2,182 research outputs found

    Foray search: An effective systematic dispersal strategy in fragmented landscapes

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    In the absence of evidence to the contrary, population models generally assume that the dispersal trajectories of animals are random, but systematic dispersal could be more efficient at detecting new habitat and may therefore constitute a more realistic assumption. Here, we investigate, by means of simulations, the properties of a potentially widespread systematic dispersal strategy termed "foray search." Foray search was more efficient in detecting suitable habitat than was random dispersal in most landscapes and was less subject to energetic constraints. However, it also resulted in considerably shorter net dispersed distances and higher mortality per net dispersed distance than did random dispersal, and it would therefore be likely to lead to lower dispersal rates toward the margins of population networks. Consequently, the use of foray search by dispersers could crucially affect the extinction-colonization balance of metapopulations and the evolution of dispersal rates. We conclude that population models need to take the dispersal trajectories of individuals into account in order to make reliable predictions

    Sled Pull Training Protocol Does Not Improve Peak Force and Increases Asymmetry in Collegiate Soccer Players

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    Speed and acceleration are trainable components that are critical determinants of success in team sports, particularly soccer. Lower extremity strength is one of many factors that determine the maximal force output and velocity of individuals, which is critical to success in sport. PURPOSE: To determine the effects of a 12-week sled pull training intervention on isometric leg strength and asymmetry. METHODS: Participants from Division 1 collegiate men (20 ± 1.5yrs, 168.28 ± 51.17cm, 73.44 ± 23.46kg) and women’s soccer (19.58 ± 1.02yrs, 167.07 ± 3.81cm, 62.46 ± 8.41kg) team performed pre-training isometric thigh pulls on force plates measuring peak force generation, bilaterally. Participants then performed a 12-week training program consisting of sled pulls performed at 80% of bodyweight, three days a week for 6 weeks followed by a 6-week maintenance phase of sled pulls conducted at 50% of bodyweight and post-intervention testing. RESULTS: The pre-training average relative peak force of the left and right legs of male participants were 14.46 ± 1.61N/kg and 14.42 ± 1.33N/kg, respectively, and 11.76 ± 0.69N/kg and 11.67 ± 1.08N/kg, respectively, of female participants. Sled pull training trended (p=0.07) to increase relative peak force in the right leg in both men (15.11 ± 2.14N/kg) and women (12.27 ± 1.31N/kg). However, training trended (p=0.09) to decrease peak left leg force in both men (13.60±2.32N/kg), but less so in women (11.19 ± 1.77N/kg). This leg specific training effect increased (pCONCLUSION: Sled pull training increased asymmetry in both men and women. The increased asymmetry could be attributed to a consistent decline in unilateral force production in the left leg in men. However, there was no consistent pattern to explain the increased asymmetry in women

    SUpporting wellbeing through PEeR-Befriending (SUPERB) feasibility trial: fidelity of peer-befriending for people with aphasia.

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    Objective To evaluate systematically the fidelity of a peer-befriending intervention for people with aphasia. Design SUpporting wellbeing through Peer-befriending (SUPERB) was a feasibility randomised controlled trial comparing usual care to usual care +peer-befriending. This paper reports on the fidelity of all intervention aspects (training and supervision of providers/befrienders; intervention visits) which was evaluated across all areas of the Behaviour Change Consortium framework. Setting Community. Participants People with aphasia early poststroke and low levels of distress, randomised to the intervention arm of the trial (n=28); 10 peer-befrienders at least 1-year poststroke. Intervention Peer-befrienders were trained (4–6 hours); and received regular supervision (monthly group while actively befriending, and one-to-one as and when needed) in order to provide six 1-hour peer-befriending visits over 3 months. Main measures Metrics included number and length of training, supervision sessions and visits. All training and supervision sessions and one (of six) visits per pair were rated against fidelity checklists and evaluated for inter-rater and intrarater reliability (Gwets AC1 agreement coefficient). Per-cent adherence to protocol was evaluated. Results All peer-befrienders received 4–6 hours training over 2–3 days as intended. There were 25 group supervision sessions with a median number attended of 14 (IQR=8–18). Twenty-six participants agreed (92.8%) to the intervention and 21 (80.8%) received all six visits (median visit length 60 min). Adherence was high for training (91.7%–100%) and supervision (83%–100%) and moderate-to-high for befriending visits (66.7%–100%). Where calculable, inter-rater and intrarater reliability was high for training and supervision (Gwets AC1 >0.90) and moderate-to-high for intervention visits (Gwets AC1 0.44–1.0). Conclusion Planning of fidelity processes at the outset of the trial and monitoring throughout was feasible and ensured good-to-high fidelity for this peer-befriending intervention. The results permit confidence in other findings from the SUPERB trial

    A Randomised Trial of Social Support Group Intervention for People with Aphasia: A Novel Application of Virtual Reality

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    About a third of strokes cause aphasia, or language loss, with profound consequences for the person’s social participation and quality of life. These problems may be mitigated by group social support. But this intervention is not available to all individuals. This study investigated whether it is feasible to deliver group social support to people with aphasia via a multi-user, virtual reality platform. It also explored the indicative effects of intervention and the costs. Intervention aimed to promote wellbeing and communicative success. It enabled participants to form new social connections and share experiences of living with aphasia. It comprised 14 sessions delivered over 6 months and was led by community based co-ordinators and volunteers. Feasibility measures comprised: recruitment and retention rates, compliance with intervention and assessment of treatment fidelity. Effects of intervention were explored using a waitlist randomised controlled design, with outcome measures of wellbeing, communication, social connectedness and quality of life. Two intervention groups were randomised to an immediate condition and two were randomised to a delayed condition. The main analysis explored scores on the measures between two time points, between which those in the immediate condition had received intervention, but those in the delayed group had not (yet). A comprehensive approach to economic data collection ensured that all costs of treatment delivery were recorded. Feasibility findings showed that the recruitment target was met (N = 34) and 85.3% (29/34) of participants completed intervention. All groups ran the 14 sessions as planned, and participants attended a mean of 11.4 sessions (s.d. 2.8), which was 81.6% of the intended dose. Fidelity checking showed minimal drift from the manualised intervention. No significant change was observed on any of the outcome measures, although the study was not powered to detect these. Costs varied across the four groups, from £7,483 - £12,562 British Pounds Sterling (10,972−10,972 - 18,419 US dollars), depending on travel costs, the relative contributions of volunteers and the number of hardware loans that were needed. The results suggest that a larger trial of remote group support, using virtual reality, would be merited. However the treatment content and regime, and the selection of outcome measures should be reviewed before conducting the trial

    Phenotypic and functional characterization of adult brain neuropoiesis

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    The modern concept of neurogenesis in the adult brain is predicated on the premise that multipotent glial cells give rise to new neurons throughout life. Although extensive evidence exists indicating that this is the case, the transition from glial to neuronal phenotype remains poorly understood. A unique monolayer cell-culture system was developed to induce, expose, and recapitulate the entire developmental series of events of subventricular zone (SVZ) neurogenesis. We show here, using immunophentoypic, ultrastructural, electrophysiological, and time-lapse analyses, that SVZ-derived glial fibrillary acidic protein(low)/A2B5(+)/nestin(+) candidate founder cells undergo metamorphosis to eventually generate large numbers of fully differentiated interneuron phenotypes. A model of postnatal neurogenesis is considered in light of known embryonic events and reveals a limited developmental potential of SVZ stem/progenitor cells, whereby ancestral cells in both embryonic and postnatal/adult settings give rise to glia and GABAergic interneurons

    Dynamic characterization of an alkali-ion battery as a source for laser-cooled atoms

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    We investigate a solid-state, reversible, alkali-ion battery (AIB) capable of regulating the density of alkali atoms in a vacuum system used for the production of laser-cooled atoms. The cold-atom sample can be used with in-vacuum chronoamperometry as a diagnostic for the voltage-controlled electrochemical reaction that sources or sinks alkali atoms into the vapor. In a combined reaction-diffusion-limited regime, we show that the number of laser-cooled atoms in a magneto-optical trap can be increased both by initially loading the AIB from the vapor for longer, and by using higher voltages across the AIB when atoms are subsequently sourced back into the vapor. The time constants associated with the change in atom number in response to a change in AIB voltage are in the range of 0.5 s - 40 s. The AIB alkali reservoir is demonstrated to survive oxidization during atmospheric exposure, simplifying reservoir loading prior to vacuum implementation as a replacement for traditional resistively-heated dispensers. The AIB capabilities may provide an improved atom number stability in next-generation atomic clocks and sensors, while also facilitating fast loading and increased interrogation times.Comment: 7 pages, 5 figure

    A magneto-optic trap using a reversible, solid-state alkali-metal source

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    We demonstrate a novel way to form and deplete a vapor-cell magneto-optic trap (MOT) using a reversible, solid-state alkali-metal source (AMS) via an applied polarized voltage. Using ~100 mW of electrical power, a trapped-atom number of 5x10^6 has been achieved starting from near zero and the timescales of the MOT formation and depletion of ~1 s. This fast, reversible, and low power alkali-atom source is desirable in both tabletop and portable cold-atom systems. The core technology of this device should translate readily to other alkali and alkaline-earth elements that could find a wide range of uses in cold-atom systems and instruments.Comment: 7 page

    Sled-pull Training Improves Maximal Horizontal Velocity in Collegiate Male and Female Soccer Players

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    The force velocity profile (FvP), which details the capacity to sprint and accelerate, is a determinant of success in soccer. To date, no data exist that details the FvP of male and female collegiate Division I soccer players. Further, there is limited insight on how training interventions may modify the FvP of either males or females. PURPOSE: The aim of this investigation was to compare FvP between collegiate male and female athletes and assess the efficacy of a 12-week sled pull training intervention. METHODS: 17 male (20.17 ± 1.38 yrs) and 12 female (19.75 ± 1.05 yrs) soccer players participated in a 12-week sled pull training intervention. FvP was measured prior, during, and after training using a 30m sprint to assess maximal horizontal force (F0), maximal horizontal speed (V0), and maximal power output (Pmax). RESULTS: The intervention improved 30m sprint times of men by 11.86% (pre: 4.35 ± 0.17s, post: 4.27 ± 0.17, p0 in both men (pre: 7.98 ± 0.36 m/s, post: 8.09 ± 0.35 m/s, p0 or Pmax. CONCLUSION: This is the first study to detail FvP in both male and female collegiate soccer players. A 12-week sled pull training intervention improves 30m sprint times and V0 in both male and female collegiate athletes, but does not improve F0 and Pmax. Thus, the sled pull intervention should be modified or paired with other training that specifically targets force and power development
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