Conduction and Transport Numbers in Metacomposites MeWO<Subscript>4</Subscript> ⋅ WO<Subscript>3</Subscript> (Me = Ca,Sr, Ba)

The conduction and transport numbers of charge carriers for composites in the systems MeWO₄-WO₃ (Me = Ca, Sr, Ba) are studied as a function of the temperature and the activity of oxygen in a gas phase. The transport numbers are determined by an emf method and are estimated from dependences of conductance on the activity of oxygen in a gas phase. The deficiencies of the given procedure as applied to investigation of properties of composite phases are analyzed. The materials under study are classified with a class of metacomposites. The concentration intervals of the ionic, mixed, and electronic conductions are determined. The conduction of composites of compositions (100 − x)MeWO₄ ⋅ xWO₃ is predominantly ionic at x ≤ 10 (Me = Ca), x ≤ 60 (Me = Sr), and x ≤ 45 (Me = Ba). The obtained data are explained in the framework of a model that represents a composite as a distributed matrix system where a film of surface phase MeW-s with a high mobility of oxygen ions plays the role of a connected matrix. It is presumed that the surface phase MeW-s possesses double-sided surface activity (α _MeW-s ≤ ) and a higher mobility with respect to MeWO₄ and WO₃. The discovered anomalies of dependences (T) and partial dependences , σ_el(T) are explained by a change in the stoichiometry, morphology, and the degree of connectedness of surface phase MeW-s caused by with a change in the temperature and composition of composites.__________Translated from Elektrokhimiya, Vol. 41, No. 6, 2005, pp. 680–693.Original Russian Text Copyright © 2005 by Neiman, Pestereva, Sharafutdinov, Kostikov.Published on the basis of a report delivered at the VII Meeting on Fundamental Problems in Solid-State Ionics (Chernogolovka-2004).     

Modulation of humoral immune response to oral BCG vaccination by Mycobacterium bovis BCG Moreau Rio de Janeiro (RDJ) in healthy adults

We hypothesize that the energy strategy of a cell is a key factor for determining how, or if, the immune system interacts with that cell. Cells have a limited number of metabolic states, in part, depending on the type of fuels the cell consumes. Cellular fuels include glucose (carbohydrates), lipids (fats), and proteins. We propose that the cell's ability to switch to, and efficiently use, fat for fuel confers immune privilege. Additionally, because uncoupling proteins are involved in the fat burning process and reportedly in protection from free radicals, we hypothesize that uncoupling proteins play an important role in immune privilege. Thus, changes in metabolism (caused by oxidative stresses, fuel availability, age, hormones, radiation, or drugs) will dictate and initiate changes in immune recognition and in the nature of the immune response. This has profound implications for controlling the symptoms of autoimmune diseases, for preventing graft rejection, and for targeting tumor cells for destruction.     

Methyl (E)-2-(2-phenylcyclopropylidene)acetate: Synthesis, isomerization, and reaction with 1,3-diphenyl-2-benzofuran

Treatment of 3-methyl-2-phenylcycloprop-2-ene-1-carboxylic acid with potassium tert-butoxide induced its isomerization into trans-2-methylidene-3-phenylcyclopropane-1-carboxylic acid which was converted into methyl ester, and heating of the latter for 1 h in toluene gave methyl (E)-2-(2-phenylcyclopropylidene)acetate. Thermal isomerization of methyl (E)-2-(2-phenylcyclopropylidene)acetate on prolonged heating in toluene afforded 5-methoxy-3-methyl-2-phenylfuran, and the reaction with 1,3-diphenyl-2-benzofuran resulted in [4 + 2]-cycloaddition at the exocyclic double bond.     

Comparative characterization of thermal isomerization rates of 6‐phenyl‐1,5‐diazabicyclo[3.1.0]hexane at convection and microwave heating

Rate constants of thermal isomerization of 6‐phenyl‐1,5‐diazabicyclo[3.1.0]hexane into 1‐(benzyl)‐4,5‐dihydro‐1H‐pyrazole at convection and microwave heating in toluene and chlorobenzene (solvents) were determined within the temperature range 90°C to 120°С. These data were used for the calculation of activation parameters of isomerization. It is shown that microwave heating increases the rate constants at the same temperature by a factor of 2 to 2.5 as compared with those using convection heating. The reason is that the effective temperature of microwave heating exceeds that of convection heating by 6°C to 9°С in toluene and by 12°C to 20°С in chlorobenzene as solvent.     

N-(4-(di-tert-butyl[F]fluorosilyl)benzyl)-2-hydroxy-N,N-dimethylethylammonium bromide ([F]SiFANBr): A novel lead compound for the development of hydrophilic SiFA-based prosthetic groups for F-labeling

¹⁸F-labeled compounds play a major role in the development of new in vivo imaging agents for Positron Emission Tomography (PET), a non invasive imaging modality depicting the biodistribution of radioactive compounds in humans. Recently we reported a new method for the introduction of fluorine-18 into a range of organic molecules exploiting the very fast ¹⁸F-¹⁹F isotope exchange of fluorosilanes (termed SiFA compounds). Here, we wish to report the labeling of the first charged SiFA molecule N-(4-(di-tert-butylfluorosilyl)benzyl)-2-hydroxy-N,N-dimethylethylammonium bromide (SiFAN⁺Br⁻) serving as a lead compound in the development of SiFA-based prosthetic groups of reduced lipophilicity for biomolecule labeling. Mild conditions for synthesis of [¹⁸F]SiFAN⁺Br⁻ and an easy purification procedure using simple C-18 solid phase cartridge have been developed yielding the [¹⁸F]SiFAN⁺Br⁻ in radiochemical yields of 34% (non-decay corrected) within 40 min. A series of kinetic experiments were performed that show high isotopic exchange rate constants. Low activation energy (15.7 kcal/mol) and a large preexponential factor (7.9 × 10¹³ M⁻¹ s⁻¹) were calculated for the isotopic exchange reaction from a corresponding Arrhenius plot. For comparison, the ¹⁸F-fluorination of ethyleneglycol-di-p-tosylate via the formation of a carbon-¹⁸F bond showed a 1.3 kcal/mol higher activation energy and a much lower preexponential factor of 2.9 × 10⁹ M⁻¹ s⁻¹. Moderate hydrophilicity (log D = 0.44), stability in aqueous media at pH up to 7.4 and a high specific activity of [¹⁸F]SiFAN⁺Br⁻ (SA = 20.4 GBq/μmol, 0.55 Ci/μmol) make this charged SiFA compound useful for the development of novel SiFA-based ¹⁸F-labeling synthons.     

Cascade Transformations of (2,2-Diaryl-3,3-dichloroaziridin-1-yl)acetates

Esters of (2,2-diaryl-3,3-dichloroaziridin-1-yl)acetic acid prepared from glycine derivatives under alkylation conditions afford esters of 2-[N-alkyl-N-(2,2-diaryl-1-cyanovinyl)amino]-3,3-diarylacrylic acid in 20-40% yield. The reaction resulting in these compounds proceeds through a cascade of 3-chloro-2-azadiene and ylide intermediates. 3-Chloro-2-azadienes originating from (2,2-diaryl-3,3-dichloroaziridin-1-yl)acetates react with primary and secondary amines at the carbon atom of imine group providing ketenimines which undergo ketenimine-nitrile rearrangement or fragmentation. The other bases (KOH, MeONa, DBU) effect dehydrochlorination of the mentioned 3-chloro-2-azadienes giving nitrile-ylides which are trapped by nucleophilic reagents. The 3-chloro-2-azadiene obtained from methyl (2,2-diaryl-3,3-dichloroaziridin-1-yl)acetate and DBU was relatively stable and was isolated as an individual compound. (2,2-diaryl-3,3-dichloroaziridin-1-yl)propionates behave as nonfunctionalized dichloroaziridines.     

1,3-dipolar cycloaddition of fluorinated azomethine ylides at the C=N bond

Azomethine ylides generated by reaction of difluorocarbene with N-alkyl- and N-arylimines derived from benzaldehyde and benzophenone react with N-benzylidenebenzenesulfonamide in a regioselective fashion, yielding the corresponding imidazolidin-4-ones via 1,3-dipolar cycloaddition at the C=N bond. Ylides generated from benzaldehyde imines give rise to mixtures of stereoisomeric 2,5-diphenyl-1-(phenylsulfonyl)-imidazolidin-4-ones, the cis isomer prevailing.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 10, 2004, pp. 1542–1548.Original Russian Text Copyright © 2004 by Novikov, Khlebnikov, Egarmin, Kopf, Kostikov.     

Thermal Isomerization of 2-Bromo-2-fluoro-1-alkylidenecyclopropanes in Polar Solvents

2-Bromo-2-fluoro-1-alkylidenecyclopropanes heated in polar solvents undergo isomerization into substituted 3-bromo-2-fluoro-1,3-butadienes. 2-Bromo-3-methyl-1-methylene-3-phenyl-2-fluorocyclopropane at heating afforded a mixture of substituted 1-(bromofluoromethylene)cyclopropane and isomeric 1-bromo-1-fluoro-1,3-butadienes.