Continuous hydride generation, using sodium tetrahydroborate(ll1) as a reductant in conjunction with atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES), has been used to form arsines selectively from arsenate (Asv), arsenite (AsV, monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA). The reaction media studied have been shown to allow the rapid determination of As111 alone, DMAA alone, Aslll + AsV and "total" arsenic, i.e., As111 + AsV + MMAA + DMAA.Interference effects produced by heavy metal ions are suppressed by the addition of masking agents.
Seven pure fuels (methane, ethane, propane, n-butane, isopentane, isooctane, and toluene) have been run in a single-cylinder production-type engine at four operating points. Measurements of the emitted engine-out hydrocarbons, NO*, CO, and C02 have been made at each condition and show effects partially explainable by changes in flame temperature and H/C ratio of the fuel. The results show that both the total engine-out hydrocarbon emissions and the distribution of individual hydrocarbon species in the exhaust gas are sensitive to the fuel used.In the case of total hydrocarbon emissions, ethane produces the lowest and toluene the highest (4X ethane) under all operating conditions. The percentage contribution of unburned fuel to the hydrocarbon emissions varies from 95% for methane fuel to 50% or below for isooctane. These percentages are affected by engine operating parameters, particularly speed and spark timing. Olefins constitute the majority of the remaining emitted hydrocarbons for alkane fuels. Toluene also emits a large percentage of unburned fuel (80%) but little olefin (1%).Benzene (6%) and benzaldehyde (6%) are major nonfuel hydrocarbon emissions from toluene but are not observed to an appreciable extent from the alkane fuels (<0.3%).
Our observation that hypoglycemia, often self-diagnosed by our patients, was seldom confirmed led the authors to establish norms for the glucose tolerance test. We first obtained values for 650 patients who were entirely free from symptoms before and during testing. The median nadir in this group was 64 mg/dl. Ten percent of the patients had plasma glucose nadirs of 47 mg/dl or below and 2.5% had values of 39 mg/dl or less. Utilizing these values in combination with clinical criteria, we confirmed hypoglycemia after glucose load in 16 (median nadir 39.5 mg/dl) of 118 patients presenting with this diagnosis, and only 5 of the 16 were hypoglycemic after their usual meals. The other 102 patients, whose many complaints were unrelated to measured plasma glucose levels, had nadirs similar to those of the control group. Placebo tests performed on 14 nonhypoglycemic patients provoked symptoms (recorded by the patients themselves) and they considered indicative of hypoglycemia. Some accepted other diagnoses after we demonstrated that their symptoms occurred when they were normoglycemic. Since nadirs of hypoglycemics and control subjects overlap, we conclude that accurate diagnosis of hypoglycemia requires that symptoms develop concurrently with low blood sugar and that they are absent at other times. Low plasma glucose must be considered only one of the criteria in diagnosing functional hypoglycemia along with a relationship between food intake, timing of symptoms, correlation of symptoms and low glucose levels, and reproducibility of test results.
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