Compact topological polarization beam splitter based on all-dielectric fishnet photonic crystals.

Conventional polarization beam splitters (PBSs) suffer energy loss and signal distortion due to backscattering caused by disturbances. Topological photonic crystals provide backscattering immunity and anti-disturbance robustness transmission owing to the topological edge states. Here, we put forward a kind of dual-polarization air hole-type fishnet valley photonic crystal with a common bandgap (CBG). The Dirac points at the K point formed by different neighboring bands for transverse magnetic and transverse electric polarizations are drawn closer via changing the filling ratio of the scatterer. Then the CBG is constructed by lifting the Dirac cones for dual polarizations within a same frequency range. We further design a topological PBS using the proposed CBG via changing the effective refractive index at the interfaces which guide polarization-dependent edge modes. Based on these tunable edge states, the designed topological PBS (TPBS) achieves efficient polarization separation and is robust against sharp bends and defects, verified by simulation results. The TPBS's footprint is approximately 22.4 × 15.2 µ m 2, allowing high-density on-chip integration. Our work has potential application in photonic integrated circuits and optical communication systems.

Dirac cones with zero refractive indices in phoxonic crystals.

In this paper, simultaneous zero refractive indices (ZRIs) for both sound and light are realized on the basis of a 2D triangular lattice phoxonic crystal (PxC) with C6v symmetry. For the phononic mode, accidental phononic Dirac degeneracy at the center of Brillouin zone (BZ) occurs at a relatively high frequency which leads to the failure of the efficient medium theory; hence, it is no longer applicable to the realization of acoustic ZRI. We thus turn to a low-frequency phononic Dirac cone located at K point, the corner of the BZ, which shows in-phase pressure field oscillations in expanded unit cells. Using zone folding, we further reveal the cause for the characteristic of acoustic ZRI. For the photonic mode, a low-frequency photonic Dirac-like cone can be achieved by adjusting the geometric parameter due to the high contrast permittivity between scatterers and the matrix. When the phononic and photonic low-frequency Dirac dispersions coexist, the PxC can be mapped into a zero-index material for both sound and light at the same time. The new mechanism for simultaneously controlling sound and light helps to achieve acousto-optic synchronous cloaking and unidirectional transmission, which are numerically demonstrated.

Enhancement of lateral Casimir force on a rotating particle near hyperbolic metamaterial.

Enhancement of weak Casimir forces is extremely important for their practical detection and subsequent applications in variety of scientific and technological fields. We study the lateral Casimir forces acting on the rotating particles with small radius of 50 nm as well as that with large radius of 500 nm near the hyperbolic metamaterial made of silicon carbide (SiC) nanowires. It is found that the lateral Casimir force acting on the small particle of 50 nm near hyperbolic metamaterial with appropriate filling fraction can be enhanced nearly four times comparing with that acting on the same particle near SiC bulk in the previous study. Such enhancement is caused by the coupling between the resonance mode excited by nanoparticle and the hyperbolic mode supported by hyperbolic metamaterial. The results obtained in this study provide an efficient method to enhance the interaction of nanoscale objects.

Mechanical modulation of spontaneous emission of nearby nanostructured black phosphorus.

In this study, we investigate the spontaneous emission of a quantum emitter nearby black phosphorus (BP) sheet. The spontaneous emission can be modulated mechanically by rotating the BP sheet when the quantum emitter is placed parallel to the sheet. The spontaneous emission is dependent on the electron doping and rotation angle of BP with respect to the x-axis. The Purcell factor decreases with the increase in rotation angle under smaller electron doping. The Purcell factor increases with the increase in rotation angle under larger electron doping. The spontaneous emission of quantum emitter nearby two types of BP ribbon arrays tailored along armchair (type I) and zigzag (type II) directions is studied in detail. The spontaneous emission of quantum emitter parallel to type I is enhanced compared with that parallel to BP sheet. The spontaneous emission decreases remarkably for the quantum emitter parallel to type II compared with that parallel to BP sheet. The spontaneous emission can be flexibly modulated by rotating BP ribbon arrays mechanically in two types. The results obtained in this study provide a new method to actively modulate the spontaneous emission.

Strong coupling between excitons and magnetic dipole quasi-bound states in the continuum in WS2-TiO2 hybrid metasurfaces.

Enhancing the light-matter interactions in two-dimensional materials via optical metasurfaces has attracted much attention due to its potential to enable breakthrough in advanced compact photonic and quantum information devices. Here, we theoretically investigate a strong coupling between excitons in monolayer WS2 and quasi-bound states in the continuum (quasi-BIC). In the hybrid structure composed of WS2 coupled with asymmetric titanium dioxide nanobars, a remarkable spectral splitting and typical anticrossing behavior of the Rabi splitting can be observed, and such strong coupling effect can be modulated by shaping the thickness and asymmetry parameter of the proposed metasurfaces, and the angle of incident light. It is found that the balance of line width of the quasi-BIC mode and local electric field enhancement should be considered since both of them affect the strong coupling, which is crucial to the design and optimization of metasurface devices. This work provides a promising way for controlling the light-matter interactions in strong coupling regime and opens the door for the future novel quantum, low-energy, distinctive nanodevices by advanced meta-optical engineering.

Design of phoxonic virtual waveguides for both electromagnetic and elastic waves based on the self-collimation effect: an application to enhance acousto-optic interaction.

The dual beam guides for transverse-electric and transverse-magnetic polarizations of electromagnetic (EM) wave and elastic wave in defect-free phoxonic crystals are reported. The realization for phoxonic virtual waveguides relies on dual flat equifrequency contours (EFCs) enabling self-collimation for EM and elastic waves. As a possible application of our work, the enhanced acousto-optic (AO) interaction in this kind of defect-free phoxonic waveguide, just as it does in defect-based waveguides, is further studied. Results show that obvious shifts of the transmission peaks of EM waves exist for both polarizations during one period of the elastic wave, and single-phonon exchange dominates the AO interaction. This kind of phoxonic virtual waveguide provides an effective platform to enhance AO interaction and exhibits some advantage over defect-based waveguides by properly manipulating the photonic and phononic dispersion surfaces.

Simultaneous localization of photons and phonons within the transparency bands of LiNbO3 phoxonic quasicrystals.

We report the properties of dual phononic-photonic band gaps and localized modes of eightfold lithium niobate (LiNbO3) phoxonic quasicrystals (PhXQCs). Complete and large phoxonic band gaps are easily achieved despite the low refractive index of LiNbO3 substrate. Point defect intentionally introduced can form localized modes within both forbidden and transparency bands over a wide range of geometric parameters. Further analysis indicates that the localized modes within transparency bands originate from the intrinsic high-order rotational symmetry of quasiperiodic structures, which resemble whispering gallery modes. LiNbO3 PhXQCs provide a good candidate to enhance phononic-photonic interaction and show considerable advantage over the periodic counterparts.

Simultaneous large band gaps and localization of electromagnetic and elastic waves in defect-free quasicrystals.

We report numerically large and complete photonic and phononic band gaps that simultaneously exist in eight-fold phoxonic quasicrystals (PhXQCs). PhXQCs can possess simultaneous photonic and phononic band gaps over a wide range of geometric parameters. Abundant localized modes can be achieved in defect-free PhXQCs for all photonic and phononic polarizations. These defect-free localized modes exhibit multiform spatial distributions and can confine simultaneously electromagnetic and elastic waves in a large area, thereby providing rich selectivity and enlarging the interaction space of optical and elastic waves. The simulated results based on finite element method show that quasiperiodic structures formed of both solid rods in air and holes in solid materials can simultaneously confine and tailor electromagnetic and elastic waves; these structures showed advantages over the periodic counterparts.

Tunable THz absorption in graphene-based heterostructures.

We investigate THz absorption properties of graphene-based heterostructures by using characteristics matrix method based on conductivity. We demonstrate that the proposed structure can lead to perfect THz absorption because of strong photon localization in the defect layer of the heterostructure. The THz absorption may be tuned continuously from 0 to 100% by controlling the chemical potential through a gate voltage. By adjusting the incident angle or the period number of the two PCs with respect to the graphene layer, one can tailor the maximum THz absorption value. The position of the THz absorption peaks can be tuned by changing either the center wavelength or the thicknesses ratio of the layers constituting the heterostructure. Our proposal may have potentially important applications in optoelectronic devices.

Prognostic value of EGFR and p-EGFR in nasopharyngeal carcinoma: A systematic review and meta-analysis.

PURPOSE: To evaluate the prognostic effect and clinical significance of epidermal growth factor receptor and its phosphorlated form (EGFR/p-EGFR) in nasopharyngeal carcinoma. METHODS: A systematic review and meta-analysis was designed. We visited PubMed, Embase, China National Knowledge Infrastructure Database, Database of Chinese sci-tech periodicals, WanFang Database, and China Biology Medicine disc to search for Chinese and English publications of prospective studies and retrospective studies investigating the association of EGFR/p-EGFR and nasopharyngeal carcinoma prognosis from inception to April 2021. The inclusion criteria were that the samples should be pathologically confirmed as nasopharyngeal carcinoma and the expression of EGFR/p-EGFR should be detected via immunohistochemistry; the study should analyze the prognostic significance of EGFR/p-EGFR in nasopharyngeal carcinoma; hazard ratio (HR) and 95% confidence interval (CI) should be reported in the study or could be derived from survival curves; and the outcomes of the study should include overall survival (OS), disease-free survival (DFS), progression-free survival (PFS), and distant metastasis-free survival (DMFS). RESULTS: A total of 18 studies evaluating 1451 samples were included. For studies that reported OS as an outcome, EGFR overexpression indicated worse OS of nasopharyngeal carcinoma patients. The heterogeneity between studies was high (I2 = 91%, P < .01), and a random-effect model was used to combine the effect size (HR = 1.71, 95% CI [1.21, 2.41], P < .01). Further sensitivity analysis and prespecified subgroup analysis were performed to detect the source of heterogeneity, and the results showed that the heterogeneity could not be eliminated. Publication bias assessed by funnel plots and Begg test and Egger test was low (Begg test: P = .846 and Egger test: P = .074). p-EGFR was not correlated with the OS of nasopharyngeal carcinoma patients (HR = 1.01, 95% CI [0.88, 1.15], P = .92). For studies that reported DFS, EGFR overexpression was associated with worse DFS in patients with nasopharyngeal carcinoma (HR = 2.53, 95% CI [1.84, 3.47], P < .01). For studies that reported PFS, EGFR overexpression was not correlated with the PFS of nasopharyngeal carcinoma patients (HR = 1.86, 95% CI [0.90, 3.82], P = .09). For studies that reported DMFS, EGFR overexpression was not correlated with the DMFS of nasopharyngeal carcinoma patients, and high heterogeneity between studies was detected (I2 = 97%, P < .01). A random-effect model was used to combine the effect size (HR = 1.80, 95% CI [0.56, 5.76], P = .32). A sensitivity analysis was conducted. Publication bias was detected to be low (Begg test: P = .817 and Egger test: P = .954). There was no correlation between p-EGFR overexpression and DMFS in patients with nasopharyngeal carcinoma (HR = 1.20, 95% CI [0.95, 1.52], P = .12). CONCLUSION: In nasopharyngeal carcinoma patients, EGFR overexpression could be used as a biomarker that predicts poor OS and DFS, but not a prognostic biomarker for PFS and DMFS. The overexpression of p-EGFR was not shown to be associated with the prognosis of nasopharyngeal carcinoma patients and could not be used as a prognostic biomarker. ETHICS AND DISSEMINATION: This study was registered on the International Platform of Registered Systematic Review and Meta-analysis Protocols (INPLASY), and reported as stated by the Preferred Reporting Items for Systematic reviews and Meta-Analyses. Neither ethical approval nor informed consent was required since this study was conducted based on previous publications. INPLASY REGISTRATION NUMBER: INPLASY 202150010.

Enhancement of Casimir Friction between Graphene-Covered Topological Insulator.

Casimir friction is theoretically studied between graphene-covered undoped bismuth selenide (Bi2Se3) in detail. In the graphene/Bi2Se3 composite structure, the coupling of the hyperbolic phonon polaritons supported by Bi2Se3 with the surface plasmons supported by graphene can lead to the hybrid surface plasmon-phonon polaritons (SPPPs). Compared with that between undoped Bi2Se3, Casimir friction can be enhanced by more than one order of magnitude due to the contribution of SPPPs. It is found that the chemical potential that can be used to modulate the optical characteristic of SPPPs plays an important role in Casimir friction. In addition, the Casimir friction between doped Bi2Se3 is also studied. The friction coefficient between doped Bi2Se3 can even be larger than that between graphene-covered undoped Bi2Se3 for suitable chemical potential due to the contribution of unusual electron surface states. The results obtained in this work are not only beneficial to the study of Casimir frictions but also extend the research ranges of topological insulators.

Wideband slow light and dispersion control in oblique lattice photonic crystal waveguides.

We find that the angle between elementary lattice vectors obviously affects the bandwidth and dispersion of slow light in photonic crystal line-defect waveguides. When the fluctuation of group index is strictly limited in a +/-1% range, the oblique lattice structures with the angle between elementary lattice vectors slightly larger than 60 degrees have broader available bandwidth of flat band slow light than triangular lattice structures. For example, for the angle 66 degrees , there are increases of the available bandwidth from 20% to 68% for several different structures. For the same angle and a +/-10% variation in group velocity, when group indices are nearly constants of 30, 48.5, 80 and 130, their corresponding bandwidths of flat band reach 20 nm, 11.8 nm, 7.3 nm and 3.9 nm around 1550 nm, respectively. The increasing of bandwidth is related to the shift of the anticrossing point towards smaller wave numbers.

Continuous generation of soliton patterns in two-dimensional dissipative media by razor, dagger, and needle potentials.

We report dynamic regimes supported by a sharp quasi-one-dimensional (1D) ("razor"), pyramid-shaped ("dagger"), and conical ("needle") potentials in the 2D complex Ginzburg-Landau (CGL) equation with cubic-quintic nonlinearity. This is a model of an active optical medium with respective expanding antiwaveguiding structures. If the potentials are strong enough, they give rise to continuous generation of expanding soliton patterns by a 2D soliton initially placed at the center. In the case of the pyramidal potential with M edges, the generated patterns are sets of M jets for M < or = 5, or expanding polygonal chains of solitons for M > or = 6. In the conical geometry, these are concentric waves expanding in the radial direction.

[Rule of acupoint selection for cancer pain based on association rule and entropy clustering].

OBJECTIVE: To analyze the rule of acupoint selection for cancer pain based on data mining. METHODS: The published literature regarding acupuncture for cancer pain in the recent 10 years was searched in PubMed, CNKI, VIP and Wanfang database. The acupoint selection was summarized and analyzed by TCMISS V2.5. RESULTS: Totally 68 literature was collected and 73 acupoint prescriptions were included, involving 117 acupoints. These acupoints were mainly in bladder meridian, stomach meridian, liver meridian and spleen meridian. Among them, 40 acupoints used more than 4 times were identified, and the top three acupoints were Zusanli (ST 36, 65 times), Neiguan (PC 6, 55 times) and Taichong (LR 3, 50 times). A total of 68 acupoint combinations used more than 19 times were identified, and the top three acupoint combinations were Zusanli (ST 36)-Neiguan (PC 6), Taichong (LR 3)-Zusanli (ST 36) and Zusanli (ST 36)-Sanyinjiao (SP 6). There were 103 acupoint combinations with strong association; based on the entropy clustering algorithm, 20 new acupoint combinations and 10 new acupoint prescriptions were obtained. CONCLUSION: The main meridians for cancer pain are bladder meridian, stomach meridian, liver meridian and spleen meridian, with Zusanli (ST 36), Neiguan (PC 6), Taichong (LR 3), Hegu (LI 4), Sanyinjiao (SP 6) and ashi points as core acupoints, and regulating spleen-stomach and treating qi-blood are the main principles.

The transmission characteristics of surface plasmon polaritons in ring resonator.

A two-dimensional nanoscale structure which consists of two metal-insulator-metal (MIM) waveguides coupled to each other by a ring resonator is designed. The transmission characteristics of surface plasmon polaritons are studied in this structure. There are several types of modes in the transmission spectrum. These modes exhibit red shift when the radius of the ring increases. The transmission properties of such structure are simulated by the Finite-Difference Time-Domain (FDTD) method, and the eignwavelengths of the ring resonator are calculated theoretically. Results obtained by the theory of the ring resonator are consistent with those from the FDTD simulations.

The efficacy of gabapentin in reducing pain intensity and morphine consumption after breast cancer surgery: A meta-analysis.

BACKGROUND: The purpose of this meta-analysis from randomized controlled trials (RCTs) was to determine the efficacy and safety of the preoperative use of gabapentin for the treatment of acute and chronic postoperative pain following breast cancer surgery. METHODS: In November 2017, a systematic computer-based search was conducted in PubMed, Embase, Web of Science, Cochrane Library, and Google databases. RCTs comparing gabapentin with placebo in patients undergoing breast cancer surgery were retrieved. The primary endpoint was the visual analog scale (VAS) after surgery and 24 hours after surgery and total morphine consumption. The secondary outcomes were incidence of chronic pain and complications (the incidence of nausea). Software Stata 12.0 was used for meta-analysis. RESULTS: Finally, 9 RCTs were included in the meta-analysis. Results indicated that gabapentin was associated with reduced pain scores after surgery and 24 hours after surgery. Meanwhile, oral gabapentin was associated with a reduction of the total morphine consumption after breast cancer surgery. Similarly, gabapentin was associated with a reduction in the incidence of chronic pain and the incidence of nausea. CONCLUSIONS: Preoperative use of gabapentin was able to reduce acute and chronic postoperative pain, total morphine consumption and the occurrence of nausea following breast cancer surgery. Further studies should determine the optimal dose of gabapentin for pain control after breast cancer surgery.

Dependence of the sliding distance of a one-dimensional atom chain on initial velocity.

In our daily lives, a body with a high initial velocity sliding freely on a rough surface moves a longer distance than that with a low initial velocity. However, such a phenomenon may not occur in the microscopic world. The dynamical behavior of a one-dimensional atom chain (1DAC) sliding on a substrate is investigated in this study by using a modified Frenkel-Kontorova model, in which the vibration of atoms on the substrate is considered. The dependence of sliding distance on initial velocity is examined. Result shows that although sliding distance is proportional to the initial value for most velocities, such a linear relation does not exist in some special velocities. This phenomenon is explained by a theoretical analysis of phonon excitation. The physical process is divided into three stages. The first stage is a superlubric sliding process with small amplitude of the vibrication of the atoms. The single-mode phonon is excited in the second stage. In the third stage, the system exhibits instability because of multiple-mode phonon excitations. In addition, the dependence of the coupling strength between 1DAC and the substrate is investigated. The findings are helpful in understanding the energy dissipation mechanism of friction.

Broadband perfect light trapping in the thinnest monolayer graphene-MoS2 photovoltaic cell: the new application of spectrum-splitting structure.

The light absorption of a monolayer graphene-molybdenum disulfide photovoltaic (GM-PV) cell in a wedge-shaped microcavity with a spectrum-splitting structure is investigated theoretically. The GM-PV cell, which is three times thinner than the traditional photovoltaic cell, exhibits up to 98% light absorptance in a wide wavelength range. This rate exceeds the fundamental limit of nanophotonic light trapping in solar cells. The effects of defect layer thickness, GM-PV cell position in the microcavity, incident angle, and lens aberration on the light absorptance of the GM-PV cell are explored. Despite these effects, the GM-PV cell can still achieve at least 90% light absorptance with the current technology. Our proposal provides different methods to design light-trapping structures and apply spectrum-splitting systems.