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By proposing an effective method for the coupled modified Dirac equation, the effects of structure inversion asymmetry on the confined states in quantum dots of three-dimensional topological ultrathin films are investigated. It is found that the presence or absence of the quantized edge states can be controlled by the inversion asymmetry potential. The tuning of the potential to the spins of edge and nonedge states is quite different. In the presence of impurities, the mixing between the edge and nonedge states can be largely enhanced and effectively tuned by the potential. The finding will be useful to design relevant nanodevices. [ABSTRACT FROM AUTHOR]

The compensation mechanisms of defect complexes in N-doped and As-doped ZnSe are investigated. The results of discrete-variational local-density-functional method within a cluster model showed that the N(sub Se)-Zn-V(sub Se) complex is a more efficient acceptor compensator than the N(sub Se)-Zn(sub int) in N-doped ZnSe. It was also shown that the As(sub Se)-Zn(sub int) complex is a more efficient acceptor compensator than the As(sub Se)-Zn-V(sub Se) complex in the As-doped ZnSe.

Dried fig leaves were used as raw materials, distilled water was used as the extraction solvent, and the microwave method was used to extract polysaccharides in the experiment. The effect of liquid-to-material ratio, microwave power and microwave extraction time on yield of polysaccharides from fig leaves were investigated. The results showed that when the liquid-to-solid ratio was 30 mL/g, the microwave power was 300 W and the microwave extraction time was 3 min, the yield of polysaccharides from fig leaves reached 11.32%, and the experiments showed good repeatability, which has certain reference value for the development and utilization of fig leaf polysaccharides. [ABSTRACT FROM AUTHOR]

A series of imine-linked covalent organic frameworks (COF) are constructed under Sc(OTf)3 catalysis in a 1,4-dioxane/mesitylene mixture. The amount of Sc(OTf)3 catalyst strongly affects the structure of the as-synthesized COFs. When 0.005 equivalent Sc(OTf)3 is used, a crystalline COF with uniform micropores and high surface area is obtained. The as-synthesized COF evolves to a disordered structure with increase in the catalyst amount. Several imine-linked COFs show NH3 sensing ability at room temperature, and the NH3 sensing performance is strongly dependent on their electric conductivity. The imine-linked COF with a disordered structure has better electric conductivity than the crystalline imine-linked COF. The NH3 sensing ability of the imine-linked COF with a disordered structure is far better than that of the imine-linked COF with a crystalline structure. The excellent NH3 sensing ability, including a short response time, large response value and high sensing selectivity, as well as lower sensor baseline resistance were observed on the imine-linked COF with a disordered structure. The imine linkage was recognized as the active site for NH3 adsorption on the imine-linked COF. Both density functional theory (DFT) calculations and an in situ UV-Vis spectra experiment confirm a hydrogen bond formation between NH3 and imine linkage during the NH3 sensing process. [ABSTRACT FROM AUTHOR]

Objectives: To compare the prevalence of chronic periodontitis between men who had semen abnormalities and those who had normozoospermia through a case–control study. Materials and Methods: Male patients who visited the assisted reproduction clinic of a large general hospital and were diagnosed with semen abnormalities were included in the case group. The control group was composed of patients of the same clinic with normozoospermia. The semen analysis included sperm concentration, count and progressive and total motility, which were measured in the laboratory. A questionnaire and clinical periodontal examination were conducted for all participants. Logistic regression was performed to explore the relationship between chronic periodontitis and male infertility. Results: A total of 192 participants were included: 63 participants (32.8%) had some type of semen abnormality (case group), while 129 participants (67.2%) had normozoospermia (control group). The case group had a significantly higher prevalence of moderate/severe periodontitis than the control group (33.3% vs. 17.8%, p =.012). The logistic regression showed that participants who had moderate/severe periodontitis had a greater chance of having semen abnormalities after adjusting for other confounding factors (OR = 3.377, p =.005). Conclusions: Periodontitis is associated with semen abnormalities and sperm motility in men. [ABSTRACT FROM AUTHOR]

A macroscopic silver nanowire (AgNW) network is grown by solid state ionics method. The ion flow during growth of the AgNW network is controlled by maintaining a current in the order of 10−7 A. Scanning electron microscopy (SEM) analysis reveals that the growth direction of AgNWs in the network is irregular and spread evenly in all directions and the nanowires are 40–160 nm in diameter. The microcosmic mechanism of silver nanostructures grown by the solid state ionics method is established by real time and in situ SEM analysis of the growth process of the AgNW networks. To study the photoelectric properties of the network, a self-supported AgNW network sample (∼1 mm wide and 8 mm long) is irradiated with lasers of different wavelengths of 375, 405, 532, 633, 808, and 1064 nm and 10.6 μm, and changes in the current between the two ends of the sample are recorded. The network displays negative photoconductance effect, and the maximum light responsivity is 43 mA W−1. The network displays light responsivity in the ultraviolet light-to-mid-infrared light region, with response times of tens of milliseconds. These findings indicate that the AgNW network has broad application prospect in ultra-wide spectrum photoelectric detection. [ABSTRACT FROM AUTHOR]

The low-lying spectra of hydrogenic impurities in magnetic quantum dots of graphene are calculated numerically from the Dirac-Weyl equation. The positive and negative energy states are attracted and repelled, respectively, by the impurities. The zero-energy level is nondegenerate and its corresponding states split by the Coulomb potential into hole-like states. Modulation effects of the Coulomb potential on the spectra are explored by varying magnetic field and dot size. These behaviors can be confirmed by the corresponding electron probability densities and binding energies, which can be tested in future experiments. [ABSTRACT FROM AUTHOR]

A new kind of phototransistor based on graphene and a superionic conductor is fabricated by depositing a layer of RbAg4I5 on transferred graphene by a vacuum thermal evaporation method. Electrons in graphene and silver ions in RbAg4I5 form an ion–electron bound state (IEBS) at the interface due to Coulomb interactions. The bound state, which can be dissociated by photons, greatly influences the electronic conductivity of graphene. The binding energy between ions and electrons is an important parameter to determine the photon energy that can be absorbed to set the free bound state. Through the back-gate bias, we realize controllable modulation of binding energy. The binding energy between electrons and silver ions linearly decreases with the increase of gate voltage, resulting in the increased number of IEBSs that can be dissociated by photons, which is proved by experimental measurement and theoretical analysis. Owing to the decrease in binding energy, the response amplitudes can be increased by up to two orders of magnitude under the illumination of lasers. This phototransistor based on graphene and RbAg4I5 achieves controllable responsivity from several mA W−1 to several hundred mA W−1 while the response speed remains unchanged on the order of 100 milliseconds. This study, on the one hand, gives a better understanding of the modulation of ions on electron transport; on the other hand, it offers a new road for us to achieve modulation of photo-responses, and it is very promising to be applied in optoelectronic devices with current circuit technology. [ABSTRACT FROM AUTHOR]

Circadian clock genes in peripheral tissues usually play an important role in regulating the circadian rhythms. Light is the most important environmental signal for synchronizing endogenous rhythms with the daily light‐dark cycle, and compound eyes are known as the principal circadian photoreceptor for photic entrainment in most moths. However, there is little evidence for circadian timing in compound eyes. In the current study, we isolated the timeless gene, designated Ha‐tim (GenBank accession number: KM233162), from the cotton bollworm Helicoverpa armigera. Ha‐tim and period (Ha‐per) showed low messenger RNA levels in the compound eyes compared to the other tested adult organs. Ha‐tim and Ha‐per transcript levels were dependent on an endogenous rhythm that fluctuated over a daily cycle in the compound eyes and heads. The cycles of Ha‐tim and Ha‐per transcript levels followed similar time courses, and identical expression patterns of the two genes were observed in the compound eyes and heads. Ha‐tim and Ha‐per were down‐regulated in the compound eyes after light exposure, copulation and starvation. These results indicated that Ha‐tim and Ha‐per transcript levels were regulated by endogenous and exogenous factors. Our study helped to improve our understanding of the circadian clock machinery in compound eyes and other peripheral tissues. [ABSTRACT FROM AUTHOR]

An interdigitated gold (Au) nanofilm was introduced on graphene, supported by a p-type silicon (p-Si) substrate, as an optoelectronic photodetector based on an Au/graphene/p-Si heterojunction by a low-cost method. Tunable photocurrent (photoconductivity) response to laser power density was realized under the modulation of the Au nanofilm and the Si layer on the carrier transport through graphene. Photoelectric measurements demonstrated that the device generated positive photocurrent when illuminated at low laser power density and negative photocurrent when illuminated at high laser power density. Positive photocurrents of 9 μA and 5 μA were generated at 1.13 μW cm−2 (power ∼ 20 nW) and 0.32 μW cm−2 (power ∼ 40 nW) under irradiation of 532 nm and 1064 nm lasers, respectively; responsivities of up to 450 A W−1 and 125 A W−1, were achieved, respectively, owing to the increase in carrier density caused by photo-induced carrier injection. At high power density, the mobility of graphene declined due to the scattering effect between carriers and phonons (bolometric effect), which was further strengthened by the local high-temperature field caused by the Au nanofilm. The negative photocurrent of up to several milliamperes was clearly observed under irradiation of 532 nm and 1064 nm lasers. The photocurrent response versus power density behavior of the photodetector could be modulated by the source–drain bias and laser wavelength. The device had a rapid response rate of the order of several hundred microseconds and good stability. The photodetector realized high-speed conversion of light density to photocurrent with different signs, demonstrating good potential for future applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

The present study aimed to examine the effects of sodium selenite on the SW982 human synovial sarcoma cell line in relation to cell viability, apoptosis and autophagy. The results indicated that sodium selenite reduced cell viability and induced apoptosis by activating caspase‑3 and members of the poly (ADP‑ribose) polymerase and Bcl‑2 protein families in SW982 cells. Furthermore, autophagy was also suppressed by sodium selenite treatment in SW982 cells, and apoptosis was upregulated in cells co‑treated with sodium selenite and the autophagy inhibitor 3‑methyladenine. By contrast, apoptosis was downregulated when sodium selenite was combined with rapamycin, an inducer of autophagy. The results indicated that autophagy may protect cells from the cytotoxicity of sodium selenite. The present study results demonstrated that sodium selenite induced apoptosis and inhibited autophagy and autophagy‑protected cells from death by antagonizing sodium selenite‑induced apoptosis in SW982 cells in vitro. [ABSTRACT FROM AUTHOR]

Traditional TiO2 based photodetectors (PDs) suffer from high dark resistance, which increases loss of photoexcited charge carriers. Here, we report a new and simple way to improve the performance of PDs based on double-walled carbon nanotube (DWCNT)/TiO2 nanotube heterojunctions. Highly ordered TiO2 nanotube arrays were fabricated using a two-step anodic oxidation method, and coated with a DWCNT film, which functioned as a semitransparent electrode and a photoactive layer. Via pre-electroforming, the device was switched from a high resistance state (HRS) to a low resistance state (LRS). At an applied bias of 1 V, the dark resistance was reduced from 926 to 0.67 kΩ, as a result of the formation of oxygen vacancy related conducting filaments. The photoresponse (ΔI = Ip − Id, where Ip and Id represents photocurrent and dark current, respectively) of the PD in LRS reached 816.76 μA W−1 under 532 nm laser illumination and 802.89 μA W−1 under 1064 nm laser irradiation, which is 965 and 3980 times higher, respectively, than those obtained from the HRS device under the same conditions. This strategy for enhancing the photoresponse of TiO2 based PDs may have applications in further improving the power conversion efficiency of dye-sensitized solar cells. [ABSTRACT FROM AUTHOR]

We explore the photoconductive properties of double-walled carbon nanotube film under laser illumination at different wavelengths in both ambient air and vacuum. In our experimental measurements, the photoconductivity of the film shows a strong dependence on the wavelength of light and can be changed from negative to positive by fully removing oxygen. We propose that competition among photoexcitation, photodesorption, and surface plasmon polaritons is responsible for these interesting phenomena. Our results are expected to provide potential applications in the field of nano-optoelectronic sensors based on carbon nanotubes. [ABSTRACT FROM AUTHOR]

A structure for visible photosensors based on double-walled carbon nanotube (DWCNT) film/Cu2O nanoparticle (NP) film/TiO2 nanotube array (TNA) heterojunctions has been fabricated. Cu2O nanoparticles reduce dark current and enhance photoresponse of the heterojunctions. Consequently, the optoelectric performance is significantly enhanced compared to that of the heterojunctions without Cu2O nanoparticles. The photocurrent-to-dark current ratio reaches ∼1 × 104 under illumination at 405 nm and ∼3 × 104 under illumination at 532 nm, which is two orders of magnitude higher than the results of double-walled carbon nanotube film/TiO2 nanotube array heterojunctions under the same illumination density. Moreover, the response speed of the heterojunctions is greatly improved. [ABSTRACT FROM AUTHOR]

TiO2 nanotube arrays with remarkable visible photoluminescence were prepared by high magnetic field annealing in air at 450 °C due to the involvement of oxygen vacancies (OVs). A field with the intensities of 0, 2, 4, 6, and 8 T were applied in the annealing processing, along the directions set at 0°, 50°, and 90° from the surface normal of the substrate. The results demonstrated that the density of oxygen vacancies in TiO2 nanotubes can be controlled by varying the intensity and direction of the magnetic field. The mechanism for the effect of the high magnetic field has been investigated. This study opens an effective way to control the oxygen vacancies in nanomaterials to improve their performance. [ABSTRACT FROM AUTHOR]

(110) ZnO/(001) Nb-1 wt %-doped SrTiO3 n-n type heteroepitaxial junctions were fabricated using the pulse laser deposition method. A diodelike current behavior was observed. Different from conventional p-n junctions or Schottky diodes, the diffusion voltage was found to increase with temperature. At all temperatures, the forward current was perfectly fitted on the thermionic emission model. The band bending at the interface can qualitatively explain our results, and the extracted high ideality factor at low temperatures, as well as large saturation currents, is ascribed to the deep-level-assisted tunneling current through the junction. [ABSTRACT FROM AUTHOR]

Macroscopic-long Ag nanowires have been synthesized through an improved solid-state ionics method and characterized at different spatial scales. Using a bundle of as-fabricated Ag nanowires to connect with two bulk Ag electrodes, two Ag heterodimensional junctions are formed into an electrical circuit. Thermo- and photoinduced electromotive forces are observed and the corresponding voltages are measured in the circuit on the macroscale. For the photoinduced voltage, the fast dynamic response of the circuit, irradiated locally by 532 nm and 10.6 μm lasers, is exhibited. The studied low-dimensional effects need to be taken into account in future applications of Ag nanowires. [ABSTRACT FROM AUTHOR]

The polarization splitting of the exciton ground state in two laterally coupled quantum dots under an in-plane electric field is investigated, and its effective tuning is designed. It is found that there are significant Stark effect and anticrossing in energy levels. Due to the coupling between inter- and intradot states, the absolute value of polarization splitting is significantly reduced, and it could be tuned to zero by the electric field for proper interdot separations. The scheme of the authors is interesting for the research on the quantum dot–based entangled-photon source. [ABSTRACT FROM AUTHOR]

Two-mode photon-assisted transport through coupled nonidentical quantum dots is studied by designing the level structure of the system. It is found that a Λ-type three-level structure can be formed by modulating the shape and size of dots or by applying electric field. Based on the three-level system, current antiresonance phenomenon occurs due to the effect of coherent population trapping. Using the asymmetry of quantum dots, oscillating current can be produced by rotating the polarization direction of linearly polarized microwave. [ABSTRACT FROM AUTHOR]