Surface tension isotherms of a free surface and grain boundaries in the Cu-Sn system

Surface tension of pure copper and its alloys with Sn has been measured at 1000°C in a hydrogen atmosphere. Surface tension of a free surface equaled 1.81 N/m for pure copper, and 1.55, 1.38, and 1.28 N/m for the alloys with 0.05, 0.22, and 0.33 at % Sn, respectively; surface tension at grain boundaries equaled 0.5 N/m for pure copper, and 0.36, 0.3, and 0.23 N/m for the alloys, respectively. Based on these data, the concentration dependence of tin absorption at a free surface and grain boundaries has been calculated. Parameters of Sn absorption at grain boundaries and a free surface of copper have been compared with those of Sb and Bi.     

Formation of Porous SiC Ceramics by Pyrolysis of Wood Impregnated with Silica

Biomorphous β-SiC ceramics were produced at 1400°C from pine wood impregnated with silica. This one-step carbothermal reduction process decreases the cost of manufacturing of SiC ceramics compared with siliconization of carbonized wood in silicon vapor. The synthesized sample exhibits a 14 m²/g surface area and has a hybrid pore structure with large 5–20 μm tubular macropores and small (<50 nm) slit-shaped mesopores. SiC whiskers of 20–400 nm in diameter and 5–20 μm in length formed within the tubular pores. These whiskers are expected to improve the filtration by removing dust particles that could otherwise penetrate through large pores. After ultrasonic milling, the powdered sample showed an average particle size of ∼30 nm. The SiC nanopowder produced in this process may be used for manufacturing SiC ceramics for structural, tribological, and other applications.     

Effectiveness and prospectives for making new refractories for heating units in mining-beneficiating combines

Conclusions The East Institute of Refractories (VostIO) has carried out research on the basis of which, taking into account foreign experience, they determined the best compositions for refractory concretes for use in calcination machines for the mining-beneficiation combines; they developed a production method and a repair procedure for linings made of concretes by guncreting.Data on the resistance of these concretes in the linings of OK-306 machines at the Northern Combine (GOK) and two OK-I-520 machines operated at the Mikhailovsk Combine since 1977 indicate that the concretes satisfy modern requirements.The approximate demand for guncrete-concretes recommended for calcination machines by 1985 will be about 25,000 tons. A large proportion of the concretes will be required primarily for conveyer machines and RPO units in which the replacement of presently imported materials by Soviet is now specified.The final decision on the matter of organizing the production of the new materials will be taken by the corresponding planning and economic committees after completion of industrial trials of the concretes in the firing zone of conveyerized and shaft furnaces and in the hearths of agglomeration machines.Translated from Ogneupory, No. 8, pp. 20–25, August, 1981.     

Polymerization of monomers initiated by silyl centers in SiO deposits prepared by pulsed laser ablation

Deposits from silicon monoxide prepared by pulsed laser ablation were allowed to react with acrylic and vinyl monomers—styrene, methyl methacrylate and 1,2 ethylene glycol dimethacrylate. It was revealed by means of FTIR, electron paramagnetic resonance (EPR), and NMR spectroscopies that silyl ?Si· reacts with monomer molecules and initiates the consecutive polymerization. Crosslinking is proved by the occurrence of bending δ(? CH₂) absorption peak at about 750 cm^?1 in FTIR spectra. Because of very low concentration of the propagating radical for styrene we used a radical scavenger N‐phenyl‐t‐butylnitrone for trapping. The measured EPR parameters were compared with the calculated ones. In case of styrene, NMR analysis manifested the presence of Si? C bonds in SiC_xO_y (x + y = 2) units, which can be taken as direct evidence of the reaction between silyl centers and monomer molecules. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4488–4492, 2006     

The event bush as a semantic-based numerical approach to natural hazard assessment (exemplified by volcanology)

The event bush is a new formalism for organizing knowledge in various fields of geoscience, particularly suitable for hazard assessment purposes. Acting as an intermediary between expert knowledge and the well-established field of Bayesian belief networks, the event bush allows at the same time a variety of other applications, linking geoscientific knowledge to the field of artificial intelligence and uniting probabilistic, deterministic, and fuzzy approaches. In this paper, we present basic principles, mathematical formulation, guidelines for application, and examples, including the connection with Bayesian belief networks. Further development of the method will include spatial and temporal modelling, implementation in mapping in GIS medium, formalization by means of predicate logic, definition of variable states in BBNs by membership functions based on the event bush semantics, and other applications.     

Friction and wear of powder coatings of epoxy composites with alumosilicate nanoparticles

The paper studies the effect of alumosilicate nanofillers of tubular and lamellar shape on the friction and wear of epoxy composites. It is shown that the influence of concentration and shape of the fillers on the tribological behavior of the composites is due to variations in their viscoelastic properties and shielding of the contact area of the matrix material with the metallic counterbody by the filler particles. The data evidence that at equal concentrations of alumosilicate fillers in the epoxy matrix, the best tribological characteristics are provided in the case of tubular-shaped particles.     

Preparation of an exponentially rising optical pulse for efficient excitation of single atoms in free space

We report on a simple method to prepare optical pulses with exponentially rising envelope on the time scale of a few ns. The scheme is based on the exponential transfer function of a fast transistor, which generates an exponentially rising envelope that is transferred first on a radio frequency carrier, and then on a coherent cw laser beam with an electro-optical phase modulator. The temporally shaped sideband is then extracted with an optical resonator and can be used to efficiently excite a single (87)Rb atom.     

Plastic deformation of the plastic matrix–hard inclusion composite system during high-temperature gas extrusion

The results of investigations of the production of abrasive rod or wire diamond tools by high-temperature gas extrusion are presented. The versions of preparation of an initial metallic workpiece filled with a mixture of abrasive diamond grains are considered. The forming of plastic materials with hard inclusions, which is caused by deformation redistribution in the volume and is accompanied by the formation of pores and discontinuities adjoined to the hard inclusions, is considered. The results obtained demonstrate the prospects of application of high-temperature gas extrusion for the production of diamond tools for various purposes.     

One‐Step Formulation of Protein Microparticles with Tailored Properties: Hard Templating at Soft Conditions

Formulation of therapeutic proteins into particulate forms is a main strategy for site‐specific and prolonged protein delivery as well as for protection against degradation. Precise control over protein particle size, dispersity, purity, as well as mild preparation conditions and minimal processing steps are highly desirable. It is, however, hard to fit all these criteria with conventional preparation techniques. Here a one‐step hard‐templating synthesis of microparticles composed of functional, non‐denatured protein is reported. The method is based on filling porous CaCO₃ microtemplates with the protein near to its isoelectric point (pI) followed by pH‐ or EDTA‐mediated dissolution of the tempplates. In principle, a wide variety of proteins can be converted into microparticles using this approach. The main requirement is an overlap of the protein insolubility and a template solubility for a certain parameter (here pH or EDTA). Here the formulation of insulin particles is studied in detail and it is shown that particles consisting of high molecular weight protein (catalase) can also be prepared. In this context, the synthesis of CaCO₃ templates with controlled size, the mechanism of the protein microparticle formation and mechanical properties of the microparticles are discussed. For the first time, the fabrication of mesoporous monodispersed CaCO₃ microtemplates with identical porocity but tuned diameter from 3 to 20 μm is demonstrated. The protein particle diameter can be adjusted by choosing the appropriate template size that is critical for successful pulmonary delivery of insulin. As a first step towards insulin delivery, the in vitro release of insulin at physiological conditions is studied.