RESUMEN
Broadband photosensors have been widely studied in various kinds of materials. Experimental results have revealed strong wavelength-dependent photoresponses in all previous reports. This limits the potential application of broadband photosensors. Therefore, finding a wavelength-insensitive photosensor is imperative in this application. Photocurrent measurements were performed in Sb2Te3 flakes at various wavelengths ranging from visible to near IR light. The measured photocurrent change was insensitive to wavelengths from 300 to 1000 nm. The observed wavelength response deviation was lower than that in all previous reports. Our results show that the corresponding energies of these photocurrent peaks are consistent with the energy difference of the density of state peaks between conduction and valence bands. This suggests that the observed photocurrent originates from these band structure peak transitions under light illumination. Contrary to the most common explanation that observed broadband photocurrent carrier is mainly from the surface state in low-dimensional materials, our experimental result suggests that bulk state band structure is the main source of the observed photocurrent and dominates the broadband photocurrent.
RESUMEN
Photoconductivities (PCs) with high responsivity in two-dimensional (2D) diindium triselenide (In2Se3) nanostructures with α-phase hexagonal structure were studied. The In2Se3 nanosheet photodetectors fabricated by focused-ion beam technique exhibit broad spectral response with wavelength range from 300 nm to 1000 nm. The In2Se3 nanosheets achieve optimal responsivity of 720 A W-1 in near-infrared region (808 nm), and detectivity of 2.2 × 1012 Jones, which were higher than several 2D material photodetectors. The physical origins that result in high photoresponse in In2Se3 nanosheets such as carrier lifetime and mobility were also characterized by time-resolved PC and field-effect transistor measurements. The fast (hundred microseconds to milliseconds) and slow (seconds and longer) current rise or decay processes were both observed during the photoresponse. The narrowing (or relaxation) of depletion region and oxygen-sensitized photoconduction mechanism were suggested to be the causes of the efficient photoresponse in the In2Se3 nanostructure detectors. All these observations suggest that α-In2Se3 nanosheets could be a promising candidate for photosensitive material applications.
RESUMEN
The evolution of sexual traits often involves correlated changes in morphology and behavior. For example, in Drosophila, divergent mating displays are often accompanied by divergent pigment patterns. To better understand how such traits co-evolve, we investigated the genetic basis of correlated divergence in wing pigmentation and mating display between the sibling species Drosophila elegans and Drosophila gunungcola. Drosophila elegans males have an area of black pigment on their wings known as a wing spot and appear to display this spot to females by extending their wings laterally during courtship. By contrast, D. gunungcola lost both of these traits. Using Multiplexed Shotgun Genotyping (MSG), we identified a â¼440 kb region on the X chromosome that behaves like a genetic switch controlling the presence or absence of male-specific wing spots. This region includes the candidate gene optomotor-blind (omb), which plays a critical role in patterning the Drosophila wing. The genetic basis of divergent wing display is more complex, with at least two loci on the X chromosome and two loci on autosomes contributing to its evolution. Introgressing the X-linked region affecting wing spot development from D. gunungcola into D. elegans reduced pigmentation in the wing spots but did not affect the wing display, indicating that these are genetically separable traits. Consistent with this observation, broader sampling of wild D. gunungcola populations confirmed that the wing spot and wing display are evolving independently: some D. gunungcola males performed wing displays similar to D. elegans despite lacking wing spots. These data suggest that correlated selection pressures rather than physical linkage or pleiotropy are responsible for the coevolution of these morphological and behavioral traits. They also suggest that the change in morphology evolved prior to the change in behavior.
Asunto(s)
Coevolución Biológica , Drosophila/genética , Evolución Molecular , Pigmentación/genética , Conducta Sexual Animal , Animales , Femenino , Genes Ligados a X , Masculino , Caracteres Sexuales , Alas de AnimalesRESUMEN
It is well known that maintenance therapy using Chai-hu-gui-zhi-tang (CHGZT), a traditional Chinese medicine, has been proven to prevent the recurrence of peptic ulcers. However, little is known as to whether or not it has protective effects against acute gastric injury. In the present study, we investigated the preventive effects of pretreatment with CHGZT extract on the development of water immersion restraint stress-induced acute gastric ulceration in male Wistar rats. The CHGZT extract (50, 250, 500 mg/kg b.w., p.o.) was given to rats before they were exposed to 2 or 4 hr of water immersion restraint stress; they were then were sacrificed immediately after stress exposure. Gastric mucosal lesions were evaluated macroscopically, and the gastric mucosal and hepatic non-protein sulfhydryls (NP-SH) were measured simultaneously. The results indicate that exposure to water immersion restraint stress resulted in the development of acute gastric stress erosions. Pretreatment with CHGZT extract caused a significant reduction of stress lesions and an increase in the gastric mucosal NP-SH and hepatic NP-SH concentrations. We conclude that the anti-ulcer response and extensive antioxidant effect of Chai-hu-gui-zhi-tang may be valuable in prevention of experimental gastric mucosal lesions in rats because it possesses preventive and gastroprotective effects.
