Nonlinear electronic circuit, Part I: Multiple routes to chaos

A nonlinear electronic oscillator, suitable for synchronized chaotic communication, is studied. This circuit is capable of transmitting discrete chaotic signals, although the chaotic modes of operation are controlled in an analog way. In Part I of this review paper the three routes to chaotic operation that appear, namely the period doubling, intermittency and crisis induced intermittency, are thoroughly studied and discussed. In all three routes to chaos the appropriate experimental distributions were calculated. Moreover, the chaotic nature of the circuit operation was evaluated by using the Grassberger-Procaccia method. Calculation of the corresponding minimum embedding dimension, the Kolmogorov-Sinai entropy as well as the maximal Lyapunov exponent give useful information in order to fully characterize the circuit operation.     

Experimental evaluation of simulated annealing algorithms for the time-cost trade-off problem

This paper evaluates variants of a simulated annealing algorithm which solve the total cost minimization problem in activity networks in the case that discrete time-cost execution modes are allowed on the project activities. This problem is a special case of the well known discrete time-cost trade-off problem (DTCTP). Based on a sample of randomly generated activity networks, formal tests of statistical significance are utilized to test both the quality of solutions and the time efficiency of algorithms versus problem factors. A procedure issued from the extreme values statistics is also applied on problem instances in order to determine, on the one hand, the confidence interval estimate of the optimum solution for each algorithm and, on the other hand, when to stop the running of an algorithm.     

Low-energy X-ray standards from hydrogenlike pionic atoms

We demonstrate the first step of a complete program, which consists in establishing an x-ray energy standard scale with the use of few-body atoms, in the few keV range. Light pionic and muonic atoms as well as one and two-electron ions from electron-cyclotron ion sources are used. The transition energies are calculable from quantum-electrodynamics, meaning that only a very limited subset need be measured and compared with theory, while providing a large number of standard lines. Here we show that circular transitions in pionic neon atoms, completely stripped from their electrons, reveal spectral lines which are narrow, symmetric, and well reproducible. We use these lines for the energy determination of transition energies in complex electronic systems, like the Kalpha(1,2) transitions in metallic Ti, which may serve as secondary standard.     

Homogeneous polynomials and extensions of Hardy‐Hilbert's inequality

If L is a continuous symmetric n‐linear form on a real or complex Hilbert space and $\widehat{L}$ is the associated continuous n‐homogeneous polynomial, then $\Vert L\Vert =\big \Vert \widehat{L}\big \Vert$. We give a simple proof of this well‐known result, which works for both real and complex Hilbert spaces, by using a classical inequality due to S. Bernstein for trigonometric polynomials. As an application, an open problem for the optimal lower bound of the norm of a homogeneous polynomial, which is a product of linear forms, is related to the so‐called permanent function of an n × n positive definite Hermitian matrix. We have also derived generalizations of Hardy‐Hilbert's inequality.     

An improved MUSCL treatment for the SPH‐ALE method: comparison with the standard SPH method for the jet impingement case

In the present work, a new implementation of the Monotone Upwind‐centered Scheme for Conservation Laws (MUSCL) ‐ Hancock scheme has been developed for the SPH‐Arbitrary Lagrangian Eulerian (ALE) method. The resulting method was tested at various benchmark cases and then it was used to simulate the jet impingement on a flat plate for several different impingement angles, in comparison with the standard SPH method and results from literature. The SPH‐ALE method proves to produce higher quality results than the standard SPH method in all cases, while the MUSCL treatment tends to remedy the issues of the numerical viscosity, inherent to the method, up to a point. Copyright © 2012 John Wiley & Sons, Ltd.     

Multi-residue analysis of pesticides,plant hormones,veterinary drugs and mycotoxins using HILIC chromatography – MS/MS in various food matrices

One of the recent trends in Analytical Chemistry is the development of economic, quick and easy hyphenated methods to be used in a field that includes analytes of different classes and physicochemical properties. In this work a multi-residue method was developed for the simultaneous determination of 28 xenobiotics (polar and hydrophilic) using hydrophilic interaction liquid chromatography technique (HILIC) coupled with triple quadrupole mass spectrometry (LC-MS/MS) technology. The scope of the method includes plant growth regulators (chlormequat, daminozide, diquat, maleic hydrazide, mepiquat, paraquat), pesticides (cyromazine, the metabolite of the fungicide propineb PTU (propylenethiourea), amitrole), various multiclass antibiotics (tetracyclines, sulfonamides quinolones, kasugamycin and mycotoxins (aflatoxin B1, B2, fumonisin B1 and ochratoxin A). Isolation of the analytes from the matrix was achieved with a fast and effective technique. The validation of the multi-residue method was performed at the levels: 10 μg/kg and 100 μg/kg in the following representative substrates: fruits-vegetables (apples, apricots, lettuce and onions), cereals and pulses (flour and chickpeas), animal products (milk and meat) and cereal based baby foods. The method was validated taking into consideration EU guidelines and showed acceptable linearity (r ≥ 0.99), accuracy with recoveries between 70 and 120% and precision with RSD ≤ 20% for the majority of the analytes studied. For the analytes that presented accuracy and precision values outside the acceptable limits the method still is able to serve as a semi-quantitative method. The matrix effect, the limits of detection and quantification were also estimated and compared with the current EU MRLs (Maximum Residue Levels) and FAO/WHO MLs (Maximum Levels) or CXLs (Codex Maximum Residue Limits). The combined and expanded uncertainty of the method for each analyte per substrate, was also estimated.     

On the feasibility of applying capture–recapture experiments for web evolution estimations

This paper proposes a novel application for estimating the size and evolution of web page populations, based on the capture–recapture methodology, which is mainly used in wildlife biological studies. Firstly, we present the necessary modifications and amendments needed for the web capture–recapture paradigm, and then we discuss the limitations confronted. The paper provides the implementation details of the proposed web capture recapture model along with its initial assessment. The anticipated outcome was to examine whether we can conduct capture–recapture experiments on the web (or a web sub-universe such as an Internet search engine directory), in order to further estimate evolution rates in web page populations.     

Pionic deuterium

Data taking of the PIONIC HYDROGEN project has been completed with a high statistics study of the strong-interaction effects in πD by measuring the Kβ X-radiation for three different target densities with a high resolution Bragg crystal spectrometer. The πD hadronic shift will provide a constraint for the πN isospin scattering lengths extracted from the πH measurement. The hadronic width is directly related to pion production at threshold.     

Precision Measurement of the Charged Pion Mass by High Resolution X-Ray Spectroscopy

A new experiment for a high-precision measurement of the pion mass at a 1 ppm level is presented. It combines an improved cyclotron trap that produces pionic and muonic atoms in a small volume with a doubly focusing crystal spectrometer to measure the corresponding exotic X-ray transitions with high accuracy and a novel type of CCD detector. The muonic X-rays lines serve as highly accurate calibration lines. The measurement has been accomplished recently. A detailed analysis of the data is on the way. This revised version was published online in July 2006 with corrections to the Cover Date.