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L F Allard

Publications and source records attributed to L F Allard.

5 recordsLinked to original sources
PubMed2006

Formation of ultrasharp vertically aligned Cu-Si nanocones by a DC plasma process.

We report an effective method for the production of ultrasharp vertically oriented silicon nanocones with tip radii as small as 5 nm. These silicon nanostructures were shaped by a high-temperature acetylene and ammonia dc plasma reactive ion etch (RIE) process. Thin-film copper deposited onto Si substrates forms a copper silicide (Cu3Si) during plasma processing, which subsequently acts as a seed material masking the single-crystal cones while the exposed silicon areas are reactive ion etched. In this process, the cone angle is sharpened continually as the structure becomes taller. Furthermore, by lithographically defining the seed material as well as employing an etch barrier material such as titanium, the cone location and substrate topography can be controlled effectively.

Acetylene↗
PubMed1976

Biological strandard for electron microprobe analysis of intracellular sodium concentration.

A method is described for the determination of the intracellular concentration of sodium in individual cells using the electron microprobe analyzer. This method gives an accuracy equal to that obtained by using flame photometry on tissues with large cell populations. Intracellular sodium was precipitated in the cell by a fixative containing pyroantimonate. Cartilaginous needles from shark fins which were equilibrated in saline solutions of differing concentrations were used as biological standards.

Animals↗
PubMedDate not supplied

Observations on normal and degenerating human otoconia.

Specimens of human otoconia obtained from autopsy material and representing various stages from fetal to advanced old age, were studied by microdissection, scanning electron microscopy, electron microprobe analysis, and x-ray powder diffraction. The typical adult otoconial configuration is a cylindrical, finely serrated body with pointed ends; crystallographically, it corresponds to a single crystal of calcite. Other, less numerous typed include jointed otoconia, pure rhombohedrons and multifaceted, presumably immature forms. Many otoconia achieve the adult configuration during fetal development. The multifaceted otoconia are most numerous, and the rhombohedrons proliferate, during childhon in the young adult, but saccular otoconia are the larger. In middle and advanced age the otoconia decrease in number, especially in the saccule. Saccular otoconia degenerate progressively in a posteroanterior direction across the macula; they assume a specific, fibours, hollowed-out appearance, which is not duplicated by either chemical etching or autolysis. Neogenesis and growth of otoconia appear to occur postnatally, with different characteristic growth potentials for those of the saccule and the utricle. Age-related saccular otoconial degeneration appears to involve the organic material, which disappears either before or simultaneously with the mineral substance.

Adolescent↗