Structure Correlation Method Research Articles

Structural health monitoring by probability density function of autoregressive-based damage features and fast distance correlation method

In this article, the autoregressive time series analysis is used to extract reliable features from vibration measurements of civil structures for damage diagnosis. To guarantee the adequacy and applicability of the time series model, Leybourne–McCabe hypothesis test is used. Subsequently, the probability density functions of the autoregressive model parameters and residuals are obtained with the aid of a kernel density estimator. The probability density function sets are considered as damage-sensitive features of the structure and fast distance correlation method is used to make decision for detecting damages in the structure. Experimental data of a well-known three-story laboratory frame and a large-scale bridge benchmark structure are used to verify the efficiency and accuracy of the proposed method. Results indicate the capability of the method to identify the location and severity of damages, even under the simulated operational and environmental variability.

Partial Discharges Identification and Localisation within Transformer Windings

This study proposes a technique that is based on the hypothesis that distinct PD sources have unique PD waveform characteristics at the point of measurement. Two different forms of PD pulses are injected into a model transformer winding at different points and by using wideband radio frequency current transformers (RFCTs), measurement data are obtained by positioning the RFCTs at the neutral-to-earth point of the winding and the bushing tap-point-to-earth. Mathematical morphology energy analysis using ordering points to identify clustering structure and signal cross correlation methods are utilized to extract information from the raw measurement data. Assessment of the relative performance of the analytical methods are examined and characterized in this study. The proposed approach allows automatic separation of PD data by source and localization of source site within the winding.

Structural correlation method for model reduction and practical estimation of patient specific parameters illustrated on heart rate regulation

We consider the inverse and patient specific problem of short term (seconds to minutes) heart rate regulation specified by a system of nonlinear ODEs and corresponding data. We show how a recent method termed the structural correlation method (SCM) can be used for model reduction and for obtaining a set of practically identifiable parameters. The structural correlation method includes two steps: sensitivity and correlation analysis. When combined with an optimization step, it is possible to estimate model parameters, enabling the model to fit dynamics observed in data. This method is illustrated in detail on a model predicting baroreflex regulation of heart rate and applied to analysis of data from a rat and healthy humans. Numerous mathematical models have been proposed for prediction of baroreflex regulation of heart rate, yet most of these have been designed to provide qualitative predictions of the phenomena though some recent models have been developed to fit observed data. In this study we show that the model put forward by Bugenhagen et al. [2] can be simplified without loss of its ability to predict measured data and to be interpreted physiologically. Moreover, we show that with minimal changes in nominal parameter values the simplified model can be adapted to predict observations from both rats and humans. The use of these methods make the model suitable for estimation of parameters from individuals, allowing it to be adopted for diagnostic procedures.

The use of the structural correlation method for the estimation of the quality of ab initio and DFT predictions of geometry parameters of related compounds in the gas phase and in solutions. An example of (O–Si)chelates with ClSiC 3O coordination center

X-ray data on the intramolecular complexes 1– 4 ( N-dimethylchlorosilylmethyl derivatives of amides, lactams, carbamides, and hydrazides of carbon acids) possessing an identical ClSiC 3O coordination center have been used for mapping the path of the S N2 substitution reaction at Si IV with the Bürgi–Dunitz method. A classic hyperbolic like representation of the reaction coordinate has been obtained using the nonlinear least squares method. The hypothesis of the unified character of the change in geometry parameters of the ClSiC 3O reaction center in 1– 4 under the influence of internal factors and the medium is corroborated based on the study of ab initio and DFT gas-phase and solution structures of a series 1– 4. The extent of deviation of calculated points from the correlation function, defined by the collective body of X-ray data for the coordination center of related compounds, may be used as an indicator of the accuracy of their geometry calculation in the isolated state and, especially, in solutions.

The crystal structure of “bis(trimethyltin)-1,3,4-thiadiazole-2,5-dithiolate” – different bonding of the two trimethyltin groups

Abstract [(CH3)3Sn]2S2(C2N2S) is monoclinic, space group P21 /c, a = 10.492(5), b = 12.257(6), c = 12.691(6) Å, β = 95.86(1)°. The zigzag chain structure of the coordination polymer can be derived by the structure correlation method. The starting point is a monomolecular symmetric bis(trimethyltin)-1,3,4-thiadiazole-2,5-dithiolate (Me3SnS)2 (C2N2S): The first of the Me3SnS moieties, bound to the atom C5 of the heterocyclus, remains tetrahedral, whereas the other, bound to C2, is transformed through the N3 atom of the neighbouring ring to a trigonal bipyramid S···(Me3Sn)···N. The three C atoms and the Sn atom of this Me3Sn group are nearly coplanar and form the equatorial plane. With the N3 atom of the starting molecule, an equivalent linking to the other neighbour takes place. The resultant plane ribbons run parallel to the crystallographic b-axis. The analysis of the bond distances and angles reveals that the regular trigonal bipyramid almost exactly represents the transition state along a chemical reaction pathway for a nucleophilic SN2 displacement at tetrahedrally coordinated tin.

New light on the mechanism of the solid state [2 + 2] cycloaddition of alkenes: a database analysis

The mechanism of the solid state [2 + 2] cycloaddition of alkenes has been investigated using the structure correlation method based on geometrical data calculated from single crystal X-ray diffraction studies retrieved from the Cambridge Structural Database (CSD). Searches were carried out for non-bonded alkene⋯alkene reactant interactions, within a limiting C⋯C separation of the sum of van der Waals radii plus 20%, and for bonded cyclobutane product fragments. The results were visualised and interpreted using principal component analysis and symmetry deformation coordinates. The reaction pathway for [2 + 2] cycloaddition was established and it was shown that (a) the alkene moieties are not required to be parallel for the reaction to occur and (b) a large twist angle of the reacting alkene fragments is permissible to form a puckered cyclobutane reaction product, as long as similar intra-annular valence angles are maintained around the four-membered ring.

Aromaticity of benzene in the facial coordination mode: a structural and theoretical study.

The effects of facial coordination of benzene to a trinuclear transition-metal cluster have been studied by structure correlation and DFT calculational methods. Data taken from the X-ray crystal structures of twelve complexes [(eta-C(5)H(4)R")Co(3)(micro(3)-eta(2):eta(2):eta(2)-C(6)H(4)RR')] 1 b-1 m were analyzed by using standard statistical methods. The prototypal facial arene ligand is considerably expanded with respect to free benzene and shows a small but highly significant Kekulè distortion (d(CC)=1.42, 1.45 A). DFT MO calculations were carried out on the model complexes [(eta-C(5)H(5))M(3)(micro-eta(2):eta(2):eta(2)-C(6)H(6))] 1 a (M=Co), 2 (M=Rh), and 3 (M=Ir). Ring currents in the facial benzene and apical cyclopentadienyl ligands have been assessed by nucleus independent chemical shift (NICS) calculations. Compared to the free ligand (with the optimized D(6h) structure as well as with D(3h) and a C(3v) geometries similar to that in the prototypal facial arene), facial benzene exhibits somewhat reduced but still substantial cyclic electron delocalization (CED). The calculated order of CED is benzene approximately [(CO)(3)Cr(eta-C(6)H(6))] 4 > 1 > 2 > 3.

Reaction Pathways by Structure Correlation Methods: SN1 Addition of Nucleophilic Ligands to Penta-coordinated V(IV) Oxo-Complexes

Reaction Pathways by Structure Correlation Methods: S_N1 Addition of Nucleophilic Ligands to Penta-coordinated V(IV) Oxo-Complexes

Conformations and Threshold Rotational Mechanisms of the (Z)-1,2-Diarylethene Moiety: A Structural Correlation Study.

The crystal structures of substituted (Z)-1,2-diarylethenes and (Z)-1,2-diarylcyclopropenes, -cyclobutenes, -cyclopentenes, and -cyclohexenes that were reported in the literature were retrieved from the Cambridge Structural Database, and the dihedral angles of the aryl rings with the double bond were plotted in a conformational map. Analysis of the data by the Structural Correlation method together with molecular mechanics calculations suggest that the conformation and the threshold rotational mechanism of the (Z)-1,2-diarylvinyl fragment strongly depend on its steric environment. In 1,2-diarylcyclopropenes the aryl rings are nearly coplanar with the double bond, whereas in 1,2-diarylcycloalkenes with larger rings a propeller conformation is adopted. The threshold rotational mechanism is the one-ring flip for (Z)-1,2-diphenylethene and 1,2-diphenylcyclobutene, and is the two-ring flip for 1,2-diarylcyclopentene and 1,2-diarylcyclohexene. The calculated rotational barriers of the aryl rings in the threshold mechanism for all systems were very low (0.2-2.4 kcal mol(-)(1)). The different conformations and rotational behaviors are dictated by an interplay of conjugation and steric effects.

Mapping of reaction pathways by structure correlation methods. A study of the ligand dissociation reaction in quasi-octahedral Re(V) and Tc(V) oxo-complexes.

Intercorrelations among geometrical parameters of a molecular fragment as found in different crystal structures are called structure correlations. Such correlations are believed to represent possible reaction pathways mapping the course of chemical reactions. Pyramidal Oâ–·ML4 oxo-complexes [MRe(V) and Tc(V)] react easily with oxygenated ligands of different basicities (H2O, RO-, ArO-, RCOO-etc.) to give quasi-octahedral Oâ–·ML4OR addition compounds which are often observed in the crystalline state and a relatively large number of structural and spectroscopic data on such complexes are available. Coordination changes from square-pyramidal to quasi-octahedral caused by the approach of the sixth ligand are found to induce systematic variations in the polyhedron geometry which are found to correlate with IR ν(Mâ–·O) stretching frequencies and pKa values of the entering ligands. According to structure correlation methods, each fragment geometry was assumed to represent a point along a single reaction pathway of the dissociation reaction Oâ–·ML4–OR→Oâ–·ML4+OR of the complex associating rather similar Oâ–·ML4 acceptors with a series of OR ligands having quite different donor properties. Assuming that the ligand pKa (or related ΔG°) values can be considered as a measure of the relative thermodynamic stabilities of the complexes, a mathematical model of the reaction pathway is proposed which, on the grounds of the Marcus rate-equilibrium theory, relates activation free energies, thermodynamic stabilities, and geometrical distances from the reaction transition state. The reliability of the model is tested, aposteriori, against experimental values of energies, bond distances and quadratic vibrational force constants.

The Deformation of Di-μμ-halide Dinuclear Five-Coordinate Copper(II) Complexes in the Crystalline State

The coordination geometries of 154 dinuclear di-\mu-chloro, di-\mu-bromo and di-\mu-fluoro five-coordinate (4 + 1) copper(II) complexes have been analyzed by the structural correlation method. Two reference CuII polyhedra have been established: (i) a trigonal bipyramid (TBP) in which the equatorial bond lengths are equal, but with the symmetry at the metal often deformed from D 3h to C 2, and (ii) an elongated square pyramid (SQP), with either a pyramidally or tetrahedrally distorted base, in which the trans valence angles are equal. Six different paths for the SQP⇌TBP deformation of the CuII coordination have been established from three criteria: (a) the location of the bridging ligands (axial and equatorial or equatorial and equatorial in TBP); (b) the nature of the deformation of the SQP base plane (pyramidal or tetrahedral); (c) whether a bridging or nonbridging bond is elongated in a SQP. The causes of the angular distortions from C 2 symmetry along the apical bond of a SQP, typical for the TBP⇌SQP Berry path, are analyzed. A progressive reduction of the tetragonal elongation of the Cu—D apical (SQP) bond length along the SQP⇌TBP transformation path and trigonal equalization of the three equatorial Cu—D (TBP) bonds are observed. The dependence of the average Cu—Cu′ distance and Cu—X—Cu′ angles on the deformation path are also established.

Analysis of Stereochemical Nonrigidity in Five-Coordinate Cyclopentadienylmetal Complexes by the Structure Correlation Method

The intramolecular cis/trans isomerization mechanism of solid-state pseudo-five-coordinate complexes of the type CpML4 was examined by the structure correlation technique, and the data revealed that the mechanism most likely proceeds via a combined Berry−turnstile mechanism.

Structure Correlation Methods in Chemical Crystallography

Abstract The structural information collected by X-ray (or neutron) diffraction studies of metallic, ionic, molecular and macromolecular crystals has increased beyond any previously imagined limit. Data are presently compiled in computer-based crystal structure databases. Making particular reference to molecular crystals, it is shown that the information collected may possess a great heuristic value, that is a great potential for guiding the discovery of new chemical facts or the formulation of new chemical theories, provided systematic methods of database analysis and crystal structure interpretation are made available. It is suggested that such methods consist of systematic correlations of structural data pertaining to single molecular fragments as found in many different crystal structures and can be collectively called (crystal) structure correlation methods (SCMs). SCMs are based on the search for and recognition of correlations among the geometrical descriptors of the fragment (structural correlatio...

ChemInform Abstract: Determination of Reaction Pathways for Pentacoordinated Metal Complexes with the Structure Correlation Method

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Determination of Reaction Paths for Pentacoordinate Metal Complexes with the Structure Correlation Method

AbstractCrystal structures potentially deliver far more information than is present in the average structural communication—if sufficient structural data on closely related molecules or molecular fragments are available, it may be possible to infer details of geometric changes occurring along certain reaction pathways for the species of interest. This geometric information is extrapolated from an analysis of the similarities between the structures of the fragment in the various crystalline environments, by a method that is now known as structure correlation analysis. Since it was first proposed twenty years ago, the method has been applied to a large variety of chemical systems, but none have received as much attention as the class of five‐coordinate compounds. Comparative analyses of the structures of pentacoordinate complexes have yielded information about the intimate mechanisms of substitution and addition/elimination reactions at tetrahedral and square‐planar complexes, and about intramolecular isomerizations of five‐coordinate compounds. Since its inception, the structure correlation method has gradually adapted techniques from other branches of science, in particular group‐theoretical and multivariate statistical techniques, which have been shown to be enormously powerful tools for probing geometrically complex systems. This review traces the development of the method of structure correlation and the evolution of these co‐opted techniques, with a specific emphasis on studies of five‐coordinate metal complexes.

Evidence for resonance-assisted hydrogen bonding. 4. Covalent nature of the strong homonuclear hydrogen bond. Study of the O-H--O system by crystal structure correlation methods

All cases of strong (2.50≤d(O--O)≤2.65 A) and very strong (d(O--O) <2.50 A) O-H---O hydrogen bonds whose geometries are known from accurate neutron or X-ray diffraction studies are reviewed and classified in chemical classes belonging to three fundamental types: (A) -O-H---O-, or negative charge assisted hydrogen bonding, (-)CAHB; (B)=O---H + --O=, or positive charge assisted hydrogen bonding, (+)CAHB; and (C) -O-H---O=, where the two oxygens are interconnected by a system of π-conjugated double bonds, or resonance-assisted hydrogen bonding, RAHB

ChemInform Abstract: Application of the Structural Correlation Method to Ring‐Flip Processes in Benzophenones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Application of the structural correlation method to ring-flip processes in benzophenones

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTApplication of the structural correlation method to ring-flip processes in benzophenonesZvi Rappoport, Silvio E. Biali, and Menahem KaftoryCite this: J. Am. Chem. Soc. 1990, 112, 21, 7742–7748Publication Date (Print):October 1, 1990Publication History Published online1 May 2002Published inissue 1 October 1990https://doi.org/10.1021/ja00177a039RIGHTS & PERMISSIONSArticle Views133Altmetric-Citations37LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (823 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Coordinative interactions in chelated complexes of silicon: XIV. Regular or irregular exchange mechanisms in pentacoordinate silicon compounds: an interpretation based on crystal structures, DNMR-data and molecular modelling

A crystal structure determination on 1-(2-(difluoromethylsilyl))- N, N-dimethylmethanamine (Ib) has revealed a strongly distorted trigonal bipyramidal coordination with N and F at apical positions. A coordinative interaction of 2,346(3) Å is present. Dynamic NMR-data for this complex and related pentacoordinated compounds indicate positional exchange of substituents at silicon with an energy barrier of 7–19 kcal/mol. For the exchange mechanism, regular (pseudorotation, turnstile rotation) and irregular processes, with bond rupture/bond reformation, are discussed. A computer simulation (MNDO-calculations) of the exchange process in 2-((methyl(trifluorosilyl)amino)methyl)pyridine (IIIa), which shows trigonal bipyramidal structure in the crystal and fluxional properties in solution, indicates that any distinction between the mechanisms is unreasonable and can be reduced to the question of which limiting Si-N distance can be regarded as still corresponding to a chemical bond. There is good agreement between the calculated and observed energy barriers. The structure correlation method is used to compare the calculated molecular transformation route with the Berry pseudorotation pathway.

On the validity of structure correlation method (SCM)

On the validity of structure correlation method (SCM)