247 research outputs found

    Relativistic Corrections to e+e−→J/ψ+ηce^+e^- \to J/\psi + \eta_c in a Potential Model

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    We compute relativistic corrections to the process e+e−→J/ψ+ηce^+e^- \to J/\psi + \eta_c and find that they resolve the discrepancy between theory and experiment.Comment: 3 pages, talk given at Quark Confinement and the Hadron Spectrum VII, Ponta Delgada, Azores, 2--7 Sept, 200

    Fostering a Sense of Social Connectedness for Minoritized Students and Faculty in Online Learning

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    Faculty and students with minoritized identities face additional systemic and social barriers such as disconnection from colleagues, inability to discern body language, and gap in communication. This paper addresses some of these barriers as well as provides practical strategies and resources for faculty and students to develop social connectedness in online learning environments. Strategies are provided for allies to support and foster change in online academic environments to build social connections and belongingness

    Want to Foster New Motor Learning Following High Contextual Interference Practice: Better Consolidate Previous Learning First

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    High contextual interference (CI) practice regimes aid in the retention and transfer of skilled actions. The elaboration perspective, still considered a viable explanation for the benefit of high CI training, proposes that a richer network of task specific knowledge is developed from random practice thus, affording the learner a variety of ways to retrieve task relevant information during delayed tests. One would expect that new tasks, similar to previously trained exemplars, will be acquired faster and retained with greater success following random as opposed to blocked practice. That is, the presence of a rich memory network should provide a suitable foundation from which to incorporate new related task knowledge. To examine this prediction subjects practiced three unique motor tasks in either a blocked or random format. Original practice consisted of nine trials for each seven-element motor sequence in a blocked or random schedule. An additional nine trials of practice with the novel motor sequence was experienced by all participants shortly after original training in the Experiment 1. While the typical retention benefit emerged for random practice for the original motor tasks, no practice schedule effect was revealed for new learning. Experiment 2 examined the possibility that increasing the interval between original training and supplemental practice with the novel motor task might benefit from a greater time interval. By increasing this interval from 2–min to 24-hr afforded individuals an opportunity to consolidate the memory network developed following random or blocked practice. Congruent with Experiment 1 the CI effect emerged in the form of superior retention of the motor tasks acquired via random practice. Moreover, following the longer temporal interval, random practice facilitated the rate at which new task information was used to execute a new skill which was also reflected in superior retention than observed following blocked practice. Interestingly, following consolidation, both practice schedules exhibited a task-independent benefit when first required to perform the novel task, and offline improvement in performance across a 24-hr interval. These data will be discussed with respect to broader learning benefits from inducing greater CI and the importance of memory consolidation for motor learning

    Applying Anodal Transcranial Direct Current Stimulation at BA6 During Repetitive Practice Enhances Motor Learning by Improving Encoding and Post-Practice Consolidation

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    Understanding how the structure of practice influences the consolidation and long-term retention of motor skills is important to maximize learning. Learning multiple motor sequences simultaneously is facilitated by using an interleaved as opposed to repetitive training schedule typically manifest as superior consolidation and long-term retention. Recent neural imaging data has highlighted the importance of earlier and more consistent recruitment of the BA6 region, in particular the supplementary motor area (SMA) and dorsal premotor area (PMd), during IP compared to repetitive practice (RP). Indeed, the emergence of greater functional connectivity of dorsal premotor region (PMd) during IP has been reported to be predictive of subsequent learning gains. The primary aim of this work was to modify the cortical activity at SMA (Experiment 1) and PMd (Experiment 2) during RP and IP using anodal or cathodal transcranial direct current stimulation (tDCS). The expectation was that increasing activity at these neural regions during RP should enhance offline gain. Conversely, down-regulating the cortical activity at these neural sites during IP should disrupt the expect learning benefit associated with this practice format. Participants were exposed to anodal tDCS at SMA (Exp1) and PMd (Exp2) of 2 mA during approximately 20-min of RP format or cathodal tDCS at these same sites while experiencing RP. Performance of three motor sequences was assessed in a RP format prior to any practice and immediately after practice, as well as 6-hr, 24-hr, and 72-hr after the completion of RP or IP. No stimulation was present during any of the test blocks. As expected, there was a robust learning benefit from IP manifest as superior early consolidation during the initial 6-hr after practice and further performance enhancement likely a result of more effective sleep-mediated consolidation. Applying anodal tDCS during RP at SMA (Experiment 1) led to increased offline gain both from superior early time-dependent as well as enhanced sleep-mediated consolidation. Administering anodal tDCS at PMd during RP (Experiment 2) also offered a learning benefit but surfaced from improved encoding during practice rather than from a change in post-practice consolidation processes. Cathodal stimulation at either SMA or PMd during IP failed to change the behavioral outcomes associated with their sham counterparts. These data then suggest that adequate activation of both neural regions, SMA complex and PMd, is important for skill acquisition but despite being neighboring neural sites within BA6 the specific contribution of each site to the evolution of novel motor memories is quite distinct

    Inclusive Production of Four Charm Hadrons in e^+ e^- Annihilation at B Factories

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    Measurements by the Belle Collaboration of the exclusive production of two charmonia in e^+ e^- annihilation differ substantially from theoretical predictions. Till now, no conclusive explanation for this remarkable discrepancy has been provided. Even the origin of the discrepancy is not identified, yet. We suggest that the measurement of four-charm events in Belle data must provide a strong constraint in identifying the origin of this large discrepancy. Our prediction of the cross section for e^+e^- -> c c-bar c c-bar, in lowest order in strong coupling constant, at sqrt{s}=10.6 GeV is about 0.1 pb. If measured four-charm cross section is compatible with the prediction based on perturbative QCD, it is very likely that factorization of hadronization process from perturbative part may be significantly violated or there exists a new production mechanism. If the cross section for the four-charm event is also larger than the prediction like that for the exclusive J/psi+eta_c production, perturbative QCD expansion itself will be proved to be unreliable and loses predictive power.Comment: 4 pages, 3 figures, version published in Phys. Rev. D as a Rapid Communicatio

    The influence of orbital rotation on the energy of closed-shell wavefunctions

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    The orbital dependence of closed-shell wavefunction energies is investigated by performing doubly-occupied configuration interaction (DOCI) calculations, representing the most general class of these wavefunctions. Different local minima are examined for planar hydrogen clusters containing two, four, and six electrons applying (spin) symmetry-broken restricted, unrestricted, and generalised orbitals with real and complex coefficients. Contrary to Hartree-Fock (HF), restricted DOCI is found to properly break bonds and thus unrestricted orbitals, while providing a quantitative improvement of the energy, are not needed to enforce a qualitatively correct bond dissociation. For the beryllium atom and the BH diatomic, the lowest possible HF energy requests symmetry-broken generalised orbitals, whereas accurate results for DOCI can be obtained within a restricted formalism. Complex orbital coefficients are shown to increase the accuracy of HF and DOCI results in certain cases. The computationally inexpensive AP1roG geminal wavefunction is proven to agree very well with all DOCI results of this study

    Learning to Place Unseen Objects Stably using a Large-scale Simulation

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    Object placement is a fundamental task for robots, yet it remains challenging for partially observed objects. Existing methods for object placement have limitations, such as the requirement for a complete 3D model of the object or the inability to handle complex shapes and novel objects that restrict the applicability of robots in the real world. Herein, we focus on addressing the Unseen Object Placement (UOP}=) problem. We tackled the UOP problem using two methods: (1) UOP-Sim, a large-scale dataset to accommodate various shapes and novel objects, and (2) UOP-Net, a point cloud segmentation-based approach that directly detects the most stable plane from partial point clouds. Our UOP approach enables robots to place objects stably, even when the object's shape and properties are not fully known, thus providing a promising solution for object placement in various environments. We verify our approach through simulation and real-world robot experiments, demonstrating state-of-the-art performance for placing single-view and partial objects. Robot demos, codes, and dataset are available at https://gistailab.github.io/uop/Comment: 8 pages (main

    The effect of attentional focus in balancing tasks: A systematic review with meta-analysis

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    Purpose: The present study was to use the aggregate data meta-analytic approach to examine the effects of attentional focus during balancing tasks in motor learning. Method: A literature search was conducted based on five electronic database searches, cross-referencing and expert review. Studies included randomized trials of external (EF) versus internal focus (IF). Risk of bias was assessed using a self-developed instrument. Random effects models using the standardized mean difference effect size (ES) were used to pooled results. Heterogeneity was examined using the Q statistic and inconsistency using I 2 . Results: Of 790 studies screened, 16 representing 541 males and females and up to 17 ES met the inclusion criteria. Analyses indicated that the EF groups outperformed the IF groups for acquisition phase (ES= 0.48, n= 16; CI95%= 0.07 to 0.90, Q= 68.7, I 2= 78.2%), retention (ES= 0.44, n= 17, CI95%= 0.14 to 0.74; Q= 26.1, I 2= 38.6%), and transfer (ES= 1.41, n= 4, CI95%= 1.00 to 1.82, Q= 22, I 2= 0%). Conclusion: The overall results suggest that EF results in better balance learning when compared to IF.UCR::Vicerrectoría de Docencia::Ciencias Sociales::Facultad de Educación::Escuela de Educación Físic
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