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Aiming to address the problems of high cost, large size and complex structure of the traditional back-to-back three-level converter, this paper proposes a new dual-port three-level converter topology. This new topology reduces the number of switching devices and optimizes the system size through device multiplexing. Firstly, the operating principle of the proposed converter topology is analyzed in detail, outlining the six effective switching states, current flow paths, and corresponding dual-port output levels of the single leg, while also discussing and the voltage stresses of each switching device. Secondly, a level-shifting pulse width modulation for the proposed converter topology is investigated and designed, and the effect of modulating wave overlap is avoided by adding DC offsets. Thirdly, the key problems of the modulation scheme under both the common frequency and different frequency operation modes, such as the modulation regime range and phase angle difference constraints are analyzed. The principles for selecting DC offsets and constraint range of two-port modulation system in each operating mode are introduced. Finally, the different operating modes are verified using the DSP-FPGA-Typhoon HIL 402 experimental platform. The experimental results show that level-shifting pulse width modulation with DC offsets makes the output power quality of the converter better and the harmonic content lower on the premise of achieving stable output of voltage and current for the proposed converter topology.

Interacting with an evanescent wave, an achiral particle can experience a lateral optical force (LOF) in a direction which is perpendicular to that of the illuminating photon momentum while the system apparently has the left–right symmetry. Here, using the Cartesian multipole expansion theory, a general relationship between LOF and spin and momentum is established. Most importantly, it is demonstrated that an anomalous LOF exerted on an isotropic achiral particle of arbitrary size and composition is proportional to the optical transverse spin in the incident evanescent wave that carries pure transverse spin associated with spin‐momentum locking. Manifesting itself as a mechanical consequence of the Berry phase effect, this anomalous LOF suggests a direct detectability of the transverse spin of light, as well as mimicking the transverse shift of light in the spin Hall effect of photons. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to investigate the prognostic significance of PD-1 inhibitor therapy in nasopharyngeal carcinoma (NPC) and to develop a nomogram to estimate individual risks. Methods: We retrospectively analyzed 162 NPC patients who were administered the PD-1 inhibitor combined with radiotherapy and chemotherapy at the Sun Yat-Sen University Cancer Center. In total, 108 NPC patients were included in the training cohort and 54 NPC patients were included in the validation cohort. Univariate and multivariate Cox survival analyses were performed to determine the prognostic factors for 1-year and 2-year progression-free survival (PFS). In addition, a nomogram model was constructed to predict the survival probability of PFS. A consistency index (C-index), a decision curve, a clinical impact curve, and a standard curve were used to measure predictive accuracy, the clinical net benefit, and the consistency of prognostic factors. Results: Univariate and multivariate analyses indicated that the metastasis stage, the levels of ALT, the AST/ALT ratio, and the LDH were independent risk factors associated with the prognosis of PD-1 inhibitor therapy. A nomogram based on these four indicators was constructed and the Kaplan–Meier survival analysis showed that patients with a higher total score have a shorter PFS. The C-index of this model was 0.732 in the training cohort and 0.847 in the validation cohort, which are higher than those for the TNM stages (training cohort: 0.617; validation cohort: 0.727; p <0.05). Decision Curve Analysis (DCA), Net Reclassification Improvement (NRI), and Integrated Discrimination Improvement (IDI) showed that our model has better prediction accuracy than TNM staging. Conclusions: Predicting PFS in NPC patients based on liver function-related indicators before PD-1 treatment may help clinicians predict the efficacy of PD-1 treatment in these patients. [ABSTRACT FROM AUTHOR]

Based on the effective medium theory, we designed a simplified transformation media bending waveguide by use of only three kinds of isotropic material in an alternating layered structure. The design can be used to guide incoming waves smoothly along the bending part of a waveguide with slight distortions. Numerical simulations are performed to illustrate its functionality. OCIS codes: 260.2710, 260.2110, 160.1190, 230.0230.

A similarity was noted between the transient responses of electrorheological fluids to square-wave electric fields with high frequency and that to the field with very low frequency, or the sudden applied direct current field. A similarity was also observed in the stress rise processes in both cases. These were the results of an examination of transient responses of the fluids to the fields in steady shear, using computational simulation method.

Linear‐dielectric‐based in‐plane optical design is attractive yet challenging in nano‐optical technologies when combined with the compatibility with complementary metal‐oxide‐semiconductor technology. Here, by exciting an electric symmetric dipole mode (ESDM), exploiting the interplay between an electric quadrupole mode and a magnetic dipole mode in a homogeneous isotropic linear dielectric rod, an in‐plane retroreflector is successfully realized in the case of no dependence on asymmetry arising from anisotropic/bianisotropic materials, complex unit cell, or asymmetric environments. The ESDM is analogous to an electric dipole (ED) in the sense that its radiation is overwhelmingly dominant in the forward and backward directions, while its phase symmetry is in stark contrast to the antisymmetry of ED modes. The studies herein show symmetric dipole modes are one of general mechanisms for retroreflection. Such a retroreflector combines many other outstanding advantages such as low loss, unitary efficiency, and simple configuration with low fabrication demands. The in‐plane manipulation for waves makes it an appealing platform for manipulating particles and developing on‐chip optical cavities, light sources in integrated optical circuits, optical parametric oscillators, and interferometers. [ABSTRACT FROM AUTHOR]

By a rigorous full-wave approach, a systemic study is made on the magnetic resonance of slotted circular cylinder resonators (SCCRs) made of a perfect conductor for the lossless case. This is a two-dimensional analog of the split-ring resonator and may serve as an alternative type of essential constituent of electromagnetic metamaterials. It is found that the resonance frequency can be modulated by changing the geometrical parameters and the dielectrics filling in the cavity and the slot. An approximate empirical expression is presented for magnetic resonance frequency of SCCRs from the viewpoint of an L-C circuit system. Finally, it is demonstrated that the SCCR structure can be miniaturized to less than 1/150 resonant wavelength in size with the dielectrics available currently. [ABSTRACT FROM AUTHOR]

Globally, nitrogen deposition increment has caused forest structural changes due to imbalanced plant nitrogen metabolism and subsequent carbon assimilation. Here, a 2 consecutive-year experiment was conducted to reveal the effects of canopy addition of nitrogen (CAN) on nitrogen absorption, assimilation, and allocation in leaves of three subtropical forest woody species ( Castanea henryi , Ardisia quinquegona , and Blastus cochinchinensis ). We hypothesized that CAN altered leaf nitrogen absorption, assimilation and partitioning of different plants in different ways in subtropical forest. It shows that CAN increased maximum photosynthetic rate (A max ), photosynthetic nitrogen use efficiency (PNUE), and metabolic protein content of the two understory species A. quinquegona and B. cochinchinensis . By contrary, for the overstory species, C. henryi , A max , PNUE, and metabolic protein content were significantly reduced in response to CAN. We found that changes in leaf nitrogen metabolism were mainly due to the differences in enzyme (e.g. Ribulose-1,5-bisphosphate carboxylase, nitrate reductase, nitrite reductase and glutamine synthetase) activities under CAN treatment. Our results indicated that C. henryi may be more susceptible to CAN treatment, and both A. quinquegona and B. cochinchinensis could better adapt to CAN treatment but in different ways. Our findings may partially explain the ongoing degradation of subtropical forest into a community dominated by small trees and shrubs in recent decades. It is possible that persistent high levels of atmospheric nitrogen deposition will lead to the steady replacement of dominant woody species in this subtropical forest. [ABSTRACT FROM AUTHOR]

Graphene is an excellent multi-functional platform for electrons, photons, and phonons due to exceptional electronic, photonic, and thermal properties. When combining its extraordinary mechanical characteristics with optical properties, graphene-based nanostructures can serve as an appealing platform for optomechanical applications at the nanoscale. Here, we demonstrate, using full-wave simulations, the emergence of extremely strong bipolar optical forces, or, optical binding and anti-binding, between a pair of coupled graphene nanoribbons, due to the remarkable confinement and enhancement of optical fields arising from the large effective mode indices. In particular, the binding and anti-binding forces, which are about two orders of magnitude stronger than that in metamaterials and high-Q resonators, can be tailored by selective excitation of either the even or the odd optical modes, achievable by tuning the relative phase of the lightwaves propagating along the two ribbons. Based on the coupled mode theory, we derive analytical formulae for the bipolar optical forces, which agree well with the numerical results. The attractive optical binding force Fby and the repulsive anti-binding force Fay exhibit a remarkably different dependence on the gap distance g between the nanoribbons and the Fermi energy EF, in the forms of UGRAPHIC DISPLAY="INLINE" ID="UGT1" SRC="UGT1"/ and Fay∝ 1/E2F. With EF dynamically tunable by bias voltage, the bipolar forces may provide a flexible handle for active control of the nanoscale optomechanical effects, and also, might be significant for optoelectronic and optothermal applications as well. [ABSTRACT FROM AUTHOR]

Previous research has focused on the involvement of reactive oxygen species (ROS) in cell wall loosening and cell extension in plant vegetative growth, but few studies have investigated ROS functions specifically in plant reproductive organs. In this study, ROS levels and antioxidant enzyme activities were assessed in Pisum sativum and Brassica chinensis pods at five developmental stages. In juvenile pods, the high levels of O2.− and.OH indicates that they had functions in cell wall loosening and cell elongation. In later developmental stages, high levels of.OH were also related to increases in cell wall thickness in lignified tissues. Throughout pod development, most of the O2.− was detected on plasma membranes of parenchyma cells and outer epidermis cells of the mesocarp, while most of the H2O2 was detected on plasma membranes of most cells throughout the mesocarp. This suggests that these sites are presumably the locations of ROS generation. The antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) apparently contributed to ROS accumulation in pod wall tissues. Furthermore, specifically SOD and POD were found to be associated with pod growth through the regulation of ROS generation and transformation. Throughout pod development, O2.− decreases were associated with increased SOD activity, while changes in H2O2 accumulation were associated with changes in CAT and POD activities. Additionally, high POD activity may contribute to the generation of.OH in the early development of pods. It is concluded that the ROS are produced in different sites of plasma membranes with the regulation of antioxidant enzymes, and that substantial ROS generation and accumulation are evident in cell elongation and cell wall loosening in pod wall cells. [ABSTRACT FROM AUTHOR]

Previous research has focused on the involvement of reactive oxygen species (ROS) in cell wall loosening and cell extension in plant vegetative growth, but few studies have investigated ROS functions specifically in plant reproductive organs. In this study, ROS levels and antioxidant enzyme activities were assessed in Pisum sativum and Brassica chinensis pods at five developmental stages. In juvenile pods, the high levels of O2.− and.OH indicates that they had functions in cell wall loosening and cell elongation. In later developmental stages, high levels of.OH were also related to increases in cell wall thickness in lignified tissues. Throughout pod development, most of the O2.− was detected on plasma membranes of parenchyma cells and outer epidermis cells of the mesocarp, while most of the H2O2 was detected on plasma membranes of most cells throughout the mesocarp. This suggests that these sites are presumably the locations of ROS generation. The antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) apparently contributed to ROS accumulation in pod wall tissues. Furthermore, specifically SOD and POD were found to be associated with pod growth through the regulation of ROS generation and transformation. Throughout pod development, O2.− decreases were associated with increased SOD activity, while changes in H2O2 accumulation were associated with changes in CAT and POD activities. Additionally, high POD activity may contribute to the generation of.OH in the early development of pods. It is concluded that the ROS are produced in different sites of plasma membranes with the regulation of antioxidant enzymes, and that substantial ROS generation and accumulation are evident in cell elongation and cell wall loosening in pod wall cells. [ABSTRACT FROM AUTHOR]

We present experimental demonstrations that the material consists of self-biased Sr-ferrite rods is the lower loss left-handed material (LHM). Clear negative refractions are observed in refraction experiments with the wedge shaped samples made from this material, and negative effective refractive index n = -1 is measured. The attenuation of the sample is about 0.55 dB/cm obtained from transmission measurements much lower than other known LHMs. Our configuration avoids the bias magnetic fields required for LHMs made of soft magnetic materials and extremely high permittivity needed for making LHMs with purely dielectrics, which greatly improves its impedance mismatch with the air. [ABSTRACT FROM AUTHOR]

It is experimentally demonstrated that within the photonic band gap induced by magnetic surface plasmon (MSP) resonance in a honeycomb magnetic photonic crystal, there can exist self-guiding electromagnetic chiral edge states whose dispersion curves are insensitive to the surface morphology when the system is truncated. The unique characteristic of the MSP induced edge states enables flexible design of robust unidirectional subwavelength waveguides that contain bends at various angles, providing an alternative way for manipulating electromagnetic waves at subwavelength scales. [ABSTRACT FROM AUTHOR]

Leaves of the two new chlorophyll b-less rice mutants VG28-1, VG30-5 and the wild type rice cv. Zhonghua 11 were subjected to temperatures 28, 36, 40, 44 and 48°C in the dark for 30 min or gradually elevated temperature from 30°C to 80°C at 0.5°C/min. The thermostability of photosynthetic apparatus was estimated by the changes in chlorophyll fluorescence parameters, photosynthetic rate and pigment content, chloroplast ultrastructure and tissue location of H2O2 accumulation. There were different patterns of Fo-temperature curves between the Chl b-less mutants and the wild type plant, and the temperature of Fo rising threshold was shifted 3°C lower in the Chl b-less mutants (48°C) than in the wild type (51°C). At temperature up to about 45°C, chloroplasts were swollen and thylakoid grana became misty accompanied with the complete loss of photosynthetic oxygen evolution in the two Chl b-less mutants, but chloroplast ultrastructure in the wild type showed no obvious alteration. After 55°C exposure, the disordered thylakoid and significant H2O2 accumulation in leaves were found in the two Chl b-less mutants, whereas in the wild type plant, less H2O2 was accumulated and the swollen thylakoid still maintained a certain extent of stacking. A large extent of the changes in qP, NPQ and Fv/Fm was consistent with the Pn decreasing rate in the Chl b-less mutants during high temperature treatment as compared with the wild type. The results indicated that the Chl b-less mutants showed a tendency for higher thermosensitivity, and loss of Chl b in LHC II could lead to less thermostability of PSII structure and function. Heat damage to photosynthetic apparatus might be partially attributed to the internal oxidative stress produced at severely high temperature. [ABSTRACT FROM AUTHOR]

The imaging properties of uniaxially anisotropic negative refractive index materials have been investigated theoretically. Based on an accurate theoretical formulation, we have discussed in detail whether and under what conditions the slabs of uniaxially anisotropic negative refractive index materials will have the power to focus perfectly all Fourier components of an image. It was shown that if the effects of absorption and dispersion can be neglected, under some particular conditions the slabs of uniaxially anisotropic negative refractive index materials will have the power to focus perfectly all E-mode or all H-mode or both E- and H-mode Fourier components of an image. It was also shown that perfect focus cannot occur in the presence of absorption and dispersion, but if the effects of absorption and dispersion are rather small, excellent focus can still occur. [Copyright &y& Elsevier]

A lattice Boltzmann method is proposed to simulate the two-dimensional membrane. Numerical simulation shows that at a critical value of membrane tension, the pattern of the membrane at transient state behaves like a standing wave with a node staying at rest. In addition, when the membrane is relatively soft or stiff, it will evolve into a steady-state close to its initial straight pattern. [ABSTRACT FROM AUTHOR]

The computer simulation method has been used to study the structural formation and transition of electro-magneto-rheological (EMR) fluids under compatible electric and magnetic fields. When the fields are applied simultaneously and perpendicularly to each other, the particles rapidly arrange into two-dimensional close-packed layer structures parallel to both fields. The layers then combine together to form thicker sheet-like structures, which finally relax into three-dimensional close-packed structures with the help of the thermal fluctuations. On the other hand, if the electric field is applied firstly to induce the body-centered tetragonal (BCT) columns in the system, and then the magnetic field is applied in the perpendicular direction, the BCT to face-centered cubic (FCC) structure transition is observed in very short time. Following that, the structure keeps on evolving due to the demagnetization effect and finally form the three-dimensional close-packed structures. [ABSTRACT FROM AUTHOR]

The genetic algorithms (GA) have been successfully applied to optimization problems in a variety of areas. In this paper, some modifications to GA are designed to study their performance and efficiency on a typical 2D system, 2D Ising spin glass. In particular, two kinds of modified GAs are compared for their searching ability (performance) and efficiency (convergence), by presenting a direct and visual criterion. Finally, some constructive comments and prospects on GA are presented. [ABSTRACT FROM AUTHOR]

We demonstrate a sharply asymmetric reflection in a geometrically symmetric magnetic metamaterial (MM) system, which originates from the coupling of electromagnetic (EM) wave to magnetic surface plasmon resonance states and the broken time reversal symmetry in MM. Based on this effect, we have designed unidirectional EM waveguide, wave bender, and beam splitter. Our simulations indicate that the designs possess the merits of robustness against strong defect and disorder, controllability with an external magnetic field, in addition to the finite working bandwidth and the high transmission efficiency. [ABSTRACT FROM AUTHOR]

Industrial pollutants induce the production of toxic reactive oxygen species (ROS) such as O2.−, H2O2, and ·OH in plants, but they have not been well quantified or localized in tissues and cells. This study evaluated the pollutant- (HSO3−, NH4NO3, Al3+, Zn2+, and Fe2+) induced toxic effects of ROS on the aerial roots of Chinese banyan (Ficus microcarpa). Root cell viability was greatly reduced by treatment with 20 mM NaHSO3, 20 mM NH4NO3, 0.2 mM AlCl3, 0.2 mM ZnSO4, or 0.2 mM FeSO4. Biochemical assay and histochemical localization showed that O2.− accumulated in roots in response to pollutants, except that the staining of O2.− under NaHSO3 treatment was not detective. Cytochemical localization further indicated that the generated O2.− was present mainly in the root cortex, and pith cells, especially in NH4NO3- and FeSO4-treated roots. The pollutants also caused greatly accumulated H2O2 and ·OH in aerial roots, which finally resulted in lipid peroxidation as indicated by increased malondialdehyde contents. We conclude that the F. microcarpa aerial roots are sensitive to pollutant-induced ROS and that the histochemical localization of O2.− via nitrotetrazolium blue chloride staining is not effective for detecting the effects of HSO3− treatment because of the treatment's bleaching effect. [ABSTRACT FROM AUTHOR]