Annealing Effect on Photovoltaic Performance of CdSe Quantum-Dots-Sensitized TiO2 Nanorod Solar Cells

Large area rutile TiO₂ nanorod arrays were grown on F:SnO₂ (FTO) conductive glass using a hydrothermal method at low temperature. CdSe quantum dots (QDs) were deposited onto single-crystalline TiO₂ nanorod arrays by a chemical bath deposition (CBD) method to make a photoelectrode. The solar cell was assembled using a CdSe-TiO₂ nanostructure as the photoanode and polysulfide solution as the electrolyte. The annealing effect on optical and photovoltaic properties of CdSe quantum-dotssensitized TiO₂ nanorod solar cells was studied systematically. A significant change of the morphology and a regular red shift of band gap of CdSe nanoparticles were observed after annealing treatment. At the same time, an improved photovoltaic performance was obtained for quantum-dots-sensitized solar cell using the annealed CdSe-TiO₂ nanostructure electrode. The power conversion efficiency improved from 0.59% to 1.45% as a consequence of the annealing effect. This improvement can be explained by considering the changes in the morphology, the crystalline quality, and the optical properties caused by annealing treatment

Double-loop sliding mode control of reentry hypersonic vehicle with RCS

In order to solve the problem of insufficient aerodynamic moment caused by thin air in the re-entry stage of hypersonic vehicle, this paper establishes an attitude angle model of hypersonic vehicle with reaction control system (RCS), and derives its affine linear model to decoupled the internal and external loop. According to the dead zone and saturation characteristics of RCS thruster, a control method to convert continuous moment into discrete switching instruction using pulse width modulation (PWM) is proposed. Since the number of thrusters is usually redundant, the installation matrix of thrusters in the body coordinate is established, and the command moment is coordinately distributed to the individual thrusters. Then a double-loop sliding mode controller (DSMC) is designed to achieve attitude stability and trajectory tracking. Finally, the simulation results show that DSMC has higher maneuverability, fewer thruster switches and stronger robustness to interference

Atomic-layer molybdenum sulfide optical modulator for visible coherent light

Coherent light sources in the visible range are playing important roles in our daily life and modern technology, since about 50% of the capability of the our human brains is devoted to processing visual information. Visible lasers can be achieved by nonlinear optical process of infrared lasers and direct lasing of gain materials, and the latter has advantages in the aspects of compactness, efficiency, simplicity, etc. However, due to lack of visible optical modulators, the directly generated visible lasers with only a gain material are constrained in continuous-wave operation. Here, we demonstrated the fabrication of a visible optical modulator and pulsed visible lasers based on atomic-layer molybdenum sulfide (MoS 2), a ultrathin two-dimensional material with about 9-10 layers. By employing the nonlinear absorption of the modulator, the pulsed orange, red and deep red lasers were directly generated. Besides, the present atomic-layer MoS 2 optical modulator has broadband modulating properties and advantages in the simple preparation process. The present results experimentally verify the theoretical prediction for the low-dimensional optoelectronic modulating devices in the visible wavelength region and may open an attractive avenue for removing a stumbling block for the further development of pulsed visible lasers

Fine Structure of the Sensilla and Immunolocalisation of Odorant Binding Proteins in the Cerci of the Migratory Locust, Locusta migratoria

Using light and electron microscopy (both scanning and transmission), we observed the presence of sensilla chaetica and hairs on the cerci of the migratory locust, Locusta migratoria L. (Orthoptera: Acrididae). Based on their fine structures, three types of sensilla chaetica were identified: long, medium, and short. Males presented significantly more numbers of medium and short sensilla chaetica than females (p<0.05). The other hairs can also be distinguished as long and short. Sensilla chaetica were mainly located on the distal parts of the cerci, while hairs were mostly found on the proximal parts. Several dendritic branches, enveloped by a dendritic sheath, are present in the lymph cavity of the sensilla chaetica. Long, medium, and short sensilla chaetica contain five, four and three dendrites, respectively. In contrast, no dendritic structure was observed in the cavity of the hairs. By immunocytochemistry experiments only odorant-binding protein 2 from L. migratoria (LmigOBP2) and chemosensory protein class I from the desert locust, Schistocerca gregaria Forsskål (SgreCSPI) strongly stained the outer lymph of sensilla chaetica of the cerci. The other two types of hairs were never labeled. The results indicate that the cerci might be involved in contact chemoreception processes

Gut microbiota influences feeding behavior via changes in olfactory receptor gene expression in Colorado potato beetles

The Colorado potato beetle (CPB) is an internationally recognized plant quarantine pest that causes serious losses to potato agricultural production. The gut microbiota plays an important role in its growth and development, and the olfactory system plays an important role in insect feeding behavior. The gut microbiota is known to be capable of inducing changes in the olfactory systems of insects. However, the way these associated gut microbes influence the feeding-related behaviors of CPBs remains unclear. To explore the relationship between them, fresh potato leaves immersed in a mixture of five antibiotics (tetracycline, penicillin, ofloxacin, ciprofloxacin, and ampicillin) at specific concentrations for 1 h were fed to adult CPBs to reduce the abundance of gut microbes. We found that the feeding behavior of CPBs was significantly affected by the gut microbiota and that Pseudomonas was significantly higher in abundance in the control group than in the antibiotic group. We then used transcriptome sequencing to explore the differences in olfactory receptor genes in the heads of non-treatment and antibiotic-fed CPBs. Through Illumina Hiseq™ sequencing and screening of differential genes, we found that the olfactory receptor gene LdecOR9 was significantly upregulated and LdecOR17 was significantly downregulated after antibiotic feeding. A real-time polymerase chain reaction was used to verify the changes in olfactory receptor gene expression in the non-treatment groups and antibiotic-treated groups. The feeding behavior was partially rescued after CPBs were re-fed with intestinal bacteria. These results indicate that a certain amount of gut microbiota can result in the loss of the olfactory discrimination ability of CPBs to host plants. In summary, this study investigated the relationship between gut microbiota and olfactory genes, providing a reference for research on microbial control

End-of-treatment anti-HBs levels and HBeAg status identify durability of HBsAg loss after PEG-IFN discontinuation

BackgroundHepatitis B surface antigen (HBsAg) loss, namely, the functional cure, can be achieved through the pegylated interferon (PEG-IFN)-based therapy. However, it is an unignorable fact that a small proportion of patients who achieved functional cure develop HBsAg reversion (HRV) and the related factors are not well described.MethodsA total of 112 patients who achieved PEG-IFN-induced HBsAg loss were recruited. HBV biomarkers and biochemical parameters were examined dynamically. HBV RNA levels were assessed in the cross-sectional analysis. The primary endpoint was HRV, defined as the reappearance of HBsAg after PEG-IFN discontinuation.ResultsHRV occurred in 17 patients during the follow-up period. Univariable analysis indicated that hepatitis B e antigen (HBeAg) status, different levels of hepatitis B surface antibody (anti-HBs), and hepatitis B core antibody (anti-HBc) at the end of PEG-IFN treatment (EOT) were significantly associated with the incidence of HRV through using the log-rank test. Additionally, time-dependent receiver operating characteristic (ROC) analysis showed that the anti-HBs was superior to anti-HBc in predictive power for the incidence of HRV during the follow-up period. Multivariable Cox proportional hazard analysis found that anti-HBs ≥1.3 log10IU/L (hazard ratio (HR), 0.148; 95% confidence interval (CI), 0.044-0.502) and HBeAg negativity (HR, 0.183; 95% CI, 0.052-0.639) at EOT were independently associated with lower incidence of HRV. Cross-sectional analysis indicated that the HBV RNA levels were significantly correlated with the HBsAg levels in patients with HRV (r=0.86, p=0.003).ConclusionsEOT HBeAg negativity and anti-HBs ≥1.3 log10IU/L identify the low risk of HRV after PEG-IFN discontinuation

Fs-laser-written thulium waveguide lasers Q-switched by graphene and MoS2

[EN]We report the generation of mid-infrared (~2 µm) high repetition rate (MHz) sub-100 ns pulses in buried thulium-doped monoclinic double tungstate crystalline waveguide lasers using two-dimensional saturable absorber materials, graphene and MoS2. The waveguide (propagation losses of ~1 dB/cm) was micro-fabricated by means of ultrafast femtosecond laser writing. In the continuous-wave regime, the waveguide laser generated 247 mW at 1849.6 nm with a slope efficiency of 48.7%. The laser operated at the fundamental transverse mode with a linearly polarized output. With graphene as a saturable absorber, the pulse characteristics were 88 ns / 18 nJ (duration / energy) at a repetition rate of 1.39 MHz. Even shorter pulses of 66 ns were achieved with MoS2. Graphene and MoS2 are therefore promising for high repetition rate nanosecond Q-switched infrared waveguide lasers

Gas nitriding of M2 high-speed steel for improving the surface mechanical properties of rolling dies

Les molettes de filetages en acier rapide M2 pour la fabrication de vis de freins de stationnement électriques sont souvent confrontées à une défaillance prématurée en service. Les dommages et l'initiation des fissures se produisent plusieurs micromètres sous la surface du filet de la filière en raison de la charge élevée de contact de roulement de surface, des effet de glissement, et par la présence de gros carbures. Une analyse de cas industriel utilisant le critère de fatigue de Dang Van montre que la nitruration augmente la résistance à la fatigue en proche surface du matériau.Les cinétiques de nitruration gazeuse de l'acier M2 sont étudiées avec plusieurs jeux de paramètres. L'augmentation du potentiel de nitruration et de la température de traitement accélère le processus de nitruration en raison de la modification des conditions aux limites et de la cinétique de la réaction thermochimique, respectivement. Le traitement de nitruration gazeuse est sensible à la propreté et à la méthode de finition mécanique de la surface traitée.Le gradient de dureté dans la couche de nitruration est généralement cohérent avec le gradient de concentration en azote, dont le maximum se situe à la surface. L'évolution des contraintes résiduelles dépend fortement du changement de volume induit par les transformations de phase provoquées par la nitruration. Elles atteignent leur maximum après l'accumulation du carbone (à une profondeur plus faible, avant que l'azote ne diminue de façon spectaculaire) et diminue près de la surface.Le potentiel limite de nitruration pour la formation de la couche de combinaison est identifié pour atteindre la dureté la plus élevée à la surface sans formation de couche de combinaison. Sa grande fragilité et sa microstructure spécifique (comme la porosité) sont des problèmes pour l’application du matériau.Les paramètres de nitruration sont finalement définis en considérant une contrainte résiduelle de compression élevée à la surface et un faible effet sur la dureté au cœur du matériau. Des mesures de résistance à l'usure sont ensuite définies et réalisées.L'usure, en particulier l'adhérence, est significative sur l'échantillon M2 non nitruré. Les paramètres de nitruration sélectionnés améliorent efficacement la résistance à l'usure de l'acier M2.Mots-clés : Nitruration gazeuse, Acier M2, Contraintes résiduelles, Dureté, Résistance à l'usure, Fatigue superficielThread rolling dies made of M2 high-speed steel for manufacturing electronic parking brake screws often face premature in-service failure. Damage and crack initiation occur several micrometers under the die thread surface. It is linked to the high surface rolling contact load, sliding effect and the presence of big carbides. An industrial case analysis using the Dang Van fatigue criterion shows that nitriding improves fatigue strength at the surface layer.The kinetics of gas nitriding of M2 steel is studied by controlling the parameters. Increasing nitriding potential and temperature accelerate the nitriding process because of the modification of the boundary condition and the thermochemical reaction kinetics, respectively. Gas nitriding is sensitive to the surface condition (cleanness and mechanical finishing).The hardness gradient in the nitriding layer is generally consistent with the nitrogen concentration gradient, of which the maximum value is at the surface. The residual stress evolution highly depends on the volume change induced by phase transformations during nitriding. It reaches the maximum after the carbon accumulates (at a lower depth before the nitrogen concentration declines harshly) and decreases near the surface.The limit nitriding potential for the compound layer formation is found to reach the highest surface hardness and avoid the compound layer due to its high brittleness and special microstructure (e.g. porosity).Nitriding parameters are finally defined by considering high compressive residual stresses at the surface and low effect on the core hardness. Wear resistance measurements are designed and carried out. The wear, especially adhesion, is significant on the non-nitrided M2 sample. The selected nitriding parameters effectively improved the wear resistance of M2 steel.Keywords: Gas nitriding, M2 steel, Residual stresses, Hardness, Wear resistance, Rolling contact failur