Phases of Mass Transfer from Hot Subdwarfs to White Dwarf Companions and Their Photometric Properties

Binary systems of a hot subdwarf B (sdB) star + a white dwarf (WD) with orbital periods less than 2–3 hr can come into contact due to gravitational waves and transfer mass from the sdB star to the WD before the sdB star ceases nuclear burning and contracts to become a WD. Motivated by the growing class of observed systems in this category, we study the phases of mass transfer in these systems. We find that because the residual outer hydrogen envelope accounts for a large fraction of an sdB star’s radius, sdB stars can spend a significant amount of time (∼tens of megayears) transferring this small amount of material at low rates (∼10−10–10−9 M ⊙ yr−1) before transitioning to a phase where the bulk of their He transfers at much faster rates ( ≳10−8 M ⊙ yr−1). These systems therefore spend a surprising amount of time with Roche-filling sdB donors at orbital periods longer than the range associated with He star models without an envelope. We predict that the envelope transfer phase should be detectable by searching for ellipsoidal modulation of Roche-filling objects with P orb = 30–100 minutes and T eff = 20,000–30,000 K, and that many (≥10) such systems may be found in the Galactic plane after accounting for reddening. We also argue that many of these systems may go through a phase of He transfer that matches the signatures of AM CVn systems, and that some AM CVn systems associated with young stellar populations likely descend from this channel.

Implicitly learning when to be ready: From instances to categories

There is growing appreciation for the role of long-term memory in guiding temporal preparation in speeded reaction time tasks. In experiments with variable foreperiods between a warning stimulus (S1) and a target stimulus (S2), preparation is affected by foreperiod distributions experienced in the past, long after the distribution has changed. These effects from memory can shape preparation largely implicitly, outside of participants’ awareness. Recent studies have demonstrated the associative nature of memory-guided preparation. When distinct S1s predict different foreperiods, they can trigger differential preparation accordingly. Here, we propose that memory-guided preparation allows for another key feature of learning: the ability to generalize across acquired associations and apply them to novel situations. Participants completed a variable foreperiod task where S1 was a unique image of either a face or a scene on each trial. Images of either category were paired with different distributions with predominantly shorter versus predominantly longer foreperiods. Participants displayed differential preparation to never-before seen images of either category, without being aware of the predictive nature of these categories. They continued doing so in a subsequent Transfer phase, after they had been informed that these contingencies no longer held. A novel rolling regression analysis revealed at a fine timescale how category-guided preparation gradually developed throughout the task, and that explicit information about these contingencies only briefly disrupted memory-guided preparation. These results offer new insights into temporal preparation as the product of a largely implicit process governed by associative learning from past experiences.

A New Foot Trajectory Planning Method for Legged Robots and Its Application in Hexapod Robots

Compared with wheeled and tracked robots, legged robots have better movement ability and are more suitable for the exploration of unknown environments. In order to further improve the adaptability of legged robots to complex terrains such as slopes, obstacle environments, and so on, this paper makes a new design of the legged robot’s foot sensing structure that can successfully provide accurate feedback of the landing information. Based on this information, a new foot trajectory planning method named three-element trajectory determination method is proposed. For each leg in one movement period, the three elements are the start point in the support phase, the end point in the support phase, and the joint angle changes in the transfer phase where the first two elements are used to control the height, distance, and direction of the movement, and the third element is used make decisions during the lifting process of the leg. For the support phase, the trajectory is described in Cartesian space, and a spline of linear function with parabolic blends is used. For the transfer phase, the trajectory is described in joint-space, and the joint angle function is designed as the superposition of the joint angle reverse-chronological function and the interpolation function which is obtained based on joint angle changes. As an important legged robot, a hexapod robot that we designed by ourselves with triangle gait is chosen to test the proposed foot trajectory planning method. Experiments show that, while the foot’s landing information can be read and based on the three-element trajectory planning method, the hexapod robot can achieve stable movement even in very complex scenes. Although the experiments are performed on a hexapod robot, our method is applicable to all forms of legged robots.

Cardiovascular, ophthalmologic and otolaryngologic medical device innovations – Progress report 2021 from the Twenty20 consortium RESPONSE

The coordinated research project “RESPONSE - Partnership for Innovation in Implant Technology”, which is one of ten BMBF-funded research consortia within the program “Twenty20 - Partnership for Innovation”, is active in the field of medical device innovation. The consortium is currently in the process of unfolding its transfer phase. This involves a portfolio of key innovations for novel medical devices, technologies and processes. Also, RESPONSE is aiming at participative technology development, integrating perspectives of patients, developers, as well as systems and innovation researchers. Particular challenges are arising from the current re-prioritization and re-scheduling of project roadmaps in order to manage and alleviate the effects of the corona crisis.

Effects of Visual and Auditory Feedback in Violin and Singing Voice Pitch Matching Tasks

Auditory-guided vocal learning is a mechanism that operates both in humans and other animal species making us capable to imitate arbitrary sounds. Both auditory memories and auditory feedback interact to guide vocal learning. This may explain why it is easier for humans to imitate the pitch of a human voice than the pitch of a synthesized sound. In this study, we compared the effects of two different feedback modalities in learning pitch-matching abilities using a synthesized pure tone in 47 participants with no prior music experience. Participants were divided into three groups: a feedback group (N = 15) receiving real-time visual feedback of their pitch as well as knowledge of results; an equal-timbre group (N = 17) receiving additional auditory feedback of the target note with a similar timbre to the instrument being used (i.e., violin or human voice); and a control group (N = 15) practicing without any feedback or knowledge of results. An additional fourth group of violin experts performed the same task for comparative purposes (N = 15). All groups were posteriorly evaluated in a transfer phase. Both experimental groups (i.e., the feedback and equal-timbre groups) improved their intonation abilities with the synthesized sound after receiving feedback. Participants from the equal-timber group seemed as capable as the feedback group of producing the required pitch with the voice after listening to the human voice, but not with the violin (although they also showed improvement). In addition, only participants receiving real-time visual feedback learned and retained in the transfer phase the mapping between the synthesized pitch and its correspondence with the produced vocal or violin pitch. It is suggested that both the effect of an objective external reward, together with the experience of exploring the pitch space with their instrument in an explicit manner, helped participants to understand how to control their pitch production, strengthening their schemas, and favoring retention.

Plantar load transfer in children: a descriptive study with two pathological case studies

Background Typical gait is often considered to be highly symmetrical, with gait asymmetries typically associated with pathological gait. Whilst gait symmetry is often expressed in symmetry ratios, measures of symmetry do not provide insight into how these asymmetries affect gait variables. To fully understand changes caused by gait asymmetry, we must first develop a normative database for comparison. Therefore, the aim of this study was to describe normative reference values of regional plantar load and present comparisons with two pathological case studies. Methods A descriptive study of the load transfer of plantar pressures in typically developed children was conducted to develop a baseline for comparison of the effects of gait asymmetry in paediatric clinical populations. Plantar load and 3D kinematic data was collected for 17 typically developed participants with a mean age of 9.4 ± 4.0 years. Two case studies were also included; a 10-year-old male with clubfoot and an 8-year-old female with a flatfoot deformity. Data was analysed using a kinematics-pressure integration technique for anatomical masking into 5 regions of interest; medial and lateral forefoot, midfoot, and medial and lateral hindfoot. Results Clear differences between the two case studies and the typical dataset were seen for the load transfer phase of gait. For case study one, lateral bias was seen in the forefoot of the trailing foot across all variables, as well as increases in contact area, force and mean pressure in the lateral hindfoot of the leading foot. For case study two, the forefoot of the trailing foot produced results very similar to the typical dataset across all variables. In the hindfoot of the leading foot, medial bias presents most notably in the force and mean pressure graphs. Conclusions This study highlights the clinical significance of the load transfer phase of gait, providing meaningful information for intervention planning.

Context-dependent reinforcement learning impairment in depression

Backgrounds:Value-based decision-making impairment in depression is a complex phenomenon: while some studies did find evidence of blunted reward learning and reward-related signals in the brain, others indicate no effect. Here we test whether such reward sensitivity deficits are dependent on the overall value of the decision problem.Methods:We used a two-armed bandit task that includes two different contexts: one ‘rich’ context where both options were associated with an overall positive expected value and a ‘poor’ context where options were associated with overall negative expected value. We tested patients (N=30) undergoing a major depressive episode and age, gender and socio-economically matched controls (N=26). To assess whether differences in learning performance were due to a decision or a value-update process, we also analysed performance in a transfer phase, performed immediately after the learning phase. ResultsHealthy subjects showed similar learning performance in the ‘rich’ and the ‘poor’ contexts, while patients showed reduced learning in the ‘poor’ context. Analysis of the transfer phase showed that the context-dependent deficit in patients generalized when options were extrapolated from their original learning context, thus suggesting that the effect of depression has to be traced to the outcome encoding, rather than the decision phase.ConclusionsOur results illustrate that reinforcement learning deficits in depression are complex and depend on the value of the context. We show that depressive patients have a specific trouble in contexts with an overall negative state value, supporting the relevance of setting up patients in a spiral of positive reinforcement.

Numerical Modeling of the Spread of Cough Saliva Droplets in a Calm Confined Space

The coronavirus disease 2019 (COVID-19) outbreak has altered the lives of everyone on a global scale due to its high transmission rate. In the current work, the droplet dispersion and evaporation originated by a cough at different velocities is studied. A multiphase computational fluid dynamic model based on fully coupled Eulerian–Lagrangian techniques was used. The evaporation, breakup, mass transfer, phase change, and turbulent dispersion forces of droplets were taken into account. A computational domain imitating an elevator that with two individuals inside was modeled. The results showed that all droplets smaller than 150 μm evaporate before 10 s at different heights. Smaller droplets of <30 µm evaporate quickly, and their trajectories are governed by Brownian movements. Instead, the trajectories of medium-sized droplets (30–80 µm) are under the influence of inertial forces, while bigger droplets move according to inertial and gravitational forces. Smaller droplets are located in the top positions, while larger (i.e., heaviest) droplets are located at the bottom.

Implicitly learning when to be ready: from instances to categories

[Manuscript submitted for review]There is growing appreciation for the role of long-term memory in guiding temporal preparation. In experiments with variable foreperiods between a warning stimulus (S1) and a target stimulus (S2), preparation is affected by foreperiod distributions experienced in the past, long after the distribution has changed. Such memory-guided preparation shapes preparation largely implicitly and outside of a participants’ control. Recent studies have demonstrated the associative nature of such memory-guided preparation. When distinct S1s predict different foreperiods, they can trigger dissociative preparation accordingly. Here, we demonstrate that memory-guided preparation allows for another key feature of learning: the ability to generalize across acquired associations and apply them to novel situations. Participants completed a foreperiod task where S1 was a unique image of either a face or a scene on each trial. Images of either category were paired with different distributions with predominantly shorter versus predominantly longer foreperiods. Participants displayed dissociative preparation to never-before seen images of either category, without being aware of the predictive nature of these categories. They continued doing so in a subsequent transfer phase, after they had been informed that these contingencies no longer held. A novel rolling regression analysis revealed at a fine timescale how category-guided preparation gradually developed throughout the task, and illustrated how instructions at the start of the transfer phase interacted with these influences from long-term memory. These results offer new insights into temporal preparation as the product of a largely implicit process governed by associative learning from past experiences.