Standard enthalpy of formation of La2CoO4(cr)

The enthalpies of reactions of La₂CoO₄(cr) and CoCl₂(cr) with hydrochloric acid were measured with an isothermal-jacket calorimeter. The results obtained and the available literature data were used to calculate the standard enthalpy of formation of La₂CoO₄(cr) at 298.15 K, Δ_f H ^o = ?2179 ± 7 kJ/mol.     

Signal recording in acoustooptical imaging of scattering media

An expression for a signal at the ultrasonic frequency from a photodetector arising when diffraction waves at the cathode mix is obtained for the case when the optical and acoustic beams are space-limited and Bragg angles are small. The alternating current generated when the scattering medium is crossed by a focused 3-MHz ultrasonic beam and illuminated by a cw He-Ne laser is measured. Satisfactory agreement between experimental results and those calculated from the formulas obtained indicates that our model treating acoustooptical interaction in the medium in terms of Raman-Nath diffraction is valid. Conditions for measuring the alternating current (which is a parameter of acoustooptical imaging) that are optimal from the viewpoint of maximizing the signal and signal-to-noise ratio are predicted theoretically and corroborated experimentally.     

Oxidative destruction of dinitrophenols by Fenton’s reagent in the presence of inorganic salts

The influence of inorganic salts on the kinetics of oxidation of 2,4-and 2,6-dinitrophenols by Fenton’s reagent, hydrogen peroxide, in the presence of iron(II) ions was studied.     

Electronic spectra of cationic forms of meso-tetrapropylporphin in a nanoporous silicate gel matrix

We have studied the fluorescence and fluorescence excitation spectra at 300 K, 77 K, and 4.2 K for silicate gel matrices colored with meso-tetrapropylporphin by impregnation of the matrix with a solution of the pigment. Comparison of the data obtained with the absorption spectra in acidified solutions and analysis of the low-temperature fine-structure vibronic spectra, and also taking into account data obtained earlier for octaethylporphin in a xerogel showed formation of two cationic forms of meso-tetrapropylporphin in the gel matrix: the short-wavelength form has a dicationic structure, while the long-wavelength form has a monocationic structure. We have traced out the correlations of the vibrational structure in the spectra of the dicationic form with data for the porphin dication, and we have drawn a number of conclusions concerning the normal vibrational modes that are active in the vibronic fluorescence and absorption spectra of the studied cationic forms. Using the AM1 semiempirical quantum chemical method, we optimized the geometry of the mesotetrapropylporphin dication: the most stable of the possible conformers is the dication structure with saddleshaped macrocycle nonplanarity. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 453–461, July–August, 2006.     

The contribution of the (t(τ)+N) component to the α-particle wave function from data on the reactions p(α,pp)t and p(α,pn)τ at incident α-particle momentum 5 GeV/c

The 2-meter liquid-hydrogen bubble chamber is exposed to a separated beam of α particles from the ITEP synchrotron. The momentum of the incident ⁴He nuclei, averaged over the fiducial volume of the chamber, is 5 GeV/c (the kinetic energy of initial protons in the nucleus rest frame is T _p =620 MeV). The spectral functions of decays α→tp and α→τn) are extracted in the 4π geometry (the latter is extracted for the first time) from the exclusive reactions αp→tpp and αp→τpn in the spectator momentum region 0<q<0.3 GeV/c. The pole dominance criteria are carefully checked. Extrapolation of the nuclear vertex function to the pole gives a lower bound on the nuclear vertex constant. Our experimental data are compared with the results of other studies and with theoretical calculations. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 2, 69–74 (25 July 1997) Published in English in the original Russian journal. Edited by Steve Torstveit.     

On Intersection Problem for Perfect Binary Codes

The main result is that to any even integer q in the interval 0 ≤ q ≤ 2^{n+1-2log(n+1)}, there are two perfect codes C₁ and C₂ of length n = 2^m − 1, m ≥ 4, such that |C₁ ∩ C₂| = q.     

Structure-property modelling of complex formation of strontium with organic ligands in water

The method of substructural molecular fragments based on representation of the molecular graph by ensembles of fragments and involving calculations of those contributions to the given property is applied to the modelling of stability constants of the complexes of strontium(II) with organic ligands in water. Reliability of predictions of developed structure-property models was examined using three different test sets of structurally diverse ligands. The obtained models have been used for generation and screening of combinatorial library of virtual ligands. Some hypothetical efficient Sr(II) binders were suggested.     

Study of nitrogen- and sulfur-containing heterocycles. 54. Properties and conversions of pyrimido[4,5-<Emphasis Type="Italic">b</Emphasis>]-1,4-benzothiazepines. Synthesis of a novel heterocyclic system: Pyrimido[5,4-<Emphasis Type="Italic">c</Emphasis>]isoquinoline

We have studied some properties and conversions of pyrimido[4,5-b]-1,4-benzothiazepines: reduction, oxidation, reactions with nucleophilic reagents (methanol, hydrazine, hydroxylamine, o-methylhydroxylamine, and thiosemicarbazide). We have synthesized derivatives of a novel heterocyclic system: pyrimido[5,4-c]isoquinoline.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1863–1872, December, 2004.For Communication 53, see [1].