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21.
BACKGROUND: Because the relative efficacy of antiarrhythmic agents on halothane-epinephrine arrhythmias has not been well characterized, this study was undertaken to comparatively evaluate the antiarrhythmic action of Na(+)-, K(+)- and Ca(2+)-channel blockers on epinephrine-induced ventricular arrhythmias during halothane anesthesia in rats. METHODS: Rats were anesthetized at random with either halothane (1.5%), isoflurane (2.0%), or pentobarbital (50 mg/kg intraperitoneally), and the lungs were mechanically ventilated with oxygen. The rats were studied in three consecutive protocols. Protocol I determined the arrhythmogenic thresholds of epinephrine during the three types of anesthesia in 33 rats. Protocol II determined the arrhythmogenic thresholds of epinephrine during halothane anesthesia in 64 rats receiving saline (control) or one of five antiarrhythmic agents. Protocol III measured the duration of epinephrine-induced arrhythmias during halothane anesthesia in 42 rats receiving saline (control) or one of five antiarrhythmic agents. RESULTS: In protocol I, the arrhythmogenic doses of epinephrine during halothane, isoflurane, or pentobarbital anesthesia were 1.7 +/- 3.2, 11.1 +/- 0.6, and 39.0 +/- 3.9 micrograms/kg, respectively, and the corresponding plasma concentrations were 4.3 +/- 0.8, 103.7 +/- 9.2, and 246.7 +/- 28.9 ng/ml, respectively. In protocol II, the arrhythmogenic doses were similar in rats receiving saline and in those receiving lidocaine. The arrhythmogenic doses in rats receiving verapamil, flecainide (Na(+)- and K(+)-channel blocker), E-4031 (K(+)-channel blocker), or amiodarone(K(+)-channel blocker with Na(+)-, Ca(2+)-, and beta-blocking activity) increased significantly, i.e., 4.2, 4.2, 5.5, and 31.7 times control (P < 0.01). In protocol III, lidocaine had no effect on the duration of arrhythmias. Flecainide, E-4031, and verapamil markedly reduced the duration of arrhythmias induced by epinephrine, 8 micrograms/kg intravenously (P < 0.01), whereas only amiodarone markedly reduced the duration of arrhythmias induced by epinephrine, 16 micrograms/kg intravenously (P < 0.01). CONCLUSIONS: It was concluded that agents with K(+)-channel blocking properties were the most effective in preventing halothane-epinephrine arrhythmias in rats. 相似文献
22.
N.J. Wagner 《Fuel》2008,87(8-9):1687-1697
With a finite amount of economically viable coal reserves in South Africa, it is becoming increasingly important to consider coal discards as vital energy resources. The energy content of discard coal is generally low and high in ash, but can be effectively utilised in power stations. However, coals weather during storage, and weathered coals behave differently to their fresh counterparts. During this investigation, discard coals from four stockpiles varying in age from 5 to 40 years were characterised chemically and petrographically, with a specific focus on the petrographic-based abnormal condition analysis to determine the degree of secondary weathering. Drop tube furnace tests were conducted to determine the combustibility of the weathered stockpiled or dumped coals relative to typical Eskom coals, and the resultant char forms were characterised. A direct correlation with the extent of weathering and combustion performance was determined, with the more weathered coals reporting enhanced combustion reactions at lower temperatures. 相似文献
23.
Coal-fired power generation facilities are the largest single anthropogenic source of mercury to the atmosphere. Global mapping of anthropogenic emissions has previously estimated the mercury emission from stationary combustion from South Africa at being 82.6 tonnes per annum, but preliminary in-house calculations have placed this at a significantly lower amount. A petrochemical facility in South Africa, utilising a significant amount of coal in its gasification and steam generation processes, undertook a project to determine a mercury mass balance across the complex, and to apportion the Hg emissions from the facility. 相似文献
24.
LC Myers MP Terranova AE Ferentz G Wagner GL Verdine 《Canadian Metallurgical Quarterly》1993,261(5125):1164-1167
The Escherichia coli Ada protein repairs methylphosphotriesters in DNA by direct, irreversible methyl transfer to one of its own cysteines. Upon methyl transfer, Ada acquires the ability to bind specific DNA sequences and thereby to induce genes that confer resistance to methylating agents. The amino-terminal domain of Ada, which comprises the methylphosphotriester repair and sequence-specific DNA binding elements, contains a tightly bound zinc ion. Analysis of the zinc binding site by cadmium-113 nuclear magnetic resonance and site-directed mutagenesis revealed that zinc participates in the autocatalytic activation of the active site cysteine and may also function as a conformational switch. 相似文献
25.
Solar cells based on hydrogenated amorphous silicon are now made from a variety of materials including alloys and microcrystalline
films. Research aimed at improving cell efficiency should emphasize studies of alloys and metastable defects. We discuss several
research topics related to the growth, structure, and electronic properties of these materials, which should lead to improved
photovoltaic devices. 相似文献
26.
GF Wagner RC Fargher C Milliken BA McKeown DH Copp 《Canadian Metallurgical Quarterly》1993,93(2):185-191
The aims of this study were to determine the most appropriate duration for the measurement of the maximal accumulated O2 deficit (MAOD), which is analogous to the anaerobic capacity, to ascertain the effects of mass, fat free mass (FFM), leg volume (Vleg) and lower body volume (V1b) on anaerobic test performance, to examine the reproducibility for peak power output (Wpeak) or maximal anaerobic power using an air-braked cycle ergometer and to produce approximations for the percentages of aerobic and anaerobic metabolism during exercise of short duration but high intensity. A group of 12 endurance trained cyclists [mean age 25.1 (SD 4.6) years; mean body mass 73.43 (SD 7.12) kg; mean maximal oxygen consumption 5.12 (SD 0.35) l.min-1; mean body fat 12.5 (SD 4.1) %] accordingly performed four counterbalanced treatments of 45, 60, 75 and 90 s of maximal cycling on an air-braked ergometer. The mean O2 deficit of 3.52 l for the 45-s treatment was significantly less (P < 0.01) than those for the 60 (3.75 l), 75 (3.80 l) and 90-s (3.75 l) treatments. These data therefore indicate that in predominantly aerobically trained subjects the O2 deficit attains a plateau after 60 s of maximal cycling on an air-braked ergometer. Statistically significant interclass correlation coefficients (P < 0.05) between the anthropometric variables (mass, FFM, Vleg and Vlb) and Wpeak or maximal anaerobic power (0.624-0.748) and MAOD (ml) or anaerobic capacity (0.666-0.772) furthermore would suggest the relevance of taking into account muscle mass during anaerobic tests.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
27.
Common Assembly Language for Microprocessors (CALM) is a set of notations, independent of any manufacturer but strongly inspired by the best existing assemblers.
The paper contains a discussion of assembler addressing modes and their expressions in CALM. A program example of the Bubble Sort subroutine written for 4 processors (hypothetical, 8085, 8086, 68000) gives an idea of CALM programs. 相似文献
28.
RE Droleskey PJ Holman KA Waldrup DE Corrier GG Wagner 《Canadian Metallurgical Quarterly》1993,79(3):424-434
Babesia odocoilei continuously cultured in white-tailed deer (Odocoileus virginianus) erythrocytes was examined by transmission and scanning electron microscopy. Merozoites, trophozoites, intermediate-stage forms, and dividing forms were observed. Merozoites possessed a single nucleus, inner membrane complex, rhoptries, free ribosomes, rough endoplasmic reticulum, and single membrane-bound vesicles. Trophozoites lacked an inner membrane complex and rhoptries. Intermediate stages were characterized by distinct segments of inner membrane complex. Dividing forms ranged from cells with an elongated nucleus to mature daughter cells joined by a ringlike structure. Babesia odocoilei was characterized by its close proximity to the erythrocyte membrane, membranous structures resembling feeding organelles, and reproduction via a method resembling budding sensu stricto. 相似文献
29.
The recent novel temperature-modulated differential scanning calorimetry (TA Instruments MDSCTM) technique has been applied
to the measurement of thermal properties of GexAsyS60 chalcogenide glasses in the glass transition region in bulk glasses
and in their thin films. The reversing and non-reversing heat flows through the glass transformation region during both heating
and cooling schedules were measured and the values of the parameters, Tg, ΔH, Cp and ΔCp, which characterize the thermal events
in the glass transition region, were determined. The structurally determined parameters, Tg, ΔH, Cp and ΔCp, reveal significant
changes with composition because in the GexAsyS60 glasses the average coordination number, 〈r〉, increases from 2.4 to 2.8
with increasing x from 0 to 40 at% Ge. A maximum in Tg, ΔH and Cp and a minimum in the heat capacity change, ΔCp, at Tg occur
near the composition for which x≈30 at% Ge. These extrema which appear in both films and bulk glasses are ascribed to a change
in the network function of Ge atoms replacing As atoms in a covalent network. Recent structural models for chalcogenide glasses
have been considered to explain the observed thermal properties.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
30.
This study investigated the impact of weblog use on individual learning in the context of university senior-level business education. As an emergent form of personal communication, weblogs enable people to publish their thoughts as webpages, and to share information and knowledge. Recognizing the potential impact of weblogs on knowledge expression and sharing, this research sought to empirically examine whether the continuous use of weblogs as online learning logs would affect student learning performance. The assumption was that effective use of weblogs promoted the constructivist models of learning by supporting both cognitive and social knowledge construction, and by reinforcing individual accountability in learning. Results from an Information Systems undergraduate course with 31 participants indicated that the performance of students' weblogs was a significant predictor of the learning outcome (while traditional coursework was not). Moreover, individuals' cognitive construction effort to build their own mental models and social construction effort to further enrich/expand knowledge resources appeared to be two key aspects of the constructivist learning with weblogs. Our results imply the potential benefit of using weblogs as a knowledge construction tool and a social learning medium 相似文献