Ultraviolet light

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

Effect of Noble Gas Doping in Single-Bubble Sonoluminescence

Abstract: The trillionfold concentration of sound energy by a trapped gas bubble, so as to emit picosecond flashes of ultraviolet light, is found to be extremely sensitive to doping with a noble gas. Increasing the noble gas content of a nitrogen bubble to about 1% dramatically stabilizes the bubble motion and increases the light emission by over an order of magnitude to a value that exceeds the sonoluminescence of either gas alone. The spectrum also strongly depends on the nature of the gas inside the bubble: Xenon yields a spectral peak at about 300 nanometers, whereas the helium spectrum is so strongly ultraviolet that its peak is obscured by the cutoff of water.

Quantification of humic acids in surface water: effects of divalent cations, pH, and filtration.

Abstract: Humic acids (HAs) content of raw water is an important analytical parameter in water treatment facilities because HAs in the presence of chlorine may lead to the formation of dangerous by-products (e.g., trihalomethanes). The concentration of HAs in water is not directly accessible by common analytical methods due to their heterogeneous chemical structure. The aim of this study was to compare two methods to assess humic acids (HAs) in surface water namely absorbance of ultraviolet light at 254 nm (UV254) and total organic carbon (TOC), as well as to evaluate the effects of calcium and magnesium concentrations, pH and sample filtration on the methods' results. An aqueous solution of a commercial HA with 10 mg L−1 was used in the present work. Quantification of the HA was carried out by both UV254 and TOC (combustion-infrared method) measurements. UV254 results were converted to TOC using a calibration curve. The effects of calcium (0–136.3 mg L−1) and magnesium (0–34.5 mg L−1) concentrations, pH (4.0, 7.0 and 9.0) and sample filtration on UV254 and TOC measurements of the HA suspension were evaluated. More accurate TOC values of HA suspensions were obtained by the combustion-infrared method than by the UV254 absorbance method. The higher differences of TOC values between unfiltered and filtered samples were detected in the presence of calcium at pH 9.0 using the spectrophotometric method.

Strong excitonic effects in the optical properties of graphitic carbon nitride g-C 3 N 4 from first principles

Abstract: Graphitic carbon nitride ($g$-C${}_{3}$N${}_{4}$) has recently triggered extensive investigations due to its potential applications, such as in direct photochemical water splitting, CO${}_{2}$ activation, and transition-metal-free spintronics. However, electronic, and particularly the optical properties of $g$-C${}_{3}$N${}_{4}$ still have not been well established. Based on one of the state-of-the-art approaches---many-body Green's function theory (i.e., $GW$ $+$ BSE)---absorption of ultraviolet light by $g$-C${}_{3}$N${}_{4}$ is found to be determined by strong excitonic effects with a significantly large binding energy assigned to the bound excitons. Dark states have also been found in $g$-C${}_{3}$N${}_{4}$, which can affect the photoluminescence yield of $g$-C${}_{3}$N${}_{4}$. We find that the band gap of $g$-C${}_{3}$N${}_{4}$ probably can be tuned by adjusting the condensation (dimensionality) to initiate excitonic absorption in the visible light region, which might help improve the solar energy conversion efficiency.

Interaction ofEscherichia coli RuvAandRuvBproteins with synthetic Holliday junctions

Abstract: TheRuvA,RuvB,andRuvCproteins of Eseherichia coli arerequired fortherecombinational repair of ultraviolet light- orchemical-induced DNAdamage. Invitro, RuvCprotein interacts withHolliday junctions inDNAand promotes their resolution byendonucleolytic cleavage. Inthis paper, weinvestigate theinteraction ofRuvAandRuvB proteins withmodelHolliday junctions. Using band-shift as- says, weshowthat RuvAbinds synthetic Holliday structures to formspecific protein-DNA complexes. Moreover, inthepres- enceofATP,theRuvAandRuvBproteins actinconcert to promote dissociation ofthesynthetic Holliday structures. The dissociation reaction requires bothRuvAandRuvBanda nucleotide cofactor (ATPordATP)andisrapid (40%ofDNA molecules dissociate within 1min). Thereaction does notoccur whenATPisreplaced byeither ADPorthenonhydrolyzable analog ofATP,adenosine 5'-(v-thioltriph osphate.

Industrial waste water treatment

Abstract: A waste water treatment system is illustrated which can be configured to be portable and which minimizes the addition of solids to be disposed of through the use of ozone for contaminant reduction to basic elements after the pH value of the waste water to be treated is properly adjusted. This ozone in one stage is combined with ultrasound to cause coagulation and precipitation. In another stage, ozone and ultraviolet light are used in a reduction process. Ion alignment using a magnetic field and an electrochemical flocculation process to which the waste water is subjected causes further coagulation and precipitation. As designed, the system can operate continuously with redundancy at appropriate points so that removal of solids from the filtration units can occur simultaneous with the overall decontamination process.