Three‐Dimensional,Time‐Resolved Profiling of Ferroelectric Domain Wall Dynamics by Spectral‐Domain Optical Coherence Tomography

We apply here spectral‐domain optical coherence tomography (SD‐OCT) for the precise detection and temporal tracking of ferroelectric domain walls (DWs) in magnesium‐doped periodically poled lithium niobate (Mg:PPLN). We reproducibly map static DWs at an axial (depth) resolution down to ～ 0.6 μm, being located up to 0.5 mm well inside the single crystalline Mg:PPLN sample. We show that a full 3‐dimensional (3D) reconstruction of the DW geometry is possible from the collected data, when applying a special algorithm that accounts for the nonlinear optical dispersion of the material. Our OCT investigation provides valuable reference information on the DWs’ polarization charge distribution, which is known to be the key to the electrical conductivity of ferroelectric DWs in such systems. Hence, we carefully analyze the SD‐OCT signal dependence both when varying the direction of incident polarization, and when applying electrical fields along the polar axis. Surprisingly, the large backreflection intensities recorded under extraordinary polarization are not affected by any electrical field, at least for field strengths below the switching threshold, while no significant signals above noise floor are detected under ordinary polarization. Finally, we employed the high‐speed SD‐OCT setup for the real‐time DW tracking upon ferroelectric domain switching under high external fields.     

Theory of error applied to factor loadings resulting from combination target factor analysis

The theory of error for target factor analysis is used to derive a simple equation from which the root-mean-square error in the factor loadings can be calculated. The method is applied to a problem in gas—liquid chromatography and is shown to agree with errors estimated by the 'jackknife' method.     

Hollow fiber membrane concentrator for on-line preconcentration

Solvent removal by membrane permeation is presented as a method for on-line preconcentration. Experiments were carried out to develop a one-step, on-line, concentration process using a microporous composite hydrophobic membrane, or a polar solvent-permeable Nafion membrane depending on the solvent. Both polar and non-polar hollow fiber membranes were found to be effective in concentrating trace analytes. A large increase in analyte enrichment factors was found for both concentrator modules. Enrichment factors as high as 18.9 were observed. Residence time and operating temperature were found to be important parameters. Several different model compounds were preconcentrated. Further, in a Nafion membrane (polar solvent-permeable), analyte interaction with membrane bound sulfonic acid residues resulted in the loss of reactive analytes such as atrazine (ATZ). All analytes were successfully concentrated and detected using a polypropylene-siloxane composite membrane system when hexane was used as the solvent.     

Geordnete Schätzfunktionen und Diskrepanz

Ohne ZusammenfassungHerrnB. L. van der Waerden zum 60. Geburtstag am 2. 2. 1963 gewidmet     

Über C - Gleichwerteilung

Zusammenfassung In der vorliegenden Arbeit wird die Wertmenge von reellen integrierbaren Funktionen in einer Ver?nderlichen in Sinne der Theorie der Gleichverteilung untersucht. Giovanni Sansone zu seinem 70. Geburtstag gewidmet.     

Estimation of convergence orders in repeated richardson extrapolation

LetA(h) be an approximation depending on a single parameterh to a fixed quantityA, and assume thatA–A(h)=c ₁ h k ₁ +c ₂ h ^k ₂ +.... Given a sequence ofh-valuesh ₁>h ₂>...>h _n and corresponding computed approximationsA(h _i ), the orders for repeated Richardson extrapolation are estimated, and the repeated extrapolation is performed. Hence in this case the algorithm described here can do the same work as Brezinski'sE-algorithm and at the same time provide a check whether repeated extrapolation is justified.