Shape memory polymer foam: active deformation, simulation and validation of space environment

Shape memory polymer foam (SMPF) is being studied extensively as potential aerospace materials as they have high compression ratio, high specific strength and high specific modulus compared to other shape memory polymers. In this paper, a composite foam with shape memory epoxy (SMEP) as matrix and polyurethane (PU) as functional phase was prepared. The SMPF has been characterized by different analytical and testing methods, and its chemical crosslinking reaction and material properties have been studied. The SMPF was installed in the shape memory polymer composite (SMPC) flexible solar array system (SMPC-FSAS), and ground environment tests and orbital validation were performed. Considering the particularity of space environment, the thermal performance test of ground space environment can effectively test the reliability of shape memory performance. Finally, the SMPC-FSAS carried on SJ-20 satellite successfully deployed on geosynchronous orbit for the first time in the world. Moving forward, SMPF assesses the feasibility of applications in the space field and provides more valuable information.

Adaptive Playback Control: A Framework for Cinematic VR Creators to Embrace Viewer Interaction

Content creators have been trying to produce engaging and enjoyable Cinematic Virtual Reality (CVR) experiences using immersive media such as 360-degree videos. However, a complete and flexible framework, like the filmmaking grammar toolbox for film directors, is missing for creators working on CVR, especially those working on CVR storytelling with viewer interactions. Researchers and creators widely acknowledge that a viewer-centered story design and a viewer’s intention to interact are two intrinsic characteristics of CVR storytelling. In this paper, we stand on that common ground and propose Adaptive Playback Control (APC) as a set of guidelines to assist content creators in making design decisions about the story structure and viewer interaction implementation during production. Instead of looking at everything CVR covers, we set constraints to focus only at cultural heritage oriented content using a guided-tour style. We further choose two vital elements for interactive CVR: the narrative progression (director vs. viewer control) and visibility of viewer interaction (implicit vs. explicit) as the main topics at this stage. We conducted a user study to evaluate four variants by combining these two elements, and measured the levels of engagement, enjoyment, usability, and memory performance. One of our findings is that there were no differences in the objective results. Combining objective data with observations of the participants’ behavior we provide guidelines as a starting point for the application of the APC framework. Creators need to choose if the viewer will have control over narrative progression and the visibility of interaction based on whether the purpose of a piece is to invoke emotional resonance or promote efficient transfer of knowledge. Also, creators need to consider the viewer’s natural tendency to explore and provide extra incentives to invoke exploratory behaviors in viewers when adding interactive elements. We recommend more viewer control for projects aiming at viewer’s participation and agency, but more director control for projects focusing on education and training. Explicit (vs. implicit) control will also yield higher levels of engagement and enjoyment if the viewer’s uncertainty of interaction consequences can be relieved.

Using intracerebral microdialysis to probe the efficacy of repurposed drugs in Alzheimer′s disease pathology

All disease-targeting drug trials completed to date have fallen short of meeting the clinical endpoint of significantly slowing cognitive decline in Alzheimer′s disease patients. Even the recently approved drug Aducanumab, has proven effective in removing amyloid-β, but does not reduce cognitive decline. This emphasizes the urgent need for novel therapeutic approaches that could reduce several AD neuropathologies simultaneously, eventually leading to improved cognitive performance. To validate whether our mouse model replicates AD neuropathology as observed in patients, we characterized the 3xTg AD mouse model to avoid premature translation of successful results. In this study we have repurposed two FDA-approved drugs, Fasudil and Lonafarnib, targeting the Wnt signaling and endosomal-lysosomal pathway respectively, to test their potential to attenuate AD pathology. Using intracerebral microdialysis, we simultaneously infused these disease-targeting drugs between 1-2 weeks, separately and also in combination, while collecting cerebrospinal fluid. We found that Fasudil reduces intracellular amyloid-β in young, and amyloid plaques in old animals, and overall cerebrospinal fluid amyloid-β. Lonafarnib reduces tau neuropathology and cerebrospinal fluid tau biomarkers in young and old animals. Co-infusion of both drugs was more effective in reducing intracellular amyloid-β than either drug alone, and appeared to improve contextual memory performance. However, an unexpected finding was that Lonafarnib treatment increased amyloid plaque size, suggesting that activating the endosomal-lysosomal system may inadvertently increase amyloid-β pathology if administered too late in the AD continuum. Taken together, these findings lend support to the application of repurposed drugs to attenuate AD neuropathology at various therapeutic time windows.

Refined Analysis of Chronic White Matter Changes after Traumatic Brain Injury and Repeated Sports-Related Concussions: Of Use in Targeted Rehabilitative Approaches?

Traumatic brain injury (TBI) or repeated sport-related concussions (rSRC) may lead to long-term memory impairment. Diffusion tensor imaging (DTI) is helpful to reveal global white matter damage but may underestimate focal abnormalities. We investigated the distribution of post-injury regional white matter changes after TBI and rSRC. Six patients with moderate/severe TBI, and 12 athletes with rSRC were included ≥6 months post-injury, and 10 (age-matched) healthy controls (HC) were analyzed. The Repeatable Battery for the Assessment of Neuropsychological Status was performed at the time of DTI. Major white matter pathways were tracked using q-space diffeomorphic reconstruction and analyzed for global and regional changes with a controlled false discovery rate. TBI patients displayed multiple classic white matter injuries compared with HC (p < 0.01). At the regional white matter analysis, the left frontal aslant tract, anterior thalamic radiation, and the genu of the corpus callosum displayed focal changes in both groups compared with HC but with different trends. Both TBI and rSRC displayed worse memory performance compared with HC (p < 0.05). While global analysis of DTI-based parameters did not reveal common abnormalities in TBI and rSRC, abnormalities to the fronto-thalamic network were observed in both groups using regional analysis of the white matter pathways. These results may be valuable to tailor individualized rehabilitative approaches for post-injury cognitive impairment in both TBI and rSRC patients.

Disrupted Mitochondrial Network Drives Deficits of Learning and Memory in a Mouse Model of FOXP1 Haploinsufficiency

Reduced cognitive flexibility, characterized by restricted interests and repetitive behavior, is associated with atypical memory performance in autism spectrum disorder (ASD), suggesting hippocampal dysfunction. FOXP1 syndrome is a neurodevelopmental disorder characterized by ASD, language deficits, global developmental delay, and mild to moderate intellectual disability. Strongly reduced Foxp1 expression has been detected in the hippocampus of Foxp1+/− mice, a brain region required for learning and memory. To investigate learning and memory performance in these animals, fear conditioning tests were carried out, which showed impaired associative learning compared with wild type (WT) animals. To shed light on the underlying mechanism, we analyzed various components of the mitochondrial network in the hippocampus. Several proteins regulating mitochondrial biogenesis (e.g., Foxo1, Pgc-1α, Tfam) and dynamics (Mfn1, Opa1, Drp1 and Fis1) were significantly dysregulated, which may explain the increased mitophagy observed in the Foxp1+/− hippocampus. The reduced activity of complex I and decreased expression of Sod2 most likely increase the production of reactive oxygen species and the expression of the pre-apoptotic proteins Bcl-2 and Bax in this tissue. In conclusion, we provide evidence that a disrupted mitochondrial network and the resulting oxidative stress in the hippocampus contribute to the altered learning and cognitive impairment in Foxp1+/− mice, suggesting that similar alterations also play a major role in patients with FOXP1 syndrome.

You can’t “count” how many items people remember in working memory: The importance of signal detection-based measures for understanding change detection performance

Change detection tasks are commonly used to measure and understand the nature of visual working memory capacity. Across two experiments, we examine whether the nature of the latent memory signals used to perform change detection are continuous or all-or-none, and consider the implications for proper measurement of performance. In Experiment 1, we find evidence from confidence reports that visual working memory is continuous in strength, with strong support for equal variance signal detection models. We then tested a critical implication of this result without relying on model comparison or confidence reports in Experiment 2 by asking whether a simple instruction change would improve performance when measured with K, an all-or-none-measure, compared to d’, a measure based on continuous strength signals. We found strong evidence that K values increased by roughly 30% despite no change in the underlying memory signals. By contrast, we found that d’ is fixed across these same instructions, demonstrating that it correctly separates response criterion from memory performance. Overall, our data call into question a large body of work using threshold measures, like K, to analyze change detection data since this metric confounds response bias with memory performance in standard change detection tasks.

Modality Effects in Free Recall: A Retrieved-Context Account

The modality effect refers to the robust finding that memory performance differs for items presented aurally, as compared with visually. Whereas auditory presentation leads to stronger recency performance in immediate recall, visual presentation often produces better primacy performance (the inverse modality effect). To investigate and model these differences, we conducted two large-scale web-based immediate free recall experiments. In both experiments, participants studied visual and auditory word lists of varying lengths and rates of presentation. We observed typical modality and inverse modality effects, while also discovering that participants were more likely to initiate recall from recent items on auditory trials than on visual trials. However, modality effects persisted regardless of the first item recalled. Meanwhile, an analysis of intrusion errors revealed that participants were more likely on visual trials than on auditory trials to erroneously recall words from one list prior. Furthermore, words presented in the same modality as the present list intruded more often than those presented in a different modality. We next developed a retrieved-context account of the modality effect by fitting the Context Maintenance and Retrieval model to data across multiple list lengths. Through our simulations, we demonstrate that the modality effect can be explained by faster contextual drift and stronger context-to-item association formation during auditory presentation, relative to visual. Our modeling shows that modality effects can arise without hypothesizing distinct memory stores for recent and remote information. Finally, we propose that modality effects may derive primarily from the temporal dynamics of stimuli, rather than their modality.

Focal neural perturbations reshape low-dimensional trajectories of brain activity supporting cognitive performance

The emergence of distributed patterns of neural activity supporting brain functions and behavior can be understood by study of the brain’s low-dimensional topology. Functional neuroimaging demonstrates that brain activity linked to adaptive behavior is constrained to low-dimensional manifolds. In human participants, we tested whether these low-dimensional constraints preserve working memory performance following local neuronal perturbations. We combined multi-session functional magnetic resonance imaging, non-invasive transcranial magnetic stimulation (TMS), and methods translated from the fields of complex systems and computational biology to assess the functional link between changes in local neural activity and the reshaping of task-related low dimensional trajectories of brain activity. We show that specific reconfigurations of low-dimensional trajectories of brain activity sustain effective working memory performance following TMS manipulation of local activity on, but not off, the space traversed by these trajectories. We highlight an association between the multi-scale changes in brain activity underpinning cognitive function.