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[en] This paper presents experimental results on the effect of various operating parameters on the synthesis of gas hydrates by a method based on the self-organizing process of boiling-condensation of a hydrate-forming gas in the volume of water. A series of experimental studies were carried out under various conditions, and optimal conditions that affect the process of hydrate formation were determined. The influence of the water column height and the boiling intensity of the hydrate-forming gas on the hydrate formation process is estimated. Freon 134a was used as a hydrate-forming gas in the studies.

[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

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[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

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[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] Experimental results of spacer grid effect on the heat transfer under supercritical pressure conditions are investigated. The experiments are carried out in an electrically heated 19-rod bundle cooled with supercritical Freon R134a. Standard spacer grids with blockage ratio of 0.29 are equipped into the bundle. The local wall temperatures and heat transfer coefficients along the flow direction of the bundle are measured. An interpolation method to determine the fully developed Nusselt number at supercritical conditions is reported. The results indicate that the enhanced heat transfer is limited within 30 bundle diameters downstream of the spacer grids. A peak heat transfer enhancement is observed near the pseudo critical region, which cannot be captured by the subcritical correlations. Considering the maximum heat transfer enhancement as a function of dimensionless temperature ratio, an original approach for deriving the grid-enhanced heat transfer correlation for supercritical applications is presented and the corresponding correlation has been established.

[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.)