Improved Parameterization for Combined Isotopomer Analysis of Diatomic Spectra and Its Application to HF and DF

A new way of representing vibration-rotation term values for multiple isotopomers of a given electronic state of a diatomic molecule is presented which resolves problems associated with the way the conventional combined isotopomer expansion represents the atomic mass-dependent JWKB and Born-Oppenheimer breakdown correction terms. Its application to infrared and microwave data for HF and DF yields new Dunham expansion coefficients and Born-Oppenheimer breakdown correction terms for this species. This procedure is implemented in a generally available computer program for fitting to various types of data involving one or several electronic states of multiple isotopomers of a diatomic molecule. Copyright 1999 Academic Press.     

Organic reactions at surfaces: A study of carnitine by secondary ion mass spectrometry

Carnitine inner salt, (CH₃)₃N⁺ CH₂CH(OH)CH₂COO^?, and carnitine hydrochloride, (CH₃)₃N⁺CH₂CH (OH)CH₂COOH Cl^?, in the solid state undergo ion-beam-induced intermolecular methyl transfer reactions as shown by (CH₃)₃N⁺ CH₂CH(OH)CH₂COOCH₃ ions at m/z 176 in their positive ion spectra. In the case of carnitine HCl, the product ion is three times as abundant as the intact cation. For the inner salt however, the product is less than one-tenth as abundant as [M + H] ⁺. In both cases, the reaction can be precluded by dissolution of the sample, supporting an intermolecular mechanism. The negative ion spectra for these compounds contain no [M ? CH₃]^? ions, suggesting that simple transmethylation does not occur. Rather it is proposed that the inner salt abstracts a methyl group from the intact carnitine cation to yield [M + CH₃]⁺ and a neutral species, the driving force being a minimization of the total number of charges desorbed into the gas phase. Thermodynamic data favor this mechanism as do data for other carnitine salts. The reaction appears to be inhibited when one reactant is present in excess. This is the case for carnitine HNO₃ and CH₃SO₃H, which tend to liberate the intact cation since the anions are large and polarizable. It is also the case for small, hard anions like fluoride, which appear to favor release of the inner salt, hence the cation at m/z 162 is of low abundance and the transmethylation product (m/z 176) is absent. The extent of the reaction is also dependent on the methods of preparation of the sample, and deposition of the salts from solution greatly reduces the extent of methyl transfer. [M ? CH₃]^? is observed when glycerol is used as a matrix, possibly due to a matrix-analyte methyl transfer reaction.     

Mining for classes and patterns in behavioural data

In this paper we compare and contrast the new data mining activity of pattern search with more traditional cluster analysis methods of data mining, in the context of credit data. In particular, we examine a set of behavioural data from a large UK bank relating to the status of current accounts over a twelve month period. We show how conventional clustering approaches can be used, for example to define broad categories of behaviour, whereas pattern search can be used to find small groups of accounts that exhibit distinctive behaviour.     

Temporally adaptive estimation of logistic classifiers on data streams

Modern technology has allowed real-time data collection in a variety of domains, ranging from environmental monitoring to healthcare. Consequently, there is a growing need for algorithms capable of performing inferential tasks in an online manner, continuously revising their estimates to reflect the current status of the underlying process. In particular, we are interested in constructing online and temporally adaptive classifiers capable of handling the possibly drifting decision boundaries arising in streaming environments. We first make a quadratic approximation to the log-likelihood that yields a recursive algorithm for fitting logistic regression online. We then suggest a novel way of equipping this framework with self-tuning forgetting factors. The resulting scheme is capable of tracking changes in the underlying probability distribution, adapting the decision boundary appropriately and hence maintaining high classification accuracy in dynamic or unstable environments. We demonstrate the scheme’s effectiveness in both real and simulated streaming environments.     

A study of stitch line formation during high speed laser patterning of thin film indium tin oxide transparent electrodes

High speed laser patterning of indium tin oxide thin films on glass is part of the production method used to produce transparent conductive electrodes for plasma display panels. Such a design consists of rows of repeating electrode structures which cover the active area of the display. Whilst the patterning process for such electrode structures exceeds the industrial acceptance criteria there are certain features that are yet to be fully understood. The visible line that occurs in-between two adjacent laser processed areas, commonly known as a stitch line, is one such feature. Previously published research claimed that the stitch line was caused by incomplete removal of the thin film however experimental results presented within this paper demonstrate that this cannot be the case and show that the stitch line is formed by redeposition of the plume of ablated material within the area of overlap with the previous pulse, and that heating of the sample by the second pulse plays a key role in stitch line formation.     

The application of high-speed TV-holography to time-resolved vibration measurements

We describe an electronic speckle pattern interferometer (ESPI) system that has enabled non-harmonic vibrations to be measured with μs temporal resolution. The short exposure period and high framing rate of a high-speed camera at up to 40,500 frames per second allow low-power CW laser illumination and fibre-optic beam delivery to be used, rather than the high peak power pulsed lasers normally used in ESPI for transient measurement. The technique has been demonstrated in the laboratory and tested in preliminary industrial trials. The ability to measure vibration with high spatial and temporal resolution, which is not provided by techniques such as scanning laser vibrometry, has many applications in manufacturing design, and in an illustrative application described here revealed previously unmeasured “rocking” vibrations of a car door. It has been possible to make the measurement on the door as part of a complete vehicle standing on its own tyres, wheels and suspension, and where the excitation was generated by the running of the vehicle's own engine.     

Development and investigation of ultrasound linear phased arrays for transrectal treatment of prostate

We used the rectangular radiator method as a numerical solution to the Rayleigh-Sommerfeld diffraction integral for calculating the acoustic fields produced by linear arrays. The appropriate phases and amplitudes of voltages applied to the elements were computed using the pseudo-inverse method. We have developed and acoustically evaluated several constructions of planar linear ultrasound phased arrays for transrectal thermotherapy of prostate diseases. The designs of the linear phased arrays used in this work were the result of compromise in terms of the choice of frequency and number and size of elements, in order to investigate a means of improving array performance which might lead to increased efficacy and safety of the thermal treatment. The results obtained are in agreement with the data of other studies and show that a linear plane phased array may be potentially useful for thermal therapy.