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1

(Relationships between microscope structure and thermodynamic properties)  

Energy Technology Data Exchange (ETDEWEB)

This paper exhibits on the molecular level, the relationships between the microscopic structure and thermodynamic properties of dilute supercritical solutions by application of the integral equation theories for molecular distribution functions. To solve the integral equations, the authors use Baxter's Wiener-Hopf factorization of the Ornstein-Zernike equations and then apply this method to binary Lennard-Jones mixtures. A number of closure relations have been used: such as the Percus-Yevick (PY), the reference hypernetted chain (RHNC), the hybrid mean spherical approximation (HMSA), and the reference interaction-site (RISM) methods. The authors examine the microstructures of several important classes of supercritical mixtures, including the usual attractive-type and the less known repulsive-type solutions. The clustering of solvent molecules for solvent-solute structures in the attractive mixtures and, correspondingly, the solvent cavitation in the repulsive mixtures are clearly demonstrated. These are shown to be responsible for the large negative growth of the solute partial molar volumes in the attractive case and the positive growth in the repulsive case.

Wu, R.S.; Lee, L.L. (School of Chemical Engineering and Materials Science, Univ. of Oklahoma, Norman, OK (US)); Cochran, D. (Chemical Technology Div., Oak Ridge National Lab., Oak Ridge, TN (US))

1990-06-01

2

Structure property relationships in various filled polymers  

Science.gov (United States)

The toughness of impact modified poly(vinyl chloride) (PVC) compounds was examined using a modified Charpy test. Increasing impact speed resulted in a quasi-brittle to ductile transition in all PVC compounds. In the quasi-brittle region, a PVC of 56,000 Mw fractured through a craze-like damage zone that could be described by a modified Dugdale model. Furthermore, the same molecular weight PVC modified with either 10 pph chlorinated polyethylene (CPE) or 10 pph methylmethacrylate-butadiene-styrene (MBS) impact modifier also conformed to the Dugdale model with the craze-like damage zone. It was found that CPE effectively improved the impact performance of PVC by shifting the quasi-brittle to ductile transition to a higher loading rate. Compared to CPE, MBS was found to be a better impact modifier and resulted in a higher quasi-brittle to ductile transition loading rate in the same PVC matrix. Fracture initiation toughness of all the materials was described by the Hayes-Williams modification of the Dugdale model. The intrinsic brittle fracture energy obtained by extrapolation to zero craze length was determined only by the PVC matrix and was independent of the impact modifier. However, the kinetics of craze growth, and hence the response to rapid loading, depended on the impact modifier. Increasing molecular weight of the PVC resin resulted in a more complex damage zone that was not amendable to the Dugdale analysis. A new in-situ infusion method was used to incorporate small amounts (ca. 1wt%) of metal and metal oxide particles into a polymer matrix. Nano-sized particles were observed by both transmission electron microscopy (TEM) and atomic force microscopy (AFM). Oxygen (O2) and carbon dioxide (CO2) transport properties of the infused materials were investigated using a dynamic diffusion approach in which both testing and purge gases can be controlled. It was discovered that trace amounts (ca. 2%) of hydrogen (H2) in the purge gas was sufficient to considerably reduce the O2 flux of FEP films infused with Palladium (Pd) nano-particles, up to two hundred fold decrease. In contrast, H2 has essentially no effect on the transport of CO2. The generality of the remarkable reduction in oxygen flux was also demonstrated with films of PP, LLDPE, PET, Nylon 6,6 infused with Pd nano-particles. This oxygen scavenging effect became more pronounced at lower oxygen concentrations. The catalytic role of Pd in the reaction of O2 and H2, and the enormous surface area provided by the dispersed nano-particles were responsible for this highly efficient oxygen scavenging effect. (Abstract shortened by UMI.)

Yu, Jiong

3

Quantitative structure-retention (property) relationships in micellar electrokinetic chromatography.  

Science.gov (United States)

Quantitative structure-retention relationships (QSRRs) attempt to quantitatively understand the relationship between structure and retention and quantitative structure-property relationships (QSPRs) to explore the prediction of molecular properties from retention in chromatography. The application of these techniques to micellar electrokinetic chromatography (MEKC) and microemulsion electrokinetic chromatography (MEEKC) using surfactants, vesicles and liposomes is reviewed. A database of system constants for the solvation parameter model is assembled and critically discussed with respect to the interpretation of solvation properties of micellar pseudophases and their use to identify correlation models for the estimation of physicochemical and environmental properties from retention in MEKC and MEEKC. The use of structure-generated descriptors to model retention in MEKC is discussed and compared with experimental-based techniques. It is shown that the possibilities of exploiting the collection of tools that underpin QSRRs and QSPRs studies are only just starting to be realized in MEKC and more work is needed to convert from these possibilities to the realization of reliable and robust models for compounds of diverse structure. PMID:18207156

Poole, Salwa K; Poole, Colin F

2008-02-22

4

Composition-Structure-Property Relationships in Boroaluminosilicate Glasses  

DEFF Research Database (Denmark)

The complicated structural speciation in boroaluminosilicate glasses leads to a mixed network former effect yielding nonlinear variation in many macroscopic properties as a function of chemical composition. Here we study the compositionâ??structureâ??property relationships in a series of sodium boroaluminosilicate glasses from peralkaline to peraluminous compositions by substituting Al2O3 for SiO2. Our results reveal a pronounced change in all the measured physical properties (density, elastic moduli, hardness, glass transition temperature, and liquid fragility) around [Al2O3]â??[Na2O]=0. The structural origin of this change is elucidated through nuclear magnetic resonance analyses and topological considerations. Furthermore, we find that addition of 1 mol% Fe2O3 exerts a complicated impact on the measured properties.

Zheng, Qiuju; Potuzak, M.

2012-01-01

5

Water Activated Carbon Organics Adsorption Structure - Property Relationships  

Directory of Open Access Journals (Sweden)

Full Text Available Investigation (determination of chemical compounds properties need time and many resources when is performed by classical way, or experimentations. Nowadays a number of quantitative structure-property relationships (QSPRs were developed in order to shorting the research and analysis time of chemical properties on classes of compounds. The ability of the molecular descriptor family (MDF was used to produce QSPRs for estimating the adsorption onto activated carbon in water. A number of sixteen organics and theirs adsorption onto activated carbon in water serves for QSPRs obtaining. The MDF methodology include the three-dimensional model of the molecules building using the HyperChem software, MDF members generating using a set of Pre Hypertext Processor (PHP programs, storing using a MySQL database server, and finally with a set of Delphi Multiple Linear Regression programs structure-property relationships findings. A number of 105319 MDF members enter into multiple linear regressions findings. Five from our best QSPRs are presented, one mono-varied, two bi-varied and two tri-varied models. The MDF QSPR methodology has big potential in finding QSPR models and is proved for adsorption onto activated carbon in water of studied organics.

Lorentz JÄNTSCHI

2004-08-01

6

Structure/property relationships in multipass GMA welding of beryllium.  

Energy Technology Data Exchange (ETDEWEB)

Beryllium is an interesting metal that has a strength to weight ratio six times that of steel. Because of its unique mechanical properties, beryllium is used in aerospace applications such as satellites. In addition, beryllium is also used in x-ray windows because it is nearly transparent to x-rays. Joining of beryllium has been studied for decades (Ref.l). Typically joining processes include braze-welding (either with gas tungsten arc or gas metal arc), soldering, brazing, and electron beam welding. Cracking which resulted from electron beam welding was recently studied to provide structure/property relationships in autogenous welds (Ref. 2). Braze-welding utilizes a welding arc to melt filler, and only a small amount of base metal is melted and incorporated into the weld pool. Very little has been done to characterize the braze-weld in terms of the structure/property relationships, especially with reference to multipass welding. Thus, this investigation was undertaken to evaluate the effects of multiple passes on microstructure, weld metal composition, and resulting material properties for beryllium welded with aluminum-silicon filler metal.

Hochanadel, P. W. (Patrick W.); Hults, W. L. (William L.); Thoma, D. J. (Dan J.); Dave, V. R. (Vivek R.); Kelly, A. M. (Anna Marie); Pappin, P. A. (Pallas A.); Cola, M. J. (Mark J.); Burgardt, P. (Paul)

2001-01-01

7

Oxide Thermoelectric Materials: A Structure-Property Relationship  

Science.gov (United States)

Recent demand for thermoelectric materials for power harvesting from automobile and industrial waste heat requires oxide materials because of their potential advantages over intermetallic alloys in terms of chemical and thermal stability at high temperatures. Achievement of thermoelectric figure of merit equivalent to unity ( ZT ? 1) for transition-metal oxides necessitates a second look at the fundamental theory on the basis of the structure-property relationship giving rise to electron correlation accompanied by spin fluctuation. Promising transition-metal oxides based on wide-bandgap semiconductors, perovskite and layered oxides have been studied as potential candidate n- and p-type materials. This paper reviews the correlation between the crystal structure and thermoelectric properties of transition-metal oxides. The crystal-site-dependent electronic configuration and spin degeneracy to control the thermopower and electron-phonon interaction leading to polaron hopping to control electrical conductivity is discussed. Crystal structure tailoring leading to phonon scattering at interfaces and nanograin domains to achieve low thermal conductivity is also highlighted.

Nag, Abanti; Shubha, V.

2014-04-01

8

Relationships between structure and mechanical properties of Inconel 718  

Energy Technology Data Exchange (ETDEWEB)

Ageing of Inconel 718 is studied. Life and tensile properties after ageing are practically independent of the quench structure. Simple ageing provides the material with a range of high properties and often makes a second ageing treatment unnecessary for the parts prior to working close to room temperature.

Loier, C.; Ottmann, M.C.; Leymonie, C. (Centre d' Essais et de Recherches sur les Materiaux, Alsthom-Atlantique, Belfort (France))

1982-12-01

9

Relationships between structure and mechanical properties of Inconel 718  

International Nuclear Information System (INIS)

Ageing of Inconel 718 is studied. Life and tensile properties after ageing are practically independent of the quench structure. Simple ageing provides the material with a range of high properties and often makes a second ageing treatment unnecessary for the parts prior to working close to room temperature

1982-01-01

10

Investigation of ion-conducting ormolytes : structure-property relationships  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Hybrid organic-inorganic composites with ionic properties, so called ormolytes (organically modified electrolytes) have been prepared by the sol-gel process from mixtures of tetraethoxysilane, tetraethylene glycol, and lithium salt. They show ionic conductivity up to 5 x 10-5 ?-1 cm-1, with activation energies around 0.6 eV. Their properties have been related to their structure using a multitechnique approach (IR, DSC, NMR, SAXS). These materials can be described as diphasic systems wit...

Judeinstein, Patrick; Schmidt, Helmut K.; Titman, J.; Stamm, M.

1994-01-01

11

Relationship between structure and properties of Dialkylphenolsulfonate additives  

Energy Technology Data Exchange (ETDEWEB)

This article describes an investigation of the structure and properties-detergent-dispersant, antioxidant, anticorrosion, antiwear, -- of Dialkyphenol-sulfonate additives. The 2,4-dialkylphenols used for this investigation were obtained by alkylation of p-cresol, p-tert-butylphenol, and p-tert-nonylphenol with olefins in the presence of benzenesulfonic acid. The formation of a micellar structure by the sulfonates in oil solutions was judged from the changes in the solution viscosity, electrical conductivity, and electrode potential.

Tankaeva, N.U.; Belov, P.S.; Korenev, K.D.; Likhterov, S.D.; Shor, G.I.; Trofimova, G.L.

1985-07-01

12

Structure-property Relationships for Methyl-terminated Alkyl Self-assembled Monolayers  

Energy Technology Data Exchange (ETDEWEB)

Structure-property relationships for methyl-terminated alkyl self-assembled monolayers (SAMs) are developed using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and atomic force microscopy (AFM). NEXAFS C K-edge spectra are used to compute the dichroic ratio, which provides a quantitative measure of the molecular structure. AFM data are analyzed with an elastic adhesive contact model, modified by a first-order elastic perturbation method to include substrate effects, to extract the monolayer mechanical properties. Using this approach, the measured mechanical properties are not influenced by the substrate, which allows universal structure-property relationships to be developed for methyl-terminated alkyl SAMs.

F DelRio; D Rampulla; C Jaye; G Stan; R Gates; D Fischer; R Cook

2011-12-31

13

Structure-property relationships and biocompatibility of carbohydrate crosslinked polyurethanes.  

Science.gov (United States)

Biocompatible and biodegradable polyurethanes (PUs) based on castor oil and polypropylene glycols (PPGs) were prepared using various carbohydrate crosslinkers: monosaccharide (glucose), disaccharide (sucrose) and polysaccharides (starch and cellulose). The mechanical and thermal properties were investigated and interpreted on the basis of SEM study. The advantage of incorporating various carbohydrates is to have tunable mechanical properties and biodegradability due to variety in their structure. The glass transition temperature and sorption behavior were dominated by the type of polyol than by the type of crosslinker. All the PUs were observed to be biodegradable as well as non-cytotoxic as revealed by MTT assay in normal lung cell line L132. The study supports the suitability of carbohydrates as important components of biocompatible PUs for development of biomedical devices. PMID:24906764

Solanki, Archana; Mehta, Jayen; Thakore, Sonal

2014-09-22

14

Quantitative Structure–Property Relationships for Aryldiazonia  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract: By the fact of finding 43 relationships, we have shown that the reduction potentials, dimerization potentials and potentials in half-equivalent point on titration of aryldiazonium cations XC6H4N+≡N (chemical reduction with K4[Fe(CN6] and TiCl3 in water, (C2H53N, (í-C4H94N+−OH, CH3OK and C10H8•−Na+ in acetone; polarographic reduction in nitromethane, sulfolane, and N,N-dimethylformamide are related linearly to the quantum chemically evaluated electron affinities (A and to the stabilization energies of radicals formed on diazonium cations reduction. Sixty six linear correlations of frequencies (ν characterizing a collection of bonds stretching vibrations of the C-N+≡N fragment in the XC6H4N+≡NY− salts with different anions in vaseline oil, N,N-dimethylformamide, acetone, ethylacetate, methanol, water, with the bonds orders of N≡N and C-N, with the charges on carbon atoms in para positions of the C6H5X molecules aromatic rings, with the mesomeric dipole moments (μm of X substituents have been found. Twelve quantitative relationships combining the μm and ν quantities with the A values have been established. The interrelations obtained have an explicitly expressed physical meaning, are featured by rather high correlation coefficients and have a predictive power in respect to redox properties, electron affinities, vibrational frequencies of aryldiazonia, as well as to mesomeric dipole moments of atomic groups in organic molecules.

Oxana I. Zhelezko

2002-07-01

15

Nano-Composites: Relationships Between Nano-Structure and Mechanical Properties: Phase II.  

Science.gov (United States)

This work aims to understand and model the structure/property relationships of polymer nanocomposites, based upon thermosetting epoxy polymers that are widely used as adhesives and matrices for fibre-reinforced composites. The work concentrates on investi...

A. C. Taylor A. J. Kinloch

2006-01-01

16

Structure-Property Relationships in Oxides Containing Tellurium  

Science.gov (United States)

Oxides of post-transition metals often show unique structures and properties due to the presence of lone pair electrons and the diffused s orbitals. The present work focuses on synthesis and characterizations of oxides containing Te, a heavy post transition metal. New series of pyrochlore oxides of the formula Cs(M,Te)2O 6 (M = Al, Ga, Cr, Fe, Co, In, Ho, Lu, Yb, Er, Ge, Rh, Ti, Zn, Ni, and Mg) have been prepared. The samples were highly colored (ranging from black to dark green) indicating a possible mixed valency for Te with appreciable charge transfer between them in the octahedral sites. Electronic conductivity was observed in some phases and could be as high as 2S/cm (M=Ge). Seebeck coefficients of conducting samples show negative values which suggest that electrons are the major charge carriers. Temperature dependence of conductivity indicates that the samples are semiconductors with, in some cases, degenerate semiconducting behavior. Detailed studies on the conduction mechanism indicate the mixed valency of tellurium which leads to semiconducting behavior and the color of the compounds. Systematic studies of cesium tellurate with CsTe2O6-x where x = 0, 0.15, 0.25, 1.5 have been investigated. On heating at slightly above 600ºC, CsTe2O6 loses oxygen resulting in cubic structure with disordered Te4+/Te6+ and oxygen vacancies. Two novel phases of CsTe2O6-x were prepared with orthorhombic structure. The first phase with x value of about 0.2-0.3 crystallizes in Pnma symmetry. At higher values of x, a new compound was discovered with a structure related to Rb4Te 8O23. Optical properties of the compounds are consistent with their colors. CsTe2O6 belongs to class II mixed valency according to Robin and Day classification. However, structures and properties of CsTe 2O6-x phases indicate that they are class I mixed valence compounds. Series of compounds with formula CsTe2-xWxO 6 with x=0.2-0.5 have been made which can be considered as solid solution of CsTe2O6 and CsTe0.5W1.5O 6. Although the two end members adopt rhombohedral and trigonal structure, these solid solution phases crystallize in cubic defect pyrochlore structure with W6+, Te6+, and Te4+ randomly occupying 16c octahedral site. The compounds show no electronic conductivity at room temperature. Novel cubic pyrochlore with the formula (CdBi)(MTe)O7, M= Al, Cr, Ga, In, Fe, Mn, and Sc were synthesized by solid state reaction using oxides of the constituent elements. Magnetic properties analyses show paramagnetism in M=Cr and Mn but antiferromagnetism with short-range correlation in M= Fe phase. All compositions are insulating. Dielectric measurements show relatively low dielectric constants which are independent of temperature and frequency. Metallic Tl2TeO6 and insulating In2TeO 6 are both known to crystallize in the Na2SiF6-type structure. We have now prepared a complete Tl2-xInxTeO6 series in a search for a compositionally controlled metal-insulator transition that might be expected if a complete solid solution can be obtained. Unit cell edges and volume vary monotonically with no indication of miscibility gap. The metal-insulator transition occurs at an x value of about 1.4, which can be rationalized on a percolation model. No superconductivity could be detected down to 5K. Rh2MO6, M = Mo, W, and Te were synthesized by solid state reaction. Electronic properties as well as thermoelectric properties were investigated and discussed. The compounds crystallize in rutile-related structure and all show relatively high electronic conductivities with Rh 2TeO6 showing the highest electronic conductivity (˜500 S/cm at room temperature) despite localized electrons in Rh3+ and Te6+. Measurable magnetic moments also indicate valence degeneracy between Rh and the M cation. The measured Seebeck coefficients are relatively low and positive indicating hole-type conduction.

Siritanon, Theeranun

17

Prediction of Environmental Properties for Chlorophenols with Posetic Quantitative Super-Structure/Property Relationships (QSSPR  

Directory of Open Access Journals (Sweden)

Full Text Available Due to their widespread use in bactericides, insecticides, herbicides, andfungicides, chlorophenols represent an important source of soil contaminants. Theenvironmental fate of these chemicals depends on their physico-chemical properties. In theabsence of experimental values for these physico-chemical properties, one can use predictedvalues computed with quantitative structure-property relationships (QSPR. As analternative to correlations to molecular structure we have studied the super-structure of areaction network, thereby developing three new QSSPR models (poset-average, cluster-expansion, and splinoid poset that can be applied to chemical compounds which can behierarchically ordered into a reaction network. In the present work we illustrate these posetQSSPR models for the correlation of the octanol/water partition coefficient (log Kow and thesoil sorption coefficient (log KOC of chlorophenols. Excellent results are obtained for allQSSPR poset models to yield: log Kow, r = 0.991, s = 0.107, with the cluster-expansionQSSPR; and log KOC, r = 0.938, s = 0.259, with the spline QSSPR. Thus, the poset QSSPRmodels predict environmentally important properties of chlorophenols.

Douglas J. Kleinc

2006-09-01

18

Structure-property relationships of flexible polyurethane foams  

Science.gov (United States)

This study examined several features of flexible polyurethane foams from a structure-property perspective. A major part of this dissertation addresses the issue of connectivity of the urea phase and its influence on mechanical and viscoelastic properties of flexible polyurethane foams and their plaque counterparts. Lithium salts (LiCl and LiBr) were used as additives to systematically alter the phase separation behavior, and hence the connectivity of the urea phase at different scale lengths. Macro connectivity, or the association of the large scale urea rich aggregates typically observed in flexible polyurethane foams was assessed using SAXS, TEM, and AFM. These techniques showed that including a lithium salt in the foam formulation suppressed the formation of the urea aggregates and thus led to a loss in the macro level connectivity of the urea phase. WAXS and FTIR were used to demonstrate that addition of LiCl or LiBr systematically disrupted the local ordering of the hard segments within the microdomains, i.e., it led to a reduction of micro level connectivity or the regularity in segmental packing of the urea phase. Based on these observations, the interaction of the lithium salt was thought to predominantly occur with the urea hard segments, and this hypothesis was confirmed using quantum mechanical calculations. Another feature of this research investigated model trisegmented polyurethanes based on monofunctional polyols, or "monos", with water-extended toluene diisocyanate (TDI) based hard segments. The formulations of the monol materials were maintained similar to those of flexible polyurethane foams with the exceptions that the conventional polyol was substituted by an oligomeric monofunctional polyether of ca. 1000 g/mol molecular weight. Plaques formed from these model systems were shown to be solid materials even at their relatively low molecular weights of 3000 g/mol and less, AFM phase images, for the first time, revealed the ability of the hard segments to self-assemble and form lath-like percolated structures, resulting in solid plaques, even though the overall volume of the system was known to be dominated by the two terminal liquid-like polyether segments. In another aspect of this research, foams were investigated in which the ratios of the 2,4 and 2,6 TDI isomers were varied. The three commercially available TDI mixtures, i.e., 65:35 2,4/2,6 TDI, 80:20 2,4/2,6 TDI, and 100:0 2,4/2,6 TDI were used. These foams were shown to display marked differences in their cellular structure (SEM), urea aggregation behavior (TEM), and in the hydrogen bonding characteristics of the hard segments (FTIR). Finally, the nanoscale morphology of a series of 'model' segmented polyurethane elastomers, based on 1,4-butanediol extended piperazine based hard segments and poly(tetramethylene oxide) soft segments, was also investigated using AFM. The monodisperse hard segments of these 'model' polyurethanes contained precisely either one, two, three, or four repeating units. Not only did AFM image the microphase separated morphology of these polyurethanes, but it also revealed that the hard domains preferentially oriented with their long axis along the radial direction of the spherulites which they formed.

Aneja, Ashish

19

An investigation of structure-property relationships in several categories of proton exchange membranes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The chemical and structural features of proton exchange membranes (PEMs) are related to their fuel cell relevant properties. The objective of this work is to understand structure-property relationships in PEMs through the fabrication and characterization of several classes of membranes. Incorporation of linear and angled monomers into the main chain of a polyimide permitted investigation of the effect of kinked versus linear polymers on membrane properties. The conductivity of angled sulfonat...

Rodgers, Marianne Phelan

2007-01-01

20

Quantitative Structure–Property Relationships for Aryldiazonia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract: By the fact of finding 43 relationships, we have shown that the reduction potentials, dimerization potentials and potentials in half-equivalent point on titration of aryldiazonium cations XC6H4N+≡N (chemical reduction with K4[Fe(CN)6] and TiCl3 in water, (C2H5)3N, (í-C4H9)4N+−OH, CH3OK and C10H8•−Na+ in acetone; polarographic reduction in nitromethane, sulfolane, and N,N-dimethylformamide) are related linearly to the quantum che...

Pankratov, Alexei N.; Zhelezko, Oxana I.

2002-01-01

 
 
 
 
21

Processing-structure-properties relationships in PLA nanocomposite films  

Science.gov (United States)

This work deals on the possibility to improve performances of PLA-based nanocomposite films, for packaging applications, through conveniently tuning materials and processing conditions in melt compounding technology. In particular, two types of polylactic acid and different types of filler selected from montmorillonites and bentonites families were used to prepare the hybrid systems by using a twin-screw extruder. The effect of biaxial drawing on morphology and properties of the nanocomposites, produced by film blowing, was investigated.

Di Maio, L.; Scarfato, P.; Garofalo, E.; Galdi, M. R.; D'Arienzo, L.; Incarnato, L.

2014-05-01

22

Structure-Property Relationship in Metal Carbides and Bimetallic Alloys  

Energy Technology Data Exchange (ETDEWEB)

The primary objective of our DOE/BES sponsored research is to use carbide and bimetallic catalysts as model systems to demonstrate the feasibility of tuning the catalytic activity, selectivity and stability. Our efforts involve three parallel approaches, with the aim at studying single crystal model surfaces and bridging the “materials gap” and “pressure gap” between fundamental surface science studies and real world catalysis. The utilization of the three parallel approaches has led to the discovery of many intriguing catalytic properties of carbide and bimetallic surfaces and catalysts. During the past funding period we have utilized these combined research approaches to explore the possibility of predicting and verifying bimetallic and carbide combinations with enhanced catalytic activity, selectivity and stability.

Chen, Jingguan [University of Delaware

2014-03-04

23

Structure property relationships in polycarbonate/polydimethylsiloxane copolymers  

International Nuclear Information System (INIS)

Block copolymers based on polycarbonate (PC) and polydimethylsiloxane (PDMS) have been known for over 40 years. These materials have achieved commercial success due to a favorable combination of low temperature impact, melt processibility, weathering resistance and unique surface properties. Most commercial products are opaque due to scattering by the PDMS domains dispersed in the PC matrix. By controlling synthesis conditions, optically opaque or transparent materials may result from the same combination of base monomers and both types of materials have been prepared and characterized. Lower PDMS block lengths lead to higher levels of light transmission. Opaque materials typically have siloxane domains in the 5 um region while low haze products can be achieved when domains are less than 20 nm. Small siloxane domain copolymers exhibit considerable mixing of PC into the PDMS blocks. This likely alters the refractive index of the PDMS phase and contributes to the low haze measured in these copolymers. (author)

2005-11-06

24

3D-WHIM pattern recognition study for bisamidines. A structure-property relationship study  

Directory of Open Access Journals (Sweden)

Full Text Available A proposed model for the interaction of bisamidine analogues with the B-DNA receptor is established by structure-property relationship studies derived from 3D-WHIM descriptor calculations. Three classes, each with relevant information about structural relationships, were determined by PCA and SIMCA analyses for molecular conformations described by 3D-WHIM descriptors for a set of 29 bisamidines with antileishmaniasis and anti-PCP activities. Shape, distribution and dimension properties mostly govern the interaction of bisamidines with B-DNA through the minor groove AT rich regions.

Menezes Fabiano A. S.

2000-01-01

25

Near-Infrared Luminescent Lanthanide Complexes of Quinolinol Ligands: Structure/Properties Relationship  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The synthesis and the characterisation of lanthanide complexes with quinolinolato ligands, a class of complexes proposed as near-infrared emitters for several optical applications, with a full investigation of the structure/property relationship, valuable for a reliable interpretation of their photo-physical properties, are described in this thesis. This work has been addressed to a detailed investigation of the proper synthetic procedures useful to prepare pure products suitable for struc...

Artizzu, Flavia

2008-01-01

26

Structure-property relationships of PEMs using fluorous-ionic copolymers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Proton exchange membranes (PEMs) are a key component in PEM fuel cells, serving as both a fuel separator and an electrolyte. The goal of this thesis work is to investigate structure-property relationships in PEMs. Specifically, the role of polymer microstructure on membrane morphology and physicochemical properties is examined. This is achieved by the design, synthesis and characterization of model polymers with controlled chain architectures and chemical composition, leading to membranes wit...

2011-01-01

27

MALDI Efficiency of Metabolites Quantitatively Associated with their Structural Properties: A Quantitative Structure-Property Relationship (QSPR) Approach  

Science.gov (United States)

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) experiments require a suitable match of the matrix and target compounds to achieve a selective and sensitive analysis. However, it is still difficult to predict which metabolites are ionizable with a given matrix and which factors lead to an efficient ionization. In the present study, we extracted structural properties of metabolites that contribute to their ionization in MALDI-MS analyses exploiting our experimental data set. The MALDI-MS experiment was performed for 200 standard metabolites using 9-aminoacridine (9-AA) as the matrix. We then developed a prediction model for the ionization profiles (both the ionizability and ionization efficiency) of metabolites using a quantitative structure-property relationship (QSPR) approach. The classification model for the ionizability achieved a 91 % accuracy, and the regression model for the ionization efficiency reached a rank correlation coefficient of 0.77. An analysis of the descriptors contributing to such model construction suggested that the proton affinity is a major determinant of the ionization, whereas some substructures hinder efficient ionization. This study will lead to the development of more rational and predictable MALDI-MS analyses.

Yukihira, Daichi; Miura, Daisuke; Fujimura, Yoshinori; Umemura, Yoshikatsu; Yamaguchi, Shinichi; Funatsu, Shinji; Yamazaki, Makoto; Ohta, Tetsuya; Inoue, Hiroaki; Shindo, Mitsuru; Wariishi, Hiroyuki

2014-01-01

28

Rare-earth transition-metal intermetallics: Structure-bonding-property relationships  

Energy Technology Data Exchange (ETDEWEB)

The explorations of rare-earth, transition metal intermetallics have resulted in the synthesis and characterization, and electronic structure investigation, as well as understanding the structure-bonding property relationships. The work has presented the following results: (1) Understanding the relationship between compositions and properties in LaFe{sub 13-x}Si{sub x} system: A detailed structural and theoretical investigation provided the understanding of the role of a third element on stabilizing the structure and controlling the transformation of cubic NaZn{sub 13}-type structures to the tetragonal derivative, as well as the relationship between the structures and properties. (2) Synthesis of new ternary rare-earth iron silicides Re{sub 2-x}Fe{sub 4}Si{sub 14-y} and proposed superstructure: This compound offers complex structural challenges such as fractional occupancies and their ordering in superstructure. (3) Electronic structure calculation of FeSi{sub 2}: This shows that the metal-semiconductor phase transition depends on the structure. The mechanism of band gap opening is described in terms of bonding and structural distortion. This result shows that the electronic structure calculations are an essential tool for understanding the relationship between structure and chemical bonding in these compounds. (4) Synthesis of new ternary rare-earth Zinc aluminides Tb{sub 3}Zn{sub 3.6}Al{sub 7.4}: Partially ordered structure of Tb{sub 3}Zn{sub 3.6}Al{sub 7.4} compound provides new insights into the formation, composition and structure of rare-earth transition-metal intermetallics. Electronic structure calculations attribute the observed composition to optimizing metal-metal bonding in the electronegative (Zn, Al) framework, while the specific ordering is strongly influenced by specific orbital interactions. (5) Synthesis of new structure type of Zn{sub 39}(Cr{sub x}Al{sub 1-x}){sub 81}: These layered structures are similar to icosahedral Mn-Al quasicrystalline compounds. Therefore, this compound may provide new insights into the formation, composition and structure of quasicrystalline materials.

Han, M.K.

2006-05-06

29

Rare-Earth Transition-Metal Intermetallics: Structure-bonding-Property Relationships  

Energy Technology Data Exchange (ETDEWEB)

Our explorations of rare-earth, transition metal intermetallics have resulted in the synthesis and characterization, and electronic structure investigation, as well as understanding the structure-bonding-property relationships. Our work has presented the following results: (1) Understanding the relationship between compositions and properties in LaFe{sub 13-x}Si{sub x} system: A detailed structural and theoretical investigation provided the understanding of the role of a third element on stabilizing the structure and controlling the transformation of cubic NaZn{sub 13}-type structures to the tetragonal derivative, as well as the relationship between the structures and properties. (2) Synthesis of new ternary rare-earth iron silicides RE{sub 2-x}Fe{sub 4}Si{sub 14-y} and proposed superstructure: This compound offers complex structural challenges such as fractional occupancies and their ordering in superstructure. (3) Electronic structure calculation of FeSi{sub 2}: This shows that the metal-semiconductor phase transition depends on the structure. The mechanism of band gap opening is described in terms of bonding and structural distortion. This result shows that the electronic structure calculations are an essential tool for understanding the relationship between structure and chemical bonding in these compounds. (4) Synthesis of new ternary rare-earth Zinc aluminides Tb{sub 3}Zn{sub 3.6}Al{sub 7.4}: Partially ordered structure of Tb{sub 3}Zn{sub 3.6}Al{sub 7.4} compound provides new insights into the formation, composition and structure of rare-earth transition-metal intermetallics. Electronic structure calculations attribute the observed composition to optimizing metal-metal bonding in the electronegative (Zn, Al) framework, while the specific ordering is strongly influenced by specific orbital interactions. (5) Synthesis of new structure type of Zn{sub 39}(Cr{sub x}Al{sub 1-x}){sub 81}: These layered structures are similar to icosahedral Mn-Al quasicrystalline compounds. Therefore, this compound may provide new insights into the formation, composition and structure of quasicrystalline materials.

Mi-Kyung Han

2006-05-01

30

Relationship between structural fractal and possible dynamic scaling properties in protein folding  

CERN Multimedia

In this letter, the possible dynamic scaling properties of protein molecules in folding are investigated theoretically by assuming that the protein molecules are percolated networks. It is shown that the fractal character and the fractal dimensionality may exist only for short sequences in large protein molecules and small protein molecules with homogeneous structure, the fractal dimensionality are obtained for different structures. We then show that there might exist the dynamic scaling properties in protein folding, the critical exponents in the folding for some small global proteins with homogeneous structure are obtained. The dynamic critical exponents of the global proteins in folding are relevant to the fractal dimensionality of its structure, which implies the close relationship between the dynamic process in protein folding and its structure kinematics.

Zou, L J; Zhu, Z G; Zou, Liang Jian; Zhu, Zheng Gang

1996-01-01

31

Quantitative structure-property relationship modeling of Grätzel solar cell dyes.  

Science.gov (United States)

With fossil fuel reserves on the decline, there is increasing focus on the design and development of low-cost organic photovoltaic devices, in particular, dye-sensitized solar cells (DSSCs). The power conversion efficiency (PCE) of a DSSC is heavily influenced by the chemical structure of the dye. However, as far as we know, no predictive quantitative structure-property relationship models for DSSCs with PCE as one of the response variables have been reported. Thus, we report for the first time the successful application of comparative molecular field analysis (CoMFA) and vibrational frequency-based eigenvalue (EVA) descriptors to model molecular structure-photovoltaic performance relationships for a set of 40 coumarin derivatives. The results show that the models obtained provide statistically robust predictions of important photovoltaic parameters such as PCE, the open-circuit voltage (V(OC)), short-circuit current (J(SC)) and the peak absorption wavelength ?(max). Some of our findings based on the analysis of the models are in accordance with those reported in the literature. These structure-property relationships can be applied to the rational structural design and evaluation of new photovoltaic materials. PMID:24222335

Venkatraman, Vishwesh; Åstrand, Per-Olof; Alsberg, Bjørn Kåre

2014-01-30

32

Structure-Property Relationships of Surfactants at Interfaces and Polyelectrolyte-Surfactant Aggregates  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The first part of this thesis is concerned with thestructure-property relationships in nonionic surfactantsystems. The main aim was to investigate how the surfactantstructure influences the adsorption at interfaces andinteractions between surfactant coated interfaces.Particularly, the effect of the structure of the surfactantheadgroups was investigated. These were sugar-based headgroupwith varying size and flexibility and poly(ethylene oxide)based headgroups with or without an additional amid...

Kjellin, Mikael

2002-01-01

33

Structure-Property Relationships and the Mixed Network Former Effect in Boroaluminosilicate Glasses  

DEFF Research Database (Denmark)

Boroaluminosilicate glasses are important materials for various applications, e.g., liquid crystal display substrates, glass fibers for reinforcement, and thermal shock-resistant glass containers. The complicated structural speciation in these glasses leads to a mixed network former effect yielding nonlinear variation in many macroscopic properties. It is therefore crucial to investigate and understand structure-property correlations in boroaluminosilicate glasses. Here we study the structure-property relationships of a range of sodium boroaluminosilicate glasses from peralkaline to peraluminous compositions by substituting Al2O3 for SiO2. We also investigate the various roles of sodium in the glasses including charge compensation of tetrahedral aluminum and boron atoms and formation of non-bridging oxygen. We find that mechanical properties (density, elastic moduli, and hardness), glass transition temperature, and kinetic and thermodynamic liquid fragilities all exhibit nonlinear variations with changes in the relative network former concentrations. The structural origin of these nonlinear variations is elucidated through nuclear magnetic resonance measurements and analysis. Finally, we explore the effect of iron on the measured properties by doping these glasses with ~1 mol% of iron oxide.

Zheng, Qiuju; Potuzak, Marcel

34

Structure-property relationships of a biopolymer network: the eggshell membrane.  

Science.gov (United States)

The eggshell membrane (ESM) is a biopolymer network that may have potential applications in biomedicine, but it also may reveal important details regarding the behaviour of biopolymer networks. In this paper, we have studied the mechanical and morphological properties of the ESM in order to reveal important structure-property relationships. Light optical microscopy and atomic force microscopy were used to assess the morphology of the ESM. The mechanical properties of membranes and individual fibres were studied by means of tensile tests and nanoindentation tests, respectively. The mechanical behaviour of ESM networks in different environmental conditions showed a non-linear and a linear regime. As for elastomers and other biopolymer systems, the non-linear regime was modelled by the Mooney-Rivlin relation. The Young's modulus in the linear regime of the network was related to the Young's modulus of the individual fibres using Gibson and Ashby analysis for cellular solids. The results of morphological characterization were used to relate the properties of individual fibres to the properties of the whole networks. This enabled us to predict the macroscopical properties of the network based on the properties of the individual fibres. It was found that the ESM networks behaved as both Mooney-Rivlin and Hookean materials in different environmental conditions. This study helps elucidate the properties of the biopolymer networks found in nature and describes important mechanical properties for the use of the ESM as a biomaterial. PMID:20227532

Torres, Fernando G; Troncoso, Omar P; Piaggio, Franco; Hijar, Alfredo

2010-09-01

35

Hybrid Mixed Media Nonwovens: An Investigation of Structure-Property Relationships  

Science.gov (United States)

There have been myriad studies on utilizing bicomponent splittables produced through spunbond/spunlace processes. These production methods have proven to yield microfibers which increase the surface area of the nonwoven structures. There has been recent focus on studying the microfibers within these nonwoven structures as well as using a multiplicity of deniers of fibers within the nonwoven. There have also been studies on producing nonwovens with fibers of differing cross-sectional shapes and diameters. The purpose of this study is to examine the properties of a nonwoven structure, marrying the concepts of multi-denier fibers with multi-shaped fibers in two configurations: three-layer and alternating. The basis for this study will be US Patent 6,964,931 B2 "Method of making Continuous Filament Web with Statistical Filament Distribution" as well as US Patent 7,981,336 B2 "Process of Making Mixed Fibers and Nonwoven Fabrics". This study addresses the melt-spinning and hydroentanglement of nonwoven webs made from bicomponent fibers in three-layer and alternating configurations. The bicomponent cross-sections that will be used include 16-segmented pie and 7-islands-in-the-sea. In this study the establishment of the utility of mixed media nonwovens will take place through property and structure analysis in order to determine the inherent properties of the mixed media structures as well as the structure-property relationships of the nonwoven fabric. Property and structure analysis will also take place on mixed media structures containing poly(lactic acid) as a sacrificial component in the bicomponent fiber after optimizing the removal conditions of the poly(lactic acid) in a sodium hydroxide (NaOH) bath.

Hollowell, Kendall Birckhead

36

Structure–property relationships and residual stress quantification of a friction stir spot welded magnesium alloy  

International Nuclear Information System (INIS)

Structure–property relationships and spatial residual stress distribution in a friction stir spot welded magnesium alloy (AZ31) sheet was investigated to elucidate the incipient deformation mechanisms and welding process parameters. Experimental results revealed a decrease in the tensile and compressive yield strengths, as well as an increase in ductility and grain size, as the tool rotational speed and shoulder depth increased. Residual stresses were measured using neutron diffraction, and a strong dependency was found between the grain size, residual stress and the welding parameters.

2012-05-01

37

Dissolution of SO3 within a lithium phosphate glass network and structure–property relationships  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The relationship between the structure and properties of glasses with composition 50Li2O.xSO3.(50?x)P2O5 (x=10–30, mol%) has been studied. SO3 can be dissolved into lithium phosphate glasses up to at least 20 mol%, while for glasses containing as much as 30 mol% SO3 it is present as crystalline Li2SO4, as seen by XRD and TEM. 31P NMR experiments have shown no bonds of the type P–O–S, thus it is thought that Li2SO4 can be homogeneously dissolved within the lithium phosphate...

He?mono, Nicola?s; Mun?oz, Francisco

2010-01-01

38

Structure-properties relationships of polyhedral oligomeric silsesquioxane (POSS filled PS nanocomposites  

Directory of Open Access Journals (Sweden)

Full Text Available The polyhedral oligomeric silsesquioxane (POSS additivated polystyrene (PS based nanocomposites were prepared by melt processing and the structure-properties relationships of the POSS-PS systems were compared to those of the neat PS. In order to investigate the effect of these structural parameters on the final properties of the polymer nanocomposites, five different kinds of POSS samples were used, in particular, POSS with different inorganic cage and with different organic pendent groups. The rheological investigation suggests clearly that the POSS acts as a plasticizer and that the processability of the PS was positively modified. The affinity between the POSS samples and the PS matrix was estimated by the calculated theoretical solubility parameters, considering the Hoy’s method and by morphology analysis. Minor difference between the solubility parameter of POSS and the matrix means better compatibility and no aggregation tendency. Furthermore, the POSS loading leads to a decrease of the rigidity, of the glass transition temperature and of the damping factor of the nanocomposite systems. The loading of different POSS molecules with open cage leads to a more pronounced effect on all the investigated properties that the loading of the POSS molecules with closed cage. Moreover, the melt properties are significantly influenced by the type of inorganic framework, by the type of the pendent organic groups and by the interaction between the POSS organic groups and the host matrix, while, the solid state properties appears to be influenced more by the kind of cage.

J. J. Schwab

2012-07-01

39

Synthesis and Quantitative Structure-Property Relationships of Side Chain-Modified Hyodeoxycholic Acid Derivatives  

Directory of Open Access Journals (Sweden)

Full Text Available Bile acids have emerged as versatile signalling compounds of a complex network of nuclear and membrane receptors regulating various endocrine and paracrine functions. The elucidation of the interconnection between the biological pathways under the bile acid control and manifestations of hepatic and metabolic diseases have extended the scope of this class of steroids for in vivo investigations. In this framework, the design and synthesis of novel biliary derivatives able to modulate a specific receptor requires a deep understanding of both structure-activity and structure-property relationships of bile acids. In this paper, we report the preparation and the critical micellization concentration evaluation of a series of hyodeoxycholic acid derivatives characterized by a diverse side chain length and by the presence of a methyl group at the alpha position with respect to the terminal carboxylic acid moiety. The data collected are instrumental to extend on a quantitative basis, the knowledge of the current structure-property relationships of bile acids and will be fruitful, in combination with models of receptor activity, to design and prioritize the synthesis of novel pharmacokinetically suitable ligands useful in the validation of bile acid-responsive receptors as therapeutic targets.

Antimo Gioiello

2013-08-01

40

Structure-property relationships in the design, assembly and applications of polyelectrolyte multilayer thin films  

Science.gov (United States)

Ultrathin films consisting of an alternating sequence of positively and negatively charged polyelectrolytes have been prepared by means of the electrostatic layer-by-layer sequential assembly technique. To augment their typical applications in the water treatment, personal care as well as the pulp and paper industry, the structure and the design of these polyelectrolytes were tailored synthetically to satisfy the requirements of different types of applications. Some were used for surface modifications, hydrophobic and hydrophilic coatings, corrosion protection, conducting and biocompatible surfaces. Others were found to be very efficient for membrane and chromatographic applications. The ease with which these multilayer coatings can be constructed, their robustness and stability make them very good candidates for industrial applications. The dissertation focuses mainly on the structure-property relationships of these polyelectrolytes and their corresponding thin films. Various polyelectrolytes were synthesized or modified in a strategic approach and gave novel and promising properties. Some of them exhibited permeabilities that were higher than any membranes reported in the literature. Also, some are potentially very useful for designing drug delivery systems such as tablets or encapsulations since they were shown to control the permeability of sample drugs and vitamins very efficiently based on their sensitivity to pH changes. Other synthesized polyelectrolytes proved to be very effective in preventing protein adsorption or promoting cell growth and differentiation. Some systems were very useful as robust stationary phases for simple chiral separations in capillary electrochromatography. Along with modifications and improvements, the approach might one day be applied commercially for chiral separations using high performance liquid chromatography and replace currently used stationary phases. Last but not least, the potential for these polyelectrolytes and their corresponding films is immense. Slight variations in their structural properties could transform into significant improvements in their physical properties and behavior. Hydrophobicity, permeability, swelling, thickness and stability are very important properties of these films and could be tuned to achieve new and unprecedented properties.

Rmaile, Hassan H.

 
 
 
 
41

Synthetic Study on the Relationship Between Structure and Sweet Taste Properties of Steviol Glycosides  

Directory of Open Access Journals (Sweden)

Full Text Available The structure activity relationship between the C16-C17 methylene double bond on the aglycone of steviol glycosides and the corresponding impact on their sweet taste has been reported here for the first time. It has been observed that converting stevioside and rebaudioside A to their corresponding ketones by switching the doubly bonded methylene on C-17 for a ketone group actually removes the sweet taste properties of these molecules completely. Regenerating the original molecules tends to restore the sweet taste of both the steviol glycosides. Thus this C16-C17 methylene double bond in rebaudioside A and stevioside can be regarded as a pharmacophore essential for the sweetness property of these molecules.

Grant Dubois

2012-04-01

42

Importance of ground properties in the relationship of ground vibration–structural hazard and land application  

Science.gov (United States)

Vibration parameters like frequency, acceleration and particle velocity play an active role in the relationship of ground vibration–structural hazard. These parameters change depending on blasting energy and the properties of rock environment. Therefore, in the first step, rock mass properties and possible directional variation were investigated by using different geophysical methods (electrical resistivity, seismic refraction and multi-channel analysis of surface wave) and current sounding information. Each method offers different sensitivities and resolutions depending on the physical characteristics of different materials. Evaluating these as a whole increased the solubility of the research. According to seismic S- and P-wave velocities, electrical resistivity and sounding information, the study area consists of consecutive sequences of alluvium, clay limestone, tuff and limestone units. And these units show variations from place to place in the study area. In the second stage, evaluations were made according to the structural hazard standards used widely in the literature and components of velocity, acceleration and frequency obtained from blasting vibration seismograph and accelerometers. As a result, it is seen that ground vibrations show different spreading properties in different directions and different hazard risks depending on the geological structure of the region.

Caylak, C.; Kocaslan, A.; Gorgulu, K.; Buyuksarac, A.; Arpaz, E.

2014-05-01

43

Relationship between structure, properties, and the radical scavenging activity of morin  

Science.gov (United States)

The relationship between structure, kinetic, thermochemical and electronic properties of the morin flavonoid was researched in order to establish the molecular characteristics related to its maximum radical scavenging activity. The reaction of morin with the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH rad ) was carried out in ethanol, through the hydrogen-atom transfer (HAT) mechanism. Morin showed the highest radical scavenging activity under conditions of excess of free radical. It was found, by means of experimental and computational methods, that 3-OH, 2'-OH and 4'-OH are the main reactive sites, as well as that the 3-O-2'-O quinone is the first product of the reaction, tending to prevail in the enol form through a tautomerism effect, whose observed structural arrangement corresponds to the 3-O semiquinone.

Mendoza-Wilson, Ana María; Santacruz-Ortega, Hisila; Balandrán-Quintana, René R.

2011-05-01

44

Probing structure-property relationships in perpendicularly magnetized Fe/Cu(001) using MXLD and XPD  

International Nuclear Information System (INIS)

Magnetic X-ray Linear Dichroism (MXLD) in Photoelectron Spectroscopy and X-Ray Photoelectron Diffraction (XPD) of the Fe 3p core level have been used to probe the magnetic structure-property relationships of perpendicularly magnetized Fe/Cu(001), in an element-specific fashion. A strong MEXLD effect was observed in the high resolution photoelectron spectroscopy of the Fe 3p at open-quotes normalclose quotes emission and was used to follow the loss of perpendicular ferromagnetic ordering as the temperature was raised toward room temperature. In parallel with this, open-quotes Forward Focussingclose quotes in XPD was used as a direct measure of geometric structure in the overlayer. These results and the implications of their correlation will be discussed. Additionally, an investigation of the effect of Mn doping of the Fe/Cu(001) will be described. These measurements were performed at the Spectromicroscopy Facility (Beamline 7.0.1) of the Advanced Light Source

1997-04-01

45

Solvent effects on the structure-property relationship of anticonvulsant hydantoin derivatives: A solvatochromic analysis  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Considering the pharmaceutical importance of hydantoins, a set of 25 derivatives of phenytoin, nirvanol and 5-methyl-5-phenylhydantoin, the lipophilicities of which were gradually increased by the introduction of different alkyl, cycloalkyl and alkenyl groups in position N3, was synthesized. Their properties under consideration were either estimated empirically, by UV/Vis spectroscopy, or calculated using established medicinal chemistry software. The UV absorption spectra of the investigated compounds were recorded in the region from 200 to 400 nm, in selected solvents of different polarities. The effects of solvent dipolarity/polarizability and solvent-solute hydrogen bonding interactions were analyzed by means of the linear solvation energy relationship (LSER concept proposed by Kamlet and Taft. Furthermore, the relationships between solvent-solute interactions and selected structural features of the solutes, which are believed to markedly affect the processes of absorption, distribution, metabolism, excretion and toxicity (ADMETox, were discussed. Satisfactory correlations were found between hydrogen bonding properties and solute size and the in silico calculated bioactivity descriptors, in particular %Abs. (human intestinal absorption, log BB (blood-brain barrier permeation and log kA (protein binding affinities parameters. In view of the results of this study, the investigated hydantoin derivatives met the pharmacokinetic criteria for pre-selection as drug candidates and qualified them for the pharmacodynamic phase of antiepileptic drug development.

Trišovi? Nemanja

2011-10-01

46

Molecular structure - nonlinear optical property relationships for a series of polymethine and squaraine molecules  

Science.gov (United States)

This dissertation reports on the investigation of the relationships between molecular structure and two-photon absorption (2PA) properties for a series of polymethine and squaraine molecules. Current and emerging applications exploiting the quadratic dependence upon laser intensity, such as two-photon fluorescence imaging, three-dimensional microfabrication, optical data storage and optical limiting, have motivated researchers to find novel materials exhibiting strong 2PA. Organic materials are promising candidates because their linear and nonlinear optical properties can be optimized for applications by changing their structures through molecular engineering. Polymethine and squaraine dyes are particularly interesting because they are fluorescent and showing large 2PA. We used three independent nonlinear spectroscopic techniques (Z-scan, two-photon fluorescence and white-light continuum pump-probe spectroscopy) to obtain the 2PA spectra revealing 2PA bands, and we confirm the experimental data by comparing the results from the different methods mentioned. By systematically altering the structure of polyemthines and squaraines, we studied the effects of molecular symmetry, strength of donor terminal groups, conjugation length of the chromophore chain, polarity of solvents, and the effects of placing bridge molecules inside the chromophore chain on the 2PA properties. We also compared polymethine, squaraine, croconium and tetraon dyes with the same terminal groups to study the effects of the different additions inserted within the chromophore chain on their optical properties. Near IR absorbing squaraine dyes were experimentally observed to show extremely large 2PA cross sections (?30000GM). A simplified three-level model was used to fit the measured 2PA spectra and detailed quantum chemical calculations revealed the reasons for the squaraine to exhibit strong 2PA. In addition, two-photon excitation fluorescence anisotropy spectra were measured through multiple 2PA transitions. A theoretical model based on four-levels with two intermediate states was derived and used for analysis of the experimental data.

Fu, Jie

47

Structure property relationship in aza-bodipy absorber materials for organic photovoltaics  

Energy Technology Data Exchange (ETDEWEB)

In this joint experimental and theoretical study, we focus on the structure property relationship of aza-bodipy dyes as active donor materials in vacuum deposited small molecule solar cells. The position of the materials HOMO can be intentionally varied by the choice of the functional group attached to the molecule. The absorption spectra show a red shift of the maximum with increasing donor strength of the substituents due to the increasing HOMO energy and decreasing band gap. Based on crystal structure data, the charge carrier mobility determining parameters like reorganization energies and transfer integrals are calculated. The results show an increasing molecular orbital overlap and significant higher transfer integrals upon planarization and rigidification of the molecule. With this information, the observed charge carrier mobility differences from experiment can be explained. In addition to the electronic properties a high thermal and photo stability is essential. From combined thermogravimetric analysis and mass spectroscopy we could determine the degradation process of the material and were able to increase the thermal stability by substitution of the involved species.

Gresser, Roland; Mueller, Toni; Hein, Moritz Philipp; Leo, Karl; Riede, Moritz [Institute of Applied Photophysics, Dresden University of Technology (Germany)

2010-07-01

48

Structure-property relationship in high-tension ceramic insulator fired at high temperature  

International Nuclear Information System (INIS)

Ceramic insulators are widely used in microelectronic devices. In this paper, the mechanical and electrical properties of porcelain ceramic insulator fired at 1350 deg. C have been investigated along with microstructural characterization using scanning electron microscopy (SEM) in order to understand the structure-property relationship of ceramic insulator. The bending and the dielectric strength were measured on various samples fired at 1350 deg. C. The bending strength (757.3 kg/cm2) and the dielectric strength (28.36 kV/mm) was found short of the desired value. The microstructural features developed clearly describe why the dielectric strength and the bending strength are not up to the mark. EDAX analysis, X-ray fluorescence (XRF) and X-ray diffractometry (XRD) techniques were also done to support the results. XRD pattern shows 70% mullite and 20% quartz peak intensity and the XRF results shows 22.64% Al2O3 that indicates low mullite formation and hence it is confirmed that it is mullite, the crystalline phase, which contribute together with quartz particle to the dielectric and mechanical strength. SEM image shows large number of microcracks that also hinder the high electrical and mechanical properties of porcelain ceramic insulator

2004-01-25

49

Qualitative and quantitative structure-property relationships analysis of multicomponent potential bioglasses.  

Science.gov (United States)

The results of a qualitative and quantitative structure-property relationships analysis of multicomponent potential bioglasses of composition (2 - y) SiO2 x 1 Na2O x 1.1 CaO x y P2O5 x x ZnO (x = 0, 0.16, 0.35, 0.78 and y = 0.10, 0.20, 0.36) are presented. Quantitative models are obtained by means of structural descriptors derived by molecular dynamics simulations and experimental data measured for density, thermal analysis, 29Si and 31P magic angle spinning NMR, and chemical durability in water. Analysis of the crystal species obtained upon glass crystallization helped in the rationalization of the structural role of the different components. Finally, glass surface characterization with scanning electron microscopy, transmission electron microscopy, and X-ray diffraction after soaking in acellular simulated body fluid demonstrated the in vitro bioactivity of the newly obtained 1.80 SiO2 x 1 Na2O x 1.1 Ca x 0.20 P2O5 x 0.16 ZnO (HP5Z5) glass, corresponding to x = 0.16 and y = 0.20. PMID:16863158

Linati, Laura; Lusvardi, Gigliola; Malavasi, Gianluca; Menabue, Ledi; Menziani, M Cristina; Mustarelli, Piercarlo; Segre, Ulderico

2005-03-24

50

Predicting total organic halide formation from drinking water chlorination using quantitative structure-property relationships.  

Science.gov (United States)

Chlorinating water which contains dissolved organic matter (DOM) produces disinfection byproducts, the majority of unknown structure. Hence, the total organic halide (TOX) measurement is used as a surrogate for toxic disinfection byproducts. This work derives a robust quantitative structure-property relationship (QSPR) for predicting the TOX formation potential of model compounds. Literature data for 49 compounds were used to train the QSPR in moles of chlorine per mole of compound (Cp) (mol-Cl/mol-Cp). The resulting QSPR has four descriptors, calibration [Formula: see text] of 0.72 and standard deviation of estimation of 0.43?mol-Cl/mol-Cp. Internal and external validation indicate that the QSPR has good predictive power and low bias (?fulvic acids and two agent-based model assemblages - gave a predicted TOX range of 136-184?µg-Cl/mg-C, consistent with experimental data for DOM, which ranged from 78 to 192?µg-Cl/mg-C. However, the limited structural variation in the training data may limit QSPR applicability; studies of more sulfur-containing compounds, heterocyclic compounds and high molecular weight compounds could lead to a more widely applicable QSPR. PMID:22003826

Luilo, G B; Cabaniss, S E

2011-10-01

51

Design, synthesis, and structure-property relationships of isoindigo-based conjugated polymers.  

Science.gov (United States)

Conjugated polymers have developed rapidly due to their promising applications in low-cost, lightweight, and flexible electronics. The development of the third-generation donor-acceptor (D-A) polymers greatly improved the device performance in organic solar cells (OSCs) and field-effect transistors (FETs). However, for further improvement of device performance, scientists need to develop new building blocks, in particular electron-deficient aromatics, and gain an in-depth understanding of the structure-property relationships. Recently, isoindigo has been used as a new acceptor of D-A conjugated polymers. An isomer of indigo, isoindigo is a less well-known dye and can be isolated as a by-product from certain biological processes. It has two lactam rings and exhibits strong electron-withdrawing character. This electron deficiency gives isoindigo-based polymers intriguing properties, such as broad absorption and high open circuit voltage in OSCs, as well as high mobility and good ambient stability in FETs. In this Account, we review our recent progress on the design, synthesis, and structure-property relationship study of isoindigo-based polymers for FETs. Starting with some discussion on carrier transport in polymer films, we provide some basic strategies towards high-performance polymer FETs. We discuss the stability issue of devices, the impediment of the alkyl side chains, and the choice of the donor part of conjugated polymers. We demonstrate that introducing the isoindigo core effectively lowers the HOMO levels of polymers and provides FETs with long-time stability. In addition, we have found that when we use inappropriate alkyl side chains or non-centrosymmetric donors, the device performance of isoindigo polymers suffers. To further improve device performance and ambient stability, we propose several design strategies, such as using farther branched alkyl chains, modulating polymer energy levels, and extending ?-conjugated backbones. We have found that using farther branched alkyl chains can effectively decrease interchain ?-? stacking distance and improve carrier mobility. When we introduce electron-deficient functional groups on the isoindigo core, the LUMO levels of the polymers markedly decrease, which significantly improves the electron mobility and device stability. In addition, we present a new polymer system called BDOPV, which is based on the concept of ?-extended isoindigo. By application of some strategies successfully used in isoindigo-based polymers, BDOPV-based polymers exhibit high mobility and good stability both in n-type and in ambipolar FETs. We believe that a synergy of molecular engineering strategies towards the isoindigo core, donor units, and side chains may further improve the performance and broaden the application of isoindigo-based polymers. PMID:24502431

Lei, Ting; Wang, Jie-Yu; Pei, Jian

2014-04-15

52

Effect of conversion on the structure-property relationships of amine-cured epoxy thermosets.  

Science.gov (United States)

The effects of conversion beyond the gel point on the structure-property relationships of epoxy thermosets using formulations representative of the most commonly used epoxy resin and amine curing agents at balanced stoichiometry with an emphasis on the thermal, tensile, and fracture properties were studied. The range of T(g) from just beyond the gel point to full conversion typically is >100 degrees C. Fracture toughness (as K(1c)) of the epoxy thermosets cured with relatively flexible amines such as ethylenediamine (EDA), diethylenetriamine (DETA), and m-xylylenediamine (MXDA) reaches near its full cure value at only approximately 65-70% conversion. The maximum in K(1c) for these types of epoxy thermosets is at approximately 90% conversion for EDA and DETA but just below its full cure for MXDA. Isophoronediamine represents a special case for fracture behavior because of its apparent substantial cyclization during cure. In the 4,4'-diaminodiphenylsulfone series, K(1c) generally increases with conversion as the concentrations of their strongly antiplasticizing soluble and pendant fractions decrease. A uniform trend of decreasing tensile modulus with increasing conversion was observed in each formulation and is consistent with the expected decrease in the cohesive energy density as monomer glass is transformed into polymer glass. PMID:20356018

Marks, Maurice J; Snelgrove, R Vernon

2009-04-01

53

Multivariate characterisation and quantitative structure-property relationship modelling of nitroaromatic compounds  

International Nuclear Information System (INIS)

A multivariate model to characterise nitroaromatics and related compounds based on molecular descriptors was calculated. Descriptors were collected from literature and through empirical, semi-empirical and density functional theory-based calculations. Principal components were used to describe the distribution of the compounds in a multidimensional space. Four components described 76% of the variation in the dataset. PC1 separated the compounds due to molecular weight, PC2 separated the different isomers, PC3 arranged the compounds according to different functional groups such as nitrobenzoic acids, nitrobenzenes, nitrotoluenes and nitroesters and PC4 differentiated the compounds containing chlorine from other compounds. Quantitative structure-property relationship models were calculated using partial least squares (PLS) projection to latent structures to predict gas chromatographic (GC) retention times and the distribution between the water phase and air using solid-phase microextraction (SPME). GC retention time was found to be dependent on the presence of polar amine groups, electronic descriptors including highest occupied molecular orbital, dipole moments and the melting point. The model of GC retention time was good, but the precision was not precise enough for practical use. An important environmental parameter was measured using SPME, the distribution between headspace (air) and the water phase. This parameter was mainly dependent on Henry's law constant, vapour pressure, log P, content of hydroxyl groups and atmospheric OH rate constant. The predictive capacity of the model substantially improved when recalculating a model using these five descriptors only

2008-07-28

54

Prediction of photosensitivity of 1,4-dihydropyridine antihypertensives by quantitative structure-property relationship.  

Science.gov (United States)

A quantitative structure-property relationships (QSPR) model, correlating the light sensitivity against theoretical molecular descriptors, was developed for a set of 1,4-dihydropyridine calcium channel antagonist drugs. These compounds are characterized by a high tendency to degradation when exposed to light, furnishing in the most of cases a related oxidation product from aromatization of the dihydropyridinic ring. Photodegradation was forced by exposing the drugs to a Xenon lamp, in accordance with the ICH international rules, and degradation kinetics was monitored by spectrophotometry. The photodegradation rates combined with a series of descriptors related to the chemical structures were computed by Partial Least Squares (PLS) multivariate analysis. An accurate selection of the variables, fitting at the best the PLS model, was performed. Two descriptors related to the substituent information on both the dihydropyridinic and benzenic rings and four molecular descriptors, were selected. The QSPR model was fully cross validated and then optimized with an external set of novel 1,4-dihydropyridine drugs, obtaining very satisfactory statistical results. The good agreement between predicted and measured photodegradation rate (R(2)=0.8727) demonstrated the high accuracy of the QSPR model in predicting the photosensitivity of the drugs belonging to this class. The model was finally proposed as an effective tool to design new congeneric molecules characterized by high photostability. PMID:19635379

Ioele, Giuseppina; De Luca, Michele; Oliverio, Filomena; Ragno, Gaetano

2009-10-15

55

Probing structure-property relationships in perpendicularly magnetized Fe/Cu(001) using MXLD and XPD  

Energy Technology Data Exchange (ETDEWEB)

Magnetic X-ray Linear Dichroism (MXLD) in Photoelectron Spectroscopy and X-Ray Photoelectron Diffraction (XPD) of the Fe 3p core level have been used to probe the magnetic structure-property relationships of perpendicularly magnetized Fe/Cu(001), in an element-specific fashion. A strong MEXLD effect was observed in the high resolution photoelectron spectroscopy of the Fe 3p at {open_quotes}normal{close_quotes} emission and was used to follow the loss of perpendicular ferromagnetic ordering as the temperature was raised toward room temperature. In parallel with this, {open_quotes}Forward Focussing{close_quotes} in XPD was used as a direct measure of geometric structure in the overlayer. These results and the implications of their correlation will be discussed. Additionally, an investigation of the effect of Mn doping of the Fe/Cu(001) will be described. These measurements were performed at the Spectromicroscopy Facility (Beamline 7.0.1) of the Advanced Light Source.

Cummins, T.R.; Waddill, G.D. [Univ. of Missouri, Rolla, MO (United States); Goodman, K.W. [Lawrence Berkeley National Lab., CA (United States)] [and others

1997-04-01

56

Multivariate characterisation and quantitative structure-property relationship modelling of nitroaromatic compounds  

Energy Technology Data Exchange (ETDEWEB)

A multivariate model to characterise nitroaromatics and related compounds based on molecular descriptors was calculated. Descriptors were collected from literature and through empirical, semi-empirical and density functional theory-based calculations. Principal components were used to describe the distribution of the compounds in a multidimensional space. Four components described 76% of the variation in the dataset. PC1 separated the compounds due to molecular weight, PC2 separated the different isomers, PC3 arranged the compounds according to different functional groups such as nitrobenzoic acids, nitrobenzenes, nitrotoluenes and nitroesters and PC4 differentiated the compounds containing chlorine from other compounds. Quantitative structure-property relationship models were calculated using partial least squares (PLS) projection to latent structures to predict gas chromatographic (GC) retention times and the distribution between the water phase and air using solid-phase microextraction (SPME). GC retention time was found to be dependent on the presence of polar amine groups, electronic descriptors including highest occupied molecular orbital, dipole moments and the melting point. The model of GC retention time was good, but the precision was not precise enough for practical use. An important environmental parameter was measured using SPME, the distribution between headspace (air) and the water phase. This parameter was mainly dependent on Henry's law constant, vapour pressure, log P, content of hydroxyl groups and atmospheric OH rate constant. The predictive capacity of the model substantially improved when recalculating a model using these five descriptors only.

Joensson, S. [Man-Technology-Environment Research Centre, Department of Natural Sciences, Orebro University, 701 82 Orebro (Sweden)], E-mail: sofie.jonsson@nat.oru.se; Eriksson, L.A. [Department of Natural Sciences and Orebro Life Science Center, Orebro University, 701 82 Orebro (Sweden); Bavel, B. van [Man-Technology-Environment Research Centre, Department of Natural Sciences, Orebro University, 701 82 Orebro (Sweden)

2008-07-28

57

Structure-Composition-Property Relationships in Polymeric Amorphous Calcium Phosphate-Based Dental Composites  

Directory of Open Access Journals (Sweden)

Full Text Available Our studies of amorphous calcium phosphate (ACP-based materials over the last decade have yielded bioactive polymeric composites capable of protecting teeth from demineralization or even regenerating lost tooth mineral. The anti-cariogenic/remineralizing potential of these ACP composites originates from their propensity, when exposed to the oral environment, to release in a sustained manner sufficient levels of mineral-forming calcium and phosphate ions to promote formation of stable apatitic tooth mineral. However, the less than optimal ACP filler/resin matrix cohesion, excessive polymerization shrinkage and water sorption of these experimental materials can adversely affect their physicochemical and mechanical properties, and, ultimately, limit their lifespan. This study demonstrates the effects of chemical structure and composition of the methacrylate monomers used to form the matrix phase of composites on degree of vinyl conversion (DVC and water sorption of both copolymers and composites and the release of mineral ions from the composites. Modification of ACP surface via introducing cations and/or polymers ab initio during filler synthesis failed to yield mechanically improved composites. However, moderate improvement in composite’s mechanical stability without compromising its remineralization potential was achieved by silanization and/or milling of ACP filler. Using ethoxylated bisphenol A dimethacrylate or urethane dimethacrylate as base monomers and adding moderate amounts of hydrophilic 2-hydroxyethyl methacrylate or its isomer ethyl-?-hydroxymethacrylate appears to be a promising route to maximize the remineralizing ability of the filler while maintaining high DVC. Exploration of the structure/composition/property relationships of ACP fillers and polymer matrices is complex but essential for achieving a better understanding of the fundamental mechanisms that govern dissolution/re-precipitation of bioactive ACP fillers, and, ultimately, the suitability of the composites for clinical evaluation.

Drago Skrtic

2009-11-01

58

Processing-structure-property relationships of carbon nanotube and nanoplatelet enabled piezoresistive sensors  

Science.gov (United States)

Individual carbon nanotubes (CNTs) possess excellent piezoresistive performance, which is manifested by the significant electrical resistance change when subject to mechanical deformation. In comparison to individual CNTs, the CNT thin films, formed by a random assembly of individual tubes or bundles, show much lower piezoresistive sensitivity. Given the progress made to date in developing CNT ensemble based-piezoresistive sensors, the related piezoresistive mechanism(s) are still not well understood. The crucial step to obtain a better understanding of this issue is to study the effects of CNT structure in the dispersion on the piezoresistivity of CNT ensemble based-piezoresistive sensors. To reach this goal, my Ph.D. research first focuses on establishing the processing-structure-property relationship of SWCNT thin film piezoresistive sensors. The key accomplishment contains: 1) developing the combined preparative ultracentrifuge method (PUM) and dynamic light scattering (DLS) method to quantitatively characterized SWCNT particle size in dispersions under various sonication conditions; 2) designing combined ultrasonication and microfluidization processing protocol for high throughput and large-scale production of high quality SWCNT dispersions; 3) fabricating varied SWCNT thin film piezoresistive sensors through spray coating technique and immersion-drying post-treatment; and 4) investigating the effect of microstructures of SWCNTs on piezoresistivity of SWCNT thin film sensors. This experimental methodology for quantitative and systematic investigation of the processing-structure-property relationships provides a means for the performance optimization of CNT ensemble based piezoresistive sensors. As a start to understand the piezoresistive mechanism, the second focus of my Ph.D. research is studying charge transport behaviors in SWCNT thin films. It was found that the temperature-dependent sheet resistance of SWCNT thin films could be explained by a 3D variable range hopping (3D-VRH) model. More importantly, a strong correlation between the length of SWCNTs and the VRH parameter T0, indicating the degree of disorder of the electronic system, has been identified. With the structure dependent transport mechanism study, a very interesting topic - how T0 changes when SWCNT thin film is under a mechanical deformation, would be helpful for better understanding the piezoresistive mechanism of SWCNT thin film sensors. As demonstrated in transport mechanism study, SWCNT thin film exhibits a negative temperature coefficient (NTC) of resistance. In contrast, another family of carbon nanomaterials, graphite nanoplatelets (GNPs), shows positive temperature coefficient (PTC) of resistance, attributed to their metallic nature. Therefore, upon a wise selection of mass ratio of SWCNTs to GNPs for fabrication of hybrid SWCNT/GNP thin film piezoresistive sensors, a near zero temperature coefficients of resistance in a broad temperature range has been achieved. This unique self-temperature compensation feature along with the high sensitivity of SWCNT/GNP hybrid sensors provides them a vantage for readily and accurately measuring the strain/stress levels in different conditions. With the unique features of SWCNT/GNP hybrid thin film sensors, my future work will focus on application exploration on SWCNT/GNP thin film sensor based devices. For example, we have demonstrated that it is potential for man-machine interaction and body monitoring when coating the hybrid sensor on highly stretchable nitrile glove. The structure health monitoring (SHM) of composite materials could also be realized by coating the thin film sensor on a glass fiber surface and then embedding the fiber sensor in composite structure.

Luo, Sida

59

Structure-property relationships of BaCeO perovskites for the oxidative dehydrogenation of alkanes  

Energy Technology Data Exchange (ETDEWEB)

The oxidative dehydrogenation (ODH) reactions for the formation of two important organic feedstocks ethylene and propylene are of great interest because of the potential in capital and energy savings associated with these reactions. Theoretically, ODH can achieve high conversions of the starting materials (ethane and propane) at lower temperatures than conventional dehydrogenation reactions. The important focus in this study of ODH catalysts is the development of a structure-property relationship for catalyst with respect to selectivity, so as to avoid the more thermodynamically favorable combustion reaction. Catalysts for the ODH reaction generally consist of mixed metal oxides. Since for the most selective catalyst lattice oxygen is known to participate in the reaction, catalysts are sought with surface oxygen atoms that are labile enough to perform dehydrogenation, but not so plentiful or weakly bound as to promote complete combustion. Also, catalysts must be able to replenish surface oxygen by transport from the bulk. Perovskite materials are candidates to fulfill these requirements. The authors are studying BaCeO{sub 3} perovskites doped with elements such as Ca, Mg, and Sr. During the ODH of the alkanes at high temperatures, the perovskite structure is not retained and a mixture of carbonates and oxides is formed, as revealed by XRD. While the Ca doped materials showed enhanced total combustion activity below 600 C, they only showed enhanced alkene production at 700 C. Bulk structural and surface changes, as monitored by powder X-ray diffraction, and X-ray photoelectron spectroscopy are being correlated with activity in order to understand the factors affecting catalyst performance, and to modify catalyst formulations to improve conversion and selectivity.

Nenoff, T.M.; Jackson, N.B.; Miller, J.E.; Sault, A.G.; Trudell, D. [Sandia National Labs., Albuquerque, NM (United States). Catalysis and Chemical Technologies Dept.

1997-12-01

60

Quantitative structure-property relationship study of the solvent polarity using wavelet neural networks.  

Science.gov (United States)

Quantitative structure-property relationship (QSPR) studies based on artificial neural network (ANN) and wavelet neural network (WNN) techniques were carried out for the prediction of solvent polarity. Experimental S' values for 69 solvents were assembled. This set included saturated and unsaturated hydrocarbons, solvents containing halogen, cyano, nitro, amide, sulfide, mercapto, sulfone, phosphate, ester, ether, etc. Semi-empirical quantum chemical calculations at AM1 level were used to find the optimum 3D geometry of the studied molecules and different quantum-chemical descriptors were calculated by the HyperChem software. A stepwise MLR method was used to select the best descriptors and the selected descriptors were used as input neurons in neural network models. The results obtained by the two methods were compared and it was shown that in WNN, the convergence speed was faster and the root mean square error of prediction set was also smaller than ANN. The average relative error in WNN was 7.9 and 6.8% for calibration and prediction set, respectively, and the results showed the ability of the WNN developed here to predict solvent polarity. PMID:17690424

Zarei, Kobra; Atabati, Morteza; Ebrahimi, Malihe

2007-08-01

 
 
 
 
61

Relationship between structure and optical properties in green fluorescent proteins: a quantum mechanical study of the chromophore environment  

International Nuclear Information System (INIS)

The present paper reports the first quantum mechanical modeling of a realistic chromophore environment of the green fluorescent proteins (GFPs). Based on density functional theory (DFT) and semiempirical calculation, we studied the effect of each amino acid in close contact with the chromophore and derived a quantitative and predictive relationship between structure and optical properties. On the basis of this relationship, the structural, optical and vibrational properties of the different states of wild-type GFP and of two mutants, EGFP (F64L/S65T) and E2GFP (F64L/S65T/T203Y), are then specifically studied. This approach can be applied to infer some structural features of spectroscopic states for which no structural data is available, such as the dark states involved in GFP photodynamics

2004-03-08

62

A quantitative structure property relationship study of electrophoretic mobility of analytes in capillary zone electrophoresis.  

Science.gov (United States)

A quantitative structure property relationship (QSPR) is proposed to calculate the electrophoretic mobility of analytes in capillary zone electrophoresis. The proposed model employs logarithm of the electrophoretic mobility (ln micro) as dependent variable and partial charge (PQ), surface area (V(2/3)), total energy (TE), heat of formation (DeltaH(f)) and molecular refractivity (MR) as independent variables whose calculated using AM1 (Austin model 1) semi-empirical quantum mechanics method by HyperChem 7.0 software. The general form of the model is: ln micro =K(0)+K(1)PQ+K(2)V(2/3)+K(3)TE+K(4)DeltaH(f)+K(5)MR, where K(0)-K(5) are the model constants computed using a least-square method. The applicability of the model on real mobility data has been studied employing five experimental data sets of beta-blockers, benzoate derivatives, non-steroidal anti-inflammatory drugs, sulfonamides and amines in different buffers. The accuracy of the model is assessed using absolute average relative deviation (AARD) and the overall AARD value. The obtained AARD for the sets studied are 1.0 (N=10), 2.1 (N=26), 0.8 (N=11), 0.6 (N=13) and 2.7% (N=18), respectively, and the overall AARD is 1.4%. The model is cross-validated using one leave out technique and the obtained overall AARD is 1.8%. To further investigate on the applicability of the proposed model, the prediction capability of the model is evaluated by employing a minimum number of six experimental data points as training set, and predicting the mobility of other data points using trained models. The obtained overall AARD (for 48 predicted data points) is 5.6%. PMID:12927104

Jouyban, A; Yousefi, B H

2003-07-01

63

Structure-dielectric property relationship for vanadium- and scandium-doped barium strontium titanate  

International Nuclear Information System (INIS)

This paper reports the results of an investigation of the structure-property relationship of vanadium (donor) and scandium (acceptor) doped Ba0.7Sr0.3TiO3. While V doping produces a fully miscible Ba0.7Sr0.3Ti1-xV xO3 alloy, Sc doping results in an inhomogeneous microstructure with grains containing a Sc-doped Ba-rich shell and an undoped Sr-rich core. This results from a solution-precipitation process that works in combination with a thermodynamic driving force for the preferential segregation of Sc into Ba-rich regions. The Curie temperature (T c) of Ba0.7Sr0.3TiO3 decreases with increasing dopant concentration from a T c of 40 deg. C for undoped material to 18 deg. C for 4 mol.% V and 22 deg. C for 4 mol.% Sc (i.e., Ba0.7Sr0.3Ti0.96V0.04O3, Ba0.7Sr0.3Ti0.96Sc0.04O3). Sc- and V-doped materials are found to have significantly reduced dielectric constants at their Curie temperature than their undoped counterpart. This is most evident for Sc doping, where a 4 mol.% concentration has a dielectric constant of 1000 at T c, a factor of 12 times smaller than undoped Ba0.7Sr0.3TiO3

2007-05-01

64

Structure-dielectric property relationship for vanadium- and scandium-doped barium strontium titanate  

Energy Technology Data Exchange (ETDEWEB)

This paper reports the results of an investigation of the structure-property relationship of vanadium (donor) and scandium (acceptor) doped Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3}. While V doping produces a fully miscible Ba{sub 0.7}Sr{sub 0.3}Ti{sub 1-x}V {sub x}O{sub 3} alloy, Sc doping results in an inhomogeneous microstructure with grains containing a Sc-doped Ba-rich shell and an undoped Sr-rich core. This results from a solution-precipitation process that works in combination with a thermodynamic driving force for the preferential segregation of Sc into Ba-rich regions. The Curie temperature (T {sub c}) of Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} decreases with increasing dopant concentration from a T {sub c} of 40 deg. C for undoped material to 18 deg. C for 4 mol.% V and 22 deg. C for 4 mol.% Sc (i.e., Ba{sub 0.7}Sr{sub 0.3}Ti{sub 0.96}V{sub 0.04}O{sub 3}, Ba{sub 0.7}Sr{sub 0.3}Ti{sub 0.96}Sc{sub 0.04}O{sub 3}). Sc- and V-doped materials are found to have significantly reduced dielectric constants at their Curie temperature than their undoped counterpart. This is most evident for Sc doping, where a 4 mol.% concentration has a dielectric constant of 1000 at T {sub c}, a factor of 12 times smaller than undoped Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3}.

Liu Shaojun [School of Materials, Arizona State University, Tempe, AZ 85287-6006 (United States); Zenou, V.Y. [School of Materials, Arizona State University, Tempe, AZ 85287-6006 (United States); Sus, I. [School of Materials, Arizona State University, Tempe, AZ 85287-6006 (United States); Kotani, T. [School of Materials, Arizona State University, Tempe, AZ 85287-6006 (United States); Schilfgaarde, M. van [School of Materials, Arizona State University, Tempe, AZ 85287-6006 (United States); Newman, N. [School of Materials, Arizona State University, Tempe, AZ 85287-6006 (United States)]. E-mail: nathan.newman@asu.edu

2007-05-15

65

Structure-mechanical properties relationship of poly(ethylene terephthalate) fibers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The correlation between the fiber structure and mechanical properties of two different poly(ethylene terephthalate) fiber types, that is, wool and cotton types produced by three producers, was studied. Fiber structure was determinedusing different analytical methods. Significant differences in the suprastructure of both types of conventional textile fibers were observed, although some slight variations in the structure existed between those fibers of the same type provided by different produc...

Z?iberna-s?ujica, Milena; Sfiligoj-smole, Majda

2012-01-01

66

Structure-Property Relationships in Polymer Derived Amorphous/Nano-Crystalline Silicon Carbide for Nuclear Applications  

International Nuclear Information System (INIS)

Silicon carbide (SiC) is a promising candidate for several applications in nuclear reactors owing to its high thermal conductivity, high melting temperature, good chemical stability, and resistance to swelling under heavy ion bombardment. However, fabricating SiC by traditional powder processing route generally requires very high temperatures for pressureless sintering. Polymer derived ceramic materials offer unique advantages such as ability to fabricate net shaped components, incorporate reinforcements and relatively low processing temperatures. Furthermore, for SiC based ceramics fabricated using polymer infiltration process (PIP), the microstructure can be tailored by controlling the processing parameters, to get an amorphous, nanocrystalline or crystalline SiC. In this work, fabrication of polymer derived amorphous and nano-grained SiC is presented and its application as an in-core material is explored. Monolithic SiC samples are fabricated by controlled pyrolysis of allyl-hydrido-poly-carbo-silane (AHPCS) under inert atmosphere. Chemical changes, phase transformations and microstructural changes occurring during the pyrolysis process are studied as a function of the processing temperature. Polymer cross-linking and polymer to ceramic conversion is studied using infrared spectroscopy (FTIR). Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) are performed to monitor the mass loss and phase change as a function of temperature. X-ray diffraction studies are done to study the intermediate phases and microstructural changes. Variation in density is carefully monitored as a function of processing temperature. Owing to shrinkage and gas evolution during pyrolysis, precursor derived ceramics are inherently porous and composite fabrication typically involves repeated cycles of polymer re-infiltration and pyrolysis. However, there is a limit to the densification that can be achieved by this method and porosity in the final materials presents difficulties in interpreting 'true' properties from bulk measurements. Hence, hardness and modulus measurements are carried out using instrumented nano-indentation to establish property--structure relationship for SiC derived from the polymer precursor. It is seen that the presence of nanocrystalline domains in amorphous SiC significantly influences the modulus and hardness. (authors)

2006-07-17

67

Structure-property relationships of a biological mesocrystal in the adult sea urchin spine  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Structuring over many length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, show how Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecul...

Seto, Jong; Ma, Yurong; Davis, Sean A.; Meldrum, Fiona; Gourrier, Aurelien; Kim, Yi-yeoun; Schilde, Uwe; Sztucki, Michael; Burghammer, Manfred; Maltsev, Sergey; Ja?ger, Christian; Co?lfen, Helmut

2012-01-01

68

Multiscale mechanics of hierarchical structure/property relationships in calcified tissues and tissue/material interfaces  

International Nuclear Information System (INIS)

This paper presents a review plus new data that describes the role hierarchical nanostructural properties play in developing an understanding of the effect of scale on the material properties (chemical, elastic and electrical) of calcified tissues as well as the interfaces that form between such tissues and biomaterials. Both nanostructural and microstructural properties will be considered starting with the size and shape of the apatitic mineralites in both young and mature bovine bone. Microstructural properties for human dentin and cortical and trabecular bone will be considered. These separate sets of data will be combined mathematically to advance the effects of scale on the modeling of these tissues and the tissue/biomaterial interfaces as hierarchical material/structural composites. Interfacial structure and properties to be considered in greatest detail will be that of the dentin/adhesive (d/a) interface, which presents a clear example of examining all three material properties, (chemical, elastic and electrical). In this case, finite element modeling (FEA) was based on the actual measured values of the structure and elastic properties of the materials comprising the d/a interface; this combination provides insight into factors and mechanisms that contribute to premature failure of dental composite fillings. At present, there are more elastic property data obtained by microstructural measurements, especially high frequency ultrasonic wave propagation (UWP) and scanning acoustic microscopy (SAM) techniques. However, atomic force microscopy (AFM) and nanoindentation (NI) of cortical and trabecular bone and the dentin-enamel junction (DEJ) among others have become available allowing correlation of the nanostructural level measurements with those made on the microstructural level

2007-04-01

69

Relationships between grade determining properties of Spanish scots and laricio pine structural timber  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In a. sample made up of 3312 boards of scots pine (pinus sylvestris) and 3318 boards of laricio pine pinus nigra Van Saltzmannii), both of Spanish provenance, and ranging in size from 100x40x2500 mm to 200x70x4500 mm, previously tested in accordance with the procedure set forth in UNE EN 408 standard, the relationships between the grade determining properties considered in the UNE EN 338 standard (bending strength, global and local modulus of elasticity in bending, density) are studied. In ad...

Ferna?ndez-golfi?n, J. I.; Diez, M. R.; Hermoso, E.

2003-01-01

70

Multiple Quantum NMR Investigations of Structure- Property Relationships in Synthetic and Aged Silicone Elastomers  

Energy Technology Data Exchange (ETDEWEB)

Complex engineering elastomeric materials are often characterized by a complex network structure obtained by crosslinking network chains with multiple chain lengths. Further, these networks are commonly filled with thixotropic reinforcing agents such as SiO{sub 2} or carbon black. Degradation of such materials often occurs via mechanisms that alter the fundamental network structure. In order to understand the effects of modifications of network structure and filler-polymer interaction on component performance, a series of model compounds have been studied by {sup 1}H multiple quantum NMR analysis and traditional mechanical property assessments. The {sup 1}H NMR data provides insight into the distribution of segmental dynamics that reveals insight into the changes in mechanical properties.

Maxwell, R; Gjersing, E; Chinn, S; Herberg, J; Eastwood, E; Bowen, D; Stephens, T

2006-09-27

71

Structure–property relationships in hybrid dental nanocomposite resins containing monofunctional and multifunctional polyhedral oligomeric silsesquioxanes  

Directory of Open Access Journals (Sweden)

Full Text Available Weiguo Wang,1,* Xiang Sun,1,* Li Huang,2,* Yu Gao,1 Jinghao Ban,1 Lijuan Shen,1 Jihua Chen1 1Department of Prosthodontics, 2Department of General Dentistry and Emergency, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China*These authors contributed equally to this workAbstract: Organic-inorganic hybrid materials, such as polyhedral oligomeric silsesquioxanes (POSS, have the potential to improve the mechanical properties of the methacrylate-based composites and resins used in dentistry. In this article, nanocomposites of methacryl isobutyl POSS (MI-POSS [bears only one methacrylate functional group] and methacryl POSS (MA-POSS [bears eight methacrylate functional groups] were investigated to determine the effect of structures on the properties of dental resin. The structures of the POSS-containing networks were determined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Monofunctional POSS showed a strong tendency toward aggregation and crystallization, while multifunctional POSS showed higher miscibility with the dimethacrylate monomer. The mechanical properties and wear resistance decreased with increasing amounts of MI-POSS, indicating that the MI-POSS agglomerates act as the mechanical weak point in the dental resins. The addition of small amounts of MA-POSS improved the mechanical and shrinkage properties. However, samples with a higher MA-POSS concentration showed lower flexural strength and flexural modulus, indicating that there is a limited range in which the reinforcement properties of MA-POSS can operate. This concentration dependence is attributed to phase separation at higher concentrations of POSS, which affects the structural integrity, and thus, the mechanical and shrinkage properties of the dental resin. Our results show that resin with 3% MA-POSS is a potential candidate for resin-based dental materials.Keywords: POSS, methacrylate monomer, dental resin, hybrid material, nanocomposite

Wang WG

2014-02-01

72

Thermal and radiochemical of neat and ATH filled EPDM : establishment of structure/properties relationships  

Digital Repository Infrastructure Vision for European Research (DRIVER)

EPDM elastomer is widely used as the insulation of low to medium voltage electrical cables used in power plants, for which the life-time prediction has been hampered by the lack of knowledge on structure/mechanical properties, and the nonexistence of pertinent criteria of structural failure. In an attempt to fill this gap, three EPDM matrices filled with 0, 33 and 100 phr of pristine and surface treated ATH were crosslinked by dicumyl peroxide at 170°C and, subsequently, aged thermally at 90...

2013-01-01

73

Structure/property relationships in HSLA steel with low carbon and manganese and increased silicon content  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The influence of an increased Si and reduced C and Mn content on structure and mechanical properties of HSLA steel plate with low carbon equivalent is investigated. With a C content of 0.06 ... 0.08 % Mn should be ? 0.8 %, and Si concentrations up to 1.0 % may be used. On air cooled 30 mm plate [MATH] has been obtained.

Ko?the, A.; Richter, J.; Gu?th, A.; Mu?sgen, B.; Baumgardt, H.

1993-01-01

74

A study of structure-property relationships in layered copper oxides  

CERN Document Server

described in Chapter Five. This investigation demonstrates that several intimate structure-compressibility relationships exist in these materials. Chapter Six continues the theme of high pressure crystallography, and examines, in detail, the crystal structure of HgBa sub 2 CuO sub 4 sub + subdelta using high pressure neutron diffraction methods. This study indicates that the pressure induced increase in T sub c observed in HgBa sub 2 CuO sub 4 sub + subdelta, may be related to pressure induced relief of structural strain at the interface between the rock-salt and perovskite type layers of this material. Chapter Seven examines the crystal structure of Hg sub 0 sub . sub 8 Cr sub 0 sub . sub 2 Ba sub 2 CuO sub 4 sub + subdelta under ambient and applied pressure. This study shows that significant distortions arise in the crystal structure of HgBa sub 2 CuO sub 4 sub + subdelta when linear HgO sub 2 units are substituted by tetrahedral CrO sub 4 units. Finally, Chapter Eight describes a simple method for the fabr...

Hyatt, N

2000-01-01

75

Kinetic Control of Aqueous Hydrolysis: Modulating Structure/Property Relationships in Inorganic Crystals  

Science.gov (United States)

A grand challenge in materials science and chemistry revolves around the preparation of materials with desired properties by controlling structure on multiple length scales. Biology approaches this challenge by evolving tactics to transform soluble precursors into materials and composites with macro-scale and atomic precision. Studies of biomineralization in siliceous sponges led to the discovery of slow, catalytic hydrolysis of molecular precursors in the biogenesis of silica skeletal elements with well defined micro- and nano-scale architectures. However, the role of aqueous hydrolysis in the limit of kinetic control is not well understood; this allows us to form a central hypothesis: that the kinetics of hydrolysis modulate the structures of materials and their properties. As a model system, the diffusion of a simple hydrolytic catalyst (such as ammonia) across an air-water interface into a metal salt solution reproduces some aspects of the chemistry found in biomineralization, namely kinetic and vectorial control. Variation of the catalyst concentration modulates the hydrolysis rate, and thus alters the resulting structure of the inorganic crystals. Using aqueous solutions of cobalt(II) chloride, each product (cobalt hydroxide chloride) forms with a unique composition, despite being prepared from identical mother liquors. Synchrotron X-ray total scattering methods are needed to locate the atomic positions in the material, which are not aptly described by a traditional crystallographic unit cell due to structural disorder. Detailed definition of the structure confirms that the hydrolysis conditions systematically modulate the arrangement of atoms in the lattice. This tightly coupled control of crystal formation and knowledge of local and average structures of these materials provides insight into the unusual magnetic properties of these cobalt hydroxides. The compounds studied show significant and open magnetization loops with little variation with composition or structure, yet subtle and systematic changes in the mean-field spin interaction strength and spin entropy loss. Meanwhile, neutron powder diffraction reveals a fully compensated ?eel state; a detailed analysis of the local structure defines the aperiodic clusters of polyhedra responsible for magnetic order. The rate of hydrolysis of metal precursors modulates the disposition of these polyhedral clusters. The strategy of kinetically controlling aqueous hydrolysis also extends to the formation of stoichiometrically ordered bimetallic crystals [MSn(OH)6], where the hydrolysis behavior for dissimilar metal cations must be controlled via counteranions or precursor selection. In the formation of these ordered double perovskite hydroxides, the rate of hydrolysis is held constant in the limit of kinetic control. Instead, the propensities of different cations to undergo controlled hydrolysis are probed by their ability to form ordered crystals. Collectively, these studies demonstrate how systematic variation in the kinetic conditions of materials preparation and the character of each solute control the structure and properties of materials, with a precision not attainable through traditional or near-equilibrium approaches.

Neilson, James R.

76

S09 Symposium KK, Structure-Property Relationships in Biomineralized and Biomimetic Composites  

Energy Technology Data Exchange (ETDEWEB)

The technical presentations and discussions at this symposium disseminated and assessed current research and defined future directions in biomaterials research, with a focus on structure-function relationships in biological and biomimetic composites. The invited and contributed talks covered a diverse range of topics from fundamental biology, physics, chemistry, and materials science to potential applications in developing areas such as light-weight composites, multifunctional and smart materials, biomedical engineering, and nanoscaled sensors. The invited speakers were chosen to create a stimulating program with a mixture of established and junior faculty, industrial and academic researchers, and American and international experts in the field. This symposium served as an excellent introduction to the area for younger scientists (graduate students and post-doctoral researchers). Direct interactions between participants also helped to promote potential future collaborations involving multiple disciplines and institutions.

David Kisailus; Lara Estroff; Himadri S. Gupta; William J. Landis; Pablo D. Zavattieri

2010-06-07

77

Structural-electrical-optical properties relationship of sodium superionic conductor sputter-deposited coatings  

International Nuclear Information System (INIS)

Thin films of various compositions in the Na2O-SiO2-P2O5-ZrO2 system were deposited in glassy form by reactive magnetron sputtering. An analysis by spectrophotometry showed an increase of the extinction coefficient (k) with the amount of Fe contamination. This contamination, originating from parasitic plasmas, was suppressed when convenient protections were used. Therefore, it was possible to produce optical clear films. A structural study by X-ray diffraction and Raman spectroscopy proved a reorganization in the amorphous state at low temperature and the appearance of a NASICON structure around 750 deg. C. The ionic conductivity, measured by impedance spectroscopy, and the optical properties were strongly affected by the thermal annealing process. The reorganization in the amorphous state and strong modifications of the ionic conductivity values and the refractive index (n) appeared in the same range of temperatures. This suggested a strong correlation between these different phenomena

2008-03-31

78

Structure and immunomodulatory property relationship in NapA of Borrelia burgdorferi.  

Science.gov (United States)

NapA from Borrelia burgdorferi is a member of the Dps-like protein family with specific immunomodulatory properties; in particular, NapA is able to induce the expression of IL-23 in neutrophils and monocytes, as well as the expression of IL-6, IL-1?, and transforming growth factor beta (TGF-?) in monocytes, via Toll-like receptor (TLR) 2. Such an activity on innate immune cells triggers a synovial fluid Th17 response. Here we report the crystal structure of NapA, determined at 2.6Å resolution, which shows that the quaternary structure of the protein is that of a dodecamer with 23 symmetry, typical of the proteins of the family. We also demonstrate that the N- and C-terminal tails, which are flexible and not visible in the crystal, are not relevant for its pro-Th17 activity. Based on the crystal structure and on the comparison with the structure of the orthologous protein from Helicobacter pylori, HP-NAP, we hypothesize that the charge distributions on the two proteins' surfaces are responsible for the interaction with TLR2 and for the different behaviors in modulating the immune response. PMID:20851780

Codolo, Gaia; Papinutto, Elena; Polenghi, Alessandra; D'Elios, Mario Milco; Zanotti, Giuseppe; de Bernard, Marina

2010-12-01

79

A Quantitative Structure-Property Relationship (QSPR Study of Aliphatic Alcohols by the Method of Dividing the Molecular Structure into Substructure  

Directory of Open Access Journals (Sweden)

Full Text Available A quantitative structure–property relationship (QSPR analysis of aliphatic alcohols is presented. Four physicochemical properties were studied: boiling point (BP, n-octanol–water partition coefficient (lg POW, water solubility (lg W and the chromatographic retention indices (RI on different polar stationary phases. In order to investigate the quantitative structure–property relationship of aliphatic alcohols, the molecular structure ROH is divided into two parts, R and OH to generate structural parameter. It was proposed that the property is affected by three main factors for aliphatic alcohols, alkyl group R, substituted group OH, and interaction between R and OH. On the basis of the polarizability effect index (PEI, previously developed by Cao, the novel molecular polarizability effect index (MPEI combined with odd-even index (OEI, the sum eigenvalues of bond-connecting matrix (SX1CH previously developed in our team, were used to predict the property of aliphatic alcohols. The sets of molecular descriptors were derived directly from the structure of the compounds based on graph theory. QSPR models were generated using only calculated descriptors and multiple linear regression techniques. These QSPR models showed high values of multiple correlation coefficient (R > 0.99 and Fisher-ratio statistics. The leave-one-out cross-validation demonstrated the final models to be statistically significant and reliable.

Bin Cheng

2011-04-01

80

Solvent effects on the absorption spectra of potentially pharmacologically active 5-alkyl-5-arylhydantoins: A structure-property relationship study  

Directory of Open Access Journals (Sweden)

Full Text Available To obtain an insight into the interactions of potential anticonvulsant drugs with their surrounding, two series of 5-methyl-5-aryl- and 5-ethyl-5-arylhydantoins were synthesized and their absorption spectra were recorded in the region from 200 to 400 nm in a set of selected solvents. The effects of solvent dipolarity/polarizability and solvent-solute hydrogen bonding interactions on the absorption maxima shifts were analyzed by means of the linear solvation energy relationship (LSER concept of Kamlet and Taft. The ratio of the contributions of specific and nonspecific solvent-solute interactions were correlated with the corresponding ADME properties of the studied compounds. The correlation equations were combined with different physicochemical parameters to generate new equations, which demonstrate the reasonable relationships between solvent-solute interactions and the structure-activity parameters. [Projekat Ministarstva nauke Republike Srbije, br. 172013

Hmuda Sleem F.

2013-01-01

 
 
 
 
81

Relationship between structure and creep properties of a predeformed austenitic steel  

International Nuclear Information System (INIS)

The effect that prior cold working with 7% and 14% deformation has upon the creep behaviour of AISI alloy 314 has been investigated at 900_0C. For short-term testing the pretreated condition exhibits a beneficial effect in terms of creep and rupture strength, whereas the ductility is reduced. With increasing test times the strength and ductility of the material gradually approach those of the recrystallized condition. From structural analyses it is concluded that as long as the high dislocation density associated with the preformed condition remains, the strength is increased and the grain boundaries are sensitive to crack nucleation and growth. On the basis of the observation that the creep properties recover fully it is concluded that prior cold work at the applied level does not damage the material. (author)

1981-05-20

82

Structure-Property Relationships in Solid AlF3 Lewis Acids  

International Nuclear Information System (INIS)

Understanding the structural cause of the high Lewis acidity in the novel solid Lewis acid AlF3 is of crucial importance to tailor this important material property to the specific needs of potential applications. Based on Al and F K-edge XAS studies, we are able to correlate high Lewis acidity with geometric distortions of the [AlF6] building blocks of AlF3. These distortions are induced by the presence of i-OPr ligands in the AlF3-x(i-OPr)x precursor material and can only be preserved by the application of a mild fluorinating agent like CCl2F2. High Lewis acidity is not caused by electronic modification of the aluminium atom, but by the better exposure of reactants to the acid site in the high surface area materials

2007-02-02

83

Structure and property relationships of amorphous CNx: a joint experimental and theoretical study  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Amorphous CNx and CNx:H have been prepared by the ion beam assisted deposition technique. Samples were characterized through X-ray and UV photoemission, IR absorption and Raman spectroscopies. These spectra have been interpreted with the aid of quantum chemical calculations based upon the Hartree-Fo [...] ck theory on several molecular models. The understanding of the electronic and structural properties of the amorphous alloy as a function of nitrogen content could help in the task of synthesizing the metastable silicon-nitride like-phase beta-C3N4 , a solid which has been predicted to be as hard as diamond. The physical picture emerging from the present study helps to clarify the difficulties in obtaining the crystalline phase of the material, suggesting new experimental directions for syntheses.

M.C. dos, Santos; F., Alvarez.

84

Structure and property relationships of amorphous CN sub x a joint experimental and theoretical study  

CERN Document Server

Amorphous CN sub x and CN sub x :H have been prepared by the ion beam assisted deposition technique. Samples were characterized through X-ray and UV photoemission, IR absorption and Raman spectroscopies. These spectra have been interpreted with the aid of quantum chemical calculations based upon the Hartree-Fock theory on several molecular models. The understanding of the electronic and structural properties of the amorphous alloy as a function of nitrogen content could help in the task of synthesizing the metastable silicon-nitride like-phase beta-C sub 3 N sub 4 , a solid which has been predicted to be as hard as diamond. The physical picture emerging from the present study helps to clarify the difficulties in obtaining the crystalline phase of the material, suggesting new experimental directions for syntheses.

Santos, M C D

2000-01-01

85

Structure-Property Relationships in Dual-Phase Cu-Al Alloys: Part II. Alloy Behavior  

Science.gov (United States)

The mechanical behavior of dual-phase Cu-Al alloys was investigated and properties were correlated to the relevant parameters: martensite volume fraction, martensite strength, and dual-phase morphology. The yield strength is markedly influenced by all parameters, being an increasing function of both martensite fraction and strength. With respect to component phases it is established that such function does not follow the law of mixtures. On the other hand, ultimate tensile strength exhibits linear dependence on volume fraction of martensite. On comparing theory with experiment, good agreement was established between true uniform strains calculated according to Mileiko's theory of composites and experimental results. High ductility levels are reachable over a rather broad range of martensite volume fraction. Depending on quench temperature, enhancement of ductility occurs via stress-induced phase transformation of martensite to fcc structure. Macrohardness measurements carried out on dual-phase structures showed linear dependence on martensite volume fraction. The data indicate that macrohardness could be predicted via linear combination of microhardness of component phases and their volume fractions. Strengthening of dual-phase alloys could be achieved, at practically no loss of ductility, by means of short time annealing. Moreover, remarkable strengthening is attainable via combinations of cold work and annealing while maintaining useful levels of ductility.

Hussein, A. A.

1982-05-01

86

Structure-property relationship of anilino-squaraines in organic solar cells.  

Science.gov (United States)

Soluble molecular semiconductors are a promising alternative to semiconducting polymers in the field of organic photovoltaics. Here, three custom-made symmetric 1,3-bis(N,N-alkylated-2,6-dihydroxy-anilino)squaraines containing systematic variations in their molecular structures are compared regarding their applicability as donor materials in bulk-heterojunction solar cells. The terminal substitution pattern of the squaraines is varied from cyclic over linear to branched including a stereogenic center. Single crystal structures are determined, and, in the case of chiral squaraine, unusual formation of stereoisomer co-crystals is revealed. The thin film absorbance spectra show characteristic signatures of H- and J-bands or hint at the formation of tautomers. The general feasibility of these model compounds for photovoltaic applications is studied by light-induced electron spin resonance spectroscopy. The impact of the different molecular substitution patterns on aggregation behavior and, consequently, their optoelectronic solid state properties including charge carrier mobility and finally the solar cell performance are investigated. PMID:24288034

Brück, S; Krause, C; Turrisi, R; Beverina, L; Wilken, S; Saak, W; Lützen, A; Borchert, H; Schiek, M; Parisi, J

2014-01-21

87

The structure-property relationships of powder processed Fe-Al-Si alloys  

Energy Technology Data Exchange (ETDEWEB)

Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic %). The powder alloys were produced with a high pressure gas atomization (HPGA) process to obtain a high fraction of metal injection molding (MIM) quality powder (D{sub 84} < 32 {micro}m). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 {micro}m. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 {micro}m to 104 {micro}m. Mechanical property testing was conducted on both extruded and sintered material using a small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25 to 550 C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase {alpha} + DO{sub 3} structure. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.

Prichard, P.D.

1998-02-23

88

Structure/property relationships in methacrylate/dimethacrylate polymers for dental applications  

Science.gov (United States)

Since its invention Bis-GMA or one of its analogs has been the main component of the polymer portion of composites for dental restorations. The need for dilution of Bis-GMA and its analogs to optimize its properties has long been recognized. Bis-GMA is a highly viscous monomer. This high viscosity leads to early vitrification, which limits conversion during cure. This viscosity also limits filler loading. Vitrification at low conversions leads to heterogeneous systems composed of low and high cross-link density phases. The low cross-link density phases behave as defects in the system; therefore, if the amount of low cross-link density phases in the system can be reduced and a more uniform network structure can be achieved, then the mechanical properties of the resin can be improved. Since the increase in viscosity during cure causes vitrification, it is logical that a system with a low initial viscosity will delay the onset of vitrification. Reactive diluents such as triethylene glycol dimethacrylate (TEGDMA) are effective at lower levels. However, large amounts negatively affect matrix properties by increasing polymerization shrinkage and water sorption. Shrinkage has been cited as one of the main deficiencies in dental composites. The goal of this project is to improve upon standard viscosity modifying comonomers such as triethylene glycol dimethacrylate. The comonomers that were explored were phenyloxyethyl methacrylate, cyclohexyl methacrylate, and tert-butylcylcohexyl methacrylate. Multicomponent systems based on analogs of ethylene glycol dimethacrylates with different length ethyl glycol chains were also examined. The substitution of monomethacrylates for TEGDMA as a comonomer resulted in enhanced or negligible affects on the mechanical properties of Bis-MEPP based polymer systems while reducing polymerization shrinkage. 129Xenon NMR and TappingMode(TM) AFM were used to characterize the heterogeneity of dimethacrylates systems during their cure cycle as well as in their final state. Using these methods the size of the high and low cross-link density phase was examined and determined to be on the order of 50--150 nanometers. Model compounds based on phenylethyl methacrylate were formulated to determine how of nadic methyl anhydride and maleic anhydride incorporate into dimethacrylate resin systems.

Mehlem, Jeremy John

89

Structure-Property Relationships of Inorganically Surface-Modified Zeolite Molecular Sieves for Nanocomposite Membrane Fabrication  

Energy Technology Data Exchange (ETDEWEB)

A multiscale experimental study of the structural, compositional, and morphological characteristics of aluminosilicate (LTA) and pure-silica (MFI) zeolite materials surface-modified with MgO{sub x}H{sub y} nanostructures is presented. These characteristics are correlated with the suitability of such materials in the fabrication of LTA/Matrimid mixed-matrix membranes (MMMs) for CO{sub 2}/CH{sub 4} separations. The four functionalization methods studied in this work produce surface nanostructures that may appear superficially similar under SEM observation but in fact differ considerably in shape, size, surface coverage, surface area/roughness, degree of attachment to the zeolite surface, and degree of zeolite pore blocking. The evaluation of these characteristics by a combination of TEM, HRTEM, N{sub 2} physisorption, multiscale compositional analysis (XPS, EDX, and ICP-AES elemental analysis), and diffraction (ED and XRD) allows improved understanding of the origin of disparate gas permeation properties observed in MMMs made with four types of surface-modified zeolite LTA materials, as well as a rational selection of the method expected to result in the best enhancement of the desired properties (in the present case, CO{sub 2}/CH{sub 4} selectivity increase without sacrificing permeability). A method based on ion exchange of the LTA with Mg{sup 2+}, followed by base-induced precipitation and growth of MgOxHy nanostructures, deemed 'ion exchange functionalization' here, offers modified particles with the best overall characteristics resulting in the most effective MMMs. LTA/Matrimid MMMs containing ion exchange functionalized particles had a considerably higher CO{sub 2}/CH{sub 4} selectivity (40) than could be obtained with the other functionalization techniques (30), while maintaining a CO{sub 2} permeability of 10 barrers. A parallel study on pure silica MFI surface nanostructures is also presented to compare and contrast with the zeolite LTA case.

Lydon, Megan E [Georgia Institute of Technology; Unocic, Kinga A [ORNL; Jones, Christopher W [Georgia Institute of Technology; Nair, Sankar [Georgia Institute of Technology

2012-01-01

90

Structure and properties relationships of beta-Al2O3 electrolyte materials  

International Nuclear Information System (INIS)

Highlights: ? The ?” phase of beta-Al2O3 was stable in high temperature and the ?” phase content increased with the sintering temperature increasing by the addition of the stabilizers. ? By using NMR, ?Al(VI) and ?Al(IV) of beta-Al2O3 moved towards down field in different systems with different stabilizers. Li+ and Mg2+ ions substituted the octahedron and tetrahedral Al3+ ions in the spinel blocks respectively, and Mg2+ stabilizer was more benefit to improve the symmetry of Al(VI) of the beta-Al2O3 than Li+ stabilizer. ? The amounts ratio of octahedron and tetrahedron (AAl(VI)/AAl(IV)) of beta-Al2O3 decreased with the ?” phase content increasing. - Abstract: Beta-Al2O3 electrolyte materials were synthesized by solid-state reaction method in this paper. The effect of different stabilizers on the ?”-phase content of the beta-Al2O3 electrolyte and the structures of aluminum-oxide polyhedron were investigated by X-ray diffraction technology (XRD) and 27Al MAS NMR, and the relationship between the ?” phase content and the amounts ratio of octahedron and tetrahedron (AAl(VI)/AAl(IV)) was summarized. The results showed that the ?” phase was stable at high temperatures and the ?” phase content increased with the temperature increasing by the addition of the stabilizers. Meanwhile, ?Al(IV) and ?Al(VI) moved towards down field, and AAl(VI)/AAl(IV) decreased with the ?” phase content increasing. The Mg2+ stabilizer was better to improve the symmetry of Al(VI) than the Li+ stabilizer.

2012-03-15

91

Relationships between grade determining properties of Spanish scots and laricio pine structural timber  

Directory of Open Access Journals (Sweden)

Full Text Available In a. sample made up of 3312 boards of scots pine (pinus sylvestris and 3318 boards of laricio pine pinus nigra Van Saltzmannii, both of Spanish provenance, and ranging in size from 100x40x2500 mm to 200x70x4500 mm, previously tested in accordance with the procedure set forth in UNE EN 408 standard, the relationships between the grade determining properties considered in the UNE EN 338 standard (bending strength, global and local modulus of elasticity in bending, density are studied. In addition to these variables, the modulus of elasticity was also considered, calculated by means of the measuring of the transmission speed of an ultrasonic pulse generated by a Sylvatest device. The global modulus of elasticity calculated by measuring the deformation at the neutral axis seems to be the best predictor of the ultimate bending strength, while the local modulus of elasticity proves to be difficult to obtain, and has a lower predictive quality, and so its elimination is suggested. The need to consider one single testing procedure to determine the global modulus of elasticity is also analyzed, along with the convenience of carrying out further studies regarding the use of ultrasonic techniques in order to predict the modulus of elasticity, due to the fact that the systems available are not sufficiently precise.

En una muestra compuesta por 3.312 piezas de madera aserrada de pino laricio (pimis nigra y 3.318 piezas de pino silvestre (pinus sylvestris de procedencia española y con dimensiones que varían entre 100x40x2.500 mm y 200x70x4.500 mm, previamente ensayada a flexión de acuerdo con el procedimiento descrito en la norma UNE EN 408, se analizan las relaciones existentes entre las propiedades indicadoras establecidas en la norma UNE EN 338 (resistencia última a flexión, módulos de elasticidad global y local en flexión, densidad. Adicionalmente a estas variables se determinó también el módulo de elasticidad obtenido mediante la medición de la velocidad de propagación de pulsos ultrasónicos generados por un equipo Sylvatest. El módulo de elasticidad global determinado mediante la medición de la deformación en la fibra neutra demuestra ser el mejor predictor de la resistencia última a la flexión, en tanto que el módulo de elasticidad local resulta ser de difícil ensayo y de inferior calidad predictiva, de donde sugiere su eliminación. Se concluye también sobre la necesidad de considerar un único ensayo para la determinación del módulo de elasticidad global y la conveniencia de seguir trabajando sobre la determinación del módulo de elasticidad mediante técnicas de ultrasonidos ya que los actuales sistemas disponibles todavía no alcanzan el suficiente grado de precisión.

Fernández-Golfín, J. I.

2003-06-01

92

Structure-property relationship in polyethylene reinforced by polyethylene-grafted multi-walled carbon nanotubes.  

Science.gov (United States)

Polyethylene-grafted multiwalled carbon nanotubes (PE-g-MWNT) were used to reinforce polyethylene (PE). The nanocomposites possessed not only improved stiffness and strength, but also increased ductility and toughness. The effects on the structure and morphology of composites due to pristine multiwalled carbon nanotubes (MWNT) and PE-g-MWNT were studied and compared using small angle X-ray scattering (SAXS), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The SAXS long period, crystalline layer thickness and crystallinity of polymer lamellar stacks were found to decrease significantly in MWNT composites, while the decreases were much smaller in PE-g-MWNT composites. PE-g-MWNT allowed a more efficient and unhindered crystallization at a lamellar level, while MWNT disrupted the order of lamellar stacks, probably because of their tendency to aggregate. The SAXS crystallinity and the mechanical properties of the composites showed similar trends as a function of MWNT content. This suggested that the improvement of the interfacial strength between polymer and carbon nanotubes was a result of synergistic effects of better dispersion of the filler, better stress transfer, due to the grafting of polymer and MWNT, and the nucleation of a crystalline phase around MWNT. The latter effect was confirmed by measurements of kinetics of non-isothermal crystallization. PMID:18572579

Causin, Valerio; Yang, Bing-Xing; Marega, Carla; Goh, Suat Hong; Marigo, Antonio

2008-04-01

93

Structure-property relationships in multilayered polymeric system and olefinic block copolymers  

Science.gov (United States)

Chapter 1. The effect of tie-layer thickness on delamination behavior of polypropylene/tie-layer/Nylon-6 multilayers is examined in this study. Various maleated polypropylene resins were compared for their effectiveness as tie-layers. Delamination failure occurred cohesively in all the multilayer systems. Two adhesion regimes were defined based on the change in slope of the linear relationship between the delamination toughness and the tie-layer thickness. The measured delamination toughness of the various tie-layers was quantitatively correlated to the damage zone length formed at the crack tip. In addition, the effect of tie-layer thickness on the multilayer tensile properties was correlated with the delamination behavior. The fracture strain of the multilayers decreased with decreasing tie-layer thickness. Examination of the prefracture damage mechanism of stretched multilayers revealed good correlation with the delamination toughness of the tie-layers. In thick tie-layers (>2microm) the delamination toughness of the tie-layers was large enough to prevent delamination of multilayers when they were stretched. In the thin tie-layers (toughness of all the tie-layers is low and consequently delamination led to premature fracture in stretched multilayers. Chapter 2. The kinetics of interdiffusion in the layer multiplying coextrusion process was studied between the miscible Nylon-6 and EVOH pair. The interdiffusion was followed by studying multilayer films of alternating Nylon-6 and EVOH layers that were coextruded with increasing number of layers. The AFM confirmed that the layers interdiffused with increasing number of layers and were forced to a homogeneous blend after several multiplications. The oxygen permeability of Nylon-6/EVOH multilayers was strongly affected by the amount of interdiffusion. The symmetry of the multilayers made it possible to model the composition profile through the layer thickness by application of Fick's law of diffusion. Subsequently, the oxygen permeability was directly related to the composition profile in each layer and changed as the interdiffusion proceeded. This methodology enabled the extraction of the mutual diffusion co-efficient, D, for the Nylon-6/EVOH system. The effect of comonomer content in EVOH on the mutual diffusion coefficient was also studied by comparing the kinetics of interdiffusion of Nylon-6 with two EVOHs containing 24 and 44 mole % ethylene. Chapter 3. Exciting new developments in polyolefin synthesis give rise to olefinic block copolymers with properties typical of thermoplastic elastomers. The block copolymers synthesized by chain shuttling technology consist of crystallizable ethylene-octene blocks with low comonomer content and high melting temperature (hard blocks), alternating with amorphous ethylene-octene blocks with high comonomer content and low glass transition temperature (soft blocks). This study describes the material science of these unique polymers as characterized by thermal analysis, X-ray diffraction, microscopy, and tensile deformation. The crystallizable blocks are long enough to form well-organized lamellar crystals with the orthorhombic unit cell and high melting temperature. The lamellae are organized into space-filling spherulites in all compositions even in copolymers with only 18 wt% hard block. The morphology is consistent with crystallization from a miscible melt. Crystallization of the hard blocks forces segregation of the noncrystallizable soft blocks into the interlamellar regions. Good separation of hard and soft blocks in the solid state is confirmed by distinct and separate beta- and alpha-relaxations in all the block copolymers. Compared to statistical ethylene-octene copolymers, the blocky architecture imparts a substantially higher crystallization temperature, a higher melting temperature and a better organized crystalline morphology, while maintaining a lower glass transition temperature. The differences between blocky and statistical copolymers become progressively more apparent as the total c

Khariwala, Devang

94

Investigation on the structure-electrical property relationship of hydrolyzed poly(vinyl alcohol) membranes  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in english This investigation explored the effects of the pre-treatment temperature on the molecular conformations and electrical performance of poly(vinyl alcohol) (PVOH) membranes. The structure and properties of the membranes were characterized by X-ray diffraction (XRD), differential scanning calorimetry ( [...] DSC), thermogravimetric analysis (TGA), Raman scattering (RS) and impedance measurements (IE). Water molecules absorbed by the PVOH membranes, which decreased in quantity as the temperature increased caused drastic change to be observed in the relative band intensities of the OH and CH2 bonds with respect to the C-C bonds. The observations for the hydrated PVOH were correlated with the proton transport behavior, which were inferred from conductivity relaxation measurements over various temperature regions and were dependent on the water content in the membrane. The results were corroborated by DSC and TGA. For example, the temperature dependence of the conductivity relaxation frequency, ?max, followed different Arrhenius-type thermally activated processes at low and high temperatures. The corresponding activation energies in the low and high temperature regions were: 1.42±0.02 and 0.23±0.02 eV, respectively. In addition, the selected fitting temperature regions and activation energies for the ?max data were equivalent (within experimental error) to the values for the dc-conductivity, ?0(T). This result indicates that the mechanisms for long range ion displacement (dc conductivity) and ion-ion or ion-polymer chain correlations are identical, (i.e., an ion-hoping occurred in the various hydrated phases of PVOH).

Jurado, J.F.; Checa, O.; Vargas, R.A..

95

Electron Backscatter Diffraction: An Important Tool for Analyses of Structure-Property Relationships in Thin-Film Solar Cells  

Science.gov (United States)

The present work gives an overview of the application of electron backscatter diffraction (EBSD) in the field of thin-film solar cells, which consist of stacks of polycrystalline layers on various rigid or flexible substrates. EBSD provides access to grain-size and local-orientation distributions, film textures, and grain-boundary types. By evaluation of the EBSD patterns within individual grains of the polycrystalline solar cell layers, microstrain distributions also can be obtained. These microstructural properties are of considerable interest for research and development of thin-film solar cells. Moreover, EBSD may be performed three-dimensionally, by alternating slicing of cross sections in a focused ion-beam machine and EBSD acquisition. To relate the microstructural properties to the electrical properties of individual layers as well as to the device performances of corresponding solar cells, EBSD can be combined with electron-beam-induced current and cathodoluminescence measurements and with various scanning-probe microscopy methods such as Kelvin-probe force, scanning spreading resistance, or scanning capacitance microscopy on identical specimen positions. Together with standard device characterization of thin-film solar cells, these scanning microscopy measurements provide the means for extensive analysis of structure-property relationships in solar-cell stacks with polycrystalline layers.

Abou-Ras, D.; Kavalakkatt, J.; Nichterwitz, M.; Schäfer, N.; Harndt, S.; Wilkinson, A. J.; Tsyrulin, K.; Schulz, H.; Bauer, F.

2013-09-01

96

Investigation of structure-property relationships in materials using Ab-initio and Semi-empirical methods  

Science.gov (United States)

Structure-property relationships of two crystal structures were investigated using computational methodologies in two different length scales:electronic and atomistic length scales. Electronic structure calculations were performed using density functional theory (DFT) with generalized gradient approximation (GGA), GGA+U (U is "on-site" electron-electron repulsion) and hybrid functional forms. Atomistic calculations were performed utilizing the semi-empirical interatomic formulation, Modified Embedded Atom Method (MEAM). Classical molecular dynamics simulations were performed on the atomistic length scale in order to investigate thermal properties. In the first study, structural, elastic and thermal properties of cementite (Fe3C) were investigated using a Modified Embedded Atom Method (MEAM) potential for iron-carbon (Fe-C) alloys. Previously developed Fe and C single element potentials were used to develop a Fe-C alloy MEAM potential, using a statistically-based optimization scheme to reproduce structural and elastic properties of cementite, the interstitial energies of C in bcc Fe as well as heat of formation of Fe-C alloys in L12 and B1 structures. The stability of cementite at high temperatures was investigated by molecular dynamics simulations. The nine single crystal elastic constants for cementite were obtained by computing total energies for strained cells. Polycrystalline elastic moduli for cementite were calculated from the single crystal elastic constants of cementite. The formation energies of (001), (010), and (100) surfaces of cementite were also calculated. The melting temperature and the variation of both the specific heat and volume with respect to temperature were investigated by performing a two-phase (solid/liquid) molecular dynamics simulation of cementite. The predictions of the potential are in good agreement with first-principles calculations and experiments. In the second study the site occupancy and magnetic properties of Zn-Sn substituted M-type Sr-hexaferrite (SrFe12-x(Zn0.5Sn 0.5)xO19 with x = 1) were investigated using first principles total-energy calculations. We find that in the ground-state configuration Zn-Sn ions preferentially occupy 4f1 and 4 f2 sites unlike the model previously suggested by Ghasemi et al. where Zn-Sn ions occupy 2b and 4f2 sites. Our model predicts a rapid increase in saturation magnetic moment as well as decrease in magnetic anisotropy compared to the pure M-type Sr-hexaferrite, which is consistent with experimental observations.

Liyanage, Laalitha S. I.

97

The geometric properties of reduced canonically symplectic spaces with symmetry, their relationship with structures on associated principal fiber bundles and some applications. Part 1  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The canonical reduction method on canonically symplectic manifolds is analized in detail, the relationships with the geometric properties of associated principal fiber bundles endowed with connection structures are stated. Some results devoted to studying geometrical properties of nonabelian Yang–Mills type gauge field quations are presented.

Prykarpatsky, Yarema A.; Samoilenko, Anatoliy M.; Prykarpatsky, Anatoliy K.

2005-01-01

98

Oligomeric surfactants as novel type of amphiphiles : structure - property relationships and behaviour with additives  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The properties of a series of well-defined new surfactant oligomers (dimers to tetramers)were examined. From a molecular point of view, these oligomeric surfactants consist of simple monomeric cationic surfactant fragments coupled via the hydrophilic ammonium chloride head groups by spacer groups (different in nature and length). Properties of these cationic surfactant oligomers in aqueous solution such as solubility, micellization and surface activity, micellar size and aggregation number we...

Wattebled, Laurent

2006-01-01

99

Imidazolium 2-substituted 4,5-dicyanoimidazolate ionic liquids: synthesis, crystal structures and structure-thermal property relationships.  

Science.gov (United States)

Thirty six novel ionic liquids (ILs) with 1-butyl-3-methylimidazolium and 3-methyl-1-octylimidazolium cations paired with 2-substitited 4,5-dicyanoimidazolate anions (substituent at C2=chloro, bromo, methoxy, vinyl, amino, methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl and phenyl) have been synthesized and characterized by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and single-crystal X-ray crystallography. The effects of cation and anion type and structure on the thermal properties of the resulting ionic liquids, including several room temperature ionic liquids (RTILs) are examined and discussed. ILs exhibited large liquid and crystallization ranges and formed glasses on cooling with glass transition temperatures in the range of -22 to -68?°C. The effects of alkyl substituents of the imidazolate anion reflected the crystallization, melting points and thermal decomposition of the ILs. The Coulombic packing force, van der Waals forces and size of the anions can be considered for altering the thermal transitions. Three crystal structures of the ILs were determined and the effects of changes to the cations and anions on the packing of the structure were investigated. PMID:24888334

Mondal, Suvendu Sekhar; Müller, Holger; Junginger, Matthias; Kelling, Alexandra; Schilde, Uwe; Strehmel, Veronika; Holdt, Hans-Jürgen

2014-06-23

100

Structure-property relationships in sol-gel-derived thin films  

Energy Technology Data Exchange (ETDEWEB)

The molecular-scale species distributions and intermediate-scale structure of silicate sols influence the microstructures of the corresponding thin films prepared by dip-coating. Using multi-step hydrolysis procedures, the authors find that, depending on the sequence and timing of the successive steps, the species distributions (determined by {sup 29}Si NMR) and intermediate scale structure (determined by SAXS) can change remarkably for sols prepared with the same nominal composition. During film formation, these kinetic effects cause differences in the efficiency of packing of the silicate species, leading to thin film structures with different porosities.

Brinker, C.J. [Sandia National Labs., Albuquerque, NM (United States). Ceramic Synthesis and Inorganic Chemistry Dept.]|[Univ. of New Mexico, Albuquerque, NM (United States). Center for Micro-Engineering Ceramics; Raman, N.K.; Sehgal, R.; Hua, D.W.; Ward, T.L. [Univ. of New Mexico, Albuquerque, NM (United States). Center for Micro-Engineering Ceramics; Logan, M.N.; Assink, R.A. [Sandia National Labs., Albuquerque, NM (United States)

1994-08-01

 
 
 
 
101

Multiple Quantum NMR Investigations of Structure Property Relationships in Synthetic and Aged Silicone Elastomers.  

Science.gov (United States)

Complex engineering elastomeric materials are often characterized by a complex network structure obtained by crosslinking network chains with multiple chain lengths. Further, these networks are commonly filled with thixotropic reinforcing agents such as S...

E. Eastwood E. Gjersing J. Herberg R. Maxwell S. Chinn T. Stephens

2006-01-01

102

Polyamides nanoparticles containing flexible linkages and their copper complexes with novel dielectric properties: Structure-property relationship  

Science.gov (United States)

We report the chemistry of nanometer-sized spherical aramides nanoparticles and their copper complexes as novel types of hybrids nanomaterials. Based on the flexible linkage type, the average diameters of the nanoparticles-containing sulfone or ether linkage were 140 nm and 190 nm, respectively, as judged by the scanning electron microscopy (SEM) photographs. Incorporation of copper (II) ions into these particles furnished polymeric complexes in (1:2) ratios with square planar geometries. The polymeric structures were proved on the basis of their IR, UV, ESR and elemental analysis data. The thermal properties of the polymers were evaluated by various techniques and results revealed the high thermal stabilities of the hybrids. The calculated limiting oxygen index (LOI) indicates that such macromolecules can be classified as self-extinguishing polymers. The dc electrical conductivity of all samples indicates either semi-conducting or metal-like nature in the regime of semiconductor behaviors. Incorporation of copper significantly improved the conductivity of the resulting complexes due to the enhanced mobility of the charge carriers upon doping. Dielectric losses are characterized by sharp peaks appearing at characteristic frequencies suggesting the presence of relaxing dipoles. The peak positions did not change with temperature indicating a non-activated process. The loss tangent increased with frequency and the peaks shifted toward the lower frequency upon doping suggesting the increase in the energy loss ratio compared to the energy storage in the dielectric. The higher value of dielectric loss at low frequency is due to the free charge motion within the materials. The reported dielectric results revealed anomalous behaviors which have not been reported earlier in similar hybrids.

Hassan, Hammed H. A. M.; Elhusseiny, Amel F.; Sweyllam, Amr M.

2011-08-01

103

Crystal structures and enzymatic properties of three formyltransferases from archaea: Environmental adaptation and evolutionary relationship  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Formyltransferase catalyzes the reversible formation of formylmethanofuran from N5-formyltetrahydromethanopterin and methanofuran, a reaction involved in the C1 metabolism of methanogenic and sulfate-reducing archaea. The crystal structure of the homotetrameric enzyme from Methanopyrus kandleri (growth temperature optimum 98°C) has recently been solved at 1.65 ? resolution. We report here the crystal structures of the formyltransferase from Methanosarcina barkeri (growth temperature optimu...

Mamat, Bjo?rn; Roth, Annette; Grimm, Clemens; Ermler, Ulrich; Tziatzios, Christos; Schubert, Dieter; Thauer, Rudolf K.; Shima, Seigo

2002-01-01

104

Systematic synthesis and study of the structure-property relationships of arylene vinylene polymers.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Much is known about the electronic, vibrational and steric effects resulting from the addition of differing organic functional groups as side chains, to the parent conjugated polymer. However the same cannot be said about the substitution of constituents of the polymer backbone itself. To this end a study is presented here which systematically studies the effects of naphthalene and anthracene substitution of the properties of poly phenylene vinylene (PPV) derivative conjugated polymers. The s...

2008-01-01

105

Exploring the Nanoworld with LEGO Bricks: Structure-Property Relationships at the Nanoscale  

Science.gov (United States)

In this activity (pages 32-41), learners learn how the atomic and molecular arrangement of matter are related to physical properties. This activity also introduces materials at the cutting edge of nanoscale science and technology, where the size of individual solid particles of material approaches molecular dimensions. Learners learn about concepts like polymer cross-linking, giant magnetoresistance, and plasmon resonance. Additional instructions are provided in Appendices 3.2 and 3.6.

University, Bradley

2012-01-01

106

Tribology, UV degradation, and structure-property-processing relationships of detonation nanodiamond-polyethylene nanocomposites  

Science.gov (United States)

Nanoscale reinforcements offer the possibility of coupling the already proven high strength to weight properties of polymer matrix composites with additional multifunctional properties such as electrical conductivity, thermal conductivity, unique optics, UV/IR radiation absorption, and enhanced wear resistance. This work presents materials based on detonation nanodiamonds dispersed in two types of polyethylene. The work begins with an understanding of nucleation phenomena. It was discovered through isothermal kinetics using differential scanning calorimetry that nanodiamonds act as nucleating agents during polyethylene crystallization. A processing technique to disperse nanodiamonds into very viscous ultra-high molecular weight polyethylene was developed and analyzed. These composites were further studied using dynamic mechanical analysis which showed increases in both stiffness and energy absorbing modes over unfilled UHMWPE. Exposure to UV degradation caused a failure of the polymer microstructure which was found to be caused by residual tensile stresses between the polymer particles formed during processing. These high stress regions were more prone to photo oxidation even though the nanodiamond particles were shown to decrease surface oxidation. Additionally, the tribological properties of UHMWPE/nanodiamond composites were investigated. Ultra-high molecular weight polyethylene is an already proven ultra tough and wear resistant polymer that is used in many high performance thermoplastic applications such as bearings, surfaces (skids/wheels), ropes/nets, and orthopedic implants. This work showed that UHMWPE loaded with 5.0wt% nanodiamonds might be a candidate to replace the currently used crosslinked polyethylene material used in orthopedic implants.

Tipton, John

107

Some aspects of the structure-property relationships in 12% Cr steels  

International Nuclear Information System (INIS)

The inter-relations between solution treatment and tempering conditions and the microstructure, impact and 5500C stress-rupture properties of 12% Cr steels containing Mo, V and Nb additions have been avaluated. It was shown that reductions in impact transition temperature and increases in toughness and rupture ductility could be achieved, by suitable choice of heat treatment, but only at the expense of lowering the rupture strength. Inclusion shape control additions (Ze or rare earths) to the 12% CrMoVNb steel minimised directional anisotropy of toughness but marginally reduced the rupture strength and increased the rupture ductility. (author)

1977-06-02

108

Thermal properties and nanodispersion behavior of synthesized β-sitosteryl acyl esters : A structure-activity relationship study  

DEFF Research Database (Denmark)

The efficiency (dose response) of cholesterol-lowering effect of phytosterols in humans depends on their chemical forms (derived or non-derived) and formulation methods in a delivery system. With a series of synthesized β-sitosteryl fatty acid esters (C2:0-C18:0 and C18:1-C18:3), this work examined their thermal properties and applications in preparation of nanodispersion with β-sitosterol as a comparison. Inspection of the melting point (Tm) and the heat of fusion (Î?H) of β-sitosteryl fatty acid esters and the chain length and unsaturation degree of fatty acyl moiety revealed a pronounced structure-property relationship. The nanodispersions prepared with β-sitosterol and β-sitosteryl saturated fatty acid (SFA) esters displayed different particle size distribution patterns (polymodal vs bimodal), mean diameter (115nm vs less than 100nm), and polydispersity index (PDI) (0.50 vs 0.23-0.38). β-sitosteryl unsaturated fatty acid (USFA) esters showed a distinctly different dispersion behavior to form nanoemulsions,rather than nanodispersions, with more homogeneous particle size distribution (monomodal, mean diameter 27-63nm and PDI 0.18-0.25). The nanodispersion of β-sitosteryl medium chain SFA ester (C14:0) demonstrated a best storage stability.

Panpipat, Worawan; Dong, Mingdong

2013-01-01

109

Structure-property relationships in flavour-barrier membranes with reduced high-temperature diffusivity  

International Nuclear Information System (INIS)

Encapsulation is used to decrease the premature release of volatile flavour ingredients while offering protection against environmental damage such as oxidation, light-induced reactions, etc. Hydroxypropyl cellulose (HPC) is investigated here as a 'smart,' temperature responsive membrane for flavour encapsulation and delivery. Gel films were synthesized and characterized by diffusion and small-angle neutron and X-ray scattering techniques. Increasing temperature typically increases the diffusion rate across a membrane; HPC, however, can be tailored to give substantially improved elevated temperature properties. Scattering results indicate processing conditions have a significant impact on membrane morphology (micro phase separation). Under certain synthetic conditions, micro phase separation is mitigated and the membranes show temperature-independent diffusivity between 25 C and 60 C.

2009-01-01

110

Predicting the adsorption properties of carbon dioxide corrosion inhibitors using a structure-activity relationship  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a study of the influence of various chemical inhibitors on the corrosion rate of mild steel in brine electrolyte under carbon dioxide conditions. The performances as corrosion inhibitors were fitted to a Temkin adsorption isotherm, and various constants of adsorption (i.e., adsorption equilibrium constants and molecular interaction constants) have been obtained. The inhibitor adsorption mechanism has been discussed in terms of thermodynamics (i.e., {delta}H, {delta}G and {delta}S) and this revealed that some compounds chemisorbed onto the steel electrode. In addition, molecular modelling was undertaken using PCSPARTAN Plus and HyperChem Professional, and the various molecular parameters have been correlated with the thermodynamic adsorption properties of the inhibitors. A four-parameter fit for both negative and positive charged molecules is discussed. (authors)

Kinsella, B.; De Marco, R.; Jefferson, A.; Pejcic, B. [Western Australian Corrosion Research Group, Department of Applied Chemistry, Curtin University of Technology, GPO Box U1987, Perth, 6845, WA (Australia); Durnie, W. [Nalco/Exxon Energy Chemicals Ltd, Hardley, Hythe, Southampton (Australia)

2004-07-01

111

Use of Quantitative Structure-Property Relationships in Predicting the Krafft Point of Anionic Surfactants  

Directory of Open Access Journals (Sweden)

Full Text Available The Krafft point is the temperature at which the solubility of hydrated surfactants crystals increases sharply with increasing temperature. Also, the concentration at which micelles are formed at the Krafft temperature is the critical micelle concentration (CMC. Therefore, knowing the Krafft point and CMC of the surfactants is important and one should have information about the conditions in which a surfactant acts. This is useful to select an appropriate surfactant for a special application. The linear relationship between the descriptors and Krafft point of anionic surfactants was modeled using multiple linear regression technique. Linear models were generated using a stepwise regression model. A set of 32 linear alkyl sulfates [RSO4Na] and sulfonates [RSO3Na], sulfates and sulfunates with an ether or ester linkage to the hydrophobic tail [R(OCH2CH2nSO4Na], [RCOO(CH2nSO3Na] were used for model generation. Among different models, two equations were selected for their good statistical results. Specification of the best model in agreement with the experiment indicates that four descriptors consisting of the Randic index, heat of formation, reciprocal of the dipole moment, and reciprocal of the volume of tail of the molecule play a major role in the prediction of Krafft point of anionic surfactants. The statistics of the best models together with the cross-validation results indicate the capability of both models in predicting the Krafft point of anionic surfactants. Different strategies, including the Akaike Information Criterion (AIC, were used for choosing the best model. It was demonstrated that the Krafft point of these compounds depends on electronic descriptors and topological characteristics, such as compactness and branching of anionic surfactants.

Mehdi Jalali-Heravi

2002-08-01

112

Electrospun single-walled carbon nanotube/polyvinyl alcohol composite nanofibers: structure-property relationships  

International Nuclear Information System (INIS)

Polyvinyl alcohol (PVA) nanofibers and single-walled carbon nanotube (SWNT)/PVA composite nanofibers have been produced by electrospinning. An apparent increase in the PVA crystallinity with a concomitant change in its main crystalline phase and a reduction in the crystalline domain size were observed in the SWNT/PVA composite nanofibers, indicating the occurrence of a SWNT-induced nucleation crystallization of the PVA phase. Both the pure PVA and SWNT/PVA composite nanofibers were subjected to the following post-electrospinning treatments: (i) soaking in methanol to increase the PVA crystallinity, and (ii) cross-linking with glutaric dialdehyde to control the PVA morphology. Effects of the PVA morphology on the tensile properties of the resultant electrospun nanofibers were examined. Dynamic mechanical thermal analyses of both pure PVA and SWNT/PVA composite electrospun nanofibers indicated that SWNT-polymer interaction facilitated the formation of crystalline domains, which can be further enhanced by soaking the nanofiber in methanol and/or cross-linking the polymer with glutaric dialdehyde

2008-07-30

113

Noncovalent interaction of dietary polyphenols with bovine hemoglobin in vitro: molecular structure/property-affinity relationship aspects.  

Science.gov (United States)

The relationship between the structural properties of selected dietary polyphenols and their affinities for bovine hemoglobin (bHB) was investigated by fluorescence analysis. The presence of an additional methoxy group on flavonoids weakened the affinities for bHB by 1.15-13.80 times. Hydroxylation on rings A, B, and C also significantly affected the affinity for bHB. The glycosylation of flavonoids decreased the affinities for bHB by 1 order of magnitude depending on the conjugation site and the class of sugar moiety. Hydrogenation of the C2?C3 double bond also decreased the binding affinity. The galloylated catechins exhibited higher binding affinities for bHB than nongalloylated. The glycosylation of resveratrol increased its affinity for bHB. The binding process with bHB was strongly influenced by the structural differences of dietary polyphenols. The affinities for bHB increased with increasing partition coefficients and decreased with increasing hydrogen bond donor and acceptor numbers of polyphenols, which suggested that the binding interaction was mainly caused by the hydrophobic force. PMID:21718067

Xiao, Jian Bo; Huo, Jiang Lei; Yang, Fan; Chen, Xiao Qing

2011-08-10

114

Structure-property relationships of smectic liquid crystalline polyacrylates as revealed by SAXS  

Directory of Open Access Journals (Sweden)

Full Text Available The influence of the chemical structure of the mesogenic groups and the length of the spacer groups on the phase behavior in a series of side-chain liquid crystalline polyacrylates (SCLCP have been studied using Small Angle X-ray Scattering (SAXS and Polarized Optical Microscopy (POM. Analyses of the mesophase arrangement in unaligned and aligned samples by magnetic field are reported. The role of the spacer length on the local packing and on the thickness of the layers encountered in the SmA and SmC mesophases is elucidated. The tilt angles theta of the mesogenic cores related to the normal of the layers in the SmC mesophases are measured. A study about the degree of order as a function of temperature for the smectic polymers was possible using SAXS measurements. A particular arrangement in one of the studied SCLCPs is related to the coexistence of two different phases.

Pereira Fabiano V.

2006-01-01

115

Structure property relationship of biological nano composites studies by combination of in-situ synchrotron scattering and mechanical tests  

International Nuclear Information System (INIS)

Biological materials represent hierarchical nano fibre composites with complicated morphology and architecture varying on the nm level. The mechanical response of those materials is influenced by many parameters like chemical composition and crystal structure of constituents, preferred orientation, internal morphology with specific sizes of features etc. In-situ wide-angle x-ray scattering (WAXS) combined with mechanical tests provide a unique means to evaluate structural changes in biological materials at specific stages of tensile experiments. In this way it is possible to identify distinct architectural/compositional elements responsible for specific mechanical characteristics of the biological materials. In this thesis, structure-property relationship is analyzed using in-situ WAXS in the tissues of Picea abies, coir fibre, bacterial cellulose and cellulose II based composites. The experiments were performed at the beamline ID01 of European synchrotron radiation facility in Grenoble, France. The tissues were strained in a tensile stage, while the structural changes were monitored using WAXS. Complex straining procedures were applied including cyclic straining. One of the main goals was to understand the stiffness recovery and strain hardening effects in the tissues. The results demonstrate that, in all cellulosics, the orientation of the cellulose crystallites is only the function of the external strain while the stiffness depends on the specific stage of the tensile experiment. Whenever the strain is increased, the tissues exhibit stiffness equal or larger than the initial one. The recovery of the mechanical function is attributed to the molecular mechanistic effects operating between the crystalline domains of the cellulose. (author)

2005-01-01

116

Structure-property-relationship of p-toluidinium tetrachloromercurate(II)  

Science.gov (United States)

The single crystals of p-toluidinium tetrachloromercurate(II) hybrid materials have been grown with perfect crystal of size 0.35 × 0.30 × 0.27 mm. The hybrid material is exposed to X-rays for 3D intensity data which is used to refine the crystal structure upto reliability-factor of 0.034. The phenyl ring has planar conformation with skeletal torsion angle of 0.003(6)° and the aromatic ring (C1-C6) forms an angle of 78.7(1)° to the plane of inorganic layer. The N-H...Cl hydrogen bonded tetramer pattern is observed in p-toluidinium tetrachloromercurate(II) and the two tetramer layers are separated by a distance of 3.925(6)Å and the minimum distance between two mercury atoms is 4.112(1)Å which is quite larger for any metallophilic interaction. The inorganic layers form zig-zag ribbons which are separated by a distance of 12.987(5)Å.

Dinesh, Kumar, Mukesh; Dalela, S.

2014-04-01

117

Structure-property relationship in aliphatic polyamide/polyaniline surface layered composites  

International Nuclear Information System (INIS)

Highlights: ? Synthesis of surface conducting polymers based on aliphatic polyamides and polyaniline. ? The study revealed the layered structure of the surface conductive composites. ? Different dielectric relaxation processes were found as a function of doping agent and polyaniline oxidation state. ? Conductivity value (10-4-10-11 S cm-1) enables the use of such composites as antistatic/electrostatic discharge materials. - Abstract: Conducting polymer composite films based on different aliphatic polyamides (PA) (PA-6, PA-11 and PA-12) have been synthesized by in situ aniline polymerization inside a surface layer of the PA host matrix. Dielectric permittivity and dielectric loss of these films are explained in terms of the interfacial polarization. The real part of permittivity is found to be higher in the PA/polyaniline (PANI) composite films than in the virgin PA polymer matrix. Such behaviour is attributed to the interaction between PA and PANI molecular chains and to the conductivity increase after the aniline polymerization. The performed confocal Raman spectrometry and X-ray diffraction studies also confirmed the presence of interactions between PA and PANI molecular chains.

2011-10-17

118

Structure-property relationship in aliphatic polyamide/polyaniline surface layered composites  

Energy Technology Data Exchange (ETDEWEB)

Highlights: {yields} Synthesis of surface conducting polymers based on aliphatic polyamides and polyaniline. {yields} The study revealed the layered structure of the surface conductive composites. {yields} Different dielectric relaxation processes were found as a function of doping agent and polyaniline oxidation state. {yields} Conductivity value (10{sup -4}-10{sup -11} S cm{sup -1}) enables the use of such composites as antistatic/electrostatic discharge materials. - Abstract: Conducting polymer composite films based on different aliphatic polyamides (PA) (PA-6, PA-11 and PA-12) have been synthesized by in situ aniline polymerization inside a surface layer of the PA host matrix. Dielectric permittivity and dielectric loss of these films are explained in terms of the interfacial polarization. The real part of permittivity is found to be higher in the PA/polyaniline (PANI) composite films than in the virgin PA polymer matrix. Such behaviour is attributed to the interaction between PA and PANI molecular chains and to the conductivity increase after the aniline polymerization. The performed confocal Raman spectrometry and X-ray diffraction studies also confirmed the presence of interactions between PA and PANI molecular chains.

Fatyeyeva, K., E-mail: kateryna.fatyeyeva@univ-rouen.fr [Institute of Bioorganic Chemistry and Petrochemistry of National Academy of Science of Ukraine, 50 Kharkivske shose, Kyiv 02160 (Ukraine); Laboratoire de Physique de l' Etat Condense, UMR CNRS 6087, Universite du Maine, Av. Olivier Messiaen, 72085 Le Mans cedex 9 (France); Laboratoire Polymeres, Biopolymeres et Surfaces, UMR 6270 and FR 3038 CNRS, Universite de Rouen, Bd. Maurice de Broglie, 76821 Mont Saint Aignan cedex (France); Pud, A.A. [Institute of Bioorganic Chemistry and Petrochemistry of National Academy of Science of Ukraine, 50 Kharkivske shose, Kyiv 02160 (Ukraine); Bardeau, J.-F.; Tabellout, M. [Laboratoire de Physique de l' Etat Condense, UMR CNRS 6087, Universite du Maine, Av. Olivier Messiaen, 72085 Le Mans cedex 9 (France)

2011-10-17

119

Relationships between soil properties and community structure of soil macroinvertebrates in oak-history forests along an acidic deposition gradient  

Energy Technology Data Exchange (ETDEWEB)

Soil macroinvertebrate communities were studied in ecologically analogous oak-hickory forests across a three-state atmospheric pollution gradient in Illinois, Indiana, and Ohio. The goal was to investigate changes in the community structure of soil fauna in study sites receiving different amounts of acidic deposition for several decades and the possible relationships between these changes and physico-chemical properties of soil. The study revealed significant differences in the numbers of soil animals among the three study sites. The sharply differentiated pattern of soil macroinvertebrate fauna seems closely linked to soil chemistry. Significant correlations of the abundance of soil macroinvertebrates with soil parameters suggest that their populations could have been affected by acidic deposition in the region. Abundance of total soil macroinvertebrates decreased with the increased cumulative loading of acidic deposition. Among the groups most sensitive to deposition were: earthworms gastropods, dipteran larvae, termites, and predatory beetles. The results of the study support the hypothesis that chronic long-term acidic deposition could aversely affect the soil decomposer community which could cause lower organic matter turnover rates leading to an increase in soil organic matter content in high deposition sites.

Kuperman, R.G. [Argonne National Lab., IL (United States). Environmental Assessment Div.

1996-02-01

120

Predicting the melting points of ionic liquids by the Quantitative Structure Property Relationship method using a topological index  

International Nuclear Information System (INIS)

Highlights: • A general topological index was proposed based on atom characters and position. • The topological index was extended for predicting melting points of ionic liquids. • A topological index was generated from anion and cation. -- Abstract: A Quantitative Structure Property Relationship (QSPR) model was developed to predict the melting points of ionic liquids (ILs) with diverse classes of cations and anions. The QSPR model was based on the general topological index (TI) proposed in our previous work. The TI was successfully used for the prediction of the decomposition temperature of ILs and the toxicity of ILs in acetylcholine esterase and Leukemia Rat Cell Line. ILs are a class of molten salts which are composed entirely of cations and anions, therefore the descriptors for ILs are generally calculated from cations and anions separately and the interaction between them is neglected. In this study, besides the two sets of TIs generated from cations and anions, a third TI was used to depict the interaction of anions and cations. The QSPR model is on the base of eight kinds of ILs, which are imidazolium, benzimidazolium, pyridinium, pyrrolidinium, ammonium, sulfonium, triazolium and guanidinium. The regression coefficient (R2) and the overall average absolute deviation (AAD) are 0.778 and 7.20%, respectively

2013-07-01

 
 
 
 
121

Structure/property relationships for the thermotropic behavior of lysine-based amphiphiles: from hexagonal to smectic phases.  

Science.gov (United States)

Amino acid-derived gemini surfactants arise as a potentially good alternative to the more conventional lipid and synthetic catanionic systems in view of their enhanced interfacial properties, increased chemical stability, and low toxicity. The presence of an amino acid as the polar headgroup allows toxicity reduction, with the simultaneous increase of biodegradability. For these compounds, the establishment of structure/function relationships from the assessment of their basic aggregation properties is therefore of the utmost interest, e.g., in the design of operative self-assembled systems (e.g., liposomes, nanotubes, etc). In this context, the study of the thermal phase behavior of the dry surfactants is a natural, straightforward first step, the more so as thermotropic liquid crystals are also relevant for practical applications. In this work, several lysine-based amphiphiles with a gemini-like configuration have been synthesized, with the amino acid side chain as the spacer group. The molecules are either esters (neutral, with C6-C12 even chains) or sodium carboxylates (anionic, with C6-C12 even chains). Upon increasing the temperature, different crystalline (cr) and liquid-crystalline (lc) phases have been detected and the corresponding thermodynamic and structural parameters determined by a combination of differential scanning calorimetry, polarizing light microscopy and small-angle X-ray scattering. The phase behavior of the amphiphiles is highly dependent on both the chain length and the presence of charge on the headgroup, with significant differences occurring within and between each group of molecules. The C6 and C8 esters form reverse hexagonal cr and lc phases, while C10 and C12 self-assemble into smectic cr and lc structures, with C10 showing also a reverse hexagonal lc phase prior to isotropization. All the carboxylate derivatives form smectic lc phases at high enough temperature prior to isotropization. The rationalization of the phase behavior and phase transition energetics of the compounds has been put forth on the basis of the intermolecular interactions at stake (van der Waals, H-bonding, electrostatic, and packing) and the molecular shape of the amphiphile. PMID:18975881

Brito, Rodrigo O; Marques, Eduardo F; Gomes, Paula; Araújo, Maria João; Pons, Ramon

2008-11-27

122

A quantitative structure- property relationship of gas chromatographic/mass spectrometric retention data of 85 volatile organic compounds as air pollutant materials by multivariate methods  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract A quantitative structure-property relationship (QSPR) study is suggested for the prediction of retention times of volatile organic compounds. Various kinds of molecular descriptors were calculated to represent the molecular structure of compounds. Modeling of retention times of these compounds as a function of the theoretically derived descriptors was established by multiple linear regression (MLR) and artificial neural network (ANN). The stepwise regression was used for th...

Sarkhosh Maryam; Ghasemi Jahan B; Ayati Mahnaz

2012-01-01

123

Structural characterization and cytotoxic properties of a 4-O-methylglucuronoxylan from castanea sativa. 2. Evidence of a structure-activity relationship.  

Science.gov (United States)

Xylans were purified from delignified holocellulose alkaline extracts of Castanea sativa (Spanish chestnut) and Argania spinosa (Argan tree) and their structures analyzed by means of GC of their per-trimethylsilylated methylglycoside derivatives and (1)H NMR spectroscopy. The structures deduced were characteristic of a 4-O-methylglucuronoxylan (MGX) and a homoxylan (HX), respectively, with degrees of polymerization ranging from 182 to 360. In the case of MGX, the regular or random distribution of 4-O-methylglucuronic acid along the xylosyl backbone--determined by MALDI mass spectrometry after autohydrolysis of the polysaccharide--varied and depended both on the botanical source from which they were extracted and on the xylan extraction procedure. The MGX also inhibited in different ways the proliferation as well as the migration and invasion capability of A431 human epidermoid carcinoma cells. These biological properties could be correlated with structural features including values of the degree of polymerization, 4-O-MeGlcA to xylose ratios, and distribution of 4-O-MeGlcA along the xylosyl backbone, giving evidence of a defined structure-activity relationship. PMID:18646856

Barbat, Aline; Gloaguen, Vincent; Moine, Charlotte; Sainte-Catherine, Odile; Kraemer, Michel; Rogniaux, Hélène; Ropartz, David; Krausz, Pierre

2008-08-01

124

The electronic structure and second-order nonlinear optical properties of donor-acceptor acetylenes - A detailed investigation of structure-property relationships  

Science.gov (United States)

A series of donor-acceptor acetylene compounds was synthesized in which systematic changes in both the conjugation length and the donor-acceptor strength were made. The effect of these structural changes on the spectroscopic and electronic properties of the molecules and, ultimately, on the measured second-order molecular hyperpolarizabilities (beta) was investigated. It was found that increases in the donor-acceptor strength resulted in increases in the magnitude of beta. For this class of molecules, the increase is dominated by the energy of the intramolecular charge-transfer transition, while factors such as the ground to excited-state dipole moment change and the transition-moment integral are much less important. Increasing the conjugation length from one to two acetylene linkers did not result in an increase in the value of beta; however, beta increased sharply in going from two acetylenes to three. This increase is attributed to the superposition of several nearly isoenergetic excited states.

Stiegman, A. E.; Graham, Eva; Khundkar, Lutfur R.; Perry, Joseph W.; Cheng, L.-T.; Perry, Kelly J.

1991-01-01

125

Geophysical properties within the San Andreas Fault Zone at the San Andreas Fault Observatory at Depth and their relationships to rock properties and fault zone structure  

Science.gov (United States)

We examine the relationships between borehole geophysical data and physical properties of fault-related rocks within the San Andreas Fault as determined from data from the San Andreas Fault Observatory at Depth borehole. Geophysical logs, cuttings data, and drilling data from the region 3- to 4-km measured depth of the borehole encompass the active part of the San Andreas Fault. The fault zone lies in a sequence of deformed sandstones, siltstone, shale, serpentinite-bearing block-in-matrix rocks, and sheared phyllitic siltstone. The borehole geophysical logs reveal the presence of a low-velocity zone from 3190 to 3410 m measured depth with Vp and Vs values 10-30% lower than the surrounding rocks and a 1-2 m thick zone of active shearing at 3301-3303 m measured depth. Seven low-velocity excursions with increased porosity, decreased density, and mud-gas kick signatures are present in the fault zone. Geologic data on grain-scale deformation and alteration are compared to borehole data and reveal weak correlations and inverse relationships to the geophysical data. In places, Vp and Vs increase with grain-scale deformation and alteration and decrease with porosity in the fault zone. The low-velocity zone is associated with a significant lithologic and structural transition to low-velocity rocks, dominated by phyllosilicates and penetratively foliated, sheared rocks. The zone of active shearing and the regions of low sonic velocity appear to be associated with clay-rich rocks that exhibit fine-scale foliation and higher porosities that may be a consequence of the fault-related shearing of foliated and fine-grained sedimentary rocks.

Jeppson, Tamara N.; Bradbury, Kelly K.; Evans, James P.

2010-12-01

126

Study on the structure-properties relationship of natural rubber/SiO2 composites modified by a novel multi-functional rubber agent  

Directory of Open Access Journals (Sweden)

Full Text Available Vulcanization property and structure-properties relationship of natural rubber (NR/silica (SiO2 composites modified by a novel multi-functional rubber agent, N-phenyl- N'-(?-triethoxysilane-propyl thiourea (STU, are investigated in detail. Results from the infrared spectroscopy (IR and X-ray photoelectron spectroscopy (XPS show that STU can graft to the surface of SiO2 under heating, resulting in a fine-dispersed structure in the rubber matrix without the connectivity of SiO2 particles as revealed by transmission electron microscopy (TEM. This modification effect reduces the block vulcanization effect of SiO2 for NR/SiO2/STU compounds under vulcanization process evidently. The 400% modulus and tensile strength of NR/SiO2/STU composites are much higher than that of NR/SiO2/TU composites, although the crystal index at the stretching ratio of 4 and crosslinking densities of NR/SiO2 composites are almost the same at the same dosage of SiO2. Consequently, a structure-property relationship of NR/SiO2/STU composites is proposed that the silane chain of STU can entangle with NR molecular chains to form an interfacial region, which is in accordance with the experimental observations quite well.

S. Y. Yang

2014-06-01

127

Relationships of flour solvent retention capacity, secondary structure and rheological properties with the cookie making characteristics of wheat cultivars.  

Science.gov (United States)

The relationships of grain, flour solvent retention capacity (SRC) and dough rheological properties with the cookie making properties of wheat cultivars were evaluated. Cultivars with higher proportion of intermolecular-?-sheets+antiparallel ? sheets and lower ?-helix had greater gluten strength. The grain weight and diameter positively correlated with the proportion of fine particles and the cookie spread factor (SF) and negatively to the grain hardness (GH) and Na2CO3 SRC. The SF was higher in the flour with a higher amount of fine particle and with a lower Na2CO3 SRC and dough stability (DS). The breaking strength (BS) of cookies was positively correlated to lactic acid (LA) SRC, DS, peak time, sedimentation value (SV), G' and G?. Na2CO3 SRC and GH were strongly correlated. The gluten performance index showed a strong positive correlation with SV, DS, G' and G?. The water absorption had a significant positive correlation with sucrose SRC and LASRC. Cultivars with higher GH produced higher amount of coarse particles in flours that had higher Na2CO3 SRC and lower cookie SF. PMID:24731313

Kaur, Amritpal; Singh, Narpinder; Kaur, Seeratpreet; Ahlawat, Arvind Kumar; Singh, Anju Mahendru

2014-09-01

128

The performance of small-pore microporous aluminophosphates in low-temperature solar energy storage: the structure-property relationship  

Energy Technology Data Exchange (ETDEWEB)

The utilization of the reversible chemical and physical sorption of water on solids provides a new thermal energy storage concept with a great potential for lossless long-term storage. The performance of microporous aluminophosphates in heat storage applications is highlighted by a comparative thermogravimetric and calorimetric study of three known materials (SAPO-34, AlPO{sub 4}-18, APO-Tric) and is correlated with their structural features. The maximum water sorption capacity is similar for all three samples and results in a stored energy density of 240 kWh m{sup -3} in the 40-140 C range. The elemental composition influences the gradual (silicoaluminophosphate SAPO-34) or sudden (aluminophosphates AlPO{sub 4}-18, APO-Tric) water uptake, with the latter being favourable in storage systems. The driving force for the determined sorption process is the formation of highly ordered water clusters in the pores, which is enabled by rapid and reversible changes in the Al coordination and optimal pore diameters. The ease with which changes in the Al coordination can occur in APO-Tric is related to the use of the fluoride route in the synthesis. The understanding of these fundamental structure/sorption relationships forms an excellent basis for predicting the storage potential of numerous known or new microporous aluminophosphates and other porous materials from their crystal structures. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Ristic, Alenka; Logar, Natasa Zabukovec; Kaucic, Venceslav [National Institute of Chemistry, Ljubljana (Slovenia); Henninger, Stefan K. [Fraunhofer Institute for Solar Energy Systems, Freiburg (Germany)

2012-05-09

129

Predicting enthalpy of vaporization for Persistent Organic Pollutants with Quantitative Structure–Property Relationship (QSPR) incorporating the influence of temperature on volatility  

Science.gov (United States)

Enthalpy of vaporization (?Hvap) is a thermodynamic property associated with the dispersal of Persistent Organic Pollutants (POPs) in the environment. Common problem in the environmental risk assessment studies is the lack of experimentally measured ?Hvap data. This problem can be solved by employing computational techniques, including QSPR (Quantitative Structure–Property Relationship) modelling to predict properties of interest. Majority of the published QSPR models can be applied to predict the enthalpy of vaporization of compounds from only one, particular group of POPs (i.e., polychlorinated biphenyls, PCBs). We have developed a more general QSPR model to estimate the ?Hvap values for 1436 polychlorinated and polybrominated benzenes, biphenyls, dibenzo-p-dioxins, dibenzofurans, diphenyl ethers, and naphthalenes. The QSPR model developed with Multiple Linear Regression analysis was characterized by satisfactory goodness-of-fit, robustness and the external predictive performance (R2 = 0.888, QCV2=0.878, QExt2=0.842, RMSEC = 5.11, RMSECV = 5.34, RMSEP = 5.74). Moreover, we quantified the temperature dependencies of vapour pressure for twelve groups of POPs based on the predictions at six different temperatures (logPL(T)). In addition, we found a simple arithmetic relationship between the logarithmic values of vapour pressure in pairs of chloro- and bromo-analogues. By employing this relationship it is possible to estimate logPL(T) for any brominated POP at any temperature utilizing only the logPL(T) value for its chlorinated analogues.

Sosnowska, Anita; Barycki, Maciej; Jagiello, Karolina; Haranczyk, Maciej; Gajewicz, Agnieszka; Kawai, Toru; Suzuki, Noriyuki; Puzyn, Tomasz

2014-04-01

130

Structure-property relationships in addition polyimides. 1: Resins from four-ring aromatic diamines containing carbonyl and methylene groups  

Science.gov (United States)

In an effort to improve the processing characteristics of addition-type polyimide resins the use of flexibilized four-ring aromatic diamine moieties was investigated. A series of 12 diamines containing carbonyl and methylene, as well as oxo and thio bridging groups, was synthesized. The diamines were polymerized with the dimethyl ester of 3.3', 4.4' - benzophenonetetracarboxylic acid (BTDE), using the monomethyl ester of nadic acid (NE) as an end-cap. The effect of diamine structure on the solubility and rheological properties during cure was determined. This paper also describes the effect of diamine structure and formulated molecular weight on the glass transition temperature and thermo-oxidative stability at elevated temperatures after various post-cure regimes. The results indicate that polyimides from some of the diamines containing methylene connecting groups have potential as matrix resins for long-term applications at temperatures up to 300 C.

Delvigs, Peter; Klopotek, David L.; Cavano, Paul J.

1994-01-01

131

Structure-Processing-Property Relationships at the Fiber-Matrix Interface in Electron-Beam Cured Composite Materials  

Energy Technology Data Exchange (ETDEWEB)

The objective of this project was to characterize the properties of the resin and the fiber- resin interface in electron beam cured materials by evaluating several structural and processing parameters. The Oak Ridge National Laboratory (ORNL) has recently determined that the interlaminar shear strength properties of electron beam cured composites were 19-28% lower than for autoclave cured composites. Low interlaminar shear strength is widely acknowledged as the key barrier to the successfid acceptance and implementation of electron beam cured composites in industry. In this project we found that simple resin modification and process improvements are unlikely to substantially improve the interlaminar shear strength properties of electron beam cured composites. However, sizings and coatings were shown to improve these properties and there appears to be significant potential for further improvement. In this work we determined that the application of epoxy-based, electron beam compatible sizings or coatings onto surface- treated, unsized carbon fibers improved the composite interlaminar shear strength by as much as 55% compared to composites fabricated from surface-treated, unsized carbon fibers and 11 YO compared to composites made from surface-treated, GP sized carbon fibers. This work has identified many promising pathways for increasing the interlaminar shear strength of electron beam cured composites. As a result of these promising developments we have recently submitted a U.S. Department of Energy-Energy Research (DOE-ER) sponsored Laboratory Technical Research-Cooperative Research and Development Agreement (LTR- CRADA) proposal entitled, "Interracial Properties of Electron Beam Cured Composites", to continue this work. If funded, ORNL will lead a 3-year, $2.6 million effort involving eight industrial partners, NASA-Langley, and the U.S. Air Force. The principal objective of this CRADA is to significantly improve the interracial properties of carbon-fiber-reinforced composites beyond the current state-of-the art electron beam cured composites for use in several DOE, DoD, and industrial applications. In addition, several papers from this Laboratory Director's Research and Development (LDRD) project will be submitted to the Society for the Advancement of Materials and Process Engineering for oral presentations and publications.

Janke, C.J.

1998-11-01

132

Tutorial on Neural Networks Using the Broyden-Fletcher-Goldfarb - Shanno (BFGS) Training Algorithm and Molecular Descriptors with Application to the Prediction of Dielectric Constants through the Development of Quantitative Structure Property Relationships (QSPRs).  

Science.gov (United States)

The use of quantitative structure property relationships (QSPRs) is proposed for the calculation of dielectric constants. A data set of 497 compounds with a wide variety of functional groups is assembled. These compounds span the dielectric constant range...

R. C. Schweitzer J. B. Morris

2000-01-01

133

Effect of Fe3O4 on the sedimentation and structure-property relationship of starch under different pHs.  

Science.gov (United States)

The nanosized ferrite (Fe3O4) was synthesized and characterized by analytical techniques such as Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, fluorescence spectroscopy and transmission electron microscopy (TEM). The structure-property relationship of starch was studied under three different pHs namely 3.8, 7.1 and 12.5. The starch treated under acidic condition was degraded. In a similar manner, the structure-property relationship of starch in the presence of ferrite nanoparticles at three different pHs, as mentioned above was studied. The starch/ferrite nanocomposite prepared under acidic condition showed a degraded structure. Further, the polymer/nanocomposite systems were characterized by analytical techniques such as FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), vibrating sample measurement (VSM), TEM and scanning electron microscopy (SEM). Finally, the settling velocity of starch under three different pHs both in the presence and absence of Fe3O4 was carried out to ensure the role of pH and effect of Fe3O4 on the settling velocity of starch. PMID:24657379

Palanikumar, S; Siva, P; Meenarathi, B; Kannammal, L; Anbarasan, R

2014-06-01

134

Optimization of anti-virulence PqsR antagonists regarding aqueous solubility and biological properties resulting in new insights in structure-activity relationships.  

Science.gov (United States)

Increasing antibiotic resistance urgently requires novel therapeutic options to combat bacterial infections. The anti-virulence therapy selectively intervening with pathogenicity without affecting bacterial viability is such a strategy to overcome resistance. We consider the virulence regulator PqsR as an attractive target in the human pathogen Pseudomonas aeruginosa, and recently discovered the first PqsR antagonists, which, however, suffered from poor aqueous solubility. In this work, the antagonists were structurally modified to become more soluble, and their structure-activity as well as structure-property relationships were studied. A novel promising compound with improved solubility and enhanced anti-virulence activity was discovered (IC50: 3.8 ?M, pyocyanin). Our findings emphasize the crucial role of substituents at the 3-position and the carbonyl group at the 4-position for ligand-receptor interactions, and illuminate the way for further optimization of PqsR antagonists as anti-virulence agents. PMID:24735643

Lu, Cenbin; Kirsch, Benjamin; Maurer, Christine K; de Jong, Johannes C; Braunshausen, Andrea; Steinbach, Anke; Hartmann, Rolf W

2014-05-22

135

The relationship between the anatomical structure of the tomato fruit pericarp (Lycopersicon esculentum Mill. and its mechanical properties  

Directory of Open Access Journals (Sweden)

Full Text Available The anatomical structure of the tomato (Lycopersicon esculentum Mill. pericarp was studied in the fruits of five determinant field cultivars. The fruits of the examined cultivars differed in their mechanical properties. Fruits of cultivars which are firm and resistant to injury (Kecskemeti 886j-2, Campbell 28, moderately firm and resistant (Atma, Wenus and soft, susceptible to injury (line No 155/84 were examined. The pericarp of the cultivars which have fruits resistant to injury had an approx. 200 µm thick covering layer (epidermis plus cuticle plus hypodermis whereas that of fruits susceptible to injury was only 100 µm thick. In the fruits resistant to injury the cuticle penetrated deeply into the hypodermis, the epidermal cells were flattened and the hypodermis was composed of 4 - 5 rows of cells. The tomato fruits resistant to injury had a thick cuticle layer on their tangential walls - whereas those more susceptible had a thick cuticle layer on these walls.

Jadwiga Borowiak

1988-12-01

136

Synthesis and structure-property relationships of donor/acceptor-functionalized bis(dehydrobenzo[18]annuleno)benzenes.  

Science.gov (United States)

Seven new bis(dehydrobenzo[18]annuleno)benzenes (bis[18]DBAs) functionalized with electron-donating dibutylamino groups and/or accepting nitro groups at various positions along the peripheries of the chromophores have been prepared. The effects of varying the donor/acceptor charge transfer pathways, chromophore lengths and molecular symmetries upon the optical band gaps are studied using UV-visible spectroscopy, and structure-property correlations are identified. It is found that bis[18]DBAs possessing donor-pi-donor and acceptor-pi-acceptor pathways exhibit the smallest band gaps, especially when an acceptor-pi-acceptor pathway is situated along the longest chromophore length in the molecule. The all-donor species is also found to exhibit efficient fluorescence with dramatic solvatochromism. The results may have value to the rational design of future NLO/TPA device components. PMID:18421388

Spitler, Eric L; Haley, Michael M

2008-05-01

137

Structure-property-processinq relationships in nanocrystalline and fine-grained NbC and Cu-NbC composites  

Energy Technology Data Exchange (ETDEWEB)

Nominal room temperature mechanical alloying (MA) has been used to synthesize the high melting temperature NbC and Cu-NbC composites. Elemental powders of Cu and Nb were alloyed in the presence of either graphite or hexane to form nanocrystalline NbC or a Cu-NbC composite. Through control of hot-isostatic- pressing (HIPing) parameters, we have been able to minimize microstructural coarsening during densification, and have processed fully dense bulk compacts of both single phase NbC and two-phase Cu-NbC while maintaining a nanocrystalline or near-nanocrystalline structure. These materials generally exhibit high strength and low fracture toughness. However, mechanical properties vary significantly depending upon the Cu content and the method of NbC synthesis (graphite or hexane).

Murphy, B.R.; Courtney, T.H.

1995-12-31

138

The mechanical properties of human adipose tissues and their relationships to the structure and composition of the extracellular matrix.  

Science.gov (United States)

Adipose tissue (AT) expansion in obesity is characterized by cellular growth and continuous extracellular matrix (ECM) remodeling with increased fibrillar collagen deposition. It is hypothesized that the matrix can inhibit cellular expansion and lipid storage. Therefore, it is important to fully characterize the ECM's biomechanical properties and its interactions with cells. In this study, we characterize and compare the mechanical properties of human subcutaneous and omental tissues, which have different physiological functions. AT was obtained from 44 subjects undergoing surgery. Force/extension and stress/relaxation data were obtained. The effects of osmotic challenge were measured to investigate the cellular contribution to tissue mechanics. Tissue structure and its response to tensile strain were determined using nonlinear microscopy. AT showed nonlinear stress/strain characteristics of up to a 30% strain. Comparing paired subcutaneous and omental samples (n = 19), the moduli were lower in subcutaneous: initial 1.6 ± 0.8 (means ± SD) and 2.9 ± 1.5 kPa (P = 0.001), final 11.7 ± 6.4 and 32 ± 15.6 kPa (P < 0.001), respectively. The energy dissipation density was lower in subcutaneous AT (n = 13): 0.1 ± 0.1 and 0.3 ± 0.2 kPa, respectively (P = 0.006). Stress/relaxation followed a two-exponential time course. When the incubation medium was exchanged for deionized water in specimens held at 30% strain, force decreased by 31%, and the final modulus increased significantly. Nonlinear microscopy revealed collagen and elastin networks in close proximity to adipocytes and a larger-scale network of larger fiber bundles. There was considerable microscale heterogeneity in the response to strain in both cells and matrix fibers. These results suggest that subcutaneous AT has greater capacity for expansion and recovery from mechanical deformation than omental AT. PMID:24105412

Alkhouli, Nadia; Mansfield, Jessica; Green, Ellen; Bell, James; Knight, Beatrice; Liversedge, Neil; Tham, Ji Chung; Welbourn, Richard; Shore, Angela C; Kos, Katarina; Winlove, C Peter

2013-12-01

139

Quantitative structure-property relationship study of n-octanol-water partition coefficients of some of diverse drugs using multiple linear regression  

International Nuclear Information System (INIS)

A quantitative structure-property relationship (QSPR) study was performed to develop models those relate the structures of 150 drug organic compounds to their n-octanol-water partition coefficients (log Po/w). Molecular descriptors derived solely from 3D structures of the molecular drugs. A genetic algorithm was also applied as a variable selection tool in QSPR analysis. The models were constructed using 110 molecules as training set, and predictive ability tested using 40 compounds. Modeling of log Po/w of these compounds as a function of the theoretically derived descriptors was established by multiple linear regression (MLR). Four descriptors for these compounds molecular volume (MV) (geometrical), hydrophilic-lipophilic balance (HLB) (constitutional), hydrogen bond forming ability (HB) (electronic) and polar surface area (PSA) (electrostatic) are taken as inputs for the model. The use of descriptors calculated only from molecular structure eliminates the need for experimental determination of properties for use in the correlation and allows for the estimation of log Po/w for molecules not yet synthesized. Application of the developed model to a testing set of 40 drug organic compounds demonstrates that the model is reliable with good predictive accuracy and simple formulation. The prediction results are in good agreement with the experimental value. The root mean square error of prediction (RMSEP) and square correlation coefficient (R2) for MLR model were 0.22 and 0.99 for the prediction set log Po/w

2007-12-05

140

Relationship between mechanical properties and homogeneous and heterogeneous structures of sintered low alloy steels; Shoketsu gokinko ni okeru kinshitsu oyobi fukinshitsu soshiki to kikaiteki seishitsu tono kankei  

Energy Technology Data Exchange (ETDEWEB)

High performance wintered 4600 steels were obtained by Metal Injection Molding (MIM) process in our previous study This seemed to be due to the fine heterogeneous structure which were consisted of bauxite, martensite and retained austenite by the segregation of Ni added as allaying element. This study has hen performed to clarify the relationship between the mechanical properties and the homogeneous and heterogeneous structures of 4600 steels using conventional powder metallurgy (P/M) process. For the wide wintered density range, the final carbon content was properly controlled by adjusting the additions carbon content and the wintering atmosphere in both prealloyed and elemental mixed powder compacts. Sintered microstructures of the prealloyed powder compacts showed the dual homogeneous structure consisted of ferrite and bauxite. On the other hand, the heterogeneous structure including martensite appeared in the elements mixed powder compacts. In the high density range over 7.3Mg/m{sup 3} at which the pores were closed, the strength of the latter was higher than that of the former. However, the strength of the P/M steels were smaller than that of the MIM steels because of the coarse heterogamous structure. 3 refs., 4 figs., 5 tabs.

Miura, H.; Honda, T. [Kumamoto University, Kumamoto (Japan). Faculty of Engineering; Takasu, M. [Kumamoto University, Kumamoto (Japan)

1995-10-15

 
 
 
 
141

Symmetric vs. asymmetric squaraines as photosensitisers in mesoscopic injection solar cells: a structure-property relationship study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A symmetric squaraine and its related non-symmetric structure are shown to have comparable efficiencies in DSCs, but with undoubtedly advantages in the low cost and casiness of synthesis for the symmetrical structure.

2012-01-01

142

Symmetric vs. asymmetric squaraines as photosensitisers in mesoscopic injection solar cells: a structure-property relationship study.  

Science.gov (United States)

A symmetric squaraine and its related non-symmetric structure are shown to have comparable efficiencies in DSCs, but with undoubtedly advantages in the low cost and easiness of synthesis for the symmetrical structure. PMID:22282151

Park, Jinhyung; Barolo, Claudia; Sauvage, Frédéric; Barbero, Nadia; Benzi, Caterina; Quagliotto, Pierluigi; Coluccia, Salvatore; Di Censo, Davide; Grätzel, Michael; Nazeeruddin, Md K; Viscardi, Guido

2012-03-14

143

Symmetric vs. asymmetric squaraines as photosensitisers in mesoscopic injection solar cells: a structure–property relationship study.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A symmetric squaraine and its related non-symmetric structure are shown to have comparable efficiencies in DSCs, but with undoubtedly advantages in the low cost and easiness of synthesis for the symmetrical structure.

2012-01-01

144

Synthesis of novel strontium-based cuprate superconducting thin films, and the relationship between their crystal structures and electrical properties  

Science.gov (United States)

Novel Sr-based cuprate thin films were investigated to explore their potential as next generation superconducting materials. Thin films of infinite-layer compound (Sr,Ca)CuO2 (no blocking layer), cuprate oxycarbonate Sr2CuO2(CO3) (carbonate blocking layer), and Tl(Sr,Ba)2Can-1CunOy (n = 2 and 3) (thin blocking layer) were synthesized using metal-organic chemical vapor deposition. The structure and defect chemistry of the blocking layers of these cuprate compounds were found to have profound effects on the transport properties both in the normal state and the superconducting state. Phase pure, epitaxial infinite-layer compound (Sr1-xCa x)CuO2 thin films were deposited on SrTiO3(100) substrates. However, these films were always semiconducting with resistivities of the order of 1 ohm- cm and with carrier concentrations of 1017~10 19cm-3, which is two to four orders of magnitude lower than the typical superconducting cuprates. The low carrier concentration was attributed to the absence of blocking layers containing a sufficient concentration of charged defects. Transport was via variable range hopping conduction. By annealing in air, the infinite-layer compound SrCuO2 thin films reacted with the CO2 in air to generate Sr 2CuO2(CO3) thin films. Upon formation of carbonate blocking layers, charger carriers were introduced into the Sr2CuO 2(CO3) thin films through the partial substitution of carbon by copper or boron in the SrCO3 blocking layers. After oxygen annealing or upon boron substitution, the carrier concentration increased up to 10 21 cm-3. A superconducting onset temperature of 34K and a zero resistivity temperature of 20K have been observed for Sr 2CuO2(C1-xBx)O3 thin films. A critical carrier density of 0.10~0.12 holes/Cu was required to render superconductivity. The effect of crystal structure on the critical current density was investigated by measuring the vortex pinning energies of Tl2Ba2CaCu 2Oy (Tl-2212) and Tl(Sr,Ba)2Ca Cu2O y (Tl- (Sr,Ba)1212) thin films. A model based on thermally activated flux flow (TAFF) was developed to describe the vortex line motion. The activation energies of the TAFF process were extracted from the magnetoresistivity measurements. Because of the thinner blocking layers, the Tl-(Sr,Ba)-1212 thin film has a higher activation energy of 77 meV compared to 27 meV of the Tl-2212 thin film at 77K and 1 tesla. The activation process was ascribed to the formation of double kinks in the flux lines. The activation energies for Tl-based and Bi-based superconducting cuprates were found to decrease exponentially with the increase of blocking layer thickness.

Chang, Kuo-Wei

2000-12-01

145

Structure-activity relationships of sandalwood odorants: total synthesis and fragrance properties of cyclopropano-beta-santalol.  

Science.gov (United States)

The synthesis and odor properties of cyclopropano-beta-santalol, a new santalol analogue, are described. The exocyclic double bond of the original molecule, beta-santalol, is replaced by a cyclopropane ring. Despite the analogies in the binding properties between the double bond and cyclopropane this change in the bulky hydrophobic part of the molecule leads to the complete loss of the characteristic sandalwood odor: in an olfactory evaluation the (Z)-product appears spicy and sweet, the (E)-isomer woody, but neither of them exhibits the typical sandalwood character. PMID:18035451

Stappen, Iris; Höfinghoff, Joris; Friedl, Susanne; Pammer, Claudia; Wolschann, Peter; Buchbauer, Gerhard

2008-07-01

146

Quantitative determination of the structure-property relationships in nuclear fuel element materials. Final report, June 1969--July 1973  

International Nuclear Information System (INIS)

New developments in quantitative microscopy are first described. The use of the described techniques to quantitatively characterize the microstructural states of nickel and uranium dioxide samples is then discussed. The determination of gas permeability, thermal conductivity, mechanical properties, and creep behavior in the characterized samples are also described. (U.S.)

1975-01-01

147

QUANTITATIVE STRUCTURE–PROPERTY RELATIONSHIP (QSPR STUDY OF KOVATS RETENTION INDICES OF SOME OF ADAMANTANE DERIVATIVES BYTHE GENETIC ALGORITHM AND MULTIPLE LINEAR REGRESSION (GA-MLR METHOD  

Directory of Open Access Journals (Sweden)

Full Text Available A quantitative structure–property relationship (QSPR study was performed to develop models those relate the structures of 65 Kovats retention index (RI of adamantane derivatives. Molecular descriptors derived solely from 3D structures of the molecular compounds. A genetic algorithm was also applied as a variable selection tool in QSPR analysis. The models were constructed using 52 molecules as training set, and predictive ability tested using 13 compounds. Modeling of RI of Adamantane derivatives as a function of the theoretically derived descriptors was established by multiple linear regression (MLR. The usefulness of the quantum chemical descriptors, calculated at the level of the DFT theories using 6-311+G** basis set for QSAR study of adamantane derivatives was examined. The use of descriptors calculated only from molecular structure eliminates the need to experimental determination of properties for use in the correlation and allows for the estimation of RI for molecules not yet synthesized. Application of the developed model to testing set of 13 drug organic compounds demonstrates that the model is reliable with goo predictive accuracy and simple formulation. The prediction results are in good agreement with the experimental value. A multi-parametric equation containing maximum Four descriptors at B3LYP/6-31+G** method with good statistical qualities (R2train=0.913, Ftrain=97.67, R2test=0.770, Ftest=3.21, Q2LOO=0.895, R2adj=0.904, Q2LGO=0.844 was obtained by Multiple Linear Regression using stepwise method.

Z. Bayat

2011-05-01

148

Quantitative structure-property relationship study of n-octanol-water partition coefficients of some of diverse drugs using multiple linear regression  

Energy Technology Data Exchange (ETDEWEB)

A quantitative structure-property relationship (QSPR) study was performed to develop models those relate the structures of 150 drug organic compounds to their n-octanol-water partition coefficients (log P{sub o/w}). Molecular descriptors derived solely from 3D structures of the molecular drugs. A genetic algorithm was also applied as a variable selection tool in QSPR analysis. The models were constructed using 110 molecules as training set, and predictive ability tested using 40 compounds. Modeling of log P{sub o/w} of these compounds as a function of the theoretically derived descriptors was established by multiple linear regression (MLR). Four descriptors for these compounds molecular volume (MV) (geometrical), hydrophilic-lipophilic balance (HLB) (constitutional), hydrogen bond forming ability (HB) (electronic) and polar surface area (PSA) (electrostatic) are taken as inputs for the model. The use of descriptors calculated only from molecular structure eliminates the need for experimental determination of properties for use in the correlation and allows for the estimation of log P{sub o/w} for molecules not yet synthesized. Application of the developed model to a testing set of 40 drug organic compounds demonstrates that the model is reliable with good predictive accuracy and simple formulation. The prediction results are in good agreement with the experimental value. The root mean square error of prediction (RMSEP) and square correlation coefficient (R{sup 2}) for MLR model were 0.22 and 0.99 for the prediction set log P{sub o/w}.

Ghasemi, Jahanbakhsh [Chemistry Department, Faculty of Sciences, Razi University, Kermanshah (Iran, Islamic Republic of)], E-mail: Jahan.ghasemi@gmail.com; Saaidpour, Saadi [Chemistry Department, Faculty of Sciences, Razi University, Kermanshah (Iran, Islamic Republic of)

2007-12-05

149

Quantitative Structure Pharmacokinetic Relationship Using Artificial Neural Network: A Review  

Directory of Open Access Journals (Sweden)

Full Text Available Quantitative structure activity relationship (QSAR has become a tool for designing in various areas like drugs, food additive, Pesticides, biochemical reactant, environmental pollutant and toxic products. In QSAR biological activity can be related with physicochemical properties and in QSPkR (Quantitative Structure Pharmacokinetic Relationship, pharmacokinetic properties can be related with physicochemical properties, relation found in terms of quantity. A number of literature and review article have been published on Quantitative structure pharmacokinetic relationship. But prediction of human pharmacokinetic properties of known and unknown is much difficult job in pharmaceutical industry. Pharmacokinetic data of animal cannot be put straightforward. Artificial neural network (ANN is used to predict the pharmacokinetic properties. Artificial neural network has basic structure like biological brain and compose of neurons which are interconnected to each other. The present review not only compiles the literature of QSPkR using ANN, but gives detail about the physicochemical properties and artificial neural network.

S. K. Singh

2009-10-01

150

Structure-activity relationships and colorimetric properties of specific probes for the putative cancer biomarker human arylamine N-acetyltransferase 1.  

Science.gov (United States)

A naphthoquinone inhibitor of human arylamine N-acetyltransferase 1 (hNAT1), a potential cancer biomarker and therapeutic target, has been reported which undergoes a distinctive concomitant color change from red to blue upon binding to the enzyme. Here we describe the use of in silico modeling alongside structure-activity relationship studies to advance the hit compound towards a potential probe to quantify hNAT1 levels in tissues. Derivatives with both a fifty-fold higher potency against hNAT1 and a two-fold greater absorption coefficient compared to the initial hit have been synthesized; these compounds retain specificity for hNAT1 and its murine homologue mNat2 over the isoenzyme hNAT2. A relationship between pKa, inhibitor potency and colorimetric properties has also been uncovered. The high potency of representative examples against hNAT1 in ZR-75-1 cell extracts also paves the way for the development of inhibitors with improved intrinsic sensitivity which could enable detection of hNAT1 in tissue samples and potentially act as tools for elucidating the unknown role hNAT1 plays in ER+ breast cancer; this could in turn lead to a therapeutic use for such inhibitors. PMID:24758871

Egleton, James E; Thinnes, Cyrille C; Seden, Peter T; Laurieri, Nicola; Lee, Siu Po; Hadavizadeh, Kate S; Measures, Angelina R; Jones, Alan M; Thompson, Sam; Varney, Amy; Wynne, Graham M; Ryan, Ali; Sim, Edith; Russell, Angela J

2014-06-01

151

Composition and structure-property relationships of chromium-diboride/molybdenum-disulphide PVD nanocomposite hard coatings deposited by pulsed magnetron sputtering  

Science.gov (United States)

The composition and structure-property relationships of physical vapour deposited coatings containing mixtures of CrB2 and MoS2 are reported. The coatings were produced by pulsed magnetron sputtering of loosely-packed powder targets formed from a blend of chromium and boron powders, alloyed with 12.8, 18.9 and 24.0 atom percent MoS2. Results of coating characterisation (by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Auger electron spectroscopy and nanoindentation measurement of hardness and elastic modulus) revealed that increasing amounts of MoS2 produced the following effects: frustration of crystallisation and phase separation; a decrease in average grain sizes (from ˜5.5 to ˜ 4.3 nm) and a decrease in coating hardness (from ˜15 to ˜ 10 GPa). Scratch testing also showed that the load-bearing capability of coatings was altered; coatings possessing an intermediate concentration of MoS2 exhibited the best behaviour with no failure observed in mechanical testing, due to an optimal nanocomposite structure. The corrosion resistance (investigated by potentiodynamic polarisation tests) however tended to improve as more MoS2 was introduced. An investigation of the effects of generating an amorphous structure by adding Ti and C into Cr-B-MoS2 coatings revealed improved corrosion behaviour, which significantly exceeded that of uncoated stainless steel and CrB2-coated samples.

Audronis, M.; Leyland, A.; Kelly, P. J.; Matthews, A.

2008-04-01

152

Composition and structure-property relationships of chromium-diboride/molybdenum-disulphide PVD nanocomposite hard coatings deposited by pulsed magnetron sputtering  

International Nuclear Information System (INIS)

The composition and structure-property relationships of physical vapour deposited coatings containing mixtures of CrB2 and MoS2 are reported. The coatings were produced by pulsed magnetron sputtering of loosely-packed powder targets formed from a blend of chromium and boron powders, alloyed with 12.8, 18.9 and 24.0 atom percent MoS2. Results of coating characterisation (by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Auger electron spectroscopy and nanoindentation measurement of hardness and elastic modulus) revealed that increasing amounts of MoS2 produced the following effects: frustration of crystallisation and phase separation; a decrease in average grain sizes (from ?5.5 to ?4.3 nm) and a decrease in coating hardness (from ?15 to ?10 GPa). Scratch testing also showed that the load-bearing capability of coatings was altered; coatings possessing an intermediate concentration of MoS2 exhibited the best behaviour with no failure observed in mechanical testing, due to an optimal nanocomposite structure. The corrosion resistance (investigated by potentiodynamic polarisation tests) however tended to improve as more MoS2 was introduced. An investigation of the effects of generating an amorphous structure by adding Ti and C into Cr-B-MoS2 coatings revealed improved corrosion behaviour, which significantly exceeded that of uncoated stainless steel and CrB2-coated samples. (orig.)

2008-04-01

153

Quantitative Structure Property Relationship Modeling for Prediction of Retention Index for a Set of Some Organic Compounds  

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One of the most ubiquitous challenges of the scientists is the theoretical evaluation of experimental parameters to validate and improve their ability. Plant essential oils and their extracts have been greatly employed in folk medicine, food flavoring, fragrance and pharmaceutical industries. This work is a part of our comprehensive investigation to correlate the experimental and calculated retention indices (RI) of the some organic compounds from K. Javidnia et al. The structures of...

2012-01-01

154

Properties–structure relationship research on LiCaPO4:Eu2+ as blue phosphor for NUV LED application  

International Nuclear Information System (INIS)

Graphical abstract: The graphical abstract shows the excitation and emission spectrum of LiCaPO4:Eu2+, and the CIE coordinates of LiCaPO4:Eu2+. The inset shows the photo of blue LED prepared by LiCaPO4:Eu2+ and NUV chip. It indicates that this phosphor can be excited by UV light and emit strong greenish-blue light. Highlights: •Pure phase blue phosphors of LiCaPO4:Eu2+ with a hexagonal structure were first prepared via solid-state method. •The crystallographic site of Eu2+ ion in the LiCaPO4 lattice was identified as 8-fold Ca2+ site. •The phosphor exhibits excellent thermal stability and the corresponding mechanism was thermal assisted ionization. •Bright and high color purity blue LED prototype based on LiCaPO4:Eu2+ phosphor was fabricated. -- Abstract: Blue-emitting phosphors of Eu2+-activated LiCaPO4 with a hexagonal structure were prepared via a conventional solid-state method. The XRD, PL spectra and thermal quenching were applied to characterize the phosphors. The crystallographic site of Eu2+ ion in the LiCaPO4 lattice was identified and discussed. The optimized LiCaPO4:0.03Eu2+ exhibits the bright greenish-blue emission with CIE coordinates of (0.119, 0.155) and a quantum efficiency of 52%. The critical energy-transfer distance was confirmed as ?18 Å by both calculated crystal structure method and experimental spectral method. The thermal stability of LiCaPO4:Eu2+ was evaluated by temperature-dependent PL spectra, and the thermal quenching mechanism was found to be thermal assisted ionization. Prototype blue LEDs with high color purity and good current stability were fabricated

2013-10-25

155

Relationship between structural and magnetic properties in (Ti,Fe)O{sub 2} powders obtained by mechanical milling  

Energy Technology Data Exchange (ETDEWEB)

Fe-doped TiO{sub 2} samples with different Fe content were prepared by mechanical alloying starting from TiO{sub 2} rutile and FeO. The samples were structurally and magnetically characterized by XRD, Moessbauer spectroscopy, X-ray absorption spectroscopy (XAS), AC-susceptibility and magnetization measurements. XAS results showed that Fe ions were incorporated into the rutile phase with oxygen coordination that was lower than that expected in this phase. The oxygen coordination number decreased with the increase of Fe{sup 2+} ions such as it was previously found in the milled samples of TiO{sub 2} doped with hematite. The RT Moessbauer spectra were reproduced using two paramagnetic interactions, one corresponding to Fe{sup 2+} ({delta}{approx}0.87 mm/s) and the other to Fe{sup 3+} ({delta}{approx}0.31 mm/s). Magnetometry measurements showed the presence of paramagnetic and ferromagnetic-like interactions at room temperature. Although saturation and coercivity of the ferromagnetic phase increased with iron, the effective magnetic moment per iron atom decreased, probably due to the precipitation of Fe rich antiferromagnetic structures.

Mudarra Navarro, A.M. [Departamento de Fisica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, IFLP-CCT La Plata-CONICET (Argentina); Bilovol, V. [LSA-INTECIN-CONICET, Facultad de Ingenieria, Universidad Nacional de Buenos Aires (Argentina); Cabrera, A.F. [Departamento de Fisica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, IFLP-CCT La Plata-CONICET (Argentina); Rodriguez Torres, C.E., E-mail: torres@fisica.unlp.edu.ar [Departamento de Fisica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, IFLP-CCT La Plata-CONICET (Argentina)

2012-08-15

156

Quantitative Structure Property Relationship Modeling for Prediction of Retention Index for a Set of Some Organic Compounds  

Directory of Open Access Journals (Sweden)

Full Text Available

One of the most ubiquitous challenges of the scientists is the theoretical evaluation of experimental parameters to validate and improve their ability. Plant essential oils and their extracts have been greatly employed in folk medicine, food flavoring, fragrance and pharmaceutical industries. This work is a part of our comprehensive investigation to correlate the experimental and calculated retention indices (RI of the some organic compounds from K. Javidnia et al. The structures of all organic compounds were drawn into the HYPERCHEM program and optimized using semi-empirical AM1 method, applying a gradient limit of 0.01 kcal/Å as a stopping criterion for optimized structures prior to geometry optimization step. Then molecular descriptors were calculated for each compound by the DRAGON software on the minimal energy conformations. The Stepwise SPSS was used for the selection of the variables that resulted in the best fitted models. By molecular modeling and calculation of descriptors, four significant descriptors (XMOD, PCD, MATS2e, GATS2e related to the retention indices values of the essential oils, were identified. After the variables selection, the MLR method used for building the regression models. The statistical figures obtained by the proposed model are R2=0.989, RMSEP=53.08, REP =3.83 and SEP =54.94. In the final step, models generated were used to predict the retention index for a set of test compounds.

Mehdi Rahimi

2012-06-01

157

Structure-property relationships of fluorinated donor/acceptor tetrakis(phenylethynyl)benzenes and bis(dehydrobenzoannuleno)benzenes.  

Science.gov (United States)

Nine new bisdonor/bisacceptor-functionalized tetrakis(phenylethynyl)benzene (TPEB) and six new bis(dehydrobenzoannuleno)benzene (DBA) chromophores have been synthesized. The compounds consist of electron-donating dibutylaniline groups connected through a conjugated phenyl-acetylene scaffold to benzotrifluoride, bis(trifluoromethyl)phenyl, or pentafluorophenyl acceptor groups. In comparison to previously reported analogues utilizing nitrophenyl or benzonitrile acceptor groups, the weaker acceptor groups exhibit visibly fluorescent intramolecular charge transfer (ICT) behavior, moderately narrow optical band gaps, moderately high quantum yields, and strong fluorescence solvatochromism. In this series of molecules, the strongly inductive fluoro acceptor groups result in optical properties similar to the resonance acceptor analogues, making them promising candidates for optical materials device components. The data also support recent investigations that question the utility of using UV/vis spectroscopy alone as a qualitative measure of conjugation. The bisDBAs exhibit weaker ICT behavior and self-association in solution than their corresponding nitro analogues, but show greater stability to decomposition via polymerization and smaller optical band gaps than their acyclic analogues. PMID:18278934

Spitler, Eric L; Monson, John M; Haley, Michael M

2008-03-21

158

Structure-property relationships for three indoline dyes used in dye-sensitized solar cells: TDDFT study of visible absorption and photoinduced charge-transfer processes.  

Science.gov (United States)

The electronic structures of three D-A-?-A indoline dyes (WS-2, WS-6, and WS-11) used in dye-sensitized solar cells (DSSCs) were studied by performing quantum chemistry calculations. The coplanarity of the A-?-A segment and distinct noncoplanarity of the indoline donor part of each dye were confirmed by checking the calculated geometric parameters. The relationships between molecular modifications and the optical properties of the dyes were derived in terms of the partial density of states, absorption spectrum, frontier molecular orbital, and excited-state charge transfer. 3D real-space analysis of the transition density (TD) and charge difference density (CDD) was also performed to further investigate the excited-state features of the molecular systems, as they provide visualized physical pictures of the charge separation and transfer. It was found that modifying the alkyl chain of the bridge unit near the acceptor unit is an efficient way to decrease dye aggregation and improve DSSC efficiency. Inserting a hexylthiophene group next to the donor unit leads to a complicated molecular structure and a decrease in the charge-transfer ability of the system, which has an unfavorable impact on DSSC performance. PMID:24154611

Li, Huixing; Chen, Maodu

2013-12-01

159

The relationship of physico-chemical properties and structure to the differential antiplasmodial activity of the cinchona alkaloids  

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Full Text Available Abstract Background The 8-amino and 9-hydroxy substituents of antimalarial cinchona alkaloids have the erythro orientation while their inactive 9-epimers are threo. From the X-ray structures a 90° difference in torsion angle between the N1-H1 and C9-O12 bonds in the two series is believed to be important. In order to kill the malaria parasite, alkaloids must cross the erythrocyte and parasite membranes to accumulate in the acid digestive vacuole where they prevent detoxication of haematin produced during haemoglobin breakdown. Methods Ionization constants, octanol/water distribution and haematin interaction are examined for eight alkaloids to explain the influence of small structural differences on activity. Results Erythro isomers have a high distribution ratio of 55:1 from plasma to the erythrocyte membrane, while for the more basic threo epimers this is only 4.5:1. This gives an increased transfer rate of the erythro drugs into the erythrocyte and thence into the parasite vacuole where their favourable conformation allows interaction with haematin, inhibiting its dimerization strongly (90 ± 7% and thereby killing the parasite. The threo compounds not only enter more slowly but are then severely restricted from binding to haematin by the gauche alignment of their N1-H1 and C9-O12 bonds. Confirmatory molecular models allowed measurement of angles and bond lengths and computation of the electronic spectrum of a quinine-haematin complex. Conclusion Differences in the antiplasmodial activity of the erythro and threo cinchona alkaloids may therefore be attributed to the cumulative effects of lipid/aqueous distribution ratio and drug-haematin interaction. Possible insights into the mechanism of chloroquine-resistance are discussed.

Meyer David J

2003-09-01

160

Differentiation between stoichiometric and anticatalytic antioxidant properties of benzoic acid analogues: a structure/redox potential relationship study.  

Science.gov (United States)

We investigated the antioxidant activities of some phenolic acid derivatives on a cell free system and on cellular and enzymatic models involved in inflammation. The stoichiometric antioxidant activities of phenolic acid derivatives were studied by measuring their capacity to scavenge the radical cation 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS(+)) and reactive oxygen species (ROS) produced by stimulated neutrophils. The anticatalytic antioxidant capacity of the molecules was evaluated on the activity of myeloperoxidase (MPO), an oxidant enzyme present in and released by the primary granules of neutrophils. The ROS produced by PMA-stimulated neutrophils were measured by lucigenin-enhanced chemiluminescence (CL) and the potential interaction of the molecules with MPO was investigated without interferences due to medium by Specific Immuno-Extraction Followed by Enzyme Detection (SIEFED). The antioxidant activities of the phenolic compounds were correlated to their redox potentials measured by differential pulse voltammetry (DPV), and discussed in relation to their molecular structure. The ability of the phenolic molecules to scavenge ABTS radicals and ROS derived from neutrophils was inversely correlated to their increased redox potential. The number of hydroxyl groups (three) and their position (catechol) were essential for their efficacy as stoichiometric antioxidants or scavengers. On MPO activity, the inhibitory capacity of the molecules was not really correlated with their redox potential. Likewise, for the inhibition of MPO activity the number of OH groups and mainly the elongation of the carboxylic group were essential, probably by facilitating the interaction with the active site or the structure of the enzyme. The redox potential measurement, combined with ABTS and CL techniques, seems to be a good technique to select stoichiometric antioxidants but not anticatalytic ones, as seen for MPO, what rather involves a direct interaction with the enzyme. PMID:24060682

Franck, Thierry; Mouithys-Mickalad, Ange; Robert, Thierry; Ghitti, Gianangelo; Deby-Dupont, Ginette; Neven, Philippe; Serteyn, Didier

2013-11-25

 
 
 
 
161

SnO2 nanocrystals synthesized by microwave-assisted hydrothermal method: towards a relationship between structural and optical properties  

International Nuclear Information System (INIS)

The exploration of novel synthetic methodologies that control both size and shape of functional nanostructure opens new avenues for the functional application of nanomaterials. Here, we report a new and versatile approach to synthesize SnO2 nanocrystals (rutile-type structure) using microwave-assisted hydrothermal method. Broad peaks in the X-ray diffraction spectra indicate the nanosized nature of the samples which were indexed as a pure cassiterite tetragonal phase. Chemically and physically adsorbed water was estimated by TGA data and FT-Raman spectra to account for a new broad peak around 560 cm?1 which is related to defective surface modes. In addition, the spherical-like morphology and low dispersed distribution size around 3–5 nm were investigated by HR-TEM and FE-SEM microscopies. Room temperature PL emission presents two broad bands at 438 and 764 nm, indicating the existence of different recombination centers. When the size of the nanospheres decreases, the relative intensity of 513 nm emission increases and the 393 nm one decreases. UV–Visible spectra show substantial changes in the optical absorbance of crystalline SnO2 nanoparticles while the existence of a small tail points out the presence of localized levels inside the forbidden band gap and supplies the necessary condition for the PL emission.

2012-03-01

162

Kinetic influences on the processing-structure-property relationships of high-performance epoxy matrices and their composites  

Energy Technology Data Exchange (ETDEWEB)

The research presented develops a fundamental understanding of the reaction kinetics of cure in epoxy resins and how they affect the rheological character of these resins and their carbon fiber reinforced composites. The well-characterized TGDDM-Novalac-DDS epoxy system was studied as a model system for comparison to commercial epoxy formulations, such as Hercules 3501-6. The determination of two reaction regimes was identified through the use of differential scanning calorimetry (DSC). The first corresponds to a region of the cure consisting predominantly of the primary-amine addition reaction while the second continues with the homopolymerization and etherification reactions becoming more significant. The effects of various processing parameters on the cure kinetics were investigated, including heating rate, moisture, composition, and the addition of a second resin, Novalac. The structural influences of the reaction kinetics with respect to heating rate and the presence of Novalac were also addressed. Application of results of the kinetic analysis to describe the rheological behavior of the TGDDM-Novalac-DSS and Hercules 3501-6 resin systems and composites was performed, using parallel-plate and squeeze-flow viscosity techniques and various theoretical modeling approaches.

Stark, E.B.

1985-01-01

163

Composition and structure-property relationships of chromium-diboride/molybdenum-disulphide PVD nanocomposite hard coatings deposited by pulsed magnetron sputtering  

Energy Technology Data Exchange (ETDEWEB)

The composition and structure-property relationships of physical vapour deposited coatings containing mixtures of CrB{sub 2} and MoS{sub 2} are reported. The coatings were produced by pulsed magnetron sputtering of loosely-packed powder targets formed from a blend of chromium and boron powders, alloyed with 12.8, 18.9 and 24.0 atom percent MoS{sub 2}. Results of coating characterisation (by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Auger electron spectroscopy and nanoindentation measurement of hardness and elastic modulus) revealed that increasing amounts of MoS{sub 2} produced the following effects: frustration of crystallisation and phase separation; a decrease in average grain sizes (from {proportional_to}5.5 to {proportional_to}4.3 nm) and a decrease in coating hardness (from {proportional_to}15 to {proportional_to}10 GPa). Scratch testing also showed that the load-bearing capability of coatings was altered; coatings possessing an intermediate concentration of MoS{sub 2} exhibited the best behaviour with no failure observed in mechanical testing, due to an optimal nanocomposite structure. The corrosion resistance (investigated by potentiodynamic polarisation tests) however tended to improve as more MoS{sub 2} was introduced. An investigation of the effects of generating an amorphous structure by adding Ti and C into Cr-B-MoS{sub 2} coatings revealed improved corrosion behaviour, which significantly exceeded that of uncoated stainless steel and CrB{sub 2}-coated samples. (orig.)

Audronis, M.; Leyland, A.; Matthews, A. [The University of Sheffield, Department of Engineering Materials, Sheffield (United Kingdom); Kelly, P.J. [Manchester Metropolitan University, Surface Engineering Group, Manchester (United Kingdom)

2008-04-15

164

Plant extracts with anti-inflammatory properties--a new approach for characterization of their bioactive compounds and establishment of structure-antioxidant activity relationships.  

Science.gov (United States)

Geranium robertianum L. (Geraniacea) and Uncaria tomentosa (Willd.) DC. (Rubiaceae) plant extracts, frequently used in traditional medicine for treatment of inflammatory and cancer diseases, were studied to identify potential bioactive compounds that may justify their therapeutic use and their underlying mechanisms of action. Since some of the pharmacological properties of these plant extracts may be linked to their antioxidant potential, the antioxidant activity, in relation to free radical scavenging, was measured by the ABTS/HRP and DPPH() assays, presenting U. tomentosa the higher activity. The antioxidant activity was also evaluated by scavenging of HOCl, the major strong oxidant produced by neutrophils and a potent pro-inflammatory agent. U. tomentosa was found to be a better protector against HOCl, which may justify its effectiveness against inflammatory diseases. SPE/LC-DAD was used for separation/purification purposes and ESI-MS/MS for identification/characterization of the major non-volatile components, mainly flavonoids and phenolic acids. The ESI-MS/MS methodology proposed can be used as a model procedure for identification/characterization of unknowns without the prerequisite for standard compounds analysis. The ESI-MS/MS data obtained were consistent with the antioxidant activity results and structure-activity relationships for the compounds identified were discussed. PMID:19201196

Amaral, Sónia; Mira, Lurdes; Nogueira, J M F; da Silva, Alda Pereira; Helena Florêncio, M

2009-03-01

165

Linear and nonlinear quantitative structure-property relationship models for solubility of some anthraquinone, anthrone and xanthone derivatives in supercritical carbon dioxide.  

Science.gov (United States)

A quantitative structure-property relation (QSPR) study was conducted on the solubility in supercritical fluid carbon dioxide (SCF-CO2) of some recently synthesized anthraquinone, anthrone and xanthone derivatives. The data set consisted of 29 molecules in various temperatures and pressures, which form 1190 solubility data. The combined data splitting-feature selection (CDFS) strategy, which previously developed in our research group, was used as descriptor selection and model development method. Modeling of the relationship between selected molecular descriptors and solubility data was achieved by linear (multiple linear regression; MLR) and nonlinear (artificial neural network; ANN) methods. The QSPR models were validated by cross-validation as well as application of the models to predict the solubility of three external set compounds, which did not have contribution in model development steps. Both linear and nonlinear methods resulted in accurate prediction whereas more accurate results were obtained by ANN model. The respective root mean square error of prediction obtained by MLR and ANN models were 0.284 and 0.095 in the term of logarithm of g solute m(-3) of SCF-CO2. A comparison was made between the models selected by CDFS method and the conventional stepwise feature selection method. It was found that the latter produced models with higher number of descriptors and lowered prediction ability, thus it can be considered as an over-fitted model. PMID:18267136

Hemmateenejad, Bahram; Shamsipur, Mojtaba; Miri, Ramin; Elyasi, Maryam; Foroghinia, Farzaneh; Sharghi, Hashem

2008-03-01

166

An investigation of the structure-property relationships in ionic polymer polymer composites (IP2Cs) manufactured by polymerization in situ of PEDOT/PSS on Nafion®117  

Science.gov (United States)

Ionic polymer polymer composites (IP2Cs) are all-organic electroactive polymers (EAPs) that show sensing and actuation capabilities when a deformation or a voltage is applied, respectively. They are fabricated starting from an ionic polymer coated on both sides with a conducting polymer as electrode element. In this work, poly(3,4-ethylendioxytiophene)-poly-(styrenesulfonate) (PEDOT/PSS) has been polymerized directly on Nafion®117 membrane and devices have been manufactured varying the polymerization time. Water and ethylene glycol (EG) have been used as solvents. The obtained IP2Cs have been characterized using thermal and mechanical analyses and electromechanically tested. The results have shown that in IP2Cs manufactured by polymerization in situ the PEDOT/PSS layer adheres very strongly on the Nafion®117 film, improving the possibility of rehydrating the devices after use. Moreover, taking into account that the different polymerization times influence the uniformity of the surface of the organic electrode and, consequently, both device stiffness and electrode conductivity, the structure-property relationships of the obtained devices have been investigated. The influence of the different solvents inside the devices has also been studied when IP2Cs have been used as actuators or sensors. Reported results show that it is possible to modulate the performances of IP2Cs by varying some manufacture parameters and the solvent.

Di Pasquale, G.; Graziani, S.; Messina, F. G.; Pollicino, A.; Puglisi, R.; Umana, E.

2014-03-01

167

Similarity Matrices Quantitative Structure-Activity Relationships for Anticonvulsant Phenylacetanilides  

Directory of Open Access Journals (Sweden)

Full Text Available Molecular graph descriptors are used in developing structure-property models, in drug design, virtual synthesis, similarity and diversity assessment. We present a new application of topological indices in computing similarity matrices that are subsequently used to develop quantitative structure-property relationship and quantitative structure-activity relationship models. The molecular structure is described by similarity matrices obtained from similarity indices calculations, when each molecule is compared to every other from the data set. Four similarity indices are introduced for the computation of the molecular similarity from a set of topological indices that numerically characterize the structure of chemical compounds. Using the multilinear regression model, the significant columns from the similarity matrices are selected as independent variables in a structure-activity study of anticonvulsant phenylacetanilides. The results obtained show that similarity matrices derived from molecular graph descriptors can provide the basis for the investigation of quantitative structure-activity relationships.

Ovidiu Ivanciuc

2004-07-01

168

The relationship of structure and optical properties of haloporphyrins: A new way to synthesize porphyrin chromophores and the investigation of their optical properties  

Energy Technology Data Exchange (ETDEWEB)

A new synthetic method of octabromoporphyrin compounds has been created to simplify the conventional multi-step synthesis and purification to a one step reaction. A series of new meso-substituted {beta}-bromoporphyrins, including tetraphenyloctabromoporphyrin (OBTPP), tetra-9-ethyl-carbazoleoctabromoporphyrin (TCarbOBP), tetra-2-thienyloctabromoporphyrin (T2-thioOBP), tetra-3-thienyloctabromoporphyrin (T3-thioOBP), tetra-5-bromo-2-thienyloctabromoporphyrin (5BrT2-thioOBP) and relative Zn porphyrins, have been prepared by this method. In this paper we discuss the synthesis of these compounds and their optical behaviors, especially the effects of the different meso-substituents on the photophysical properties. In order to investigate the different optical properties of porphyrins with {beta}-bromo-substitution and without {beta}-bromo-substitution, corresponding non-brominated meso-substituted porphyrins have also been synthesized and studied.

Su Weijie [Air Force Research Laboratory, Materials and Manufacturing Directorate, WPAFB, OH (United States); AT and T Government Solutions, 2940 Presidential Drive, Suite 390, Fairborn, OH 45324 (United States)]. E-mail: weijie.su@wpafb.af.mil; Singh, Kristi [Air Force Research Laboratory, Materials and Manufacturing Directorate, WPAFB, OH (United States); UES Inc., 4401 Dayton-Xenia Road, Dayton, OH 45432-1894 (United States); Rogers, Joy [Air Force Research Laboratory, Materials and Manufacturing Directorate, WPAFB, OH (United States); UES Inc., 4401 Dayton-Xenia Road, Dayton, OH 45432-1894 (United States); Slagle, Jon [Air Force Research Laboratory, Materials and Manufacturing Directorate, WPAFB, OH (United States); AT and T Government Solutions, 2940 Presidential Drive, Suite 390, Fairborn, OH 45324 (United States); Fleitz, Paul [Air Force Research Laboratory, Materials and Manufacturing Directorate, WPAFB, OH (United States)

2006-07-25

169

Structure-activity relationships among mycotoxins.  

Science.gov (United States)

Relationships between structural features and biological effects of mycotoxins are reviewed. Structure-activity relationships are characterized at the molecular, subcellular, cellular, or supracellular level. Major chemical and physicochemical factors responsible for bioactivity of mycotoxins are stressed. A variety of chemical families of mycotoxins are then discussed from the point of view of structure-activity relationships. The structurally related families comprise small lactones, macrocyclic lactones, isocoumarin derivatives, aflatoxins and related compounds trichothecenes, anthraquinones, indole-derived tremorgens and selected amino acid-derived mycotoxins such as sporidesmins and cyclosporines. Biological effects of mycotoxins include acute and chronic toxicity, antimicrobial activity, mutagenicity and genotoxicity, carcinogenicity and biochemical modes of action. PMID:2688934

Betina, V

1989-01-01

170

QSAR in Chromatography: Quantitative Structure-Retention Relationships (QSRRs)  

Science.gov (United States)

To predict a given physicochemical or biological property, the relationships can be identified between the chemical structure and the desired property. Ideally these relationships should be described in reliable quantitative terms. To obtain statistically significant relationships, one needs relatively large series of property parameters. Chromatography is a unique method which can provide a great amount of quantitatively precise, reproducible, and comparable retention data for large sets of structurally diversified compounds (analytes). On the other hand, chemometrics is recognized as a valuable tool for accomplishing a variety of tasks in a chromatography laboratory. Chemometrics facilitates the interpretation of large sets of complex chromatographic and structural data. Among various chemometric methods, multiple regression analysis is most often performed to process retention data and to extract chemical information on analytes. And the methodology of quantitative structure-(chromatographic) retention relationships (QSRRs) is mainly based on multiple regression analysis. QSRR can be a valuable source of knowledge on both the nature of analytes and of the macromolecules forming the stationary phases. Therefore, quantitative structure-retention relationships have been considered as a model approach to establish strategy and methods of property predictions.

Kaliszan, Roman; B?czek, Tomasz

171

Using Theoretical Descriptors in Structural Activity Relationships: 4. Molecular Orbital Basicity and Electrostatic Basicity.  

Science.gov (United States)

Quantitative Structure Activity Relationships (QSAR) have been used to develop predictive equations for numerous biological and physicocochemical properties. Linear Solvation Energy Relationship (LSER), a sub-set of QSAR have been used by Kamlet and Taft ...

G. R. Famini

1988-01-01

172

Molecular Structure - Optical Property Relationships for a Series of Non-Centrosymmetric Two-photon Absorbing Push-Pull Triarylamine Molecules  

Science.gov (United States)

This article reports on a comprehensive study of the two-photon absorption (2PA) properties of six novel push-pull octupolar triarylamine compounds as a function of the nature of the electron-withdrawing groups. These compounds present an octupolar structure consisting of a triarylamine core bearing two 3,3?-bis(trifluoromethyl)phenyl arms and a third group with varying electron-withdrawing strength (H DFT calculations of the two-photon transition oscillator strengths.

Vivas, Marcelo G.; Silva, Daniel L.; Malinge, Jeremy; Boujtita, Mohammed; Zalesny, Robert; Bartkowiak, Wojciech; Agren, Hans; Canuto, Sylvio; De Boni, Leonardo; Ishow, Elena; Mendonca, Cleber R.

2014-01-01

173

From building blocks of proteins to drugs: A quantum chemical study on structure-property relationships of phenylalanine, tyrosine and dopa  

CERN Document Server

Density functional theory and ab initio methods have been employed to address the impacts of hydroxyl (OH) group substitutions on the physico-chemical properties of levodopa (or L-dopa) against the natural amino acids, phenylalanine and tyrosine. L-dopa, which is an important therapeutic drug for Parkinson's disease, shares structural homology with the amino acids, whose structures differ only by OH substitutions in their phenyl side chains. It is revealed that the backbone geometries of the aromatic molecules do not show apparent OH-dependent differences; however, their other molecular-level properties, such as molecular dipole moment, electronic properties and aromaticity, change significantly. The core binding energy spectra indicate that the atom sites that undergo modifications exhibit large energy shifts, so as to accommodate the changes in the intra-molecular chemical environment of the molecules. The binding energies of the modified C 1s sites in the molecules shift as much as 1.8 eV, whereas the elec...

Ganesan, Aravindhan; Wang, Feng

2014-01-01

174

Structured Questionnaire To Measure Therapeutic Relationship  

Directory of Open Access Journals (Sweden)

Full Text Available The study attempts to develop and validate a new instrument to measure therapeutic relationship for use with high hospital principals and hospital employees. By using the three domains of therapeutic relationship, namely Patient factor, Therapist factors and Environmental factors, a primary questionnaire with 142 – item was developed and tested based on a sample of 250 hospital employees drawn from 4 hospitals representing in Iran. KMO Measure of Sampling Adequacy (.832 and Bartlett's Test of Sphericity (1345.32 and Analysis of Scree Plot have shown that the properties of sample are appropriate for factor analysis. Factor analysis for the final items items were made from which 64 items were extracted which had factor loading of >0.5 on the four domains. The properties of reliability and validity have borne significant results which show this instrument can be considered suitable to determine the position of therapeutic relationship in hospital employees.

FatemehKhoshnavafomani

2012-10-01

175

Electromechanical actuation of buckypaper actuator: Material properties and performance relationships  

International Nuclear Information System (INIS)

Carbon nanotubes can be assembled into macroscopic thin film materials called buckypapers. To incorporate buckypaper actuators into engineering systems, it is of high importance to understand their material property-actuation performance relationships in order to model and predict the behavior of these actuators. The electromechanical actuation of macroscopic buckypaper structures and their actuators, including single and multi-walled carbon nanotube buckypapers and aligned single-walled nanotube buckypapers, were analyzed and compared. From the experimental evidence, this Letter discusses the effects of the fundamental material properties, including Young modulus and electrical double layer properties, on actuation performance of the resultant actuators. -- Highlights: ? In this study we identified the figure of merit of the electromechanical conversion. ? Different type of buckypaper was realized and characterized for actuation properties. ? The results demonstrated the potential of Buckypapers/Nafion for actuation

2012-02-27

176

Electromechanical actuation of buckypaper actuator: Material properties and performance relationships  

Energy Technology Data Exchange (ETDEWEB)

Carbon nanotubes can be assembled into macroscopic thin film materials called buckypapers. To incorporate buckypaper actuators into engineering systems, it is of high importance to understand their material property-actuation performance relationships in order to model and predict the behavior of these actuators. The electromechanical actuation of macroscopic buckypaper structures and their actuators, including single and multi-walled carbon nanotube buckypapers and aligned single-walled nanotube buckypapers, were analyzed and compared. From the experimental evidence, this Letter discusses the effects of the fundamental material properties, including Young modulus and electrical double layer properties, on actuation performance of the resultant actuators. -- Highlights: ? In this study we identified the figure of merit of the electromechanical conversion. ? Different type of buckypaper was realized and characterized for actuation properties. ? The results demonstrated the potential of Buckypapers/Nafion for actuation.

Cottinet, P.-J.; Souders, C.; Tsai, S.-Y. [High-Performance Materials Institute, Florida State University, 2005 Levy Ave., Tallahassee, FL 32310 (United States); Liang, R., E-mail: liang@eng.fsu.edu [High-Performance Materials Institute, Florida State University, 2005 Levy Ave., Tallahassee, FL 32310 (United States); Wang, B.; Zhang, C. [High-Performance Materials Institute, Florida State University, 2005 Levy Ave., Tallahassee, FL 32310 (United States)

2012-02-27

177

Validating the German Version of the Quality of Relationship Inventory: Confirming the Three-Factor Structure and Report of Psychometric Properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Research on psychosocial influences such as relationship characteristics has received increased attention in the clinical as well as social-psychological field. Several studies demonstrated that the quality of relationships, in particular with respect to the perceived support within intimate relationships, profoundly affects individuals' mental and physical health. There is, however, a limited choice of valid and internationally known assessments of relationship quality in Germany. We report ...

Reiner, Iris; Beutel, Manfred; Skaletz, Christian; Bra?hler, Elmar; Sto?bel-richter, Yve

2012-01-01

178

On relationships between algebraic properties of groups and rings in some model-theoretic contexts  

CERN Document Server

We study relationships between certain algebraic properties of groups and rings definable in a first order structure or $*$-closed in a compact $G$-space. As a consequence, we obtain a few structural results about $\\omega$-categorical rings as well as about small, $nm$-stable compact $G$-rings, and we also obtain surprising relationships between some conjectures concerning small profinite groups.

Krupinski, Krzysztof

2010-01-01

179

Porous Materials - Structure and Properties  

DEFF Research Database (Denmark)

The paper presents some viewpoints on the description of the pore structure and the modelling of the properties of the porous building materials. Two examples are given , where it has been possible to connect the pore structure to the properties: Shrinkage of autoclaved aerated concrete and the properties of lime mortar.

Nielsen, Anders

1997-01-01

180

Novel Self-Dyed Wholly Aromatic Polyamide-Hydrazides Covalently Bonded with Azo Groups in Their Main Chains: 1. Structure-Property Relationships  

Directory of Open Access Journals (Sweden)

Full Text Available Twelve novel intrinsically colored wholly aromatic azopolyamide-hydrazides containing various proportions of para- and meta-phenylene units were successfully synthesized by a low temperature (?10 °C solution polycondensation reaction of either 4-amino-3-hydroxybenzhydrazide (4A3HBH or 3-amino-4-hydroxybenzhydrazide (3A4HBH with an equimolar amount of either 4,4'-azodibenzoyl chloride (4,4'ADBC, 3,3'-azodibenzoyl chloride (3,3'ADBC, or mixtures of various molar ratios of 4,4'ADBC and 3,3'ADBC in anhydrous N,N-dimethyl acetamide (DMAc containing 3% (wt/v LiCl as a solvent. The structures of the polymers were proven by elemental analysis, FTIR, 1H- and 13C-NMR spectroscopy. The polymers’ properties were strongly affected by their various structures. The intrinsic viscosities of the polymers were ranged from 0.7 to 4.75 dL g?1 and increased with the para-phenylene units content. The polymers are partially soluble in DMAc, dimethyl formamide (DMF and N-methyl-2-pyrrolidone (NMP. Their solubility increases with the introduction of meta-phenylene moieties into the polymer chains. The polymers exhibit a great affinity for water sorption. Their hydrophilicity increases as a function of the content of meta-phenylene rings incorporated into the polymer. Mechanical properties of the polymer films are improved markedly by substitution of para-phenylene units for meta-phenylene units. The completely para-oriented type polymer has the best thermal and thermo-oxidative stability relative to those of the other polymers.

Nadia A. Mohamed

2012-11-01

 
 
 
 
181

The relationship between the electronic structure and thermoelectric properties of Zintl compounds M2Zn5As4 (M = K, Rb).  

Science.gov (United States)

The electronic structure and the thermoelectric properties of M2Zn5As4 (M = K, Rb) are studied by the first principles and the semiclassical BoltzTraP theory. It is determined that they are semiconductors with an indirect band gap of about 1 eV, which is much larger than that of Ca5Al2Sb6 (0.50 eV). The calculated electronic localization function indicates that they are typical Zintl bonding compounds. The combination of heavy and light bands near the valence band maximum may improve their thermoelectric performance. Rb2Zn5As4 exhibits relatively large Seebeck coefficients, high electrical conductivities, and the large "maximum" thermoelectric figures of merit (ZeT). Compared with Ca5Al2Sb6, the highest ZeT of Rb2Zn5As4 appears at relatively low carrier concentration. For Rb2Zn4As5, the p-type doping may achieve a higher thermoelectric performance than n-type doping. The thermoelectric properties of Rb2Zn5As4 are possibly superior to those of Ca5Al2Sb6. PMID:24522347

Yang, Gui; Yang, Jueming; Yan, Yuli; Wang, Yuanxu

2014-03-28

182

Viscoelastic property and macromolecular structure of coal  

Energy Technology Data Exchange (ETDEWEB)

A film of coal extract-solvent gel was prepared, which contained 40-60 wt% of the solvent. Viscoelastic properties, that is, stress-strain relationship, was measured by thermal mechanical analysis of the film. The analyses using differential scanning calorimetry and thermogravimetry were also carried out to determine the thermal behaviour of the extract and solvent. The results obtained were discussed from the point of macromolecular structure, especially crosslinking structure of coal. 6 refs., 4 figs., 1 tab.

Iino, M.; Watanaba, H.; Takanohashi, T. [Tohoku University, Sendai (Japan). Institute of Chemical Reaction Science

1995-12-31

183

Relationships between crystal structure and magneto-transport properties in C.M.R. thin film of lacunar Lanthanum manganite before and after annealing  

International Nuclear Information System (INIS)

La0.8MnO3-? epitaxial thin films have been deposited by Injection-MOCVD on MgO. As-deposited film has a semiconducting-metal and para-ferromagnetic transition at about 220 K ; after annealing under air for 3 h at 700 deg. C, this transition temperature is about 310 K. The crystal structure of the film has been studied by XRD and TEM, before and after annealing. XR data collections have been recorded from an 1 mm2 thin film piece, using a conventional 4-circles-diffractometer designed for single crystals. In both cases the apparent symmetry is cubic with a cell parameter twice that of the classical perovskite. In fact, the true crystal structure is monoclinic with microdomain twinning. Atomic positions of all the atoms have been determined. Improvement of the magneto-transport properties after annealing is due to strengthening of the magnetic exchange interactions (Mn-O-Mn angles change from about 165 deg. to 176 deg.) and to increasing of the Mn4+/Mn3+ ratio

2001-05-01

184

Redox property-local structure relationships in the Rh-loaded CeO{sub 2}-ZrO{sub 2} mixed oxides  

Energy Technology Data Exchange (ETDEWEB)

The local structure of the M-O bond in CeO{sub 2}-ZrO{sub 2} mixed oxides is investigated with the aim of finding a correlation between structural parameters and oxygen exchange properties. It is found that insertion of ZrO{sub 2} into the CeO{sub 2} lattice strongly perturbs the symmetry of the M-O bond. As the content of CeO{sub 2} in CeO{sub 2}-ZrO{sub 2} solid solution is increased from 20 to 80 mol%, tetragonal, (t, t{prime}, t{double_prime}) and cubic phases are formed. The local symmetry of the Zr-O bond is strongly perturbed by the increase in CeO{sub 2} content while no significant modification of the first Ce-O coordination sphere is found, except for lengthening of the Ce-O bond consistent with lattice parameter increase. The perturbation of the Zr-O coordination sphere, which leads to highly disordered oxygen in the lattice, is indicated as responsible for the high oxygen mobility in CeO{sub 2}-ZrO{sub 2} mixed oxides.

Vlaic, G.; Monte, R. di; Fornasiero, P.; Fonda, E.; Kaspar, J.; Graziani, M. [Univ. di Trieste (Italy). Dipt. di Scienze Chimiche

1999-03-10

185

Investigation of structure-dielectric property relationships in zirconium oxide, tantalum pentoxide, and oxide-polymer laminate films for high energy density capacitor applications  

Science.gov (United States)

Pulsed power applications involve transformation of electrical energy into high-peak power pulses through capacitors. There is an immediate need for fast-response capacitors with decreased volume, weight, and cost for pulsed power applications and power distribution systems. This research challenge is dominated by energy density. Energy density is directly related to dielectric properties such as dielectric polarization, conductivity and breakdown strength of the capacitor dielectric. This research work correlates processing and microstructure of single and multiple component dielectric films with their dielectric properties. The inorganic materials studied in this dissertation include zirconium oxide (ZrO2) and tantalum pentoxide (Ta 2O5) reactive sputtered films. Film crystallization & structure was studied as a function of sputtering growth variables such as sputtering power, sputtering pressure, source frequency, oxygen pressure, substrate temperature, substrate material, and post-deposition annealing temperature. Polycrystalline phase of ZrO2 and amorphous phase of Ta2O 5 were obtained for most sputtering growth variables. Although the amorphous films have lower permittivity (32 for amorphous & 51 for polycrystalline at 1 kHz), they also have lower AC and DC conductivities (3.4x10-8 S/m for amorphous & 12.2x10 -8 S/m for polycrystalline at 1 kHz), which result in high breakdown strength than polycrystalline films. Amorphous Ta2O5 films are found to be ideal for high-energy density capacitors with energy density of 14 J/cm3 because of their high permittivity, low leakage current density, and high dielectric breakdown strength. Oxide films were combined with different polymers (polyvinyldene flouride-triflouroethylene, polypropylene and polyethylene terephthalate) to produce two different kinds of laminate composites---oxide on polymer and polymer on oxide. Permittivity and conductivity differences in the polymer and oxide films result in an impedance contrast of generally greater than 100 between the constituents. Low and high field dielectric properties were characterized for both laminate composites. All the dielectric films were characterized by impedance spectroscopy at frequencies ranging from 10 mHz to 1 MHz at different temperatures. Complex impedance and modulus analyses were used to resolve the contributions of individual microstructural features (such as grain, grain boundary & interface) from the overall film and composite electrical properties. Activation energies related to electro-active regions (grain boundary ˜1.1 eV, grain ˜0.5 eV) in the film structure were also determined from the temperature dependent impedances. The overall polarization of composite was higher by at least 25% than the sum of the polarizations from the individual layers for all composites. Plasma processed Ta2O5-Polypropylene laminate composite resulted in breakdown strength of ˜870 MV/m, which approximately 10% higher breakdown strength than its highest breakdown constituent (˜775 MV/m). These improved properties were attributed to bulk polymer modification, interface charge blocking/trapping and impedance contrast within the composite. The effect of impedance contrast on breakdown strength was modeled through permittivity contrast using Monte Carlo method. The breakdown model explored the electrostatic effects of adding a high permittivity barrier within an existing dielectric on the breakdown tree. The model also provided knowledge on various breakdown tree characteristics such as speed and shape. The Monte Carlo simulation results suggest that the experimentally observed impedance contrast of 1000 between the layers of the laminate composite can result in improved breakdown strength.

Sethi, Guneet

186

The refined 1.9-A X-ray crystal structure of D-Phe-Pro-Arg chloromethylketone-inhibited human alpha-thrombin: structure analysis, overall structure, electrostatic properties, detailed active-site geometry, and structure-function relationships.  

Science.gov (United States)

Thrombin is a multifunctional serine proteinase that plays a key role in coagulation while exhibiting several other key cellular bioregulatory functions. The X-ray crystal structure of human alpha-thrombin was determined in its complex with the specific thrombin inhibitor D-Phe-Pro-Arg chloromethylketone (PPACK) using Patterson search methods and a search model derived from trypsinlike proteinases of known spatial structure (Bode, W., Mayr, I., Baumann, U., Huber, R., Stone, S.R., & Hofsteenge, J., 1989, EMBO J. 8, 3467-3475). The crystallographic refinement of the PPACK-thrombin model has now been completed at an R value of 0.156 (8 to 1.92 A); in particular, the amino- and the carboxy-termini of the thrombin A-chain are now defined and all side-chain atoms localized; only proline 37 was found to be in a cis-peptidyl conformation. The thrombin B-chain exhibits the characteristic polypeptide fold of trypsinlike serine proteinases; 195 residues occupy topologically equivalent positions with residues in bovine trypsin and 190 with those in bovine chymotrypsin with a root-mean-square (r.m.s.) deviation of 0.8 A for their alpha-carbon atoms. Most of the inserted residues constitute novel surface loops. A chymotrypsinogen numbering is suggested for thrombin based on the topological equivalences. The thrombin A-chain is arranged in a boomeranglike shape against the B-chain globule opposite to the active site; it resembles somewhat the propeptide of chymotrypsin(ogen) and is similarly not involved in substrate and inhibitor binding. Thrombin possesses an exceptionally large proportion of charged residues. The negatively and positively charged residues are not distributed uniformly over the whole molecule, but are clustered to form a sandwichlike electrostatic potential; in particular, two extended patches of mainly positively charged residues occur close to the carboxy-terminal B-chain helix (forming the presumed heparin-binding site) and on the surface of loop segment 70-80 (the fibrin[ogen] secondary binding exosite), respectively; the negatively charged residues are more clustered in the ringlike region between both poles, particularly around the active site. Several of the charged residues are involved in salt bridges; most are on the surface, but 10 charged protein groups form completely buried salt bridges and clusters. These electrostatic interactions play a particularly important role in the intrachain stabilization of the A-chain, in the coherence between the A- and the B-chain, and in the surface structure of the fibrin(ogen) secondary binding exosite (loop segment 67-80).(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1304349

Bode, W; Turk, D; Karshikov, A

1992-04-01

187

Technetium-99m radiopharmaceuticals structure activity relationships  

International Nuclear Information System (INIS)

The development of 99Tc radiopharmaceuticals with higher organ or functional specificity depends on obtaining more information regarding the chemical structure, biodistribution an localization mechanisms of the compounds; also the chemical properties e.g. stability against ligand exchange. Properties of various oxidation states of Tc compounds and the types of ligands that stabilise them, ligand exchange with biostructures etc. must be studied. (U.K.)

1982-01-01

188

Quantitative structure-chromatographic retention relationships  

Energy Technology Data Exchange (ETDEWEB)

This book provides a wide-ranging overview of quantitative structure-retention relationships (QSRR). It brings together a great deal of information that previously was scattered in various parts of the literature. Although the book covers a lot of material, it provides the reader with sufficient background to read the related literature. In addition to QSRR, the book covers some topics related to quantitative structure-activity relationships (QSAR), where activity refers to biological activity. Overall, the book is well written and easy to understand. It would have been helpful to the reader if the chapter numbers had been included in the running heads. The book is divided by subject into 12 chapters, each with references. Works published through 1985 are included; hence, some recent literature is not covered. However, the book is heavily referenced, and each reference has the full title of the work as well as source and author information.

Kaliszan, R.

1987-01-01

189

Molecular structure-optical property relationships for a series of non-centrosymmetric two-photon absorbing push-pull triarylamine molecules.  

Science.gov (United States)

This article reports on a comprehensive study of the two-photon absorption (2PA) properties of six novel push-pull octupolar triarylamine compounds as a function of the nature of the electron-withdrawing groups. These compounds present an octupolar structure consisting of a triarylamine core bearing two 3,3'-bis(trifluoromethyl)phenyl arms and a third group with varying electron-withdrawing strength (H < CN < CHO < NO2 < Cyet < Vin). The 2PA cross-sections, measured by using the femtosecond open-aperture Z-scan technique, showed significant enhancement from 45 up to 125?GM for the lowest energy band and from 95 up to 270?GM for the highest energy band. The results were elucidated based on the large changes in the transition and permanent dipole moments and in terms of (i) EWG strength, (ii) degree of donor-acceptor charge transfer and (iii) electronic coupling between the arms. The 2PA results were eventually supported and confronted with theoretical DFT calculations of the two-photon transition oscillator strengths. PMID:24658327

Vivas, Marcelo G; Silva, Daniel L; Malinge, Jérémy; Boujtita, Mohammed; Zale?ny, Robert; Bartkowiak, Wojciech; Ågren, Hans; Canuto, Sylvio; De Boni, Leonardo; Ishow, Eléna; Mendonca, Cleber R

2014-01-01

190

Relationship between structural properties and electrochemical characteristics of monolithic carbon xerogel-based electrochemical double-layer electrodes in aqueous and organic electrolytes  

Energy Technology Data Exchange (ETDEWEB)

The impact of the micropore width, external surface area, and meso-/macropore size on the charging performance of electrochemical double-layer capacitor (EDLC) electrodes is systematically investigated. Nonactivated carbon xerogels are used as model electrodes in aqueous and organic electrolytes. Monolithic porous model carbons with different structural parameters are prepared using a resorcinol-formaldehyde-based sol-gel process and subsequent pyrolysis of the organic precursors. Electrochemical properties are characterized by utilizing them as EDLC half-cells operated in aqueous and organic electrolytes, respectively. Experimental data derived for organic electrolytes reveals that the respective ions cannot enter the micropores within the skeleton of the meso- and macroporous carbons. Therefore the total capacitance is limited by the external surface formed by the interface between the meso-/macropores and the microporous carbon particles forming the xerogel skeleton. In contrast, for aqueous electrolytes the total capacitance solely depends on the total surface area, including interfaces at the micropore scale. For both types of electrolytes the charging rate of the electrodes is systematically enhanced when increasing the diameter of the carbon xerogel particles from 10 to 75 nm and the meso-/macropore size from 10 to 121 nm. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Zeller, Mario [Bavarian Center for Applied Energy Research e.V. (ZAE Bayern), Wuerzburg (Germany); Institute of Radiology, University Clinic, University of Wuerzburg (Germany); Lorrmann, Volker; Reichenauer, Gudrun; Wiener, Matthias [Bavarian Center for Applied Energy Research e.V. (ZAE Bayern), Wuerzburg (Germany); Pflaum, Jens [Bavarian Center for Applied Energy Research e.V. (ZAE Bayern), Wuerzburg (Germany); Department of Experimental Physics VI, Julius-Maximilians-University of Wuerzburg (Germany)

2012-05-15

191

Rational Formulation of Alternative Fuels using QSPR Methods: Application to Jet Fuels Développement d’un outil d’aide à la formulation des carburants alternatifs utilisant des méthodes QSPR (Quantitative Structure Property Relationship: application aux carburéacteurs  

Directory of Open Access Journals (Sweden)

Full Text Available Alternative fuels are a promising solution for road transport but also for aircraft. In the aviation field, a huge amount of work has been done in the past years with the approval to use up to 50 % by volume of SPK (Synthetic Paraffinic Kerosene in blends with conventional fossil Jet A-1. SPK are Fischer-Tropsch (FT fuels but also Hydroprocessed Esters and Fatty Acids (HEFA. However, these alternative fuels can have different chemical properties depending on the process used for their production. These properties include normal to iso paraffin ratio, carbon chain length and level of branching. R&D studies of alternative fuels are based on the evaluation of products coming from identified production processes. However, it appears that a better way of studying them could be firstly to determine the best chemical composition regarding aviation problems and secondly to find the best process and finishing process in order to obtain such a product. The objective of this work is to design a tool that aims to guide the future formulation of alternative fuels for aviation through the prediction of targeted physical properties. Thus, it is proposed to apply a methodology that identifies relationships between the structure and properties of a molecule (QSPR for Quantitative Structure Property Relationship, with the aim of establishing predictive models. These models will be built for hydrocarbons (normal and iso paraffins, naphthenes, aromatics, etc. and oxygenated compounds (esters and alcohols. For aviation, oxygenated compounds are not considered as a drop-in fuel. It could be seen as a disruptive solution in a long term view. There are concerns with oxygenates in aviation that are covered in this paper such as the flash point but others such as the energetic content, the water affinity that are not taken into account in this paper. The properties currently studied are flash point, cetane number, density and viscosity. The data sets will contain data from the literature, from experimental measurements and from molecular simulations for complex molecules. The interest of such models in the selection of molecules can be shown for example by the trade-off between cold flow properties and density of paraffinic compounds. If the carbon chain length is too high, the cold flow properties are compromised. One solution can be to increase branching or incorporate fuel base with good cold flow properties such as naphthenic or aromatic compounds. However, this leads to a decrease in density below the jet fuel specification. Again, using naphthenic of alkyl-aromatic compounds produced from biomass can help. Le développement des carburants alternatifs est en plein essor, notamment dans le domaine aéronautique. Cela se concrétise par la possibilité d’incorporer jusqu’à 50 % de carburants de synthèse de type Fischer- Tropsch (FT ou hydroprocessed esters and fatty acids (HEFA dans du carburéacteur. De même, ces carburants paraffiniques se développent pour le transport terrestre en parallèle des biocarburants à base d’esters ou d’alcool actuellement disponibles. La formulation de ces carburants alternatifs est actuellement basée sur une sélection des produits via des critères physiques. L’atteinte de ces critères se fait souvent par des formulations empiriques et ce type de fonctionnement ne s’avère pas très efficace et montre ses limites. En effet, les carburants alternatifs présentent des propriétés chimiques qui peuvent être différentes en fonction du procédé (répartition n-paraffines/iso-paraffines, longueur de chaîne, ramification, etc. et donc modulable. Ainsi, une nouvelle voie pourrait être envisagée visant à déterminer par le calcul, la molécule (ou le mélange de molécules la plus à même de répondre au cahier des charges du carburant, puis à étudier ou à optimiser les voies de synthèse permettant d’accéder à ces produits. Le travail présenté a pour objectif le développement et l’application de méthodes QSPR (Quantitative Structure Property Relationship perm

Saldana D.A.

2013-06-01

192

Structural relationships in high temperature superconductors  

International Nuclear Information System (INIS)

The recent discovery of two types of metallic copper oxide compounds which are superconducting to above 900K has renewed interest in the search for new high temperature superconducting materials. It is significant that both classes of compounds, La/sub 2-x/Sr/sub x/CuO/sub 4-y/ and YBa2Cu3O/sub 7-?/ are intimately related to the extensively studied perovskite family. Both compounds contain highly oxidized, covalently bonded Cu-O sublattices, however, they differ in geometry. In this paper we discuss the relationship of these features to the superconducting properties. 30 refs., 6 figs

1987-07-06

193

Relationships between toxicity and structure of aliphatic nitriles.  

Science.gov (United States)

A retrospective structure-activity relationship (SAR) comparison was undertaken of several of the toxicological properties (acute and subchronic toxicity, teratogenicity, and biochemical mechanism studies) of a series of structurally similar aliphatic nitriles based on available published data. Members of this chemical class included several mononitriles (aceto-, propio-, butyro-, and acrylonitrile), dinitriles (succino- and adiponitrile), and cyanohydrin derivatives (lactonitrile and acetone cyanohydrin). Broadly defined, retrospective SAR analysis suggested that the toxicological profiles of this group of aliphatic nitriles were similar; however, unique differences were observed within each of the toxicity categories and nitrile subclasses as the toxicological focus narrowed. Additionally, the toxicological properties associated with acetonitrile, the first of this chemically similar series, were unique and quite different from others within the homologous series. Finally, knowledge regarding the mechanism of toxicological action provided valuable information in relating toxicological properties among the aliphatic nitriles. PMID:3803764

Johannsen, F R; Levinskas, G J

1986-11-01

194

Thermozymes: biotechnology and structure-function relationships.  

Science.gov (United States)

Recent findings on the biochemical and molecular features of the following thermozymes are presented, based on their biotechnological use: alpha-amylase and amylopullulanase, used in starch processing; glucose isomerase, used in sweetener production; alcohol dehydrogenase, used in chemical synthesis; and alkaline phosphatase, used in diagnostics. The corresponding genes and recombinant proteins have been characterized in terms of sequence similarities, specific activities, thermophilicity, and unfolding kinetics. Site-directed and nested deletion mutagenesis were used to understand structure-function relationships. All these thermozymes display higher stability and activity than their counterparts currently used in the biotechnology industry. PMID:9783163

Zeikus, J G; Vieille, C; Savchenko, A

1998-08-01

195

The Effect of a Rapid Heating Rate, Mechanical Vibration and Surfactant Chemistry on the Structure–Property Relationships of Epoxy/Clay Nanocomposites  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The role of processing conditions and intercalant chemistry in montmorillonite clays on the dispersion, morphology and mechanical properties of two epoxy/clay nanocomposite systems was investigated in this paper. This work highlights the importance of employing complementary techniques (X-ray diffraction, small angle X-ray scattering, optical microscopy and transmission electron microscopy) to correlate nanomorphology to macroscale properties. Materials were prepared using an out of autoclave...

Betime Nuhiji; Darren Attard; Gordon Thorogood; Tracey Hanley; Kevin Magniez; Jenny Bungur; Bronwyn Fox

2013-01-01

196

Structural relationships and vasorelaxant activity of monoterpenes  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background and purpose of the study The hypotensive activity of the essential oil of Mentha x villosa and its main constituent, the monoterpene rotundifolone, have been reported. Therefore, our objective was to evaluate the vasorelaxant effect of monoterpenes found in medicinal plants and establish the structure-activity relationship of rotundifolone and its structural analogues on the rat superior mesenteric artery. Methods Contractions of the vessels were induced with 10??M of phenylephine (Phe in rings with endothelium. During the tonic phase of the contraction, the monoterpenes (10-8 - 10-3, cumulatively were added to the organ bath. The extent of relaxation was expressed as the percentage of Phe-induced contraction. Results The results from the present study showed that both oxygenated terpenes (rotundifolone, (+-limonene epoxide, pulegone epoxide, carvone epoxide, and (+-pulegone and non-oxygenated terpene ((+-limonene exhibit relaxation activity. The absence of an oxygenated molecular structure was not a critical requirement for the molecule to be bioactive. Also it was found that the position of ketone and epoxide groups in the monoterpene structures influence the vasorelaxant potency and efficacy. Major conclusion The results suggest that the presence of functional groups in the chemical structure of rotundifolone is not essential for its vasorelaxant activity.

Cardoso Lima Tamires

2012-09-01

197

Distributing Correlation Coefficients of Linear Structure-Activity/Property Models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Quantitative structure-activity/property relationships are mathematical relationships linking chemical structure and activity/property in a quantitative manner. These in silico approaches are frequently used to reduce animal testing and risk-assessment, as well as to increase time- and cost-effectiveness in characterization and identification of active compounds. The aim of our study was to investigate the pattern of correlation coefficients distribution associated to simple linear relationsh...

Ja?ntschi, Lorentz; Bolboaca, Sorana D.

2011-01-01

198

Structure-activity relationships of anthocyanidin glycosylation.  

Science.gov (United States)

This paper summarizes the main achievements about the structure-activity relationships of anthocyanidin glycosylation. Anthocyanidin glycosylation is the essential step of anthocyanin biosynthesis and also the prerequisite of the further modifications of anthocyanins, which is jointly characterized by the glycosylation site, the type and number of the glycosyl as well as the glycosidic bond type. It generally enhances the stability, results in the hypsochromic effect and blueing, decreases the bioavailability and anticancer activity, and decreases, increases, or does not change the antioxidant activity of the anthocyanidins or anthocyanins, which is synergetically determined by the glycosylation site and the type and number of the glycosyl. Thereinto, in nature, the blue hues caused by the glycosylation may also be reinforced by the formation of the anthocyanic vacuolar inclusions. This review could provide a reference for the research of the structure-optimizing and function-exploiting of anthocyanins. PMID:24792223

Zhao, Chang Ling; Chen, Zhong Jian; Bai, Xue Song; Ding, Can; Long, Ting Ju; Wei, Fu Gang; Miao, Kang Ru

2014-08-01

199

Structure-property relationships of DEAEM-containing bone cements: effect of the substitution of a methylene group by an aromatic ring.  

Science.gov (United States)

New aromatic methacrylates were prepared by substitution of a methylene group from diethylaminoethyl methacrylate (DEAEM) by an aromatic ring at two different positions. Diethylamino benzyl methacrylate (DEABM) and N-methacryloyloxyethyl)-N-ethyl-m-toluidine (MEET) were polymerized and incorporated as co-monomers in bone cement formulations. Cements were evaluated in terms of curing and mechanical properties in addition to changes in their glass transition temperature by DSC and surface properties by contact angle measurements. The immediate effect of the presence of an aromatic ring within the amino methacrylate was that it modified the bone cements' physical appearance, as colored products were obtained. It was also observed that peak temperature increased and setting time decreased by the use of DEABM and MEET instead of DEAEM. Simultaneously, both tensile and compressive strength of bone cements were improved; this effect was related to a higher glass transition temperature. In addition, surface properties of cements were modified by the incorporation of the aromatic ring, being more hydrophilic at low molar fractions and more hydrophobic at high molar fractions. Based on these studies, it is concluded that the position of the aromatic ring within the amino methacrylate modified not only the cement's appearance, but also the setting and mechanical properties. PMID:17274447

Cervantes-Uc, J M; Cauich-Rodríguez, J V; Vázquez-Torres, H

2007-01-01

200

Discovery of substituted lactams as novel dual orexin receptor antagonists. Synthesis, preliminary structure-activity relationship studies and efforts towards improved metabolic stability and pharmacokinetic properties. Part 1.  

Science.gov (United States)

Starting from a thiazolidin-4-one HTS hit, a novel series of substituted lactams was identified and developed as dual orexin receptor antagonists. In this Letter, we describe our initial efforts towards the improvement of potency and metabolic stability. These investigations delivered optimized lead compounds with CNS drug-like properties suitable for further optimization. PMID:24447850

Sifferlen, Thierry; Boller, Amandine; Chardonneau, Audrey; Cottreel, Emmanuelle; Hoecker, Johannes; Aissaoui, Hamed; Williams, Jodi T; Brotschi, Christine; Heidmann, Bibia; Siegrist, Romain; Gatfield, John; Treiber, Alexander; Brisbare-Roch, Catherine; Jenck, Francois; Boss, Christoph

2014-02-15

 
 
 
 
201

Structure-cytotoxicity relationships for dietary flavonoids  

DEFF Research Database (Denmark)

The cytotoxicity of a large series of dietary flavonoids was tested in a non-tumorigenic mouse and two human cancer cell lines, using the neutral red dye exclusion assay. All compounds tested exhibited a concentration-dependent cytotoxic action in the employed cell lines. The relative cytotoxicity of the flavonoids, however, Tvas found to vary greatly among the different cell Lines. With a few exceptions, the investigated flavonoids were more cytotoxic to the human cancer cell lines, than the mouse cell line. The differences in cytotoxicity were accounted for in part by differences in cellular uptake and metabolic capacity among the different cell types. In 3T3 cells fairly consistent structure-cytotoxicity relationships were found. The most cytotoxic structures tested in 3T3 cells were flavonoids with adjacent 3',4' hydroxy groups on the B-ring, such as luteolin, quercetin, myricetin, fisetin, eriodictyol, and taxifolin. The structural requirements for cytotoxicity in the human cell lines, however, were lessclear. Reduction of the cytotoxic response of the 3',4'-hydroxylated flavonoid, quercetin, by the hydroxyl radical scavenger mannitol and the metal chelator desferozamine suggests that reactive oxygen species, produced from redox cycling of the catechol structure with molecular oxygen, is responsible in part for the cytotoxicity of this subgroup of flavonoids.

Breinholt, V.; Dragsted, L.O.

1998-01-01

202

Structural Relationships and Vasorelaxant Activity of Monoterpenes  

Directory of Open Access Journals (Sweden)

Full Text Available Background and purpose of the study The hypotensive activity of the essential oil of Mentha x villosa and its main constituent, the monoterpene rotundifolone, have been reported. Therefore, our objective was to evaluate the vasorelaxant effect of monoterpenes found in medicinal plants and establish the structureactivity relationship of rotundifolone and its structural analogues on the rat superior mesenteric artery. Methods:Contractions of the vessels were induced with 10 muM of phenylephine (Phe in rings with endothelium. During the tonic phase of the contraction, the monoterpenes (10-8 - 10-3, cumulatively were added to the organ bath. The extent of relaxation was expressed as the percentage of Phe-induced contraction. Results:The results from the present study showed that both oxygenated terpenes (rotundifolone, (+- limonene epoxide, pulegone epoxide, carvone epoxide, and (+-pulegone and nonoxygenated terpene ((+-limonene exhibit relaxation activity. The absence of an oxygenated molecular structure was not a critical requirement for the molecule to be bioactive. Also it was found that the position of ketone and epoxide groups in the monoterpene structures influence the vasorelaxant potency and efficacy. Major conclusion The results suggest that the presence of functional groups in the chemical structure of rotundifolone is not essential for its vasorelaxant activity.

Tamires Cardoso Lima

2012-09-01

203

Structure-to-property relationships in addition cured polymers. 4: Correlations between thermo-oxidative weight losses of norbornenyl cured polyimide resins and their composites  

Science.gov (United States)

Relationships are identified between the thermo-oxidative stability (TOS) at 316 C of a wide variety of PMR (polymerization of monomeric reactants) addition cured polyimide resins and their corresponding graphite fiber composites. Weight loss results at 316 C confirmed the expected relationship of increasing aliphatic endcap content with decreasing TOS. Moreover, the resin TOS study also showed an unexpected linear correlation of decreasing weight loss to increasing ratio of benzylic diamine to aliphatic endcap in the range of the stoichiometries studied. Only after long term 316 C aging does the dianhydride used with the benzylic diamines become an additional factor in influencing the amount of PMR resin and composite weight losses. Also, the benzylic systems consistently showed much lower resin and composite weight losses at 316 C than the corresponding nonbenzylic norbornenyl resins and composites, except when the nonbenzylic diamine monomer does not contain a connecting group. Instead, this diamine resulted in a 316 C resin and composite weight loss that was only competitive with benzylic type diamines. Results show excellent correlation between TOS of all graphite fiber PMR composites and resins.

Alston, William B.

1992-01-01

204

The Effect of a Rapid Heating Rate, Mechanical Vibration and Surfactant Chemistry on the Structure–Property Relationships of Epoxy/Clay Nanocomposites  

Directory of Open Access Journals (Sweden)

Full Text Available The role of processing conditions and intercalant chemistry in montmorillonite clays on the dispersion, morphology and mechanical properties of two epoxy/clay nanocomposite systems was investigated in this paper. This work highlights the importance of employing complementary techniques (X-ray diffraction, small angle X-ray scattering, optical microscopy and transmission electron microscopy to correlate nanomorphology to macroscale properties. Materials were prepared using an out of autoclave manufacturing process equipped to generate rapid heating rates and mechanical vibration. The results suggested that the quaternary ammonium surfactant on C30B clay reacted with the epoxy during cure, while the primary ammonium surfactant (I.30E catalysed the polymerisation reaction. These effects led to important differences in nanocomposite clay morphologies. The use of mechanical vibration at 4 Hz prior to matrix gelation was found to facilitate clay dispersion and to reduce the area fraction of I.30E clay agglomerates in addition to increasing flexural strength by over 40%.

Kevin Magniez

2013-08-01

205

Study of the structure-properties relationship of Fe-Al, Nb-Al and Ni-Ti intermetallic coatings obtained by thermal spray technologies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Due to the current interest on intermetallic compounds (IMCs), specially for their use at high temperatures being capable to substitute superalloys and, for the lately improvement of their lack of ductility, this work evaluates the use of intermetallics as coatings by using Thermal Spray technologies, thus providing improved surface component properties. The IMCs chosen for this study have been the following: FeAl, NiTi and NbAl3. Regarding their high Al contents, the aluminides present low d...

Cinca I Luis, Nu?ria

2008-01-01

206

Study of the structure-properties relationship of Fe-Al, Nb-Al and Ni-Ti intermetallic coatings obtained by thermal spray technologies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

[eng] Due to the current interest on intermetallic compounds (IMCs), specially for their use at high temperatures being capable to substitute superalloys and, for the lately improvement of their lack of ductility, this work evaluates the use of intermetallics as coatings by using Thermal Spray technologies, thus providing improved surface component properties. The IMCs chosen for this study have been the following: FeAl, NiTi and NbAl3. Regarding their high Al contents, the aluminides present...

Cinca I Luis, Nu?ria

2008-01-01

207

Properties of fast solitary structures  

Directory of Open Access Journals (Sweden)

Full Text Available We present detailed observations of electromagnetic waves and particle distributions from the Fast Auroral SnapshoT (FAST satellite which reveal many important properties of large-amplitude, spatially-coherent plasma structures known as "fast solitary structures" or "electron phase space holes". Similar structures have been observed in several regions of the magnetosphere including the auroral zone, plasma sheet boundary layer, and bow shock. There has been rapid theoretical progress in understanding these structures. Solitary structures can develop from bidirectional electron beams. Once developed, the one-dimensional properties parallel to the magnetic field can be adequately described by analytical treatment as BGK structures. There remains, however, several unanswered questions. The origin of the bidirectional electron beams, the development of two-or three-dimensional structures, and the observed association with the ion cyclotron frequency are not well understood.

R. E. Ergun

1999-01-01

208

Characterization of Enzyme Structure-Function Relationship of Adenylosuccinate Lyase  

Science.gov (United States)

Adenylosuccinate lyase (ADSL) is an enzyme involved in de novo purine biosynthesis required for several important biological functions. Occasionally disturbances within the enzyme occur, causing a disorder known as ADSL deficiency. It is likely these mutations affect the formation of the tetramer structure by protein misfolding or aggregation. We are beginning to study fundamental properties of the enzyme structure-function relationship of Wild-Type ADSL compared to mutants associated with ADSL Deficiency with two major studies: i) Stability and formation of multimeric complexes in a heterogeneous pool of other structures, ii) Enzymatic activity and reaction kinetics studies by measuring reaction rates of the conversion of substrate into products and enzyme substrate complex formation equilibrium. Our group has successfully expressed Wild-Type (WT) and the mutants R426H and A291V in a protein expression vector and have measured their respective enzyme activity after purification. Modelling approaches for molecular interactions of monomer subunits show the trimer structure could be problematic. We have also carried out our preliminary analysis of the structure-function relationship using microscopic model for the A291V mutant compared to the WT protein.

Ray, Stephen; Patterson, David; Ghosh, Kingshuk; Wilkinson, Terry; Shaheen, Sean

2009-10-01

209

Relationship between structure and properties in high-temperature Bi(Al0.5Fe0.5)O3-PbTiO3 piezoelectric ceramics  

International Nuclear Information System (INIS)

Highlights: ? Low-cost Bi-based high temperature piezoceramics. ? A new high temperature system with Curie point >478 deg. C, compared to BiScO3-PbTiO3 (450 deg. C). ? Effectively improve the poling conditions. - Abstract: Ceramic samples of xBi(Al0.5Fe0.5)O3-(1 - x)PbTiO3 (BAF-PT, x = 0.05-0.5) solid solutions were fabricated using the conventional solid state reaction method. X-ray diffraction analysis revealed that all compositions can form single perovskite phase with tetragonal symmetry. The relationship between the tetragonal lattice parameters, tetragonality c/a, cell volume, and ferro-piezoelectric characterization as a function of x was systematically investigated. The BAF modification can effectively improve the poling condition at a proper BAF content. A combination of piezoelectric constant of d33 (50-60 pC/N), electromechanical planar coupling coefficients of kp (20.3-22.5%), and high Curie temperature Tc (>478 deg. C) suggested that BAF-PT could be a good candidate for high-temperature piezoelectric applications.

2011-05-05

210

Unveiling structure-property relationships in Sr2Fe(1.5)Mo(0.5)O(6-?), an electrode material for symmetric solid oxide fuel cells.  

Science.gov (United States)

We characterize experimentally and theoretically the promising new solid oxide fuel cell electrode material Sr(2)Fe(1.5)Mo(0.5)O(6-?) (SFMO). Rietveld refinement of powder neutron diffraction data has determined that the crystal structure of this material is distorted from the ideal cubic simple perovskite, instead belonging to the orthorhombic space group Pnma. The refinement revealed the presence of oxygen vacancies in the as-synthesized material, resulting in a composition of Sr(2)Fe(1.5)Mo(0.5)O(5.90(2)) (? = 0.10(2)). DFT+U theory predicts essentially the same concentration of oxygen vacancies. Theoretical analysis of the electronic structure allows us to elucidate the origin of this nonstoichiometry and the attendant mixed ion-electron conductor character so important for intermediate temperature fuel cell operation. The ease with which SFMO forms oxygen vacancies and allows for facile bulk oxide ion diffusivity is directly related to a strong hybridization of the Fe d and O p states, which is also responsible for its impressive electronic conductivity. PMID:22449102

Muñoz-García, Ana B; Bugaris, Daniel E; Pavone, Michele; Hodges, Jason P; Huq, Ashfia; Chen, Fanglin; zur Loye, Hans-Conrad; Carter, Emily A

2012-04-18

211

Properties–structure relationship research on LiCaPO{sub 4}:Eu{sup 2+} as blue phosphor for NUV LED application  

Energy Technology Data Exchange (ETDEWEB)

Graphical abstract: The graphical abstract shows the excitation and emission spectrum of LiCaPO{sub 4}:Eu{sup 2+}, and the CIE coordinates of LiCaPO{sub 4}:Eu{sup 2+}. The inset shows the photo of blue LED prepared by LiCaPO{sub 4}:Eu{sup 2+} and NUV chip. It indicates that this phosphor can be excited by UV light and emit strong greenish-blue light. Highlights: •Pure phase blue phosphors of LiCaPO{sub 4}:Eu{sup 2+} with a hexagonal structure were first prepared via solid-state method. •The crystallographic site of Eu{sup 2+} ion in the LiCaPO{sub 4} lattice was identified as 8-fold Ca{sup 2+} site. •The phosphor exhibits excellent thermal stability and the corresponding mechanism was thermal assisted ionization. •Bright and high color purity blue LED prototype based on LiCaPO{sub 4}:Eu{sup 2+} phosphor was fabricated. -- Abstract: Blue-emitting phosphors of Eu{sup 2+}-activated LiCaPO{sub 4} with a hexagonal structure were prepared via a conventional solid-state method. The XRD, PL spectra and thermal quenching were applied to characterize the phosphors. The crystallographic site of Eu{sup 2+} ion in the LiCaPO{sub 4} lattice was identified and discussed. The optimized LiCaPO{sub 4}:0.03Eu{sup 2+} exhibits the bright greenish-blue emission with CIE coordinates of (0.119, 0.155) and a quantum efficiency of 52%. The critical energy-transfer distance was confirmed as ?18 Å by both calculated crystal structure method and experimental spectral method. The thermal stability of LiCaPO{sub 4}:Eu{sup 2+} was evaluated by temperature-dependent PL spectra, and the thermal quenching mechanism was found to be thermal assisted ionization. Prototype blue LEDs with high color purity and good current stability were fabricated.

Zhang, Xinguo, E-mail: mpcc1@qq.com [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Mo, Fuwang; Zhou, Liya [School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Gong, Menglian [State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

2013-10-25

212

SnO{sub 2} nanocrystals synthesized by microwave-assisted hydrothermal method: towards a relationship between structural and optical properties  

Energy Technology Data Exchange (ETDEWEB)

The exploration of novel synthetic methodologies that control both size and shape of functional nanostructure opens new avenues for the functional application of nanomaterials. Here, we report a new and versatile approach to synthesize SnO{sub 2} nanocrystals (rutile-type structure) using microwave-assisted hydrothermal method. Broad peaks in the X-ray diffraction spectra indicate the nanosized nature of the samples which were indexed as a pure cassiterite tetragonal phase. Chemically and physically adsorbed water was estimated by TGA data and FT-Raman spectra to account for a new broad peak around 560 cm{sup -1} which is related to defective surface modes. In addition, the spherical-like morphology and low dispersed distribution size around 3-5 nm were investigated by HR-TEM and FE-SEM microscopies. Room temperature PL emission presents two broad bands at 438 and 764 nm, indicating the existence of different recombination centers. When the size of the nanospheres decreases, the relative intensity of 513 nm emission increases and the 393 nm one decreases. UV-Visible spectra show substantial changes in the optical absorbance of crystalline SnO{sub 2} nanoparticles while the existence of a small tail points out the presence of localized levels inside the forbidden band gap and supplies the necessary condition for the PL emission.

Mendes, Paulo G. [UEPG-Universidade Estadual de Ponta Grossa, Department of Materials Science, INCTMN, LIMAC, CIPP (Brazil); Moreira, Mario L., E-mail: mlucio@liec.ufscar.br [UNESP-Universidade Estadual Paulista, Department of Physical Chemistry, Institute of Chemistry, INCTMN, LIEC (Brazil); Tebcherani, Sergio M. [UEPG-Universidade Estadual de Ponta Grossa, Department of Materials Science, INCTMN, LIMAC, CIPP (Brazil); Orlandi, Marcelo O. [UNESP-Universidade Estadual Paulista, Department of Physical Chemistry, Institute of Chemistry, INCTMN, LIEC (Brazil); Andres, J. [University of Jaume I, Department of Experimental Sciences (Spain); Li, Maximu S. [USP, Instituto de Fisica, INCTMN (Brazil); Diaz-Mora, Nora [Parque Tecnologico de Itaipu (PTI), Laboratorio de Materiais (LAMAT/UNIOESTE) (Brazil); Varela, Jose A.; Longo, Elson [UNESP-Universidade Estadual Paulista, Department of Physical Chemistry, Institute of Chemistry, INCTMN, LIEC (Brazil)

2012-03-15

213

Structure-property relationships in off-resonant third-order nonlinearities of conducting polymers. Pt. 1. Poly(aromatic amines) and ring-S-heteroatom-containing polymers  

Energy Technology Data Exchange (ETDEWEB)

Presented in this work are initial, systematic studies of third-order nonlinear optical (NLO) susceptibilities using degenerate four-wave mixing measurements in solution at 1.064 [mu]m and their relation with structural features for a series of poly(aromatic amines) and S-heteroatom aromatic ring-containing processible conducting polymers the syntheses of which have already been reported. These include poly(diphenylamine) and other analogues of polyaniline, poly(aminoquinolines), poly(1-aminopyrene), poly(3-aminopyridine), poly(3-aminopyrazole), poly(aminothiazoles), poly(aminothiadiazoles) and poly(isothianaphthene), among others. The effects of dopant type and level and related variables are also reported. Many of the polymers show appreciable nonlinearities, typical values of [chi][sup (3)][sub xxxx] being 1.3 x 10[sup -10] e.s.u. for poly(diphenylamine) and 2.7 x 10[sup -10] e.s.u. for poly(1-aminopyrene). Among other findings, it is observed that introduction of multiple fused aromatic rings in the polymer backbone very significantly enhances the nonlinearity and that lower doping levels consistently yield higher nonlinearities for all polymers observed. Polymers containing S and N heteroatoms in the same ring along the polymer chain exhibit negligible nonlinearities. The time response for all polymers is found to be faster than 40 ps. Z-scan and two-photon absorption measurements are used together with other methods to demonstrate the purely off-resonant character of the third-order nonlinear susceptibilities observed for representative polymers. (orig.).

Chandrasekhar, P. (Gumbs, Inc., East Brunswick, NJ (United States)); Thorne, J.R.G.; Hochstrasser, R.M. (Dept. of Chemistry, Univ. of Pennsylvania, Philadelphia (United States))

1993-01-01

214

Foldamers structure, properties and applications  

CERN Document Server

This truly comprehensive treatise of foldamers, from synthesis to applications in bio-, material-, and nanoscience is at once an introduction to the topic, while providing in-depth accounts on various aspects clearly aimed at the specialist.The book is clearly structured, with the first part concentrating on structure and foldamer design concepts, while the second part covers functional aspects from properties to applications. The international team of expert authors provides overviews of synthetic approaches as well as analytical techniques.

Hecht, Stefan

2007-01-01

215

Some properties of galaxy structures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We analysed some properties of galaxies structures based on PF Catalogue of galaxy structures (Panko & Flin 2006) and Tully NBG Catalog (Tully 1988) At first, we analyzed the orientation of galaxies in the 247 optically selected rich Abell clusters, having in the area considered as cluster at least 100 members. The distribution of the position angles of the galaxy as well as two angles describing the spatial orientation of galaxy plane were tested for isotropy, applying thre...

Flin, Piotr; Biernacka, Monika; Godlowski, Wlodzimierz; Panko, Elena; Piwowarska, Paulina

2011-01-01

216

Relationships between properties and functional targets of Chinese herbs  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract: Functional targets are the objects that Chinese herbal medicines act directly upon. If the relationships between the properties of Chinese herbs and their functional targets were analyzed clearly, it would benefit the overall understanding of the holistic mechanisms of Chinese herbal treatments. In this paper, data regarding the properties of Chinese herbs and their functional targets were collected from the 2005 edition of The People’s Republic of China Pharmacopoeia. After analyzing and assessing the data, the relationships were defined between the four qi, meridian entry and medicinal functional targets and between the four qi, five flavors and mode of function. Then the relationships between a single herbal medicine and a prescription were analyzed, and the results conformed with the traditional knowledge of Chinese herbal nature and efficacy. This demonstrated that the holistic mechanisms of the properties of Chinese herbs adhere to the findings, which may be beneficial for the development and compatibility of Chinese herbal medicines.

Bin Xiao

2011-07-01

217

Structural Analysis of Laplacian Spectral Properties in Complex Electric Grids  

CERN Document Server

Motivated by recent interest for power grid architectures, we study the relationship between structural features of electrical transmission networks and the behavior of certain dynamical processes taking place in the network. The spectrum of the Laplacian matrix plays a key role in a wide range of networked dynamical problems, from transient stability analysis to distributed control. Using methods from algebraic graph theory and convex optimization, we study the relationship between structural features of the network and spectral properties of the Laplacian matrix. We illustrate our results by studying the influence of structural properties on the Laplacian eigenvalues of the American (western states), Spanish and French high-voltage transmission networks.

Preciado, Victor M; Verghese, George C

2011-01-01

218

Structural properties of 3-dimensional carbon clusters  

Energy Technology Data Exchange (ETDEWEB)

Structural properties of 3d carbon clusters were calculated employing recently developed model potential energy functions for carbon. Primarily, spherical shell structures were included in the present investigation. Configurations corresponding to local energy minima were calculated for various shells of an icosahedron containing different number of C atoms. For C{sub 60}, the two low-lying isomers, the buckminsterfullerene and truncated dodecahedron, were found to be almost isoenergetic. It was also found that fully relaxed structures of C{sub 90} and C{sub 120} have energies very comparable to that of C{sub 60}. Furthermore, a systematic analysis carried out in this study for carbon clusters with varying dimensionalities, revealed an interesting relationship between the bond lengths and the distribution of bond angles. In all cases, shorter bond distances were found to be associated with larger bond angles. (orig.).

Halicioglu, T. (Stanford Univ., CA (USA). Dept. of Materials Science and Engineering)

1991-01-01

219

Structural properties of 3-dimensional carbon clusters  

International Nuclear Information System (INIS)

Structural properties of 3d carbon clusters were calculated employing recently developed model potential energy functions for carbon. Primarily, spherical shell structures were included in the present investigation. Configurations corresponding to local energy minima were calculated for various shells of an icosahedron containing different number of C atoms. For C60, the two low-lying isomers, the buckminsterfullerene and truncated dodecahedron, were found to be almost isoenergetic. It was also found that fully relaxed structures of C90 and C120 have energies very comparable to that of C60. Furthermore, a systematic analysis carried out in this study for carbon clusters with varying dimensionalities, revealed an interesting relationship between the bond lengths and the distribution of bond angles. In all cases, shorter bond distances were found to be associated with larger bond angles. (orig.)

1990-09-10

220

Structure-activity relationships in Werner clathrates  

International Nuclear Information System (INIS)

The synthesis and characterization of a series of inorganic coordination compounds which, upon crystallization, have the ability to include solvent or guest molecules spatially within the lattice are reported. The compounds have the following general formula: [NiX2B4] - where X is isothiocyanate or bromine and B is 4-ethylpyridine, 4-vinylpiridine or 3,5-dimethylpyridine; [NiX2B2]n - where X is isothiocyanate, B is 2-aminopyridine and n indicates it is a polymer; [NiX2AB2]2 - where X is isothiocyanate, B is 3-aminopyridine (two of these four ligands in the dimer are bridging) and A is water. The various guest molecules have been carefully chosen, according to their point symmetry, which is a key factor in yielding structures of a particular type. The structures of seventeen compounds have been elucidated by single crystal x-ray analysis. The difficulty has been found to lie in refining disordered guest molecules. Other techniques employed in the initial characterization of these compounds are Microanalysis, Mass Spectrometry and UV/Visible Spectrophotometry. An intramolecular potential energy study on the [Ni(NCS)2(3,5-diMepy)4] complex reveals that the orthohydrogens on the 3,5-dimethylpyridine ligands control the conformation of the molecule. Packing densities and volume comparisons of the [Ni(NCS)2(4-Etpy)4] and [Ni(NCS)2(4-Vipy)4] complexes and their clathrates have been carried out. The exact sizes and shapes of the cavities in which the guest molecules are located in the x-ray crystal structures have been evaluated by both intermolecular potential energy and molecular volume calculations. Thermodynamic and spectroscopic properties of the [Ni(NCS)2(4-Etpy)4] and [Ni(NCS)2(4-Vipy)4] clathrates have been studied in both solution and the solid state. The techniques used are x-ray powder diffractometry, IR spectroscopy and Thermogravimetry (including Differential Thermal Analysis). 70 figs., 35 tabs., 125 refs

1987-01-01

 
 
 
 
221

Estimation of exposure and ecotoxicity of chemicals by computer based structure-property and structure-activity relationships; Abschaetzung des umweltchemischen und oekotoxikologischen Verhaltens von Stoffen durch computergestuetzte Analyse von Struktur und Verhalten sowie von Struktur und Wirkung  

Energy Technology Data Exchange (ETDEWEB)

Risk assessment of chemicals requires comprehensive data material, which often is not available. To provide substitutes for the lacking experimental ecotoxicological and physico-chemical data, a software-system (SAR-System) has been developed comprising more than 90 estimation models for relevant endpoints. The approach is based on qualitative structure-activity relationships (QSAR). Two major aspects characterize the SAR-System: (1) The implemented models were tested for their validity and application range. (2) The QSARs are accessible by a menu-driven programme package. The following endpoints are included: Physico-chemical Data: 1-Octanol/water-partition-coefficient log P{sub ow}, vapour pressure, water solubility, pK{sub a}-value, boiling point. Biological Data: Toxicity towards fish, daphnia, tetrahymenae, algae, bacteria and mammals, mutagenicity. Distribution: Soil sorption, bioconcentration, Henry-Constant, Mackay (Level I). Degradation: Photodegradation, biodegradability. (orig.) [Deutsch] Die Bewertung von Chemikalien in der Umwelt erfordert eine Vielzahl von haeufig nicht verfuegbaren Stoffdaten. Um experimentelle oekotoxikologische und physikochemische Daten zu ergaenzen, wurde ein Software-System (SAR-System) entwickelt, welches ueber 90 Schaetzverfahren auf der Basis von Quantitativen Struktur-Aktivitaets-Beziehungen (QSAR) enthaelt. Zwei wesentliche Kriterien zeichnen das SAR-System aus: 1) Die implementierten Modelle wurden einer Validierung zur Feststellung des gueltigen Anwendungsbereichs unterzogen. 2) Die Schaetzverfahren sind ueber ein benutzerfreundliches, ausschliesslich menuegesteuertes Programmpaket zugaenglich. Zu folgenden Parametern stehen Schaetzverfahren zur Verfuegung: Physiko-chemische Daten: 1-Octanol/Wasser-Verteilungskoeffizient log P{sub ow}, Dampfdruck, Wasserloeslichkeit, pK{sub a}-Wert, Siedepunkt. Biologische Endpunkte: Toxizitaet gegenueber Fischen, Daphnien, Tetrahymenae, Algen, Bakterien und Saeugetieren, Mutagenitaet. Verteilung: Bodensorption, Biokonzentration, Henry-Konstante, Mackay (Level I). Abbau: Photoabbau, Bioabbaubarkeit. (orig.)

Jaeckel, H. [Fraunhofer-Institut fuer Umweltchemie und Oekotoxikologie, Schmallenberg (Germany); Mueller, M. [Fraunhofer-Institut fuer Umweltchemie und Oekotoxikologie, Schmallenberg (Germany); Nendza, M. [Fraunhofer-Institut fuer Umweltchemie und Oekotoxikologie, Schmallenberg (Germany); Klein, W. [Fraunhofer-Institut fuer Umweltchemie und Oekotoxikologie, Schmallenberg (Germany); Gies-Reuschel, A. [Umweltbundesamt, Berlin (Germany)

1993-12-31

222

Distributing Correlation Coefficients of Linear Structure-Activity/Property Models  

Directory of Open Access Journals (Sweden)

Full Text Available Quantitative structure-activity/property relationships are mathematical relationships linking chemical structure and activity/property in a quantitative manner. These in silico approaches are frequently used to reduce animal testing and risk-assessment, as well as to increase time- and cost-effectiveness in characterization and identification of active compounds. The aim of our study was to investigate the pattern of correlation coefficients distribution associated to simple linear relationships linking the compounds structure with their activities. A set of the most common ordnance compounds found at naval facilities with a limited data set with a range of toxicities on aquatic ecosystem and a set of seven properties was studied. Statistically significant models were selected and investigated. The probability density function of the correlation coefficients was investigated using a series of possible continuous distribution laws. Almost 48% of the correlation coefficients proved fit Beta distribution, 40% fit Generalized Pareto distribution, and 12% fit Pert distribution.

Sorana D. BOLBOACA

2011-12-01

223

Structural properties of macromolecular solutions  

Energy Technology Data Exchange (ETDEWEB)

The authors report measurements of viscosity and light scattering in an aqueous solution of BSA. Like the lysozyme solutions previously investigated, the BSA solutions show thixotropic properties. Optical measurements of both elastic and inelastic light scattering indicate the existence of a structure in which the BSA molecule tends to clusterize, each cluster being correlated to the others. A K-dependent diffusion coefficient D(K) is found. The static structure factor deduced from the values of DL(K) agrees well with the indications given by the elastically scattered intensity I(K). Also, the statical properties of scattered light appear to be consistent with the proposed model. A qualitative explanation, in terms of a dominant component in the fluctuations of concentration, is briefly sketched. 16 references.

Giordano, R.; Maisano, G.; Mallamace, F.; Micali, N.; Wanderlingh, F.

1981-11-15

224

The structure-mechanical relationship of palm vascular tissue.  

Science.gov (United States)

The structure-mechanical relationship of palm sheath is studied with numerical and experimental methods. The cellular structure of the vascular tissue is rebuilt with an image-based reconstruction method and used to create finite element models. The validity of the models is firstly verified with the results from the tensile tests. Then, the cell walls inside each of the specific regions (fiber cap, vessel, xylem, etc.) are randomly removed to obtain virtually imperfect structures. By comparing the magnitudes of performance degradation in the different imperfect structures, the influences of each region on the overall mechanical performances of the vascular tissue are discussed. The longitudinal stiffness and yield strength are sensitive to the defects in the vessel regions. While in the transverse directions (including the radial and tangential directions), the parenchymatous tissue determines the mechanical properties of the vascular tissue. Moreover, the hydraulic, dynamic response and energy absorption behavior of the vascular tissue are numerically explored. The flexibility of natural palm tissue enhances its impact resistance. Under the quasi-static compression, the cell walls connecting the fiber cap and the vessel dissipate more energy. The dominant role of the fiber cap in the plastic energy dissipation under high-speed impact is observed. And the radially-arranged fiber cap also allows the palm tissue to improve its tangential mechanical performances under hydraulic pressure. PMID:24768963

Wang, Ningling; Liu, Wangyu; Huang, Jiale; Ma, Ke

2014-08-01

225

Crosslinking-property relationships in PMR polyimide composites. I  

Science.gov (United States)

The thermooxidatively-induced crosslinking/ physical and mechanical property relationships of graphite fiber-reinforced PMR polyimide-matrix composites were studied during isothermal exposure of the composite specimens at 288 C in air for periods of up to 5000 hr. The crosslinking densities due to this treatment were estimated on the basis of the kinetic theory of rubber elasticity and shifts in the glass transition temperature T(g). Several linear relationships are noted between crosslink density and physical and mechanical properties: T(g), initial weight loss, and elevated temperature interlaminar shear strength increase with crosslink density, while initial moisture absorption decreases. After achieving the highest crosslink density, several of the composite properties begin to decrease from their maximum values.

Pater, R. H.; Whitley, K.; Morgan, C.; Chang, A.

1987-01-01

226

Asymptotic Properties of Parameters for Linear Circular Functional Relationship Model  

Directory of Open Access Journals (Sweden)

Full Text Available This study discusses the asymptotic properties of parameters for unreplicated linear circular functional relationship model. The model is formulated assuming both variables are circular, subject to errors and there is a linear relationship between them. The Maximum Likelihood Estimation (MLE have been used to estimate the slope parameters (β, intercept (α and error concentration parameters for both variables which are κ and v, respectively. The Fisher information matrix have been derived and based on this we estimated the asymptotic covariance matrix of

A.G. Hussin

2008-01-01

227

Some Properties of Galaxy Structures  

Science.gov (United States)

We analysed some properties of galaxies structures based on the PF catalog of galaxy structures (Panko & Flin 2006) and the Tully NBG catalog (Tully 1988). At first, we analyzed the orientation of galaxies in the 247 optically selected rich Abell clusters, having at least 100 members. The distribution of the position angles of galaxies as well as of two angles describing spatial orientation of the galaxy planes were tested for isotropy, applying three statistical tests. We found the relation between the anisotropy and the cluster richness. The relation between the galaxy alignment and the Bautz-Morgan morphological type of the parent cluster is not present. A statistically marginal relation between the velocity dispersion and cluster richness is observed. We also analyzed ellipticities for 6188 low redshift (z < 0.18) poor and rich galaxy structures which have been examined along with their evolution. Finally, we analyzed the Binggeli effect and found that the orientation of galaxy groups in the Local Supercluster (LSC), is strongly correlated with the distribution of neighbouring groups in the scale up to about 20 Mpc. Analysis of galaxy structures from the PF catalog shows quite different situation -- the efect is observed only for more elongated structures (e ? 0.3). The effect is present in a distance range of about 60 h-1 Mpc.

Flin, Piotr; Biernacka, Monika; God?owski, W?odzimierz; Panko, Elena; Piwowarska, Paulina

228

Relationship between Static Stiffness and Modal Stiffness of Structures  

Directory of Open Access Journals (Sweden)

Full Text Available This paper derives the relationship between the static stiffness and modal stiffness of a structure. The static stiffness and modal stiffness are two important concepts in both structural statics and dynamics. Although both stiffnesses indicate the capacity of the structure to resist deformation, they are obtained using different methods. The former is calculated by solving the equations of equilibrium and the latter can be obtained by solving an eigenvalue problem. A mathematical relationship between the two stiffnesses was derived based on the definitions of two stiffnesses. This relationship was applicable to a linear system and the derivation of relationships does not reveal any other limitations. Verification of the relationship was given by using several examples. The relationship between the two stiffnesses demonstrated that the modal stiffness of the fundamental mode was always larger than the static stiffness of a structure if the critical point and the maximum mode value are at the same node, i.e. for simply supported beam and seven storeys building are 1.5% and 15% respectively. The relationship could be applied into real structures, where the greater the number of modes being considered, the smaller the difference between the modal stiffness and the static stiffness of a structure.

Tianjian Ji Tianjian Ji

2010-02-01

229

Quasicrystals Structure and Physical Properties  

CERN Document Server

A comprehensive and up-to-date review, covering the broad range of this outstanding class of materials among intermetallic alloys. Starting with metallurgy and characterization, the authors continue on to structure and mathematical modeling. They use this basis to move on to dealing with electronic, magnetic, thermal, dynamic and mechanical properties, before finally providing an insight into surfaces and thin films. The authors belong to a research program on quasicrystals, sponsored by the German Research Society and managed by Hans-Rainer Trebin, such that most of the latest results are pre

Trebin, Hans-Rainer

2003-01-01

230

Some properties of galaxy structures  

CERN Multimedia

We analysed some properties of galaxies structures based on PF Catalogue of galaxy structures (Panko & Flin 2006) and Tully NBG Catalog (Tully 1988) At first, we analyzed the orientation of galaxies in the 247 optically selected rich Abell clusters, having in the area considered as cluster at least 100 members. The distribution of the position angles of the galaxy as well as two angles describing the spatial orientation of galaxy plane were tested for isotropy, applying three statistical tests. We found that anisotropy increases with the number of member galaxies, which means there exists the relation between anisotropy and cluster richness. We do not find connection of galaxy alignment and Bautz - Morgan morphological type of parent cluster. The statistically marginal relation between velocity dispersion and cluster richness was observed. However it was found that velocity dispersion decreases with Bautz - Morgan type at almost $3 \\sigma$ level. Separately we analyzed ellipticities for 6188 low redshift ...

Flin, Piotr; Godlowski, Wlodzimierz; Panko, Elena; Piwowarska, Paulina

2011-01-01

231

Properties-microstructure-processing relationships of monolithic fuel forms  

International Nuclear Information System (INIS)

Monolithic U-Mo alloys are the fuel of choice to convert the remaining reactors worldwide still using HEU to LEU for the RERTR program. Since the thin fuel alloys must be encapsulated in aluminum alloy cladding, material properties are extremely important for the fabricability of fuel plates prior to irradiation. Thus, the material properties of the thin fuel alloys are dependent upon the microstructure of the alloy, and consequently dependent upon the manner in which the fuel is processed. Marked differences in fuel properties have been observed as a function of both post foil fabrication and post fuel plate fabrication. The current paper seeks to document some of the property-microstructure-processing relationships observed for HEU-10Mo monolithic fuel alloys. (authors)

2007-09-09

232

The Association between Current Intergenerational Family Relationships and Sibling Structure.  

Science.gov (United States)

The authors examined the relationship between sibling structure variables (i.e., gender, number of sisters, number of brothers, sibling spacing, number of siblings, and birth order, all men, and all women siblings) and current relationships with parents and spouse/partners. Participants included 519 adults between the ages of 19 and 59 years. Two…

Lawson, David M.; Brossart, Daniel F.

2004-01-01

233

Relationship between thermophysical and mechanical properties of metallic glasses  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Mechanical (elastic moduli, yield strength, hardness) and thermophysical (glass transition, fragility indexes, heat content of shear bands) properties of metallic glasses are discussed and compared using an extensive database containing values for different families of alloys. The relationships between some of the above quantities are analysed to get insight into the shear band energetics and propagation. The failure by shear and the consequent temperature rise due to the release of elasti...

Battezzati, Livio; Rizzi, Paola; Baldissin, Daniele

2010-01-01

234

Elastic properties of chalcopyrite structured solids  

International Nuclear Information System (INIS)

Highlights: ? In this paper the authors have been evaluated six independent elastic stiffness constants, C11, C12, C13, C22, C33 and C44 for chalcopyrite (AIBIIIC2VI and AIIBIVC2V) structured solids with the help of ionic charge theory. ? The proposed relationship only the kBTm/? normalization and ionic charge are required as input, the computation of elastic constants itself is trivial, and the accuracy of the results compares well with experimental values. ? The method turns out to be widely applicable. - Abstract: Elastic properties (i.e. six independent elastic stiffness constants, C11, C12, C13, C33, C44 and C66) of chalcopyrite structured solids were evaluated. Values of C11, C33, C44, C66, of AIBIIIC2VI and AIIBIVC2V chalcopyrite semiconductors exhibit a linear relationship when plotted against the kBTm/? (kB = Boltzmann's constant, Tm = melting temperature, ? = atomic volume) normalization, but fall on two straight lines according to the product of ionic charges of the compounds. The calculated results are compared with available experimental data and previous calculations based on phenomenological models.

2012-02-15

235

ProKware: integrated software for presenting protein structural properties in protein tertiary structures.  

Science.gov (United States)

Protein tertiary structure plays an essential role in deciphering protein functions, especially protein structural properties, including domains, active sites and post-translational modifications. These properties typically yield useful clues for understanding protein functions. This work presents an integrated software, named ProKware, that presents protein structural properties in protein tertiary structures, such as domains, functional sites, families, active sites, binding sites, post-translational modifications and domain-domain interaction. Using this web-based and Windows-based interface, users can manipulate and visualize three-dimensional protein structures, as well as the supported structural properties that are curated in the protein knowledge database. ProKware is an effective and convenient solution for investigating protein functions and structural relationships. This software can be accessed on the internet at http://ProKware.mbc.nctu.edu.tw/. PMID:16845116

Hung, Jui-Hung; Huang, Hsien-Da; Lee, Tzong-Yi

2006-07-01

236

Structure-function relationships in telomerase genes.  

Science.gov (United States)

The TERT (telomerase reverse transcriptase) subunit of telomerase is an intensively studied macromolecule due to its key importance in maintaining genome integrity and role in cellular aging and cancer. In an effort to provide an up-to-date overview of the topic, we discuss the structure of TERT genes, their alternative splicing products and their functions. Nucleotide databases contain more than 90 full-length cDNA sequences of telomerase protein subunits. Numerous in silico, in vitro and in vivo experimental techniques have revealed a great deal of structural and functional data describing particular features of the telomerase subunit in various model organisms. We explore whether particular findings are generally applicable to telomerases or species-specific. We also discuss in an evolutionary context the role of identified functional TERT subdomains. PMID:19419346

Sýkorová, Eva; Fajkus, Jirí

2009-07-01

237

The structure of new germanates, gallates, borates and silicates with laser, piezo, ferroelectric and ion conducting properties  

International Nuclear Information System (INIS)

The results of structure investigation of more than 50 new crystalline germanates, gallates, borogermanates, borates, and silicates with laser, piezo, ferroelectric, and ion-conducting properties are described. The structure - properties relationship is examined. 71 refs.; 24 figs.; 10 tabs

1994-01-01

238

A genetic algorithm for structure-activity relationships: software implementation  

CERN Multimedia

The design and the implementation of a genetic algorithm are described. The applicability domain is on structure-activity relationships expressed as multiple linear regressions and predictor variables are from families of structure-based molecular descriptors. An experiment to compare different selection and survival strategies was designed and realized. The genetic algorithm was run using the designed experiment on a set of 206 polychlorinated biphenyls searching on structure-activity relationships having known the measured octanol-water partition coefficients and a family of molecular descriptors. The experiment shows that different selection and survival strategies create different partitions on the entire population of all possible genotypes.

Jantschi, Lorentz

2009-01-01

239

Investigation of structure-properties relationship in a novel family of halogenoantimonates(III) and halogenobismuthates(III) with morpholinium cation: [NH2(C2H4)2O]MX4. Crystal structure, phase transitions and dynamics of molecules.  

Science.gov (United States)

Three new organic-inorganic hybrids based on halogenoantimonates(III) and halogenobismuthates(III) with the morpholinium cation, [NH2(C2H4)2O]SbCl4, [NH2(C2H4)2O]SbBr4 and [NH2(C2H4)2O]BiBr4, have been prepared and characterized with DSC, TGA, DTA and single-crystal X-ray diffraction. The common feature of the crystal structures of the studied compounds is the presence of polyanionic ([MX4]?(-)) and morpholinium (head-to-tail configuration) chains, which expand themselves parallel to each other. The antimonate derivatives are isomorphous, crystallizing in a centrosymmetric orthorhombic Pbca space group and show no phase transitions (PTs) between 110 and 370 K. On the other hand, [NH2(C2H4)2O]BiBr4 undergoes two first-order structural PTs: I ? II at 321/343 K (cooling/heating) and II ? III at 285/289 K (cooling/heating). The mechanism of the PTs is discussed on the basis of crystallographic data and (1)H NMR and infrared spectroscopy. The PT at 343 K is accompanied by a spectacular switching of the spin-lattice T1 relaxation pathway. Structural parameters analysis has been performed to discuss a structure-properties relationship. PMID:23999763

Owczarek, Magdalena; Jakubas, Ryszard; Pietraszko, Adam; Medycki, Wojciech; Baran, Jan

2013-11-14

240

Morphology-Property Relationship in Rubber-Based Nanocomposites: Some Recent Developments  

Science.gov (United States)

Recently, rubber nanocomposites reinforced with a low volume fraction of nanofillers have attracted great interest due to their fascinating properties. Incorporation of nanofillers such as layered and fibrillated silicate clays, carbon nanotubes and nanofibers, calcium carbonate, metal oxides, or silica nanoparticles into elastomers can significantly improve their mechanical, thermal, dynamic mechanical, electrical, aging, barrier, adhesion, and flame retardancy properties. These also significantly alter the rheological behavior of polymers, even at low filler loading. The properties of nanocomposites depend greatly on the structure of the polymer matrices, the nature of nanofillers, and the method by which they are prepared. It has been established that uniform dispersion of nanofillers in rubber matrices is a general prerequisite for achieving desired mechanical, rheological, and physical characteristics. This review paper addresses some recent developments on the morphology-property relationship of rubber-based nanocomposites reinforced with various nanoparticles. New insights into understanding the properties of these nanocomposites and morphology development will be discussed.

Bhowmick, A. K.; Bhattacharya, M.; Mitra, S.; Kumar, K. Dinesh; Maji, P. K.; Choudhury, A.; George, J. J.; Basak, G. C.

 
 
 
 
241

Structure-activity relationship study of anoplin.  

Science.gov (United States)

Anoplin is a decapeptide amide, GLLKRIKTLL-NH2 derived from the venom sac of the solitary spider wasp, Anoplius samariensis. It is active against Gram-positive and Gram-negative bacteria and is not hemolytic towards human erythrocytes. The present paper reports a structure-activity study of anoplin based on 37 analogues including an Ala-scan, C- and N-truncations, and single and multiple residue substitutions with various amino acids. The analogues were tested for antibacterial activity against both S. aureus ATCC 25923 and E. coli ATCC 25922, and several potent antibacterial analogues were identified. The cytotoxicity of the analogues against human erythrocytes was assessed in a hemolytic activity assay. The antibacterial activity and selectivity of the analogues against S. aureus and E. coli varied considerably, depending on the hydrophobicity and position of the various substituted amino acids. In certain cases the selectivity for Gram-positive and Gram-negative bacteria was either reversed or altogether eliminated. In addition, it was generally found that antibacterial activity coincided with hemolytic activity. PMID:15635634

Ifrah, Dan; Doisy, Xavier; Ryge, Trine S; Hansen, Paul R

2005-02-01

242

Relating Dynamic Properties to Atomic Structure in Metallic Glasses  

Energy Technology Data Exchange (ETDEWEB)

Atomic packing in metallic glasses is not completely random but displays various degrees of structural ordering. While it is believed that local structures profoundly affect the properties of glasses, a fundamental understanding of the structure–property relationship has been lacking. In this article, we provide a microscopic picture to uncover the intricate interplay between structural defects and dynamic properties of metallic glasses, from the perspective of computational modeling. Computational methodologies for such realistic modeling are introduced. Exploiting the concept of quasi-equivalent cluster packing, we quantify the structural ordering of a prototype metallic glass during its formation process, with a new focus on geometric measures of subatomic “voids.” Atomic sites connected with the voids are found to be crucial in terms of understanding the dynamic, including vibrational and atomic transport, properties. Normal mode analysis is performed to reveal the structural origin of the anomalous boson peak (BP) in the vibration spectrum of the glass, and its correlation with atomic packing cavities. Through transition-state search on the energy landscape of the system, such structural disorder is found to be a facilitating factor for atomic diffusion, with diffusion energy barriers and diffusion pathways significantly varying with the degree of structural relaxation/ordering. The implications of structural defects for the mechanical properties of metallic glasses are also discussed.

Sheng, H.W.; Ma, E.; Kramer, Matthew J.

2012-07-18

243

Filler influence on properties of polymer structures ??????? ??????????? ?? ??????? ???????????? ?????????? ???????? ????? ??????????? ?? ?????? ?????????? ?????????? ????????  

Directory of Open Access Journals (Sweden)

Full Text Available  Influence of filler on properties of polymer structures has been studied. Influence of filler surface change on the process of polymer structures formation has been shown. ??????????? ??????? ??????????? ?? ??????? ???????????? ?????????? ????????. ???????? ??????????? ????????????????? ??????? ??????????? ?? ??????? ???????????? ?????????? ???????? ?????????? ??????????? ???????????. ?????????? ????? ??????????? ?? ?????? ?????????? ?????????? ????????. ???????? ?????????? ???????????????? ?????? ??????????? ?? ?????? ?????????? ?????????? ???????? ?????? ???????? ???????????.

?.?. ?????????

2004-02-01

244

Relationships between structures of hydroxyflavones and their antioxidative effects.  

Science.gov (United States)

Even hydroxyflavones show diverse biological functions, they have two common features such as showing antioxidative effects and containing hydroxyl groups. The authors tested the antioxidative effects of thirty hydroxyflavones using 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay. While the scavenging activity of galangin, 3,5,7-trihydroxyflavone was 52.5%, fisetin, 3,7,3',4'-tetrahydroxyflavone showed 85.2%. To investigate the relationships between the structures of hydroxyflavones and their antioxidative effects, the three-dimensional quantitative structure-activity relationships were examined. PMID:20692831

Hyun, Jiye; Woo, Yoonkyung; Hwang, Do-Seok; Jo, Geunhyeong; Eom, Sunglock; Lee, Younggiu; Park, Jun Cheol; Lim, Yoongho

2010-09-15

245

A structurally-based model of irradiated graphite properties  

Energy Technology Data Exchange (ETDEWEB)

In this paper, we describe a model of irradiated graphite properties that is based on an understanding of the interconnection of the structure. Simplified conceptual models have enabled us to explain many of the correlations that exist between irradiated graphite material properties and derive mathematical formulations that appear to be of widespread applicability. The principles of the model are illustrated with reference to the irradiation 'structure term' of Young's modulus. It is shown that the currently used definition may be considered to be a combination of three separate processes - pore closure driven densification, increased structural interconnectivity and (latterly) pore generation. It is the structural interconnectivity component that is most closely linked to the changes in other properties such as dimensional change rate and coefficient of thermal expansion, and this relationship is used to direct the mathematical formulations.

Bradford, Mark R. [Design Authority, British Energy, Barnett Way, Barnwood, Gloucester GL4 3RS (United Kingdom)], E-mail: mark.r.bradford@british-energy.com; Steer, Alan G. [Design Authority, British Energy, Barnett Way, Barnwood, Gloucester GL4 3RS (United Kingdom)

2008-10-31

246

A structurally-based model of irradiated graphite properties  

International Nuclear Information System (INIS)

In this paper, we describe a model of irradiated graphite properties that is based on an understanding of the interconnection of the structure. Simplified conceptual models have enabled us to explain many of the correlations that exist between irradiated graphite material properties and derive mathematical formulations that appear to be of widespread applicability. The principles of the model are illustrated with reference to the irradiation 'structure term' of Young's modulus. It is shown that the currently used definition may be considered to be a combination of three separate processes - pore closure driven densification, increased structural interconnectivity and (latterly) pore generation. It is the structural interconnectivity component that is most closely linked to the changes in other properties such as dimensional change rate and coefficient of thermal expansion, and this relationship is used to direct the mathematical formulations

2008-10-31

247

Organizational Structure: A Review of Structural Dimensions and their Conceptual Relationships with Individual Attitudes, and Behavior.  

Science.gov (United States)

The paper reviews aspects of organizational structure and the conceptual relationships between organizational structure and individual attitudes and behavior. The review is separated into the following five parts: (1) the rationale underlying the developm...

L. R. James A. P. Jones

1974-01-01

248

Microstructure-mechanical property relationships in modified 3 chrome steels  

International Nuclear Information System (INIS)

In this paper, the effects of Ni, Mn, Cr and Mo additions to 2.25Cr-1Mo steel have been studied. Microstructural evidence, from analytical transmission electron microscopy studies, is presented to show how these alloy additions modify the continuously cooled bainitic structures; tempering kinetics; and the structures and compositions of the alloy carbides compared to those observed in tempered commercial 2.25Cr-1Mo pressure vessel steels. The results indicate that significant improvements in hydrogen attack resistance and creep rupture properties can be achieved in 3Cr-1Mo-1Ni and 3Cr-1.5Mo steels by microstructural design based on Larson Miller Parameters

1986-01-01

249

Structure-Biodegradation Relationship Study of Commercial Linear Alkylbenzene Sulfonates  

Directory of Open Access Journals (Sweden)

Full Text Available Biodegradation (metabolism by microorganisms is one of the most important processes determining the fate of organic chemicals in the environment. Structure-biodegradation relationships for linear alkylbenzene sulfonates (LAS can be used to interpret the mechanism of LAS biodegradation and predict biodegradation rates by using theoretical descriptors computed from the chemical structure. Relationships between the electronic structure and biodegradability of commercial LAS are investigated by using semiempirical quantum chemistry method with the PM3 Hamiltonian. Electronic and stereo effects are the main factors affecting the course of LAS biodegradation, and oxygen atoms may be the real donors. The different biodegradation rates of these compounds can be modeled by using some structural and electronic parameters such as the energy of frontier molecular orbitals, the dipole moment, the bonding orbital parameters, the charge density and the net charges at the active site.

Li Li

2003-06-01

250

Exploring Solid-State Structure and Physical Properties: A Molecular and Crystal Model Exercise  

Science.gov (United States)

A crystal model laboratory exercise is presented that allows students to examine relations among the microscopic-macroscopic-symbolic levels, using crystalline mineral samples and corresponding crystal models. Students explore the relationship between solid-state structure and crystal form. Other structure-property relationships are explored. The…

Bindel, Thomas H.

2008-01-01

251

Structural and electronic properties of atomic chains  

International Nuclear Information System (INIS)

Structural and electronic properties of atomic chains are investigated in terms of transfer-matrix-technique within Landauer-model for electrical conductance. The role of structural defects (within deterministic and statistical models) in formation of resistivity and spectral properties is shown. A semi-phenomenological approach to elastic electron scattering on the ad atomic complex is considered. 33 refs.; 4 figs. (author)

1991-01-01

252

Structural and dynamical properties of Yukawa balls  

Energy Technology Data Exchange (ETDEWEB)

To study the structural and dynamical properties of finite 3D dust clouds (Yukawa balls) new diagnostic tools have been developed. This contribution describes the progress towards 3D diagnostics for measuring the particle positions. It is shown that these diagnostics are capable of investigating the structural and dynamical properties of Yukawa balls and gaining insight into their basic construction principles.

Block, D [IEAP, Christian-Albrechts-Universitaet, D-24098 Kiel (Germany); Kroll, M [IEAP, Christian-Albrechts-Universitaet, D-24098 Kiel (Germany); Arp, O [IEAP, Christian-Albrechts-Universitaet, D-24098 Kiel (Germany); Piel, A [IEAP, Christian-Albrechts-Universitaet, D-24098 Kiel (Germany); Kaeding, S [Institut fuer Physik, Ernst-Moritz-Arndt-Universitaet, D-24098 Greifswald (Germany); Ivanov, Y [Institut fuer Physik, Ernst-Moritz-Arndt-Universitaet, D-24098 Greifswald (Germany); Melzer, A [Institut fuer Physik, Ernst-Moritz-Arndt-Universitaet, D-24098 Greifswald (Germany); Henning, C [ITAP, Christian-Albrechts-Universitaet, D-24098 Kiel (Germany); Baumgartner, H [ITAP, Christian-Albrechts-Universitaet, D-24098 Kiel (Germany); Ludwig, P [ITAP, Christian-Albrechts-Universitaet, D-24098 Kiel (Germany); Bonitz, M [ITAP, Christian-Albrechts-Universitaet, D-24098 Kiel (Germany)

2007-12-15

253

Structural and dynamical properties of Yukawa balls  

International Nuclear Information System (INIS)

To study the structural and dynamical properties of finite 3D dust clouds (Yukawa balls) new diagnostic tools have been developed. This contribution describes the progress towards 3D diagnostics for measuring the particle positions. It is shown that these diagnostics are capable of investigating the structural and dynamical properties of Yukawa balls and gaining insight into their basic construction principles

2007-12-01

254

Microstructure and thermomechanical properties relationship of segmented thermoplastic polyurethane (TPU)  

Science.gov (United States)

Thermoplastic polyurethanes (TPU) are important polymeric materials for seals. In competition with Acrylonitrile butadiene rubbers (NBR), TPU exhibits higher strength and a considerable better abrasion resistance. The advantage of NBR over TPU is a smaller compression set but however TPU excels in its much shorter processing cycle times. Generally a TPU is a block copolymer composed of hard and soft segments, which plays an important role in determining the material properties. TPU can be processed either to ready moulded parts or can be incorporated by multi component moulding, in both cases it shows decent mechanical properties. In the present work, the relationship between melt-process induced TPU morphology and resultant thermo mechanical properties were examined and determined by means of quasi-static tensile test, creep experiment, tension test and dynamical mechanical analysis (DMA). Scanning electron beam microscope (SEM) and differential scanning calorimeter (DSC) were used to study the morphology of the samples. A significant mathematical description of the stress-strain behaviour of TPU was found using a 3 term approach. Moreover it became evident that processing conditions such as processing temperature have crucial influence on morphology as well as short and long-term performance. To be more precise, samples processed at higher temperatures showed a lack of large hard segment agglomerates, a smaller strength for strains up to 250% and higher creep compliance.

Frick, Achim; Borm, Michael; Kaoud, Nouran; Kolodziej, Jan; Neudeck, Jens

2014-05-01

255

ODS steel fabrication: relationships between process, microstructure and mechanical properties  

International Nuclear Information System (INIS)

Oxide Dispersion Strengthened (ODS) steels are promising candidate materials for generation IV and fusion nuclear energy systems thanks to their excellent thermal stability, high-temperature creep strength and good irradiation resistance. Their superior properties are attributed both to their nano-structured matrix and to a high density of Y-Ti-O nano-scale clusters (NCs). ODS steels are generally prepared by Mechanical Alloying of a pre-alloyed Fe-Cr-W-Ti powder with Y2O3 powder. A fully dense bar or tube is then produced from this nano-structured powder by the mean of hot extrusion. The aim of this work was to determine the main parameters of the process of hot extrusion and to understand the link between the fabrication process, the microstructure and the mechanical properties. The material microstructure was characterized at each step of the process and bars were extruded with varying hot extrusion parameters so as to identify the impact of these parameters. Temperature then appeared to be the main parameter having a great impact on microstructure and mechanical properties of the extruded material. We then proposed a cartography giving the microstructure versus the process parameters. Based on these results, it is possible to control very accurately the obtained material microstructure and mechanical properties setting the extrusion parameters. (author)

2011-01-01

256

Exploring structure-function relationships between TRP and Kv channels  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The molecular mechanisms underlying the activation of Transient Receptor Potential (TRP) ion channels are poorly understood when compared to those of the voltage-activated potassium (Kv) channels. The architectural and pharmacological similarities between the members of these two families of channels suggest that their structure-function relationships may have common features. We explored this hypothesis by replacing previously identified domains and critical structural motifs of the membrane...

Kalia, Jeet; Swartz, Kenton J.

2013-01-01

257

Structural property of platinum mononitride  

International Nuclear Information System (INIS)

The structural stability and pressure-induced structural phase transition of platinum mononitride (PtN), as well as its electronic structure, were studied using the full potential augmented plane wave plus local orbitals method with the generalized gradient approximation (GGA) exchange-correlation functional. The total energy calculations show that the optimized wurtzite structure is most stable energetically among four structures: zinc blende, rocksalt, CsCl and wurtzite, which reveals the platinum mononitride PtN perhaps crystallizes in the wurtzite structure; the pressure of phase transition from wurtzite to rocksalt is predicted to be 41.4 GPa.The calculated bulk modulus of the wurtzite structure is 99.41 GPa, which is smaller than that of the other three structures and face-centered cubic Pt. The band structure calculations show wurtzite PtN is metallic

2007-10-01

258

Structural property of platinum mononitride  

Energy Technology Data Exchange (ETDEWEB)

The structural stability and pressure-induced structural phase transition of platinum mononitride (PtN), as well as its electronic structure, were studied using the full potential augmented plane wave plus local orbitals method with the generalized gradient approximation (GGA) exchange-correlation functional. The total energy calculations show that the optimized wurtzite structure is most stable energetically among four structures: zinc blende, rocksalt, CsCl and wurtzite, which reveals the platinum mononitride PtN perhaps crystallizes in the wurtzite structure; the pressure of phase transition from wurtzite to rocksalt is predicted to be 41.4 GPa.The calculated bulk modulus of the wurtzite structure is 99.41 GPa, which is smaller than that of the other three structures and face-centered cubic Pt. The band structure calculations show wurtzite PtN is metallic.

Yu, L.H. [Department of Physics, Huazhong University of Science and Technology, WuHan 430074 (China)]. E-mail: yulihua-wuhan@sohu.com; Yao, K.L. [Department of Physics, Huazhong University of Science and Technology, WuHan 430074 (China); International Center of Material Physics, Chinese Academy of Science, ShengYang 110015 (China); Liu, Z.L. [Department of Physics, Huazhong University of Science and Technology, WuHan 430074 (China); Zhang, Y.S. [Department of Physics, Huazhong University of Science and Technology, WuHan 430074 (China)

2007-10-01

259

Structure-radical scavenging activity relationships of flavonoids  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The relationship between the structural characteristics of 29 flavonoids and their antiradical activity was studied. The obtained results suggest that the free radical scavenger potential of these polyphenolic compounds closely depends on the particular substitution pattern of free hydroxyl groups on the flavonoid skeleton. The possible mechanism of action of flavonoids lacking B ring OHs as free radical scavengers has been proposed.

Amic?, Dragan; Davidovic?-amic?, Dus?anka; Bes?lo, Drago; Trinajstic?, Nenad

2003-01-01

260

Structure and activity relationships of tartrate-based TACE inhibitors.  

Science.gov (United States)

The syntheses and structure-activity relationships of the tartrate-based TACE inhibitors are discussed. The optimization of both the prime and non-prime sites led to compounds with picomolar activity. Several analogs demonstrated good rat pharmacokinetics. PMID:20638281

Li, Dansu; Popovici-Muller, Janeta; Belanger, David B; Caldwell, John; Dai, Chaoyang; David, Maria; Girijavallabhan, Vinay M; Lavey, Brian J; Lee, Joe F; Liu, Zhidan; Mazzola, Rob; Rizvi, Razia; Rosner, Kristin E; Shankar, Bandarpalle; Spitler, Jim; Ting, Pauline C; Vaccaro, Henry; Yu, Wensheng; Zhou, Guowei; Zhu, Zhaoning; Niu, Xiaoda; Sun, Jing; Guo, Zhuyan; Orth, Peter; Chen, Shiying; Kozlowski, Joseph A; Lundell, Daniel J; Madison, Vincent; McKittrick, Brian; Piwinski, John J; Shih, Neng-Yang; Shipps, Gerald W; Siddiqui, M Arshad; Strickland, Corey O

2010-08-15

 
 
 
 
261

Structure, processing, and properties of potatoes  

Science.gov (United States)

The objective of this experiment and lesson intended for high school students in an engineering or materials science course or college freshmen is to demonstrate the relation between processing, structure, and thermodynamic and physical properties. The specific objectives are to show the effect of structure and structural changes on thermodynamic properties (specific heat) and physical properties (compressive strength); to illustrate the first law of thermodynamics; to compare boiling a potato in water with cooking it in a microwave in terms of the rate of structural change and the energy consumed to 'process' the potato; and to demonstrate compression testing.

Lloyd, Isabel K.; Kolos, Kimberly R.; Menegaux, Edmond C.; Luo, Huy; Mccuen, Richard H.; Regan, Thomas M.

1992-01-01

262

Carbon fibers: precursor systems, processing, structure, and properties.  

Science.gov (United States)

This Review gives an overview of precursor systems, their processing, and the final precursor-dependent structure of carbon fibers (CFs) including new developments in precursor systems for low-cost CFs. The following CF precursor systems are discussed: poly(acrylonitrile)-based copolymers, pitch, cellulose, lignin, poly(ethylene), and new synthetic polymeric precursors for high-end CFs. In addition, structure-property relationships and the different models for describing both the structure and morphology of CFs will be presented. PMID:24668878

Frank, Erik; Steudle, Lisa M; Ingildeev, Denis; Spörl, Johanna M; Buchmeiser, Michael R

2014-05-19

263

Phase diagram and structure-property relationships in the lead-free piezoelectric system: Na0.5K0.5NbO3-LiTaO3.  

Science.gov (United States)

A phase-diagram for the Na(0.5)K(0.5)NbO(3)-LiTaO(3) solid solution series (NKN-LT) is presented for compositions ? 10 mol% LT, based on the combined results of temperaturevariable X-ray powder diffraction and dielectric measurements. In addition to the reported orthorhombic and tetragonal polymorphs of NKN-LT, a monoclinic phase is revealed. Changes to electrical properties as a function of LT substitution are correlated to phase content. Increasing the LT content from 5 to 7 mol% LT led to improved temperature stability of piezoelectric properties because of the avoidance of the monoclinic-tetragonal polymorphic phase transition during thermal cycling (at >25°C). For 7 mol% LT samples: d(33) = 200 pC/N; T(c) = 440°C; ?(r) = 550 and tan ? = 0.02 (at 20°C). Modification of this composition by solid solution with BiScO(3) led to a decrease in d(33) values. Transmission electron microscopy of a sample of 0.95[0.93 NKN-0.07LT]-0.05BiScO(3) indicated a core-shell grain structure which led to temperature-stable dielectric properties. PMID:21937313

Skidmore, Thomas A; Comyn, Timothy P; Bell, Andrew J; Zhu, Fangyuan; Milne, Steven J

2011-09-01

264

Molecular Structures and Functional Relationships in Clostridial Neurotoxins  

Energy Technology Data Exchange (ETDEWEB)

The seven serotypes of Clostridium botulinum neurotoxins (A-G) are the deadliest poison known to humans. They share significant sequence homology and hence possess similar structure-function relationships. Botulinum neurotoxins (BoNT) act via a four-step mechanism, viz., binding and internalization to neuronal cells, translocation of the catalytic domain into the cytosol and finally cleavage of one of the three soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNARE) causing blockage of neurotransmitter release leading to flaccid paralysis. Crystal structures of three holotoxins, BoNT/A, B and E, are available to date. Although the individual domains are remarkably similar, their domain organization is different. These structures have helped in correlating the structural and functional domains. This has led to the determination of structures of individual domains and combinations of them. Crystal structures of catalytic domains of all serotypes and several binding domains are now available. The catalytic domains are zinc endopeptidases and share significant sequence and structural homology. The active site architecture and the catalytic mechanism are similar although the binding mode of individual substrates may be different, dictating substrate specificity and peptide cleavage selectivity. Crystal structures of catalytic domains with substrate peptides provide clues to specificity and selectivity unique to BoNTs. Crystal structures of the receptor domain in complex with ganglioside or the protein receptor have provided information about the binding of botulinum neurotoxin to the neuronal cell. An overview of the structure-function relationship correlating the 3D structures with biochemical and biophysical data and how they can be used for structure-based drug discovery is presented here.

Swaminathan S.

2011-12-01

265

Relationships between structures and performance of SOFC anodes  

DEFF Research Database (Denmark)

The nickel-YSZ cermet of the state-of-the-art anode-supported solid oxide fuel cell (SOFC) degrades upon redox cycling. The degradation is a critical issue for the commercialization of the technology. Nickel-YSZ cermets with variable composition and microstructure were examined during redox cycling to obtain knowledge of the degradation mechanism, and to identify parameters and characterization tools to improve the cermet. The investigation techniques included direct observations of the microstructure (light microscopy, scanning electron microscopy, environmental scanning electron microscopy, image analysis), bulk measurements (porosity, dilatometry, mechanical properties), measurements of the electrical performance (direct current conductivity, impedance spectroscopy), measurements of the redox kinetics (thermo gravimetric analysis, synchrotron), and application of simple models of the layered system. A model of the redox mechanism on the microstructural level was described. The degradation related to redox cycling was ascribed to a dynamic reorganization of the Ni/NiO phase, when in the reduced state and upon re-oxidation. The redistribution generated fractures in the YSZ matrix, and bulk expansion of the cermet structure upon oxidation. The bulk expansion promoted cracking of the electrolyte. The redistribution of the reduced nickel phase was observed to occur as rounding of the particles, and nickel sintering. The degree of sintering depended on the temperature, the composition of the ceramic component, and possibly on the local porosity. The redistribution of the NiO phase upon oxidation was seen to depend on the kinetics and the local porosity. At higher temperatures the oxide growth involved fragmentation of the particles. At lower temperatures the growth occurred in the form of an external oxide peel. The mechanical strength of the ceramic component was indicated as a technological potential parameter for improving the redox stability. However, considerable strengthening was indicated to be required. Strengthening that will result in a reduction of the bulk expansion upon re-oxidation with a factor of two was estimated. Modification of the cermet composition with additives was indicated as a possibility for improving the redox stability. Significant strengthening and reduction of the nickel sintering were indicated achievable with additives. However, further experimental work will be required to discover the full potential of the application of additives. The future work will be empirically based, or include detailed descriptions of the relationships between microstructural parameters and the cermet bulk properties.

Klemensø, Trine; Mogensen, Mogens Bjerg

2006-01-01

266

Electronic Structure, Lattice Dynamics and Thermoelectric Properties of PbTe from First-Principles Calculation  

International Nuclear Information System (INIS)

The electronic structure and the lattice dynamics of lead telluride (PbTe) are investigated by using the density functional theory. The thermoelectric properties are then calculated using the semi-classical Boltzmann theory. Moreover, the relationships among the thermoelectric properties, the electronic structure and the lattice dynamics are also studied. Some strategies aiming at optimizing the thermoelectric properties are proposed. The related theoretical calculations therefore give a valuable insight on how to further enhance the thermoelectric properties of PbTe

2013-01-01

267

Relationship between structure and ''decorporative'' efficiency in the diphosphonate chemical series  

International Nuclear Information System (INIS)

Molecular structure of some diphosphonates was studied by topological analysis. The investigated activity was the efficiency of the molecules to remove injected plutonium from the organism, in order to correlate some topological properties of these molecules to their decorporating ability. The studied polyphosphonates have been divided into two families: unprotected and protected compounds. Only unprotected compounds clearly show structure activity relationships. Though structurally different from the rest of the family, LICAM (C) well fits the correlation. An interpretation was that a better efficiency might be related to the branching of the molecules

1988-01-01

268

Analysis and characterization methodology for Portland cement concretes: relationship between porous structure and strength  

International Nuclear Information System (INIS)

In this work a general methodology is presented for studying fundamental problems associated with concretes of cement Portland. As an example of application some results of structural characterization and analysis of different concretes are shown. The analyzed materials were C15, C40 and C80, according to NBR8953. The structural characterization was carried out by x-ray diffraction, mercury porosimetry and nitrogen gas adsorption. The aim of this work was the search for relationships between the porous structure of concretes and their mechanical properties. (author)

1998-06-03

269

Abnormal structure-function relationship in spasmodic dysphonia.  

Science.gov (United States)

Spasmodic dysphonia (SD) is a primary focal dystonia characterized by involuntary spasms in the laryngeal muscles during speech production. Although recent studies have found abnormal brain function and white matter organization in SD, the extent of gray matter alterations, their structure-function relationships, and correlations with symptoms remain unknown. We compared gray matter volume (GMV) and cortical thickness (CT) in 40 SD patients and 40 controls using voxel-based morphometry and cortical distance estimates. These measures were examined for relationships with blood oxygen level-dependent signal change during symptomatic syllable production in 15 of the same patients. SD patients had increased GMV, CT, and brain activation in key structures of the speech control system, including the laryngeal sensorimotor cortex, inferior frontal gyrus (IFG), superior/middle temporal and supramarginal gyri, and in a structure commonly abnormal in other primary dystonias, the cerebellum. Among these regions, GMV, CT and activation of the IFG and cerebellum showed positive relationships with SD severity, while CT of the IFG correlated with SD duration. The left anterior insula was the only region with decreased CT, which also correlated with SD symptom severity. These findings provide evidence for coupling between structural and functional abnormalities at different levels within the speech production system in SD. PMID:21666131

Simonyan, Kristina; Ludlow, Christy L

2012-02-01

270

Investigation into crystal structure and properties of GaTe hexagonal films  

International Nuclear Information System (INIS)

Different investigation techniques are employed to study a change of the structural state, electrical and optical properties of hexagonal GaTe films at annealing in the temperature interval of 300-500 deg. The relationship is shown between changes of the structure and physical properties of the films

1986-01-01

271

Simple isatin derivatives as free radical scavengers: Synthesis, biological evaluation and structure-activity relationship  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract To develop more potent small molecules with enhanced free radical scavenger properties, a series of N-substituted isatin derivatives was synthesized, and the cytoprotective effect on the apoptosis of PC12 cells induced by H2O2 was screened. All these compounds were found to be active, and N-ethyl isatin was found with the most potent activity of 69.7% protective effect on PC12 cells. Structure-activity relationship analyses showed the...

Chen Gang; Wang Ye; Hao Xiaojiang; Mu Shuzhen; Sun Qianyun

2011-01-01

272

Structure-activity relationship study of collagen derived anti-angiogenic biomimetic peptides  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Structure-activity relationship (SAR) studies are essential in the generation of peptides with enhanced activity and efficacy as therapeutic agents. In this study we report a SAR study for a family of mimetic peptides derived from type IV collagen with potent anti-angiogenic properties. The SAR study was conducted using a number of validated in vitro assays including cell proliferation, adhesion, migration and tubule formation. We report a critical sequence (NINNV) within this peptide series ...

Rosca, Elena V.; Koskimaki, Jacob E.; Pandey, Niranjan B.; Tamiz, Amir P.; Popel, Aleksander S.

2012-01-01

273

Quantitative structure-permeation relationship for iontophoretic transport across the skin  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective was to relate the efficiency of a charged drug to carry current across the skin during iontophoresis to its structural and/or physicochemical properties. The corollary was the establishment of a predictive relationship useful to predict the feasibility of iontophoretic drug delivery, and for the selection and optimization of drug candidates for this route of administration. A dataset of 16 cations, for which iontophoretic fluxes have been measured under identical conditions, wit...

Mudry, Blaise; Carrupt, Pierre-alain; Guy, Richard H.; Delgado-charro, M. Begon?a

2007-01-01

274

Absorption and Tissue Distribution of Drug-Like Compounds: Quantitative Structure-Activity Relationship Analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective of this work was to develop mechanistic quantitative structure activity relationship models that would facilitate the assessment of drug properties related to their absorption and distribution in the body. The analysis involved several parameters reflecting the rate of passive diffusion across brain endothelium and intestinal epithelium, and thermodynamic constants related to drug distribution between plasma and tissues. Permeation through cellular transport barriers was modeled...

Lanevskij, Kiril

2011-01-01

275

Using a cloud electrification model to study relationships between lightning activity and cloud microphysical structure  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this study a one-dimensional numerical cloud electrification model, called the Explicit Microphysics Thunderstorm Model (EMTM), is used to find quantitative relationships between the simulated electrical activity and microphysical properties in convective clouds. The model, based on an explicit microphysics scheme coupled to an ice–ice noninductive electrification scheme, allows us to interpret the connection of cloud microphysical structure with charge density distribution within the cl...

Formenton, M.; Panegrossi, G.; Casella, D.; Dietrich, S.; Mugnai, A.; Sano?, P.; Di Paola, F.; -d Betz, H.; Price, C.; Yair, Y.

2013-01-01

276

Relationship between silver concentration with microstructural and mechanical properties of rolled AlZn alloy  

International Nuclear Information System (INIS)

The relationship of Ag addition on microstructural and mechanical properties of rolled AlZn alloy was investigated. AlZn alloys were prepared by metal mould casting method and the Ag addition was done by Vortex technique. Microstructural characterization of AlZnAg specimens was analyzed by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Results show that the phases of the as-cast state alloy are solid solution zinc-rich hexagonal close-packed (hcp) crystal structure, named ?-phase and ?-Al solid solution with Zn dissolved into the matrix. The silver concentration in AlZn alloy influences the volume of AgZn3 precipitates. The mechanical properties, especially the flow stress and elongation of the alloy were improved by the Ag addition. The Vortex method was used in order to diminish the process cost, generating an alloy with homogenous microstructure, less casting porosity and better mechanical properties.

2010-05-25

277

Study of the relationship between the crystal structure of nanolayers and electrical properties in Al{sub x}Ga{sub 1-x}As/In{sub y}Ga{sub 1-y}As pseudobinary heterostructures by double-crystal X-ray diffraction  

Energy Technology Data Exchange (ETDEWEB)

The structural parameters of individual layers of samples of a Al{sub x}Ga{sub 1-x}As/In{sub y}Ga{sub 1-y}As/GaAs pseudomorphic heterostructure have been determined by double-crystal X-ray diffraction. A relationship of the technological parameters of fabrication of heterostructures with their structural and electrical properties is established. The increase in the mobility of the 2D electron gas in the samples under study, caused by the increase in the growth temperature of the Al{sub x}Ga{sub 1-x}As spacer layer and the decrease in the time of silicon {delta} doping from the two sides of the quantum well, correlates well with the degree of the sample structural quality.

Imamov, R. M., E-mail: imamov@ns.crys.ras.ru; Subbotin, I. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Galiev, G. B. [Russian Academy of Sciences, Institute of UHF Semiconductor Electronics (Russian Federation)

2008-03-15

278

Structure-property relationships of novel microwave dielectric ceramics with low sintering temperatures: (Na0.5xBi0.5xCa1-x)MoO4.  

Science.gov (United States)

A novel series of microwave dielectric ceramics (Na0.5xBi0.5xCa1-x)MoO4 (0 ? x ? 0.6) was synthesized by the solid state reaction method. The crystal structures, microstructures, dielectric responses, and vibrational properties were investigated using X-ray diffraction, scanning electron microscopy, a microwave network analyzer, and terahertz, Raman and infrared spectroscopies. All the samples could be sintered well below 850 °C and a scheelite solid solution could be formed without any secondary phase. At x = 0.5 and x = 0.6, low-firing (750-775 °C) high performance microwave dielectric materials were obtained with permittivities of 19.1-21.9, Q × f values of 20?660-22?700 GHz, and near-zero temperature coefficients. The factors affecting microwave dielectric properties were discussed based on the vibrational data. As revealed by Raman spectroscopy, the disorder degree grows with x rising, which might increase the permittivities and decrease the Q × f values. The infrared spectra were analyzed using the classical harmonic oscillator model, and the complex dielectric responses gained from the fits were extrapolated down to the microwave and THz range. It is believed that the external vibration modes located at low frequencies dominate the main dielectric polarization contributions, especially the Na-O/Bi-O translational mode. This result indicates that the microwave dielectric properties of (Na0.5xBi0.5xCa1-x)MoO4 ceramics mainly depend on the behavior of AO8 polyhedra. PMID:24967993

Guo, Jing; Zhou, Di; Li, Yong; Shao, Tao; Qi, Ze-Ming; Jin, Biao-Bing; Wang, Hong

2014-07-15

279

Structuring strategy and relationships in North American gas markets  

International Nuclear Information System (INIS)

Duke Energy's experience in strategy development and structuring relationships with other companies were described. Included was a description of their partnership with PanEnergy and Mobil and a merger between PanEnergy and Duke. In developing their growth strategy, Duke Energy was guided by the following considerations: (1) an assessment of the market, (2) the identification of opportunities, (3) a self-assessment, (4) the establishment of goals, and (5) determining strategic alternatives. The advantages and disadvantages of different structuring relationships were reviewed. Duke Energy's approach to Ontario's residential market and their agreement with Alliance Gas Management were also discussed. The goal of the Alliance Gas management agreement was to simplify Alliance's wholesale gas supply management needs and to allow Alliance access to diverse gas supplies. figs

1998-04-14

280

Bank Image Structure: The Relationship to Consumer Behaviour  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the results of a study of the relationship between the bank image, its structure as a reflection in the minds of individuals and behavioural tendencies in relation to banks. Attitudinal scales were used to identify the contents of the particular banks’ image. The structure of the image was identified by means of factor analysis. The study found that the respondents’ behavioural tendencies, i.e. their willingness to be a client of or to recommend a particular bank, are related to different content components of particular banks and mainly to respondents’ needs. Based on the results, the study identifies the danger that the results of the bank image analysis can be misinterpreted if the respondents’ relationship to the bank is underestimated.

Lukasova Ruzena

2014-03-01

 
 
 
 
281

Antitrypanosomal structure-activity-relationship study of synthetic cynaropicrin derivatives.  

Science.gov (United States)

Cynaropicrin is a guaianolide sesquiterpene lactone with a 5-7-5 tricyclic skeleton, four exo-olefins, and two hydroxyl groups. Recently, it was found that the compound is a potent in vitro and in vivo inhibitor of the protozoan parasite Trypanosoma brucei, which causes human African trypanosomiasis (HAT; sleeping sickness). In this Letter, chemical derivatization of cynaropicrin and the structure-activity-relationship (SAR) study against T. brucei is described. PMID:24433861

Usuki, Toyonobu; Sato, Makiko; Hara, Shihori; Yoshimoto, Yukiko; Kondo, Ryosuke; Zimmermann, Stefanie; Kaiser, Marcel; Brun, Reto; Hamburger, Matthias; Adams, Michael

2014-02-01

282

Abnormal Structure–Function Relationship in Spasmodic Dysphonia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Spasmodic dysphonia (SD) is a primary focal dystonia characterized by involuntary spasms in the laryngeal muscles during speech production. Although recent studies have found abnormal brain function and white matter organization in SD, the extent of gray matter alterations, their structure–function relationships, and correlations with symptoms remain unknown. We compared gray matter volume (GMV) and cortical thickness (CT) in 40 SD patients and 40 controls using voxel-based morphometry and ...

Simonyan, Kristina; Ludlow, Christy L.

2012-01-01

283

A note on network structure: functional relationships between network indicators  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Two important aspects of network structure are network density and network centrality. These two aspects highlight different characteristics of a network. Empirical studies tend to find that one or the other is the better explanatory variable for certain aspects of corporate behaviour. This note makes a simple and compelling point. There is a hill-shaped relationship between network density and network centrality. A purely stochastic process of alliance formation will lead to a hill-shap...

2003-01-01

284

Deriving the Properties of Structural Focus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper proposes a theory of structural focus derived via focus movement which can account for all the focus-related facts attested in Hungarian, among them facts which other current theories cannot explain. It will claim that focus movement serves the purpose of creating a predicate?subject structure, in which the focus-moved constituent functions as a specificational predicate. The properties of both the focus and the background follow from the independently established properties o...

Kiss, Katalin E?

2009-01-01

285

Structure property relations in complex copolymer systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A thorough investigation was made of the structure-property relation of well-defined statistical, gradient and block copolymers of various compositions. Among the copolymers studied were those which were synthesized using isobornyl acrylate (IBA) and n-butyl acrylate (nBA) monomer units. The copolymers exhibited several unique properties that make them suitable materials for a range of applications. The thermomechanical properties of these new materials were compared to acrylate homopolymers....

Juhari, Ahmad Azhar

2010-01-01

286

Metallic superlattices: Structural and elastic properties  

Energy Technology Data Exchange (ETDEWEB)

The fabrication and structural characterization of metallic superlattices is discussed. Methods to determine the elastic properties of these materials (which can only be prepared as thin films) are reviewed and the results obtained using various techniques are summarized. Contrary to theoretical expectation, the elastic properties are found to depend on the modulation wavelength. 52 refs., 6 figs.

Grimsditch, M. (Argonne National Lab., IL (USA)); Schuller, I.K. (California Univ., San Diego, La Jolla, CA (USA). Dept. of Physics)

1990-01-01

287

Structure-activity relationship observations for the bagworm moth pheromone.  

Science.gov (United States)

Structure-activity relationship (SAR) observations were made for the bagworm moth pheromone, (R)-2-pentyl decanoate, and a series of analogs with modifications in the alcohol portion of the molecule. Observed attractiveness of these analogs was related to molecular structure and their physical attributes using computational chemistry. Electrostatic potential and Van der Waals (VdW) electrostatic coded surface three-dimensional (3D) maps of the molecular mechanics (MM) minimized lowest energy conformation of the pheromone show that size, shape, charge distribution, and chirality of the molecule are related to attractiveness. PMID:24226087

Warthen, J D; Klun, J A; Devilbiss, E D

1996-07-01

288

[Structure-activity relationships of histone deacetylase inhibitors].  

Science.gov (United States)

Among those enzymes that regulate gene expression, histone deacetylases (HDACs) play important roles in cell cycles. Extensive studies were carried out in the field of HDACs and the applications of HDAC inhibitors (HDACIs) as chemotherapeutic interventions for diverse diseases. HDACIs have moved from laboratories to clinic uses. Huge bodies of related research results were well documented and dispersed in literature. According to our understanding, HDACIs can be broadly classified as hydroxamic acids, cyclic tetrapeptides, short chain fatty acids, benzamides and electrophilic ketones. Herein, we are going to review the design and their structure-activity relationships of HDACIs and according to their structural catalogs. PMID:20055127

Tan, Yu-Mei; Huang, Wen-Yuan; Yu, Nie-Fang

2009-10-01

289

Relationship between oxygen chemical potential, annealing conditions, and superconducting properties of YBa2Cu3Ox  

International Nuclear Information System (INIS)

A strong relationship between superconducting properties, oxygen chemical potential, and heat treatment during preparation of YBa2Cu3Ox is investigated. Resistivity measurements as a function of temperature, isochoric solid-gas equilibrium determination, and thermogravimetric studies under different gas atmospheres were carried out. The results can be explained either by a quasi-binary solid solution of oxygen in YBa2Cu3Ox or by a coexistence of two ternary solid solutions of different structures. There is a high mobility of oxygen in the lattice and superconductivity is very sensitive to small changes in the oxygen occupation ?x

1988-03-01

290

Evaluation of Relationship Between Mechanical Properties of High Strength Self Compacting Concrete  

Directory of Open Access Journals (Sweden)

Full Text Available In the present experimental investigation an attempt is made to report relationship between compressive strength , Split tensile Strength and Flexural Strength of High Strength Self Compacting Concrete with mineral admixtures . It is well known that the properties of concrete are affected by cementitious matrix,aggregate and the transition zone between the two phases. Reducing water powder ratio and addition of pozollona admixtures like Fly ash and Micro silica are often used to modify the micro structure of the matrix and to optimize the transition zone.

S.SeshaPhani

2013-01-01

291

Toward the recognition of structure-function relationships in galactomannans.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper the determination of the physical/rheological characteristics is described for a series of commercial galactomannans of which the structural details have been reported previously. Both solubility of the galactomannans and rheological properties of galactomannan solutions and galactomannan/xanthan mixtures were determined. Using a statistical analysis approach an attempt was undertaken to recognize correlations between structural and rheological data. The best correlation found w...

2002-01-01

292

The macromolecular structure of coal-Its relationship to diffusion and reaction processes in coals  

Energy Technology Data Exchange (ETDEWEB)

The present paper is concerned mainly with some rather specific aspects of the problem of characterization of the macromolecular structure of coals, and their relationship to key reaction processes and physical properties. The main characterization technique used throughout this work is solvent swelling, as has been used extensively in recent years to characterize the extent of crosslinking in coals. This classic technique was originally developed for examination of extents of crosslinking in polymers. The present paper considers two entirely different aspects of the relationship between macromolecular structure and reactivity and transport in coals. The first aspect concerns the reactions of crosslinking in coals during thermal treatment. This topic has been previously explored using the solvent swelling methodology. Here the work is extended to consider how the colloidal structure of coal is affected by moisture removal, and by further heating. The second aspect concerns the diffusive transport of solvent species in coals, and the activation energies for such processes.

Suuberg, E.M.; Otake, Yoshi; Deevi, S. (Brown Univ., Providence, RI (USA))

1988-01-01

293

The Relationship between Radial Bone Properties and Disease Activity and Physical Function in Individuals with Rheumatoid Arthritis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Purpose: People with rheumatoid arthritis (RA) are at increased risk for osteoporosis. This study explored the relationships between compartment-specific (cortical and trabecular) bone properties in the distal radius, a common site for osteoporotic fracture, and RA-related pain, upper-limb disease activity, and hand function in adults diagnosed within the previous 8 years. Methods: Cortical and trabecular bone properties (mass, density, and apparent trabecular structure) were assessed at the ...

2012-01-01

294

A compilation of structural property data for computer impact calculation (5/5)  

International Nuclear Information System (INIS)

The paper describes structural property data for computer impact calculations of nuclear fuel shipping casks. Four kinds of material data, mild steel, stainless steel, lead and wood are compiled. These materials are main structural elements of shipping casks. Structural data such as, the coefficient of thermal expansion, the modulus of longitudinal elasticity, the modulus of transverse elasticity, the Poisson's ratio and stress and strain relationships, have been tabulated against temperature or strain rate. This volume 5 involve structural property data of wood. (author)

1988-01-01

295

A compilation of structural property data for computer impact calculation (4/5)  

International Nuclear Information System (INIS)

The paper describes structural property data for computer impact calculations of nuclear fuel shipping casks. Four kinds of material data, mild steel, stainless steel, lead and wood are compiled. These materials are main structural elements of shipping casks. Structural data such as, the coefficient of thermal expansion, the modulus of longitudinal elasticity, the modulus of transverse elasticity, the Poisson's ratio and stress and strain relationships, have been tabulated against temperature or strain rate. This volume 4 involve structural property data of lead. (author)

1988-01-01

296

THE RELATIONSHIP BETWEEN CORONAL DIMMING AND CORONAL MASS EJECTION PROPERTIES  

International Nuclear Information System (INIS)

Coronal dimmings are closely related to the footpoints of coronal mass ejections (CMEs) and, as such, offer information about CME origins and evolution. In this paper, we investigate the relationship between CME and dimming properties. In particular, we compare CME quantities for events with and without associated dimmings. We find that dimming-associated CMEs, on average, have much higher speeds than non-dimming-associated events. In fact, CMEs without an associated dimming do not appear to travel faster than 800 km s-1, i.e., the fast solar wind speed. Dimming-associated events are also more likely to be associated with flares, and those flares tend to have the highest magnitudes. We propose that each of these phenomena is affected by the energy available in the source region. Highly energetic source regions produce fast CMEs that are accompanied by larger flares and visible dimmings, while less energetic source regions produce slow CMEs that are accompanied by smaller flares and may or may not have dimmings. The production of dimmings in the latter case may depend on a number of factors including initiation height of the CME, source region magnetic configuration, and observational effects. These results have important implications for understanding and predicting CME initiations.

2009-11-01

297

Structure and functional properties of colloidal systems  

CERN Multimedia

Presents the connections between structure and functional aspects in colloid and interface science. This title describes techniques to functionalize colloids, characterization methods, the physical fundamentals of structure formation, diffusion dynamics, transport properties in equilibrium, and the physical fundamentals of nonequilibrium systems.

Hidalgo-Alvarez, Roque

2009-01-01

298

Quantitative structure-activity relationship study of antitubercular fluoroquinolones.  

Science.gov (United States)

Quantitative structure-activity relationship study on three diverse sets of structurally similar fluoroquinolones was performed using a comprehensive set of molecular descriptors. Multiple linear regression technique was applied as a preprocessing tool to find the set of relevant descriptors (10) which are subsequently used in the artificial neural networks approach (non-linear procedure). The biological activity in the series (minimal inhibitory concentration (?g/mL) was treated as negative decade logarithm, pMIC). Using the non-linear technique counter propagation artificial neural networks, we obtained good predictive models. All models were validated using cross validation leave-one-out procedure. The results (the best models: Assay1, R = 0.8108; Assay2, R = 0.8454, and Assay3, R = 0.9212) obtained on external, previously excluded test datasets show the ability of these models in providing structure-activity relationship of fluoroquinolones. Thus, we demonstrated the advantage of non-linear approach in prediction of biological activity in these series. Furthermore, these validated models could be proficiently used for the design of novel structurally similar fluoroquinolone analogues with potentially higher activity. PMID:20229318

Minovski, Nikola; Vra?ko, Marjan; Solmajer, Tom

2011-05-01

299

Structure-function relationship of working memory activity with hippocampal and prefrontal cortex volumes.  

Science.gov (United States)

A rapidly increasing number of studies are quantifying the system-level network architecture of the human brain based on structural-to-structural and functional-to-functional relationships. However, a largely unexplored area is the nature and existence of "cross-modal" structural-functional relationships, in which, for example, the volume (or other morphological property) of one brain region is related to the functional response to a given task either in that same brain region, or another brain region. The present study investigated whether the gray matter volume of a selected group of structures (superior, middle, and inferior frontal gyri, thalamus, and hippocampus) was correlated with the fMRI response to a working memory task, within a mask of regions previously identified as involved with working memory. The subjects included individuals with schizophrenia, their siblings, and healthy controls (n = 154 total). Using rigorous permutation testing to define the null distribution, we found that the volume of the superior and middle frontal gyri was correlated with working memory activity within clusters in the intraparietal sulcus (i.e., dorsal parietal cortex) and that the volume of the hippocampus was correlated with working memory activity within clusters in the dorsal anterior cingulate cortex and left inferior frontal gyrus. However, we did not find evidence that the identified structure-function relationships differed between subject groups. These results show that long-distance structural-functional relationships exist within the human brain. The study of such cross-modal relationships represents an additional approach for studying systems-level interregional brain networks. PMID:22362200

Harms, Michael P; Wang, Lei; Csernansky, John G; Barch, Deanna M

2013-01-01

300

Structure and Properties of Compressed Borate Glasses  

DEFF Research Database (Denmark)

While the influence of thermal history on the structure and properties of glasses has been thoroughly studied in the past century, the influence of pressure history has received considerably less attention. In this study, we investigate the pressure-induced changes in structure and properties in a series of borate glasses. Upon isostatic compression, NMR experiments show that the fraction of tetrahedral boron increases, leading to an overall decrease of the molar volume of the network. We correlate these structural changes with changes in elastic moduli from Brillouin scattering experiments, hardness and crack formation from nanoindentation experiments, and overshoot in isobaric heat capacity from DSC experiments at ambient pressure. The influence of the initial boron speciation on the degree of changes in structure and properties will also be discussed.

Smedskjær, Morten Mattrup; Bauer, U.

 
 
 
 
301

Structural Property Analysis of Petri Net  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Petri net synthesis can avoid the state exploration problem by guaranteeing the correctness in the Petri net while incrementally expanding the net. This paper proposes the conditions imposed on a synthesis shared pp subnet under which the following structural properties will be preserved: structural boundedness, structural liveness, conservativeness, repetitiveness, consistency, P-invariant, T-invariant and fairness. Such results release the designer's burden for having to provide different m...

Chuanliang Xia

2012-01-01

302

Slope failure at Bukit Antarabangsa, Ampang, Selangor and its relationship to physical soil properties  

International Nuclear Information System (INIS)

Slope failure which occurred on 6 December 2008 at Bukit Antarabangsa, Ampang Selangor has caused mortalities and loss of properties whereas more than 20 houses were flattened. Prior to slope failure, it was heavily down poured for a few hours that increased the soil saturation and plasticity properties. A total of 10 soil samples were randomly taken from stable and unstable slopes to determine physical soil properties, infiltration rate and their relationship to rainfall pattern. Soils were analyzed in terms of their physical properties; five years (2005-2009) of daily rainfalls were analyzed to determine their relationship to infiltration rate at each sampling station. Infiltration rate is determined by using infiltrometer double ring. Analysis of physical soils properties shows that soil texture was dominated by sandy soil with relatively high percentage of sand. Values of clay dispersion coefficient were relatively stable to very stable from 0.013 % to 11.85 % and organic content from 1.38 % to 2.74 %. Range of porosity was from 50.12 % to 62.31 %, while the average levels of hydraulic conductivity was from level 2 to 5 or relatively slow to fast. Percentage of soil aggregate stability was from 5.12 % to 48.42 % and this value indicates that relative strength of soil mechanical pressure is inversely proportional to the percentage of water content. Soil plasticity value was high to very high but characterized by inactive colloids. Distribution of monthly rainfall was from 38 mm to 427 mm. The infiltration rate during sampling time was from 3.0 cm/ hr to 7.0 cm/ hr; but it was expected from 10.94 cm/ hr to 915.05 cm/ hr during slope failures. Overall, it was interpreted that physical soil properties was closely interrelated with slope stability, structure of sandy soil will enhanced soil porosity stage and enhance the infiltration process during heavy rainfall, and finally triggering of slope failure. (author)

2008-12-06

303

Relationship between Single Walled Carbon Nanotubes Individual Dispersion Behavior and Properties of Electrospun Nanofibers  

Directory of Open Access Journals (Sweden)

Full Text Available The dispersion stability behavior of single walled carbon nanotube (SWCNT has important effects on morphological and mechanical properties of SWCNT/polymer composite nanofibers. The relationship of the dispersion conditions with morphological and mechanical characteristics for SWCNT / polyacrylonitrile (PAN / polyvinylpyrrolidone (PVP composite nanofibers have been examined. The SEM and TEM analyses of the nanofibers revealed that the deformation in the nanofiber structures increases with increasing SWCNT concentration. Our data indicate that with increasing the amount of SWCNT (from 0 to 2 wt %, the average nanofiber diameter was increased from 163±19 nm to 307±34 nm. Tensile results showed that only 2 wt % SWCNT loading to the electrospun composite nanofibers gave rise to 10-fold and 3-fold increase in the tensile modulus and tenacity of nanofiber layers, respectively. Essentially, high mechanical properties and uniform morphology of the composite naofibers were found at SWCNT concentration of ~2 wt % due to their stable and individual dispersion.

Haji A.

2013-09-01

304

Structure-properties relations of the drawn poly(ethylene terephthalate) filament sewing thread  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This article presents research into draw ratio influence on the structure-properties relationship of drawn PET filament threads. Structural modification influence due to the drawing conditions, i.e., the birefringence and filament crystallinity, on the mechanical properties was investigated, as well as the shrinkage and dynamic mechanical properties of the drawn threads. Increasing draw ratio causes a linear increase in the birefringence, degree of crystallinity, filament shrinkage, and a dec...

Rudolf, Andreja; Sfiligoj-smole, Majda

2012-01-01

305

Structural properties of prokaryotic promoter regions correlate with functional features.  

Science.gov (United States)

The structural properties of the DNA molecule are known to play a critical role in transcription. In this paper, the structural profiles of promoter regions were studied within the context of their diversity and their function for eleven prokaryotic species; Escherichia coli, Klebsiella pneumoniae, Salmonella Typhimurium, Pseudomonas auroginosa, Geobacter sulfurreducens Helicobacter pylori, Chlamydophila pneumoniae, Synechocystis sp., Synechoccocus elongates, Bacillus anthracis, and the archaea Sulfolobus solfataricus. The main anchor point for these promoter regions were transcription start sites identified through high-throughput experiments or collected within large curated databases. Prokaryotic promoter regions were found to be less stable and less flexible than the genomic mean across all studied species. However, direct comparison between species revealed differences in their structural profiles that can not solely be explained by the difference in genomic GC content. In addition, comparison with functional data revealed that there are patterns in the promoter structural profiles that can be linked to specific functional loci, such as sigma factor regulation or transcription factor binding. Interestingly, a novel structural element clearly visible near the transcription start site was found in genes associated with essential cellular functions and growth in several species. Our analyses reveals the great diversity in promoter structural profiles both between and within prokaryotic species. We observed relationships between structural diversity and functional features that are interesting prospects for further research to yet uncharacterized functional loci defined by DNA structural properties. PMID:24516674

Meysman, Pieter; Collado-Vides, Julio; Morett, Enrique; Viola, Roberto; Engelen, Kristof; Laukens, Kris

2014-01-01

306

Barley stripe mosaic virus: structure and relationship to the tobamoviruses.  

Science.gov (United States)

Barley stripe mosaic virus (BSMV) is the type member of the genus Hordeivirus, rigid, rod-shaped viruses in the family Virgaviridae. We have used fiber diffraction and cryo-electron microscopy to determine the helical symmetry of BSMV to be 23.2 subunits per turn of the viral helix, and to obtain a low-resolution model of the virus by helical reconstruction methods. Features in the model support a structural relationship between the coat proteins of the hordeiviruses and the tobamoviruses. PMID:23725818

Kendall, Amy; Williams, Dewight; Bian, Wen; Stewart, Phoebe L; Stubbs, Gerald

2013-09-01

307

Relationship between antimold activity and molecular structure of cinnamaldehyde analogues.  

Science.gov (United States)

A quantitative structure-activity relationship (QSAR) modeling of the antimold activity of cinnamaldehyde analogues against of Aspergillus niger and Paecilomyces variotii was presented. The molecular descriptors of cinnamaldehyde analogues were calculated by the CODESSA program, and these descriptors were selected by best multi-linear regression method (BMLR). Satisfactory multilinear regression models of Aspergillus niger and Paecilomyces variotii were obtained with R(2)=0.9099 and 0.9444, respectively. The models were also satisfactorily validated using internal validation and leave one out validation. The QSAR models provide the guidance for further synthetic work. PMID:23374870

Zhang, Yuanyuan; Li, Shujun; Kong, Xianchao

2013-03-01

308

Structural properties of the Hugoniot curve  

International Nuclear Information System (INIS)

This report is devoted to the structural properties analysis of the HUGONIOT curve, independently of the equation of state (E 0 S) display. The general properties so coming out are applied to the shock waves interacting studies. When phase transitions are present we investigate the splitting of shock waves and also the rarefaction waves. To end with, we present the shock instabilities and the non-uniqueness of solutions when specific E 0 S are present. (author)

2002-01-01

309

The structure?activity relationship in herbicidal monosubstituted sulfonylureas  

Energy Technology Data Exchange (ETDEWEB)

The herbicide sulfonylurea (SU) belongs to one of the most important class of herbicides worldwide. It is well known for its ecofriendly, extreme low toxicity towards mammals and ultralow dosage application. The original inventor, G Levitt, set out structure-activity relationship (SAR) guidelines for SU structural design to attain superhigh bioactivity. A new approach to SU molecular design has been developed. After the analysis of scores of SU products by X-ray diffraction methodology and after greenhouse herbicidal screening of 900 novel SU structures synthesized in the authors laboratory, it was found that several SU structures containing a monosubstituted pyrimidine moiety retain excellent herbicidal characteristics, which has led to partial revision of the Levitt guidelines. Among the novel SU molecules, monosulfuron and monosulfuron-ester have been developed into two new herbicides that have been officially approved for field application and applied in millet and wheat fields in China. A systematic structural study of the new substrate-target complex and the relative mode of action in comparison with conventional SU has been carried out. A new mode of action has been postulated.

Li, Zheng-Ming; Ma, Yi; Guddat, Luke; Cheng, Pei-Quan; Wang, Jian-Guo; Pang, Siew S; Dong, Yu-Hui; Lai, Cheng-Ming; Wang, Ling-Xiu; Jia, Guo-Feng; Li, Yong-Hong; Wang, Su-Hua; Liu, Jie; Zhao, Wei-Guang; Wang, Bao-Lei (Nankai); (Queens); (Chinese Aca. Sci.)

2012-05-24

310

Correlated structure-optical properties studies of plasmonic nanoparticles  

Science.gov (United States)

Interest in nanotechnology is driven by unprecedented means to tailor the physical behaviour via structure and composition. Unlike bulk materials, minute changes in size and shape can affect the optical properties of nanoparticles. Characterization, understanding, and prediction of such structure-function relationships is crucial to the development of novel applications such as plasmonic sensors, devices, and drug delivery systems. Such knowledge has been recently vastly expanded through systematic, high throughput correlated measurements, where the localized surface plasmon resonance (LSPR) is probed optically and the particle shape investigated with electron microscopy. This paper will address some of the recent experimental advances in single particle studies that provide new insight not only on the effects of size, composition, and shape on plasmonic properties but also their interrelation. Plasmon resonance frequency and decay, substrate effects, size, shape, and composition will be explored for a variety of plasmonic systems.

Ringe, Emilie; Van Duyne, Richard P.; Marks, Laurence D.

2014-06-01

311

Structural relationships in rare earth-transition metal hydrides  

Energy Technology Data Exchange (ETDEWEB)

Several structural types of form AB/sub 2/, AB/sub 3/, A/sub 2/B/sub 7/, and AB/sub 5/ (A = rare earth, B = transition metal) are known to be closely related, with local environments which are very similar among the different compounds. Based on these relationships, we suggest that hydride phases A/sub l/B/sub m/H/sub n/ should be related according to the relationships n(AB/sub 3/) = 1/3n(AB/sub 5/) + 2/3n(AB/sub 2/) and n(A/sub 2/B/sub 7/) = n(AB/sub 5/) + n(AB/sub 2/) where the n(AB/sub m/) are observed hydrogen phase concentrations. It is shown that the phases observed in pressure-composition isotherms for AB/sub 3/ and A/sub 2/B/sub 7/ systems can be understood from this viewpoint. A discussion is given of the maximum hydrogen concentration possible in the compounds having these structure types.

Dunlap, B.D.; Viccaro, P.J.; Shenoy, G.K.

1980-01-01

312

Structural and mechanical properties of platinum carbide.  

Science.gov (United States)

Platinum carbide (PtC) was synthesized under extreme conditions and considered as a potential candidate for superhard materials. However, the unsettled issue concerning the structural identification has impeded the full understanding of its physical and chemical properties. Here, we examine by first-principles calculations the crystal structure under high pressure and ideal strength along several high-symmetry directions under large deformation. The current calculations reveal that the zinc blende structure is the thermodynamically stable phase, and the simulated X-ray diffraction data are in excellent agreement with the experimental pattern. Further strain-stress calculations indicate that anomalous fluctuating behaviors of ideal strength occur in PtC. These results are expected to broaden our understanding of the structural and mechanical properties for other potential superhard materials formed by heavy transition metals and light elements. PMID:24832702

Li, Qian; Zhang, Xinxin; Liu, Hanyu; Wang, Hui; Zhang, Miao; Li, Quan; Ma, Yanming

2014-06-01

313

Metallophthalocyanine thin films: Structure and physical properties  

Science.gov (United States)

Organic semiconductors represent a class of carbon-based compounds with a tremendous potential to exhibit novel physical properties, and to be used in new and important applications. They display different properties compared to their inorganic counterparts, and present many advantages such as unlimited potential to be synthesized in new molecular structures, and capability of being processed inexpensively. Metallophthalocyanines (MPc) belong to the small-molecule group of organic semiconductors, and represent a model system for the whole class of flat, organic molecules. This dissertation presents a study of the structure and the electrical and magnetic properties of thin phthalocyanine films and phthalocyanine-based devices. Chapter one gives an introduction to the general properties of organic semiconductors and the wide range of their physical properties. In particular, the metallophtalocyanines are introduced as being a model system for the small-molecule group of organic semiconductors. Metallophthalocyanines are very well suited to be grown in thin films using organic molecular beam deposition (OMBD) techniques. Chapter two discusses the fabrication of thin phthalocyanine films and devices using OMBD, and the study of their structural properties using a wide range of experimental methods. The molecular shape anisotropy, combined with the interplay between intermolecular and the molecule-substrate interactions, determine different thin film structures that can be controlled by the fabrication conditions. The structure of phthalocyanine thin films determines their electrical transport properties. Chapter three investigates the electrical transport properties of hybrid metal-organic sandwich devices. These properties are controlled not only by the organic film, but also by the metal-organic interfaces. It was found that the low-voltage regime is linear, i.e. Ohmic, for a wide range of temperatures and organic layer thicknesses. The conductance increases exponentially with the temperature and decreases exponentially with the thickness. This behavior was explained with a model that incorporates tunneling between localized states with thermally-induced overlap. Chapter 4 studies the magnetic properties of MPcs. They are controlled by the central metal ion, and the type of molecular stacking in thin films, and were studied using DC magnetometry and magneto-optical techniques. Experimental data suggest the existence of two different magnetic regimes as a function of temperature.

Colesniuc, Corneliu Nicolai

314

EFFECT OF WEAVE STRUCTURE ON FABRIC PROPERTIES  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Idea about raw material consumption, crimp and load elongation characteristics of woven fabrics is very important in many respects including designing of woven fabrics and fashion making. In the present paper the effect of weave structure on raw material consumption, crimp and load elongation characteristics etc.of woven fabrics have been concentrated. It was observed that the weave structure have substantial effect on the yarn consumption and fabric properties like crimp and load elongation ...

2011-01-01

315

Lanthanide acylpyrazolonates: synthesis, properties and structural features  

International Nuclear Information System (INIS)

Data concerning synthesis and structural features of lanthanide acylpyrazolonates including tris-complexes, heteroligand complexes with aromatic N-heterocycles and phosphorus-containing ligands and anionic tetrakis-complexes are summarized. The effect of substituents in the acyl moiety on the structural and luminescence properties of the compounds is considered. The key features of acylpyrazolonate coordination polymers and bis(acylpyrazolonates) of rare earth elements are discussed. The bibliography includes 71 references.

2012-12-31

316

Structure and Properties of Dense Silica Glass  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The O K-edge x-ray Raman scattering (XRS), Brillouin scattering and diffraction studies on silica glass at high pressure have been elucidated in a unified manner using model structures obtained from First-Principles molecular dynamics calculations. This study provides a comprehensive understanding on how the structure is related to the physical and electronic properties. The origin of the “two peak” pattern in the XRS is found to be the result of increased packing of oxygen near the Si an...

2012-01-01

317

A validation of the Experiences in Close Relationships-Relationship Structures scale (ECR-RS) in adolescents.  

Science.gov (United States)

Emerging evidence points toward a two-dimensional attachment construct: avoidance and anxiety. The Experiences in Close Relationships-Relationship Structures scale (ECR-RS; Fraley, Heffernan, Vicary, & Brumbaugh, 2011) is a questionnaire assessing two-dimensional relationship-specific attachment structures in adults and, hence, moves beyond the traditional focus on romantic relationships. The present article explored the psychometric abilities of the ECR-RS across parental and best friend domains in a sample of 15 to 18-year-olds (n = 1999). Two oblique factors were revealed across domains, exhibiting satisfactory construct validity, including factor-specific links to the model of adult attachment (Bartholomew & Horowitz, 1991), and independent factor discrimination between subgroups. A robust validation supports the application of the ECR-RS to assessing relationship-specific adolescent attachment structures. PMID:24215182

Feddern Donbaek, Dagmar; Elklit, Ask

2014-01-01

318

Short range ordering and microstructure property relationship in amorphous alloys  

Energy Technology Data Exchange (ETDEWEB)

A novel algorithm, ''Next Neighbourhood Evaluation (NNE)'', is enunciated during the course of this work, to elucidate the next neighbourhood atomic vicinity from the data, analysed using tomographic atom probe (TAP) that allows specifying atom positions and chemical identities of the next neighbouring atoms for multicomponent amorphous materials in real space. The NNE of the Pd{sub 55}Cu{sub 23}P{sub 22} bulk amorphous alloy reveals that the Pd atoms have the highest probability to be the next neighbours to each other. Moreover, P-P correlation corroborates earlier investigations with scattering techniques that P is not a direct next neighbour to another P atom. Analogous investigations on the Fe{sub 40}Ni{sub 40}B{sub 20} metallic glass ribbons, in the as quenched state and for a state heat treated at 350 C for 1 hour insinuate a pronounced elemental inhomogeneity for the annealed state, though, it also depicts glimpse of a slight inhomogeneity for B distribution even for the as quenched sample. Moreover, a comprehensive microstructural investigation has been carried out on the Zr{sub 53}Co{sub 23.5}Al{sub 23.5} glassy system. TEM and TAP investigations evince that the as cast bulk samples constitutes a composite structure of an amorphous phase and crystalline phase(s). The crystallization is essentially triggered at the mould walls due to heterogeneous nucleation. The three dimensional atomic reconstruction maps of the volume analysed by TAP reveal a complex stereological interconnected network of two phases. The phase that is rich in Zr and Al concentration is depleted in Co concentration while the phase that is rich in Co concentration is depleted both in Zr and Al. Zr{sub 53}Co{sub 23.5}Al{sub 23.5} glassy splat samples exhibit a single exothermic crystallization peak contrary to the as cast bulk sample with a different T{sub g} temperature. A single homogeneous amorphous phase revealed by TEM investigations depicts that the faster cooling rate during splat quenching is sufficient for the vitrification of this alloy system. Zr{sub 53}Co{sub 23.5}Al{sub 23.5} bulk samples and splat samples, both exhibit very soft ferromagnetic properties. The heat treatment of as cast bulk sample results in an increase in net magnetization. The crystallization kinetics during the heat treatment, effects both the remanent magnetization, M{sub r} and coercivity, H{sub c} accordingly. Intriguingly, a salient increase in soft ferromagnetic properties is recorded for the heat treated splat samples. (orig.)

Shariq, A.

2006-07-01

319

Study of different rolling and continuous cooling conditions on the relationship structure/properties of low-carbon bainitic steels; Analise da influencia dos parametros de laminacao na microestrutura / propriedades mecanicas de acos microligados bainiticos  

Energy Technology Data Exchange (ETDEWEB)

This work shows a study in laboratory, of the influence of different rolling conditions, continuous cooling and chemical composition on bainitic microstructure and properties of a low carbon Nb-Ti-B steel another one with addition of Cu-Ni-Cr. The results showed that in both steels were possible to obtain a bainitic microstructure with different levels of mechanical properties depending on the proportion of acicular constituents. (author) 5 refs., 17 figs., 2 tabs.

Felipe Filho, Rubens; Germano, Roberto L.S. [Companhia Siderurgica Nacional, Volta Redonda, RJ (Brazil); Santos, Dagoberto B. [Minas Gerais Univ., Belo Horizonte, MG (Brazil). Dept. de Engenharia Metalurgica

1996-12-31

320

Phase relationships, basic metallurgy and superconducting properties of Nb_3Sn and related compounds  

International Nuclear Information System (INIS)

The phase relationships and the superconducting properties of Nb_3Sn are compared with those of other high Tsub(c) compounds crystallizing in the A15 structure: Nb_3Al, Nb_3Ga, Nb_3Ge, V_3Si, V_3Ga ... Characteristic differences of these systems, i.e., the shape of the A15 phase field, the variation of Tsub(c) with composition or with atomic ordering, are discussed. Recent methods leading to the accurate determination of the phase relationships in these systems up to 2000 "0C are reviewed. The discussion is extended to the low temperature relationships in Nb_3Sn and V_3Si with the corresponding tetragonal modifications. Methods for observing these low temperature details and recent results about their influence on Tsub(c) are presented. In the case of Nb_3Sn, the factors influencing the formation of the low temperature tetragonal phase, such as hydrostatic pressure, precompression in multifilamentary wires, or hydrogen loading, are discussed. (orig.)

1981-01-01

 
 
 
 
321

Structural and Magnetic Properties of Trigonal Iron  

CERN Document Server

First principles calculations of the electronic structure of trigonal iron were performed using density function theory. The results are used to predict lattice spacings, magnetic moments and elastic properties; these are in good agreement with experiment for both the bcc and fcc structures. We find however, that in extracting these quantities great care must be taken in interpreting numerical fits to the calculated total energies. In addition, the results for bulk iron give insight into the properties of thin iron films. Thin films grown on substrates with mismatched lattice constants often have non-cubic symmetry. If they are thicker than a few monolayers their electronic structure is similar to a bulk material with an appropriately distorted geometry, as in our trigonal calculations. We recast our bulk results in terms of an iron film grown on the (111) surface of an fcc substrate, and find the predicted strain energies and moments accurately reflect the trends for iron growth on a variety of substrates.

Fox, S

1995-01-01

322

Structure and Antioxidant Activity Relationships of Isoflavonoids from Dalbergia parviflora  

Directory of Open Access Journals (Sweden)

Full Text Available The antioxidant activities of 24 isoflavonoids that were previously isolated as pure compounds from Dalbergia parviflora were evaluated using three different in vitro antioxidant-based assay systems: xanthine/xanthine oxidase (X/XO, ORAC, and DPPH. The isolates consisted of three subgroups, namely isoflavones, isoflavanones, and isoflavans, each of which appeared to have diversified substituents, and were thus ideal for the study of their structure-activity relationships (SARs. The SAR analysis was performed using the results obtained from both the inter-subgroup isoflavonoids with the same substitution pattern and the intra-subgroup compounds with different substitution patterns. The inter-subgroup comparison showed that the isoflavones exhibited the highest antioxidant activities based on all three assays. The intra-subgroup analysis showed that the additional presence of an OH group in Ring B at either R3? or R5? from the basic common structure of the R7-OH of Ring A and the R4?-OH (or -OMe of Ring B greatly increased the antioxidant activities of all of the isoflavonoid subgroups and that other positions of OH and OMe substitutions exerted different effects on the activities depending on the subgroup and assay type. Therefore, based on the structural diversity of the isoflavonoids in D. parviflora, the present study provides the first clarification of the detailed antioxidant SARs of isoflavonoids.

Worrawat Promden

2014-02-01

323

Electron density - structure relationships in some perovskite-type compounds  

International Nuclear Information System (INIS)

Experimentally measured electron-deformation densities for the structurally related compounds dipotassium palladium tetrachloride, K2PdCl4, dipotassium silicon hexafluoride, K2SiF6, dipotassium palladium hexachloride, K2PdCl6, and dipotassium nickel tetrafluoride, K2NiF4, contain significant features in interatomic regions. The topographical relationship of interatom depletions to the structural geometry indicates that they originate from non-bonded interactions between atoms. The ?? maps for K2PdCl4 and K2PdCl6 show unexpected structure near the K atoms. Low-temperature studies on K2SiF6 and K2PdCl4 indicate that these features are not due to anharmonic thermal motion, in marked contrast to those near the halide atoms. For the new low-temperature analysis included in the study: K2SiF6, cubic, Fm anti 3m, Mr = 220.27, a = 8.046 (2) A, V = 520.9 (4) A3, Z = 4, Dx = 2.81 (2) Mg m-3, ?(Mo K?) = 2.09 mm-1, F(000) = 424, T = 110 K, R = 0.070, wR = 0.024, S = 1.47 (9) for 129 independent reflections. (orig.)

1995-12-01

324

Structure-activity relationship study of collagen-derived anti-angiogenic biomimetic peptides.  

Science.gov (United States)

Structure-activity relationship (SAR) studies are essential in the generation of peptides with enhanced activity and efficacy as therapeutic agents. In this study, we report a Structure-activity relationship study for a family of mimetic peptides derived from type IV collagen with potent anti-angiogenic properties. The Structure-activity relationship study was conducted using a number of validated in vitro assays including cell proliferation, adhesion, migration, and tubule formation. We report a critical sequence (NINNV) within this peptide series, which is required for the potent anti-angiogenic activity. Detailed amino acid substitutions resulted in peptides with superior efficacy. Specifically, substitutions with isoleucine at positions 12 and 18 along with the substitution of the methionine at position 10 with the non-natural amino acid D-alanine led to an increase in potency by two orders of magnitude over the parent peptide. Several mimetic peptides in this series exhibit a significant improvement of activity over the parent peptide. This improved in vitro activity is expected to correlate with an increase in in vivo activity leading to effective peptides for anti-angiogenic therapy for different disease applications including cancer and age-related macular degeneration. PMID:22405100

Rosca, Elena V; Koskimaki, Jacob E; Pandey, Niranjan B; Tamiz, Amir P; Popel, Aleksander S

2012-07-01

325

Structural equation models of relationships between exercise and cognitive abilities.  

Science.gov (United States)

Data were obtained from 300 men and women aged 55 to 91. Separate structural equation models of relationships between physical exercise and 3 cognitive performance variables--reaction time, working memory, and reasoning--fit the data well. Other variables in the models were age, health, education, and morale. Age and exercise affected each performance variable directly; education had a direct effect on reasoning only. There were also indirect effects of age and health on performance variables, mediated through exercise. The main hypothesis of the study, that exercise contributes to performance, was supported. A large decrease in model fit resulted when the path from exercise to each performance variable was deleted. Hypotheses that age-related deficits are primarily accounted for by lack of exercise or by poor health were not supported. PMID:2242248

Clarkson-Smith, L; Hartley, A A

1990-09-01

326

Structure-Activity Relationship of Fluoroquinolones Against K. pneumoniae  

Science.gov (United States)

The structure-activity relationship of fluoroquinolones, which show anti-K. pneumoniae activity, was studied by using principal component analysis (PCA) and hierarchical cluster analysis (HCA). The PCA results showed that the lowest unoccupied molecular orbital energy, energy difference between the highest occupied and the lowest unoccupied molecular orbital, dipole moment, net atomic charge on atom I, molecular polarizability, partition coefficient and molecular refractivity of these compounds are responsible for the separation between high-activity and low-activity groups. The HCA results were similar to those obtained with PCA. By using the chemometric results, four synthetic compounds were analyzed through PCA and HCA, and three of them are proposed as active molecules against K. pneumoniae which is consistent with the results of clinical experiments. The methodologies of PCA and HCA provide a reliable rule for classifying new fluoroquinolones with anti-K. pneumoniae activity.

Li, Xiao-hong; Zhang, Rui-zhou; Cheng, Xin-lu; Yang, Xiang-dong

2007-04-01

327

Unravelling the materials genome: Symmetry relationships in alloy properties  

International Nuclear Information System (INIS)

Highlights: ? Research strategy for Accelerated Metallurgy project is outlined. ? Surprising symmetry among atomic, nanoscale and mechanical properties. ? Generalisation of Ashby diagrams via principal component analysis. ? Atomic-related properties can be described with linear regression. ? Mechanical properties modelled via Kocks–Mecking-type physical method. -- Abstract: Metals and alloys have been indispensable for technological progress, but only a fraction of the possible ternary systems (combinations of three elements) is known. Statistical inference methods combined with physical models are presented to discover new systems of enhanced properties. It is demonstrated that properties originating from atomic-level interactions can be described employing a linear regression analysis, but properties incorporating microstructural and thermal history effects require a balance between physical and statistical modelling. In spite of this, there is a remarkable degree of symmetry among all properties, and by employing a principal components analysis it is shown that ten properties essential to engineering can be described well in a three dimensional space. This will aid in the discovery of novel alloying systems

2013-07-25

328

Unravelling the materials genome: Symmetry relationships in alloy properties  

Energy Technology Data Exchange (ETDEWEB)

Highlights: ? Research strategy for Accelerated Metallurgy project is outlined. ? Surprising symmetry among atomic, nanoscale and mechanical properties. ? Generalisation of Ashby diagrams via principal component analysis. ? Atomic-related properties can be described with linear regression. ? Mechanical properties modelled via Kocks–Mecking-type physical method. -- Abstract: Metals and alloys have been indispensable for technological progress, but only a fraction of the possible ternary systems (combinations of three elements) is known. Statistical inference methods combined with physical models are presented to discover new systems of enhanced properties. It is demonstrated that properties originating from atomic-level interactions can be described employing a linear regression analysis, but properties incorporating microstructural and thermal history effects require a balance between physical and statistical modelling. In spite of this, there is a remarkable degree of symmetry among all properties, and by employing a principal components analysis it is shown that ten properties essential to engineering can be described well in a three dimensional space. This will aid in the discovery of novel alloying systems.

Toda-Caraballo, Isaac [Department of Materials Science and Metallurgy, University of Cambridge New Museums Site, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Galindo-Nava, Enrique I. [Department of Materials Science and Metallurgy, University of Cambridge New Museums Site, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Delft University of Technology, Mekelweg 2, Delft 2628 CD (Netherlands); Rivera-Díaz-del-Castillo, Pedro E.J., E-mail: pejr2@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge New Museums Site, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom)

2013-07-25

329

Structure and properties of rediation crosslinked LDPE-EPDM blends  

International Nuclear Information System (INIS)

The regularity of radiation crosslinking and the radiation effect on the structure and property of LDPE (low density polyethylene)-EPDM (copolymer of ethylene-propylene)blends are reported in this paper. The results show that radiation crosslinking effect on LDPE/EPDM blends is either similar to pure LDPE or EPDM, depending upon which one is the main component in the blends. When the content of LDPE is higher than that of EPDM crosslinking of the blend is close to pure LDPE. The relationship between S+S1/2 and 1/R does not comply with Charlesby-Pinner's equation. While for blends rich in EPDM, a linear relationship is observed at high doses. The higher the content of EPDM in the blend, the easier is the blend to be crosslinked because of the presence of unsaturated bond in EPDM. The crystaline extent and density of the blend increases with increasing LDPE content in the blends. No obvious change of crystaline extent is observed in the dose range used. There is a close relationship between mechanical property and composition of the blends. The tensile strength (Ts) increases with increase in LDPE content, whereas the elongation (E%) shows a reverse effect. The effect of radiation dose on Ts is insignificant. However the elongation (E%) is seriousely affected

1988-01-01

330

Relationship between structure and catalytic performance of dealuminated Y zeolites  

International Nuclear Information System (INIS)

Dealuminated Y zeolites which have been prepared by hydrothermal and chemical treatments show differences in catalytic performance when tested fresh; however, these differences disappear after the zeolites have been steamed. The catalytic behavior of fresh and steamed zeolites is directly related to zeolite structural and chemical characteristics. Such characteristics determine the strength and density of acid sites for catalytic cracking. Dealuminated zeolites were characterized using x-ray diffraction, porosimetry, solid-state NMR and elemental analysis. Hexadecane cracking was used as a probe reaction to determine catalytic properties. Cracking activity was found to be proportional to total aluminum content in the zeolite. Product selectivity was dependent on unit cell size, presence of extra framework alumina and spatial distribution of active sites. The results from this study elucidate the role that zeolite structure plays in determining catalytic performance

1988-09-25

331

Definition and properties of ideal amorphous structures  

International Nuclear Information System (INIS)

Full text: Amorphous structure is usually defined by what it is not (ie, no crystalline peaks in XRS, no bond correlation in NMR), rather than by what it is. The interest in defining the structure of non-crystalline materials is long standing; packing geometry of spheres, molecular structure of glassy SiO2, or the structure of atactic polymers are prime examples. The earliest definitions of amorphous structure were in terms of a microcrystallite model of Valenkov, or continuous random network by Zachariasen. The random close packing of spheres of equal size, and an amorphous structure, composed of freely jointed linear chains of hard spheres, has been described mathematically in terms of a linear homogeneous Poisson process. This paper aims to describe some geometrical, kinematic, and topological properties of these two ideal amorphous structures, which belong to the same amorphous class. The geometry of packing is elucidated, and the use of Voronoi tessellation method for measuring the structures is described. The ideal amorphous solid has no symmetry elements; its volume can not be divided into identical unit cells. However, there is a volume element small enough to allow the distinction of its nanoscopic inhomogeneities, and sufficiently large enough to represent, accurately the overall behaviour. We define this volume element, the representative volume element. Suitable boundary conditions must be prescribed for a choice of RVE, and satisfy certain requirements. Topologically, a catchment region on the Born-Oppenheimer potential energy surface over nuclear configuration space, is defined by Mezey and Bader as an energetically stable geometry of the open region of R3 traversed by all the trajectories which terminate at a local maximum. Two topological properties will be described: (i) the boundaries of the catchment region as a direct geometrical correspondence to the Voronoi polyhedron for a given atom in a given structure, and (ii) the constriction points, described previously, as an inherent characteristic of IAS type II (and possibly others)

2002-02-01

332

Aldehyde dehydrogenase from human erythrocytes: structural relationship to the liver cytosolic isozyme.  

Science.gov (United States)

Human red cell aldehyde dehydrogenase (ALDH) resembles the liver cytosolic isozyme in numerous physicochemical properties. This study was undertaken to establish the structural relationship between the erythrocyte and liver ALDH isozymes. The purified red cell ALDH was S-(14C)-carboxymethylated, and cleaved with trypsin. The tryptic digest was fractionated using Sephadex and reversed-phase chromatography. All peptides analyzed were identified within the liver cytosolic enzyme structure. In each case the sequence obtained corresponds exactly to a segment from the human liver cytosolic ALDH. Thus, the erythrocyte enzyme, by virtue of its chemical and structural identity with the liver cytosolic enzyme, may serve as a suitable peripheral enzyme model to understand the cause and mechanism of alcohol abuse-related changes in liver cytosolic ALDH that has been found to be reduced in alcoholics. PMID:2776714

Agarwal, D P; Cohn, P; Goedde, H W; Hempel, J

1989-01-01

333

Critically Evaluated Database of Environmental Properties: The Importance of Thermodynamic Relationships, Chemical Family Trends, and Prediction Methods  

Science.gov (United States)

A database containing Henry's law constants, infinite dilution activity coefficients, and solubility data of industrially important chemicals has been compiled for aqueous systems. These properties are important in predicting the fate and transport of chemicals in the environment. The structure of this database is compatible with the existing 801 database and DIADEM interface, and data are included for a subset of compounds found in the 801 database. Thermodynamic relationships, chemical family trends, and predicted values were carefully considered when designating recommended values.

Brockbank, Sarah A.; Russon, Jenna L.; Giles, Neil F.; Rowley, Richard L.; Wilding, W. Vincent

2013-11-01

334

Relationship between properties characterizing independence equivalence in Bayesian networks and compositional models.  

Czech Academy of Sciences Publication Activity Database

equivalence problemKód oboru RIV: IN - Informatika http://library.utia.cas.cz/separaty/2010/MTR/kratochvil-relationship between properties characterizing independence equivalence in bayesian networks and compositional models.pdf

Kratochvíl, Václav

335

Evaluation of the structure–activity relationship of thrombin with thrombin binding aptamers by voltammetry and atomic force microscopy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The structure–activity relationship of the complex between thrombin and thrombin binding aptamers (TBA) was evaluated by differential pulse voltammetry at a glassy carbon electrode and atomic force microscopy at a highly oriented pyrolytic graphite electrode. The effects on the interaction with thrombin of TBA primary and secondary structures as well as of its folding properties in the presence of alkaline metals were investigated. The complex between thrombin and single stranded aptamers i...

Diculescu, Victor Constantin; Chiorcea-paquim, Ana-maria; Eritja, Ramon; Oliveira-brett, Ana Maria

2011-01-01

336

The NBS: Processing/Microstructure/Property Relationships in 2024 Aluminum Alloy Plates  

Science.gov (United States)

As received plates of 2024 aluminum alloy were examined. Topics covered include: solidification segregation studies; microsegregation and macrosegregation in laboratory and commercially cast ingots; C-curves and nondestructive evaluation; time-temperature precipitation diagrams and the relationships between mechanical properties and NDE measurements; transmission electron microscopy studies; the relationship between microstructure and properties; ultrasonic characterization; eddy-current conductivity characterization; the study of aging process by means of dynamic eddy current measurements; and Heat flow-property predictions, property degradations due to improve quench from the solution heat treatment temperature.

Ives, L. K.; Swartzendruber, W. J.; Boettinger, W. J.; Rosen, M.; Ridder, S. D.

1983-01-01

337

Structural properties of warm dense matter  

International Nuclear Information System (INIS)

We investigate the structure in warm dense matter by ab initio simulations and classical fluid equations. This comparison yields valuable information on the system properties such as effective ion-ion interactions and charge states. Extensions to systems with multiple ion species are discussed and the limits of reduced descriptions are demonstrated. The structural information is then used to predict the signal strength in x-ray scattering experiments which, in turn, can be used as diagnostics for warm dense fluids. Here, we need to consider the inelastic feature due to the dynamic response of free electrons as well as the elastic (Rayleigh) peak related to the static ion structure. In a last example, we apply ab initio simulations to calculate the ionic structure in highly excited graphite close to melting.

2010-04-01

338

Quantitative structureâ??property relationship for thermal decomposition temperature of ionic liquids  

DEFF Research Database (Denmark)

In this study, a wide literature survey has been conducted to gather an extensive set of thermal decomposition temperature (Td) data for ionic liquids (ILs). A data set consisting of Td data for 586 ILs was collated from 71 different literature sources. Using this data set, a reliable quantitative structure-property relationship has been developed. In order to consider the effects of the anion and cation on the Td of ILs, both anion-based and cation-based molecular descriptors were considered. Finally, a genetic function approximation method was used which selected 6 molecular descriptors for anions, and 6 molecular descriptors for cations to develop the model. The predictive capability of the 12-parameter model was evaluated using several validation techniques. Its applicability domain is discussed. The proposed model produces an acceptable average relative deviation of less than 5.2% taking into consideration all 586 experimental data values.

Gharagheizi, Farhad; Sattari, Mehdi

2012-01-01

339

Rational Formulation of Alternative Fuels using QSPR Methods: Application to Jet Fuels Développement d’un outil d’aide à la formulation des carburants alternatifs utilisant des méthodes QSPR (Quantitative Structure Property Relationship): application aux carburéacteurs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Alternative fuels are a promising solution for road transport but also for aircraft. In the aviation field, a huge amount of work has been done in the past years with the approval to use up to 50 % by volume of SPK (Synthetic Paraffinic Kerosene) in blends with conventional fossil Jet A-1. SPK are Fischer-Tropsch (FT) fuels but also Hydroprocessed Esters and Fatty Acids (HEFA). However, these alternative fuels can have different chemical properties depending on the process used for their...

2013-01-01

340

Theoretical free energies of electron transfer, electrochemical properties, electron transfer kinetic and quantitative structural relationships studies of alkynyldihydrofullerene in [X-UT-Y][R-C60–M+] supramolecular complexes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The isolated pentagon rule (IPR) states that all pentagonal carbon rings are isolated in the most stable fullerenes. Fullerenes (buckministerfullerene) are a class of spherical carbon allotrope group with unique properties. Electron transfer between fullerene C60 derivatives such as alkynyldihydrofullerene (1-alkynyl-C60 carbanion) and other molecules are thought to involve the transfer of electrons between molecules surrounding the fulle...

Avat Arman Taherpour; Masomeh Tayebi-Suraki; Nosratollah Mahdizadeh

2012-01-01

 
 
 
 
341

Structure and Frictional Properties of Colloid Gel  

Directory of Open Access Journals (Sweden)

Full Text Available Polymer gels are known to be opaque when the preparation conditions, such as the reaction temperature and the composition, are changed. The increase of the opaqueness of the gel suggests strongly the change of network structure. Here, we are going to review the recent studies on the structure and the frictional study of the opaque poly(acrylamide gel. The results indicate that the opaque poly(acrylamide gel consists of the fractal aggregate of the colloidal particles of sub-micrometer in size. The density of the colloid particle is calculated from the structural parameters and is found to be of the order of about 1 g/cm3. The results indicate that the main chain component and the cross-linker is densely cross-linked into the particle. The frictional property of poly(acrylamide gel is analyzed in terms of the structural parameters of the gel. It is found that the frictional property of the opaque gel is well explained in terms of the structural parameters of the opaque gel.

Masayuki Tokita

2014-03-01

342

Quantitative structure-cytotoxicity relationship of phenylpropanoid amides.  

Science.gov (United States)

Background: A total of 12 phenylpropanoid amides were subjected to quantitative structure-activity relationship (QSAR) analysis, based on their cytotoxicity, tumor selectivity and anti-HIV activity, in order to investigate on their biological activities. Materials and Methods: Cytotoxicity against four human oral squamous cell carcinoma (OSCC) cell lines and three human oral normal cells was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Tumor selectivity was evaluated by the ratio of the mean CC50 (50% cytotoxic concentration) against normal oral cells to that against OSCC cell lines. Anti-HIV activity was evaluated by the ratio of CC50 to EC50 (50% cytoprotective concentration from HIV infection). Physicochemical, structural, and quantum-chemical parameters were calculated based on the conformations optimized by the LowModeMD method followed by density functional theory (DFT) method. Results: Twelve phenylpropanoid amides showed moderate cytotoxicity against both normal and OSCC cell lines. N-Caffeoyl derivatives coupled with vanillylamine and tyramine exhibited relatively higher tumor selectivity. Cytotoxicity against normal cells was correlated with descriptors related to electrostatic interaction such as polar surface area and chemical hardness, whereas cytotoxicity against tumor cells correlated with free energy, surface area and ellipticity. The tumor-selective cytotoxicity correlated with molecular size (surface area) and electrostatic interaction (the maximum electrostatic potential). Conclusion: The molecular size, shape and ability for electrostatic interaction are useful parameters for estimating the tumor selectivity of phenylpropanoid amides. PMID:24982367

Shimada, Chiyako; Uesawa, Yoshihiro; Ishihara, Mariko; Kagaya, Hajime; Kanamoto, Taisei; Terakubo, Shigemi; Nakashima, Hideki; Takao, Koichi; Saito, Takayuki; Sugita, Yoshiaki; Sakagami, Hiroshi

2014-07-01

343

The structural acoustic properties of stiffened shells  

DEFF Research Database (Denmark)

Plates stiffened with ribs can be modeled as homogeneous isotropic or orthotropic plates, and modeling such an equivalent plate numerically with, say, the finite element method is, of course, far more economical in terms of computer resources than modelling the complete, stiffened plate. This is important when a number of stiffened plates are combined in a complicated structure composed of many plates. However, whereas the equivalent plate theory is well established there is no similar established theory for stiffened shells. This paper investigates the mechanical and structural acoustic properties of curved shells with stiffening ribs. Finite element simulations and experimental data will be compared and discussed.

Luan, Yu

2008-01-01

344

Structural and tunneling properties of Si nanowires  

We investigate the electronic structure and electron transport properties of Si nanowires attached to Au electrodes from first principles using density functional theory and the nonequilibrium Green\\'s function method. We systematically study the dependence of the transport properties on the diameter of the nanowires, on the growth direction, and on the length. At the equilibrium Au-nanowire distance we find strong electronic coupling between the electrodes and nanowires, which results in a low contact resistance. With increasing nanowire length we study the transition from metallic to tunneling conductance for small applied bias. For the tunneling regime we investigate the decay of the conductance with the nanowire length and rationalize the results using the complex band structure of the pristine nanowires. The conductance is found to depend strongly on the growth direction, with nanowires grown along the ?110? direction showing the smallest decay with length and the largest conductance and current.

Montes, E.

2013-12-06

345

Enhancing the value of commodity polymers: Part 1. Structure-property relationships in composite materials based on maleated polypropylene/inorganic phosphate glasses. Part 2. New value-added applications for polyesters  

Science.gov (United States)

The first part of the thesis (Chapters 2 & 3) describes a new class of organic polymer/inorganic glass composite materials with property improvements that are impossible to achieve with classical polymer blends or composites. These materials exhibit good processability, superior mechanical performance, good thermal stability, and have excellent gas barrier properties. Low glass transition temperature phosphate glasses (Pglass) are used as inorganic fillers and slightly maleated polypropylene is used as the organic polymer matrix. The Pglass, which was dispersed as spherical droplets in the unoriented composites can be elongated into high aspect ratio platelets during the biaxial stretching process. Biaxially oriented films exhibited a brick wall type microstructure with highly aligned inorganic platelets in a ductile organic matrix and the oxygen barrier properties are significantly improved due to presence of Pglass platelets as impermeable inclusions. Mechanical properties of the biaxially oriented films showed significant improvements compared to neat polymer due to uniform dispersion of the Pglass platelets. Properly dispersed and aligned platelets have proven to be very effective for increasing the composite modulus. These developed materials therefore show promise to help fulfill the ever increasing demand for new advanced materials for a wide variety of advanced packaging applications because of their gas barrier properties, flexibility, transparency, mechanical strength and performance under humid conditions. The second part of the thesis (Chapters 4 & 5) describes new value-added applications for polyesters. Chapter 4 reports a novel process for the decolorization of green and blue colored PET bottle flakes using hydrogen peroxide. The decolorized flakes were characterized for color, intrinsic viscosity values. Decolorized flakes exhibited color values similar to those of colorless recycled PET and even though IV values decreased, bleached flakes still exhibit useful molecular weight. The consumption of H2O2 during the bleaching process was quantified by titrating the residual peroxide using a standard solution of potassium permanganate. Chapter 5 reports synthesis of ductile amorphous polymers which change their color as a function of mechanical deformation. Cyano--OPV moieties were covalently incorporated into the backbone of amorphous polyester PETG. The materials exhibit a significant color change upon compression consistent with efficient breakup of the dye aggregates upon deformation and therefore can be useful for technological applications that require smart coatings with integrated scratch detectors.

Gupta, Mohit

346

Magnetic properties, crystallography and interface structure of Co/CoO bilayers  

Science.gov (United States)

The layers' structure, interlayer boundaries and magnetic properties of Co/CoO films sputtered on single-crystal MgO(1 0 0) and Al 2O 3(1 1 0) substrates have been investigated. The relationship between the structure and magnetic properties is analyzed. The NGR investigations of 57Co atomic probes on the Co film surface and Co/CoO interface have been carried out.

Ustinov, V. V.; Popov, V. V.; Kaigorodov, V. N.; Krinitsina, T. P.; Matveev, S. A.; Milyaev, M. A.; Burhanov, A. M.; Kravtsov, E. A.; Blinov, I. V.

2007-03-01

347

Magnetic properties, crystallography and interface structure of Co/CoO bilayers  

Energy Technology Data Exchange (ETDEWEB)

The layers' structure, interlayer boundaries and magnetic properties of Co/CoO films sputtered on single-crystal MgO(1 0 0) and Al{sub 2}O{sub 3}(1 1 0) substrates have been investigated. The relationship between the structure and magnetic properties is analyzed. The NGR investigations of {sup 57}Co atomic probes on the Co film surface and Co/CoO interface have been carried out.

Ustinov, V.V. [Institute of Metal Physics, Ural Division of Russian Academy of Sciences, 18, S. Kovalevskaya Street, Ekaterinburg 620041 (Russian Federation); Popov, V.V. [Institute of Metal Physics, Ural Division of Russian Academy of Sciences, 18, S. Kovalevskaya Street, Ekaterinburg 620041 (Russian Federation); Kaigorodov, V.N. [Institute of Metal Physics, Ural Division of Russian Academy of Sciences, 18, S. Kovalevskaya Street, Ekaterinburg 620041 (Russian Federation); Krinitsina, T.P. [Institute of Metal Physics, Ural Division of Russian Academy of Sciences, 18, S. Kovalevskaya Street, Ekaterinburg 620041 (Russian Federation)]. E-mail: krinitsina@imp.uran.ru; Matveev, S.A. [Institute of Metal Physics, Ural Division of Russian Academy of Sciences, 18, S. Kovalevskaya Street, Ekaterinburg 620041 (Russian Federation); Milyaev, M.A. [Institute of Metal Physics, Ural Division of Russian Academy of Sciences, 18, S. Kovalevskaya Street, Ekaterinburg 620041 (Russian Federation); Burhanov, A.M. [Institute of Metal Physics, Ural Division of Russian Academy of Sciences, 18, S. Kovalevskaya Street, Ekaterinburg 620041 (Russian Federation); Kravtsov, E.A. [Institute of Metal Physics, Ural Division of Russian Academy of Sciences, 18, S. Kovalevskaya Street, Ekaterinburg 620041 (Russian Federation); Blinov, I.V. [Institute of Metal Physics, Ural Division of Russian Academy of Sciences, 18, S. Kovalevskaya Street, Ekaterinburg 620041 (Russian Federation)

2007-03-15

348

Structure and properties of composite polyolefin materials  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis is based on three main studies, all dealing with structure-property investigation of semicrystalline polyolefin-based composites. Low density poly(ethylene) (LDPE) and isotactic poly(propylene) (iPP) were chosen as parts of the composites materials and they were investigated either separately (as homoploymers), either in blend systems with the composition LDPE/iPP 80/20 or as filled matrix with layered silicate (montmorillonite). The beneficial influence of adding e...

Pryadilova, Olga

2006-01-01

349

Multimode interference structuresproperties and applications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of this paper is to present operating principles and properties of multimode interference (MMI) structures and their basic applications in optoelectronic circuits. We discuss the principles of direct, mirrored and multiple image formation for the general and restricted interference. We also show the possibility of self-imaging effects in gradient index waveguides. Based on the above, we present MMI applications in splitters and couplers N×M technology of different configurations...

Marek Blahut; Damian Kasprzak

2004-01-01

350

Relationship between silver concentration with microstructural and mechanical properties of rolled AlZn alloy  

Energy Technology Data Exchange (ETDEWEB)

The relationship of Ag addition on microstructural and mechanical properties of rolled AlZn alloy was investigated. AlZn alloys were prepared by metal mould casting method and the Ag addition was done by Vortex technique. Microstructural characterization of AlZnAg specimens was analyzed by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Results show that the phases of the as-cast state alloy are solid solution zinc-rich hexagonal close-packed (hcp) crystal structure, named {eta}-phase and {alpha}-Al solid solution with Zn dissolved into the matrix. The silver concentration in AlZn alloy influences the volume of AgZn{sub 3} precipitates. The mechanical properties, especially the flow stress and elongation of the alloy were improved by the Ag addition. The Vortex method was used in order to diminish the process cost, generating an alloy with homogenous microstructure, less casting porosity and better mechanical properties.

Valdez, S., E-mail: svaldez@fis.unam.mx [Instituto de Ciencias Fisicas-Universidad Nacional Autonoma de Mexico, Av. Universidad S/N, Col. Chamilpa, 062210 Cuernavaca, Morelos (Mexico); Perez, R.; Rodriguez-Diaz, R.A. [Instituto de Ciencias Fisicas-Universidad Nacional Autonoma de Mexico, Av. Universidad S/N, Col. Chamilpa, 062210 Cuernavaca, Morelos (Mexico); Angeles-Chavez, C. [Instituto Mexicano del Petroleo, Eje central Lazaro Cardenas 152, Mexico D.F. 07730 (Mexico); Casolco, S.R. [Instituto Tecnologico y de Estudios Superiores de Monterrey, Campus Puebla, Via Atlixcayotl 2301. Puebla, Pue. 2800 (Mexico)

2010-05-25

351

Numerical calculations of effective elastic properties of two cellular structures  

CERN Document Server

Young's moduli of regular two-dimensional truss-like and eye-shape-like structures are simulated by using the finite element method. The structures are the idealizations of soft polymeric materials used in the electret applications. In the simulations size of the representative smallest units are varied, which changes the dimensions of the cell-walls in the structures. A power-law expression with a quadratic as the exponential term is proposed for the effective Young's moduli of the systems as a function of the solid volume fraction. The data is divided into three regions with respect to the volume fraction; low, intermediate and high concentrations. The parameters of the proposed power-law expression in each region are later represented as a function of the structural parameters, unit-cell dimensions. The presented expression can be used to predict structure/property relationship in materials with similar cellular structures. It is observed that the structures with volume fractions of solid higher than 0.15 ...

Tuncer, E

2004-01-01

352

Crystal structure, electronic structure, and thermoelectric properties of ?-Zn4Sb3 from first principles  

Science.gov (United States)

Due to its complex and disordered structure, the relationship between crystal structure and electronic properties of ?-Zn4Sb3 is still ambiguous. The effect of Zn vacancy and interstitial on the structure, bonding, electronic properties, and thermoelectric properties of ?-Zn4Sb3 has been investigated by ab initio calculations in this work. It is demonstrated that the Zn-Zn bond distance increases significantly whereas the Zn-Sb bond distance increases slightly after fully optimization and relaxation. This abnormality is explained by exploring the bonding properties, which may attribute to the Zn deficiency and the disordered distributions of Zn in ?-Zn4Sb3 . Our calculations show that ?-Zn4Sb3 is a p -type degenerated semiconductor with an indirect gap of 0.26 eV and a direct gap of 0.33 eV. An opposite effect on the electrical conductivity and Seebeck coefficient is found for both p -type and n -type dopants. Thus doping may not be exceptionally beneficial for improving the thermoelectric properties of ?-Zn4Sb3 .

Qiu, A. N.; Zhang, L. T.; Wu, J. S.

2010-01-01

353

Structure and magnetic properties of powder HITPERM material  

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Full Text Available Purpose: The aim of the work is to investigate the structure and magnetic properties of the cobalt based HITPERM amorphous alloy Co68Fe4Mo1Si13.5B13.5 subjected high-energy ball milling and to the isothermal annealing to a combination of these two technologies.Design/methodology/approach: The nanocrystalline ferromagnetic powders were manufactured by high-energy ball milling of metallic glasses ribbons in as state. Using the HFQS program the distributions of the magnetic hyperfine P(H fields were determined for spectra smoothed in this way, employing the Hesse-Rübartsch method. Observations of the structure of powders were made on the OPTON DSM-940 scanning electron microscope. The diffraction examinations and examinations of thin foils were made on the JEOL JEM 200CX transmission electron microscope equipped in equipped with the EDS LINK ISIS X- ray energy dispersive spectrometer made by Oxford. Graphical analyses of the obtained X-ray diffraction patterns, as well as of the HC=f(TA relationship were made using the MICROCAL ORIGIN 6.0 program.Findings: The analysis of the structure and magnetic properties test results of the HITPERM powders alloy Co68Fe4Mo1Si13.5B13.5 obtained in the high-energy ball of milling process proved that the process causes significant decrease in the magnetic properties. The magnetic properties of this material and structure and may be improved by means of a proper choice of parameters of this process as well as the final thermal treatment.Research limitations/implications: For the soft magnetic powder material, further magnetical, composition examinations and structure are planed.Practical implications: Feature an alternative to solid alloys are the amorphous and nanocrystalline metal powders obtained by milling of metallic glasses and make it possible to obtain the ferromagnetic nanocomposites, whose dimensions and shape can be freely formed.Originality/value: The paper presents results of influence of parameters of the high-energy ball milling process on magnetic properties and structure of soft magnetic powder HITPERM alloy obtained in this technique. The paper compares magnetic properties and structure of the HITPERM alloy obtained in high-energy ball milling process, melt spinning technique and in a combination of these two technologies.

J.E. Fr?ckowiak

2007-03-01

354

Scientific habits of mind: A reform of structure and relationships  

Science.gov (United States)

This research was designed to broaden current elementary science reform efforts by including the voices of our young scientists. Ten high school students who were defined as possessing both coherent science knowledge and scientific habits of mind were selected for the study. Through a three-part series of in-depth, phenomenological interviews, these students revealed early childhood experiences from birth through age ten to which they attributed their development of science knowledge and scientific habits of mind. Educational connoisseurship and criticism provided the framework through which the experiences were analyzed. The research revealed the overwhelming role of scientific habits of mind in the current success of these young scientists. Scientific habits of mind were developed through the structures and relationships in the home. Parents of the participants provided a non-authoritarian, fun, playful, tolerant atmosphere in which messes and experimentation were the norm. Large blocks of uninterrupted, unstructured time and space that "belonged" to the child allowed these children to follow where curiosity led. Frequently, the parent modeled scientific habits of mind. Good discipline in the minds of these families had nothing to do with punishments, rewards, or rules. The parents gave the children responsibilities, "free rein," and their trust, and the children blossomed in that trust and mutual respect. Parents recognized and supported the uniqueness, autonomy, interests, and emotions of the child. Above all, the young scientists valued the time, freedom, patience, and emotional support provided by their parents. For girls, construction toys, hot wheels, sand boxes, and outdoor experiences were particularly important. Art classes, free access to art media, sewing, music, and physical activity facilitated observational skills and spatial relationship development. The girls knew that doing traditionally masculine and feminine activities were acceptable and celebrated by both parents. The time has come to include scientific habits of mind in science education reform. The time has come for science education reform to espouse fun and playfulness, large blocks of unstructured time, responsibility and trust, emotional support, and caring teacher-child relationships. The time has come to listen to the voices of our young scientists.

Mooney, Linda Beth

355

Quantitative Studies on Structure-DPPH• Scavenging Activity Relationships of Food Phenolic Acids  

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Full Text Available Phenolic acids are potent antioxidants, yet the quantitative structure-activity relationships of phenolic acids remain unclear. The purpose of this study was to establish 3D-QSAR models able to predict phenolic acids with high DPPH• scavenging activity and understand their structure-activity relationships. The model has been established by using a training set of compounds with cross-validated q2 = 0.638/0.855, non-cross-validated r2 = 0.984/0.986, standard error of estimate = 0.236/0.216, and F = 139.126/208.320 for the best CoMFA/CoMSIA models. The predictive ability of the models was validated with the correlation coefficient r2pred = 0.971/0.996 (>0.6 for each model. Additionally, the contour map results suggested that structural characteristics of phenolics acids favorable for the high DPPH• scavenging activity might include: (1 bulky and/or electron-donating substituent groups on the phenol ring; (2 electron-donating groups at the meta-position and/or hydrophobic groups at the meta-/ortho-position; (3 hydrogen-bond donor/electron-donating groups at the ortho-position. The results have been confirmed based on structural analyses of phenolic acids and their DPPH• scavenging data from eight recent publications. The findings may provide deeper insight into the antioxidant mechanisms and provide useful information for selecting phenolic acids for free radical scavenging properties.

Jie Pang

2012-11-01

356

Quantitative Structure ? Antiprotozoal Activity Relationships of Sesquiterpene Lactones  

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Full Text Available Prompted by results of our previous studies where we found high activity of some sesquiterpene lactones (STLs against Trypanosoma brucei rhodesiense (which causes East African sleeping sickness, we have now conducted a structure-(in-vitro-activity study on a set of 40 STLs against T. brucei rhodesiense, T. cruzi, Leishmania donovani and Plasmodium falciparum. Furthermore, cytotoxic activity against L6 rat skeletal myoblast cells was assessed. Some of the compounds possess high activity, especially against T. brucei (e.g. helenalin and some of its esters with IC50-values of 0.05-0.1 µM, which is about 10 times lower than their cytotoxic activity. It was found that all investigated antiprotozoal activities are significantly correlated with cytotoxicity and the major determinants for activity are a,b-unsaturated structural elements, also known to be essential for other biological activities of STLs. It was observed, however, that certain compounds are considerably more toxic against protozoa than against mammalian cells while others are more cytotoxic than active against the protozoa. A comparative QSAR analysis was therefore undertaken, in order to discern the antiparasitic activity of STLs against T. brucei and cytotoxicity. Both activities were found to depend to a large extent on the same structural elements and molecular properties. The observed variance in the biological data can be explained in terms of subtle variations in the relative influences of various molecular descriptors.

Reto Brun

2009-06-01

357

Genotype diversity in structure of amylopectin of waxy rice and its influence on gelatinization properties.  

Science.gov (United States)

A set of 13 waxy rice genotypes prepared by chemically-induced mutation of non-waxy rice variety TNG67 and 7 waxy rice varieties widely planted in Taiwan were screened for various structural and gelatinization properties of starches. Wide variation on physicochemical properties and molecular structure of amylopectin for the 20 waxy rice starches were obtained and relationship between gelatinization properties and molecular structure of starch were discussed. More attributes on swelling and gelatinization thermal properties, comparing to pasting attributes, showed significant correlation with molecular structure parameters. The swelling and gelatinization thermal properties of waxy rice starch did not show significant correlation with molecular size of amylopectin, while significant correlations were found between the swelling or gelatinization thermal properties and chain length of amylopectin. Results suggest that the swelling and pasting of waxy starch is essentially dominated by granule architecture and is dependent on the interactions among amylopectin chains. PMID:23399229

Lin, Jheng-Hua; Singh, Harinder; Ciao, Jhih-Ying; Kao, Wen-Tzu; Huang, Wei-Hsiang; Chang, Yung-Ho

2013-02-15

358

Relationship between structure and properties in high-temperature Bi(Al{sub 0.5}Fe{sub 0.5})O{sub 3}-PbTiO{sub 3} piezoelectric ceramics  

Energy Technology Data Exchange (ETDEWEB)

Highlights: > Low-cost Bi-based high temperature piezoceramics. > A new high temperature system with Curie point >478 deg. C, compared to BiScO{sub 3}-PbTiO{sub 3} (450 deg. C). > Effectively improve the poling conditions. - Abstract: Ceramic samples of xBi(Al{sub 0.5}Fe{sub 0.5})O{sub 3}-(1 - x)PbTiO{sub 3} (BAF-PT, x = 0.05-0.5) solid solutions were fabricated using the conventional solid state reaction method. X-ray diffraction analysis revealed that all compositions can form single perovskite phase with tetragonal symmetry. The relationship between the tetragonal lattice parameters, tetragonality c/a, cell volume, and ferro-piezoelectric characterization as a function of x was systematically investigated. The BAF modification can effectively improve the poling condition at a proper BAF content. A combination of piezoelectric constant of d{sub 33} (50-60 pC/N), electromechanical planar coupling coefficients of k{sub p} (20.3-22.5%), and high Curie temperature T{sub c} (>478 deg. C) suggested that BAF-PT could be a good candidate for high-temperature piezoelectric applications.

Yao Zhonghua, E-mail: yaozhhua@whut.edu.cn [Key Laboratory of Advanced Technology for Specially Functional Materials, Ministry of Education, Wuhan University of Technology, Wuhan 430070 (China); Peng Liyuan [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Liu Hanxing, E-mail: lhxhp@whut.edu.cn [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Hao Hua; Cao Minghe; Yu Zhiyong [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

2011-05-05

359

Biological studies on 1,2-benzisothiazole derivatives. IV. Relationships between chemical structure and genotoxicity.  

Science.gov (United States)

This paper describes in vitro evaluation by Bacillus subtilis rec-assay and Salmonella-microsome assay of the genotoxic properties of some 1,2-benzisothiazole and 1,2-benzisothiazolin-3-one derivatives, containing groups (aromatic nitro, aromatic amino, epoxide groups) often associated with mutagenic properties and defined as "alerting groups". Compounds 2, 3, 4, 7, 8, 9, 11, 14, 16, 20, 21 and 22 exhibited DNA-damaging activity. The Salmonella-microsome assay confirmed the genotoxic activity of these compounds, which was also demonstrated for compounds 5, 6, 10, 12, 13, 15, 17, 18, 19, 25 and 27. Relationships between chemical structure and genotoxic activity showed that all the 1,2-benzisothiazole derivatives containing an alerting group were active. On the contrary, among 1,2-benzisothiazolin-3-one derivatives, compounds 24 and 26 were non-mutagenic, although an alerting group was present in the molecule. PMID:1953924

Zani, F; Maggiali, C A; Mingiardi, M R; Mazza, P

1991-05-01

360

Synthesis of Li1+xMIIIxTi2-x(PO4)3 with nasicon structure, using sol-gel methods. Study of the relationship microstructure electrical properties  

International Nuclear Information System (INIS)

Compounds of formula Li1+xMIIIxTi2-x(PO4)3 with MIII = Cr, Fe and x = 0 and 0.05 have been prepared at soft temperatures using the Pechini synthesis method, based on sol-gel chemistry. The structural and microstructural characterization by X-ray diffraction and Scanning Electron Microscopy (SEM), shows that all of them crystallize in a NASICON-type structure with similar lattice parameters. Doping with Fe and Cr, causes an increase of the density of the samples after sinterization what clearly improves the ionic conductivity of the original material, LiTi2(PO4)3 until values of 9x10-4 S cm-1 at room temperature in the chromium-doped material. (Author)

2010-01-01

 
 
 
 
361

Low temperature structure and properties of graphite lamellar compounds  

Science.gov (United States)

The main initial objective of this E.R.O. supported research was a better understanding of the relationships between the structure and certain electronic properties of graphite intercalation compounds (GIC's) which might lead to the synthesis of compounds with a high electrical conductivity. In order to achieve this, three kinds of research were developed (1) Much time was devoted to preparing samples of pure compounds, without macroscopic defects such as cleavages or curvatures, and with a mosaic spread as low as possible. (2) X-ray methods have been set up which permit a quantitative study of the defects in the compounds at room temperature and allow following the change in the structure from 300 K to about 10 K especially the variation of the identity period along the c axis perpendicular to the graphite sheets. (3) The in-plane electrical resistivity of several compounds was measured as a function of both stage and temperature, by using a contactless inductive method.

Guerard, D.; Herold, A.; Lelaurain, M.; McRae, E.

362

Correlação entre propriedades mecânicas e parâmetros estruturais de poliuretanos à base de poli(épsilon-caprolactona) / Relationships between mechanical properties and structural parameters of polyurethanes containing poly(epsilon-caprolactone)  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese No presente trabalho foram preparados poliuretanos (PUs) segmentados. Primeiramente foi obtido um pré-polímero (PP) a partir da reação de 2,4 e 2,6 - diisocianato de tolileno (TDI) e poli(épsilon-caprolactona) diol (PCL). A PCL é um poliéster biodegradável que constituiu o segmento flexível do PU. O [...] segmento rígido foi constituído por unidades uretânicas provenientes da ligação entre as extremidades isocianato do PP e as hidroxilas do extensor de cadeia: 1,4 - butanodiol (BDO), ou sacarose (SAC), ou glicose (GLY). Foram avaliadas as propriedades mecânicas e dinâmico-mecânicas dos poliuretanos obtidos e estas foram correlacionadas com os parâmetros estruturais. Os resultados foram justificados com base na intensidade das interações de hidrogênio, na mistura de fases, no volume dos extensores cíclicos e na presença de ligações cruzadas. Estes PUs estão sendo estudados com vistas à preparação de materiais biodegradáveis com propriedades mecânicas úteis. Abstract in english Segmented polyurethanes containing polycaprolactone as soft segment were prepared taking into account the biodegradable character of this compound. The hard block was produced by the reaction between tolylene diisocyanate and a chain extender (1,4 butanediol, sucrose or glucose). The mechanical and [...] dynamical properties were evaluated as a function of the contents of rigid blocks. The results were analyzed on the basis of the intermolecular interactions, mainly H bonds, phase mixture, volume of cyclic chain extenders and crosslinking. These polyurethanes are being studied aiming at the preparation of biodegradable materials with useful mechanical properties.

Kloss, Juliana; Bugay, Caroline; Akcelrud, Leni; Zawadzki, Sônia F.; Wang, Shu-Hui.

363

Properties of coronal mass ejections and relationship with solar flares  

Science.gov (United States)

Coronal mass ejections (CMEs) associated with flares are thought to be faster than those associated with filament eruptions. However, Hundhausen (1997) examined that the relationship between CME kinetic energy and X-ray flare peak intensity, and found that there is only a weak correlation. We have measured the speed, size, location, and acceleration of more than 4000 CMEs observed by the SOHO LASCO Coronagraph from January 1996 through December 2001, providing a good opportunity to revisit the relationship between CMEs and flares. We identified flare-CME pairs as follows: Since the field of view of the LASCO C2 coronagraph limited to heliocentric distances over 2 solar radii (Ro), we cannot obtain the CME start time accurately. So, we assume that the CMEs start from 1 Ro, and estimate the start time from their height-time trajectories. Then, we looked for CMEs that occurred within flare impulsive phase. This way, we found 239 flare-CME pairs. We found a weak correlation between the CME speed and flare X-ray peak flux (correlation coefficient = 0.52). When we isolated the limb events (based on the solar source of the CMEs), we found the correlation to be poorer (0.44). We compare our results with those of Hundhausen.

Yashiro, S.; Gopalswamy, N.; Michalek, G.; Howard, R. A.

2002-05-01

364

Structure-Odor Relationships for Pyrazines with Support Vector Machines  

Directory of Open Access Journals (Sweden)

Full Text Available The flavor class prediction of chemical compounds can be efficiently performed with structure-odor relationships (SOR, leading to a better understanding of the mechanism of odor perception. SOR models for various odor classes were developed with a wide variety of structural descriptors and statistical equations. We have investigated the application of support vector machines (SVM for the classification of 98 tetra-substituted pyrazines representing three odor classes, namely 32 green, 23 nutty, and 43 bell-pepper. The chemical structure of the pyrazines was encoded by five theoretical descriptors, namely the sum of electrotopological indices, the number of carbon atoms of the substituent R2, the charge on the first atom of the substituent R4 computed with an ab initio method (Hartee-Fock with a 3-21G basis set, and the molecular surface of the substituents R1 and R3. Three sets of SVM experiments were performed for the classification of pyrazines, each one considering the classification of one class of compounds against the compounds from the remaining two classes. The SVM models were computed with the dot, polynomial, radial basis function, neural, and anova kernels. The leave-10%-out cross-validation results represent the main criterion for selecting the best SVM model that has the highest prediction power. The results obtained demonstrate that the SVM classification of pyrazines in aroma classes depends strongly on the kernel type and various parameters that control the kernel shape. In general, the neural kernel gives the worst results. The best predictions were obtained with the polynomial kernel of degree 2 for the green and bell-pepper classes, and with the anova kernel (? = 0.5 and d = 1 for the nutty pyrazines. The classification of chemical compounds in odor classes with SOR models can be efficiently made with support vector machines. The solution of the SVM model is a unique hyperplane that guarantees a maximum separation between two classes of chemical compounds. This hyperplane can be computed very fast and represents the solution of a quadratic programming problem, but the classification results depend on the kernel type and structural descriptors. The identification of the optimum predictive kernel and elimination of the overfitted SVM models requires extensive cross-validation experiments.

Ovidiu Ivanciuc

2002-05-01

365

Molecular and electronic structure of cyclic trinuclear gold(i) carbeniate complexes: insights for structure/luminescence/conductivity relationships.  

Science.gov (United States)

An experimental and computational study of correlations between solid-state structure and optical/electronic properties of cyclotrimeric gold(I) carbeniates, [Au3(RN?COR')3] (R, R' = H, Me, (n)Bu, or (c)Pe), is reported. Synthesis and structural and photophysical characterization of novel complexes [Au3(MeN?CO(n)Bu)3], [Au3((n)BuN?COMe)3], [Au3((n)BuN?CO(n)Bu)3], and [Au3((c)PeN?COMe)3] are presented. Changes in R and R' lead to distinctive variations in solid-state stacking, luminescence spectra, and conductive properties. Solid-state emission and excitation spectra for each complex display a remarkable dependence on the solid-state packing of the cyclotrimers. The electronic structure of [Au3(RN?COR')3] was investigated via molecular and solid-state simulations. Calculations on [Au3(HN?COH)3] models indicate that the infinitely extended chain of eclipsed structures with equidistant Au--Au intertrimer aurophilic bonding can have lower band gaps, smaller Stokes shifts, and reduced reorganization energies (?). The action of one cyclotrimer as a molecular nanowire is demonstrated via fabrication of an organic field effect transistor and shown to produce a p-type field effect. Hole transport for the same cyclotrimer-doped within a poly(9-vinylcarbazole) host-produced a colossal increase in current density from ?1 to ?1000 mA/cm(2). Computations and experiments thus delineate the complex relationships between solid-state morphologies, electronic structures, and optoelectronic properties of gold(I) carbeniates. PMID:24961904

McDougald, Roy N; Chilukuri, Bhaskar; Jia, Huiping; Perez, Michael R; Rabaâ, Hassan; Wang, Xiaoping; Nesterov, Vladimir N; Cundari, Thomas R; Gnade, Bruce E; Omary, Mohammad A

2014-07-21

366

Mistura polipropileno/poliestireno: um exemplo da relação processamento-estrutura-propriedade no ensino de polímeros Polypropylene/polystyrene blend: an example of the processing-structure-property relationship in the education of polymers  

Directory of Open Access Journals (Sweden)

Full Text Available As misturas ou blendas poliméricas continuam, apesar de seu longo estudo, a ser foco de pesquisas em diferentes áreas. A mistura de polipropileno e poliestireno é uma das mais estudadas principalmente pelo baixo custo e relevância tecnológica destes materiais. Neste trabalho, os alunos da disciplina Processamento de Polímeros I (PG24 no Programa de Pós-Graduação em Ciência dos Materiais (PGCIMAT-UFRGS, realizaram em aula todo o processamento dos polímeros (polipropileno e poliestireno e a produção das misturas poliméricas. A seguir, cada aluno ficou responsável por realizar um tipo de caracterização, que incluía a preparação das amostras, a análise em si e a discussão dos resultados da referida análise. Subsequentemente, os resultados foram confrontados em aula, onde se buscou as correlações existentes. E por fim, todos os alunos fizeram a revisão deste artigo, incluindo sugestões e críticas. Como esperado, a mistura de polipropileno e poliestireno forma uma blenda imiscível. Além disso, o processamento afetou as características dos polímeros, induzindo redução de massa molar e, como reflexo, redução de suas propriedades físicas. Na mistura PP/PS a separação de fase produziu domínios de PS da ordem de micra, com fraca adesão à matriz, o que explica essa perda de propriedades mecânicas.Polymer blends remain an important research topic in different areas, in spite of innumerous studies over the years. In particular, mixtures of polypropylene and polystyrene are among the most studied, mainly owing to their low cost and technological relevance. In this work, the students enrolled in the discipline Polymer Processing I (PG24 in the Materials Science Graduate Program (PGCIMAT-UFRGS produced blends of polypropylene and polystyrene, where all polymer processing steps were performed during lab classes. Then, each student undertook a characterization procedure with a specific technique, which included samples preparation, the analysis itself and discussion of the results. Subsequently, the results were confronted in the classroom, where we sought the correlations. Finally, all students reviewed this article, including suggestions and criticisms. As expected, the mixture of polystyrene and polypropylene formed an immiscible blend. Furthermore, the processing affected the characteristics of the polymers, leading to a reduction in molecular weight, and as a result a drop in its physical properties. In the PP/PS mixtures, phase separation produced PS domains with micrometers in size, and low adhesion to the PP matrix, which explains the loss of mechanical properties.

Ricardo V. B. Oliveira

2013-01-01

367

Structure activity relationships to assess new chemicals under TSCA  

International Nuclear Information System (INIS)

Under Section 5 of the Toxic Substances Control Act (TSCA), manufacturers must notify the US Environmental Protection Agency (EPA) 90 days before manufacturing, processing, or importing a new chemical substance. This is referred to as a premanufacture notice (PMN). The PMN must contain certain information including chemical identity, production volume, proposed uses, estimates of exposure and release, and any health or environmental test data that are available to the submitter. Because there is no explicit statutory authority that requires testing of new chemicals prior to their entry into the market, most PMNs are submitted with little or no data. As a result, EPA has developed special techniques for hazard assessment of PMN chemicals. These include (1) evaluation of available data on the chemical itself, (2) evaluation of data on analogues of the PMN, or evaluation of data on metabolites or analogues of metabolites of the PMN, (3) use of quantitative structure activity relationships (QSARs), and (4) knowledge and judgement of scientific assessors in the interpretation and integration of the information developed in the course of the assessment. This approach to evaluating potential hazards of new chemicals is used to identify those that are most in need of addition review of further testing. It should not be viewed as a replacement for testing. 4 tabs

1990-06-27

368

Review of Quantitative Structure - Activity Relationships for Acute Mammalian Toxicity  

Directory of Open Access Journals (Sweden)

Full Text Available This paper reviews Quantitative Structure-Activity Relationship (QSAR models for acute mammalian toxicity published in the last decade. A number of QSAR models based on cytotoxicity data from mammalian cell lines are also included because of their possible use as a surrogate system for predicting acute toxicity to mammals. On the basis of the review, the following conclusions can be made: i a relatively small number of models for in vivo toxicity are published in the literature. This is due to the nature of the endpoint - acute systemic toxicity is usually related to whole body phenomena and therefore is very complex. The complexity of the mechanisms involved leads to difficulties in the QSAR modelling; ii most QSAR models identify hydrophobicity as a parameter of high importance for the modelled toxicity. In addition, many models indicate the role of the electronic and steric effects; iii most of the literature-based models are restricted to single chemical classes. Models based on more heterogeneous data sets are those incorporated in expert systems. In general, the QSAR models for mammalian toxicity identified in this review are considered useful for investigating the mechanisms of toxicity of defined chemical classes. However, for predictive purposes in the regulatory assessment of chemicals most of the models require additional information to satisfy internationally agreed validation principles. In addition, the development of new models covering larger chemical domains would be useful for the regulatory assessment of chemicals.

Iglika Lessigiarska

2006-12-01

369

Quantitative structure activity relationships of some pyridine derivatives as corrosion inhibitors of steel in acidic medium.  

Science.gov (United States)

Quantum chemical calculations using the density functional theory (B3LYP/6-31G DFT) and semi-empirical AM1 methods were performed on ten pyridine derivatives used as corrosion inhibitors for mild steel in acidic medium to determine the relationship between molecular structure and their inhibition efficiencies. Quantum chemical parameters such as total negative charge (TNC) on the molecule, energy of highest occupied molecular orbital (E (HOMO)), energy of lowest unoccupied molecular orbital (E (LUMO)) and dipole moment (?) as well as linear solvation energy terms, molecular volume (Vi) and dipolar-polarization (?) were correlated to corrosion inhibition efficiency of ten pyridine derivatives. A possible correlation between corrosion inhibition efficiencies and structural properties was searched to reduce the number of compounds to be selected for testing from a library of compounds. It was found that theoretical data support the experimental results. The results were used to predict the corrosion inhibition of 24 related pyridine derivatives. PMID:21695505

El Ashry, El Sayed H; El Nemr, Ahmed; Ragab, Safaa

2012-03-01

370

Relationship between radical scavenging effects and anticorrosive properties of polyphenols  

Energy Technology Data Exchange (ETDEWEB)

The radical scavenging effects and anticorrosive properties of polyphenols (gallic acid [GA] and two gallotannins) that contained ortho-trihydroxyl aromatic rings but different numbers of GA moieties and different molecular masses were studied. Scavenging of the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) by the polyphenols was studied by electron spin resonance (ESR). The ESR spectra of the reaction products of the polyphenols and hydrated ferric sulfate were recorded. The anticorrosive properties of the polyphenols were studied by gravimetric and linear polarization measurements. X-ray analysis and mercury porosimetry were used to investigate the rust and its phase components converted by the polyphenols. An increase in the molecular mass (and the number of GA moieties) was found to increase the ability of the polyphenols to scavenge DPPH radicals and to convert the rust. Thus, evaluation of the scavenging effect was shown effective as a fast method to estimate and predict the usefulness of various polyphenols for anticorrosive applications.

Gust, J. [Building Research Inst., Warsaw (Poland); Wawer, I. [Univ. of Warsaw (Poland). Dept. of Chemistry

1995-01-01

371

Relationships between supercontraction and mechanical properties of spider silk  

Science.gov (United States)

Typical spider dragline silk tends to outperform other natural fibres and most man-made filaments. However, even small changes in spinning conditions can have large effects on the mechanical properties of a silk fibre as well as on its water uptake. Absorbed water leads to significant shrinkage in an unrestrained dragline fibre and reversibly converts the material into a rubber. This process is known as supercontraction and may be a functional adaptation for the silk's role in the spider's web. Supercontraction is thought to be controlled by specific motifs in the silk proteins and to be induced by the entropy-driven recoiling of molecular chains. In analogy, in man-made fibres thermal shrinkage induces changes in mechanical properties attributable to the entropy-driven disorientation of `unfrozen' molecular chains (as in polyethylene terephthalate) or the `broken' intermolecular hydrogen bonds (as in nylons). Here we show for Nephila major-ampullate silk how in a biological fibre the spinning conditions affect the interplay between shrinkage and mechanical characteristics. This interaction reveals design principles linking the exceptional properties of silk to its molecular orientation.

Liu, Yi; Shao, Zhengzhong; Vollrath, Fritz

2005-12-01

372

Structural material properties for fusion application  

International Nuclear Information System (INIS)

Materials properties requirements for structural applications in the forthcoming and future fusion machines are analyzed with emphasis on safety requirements. It is shown that type 316L(N) used in the main structural components of ITER is code qualified and together with limits imposed on its service conditions and neutron radiation levels, can adequately satisfy ITER vacuum vessel licensing requirements. For the in-vessel components, where nonconventional fabrication methods, such as HIPing, are used, design through materials properties, data is combined with tests on representative mockups to meet the requirements. For divertor parts, where the operating conditions are too severe for components to last throughout the reactor life, replacement of most exposed parts is envisaged. DEMO operating conditions require extension of ITER design criteria to high temperature and high neutron dose rules, as well as to compatibility with cooling and tritium breeding media, depending on the blanket concept retained. The structural material favoured in EU is Eurofer steel, low activation martensitic steel with good ductility and excellent resistance to radiation swelling. However, this material, like other ferritic / martensitic steels, requires post-weld annealing and is sensitive to low temperature irradiation embrittlement. Furthermore, it shows cyclic softening during fatigue, complicating design against fatigue and creep-fatigue. (au)

2008-10-01

373

Properties and structure of aromatic ester solvents.  

Science.gov (United States)

This paper reports on an experimental and theoretical study of the aromatic ester solvents family. Several compounds were selected to analyze the different factors that influence their liquid-state properties and structures. The pressure-volume-temperature behavior of these fluids was measured accurately over wide temperature and pressure ranges and correlated successfully with the empirical TRIDEN equation. From the measured data the relevant derived coefficients of isothermal compressibility, isobaric expansibility, and internal pressure were calculated. The statistical associating fluid theory (SAFT) and perturbed chain statistical associating fluid theory (PC-SAFT) molecularly based equations of state were used to predict the PVT behavior with model parameters obtained from the correlation of available saturation literature data; the results provided by PC-SAFT equations of state were clearly superior for all of the studied solvents. The fluid's molecular level structure was studied by quantum computations at the B3LYP/6-311++g** level and classical molecular dynamics simulations in the NPT ensemble with the OPLS-AA forcefield. Molecular parameters, such as torsional barriers or cluster energetics, were analyzed as a function of ester structures. The molecular dynamics study provides, on one hand, theoretical values of thermophysical properties, which are compared with the experimental ones, and, on the other hand, valuable molecular level structural information. On the basis of both macroscopic and microscopic studies complex fluid structures were inferred with important effects arising from the geometries of the studied molecules and from the existence of remarkable intermolecular forces of dominating dipolar nature. PMID:17411084

Aparicio, Santiago; Alcalde, Rafael; Dávila, María J; García, Begoña; Leal, José M

2007-05-01

374

Preliminary analysis of the relationship between structure and anthelmintic activity of condensed tannins in cattle nematodes  

DEFF Research Database (Denmark)

Some plant secondary metabolites as tannins have direct anthelminthic properties and may play a role in the control of nematodes in livestock. However, their great diversity in structural characteristics and different levels of content in plants are responsible for a highly variable response in anthelmintic activity, as measured in vitro. The aim of the present study was to assess the relationship between tannin structure and anthelmintic activity using an in vitro assay. We used a series of purified tannins (from 65% to 100% of purity) characterized for their degree of polymerization (mDP), prodelphinidin/procyanidin (PC/PD) ratio and cis/trans ratio by thiolytic degradation. Tannins diluted in two concentrations in water, epigallocatechin gallate (EGCG), positive (ivermectin) and negative (water) controls were examined by the Larval Feeding Inhibition Assay (LFIA) with first stage larvae (L1) of the cattle nematode Cooperia oncophora in triplicates. All extracted condensed tannins, in particular sainfoin, white clover and pine tree inhibited the feeding of L1 at the high concentration. There was a trend towards lower inhibition with decreasing PD/PC ratio. However, despite black currantâ??s 95 % of PD, it showed a low inhibition which could be related to a very low cis/trans ratio. Based on these preliminary findings it is difficult to define a relationship between the structural parameters and anthelmintic activity.

Enemark, Heidi L.

2013-01-01

375

Structural properties of impact ices accreted on aircraft structures  

Science.gov (United States)

The structural properties of ice accretions formed on aircraft surfaces are studied. The overall objectives are to measure basic structural properties of impact ices and to develop finite element analytical procedures for use in the design of all deicing systems. The Icing Research Tunnel (IRT) was used to produce simulated natural ice accretion over a wide range of icing conditions. Two different test apparatus were used to measure each of the three basic mechanical properties: tensile, shear, and peeling. Data was obtained on both adhesive shear strength of impact ices and peeling forces for various icing conditions. The influences of various icing parameters such as tunnel air temperature and velocity, icing cloud drop size, material substrate, surface temperature at ice/material interface, and ice thickness were studied. A finite element analysis of the shear test apparatus was developed in order to gain more insight in the evaluation of the test data. A comparison with other investigators was made. The result shows that the adhesive shear strength of impact ice typically varies between 40 and 50 psi, with peak strength reaching 120 psi and is not dependent on the kind of substrate used, the thickness of accreted ice, and tunnel temperature below 4 C.

Scavuzzo, R. J.; Chu, M. L.

1987-01-01

376

Relationship between transport properties and phase transformations in mixed-conducting oxides  

Science.gov (United States)

To elucidate the relationship between transport properties and phase transformations in mixed-conducting oxides, Sr 0.9Ca 0.1Co 0.89Fe 0.11O 3-? (SCCFO) and SrCoO 3-? (SCO) were chosen as the model materials and have been investigated in detail. Oxygen permeation measurements verified that both oxides are well permeable to oxygen at elevated temperatures, e.g., at 900 °C during a cooling procedure, oxygen permeation rates as large as 1.5 and 2.0 mL/min/cm 2