Porous structure of synthetic opals

Some adsorption, structural, and annihilation characteristics of synthetic opals are measured. An analysis of these characteristics makes it possible to conclude that the total porosity in opals comprises macropores, which are in essence the voids between structure-forming spheres, and nanopores connected to the substructure of the spheres. The systems of macropores and nanopores are separated by narrow channels that collapse upon the thermal treatment of opals. The sizes of primary a-SiO₂ particles and nanopores, which correspond to the voids between these particles, are estimated.     

Structure and thermal properties of double complex salts [RuNO(NH<Subscript>3</Subscript>)<Subscript>4</Subscript>(H<Subscript>2</Subscript>O)]<Subscript>2</Subscript>[MCl<Subscript>4</Subscript>]Cl<Subscript>4</Subscript>·2H<Subscript>2</Subscript>O,M = Pt,Pd

Double complex salts (DCS) [RuNO(NH₃)₄(H₂O)]₂[MCl₄]Cl₄·2H₂O, M = Pt (I) and Pd (II), are prepared and characterized using IR spectroscopy, single crystal and powder X-ray diffraction, and thermogravimetric analysis. Crystalline phases of I and II are isostructural (P2(1)/n space group) and have the following crystallographic characteristics: a = 6.689 Å, b = 15.609 Å, c = 12.348 Å, V = 1289.1 ų, Z = 2, d _x = 2.425 g/cm³ (I) and a = 6.637 Å, b = 15.521 Å, c = 12.244 Å, V = 1261.2 ų, Z = 2, d _x = 2.255 g/cm³ (II). The thermolysis of the obtained DCS in the hydrogen atmosphere affords two-phase mixtures of limited solid solutions of the metals: hcp for ruthenium-based ones and fcc for Pt or Pd based solutions. On decomposition in the helium atmosphere the products contain a minor amount of RuO₂. For the phases obtained during thermolysis the parameters are determined and the compositions are estimated. The heating of I to 400°C in the helium-air atmosphere yields a nanocrystalline composite Pt+RuO₂ with CSR of ～20 nm.     

The thermodynamic properties of 4-pentenoic acid

The enthalpy of formation of liquid 4-pentenoic acid was determined by combustion calorimetry. The vapor pressure and enthalpy of vaporization of the compound were measured by the transfer method over the temperature range 289–324 K. Conformational analysis was performed. The equilibrium structure, fundamental vibrations, moments of inertia, and total energy of the stablest acid conformers were calculated by the B3LYP/6-311G(d, p) and G3MP2 quantum-chemical methods. The experimental IR spectrum and calculated vibrational frequencies were used to assign IR bands. The thermodynamic properties of monomeric 4-pentenoic acid in the ideal gas state were calculated over the temperature range 0–1500 K. Additive and quantum-chemical methods were used to estimate the Δ_f H°(g) and Δ_vap H° values. Close agreement between the calculation results and experimental data was obtained. It was shown that additive and quantum-chemical methods could be used for estimating the enthalpies of formation and vaporization of nonconjugated alkenoic acids.     

Immunomodulatory properties of silver-containing nanocomposite on the basis of polyvinyltriazole

Russian Chemical Bulletin - The water-soluble nanocomposite with the uniform distribution of silver nanoparticles in polymer matrix was synthesized on the basis of poly-1-vinyl-1,2,4-triazole....     

Physicochemical aspects of preservation of cellulose paper with polymers

The process of preservation of newspaper with aqueous solutions and dispersions of acrylic copolymers is considered from the instant of impregnation till removal of the polymeric preservative from paper.     

Formation of nitrosothiols by the reaction of different forms of hemoglobin with (tetranitrosyl)bis(pyrimidin-2-ylthio)diiron

The reaction of hemoglobin (Hb), oxyhemoglobin (HbO₂), and methemoglobin (metHb) with the tetranitrosyl iron complex of the fu₂-S type [Fe₂(SC₄H₃N₂)₂(NO)₄] (1) was studied. The reaction results in the nitrosylation of the free SH group of 93-β-cysteine in these forms of hemoglobin. The change in the Hb, HbO₂, and metHb concentrations was monitored by spectrophotometry, recording the difference absorption spectra of the experimental systems with these forms of hemoglobin and the buffer containing complex 1 in the same concentration. The absorption spectra were processed to obtain the components using the MATHCAD method. The nitrosothiol concentration was determined by the Saville reaction. In a protic medium containing 3.3% DMSO, complex 1 spontaneously generates NO due to hydrolysis (k = 3.7 · 10^-4 s^-1). Oxyhemoglobin reacts with evolved NO to form metHb. Complex 1 reduces metHb with a high rate to yield Hb (k = 6.7 · 10^-3 s^-1) followed by the formation of HbNO (k = 6.5 · 10^-3 s^-1). Oxidized complex 1 yields NO with a higher rate than the starting complex does. The reaction of HbO₂ and metHb (0.02 mmo1 L^-1) with complex 1 affords nitrosothiols in micromolar concentration during 5 min, and no nitrosothiol is formed in the case of Hb.     

Efficient shift scheduling in the retail sector through two-stage optimization

Efficient workforce scheduling has an important impact on store profit and customer service. Standard scheduling problems do not recognize the effect of staff availability on customer sales, however, even though the latter is an important factor in the retail sector. In this paper a two-stage model is proposed for this purpose. In the first stage a sales response model is used to specify hourly staff requirements. The output of the sales response model is then used as the input of a mixed integer optimization model, which finds an optimum assignment of the staff to daily shifts. Simulations are used to validate the sales response function, and to revise the model for more accurate results. In the simulations, customer arrivals and sales response error values are generated using appropriate distribution functions. As a case study the proposed model is applied to a Turkish retailer in the apparel sector.     

An exponential form of the normalized time correlation function

In the present work, a chain of the Zwanzig–Mori equations is considered for normalized time correlation functions (NTCFs). A solution to the chain of equations is derived under assumption that any NTCF has an exponential form. It is demonstrated that the solution obtained does not satisfy the condition that the NTCF is equal to unity at the initial moment of time. For this reason, exponential NTCFs are approximate, they meet an approximate dynamics. Exactly exponential dynamics is impossible.     

The temperature dependence of parachor

The results obtained in studying the temperature dependence of parachor are presented. The concepts of the parachor at the critical point and reduced parachor are introduced. The approach based on scaling principles and the assumption of a universal character of changes in crossover functions at critical exponents was used to obtain a universal temperature dependence of the reduced parachor. The dependence of the parachor at the critical point on the critical molar volume was established. The constituents of parachor were determined for halogenated hydrocarbons.     

Production and characteristics of substituted lanthanum niobate LaNb<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>W<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>4 + δ</Subscript>

Solid solutions LaNb_1–x W _x O_{4 + δ} (x = 0.02–0.10, Δx = 0.02) were investigated, which crystallize in the monoclinic system (space group I2/c) at room temperature and undergo a phase transition into the tetragonal modification with increasing temperature. The stability of various modifications was analyzed by high-temperature X-ray powder diffraction analysis. The electrical conductivity of sintered samples was studied by impedance spectroscopy. Insertion of tungsten into the niobium sublattice leads to an increase in the conductivity of the solid solutions.