Optically and Electrically Tunable Dirac Points and Zitterbewegung in Graphene-Based Photonic Superlattices

We demonstrate that graphene-based photonic superlattices provide a versatile platform for electrical and all-optical control of photonic beams with deep-subwavelength accuracy. Specifically, by inserting graphene sheets into periodic metallo-dielectric structures one can design optical superlattices that posses photonic Dirac points (DPs) at frequencies at which the spatial average of the permittivity of the superlattice, $\bar{ \varepsilon}$, vanishes. Similar to the well-known zero-$\bar{n}$ bandgaps, we show that these zero-$\bar{\varepsilon}$ DPs are highly robust against structural disorder. We also show that, by tuning the graphene permittivity via the optical Kerr effect or electrical doping, one can induce a spectral variation of the DP exceeding \SI{30}{\nano\meter}, at mid-IR and THz frequencies. The implications of this wide tunability for the photonic Zitterbewegung effect in a vicinity of the DP are explored too.Comment: 5 pages, 5 figures, to appear in Phys. Rev. B as a Rapid Communicatio

Surface modes in plasmonic Bragg fibers with negative average permittivity

We investigate surface modes in plasmonic Bragg fibers composed of nanostructured coaxial cylindrical metal-dielectric multilayers. We demonstrate that the existence of surface modes is determined by the sign of the spatially averaged permittivity of the plasmonic Bragg fiber, \bar{% \varepsilon}. Specifically, localized surface modes occur at the interface between the cylindrical core with $\bar{\varepsilon}<0$ and the outermost uniform dielectric medium, which is similar to the topologically protected plasmonic surface modes at the interface between two different one-dimensional planar metal-dielectric lattices with opposite signs of the averaged permittivity. Moreover, when increasing the number of dielectric-metal rings, the propagation constant of surface modes with different azimuthal mode numbers is approaching that of surface plasmon polaritons formed at the corresponding planar metal/dielectric interface. Robustness of such surface modes of plasmonic Bragg fibers is demonstrated too.Comment: 10 pages, 5 figures, Optics Express, to be publishe

Topologically enhanced nonlinear optical response of graphene nanoribbon heterojunctions

We study the nonlinear optical properties of heterojunctions made of graphene nanoribbons (GNRs) consisting of two segments with either the same or different topological properties. By utilizing a quantum mechanical approach that incorporates distant-neighbor interactions, we demonstrate that the presence of topological interface states significantly enhances the second- and third-order nonlinear optical response of GNR heterojunctions that are created by merging two topologically inequivalent GNRs. Specifically, GNR heterojunctions with topological interface states display third-order harmonic hyperpolarizabilities that are more than two orders of magnitude larger than those of their similarly sized counterparts without topological interface states, whereas the secondorder harmonic hyperpolarizabilities exhibit a more than ten-fold contrast between heterojunctions with and without topological interface states. Additionally, we find that the topological state at the interface between two topologically distinct GNRs can induce a noticeable red-shift of the quantum plasmon frequency of the heterojunctions. Our results reveal a general and profound connection between the existence of topological states and an enhanced nonlinear optical response of graphene nanostructures and possible other photonic systems.Comment: 7 pages,5 figure

Profiling analysis of long non-coding RNAs in early postnatal mouse hearts

Mammalian cardiomyocytes undergo a critical hyperplastic-to-hypertrophic growth transition at early postnatal age, which is important in establishing normal physiological function of postnatal hearts. In the current study, we intended to explore the role of long non-coding (lnc) RNAs in this transitional stage. We analyzed lncRNA expression profiles in mouse hearts at postnatal day (P) 1, P7 and P28 via microarray. We identified 1,146 differentially expressed lncRNAs with more than 2.0-fold change when compared the expression profiles of P1 to P7, P1 to P28, and P7 to P28. The neighboring genes of these differentially expressed lncRNAs were mainly involved in DNA replication-associated biological processes. We were particularly interested in one novel cardiac-enriched lncRNA, ENSMUST00000117266, whose expression was dramatically down-regulated from P1 to P28 and was also sensitive to hypoxia, paraquat, and myocardial infarction. Knockdown ENSMUST00000117266 led to a significant increase of neonatal mouse cardiomyocytes in G0/G1 phase and reduction in G2/M phase, suggesting that ENSMUST00000117266 is involved in regulating cardiomyocyte proliferative activity and is likely associated with hyperplastic-to-hypertrophic growth transition. In conclusion, our data have identified a large group of lncRNAs presented in the early postnatal mouse heart. Some of these lncRNAs may have important functions in cardiac hyperplastic-to-hypertrophic growth transition

Efficacy and pharmacoeconomic advantages of Fufang Huangbai Fluid hydropathic compress in diabetic foot infections: a comparative clinical study with antimicrobial calcium alginate wound dressing

Objective: To compare the intervention effects and pharmacoeconomic advantages of Fufang Huangbai Fluid (FFHB) hydropathic compress versus Antimicrobial Calcium Alginate Wound Dressing (ACAWD) in the treatment of diabetic foot infections (DFI).Methods: Patients with DF who were hospitalized in the peripheral vascular Department of Dongzhimen Hospital of Beijing University of Chinese Medicine from December 2020 to February 2022 and met the inclusion and excluding criteria were allocated into the experimental group and control group through minimization randomization. The experimental group was treated with FFHB hydropathic compress for 2 weeks, while the control group was treated with ACAWD for the same duration. The wound healing of both groups was monitored for 1 month post-discharge. Clinical data from all eligible patients were collected, and differences in various indices between cohorts were analyzed.Results: 22 in the experimental group (including two fell off) and 20 in the control group. After the treatment, the negative rate of wound culture in the experimental group was 30% and that in the control group was 10%, There was no significant difference in the negative rate of wound culture and change trend of minimum inhibitory concentration (MIC) value of drug sensitivity (p &gt; 0.05). The infection control rate of the experimental group was 60%, and that of the control group was 25%. The difference between the two groups was statistically significant (χ2 = 5.013, p = 0.025). The median wound healing rate of the experimental group was 34.4% and that of the control group was 33.3%. There was no significant difference between the two groups (p &gt; 0.05). During the follow-up 1 month later, the wound healing rate in the experimental group was higher, and the difference was statistically significant (p = 0.047). Pharmacoeconomic evaluations indicated that the experimental group had greater cost-effectiveness compared to the control group.Conclusion: In the preliminary study, FFHB demonstrated comparable pathogenic and clinical efficacy to ACAWD in the treatment of mild DF infection, and exhibited superior pharmacoeconomic advantages. With the aid of infection control, the wound healing rate in the FFHB group showed notable improvement. Nevertheless, due to the limited sample size, larger-scale studies are warranted to further validate these findings.Clinical Trial Registration: (https://www.chictr.org.cn/showproj.aspx?proj=66175), identifier (ChiCTR2000041443)

Topological interface modes in photonic superlattices containing negative-index materials

We study the topological properties of one-dimensional photonic superlattices consisting of alternating layers of positive- and negative-index materials. We find that Zak phases of photonic bands of such superlattices are related to the signs of the spatial average of their permittivity and permeability, and the polarization of incident light. Specifically, the Zak phases for transverse electric (TE) waves (transverse magnetic (TM) waves) are determined by only the sign of the spatially averaged permittivity (permeability) of the lattices. Only a single-polarized (TM or TE) topological interface mode occurs at the interface between air and the superlattice with single-negative average permittivity or permeability. The crucial dependence of the topological property of the superlattice on the light polarization suggests a polarization filter application. The topologically protected interface modes for both TM and TE polarizations can coexist at the interface separating air and the superlattices with simultaneously negative signs of averaged permittivity and permeability. The robustness of such topological interface modes for both TM and TE polarizations is also demonstrated

Fundamental solitons in the nonlinear fractional Schrödinger equation with a

We address the existence and stability of fundamental solitons in a $\mathcal{PT}$ -symmetric Gaussian potential embedded into a material with fractional effects. Fundamental solitary waves with low power both in defocusing and focusing medium originate from the same eigenmode, and the smaller the Lévy index, the narrower the width of solitons. The linear stability analysis of fundamental solitons has been carried out in fractional dimension. $\mathcal{PT}$ -symmetric solitons are completely stable for a moderate Lévy index and gain/loss coefficient in a wide existence region

Dry and Wet Deposition Fluxes and Source of Atmospheric Mercury in the Forest in Southeast China

Studying atmospheric mercury (Hg) deposition in a forest system is a key step to understanding Hg biogeochemical cycles. However, observations based on Hg deposition fluxes in worldwide stations under forest ecosystems tend to differ considerably. In this work, a sampling station was set up in Dinghu Mountain to study the atmospheric Hg’s dry and wet deposition in typical forest ecosystems in Southeast China. One hundred and two atmospheric dry and wet deposition samples were collected with an automatic sampler from March 2009 to February 2010, and concentrations of Hg, magnesium (Mg), calcium (Ca), cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), and chromium (Cr) were detected. The results showed that the annual rainfall weighted average Hg concentration was 56.8 ng L−1, and 79.8 ng L−1 in the dry deposition. The mean total deposition flux was 158.8 μg m−2, and the wet deposition was predominant. The highest and lowest concentrations were detected in the high-temperature rainy season. Generally, the wet deposition flux was notably positively correlated with the rainfall. The source of atmospheric Hg deposition in Dinghu Mountain was analyzed using principal component analysis (PCA). The main source of Hg in precipitation was soil dust, followed by coal and fuel (automobile exhaust). The primary source of Hg in dry deposition was fuel (automobile exhaust), followed by soil dust, which indicates that Dinghu Mountain has been polluted by the anthropogenic sources of Hg