EFFECTS OF DYNAMIC FATIGUE ON RATE OF VELOCITY AND TORQUE DEVELOPMENT IN MALES AND FEMALES

EFFECTS OF DYNAMIC FATIGUE ON RATE OF VELOCITY AND TORQUE DEVELOPMENT IN MALES AND FEMALES Anna G. Conroy, Phuong L. Ha, Benjamin E. Dalton, Michaela G. Alesi, Tyler M. Smith, Trisha A. VanDusseldorp, Yuri Feito, Garrett M. Hester. Kennesaw State University, Kennesaw, GA 30144 Time-dependent measures such as rate of velocity (RVD; Δvelocity/Δtime) and torque (RTD; Δtorque/Δtime) development are important contributors to peak power during a dynamic muscle contraction. However, sex differences in the fatigability of these parameters remain relatively unexplored. Purpose: To determine sex differences for RVD and RTD of the plantar flexors (PFs) during a dynamic fatiguing task. Methods: Recreationally active males (n=14; 22.4±2.2 yrs) and females (n=15; 20.9±2.5 yrs) performed a fatiguing task of the PFs consisting of 60 maximal concentric isotonic contractions at 30% of their maximal isometric strength using a dynamometer. RVD and RTD were obtained from the first five contractions of the fatigue task and five maximal isotonic contractions performed after the fatigue task. Strong verbal encouragement was provided, and participants were instructed to perform the muscle contractions “as hard and fast as possible”. RVD and RTD were calculated as the linear slope of the velocity- and torque-time curve, respectively. Two-way (time ´ sex) repeated measures ANOVAs were used to determine sex differences across time. Results: Regardless of sex, RVD was decreased (-14%; p\u3c0.001), however, RTD was reduced in males (-18%; p=0.001) but not females (-8%; p=0.162) following the fatigue protocol. Conclusions: These data indicate that fatigue-induced decrements in quick velocity and torque production during dynamic exercise are different between sexes. Females appear to preserve the ability to produce torque quickly better than males in a fatigued state. Keywords: Fatigue, sex differences, skeletal muscle, powe

The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. II. Results

The spectral absorption lines in early-type galaxies contain a wealth of information regarding the detailed abundance pattern, star formation history, and stellar initial mass function (IMF) of the underlying stellar population. Using our new population synthesis model that accounts for the effect of variable abundance ratios of 11 elements, we analyze very high quality absorption line spectra of 38 early-type galaxies and the nuclear bulge of M31. These data extend to 1um and they therefore include the IMF-sensitive spectral features NaI, CaII, and FeH at 0.82um, 0.86um and 0.99um, respectively. The models fit the data well, with typical rms residuals ~1%. Strong constraints on the IMF and therefore the stellar mass-to-light ratio, (M/L)_stars, are derived for individual galaxies. We find that the IMF becomes increasingly bottom-heavy with increasing velocity dispersion and [Mg/Fe]. At the lowest dispersions and [Mg/Fe] values the derived IMF is consistent with the Milky Way IMF, while at the highest dispersions and [Mg/Fe] values the derived IMF contains more low-mass stars (is more bottom-heavy) than even a Salpeter IMF. Our best-fit (M/L)_stars values do not exceed dynamically-based M/L values. We also apply our models to stacked spectra of four metal-rich globular clusters in M31 and find an (M/L)_stars that implies fewer low-mass stars than a Milky Way IMF, again agreeing with dynamical constraints. We discuss other possible explanations for the observed trends and conclude that variation in the IMF is the simplest and most plausible.Comment: 16 pages, 13 figures, ApJ accepte

Stars that Move Together Were Born Together

It is challenging to reliably identify stars that were born together outside of actively star-forming regions and bound stellar systems. However, co-natal stars should be present throughout the Galaxy, and their demographics can shed light on the clustered nature of star formation and the dynamical state of the disk. In previous work we presented a set of simulations of the Galactic disk that followed the clustered formation and dynamical evolution of 4 billion individual stars over the last 5 Gyr. The simulations predict that a high fraction of co-moving stars with physical and 3D velocity separation of $\Delta r < 20$ pc and $\Delta v < 1.5$ km s$^{-1}$ are co-natal. In this \textit{Letter}, we use \textit{Gaia} DR2 and LAMOST DR4 data to identify and study co-moving pairs. We find that the distribution of relative velocities and separations of pairs in the data is in good agreement with the predictions from the simulation. We identify 111 co-moving pairs in the Solar neighborhood with reliable astrometric and spectroscopic measurements. These pairs show a strong preference for having similar metallicities when compared to random field pairs. We therefore conclude that these pairs were very likely born together. The simulations predict that co-natal pairs originate preferentially from high-mass and relatively young ($< 1$ Gyr) star clusters. \textit{Gaia} will eventually deliver well-determined metallicities for the brightest stars, enabling the identification of thousands of co-natal pairs due to disrupting star clusters in the solar neighborhood.Comment: 6 pages, 4 figures, 1 table. Submitted to ApJL. Catalog here: http://harshilkamdar.github.io/2019/04/03/pairs.htm

The relationship between various live animal scores/measurements and carcass classification for conformation and fatness with meat yield and distribution, and ultimate carcass value

End of project reportAccordingly, the primary objectives of the following study were to: (1) determine the relationship of live animal muscular and skeletal scores, ultrasonically scanned muscle and fat depth measurements of the m. longissimus dorsi, and carcass conformation and fat scores with kill-out proportion, carcass composition and value. (2) Specifically develop and test the accuracy of prediction equations for carcass meat, fat and bone proportions, derived from carcass conformation and fat scores, and develop prediction equations for total carcass composition from hind-quarter composition

Regional head quarter’s dual agency role: micro-political strategies of alignment and self interest

Increased research focus on the networked perspective of the MNE reflects a greater delegation of responsibility from corporate headquarters (CHQ) to subsidiary and intermediary units such as regional headquarters (RHQ). This shift has increased the intensity of political interactions between key actors within the MNE. Despite the recent rise in studies on the micro-political perspective of the MNE, to date little empirical work has explored this issue in the context of the CHQ-RHQ relationship. Drawing insights from agency theory and micro-politics, we focus on the context in which RHQs develop micro-political strategies in order to manage the flow and exchange of knowledge with CHQ. We show how RHQ may exhibit a ‘dual agency’ role when dealing with CHQ, in that it is characterised as a principal and agent, each requiring different micro-political knowledge strategies. As a principal, RHQ will develop micro-political knowledge strategies to increase alignment with CHQ. As an agent, RHQ develops micro-political knowledge strategies to pursue its own self-interests. Having identified different RHQ agency roles, we develop a conceptual model that outlines how alignment and self-interest seeking behaviours from RHQ manifest through different micro-political knowledge strategies in its agency relationship with CHQ