Creating pairs of exceptional points for arbitrary polarization control: asymmetric vectorial wavefront modulation.

Exceptional points (EPs) can achieve intriguing asymmetric control in non-Hermitian systems due to the degeneracy of eigenstates. Here, we present a general method that extends this specific asymmetric response of EP photonic systems to address any arbitrary fully-polarized light. By rotating the meta-structures at EP, Pancharatnam-Berry (PB) phase can be exclusively encoded on one of the circular polarization-conversion channels. To address any arbitrary wavefront, we superpose the optical signals originating from two orthogonally polarized -yet degenerate- EP eigenmodes. The construction of such orthogonal EP eigenstates pairs is achieved by applying mirror-symmetry to the nanostructure geometry flipping thereby the EP eigenmode handedness from left to right circular polarization. Non-Hermitian reflective PB metasurfaces designed using such EP superposition enable arbitrary, yet unidirectional, vectorial wavefront shaping devices. Our results open new avenues for topological wave control and illustrate the capabilities of topological photonics to distinctively operate on arbitrary polarization-state with enhanced performances.

Asymmetric Full-Color Vectorial Meta-holograms Empowered by Pairs of Exceptional Points.

Holography holds tremendous promise in applications such as immersive virtual reality and optical communications. With the emergence of optical metasurfaces, planar optical components that have the remarkable ability to precisely manipulate the amplitude, phase, and polarization of light on the subwavelength scale have expanded the potential applications of holography. However, the realization of metasurface-based full-color vectorial holography remains particularly challenging. Here, we report a general approach utilizing a modified Gerchberg-Saxton algorithm to achieve spatially aligned full-color display and incorporating wavelength information with an image compensation strategy. We combine the Pancharatnam-Berry phase and pairs of exceptional points to address the issue of redundant twin images that generally appear for the two orthogonal circular polarizations and to enable full polarization control of the vectorial field. Our results enable the realization of an asymmetric full-color vectorial meta-hologram, paving the way for the development of full-color display, complex beam generation, and secure data storage applications.

Free-Standing Stable Silicon-Based Anode with Exceptional Flexibility Realized by a Multifunctional Structure Design in Multiple Dimensions.

Cyclized polyacrylonitrile (cPAN) with decently flexible, elastic, and conductive properties is a promising substrate or binder material for flexible devices. However, it is infeasible to accommodate the large volume expansion and contribute the exceptional rate capability of silicon anodes in lithium-ion batteries only counting on the limited elasticity and conductivity of cPAN. Herein, we report a robust silicon/carbon-cPAN-graphene (SC-CP-G) composite membrane with excellent flexibility based on a multifunctional structure design in multiple dimensions, which can be used as a free-standing integrated anode for lithium ion batteries. In this integrated electrode, silicon nanoparticles are encapsulated in porous carbon with in situ formed confined space, and the silicon/carbon particles are further embedded in cPAN nanofibers, which are inextricably interwoven with a reduced graphene oxide film, forming an interpenetrating network architecture. The unique hierarchical and functional structure design greatly improves the mechanical performance, cycling stability, and capacity accessibility of silicon electrodes, delivering a specific capacity of 1847 mA h g-1 at 2 A g-1 and a capacity retention of 87% after 150 cycles.

Commercially Viable Hybrid Li-Ion/Metal Batteries with High Energy Density Realized by Symbiotic Anode and Prelithiated Cathode.

The energy density of commercial lithium (Li) ion batteries with graphite anode is reaching the limit. It is believed that directly utilizing Li metal as anode without a host could enhance the battery's energy density to the maximum extent. However, the poor reversibility and infinite volume change of Li metal hinder the realistic implementation of Li metal in battery community. Herein, a commercially viable hybrid Li-ion/metal battery is realized by a coordinated strategy of symbiotic anode and prelithiated cathode. To be specific, a scalable template-removal method is developed to fabricate the porous graphite layer (PGL), which acts as a symbiotic host for Li ion intercalation and subsequent Li metal deposition due to the enhanced lithiophilicity and sufficient ion-conducting pathways. A continuous dissolution-deintercalation mechanism during delithiation process further ensures the elimination of dead Li. As a result, when the excess plating Li reaches 30%, the PGL could deliver an ultrahigh average Coulombic efficiency of 99.5% for 180 cycles with a capacity of 2.48 mAh cm-2 in traditional carbonate electrolyte. Meanwhile, an air-stable recrystallized lithium oxalate with high specific capacity (514.3 mAh g-1) and moderate operating potential (4.7-5.0 V) is introduced as a sacrificial cathode to compensate the initial loss and provide Li source for subsequent cycles. Based on the prelithiated cathode and initial Li-free symbiotic anode, under a practical-level 3 mAh capacity, the assembled hybrid Li-ion/metal full cell with a P/N ratio (capacity ratio of LiNi0.8Co0.1Mn0.1O2 to graphite) of 1.3 exhibits significantly improved capacity retention after 300 cycles, indicating its great potential for high-energy-density Li batteries.

Gradient Structure Design of a Floatable Host for Preferential Lithium Deposition.

Herein, a novel sandwichlike host with expandable accommodation and gradient characteristics of lithiophilicity and conductivity is prepared by constructing a reduced graphene oxide (rGO)/SiO2/rGO intercalated structure on the basis of electrospraying and coating an additional PVDF-HFP layer on the top surface. This gradient host electrode enables preferential, ordered, and uniform Li deposition in the SiO2-embedded interlayer space. The dendrite growth and isolated Li are suppressed by the combined rGO/PVDF-HFP layer with robust, flexible, and floatable features, which could function as an artificial solid-electrolyte interphase to impede reckless electrolyte infiltration, homogenize the Li ion flux distribution, and build a stable electrochemical interface. The designed electrodes could be stably cycled with a high capacity of 5 mAh cm-2 and give rise to a high average Coulombic efficiency (CE) of 99.14%. Furthermore, the derived full cells can deliver an average CE of 99.87% in 300 cycles with a capacity retention of 90.22% and successfully operate under lean electrolyte conditions.

Improving pretend play for children with autism through experiencing the stimulus properties of real objects.

Children with autism spectrum disorder (ASD) often lack symbolic play skills. Attribution of pretend properties (APP) is a type of symbolic play in which a child tacts pretend properties of an object (e.g., smelling a toy flower and saying, "It smells like a rose!"). Three Chinese boys (5-6 years of age) with ASD served as participants. A multiple-probe design across 5 objects was used to determine the effects of an intervention that involved having the child experience and tact sensory properties of real objects (e.g., rose). Corresponding test objects, including mock (e.g., a toy flower) and arbitrary objects (e.g., a stick), were used to evaluate whether tact responses for sensory properties were transferred. Results indicated that all 3 children emitted tacts of stimulus properties for test objects and maintained the skill for 7 to 10 weeks following the intervention. Two participants also tacted novel (nontarget) properties for test objects.

Increased recruitment of endogenous stem cells and chondrogenic differentiation by a composite scaffold containing bone marrow homing peptide for cartilage regeneration.

Even small cartilage defects could finally degenerate to osteoarthritis if left untreated, owing to the poor self-healing ability of articular cartilage. Stem cell transplantation has been well implemented as a common approach in cartilage tissue engineering but has technical complexity and safety concerns. The stem cell homing-based technique emerged as an alternative promising therapy for cartilage repair to overcome traditional limitations. In this study, we constructed a composite hydrogel scaffold by combining an oriented acellular cartilage matrix (ACM) with a bone marrow homing peptide (BMHP)-functionalized self-assembling peptide (SAP). We hypothesized that increased recruitment of endogenous stem cells by the composite scaffold could enhance cartilage regeneration. Methods: To test our hypothesis, in vitro proliferation, attachment and chondrogenic differentiation of rabbit mesenchymal stem cells (MSCs) were tested to confirm the bioactivities of the functionalized peptide hydrogel. The composite scaffold was then implanted into full-thickness cartilage defects on rabbit knee joints for cartilage repair, in comparison with microfracture or other sample groups. Stem cell recruitment was monitored by dual labeling with CD29 and CD90 under confocal microcopy at 1 week after implantation, followed by chondrogenic differentiation examined by qRT-PCR. Repaired tissue of the cartilage defects was evaluated by histological and immunohistochemistry staining, microcomputed tomography (micro-CT) and magnetic resonance imaging (MRI) at 3 and 6 months post-surgery. Macroscopic and histological scoring was done to evaluate the optimal in vivo repair outcomes of this composite scaffold. Results: The functionalized SAP hydrogels could stimulate rabbit MSC proliferation, attachment and chondrogenic differentiation during in vitro culture. At 7 days after implantation, increased recruitment of MSCs based on CD29+ /CD90+ double-positive cells was found in vivo in the composite hydrogel scaffold, as well as upregulation of cartilage-associated genes (aggrecan, Sox9 and type II collagen). After 3 and 6 months post-surgery, the articular cartilage defect in the composite scaffold-treated group was fully covered with cartilage-like tissue with a smooth surface, which was similar to the surrounding native cartilage, according to the results of histological and immunohistochemistry staining, micro-CT and MRI analysis. Macroscopic and histological scoring confirmed that the quality of cartilage repair was significantly improved with implantation of the composite scaffold at each timepoint, in comparison with microfracture or other sample groups. Conclusion: Our findings demonstrated that the composite scaffold could enhance endogenous stem cell homing and chondrogenic differentiation and significantly improve the therapeutic outcome of chondral defects. The present study provides a promising approach for in vivo cartilage repair without cell transplantation. Optimization of this strategy may offer great potential and benefits for clinical application in the future.

[Brain-derived neurotrophic factor and neural stem cells transplantation in treatment of hypoxic-ischemic brain injury in rats].

OBJECTIVE: To investigate the effects of brain-derived neurotrophic factor (BDNF) on survival, migration and differentiation of neural stem cells (NSCs) transplanted into the brain of newborn rats with hypoxic-ischemic brain damage and the recovery of nervous functions. METHODS: The NSCs were separated from hippocampus of neonatal Wistar rats within 24 h after birth. Brdu, NSE and GFAP were used as markers of differentiation and proliferation of NSCs. The newborn rats were subjected to hypoxic-ischemic condition to induce brain damage. Seven days later, NSCs transplantation was performed for the animals. The rats were divided into normal control group, HIBD group, PBS group, NSCs transplantation group, BDNF group and BDNF + NSCs transplantation group randomly. At 4 weeks after transplantation the nervous function of rats was observed by Y-maze and nerve behavior test. After they were sacrificed, the rat brains were examined by immunocytochemistry for Brdu and by immunofluorescence for NSE/Brdu. RESULTS: The hippocampus NSCs of newborn rat could be well cultured and they expressed nestin and they could differentiate into NSE, GFAP. Most of NSCs survived in cerebral ventricle 4 weeks after transplantation in brain through Brdu immunocytochemistry and they migrated into regions of brain extensively, especially to the injured side of cortex and hippocampus. The number of living NSCs in the injured side of cortex and hippocampus of BDNF + NSCs transplantation group increased evidently and the percentage of NSCs differentiated into NSE was higher than that in the NSCs transplantation group (P < 0.05). The nerve function recovery of the rats in BDNF and NSCs treated group was significantly better than that in the other groups (P < 0.05). The NSCs group had no prominent changes as compared with the model groups (P > 0.05). CONCLUSIONS: NSCs can be isolated from newborn rats hippocampus and cultured in vivo. NSCs can survive, migrate and differentiate into neurons through cerebral ventricle. BDNF could significantly accelerate proliferation and differentiation of NSCs transplanted into the brain of rats with HIBD. The nervous function recovery was improved prominently by transplantation of NSCs with BDNF application, which may become a potentially effective method to treat HIBD.

[Combined transplantation of neurotrophin-3 and neural stem cells in treatment of hypoxic-ischemic brain injury in rats].

OBJECTIVE: To evaluate the efficacy of combined transplantation of neurotrophin-3 and neural stem cells in treatment of hypoxic-ischemic brain injury in rats, and study the possible mechanism. METHODS: Neural stem cells (NSCs) isolated from hippocampi of newborn wistar rats were cultured and identified. The hypoxic-ischemic brain injury models established with 7-day-old wistar rats, and neural stem cells or others were transplantated into the ipsilateral ventricles 7 days later. The 7-day-old rats were randomized into 5 groups: normal group, model group, sham-transplantation group, NSCs transplantation group, and NT-3 combined with NSCs transplantation group. There were 12 rats per group. The functional test and immunohistochemistry were examined 4 weeks later. RESULTS: The neural stem cells from new-born rats' hippocampi were successfully cultured. It was found that they formed typical neurospheres in suspension, and the majorities of cells expressed nestin, which was the marker for neural stem cells. The rats from combined transplantation group performed significantly better in the ability to study and in memory and the limb function than the rats from NSCs transplantation group (P < 0.05). The rate of neural stem cells differentiating into neurons from combined transplantation group was higher, too (50% vs. 30%). CONCLUSION: Combined NT-3 and NSCs transplantation could improve the ability to study, memory and the limb function of rats after hypoxic-ischemic brain injury, and improve the rate of NSCs differentiating neurons. Combined NT-3 and NSCs transplantation had better effects on hypoxic-ischemic rats than transplantation of NSCs alone.