[PHOTOCHEMICAL FORMATION OF HYDRAZINE FROM AMMONIUM COMPOUNDS IN AQUEOUS SOLUTION].
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Ammonium Compounds↗
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Experiments on the theory of photochemical formation of carcinogens from skin fats.
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Carcinogens↗
[Identification of photoproducts for PCB congeners by the new retention index system].
Polychlorinated biphenyls (PCBs) are a kind of priority pollutants, constituting a complex group of 209 congeners ranging from monochloro to decachlorobiphenyls. Because of the shortcomings of retention time data and the lack of suitable retention index systems, the congeners analysis of PCBs is one of the most challenging tasks in capillary column gas chromatography (GC), especially due to the fact that the isomers of PCBs can not be identified by GC-MS. A new retention index system, suitable for analysis of PCB congeners in the environmental samples by temperature-programmed capillary gas chromatography with ECD, has been developed recently by Chu et al. In this paper, retention indexes of all 209 PCB congeners were calculated according to the new retention index system from their respective retention times reported by other authors. The photoproducts of PCB87, PCB138 and PCB169 were identified with the new retention index system and confirmed by GC-MS. The deviations of retention indexes for all photoproducts were within 3 index units. It was testified that the above retention index system was reliable during the identification of PCB congeners and would have wide applicability. Based on the formations of coplanar PCB congeners (PCB77 and PCB126) during the photodegradations of PCB138 and PCB169, it was proposed that toxic equivalence (TEQ) should be used as a kind of quality indicator for the studies of the photolysis of PCBs.
Chromatography, Gas↗
[Raman spectra and photoluminescence spectra of InGaN/GaN multiquantum wells annealed].
InGaN/GaN multiquantum well, grown by MOCVD on a sapphire substrate and annealed under the conditions of 700 and 900 degrees C x (20 min)(-1), was studied by means of mirco-Raman spectroscopy and photoluminescence. The Raman peak of E2, A1 showed red shift after multiquantum were wells annealed, and the HWHM of Raman peakdecreased imperceptibly. Moreover,the photoluminescence peak of the sample annealed under the condition of 700 degrees x (20 min)(-1) showed a red shift, then appeared a blue shift under the condition of 900 degrees C x (20 min)(-1). These results clearly showed that the sample annealed induced strain stress relief that could explain Raman peak shift, but the piezoelectric field induced the quantum-confined Stark effect, which can't agree with the photoluminescence experiment. Sample annealed could change the width of quantum well and InGa phase segregated; these factors influencing structure of quantum well could explain the results of photoluminescence spectra.
Gallium↗
[Synthesis and photoluminescence properties of Tb(3+) -acetylacetone ternary complexes doped with La3+ or Y3+].
Four series of solid complexes including RE(x) Tb(1-x) (acac)3 phen and RE(x) Tb(1-x) (acac)3 bipy (RE = La, Y; x = 0, 0.10, 0.20, 0.30, 0.50, 0.70, 0.90, 1.00) were synthesized. These complexes were characterized by IR spectra and XRD. Photoluminescence (PL) properties of these complexes were studied. The relation between their fluorescence intensities and the content of doped ions was also discussed. The experimental results show that the PL intensity of Tb3+ was sensitized by La3+ or Y3+ , and La3+ is better than Y3+ in enhancing the fluorescence of Tb3+. When x = 0.1-0.3, the fluorescence intensities of most doped complexes are stronger than their corresponding pure Tb3+ complex.
Fluorescence↗
[Synthesis of a novel rare earth light conversion agent and study on its compatibility in plastics].
2-octyl-1, 3-diphenol-1, 3-propdione was synthesized by phase transfer catalysis and its Sm complexes were prepared. These compounds were characterized by IR, EA, UV and 1H NMR; Sm complex and its mixture doped with PE and PVC show photoluminescence at 650 nm. There is excellent compatibility between Sm complex and plastics by the addition of long carbon chain. Therefore, Sm complex with long carbon chain is a superior light conversion agent with good compatibility in resins with emission wavelength suitable to the 643 and 660 nm for plants' photosynthesis.
Catalysis↗
[Influence of excitation light wavelength on the fluorescence spectra of ethanol solutions].
Ethanol solution can emit visible fluorescence when induced by UV light. With emission spectral profiles similar on the whole, the peaks are red-shifted distinctly when the excitation light alters from 200 to 250 nm. And the spectral profiles of ethanol solutions with different concentrations are also red-shifted when induced by the same wavelength of excitation light. A thorough analysis of the rule of spectrum peaks that are red-shifted is carried out and discussed in theory and in experiment. Investigation on the intrinsic fluorescence spectrum of ethanol solution and its characteristics will contribute to the study of the fluorescence spectra when ethanol serves as a solute and hydrolysis catalyst. Especially, this study will also help to offer a sensitive method of the determination of ethanol.
Ethanol↗
[Effects of chemical sensitization on photoelectron time-resolved spectrum].
The time-resolved spectra of free photoelectrons and shallow-trapped electrons in the T-grains AgBrI emulsion were simultaneously detected with microwave absorption and dielectric spectrum detection technique. The results indicate that the electron trap effects of sulfur sensitization centers and sulfur-plus-gold sensitization centers are different with equal quantities of Na2S2O3 added. The sulfur sensitization centers acted as a deep electron trap to pick up the electronic decay because of increasing the number of deep trapped electrons, while the sulfur-plus-gold sensitization centers as a shallow electron trap decrease the electronic decay through effectively controlling the recombination between the electrons and the holes. The depth of sulfur-plus-gold sensitization center is shallower than that of sulfur sensitization center after the KAuCl4 is added. The effects of sulfur sensitization center and sulfur-plus-gold sensitization center on the photoelectron decay are different in different sections of decay curves through the change in electron time-resolved spectra.
Algorithms↗
[Determination of fleroxacin by photochemical fluorescence of zinc-fleroxacin complex].
Based on the complex formed by Zn2+ which can strengthen the relative fluorescence intensity of fleroxacin evidently, a novel photochemical fluorescence method was developed. The effects of the acidity, the concentration ratio of Zn2+ to fleroxacin, and the time for illumination were studied. Under the optimum experiment conditions, the linear range of the determination was 5.00 x 10(-8) - 5.00 x 10(-6) mol x L(-1). The detection limit was 4.2 x 10(-8) mol x L(-1). The relative standard deviation of the determination of fleroxacin (5.0 x 10(-7) mol x L(-1)) was 1.7% (n = 20). The method was successfully applied to the determination of fleroxacin in specimens, and the recoveries were in the range of 95.0%-105%. The mechanism of this system is proposed.
Fleroxacin↗
[A silicon phthalocyanine axially substituted by nipagin: synthesis, molecular spectroscopic properties, and in vitro photodynamic activities].
A new silicon phthalocyanine axially substituted by Nipagin, i.e. bis(4-methoxycarboxyl phenoxy)phthalocyaninatosilicon, has been synthesized and characterized by IR, NMR, HPLC and elemental analysis. Its electronic absorption spectra and fluorescence spectra in different solvents were investigated. It was found that the compound existed in the form of monomer in a saline solution containing 2% (phi) Cremophor EL and 20% (phi) propanediol. The electronic absorption spectra of the compound in the above saline solution were typical for non-aggregated phthalocyanines, showing an intense and sharp Q band at 683 nm with a molar absorption coefficient of 7.47 x 10(4) mol(-1) x L x cm(-1). The compound exhibited a relatively strong fluorescence emission at 690 nm with a quantum yield of 0.34 and with a fluorescence lifetime of 4.7 ns. The primary in vitro assay showed the compound had photodynamic killing activities against B16 melanoma cells with a LD50(half lethal dose) of 1.2 x 10(-4) mol x L(-1).
Chromatography, High Pressure Liquid↗
[Ozone and carbon monoxide concentration distribution on Taishan Mountain].
The concentrations of ozone (O3) and carbon monoxide (CO) on the top of Taishan Mountain were monitored, and the variations and correlation were studied. The results show that the frequency of O3 hourly concentrations more than the first-degree of National Ambient Air Quality Standard(GB-3095-1996, NAAQS) was 15.81%, and the frequency of CO concentrations more than the first-degree of NAAQS was zero. The variation of O3 concentrations appears in a narrow scope, which indicates that there is scarcely influenced by the pollution of industry around. The diurnal variation of the concentrations of O3 and that of CO both present two peaks with the peaks of O3 in the behind of CO, which indicates that the concentration variations of O3 and its precursor CO are primarily controlled by local photochemical reaction process. The daily concentrations of O3 correlated well with CO.
Air↗
[Acidic components of precipitation: humid deposition of S, N and Cl compounds].
Precipitation samples have been gathered using recipients that differentiate the dry deposition of the humidity in three stations in Spain: one urban (Madrid) and two at base levels (San Pablo de los Montes and Granada). The study is centred on the components of an acid character, for which significant special variations of the sulphate and nitrate concentrations have been obtained. The levels, highest in Madrid and lowest in San Pablo, show the influence of the emitting focal points. A study of the seasonal variations in San Pablo show that the concentrations in summer are more than double than those in winter, probably due to the intervention of the photochemical formation processes of these contaminants. Also studies of humidity deposition are carried out, from which one can observe greater monthly values that are greater in Madrid than in other stations, in spite of having less rainfall. Likewise, episodes of "acid rain" and "red rain" are commented on.
Acid Rain↗
In vitro response of human bone marrow progenitor cells to superoxide radicals.
Human bone marrow progenitor cells, grown on solid agar, developed colonies of the white blood cell series, principally granulocytes, monocytes and macrophages. Following exposure to superoxide radicals, generated photochemically, a fraction of the progenitor cells was inactivated as evidenced by loss of colony formation. The loss in proliferative capacity depended on the illumination time and individual nature of the donated specimens. Protection of the progenitor cells by active superoxide dismutase depended on the illumination time and temperature. Inactive superoxide dismutase and active catalase did not protect the cells from the photochemical inactivation process.
Colony-Forming Units Assay↗
Kinetics of drug degradation. Part 58: a method of preparation and the stability of 3% aqueous indometacin solution.
A method was worked out which allows one to obtain 3% aqueous indometacin solution. The above can be done by solubilization of indometacin by means of ethyl carbamate and ethylurea in the concentration of 30% each and boiling the mixture for 30 s. The stability of indometacin in the above solution was checked with respect to elevated temperatures and exaggerated UV light conditions and compared with the stability of the same solution but without the solubilizing agents. It appears that the solubilizing agents diminish both the hydrolytic as well as the photochemical degradation processes of indometacin. 3% aqueous indometacin solution is stable for 25 months at 20 degrees C, and it is practically non-susceptible to the effects of diffused light for many years. The indometacin solution proposed shows low acidity (pH = 6.95). It is believed that the above solution can be introduced to everyday medical treatment.
Biological Availability↗
[Patterns of variations for air concentrations of some pollutants].
Patterns of diurnal variations for the air concentration of some pollutants emitted from motorvehicles are presented. Primary pollutants (carbon monoxide, nitric oxide and reactive hydrocarbons) and secondary pollutants (ozone and nitrogen dioxide) are continuously monitored since 1974. Different typical patterns have been obtained in the winter and in the summer season. The values of r for 14 regression curves calculated for couples of primary pollutants are in the range from 0.73 to 0.95, indicating their common source. Diurnal patterns obtained for summer and winter are discussed in the light of photochemical atmospheric processes Values for the ratio NO/NO2 are higher than 1 in the winter season; the same ratio is lower than 1 in summer, from 13 to 24 hours.
Air Pollutants↗
Photochemical oxidation of p-chlorophenol by UV/H2O2 and photo-Fenton process. A comparative study.
In this study, photochemical advanced oxidation processes (AOPs) utilizing the combinations of UV/H2O2 and the photo-Fenton reaction (UV + classical Fenton reaction) were investigated in lab-scale experiments for the degradation of p-chlorophenol. The study showed that the photo-Fenton process, (a mixture of hydrogen peroxide and ferrous or ferric ion), was the most effective treatment process under acidic conditions and produced a higher rate of degradation of p-chlorophenol at a very short radiation time. It accelerated the oxidation rate by 5-9 times the rate for the UV/H2O2 process. The reaction was found to follow the first order, the reaction was influenced by the pH, the input concentration of H2O2 and the amount of the iron catalyst and the type of iron salt. The experimental results showed that the optimum conditions were obtained at a pH value of 3, with 0.03 mol/l H2O2, and 1 mmol/l Fe(II) for the UV/H2O2/Fe(II) system and 0.01 mol/l H2O2 and, 0.4 mmol/l Fe(III) for the UV/H2O2/Fe(III) system. The reactions were accompanied by the generation of Cl- which reached its maximum value at a short reaction time when using the photo-Fenton process. Finally a rough comparison of the specific energy consumption shows that photo-Fenton process reduced the energy consumption by at least 73 to 83% compared with the UV/H2O2 process.
Chlorophenols↗
Pathogen inactivation of platelets with a photochemical treatment with amotosalen HCl and ultraviolet light: process used in the SPRINT trial.
BACKGROUND: A photochemical treatment (PCT) system has been developed to inactivate a broad spectrum of pathogens and white blood cells in platelet (PLT) products. The system comprises PLT additive solution (PAS III), amotosalen HCl, a compound adsorption device (CAD), a microprocessor-controlled ultraviolet A light source, and a commercially assembled system of interconnected plastic containers. STUDY DESIGN AND METHODS: A clinical prototype of the PCT system was used in a large, randomized, controlled, double-blind, Phase III clinical trial (SPRINT) that compared the efficacy and safety of PCT apheresis PLTs to untreated apheresis PLTs. The ability of multiple users was assessed in a blood center setting to perform the PCT and meet target process specifications. RESULTS: Each parameter was evaluated for 2237 to 2855 PCT PLT products. PCT requirements with respect to mean PLT dose, volume, and plasma content were met. Transfused PCT PLT products contained a mean of 3.6 x 10(11) +/- 0.7 x 10(11) PLTs. The clinical process, which included trial-specific samples, resulted in a mean PLT loss of 0.8 x 10(11) +/- 0.6 x 10(11) PLTs per product. CAD treatment effectively reduced the amotosalen concentration from a mean of 31.9 +/- 5.3 micromol per L after illumination to a mean of 0.41 +/- 0.56 micromol per L after CAD. In general, there was little variation between sites for any parameter. CONCLUSIONS: The PCT process was successfully implemented by 12 blood centers in the United States to produce PCT PLTs used in a prospective, randomized trial where therapeutic efficacy of PCT PLTs was demonstrated. Process control was achieved under blood bank operating conditions.
Animals↗
Cross-linked transfer RNA functions in all steps of the translation process.
A specific photochemical reaction between 4-thiouridine and cytosine cross-links two arms of transfer RNA. This cross-link, introduced into phenylalanine transfer RNA and arginine transfer RNA, limits the conformational freedom of the molecule. Both modified transfer RNA's are capable of functioning in all steps of protein synthesis with this restraint on allowable conformations.
Arginine↗