• 한국자원식물학회지
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• 제31권5호
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• pp.522-530
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• 2018

Brachypodium distachyon has been developed as a monocot model plant for temperate grasses and bioenergy crops. Although B. distachyon research is moving forward rapidly, the study of photoresponses has not been explored. To extend our knowledge of responses to light in monocots, we performed photoresponse analysis of B. distachyon using two inbred lines, Bd21 and Bd21-3. In this study, we first compared growing phenotypes between the two lines and investigated coleoptile and primary leaf growths under dark, far-red, red, and white light conditions. The results showed that the growth of the two lines were similar until tillering stage, but other developmental stages from heading to senescence were much delayed in Bd21-3, which resulted in increased height and tiller numbers. Under different light conditions, primary leaf lengths were kept increasing during the growth period, whereas the coleoptile extension was inhibited 4 to 7 days after growth depending on the light conditions applied. These results suggest that the responses to light in B. distachyon can be examined by measuring coleoptile lengths approximately 7 days after seedling growth. Moreover, we selected light-responsive genes known in Arabidopsis thaliana, such as chlorophyll A/B binding protein (CAB), light-harvesting chlorophyll binding protein (Lhcb) and chalcone synthase (CHS), and confirmed their light-induced gene expression in B. distachyon. Therefore, the present study suggests that the inhibition of coleoptile growth can be used as the parameter to analyze photoresponses in the monocot model plant, and also provide the reference genes whose expression is induced by far-red and red light treatment.

• 한국환경농학회지
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• 제11권3호
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• pp.253-260
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• 1992

이동성의 생명체는 자신에게 불리한 환경을 피해 이동할 수 있는 자기 방어 기구를 갖고 있다. 본 연구에서는 미꾸라지(Misgurunus mizolepis G${\"{U}}$THER)가 보이는 photodispersal 현상도 광증감반응을 통해 피부세포를 손상시킬 수 있는 해로운 광자극을 피하기 위한 일종의 방어 전략일 것이라 가정하고 이를 뒷받침할 수 있는 다음과 같은 결과들을 얻었다. 첫째, 암소에서 적용된 미꾸라지는 빛에 노출되면 즉시 운동성의 증가를 보이고 황색 또는 적색광에 비해 특히 청색광에 민감하게 반응하였다. 둘째 눈을 멀게한 미꾸라지도 광반응을 보였으며 청색광에 비교적 예민하게 반응하였다. 셋째, 미꾸라지 피부조직에는 활성산소를 생성시킬수 있는 청색광 흡수 광증감색소가 최소 두종류가 존재하고 있었으며 그 중 하나는 리보플라빈으로 동정되었다.

• 한국수산과학회지
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• 제50권4호
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• pp.413-420
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• 2017

The increase in the number of mud shrimps Upogebia major is a concern because of their negative effects on shellfish aquaculture, including Manila clam Venerupis philippinatum along the west coast of Korea. This study developed a behavioral analysis system for aquatic animals using a set of monochromatic light-emitting diode (LED) modules covering the visible light range at similar intervals. Movements of mud shrimp were monitored using a tracking system under illumination with infra-red light and an LED of 660 nm wavelength without provoking stimulation. The minimum light intensity needed to induce a photoresponse by the mud shrimp was $10{\mu}mole/m^2/s$ under the conditions tested. Of the six kinds of LED illuminations tested, the most sensitive response was obtained with illumination with the 505 nm LED, followed in order by LEDs with peak wavelengths of $525nm{\fallingdotseq}465nm$ > $405nm{\fallingdotseq}590nm$ > 660 nm. These findings should help to identify LED sources that efficiently induce movement of the mud shrimp and also for monitoring movement without stimulating.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.234-234
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• 2010

The PR transitions in asymmetric dot-in-double-quantum-well (DdWELL) photodetector is identified by bias-dependent spectral behaviors. Discrete n-i-n infrared photodetectors were fabricated on a 30-period asymmetric InAs-QD/[InGaAs/GaAs]/AlGaAs DdWELL wafer that was prepared by MBE technique. A 2.0-monolayer (ML) InAs QD ensemble was embedded in upper combined well of InGaAs/GaAs and each stack is separated by a 50-nm AlGaAs barrier. Each pixel has circular aperture of 300 um in diameter, and the mesa cell ($410{\times}410\;{\mu}m^2$) was defined by shallow etching. PR measurements were performed in the spectral range of $3{\sim}13\;{\mu}m$ (~ 100-400 meV) by using a Fourier-transform infrared (FTIR) spectrometer and a low-noise preamplifier. The asymmetric photodetector exhibits unique transition behaviors that near-/far-infrared (NIR/FIR) photoresponse (PR) bands are blue/red shifted by the electric field, contrasted to mid-infrared (MIR) with no dependence. In addition, the MIR-FIR dual-band spectra change into single-band feature by the polarity. A four-level energy band model is proposed for the transition scheme, and the field dependence of FIR bands numerically calculated by a simplified DdWELL structure is in good agreement with that of the PR spectra. The wavelength shift by the field strength and the spectral change by the polarity are discussed on the basis of four-level transition.

• 한국재료학회지
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• 제29권7호
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• pp.456-462
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• 2019

ZnO thin-films are grown on a p-Si(111) substrate by RF sputtering. The effects of growth temperature and $O_2$ mixture ratio on the ZnO films are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and room-temperature photoluminescence (PL) measurements. All the grown ZnO thin films show a strong preferred orientation along the c-axis, with an intense ultraviolet emission centered at 377 nm. However, when $O_2$ is mixed with the sputtering gas, the half width at half maximum (FWHM) of the XRD peak increases and the deep-level defect-related emission PL band becomes pronounced. In addition, an n-ZnO/p-Si heterojunction diode is fabricated by photolithographic processes and characterized using its current-voltage (I-V) characteristic curve and photoresponsivity. The fabricated n-ZnO/p-Si heterojunction diode exhibits typical rectifying I-V characteristics, with turn-on voltage of about 1.1 V and ideality factor of 1.7. The ratio of current density at ${\pm}3V$ of the reverse and forward bias voltage is about $5.8{\times}10^3$, which demonstrates the switching performance of the fabricated diode. The photoresponse of the diode under illumination of chopped with 40 Hz white light source shows fast response time and recovery time of 0.5 msec and 0.4 msec, respectively.

• Journal of Photoscience
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• 제9권2호
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• pp.44-46
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• 2002

In the vertebrate retina, rods mediate twilight vision and cones daylight vision. Rods have been purified easily from the retina, and thus the phototransduction mechanism in rods is now well documented. However, it has not been possible to purify cones in large quantities, and therefore, the knowledge on the mechanism in cones is limited. Here we report purification of carp (Cyprinus carpio) cones with a stepwise Percoll gradient. Using purified cells, we compared the phototransduction mechanism between rods and cones. The results showed that both transducin activation and phosphodiesterase activation are less effective, and visual pigment phosphorylation is faster in cones. These differences explain lower light-sensitivity and briefer photoresponse time course in cones.

• 한국세라믹학회지
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• 제24권4호
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• pp.369-375
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• 1987

The effects of dopant Al2O3 and surface roughness on the photoelectrochemical conversion of TiO2 ceramic electrodes were investigated. The photocurrent increased with increasing the amount of dopant Al2O3 up to 0.1wt% and 0.05wt% in the specimens reduced at 700$^{\circ}C$ and 800$^{\circ}C$, respectively, and then decreased. However, the photoresponse appeared around 415 nm, which very closely corresponds to the energy band gap of TiO2(∼3.0eV), regardless of reduction temperature and the amount of Al2O3. And the photocurrent increased with increasing surface roughness in the undoped TiO2 ceramic electrode.

• 센서학회지
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• 제25권4호
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• pp.252-256
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• 2016

Epitaxially grown GaN layers have a high surface state density, which typically results in a surface leakage current and a photoresponse in undesirable wavelengths in GaN optoelectronic devices. Surface passivation is, therefore, an important process necessary to prevent performance degradation of GaN UV photodetectors. In this study, we propose oxygen-enhanced thermal treatment as a simple surface passivation process without capping layers. The GaN UV photodetector fabricated using a thermal annealing process exhibits improved electrical and photoresponsive characteristics such as a reduced dark current and an enhanced photoresponsive current and UV-to-visible rejection ratio. The results of this study show that the proposed surface passivation method would be useful to enhance the reliability of GaN-based optoelectronic devices.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1993년도 추계학술대회 논문집
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• pp.60-63
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• 1993

We have prepared n-CdS/p-InP hetero- junction solar cells by thermal evaporation. The efficiency under the optium conditions without the grid line contact was 7.3%, and the solar cell having glid line contact with SiO AR coating was the open circuit voltage of 0.71V, the short circuit voltage current density of 15mA/cm$^2$, the fill factor of 0.73, and the efficiency of 11.5%. As result of photoresponse in 400-1000nm wavelength the cutoff of n-CdS/p-InP solar at 500nm results from absorption by the CdS \"window\" and the cutoff at 930 nm result from absorption by the InP.

• 한국세라믹학회지
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• 제22권4호
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• pp.9-14
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• 1985

The quantum efficiency vs. wavelength curves with different reducing treatments for the 99.99% and 98.5% $TiO_2$ ceramic electrodes have been analyzed according to the Schottky barrier model of the semiconductor-elect-rolyte interface, The model allows the main physical parameters governing the photoelectrochemical properties of the semicon-ductor to be determined. According to these data the impurity ions as three valence state ($Fe^{3+})$ in the $TiO_2$ raw materials have great influence on the photoresponse and the $TiO_2$ ceramic electrodes show much lower quantum efficiency than the $TiO_2$ single crystal due to existence of the recombination centers.