Twisted van der Waals Quantum Materials: Fundamentals, Tunability, and Applications.

Twisted van der Waals (vdW) quantum materials have emerged as a rapidly developing field of two-dimensional (2D) semiconductors. These materials establish a new central research area and provide a promising platform for studying quantum phenomena and investigating the engineering of novel optoelectronic properties such as single photon emission, nonlinear optical response, magnon physics, and topological superconductivity. These captivating electronic and optical properties result from, and can be tailored by, the interlayer coupling using moiré patterns formed by vertically stacking atomic layers with controlled angle misorientation or lattice mismatch. Their outstanding properties and the high degree of tunability position them as compelling building blocks for both compact quantum-enabled devices and classical optoelectronics. This paper offers a comprehensive review of recent advancements in the understanding and manipulation of twisted van der Waals structures and presents a survey of the state-of-the-art research on moiré superlattices, encompassing interdisciplinary interests. It delves into fundamental theories, synthesis and fabrication, and visualization techniques, and the wide range of novel physical phenomena exhibited by these structures, with a focus on their potential for practical device integration in applications ranging from quantum information to biosensors, and including classical optoelectronics such as modulators, light emitting diodes, lasers, and photodetectors. It highlights the unique ability of moiré superlattices to connect multiple disciplines, covering chemistry, electronics, optics, photonics, magnetism, topological and quantum physics. This comprehensive review provides a valuable resource for researchers interested in moiré superlattices, shedding light on their fundamental characteristics and their potential for transformative applications in various fields.

Enhancing quantum teleportation efficacy with noiseless linear amplification.

Quantum teleportation constitutes a fundamental tool for various applications in quantum communication and computation. However, state-of-the-art continuous-variable quantum teleportation is restricted to moderate fidelities and short-distance configurations. This is due to unavoidable experimental imperfections resulting in thermal decoherence during the teleportation process. Here we present a heralded quantum teleporter able to overcome these limitations through noiseless linear amplification. As a result, we report a high fidelity of 92% for teleporting coherent states using a modest level of quantum entanglement. Our teleporter in principle allows nearly complete removal of loss induced onto the input states being transmitted through imperfect quantum channels. We further demonstrate the purification of a displaced thermal state, impossible via conventional deterministic amplification or teleportation approaches. The combination of high-fidelity coherent state teleportation alongside the purification of thermalized input states permits the transmission of quantum states over significantly long distances. These results are of both practical and fundamental significance; overcoming long-standing hurdles en route to highly-efficient continuous-variable quantum teleportation, while also shining new light on applying teleportation to purify quantum systems from thermal noise.

Multiparameter Estimation with Two-Qubit Probes in Noisy Channels.

This work compares the performance of single- and two-qubit probes for estimating several phase rotations simultaneously under the action of different noisy channels. We compute the quantum limits for this simultaneous estimation using collective and individual measurements by evaluating the Holevo and Nagaoka-Hayashi Cramér-Rao bounds, respectively. Several quantum noise channels are considered, namely the decohering channel, the amplitude damping channel, and the phase damping channel. For each channel, we find the optimal single- and two-qubit probes. Where possible we demonstrate an explicit measurement strategy that saturates the appropriate bound and we investigate how closely the Holevo bound can be approached through collective measurements on multiple copies of the same probe. We find that under the action of the considered channels, two-qubit probes show enhanced parameter estimation capabilities over single-qubit probes for almost all non-identity channels, i.e., the achievable precision with a single-qubit probe degrades faster with increasing exposure to the noisy environment than that of the two-qubit probe. However, in sufficiently noisy channels, we show that it is possible for single-qubit probes to outperform maximally entangled two-qubit probes. This work shows that, in order to reach the ultimate precision limits allowed by quantum mechanics, entanglement is required in both the state preparation and state measurement stages. It is hoped the tutorial-esque nature of this paper will make it easily accessible.

On the equivalence between squeezing and entanglement potential for two-mode Gaussian states.

The maximum amount of entanglement achievable under passive transformations by continuous-variable states is called the entanglement potential. Recent work has demonstrated that the entanglement potential is upper-bounded by a simple function of the squeezing of formation, and that certain classes of two-mode Gaussian states can indeed saturate this bound, though saturability in the general case remains an open problem. In this study, we introduce a larger class of states that we prove saturates the bound, and we conjecture that all two-mode Gaussian states can be passively transformed into this class, meaning that for all two-mode Gaussian states, entanglement potential is equivalent to squeezing of formation. We provide an explicit algorithm for the passive transformations and perform extensive numerical testing of our claim, which seeks to unite the resource theories of two characteristic quantum properties of continuous-variable systems.

Approaching optimal entangling collective measurements on quantum computing platforms.

Entanglement is a fundamental feature of quantum mechanics and holds great promise for enhancing metrology and communications. Much of the focus of quantum metrology so far has been on generating highly entangled quantum states that offer better sensitivity, per resource, than what can be achieved classically. However, to reach the ultimate limits in multi-parameter quantum metrology and quantum information processing tasks, collective measurements, which generate entanglement between multiple copies of the quantum state, are necessary. Here, we experimentally demonstrate theoretically optimal single- and two-copy collective measurements for simultaneously estimating two non-commuting qubit rotations. This allows us to implement quantum-enhanced sensing, for which the metrological gain persists for high levels of decoherence, and to draw fundamental insights about the interpretation of the uncertainty principle. We implement our optimal measurements on superconducting, trapped-ion and photonic systems, providing an indication of how future quantum-enhanced sensing networks may look.

A new entropic quantum correlation measure for adversarial systems.

Quantum correlation often refers to correlations exhibited by two or more local subsystems under a suitable measurement. These correlations are beyond the framework of classical statistics and the associated classical probability distribution. Quantum entanglement is the most well-known of such correlations and plays an important role in quantum information theory. However, there exist non-entangled states that still possess quantum correlations which cannot be described by classical statistics. One such measure that captures these non-classical correlations is discord. Here we introduce a new measure of quantum correlations which we call entropic accord that fits between entanglement and discord. It is defined as the optimised minimax mutual information of the outcome of the projective measurements between two parties. We show a strict hierarchy exists between entanglement, entropic accord and discord for two-qubit states. We study two-qubit states which shows the relationship between the three entropic quantities. In addition to revealing a class of correlations that are distinct from discord and entanglement, the entropic accord measure can be inherently more intuitive in certain contexts.

12.6 dB squeezed light at 1550 nm from a bow-tie cavity for long-term high duty cycle operation.

Squeezed states are an interesting class of quantum states that have numerous applications. This work presents the design, characterization, and operation of a bow-tie optical parametric amplifier (OPA) for squeezed vacuum generation. We report the high duty cycle operation and long-term stability of the system that makes it suitable for post-selection based continuous-variable quantum information protocols, cluster-state quantum computing, quantum metrology, and potentially gravitational wave detectors. Over a 50 hour continuous operation, the measured squeezing levels were greater than 10 dB with a duty cycle of 96.6%. Alternatively, in a different mode of operation, the squeezer can also operate 10 dB below the quantum noise limit over a 12 hour period with no relocks, with an average squeezing of 11.9 dB. We also measured a maximum squeezing level of 12.6 dB at 1550 nm. This represents one of the best reported squeezing results at 1550 nm to date for a bow-tie cavity. We discuss the design aspects of the experiment that contribute to the overall stability, reliability, and longevity of the OPA, along with the automated locking schemes and different modes of operation.

Enhancing the precision limits of interferometric satellite geodesy missions.

Satellite geodesy uses the measurement of the motion of one or more satellites to infer precise information about the Earth's gravitational field. In this work, we consider the achievable precision limits on such measurements by examining approximate models for the three main noise sources in the measurement process of the current Gravitational Recovery and Climate Experiment (GRACE) Follow-On mission: laser phase noise, accelerometer noise and quantum noise. We show that, through time-delay interferometry, it is possible to remove the laser phase noise from the measurement, allowing for almost three orders of magnitude improvement in the signal-to-noise ratio. Several differential mass satellite formations are presented which can further enhance the signal-to-noise ratio through the removal of accelerometer noise. Finally, techniques from quantum optics have been studied, and found to have great promise for reducing quantum noise in other alternative mission configurations. We model the spectral noise performance using an intuitive 1D model and verify that our proposals have the potential to greatly enhance the performance of near-future satellite geodesy missions.

The Canadian Glomerulonephritis Registry (CGNR) and Translational Research Initiative: Rationale and Clinical Research Protocol.

Background: Glomerulonephritis (GN) is a leading cause of kidney failure and accounts for 20% of incident cases of end-stage kidney disease (ESKD) in Canada annually. Reversal of kidney injury and prevention of progression to kidney failure is possible; however, limited knowledge of underlying disease mechanisms and lack of noninvasive biomarkers and therapeutic targets are major barriers to successful therapeutic intervention. Multicenter approaches that link longitudinal clinical and outcomes data with serial biologic specimen collection would help bridge this gap. Objective: To establish a national, patient-centered, multidimensional web-based clinical database and federated virtual biobank to conduct human-based molecular and clinical research in GN in Canada. Design: Multicenter, prospective observational registry, starting in 2019. Setting: Nine participating Canadian tertiary care centers. Patients: Adult patients with a histopathologic pattern of injury consistent with IgA nephropathy, focal and segmental glomerulosclerosis, minimal change disease, membranous nephropathy, C3 glomerulopathy, and membranoproliferative GN recruited within 24 months of biopsy. Measurements: Initial visits include detailed clinical, histopathological, and laboratory data collection, blood, urine, and tonsil swab biospecimen collection, and a self-administered quality of life questionnaire. Follow-up clinical and laboratory data collection, biospecimen collection, and questionnaires are obtained every 6 months thereafter. Methods: Patients receive care as defined by their physician, with study visits scheduled every 6 months. Patients are followed until death, dialysis, transplantation, or withdrawal from the study. Key outcomes include a composite of ESKD or a 40% decline in estimated glomerular filtration rate (eGFR) at 2 years, rate of kidney function decline, and remission of proteinuria. Clinical and molecular phenotypical data will be analyzed by GN subtype to identify disease predictors and discover therapeutic targets. Limitations: Given the relative rarity of individual glomerular diseases, one of the major challenges is patient recruitment. Initial registry studies may be underpowered to detect small differences in clinically meaningful outcomes such as ESKD or death due to small sample sizes and short duration of follow-up in the initial 2-year phase of the study. Conclusions: The Canadian Glomerulonephritis Registry (CGNR) supports national collaborative efforts to study glomerular disease patients and their outcomes. Trial registration: NCT03460054.

Contexte: Les glomérulonéphrites (GN) sont des causes importantes d'insuffisance rénale; elles représentent 20 % des cas incidents d'insuffisance rénale terminale (IRT) au Canada chaque année. Inverser la néphropathie et prévenir la progression vers l'insuffisance rénale est possible, mais deux obstacles majeurs freinent la réussite de l'intervention thérapeutique: une compréhension limitée des mécanismes sous-jacents de la maladie, de même que l'absence de biomarqueurs non invasifs et de cibles thérapeutiques. Les approches multicentriques reliant les données cliniques longitudinales et les résultats de santé à la collecte d'échantillons biologiques en série permettraient de combler cette lacune. Objectif: Créer une base de données cliniques nationale en ligne, multidimensionnelle et axée sur le patient, de même qu'une biobanque virtuelle fédérée pour permettre de mener des recherches moléculaires et cliniques humaines sur les GN au Canada. Type d'étude: Registre d'observation prospectif multicentrique débuté en 2019. Cadre: Neuf centres de soins tertiaires canadiens. Sujets: Des patients adultes recrutés dans les 24 mois suivant la biopsie et présentant un profil histopathologique de lésion compatible avec une néphropathie à IgA, une hyalinose segmentaire et focale, une maladie à changement minime, une glomérulonéphrite extra-membraneuse, une glomérulopathie à C3 et une glomérulonéphrite membranoproliférative. Mesures: La première visite comporte une collecte détaillée des données cliniques, histopathologiques et de laboratoire, la collecte d'échantillons biologiques (sang, urine et écouvillonnage des amygdales), ainsi qu'un questionnaire autoadministré sur la qualité de vie. Pour le suivi, la collecte des données cliniques et de laboratoire, la collecte des échantillons biologiques et les questionnaires s'effectuent tous les six mois. Méthodologie: Les patients reçoivent des soins comme établi par leur médecin, et les visites d'étude sont programmées tous les six mois. Les patients sont suivis jusqu'au décès ou jusqu'à la dialyse, à la transplantation ou au retrait de l'étude. Un critère de jugement combiné (IRT, ou diminution de 40 % du débit de filtration glomérulaire estimé après deux ans), ainsi que le taux de déclin de la fonction rénale et la rémission de la protéinurie sont les principaux critères de jugement. Les données phénotypiques cliniques et moléculaires seront analysées par sous-types de GN afin d'identifier les prédicteurs de la maladie et de découvrir de nouvelles cibles thérapeutiques. Limites: Le recrutement des sujets demeure un des principaux défis puisque les maladies glomérulaires prises individuellement sont relativement rares. La faible taille des échantillons et la courte durée du suivi pendant les deux ans de la phase initiale de l'étude pourraient faire en sorte que les études initiales issues du registre ne soient pas assez puissantes pour détecter de légères différences dans les résultats cliniquement significatifs comme l'IRT ou le décès. Conclusion: Le Canadian Glomerulonephritis Registry (CGNR) appuie les efforts de collaboration nationale visant à étudier les patients atteints de maladies glomérulaires et leur évolution clinique. Enregistrement de l'essai: NCT03460054.

Immunoglobulin A nephropathy is characterized by anticommensal humoral immune responses.

IgA nephropathy (IgAN) is a leading cause of kidney failure, yet little is known about the immunopathogenesis of this disease. IgAN is characterized by deposition of IgA in the kidney glomeruli, but the source and stimulus for IgA production are not known. Clinical and experimental data suggest a role for aberrant immune responses to mucosal microbiota in IgAN, and in some countries with high disease prevalence, tonsillectomy is regarded as standard-of-care therapy. To evaluate the relationship between microbiota and mucosal immune responses, we characterized the tonsil microbiota in patients with IgAN versus nonrelated household-matched control group participants and identified increased carriage of the genus Neisseria and elevated Neisseria-targeted serum IgA in IgAN patients. We reverse-translated these findings in experimental IgAN driven by BAFF overexpression in BAFF-transgenic mice rendered susceptible to Neisseria infection by introduction of a humanized CEACAM-1 transgene (B × hC-Tg). Colonization of B × hC-Tg mice with Neisseria yielded augmented levels of systemic Neisseria-specific IgA. Using a custom ELISPOT assay, we discovered anti-Neisseria-specific IgA-secreting cells within the kidneys of these mice. These findings suggest a role for cytokine-driven aberrant mucosal immune responses to oropharyngeal pathobionts, such as Neisseria, in the immunopathogenesis of IgAN. Furthermore, in the presence of excess BAFF, pathobiont-specific IgA can be produced in situ within the kidney.

Adipose Tissue-Derived Mesenchymal Stem Cells (ADMSCs) and ADMSC-Derived Secretome Expedited Wound Healing in a Rodent Model - A Preliminary Study.

INTRODUCTION: The biological role of mesenchymal stem cells (MSCs) in wound healing has been demonstrated. However, there were limited studies on the healing effect of secretome which consists of many biological factors secreted by MSCs. In this study, we aimed to compare the therapeutic effects of secretome with MSCs on facilitating wound healing. METHODS: Green fluorescent protein labelled adipose-derived MSCs (GFP-ADMSCs) or secretome was injected in the full-thickness skin excision model on SD rats. The wound healing process was evaluated by calculating the healing rate and the histological examinations on skin biopsy. The cell viability, proliferation and mobility of the rat dermal fibroblasts were compared after different treatments. The inflammatory response in macrophages was indicated by the level of nitric oxide (NO) and inflammatory cytokines through NO assay and ELISA. RESULTS: On day 5 and day 14, both MSCs and secretome accelerated the wound healing, secretome further enhanced the process. GFP-MSCs were detected 10 days after transplantation. The level of IL-6 and TNF-α in blood was reduced after MSCs and secretome treatments. The expressions of VEGF and PCNA were increased after treatment, higher intensity of VEGF was observed in secretome-injected tissue. The concentrations of total protein and VEGF in secretome were 2.2 ± 0.5 mg/mL and 882.0 ± 72.7 pg/mL, respectively. The cell viability and proliferation of FR were promoted significantly after the treatment. The scratch test showed that secretome accelerated the wound healing speed. Secretome reduced the metabolism of macrophages remarkably, but it did not decrease the level of macrophage-secreted NO. The expression of the pro-inflammatory cytokines (IL-6, MCP-1 and TNF-α) was downregulated significantly. CONCLUSION: Our study indicated both MSCs and MSCs-derived secretome enhanced the wound healing process in early phase. Secretome further promoted the healing effects through promoting the fibroblast proliferation and migration and suppressing the inflammatory response.

Topical application of adipose tissue-derived mesenchymal stem cells (ADMSCs) reduced cerebral edema in experimental traumatic brain injury (TBI)-a preliminary study.

BACKGROUND: Our previous studies showed that topical application of mesenchymal stem cells (MSCs) improved functional recovery in rat traumatic brain injury (TBI) model, and hypoxic precondition further enhanced the therapeutic effects of MSCs. There was no previous study on the attenuation of cerebral edema by MSCs. We investigated whether topical application of normoxic and hypoxic MSCs could reduce cerebral edema in an experimental TBI model. METHODS: Two million normoxic (N = 24) and hypoxic (N = 24) MSCs were applied topically to exposed the cerebral cortex in a controlled cortical impact (CCI) model. The MSCs were fixed in position with fibrin glue. No treatment was given to control animals (TBI only: n = 24). After surgery, four animals in each group were sacrificed daily (day 1 to day 6) for edema evaluation. Normal animals without TBI were used as reference (n = 4). The expressions of GFAP, AQP4, and MMP9 were also investigated by immunofluorescence staining and RT-PCR at day 3. RESULTS: The edema peaked within 3 days after TBI. Compared with the control, hypoxic MSCs reduced brain water content significantly (p < 0.05). Both hypoxic and normoxic MSCs downregulated the expression of MMP9 and normalized AQP4 distribution to astrocyte end feet. CONCLUSION: Our preliminary study showed that topical application of hypoxic MSCs suppressed both vasogenic and cytotoxic edema formation.

Supertransport of excitons in atomically thin organic semiconductors at the 2D quantum limit.

Long-range and fast transport of coherent excitons is important for the development of high-speed excitonic circuits and quantum computing applications. However, most of these coherent excitons have only been observed in some low-dimensional semiconductors when coupled with cavities, as there are large inhomogeneous broadening and dephasing effects on the transport of excitons in their native states in materials. Here, by confining coherent excitons at the 2D quantum limit, we first observed molecular aggregation-enabled 'supertransport' of excitons in atomically thin two-dimensional (2D) organic semiconductors between coherent states, with a measured high effective exciton diffusion coefficient of ~346.9 cm2/s at room temperature. This value is one to several orders of magnitude higher than the values reported for other organic molecular aggregates and low-dimensional inorganic materials. Without coupling to any optical cavities, the monolayer pentacene sample, a very clean 2D quantum system (~1.2 nm thick) with high crystallinity (J-type aggregation) and minimal interfacial states, showed superradiant emission from Frenkel excitons, which was experimentally confirmed by the temperature-dependent photoluminescence (PL) emission, highly enhanced radiative decay rate, significantly narrowed PL peak width and strongly directional in-plane emission. The coherence in monolayer pentacene samples was observed to be delocalised over ~135 molecules, which is significantly larger than the values (a few molecules) observed for other organic thin films. In addition, the supertransport of excitons in monolayer pentacene samples showed highly anisotropic behaviour. Our results pave the way for the development of future high-speed excitonic circuits, fast OLEDs, and other optoelectronic devices.

Photothermally induced transparency.

Induced transparency is a common but remarkable effect in optics. It occurs when a strong driving field is used to render an otherwise opaque material transparent. The effect is known as electromagnetically induced transparency in atomic media and optomechanically induced transparency in systems that consist of coupled optical and mechanical resonators. In this work, we introduce the concept of photothermally induced transparency (PTIT). It happens when an optical resonator exhibits nonlinear behavior due to optical heating of the resonator or its mirrors. Similar to the established mechanisms for induced transparency, PTIT can suppress the coupling between an optical resonator and a traveling optical field. We further show that the dispersion of the resonator can be modified to exhibit slow or fast light. Because of the relatively slow thermal response, we observe the bandwidth of the PTIT to be 2π × 15.9 Hz, which theoretically suggests a group velocity of as low as 5 m/s.

Mesenchymal Stem Cells Combined with Tissue Fusion Technology Promoted Wound Healing in Porcine Bowel Anastomosis.

OBJECTIVE: To evaluate the possible biological effect of allogenic mesenchymal stem cells (MSCs) combined with tissue fusion technology on the anastomosis. METHODS: Sixteen pigs were divided into a 7 d group and 14 d group, each of which was further subdivided into an MSC-treated group and a control group. Five anastomoses per animal were established using LigaSure ForceTriad (Covidien, MA, USA), a tissue sealing system. Cell migration and tissue-specific differentiation potency, in addition to potential cytokine and genetic changes, were investigated. RESULTS: There were no significant between-group differences in postoperative complications and anastomosis burst pressure. The number of proliferating cell nuclear antigen- (PCNA-) positive cells was significantly higher in the MSC-treated group as compared with that in the control group (P = 0.021). Labeled MSCs were found in the mucosal layer, villus, and lamina propria, as well as in the lamina muscularis mucosae, where they exhibited characteristics of smooth muscle cells. CONCLUSIONS: Grafted MSCs significantly promoted epithelial and connective cell proliferation and maintained their cell migration capacity and differentiation potential in the fused anastomotic tissues, without causing severe postoperative complications.

The Time Course of Cognitive Deficits in Experimental Subarachnoid Hemorrhage.

Subarachnoid hemorrhage (SAH) is a devastating stroke type. Approximately 50% of survivors suffer from the permanent disability, caused by the cognitive deficits. To enrich the pre-clinical research on the neurological deficits after SAH, we investigate the temporal cognitive deficits and the longitudinal course of cognitive recovery in endovascular perforation SAH murine model. The SAH mice show reproducible body weakness and headache-symbolized moaning symptoms, which is closed to clinical patients. SAH mice exhibit significantly impaired cognitive function in domains of learning ability, short-term and long-term memory. The cognitive deficits occur mostly in the early phase and recover gradually till day 10 after SAH. The systematical assessments of cognitive function after experimental aneurysmal SAH elucidate the time course of cognitive deficits and provide the time window of potential interventions.

Topically applied adipose-derived mesenchymal stem cell treatment in experimental focal cerebral ischemia.

In this study, the neuro-modulation effect of topical mesenchymal stem cells (MSCs) was tested in a rodent middle carotid artery occlusion (MCAO) model. Twenty-four hours after MCAO, craniotomy was made and 0.8 × 106 GFP-MSCs were topically applied to the exposed parietal cortex. The MSCs were fixed in position by a thin layer of fibrin glue (N = 30). In the control group, saline were topically applied to the ipsilateral parietal cortex (N = 30). Three days after topical application, few GFP-positive cells were found in the ischemic penumbra. They expressed GFAP and NeuN. Topical MSCs triggered microglial activation, astrocytosis and cellular proliferation at day 3. The recovery of neurological functions were significantly enhanced as determined in Rotarod test and Morris Water Maze test with smaller infarct volume. PCR array showed that expressions of ten genes of neurogenesis were altered in the penumbra region (fold change > 1.25, p < 0.05) in MSCs group: Apoe, Ascl1, Efnb1, Mef2c, Nog, A100a6 and B2m were up-regulated; Pax2, Pax3 and Th were down-regulated. In conclusion, topical application provided a direct and effective transplant method for the delivery of MSCs to the surface of ipsilateral cerebral cortex and the topical MSCs could improve the neurological function from cerebral ischemia resulting from a major cerebral artery occlusion in a rodent experimental model.

The Dynamics of Microglial Polarization Reveal the Resident Neuroinflammatory Responses After Subarachnoid Hemorrhage.

Neuroinflammation plays a critical role in the pathogenesis of subarachnoid hemorrhage (SAH). Microglia, as the resident immune cells, orchestrate neuroinflammation distinctly in neurological diseases with different polarization statuses. However, microglial polarizations in the neuroinflammatory responses after SAH are not fully understood. In this study, we investigated the dynamics of microglial reaction in an endovascular perforated SAH model. By using the Cx3cr1GFP/GFP Ccr2RFP/RFP transgenic mice, we found that the reactive immune cells were largely from resident microglia pool rather than infiltrating macrophages. Immunostaining and real-time PCR were employed to analyze the temporal microglial polarization and the resulting inflammatory responses. Our results showed that microglia accumulated immediately after SAH with a centrifugal spreading through the Cortex Adjacent to the Perforated Site (CAPS) to the remote motor cortex. Microglia polarized dynamically from M1 to M2 phenotype along with the morphological transformation from ramified to amoeboid shapes. The ramified microglia demonstrated the M1 property, which suggested the function-related microglial polarization occurred prior to morphological transformation after SAH. Bipolar-shaped microglia appeared as the intermediate and transitional status with the capacity of bidirectional polarization. The microglial polarization status is distinct in molecular inflammatory responses; M1-related pro-inflammation was predominant in the early phase and subsequently transited to the M2-related anti-inflammation. The systematic characterization of the dynamics of microglial polarization in this study contributes to the understanding of the origin of neuroinflammatory responses after SAH and provides key foundation for further investigations to develop target treatment.

Atomic localization of quantum emitters in multilayer hexagonal boron nitride.

The recent discovery of single-photon emitting defects hosted by the two-dimensional wide band gap semiconductor hexagonal boron nitride (hBN) has inspired a great number of experiments. Key characteristics of these quantum emitters are their capability to operate at room temperature with a high luminosity. In spite of large theoretical and experimental research efforts, the exact nature of the emission remains unresolved. In this work we utilize layer-by-layer etching of multilayer hBN to localize the quantum emitters with atomic precision. Our results suggest the position of the emitters correlates with the fabrication method: emitters formed under plasma treatment are always in close proximity to the crystal surface, while emitters created under electron irradiation are distributed randomly throughout the entire crystal. This disparity could be traced back to the lower kinetic energy of the ions in the plasma compared to the kinetic energy of the electrons in the particle accelerator. The emitter distance to the surface also correlates with the excited state lifetime: near-surface emitters have a shorter one compared to emitters deep within the crystal. Finite-difference time-domain and density functional theory simulations show that optical and electronic effects are not responsible for this difference, indicating effects such as coupling to surface defects or phonons might cause the reduced lifetime. Our results pave a way toward identification of the defect, as well as engineering the emitter properties.

The neuroprotection of hypoxic adipose tissue-derived mesenchymal stem cells in experimental traumatic brain injury.

Traumatic brain injury is one of the leading causes of mortality and morbidity worldwide. At present there is no effective treatment. Previous studies have demonstrated that topical application of adipose tissue-derived mesenchymal stem cells can improve functional recovery in experimental traumatic brain injury. In this study, we evaluated whether hypoxic preconditioned mesenchymal stem cells could enhance the recovery from traumatic brain injury. Traumatic brain injury was induced with an electromagnetically controlled cortical impact device. Two million mesenchymal stem cells derived from the adipose tissue of transgenic green fluorescent protein Sprague-Dawley rats were cultured under either hypoxic (2.5% O2 for 18 hours) (N = 30) or normoxic (18% O2) (N = 30) conditions, then topically applied to the exposed cerebral cortex within 1 hour after traumatic brain injury. A thin layer of fibrin was used to fix the cells in position. No treatment was given to the animals with traumatic brain injury (N = 30). Animals that underwent craniectomy without traumatic brain injury were treated as the sham group (N = 15). Neurological functions were evaluated with water maze, Roto-rod and gait analysis. Animals were sacrificed at days 3, 7, and 14 for microscopic examinations and real-time polymerase chain reaction analysis. The rats treated with hypoxic mesenchymal stem cells showed the greatest improvement in neurological function recovery. More green fluorescent protein-positive cells were found in the injured brain parenchyma treated with hypoxic mesenchymal stem cells that co-expressed glial fibrillary acidic protein, Nestin, and NeuN. Moreover, there was early astrocytosis triggered by the infiltration of more glial fibrillary acidic protein-positive cells and microgliosis was suppressed with fewer ionized calcium binding adapter molecule 1-positive cells in the penumbra region of hypoxic mesenchymal stem cells group at day 3. Compared with normoxic mesenchymal stem cells and traumatic brain injury only groups, there was significantly (p < 0.05) less neuronal death in both the hippocampus and penumbral regions in sections treated with hypoxic mesenchymal stem cells as determined by Cresyl violet and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining respectively. The expression of pro-inflammatory genes (interleukin 6, interleukin 1a, interleukin 1b, tumor necrosis factor α) was upregulated and apoptotic gene (Caspase-3) expression was suppressed at day 3. Anti-inflammatory (interleukin 10) and anti-apoptotic (BCL2 associated agonist of cell death) gene expression was upregulated at days 7 and 14. Our study showed that a hypoxic precondition enhanced the beneficial effects of mesenchymal stem cells on neurological recovery after traumatic brain injury.