.

PubMed

Reina, P; Cointry, G R; Nocciolino, L; Feldman, S; Ferretti, J L; Rittweger, J; Capozza, R F

2015-03-01

To compare the independent influence of mechanical and non-mechanical factors on bone features, multiple regression analyses were performed between pQCT indicators of radius and tibia bone mass, mineralization, design and strength as determined variables, and age or time since menopause (TMP), body mass, bone length and regional muscles' areas as selected determinant factors, in Caucasian, physically active, untrained healthy men and pre- and post-menopausal women. In men and pre-menopausal women, the strongest influences were exerted by muscle area on radial features and by both muscle area and bone length on the tibia. Only for women, was body mass a significant factor for tibia traits. In men and pre-menopausal women, mass/design/strength indicators depended more strongly on the selected determinants than the cortical vBMD did (p<0.01-0.001 vs n.s.), regardless of age. However, TMP was an additional factor for both bones (p<0.01-0.001). The selected mechanical factors (muscle size, bone lengths) were more relevant than age/TMP or body weight to the development of allometrically-related bone properties (mass/design/strength), yet not to bone tissue 'quality' (cortical vBMD), suggesting a determinant, rather than determined role for cortical stiffness. While the mechanical impacts of muscles and bone levers on bone structure were comparable in men and pre-menopausal women, TMP exerted a stronger impact than allometric or mechanical factors on bone properties, including cortical vBMD.

The challenge for genetic epidemiologists: how to analyze large numbers of SNPs in relation to complex diseases.

PubMed

Heidema, A Geert; Boer, Jolanda M A; Nagelkerke, Nico; Mariman, Edwin C M; van der A, Daphne L; Feskens, Edith J M

2006-04-21

Genetic epidemiologists have taken the challenge to identify genetic polymorphisms involved in the development of diseases. Many have collected data on large numbers of genetic markers but are not familiar with available methods to assess their association with complex diseases. Statistical methods have been developed for analyzing the relation between large numbers of genetic and environmental predictors to disease or disease-related variables in genetic association studies. In this commentary we discuss logistic regression analysis, neural networks, including the parameter decreasing method (PDM) and genetic programming optimized neural networks (GPNN) and several non-parametric methods, which include the set association approach, combinatorial partitioning method (CPM), restricted partitioning method (RPM), multifactor dimensionality reduction (MDR) method and the random forests approach. The relative strengths and weaknesses of these methods are highlighted. Logistic regression and neural networks can handle only a limited number of predictor variables, depending on the number of observations in the dataset. Therefore, they are less useful than the non-parametric methods to approach association studies with large numbers of predictor variables. GPNN on the other hand may be a useful approach to select and model important predictors, but its performance to select the important effects in the presence of large numbers of predictors needs to be examined. Both the set association approach and random forests approach are able to handle a large number of predictors and are useful in reducing these predictors to a subset of predictors with an important contribution to disease. The combinatorial methods give more insight in combination patterns for sets of genetic and/or environmental predictor variables that may be related to the outcome variable. As the non-parametric methods have different strengths and weaknesses we conclude that to approach genetic association studies using the case-control design, the application of a combination of several methods, including the set association approach, MDR and the random forests approach, will likely be a useful strategy to find the important genes and interaction patterns involved in complex diseases.

The relationship between biomechanical variables and driving performance during the golf swing.

PubMed

Chu, Yungchien; Sell, Timothy C; Lephart, Scott M

2010-09-01

Swing kinematic and ground reaction force data from 308 golfers were analysed to identify the variables important to driving ball velocity. Regression models were applied at four selected events in the swing. The models accounted for 44-74% of variance in ball velocity. Based on the regression analyses, upper torso-pelvis separation (the X-Factor), delayed release (i.e. the initiation of movement) of the arms and wrists, trunk forward and lateral tilting, and weight-shifting during the swing were significantly related to ball velocity. Our results also verify several general coaching ideas that were considered important to increased ball velocity. The results of this study may serve as both skill and strength training guidelines for golfers.

Interlaboratory study for nickel alloy 625 made by laser powder bed fusion to quantify mechanical property variability.

PubMed

Brown, Christopher U; Jacob, Gregor; Stoudt, Mark; Moylan, Shawn; Slotwinski, John; Donmez, Alkan

2016-08-01

Six different organizations participated in this interlaboratory study to quantify the variability in the tensile properties of Inconel 625 specimens manufactured using laser-powder-bed-fusion additive manufacturing machines. The tensile specimens were heat treated and tensile tests conducted until failure. The properties measured were yield strength, ultimate tensile strength, elastic modulus, and elongation. Statistical analysis revealed that between-participant variability for yield strength, ultimate tensile strength, and elastic modulus values were significantly higher (up to 4 times) than typical within-participant variations. Only between-participant and within-participant variability were both similar for elongation. A scanning electron microscope was used to examine one tensile specimen for fractography. The fracture surface does not have many secondary cracks or other features that would reduce the mechanical properties. In fact, the features largely consist of microvoid coalescence and are entirely consistent with ductile failure.

Interlaboratory study for nickel alloy 625 made by laser powder bed fusion to quantify mechanical property variability

PubMed Central

Brown, Christopher U.; Jacob, Gregor; Stoudt, Mark; Moylan, Shawn; Slotwinski, John; Donmez, Alkan

2017-01-01

Six different organizations participated in this interlaboratory study to quantify the variability in the tensile properties of Inconel 625 specimens manufactured using laser-powder-bed-fusion additive manufacturing machines. The tensile specimens were heat treated and tensile tests conducted until failure. The properties measured were yield strength, ultimate tensile strength, elastic modulus, and elongation. Statistical analysis revealed that between-participant variability for yield strength, ultimate tensile strength, and elastic modulus values were significantly higher (up to 4 times) than typical within-participant variations. Only between-participant and within-participant variability were both similar for elongation. A scanning electron microscope was used to examine one tensile specimen for fractography. The fracture surface does not have many secondary cracks or other features that would reduce the mechanical properties. In fact, the features largely consist of microvoid coalescence and are entirely consistent with ductile failure. PMID:28243032

Interlaboratory Study for Nickel Alloy 625 Made by Laser Powder Bed Fusion to Quantify Mechanical Property Variability

NASA Astrophysics Data System (ADS)

Brown, Christopher U.; Jacob, Gregor; Stoudt, Mark; Moylan, Shawn; Slotwinski, John; Donmez, Alkan

2016-08-01

Six different organizations participated in this interlaboratory study to quantify the variability in the tensile properties of Inconel 625 specimens manufactured using laser powder bed fusion-additive manufacturing machines. The tensile specimens were heat treated and tensile tests were conducted until failure. The properties measured were yield strength, ultimate tensile strength, elastic modulus, and elongation. Statistical analysis revealed that between-participant variability for yield strength, ultimate tensile strength, and elastic modulus values were significantly higher (up to four times) than typical within-participant variations. Only between-participant and within-participant variability were both similar for elongation. A scanning electron microscope was used to examine one tensile specimen for fractography. The fracture surface does not have many secondary cracks or other features that would reduce the mechanical properties. In fact, the features largely consist of microvoid coalescence and are entirely consistent with ductile failure.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levine, Paul A.; Randerson, James T.; Swenson, Sean C.

The relationship between terrestrial water storage (TWS) and atmospheric processes has important implications for predictability of climatic extremes and projection of future climate change. In places where moisture availability limits evapotranspiration (ET), variability in TWS has the potential to influence surface energy fluxes and atmospheric conditions. Where atmospheric conditions, in turn, influence moisture availability, a full feedback loop exists. Here we developed a novel approach for measuring the strength of both components of this feedback loop, i.e., the forcing of the atmosphere by variability in TWS and the response of TWS to atmospheric variability, using satellite observations of TWS, precipitation,more » solar radiation, and vapor pressure deficit during 2002–2014. Our approach defines metrics to quantify the relationship between TWS anomalies and climate globally on a seasonal to interannual timescale. Metrics derived from the satellite data were used to evaluate the strength of the feedback loop in 38 members of the Community Earth System Model (CESM) Large Ensemble (LENS) and in six models that contributed simulations to phase 5 of the Coupled Model Intercomparison Project (CMIP5). We found that both forcing and response limbs of the feedback loop in LENS were stronger than in the satellite observations in tropical and temperate regions. Feedbacks in the selected CMIP5 models were not as strong as those found in LENS, but were still generally stronger than those estimated from the satellite measurements. Consistent with previous studies conducted across different spatial and temporal scales, our analysis suggests that models may overestimate the strength of the feedbacks between the land surface and the atmosphere. Lastly, we describe several possible mechanisms that may contribute to this bias, and discuss pathways through which models may overestimate ET or overestimate the sensitivity of ET to TWS.« less

Isometric strength testing as a means of controlling medical incidents on strenuous jobs.

PubMed

Keyserling, W M; Herrin, G D; Chaffin, D B

1980-05-01

This investigation was performed to determine if isometric strength tests can be used to select workers for strenuous jobs and to reduce occupational injuries which are caused by a mismatch between worker strength and job strength requirements. Twenty jobs in a tire and rubber plant were studied biomechanically to identify critical strength-demanding tasks. Four strength tests were designed to simulate these tasks, and performance criteria were established for passing the tests. New applicants were administered the tests during their preplacement examinations to determine if they possessed sufficient strength to qualify for the jobs. The medical incidence rate of employees who were selected using the strength tests was approximately one-third that of employees selected using traditional medical criteria. It was concluded that isometric strength tests can be used to reduce occupational injuries and should be considered for implementation in industries with strenuous jobs.

Correlates of low back pain in a general population sample: a multidisciplinary perspective.

PubMed

Roncarati, A; McMullen, W

1988-06-01

This study identifies correlates of low back pain in a general population sample and defines a profile of subjects with low back pain. A multidisciplinary approach was employed that required surveying and physically assessing 674 subjects on 105 variables in biographical, anatomical, strength and flexibility measurement categories. No attempt was made to select subjects from specific occupational, age, athletic, psychological and anatomical groups or subjects with specific biographical features, which may have resulted in a sample that was atypical of the general population. The results of this study based on a causal comparative ex post facto research design corroborated selected findings of previous research conducted on nongeneral population samples. These findings include relationships between low back pain and age, body type, sex, stress, smoking, selected types of physical activity, occupation and previous injuries to the neck, shoulders, back and upper legs, as well as previous episodes of low back pain. Additional correlates of low back pain that were identified and have little or controversial review in the back literature include: delayed low back pain syndrome caused by abrupt changes in running frequency, Q angle, pes cavus, leg length (right and left), trunk length, genu recurvatum and multiplane strength and flexibility limitations in the hip joints.

[Application of quality by design in granulation process for ginkgo leaf tablet (Ⅱ)： identification of critical quality attributes].

PubMed

Xu, Bing; Cui, Xiang-Long; Yang, Chan; Wang, Xin; Shi, Xin-Yuan; Qiao, Yan-Jiang

2017-03-01

Quality by design (QbD) highlights the concept of "begin with the end", which means to thoroughly understand the target product quality first, and then guide pharmaceutical process development and quality control throughout the whole manufacturing process. In this paper, the Ginkgo biloba granules intermediates were taken as the research object, and the requirements of the tensile strength of tablets were treated as the goals to establish the methods for identification of granules' critical quality attributes (CQAs) and establishment of CQAs' limits. Firstly, the orthogonal partial least square (OPLS) model was adopted to build the relationship between the micromeritic properties of 29 batches of granules and the tensile strength of ginkgo leaf tablets, and thereby the potential critical quality attributes (pCQAs) were screened by variable importance in the projection (VIP) indexes. Then, a series of OPLS models were rebuilt by reducing pCQAs variables one by one in view of the rule of VIP values from low to high in sequence. The model performance results demonstrated that calibration and predictive performance of the model had no decreasing trend after variables reduction. In consideration of the results from variables selection as well as the collinearity test and testability of the pCQAs, the median particle size (D₅₀) and the bulk density (Da) were identified as critical quality attributes (CQAs). The design space of CQAs was developed based on a multiple linear regression model established between the CQAs (D₅₀ and Da) and the tensile strength. The control constraints of the CQAs were determined as 170 μm< D₅₀<500 μm and 0.30 g•cm⁻³

The association between neighbourhoods and educational achievement, a systematic review and meta-analysis.

PubMed

Nieuwenhuis, Jaap; Hooimeijer, Pieter

2016-01-01

Many studies have examined the effects of neighbourhoods on educational outcomes. The results of these studies are often conflicting, even if the same independent variables (such as poverty, educational climate, social disorganisation, or ethnic composition) are used. A systematic meta-analysis may help to resolve this lack of external validity. We identified 5516 articles from which we selected 88 that met all of the inclusion criteria. Using meta-regression, we found that the relation between neighbourhoods and individual educational outcomes is a function of neighbourhood poverty, the neighbourhood's educational climate, the proportion of ethnic/migrant groups, and social disorganisation in the neighbourhood. The variance in the findings from different studies can partly be explained by the sampling design and the type of model used in each study. More important is the use of control variables (school, family SES, and parenting variables) in explaining the variation in the strength of neighbourhood effects.

[A Structural Equation Model on Family Strength of Married Working Women].

PubMed

Hong, Yeong Seon; Han, Kuem Sun

2015-12-01

The purpose of this study was to identify the effect of predictive factors related to family strength and develop a structural equation model that explains family strength among married working women. A hypothesized model was developed based on literature reviews and predictors of family strength by Yoo. This constructed model was built of an eight pathway form. Two exogenous variables included in this model were ego-resilience and family support. Three endogenous variables included in this model were functional couple communication, family stress and family strength. Data were collected using a self-report questionnaire from 319 married working women who were 30~40 of age and lived in cities of Chungnam province in Korea. Data were analyzed with PASW/WIN 18.0 and AMOS 18.0 programs. Family support had a positive direct, indirect and total effect on family strength. Family stress had a negative direct, indirect and total effect on family strength. Functional couple communication had a positive direct and total effect on family strength. These predictive variables of family strength explained 61.8% of model. The results of the study show a structural equation model for family strength of married working women and that predicting factors for family strength are family support, family stress, and functional couple communication. To improve family strength of married working women, the results of this study suggest nursing access and mediative programs to improve family support and functional couple communication, and reduce family stress.

Reactive Strength Index: A Poor Indicator of Reactive Strength?

PubMed

Healy, Robin; Kenny, Ian; Harrison, Drew

2017-11-28

The primary aim was to assess the relationships between reactive strength measures and associated kinematic and kinetic performance variables achieved during drop jumps. A secondary aim was to highlight issues with the use of reactive strength measures as performance indicators. Twenty eight national and international level sprinters, consisting of fourteen men and women, participated in this cross-sectional analysis. Athletes performed drop jumps from a 0.3 m box onto a force platform with dependent variables contact time (CT), landing time (TLand), push-off time (TPush), flight time (FT), jump height (JH), reactive strength index (RSI, calculated as JH / CT), reactive strength ratio (RSR, calculated as FT / CT) and vertical leg spring stiffness (Kvert) recorded. Pearson's correlation test found very high to near perfect relationships between RSI and RSR (r = 0.91 to 0.97), with mixed relationships found between RSI, RSR and the key performance variables, (Men: r = -0.86 to -0.71 between RSI/RSR and CT, r = 0.80 to 0.92 between RSI/RSR and JH; Women: r = -0.85 to -0.56 between RSR and CT, r = 0.71 between RSI and JH). This study demonstrates that the method of assessing reactive strength (RSI versus RSR) may be influenced by the performance strategies adopted i.e. whether an athlete achieves their best reactive strength scores via low CTs, high JHs or a combination. Coaches are advised to limit the variability in performance strategies by implementing upper and / or lower CT thresholds to accurately compare performances between individuals.

Effects of Darwinian Selection and Mutability on Rate of Broadly Neutralizing Antibody Evolution during HIV-1 Infection

PubMed Central

Sheng, Zizhang; Schramm, Chaim A.; Connors, Mark; Morris, Lynn; Mascola, John R.; Kwong, Peter D.; Shapiro, Lawrence

2016-01-01

Accumulation of somatic mutations in antibody variable regions is critical for antibody affinity maturation, with HIV-1 broadly neutralizing antibodies (bnAbs) generally requiring years to develop. We recently found that the rate at which mutations accumulate decreases over time, but the mechanism governing this slowing is unclear. In this study, we investigated whether natural selection and/or mutability of the antibody variable region contributed significantly to observed decrease in rate. We used longitudinally sampled sequences of immunoglobulin transcripts of single lineages from each of 3 donors, as determined by next generation sequencing. We estimated the evolutionary rates of the complementarity determining regions (CDRs), which are most significant for functional selection, and found they evolved about 1.5- to 2- fold faster than the framework regions. We also analyzed the presence of AID hotspots and coldspots at different points in lineage development and observed an average decrease in mutability of less than 10 percent over time. Altogether, the correlation between Darwinian selection strength and evolutionary rate trended toward significance, especially for CDRs, but cannot fully explain the observed changes in evolutionary rate. The mutability modulated by AID hotspots and coldspots changes correlated only weakly with evolutionary rates. The combined effects of Darwinian selection and mutability contribute substantially to, but do not fully explain, evolutionary rate change for HIV-1-targeting bnAb lineages. PMID:27191167

Normative Measurements of Grip and Pinch Strengths of 21st Century Korean Population

PubMed Central

Shim, Jin Hee; Kim, Jin Soo; Lee, Dong Chul; Ki, Sae Hwi; Yang, Jae Won; Jeon, Man Kyung; Lee, Sang Myung

2013-01-01

Background Measuring grip and pinch strength is an important part of hand injury evaluation. Currently, there are no standardized values of normal grip and pinch strength among the Korean population, and lack of such data prevents objective evaluation of post-surgical recovery in strength. This study was designed to establish the normal values of grip and pinch strength among the healthy Korean population and to identify any dependent variables affecting grip and pinch strength. Methods A cross-sectional study was carried out. The inclusion criterion was being a healthy Korean person without a previous history of hand trauma. The grip strength was measured using a Jamar dynamometer. Pulp and key pinch strength were measured with a hydraulic pinch gauge. Intra-individual and inter-individual variations in these variables were analyzed in a standardized statistical manner. Results There were a total of 336 healthy participants between 13 and 77 years of age. As would be expected in any given population, the mean grip and pinch strength was greater in the right hand than the left. Male participants (137) showed mean strengths greater than female participants (199) when adjusted for age. Among the male participants, anthropometric variables correlated positively with grip strength, but no such correlations were identifiable in female participants in a statistically significant way. Conclusions Objective measurements of hand strength are an important component of hand injury evaluation, and population-specific normative data are essential for clinical and research purposes. This study reports updated normative hand strengths of the South Korean population in the 21st century. PMID:23362480

Plausible Effect of Weather on Atlantic Meridional Overturning Circulation with a Coupled General Circulation Model

NASA Astrophysics Data System (ADS)

Liu, Zedong; Wan, Xiuquan

2018-04-01

The Atlantic meridional overturning circulation (AMOC) is a vital component of the global ocean circulation and the heat engine of the climate system. Through the use of a coupled general circulation model, this study examines the role of synoptic systems on the AMOC and presents evidence that internally generated high-frequency, synoptic-scale weather variability in the atmosphere could play a significant role in maintaining the overall strength and variability of the AMOC, thereby affecting climate variability and change. Results of a novel coupling technique show that the strength and variability of the AMOC are greatly reduced once the synoptic weather variability is suppressed in the coupled model. The strength and variability of the AMOC are closely linked to deep convection events at high latitudes, which could be strongly affected by the weather variability. Our results imply that synoptic weather systems are important in driving the AMOC and its variability. Thus, interactions between atmospheric weather variability and AMOC may be an important feedback mechanism of the global climate system and need to be taken into consideration in future climate change studies.

Physiological responses to wearing the space shuttle launch and entry suit and the prototype advanced crew escape suit compared to the unsuited condition

NASA Technical Reports Server (NTRS)

Barrows, Linda H.; Mcbrine, John J.; Hayes, Judith C.; Stricklin, Marcella D.; Greenisen, Michael C.

1993-01-01

The launch and entry suit (LES) is a life support suit worn during Orbiter ascent and descent. The impact of suit weight and restricted mobility on egress from the Orbiter during an emergency is unknown. An alternate suit - the advanced crew escape suite (ACES) - is being evaluated. The physiological responses to ambulatory exercise of six subjects wearing the LES and ACES were measured and compared to those measurements taken while unsuited. Dependent variables included heart rate and metabolic response to treadmill walking at 5.6 km/h (3.5 mph), and also bilateral concentric muscle strength about the knee, shoulder, and elbow. No significant (p greater than 0.06) differences in heart rate or metabolic variables were measured in either suit while walking at 5.6 km/h. Significant (p less than 0.05) decreases in all metabolic variables were remarked when both suits were compared to the unsuited condition. There were no significant (p greater than 0.05) differences among the three suit conditions at 30 or 180 deg/s for muscles about the elbow and knee; however, about the shoulder, a significant (p = 0.0215) difference between the ACES and the unsuited condition was noted. Therefore, wearing a life support suit while performing Orbiter egress imposes a significant metabolic demand on crewmembers. Selective upper body strength movements may be compromised.

Causal language and strength of inference in academic and media articles shared in social media (CLAIMS): A systematic review.

PubMed

Haber, Noah; Smith, Emily R; Moscoe, Ellen; Andrews, Kathryn; Audy, Robin; Bell, Winnie; Brennan, Alana T; Breskin, Alexander; Kane, Jeremy C; Karra, Mahesh; McClure, Elizabeth S; Suarez, Elizabeth A

2018-01-01

The pathway from evidence generation to consumption contains many steps which can lead to overstatement or misinformation. The proliferation of internet-based health news may encourage selection of media and academic research articles that overstate strength of causal inference. We investigated the state of causal inference in health research as it appears at the end of the pathway, at the point of social media consumption. We screened the NewsWhip Insights database for the most shared media articles on Facebook and Twitter reporting about peer-reviewed academic studies associating an exposure with a health outcome in 2015, extracting the 50 most-shared academic articles and media articles covering them. We designed and utilized a review tool to systematically assess and summarize studies' strength of causal inference, including generalizability, potential confounders, and methods used. These were then compared with the strength of causal language used to describe results in both academic and media articles. Two randomly assigned independent reviewers and one arbitrating reviewer from a pool of 21 reviewers assessed each article. We accepted the most shared 64 media articles pertaining to 50 academic articles for review, representing 68% of Facebook and 45% of Twitter shares in 2015. Thirty-four percent of academic studies and 48% of media articles used language that reviewers considered too strong for their strength of causal inference. Seventy percent of academic studies were considered low or very low strength of inference, with only 6% considered high or very high strength of causal inference. The most severe issues with academic studies' causal inference were reported to be omitted confounding variables and generalizability. Fifty-eight percent of media articles were found to have inaccurately reported the question, results, intervention, or population of the academic study. We find a large disparity between the strength of language as presented to the research consumer and the underlying strength of causal inference among the studies most widely shared on social media. However, because this sample was designed to be representative of the articles selected and shared on social media, it is unlikely to be representative of all academic and media work. More research is needed to determine how academic institutions, media organizations, and social network sharing patterns impact causal inference and language as received by the research consumer.

Causal language and strength of inference in academic and media articles shared in social media (CLAIMS): A systematic review

PubMed Central

Smith, Emily R.; Moscoe, Ellen; Audy, Robin; Bell, Winnie; Brennan, Alana T.; Breskin, Alexander; Kane, Jeremy C.; Suarez, Elizabeth A.

2018-01-01

Background The pathway from evidence generation to consumption contains many steps which can lead to overstatement or misinformation. The proliferation of internet-based health news may encourage selection of media and academic research articles that overstate strength of causal inference. We investigated the state of causal inference in health research as it appears at the end of the pathway, at the point of social media consumption. Methods We screened the NewsWhip Insights database for the most shared media articles on Facebook and Twitter reporting about peer-reviewed academic studies associating an exposure with a health outcome in 2015, extracting the 50 most-shared academic articles and media articles covering them. We designed and utilized a review tool to systematically assess and summarize studies’ strength of causal inference, including generalizability, potential confounders, and methods used. These were then compared with the strength of causal language used to describe results in both academic and media articles. Two randomly assigned independent reviewers and one arbitrating reviewer from a pool of 21 reviewers assessed each article. Results We accepted the most shared 64 media articles pertaining to 50 academic articles for review, representing 68% of Facebook and 45% of Twitter shares in 2015. Thirty-four percent of academic studies and 48% of media articles used language that reviewers considered too strong for their strength of causal inference. Seventy percent of academic studies were considered low or very low strength of inference, with only 6% considered high or very high strength of causal inference. The most severe issues with academic studies’ causal inference were reported to be omitted confounding variables and generalizability. Fifty-eight percent of media articles were found to have inaccurately reported the question, results, intervention, or population of the academic study. Conclusions We find a large disparity between the strength of language as presented to the research consumer and the underlying strength of causal inference among the studies most widely shared on social media. However, because this sample was designed to be representative of the articles selected and shared on social media, it is unlikely to be representative of all academic and media work. More research is needed to determine how academic institutions, media organizations, and social network sharing patterns impact causal inference and language as received by the research consumer. PMID:29847549

The AGT Gene M235T Polymorphism and Response of Power-Related Variables to Aerobic Training

PubMed Central

Aleksandra, Zarębska; Zbigniew, Jastrzębski; Waldemar, Moska; Agata, Leońska-Duniec; Mariusz, Kaczmarczyk; Marek, Sawczuk; Agnieszka, Maciejewska-Skrendo; Piotr, Żmijewski; Krzysztof, Ficek; Grzegorz, Trybek; Ewelina, Lulińska-Kuklik; Semenova, Ekaterina A.; Ahmetov, Ildus I.; Paweł, Cięszczyk

2016-01-01

The C allele of the M235T (rs699) polymorphism of the AGT gene correlates with higher levels of angiotensin II and has been associated with power and strength sport performance. The aim of the study was to investigate whether or not selected power-related variables and their response to a 12-week program of aerobic dance training are modulated by the AGT M235T genotype in healthy participants. Two hundred and one Polish Caucasian women aged 21 ± 1 years met the inclusion criteria and were included in the study. All women completed a 12-week program of low and high impact aerobics. Wingate peak power and total work capacity, 5 m, 10 m, and 30 m running times and jump height and jump power were determined before and after the training programme. All power-related variables improved significantly in response to aerobic dance training. We found a significant association between the M235T polymorphism and jump-based variables (squat jump (SJ) height, p = 0.005; SJ power, p = 0.015; countermovement jump height, p = 0.025; average of 10 countermovement jumps with arm swing (ACMJ) height, p = 0.001; ACMJ power, p = 0.035). Specifically, greater improvements were observed in the C allele carriers in comparison with TT homozygotes. In conclusion, aerobic dance, one of the most commonly practiced adult fitness activities in the world, provides sufficient training stimuli for augmenting the explosive strength necessary to increase vertical jump performance. The AGT gene M235T polymorphism seems to be not only a candidate gene variant for power/strength related phenotypes, but also a genetic marker for predicting response to training. Key points Aerobic dance provides sufficient training stimuli for the improvement of explosive power. The AGT gene M235T polymorphism is associated with individual variation in the change of power-related phenotypes in response to aerobic dance training. The C allele carriers of the AGT gene M235T polymorphism show greater improvements of jump-based variables in comparison with TT homozygotes. PMID:27928207

Assessment of historical and projected segments of US and world civil and military rotorcraft markets, 1960 - 1990

NASA Technical Reports Server (NTRS)

Yates, W. J.

1981-01-01

The geographic climatic, political, economic and demographic environment of 75 countries was analyzed with respect to helicopter procurement history and usage. Key environmental indicators which are variables were projected into strengths and weaknesses of U.S. technology are reviewed. The civil market sensitivity to new technology is forecast with selected premises as to vehicle life, noise standards, fuel costs, GNP expansion and traffic growth. The forecast is based on a scenario of helicopter technology improvements resulting in increased size and performance.

Association of balance, strength, and power measures in young adults.

PubMed

Muehlbauer, Thomas; Gollhofer, Albert; Granacher, Urs

2013-03-01

The purpose of this study was to investigate the relationship between variables of static/dynamic balance, isometric strength, and power. Twenty-seven young healthy adults (mean age: 23 ± 4 years) performed measurements of static (unperturbed)/dynamic (perturbed) balance, isometric strength (i.e., maximal isometric torque [MIT]; rate of torque development [RTD] of the plantar flexor), and power (i.e., countermovement jump [CMJ] height and power). No significant associations were found between variables of static and dynamic balance (r = -0.090 to +0.329, p > 0.05) and between measures of static/dynamic balance and isometric strength (r = +0.041 to +0.387, p > 0.05) and static/dynamic balance and power (r = -0.076 to +0.218, p > 0.05). Significant positive correlations (r) were detected between variables of power and isometric strength ranging from +0.458 to +0.689 (p < 0.05). Furthermore, simple regression analyses revealed that a 10% increase in mean CMJ height (4.1 cm) was associated with 22.9 N·m and 128.4 N·m·s better MIT and RTD, respectively. The nonsignificant correlation between static and dynamic balance measures and between static/dynamic balance, isometric strength, and power variables implies that these capacities may be independent of each other and may have to be tested and trained complementarily.

Computational simulation of probabilistic lifetime strength for aerospace materials subjected to high temperature, mechanical fatigue, creep and thermal fatigue

NASA Technical Reports Server (NTRS)

Boyce, Lola; Bast, Callie C.; Trimble, Greg A.

1992-01-01

This report presents the results of a fourth year effort of a research program, conducted for NASA-LeRC by the University of Texas at San Antonio (UTSA). The research included on-going development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subject to a number of effects or primitive variables. These primitive variables may include high temperature, fatigue or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation has been randomized and is included in the computer program, PROMISS. Also included in the research is the development of methodology to calibrate the above-described constitutive equation using actual experimental materials data together with regression analysis of that data, thereby predicting values for the empirical material constants for each effect or primitive variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from industry and the open literature for materials typically for applications in aerospace propulsion system components. Material data for Inconel 718 has been analyzed using the developed methodology.

Computational simulation of probabilistic lifetime strength for aerospace materials subjected to high temperature, mechanical fatigue, creep, and thermal fatigue

NASA Technical Reports Server (NTRS)

Boyce, Lola; Bast, Callie C.; Trimble, Greg A.

1992-01-01

The results of a fourth year effort of a research program conducted for NASA-LeRC by The University of Texas at San Antonio (UTSA) are presented. The research included on-going development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subjected to a number of effects or primitive variables. These primitive variables may include high temperature, fatigue, or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation was randomized and is included in the computer program, PROMISC. Also included in the research is the development of methodology to calibrate the above-described constitutive equation using actual experimental materials data together with regression analysis of that data, thereby predicting values for the empirical material constants for each effect or primitive variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from industry and the open literature for materials typically for applications in aerospace propulsion system components. Material data for Inconel 718 was analyzed using the developed methodology.

Confined compressive strength analysis can improve PDC bit selection. [Polycrystalline Diamond Compact

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fabain, R.T.

1994-05-16

A rock strength analysis program, through intensive log analysis, can quantify rock hardness in terms of confined compressive strength to identify intervals suited for drilling with polycrystalline diamond compact (PDC) bits. Additionally, knowing the confined compressive strength helps determine the optimum PDC bit for the intervals. Computing rock strength as confined compressive strength can more accurately characterize a rock's actual hardness downhole than other methods. the information can be used to improve bit selections and to help adjust drilling parameters to reduce drilling costs. Empirical data compiled from numerous field strength analyses have provided a guide to selecting PDC drillmore » bits. A computer analysis program has been developed to aid in PDC bit selection. The program more accurately defines rock hardness in terms of confined strength, which approximates the in situ rock hardness downhole. Unconfined compressive strength is rock hardness at atmospheric pressure. The program uses sonic and gamma ray logs as well as numerous input data from mud logs. Within the range of lithologies for which the program is valid, rock hardness can be determine with improved accuracy. The program's output is typically graphed in a log format displaying raw data traces from well logs, computer-interpreted lithology, the calculated values of confined compressive strength, and various optional rock mechanic outputs.« less

Correlation of Titleist Performance Institute (TPI) level 1 movement screens and golf swing faults.

PubMed

Gulgin, Heather R; Schulte, Brian C; Crawley, Amy A

2014-02-01

Although some research in the past has examined how physical limitations in strength or flexibility affect a golfer's performance, the performance outcome most measured was driving distance. Currently, there are no data that have examined the relationship between selected strength and flexibility variables and golf swing faults. The purpose of this study was to examine the relationship between Titleist Performance Institute (TPI) level 1 movement screen variables and 14 common golf swing faults. Thirty-six male and female golfers (mean age, 25.4 ± 9.9 years; height, 175.9 ± 16.2 cm; mass, 76.2 ± 14.6 kg; handicap, 14.2 ± 10.4) participated. Twelve physical tests of strength, flexibility, and balance were assessed using the TPI level 1 golf fitness screening tool. Golfers then hit 4 golf shots (with a 5-iron) while being videoed, and those were then analyzed for 14 different golf swing faults (using V1Pro software). Three significant associations between a physical limitation and a particular golf swing fault were found: toe touch and early hip extension (p = 0.015), bridge on right side with both early hip extension (p = 0.050), and loss of posture (p = 0.028). In addition, an odds ratio showed that when a golfer could not overhead deep squat or single leg balance on left side, they were 2-3 times more likely to exhibit a early hip extension, loss of posture, or slide during the golf swing, as compared with those who could perform a correct overhead deep squat. Based on our findings, it is important for the golf fitness professional to particularly address a golfer's core strength, balance, and hamstring flexibility to help avoid common golf swing faults, which affect a golfer's ball striking ability and ultimately their performance.

Physical Activity Energy Expenditure and Sarcopenia in Black South African Urban Women.

PubMed

Kruger, Herculina S; Havemann-Nel, Lize; Ravyse, Chrisna; Moss, Sarah J; Tieland, Michael

2016-03-01

Black women are believed to be genetically less predisposed to age-related sarcopenia. The objective of this study was to investigate lifestyle factors associated with sarcopenia in black South African (SA) urban women. In a cross-sectional study, 247 women (mean age 57 y) were randomly selected. Anthropometric and sociodemographic variables, dietary intakes, and physical activity were measured. Activity was also measured by combined accelerometery/heart rate monitoring (ActiHeart), and HIV status was tested. Dual energy x-ray absorptiometry was used to measure appendicular skeletal mass (ASM). Sarcopenia was defined according to a recently derived SA cutpoint of ASM index (ASM/height squared) < 4.94 kg/m(2). In total, 8.9% of the women were sarcopenic, decreasing to 8.1% after exclusion of participants who were HIV positive. In multiple regressions with ASM index, grip strength, and gait speed, respectively, as dependent variables, only activity energy expenditure (β = .27) was significantly associated with ASM index. Age (β = -.50) and activity energy expenditure (β = .17) were significantly associated with gait speed. Age (β = -.11) and lean mass (β = .21) were significantly associated with handgrip strength. Sarcopenia was prevalent among these SA women and was associated with low physical activity energy expenditure.

Strength Asymmetry and Landing Mechanics at Return to Sport after ACL Reconstruction

PubMed Central

Schmitt, Laura C.; Paterno, Mark V.; Ford, Kevin R.; Myer, Gregory D.; Hewett, Timothy E.

2014-01-01

Purpose Evidence-based quadriceps femoris muscle (QF) strength guidelines for return to sport following anterior cruciate ligament (ACL) reconstruction are lacking. This study investigated the impact of QF strength asymmetry on knee landing biomechanics at the time of return to sport following ACL reconstruction. Methods Seventy-seven individuals (17.4 years) at the time of return to sport following primary ACL reconstruction (ACLR group) and 47 uninjured control individuals (17.0 years) (CTRL group) participated. QF strength was assessed and Quadriceps Index calculated (QI = [involved strength/uninvolved strength]*100%). The ACLR group was sub-divided based on QI: High Quadriceps (HQ, QI≥90%) and Low-Quadriceps (LQ, QI<85%). Knee kinematic and kinetic variables were collected during a drop vertical jump maneuver. Limb symmetry during landing, and discrete variables were compared among the groups with multivariate analysis of variance and linear regression analyses. Results The LQ group demonstrated worse asymmetry in all kinetic and ground reaction force variables compared to the HQ and CTRL groups, including reduced involved limb peak knee external flexion moments (p<.001), reduced involved limb (p=.003) and increased uninvolved limb (p=.005) peak vertical ground reaction forces, and higher uninvolved limb peak loading rates (p<.004). There were no differences in the landing patterns between the HQ and CTRL groups on any variable (p>.05). In the ACLR group, QF strength estimated limb symmetry during landing after controlling for graft type, meniscus injury, knee pain and symptoms. Conclusion At the time of return to sport, individuals post-ACL reconstruction with weaker QF demonstrate altered landing patterns. Conversely, those with nearly symmetrical QF strength demonstrate landing patterns similar to uninjured individuals. Consideration of an objective QF strength measure may aid clinical decision-making to optimize sports participation following ACL reconstruction. PMID:25373481

Ross Sea Till Properties: Implications for Ice Sheet Bed Interaction

NASA Astrophysics Data System (ADS)

Halberstadt, A. R.; Anderson, J. B.; Simkins, L.; Prothro, L. O.; Bart, P. J.

2015-12-01

Since the discovery of a pervasive shearing till layer underlying Ice Stream B, the scientific community has categorized subglacial diamictons as either deformation till or lodgement till primarily based on shear strength. Deformation till is associated with streaming ice, formed through subglacial deformation of unconsolidated sediments. Lodgement till is believed to be deposited by the plastering of sediment entrained at the base of slow-flowing ice onto a rigid bed. Unfortunately, there has been a paucity of quantitative data on the spatial distribution of shear strength across the continental shelf. Cores collected from the Ross Sea on cruises NBP1502 and NBP9902 provide a rich dataset that can be used to interpret till shear strength variability. Till strengths are analyzed within the context of: (1) geologic substrate; (2) water content and other geotechnical properties; (3) ice sheet retreat history; and (4) geomorphic framework. Tills display a continuum of shear strengths rather than a bimodal distribution, suggesting that shear strength cannot be used to distinguish between lodgement and deformation till. Where the substrate below the LGM unconformity is comprised of older lithified deposits, till shear strengths are both highly variable within the till unit, as well as highly variable between cores. Conversely, where ice streams flowed across unconsolidated Plio-Pleistocene deposits, shear strengths are low and less variable within the unit and between cores. This suggests greater homogenization of cannibalized tills, and possibly a deeper pervasive shear layer. Coarser-grained tills are observed on banks and bank slopes, with finer tills in troughs. Highly variable and more poorly sorted tills are found in close proximity to sediment-based subglacial meltwater channels, attesting to a change in ice-bed interaction as subglacial water increases. Pellets (rounded sedimentary clasts of till matrix) are observed in Ross Sea cores, suggesting a history of deformation responsible for pellet formation. Till strength was measured in a variety of environments, including mega-scale lineations and grounding zone wedges; ongoing work focuses on evaluating till shear strengths within a geomorphic context. These analyses are used to re-evaluate till genesis, transport, and characterization.

The identification of high potential archers based on fitness and motor ability variables: A Support Vector Machine approach.

PubMed

Taha, Zahari; Musa, Rabiu Muazu; P P Abdul Majeed, Anwar; Alim, Muhammad Muaz; Abdullah, Mohamad Razali

2018-02-01

Support Vector Machine (SVM) has been shown to be an effective learning algorithm for classification and prediction. However, the application of SVM for prediction and classification in specific sport has rarely been used to quantify/discriminate low and high-performance athletes. The present study classified and predicted high and low-potential archers from a set of fitness and motor ability variables trained on different SVMs kernel algorithms. 50 youth archers with the mean age and standard deviation of 17.0 ± 0.6 years drawn from various archery programmes completed a six arrows shooting score test. Standard fitness and ability measurements namely hand grip, vertical jump, standing broad jump, static balance, upper muscle strength and the core muscle strength were also recorded. Hierarchical agglomerative cluster analysis (HACA) was used to cluster the archers based on the performance variables tested. SVM models with linear, quadratic, cubic, fine RBF, medium RBF, as well as the coarse RBF kernel functions, were trained based on the measured performance variables. The HACA clustered the archers into high-potential archers (HPA) and low-potential archers (LPA), respectively. The linear, quadratic, cubic, as well as the medium RBF kernel functions models, demonstrated reasonably excellent classification accuracy of 97.5% and 2.5% error rate for the prediction of the HPA and the LPA. The findings of this investigation can be valuable to coaches and sports managers to recognise high potential athletes from a combination of the selected few measured fitness and motor ability performance variables examined which would consequently save cost, time and effort during talent identification programme. Copyright © 2017 Elsevier B.V. All rights reserved.

Estimation of 1RM for knee extension based on the maximal isometric muscle strength and body composition.

PubMed

Kanada, Yoshikiyo; Sakurai, Hiroaki; Sugiura, Yoshito; Arai, Tomoaki; Koyama, Soichiro; Tanabe, Shigeo

2017-11-01

[Purpose] To create a regression formula in order to estimate 1RM for knee extensors, based on the maximal isometric muscle strength measured using a hand-held dynamometer and data regarding the body composition. [Subjects and Methods] Measurement was performed in 21 healthy males in their twenties to thirties. Single regression analysis was performed, with measurement values representing 1RM and the maximal isometric muscle strength as dependent and independent variables, respectively. Furthermore, multiple regression analysis was performed, with data regarding the body composition incorporated as another independent variable, in addition to the maximal isometric muscle strength. [Results] Through single regression analysis with the maximal isometric muscle strength as an independent variable, the following regression formula was created: 1RM (kg)=0.714 + 0.783 × maximal isometric muscle strength (kgf). On multiple regression analysis, only the total muscle mass was extracted. [Conclusion] A highly accurate regression formula to estimate 1RM was created based on both the maximal isometric muscle strength and body composition. Using a hand-held dynamometer and body composition analyzer, it was possible to measure these items in a short time, and obtain clinically useful results.

Muscular Strength and Power in 3-to 7-Year-Old Children.

PubMed

Fry, Andrew C; Irwin, Carol C; Nicoll, Justin X; Ferebee, David E

2015-08-01

To determine absolute and relative (adjusted for body mass) strength, mean power, and mean velocity for upper and lower body resistance exercises, forty-seven young boys and girls participated in maximal strength testing. Healthy young boys and girls, ages 3- to 7-years old, were tested for one-repetition maximum (1-RM) strength, and 70% of 1-RM to determine mean power and mean velocity on the chest press and leg press exercises. Adult weight machines were modified to accommodate the smaller size and lower strength levels of the children. A 2 × 4 (sex × age) ANOVA was used to determine age and sex differences in performance. No interaction or sex differences were observed for any variable at any age. 1-RM strength, mean power, and mean velocity significantly increased across ages (p ≤ .05). When adjusted for body mass, the changes were insignificant, with one exception. Relative mean power for the bench press increased with age. Data indicated children from 3-7 years of age are capable of performing strength and power tests, but may require more attempts at maximal loads compared with adults. It appears that muscular strength and velocity during this stage of development are primarily dependent on increasing body mass, whereas power is influenced by additional variable(s).

Time perspective and weight management behaviors in newly diagnosed Type 2 diabetes: a mediational analysis.

PubMed

Hall, Peter A; Fong, Geoffrey T; Cheng, Alice Y

2012-12-01

The primary objective of the current study was to examine the extent to which domain-specific time perspective predicts weight management behaviors (dietary behavior and physical activity) among those newly diagnosed with Type 2 diabetes. A secondary objective was to test potential mediators of the hypothesized effect (behavioral intention, self-efficacy and control beliefs). A total of 204 adults newly diagnosed (≤6 months) with Type 2 diabetes participated in the study, which included a baseline assessment of domain-general and domain-specific time perspective, as well as strength of intention to perform two weight-management behaviors (dietary choice and physical activity); both weight-management behaviors were assessed again at 6 month follow-up. Hierarchical multiple regression analyses revealed a prospective association between domain-specific time perspective and uptake of weight management behaviors. Individuals with newly diagnosed T2DM possessing a future-oriented time perspective reported making less frequent fatty food choices and greater increases in physical activity over the 6-month follow-up interval. These effects were selectively mediated by intention strength, and not competing social cognitive variables. For both behaviors, the total effects and meditational models were robust to adjustments for demographics, body composition and disease variables. A future-oriented time perspective is prospectively associated with superior uptake of weight management behaviors among those with newly diagnosed Type 2 diabetes. The facilitating effect of future-oriented thinking appears to occur via enhanced strength of intentions to perform weight management behaviors.

Polymeric behavior evaluation of PVP K30-poloxamer binary carrier for solid dispersed nisoldipine by experimental design.

PubMed

Kyaw Oo, May; Mandal, Uttam K; Chatterjee, Bappaditya

2017-02-01

High melting point polymeric carrier without plasticizer is unacceptable for solid dispersion (SD) by melting method. Combined polymer-plasticizer carrier significantly affects drug solubility and tableting property of SD. To evaluate and optimize the combined effect of a binary carrier consisting PVP K30 and poloxamer 188, on nisoldipine solubility and tensile strength of amorphous SD compact (SD compact ) by experimental design. SD of nisoldpine (SD nisol ) was prepared by melt mixing with different PVP K30 and poloxamer amount. A 3 2 factorial design was employed using nisoldipine solubility and tensile strength of SD compact as response variables. Statistical optimization by design expert software, and SD nisol characterization using ATR FTIR, DSC and microscopy were done. PVP K30:poloxamer, at a ratio of 3.73:6.63, was selected as the optimized combination of binary polymeric carrier resulting nisoldipine solubility of 115 μg/mL and tensile strength of 1.19 N/m 2 . PVP K30 had significant positive effect on both responses. Increase in poloxamer concentration after a certain level decreased nisoldipine solubility and tensile strength of SD compact . An optimized PVP K30-poloxamer binary composition for SD carrier was developed. Tensile strength of SD compact can be considered as a response for experimental design to optimize SD.

The relationships of waist and mid-thigh circumference with performance of college golfers

PubMed Central

Son, Seungbum; Han, Kunho; So, Wi-Young

2016-01-01

[Purpose] Our aim was to evaluate the relationships between waist and mid-thigh circumference, used as proxy measures of trunk and lower limb strengths, respectively, and selected parameters of driver and putting performance in Korean college golfers. [Subjects and Methods] The participants were 103 college golfers (81 male, 20 to 27 years old). Measurements of body composition, waist and mid-thigh circumference, and grip strength, as well as assessment of golf performance, including driver distance, driver swing speed, putting accuracy, and putting consistency, were performed at the golf performance laboratory at Konkuk University in Chungju-si, Republic of Korea. Average round score was obtained from 10 rounds of golf completed during the study period. The relationships between strength measures and golf performance were evaluated by partial correlation analysis, with adjustment for age, golf experience, and body mass index. [Results] Waist circumference did not correlate with any of the performance variables in both males and females. Mid-thigh circumference correlated with putting consistency (r = 0.364) in males and with putting consistency (r = 0.490) and accuracy (r = 0.547) in females. No other significant correlations between waist and mid-thigh circumference and golf performance were identified. [Conclusion] Lower limb strength may be an important component of putting performance. Further studies are needed to fully characterize the contributions of trunk strength to performance. PMID:27134346

Effect of Various Laser Surface Treatments on Repair Shear Bond Strength of Aged Silorane-Based Composite

PubMed Central

Alizadeh Oskoee, Parnian; Savadi Oskoee, Siavash; Rikhtegaran, Sahand; Pournaghi-Azar, Fatemeh; Gholizadeh, Sarah; Aleyasin, Yasaman; Kasrae, Shahin

2017-01-01

Introduction: Successful repair of composite restorations depends on a strong bond between the old composite and the repair composite. This study sought to assess the repair shear bond strength of aged silorane-based composite following surface treatment with Nd:YAG, Er,Cr:YSGG and CO2 lasers. Methods: Seventy-six Filtek silorane composite cylinders were fabricated and aged by 2 months of water storage at 37°C. The samples were randomly divided into 4 groups (n=19) of no surface treatment (group 1) and surface treatment with Er,Cr:YSGG (group 2), Nd:YAG (group 3) and CO2 (group 4) lasers. The repair composite was applied and the shear bond strength was measured. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey posthoc test. Prior to the application of the repair composite, 2 samples were randomly selected from each group and topographic changes on their surfaces following laser irradiation were studied using a scanning electron microscope (SEM). Seventeen other samples were also fabricated for assessment of cohesive strength of composite. Results: The highest and the lowest mean bond strength values were 8.99 MPa and 6.69 MPa for Er,Cr:YSGG and control groups, respectively. The difference in the repair bond strength was statistically significant between the Er,Cr:YSGG and other groups. Bond strength of the control, Nd:YAG and CO2 groups was not significantly different. The SEM micrographs revealed variable degrees of ablation and surface roughness in laser-treated groups. Conclusion: Surface treatment with Er,Cr:YSGG laser significantly increase the repair bond strength of aged silorane-based composite resin. PMID:29071025

Characterization of the porosity of human dental enamel and shear bond strength in vitro after variable etch times: initial findings using the BET method.

PubMed

Nguyen, Trang T; Miller, Arthur; Orellana, Maria F

2011-07-01

(1) To quantitatively characterize human enamel porosity and surface area in vitro before and after etching for variable etching times; and (2) to evaluate shear bond strength after variable etching times. Specifically, our goal was to identify the presence of any correlation between enamel porosity and shear bond strength. Pore surface area, pore volume, and pore size of enamel from extracted human teeth were analyzed by Brunauer-Emmett-Teller (BET) gas adsorption before and after etching for 15, 30, and 60 seconds with 37% phosphoric acid. Orthodontic brackets were bonded with Transbond to the samples with variable etch times and were subsequently applied to a single-plane lap shear testing system. Pore volume and surface area increased after etching for 15 and 30 seconds. At 60 seconds, this increase was less pronounced. On the contrary, pore size appears to decrease after etching. No correlation was found between variable etching times and shear strength. Samples etched for 15, 30, and 60 seconds all demonstrated clinically viable shear strength values. The BET adsorption method could be a valuable tool in enhancing our understanding of enamel characteristics. Our findings indicate that distinct quantitative changes in enamel pore architecture are evident after etching. Further testing with a larger sample size would have to be carried out for more definitive conclusions to be made.

The effect of forging history on the strength and microstructure of TDNiCr /Ni-20Cr-2ThO2/

NASA Technical Reports Server (NTRS)

Filippi, A. M.

1975-01-01

Forging variables were evaluated to determine their influence on the elevated temperature strength and microstructure of TDNiCr. Grain size was the principal microstructural feature related to elevated temperature strength and was controlled primarily by the thermomechanical variables of forging temperature and final annealing condition. Tests at 1366 K revealed a factor of eight increase in tensile strength as grain size increased from 1 to 150 microns, while stress-rupture strength improved by three to five times as grain size increased from 15 to 150 microns. Forged material of grain size greater than or equal to about 150 microns displayed a level of elevated temperature strength comparable to that of optimized TDNiCr sheet. The presence of a preponderance of small twins and a strong preferred orientation may have also been factors contributing to the excellent high temperature strength of large grain forged material.

The importance of physical strength to human males.

PubMed

Sell, Aaron; Hone, Liana S E; Pound, Nicholas

2012-03-01

Fighting ability, although recognized as fundamental to intrasexual competition in many nonhuman species, has received little attention as an explanatory variable in the social sciences. Multiple lines of evidence from archaeology, criminology, anthropology, physiology, and psychology suggest that fighting ability was a crucial aspect of intrasexual competition for ancestral human males, and this has contributed to the evolution of numerous physical and psychological sex differences. Because fighting ability was relevant to many domains of interaction, male psychology should have evolved such that a man's attitudes and behavioral responses are calibrated according to his formidability. Data are reviewed showing that better fighters feel entitled to better outcomes, set lower thresholds for anger/aggression, have self-favoring political attitudes, and believe more in the utility of warfare. New data are presented showing that among Hollywood actors, those selected for their physical strength (i.e., action stars) are more likely to believe in the utility of warfare.

A Superstrong Adjustable Permanent Magnet for the Final Focus Quadrupole in a Linear Collider

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mihara, T.

A super strong permanent magnet quadrupole (PMQ) was fabricated and tested. It has an integrated strength of 28.5T with overall length of 10 cm and a 7mm bore radius. The final focus quadrupole of a linear collider needs a variable focal length. This can be obtained by slicing the magnet into pieces along the beamline direction and rotating these slices. But this technique may lead to movement of the magnetic center and introduction of a skew quadrupole component when the strength is varied. A ''double ring structure'' can ease these effects. A second prototype PMQ, containing thermal compensation materials andmore » with a double ring structure, has been fabricated. Worm gear is selected as the mechanical rotating scheme because the double ring structure needs a large torque to rotate magnets. The structure of the second prototype PMQ is shown.« less

Dielectric breakdown of additively manufactured polymeric materials

DOE PAGES

Monzel, W. Jacob; Hoff, Brad W.; Maestas, Sabrina S.; ...

2016-01-11

Dielectric strength testing of selected Polyjet-printed polymer plastics was performed in accordance with ASTM D149. This dielectric strength data is compared to manufacturer-provided dielectric strength data for selected plastics printed using the stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS) methods. Tested Polyjet samples demonstrated dielectric strengths as high as 47.5 kV/mm for a 0.5 mm thick sample and 32.1 kV/mm for a 1.0 mm sample. As a result, the dielectric strength of the additively manufactured plastics evaluated as part of this study was lower than the majority of non-printed plastics by at least 15% (with themore » exception of polycarbonate).« less

Dielectric breakdown of additively manufactured polymeric materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monzel, W. Jacob; Hoff, Brad W.; Maestas, Sabrina S.

Dielectric strength testing of selected Polyjet-printed polymer plastics was performed in accordance with ASTM D149. This dielectric strength data is compared to manufacturer-provided dielectric strength data for selected plastics printed using the stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS) methods. Tested Polyjet samples demonstrated dielectric strengths as high as 47.5 kV/mm for a 0.5 mm thick sample and 32.1 kV/mm for a 1.0 mm sample. As a result, the dielectric strength of the additively manufactured plastics evaluated as part of this study was lower than the majority of non-printed plastics by at least 15% (with themore » exception of polycarbonate).« less

Enhanced fluidity liquid chromatography of inulin fructans using ternary solvent strength and selectivity gradients.

PubMed

Bennett, Raffeal; Olesik, Susan V

2018-01-25

The value of exploring selectivity and solvent strength ternary gradients in enhanced fluidity liquid chromatography (EFLC) is demonstrated for the separation of inulin-type fructans from chicory. Commercial binary pump systems for supercritical fluid chromatography only allow for the implementation of ternary solvent strength gradients which can be restrictive for the separation of polar polymeric analytes. In this work, a custom system was designed to extend the capability of EFLC to allow tuning of selectivity or solvent strength in ternary gradients. Gradient profiles were evaluated using the Berridge function (RF 1 ), normalized resolution product (NRP), and gradient peak capacity (P c ). Selectivity gradients provided the separation of more analytes over time. The RF 1 function showed favor to selectivity gradients with comparable P c to that of solvent strength gradients. NRP did not strongly correlate with P c or RF 1 score. EFLC with the hydrophilic interaction chromatography, HILIC, separation mode was successfully employed to separate up to 47 fructan analytes in less than 25 min using a selectivity gradient. Copyright © 2017 Elsevier B.V. All rights reserved.

Changes in Knee Biomechanics After a Hip-Abductor Strengthening Protocol for Runners With Patellofemoral Pain Syndrome

PubMed Central

Ferber, Reed; Kendall, Karen D.; Farr, Lindsay

2011-01-01

Abstract Context: Very few authors have investigated the relationship between hip-abductor muscle strength and frontal-plane knee mechanics during running. Objective: To investigate this relationship using a 3-week hip-abductor muscle-strengthening program to identify changes in strength, pain, and biomechanics in runners with patellofemoral pain syndrome (PFPS). Design: Cohort study. Setting: University-based clinical research laboratory. Patients or Other Participants: Fifteen individuals (5 men, 10 women) with PFPS and 10 individuals without PFPS (4 men, 6 women) participated. Intervention(s): The patients with PFPS completed a 3-week hip-abductor strengthening protocol; control participants did not. Main Outcome Measure(s): The dependent variables of interest were maximal isometric hip-abductor muscle strength, 2-dimensional peak knee genu valgum angle, and stride-to-stride knee-joint variability. All measures were recorded at baseline and 3 weeks later. Between-groups differences were compared using repeated-measures analyses of variance. Results: At baseline, the PFPS group exhibited reduced strength, no difference in peak genu valgum angle, and increased stride-to-stride knee-joint variability compared with the control group. After the 3-week protocol, the PFPS group demonstrated increased strength, less pain, no change in peak genu valgum angle, and reduced stride-to-stride knee-joint variability compared with baseline. Conclusions: A 3-week hip-abductor muscle-strengthening protocol was effective in increasing muscle strength and decreasing pain and stride-to-stride knee-joint variability in individuals with PFPS. However, concomitant changes in peak knee genu valgum angle were not observed. PMID:21391799

Intraspecific divergence in sperm morphology of the green sea urchin, Strongylocentrotus droebachiensis: implications for selection in broadcast spawners

PubMed Central

2008-01-01

Background Sperm morphology can be highly variable among species, but less is known about patterns of population differentiation within species. Most studies of sperm morphometric variation are done in species with internal fertilization, where sexual selection can be mediated by complex mating behavior and the environment of the female reproductive tract. Far less is known about patterns of sperm evolution in broadcast spawners, where reproductive dynamics are largely carried out at the gametic level. We investigated variation in sperm morphology of a broadcast spawner, the green sea urchin (Strongylocentrotus droebachiensis), within and among spawnings of an individual, among individuals within a population, and among populations. We also examined population-level variation between two reproductive seasons for one population. We then compared among-population quantitative genetic divergence (QST) for sperm characters to divergence at neutral microsatellite markers (FST). Results All sperm traits except total length showed strong patterns of high diversity among populations, as did overall sperm morphology quantified using multivariate analysis. We also found significant differences in almost all traits among individuals in all populations. Head length, axoneme length, and total length had high within-male repeatability across multiple spawnings. Only sperm head width had significant within-population variation across two reproductive seasons. We found signatures of directional selection on head length and head width, with strong selection possibly acting on head length between the Pacific and West Atlantic populations. We also discuss the strengths and limitations of the QST-FST comparison. Conclusion Sperm morphology in S. droebachiensis is highly variable, both among populations and among individuals within populations, and has low variation within an individual across multiple spawnings. Selective pressures acting among populations may differ from those acting within, with directional selection implicated in driving divergence among populations and balancing selection as a possible mechanism for producing variability among males. Sexual selection in broadcast spawners may be mediated by different processes from those acting on internal fertilizers. Selective divergence in sperm head length among populations is associated with ecological differences among populations that may play a large role in mediating sexual selection in this broadcast spawner. PMID:18851755

Scale-Dependent Habitat Selection and Size-Based Dominance in Adult Male American Alligators

PubMed Central

Strickland, Bradley A.; Vilella, Francisco J.; Belant, Jerrold L.

2016-01-01

Habitat selection is an active behavioral process that may vary across spatial and temporal scales. Animals choose an area of primary utilization (i.e., home range) then make decisions focused on resource needs within patches. Dominance may affect the spatial distribution of conspecifics and concomitant habitat selection. Size-dependent social dominance hierarchies have been documented in captive alligators, but evidence is lacking from wild populations. We studied habitat selection for adult male American alligators (Alligator mississippiensis; n = 17) on the Pearl River in central Mississippi, USA, to test whether habitat selection was scale-dependent and individual resource selectivity was a function of conspecific body size. We used K-select analysis to quantify selection at the home range scale and patches within the home range to determine selection congruency and important habitat variables. In addition, we used linear models to determine if body size was related to selection patterns and strengths. Our results indicated habitat selection of adult male alligators was a scale-dependent process. Alligators demonstrated greater overall selection for habitat variables at the patch level and less at the home range level, suggesting resources may not be limited when selecting a home range for animals in our study area. Further, diurnal habitat selection patterns may depend on thermoregulatory needs. There was no relationship between resource selection or home range size and body size, suggesting size-dependent dominance hierarchies may not have influenced alligator resource selection or space use in our sample. Though apparent habitat suitability and low alligator density did not manifest in an observed dominance hierarchy, we hypothesize that a change in either could increase intraspecific interactions, facilitating a dominance hierarchy. Due to the broad and diverse ecological roles of alligators, understanding the factors that influence their social dominance and space use can provide great insight into their functional role in the ecosystem. PMID:27588947

Scale-dependent habitat selection and size-based dominance in adult male American alligators

USGS Publications Warehouse

Strickland, Bradley A.; Vilella, Francisco; Belant, Jerrold L.

2016-01-01

Habitat selection is an active behavioral process that may vary across spatial and temporal scales. Animals choose an area of primary utilization (i.e., home range) then make decisions focused on resource needs within patches. Dominance may affect the spatial distribution of conspecifics and concomitant habitat selection. Size-dependent social dominance hierarchies have been documented in captive alligators, but evidence is lacking from wild populations. We studied habitat selection for adult male American alligators (Alligator mississippiensis; n = 17) on the Pearl River in central Mississippi, USA, to test whether habitat selection was scale-dependent and individual resource selectivity was a function of conspecific body size. We used K-select analysis to quantify selection at the home range scale and patches within the home range to determine selection congruency and important habitat variables. In addition, we used linear models to determine if body size was related to selection patterns and strengths. Our results indicated habitat selection of adult male alligators was a scale-dependent process. Alligators demonstrated greater overall selection for habitat variables at the patch level and less at the home range level, suggesting resources may not be limited when selecting a home range for animals in our study area. Further, diurnal habitat selection patterns may depend on thermoregulatory needs. There was no relationship between resource selection or home range size and body size, suggesting size-dependent dominance hierarchies may not have influenced alligator resource selection or space use in our sample. Though apparent habitat suitability and low alligator density did not manifest in an observed dominance hierarchy, we hypothesize that a change in either could increase intraspecific interactions, facilitating a dominance hierarchy. Due to the broad and diverse ecological roles of alligators, understanding the factors that influence their social dominance and space use can provide great insight into their functional role in the ecosystem.

Effect of concrete strength gradation to the compressive strength of graded concrete, a numerical approach

NASA Astrophysics Data System (ADS)

Pratama, M. Mirza Abdillah; Aylie, Han; Gan, Buntara Sthenly; Umniati, B. Sri; Risdanareni, Puput; Fauziyah, Shifa

2017-09-01

Concrete casting, compacting method, and characteristic of the concrete material determine the performance of concrete as building element due to the material uniformity issue. Previous studies show that gradation in strength exists on building member by nature and negatively influence the load carrying capacity of the member. A pilot research had modeled the concrete gradation in strength with controllable variable and observed that the weakest material determines the strength of graded concrete through uniaxial compressive loading test. This research intends to confirm the recent finding by a numerical approach with extensive variables of strength disparity. The finite element analysis was conducted using the Strand7 nonlinear program. The results displayed that the increase of strength disparity in graded concrete models leads to the slight reduction of models strength. A substantial difference in displacement response is encountered on the models for the small disparity of concrete strength. However, the higher strength of concrete mix in the graded concrete models contributes to the rise of material stiffness that provides a beneficial purpose for serviceability of building members.

Spatiotemporal variation in local adaptation of a specialist insect herbivore to its long-lived host plant.

PubMed

Kalske, Aino; Leimu, Roosa; Scheepens, J F; Mutikainen, Pia

2016-09-01

Local adaptation of interacting species to one another indicates geographically variable reciprocal selection. This process of adaptation is central in the organization and maintenance of genetic variation across populations. Given that the strength of selection and responses to it often vary in time and space, the strength of local adaptation should in theory vary between generations and among populations. However, such spatiotemporal variation has rarely been explicitly demonstrated in nature and local adaptation is commonly considered to be relatively static. We report persistent local adaptation of the short-lived herbivore Abrostola asclepiadis to its long-lived host plant Vincetoxicum hirundinaria over three successive generations in two studied populations and considerable temporal variation in local adaptation in six populations supporting the geographic mosaic theory. The observed variation in local adaptation among populations was best explained by geographic distance and population isolation, suggesting that gene flow reduces local adaptation. Changes in herbivore population size did not conclusively explain temporal variation in local adaptation. Our results also imply that short-term studies are likely to capture only a part of the existing variation in local adaptation. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

SU-E-T-155: Calibration of Variable Longitudinal Strength 103Pd Brachytherapy Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reed, J; Radtke, J; Micka, J

Purpose: Brachytherapy sources with variable longitudinal strength (VLS) allow for a customized intensity along the length of the source. These have applications in focal brachytherapy treatments of prostate cancer where dose boosting can be achieved through modulation of intra-source strengths. This work focused on development of a calibration methodology for VLS sources based on measurements and Monte Carlo (MC) simulations of five 1 cm {sup 10} {sup 3}Pd sources each containing four regions of variable {sup 103}Pd strength. Methods: The air-kerma strengths of the sources were measured with a variable-aperture free-air chamber (VAFAC). Source strengths were also measured using amore » well chamber. The in-air azimuthal and polar anisotropy of the sources were measured by rotating them in front of a NaI scintillation detector and were calculated with MC simulations. Azimuthal anisotropy results were normalized to their mean intensity values. Polar anisotropy results were normalized to their average transverse axis intensity values. The relative longitudinal strengths of the sources were measured via on-contact irradiations with radiochromic film, and were calculated with MC simulations. Results: The variable {sup 103}Pd loading of the sources was validated by VAFAC and well chamber measurements. Ratios of VAFAC air-kerma strengths and well chamber responses were within ±1.3% for all sources. Azimuthal anisotropy results indicated that ≥95% of the normalized values for all sources were within ±1.7% of the mean values. Polar anisotropy results indicated variations within ±0.3% for a ±7.6° angular region with respect to the source transverse axis. Locations and intensities of the {sup 103}Pd regions were validated by radiochromic film measurements and MC simulations. Conclusion: The calibration methodology developed in this work confirms that the VLS sources investigated have a high level of polar uniformity, and that the strength and longitudinal intensity can be verified experimentally and through MC simulations. {sup 103}Pd sources were provided by CivaTech Oncology, Inc.« less

The Structure of Character Strengths: Variable- and Person-Centered Approaches

PubMed Central

Najderska, Małgorzata; Cieciuch, Jan

2018-01-01

This article examines the structure of character strengths (Peterson and Seligman, 2004) following both variable-centered and person-centered approaches. We used the International Personality Item Pool-Values in Action (IPIP-VIA) questionnaire. The IPIP-VIA measures 24 character strengths and consists of 213 direct and reversed items. The present study was conducted in a heterogeneous group of N = 908 Poles (aged 18–78, M = 28.58). It was part of a validation project of a Polish version of the IPIP-VIA questionnaire. The variable-centered approach was used to examine the structure of character strengths on both the scale and item levels. The scale-level results indicated a four-factor structure that can be interpreted based on four of the five personality traits from the Big Five theory (excluding neuroticism). The item-level analysis suggested a slightly different and limited set of character strengths (17 not 24). After conducting a second-order analysis, a four-factor structure emerged, and three of the factors could be interpreted as being consistent with the scale-level factors. Three character strength profiles were found using the person-centered approach. Two of them were consistent with alpha and beta personality metatraits. The structure of character strengths can be described by using categories from the Five Factor Model of personality and metatraits. They form factors similar to some personality traits and occur in similar constellations as metatraits. The main contributions of this paper are: (1) the validation of IPIP-VIA conducted in variable-centered approach in a new research group (Poles) using a different measurement instrument; (2) introducing the person-centered approach to the study of the structure of character strengths. PMID:29515482

Effect of Training on Physiological and Biochemical Variables of Soccer Players of Different Age Groups

PubMed Central

Manna, Indranil; Khanna, Gulshan Lal; Chandra Dhara, Prakash

2010-01-01

Purpose To find out the effect of training on selected physiological and biochemical variables of Indian soccer players of different age groups. Methods A total of 120 soccer players volunteered for the study, were divided (n = 30) into 4 groups: (i) under 16 years (U16), (ii) under 19 years (U19), (iii) under 23 years (U23), (iv) senior (SR). The training sessions were divided into 2 phases (a) Preparatory Phase (PP, 8 weeks) and (b) Competitive Phase (CP, 4 weeks). The training program consisted of aerobic, anaerobic and skill development, and were completed 4 hrs/day; 5 days/week. Selected physiological and biochemical variables were measured at zero level (baseline data, BD) and at the end of PP and CP. Results A significant increase (P < 0.05) in lean body mass (LBM), VO2max, anaerobic power, grip and back strength, urea, uric acid and high density lipoprotein cholesterol (HDL-C); and a significant decrease (P < 0.05) in body fat, hemoglobin (Hb), total cholesterol (TC), triglyceride (TG) and low density lipoprotein cholesterol (LDL-C) were detected in some groups in PP and CP phases of the training when compare to BD. However, no significant change was found in body mass and maximal heart rate of the players after the training program. Conclusion This study would provide useful information for training and selection of soccer players of different age groups. PMID:22375187

DOE Office of Scientific and Technical Information (OSTI.GOV)

Downes, R.A.

Galactic plane ultraviolet-excess (uv-excess) objects covering about 1000 square degrees of sky were surveyed. Photographic plates were obtained with both uv and blue filters, to select the uv-excess candidates, which were then observed spectroscopically to determine their classification. Most of the objects selected were nearby early-type stars with low interstellar reddening; however, a collection of hot white dwarfs, subdwarf O (sdO) stars, subdwarf B (sdB) stars, and cataclysmic variables was also found. Photoelectric photometry was obtained for these stars and a statistical analysis was performed to determine the space densities and scale heights for the four classes of objects. Severalmore » interesting objects (or class of objects) were discovered, and data for some of these stars are presented. Among the peculiar objects found are an emission-line white dwarf similar to the pulsating PG 1159 stars, a Population II Wolf-Rayet star, a previously catalogued object with a strong Fe II emission-line spectrum, and a new class of object, resembling the sdB stars, that shows variable strength H..cap alpha.. absorption, with the H..cap alpha.. line sometimes completely filled in.« less

Divergence and evolution of assortative mating in a polygenic trait model of speciation with gene flow.

PubMed

Sachdeva, Himani; Barton, Nicholas H

2017-06-01

Assortative mating is an important driver of speciation in populations with gene flow and is predicted to evolve under certain conditions in few-locus models. However, the evolution of assortment is less understood for mating based on quantitative traits, which are often characterized by high genetic variability and extensive linkage disequilibrium between trait loci. We explore this scenario for a two-deme model with migration, by considering a single polygenic trait subject to divergent viability selection across demes, as well as assortative mating and sexual selection within demes, and investigate how trait divergence is shaped by various evolutionary forces. Our analysis reveals the existence of sharp thresholds of assortment strength, at which divergence increases dramatically. We also study the evolution of assortment via invasion of modifiers of mate discrimination and show that the ES assortment strength has an intermediate value under a range of migration-selection parameters, even in diverged populations, due to subtle effects which depend sensitively on the extent of phenotypic variation within these populations. The evolutionary dynamics of the polygenic trait is studied using the hypergeometric and infinitesimal models. We further investigate the sensitivity of our results to the assumptions of the hypergeometric model, using individual-based simulations. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

Is protective equipment useful in preventing concussion? A systematic review of the literature.

PubMed

Benson, B W; Hamilton, G M; Meeuwisse, W H; McCrory, P; Dvorak, J

2009-05-01

To determine if there is evidence that equipment use reduces sport concussion risk and/or severity. 12 electronic databases were searched using a combination of Medical Subject Headings and text words to identify relevant articles. Specific inclusion and exclusion criteria were used to select studies for review. Data extracted included design, study population, exposure/outcome measures and results. The quality of evidence was assessed based on epidemiologic criteria regarding internal and external validity (ie, strength of design, sample size/power calculation, selection bias, misclassification bias, control of potential confounding and effect modification). In total, 51 studies were selected for review. A comparison between studies was difficult due to the variability in research designs, definition of concussion, mouthguard/helmet/headgear/face shield types, measurements used to assess exposure and outcomes, and variety of sports assessed. The majority of studies were observational, with 23 analytical epidemiologic designs related to the subject area. Selection bias was a concern in the reviewed studies, as was the lack of measurement and control for potentially confounding variables. There is evidence that helmet use reduces head injury risk in skiing, snowboarding and bicycling, but the effect on concussion risk is inconclusive. No strong evidence exists for the use of mouthguards or face shields to reduce concussion risk. Evidence is provided to suggest that full facial protection in ice hockey may reduce concussion severity, as measured by time loss from competition.

Individualised training to address variability of radiologists' performance

NASA Astrophysics Data System (ADS)

Sun, Shanghua; Taylor, Paul; Wilkinson, Louise; Khoo, Lisanne

2008-03-01

Computer-based tools are increasingly used for training and the continuing professional development of radiologists. We propose an adaptive training system to support individualised learning in mammography, based on a set of real cases, which are annotated with educational content by experienced breast radiologists. The system has knowledge of the strengths and weakness of each radiologist's performance: each radiologist is assessed to compute a profile showing how they perform on different sets of cases, classified by type of abnormality, breast density, and perceptual difficulty. We also assess variability in cognitive aspects of image perception, classifying errors made by radiologists as errors of search, recognition or decision. This is a novel element in our approach. The profile is used to select cases to present to the radiologist. The intelligent and flexible presentation of these cases distinguishes our system from existing training tools. The training cases are organised and indexed by an ontology we have developed for breast radiologist training, which is consistent with the radiologists' profile. Hence, the training system is able to select appropriate cases to compose an individualised training path, addressing the variability of the radiologists' performance. A substantial part of the system, the ontology has been evaluated on a large number of cases, and the training system is under implementation for further evaluation.

NEW METHODOLOGY FOR DEVELOPMENT OF ORODISPERSIBLE TABLETS USING HIGH-SHEAR GRANULATION PROCESS.

PubMed

Ali, Bahaa E; Al-Shedfat, Ramadan I; Fayed, Mohamed H; Alanazi, Fars K

2017-05-01

Development of orodispersible delivery system of high mechanical properties and low disintegration time is a big challenge. The aim of the current work was to assess and optimize the high shear granulation process as a new methodology for development of orodispersible tablets of high quality attributes using design of experiment approach. A two factor, three levels (32), full factorial design was carried out to investigate the main and interaction effects of independent variables, water amount (XI) and granulation time (X2) on the characteristics of granules and final product, tablet. The produced granules were analyzed for their granule size, density and flowability. Furthermore, the produced tablets were tested for: weight variation, breaking force/ crushing strength, friability, disintegration time and drug dissolution. Regression analysis results of multiple linear models showed a high correlation between the adjusted R-squared and predicted R-squared for all granules and tablets characteristics, the difference is less than 0.2. All dependent responses of granules and tablets were found to be impacted significantly (p < 0.05) by the two independent variables. However, water amount demonstrated the most dominant effect for all granules and tablet characteristics as shown by higher its coefficient estimate for all selected responses. Numerical optimization using desirability function was performed to optimize the variables under study to provide orodispersible system within the USP limit with respect of mechanical properties and disintegration time. It was found that the higher desirability (0.915) could be attained at the low level pf water (180 g) and short granulation time (1.65 min). Eventually, this study provides the formulator with helpful information in selecting the proper level of water and granulation time to provide an orodispersible system of high crushing strength and very low disintegration time, when high shear granulation methodology was used as a method of manufacture.

Estimating the concrete compressive strength using hard clustering and fuzzy clustering based regression techniques.

PubMed

Nagwani, Naresh Kumar; Deo, Shirish V

2014-01-01

Understanding of the compressive strength of concrete is important for activities like construction arrangement, prestressing operations, and proportioning new mixtures and for the quality assurance. Regression techniques are most widely used for prediction tasks where relationship between the independent variables and dependent (prediction) variable is identified. The accuracy of the regression techniques for prediction can be improved if clustering can be used along with regression. Clustering along with regression will ensure the more accurate curve fitting between the dependent and independent variables. In this work cluster regression technique is applied for estimating the compressive strength of the concrete and a novel state of the art is proposed for predicting the concrete compressive strength. The objective of this work is to demonstrate that clustering along with regression ensures less prediction errors for estimating the concrete compressive strength. The proposed technique consists of two major stages: in the first stage, clustering is used to group the similar characteristics concrete data and then in the second stage regression techniques are applied over these clusters (groups) to predict the compressive strength from individual clusters. It is found from experiments that clustering along with regression techniques gives minimum errors for predicting compressive strength of concrete; also fuzzy clustering algorithm C-means performs better than K-means algorithm.

Estimating the Concrete Compressive Strength Using Hard Clustering and Fuzzy Clustering Based Regression Techniques

PubMed Central

Nagwani, Naresh Kumar; Deo, Shirish V.

2014-01-01

Understanding of the compressive strength of concrete is important for activities like construction arrangement, prestressing operations, and proportioning new mixtures and for the quality assurance. Regression techniques are most widely used for prediction tasks where relationship between the independent variables and dependent (prediction) variable is identified. The accuracy of the regression techniques for prediction can be improved if clustering can be used along with regression. Clustering along with regression will ensure the more accurate curve fitting between the dependent and independent variables. In this work cluster regression technique is applied for estimating the compressive strength of the concrete and a novel state of the art is proposed for predicting the concrete compressive strength. The objective of this work is to demonstrate that clustering along with regression ensures less prediction errors for estimating the concrete compressive strength. The proposed technique consists of two major stages: in the first stage, clustering is used to group the similar characteristics concrete data and then in the second stage regression techniques are applied over these clusters (groups) to predict the compressive strength from individual clusters. It is found from experiments that clustering along with regression techniques gives minimum errors for predicting compressive strength of concrete; also fuzzy clustering algorithm C-means performs better than K-means algorithm. PMID:25374939

Strength training, but not endurance training, reduces motor unit discharge rate variability.

PubMed

Vila-Chã, Carolina; Falla, Deborah

2016-02-01

This study evaluates and compares the effects of strength and endurance training on motor unit discharge rate variability and force steadiness of knee extensor muscles. Thirty sedentary healthy men (age, 26.0±3.8yrs) were randomly assigned to strength training, endurance training or a control group. Conventional endurance and strength training was performed 3days per week, over a period of 6weeks. Maximum voluntary contraction (MVC), time to task failure (at 30% MVC), coefficient of variation (CoV) of force and of the discharges rates of motor units from the vastus medialis obliquus and vastus lateralis were determined as subjects performed 20% and 30% MVC knee extension contractions before and after training. CoV of motor unit discharges rates was significantly reduced for both muscles following strength training (P<0.001), but did not change in the endurance (P=0.875) or control group (P=0.995). CoV of force was reduced after the strength training intervention only (P<0.01). Strength training, but not endurance training, reduces motor unit discharge rate variability and enhances force steadiness of the knee extensors. These results provide new insights into the neuromuscular adaptations that occur with different training methods. Copyright © 2015 Elsevier Ltd. All rights reserved.

Influences of physical fitness on bone mass in women with fibromyalgia.

PubMed

Gómez-Cabello, Alba; Vicente-Rodríguez, Germán; Navarro-Vera, Isabel; Martinez-Redondo, Diana; Díez-Sánchez, Carmen; Casajús, José Antonio

2015-04-01

The aim of this study was to provide information about the relationship of bone mineral content (BMC) and density (BMD) with some physical-fitness-related variables in a sample of women with fibromyalgia (FM) and age-matched women without FM. Twenty-eight women clinically diagnosed with FM (age 51.1 ± 8.4 yr, M ± SD) and 22 age-matched controls participated in the study. Whole-body BMC and BMD, lean mass, handgrip strength, quadriceps strength, and cardiovascular fitness were measured in all participants. The association between physical-fitness variables and bone-related variables was tested by linear regression controlling for body weight as a possible confounder. There were no differences in BMC or BMD between groups. Women with FM had lower values of handgrip strength, quadriceps strength, and VO2peak than the control group. Handgrip strength and aerobic capacity were associated with BMC and BMD and quadriceps strength was associated with BMD in women with FM; however, only VO2peak was associated with BMC in the group of women without FM. Bone mass of women with FM may be more susceptible to changes in physical fitness than that of the women without fibromyalgia.

Not All Is Lost: Old Adults Retain Flexibility in Motor Behaviour during Sit-to-Stand

PubMed Central

Greve, Christian; Zijlstra, Wiebren; Hortobágyi, Tibor; Bongers, Raoul M.

2013-01-01

Sit-to-stand is a fundamental activity of daily living, which becomes increasingly difficult with advancing age. Due to severe loss of leg strength old adults are required to change the way they rise from a chair and maintain stability. Here we examine whether old compared to young adults differently prioritize task-important performance variables and whether there are age-related differences in the use of available motor flexibility. We applied the uncontrolled manifold analysis to decompose trial-to-trial variability in joint kinematics into variability that stabilizes and destabilizes task-important performance variables. Comparing the amount of variability stabilizing and destabilizing task-important variables enabled us to identify the variable of primary importance for the task. We measured maximal isometric voluntary force of three muscle groups in the right leg. Independent of age and muscle strength, old and young adults similarly prioritized stability of the ground reaction force vector during sit-to-stand. Old compared to young adults employed greater motor flexibility, stabilizing ground reaction forces during sit-to-sand. We concluded that freeing those degrees of freedom that stabilize task-important variables is a strategy used by the aging neuromuscular system to compensate for strength deficits. PMID:24204952

Discriminant analysis of cardiovascular and respiratory variables for classification of road cyclists by specialty.

PubMed

Nikolić, Biljana; Martinović, Jelena; Matić, Milan; Stefanović, Đorđe

2018-05-29

Different variables determine the performance of cyclists, which brings up the question how these parameters may help in their classification by specialty. The aim of the study was to determine differences in cardiorespiratory parameters of male cyclists according to their specialty, flat rider (N=21), hill rider (N=35) and sprinter (N=20) and obtain the multivariate model for further cyclists classification by specialties, based on selected variables. Seventeen variables were measured at submaximal and maximum load on the cycle ergometer Cosmed E 400HK (Cosmed, Rome, Italy) (initial 100W with 25W increase, 90-100 rpm). Multivariate discriminant analysis was used to determine which variables group cyclists within their specialty, and to predict which variables can direct cyclists to a particular specialty. Among nine variables that statistically contribute to the discriminant power of the model, achieved power on the anaerobic threshold and the produced CO2 had the biggest impact. The obtained discriminatory model correctly classified 91.43% of flat riders, 85.71% of hill riders, while sprinters were classified completely correct (100%), i.e. 92.10% of examinees were correctly classified, which point out the strength of the discriminatory model. Respiratory indicators mostly contribute to the discriminant power of the model, which may significantly contribute to training practice and laboratory tests in future.

Relationship between grip, pinch strengths and anthropometric variables, types of pitch throwing among Japanese high school baseball pitchers.

PubMed

Tajika, Tsuyoshi; Kobayashi, Tsutomu; Yamamoto, Atsushi; Shitara, Hitoshi; Ichinose, Tsuyoshi; Shimoyama, Daisuke; Okura, Chisa; Kanazawa, Saeko; Nagai, Ayako; Takagishi, Kenji

2015-03-01

Grip and pinch strength are crucially important attributes and standard parameters related to the functional integrity of the hand. It seems significant to investigate normative data for grip and pinch strength of baseball players to evaluate their performance and condition. Nevertheless, few reports have explained the association between grip and pinch strength and anthropometric variables and types of pitch throwing for baseball pitchers. The aim of this study was to measure and evaluate clinical normative data for grip and tip, key, palmar pinch strength and to assess the relationship between these data and anthropometric variables and types of pitch throwing among Japanese high-school baseball pitchers. One hundred-thirty three healthy high school baseball pitchers were examined and had completed a self-administered questionnaire including items related to age, hand dominance, throwing ratio of type of pitch. A digital dynamometer was used to measure grip strength and a pinch gauge to measure tip, key and palmer pinch in both dominant and nondominant side. Body composition was measured by the multi frequency segmental body composition analyzer. Grip strength and tip and palmer pinch strength in dominant side were statistically greater than them in nondominant side (P < 0.05). There were significant associations between grip strength and height (r = 0.33, P < 0.001), body mass (r = 0.50, P < 0.001), BMI (r = 0.37, P < 0.001), muscle mass of upper extremity (r = 0.56, P < 0.001), fat free mass (r = 0.57, P < 0.001), fat mass (r = 0.22, P < 0.05) in dominant side. A stepwise multiple regression analysis revealed that fat free mass and tip, palmer, key pinch strength were predictors of grip strength in dominant side. No statistical significant correlations were found between the throwing ratio of types of pitches thrown and grip strength and tip, key, palmar pinch strength. Our result provides normative values and evidences for grip and pinch strengths in high school baseball pitchers.

The cross education of strength and skill following unilateral strength training in the upper and lower limbs.

PubMed

Green, Lara A; Gabriel, David A

2018-04-18

Cross education is the strength gain or skill improvement transferred to the contralateral limb following unilateral training or practice. The present study examined the transfer of both strength and skill following a strength training program. Forty participants (20M, 20F) completed a 6-week unilateral training program of dominant wrist flexion or dorsiflexion. Strength, force variability, and muscle activity were assessed pre-training, post-training, and following 6-weeks of detraining (retention). Analyses of covariance compared the experimental limb (trained or untrained) to the control (dominant or non-dominant). There were no sex differences in the training response. Cross education of strength at post-training was 6% (p<0.01) in the untrained arm and 13% (p<0.01) in the untrained leg. Contralateral strength continued to increase following detraining to 15% in the arm (p<0.01) and 14% in the leg (p<0.01). There was no difference in strength gains between upper and lower limbs (p>0.05). Cross education of skill (force variability) demonstrated greater improvements in the untrained limbs compared to the control limbs during contractions performed without concurrent feedback. Significant increases in V-wave amplitude (p=0.02) and central activation (p<0.01) were highly correlated with contralateral strength gains. There was no change in agonist amplitude or motor unit firing rates in the untrained limbs (p>0.05). The neuromuscular mechanisms mirrored the force increases at post-training and retention supporting central drive adaptations of cross education. The continued strength increases at retention identified the presence of motor learning in cross education, as confirmed by force variability.

The Relationship Between Higher Order Need Strength and Sensitivity to Environmental Variations.

ERIC Educational Resources Information Center

Beehr, Terry A.; And Others

Higher order need strength (HONS) has been shown to moderate the relationship between work role characteristics and some traditional dependent variables in organizations. It was hypothesized that employees with strong HONS might be more sensitive to variability in their work environments than people with weaker HONS. This would happen because…

Evolutionary variation in the mechanics of fiddler crab claws

PubMed Central

2013-01-01

Background Fiddler crabs, genus Uca, are classic examples of how intense sexual selection can produce exaggerated male traits. Throughout the genus the enlarged “major” cheliped (claw) of the male fiddler crab is used both as a signal for attracting females and as a weapon for combat with other males. However, the morphology of the major claw is highly variable across the approximately 100 species within the genus. Here we address variation, scaling, and correlated evolution in the mechanics of the major claw by analyzing the morphology and mechanical properties of the claws of 21 species of fiddler crabs from the Pacific, Gulf and Atlantic coasts of the Americas. Results We find that the mechanics that produce claw closing forces, the sizes of claws and the mechanical strength of the cuticle of claws are all highly variable across the genus. Most variables scale isometrically with body size across species but claw force production scales allometrically with body size. Using phylogenetically independent contrasts, we find that the force that a claw can potentially produce is positively correlated with the strength of the cuticle on the claw where forces are delivered in a fight. There is also a negative correlation between the force that a claw can potentially produce and the size of the claw corrected for the mass of the claw. Conclusions These relationships suggest that there has been correlated evolution between force production and armoring, and that there is a tradeoff between claw mechanics for signaling and claw mechanics for fighting. PMID:23855770

Linking seasonal home range size with habitat selection and movement in a mountain ungulate.

PubMed

Viana, Duarte S; Granados, José Enrique; Fandos, Paulino; Pérez, Jesús M; Cano-Manuel, Francisco Javier; Burón, Daniel; Fandos, Guillermo; Aguado, María Ángeles Párraga; Figuerola, Jordi; Soriguer, Ramón C

2018-01-01

Space use by animals is determined by the interplay between movement and the environment, and is thus mediated by habitat selection, biotic interactions and intrinsic factors of moving individuals. These processes ultimately determine home range size, but their relative contributions and dynamic nature remain less explored. We investigated the role of habitat selection, movement unrelated to habitat selection and intrinsic factors related to sex in driving space use and home range size in Iberian ibex, Capra pyrenaica . We used GPS collars to track ibex across the year in two different geographical areas of Sierra Nevada, Spain, and measured habitat variables related to forage and roost availability. By using integrated step selection analysis (iSSA), we show that habitat selection was important to explain space use by ibex. As a consequence, movement was constrained by habitat selection, as observed displacement rate was shorter than expected under null selection. Selection-independent movement, selection strength and resource availability were important drivers of seasonal home range size. Both displacement rate and directional persistence had a positive relationship with home range size while accounting for habitat selection, suggesting that individual characteristics and state may also affect home range size. Ibex living at higher altitudes, where resource availability shows stronger altitudinal gradients across the year, had larger home ranges. Home range size was larger in spring and autumn, when ibex ascend and descend back, and smaller in summer and winter, when resources are more stable. Therefore, home range size decreased with resource availability. Finally, males had larger home ranges than females, which might be explained by differences in body size and reproductive behaviour. Movement, selection strength, resource availability and intrinsic factors related to sex determined home range size of Iberian ibex. Our results highlight the need to integrate and account for process dependencies, here the interdependence of movement and habitat selection, to understand how animals use space. This study contributes to understand how movement links environmental and geographical space use and determines home range behaviour in large herbivores.

Introgression of a Block of Genome Under Infinitesimal Selection.

PubMed

Sachdeva, Himani; Barton, Nicholas H

2018-06-12

Adaptive introgression is common in nature and can be driven by selection acting on multiple, linked genes. We explore the effects of polygenic selection on introgression under the infinitesimal model with linkage. This model assumes that the introgressing block has an effectively infinite number of loci, each with an infinitesimal effect on the trait under selection. The block is assumed to introgress under directional selection within a native population that is genetically homogeneous. We use individual-based simulations and a branching process approximation to compute various statistics of the introgressing block, and explore how these depend on parameters such as the map length and initial trait value associated with the introgressing block, the genetic variability along the block, and the strength of selection. Our results show that the introgression dynamics of a block under infinitesimal selection are qualitatively different from the dynamics of neutral introgression. We also find that in the long run, surviving descendant blocks are likely to have intermediate lengths, and clarify how their length is shaped by the interplay between linkage and infinitesimal selection. Our results suggest that it may be difficult to distinguish the long-term introgression of a block of genome with a single strongly selected locus from the introgression of a block with multiple, tightly linked and weakly selected loci. Copyright © 2018, Genetics.

Biomechanical, anthropometric, and psychological determinants of barbell back squat strength.

PubMed

Vigotsky, Andrew D; Bryanton, Megan A; Nuckols, Greg; Beardsley, Chris; Contreras, Bret; Evans, Jessica; Schoenfeld, Brad J

2018-02-27

Previous investigations of strength have only focused on biomechanical or psychological determinants, while ignoring the potential interplay and relative contributions of these variables. The purpose of this study was to investigate the relative contributions of biomechanical, anthropometric, and psychological variables to the prediction of maximum parallel barbell back squat strength. Twenty-one college-aged participants (male = 14; female = 7; age = 23 ± 3 years) reported to the laboratory for two visits. The first visit consisted of anthropometric, psychometric, and parallel barbell back squat one-repetition maximum (1RM) testing. On the second visit, participants performed isometric dynamometry testing for the knee, hip, and spinal extensors in a sticking point position-specific manner. Multiple linear regression and correlations were used to investigate the combined and individual relationships between biomechanical, anthropometric, and psychological variables and squat 1RM. Multiple regression revealed only one statistically predictive determinant: fat free mass normalized to height (standardized estimate ± SE = 0.6 ± 0.3; t(16) = 2.28; p = 0.037). Correlation coefficients for individual variables and squat 1RM ranged from r = -0.79-0.83, with biomechanical, anthropometric, experiential, and sex predictors showing the strongest relationships, and psychological variables displaying the weakest relationships. These data suggest that back squat strength in a heterogeneous population is multifactorial and more related to physical rather than psychological variables.

The variability of the Atlantic meridional circulation since 1980, as hindcast by a data-driven nonlinear systems model

NASA Astrophysics Data System (ADS)

Ayala-Solares, J. R.; Wei, Hua-Liang; Bigg, G. R.

2018-06-01

The Atlantic meridional overturning circulation (AMOC), an important component of the climate system, has only been directly measured since the RAPID array's installation across the Atlantic at 26°N in 2004. This has shown that the AMOC strength is highly variable on monthly timescales; however, after an abrupt, short-lived, halving of the strength of the AMOC early in 2010, its mean has remained 15% below its pre-2010 level. To attempt to understand the reasons for this variability, we use a control systems identification approach to model the AMOC, with the RAPID data of 2004-2017 providing a trial and test data set. After testing to find the environmental variables, and systems model, that allow us to best match the RAPID observations, we reconstruct AMOC variation back to 1980. Our reconstruction suggests that there is inter-decadal variability in the strength of the AMOC, with periods of both weaker flow than recently, and flow strengths similar to the late 2000s, since 1980. Recent signs of weakening may therefore not reflect the beginning of a sustained decline. It is also shown that there may be predictive power for AMOC variability of around 6 months, as ocean density contrasts between the source and sink regions for the North Atlantic Drift, with lags up to 6 months, are found to be important components of the systems model.

The effect of trait type and strength of selection on heritability and evolvability in an island bird population.

PubMed

Wheelwright, Nathaniel T; Keller, Lukas F; Postma, Erik

2014-11-01

The heritability (h(2) ) of fitness traits is often low. Although this has been attributed to directional selection having eroded genetic variation in direct proportion to the strength of selection, heritability does not necessarily reflect a trait's additive genetic variance and evolutionary potential ("evolvability"). Recent studies suggest that the low h(2) of fitness traits in wild populations is caused not by a paucity of additive genetic variance (VA ) but by greater environmental or nonadditive genetic variance (VR ). We examined the relationship between h(2) and variance-standardized selection intensities (i or βσ ), and between evolvability (IA :VA divided by squared phenotypic trait mean) and mean-standardized selection gradients (βμ ). Using 24 years of data from an island population of Savannah sparrows, we show that, across diverse traits, h(2) declines with the strength of selection, whereas IA and IR (VR divided by squared trait mean) are independent of the strength of selection. Within trait types (morphological, reproductive, life-history), h(2) , IA , and IR are all independent of the strength of selection. This indicates that certain traits have low heritability because of increased residual variance due to the age at which they are expressed or the multiple factors influencing their expression, rather than their association with fitness. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Hybrid robust model based on an improved functional link neural network integrating with partial least square (IFLNN-PLS) and its application to predicting key process variables.

PubMed

He, Yan-Lin; Xu, Yuan; Geng, Zhi-Qiang; Zhu, Qun-Xiong

2016-03-01

In this paper, a hybrid robust model based on an improved functional link neural network integrating with partial least square (IFLNN-PLS) is proposed. Firstly, an improved functional link neural network with small norm of expanded weights and high input-output correlation (SNEWHIOC-FLNN) was proposed for enhancing the generalization performance of FLNN. Unlike the traditional FLNN, the expanded variables of the original inputs are not directly used as the inputs in the proposed SNEWHIOC-FLNN model. The original inputs are attached to some small norm of expanded weights. As a result, the correlation coefficient between some of the expanded variables and the outputs is enhanced. The larger the correlation coefficient is, the more relevant the expanded variables tend to be. In the end, the expanded variables with larger correlation coefficient are selected as the inputs to improve the performance of the traditional FLNN. In order to test the proposed SNEWHIOC-FLNN model, three UCI (University of California, Irvine) regression datasets named Housing, Concrete Compressive Strength (CCS), and Yacht Hydro Dynamics (YHD) are selected. Then a hybrid model based on the improved FLNN integrating with partial least square (IFLNN-PLS) was built. In IFLNN-PLS model, the connection weights are calculated using the partial least square method but not the error back propagation algorithm. Lastly, IFLNN-PLS was developed as an intelligent measurement model for accurately predicting the key variables in the Purified Terephthalic Acid (PTA) process and the High Density Polyethylene (HDPE) process. Simulation results illustrated that the IFLNN-PLS could significant improve the prediction performance. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Evidences on weaknesses and strengths from health financing after decentralization: lessons from Latin American countries.

PubMed

Arredondo, Armando; Orozco, Emanuel; De Icaza, Esteban

2005-01-01

The main objective was to identify trends and evidence on health financing after health care decentralization. Evaluative research with a before-after design integrating qualitative and quantitative analysis. Taking into account feasibility, political and technical criteria, three Latin American countries were selected as study populations: Mexico, Nicaragua and Peru. The methodology had two main phases. In the first phase, the study referred to secondary sources of data and documents to obtain information about the following variables: type of decentralization implemented, source of finance, funds of financing, providers, final use of resources and mechanisms for resource allocation. In the second phase, the study referred to primary data collected in a survey of key personnel from the health sectors of each country. The trends and evidence reported in all five financing indicators may identify major weaknesses and strengths in health financing. Weaknesses: a lack of human resources trained in health economics who can implement changes, a lack of financial resource independence between the local and central levels, the negative behavior of the main macro-economic variables, and the difficulty in developing new financing alternatives. Strengths: the sharing between the central level and local levels of responsibility for financing health services, the implementation of new organizational structures for the follow-up of financial changes at the local level, the development and implementation of new financial allocation mechanisms taking as a basis the efficiency and equity principles, new technique of a per-capita adjustment factor corrected at the local health needs, and the increase of financing contributions from households and local levels of government.

Nutritional status is the major factor affecting grip strength of African HIV patients before and during antiretroviral treatment.

PubMed

Filteau, S; PrayGod, G; Woodd, S L; Friis, H; Heimburger, D C; Koethe, J R; Kelly, P; Kasonka, L; Rehman, A M

2017-10-01

Low grip strength is a marker of frailty and a risk factor for mortality among HIV patients and other populations. We investigated factors associated with grip strength in malnourished HIV patients at referral to ART, and at 12 weeks and 2-3 years after starting ART. The study involved HIV-infected Zambian and Tanzanian participants recruited to the NUSTART trial when malnourished (body mass index <18.5 kg/m 2 ) and requiring ART. The relationship of grip strength to nutritional, infectious and demographic factors was assessed by multivariable linear regression at referral for ART (n = 1742) and after 12 weeks (n = 778) and 2-3 years of ART (n = 273). In analyses controlled only for sex, age and height, most nutrition and infection-related variables were associated with grip strength. However, in multivariable analyses, consistent associations were seen for fat-free mass index, mid-upper arm circumference, haemoglobin and systolic blood pressure, and a variable association with fat mass index in men. C-reactive protein and CD4 count had limited independent effects on grip strength, while receiving tuberculosis treatment was associated with weaker grip strength. In this population of originally malnourished HIV patients, poor grip strength was more strongly and independently associated with nutritional than with infection and inflammation variables. Programmes to improve health and survival of HIV patients should incorporate nutritional assessment and management and could use grip strength as a functional indicator of improving nutrition. © 2017 John Wiley & Sons Ltd.

Strength Training Following Hematopoietic Stem Cell Transplantation

PubMed Central

Hacker, Eileen Danaher; Larson, Janet; Kujath, Amber; Peace, David; Rondelli, Damiano; Gaston, Lisa

2010-01-01

Background Patients receiving high-dose chemotherapy and hematopoietic stem cell transplantation (HSCT) experience considerable reductions in physical activity and deterioration of their health status. Objective The purpose of this pilot study was to test the effects of strength training compared to usual activity on physical activity, muscle strength, fatigue, health status perceptions, and quality of life following HSCT. Interventions/Methods Nineteen subjects were randomized to the exercise or control group. Moderate intensity strength training began following discharge from the hospital. Dependent variables included physical activity, muscle strength, fatigue, health status perceptions and quality of life. Variables were measured prior to admission to the hospital for HSCT, day 8 following HSCT, and six weeks following discharge from the hospital. Results Significant time effects were noted for many variables with anticipated declines in physical activity, muscle strength, fatigue, and health status perceptions immediately after HSCT with subsequent improvements six weeks following hospital discharge. One group effect was noted with subjects in the exercise group reporting less fatigue than subjects in the control group. Although no significant interactions were detected, the trends suggest that the exercise group may be more physically active following the intervention compared to the usual activity group. Conclusions This study demonstrates the potential positive effects of strength training on physical activity, fatigue, and quality of life in people receiving high-dose chemotherapy and HSCT. Implications for Practice Preliminary evidence is provided for using strength training to enhance early recovery following HSCT. Elastic resistance bands are easy to use and relatively inexpensive. PMID:21116175

Varying strength of cognitive markers and biomarkers to predict conversion and cognitive decline in an early-stage-enriched mild cognitive impairment sample.

PubMed

Egli, Simone C; Hirni, Daniela I; Taylor, Kirsten I; Berres, Manfred; Regeniter, Axel; Gass, Achim; Monsch, Andreas U; Sollberger, Marc

2015-01-01

Several cognitive, neuroimaging, and cerebrospinal fluid (CSF) markers predict conversion from mild cognitive impairment (MCI) to Alzheimer's disease (AD) dementia. However, predictors might be more or less powerful depending on the characteristics of the MCI sample. To investigate which cognitive markers and biomarkers predict conversion to AD dementia and course of cognitive functioning in a MCI sample with a high proportion of early-stage MCI patients. Variables known to predict progression in MCI patients and hypothesized to predict progression in early-stage MCI patients were selected. Cognitive (long-delay free recall, regional primacy score), imaging (hippocampal and entorhinal cortex volumes, fornix fractional anisotropy), and CSF (Aβ1-42/t-tau, Aβ1-42) variables from 36 MCI patients were analyzed with Cox regression and mixed-effect models to determine their individual and combined abilities to predict time to conversion to AD dementia and course of global cognitive functioning, respectively. Those variables hypothesized to predict the course of early-stage MCI patients were most predictive for MCI progression. Specifically, regional primacy score (a measure of word-list position learning) most consistently predicted conversion to AD dementia and course of cognitive functioning. Both the prediction of conversion and course of cognitive functioning were maximized by including CSF Aβ1-42 and fornix integrity biomarkers, respectively, indicating the complementary information carried by cognitive variables and biomarkers. Predictors of MCI progression need to be interpreted in light of the characteristics of the respective MCI sample. Future studies should aim to compare predictive strengths of markers between early-stage and late-stage MCI patients.

Influence of quality control variables on failure of graphite/epoxy under extreme moisture conditions

NASA Technical Reports Server (NTRS)

Clements, L. L.; Lee, P. R.

1980-01-01

Tension tests on graphite/epoxy composites were performed to determine the influence of various quality control variables on failure strength as a function of moisture and moderate temperatures. The extremely high and low moisture contents investigated were found to have less effect upon properties than did temperature or the quality control variables of specimen flaws and prepreg batch to batch variations. In particular, specimen flaws were found to drastically reduce the predicted strength of the composite, whereas specimens from different batches of prepreg displayed differences in strength as a function of temperature and extreme moisture exposure. The findings illustrate the need for careful specimen preparation, studies of flaw sensitivity, and careful quality control in any study of composite materials.

Relationships between field-based measures of strength and power and golf club head speed.

PubMed

Read, Paul J; Lloyd, Rhodri S; De Ste Croix, Mark; Oliver, Jon L

2013-10-01

Increased golf club head speed (CHS) has been shown to result in greater driving distances and is also correlated with golf handicap. The purpose of this study was to investigate the relationships between field-based measures of strength and power and golf CHS with a secondary aim to determine the reliability of the selected tests. A correlation design was used to assess the following variables: anthropometrics, squat jump (SJ) height and squat jump peak power (SJPP), unilateral countermovement jump (CMJ) heights (right leg countermovement jump and left leg countermovement jump [LLCMJ]), bilateral CMJ heights, countermovement jump peak power (CMJPP), and medicine ball seated throw (MBST) and medicine ball rotational throw (MBRT). Fouty-eight male subjects participated in the study (age: 20.1 ± 3.2 years, height: 1.76 ± 0.07 m, mass: 72.8 ± 7.8 kg, handicap: 5.8 ± 2.2). Moderate significant correlations were reported between CHS and MBRT (r = 0.67; p < 0.01), MBST (r = 0.63; p < 0.01), CMJPP (r = 0.54; p < 0.01), and SJPP (r = 0.53; p < 0.01). Weak significant correlations (r = 0.3-0.5) were identified between CHS and the other remaining variables excluding LLCMJ. Stepwise multiple regression analysis identified that the MBST and SJ were the greatest predictors of CHS, explaining 49% of the variance. Additionally the intraclass correlation coefficients reported for tests of CHS and all performance variables were deemed acceptable (r = 0.7-0.9). The results of this study suggest that the strength and conditioning coach can accurately assess and monitor the physical abilities of golf athletes using the proposed battery of field tests. Additionally, movements that are more concentrically dominant in nature may display stronger relationships with CHS due to MBST and SJ displaying the highest explained variance after a stepwise linear regression.

Reliability analysis of structures under periodic proof tests in service

NASA Technical Reports Server (NTRS)

Yang, J.-N.

1976-01-01

A reliability analysis of structures subjected to random service loads and periodic proof tests treats gust loads and maneuver loads as random processes. Crack initiation, crack propagation, and strength degradation are treated as the fatigue process. The time to fatigue crack initiation and ultimate strength are random variables. Residual strength decreases during crack propagation, so that failure rate increases with time. When a structure fails under periodic proof testing, a new structure is built and proof-tested. The probability of structural failure in service is derived from treatment of all the random variables, strength degradations, service loads, proof tests, and the renewal of failed structures. Some numerical examples are worked out.

Validity Evidence for the Measurement of the Strength of Motivation for Medical School

ERIC Educational Resources Information Center

Kusurkar, Rashmi; Croiset, Gerda; Kruitwagen, Cas; ten Cate, Olle

2011-01-01

The Strength of Motivation for Medical School (SMMS) questionnaire is designed to determine the strength of motivation of students particularly for medical study. This research was performed to establish the validity evidence for measuring strength of motivation for medical school. Internal structure and relations to other variables were used as…

[Silvicultural treatments and their selection effects].

PubMed

Vincent, G

1973-01-01

Selection can be defined in terms of its observable consequences as the non random differential reproduction of genotypes (Lerner 1958). In the forest stands we are selecting during the improvements-fellings and reproduction treatments the individuals surpassing in growth or in production of first-class timber. However the silvicultural treatments taken in forest stands guarantee a permanent increase of forest production only in such cases, if they have been taken with respect to the principles of directional (dynamic) selection. These principles require that the trees determined for further growing and for forest regeneration are selected by their hereditary properties, i.e. by their genotypes.For making this selection feasible, our study deals with the genetic parameters and gives some examples of the application of the response, the selection differential, the heritability in the narrow and in the broad sense, as well as of the genetic and genotypic gain. On the strength of this parameter we have the possibility to estimate the economic success of several silvicultural treatments in forest stands.The mentioned examples demonstrate that the selection measures of a higher intensity will be manifested in a higher selection differential, in a higher genetic and genotypic gain and that the mentioned measures show more distinct effects in the variable populations - in natural forest - than in the population characteristic by a smaller variability, e.g. in many uniform artificially established stands.The examples of influences of different selection on the genotypes composition of population prove that genetics instructs us to differentiate the different genotypes of the same species and gives us at the same time a new criterions for evaluating selectional treatments. These criterions from economic point of view is necessary to consider in silviculture as advantageous even for the reason that we can judge from these criterions the genetical composition of forest stands in the following generation, it means, within the scope of time for more than a human age.

Evidence Inhibition Responds Reactively to the Salience of Distracting Information during Focused Attention

PubMed Central

Wyatt, Natalie; Machado, Liana

2013-01-01

Along with target amplification, distractor inhibition is regarded as a major contributor to selective attention. Some theories suggest that the strength of inhibitory processing is proportional to the salience of the distractor (i.e., inhibition reacts to the distractor intensity). Other theories suggest that the strength of inhibitory processing does not depend on the salience of the distractor (i.e., inhibition does not react to the distractor intensity). The present study aimed to elucidate the relationship between the intensity of a distractor and its subsequent inhibition during focused attention. A flanker task with a variable distractor-target stimulus-onset asynchrony (SOA) was used to measure both distractor interference and distractor inhibition. We manipulated the intensity of the distractor in two separate ways, by varying its distance from the target (Experiment 1) and by varying its brightness (Experiment 2). The results indicate that more intense distractors were associated with both increased interference and stronger distractor inhibition. The latter outcome provides novel support for the reactive inhibition hypothesis, which posits that inhibition reacts to the strength of distractor input, such that more salient distractors elicit stronger inhibition. PMID:23646147

Divergent selection for fiber length and bundle strength and correlated responses in cotton

USDA-ARS?s Scientific Manuscript database

Cotton breeders must develop cultivars to meet the demand for longer, stronger, and more uniform fibers. In the current study, two cycles of divergent selection for fiber upper-half mean length (UHML) and bundle strength (Str) were conducted within five diverse parental combinations selected based o...

Natural selection on thermal performance in a novel thermal environment

PubMed Central

Logan, Michael L.; Cox, Robert M.; Calsbeek, Ryan

2014-01-01

Tropical ectotherms are thought to be especially vulnerable to climate change because they are adapted to relatively stable temperature regimes, such that even small increases in environmental temperature may lead to large decreases in physiological performance. One way in which tropical organisms may mitigate the detrimental effects of warming is through evolutionary change in thermal physiology. The speed and magnitude of this response depend, in part, on the strength of climate-driven selection. However, many ectotherms use behavioral adjustments to maintain preferred body temperatures in the face of environmental variation. These behaviors may shelter individuals from natural selection, preventing evolutionary adaptation to changing conditions. Here, we mimic the effects of climate change by experimentally transplanting a population of Anolis sagrei lizards to a novel thermal environment. Transplanted lizards experienced warmer and more thermally variable conditions, which resulted in strong directional selection on thermal performance traits. These same traits were not under selection in a reference population studied in a less thermally stressful environment. Our results indicate that climate change can exert strong natural selection on tropical ectotherms, despite their ability to thermoregulate behaviorally. To the extent that thermal performance traits are heritable, populations may be capable of rapid adaptation to anthropogenic warming. PMID:25225361

Natural selection on thermal performance in a novel thermal environment.

PubMed

Logan, Michael L; Cox, Robert M; Calsbeek, Ryan

2014-09-30

Tropical ectotherms are thought to be especially vulnerable to climate change because they are adapted to relatively stable temperature regimes, such that even small increases in environmental temperature may lead to large decreases in physiological performance. One way in which tropical organisms may mitigate the detrimental effects of warming is through evolutionary change in thermal physiology. The speed and magnitude of this response depend, in part, on the strength of climate-driven selection. However, many ectotherms use behavioral adjustments to maintain preferred body temperatures in the face of environmental variation. These behaviors may shelter individuals from natural selection, preventing evolutionary adaptation to changing conditions. Here, we mimic the effects of climate change by experimentally transplanting a population of Anolis sagrei lizards to a novel thermal environment. Transplanted lizards experienced warmer and more thermally variable conditions, which resulted in strong directional selection on thermal performance traits. These same traits were not under selection in a reference population studied in a less thermally stressful environment. Our results indicate that climate change can exert strong natural selection on tropical ectotherms, despite their ability to thermoregulate behaviorally. To the extent that thermal performance traits are heritable, populations may be capable of rapid adaptation to anthropogenic warming.

Optimal design of a thermally stable composite optical bench

NASA Technical Reports Server (NTRS)

Gray, C. E., Jr.

1985-01-01

The Lidar Atmospheric Sensing Experiment will be performed aboard an ER-2 aircraft; the lidar system used will be mounted on a lightweight, thermally stable graphite/epoxy optical bench whose design is presently subjected to analytical study and experimental validation. Attention is given to analytical methods for the selection of such expected laminate properties as the thermal expansion coefficient, the apparent in-plane moduli, and ultimate strength. For a symmetric laminate in which one of the lamina angles remains variable, an optimal lamina angle is selected to produce a design laminate with a near-zero coefficient of thermal expansion. Finite elements are used to model the structural concept of the design, with a view to the optical bench's thermal structural response as well as the determination of the degree of success in meeting the experiment's alignment tolerances.

The Role of Character Strengths in Adolescent Romantic Relationships: An Initial Study on Partner Selection and Mates' Life Satisfaction

ERIC Educational Resources Information Center

Weber, Marco; Ruch, Willibald

2012-01-01

The present study investigated the role of 24 character strengths in 87 adolescent romantic relationships focusing on their role in partner selection and their role in mates' life satisfaction. Measures included the Values in Action Inventory of Strengths for Youth, the Students' Life Satisfaction Scale, and an Ideal Partner Profiler for the…

Directional selection in temporally replicated studies is remarkably consistent.

PubMed

Morrissey, Michael B; Hadfield, Jarrod D

2012-02-01

Temporal variation in selection is a fundamental determinant of evolutionary outcomes. A recent paper presented a synthetic analysis of temporal variation in selection in natural populations. The authors concluded that there is substantial variation in the strength and direction of selection over time, but acknowledged that sampling error would result in estimates of selection that were more variable than the true values. We reanalyze their dataset using techniques that account for the necessary effect of sampling error to inflate apparent levels of variation and show that directional selection is remarkably constant over time, both in magnitude and direction. Thus we cannot claim that the available data support the existence of substantial temporal heterogeneity in selection. Nonetheless, we conject that temporal variation in selection could be important, but that there are good reasons why it may not appear in the available data. These new analyses highlight the importance of applying techniques that estimate parameters of the distribution of selection, rather than parameters of the distribution of estimated selection (which will reflect both sampling error and "real" variation in selection); indeed, despite availability of methods for the former, focus on the latter has been common in synthetic reviews of the aspects of selection in nature, and can lead to serious misinterpretations. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

Strength validation and fire endurance of glued-laminated timber beams

Treesearch

E. L. Schaffer; C. M. Marx; D. A. Bender; F. E. Woeste

A previous paper presented a reliability-based model to predict the strength of glued-laminated timber beams at both room temperature and during fire exposure. This Monte Carlo simulation procedure generates strength and fire endurance (time-to-failure, TTF) data for glued- laminated beams that allow assessment of mean strength and TTF as well as their variability....

Effects of acute upper-body vibration on strength and power variables in climbers.

PubMed

Cochrane, Darryl J; Hawke, Emma J

2007-05-01

Whole-body vibration training has recently received a lot of attention with reported enhancements of strength and power qualities in athletes. This study investigated whether upper-body vibration would be able to augment muscular attributes for climbing performance. Twelve healthy active climbers volunteered for the study. All participants underwent 3 treatments--arm cranking (AC), upper-body vibration (UBV), and non-UBV (NUBV)--in a balanced random order, conducted on separate days. Upper-body vibration was generated via a commercialized electric-powered dumbbell with a rotating axis that delivered oscillatory movements to the shoulders and arms. The UBV treatment consisted of performing 5 upper-body exercises for a total duration of 5 minutes. The UBV frequency was set at 26 Hz, amplitude 3 mm. For the NUBV treatment, the participants performed the exact exercises and time constraints as UBV; however, the vibration dumbbell was set at 0 Hz and 0 mm amplitude. The third treatment consisted of AC, which was performed at 75 k.min(-1) for 5 minutes. Pre- and postmuscular performance measures of medicine ball throw, hand grip strength, and a specific climbing maneuver were performed after each treatment. There were no significant treatment differences on medicine ball throw, hand grip strength, and the specific climbing maneuver. Acute UBV exposure did not demonstrate the expected potential neuromuscular enhancements on the climbing performance tests selected for this study.

Strength and fatigability of selected muscles in upper limb: assessing muscle imbalance relevant to tennis elbow.

PubMed

Alizadehkhaiyat, O; Fisher, A C; Kemp, G J; Frostick, S P

2007-08-01

The aetiology of tennis elbow has remained uncertain for more than a century. To examine muscle imbalance as a possible pathophysiological factor requires a reliable method of assessment. This paper describes the development of such a method and its performance in healthy subjects. We propose a combination of surface and fine-wire EMG of shoulder and forearm muscles and wrist strength measurements as a reliable tool for assessing muscle imbalance relevant to the pathophysiology of tennis elbow. Six healthy volunteers participated. EMG data were acquired at 50% maximal voluntary isometric contraction from five forearm muscles during grip and three shoulder muscles during external rotation and abduction, and analysed using normalized median frequency slope as a fatigue index. Wrist extension/flexion strength was measured using a purpose-built dynamometer. Significant negative slope of median frequency was found for all muscles, with good reproducibility, and no significant difference in slope between the different muscles of the shoulder and the wrist. (Amplitude slope showed high variability and was therefore unsuitable for this purpose.) Wrist flexion was 27+/-8% stronger than extension (mean+/-SEM, p=0.006). This is a reliable method for measuring muscle fatigue in forearm and shoulder. EMG and wrist strength studies together can be used for assessing and identifying the muscle balance in the wrist-forearm-shoulder chain.

Multi-site study of diffusion metric variability: effects of site, vendor, field strength, and echo time on regions-of-interest and histogram-bin analyses.

PubMed

Helmer, K G; Chou, M-C; Preciado, R I; Gimi, B; Rollins, N K; Song, A; Turner, J; Mori, S

2016-02-27

It is now common for magnetic-resonance-imaging (MRI) based multi-site trials to include diffusion-weighted imaging (DWI) as part of the protocol. It is also common for these sites to possess MR scanners of different manufacturers, different software and hardware, and different software licenses. These differences mean that scanners may not be able to acquire data with the same number of gradient amplitude values and number of available gradient directions. Variability can also occur in achievable b-values and minimum echo times. The challenge of a multi-site study then, is to create a common protocol by understanding and then minimizing the effects of scanner variability and identifying reliable and accurate diffusion metrics. This study describes the effect of site, scanner vendor, field strength, and TE on two diffusion metrics: the first moment of the diffusion tensor field (mean diffusivity, MD), and the fractional anisotropy (FA) using two common analyses (region-of-interest and mean-bin value of whole brain histograms). The goal of the study was to identify sources of variability in diffusion-sensitized imaging and their influence on commonly reported metrics. The results demonstrate that the site, vendor, field strength, and echo time all contribute to variability in FA and MD, though to different extent. We conclude that characterization of the variability of DTI metrics due to site, vendor, field strength, and echo time is a worthwhile step in the construction of multi-center trials.

Functional High-Intensity Circuit Training Improves Body Composition, Peak Oxygen Uptake, Strength, and Alters Certain Dimensions of Quality of Life in Overweight Women.

PubMed

Sperlich, Billy; Wallmann-Sperlich, Birgit; Zinner, Christoph; Von Stauffenberg, Valerie; Losert, Helena; Holmberg, Hans-Christer

2017-01-01

The effects of circuit-like functional high-intensity training (Circuit HIIT ) alone or in combination with high-volume low-intensity exercise (Circuit combined ) on selected cardio-respiratory and metabolic parameters, body composition, functional strength and the quality of life of overweight women were compared. In this single-center, two-armed randomized, controlled study, overweight women performed 9-weeks (3 sessions·wk -1 ) of either Circuit HIIT ( n = 11), or Circuit combined ( n = 8). Peak oxygen uptake and perception of physical pain were increased to a greater extent ( p < 0.05) by Circuit HIIT , whereas Circuit combined improved perception of general health more ( p < 0.05). Both interventions lowered body mass, body-mass-index, waist-to-hip ratio, fat mass, and enhanced fat-free mass; decreased ratings of perceived exertion during submaximal treadmill running; improved the numbers of push-ups, burpees, one-legged squats, and 30-s skipping performed, as well as the height of counter-movement jumps; and improved physical and social functioning, role of physical limitations, vitality, role of emotional limitations, and mental health to a similar extent (all p < 0.05). Either forms of these multi-stimulating, circuit-like, multiple-joint training can be employed to improve body composition, selected variables of functional strength, and certain dimensions of quality of life in overweight women. However, Circuit HIIT improves peak oxygen uptake to a greater extent, but with more perception of pain, whereas Circuit combined results in better perception of general health.

What are the most effective risk-reduction strategies in sport concussion?

PubMed

Benson, Brian W; McIntosh, Andrew S; Maddocks, David; Herring, Stanley A; Raftery, Martin; Dvorák, Jirí

2013-04-01

To critically review the evidence to determine the efficacy and effectiveness of protective equipment, rule changes, neck strength and legislation in reducing sport concussion risk. Electronic databases, grey literature and bibliographies were used to search the evidence using Medical Subject Headings and text words. Inclusion/exclusion criteria were used to select articles for the clinical equipment studies. The quality of evidence was assessed using epidemiological criteria regarding internal/external validity (eg, strength of design, sample size/power, bias and confounding). No new valid, conclusive evidence was provided to suggest the use of headgear in rugby, or mouth guards in American football, significantly reduced players' risk of concussion. No evidence was provided to suggest an association between neck strength increases and concussion risk reduction. There was evidence in ice hockey to suggest fair-play rules and eliminating body checking among 11-years-olds to 12-years-olds were effective injury prevention strategies. Evidence is lacking on the effects of legislation on concussion prevention. Equipment self-selection bias was a common limitation, as was the lack of measurement and control for potential confounding variables. Lastly, helmets need to be able to protect from impacts resulting in a head change in velocities of up to 10 and 7 m/s in professional American and Australian football, respectively, as well as reduce head resultant linear and angular acceleration to below 50 g and 1500 rad/s(2), respectively, to optimise their effectiveness. A multifactorial approach is needed for concussion prevention. Future well-designed and sport-specific prospective analytical studies of sufficient power are warranted.

Functional High-Intensity Circuit Training Improves Body Composition, Peak Oxygen Uptake, Strength, and Alters Certain Dimensions of Quality of Life in Overweight Women

PubMed Central

Sperlich, Billy; Wallmann-Sperlich, Birgit; Zinner, Christoph; Von Stauffenberg, Valerie; Losert, Helena; Holmberg, Hans-Christer

2017-01-01

The effects of circuit-like functional high-intensity training (CircuitHIIT) alone or in combination with high-volume low-intensity exercise (Circuitcombined) on selected cardio-respiratory and metabolic parameters, body composition, functional strength and the quality of life of overweight women were compared. In this single-center, two-armed randomized, controlled study, overweight women performed 9-weeks (3 sessions·wk−1) of either CircuitHIIT (n = 11), or Circuitcombined (n = 8). Peak oxygen uptake and perception of physical pain were increased to a greater extent (p < 0.05) by CircuitHIIT, whereas Circuitcombined improved perception of general health more (p < 0.05). Both interventions lowered body mass, body-mass-index, waist-to-hip ratio, fat mass, and enhanced fat-free mass; decreased ratings of perceived exertion during submaximal treadmill running; improved the numbers of push-ups, burpees, one-legged squats, and 30-s skipping performed, as well as the height of counter-movement jumps; and improved physical and social functioning, role of physical limitations, vitality, role of emotional limitations, and mental health to a similar extent (all p < 0.05). Either forms of these multi-stimulating, circuit-like, multiple-joint training can be employed to improve body composition, selected variables of functional strength, and certain dimensions of quality of life in overweight women. However, CircuitHIIT improves peak oxygen uptake to a greater extent, but with more perception of pain, whereas Circuitcombined results in better perception of general health. PMID:28420999

Experimental reduction in interaction intensity strongly affects biotic selection.

PubMed

Sletvold, Nina; Ågren, Jon

2016-11-01

The link between biotic interaction intensity and strength of selection is of fundamental interest for understanding biotically driven diversification and predicting the consequences of environmental change. The strength of selection resulting from biotic interactions is determined by the strength of the interaction and by the covariance between fitness and the trait under selection. When the relationship between trait and absolute fitness is constant, selection strength should be a direct function of mean population interaction intensity. To test this prediction, we excluded pollinators for intervals of different length to induce five levels of pollination intensity within a single plant population. Pollen limitation (PL) increased from 0 to 0.77 across treatments, accompanied by a fivefold increase in the opportunity for selection. Trait-fitness covariance declined with PL for number of flowers, but varied little for other traits. Pollinator-mediated selection on plant height, corolla size, and spur length increased by 91%, 34%, and 330%, respectively, in the most severely pollen-limited treatment compared to open-pollinated plants. The results indicate that realized biotic selection can be predicted from mean population interaction intensity when variation in trait-fitness covariance is limited, and that declines in pollination intensity will strongly increase selection on traits involved in the interaction. © 2016 by the Ecological Society of America.

Greater sage-grouse (Centrocercus urophasianus) nesting and brood-rearing microhabitat in Nevada and California—Spatial variation in selection and survival patterns

USGS Publications Warehouse

Coates, Peter S.; Brussee, Brianne E.; Ricca, Mark A.; Dudko, Jonathan E.; Prochazka, Brian G.; Espinosa, Shawn P.; Casazza, Michael L.; Delehanty, David J.

2017-08-10

Greater sage-grouse (Centrocercus urophasianus; hereinafter, "sage-grouse") are highly dependent on sagebrush (Artemisia spp.) dominated vegetation communities for food and cover from predators. Although this species requires the presence of sagebrush shrubs in the overstory, it also inhabits a broad geographic distribution with significant gradients in precipitation and temperature that drive variation in sagebrush ecosystem structure and concomitant shrub understory conditions. Variability in understory conditions across the species’ range may be responsible for the sometimes contradictory findings in the scientific literature describing sage-grouse habitat use and selection during important life history stages, such as nesting. To help understand the importance of this variability and to help guide management actions, we evaluated the nesting and brood-rearing microhabitat factors that influence selection and survival patterns in the Great Basin using a large dataset of microhabitat characteristics from study areas spanning northern Nevada and a portion of northeastern California from 2009 to 2016. The spatial and temporal coverage of the dataset provided a powerful opportunity to evaluate microhabitat factors important to sage-grouse reproduction, while also considering habitat variation associated with different climatic conditions and areas affected by wildfire. The summary statistics for numerous microhabitat factors, and the strength of their association with sage-grouse habitat selection and survival, are provided in this report to support decisions by land managers, policy-makers, and others with the best-available science in a timely manner.

RELAX: detecting relaxed selection in a phylogenetic framework.

PubMed

Wertheim, Joel O; Murrell, Ben; Smith, Martin D; Kosakovsky Pond, Sergei L; Scheffler, Konrad

2015-03-01

Relaxation of selective strength, manifested as a reduction in the efficiency or intensity of natural selection, can drive evolutionary innovation and presage lineage extinction or loss of function. Mechanisms through which selection can be relaxed range from the removal of an existing selective constraint to a reduction in effective population size. Standard methods for estimating the strength and extent of purifying or positive selection from molecular sequence data are not suitable for detecting relaxed selection, because they lack power and can mistake an increase in the intensity of positive selection for relaxation of both purifying and positive selection. Here, we present a general hypothesis testing framework (RELAX) for detecting relaxed selection in a codon-based phylogenetic framework. Given two subsets of branches in a phylogeny, RELAX can determine whether selective strength was relaxed or intensified in one of these subsets relative to the other. We establish the validity of our test via simulations and show that it can distinguish between increased positive selection and a relaxation of selective strength. We also demonstrate the power of RELAX in a variety of biological scenarios where relaxation of selection has been hypothesized or demonstrated previously. We find that obligate and facultative γ-proteobacteria endosymbionts of insects are under relaxed selection compared with their free-living relatives and obligate endosymbionts are under relaxed selection compared with facultative endosymbionts. Selective strength is also relaxed in asexual Daphnia pulex lineages, compared with sexual lineages. Endogenous, nonfunctional, bornavirus-like elements are found to be under relaxed selection compared with exogenous Borna viruses. Finally, selection on the short-wavelength sensitive, SWS1, opsin genes in echolocating and nonecholocating bats is relaxed only in lineages in which this gene underwent pseudogenization; however, selection on the functional medium/long-wavelength sensitive opsin, M/LWS1, is found to be relaxed in all echolocating bats compared with nonecholocating bats. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Metallurgical characterization of the fracture of several high strength aluminum alloys

NASA Technical Reports Server (NTRS)

Bhandarkar, M. D.; Lisagor, W. B.

1977-01-01

The fracture behavior for structural aluminum alloys (2024, 6061, 7075, and 7178) was examined in selected heat treatments. The investigation included tensile, shear, and precracked notch-bend specimens fractured at ambient temperature under monotonic loading. Specimens were obtained from thin sheets and thick plates and were tested in longitudinal and transverse orientations at different strain rates. Microstructures of alloys were examined using the optical microscope and the scanning electron microscope with associated energy dispersive X ray chemical analysis. Several different types of second phase particles, some not reported by other investigators, were identified in the alloys. Fracture morphology was related to microstructural variables, test variables, and type of commercial product. Specimen orientation examined in the present investigation had little effect on fracture morphology. Test strain rate changes resulted in some change in shear fracture morphology, but not in fracture morphology of tensile specimens.

TRO-2D - A code for rational transonic aerodynamic optimization

NASA Technical Reports Server (NTRS)

Davis, W. H., Jr.

1985-01-01

Features and sample applications of the transonic rational optimization (TRO-2D) code are outlined. TRO-2D includes the airfoil analysis code FLO-36, the CONMIN optimization code and a rational approach to defining aero-function shapes for geometry modification. The program is part of an effort to develop an aerodynamically smart optimizer that will simplify and shorten the design process. The user has a selection of drag minimization and associated minimum lift, moment, and the pressure distribution, a choice among 14 resident aero-function shapes, and options on aerodynamic and geometric constraints. Design variables such as the angle of attack, leading edge radius and camber, shock strength and movement, supersonic pressure plateau control, etc., are discussed. The results of calculations of a reduced leading edge camber transonic airfoil and an airfoil with a natural laminar flow are provided, showing that only four design variables need be specified to obtain satisfactory results.

Humidity effects on wire insulation breakdown strength.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Appelhans, Leah

2013-08-01

Methods for the testing of the dielectric breakdown strength of insulation on metal wires under variable humidity conditions were developed. Two methods, an ASTM method and the twisted pair method, were compared to determine if the twisted pair method could be used for determination of breakdown strength under variable humidity conditions. It was concluded that, although there were small differences in outcomes between the two testing methods, the non-standard method (twisted pair) would be appropriate to use for further testing of the effects of humidity on breakdown performance. The dielectric breakdown strength of 34G copper wire insulated with double layermore » Poly-Thermaleze/Polyamide-imide insulation was measured using the twisted pair method under a variety of relative humidity (RH) conditions and exposure times. Humidity at 50% RH and below was not found to affect the dielectric breakdown strength. At 80% RH the dielectric breakdown strength was significantly diminished. No effect for exposure time up to 140 hours was observed at 50 or 80%RH.« less

Biomechanics and Strength of Manual Wheelchair Users

PubMed Central

Ambrosio, Fabrisia; Boninger, Michael L; Souza, Aaron L; Fitzgerald, Shirley G; Koontz, Alicia M; Cooper, Rory A

2005-01-01

Background/Objective: Previous investigations have identified muscular imbalance in the shoulder as a source of pain and injury in manual wheelchair users. Our aim was to determine whether a correlation exists between strength and pushrim biomechanical variables including: tangential (motive) force (Ft), radial force (Fr), axial force (Fz), total (resultant) force (FR), fraction of effective force (FEF), and cadence. Methods: Peak isokinetic shoulder strength (flexion [FLX], extension [EXT], abduction [ABD], adduction [ADD], internal rotation [IR], and external rotation [ER]) was tested in 22 manual wheelchair users with a BioDex system for 5 repetitions at 60°/s. Subjects then propelled their own manual wheelchair at 2 speeds, 0.9 m/s (2 mph) and 1.8 m/s (4 mph), for 20 seconds, during which kinematic (OPTOTRAK) and kinetic (SMARTWHEEL) data were collected. Peak isokinetic forces in the cardinal planes were correlated with pushrim biomechanical variables. Results: All peak torque strength variables correlated significantly (P ≤ 0.05) with Ft, Fr, and FR, but were not significantly correlated with Fz, FEF, or cadence. Finally, there were no relationships found between muscle strength ratios (for example, FLX/EXT) and Ft, Fr, FR, Fz, or FEF. Conclusion: There was a correlation between strength and force imparted to the pushrim among wheelchair users; however, there was no correlation found in wheelchair propulsion or muscle imbalance. Clinicians should be aware of this, and approach strength training and training in wheelchair propulsion techniques separately. PMID:16869087

Correlation between strength properties in standard test specimens and molded phenolic parts

NASA Technical Reports Server (NTRS)

Turner, P S; Thomason, R H

1946-01-01

This report describes an investigation of the tensile, flexural, and impact properties of 10 selected types of phenolic molding materials. The materials were studied to see in what ways and to what extent their properties satisfy some assumptions on which the theory of strength of materials is based: namely, (a) isotropy, (b) linear stress-strain relationship for small strains, and (c) homogeneity. The effect of changing the dimensions of tensile and flexural specimens and the span-depth ratio in flexural tests were studied. The strengths of molded boxes and flexural specimens cut from the boxes were compared with results of tests on standard test specimens molded from the respective materials. The nonuniformity of a material, which is indicated by the coefficient of variation, affects the results of tests made with specimens of different sizes and tests with different methods of loading. The strength values were found to depend on the relationship between size and shape of the molded specimen and size and shape of the fillers. The most significant variations observed within a diversified group of materials were found to depend on the orientation of fibrous fillers. Of secondary importance was the dependence of the variability of test results on the pieces of filler incorporated into the molding powder as well as on the size of the piece. Static breaking strength tests on boxes molded from six representative phenolic materials correlated well with falling-ball impact tests on specimens cut from molded flat sheets. Good correlation was obtained with Izod impact tests on standard test specimens prepared from the molding materials. The static breaking strengths of the boxes do not correlate with the results of tensile or flexural tests on standard specimens.

Sources of strength-training information and strength-training behavior among Japanese older adults.

PubMed

Harada, Kazuhiro; Shibata, Ai; Lee, Euna; Oka, Koichiro; Nakamura, Yoshio

2016-03-01

The promotion of strength training is now recognized as an important component of public health initiatives for older adults. To develop successful communication strategies to increase strength-training behavior among older adults, the identification of effective communication channels to reach older adults is necessary. This study aimed to identify the information sources about strength training that were associated with strength-training behaviors among Japanese older adults. The participants were 1144 adults (60-74 years old) randomly sampled from the registry of residential addresses. A cross-sectional questionnaire survey was conducted. The independent variables were sources of strength-training information (healthcare providers, friends, families, radio, television, newspapers, newsletters, posters, books, magazines, booklets, the Internet, lectures, other sources), and the dependent variable was regular strength-training behavior. Logistic regression analysis was used to identify potential relationships. After adjusting for demographic factors and all other information sources, strength-training information from healthcare providers, friends, books and the Internet were positively related to regular strength-training behavior. The findings of the present study contribute to a better understanding of strength-training behavior and the means of successful communication directed at increasing strength training among older adults. The results suggest that healthcare providers, friends, books and the Internet are effective methods of communication for increasing strength-training behaviors among older adults. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Associations Between Balance and Muscle Strength, Power Performance in Male Youth Athletes of Different Maturity Status.

PubMed

Hammami, Raouf; Chaouachi, Anis; Makhlouf, Issam; Granacher, Urs; Behm, David G

2016-11-01

Balance, strength and power relationships may contain important information at various maturational stages to determine training priorities. The objective was to examine maturity-specific relationships of static/dynamic balance with strength and power measures in young male athletes. Soccer players (N = 130) aged 10-16 were assessed with the Stork and Y balance (YBT) tests. Strength/power measures included back extensor muscle strength, standing long jump (SLJ), countermovement jump (CMJ), and 3-hop jump tests. Associations between balance with strength/power variables were calculated according to peak-height-velocity (PHV). There were significant medium-large sized correlations between all balance measures with back extensor strength (r = .486-.791) and large associations with power (r = .511-.827). These correlation coefficients were significantly different between pre-PHV and circa PHV as well as pre-PHV and post-PHV with larger associations in the more mature groups. Irrespective of maturity-status, SLJ was the best strength/power predictor with the highest proportion of variance (12-47%) for balance (i.e., Stork eyes opened) and the YBT was the best balance predictor with the highest proportion of variance (43-78%) for all strength/power variables. The associations between balance and muscle strength/power measures in youth athletes that increase with maturity may imply transfer effects from balance to strength/power training and vice versa in youth athletes.

A search variability in the UV spectrum of Pi Aquarii and Fe 3 shell lines of Be stars

NASA Technical Reports Server (NTRS)

1984-01-01

Several short U1 and U2 observations of Be stars are obtained with the Copernicus satellite. Pi Aquarii (B1 IV-Ve) is observed with the U1 and U2 spectrometers. These scans are compared with earlier observations. Variations in the strengths and profiles of selected shell and photospheric features are examined. In order to study possible changes in the temperature of the circumstellar envelope, features covering a wide range in ionization are observed. Included in the observing program are lines of O VI, N V, Si IV, Si III, S III, Fe III, and N I.

HIGH-SHEAR GRANULATION PROCESS: INFLUENCE OF PROCESSING PARAMETERS ON CRITICAL QUALITY ATTRIBUTES OF ACETAMINOPHEN GRANULES AND TABLETS USING DESIGN OF EXPERIMENT APPROACH.

PubMed

Fayed, Mohamed H; Abdel-Rahman, Sayed I; Alanazi, Fars K; Ahmed, Mahrous O; Tawfeek, Hesham M; Al-Shedfat, Ramadan I

2017-01-01

Application of quality by design (QbD) in high shear granulation process is critical and need to recognize the correlation between the granulation process parameters and the properties of intermediate (granules) and corresponding final product (tablets). The present work examined the influence of water amount (X,) and wet massing time (X2) as independent process variables on the critical quality attributes of granules and corresponding tablets using design of experiment (DoE) technique. A two factor, three level (32) full factorial design was performed; each of these variables was investigated at three levels to characterize their strength and interaction. The dried granules have been analyzed for their size distribution, density and flow pattern. Additionally, the produced tablets have been investigated for weight uniformity, crushing strength, friability and percent capping, disintegration time and drug dissolution. Statistically significant impact (p < 0.05) of water amount was identified for granule growth, percent fines and distribution width and flow behavior. Granule density and compressibility were found to be significantly influenced (p < 0.05) by the two operating conditions. Also, water amount has significant effect (p < 0.05) on tablet weight unifornity, friability and percent capping. Moreover, tablet disintegration time and drug dissolution appears to be significantly influenced (p < 0.05) by the two process variables. On the other hand, the relationship of process parameters with critical quality attributes of granule and final product tablet was identified and correlated. Ultimately, a judicious selection of process parameters in high shear granulation process will allow providing product of desirable quality.

Personality and Behavior in Social Dilemmas: Testing the Situational Strength Hypothesis and the Role of Hypothetical Versus Real Incentives.

PubMed

Lozano, José H

2016-02-01

Previous research aimed at testing the situational strength hypothesis suffers from serious limitations regarding the conceptualization of strength. In order to overcome these limitations, the present study attempts to test the situational strength hypothesis based on the operationalization of strength as reinforcement contingencies. One dispositional factor of proven effect on cooperative behavior, social value orientation (SVO), was used as a predictor of behavior in four social dilemmas with varying degree of situational strength. The moderating role of incentive condition (hypothetical vs. real) on the relationship between SVO and behavior was also tested. One hundred undergraduates were presented with the four social dilemmas and the Social Value Orientation Scale. One-half of the sample played the social dilemmas using real incentives, whereas the other half used hypothetical incentives. Results supported the situational strength hypothesis in that no behavioral variability and no effect of SVO on behavior were found in the strongest situation. However, situational strength did not moderate the effect of SVO on behavior in situations where behavior showed variability. No moderating effect was found for incentive condition either. The implications of these results for personality theory and assessment are discussed. © 2014 Wiley Periodicals, Inc.

Ankle Plantarflexor Spasticity Does Not Restrict the Recovery of Ankle Plantarflexor Strength or Ankle Power Generation for Push-Off During Walking Following Traumatic Brain Injury.

PubMed

Williams, Gavin; Banky, Megan; Olver, John

2016-01-01

The main aim of this project was to determine the impact of plantarflexor spasticity on muscle performance for ambulant people with traumatic brain injury (TBI). A large metropolitan rehabilitation hospital. Seventy-two ambulant people with TBI who were attending physiotherapy for mobility limitations. Twenty-four participants returned for a 6-month follow-up reassessment. Cross-sectional cohort study. Self-selected walking speed, Tardieu scale, ankle plantarflexor strength, and ankle power generation (APG). Participants with ankle plantarflexor spasticity had significantly lower self-selected walking speed; however, there was no significant difference in ankle plantarflexor strength or APG. Participants with ankle plantarflexor spasticity were not restricted in the recovery of self-selected walking speed, ankle plantarflexor strength, or APG, indicating equivalent ability to improve their mobility over time despite the presence of spasticity. Following TBI, people with ankle plantarflexor spasticity have significantly greater mobility limitations than those without spasticity, yet retain the capacity for recovery of self-selected walking speed, ankle plantarflexor strength, and APG.

Influence of the Bermuda High on interannual variability of summertime ozone in the Houston-Galveston-Brazoria region

NASA Astrophysics Data System (ADS)

Wang, Yuxuan; Jia, Beixi; Wang, Sing-Chun; Estes, Mark; Shen, Lu; Xie, Yuanyu

2016-12-01

The Bermuda High (BH) quasi-permanent pressure system is the key large-scale circulation pattern influencing summertime weather over the eastern and southern US. Here we developed a multiple linear regression (MLR) model to characterize the effect of the BH on year-to-year changes in monthly-mean maximum daily 8 h average (MDA8) ozone in the Houston-Galveston-Brazoria (HGB) metropolitan region during June, July, and August (JJA). The BH indicators include the longitude of the BH western edge (BH-Lon) and the BH intensity index (BHI) defined as the pressure gradient along its western edge. Both BH-Lon and BHI are selected by MLR as significant predictors (p < 0.05) of the interannual (1990-2015) variability of the HGB-mean ozone throughout JJA, while local-scale meridional wind speed is selected as an additional predictor for August only. Local-scale temperature and zonal wind speed are not identified as important factors for any summer month. The best-fit MLR model can explain 61-72 % of the interannual variability of the HGB-mean summertime ozone over 1990-2015 and shows good performance in cross-validation (R2 higher than 0.48). The BH-Lon is the most important factor, which alone explains 38-48 % of such variability. The location and strength of the Bermuda High appears to control whether or not low-ozone maritime air from the Gulf of Mexico can enter southeastern Texas and affect air quality. This mechanism also applies to other coastal urban regions along the Gulf Coast (e.g., New Orleans, LA, Mobile, AL, and Pensacola, FL), suggesting that the BH circulation pattern can affect surface ozone variability through a large portion of the Gulf Coast.

Asymmetry of Muscle Strength in Elite Athletes

ERIC Educational Resources Information Center

Drid, Patrik; Drapsin, Miodrag; Trivic, Tatjana; Lukac, Damir; Obadov, Slavko; Milosevic, Zoran

2009-01-01

"Study aim": To determine muscle strength variables in elite judoists and wrestlers since thigh muscle strength and bilaterally balanced flexor-to-extensor ratio minimise injury risk and are desirable for achieving sport successes. "Material and methods": Judoists, wrestlers and untrained subjects, 10 each, were subjected to isokinetic strength…

Predicting the admission into medical school of African American college students who have participated in summer academic enrichment programs.

PubMed

Hesser, A; Cregler, L L; Lewis, L

1998-02-01

To identify cognitive and noncognitive variables as predictors of the admission into medical school of African American college students who have participated in summer academic enrichment programs (SAEPs). The study sample comprised 309 African American college students who participated in SAEPs at the Medical College of Georgia School of Medicine from 1980 to 1989 and whose educational and occupational statuses were determined by follow-up tracking. A three-step logistic regression was used to analyze the data (with alpha = .05); the criterion variable was admission to medical school. The 17 predictor variables studied were one of two types, cognitive and noncognitive. The cognitive variables were (1) Scholastic Aptitude Test mathematics (SAT-M) score, (2) SAT verbal score, (3) college grade-point average (GPA), (4) college science GPA, (5) SAEP GPA, and (6) SAEP basic science GPA (BSGPA). The noncognitive variables were (1) gender, (2) highest college level at the time of the last SAEP application, (3) type of college attended (historically African American or predominately white), (4) number of SAEPs attended, (5) career aspiration (physician or another health science option) (6) parents who were professionals, (7) parents who were health care role models, (8) evidence of leadership, (9) evidence of community service, (10) evidence of special motivation, and (11) strength of letter of recommendation in the SAEP application. For each student the rating scores for the last four noncognitive variables were determined by averaging the ratings of two judges who reviewed relevant information in each student's file. In step 1, which explained 20% of the admission decision variance, SAT-M score, SAEP BSGPA, and college GPA were the three significant cognitive predictors identified. In step 2, which explained 31% of the variance, the three cognitive predictors identified in step 1 were joined by three noncognitive predictors: career aspiration, type of college, and number of SAEPs attended. In step 3, which explained 29% of the variance, two cognitive variables (SAT-M score and SAEP BSGPA) and two noncognitive variables (career aspiration and strength of recommendation letter) were identified. The results support the concept of using both cognitive and noncognitive variables when selecting African American students for pre-medical school SAEPs.

Serial position effects are sensitive predictors of conversion from MCI to Alzheimer's disease dementia.

PubMed

Egli, Simone C; Beck, Irene R; Berres, Manfred; Foldi, Nancy S; Monsch, Andreas U; Sollberger, Marc

2014-10-01

It is unclear whether the predictive strength of established cognitive variables for progression to Alzheimer's disease (AD) dementia from mild cognitive impairment (MCI) varies depending on time to conversion. We investigated which cognitive variables were best predictors, and which of these variables remained predictive for patients with longer times to conversion. Seventy-five participants with MCI were assessed on measures of learning, memory, language, and executive function. Relative predictive strengths of these measures were analyzed using Cox regression models. Measures of word-list position-namely, serial position scores-together with Short Delay Free Recall of word-list learning best predicted conversion to AD dementia. However, only serial position scores predicted those participants with longer time to conversion. Results emphasize that the predictive strength of cognitive variables varies depending on time to conversion to dementia. Moreover, finer measures of learning captured by serial position scores were the most sensitive predictors of AD dementia. Copyright © 2014 The Alzheimer's Association. Published by Elsevier Inc. All rights reserved.

Age-Related Variability in Tongue Pressure Patterns for Maximum Isometric and Saliva Swallowing Tasks

PubMed Central

Peladeau-Pigeon, Melanie

2017-01-01

Purpose The ability to generate tongue pressure plays a major role in bolus transport in swallowing. In studies of motor control, stability or variability of movement is a feature that changes with age, disease, task complexity, and perturbation. In this study, we explored whether age and tongue strength influence the stability of the tongue pressure generation pattern during isometric and swallowing tasks in healthy volunteers. Method Tongue pressure data, collected using the Iowa Oral Performance Instrument, were analyzed from 84 participants in sex-balanced and decade age-group strata. Tasks included maximum anterior and posterior isometric pressures and regular-effort saliva swallows. The cyclic spatiotemporal index (cSTI) was used to capture stability (vs. variability) in patterns of pressure generation. Mixed-model repeated measures analyses of covariance were performed separately for each task (anterior and posterior isometric pressures, saliva swallows) with between-participant factors of age group and sex, a within-participant factor of task repetition, and a continuous covariate of tongue strength. Results Neither age group nor sex effects were found. There was no significant relationship between tongue strength and the cSTI on the anterior isometric tongue pressure task (r = −.11). For the posterior isometric tongue pressure task, a significant negative correlation (r = −.395) was found between tongue strength and the cSTI. The opposite pattern of a significant positive correlation (r = .29) between tongue strength and the cSTI was seen for the saliva swallow task. Conclusions Tongue pressure generation patterns appear highly stable across repeated maximum isometric and saliva swallow tasks, despite advancing age. Greater pattern variability is seen with weaker posterior isometric pressures. Overall, saliva swallows had the lowest pressure amplitudes and highest pressure pattern variability as measured by the cSTI. PMID:29114767

Meta-analysis of the effect of strengthening interventions in individuals with cerebral palsy.

PubMed

Park, Eun-Young; Kim, Won-Ho

2014-02-01

This study aimed to investigate the evidence that strengthening interventions can improve muscle strength and activity in individuals with cerebral palsy. The search focused on studies that employed strength training for children with cerebral palsy for which six electronic databases were used to extract literature published from 2001 to 2012. The key terms used in these searches were combined strength training, strengthening, weight training, weight lifting, resistance, and cerebral palsy. The quality of each study was assessed using the PEDro (Physiotherapy Evidence Database) scale. Thirteen randomized controlled trial studies were selected and divided into categories according to program type, mode, and outcome measures. The overall effect sizes of each study and types of strengthening were large. Strengthening exercise improved muscle strength to a greater degree, when practiced 3 times per week in 40-50 min sessions than in other categories of session length, and greater improvement was observed in younger children than in older. The effect size of the activities and variables related to gait, except for gait endurance, were medium to large. The effect size of individual muscles was large, but the effect sizes for ankle plantar flexor, hip abductor/adductor, and extensor were insignificant. Strengthening interventions are useful for increasing muscle strength in individuals with cerebral palsy, specifically in youth and children, and optimal exercise consisted of 40- to 50-min sessions performed 3 times per week. Although strengthening interventions may improve activities, including gait, more studies that are rigorous are needed to determine the contributions to gross motor function. Copyright © 2013 Elsevier Ltd. All rights reserved.

Planar-focusing cathodes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewellen, J. W.; Noonan, J.; Accelerator Systems Division

2005-01-01

Conventional {pi}-mode rf photoinjectors typically use magnetic solenoids for emittance compensation. This provides independent focusing strength but can complicate rf power feed placement, introduce asymmetries (due to coil crossovers), and greatly increase the cost of the photoinjector. Cathode-region focusing can also provide for a form of emittance compensation. Typically this method strongly couples focusing strength to the field gradient on the cathode, however, and usually requires altering the longitudinal position of the cathode to change the focusing. We propose a new method for achieving cathode-region variable-strength focusing for emittance compensation. The new method reduces the coupling to the gradient onmore » the cathode and does not require a change in the longitudinal position of the cathode. Expected performance for an S-band system is similar to conventional solenoid-based designs. This paper presents the results of rf cavity and beam dynamics simulations of the new design. We have proposed a method for performing emittance compensation using a cathode-region focusing scheme. This technique allows the focusing strength to be adjusted somewhat independently of the on-axis field strength. Beam dynamics calculations indicate performance should be comparable to presently in-use emittance compensation schemes, with a simpler configuration and fewer possibilities for emittance degradation due to the focusing optics. There are several potential difficulties with this approach, including cathode material selection, cathode heating, and peak fields in the gun. We hope to begin experimenting with a cathode of this type in the near future, and several possibilities exist for reducing the peak gradients to more acceptable levels.« less

Improvement of isometric dorsiflexion protocol for assessment of tibialis anterior muscle strength.

PubMed

Siddiqi, Ariba; Arjunan, Sridhar P; Kumar, Dinesh

2015-01-01

It is important to accurately estimate the electromyogram (EMG)/force relationship of triceps surae (TS) muscle for detecting strength deficit of tibalis anterior (TA) muscle. In literature, the protocol for recording EMG and force of dorsiflexion have been described, and the necessity for immobilizing the ankle has been explained. However, there is a significant variability of the results among researchers even though they report the fixation of the ankle. We have determined that toe extension can cause significant variation in the dorsiflexion force and EMG of TS and this can occur despite following the current guidelines which require immobilizing the ankle. The results also show that there was a large increase in the variability of the force and the RMS of EMG of TS when the toes were not strapped compared with when they were strapped. Thus, with the current guidelines, where there are no instructions regarding the necessity of strapping the toes, the EMG/force relationship of TS could be incorrect and give an inaccurate assessment of the dorsiflexor TA strength. In summary, •Current methodology to estimate the dorsiflexor TA strength with respect to the TS activity, emphasizing on ankle immobilization is insufficient to prevent large variability in the measurements.•Toe extension during dorsiflexion was found to be one source of variability in estimating the TA strength.•It is recommended that guidelines for recording force and EMG from TA and TS muscles should require the strapping of the toes along with the need for immobilizing the ankle.

Selection on spur shape in Impatiens capensis.

PubMed

Young, Helen J

2008-06-01

Rapid speciation within some plant families has been attributed to the evolution of floral spurs and to the effect of spur length on plant reproductive success. The flowers of Impatiens capensis (jewelweed) possess a long, curved spur in which nectar is produced and stored. Spur length and curvature varies among plants within one population. Here I document that spur shape is variable in natural populations, variation within plants is less than variation among plants, and spur shape is correlated with components of female and male reproductive success. The apparent natural selection is weakly directional in 1 of 2 years, with greatest seed production and pollen removal occurring in flowers with the greatest spur curvature. Bee pollinator visit length is longest at flowers with highly curved spurs, and they leave less nectar in these spurs than in flowers with straighter spurs. Spur angle evolution may be limited, at least in part, by opposing selection by nectar-robbers who prefer to visit flowers with greater spur curvature. Other factors that might contribute to the maintenance of spur angle variation are temporal variation in the strength of selection and potential genetic correlations of spur shape with other traits under selection.

Effects of 12 weeks combined aerobic and resistance exercise on heart rate variability in type 2 diabetes mellitus patients.

PubMed

Kang, Seol-Jung; Ko, Kwang-Jun; Baek, Un-Hyo

2016-07-01

[Purpose] This study evaluated the effects of 12 weeks combined aerobic and resistance exercise on heart rate variability in patients with Type 2 diabetes mellitus. [Subjects and Methods] The subjects were 16 female patients with Type 2 diabetes mellitus selected among the participants of a chronic disease management exercise class at C Region Public Health Center in South Korea. Subjects were randomly assigned to the exercise group (n=8; age, 55.97 ± 7.37) or the control group (n=8; age, 57.53 ± 4.63) The exercise group performed aerobic and resistance exercises for 60 minutes per day, 3 times per week for 12 weeks. Anthropometric measurements, biochemical markers, physical fitness, and heart rate variability were examined. [Results] After 12 weeks of exercise, weight, body fat percentage, waist circumference, blood glucose, insulin resistance, glycated hemoglobin level, systolic blood pressure, and diastolic blood pressure significantly decreased and cardiorespiratory fitness and muscular strength significantly increased in the exercise group. Although heart rate variability measures showed favorable changes with the exercise program, none were significant. [Conclusion] Although the exercise program did not show notable changes in heart rate variability in patients with Type 2 diabetes within the timeframe of the study, exercise may contribute to the prevention and control of cardiovascular autonomic neuropathy.

Changes in muscle strength in individuals with statin-induced myopathy: A summary of 3 investigations.

PubMed

Panza, Gregory A; Taylor, Beth A; Dada, Marcin R; Thompson, Paul D

2015-01-01

There are inconsistent findings regarding muscular weakness in individuals with statin-induced myalgia. We used rigorous muscle testing to compare findings from 3 investigations in 3 different study populations to determine if statin myalgia is associated with measurable weakness. In all 3 studies, we measured maximal isometric handgrip strength, resting respiratory exchange ratio (RER), and knee extensor isometric and isokinetic force. In 2 of the 3 studies, elbow flexor isometric and isokinetic force and knee endurance fatigue index were also assessed. Knee extensor and elbow flexor measurements were obtained using an isokinetic dynamometer. Resting RER was measured using a metabolic breath-by-breath collection method. Measurement outcomes were compared on vs off drug. In study 1, 18 participants fit the criteria for statin myalgia. Participants taking atorvastatin 80 mg daily had significantly lower muscle strength in 5 (P < .05) of 14 measured variables. Participants on placebo (N = 10) with myalgia had significantly lower muscle strength in 4 (P < .05) of 14 measured variables. In study 2, 18 participants tested positive for statin-induced myalgia when receiving simvastatin 20 mg daily and displayed no significant muscle strength changes (all P > .05). In study 3, 11 patients with statin-induced myalgia completed the study and had a significant decrease in 2 (P < .05) of 10 leg muscle strength variables. In all 3 studies, no significant changes were shown for handgrip strength or RER (all P > .05). Our results indicate that after a short-term treatment with statin therapy, a rigorous muscle strength protocol does not show decrements of muscle strength in subjects with statin myalgia. Short-term treatment with statin therapy is not common in clinical practice. Thus, future studies should examine the effects of prolonged statin therapy on muscle strength. Published by Elsevier Inc.

Influence of muscle strength, physical activity and weight on bone mass in a population-based sample of 1004 elderly women.

PubMed

Gerdhem, P; Ringsberg, K A M; Akesson, K; Obrant, K J

2003-09-01

High physical activity level has been associated with high bone mass and low fracture risk and is therefore recommended to reduce fractures in old age. The aim of this study was to estimate the effect of potentially modifiable variables, such as physical activity, muscle strength, muscle mass and weight, on bone mass in elderly women. The influence of isometric thigh muscle strength, self-estimated activity level, body composition and weight on bone mineral density (dual energy X-ray absorptiometry; DXA) in total body, hip and spine was investigated. Subjects were 1004 women, all 75 years old, taking part in the Malmö Osteoporosis Prospective Risk Assessment (OPRA) study. Physical activity and muscle strength accounted for 1-6% of the variability in bone mass, whereas weight, and its closely associated variables lean mass and fat mass, to a much greater extent explained the bone mass variability. We found current body weight to be the variable with the most substantial influence on the total variability in bone mass (15-32% depending on skeletal site) in a forward stepwise regression model. Our findings suggest that in elderly women, the major fracture-preventive effect of physical activity is unlikely to be mediated through increased bone mass. Retaining or even increasing body weight is likely to be beneficial to the skeleton, but an excess body weight increase may have negative effects on health. Nevertheless, training in elderly women may have advantages by improving balance, co-ordination and mobility and therefore decreasing the risk of fractures.

Promoter architecture dictates cell-to-cell variability in gene expression.

PubMed

Jones, Daniel L; Brewster, Robert C; Phillips, Rob

2014-12-19

Variability in gene expression among genetically identical cells has emerged as a central preoccupation in the study of gene regulation; however, a divide exists between the predictions of molecular models of prokaryotic transcriptional regulation and genome-wide experimental studies suggesting that this variability is indifferent to the underlying regulatory architecture. We constructed a set of promoters in Escherichia coli in which promoter strength, transcription factor binding strength, and transcription factor copy numbers are systematically varied, and used messenger RNA (mRNA) fluorescence in situ hybridization to observe how these changes affected variability in gene expression. Our parameter-free models predicted the observed variability; hence, the molecular details of transcription dictate variability in mRNA expression, and transcriptional noise is specifically tunable and thus represents an evolutionarily accessible phenotypic parameter. Copyright © 2014, American Association for the Advancement of Science.

Variability of strength measurement in postmenopausal women who are overweight or obese: a Monet study.

PubMed

St-Onge, Maxime; Mathieu, Marie-Eve; Tousignant, Benoit; Faraj, May; Lavoie, Jean-Marc

2009-12-01

The main objective of this study was to establish whether a stable measurement of strength could be obtained without prior exercise familiarization in postmenopausal women who were overweight or obese. A second objective was to evaluate the influence of physical activity on the variability of strength measurement. Thirty postmenopausal women (age: 57.9 yr; SD: 5 yr; body mass index: 31.0 kg/m2; SD: 4 kg/m2) underwent 3 strength testing sessions (48 hr apart) each including 3 exercises (leg press, chest press, and lat pull down). Energy expenditure was measured before the strength testing week with the doubly labelled water method over a 10-day period. Resting metabolic rate was measured by indirect calorimetry. Physical activity energy expenditure was calculated as follows: total energy expenditure x 0.9, minus the resting metabolic rate. Repeated analysis of variance and paired t-test were used to assess the difference and the reliability of the testing sequence. Results from leg press and chest press exercises indicated no significant difference among the 3 testing sessions. The lat pull down exercise was associated with a significant systematic bias between sessions 1 and 2 (mean difference: 1.4 kg; SD: 3 kg; 95% confidence intervals; 0.2-2.7 kg), but the difference disappeared at the third testing session (mean difference: 0.7 kg; SD: 3 kg; 95% confidence intervals; 0.5-2 kg). Physical activity did not influence the variability of the strength results. Overall, our results showed that a relatively stable strength measurement can be obtained within a maximum of 3 testing sessions without prior familiarization. In addition, physical activity did not influence strength testing in postmenopausal women who were overweight or obese.

Motivation of medical students: selection by motivation or motivation by selection.

PubMed

Wouters, Anouk; Croiset, Gerda; Galindo-Garre, Francisca; Kusurkar, Rashmi A

2016-01-29

Medical schools try to implement selection procedures that will allow them to select the most motivated students for their programs. Though there is a general feeling that selection stimulates student motivation, conclusive evidence for this is lacking. The current study aims to use the perspective of Self-determination Theory (SDT) of motivation as a lens to examine how medical students' motivation differs in relation to different selection procedures. The hypotheses were that 1) selected students report higher strength and autonomous motivation than non-selected students, and 2) recently selected students report higher strength and autonomous motivation than non-selected students and students who were selected longer ago. First- (Y1) and fourth-year (Y4) medical students in the six-year regular programme and first-year students in the four-year graduate entry programme (GE) completed questionnaires measuring motivation strength and type (autonomous-AM, controlled-CM). Scores were compared between students admitted based on selection, lottery or top pre-university GPA (top GPA) using ANCOVAs. Selected students' answers on open-ended questions were analysed using inductive thematic analysis to identify reasons for changes in motivation. The response rate was 61.4 % (n = 357). Selected students (Y1, Y4 and GE) reported a significantly higher strength of motivation than non-selected students (Y1 and Y4 lottery and top GPA) (p < 0.01). Recently selected students (Y1 and GE) reported significantly higher strength (p < 0.01) and higher AM (p < 0.01) and CM (p < 0.05) than non-selected students (lottery and top GPA) and Y4 students who were selected three years ago. Students described that being selected enhanced their motivation as they felt autonomous, competent and that they belonged to a special group. These reported reasons are in alignment with the basic psychological needs described by Self-Determination Theory as important in enhancing autonomous motivation. A comprehensive selection procedure, compared to less demanding admission procedures, does not seem to yield a student population which stands out in terms of autonomous motivation. The current findings indicate that selection might temporarily enhance students' motivation. The mechanism through which this occurs seems to be through feelings of autonomy, competence and relatedness inspired by selection.

The Health Impact of Child Labor in Developing Countries: Evidence From Cross-Country Data

PubMed Central

Roggero, Paola; Mangiaterra, Viviana; Bustreo, Flavia; Rosati, Furio

2007-01-01

Objectives. Research on child labor and its effect on health has been limited. We sought to determine the impact of child labor on children’s health by correlating existing health indicators with the prevalence of child labor in selected developing countries. Methods. We analyzed the relationship between child labor (defined as the percentage of children aged 10 to14 years who were workers) and selected health indicators in 83 countries using multiple regression to determine the nature and strength of the relation. The regression included control variables such as the percentage of the population below the poverty line and the adult mortality rate. Results. Child labor was significantly and positively related to adolescent mortality, to a population’s nutrition level, and to the presence of infectious disease. Conclusions. Longitudinal studies are required to understand the short- and long-term health effects of child labor on the individual child. PMID:17194870

14 CFR 23.627 - Fatigue strength.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Fatigue strength. The structure must be designed, as far as practicable, to avoid points of stress concentration where variable stresses above the fatigue limit are likely to occur in normal service. ...

14 CFR 23.627 - Fatigue strength.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Fatigue strength. The structure must be designed, as far as practicable, to avoid points of stress concentration where variable stresses above the fatigue limit are likely to occur in normal service. ...

14 CFR 23.627 - Fatigue strength.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Fatigue strength. The structure must be designed, as far as practicable, to avoid points of stress concentration where variable stresses above the fatigue limit are likely to occur in normal service. ...

14 CFR 23.627 - Fatigue strength.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Fatigue strength. The structure must be designed, as far as practicable, to avoid points of stress concentration where variable stresses above the fatigue limit are likely to occur in normal service. ...

14 CFR 23.627 - Fatigue strength.

Code of Federal Regulations, 2011 CFR

2011-01-01

... Fatigue strength. The structure must be designed, as far as practicable, to avoid points of stress concentration where variable stresses above the fatigue limit are likely to occur in normal service. ...

Longitudinal variability of complexities associated with equatorial electrojet

NASA Astrophysics Data System (ADS)

Rabiu, A. B.; Ogunjo, S. T.; Fuwape, I. A.

2017-12-01

Equatorial electrojet indices obtained from ground based magnetometers at 6 representative stations across the magnetic equatorial belt for the year 2009 (mean annual sunspot number Rz = 3.1) were treated to nonlinear time series analysis technique to ascertain the longitudinal dependence of the chaos/complexities associated with the phenomena. The selected stations were along the magnetic equator in the South American (Huancayo, dip latitude -1.80°), African (Ilorin, dip latitude -1.82°; Addis Ababa, dip latitude - 0.18°), and Philippine (Langkawi, dip latitude -2.32°; Davao, dip latitude -1.02°; Yap, dip latitude -1.49°) sectors. The non-linear quantifiers engaged in this work include: Recurrence rate, determinism, diagonal line length, entropy, laminarity, Tsallis entropy, Lyapunov exponent and correlation dimension. Ordinarily the EEJ was found to undergo variability from one longitudinal representative station to another, with the strongest EEJ of about 192.5 nT at the South American axis at Huancayo. The degree of complexity in the EEJ was found to vary qualitatively from one sector to another. Probable physical mechanisms responsible for longitudinal variability of EEJ strength and its complexities were highlighted.

Monitor Variability of Millimeter Lines in IRC+10216

NASA Astrophysics Data System (ADS)

He, J. H.; Dinh-V-Trung; Hasegawa, T. I.

2017-08-01

A single dish monitoring of millimeter maser lines SiS J = 14-13 and HCN {ν }2={1}f J = 3-2 and several other rotational lines is reported for the archetypal carbon star IRC+10216. Relative line strength variations of 5% ∼ 30% are found for eight molecular line features with respect to selected reference lines. Definite line-shape variations are found in limited velocity intervals of the SiS and HCN line profiles. The asymmetrical line profiles of the two lines are mainly due to the varying components. The dominant varying components of the line profiles have similar periods and phases to the IR light variation, though both quantities show some degree of velocity dependence; there is also variability asymmetry between the blue and red line wings of both lines. Combining the velocities and amplitudes with a wind velocity model, we suggest that the line profile variations are due to SiS and HCN masing lines emanating from the wind acceleration zone. The possible link of the variabilities to thermal, dynamical, and/or chemical processes within or under this region is also discussed.

Selection by pollinators on floral traits in generalized Trollius ranunculoides (Ranunculaceae) along altitudinal gradients.

PubMed

Zhao, Zhi-Gang; Wang, Yi-Ke

2015-01-01

Abundance and visitation of pollinator assemblages tend to decrease with altitude, leading to an increase in pollen limitation. Thus increased competition for pollinators may generate stronger selection on attractive traits of flowers at high elevations and cause floral adaptive evolution. Few studies have related geographically variable selection from pollinators and intraspecific floral differentiation. We investigated the variation of Trollius ranunculoides flowers and its pollinators along an altitudinal gradient on the eastern Qinghai-Tibet Plateau, and measured phenotypic selection by pollinators on floral traits across populations. The results showed significant decline of visitation rate of bees along altitudinal gradients, while flies was unchanged. When fitness is estimated by the visitation rate rather than the seed number per plant, phenotypic selection on the sepal length and width shows a significant correlation between the selection strength and the altitude, with stronger selection at higher altitudes. However, significant decreases in the sepal length and width of T. ranunculoides along the altitudinal gradient did not correspond to stronger selection of pollinators. In contrast to the pollinator visitation, mean annual precipitation negatively affected the sepal length and width, and contributed more to geographical variation in measured floral traits than the visitation rate of pollinators. Therefore, the sepal size may have been influenced by conflicting selection pressures from biotic and abiotic selective agents. This study supports the hypothesis that lower pollinator availability at high altitude can intensify selection on flower attractive traits, but abiotic selection is preventing a response to selection from pollinators.

Selection by Pollinators on Floral Traits in Generalized Trollius ranunculoides (Ranunculaceae) along Altitudinal Gradients

PubMed Central

Zhao, Zhi-Gang; Wang, Yi-Ke

2015-01-01

Abundance and visitation of pollinator assemblages tend to decrease with altitude, leading to an increase in pollen limitation. Thus increased competition for pollinators may generate stronger selection on attractive traits of flowers at high elevations and cause floral adaptive evolution. Few studies have related geographically variable selection from pollinators and intraspecific floral differentiation. We investigated the variation of Trollius ranunculoides flowers and its pollinators along an altitudinal gradient on the eastern Qinghai-Tibet Plateau, and measured phenotypic selection by pollinators on floral traits across populations. The results showed significant decline of visitation rate of bees along altitudinal gradients, while flies was unchanged. When fitness is estimated by the visitation rate rather than the seed number per plant, phenotypic selection on the sepal length and width shows a significant correlation between the selection strength and the altitude, with stronger selection at higher altitudes. However, significant decreases in the sepal length and width of T. ranunculoides along the altitudinal gradient did not correspond to stronger selection of pollinators. In contrast to the pollinator visitation, mean annual precipitation negatively affected the sepal length and width, and contributed more to geographical variation in measured floral traits than the visitation rate of pollinators. Therefore, the sepal size may have been influenced by conflicting selection pressures from biotic and abiotic selective agents. This study supports the hypothesis that lower pollinator availability at high altitude can intensify selection on flower attractive traits, but abiotic selection is preventing a response to selection from pollinators. PMID:25692295

The Importance of Muscular Strength: Training Considerations.

PubMed

Suchomel, Timothy J; Nimphius, Sophia; Bellon, Christopher R; Stone, Michael H

2018-04-01

This review covers underlying physiological characteristics and training considerations that may affect muscular strength including improving maximal force expression and time-limited force expression. Strength is underpinned by a combination of morphological and neural factors including muscle cross-sectional area and architecture, musculotendinous stiffness, motor unit recruitment, rate coding, motor unit synchronization, and neuromuscular inhibition. Although single- and multi-targeted block periodization models may produce the greatest strength-power benefits, concepts within each model must be considered within the limitations of the sport, athletes, and schedules. Bilateral training, eccentric training and accentuated eccentric loading, and variable resistance training may produce the greatest comprehensive strength adaptations. Bodyweight exercise, isolation exercises, plyometric exercise, unilateral exercise, and kettlebell training may be limited in their potential to improve maximal strength but are still relevant to strength development by challenging time-limited force expression and differentially challenging motor demands. Training to failure may not be necessary to improve maximum muscular strength and is likely not necessary for maximum gains in strength. Indeed, programming that combines heavy and light loads may improve strength and underpin other strength-power characteristics. Multiple sets appear to produce superior training benefits compared to single sets; however, an athlete's training status and the dose-response relationship must be considered. While 2- to 5-min interset rest intervals may produce the greatest strength-power benefits, rest interval length may vary based an athlete's training age, fiber type, and genetics. Weaker athletes should focus on developing strength before emphasizing power-type training. Stronger athletes may begin to emphasize power-type training while maintaining/improving their strength. Future research should investigate how best to implement accentuated eccentric loading and variable resistance training and examine how initial strength affects an athlete's ability to improve their performance following various training methods.

Proprioceptive deficit in patients with complete tearing of the anterior cruciate ligament.

PubMed

Godinho, Pedro; Nicoliche, Eduardo; Cossich, Victor; de Sousa, Eduardo Branco; Velasques, Bruna; Salles, José Inácio

2014-01-01

To investigate the existence of proprioceptive deficits between the injured limb and the uninjured (i.e. contralateral normal) limb, in individuals who suffered complete tearing of the anterior cruciate ligament (ACL), using a strength reproduction test. Sixteen patients with complete tearing of the ACL participated in the study. A voluntary maximum isometric strength test was performed, with reproduction of the muscle strength in the limb with complete tearing of the ACL and the healthy contralateral limb, with the knee flexed at 60°. The meta-intensity was used for the procedure of 20% of the voluntary maximum isometric strength. The proprioceptive performance was determined by means of absolute error, variable error and constant error values. Significant differences were found between the control group and ACL group for the variables of absolute error (p = 0.05) and constant error (p = 0.01). No difference was found in relation to variable error (p = 0.83). Our data corroborate the hypothesis that there is a proprioceptive deficit in subjects with complete tearing of the ACL in an injured limb, in comparison with the uninjured limb, during evaluation of the sense of strength. This deficit can be explained in terms of partial or total loss of the mechanoreceptors of the ACL.

Body image, nutritional status, abdominal strength, and cardiorespiratory fitness in children and adolescents practicing sports.

PubMed

Schubert, Alexandre; Januário, Renata Selvatici B; Casonatto, Juliano; Sonoo, Christi Noriko

2013-01-01

To verify the association between nutritional status, physical fitness, and body image in children and adolescents. This cross-sectional study included 401 students (236 boys and 165 girls) aged between 8 and 16 years that were regularly enrolled in sports in the local clubs. The nutritional status was evaluated by the body mass index. Students were assessed for satisfaction with body image, abdominal strength resistance, and cardiorespiratory fitness. The variables were assessed on the same day following a standardized order. In order to verify relationships between variables, the chi-square test was used. Afterwards, the binary logistic regression was applied to identify the magnitude of the associations, considering p<0.05 as significant. Association was found between body image and body mass index (p=0.001), abdominal strength resistance (p=0.005) and cardiorespiratory fitness (p=0.001). The Odds Ratio for presenting the body image insatisfaction for those who have not achieved the expected values for the health criteria in abdominal strength resistance and cardiorespiratory fitness were 2.14 and 2.42 times respectively, and for those with overweight and obesity, 2.87 times. Insatisfaction with body image is associated with body mass index and also with physical fitness, abdominal strength resistance, and cardiorespiratory fitness variables.

Evidentiary, extraevidentiary, and deliberation process predictors of real jury verdicts.

PubMed

Devine, Dennis J; Krouse, Paige C; Cavanaugh, Caitlin M; Basora, Jaime Colon

2016-12-01

In contrast to the extensive literature based on mock jurors, large-sample studies of decision making by real juries are relatively rare. In this field study, we examined relationships between jury verdicts and variables representing 3 classes of potential determinants-evidentiary, extraevidentiary, and deliberation process-using a sample of 114 criminal jury trials. Posttrial data were collected from 11 presiding judges, 31 attorneys, and 367 jurors using a Web-based questionnaire. The strength of the prosecution's evidence was strongly related to the occurrence of a conviction, whereas most extraevidentiary and deliberation process variables were only weakly to modestly related in bivariate form and when the prosecution's evidence strength was controlled. Notable exceptions to this pattern were jury demographic diversity as represented by the number of different race-gender subgroups (e.g., Black males) present in the jury, and several deliberation process variables reflecting advocacy for acquittal (e.g., presence of an identifiable proacquittal faction within the jury and proacquittal advocacy by the foreperson). Variables reflecting advocacy for conviction were essentially unrelated to jury verdict. Sets of extraevidentiary and deliberation variables were each able to modestly improve the explanation of jury verdicts over prosecution evidence strength in multivariate models. This study highlights the predictive efficacy of prosecution evidence strength with respect to jury verdicts, as well as the potential importance of jury demographic diversity and advocacy for acquittal during deliberation. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Ratings of Perceived Exertion During Acute Resistance Exercise Performed at Imposed and Self-Selected Loads in Recreationally Trained Women.

PubMed

Cotter, Joshua A; Garver, Matthew J; Dinyer, Taylor K; Fairman, Ciaran M; Focht, Brian C

2017-08-01

Cotter, JA, Garver, MJ, Dinyer, TK, Fairman, CM, and Focht, BC. Ratings of perceived exertion during acute resistance exercise performed at imposed and self-selected loads in recreationally trained women. J Strength Cond Res 31(8): 2313-2318, 2017-Resistance exercise (RE) is commonly used to elicit skeletal muscle adaptation. Relative intensity of a training load links closely with the outcomes of regular RE. This study examined the rating of perceived exertion (RPE) responses to acute bouts of RE using imposed (40% and 70% of 1 repetition maximum [1RM]) and self-selected (SS) loads in recreationally trained women. Twenty physically active women (23.15 ± 2.92 years), who reported regular RE training of at least 3 weekly sessions for the past year, volunteered to participate. During the initial visit, participants completed 1RM testing on 4 exercises in the following order: leg extension, chest press, leg curl, and lat pull-down. On subsequent visits, the same exercises were completed at the SS or imposed loads. The RPE was assessed after the completion of each set of exercises during the 3 RE conditions using the Borg-15 category scale. Self-selected loads corresponded to an average of approximately 57%1RM (±7.62). Overall, RPE increased with load (40%1RM = 11.26 [±1.95]; SS 57%1RM = 13.94 [±1.58]; and, 70%1RM = 15.52 [±2.05]). Reflecting the linear pattern found between load and perceived effort, the present data provide evidence that RPE levels less than 15 likely equate to loads which are not consistent with contemporary American College of Sports Medicine (ACSM) guidelines for enhancing musculoskeletal health which includes strength and hypertrophy. Women desiring increases in strength and lean mass likely need to train at an exertion level at or surpassing a rating of 15 on the Borg-15 category. This article examined the modification of training load on perceived exertion, but other variables, such as the number of repetitions completed, may also be targeted to achieve a desired RPE. The primary understanding is that women who engage in RE may not self-select loads that are consistent with the ACSM recommendations for musculoskeletal health.

Evaluation of strength-controlling defects in paper by stress concentration analyses

Treesearch

John M. Considine; David W. Vahey; James W. Evans; Kevin T. Turner; Robert E. Rowlands

2011-01-01

Cellulosic webs, such as paper materials, are composed of an interwoven, bonded network of cellulose fibers. Strength-controlling parameters in these webs are influenced by constituent fibers and method of processing and manufacture. Instead of estimating the effect on tensile strength of each processing/manufacturing variable, this study modifies and compares the...

Positive Psychological Strengths and School Engagement in Primary School Children

ERIC Educational Resources Information Center

Wilkins, Bronwyn; Boman, Peter; Mergler, Amanda

2015-01-01

A sizeable body of research has investigated the impact of specific character strengths or traits on significant outcomes. Some recent research is beginning to consider the effects of groups of strengths, combined as a higher order variable and termed covitality. This study investigated the combined influence of four positive character traits,…

Hand grip strength and associated factors in non-institutionalised men and women 50 years and older in South Africa.

PubMed

Ramlagan, Shandir; Peltzer, Karl; Phaswana-Mafuya, Nancy

2014-01-07

Little is known about the prevalence, predictors and gender differences in hand grip strength of older adults in Africa. This study aims to investigate social and health differences in hand grip strength among older adults in a national probability sample of older South Africans who participated in the Study of Global Ageing and Adults Health (SAGE wave 1) in 2008. We conducted a national population-based cross-sectional study with a sample of 3840 men and women aged 50 years or older in South Africa. The questionnaire included socio-demographic characteristics, health variables, and anthropometric measurements. Linear multivariate regression analysis was performed to assess the association of social factors, health variables and grip strength. The mean overall hand grip strength was 37.9 kgs for men (mean age 61.1 years, SD = 9.1) and 31.5 kgs for women (mean age 62.0 years, SD = 9.7). In multivariate analysis among men, greater height, not being underweight and lower functional disability was associated with greater grip strength, and among women, greater height, better cognitive functioning, and lower functional disability were associated with greater grip strength. Greater height and lower functional disability were found for both older South African men and women to be significantly associated with grip strength.

Anthropometric, biomechanical, and isokinetic strength predictors of ball release speed in high-performance cricket fast bowlers.

PubMed

Wormgoor, Shohn; Harden, Lois; Mckinon, Warrick

2010-07-01

Fast bowling is fundamental to all forms of cricket. The purpose of this study was to identify parameters that contribute to high ball release speeds in cricket fast bowlers. We assessed anthropometric dimensions, concentric and eccentric isokinetic strength of selected knee and shoulder muscle groups, and specific aspects of technique from a single delivery in 28 high-performance fast bowlers (age 22.0 +/- 3.0 years, ball release speed 34.0 +/- 1.3 m s(-1)). Six 50-Hz cameras and the Ariel Performance Analysis System software were used to analyse the fast and accurate deliveries. Using Pearson's correlation, parameters that showed significant associations with ball release speed were identified. The findings suggest that greater front leg knee extension at ball release (r=0.52), shoulder alignment in the transverse plane rotated further away from the batsman at front foot strike (r=0.47), greater ankle height during the delivery stride (r=0.44), and greater shoulder extension strength (r=0.39) contribute significantly to higher ball release speeds. Predictor variables failed to allow their incorporation into a multivariate model, which is known to exist in less accomplished bowlers, suggesting that factors that determine ball release speed found in other groups may not apply to high-performance fast bowlers.

Effect of process variables on the calorific value and compressive strength of the briquettes made from high moisture Empty Fruit Bunches (EFB)

NASA Astrophysics Data System (ADS)

Helwani, Z.; Fatra, W.; Arifin, L.; Othman, M. R.; Syapsan

2018-04-01

In this study, the manual hydraulic press was designed to prepare the briquettes from selected biomass waste. Each biomass was sun-dried and milled into small particle sizes before mixing with crude glycerol that used as a biomass binder. The effects of applied pressure levels of 100, 110, 120 bars, the particle size of 60, 80 and 100 mesh and the binder composition on the density, compressive strength and calorific heating value of the prepared briquettes were investigated using response surface methodology (RSM). Results showed that the briquettes have an average inside diameter, average outside diameter, and height of 12, 38, and 25-30 mm, respectively. The density of the briquettes increased with increasing the applied pressure, was in the range of 623-923 kg/m3. The densest briquettes were obtained at 80 mesh of particle size, 53:47 binder composition ratio and 110 bars of pressurizing. The heating value of the briquette reached up to 28.99 MJ/kg obtained on the particle size of 80 mesh, 53:47 binder composition, and 110 bars and the best compressive strength of 6.991 kg/cm2 obtained at a particle size of 100 mesh, 60:40 binder composition, and 120 bars. Process conditions influence the calorific value significantly.

Clinimetric properties of lower limb neurological impairment tests for children and young people with a neurological condition: A systematic review

PubMed Central

Locke, Melissa; Hill, Bridget; Wells, Cherie; Bialocerkowski, Andrea

2017-01-01

Background Clinicians and researchers require sound neurological tests to measure changes in neurological impairments necessary for clinical decision-making. Little evidence-based guidance exists for selecting and interpreting an appropriate, paediatric-specific lower limb neurological test aimed at the impairment level. Objective To determine the clinimetric evidence underpinning neurological impairment tests currently used in paediatric rehabilitation to evaluate muscle strength, tactile sensitivity, and deep tendon reflexes of the lower limb in children and young people with a neurological condition. Methods Thirteen databases were systematically searched in two phases, from the date of database inception to 16 February 2017. Lower limb neurological impairment tests were first identified which evaluated muscle strength, tactile sensitivity or deep tendon reflexes in children or young people under 18 years of age with a neurological condition. Papers containing clinimetric evidence of these tests were then identified. The methodological quality of each paper was critically appraised using standardised tools and clinimetric evidence synthesised for each test. Results Thirteen papers were identified, which provided clinimetric evidence on six neurological tests. Muscle strength tests had the greatest volume of clinimetric evidence, however this evidence focused on reliability. Studies were variable in quality with inconsistent results. Clinimetric evidence for tactile sensitivity impairment tests was conflicting and difficult to extrapolate. No clinimetric evidence was found for impairment tests of deep tendon reflexes. Conclusions Limited high-quality clinimetric evidence exists for lower limb neurological impairment tests in children and young people with a neurological condition. Results of currently used neurological tests, therefore, should be interpreted with caution. Robust clinimetric evidence on these tests is required for clinicians and researchers to effectively select and evaluate rehabilitation interventions. PMID:28671957

Probabilistic Modeling of Ceramic Matrix Composite Strength

NASA Technical Reports Server (NTRS)

Shan, Ashwin R.; Murthy, Pappu L. N.; Mital, Subodh K.; Bhatt, Ramakrishna T.

1998-01-01

Uncertainties associated with the primitive random variables such as manufacturing process (processing temperature, fiber volume ratio, void volume ratio), constituent properties (fiber, matrix and interface), and geometric parameters (ply thickness, interphase thickness) have been simulated to quantify the scatter in the first matrix cracking strength (FMCS) and the ultimate tensile strength of SCS-6/RBSN (SiC fiber (SCS-6) reinforced reaction-bonded silicon nitride composite) ceramic matrix composite laminate at room temperature. Cumulative probability distribution function for the FMCS and ultimate tensile strength at room temperature (RT) of (0)(sub 8), (0(sub 2)/90(sub 2), and (+/-45(sub 2))(sub S) laminates have been simulated and the sensitivity of primitive variables to the respective strengths have been quantified. Computationally predicted scatter of the strengths for a uniaxial laminate have been compared with those from limited experimental data. Also the experimental procedure used in the tests has been described briefly. Results show a very good agreement between the computational simulation and the experimental data. Dominating failure modes in (0)(sub 8), (0/90)(sub s) and (+/-45)(sub S) laminates have been identified. Results indicate that the first matrix cracking strength for the (0)(sub S), and (0/90)(sub S) laminates is sensitive to the thermal properties, modulus and strengths of both the fiber and matrix whereas the ultimate tensile strength is sensitive to the fiber strength and the fiber volume ratio. In the case of a (+/-45)(sub S), laminate, both the FMCS and the ultimate tensile strengths have a small scatter range and are sensitive to the fiber tensile strength as well as the fiber volume ratio.

The role of selection on evolutionary rescue

NASA Astrophysics Data System (ADS)

Amirjanov, Adil

The paper investigates the role of selection on evolutionary rescue of population. The statistical mechanics technique is used to model dynamics of a population experiencing a natural selection and an abrupt change in the environment. The paper assesses the selective pressure produced by two different mechanisms: by strength of resistance and by strength of selection (by intraspecific competition). It is shown that both mechanisms are capable of providing an evolutionary rescue of population in particular conditions. However, for a small level of an extinction rate, the population cannot be rescued without intraspecific competition.

A lower extremity strength-based profile of NCAA Division I women's basketball and gymnastics athletes: implications for knee joint injury risk assessment.

PubMed

Thompson, Brennan J; Cazier, Curtis S; Bressel, Eadric; Dolny, Dennis G

2018-08-01

This study aimed to provide a comprehensive strength-based physiological profile of women's NCAA Division I basketball and gymnastic athletes; and to make sport-specific comparisons for various strength characteristics of the knee flexor and extensor muscles. A focus on antagonist muscle balance (hamstrings-to-quadriceps ratios, H:Q) was used to elucidate vulnerabilities in these at-risk female athletes. Fourteen NCAA Division I women's basketball and 13 gymnastics athletes performed strength testing of the knee extensors and flexors. Outcome measures included absolute and relative (body mass normalised) peak torque (PT), rate of torque development at 50, 100, 200 ms (RTD50 etc.) and H:Q ratios of all variables. The basketball athletes had greater absolute strength for all variables except for isokinetic PT at 240°s -1 and isometric RTD50 for the knee extensors. Gymnasts showed ~20% weaker body mass relative concentric PT for the knee flexors at 60 and 120°·s -1 , and decreased conventional H:Q ratios at 60 and 240°·s -1 (~15%). These findings suggest that collegiate level gymnastics athletes may be prone to increased ACL injury risk due to deficient knee flexor strength and H:Q strength imbalance. Coaches may use these findings when implementing injury prevention screening and/or for individualised strength training programming centered around an athletes strength-related deficits.

Effect of a New Surface Treatment Solution on the Bond Strength of Composite to Enamel

DTIC Science & Technology

2016-06-01

enamel ( Erickson et al., 2005). More significantly, clinical studies have shown significantly less marginal defects and staining with selective...using phosphoric acid. Erickson et al., (2009) also found improved bond strengths with a selective-etch step and attributed this to the degree of...cut enamel and dentin. Oper Dent 2005;30(1):39-49. Erickson RL, Barkmeier WW, Kimmes NS. Bond strength of self-etch adhesives to pre-etched

Engineering Properties and Correlation Analysis of Fiber Cementitious Materials

PubMed Central

Lin, Wei-Ting; Wu, Yuan-Chieh; Cheng, An; Chao, Sao-Jeng; Hsu, Hui-Mi

2014-01-01

This study focuses on the effect of the amount of silica fume addition and volume fraction of steel fiber on the engineering properties of cementitious materials. Test variables include dosage of silica fume (5% and 10%), water/cement ratio (0.35 and 0.55) and steel fiber dosage (0.5%, 1.0% and 2.0%). The experimental results included: compressive strength, direct tensile strength, splitting tensile strength, surface abrasion and drop-weight test, which were collected to carry out the analysis of variance to realize the relevancy and significance between material parameters and those mechanical properties. Test results illustrate that the splitting tensile strength, direct tensile strength, strain capacity and ability of crack-arresting increase with increasing steel fiber and silica fume dosages, as well as the optimum mixture of the fiber cementitious materials is 5% replacement silica fume and 2% fiber dosage. In addition, the Pearson correlation coefficient was conducted to evaluate the influence of the material variables and corresponds to the experiment result. PMID:28788256

A Shock-Refracted Acoustic Wave Model for Screech Amplitude in Supersonic Jets

NASA Technical Reports Server (NTRS)

Kandula, Max

2007-01-01

A physical model is proposed for the estimation of the screech amplitude in underexpanded supersonic jets. The model is based on the hypothesis that the interaction of a plane acoustic wave with stationary shock waves provides amplification of the transmitted acoustic wave upon traversing the shock. Powell's discrete source model for screech incorporating a stationary array of acoustic monopoles is extended to accommodate variable source strength. The proposed model reveals that the acoustic sources are of increasing strength with downstream distance. It is shown that the screech amplitude increases with the fully expanded jet Mach number. Comparisons of predicted screech amplitude with available test data show satisfactory agreement. The effect of variable source strength on the directivity of the fundamental (first harmonic, lowest frequency mode) and the second harmonic (overtone) is found to be unimportant with regard to the principal lobe (main or major lobe) of considerable relative strength, and is appreciable only in the secondary or minor lobes (of relatively weaker strength).

A Shock-Refracted Acoustic Wave Model for the Prediction of Screech Amplitude in Supersonic Jets

NASA Technical Reports Server (NTRS)

Kandula, Max

2007-01-01

A physical model is proposed for the estimation of the screech amplitude in underexpanded supersonic jets. The model is based on the hypothesis that the interaction of a plane acoustic wave with stationary shock waves provides amplification of the transmitted acoustic wave upon traversing the shock. Powell's discrete source model for screech incorporating a stationary array of acoustic monopoles is extended to accommodate variable source strength. The proposed model reveals that the acoustic sources are of increasing strength with downstream distance. It is shown that the screech amplitude increases with the fuiiy expanded jet Mach number. Comparisons of predicted screech amplitude with available test data show satisfactory agreement. The effect of variable source strength on directivity of the fundamental (first harmonic, lowest frequency mode) and the second harmonic (overtone) is found to be unimportant with regard to the principal lobe (main or major lobe) of considerable relative strength, and is appreciable only in the secondary or minor lobes (of relatively weaker strength

Integrating Mediators and Moderators in Research Design

ERIC Educational Resources Information Center

MacKinnon, David P.

2011-01-01

The purpose of this article is to describe mediating variables and moderating variables and provide reasons for integrating them in outcome studies. Separate sections describe examples of moderating and mediating variables and the simplest statistical model for investigating each variable. The strengths and limitations of incorporating mediating…

Generalized Reliability Methodology Applied to Brittle Anisotropic Single Crystals. Degree awarded by Washington Univ., 1999

NASA Technical Reports Server (NTRS)

Salem, Jonathan A.

2002-01-01

A generalized reliability model was developed for use in the design of structural components made from brittle, homogeneous anisotropic materials such as single crystals. The model is based on the Weibull distribution and incorporates a variable strength distribution and any equivalent stress failure criteria. In addition to the reliability model, an energy based failure criterion for elastically anisotropic materials was formulated. The model is different from typical Weibull-based models in that it accounts for strength anisotropy arising from fracture toughness anisotropy and thereby allows for strength and reliability predictions of brittle, anisotropic single crystals subjected to multiaxial stresses. The model is also applicable to elastically isotropic materials exhibiting strength anisotropy due to an anisotropic distribution of flaws. In order to develop and experimentally verify the model, the uniaxial and biaxial strengths of a single crystal nickel aluminide were measured. The uniaxial strengths of the <100> and <110> crystal directions were measured in three and four-point flexure. The biaxial strength was measured by subjecting <100> plates to a uniform pressure in a test apparatus that was developed and experimentally verified. The biaxial strengths of the single crystal plates were estimated by extending and verifying the displacement solution for a circular, anisotropic plate to the case of a variable radius and thickness. The best correlation between the experimental strength data and the model predictions occurred when an anisotropic stress analysis was combined with the normal stress criterion and the strength parameters associated with the <110> crystal direction.

Occupational-Specific Strength Predicts Astronaut-Related Task Performance in a Weighted Suit.

PubMed

Taylor, Andrew; Kotarsky, Christopher J; Bond, Colin W; Hackney, Kyle J

2018-01-01

Future space missions beyond low Earth orbit will require deconditioned astronauts to perform occupationally relevant tasks within a planetary spacesuit. The prediction of time-to-completion (TTC) of astronaut tasks will be critical for crew safety, autonomous operations, and mission success. This exploratory study determined if the addition of task-specific strength testing to current standard lower body testing would enhance the prediction of TTC in a 1-G test battery. Eight healthy participants completed NASA lower body strength tests, occupationally specific strength tests, and performed six task simulations (hand drilling, construction wrenching, incline walking, collecting weighted samples, and dragging an unresponsive crewmember to safety) in a 48-kg weighted suit. The TTC for each task was recorded and summed to obtain a total TTC for the test battery. Linear regression was used to predict total TTC with two models: 1) NASA lower body strength tests; and 2) NASA lower body strength tests + occupationally specific strength tests. Total TTC of the test battery ranged from 20.2-44.5 min. The lower body strength test alone accounted for 61% of the variability in total TTC. The addition of hand drilling and wrenching strength tests accounted for 99% of the variability in total TTC. Adding occupationally specific strength tests (hand drilling and wrenching) to standard lower body strength tests successfully predicted total TTC in a performance test battery within a weighted suit. Future research should couple these strength tests with higher fidelity task simulations to determine the utility and efficacy of task performance prediction.Taylor A, Kotarsky CJ, Bond CW, Hackney KJ. Occupational-specific strength predicts astronaut-related task performance in a weighted suit. Aerosp Med Hum Perform. 2018; 89(1):58-62.

Probabilistic micromechanics for metal matrix composites

NASA Astrophysics Data System (ADS)

Engelstad, S. P.; Reddy, J. N.; Hopkins, Dale A.

A probabilistic micromechanics-based nonlinear analysis procedure is developed to predict and quantify the variability in the properties of high temperature metal matrix composites. Monte Carlo simulation is used to model the probabilistic distributions of the constituent level properties including fiber, matrix, and interphase properties, volume and void ratios, strengths, fiber misalignment, and nonlinear empirical parameters. The procedure predicts the resultant ply properties and quantifies their statistical scatter. Graphite copper and Silicon Carbide Titanlum Aluminide (SCS-6 TI15) unidirectional plies are considered to demonstrate the predictive capabilities. The procedure is believed to have a high potential for use in material characterization and selection to precede and assist in experimental studies of new high temperature metal matrix composites.

Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing.

PubMed

Luecke, William E; Slotwinski, John A

2014-01-01

Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands.

Seasonal mean pressure reconstruction for the North Atlantic (1750 1850) based on early marine data

NASA Astrophysics Data System (ADS)

Gallego, D.; Garcia-Herrera, R.; Ribera, P.; Jones, P. D.

2005-12-01

Measurements of wind strength and direction abstracted from European ships' logbooks during the recently finished CLIWOC project have been used to produce the first gridded Sea Level Pressure (SLP) reconstruction for the 1750-1850 period over the North Atlantic based solely on marine data. The reconstruction is based on a spatial regression analysis calibrated by using data taken from the ICOADS database. An objective methodology has been developed to select the optimal calibration period and spatial domain of the reconstruction by testing several thousands of possible models. The finally selected area, limited by the performance of the regression equations and by the availability of data, covers the region between 28° N and 52° N close to the European coast and between 28° N and 44° N in the open Ocean. The results provide a direct measure of the strength and extension of the Azores High during the 101 years of the study period. The comparison with the recent land-based SLP reconstruction by Luterbacher et al. (2002) indicates the presence of a common signal. The interannual variability of the CLIWOC reconstructions is rather high due to the current scarcity of abstracted wind data in the areas with best response in the regression. Guidelines are proposed to optimize the efficiency of future abstraction work.

Seasonal mean pressure reconstruction for the North Atlantic (1750 1850) based on early marine data

NASA Astrophysics Data System (ADS)

Gallego, D.; Garcia-Herrera, R.; Ribera, P.; Jones, P. D.

2005-08-01

Measures of wind strength and direction abstracted from European ships' logbooks during the recently finished CLIWOC project have been used to produce the first gridded Sea Level Pressure (SLP) reconstruction for the 1750-1850 period over the North Atlantic based solely on marine data. The reconstruction is based on a spatial regression analysis calibrated by using data taken from the ICOADS database. An objective methodology has been developed to select the optimal calibration period and spatial domain of the reconstruction by testing several thousands of possible models. The finally selected area, limited by the performance of the regression equations and by the availability of data, covers the region between 28°N and 52°N close to the European coast and between 28°N and 44°N in the open Ocean. The results provide a direct measure of the strength and extension of the Azores High during the 101 years of the study period. The comparison with the recent land-based SLP reconstruction by Luterbacher et al. (2002) indicates the presence of a common signal. The interannual variability of the CLIWOC reconstructions is rather high due to the current scarcity of abstracted wind data in the areas with best response in the regression. Guidelines are proposed to optimize the efficiency of future abstraction work.

Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing

PubMed Central

Luecke, William E; Slotwinski, John A

2014-01-01

Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands. PMID:26601037

Combat Stress Decreases Memory of Warfighters in Action.

PubMed

Delgado-Moreno, Rosa; Robles-Pérez, José Juan; Clemente-Suárez, Vicente Javier

2017-08-01

The present research aimed to analyze the effect of combat stress in the psychophysiological response and attention and memory of warfighters in a simulated combat situation. Variables of blood oxygen saturation, heart rate, blood glucose, blood lactate, body temperature, lower body muscular strength manifestation, cortical arousal, autonomic modulation, state anxiety and memory and attention through a postmission questionnaire were analyzed before and after a combat simulation in 20 male professional Spanish Army warfighters. The combat simulation produces a significant increase (p < 0.05) in explosive leg strength, rated perceived exertion, blood glucose, blood lactate, somatic anxiety, heart rate, and low frequency domain of the HRV (LF) and a significant decrease of high frequency domain of the heart rate variability (HF). The percentage of correct response in the postmission questionnaire parameters show that elements more related with a physical integrity threat are the most correctly remembered. There were significant differences in the postmission questionnaire variables when participants were divided by the cortical arousal post: sounds no response, mobile phone correct, mobile phone no response, odours correct. The correlation analysis showed positive correlations: LF post/body temperature post, HF post/correct sound, body temperature post/glucose post, CFFTpre/lactate post, CFFT post/wrong sound, glucose post/AC pre, AC post/wrong fusil, AS post/SC post and SC post/wrong olfactory; and negative correlations: LF post/correct sound, body temperature post/lactate post and glucose post/lactate post. This data suggest that combat stress actives fight-flight system of soldiers. As conclusion, Combat stress produces an increased psychophysiological response that cause a selective decrease of memory, depending on the nature, dangerous or harmless of the objects.

Diagnostic ultrasound estimates of muscle mass and muscle quality discriminate between women with and without sarcopenia

PubMed Central

Ismail, Catheeja; Zabal, Johannah; Hernandez, Haniel J.; Woletz, Paula; Manning, Heather; Teixeira, Carla; DiPietro, Loretta; Blackman, Marc R.; Harris-Love, Michael O.

2015-01-01

Introduction: Age-related changes in muscle mass and muscle tissue composition contribute to diminished strength in older adults. The objectives of this study are to examine if an assessment method using mobile diagnostic ultrasound augments well-known determinants of lean body mass (LBM) to aid sarcopenia staging, and if a sonographic measure of muscle quality is associated with muscle performance. Methods: Twenty community-dwelling female subjects participated in the study (age = 43.4 ± 20.9 years; BMI: 23.8, interquartile range: 8.5). Dual energy X-ray absorptiometry (DXA) and diagnostic ultrasound morphometry were used to estimate LBM. Muscle tissue quality was estimated via the echogenicity using grayscale histogram analysis. Peak force was measured with grip dynamometry and scaled for body size. Bivariate and multiple regression analyses were used to determine the association of the predictor variables with appendicular lean mass (aLM/ht2), and examine the relationship between scaled peak force values and muscle echogenicity. The sarcopenia LBM cut point value of 6.75 kg/m2 determined participant assignment into the Normal LBM and Low LBM subgroups. Results: The selected LBM predictor variables were body mass index (BMI), ultrasound morphometry, and age. Although BMI exhibited a significant positive relationship with aLM/ht2 (adj. R2 = 0.61, p < 0.001), the strength of association improved with the addition of ultrasound morphometry and age as predictor variables (adj. R2 = 0.85, p < 0.001). Scaled peak force was associated with age and echogenicity (adj. R2 = 0.53, p < 0.001), but not LBM. The Low LBM subgroup of women (n = 10) had higher scaled peak force, lower BMI, and lower echogenicity values in comparison to the Normal LBM subgroup (n = 10; p < 0.05). Conclusions: Diagnostic ultrasound morphometry values are associated with LBM, and improve the BMI predictive model for aLM/ht2 in women. In addition, ultrasound proxy measures of muscle quality are more strongly associated with strength than muscle mass within the study sample. PMID:26578974

Diagnostic ultrasound estimates of muscle mass and muscle quality discriminate between women with and without sarcopenia.

PubMed

Ismail, Catheeja; Zabal, Johannah; Hernandez, Haniel J; Woletz, Paula; Manning, Heather; Teixeira, Carla; DiPietro, Loretta; Blackman, Marc R; Harris-Love, Michael O

2015-01-01

Age-related changes in muscle mass and muscle tissue composition contribute to diminished strength in older adults. The objectives of this study are to examine if an assessment method using mobile diagnostic ultrasound augments well-known determinants of lean body mass (LBM) to aid sarcopenia staging, and if a sonographic measure of muscle quality is associated with muscle performance. Twenty community-dwelling female subjects participated in the study (age = 43.4 ± 20.9 years; BMI: 23.8, interquartile range: 8.5). Dual energy X-ray absorptiometry (DXA) and diagnostic ultrasound morphometry were used to estimate LBM. Muscle tissue quality was estimated via the echogenicity using grayscale histogram analysis. Peak force was measured with grip dynamometry and scaled for body size. Bivariate and multiple regression analyses were used to determine the association of the predictor variables with appendicular lean mass (aLM/ht(2)), and examine the relationship between scaled peak force values and muscle echogenicity. The sarcopenia LBM cut point value of 6.75 kg/m(2) determined participant assignment into the Normal LBM and Low LBM subgroups. The selected LBM predictor variables were body mass index (BMI), ultrasound morphometry, and age. Although BMI exhibited a significant positive relationship with aLM/ht(2) (adj. R (2) = 0.61, p < 0.001), the strength of association improved with the addition of ultrasound morphometry and age as predictor variables (adj. R (2) = 0.85, p < 0.001). Scaled peak force was associated with age and echogenicity (adj. R (2) = 0.53, p < 0.001), but not LBM. The Low LBM subgroup of women (n = 10) had higher scaled peak force, lower BMI, and lower echogenicity values in comparison to the Normal LBM subgroup (n = 10; p < 0.05). Diagnostic ultrasound morphometry values are associated with LBM, and improve the BMI predictive model for aLM/ht(2) in women. In addition, ultrasound proxy measures of muscle quality are more strongly associated with strength than muscle mass within the study sample.

The resistance of selected high strength alloys to embrittlement by a hydrogen environment. [iron and cobalt base alloys

NASA Technical Reports Server (NTRS)

Benson, R. B., Jr.

1974-01-01

Selected high strength iron base and cobalt base alloys were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature. These alloys were strengthened initially by cold working which produced strain induced martensite and fcc mechanical twins in an fcc matrix. Heat treatment of the cobalt base alloy after cold working produced carbide precipitates with retention of an hcp epsilon phase which increased the yield strength level. High strength alloys can be produced which have some resistance to degradation of mechanical properties by a hydrogen environment under certain conditions.

A Framework for the Analysis of the Reserve Officer Augmentation Process in the United States Marine Corps

DTIC Science & Technology

1987-12-01

occupation group, category (i.e., strength, loss, etc.), years of commissioned service (YCS), grade, occupation, source of commission, education, sex ...OF MCORP OUTPUT OCCUPATION GROUP: All CAT: Strength YCS: 01 - 09 GRADE: All Unrestricted Officers OCCUPATION: All SOURCE: All EDUCATION: All SEX : All...source of commission, sex , MOS, GCT, and other pertinent variables such as the performance index. A Probit or Logit model could be utilized. The variables

National Databases for Neurosurgical Outcomes Research: Options, Strengths, and Limitations.

PubMed

Karhade, Aditya V; Larsen, Alexandra M G; Cote, David J; Dubois, Heloise M; Smith, Timothy R

2017-08-05

Quality improvement, value-based care delivery, and personalized patient care depend on robust clinical, financial, and demographic data streams of neurosurgical outcomes. The neurosurgical literature lacks a comprehensive review of large national databases. To assess the strengths and limitations of various resources for outcomes research in neurosurgery. A review of the literature was conducted to identify surgical outcomes studies using national data sets. The databases were assessed for the availability of patient demographics and clinical variables, longitudinal follow-up of patients, strengths, and limitations. The number of unique patients contained within each data set ranged from thousands (Quality Outcomes Database [QOD]) to hundreds of millions (MarketScan). Databases with both clinical and financial data included PearlDiver, Premier Healthcare Database, Vizient Clinical Data Base and Resource Manager, and the National Inpatient Sample. Outcomes collected by databases included patient-reported outcomes (QOD); 30-day morbidity, readmissions, and reoperations (National Surgical Quality Improvement Program); and disease incidence and disease-specific survival (Surveillance, Epidemiology, and End Results-Medicare). The strengths of large databases included large numbers of rare pathologies and multi-institutional nationally representative sampling; the limitations of these databases included variable data veracity, variable data completeness, and missing disease-specific variables. The improvement of existing large national databases and the establishment of new registries will be crucial to the future of neurosurgical outcomes research. Copyright © 2017 by the Congress of Neurological Surgeons

Developing a Markov Model for Forecasting End Strength of Selected Marine Corps Reserve (SMCR) Officers

DTIC Science & Technology

2013-03-01

moving average ( ARIMA ) model because the data is not a times series. The best a manpower planner can do at this point is to make an educated assumption...MARKOV MODEL FOR FORECASTING END STRENGTH OF SELECTED MARINE CORPS RESERVE (SMCR) OFFICERS by Anthony D. Licari March 2013 Thesis Advisor...March 2013 3. REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE DEVELOPING A MARKOV MODEL FOR FORECASTING END STRENGTH OF

Do physiological measures predict selected CrossFit(®) benchmark performance?

PubMed

Butcher, Scotty J; Neyedly, Tyler J; Horvey, Karla J; Benko, Chad R

2015-01-01

CrossFit(®) is a new but extremely popular method of exercise training and competition that involves constantly varied functional movements performed at high intensity. Despite the popularity of this training method, the physiological determinants of CrossFit performance have not yet been reported. The purpose of this study was to determine whether physiological and/or muscle strength measures could predict performance on three common CrossFit "Workouts of the Day" (WODs). Fourteen CrossFit Open or Regional athletes completed, on separate days, the WODs "Grace" (30 clean and jerks for time), "Fran" (three rounds of thrusters and pull-ups for 21, 15, and nine repetitions), and "Cindy" (20 minutes of rounds of five pull-ups, ten push-ups, and 15 bodyweight squats), as well as the "CrossFit Total" (1 repetition max [1RM] back squat, overhead press, and deadlift), maximal oxygen consumption (VO2max), and Wingate anaerobic power/capacity testing. Performance of Grace and Fran was related to whole-body strength (CrossFit Total) (r=-0.88 and -0.65, respectively) and anaerobic threshold (r=-0.61 and -0.53, respectively); however, whole-body strength was the only variable to survive the prediction regression for both of these WODs (R (2)=0.77 and 0.42, respectively). There were no significant associations or predictors for Cindy. CrossFit benchmark WOD performance cannot be predicted by VO2max, Wingate power/capacity, or either respiratory compensation or anaerobic thresholds. Of the data measured, only whole-body strength can partially explain performance on Grace and Fran, although anaerobic threshold also exhibited association with performance. Along with their typical training, CrossFit athletes should likely ensure an adequate level of strength and aerobic endurance to optimize performance on at least some benchmark WODs.

The left hand second to fourth digit ratio (2D:4D) is not related to any physical fitness component in adolescent girls.

PubMed

Peeters, Maarten W; Van Aken, Katrijn; Claessens, Albrecht L

2013-01-01

The second to fourth-digit-ratio (2D:4D), a putative marker of prenatal androgen action and a sexually dimorphic trait, has been suggested to be related with fitness and sports performance, although results are not univocal. Most studies however focus on a single aspect of physical fitness or one sports discipline. In this study the 2D:4D ratio of 178 adolescent girls (age 13.5-18 y) was measured on X-rays of the left hand. The relation between 2D:4D digit ratio and multiple aspects of physical fitness (balance, speed of limb movement, flexibility, explosive strength, static strength, trunk strength, functional strength, running speed/agility, and endurance) was studied by correlation analyses and stepwise multiple regression. For comparison the relation between these physical fitness components and a selected number of objectively measured anthropometric traits (stature, mass, BMI, somatotype components and the Bayer & Bailey androgyny index) are presented alongside the results of 2D:4D digit ratio. Left hand 2D:4D digit ratio (0.925±0.019) was not significantly correlated with any of the physical fitness components nor any of the anthropometric variables included in the present study. 2D:4D did not enter the multiple stepwise regression for any of the physical fitness components in which other anthropometric traits explained between 9.2% (flexibility) and 33.9% (static strength) of variance. Unlike other anthropometric traits the 2D:4D digit ratio does not seem to be related to any physical fitness component in adolescent girls and therefore most likely should not be considered in talent detection programs for sporting ability in girls.

Probabilistic micromechanics of woven ceramic matrix composites

NASA Astrophysics Data System (ADS)

Goldsmith, Marlana

Woven ceramic matrix composites are a special class of composite materials that are of current interest for harsh thermo-structural conditions such as those encountered by hypersonic vehicle systems and turbine engine components. Testing of the materials is expensive, especially as materials are constantly redesigned. Randomness in the tow architecture, as well as the randomly shaped and spaced voids that are produced as a result of the manufacturing process, are features that contribute to variability in stiffness and strength. The goal of the research is to lay a foundation in which characteristics of the geometry can be translated into material properties. The research first includes quantifying the architectural variability based on 2D micrographs of a 5 harness satin CVI (Chemical Vapor Infiltration) SiC/SiC composite. The architectural variability is applied to a 2D representative volume element (RVE) in order to evaluate which aspects of the architecture are important to model in order to capture the variability found in the cross sections. Tow width, tow spacing, and tow volume fraction were found to have some effect on the variability, but voids were found to have a large influence on transverse stiffness, and a separate study was conducted to determine which characteristics of the voids are most critical to model. It was found that the projected area of the void perpendicular to the transverse direction and the number of voids modeled had a significant influence on the stiffness. The effect of varying architecture on the variability of in-plane tensile strength was also studied using the Brittle Cracking Model for Concrete in the commercial finite element software, Abaqus. A maximum stress criterion is used to evaluate failure, and the stiffness of failed elements is gradually degraded such that the energy required to open a crack (fracture energy) is dissipated during this degradation process. While the varying architecture did not create variability in the in-plane stiffness, it does contribute significantly to the variability of in-plane strength as measured by a 0.02% offset method. Applying spatially random strengths for the constituents did not contribute to variability in strength as measured by the 0.02% offset. The results of this research may be of interest to those designing materials, as well as those using the material in their design. Having an idea about which characteristics of the architecture affect variability in stiffness may provide guidance to the material designer with respect to which aspects of the architecture can be controlled or improved to decrease the variability of the material properties. The work will also be useful to those desiring to use the complex materials by determining how to link the architectural properties to the mechanical properties with the ultimate goal of reducing the required number of tests.

Predicting use of ineffective vegetable parenting practices with the Model of Goal Directed Behavior.

PubMed

Baranowski, Tom; Beltran, Alicia; Chen, Tzu-An; Thompson, Debbe; O'Connor, Teresia; Hughes, Sheryl; Diep, Cassandra; Baranowski, Janice C

2015-04-01

Increasing a parent's ability to influence a child's vegetable intake may require reducing the parent's use of ineffective vegetable parenting practices. The present study was designed to understand the psychosocial influences on ineffective vegetable parenting practices. A cross-sectional web-based survey was conducted to model use of ineffective vegetable parenting practices using validated scales from a Model of Goal Directed Vegetable Parenting Practices. The dependent variable was a composite ineffective vegetable parenting practices index. The independent variables included validated subscales of intention, habit, perceived barriers, desire, competence, autonomy, relatedness, attitudes, norms, perceived behavioural control and anticipated emotions. Models were analysed using block regression with backward deletion. Parents of 307 pre-school children (3-5 years old). Variables significantly positively related to ineffective vegetable parenting practices in order of relationship strength included habit of controlling vegetable practices (standardized β=0·349, P<0·0001) and desire (standardized β=0·117, P=0·025). Variables significantly negatively related to ineffective vegetable parenting practices in order of relationship strength included perceived behavioural control of negative parenting practices (standardized β=-0·215, P<0000), the habit of active child involvement in vegetable selection (standardized β=-0·142, P=0·008), anticipated negative parent emotional response to child vegetable refusal (standardized β=-0·133, P=0·009), autonomy (standardized β=-0·118, P=0.014), attitude about negative effects of vegetables (standardized β=-0·118, P=0·015) and descriptive norms (standardized β=-0·103, P=0·032). The model accounted for 40·5 % of the variance in use of ineffective vegetable parenting practices. The present study is the first report of psychometrically tested scales to predict use of ineffective vegetable parenting practices. Innovative intervention procedures will need to be designed and tested to reduce ineffective vegetable parenting practices.

Hand grip strength and anthropometric characteristics in Italian female national basketball teams.

PubMed

Pizzigalli, Luisa; Micheletti Cremasco, Margherita; LA Torre, Antonio; Rainoldi, Alberto; Benis, Roberto

2017-05-01

The aim of this study was to investigate the influence of hand and body dimensions on hand grip strength and to define a reference scale for talent identification in basketball players. Body and hand anthropometric data and the maximal handgrip strength of 109 female Italian basketball National players (Under14-Seniores) were measured. Handgrip strength and arm length trend increased, raising the statistical significant differences only for players from the age of 19 (U20, Seniores) with respect to sub-elite groups (U14, U15) (P<0.05). Handgrip strength showed low positive correlations with height and Body Mass Index but a positive relationships with arm length (r=0.5; P<0.001). Findings underline training and years of practice have effects on increasing handgrip strength. Data show that to select female basketball players by arm length means selecting by handgrip strength. Thus it is possible to suggest that in addition to height, arm length could also be considered a useful parameter in young female talent identification.

A brief review of strength and ballistic assessment methodologies in sport.

PubMed

McMaster, Daniel Travis; Gill, Nicholas; Cronin, John; McGuigan, Michael

2014-05-01

An athletic profile should encompass the physiological, biomechanical, anthropometric and performance measures pertinent to the athlete's sport and discipline. The measurement systems and procedures used to create these profiles are constantly evolving and becoming more precise and practical. This is a review of strength and ballistic assessment methodologies used in sport, a critique of current maximum strength [one-repetition maximum (1RM) and isometric strength] and ballistic performance (bench throw and jump capabilities) assessments for the purpose of informing practitioners and evolving current assessment methodologies. The reliability of the various maximum strength and ballistic assessment methodologies were reported in the form of intra-class correlation coefficients (ICC) and coefficient of variation (%CV). Mean percent differences (Mdiff = [/Xmethod1 - Xmethod2/ / (Xmethod1 + Xmethod2)] x 100) and effect size (ES = [Xmethod2 - Xmethod1] ÷ SDmethod1) calculations were used to assess the magnitude and spread of methodological differences for a given performance measure of the included studies. Studies were grouped and compared according to their respective performance measure and movement pattern. The various measurement systems (e.g., force plates, position transducers, accelerometers, jump mats, optical motion sensors and jump-and-reach apparatuses) and assessment procedures (i.e., warm-up strategies, loading schemes and rest periods) currently used to assess maximum isometric squat and mid-thigh pull strength (ICC > 0.95; CV < 2.0%), 1RM bench press, back squat and clean strength (ICC > 0.91; CV < 4.3%), and ballistic (vertical jump and bench throw) capabilities (ICC > 0.82; CV < 6.5%) were deemed highly reliable. The measurement systems and assessment procedures employed to assess maximum isometric strength [M(Diff) = 2-71%; effect size (ES) = 0.13-4.37], 1RM strength (M(Diff) = 1-58%; ES = 0.01-5.43), vertical jump capabilities (M(Diff) = 2-57%; ES = 0.02-4.67) and bench throw capabilities (M(Diff) = 7-27%; ES = 0.49-2.77) varied greatly, producing trivial to very large effects on these respective measures. Recreational to highly trained athletes produced maximum isometric squat and mid-thigh pull forces of 1,000-4,000 N; and 1RM bench press, back squat and power clean values of 80-180 kg, 100-260 kg and 70-140 kg, respectively. Mean and peak power production across the various loads (body mass to 60% 1RM) were between 300 and 1,500 W during the bench throw and between 1,500 and 9,000 W during the vertical jump. The large variations in maximum strength and power can be attributed to the wide range in physical characteristics between different sports and athletic disciplines, training and chronological age as well as the different measurement systems of the included studies. The reliability and validity outcomes suggest that a number of measurement systems and testing procedures can be implemented to accurately assess maximum strength and ballistic performance in recreational and elite athletes, alike. However, the reader needs to be cognisant of the inherent differences between measurement systems, as selection will inevitably affect the outcome measure. The strength and conditioning practitioner should also carefully consider the benefits and limitations of the different measurement systems, testing apparatuses, attachment sites, movement patterns (e.g., direction of movement, contraction type, depth), loading parameters (e.g., no load, single load, absolute load, relative load, incremental loading), warm-up strategies, inter-trial rest periods, dependent variables of interest (i.e., mean, peak and rate dependent variables) and data collection and processing techniques (i.e., sampling frequency, filtering and smoothing options).

Transformational leadership and group interaction as climate antecedents: a social network analysis.

PubMed

Zohar, Dov; Tenne-Gazit, Orly

2008-07-01

In order to test the social mechanisms through which organizational climate emerges, this article introduces a model that combines transformational leadership and social interaction as antecedents of climate strength (i.e., the degree of within-unit agreement about climate perceptions). Despite their longstanding status as primary variables, both antecedents have received limited empirical research. The sample consisted of 45 platoons of infantry soldiers from 5 different brigades, using safety climate as the exemplar. Results indicate a partially mediated model between transformational leadership and climate strength, with density of group communication network as the mediating variable. In addition, the results showed independent effects for group centralization of the communication and friendship networks, which exerted incremental effects on climate strength over transformational leadership. Whereas centralization of the communication network was found to be negatively related to climate strength, centralization of the friendship network was positively related to it. Theoretical and practical implications are discussed.

Phenology of Scramble Polygyny in a Wild Population of Chrysolemid Beetles: The Opportunity for and the Strength of Sexual Selection

PubMed Central

Baena, Martha Lucía; Macías-Ordóñez, Rogelio

2012-01-01

Recent debate has highlighted the importance of estimating both the strength of sexual selection on phenotypic traits, and the opportunity for sexual selection. We describe seasonal fluctuations in mating dynamics of Leptinotarsa undecimlineata (Coleoptera: Chrysomelidae). We compared several estimates of the opportunity for, and the strength of, sexual selection and male precopulatory competition over the reproductive season. First, using a null model, we suggest that the ratio between observed values of the opportunity for sexual selections and their expected value under random mating results in unbiased estimates of the actual nonrandom mating behavior of the population. Second, we found that estimates for the whole reproductive season often misrepresent the actual value at any given time period. Third, mating differentials on male size and mobility, frequency of male fighting and three estimates of the opportunity for sexual selection provide contrasting but complementary information. More intense sexual selection associated to male mobility, but not to male size, was observed in periods with high opportunity for sexual selection and high frequency of male fights. Fourth, based on parameters of spatial and temporal aggregation of female receptivity, we describe the mating system of L. undecimlineata as a scramble mating polygyny in which the opportunity for sexual selection varies widely throughout the season, but the strength of sexual selection on male size remains fairly weak, while male mobility inversely covaries with mating success. We suggest that different estimates for the opportunity for, and intensity of, sexual selection should be applied in order to discriminate how different behavioral and demographic factors shape the reproductive dynamic of populations. PMID:22761675

Time-Dependent Behavior of High-Strength Kevlar and Vectran Webbing

NASA Technical Reports Server (NTRS)

Jones, Thomas C.; Doggett, William R.

2014-01-01

High-strength Kevlar and Vectran webbings are currently being used by both NASA and industry as the primary load-bearing structure in inflatable space habitation modules. The time-dependent behavior of high-strength webbing architectures is a vital area of research that is providing critical material data to guide a more robust design process for this class of structures. This paper details the results of a series of time-dependent tests on 1-inch wide webbing including an initial set of comparative tests between specimens that underwent realtime and accelerated creep at 65 and 70% of their ultimate tensile strength. Variability in the ultimate tensile strength of the webbings is investigated and compared with variability in the creep life response. Additional testing studied the effects of load and displacement rate, specimen length and the time-dependent effects of preconditioning the webbings. The creep test facilities, instrumentation and test procedures are also detailed. The accelerated creep tests display consistently longer times to failure than their real-time counterparts; however, several factors were identified that may contribute to the observed disparity. Test setup and instrumentation, grip type, loading scheme, thermal environment and accelerated test postprocessing along with material variability are among these factors. Their effects are discussed and future work is detailed for the exploration and elimination of some of these factors in order to achieve a higher fidelity comparison.

Pathway-Based Kernel Boosting for the Analysis of Genome-Wide Association Studies

PubMed Central

Manitz, Juliane; Burger, Patricia; Amos, Christopher I.; Chang-Claude, Jenny; Wichmann, Heinz-Erich; Kneib, Thomas; Bickeböller, Heike

2017-01-01

The analysis of genome-wide association studies (GWAS) benefits from the investigation of biologically meaningful gene sets, such as gene-interaction networks (pathways). We propose an extension to a successful kernel-based pathway analysis approach by integrating kernel functions into a powerful algorithmic framework for variable selection, to enable investigation of multiple pathways simultaneously. We employ genetic similarity kernels from the logistic kernel machine test (LKMT) as base-learners in a boosting algorithm. A model to explain case-control status is created iteratively by selecting pathways that improve its prediction ability. We evaluated our method in simulation studies adopting 50 pathways for different sample sizes and genetic effect strengths. Additionally, we included an exemplary application of kernel boosting to a rheumatoid arthritis and a lung cancer dataset. Simulations indicate that kernel boosting outperforms the LKMT in certain genetic scenarios. Applications to GWAS data on rheumatoid arthritis and lung cancer resulted in sparse models which were based on pathways interpretable in a clinical sense. Kernel boosting is highly flexible in terms of considered variables and overcomes the problem of multiple testing. Additionally, it enables the prediction of clinical outcomes. Thus, kernel boosting constitutes a new, powerful tool in the analysis of GWAS data and towards the understanding of biological processes involved in disease susceptibility. PMID:28785300

Pathway-Based Kernel Boosting for the Analysis of Genome-Wide Association Studies.

PubMed

Friedrichs, Stefanie; Manitz, Juliane; Burger, Patricia; Amos, Christopher I; Risch, Angela; Chang-Claude, Jenny; Wichmann, Heinz-Erich; Kneib, Thomas; Bickeböller, Heike; Hofner, Benjamin

2017-01-01

The analysis of genome-wide association studies (GWAS) benefits from the investigation of biologically meaningful gene sets, such as gene-interaction networks (pathways). We propose an extension to a successful kernel-based pathway analysis approach by integrating kernel functions into a powerful algorithmic framework for variable selection, to enable investigation of multiple pathways simultaneously. We employ genetic similarity kernels from the logistic kernel machine test (LKMT) as base-learners in a boosting algorithm. A model to explain case-control status is created iteratively by selecting pathways that improve its prediction ability. We evaluated our method in simulation studies adopting 50 pathways for different sample sizes and genetic effect strengths. Additionally, we included an exemplary application of kernel boosting to a rheumatoid arthritis and a lung cancer dataset. Simulations indicate that kernel boosting outperforms the LKMT in certain genetic scenarios. Applications to GWAS data on rheumatoid arthritis and lung cancer resulted in sparse models which were based on pathways interpretable in a clinical sense. Kernel boosting is highly flexible in terms of considered variables and overcomes the problem of multiple testing. Additionally, it enables the prediction of clinical outcomes. Thus, kernel boosting constitutes a new, powerful tool in the analysis of GWAS data and towards the understanding of biological processes involved in disease susceptibility.

Comparative study of mechanical properties of direct core build-up materials

PubMed Central

Kumar, Girish; Shivrayan, Amit

2015-01-01

Background and Objectives: The strength greatly influences the selection of core material because core must withstand forces due to mastication and para-function for many years. This study was conducted to evaluate certain mechanical properties of commonly used materials for direct core build-up, including visible light cured composite, polyacid modified composite, resin modified glass ionomer, high copper amalgam, and silver cermet cement. Materials and Methods: All the materials were manipulated according to the manufacturer's recommendations and standard test specimens were prepared. A universal testing machine at different cross-head speed was used to determine all the four mechanical properties. Mean compressive strength, diametral tensile strength, flexural strength, and elastic modulus with standard deviations were calculated. Multiple comparisons of the materials were also done. Results: Considerable differences in compressive strength, diametral tensile strength, and flexural strength were observed. Visible light cured composite showed relatively high compressive strength, diametral tensile strength, and flexural strength compared with the other tested materials. Amalgam showed the highest value for elastic modulus. Silver cermet showed less value for all the properties except for elastic modulus. Conclusions: Strength is one of the most important criteria for selection of a core material. Stronger materials better resist deformation and fracture provide more equitable stress distribution, greater stability, and greater probability of clinical success. PMID:25684905

Shoulder functional ratio in elite junior tennis players.

PubMed

Saccol, Michele Forgiarini; Gracitelli, Guilherme Conforto; da Silva, Rogério Teixeira; Laurino, Cristiano Frota de Souza; Fleury, Anna Maria; Andrade, Marília dos Santos; da Silva, Antonio Carlos

2010-02-01

To evaluate shoulder rotation strength and compare the functional ratio between shoulders of elite junior tennis players. This cross-sectional study evaluated muscular rotation performance of 40 junior tennis players (26 male and 14 female) with an isokinetic dynamometer. Strength variables of external (ER) and internal rotators (IR) in concentric and eccentric modes were considered. For the peak torque functional ratio, the eccentric strength of the ER and the concentric strength of the IR were calculated. All variables related to IR were significantly higher on the dominant compared to the non-dominant side in males and females (p<0.05), but only boys exhibited this dominance effect in ER (p<0.05 and p<0.001). Regarding functional ratios, they were significantly lower for the dominant shoulder (p<0.001) and below 1.00 for both groups, indicating that the eccentric strength of the ER was not greater than the concentric strength of the IR. Elite junior tennis players without shoulder injury have shoulder rotation muscle strength imbalances that alter the normal functional ratio between rotator cuff muscles. Although these differences do not seem to affect the athletic performance, detection and prevention with exercise programs at an early age are recommended. Crown Copyright 2009. Published by Elsevier Ltd. All rights reserved.

Variable Resistance Training Promotes Greater Strength and Power Adaptations Than Traditional Resistance Training in Elite Youth Rugby League Players.

PubMed

Rivière, Maxence; Louit, Loic; Strokosch, Alasdair; Seitz, Laurent B

2017-04-01

Rivière, M, Louit, L, Strokosch, A, and Seitz, LB. Variable resistance training promotes greater strength and power adaptations than traditional resistance training in elite youth rugby league players. J Strength Cond Res 31(4): 947-955, 2017-The purpose of this study was to examine the strength, velocity, and power adaptations in youth rugby league players in response to a variable resistance training (VRT) or traditional free-weight resistance training (TRAD) intervention. Sixteen elite youth players were assigned to a VRT or TRAD group and completed 2 weekly upper- and lower-body strength and power sessions for 6 weeks. Training programs were identical except that the VRT group trained the bench press exercise with 20% of the prescribed load coming from elastic bands. Bench press 1 repetition maximum (1RM) and bench press mean velocity and power at 35, 45, 65, 75, and 85% of 1RM were measured before and after the training intervention, and the magnitude of the changes was determined using effect sizes (ESs). The VRT group experienced larger increases in both absolute (ES = 0.46 vs. 0.20) and relative (ES = 0.41 vs. 0.19) bench press 1RM. Similar results were observed for mean velocity as well as both absolute and relative mean power at 35, 45, 65, 75, and 85% of 1RM. Furthermore, both groups experienced large gains in both velocity and power in the heavier loads but small improvements in the lighter loads. The improvements in both velocity and power against the heavier loads were larger for the VRT group, whereas smaller differences existed between the 2 groups in the lighter loads. Variable resistance training using elastic bands may offer a greater training stimulus than traditional free-weight resistance training to improve upper-body strength, velocity, and power in elite youth rugby league players.

Hand grip strength and associated factors in non-institutionalised men and women 50 years and older in South Africa

PubMed Central

2014-01-01

Background Little is known about the prevalence, predictors and gender differences in hand grip strength of older adults in Africa. This study aims to investigate social and health differences in hand grip strength among older adults in a national probability sample of older South Africans who participated in the Study of Global Ageing and Adults Health (SAGE wave 1) in 2008. Methods We conducted a national population-based cross-sectional study with a sample of 3840 men and women aged 50 years or older in South Africa. The questionnaire included socio-demographic characteristics, health variables, and anthropometric measurements. Linear multivariate regression analysis was performed to assess the association of social factors, health variables and grip strength. Results The mean overall hand grip strength was 37.9 kgs for men (mean age 61.1 years, SD = 9.1) and 31.5 kgs for women (mean age 62.0 years, SD = 9.7). In multivariate analysis among men, greater height, not being underweight and lower functional disability was associated with greater grip strength, and among women, greater height, better cognitive functioning, and lower functional disability were associated with greater grip strength. Conclusions Greater height and lower functional disability were found for both older South African men and women to be significantly associated with grip strength. PMID:24393403

Associations Between Measures of Balance and Lower-Extremity Muscle Strength/Power in Healthy Individuals Across the Lifespan: A Systematic Review and Meta-Analysis.

PubMed

Muehlbauer, Thomas; Gollhofer, Albert; Granacher, Urs

2015-12-01

It has frequently been reported that balance and lower-extremity muscle strength/power are associated with sports-related and everyday activities. Knowledge about the relationship between balance, strength, and power are important for the identification of at-risk individuals because deficits in these neuromuscular components are associated with an increased risk of sustaining injuries and falls. In addition, this knowledge is of high relevance for the development of specifically tailored health and skill-related exercise programs. The objectives of this systematic literature review and meta-analysis were to characterize and, if possible, quantify associations between variables of balance and lower-extremity muscle strength/power in healthy individuals across the lifespan. A computerized systematic literature search was performed in the electronic databases PubMed, Web of Science, and SPORTDiscus up to March 2015 to capture all relevant articles. A systematic approach was used to evaluate the 996 articles identified for initial review. Studies were included only if they investigated healthy individuals aged ≥6 years and tested at least one measure of static steady-state balance (e.g., center of pressure [CoP] displacement during one-legged stance), dynamic steady-state balance (e.g., gait speed), proactive balance (e.g., distance in the functional-reach-test), or reactive balance (e.g., CoP displacement during perturbed one-legged stance), and one measure of maximal strength (e.g., maximum voluntary contraction), explosive force (e.g., rate of force development), or muscle power (e.g., jump height). In total, 37 studies met the inclusionary criteria for review. The included studies were coded for the following criteria: age (i.e., children: 6-12 years, adolescents: 13-18 years, young adults: 19-44 years, middle-aged adults: 45-64 years, old adults: ≥65 years), sex (i.e., female, male), and test modality/outcome (i.e., test for the assessment of balance, strength, and power). Studies with athletes, patients, and/or people with diseases were excluded. Pearson's correlation coefficients were extracted, transformed (i.e., Fisher's z-transformed r z value), aggregated (i.e., weighted mean r z value), back-transformed to r values, classified according to their magnitude (i.e., small: r ≤ 0.69, medium: r ≤ 0.89, large: r ≥ 0.90), and, if possible, statistically compared. Heterogeneity between studies was assessed using I2 and Chi-squared (χ2) statistics. Three studies examined associations between balance and lower-extremity muscle strength/power in children, one study in adolescents, nine studies in young adults, three studies in middle-aged adults, and 23 studies in old adults. Overall, small-sized associations were found between variables of balance and lower-extremity muscle strength/power, irrespective of the age group considered. In addition, small-sized but significantly larger correlation coefficients were found between measures of dynamic steady-state balance and maximal strength in children (r = 0.57) compared with young (r = 0.09, z = 3.30, p = 0.001) and old adults (r = 0.35, z = 2.94, p = 0.002) as well as in old compared with young adults (z = 1.95, p = 0.03). Even though the reported results provided further insight into the associations between measures of balance and lower-extremity muscle strength/power, they did not allow us to deduce cause and effect relations. Further, the investigated associations could be biased by other variables such as joint flexibility, muscle mass, and/or auditory/visual acuity. Our systematic review and meta-analysis showed predominately small-sized correlations between measures of balance and lower-extremity muscle strength/power in children, adolescents, and young, middle-aged, and old adults. This indicates that these neuromuscular components are independent of each other and should therefore be tested and trained complementarily across the lifespan. Significantly larger but still small-sized associations were found between measures of dynamic steady-state balance and maximal strength in children compared with young and old adults as well as in old compared with young adults. These findings imply that age/maturation may have an impact on the association of selected components of balance and lower-extremity muscle strength.

Intraspecific venom variation in the medically significant Southern Pacific Rattlesnake (Crotalus oreganus helleri): biodiscovery, clinical and evolutionary implications.

PubMed

Sunagar, Kartik; Undheim, Eivind A B; Scheib, Holger; Gren, Eric C K; Cochran, Chip; Person, Carl E; Koludarov, Ivan; Kelln, Wayne; Hayes, William K; King, Glenn F; Antunes, Agosthino; Fry, Bryan Grieg

2014-03-17

Due to the extreme variation of venom, which consequently results in drastically variable degrees of neutralization by CroFab antivenom, the management and treatment of envenoming by Crotalus oreganus helleri (the Southern Pacific Rattlesnake), one of the most medically significant snake species in all of North America, has been a clinician's nightmare. This snake has also been the subject of sensational news stories regarding supposed rapid (within the last few decades) evolution of its venom. This research demonstrates for the first time that variable evolutionary selection pressures sculpt the intraspecific molecular diversity of venom components in C. o. helleri. We show that myotoxic β-defensin peptides (aka: crotamines/small basic myotoxic peptides) are secreted in large amounts by all populations. However, the mature toxin-encoding nucleotide regions evolve under the constraints of negative selection, likely as a result of their non-specific mode of action which doesn't enforce them to follow the regime of the classic predator-prey chemical arms race. The hemorrhagic and tissue destroying snake venom metalloproteinases (SVMPs) were secreted in larger amounts by the Catalina Island and Phelan rattlesnake populations, in moderate amounts in the Loma Linda population and in only trace levels by the Idyllwild population. Only the Idyllwild population in the San Jacinto Mountains contained potent presynaptic neurotoxic phospholipase A2 complex characteristic of Mohave Rattlesnake (Crotalus scutulatus) and Neotropical Rattlesnake (Crotalus durissus terrificus). The derived heterodimeric lectin toxins characteristic of viper venoms, which exhibit a diversity of biological activities, including anticoagulation, agonism/antagonism of platelet activation, or procoagulation, appear to have evolved under extremely variable selection pressures. While most lectin α- and β-chains evolved rapidly under the influence of positive Darwinian selection, the β-chain lectin of the Catalina Island population appears to have evolved under the constraint of negative selection. Both lectin chains were conspicuously absent in both the proteomics and transcriptomics of the Idyllwild population. Thus, we not only highlight the tremendous biochemical diversity in C. o. helleri's venom-arsenal, but we also show that they experience remarkably variable strengths of evolutionary selection pressures, within each toxin class among populations and among toxin classes within each population. The mapping of geographical venom variation not only provides additional information regarding venom evolution, but also has direct medical implications by allowing prediction of the clinical effects of rattlesnake bites from different regions. Such information, however, also points to these highly variable venoms as being a rich source of novel toxins which may ultimately prove to be useful in drug design and development. These results have direct implications for the treatment of envenomed patients. The variable venom profile of Crotalus oreganus helleri underscores the biodiscovery potential of novel snake venoms. Copyright © 2014 Elsevier B.V. All rights reserved.

Broad Hβ Emission-line Variability in a Sample of 102 Local Active Galaxies

NASA Astrophysics Data System (ADS)

Runco, Jordan N.; Cosens, Maren; Bennert, Vardha N.; Scott, Bryan; Komossa, S.; Malkan, Matthew A.; Lazarova, Mariana S.; Auger, Matthew W.; Treu, Tommaso; Park, Daeseong

2016-04-01

A sample of 102 local (0.02 ≤ z ≤ 0.1) Seyfert galaxies with black hole masses MBH > 107M⊙ was selected from the Sloan Digital Sky Survey (SDSS) and observed using the Keck 10 m telescope to study the scaling relations between MBH and host galaxy properties. We study profile changes of the broad Hβ emission line within the three to nine year time frame between the two sets of spectra. The variability of the broad Hβ emission line is of particular interest, not only because it is used to estimate MBH, but also because its strength and width are used to classify Seyfert galaxies into different types. At least some form of broad-line variability (in either width or flux) is observed in the majority (∼66%) of the objects, resulting in a Seyfert-type change for ∼38% of the objects, likely driven by variable accretion and/or obscuration. The broad Hβ line virtually disappears in 3/102 (∼3%) extreme cases. We discuss potential causes for these changing look active galactic nuclei. While similar dramatic transitions have previously been reported in the literature, either on a case-by-case basis or in larger samples focusing on quasars at higher redshifts, our study provides statistical information on the frequency of Hβ line variability in a sample of low-redshift Seyfert galaxies.

A New Approach to Extreme Value Estimation Applicable to a Wide Variety of Random Variables

NASA Technical Reports Server (NTRS)

Holland, Frederic A., Jr.

1997-01-01

Designing reliable structures requires an estimate of the maximum and minimum values (i.e., strength and load) that may be encountered in service. Yet designs based on very extreme values (to insure safety) can result in extra material usage and hence, uneconomic systems. In aerospace applications, severe over-design cannot be tolerated making it almost mandatory to design closer to the assumed limits of the design random variables. The issue then is predicting extreme values that are practical, i.e. neither too conservative or non-conservative. Obtaining design values by employing safety factors is well known to often result in overly conservative designs and. Safety factor values have historically been selected rather arbitrarily, often lacking a sound rational basis. To answer the question of how safe a design needs to be has lead design theorists to probabilistic and statistical methods. The so-called three-sigma approach is one such method and has been described as the first step in utilizing information about the data dispersion. However, this method is based on the assumption that the random variable is dispersed symmetrically about the mean and is essentially limited to normally distributed random variables. Use of this method can therefore result in unsafe or overly conservative design allowables if the common assumption of normality is incorrect.

The discovery of indicator variables for QSAR using inductive logic programming

NASA Astrophysics Data System (ADS)

King, Ross D.; Srinivasan, Ashwin

1997-11-01

A central problem in forming accurate regression equations in QSAR studies isthe selection of appropriate descriptors for the compounds under study. Wedescribe a novel procedure for using inductive logic programming (ILP) todiscover new indicator variables (attributes) for QSAR problems, and show thatthese improve the accuracy of the derived regression equations. ILP techniqueshave previously been shown to work well on drug design problems where thereis a large structural component or where clear comprehensible rules arerequired. However, ILP techniques have had the disadvantage of only being ableto make qualitative predictions (e.g. active, inactive) and not to predictreal numbers (regression). We unify ILP and linear regression techniques togive a QSAR method that has the strength of ILP at describing stericstructure, with the familiarity and power of linear regression. We evaluatedthe utility of this new QSAR technique by examining the prediction ofbiological activity with and without the addition of new structural indicatorvariables formed by ILP. In three out of five datasets examined the additionof ILP variables produced statistically better results (P < 0.01) over theoriginal description. The new ILP variables did not increase the overallcomplexity of the derived QSAR equations and added insight into possiblemechanisms of action. We conclude that ILP can aid in the process of drugdesign.

Family Dynamics and Personal Strengths among Dementia Caregivers in Argentina

PubMed Central

Elnasseh, Aaliah G.; Trujillo, Michael A.; Peralta, Silvina Victoria; Stolfi, Miriam E.; Morelli, Eliana; Perrin, Paul B.

2016-01-01

This study examined whether healthier family dynamics were associated with higher personal strengths of resilience, sense of coherence, and optimism among dementia caregivers in Argentina. Caregivers are usually required to assist individuals with dementia, and family members have typically fulfilled that role. Personal strengths such as resilience, sense of coherence, and optimism have been shown to protect caregivers from some of the negative experiences of providing care, though the family-related variables associated with these personal strengths are largely unknown. Hierarchical multiple regressions investigated the extent to which family dynamics variables are associated with each of the caregiver personal strengths after controlling for demographic and caregiver characteristics. A sample of 105 caregivers from Argentina completed a set of questionnaires during a neurologist visit. Family dynamics explained 32% of the variance in resilience and 39% of the variance in sense of coherence. Greater family empathy and decreased family problems were uniquely associated with higher resilience. Greater communication and decreased family problems were uniquely associated with higher sense of coherence. Optimism was not found to be significantly associated with family dynamics. These results suggest that caregiver intervention research focused on the family may help improve caregiver personal strengths in Argentina and other Latin American countries. PMID:27413574

On the comparison of the strength of morphological integration across morphometric datasets.

PubMed

Adams, Dean C; Collyer, Michael L

2016-11-01

Evolutionary morphologists frequently wish to understand the extent to which organisms are integrated, and whether the strength of morphological integration among subsets of phenotypic variables differ among taxa or other groups. However, comparisons of the strength of integration across datasets are difficult, in part because the summary measures that characterize these patterns (RV coefficient and r PLS ) are dependent both on sample size and on the number of variables. As a solution to this issue, we propose a standardized test statistic (a z-score) for measuring the degree of morphological integration between sets of variables. The approach is based on a partial least squares analysis of trait covariation, and its permutation-based sampling distribution. Under the null hypothesis of a random association of variables, the method displays a constant expected value and confidence intervals for datasets of differing sample sizes and variable number, thereby providing a consistent measure of integration suitable for comparisons across datasets. A two-sample test is also proposed to statistically determine whether levels of integration differ between datasets, and an empirical example examining cranial shape integration in Mediterranean wall lizards illustrates its use. Some extensions of the procedure are also discussed. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Analysis of the association between isokinetic knee strength with offensive and defensive jumping capacity in high-level female volleyball athletes.

PubMed

Sattler, Tine; Sekulic, Damir; Esco, Michael R; Mahmutovic, Ifet; Hadzic, Vedran

2015-09-01

Isokinetic-knee-strength was hypothesized to be an important factor related to jumping performance. However, studies examining this relation among elite female athletes and sport-specific jumps are lacking. This investigation determined the influence of isokinetic-knee flexor/extensor strength measures on spike-jump (offensive) and block-jump (defensive) performance among high-level female volleyball players. Cross-sectional laboratory study. Eighty-two female volleyball athletes (age = 21.3 ± 3.8 years, height = 175.4 ± 6.76 cm, and weight = 68.29 ± 8.53 kg) volunteered to participate in this study. The studied variables included spike-jump and block-jump performance and a set of isokinetic tests to evaluate the eccentric and concentric strength capacities of the knee extensors (quadriceps - Q), and flexors (hamstring - H) for both legs. Both jumping tests showed high intra-session reliability (ICC of 0.87 and 0.95 for spike-jump and block-jump, respectively). The athletes were clustered into three achievement-groups based on their spike-jump and block-jump performances. For the block-jump, ANOVA identified significant differences between achievement-groups for all isokinetic variables except the Right-Q-Eccentric-Strength. When observed for spike-jump, achievement-groups differed significantly in all tests but Right-H-Concentric-Strength. Discriminant canonical analysis showed that the isokinetic-strength variables were more associated with block-jump then spike-jump-performance. The eccentric isokinetic measures were relatively less important determinants of block-jump than for the spike-jump performance. Data support the hypothesis of the importance of isokinetic strength measures for the expression of rapid muscular performance in volleyball. The results point to the necessity of the differential approach in sport training for defensive and offensive duties. Copyright © 2014 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Effect of Sequencing Strength and Endurance Training in Young Male Soccer Players.

PubMed

Makhlouf, Issam; Castagna, Carlo; Manzi, Vincenzo; Laurencelle, Louis; Behm, David G; Chaouachi, Anis

2016-03-01

This study examined the effects of strength and endurance training sequence (strength before or after endurance) on relevant fitness variables in youth soccer players. Fifty-seven young elite-level male field soccer players (13.7 ± 0.5 years; 164 ± 8.3 cm; 53.5 ± 8.6 kg; body fat; 15.6 ± 3.9%) were randomly assigned to a control (n = 14, CG) and 3 experimental training groups (twice a week for 12 weeks) strength before (SE, n = 15), after (ES, n = 14) or on alternate days (ASE, n = 14) with endurance training. A significant (p = 0.001) intervention main effect was detected. There were only trivial training sequence differences (ES vs. SE) for all variables (p > 0.05). The CG showed large squat 1 repetition maximum (1RM) and medium sprint, change of direction ability, and jump improvements. ASE demonstrated a trivial difference in endurance performance with ES and SE (p > 0.05). Large to medium greater improvements for SE and ES were reported compared with ASE for sprinting over 10 and 30 m (p < 0.02). The SE squat 1RM was higher than in ASE (moderate, p < 0.02). Postintervention differences between ES and SE with CG fitness variables were small to medium (p ≤ 0.05) except for a large SE advantage with the Yo-Yo intermittent recovery test (p < 0.001, large). This study showed no effect of intrasession training sequence on soccer fitness-relevant variables. However, combining strength and endurance within a single training session provided superior results vs. training on alternate days. Concurrent training may be considered as an effective and safe training method for the development of the prospective soccer player.

Eight Weeks of Strength and Power Training Improves Club Head Speed in Collegiate Golfers.

PubMed

Oranchuk, Dustin J; Mannerberg, Jason M; Robinson, Tracey L; Nelson, Megan C

2018-02-14

Club head speed (CHS) is a major determinant of drive distance, a key component of golf performance. The purpose of this study was to determine the indirect effects of an eight-week strength and power program on CHS. Twelve (6 male, 6 female) NCAA Division II golfers (20.3±1.5 years) randomly assigned to an intervention or control group, underwent either a periodized strength and power program consisting of high-load barbell movements or a bodyweight and rotational movement focused resistance training program. Outcomes were CHS, countermovement jump (CMJ) height, and 1RM back squat (BS), power clean (PC), and deadlift (DL). Dependent t-tests were utilized to assess differences in outcome variables pre-to-post for each group, independent t-tests were utilized to assess differences between groups, and Pearson correlations were utilized to assess associations between CHS and outcome variables. On average, the intervention group experienced improvements in all outcome variables except peak CHS (p=0.60); the control group displayed no changes in any outcome variable except a decrease in average CHS (p=0.028). Compared to the control group, the intervention group experienced greater improvements in average CHS, BS, PC, and average and peak CMJ height (p<0.05). Additionally, CHS had large associations with PC (r=0.70, p=0.012), BS (r=0.64, p=0.025), DL (r=0.54, p=0.068) and CMJ (r=0.73, p=0.007). These results suggest improving muscular strength and power by increasing PC, BS, and CMJ is associated with increased CHS in collegiate golfers. Integrating a high-load, barbell-focused strength and power program may be beneficial for improving CHS and indirectly, golf performance.

The influence of anthropological features on ball flight speed in handball.

PubMed

Srhoj, Vatromir; Rogulj, Nenad; Papić, Vladan; Foretić, Nikola; Cavala, Marijana

2012-09-01

The purpose of this study, done on the sample of 41 students of Faculty of Kinesiologyi in Split was to determinate the differences in anthropological characteristics between students who achieved above average and students who achieved under average ball flight speed after jump shoot in handball. Anthropological characteristics were defined by 16 variables, 6 of them were used for the estimation of morphological characteristics, 7 variables for evaluation of motor characteristics and one variable each for evaluation of kinetic, kinematics and technical parameters of shooting. The significant differences were determined in variables for evaluation of longitudinal dimensionality of dominant arm, explosive strength of pull-out agility, strength of the hand grip, hand flexion ability for the ball throw-out and finally, correct and sound technique of the throw-out movement.

Damage tolerance of a composite sandwich with interleaved foam core

NASA Astrophysics Data System (ADS)

Ishai, Ori; Hiel, Clement

A composite sandwich panel consisting of carbon fiber-reinforced plastic (CFRP) skins and a syntactic foam core was selected as an appropriate structural concept for the design of wind tunnel compressor blades. Interleaving of the core with tough interlayers was done to prevent core cracking and to improve damage tolerance of the sandwich. Simply supported sandwich beam specimens were subjected to low-velocity drop-weight impacts as well as high velocity ballistic impacts. The performance of the interleaved core sandwich panels was characterized by localized skin damage and minor cracking of the core. Residual compressive strength (RCS) of the skin, which was derived from flexural test, shows the expected trend of decreasing with increasing size of the damage, impact energy, and velocity. In the case of skin damage, RCS values of around 50 percent of the virgin interleaved reference were obtained at the upper impact energy range. Based on the similarity between low-velocity and ballistic-impact effects, it was concluded that impact energy is the main variable controlling damage and residual strength, where as velocity plays a minor role.

Natural Tissue Microenvironmental Conditions Modulate Adhesive Material Performance

PubMed Central

Oliva, Nuria; Shitreet, Sagi; Abraham, Eytan; Stanley, Butch; Edelman, Elazer R.; Artzi, Natalie

2015-01-01

We designed and optimized tissue-responsive adhesive materials by matching material and tissue properties. A two-component material based on dextran aldehyde and dendrimer amine provides a cohesive gel through aldehyde–amine cross-linking and an adhesive interface created by a dextran aldehyde-selective reaction with tissue amines. By altering aldehyde–amine chemistry, we examined how variations in tissue surfaces (serosal amine density in the duodenum, jejunum, and ileum) affect interactions with adhesive materials of varied compositions (aldehyde content). Interestingly, the same adhesive formulation reacts differentially with the three regions of the small intestine as a result of variation in the tissue amine density along the intestinal tract, affecting the tissue–material interfacial morphology, adhesion strength, and adhesive mechanical properties. Whereas tissues provide chemical anchors for interaction with materials, we were able to tune the adhesion strength for each section of the small intestine tissue by altering the adhesive formulation using a two-component material with flexible variables aimed at controlling the aldehyde/amine ratio. This tissue-specific approach should be applied to the broad spectrum of biomaterials, taking into account specific microenvironmental conditions in material design. PMID:23046479

Damage tolerance of a composite sandwich with interleaved foam core

NASA Technical Reports Server (NTRS)

Ishai, Ori; Hiel, Clement

1992-01-01

A composite sandwich panel consisting of carbon fiber-reinforced plastic (CFRP) skins and a syntactic foam core was selected as an appropriate structural concept for the design of wind tunnel compressor blades. Interleaving of the core with tough interlayers was done to prevent core cracking and to improve damage tolerance of the sandwich. Simply supported sandwich beam specimens were subjected to low-velocity drop-weight impacts as well as high velocity ballistic impacts. The performance of the interleaved core sandwich panels was characterized by localized skin damage and minor cracking of the core. Residual compressive strength (RCS) of the skin, which was derived from flexural test, shows the expected trend of decreasing with increasing size of the damage, impact energy, and velocity. In the case of skin damage, RCS values of around 50 percent of the virgin interleaved reference were obtained at the upper impact energy range. Based on the similarity between low-velocity and ballistic-impact effects, it was concluded that impact energy is the main variable controlling damage and residual strength, where as velocity plays a minor role.

A case study of multi-seam coal mine entry stability analysis with strength reduction method

PubMed Central

Tulu, Ihsan Berk; Esterhuizen, Gabriel S; Klemetti, Ted; Murphy, Michael M.; Sumner, James; Sloan, Michael

2017-01-01

In this paper, the advantage of using numerical models with the strength reduction method (SRM) to evaluate entry stability in complex multiple-seam conditions is demonstrated. A coal mine under variable topography from the Central Appalachian region is used as a case study. At this mine, unexpected roof conditions were encountered during development below previously mined panels. Stress mapping and observation of ground conditions were used to quantify the success of entry support systems in three room-and-pillar panels. Numerical model analyses were initially conducted to estimate the stresses induced by the multiple-seam mining at the locations of the affected entries. The SRM was used to quantify the stability factor of the supported roof of the entries at selected locations. The SRM-calculated stability factors were compared with observations made during the site visits, and the results demonstrate that the SRM adequately identifies the unexpected roof conditions in this complex case. It is concluded that the SRM can be used to effectively evaluate the likely success of roof supports and the stability condition of entries in coal mines. PMID:28239503

A case study of multi-seam coal mine entry stability analysis with strength reduction method.

PubMed

Tulu, Ihsan Berk; Esterhuizen, Gabriel S; Klemetti, Ted; Murphy, Michael M; Sumner, James; Sloan, Michael

2016-03-01

In this paper, the advantage of using numerical models with the strength reduction method (SRM) to evaluate entry stability in complex multiple-seam conditions is demonstrated. A coal mine under variable topography from the Central Appalachian region is used as a case study. At this mine, unexpected roof conditions were encountered during development below previously mined panels. Stress mapping and observation of ground conditions were used to quantify the success of entry support systems in three room-and-pillar panels. Numerical model analyses were initially conducted to estimate the stresses induced by the multiple-seam mining at the locations of the affected entries. The SRM was used to quantify the stability factor of the supported roof of the entries at selected locations. The SRM-calculated stability factors were compared with observations made during the site visits, and the results demonstrate that the SRM adequately identifies the unexpected roof conditions in this complex case. It is concluded that the SRM can be used to effectively evaluate the likely success of roof supports and the stability condition of entries in coal mines.

Psychological Resilience and Depressive Symptoms in Older Adults Diagnosed with Post-polio Syndrome

PubMed Central

Pierini, Diana; Stuifbergen, Alexa

2012-01-01

Depression is a serious co-morbidity in persons with disability, yet few studies have focused on depressive symptoms in persons aging with post-polio syndrome (PPS). We used a resilience conceptual framework that focused on patient psychosocial strengths to investigate the relationship between psychological resilience factors (acceptance, self-efficacy, personal resources, interpersonal relationships, self-rated health, spiritual growth, and stress management) and depressive symptoms in a large sample (n = 630) of persons over age 65 who were diagnosed with PPS. A higher percentage (40%) of the sample scored ≥ 10 on the CES-D 10 than was previously cited in other studies; however, 53% of the sample had good or excellent self-rated health, suggesting psychological resilience. Depression scores were regressed on seven selected resilience factors after controlling for functional limitations. Four of the seven variables accounted for 30% of the variance in depressive symptoms with spiritual growth representing the main predictor (β = −.26). The implications for rehabilitation nurses in developing a patient-strengths perspective in the assessment and counseling of individuals aging with PPS are discussed. PMID:20681392

Muscle strength and areal bone mineral density at the hip in women: a cross-sectional study.

PubMed

Pasco, Julie A; Holloway, Kara L; Brennan-Olsen, Sharon L; Moloney, David J; Kotowicz, Mark A

2015-05-24

Muscle strengthening exercises are promoted for building and maintaining a healthy skeleton. We aimed to investigate the relationship between muscle strength and areal bone mineral density (BMD) at the hip in women aged 26-97 years. This cross-sectional study utilises data from 863 women assessed for the Geelong Osteoporosis Study. Measures of hip flexor and abductor strength were made using a hand-held dynamometer (Nicholas Manual Muscle Tester). The maximal measure from three trials on each leg was used for analyses. BMD was measured at the hip using dual energy x-ray absorptiometry (DXA; Lunar DPX-L). Total lean mass, body fat mass and appendicular lean mass were determined from whole body DXA scans. Linear regression techniques were used with muscle strength as the independent variable and BMD as the dependent variable. Models were adjusted for age and indices of body composition. Measures of age-adjusted hip flexor strength and hip abductor strength were positively associated with total hip BMD. For each standard deviation (SD) increase in hip flexor strength, the increase in mean total hip BMD (SD) was 10.4 % (p = 0.009). A similar pattern was observed for hip abductor strength, with an increase in mean total hip BMD of 22.8 % (p = 0.025). All associations between hip muscle strength and total hip BMD were independent of height, but were nullified after adjusting for appendicular lean mass or total lean mass. There was a positive association observed between muscle strength and BMD at the hip. However, this association was explained by measures of lean mass.

Probabilistic simulation of uncertainties in composite uniaxial strengths

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Stock, T. A.

1990-01-01

Probabilistic composite micromechanics methods are developed that simulate uncertainties in unidirectional fiber composite strengths. These methods are in the form of computational procedures using composite mechanics with Monte Carlo simulation. The variables for which uncertainties are accounted include constituent strengths and their respective scatter. A graphite/epoxy unidirectional composite (ply) is studied to illustrate the procedure and its effectiveness to formally estimate the probable scatter in the composite uniaxial strengths. The results show that ply longitudinal tensile and compressive, transverse compressive and intralaminar shear strengths are not sensitive to single fiber anomalies (breaks, intergacial disbonds, matrix microcracks); however, the ply transverse tensile strength is.

A multi-site study on medical school selection, performance, motivation and engagement.

PubMed

Wouters, A; Croiset, G; Schripsema, N R; Cohen-Schotanus, J; Spaai, G W G; Hulsman, R L; Kusurkar, R A

2017-05-01

Medical schools seek ways to improve their admissions strategies, since the available methods prove to be suboptimal for selecting the best and most motivated students. In this multi-site cross-sectional questionnaire study, we examined the value of (different) selection procedures compared to a weighted lottery procedure, which includes direct admission based on top pre-university grade point averages (≥8 out of 10; top-pu-GPA). We also considered whether students had participated in selection, prior to being admitted through weighted lottery. Year-1 (pre-clinical) and Year-4 (clinical) students completed standard validated questionnaires measuring quality of motivation (Academic Self-regulation Questionnaire), strength of motivation (Strength of Motivation for Medical School-Revised) and engagement (Utrecht Work Engagement Scale-Student). Performance data comprised GPA and course credits in Year-1 and clerkship performance in Year-4. Regression analyses were performed. The response rate was 35% (387 Year-1 and 273 Year-4 students). Top-pu-GPA students outperformed selected students. Selected Year-1 students reported higher strength of motivation than top-pu-GPA students. Selected students did not outperform or show better quality of motivation and engagement than lottery-admitted students. Participation in selection was associated with higher engagement and better clerkship performance in Year-4. GPA, course credits and strength of motivation in Year-1 differed between students admitted through different selection procedures. Top-pu-GPA students perform best in the medical study. The few and small differences found raise questions about the added value of an extensive selection procedure compared to a weighted lottery procedure. Findings have to be interpreted with caution because of a low response rate and small group sizes.

Physique and motor performance characteristics of US national rugby players.

PubMed

Carlson, B R; Carter, J E; Patterson, P; Petti, K; Orfanos, S M; Noffal, G J

1994-08-01

Anthropometric and performance data were collected on 65 US rugby players (mean age = 26.3 years) to make comparison on these characteristics by player position and performance level. Anthropometry included stature, body mass, nine skinfolds, two girths and two bone breadths. Skinfold patterns, estimated percent fat and Heath-Carter somatotypes were calculated from anthropometry. Motor performance measures included standing vertical jump, 40 yard dash, 110 yard dash, shuttle run, repeated jump in place, push-up, sit-up and squat thrust. Descriptive statistics were used for the total sample as well as selected sub-groups. Discriminant function analyses were employed to determine which combination of variables best discriminated between position and level of performance for the anthropometric and performance data. The results indicated that forwards were taller, heavier and had more subcutaneous adiposity than backs. Additionally, forwards and backs differed in somatotypes, with forwards being more endo-mesomorphic than backs and with a greater scatter about their mean. The anthropometric variables that best discriminated between backs and forwards were body mass, femur breadth and arm girth, with 88% correctly classified using these variables. The motor performance variables that best discriminated between backs and forwards were repeated jump in place, push-up and standing vertical jump, with 76% correct classification using these variables. Classification into three playing levels was unsatisfactory using either anthropometric or motor performance variables. These data can be used to assess present status and change in players, or potential national players, by position to locate strengths and weaknesses.

Probabilistic lifetime strength of aerospace materials via computational simulation

NASA Technical Reports Server (NTRS)

Boyce, Lola; Keating, Jerome P.; Lovelace, Thomas B.; Bast, Callie C.

1991-01-01

The results of a second year effort of a research program are presented. The research included development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic phenomenological constitutive relationship, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subjected to a number of effects of primitive variables. These primitive variables often originate in the environment and may include stress from loading, temperature, chemical, or radiation attack. This multifactor interaction constitutive equation is included in the computer program, PROMISS. Also included in the research is the development of methodology to calibrate the constitutive equation using actual experimental materials data together with the multiple linear regression of that data.

STS-3/OSS-1 Plasma Diagnostics Package (PDP) measurements of Orbiter transmitter and subsystem electromagnetic interference

NASA Technical Reports Server (NTRS)

Shawhan, S. D.; Murphy, G.

1983-01-01

The plasma diagnostics package receiver system is described to identify the various antennas and to characterize the complement of receivers which cover the frequency range of 30 Hz to 800 Hz and S-band at 2200 + or - 300 MHz. Sample results are presented to show the variability of electromagnetic effects associated with the orbiter and the time variability of these effects. The electric field and magnetic field maximum and minimum field strength spectra observed during the mission at the pallet location are plotted. Values are also derived for the maximum UHF transmitter and S-band transmitter field strengths. Calibration data to convert from the survey plots to actual narrowband and broadband field strengths are listed.

Phenotypic selection on flowering phenology and pollination efficiency traits between Primula populations with different pollinator assemblages.

PubMed

Wu, Yun; Li, Qing-Jun

2017-10-01

Floral traits have largely been attributed to phenotypic selection in plant-pollinator interactions. However, the strength of this link has rarely been ascertained with real pollinators. We conducted pollinator observations and estimated selection through female fitness on flowering phenology and floral traits between two Primula secundiflora populations. We quantified pollinator-mediated selection by subtracting estimates of selection gradients of plants receiving supplemental hand pollination from those of plants receiving open pollination. There was net directional selection for an earlier flowering start date at populations where the dominant pollinators were syrphid flies, and flowering phenology was also subjected to stabilized quadratic selection. However, a later flowering start date was significantly selected at populations where the dominant pollinators were legitimate (normal pollination through the corolla tube entrance) and illegitimate bumblebees (abnormal pollination through nectar robbing hole which located at the corolla tube), and flowering phenology was subjected to disruptive quadratic selection. Wider corolla tube entrance diameter was selected at both populations. Furthermore, the strength of net directional selection on flowering start date and corolla tube entrance diameter was stronger at the population where the dominant pollinators were syrphid flies. Pollinator-mediated selection explained most of the between-population variations in the net directional selection on flowering phenology and corolla tube entrance diameter. Our results suggested the important influence of pollinator-mediated selection on floral evolution. Variations in pollinator assemblages not only resulted in variation in the direction of selection but also the strength of selection on floral traits.

Analysis of adolescent profiles by gender: strengths, attitudes toward violence and sexism.

PubMed

Ferragut, Marta; Blanca, Maria J; Ortiz-Tallo, Margarita

2014-02-20

The present study analyzes the profiles of boys and girls, considering gender, in the early stages of adolescence in the variables of character strengths, attitudes toward diversity and violence, and sexism. The aim is to explore the gender differences, whether the variables in each set differ from one another and whether these differences are maintained in profiles for boys and girls. The participants were 527 students (mean age = 12.21 and SD = 0.53) from the city of Málaga (Spain). Profile analysis was used to analyze data. The results, using an alpha of 0.0021 for each contrast, indicate that boys and girls differ in their character strengths, particularly in the case of girls, whose prominent strengths relate to pro-social behavior and peer relationships, where Cohen´s d are higher than .30. Moreover, boys justify attitudes of violence to a greater extent (Cohen´s d from .44 to .81) and show greater agreement with sexist beliefs (d = .63). The research suggests that it would be of interest to encourage advancement in character strengths at this age.

Influence of Hip Abductor Strength on Functional Outcomes Before and After Total Knee Arthroplasty: Post Hoc Analysis of a Randomized Controlled Trial.

PubMed

Loyd, Brian J; Jennings, Jason M; Judd, Dana L; Kim, Raymond H; Wolfe, Pamela; Dennis, Douglas A; Stevens-Lapsley, Jennifer E

2017-09-01

Total knee arthroplasty (TKA) is associated with declines in hip abductor (HA) muscle strength; however, a longitudinal analysis demonstrating the influence of TKA on trajectories of HA strength change has not been conducted. The purpose of this study was to quantify changes in HA strength from pre-TKA through 3 months post-TKA and to characterize the relationship between HA strength changes and physical performance. This study is a post hoc analysis of a randomized controlled trial. Data from 162 participants (89 women, mean age = 63 y) were used for analysis. Data were collected by masked assessors preoperatively and at 1 and 3 months following surgery. Outcomes included: Timed "Up and Go" test (TUG), Stair Climbing Test (SCT), Six-Minute Walk Test (6MWT), and walking speed. Paired t tests were used for between- and within-limb comparisons of HA strength. Multivariable regression was used to determine contributions of independent variables, HA and knee extensor strength, to the dependent variables of TUG, SCT, 6MWT, and walking speed at each time point. Hip abductor strength was significantly lower in the surgical limb pre-TKA (mean = 0.015; 95% CI = 0.010-0.020), 1 month post-TKA (0.028; 0.023-0.034), and 3 months post-TKA (0.02; 0.014-0.025) compared with the nonsurgical limb. Hip abductor strength declined from pre-TKA to 1 month post-TKA (18%), but not at the 3-month time point (0%). Hip abductor strength independently contributed to performance-based outcomes pre-TKA; however, this contribution was not observed post-TKA. The post hoc analysis prevents examining all outcomes likely to be influenced by HA strength. Surgical limb HA strength is impaired prior to TKA, and worsens following surgery. Furthermore, HA strength contributes to performance-based outcomes, supporting the hypothesis that HA strength influences functional recovery. © 2017 American Physical Therapy Association

The role of commitment strength in enhancing safe water consumption: mediation analysis of a cluster-randomized trial.

PubMed

Inauen, Jennifer; Tobias, Robert; Mosler, Hans-Joachim

2014-11-01

The objectives of this study were to investigate the importance of commitment strength in the theory of planned behaviour (TPB) and to test whether behaviour change techniques (BCTs) aimed at increasing commitment strength indeed promote switching to arsenic-safe wells by changing commitment strength. A cluster-randomized controlled trial with four arms was conducted to compare an information-only intervention to information plus one, two, or three commitment-enhancing BCTs. Randomly selected households (N = 340) of Monoharganj, Bangladesh, in seven geographically separate areas, whose members were drinking arsenic-contaminated water at baseline and had access to arsenic-safe wells, participated in this trial. The areas were randomly allocated to the four intervention arms. Water consumption behaviour, variables of the TPB, commitment strength, and socio-demographic characteristics were assessed at baseline and at 3-month follow-up by structured face-to-face interviews. Mediation analysis was used to investigate the mechanisms of behaviour change. Changes in commitment strength significantly increased the explanatory power of the TPB to predict well-switching. Commitment-enhancing BCTs - public self-commitment, implementation intentions, and reminders - increased the behaviour change effects of information by up to 50%. Mediation analyses confirmed that the BCTs indeed increased well-switching by increasing commitment strength. Unexpectedly, however, mediation via changes in behavioural intentions was the strongest mechanism of the intervention effects. Commitment is an important construct to consider in water- and health-related behaviour change and may be for other health behaviours as well. BCTs that alter behavioural intentions and commitment strength proved highly effective at enhancing the behaviour change effects of information alone. Statement of contribution What is already known on this subject? Millions of people drink contaminated water even if they have access to safe water alternatives and despite increased awareness of the consequences to health. The theory of planned behaviour (TPB) and commitment strength are predictive of safe water consumption. The potentially commitment-enhancing behaviour change techniques (BCTs) - reminders, implementation intentions, and public self-commitment - can promote health behaviours, including safe water consumption. What does this study add? Changes in commitment strength significantly added to the prediction of switching to arsenic-safe wells by the TPB. Information-plus-BCTs aimed at increasing commitment strength led to >50% more well-switching than information alone. Behaviour change effects of the BCTs were mediated by changes in commitment strength and behavioural intentions. © 2013 The British Psychological Society.

Five Guidelines for Selecting Hydrological Signatures

NASA Astrophysics Data System (ADS)

McMillan, H. K.; Westerberg, I.; Branger, F.

2017-12-01

Hydrological signatures are index values derived from observed or modeled series of hydrological data such as rainfall, flow or soil moisture. They are designed to extract relevant information about hydrological behavior, such as to identify dominant processes, and to determine the strength, speed and spatiotemporal variability of the rainfall-runoff response. Hydrological signatures play an important role in model evaluation. They allow us to test whether particular model structures or parameter sets accurately reproduce the runoff generation processes within the watershed of interest. Most modeling studies use a selection of different signatures to capture different aspects of the catchment response, for example evaluating overall flow distribution as well as high and low flow extremes and flow timing. Such studies often choose their own set of signatures, or may borrow subsets of signatures used in multiple other works. The link between signature values and hydrological processes is not always straightforward, leading to uncertainty and variability in hydrologists' signature choices. In this presentation, we aim to encourage a more rigorous approach to hydrological signature selection, which considers the ability of signatures to represent hydrological behavior and underlying processes for the catchment and application in question. To this end, we propose a set of guidelines for selecting hydrological signatures. We describe five criteria that any hydrological signature should conform to: Identifiability, Robustness, Consistency, Representativeness, and Discriminatory Power. We describe an example of the design process for a signature, assessing possible signature designs against the guidelines above. Due to their ubiquity, we chose a signature related to the Flow Duration Curve, selecting the FDC mid-section slope as a proposed signature to quantify catchment overall behavior and flashiness. We demonstrate how assessment against each guideline could be used to compare or choose between alternative signature definitions. We believe that reaching a consensus on selection criteria for hydrological signatures will assist modelers to choose between competing signatures, facilitate comparison between hydrological studies, and help hydrologists to fully evaluate their models.

Experience-Dependent Regulation of Presynaptic NMDARs Enhances Neurotransmitter Release at Neocortical Synapses

ERIC Educational Resources Information Center

Urban-Ciecko, Joanna; Wen, Jing A.; Parekh, Puja K.; Barth, Alison L.

2015-01-01

Sensory experience can selectively alter excitatory synaptic strength at neocortical synapses. The rapid increase in synaptic strength induced by selective whisker stimulation (single-row experience/SRE, where all but one row of whiskers has been removed from the mouse face) is due, at least in part, to the trafficking of AMPA receptors (AMPARs)…

The Interrelationship of Social Anxiety with Anxiety, Depression, Locus of Control, Ways of Coping and Ego Strength amongst University Students

ERIC Educational Resources Information Center

Shepherd, Robin-Marie; Edelman, Robert J.

2009-01-01

This is the first study to investigate the interrelationship of social anxiety with the variables anxiety, depression, locus of control, ego strength and ways of coping in a sample of university students. There were high scores of social anxiety which were related to high scores on measures of anxiety and depression, low ego strength, external…

Resistance Training Increases the Variability of Strength Test Scores

DTIC Science & Technology

2009-06-08

standard deviations for pretest and posttest strength measurements. This information was recorded for every strength test used in a total of 377 samples...significant if the posttest standard deviation consistently was larger than the pretest standard deviation. This condition could be satisfied even if...the difference in the standard deviations was small. For example, the posttest standard deviation might be 1% larger than the pretest standard

Launch Vehicle Production and Operations Cost Metrics

NASA Technical Reports Server (NTRS)

Watson, Michael D.; Neeley, James R.; Blackburn, Ruby F.

2014-01-01

Traditionally, launch vehicle cost has been evaluated based on $/Kg to orbit. This metric is calculated based on assumptions not typically met by a specific mission. These assumptions include the specified orbit whether Low Earth Orbit (LEO), Geostationary Earth Orbit (GEO), or both. The metric also assumes the payload utilizes the full lift mass of the launch vehicle, which is rarely true even with secondary payloads.1,2,3 Other approaches for cost metrics have been evaluated including unit cost of the launch vehicle and an approach to consider the full program production and operations costs.4 Unit cost considers the variable cost of the vehicle and the definition of variable costs are discussed. The full program production and operation costs include both the variable costs and the manufacturing base. This metric also distinguishes operations costs from production costs, including pre-flight operational testing. Operations costs also consider the costs of flight operations, including control center operation and maintenance. Each of these 3 cost metrics show different sensitivities to various aspects of launch vehicle cost drivers. The comparison of these metrics provides the strengths and weaknesses of each yielding an assessment useful for cost metric selection for launch vehicle programs.

Reliability Based Design for a Raked Wing Tip of an Airframe

NASA Technical Reports Server (NTRS)

Patnaik, Surya N.; Pai, Shantaram S.; Coroneos, Rula M.

2011-01-01

A reliability-based optimization methodology has been developed to design the raked wing tip of the Boeing 767-400 extended range airliner made of composite and metallic materials. Design is formulated for an accepted level of risk or reliability. The design variables, weight and the constraints became functions of reliability. Uncertainties in the load, strength and the material properties, as well as the design variables, were modeled as random parameters with specified distributions, like normal, Weibull or Gumbel functions. The objective function and constraint, or a failure mode, became derived functions of the risk-level. Solution to the problem produced the optimum design with weight, variables and constraints as a function of the risk-level. Optimum weight versus reliability traced out an inverted-S shaped graph. The center of the graph corresponded to a 50 percent probability of success, or one failure in two samples. Under some assumptions, this design would be quite close to the deterministic optimum solution. The weight increased when reliability exceeded 50 percent, and decreased when the reliability was compromised. A design could be selected depending on the level of risk acceptable to a situation. The optimization process achieved up to a 20-percent reduction in weight over traditional design.

Association of lower extremity range of motion and muscle strength with physical performance of community-dwelling older women.

PubMed

Jung, Hungu; Yamasaki, Masahiro

2016-12-08

Reduced lower extremity range of motion (ROM) and muscle strength are related to functional disability in older adults who cannot perform one or more activities of daily living (ADL) independently. The purpose of this study was to determine which factors of seven lower extremity ROMs and two muscle strengths play dominant roles in the physical performance of community-dwelling older women. Ninety-five community-dwelling older women (mean age ± SD, 70.7 ± 4.7 years; age range, 65-83 years) were enrolled in this study. Seven lower extremity ROMs (hip flexion, hip extension, knee flexion, internal and external hip rotation, ankle dorsiflexion, and ankle plantar flexion) and two muscle strengths (knee extension and flexion) were measured. Physical performance tests, including functional reach test (FRT), 5 m gait test, four square step test (FSST), timed up and go test (TUGT), and five times sit-to-stand test (FTSST) were performed. Stepwise regression models for each of the physical performance tests revealed that hip extension ROM and knee flexion strength were important explanatory variables for FRT, FSST, and FTSST. Furthermore, ankle plantar flexion ROM and knee extension strength were significant explanatory variables for the 5 m gait test and TUGT. However, ankle dorsiflexion ROM was a significant explanatory variable for FRT alone. The amount of variance on stepwise multiple regression for the five physical performance tests ranged from 25 (FSST) to 47% (TUGT). Hip extension, ankle dorsiflexion, and ankle plantar flexion ROMs, as well as knee extension and flexion strengths may play primary roles in the physical performance of community-dwelling older women. Further studies should assess whether specific intervention programs targeting older women may achieve improvements in lower extremity ROM and muscle strength, and thereby play an important role in the prevention of dependence on daily activities and loss of physical function, particularly focusing on hip extension, ankle dorsiflexion, and ankle plantar flexion ROMs as well as knee extension and flexion strength.

3D Rheological Modeling of NW Intraplate Europe, Deciphering Spatial Integrated strength patterns, Mechanical Strong Layering and EET

NASA Astrophysics Data System (ADS)

Beekman, F.; Hardebol, N.; Cloetingh, S.; Tesauro, M.

2006-12-01

Better understanding of 3D rheological heterogeneity of the European Lithosphere provide the key to tie the recorded intraplate deformation pattern to stress fields transmitted into plate interior from plate boundary forces. The first order strain patterns result from stresses transmitted through the European lithosphere that is marked by a patchwork of high strength variability from inherited structural and compositional heterogeneities and upper mantle thermal perturbations. As the lithospheric rheology depends primarily on its spatial structure, composition and thermal estate, the 3D strength model for the European lithosphere relies on a 3D compositional model that yields the compositional heterogeneities and an iteratively calculated thermal cube using Fouriers law for heat conduction. The accurate appraisal of spatial strength variability results from proper mapping and integration of the geophysical compositional and thermal input parameters. Therefore, much attention has been paid to a proper description of first order structural and tectonic features that facilitate compilation of the compositional and thermal input models. As such, the 3D strength model reflects the thermo-mechanical structure inherited from the Europeans polyphase deformation history. Major 3D spatial mechanical strength variability has been revealed. The East-European and Fennoscandian Craton to the NE exhibit high strength (30-50 1012 N/m) from low mantle temperatures and surface heatflow of 35-60 mW/m2 while central and western Europe reflect a polyphase Phanerozoic thermo- tectonic history. Here, regions with high rigidity are formed primarily by patches of thermally stabilized Variscan Massifs (e.g. Rhenish, Armorican, Bohemian, and Iberian Massif) with low heatflow and lithospheric thickness values (50-65 mW/m2; 110-150 km) yielding strengths of ~15-25 1012 N/m. In contrast, major axis of weakened lithosphere coincides with Cenozoic Rift System (e.g. Upper and Lower Rhine Grabens, Pannonian Basin and Massif Central) attributed to the presence of tomographically imaged plumes. This study has elucidated the memory of the present-days Europeans lithosphere induced by compositional and thermal heterogeneities. The resulting lateral strength variations has a clear signature of the pst lithospheres polyphase deformation and also entails active tectonics, tectonically induced topography and surface processes.

[Comparative clinical study of 2 surgical techniques for trapeziometacarpal osteoarthritis].

PubMed

Martínez-Martínez, F; García-Hortelano, S; García-Paños, J P; Moreno-Fernández, J M; Martín-Ferrero, M Á

2016-01-01

In trapeziometacarpal osteoarthritis (or rhizarthrosis), there is great controversy over the surgical technique to choose: simple trapeziectomy, resection-interposition arthroplasty, interposition arthroplasty suspension-or arthroplasty with implant or prosthesis. These latter 2 are the most used without consensus in the literature on the technique to choose and without sufficient comparative studies. The objective is to compare the 2 techniques most used today: suspension-interposition arthroplasty and arthroplasty with prosthesis. A prospective study was conducted on 15 patients diagnosed with grade 2-3 rhizarthrosis treated with interposition arthroplasty-suspension (group 1) and 15 with prosthesis (group 2) showing clinical outcomes, advantages and disadvantages of each. The study variables were the visual analogue scale (VAS), the DASH questionnaire, the grip strength, the strength of end to end and end-lateral clamp, the joint balance adduction-abduction and preemption-retropositioning, and the opposition. The 2 groups are from 2 different hospitals operated on by a hand surgeon from the Hand Unit. The follow-up time for all patients included in the study was 12 months. The VAS, DASH and grip strength at 12 months did not show significant differences. As regards the strength of end to end and end-lateral clamp, group 2 showed the highest values in all follow-up periods with statistically significant differences. Patient selection and surgical experience is essential, given the satisfactory results of both techniques. Arthroplasty prosthesis is reserved for grades 2 and 3, middle-aged patients, good trapezium architecture, and experienced surgeons. Copyright © 2014 SECOT. Published by Elsevier Espana. All rights reserved.

The effect of hand dimensions, hand shape and some anthropometric characteristics on handgrip strength in male grip athletes and non-athletes.

PubMed

Fallahi, Ali Asghar; Jadidian, Ali Akbar

2011-09-01

It has been suggested that athletes with longer fingers and larger hand surfaces enjoy stronger grip power. Therefore, some researchers have examined a number of factors and anthropometric variables that explain this issue. To our knowledge, the data is scarce. Thus, the aim of this study was to investigate the effect of hand dimensions, hand shape and some anthropometric characteristics on handgrip strength in male grip athletes and non-athletes. 80 subjects aged between 19 and 29 participated in this study in two groups including: national and collegian grip athletes (n=40), and non-athletes (n=40). Body height and mass were measured to calculate body mass index. The shape of the dominant hand was drawn on a piece of paper with a thin marker so that finger spans, finger lengths, and perimeters of the hand could be measured. The hand shape was estimated as the ratio of the hand width to hand length. Handgrip strength was measured in the dominant and non-dominant hand using a standard dynamometer. Descriptive statistics were used for each variable and independent t test was used to analyze the differences between the two groups. The Pearson correlation coefficient test was used to evaluate the correlation between studied variables. Also, to predict important variables in handgrip strength, the linear trend was assessed using a linear regression analysis. There was a significant difference between the two groups in absolute handgrip strength (p<0.001) and handgrip/height ratio (p<0.001). The indices of body height, body mass, lean body mass and body fat content (p<0.001) were significantly greater in grip athletes. All hand variables except FS1-4 (p>0.05) were significantly different between the groups (p<0.001). After controlling body mass all hand anthropometric characteristics except thumb length (r=0.240, p= 0.135), hand shape (r=-0.029, p=0.858), middle finger length (r=0.305, p=0.056) and forearm circumference (r=0.162, p=0.319) significantly correlated with handgrip strength in grip athletes, but not in non-athletes, except for forearm circumference (r=0.406, p=0.010). The results showed that handgrip strength and some of the hand dimensions may be different in athletes who have handgrip movements with an object or opponent in comparison to non-athletes. Also, there was a significant positive correlation between handgrip strength and most of the hand dimensions in grip athletes. Therefore, these can be used in talent identification in handgrip-related sports and in clinical settings as well.

The Effect of Hand Dimensions, Hand Shape and Some Anthropometric Characteristics on Handgrip Strength in Male Grip Athletes and Non-Athletes

PubMed Central

Fallahi, Ali Asghar; Jadidian, Ali Akbar

2011-01-01

It has been suggested that athletes with longer fingers and larger hand surfaces enjoy stronger grip power. Therefore, some researchers have examined a number of factors and anthropometric variables that explain this issue. To our knowledge, the data is scarce. Thus, the aim of this study was to investigate the effect of hand dimensions, hand shape and some anthropometric characteristics on handgrip strength in male grip athletes and non-athletes. 80 subjects aged between 19 and 29 participated in this study in two groups including: national and collegian grip athletes (n=40), and non-athletes (n=40). Body height and mass were measured to calculate body mass index. The shape of the dominant hand was drawn on a piece of paper with a thin marker so that finger spans, finger lengths, and perimeters of the hand could be measured. The hand shape was estimated as the ratio of the hand width to hand length. Handgrip strength was measured in the dominant and non-dominant hand using a standard dynamometer. Descriptive statistics were used for each variable and independent t test was used to analyze the differences between the two groups. The Pearson correlation coefficient test was used to evaluate the correlation between studied variables. Also, to predict important variables in handgrip strength, the linear trend was assessed using a linear regression analysis. There was a significant difference between the two groups in absolute handgrip strength (p<0.001) and handgrip/height ratio (p<0.001). The indices of body height, body mass, lean body mass and body fat content (p<0.001) were significantly greater in grip athletes. All hand variables except FS1-4 (p>0.05) were significantly different between the groups (p<0.001). After controlling body mass all hand anthropometric characteristics except thumb length (r=0.240, p= 0.135), hand shape (r=−0.029, p=0.858), middle finger length (r=0.305, p=0.056) and forearm circumference (r=0.162, p=0.319) significantly correlated with handgrip strength in grip athletes, but not in non-athletes, except for forearm circumference (r=0.406, p=0.010). The results showed that handgrip strength and some of the hand dimensions may be different in athletes who have handgrip movements with an object or opponent in comparison to non-athletes. Also, there was a significant positive correlation between handgrip strength and most of the hand dimensions in grip athletes. Therefore, these can be used in talent identification in handgrip-related sports and in clinical settings as well. PMID:23486361

Mechanisms Governing Interannual Variability of Stratosphere-to-Troposphere Ozone Transport

NASA Astrophysics Data System (ADS)

Albers, John R.; Perlwitz, Judith; Butler, Amy H.; Birner, Thomas; Kiladis, George N.; Lawrence, Zachary D.; Manney, Gloria L.; Langford, Andrew O.; Dias, Juliana

2018-01-01

Factors governing the strength and frequency of stratospheric ozone intrusions over the Pacific-North American region are considered for their role in modulating tropospheric ozone on interannual timescales. The strength of the association between two major modes of climate variability—the El Niño-Southern Oscillation (ENSO) and the Northern Annular Mode (NAM)—and the amount of ozone contained in stratospheric intrusions are tested in the context of two mechanisms that modulate stratosphere-to-troposphere transport (STT) of ozone: (StratVarO3) the winter season buildup of ozone abundances in the lowermost stratosphere (LMS) and (JetVar) Pacific jet and wave breaking variability during spring. In essence, StratVarO3 corresponds to variability in the amount of ozone per intrusion, while JetVar governs the frequency of intrusions. The resulting analysis, based on two different reanalysis products, suggests that StratVarO3 is more important than JetVar for driving interannual variations in STT of ozone over the Pacific-North American region. In particular, the abundance of ozone in the LMS at the end of winter is shown to be a robust indicator of the amount of ozone that will be contained in stratospheric intrusions during the ensuing spring. Additionally, it is shown that the overall strength of the winter season stratospheric NAM is a useful predictor of ozone intrusion strength. The results also suggest a nuanced relationship between the phase of ENSO and STT of ozone. While ENSO-related jet variability is associated with STT variability, it is wave breaking frequency rather than typical ENSO teleconnection patterns that is responsible for the ENSO-STT relationship.

Carry-Over of Force Production Symmetry in Athletes of Differing Strength Levels.

PubMed

Bailey, Christopher A; Sato, Kimitake; Burnett, Angus; Stone, Michael H

2015-11-01

This study sought to determine the level of association between bilateral force production symmetry assessment methods (standing weight distribution [WtD], unloaded and lightly loaded jumps, and isometric strength) and to determine whether the amount of symmetry carry-over between these tasks differs for strong and weak athletes. Subjects for this study included male (n = 31) and female (n = 32) athletes from National Collegiate Athletic Association Division I sports. Athletes performed WtD, unloaded and lightly loaded (20 kg) static and countermovement jumps, and isometric midthigh pull (IMTP) assessments on 2 adjacent force plates. Ground reaction force data were used to calculate symmetry variables and performance-related variables. Using Pearson zero order correlations, evaluations of the amount of symmetry carry-over were made. Weight distribution correlated strongly with jump peak force (PF) (r = 0.628-0.664). Strong relationships were also observed between loading conditions for jump variables (r = 0.568-0.957) as were the relationships between jump types for PF, peak power, and net impulse (r = 0.506-0.834). Based on the pooled sample, there was a lack of association between IMTP and WtD for jump symmetry variables. However, when examining strong and weak groups, rate of force development showed moderate to strong symmetry carry-over in the strongest athletes (r = 0.416-0.589). Stronger athletes appear to display similar explosive strength symmetry characteristics in dynamic and isometric assessments, unlike weaker athletes. Strength seems to influence the amount of force production symmetry carry-over between bilateral assessments. There may be optimal loads and variables for symmetry assessment, but these may differ based on population characteristics.

HIGH SHEAR GRANULATION PROCESS: ASSESSING IMPACT OF FORMULATION VARIABLES ON GRANULES AND TABLETS CHARACTERISTICS OF HIGH DRUG LOADING FORMULATION USING DESIGN OF EXPERIMENT METHODOLOGY.

PubMed

Fayed, Mohamed H; Abdel-Rahman, Sayed I; Alanazi, Fars K; Ahmed, Mahrous O; Tawfeek, Hesham M; Ali, Bahaa E

2017-03-01

High shear wet granulation is a significant component procedure in the pharmaceutical industry. The objective of the study was to investigate the influence of two independent formulation variables; polyvinypyrrolidone (PVP) as a binder (X,) and croscarmellose sodium (CCS) as a disintegrant (X2) on the crit- ical quality attributes of acetaminophen granules and their corresponding tablets using design of experiment (DoE) approach. A two factor, three level (32) full factorial design has been applied; each variable was investi- gated at three levels to characterize their strength and interaction. The dried granules have been analyzed for their density, granule size and flowability. Additionally, the produced tablets have been investigated for: break- ing force, friability, disintegration time and t. of drug dissolution. The analysis of variance (ANOVA) showed that the two variables had a significant impact (p < 0.05) on granules and tablets characteristics, while only the binder concentration influenced the tablets friability. Furthermore, significant interactions (p < 0.05) between the two variables, for granules and tablets attributes, were also found. However, variables interaction showed minimal effect for granules flowability as well as tablets friability. Desirability function was carried out to opti- mize the variables under study to obtain product within the USP limit. It was found that the higher desirability (0.985) could be obtained at the medium level of PVP and low level of CCS. Ultimately, this study supplies the formulator with beneficial tools in selecting the proper level of binder and disintegrant to attain product with desired characteristics.

The assessment of bond strength between heat damaged concrete and high strength fibre reinforced concrete

NASA Astrophysics Data System (ADS)

Zahid, M. Z. A. Mohd; Muhamad, K.

2017-09-01

The aim of this study is to assess the bond strength between heat damaged concrete and high strength fibre reinforced concrete (HPFRC). Firstly, this paper presents the various steps taken to prepare the HPFRC with self-compacting property. The minimum targeted slump flow is 600 mm and minimum targeted compressive strength is 80 MPa. The key mix variables considered are such as type of superplasticizer, water cement ratio and silica fume content. Then, the bond strength between the heat damaged concrete with HPFRC was examined. The experimental parameters are heating temperature, surface treatment technique and curing method and the results show that, all experimental parameters are significantly affected the bond strength between heat damaged concrete and HPFRC.

Demographic and health situation of children in conditions of economic destabilization in the Ukraine.

PubMed

Pantyley, Viktoriya

2014-01-01

In new conditions of socio-economic development in the Ukraine, the health of the population of children is considered as the most reliable indicator of socio-economic development of the country. The primary goal of the study was analysis of the effect of contemporary socio-economic transformations, their scope, and strength of effect on the demographic and social situation of children in various regions of the Ukraine. The methodological objectives of the study were as follows: development of a synthetic measure of the state of health of the population of children, based on the Hellwig's method, and selection of districts in the Ukraine according to the present health-demographic situation of children. The study was based on statistical data from the State Statistics Service of Ukraine, Centre of Medical Statistics in Kiev, Ukrainian Ministry of Defence, as well as Ministry of Education and Science, Youth and Sports of Ukraine. The following research methods were used: analysis of literature and Internet sources, selection and analysis of statistical materials, cartographic and statistical methods. Basic indices of the demographic and health situation of the population of children were analyzed, as well as factors of a socio-economic nature which affect this situation. A set of variables was developed for the synthetic evaluation of the state of health of the population of children. The typology of the Ukrainian districts was performed according to the state of health of the child population, based on the Hellwig's taxonomic method. Deterioration was observed of selected quality parameters, as well as a change in the strength and directions of effect of factors of organizational-institutional, socioeconomic, historical and cultural nature on the population of children potential.

Population dynamics with a mixed type of sexual and asexual reproduction in a fluctuating environment

PubMed Central

2012-01-01

Background Carassius gibelio, a cyprinid fish from Eurasia, has the ability to reproduce both sexually and asexually. This fish is also known as an invasive species which colonized almost all continental Europe, most likely originating from Asia and Eastern Europe. Populations of both sexually and asexually reproducing individuals exist in sympatry. In this study we try to elucidate the advantages of such a mixed type of reproduction. We investigate the dynamics of two sympatric populations with sexual and asexual reproduction in a periodically fluctuating environment. We define an individual-based computational model in which genotypes are represented by L loci, and the environment is composed of L resources for which the two populations compete. Results Our model demonstrates advantageous population dynamics where the optimal percentage of asexual reproduction depends on selection strength, on the number of selected loci and on the timescale of environmental fluctuations. We show that the sexual reproduction is necessary for "generating" fit genotypes, while the asexual reproduction is suitable for "amplifying" them. The simulations show that the optimal percentage of asexual reproduction increases with the length of the environment stability period and decrease with the strength of the selection and the number of loci. Conclusions In this paper we addressed the advantages of a mixed type of sexual and asexual reproduction in a changing environment and explored the idea that a species that is able to adapt itself to environmental fluctuation can easily colonize a new habitat. Our results could provide a possible explanation for the rapid and efficient invasion of species with a variable ratio of sexual and asexual reproduction such as Carassius gibelio. PMID:22489797

Canonical Measure of Correlation (CMC) and Canonical Measure of Distance (CMD) between sets of data. Part 3. Variable selection in classification.

PubMed

Ballabio, Davide; Consonni, Viviana; Mauri, Andrea; Todeschini, Roberto

2010-01-11

In multivariate regression and classification issues variable selection is an important procedure used to select an optimal subset of variables with the aim of producing more parsimonious and eventually more predictive models. Variable selection is often necessary when dealing with methodologies that produce thousands of variables, such as Quantitative Structure-Activity Relationships (QSARs) and highly dimensional analytical procedures. In this paper a novel method for variable selection for classification purposes is introduced. This method exploits the recently proposed Canonical Measure of Correlation between two sets of variables (CMC index). The CMC index is in this case calculated for two specific sets of variables, the former being comprised of the independent variables and the latter of the unfolded class matrix. The CMC values, calculated by considering one variable at a time, can be sorted and a ranking of the variables on the basis of their class discrimination capabilities results. Alternatively, CMC index can be calculated for all the possible combinations of variables and the variable subset with the maximal CMC can be selected, but this procedure is computationally more demanding and classification performance of the selected subset is not always the best one. The effectiveness of the CMC index in selecting variables with discriminative ability was compared with that of other well-known strategies for variable selection, such as the Wilks' Lambda, the VIP index based on the Partial Least Squares-Discriminant Analysis, and the selection provided by classification trees. A variable Forward Selection based on the CMC index was finally used in conjunction of Linear Discriminant Analysis. This approach was tested on several chemical data sets. Obtained results were encouraging.

Estimating the parameters of background selection and selective sweeps in Drosophila in the presence of gene conversion

PubMed Central

Campos, José Luis; Charlesworth, Brian

2017-01-01

We used whole-genome resequencing data from a population of Drosophila melanogaster to investigate the causes of the negative correlation between the within-population synonymous nucleotide site diversity (πS) of a gene and its degree of divergence from related species at nonsynonymous nucleotide sites (KA). By using the estimated distributions of mutational effects on fitness at nonsynonymous and UTR sites, we predicted the effects of background selection at sites within a gene on πS and found that these could account for only part of the observed correlation between πS and KA. We developed a model of the effects of selective sweeps that included gene conversion as well as crossing over. We used this model to estimate the average strength of selection on positively selected mutations in coding sequences and in UTRs, as well as the proportions of new mutations that are selectively advantageous. Genes with high levels of selective constraint on nonsynonymous sites were found to have lower strengths of positive selection and lower proportions of advantageous mutations than genes with low levels of constraint. Overall, background selection and selective sweeps within a typical gene reduce its synonymous diversity to ∼75% of its value in the absence of selection, with larger reductions for genes with high KA. Gene conversion has a major effect on the estimates of the parameters of positive selection, such that the estimated strength of selection on favorable mutations is greatly reduced if it is ignored. PMID:28559322

Do Psychosocial Factors Predict Muscle Strength, Pain, or Physical Performance in Patients With Knee Osteoarthritis?

PubMed

Baert, Isabel A C; Meeus, Mira; Mahmoudian, Armaghan; Luyten, Frank P; Nijs, Jo; Verschueren, Sabine M P

2017-09-01

The aim of this study was to examine the relationship of psychosocial factors, namely, pain catastrophizing, kinesiophobia, and maladaptive coping strategies, with muscle strength, pain, and physical performance in patients with knee osteoarthritis (OA)-related symptoms. A total of 109 women (64 with knee OA-related symptoms) with a mean age of 65.4 years (49-81 years) were recruited for this study. Psychosocial factors were quantified by the Pain Catastrophizing Scale, Tampa Scale for Kinesiophobia, and Pain Coping Inventory. Clinical features were assessed using isometric and isokinetic knee muscle strength measurements, visual analog scale, Western Ontario and McMaster Universities Osteoarthritis Index, and functional tests. Associations were examined using correlation and regression analysis. In knee OA patients, pain catastrophizing, kinesiophobia, and coping strategy explained a significant proportion of the variability in isometric knee extension and flexion strength (6.3%-9.2%), accounting for more overall variability than some demographic and medical status variables combined. Psychosocial factors were not significant independent predictors of isokinetic strength, knee pain, or physical performance. In understanding clinical features related to knee OA, such as muscle weakness, pain catastrophizing, kinesiophobia, and coping strategy might offer something additional beyond what might be explained by traditional factors, underscoring the importance of a biopsychosocial approach in knee OA management. Further research on individual patient characteristics that mediate the effects of psychosocial factors is, however, required in order to create opportunities for more targeted, personalized treatment for knee OA.

Variable Selection in the Presence of Missing Data: Imputation-based Methods.

PubMed

Zhao, Yize; Long, Qi

2017-01-01

Variable selection plays an essential role in regression analysis as it identifies important variables that associated with outcomes and is known to improve predictive accuracy of resulting models. Variable selection methods have been widely investigated for fully observed data. However, in the presence of missing data, methods for variable selection need to be carefully designed to account for missing data mechanisms and statistical techniques used for handling missing data. Since imputation is arguably the most popular method for handling missing data due to its ease of use, statistical methods for variable selection that are combined with imputation are of particular interest. These methods, valid used under the assumptions of missing at random (MAR) and missing completely at random (MCAR), largely fall into three general strategies. The first strategy applies existing variable selection methods to each imputed dataset and then combine variable selection results across all imputed datasets. The second strategy applies existing variable selection methods to stacked imputed datasets. The third variable selection strategy combines resampling techniques such as bootstrap with imputation. Despite recent advances, this area remains under-developed and offers fertile ground for further research.

Retention of neodymium by dolomite at variable ionic strength as probed by batch and column experiments.

PubMed

Emerson, H P; Zengotita, F; Richmann, M; Katsenovich, Y; Reed, D T; Dittrich, T M

2018-10-01

The results presented in this paper highlight the complexity of adsorption and incorporation processes of Nd with dolomite and significantly improve upon previous work investigating trivalent actinide and lanthanide interactions with dolomite. Both batch and mini column experiments were conducted at variable ionic strength. These data highlight the strong chemisorption of Nd to the dolomite surface (equilibrium K d 's > 3000 mL/g) and suggest that equilibrium adsorption processes may not be affected by ionic strength based on similar results at 0.1 and 5.0 M ionic strength in column breakthrough and equilibrium batch (>5 days) results. Mini column experiments conducted over approximately one year also represent a significant development in measurement of sorption of Nd in the presence of flow as previous large-scale column experiments did not achieve breakthrough likely due to the high loading capacity of dolomite for Nd (up to 240 μg/g). Batch experiments in the absence of flow show that the rate of Nd removal increases with increasing ionic strength (up to 5.0 M) with greater removal at greater ionic strength for a 24 h sampling point. We suggest that the increasing ionic strength induces increased mineral dissolution and re-precipitation caused by changes in activity with ionic strength that lead to increased removal of Nd through co-precipitation processes. Copyright © 2018 Elsevier Ltd. All rights reserved.

A cross-sectional analysis of age and sex patterns in grip strength, tooth loss, near vision and hearing levels in Chinese aged 50-74 years.

PubMed

Wu, Yili; Pang, Zengchang; Zhang, Dongfeng; Jiang, Wenjie; Wang, Shaojie; Li, Shuxia; Kruse, Torben A; Christensen, Kaare; Tan, Qihua

2012-01-01

By focusing on four health variables, handgrip strength, near visual acuity, tooth loss and hearing level, this study examined the different patterns of age-related changes in these variables in Chinese aged from 50 to 74 years, as well as explored the relationship among the variables in a cross-sectional sample of 2006 individuals. The data exhibited high quality with a low missing rate of under 5% in any age groups for each variable. Effects of age and sex on the changes in the four health variables were assessed using multiple regression models with age and sex interactions included. Upon the highly significant effects of age on all four measurements, we observed substantially higher grip strength for men who, however, exhibited a faster age-related decline than for women. No sex difference or age-sex interaction was found in the number of teeth lost. Near visual acuity displayed a faster age-related decline in women than in men but neither the overall sex difference nor age-sex interaction reached statistical significance. For hearing function, while no sex difference was found at middle frequency, women had better sensitivity at high frequency and men were more sensitive at low frequency. Multivariate analysis did not support an age-related common mechanism underlying the four health variables. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Material selection indices for design of surgical instruments with long tubular shafts.

PubMed

Nelson, Carl A

2013-02-01

In any medical device design process, material selection plays an important role. For devices which sustain mechanical loading, strength and stiffness requirements can be significant drivers of the design. This paper examines the specific case of minimally invasive surgical instruments, including robotic instruments, having long, tubular shafts. Material properties-based selection indices are derived for achieving high performance of these devices in terms of strength and stiffness, and the use of these indices for informing the medical device design problem is illustrated.

Effects of Neuromuscular Training on Children and Young Adults with Down Syndrome: Systematic Review and Meta-Analysis.

PubMed

Sugimoto, Dai; Bowen, Samantha L; Meehan, William P; Stracciolini, Andrea

2016-08-01

To synthesize existing research evidence and examine effects of neuromuscular training on general strength, maximal strength, and functional mobility tasks in children and young adults with Down syndrome. PubMed and EBSCO were used as a data source. To attain the aim of this study, literature search was performed under following inclusion criteria: (1) included participants with Down syndrome, (2) implemented a neuromuscular training intervention and measured outcome variables of general strength, maximal strength, and functional mobility tasks, (3) had a group of participants whose mean ages were under 30 years old, (4) employed a prospective controlled design, and (5) used mean and standard deviations to express the outcome variables. Effect size was calculated from each study based on pre- and post-testing value differences in general strength, maximal strength, and functional mobility tasks between control and intervention groups. The effect size was further classified in to one of the following categories: small, moderate, and large effects. Seven studies met inclusion criteria. Analysis indicated large to moderate effects on general strength, moderate to small effects on maximal strength, and small effect on functional mobility tasks by neuromuscular training. Although there were limited studies, the results showed that neuromuscular training could be used as an effective intervention in children and young adults with Down syndrome. Synthesis of seven reviewed studies indicated that neuromuscular training could be beneficial to optimize general and maximal muscular strength development in children and young adults with Down syndrome. Copyright © 2016 Elsevier Ltd. All rights reserved.

Measuring change in social interaction skills of young children with autism.

PubMed

Cunningham, Allison B

2012-04-01

Designing effective treatments for improving early social behaviors in autism has been identified as a critical research need. One barrier to drawing conclusions about optimal treatments for children with autism is the use of highly varied dependent measures in the treatment literature. Contributing to this is the absence of "gold standard" assessment batteries. This is particularly true for assessing changes in social interaction impairments in very young children with autism. This paper addresses this issue by reviewing variables important in the development and evaluation of assessment measures, discussing previous studies' choices of socially-related dependent measures, and the strengths, limitations, and research questions pertaining to them. It concludes with recommendations for measurement selection and future directions for research.

Associations among facial masculinity, physical strength, fluctuating asymmetry and attractiveness in young men and women.

PubMed

Van Dongen, Stefan

2014-01-01

Studies of the process of human mate selection and attractiveness have assumed that selection favours morphological features that correlate with (genetic) quality. Degree of masculinity/femininity and fluctuating asymmetry (FA) may signal (genetic) quality, but what information they harboured and how they relate to fitness is still debated. To study strength of associations between facial masculinity/femininity, facial FA, attractiveness and physical strength in humans. Two-hundred young males and females were studied by measuring facial asymmetry and masculinity on the basis of frontal photographs. Attractiveness was determined on the basis of scores given by an anonymous panel, and physical strength using hand grip strength. Patterns differed markedly between males and females and analysis method used (univariate vs multivariate). Overall, no associations between FA and attractiveness, masculinity and physical strength were found. In females, but not males, masculinity and attractiveness correlated negatively and masculinity and physical strength correlated positively. Further research into the differences between males and females in associations between facial morphology, attractiveness and physical strength is clearly needed. The use of a multivariate approach can increase our understanding of which regions of the face harbour specific information of hormone levels and perhaps behavioural traits.

Predictors of professional behaviour and academic outcomes in a UK medical school: A longitudinal cohort study.

PubMed

Adam, Jane; Bore, Miles; Childs, Roy; Dunn, Jason; Mckendree, Jean; Munro, Don; Powis, David

2015-01-01

Over the past 70 years, there has been a recurring debate in the literature and in the popular press about how best to select medical students. This implies that we are still not getting it right: either some students are unsuited to medicine or the graduating doctors are considered unsatisfactory, or both. To determine whether particular variables at the point of selection might distinguish those more likely to become satisfactory professional doctors, by following a complete intake cohort of students throughout medical school and analysing all the data used for the students' selection, their performance on a range of other potential selection tests, academic and clinical assessments throughout their studies, and records of professional behaviour covering the entire five years of the course. A longitudinal database captured the following anonymised information for every student (n = 146) admitted in 2007 to the Hull York Medical School (HYMS) in the UK: demographic data (age, sex, citizenship); performance in each component of the selection procedure; performance in some other possible selection instruments (cognitive and non-cognitive psychometric tests); professional behaviour in tutorials and in other clinical settings; academic performance, clinical and communication skills at summative assessments throughout; professional behaviour lapses monitored routinely as part of the fitness-to-practise procedures. Correlations were sought between predictor variables and criterion variables chosen to demonstrate the full range of course outcomes from failure to complete the course to graduation with honours, and to reveal clinical and professional strengths and weaknesses. Student demography was found to be an important predictor of outcomes, with females, younger students and British citizens performing better overall. The selection variable "HYMS academic score", based on prior academic performance, was a significant predictor of components of Year 4 written and Year 5 clinical examinations. Some cognitive subtest scores from the UK Clinical Aptitude Test (UKCAT) and the UKCAT total score were also significant predictors of the same components, and a unique predictor of the Year 5 written examination. A number of the non-cognitive tests were significant independent predictors of Years 4 and 5 clinical performance, and of lapses in professional behaviour. First- and second-year tutor ratings were significant predictors of all outcomes, both desirable and undesirable. Performance in Years 1 and 2 written exams did not predict performance in Year 4 but did generally predict Year 5 written and clinical performance. Measures of a range of relevant selection attributes and personal qualities can predict intermediate and end of course achievements in academic, clinical and professional behaviour domains. In this study HYMS academic score, some UKCAT subtest scores and the total UKCAT score, and some non-cognitive tests completed at the outset of studies, together predicted outcomes most comprehensively. Tutor evaluation of students early in the course also identified the more and less successful students in the three domains of academic, clinical and professional performance. These results may be helpful in informing the future development of selection tools.

Relationship between strength, power, speed, and change of direction performance of female softball players.

PubMed

Nimphius, Sophia; McGuigan, Michael R; Newton, Robert U

2010-04-01

The purpose of this study was to investigate (a) the cross-sectional relationship of strength, power, and performance variables in trained female athletes and (b) determine if the relationship between these variables changes over the course of a season. Ten female softball players (age = 18.1 +/- 1.6 years, height = 166.5 +/- 8.9 cm, and weight = 72.4 +/- 10.8 kg) from a state Australian Institute of Sport softball team were tested for maximal lower body strength (one repetition maximum [1RM]), peak force (PF), peak velocity (PV), and peak power (PP) during jump squats unloaded and loaded, unloaded countermovement vertical jump height (VJH) 1 base and 2 base sprint performance and change of direction performance on dominant and nondominant sides. The testing sessions occurred pre, mid, and post a 20-week training period. Relationship between body weight (BW), relative strength (1RM/BW), VJH, relative PP, relative PF, PV, speed, and change of direction variables were assessed by Pearson product-moment correlation coefficient at each testing session. Significant relationships were found across all time points with BW, speed, and change of direction measures (r = 0.70-0.93) and relative strength and measures of speed and change of direction ability (r = -0.73-0.85). There were no significant relationships between VJH and any measure of performance at any time point. In conclusion, BW and relative strength have strong to very strong correlations with speed and change of direction ability, and these correlations remain consistent over the course of the season. However, it seems as if many relationships vary with time, and their relationships should therefore be investigated longitudinally to better determine if these cross-sectional relationships truly reflect a deterministic relationship.

Effect of a 6-week strengthening program on shoulder and scapular-stabilizer strength and scapular kinematics in division I collegiate swimmers.

PubMed

Hibberd, Elizabeth E; Oyama, Saki; Spang, Jeffrey T; Prentice, William; Myers, Joseph B

2012-08-01

Shoulder injuries are common in swimmers because of the demands of the sport. Muscle imbalances frequently exist due to the biomechanics of the sport, which predispose swimmers to injury. To date, an effective shoulder-injury-prevention program for competitive swimmers has not been established. To assess the effectiveness of a 6-wk strengthening and stretching intervention program on improving glenohumeral and scapular muscle strength and scapular kinematics in collegiate swimmers. Randomized control trial. University biomechanics research laboratory. Forty-four Division I collegiate swimmers. The intervention program was completed 3 times per week for 6 wk. The program included strengthening exercises completed using resistance tubing-scapular retraction (Ts), scapular retraction with upward rotation (Ys), scapular retraction with downward rotation (Ws), shoulder flexion, low rows, throwing acceleration and deceleration, scapular punches, shoulder internal rotation at 90° abduction, and external rotation at 90° abduction-and 2 stretching exercises: corner stretch and sleeper stretch. Scapular kinematics and glenohumeral and scapular muscle strength assessed preintervention and postintervention. There were no significant between-groups differences in strength variables at pre/post tests, although shoulder-extension and internal-rotation strength significantly increased in all subjects regardless of group assignment. Scapular kinematic data revealed increased scapular internal rotation, protraction, and elevation in all subjects at posttesting but no significant effect of group on the individual kinematic variables. The current strengthening and stretching program was not effective in altering strength and scapular kinematic variables but may serve as a framework for future programs. Adding more stretching exercises, eliminating exercises that overlap with weight-room training and swim training, and timing of implementation may yield a more beneficial program for collegiate swimmers.

Effects of Recent Regional Soil Moisture Variability on Global Net Ecosystem CO2 Exchange

NASA Astrophysics Data System (ADS)

Jones, L. A.; Madani, N.; Kimball, J. S.; Reichle, R. H.; Colliander, A.

2017-12-01

Soil moisture exerts a major regional control on the inter-annual variability of the global land sink for atmospheric CO2. In semi-arid regions, annual biomass production is closely coupled to variability in soil moisture availability, while in cold-season-affected regions, summer drought offsets the effects of advancing spring phenology. Availability of satellite solar-induced fluorescence (SIF) observations and improvements in atmospheric inversions has led to unprecedented ability to monitor atmospheric sink strength. However, discrepancies still exist between such top-down estimates as atmospheric inversion and bottom-up process and satellite driven models, indicating that relative strength, mechanisms, and interaction of driving factors remain poorly understood. We use soil moisture fields informed by Soil Moisture Active Passive Mission (SMAP) observations to compare recent (2015-2017) and historic (2000-2014) variability in net ecosystem land-atmosphere CO2 exchange (NEE). The operational SMAP Level 4 Carbon (L4C) product relates ground-based flux tower measurements to other bottom-up and global top-down estimates to underlying soil moisture and other driving conditions using data-assimilation-based SMAP Level 4 Soil Moisture (L4SM). Droughts in coastal Brazil, South Africa, Eastern Africa, and an anomalous wet period in Eastern Australia were observed by L4C. A seasonal seesaw pattern of below-normal sink strength at high latitudes relative to slightly above-normal sink strength for mid-latitudes was also observed. Whereas SMAP-based soil moisture is relatively informative for short-term temporal variability, soil moisture biases that vary in space and with season constrain the ability of the L4C estimates to accurately resolve NEE. Such biases might be caused by irrigation and plant-accessible ground-water. Nevertheless, SMAP L4C daily NEE estimates connect top-down estimates to variability of effective driving factors for accurate estimates of regional-to-global land-atmosphere CO2 exchange.

A comprehensive strength testing protocol offers no clinical value in predicting risk of hamstring injury: a prospective cohort study of 413 professional football players.

PubMed

van Dyk, Nicol; Bahr, Roald; Burnett, Angus F; Whiteley, Rod; Bakken, Arnhild; Mosler, Andrea; Farooq, Abdulaziz; Witvrouw, Erik

2017-12-01

Hamstring injuries remain prevalent across a number of professional sports. In football, the incidence has even increased by 4% per year at the Champions League level over the last decade. The role of muscle strength or strength ratios and their association with risk of hamstring injury remain restricted by small sample sizes and inconclusive results. The purpose of this study is to identify risk factors for hamstring injury in professional football players in an adequately powered, prospective cohort study. Using both established (isokinetic) and novel (eccentric hamstring test device) measures of muscle strength, we aimed to investigate the relationship between these strength characteristics over the entire range of motion with risk of hamstring injury. All teams (n=18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their annual periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar. Variables included isokinetic strength, Nordic hamstring exercise strength and dynamic hamstring: quadriceps ratios. Of the 413 players included (68.2% of all league players), 66 suffered a hamstring injury over the two seasons. Only isokinetic quadriceps concentric at 300°/s (adjusted for bodyweight) was associated with risk of hamstring injury when considered categorically. Age, body mass and playing position were also associated with risk of hamstring injury. None of the other 23 strength variables examined were found to be associated with hamstring injury. The clinical value of isolated strength testing is limited, and its use in musculoskeletal screening to predict future hamstring injury is unfounded. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Comparison of physical and mechanical properties of river sand concrete with quarry dust concrete

NASA Astrophysics Data System (ADS)

Opara, Hyginus E.; Eziefula, Uchechi G.; Eziefula, Bennett I.

2018-03-01

This study compared the physical and mechanical properties of river sand concrete with quarry dust concrete. The constituent materials were batched by weight. The water-cement ratio and mix ratio selected for the experimental investigation were 0.55 and 1:2:4, respectively. The specimens were cured for 7, 14, 21 and 28 days. Slump, density and compressive strength tests were carried out. The results showed that river sand concrete had greater density and compressive strength than quarry dust concrete for all curing ages. At 28 days of curing, river sand concrete exceeded the target compressive strength by 36%, whereas quarry dust concrete was less than the target compressive strength by 12%. Both river sand concrete and quarry dust concrete for the selected water/cement ratio and mix ratio are suitable for non-structural applications and lightly-loaded members where high strength is not a prerequisite.

Observational evidence and strength of evidence domains: case examples

PubMed Central

2014-01-01

Background Systematic reviews of healthcare interventions most often focus on randomized controlled trials (RCTs). However, certain circumstances warrant consideration of observational evidence, and such studies are increasingly being included as evidence in systematic reviews. Methods To illustrate the use of observational evidence, we present case examples of systematic reviews in which observational evidence was considered as well as case examples of individual observational studies, and how they demonstrate various strength of evidence domains in accordance with current Agency for Healthcare Research and Quality (AHRQ) Evidence-based Practice Center (EPC) methods guidance. Results In the presented examples, observational evidence is used when RCTs are infeasible or raise ethical concerns, lack generalizability, or provide insufficient data. Individual study case examples highlight how observational evidence may fulfill required strength of evidence domains, such as study limitations (reduced risk of selection, detection, performance, and attrition); directness; consistency; precision; and reporting bias (publication, selective outcome reporting, and selective analysis reporting), as well as additional domains of dose-response association, plausible confounding that would decrease the observed effect, and strength of association (magnitude of effect). Conclusions The cases highlighted in this paper demonstrate how observational studies may provide moderate to (rarely) high strength evidence in systematic reviews. PMID:24758494

The Strength and Characteristics of VPPA Welded 2219-T87 Aluminum Alloy

NASA Technical Reports Server (NTRS)

Jemian, W. A.

1985-01-01

A study of the variable polarity plasma arc (VPPA) welding process and those factors that control the structure and properties of VPPA welded aluminum alloy 2219-T87 was conducted. The importance of joint preparation, alignment of parts and welding process variables are already established. Internal weld defects have been eliminated. However, a variation of properties was found to be due to the size variation of interdendritic particles in the fusion zone. These particles contribute to the void formation process, which controls the ultimate tensile strength of the welded alloy. A variation of 150 microns in particle size correlated with a 10 ksi variation of ultimate tensile strength. It was found that all fracture surfaces were of the dimple rupture type, with fracture initiating within the fusion zone.

INTRINSIC REGULATION OF HEMOGLOBIN EXPRESSION BY VARIABLE SUBUNIT INTERFACE STRENGTHS

PubMed Central

Manning, James M.; Popowicz, Anthony M.; Padovan, Julio C.; Chait, Brian T.; Manning, Lois R.

2012-01-01

SUMMARY The expression of the six types of human hemoglobin subunits over time is currently considered to be regulated mainly by transcription factors that bind to upstream control regions of the gene (the “extrinsic” component of regulation). Here we describe how subunit pairing and further assembly to tetramers in the liganded state is influenced by the affinity of subunits for one another (the “intrinsic” component of regulation). The adult hemoglobin dimers have the strongest subunit interfaces and the embryonic hemoglobins are the weakest with fetal hemoglobins of intermediate strength, corresponding to the temporal order of their expression. These variable subunit binding strengths and the attenuating effects of acetylation contribute to the differences with which these hemoglobin types form functional O2-binding tetramers consistent with gene switching. PMID:22129306

Factors influencing the thermally-induced strength degradation of B/Al composites

NASA Technical Reports Server (NTRS)

Dicarlo, J. A.

1982-01-01

Literature data related to the thermally-induced strength degradation of B/Al composites were examined in the light of fracture theories based on reaction-controlled fiber weakening. Under the assumption of a parabolic time-dependent growth for the interfacial reaction product, a Griffith-type fracture model was found to yield simple equations whose predictions were in good agreement with data for boron fiber average strength and for B/Al axial fracture strain. The only variables in these equations were the time and temperature of the thermal exposure and an empirical factor related to fiber surface smoothness prior to composite consolidation. Such variables as fiber diameter and aluminum alloy composition were found to have little influence. The basic and practical implications of the fracture model equations are discussed.

Strength training improves the tri-digit finger-pinch force control of older adults.

PubMed

Keogh, Justin W; Morrison, Steve; Barrett, Rod

2007-08-01

To investigate the effect of unilateral upper-limb strength training on the finger-pinch force control of older men. Pretest and post-test 6-week intervention study. Exercise science research laboratory. Eleven neurologically fit older men (age range, 70-80y). The strength training group (n=7) trained twice a week for 6 weeks, performing dumbbell bicep curls, wrist flexions, and wrists extensions, while the control group subjects (n=4) maintained their normal activities. Changes in force variability, targeting error, peak power frequency, proportional power, sample entropy, digit force sharing, and coupling relations were assessed during a series of finger-pinch tasks. These tasks involved maintaining a constant or sinusoidal force output at 20% and 40% of each subject's maximum voluntary contraction. All participants performed the finger-pinch tasks with both the preferred and nonpreferred limbs. Analysis of covariance for between-group change scores indicated that the strength training group (trained limb) experienced significantly greater reductions in finger-pinch force variability and targeting error, as well as significantly greater increases in finger-pinch force, sample entropy, bicep curl, and wrist flexion strength than did the control group. A nonspecific upper-limb strength-training program may improve the finger-pinch force control of older men.

Is strength of handedness reliable over repeated testing? An examination of typical development and autism spectrum disorder

PubMed Central

Scharoun, Sara M.; Bryden, Pamela J.

2015-01-01

Despite a lack of agreement concerning the age at which adult-like patterns of handedness emerge, it is generally understood that hand preference presents early in life and development is variable. Young children (ages 3–5 years) are described as having weak hand preference; however, older children (ages 7–10 years) display stronger patterns. Here, strength of hand preference refers to reliable use of the preferred hand. In comparison to their typically developing (TD) peers, individuals with autism spectrum disorder (ASD) are described as having a weak hand preference. This study aimed to extend the literature to assess three measures of handedness (Waterloo Handedness Questionnaire – WHQ, Annett pegboard – AP, and WatHand Cabinet Test – WHCT) in two repeated sessions. The first research question aimed to delineate if the strength of hand use changes across testing sessions as a function of age in typical development. Right-handed children reported a reliable preference for the right hand on the WHQ, similar to adults. A marginally significant difference was revealed between 3- to 4- and 5- to 6-year-olds on the AP. This was attributed to weak lateralization in 3- to 4-year-olds, where the establishment of hand preference by age 6 leads to superior performance with the preferred hand in 5- to 6-year-olds. Finally, for the WHCT, 3- to 4-year-olds had the highest bimanual score, indicating use of the same hand to lift the cabinet door and retrieve an object. It is likely that the task was not motorically complex enough to drive preferred hand selection for older participants. The second research question sought to determine if there is difference between (TD) children and children with ASD. No differences were revealed; however, children with ASD did display variable AP performance, providing partial support for previous literature. Findings will be discussed in light of relevant literature. PMID:25691875

Individual Differences in the Frequency-Following Response: Relation to Pitch Perception

PubMed Central

Coffey, Emily B. J.; Colagrosso, Emilia M. G.; Lehmann, Alexandre; Schönwiesner, Marc; Zatorre, Robert J.

2016-01-01

The scalp-recorded frequency-following response (FFR) is a measure of the auditory nervous system’s representation of periodic sound, and may serve as a marker of training-related enhancements, behavioural deficits, and clinical conditions. However, FFRs of healthy normal subjects show considerable variability that remains unexplained. We investigated whether the FFR representation of the frequency content of a complex tone is related to the perception of the pitch of the fundamental frequency. The strength of the fundamental frequency in the FFR of 39 people with normal hearing was assessed when they listened to complex tones that either included or lacked energy at the fundamental frequency. We found that the strength of the fundamental representation of the missing fundamental tone complex correlated significantly with people's general tendency to perceive the pitch of the tone as either matching the frequency of the spectral components that were present, or that of the missing fundamental. Although at a group level the fundamental representation in the FFR did not appear to be affected by the presence or absence of energy at the same frequency in the stimulus, the two conditions were statistically distinguishable for some subjects individually, indicating that the neural representation is not linearly dependent on the stimulus content. In a second experiment using a within-subjects paradigm, we showed that subjects can learn to reversibly select between either fundamental or spectral perception, and that this is accompanied both by changes to the fundamental representation in the FFR and to cortical-based gamma activity. These results suggest that both fundamental and spectral representations coexist, and are available for later auditory processing stages, the requirements of which may also influence their relative strength and thus modulate FFR variability. The data also highlight voluntary mode perception as a new paradigm with which to study top-down vs bottom-up mechanisms that support the emerging view of the FFR as the outcome of integrated processing in the entire auditory system. PMID:27015271

Influences of cement source and sample of cement source on compressive strength variability of gravel aggregate concrete.

DOT National Transportation Integrated Search

2013-06-01

The strength of concrete is influenced by each constituent material used in the concrete : mixture and the proportions of each ingredient. Water-cementitious ratio, cementitious materials, air : content, chemical admixtures, and type of coarse aggreg...

Some difficulties and inconsistencies when using habit strength and reasoned action variables in models of metered household water conservation.

PubMed

Jorgensen, Bradley S; Martin, John F; Pearce, Meryl; Willis, Eileen

2013-01-30

Research employing household water consumption data has sought to test models of water demand and conservation using variables from attitude theory. A significant, albeit unrecognised, challenge has been that attitude models describe individual-level motivations while consumption data is recorded at the household level thereby creating inconsistency between units of theory and measurement. This study employs structural equation modelling and moderated regression techniques to addresses the level of analysis problem, and tests hypotheses by isolating effects on water conservation in single-person households. Furthermore, the results question the explanatory utility of habit strength, perceived behavioural control, and intentions for understanding metered water conservation in single-person households. For example, evidence that intentions predict water conservation or that they interact with habit strength in single-person households was contrary to theoretical expectations. On the other hand, habit strength, self-reports of past water conservation, and perceived behavioural control were good predictors of intentions to conserve water. Copyright © 2012 Elsevier Ltd. All rights reserved.

Considerations for an exercise prescription

NASA Technical Reports Server (NTRS)

Convertino, Victor A.

1989-01-01

A number of past and most recent research findings that describe some of the physiological responses to exercise in man and their relationship with exposure to various gravitational environments are discussed. Most of the data pertain to adaptations of the cardiovascular and body fluid systems. It should be kept in mind that the data from studies on microgravity simulation in man include exposures of relatively short duration (5 hours to 14 days). However, it is argued that the results may provide important guidelines for the consideration of many variables which are pertinent to the development of exercise prescription for long-duration space flight. The following considerations for exercise prescriptions during long-duration space flight are noted: (1) Relatively high aerobic fitness and strength, especially of the upper body musculature, should be a criterion for selection of astronauts who will be involved in EVA, since endurance and strength appear to be predominant characteristics for work performance. (2) Some degree of upper body strength will probably be required for effective performance of EVA. However, the endurance and strength required by the upper body for EVA can probably be obtained through preflight exercise prescription which involves swimming. (3) Although some degree of arm exercise may be required to maintain preflight endurance and strength, researchers propose that regular EVA will probably be sufficient to maintain the endurance and strength required to effectively perform work tasks during space flight. (4) A minimum of one maximal aerobic exercise every 7 to 10 days during space flight may be all that is necessary for maintenance of normal cardiovascular responsiveness and replacement of body fluids for reentry following prolonged space flight. (5) The possible reduction in the amount of exercise required for maintenance of cardiovascular system and body fluids in combination with the use of electromyostimulation (EMS) or methods other than conventional exercise for maintaining size and strength of muscles and bones needs great consideration for further research. These approaches represent a potential solution to the problem of compromising valuable time for exercise that is needed for daily operations.

Dietary stress does not strengthen selection against single deleterious mutations in Drosophila melanogaster

PubMed Central

MacLellan, K; Kwan, L; Whitlock, M C; Rundle, H D

2012-01-01

Stress is generally thought to increase the strength of selection, although empirical results are mixed and general conclusions are difficult because data are limited. Here we compare the fitness effects of nine independent recessive mutations in Drosophila melanogaster in a high- and low-dietary-stress environment, estimating the strength of selection on these mutations arising from both a competitive measure of male reproductive success and productivity (female fecundity and the subsequent survival to adulthood of her offspring). The effect of stress on male reproductive success has not been addressed previously for individual loci and is of particular interest with respect to the alignment of natural and sexual selection. Our results do not support the hypothesis that stress increases the efficacy of selection arising from either fitness component. Results concerning the alignment of natural and sexual selection were mixed, although data are limited. In the low-stress environment, selection on mating success and productivity were concordant for five of nine mutations (four out of four when restricted to those with significant or near-significant productivity effects), whereas in the high-stress environment, selection aligned for seven of nine mutations (two out of two when restricted to those having significant productivity effects). General conclusions as to the effects of stress on the strength of selection and the alignment of natural and sexual selection await data from additional mutations, fitness components and stressors. PMID:21792225

Anthropometric measures as fitness indicators in primary school children: The Health Oriented Pedagogical Project (HOPP).

PubMed

Mamen, Asgeir; Fredriksen, Per Morten

2018-05-01

As children's fitness continues to decline, frequent and systematic monitoring of fitness is important. Easy-to-use and low-cost methods with acceptable accuracy are essential in screening situations. This study aimed to investigate how the measurements of body mass index (BMI), waist circumference (WC) and waist-to-height ratio (WHtR) relate to selected measurements of fitness in children. A total of 1731 children from grades 1 to 6 were selected who had a complete set of height, body mass, running performance, handgrip strength and muscle mass measurements. A composite fitness score was established from the sum of sex- and age-specific z-scores for the variables running performance, handgrip strength and muscle mass. This fitness z-score was compared to z-scores and quartiles of BMI, WC and WHtR using analysis of variance, linear regression and receiver operator characteristic analysis. The regression analysis showed that z-scores for BMI, WC and WHtR all were linearly related to the composite fitness score, with WHtR having the highest R 2 at 0.80. The correct classification of fit and unfit was relatively high for all three measurements. WHtR had the best prediction of fitness of the three with an area under the curve of 0.92 ( p < 0.001). BMI, WC and WHtR were all found to be feasible measurements, but WHtR had a higher precision in its classification into fit and unfit in this population.

Inference on the Strength of Balancing Selection for Epistatically Interacting Loci

PubMed Central

Buzbas, Erkan Ozge; Joyce, Paul; Rosenberg, Noah A.

2011-01-01

Existing inference methods for estimating the strength of balancing selection in multi-locus genotypes rely on the assumption that there are no epistatic interactions between loci. Complex systems in which balancing selection is prevalent, such as sets of human immune system genes, are known to contain components that interact epistatically. Therefore, current methods may not produce reliable inference on the strength of selection at these loci. In this paper, we address this problem by presenting statistical methods that can account for epistatic interactions in making inference about balancing selection. A theoretical result due to Fearnhead (2006) is used to build a multi-locus Wright-Fisher model of balancing selection, allowing for epistatic interactions among loci. Antagonistic and synergistic types of interactions are examined. The joint posterior distribution of the selection and mutation parameters is sampled by Markov chain Monte Carlo methods, and the plausibility of models is assessed via Bayes factors. As a component of the inference process, an algorithm to generate multi-locus allele frequencies under balancing selection models with epistasis is also presented. Recent evidence on interactions among a set of human immune system genes is introduced as a motivating biological system for the epistatic model, and data on these genes are used to demonstrate the methods. PMID:21277883

The Strength of Selection against Neanderthal Introgression

PubMed Central

Juric, Ivan

2016-01-01

Hybridization between humans and Neanderthals has resulted in a low level of Neanderthal ancestry scattered across the genomes of many modern-day humans. After hybridization, on average, selection appears to have removed Neanderthal alleles from the human population. Quantifying the strength and causes of this selection against Neanderthal ancestry is key to understanding our relationship to Neanderthals and, more broadly, how populations remain distinct after secondary contact. Here, we develop a novel method for estimating the genome-wide average strength of selection and the density of selected sites using estimates of Neanderthal allele frequency along the genomes of modern-day humans. We confirm that East Asians had somewhat higher initial levels of Neanderthal ancestry than Europeans even after accounting for selection. We find that the bulk of purifying selection against Neanderthal ancestry is best understood as acting on many weakly deleterious alleles. We propose that the majority of these alleles were effectively neutral—and segregating at high frequency—in Neanderthals, but became selected against after entering human populations of much larger effective size. While individually of small effect, these alleles potentially imposed a heavy genetic load on the early-generation human–Neanderthal hybrids. This work suggests that differences in effective population size may play a far more important role in shaping levels of introgression than previously thought. PMID:27824859

Ultrasonic evaluation of the strength of unidirectional graphite-polyimide composites

NASA Technical Reports Server (NTRS)

Vary, A.; Bowles, K. J.

1977-01-01

An acoustic-ultrasonic method is described that was successful in ranking unidirectional graphite-polyimide composite specimens according to variations in interlaminar shear strength. Using this method, a quantity termed the stress wave factor was determined. It was found that this factor increases directly with interlaminar shear strength. The key variables in this investigation were composite density, fiber weight fraction, and void content. The stress wave factor and other ultrasonic factors that were studied were found to provide a powerful means for nondestructive evaluation of mechanical strength properties.

Efficient Variable Selection Method for Exposure Variables on Binary Data

NASA Astrophysics Data System (ADS)

Ohno, Manabu; Tarumi, Tomoyuki

In this paper, we propose a new variable selection method for "robust" exposure variables. We define "robust" as property that the same variable can select among original data and perturbed data. There are few studies of effective for the selection method. The problem that selects exposure variables is almost the same as a problem that extracts correlation rules without robustness. [Brin 97] is suggested that correlation rules are possible to extract efficiently using chi-squared statistic of contingency table having monotone property on binary data. But the chi-squared value does not have monotone property, so it's is easy to judge the method to be not independent with an increase in the dimension though the variable set is completely independent, and the method is not usable in variable selection for robust exposure variables. We assume anti-monotone property for independent variables to select robust independent variables and use the apriori algorithm for it. The apriori algorithm is one of the algorithms which find association rules from the market basket data. The algorithm use anti-monotone property on the support which is defined by association rules. But independent property does not completely have anti-monotone property on the AIC of independent probability model, but the tendency to have anti-monotone property is strong. Therefore, selected variables with anti-monotone property on the AIC have robustness. Our method judges whether a certain variable is exposure variable for the independent variable using previous comparison of the AIC. Our numerical experiments show that our method can select robust exposure variables efficiently and precisely.

Correlation of anthropometric variables, conditional and exercise habits in activite olders

PubMed Central

Ramos Bermúdez, Santiago; Parra Sánchez, José H

2012-01-01

Objective: This study sought to correlate the anthropometric and functional variables, and exercise habits in a group of elderly adults who regularly attend exercise programs. Method: Participation of 217 subjects between 60 and 85 years of age, from 13 regions of Colombia. Anthropometric and functional assessment was conducted as a questionnaire on exercise habits. Results: Negative correlations were shown between exercise habits and body fat and positive correlations between hand strength and VO2 max. (r = 0.4), age was negatively associated to functional variables. Conclusions: The functional capacity is influenced by increased age and body fat. With higher frequencies of physical exercise, VO2 max. and strength improved, but less body fat was observed. PMID:24893195

Variable Permanent Magnet Quadrupole

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mihara, T.; Iwashita, Y.; /Kyoto U.

A permanent magnet quadrupole (PMQ) is one of the candidates for the final focus lens in a linear collider. An over 120 T/m strong variable permanent magnet quadrupole is achieved by the introduction of saturated iron and a 'double ring structure'. A fabricated PMQ achieved 24 T integrated gradient with 20 mm bore diameter, 100 mm magnet diameter and 20 cm pole length. The strength of the PMQ is adjustable in 1.4 T steps, due to its 'double ring structure': the PMQ is split into two nested rings; the outer ring is sliced along the beam line into four partsmore » and is rotated to change the strength. This paper describes the variable PMQ from fabrication to recent adjustments.« less

Study on creep of fiber reinforced ultra-high strength concrete based on strength

NASA Astrophysics Data System (ADS)

Peng, Wenjun; Wang, Tao

2018-04-01

To complement the creep performance of ultra-high strength concrete, the long creep process of fiber reinforced concrete was studied in this paper. The long-term creep process and regularity of ultra-high strength concrete with 0.5% PVA fiber under the same axial compression were analyzed by using concrete strength (C80/C100/C120) as a variable. The results show that the creep coefficient of ultra-high strength concrete decreases with the increase of concrete strength. Compared with ACI209R (92), GL2000 models, it is found that the predicted value of ACI209R (92) are close to the experimental value, and the creep prediction model suitable for this experiment is proposed based on ACI209R (92).

Evaluation of pavement design in Virginia based on layer deflections, subgrade and its moisture content.

DOT National Transportation Integrated Search

1970-01-01

In this investigation, the optimum structural strength contributed by a material to the overall strength of the pavement was studied for cases applicable to Virginia. The variables were (a) the modulus of elasticity or the thickness equivalency of th...

Neighborhood Research from a Spatially Oriented Strengths Perspective

ERIC Educational Resources Information Center

Mowbray, Carol T.; Woolley, Michael E.; Grogan-Kaylor, Andrew; Gant, Larry M.; Gilster, Megan E.; Williams Shanks, Trina R.

2007-01-01

Research investigating neighborhood effects on children and families has been largely deficit and individual-focused, investigated structural variables, and has typically produced equivocal findings and small effect sizes. We suggest an approach focused on community strengths and resources that stresses the role of measures of social interaction…

What we talk about when we talk about access deficits

PubMed Central

Mirman, Daniel; Britt, Allison E.

2014-01-01

Semantic impairments have been divided into storage deficits, in which the semantic representations themselves are damaged, and access deficits, in which the representations are intact but access to them is impaired. The behavioural phenomena that have been associated with access deficits include sensitivity to cueing, sensitivity to presentation rate, performance inconsistency, negative serial position effects, sensitivity to number and strength of competitors, semantic blocking effects, disordered selection between strong and weak competitors, correlation between semantic deficits and executive function deficits and reduced word frequency effects. Four general accounts have been proposed for different subsets of these phenomena: abnormal refractoriness, too much activation, impaired competitive selection and deficits of semantic control. A combination of abnormal refractoriness and impaired competitive selection can account for most of the behavioural phenomena, but there remain several open questions. In particular, it remains unclear whether access deficits represent a single syndrome, a syndrome with multiple subtypes or a variable collection of phenomena, whether the underlying deficit is domain-general or domain-specific, whether it is owing to disorders of inhibition, activation or selection, and the nature of the connection (if any) between access phenomena in aphasia and in neurologically intact controls. Computational models offer a promising approach to answering these questions. PMID:24324232

[Oxygen peak consumption is a better predictor of cardiovascular risk than handgrip strength in older Chilean women].

PubMed

Farías-Valenzuela, Claudio; Pérez-Luco, Cristian; Ramírez-Campillo, Rodrigo; Álvarez, Cristian; Castro-Sepúlveda, Mauricio

Handgrip strength (HS) and peak oxygen consumption (Vo2peak) are powerful predictors of cardiovascular risk, although it is unknown which of the two variables is the better predictor. The objective of the following study was to relate HS and Vo2peak to cardiovascular risk markers in older Chilean women. Physically active adult women (n=51; age, 69±4.7years) participated in this study. The HS and Vo2peak were evaluated and related to the anthropometric variables of body mass, body mass index (BMI), waist circumference (WC), hip circumference (HC), waist ratio (WR), and waist height ratio (WHR), as well as with the cardiovascular variables systolic (SBP) and diastolic (DBP) and cardiac recovery in one minute (RHR1). A multilinear regression model was used for the analysis of the associated variables (P<.05). The cardiovascular risk markers associated (P<.05) with the handgrip strength of the dominant limb (HS DL ) were body mass, BMI, WR, and WHR. The handgrip strength of the non-dominant limb (HS NDL ) was associated with body mass. Vo2peak was associated with body mass, BMI, HC and RHR1. The multilinear regression model showed a value of r=0.43 in HS DL , r=0.39 in HS NDL and r=0.69 in peak Vo2. Although HS and Vo2peak were related to cardiovascular risk markers, Vo2peak offers greater associative power with these cardiovascular risk factors. Copyright © 2017 SEGG. Publicado por Elsevier España, S.L.U. All rights reserved.

Spatial variability in land-atmosphere coupling strength at the ARM Southern Great Plains site under different cloud regimes

NASA Astrophysics Data System (ADS)

Tang, Q.; Xie, S.; Zhang, Y.

2016-12-01

The paucity of land/soil observations is a long-standing limitation for land-atmosphere (LA) coupling studies, in particular for estimating the spatial variability in the coupling strengths. Spatially dense atmospheric radiation measurement (ARM) sites deployed at the U.S. Southern Great Plains (SGP) covers a wide range of vegetation, surface, and soil types, and thus allow us to observe the spatial patterns of LA coupling. The upcoming "super site" at SGP will facilitate these studies at even finer scales. While many previous studies have focused only on the observations from the central facility (CF) site or the domain mean from multiple sites, in the present work we examine the robustness of many key surface and land observations (e.g., radiation, turbulence fluxes, soil moisture, etc.) at extended sites besides the CF site for a decade. The coupling strengths are estimated with temporal covariations between important variables. We subsample the data to different categories based on different cloud regimes (e.g., clear sky, shallow cumulus, and deep cumulus. These cloud regimes are strongly impacted by local factors. The spatial variability of coupling strengths at different ARM sites is assessed with respect to dominant drivers (i.e., vegetation, land type, etc.). The results of this study will provide insights for improving the representation of LA coupling in climate models by providing observational constraints to parameterizations, e.g., shallow convective schemes. This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-698523

Improvement of isometric dorsiflexion protocol for assessment of tibialis anterior muscle strength☆

PubMed Central

Siddiqi, Ariba; Arjunan, Sridhar P.; Kumar, Dinesh

2015-01-01

It is important to accurately estimate the electromyogram (EMG)/force relationship of triceps surae (TS) muscle for detecting strength deficit of tibalis anterior (TA) muscle. In literature, the protocol for recording EMG and force of dorsiflexion have been described, and the necessity for immobilizing the ankle has been explained. However, there is a significant variability of the results among researchers even though they report the fixation of the ankle. We have determined that toe extension can cause significant variation in the dorsiflexion force and EMG of TS and this can occur despite following the current guidelines which require immobilizing the ankle. The results also show that there was a large increase in the variability of the force and the RMS of EMG of TS when the toes were not strapped compared with when they were strapped. Thus, with the current guidelines, where there are no instructions regarding the necessity of strapping the toes, the EMG/force relationship of TS could be incorrect and give an inaccurate assessment of the dorsiflexor TA strength. In summary, • Current methodology to estimate the dorsiflexor TA strength with respect to the TS activity, emphasizing on ankle immobilization is insufficient to prevent large variability in the measurements. • Toe extension during dorsiflexion was found to be one source of variability in estimating the TA strength. • It is recommended that guidelines for recording force and EMG from TA and TS muscles should require the strapping of the toes along with the need for immobilizing the ankle. PMID:26150978

Correcting the use of the term "power" in the strength and conditioning literature.

PubMed

Knudson, Duane V

2009-09-01

Many strength and conditioning papers have incorrectly adopted the colloquial use of the term "power" as a measure of short-term, high-intensity muscular performance despite a long history of research and editorials critical of this practice. This has lead to confusion, incorrect interpretations, and conflicting results in the literature. This paper summarizes the scientific evidence on external mechanical power as a short-term, high-intensity neuromuscular (anaerobic) performance or training variable. Many problems in the measurement and use of power in strength and conditioning research were identified, as well as problems in the use of the vertical jump as a field test of power. A critical review of the biomechanics, measurement, and training research does not support this colloquial use of the term "power." More research is needed that improves our understanding of the domains of muscular strength or neuromuscular performance, as well as partial correlation and multiple regression analyses to document the unique associations between these domains, biomechanical variables, training effects, and sport performance. Strength and conditioning research should limit the use of the term power to the true mechanical definition and provide several specific and measurement details on this measurement.

Effects of trunk stability on isometric knee extension muscle strength measurement while sitting.

PubMed

Hirano, Masahiro; Gomi, Masahiro; Katoh, Munenori

2016-09-01

[Purpose] This study aimed to investigate the effect of trunk stability on isometric knee extension muscle strength measurement while sitting by performing simultaneous measurements with a handheld dynamometer (HHD) and an isokinetic dynamometer (IKD) in the same seated condition. [Subjects and Methods] The subjects were 30 healthy volunteers. Isometric knee extension muscle strength was simultaneously measured with a HHD and an IKD by using an IKD-specific chair. The measurement was performed twice. Measurement instrument variables and the number of measurements were examined by using the analysis of variance and correlation tests. [Results] The measurement instrument variables and the number of measurements were not significantly different. The correlation coefficients between the HHD and IKD measurements were ≥0.96. [Conclusion] Isometric knee extension muscle strength measurement using the HHD in the sitting position resulted in a lower value than that using the IKD, presumably because of the effect of trunk stability on the measurement. In the same seated posture with trunk stability, no significant difference in measurement values was observed between the HHD and IKD. The present findings suggest that trunk stability while seated during isometric knee extension muscle strength measurement influenced the HHD measurement.

Effects of Mental Imagery on Muscular Strength in Healthy and Patient Participants: A Systematic Review

PubMed Central

Slimani, Maamer; Tod, David; Chaabene, Helmi; Miarka, Bianca; Chamari, Karim

2016-01-01

The aims of the present review were to (i) provide a critical overview of the current literature on the effects of mental imagery on muscular strength in healthy participants and patients with immobilization of the upper extremity (i.e., hand) and anterior cruciate ligament (ACL), (ii) identify potential moderators and mediators of the “mental imagery-strength performance” relationship and (iii) determine the relative contribution of electromyography (EMG) and brain activities, neural and physiological adaptations in the mental imagery-strength performance relationship. This paper also discusses the theoretical and practical implications of the contemporary literature and suggests possible directions for future research. Overall, the results reveal that the combination of mental imagery and physical practice is more efficient than, or at least comparable to, physical execution with respect to strength performance. Imagery prevention intervention was also effective in reducing of strength loss after short-term muscle immobilization and ACL. The present review also indicates advantageous effects of internal imagery (range from 2.6 to 136.3%) for strength performance compared with external imagery (range from 4.8 to 23.2%). Typically, mental imagery with muscular activity was higher in active than passive muscles, and imagining “lifting a heavy object” resulted in more EMG activity compared with imagining “lifting a lighter object”. Thus, in samples of students, novices, or youth male and female athletes, internal mental imagery has a greater effect on muscle strength than external mental imagery does. Imagery ability, motivation, and self-efficacy have been shown to be the variables mediating the effect of mental imagery on strength performance. Finally, the greater effects of internal imagery than those of external imagery could be explained in terms of neural adaptations, stronger brain activation, higher muscle excitation, greater somatic and sensorimotor activation and physiological responses such as blood pressure, heart rate, and respiration rate. Key points Coupling mental imagery with physical training is the best suited intervention for improving strength performance. An examination of potential moderator variables revealed that the effectiveness of mental imagery on strength performance may vary depending on the appropriate matching of muscular groups, the characteristics of mental imagery interventions, training duration, and type of skills. Self-efficacy, motivation, and imagery ability were the mediator variables in the mental imagery-strength performance relationship. Greater effects of internal imagery perspective on strength performance than those of external imagery could be explained in terms of neural adaptations, stronger brain activation, higher muscles excitation, greater somatic and sensorimotor activation, and higher physiological responses such as blood pressure, heart rate, and respiration rate. Mental imagery prevention interventions may provide a valuable tool to improve the functional recovery after short-term muscle immobilization and anterior cruciate ligament in patients. PMID:27803622

Modulating influences of memory strength and sensitivity of the retrieval test on the detectability of the sleep consolidation effect.

PubMed

Schoch, Sarah F; Cordi, Maren J; Rasch, Björn

2017-11-01

Emotionality can increase recall probability of memories as emotional information is highly relevant for future adaptive behavior. It has been proposed that memory processes acting during sleep selectively promote the consolidation of emotional memories, so that neutral memories no longer profit from sleep consolidation after learning. This appears as a selective effect of sleep for emotional memories. However, other factors contribute to the appearance of a consolidation benefit and influence this interpretation. Here we show that the strength of the memory trace before sleep and the sensitivity of the retrieval test after sleep are critical factors contributing to the detection of the benefit of sleep on memory for emotional and neutral stimuli. 228 subjects learned emotional and neutral pictures and completed a free recall after a 12-h retention interval of either sleep or wakefulness. We manipulated memory strength by including an immediate retrieval test before the retention interval in half of the participants. In addition, we varied the sensitivity of the retrieval test by including an interference learning task before retrieval testing in half of the participants. We show that a "selective" benefit of sleep for emotional memories only occurs in the condition with high memory strength. Furthermore, this "selective" benefit disappeared when we controlled for the memory strength before the retention interval and used a highly sensitive retrieval test. Our results indicate that although sleep benefits are more robust for emotional memories, neutral memories similarly profit from sleep after learning when more sensitive indicators are used. We conclude that whether sleep benefits on memory appear depends on several factors, including emotion, memory strength and sensitivity of the retrieval test. Copyright © 2017 Elsevier Inc. All rights reserved.

Relationships Among Lower Body Strength, Power, and Performance of Functional Tasks

NASA Technical Reports Server (NTRS)

Ploutz-Snyder, Lori; Ryder, J.; Hackney, K.; Scott-Pandorf, M.; Redd, E.; Buxton, R.; Bloomberg, J.

2010-01-01

There is a large degree of variability among crewmembers with respect to decrements in muscle strength and power following long duration spaceflight, ranging from 0 to approx.30% reductions. The purpose of this study was to investigate the influence of varying decrements in lower body muscle strength and power (relative to body weight) on the performance of 2 occupationally relevant tasks (ladder climb and supine egress & walk). Seventeen participants with leg strength similar to US crewmembers performed a leg press power test, an isokinetic knee extension strength test and they were asked to complete the 2 functional tasks as quickly as possible. On additional test days the participants were asked to repeat the functional tasks under 3 conditions where a different external load was applied each time using a weighted suit in order to experimentally manipulate participants strength/body weight and power/body weight ratios. The weight in the suit ranged from 20-120% of body weight and was distributed in proportion to limb segment weights to minimize changes in center of gravity. The ladder task consisted of climbing 40 rungs on a ladder treadmill as fast as possible. The supine egress & walk task consisted of rising from a supine position and walking through an obstacle course. Results show a relatively linear relationship between strength/body weight and task time and power/body weight with task time such that the fastest performance times are associated with higher strength and power with about half the variance in task time is accounted for by a single variable (either strength or power). For the average person, a 20% reduction in power/body weight (from 18 to 14.4 W/kg) induces an increase (slowing) of about 10 seconds in the ladder climb task from 14 to 24 seconds (approx.70%) and a slowing of the supine egress & walk task from 14 to 21 seconds (approx.50%). Similar relationships were observed with strength/body weight and task performance. For the average person, a 20% reduction in strength/body weight (from 2.1 to 1.7 Nm/kg) resulted in a slowing of the ladder climb from 10.5 to 24 seconds (approx.128%) and a slowing of the supine egress & walk from 11 to 20 seconds (approx.82%). These data suggest that the single variable of either low body muscle strength or power, relative to body weight is predictive of about 50% of the variance in task performance time, and that considerable slowing in task performance is associated with relatively typical decrements in muscle performance seen with long duration spaceflight. The observation of a relatively linear relationship between strength/power and task time suggests that across the full spectrum of initial crew strengths and typical decrements in strength previously observed, that task performance would be expected to be slowed following long duration spaceflight. These data will be confirmed in actual spaceflight with subsequent studies.

Tensile Properties and Integrity of Clean Room and Low-Modulus Disposable Nitrile Gloves: A Comparison of Two Dissimilar Glove Types

PubMed Central

Phalen, Robert N.; Wong, Weng kee

2012-01-01

Background: The selection of disposable nitrile exam gloves is complicated by (i) the availability of several types or formulations, (ii) product variability, and (iii) an inability of common quality control tests to detect small holes in the fingers. Differences in polymer formulation (e.g. filler and plasticizer/oil content) and tensile properties are expected to account for much of the observed variability in performance. Objectives: This study evaluated the tensile properties and integrity (leak failure rates) of two glove choices assumed to contain different amounts of plasticizers/oils. The primary aims were to determine if the tensile properties and integrity differed and if associations existed among these factors. Additional physical and chemical properties were evaluated. Methods: Six clean room and five low-modulus products were evaluated using the American Society for Testing and Materials Method D412 and a modified water-leak test to detect holes capable of passing a virus or chemical agent. Results: Significant differences in the leak failure rates and tensile properties existed between the two glove types (P ≤ 0.05). The clean room gloves were about three times more likely to have leak failures (chi-square; P = 0.001). No correlation was observed between leak failures and tensile properties. Solvent extract, an indication of added plasticizer/oil, was not associated with leak failures. However, gloves with a maximum modulus <4 MPa or area density (AD) <11 g cm−2 were about four times less likely to leak. Conclusions: On average, the low-modulus gloves were a better choice for protection against aqueous chemical or biological penetration. The observed variability between glove products indicated that glove selection cannot rely solely on glove type or manufacturer labeling. Measures of modulus and AD may aid in the selection process, in contrast with common measures of tensile strength and elongation at break. PMID:22201179

Tensile properties and integrity of clean room and low-modulus disposable nitrile gloves: a comparison of two dissimilar glove types.

PubMed

Phalen, Robert N; Wong, Weng Kee

2012-05-01

The selection of disposable nitrile exam gloves is complicated by (i) the availability of several types or formulations, (ii) product variability, and (iii) an inability of common quality control tests to detect small holes in the fingers. Differences in polymer formulation (e.g. filler and plasticizer/oil content) and tensile properties are expected to account for much of the observed variability in performance. This study evaluated the tensile properties and integrity (leak failure rates) of two glove choices assumed to contain different amounts of plasticizers/oils. The primary aims were to determine if the tensile properties and integrity differed and if associations existed among these factors. Additional physical and chemical properties were evaluated. Six clean room and five low-modulus products were evaluated using the American Society for Testing and Materials Method D412 and a modified water-leak test to detect holes capable of passing a virus or chemical agent. Significant differences in the leak failure rates and tensile properties existed between the two glove types (P ≤ 0.05). The clean room gloves were about three times more likely to have leak failures (chi-square; P = 0.001). No correlation was observed between leak failures and tensile properties. Solvent extract, an indication of added plasticizer/oil, was not associated with leak failures. However, gloves with a maximum modulus <4 MPa or area density (AD) <11 g cm(-2) were about four times less likely to leak. On average, the low-modulus gloves were a better choice for protection against aqueous chemical or biological penetration. The observed variability between glove products indicated that glove selection cannot rely solely on glove type or manufacturer labeling. Measures of modulus and AD may aid in the selection process, in contrast with common measures of tensile strength and elongation at break.

Predicting Species Distributions Using Record Centre Data: Multi-Scale Modelling of Habitat Suitability for Bat Roosts.

PubMed

Bellamy, Chloe; Altringham, John

2015-01-01

Conservation increasingly operates at the landscape scale. For this to be effective, we need landscape scale information on species distributions and the environmental factors that underpin them. Species records are becoming increasingly available via data centres and online portals, but they are often patchy and biased. We demonstrate how such data can yield useful habitat suitability models, using bat roost records as an example. We analysed the effects of environmental variables at eight spatial scales (500 m - 6 km) on roost selection by eight bat species (Pipistrellus pipistrellus, P. pygmaeus, Nyctalus noctula, Myotis mystacinus, M. brandtii, M. nattereri, M. daubentonii, and Plecotus auritus) using the presence-only modelling software MaxEnt. Modelling was carried out on a selection of 418 data centre roost records from the Lake District National Park, UK. Target group pseudoabsences were selected to reduce the impact of sampling bias. Multi-scale models, combining variables measured at their best performing spatial scales, were used to predict roosting habitat suitability, yielding models with useful predictive abilities. Small areas of deciduous woodland consistently increased roosting habitat suitability, but other habitat associations varied between species and scales. Pipistrellus were positively related to built environments at small scales, and depended on large-scale woodland availability. The other, more specialist, species were highly sensitive to human-altered landscapes, avoiding even small rural towns. The strength of many relationships at large scales suggests that bats are sensitive to habitat modifications far from the roost itself. The fine resolution, large extent maps will aid targeted decision-making by conservationists and planners. We have made available an ArcGIS toolbox that automates the production of multi-scale variables, to facilitate the application of our methods to other taxa and locations. Habitat suitability modelling has the potential to become a standard tool for supporting landscape-scale decision-making as relevant data and open source, user-friendly, and peer-reviewed software become widely available.

An integrated, quality by design (QbD) approach for design, development and optimization of orally disintegrating tablet formulation of carbamazepine.

PubMed

Mishra, Saurabh M; Rohera, Bhagwan D

2017-11-01

The objective of the present study was to design and develop a formulation for orally disintegrating tablets (ODTs) of carbamazepine using quality by design principles. The target product profile (TPP) and quality target product profile (QTPP) of ODTs were identified. Risk assessment was carried out by leveraging prior knowledge and experience to define the criticality of factors based on their impact by Ishikawa fishbone diagram and preliminary hazard analysis tool. Box-Behnken response surface methodology was used to study the effect of critical factors on various attributes of ODTs. The independent factors selected were compression pressure (X 1 ), concentration of sublimating agent (volatile material) (X 2 ), disintegrant concentration (X 3 ) and the responses were tablet crushing strength, tablet porosity, disintegration time, water absorption time, tablet friability and drug dissolution. ANOVA and lack of fit test illustrated that selected independent variables had significant effect on the response variables, and excellent correlation was observed between actual and predicted values. Optimization by desirability function indicated that compression pressure, X 1 (1534 lbs), ammonium bicarbonate concentration, X 2 (7.68%) and Kollidon ® CL-SF concentration, X 3 (6%) were optimum to prepare ODT formulation of carbamazepine of desired attributes complying with QTPP. Thus, in the present study, a high level of assurance was established for ODT product quality and performance.

Variation in the ciliary neurotrophic factor gene and muscle strength in older Caucasian women.

PubMed

Arking, Dan E; Fallin, Daniele M; Fried, Linda P; Li, Tao; Beamer, Brock A; Xue, Qian Li; Chakravarti, Aravinda; Walston, Jeremy

2006-05-01

To determine whether genetic variants in the ciliary neurotrophic factor (CNTF) gene are associated with muscle strength in older women. Cross-sectional analysis of baseline data from the Women's Health and Aging Studies I (1992) and II (1994), complementary population-based studies. Twelve contiguous ZIP code areas in Baltimore, Maryland. Three hundred sixty-three Caucasian, community-dwelling women aged 70 to 79. Participants were genotyped at the CNTF locus for eight single nucleotide polymorphisms (SNPs), including the null allele rs1800169. The dependent variables were grip strength and the frailty syndrome, identified as presence of three or more of five frailty indicators (weakness, slowness, weight loss, low physical activity, exhaustion). In addition to genotypes, independent variables of body mass index (BMI) and osteoarthritis of the hands were included. Using multivariate linear regression, single SNP analysis identified five SNPs significantly associated with grip strength (P<.05), after adjusting for age, BMI, and osteoarthritis. Haplotype analysis was performed, and a single haplotype associated with grip strength was identified (P<.01). The rs1800169 null allele fully explained the association between this haplotype and grip strength under a recessive model, with individuals homozygous for the null allele exhibiting a 3.80-kg lower (95% confidence interval=1.01-6.58) grip strength. No association was seen between the CNTF null allele and frailty. Individuals homozygous for the CNTF null allele had significantly lower grip strength but did not exhibit overt frailty. Larger prospective studies are needed to confirm this finding and extend it to additional populations.

Investigation of Dynamics in BMIM TFSA Ionic Liquid through Variable Temperature and Pressure NMR Relaxometry and Diffusometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pilar, Kartik; Rua, Armando; Suarez, Sophia N.

A comprehensive variable temperature, pressure and frequency multinuclear ( 1H, 2H, and 19F) magnetic resonance study was undertaken on selectively deuterated 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMIM TFSA) ionic liquid isotopologues. This study builds on our earlier investigation of the effects of increasing alkyl chain length on diffusion and dynamics in imidazolium-based TFSA ionic liquids. Fast field cycling 1H T 1 data revealed multiple modes of motion. Through calculation of diffusion coefficient (D) values and activation energies, the low- and high-field regimes were assigned to the translational and reorientation dynamics respectively. Variable-pressure 2H T 1 measurements reveal site-dependent interactions in the cation withmore » strengths in the order MD 3 > CD 3 > CD 2, indicating dissimilarities in the electric field gradients along the alkyl chain, with the CD 2 sites having the largest gradient. Additionally, the α saturation effect in T 1 vs. P was observed for all three sites, suggesting significant reduction of the short-range rapid reorientational dynamics. This reduction was also deduced from the variable pressure 1H T 1 data, which showed an approach to saturation for both the methyl and butyl group terminal methyl sites. Pressure-dependent D measurements show independent motions for both cations and anions, with the cations having greater D values over the entire pressure range.« less

Investigation of Dynamics in BMIM TFSA Ionic Liquid through Variable Temperature and Pressure NMR Relaxometry and Diffusometry

DOE PAGES

Pilar, Kartik; Rua, Armando; Suarez, Sophia N.; ...

2017-05-11

A comprehensive variable temperature, pressure and frequency multinuclear ( 1H, 2H, and 19F) magnetic resonance study was undertaken on selectively deuterated 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMIM TFSA) ionic liquid isotopologues. This study builds on our earlier investigation of the effects of increasing alkyl chain length on diffusion and dynamics in imidazolium-based TFSA ionic liquids. Fast field cycling 1H T 1 data revealed multiple modes of motion. Through calculation of diffusion coefficient (D) values and activation energies, the low- and high-field regimes were assigned to the translational and reorientation dynamics respectively. Variable-pressure 2H T 1 measurements reveal site-dependent interactions in the cation withmore » strengths in the order MD 3 > CD 3 > CD 2, indicating dissimilarities in the electric field gradients along the alkyl chain, with the CD 2 sites having the largest gradient. Additionally, the α saturation effect in T 1 vs. P was observed for all three sites, suggesting significant reduction of the short-range rapid reorientational dynamics. This reduction was also deduced from the variable pressure 1H T 1 data, which showed an approach to saturation for both the methyl and butyl group terminal methyl sites. Pressure-dependent D measurements show independent motions for both cations and anions, with the cations having greater D values over the entire pressure range.« less

Statistical Methods for Quality Control of Steel Coils Manufacturing Process using Generalized Linear Models

NASA Astrophysics Data System (ADS)

García-Díaz, J. Carlos

2009-11-01

Fault detection and diagnosis is an important problem in process engineering. Process equipments are subject to malfunctions during operation. Galvanized steel is a value added product, furnishing effective performance by combining the corrosion resistance of zinc with the strength and formability of steel. Fault detection and diagnosis is an important problem in continuous hot dip galvanizing and the increasingly stringent quality requirements in automotive industry has also demanded ongoing efforts in process control to make the process more robust. When faults occur, they change the relationship among these observed variables. This work compares different statistical regression models proposed in the literature for estimating the quality of galvanized steel coils on the basis of short time histories. Data for 26 batches were available. Five variables were selected for monitoring the process: the steel strip velocity, four bath temperatures and bath level. The entire data consisting of 48 galvanized steel coils was divided into sets. The first training data set was 25 conforming coils and the second data set was 23 nonconforming coils. Logistic regression is a modeling tool in which the dependent variable is categorical. In most applications, the dependent variable is binary. The results show that the logistic generalized linear models do provide good estimates of quality coils and can be useful for quality control in manufacturing process.

The Sterilization Effect of Cooperative Treatment of High Voltage Electrostatic Field and Variable Frequency Pulsed Electromagnetic Field on Heterotrophic Bacteria in Circulating Cooling Water

NASA Astrophysics Data System (ADS)

Gao, Xuetong; Liu, Zhian; Zhao, Judong

2018-01-01

Compared to other treatment of industrial circulating cooling water in the field of industrial water treatment, high-voltage electrostatic field and variable frequency pulsed electromagnetic field co-sterilization technology, an advanced technology, is widely used because of its special characteristics--low energy consumption, nonpoisonous and environmentally friendly. In order to get a better cooling water sterilization effect under the premise of not polluting the environment, some experiments about sterilization of heterotrophic bacteria in industrial circulating cooling water by cooperative treatment of high voltage electrostatic field and variable frequency pulsed electromagnetic field were carried out. The comparison experiment on the sterilization effect of high-voltage electrostatic field and variable frequency pulsed electromagnetic field co-sterilization on heterotrophic bacteria in industrial circulating cooling water was carried out by change electric field strength and pulse frequency. The results show that the bactericidal rate is selective to the frequency and output voltage, and the heterotrophic bacterium can only kill under the condition of sweep frequency range and output voltage. When the voltage of the high voltage power supply is 4000V, the pulse frequency is 1000Hz and the water temperature is 30°C, the sterilization rate is 48.7%, the sterilization rate is over 90%. Results of this study have important guiding significance for future application of magnetic field sterilization.

Evaluation and comparison of transverse and impact strength of different high strength denture base resins.

PubMed

Gupta, Abhinav; Tewari, R K

2016-01-01

The present study was undertaken to evaluate and compare the impact strength and transverse strength of the high-impact denture base materials. A conventional heat polymerized acrylic resin was used as a control. The entire experiment was divided into four main groups with twenty specimens each according to denture base material selected Trevalon, Trevalon Hi, DPI Tuff and Metrocryl Hi. These groups were further subgrouped into the two parameters selected, impact strength and flexural strength with ten specimens each. These specimens were then subjected to transverse bend tests with the help of Lloyds instrument using a three point bend principle. Impact tests were undertaken using an Izod-Charpy digital impact tester. This study was analyzed with one-way analysis of variance using Fisher f-test and Bonferroni t-test. There was a significant improvement in the impact strength of high-impact denture base resins as compared to control (Trevalon). However, in terms of transverse bend tests, only DPI Tuff showed higher transverse strength in comparison to control. Trevalon Hi and Metrocryl Hi showed a decrease in transverse strength. Within the limits of this in vitro study, (1) There is a definite increase in impact strength due to the incorporation of butadiene styrene rubber in this high strength denture base materials as compared to Trevalon used as a control. (2) Further investigations are required to prevent the unduly decrease of transverse strength. (3) It was the limitation of the study that the exact composition of the high-impact resins was not disclosed by the manufacturer that would have helped in better understanding of their behavior.

The Impact of Variability of Selected Geological and Mining Parameters on the Value and Risks of Projects in the Hard Coal Mining Industry

NASA Astrophysics Data System (ADS)

Kopacz, Michał

2017-09-01

The paper attempts to assess the impact of variability of selected geological (deposit) parameters on the value and risks of projects in the hard coal mining industry. The study was based on simulated discounted cash flow analysis, while the results were verified for three existing bituminous coal seams. The Monte Carlo simulation was based on nonparametric bootstrap method, while correlations between individual deposit parameters were replicated with use of an empirical copula. The calculations take into account the uncertainty towards the parameters of empirical distributions of the deposit variables. The Net Present Value (NPV) and the Internal Rate of Return (IRR) were selected as the main measures of value and risk, respectively. The impact of volatility and correlation of deposit parameters were analyzed in two aspects, by identifying the overall effect of the correlated variability of the parameters and the indywidual impact of the correlation on the NPV and IRR. For this purpose, a differential approach, allowing determining the value of the possible errors in calculation of these measures in numerical terms, has been used. Based on the study it can be concluded that the mean value of the overall effect of the variability does not exceed 11.8% of NPV and 2.4 percentage points of IRR. Neglecting the correlations results in overestimating the NPV and the IRR by up to 4.4%, and 0.4 percentage point respectively. It should be noted, however, that the differences in NPV and IRR values can vary significantly, while their interpretation depends on the likelihood of implementation. Generalizing the obtained results, based on the average values, the maximum value of the risk premium in the given calculation conditions of the "X" deposit, and the correspondingly large datasets (greater than 2500), should not be higher than 2.4 percentage points. The impact of the analyzed geological parameters on the NPV and IRR depends primarily on their co-existence, which can be measured by the strength of correlation. In the analyzed case, the correlations result in limiting the range of variation of the geological parameters and economics results (the empirical copula reduces the NPV and IRR in probabilistic approach). However, this is due to the adjustment of the calculation under conditions similar to those prevailing in the deposit.

Still No Evidence for the Encoding Variability Hypothesis: A Reply to Jang, Mickes, and Wixted (2012) and Starns, Rotello, and Ratcliff (2012)

ERIC Educational Resources Information Center

Koen, Joshua D.; Yonelinas, Andrew P.

2013-01-01

Koen and Yonelinas (2010) contrasted the recollection and encoding variability accounts of the finding that old items are associated with more variable memory strength than new items. The study indicated that (a) increasing encoding variability did not lead to increased measures of old item variance, and (b) old item variance was directly related…

Validity evidence for the measurement of the strength of motivation for medical school.

PubMed

Kusurkar, Rashmi; Croiset, Gerda; Kruitwagen, Cas; ten Cate, Olle

2011-05-01

The Strength of Motivation for Medical School (SMMS) questionnaire is designed to determine the strength of motivation of students particularly for medical study. This research was performed to establish the validity evidence for measuring strength of motivation for medical school. Internal structure and relations to other variables were used as the sources of validity evidence. The SMMS questionnaire was filled out by 1,494 medical students in different years of medical curriculum. The validity evidence for the internal structure was analyzed by principal components analysis with promax rotation. Validity evidence for relations to other variables was tested by comparing the SMMS scores with scores on the Academic Motivation Scale (AMS) and the exhaustion scale of Maslach Burnout Inventory-Student Survey (MBI-SS) for measuring study stress. Evidence for internal consistency was determined through the Cronbach's alpha for reliability. The analysis showed that the SMMS had a 3-factor structure. The validity in relations to other variables was established as both, the subscales and full scale scores significantly correlated positively with the intrinsic motivation scores and with the more autonomous forms of extrinsic motivation, the correlation decreasing and finally becoming negative towards the extrinsic motivation end of the spectrum. They also had significant negative correlations with amotivation scale of the AMS and exhaustion scale of MBI-SS. The Cronbach's alpha for reliability of the three subscales and full SMMS scores was 0.70, 0.67, 0.55 and 0.79. The strength of motivation for medical school has a three factor structure and acceptable validity evidence was found in our study.

Association of knee confidence with pain, knee instability, muscle strength, and dynamic varus-valgus joint motion in knee osteoarthritis.

PubMed

Skou, Søren T; Wrigley, Tim V; Metcalf, Ben R; Hinman, Rana S; Bennell, Kim L

2014-05-01

To investigate associations between self-reported knee confidence and pain, self-reported knee instability, muscle strength, and dynamic varus-valgus joint motion during walking. We performed a cross-sectional analysis of baseline data from 100 participants with symptomatic and radiographic medial tibiofemoral compartment osteoarthritis (OA) and varus malalignment recruited for a randomized controlled trial. The extent of knee confidence, assessed using a 5-point Likert scale item from the Knee Injury and Osteoarthritis Outcome Score, was set as the dependent variable in univariable and multivariable ordinal regression, with pain during walking, self-reported knee instability, quadriceps strength, and dynamic varus-valgus joint motion during walking as independent variables. One percent of the participants were not troubled with lack of knee confidence, 17% were mildly troubled, 50% were moderately troubled, 26% were severely troubled, and 6% were extremely troubled. Significant associations were found between worse knee confidence and higher pain intensity, worse self-reported knee instability, lower quadriceps strength, and greater dynamic varus-valgus joint motion. The multivariable model consisting of the same variables significantly accounted for 24% of the variance in knee confidence (P < 0.001). Worse knee confidence is associated with higher pain, worse self-reported knee instability, lower quadriceps muscle strength, and greater dynamic varus-valgus joint motion during walking. Since previous research has shown that worse knee confidence is predictive of functional decline in knee OA, addressing lack of knee confidence by treating these modifiable impairments could represent a new therapeutic target. Copyright © 2014 by the American College of Rheumatology.

Effect of Ankle Range of Motion (ROM) and Lower-Extremity Muscle Strength on Static Balance Control Ability in Young Adults: A Regression Analysis

PubMed Central

Kim, Seong-Gil

2018-01-01

Background The purpose of this study was to investigate the effect of ankle ROM and lower-extremity muscle strength on static balance control ability in young adults. Material/Methods This study was conducted with 65 young adults, but 10 young adults dropped out during the measurement, so 55 young adults (male: 19, female: 36) completed the study. Postural sway (length and velocity) was measured with eyes open and closed, and ankle ROM (AROM and PROM of dorsiflexion and plantarflexion) and lower-extremity muscle strength (flexor and extensor of hip, knee, and ankle joint) were measured. Pearson correlation coefficient was used to examine the correlation between variables and static balance ability. Simple linear regression analysis and multiple linear regression analysis were used to examine the effect of variables on static balance ability. Results In correlation analysis, plantarflexion ROM (AROM and PROM) and lower-extremity muscle strength (except hip extensor) were significantly correlated with postural sway (p<0.05). In simple correlation analysis, all variables that passed the correlation analysis procedure had significant influence (p<0.05). In multiple linear regression analysis, plantar flexion PROM with eyes open significantly influenced sway length (B=0.681) and sway velocity (B=0.011). Conclusions Lower-extremity muscle strength and ankle plantarflexion ROM influenced static balance control ability, with ankle plantarflexion PROM showing the greatest influence. Therefore, both contractile structures and non-contractile structures should be of interest when considering static balance control ability improvement. PMID:29760375

Effect of Ankle Range of Motion (ROM) and Lower-Extremity Muscle Strength on Static Balance Control Ability in Young Adults: A Regression Analysis.

PubMed

Kim, Seong-Gil; Kim, Wan-Soo

2018-05-15

BACKGROUND The purpose of this study was to investigate the effect of ankle ROM and lower-extremity muscle strength on static balance control ability in young adults. MATERIAL AND METHODS This study was conducted with 65 young adults, but 10 young adults dropped out during the measurement, so 55 young adults (male: 19, female: 36) completed the study. Postural sway (length and velocity) was measured with eyes open and closed, and ankle ROM (AROM and PROM of dorsiflexion and plantarflexion) and lower-extremity muscle strength (flexor and extensor of hip, knee, and ankle joint) were measured. Pearson correlation coefficient was used to examine the correlation between variables and static balance ability. Simple linear regression analysis and multiple linear regression analysis were used to examine the effect of variables on static balance ability. RESULTS In correlation analysis, plantarflexion ROM (AROM and PROM) and lower-extremity muscle strength (except hip extensor) were significantly correlated with postural sway (p<0.05). In simple correlation analysis, all variables that passed the correlation analysis procedure had significant influence (p<0.05). In multiple linear regression analysis, plantar flexion PROM with eyes open significantly influenced sway length (B=0.681) and sway velocity (B=0.011). CONCLUSIONS Lower-extremity muscle strength and ankle plantarflexion ROM influenced static balance control ability, with ankle plantarflexion PROM showing the greatest influence. Therefore, both contractile structures and non-contractile structures should be of interest when considering static balance control ability improvement.

Rehearsal and Interitem Associations.

ERIC Educational Resources Information Center

Medlin, Richard G.

The developmental memory research with children indicates that highly variable rehearsal leads to better overall recall and that the strength of interitem associations may play some role in improving recall. This paper reports on two experiments to investigate the interplay between the number and strength of interitem associations, and how each is…

Input variable selection for data-driven models of Coriolis flowmeters for two-phase flow measurement

NASA Astrophysics Data System (ADS)

Wang, Lijuan; Yan, Yong; Wang, Xue; Wang, Tao

2017-03-01

Input variable selection is an essential step in the development of data-driven models for environmental, biological and industrial applications. Through input variable selection to eliminate the irrelevant or redundant variables, a suitable subset of variables is identified as the input of a model. Meanwhile, through input variable selection the complexity of the model structure is simplified and the computational efficiency is improved. This paper describes the procedures of the input variable selection for the data-driven models for the measurement of liquid mass flowrate and gas volume fraction under two-phase flow conditions using Coriolis flowmeters. Three advanced input variable selection methods, including partial mutual information (PMI), genetic algorithm-artificial neural network (GA-ANN) and tree-based iterative input selection (IIS) are applied in this study. Typical data-driven models incorporating support vector machine (SVM) are established individually based on the input candidates resulting from the selection methods. The validity of the selection outcomes is assessed through an output performance comparison of the SVM based data-driven models and sensitivity analysis. The validation and analysis results suggest that the input variables selected from the PMI algorithm provide more effective information for the models to measure liquid mass flowrate while the IIS algorithm provides a fewer but more effective variables for the models to predict gas volume fraction.

Short-term Periodization Models: Effects on Strength and Speed-strength Performance.

PubMed

Hartmann, Hagen; Wirth, Klaus; Keiner, Michael; Mickel, Christoph; Sander, Andre; Szilvas, Elena

2015-10-01

Dividing training objectives into consecutive phases to gain morphological adaptations (hypertrophy phase) and neural adaptations (strength and power phases) is called strength-power periodization (SPP). These phases differ in program variables (volume, intensity, and exercise choice or type) and use stepwise intensity progression and concomitant decreasing volume, converging to peak intensity (peaking phase). Undulating periodization strategies rotate these program variables in a bi-weekly, weekly, or daily fashion. The following review addresses the effects of different short-term periodization models on strength and speed-strength both with subjects of different performance levels and with competitive athletes from different sports who use a particular periodization model during off-season, pre-season, and in-season conditioning. In most periodization studies, it is obvious that the strength endurance sessions are characterized by repetition zones (12-15 repetitions) that induce muscle hypertrophy in persons with a low performance level. Strictly speaking, when examining subjects with a low training level, many periodization studies include mainly hypertrophy sessions interspersed with heavy strength/power sessions. Studies have demonstrated equal or statistically significant higher gains in maximal strength for daily undulating periodization compared with SPP in subjects with a low to moderate performance level. The relatively short intervention period and the lack of concomitant sports conditioning call into question the practical value of these findings for competitive athletes. Possibly owing to differences in mesocycle length, conditioning programs, and program variables, competitive athletes either maintained or improved strength and/or speed-strength performance by integrating daily undulating periodization and SPP during off-season, pre-season and in-season conditioning. In high-performance sports, high-repetition strength training (>15) should be avoided because it does not provide an adequate training stimulus for gains in muscle cross-sectional area and strength performance. High-volume circuit strength training performed over 2 years negatively affected the development of the power output and maximal strength of the upper extremities in professional rugby players. Indeed, meta-analyses and results with weightlifters, American Football players, and throwers confirm the necessity of the habitual use of ≥80% 1 RM: (1) to improve maximal strength during the off-season and in-season in American Football, (2) to reach peak performance in maximal strength and vertical jump power during tapering in track-and-field, and (3) to produce hypertrophy and strength improvements in advanced athletes. The integration and extent of hypertrophy strength training in in-season conditioning depend on the duration of the contest period, the frequency of the contests, and the proportion of the conditioning program. Based on the literature, 72 h between hypertrophy strength training and strength-power training should be provided to allow for adequate regeneration times and therefore maximal stimulus intensities in training. This conclusion is only valid if the muscle is not trained otherwise during this regeneration phase. Thus, rotating hypertrophy and strength-power sessions in a microcycle during the season is a viable option. Comparative studies in competitive athletes who integrated strength training during pre-season conditioning confirm a tendency for gains in explosive strength and statistically significant improvements in medicine ball throw through SPP but not through daily undulating periodization. These findings indicate that to maximize the speed-strength in the short term (peaking), elite athletes should perform strength-power training twice per week. It is possible to perform a single strength-power session with the method of maximum explosive strength actions moving high-weight loads (90% 1 repetition maximum [RM]) at least 1-2 days before competition because of the shorter regeneration times and potentiation effects. Compared with ballistic strength training (30% 1 RM), this method has been shown to provide statistically superior gains in maximal strength, peak power, impulse size, and explosive strength during tapering in track-and-field throwers. The speed-strength performance in drop jumps of strength-trained subjects showed potentiation effects 48-148 h after a single strength-power training session. Regarding neuromuscular performance, plyometric exercises can even be performed after strength-power training on the same day if a minimum rest period of 3 h is provided.

Earthquake stress drop and laboratory-inferred interseismic strength recovery

USGS Publications Warehouse

Beeler, N.M.; Hickman, S.H.; Wong, T.-F.

2001-01-01

We determine the scaling relationships between earthquake stress drop and recurrence interval tr that are implied by laboratory-measured fault strength. We assume that repeating earthquakes can be simulated by stick-slip sliding using a spring and slider block model. Simulations with static/kinetic strength, time-dependent strength, and rate- and state-variable-dependent strength indicate that the relationship between loading velocity and recurrence interval can be adequately described by the power law VL ??? trn, where n=-1. Deviations from n=-1 arise from second order effects on strength, with n>-1 corresponding to apparent time-dependent strengthening and n<-1 corresponding to weakening. Simulations with rate and state-variable equations show that dynamic shear stress drop ????d scales with recurrence as d????d/dlntr ??? ??e(b-a), where ??e is the effective normal stress, ??=??/??e, and (a-b)=d??ss/dlnV is the steady-state slip rate dependence of strength. In addition, accounting for seismic energy radiation, we suggest that the static shear stress drop ????s scales as d????s/dlntr ??? ??e(1+??)(b-a), where ?? is the fractional overshoot. The variation of ????s with lntr for earthquake stress drops is somewhat larger than implied by room temperature laboratory values of ?? and b-a. However, the uncertainty associated with the seismic data is large and the discrepancy between the seismic observations and the rate of strengthening predicted by room temperature experiments is less than an order of magnitude. Copyright 2001 by the American Geophysical Union.

Estimation of mechanical properties of nanomaterials using artificial intelligence methods

NASA Astrophysics Data System (ADS)

Vijayaraghavan, V.; Garg, A.; Wong, C. H.; Tai, K.

2014-09-01

Computational modeling tools such as molecular dynamics (MD), ab initio, finite element modeling or continuum mechanics models have been extensively applied to study the properties of carbon nanotubes (CNTs) based on given input variables such as temperature, geometry and defects. Artificial intelligence techniques can be used to further complement the application of numerical methods in characterizing the properties of CNTs. In this paper, we have introduced the application of multi-gene genetic programming (MGGP) and support vector regression to formulate the mathematical relationship between the compressive strength of CNTs and input variables such as temperature and diameter. The predictions of compressive strength of CNTs made by these models are compared to those generated using MD simulations. The results indicate that MGGP method can be deployed as a powerful method for predicting the compressive strength of the carbon nanotubes.

Factors influencing the thermally-induced strength degradation of B/Al composites

NASA Technical Reports Server (NTRS)

Dicarlo, J. A.

1983-01-01

Literature data related to the thermally-induced strength degradation of B/Al composites were examined in the light of fracture theories based on reaction-controlled fiber weakening. Under the assumption of a parabolic time-dependent growth for the interfacial reaction product, a Griffith-type fracture model was found to yield simple equations whose predictions were in good agreement with data for boron fiber average strength and for B/Al axial fracture strain. The only variables in these equations were the time and temperature of the thermal exposure and an empirical factor related to fiber surface smoothness prior to composite consolidation. Such variables as fiber diameter and aluminum alloy composition were found to have little influence. The basic and practical implications of the fracture model equations are discussed. Previously announced in STAR as N82-24297

Compressive strength of human openwedges: a selection method

NASA Astrophysics Data System (ADS)

Follet, H.; Gotteland, M.; Bardonnet, R.; Sfarghiu, A. M.; Peyrot, J.; Rumelhart, C.

2004-02-01

A series of 44 samples of bone wedges of human origin, intended for allograft openwedge osteotomy and obtained without particular precautions during hip arthroplasty were re-examined. After viral inactivity chemical treatment, lyophilisation and radio-sterilisation (intended to produce optimal health safety), the compressive strength, independent of age, sex and the height of the sample (or angle of cut), proved to be too widely dispersed [ 10{-}158 MPa] in the first study. We propose a method for selecting samples which takes into account their geometry (width, length, thicknesses, cortical surface area). Statistical methods (Principal Components Analysis PCA, Hierarchical Cluster Analysis, Multilinear regression) allowed final selection of 29 samples having a mean compressive strength σ_{max} =103 MPa ± 26 and with variation [ 61{-}158 MPa] . These results are equivalent or greater than average materials currently used in openwedge osteotomy.

Properties of indirect composites reinforced with monomer-impregnated glass fiber.

PubMed

Tanoue, Naomi; Sawase, Takashi; Matsumura, Hideo; McCabe, John F

2012-07-01

Sufficient flexural strength is required for long-term clinical use of fixed partial dentures made with fiber-reinforced composite. The flexural strengths of indirect composite materials reinforced with a monomer-preimpregnated glass fiber material were determined to evaluate the compatibility of the composites to glass fiber material. Four types (microhybrid, nanohybrid, microfilled, and minifilled) of indirect composites and a unidirectional long glass fiber material were selected for investigation. The composites were placed on a fiber plate and polymerized in accordance with the respective manufacturer's instructions. Rectangular bar fiber-composite specimens were machined and the flexural strength was calculated. The flexural strength of each indirect composite was also measured. The microfilled composite with the lowest filler content (70 wt%) exhibited the highest increase ratio using the fiber, although its strength without fiber reinforcement was the lowest (62.1 MPa). The fiber-microhybrid specimen demonstrated the highest mean strength (355.9 MPa), although the filler content of the microhybrid composite was comparatively low (73 wt%). The type of composite material should be considered for the selection of an optimal fiber-composite combination.

Impact of Selected Parameters on the Fatigue Strength of Splices on Multiply Textile Conveyor Belts

NASA Astrophysics Data System (ADS)

Bajda, Mirosław; Błażej, Ryszard; Hardygóra, Monika

2016-10-01

Splices are the weakest points in the conveyor belt loop. The strength of these joints, and thus their design as well as the method and quality of splicing, determine the strength of the whole conveyor belt loop. A special zone in a splice exists, where the stresses in the adjacent plies or cables differ considerably from each other. This results in differences in the elongation of these elements and in additional shearing stresses in the rubber layer. The strength of the joints depends on several factors, among others on the parameters of the joined belt, on the connecting layer and the technology of joining, as well as on the materials used to make the joint. The strength of the joint constitutes a criterion for the selection of a belt suitable for the operating conditions, and therefore methods of testing such joints are of great importance. This paper presents the method of testing fatigue strength of splices made on multi-ply textile conveyor belts and the results of these studies.

The strengths of r- and K-selection shape diversity-disturbance relationships.

PubMed

Bohn, Kristin; Pavlick, Ryan; Reu, Björn; Kleidon, Axel

2014-01-01

Disturbance is a key factor shaping species abundance and diversity in plant communities. Here, we use a mechanistic model of vegetation diversity to show that different strengths of r- and K-selection result in different disturbance-diversity relationships. R- and K-selection constrain the range of viable species through the colonization-competition tradeoff, with strong r-selection favoring colonizers and strong K-selection favoring competitors, but the level of disturbance also affects the success of species. This interplay among r- and K-selection and disturbance results in different shapes of disturbance-diversity relationships, with little variation of diversity with no r- and no K-selection, a decrease in diversity with r-selection with disturbance rate, an increase in diversity with K-selection, and a peak at intermediate values with strong r- and K-selection. We conclude that different disturbance-diversity relationships found in observations may reflect different intensities of r- and K-selection within communities, which should be inferable from broader observations of community composition and their ecophysiological trait ranges.

The Relation between Recombination Rate and Patterns of Molecular Evolution and Variation in Drosophila melanogaster

PubMed Central

Campos, José L.; Halligan, Daniel L.; Haddrill, Penelope R.; Charlesworth, Brian

2014-01-01

Genetic recombination associated with sexual reproduction increases the efficiency of natural selection by reducing the strength of Hill–Robertson interference. Such interference can be caused either by selective sweeps of positively selected alleles or by background selection (BGS) against deleterious mutations. Its consequences can be studied by comparing patterns of molecular evolution and variation in genomic regions with different rates of crossing over. We carried out a comprehensive study of the benefits of recombination in Drosophila melanogaster, both by contrasting five independent genomic regions that lack crossing over with the rest of the genome and by comparing regions with different rates of crossing over, using data on DNA sequence polymorphisms from an African population that is geographically close to the putatively ancestral population for the species, and on sequence divergence from a related species. We observed reductions in sequence diversity in noncrossover (NC) regions that are inconsistent with the effects of hard selective sweeps in the absence of recombination. Overall, the observed patterns suggest that the recombination rate experienced by a gene is positively related to an increase in the efficiency of both positive and purifying selection. The results are consistent with a BGS model with interference among selected sites in NC regions, and joint effects of BGS, selective sweeps, and a past population expansion on variability in regions of the genome that experience crossing over. In such crossover regions, the X chromosome exhibits a higher rate of adaptive protein sequence evolution than the autosomes, implying a Faster-X effect. PMID:24489114

Isokinetic Dynamometry in Healthy Versus Sarcopenic and Malnourished Elderly: Beyond Simple Measurements of Muscle Strength.

PubMed

Cramer, Joel T; Jenkins, Nathaniel D M; Mustad, Vikkie A; Weir, Joseph P

2017-06-01

This study quantified systematic and intraindividual variability among three repetitions of concentric isokinetic knee extension and flexion tests to determine velocity-related differences in peak torque (PT) and mean power (MP) in healthy elderly (HE) versus sarcopenic and malnourished elderly (SME). In total, 107 HE ( n = 54 men, n = 53 women) and 261 SME ( n = 101 men, n = 160 women) performed three maximal concentric isokinetic knee extension and flexion repetitions at 60°·s -1 and 180°·s -1 . PT for Repetition 3 was lower than Repetitions 1 and 2, while MP for Repetition 1 was lower than Repetitions 2 and 3 in SME. Intraindividual variability among repetitions was correlated with strength, but not age, and was greater in SME, during knee flexion, and at 180°·s -1 . Velocity-related decreases in PT from 60°·s -1 to 180°·s -1 were more pronounced in SME. In summary, (a) the repetition with the highest PT value may be the best indicator of maximal strength, while the average may indicate strength maintenance in SME; (b) intraindividual variability among repetitions reflects functional decrements from HE to SME; and (c) decreases in PT from 60°·s to 180°·s may reflect greater losses of fast-twitch (type II) fiber function.

Is social interaction associated with alcohol consumption in Uganda?

PubMed

Tumwesigye, Nazarius Mbona; Kasirye, Rogers; Nansubuga, Elizabeth

2009-07-01

Little is documented about the association of alcohol consumption and social interaction in Uganda, a country with one of the highest per capita alcohol consumptions in the world. This paper describes the pattern of social interaction by sex and establishes the relationship between social interaction and alcohol consumption with and without the consideration of confounders. The data used had 1479 records and were collected in a survey in 2003. The study was part of a multinational study on Gender, Alcohol, and Culture International Study (GENACIS). Each question on social interaction had been pre-coded in a way that quantified the extent of social interaction. The sum of responses on interaction questions gave a summative score which was used to compute summary indices on social interaction. Principal component analysis (PCA) was used to identify the best combination of variables for a social interaction index. The index was computed by a prediction using a PCA model developed from the selected variables. The index was categorised into quintiles and used in bivariate and multivariate logistic regression analysis of alcohol consumption and social interaction. The stronger the social interaction the more the likelihood of taking alcohol frequently (chi(trend)(2)=4.72, p<0.001). The strength of the association remains significant even after controlling for sex, age group and education level (p=0.008). The strength of relationship between social interaction and heavy consumption of alcohol gets weak in multivariate analysis. Communication messages meant to improve health, well-being and public order need to incorporate dangers of negative influence of social interaction.

Patterns of morphological variation in enamel–dentin junction and outer enamel surface of human molars

PubMed Central

Morita, Wataru; Yano, Wataru; Nagaoka, Tomohito; Abe, Mikiko; Ohshima, Hayato; Nakatsukasa, Masato

2014-01-01

Tooth crown patterning is governed by the growth and folding of the inner enamel epithelium (IEE) and the following enamel deposition forms outer enamel surface (OES). We hypothesized that overall dental crown shape and covariation structure are determined by processes that configurate shape at the enamel–dentine junction (EDJ), the developmental vestige of IEE. This this hypothesis was tested by comparing patterns of morphological variation between EDJ and OES in human permanent maxillary first molar (UM1) and deciduous second molar (um2). Using geometric morphometric methods, we described morphological variation and covariation between EDJ and OES, and evaluated the strength of two components of phenotypic variability, canalization and morphological integration, in addition to the relevant evolutionary flexibility, i.e. the ability to respond to selective pressure. The strength of covariation between EDJ and OES was greater in um2 than in UM1, and the way that multiple traits covary between EDJ and OES was different between these teeth. The variability analyses showed that EDJ had less shape variation and a higher level of morphological integration than OES, which indicated that canalization and morphological integration acted as developmental constraints. These tendencies were greater in UM1 than in um2. On the other hand, EDJ and OES had a comparable level of evolvability in these teeth. Amelogenesis could play a significant role in tooth shape and covariation structure, and its influence was not constant among teeth, which may be responsible for the differences in the rate and/or period of enamel formation. PMID:24689536

Handgrip Strength as a Darwinian Fitness Indicator in Men.

PubMed

Gallup, Andrew C; Fink, Bernhard

2018-01-01

Handgrip strength (HGS) is a robust measure of overall muscular strength and function, and has long been predictive of a multitude of health factors and physical outcomes for both men and women. The fact that HGS represents such a ubiquitous measure of health and vitality may reflect the significance of this trait during human evolution. This trait is also highly sexually dimorphic due to influences of androgenic hormones and fat-free body mass, suggesting that it has been further elaborated through sexual selection. Consistent with this view, research within evolutionary psychology and related fields has documented distinct relationships between HGS and measures of social and sexual behavior, especially in men. Here, we review studies across different societies and cultural contexts showing that male HGS predicts measures of aggression and social dominance, perceived formidability, male-typical body morphology and movement, courtship display, physical attractiveness, and sexual behavior and reproductive fitness. These findings underscore the value of including HGS as an independent measure within studies examining human sexual selection, and corroborate existing research suggesting that specific features of physical strength have and continue to be under positive directional selection in men.

Exploring relationships between Dairy Herd Improvement monitors of performance and the Transition Cow Index in Wisconsin dairy herds.

PubMed

Schultz, K K; Bennett, T B; Nordlund, K V; Döpfer, D; Cook, N B

2016-09-01

Transition cow management has been tracked via the Transition Cow Index (TCI; AgSource Cooperative Services, Verona, WI) since 2006. Transition Cow Index was developed to measure the difference between actual and predicted milk yield at first test day to evaluate the relative success of the transition period program. This project aimed to assess TCI in relation to all commonly used Dairy Herd Improvement (DHI) metrics available through AgSource Cooperative Services. Regression analysis was used to isolate variables that were relevant to TCI, and then principal components analysis and network analysis were used to determine the relative strength and relatedness among variables. Finally, cluster analysis was used to segregate herds based on similarity of relevant variables. The DHI data were obtained from 2,131 Wisconsin dairy herds with test-day mean ≥30 cows, which were tested ≥10 times throughout the 2014 calendar year. The original list of 940 DHI variables was reduced through expert-driven selection and regression analysis to 23 variables. The K-means cluster analysis produced 5 distinct clusters. Descriptive statistics were calculated for the 23 variables per cluster grouping. Using principal components analysis, cluster analysis, and network analysis, 4 parameters were isolated as most relevant to TCI; these were energy-corrected milk, 3 measures of intramammary infection (dry cow cure rate, linear somatic cell count score in primiparous cows, and new infection rate), peak ratio, and days in milk at peak milk production. These variables together with cow and newborn calf survival measures form a group of metrics that can be used to assist in the evaluation of overall transition period performance. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Mechanical performance of encapsulated restorative glass-ionomer cements for use with Atraumatic Restorative Treatment (ART).

PubMed

Molina, Gustavo Fabián; Cabral, Ricardo Juan; Mazzola, Ignacio; Lascano, Laura Brain; Frencken, Jo E

2013-01-01

The Atraumatic Restorative Treatment (ART) approach was suggested to be a suitable method to treat enamel and dentine carious lesions in patients with disabilities. The use of a restorative glass-ionomer with optimal mechanical properties is, therefore, very important. To test the null-hypotheses that no difference in diametral tensile, compressive and flexural strengths exists between: (1) The EQUIA system and (2) The Chemfil Rock (encapsulated glass-ionomers; test materials) and the Fuji 9 Gold Label and the Ketac Molar Easymix (hand-mixed conventional glass-ionomers; control materials); (3) The EQUIA system and Chemfil Rock. Specimens for testing flexural (n = 240) and diametral tensile (n=80) strengths were prepared according to standardized specifications; the compressive strength (n=80) was measured using a tooth-model of a class II ART restoration. ANOVA and Tukey B tests were used to test for significant differences between dependent and independent variables. The EQUIA system and Chemfil Rock had significantly higher mean scores for all the three strength variables than the Fuji 9 Gold Label and Ketac Molar Easymix (α=0.05). The EQUIA system had significant higher mean scores for diametral tensile and flexural strengths than the Chemfil Rock (α=0.05). The two encapsulated high-viscosity glass-ionomers had significantly higher test values for diametral tensile, flexural and compressive strengths than the commonly used hand-mixed high-viscosity glass-ionomers.

Effect of Loading Rates and Surface Conditions on the Flexural Strength of Borosilicate Glass

DTIC Science & Technology

2009-01-01

strength of etched soda - lime glass rods.32 According to this model, an idealized surface crack is uniformly attacked by acid at every point so that this...R. Lin, ‘‘Effect of Polymer Coatings on the Strength and Fatigue Behavior of Indented Soda - Lime Glass ,’’ Glass Technol., 32 [2] 51–4 (1991). 10J. J...Scott Glaesemann, K. Jakus, and J. E. Ritter Jr., ‘‘Strength Variability of Indented Soda - Lime Glass ,’’ J. Am. Ceram. Soc., 70 [6] 441–4 (1987). 12C

Development of modified release diltiazem HCl tablets using composite index to identify optimal formulation.

PubMed

Gohel, M C; Patel, M M; Amin, A F

2003-05-01

This article reports the preparation of tartaric acid treated ispaghula husk powder for the development of modified release tablets of diltiazem HCl by adopting direct compression technique and a 32 full factorial design. The modified ispaghula husk powder showed superior swelling and gelling as compared to untreated powder. Addition of compaction augmenting agent such as dicalcium phosphate was found to be essential for obtaining tablets with adequate crushing strength. In order to improve the crushing strength of diltiazem HCl tablets, to modulate drug release pattern, and to obtain similarity of dissolution profiles in distilled water and simulated gastric fluid (pH 1.2), modified guar gum was used along with modified ispaghula husk powder and tartaric acid. A novel composite index, which considers a positive or a negative deviation from an ideal value, was calculated considering percentage drug release in 60, 300, and 540 min as dependent variables for the selection of a most appropriate batch. Polynomial equation and contour plots are presented. The concept of similarity factor (f2) was used to prove similarity of dissolution in water and simulated gastric fluid (pH 1.2).

Vertebral body bone strength: the contribution of individual trabecular element morphology.

PubMed

Parkinson, I H; Badiei, A; Stauber, M; Codrington, J; Müller, R; Fazzalari, N L

2012-07-01

Although the amount of bone explains the largest amount of variability in bone strength, there is still a significant proportion unaccounted for. The morphology of individual bone trabeculae explains a further proportion of the variability in bone strength and bone elements that contribute to bone strength depending on the direction of loading. Micro-CT imaging enables measurement of bone microarchitecture and subsequently mechanical strength of the same sample. It is possible using micro-CT data to perform morphometric analysis on individual rod and plate bone trabeculae using a volumetric spatial decomposition algorithm and hence determine their contribution to bone strength. Twelve pairs of vertebral bodies (T12/L1 or L4/L5) were harvested from human cadavers, and bone cubes (10 × 10 × 10 mm) were obtained. After micro-CT imaging, a volumetric spatial decomposition algorithm was applied, and measures of individual trabecular elements were obtained. Bone strength was measured in compression, where one bone specimen from each vertebral segment was tested supero-inferiorly (SI) and the paired specimen was tested antero-posteriorly (AP). Bone volume fraction was the strongest individual determinant of SI strength (r(2) = 0.77, p < 0.0001) and AP (r(2) = 0.54, p < 0.0001). The determination of SI strength was improved to r(2) = 0.87 with the addition of mean rod length and relative plate bone volume fraction. The determination of AP strength was improved to r(2) = 0.85 with the addition of mean rod volume and relative rod bone volume fraction. Microarchitectural measures of individual trabeculae that contribute to bone strength have been identified. In addition to the contribution of BV/TV, trabecular rod morphology increased the determination of AP strength by 57%, whereas measures of trabecular plate and rod morphology increased determination of SI strength by 13%. Decomposing vertebral body bone architecture into its constituent morphological elements shows that trabecular element morphology has specific functional roles to assist in maintaining skeletal integrity.

Hamstring and Quadriceps Isokinetic Strength Deficits Are Weak Risk Factors for Hamstring Strain Injuries: A 4-Year Cohort Study.

PubMed

van Dyk, Nicol; Bahr, Roald; Whiteley, Rodney; Tol, Johannes L; Kumar, Bhavesh D; Hamilton, Bruce; Farooq, Abdulaziz; Witvrouw, Erik

2016-07-01

A hamstring strain injury (HSI) has become the most common noncontact injury in soccer. Isokinetic muscle strength deficits are considered a risk factor for HSIs. However, underpowered studies with small sample sizes unable to determine small associations have led to inconclusive results regarding the role of isokinetic strength and strength testing in HSIs. To examine whether differences in isokinetic strength measures of knee flexion and extension represent risk factors for hamstring injuries in a large cohort of professional soccer players in an adequately powered study design. Cohort study; Level of evidence, 2. A total of 614 professional soccer players from 14 teams underwent isokinetic strength testing during preseason screening. Testing consisted of concentric knee flexion and extension at 60 deg/s and 300 deg/s and eccentric knee extension at 60 deg/s. A clustered multiple logistic regression analysis was used to identify variables associated with the risk of HSIs. Receiver operating characteristic (ROC) curves were calculated to determine sensitivity and specificity. Of the 614 players, 190 suffered an HSI during the 4 seasons. Quadriceps concentric strength at 60 deg/s (odds ratio [OR], 1.41; 95% CI, 1.03-1.92; P = .03) and hamstring eccentric strength at 60 deg/s (OR, 1.37; 95% CI, 1.01-1.85; P = .04) adjusted for bodyweight were independently associated with the risk of injuries. The absolute differences between the injured and uninjured players were 6.9 N·m and 9.1 N·m, with small effect sizes (d < 0.2). The ROC analyses showed an area under the curve of 0.54 and 0.56 for quadriceps concentric strength and hamstring eccentric strength, respectively, indicating a failed combined sensitivity and specificity of the 2 strength variables identified in the logistic regression models. This study identified small absolute strength differences and a wide overlap of the absolute strength measurements at the group level. The small associations between lower hamstring eccentric strength and lower quadriceps concentric strength with HSIs can only be considered as weak risk factors. The identification of these risk factors still does not allow the identification of individual players at risk. The use of isokinetic testing to determine the association between strength differences and HSIs is not supported. © 2016 The Author(s).

Do physiological measures predict selected CrossFit® benchmark performance?

PubMed Central

Butcher, Scotty J; Neyedly, Tyler J; Horvey, Karla J; Benko, Chad R

2015-01-01

Purpose CrossFit® is a new but extremely popular method of exercise training and competition that involves constantly varied functional movements performed at high intensity. Despite the popularity of this training method, the physiological determinants of CrossFit performance have not yet been reported. The purpose of this study was to determine whether physiological and/or muscle strength measures could predict performance on three common CrossFit “Workouts of the Day” (WODs). Materials and methods Fourteen CrossFit Open or Regional athletes completed, on separate days, the WODs “Grace” (30 clean and jerks for time), “Fran” (three rounds of thrusters and pull-ups for 21, 15, and nine repetitions), and “Cindy” (20 minutes of rounds of five pull-ups, ten push-ups, and 15 bodyweight squats), as well as the “CrossFit Total” (1 repetition max [1RM] back squat, overhead press, and deadlift), maximal oxygen consumption (VO2max), and Wingate anaerobic power/capacity testing. Results Performance of Grace and Fran was related to whole-body strength (CrossFit Total) (r=−0.88 and −0.65, respectively) and anaerobic threshold (r=−0.61 and −0.53, respectively); however, whole-body strength was the only variable to survive the prediction regression for both of these WODs (R2=0.77 and 0.42, respectively). There were no significant associations or predictors for Cindy. Conclusion CrossFit benchmark WOD performance cannot be predicted by VO2max, Wingate power/capacity, or either respiratory compensation or anaerobic thresholds. Of the data measured, only whole-body strength can partially explain performance on Grace and Fran, although anaerobic threshold also exhibited association with performance. Along with their typical training, CrossFit athletes should likely ensure an adequate level of strength and aerobic endurance to optimize performance on at least some benchmark WODs. PMID:26261428

Evaluating the time and temperature dependent biaxial strength of Gore-Select ® series 57 proton exchange membrane using a pressure loaded blister test

NASA Astrophysics Data System (ADS)

Grohs, Jacob R.; Li, Yongqiang; Dillard, David A.; Case, Scott W.; Ellis, Michael W.; Lai, Yeh-Hung; Gittleman, Craig S.

Temperature and humidity fluctuations in operating fuel cells impose significant biaxial stresses in the constrained proton exchange membranes (PEMs) of a fuel cell stack. The strength of the PEM, and its ability to withstand cyclic environment-induced stresses, plays an important role in membrane integrity and consequently, fuel cell durability. In this study, a pressure loaded blister test is used to characterize the biaxial strength of Gore-Select ® series 57 over a range of times and temperatures. Hencky's classical solution for a pressurized circular membrane is used to estimate biaxial strength values from burst pressure measurements. A hereditary integral is employed to construct the linear viscoelastic analog to Hencky's linear elastic exact solution. Biaxial strength master curves are constructed using traditional time-temperature superposition principle techniques and the associated temperature shift factors show good agreement with shift factors obtained from constitutive (stress relaxation) and fracture (knife slit) tests of the material.

Synthesis, quantitative structure-property relationship study of novel fluorescence active 2-pyrazolines and application.

PubMed

Girgis, Adel S; Basta, Altaf H; El-Saied, Houssni; Mohamed, Mohamed A; Bedair, Ahmad H; Salim, Ahmad S

2018-03-01

A variety of fluorescence-active fluorinated pyrazolines 13-33 was synthesized in good yields through cyclocondensation reaction of propenones 1-9 with aryl hydrazines 10-12 . Some of the synthesized compounds provided promising fluorescence properties with quantum yield ( Φ ) higher than that of quinine sulfate (standard reference). Quantitative structure-property relationship studies were undertaken supporting the exhibited fluorescence properties and estimating the parameters governing properties. Five synthesized fluorescence-active pyrazolines ( 13 , 15 , 18 , 19 and 23 ) with variable Φ were selected for treating two types of paper sheets (Fabriano and Bible paper). These investigated fluorescence compounds, especially compounds 19 and 23 , provide improvements in strength properties of paper sheets. Based on the observed performance they can be used as markers in security documents.

Synthesis, quantitative structure–property relationship study of novel fluorescence active 2-pyrazolines and application

PubMed Central

Girgis, Adel S.; El-Saied, Houssni; Mohamed, Mohamed A.; Bedair, Ahmad H.; Salim, Ahmad S.

2018-01-01

A variety of fluorescence-active fluorinated pyrazolines 13–33 was synthesized in good yields through cyclocondensation reaction of propenones 1–9 with aryl hydrazines 10–12. Some of the synthesized compounds provided promising fluorescence properties with quantum yield (Φ) higher than that of quinine sulfate (standard reference). Quantitative structure–property relationship studies were undertaken supporting the exhibited fluorescence properties and estimating the parameters governing properties. Five synthesized fluorescence-active pyrazolines (13, 15, 18, 19 and 23) with variable Φ were selected for treating two types of paper sheets (Fabriano and Bible paper). These investigated fluorescence compounds, especially compounds 19 and 23, provide improvements in strength properties of paper sheets. Based on the observed performance they can be used as markers in security documents. PMID:29657796

Logistic regression applied to natural hazards: rare event logistic regression with replications

NASA Astrophysics Data System (ADS)

Guns, M.; Vanacker, V.

2012-06-01

Statistical analysis of natural hazards needs particular attention, as most of these phenomena are rare events. This study shows that the ordinary rare event logistic regression, as it is now commonly used in geomorphologic studies, does not always lead to a robust detection of controlling factors, as the results can be strongly sample-dependent. In this paper, we introduce some concepts of Monte Carlo simulations in rare event logistic regression. This technique, so-called rare event logistic regression with replications, combines the strength of probabilistic and statistical methods, and allows overcoming some of the limitations of previous developments through robust variable selection. This technique was here developed for the analyses of landslide controlling factors, but the concept is widely applicable for statistical analyses of natural hazards.

VRACK: measuring pedal kinematics during stationary bike cycling.

PubMed

Farjadian, Amir B; Kong, Qingchao; Gade, Venkata K; Deutsch, Judith E; Mavroidis, Constantinos

2013-06-01

Ankle impairment and lower limb asymmetries in strength and coordination are common symptoms for individuals with selected musculoskeletal and neurological impairments. The virtual reality augmented cycling kit (VRACK) was designed as a compact mechatronics system for lower limb and mobility rehabilitation. The system measures interaction forces and cardiac activity during cycling in a virtual environment. The kinematics measurement was added to the system. Due to the constrained problem definition, the combination of inertial measurement unit (IMU) and Kalman filtering was recruited to compute the optimal pedal angular displacement during dynamic cycling exercise. Using a novel benchmarking method the accuracy of IMU-based kinematics measurement was evaluated. Relatively accurate angular measurements were achieved. The enhanced VRACK system can serve as a rehabilitation device to monitor biomechanical and physiological variables during cycling on a stationary bike.

Synthesis, quantitative structure-property relationship study of novel fluorescence active 2-pyrazolines and application

NASA Astrophysics Data System (ADS)

Girgis, Adel S.; Basta, Altaf H.; El-Saied, Houssni; Mohamed, Mohamed A.; Bedair, Ahmad H.; Salim, Ahmad S.

2018-03-01

A variety of fluorescence-active fluorinated pyrazolines 13-33 was synthesized in good yields through cyclocondensation reaction of propenones 1-9 with aryl hydrazines 10-12. Some of the synthesized compounds provided promising fluorescence properties with quantum yield (Φ) higher than that of quinine sulfate (standard reference). Quantitative structure-property relationship studies were undertaken supporting the exhibited fluorescence properties and estimating the parameters governing properties. Five synthesized fluorescence-active pyrazolines (13, 15, 18, 19 and 23) with variable Φ were selected for treating two types of paper sheets (Fabriano and Bible paper). These investigated fluorescence compounds, especially compounds 19 and 23, provide improvements in strength properties of paper sheets. Based on the observed performance they can be used as markers in security documents.

Experimental Study on Dissimilar Friction Stir welding of Aluminium Alloys (5083-H111 and 6082-T6) to investigate the mechanical properties

NASA Astrophysics Data System (ADS)

Kumar, H. M. Anil; Venkata Ramana, V.; Pawar, Mayur

2018-03-01

Friction stir welding is an innovative technology in the joining realm of metals and alloys. This technique is highly economical and suitable especially for non ferrous alloys compared to ferrous alloys. It finds many applications in various fields of aeronautics, automobile, ship building industries etc. The paper presents the comparative results of mechanical properties such as tensile strength, microstructure, macro structure and hardness on the similar and dissimilar aluminum alloys AA5083-H111 and AA6082-T6 under certain selected variables - constant tool rotational speed, its tilt angle, welding speed using friction stir welding process. It is observed from the experimental results that joint efficiency of dissimilar aluminium alloys is higher than the similar aluminum alloys.

Relations among religiosity, health, happiness, and anxiety for Kuwaiti adolescents.

PubMed

Baroun, Khader A

2006-12-01

The present study investigated correlations among religiosity, health, happiness, and anxiety for 941 Kuwaiti adolescents. A convenience sample of male (n=408) and female (n=533) students (M age = 16.5, SD = 1.2 yr.) was randomly selected from secondary school students of different districts of the State of Kuwait. The Intrinsic Religious Motivation scale, the Kuwait University Anxiety Scale, and six self-rating scales assessing religiosity, strength of religious belief, physical health, mental health, happiness, and life satisfaction were applied to assess correlations among Kuwaiti adolescents. Analysis showed boys had significantly higher mean scores than girls on all measures except anxiety, on which girls scored significantly higher than boys. There also were significant and positive correlations among the variables, except for anxiety, which was significant and negative.

Identification of solid state fermentation degree with FT-NIR spectroscopy: Comparison of wavelength variable selection methods of CARS and SCARS.

PubMed

Jiang, Hui; Zhang, Hang; Chen, Quansheng; Mei, Congli; Liu, Guohai

2015-01-01

The use of wavelength variable selection before partial least squares discriminant analysis (PLS-DA) for qualitative identification of solid state fermentation degree by FT-NIR spectroscopy technique was investigated in this study. Two wavelength variable selection methods including competitive adaptive reweighted sampling (CARS) and stability competitive adaptive reweighted sampling (SCARS) were employed to select the important wavelengths. PLS-DA was applied to calibrate identified model using selected wavelength variables by CARS and SCARS for identification of solid state fermentation degree. Experimental results showed that the number of selected wavelength variables by CARS and SCARS were 58 and 47, respectively, from the 1557 original wavelength variables. Compared with the results of full-spectrum PLS-DA, the two wavelength variable selection methods both could enhance the performance of identified models. Meanwhile, compared with CARS-PLS-DA model, the SCARS-PLS-DA model achieved better results with the identification rate of 91.43% in the validation process. The overall results sufficiently demonstrate the PLS-DA model constructed using selected wavelength variables by a proper wavelength variable method can be more accurate identification of solid state fermentation degree. Copyright © 2015 Elsevier B.V. All rights reserved.

Identification of solid state fermentation degree with FT-NIR spectroscopy: Comparison of wavelength variable selection methods of CARS and SCARS

NASA Astrophysics Data System (ADS)

Jiang, Hui; Zhang, Hang; Chen, Quansheng; Mei, Congli; Liu, Guohai

2015-10-01

The use of wavelength variable selection before partial least squares discriminant analysis (PLS-DA) for qualitative identification of solid state fermentation degree by FT-NIR spectroscopy technique was investigated in this study. Two wavelength variable selection methods including competitive adaptive reweighted sampling (CARS) and stability competitive adaptive reweighted sampling (SCARS) were employed to select the important wavelengths. PLS-DA was applied to calibrate identified model using selected wavelength variables by CARS and SCARS for identification of solid state fermentation degree. Experimental results showed that the number of selected wavelength variables by CARS and SCARS were 58 and 47, respectively, from the 1557 original wavelength variables. Compared with the results of full-spectrum PLS-DA, the two wavelength variable selection methods both could enhance the performance of identified models. Meanwhile, compared with CARS-PLS-DA model, the SCARS-PLS-DA model achieved better results with the identification rate of 91.43% in the validation process. The overall results sufficiently demonstrate the PLS-DA model constructed using selected wavelength variables by a proper wavelength variable method can be more accurate identification of solid state fermentation degree.

Behavioral Variables Associated with Obesity in Police Officers

PubMed Central

CAN, S. Hakan; HENDY, Helen M.

2014-01-01

Past research has documented that non-behavioral variables (such as long work hours, exposure to police stressors) are associated with obesity risk in police officers, but limited research has examined behavioral variables that might be targeted by Employee Assistance Programs for police weight management. The present study compared non-obese and obese officers for behavioral variables found associated with obesity in other adult samples: physical activity (cardiovascular, strength-training, stretching), sleep duration, and consumption of alcohol, fruit and vegetables, and snack foods. Participants included 172 male police officers who completed questionnaires to report height and weight, used to calculate body mass index (BMI = kg/m2) and to divide them into “non-obese” and “obese” groups. They also reported the above behaviors and six non-behavioral variables found associated with obesity risk: age, health problems, family support, police work hours, police stressors, police support. ANCOVAs compared each behavioral variable across obesity status (non-obese, obese), with the six non-behavioral variables used as covariates. Results revealed that cardiovascular and strength-training physical activity were the only behavioral variables that differed significantly between non-obese and obese police officers. The use of self-reported height and weight values may provide Employee Assistance Program with improved cost, time, and officer participation. PMID:24694574

Examining the causes of memory strength variability: Recollection, attention failure, or encoding variability?

PubMed Central

Koen, Joshua D.; Aly, Mariam; Wang, Wei-Chun; Yonelinas, Andrew P.

2013-01-01

A prominent finding in recognition memory is that studied items are associated with more variability in memory strength than new items. Here, we test three competing theories for why this occurs - the encoding variability, attention failure, and recollection accounts. Distinguishing amongst these theories is critical because each provides a fundamentally different account of the processes underlying recognition memory. The encoding variability and attention failure accounts propose that old item variance will be unaffected by retrieval manipulations because the processes producing this effect are ascribed to encoding. The recollection account predicts that both encoding and retrieval manipulations that preferentially affect recollection will affect memory variability. These contrasting predictions were tested by examining the effect of response speeding (Experiment 1), dividing attention at retrieval (Experiment 2), context reinstatement (Experiment 3), and increased test delay (Experiment 4) on recognition performance. The results of all four experiments confirmed the predictions of the recollection account, and were inconsistent with the encoding variability account. The evidence supporting the attention failure account was mixed, with two of the four experiments confirming the account and two disconfirming the account. These results indicate that encoding variability and attention failure are insufficient accounts of memory variance, and provide support for the recollection account. Several alternative theoretical accounts of the results are also considered. PMID:23834057

Using Spoken Language Benchmarks to Characterize the Expressive Language Skills of Young Children With Autism Spectrum Disorders

PubMed Central

Weismer, Susan Ellis

2015-01-01

Purpose Spoken language benchmarks proposed by Tager-Flusberg et al. (2009) were used to characterize communication profiles of toddlers with autism spectrum disorders and to investigate if there were differences in variables hypothesized to influence language development at different benchmark levels. Method The communication abilities of a large sample of toddlers with autism spectrum disorders (N = 105) were characterized in terms of spoken language benchmarks. The toddlers were grouped according to these benchmarks to investigate whether there were differences in selected variables across benchmark groups at a mean age of 2.5 years. Results The majority of children in the sample presented with uneven communication profiles with relative strengths in phonology and significant weaknesses in pragmatics. When children were grouped according to one expressive language domain, across-group differences were observed in response to joint attention and gestures but not cognition or restricted and repetitive behaviors. Conclusion The spoken language benchmarks are useful for characterizing early communication profiles and investigating features that influence expressive language growth. PMID:26254475

Different nano-particles volume fraction and Hartmann number effects on flow and heat transfer of water-silver nanofluid under the variable heat flux

NASA Astrophysics Data System (ADS)

Forghani-Tehrani, Pezhman; Karimipour, Arash; Afrand, Masoud; Mousavi, Sayedali

2017-01-01

Nanofluid flow and heat transfer composed of water-silver nanoparticles is investigated numerically inside a microchannel. Finite volume approach (FVM) is applied and the effects of gravity are ignored. The whole length of Microchannel is considered in three sections as l1=l3=0.151 and l2=0.71. The linear variable heat flux affects the microchannel wall in the length of l2 while a magnetic field with strength of B0 is considered over the whole domain of it. The influences of different values of Hartmann number (Ha=0, 10, 20), volume fraction of the nanoparticles (ɸ=0, 0.02, 0.04) and Reynolds number (Re=10, 50, 200) on the hydrodynamic and thermal properties of flow are reported. The investigation of slip velocity variations under the effects of a magnetic field are presented for the first time (to the best knowledge of author) while the non-dimensional slip coefficient are selected as B=0.01, 0.05, 0.1 at different states.

Individualistic and Time-Varying Tree-Ring Growth to Climate Sensitivity

PubMed Central

Carrer, Marco

2011-01-01

The development of dendrochronological time series in order to analyze climate-growth relationships usually involves first a rigorous selection of trees and then the computation of the mean tree-growth measurement series. This study suggests a change in the perspective, passing from an analysis of climate-growth relationships that typically focuses on the mean response of a species to investigating the whole range of individual responses among sample trees. Results highlight that this new approach, tested on a larch and stone pine tree-ring dataset, outperforms, in terms of information obtained, the classical one, with significant improvements regarding the strength, distribution and time-variability of the individual tree-ring growth response to climate. Moreover, a significant change over time of the tree sensitivity to climatic variability has been detected. Accordingly, the best-responder trees at any one time may not always have been the best-responders and may not continue to be so. With minor adjustments to current dendroecological protocol and adopting an individualistic approach, we can improve the quality and reliability of the ecological inferences derived from the climate-growth relationships. PMID:21829523

Physiological correlates of skating performance in women's and men's ice hockey.

PubMed

Gilenstam, Kajsa M; Thorsen, Kim; Henriksson-Larsén, Karin B

2011-08-01

The purpose of the current investigation was to identify relationships between physiological off-ice tests and on-ice performance in female and male ice hockey players on a comparable competitive level. Eleven women, 24 ± 3.0 years, and 10 male ice hockey players, 23 ± 2.4 years, were tested for background variables: height, body weight (BW), ice hockey history, and lean body mass (LBM) and peak torque (PT) of the thigh muscles, VO2peak and aerobic performance (Onset of Blood Lactate Accumulation [OBLA], respiratory exchange ratio [RER1]) during an incremental bicycle ergometer test. Four different on-ice tests were used to measure ice skating performance. For women, skating time was positively correlated (p < 0.05) to BW and negatively correlated to LBM%, PT/BW, OBLA, RER 1, and VO2peak (ml O2·kg(-1) BW(-1)·min(-1)) in the Speed test. Acceleration test was positively correlated to BW and negatively correlated to OBLA and RER 1. For men, correlation analysis revealed only 1 significant correlation where skating time was positively correlated to VO2peak (L O2·min(-1)) in the Acceleration test. The male group had significantly higher physiological test values in all variables (absolute and relative to BW) but not in relation to LBM. Selected off-ice tests predict skating performance for women but not for men. The group of women was significantly smaller and had a lower physiological performance than the group of men and were slower in the on-ice performance tests. However, gender differences in off-ice variables were reduced or disappeared when values were related to LBM, indicating a similar capacity of producing strength and aerobic power in female and male hockey players. Skating performance in female hockey players may be improved by increasing thigh muscle strength, oxygen uptake, and relative muscle mass.

Tree Ring Analyses Unlock a Century of Hydroclimatic Variability Across the Himalayas

NASA Astrophysics Data System (ADS)

Brunello, C. F.; Andermann, C.; Helle, G.; Comiti, F.; Tonon, G.; Hovius, N.

2017-12-01

Climate change has altered precipitation patterns and impacted the spatio-temporal distribution and availability of water in high mountain environments. For example, intensification of the Indian Summer Monsoon (ISM) increases the potential for moisture laden air to breach the Himalayan orographic barrier and penetrate into the arid, elevated southern Tibetan Plateau, with geomorphological and hydrological consequences. Such trends should be considered against a solid background, but a consistent record of centennial monsoon dynamics in the trans-Himalayan region has never been developed. Instrumental data are sparse and only cover a limited time period as well as remotely sensed information. Meanwhile, models have major systematic bias and substantial uncertainty in reproducing ISM interannual variability. In this context, hydro-climatic proxies, such as oxygen stable isotope ratios in cellulose of tree rings, are a valuable source of data, especially because isotope mass spectroscopy can unlock yearly resolved information by tracing the isotopic signature (18O) stored within each growth ring. Here we present three centennial records of monsoon dynamics, along a latitudinal transect, spanning a pronounced precipitation gradient across the Himalayan orogen. Three sites were selected along the Kali Gandaki valley in the central Himalayas (Nepal), this valley connects the wet, monsoon dominated Gangetic plain with the arid Tibetan Plateau. Our transect covers the sensitive northern end of the precipitation gradient, located in the upper part of the catchment. Our results show that inter-annual variation of monsoon strength can be reconstructed by tree ring δ18O. The inferred monsoon dynamics are compared against independent constraints on precipitation, snow cover and river discharge. Different water sources contribute disproportionally at the three sites, reflecting spatial and temporal shifts of the westerlies and the Indian summer monsoon. These two dominant sources of humidity are complemented by recycled continental circulation characterizing pre-monsoon rainfall. Our yearly resolved records of monsoon strength provide insights into anomalous hydro-climatic years and highlight the importance of precipitation variability for the hydrological processes in high mountain regions.

State-of-the-Art pH Electrode Quality Control for Measurements of Acidic, Low Ionic Strength Waters.

ERIC Educational Resources Information Center

Stapanian, Martin A.; Metcalf, Richard C.

1990-01-01

Described is the derivation of the relationship between the pH measurement error and the resulting percentage error in hydrogen ion concentration including the use of variable activity coefficients. The relative influence of the ionic strength of the solution on the percentage error is shown. (CW)

Transient impact of prolonged versus repetitive stretch on hand motor control in chronic stroke.

PubMed

Triandafilou, Kristen M; Ochoa, Jose; Kang, Xuan; Fischer, Heidi C; Stoykov, Mary Ellen; Kamper, Derek G

2011-01-01

The purpose of this study was to investigate the influence of prolonged and repetitive passive range of motion (PROM) stretching of the fingers on hand function in stroke survivors. Fifteen chronic stroke survivors with moderate to severe hand impairment took part in the study. Participants underwent 3 experimental sessions consisting of 30 minutes of rest, prolonged, or repetitive stretching of the finger flexor muscles by a powered glove orthosis (X-Glove). Outcome measures, comprised of 3 selected tasks from the Graded Wolf Motor Function Test (GWMFT), grip strength, lateral pinch strength, and grip relaxation time, were recorded at the start and end of each session. Change in outcome score for each session was used for analysis. Data suggested a trend for improvement following stretching, especially for the repetitive PROM case. For one GWMFT task (lift washcloth), the effect of stretching condition on performance time approached a statistical significance (P = .015), with repetitive PROM stretching producing the greatest mean reduction. Similarly, repetitive stretching led to a 12% ± 16% increase in grip strength, although this change was not statistically different across groups (P = .356); and grip termination time was reduced, albeit non-significantly, by 66% ± 133%. Repetitive PROM stretching exhibited trends to be more effective than prolonged stretching for improving hand motor control. Although the results were highly variable and the effects are undoubtedly transient, an extended period of repetitive PROM stretching may prove advantageous prior to hand therapy sessions to maximize treatment.

Effect of intermittent eccentric contractions on symptoms of muscle microinjury.

PubMed

Teague, B N; Schwane, J A

1995-10-01

The purpose was to determine whether varying the duration of rest between contractions affects selected symptoms of eccentric contraction-induced skeletal muscle microinjury. Thirty-three women were assigned to three groups (N = 11). Each performed one bout of exercise with each arm involving 10 eccentric contractions of the elbow flexor muscles, lowering a load equaling 60% of maximal static force. One arm exercised continuously; the other exercised with rest periods of 15 s, 5 min, or 10 min between contractions, depending on the group. Preexercise and 0, 24, and 48 h postexercise, symptoms of microinjury in the elbow flexor muscles were assessed: soreness and changes in strength, resting elbow angle ("musculotendinous stiffness"), and arm girth ("swelling"). For all groups combined, 10 continuous contractions caused changes (P < 0.05) in all variables at every measurement time. For example, soreness ratings (0-10 scale) were 4.3 +/- 2.0 (24 h) and 4.3 +/- 2.1 (48 h) and strength was reduced 18% 0 h postexercise. Responses were similar with 15 s of rest between contractions. Although they were moderated, symptoms occurred even with 5 and 10 min of rest. With 10 min between contractions, soreness occurred (e.g., 2.4 +/- 1.5 [24 h]) and strength was 17% reduced 0 h postexercise. Results are most consistent with a mechanical cause of eccentric contraction-induced muscle microinjury, rather than a metabolic or other factor with a short recovery time, although involvement of the latter cannot be ruled out.

Relationship between performance variables and baseball ability in youth baseball players.

PubMed

Nakata, Hiroki; Nagami, Tomoyuki; Higuchi, Takatoshi; Sakamoto, Kiwako; Kanosue, Kazuyuki

2013-10-01

The present study investigated the relationship of performance variables and anthropometric measurements on baseball ability in 164 youth baseball players (age: 6.4-15.7 years). To evaluate their baseball performance, ball speeds in pitching and batting were recorded and kinetic energies of the pitched and hit balls were calculated. To record anthropometric and physical fitness characteristics, height and weight were measured and a battery of physical fitness tests covering standing long jump, side steps, sit-ups, 10-m sprint, trunk flexion, back strength, and grip strengths of both hands were conducted. The results of a multiple regression analysis revealed several significant predictors: age, body mass index (BMI), standing long jump, 10-m sprint, and grip strength for pitched ball kinetic energy and age, BMI, standing long jump, and back strength for hit ball kinetic energy. This study provides scientific evidence that relates certain specific physical performance tests and body characteristics with high achievement in the actual performance of pitching and batting. Youth players, their parents, coaches, and trainers would benefit by addressing these characteristics when planning training programs to improve the baseball performance of youth players.

Determinants of the mechanical properties of bones

NASA Technical Reports Server (NTRS)

Martin, R. B.

1991-01-01

The mechanical properties of bones are governed by the same principles as those of man-made load-bearing structures, but the organism is able to adapt its bone structure to changes in skeletal loading. In this overview of the determinants of the strength and stiffness of bone, a continuum approach has been taken, in which the behavior of a macroscopic structure depends on its shape and size, and on the mechanical properties of the material within. The latter are assumed to depend on the composition (porosity and mineralization) and organization (trabecular or cortical bone architecture, collagen fiber orientation, fatigue damage) of the bone. The effects of each of these factors are reviewed. Also, the possible means of non-invasively estimating the strength or other mechanical properties of a bone are reviewed, including quantitative computed tomography, photon absorptiometry, and ultrasonic measurements. The best estimates of strength have been obtained with photon absorptiometry and computed tomography, which at best are capable of accounting for 90% of the strength variability in a simple in vitro test, but results from different laboratories have been highly variable.

The Impact of an Ego Depletion Manipulation on Performance-Based and Self-Report Assessment Measures.

PubMed

Charek, Daniel B; Meyer, Gregory J; Mihura, Joni L

2016-10-01

We investigated the impact of ego depletion on selected Rorschach cognitive processing variables and self-reported affect states. Research indicates acts of effortful self-regulation transiently deplete a finite pool of cognitive resources, impairing performance on subsequent tasks requiring self-regulation. We predicted that relative to controls, ego-depleted participants' Rorschach protocols would have more spontaneous reactivity to color, less cognitive sophistication, and more frequent logical lapses in visualization, whereas self-reports would reflect greater fatigue and less attentiveness. The hypotheses were partially supported; despite a surprising absence of self-reported differences, ego-depleted participants had Rorschach protocols with lower scores on two variables indicative of sophisticated combinatory thinking, as well as higher levels of color receptivity; they also had lower scores on a composite variable computed across all hypothesized markers of complexity. In addition, self-reported achievement striving moderated the effect of the experimental manipulation on color receptivity, and in the Depletion condition it was associated with greater attentiveness to the tasks, more color reactivity, and less global synthetic processing. Results are discussed with an emphasis on the response process, methodological limitations and strengths, implications for calculating refined Rorschach scores, and the value of using multiple methods in research and experimental paradigms to validate assessment measures. © The Author(s) 2015.

Exercise and BMI z-score in Overweight and Obese Children and Adolescents: A Systematic Review and Network Meta-Analysis of Randomized Trials.

PubMed

Kelley, George A; Kelley, Kristi S; Pate, Russell R

2017-05-01

Examine the effects of selected types of exercise (aerobic, strength training, both) on BMI z-score in overweight and obese children and adolescents. Randomized exercise intervention trials ≥ 4 weeks were included. Studies were retrieved by searching six electronic databases, cross-referencing and expert review. Dual selection and abstraction occurred. Risk of bias and confidence in cumulative evidence were assessed. Network meta-analysis was performed using multivariate random-effects meta-regression models while surface under the cumulative ranking curves were used to calculate a hierarchy of exercise treatments. The number needed to treat (NNT) and percentile improvement (U 3 ) were also calculated. Thirty-four studies representing 2,239 participants were included. Median exercise occurred 3 times per week, 50 minutes per session over a 12-week period. Statistically significant reductions in BMI z-score were found for aerobic exercise and combined aerobic and strength exercise, but not strength training alone (M±SD, 95% CI: aerobic, -0.10, -0.15 to -0.05; aerobic and strength, -0.11, -0.19 to -0.03; strength, 0.04, -0.07 to 0.15). Combined aerobic and strength training was ranked best, followed by aerobic exercise and strength training. The NNT was 2 for both aerobic exercise and combined aerobic exercise and strength training. Percentile improvements were 28.8% for aerobic exercise and 31.5% for combined aerobic exercise and strength training. Confidence in effect estimates was ranked as low for aerobic exercise and very low for combined aerobic and strength training as well as strength training. Aerobic exercise and combined aerobic exercise and strength training are associated with reductions in BMI z-score. © 2016 Chinese Cochrane Center, West China Hospital of Sichuan University and John Wiley & Sons Australia, Ltd.

Exercise and BMI z-score in Overweight and Obese Children and Adolescents: A Systematic Review and Network Meta-Analysis of Randomized Trials

PubMed Central

George, Kelley; Kristi, Kelley; Russell, Pate

2017-01-01

Aim Examine the effects of selected types of exercise (aerobic, strength training, both) on BMI z-score in overweight and obese children and adolescents. Methods Randomized exercise intervention trials ≥ 4 weeks were included. Studies were retrieved by searching six electronic databases, cross-referencing and expert review. Dual selection and abstraction occurred. Risk of bias and confidence in cumulative evidence were assessed. Network meta-analysis was performed using multivariate random-effects meta-regression models while surface under the cumulative ranking curves were used to calculate a hierarchy of exercise treatments. The number needed to treat (NNT) and percentile improvement (U3) were also calculated. Results Thirty-four studies representing 2,239 participants were included. Median exercise occurred 3 times per week, 50 minutes per session over a 12-week period. Statistically significant reductions in BMI z-score were found for aerobic exercise and combined aerobic and strength exercise, but not strength training alone (M±SD, 95% CI: aerobic, -0.10, -0.15 to -0.05; aerobic and strength, -0.11, -0.19, -0.03; strength, 0.04, -0.07 to 0.15). Combined aerobic and strength training was ranked best, followed by aerobic exercise and strength training. The NNT was 2 for both aerobic exercise and combined aerobic exercise and strength training. Percentile improvements were 28.8% for aerobic exercise and 31.5% for combined aerobic exercise and strength training. Confidence in effect estimates was ranked as low for aerobic exercise and very low for combined aerobic and strength training as well as strength training. Conclusions Aerobic exercise and combined aerobic exercise and strength training are associated with reductions in BMI z-score. PMID:27792271

Improved statistical signal detection in pharmacovigilance by combining multiple strength-of-evidence aspects in vigiRank.

PubMed

Caster, Ola; Juhlin, Kristina; Watson, Sarah; Norén, G Niklas

2014-08-01

Detection of unknown risks with marketed medicines is key to securing the optimal care of individual patients and to reducing the societal burden from adverse drug reactions. Large collections of individual case reports remain the primary source of information and require effective analytics to guide clinical assessors towards likely drug safety signals. Disproportionality analysis is based solely on aggregate numbers of reports and naively disregards report quality and content. However, these latter features are the very fundament of the ensuing clinical assessment. Our objective was to develop and evaluate a data-driven screening algorithm for emerging drug safety signals that accounts for report quality and content. vigiRank is a predictive model for emerging safety signals, here implemented with shrinkage logistic regression to identify predictive variables and estimate their respective contributions. The variables considered for inclusion capture different aspects of strength of evidence, including quality and clinical content of individual reports, as well as trends in time and geographic spread. A reference set of 264 positive controls (historical safety signals from 2003 to 2007) and 5,280 negative controls (pairs of drugs and adverse events not listed in the Summary of Product Characteristics of that drug in 2012) was used for model fitting and evaluation; the latter used fivefold cross-validation to protect against over-fitting. All analyses were performed on a reconstructed version of VigiBase(®) as of 31 December 2004, at around which time most safety signals in our reference set were emerging. The following aspects of strength of evidence were selected for inclusion into vigiRank: the numbers of informative and recent reports, respectively; disproportional reporting; the number of reports with free-text descriptions of the case; and the geographic spread of reporting. vigiRank offered a statistically significant improvement in area under the receiver operating characteristics curve (AUC) over screening based on the Information Component (IC) and raw numbers of reports, respectively (0.775 vs. 0.736 and 0.707, cross-validated). Accounting for multiple aspects of strength of evidence has clear conceptual and empirical advantages over disproportionality analysis. vigiRank is a first-of-its-kind predictive model to factor in report quality and content in first-pass screening to better meet tomorrow's post-marketing drug safety surveillance needs.

Relationships Between Countermovement Jump Ground Reaction Forces and Jump Height, Reactive Strength Index, and Jump Time.

PubMed

Barker, Leland A; Harry, John R; Mercer, John A

2018-01-01

Barker, LA, Harry, JR, and Mercer, JA. Relationships between countermovement jump ground reaction forces and jump height, reactive strength index, and jump time. J Strength Cond Res 32(1): 248-254, 2018-The purpose of this study was to determine the relationship between ground reaction force (GRF) variables to jump height, jump time, and the reactive strength index (RSI). Twenty-six, Division-I, male, soccer players performed 3 maximum effort countermovement jumps (CMJs) on a dual-force platform system that measured 3-dimensional kinetic data. The trial producing peak jump height was used for analysis. Vertical GRF (Fz) variables were divided into unloading, eccentric, amortization, and concentric phases and correlated with jump height, RSI (RSI = jump height/jump time), and jump time (from start to takeoff). Significant correlations were observed between jump height and RSI, concentric kinetic energy, peak power, concentric work, and concentric displacement. Significant correlations were observed between RSI and jump time, peak power, unload Fz, eccentric work, eccentric rate of force development (RFD), amortization Fz, amortization time, second Fz peak, average concentric Fz, and concentric displacement. Significant correlations were observed between jump time and unload Fz, eccentric work, eccentric RFD, amortization Fz, amortization time, average concentric Fz, and concentric work. In conclusion, jump height correlated with variables derived from the concentric phase only (work, power, and displacement), whereas Fz variables from the unloading, eccentric, amortization, and concentric phases correlated highly with RSI and jump time. These observations demonstrate the importance of countermovement Fz characteristics for time-sensitive CMJ performance measures. Researchers and practitioners should include RSI and jump time with jump height to improve their assessment of jump performance.

Factors that Explain the Cancer-Related Insomnia.

PubMed

Galiano-Castillo, Noelia; Arroyo-Morales, Manuel; Ariza-Garcia, Angélica; Fernández-Lao, Carolina; Fernández-Fernández, Andrés J; Cantarero-Villanueva, Irene

2017-07-01

A better understanding of cancer related insomnia and its relationship with other associated factors is necessary to improve its management. To clarify the relationship between insomnia and treatment related variables, sociodemographic data, health related fitness, pain, anxiety, and depression in breast cancer patients. One hundred twenty-three patients participated in this cross-sectional study. As a primary variable was insomnia using The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 version. Other variables included: stage of treatment, type of treatment, multiple sit to stand test, trunk curl test, 6-min walk test, back muscle strength test, the Brief Pain Inventory short form and the Hospital Anxiety and Depression Scale. Insomnia was negatively associated with the treatment stage (p = 0.01), the 6-min walk test (p = 0.01) and the back muscle strength test (p = 0.01), while it was positively associated with the type of treatment (p = 0.01) and the multiple sit-to-stand test (p = 0.05). In addition, higher levels of insomnia were associated with higher scores on the Brief Pain Inventory short form (p = 0.01) and the Hospital Anxiety and Depression Scale (p = 0.01). Anxiety, type of treatment, back muscle strength, pain severity and stage of treatment were predictors of insomnia, and when they were combined they explained 51.2% of insomnia in our sample. The variability in insomnia related breast cancer is explained by anxiety, type of treatment, pain, treatment stage, and back muscle strength. Clinicians should take these results into account when generating cancer care programs to control pain and health-related-fitness (Registration of Trials NCT01801527). © 2017 Wiley Periodicals, Inc.

Quantifying Variability of Avian Colours: Are Signalling Traits More Variable?

PubMed Central

Delhey, Kaspar; Peters, Anne

2008-01-01

Background Increased variability in sexually selected ornaments, a key assumption of evolutionary theory, is thought to be maintained through condition-dependence. Condition-dependent handicap models of sexual selection predict that (a) sexually selected traits show amplified variability compared to equivalent non-sexually selected traits, and since males are usually the sexually selected sex, that (b) males are more variable than females, and (c) sexually dimorphic traits more variable than monomorphic ones. So far these predictions have only been tested for metric traits. Surprisingly, they have not been examined for bright coloration, one of the most prominent sexual traits. This omission stems from computational difficulties: different types of colours are quantified on different scales precluding the use of coefficients of variation. Methodology/Principal Findings Based on physiological models of avian colour vision we develop an index to quantify the degree of discriminable colour variation as it can be perceived by conspecifics. A comparison of variability in ornamental and non-ornamental colours in six bird species confirmed (a) that those coloured patches that are sexually selected or act as indicators of quality show increased chromatic variability. However, we found no support for (b) that males generally show higher levels of variability than females, or (c) that sexual dichromatism per se is associated with increased variability. Conclusions/Significance We show that it is currently possible to realistically estimate variability of animal colours as perceived by them, something difficult to achieve with other traits. Increased variability of known sexually-selected/quality-indicating colours in the studied species, provides support to the predictions borne from sexual selection theory but the lack of increased overall variability in males or dimorphic colours in general indicates that sexual differences might not always be shaped by similar selective forces. PMID:18301766

The Relationship of Core Strength and Activation and Performance on Three Functional Movement Screens.

PubMed

Johnson, Caleb D; Whitehead, Paul N; Pletcher, Erin R; Faherty, Mallory S; Lovalekar, Mita T; Eagle, Shawn R; Keenan, Karen A

2018-04-01

Johnson, CD, Whitehead, PN, Pletcher, ER, Faherty, MS, Lovalekar, MT, Eagle, SR, and Keenan, KA. The relationship of core strength and activation and performance on three functional movement screens. J Strength Cond Res 32(4): 1166-1173, 2018-Current measures of core stability used by clinicians and researchers suffer from several shortcomings. Three functional movement screens appear, at face-value, to be dependent on the ability to activate and control core musculature. These 3 screens may present a viable alternative to current measures of core stability. Thirty-nine subjects completed a deep squat, trunk stability push-up, and rotary stability screen. Scores on the 3 screens were summed to calculate a composite score (COMP). During the screens, muscle activity was collected to determine the length of time that the bilateral erector spinae, rectus abdominis, external oblique, and gluteus medius muscles were active. Strength was assessed for core muscles (trunk flexion and extension, trunk rotation, and hip abduction and adduction) and accessory muscles (knee flexion and extension and pectoralis major). Two ordinal logistic regression equations were calculated with COMP as the outcome variable, and: (a) core strength and accessory strength, (b) only core strength. The first model was significant in predicting COMP (p = 0.004) (Pearson's Chi-Square = 149.132, p = 0.435; Nagelkerke's R-Squared = 0.369). The second model was significant in predicting COMP (p = 0.001) (Pearson's Chi-Square = 148.837, p = 0.488; Nagelkerke's R-Squared = 0.362). The core muscles were found to be active for most screens, with percentages of "time active" for each muscle ranging from 54-86%. In conclusion, performance on the 3 screens is predicted by core strength, even when accounting for "accessory" strength variables. Furthermore, it seems the screens elicit wide-ranging activation of core muscles. Although more investigation is needed, these screens, collectively, seem to be a good assessment of core strength.

[Correlations Between Joint Proprioception, Muscle Strength, and Functional Ability in Patients with Knee Osteoarthritis].

PubMed

Chen, Yoa; Yu, Yong; He, Cheng-qi

2015-11-01

To establish correlations between joint proprioception, muscle flexion and extension peak torque, and functional ability in patients with knee osteoarthritis (OA). Fifty-six patients with symptomatic knee OA were recruited in this study. Both proprioceptive acuity and muscle strength were measured using the isomed-2000 isokinetic dynamometer. Proprioceptive acuity was evaluated by establishing the joint motion detection threshold (JMDT). Muscle strength was evaluated by Max torque (Nm) and Max torque/weight (Nm/ kg). Functional ability was assessed by the Western Ontario and McMaster Universities Osteoarthritis Index physical function (WOMAC-PF) questionnaire. Correlational analyses were performed between proprioception, muscle strength, and functional ability. A multiple stepwise regression model was established, with WOMAC-PF as dependent variable and patient age, body mass index (BMI), visual analogue scale (VAS)-score, mean grade for Kellgren-Lawrance of both knees, mean strength for quadriceps and hamstring muscles of both knees, and mean JMDT of both knees as independent variables. Poor proprioception (high JMDT) was negatively correlated with muscle strength (P<0.05). There was no significant correlation between knee proprioception (high JMDT) and joint pain (WOMAC pain score), and between knee proprioception (high JMDT) and joint stiffness (WOMAC stiffness score). Poor proprioception (high JMDT) was correlated with limitation in functional ability (WOMAC physical function score r=0.659, P<0.05). WOMAC score was correlated with poor muscle strength (quadriceps muscle strength r = -0.511, P<0.05, hamstring muscle strength r = -0.408, P<0.05). The multiple stepwise regression model showed that high JMDT C standard partial regression coefficient (B) = 0.385, P<0.50 and high VAS-scale score (B=0.347, P<0.05) were significant predictors of WOMAC-PF score. Patients with poor proprioception is associated with poor muscle strength and limitation in functional ability. Patients with symptomatic OA of knees commonly endure with moderate to considerable dysfunction, which is associated with poor proprioception (high JMDT) and high VAS-scale score.

Geospatial Predictive Modelling for Climate Mapping of Selected Severe Weather Phenomena Over Poland: A Methodological Approach

NASA Astrophysics Data System (ADS)

Walawender, Ewelina; Walawender, Jakub P.; Ustrnul, Zbigniew

2017-02-01

The main purpose of the study is to introduce methods for mapping the spatial distribution of the occurrence of selected atmospheric phenomena (thunderstorms, fog, glaze and rime) over Poland from 1966 to 2010 (45 years). Limited in situ observations as well the discontinuous and location-dependent nature of these phenomena make traditional interpolation inappropriate. Spatially continuous maps were created with the use of geospatial predictive modelling techniques. For each given phenomenon, an algorithm identifying its favourable meteorological and environmental conditions was created on the basis of observations recorded at 61 weather stations in Poland. Annual frequency maps presenting the probability of a day with a thunderstorm, fog, glaze or rime were created with the use of a modelled, gridded dataset by implementing predefined algorithms. Relevant explanatory variables were derived from NCEP/NCAR reanalysis and downscaled with the use of a Regional Climate Model. The resulting maps of favourable meteorological conditions were found to be valuable and representative on the country scale but at different correlation ( r) strength against in situ data (from r = 0.84 for thunderstorms to r = 0.15 for fog). A weak correlation between gridded estimates of fog occurrence and observations data indicated the very local nature of this phenomenon. For this reason, additional environmental predictors of fog occurrence were also examined. Topographic parameters derived from the SRTM elevation model and reclassified CORINE Land Cover data were used as the external, explanatory variables for the multiple linear regression kriging used to obtain the final map. The regression model explained 89 % of annual frequency of fog variability in the study area. Regression residuals were interpolated via simple kriging.

Success in the TACP Training Program An Objective Method for Selecting Battlefield Airmen

DTIC Science & Technology

2009-12-23

rationale and evaluation of the physical training doctrine. J Strength Cond Res. 2009 Jul;23(4):1353-62. Interventions used to improve retention...week training programs on military physical performance. J Strength Cond Res. 2008 Mar;22(2):524-34. Muza SR. Military applications of hypoxic...1    Success in the TACP Training Program An Objective Method for Selecting Battlefield Airmen FINAL REPORT December 23, 2009

Normal reference values of strength in pelvic floor muscle of women: a descriptive and inferential study.

PubMed

Chevalier, Francine; Fernandez-Lao, Carolina; Cuesta-Vargas, Antonio Ignacio

2014-11-25

To describe the clinical, functional and quality of life characteristics in women with Stress Urinary Incontinence (SUI). In addition, to analyse the relationship between the variables reported by the patients and those informed by the clinicians, and the relationship between instrumented variables and the manual pelvic floor strength assessment. Two hundred and eighteen women participated in this observational, analytical study. An interview about Urinary Incontinence and the quality of life questionnaires (EuroQoL-5D and SF-12) were developed as outcomes reported by the patients. Manual muscle testing and perineometry as outcomes informed by the clinician were assessed. Descriptive and correlation analysis were carried out. The average age of the subjects was (39.93 ± 12.27 years), (24.49 ± 3.54 BMI). The strength evaluated by manual testing of the right levator ani muscles was 7.79 ± 2.88, the strength of left levator ani muscles was 7.51 ± 2.91 and the strength assessed with the perineometer was 7.64 ± 2.55. A positive correlation was found between manual muscle testing and perineometry of the pelvic floor muscles (p < .001). No correlation was found between outcomes of quality of life reported by the patients and outcomes of functional capacity informed by the physiotherapist. A stratification of the strength of pelvic floor muscles in a normal distribution of a large sample of women with SUI was done, which provided the clinic with a baseline. There is a relationship between the strength of the pelvic muscles assessed manually and that obtained by a perineometer in women with SUI. There was no relationship between these values of strength and quality of life perceived.

Effects of 18-week in-season heavy-resistance and power training on throwing velocity, strength, jumping, and maximal sprint swim performance of elite male water polo players.

PubMed

Ramos Veliz, Rafael; Requena, Bernardo; Suarez-Arrones, Luis; Newton, Robert U; Sáez de Villarreal, Eduardo

2014-04-01

We examined the effects of 18 weeks of strength and high-intensity training on key sport performance measures of elite male water polo (WP) players. Twenty-seven players were randomly assigned to 2 groups, control (in-water training only) and strength group, (strength training sessions [twice per week] + in-water training). In-water training was conducted 5 d·wk. Twenty-meter maximal sprint swim, maximal dynamic strength 1-repetition maximum (1RM) for upper bench press (BP) and lower full squat (FS) body, countermovement jump (CMJ), and throwing velocity were measured before and after the training. The training program included upper and lower body strength and high-intensity exercises (BP, FS, military press, pull-ups, CMJ loaded, and abs). Baseline-training results showed no significant differences between the groups in any of the variables tested. No improvement was found in the control group; however, meaningful improvement was found in all variables in the experimental group: CMJ (2.38 cm, 6.9%, effect size [ES] = 0.48), BP (9.06 kg, 10.53%, ES = 0.66), FS (11.06 kg, 14.21%, ES = 0.67), throwing velocity (1.76 km·h(-1), 2.76%, ES = 0.25), and 20-m maximal sprint swim (-0.26 seconds, 2.25%, ES = 0.29). Specific strength and high-intensity training in male WP players for 18 weeks produced a positive effect on performance qualities highly specific to WP. Therefore, we propose modifications to the current training methodology for WP players to include strength and high-intensity training for athlete preparation in this sport.

Relationship between lower limb muscle strength, self-reported pain and function, and frontal plane gait kinematics in knee osteoarthritis.

PubMed

Park, Sang-Kyoon; Kobsar, Dylan; Ferber, Reed

2016-10-01

The relationship between muscle strength, gait biomechanics, and self-reported physical function and pain for patients with knee osteoarthritis is not well known. The objective of this study was to investigate these relationships in this population. Twenty-four patients with knee osteoarthritis and 24 healthy controls were recruited. Self-reported pain and function, lower-limb maximum isometric force, and frontal plane gait kinematics during treadmill walking were collected on all patients. Between-group differences were assessed for 1) muscle strength and 2) gait biomechanics. Linear regressions were computed within the knee osteoarthritis group to examine the effect of muscle strength on 1) self-reported pain and function, and 2) gait kinematics. Patients with knee osteoarthritis exhibited reduced hip external rotator, knee extensor, and ankle inversion muscle force output compared with healthy controls, as well as increased peak knee adduction angles (effect size=0.770; p=0.013). Hip abductor strength was a significant predictor of function, but not after controlling for covariates. Ankle inversion, hip abduction, and knee flexion strength were significant predictors of peak pelvic drop angle after controlling for covariates (34.4% unique variance explained). Patients with knee osteoarthritis exhibit deficits in muscle strength and while they play an important role in the self-reported function of patients with knee osteoarthritis, the effect of covariates such as sex, age, mass, and height was more important in this relationship. Similar relationships were observed from gait variables, except for peak pelvic drop, where hip, knee, and ankle strength remained important predictors of this variable after controlling for covariates. Copyright © 2016 Elsevier Ltd. All rights reserved.

Muscle strength and golf performance: a critical review.

PubMed

Torres-Ronda, Lorena; Sánchez-Medina, Luis; González-Badillo, Juan J

2011-01-01

Golf has become an increasingly popular sport and a growing body of research trying to identify its main physical requirements is being published. The aim of this review was twofold: first, to examine the existing scientific literature regarding strength training and golf in healthy, non-injured, subjects; and second, to reach conclusions that could provide information on how to design more effective strength training programs to improve golf performance as well as directions for future research. Studies which analyzed the relationship between muscle strength, swing performance variables (club head speed, driving distance, ball speed) and skill (handicap, score) were reviewed. Changes in swing performance following different strength training programs were also investigated. Finally, a critical analysis about the methodologies used was carried out. The results of the reviewed studies seem to indicate that: 1) a positive relationship exists between handicap and swing performance (even though few studies have investigated this issue); 2) there is a positive correlation between skill (handicap and/or score) and muscle strength; and 3) there is a relationship between driving distance, swing speed, ball speed and muscle strength. Results suggest that training leg-hip and trunk power as well as grip strength is especially relevant for golf performance improvement. Studies that analyzed variations in swing performance following resistance-only training programs are scarce, thus it is difficult to prove whether the observed improvements are attributable to changes in strength levels. Many of the studies reviewed presented some methodological errors in their design and not all strength assessment protocols seemed appropriate. Further studies should determine muscle strength needs in relation to final swing performance, using well designed experiments and strict isoinertial assessment protocols which adequately relate to specific golf motion, age and skill level. More studies with elite participants, either professional or amateur, would be especially desirable. Key pointsPOSITIVE CORRELATIONS EXIST BETWEEN: 1) handicap and swing performance variables; 2) muscle strength and skill (handicap and/or golf score); and 3) driving dis-tance, swing speed, ball speed and muscle strength.Leg-hip, trunk power and grip strength seem espe-cially relevant for golf performance improvement.Further research should determine muscle strength needs in relation to final swing performance, using well designed experiments and strict assessment pro-tocols which adequately relate to specific golf mo-tion, age and skill level.

Muscle Strength And Golf Performance: A Critical Review

PubMed Central

Torres-Ronda, Lorena; Sánchez-Medina, Luis; González-Badillo, Juan J.

2011-01-01

Golf has become an increasingly popular sport and a growing body of research trying to identify its main physical requirements is being published. The aim of this review was twofold: first, to examine the existing scientific literature regarding strength training and golf in healthy, non-injured, subjects; and second, to reach conclusions that could provide information on how to design more effective strength training programs to improve golf performance as well as directions for future research. Studies which analyzed the relationship between muscle strength, swing performance variables (club head speed, driving distance, ball speed) and skill (handicap, score) were reviewed. Changes in swing performance following different strength training programs were also investigated. Finally, a critical analysis about the methodologies used was carried out. The results of the reviewed studies seem to indicate that: 1) a positive relationship exists between handicap and swing performance (even though few studies have investigated this issue); 2) there is a positive correlation between skill (handicap and/or score) and muscle strength; and 3) there is a relationship between driving distance, swing speed, ball speed and muscle strength. Results suggest that training leg-hip and trunk power as well as grip strength is especially relevant for golf performance improvement. Studies that analyzed variations in swing performance following resistance-only training programs are scarce, thus it is difficult to prove whether the observed improvements are attributable to changes in strength levels. Many of the studies reviewed presented some methodological errors in their design and not all strength assessment protocols seemed appropriate. Further studies should determine muscle strength needs in relation to final swing performance, using well designed experiments and strict isoinertial assessment protocols which adequately relate to specific golf motion, age and skill level. More studies with elite participants, either professional or amateur, would be especially desirable. Key points Positive correlations exist between: 1) handicap and swing performance variables; 2) muscle strength and skill (handicap and/or golf score); and 3) driving dis-tance, swing speed, ball speed and muscle strength. Leg-hip, trunk power and grip strength seem espe-cially relevant for golf performance improvement. Further research should determine muscle strength needs in relation to final swing performance, using well designed experiments and strict assessment pro-tocols which adequately relate to specific golf mo-tion, age and skill level. PMID:24149290

Development of an integrated digital hand grip dynamometer and norm of hand grip strength.

PubMed

Chang, Ho; Chen, Chih-Hao; Huang, Tung-Sun; Tai, Chun-Yen

2015-01-01

This study designs and fabricates a novel integrated digital hand grip dynamometer and analyzes collected grip strength data. The dynamometer directly stores collected data in a computer, unlike those on the market that cannot directly store information. A strain gauge load cell is used as a force sensor. The dynamometer is designed to maximize ergonomics. Excitation voltage of the load cell is 5 V, and a 9 V battery supplies power to its circuit. The signal receiver is National Instruments (NI) data acquisition (DAQ) card that transmits signals to the computer. The operation system is designed using LabView. This study assesses the correlation between variables of collected data. The correlation coefficients for height, weight and palm length were 0.793, 0.609 and 0.715, respectively, indicating that variables were moderately to strongly correlate with grip strength.

Heart rate variability reflects self-regulatory strength, effort, and fatigue.

PubMed

Segerstrom, Suzanne C; Nes, Lise Solberg

2007-03-01

Experimental research reliably demonstrates that self-regulatory deficits are a consequence of prior self-regulatory effort. However, in naturalistic settings, although people know that they are sometimes vulnerable to saying, eating, or doing the wrong thing, they cannot accurately gauge their capacity to self-regulate at any given time. Because self-regulation and autonomic regulation colocalize in the brain, an autonomic measure, heart rate variability (HRV), could provide an index of self-regulatory strength and activity. During an experimental manipulation of self-regulation (eating carrots or cookies), HRV was elevated during high self-regulatory effort (eat carrots, resist cookies) compared with low self-regulatory effort (eat cookies, resist carrots). The experimental manipulation and higher HRV at baseline independently predicted persistence at a subsequent anagram task. HRV appears to index self-regulatory strength and effort, making it possible to study these phenomena in the field as well as the lab.

Comparison of basic physical fitness, aerobic capacity, and isokinetic strength between national and international level high school freestyle swimmers

PubMed Central

Bae, Young-Hyeon; Yu, Jae-Ho; Lee, Suk Min

2016-01-01

[Purpose] This study aimed to compare basic physical fitness, aerobic capacity, and isokinetic strength between international and national level freestyle high school student swimmers. [Subjects and Methods] A total of 28 participants (14 international level swimmers and 14 national level freestyle high school student swimmers) with no known pathology were included. We used a cross-sectional study to examine three variables: basic physical fitness, aerobic capacity, and isokinetic strength. [Results] The mean values of these variables in the international level swimmers were higher than those in the national level swimmers. Swimmers are generally physically fit with a good competition record. [Conclusion] An appropriate training program, which considers specific individual characteristics is likely to have a positive impact on the improvement of total physical fitness, and subsequently, on the performance of the freestyle high school swimmer. PMID:27134379

Synoptic-scale behavior of the extratropical tropopause inversion layer

NASA Astrophysics Data System (ADS)

Pilch Kedzierski, Robin; Matthes, Katja; Bumke, Karl

2015-11-01

High-resolution GPS radio occultation temperature profiles from the COSMIC satellite mission (2007-2013) are used to obtain daily snapshots of the strength of the extratropical tropopause inversion layer (TIL). Its horizontal structure and day-to-day variability are linked to the synoptic situation at near-tropopause level. The strength of the TIL in cyclonic as well as anticyclonic conditions is investigated by separating relative vorticity into curl and shear terms. The analysis shows that the TIL has high zonal variability, and its strength is instantaneously adjusted to the synoptic situation at near-tropopause level. Our key finding is that the TIL within midlatitude ridges in winter is as strong as or stronger than the TIL in polar summer. The strongest TIL in anticyclonic conditions is related to the shear term, while the weaker TIL in cyclonic conditions is enhanced by the curl term.

Mesoscale Variability of the Caribbean Sea from GEOSAT

DTIC Science & Technology

1991-03-01

the basin. In other words, negatives Figre 11 GEOSAT detection values should be interpreted as "less positive", unless the strength of the negative...km to the southwest. On June 17, feature A has doubled its strength to +20 cm and is displaced 360 km to the west, indicating an approximate speed of...independently from the main flow of the Caribbean cui-rent. This cyclonic anomaly matches in position and strength the one that appeared in the models in

A fundamental approach to adhesion: Synthesis, surface analysis, thermodynamics and mechanics

NASA Technical Reports Server (NTRS)

Dwight, D. W.; Wightman, J. P.

1977-01-01

The effects of composites as adherends was studied. Several other variables were studied by fractography: aluminum powder adhesive filler, fiber glass cloth scrim or adhesive carrier, new adhesives PPQ-413 and LARC-13, and strength-test temperature. When the new results were juxtaposed with previous work, it appeared that complex interactions between adhesive, adherend, bonding, and testing conditions govern the observed strength and fracture-surface features. The design parameters likely to have a significant effect upon strength-test results are listed.

The power of habits: unhealthy snacking behaviour is primarily predicted by habit strength.

PubMed

Verhoeven, Aukje A C; Adriaanse, Marieke A; Evers, Catharine; de Ridder, Denise T D

2012-11-01

Although increasing evidence shows the importance of habits in explaining health behaviour, many studies still rely solely on predictors that emphasize the role of conscious intentions. The present study was designed to test the importance of habit strength in explaining unhealthy snacking behaviour in a large representative community sample (N= 1,103). To test our hypothesis that habits are crucial when explaining unhealthy snacking behaviour, their role was compared to the 'Power of Food', a related construct that addresses sensitivity to food cues in the environment. Moreover, the relation between Power of Food and unhealthy snacking habits was assessed. A prospective design was used to determine the impact of habits in relation to intention, Power of Food and a number of demographic variables. One month after filling out the questionnaire, including measures of habit strength and Power of Food, participants reported their unhealthy snacking behaviour by means of a 7-day snack diary. Results showed that habit strength was the most important predictor, outperforming all other variables in explaining unhealthy snack intake. The findings demonstrate that snacking habits provide a unique contribution in explaining unhealthy snacking behaviour, stressing the importance of addressing habit strength in further research and interventions concerning unhealthy snacking behaviour. ©2012 The British Psychological Society.

Adjustment of measures of strength and power in youth male athletes differing in body mass and maturation.

PubMed

Meylan, Cesar Marius; Cronin, John; Hopkins, Will G; Oliver, Jonathan

2014-02-01

Adjustment for body mass and maturation of strength, power, and velocity measures of young athletes is important for talent development. Seventy-four youth male athletes performed a ballistic leg press test at five loads relative to body mass. The data were analyzed in maturity groups based on years from peak height velocity: -2.5 to -0.9 y (n = 29); -1.0 to 0.4 y (n = 28); and 0.5 to 2.0 y (n = 16). Allometric scaling factors representing percent difference in performance per percent difference in body mass were derived by linear regression of log-transformed variables, which also permitted adjustment of performance for body mass. Standardized differences between groups were assessed via magnitude-based inference. Strength and power measures showed a greater dependency on body mass than velocity-related variables (scaling factors of 0.56-0.85 vs. 0.42-0.14%/%), but even after adjustment for body mass most differences in strength and power were substantial (7-44%). In conclusion, increases in strength and power with maturation are due only partly to increases in body mass. Such increases, along with appropriate adjustment for body mass, need to be taken into account when comparing performance of maturing athletes.

Bond and fracture strength of metal-ceramic restorations formed by selective laser sintering

PubMed Central

Bae, Eun-Jeong; Kim, Woong-Chul; Kim, Hae-Young

2014-01-01

PURPOSE The purpose of this study was to compare the fracture strength of the metal and the bond strength in metal-ceramic restorations produced by selective laser sintering (SLS) and by conventional casting (CAST). MATERIALS AND METHODS Non-precious alloy (StarLoy C, DeguDent, Hanau, Germany) was used in CAST group and metal powder (SP2, EOS GmbH, Munich, Germany) in SLS group. Metal specimens in the form of sheets (25.0 × 3.0 × 0.5 mm) were produced in accordance with ISO 9693:1999 standards (n=30). To measure the bond strength, ceramic was fired on a metal specimen and then three-point bending test was performed. In addition, the metal fracture strength was measured by continuing the application of the load. The values were statistically analyzed by performing independent t-tests (α=.05). RESULTS The mean bond strength of the SLS group (50.60 MPa) was higher than that of the CAST group (46.29 MPa), but there was no statistically significant difference. The metal fracture strength of the SLS group (1087.2 MPa) was lower than that of the CAST group (2399.1 MPa), and this difference was statistically significant. CONCLUSION In conclusion the balling phenomenon and the gap formation of the SLS process may increase the metal-ceramic bond strength. PMID:25177469

Bateman's principle is reversed in a cooperatively breeding bird.

PubMed

Apakupakul, Kathleen; Rubenstein, Dustin R

2015-04-01

Bateman's principle is not only used to explain sex differences in mating behaviour, but also to determine which sex has the greater opportunity for sexual selection. It predicts that the relationship between the number of mates and the number of offspring produced should be stronger for males than for females. Yet, it is unclear whether Bateman's principle holds in cooperatively breeding systems where the strength of selection on traits used in intrasexual competition is high in both sexes. We tested Bateman's principle in the cooperatively breeding superb starling (Lamprotornis superbus), finding that only females showed a significant, positive Bateman gradient. We also found that the opportunity for selection was on average higher in females, but that its strength and direction oscillated through time. These data are consistent with the hypothesis that sexual selection underlies the female trait elaboration observed in superb starlings and other cooperative breeders. Even though the Bateman gradient was steeper for females than for males, the year-to-year oscillation in the strength and direction of the opportunity for selection likely explains why cooperative breeders do not exhibit sexual role reversal. Thus, Bateman's principle may not hold in cooperative breeders where both sexes appear to be under mutually strong sexual selection. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Genetic differentiation and selection against migrants in evolutionarily replicated extreme environments.

PubMed

Plath, Martin; Pfenninger, Markus; Lerp, Hannes; Riesch, Rüdiger; Eschenbrenner, Christoph; Slattery, Patrick A; Bierbach, David; Herrmann, Nina; Schulte, Matthias; Arias-Rodriguez, Lenin; Rimber Indy, Jeane; Passow, Courtney; Tobler, Michael

2013-09-01

We investigated mechanisms of reproductive isolation in livebearing fishes (genus Poecilia) inhabiting sulfidic and nonsulfidic habitats in three replicate river drainages. Although sulfide spring fish convergently evolved divergent phenotypes, it was unclear if mechanisms of reproductive isolation also evolved convergently. Using microsatellites, we found strongly reduced gene flow between adjacent populations from different habitat types, suggesting that local adaptation to sulfidic habitats repeatedly caused the emergence of reproductive isolation. Reciprocal translocation experiments indicate strong selection against immigrants into sulfidic waters, but also variation among drainages in the strength of selection against immigrants into nonsulfidic waters. Mate choice experiments revealed the evolution of assortative mating preferences in females from nonsulfidic but not from sulfidic habitats. The inferred strength of sexual selection against immigrants (RI(s)) was negatively correlated with the strength of natural selection (RI(m)), a pattern that could be attributed to reinforcement, whereby natural selection strengthens behavioral isolation due to reduced hybrid fitness. Overall, reproductive isolation and genetic differentiation appear to be replicated and direct consequences of local adaptation to sulfide spring environments, but the relative contributions of different mechanisms of reproductive isolation vary across these evolutionarily independent replicates, highlighting both convergent and nonconvergent evolutionary trajectories of populations in each drainage. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

Greater association of peak neuromuscular performance with cortical bone geometry, bone mass and bone strength than bone density: A study in 417 older women.

PubMed

Belavý, Daniel L; Armbrecht, Gabriele; Blenk, Tilo; Bock, Oliver; Börst, Hendrikje; Kocakaya, Emine; Luhn, Franziska; Rantalainen, Timo; Rawer, Rainer; Tomasius, Frederike; Willnecker, Johannes; Felsenberg, Dieter

2016-02-01

We evaluated which aspects of neuromuscular performance are associated with bone mass, density, strength and geometry. 417 women aged 60-94years were examined. Countermovement jump, sit-to-stand test, grip strength, forearm and calf muscle cross-sectional area, areal bone mineral content and density (aBMC and aBMD) at the hip and lumbar spine via dual X-ray absorptiometry, and measures of volumetric vBMC and vBMD, bone geometry and section modulus at 4% and 66% of radius length and 4%, 38% and 66% of tibia length via peripheral quantitative computed tomography were performed. The first principal component of the neuromuscular variables was calculated to generate a summary neuromuscular variable. Percentage of total variance in bone parameters explained by the neuromuscular parameters was calculated. Step-wise regression was also performed. At all pQCT bone sites (radius, ulna, tibia, fibula), a greater percentage of total variance in measures of bone mass, cortical geometry and/or bone strength was explained by peak neuromuscular performance than for vBMD. Sit-to-stand performance did not relate strongly to bone parameters. No obvious differential in the explanatory power of neuromuscular performance was seen for DXA aBMC versus aBMD. In step-wise regression, bone mass, cortical morphology, and/or strength remained significant in relation to the first principal component of the neuromuscular variables. In no case was vBMD positively related to neuromuscular performance in the final step-wise regression models. Peak neuromuscular performance has a stronger relationship with leg and forearm bone mass and cortical geometry as well as proximal forearm section modulus than with vBMD. Copyright © 2015 Elsevier Inc. All rights reserved.

Alternate methods for FAAT S-curve generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaufman, A.M.

The FAAT (Foreign Asset Assessment Team) assessment methodology attempts to derive a probability of effect as a function of incident field strength. The probability of effect is the likelihood that the stress put on a system exceeds its strength. In the FAAT methodology, both the stress and strength are random variables whose statistical properties are estimated by experts. Each random variable has two components of uncertainty: systematic and random. The systematic uncertainty drives the confidence bounds in the FAAT assessment. Its variance can be reduced by improved information. The variance of the random uncertainty is not reducible. The FAAT methodologymore » uses an assessment code called ARES to generate probability of effect curves (S-curves) at various confidence levels. ARES assumes log normal distributions for all random variables. The S-curves themselves are log normal cumulants associated with the random portion of the uncertainty. The placement of the S-curves depends on confidence bounds. The systematic uncertainty in both stress and strength is usually described by a mode and an upper and lower variance. Such a description is not consistent with the log normal assumption of ARES and an unsatisfactory work around solution is used to obtain the required placement of the S-curves at each confidence level. We have looked into this situation and have found that significant errors are introduced by this work around. These errors are at least several dB-W/cm{sup 2} at all confidence levels, but they are especially bad in the estimate of the median. In this paper, we suggest two alternate solutions for the placement of S-curves. To compare these calculational methods, we have tabulated the common combinations of upper and lower variances and generated the relevant S-curves offsets from the mode difference of stress and strength.« less

Mobility, proprioception, strength and FMS as predictors of injury in professional footballers

PubMed Central

Yeung, Jonathan; Cleves, Andrew; Griffiths, Hywell; Nokes, Len

2016-01-01

Background The premise of this study was to investigate if anthropometric variables such as mobility, proprioception, strength and modified Functional Movement Screen (mFMS) could be used as primary indicators of injury risk in an English Championship division football team. This study focused on moderate injuries occurring in the lower extremities, during the 2014/2015 competitive season. Methods To differentiate between minor, moderate and severe injuries, this study classified moderate injuries as an injury with an average injury severity of 2–28 days. This study is composed of 4 individual investigations. Each variable was assessed against 2 groups: injured (n=6) and non-injured (n=10). The 2 groups were compiled from the first team, with the criteria that each participant of this study required: full preseason assessment and injury history for the time period, 1 July 2014 to 19 March 2015. A Mann-Whitney U test (0.05% significance) was applied to statistically analyse if each variable showed any variation across the 2 groups. Effect size was estimated with Cliff's d. Results Strength asymmetry displayed significant difference (p=0.007), mobility, proprioception and mFMS did not (p=0.263, p=0.792 and p=0.181, respectively). Mean scores for mobility, proprioception, strength asymmetry and mFMS for injured versus non-injured players (effect size) were: 40.00 vs 38.00 (0.37), 10.33 vs 10.20 (0.10), 61.13 vs 30.40 (0.80) and 7.33 vs 8.90 (−0.4), respectively. Conclusions This study found no relationship between mobility/proprioception and injury risk; however, strength asymmetry was statistically significant in predicting injury and mFMS exhibited enough positive difference for recommendation of further investigation. PMID:27900187

In vivo short-term precision of hip structure analysis variables in comparison with bone mineral density using paired dual-energy X-ray absorptiometry scans from multi-center clinical trials.

PubMed

Khoo, Benjamin C C; Beck, Thomas J; Qiao, Qi-Hong; Parakh, Pallav; Semanick, Lisa; Prince, Richard L; Singer, Kevin P; Price, Roger I

2005-07-01

Hip structural analysis (HSA) is a technique for extracting strength-related structural dimensions of bone cross-sections from two-dimensional hip scan images acquired by dual energy X-ray absorptiometry (DXA) scanners. Heretofore the precision of the method has not been thoroughly tested in the clinical setting. Using paired scans from two large clinical trials involving a range of different DXA machines, this study reports the first precision analysis of HSA variables, in comparison with that of conventional bone mineral density (BMD) on the same scans. A key HSA variable, section modulus (Z), biomechanically indicative of bone strength during bending, had a short-term precision percentage coefficient of variation (CV%) in the femoral neck of 3.4-10.1%, depending on the manufacturer or model of the DXA equipment. Cross-sectional area (CSA), a determinant of bone strength during axial loading and closely aligned with conventional DXA bone mineral content, had a range of CV% from 2.8% to 7.9%. Poorer precision was associated with inadequate inclusion of the femoral shaft or femoral head in the DXA-scanned hip region. Precision of HSA-derived BMD varied between 2.4% and 6.4%. Precision of DXA manufacturer-derived BMD varied between 1.9% and 3.4%, arising from the larger analysis region of interest (ROI). The precision of HSA variables was not generally dependent on magnitude, subject height, weight, or conventional femoral neck densitometric variables. The generally poorer precision of key HSA variables in comparison with conventional DXA-derived BMD highlights the critical roles played by correct limb repositioning and choice of an adequate and appropriately positioned ROI.

Interannual variability in the gravity wave drag - vertical coupling and possible climate links

NASA Astrophysics Data System (ADS)

Šácha, Petr; Miksovsky, Jiri; Pisoft, Petr

2018-05-01

Gravity wave drag (GWD) is an important driver of the middle atmospheric dynamics. However, there are almost no observational constraints on its strength and distribution (especially horizontal). In this study we analyze orographic GWD (OGWD) output from Canadian Middle Atmosphere Model simulation with specified dynamics (CMAM-sd) to illustrate the interannual variability in the OGWD distribution at particular pressure levels in the stratosphere and its relation to major climate oscillations. We have found significant changes in the OGWD distribution and strength depending on the phase of the North Atlantic Oscillation (NAO), quasi-biennial oscillation (QBO) and El Niño-Southern Oscillation. The OGWD variability is shown to be induced by lower-tropospheric wind variations to a large extent, and there is also significant variability detected in near-surface momentum fluxes. We argue that the orographic gravity waves (OGWs) and gravity waves (GWs) in general can be a quick mediator of the tropospheric variability into the stratosphere as the modifications of the OGWD distribution can result in different impacts on the stratospheric dynamics during different phases of the studied climate oscillations.

Resolving the Conflict Between Associative Overdominance and Background Selection

PubMed Central

Zhao, Lei; Charlesworth, Brian

2016-01-01

In small populations, genetic linkage between a polymorphic neutral locus and loci subject to selection, either against partially recessive mutations or in favor of heterozygotes, may result in an apparent selective advantage to heterozygotes at the neutral locus (associative overdominance) and a retardation of the rate of loss of variability by genetic drift at this locus. In large populations, selection against deleterious mutations has previously been shown to reduce variability at linked neutral loci (background selection). We describe analytical, numerical, and simulation studies that shed light on the conditions under which retardation vs. acceleration of loss of variability occurs at a neutral locus linked to a locus under selection. We consider a finite, randomly mating population initiated from an infinite population in equilibrium at a locus under selection. With mutation and selection, retardation occurs only when S, the product of twice the effective population size and the selection coefficient, is of order 1. With S >> 1, background selection always causes an acceleration of loss of variability. Apparent heterozygote advantage at the neutral locus is, however, always observed when mutations are partially recessive, even if there is an accelerated rate of loss of variability. With heterozygote advantage at the selected locus, loss of variability is nearly always retarded. The results shed light on experiments on the loss of variability at marker loci in laboratory populations and on the results of computer simulations of the effects of multiple selected loci on neutral variability. PMID:27182952

Quantitative and qualitative optimization of allergen extraction from peanut and selected tree nuts. Part 2. Optimization of buffer and ionic strength using a full factorial experimental design.

PubMed

L'Hocine, Lamia; Pitre, Mélanie

2016-03-01

A full factorial design was used to assess the single and interactive effects of three non-denaturing aqueous (phosphate, borate, and carbonate) buffers at various ionic strengths (I) on allergen extractability from and immunoglobulin E (IgE) immunoreactivity of peanut, almond, hazelnut, and pistachio. The results indicated that the type and ionic strength of the buffer had different effects on protein recovery from the nuts under study. Substantial differences in protein profiles, abundance, and IgE-binding intensity with different combinations of pH and ionic strength were found. A significant interaction between pH and ionic strength was observed for pistachio and almond. The optimal buffer system conditions, which maximized the IgE-binding efficiency of allergens and provided satisfactory to superior protein recovery yield and profiles, were carbonate buffer at an ionic strength of I=0.075 for peanut, carbonate buffer at I=0.15 for almond, phosphate buffer at I=0.5 for hazelnut, and borate at I=0.15 for pistachio. The buffer type and its ionic strength could be manipulated to achieve the selective solubility of desired allergens. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Pelvic floor muscle strength and body self-perception among Brazilian pregnant women.

PubMed

Sacomori, Cinara; Cardoso, Fernando Luiz; Vanderlinde, Cristiane

2010-12-01

To examine the relationship between pelvic floor muscle strength and body self-perception variables in pregnant women; and, more specifically, to determine the influence of the number of pregnancies (primigravidas vs multigravidas) on the strength of contraction of the pelvic floor muscles and on the body self-perception of pregnant women. Comparative cross-sectional research. Public health centres from Florianópolis, Brazil. Thirty-five pregnant women (18 primigravidas, 17 multigravidas) with a mean age of 25.5 (standard deviation 5.7) years. Pelvic floor strength measured through manual palpation, and body self-perception using the Questionnaire of Corporeality and Human Sexuality. Pelvic floor muscle strength was positively correlated with schooling [rho (ρ)=0.496] and body self-perception variables: finding the body beautiful (ρ=0.476), finding the body sexy (ρ=0.520), feeling that others find them sexy (ρ=0.364), finding the body proportional (ρ=0.412), touching the body generally (ρ=0.554) and recognising the smell of the body (ρ=0.454). Primigravidas found their bodies more beautiful and were more satisfied with their bodies. On a scale of 0 to 6, multigravid participants expressed a greater wish than primigravid participants to be thinner (median difference 2, 95% confidence interval 0-3, P=0.03). Pelvic floor strength did not differ between groups. The results suggest a relationship between pelvic floor muscle strength and body self-perception. Professionals involved in women's health may have a role in helping their patients to understand their bodies. Copyright © 2010 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.

Residual shear strength variability as a primary control on movement of landslides reactivated by earthquake-induced ground motion: Implications for coastal Oregon, U.S.

USGS Publications Warehouse

Schulz, William H.; Wang, Gonghui

2014-01-01

Most large seismogenic landslides are reactivations of preexisting landslides with basal shear zones in the residual strength condition. Residual shear strength often varies during rapid displacement, but the response of residual shear zones to seismic loading is largely unknown. We used a ring shear apparatus to perform simulated seismic loading tests, constant displacement rate tests, and tests during which shear stress was gradually varied on specimens from two landslides to improve understanding of coseismic landslide reactivation and to identify shear strength models valid for slow gravitational failure through rapid coseismic failure. The landslides we studied represent many along the Oregon, U.S., coast. Seismic loading tests resulted in (1) catastrophic failure involving unbounded displacement when stresses represented those for the existing landslides and (2) limited to unbounded displacement when stresses represented those for hypothetical dormant landslides, suggesting that coseismic landslide reactivation may be significant during future great earthquakes occurring near the Oregon Coast. Constant displacement rate tests indicated that shear strength decreased exponentially during the first few decimeters of displacement but increased logarithmically with increasing displacement rate when sheared at 0.001 cm s−1 or greater. Dynamic shear resistance estimated from shear strength models correlated well with stresses observed during seismic loading tests, indicating that displacement rate and amount primarily controlled failure characteristics. We developed a stress-based approach to estimate coseismic landslide displacement that utilizes the variable shear strength model. The approach produced results that compared favorably to observations made during seismic loading tests, indicating its utility for application to landslides.

Effect of 8 weeks of free-weight and machine-based strength training on strength and power performance

PubMed Central

Wirth, Klaus; Hartmann, Hagen; Sander, Andre; Mickel, Christoph

2016-01-01

Abstract The aim of this study was to evaluate the effectiveness of free-weight and machine-based exercises to increase different strength and speed-strength variables. One hundred twenty male participants (age: 23.8 ± 2.5 years; body height: 181.0 ± 6.8 cm; body mass: 80.2 ± 8.9 kg) joined the study. The 2 experimental groups completed an 8 week periodized strength training program that included 2 training sessions per week. The exercises that were used in the strength training programs were the parallel barbell squat and the leg press. Before and after the training period, the 1-repetition-maximum in the barbell squat and the leg press, the squat jump, the countermovement jump and unilateral isometric force (maximal isometric force and the rate of force development) were evaluated. To compare each group pre vs. post-intervention, analysis of variance with repeated measures and Scheffé post-hoc tests were used. The leg press group increased their 1-repetition-maximum significantly (p < 0.001), while in the squat group such variables as 1-repetition-maximum, the squat jump and the countermovement jump increased significantly (p < 0.001). The maximal isometric force showed no statistically significant result for the repeated measures factor, while the rate of force development of the squat group even showed a statistically significant decrease. Differences between the 2 experimental groups were detected for the squat jump and the countermovement jump. In comparison with the leg press, the squat might be a better strength training exercise for the development of jump performance. PMID:28149424

Effect of 8 weeks of free-weight and machine-based strength training on strength and power performance.

PubMed

Wirth, Klaus; Keiner, Michael; Hartmann, Hagen; Sander, Andre; Mickel, Christoph

2016-12-01

The aim of this study was to evaluate the effectiveness of free-weight and machine-based exercises to increase different strength and speed-strength variables. One hundred twenty male participants (age: 23.8 ± 2.5 years; body height: 181.0 ± 6.8 cm; body mass: 80.2 ± 8.9 kg) joined the study. The 2 experimental groups completed an 8 week periodized strength training program that included 2 training sessions per week. The exercises that were used in the strength training programs were the parallel barbell squat and the leg press. Before and after the training period, the 1-repetition-maximum in the barbell squat and the leg press, the squat jump, the countermovement jump and unilateral isometric force (maximal isometric force and the rate of force development) were evaluated. To compare each group pre vs. post-intervention, analysis of variance with repeated measures and Scheffé post-hoc tests were used. The leg press group increased their 1-repetition-maximum significantly (p < 0.001), while in the squat group such variables as 1-repetition-maximum, the squat jump and the countermovement jump increased significantly (p < 0.001). The maximal isometric force showed no statistically significant result for the repeated measures factor, while the rate of force development of the squat group even showed a statistically significant decrease. Differences between the 2 experimental groups were detected for the squat jump and the countermovement jump. In comparison with the leg press, the squat might be a better strength training exercise for the development of jump performance.

[The effect of 24 weeks of moderate-to-high intensity strength training on the elderly].

PubMed

Solà Serrabou, Marta; López del Amo, José Luis; Valero, Oliver

2014-01-01

Strength programs have been seen to be useful in minimizing the effects of sarcopenia, although intervention protocols may vary in their content and characteristics. The aim of this study was to demonstrate the influence of a particular strength protocol for the elderly. A total of 35 individuals took part in the study, with 18 in the exercise group (4 men and 14 women), and 17 in the control group (4 men and 13 women). The average age was 73. The exercise group carried out a strength training program at moderate to high intensity over 24 weeks. Strength was evaluated using the chair stand test, 2-minute step and 2 vertical jumps-squat jump (SJ), and countermovement jump (CMJ). Falls in both groups were also compared before and after the intervention, as well as their relationship with the chair stand variable. A tendency towards improvement was observed in all tests, with the exception of CMJ; while the control group showed a tendency in the opposite direction. Contrast between the two groups at the end of the intervention was notable in all the tests. An inverse relationship between the chair stand strength variable and the number of falls was evident. According to the results achieved, the training was perceived to exercise a positive influence on both the strength of the elderly people and a reduction of the number of falls. The gap between the two groups widened towards the end of the intervention. Copyright © 2013 SEGG. Published by Elsevier Espana. All rights reserved.