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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 2 (1970), S. 233-249 
    ISSN: 1572-9613
    Keywords: Local operators ; coarse-graining ; microcanonical ensemble ; foundations of statistical mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The results of the first paper in this series are generalized to include spin, permutation symmetry, and time dependence. In particular, the question of time invariance of localness in the Heisenberg picture is discussed and it is conjectured that an operator that is initially local will remain local over time. In order to treat macroscopic systems, it is shown that the ensemble decomposition of the previous paper can be used to “coarsegrain” configuration space. Finally, a physical interpretation of the ensemble decomposition in terms of “redundant macroscopic information” is used to give a derivation of the generalized microcanonical average.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 2 (1970), S. 213-232 
    ISSN: 1572-9613
    Keywords: Local operators ; ensemble average ; microcanonical ensemble ; foundations of statistical mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this and the following paper, a new approach for the justification of ensembles in statistical mechanics is given. The essential physical idea is that a measurement is an average of values arising from disjoint regions in three-space. This idea is given a mathematical basis in terms of a class of operators called “local operators,” and the first paper is devoted primarily to the development of the properties of local operators. In particular, a complete characterization of the bounded local operators on ℒ2 spaces of finite measure is given. Two results of importance for statistical mechanics are also derived. First, it is shown that the observables of quantum mechanics are local operators. Second, it is shown that the expectation value of an observable for a pure state can be written formally as an ensemble average. In the following paper, these results are used to develop a new approach for the justification of statistical ensembles.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Digestive diseases and sciences 41 (1996), S. 505-511 
    ISSN: 1573-2568
    Keywords: gastroesophageal reflux ; posture ; atypical reflux symptoms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In summary, we evaluated a 39-year-old man two years after partial esophagectomy and gastroesophageal anastomosis. He had developed recurrent Barrett's esophagus and atypical reflux symptoms. We found free reflux and no antireflux barrier at the hiatus or the esophagogastric anastomosis. Three different reflux techniques performed simultaneously demonstrated that the composition of refluxant varied with posture, explaining the atypical nature of the symptoms. In the left recumbent posture, the refluxate was comprised of acidified liquid and gaseous gastric contents with the patient complaining of heartburn and chest pain. In the right recumbent posture the refluxate was composed of only nonacidic gas, and the patient complained of chest pain without heartburn. We propose that multiple reflux tests performed simultaneously in the setting where a patient experiences his atypical symptoms may help clarify their origin. Furthermore, this case illustrates how posture may dramatically influence refluxant composition.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Digestive diseases and sciences 36 (1991), S. 565-571 
    ISSN: 1573-2568
    Keywords: gastroesophageal reflux ; chest pain ; acid perfusion test ; esophageal pH monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The acid perfusion (Bernstein) test and esophageal pH monitoring are the two most popular tests for identifying esophageal acid sensitivity in difficult cases of reflux disease. Therefore, we prospectively compared these test results in 75 consecutive noncardiac chest pain patients who had both an acid perfusion test and chest pain during 24-hr pH testing. A positive acid perfusion test was defined by the replication of the patient's typical chest pain twice by the acid infusion. Esophageal pH testing identified abnormal amounts of acid reflux and correlated symptoms with acid reflux-the “symptom index.” Fifteen patients (20%) had a positive acid perfusion test while 45 patients (59%) had a positive symptom index (range 6–100%). Only 9/34 (26%) patients with abnormal reflux had a positive acid perfusion test. Although it had excellent specificity (83–94%), the acid perfusion test had poor sensitivity (32–46%) when compared to the symptom index regardless of the percent positive cutoff level. The best positive predictive value for the acid perfusion test was 87%, but this occurred when the test sensitivity was 32%. Modifying the end point of a positive acid perfusion test to include heartburn improves the sensitivity (52–67%) while markedly compromising specificity and positive predictive value. Thus, esophageal pH monitoring correlating symptoms with acid reflux is superior to the acid perfusion test for identifying an acid sensitive esophagus in patients with noncardiac chest pain.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-2568
    Keywords: erythromycin ; gastroesophageal reflux ; esophageal motility ; prokinetic drugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Erythromycin, a possible motilin agonist, is a potent gastrokinetic agent that may increase the lower esophageal sphincter pressure. Therefore, we assessed the effects of erythromycin in two dosages (250 and 500 mgper os four times a day) on esophageal pH and pressure profiles in reflux patients using prolonged ambulatory monitoring systems. Studies were blinded, placebo-controlled with randomized crossover design. Patients took each drug for three days prior to studies, with erythromycin serum levels obtained the day of esophageal studies. Erythromycin 250 mg four times a day had no effect on esophageal contraction pressures or peristalsis during the day or meal periods. In the supine position, however, erythromycin significantly (P=0.012) decreased esophageal contraction velocity and showed a strong trend (P=0.059) towards increasing the percentage of peristaltic waves. Despite these potentially beneficial effects on esophageal clearance, no significant difference in acid exposure times during 24-hr pH studies were observed between placebo and low-dose erythromycin. High-dose erythromycin (500 mg four times a day) was associated with drug levels in the typical antibiotic efficacy range (normal 1–3 µg/ml; patients 1.7–7.0 µg/ml), but, here again, there was no significant difference in all acid reflux parameters between placebo and erythromycin phases. Therefore, “standard” doses of erythromycin have no important clinical effects on esophageal pressures or acid reflux parameters.
    Type of Medium: Electronic Resource
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