Biography:

In the past J.L. O'Brien has collaborated on articles with J.S. Haggerty and W.J. Leombruno. One of their most recent publications is Growth and characterization of single crystal ZrB2. Which was published in journal Journal of Crystal Growth.

More information about J.L. O'Brien research including statistics on their citations can be found on their Copernicus Academic profile page.

J.L. O'Brien's Articles: (4)

Growth and characterization of single crystal ZrB2

AbstractSingle crystals of ZrB2 have been grown by an RF induction heated floating zone process under high ambient pressures. Pressures up to 20 atm were used to control the stoichiometry of the crystals by reducing volatilization from the melt. The boron losses are more than twice that of Zr from the diboride melt. The effect of pressure on material losses by volatilization is discussed in terms of a model in which the rate controlling step is diffusion through a convection boundary layer.Oriented plate-like precipitates were observed in the ZrB2 single crystals. The nature of precipitate particles observed in two crystallographic orientations is discussed. Transmission electron microscopy analyses were used to identify the structure of the precipitates, lattice parameters and relative crystallographic orientations to the ZrB2 matrix lattice. Laser microprobe analysis of extracted particles was used to characterized them chemically. The match between the crystal lattices strongly influences the morphology of the precipitate particles.

Structure and orientation of the second phase in ZrB2 crystals

AbstractThe nature of two orientated precipitates observed in high purity ZrB2 single crystals is discussed. Optical and electron microscopy were used to identify the precipitates' crystal structures and their relative orientations to the ZrB2 matrix lattice. Laser microprobe analysis of extracted particles was used to characterize them chemically. The morphology of the particles is determined by the match between the crystal lattices.

Regular PaperMolecular characterization of a third malic enzyme-like AP65 adhesin gene ofTrichomonas vaginalis

AbstractAdherence to the vaginal epithelium by the sexually transmitted parasiteTrichomonas vaginalisis mediated by four trichomonad surface proteins (AP65, AP51, AP33 and AP23). We recently showed that the 65-kDa adhesin is a member of a multigene family comprised of two similar but distinct proteins, AP65-1 and AP65-2, encoded by the genesap65-1andap65-2, respectively. An additional immuno-crossreactive clone, the 1.2 kb F11.1 cDNA, was isolated from a phagemid expression library and encoded a fusion protein of ≈ 46 000 daltons (46 kDa) that bound to HeLa cell surfaces. A significant portion of the 5′ end was missing which, using the 5′-RACE method, was obtained and combined with the F11.1 clone to give a full-length cDNA. Theap65-3gene encoded for a protein of 567 amino acids with a molecular mass of 63.1 kDa. The gene showed 88% and 96% identity at the DNA level withap65-1andap65-2, respectively. Restriction mapping confirmed that the three AP65 genes are different. Southern analysis revealed that theap65-3gene is present in theT. vaginalisgenome in multiple copies. Experiments with agar clones of trichomonads showed that each gene of the multigene family is present in all parasites, and Northern analysis showed thatap65-3is expressed and transcriptionally regulated by iron. Theap65-3gene had a leader sequence and, as withap65-1andap65-2, showed significant homology to malic enzyme. Finally, analysis of the 3′-untranslated regions revealed that the transcript ofap65-3had a long poly (A) tail in comparison toap65-1andap65-2. Even more intriguing, sequences were found that may relate to differential degradation of select AP65 transcripts, such as the sequence motifs AUUUA forap65-1mRNA and UUAUUUAU for theap65-2mRNA, which were not found forap65-3.

Regular ArticleVariational Boundary-Element Analysis of Small-Amplitude Fluid Oscillation in a Low-Gravity Environment

AbstractA variational boundary element technique is developed to analyse the small-amplitude oscillation of an incompressible, inviscid fluid contained in a rigid tank of arbitrary geometry under low-gravity conditions. Due to the influence of surface tension, the fluid usually oscillates about a curved free surface, which must first be determined by the solution of a nonlinear equilibrium problem. All of the energy expression for the linear vibration problem are derived in terms of the normal displacement of the fluid boundary, which leads to a generalized eigenproblem. Numerical results are presented for several two- and three-dimensional evaluation problems; whenever possible, comparisons are made with known analytical solutions. The results indicate that the boundary element technique is robust and accurate.

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