The geometry of the vergence-accommodation conflict in mixed reality systems.

Mixed reality technologies, such as virtual (VR) and augmented (AR) reality, present promising opportunities to advance education and professional training due to their adaptability to diverse contexts. Distortions in the perceived distance in such mediated conditions, however, are well documented and have imposed nontrivial challenges that complicate and limit transferring task performance in a virtual setting to the unmediated reality (UR). One potential source of the distance distortion is the vergence-accommodation conflict-the discrepancy between the depth specified by the eyes' accommodative state and the angle at which the eyes converge to fixate on a target. The present study involved the use of a manual pointing task in UR, VR, and AR to quantify the magnitude of the potential depth distortion in each modality. Conceptualizing the effect of vergence-accommodation offset as a constant offset to the vergence angle, a model was developed based on the stereoscopic viewing geometry. Different versions of the model were used to fit and predict the behavioral data for all modalities. Results confirmed the validity of the conceptualization of vergence-accommodation as a device-specific vergence offset, which predicted up to 66% of the variance in the data. The fitted parameters indicate that, due to the vergence-accommodation conflict, participants' vergence angle was driven outwards by approximately 0.2°, which disrupted the stereoscopic viewing geometry and produced distance distortion in VR and AR. The implications of this finding are discussed in the context of developing virtual environments that minimize the effect of depth distortion.

Prolonged exposure to mixed reality alters task performance in the unmediated environment.

The popularity of mixed reality (MR) technologies, including virtual (VR) and augmented (AR) reality, have advanced many training and skill development applications. If successful, these technologies could be valuable for high-impact professional training, like medical operations or sports, where the physical resources could be limited or inaccessible. Despite MR's potential, it is still unclear whether repeatedly performing a task in MR would affect performance in the same or related tasks in the physical environment. To investigate this issue, participants executed a series of visually-guided manual pointing movements in the physical world before and after spending one hour in VR or AR performing similar movements. Results showed that, due to the MR headsets' intrinsic perceptual geometry, movements executed in VR were shorter and movements executed in AR were longer than the veridical Euclidean distance. Crucially, the sensorimotor bias in MR conditions also manifested in the subsequent post-test pointing task; participants transferring from VR initially undershoot whereas those from AR overshoot the target in the physical environment. These findings call for careful consideration of MR-based training because the exposure to MR may perturb the sensorimotor processes in the physical environment and negatively impact performance accuracy and transfer of training from MR to UR.

Scaffold Infiltrated Cathodes for Low-Temperature Solid Oxide Fuel Cells.

Lowering the operating temperature of solid oxide fuel cells (SOFCs) and electrolysis cells (SOECs) to reduce system cost and increase lifetime is the key to widely deploy this highly efficient energy technology, but the high cathode polarization losses at low temperatures limit overall cell performance. Here we demonstrate that by engineering a universal ceria-based scaffold with infiltrated nanoscale electrocatalysts, a low cathode polarization <0.25 Ω·cm2 with remarkably high performance 1 W/cm2 at 550 °C is achieved. The combination of low processing and operating temperature restrains the nanosized electrocatalysts, not only allowing fast oxygen transport but also providing an essential electronically connective network to facilitate electrochemical reactions without requiring the high-temperature processing of a separate cathode layer. Moreover, excellent SOFC durability was demonstrated for over 500 h. This work shows a promising pathway to reduce processing/system costs with all scalable ceramic processing techniques for the future development of low-temperature SOFCs and SOECs.

Strain Heterogeneity and Extended Defects in Halide Perovskite Devices.

Strain is an important property in halide perovskite semiconductors used for optoelectronic applications because of its ability to influence device efficiency and stability. However, descriptions of strain in these materials are generally limited to bulk averages of bare films, which miss important property-determining heterogeneities that occur on the nanoscale and at interfaces in multilayer device stacks. Here, we present three-dimensional nanoscale strain mapping using Bragg coherent diffraction imaging of individual grains in Cs0.1FA0.9Pb(I0.95Br0.05)3 and Cs0.15FA0.85SnI3 (FA = formamidinium) halide perovskite absorbers buried in full solar cell devices. We discover large local strains and striking intragrain and grain-to-grain strain heterogeneity, identifying distinct islands of tensile and compressive strain inside grains. Additionally, we directly image dislocations with surprising regularity in Cs0.15FA0.85SnI3 grains and find evidence for dislocation-induced antiphase boundary formation. Our results shine a rare light on the nanoscale strains in these materials in their technologically relevant device setting.

Long-term teduglutide associated with improved response in pediatric short bowel syndrome-associated intestinal failure.

OBJECTIVES: Patients with short bowel syndrome-associated intestinal failure (SBS-IF) require long-term parenteral nutrition and/or intravenous fluids (PN/IV) to maintain fluid or nutritional balance. We report the long-term safety, efficacy, and predictors of response in pediatric patients with SBS-IF receiving teduglutide over 96 weeks. METHODS: This was a pooled, post hoc analysis of two open-label, long-term extension (LTE) studies (NCT02949362 and NCT02954458) in children with SBS-IF. Endpoints included treatment-emergent adverse events (TEAEs) and clinical response (≥20% reduction in PN/IV volume from baseline). A multivariable linear regression identified predictors of teduglutide response; the dependent variable was mean change in PN/IV volume at each visit over 96 weeks. RESULTS: Overall, 85 patients were analyzed; 78 patients received teduglutide in the parent and/or LTE studies (any teduglutide [TED] group), while seven patients did not receive teduglutide in either the parent or LTE studies. Most TEAEs were moderate or severe in intensity in both groups. By week 96, 82.1% of patients from the any TED group achieved a clinical response, with a mean fluid decrease of 30.1 mL/kg/day and an energy decrease of 21.6 kcal/kg/day. Colon-in-continuity, non-White race, older age at baseline, longer duration of teduglutide exposure, and increasing length of remaining small intestine were significantly associated with a reduction in mean PN/IV volume requirements. CONCLUSIONS: In pediatric patients with SBS-IF, teduglutide treatment resulted in long-term reductions in PN/IV requirements. The degree of PN/IV volume reduction depended on the duration of teduglutide exposure, underlying bowel anatomy, and demographics.

Resolving length-scale-dependent transient disorder through an ultrafast phase transition.

Material functionality can be strongly determined by structure extending only over nanoscale distances. The pair distribution function presents an opportunity for structural studies beyond idealized crystal models and to investigate structure over varying length scales. Applying this method with ultrafast time resolution has the potential to similarly disrupt the study of structural dynamics and phase transitions. Here we demonstrate such a measurement of CuIr2S4 optically pumped from its low-temperature Ir-dimerized phase. Dimers are optically suppressed without spatial correlation, generating a structure whose level of disorder strongly depends on the length scale. The redevelopment of structural ordering over tens of picoseconds is directly tracked over both space and time as a transient state is approached. This measurement demonstrates the crucial role of local structure and disorder in non-equilibrium processes as well as the feasibility of accessing this information with state-of-the-art XFEL facilities.

Teduglutide improves liver chemistries in short bowel syndrome-associated intestinal failure: Post hoc analysis.

BACKGROUND: Chronic hepatic complications are common in patients with short bowel syndrome-associated intestinal failure (SBS-IF). Teduglutide, a glucagon-like peptide-2 analogue, demonstrated efficacy in reducing parenteral nutrition and/or intravenous fluid dependence among patients with SBS-IF in phase 3 clinical studies. METHODS: This was a post hoc analysis of pooled data from two separate randomized, double-blind, placebo-controlled, multinational phase 3 clinical studies. Adult patients with SBS-IF with parenteral nutrition and/or intravenous fluid dependence without liver disease at baseline were randomized to treatment with the glucagon-like peptide-2 analogue teduglutide (0.05 or 0.10 mg/kg/day) or placebo subcutaneously once daily for 24 weeks. Mixed-effects models assessed the baseline predictors of change in liver chemistries. RESULTS: Between baseline and week 24, teduglutide treatment (n = 109) was associated with least squares mean reductions in aspartate aminotransferase (-7.51 IU/L; P = 0.014), alanine aminotransferase (-12.15 IU/L; P = 0.002), and bilirubin (-5.03 µmol/L [-0.057 mg/dl]; P < 0.001) compared with that of the placebo (n = 59). These values were independent of reductions in parenteral nutrition and/or intravenous fluid dependence. CONCLUSION: Teduglutide treatment was associated with reductions in liver chemistries by week 24, which is beneficial for patients with SBS-IF beyond improvements in parenteral nutrition and/or intravenous fluid dependence. Future studies should examine how long-term teduglutide might mitigate the risk of liver disease in patients with SBS-IF.

Emergence of liquid following laser melting of gold thin films.

X-ray structural science is undergoing a revolution driven by the emergence of X-ray Free-electron Laser (XFEL) facilities. The structures of crystalline solids can now be studied on the picosecond time scale relevant to phonons, atomic vibrations which travel at acoustic velocities. In the work presented here, X-ray diffuse scattering is employed to characterize the time dependence of the liquid phase emerging from femtosecond laser-induced melting of polycrystalline gold thin films using an XFEL. In a previous analysis of Bragg peak profiles, we showed the supersonic disappearance of the solid phase and presented a model of pumped hot electrons carrying energy from the gold surface to scatter at internal grain boundaries. This generates melt fronts propagating relatively slowly into the crystal grains. By conversion of diffuse scattering to a partial X-ray pair distribution function, we demonstrate that it has the characteristic shape obtained by Fourier transformation of the measured F(Q). The diffuse signal fraction increases with a characteristic rise-time of 13 ps, roughly independent of the incident pump fluence and consequent final liquid fraction. This suggests the role of further melt-front nucleation processes beyond grain boundaries.