Solid State Physics

Contains reports on four research projects

Solid State Physics

Contains reports on six research projects

A new kind of oscillating crucible viscometer

A new oscillating crucible viscometer, having a torus shaped crucible, is presented. The geometry of the torus allows a rigorous treatment of the fluidodynamical problem for an oscillating viscous liquid. The damping coefficient δ is shown to characterize two possible distinct zones of oscillation: In the first zone, δ rises when the viscosity η of the liquid rises; in the second one, δ is lowered by an increase of η. The second zone proves to be much more convenient for fixing the working point of the instrument because here the sensitivity is expected to be twice that of the first zone. Some preliminary experiments have confirmed the results of the theory. © 1971 The American Institute of Physics

Critical aspects of bayesian analysis: The imprecision in performance assessing and the choice of decision limits

Using as an experimental model the results obtained in assaying thyroid hormones and tumor markers, two peculiar aspects of the Bayesian analysis are considered: (a) the imprecision associated with the assessment of diagnostic sensitivity, specificity and predictive value, and (b) the implications of the choice of the cutoff point (ie, the medical decision limit). As for the former aspect, still largely disregarded in the literature, no significant difference results when applying binomial statistics or the "bootstrap" resampling technique for uncertainty evaluations; the critical effects on the imprecision extent related to the size of available statistical samples and of the cutoff value are confirmed, no effect being instead related to the extent of distribution skewness. The choice of decision limit (eg, the limit corresponding to the maximum efficiency, to the maximum Youden's index or to a given specificity) obviously proves crucial in establishing the diagnostic value of test results; furthermore, the use of maximum-efficiency cutoff points looks questionable when low prevalences are concerned. Thus, rather than from some rigid criteria, this choice should proceed from a comparative analysis of operational curves obtained for given cutoff values, such as the functions prevalence vs predictive value or prevalence vs misclassification rate

Turbulent Boundary Layers and their Control: Quantitative Flow Visualization Results

Results obtained by applying PIV to canonical turbulent boundary layers and to wall flows under the action of external forcing produced by spanwise wall oscillations are shown and analyzed. In particular, results obtained at the Aerodynamic Laboratory of the Politecnico di Torino are discussed, with reference, where it is possible, to results produced in other laboratories. For both flows, PIV images in planes streamwise-normal and parallel to the wall are analyzed

Radioimmunoassay of unconjugated and total serum estetrol using a 125I-iodinated tracer

A radioimmunossay (RIA) for the measurement of both unconjugated and total serum estetrol has been developed, using an antiserum to an E4-3-conjugate and a 125I-radioiodinated E4 tracer. Assay of dried ethyl ether extracts was used for the determination of unconjugated E4, while a direct measurement of unextracted hydrolyzed serum in the presence of 0.3% 8-anilino-1-naphthalene sulphonic acid (ANS) proved adequate for total E4. Assay reliability was evaluated and the procedure standardized through a series of tests aimed at assessing accuracy, sensitivity and precision. No steroidal interference was found to practically affect the assay (0.3% estriol cross-reactivity), nor were solvent and sample blanks observed in the case of unconjugated E4. For total E4 assay, the sample blank effects were acceptably overcome by using hydrolyzed male serum and 0.3% ANS, as a standard diluent. An interassay variability amounting to approximately 10 and 6% resulted for unconjugated E4 and total E4 RIA, respectively. A number of serum samples (285 for unconjugated E4, 147 for total E4) randomly collected throughout normal pregnancy were assayed. The unconjugated E4 levels at 15th week and at term were 62.7 +/- 22.6 and 766.5 +/- 208.2 (SD) pg/ml, respectively. Total E4 was about 6--7 times higher than the levels of free E4 and increased 7 times from the 15th week to term