Exploiting damped techniques for nonlinear conjugate gradient methods

In this paper we propose the use of damped techniques within Nonlinear Conjugate Gradient (NCG) methods. Damped techniques were introduced by Powell and recently reproposed by Al-Baali and till now, only applied in the framework of quasi-Newton methods. We extend their use to NCG methods in large scale unconstrained optimization, aiming at possibly improving the efficiency and the robustness of the latter methods, especially when solving difficult problems. We consider both unpreconditioned and Preconditioned NCG. In the latter case, we embed damped techniques within a class of preconditioners based on quasi-Newton updates. Our purpose is to possibly provide efficient preconditioners which approximate, in some sense, the inverse of the Hessian matrix, while still preserving information provided by the secant equation or some of its modifications. The results of an extensive numerical experience highlights that the proposed approach is quite promising.     

Polonium 210Po activities in human blood of patients with ischaemic heart disease from Gdańsk in Poland

The determination of polonium ²¹⁰Po in human blood samples is presented and discussed in this paper. The human blood samples were collected from patients of Medical University of Gdańsk with ischaemic heart disease (morbus ischaemicus cordis, MIC). The polonium concentrations in analyzed human blood samples are very differentiated. ²¹⁰Po is of particular interest in public health and although is present in the environment in extremely low amounts, it is easily bioaccumulated to the human body. The study shows that the amount of ²¹⁰Po that is incorporated into the human body depends on the food habits and some difference in its levels could be observed between smokers and non-smokers.     

On mixed joint discrete universality for a class of zeta-functions. II

We investigate the mixed joint discrete value distribution and the mixed joint discrete universality for the pair consisting of a rather general form of zeta-function with an Euler product and a periodic Hurwitz zeta-function with transcendental parameter. The common differences of relevant arithmetic progressions are not necessarily the same. Also some generalizations are given. For this purpose, certain arithmetic conditions on the common differences are used.

     

Simultaneous Anodic Stripping Voltammetric Determination of Pb and Cd,Using a Vibrating Gold Microwire Electrode,Assisted by Chemometric Techniques

Simultaneous anodic stripping voltammetric determination of Pb and Cd is restricted on gold electrodes as a result of the overlapping of these two peaks. This work describes the quantitative determination of a binary mixture system of Pb and Cd, at low concentration levels (up to 15.0 and 10.0 µg L^?1 for Pb and Cd, respectively) by differential pulse anodic stripping voltammetry (DPASV; deposition time of 30 s), using a green electrode (vibrating gold microwire electrode) without purging in a chloride medium (0.5 M NaCl) under moderate acidic conditions (HCl 1.0 mM), assisted by chemometric tools. The application of multivariate curve resolution alternating least squares (MCR‐ALS) for the resolution and quantification of both metals is shown. The optimized MCR‐ALS models showed good prediction ability with concentration prediction errors of 12.4 and 11.4 % for Pb and Cd, respectively. The quantitative results obtained by MCR‐ALS were compared to those obtained with partial least squares (PLS) and classical least squares (CLS) regression methods. For both metals, PLS and MCR‐ALS results are comparable and superior to CLS. For Cd, as a result of the peak shift problem, the application of CLS was unsuitable. MCR‐ALS provides additional advantage compared to PLS since it estimates the pure response of the analytes signal. Finally, the built up multivariate calibration models, based either in MCR‐ALS or PLS regression, allowed to quantify concentrations of Pb and Cd in surface river water samples, with satisfactory results.     

Extension and application of multivariate curve resolution-alternating least squares to four-way quadrilinear data-obtained in the investigation of pollution patterns on Yamuna River,India—A case study

This study focuses on the development and extension of Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) to the analysis of four-way datasets. The proposed extension of the MCR-ALS method with non-negativity and the newly developed quadrilinear constraints can be exploited to summarize and manage huge multidimensional datasets and resolve their four way component profiles. In this study, its application is demonstrated by analyzing a four-way data set obtained in a long term environmental monitoring study (15 sampling sites × 9 variables × 12 months × 7 years) belonging to the Yamuna River, one of the most polluted rivers of India and the largest tributary of the Ganges river. MCR-ALS resolved pollution profiles described appropriately the major observed changes on pH, organic pollution, bacteriological pollution and temperature, along with their spatial and temporal distribution patterns for the studied stretch of Yamuna River. Results obtained by MCR-ALS have also been compared with those obtained by another multi-way method, PARAFAC. The methodology used in this study is completely general and it can be applied to other multi-way datasets.     

Application of principal component analysis to the study of multiple equilibria systems : Study of copper(II)/salicylate/mono-, di- and triethanolamine systems

Principal component analysis is applied to the study of multiple equilibria systems based on copper (Il) ion with salicylate and mono-, di- or triethanolamine as ligands. A procedure based on evolving factor analysis is described which allows the model-free determination of distribution plots and of the individual spectra of the various species formed in the course of a spectrophotometric titration. The results are compared with those obtained by using least-squares methods.     

A critical comparison of computer programs for the potentiometric determination of stability constants

The performance of five of the best-known computer programs LETAGROP, SCOGS, MINIQUAD, SUPERQUAD and ESTA, is critically discussed. All these programs are based on least-squares refinement procedures but differ in some important aspects: (a) the definition of the residuals function; (b) the minimization procedure; (c) the statistical and weighting parameters. Each of these aspects is evaluated and the programs are compared on this basis.     

Micromachined bulk PZT tissue contrast sensor for fine needle aspiration biopsy

This paper describes a micromachined piezoelectric sensor, integrated into a cavity at the tip of a biopsy needle, and preliminary experiments to determine if such a device can be used for real-time tissue differentiation, which is needed for needle positioning guidance during fine needle aspiration (FNA) biopsy. The sensor is fabricated from bulk lead zirconate titanate (PZT), using a customized process in which micro electro-discharge machining is used to form a steel tool that is subsequently used for batch-mode ultrasonic micromachining of bulk PZT ceramic. The resulting sensor is 50 microm thick and 200 microm in diameter. It is placed in the biopsy needle cavity, against a steel diaphragm which is 300 microm diameter and has an average thickness of 23 microm. Devices were tested in materials that mimic the ultrasound characteristics of human tissue, used in the training of physicians, and with porcine fat and muscle tissue. In both schemes, the magnitude and frequency of an electrical impedance resonance peak showed tissue-specific characteristics as the needle was inserted. For example, in the porcine tissue, the impedance peak frequency changed approximately 13 MHz from the initial 163 MHz, and the magnitude changed approximately 1600 Omega from the initial 2100 Omega, as the needle moved from fat to muscle. Samples including oils and saline solution were tested for calibration, and an empirical tissue contrast model shows an approximately proportional relationship between measured frequency shift and sample acoustic impedance. These results suggest that the device can complement existing methods for guidance during biopsies.