Kinetics of clustering and precipitation in LiF doped with MgF2

An experimental study of the kinetics of clustering and precipitation in the system LiF:MgF₂ has been undertaken. The results showed that the pre-plateau region of the ageing curves is due to a homogeneous clustering reaction dominated by third-order kinetics with an activation energy of 0.85 ± 0.05 eV. The trimer binding energy was found to be 0.95 ± 0.05 eV. The post-plateau reaction has been shown to be a precipitation reaction in which a Suzuki phase is formed. These kinetic data have been analysed in terms of an Avrami equation and shown to be consistent with the idea of precipitate particles growing from a solid solution.     

Isobaric tagging approaches in quantitative proteomics: the ups and downs

Isobaric tagging has proven to be a popular quantitative proteomics tool and has been rapidly adopted to study a wide range of biological questions in the few years since its commercialization. While the flexibility and multiplexing capacity afforded by this technology are clear attractions, it is not without its shortcomings. As the speed and sensitivity of mass spectrometers have improved and the application of isobaric tags to all manner of biological systems has increased, significant issues with quantitative accuracy and precision have come to light. Here we review the issues associated with the use of isobaric tagging methods and discuss the possible solutions which have been proposed to improve their precision and accuracy to approach the levels required within quantitative proteomics.     

A simple method for phase wraps elimination or reduction in spatial fringe patterns

In this paper, we propose a simple method for processing a 2D wrapped phase map that contains a spatial carrier signal in order to completely eliminate, or greatly reduce, the number of phase wraps in the image. The 2D Fourier transform of the wrapped phase map is calculated. Then the spectrum is shifted to the origin in frequency space. After that, the inverse 2D Fourier transform is computed. Finally, a four-quadrant arctangent function is used to calculate the angle of the complex array that was produced by the inverse 2D Fourier transform. This produces a phase map with a smaller number of 2π phase jumps than the original phase map. In some cases, all of the phase wraps are eliminated and there is therefore no need to unwrap the resultant phase map. The reduction of the number of 2π phase jumps can reduce the execution time and improve the noise performance of some phase unwrapping algorithms such as the Flynn method. The validation of the proposed algorithm is demonstrated experimentally and also via computer-simulation.     

The Application of Digital Filtering to Phase Recovery when Surface Contouring using Fringe Projection Techniques

If structured light consisting of parallel stripes, or fringes, is projected onto a surface, then the surface acts as a phase modulator, with the amount of modulation at any point depending upon the height of the surface at that point. In recent years considerable effort has been devoted to the problem of fringe demodulation, with prominence given to techniques using fringe-phase stepping and Fourier analysis. It has long been known that phase demodulation is possible using a system of filters, and the technique has been widely used in the related area of frequency demodulation in radio. In this paper the development of phase demodulation using a system of digital filters is considered. For the accurate recovery of image phase it is necessary for the filters to introduce zero phase shift, or to have a phase shift proportional to frequency. The design of the digital filters is considered and their performance is assessed using the signal from a real modulated fringe pattern and a simulated signal. It is shown that the demodulation technique works well, even with a poor signal-to-noise ratio. © 1997 Elsevier Science Ltd. All rights reserved.     

Three-dimensional Fourier Fringe Analysis

Over the years two-dimensional Fourier Fringe Analysis (2D-FFA) has demonstrated both its capability and its relative robustness in analysing fringe patterns within a short time-frame from static objects. Nowadays, there is an increasing demand to measure dynamic objects. Today 2D-FFA is seen as a fast and flexible method of processing fringe patterns for dynamic objects. But it is still inherently a 2D approach, i.e. it deals with three-dimensional data (video sequences) on an individual 2D frame-by-frame basis. In this paper, a novel three-dimensional Fourier Fringe Analysis (3D-FFA) algorithm is proposed to demodulate fringe pattern sequences taken from dynamic objects. This technique processes the stack of fringe patterns as a single 3D volume, not as a set of individual 2D frames that are each processed in isolation. The proposed algorithm has been evaluated on both computer simulated and real dynamic objects. Results show that the proposed technique is able to demodulate fringe pattern volumes successfully.     

Computer generated optoacoustic spectra for a two-layer solid sample system

Summary A computer program has been devised to generate from two optoacoustic spectra of a two-layer solid sample, spectra at any phase angle from 0°–360°.

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Computer-erzeugte optoakustische Spektren für ein Zweischichtsystem einer festen Probe

Zusammenfassung Ein Computer-Programm wurde ausgearbeitet, mit dessen Hilfe aus einem experimentell aufgenommenen optoakustischen Spektrum einer festen Zweischichtenprobe Spektren für jeden beliebigen Phasenwinkel von 0°–360° erstellt werden können.

     

Aqueous solutions containing amino acids and peptides. Part 21. The enthalpic coefficients at 298.15 K for the interaction of N-acetyl-l-prolinamide with some 2-(N-acetylamino)acyl amides

Enthalpies of dilution of N-acetyl-l-prolinamide and equimolal solutions of this with N-acetylglycinamide, N-acetyl-l-alaninamide, N-acetyl-l-valinamide and N-acetyl-l-leucinamide have been determined at 298.15 K using a microcalorimetric procedure. The results obtained were used to calculate the pairwise enthalpic virial coefficients for both like—like (homotactic) and like—unlike (heterotactic) solute interactions. It is shown that the data can be predicted rather well using a group additivity approach with parameters obtained from earlier studies on α-amino and α-imino acid derivatives.     

Sub-Coulomb transfer reactions on 208Pb with carbon and oxygen projectiles

Single-neutron transfers induced by ^{12, 13}C and ^{16, 17, 18}O projectiles on ²⁰⁸Pb and the ¹²C(¹⁷O, ¹⁶O)¹³C reaction have been studied at energies close to the Coulomb barrier. These processes are well described by the distorted-wave Born approximation. Coupled-channels effects are found to be small. Normalization factors have been determined for all projectile and target transitions, and also for the triton-deuteron overlap by comparison with previous measurements of the ²⁰⁸Pb(d, t)²⁰⁷Pb reaction. The root-mean-square (rms) radii of single-particle neutron wave functions in ²⁰⁸Pb and ²⁰⁹Pb were calculated using known spectroscopic factors. The distribution of the point neutron excess density in the surface region of ²⁰⁸Pb has been derived and its rms radius determined to be 5.93 ± 0.13 fm with a local potential model. This is in good agreement with theoretical predictions, but is considerably larger than estimates based on Coulomb energy differences. The phenomena of core polarisation by the odd particle or hole outside ²⁰⁸Pb is discussed using the single-particle orbitals determined in this work.