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Abstract Background Exercise has various health benefits for people with Parkinson’s disease (PD). However, implementing exercise into daily life and long-term adherence remain challenging. To increase a sustainable engagement with physical activity of people with PD, interventions that are motivating, accessible, and scalable are needed. We primarily aim to investigate whether a smartphone app (STEPWISE app) can increase physical activity (i.e., step count) in people with PD over one year. Our second aim is to investigate the potential effects of the intervention on physical fitness, and motor- and non-motor function. Our third aim is to explore whether there is a dose-response relationship between volume of physical activity and our secondary endpoints. Methods STEPWISE is a double-blind, randomized controlled trial. We aim to include 452 Dutch people with PD who can walk independently (Hoehn & Yahr stages 1–3) and who do not take more than 7,000 steps per day prior to inclusion. Physical activity levels are measured as step counts on the participant’s own smartphone and scaled as percentage of each participant’s baseline. Participants are randomly assigned to an active control group with an increase of 5–20% (active controls) or any of the three intervention arms with increases of 25–100% (intermediate dose), 50–200% (large dose), or 100–400% (very large dose). The primary endpoint is change in step count as measured by the STEPWISE smartphone app from baseline to 52 weeks. For our primary aim, we will evaluate the between-group difference in average daily step count change from baseline to 52 weeks. For our second aim, measures of physical fitness, and motor- and non-motor function are included. For our third aim, we will associate 52-week changes in step count with 52-week changes in secondary outcomes. Discussion This trial evaluates the potential of a smartphone-based intervention to increase activity levels in people with PD. We envision that motivational apps will increase adherence to physical activity recommendations and could permit conduct of remote clinical trials of exercise for people with PD or those at risk of PD. Trial registration ClinicalTrials.gov; NCT04848077; 19/04/2021. Clinicaltrials.gov/ct2/show/NCT04848077.

Blue supergiants are the brightest stars in their host galaxies, and yet their evolutionary status has been a long-standing problem in stellar astrophysics. In this pioneering work, we present a large sample of 59 early B-type supergiants in the Large Magellanic Cloud with newly derived stellar parameters and identify the signatures of stars born from binary mergers among them. We simulate novel 1D merger models of binaries consisting of post main-sequence giants with helium-rich cores (primaries) and main-sequence companions (secondaries), and consider the effects of interaction of the secondary with the core of the primary along with the mixing induced by the merger in the envelope. Thereafter, the evolution of the newborn 17–43 $\,{{\rm{M}}}_{\odot }$ stars is followed until core-carbon depletion, close to their final pre-explosion stage. Unlike stars born alone with comparable masses, stars born from mergers of evolved binaries are blue throughout their core helium-burning phase and replicate the surface gravities and Hertzsprung–Russell diagram positions of most of our sample, thus indicating that B-type supergiants structurally resemble stars born from such mergers. Moreover, the large nitrogen-to-carbon and nitrogen-to-oxygen number ratios, coupled with helium enhancements exhibited by at least half our data sample, is uniquely reproduced by our merger models. Collectively, these findings provide compelling evidence toward the important role of binary mergers in producing the currently observed population of blue supergiants in our Universe.

Massive stars mainly form in close binaries, where their mutual interactions can profoundly alter their evolutionary paths. Evolved binaries consisting of a massive OB-type main-sequence star with a stripped helium star or a compact companion represent a crucial stage in the evolution toward double compact objects, whose mergers are (potentially) detectable via gravitational waves. The recent detection of X-ray-quiet OB+black hole binaries and OB+stripped helium star binaries has set the stage for discovering more of these systems in the near future. In this work, based on 3670 detailed binary-evolution models and using empirical distributions of initial binary parameters, we compute the expected population of such evolved massive binaries in coeval stellar populations, including stars in star clusters and in galaxies with starburst activities, for ages up to 100 Myr. Our results are vividly illustrated in an animation that shows the evolution of these binaries in the color–magnitude diagram over time. We find that the number of OB+black hole binaries peaks around 10 Myr, and OB+neutron star binaries are most abundant at approximately 20 Myr. Both black holes and neutron stars can potentially be found in populations with ages up to 90 Myr. Additionally, we analyze the properties of such binaries at specific ages. We find that OB+helium stars and OB+black hole binaries are likely to be identifiable as single-lined spectroscopic binaries. Our research serves as a guide for future observational efforts to discover such binaries in young star clusters and starburst environments.

Background: Natural health products have emerged as a potential symptomatic therapeutic approach for people with Parkinson's disease (PD). Objective: To determine the prevalence of natural health product use, interest in natural health products, awareness of potential herb-drug interactions, and consultation of healthcare professionals regarding natural health products use among people with PD. Methods: Cross-sectional 4-item survey embedded in the PRIME-NL study, which is a population-based cohort of PD. Results: Of 367 people with PD, 36% reported having used natural health products to alleviate PD-related symptoms, with coffee, cannabis and turmeric being the most popular. Furthermore, 71% of people with PD were interested in learning more about natural health products. 39% of natural health products users were aware that these products could interact with PD medication and 39% had discussed their use with their healthcare professional. Conclusions: Natural health products are commonly used to alleviate symptoms by people with PD, but most users are unaware that these products can interact with PD medication and do not discuss their consumption with their healthcare professional. Plain Language Summary: Parkinson's disease is a complex neurodegenerative disorder for which current treatments are limited to symptomatic relief, and prescribed medication often causes side effects. In this context, there is an increasing interest in non-pharmacological interventions, and people living with Parkinson's disease may want to explore natural health products to alleviate disease-associated symptoms. Examples of these products include cannabis, coffee, or velvet bean (as a natural source of Levodopa). However, it remains unclear how many people with Parkinson's disease have ever used, or wish to use, natural health products to relieve disease-related symptoms. In addition, limited information is available to evaluate whether they are aware of possible interactions between these products and prescribed medication. Therefore, the aim of this study was to investigate these questions in a large representative group of people with Parkinson's disease. A total of 367 people responded to the survey, and 36% reported that they had used natural health products to relieve Parkinson's disease-related symptoms. Among the supplements listed in our survey, coffee (16%), cannabis (13%) and turmeric (10%) were the most popular. Additionally, 71% of participants were interested in learning more about natural health products, and we found that 39% of natural health product users were aware of possible interactions with prescribed Parkinson's disease medication. However, it appeared that only 39% of users had discussed these supplements with their healthcare provider. These observations are important because a concern regarding the integration of natural health products into clinical practice is their potential interactions with prescribed medication. Therefore, these findings support the need for additional research efforts into the health benefits and safety of these products. We conclude that natural health products are used by people with Parkinson's disease to provide symptomatic relief, and open discussions with their healthcare providers are encouraged to ensure efficacy and safety. [ABSTRACT FROM AUTHOR]

. We present UVIT/Astrosat UV photometry of the RSG population of the Small Cloud galaxy (SMC). As RSGs are extremely faint in the far-UV, these observations directly probe potential companion stars. From a sample of 861 SMC RSGs, we find 88 have detections at far-UV wavelengths: a clear signature of binarity. Stellar parameters are determined for both components, which allows us to study - for the first time - the mass-ratio (q) distribution of RSG binary systems. We find a flat mass-ratio distribution best describes the observations up to MRSG ∼15M⊙. We account for our main observing bias (i.e. the limiting magnitude of the UVIT survey) to determine the intrinsic RSG binary fraction of 18.8 ± 1.5 %, for mass-ratios in the range 0.3.< q <1.0 and orbital periods approximately in the range 3

Since massive stars form preferentially as members of close binary systems, we use dense grids of detailed binary evolution models to explore how binary evolution shapes the main-sequence morphology of young star clusters. We propose that binary mergers might be the origin of the blue main sequence stars in young star clusters. Our results imply that stars may either form by accretion, or through a binary merger, and that both paths lead to distinctly different spins, magnetic fields, and stellar mass distributions. [ABSTRACT FROM AUTHOR]

We probe how common extremely rapid rotation is among massive stars in the early universe by measuring the OBe star fraction in nearby metal-poor dwarf galaxies. We apply a new method that uses broad-band photometry to measure the galaxy-wide OBe star fractions in the Magellanic Clouds and three more distant, more metal-poor dwarf galaxies. We find OBe star fractions of ∼20% in the Large Magallanic Cloud (0.5 Z ȯ), and ∼30% in the Small Magellanic Cloud (0.2 Z ȯ) as well as in the so-far unexplored metallicity range 0.1 Z / Z ȯ < 0.2 occupied by the other three dwarf galaxies. Our results imply that extremely rapid rotation is common among massive stars in metal-poor environments such as the early universe. [ABSTRACT FROM AUTHOR]

Several dietary patterns and nutritional supplements have been linked to the development, progression, and symptomatic treatment of Parkinson's disease (PD). Most of the evidence, at this point, is preliminary and based largely on observational studies. Interventional studies are scarce, so the evidence on effectiveness remains inconclusive. Dietary interventions could, analogous to exercise, potentially have a beneficial effect on disease symptoms as well as on the progression of the disease and should therefore be researched in high quality studies. Further work is also needed to study whether dietary interventions, when applied to an at-risk population, have any potential to postpone the onset of manifest PD. In this paper, we summarize all ongoing clinical trials on dietary interventions in PD. We found 10 ongoing studies, all aimed at a different intervention. These studies are mostly exploratory in nature or represent phase I or phase II trials focusing on safety, biological responses, and symptomatic effects. Taken together, we conclude that research on dietary interventions in persons with PD is still in its early days. The results of the various ongoing trials are expected to generate new hypotheses and will help to shape the agenda for future research on this important topic. [ABSTRACT FROM AUTHOR]

Gait quality characteristics obtained from accelerometry during daily life are predictive of falls in older people but it is unclear how they relate to fall risk. Our aim was to test whether these gait quality characteristics are associated with the severity of fall risk. We collected one week of trunk accelerometry data from 279 older people (aged 65–95 years; 69.5% female). We used linear regression to investigate the association between six daily-life gait quality characteristics and categorized physiological fall risk (QuickScreen). Logarithmic rate of divergence in the vertical (VT) and anteroposterior (AP) direction were significantly associated with the level of fall risk after correction for walking speed (both p < 0.01). Sample entropy in VT and the mediolateral direction and the gait quality composite were not significantly associated with the level of fall risk. We found significant differences between the high fall risk group and the very low- and low-risk groups, the moderate- and very low-risk and the moderate and low-risk groups for logarithmic rate of divergence in VT and AP (all p ≤ 0.01). We conclude that logarithmic rate of divergence in VT and AP are associated with fall risk, making them feasible to assess the physiological fall risk in older people.

Purpose of Review: Many studies have identified positive effects of physiotherapy and exercise for persons with Parkinson's disease (PD). Most work has thus far focused on the therapeutic modality of exercise as used within physiotherapy programs. Stimulated by these positive findings, there is now a strong move to take exercise out of the clinical setting and to deliver the interventions in the community. Although the goals and effects of many such community-based exercise programs overlap with those of physiotherapy, it has also become more clear that both exercise modalities also differ in various ways. Here, we aim to comprehensively review the evidence for community-based exercise in PD. Recent Findings: Many different types of community-based exercise for people with PD are emerging and they are increasingly being studied. There is a great heterogeneity considering the types of exercise, study designs, and outcome measures used in research on this subject. While this review is positive regarding the feasibility and potential effects of community-based exercise, it is also evident that the general quality of these studies needs improvement. Summary: By focusing on community-based exercise, we hope to generate more knowledge on the effects of a wide range of different exercise modalities that can be beneficial for people with PD. This knowledge may help people with PD to select the type and setting of exercise activity that matches best with their personal abilities and preferences. As such, these insights will contribute to an improved self-management of PD. [ABSTRACT FROM AUTHOR]

Background: Exercise has various health benefits for people with Parkinson's disease (PD). However, implementing exercise into daily life and long-term adherence remain challenging. To increase a sustainable engagement with physical activity of people with PD, interventions that are motivating, accessible, and scalable are needed. We primarily aim to investigate whether a smartphone app (STEPWISE app) can increase physical activity (i.e., step count) in people with PD over one year. Our second aim is to investigate the potential effects of the intervention on physical fitness, and motor- and non-motor function. Our third aim is to explore whether there is a dose-response relationship between volume of physical activity and our secondary endpoints. Methods: STEPWISE is a double-blind, randomized controlled trial. We aim to include 452 Dutch people with PD who can walk independently (Hoehn & Yahr stages 1–3) and who do not take more than 7,000 steps per day prior to inclusion. Physical activity levels are measured as step counts on the participant's own smartphone and scaled as percentage of each participant's baseline. Participants are randomly assigned to an active control group with an increase of 5–20% (active controls) or any of the three intervention arms with increases of 25–100% (intermediate dose), 50–200% (large dose), or 100–400% (very large dose). The primary endpoint is change in step count as measured by the STEPWISE smartphone app from baseline to 52 weeks. For our primary aim, we will evaluate the between-group difference in average daily step count change from baseline to 52 weeks. For our second aim, measures of physical fitness, and motor- and non-motor function are included. For our third aim, we will associate 52-week changes in step count with 52-week changes in secondary outcomes. Discussion: This trial evaluates the potential of a smartphone-based intervention to increase activity levels in people with PD. We envision that motivational apps will increase adherence to physical activity recommendations and could permit conduct of remote clinical trials of exercise for people with PD or those at risk of PD. Trial registration: ClinicalTrials.gov; NCT04848077; 19/04/2021. Clinicaltrials.gov/ct2/show/NCT04848077. [ABSTRACT FROM AUTHOR]

People are known to be very poor at visually judging acceleration. Yet, they are extremely proficient at intercepting balls that fall under gravitational acceleration. How is this possible? We previously found that people make systematic errors when trying to tap on targets that move with different constant accelerations or decelerations on interleaved trials. Here, we show that providing contextual information that indicates how the target will decelerate on the next trial does not reduce such errors. Such errors do rapidly diminish if the same deceleration is present on successive trials. After observing several targets move with a particular acceleration or deceleration without attempting to tap on them, participants tapped as if they had never experienced the acceleration or deceleration. Thus, people presumably deal with acceleration when catching or hitting a ball by compensating for the errors that they made on preceding attempts.

Despite increasing evidence on exercise in Parkinson's disease (PD) it remains unclear what type and intensity of exercise are most effective. Currently, most evidence favors moderate- to high-intensity aerobic exercise for its positive effects on motor symptoms as well as disease modifying potential. On the other hand, observational studies have shown that the sheer volume of exercise matters as well, independent of intensity. So far, the efficacy of the volume of exercise has not been confirmed by randomized controlled trials (RCTs). Here, we provide an overview of the ongoing RCTs that promote physical activity in daily life in PD. We found seven RCTs with sample sizes between 30 and 452 and a follow-up between 4 weeks and 12 months. Steps per day is the most commonly reported primary outcome measure. The ongoing RCTs will provide evidence for feasibility, whereafter the PD research field is ready for a next step and to explore the effect of physical activity on disease progression and PD symptoms. [ABSTRACT FROM AUTHOR]

Gait quality characteristics obtained from daily-life accelerometry are clinically relevant for fall risk in older adults but it is unknown whether these characteristics are responsive to changes in gait quality. We aimed to test whether accelerometry-based daily-life gait quality characteristics are reliable and responsive to changes over one year in older adults who experienced a fall or an exercise intervention. One-week trunk acceleration data were collected from 522 participants (65–97 years), at baseline and after one year. We calculated median values of walking speed, regularity (sample entropy), stability (logarithmic rate of divergence per stride), and a gait quality composite score, across all 10-s gait epochs derived from one-week gait episodes. Intraclass correlation coefficients (ICC) and limits of agreement (LOA) were determined for 198 participants who did not fall nor participated in an exercise intervention during follow-up. For responsiveness to change, we determined the number of participants who fell (n = 209) or participated in an exercise intervention (n = 115) that showed a change beyond the LOA. ICCs for agreement between baseline and follow-up exceeded 0.70 for all gait quality characteristics except for vertical gait stability (ICC = 0.69, 95% CI [0.62, 0.75]) and walking speed (ICC = 0.68, 95% CI [0.62, 0.74]). Only walking speed, vertical and mediolateral gait stability changed significantly in the exercisers over one year but effect sizes were below 0.2. The characteristic associated with most fallers beyond the LOA was mediolateral sample entropy (4.8% of fallers). For the exercisers, this was gait stability in three directions and the gait quality composite score (2.6% of exercisers). The gait quality characteristics obtained by median values over one week of trunk accelerometry were not responsive to presumed changes in gait quality after a fall or an exercise intervention in older people. This is likely due to large (within subjects) differences in gait behaviour that participants show in daily life. [ABSTRACT FROM AUTHOR]

Converging lines of evidence suggest that aerobic exercise impacts Parkinson's disease (PD) motor symptoms and might slow it's progression. We provide an overview of the ongoing randomized clinical trials (RCTs) on aerobic exercise in PD. We found six RCTs with sample sizes between 28 and 370 and a follow-up between 8 weeks and 18 months. PD motor symptoms is mostly used as primary outcome while various secondary outcomes are reported. We need more trials that use both clinical endpoints and markers of neuroplasticity, and provide insight into the optimal exercise mode, duration and intensity. [ABSTRACT FROM AUTHOR]

We aim to identify and characterize binary systems containing red supergiant (RSG) stars in the Small Magellanic Cloud (SMC) using a newly available ultraviolet (UV) point source catalogue obtained using the Ultraviolet Imaging Telescope (UVIT) on board AstroSat. We select a sample of 560 SMC RSGs based on photometric and spectroscopic observations at optical wavelengths and cross-match this with the far-UV point source catalogue using the UVIT F172M filter, finding 88 matches down to m F 172 M  = 20.3 ABmag, which we interpret as hot companions to the RSGs. Stellar parameters (luminosities, effective temperatures, and masses) for both components in all 88 binary systems are determined and we find mass distributions in the ranges 6.1 < M / M ⊙ < 22.3 for RSGs and 3.7 < M / M ⊙ < 15.6 for their companions. The most massive RSG binary system in the SMC has a combined mass of 32 ± 4 M⊙, with a mass ratio (q) of 0.92. By simulating observing biases, we find an intrinsic multiplicity fraction of |$18.8\, \pm \, 1.5\, {{\ \rm per\ cent}}$| for mass ratios in the range 0.3 < q < 1.0 and orbital periods approximately in the range |$3 \lt \log P [\rm days] \lt 8$|⁠. By comparing our results with those of a similar mass on the main sequence, we determine the fraction of single stars to be ∼20  per cent and argue that the orbital period distribution declines rapidly beyond log  P ∼ 3.5. We study the mass-ratio distribution of RSG binary systems and find that a uniform distribution best describes the data below 14 M⊙. Above 15 M⊙, we find a lack of high mass ratio systems. [ABSTRACT FROM AUTHOR]

. We present UVIT/Astrosat UV photometry of the RSG population of the Small Cloud galaxy (SMC). As RSGs are extremely faint in the far-UV, these observations directly probe potential companion stars. From a sample of 861 SMC RSGs, we find 88 have detections at far-UV wavelengths: a clear signature of binarity. Stellar parameters are determined for both components, which allows us to study - for the first time - the mass-ratio (q) distribution of RSG binary systems. We find a flat mass-ratio distribution best describes the observations up to MRSG ∼15M⊙. We account for our main observing bias (i.e. the limiting magnitude of the UVIT survey) to determine the intrinsic RSG binary fraction of 18.8 ± 1.5 %, for mass-ratios in the range 0.3.< q <1.0 and orbital periods approximately in the range 3

Since massive stars form preferentially as members of close binary systems, we use dense grids of detailed binary evolution models to explore how binary evolution shapes the main-sequence morphology of young star clusters. We propose that binary mergers might be the origin of the blue main sequence stars in young star clusters. Our results imply that stars may either form by accretion, or through a binary merger, and that both paths lead to distinctly different spins, magnetic fields, and stellar mass distributions. [ABSTRACT FROM AUTHOR]

Exercise is increasingly being recognized as a key element in the overall management of persons living with Parkinson's disease (PD) but various (disease-specific) barriers may impede even motivated patients to participate in regular exercise. We aimed to provide a comprehensive review of the various barriers and motivators for exercise in persons with PD. We scrutinized data on compliance-related factors published in cross-sectional studies, randomized controlled trials and reviews. We classified the barriers and motivators to exercise from a patient perspective according to the International Classification of Functioning, Disability and Health. We present an overview of the large range of potential motivators and barriers for exercise in persons with PD. Healthcare professionals should consider a wide and comprehensive range of factors, in order to identify which specific determinants matter most for each individual. Only when persons with PD are adequately motivated in a way that appeals to them and after all person-specific barriers have been tackled, we can begin to expect their long-term adherence to exercise. Such long-term compliance will be essential if exercise is to live up to its expectations, including the hope that prolonged engagement in regular exercise might help to modify the otherwise relentlessly progressive course of PD. [ABSTRACT FROM AUTHOR]

Context. The evolution of massive stars is strongly influenced by internal mixing processes such as semiconvection, convective core overshooting, and rotationally induced mixing. None of these processes are currently well constrained. Aims. We investigate models for massive stars in the Small Magellanic Cloud (SMC), for which stellar-wind mass loss is less important than for their metal-rich counterparts. We aim to constrain the various mixing efficiencies by comparing model results to observations. Methods. For this purpose, we use the stellar-evolution code MESA to compute more than 60 grids of detailed evolutionary models for stars with initial masses of 9...100 M⊙, assuming different combinations of mixing efficiencies of the various processes in each grid. Our models evolve through core hydrogen and helium burning, such that they can be compared with the massive main sequence and supergiant population of the SMC. Results. We find that for most of the combinations of the mixing efficiencies, models in a wide mass range spend core-helium burning either only as blue supergiants, or only as red supergiants. The latter case corresponds to models that maintain a shallow slope of the hydrogen/helium (H/He) gradient separating the core and the envelope of the models. Only a small part of the mixing parameter space leads to models that produce a significant number of blue and red supergiants, which are both in abundance in the SMC. Some of our grids also predict a cut-off in the number of red supergiants above log L/L⊙ = 5...5.5. Interestingly, these models contain steep H/He gradients, as is required to understand the hot, hydrogen-rich Wolf-Rayet stars in the SMC. We find that unless it is very fast, rotation has a limited effect on the H/He profiles in our models. Conclusions. While we use specific implementations of the considered mixing processes, they comprehensively probe the two first-order structural parameters, the core mass and the H/He gradient in the core-envelope interface. Our results imply that in massive stars, mixing during the main-sequence evolution leads to a moderate increase in the helium core masses, and also that the H/He gradients above the helium cores become very steep. Our model grids can be used to further refine the various mixing efficiencies with the help of future observational surveys of the massive stars in the SMC, and thereby help to considerably reduce the uncertainties in models of massive star evolution. [ABSTRACT FROM AUTHOR]

Stripped-envelope stars form in binary systems after losing mass through Roche-lobe overflow. They bear astrophysical significance as sources of UV and ionizing radiation in older stellar populations and, if sufficiently massive, as stripped supernova progenitors. Binary evolutionary models predict that they are common, but only a handful of subdwarfs with B-type companions are known. The question is whether a large population of such systems has evaded detection as a result of biases, or whether the model predictions are wrong. We reanalyze the well-studied post-interaction binary φ Persei. Recently, new data have improved the orbital solution of the system, which contains an ~1.2M⊙ stripped-envelope star and a rapidly rotating ~9.6M⊙ Be star. We compare with an extensive grid of evolutionary models using a Bayesian approach and constrain the initial masses of the progenitor to 7.2 ± 0.4M⊙ for the stripped star and 3.8 ± 0.4M⊙ for the Be star. The system must have evolved through near-conservative mass transfer. These findings are consistent with earlier studies. The age we obtain, 57 ± 9 Myr, is in excellent agreement with the age of the α Persei cluster. We note that neither star was initially massive enough to produce a core-collapse supernova, but mass exchange pushed the Be star above the mass threshold. We find that the subdwarf is overluminous for its mass by almost an order of magnitude, compared to the expectations for a helium core burning star. We can only reconcile this if the subdwarf resides in a late phase of helium shell burning, which lasts only 2–3% of the total lifetime as a subdwarf. Assuming continuous star formation implies that up to ~50 less evolved, dimmer subdwarfs exist for each system similar to φ Persei, but have evaded detection so far. Our findings can be interpreted as a strong indication that a substantial population of stripped-envelope stars indeed exists, but has so far evaded detection because of observational biases and lack of large-scale systematic searches. [ABSTRACT FROM AUTHOR]

Context. The majority of the Wolf-Rayet (WR) stars represent the stripped cores of evolved massive stars who lost most of their hydrogen envelope. Wind stripping in single stars is expected to be inefficient in producing WR stars in metal-poor environments such as the Small Magellanic Cloud (SMC). While binary interaction can also produce WR stars at low metallicity, it is puzzling that the fraction of WR binaries appears to be about 40%, independent of the metallicity. Aims. We aim to use the recently determined physical properties of the twelve known SMC WR stars to explore their possible formation channels through comparisons with stellar models. Methods. We used the MESA stellar evolution code to construct two grids of stellar models with SMC metallicity. One of these consists of models of rapidly rotating single stars, which evolve in part or completely chemically homogeneously. In a second grid, we analyzed core helium burning stellar models assuming constant hydrogen and helium gradients in their envelopes. Results. We find that chemically homogeneous evolution is not able to account for the majority of the WR stars in the SMC. However, in particular the apparently single WR star SMC AB12, and the double WR system SMC AB5 (HD 5980) appear consistent with this channel. We further find a dichotomy in the envelope hydrogen gradients required to explain the observed temperatures of the SMC WR stars. Shallow gradients are found for the WR stars with O star companions, while much steeper hydrogen gradients are required to understand the group of hot apparently single WR stars. Conclusions. The derived shallow hydrogen gradients in the WR component of the WR+O star binaries are consistent with predictions from binary models where mass transfer occurs early, in agreement with their binary properties. Since the hydrogen profiles in evolutionary models of massive stars become steeper with time after the main sequence, we conclude that most of the hot (Teff > 60 kK ) apparently single WR stars lost their envelope after a phase of strong expansion, e.g., as the result of common envelope evolution with a lower mass companion. The so far undetected companions, either main sequence stars or compact objects, are then expected to still be present. A corresponding search might identify the first immediate double black hole binary progenitor with masses as high as those detected in GW150914. [ABSTRACT FROM AUTHOR]

Most massive stars, the progenitors of core-collapse supernovae, are in close binary systems and may interact with their companion through mass transfer or merging. We undertake a population synthesis study to compute the delay-time distribution of core-collapse supernovae, that is, the supernova rate versus time following a starburst, taking into account binary interactions. We test the systematic robustness of our results by running various simulations to account for the uncertainties in our standard assumptions. We find that a significant fraction, 15+9-8%, of core-collapse supernovae are "late", that is, they occur 50-200 Myr after birth, when all massive single stars have already exploded. These late events originate predominantly from binary systems with at least one, or, in most cases, with both stars initially being of intermediate mass (4-8 M⊙). The main evolutionary channels that contribute often involve either the merging of the initially more massive primary star with its companion or the engulfment of the remaining core of the primary by the expanding secondary that has accreted mass at an earlier evolutionary stage. Also, the total number of core-collapse supernovae increases by 14+15-14% because of binarity for the same initial stellar mass. The high rate implies that we should have already observed such late core-collapse supernovae, but have not recognized them as such. We argue that φ Persei is a likely progenitor and that eccentric neutron star - white dwarf systems are likely descendants. Late events can help explain the discrepancy in the delay-time distributions derived from supernova remnants in the Magellanic Clouds and extragalactic type Ia events, lowering the contribution of prompt Ia events. We discuss ways to test these predictions and speculate on the implications for supernova feedback in simulations of galaxy evolution. [ABSTRACT FROM AUTHOR]

People with a Gly2019Ser mutation in the leucine-rich repeat kinase 2 (LRRK2 G2019S) are at increased risk of developing Parkinson's disease (PD). Recent evidence suggests that exercise may delay or prevent the development of clinically overt symptoms of PD in people at risk of PD. We determined whether LRRK2 G2019S mutation carriers with and without manifest PD are aware of the relationship between exercise and PD and how they differ in awareness, barriers and motivators to exercise. We deployed a survey among 4422 LRRK2 G2019S mutation carriers. In total, 505 (11.4%) of them completed the survey, of whom 105 had self-reported manifest PD. Ninety-two percent of the LRRK2 G2019S mutation carriers with manifest PD and 63% of those with non-manifest PD were aware of the relationship between exercise and PD. Lack of motivation was the top barrier for those without manifest PD, while having an injury/disability was the most common barrier for those with manifest PD. Improvement of body functioning was the top motivator for both. The fact that many at-risk individuals are not aware of the importance of exercise and would exercise more with fewer barriers creates opportunities for trials using exercise as a possible prevention strategy for PD. • One third of non-manifest LRRK2 G2019S mutation carriers was not aware that exercise might help to slow down PD development. • Many respondents experienced barriers for exercise and reported that they would exercise more when they have fewer barriers. • Top barriers were lack of motivation (mutation carriers without manifest PD) and disability (those with manifest PD). • Awareness of the benefits of exercise for PD prevention can be increased, particularly among non-manifest mutation carriers. • These results show opportunities for trials using exercise as a possible prevention strategy for PD. [ABSTRACT FROM AUTHOR]

People are known to be very poor at visually judging acceleration. Yet, they are extremely proficient at intercepting balls that fall under gravitational acceleration. How is this possible? We previously found that people make systematic errors when trying to tap on targets that move with different constant accelerations or decelerations on interleaved trials. Here, we show that providing contextual information that indicates how the target will decelerate on the next trial does not reduce such errors. Such errors do rapidly diminish if the same deceleration is present on successive trials. After observing several targets move with a particular acceleration or deceleration without attempting to tap on them, participants tapped as if they had never experienced the acceleration or deceleration. Thus, people presumably deal with acceleration when catching or hitting a ball by compensating for the errors that they made on preceding attempts. [ABSTRACT FROM AUTHOR]

The fluidity of the plasma membrane is thought to play a role in the activation of blood platelets. We investigated the lateral diffusion of the lipophilic probe 1.1'-ditetradecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiIC14) and derivatives in the plasma membrane of the megakaryoblast MEG-01 by fluorescence recovery after photobleaching. The lateral diffusion coefficient (D) of DiIC14 in an unstimulated cell was /3.53±0.06)×10-1 cm²/s with a mobile fraction of 75%. Similar data were found with DiIC12 and DiIC18, but lipophilic probes specific for the outer leaflet showed a slower diffusion with a D value of (2.99±0.31)×10-9 cm&usp2;/s and a mobile fraction of 58%. Stimulation with platelet-activating agents decreased the diffusion of DiIC14, within 2 min, but left the mobile fraction unchanged. Signal processing was required for the decrease in D as D-Phenylalanyl-L-prolyl-L-arginyl-chloromethane-treated thrombin, which binds normally to the thrombin receptor but fails to activate the cell, had no effect. The decrease in D was accompanied by an increase in cytosolic Ca2+ content. [Ca2+]i, and studies using different concentrations of thrombin, the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethylester and the Ca2+ ionophore ionomycin revealed that lipid mobilty in the plasma membrane is regulated by Ca2+. In contrast, treatment thought to interfere with the mobility of membrane proloins had little effect. We conclude that the rigidification of thc plasma membrane during cell activation is caused by an increase in [Ca2+]i and is therefore a late event and might only contribute to signal transduction at steps downstream of the mobilization/influx of Ca2+. [ABSTRACT FROM AUTHOR]

In the present study we measured membrane fluidity as the lateral mobility of the lipid probe 1,1′-ditetradecyl-3,3,3′,3′ -tetramethylindocarbocyanine perchlorate by fluorescence recovery after photobleaching in the plasma membrane of a single megakaryocyte, the progenitor cell of platelets. Megakaryocytes after 13 days in culture (maturation stage III) had a lateral diffusion coefficient (D) of (4.56 plusmn; 0.10) x 10-9 cm²/s and a mobile fraction of 65 ± 2% (means ± SEM, n = 140). Megakaryocytes isolated from rib had a similar D and mobile fraction. Stimulation with α-thrombin (1-10 U/ml) induced a dose-dependent decrease in D to (3.40 ± 0.22) x 10-9 cm2/s between 1-5 min after stimulation (P < 0.001). The mobile fraction did not change. A similar decrease in D was found following stimulation with ADP (20 µM) and ionomycin (100 nM). Modulation of calpain I activity with calpain I inhibitor or tetracain had no effect. Pretreatment with cytochalasin B or colchicine decreased D to (3.64 ± 0.29) x 10-9 cm2/s (P &ly; 0.003) and (3.96 &plusmn 0.18) x 10-9 cm2/s (P &ly; 0.013) respectively. After stimulation D decreased further in cytochalasin-treated cells (3.37 ± 0.16) x 10-9 cm2/s (P < 0.020) but remained at the same level in colchicine-treated cells. Both treatments increased the mobile fraction to 73-75% in stimulated megakaryocytes (P < 0.03). These data indicate that the diffusion velocity of lipids in megakaryocytes is low and decreases further after stimulation. These changes are independent of calpain I. Treatments that decrease the cytoskeletal mass and thereby increase the mobility of proteins in the plasma membrane increase the number of lipids that participate in this process. [ABSTRACT FROM AUTHOR]