Strong affinity of polysulfide intermediates to multi-functional binder for practical application in lithium-sulfur batteries

Binder, one of the most important battery components, plays a critical role in lithium-sulfur batteries. Poly(vinylidene difluoride) (PVDF), a commonly used binder in lithium-sulfur batteries, does not have a strong affinity to the intermediate polysulfides, however, leading to fast capacity fading with electrochemical cycling. Herein, copolymers of vinylidene difluoride with other monomers are used as multi-functional binders to enhance the electrochemical performance of lithium-sulfur batteries. Compared to the PVDF, the copolymer, poly(vinylidene difluoride-trifluoroethylene) (P(VDF-TRFE)) binder exhibits higher adhesion strength, less porosity, and stronger chemical interaction with polysulfides, which helps to keep the polysulfides within the cathode region, thereby improving the electrochemical performance of the lithium-sulfur battery. As a result, sulfur electrode with P(VDF-TRFE) binder delivered a high capacity of 801 mA h g-1 at 0.2 C after 100 cycles, which is nearly 80% higher capacity than the corresponding sulfur cathode with PVDF binder

The Structural, Electronic, and Optical Properties of Ge/Si Quantum Wells: Lasing at a Wavelength of 1550 nm

The realization of a fully integrated group IV electrically driven laser at room temperature is an essential issue to be solved. We introduced a novel group IV side-emitting laser at a wavelength of 1550 nm based on a 3-layer Ge/Si quantum well (QW). By designing this scheme, we showed that the structural, electronic, and optical properties are excited for lasing at 1550 nm. The preliminary results show that the device can produce a good light spot shape convenient for direct coupling with the waveguide and single-mode light emission. The laser luminous power can reach up to 2.32 mW at a wavelength of 1550 nm with a 300-mA current. Moreover, at room temperature (300 K), the laser can maintain maximum light power and an ideal wavelength (1550 nm). Thus, this study provides a novel approach to reliable, efficient electrically pumped silicon-based lasers

Eye movement characteristics in a mental rotation task presented in virtual reality

IntroductionEye-tracking technology provides a reliable and cost-effective approach to characterize mental representation according to specific patterns. Mental rotation tasks, referring to the mental representation and transformation of visual information, have been widely used to examine visuospatial ability. In these tasks, participants visually perceive three-dimensional (3D) objects and mentally rotate them until they identify whether the paired objects are identical or mirrored. In most studies, 3D objects are presented using two-dimensional (2D) images on a computer screen. Currently, visual neuroscience tends to investigate visual behavior responding to naturalistic stimuli rather than image stimuli. Virtual reality (VR) is an emerging technology used to provide naturalistic stimuli, allowing the investigation of behavioral features in an immersive environment similar to the real world. However, mental rotation tasks using 3D objects in immersive VR have been rarely reported.MethodsHere, we designed a VR mental rotation task using 3D stimuli presented in a head-mounted display (HMD). An eye tracker incorporated into the HMD was used to examine eye movement characteristics during the task synchronically. The stimuli were virtual paired objects oriented at specific angular disparities (0, 60, 120, and 180°). We recruited thirty-three participants who were required to determine whether the paired 3D objects were identical or mirrored.ResultsBehavioral results demonstrated that the response times when comparing mirrored objects were longer than identical objects. Eye-movement results showed that the percent fixation time, the number of within-object fixations, and the number of saccades for the mirrored objects were significantly lower than that for the identical objects, providing further explanations for the behavioral results.DiscussionIn the present work, we examined behavioral and eye movement characteristics during a VR mental rotation task using 3D stimuli. Significant differences were observed in response times and eye movement metrics between identical and mirrored objects. The eye movement data provided further explanation for the behavioral results in the VR mental rotation task

Experimental evidence to understand mechanical causes of retinal detachment following blunt trauma.

PURPOSE: This study aimed to perform an in vitro experiment to simulate retinal detachment caused by blunt impact, and provide experimental evidence to understand mechanical causes of traumatic retinal detachment. METHODS: The experiment was conducted on twenty-two fresh porcine eyes using a bespoke pendulum testing device at two energy levels (0.1J for low energy and 1.0J for high energy). We examined dynamic forces and mechanical responses to the impact, including global deformations, intraocular pressure changes and the energy absorption. Another set of twenty-two eyes underwent pathological examination immediately after being subjected to blunt impact. Twelve additional intact eyes were examined as controls. All pathological sections were scored to indicate whether retinal detachment had occurred. RESULTS: A dynamic variation in intraocular pressure was detected following impact and exhibited an approximate sinusoidal oscillation-attenuation profile. The peaks of impact force were 12.9 ± 1.9 N at low-energy level and 34.8 ± 9.8 N at high-energy level, showing a significant difference (p < 0.001). The positive and negative peaks of intraocular pressure were 149.4 ± 18.9 kPa and -10.9 ± 7.2 kPa at low-energy level, and 274.5 ± 55.2 kPa and -35.7 ± 23.7 kPa at high-energy level, showing significant differences (p < 0.001 for both levels). Retinal detachments were observed in damaged eyes while few detachments were found in control eyes. The occurrence rate of retinal detachment differed significantly (p < 0.05) between the high- and low-energy impact groups. CONCLUSIONS: This study provided experimental evidence that shockwaves produced by blunt trauma break the force equilibrium and lead to the oscillation and negative pressure, which mainly contribute to traumatic retinal detachment