A comparison of the performance of molecular descriptors of different types was conducted. The study was concentrated on determining which descriptors are included in the best linear multivariate regression models constructed for modeling various physicochemical properties (melting point, boiling point, refractive index, molar volume, and density) and biological activities (anaesthetic activity, narcotic activity, sweetness intensity). A total of 84 molecular descriptors published over the past 2 decades was included in this study, plus some of their normalized and squared forms. It was shown that, for the estimation of physicochemical properties, the best small regression models with one to four parameters are mainly comprised of "classical" topological indices such as the Randić index, Wiener index, and molecular connectivity indices. For the correlation of biological activity, combinations of topological indices with geometrical descriptors produced regression models of the best quality. In-house developed software was used for generation of the molecular descriptors (the GROUND program) and for the statistical QSAR/QSPR analysis (the GROUNDSTAT program).

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We present the results of the first joint search for gravitational-wave bursts by the LIGO and GEO 600 detectors. We search for bursts with characteristic central frequencies in the band 768-2048 Hz in the data acquired between 22 February and 23 March, 2005 (fourth LSC Science Run-S4). We discuss the inclusion of the GEO 600 data in the Waveburst-CorrPower pipeline that first searches for coincident excess power events without taking into account differences in the antenna responses or strain sensitivities of the various detectors. We compare the performance of this pipeline to that of the coherent Waveburst pipeline based on the maximum likelihood statistic. This likelihood statistic is derived from a coherent sum of the detector data streams that takes into account the antenna patterns and sensitivities of the different detectors in the network. We find that the coherent Waveburst pipeline is sensitive to signals of amplitude 30-50% smaller than the Waveburst-CorrPower pipeline. We perform a search for gravitational-wave bursts using both pipelines and find no detection candidates in the S4 data set when all four instruments were operating stably. PACS numbers: 04.80.Nn, 95.30.Sf, 95.85.Sz (Some figures in this article are in colour only in the electronic version)

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