Influence of dynamic strength index on countermovement jump force-, power-, velocity-, and displacement-time curves

The dynamic strength index (DSI), often calculated as the ratio of countermovement jump (CMJ) propulsion peak force to isometric mid-thigh pull (IMTP) peak force, is said to inform whether ballistic or maximal strength training is warranted for a given athlete. CMJ propulsion peak force is highly influenced by jump strategy, however, which is not highlighted by the DSI alone. This study aimed to quantitatively compare CMJ force-, power-, velocity-, and displacement-time curves between athletes who achieved high versus low DSI scores. Fifty-three male collegiate athletes performed three CMJs and IMTPs on a force platform. Athletes were ranked based on DSI score and the CMJ kinetic and kinematic-time curves of the bottom and top twenty athletes were compared. The low DSI group (0.55 ± 0.10 vs. 0.92 ± 0.11) produced greater IMTP peak force (46.7 ± 15.0 vs. 31.1 ± 6.6 N·kg−1) but a larger braking net impulse in the CMJ, leading to greater braking velocity and larger countermovement displacement. This strategy resulted in a similar CMJ propulsion peak force (25.9 ± 2.2 vs. 25.4 ± 3.1 N·kg−1) to the high DSI group. These results, taken together with those of previous studies, support the notion of ballistic versus maximal strength training likely being better suited to low versus high DSI scorers, respectively

Grain dynamics in zero gravity

The dynamics of granular materials has proved difficult to model, primarily because of the complications arising from inelastic losses, friction, packing, and the effect of many grains being in contact simultaneously. The kinetic model of granular systems is similar to the kinetic theory of gases, except that collisional energy losses are always present in the former and must be treated explicity. Few granular materials on Earth are describable by this limiting model, since gravity tends to collapse the grains into a high density state where Coulombic friction effects are dominant. The planned Space Station offers an unusual opportunity to test the kinetic grain model and to explore its predictions. Without gravity, the regime of low interparticle velocities (where an elastic description of the collision is still valid) can be investigated. This will allow for direct interpretation by dynamical computer simulations as well as by the kinetic theory. The dynamics of spherical grains inside a clear box would be examined. Results would be compared with the predictions of the kinetic theory and computer simulations

On the sputtering of binary compounds

A simple physical model is presented to describe some aspects of the sputtering of compound targets. In particular, expressions are developed for the partial sputtering yields for binary systems in terms of the elemental sputtering rates, the stoichiometric concentrations and surface binding energy. The partial yields depend non-linearly on the bulk target concentrations. Comparison of the theoretical predictions with the data on sputtering of PtSi, NiSi and Cu3Au indicates that the general features are well described

Grain dynamics in zero gravity

The dynamics of granular materials has proved difficult to model, primarily because of the complications arising from inelastic losses, friction, packing, and the effect of many grains being in contact simultaneously. One interesting limit for which it was recently possible to construct a theory is that where the grain-grain interactions are dominated by binary collisions. The kinetic model of granular systems if similar to the kinetic theory of gases, except that collisional energy losses are always present in the former and must be treated explicitly. Few granular materials on Earth are describable by this limiting model, since gravity tends to collapse the grains into a high-density state where Coulombic friction effects are dominant. The planned Space Station offers an unusual opportunity to test the kinetic grain model and to explore its predictions. Without gravity, the regime of low interparticle velocities, where an elastic description of the collision is still valid, is investigated. This will allow direct interpretation by dynamical computer simulations as well as by kinetic theory

Material Significance in Identification of Indigenous Occupation at Penny Site, Cape Canaveral, Florida

This document is a student report containing details of the artifacts collected at the Penny site (8BR158) in the 2022 field season

Social Media Marketing Strategies in the Organic Food Industry

This study used content analysis to review the social media marketing strategies of the organic food industry. The results reveal which social media channels are being used and which social media marketing strategies are being used. Qualitative techniques were used to generate a pool of eight organic companies. The social media channels used were highlighted by Chanthinok, Ussahawanitichakit, and Jhundra-indra (2015) as those used by frequency and the ability of the application to achieve the desired marketing goal. The marketing strategies assessed were categorized first as transformational or informational and then further subcategorized by the way it is perceived by the consumer. This study confirmed the greater use of transformational messaging by the organic food industry

Social Capital and Violence across Racial and Ethnic Samples of Adolescents

Using a national sample of adolescents, results of this study demonstrate the important role family and school social capital plays in protecting both White and selected non- White students against violent outcomes. For example, parent-child relationship was associated with reduced violence for Black and White adolescents but not for Hispanics. School affiliation was significant in models for Hispanic and White adolescents but not in models for Black students. Sports participation was associated with greater violence among Hispanics and Whites, but not Blacks. Interestingly, club participation was significant for Whites, but, like sports, it was associated with greater violence. Parental monitoring and religious participation were significant only for Whites while neighbor involvement was significant only for Blacks