Observation of a Sharp Transition in Contact Angle in the Wetting of Graphite by Solid Pb-Ni Alloys

The wetting of Pb-Ni crystals on graphite has been observed at 558 K in a Scanning Auger Microprobe. Samples were prepared so as to produce 10 m crystals of Pb with Ni contents increasing from 0 to 0.3 wt% along one axis of the graphite substrate. In the low Ni region, the contact angle was found to decrease slowly from 119° to 98° with increasing Ni content. In the region of high Ni content, a constant contact angle of 83° was measured. In between, crystals with contact angles of 98° and 83° were observed to coexist, near the limit of solubility of Ni in Pb, indicating the presence of a first order transition in contact angle. The continuous decrease in contact angle, in the low Ni region, is due to Ni adsorption at the Pb-graphite interface, which leads to a decrease in interfacial energy. The constant contact angle in the high Ni region is associated with the precipitation of a Ni-rich phase. Various hypotheses are advanced to account for the first order transition in contact angle as a function of Ni concentration.     

β-Decay schemes of very neutron-rich sodium isotopes and their descendants

The γ-activities from the β-decay of Na isotopes up to ³⁴Na, formed in high-energy fragmentation and analysed through mass-spectrometry techniques, are observed as well as those from their Mg descendants. The I_γ, intensities, the β-delayed one- and two-neutron probabilities and the I_β intensities are measured. Decay schemes are proposed. We confirm, from the low location of the first 2⁺ level of ³²Mg, the occurrence of a nuclear deformation at $\text{Z ? 11, N ? 20}$.     

Copper-free monomeric and dendritic palladium catalysts for the Sonogashira reaction: substituent effects, synthetic applications, and the recovery and re-use of the catalysts

A series of bis(tert-butylphosphine)- and bis(cyclohexylphosphine)-functionalized Pd(II) monomers and polyamino (DAB) dendritic catalysts were synthesized and investigated for Sonogashira carbon-carbon coupling reactions in a copper-free procedure. The influence of phosphine substituents (tBu versus Cy) on the reaction kinetics was investigated by a GPC technique to monitor the reactions. The dendritic catalysts containing the cyclohexylphosphine ligands could be recovered and reused without loss of efficiency until the fifth cycle. The dendritic Pd(II) catalysts show a negative dendritic effect, that is, the catalyst efficiency decreases as the dendrimer generation increases.     

Stability of $$\mathcal{P}(S)$$ under Finite Perturbation

Abstract. T. Kato [9] found an important property of semi-Fredholm pencils, now called the Kato decomposition. Few years later, M.A. Kaashoek [7] introduced operators having the property as a generalization of semi-Fredholm operators. In [4], it is proved that these two notions are linked. The aim of this work is to study the stability of the property under finite perturbation.     

Long-lasting stable cavitation

Stable cavitation is produced on the surface of a special target, i.e., an abrasive foil with a grain size of about 15 microm, insonified by a 473 kHz focused beam. Cavitation bubbles are first created by a pressure of about 2 MPa. Progressive reduction of the pressure to about 100 kPa leads to a state of stable cavitation characterized by strong stable emission of the half-order subharmonic. This state can be maintained for five hours if the defining parameters (position and pressure) are optimized and constant to within a few percent. There is strong evidence for the presence of "latent" cavitation bubbles, which can persist for a few minutes without being excited.     

Mitochondrial activities in human cultured skin fibroblasts contaminated by <Emphasis Type="Italic">Mycoplasma hyorhinis</Emphasis>

Background  

Mycoplasma contaminations are a recurrent problem in the use of cultured cells, including human cells, especially as it has been shown to impede cell cycle, triggering cell death under various conditions. More specific consequences on cell metabolism are poorly known.     

Enantioselective synthesis of BMS-204352 (MaxiPost) using N-fluoroammonium salts of cinchona alkaloids (F-CA-BF4)

The enantioselective synthesis of a potent Maxi-K potassium channel opener (BMS-204352) mediated by N-fluoroammonium salts of cinchona alkaloids is described. Two synthetic pathways were evaluated. An ee as high as 88% was achieved (>99% after a single recrystallisation).     

Dissimilar material joining using laser (aluminum to steel using zinc-based filler wire)

Joining steel with aluminum involving the fusion of one or both materials is possible by laser beam welding technique. This paper describes a method, called laser braze welding, which is a suitable process to realize this structure. The main problem with thermal joining of steel/aluminum assembly with processes such as TIG or MIG is the formation of fragile intermetallic phases, which are detrimental to the mechanical performances of such joints. Braze welding permits a localized fusion of the materials resulting in a limitation on the growth of fragile phases. This article presents the results of a statistical approach for an overlap assembly configuration using a filler wire composed of 85% Zn and 15% Al. Tensile tests carried on these assemblies demonstrate a good performance of the joints. The fracture mechanisms of the joints are analyzed by a detailed characterization of the seams.