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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 37 (1992), S. 667-672 
    ISSN: 1573-2568
    Keywords: prolonged esophageal pH monitoring ; gastric pH monitoring ; lower esophageal sphincter ; gastroesophageal reflux disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recent studies have suggested that combined monitoring of the esophagus and stomach for prolonged periods may be the best method for investigating patients with upper gastrointestinal complaints. However, the effects of an electrode across the LES on esophageal reflux parameters have not been extensively studied. We studied 10 healthy volunteers and 10 patients with GERD twice with 24-hr pH monitoring. In phase 1, two glass electrodes were placed 1 cm below the UES and 5 cm above the LES. One week later in phase 2, patients were restudied with one electrode 5 cm above and one 5 cm below the LES. Although total acid exposure remained the same in healthy volunteers, three volunteers who spontaneously refluxed at night had abnormal prolongation of their supine acid exposure during phase 2 of the study. In patients with GERD, the electrode across the LES resulted in significant (P=0.01) increase in supine acid exposure and showed a strong tendency for the number of reflux episodes 〉5 min supine (P=0.02) and longest reflux episode supine (P=0.06) to increase without a change in the number of reflux episodes. In conclusion, a small glass electrode across the LES results in prolongation of supine acid exposure in both healthy volunteers spontaneously refluxing at night and the majority of patients with GERD. This results from the electrode interfering with clearance of refluxed acid in the supine position. Thus, combined esophageal and gastric pH monitoring may have important limitations in investigating gastroesophageal symptoms.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-2568
    Keywords: prolonged ambulatory esophageal pH monitoring ; gastroesophageal reflux disease ; lower esophageal sphincter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Limiting the widespread use of 24-hr pH monitoring is the necessity of manometrically placing the pH probe 5 cm above the proximal lower esophageal sphincter (LES) border. Therefore, we prospectively compared LES localization by gastroesophageal pH step-up with manometry in 71 patients and 14 asymptomatic volunteers. The gastroesophageal pH step-up significantly correlated with the proximal LES border in patients (r=0.53, P〈0.0001) and volunteers (r=0.91, P〈0.0001). Based on previously published criteria, the pH step-up value was considered acceptably accurate if it was within ±3 cm (6 cm total span) of the manometrically determined proximal LES border. In 58% of patients and 29% of volunteers the pH step-up occurred outside this accuracy range. Esophagitis (P=0.015) and abnormal reflux parameters (P=0.002) were variables contributing to this error. Subsequent analysis found that the pH step-up overestimated the proximal LES border and occurred at the midportion of the sphincter. The pH step-up still inaccurately located the mid LES in 34% of patients. Therefore, manometry should remain the standard for accurate LES localization prior to placing the pH probe.
    Type of Medium: Electronic Resource
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