The peculiarities of physical network formation in carboxyl-containing poly(dimethylcarbosiloxane)

An unusual effect of physical network formation during heating or at room temperature alter previous heating was found for originally liquid poly(dimethylcarbosiloxane) containing 0.5 – 2.5 mol% of side carboxyl groups by means of the measurement of its Theological properties. The reason for this behaviour is supposed to be the predominance of intramolecular hydrogen bonding of COOH groups in original polymer and the intra– to Intermolecular bonds rearrangement during heating. The alternative reason can be the microphase separation with domains of COOH groups. The reversibility of the network is confirmed by the decrease in the elasticity modulus, development of irreversible deformation on further heating and by break-up of Junctions on the addition of small amounts of polar liquids.     

Kinetics of Thermal Decomposition of Solid Propellant Based on Aluminum and Ammonium Perchlorate

Kinetic regularities of the mass loss and heat and-gas release were studied in the thermal decomposition of a solid propellant composed of aluminum, ammonium perchlorate, and a polymer binder. It was shown that, under heating from 40 to 340°C under permanent vacuum conditions, propellant samples decompose without ignition, with the limiting mass loss in the decomposition being 48%. When experiments were performed in air, the propellant formulation decomposes with sharp ignition, with the inflammation temperature (270–287°C) and amount of volatiles released by this instant of time (10–16 wt %) dependent on the heating rate. The kinetic regularities of the mass loss in the decomposition of a solid propellant were described in terms of the polychromatic kinetics model that assumes that the reaction system has ensembles of particles differing in reactivity. The distribution functions of the mass fractions of the propellant by activation energies of decomposition were calculated. The heat release kinetics in the decomposition of a propellant formulation in the temperature range 153–270°C in a closed evacuated system is described by a sum of equations for two parallel reactions: 1st-order reaction with a heat effect Q₁ = 200 ± 5 kJ kg^–1 and 1st-order autocatalysis with heat effect Q₂ = 1900 ± 50 kJ kg–1. The rate constants and the activation parameters of the process were determined.

     

Probable Mechanisms of Doxorubicin Antitumor Activity Enhancement by Ginsenoside Rh2

Ginsenoside Rh2 increases the efficacy of doxorubicin (DOX) treatment in murine models of solid and ascites Ehrlich’s adenocarcinoma. In a solid tumor model (treatment commencing 7 days after inoculation), DOX + Rh2 co-treatment was significantly more efficacious than DOX alone. If treatment was started 24 h after inoculation, the inhibition of tumor growth of a solid tumor for the DOX + Rh2 co-treatment group was complete. Furthermore, survival in the ascites model was dramatically higher for the DOX + Rh2 co-treatment group than for DOX alone. Mechanisms underlying the combined DOX and Rh2 effects were studied in primary Ehrlich’s adenocarcinoma-derived cells and healthy mice’s splenocytes. Despite the previously established Rh2 pro-oxidant activity, DOX + Rh2 co-treatment revealed no increase in ROS compared to DOX treatment alone. However, DOX + Rh2 treatment was more effective in suppressing Ehrlich adenocarcinoma cell adhesion than either treatment alone. We hypothesize that the benefits of DOX + Rh2 combination treatment are due to the suppression of tumor cell attachment/invasion that might be effective in preventing metastatic spread of tumor cells. Ginsenoside Rh2 was found to be a modest activator in a Neh2-luc reporter assay, suggesting that Rh2 can activate the Nrf2-driven antioxidant program. Rh2-induced direct activation of Nrf2 might provide additional benefits by minimizing DOX toxicity towards non-cancerous cells.     

Random Copolymers of Styrene with Pendant Fluorophore Moieties: Synthesis and Applications as Fluorescence Sensors for Nitroaromatics

Five random copolymers comprising styrene and styrene with pendant fluorophore moieties, namely pyrene, naphthalene, phenanthrene, and triphenylamine, in molar ratios of 10:1, were synthesized and employed as fluorescent sensors. Their photophysical properties were investigated using absorption and emission spectral analyses in dichloromethane solution and in solid state. All copolymers possessed relative quantum yields up to 0.3 in solution and absolute quantum yields up to 0.93 in solid state, depending on their fluorophore components. Fluorescence studies showed that the emission of these copolymers is highly sensitive towards various nitroaromatic compounds, both in solution and in the vapor phase. The detection limits of these fluorophores for nitroaromatic compounds in dichloromethane solution proved to be in the range of 10⁻⁶ to 10⁻⁷ mol/L. The sensor materials for new hand-made sniffers based on these fluorophores were prepared by electrospinning and applied for the reliable detection of nitrobenzene vapors at 1 ppm in less than 5 min.     

Heat Effects of the Thermal Decomposition of Amidoboranes of Potassium,Calcium, and Strontium

Thermal effects of the decomposition of potassium, calcium, and strontium amidoboranes at 354, 421, and 483 K are determined via drop calorimetry. The processes of decomposition are weakly exothermic and accompanied by the evolution of hydrogen. Upon the decomposition of calcium amidoborane at 421 K, a prolonged exothermic process is first observed; it is then followed by an endothermic effect, due possibly to the slow structural rearrangement of the product of decomposition. The solid products of decomposition are characterized by solid-state ¹¹В NMR, FTIR spectroscopy, and mass spectrometry.     

Photonuclear production and radiochemical separation of medically relevant radionuclides: 67Cu

Journal of Radioanalytical and Nuclear Chemistry - Production of medical radionuclide 67Cu by the irradiation of Zn of natural isotopic composition by bremsstrahlung photons of maximum energy of...     

Iminoquinones and Diimines,N-Hetero Analogues of 9,10-Phenanthrenequinone,in Coordination Chemistry

Russian Journal of Coordination Chemistry - The synthesis of N-hetero analogs of 9,10-phenanthrenequinones is discussed. The features of their structure are considered. Information on the use of...     

A simple and convenient method for synthesizing dipyrido[1,2-a :1′,2′-a′]benzo[1,2-d:5,4-d]diimidazole-6,13-dione

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Tutte polynomials of vertex-weighted graphs and group cohomology

Theoretical and Mathematical Physics - We construct a generalization of the Tutte polynomial for vertex-weighted graphs for which the coefficients of the “deletion–contraction”...     

Reliability of the direct ICP-MS analysis of volcanic ash nanoparticles

In the present work, major and trace element concentrations in suspensions of volcanic ash nanoparticles were determined by ICP-MS after either the acid digestion of the suspensions or the direct analysis of these suspensions. The results obtained were compared. Since the acid digestion can be accompanied by an important dilution or can consist in different steps of evaporation and dilution, the determination of some trace element concentrations became limited because of the limit of detection of the analytical instrument. Therefore, analysis after acid digestion of suspensions and direct analysis after acidification of these suspensions were carried out and compared. The concentration of Al, Fe, Y, La, Ce, Pr, Gd, Ho, Cu, Tl and Pb determined by both preparation procedures were in agreement. The values of relative standard deviation are in the range from 1% to 14%. These results prove the reliability of the direct ICP-MS analysis and the possibility of its further application in hyphenated systems for the dimensional and elemental characterisation of natural mineral nanoparticles.