QSAR prediction of toxicity of nitrobenzenes

A QSAR analysis has been carried out on the toxicities of 40 mono-substituted nitrobenzenes using recently introduced PI and Sz indices, as well as older molecular redundancy (MRI) and Balaban indices (J). The results have shown that no statistically significant mono-parametric QSAR models are possible. Also, that along with PI, Sz, MRI and J indices are the appropriate parameters to be used in developing multiparametric QSAR models. The toxicities of nitrobenzenes are well predicted by a penta-parametric model consisting of PI, Sz, J, MRI and Ip(1) (an indicator parameter taking care of the effect of substitution at 2-position) as the correlating parameters. The predictive ability of the model is determined by a cross-validation method.     

Quantitative structure activity relationship studies on 3-triazines using van der Waal volume and molecular connectivity index

QSAR studies have been performed on the homologues of 3-triazines, using molecular connectivity index and van der Waal volume as structural parameters. The regression analysis has shown good correlation between antitumour activity and the two structural parameters.     

Phenotypic Stability of Mixtures – Relations Between the Stability Parameters of a Mixture and Its Components

For each of the two stability parameters (‘regression coefficient’ and ‘sum of squared deviations from the regression’) of the common regression approach (= regression of the yield of population i in environment j on the environmental index of this evironment j which often has been estimated by the mean of all tested populations in this environment j) the phenotypic stability of a mixture and it's components have been analysed theoretically. It can be shown that in practical applications (for example: variety testing) the regression coefficient of a mixture often can be sufficiently approximated by the arithmetic mean of the regression coefficients of the components grown singly. This simple relation between a mixture and it's components don't hold for the second stability parameter ‘sum of squared deviations from the regression’. The exact relation has been deduced and useful and clear approximations are discussed. All the theoretical results are demonstrated and applied using the well-known experimental barley data of Sandfaer (1970).     

QSAR study on (13)C NMR chemical shifts on carbinol carbon atoms

QSAR calculations of (13)C NMR chemical shifts (ppm, TMS=0) on carbinol carbon atoms have been attempted using a large set of distance based topological indices: Wiener (W)-, Szeged (Sz)-, PI (Padmakar-Ivan) and Connectivity ((m)chi, (m)chi(v)) indices. The regression analysis has shown that excellent results are obtained in multiparametric regression. The predictive power of the proposed models are discussed using cross-validated parameters.     

QSAR Studies on some antimalarial sulfonamides

Antimalarial activity of a series of sulfonamide derivatives (2,4-diamino-6-quinazoline sulfonamides) was modeled topologically using Wiener (W)-, and Szeged (Sz)-indices. The regression analysis of the data has shown that better results are obtained in multiparametric regressions upon introduction of indicator parameters. Predicting ability of the models was tested by r²_cv values. It was observed that models based on W index gave slightly better results than those in which Sz is involved.     

System analysis of heart rate variability,hemodynamics, and bioelectrical activity of the human brain at moderate altitudes

Heart rate variability (HRV), hemodynamics, cerebral α rhythm, and systemic relations between them have been investigated in 35 normal human subjects at the age of 37.2 ± 3.8 years. The results of comprehensive clinical, functional and instrumental HRV investigation, electroencephalography (EEG) using 21 monopolar electrodes, and blood pressure (BP) monitoring were embodied in mathematical models that describe the relations of these parameters, multiple regression equations, and generated 3D diagrams. It has been found that a relative increase in the LF range and a decrease in HF one are accompanied by elevations of BP. The EEG α amplitude has been depressed, and α index has decreased. The HRV reduction and modification of the α rhythm structure have been demonstrated to affect the BP values. These data indicate interactions and close relations between the autonomic and central nervous systems and BP.     

Correlations between the benzene character of acenes or helicenes and simple molecular descriptors

Aromatic stabilities of acenes and helicenes, which are responsible for their biological, environmental and cancerous behavior have been modeled using a newly introduced Sadhana (Sd) and A indices. The results are compared with those obtained from PI (Padmakar-Ivan) index. The regression analysis has shown that excellent results are obtained by considering acenes and helicenes as separate classes of isomeric benzenoid hydrocarbons and that A index is better index than both PI and Sd indices.     

Study on quantitative structure-toxicity relationships of benzene derivatives acting by narcosis

Hydrophobicity (logP) as well as quantiative structure-toxicity relationships (QSTRs) of some benzene derivatives acting by narcosis have been established based on narcotic mechanisms of action and toxicity data to the fathead minnow, Daphnia magna and Vibrio fischeri using information-theoretic topological index (Id). Excellent results are obtained in multiparametric regression upon introduction of dummy parameters (indicator variables). Consistent increase in R(2)(A) values indicated that inspite of collinarity between Id and one of the indicator variables (I(3-6)) the proposed models are statistically significant.     

Comparison of Vegetation Indices and Red-edge Parameters for Estimating Grassland Cover from Canopy Reflectance Data

There has been a great deal of Interests in the estimation of grassland biophysical parameters such as percentage of vegetation cover （PVC）, aboveground biomass, and leaf-area index with remote sensing data at the canopy scale. In this paper, the percentage of vegetation cover was estimated from vegetation indices using Moderate Resolution Imaging Spectroradiometer （MODIS） data and red-edge parameters through the first derivative spectrum from in situ hypserspectral reflectance data. Hyperspectral reflectance measurements were made on grasslands in Inner Mongolia, China, using an Analytical Spectral Devices spectroradiometer. Vegetation indices such as the difference, simple ratio, normalized difference, renormalized difference, soil-adjusted and modified soil-adjusted vegetation indices （DVI, RVI, NDVI, RDVI, SAVI L=0.5 end MSAVI2） were calculated from the hyperspectral reflectance of various vegetation covers. The percentage of vegetation cover was estimated using an unsupervised spectral-contextual classifier automatically. Relationships between percentage of vegetation cover and various vegetation indices and red-edge parameters were compared using a linear and second-order polynomial regression. Our analysis indicated that MSAVI2 and RVI yielded more accurate estimations for a wide range of vegetation cover than other vegetation indices and red-edge parameters for the linear and second-order polynomial regression, respectively.     

QSAR studies on psychotomimetic phenylalkylamines

Quantitative Structure-Activity Relationship (QSAR) studies on a series of psychotomimetic phenylalkylamines have been made using a combination of Minimum Topological Difference (MTD) method and topological methodology. The topological indices used being a pool of distance-based topological indices. The regression analyses have shown that excellent results are obtained in multiparametric model containing MTD parameters, topological indices in that quantum chemical parameters has to be introduced. The predictive power of the proposed model is discussed on the basis of cross-validation parameters.