Connection between centre vortices and instantons through gauge-field smoothing

A recent lattice study of the Landau-gauge overlap quark propagator has shown a connection between centre vortices and dynamical chiral symmetry breaking in $\mathrm{SU}(3)$ gauge theory. We further investigate this relationship through an exploration of the connection to the instanton degrees of freedom. After identifying centre vortices on the lattice in maximal centre gauge, we smooth configurations using multiple algorithms. We are able to create an instanton liquid-like background on configurations consisting solely of centre vortices, analogous to that found on Monte-carlo generated configurations after similar smoothing. Through calculations of the static quark potential and Landau-gauge overlap propagator, we show that this background is able to reproduce all salient long-range features of the original configurations. Thus we conclude that the information necessary to recreate the long-range structure of $\mathrm{SU}(3)$ gauge theory is contained within the centre vortex degrees of freedom.Comment: Version published in PR

Aging, cognition, and motor behavior: A lab-to-life approach to improving quality of life in later adulthood

An important challenge facing our health care system is to maintain and improve functional independence, and thus overall quality of life, in older adults. It is estimated that by 2030 nearly 20% of the US population will be over the age of 65, and that proportion will continue to rise over the coming decades. Advancing age comes with significant declines in cognitive and physical function that contribute to diminished functional independence. In the Aging, Cognition, and Action Lab we use computerized cognitive assessments, and a state-of-the-art robotic device for studying upper limb movement to identify age-related changes in the cognitive mechanisms underlying deficits in adaptive motor behavior. By leveraging our understanding of how these basic mechanisms change with aging, we can design carefully targeted interventions aimed at improving functional independence in older populations. In this TechTalk I will highlight some of our current and future work in this area.https://digitalcommons.mtu.edu/techtalks/1043/thumbnail.jp

The impact of multisensory components in worship

https://place.asburyseminary.edu/ecommonsatsdissertations/1437/thumbnail.jp

A critical examination of compound stability predictions from machine-learned formation energies

Machine learning has emerged as a novel tool for the efficient prediction of material properties, and claims have been made that machine-learned models for the formation energy of compounds can approach the accuracy of Density Functional Theory (DFT). The models tested in this work include five recently published compositional models, a baseline model using stoichiometry alone, and a structural model. By testing seven machine learning models for formation energy on stability predictions using the Materials Project database of DFT calculations for 85,014 unique chemical compositions, we show that while formation energies can indeed be predicted well, all compositional models perform poorly on predicting the stability of compounds, making them considerably less useful than DFT for the discovery and design of new solids. Most critically, in sparse chemical spaces where few stoichiometries have stable compounds, only the structural model is capable of efficiently detecting which materials are stable. The nonincremental improvement of structural models compared with compositional models is noteworthy and encourages the use of structural models for materials discovery, with the constraint that for any new composition, the ground-state structure is not known a priori. This work demonstrates that accurate predictions of formation energy do not imply accurate predictions of stability, emphasizing the importance of assessing model performance on stability predictions, for which we provide a set of publicly available tests

Comunità, emigrazione e flussi: note su alcuni recenti studi

The debate about migration in the XXIst Centur

Control strategy for a hand balance

The goal of this study was to investigate the control strategy employed by gymnasts in maintaining a hand balance. It was hypothesized that a “wrist strategy” was used in which perturbations in the sagittal plane were corrected using variations in wrist flexor torque with synergistic shoulder and hip torques acting to preserve a fixed body configuration. A theoretical model of wrist strategy indicated that control could be effected using wrist torque that was a linear function of mass center displacement and velocity. Four male gymnasts executed hand balances and 2-dimensional inverse dynamics was used to determine net joint torque time histories at the wrist, shoulder, and hip joints in the sagittal plane. Wrist torque was regressed against mass center position and velocity values at progressively earlier times. It was found that all gymnasts used the wrist strategy, with time delays ranging from 160 to 240 ms. The net joint torques at the shoulder and hip joints were regressed against the torques required to maintain a fixed configuration. This fixed configuration strategy accounted for 86% of the variance in the shoulder torque and 86% of the variance in the hip torque although the actual torques exceeded the predicted torques by 7% and 30%, respectively. The estimated time delays are consistent with the use of long latency reflexes, whereas the role of vestibular and visual information in maintaining a hand balance is less certain

Centre vortex effects on the overlap quark propagator

We investigate the role of centre vortices in dynamical mass generation using overlap fermions. The exact chiral symmetry that the overlap fermion action possesses yields a distinctive response to the underlying topology of the gauge field, leading to novel results. We study the quark propagator and associated mass function on gauge field backgrounds featuring the removal of centre vortices as well as on vortex-only backgrounds. The effect of cooling vortex-only backgrounds on the overlap quark propagator is also presented.D. Trewartha, W. Kamleh and D. Leinwebe

CAN THE SPLIT-STEP CUTTING TECHNIQUE REDUCE LOADING AND MAINTAIN PERFORMANCE?

INTRODUCTION: Cutting (evasive running) movements are integral to performance in many field- and court-based sports but have been associated with lower limb injuries. This injury risk is attributed to a combination of lower limb geometry and high forces acting together to stress anatomical structures, particularly at the ankle and knee joint. Alternative positioning of the stance foot and adjusted orientation of the lower limbs through changes to the cutting technique may reduce loading (e.g. Besier et al., 2001) but technique interventions for cutting have not been explicitly investigated in-depth. Therefore, the aim of this study was to compare the biomechanical characteristics of unplanned side-step (single foot contact) and split-step (double foot contact) cutting techniques, particularly relating to lower limb loading and ground reaction impulses generated during the primary cutting step. It was expected that the split-step would reduce joint loading and maintain performance requirements