Structural analysis of oligomeric molecules formed from the reaction products of oleic acid ozonolysis

The products arising from the ozonolysis of oleic acid (cis-9-octadecenoic acid) in solution have been studied using negative ion mode electrospray ionization ion trap mass spectrometry. Oleic acid is an important component of atmospheric organic aerosol and is a key model species in predicting aerosol physical and chemical characteristics. The four predicted reaction products, 1-nonanal, nonanoic acid, 9-oxononanoic acid, and azelaic acid, were all observed in roughly equal yields. In addition to these products a large number of higher molecular weight compounds were detected with m/z ratios of up to 1000 Daltons. Tandem mass spectrometry of these larger ions revealed thatthey represented a complex mixture of linear alpha-acyloxyalkyl hydroperoxides, secondary ozonides, and cyclic diperoxides, formed by reactions between ozonolysis products and Criegee intermediates. These comprise the first directly elucidated structures of large oligomeric species from oleic acid ozonolysis. The degree of oligomerization and hence molecular weight distribution was observed to increase with reaction time in solution.     

ELISA as an affordable methodology for monitoring groundwater contamination by pesticides in low-income countries

The traditional instrumental technology for pesticide residue analysis is too expensive and labor-intense to meet the regional needs concerning environmental monitoring. ELISA methodology was used for a pilot scale study of groundwater quality in an agricultural region a few kilometers southwest of Montevideo, the capital city of Uruguay. The study spanned 2 years and examined concentrations (detection limits are given in [ppb]) of two triazine herbicides (simazine [0.3] and atrazine [0.4]) and the carbamate insecticide carbaryl [10] and its major metabolite 1-naphthol [17]. In general, pesticide concentrations were below detection limits in the samples tested and in all cases were well below the maximum contaminant levels set by the U.S. EPA. 1-Naphthol was detected frequently by ELISA, but the assay may have tended to systematically overestimate this analyte. To our knowledge, this is the first study of its type in Uruguay and perhaps the first systematic approach to monitoring for organic pesticides in groundwater water sources in the temperate region of South America.     

High resolution techniques for Loran-C skywave delay estimation

Two high-resolution estimation techniques are applied to the problem of estimating the delays of the skywave components of signals input to Loran-C receivers. Their performance is evaluated and compared with that of a Fourier-based spectral-division technique. Simulation results show that the high-resolution algorithms improve the accuracy of the estimates significantly and estimate the skywave delay successfully in situations in which the Fourier-based method fails     

Characterization of d.c.jet CVD diamond films on molybdenum

Diamond films grown using a thermal plasma technique are characterized using a variety of techniques. The relationships between the chemistry, morphology, and mechanical properties are explored using microscopy, Raman spectroscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. The characteristics of films grown using two different nucleation enhancement techniques are shown. Films grown using high methane concentrations at the beginning of growth produce large grained columnar films, whereas films grown on substrates which have been treated with a diamond polishing step show nanocrystalline structures. Variations in sp³ and sp² bonding and peak shifts are tracked through the thickness of the film, corresponding to variations in the methane concentration during growth. Stresses are measured using peak shifts and beam bending techniques. Adhesion is tested using indentations, and is shown to increase both as growth temperatures and surface roughness increase.     

A Feature-Based Serial Approach to Classifier Combination

: A new approach to the serial multi-stage combination of classifiers is proposed. Each classifier in the sequence uses a smaller subset of features than the subsequent classifier. The classification provided by a classifier is rejected only if its decision is below a predefined confidence level. The approach is tested on a two-stage combination of k-Nearest Neighbour classifiers. The features to be used by the first classifier in the combination are selected by two stand-alone algorithms (Relief and Info-Fuzzy Network, or IFN) and a hybrid method, called ‘IFN + Relief’. The feature-based approach is shown empirically to provide a substantial decrease in the computational complexity, while maintaining the accuracy level of a single-stage classifier or even improving it. Received: 24 November 2000, Received in revised form: 30 November 2001, Accepted: 05 June 2002 ID="A1" Correspondence and offprint requests to: M. Last, Department of Information Systems Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel. Email: mlast@bgumail.bgu.ac.il     

Offline correction of microwave-network-analyser reflection-coefficient errors

This program has been developed to correct certain errors arising in the use of microwave-network-analyser systems. In using a network analyser to measure the reflection coefficient, errors arise from imperfections in directional couplers, source and other mismatches and crosstalk and inaccurate tracking between test and reference channels. This program facilitates calibration of the system and corrects the measurement data obtained. The use of error correction can also extend the useful frequency range of the analyser. In addition, the program can modify data for various reference planes and has facilities for graphical output on a Smith-chart display. The program was designed to run on an ICL 4100 series computer with incremental plotter, magnetic tape handlers and paper-tape station, in addition to card reader and line-printer.     

Novel analysis of pulse propagation on nonlinear delay lines

A rigorous method of analysis recently proposed for the nonlinear-transmission-line harmonic generator is applied to the propagation of pulse waveforms on a nonlinear delay line. Experimental voltage/time waveforms are compared with theoretical predictions.     

Using a neural network in the software testing process

Software testing forms an integral part of the software development life cycle. Since the objective of testing is to ensure the conformity of an application to its specification, a test “oracle” is needed to determine whether a given test case exposes a fault or not. Using an automated oracle to support the activities of human testers can reduce the actual cost of the testing process and the related maintenance costs. In this paper, we present a new concept of using an artificial neural network as an automated oracle for a tested software system. A neural network is trained by the backpropagation algorithm on a set of test cases applied to the original version of the system. The network training is based on the “black‐box” approach, since only inputs and outputs of the system are presented to the algorithm. The trained network can be used as an artificial oracle for evaluating the correctness of the output produced by new and possibly faulty versions of the software. We present experimental results of using a two‐layer neural network to detect faults within mutated code of a small credit approval application. The results appear to be promising for a wide range of injected faults. ? 2002 John Wiley & Sons, Inc.