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[en] A brief introduction is given on how the ozone layer formed and about the factors depleted ozone layer such as chloro bromo compounds and so on; then, it follows the processes which destroy the troposphere. The damaging effect of ultraviolet radiation is described. Finally,the action taken to reduce the depletion of ozone layer is presented
[en] The method described (freon 12) has the advantage of being inexpensive and relatively simple, the sensitivity lying between those of the traditional pneumatic trial and the different vacuum trials. The results obtained can be considered as highly satisfactory
[fr]La methode decrite (freon 12) presente l'avantage de faire appel a des moyens peu couteux et a une technique relativement simple, la sensibilite etant situee entre celle de l'epreuve pneumatique classique et celles des differentes epreuves sous vide. Les resultats obtenus peuvent etre consideres comme tres satisfaisants
[en] Complete text of publication follows. Mechanisms of reactions under the influence of light on the methyloxirane (MO) radical cations (RC) obtained by xray irradiation and stabilized in freonic matrices at 77 K are investigated by the ESR and UV-VIS spectroscopy as well as quantum chemistry (TD DFT, PBE1). The positions of two peaks in the UV-visible spectra are similar in both freons (λ1 ∼ 435 nm for < band 1> and 530 nm for < band 2>). The absorption coefficients are estimated to be 1.9 l/(mol cm) and 3.3 l/(mol cm) respectively, while the quantum yields of the reactions taking place under the influence of light (λ1 = 436 nm and λ2 = 546 nm) are approximately ψ = 0.03 and ψ = 0.02. As direct measurement of the hyperfine couplings in the ESR spectra proved problematic due to the complicated spectra, modeling of the spectra was carried out. The modeling was based on the results of the TD DFT calculations with further optimization for the better accommodation of experimental results, the most intriguing of which is the rather large doublet coupling constant arising in the ESR spectra corresponding to the 435 nm peak in the UV-VIS spectra. It's also necessary to mention that the quantum chemical calculations predict potential minima for two < ring-closed> forms for the MO RC (differentiated by the C-C bond length: 1.46 A versus 1.72 A which is the one with the large doublet coupling) as well as two < ring-open> forms. With the modeling being successful in separating individual experimental spectra attributed to three different forms of the MO RC it is discovered that the conclusions of Shida et al. are erroneous and the interpretation of the reversible photoinduced changes as cis-trans isomerisation of the < ring-open> forms of the RC must be substituted with an explanation taking a process that involves the < ring-closed> forms into account. ESR spectrum with the large doublet due to the < ring-closed> form with a longer C-C bond which arise from photochemical excitation (as opposed to the other cyclical form that doesn't exist at T 77 K) while the original spectrum observed immediately after irradiation is attributed to the mixture of the < ring-open> forms of the RC. The work was supported by the grant of RFBR (07-03-00105) and the program of Presidium of RAS ChD-01.
[en] Multiphoton ionization (MPI) fragments produced by 308 nm (XeCl) photons for CF3I and CH3Br symmetric top molecules have been measured. The cross sections and the relative fragments produced in each case vary considerably and are discussed separately. The high symmetry of molecules (such as CF3I and CH3Br) results in many transitions being weak or forbidden to normal one-photon spectroscopy whereas multiphoton spectroscopy with its different selection rules can reveal these forbidden transitions. Thus, MPI spectroscopy opens new pathways towards the understanding of excited electronic properties of polyatomic molecules. (G.Q.)
[en] The gas-phase co-pyrolysis of styrene with CHClF2 in a flow reactor at 550–650 °C gives 2,3-difluoronaphthalene in two parallel reaction channels. The main channel includes decomposition of CHClF2 to difluorocarbene, whose subsequent cycloaddition to styrene affords 1,1-difluoro-2-phenylcyclopropane. This compound rearranges to 2-fluoroindene giving finally difluoronaphthalene upon the second difluorocarbene cycloaddition and subsequent aromatization of the resulting cycloadduct. The second reaction channel consists in aromatization of 1,1,2,2-tetrafluoro-3-phenylcyclobutane, which is formed by the [2+2]-cycloaddition of styrene to tetrafluoroethylene, a product of difluorocarbene dimerization.
[en] The tests were part of the CFC replacement program to identify and test alternate coolants to replace CFC-114 being used in the uranium enrichment plants at Paducah and Portsmouth. The coolants tested, C4F10 and C4F8, were selected based on their compatibility with the uranium hexafluoride process gas and how well the boiling temperature and vapor pressure matched that of CFC-114. However, the heat of vaporization of both coolants is lower than that of CFC-114 requiring larger coolant mass flow than CFC-114 to remove the same amount of heat. The vapor pressure of these coolants is higher than CFC-114 within the cascade operational range, and each coolant can be used as a replacement coolant with some limitation at 3,300 hp operation. The results of the CFC-114/C4F10 mixture tests show boiling heat transfer coefficient degraded to a minimum value with about 25% C4F10 weight mixture in CFC-114 and the degree of degradation is about 20% from that of CFC-114 boiling heat transfer coefficient. This report consists of the final reports from Cudo Technologies, Ltd