Abstract
Van der Waals heterobilayers of transition metal dichalcogenides with spin–valley coupling of carriers in different layers have emerged as a new platform for exploring spin/valleytronic ...applications. The interlayer coupling was predicted to exhibit subtle changes with the interlayer atomic registry. Manually stacked heterobilayers, however, are incommensurate with the inevitable interlayer twist and/or lattice mismatch, where the properties associated with atomic registry are difficult to access by optical means. Here, we unveil the distinct polarization properties of valley-specific interlayer excitons using epitaxially grown, commensurate WSe
2
/MoSe
2
heterobilayers with well-defined (AA and AB) atomic registry. We observe circularly polarized photoluminescence from interlayer excitons, but with a helicity opposite to the optical excitation. The negative circular polarization arises from the quantum interference imposed by interlayer atomic registry, giving rise to distinct polarization selection rules for interlayer excitons. Using selective excitation schemes, we demonstrate the optical addressability for interlayer excitons with different valley configurations and polarization helicities.
The oxygen evolution reaction (OER) is the performance-limiting half reaction of water splitting, which can be used to produce hydrogen fuel using renewable energies. Whereas a number of transition ...metal oxides and oxyhydroxides have been developed as promising OER catalysts in alkaline medium, the mechanisms of OER on these catalysts are not well understood. Here we combine electrochemical and in situ spectroscopic methods, particularly operando X-ray absorption and Raman spectroscopy, to study the mechanism of OER on cobalt oxyhydroxide (CoOOH), an archetypical unary OER catalyst. We find the dominating resting state of the catalyst as a Co(IV) species CoO2. Through oxygen isotope exchange experiments, we discover a cobalt superoxide species as an active intermediate in the OER. This intermediate is formed concurrently to the oxidation of CoOOH to CoO2. Combing spectroscopic and electrokinetic data, we identify the rate-determining step of the OER as the release of dioxygen from the superoxide intermediate. The work provides important experimental fingerprints and new mechanistic perspectives for OER catalysts.
We explore a network of electronic quantum valley Hall states in the moiré crystal of minimally twisted bilayer graphene. In our transport measurements, we observe Fabry-Pérot and Aharanov-Bohm ...oscillations that are robust in magnetic fields ranging from 0 to 8 T, which is in strong contrast to more conventional two-dimensional systems where trajectories in the bulk are bent by the Lorentz force. This persistence in magnetic field and the linear spacing in density indicate that charge carriers in the bulk flow in topologically protected, one-dimensional channels. With this work, we demonstrate coherent electronic transport in a lattice of topologically protected states.
Battery energy storage systems are often adopted to buffer the difference between the intermittent solar power and the load demand in power grids. The costs of such photovoltaic (PV) battery systems ...increase as the required energy storage increases. In this paper, a new configuration comprising the PV panels, a series dc electric spring (series ES) and a noncritical load is proposed to reduce the battery storage capacity of dc microgrids that have substantial PV installations. This arrangement forms a PV-embedded series dc ES (PVES). An optimization method considering the minimization of electricity bills of the dc microgrids is included to size the storage capacity and to determine the rating of the PV that are connected to the series ES. Experiments on a 48-V isolated dc grid and simulations on a 400-kVA grid-connected dc microgrid have been conducted to verify the storage reduction feature of the PVES. Both sets of results show that the PVES can tackle the intermittency of the solar power with a smaller storage capacity than that typically required in dc grids with PV installations.
The number of emergency department (ED) visits has significantly declined since the COVID-19 pandemic. In Taiwan, an aged society, it is unknown whether older adults are accessing emergency care ...during the COVID-19 epidemic. Therefore, this study aimed to investigate the impact of COVID-19 on the ED visits and triage, admission, and intensive care unit (ICU) hospitalization of the geriatric population in a COVID-19-dedicated medical center throughout various periods of the epidemic.
A retrospective chart review of ED medical records from April 9 to August 31, 2021 were conducted, and demographic information was obtained from the hospital's computer database. The period was divided into pre-, early-, peak-, late-, and post-epidemic stages. For statistical analysis, one-way analysis of variance followed by multiple comparison tests (Bonferroni correction) were used.
A statistically significant decrease in the total number of patients attending the ED was noted during the peak-, late-, and post-epidemic stages. In the post-epidemic stage, the number of older patients visiting ED was nearly to that of the pre-epidemic stage, indicating that older adults tend to seek care at the ED earlier than the general population. Throughout the entire epidemic period, there was no statistically significant reduction in the number of the triage 1& 2 patients seeking medical attention at the emergency department. In the entire duration of the epidemic, there was no observed reduction in the admission of elderly patients to our hospital or ICU through the ED. However, a statistically significant decrease was observed in the admission of the general population during the peak epidemic stage.
During the peak of COVID-19 outbreak, the number of ED visits was significantly affected. However, it is noteworthy that as the epidemic was gradually controlled, the older patients resumed their ED visits earlier that the general population as indicated by the surge in their number. Additionally, in the patient group of triage 1& 2, which represents a true emergency, the number did not show a drastic change.
Accumulating evidence has shown transcranial low-intensity ultrasound can be potentially a non-invasive neural modulation tool to treat brain diseases. However, the underlying mechanism remains ...elusive and the majority of studies on animal models applying rather high-intensity ultrasound that cannot be safely used in humans. Here, we showed low-intensity ultrasound was able to activate neurons in the mouse brain and repeated ultrasound stimulation resulted in adult neurogenesis in specific brain regions. In vitro calcium imaging studies showed that a specific ultrasound stimulation mode, which combined with both ultrasound-induced pressure and acoustic streaming mechanotransduction, is required to activate cultured cortical neurons. ASIC1a and cytoskeletal proteins were involved in the low-intensity ultrasound-mediated mechanotransduction and cultured neuron activation, which was inhibited by ASIC1a blockade and cytoskeleton-modified agents. In contrast, the inhibition of mechanical-sensitive channels involved in bilayer-model mechanotransduction like Piezo or TRP proteins did not repress the ultrasound-mediated neuronal activation as efficiently. The ASIC1a-mediated ultrasound effects in mouse brain such as immediate response of ERK phosphorylation and DCX marked neurogenesis were statistically significantly compromised by ASIC1a gene deletion. Collated data suggest that ASIC1a is the molecular determinant involved in the mechano-signaling of low-intensity ultrasound that modulates neural activation in mouse brain.
Excitons in monolayer semiconductors have a large optical transition dipole for strong coupling with light. Interlayer excitons in heterobilayers feature a large electric dipole that enables strong ...coupling with an electric field and exciton-exciton interaction at the cost of a small optical dipole. We demonstrate the ability to create a new class of excitons in hetero- and homobilayers that combines advantages of monolayer and interlayer excitons, i.e., featuring both large optical and electric dipoles. These excitons consist of an electron confined in an individual layer, and a hole extended in both layers, where the carrier-species-dependent layer hybridization can be controlled through rotational, translational, band offset, and valley-spin degrees of freedom. We observe different species of layer-hybridized valley excitons, which can be used for realizing strongly interacting polaritonic gases and optical quantum controls of bidirectional interlayer carrier transfer.
The giant second‐order nonlinearity of SnS with ferroelectric stacking is reported. Based on theoretical calculations, the susceptibility of second harmonic generation (SHG) from SnS with ...ferroelectric stacking is up to 1354 pm V−1, which is three orders of magnitude higher than the values of traditional nonlinear crystals such as BBO and KTP. The SHG from ferroelectric SnS few layers is experimentally measured and its intensity is found to be 131 times larger than that of a MoS2 monolayer under the same experimental conditions, with a photon energy of 1.55 eV. The SHG susceptibility is determined to be on the order of 100 pm V−1. Numerous SnS flakes are systematically investigated using polarization‐resolved SHG. Micrometer‐sized flakes with a single domain are found, and their SHG anisotropic patterns fit well with the theoretical calculations derived from first‐principles methods. The variation in SHG anisotropic patterns, attributed to SHG interference from multiple domains, is investigated both theoretically and experimentally. Additionally, the impact of stacking disorder on the SHG anisotropic pattern is explored. It is demonstrated that polarization‐resolved SHG microscopy is a valuable tool for identifying domains in SnS flakes and examining stacking disorder.
Giant second‐order nonlinearity of SnS with ferroelectric stacking is reported. Its second harmonic generation (SHG) susceptibility, on the order of 1000 pm V−1, is three orders of magnitude higher than the values of traditional nonlinear crystals such as BBO and KTP. The SHG anisotropy of single‐domain and multi‐domain SnS flakes is systematically investigated.
Atopic dermatitis (AD) is a complex, chronic inflammatory skin disease. An estimated 57.5% of asthmatic patients and 50.7% of rhinitis patients are allergic to cockroaches in Taiwan. However, the ...role of cockroaches in the pathogenesis of AD is undetermined. Oral tolerance might be another strategy for protecting against AD and allergic inflammation by regulating T helper 2 (Th2) immune responses. Aim to examine the underlying immunologic mechanism, we developed an AD-like murine model by skin-brushing with cockroach Per a 2. We also investigated whether the systemic inflammation of AD in this murine model could be improved by specific tolerance to Lactococcus lactis-expressing Per a 2, which was administered orally. Repeated painting of Per a 2 without adjuvant to the skin of mice resulted in increased total IgE, Per a 2-specific IgE, and IgG1, but not IgG2a. In addition, epidermal thickening was significantly increased, there were more scratch episodes, and there were increases in total white blood cells (eosinophil, neutrophil, and lymphocyte) and Th2 cytokines (Interleukin (IL)-4, IL-5, IL-9, and IL-13) in a dose-dependent manner. The results revealed that oral administration of L. lactis-Per a 2 ameliorated Per a 2-induced scratch behavior and decreased the production of total IgE, Per a 2-specific IgE, and IgG1. Furthermore, L. lactis-Per a 2 treatment also suppressed inflammatory infiltration, expressions of thymic stromal lymphopoietin (TSLP) and IL-31 in skin lesions, and downregulated splenic IL-4 and IL-13 in Per a 2-induced AD mice. This study provides evidence supporting that repeated brushing of aeroallergens to the skin leads to atopic dermatitis phenotypes and oral allergen-specific immune tolerance can ameliorate AD-like symptoms and systemic inflammation and prevent progression of atopic march.
The progression of allergic diseases from atopic dermatitis in childhood to other allergic conditions such as asthma in later life is often referred to as the atopic march. In order to study the ...relationship between cutaneous sensitization by aeroallergen and atopic march, we established a mouse model to test the hypothesis using American cockroaches and house dust mites as the model allergens. Mice were sensitized via skin with native cockroach extract (CraA) or recombinant Per a 2 and Der p 2 proteins without adjuvant. Each mouse was subjected to a total of three 1-week patching sensitizations with a 2-week interval in between each application. The resulting immunological variables in sera, scratching behavior, airway hyperresponsiveness (AHR), and pathology of skin lesions and nasal mucosa were evaluated. In mice, application of CraA, rPer a 2, and rDer p 2 aeroallergens through skin patching induced significantly high levels of both total IgE and specific IgEs. The epicutaneous sensitization after a subsequent allergen challenge showed a significant increase in scratch bouts, AHR, epidermal thickness, and eosinophil counts in the skin compared with the control mice. In addition, stimulation of murine splenocytes with allergens increased higher levels of Th2 cytokines, anti-inflammatory cytokines, and chemokines excretion. Our study provides evidence supporting that epicutaneous sensitization to aeroallergens also led to nasal and airway symptoms comparable to atopic march as described in humans. We hope this new allergy model will be useful in the development of new preventive and therapeutic strategies aimed at stopping the atopic march.
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