Search results for "violet"

Operational considerations to improve total ozone measurements with a Microtops II ozone monitor

2012

A Microtops II "ozone monitor" with UV channels centered at 305.5, 312.5, and 320 nm has been used routinely in six experimental campaigns carried out in several geographic locations and seasons, covering latitudes from 35 to 68° N during the last ten years (2001–2011). The total ozone content is retrieved by Microtops II by using different combinations (Channel I, 305.5/312.5 nm; Channel II, 312.5/320 nm; and Channel III, 305.5/312.5/320 nm) of the signals at the three ultraviolet wavelengths. The long-term performance of the total ozone content determination has been studied taking into account the sensitivities to the calibration, airmass, temperature and aerosols. When a calibration was…

MEASUREMENT AND ANALYSIS OF ULTRAVIOLET SOLAR IRRADIATION IN VALENCIA, SPAIN

1996

Experimental data concerning the integrated total ultraviolet radiation (290–385 nm band) on a horizontal surface measured at Valencia (Spain) during the period March 1991 to December 1994 have been analysed. A study of the most representative statistical indexes: arithmetic mean (M), median (Md), standard deviation (SD), maximum (Mx), minimum (Mn), first (Q1) and third (Q3) quartiles, percentiles 5 (P5) and 95 (P95), interquartile range (Q3 –Q1) and coefficient of quartile variation (V), of the UV radiation for this period has been carried out. The study has focused on both the hourly and the daily values of irradiance. The UV irradiance measured shows quite stable values within the period…

Comparison of global ultraviolet (290–385 nm) and global irradiation measured during the warm season in valencia, spain

1994

This paper studies data of ultraviolet (290–385 nm band) horizontal solar irradiation and global horizontal solar irradiation measured at Valencia (Spain) during the period March 1991 to September 1991. Analysis of error estimations and correlation coefficients show that the 10 minute, hourly, and daily values of ultraviolet (UV) and global irradiation are highly correlated. Improved figures and less dependence on location are achieved by defining a clearness index for the UV 290–385 nm band and relating it to the conventional whole-band clearness index. The novel clearness index obtained from Valencia data is approximately half of the conventional clearness index. Considering solar elevati…

Deconvolution procedure of the UV-vis spectra. A powerful tool for the estimation of the binding of a model drug to specific solubilisation loci of b…

2015

UV-vis-spectra evolution of Nile Red loaded into Tween 20 micelles with pH and [Tween 20] have been analysed in a non-conventional manner by exploiting the deconvolution method. The number of buried sub-bands has been found to depend on both pH and bio-surfactant concentration, whose positions have been associated to Nile Red confined in aqueous solution and in the three micellar solubilisation sites. For the first time, by using an extended classical two-pseudo-phases-model, the robust treatment of the spectrophotometric data allows the estimation of Nile Red binding constant to the available loci. Hosting capability towards Nile Red is exalted by the pH enhancement. Comparison between bin…

Can ultraviolet cues function as aposematic signals?

2001

The fact that birds are sensitive to ultraviolet light (UV, 320–400 nm) has been largely ignored by previous studies of aposematism. Therefore, in the present article we investigated whether great tits preferred ultraviolet-reflecting colors compared to colors without UV reflection and whether UV cues alone could function as aposematic signals. We were able to manipulate prey visibility in UV light by changing the UV reflectance of prey items as well as altering the lighting conditions. In order to perform a preference experiment we used three pairs of colors (green UV vs. green, gray UV vs. gray, yellow UV vs. yellow) on a black background. The birds ate both UV types equally for all three…

The inhibition of Ca2+-ATPases of human erythrocyte membranes by covalent binding of ATP derivatives.

1982

UV-induced cross-linking of Tet repressor to DNA containing tet operator sequences and 8-azidoadenines.

1990

The synthesis of 8-azido-2'-deoxyadenosine-5'-triphosphate is described. The photoreactive dATP analog was characterized by thin layer chromatography, proton resonance spectroscopy, infrared spectroscopy and UV spectroscopy. Its photolysis upon UV irradiation was studied. After incorporation of this dATP analog into DNA containing the tet operator sequence the investigation of the interactions between tet operator DNA and Tet repressor protein by UV photocross-linking becomes possible. Photocross-linking of protein to DNA was demonstrated by the reduced migration of the DNA in SDS polyacrylamide gel electrophoresis. Addition of the inducer tetracycline prior to UV irradiation significantly …

The Low-Affinity ATP Binding Site of the Escherichia coli SecA Dimer Is Localized at the Subunit Interface

1997

The homodimeric SecA protein is the ATP-dependent force generator in the Escherichia coli precursor protein translocation cascade. SecA contains two essential nucleotide binding sites (NBSs), i.e., NBS1 and NBS2 that hind ATP with high and low affinity, respectively. The photoactivatable bifunctional cross-linking agent 3'-arylazido-8-azidoadenosine 5'-triphosphate (diN(3)ATP) was used to investigate the spatial arrangement of the nucleotide binding sites of SecA, DiN(3)ATP is an authentic ATP analogue as it supports SecA-dependent precursor protein translocation and translocation ATPase, UV-induced photo-cross-linking of the diN(3)ATP-bound SecA results in the formation of stable dimeric s…

Solar PAR and UVR modify the community composition and photosynthetic activity of sea ice algae

2015

The effects of increased photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) on species diversity, biomass and photosynthetic activity were studied in fast ice algal communities. The experimental set-up consisted of nine 1.44 m(2) squares with three treatments: untreated with natural snow cover (UNT), snow-free (PAR + UVR) and snow-free ice covered with a UV screen (PAR). The total algal biomass, dominated by diatoms and dinoflagellates, increased in all treatments during the experiment. However, the smaller biomass growth in the top 10-cm layer of the PAR + UVR treatment compared with the PAR treatment indicated the negative effect of UVR. Scrippsiella complex (mainly…

Photocatalytic oxidation mechanism of benzonitrile in aqueous suspensions of titanium dioxide

2007

Abstract The photocatalytic oxidation of benzonitrile was carried out in aqueous suspensions (pH 11) of commercial polycrystalline TiO 2 (Merck and Degussa P25) irradiated by ultraviolet light. The rate of decomposition was dependent on the concentration of benzonitrile and followed a pseudo-first order kinetics. The complete mineralization of a 0.70 mM benzonitrile solution was achieved in ca. 8 h by using TiO 2 Degussa P25, whereas the substrate was only partially mineralized even after 14 h of irradiation in the presence of TiO 2 Merck. The final oxidation products were carbonate and nitrate. The appearance and the evolution of organic and inorganic intermediate species were also investi…