Electrochemical Oxidation of Am(III) Ions in HNO3 Solutions

Formal oxidation potentials (E0 ^p) of the Am(IV)/Am(III) couple were measured and the kinetics of electrochemical oxidation of Am(III) on platinum electrode in concentrated solutions of nitric acid (1-6 M) containing potassium phosphotungstate K_{1 0}P₂W_{1 7}O_{6 1} (KPW) was studied. The formal potential E0 ^p only slightly depends on the concentration of HNO₃ and is shifted toward the negative region by 1.0 V as compared with the standard values. The extent of Am(III) oxidation increases with increasing KPW concentration and decreasing concentration of nitric acid. Electrochemical oxidation of Am(III) is accompanied by radiochemical reduction of Am(IV) and is described by the equation -dC _{A m ( I I I )}/dt = (k + k ₁)C _Am(III) - k ₁ C ₀ - k ₀, where k is the apparent rate constant of electrochemical oxidation of Am(III), k ₁ is the apparent rate constant of Am(IV) reduction, and k ₀ is the constant of radiation-chemical reduction of Am(IV).     

Sorption properties of silicate materials based on Ca2SiO4 in humic acid solutions

The effect of humic acids (HA) in river water on the sorption properties of metallurgical slag (major component Ca₂SiO₄) was revealed in batch sorption experiments. Interaction of HA with sorbate cations in solution and with the sorbent surface affects the character of the sorption process found previously for dicalcium silicate. This interaction results in a decrease in the affinity of dicalcium silicate to multiple-charged cations [REE(III), U(VI), Th(IV)] in their sorption from river water by more than an order of magnitude. Possible chemical transformations responsible for a decrease in the sorption affinity of the silicate sorbent are discussed: complexation of HA with metal cations in the aqueous phase and competing reactions of the sorption of HA and calcium humate complexes on the surface of sorbent particles.     

Experimental investigation of a matrix receiver for a 3-mm waveband imaging system

The characteristics of a planar 8 × 8 array of a 3-mm waveband receiver antenna elements loaded with low-barrier planar Mott diodes have been studied. Experimental data on the radiation-directivity patterns (RP) and sensitivity of antenna elements in the two-dimensional array are presented. The average RP width for central elements amounts to ～35° in the E plane and ～50° in the H plane. In the operating frequency range (90–100 GHz) of the matrix receiver, the average voltage responsivity is on the order of 9000 V/W at a noise equivalent power of about 5 × 10^?12 W/Hz^1/2.     

Hydrodynamics of rising bubbles and drops

Conclusion An analysis of the problem concerning the interaction of moving single formations (bubbles and drops) with the surrounding carrying medium shows the possibility of describing real physical processes within the frameworks of the models of ideal and viscous liquids. Generalization of experimental and theoretical data is made by constructing charts of flow modes. A successful selection of the dimensionless numbersR andR as coordinates made it possible to arrange in an ordered fashion in the diagram all of the media by means of the parameter M, with the data for each specific medium being located on a certain straight line whose slope is determined by M. Vast computational data both of the present author and of other investigators for the region of small and intermediate values of dimensionless parameters, converted into theR ,R functions, made it possible to fully display the region inaccessible for investigation when the effect of all the parameters is significant and their number cannot be reduced. The use of these very parameters for correlating the data of the problem of steady rise of a drop made it possible to simply demonstrate the influence both of the presence of the medium itself and its motion on the drop rise. Comparison of the data with the problem of bubble rise can be made by simple superposition of diagrams. The logical clarity of the parametersR , which is equal to the ratio of the equivalent radiusa of a bubble (drop) to the capillary constant of the surrounding medium , allowed the determination of a certain critical sizea after which waves appear on the surface at the back side of the bubble (drop) when the value ofa is higher than 2-3. Another form of instability of steady rise is associated with the formation of a stagnant zone and with the separation of flow from the surface of a bubble or drop characteristic for surrounding media with small values of M. The use of the parametersR andR will definitely significantly simplify the analysis of more complex problems, for example, the problems of the motion of bubbles and drops in tubes with liquid and also the change in the external conditions (reduced or increased gravitation).Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 1, pp. 93–123, January, 1994.     

Phase Relations in the Li–V2O5–Cu System at 600°C and Cathodic Properties of Cu x V2O5

The phase relations in the Li–V₂O₅–Cu system at 600°C are studied by x-ray diffraction. The existence of the known vanadium bronzes M _x V₂O₅ (M = Li, Cu) is confirmed, and the composition ranges of the related solid solutions are determined. -Li _x V₂O₅ (0.22 x 0.49) and -Li _x V₂O₅ (0.88 x 1.0) are shown to dissolve Cu, forming Li _x Cu _y V₂O₅ solid solutions with y = 0.72 – 1.48x and y = 0.58 – 0.18x, respectively. Cu _x Li _y V₂O₅ solid solutions (y= 0.51 – 0.76 x) are only obtained from -Cu _x V₂O₅ (0.24 x 0.67). -Li _x V₂O₅ and -Cu _x V₂O₅ form a continuous series of solid solutions. The cathodic properties of Li–V₂O₅–Cu materials in high-temperature pulsed lithium batteries are investigated.     

Aero-optic effects in turbulent flows

Large-scale vortices and related aero-optic effects in a turbulent boundary layer, a free mixing layer, and an underwater stream have been mathematically simulated. The results are used for the analysis of distortions in the wavefront-phase function of a coherent light beam, which are induced by turbulent fluctuations in the parameters of the medium. The results of numerical calculations are compared to the experimental data and to a solution of the Reynolds equations.     

A broad-spectrum microbicide with virucidal activity against sexually transmitted viruses

Sodium dodecyl sulfate (SDS), an alkyl sulfate surfactant derived from an organic alcohol, possesses surfactant properties but also denatures and unfolds both monomeric and subunit proteins. In preliminary experiments, we demonstrated that SDS is a potent inactivator of herpes simplex virus type 2 and human immunodeficiency virus type 1 at concentrations comparable to those used for the surfactant nonoxynol-9. We hypothesized that SDS might be capable of denaturing the capsid proteins of nonenveloped viruses. In this report, we demonstrate inactivation of rabbit, bovine, and human papillomaviruses after brief treatment with dilute solutions of SDS. Effective concentrations were nontoxic to rabbit skin and to split-thickness grafts of human foreskin epithelium. This is the first report of a microbicidal surfactant that will inactivate papillomaviruses. We propose that SDS is now a candidate microbicide for formulation and testing with humans.     

Perinatal brain iron deficiency increases the vulnerability of rat hippocampus to hypoxic ischemic insult

The translational initiation codon for thymidylate synthase (TS) mRNA is located in a unique stem-loop structure which contains an internal cytosine-cytosine (CC) bubble. This stem-loop structure is thought to be important in the regulation of TS translation, which is itself an important target for anticancer drugs, such as 5-fluorouracil. Internal bubble or bulge structures are candidate receptors for the aminoglycoside antibiotics. It is shown here that aminoglycosides bind in a specific and saturable fashion with dissociation constants of approximately 1 microM to a TS mRNA site 1 construct and that the binding site for the aminoglycosides is located in the CC bubble region. In fact, the CC bubble, when grafted into other stem-loop structures, confers aminoglycoside binding on them. These studies reveal an additional binding domain for aminoglycosides and also suggest how novel anti-cancer drugs might be designed that affect TS mRNA translation rather than enzyme function.