1,512 research outputs found
Changes in Power Output in NCAA Football Linemen During Competitive Season
Changes in Power Output in NCAA Football Linemen During Competitive Season.
Posey, Q., R. Cole, and J. Priest, Tarleton State University, Stephenville, TX 76402
Introduction
Measuring power is a practice currently being developed by researchers. An available tool is the TENDO Weightlifting Analyzer (TWA). Although the TWA is a common research tool, there is little published research. The purpose of this study is to analyze OL and DL power output during in-season football.
Methods
Experimental Approach
Seventeen NCAA division II football players in the Lone Start Conference were monitored during organized in-season weight training workouts. TWA measured and recorded their last set of squat. Bio feedback provided by the TWA was used to analyze each group.
Subjects
Seventeen NCAA division II football players (Age 21.1 ± 4.6 yrs, Ht. 1.6 ± 0.01m, Wt. 123.1 ± 7.4 kg , BMI 35.3 ± 3.2 kg.m-2), volunteered for the study, and had previously trained at least twice per week for 12 weeks. Subjects were familiarized with the TWA and squat protocol during pre-season.
Protocol
All subjects were required to lift four times a week. On the third workout of every week subjects back-squatted. All subjects completed a standardized warm-up. Subjects determine their own lifting weight. Researchers monitored squats and emphasized bar speed. The TWA was attached to the outside of the bar and measured average power (AP) and peak power (PP) output. Measurements were uploaded from the TWA into TENDO Sports Machine computer program and exported to Microsoft ExcelÂź.
Results
Repeated measures ANOVA revealed no change in AP (F(3,45)=0.996, p\u3e.05), change in overall PP (F(3,45)=15.3, p\u3c.001) across 4 measures of the competitive season. No group interaction for AP (F(3,45)=.488, p\u3e.05), but PP by group interaction (F(3,45)=6.07, p=.001).
AP 1 (W) AP 2 (W) AP 3 (W) AP 4 (W) PP 1 (W) PP 2 (W) PP 3 (W) PP4 (W)
OL 911 ± 136 910 ± 124 850 ± 89 893 ± 19 1507 ± 251 1775 ± 258 1207 ± 141 1690 ±142
DL 947 ± 214 905 ± 184 904 ± 184 880 ± 110 1605 ± 343 1728 ± 487 1637 ± 317 1801 ± 215
Table 1. Average (AP) and Peak Power (PP) of Offensive (OL) and Defensive Linesmen (DL) During Competitive Season.
Discussion
The competitive football season produced normal bumps, bruises, and sprains which impacted the results obtained from bi-weekly measures of AP and PP. The observed changes in PP were attributed to the changes in peak bar velocities for this instantaneous measure, whereas the stability of AP was explained by the less volatile factor of average bar velocities.
Conclusion
Organized in-season weight training activities are effective at maintaining power output of offensive and defensive linemen
Consequences of spontaneous reconnection at a two-dimensional non-force-free current layer
Magnetic neutral points, where the magnitude of the magnetic field vanishes
locally, are potential locations for energy conversion in the solar corona. The
fact that the magnetic field is identically zero at these points suggests that
for the study of current sheet formation and of any subsequent resistive
dissipation phase, a finite beta plasma should be considered, rather than
neglecting the plasma pressure as has often been the case in the past. The
rapid dissipation of a finite current layer in non-force-free equilibrium is
investigated numerically, after the sudden onset of an anomalous resistivity.
The aim of this study is to determine how the energy is redistributed during
the initial diffusion phase, and what is the nature of the outward transmission
of information and energy. The resistivity rapidly diffuses the current at the
null point. The presence of a plasma pressure allows the vast majority of the
free energy to be transferred into internal energy. Most of the converted
energy is used in direct heating of the surrounding plasma, and only about 3%
is converted into kinetic energy, causing a perturbation in the magnetic field
and the plasma which propagates away from the null at the local fast
magnetoacoustic speed. The propagating pulses show a complex structure due to
the highly non-uniform initial state. It is shown that this perturbation
carries no net current as it propagates away from the null. The fact that,
under the assumptions taken in this paper, most of the magnetic energy released
in the reconnection converts internal energy of the plasma, may be highly
important for the chromospheric and coronal heating problem
Gravitational collapse of spherically symmetric plasmas in Einstein-Maxwell spacetimes
We utilize a recent formulation of a spherically symmetric spacetime endowed
with a general decomposition of the energy momentum tensor [Phys. Rev. D, 75,
024031 (2007)] to derive equations governing spherically symmetric
distributions of electromagnetic matter. We show the system reduces to the
Reissner-Nordstrom spacetime in general, spherically symmetric coordinates in
the vacuum limit. Furthermore, we show reduction to the charged Vaidya
spacetime in non-null coordinates when certain equations of states are chosen.
A model of gravitational collapse is discussed whereby a charged fluid resides
within a boundary of finite radial extent on the initial hypersurface, and is
allowed to radiate charged particles. Our formalism allows for the discussion
of all regions in this model without the need for complicated matching schemes
at the interfaces between successive regions. As further examples we consider
the collapse of a thin shell of charged matter onto a Reissner-Nordstrom black
hole. Finally, we reduce the entire system of equations to the static case such
that we have the equations for hydrostatic equilibrium of a charged fluid.Comment: Accepted for publication in Phys. Rev.
Sticks and carrots for reducing property-level risks from floods: an EU-US comparative perspective
In discussing legal and policy frameworks for flood risk management, the attention is often put on increasing resilience in public spaces. In terms of private properties, discussions are geared toward enhancing the adaptive capacity of future developments. This paper focuses on the instruments associated with resilience of existing privately owned residential buildings mainly from the perspective of post-flood policies and compensation regimes. The paper scrutinizes the relevant legal and policy landscapes in the United States, the European Union and two Member States â the UK and the Netherlands. The goal is to provide mutual lessons learned between the EU, its Member States, and the US and to set forth generally applicable recommendations for improving post-flood policies for existing buildings
Dealing with flood damages: will prevention, mitigation and ex-post compensation provide for a resilient triangle?
There is a wealth of literature on the design of ex-post compensation mechanisms for natural disasters. However, more research needs to be done on the manner in which these mechanisms could steer citizens toward adopting individual level preventive and protection measures in the face of flood risks. This paper provides a comparative legal analysis of the financial compensation mechanisms following floods, be it through insurance, public funds or a combination of both, with an empirical focus on Belgium, the Netherlands, England and France. Similarities and differences between the methods in which these compensation mechanisms for flood damages enhance resilience are analyzed. The comparative analysis especially focuses on the link between the recovery strategy on the one hand and prevention and mitigation strategies on the other. There is great potential within the recovery strategy for promoting preventive action, for example in terms of discouraging citizens from living in high-risk areas, or encouraging the uptake of mitigation measures, such as adaptive building. However, this large potential is yet to be realized, in part due to insufficient consideration and promotion of these connections within existing legal frameworks. Recommendations are made about how the linkages between strategies can be further improved. These recommendations relate to, amongst others, the promotion of resilient reinstatement through recovery mechanisms and the removal of legal barriers preventing the establishment of link-inducing measures
Interaction of intermediate energy protons with light nuclei
Interaction of intermediate energy protons with light nucle
Distinguishing Solar Flare Types by Differences in Reconnection Regions
Observations show that magnetic reconnection and its slow shocks occur in
solar flares. The basic magnetic structures are similar for long duration event
(LDE) flares and faster compact impulsive (CI) flares, but the former require
less non-thermal electrons than the latter. Slow shocks can produce the
required non-thermal electron spectrum for CI flares by Fermi acceleration if
electrons are injected with large enough energies to resonate with scattering
waves. The dissipation region may provide the injection electrons, so the
overall number of non-thermal electrons reaching the footpoints would depend on
the size of the dissipation region and its distance from the chromosphere. In
this picture, the LDE flares have converging inflows toward a dissipation
region that spans a smaller overall length fraction than for CI flares. Bright
loop-top X-ray spots in some CI flares can be attributed to particle trapping
at fast shocks in the downstream flow, the presence of which is determined by
the angle of the inflow field and velocity to the slow shocks.Comment: 15 pages TeX and 2 .eps figures, accepted to Ap.J.Let
Paraphrases and summaries: A means of clarification or a vehicle for articulating a preferred version of student accounts?
The use of group discussions as a means to facilitate learning from experiences is well documented in adventure education literature. Priest and Naismith (1993) assert that the use of the circular discussion method, where the leader poses questions to the participants, is the most common form of facilitation in adventure education. This paper draws on transcripts of facilitation sessions to argue that the widely advocated practice of leader summaries or paraphrases of student responses in these sessions functions as a potential mechanism to control and sponsor particular knowledge(s). Using transcripts from recorded facilitation sessions the analysis focuses on how the leader paraphrases the studentsâ responses and how these paraphrases or âformulationsâ function to modify or exclude particular aspects of the studentsâ responses. I assert that paraphrasing is not simply a neutral activity that merely functions to clarify a student response, it is a subtle means by which the leader of the session can, often inadvertently or unknowingly, alter the studentâs reply with the consequence of favouring particular knowledge(s). Revealing the subtle work that leader paraphrases perform is of importance for educators who claim to provide genuine opportunities for students to learn from their experience
Locating current sheets in the solar corona
Current sheets are essential for energy dissipation in the solar corona, in
particular by enabling magnetic reconnection. Unfortunately, sufficiently thin
current sheets cannot be resolved observationally and the theory of their
formation is an unresolved issue as well. We consider two predictors of coronal
current concentrations, both based on geometrical or even topological
properties of a force free coronal magnetic field. First, there are
separatrices related to magnetic nulls. Through separatrices the magnetic
connectivity changes discontinuously. Coronal magnetic nulls are, however, very
rare. At second, inspired by the concept of generalized magnetic reconnection
without nulls, quasi-separatrix layers (QSL) were suggested. Through QSL the
magnetic connectivity changes continuously, though strongly. The strength of
the connectivity change can be quantified by measuring the squashing of the
flux tubes which connect the magnetically conjugated photospheres.
We verify the QSL and separatrix concepts by comparing the sites of magnetic
nulls and enhanced squashing with the location of current concentrations in the
corona. Due to the known difficulties of their direct observation we simulated
the coronal current sheets by numerically calculating the response of the
corona to energy input from the photosphere heating a simultaneously observed
EUV Bright Point. We did not find coronal current sheets not at the
separatrices but at several QSL locations. The reason is that although the
geometrical properties of force free extrapolated magnetic fields can indeed,
hint at possible current concentrations, a necessary condition for current
sheet formation is the local energy input into the corona
Deconstructing active region AR10961 using STEREO, HINODE, TRACE and SOHO
Active region 10961 was observed over a five day period (2007 July 2-6) by instrumentation on-board STEREO, Hinode, TRACE and SOHO. As it progressed from Sun centre to the solar limb a comprehensive analysis of the EUV, X-ray and magnetic field data reveals clearly observable changes in the global nature of the region.
Temperature analyses undertaken using STEREO EUVI double filter ratios and XRT single and combined filter ratios demonstrate an overall cooling of the region from between 1.6 - 3.0 MK to 1.0 - 2.0 MK over the five days. Similarly, Hinode EIS density measurements show a corresponding increase in density of 27%. Moss, cool (1 MK) outer loop areas and hotter core loop regions were examined and compared with potential magnetic field extrapolations from SOHO MDI magnetogram data. In particular it was found that the potential field model was able to predict the structure of the hotter X-ray loops and that the larger cool loops seen in 171 Angstrom images appeared to follow the separatrix surfaces. The reasons behind the high density moss regions only observed on one side of the active region are examined further
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