ABSTRACT
An SO2 gas sensor was developed by using a hydrogen sulfite-selective electrode positioned behind a gas-permeable membrane (GPM). The hydrogen sulfite-selective electrode was prepared by incorporating a multicyclic guanidinium ionophore in a plasticized poly(vinyl chloride) membrane. This gas sensor presents important advantages over the conventional Severinghaus-type SO2 gas sensor that contains a pH electrode immersed in an internal solution behind the GPM. The Severinghaus gas sensor suffers interferences from weak acids that can cross the GPM as gases and change the pH of the internal solution. In contrast, in the proposed sensor, the excellent selectivity of the HSO3- electrode and the ability of the GPM to discriminate gaseous from nongaseous species combine to generate the most selective potentiometric SO2 gas sensor reported to date.
Subject(s)
Air Pollutants/analysis , Guanidine/chemistry , Sulfur Dioxide/analysis , Gases , Ionophores , PotentiometryABSTRACT
[formula: see text] The scope of the palladium-catalyzed cross coupling reaction of aryl halides with phenyltrimethoxysilane has been expanded to include aryl bromides, heteroaryl bromides, and aryl chlorides. A more general Pd(0)-catalyst/ligand system has been developed to activate bromides: palladium(II) acetate (Pd(OAc)2) is activated with triphenylphosphine (PPh3) or tri-o-tolylphosphine (P(o-tol)3) (1:2 molar ratio of Pd:phosphine). Coupling of aryl chloride derivatives required addition of 2-(dicyclohexylphosphino)biphenyl (Buchwald's ligand) to Pd2dba3 (tris-(dibenzylideneacetone)dipalladium(0)) (1:1.5 molar ratio of Pd:phosphine).
Subject(s)
Siloxanes/chemistry , Catalysis , Ligands , Organosilicon Compounds/chemistry , Palladium , Thiophenes/chemistryABSTRACT
Major reform in nursing education is underway, with increased emphasis being placed on the importance of the teacher-student relationship. An instrument for evaluation of teaching effectiveness, developed at the Oregon Health Sciences University School of Nursing, attempts to capture the student's perception of the quality of the teacher-student relationship as well as other salient aspects of teaching practices. The evaluation tool contains 26 items evaluating teaching effectiveness and 14 items that evaluate the course. The teaching effectiveness items yield five scales including: knowledge and expertise, facilitative teaching methods, communication style, use of own experiences, and feedback. Psychometric testing has been completed and there is evidence of construct validity in relation to teaching effectiveness and internal consistency reliability for the five scales.
Subject(s)
Employee Performance Appraisal , Faculty, Nursing/standards , Psychometrics , Teaching/standards , Analysis of Variance , Effect Modifier, Epidemiologic , Factor Analysis, Statistical , Humans , Interpersonal Relations , Nursing Education Research , Oregon , Professional Competence , Regression Analysis , Reproducibility of Results , StudentsSubject(s)
Antibody Formation , Nucleic Acid Hybridization , RNA/analysis , Ribonucleases/pharmacology , Analysis of Variance , Animals , Autoradiography , Cells, Cultured , DNA/biosynthesis , Deoxyribonucleases/pharmacology , Hemolytic Plaque Technique , In Vitro Techniques , Mice , RNA/biosynthesis , Spleen/cytology , Spleen/metabolism , Thymidine/metabolism , Tritium , Uridine/metabolismABSTRACT
A method has been described for obtaining radioautographs of plaque-forming cells. The method permits radioautographic analyses of small numbers of plaque-forming cells amidst large populations of non-plaque-forming cells. Spleen cells that were pulse-labeled with tritiated thymidine could be categorized readily as labeled or not labeled. Using this method it was found that (a) at least 55% of plaque-forming cells which appear 3 days after a maximal stimulus of 4 x 10(8) sheep red cells are still capable of DNA synthesis, and must have arisen by cell proliferation; (b) the rate of proliferation of plaque-forming cells is proportional to the log of the dose of antigen; (c) the S period of plaque-forming cells is at least 2 hr, appears to be constant, and is not influenced by antigen dose. The results suggest that antigen stimulates proliferation of plaque-forming cells by hastening their transit through the G(1) phase of the generative cycle.
