Ultraviolet light

About: Ultraviolet light is a research topic. Over the lifetime, 49494 publications have been published within this topic receiving 843151 citations.

Fractal Organic Hazes Provided an Ultraviolet Shield for Early Earth

Abstract: The Archean Earth (3.8 to 2.5 billion years ago) was probably enshrouded by a photochemical haze composed of fractal aggregate hydrocarbon aerosols. The fractal structure of the aerosols would have had a strong effect on the radiative properties of the haze. In this study, a fractal aggregate haze was found to be optically thick in the ultraviolet wavelengths while remaining relatively transparent in the mid-visible wavelengths. At an annual production rate of 10 14 grams per year and an average monomer radius of 50 nanometers, the haze would have provided a strong shield against ultraviolet light while causing only minimal antigreenhouse cooling.

Benzotriazole, benzothiazole, and benzophenone compounds in indoor dust from the United States and East Asian countries

Abstract: Organic corrosion inhibitors (OCIs), including ultraviolet light filters, are widely used in plastics, rubbers, colorants, and coatings to increase the performance of products. Derivatives of benzotriazole (BTR), benzothiazole (BTH), and benzophenone (BP) are high-production volume OCIs that have been detected in the environment and human tissues. However, knowledge of their occurrence in indoor environments, as well as human exposure to them, is still lacking. In this study, BTR, BTH, BP and their 12 derivatives were determined in indoor dust for the first time. All three groups of OCIs were found in all 158 indoor dust samples from the U.S. and three East Asian countries (China, Japan, and Korea). The geometric mean (GM) concentration of the sum of six BTRs (GM CΣBTRs) ranged from 20 to 90 ng/g among the four countries studied, with a maximum CΣBTRs of ∼2000 ng/g found in a dust sample from China. Tolyltriazole was the major derivative of BTR measured in dust. GM CΣBTHs in indoor dust from the four countries ranged from 600 to 2000 ng/g. 2-OH-BTH was the predominant BTH in dust from the U.S., Japan, and Korea. GM CΣBPs in dust ranged from 80 to 600 ng/g, with 2-OH-4-MeO-BP and 2,4-2OH-BP, contributing to the majority of ∑BP concentrations. Based on the concentrations of three types of OCIs in indoor dust, human exposure through dust ingestion was calculated. Daily intake of OCIs through dust ingestion was higher for people in the U.S., Japan, and Korea than in China; the residents in urban China are exposed to higher levels of OCIs via dust ingestion than are those in rural China.

Solid-phase photocatalytic degradation of polyethylene plastic under UV and solar light irradiation

Abstract: This paper investigated solid-phase photocatalytic degradation of polyethylene (PE) plastic with TiO2 in the ambient air under solar and ultraviolet light irradiation. The photodegradation of the composite plastic was compared with that of pure PE through weight loss monitoring, scanning electron microscopic (SEM) analysis, gas chromatography (GC), FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS). PE-TiO2 composite plastic can be efficiently decomposed and the main products are CO2 and water. The weight-loss of PE-TiO2 (1 wt%) film reached 42% under solar irradiation for 300 h. The degradation rate can be controlled by changing the content of TiO2 nanoparticles in PE plastic. The degradation of composite plastic initiated on PE-TiO2 interface and then extended into polymer matrix induced by the diffusion of the reactive oxygen species generated on TiO2 particle surface. The present study demonstrates that the polymer-TiO2 compositing is a practical and promising way to degrade the plastic waste under solar light without any pollution.

Resistance of Spores of Bacillus Species to Ultraviolet Light

Abstract: Dormant spores of the various Bacillus species, including B. subtilis, are 5 to 50 times more resistant to UV radiation than are the corresponding growing cells. This elevated spore UV resistance is due to: a) the photochemistry of DNA within spores, as UV generates few if any cyclobutane dimers, but rather a photoproduct (Fig. 1) called spore photoproduct (SP; 5-thyminyl-5,6-dihydrothymine); and b) DNA repair, in particular SP-specific repair, during spore germination. The novel UV photochemistry of spore DNA is largely due to its saturation with a group of small, acid-soluble proteins (SASP), which are unique to spores and whose binding alters the DNA conformation and thus its photochemistry. SP-specific repair is also unique to spores and is carried out by a light-independent SP-lyase, an iron-sulfur protein that utilizes S-adenosylmethionine to catalyze SP monomerization without DNA backbone cleavage.

Subwavelength photolithography based on surface-plasmon polariton resonance

Abstract: The use of surface-plasmon polariton (SPP) resonance in the optical near field of a metallic mask to produce fine patterns with a resolution of subwavelength scale is proposed. Preliminary numerical simulations indicate that the critical resolution is determined mainly by the thickness of the metallic mask. The surface of the metallic mask on the illuminated side collects light through SPP coupling, and the interference of SPPs on the exit side of the metallic mask results in enhanced optical intensity with high spatial resolution, which can facilitate nanolithography efficiently by use of conventional photoresist with simple visible or ultraviolet light sources. Several schemes for sub-half-wavelength lithography based on SPPs are described. Inasmuch as the technique is not diffraction limited, nanostructures can be reproduced photolithographically.