Flat-band Friedrich-Wintgen bound states in the continuum based on borophene metamaterials.

Many applications involve the phenomenon of a material absorbing electromagnetic radiation. By exploiting wave interference, the efficiency of absorption can be significantly enhanced. Here, we propose Friedrich-Wintgen bound states in the continuum (F-W BICs) based on borophene metamaterials to realize coherent perfect absorption with a dual-band absorption peak in commercially important communication bands. Metamaterials consist of borophene gratings and a borophene sheet that can simultaneously support a Fabry-Perot plasmon resonance and a guided plasmon mode. The formation and dynamic modulation of the F-W BIC can be achieved by adjusting the width or carrier density of the borophene grating, while the strong coupling leads to the anti-crossover behavior of the absorption spectrum. Due to the weak angular dispersion originating from the intrinsic flat-band characteristic of the deep sub-wavelength periodic structure, the proposed plasmonic system exhibits almost no change in wavelength and absorption at large incident angles (within 70 degrees). In addition, we employ the temporal coupled-mode theory including near- and far-field coupling to obtain strong critical coupling, successfully achieve coherent perfect absorption, and can realize the absorption switch by changing the phase difference between the two coherent beams. Our findings can offer theoretical support for absorber design and all-optical tuning.

Optical force conversion and conveyor belt effect with coupled graphene plasmon waveguide modes.

We propose a double-layer graphene sheets side coupling to a strip of graphene to obtain the optical pulling or pushing force. Combined with coupled mode theory and finite-difference time-domain simulations, it is found that the conveyor belt effect can be realized in conjunction with the lateral optical equilibrium effect upon the radiation loss κe equal to the intrinsic loss κo. The maximum total optical force acting on the strip in the symmetric mode (S-mode) can be up to ∼5.95 in the unit of 1/c and the anti-symmetric (AS-mode) mode reach ∼2.75 1/c. The optical trapping potential Ux and optical trapping force Fx for the S-mode have a value around -22.5 kBT/W and 240 pN/W, while for the AS-mode can up to ∼-56 kBT/W and 520 pN/W, respectively. Our work opens a new avenue for optical manipulation with potential applications in optoelectronic devices and lab-on-a-chip platforms.

Analytical investigation of unidirectional reflectionless phenomenon near the exceptional points in graphene plasmonic system.

We propose a two-dimensional array made of a double-layer of vertically separated graphene nanoribbons. The transfer matrix method and coupled mode theory are utilized to quantitatively depict the transfer properties of the system. We present a way to calculate the radiative and the intrinsic loss factors, combined with finite-difference time-domain simulation, conducting the complete analytical analysis of the unidirectional reflectionless phenomenon. By adjusting the Fermi energy and the vertical distance between two graphene nanoribbons, the plasmonic resonances are successfully excited, and the unique phenomena can be realized at the exceptional points. Our research presents the potential in the field of optics and innovative technologies to create advanced optical devices that operate in the mid-infrared range, such as terahertz antennas and reflectors.

Personalized Biomarkers and Neuropsychological Status Can Predict Post-Stroke Fatigue.

Post-stroke fatigue (PSF) is a common complication of stroke that has a negative impact on prognosis and recovery. We aimed to investigate the relationship between PSF and demographics, mood disorders, sleep disorders, and other clinical characteristics of patients with stroke. In this exploratory cross-sectional study, we collected data on sociodemographic characteristics, biological indicators, and imaging features and evaluated patients using neuropsychological scales. Patients were assessed using the Fatigue Severity Scale, Hamilton Depression Rating Scale, Hamilton Anxiety Scale, and Pittsburgh Sleep Quality Index. Magnetic resonance imaging scans were primarily used to evaluate infarctions and white matter lesions. The correlation between the PSF of patients with stroke and clinical indicators was obtained by logistic regression analysis and power analysis. We observed an independent association between fatigue severity and female sex (odds ratio [OR], 2.12; 95% confidence interval [CI], 1.14-3.94), depressive state (OR, 1.50; 95% CI, 1.01-1.73), and sleep disorders (OR, 1.58; 95% CI, 1.01-1.98). High levels of blood glucose, serum uric acid, and homocysteine and low levels of serum triiodothyronine were strongly associated with poor functional outcomes in patients with stroke. Further studies are needed to elucidate how specific structural lesions and anxiety symptoms are related to early PSF.

Extreme enhancement of optical force via the acoustic graphene plasmon mode.

We have investigated the effect of enhanced optical force via the acoustic graphene plasmon (AGP) cavities with the ultra-small mode volumes. The AGP mode can generate stronger field confinement and higher momentum, which could provide giant optical force, and has no polarization preference for the optical source. We have demonstrated that the trapping potential and force applied on polystyrene nanoparticle in the AGP cavities are as high as -13.6 × 102 kBT/mW and 2.5 nN/mW, respectively. The effect of radius of rounded corners and gap distance of AGP cavities on the optical force has been studied. Compared with an ideal nanocube, nanocube with rounded corners is more in line with the actual situation of the device. These results show that the larger radius of nanocube rounded corners, the smaller trapping potential and force provided by AGP cavities. Our results pave a new idea for the investigation of optical field and optical force via acoustic plasmon mode.

Polaritonic coherent perfect absorption based on self-hybridization of a quasi-bound state in the continuum and exciton.

Enhancement of light-matter interactions is of great importance for many nanophotonic devices, and one way to achieve it is to feed energy perfectly to the strongly coupled system. Here, we propose gap-perturbed dimerized gratings based on bulk WS2 for flexible control of the strong coupling or self-hybridization of a quasi-bound state in the continuum (quasi-BIC) and exciton. The simulation results show that when a gap perturbation is introduced into the system resulting in the Brillouin zone folding, BIC transforms into quasi-BIC whose quality factor (Q-factor) is related to the value of gap perturbation. The strong coupling results in the anti-crossover behavior of the absorption spectra, and thus a Rabi splitting energy of 0.235 eV is obtained. With the assistance of temporal coupled-mode theory, the conditions for the strong critical coupling are obtained, and finally successful achievement of polaritonic coherent perfect absorption in the proposed system. This work could provide ideas for enhancing light-matter interactions and strong theoretical support for all-optical tuning and modulation.

Unified model for plasmon-induced transparency with direct and indirect coupling in borophene-integrated metamaterials.

We propose, both numerically and theoretically, a uniform model to investigate the plasmonically induced transparency effect in plasmonic metamaterial consisting of dual-layer spatially separated borophene nanoribbons array. The dynamic transfer properties of light between two borophene resonators can be effectively described by the proposed model, with which we can distinguish and connect the direct and indirect coupling schemes in the metamaterial system. By adjusting the electron density and separation of two borophene ribbons, the proposed metamaterials enable a narrow band in the near-infrared region to reach high transmission. It provides a new, to the best of our knowledge, platform for optoelectronic integrated high-performance devices in the communication band.

Exogenous citrate restores the leaf metabolic profiles of navel orange plants under boron deficiency.

Boron (B) is an essential micronutrient for higher plants, and its deficiency causes a change in the citrate concentration in leaves of young navel orange plants. Although citrate has been implicated in the regulation of gene expression for many transcripts, it is unclear whether citrate can affect metabolic profiling under B deficiency and if so, how many metabolites are affected. In this study, GC-TOF-MS-based untargeted metabolite profiling was used to identify the physiological effects of exogenous citrate on recovery of metabolites in B-deficient orange plants. There were 31 increased and 24 decreased metabolites in the boron-deficient (BD) group leaves relative to those of the boron-adequate (BA) group. Boron deficiency-induced changes in many metabolites were restored to the level of BA (control) group leaves or showed a recovery tendency at 1 week after citrate supply (foliar application of citrate, BDFC), including 11 organic acids, 9 sugars and polyols, 10 amino acids, and 4 other compounds. To compare with the metabolic recovery effects of exogenous citrate on B deficiency, exogenous application of B (borate) was also performed under same conditions (BDFB), and similar effects on the regulation of metabolic homeostasis under B deficiency were observed. Both the results of principal component analysis (PCA) and hierarchical cluster analysis (HCA) showed that BA, BDFC, and BDFB were relatively similar and clustered close to each other. There are different responsive and regulatory mechanisms to the additions of exogenous citrate in navel orange leaves under B adequate and deficient conditions. Based on these results, we suggest that citrate is an important component of the B deficiency stress response, and exogenous application of citrate generally restores the leaf metabolic profiles of navel orange plants under boron deficiency, which might play a positive role in this stress tolerance.

Association Between Stroke Characteristics and Post-Stroke Fatigue: A Meta-Analysis.

Background: Post-stroke fatigue (PSF), a highly distressing symptom, could exert an influence on the quality of life of stroke survivors. A previous meta-analysis reported that PSF was associated with mood disturbances such as depressive symptoms and anxiety. However, the association between stroke characteristics (stroke type and location) and PSF remains unclear. Objective: We performed a meta-analysis to study the association between stroke characteristics and PSF. Material and Methods: We conducted a search of electronic databases (PubMed, Web of Science, Cochrane Library) from the inception of all databases up to July 9, 2019. The quality of eligible articles was evaluated. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were applied to represent the combined effect value of each study. Results: Eight eligible studies including a total of 1816 stoke patients were identified. Three studies discussed the association between stroke type and PSF, and five studies investigated the relationship between stroke location and PSF. The results demonstrated PSF had a strong correlation with stroke type (OR = 2.42, 95% CI = [1.27, 4.61], P = 0.007) but was not relevant to stroke location, indicating that PSF was a complex, heterogeneous syndrome and that stroke characteristics may play only a very small role in the risk of developing PSF. Conclusions: Our meta-analysis indicated that PSF was closely relevant to stroke type and had no significant relationship with stroke location. However, the findings should be interpreted cautiously. Thus, we suggest an updated meta-analysis on this subject when more comprehensive studies that explore the above issue are available.

Tunable plasmonically induced transparency with giant group delay in gain-assisted graphene metamaterials.

We propose a graphene metamaterial consisting of several layers of longitudinally separated graphene nanoribbon array embedded into gain-assisted medium, demonstrating electromagnetically induced transparency-like spectra. Combined with finite-difference time-domain simulations, the transfer matrix method and temporal coupled-mode theory are adopted to quantitatively describe its transmission characteristics. These transmission characteristics can be tuned by altering the gain level in medium layer and the Fermi energy level in graphene. Additionally, it is the incorporation between gain medium and graphene nanoribbons with optimized geometrical parameters and Fermi energy level that the destructive interference between high order graphene plasmonic modes can be obtained, suggesting drastic phase transition with giant group delay and ultra-high group index up to 180 ps and 104, respectively. Our results can achieve efficient slow light effects for better optical buffers and other nonlinear applications.

Light-matter interactions enhanced by quasi-bound states in the continuum in a graphene-dielectric metasurface.

In this paper, we propose a graphene-dielectric metasurface to enhance the light-matter interactions in graphene. The dielectric metasurface consists of periodically arranged silicon split rings placed on the silica substrate, which supports a symmetry-protected bound state in the continuum (BIC). When perturbation is introduced into the system to break symmetry, the BIC will transform into the quasi-BIC with high quality (Q)-factor. As the graphene layer is integrated with the dielectric metasurface, the absorption of graphene can be enhanced by the quasi-BIC resonance and a bandwidth-tunable absorber can be achieved by optimizing the Fermi energy of graphene and the asymmetry parameter of the metasurface to satisfy the critical coupling condition. By varying the Fermi energy of graphene, the quasi-BIC resonances can be effectively modulated and the max transmission intensity difference is up to 81% and a smaller asymmetry parameter will lead to better modulation performance. Our results may provide theoretical support for the design of absorber and modulator based on the quasi-BIC.

Ultrathin multi-band coherent perfect absorber in graphene with high-contrast gratings.

High-contrast gratings (HCGs) can be designed as a resonator with high-quality factor and surface-normal emission, which are excellent characters for designing optical devices. In this work, we combine HCGs with plasmonic graphene structure to achieve an ultrathin five-band coherent perfect absorber (CPA). The presented CPA can achieve multi- and narrow-band absorption with high intensity under a relatively large incident angle. The good agreement between theoretical analysis and numerical simulated results demonstrates that our proposed HCGs-based structure is feasible to realize CPA. Besides, by dynamically adjusting the Fermi energy of graphene, we realize the active tunability of resonance frequency and absorption intensity simultaneously. Benefitting from the combination of HCGs and the one-atom thickness of graphene, the proposed device possesses an extremely thin feature. Our work proposes a novel method to manipulate coherent perfect absorption and is helpful to design tunable multi-band and ultrathin absorbers.

Genome-Wide Identification of Long Non-coding RNA in Trifoliate Orange (Poncirus trifoliata (L.) Raf) Leaves in Response to Boron Deficiency.

Long non-coding RNAs (lncRNAs) play important roles in plant growth and stress responses. As a dominant abiotic stress factor in soil, boron (B) deficiency stress has impacted the growth and development of citrus in the red soil region of southern China. In the present work, we performed a genome-wide identification and characterization of lncRNAs in response to B deficiency stress in the leaves of trifoliate orange (Poncirus trifoliata), an important rootstock of citrus. A total of 2101 unique lncRNAs and 24,534 mRNAs were predicted. Quantitative real-time polymerase chain reaction (qRT-PCR) experiments were performed for a total of 16 random mRNAs and lncRNAs to validate their existence and expression patterns. Expression profiling of the leaves of trifoliate orange under B deficiency stress identified 729 up-regulated and 721 down-regulated lncRNAs, and 8419 up-regulated and 8395 down-regulated mRNAs. Further analysis showed that a total of 84 differentially expressed lncRNAs (DELs) were up-regulated and 31 were down-regulated, where the number of up-regulated DELs was 2.71-fold that of down-regulated. A similar trend was also observed in differentially expressed mRNAs (DEMs, 4.21-fold). Functional annotation of these DEMs was performed using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, and the results demonstrated an enrichment of the categories of the biosynthesis of secondary metabolites (including phenylpropanoid biosynthesis/lignin biosynthesis), plant hormone signal transduction and the calcium signaling pathway. LncRNA target gene enrichment identified several target genes that were involved in plant hormones, and the expression of lncRNAs and their target genes was significantly influenced. Therefore, our results suggest that lncRNAs can regulate the metabolism and signal transduction of plant hormones, which play an important role in the responses of citrus plants to B deficiency stress. Co-expression network analysis indicated that 468 significantly differentially expressed genes may be potential targets of 90 lncRNAs, and a total of 838 matched lncRNA-mRNA pairs were identified. In summary, our data provides a rich resource of candidate lncRNAs and mRNAs, as well as their related pathways, thereby improving our understanding of the role of lncRNAs in response to B deficiency stress, and in symptom formation caused by B deficiency in the leaves of trifoliate orange.

Dirac semimetals based tunable narrowband absorber at terahertz frequencies.

In this paper, a bulk Dirac semimetals (BDSs) based tunable narrowband absorber at terahertz frequencies is proposed and it has the attractive property of being polarization-independent at normal incidence because of its 90° rotational symmetry. Numerical results show that the absorption bandwidth is about 1.469e-2 THz and the total quality factor Q, defined as Q = f0/Δf, reaches about 94.6, which can be attributed to the low power loss of the guided mode resonance in the dielectric layer. The simulation results are analyzed with coupled mode theory. Interestingly, on the premise of maintaining the absorbance at a level greater than 0.95, the absorption frequency can be tuned from 1.381 to 1.395 THz by varying the Fermi energy of BDSs from 50 to 80 meV. Our results may also provide potential applications in optical filter and bio-chemical sensing.

Tunable graphene-based plasmonic multispectral and narrowband perfect metamaterial absorbers at the mid-infrared region.

We numerically investigate the optical performance of a periodically patterned H-shaped graphene array by the finite-difference time-domain (FDTD) in the mid-infrared region. The simulated results reveal that absorption spectra of the proposed structure consist of two dramatic narrowband perfect absorption peaks located at 6.3 µm (Mode 1) and 8.6 µm (Mode 2) with high absorption coefficients of 99.65% and 99.80%, respectively. Two impressive absorption bandwidths that are the full width at half-maximum (FWHM) of the resonant frequency of 90 nm and 188 nm are obtained. The dipole resonance mode is supported by graphene ribbon at a wavelength of 6.3 µm. While the other absorption, attributed to the hybridized mode, is a new resonance that is different from the dipole resonance. The spectral position of the absorption peaks can be dynamically tuned by controlling the refractive index of the dielectric and the Fermi energy of graphene. Furthermore, we can obtain multispectral absorption peaks by applying multilayer graphene arrays. These design approaches enable us to control the number of absorption spectra and such absorbers will benefit the easy-to-fabricate nanophotonic devices for optical filtering, thermal detectors, and electromagnetic wave energy storage.

Toroidal resonance based optical modulator employing hybrid graphene-dielectric metasurface.

In this paper, we demonstrate the combination of a dielectric metasurface with a graphene layer to realize a high performance toroidal resonance based optical modulator. The dielectric metasurface consists of two mirrored asymmetric silicon split-ring resonators (ASSRRs) that can support strong toroidal dipolar resonance with narrow line width (~0.77 nm) and high quality (Q)-factor (~1702) and contrast ratio (~100%). Numerical simulation results show that the transmission amplitude of the toroidal dipolar resonance can be efficiently modulated by varying the Fermi energy EF when the graphene layer is integrated with the dielectric metasurface, and a max transmission coefficient difference up to 78% is achieved indicating that the proposed hybrid graphene/dielectric metasurface shows good performance as an optical modulator. The effects of the asymmetry degree of the ASSRRs on the toroidal dipolar resonance are studied and the efficiency of the transmission amplitude modulation of graphene is also investigated. Our results may also provide potential applications in optical filter and bio-chemical sensing.

The Nodulin 26-like intrinsic membrane protein OsNIP3;2 is involved in arsenite uptake by lateral roots in rice.

Previous studies have shown that the Nodulin 26-like intrinsic membrane protein (NIP) Lsi1 (OsNIP2;1) is involved in arsenite [As(III)] uptake in rice (Oryza sativa). However, the role of other rice NIPs in As(III) accumulation in planta remains unknown. In the present study, we investigated the role OsNIP3;2 in As(III) uptake in rice. When expressed in Xenopus laevis oocytes, OsNIP3;2 showed a high transport activity for As(III). Quantitative real-time RT-PCR showed that the expression of OsNIP3;2 was suppressed by 5 µM As(III), but enhanced by 20 and 100 µM As(III). Transgenic rice plants expressing OsNIP3;2pro-GUS showed that the gene was predominantly expressed in the lateral roots and the stele region of the primary roots. Transient expression of OsNIP3;2:GFP fusion protein in rice protoplasts showed that the protein was localized in the plasma membrane. Knockout of OsNIP3;2 significantly decreased As concentration in the roots, but had little effect on shoot As concentration. Synchrotron microfocus X-ray fluorescence showed decreased As accumulation in the stele of the lateral roots in the mutants compared with wild-type. Our results indicate that OsNIP3;2 is involved in As(III) uptake by lateral roots, but its contribution to As accumulation in the shoots is limited.

Microglia P2Y6 receptor is related to Parkinson's disease through neuroinflammatory process.

BACKGROUND: Microglia in the central nervous system (CNS) were reported to play crucial role in neurodegeneration. Previous studies showed that P2Y6 receptor (P2Y6R) mainly contributed to microglia activation and phagocytosis in CNS. However, the level of P2Y6R in Parkinson's disease (PD) patients is unclear. Therefore, we measured the level of P2Y6R in PD patients and speculated whether it could be a potential biomarker for PD. Given on the basis that P2Y6R was higher in PD patients, we further explored the mechanisms underlying P2Y6R in the pathogenesis of PD. METHODS: We tested the expression level of P2Y6R in the peripheral blood mononuclear cells (PBMCs) among 145 PD patients, 170 healthy controls, and 30 multiple system atrophy (MSA) patients. We also used a lipopolysaccharide (LPS)-stimulated microglial cell culture model to investigate (i) the effects of LPS on P2Y6R expression with western blot and RT-PCR, (ii) the effects of LPS on UDP expression using HPLC, (iii) the effects of UDP/P2Y6R signaling on cytokine expression using western blot, RT-PCR, and ELISA, and (iv) the signaling pathways activated by the P2Y6R involved in the neuroinflammation. RESULTS: Expression levels of P2Y6R in PD patients were higher than healthy controls and MSA patients. P2Y6R could be a good biomarker of PD. P2Y6R was also upregulated in LPS-treated BV-2 cells and involved in proinflammatory cytokine release through an autocrine loop based on LPS-triggered UDP secretion and accelerated neuroinflammatory responses through the ERK1/2 pathway. Importantly, blocking UDP/P2Y6R signaling could reverse these pathological processes. CONCLUSIONS: P2Y6R may be a potential clinical biomarker of PD. Blocking P2Y6R may be a potential therapeutic approach to the treatment of PD patients through inhibition of microglia-activated neuroinflammation.

Different metabolite profile and metabolic pathway with leaves and roots in response to boron deficiency at the initial stage of citrus rootstock growth.

Boron (B) is a microelement required for higher plants, and B deficiency has serious negative effect on metabolic processes. We concentrated on the changes in metabolite profiles of trifoliate orange leaves and roots as a consequence of B deficiency at the initial stage of growth by gas chromatography-mass spectrometry (GC-MS)-based metabolomics. Enlargement and browning of root tips were observed in B-deficient plants, while any obvious symptom was not recorded in the leaves after 30 days of B deprivation. The distinct patterns of alterations in metabolites observed in leaves and roots due to B deficiency suggest the presence of specific organ responses to B starvation. The accumulation of soluble sugars was occurred in leaves, which may be attributed to down-regulated pentose phosphate pathway (PPP) and amino acid biosynthesis under B deficiency, while the amount of most amino acids in roots was increased, indicating that the effects of B deficiency on amino acids metabolism in trifoliate orange may be a consequence of disruptions in root tissues and decreased protein biosynthesis. Several important products of shikimate pathway were also significantly affected by B deficiency, which may be related to abnormal growth of roots induced by B deficiency. Conclusively, our results revealed a global perspective of the discriminative metabolism responses appearing between B-deprived leaves and roots and provided new insight into the relationship between B deficiency symptom in roots and the altered amino acids profiling and shikimate pathway induced by B deficiency during seedling establishment.

Difference of Nonlinear Degree between Healthy and Diabetic Rat Erythocyte Fluorescence Spectrum.

Diabetes mellitus is one kind of chronic diseases which seriously threaten human health. It is very important to diagnose in the early stage. With the development of diabetes, the structure and function of erythrocyte in the blood will change. So the peak position and peak height of erythrocyte fluorescence spectrum are different. These differences can be used to determine the status of diabetes. In the selection of the difference of spectral signal as the feature vector, the nonlinear degree of fluorescence spectrum can be used as the feature vector. In order to describe the nonlinearity of the fluorescence spectrum signal, the nonlinear degree of the signal is described with the delay vector variance (DVV) method. By using the method of iterative amplitude adjusted Fourier transformation (IAAFT) to generate surrogate data of raw data, the nonlinear characteristic of the raw data is determined by comparing the DVV of the original data and the surrogate data. The variance of the original data is the horizontal coordinates, and the variance of the surrogate data is the longitudinal coordinates, thus the DVV scatter plot is drawn. The DVV scatter plot of healthy rat erythrocyte fluorescence spectrum is almost coincident with its diagonal, which means the nonlinear degree of healthy rat erythrocyte fluorescence spectrum is lower. The DVV scatter plot of diabetic rat erythrocyte fluorescence spectrum deviates from its diagonal, which means the nonlinear degree of healthy rat erythrocyte fluorescence spectrum is higher, also the corresponding amino acid spectrum nonlinearity is deeper. Therefore, it is proposed that the nonlinear difference between the healthy and diabetic fluorescence spectrum can be used as a feature of early diabetes diagnosis.