Application of denoising methods to regularizationof ill-posed problems

Linear systems of equations and linear least-squares problems with a matrix whose singular values “cluster” at the origin and with an error-contaminated data vector arise in many applications. Their numerical solution requires regularization, i.e., the replacement of the given problem by a nearby one, whose solution is less sensitive to the error in the data. The amount of regularization depends on a parameter. When an accurate estimate of the norm of the error in the data is known, this parameter can be determined by the discrepancy principle. This paper is concerned with the situation when the error is white Gaussian and no estimate of the norm of the error is available, and explores the possibility of applying a denoising method to both reduce this error and to estimate its norm. Applications to image deblurring are presented.     

Selectivity differences of water‐soluble vitamins separated on hydrophilic interaction stationary phases

In this study, the retention behavior and selectivity differences of water‐soluble vitamins were evaluated with three types of polar stationary phases (i.e. an underivatized silica phase, an amide phase, and an amino phase) operated in the hydrophilic interaction chromatographic mode with ESI mass spectrometric detection. The effects of mobile phase composition, including buffer pH and concentration, on the retention and selectivity of the vitamins were investigated. In all stationary phases, the neutral or weakly charged vitamins exhibited very weak retention under each of the pH conditions, while the acidic and more basic vitamins showed diverse retention behaviors. With the underivatized silica phase, increasing the salt concentration of the mobile phase resulted in enhanced retention of the acidic vitamins, but decreased retention of the basic vitamins. These observations thus signify the involvement of secondary mechanisms, such as electrostatic interaction in the retention of these analytes. Under optimized conditions, a baseline separation of all vitamins was achieved with excellent peak efficiency. In addition, the effects of water content in the sample on retention and peak efficiency were examined, with sample stacking effects observed when the injected sample contained a high amount of water.     

An electrostatic charge meter using a microcontroller offers advanced features and easier ATEX certification

The development of a microcontroller-based electrostatic charge meter is described. The meter is of the non-contact type and provides a reading of surface voltage by integrating the current supplied to the probe head to keep it at earth potential as the instrument is brought to within a specified distance of the target. The use of a microcontroller allows the use of a small number of components and the resetting of the integrator without relays or switches as well as self-calibration and auto-ranging. The minimal use of capacitors and complete lack of inductance facilitates ATEX certification.     

Probing with Synthetic Peptides the Interactive Properties of N-Butylphenyl and Cholesterol-10-Undecenaoate Phases Immobilised onto Open Tubular Electrochromatographic Capillaries

This study investigates the impact of peptide primary structure and the characteristics of two different types of immobilised hydrophobic ligands on the open tubular electro-chromatographic migration behaviour of a family of related synthetic peptide analogues. The results further document the important role that mixed mode electrophoretic/chromatographic processes play in determining peptide selectivity in OTCEC systems. Procedures to fine-tune selectivity of closely related peptides in these systems have been established with buffer electrolytes of different composition in terms of the organic solvent content and different pH conditions.Dedicated to Professor K. Jinno on the occasion of his 60^th birthday.     

A heuristic method for the minimum toll booth problem

This paper addresses the toll pricing problem in which the objective is to minimize the number of required toll facilities in a traffic network. The problem is shown to be NP-hard. To obtain a solution in a reasonable time, an effective metaheuristic algorithm is developed. The algorithm uses a local search technique in which the neighborhood function employs the dynamic slope scaling procedure to deal with the fixed charge nature of the objective function. Numerical results from 50 randomly generated and three real networks are reported.     

Interactions between an amphipathic di‐histidine peptide and a metal affinity chromatographic resin derived from a bis(tacn)butane chelating ligand

The interactive behavior of an amphipathic peptide with the Cu²⁺, Ni²⁺, and Zn²⁺ complexes of 1,4‐bis(triazacyclonon‐1‐yl)butane), bis(tacn)^but, immobilized onto Sepharose CL‐4B, has been investigated. The effects of incubation time, as well as the incubation buffer pH and ionic strength, have been examined. The binding data have been interrogated using Langmuir, Langmuir‐Freundlich, bi‐Langmuir, and Temkin isothermal models and Scatchard plots. These results confirm that this amphipathic peptide binds with relatively high capacities to the immobilized Cu²⁺‐ and Ni²⁺‐1,4‐bis(triazacyclonon‐1‐yl)butane)‐Sepharose CL‐4B sorbents via at least two discrete sites. However, the corresponding immobilized Zn²⁺‐sorbent had low binding capacity. Moreover, the magnitude of the binding capacities of these sorbents was dependent on the pH and ionic strength of the incubation buffer. These results are relevant to the isolation of E. coli expressed recombinant proteins that incorporate this and related amphipathic peptide tags, containing two or more histidine residues, located at the N‐ or C‐terminus of the recombinant protein, and the co‐purification of low abundance host cell proteins of diverse structure, by immobilized metal ion affinity chromatographic methods.