Infra red and Ultraviolet radiation Research Papers (original) (raw)

This paper reviews the device physics and technology of optoelectronic devices based on semiconductors of the GaN family, operating in the spectral regions from deep UV to Terahertz. Such devices include LEDs, lasers, detectors,... more

This paper reviews the device physics and technology of optoelectronic devices based on semiconductors of the GaN family, operating in the spectral regions from deep UV to Terahertz. Such devices include LEDs, lasers, detectors, electroabsorption modulators and devices based on intersubband transitions in AlGaN quantum wells (QWs). After a brief history of the development of the field, we describe how the unique crystal structure, chemical bonding, and resulting spontaneous and piezoelectric polarizations in heterostructures affect the design, fabrication and performance of devices based on these materials. The heteroepitaxial growth and the formation and role of extended defects are addressed. The role of the chemical bonding in the formation of metallic contacts to this class of materials is also addressed. A detailed discussion is then presented on potential origins of the high performance of blue LEDs and poorer performance of green LEDs (green gap), as well as of the efficiency reduction of both blue and green LEDs at high injection current (efficiency droop). The relatively poor performance of deep-UV LEDs based on AlGaN alloys and methods to address the materials issues responsible are similarly addressed. Other devices whose state-of-the-art performance and materials-related issues are reviewed include violet-blue lasers, 'visible blind' and 'solar blind' detectors based on photoconductive and photovoltaic designs, and electroabsorption modulators based on bulk GaN or GaN/AlGaN QWs. Finally, we describe the basic physics of intersubband transitions in AlGaN QWs, and their applications to near-infrared and terahertz devices.

ABSTRACT Space astronomy in the last 40 years has largely been done from spacecraft in low Earth orbit (LEO) for which the technology is proven and delivery mechanisms are readily available. However, new opportunities are arising with the... more

ABSTRACT Space astronomy in the last 40 years has largely been done from spacecraft in low Earth orbit (LEO) for which the technology is proven and delivery mechanisms are readily available. However, new opportunities are arising with the surge in commercial aerospace missions. We describe here one such possibility: deploying a small instrument on the Moon. This can be accomplished by flying onboard the Indian entry to the Google Lunar X PRIZE competition, Team Indus mission, which is expected to deliver a nearly 30 kgs of payloads to the Moon, with a rover as its primary payload. We propose to mount a wide-field far-UV (130–180 nm) imaging telescope as a payload on the Team Indus lander. Our baseline operation is a fixed zenith pointing but with the option of a mechanism to allow observations of different attitudes. Pointing towards intermediate ecliptic latitude (50∘ or above) ensures that the Sun is at least 40∘ off the line of sight at all times. In this position, the telescope can cover higher galactic latitudes as well as parts of Galactic plane. The scientific objectives of such a prospective are delineated and discussed.

The potential of laser cleaning for paintings as an alternative to traditional cleaning methods has been recognized, and studies using industrial laser equipment have shown some potential. Irradiation at a wavelength of 248 nm has shown... more

The potential of laser cleaning for paintings as an alternative to traditional cleaning methods has been recognized, and studies using industrial laser equipment have shown some potential. Irradiation at a wavelength of 248 nm has shown to be the most promising for natural resin varnish and overpaint removal, because it is strongly absorbed by triterpenoid varnish functional groups and associated degradation products (Georgiou 1998). However, it has been suggested that a minimal varnish thickness should remain intact to prevent any radiation from being absorbed by the underlying layers. This is because some painting materials have also shown sensitivity to laser radiation (Bordalo 2006). Research into the mechanisms of alterations which may occur due to laser radiation on resins, pigments and oils and its long-term effects has been scarce, and dispersed in its approach because of the multitude of different materials present in the paint layers (Chappé 2003, Sobott 2003, Melessanaki 2006). Thus, the systematic study of laser radiation interaction with paint materials is still important. The aim of this study was to advance the understanding of the effects that KrF excimer laser irradiation has on pigmented oil paint layers.

BACKGROUND: Ultraviolet-C (UV-C) has proven effective in extending shelf-life, reducing disease incidence and increasing the levels of health-promoting compounds in several crops.While most studieswere conducted at the postharvest stage,... more

BACKGROUND: Ultraviolet-C (UV-C) has proven effective in extending shelf-life, reducing disease incidence and increasing the
levels of health-promoting compounds in several crops.While most studieswere conducted at the postharvest stage, our study
examined the effect of preharvest UV-C application in three strawberry cultivars (Fragaria × ananassa Duch. ’Albion’, ’Charlotte’
and ’Seascape’). UV-C treatmentwas applied from the onset of flowering until the fruits reached commercial maturity on plants
grown for two consecutive seasons under greenhouse conditions. The phytochemical profiles and antioxidant capacity of the
fruits were assessed at harvest.
RESULTS: The ellagic acid and kaempferol-3-glucuronide contents were significantly increased only in fruits of the cultivar
’Albion’ collected fromUV-C-treated plants in season 1. UV-C did not consistently affect the other phenolic compounds thatwere
measured. Based on the results of the ferric-reducing antioxidant power, oxygen radical absorbance capacity and total phenolic
content assays, the antioxidant capacity of the three strawberry cultivars was not affected by UV-C. Season and cultivar had a
decisive impact on these parameters.
CONCLUSION: The effect of preharvest UV-C on the levels of bioactive compounds in strawberry fruits appears to be cultivardependent,
with season or growing conditions having a significant impact.
© 2014 Her Majesty the Queen in Right of Canada Journal of the Science of Food and Agriculture © 2014 Society of Chemical
Industry

Fluorescent lamps rely on mercury as the source of ultraviolet radiation for the production of visible light. Partitioning of mercury among vapor phase, loose phosphor powders produced during breaking and washing steps, glass matrices,... more

Goal. The photoluminescence (fluorescence) of visible light from cocoons of silkworms of different breeds under the influence of ultraviolet radiation was studied. Material and method. The analysis was performed by means of an automatic... more

Goal. The photoluminescence (fluorescence) of visible light from cocoons of silkworms of different breeds under the influence of ultraviolet radiation was studied.
Material and method. The analysis was performed by means of an automatic spectrophotometric measuring complex, including SPEKOL 11 spectrophotometer and a computer.
Results. The configuration and techniques of measurement are explaned. The fluorescence spectra of 185 samples have been obtained, spectral and colorimetric parameters characterizing the cocoon irradiation have been proposed. The correlation coefficients between parameters of fluorescence and technological parameters of cocoons were calculated.

In this research, the erythemally effective UV measured using miniaturized polysulphone dosimeters to over 1250 individual body sites and collected over a 4-year period is presented relative to the total exposed skin surface area (SSA) of... more

In this research, the erythemally effective UV measured using miniaturized polysulphone dosimeters to over 1250 individual body sites and collected over a 4-year period is presented relative to the total exposed skin surface area (SSA) of a life-size manikin model. A new term is also introduced, the mean exposure fraction (MEF). The MEF is used to weight modeled or measured horizontal plane UV exposures to the total unprotected SSA of an individual and is defined as the ratio of exposure per unit area received by the unprotected skin surfaces of the body relative to the exposure received on a horizontal plane. The MEF has been calculated for a range of solar zenith angles (SZA) to provide a sunburning energy data set weighted to the actual SSA of a typically clothed individual. For this research, the MEF was determined as 0.15, 0.26 and 0.41 in the SZA ranges 0°-30°, 30°-50° and 50°-80° providing information that can be used in a variety of different ambient, latitudinal and seasonal climates where total human body UV exposure information is not available.

A technique has previously been described for secondary school-aged children to make ultraviolet (UV) dosimeters from highlighter pen ink drawn onto strips of paper. This technique required digital comparison of exposed ink paper strips... more

A technique has previously been described for secondary school-aged children to make ultraviolet (UV) dosimeters from highlighter pen ink drawn onto strips of paper. This technique required digital comparison of exposed ink paper strips with unexposed ink paper strips to determine a simple calibration function relating the degree of ink fading to measured levels of UV exposure. In this article, the ink calibration process is discussed in relation to activities that can be performed by primary school-aged children. Further extension of the technique is discussed in relation to UV absorption by various transparent materials, and a simple exercise is explained that could be used by primary and secondary students to measure and calibrate UV exposures using a glass plate dosimeter.

Numerous studies have conclusively shown how solar ultraviolet radiation (UV) (290-400 nm) has a negative impact upon underwater ecosystems. As a consequence of this, UV must be accurately evaluated in aquatic locations by employing a... more

Numerous studies have conclusively shown how solar ultraviolet radiation (UV) (290-400 nm) has a negative impact upon underwater ecosystems. As a consequence of this, UV must be accurately evaluated in aquatic locations by employing a non-invasive measurement technique in order to better understand the damage it causes on both a macro and micro scale and provide solutions on how to manage its impact over both short and long time scales. Specifically, the UVB (290-320 nm) has the highest potential for causing stress to marine organisms. This manuscript details the deployment of a cost-effective and easily useable UVB detection dosimeter based on polyphenylene oxide (PPO) combined with a neutral density filter (NDF) derived from polyethylene. A long-term calibration regime performed over an extensive solar zenith angle range (SZA) in summer at a semi-tropical location showed that the PPO dosimeter used in conjunction with a polyethylene NDF could measure UVB exposures underwater up to 125 h in daylight (11-12 days approximately) before reaching near total saturation, providing an exposure limit as much as seven times greater that what was previously achievable with PPO dosimeters deployed without an NDF and approximately 42 times larger than those measured previously with polysulphone dosimeters.

Smartphones are used widely by the general public and students. They are one of the most popular and easily accessible technologies. These devices were originally designed as a means of communication. However, they have evolved into a... more

Smartphones are used widely by the general public and students. They are one of the most popular and easily accessible technologies. These devices were originally designed as a means of communication. However, they have evolved into a mobile computing platform with built in sensors and the ability to access a vast number of applications. This study describes research that demonstrates how the smartphone can be used to detect solar ultraviolet-A radiation and how this integrates with the skills described as part of the middle school Australian Curriculum. It also outlines how smartphones can be used to support sun protection policies within schools.