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Notes: Ultrahigh-vacuum surface studies of hydrogen ion interactions with silicon carbide thin films were performed to provide new insights into the mechanisms of diamond thin-film nucleation. These experiments were carried out at room temperature using hydrogen ions with energies of 10, 100, 500, and 2000 eV. In situ analyses using Auger electron spectroscopy indicated that silicon atoms were removed from the surface and near-surface layers of the film, and the resulting carbon-rich layers were converted to a mixture of sp2 and sp3 carbon. The relative amounts of sp2 and sp3 species formed were strongly dependent upon ion energy. The highest concentration of sp3 carbon was obtained using 500 eV ions. Theoretical considerations suggest this behavior was the result of both chemical and energy transfer effects. © 1995 American Institute of Physics.

Notes: Auger electron spectroscopy has been used as an in situ diagnostic in ultrahigh vacuum studies of diamond nucleation and growth on silicon. It is demonstrated that sp3-bonded carbon can be formed under ultrahigh vacuum conditions in the absence of excess hydrogen using a flux of C2H4 molecules. For the conditions reported here, a silicon adlayer is always present on the surface of the growing thin film. The presence of this adlayer suggests that the formation of sp3-bonded carbon occurs by a surfactant mediated process. Specifically, silicon is thought to maintain the template for sp3-carbon growth by minimizing the surface free energy for this structure. Further, the silicon adlayer is thought to enhance the growth kinetics of sp3 carbon by providing a more reactive growth surface than a hydrogen-terminated carbon surface. © 1998 American Institute of Physics.

Notes: Nine polymorphic nuclear-gene (allozyme) loci were surveyed among 491 red drum (Sciaenops ocellatus) sampled in 1988 and 1989 from nearshore localities in the northern Gulf of Mexico (Gulf) and the Atlantic coast of the southeastern United States (Atlantic). Data were combined with those from a previous study to generate a data set of 762 individuals representing 11 sample localities in the Gulf and 175 individuals representing five sample localities in the Atlantic. The combined data set included individuals from the 1986 and 1987 year classes and permitted rigorous testing of both temporal and spatial genetic heterogeneity. Average heterozygosity-per-locus values (estimated using 33 assumed monomorphic loci) were 0·048 (Gulf red drum) and 0·046 (Atlantic red drum). Tests of heterogeneity in allele frequencies between year classes at individual localities and across regions (Gulf and Atlantic) were non-significant. Tests of spatial (geographic) heterogeneity indicated that red drum are weakly subdivided: genetically-differentiated subpopulations occur in the northern Gulf and along the south-eastern Atlantic coast. Genetic data were consistent with the hypothesis that red drum within the Gulf and along the Atlantic coast comprise singie subpopulalions. Genetic differences between Gulf and Atlantic red drum seem likeiy to stem from historical or recent interactions between dispersal and impediments to gene flow.

Notes: Improved methods for obtaining, preparing, and staining fish chromosomes are described. Included are procedures for resolving serial or G-type bands. A brief review of various metaphase banding procedures and their use in fishes is also presented.

Notes: In phylogenetic analyses, conducted on the ND4L gene and part of the ND4 gene from species of the genus Pimephales, maximum parsimony yielded four trees, with the strict consensus providing no resolution of relationships among species. Maximum likelihood and minimum evolution methods yielded identical tree topologies, which differed from previous hypotheses of relationships for these species. If this topology is correct, it implies independent evolution of morphological characters, possibly associated with convergent trophic specialization.

Notes: Background There is a current need for a reliable prognostic marker for melanoma patients, particularly those with stage 2 and stage 3 disease, so that adjuvant therapies can be directed appropriately. Objectives To establish whether or not the use of tyrosinase-specific or melanA/MART-1-specific reverse transcriptase-coupled–polymerase chain reaction (RT–PCR) of peripheral blood cells detects preclinical disease progression in patients with malignant melanoma. Methods Two hundred and ninety-nine patients with melanoma in clinical stages 1–4 were observed in this study. Samples were obtained sequentially from 153 of these patients at 4-week intervals over a period of up to 2 years and correlated with clinical evidence of disease activity. Tyrosinase and melanA/MART-1 amplicons were analysed by agarose gel electrophoresis and Southern blot hybridization subsequent to a single round of amplification. Results We demonstrated a statistically significant increase in tyrosinase RT–PCR positivity with advancing stage of melanoma progression. The percentage tyrosinase positivity in 910 samples tested was: stage 1, 135 samples, 34% positive; stage 2, 196 samples, 51% positive; stage 3, 423 samples, 50% positive; and stage 4, 156 samples, 65% positive. The positivity rate for individual patients tested sequentially was higher if only one positive test was required to label a patient positive, at 42%, 65%, 82% and 81% for patients in stages 1–4, respectively. However, we did not find a clear pattern of conversion from negativity to positivity in patients who progressed during the study from stage 2 to stage 3 or stage 3 to stage 4, and found no clear evidence of increased positivity rates in the 6-week period following melanoma-related surgery in patients with stage 3 and 4 disease. The positivity rate for melanA/MART-1 was lower for both patients and samples, and no melanA/MART-1-positive sample was negative for tyrosinase. Conclusions We conclude that the presence of circulating tyrosinase-positive cells as detected by this method appears to be a discontinuous rather than a continuous phenomenon, even in patients with stage 4 disease. For this reason the assay cannot be recommended as a method of sequentially monitoring individual patients in a clinical setting.