Journal articles: 'Theoretical descriptors'

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Dale, Stephen G., and Erin R. Johnson. "Theoretical Descriptors of Electrides." Journal of Physical Chemistry A 122, no. 49 (October 19, 2018): 9371–91. http://dx.doi.org/10.1021/acs.jpca.8b08548.

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Lopesino, C., F. Balibrea-Iniesta, V. J. García-Garrido, S. Wiggins, and A. M. Mancho. "A Theoretical Framework for Lagrangian Descriptors." International Journal of Bifurcation and Chaos 27, no. 01 (January 2017): 1730001. http://dx.doi.org/10.1142/s0218127417300014.

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This paper provides a theoretical background for Lagrangian Descriptors (LDs). The goal of achieving rigorous proofs that justify the ability of LDs to detect invariant manifolds is simplified by introducing an alternative definition for LDs. The definition is stated for [Formula: see text]-dimensional systems with general time dependence, however we rigorously prove that this method reveals the stable and unstable manifolds of hyperbolic points in four particular 2D cases: a hyperbolic saddle point for linear autonomous systems, a hyperbolic saddle point for nonlinear autonomous systems, a hyperbolic saddle point for linear nonautonomous systems and a hyperbolic saddle point for nonlinear nonautonomous systems. We also discuss further rigorous results which show the ability of LDs to highlight additional invariants sets, such as [Formula: see text]-tori. These results are just a simple extension of the ergodic partition theory which we illustrate by applying this methodology to well-known examples, such as the planar field of the harmonic oscillator and the 3D ABC flow. Finally, we provide a thorough discussion on the requirement of the objectivity (frame-invariance) property for tools designed to reveal phase space structures and their implications for Lagrangian descriptors.

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Rivera, Jose Luis, Pedro Navarro-Santos, Luis Hernandez-Gonzalez, and Roberto Guerra-Gonzalez. "Reactivity of Alkyldibenzothiophenes Using Theoretical Descriptors." Journal of Chemistry 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/215074.

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Theoretical calculations of the reactivity of dibenzothiophene and its methyl, dimethyl, and trimethyl derivatives show that local reactivity descriptors reproduce their experimental desulfurization reactivity trend if the first desulfurization step involves directly the sulfur atom, which only occurs if the sulfur atom is blocked at most by one methyl group. In the series of molecules{4,7-dimethyldibenzothiophene,x,4,7-trimethyldibenzothiophene (x=1,2,3)}, the most reactive molecule is 2,4,7-trimethyldibenzothiophene, and local descriptors show that the reactivity is linked to the activity of the sulfur atom, which is higher in 2,4,7-trimethyldibenzothiophene due to the position of the third methyl substitute, located in theparaposition with respect to the carbon bonded to the sulfur atom. The electrostatic potential of 2,4,7-trimethyldibenzothiophene shows one effective adsorption site, while 1,4,7-trimethyldibenzothiophene and 3,4,7-trimethyldibenzothiophene have more sites, contributing to the higher reactivity of 2,4,7-trimethyldibenzothiophene. The index of reactivity of other descriptors was evaluated and the effect of the position of the methyl substituents on adsorption parameters, as the dipole moment and the atomic charges were also studied.

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Kanari, Lida, Adélie Garin, and Kathryn Hess. "From Trees to Barcodes and Back Again: Theoretical and Statistical Perspectives." Algorithms 13, no. 12 (December 11, 2020): 335. http://dx.doi.org/10.3390/a13120335.

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Methods of topological data analysis have been successfully applied in a wide range of fields to provide useful summaries of the structure of complex data sets in terms of topological descriptors, such as persistence diagrams. While there are many powerful techniques for computing topological descriptors, the inverse problem, i.e., recovering the input data from topological descriptors, has proved to be challenging. In this article, we study in detail the Topological Morphology Descriptor (TMD), which assigns a persistence diagram to any tree embedded in Euclidean space, and a sort of stochastic inverse to the TMD, the Topological Neuron Synthesis (TNS) algorithm, gaining both theoretical and computational insights into the relation between the two. We propose a new approach to classify barcodes using symmetric groups, which provides a concrete language to formulate our results. We investigate to what extent the TNS recovers a geometric tree from its TMD and describe the effect of different types of noise on the process of tree generation from persistence diagrams. We prove moreover that the TNS algorithm is stable with respect to specific types of noise.

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Babatunde, Olasupo Sabitu Babatunde, Adamu Uzairu, Gideon Adamu Shallangwa, and Sani Uba. "THEORETICAL AND INSILCO PHARMACOKINETIC INVESTIGATIONS ON SOME PHENYL PIPERIDINE DERIVATIVES AS NOVEL ANTIDEPRESSANT AGENTS." Journal of Engineering and Exact Sciences 6, no. 2 (June 17, 2020): 0107–28. http://dx.doi.org/10.18540/jcecvl6iss2pp0107-0128.

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A theoretical bioinformatic investigation was carried out on some Inhibitors of serotonin transporter (SERT) of Phenyl piperidine derivatives using Density Functional Theory (DFT/B3LYP/6-31G*) at ground state with Spartan 14 V1.1.4 software in modeling the antipsychotic activity of the compounds. The molecular descriptors were computed using the PaDEL-Descriptor software 2.20 version. Penta-parametric Multi-linear regression models were developed using the MLR-GFA for selecting the most important descriptors. The statistical parameters for the best model are; R2Train= 0.8572, R 2adj = 0.8274, R2Test = 0.678, Q2cv (LOO) = 0.7664, Ꭓ2= 0.0036, r2m (LOO)= 0.694 and Delta r2m (LOO)= 0.0051). Also, the estimated Chi-squared (Ꭓ2= 0.0036), Root-mean squared error (RMSE= 0.168) and and

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Kreiner, Hamutal, and Eyal Gamliel. "“Alive” or “not dead”: The contribution of descriptors to attribute-framing bias." Quarterly Journal of Experimental Psychology 72, no. 12 (July 18, 2019): 2776–87. http://dx.doi.org/10.1177/1747021819862508.

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Attribute-framing bias (AFB) refers to bias in evaluating positively framed objects more favourably than the same objects framed negatively. In most AFB studies, framing is manipulated by contrasting the positive and negative outcomes, using the corresponding positive (success) or negative (failure) labels as descriptors. This study examined the unique contributions of the outcomes of the scenario and the labels describing these outcomes by manipulating them orthogonally. In three experiments, framing scenarios were presented to participants with either positive outcomes rendered with positive (65% passed) or negative (65% didn’t fail) descriptors, or negative outcomes rendered with positive (35% didn’t pass) or negative (35% failed) descriptors. All experiments revealed a strong effect for the outcome with a weaker effect for the descriptor valence, suggesting that outcomes have a stronger influence on AFB than do descriptors. We discuss the results within a theoretical framework that maps the outcome effects onto attention mechanisms and descriptor effects onto association-activation mechanisms.

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Park, Jung, Cho, Moon, and Han. "Theoretical Evaluation of Water Cloud Model Vegetation Parameters." Remote Sensing 11, no. 8 (April 12, 2019): 894. http://dx.doi.org/10.3390/rs11080894.

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The advantage of implementing the Water Cloud Model (WCM) is in being able to express complex scattering characteristics in a vegetated area with simple bulk vegetation descriptors. However, there has been a lack of understanding or consensus about the optimal set of vegetation descriptors. In this paper, the original and improved expressions of WCM are evaluated and the optimal vegetation descriptors are presented by examining the relationship between WCM vegetation parameters and the theoretical scattering model predictions. In addition, the condition-specific regression relationship between bulk vegetation descriptors and theoretical scattering and attenuation coefficients, expressed by the A and B parameters in the WCM, is analyzed in relation to the shape, size, and orientation distribution of the scatterer. Furthermore, the influence of radar observation conditions on the parameterization of the WCM is presented. The results show that the particle moisture content and the vegetation water content can be the optimal vegetation descriptors, denoted by the V1 and V2 variables in the WCM, respectively.

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Nandi, Sisir, and Manish Bagchi. "QSAR of Chalcones Utilizing Theoretical Molecular Descriptors." Current Computer Aided-Drug Design 11, no. 2 (September 4, 2015): 184–93. http://dx.doi.org/10.2174/1573409911666150702101559.

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Bashiri, Fereshteh S., Reihaneh Rostami, Peggy Peissig, Roshan M. D’Souza, and Zeyun Yu. "An Application of Manifold Learning in Global Shape Descriptors." Algorithms 12, no. 8 (August 16, 2019): 171. http://dx.doi.org/10.3390/a12080171.

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With the rapid expansion of applied 3D computational vision, shape descriptors have become increasingly important for a wide variety of applications and objects from molecules to planets. Appropriate shape descriptors are critical for accurate (and efficient) shape retrieval and 3D model classification. Several spectral-based shape descriptors have been introduced by solving various physical equations over a 3D surface model. In this paper, for the first time, we incorporate a specific manifold learning technique, introduced in statistics and machine learning, to develop a global, spectral-based shape descriptor in the computer graphics domain. The proposed descriptor utilizes the Laplacian Eigenmap technique in which the Laplacian eigenvalue problem is discretized using an exponential weighting scheme. As a result, our descriptor eliminates the limitations tied to the existing spectral descriptors, namely dependency on triangular mesh representation and high intra-class quality of 3D models. We also present a straightforward normalization method to obtain a scale-invariant and noise-resistant descriptor. The extensive experiments performed in this study using two standard 3D shape benchmarks—high-resolution TOSCA and McGill datasets—demonstrate that the present contribution provides a highly discriminative and robust shape descriptor under the presence of a high level of noise, random scale variations, and low sampling rate, in addition to the known isometric-invariance property of the Laplace–Beltrami operator. The proposed method significantly outperforms state-of-the-art spectral descriptors in shape retrieval and classification. The proposed descriptor is limited to closed manifolds due to its inherited inability to accurately handle manifolds with boundaries.

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DENTSORAS, A. J. "Information generation during design: Information importance and design effort." Artificial Intelligence for Engineering Design, Analysis and Manufacturing 19, no. 1 (February 2005): 19–32. http://dx.doi.org/10.1017/s089006040505002x.

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The present paper studies the process of information generation during design and focuses on the relationship between the information importance and the required effort for its generation. Multiple associative relationships among design entities (handled as design descriptors) are used to represent the design knowledge. The characteristics of the dependent and the primary descriptors are examined and their distinct roles in the design process are discussed. Term definitions concerning the information importance and the design effort are also introduced. The descriptors are used to form a matrix. A number of operations on this matrix results in its transformation, with the final matrix reflecting the quantitative relationship between the information importance and the design effort. From the aforementioned matrix, a unique sorted list for the primary design descriptors is produced. Following this list during descriptor instantiation ensures the production of design information of maximum importance with the least effort in the early design stages. The design of a belt conveyor is used as a basis for a better understanding of the theoretical analysis and for a demonstration of the use of the suggested descriptor list.

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Motoc, I., G. R. Marshall, R. A. Dammkoehler, and J. Labanowski. "Molecular Shape Descriptors. 1. Three-Dimensional Molecular Shape Descriptor." Zeitschrift für Naturforschung A 40, no. 11 (November 1, 1985): 1108–13. http://dx.doi.org/10.1515/zna-1985-1106.

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The paper presents and illustrates a method which uses numerical integration of the van der Waals envelope(s) to calculate with desired accuracy the molecular van der Waals volume and the three-dimensional molecular shape descriptor defined as the twin-number [OV(α, β); NOV(β, α), where OV and NOV represent the overlapping and, respectively, the nonoverlapping van der Waals volumes of the molecules α and ß superimposed according to appropriate criteria.

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Balaban, A. T. "Local (Atomic) and Global (Molecular) Graph-Theoretical Descriptors." SAR and QSAR in Environmental Research 3, no. 2 (August 1995): 81–95. http://dx.doi.org/10.1080/10629369508233996.

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Cocchi, Marina, M. Cristina Menziani, Pier G. De Benedetti, and Gabriele Cruciani. "Theoretical versus empirical molecular descriptors in monosubstituted benzenes." Chemometrics and Intelligent Laboratory Systems 14, no. 1-3 (April 1992): 209–24. http://dx.doi.org/10.1016/0169-7439(92)80105-d.

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C. Basak, Subhash, Denise Mills, Hisham A. El-Masri, Moiz M. Mumtaz, and Douglas M. Hawkins. "Predicting blood:air partition coefficients using theoretical molecular descriptors." Environmental Toxicology and Pharmacology 16, no. 1-2 (March 2004): 45–55. http://dx.doi.org/10.1016/j.etap.2003.09.002.

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15

Klyukin, Ilya N., Yulia S. Vlasova, Alexander S. Novikov, Andrey P. Zhdanov, Konstantin Y. Zhizhin, and Nikolay T. Kuznetsov. "Theoretical Study of closo-Borate Anions [BnHn]2− (n = 5–12): Bonding, Atomic Charges, and Reactivity Analysis." Symmetry 13, no. 3 (March 12, 2021): 464. http://dx.doi.org/10.3390/sym13030464.

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This study has focused on the structure, bonding, and reactivity analysis of closo-borate anions [BnHn]2− (n = 5–12). Several descriptors of B–H interactions have been calculated. It has been found that the values of electron density and total energy at bond critical point are the most useful descriptors for investigation of B–H interactions. Using results from the descriptor analysis, one may conclude that orbital interactions in [BnHn]2− increase with increasing the boron cluster size. Several approaches to estimate atomic charges have been applied. Boron atoms in apical positions have more negative values of atomic charges as compared with atoms from equatorial positions. The mean values of boron and hydrogen atomic charges tend to be more positive with the increasing of boron cluster size. Global and local reactivity descriptors using conceptual density functional theory (DFT) theory have been calculated. Based on this theory, the closo-borate anions [BnHn]2− (n = 5–9) can be considered strong and moderate electrophiles, while the closo-borate anions [BnHn]2− (n = 10–12) can be considered marginal electrophiles. Fukui functions for electrophilic attack have been calculated. Fukui functions correlate well with atomic charges of the closo-borate anions. Boron atoms in apical positions have the most positive values of Fukui functions.

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Ouafy, Hayat EL, Mouna Aamor, Mustapha Oubenali, Mohamed Mbarki, Aziz EL Haimouti, and Tarik EL Ouafy. "Theoretical study of the stability and reactivity of salicylic acid isomers by the DFT method." Current Chemistry Letters 11, no. 2 (2022): 183–90. http://dx.doi.org/10.5267/j.ccl.2022.2.002.

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The FT-IR spectrum of salicylic acid (SA) was studied in the region 10-4000 cm-1. The optimized molecular geometry and fundamental vibration frequencies are interpreted using structural optimizations based on the Functional Density Theory (DFT) method. Additionally, we used B3LYP / 6-311G (d, p) to determine the chemical descriptor, the ionization potential (I), the electron affinity (A), the chemical potential (μ), the chemical hardness (η). Nonlinear optical descriptors (NLO) such as dipole moment (μ), polarizability (α), first hyperpolarizability (β) and second hyperpolarizability (γ), 3D maps of HOMO and LUMO orbitals, lengths and Bond angles of salicylic acid isomers are also determined by both DFT and MP2 (The Møller-Plesset theory of order 2 perturbation) methods. The overall descriptors and the non-linear optical properties confirmed that salicylic acid is the reactive molecule and para-hydroxybenzoic acid is the stable molecule. An electrostatic molecular potential (MEP) study was also performed to determine the reactivity of molecules.

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Zuorro, Antonio. "Water Activity Prediction in Sugar and Polyol Systems Using Theoretical Molecular Descriptors." International Journal of Molecular Sciences 22, no. 20 (October 13, 2021): 11044. http://dx.doi.org/10.3390/ijms222011044.

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Water activity is a key factor in the development of pharmaceutical, cosmetic, and food products. In aqueous solutions of nonelectrolytes, the Norrish model provides a simple and effective way to evaluate this quantity. However, it contains a parameter, known as the Norrish constant, that must be estimated from experimental data. In this study, a new strategy is proposed for the prediction of water activity in the absence of experimental information, based on the use of theoretical molecular descriptors for characterizing the effects of a solute. This approach was applied to the evaluation of water activity in the presence of sugars (glucose, fructose, xylose, sucrose) and polyols (sorbitol, xylitol, glycerol, erythritol). The use of two descriptors related to the constitutional and connectivity properties of the solutes was first investigated. Subsequently, a new theoretical descriptor, named the global information index (G), was developed. By using this index, the water activity curves in the binary systems were reconstructed. The positive results obtained support the proposed strategy, as well as the possibility of including, in a single information index, the main molecular features of a solute that determine its effects on water activity.

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Chen, Jing, Yunjing Gao, Xiaoyan Hu, Dongdong Qin, and Xiaoquan Lu. "Descriptor selection based on variable stability for predicting inhibitor activity." Journal of Theoretical and Computational Chemistry 16, no. 08 (December 2017): 1750074. http://dx.doi.org/10.1142/s0219633617500742.

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Quantitative structure-activity relationship (QSAR) has been a technique to study the relationship between chemical structures and properties, and variable selection is an important problem for finding the informative variables and building reliable models. A variable selection method based on variable stability is proposed and used for selecting the informative descriptors in the QSAR model of inhibitors. In the method, a series of models are built by leave-one-out cross validation (LOOCV), and variable stability is defined as the ratio of the absolute mean value and standard deviation of the regression coefficients in the models for a descriptor. Therefore, the descriptors with larger stabilities are more informative to the model. To further enhance the difference among the descriptors, an exponential parameter is used to modify the standard deviation. The results show that 13 descriptors are selected as informative ones from 1217 descriptors for the QSAR model of inhibitors. An effective prediction model can be constructed by them.

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Malik, Arfa Abrar, Wenhong Yang, Zhifeng Ma, and Wen-Hua Sun. "The Catalytic Activities of Carbocyclic Fused Pyridineimine Nickel Complexes Analogues in Ethylene Polymerization by Modeling Study." Catalysts 9, no. 6 (June 12, 2019): 520. http://dx.doi.org/10.3390/catal9060520.

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In this work, two carbocyclic fused pyridineimine nickel analogue systems (Ni1 and Ni2) with different fused member rings were investigated to reveal the relationship between catalyst structure and reaction activity. Multiple linear regression analysis was performed by means of five electronic descriptors and two steric descriptors, including the Hammett constant (F), effective net charge (Qeff), energy difference (ΔE), HOMO–LUMO energy gap (Δε1, Δε2), open cone angle (θ), and bite angle (β). Very good values of correlation coefficient (R2) over 0.938 were obtained by using a combination of effective net charge (Qeff) and open cone angle (θ) for both individual analysis and comparisons between analogue systems. By analyzing the contribution of descriptors, it indicates that the dominant descriptor is effective net charge (Qeff) in the Ni1 system and open cone angle (θ) in Ni2 systems, respectively. This may explain the different variation trends of catalytic activities in two Ni complexes systems as a function of substituents.

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Gramatica, P., V. Consonni, and M. Pavan. "Prediction of aromatic amines mutagenicity from theoretical molecular descriptors." SAR and QSAR in Environmental Research 14, no. 4 (August 1, 2003): 237–50. http://dx.doi.org/10.1080/1062936032000101484.

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Heimstad, E. S., A. O. Smalås, and R. Kallenborn. "Environmental fate of chlorinated bornanes estimated by theoretical descriptors." Chemosphere 43, no. 4-7 (May 2001): 665–74. http://dx.doi.org/10.1016/s0045-6535(00)00419-7.

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Norinder, Ulf. "Theoretical amino acid descriptors. Application to bradykinin potentiating peptides." Peptides 12, no. 6 (November 1991): 1223–27. http://dx.doi.org/10.1016/0196-9781(91)90198-x.

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Chakraborty, Tanmoy, and Seema Dhail. "Theoretical Study of Lamivudine Derivatives Invoking DFT based Descriptors." International Journal of Chemoinformatics and Chemical Engineering 4, no. 2 (July 2015): 37–45. http://dx.doi.org/10.4018/ijcce.2015070103.

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Recently Maria S. Gualdesi et al., have reported about bioactive lamivudine and its carbonate derivatives with proved activity against human immunodeficiency disease (anti-HIV) and hepatitis B viruses (anti-HBV) respectively in simulated gastric and intestinal fluids samples. This is one of the simplest, sensitive, accurate and precise assays for determining all the compounds which are readily adaptable for routine use in clinical laboratories. Employing simple chromatographic technique, they have lucidly explained the kinetic and stability features of lamivudine and its carbonate derivatives. But a theoretical quantum mechanical study of aforesaid compounds is yet to explore. In this report, the authors have made a correlation between experimental properties of lamivudine derivatives with their theoretical counterparts. They have invoked DFT based global and local descriptors to explore the effect of substituents on activity and mechanistic pathway of instant compounds respectively. Their computed data reveals a hand to hand relationship between experimental and theoretical parameters. Finally, a QSAR model has been proposed in terms of DFT based global descriptors.

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Gramatica, Paola, and Ester Papa. "QSAR Modeling of Bioconcentration Factor by theoretical molecular descriptors." QSAR & Combinatorial Science 22, no. 3 (April 2003): 374–85. http://dx.doi.org/10.1002/qsar.200390027.

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De Benedetti, P. G., M. C. Menziani, M. Cocchi, and F. Fanelli. "Prototropic molecular forms and theoretical descriptors in QSAR analysis." Journal of Molecular Structure: THEOCHEM 333, no. 1-2 (March 1995): 1–17. http://dx.doi.org/10.1016/0166-1280(94)04017-m.

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Troche, Karla S., Scheila F. Braga, Vitor R. Coluci, and Douglas S. Galvão. "Carcinogenic classification of polycyclic aromatic hydrocarbons through theoretical descriptors." International Journal of Quantum Chemistry 103, no. 5 (2005): 718–30. http://dx.doi.org/10.1002/qua.20529.

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Papa, Ester, Alessandro Sangion, Olivier Taboureau, and Paola Gramatica. "Quantitative Prediction of Rat Hepatotoxicity by Molecular Structure." International Journal of Quantitative Structure-Property Relationships 3, no. 2 (July 2018): 49–60. http://dx.doi.org/10.4018/ijqspr.2018070104.

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In this article, Quantitative Structure Activity Relationships (QSAR) were generated to link the structure of over 120 heterogeneous drugs to rat hepatotoxicity. Existing studies, performed on the same data set, could not highlight relevant structure-activity relationships, and suggested models for the prediction of hepatotoxicity based on genomic data. Binary activity responses were used for the development of classification QSARs using theoretical molecular descriptors calculated with the software PaDEL-Descriptor. A statistically powerful QSAR based on six descriptors was generated by using k-Nearest Neighbour (k-NN) method and by applying the Genetic Algorithm (GA) as variable selection procedure. The new k-NN QSAR outperforms published models by providing better accuracy and less false negatives. This model is a valid alternative to approaches based on genomic descriptors, which cannot be used in virtual screening of new compounds (pre- or post-synthesis) without experimental data.

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Sapkota, Kamal Raj. "Study on QSPR Method for Theoretical Calculation of Boiling Point of Some organic Compounds." Himalayan Physics 3 (January 1, 2013): 93–95. http://dx.doi.org/10.3126/hj.v3i0.7316.

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Quantitative structure-property relationship (QSPR) models based on molecular descriptors derived from molecular structures have been developed for the prediction of boiling point using a set of 25 organic compounds. The molecular descriptors used to represent molecular structure include topological indices and constitutional descriptors. Forward stepwise regression was used to construct the QSPR models. Multiple linear regressions is utilized to construct the linear prediction model. The prediction result agrees well with the experimental value of these properties.The Himalayan PhysicsVol. 3, No. 3, July 2012Page: 93-95

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Farmanzadeh, Davood, and Hamid Rezainejad. "Theoretical study ofFeB35+nN36-n(n = 0, 1) nanocages: Chemical reactivity descriptors." Journal of Theoretical and Computational Chemistry 14, no. 04 (June 2015): 1550026. http://dx.doi.org/10.1142/s0219633615500261.

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In this study, by the density functional theory (DFT) method-based reactivity descriptors, the electronic properties and chemical reactivity of Fe substituted nanocage, FeB35+nN36-n(n = 0, 1), were investigated in gaseous and aqueous phases. The calculated binding energies of Fe atoms revealed that the substituting Fe atom in some locations of nanocage make the system more stable. The calculated global descriptors showed that the substituted Fe remarkably increases the chemical reactivity of B36N36. Also, local descriptors showed that the high reactivity of substituted nanocages is mainly related to Fe atom and these chemical species are more talented for nucleophilic attacks. The results of this work may be useful to investigate the effects of substituted metals in chemical reactivity of BN nanostructures.

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Sun, Danyu, Xixuan Zhao, and Jiangming Kan. "Performance Evaluation of Color Descriptors under Illumination Variation." Journal of Sensors 2021 (September 4, 2021): 1–16. http://dx.doi.org/10.1155/2021/6687087.

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Color descriptors, which involve the extraction of color information that is robust to illumination variation, are indispensable for accessing reliable visual information as illumination variation is inevitable in many practical cases. There has been many color descriptors proposed in literature, but the performance of different color descriptors in different scenes under illumination variation and the influence of the surface characteristics have not been investigated. In this paper, we first systematically introduced the theoretical basis of color descriptors, categorized the existing color descriptors according to the theoretical basis, and then compared the performance of different color descriptors utilized for image recognition and image retrieval tasks on both the indoor and outdoor image datasets. We adopted the recognition rate and normalized average rank as the evaluation criteria to measure the performance of color descriptors. Experiment results show that the color moment invariants (CMI) provide the optimal balance between the performance and dimensions in most tests, and color descriptors derived from physical reflectance models are more suitable for object recognition and image retrieval. We also concluded the best color descriptors for each kind of scene and surface characteristics.

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Poggesi, Simone, Amanda Dupas de Matos, Edoardo Longo, Danila Chiotti, Ulrich Pedri, Daniela Eisenstecken, Peter Robatscher, and Emanuele Boselli. "Chemosensory Profile of South Tyrolean Pinot Blanc Wines: A Multivariate Regression Approach." Molecules 26, no. 20 (October 15, 2021): 6245. http://dx.doi.org/10.3390/molecules26206245.

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A multivariate regression approach based on sensory data and chemical compositions has been applied to study the correlation between the sensory and chemical properties of Pinot Blanc wines from South Tyrol. The sensory properties were identified by descriptive analysis and the chemical profile was obtained by HS-SPME-GC/MS and HPLC. The profiles of the most influencing (positively or negatively) chemical components have been presented for each sensory descriptor. Partial Least Square Regression (PLS) and Principal Component Regression (PCR) models have been tested and applied. Visual (clarity, yellow colour), gustatory (sweetness, sourness, saltiness, bitterness, astringency, and warmness) and olfactory (overall intensity, floral, apple, pear, tropical fruit, dried fruit, fresh vegetative, spicy, cleanness, and off-odours) descriptors have been correlated with the volatile and phenolic profiles, respectively. Each olfactory descriptor was correlated via a PCR model to the volatile compounds, whereas a comprehensive PLS2 regression model was built for the correlation between visual/gustatory descriptors and the phenolic fingerprint. “Apple” was the olfactory descriptor best modelled by PCR, with an adjusted R2 of 0.72, with only 20% of the validation samples falling out of the confidence interval (α = 95%). A PLS2 with 6 factors was chosen as the best model for gustatory and visual descriptors related to the phenolic compounds. Finally, the overall quality judgment could be explained by a combination of the calibrated sensory descriptors through a PLS model. This allowed the identification of sensory descriptors such as “olfactory intensity”, “warmness”, “apple”, “saltiness”, “astringency”, “cleanness”, “clarity” and “pear”, which relevantly contributed to the overall quality of Pinot Blanc wines from South Tyrol, obtained with two different winemaking processes and aged in bottle for 18 months.

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Purvis, George D. "Size-intensive descriptors." Journal of Computer-Aided Molecular Design 22, no. 6-7 (March 21, 2008): 461–68. http://dx.doi.org/10.1007/s10822-008-9209-4.

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Xin, Xin, Chen Li, Delu Gao, and Dunyou Wang. "Catalytic Descriptors to Investigate Catalytic Power in the Reaction of Haloalkane Dehalogenase Enzyme with 1,2-Dichloroethane." International Journal of Molecular Sciences 22, no. 11 (May 29, 2021): 5854. http://dx.doi.org/10.3390/ijms22115854.

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Enzymes play a fundamental role in many biological processes. We present a theoretical approach to investigate the catalytic power of the haloalkane dehalogenase reaction with 1,2-dichloroethane. By removing the three main active-site residues one by one from haloalkane dehalogenase, we found two reactive descriptors: one descriptor is the distance difference between the breaking bond and the forming bond, and the other is the charge difference between the transition state and the reactant complex. Both descriptors scale linearly with the reactive barriers, with the three-residue case having the smallest barrier and the zero-residue case having the largest. The results demonstrate that, as the number of residues increases, the catalytic power increases. The predicted free energy barriers using the two descriptors of this reaction in water are 23.1 and 24.2 kcal/mol, both larger than the ones with any residues, indicating that the water solvent hinders the reactivity. Both predicted barrier heights agree well with the calculated one at 25.2 kcal/mol using a quantum mechanics and molecular dynamics approach, and also agree well with the experimental result at 26.0 kcal/mol. This study shows that reactive descriptors can also be used to describe and predict the catalytic performance for enzyme catalysis.

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C. Basak, Subhash, Denise Mills, Rajni Garg, and Barun Bhhatarai. "A QSAR Study of HIV Protease Inhibitors Using Theoretical Descriptors." Current Computer Aided-Drug Design 6, no. 4 (December 1, 2010): 269–82. http://dx.doi.org/10.2174/1573409911006040269.

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Boukhvalov, D. W., and T. H. Yoon. "Development of Theoretical Descriptors for Cytotoxicity Evaluation of Metallic Nanoparticles." Chemical Research in Toxicology 30, no. 8 (July 10, 2017): 1549–55. http://dx.doi.org/10.1021/acs.chemrestox.7b00026.

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Famini, George R., Valery P. Loumbev, Eric K. Frykman, and Leland Y. Wilson. "Using Theoretical Descriptors in a Correlation Analysis of Adenosine Activity." Quantitative Structure-Activity Relationships 17, no. 06 (December 1998): 558–64. http://dx.doi.org/10.1002/(sici)1521-3838(199812)17:06<558::aid-qsar558>3.0.co;2-1.

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Famini, George R., Valery P. Loumbev, Eric K. Frykman, and Leland Y. Wilson. "Using Theoretical Descriptors in a Correlation Analysis of Adenosine Activity." Quantitative Structure-Activity Relationships 17, no. 06 (December 1998): 558–64. http://dx.doi.org/10.1002/(sici)1521-3838(199812)17:06<558::aid-qsar558>3.3.co;2-t.

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Ahmad, Iftikhar, Maqbool Ahmad Chaudhry, Tarkan Öner, Tariq Mahmood, and Muhammad Hussain. "Molecular Descriptors on Line Graphs of Cactus Chains and Rooted Products Graphs." Journal of Chemistry 2022 (April 4, 2022): 1–6. http://dx.doi.org/10.1155/2022/2154288.

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The application of graph theory in the study of molecular physical and chemical properties involves theoretical mathematical chemistry. Atoms, represented by vertices, and edges, represented by bonds between them, are detailed in simple graphs called chemical graphs. The mathematical derivation of the numerical value of a graph is called the molecular descriptor of the graph. Any connected graph wherein no edge is contained in exclusive of a single cycle is called a cactus graph. In the research in this article, expressions for various molecular descriptors of line graph of the graph obtained by the rooted product of the cycle and path graphs are constructed. This article obtained the calculation of molecular descriptors for line graphs of chain ortho cactus and chain para cactus graphs. To predict the biological activity of a compound, the generalized Zagreb index, the first Zagreb index M 1 G , the second Zagreb index M 2 G , the F-index, the general Randic index, the symmetric division, the atom bond connectivity (ABC), and the geometric arithmetic (GA) descriptors are created.

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Bikker, Jack Andrew, and Donald Fredric Weaver. "Theoretical studies applicable to the design of novel anticonvulsants: an AM1 molecular orbital structure–activity study of dihydropyridine calcium channel antagonists." Canadian Journal of Chemistry 70, no. 9 (September 1, 1992): 2449–60. http://dx.doi.org/10.1139/v92-310.

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The development and synthesis of anticonvulsant new chemical entities that are distinct from the cyclic ureides in current clinical use is a continuing neuropharmacologic priority. The design of neuronal specific dihydropyridines active at the L-type calcium channel protein represents a rational approach to this design problem. To provide the structural data required for the design of anticonvulsant dihydropyridines, an AM1 semi-empirical molecular orbital study has been undertaken. Forty-six dihydropyridine calcium channel antagonists have been fully optimized at the AM1 level. Each of the 46 analogues was considered in six conformations to provide a systematic evaluation of changes in ester and phenyl ring orientation. The calculational validity of the AM1 Hamiltonian when applied to dihydropyridines was demonstrated by comparing AM1-optimized structures to experimental (X-ray crystallographic) and abinitio molecular orbital (STO 3G basis set) geometries. For each dihydropyridine, 79 AM1-derived geometric and electronic descriptors were obtained. The resulting descriptor matrix comparing structural descriptors with biological activity was statistically reduced to provide regression and discriminant structure–activity models for dihydropyridine calcium channel antagonism.

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D’Archivio, Angelo A., and Andrea Giannitto. "Characterisation of Gas-Chromatographic Poly(Siloxane) Stationary Phases by Theoretical Molecular Descriptors and Prediction of McReynolds Constants." International Journal of Molecular Sciences 20, no. 9 (April 29, 2019): 2120. http://dx.doi.org/10.3390/ijms20092120.

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Retention in gas–liquid chromatography is mainly governed by the extent of intermolecular interactions between the solute and the stationary phase. While molecular descriptors of computational origin are commonly used to encode the effect of the solute structure in quantitative structure–retention relationship (QSRR) approaches, characterisation of stationary phases is historically based on empirical scales, the McReynolds system of phase constants being one of the most popular. In this work, poly(siloxane) stationary phases, which occupy a dominant position in modern gas–liquid chromatography, were characterised by theoretical molecular descriptors. With this aim, the first five McReynolds constants of 29 columns were modelled by multilinear regression (MLR) coupled with genetic algorithm (GA) variable selection applied to the molecular descriptors provided by software Dragon. The generalisation ability of the established GA-MLR models, evaluated by both external prediction and repeated calibration/evaluation splitting, was better than that reported in analogous studies regarding nonpolymeric (molecular) stationary phases. Principal component analysis on the significant molecular descriptors allowed to classify the poly(siloxanes) according to their chemical composition and partitioning properties. Development of QSRR-based models combining molecular descriptors of both solutes and stationary phases, which will be applied to transfer retention data among different columns, is in progress.

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Pekař, Miloslav. "Reaction-Diffusion Systems: Self-Balancing Diffusion and the Use of the Extent of Reaction as a Descriptor of Reaction Kinetics." International Journal of Molecular Sciences 23, no. 18 (September 10, 2022): 10511. http://dx.doi.org/10.3390/ijms231810511.

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Self-balancing diffusion is a theoretical concept that restricts the introduction of extents of reactions. This concept is analyzed in detail for general mass- and molar-based balances of reaction-diffusion mixtures, in relation to non-self-balancing cases, and with respect to its practical consequences. Self-balancing is a mathematical restriction on the divergences of diffusion fluxes. Fulfilling this condition enables the proper introduction of the extents of (independent) reactions that reduce the number of independent variables in thermodynamic descriptions. A note on a recent generalization of the concept of reaction and diffusion extents is also included. Even in the case of self-balancing diffusion, such extents do not directly replace reaction rates. Concentration changes caused by reactions (not by diffusion) are properly described by rates of independent reactions, which are instantaneous descriptors. If an overall descriptor is needed, the traditional extents of reactions can be used, bearing in mind that they include diffusion-caused changes. On the other hand, rates of independent reactions integrated with respect to time provide another overall, but reaction-only-related descriptor.

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Morales, Juan F., Lucas N. Alberca, Sara Chuguransky, Mauricio E. Di Ianni, Alan Talevi, and Maria E. Ruiz. "Molecular Topology and Other Promiscuity Determinants as Predictors of Therapeutic Class - A Theoretical Framework to Guide Drug Repositioning?" Current Topics in Medicinal Chemistry 18, no. 13 (October 4, 2018): 1110–22. http://dx.doi.org/10.2174/1568026618666180801091642.

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Much interest has been paid in the last decade on molecular predictors of promiscuity, including molecular weight, log P, molecular complexity, acidity constant and molecular topology, with correlations between promiscuity and those descriptors seemingly being context-dependent. It has been observed that certain therapeutic categories (e.g. mood disorders therapies) display a tendency to include multi-target agents (i.e. selective non-selectivity). Numerous QSAR models based on topological descriptors suggest that the topology of a given drug could be used to infer its therapeutic applications. Here, we have used descriptive statistics to explore the distribution of molecular topology descriptors and other promiscuity predictors across different therapeutic categories. Working with the publicly available ChEMBL database and 14 molecular descriptors, both hierarchical and non-hierchical clustering methods were applied to the descriptors mean values of the therapeutic categories after the refinement of the database (770 drugs grouped into 34 therapeutic categories). On the other hand, another publicly available database (repoDB) was used to retrieve cases of clinically-approved drug repositioning examples that could be classified into the therapeutic categories considered by the aforementioned clusters (111 cases), and the correspondence between the two studies was evaluated. Interestingly, a 3- cluster hierarchical clustering scheme based on only 14 molecular descriptors linked to promiscuity seem to explain up to 82.9% of approved cases of drug repurposing retrieved of repoDB. Therapeutic categories seem to display distinctive molecular patterns, which could be used as a basis for drug screening and drug design campaigns, and to unveil drug repurposing opportunities between particular therapeutic categories.

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Martín Pendás, A., and E. Francisco. "Real space bond orders are energetic descriptors." Physical Chemistry Chemical Physics 20, no. 23 (2018): 16231–37. http://dx.doi.org/10.1039/c8cp02485e.

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Ogunyemi, Babatunde Temitope, and Sunday Gbenga Borisade. "THEORETICAL MODELING OF IMINOISATIN DERIVATIVES AS CORROSION INHIBITORS OF STEEL IN ACID SOLUTION." FUDMA JOURNAL OF SCIENCES 4, no. 3 (September 30, 2020): 672–78. http://dx.doi.org/10.33003/fjs-2020-0403-372.

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The effect of two iminoisatin derivatives [1-morpholinomethyl-3(1-N-dithiooxamide) iminoisatin (molecule 1)] and 1-diphenylaminomethyl-3(1-N-dithiooxamide) iminoisatin (molecule 2) on corrosion inhibition were theoretically investigated using quantum mechanical method. Their electronic parameters and quantum chemical descriptors that predict their adsorption and hence their inhibition efficiency were estimated using the DFT//B3LYP/6-31G (d) method. The results established a relationship between the quantum descriptors and corrosion inhibition efficiency, and also confirmed molecule 2 to be a better corrosion inhibitor and provide a guide to the synthesis of more efficient organic corrosion inhibitors.

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Bologa, Cristian, Tharun Kumar Allu, Marius Olah, Michael A. Kappler, and Tudor I. Oprea. "Descriptor collision and confusion: Toward the design of descriptors to mask chemical structures." Journal of Computer-Aided Molecular Design 19, no. 9-10 (September 2005): 625–35. http://dx.doi.org/10.1007/s10822-005-9020-4.

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Rostami, Mohammad, David Isele, and Eric Eaton. "Using Task Descriptions in Lifelong Machine Learning for Improved Performance and Zero-Shot Transfer." Journal of Artificial Intelligence Research 67 (March 29, 2020): 673–704. http://dx.doi.org/10.1613/jair.1.11304.

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Knowledge transfer between tasks can improve the performance of learned models, but requires an accurate estimate of inter-task relationships to identify the relevant knowledge to transfer. These inter-task relationships are typically estimated based on training data for each task, which is inefficient in lifelong learning settings where the goal is to learn each consecutive task rapidly from as little data as possible. To reduce this burden, we develop a lifelong learning method based on coupled dictionary learning that utilizes high-level task descriptions to model inter-task relationships. We show that using task descriptors improves the performance of the learned task policies, providing both theoretical justification for the benefit and empirical demonstration of the improvement across a variety of learning problems. Given only the descriptor for a new task, the lifelong learner is also able to accurately predict a model for the new task through zero-shot learning using the coupled dictionary, eliminating the need to gather training data before addressing the task.

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Famini, George R., Benjamin C. Marquez, and Leland Y. Wilson. "Using theoretical descriptors in quantitative structure–activity relationships: gas phase acidity." J. Chem. Soc., Perkin Trans. 2, no. 4 (1993): 773–82. http://dx.doi.org/10.1039/p29930000773.

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Toulhoat, Hervé, and Pascal Raybaud. "Kinetic interpretation of catalytic activity patterns based on theoretical chemical descriptors." Journal of Catalysis 216, no. 1-2 (May 2003): 63–72. http://dx.doi.org/10.1016/s0021-9517(02)00118-5.

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Wilson, Leland Y., and George R. Famini. "Using theoretical descriptors in quantitative structure-activity relationships: some toxicological indices." Journal of Medicinal Chemistry 34, no. 5 (May 1991): 1668–74. http://dx.doi.org/10.1021/jm00109a021.

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T. Cronce, Donald, G. R. Famini, J. A. De Soto, and L. Y. Wilson. "Using theoretical descriptors in quantitative structure–property relationships: some distribution equilibria." Journal of the Chemical Society, Perkin Transactions 2, no. 6 (1998): 1293. http://dx.doi.org/10.1039/a802302f.

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Journal articles on the topic 'Theoretical descriptors'

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