Atmosphere ultraviolet irradiation

Fluorescent ultraviolet lamps within an apparatus that allows condensation cycles rather than the water spray typical of xenon arc tests have been developed for plastics testing (279). The spectral cutoff wavelength of the lamps used in the apparatus determines the severity of the test. Ultraviolet B (UVB) 313 lamps allow a significant irradiance component below 290 nm, which is normally filtered out by the earth s atmosphere. Ultraviolet A (UVA)... 

Priebe et al. [79] investigated the chemical stabiHty of iodixanol under accelerating cleavage of the central bridge under ultraviolet irradiation by a Norrish Type-II reaction. Basic conditions (pH 14) combined with heat (60 °C) initiated a cyclisation reaction. On the other hand, less than 1 % iodixanol decomposed in solution heated to 140 °C for 2 days or under both basic conditions (pH 11,20°C, 5 days) and acidic conditions (pH 0.4,80 °C, 5 days) or under an oxygen atmosphere (100°C,3 days). 

Ultraviolet irradiation of CCXLV, which is obtained by the condensation of diphenylketene and diphenyldiazomethane, in hydroxylic solvents, effects its cleavage into the starting materials in the presence of carboxylic acids or alcohols, photoaddition takes place with the formation of benzilic acid derivatives.167 On the other hand, irradiation of CCXLV in benzene containing acetic acid and/or methanol produces CCXLVI and CCXLVII, respectively. Irradiation in the presence of diphenylmethane under nitrogen atmosphere yields phenylacetic acid. 

Zerefos C.S., Factors influencing the transmission of solar ultraviolet irradiance through the Earth s atmosphere, in Solar Ultraviolet Radiation, Modelling, Measurements and Effects, edited by C.S. Zerefos and A.F. Bais, pp. 133-142, NATO-ASI Series, vol.52, Springer Verlag, 1997. 

Following the report on The Chemistry of the Atmosphere, it appears urgent to intensify sustained observational work in order to establish facts about any eventual evolution of our global environment. Such facts need to be gathered not only for physical parameters (temperature, albedo, variations of the solar ultraviolet irradiance below 3200 A, diffusion coefficients, aerosols, etc.) but also for a growing number of chemical species whose telluric concentrations are ultimately controlling the state of that environment. In 1960, a dozen molecules were known to exist in our atmosphere by 1980, 25 more species have been added to these and experimenters are asked now to look for another 40 molecules likely to play a role in the complex aeronomical scheme outlined by Professor M. Nicolet. 

Varotsos C. Alexandris D. Chronopoulos G. and Tzanis C. (2001). Aircraft observations of the solar ultraviolet irradiance throughout the troposphere. Journal of Geophysical Research-Atmospheres, 106(D14), 14843-14854. 

The above methods yield the rrans-form. White needles from benzene or alcohol, mp 200 -201. Can be sublimed or distilled at atmospheric press, with very little decompn. Absorption spectrum Purvis, J. Chem. Soc. 107, 97] (1906). One gram dissolves in about 100 ml alcohol ai 25. Ultraviolet irradiation of a soln in water-alcohol-ammonia gives the cis-form in 22% yield Wollring, Ber. 47, 112 (1914). Minute needles from toluene + meihanol, mp 158. By re-irradiation of a chloroform soln containing a trace of hro-mine, the more stable trans-form is regenerated. 

Ozone in the earth s atmosphere shields the surface from damaging ultraviolet irradiation in the 280 - 320 nm region (equation 1). Nature maintains a delicate balance between this natural process which depletes ozone, and other natural... 

In the atmosphere, TAL is decomposed photocat-alytically by ultraviolet irradiation, by ozone, or by hydroxyl radicals to the more stable, water-soluble ionic tri- and dialkylated species. Monoalkyl-lead cations are assumed to be very unstable. The... 

Atmospheric oxidants or sulfur oxides oxidize PAH to compounds including quinones, which are carcinogenic. PAH vary in their sensitivity to photooxidation. For example, 60% of B[a]P in soot particles was degraded under light in 40 minutes, whereas several other PAH showed little or no photooxidation (Thomas etal., 1968). On exposure of equimolar concentrations of B[a]P and benz[a]anthracene to a simulated atmosphere of ozone and ultraviolet irradiation, more than half of B[a]P was degraded in 30 minutes compared with only 20% degradation of benz[a]anthracene. 

Cross-linking of 1 by photochemical means to produce 5B was achieved in both air and argon atmospheres. Ultraviolet (UV) irradiation of the polymer 1 resulted in a decrease of tiie intensity of the triple bond absorption (2170 cm" ) as determined from FTIR spectroscopy. Even after irradiating for 4 days, the brown film 5B still showed some absorption due to the triple bond. Comparison of the... 

A. Diethyl propionylsuccinate (1). A solution of 412 g. (2.4 mole) of diethyl maleate (Note 1), 278 g. (4.8 mole) of freshly distilled propionaldehyde (Note 2), and 1.2 g. (0.0048 mole) of benzoyl peroxide in a normal 2-1. Pyrex flask is heated under reflux while undergoing irradiation with an ultraviolet lamp (Note 3). The initial reflux temperature is 60°. After 2 hours another 1.2 g. (0.0048 mole) of benzoyl peroxide is added. Strong reflux and irradiation are maintained throughout the entire reaction period. After 18 hours total time, the internal pot temperature reaches 68°. At this point the last 1.2 g. (0.0048 mole) of benzoyl peroxide is added, and the reaction is continued for a total of 30 hours, at which time the pot temperature reaches 74.5°. The reflux condenser is then replaced by a distillation head. The excess propionaldehyde (119 g.) is distilled under atmospheric pressure, b.p. 48-49°. Succinate 1 is distilled under reduced pressure. The main fraction, b.p. 145-151.5° (15-16 mm), provides 417-449 g. (75-81%) of product having sufficient purity for use in the next step (Note 4). 

Solid com and cassava starches have been irradiated with 337.8-nm pulsing ultraviolet light (2.6 ns with a peak power of 100 kW) emitted by an atmospheric-pressure nitrogen laser.270a Small changes could be observed in the water solubility of the irradiated starches, their water-binding capacity, and the iodine uptake, provided that promoters (1% w/w) were introduced. The activity of three promoters tested—ZnO, TiOz, and MgO—and the susceptibility of both starch varieties to the irradiation were approximately the same. 

Besides being desiccated and irradiated, microorganisms traveling in space will be exposed to space vacuum that can reach 10-14 pascal (a unit of pressure—100 Pa = 1 mbar).57 The result is extreme dehydration, and naked spores can survive for only days if exposed to space vacuum. Survival of spores is increased if they are associated with various chemicals such as sugars, or are embedded in salt crystals. Nicholson et al. (2000) discuss the various stresses that a microbial cell or spore would have to endure to survive interplanetary travel.58 They include the process that transports them out of Earth s atmosphere, such as volcanic eruptions and bolide impacts, long periods of transit in the cold of space, and atmospheric entry into a new planetary home. Spores have been shown to survive the shock conditions of a meteorite impact and the ultraviolet radiation and low temperature of space.59 It is clear that panspermia is possible and even probable if bacterial spores become embedded in rocks that are ejected from one planet and eventually enter the atmosphere of another. Bacterial... 

Models of irradiated disks predict four chemically distinct zones (see Fig. 4.1). (I) Zone of ices in the cold mid-plane opaque to incoming radiation. Chemistry in this region is dominated by cold gas-phase and grain-surface reactions. Here Infrared Space Observatory (ISO) and Spitzer observations confirmed the existence of ices, various silicates and PAHs (polycyclic aromatic hydrocarbons e.g. van den Ancker et al. 2000 van Dishoeck 2004 Bouwman et al. 2008). (II) Zone of molecules, a warm molecular layer adjacent to the mid-plane, dominated by ultraviolet/X-ray-driven photochemistry (III) the heavily irradiated zone of radicals, a hot dilute disk atmosphere deficient in molecules and (IV) the inner zone, inside of the ice line where terrestrial planets form. 

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