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Osmium

About: Osmium is a research topic. Over the lifetime, 4255 publications have been published within this topic receiving 80166 citations. The topic is also known as: Os & element 76.


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Journal ArticleDOI
12 Jun 1998-Science
TL;DR: By converting the ions generated in an electrochemical half-cell reaction to a fluorescence signal, the most active compositions in a large electrode array have been identified.
Abstract: Combinatorial screening of electrochemical catalysts by current-voltage methods can be unwieldy for large sample sizes. By converting the ions generated in an electrochemical half-cell reaction to a fluorescence signal, the most active compositions in a large electrode array have been identified. A fluorescent acid-base indicator was used to image high concentrations of hydrogen ions, which were generated in the electrooxidation of methanol. A 645-member electrode array containing five elements (platinum, ruthenium, osmium, iridium, and rhodium), 80 binary, 280 ternary, and 280 quaternary combinations was screened to identify the most active regions of phase space. Subsequent “zoom” screens pinpointed several very active compositions, some in ternary and quaternary regions that were bounded by rather inactive binaries. The best catalyst, platinum(44)/ruthenium(41)/osmium(10)/iridium(5) (numbers in parentheses are atomic percent), was significantly more active than platinum(50)/ruthenium(50) in a direct methanol fuel cell operating at 60°C, even though the latter catalyst had about twice the surface area of the former.

904 citations

Journal ArticleDOI
TL;DR: The staining characteristics suggest the fibrous material of chick embryo mitochondria to be a nucleic acid-containing structure, and its variable appearance after different fixations parallels that previously reported for the nucleoplasm of bacteria and blue-green algae.
Abstract: Chick embryo mitochondria, studied with the electron microscope, show crista-free areas of low electron opacity. These areas are observable after fixation with osmium tetroxide, calcium permanganate, potassium permanganate, formaldehyde, acrolein, acrolein followed by osmium tetroxide, uranyl acetate followed by calcium permanganate, and acetic acid-alcohol. Staining of sections with lead hydroxide or uranyl acetate, or with both, resulted in an increased density of a fibrous material within these areas. The appearance of the fibrous structures varied with the fixative employed; after fixation with osmium tetroxide the material was clumped and bar-like (up to 400 A in diameter), whereas after treatment of osmium tetroxide-fixed tissues with uranyl acetate before dehydration the fibrous structures could be visualized as 15 to 30 A fibrils. Treatment with ethylenediaminetetraacetate (EDTA) in place of uranyl acetate coarsened the mitochondrial fibrils. After fixation with calcium permanganate or potassium permanganate, or a double fixation by uranyl acetate followed by calcium permanganate, the fibers appeared to have a pattern and ultrastructure similar to that observed after the osmium tetroxide-uranyl acetate technique, except that some of them had a slightly greater diameter (up to 50 A). Other fixatives did not preserve the fibers so well. The fibers appeared strongly clumped by formaldehyde fixation, and were difficult to identify after fixation with acrolein or acetic acid-alcohol. The staining of nucleic acid-containing structures by uranyl acetate and lead hydroxide was improved by treatment of osmium tetroxide-fixed sections with hydrogen peroxide, and the mitochondrial fibers also had an increased density in the electron beam after this procedure. The staining characteristics suggest the fibrous material of chick embryo mitochondria to be a nucleic acid-containing structure, and its variable appearance after different fixations parallels that previously reported, or described in this paper, for the nucleoplasm of bacteria and blue-green algae. The results, in addition to those described in the accompanying communication, indicate that these mitochondria contain DNA.

513 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202344
2022137
202138
202044
201938
201852