Tarleton State University

A key question for climate change adaptation is whether existing cropping systems can become less sensitive to climate variations. We use a field-level data set on maize and soybean yields in the central United States for 1995 through 2012 to examine changes in drought sensitivity. Although yields have increased in absolute value under all levels of stress for both crops, the sensitivity of maize yields to drought stress associated with high vapor pressure deficits has increased. The greater sensitivity has occurred despite cultivar improvements and increased carbon dioxide and reflects the agronomic trend toward higher sowing densities. The results suggest that agronomic changes tend to translate improved drought tolerance of plants to higher average yields but not to decreasing drought sensitivity of yields at the field scale.

The health, fitness and other advantages of youth sports participation are well recognised. However, there are considerable challenges for all stakeholders involved-especially youth athletes-in trying to maintain inclusive, sustainable and enjoyable participation and success for all levels of individual athletic achievement. In an effort to advance a more unified, evidence-informed approach to youth athlete development, the IOC critically evaluated the current state of science and practice of youth athlete development and presented recommendations for developing healthy, resilient and capable youth athletes, while providing opportunities for all levels of sport participation and success. The IOC further challenges all youth and other sport governing bodies to embrace and implement these recommended guiding principles.

Longitudinal changes in height, weight and physical performance were studied in 33 Flemish male youth soccer players from the Ghent Youth Soccer Project. The players' ages at the start of the study ranged from 10.4 to 13.7 years, with a mean age of 12.2 +/- 0.7 years. Longitudinal changes were studied over a 5 year period. Peak height velocity and peak weight velocity were determined using non-smoothed polynomials. The estimations of peak height velocity, peak weight velocity and age at peak height velocity were 9.7 +/- 1.5 cm x year-1, 8.4 +/- 3.0 kg x year-1 and 13.8 +/- 0.8 years, respectively. Peak weight velocity occurred, on average, at the same age as peak height velocity. Balance, speed of limb movement, trunk strength, upper-body muscular endurance, explosive strength, running speed and agility, cardiorespiratory endurance and anaerobic capacity showed peak development at peak height velocity. A plateau in the velocity curves was observed after peak height velocity for upper-body muscular endurance, explosive strength and running speed. Flexibility exhibited peak development during the tear after peak height velocity. Trainers and coaches should be aware of the individual characteristics of the adolescent growth spurt and the training load should also be individualized at this time.

The search for talent is pervasive in youth sports. Selection/exclusion in many sports follows a maturity-related gradient largely during the interval of puberty and growth spurt. As such, there is emphasis on methods for assessing maturation. Commonly used methods for assessing status (skeletal age, secondary sex characteristics) and estimating timing (ages at peak height velocity (PHV) and menarche) in youth athletes and two relatively recent anthropometric (non-invasive) methods (status-percentage of predicted near adult height attained at observation, timing-predicted maturity offset/age at PHV) are described and evaluated. The latter methods need further validation with athletes. Currently available data on the maturity status and timing of youth athletes are subsequently summarised. Selection for sport and potential maturity-related correlates are then discussed in the context of talent development and associated models. Talent development from novice to elite is superimposed on a constantly changing base-the processes of physical growth, biological maturation and behavioural development, which occur simultaneously and interact with each other. The processes which are highly individualised also interact with the demands of a sport per se and with involved adults (coaches, trainers, administrators, parents/guardians).

This study included 235 Canadian Olympic athletes who participated in the 1984 Olympic Games in Sarajevo and Los Angeles. Individual interviews were carried out with 75 athletes and a questionnaire was completed by another 160 to assess their mental readiness for the Olympic Games and factors related to mental readiness. Common elements of success were identified, as well as factors that interfered with optimal performance at the Olympic Games. Statistically significant links were found between Olympic performance outcome and certain mental skills.

PURPOSE: This study was conducted to determine the effect of physical education class enrollment and physical activity on academic achievement in middle school children. METHODS: Participants were 214 sixth-grade students randomly assigned to physical education during either first or second semesters. Moderate and vigorous physical activity (MVPA) (number of 30-min time blocks) outside of school was assessed using the 3-d physical activity recall (3DPAR). The 3DPAR time blocks were converted to ordinal data with scores of 1 (no activity), 2 (some activity), or 3 (activity meeting Healthy People 2010 guidelines). Academic achievement was assessed using grades from four core academic classes and standardized test scores (Terra Nova percentiles). RESULTS: Grades were similar regardless of whether students were enrolled in physical education during first or second semesters. Physical education classes averaged only 19 min of MVPA. Students who either performed some or met Healthy People 2010 guidelines for vigorous activity had significantly higher grades (P < 0.05) than students who performed no vigorous activity in both semesters. Moderate physical activity did not affect grades. Standardized test scores were not significantly related to physical education class enrollment or physical activity levels. CONCLUSION: Although academic achievement was not significantly related to physical education enrollment, higher grades were associated with vigorous physical activity, particularly activity meeting recommended Healthy People 2010 levels.

OBJECTIVES: To determine the relationships between physical and performance characteristics and level of skill in youth soccer players aged 12-16 years. METHODS: Anthropometry, maturity status, functional and sport-specific parameters were assessed in elite, sub-elite, and non-elite youth players in four age groups: U13 (n = 117), U14 (n = 136), U15 (n = 138) and U16 (n = 99). RESULTS: Multivariate analyses of covariance by age group with maturity status as the covariate showed that elite players scored better than the non-elite players on strength, flexibility, speed, aerobic endurance, anaerobic capacity and several technical skills (p<0.05). Stepwise discriminant analyses showed that running speed and technical skills were the most important characteristics in U13 and U14 players, while cardiorespiratory endurance was more important in U15 and U16 players. The results suggest that discriminating characteristics change with competitive age levels. CONCLUSIONS: Characteristics that discriminate youth soccer players vary by age group. Talent identification models should thus be dynamic and provide opportunities for changing parameters in a long-term developmental context.

OBJECTIVE: To derive optimal body mass index (BMI) and waist circumference thresholds for children and adolescents, to predict risk factor clustering. DESIGN: Cross-sectional receiver operating characteristic curve analysis. SETTING: The Bogalusa Heart Study, a community-based study of cardiovascular disease risk factors in early life. PARTICIPANTS: A total of 2597 black and white children and adolescents, 5 to 18 years of age, who were examined between 1992 and 1994. MAIN OUTCOME MEASURES: The presence or absence of > or =3 age-adjusted risk factors (low high-density lipoprotein cholesterol level, high low-density lipoprotein cholesterol level, high triglyceride level, high glucose level, high insulin level, and high blood pressure) was predicted from age-adjusted BMI and waist circumference values. RESULTS: The areas under the receiver operating characteristic curves were significantly different from 0.5 for both BMI and waist circumference for all gender/race groups, ranging from 0.73 to 0.82. The optimal BMI thresholds were at the 53rd and 50th percentiles for white and black male subjects, respectively, and at the 57th and 51st percentiles for white and black female subjects, respectively. Similarly, the optimal waist circumference thresholds were at the 56th and 50th percentiles for white and black male subjects, respectively, and at the 57th and 52nd percentiles for white and black female subjects, respectively. The sensitivity and specificity at the thresholds were similar for all gender/race groups, ranging from 67% to 75%. CONCLUSIONS: The use of BMI and waist circumference for the prediction of risk factor clustering among children and adolescents has significant clinical utility. In this sample, race and gender differences in the optimal thresholds were minimal.

This study considers relationships among motor coordination (MC), physical fitness (PF) and physical activity (PA) in children followed longitudinally from 6 to 10 years. It is hypothesized that MC is a significant and primary predictor of PA in children. Subjects were 142 girls and 143 boys. Height, weight and skinfolds; PA (Godin-Shephard questionnaire); MC (Körperkoordination Test für Kinder); and PF (five fitness items) were measured. Hierarchical linear modeling with MC and PF as predictors of PA was used. The retained model indicated that PA at baseline differed significantly between boys (48.3 MET/week) and girls (40.0 MET/week). The interaction of MC and 1 mile run/walk had a positive influence on level of PA. The general trend for a decrease in PA level across years was attenuated or amplified depending on initial level of MC. The estimated rate of decline in PA was negligible for children with higher levels of MC at 6 years, but was augmented by 2.58 and 2.47 units each year, respectively, for children with low and average levels of initial MC. In conclusion MC is an important predictor of PA in children 6-10 years of age.

Abstract The Standardized Precipitation Index (SPI) is now widely used throughout the world in both a research and an operational mode. For arid climates, or those with a distinct dry season where zero values are common, the SPI at short time scales is lower bounded, referring to non‐normally distributed in this study. In these cases, the SPI is always greater than a certain value and fails to indicate a drought occurrence. The nationwide statistics based on our study suggest that the non‐normality rates are closely related to local precipitation climates. In the eastern United States, SPI values at short time scales can be used in drought/flood monitoring and research in any season, while in the western United States, because of its distinct seasonal precipitation distribution, the appropriate usage and interpretation of this index becomes complicated. This would also be the case for all arid climates. From a mathematical point of view, the non‐normally distributed SPI is caused by a high probability of no‐rain cases represented in the mixed distribution that is employed in the SPI construction. From a statistical point of view, the 2‐parameter gamma model used to estimate the precipitation probability density function and the limited sample size in dry areas and times would also reduce the confidence of the SPI values. On the basis of the results identified within this study, we recommend that the SPI user be cautious when applying short‐time‐scale SPIs in arid climatic regimes, and interpret the SPI values appropriately. In dry climates, the user should focus on the duration of the drought rather than on just its severity. It is also worth noting that the SPI results from a statistical product of the input data. This character makes it difficult to link the SPI data to the physical functioning of the Earth system. Copyright © 2006 Royal Meteorological Society.

Soils maps of China have been generated at different scales from ground surveys and laboratory analyses. A comprehensive effort coordinated by the Office for the Second National Soil Survey of China resulted in a series of soil maps covering the extent of the country at a scale of 1:1,000,000. The map series is now being converted from its current paper form to a digital format. The 1:1,000,000 digital soil map of China will consist of three parts: soil mapping unit boundaries, soil attributes, and the “reference system for Chinese soils.”The spatial data is based on the soil genetic classification of China, consisting of 12 orders, 61 great groups, 235 subgroups, and 909 families. The 1:1,000,000 soil maps are delineated based on the soil family definitions. The sampled soil attributes included physical, chemical, and fertility properties measured for 2473 soil species (series) (known as TuZhong in Chinese). The reference system for Chinese soils will use the attribute data for each soil species (series) to cross reference soil names in three classification systems, namely, Soil Genetic Classification of China, U.S. soil taxonomy, and the FAO World Reference Base for Soil Resources (WRB). The cross‐reference system will be constructed in a relational database so that any Chinese or international scientists can access equivalent names for a soil in any of the three systems.

ABSTRACT BIO-BANDING IS THE PROCESS OF GROUPING ATHLETES ON THE BASIS OF ATTRIBUTES ASSOCIATED WITH GROWTH AND MATURATION RATHER THAN CHRONOLOGICAL AGE. CHILDREN OF THE SAME AGE VARY CONSIDERABLY IN BIOLOGICAL MATURATION WITH SOME INDIVIDUALS MATURING IN ADVANCE OR DELAY OF THEIR PEERS. THE TIMING OF MATURATION HAS IMPORTANT IMPLICATIONS FOR COMPETITION, TALENT IDENTIFICATION, AND TRAINING. INCREASED AWARENESS AND INTEREST IN THE SUBJECT OF MATURATION HAS SPARKED A RENEWED INTEREST IN THE STUDY AND APPLICATION OF BIO-BANDING. THIS OVERVIEW DESCRIBES THE PURPOSE AND PROCESS OF BIO-BANDING, POTENTIAL BENEFITS AND LIMITATIONS, AND DESCRIBES SOME RECENT ADVANCES IN ITS APPLICATION IN YOUTH SPORTS.

While progress has been made in recent years to understand the differences among family firms, insights remain fragmented due, in part, to an incomplete understanding of heterogeneity and the scope of differences that exist among family firms. Given this, we offer a definition of and review the literature on family firm heterogeneity. A latent semantic analysis of 781 articles from 33 journals identified nine common themes of family firm heterogeneity. For each theme, we review scholarly progress made and highlight differences among family firms. Additionally, we offer directions for advancing the study of family firm heterogeneity.

Biofilms are aggregates of bacteria, in most cases, which are resistant usually to broad-spectrum antibiotics in their typical concentrations or even in higher doses. A trend of increasing multi-drug resistance in biofilms, which are responsible for emerging life-threatening nosocomial infections, is becoming a serious problem. Biofilms, however, are at various sensitivity levels to environmental factors and are versatile in infectivity depending on virulence factors. This review presents the fundamental information about biofilms: formation, antibiotic resistance, impacts on public health and alternatives to conventional approaches. Novel developments in micro-biosystems that help reveal the new treatment tools by sensing and characterization of biofilms will also be discussed. Understanding the formation, structure, physiology and properties of biofilms better helps eliminate them by the usage of appropriate antibiotics or their control by novel therapy approaches, such as anti-biofilm molecules, effective gene editing, drug-delivery systems and probiotics.

The black soldier fly, Hermetia illucens L., was reared on a grain-based diet at 27, 30, and 36 degrees C. Survival of 4- to 6-d-old larvae to adults averaged 74-97% at 27 and 30 degrees C but was only 0.1% at 36 degrees C. Flies required a mean of approximately 4 d (11%) longer to complete larval and pupal development at 27 degrees C than at 30 degrees C. At 27 and 30 degrees C, females weighed an average of 17-19% more than males but required an average of 0.6-0.8 d (3.0-4.3%) longer to complete larval development. At both temperatures, adult females lived an average of approximately 3.5 d less than adult males. The duration of larval development was a significant predictor of adult longevity. Temperature differences of even 3 degrees C produce significant fitness tradeoffs for males and females, influencing life history attributes and having practical applications for forensic entomology.

In this study, we compared the growth, maturity status, functional capacity, sport-specific skill, and goal orientation of 159 male soccer players, aged 11-12 (n = 87) and 13-14 years (n = 72) years, who at follow-up 2 years later discontinued participation (dropout), continued at the same standard (club) or moved to a higher level (elite). Age group-specific multivariate analysis of variance was used for comparisons. Among 11- to 12-year-old players at baseline, a gradient of elite > club > dropout was suggested for size and function, although differences were not consistently significant. Elite players performed significantly better in only two of the four skills, dribbling and ball control. A gradient of elite > club > dropout was more clearly defined among 13- to 14-year-old players at baseline. Elite players were older chronologically and skeletally, larger in body size and performed better in functional capacities and three skill tests than club players and dropouts. Baseline task and ego orientation did not differ among dropouts and club and elite players at follow-up in either age group. The results suggest an important role for growth and maturity status, functional capacities, and sport-specific skills as factors in attrition, persistence, and moving up in youth soccer.

OBJECTIVES: In adult populations, it is recognized widely that waist circumference (WC) predicts health risk beyond that predicted by BMI alone; current recommendations for adults are that a combination of BMI and WC be used to classify obesity-related health risk. For children and adolescents, however, little is known about the combined influence of BMI and WC on health outcomes. The objectives of this study were to determine whether BMI and WC predict coronary artery disease (CAD) risk factors independently for children and adolescents and to assess the clinical utility of using WC in combination with BMI to identify CAD risk. METHODS: Subjects included 2597 black and white, 5- to 18-year-old, male and female youths. Outcome measures included 7 CAD risk factors. In the first analysis step, BMI and WC were used as continuous variables to predict CAD risk factors. In the second analysis step, participants were placed into normal-weight, overweight, and obese BMI categories and, within each BMI category, CAD risk factors were compared for groups with low and high WC values. RESULTS: When BMI and WC were included in the same regression model to predict CAD risk factors, the added variance above that predicted by BMI or WC alone was minimal, which indicated that BMI and WC did not have independent effects on the risk factors. For example, for systolic blood pressure, BMI alone explained 7.3% of the variance, WC alone explained 7.7% of the variance, and the combination of BMI and WC explained 8.1% of the variance. When BMI and WC values were categorized with a threshold approach, WC provided information on CAD risk beyond that provided by BMI alone, particularly when the categories were used to predict elevated CAD risk factor levels. For instance, in the overweight BMI category, the high-WC group was approximately 2 times more likely to have high triglyceride levels, high insulin levels, and the metabolic syndrome, compared with the low-WC group. CONCLUSION: These findings provide some evidence that a combination of BMI and WC should be used in clinical settings to evaluate the presence of elevated health risk among children and adolescents.

Abstract Black soldier flies, Hermetia illucens L., are a common colonizer of animal wastes. However, all published development data for this species are from studies using artificial diets. This study represents the first examining black soldier fly development on animal wastes. Additionally, this study examined the ability of black soldier fly larvae to reduce dry matter and associated nutrients in manure. Black soldier fly larvae were fed four rates of dairy manure to determine their effects on larval and adult life history traits. Feed rate affected larval and adult development. Those fed less ration daily weighed less than those fed a greater ration. Additionally, larvae provided the least amount of dairy manure took longer to develop to the prepupal stage; however, they needed less time to reach the adult stage. Adults resulting from larvae provided 27 g dairy manure/d lived 3–4 d less than those fed 70 g dairy manure. Percentage survivorship to the prepupal or adult stages did not differ across treatments. Larvae fed 27 g dairy manure daily reduced manure dry matter mass by 58%, whereas those fed 70 g daily reduced dry matter 33%. Black soldier fly larvae were able to reduce available P by 61–70% and N by 30–50% across treatments. Based on results from this study, the black soldier fly could be used to reduce wastes and associated nutrients in confined bovine facilities.

BACKGROUND: Participants in many youth sports are commonly combined into age groups spanning 2 years. AIM: The study compared variation in size, function, sport-specific skill and goal orientation associated with differences in biological maturity status of youth soccer players within two competitive age groups. METHODS: The sample included 159 male soccer players in two competitive age groups, 11-12 years (n=87) and 13-14 years (n=72). Weight, height, sitting height and four skinfolds, four functional capacities, four soccer skills and goal orientation were measured. Skeletal maturity was assessed using the Fels method. Each player was classified as late, on time or early maturing based on the difference between skeletal and chronological ages. ANOVA was used to compare characteristics of players across maturity groups. RESULTS: Late, on time and early maturing boys are represented among 11-12-year-olds, but late maturing boys are under-represented among 13-14-year-olds. Players in each age group advanced in maturity are taller and heavier than those on time and late in skeletal maturity, but players of contrasting maturity status do not differ, with few exceptions, in functional capacities, soccer-specific skills and goal orientation. CONCLUSION: Variation in body size associated with maturity status in youth soccer players is similar to that for adolescent males in general, but soccer players who vary in maturity status do not differ in functional capacities, soccer-specific skills and goal orientation.

The aim of this study was to estimate the contribution of experience, body size and maturity status to variation in sport-specific skills of adolescent soccer players. The participants were 69 players aged 13.2-15.1 years from three clubs that competed in the highest division for their age group. Height and body mass were measured and stage of pubic hair development was assessed at clinical examination. Years of experience in football was obtained at interview. Six football skill tests were administered: ball control with the body, ball control with the head, dribbling with a pass, dribbling speed, shooting accuracy and passing accuracy. Multiple linear regression analysis was used to estimate the relative contributions of age, stage of sexual maturity, height, body mass and years of formal training in soccer to the six skill tests. Age, experience, body size and stage of puberty contributed significantly but in different combinations to the variance in four of the six skill tests: dribbling with a pass (21%; age, stage of maturity), ball control with the head (14%; stage of maturity, height, body height x body mass interaction), ball control with the body (13%; stage of maturity, years of training) and shooting accuracy (8%; stage of maturity, height; borderline significance, P = 0.06). There were no significant predictors for the tests of dribbling speed and passing accuracy. In conclusion, age, experience, body size and stage of puberty contributed relatively little to variation in performance in four of the six soccer-specific skill tests in adolescent footballers aged 13-15 years.