Home About us Contact
|
Home About us Contact | ||
|
|
||
Test Shows (test + shows)
Selected AbstractsPrediction of protein structural class by amino acid and polypeptide compositionFEBS JOURNAL, Issue 17 2002Rui-yan Luo A new approach of predicting structural classes of protein domain sequences is presented in this paper. Besides the amino acid composition, the composition of several dipeptides, tripeptides, tetrapeptides, pentapeptides and hexapeptides are taken into account based on the stepwise discriminant analysis. The result of jackknife test shows that this new approach can lead to higher predictive sensitivity and specificity for reduced sequence similarity datasets. Considering the dataset PDB40-B constructed by Brenner and colleagues, 75.2% protein domain sequences are correctly assigned in the jackknife test for the four structural classes: all-,, all-,, ,/, and , + ,, which is improved by 19.4% in jackknife test and 25.5% in resubstitution test, in contrast with the component-coupled algorithm using amino acid composition alone (AAC approach) for the same dataset. In the cross-validation test with dataset PDB40-J constructed by Park and colleagues, more than 80% predictive accuracy is obtained. Furthermore, for the dataset constructed by Chou and Maggiona, the accuracy of 100% and 99.7% can be easily achieved, respectively, in the resubstitution test and in the jackknife test merely taking the composition of dipeptides into account. Therefore, this new method provides an effective tool to extract valuable information from protein sequences, which can be used for the systematic analysis of small or medium size protein sequences. The computer programs used in this paper are available on request. [source] Selection of evolutionary models for phylogenetic hypothesis testing using parametric methodsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2001B. C. Emerson Recent molecular studies have incorporated the parametric bootstrap method to test a priori hypotheses when the results of molecular based phylogenies are in conflict with these hypotheses. The parametric bootstrap requires the specification of a particular substitutional model, the parameters of which will be used to generate simulated, replicate DNA sequence data sets. It has been both suggested that, (a) the method appears robust to changes in the model of evolution, and alternatively that, (b) as realistic model of DNA substitution as possible should be used to avoid false rejection of a null hypothesis. Here we empirically evaluate the effect of suboptimal substitution models when testing hypotheses of monophyly with the parametric bootstrap using data sets of mtDNA cytochrome oxidase I and II (COI and COII) sequences for Macaronesian Calathus beetles, and mitochondrial 16S rDNA and nuclear ITS2 sequences for European Timarcha beetles. Whether a particular hypothesis of monophyly is rejected or accepted appears to be highly dependent on whether the nucleotide substitution model being used is optimal. It appears that a parameter rich model is either equally or less likely to reject a hypothesis of monophyly where the optimal model is unknown. A comparison of the performance of the Kishino,Hasegawa (KH) test shows it is not as severely affected by the use of suboptimal models, and overall it appears to be a less conservative method with a higher rate of failure to reject null hypotheses. [source] Pressure-Sensitive Adhesive Blend Films for Low-Tack ApplicationsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 7 2007Peter Müller-Buschbaum Abstract Polymer blend films consisting of a tacky and a nonadhesive component are promising candidates for low-tack applications. Immiscibility of both components results in a phase separation process yielding a tacky matrix with glassy objects embedded. The influence of the blending ratio of the components poly(n -butyl acrylate) (PnBA) and polystyrene (PS) is addressed. The mechanical information resulting from the tack test shows the possibility of varying the bonding strength of the PSA blend over a wide range. The macroscopic and microscopic structural characterization with optical microscopy and ultrasmall angle X-ray scattering (USAXS) shows that the blend PnBA/PS exhibits similarities to common filler systems as well as deviates regarding installed structures. Due to the large domain size on a microscopic level, only the tacky component, PnBA, defines the adhesive behavior. The nonadhesive component limits the contact area between the adhesive and the substrate. [source] E+A and companion galaxies , I. A catalogue and statisticsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008Chisato Yamauchi ABSTRACT Based on our intensive spectroscopic campaign with the GoldCam spectrograph on the Kitt Peak National Observatory (KPNO) 2.1-m telescope, we have constructed the first catalogue of E+A galaxies with spectroscopic companion galaxies, and investigated a probability that an E+A galaxy has close companion galaxies. We selected 660 E+A galaxies with 4.0 Å < H, EW at a redshift of <0.167 from the Data Release 5 of the Sloan Digital Sky Survey (SDSS). We selected their companion candidates from the SDSS imaging data, and classified them into true companions, fore/background galaxies and companion candidates using the SDSS and our KPNO spectra. We observed 26 companion candidates of E+A galaxies at the KPNO to measure their redshifts. Their spectra showed that 17 targets are true companion galaxies. The number of spectroscopically confirmed E+A's companions is now 34. This becomes the first catalogue of E+A galaxies with spectroscopic companion systems. We found that E+A galaxies have 54 per cent larger probability of having companion galaxies (7.88 per cent) as compared to the comparison sample of normal galaxies (5.12 per cent). A statistical test shows that the probabilities are different with 99.7 per cent significance. Our results based on spectroscopy tighten the connection between the dynamical merger/interaction and the origin of E+A galaxies. [source] The bimodal spiral galaxy surface brightness distributionMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2000Eric F. Bell We have assessed the significance of Tully and Verheijen's bimodal Ursa Major Cluster spiral galaxy near-infrared surface brightness distribution, focusing on whether this bimodality is simply an artefact of small number statistics. A Kolmogorov,Smirnov style of significance test shows that the total distribution is fairly represented by a single-peaked distribution, but that their isolated galaxy subsample (with no significant neighbours within a projected distance of ,80 kpc) is bimodal at the 96 per cent level. We have also investigated the assumptions underlying the isolated galaxy surface brightness distribution, finding that the (often large) inclination corrections used in the construction of this distribution reduce the significance of the bimodality. We conclude that the Ursa Major Cluster data set is insufficient to establish the presence of a bimodal near-infrared surface brightness distribution: an independent sample of ,100 isolated, low-inclination galaxies is required to establish bimodality at the 99 per cent level. [source] Civic Knowledge of High School Students in Israel: Personal and Contextual DeterminantsPOLITICAL PSYCHOLOGY, Issue 4 2007Professor Orit Ichilov Past research on civic education suggests that students' performance is largely influenced by individual socioeconomic background and motivational factors. There has been little attention to the effects of school and classroom ideological and social attributes, such as the socioeconomic make-up of the school or classroom, or how interested in politics are a student's classmates. The results of the present study support the contention that contextual effects play a vital role in determining students' civic knowledge scores. Analysis of Israeli 11th graders' performance on the International Association for the Evaluation of Educational Achievement (IEA) civic knowledge test shows that while individual backgrounds and motivations play a significant role, school and classroom contexts greatly contribute to civic knowledge acquisition. [source] Tracing the distribution and evolution of lactase persistence in Southern Europe through the study of the T -13910 variantAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 2 2009Paolo Anagnostou We investigated the occurrence and intra-allelic variability of the T -13910 variant located upstream of the lactase gene in 965 individuals from 20 different locations of Italy and Greece. The T -13910 frequency ranges from 0.072 (Sardinia) to 0.237 (North-East Italy), with a statistically significant difference between North-East Italians and other Italian populations. The comparison of the lactose tolerance predicted by T -13910 and that assessed by other studies using physiological tests shows a one-way statistically significant discrepancy that could be due to sampling differences. However, the possible role of other genetic factors underlying lactase persistence is worth exploring. The time of the most recent common ancestor and departures from neutrality of the T -13910 allele were assessed using three microsatellite loci. Time estimates were found to be congruent with the appearance of dairy farming in Southern Europe and the occurrence of a single introgression event. Robust signals of selection can be observed in North-East Italy only. We discuss the possible role of cultural traits and genetic history in determining these observed micro-evolutionary patterns. Am. J. Hum. Biol. 2009. © 2008 Wiley-Liss, Inc. [source] | ||||||||||