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Search Results: 1 - 10 of 130470 matches for " V. Ostafe "
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Spectral SAR Ecotoxicology of Ionic Liquids: The Daphnia magna Case
Mihai V. Putz,Ana-Maria Lacr m ,Vasile Ostafe
International Journal of Ecology , 2007, DOI: 10.1155/2007/12813
Abstract: Aiming to provide a unified theory of ionic liquids ecotoxicity, the recent spectral structure activity relationship (S-SAR) algorithm is employed for testing the two additive models of anionic-cationic interaction containing ionic liquid activity: the causal and the endpoint, |0
A Spectral-SAR Model for the Anionic-Cationic Interaction in Ionic Liquids: Application to Vibrio fischeri Ecotoxicity
Ana-Maria Lacr?m?,Mihai V. Putz,Vasile Ostafe
International Journal of Molecular Sciences , 2007, DOI: 10.3390/i8080842
Abstract: Within the recently launched the spectral-structure activity relationship (S-SAR)analysis, the vectorial anionic-cationic model of a generic ionic liquid is proposed, alongwith the associated algebraic correlation factor in terms of the measured and predictedactivity norms. The reliability of the present scheme is tested by assessing the Hanschfactors, i.e. lipophylicity, polarizability and total energy, to predict the ecotoxicityendpoints of wide types of ionic liquids with ammonium, pyridinium, phosphonium,choline and imidazolium cations on the aquatic bacteria Vibrio fischeri. The results, whileconfirming the cationic dominant influence when only lipophylicity is considered,demonstrate that the anionic effect dominates all other more specific interactions. It wasalso proved that the S-SAR vectorial model predicts considerably higher activity for theionic liquids than for its anionic and cationic subsystems separately, in all consideredcases. Moreover, through applying the least norm-correlation path principle, the completetoxicological hierarchies are presented, unfolding the ecological rules of combined cationicand anionic influences in ionic liquid toxicity.
Full Analytic Progress Curves of Enzymic Reactions in Vitro
Mihai V. Putz,Ana-Maria Lacrama,Vasile Ostafe
International Journal of Molecular Sciences , 2006, DOI: 10.3390/i7110469
Abstract: Assuming the in vitro conditions for the enzyme-catalyzed reactions, the basic Michaelis-Menten description is modified in a logistic (mathematical) manner such that the inherent limitations that appear in the previous method are removed. Beside its generality, the reliability of the present approach is proved through applications on the competitive multi- and bi- substrate enzyme catalyses.
ASSAY OF ASCORBIC ACID BY RP-HPLC IN SAMPLES CONTAINING ALSO CITRIC ACID
V. Ostafe,C. Brumaru,Gabriela Papoe,Ioana Lupsa
Annals of West University of Timi?oara : Series of Biology , 1999,
Abstract: The ascorbic acid is widely used as antioxidant in food products. As this substance is a very unstable substance, its concentration needs an accurate monitorization. A RP-HPLC method was used for identification and quantification of ascorbic acid in mixtures used in sausage industry. Reliable results are obtained even the samples contain high quantities of citric acid. The regression coefficient of standard curve is 0.999.
Interpretation of ECG Signal with a Multi-Layer Neural Network
Dumitru Ostafe
Journal of Applied Computer Science & Mathematics , 2008,
Abstract: In this article there are introduced the resultsobtained in the interpretation of the components of abiomedical signal, ECG, by using a multi-layer neuralnetwork, using the backpropagation algorithm. The neuralnetwork was simulated with the Neuroshell2.0 program. Thenew obtained network was used within the program ofautomate diagnosing of the ECG.
Multivariate Permutation Polynomial Systems and Nonlinear Pseudorandom Number Generators
Alina Ostafe
Mathematics , 2009,
Abstract: In this paper we study a class of dynamical systems generated by iterations of multivariate permutation polynomial systems which lead to polynomial growth of the degrees of these iterations. Using these estimates and the same techniques studied previously for inversive generators, we bound exponential sums along the orbits of these dynamical systems and show that they admit much stronger estimates on average over all initial values than in the general case and thus can be of use for pseudorandom number generation.
On some extensions of the Ailon-Rudnick Theorem
Alina Ostafe
Mathematics , 2015,
Abstract: In this paper we present some extensions of the Ailon-Rudnick Theorem, which says that if $f,g\in{\mathbb C}[T]$, then $\gcd(f^n-1,g^m-1)$ is bounded for all $n,m\ge 1$. More precisely, using a uniform bound for the number of torsion points on curves and results on the intersection of curves with algebraic subgroups of codimension at least $2$, we present two such extensions in the univariate case. We also give two multivariate analogues of the Ailon-Rudnick Theorem based on Hilbert's irreducibility theorem and a result of Granville and Rudnick about torsion points on hypersurfaces.
Polynomial Values in Affine Subspaces of Finite Fields
Alina Ostafe
Mathematics , 2014,
Abstract: In this paper we introduce a new approach and obtain new results for the problem of studying polynomial images of affine subspaces of finite fields. We improve and generalise several previous known results, and also extend the range of such results to polynomials of degrees higher than the characteristic of the field. Such results have a wide scope of applications similar to those associated with their counterparts studying consecutive intervals over prime fields instead of affine subspaces. Here we give only two immediate consequences: to a bound on the size of the intersection of orbits of polynomial dynamical systems with affine subspaces and to the Waring problem in affine subspaces. These results are based on estimates for a certain new type of exponential sums.
Alert-QSAR. Implications for Electrophilic Theory of Chemical Carcinogenesis
Mihai V. Putz,Cosmin Iona?cu,Ana-Maria Putz,Vasile Ostafe
International Journal of Molecular Sciences , 2011, DOI: 10.3390/ijms12085098
Abstract: Given the modeling and predictive abilities of quantitative structure activity relationships (QSARs) for genotoxic carcinogens or mutagens that directly affect DNA, the present research investigates structural alert (SA) intermediate-predicted correlations ASA of electrophilic molecular structures with observed carcinogenic potencies in rats (observed activity, A = Log[1/TD 50], i.e., ASA=f(X1SA,X2SA,...)). The present method includes calculation of the recently developed residual correlation of the structural alert models, i.e., ARASA=f(A- ASA ,X1SA,X2SA,...) . We propose a specific electrophilic ligand-receptor mechanism that combines electronegativity with chemical hardness-associated frontier principles, equality of ligand-reagent electronegativities and ligand maximum chemical hardness for highly diverse toxic molecules against specific receptors in rats. The observed carcinogenic activity is influenced by the induced SA-mutagenic intermediate effect, alongside Hansch indices such as hydrophobicity (LogP), polarizability (POL) and total energy (Etot), which account for molecular membrane diffusion, ionic deformation, and stericity, respectively. A possible QSAR mechanistic interpretation of mutagenicity as the first step in genotoxic carcinogenesis development is discussed using the structural alert chemoinformation and in full accordance with the Organization for Economic Co-operation and Development QSAR guidance principles.
Regression Methods Used in Determining the Architecture of a Multilayer Neuronal Network
Dumitru Ostafe,Paul Pascu
Journal of Applied Computer Science & Mathematics , 2007,
Abstract: This article presents the way in which we candetermine the architecture of a neuronal network byusing regression methods starting from the resultsobtained by grouping the input data.
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