ABSTRACT
Dear colleagues: Our loyal friend Kuan-Teh Jeang, "Teh" to friends and colleagues, passed away unexpectedly at the age of 54 on the evening of January 27, 2013. Great shock and sorrow was apparent in the avalanche of email messages by the very many international colleagues with whom Teh interacted over the years. Many of us came to know Teh as an energetic and gifted scientist for whom we had much respect and affection.
Subject(s)
HIV Infections/history , HIV Infections/virology , HTLV-I Infections/history , HTLV-I Infections/virology , History, 20th Century , History, 21st Century , Humans , Mentors/history , National Institutes of Health (U.S.)/history , Periodicals as Topic/history , United States , Virology/historyABSTRACT
Small-scale developments have been made to an off-the-shelf continuous-flow gas chromatography/isotope-ratio mass spectrometry (CF-GC/IRMS) system to allow high-precision isotopic analysis of methane (CH(4)) and carbon dioxide (CO(2)) at ambient concentrations. The repeatability (1sigma) obtainable with this system is 0.05 per thousand for delta(13)C of CH(4), 0.03 per thousand for delta(13)C of CO(2), and 0.05 per thousand for delta(18)O of CO(2) for ten consecutive analyses of a standard tank. An automated inlet system, which allows diurnal studies of CO(2) and CH(4) isotopes, is also described. The improved precision for CH(4) analysis was achieved with the use of a palladium powder on quartz wool catalyst in the combustion furnace, which increased the efficiency of oxidation of CH(4) to CO(2). The automated inlet further improved the precision for both CH(4) and CO(2) analysis by keeping the routine constant. The method described provides a fast turn-around in samples, with accurate, reproducible results, and would allow a long-term continuous record of CH(4) or CO(2) isotopes at a site to be made, providing information about changing sources of the gases both seasonally and interannually.
Subject(s)
Air Pollution/analysis , Atmosphere/analysis , Carbon Dioxide/analysis , Flow Injection Analysis/instrumentation , Gas Chromatography-Mass Spectrometry/instrumentation , Methane/analysis , Robotics/instrumentation , Carbon Radioisotopes , Environmental Monitoring/instrumentation , Environmental Monitoring/methods , Equipment Design , Equipment Failure Analysis , Flow Injection Analysis/methods , Gas Chromatography-Mass Spectrometry/methods , Reproducibility of Results , Robotics/methods , Sensitivity and SpecificityABSTRACT
The effectiveness of sodium hypochlorite (NaOCl) (2.5%) or iodine (10%) for decontamination of the operation field (tooth, rubber dam, and gasket [Oraseal]) was compared by using bacterial cultivation. In addition, the final samples were also assessed for bacteria by using polymerase chain reaction. Teeth (n = 63) receiving root canal treatment were polished with pumice, isolated with rubber dam, and their margins sealed with Oraseal. The operation field was disinfected with hydrogen peroxide (30%), followed by iodine (n = 31) or NaOCl (n = 32), before and after access cavity preparation. The operation field was sampled before and after each decontamination, giving four samples per field. After the final decontamination, there was no significant difference (p = 0.602, 0.113, 0.204) in recovery of cultivable bacteria from various sites in either group. However, bacterial DNA could be detected significantly (p = 0.010) more frequently from the tooth surfaces after iodine (45%) compared with NaOCl (13%) decontamination, although on the rubber dam or Oraseal surfaces there was no difference. Root canal sampling for polymerase chain reaction might be better preceded by NaOCl decontamination than by iodine, based on the findings.
