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1

Structure--properties relationships for manganese perovskites  

Energy Technology Data Exchange (ETDEWEB)

By combining the results of dc magnetization, ac susceptibility, magnetoresistivity, magnetostriction, and x-ray and neutron powder diffraction data for stoichiometric La{sub 1{minus}x}Sr{sub x}MnO{sub 3} the authors have constructed a phase diagram that describes the magnetic, transport, and structural properties and the relationships among them as a function of composition and temperature. Correlations among physical and structural properties have been observed that are consistent with a competition between ferromagnetism and JT distortion. A metallic state occurs below the Curie temperature when both coherent and incoherent JT distortions are suppressed.

Dabrowski, B.; Xiong, X.; Chmaissem, O.; Bukowski, Z.; Jorgensen, J. D.

1999-10-14

2

Structure property relationships in peat bitumens  

Energy Technology Data Exchange (ETDEWEB)

Many investigations have been carried out into the chemical structure of peat bitumens. Their constitution is variable, being a function of both peat source and extraction chemisty, however, the total range of species likely to be encountered in these materials is now well established. Despite the extensive chemical investigation, little attention has been paid to the equally important area of physical analysis and description of the bitumen and its constituents. Given their potential practical uses this omission is surprising. Applications in construction materials, for example as road binders or in proprietary products such as wax finishing compounds, impose stringent physical and mechanical requirements, yet there is little published information on these aspects of bitumen behaviour. Development of these and other uses for peat bitumen will be facilitated by detailed descriptions of physical behaviour. The work described here is an examination of some of the physical properties of peat bitumen and their relationship with the materials chemical structure. Rheological behaviour is the most important property from an applications point of view, and is therefore the focus of the work. Attention has also been directed to the effects of heat on flow behaviour, as it is well established that peat bitumens are thermally sensitive. Because of the inherent variability of peat bitumens an associated chemical characterisation is included here to allow comparison to be made with materials from other sources.

Leahy, J.J.; Drake, J.A.G.; Birkinshaw, C. (University of Limerick (Ireland))

1990-01-01

3

Structure-property relationships in fluorinated polyimides  

Energy Technology Data Exchange (ETDEWEB)

Over the past several years we have been exploring new fluorinated polyimides for electronics applications. In this paper we explore the effects of fluorine incorporation into polyimides by various methods. These include backbone modification via fluorinated linking groups and/or aromatic ring substitution, and incorporation of pendant fluoroalkyl side chains. Factors such as structural and positional isomerism of certain fluorinated groups on the properties of polyimide films are also considered. The properties investigated include dielectric constant, moisture absorption, thermal expansion coefficient, thermal stability, glass transition temperature, mechanical properties and solubility. The goal of this work has been to define the most fortuitous method of fluorine incorporation that will allow the optimum combination of properties for electronics.

Auman, B.C. [DuPont Electronic Materials, Wilmington, DE (United States)

1995-12-01

4

Structural property relationships in conjugated polymers  

Science.gov (United States)

The synthesis of a series of PPV derivative polymers by the Wittig-Horner reaction is described. The structure of each polymer is varied and the effects of these variations on the optical properties is explored. The effects of alkyloxy side chains is observed between the PPV derivatives Poly(-p-phenylvinylene-co-2,5-bis-octyloxy phenylvinylene.) PPV-OPV and Poly (para-2,5-bis-(n-octyloxy)-phenylvinylene) POPV. The phenyl units of the soluble PPV derivative POPV are replaced by alternate naphthyl units in the polymer Poly(2,5-bis(n-octyloxy)-1,4-phenylene vinylene-1,5-bis(n-octyloxy)-2,6-naphthylene vinylene) POPN-ONV and then fully by naphthyl units in Poly(2,6-bis-(n-octyloxy)-1,5-NaphthyleneVinylene) PONV. The addition of alkyloxy sidechains served to red shift the fluorescence emission as expected. The systematic conversion of phenyl to naphthyl units blue shifted the emission considerably while reducing the Stokes shift. There is evidence to suggest some localization of the pi electrons over the aromatic units of the polymer backbone. PONV is shown to have greater stability towards photo-oxidation then either POPV or PPV-OPV.

Lynch, P.; O'Neill, L.; Whelan, J.; McNamara, M.; Byrne, H. J.

2005-06-01

5

Electron beam crosslinked PVC : structure property relationships  

International Nuclear Information System (INIS)

[en] PVC is used extensively for its insulating properties for the manufacture of wires and cables and for other applications. Its gradual degradation, oxidation and even dehydro chlorination restricts use for long lasting period in installations such as high temperature zones, underground cables, communication systems, electro-nuclear facilities, etc. The technological properties and performance characteristics of PVC based insulation can be improved via crosslinking by high-energy electrons. PVC is however a polymer, which on irradiation predominantly undergoes degradation. To avoid degradation, it needs to be compounded with sensitizing agents or multifunctional monomers so that crosslinking is the predominant reaction. Radiation cross linkable formulations are complex mixtures of resin and various additives incorporated for achieving desired technological and performance characteristics, ease of processing and improving quality. The proper choice of additives and sensitizing agents enable low dose requirements for efficient crosslinking and improvements in various technological properties. The purposes of this work was to investigate the effect of using a binary sensitizer blend of a trifunctional monomer and a rubber in PVC, and develop suitable electron beam cross linkable formulations for wire insulation. This paper presents some aspects of the investigations and development of insulation demonstrated at industrial scale

2001-01-01

6

Processing-structure-microstructure-property relationships in polymer nanocomposites  

Science.gov (United States)

The optimal development of polymer nanocomposites using carbon nanotube (CNTs) and carbon nanofiber (CNFs) fillers requires a complete understanding of processing-structure-property relationships. The purpose of this understanding is to determine the optimal approach for processing polymer nanocomposites with engineered microstructures and enhanced material properties. In this research, two processing techniques were investigated: solvent processing and twin screw extrusion. The former is a batch process which employs mixing a polymer solution with a filler suspension using long mixing times and low levels of shear mixing. The latter is a continuous process that mixes polymer melts with solid nanoscale ingredients using high levels of shear mixing for a short mixing time. Previous studies conducted on polymer-CNT/CNF using these processes have focused mainly on processing-microstructure and structure-property relationships using one technique or the other. This research focuses on understanding the processing-property relationships by comparing the structure-property relationships resulting from the two processes. Furthermore, the effect of ingredients and processing parameters within each process on microstructure and structure-property relationships was investigated. The microstructural features, namely, distribution of agglomerates, dispersion, alignment, and aspect ratio of the filler were studied using optical, scanning electron, confocal and transmission electron microscopy, respectively. The composition of the filler was determined using thermogravimetric analysis. The electrical, rheological, thermo-oxidative and mechanical properties of the composites were also investigated. Many significant insights related to processing-structure-property relationships were obtained including: (a) deagglomeration is a critical combination of the magnitude of shear rate and the residence time, (b) the structure-property relationships can be modeled using a new methodology based on the degree of percolation by representing the material as an interpenetrating phase composite, (c) annealing can re-establish interconnectivity and improve electrical properties, (d) the degree of dispersion can be resolved using thermogravimetric analysis, and (e) increasing extrusion speed inhibits thermal decomposition and begins to asymptotically increase strength and stiffness through reduction in aspect ratio and size of agglomerates. Finally, a new combinatorial approach was developed for rapidly determining processing-structure relationships of polymer nanocomposites. This dissertation has broad implications in the processing of high performance and multifunctional polymer nanocomposites, combinatorial materials science, and histopathology.

Kota, Arun Kumar

7

Structure-Property Relationships in Novel High Pressure Superhard Materials  

Science.gov (United States)

Research on novel high-pressure superhard materials (those approaching diamond and cubic boron nitride in hardness) is driven by both scientific and practical objectives: the desire to understand their structure and bonding, which determine the unique properties of these materials, on one hand, and the demand of modern technologies for robust materials with superior properties, on the other. Structure-property relationships in newly synthesised superhard materials, as well as some methodological aspects of their characterisation are in focus of the present paper.

Dubrovinskaia, Natalia; Dubrovinsky, Leonid

8

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 composition–structure–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]–[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

9

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

10

Structure-Property Relationship of Perfluorinated Sulfonic Acid (PFSA) Membranes  

Science.gov (United States)

Perfluorosulfonic-acid (PFSA) membrane is the most commonly used ionomer in electrochemical energy storage and conversion devices thanks to its remarkable proton conductivity, perm-selectivity, wide electrochemical window, and mechanical stability. Most of these properties are the result of the membrane's phase-separated nanostructure where ions and solvents transport through the hydrated domains while the surrounding hydrophobic PTFE backbone acts as a mechanical support. Thus, it is essential to understand the solvent- and humidity-induced morphological changes and their associated impact on the membrane's properties for optimizing the structure-property relationship desired by the electrochemical devices. In this talk, correlations among the mechanical (e.g., modulus), electrochemical (e.g., ionic conductivity) and nanostructural (e.g., domain spacing) properties during hydration is discussed. Moreover, the impact of thermal history, mechanical reinforcement, and side-chain length on the structure-property correlation is examined. Even though the properties vary for the membranes investigated, similar correlations are found between the degree of hydration, domain spacing, and ionic conductivity.

Kusoglu, Ahmet; Weber, Adam

2013-03-01

11

Quantitative structure-property relationships modeling of skin irritation.  

UK PubMed Central (United Kingdom)

Interest in developing procedures for estimating skin irritation potential of chemicals has been increasing as a result of concerns regarding animal welfare and costs involved in experimental irritation studies. In response to these concerns, a number of expert systems and quantitative structure-activity relationship (QSAR) models have been proposed for predicting the skin irritation potential of compounds. However, these models require as input independent estimates of several physiochemical properties. Hence, to predict skin irritation potential using these models often requires additional models capable of estimating the physiochemical properties of diverse structures; a requirement that most literature QSARs fail to meet. In the work reported here, we developed a skin irritation QSPR model based on rabbit Draize test data for 186 compounds, which included chemicals from diverse molecular classes. The effectiveness of using a combination of traditional, functional group and structural descriptors has been studied. Our non-linear QSPR model is capable of predicting the skin irritation potential of chemical compounds with an R2 of 0.78. Further, the final set of descriptors used to model skin irritation was analyzed to elucidate the effects of molecular size, reactivity and skin penetration on skin irritation.

Golla S; Madihally S; Robinson RL Jr; Gasem KA

2009-02-01

12

Structure-property relationship of cast Ti-Nb alloys.  

UK PubMed Central (United Kingdom)

The present work is a study of the microstructure, mechanical properties and corrosion behaviour of a series of binary Ti-Nb alloys with Nb contents up to 35 wt%, with emphasis placed on the structure-property relationship of the alloys. The results indicate that crystal structure and morphology of the Ti-Nb alloys are sensitive to the Nb content. The cast c.p. Ti has a hexagonal alpha phase with a lath type morphology. The alloys containing 15 wt% or less Nb are dominated by a hexagonal alpha' phase with an acicular, martensitic structure. When containing 17.5-25 wt% Nb, the alloys are primarily comprised of an orthorhombic alpha" phase. With 27.5 wt% Nb, metastable beta phase starts to be retained. With Nb contents higher than 30 wt%, the equi-axed beta phase is almost entirely retained. Small amounts of omega phase are detected in alloys containing 27.5 and 30 wt% Nb. Among all present alloys, Ti-10Nb and Ti-27.5Nb exhibit the highest strengths, while the alpha"-dominated (17.5 and 20Nb) and beta-dominated (> 30Nb) alloys have the lowest moduli. All Ti-Nb alloys show excellent corrosion resistance in Hank's solution at 37 degrees C. From the present data, the microhardness, bending strength and modulus of the various phases in Ti-Nb alloys are compared and tentatively summarized as follows: Microhardness: omega > alpha' > alpha" > beta > alpha (c.p. Ti) Bending strength: omega > alpha' > alpha" > beta > alpha (c.p. Ti) Bending modulus: omega > alpha (c.p. Ti) > alpha' > alpha" > beta

Lee CM; Ju CP; Chern Lin JH

2002-04-01

13

Computational design and structure-property relationship studies on heptazines.  

UK PubMed Central (United Kingdom)

This study aimed to design novel nitrogen-rich heptazine derivatives as high energy density materials (HEDM) by exploiting systematic structure-property relationships. Molecular structures with diverse energetic substituents at varying positions in the basic heptazine ring were designed. Density functional techniques were used for prediction of gas phase heat of formation by employing an isodesmic approach, while crystal density was assessed by packing calculations. The results reveal that nitro derivatives of heptazine possess a high heat of formation and further enhancement was achieved by the substitution of nitro heterocycles. The crystal packing density of the designed compounds varied from 1.8 to 2 g cm(-3), and hence, of all the designed molecules, nitro derivatives of heptazine exhibit better energetic performance characteristics in terms of detonation velocity and pressure. The calculated band gap of the designed molecules was analyzed to establish sensitivity correlations, and the results reveal that, in general, amino derivatives possess better insensitivity characteristics. The overall performance of the designed compounds was moderate, and such compounds may find potential applications in gas generators and smoke-free pyrotechnic fuels as they are rich in nitrogen content.

Ghule VD; Sarangapani R; Jadhav PM; Pandey RK

2011-11-01

14

Cement-aggregate compatibility and structure property relationships including modelling  

Energy Technology Data Exchange (ETDEWEB)

The role of aggregate, and its interface with cement paste, is discussed with a view toward establishing models that relate structure to properties. Both short (nm) and long (mm) range structure must be considered. The short range structure of the interface depends not only on the physical distribution of the various phases, but also on moisture content and reactivity of aggregate. Changes that occur on drying, i.e. shrinkage, may alter the structure which, in turn, feeds back to alter further drying and shrinkage. The interaction is dynamic, even without further hydration of cement paste, and the dynamic characteristic must be considered in order to fully understand and model its contribution to properties. Microstructure and properties are two subjects which have been pursued somewhat separately. This review discusses both disciplines with a view toward finding common research goals in the future. Finally, comment is made on possible chemical reactions which may occur between aggregate and cement paste.

Jennings, H.M.; Xi, Y.

1993-07-15

15

Structure-mechanical property relationships in ion implanted ceramics  

Energy Technology Data Exchange (ETDEWEB)

Although the majority of research and development involving ion implantation has been devoted to the doping of semiconductors, there has also been much activity toward altering the chemical, physical, and mechanical properties of metals and alloys. In recent years, there has been a resurgence of interest in the use of ion beams to alter the properties of insulating materials. As a class of materials, insulators exhibit a range of properties, structures, phases, chemical bonding types, etc. This paper will consider the portion of that class called ceramics, primarily the crystalline oxides and carbides that find technological applications today. 30 refs., 10 figs., 1 tab.

McHargue, C.J.; White, C.W.; Sklad, P.S.; O' Hern, M.E.; Joslin, D.L.; Farlow, G.C.

1989-01-01

16

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

17

Structure-property relationships in discotic and elliptical mesogens  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Liquid crystals are a promising class of materials used in or proposed for a wide variety of applications, ranging from liquid crystal displays and light emitting diodes to photovoltaic devices and field effect transistors. Many molecular level structural features are known to influence the properti...

Lavigueur, Christine

18

Structure-property relationships in silica-siloxane nanocomposite materials  

Energy Technology Data Exchange (ETDEWEB)

The simultaneous formation of a filler phase and a polymer matrix via in situ sol-gel techniques provides silica-siloxane nanocomposite materials of high strength. This study concentrates on the effects of temperature and relative humidity on a trimodal polymer system in an attempt to accelerate the reaction as well as evaluate subtle process- structure-property relations. It was found that successful process acceleration is only viable for high humidity systems when using the tin(IV) catalyst dibutyltin dilaurate. Processes involving low humidity were found to be very temperature and time dependent. Bimodal systems were investigated and demonstrated that the presence of a short-chain component led to enhanced material strength. This part of the study also revealed a link between the particle size and population density and the optimization of material properties.

Ulibarri, T.A.; Derzon, D.K.; Wang, L.C.

1997-03-01

19

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.

Teodora Ivanciuc; Ovidiu Ivanciuc; Douglas J. Kleinc

2006-01-01

20

Some relationships for coupled structures and their application to measurement of structural dynamic properties in situ  

Science.gov (United States)

Three relationships are presented for indirect determination of the structural dynamic properties of substructures, namely the blocked force, mobility and free velocity. First, it is shown that the blocked force of a vibration source can be obtained from measurements made in situ, i.e. when the source is connected to a receiver structure. This potentially removes the need for special test rigs employing blocked terminations. A corollary of this relationship is that a theoretically exact transfer path analysis can be made on a fully assembled structure, such as a vehicle. Next, a relationship for indirect measurement of substructure mobility is derived. In this case, it is necessary to separate the substructures, but the advantage is that excitation is only required at user defined points on the substructures; excitation at the contact points is not required, so commonly encountered measurement difficulties can be avoided. Finally, it is shown that the free velocity of a vibration source can be obtained indirectly from measurements made in the installed condition; the need for a free suspension, which is impossible in practise for many important vibration sources, is thus avoided. The relationships are validated using semi-analytical simulations of rods and beams, and errors are briefly discussed.

Moorhouse, A. T.; Evans, T. A.; Elliott, A. S.

2011-07-01

 
 
 
 
21

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 parameter...

N. Tz. Dintcheva; E. Morici; R. Arrigo; F. P. La Mantia; V. Malatesta; J. J. Schwab

22

MOLECULAR GEOMETRY AND STRUCTURE-PROPERTY RELATIONSHIPS FOR 1,2-DITHIOLE-3-THIONE DERIVATIVES  

Directory of Open Access Journals (Sweden)

Full Text Available Molecular geometry, electronic structure, effect of the substitution and structure physical-chemical property relationship for 1,2-dithiole-3-thione derivatives, have been studied by molecular mechanics, PM3, Ab initio, DFT and QSAR method. In the present work, the calculated values, namely net charges, bond lengths, dipole moments, electron-affinities, heats of formation and QSAR properties, are reported and discussed in terms of the biological activity of 1,2-dithiole-3-thione derivatives.

BELAIDI S.; MELKEMI N.; BOUZIDI D.

2012-01-01

23

Monoamine oxidase inhibitory properties of some benzazoles: Structure-; Activity relationships  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Benzazoles containing two or three nitrogen atoms were screened for their inhibitory activity toward monoamine oxidases MAO-A and MAO-B. In order to clarify the mechanism of interaction of these compounds with the enzyme, their electronic structure was calculated at the ab initio level and the influ...

Grandi, Teresa; Sparatore, Fabio; Gnerre, Carmela; Crivori, Patrizia; Carrupt, Pierre-Alain; Testa, Bernard

24

Structure Property Relationships in Ti3SiC2.  

Science.gov (United States)

The dislocation structure of a typical low angle boundary associated with a kink band in a sample of Ti3SiC2 deformed at room temperature was studied by HRTEM. The boundary had both tilt and twist components. To account for both, the boundary was interpre...

M. W. Barwoum L. Farber I. Levin

1999-01-01

25

Structure-property-processing relationships in Kevlar fibers  

Energy Technology Data Exchange (ETDEWEB)

Molecular simulations are carried out to elucidate the differences in the properties of the commercial fibers Kevlar 29, Kevlar 49 and Kevlar 149, which are manufactured under different processing conditions, and are composed of poly(p-phenylene teraphthalamide) (PPTA). In going from Kevlar 29 to Kevlar 49 to Kevlar 149, the axial Young`s modulus increases significantly and the torsion modulus decreases significantly, while the compressive strength stays roughly the same. Previous investigators have shown that the increase in the Young`s modulus arises from increased axial orientation. The present paper addresses the torsion modulus and compressive strength of the fibers.

Lacks, D.J. [Tulane Univ., New Orleans, LA (United States)

1996-12-31

26

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)

2005-01-01

27

Structure property relationships in polycarbonate/polydimethylsiloxane copolymers  

Energy Technology Data Exchange (ETDEWEB)

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)

Pixton, Matthew R.; Rosenquist, Niles; Rajagopalan, Srini; Moghe, Nitin [The General Electric Company, Mt. Vernon, IN (United States)]. E-mails: matt.pixton@ge.com; niles.rosenquist@ge.com; srini.rajagopalan@ge.com; nitin.moghe@ge.com

2005-07-01

28

Relationships between texture, mechanical properties and structure of cornflakes  

UK PubMed Central (United Kingdom)

Hominies and flours derived from four corn varieties were prepared according to industrial recipes and processed as petals by extrusion cooking (SME = 150 J g?¹, T(die) = 130 °C) and a batch thermal process (100 °C, 50 min). Flake texture was evaluated by crushing bulk petals in a Kramer cell and comparing measurements to those obtained for commercial cornflakes, previously graded by a trained sensory analysis panel. Depending on the corn variety, various results were found in regard to crispness. Bending moduli of dense extruded materials (E(s) from 0.5 to 2.1 GPa) were found to be correlated to the texture of petals derived from the same blends. Results obtained at different scales showed that the expanded microstructure of flakes, determined by X-ray tomography, and the morphology of their constitutive materials, deduced from confocal scanning light microscopy and RVA, primarily depended on the process used rather than on the corn variety. Adhesion between protein aggregates and amorphous starch matrix was inferred from the mechanical properties involved in texture.

Chaunier L; Della Valle G; Lourdin D

2007-05-01

29

Derivatives of Ergot-alkaloids: Molecular structure, physical properties, and structure-activity relationships  

Science.gov (United States)

A comprehensive screening of fifteen functionalized Ergot-alkaloids, containing bulk aliphatic cyclic substituents at D-ring of the ergoline molecular skeleton was performed, studying their structure-active relationships and model interactions with ?2A-adreno-, serotonin (5HT2A) and dopamine D3 (D3A) receptors. The accounted high affinity to the receptors binding loops and unusual bonding situations, joined with the molecular flexibility of the substituents and the presence of proton accepting/donating functional groups in the studied alkaloids, may contribute to further understanding the mechanisms of biological activity in vivo and in predicting their therapeutic potential in central nervous system (CNS), including those related the Schizophrenia. Since the presented correlation between the molecular structure and properties, was based on the comprehensively theoretical computational and experimental physical study on the successfully isolated derivatives, through using routine synthetic pathways in a relatively high yields, marked these derivatives as 'treasure' for further experimental and theoretical studied in areas such as: (a) pharmacological and clinical testing; (b) molecular-drugs design of novel psychoactive substances; (c) development of the analytical protocols for determination of Ergot-alkaloids through a functionalization of the ergoline-skeleton, and more.

Ivanova, Bojidarka B.; Spiteller, Michael

2012-09-01

30

Probing Structure Property Relationships in Complex Engineering Silicones by 1H NMR  

Energy Technology Data Exchange (ETDEWEB)

It is generally accepted that the properties of polymeric materials are controlled by the network structure and the reactions by which they have been constructed. These properties include the bulk moduli at creation, but also the properties as a function of age during use. In order to interpret mechanical properties and predict the time dependent changes in these properties, detailed knowledge of the effect of structural changes must be obtained. The degree and type of crosslinking, the molecular weight between crosslinks, the number of elastically ineffective chains (loops, dangling chain ends, sol-fraction) must be characterized. A number of theoretical and experimental efforts have been reported in the last few years on model networks prepared by endlinking reactions and the relationships of those structures with the ultimate mechanical properties. A range of experimental methods have been used to investigate structure including rheometric, scattering, infrared, {sup 29}Si MAS and CPMAS, {sup 1}H relaxation measurements, and recently {sup 1}H multiple quantum methods. Characterization of the growth of multiple quantum coherences have recently been shown to provide detailed insight into silicone network structure by the ability to selective probe the individual components of the polymer network, such as the polymer-filler interface or network chains. We have employed recently developed MQ methods to investigate the structure-property relationships in a series of complex, endlinked filled-PDMS blends. Here, a systematic study of the relationship between the molecular formulation, as dictated by the amount and type of crosslinks present and by the remaining network chains, and the segmental dynamics as observed by MQ NMR was performed.

Chinn, S C; Gjersing, E L; Maxwell, R S; Eastwood, E; Bowen, D; Stephens, T

2006-07-14

31

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

32

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

33

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

34

Synthetic study on the relationship between structure and sweet taste properties of steviol glycosides.  

UK PubMed Central (United Kingdom)

The structure activity relationship between the C??-C?? 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 C??-C?? methylene double bond in rebaudioside A and stevioside can be regarded as a pharmacophore essential for the sweetness property of these molecules.

Upreti M; Dubois G; Prakash I

2012-01-01

35

On the structure-property relationship of rapidly solidified high temperature application aluminium alloys  

International Nuclear Information System (INIS)

The phases responsible for high temperature strength and ductility of Al-Fe based alloys, specifically Al-Fe-Mo alloys, have yet to be unambiguously identified. The phases appear to vary slightly under different experimental and processing conditions. This poses some queries concerning the reproducibility of mechanical properties of these alloys. In this paper an attempt is made to address these points and focus on the structure-property relationships of Al-Fe-Mo and Al-Fe-V rapidly solidified powder alloys. 10 refs

1991-01-01

36

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

37

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.

N. Tz. Dintcheva; E. Morici; R. Arrigo; F. P. La Mantia; V. Malatesta; J. J. Schwab

2012-01-01

38

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.

Paola Sabbatini; Paolo Filipponi; Roccaldo Sardella; Benedetto Natalini; Roberto Nuti; Antonio Macchiarulo; Roberto Pellicciari; Antimo Gioiello

2013-01-01

39

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Um modelo para a interação de bisamidinas aromáticas com o B-DNA foi estabelecido através de estudos de relações estruturas-propriedades derivadas dos cálculos de descritores tridimensionais WHIM-3D. Uma análise de componentes principais, PCA, dos descritores revelou três componentes principais significativas e agrupou as bisamidinas em diferentes conformações: estendida, semi-estendida e semifechada com interações tipo pi-pi e também por ligações de hidro (more) gênio. O método SIMCA classificou as conformações de acordo com essas características. A interação das 29 bisamidinas estudadas com o B-DNA dá-se através de suas propriedades de forma, distribuição e dimensão. Abstract in english 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 dimens (more) ion properties mostly govern the interaction of bisamidines with B-DNA through the minor groove AT rich regions.

Menezes, Fabiano A. S.; Montanari, Carlos A.; Bruns, Roy E.

2000-08-01

40

Quantitative structure-property relationship modeling of skin sensitization: a quantitative prediction.  

UK PubMed Central (United Kingdom)

A quantitative structure-property relationship (QSPR) model for predicting the skin sensitization effects of chemical compounds has been developed. An extensive database of test results from three exclusive test procedures was used for QSPR model development. Since the experimental procedure and end-point ranking of data for local lymph node assay (LLNA), guinea pig maximization test (GPMT), and Federal Institute for Health Protection of Consumers and Veterinary Medicine (BgVV) are different, three separate QSPR models were developed. Effective non-linear regression models were used for QSPR model development. The predictive capability of the final QSPR models was further improved by using a combination of literature-recommended and structural descriptors. The resultant QSPR models are capable of predicting skin sensitization of the diverse set of molecules considered with accuracies of 90%, 95%, and 90% for the LLNA, GPMT, and BgVV datasets, respectively.

Golla S; Madihally S; Robinson RL Jr; Gasem KA

2009-04-01

 
 
 
 
41

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

Science.gov (United States)

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. PMID:21999701

Trišovi?, Nemanja; Valenti?, Nataša; Uš?umli?, Gordana

2011-10-14

42

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; Valenti? Nataša; Uš?umli? Gordana

2011-01-01

43

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

UK PubMed Central (United Kingdom)

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? N; Valenti? N; Uš?umli? G

2011-01-01

44

Structure Versus Properties Relationship of Poly(lactic acid). I. Effect of Crystallinity on Barrier Properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Poly(lactic acid) is at present the most promising and commercially available bio-based and biocompostable (bio)plastic. The properties of PLA, however, are rather poor, notably its low glass transition temperature T-g of similar to 55 degrees C, its intrinsic low crystallization rate and the limite...

DRIESKENS, Marjoleine; Peeters, Roos; MULLENS, Jules; Franco, Dirk; Lemstra, Pieter J.; Hristova-Bogaerds, Denka G.

45

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

Energy Technology Data Exchange (ETDEWEB)

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/cm{sup 2}) 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% Al{sub 2}O{sub 3} 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.

Islam, Rashed Adnan; Chan, Y.C.; Islam, Md. Fakhrul

2004-01-25

46

Structure-property relationship for cellular accumulation of macrolones in human polymorphonuclear leukocytes (PMNs).  

UK PubMed Central (United Kingdom)

Macrolones are a new class of antimicrobial compounds consisting of a macrolide scaffold linked to a 4-quinolone-3-carboxylic acid moiety via C(4?) position of a macrolide. As macrolides are known to possess favorable pharmacokinetic properties by accumulating in inflammatory cells, in this study we determined the intensity of accumulation in human polymorphonuclear leukocytes (PMNs) of 57 compounds of the macrolone class and analyzed the relationship between the molecular structure and this cellular pharmacokinetic property. Accumulation of macrolones ranged from 0 to 5.5-fold higher than the standard macrolide azithromycin. Distinct structural features in all three considered molecule parts: the macrolide scaffold, quinolone moiety and the linker, affect cellular accumulation. Interestingly, while the parent macrolide, azithromycin, accumulates approximately 3-fold more than clarithromycin, among macrolones all clarithromycin derivatives accumulated in PMNs significantly more than their azithromycin counterparts. Modeling cellular accumulation of macrolones with simple molecular descriptors, as well as with the measured octanol-water distribution coefficient, revealed that the number of hydrogen bond donors and secondary amide groups negatively contribute to macrolone accumulation, while lipophilicity makes a positive contribution.

Muni? Kos V; Koštrun S; Fajdeti? A; Bosnar M; Kelneri? Ž; Stepani? V; Erakovi? Haber V

2013-05-01

47

Poly(2,7-carbazole)s: structure-property relationships.  

UK PubMed Central (United Kingdom)

Conjugated polymers combine the interesting optical and electrical properties of metals with the processing advantages and mechanical properties of traditional synthetic polymers. With clever use of a variety of synthetic tools, researchers have prepared highly pure polymers with optimized physical properties during the past 30 years. For example, the synthesis of well-defined polyacetylenes, polyphenylenes, polythiophenes, polyfluorenes, and other conjugated polymers have significantly improved the performance of these polymeric materials. However, one important class of conjugated polymers was missing from this chemical inventory: easy access to well-defined poly(2,7-carbazole)s and related polymers. This Account highlights advances in the synthesis of poly(2,7-carbazole) derivatives since they were first reported in 2001. Starting from 2-nitro-biphenyl derivatives, 2,7-functionalized carbazoles are typically obtained from Cadogan ring-closure reactions. In a second step, Yamamoto, Stille, Suzuki, or Horner-Emmons coupling polymerization leads to various poly(2,7-carbazole) derivatives. We discuss the characterization of their optical and electrical properties with a strong emphasis on the structure-property relationships. In addition, we carefully evaluate these polymers as active components in light-emitting diodes, transistors, and photovoltaic cells. In particular, several low band gap poly(2,7-carbazole) derivatives have revealed highly promising features for solar cell applications with hole mobilities of about 3 x 10(-3) cm2 V(-1) s(-1) and power conversion efficiencies up to 4.8%. Finally, we show how these new synthetic strategies have led to the preparation of novel poly(heterofluorene) derivatives and ladder-type conjugated polymers.

Blouin N; Leclerc M

2008-09-01

48

Structure and NLO property relationship in a novel chalcone co-crystal  

Science.gov (United States)

Single crystals of a chalcone co-crystal (C18H19NO4/C17H16NO3Br; 0.972/0.028) have been grown by slow evaporation from solution. The powder second harmonic generation (SHG) efficiency of this chalcone co-crystal is 7 times that of urea. The dependence of second harmonic (SH) intensity on particle size revealed the existence of phase matching direction in this crystal. The large SHG efficiency observed is mainly due to the unidirectional alignment of molecular dipoles, in which the dipole moment of each molecule adds to establish a net polarization. The weak N-H ???O hydrogen-bond interactions help to stabilize the noncentrosymmetric crystal packing and also contribute partly to the SHG. The better thermal stability, transparency and high laser damage resistance (>1.5 GW cm-2 at 532 nm, 8 ns) of this chalcone co-crystal indicate that it is a promising material for frequency doubling of diode lasers down to 470 nm. This molecule also shows a third-order NLO response and good optical limiting property of 8 ns laser pulses at 532 nm. The mechanism for optical limiting in this chalcone was attributed to two-photon induced excited state absorption that leads to reverse saturable absorption. The structure-property relationship in this chalcone and related compounds is discussed based on the experimental results and semiempherical hyperpolarizability calculations.

Ravindra, H. J.; Chandrashekaran, K.; Harrison, W. T. A.; Dharmaprakash, S. M.

2009-03-01

49

Thermal properties and nanodispersion behavior of synthesized ?-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 ?-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 ?-sitosterol as a comparison. Inspection of the melting point (Tm) and the heat of fusion (?H) of ?-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 ?-sitosterol and ?-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). ?-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 ?-sitosteryl medium chain SFA ester (C14:0) demonstrated a best storage stability.

Panpipat, Worawan; Dong, Mingdong

2013-01-01

50

Understanding quantitative structure-property relationships uncertainty in environmental fate modeling.  

UK PubMed Central (United Kingdom)

In cases in which experimental data on chemical-specific input parameters are lacking, chemical regulations allow the use of alternatives to testing, such as in silico predictions based on quantitative structure-property relationships (QSPRs). Such predictions are often given as point estimates; however, little is known about the extent to which uncertainties associated with QSPR predictions contribute to uncertainty in fate assessments. In the present study, QSPR-induced uncertainty in overall persistence (POV ) and long-range transport potential (LRTP) was studied by integrating QSPRs into probabilistic assessments of five polybrominated diphenyl ethers (PBDEs), using the multimedia fate model Simplebox. The uncertainty analysis considered QSPR predictions of the fate input parameters' melting point, water solubility, vapor pressure, organic carbon-water partition coefficient, hydroxyl radical degradation, biodegradation, and photolytic degradation. Uncertainty in POV and LRTP was dominated by the uncertainty in direct photolysis and the biodegradation half-life in water. However, the QSPRs developed specifically for PBDEs had a relatively low contribution to uncertainty. These findings suggest that the reliability of the ranking of PBDEs on the basis of POV and LRTP can be substantially improved by developing better QSPRs to estimate degradation properties. The present study demonstrates the use of uncertainty and sensitivity analyses in nontesting strategies and highlights the need for guidance when compounds fall outside the applicability domain of a QSPR.

Sarfraz Iqbal M; Golsteijn L; Öberg T; Sahlin U; Papa E; Kovarich S; Huijbregts MA

2013-04-01

51

Synthesis of self-threading bithiophenes and their structure-property relationships regarding cyclic side-chains with atomic precision.  

UK PubMed Central (United Kingdom)

We have recently reported a self-threading polythiophene as a new family of insulated molecular wires. Herein, we focused on the structure-property relationships of the unique three-dimensional architecture of the monomer. We have synthesized nine self-threading bithiophene monomers that have cyclic side-chains of different size and flexibility: i.e., 21-, 22-, 23-, 24-, 26-, and 30-membered rings composed of paraffinic, olefinic, or alkynic chains. To investigate their structure-property relationships, (1) H?NMR spectroscopy, UV absorption, and fluorescence spectroscopy measurements were conducted. We found that cyclic side-chains define the movable range of the dihedral angle of the bithiophene backbone, thereby affecting its photophysical properties. Therefore, the ability to design a structure with atomic precision as described herein would lead to the fine-tuning of the electronic properties of insulated molecular wires.

Ouchi Y; Sugiyasu K; Ogi S; Sato A; Takeuchi M

2012-01-01

52

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

53

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.

Justin N. R. O’Donnell; Gary E. Schumacher; Joseph M. Antonucci; Drago Skrtic

2009-01-01

54

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

55

Structural properties of silver nanoparticle agglomerates based on transmission electron microscopy: relationship to particle mobility analysis  

International Nuclear Information System (INIS)

In this work, the structural properties of silver nanoparticle agglomerates generated using condensation and evaporation method in an electric tube furnace followed by a coagulation process are analyzed using Transmission Electron Microscopy (TEM). Agglomerates with mobility diameters of 80, 120, and 150 nm are sampled using the electrostatic method and then imaged by TEM. The primary particle diameter of silver agglomerates was 13.8 nm with a standard deviation of 2.5 nm. We obtained the relationship between the projected area equivalent diameter (dpa) and the mobility diameter (dm), i.e., dpa = 0.92 ± 0.03 dm for particles from 80 to 150 nm. We obtained fractal dimensions of silver agglomerates using three different methods: (1) Df = 1.84 ± 0.03, 1.75 ± 0.06, and 1.74 ± 0.03 for dm = 80, 120, and 150 nm, respectively from projected TEM images using a box counting algorithm; (2) fractal dimension (DfL) = 1.47 based on maximum projected length from projected TEM images using an empirical equation proposed by Koylu et al. (1995) Combust Flame 100:621-633; and (3) mass fractal-like dimension (Dfm) = 1.71 theoretically derived from the mobility analysis proposed by Lall and Friedlander (2006) J Aerosol Sci 37:260-271. We also compared the number of primary particles in agglomerate and found that the number of primary particles obtained from the projected surface area using an empirical equation proposed by Koylu et al. (1995) Combust Flame 100:621-633 is larger than that from using the relationship, dpa = 0.92 ± 0.03 dm or from using the mobility analysis.

2009-01-01

56

Structural properties of silver nanoparticle agglomerates based on transmission electron microscopy: relationship to particle mobility analysis  

Energy Technology Data Exchange (ETDEWEB)

In this work, the structural properties of silver nanoparticle agglomerates generated using condensation and evaporation method in an electric tube furnace followed by a coagulation process are analyzed using Transmission Electron Microscopy (TEM). Agglomerates with mobility diameters of 80, 120, and 150 nm are sampled using the electrostatic method and then imaged by TEM. The primary particle diameter of silver agglomerates was 13.8 nm with a standard deviation of 2.5 nm. We obtained the relationship between the projected area equivalent diameter (d{sub pa}) and the mobility diameter (d{sub m}), i.e., d{sub pa} = 0.92 {+-} 0.03 d{sub m} for particles from 80 to 150 nm. We obtained fractal dimensions of silver agglomerates using three different methods: (1) D{sub f} = 1.84 {+-} 0.03, 1.75 {+-} 0.06, and 1.74 {+-} 0.03 for d{sub m} = 80, 120, and 150 nm, respectively from projected TEM images using a box counting algorithm; (2) fractal dimension (D{sub fL}) = 1.47 based on maximum projected length from projected TEM images using an empirical equation proposed by Koylu et al. (1995) Combust Flame 100:621-633; and (3) mass fractal-like dimension (D{sub fm}) = 1.71 theoretically derived from the mobility analysis proposed by Lall and Friedlander (2006) J Aerosol Sci 37:260-271. We also compared the number of primary particles in agglomerate and found that the number of primary particles obtained from the projected surface area using an empirical equation proposed by Koylu et al. (1995) Combust Flame 100:621-633 is larger than that from using the relationship, d{sub pa} = 0.92 {+-} 0.03 d{sub m} or from using the mobility analysis.

Shin, Weon Gyu; Wang Jing [University of Minnesota, Department of Mechanical Engineering (United States); Mertler, Michael; Sachweh, Bernd [Fine Particle Technology and Particle Characterization, BASF SE (Germany); Fissan, Heinz [Institute of Energy and Environmental Technology e. V. (IUTA) (Germany); Pui, David Y. H., E-mail: dyhpui@umn.ed [The University of Minnesota, Department of Mechanical Engineering (United States)

2009-01-15

57

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

58

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

UK PubMed Central (United Kingdom)

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.

Zarei K; Atabati M; Ebrahimi M

2007-08-01

59

SMILES-based quantitative structure-property relationships for half-wave potential of N-benzylsalicylthioamides.  

UK PubMed Central (United Kingdom)

Optimal descriptors calculated with Simplified Molecular Input Line Entry System (SMILES) notation have been used in quantitative structure-property relationships (QSPR) of half-wave potential of N-benzylsalicylthioamides. The QSPR developed is one-variable model based on the optimal descriptors calculated with the Monte Carlo method. The approach has been checked up with three random splits into the training and test sets. Mechanistic interpretations (structural alerts related to the half-wave potential) of the model are discussed.

Nesmerak K; Toropov AA; Toropova AP; Kohoutova P; Waisser K

2013-09-01

60

Structure-property-performance relationships of new high temperature relaxors for capacitor applications  

Science.gov (United States)

This thesis extends the investigations on perovskite solid solutions based on PbTiO3-Bi(Me',Me")O3 (Me' = Sc3+, Zn2+, Mg2+, Ni2+, In3+ , Fe3+, etc. and Me" = Ti4+, Nb 5+, W6+) systems. The ferroelectric transition temperature (TC) behavior was considered in the tetragonal phase region of the PbTiO 3-Bi(Me',Me")O3 systems. Trends in the TC compositional dependence exhibited three main cases: case 1, a continued increase in transition temperature above the end-member PbTiO3 (495°C); case 2, an increase and then decrease of the transition temperature; and case 3, a continuous decrease in the transition temperature with Bi(Me',Me")O 3 additions. New relaxor materials were developed from the PbTiO3-Bi(Me',Me")O 3 solid solutions; specifically, the Bi(Mg3/4W1/4)O 3-PbTiO3 (BMW-PT) binary solid solution and BiScO3-Pb(Mg 1/3Nb2/3)O3-PbTiO3 (BS-PMN-PT) ternary solid solution were investigated. Permittivity, polarization and pyroelectric measurements were performed on BMW-PT and BS-PMN-PT compositions with respect to temperature with characteristic relaxor behavior observed. The complex solid solution BMW-PT exhibited a morphotropic phase boundary at ˜48 mol% PbTiO3 with a corresponding TC of 205°C. On further structural analysis with diffraction contrast transmission electron microscopy along with x-ray diffraction, evidence of B-site ordering was observed. The BS-PMN-PT proved to be a model system with high temperature relaxor properties of Tmax ˜ 250°C to 300°C and ?max ˜ 14,000 to 17,000 at 1 kHz. The deviation temperature, TD, or temperature of the onset of local spontaneous polarization, was determined by thermal strain measurement and high temperature dielectric measurement to be approximately 600°C; up to 250°C higher than any reported value for relaxor ferroelectrics. The frequency dependence of the temperature of the permittivity maximum was found to follow the Vogel-Fulcher relationship, with an activation energy (EA) of ˜0.1 eV, and a freezing temperature (Tf) of ˜150°C. Static and in-situ transmission electron microscopy investigations of the BS-PMN-PT compositions demonstrated a frustrated microstructure of nanometer scale regions and were used to establish structure-property relationships with different electric field and thermal histories. A comparative study of the key relaxor parameters, EA, T f, and TD was tabulated with previously investigated relaxor ferroelectrics. These parameters were found to scale relative to other lead-based perovskite relaxor ferroelectric compounds and solid solutions, with the BS-PMN-PT ternary system exhibiting the highest temperature behavior. Finally, to demonstrate one possible application area for these materials, multilayer ceramic capacitor devices were designed for operation at 300°C and up to 10 kHz. The voltage saturation was found to be extremely encouraging at 300°C with observed changes in capacitance (˜3%) on the application of 10 kV/cm. The insulation resistivity followed an Arrhenius behavior and at 300°C was ˜1010 O-cm. Weibull statistics were used to estimate a characteristic breakdown field at 300°C for the BS-PMN-PT multilayer capacitors of ˜40 kV/cm. Current-voltage measurements were performed to voltages up to breakdown and exhibited Ohmic behavior, indicating intrinsically controlled conduction. Highly accelerated life time tests were performed on BS-PMN-PT capacitors. It was observed that silver migration from termination electrodes caused premature failure at elevated temperature.

Stringer, Craig J.

 
 
 
 
61

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

International Nuclear Information System (INIS)

[en] 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

2007-01-01

62

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

63

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

64

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

UK PubMed Central (United Kingdom)

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%.

Jouyban A; Yousefi BH

2003-07-01

65

Structure-property relationships in self-assembling peptide hydrogels, homopolypeptides and polysaccharides  

Science.gov (United States)

The main objective of this dissertation is to investigate quantitative structure-property relationships in a variety of molecular systems including de novo designed peptides, peptide amphiphiles, polysaccharides and high molecular weight polypeptides. Peptide molecules consisting of 20 amino acids were designed to undergo thermally triggered intramolecular folding into asymmetric beta-hairpins and intermolecular self-assembly via a strand swapping mechanism into physically crosslinked fibrillar hydrogels. The self-assembly mechanism was confirmed by multiple characterization techniques such as circular dichroism and FITR spectroscopy, atomic force and transmission electron microscopy and small angle neutron scattering. Three distinct fibrillar nanostructures, i.e. non-twisted, twisted and laminated were produced, depending on the degree of strand asymmetry and peptide registry. Differences in the fibrillar morphology have a direct consequence on the mechanical properties of the hydrogels, with the laminated hydrogels exhibiting a significantly higher elastic modulus as compared to the twisted or non-twisted fibrillar hydrogels. SANS and cryo-TEM data reveal that the self-assembled fibrils form networks that are fractal in nature. Models employed to elucidate the fractal behavior can relate changes in the correlation lengths, low q (network), and high q (fibrillar) fractal exponents to the distinct fibrillar nanomorphology. The fractal dimension of the networks varies significantly, from a mass to a surface fractal and can be directly related to the local fibrillar morphology and changes in the peptide concentration. Transitions in the fractal behavior seen in the high q regime can be attributed to self-assembly kinetics. An identical model can be used to establish a direct correlation between the bulk properties and changes in both, the network density and underlying morphology, of a modified peptide-based hydrogel. As in the case of asymmetric peptides, changes in the fractal dimensions at the network and the individual fibril lengthscales are substantiated in the real space by cryo-TEM. Additionally, a study of the gel microstructure by USANS indicates well-defined microporosity, an important characteristic for cellular substrate applications. Preliminary cell viability and anchorage studies at varying hydrogel stiffness confirm cell adhesion at early stages of cell culture within the window of stiffness investigated. The universal applicability of the fractal model to hydrogel networks is demonstrated by doubly crosslinked hyaluronic acid based gels consisting of highly crosslinked hydrogel particles embedded in and covalently bonded to a loosely connected secondary network. An increase in the high q mass fractal dimension of the secondary network compared to gels with no particles is ascribed to the increase in the density of network due to addition of the crosslinked hydrogel particles. A morphological investigation of peptide amphiphiles discloses the delicate balance of hydrophobic and hydrophilic amino acids in these molecules leading to multiple, distinct nanostructures. Direct repercussions of the nanostructure on fibrillar aggregation, orientation, network and nematic behavior is seen. Finally, the dependence of molecular weight of a high molecular weight homopolypeptide, poly(L-lysine) on its secondary conformation in polypeptide-clay nanocomposites has been explored. The matrix polypeptide is found to fold into beta-sheets when cast as films irrespective of the initial secondary structure in solution, a tendency that is attributed to film casting conditions and high molecular weight.

Hule, Rohan A.

66

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

67

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

68

Structure-property relationships in dimethacrylate networks based on Bis-GMA, UDMA and TEGDMA.  

UK PubMed Central (United Kingdom)

OBJECTIVES: In this work the influence of structural heterogeneity of poly(dimethacrylate)s on mechanical properties was investigated. Rigid aromatic dimethacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA) and flexible aliphatic urethane dimethacrylate (UDMA) have been chosen for room-temperature homopolymerizations and copolymerizations induced by a camphorquinone/N,N-dimethylaminoethyl methacrylate photoinitiating system. METHODS: The following mechanical properties of poly(dimethacrylate)s were investigated: flexural modulus, flexural strength, impact strength and hardness. Atomic force microscopy (AFM) and X-ray powder diffraction (XRPD) were used to describe the morphology of polymer networks. RESULTS: AFM observations showed that the heterogeneity of networks is spatially organized due to the formation of microgels and their agglomeration. Observed agglomerates are unidirectionally oriented, parallel to the direction of polymerization shrinkage. Of all the investigated mechanical properties of poly(dimethacrylate)s, the impact resistance appeared to be the least. The origin of this brittleness could be the presence of heterogeneities which were quantitatively characterized by means of XRPD. The impact resistance was shown to be related to the size of network heterogeneities which is probably influenced by intermolecular interactions, such as hydrogen bonding. SIGNIFICANCE: Differences in monomer structure resulted in significantly different morphology and physical properties of the polymer networks which had been studied. The size and shape of heterogeneities affected the final mechanical properties of the polymers, especially impact resistance. In addition, the combined application of XRPD and AFM techniques can be a successful tool in the analysis of the dimethacrylate network morphology, and finally, in investigations on methacrylate-based dental materials.

Barszczewska-Rybarek IM

2009-09-01

69

Structure-property relationships in isotactic poly(propylene)/ethylene propylene rubber/montmorillonite nanocomposites.  

Science.gov (United States)

Nanocomposites based on isotactic polypropylene/ethylene propylene rubber (iPP/EPR) were prepared adding different amounts of montmorillonite and maleated polypropylene. The structure and morphology of the samples were characterized by small angle X-ray scattering, wide angle X-ray diffraction, electronic and optical microscopy and differential scanning calorimetry, iPP showed a polymorphic behavior. Clay disrupted the ordered crystallization of iPP and had a key role in shaping the distribution of iPP and EPR phases: larger filler contents brought about smaller, less coalesced and more homogeneous rubber domains. Clay distributed itself only in the continuous phase and not in the rubber domains. Tactoids persisted on the surface of the sample, while delamination proceeded to a greater degree in the bulk of the materials. Melt flow rate, impact strength, flexural and tensile properties, were also measured and a structure-property correlation was sought. Clay produced its most significant effect on physical-mechanical properties by controlling the size of rubber domains in the heterophasic matrix. This allowed to obtain nanocomposites with increased stiffness and impact strength, a remarkable achievement for polymer layered-silica nanocomposites that usually suffer the drawback of being stiffer than the unfilled matrix, but at the same time with a lower resistance to impact. A beneficial effect of clay on thermal stability was also observed. PMID:18572583

Causin, Valerio; Marega, Carla; Marigo, Antonio; Ferraro, Giuseppe; Ferrara, Angelo; Selleri, Roberta

2008-04-01

70

Structure-property relationships in isotactic poly(propylene)/ethylene propylene rubber/montmorillonite nanocomposites.  

UK PubMed Central (United Kingdom)

Nanocomposites based on isotactic polypropylene/ethylene propylene rubber (iPP/EPR) were prepared adding different amounts of montmorillonite and maleated polypropylene. The structure and morphology of the samples were characterized by small angle X-ray scattering, wide angle X-ray diffraction, electronic and optical microscopy and differential scanning calorimetry, iPP showed a polymorphic behavior. Clay disrupted the ordered crystallization of iPP and had a key role in shaping the distribution of iPP and EPR phases: larger filler contents brought about smaller, less coalesced and more homogeneous rubber domains. Clay distributed itself only in the continuous phase and not in the rubber domains. Tactoids persisted on the surface of the sample, while delamination proceeded to a greater degree in the bulk of the materials. Melt flow rate, impact strength, flexural and tensile properties, were also measured and a structure-property correlation was sought. Clay produced its most significant effect on physical-mechanical properties by controlling the size of rubber domains in the heterophasic matrix. This allowed to obtain nanocomposites with increased stiffness and impact strength, a remarkable achievement for polymer layered-silica nanocomposites that usually suffer the drawback of being stiffer than the unfilled matrix, but at the same time with a lower resistance to impact. A beneficial effect of clay on thermal stability was also observed.

Causin V; Marega C; Marigo A; Ferraro G; Ferrara A; Selleri R

2008-04-01

71

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

UK PubMed Central (United Kingdom)

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 P(OW)), 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 (SX(1CH)) 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.

Liu F; Cao C; Cheng B

2011-01-01

72

Electron irradiation effects on partially fluorinated polymer films: Structure-property relationships  

International Nuclear Information System (INIS)

The effects of electron beam irradiation on two partially fluorinated polymer films i.e. poly(vinylidene fluoride) (PVDF) and poly(ethylene-tetrafluoroethylene) copolymer (ETFE) are studied at doses ranging from 100 to 1200 kGy in air at room temperature. Chemical structure, thermal and mechanical properties of irradiated films are investigated. FTIR show that both PVDF and ETFE films undergo similar changes in their chemical structures including the formation of carbonyl groups and double bonding. The changes in melting and crystallisation temperatures (Tm and Tc) in both irradiated films are functions of irradiation dose and reflect the disorder in the chemical structure caused by the competition between crosslinking and chain scission. The heat of melting (?Hm) and the degree of crystallinity (Xc) of PVDF films show no significant changes with the dose increase, whereas those of ETFE films are reduced rapidly after the first 100 kGy. The tensile strength of PVDF films is improved by irradiation compared to its rapid deterioration in ETFE films, which stemmed from the degradation prompted by the presence of radiation sensitive tetrafluoroethylene (TFE) comonomer units. The elongation at break of both films drops gradually with the dose increase indicating the formation of predominant crosslinked structures at high doses. However, the response of each polymer to crosslinking and main chain scission at various irradiation doses varies from PVDF to ETFE films.

2003-01-01

73

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

74

Relationship Between Structure and Dynamic Mechanical Properties of a Carbon Nanofiber Reinforced Elastomeric Nanocomposite  

International Nuclear Information System (INIS)

The tensile and dynamic mechanical properties of a nanocomposite, containing modified carbon nanofibers (MCNFs) homogenously dispersed in an elastomeric ethylene/propylene (EP) copolymer semicrystalline matrix (84.3 wt% P), have been correlated with the structure development. These properties were characterized by in situ synchrotron X-ray diffraction during stretching, dynamic mechanical analysis and X-ray analysis techniques over a wide temperature range. Upon sequential drawing, the tensile strength of the nanocomposite film was notably higher than that of the unfilled polymer even though both samples exhibited a similar amount of crystal fraction and the same degree of crystal orientation, revealing the effect of nanofiller reinforcement in the semicrystalline matrix. The mechanical spectra of the 10 wt% MCNF filled samples in both stretched and non-stretched states showed broadening of the elastic modulus at high temperatures, where the corresponding crystallinity index also decreased. It is conceivable that a significant fraction of chain orientation is induced in the vicinity of the nanofillers during stretching, and these stretched chains with reduced mobility significantly enhance the thermal mechanical properties.

2006-01-01

75

Relationship Betwen Structure and Dynamic Mechanical Properties of a Carbon Nanofiber Reinforced Elastomeric Nanocomposite  

Energy Technology Data Exchange (ETDEWEB)

The tensile and dynamic mechanical properties of a nanocomposite, containing modified carbon nanofibers (MCNFs) homogenously dispersed in an elastomeric ethylene/propylene (EP) copolymer semicrystalline matrix (84.3 wt% P), have been correlated with the structure development. These properties were characterized by in situ synchrotron X-ray diffraction during stretching, dynamic mechanical analysis and X-ray analysis techniques over a wide temperature range. Upon sequential drawing, the tensile strength of the nanocomposite film was notably higher than that of the unfilled polymer even though both samples exhibited a similar amount of crystal fraction and the same degree of crystal orientation, revealing the effect of nanofiller reinforcement in the semicrystalline matrix. The mechanical spectra of the 10 wt% MCNF filled samples in both stretched and non-stretched states showed broadening of the elastic modulus at high temperatures, where the corresponding crystallinity index also decreased. It is conceivable that a significant fraction of chain orientation is induced in the vicinity of the nanofillers during stretching, and these stretched chains with reduced mobility significantly enhance the thermal mechanical properties.

Kelarakis,A.; Yoon, K.; Somani, R.; Sics, I.; Chen, X.; Hsiao, B.; Chu, B.

2006-01-01

76

????????????????????? Relationship between Thermal Properties and Their Chemical Structure in Phenanthroimidazole-Based Material  

Directory of Open Access Journals (Sweden)

Full Text Available ?????????????????????????????????????????????????????????????????????1,2-???–??????????????????????????????1,2??????????????????????????????????????????????????????????????????????????????????????????????2?????????????????????????????????????????????????????????????????????Phenanthroimidazole and its derivatives have attracted more and more attention in preparing bipolar and high-efficiency saturated blue emitters due to their excellent thermal properties. To discuss the effect on the glass transi- tion temperature and thermal decomposition temperature originating from the chemical structure change in phenan- throimidazole-based material, such as the linked position and different substituent groups, 1,2-diphenyl-phenan- thro[9,10-d]-imidazole is chosen as a model compound based on the current results. By tuning the substituent structure and linked mode in the imidazole ring 1,2-position, some regularities are revealed. The analysis results show that the Tg decreases with the increase of the molecular steric and rises with the increases of conjugated degree and planarity, simultaneously, 2-position of imidazole ring plays a more important role in all substituent positions. The Td is enhanced with the increase of molecular weight, conjugation and molecular planarity. All of these would provide some valuable suggestions for the design of phenanthroimidazole-based materials with excellent thermal properties.

???; ???; ???

2013-01-01

77

Relationship between channel and sorption properties in coordination polymers with interdigitated structures.  

UK PubMed Central (United Kingdom)

Porous coordination polymers constructed from Zn(2+) and isophthalate with linear bipyridyl-type ligands were synthesized. [Zn(ip)(bpb)](n) (CID-21; ip=isophthalate, bpb=1,4-bis(4-pyridyl)benzene), [Zn(ip)(bpt)](n) (CID-22; bpt=3,6-bis(4-pyridyl)-1,2,4,5-tetrazine), and [Zn(ip)(bpa)](n) (CID-23; bpa=1,4-bis(4-pyridyl)acetylene) all have interdigitated structures of layers and similar void volumes (?27%). In these compounds, 1D bottleneck-type channels run along the perpendicular direction of the layer stacking and their properties are strongly dominated by the dipyridyl linker ligands. Because of the difference in packing of 2D layers, CID-21 and CID-22 have relatively rigid porous structures, whereas CID-23 has greater flexibility, as indicated by the results of powder X-ray diffraction studies. The micropores of CID-22 surrounded by tetrazine moieties adsorb polar molecules, such as methanol and water. The higher affinity of CID-22 for water than CID-21 is supported by a theoretical study. The 1D channel of CID-23 is wider than that of the other two compounds, which enables the incorporation of aromatic molecules. This is because the shape of the bpa linker ligand generates a wider pore diameter (8.6 Å). Only CID-23 can adsorb a benzene molecule and the isotherm of benzene has a gate-opening-type profile. This offers proof of the guest accommodation process through large structural transformation from a nonporous to a porous structure. The flexibility and restricted pore space of CID-23, at 298 K, allows only benzene, but not cyclohexane, to enter the channels. The porous structure exhibits clear selectivity for these similar guests. The incorporation of an elongated dipyridyl linker ligand in the 2D coordination layers provides a strategy for the design of microporous compounds with different flexibilities, microporous environments, and separation abilities.

Hijikata Y; Horike S; Sugimoto M; Sato H; Matsuda R; Kitagawa S

2011-04-01

78

Relationship between channel and sorption properties in coordination polymers with interdigitated structures.  

Science.gov (United States)

Porous coordination polymers constructed from Zn(2+) and isophthalate with linear bipyridyl-type ligands were synthesized. [Zn(ip)(bpb)](n) (CID-21; ip=isophthalate, bpb=1,4-bis(4-pyridyl)benzene), [Zn(ip)(bpt)](n) (CID-22; bpt=3,6-bis(4-pyridyl)-1,2,4,5-tetrazine), and [Zn(ip)(bpa)](n) (CID-23; bpa=1,4-bis(4-pyridyl)acetylene) all have interdigitated structures of layers and similar void volumes (?27%). In these compounds, 1D bottleneck-type channels run along the perpendicular direction of the layer stacking and their properties are strongly dominated by the dipyridyl linker ligands. Because of the difference in packing of 2D layers, CID-21 and CID-22 have relatively rigid porous structures, whereas CID-23 has greater flexibility, as indicated by the results of powder X-ray diffraction studies. The micropores of CID-22 surrounded by tetrazine moieties adsorb polar molecules, such as methanol and water. The higher affinity of CID-22 for water than CID-21 is supported by a theoretical study. The 1D channel of CID-23 is wider than that of the other two compounds, which enables the incorporation of aromatic molecules. This is because the shape of the bpa linker ligand generates a wider pore diameter (8.6 Å). Only CID-23 can adsorb a benzene molecule and the isotherm of benzene has a gate-opening-type profile. This offers proof of the guest accommodation process through large structural transformation from a nonporous to a porous structure. The flexibility and restricted pore space of CID-23, at 298 K, allows only benzene, but not cyclohexane, to enter the channels. The porous structure exhibits clear selectivity for these similar guests. The incorporation of an elongated dipyridyl linker ligand in the 2D coordination layers provides a strategy for the design of microporous compounds with different flexibilities, microporous environments, and separation abilities. PMID:21433150

Hijikata, Yuh; Horike, Satoshi; Sugimoto, Masayuki; Sato, Hiroshi; Matsuda, Ryotaro; Kitagawa, Susumu

2011-03-23

79

Electron irradiation effects on partially fluorinated polymer films: Structure-property relationships  

CERN Multimedia

The effects of electron beam irradiation on two partially fluorinated polymer films i.e. poly(vinylidene fluoride) (PVDF) and poly(ethylene-tetrafluoroethylene) copolymer (ETFE) are studied at doses ranging from 100 to 1200 kGy in air at room temperature. Chemical structure, thermal and mechanical properties of irradiated films are investigated. FTIR show that both PVDF and ETFE films undergo similar changes in their chemical structures including the formation of carbonyl groups and double bonding. The changes in melting and crystallisation temperatures (T sub m and T sub c) in both irradiated films are functions of irradiation dose and reflect the disorder in the chemical structure caused by the competition between crosslinking and chain scission. The heat of melting (DELTA H sub m) and the degree of crystallinity (X sub c) of PVDF films show no significant changes with the dose increase, whereas those of ETFE films are reduced rapidly after the first 100 kGy. The tensile strength of PVDF films is improved b...

Nasef, M M

2003-01-01

80

Structure-Property Relationships in Solid AlF3 Lewis Acids  

International Nuclear Information System (INIS)

[en] 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

 
 
 
 
81

Relationship between molecular structure and photoelectric properties in a series of nitro-substituted fluorenone derivatives  

Energy Technology Data Exchange (ETDEWEB)

The photoconductivity of vacuum evaporated thin films of fluorenone and its nitro-substituted derivatives is investigated. A substantial effect of the molecular structure on photoelectric properties is revealed. It is demonstrated that the increase of the number of nitro groups in the molecule leads to photosensitivity enhancement from 0.018 for nitrofluorenone to 0.60 for tetranitrofluorenone. The enhancement is caused by the increased probability of the electron-hole pair formation during the initial stage of photogeneration. The average radius for a thermalized pair decreases from 2.75 to 2.0 nm with the substitution. The activation energy of steady-state photoconductivity for the nitro derivatives coincides with the photogeneration activation energy calculated from the Onsager model.

Bulyshev, Y.S.; Andrievskii, A.M.; Dyumaev, K.M.; Kashirskii, I.M.; Poplavskii, A.N.; Sinitskii, V.V.

1986-07-01

82

Rare earth-doped lead borate glasses and transparent glass-ceramics: structure-property relationship.  

UK PubMed Central (United Kingdom)

Correlation between structure and optical properties of rare earth ions in lead borate glasses and glass-ceramics was evidenced by X-ray-diffraction, Raman, FT-IR and luminescence spectroscopy. The rare earths were limited to Eu(3+) and Er(3+) ions. The observed BO(3)?BO(4) conversion strongly depends on the relative PbO/B(2)O(3) ratios in glass composition, giving important contribution to the luminescence intensities associated to (5)D(0)-(7)F(2) and (5)D(0)-(7)F(1) transitions of Eu(3+). The near-infrared luminescence and up-conversion spectra for Er(3+) ions in lead borate glasses before and after heat treatment were measured. The more intense and narrowing luminescence lines suggest partial incorporation of Er(3+) ions into the orthorhombic PbF(2) crystalline phase, which was identified using X-ray diffraction analysis.

Pisarski WA; Pisarska J; M?czka M; Lisiecki R; Grobelny ?; Goryczka T; Dominiak-Dzik G; Ryba-Romanowski W

2011-08-01

83

Rare earth-doped lead borate glasses and transparent glass-ceramics: structure-property relationship.  

Science.gov (United States)

Correlation between structure and optical properties of rare earth ions in lead borate glasses and glass-ceramics was evidenced by X-ray-diffraction, Raman, FT-IR and luminescence spectroscopy. The rare earths were limited to Eu(3+) and Er(3+) ions. The observed BO(3)?BO(4) conversion strongly depends on the relative PbO/B(2)O(3) ratios in glass composition, giving important contribution to the luminescence intensities associated to (5)D(0)-(7)F(2) and (5)D(0)-(7)F(1) transitions of Eu(3+). The near-infrared luminescence and up-conversion spectra for Er(3+) ions in lead borate glasses before and after heat treatment were measured. The more intense and narrowing luminescence lines suggest partial incorporation of Er(3+) ions into the orthorhombic PbF(2) crystalline phase, which was identified using X-ray diffraction analysis. PMID:21093353

Pisarski, W A; Pisarska, J; M?czka, M; Lisiecki, R; Grobelny, ?; Goryczka, T; Dominiak-Dzik, G; Ryba-Romanowski, W

2010-04-28

84

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

CERN Multimedia

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

Quantitative structure-activity relationship to predict toxicological properties of benzene derivative compounds.  

UK PubMed Central (United Kingdom)

TOPological Sub-structural MOlecular DEsign (TOPS-MODE) was used to assess acute aquatic toxicity of a series of 69 benzene derivatives. The obtained model was able to explain more than 88% of data variance, stressing the importance of molecule hydrophobicity and its dipolar moment, as well as the distance between their bonds to describe the property under study. On the other hand, this model was better than those obtained with Dragon software (Constitutional, Galvez topological charges indices and BCUT) using the same number of variables. This approach proved to be a very good method to assess acute aquatic toxicity of these king of compounds, which could be applied to other series of substances.

González MP; Helguera AM; Cabrera MA

2005-03-01

86

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

Science.gov (United States)

Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape PN 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 (Dsb{84} small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25sp°C to 550sp°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 + DOsb3 structure. The extruded material developed higher yield strength at temperatures below the DBTT, but the sintered material developed higher strengths above the DBTT. The fracture energy of these alloys was higher at all test temperatures, which indicated the importance of grain size and pore interaction with crack propagation. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.

Prichard, Paul Dehnhardt

87

Structure-property relationships in heterophasic thermoplastic elastomers filled with montmorillonite.  

UK PubMed Central (United Kingdom)

Polypropylene (PP)/ethylene-propylene rubber (EPR)/Montmorillonite ternary nanocomposites with a phase separated morphology were studied in this work. Wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to investigate the samples. One of the aim of this work was to separate the effects of rubber and clay content on the structure, morphology and mechanical properties of the samples. The presence of clay favored the formation of gamma phase and disrupted the lamellar framework. Clay had moreover a major role in shaping the phase separated morphology of the samples. Atomic Force Microscopy showed that the shear exerted by the clay layers was key for inducing a shish kebab morphology in the polymer matrix. Rubber content decreased the degree of crystallinity at a crystalline cell level and induced the formation of a double population of lamellar stacks. The mechanical properties of the samples primarily depended on rubber content, and they were secondarily tuned by the effect of clay. This synergistic effect allowed to obtain composites with increased stiffness, ductility and toughness, oppositely to what is frequently found.

Causin V; Marega C; Saini R; Neppalli R; Ferrara G; Adhikari R; Marigo A

2012-03-01

88

Structure-property relationships in heterophasic thermoplastic elastomers filled with montmorillonite.  

Science.gov (United States)

Polypropylene (PP)/ethylene-propylene rubber (EPR)/Montmorillonite ternary nanocomposites with a phase separated morphology were studied in this work. Wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to investigate the samples. One of the aim of this work was to separate the effects of rubber and clay content on the structure, morphology and mechanical properties of the samples. The presence of clay favored the formation of gamma phase and disrupted the lamellar framework. Clay had moreover a major role in shaping the phase separated morphology of the samples. Atomic Force Microscopy showed that the shear exerted by the clay layers was key for inducing a shish kebab morphology in the polymer matrix. Rubber content decreased the degree of crystallinity at a crystalline cell level and induced the formation of a double population of lamellar stacks. The mechanical properties of the samples primarily depended on rubber content, and they were secondarily tuned by the effect of clay. This synergistic effect allowed to obtain composites with increased stiffness, ductility and toughness, oppositely to what is frequently found. PMID:22754991

Causin, Valerio; Marega, Carla; Saini, Roberta; Neppalli, Ramesh; Ferrara, Giuseppe; Adhikari, Rameshwar; Marigo, Antonio

2012-03-01

89

Quantitative Structure-Property Relationship Evaluation of Structural Descriptors Derived from the Distance and Reverse Wiener Matrices  

Directory of Open Access Journals (Sweden)

Full Text Available Structural descriptors derived from the molecular graph are widely used in developing QSPR and QSAR models, in chemical database searching, drug design, toxicology, virtual screening of combinatorial libraries, similarity and diversity assessment. As a consequence of the significant interest in defining additional structural descriptors for QSPR and QSAR models, we present new molecular descriptors computed from the reverse Wiener RW and reciprocal reverse Wiener RRW matrices. The graph structural descriptors computed with the distance D, reciprocal distance RD, RW, and RRW matrices are used to develop quantitative structure-property models for the boiling temperature, molar heat capacity, standard Gibbs energy of formation, vaporization enthalpy, refractive index, and density of 134 alkanes C6-C10.

Ovidiu Ivanciuc; Teodora Ivanciuc; Alexandru T. Balaban

2002-01-01

90

Relationships between the chemical structure and the biological properties of some eremophilane compounds related to PR toxin.  

UK PubMed Central (United Kingdom)

The problem of the chemical structure--biological effects relationships has been studied for various eremophilane compounds related to PR toxin (PRT), a mycotoxin synthesized by Penicillium roqueforti. The biological tests were based on in vivo toxicity for male Swiss mice and inhibition of in vitro transcription and tranlation. The results showed a good correlation between the responses obtained for the three tests by the different compounds; thus, the toxic potency and the capacity of inhibiting transcription and translation should be directed by a common chemical structure. The data also indicated that the biological properties are related to the existence of an aldehyde group in position 12. In addition, evidence has been obtained demonstrating the hydrolysis of PRT imine with formation of a PRT-like compound.

Moulé Y; Moreau S; Bousquet JF

1977-05-01

91

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

92

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

UK PubMed Central (United Kingdom)

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.

Causin V; Yang BX; Marega C; Goh SH; Marigo A

2008-04-01

93

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.; Diez, M.R.; Hermoso, E.

2003-01-01

94

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 (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

95

Investigation of structure-property relationships of multi-branched two-photon absorption chromophores based on ?-conjugation core  

International Nuclear Information System (INIS)

To investigate the effect of conjugated-core structure of multi-branched chromophore on linear and nonlinear optical properties, three novel multi-branched organic chromophores, 3-(3,5-bis(9-butyl-9H-carbazol-6-yl)phenyl)-6-(4-(2,6-diphenylpyidin-4-yl) styryl)-9-butyl-9H-carbazole (W1), 1-(9-butyl-9H-carbazol-6-yl) phenyl)-3,5-bis(3-(4-(2,6-diphenylpyidin-4-yl)styryl) -9-butyl-9H-carbazole-6-yl)benzene (W2) and 1,3,5-tri(3-(4-(2,6-diphenylpyidin-4-yl)styryl)-9-butyl-9H-carbazole-6-yl) benzene (W3) have been synthesized and characterized. Their linear absorption, one- and two-photon fluorescence properties have been investigated. All these chromophores show intense one-photon fluorescence and high fluorescence quantum yields. When exited by a Ti:sapphire laser, these chromophores exhibit strong two-photon-excited fluorescence. The two-photon absorption cross sections of W1, W2 and W3 were calculated to be 69 GM, 112 GM and 173 GM in DMF, respectively. The ratio of the three compounds from the experiment is 1:1.6:2.5. Structure-property relationships are discussed based on photophysical data and theoretical calculation, which indicate a linear enhancement in one- and two-photon absorption and emission in going from W1 via W2 to W3.

2009-03-30

96

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

97

Structure-property relationships of irradiation crosslinked flexible PVC: Pt. 2  

International Nuclear Information System (INIS)

[en] Tensile properties at room temperature and at 1300C have been measured for two series of irradiation crosslinked plasticized poly(vinyl chloride) (PVC) samples. The samples have also been examined by thermomechanical analysis. Experimental variables consisted of irradiation dose and the amount of the crosslinking agent (trimethylolpropane trimethacrylate (TMPTMA)). Crosslinking caused only minor changes in room temperature properties but a significant change in tensile properties at 1300C and in softening temperature. For this to be observed, a gel content of at least 40% is required. Properties depend on both gel content, and network type, which are in turn controlled by irradiation dose and TMPTMA content. (author)

1989-01-01

98

Relationship of structure to properties of some anionic surfactants as collectors in the flotation process. 2: Effect of phenyl group  

Energy Technology Data Exchange (ETDEWEB)

Surface and thermodynamic properties of four synthetic anionic surfactants are studied. The properties of these surfactants are correlated with their flotation performance to upgrade a petroleum coke sample to minimize its impurities. The surfactants are isomers for dodecylbenzenesulfonate of the same molecular weight, but the benzene ring is attached to different carbon atoms along the dodecyl chain. The results show that the position of benzene ring, attached to the carbon chain, affects their surface and thermodynamic properties. The values of critical micelle concentration (cmc), minimum area per molecule (A{sub min}), effectiveness ({Pi}{sub cmc}), and efficiency (pC{sub 20}), to reduce surface tension of water, are decreased with changing the position of benzene ring from carbon atom number 3 to 5. Increasing temperature is accompanied by an increase in each of cmc, minimum area per molecule (A{sub min}), Gibbs energy of micellization ({Delta}G{degree}{sub mic}), and adsorption ({Delta}G{degree}{sub ad}). Meanwhile, the values of surface tension ({gamma}{sub cmc}) at cmc, surface excess concentration ({Gamma}{sub max}), and effectiveness ({Pi}{sub cmc}) to reduce surface tension of water are decreased. There is a good relationship between the structure of a surfactant and its efficiency as a collector. Changing the position of the phenyl group along the alkyl chain of a surfactant toward its central carbon atom (6{phi}C12) improves its efficiency as a collector.

Abdel-Khalek, N.A. [Univ. of Florida, Gainesville, FL (United States); Omar, A.M.A. [Egyptian Petroleum Research Inst., Cairo (Egypt)

1999-01-01

99

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

100

Onium salt structure/property relationships in poly(4-tert-butyloxycarbonyloxystyrene) deep-UV resists  

Science.gov (United States)

A series of sulfonium and iodonium salts was synthesized and the effect of onium slat structure on UV absorbance, thermal stability, and solubility in propylene glycol methyl ether acetate (PGMEA) was assessed. Several of these onium salts gave usable deep UV photoresists when combined with poly(4-tert-butyloxy-carbonloxystyrene). The lithographic sensitivity and latent image stability of these photoresists were strongly influenced by the structure of the incorporated onium salt.

Schwartzkopf, George; Niazy, Nagla N.; Das, Siddhartha; Surendran, Geetha; Covington, John B.

1991-06-01

 
 
 
 
101

Relationship between structural and physical properties in hexagonal boron nitride ceramics  

Energy Technology Data Exchange (ETDEWEB)

Density, hardness, Young`s modulus and graphitization index were evaluated in a series of hexagonal boron nitride ceramics prepared by hot pressing of turbostratic boron nitride powder. Relationships between these parameters were characterized with equations having regression coefficients higher than 0.8. Based on these characteristics, a novel model of turbostratic disorder in hexagonal boron nitride crystals has been proposed, suggesting a declination between boron nitride layers and an existence of sites with a secondary hybridization of electronic orbitals contributed by both sp{sup 2} and sp{sup 3}. (orig.)

Hubacek, M. [Nippon Steel Corp., Kawasaki (Japan). Adv. Technol. Res. Labs.; Ueki, M. [Nippon Steel Corp., Kawasaki (Japan). Adv. Technol. Res. Labs.; Novak, M. [Institute of Chemical Technology, Prague (Czech Republic); Brozek, V. [Institute of Chemical Technology, Prague (Czech Republic)

1996-09-01

102

Structure-property relationships in thermomechanically treated beryllia dispersed nickel alloys  

International Nuclear Information System (INIS)

BeO dispersed nickel alloys, produced by powder metallurgy techniques, were studied extensively in stress rupture at 815, 982, and 10930C (1088, 1255, and 1366 K) and by transmission electron microscopy. The alloys were subjected to a variety of thermomechanical treatments (TMT) to determine the benefits of TMT on properties. It is shown that the use of intermediate annealing treatments after 10 percent reduction steps is highly beneficial on both low and high temperature properties. It is indicated that the high temperature strength is not primarily dependent on the grain aspect ratio or texture but depends strongly on the dislocation density and distribution of dislocations in a stable substructure which is pinned by the fine oxide dispersion. (22 fig) (U.S.)

1975-01-01

103

Structure-properties relationships of lithium electrolytes based on ionic liquid.  

Science.gov (United States)

Low-melting ionic liquid, IL, based on small aliphatic quaternary ammonium cations ([R(1)R(2)R(3)NR](+), where R(1), R(2), R(3) = CH(3) or C(2)H(5), R = C(3)H(7), C(4)H(9), C(6)H(13), C(8)H(17), CF(3)C(3)H(6)) and imide anion were prepared and characterized. The physicochemical and electrochemical properties of these ILs, including melting point, glass transition, and degradation temperatures; viscosity; density; ionic conductivity; diffusion coefficient; and electrochemical stability, were determined. Heteronuclear Overhauser NMR spectroscopy experiments were also performed to point out the presence of pair correlation between the different moieties. The LiTFSI addition effect on the IL properties was studied with the same methodology. Some nanoscale organization with segregation of polar and apolar domains was observed. ILs with small alkyl chain length or fluorinated ammonium exhibit very high electrochemical stability in oxidation. PMID:20039688

Le, My Loan Phung; Alloin, Fannie; Strobel, Pierre; Leprêtre, Jean-Claude; Pérez del Valle, Carlos; Judeinstein, Patrick

2010-01-21

104

Structure-properties relationships of lithium electrolytes based on ionic liquid.  

UK PubMed Central (United Kingdom)

Low-melting ionic liquid, IL, based on small aliphatic quaternary ammonium cations ([R(1)R(2)R(3)NR](+), where R(1), R(2), R(3) = CH(3) or C(2)H(5), R = C(3)H(7), C(4)H(9), C(6)H(13), C(8)H(17), CF(3)C(3)H(6)) and imide anion were prepared and characterized. The physicochemical and electrochemical properties of these ILs, including melting point, glass transition, and degradation temperatures; viscosity; density; ionic conductivity; diffusion coefficient; and electrochemical stability, were determined. Heteronuclear Overhauser NMR spectroscopy experiments were also performed to point out the presence of pair correlation between the different moieties. The LiTFSI addition effect on the IL properties was studied with the same methodology. Some nanoscale organization with segregation of polar and apolar domains was observed. ILs with small alkyl chain length or fluorinated ammonium exhibit very high electrochemical stability in oxidation.

Le ML; Alloin F; Strobel P; Leprêtre JC; Pérez del Valle C; Judeinstein P

2010-01-01

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

Thermal properties and nanodispersion behavior of synthesized b-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 b-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 b-sitosterol as a comparison. Inspection of the melting point (Tm) and the heat of fusion (DH) of b-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 b-sitosterol and b-sitosteryl saturated fatty acid (SFA) esters displayed different particle size distribution patterns (polymodal vs bimodal), mean diameter (115 nm vs less than 100 nm), and polydispersity index (PDI) (0.50 vs 0.23–0.38). b-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 27–63 nm and PDI 0.18–0.25). The nanodispersion of b-sitosteryl medium chain SFA ester (C14:0) demonstrated a best storage stability.

Panpipat, Worawan; Dong, Mingdong

2013-01-01

107

Synthesis and Transistor Properties of Asymmetric Oligothiophenes: Relationship between Molecular Structure and Device Performance.  

Science.gov (United States)

A series of three thiophene-naphthalene-based asymmetric oligomers-5-decyl-2,2':5',2'':5'',2'''-quaterthiophene (DtT), 5-decyl-5''-(naphthalen-2-yl)-2,2':5',2''-terthiophene (D3TN), and 5-(4-decylphenyl)-5'-(naphthalen-2-yl)-2,2'-bithiophene (DP2TN)-was synthesized by Suzuki cross-coupling reactions. The long alkyl side chains improved both the solubility of the oligomers in solvents and their tendency to self-assemble. UV/Vis absorption measurements suggested that DtT, D3TN, and DP2TN form H-type aggregates with a face-to-face packing structure. In addition, the three oligomers were found to adopt vertically aligned crystalline structures in films deposited on substrates, as revealed by grazing-incidence wide-angle X-ray scattering. These oligomers were used as the active layers of p-type organic field-effect transistors, and the resulting devices showed field-effect mobilities of 3.3×10(-3) ?cm(2) ?V(-1) ?s(-1) for DtT, 1.6×10(-2) ?cm(2) ?V(-1) ?s(-1) for D3TN, and 3.7×10(-2) ?cm(2) ?V(-1) ?s(-1) for DP2TN. The differences in transistor performances were attributed to the degree of ? overlap and the morphological differences determined by the molecular structures. PMID:24108597

An, Tae Kyu; Jang, Sang Hun; Kim, Seul-Ong; Jang, Jaeyoung; Hwang, Jihun; Cha, Hyojung; Noh, Young Ri; Yoon, Soon Byung; Yoon, Yong Jin; Kim, Lae Ho; Chung, Dae Sung; Kwon, Soon-Ki; Kim, Yun-Hi; Lee, Sang-Gyeong; Park, Chan Eon

2013-09-17

108

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

International Nuclear Information System (INIS)

[en] 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

109

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

110

Quantitative structure-property relationships of potentially bioactive fluoro phospho-silicate glasses.  

UK PubMed Central (United Kingdom)

In this work, the glass transition temperature and chemical durability of bioactive phospho-silicate glasses were experimentally determined and correlated to the structural descriptor Fnet derived from classical molecular dynamics simulations. The replacement of CaF2 for Na2O in the parent glass 45S5 enhances both chemical durability and density, while the replacement of CaF2 for CaO lowers chemical durability. The proposed descriptor, Fnet, provides satisfactorily correlations with glass transition temperature and chemical durability over a wide range of compositions.

Lusvardi G; Malavasi G; Tarsitano F; Menabue L; Menziani MC; Pedone A

2009-07-01

111

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

2011-07-11

112

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

UK PubMed Central (United Kingdom)

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.

Xiao JB; Huo JL; Yang F; Chen XQ

2011-08-01

113

2D Quantitative Structure-Property Relationship Study of Mycotoxins by Multiple Linear Regression and Support Vector Machine  

Directory of Open Access Journals (Sweden)

Full Text Available In the present work, support vector machines (SVMs) and multiple linear regression (MLR) techniques were used for quantitative structure–property relationship (QSPR) studies of retention time (tR) in standardized liquid chromatography–UV–mass spectrometry of 67 mycotoxins (aflatoxins, trichothecenes, roquefortines and ochratoxins) based on molecular descriptors calculated from the optimized 3D structures. By applying missing value, zero and multicollinearity tests with a cutoff value of 0.95, and genetic algorithm method of variable selection, the most relevant descriptors were selected to build QSPR models. MLRand SVMs methods were employed to build QSPR models. The robustness of the QSPR models was characterized by the statistical validation and applicability domain (AD). The prediction results from the MLR and SVM models are in good agreement with the experimental values. The correlation and predictability measure by r2 and q2 are 0.931 and 0.932, repectively, for SVM and 0.923 and 0.915, respectively, for MLR. The applicability domain of the model was investigated using William’s plot. The effects of different descriptors on the retention times are described.

Roya Khosrokhavar; Jahan Bakhsh Ghasemi; Fereshteh Shiri

2010-01-01

114

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

115

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

International Nuclear Information System (INIS)

[en] 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

Stars, dendrimers and hyperbranched polymers: Towards understanding structure-property relationships for single molecule constructs  

Energy Technology Data Exchange (ETDEWEB)

New families of tetrahedral core molecules for synthesizing star and hyperbranched polymers are based on new adamantane derivatives. Four-arm structures have been obtained that are capable of chain extension and thermal conversion to highly crosslinked materials. Hyperbranched and star polymers containing siloxysilane repeat units have also been made through polyaddition hydrosilation reactions with star nodes and A-B monomers or A-B{sub 3} monomers. Terminal functionalization has been demonstrated for a variety of reactive and interactive groups that offer possibilities for use in artificial blood and interfacial microreactors. Combination of rigid tetrahedral cores with start or hyperbranched arms should make available new families of materials for composite synthesis, fiber interphase, formation and impact modification.

Mathias, L.J.; Reichert, V.R.; Carothers, T.W.; Bozen, R.M. [Univ. of Southern Mississippi, Hattiesburg, MS (United States)

1993-12-31

117

Structure-property relationships of irradiation crosslinked flexible PVC: Pt. 1  

International Nuclear Information System (INIS)

[en] An investigation has been carried out into the effect of irradiation dose and the amount of the unsaturated monomer trimethylolpropane trimethacrylate (TMPTMA) on the irradiation of a di-iso-octyl phthalate (DIOP) plasticized PVC compound. The type of network structure produced and the extent of deterioration of the PVC after crosslinking have been studied. Within the dose range studied, the degradation caused by the electron beam was found to be minimal, but the residual unsaturation in the crosslinked PVC was significant, implying inefficient use of crosslinking agent. Gel yield increased with increased irradiation dose and TMPTMA content, but crosslink density decreased at higher irradiation levels, suggesting the formation of a looser network. The phthalate plasticizer was not involved in gel formation. (author)

1988-01-01

118

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.; Borsali Redouane; Ritter Olga M.S.; Gonçalves Paulo F.; Merlo Aloir A.; Silveira Nadya P. da

2006-01-01

119

A study of the relationship between structure and properties of cadmium phosphate glasses  

Science.gov (United States)

It analysed the structure and chemical durability which it follows in CdO content in Cadmium phosphate glasses. We prepared glasses with the composition, xCdO-(100- x)P2O5 ( x = 10 mol. % to 50 mol. %), and analyzed their density ( ?), molar volume ( V M ), glass transition/softening temperature ( T g / T d ), thermal expansion coefficient ( ?), fourier transform infrared spectroscopy, and dissolution rate. All of these of the values were found to vary with the CdO content of the glasses. It is observed that the dissolution rate increase with with CdO contents. This suggests that Cadmium ion breaks the p-o-p bonds.

Choi, Won-Gyu; Kim, Tae-Hee; Gwoo, Dong-Gun; Kee, Kyung-Bum; Kim, Jong-Hwan; Han, Kyung-Suk; Ryu, Bong-Ki

2013-01-01

120

Relationship between structure characteristics and thermal conversion property of Shenmu maceral concentrates  

Energy Technology Data Exchange (ETDEWEB)

Vitrinite and inertinite separated from Shenmu coal using sink-float method combined with hand-picking were systematically investigated by ultimate analysis, FT-IR, {sup 13}C NMR and TG/DTG. The results showed that the optimum density for separation of vitrinite and inertinite from Shenmu coal was 1.320 g/cm{sup 3} - 1.324 g/cm{sup 3} and 1.378 g/cm{sup 3} - 1.382 g/cm{sup 3} respectively. The purity of vitrinite and inertinite was 97.55% and 96.90% at this separation condition. Vitrinite had higher hydrogen content, lower aromaticity of 0.51 and a large amount of hydrogen bonds, while inertinite had higher carbon content and aromaticity of 0.76, and those of parent coal was in the middle of them with aromaticity of 0.68. The result of FTIR showed that at the same temperature vitrinite had more hydrogen bonds, higher aliphatic hydrogen content and lower H{sub ar}/H{sub al} ratio. With increasing temperature, the content of aromatic hydrogen and H{sub ar}/H{sub al} ratio all increased and the aliphatic hydrogen decreased. The result of TG/DTG showed that vitrinite had higher thermal stability than inertinite and the remaining volatile matter in vitrinite was lower than that in inertinite at the same H{sub ar}/H{sub al} ratio, which was consistent with the fact that inertinite had higher aromaticity and lower aliphatic hydrogen content and suggested that the chemical property of maceral affected it reactivity. 15 refs., 4 figs., 5 tabs.

Sun, Q.; Li, W.; Li, D.; Chen, H.; Li, B.; Bai, X.; Li, W. [Chinese Academy of Sciences, Taiyuan (China). State Key Lab. of Coal Conversion

2003-04-01

 
 
 
 
121

Elucidating the Structure-Activity Relationships of the Vasorelaxation and Antioxidation Properties of Thionicotinic Acid Derivatives  

Directory of Open Access Journals (Sweden)

Full Text Available Nicotinic acid, known as vitamin B3, is an effective lipid lowering drug and intense cutaneous vasodilator. This study reports the effect of 2-(1-adamantylthio)nicotinic acid (6) and its amide 7 and nitrile analog 8 on phenylephrine-induced contraction of rat thoracic aorta as well as antioxidative activity. It was found that the tested thionicotinic acid analogs 6-8 exerted maximal vasorelaxation in a dose-dependent manner, but their effects were less than acetylcholine (ACh)-induced nitric oxide (NO) vasorelaxation. The vasorelaxations were reduced, apparently, in both NG-nitro-L-arginine methyl ester (L-NAME) and indomethacin (INDO). Synergistic effects were observed in the presence of L-NAME plus INDO, leading to loss of vasorelaxation of both the ACh and the tested nicotinic acids. Complete loss of the vasorelaxation was noted under removal of endothelial cells. This infers that the vasorelaxations are mediated partially by endothelium-induced NO and prostacyclin. The thionicotinic acid analogs all exhibited antioxidant properties in both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide dismutase (SOD) assays. Significantly, the thionicotinic acid 6 is the most potent vasorelaxant with ED50 of 21.3 nM and is the most potent antioxidant (as discerned from DPPH assay). Molecular modeling was also used to provide mechanistic insights into the vasorelaxant and antioxidative activities. The findings reveal that the thionicotinic acid analogs are a novel class of vasorelaxant and antioxidant compounds which have potential to be further developed as promising therapeutics.

Supaluk Prachayasittikul; Orapin Wongsawatkul; Apilak Worachartcheewan; Chanin Nantasenamat; Somsak Ruchirawat; Virapong Prachayasittikul

2010-01-01

122

Composition-structure-property-performance relationship inMn-substituted LiMn2O4  

Energy Technology Data Exchange (ETDEWEB)

The spinel LiMn{sub 2}O{sub 4} has been extensively studied as a positive electrode active material in lithium rechargeable batteries. Partial substitution of Mn by another metal has also been the subject of recent study in an effort to improve the cycling performance. In general, the literature has shown that Mn substitution results in improved cycling stability at the expense of capacity (1,2). Resistance to the formation of tetragonal phase upon lithiation of the starting spinel (via a higher nominal Mn oxidation state in the substituted spinel) has been suggested as a mechanism for the improved performance. The degree of substitution is an important factor to optimize in order to minimize capacity loss and costs. The spectroscopic investigations on LiMn{sub 2}O{sub 4} described in the previous paper (LixMn2O4) confirmed that the cooperative Jahn-Teller effect (CJTE) from the [Mn{sup 3+}O{sub 6}] octahedra is the mechanism for the cubic to tetragonal phase transformation. The driving force for the CJTE is based upon the electronic structure, therefore changes in electronic structure should lead to changes in the phase behavior. The fact that the LiMn{sub 1.5}Ni{sub 0.5}O{sub 4} does not form tetragonal phase upon discharging (FUJI3, MUCK?), unlike the 100% Mn{sup 4+} spinel Li{sub 4}Mn{sub 5}O{sub 12} (THAC5), led to the hypothesis that an increased degree of covalency as a source for the behavior. An increased covalence would remove the driving force for the transformation, the increased electronic stability achieved in tetragonally-distorted [Mn{sup 3+}O{sub 6}] octahedra, due to a change in electron density and widening of the Mn 3d bands. The STH field is dependent upon the amount of unpaired spin density transferred between the magnetic (transition-metal) and diamagnetic ions through an intermittent oxygen ion, attributable to overlap and electron transfer effects. Therefore, the magnitude of the STH coupling constant reflects the degree of covalency (GESC, HUAN). In the case of LiMn{sub 2-y}Me{sub y}O{sub 4}, the STH coupling constant characterizes the amount of unpaired spin density transferred to the Li{sup +} from the Mn, Co, or Ni. Similarly, the La/Lb ratio of the Mn L-XES is sensitive to the amount of electron density at the Mn site as a higher ratio indicates that the Mn 3d{sub 5/2} level is more populated (GRUS1). An investigation into the effects of Mn-substitution on the electronic structure along with the ramifications to the phase behavior upon changing lithium content was carried out. To accomplish this, a set of LiMn{sub 2-y}Me{sub y}O{sub 4} with Me = Li, Co, or Ni over a range of y were synthesized, characterized, and subjected to changes in lithium content by various techniques.

Horne, Craig R.; Richardson, Thomas J.; Gee, B.; Tucker, Mike; Grush, Melissa M.; Bergmann, Uwe; Striebel, Kathryn A.; Cramer, StephenP.; Reimer, Jeffrey A.; Cairns, Elton J.

2001-03-09

123

Structure-Property Relationship of Amplified Spontaneous Emission in Organic Semiconductor Materials: TPD, DPABP and NPB.  

UK PubMed Central (United Kingdom)

N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD) was demonstrated to be suitable for stimulated emission in doping and non-doping planar waveguide structure, but the mechanism for its lasing is of ambiguity. With the aim of providing a microscopic picture for its lasing, we performed a combined experimental and theortical investigation of the absorption, photoluminescence (PL) and stimulated emission of TPD and other two similar molecules: 1,4-bis (diphenylamino)biphenyl (DPABP) and N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4''-diamine (NPB). It was found that DPABP shows the same amplified spontaneous emission (ASE) characteristics as TPD, but NPB did not. In theory, Density Functional Theory (DFT) and Frank-Condon Principle were used to analyze the molecular geometry in the electronic ground state as well as the optically excited state and the vibrational levels in electronic ground state, respectively. The calculation results show that for TPD and DPABP, several strongly elongated high-frequency modes (1199-1664 cm-1) in the carbon rings contribute to distinct first vibronic sideband in the PL spectra, which form an effective "four-level" system for lasing. For NPB, when the peripheral toluene or benzene is replaced with naphthyl, a number of strongly elongated low-frequency modes (11-689 cm-1) deriving from naphthyl leads to a series of energy sublevels which destroys the "four-level" systerm. Our results provided a new insight and better understanding into the lasing of organic molecules.

Wu Z; Ma L; Liu P; Zhou C; Ning S; El-Shafei A; Zhao X; Hou X

2013-09-01

124

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese A influência da estrutura química dos grupos mesogênicos e do tamanho dos grupos espaçadores, no comportamento de fase de uma série de cristais líquidos poliméricos de cadeia lateral (SCLCP), foram estudados utilizando-se espalhamento de raios-X a Baixo Ângulo (SAXS) e Microscopia Ótica de Luz Polarizada (POM). Análises do arranjo das mesofases em amostras não orientadas e orientadas por ação do campo magnético são descritas. O papel do tamanho do espaçado (more) r lateral no empacotamento local e na largura da camada esmética determinados nas mesofases SmA e SmC é elucidado. Os ângulos teta formados entre os grupos mesogênicos e a normal às camadas nas mesofases SmC foram determinados. Um estudo a respeito do grau de ordem em função da temperatura, para os polímeros esméticos foi possível através de medidas de SAXS. Uma ordenação particular em um dos SCLCPs estudados é relacionada com a coexistência de duas fases distintas. Abstract in english 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 layer (more) s 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.; Borsali, Redouane; Ritter, Olga M.S.; Gonçalves, Paulo F.; Merlo, Aloir A.; Silveira, Nadya P. da

2006-04-01

125

Computational methods for microstructure-property relationships  

CERN Multimedia

Computational Methods for Microstructure-Property Relationships introduces state-of-the-art advances in computational modeling approaches for materials structure-property relations. Written with an approach that recognizes the necessity of the engineering computational mechanics framework, this volume provides balanced treatment of heterogeneous materials structures within the microstructural and component scales. Encompassing both computational mechanics and computational materials science disciplines, this volume offers an analysis of the current techniques and selected topics important to i

Ghosh, Somnath

2010-01-01

126

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

127

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

Energy Technology Data Exchange (ETDEWEB)

Soil macroinvertebrate communities were studied in ecologically analogous oak-hickory forests in Illinois, Indiana and Ohio 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 adversely 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 Laboratory, Argonne, IL (United States). Environmental Assessment Division

1996-09-01

128

Analysis of structure-property relationships in isolated cells during OD treatments. Effect of initial structure on the cell behaviour  

UK PubMed Central (United Kingdom)

Isolated apple cells were osmotically dehydrated in sucrose solutions (25%, 35% and 45% (w/w)) inside a heating/cooling stage with temperature control (30°C), and examined by video-microscopy. The purpose of this work was to analyse the progress of cell microstructural changes by direct observation and further study of the digital images captured during the treatments. Cell features were identified and measured. Protoplast shrinkage increased as did sucrose concentration; however, the cell wall underwent more deformation at the lowest concentration assayed. High sucrose concentration led to an almost instantaneous protoplast separation since the membrane-to-wall linkers did not resist the stretching of the contracting protoplast; this response frequently resulted in membrane lysis and loss of cellular compartmentation. Cells structure was characterized and was proved to be related to the phenomenon undergone by the cell (shrinkage, complete plasmolysis, or membrane lysis). The response of the cell was found to be a function not only of the osmotic solution concentration but also of initial cell microstructural features. Results also suggested that a better preservation of membrane integrity and membrane-to-wall connections might be achieved if cells are dehydrated in increasingly concentrated OS solutions.

Segui? L; Fito PJ; Fito P

2010-08-01

129

Relationships between the composition and fluidity of British coals and the structural properties and reactivity of the corresponding cokes produced on the 250-kg scale of carbonization  

Energy Technology Data Exchange (ETDEWEB)

The carbonizing behaviour of selected British coals was examined with the 250-kg oven from the standpoint of formulating blends to produce coke of a quality suitable for use in modern blast furnaces. A detailed study was made of the chemical composition of the coals, their coking and fluid properties, the structural characteristics and reactivity of the corresponding cokes, and the relationship between these parameters. (9 refs.)

1982-12-01

130

Propriedades químico-quânticas empregadas em estudos das relações estrutura-atividade Quantum chemical properties used in structure-activity relationship studies  

Directory of Open Access Journals (Sweden)

Full Text Available In this work we show that structure-activity relationship studies are of great importance in modern chemistry and biochemistry. In order to obtain a significant correlation, it is crucial that appropriate descriptors be employed. Thus, quantum chemical calculations are an attractive source of new molecular descriptors which can, in principle, express all the electronic and geometric properties of molecules and their interactions with the biological receptor.

Agnaldo Arroio; Káthia M. Honório; Albérico B. F. da Silva

2010-01-01

131

Structure-property relationship of perylene bisimide macrocycles probed by atomic force microscopy and single-molecule fluorescence spectroscopy.  

Science.gov (United States)

Properties of a series of acetylene-linked perylene bisimide (PBI) macrocycles with different ring size composed of three to six PBI dyes were investigated by atomic force microscopy (AFM) and single-molecule fluorescence spectroscopy in a condensed phase. It was demonstrated that the structures of PBI cyclic arrays (CNs, N = 3, 4, 5, and 6) become distorted with increasing the ring size through molecular dynamics (MD) simulations (PM6-DH2 method) and AFM height images of CNs on highly ordered pyrolytic graphite (HOPG) surface. The MD simulations showed that only C5 and C6 rings are highly flexible molecules whose planarization goes along with a significant energetic penalty. Accordingly, both molecules did not show ordered adlayers on a HOPG surface. In contrast, C3 and C4 are far more rigid molecules leading to well-ordered hexagonal (C3) and rectangular (C4) 2D lattices. At the single-molecule level, we showed that the fluorescence properties of single CNs are affected by the structural changes. The fluorescence lifetimes of CNs became shorter and their distributions became broader due to the structural distortions with increasing the ring size. Furthermore, the CNs of smaller ring size exhibit a higher photostability and an efficient excitation energy transfer (EET) due to the more well-defined and planar structures compared to the larger CNs. Consequently, these observations provide evidence that not only PBI macrocycles are promising candidates for artificial light-harvesting systems, but also the photophysical properties of CNs are strongly related to the structural rigidity of CNs. PMID:23656366

Lee, Ji-Eun; Stepanenko, Vladimir; Yang, Jaesung; Yoo, Hyejin; Schlosser, Felix; Bellinger, Daniel; Engels, Bernd; Scheblykin, Ivan G; Würthner, Frank; Kim, Dongho

2013-05-14

132

Structure-property relationship of perylene bisimide macrocycles probed by atomic force microscopy and single-molecule fluorescence spectroscopy.  

UK PubMed Central (United Kingdom)

Properties of a series of acetylene-linked perylene bisimide (PBI) macrocycles with different ring size composed of three to six PBI dyes were investigated by atomic force microscopy (AFM) and single-molecule fluorescence spectroscopy in a condensed phase. It was demonstrated that the structures of PBI cyclic arrays (CNs, N = 3, 4, 5, and 6) become distorted with increasing the ring size through molecular dynamics (MD) simulations (PM6-DH2 method) and AFM height images of CNs on highly ordered pyrolytic graphite (HOPG) surface. The MD simulations showed that only C5 and C6 rings are highly flexible molecules whose planarization goes along with a significant energetic penalty. Accordingly, both molecules did not show ordered adlayers on a HOPG surface. In contrast, C3 and C4 are far more rigid molecules leading to well-ordered hexagonal (C3) and rectangular (C4) 2D lattices. At the single-molecule level, we showed that the fluorescence properties of single CNs are affected by the structural changes. The fluorescence lifetimes of CNs became shorter and their distributions became broader due to the structural distortions with increasing the ring size. Furthermore, the CNs of smaller ring size exhibit a higher photostability and an efficient excitation energy transfer (EET) due to the more well-defined and planar structures compared to the larger CNs. Consequently, these observations provide evidence that not only PBI macrocycles are promising candidates for artificial light-harvesting systems, but also the photophysical properties of CNs are strongly related to the structural rigidity of CNs.

Lee JE; Stepanenko V; Yang J; Yoo H; Schlosser F; Bellinger D; Engels B; Scheblykin IG; Würthner F; Kim D

2013-06-01

133

The relationship between chemical structure and dielectric properties of plasma-enhanced chemical vapor deposited polymer thin films  

International Nuclear Information System (INIS)

[en] Polymer dielectric films fabricated by plasma enhanced chemical vapor deposition (PECVD) have unique properties due to their dense crosslinked bulk structure. These spatially uniform films exhibit good adhesion to a variety of substrates, excellent chemical inertness, high thermal resistance, and are formed from an inexpensive, solvent-free, room temperature process. In this work, we studied the dielectric properties of plasma polymerized (PP) carbon-based polymer thin films prepared from two precursors, benzene and octafluorocyclobutane. Two different monomer feed locations, directly in the plasma zone or in the downstream region (DS) and two different pressures, 80 Pa (high pressure) or 6.7 Pa (low pressure), were used. The chemical structure of the PECVD films was examined by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. The dielectric constant (? r) and dielectric loss (tan ?) of the films were investigated over a range of frequencies up to 1 MHz and the dielectric strength (breakdown voltage) (F b) was characterized by the current-voltage method. Spectroscopic ellipsometry was performed to determine the film thickness and refractive index. Good dielectric properties were exhibited, as PP-benzene films formed in the high pressure, DS region showed a Fb of 610 V/?m, an ? r of 3.07, and a tan ? of 7.0 x 10-3 at 1 kHz. The PECVD processing pressure has a significant effect on final film structure and the film's physical density has a strong impact on dielectric breakdown strength. Also noted was that the residual oxygen content in the PP-benzene films significantly affected the frequency dependences of the dielectric constant and loss

2007-02-26

134

The relationship between chemical structure and dielectric properties of plasma-enhanced chemical vapor deposited polymer thin films  

Energy Technology Data Exchange (ETDEWEB)

Polymer dielectric films fabricated by plasma enhanced chemical vapor deposition (PECVD) have unique properties due to their dense crosslinked bulk structure. These spatially uniform films exhibit good adhesion to a variety of substrates, excellent chemical inertness, high thermal resistance, and are formed from an inexpensive, solvent-free, room temperature process. In this work, we studied the dielectric properties of plasma polymerized (PP) carbon-based polymer thin films prepared from two precursors, benzene and octafluorocyclobutane. Two different monomer feed locations, directly in the plasma zone or in the downstream region (DS) and two different pressures, 80 Pa (high pressure) or 6.7 Pa (low pressure), were used. The chemical structure of the PECVD films was examined by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. The dielectric constant ({epsilon} {sub r}) and dielectric loss (tan {delta}) of the films were investigated over a range of frequencies up to 1 MHz and the dielectric strength (breakdown voltage) (F {sub b}) was characterized by the current-voltage method. Spectroscopic ellipsometry was performed to determine the film thickness and refractive index. Good dielectric properties were exhibited, as PP-benzene films formed in the high pressure, DS region showed a F{sub b} of 610 V/{mu}m, an {epsilon} {sub r} of 3.07, and a tan {delta} of 7.0 x 10{sup -3} at 1 kHz. The PECVD processing pressure has a significant effect on final film structure and the film's physical density has a strong impact on dielectric breakdown strength. Also noted was that the residual oxygen content in the PP-benzene films significantly affected the frequency dependences of the dielectric constant and loss.

Jiang Hao [Materials Sci and Tech Applications, LLC, 409 Maple Springs Drive, Dayton OH 45458 (United States)]. E-mail: hao.jiang@wpafb.af.mil; Hong Lianggou [Materials Sci and Tech Applications, LLC, 409 Maple Springs Drive, Dayton OH 45458 (United States); Venkatasubramanian, N. [Research Institute, University of Dayton, 300 College Park, Dayton, OH 45469-0168 (United States); Grant, John T. [Research Institute, University of Dayton, 300 College Park, Dayton, OH 45469-0168 (United States); Eyink, Kurt [Air Force Research Laboratory, Materials Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433-7707 (United States); Wiacek, Kevin [Air Force Research Laboratory, Propulsion Directorate, 1950 Fifth Street, Wright-Patterson Air Force Base, OH 45433-7251 (United States); Fries-Carr, Sandra [Air Force Research Laboratory, Propulsion Directorate, 1950 Fifth Street, Wright-Patterson Air Force Base, OH 45433-7251 (United States); Enlow, Jesse [Air Force Research Laboratory, Materials Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433-7707 (United States); Bunning, Timothy J. [Air Force Research Laboratory, Materials Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433-7707 (United States)

2007-02-26

135

Structure property relationships in the ATi2O4 (A=Na, Ca) family of reduced titanates  

International Nuclear Information System (INIS)

Reduced titanates in the ATi2O4 (A=Li, Mg) spinel family exhibit a variety of interesting electronic and magnetic properties, most notably superconductivity in the mixed-valence spinel, Li1+ x Ti2- x O4. The sodium and calcium analogs, NaTi2O4 and CaTi2O4, each differ in structure, the main features of which are double rutile-type chains composed of edge-sharing TiO6 octahedra. We report for the first time, the properties and band structures of these two materials. XANES spectroscopy at the Ti K-edge was used to probe the titanium valence. The absorption edge position and the pre-edge spectral features observed in the XANES data confirm the assignment of Ti3+ in CaTi2O4 and mixed-valence Ti3+/Ti4+ in NaTi2O4. Temperature-dependent resistivity and magnetic susceptibility studies are consistent with the classification of both NaTi2O4 and CaTi2O4 as small band-gap semiconductors, although changes in the high-temperature magnetic susceptibility of CaTi2O4 suggest a possible insulator-metal transition near 700 K. Band structure calculations agree with the observed electronic properties of these materials and indicate that while Ti-Ti bonding is of minimal importance in NaTi2O4, the titanium atoms in CaTi2O4 are weakly dimerized at room temperature. -- Graphical abstract: Normalized titanium K-edge XANES spectra confirm mixed-valence for NaTi2O4 with an edge energy intermediate between Ti3+ oxides such as CaTi2O4, MgTi2O4 and Ti2O3, and Ti4+ containing oxides such as TiO2.

2006-01-01

136

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

137

Using quantitative structural property relationships, chemical fate models, and the chemical partitioning space to investigate the potential for long range transport and bioaccumulation of complex halogenated chemical mixtures.  

UK PubMed Central (United Kingdom)

Some substances are mixtures of very large number of constituents which vary widely in their properties, and thus also in terms of their environmental fate and the hazard that they may pose to humans and the environment. Examples of such substances include industrial chemicals such as the chlorinated paraffins, technical pesticides such as toxaphene, and unintended combustion side products, such as mixed halogenated dibenzo-p-dioxins and dibenzofurans. Here we describe a simple graphical superposition method that could precede a more detailed hazard assessment for such substances. First, partitioning and degradation properties for each individual constituent of a mixture are estimated with high-throughput quantitative structure-property relationships. Placed in a chemical partitioning space, i.e. a coordinate system defined by two partitioning coefficients, the mixtures appear as 'clouds'. When model-derived hazard assessment metrics, such as the potential for bioaccumulation and long range transport, are superimposed on these clouds, the resulting maps identify the constituents with the highest value for a particular parameter and thus potentially the greatest hazard. The maps also indicate transparently how the potential for long range transport and bioaccumulation is dependent on structural attributes, such as chain length, and the degree and type of halogenation. In contrast to previous approaches, in which the mixture is represented by a single set of properties or those of a few selected constituents, the whole range of environmental fate behaviors displayed by the constituents of a mixture are being considered. The approach is illustrated with three sets of chemical substances.

Gawor A; Wania F

2013-08-01

138

Characterization of structure-antioxidant activity relationship of peptides in free radical systems using QSAR models: key sequence positions and their amino acid properties.  

Science.gov (United States)

Antioxidative peptides have attracted increasing attention from researchers because of their antioxidant properties as natural materials in functional food and for applications in medicine. However, the relationship between structure and activity (SAR) remains unclear, especially in antioxidative peptides in free radical systems. Antioxidative peptides with different lengths were obtained from the literature, measured using different methods, and were organized into three databases, namely, Trolox-equivalent antioxidant capacity (TEAC), oxygen radical absorption capacity (ORAC), and superoxide radical (SOR). After the peptides were processed using the two-terminal position numbering method, quantitative SAR modeling was performed on antioxidative peptides in the three databases. The vectors of hydrophobic, steric, and electronic properties (VHSE) and the divided physicochemical property scores descriptors (DPPS) were selected from 17 physicochemical descriptors to express electronic, hydrophobic, and steric properties (or hydrogen bonding) of the three (or four) external amino acids in the N-terminal and C-terminal positions. Models were estimated using partial least squares regression and validated through full cross-validation and external validation (R(2)>0.7, Q(2)>0.5 for TEAC; R(2)>0.9, Q(2)>0.5 for ORAC and SOR). The results found a relationship between the physicochemical properties of the C-terminal and N-terminal regions and antioxidant potency. The properties of amino acids at C-terminal regions were more important than those at the N-terminal regions for predicting antioxidant activity. The properties of amino acids at C(2)>C(1) for TEAC, C(3)>C(4)>C(1) for ORAC, and C(4)>C(1)>N(1) for SOR were highly correlated with antioxidant activity. Although electronic property most significantly contributed to antioxidant activity in the three free radical systems, it had complex effects at each position. Bulky hydrophobic amino acids at the C-terminal were related to the antioxidant activity of peptides in the three free radical systems. For peptides in the TEAC database, the relationship between the N-terminal segment (N(2), N(3)) and the activity increased when longer peptides were included, which reflects the likely influence of stericity. This study contributes to the ongoing research on antioxidants in food and its application in medicine. PMID:23127747

Li, Yao-Wang; Li, Bo

2012-11-02

139

Characterization of structure-antioxidant activity relationship of peptides in free radical systems using QSAR models: key sequence positions and their amino acid properties.  

UK PubMed Central (United Kingdom)

Antioxidative peptides have attracted increasing attention from researchers because of their antioxidant properties as natural materials in functional food and for applications in medicine. However, the relationship between structure and activity (SAR) remains unclear, especially in antioxidative peptides in free radical systems. Antioxidative peptides with different lengths were obtained from the literature, measured using different methods, and were organized into three databases, namely, Trolox-equivalent antioxidant capacity (TEAC), oxygen radical absorption capacity (ORAC), and superoxide radical (SOR). After the peptides were processed using the two-terminal position numbering method, quantitative SAR modeling was performed on antioxidative peptides in the three databases. The vectors of hydrophobic, steric, and electronic properties (VHSE) and the divided physicochemical property scores descriptors (DPPS) were selected from 17 physicochemical descriptors to express electronic, hydrophobic, and steric properties (or hydrogen bonding) of the three (or four) external amino acids in the N-terminal and C-terminal positions. Models were estimated using partial least squares regression and validated through full cross-validation and external validation (R(2)>0.7, Q(2)>0.5 for TEAC; R(2)>0.9, Q(2)>0.5 for ORAC and SOR). The results found a relationship between the physicochemical properties of the C-terminal and N-terminal regions and antioxidant potency. The properties of amino acids at C-terminal regions were more important than those at the N-terminal regions for predicting antioxidant activity. The properties of amino acids at C(2)>C(1) for TEAC, C(3)>C(4)>C(1) for ORAC, and C(4)>C(1)>N(1) for SOR were highly correlated with antioxidant activity. Although electronic property most significantly contributed to antioxidant activity in the three free radical systems, it had complex effects at each position. Bulky hydrophobic amino acids at the C-terminal were related to the antioxidant activity of peptides in the three free radical systems. For peptides in the TEAC database, the relationship between the N-terminal segment (N(2), N(3)) and the activity increased when longer peptides were included, which reflects the likely influence of stericity. This study contributes to the ongoing research on antioxidants in food and its application in medicine.

Li YW; Li B

2013-02-01

140

The Mechanical Properties of Human Adipose Tissues and their Relationships to the Structure and Composition of the Extracellular Matrix.  

UK PubMed Central (United Kingdom)

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. It is therefore 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 was determined using nonlinear microscopy. AT showed non-linear stress-strain characteristics up to 30% strain. Comparing paired subcutaneous and omental samples (n=19) the moduli were lower in subcutaneous: initial 1.6±0.8KPa (mean±SD) and 2.9±1.5KPa (p=0.001), final 11.7±6.4KPa and 32±15.6KPa (p<0.001) respectively. The energy dissipation density was lower in subcutaneous AT (n=13): 0.1±0.1KPa and 0.3±0.2KPa 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 significantly increased. Nonlinear microscopy revealed collagen and elastin networks in close proximity to adipocytes and a larger-scale network of larger fiber bundles. There was considerable micro-scale 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.

Alkhouli N; Mansfield J; Green E; Bell J; Knight B; Liversedge N; Tham JC; Welbourn R; Shore AC; Kos K; Winlove CP

2013-10-01

 
 
 
 
141

Processing/structure/property relationship of multi-scaled PCL and PCL-HA composite scaffolds prepared via gas foaming and NaCl reverse templating.  

UK PubMed Central (United Kingdom)

In this study, we investigated the processing/structure/property relationship of multi-scaled porous biodegradable scaffolds prepared by combining the gas foaming and NaCl reverse templating techniques. Poly(?-caprolactone) (PCL), hydroxyapatite (HA) nano-particles and NaCl micro-particles were melt-mixed by selecting different compositions and subsequently gas foamed by a pressure-quench method. The NaCl micro-particles were finally removed from the foamed systems in order to allow for the achievement of the multi-scaled scaffold pore structure. The control of the micro-structural properties of the scaffolds was obtained by the optimal combination of the NaCl templating concentration and the composition of the CO(2)-N(2) mixture as the blowing agent. In particular, these parameters were accurately selected to allow for the fabrication of PCL and PCL-HA composite scaffolds with multi-scaled open pore structures. Finally, the biocompatibility of the scaffolds has been assessed by cultivating pre-osteoblast MG63 cells in vitro, thus demonstrating their potential applications for bone regeneration. Biotechnol. Bioeng. © 2010 Wiley Periodicals, Inc.

Salerno A; Zeppetelli S; Di Maio E; Iannace S; Netti PA

2010-12-01

142

Processing/structure/property relationship of multi-scaled PCL and PCL-HA composite scaffolds prepared via gas foaming and NaCl reverse templating.  

UK PubMed Central (United Kingdom)

In this study, we investigated the processing/structure/property relationship of multi-scaled porous biodegradable scaffolds prepared by combining the gas foaming and NaCl reverse templating techniques. Poly(?-caprolactone) (PCL), hydroxyapatite (HA) nano-particles and NaCl micro-particles were melt-mixed by selecting different compositions and subsequently gas foamed by a pressure-quench method. The NaCl micro-particles were finally removed from the foamed systems in order to allow for the achievement of the multi-scaled scaffold pore structure. The control of the micro-structural properties of the scaffolds was obtained by the optimal combination of the NaCl templating concentration and the composition of the CO2-N2 mixture as the blowing agent. In particular, these parameters were accurately selected to allow for the fabrication of PCL and PCL-HA composite scaffolds with multi-scaled open pore structures. Finally, the biocompatibility of the scaffolds has been assessed by cultivating pre-osteoblast MG63 cells in vitro, thus demonstrating their potential applications for bone regeneration.

Salerno A; Zeppetelli S; Di Maio E; Iannace S; Netti PA

2011-04-01

143

Processing/structure/property relationship of multi-scaled PCL and PCL-HA composite scaffolds prepared via gas foaming and NaCl reverse templating.  

Science.gov (United States)

In this study, we investigated the processing/structure/property relationship of multi-scaled porous biodegradable scaffolds prepared by combining the gas foaming and NaCl reverse templating techniques. Poly(?-caprolactone) (PCL), hydroxyapatite (HA) nano-particles and NaCl micro-particles were melt-mixed by selecting different compositions and subsequently gas foamed by a pressure-quench method. The NaCl micro-particles were finally removed from the foamed systems in order to allow for the achievement of the multi-scaled scaffold pore structure. The control of the micro-structural properties of the scaffolds was obtained by the optimal combination of the NaCl templating concentration and the composition of the CO2-N2 mixture as the blowing agent. In particular, these parameters were accurately selected to allow for the fabrication of PCL and PCL-HA composite scaffolds with multi-scaled open pore structures. Finally, the biocompatibility of the scaffolds has been assessed by cultivating pre-osteoblast MG63 cells in vitro, thus demonstrating their potential applications for bone regeneration. PMID:21404268

Salerno, A; Zeppetelli, S; Di Maio, E; Iannace, S; Netti, P A

2010-12-14

144

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

145

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 the selection of the variables which gives the best-fitted models. After variable selection ANN, MLR methods were used with leave-one-out cross validation for building the regression models. The prediction results are in very good agreement with the experimental values. MLR as the linear regression method shows good ability in the prediction of the retention times of the prediction set. This provided a new and effective method for predicting the chromatography retention index for the volatile organic compounds.

Sarkhosh Maryam; Ghasemi Jahan B; Ayati Mahnaz

2012-01-01

146

Structure-property relationships of antiferroelectric Pb(Zr, Ti)O{sub 3} based materials: Hydrostatic depoling characteristics  

Energy Technology Data Exchange (ETDEWEB)

A novel technique has been developed for the synthesis of homogeneous, weakly agglomerated highly filterable Pb(Zr, Ti)O{sub 3} (PZT) powders. PZT 95/5 based ceramics were fabricated from these powders to determine interrelationships among microstructure, dielectric properties and pressure induced ferroelectric (FE) to antiferroelectric (AFE) phase transitions. Initial measurements indicate that microstructure has a substantial effect on hydrostatic depoling characteristics. While smaller grain size materials and higher switching pressures, subtleties in microstructure, which may include entrapped porosity, resulted in a more diffuse depoling characteristic. In addition, greater than 90% dense materials were obtained at process temperatures as low at 900{degrees}C. were only 30% of the values of PZT 95/5 fired at 1300{degrees}C, the dielectric constants of the 900{degrees}C materials were almost a factor of two higher. Backscattered electron Kikuchi pattern analysis determined that adjacent, nonlinear, irregularly shaped domain structures observed by electron channel imaging were 109{degrees} domains.

Tuttle, B.; Voigt, J.; Moore, R. [and others

1997-09-01

147

Structure-property relationship of ion-beam sputtered Nd-Fe-B magnetic thin films on (111)silicon  

Energy Technology Data Exchange (ETDEWEB)

A focusing grid broad beam Kaufman source, using argon ions on a target of nominal composition Nd{sub 2}Fe{sub 14}B has been employed to sputter deposit magnetic thin films of thicknesses ranging from 800 {angstrom} to 1300 {angstrom} on silicon-(111) substrates at room temperature. These films were characterized for their composition depth profile by Rutherford Backscattering Spectroscopy, while x-ray diffraction was used to study the crystallographic structure. Due to a close match between (111) Si with (220) Nd{sub 2}Fe{sub 14}B lattice spacings, preferred crystallographic texturing was expected, and experimental results showed a greatly enhanced (220) texture. The degradation in magnetic properties was attributed to the presence of oxygen in the films as indicated by concentration depth profiles. It is premised that another significant role of oxygen may be to relieve the misfit strain across the interface by its incorporation within the Nd{sub 2}Fe{sub 14}B phase.

Nazareth, A.S.; Sood, D.K.; Zmood, R.B. [Royal Melbourne Inst. of Tech. (Australia). Dept. of Electrical Engineering; Chopra, H.D. [Monash Univ., Clayton, Victoria (Australia). Dept. of Materials Engineering

1995-12-31

148

Notes on quantitative structure-property relationships (QSPR), part 3: density functions origin shift as a source of quantum QSPR algorithms in molecular spaces.  

UK PubMed Central (United Kingdom)

A general algorithm implementing a useful variant of quantum quantitative structure-property relationships (QQSPR) theory is described. Based on quantum similarity framework and previous theoretical developments on the subject, the present QQSPR procedure relies on the possibility to perform geometrical origin shifts over molecular density function sets. In this way, molecular collections attached to known properties can be easily used over other quantum mechanically well-described molecular structures for the estimation of their unknown property values. The proposed procedure takes quantum mechanical expectation value as provider of causal relation background and overcomes the dimensionality paradox, which haunts classical descriptor space QSPR. Also, contrarily to classical procedures, which are also attached to heavy statistical gear, the present QQSPR approach might use a geometrical assessment only or just some simple statistical outline or both. From an applied point of view, several easily reachable computational levels can be set up. A Fortran 95 program: QQSPR-n is described with two versions, which might be downloaded from a dedicated web site. Various practical examples are provided, yielding excellent results. Finally, it is also shown that an equivalent molecular space classical QSPR formalism can be easily developed.

Carbó-Dorca R

2013-04-01

149

Fundamental structure-property relationships towards engineering of an integrated NP0 capacitor for bismuth pyrochlore systems  

Science.gov (United States)

A comprehensive investigation of the processing-structure-property-performance (PSPP) interrelationship in the Bi2O3-ZnO-Nb2O 5 (BZN) pyrochlore system towards engineering of an integrated NP0 capacitor with silver electrodes for LTCC (low temperature cofire ceramics) microwave applications is presented. Using the BZN system as a model several specific areas or research are investigated and then correlated to obtain a global understanding of the PSPP interrelationship governing Bi-based pyrochlores. The first area of investigation covers the phase formation for the cubic pyrochlore with nominal composition Bi3/2ZnNb3/2O 7 and monoclinic zirconolite Bi2Zn2/3Nb4/3 O7 compounds through XRD (X-ray diffraction) phase analysis. Formation reactions sequences are identified. In both phases, BNbO4 is found to be a precursor reacting primarily with ZnO. It is also found that in order to kinetically limit the residual BiNbO4, the calcination and sintering profiles should spend limited time at temperatures between 650°C and 750°C. It is shown that high ZnO activity is essential for the phase formation process and therefore the process is extremely dependent on milling and mixing. In addition, alternative processing routes are studied to ensure phase purity. Batching with excess ZnO and low pO2 processing atmospheres are demonstrated as successful options to reduce residual BiNbO4. The solubility of the main BZN phases to ZnO is investigated revealing a wide compositional windows resulting in single phase ceramic. These results serve as a guide for the appropriate modifications in batching and processing required to obtain a BZN composite ceramic exhibiting desirable NP0 characteristics (temperature coefficient of capacitance (TCC) ˜15 ppm/°C, mean dielectric constant of 96 and dielectric loss ˜0.001 at 1 MHz), which can be densified at 950°C with no sintering additives. The second area covers the phase refinement of the main phases in the Bi2O3ZnO-Nb2O5 pyrochlore system performed via detailed XRD, Neutron Diffraction (ND) and Transmission Electron Microscopy (TEM). Essential and unique features in this phase are revealed by ND analysis like the sheet like structure based on HTB- (hexagonal tungsten bronze) like layers formed by [Nb(Zn)O6] octahedra and stacked along the c-axis. (Abstract shortened by UMI.)

Nino, Juan C.

150

Synthesis, fluorescence, and two-photon absorption of a series of elongated rodlike and banana-shaped quadrupolar fluorophores: a comprehensive study of structure-property relationships.  

UK PubMed Central (United Kingdom)

An extensive series of push-push and pull-pull derivatives was prepared from the symmetrical functionalization of an ambivalent core with conjugated rods made from arylene-vinylene or arylene-ethynylene building blocks, bearing different acceptor or donor end-groups. Their absorption and photoluminescence, as well as their two-photon-absorption (TPA) properties in the near infrared (NIR) region, were systematically investigated to derive structure-property relationships and to lay the guidelines for both spectral tuning and amplification of molecular TPA in the target region. Whatever the nature of the core or of the connectors, push-push systems were found to be more efficient than pull-pull systems, and planarization of the core (fluorene versus biphenyl) always leads to an increase in the TPA cross sections. In contrast, increasing the conjugation length as well as replacement of a phenylene moiety by a thienylene moiety in the conjugated rods did not necessarily lead to increased TPA responses. The present study also demonstrated that the topology of the conjugated rods can dramatically influence the TPA properties. This is of particular interest in terms of molecular engineering for specific applications, as both TPA properties and photoluminescence characteristics can be considerably affected. Thus, it becomes possible to optimize the transparency/TPA and fluorescence/TPA efficiency trade-offs for optical limiting in the red-NIR region (700-900 nm) and for two-photon-excited fluorescence (TPEF) microscopy applications, respectively.

Mongin O; Porrès L; Charlot M; Katan C; Blanchard-Desce M

2007-01-01

151

On the Development and Use of Large Chemical Similarity Networks, Informatics Best Practices and Novel Chemical Descriptors Towards Materials Quantitative Structure Property Relationships  

Science.gov (United States)

After decades of development and use in a variety of application areas, Quantitative Structure Property Relationships (QSPRs) and related descriptor-based statistical learning methods have achieved a level of infamy due to their misuse. The field is rife with past examples of overtrained models, overoptimistic performance assessment, and outright cheating in the form of explicitly removing data to fit models. These actions do not serve the community well, nor are they beneficial to future predictions based on established models. In practice, in order to select combinations of descriptors and machine learning methods that might work best, one must consider the nature and size of the training and test datasets, be aware of existing hypotheses about the data, and resist the temptation to bias structure representation and modeling to explicitly fit the hypotheses. The definition and application of these best practices is important for obtaining actionable modeling outcomes, and for setting user expectations of modeling accuracy when predicting the endpoint values of unknowns. A wide variety of statistical learning approaches, descriptor types, and model validation strategies are explored herein, with the goals of helping end users understand the factors involved in creating and using QSPR models effectively, and to better understand relationships within the data, especially by looking at the problem space from multiple perspectives. Molecular relationships are commonly envisioned in a continuous high-dimensional space of numerical descriptors, referred to as chemistry space. Descriptor and similarity metric choice influence the partitioning of this space into regions corresponding to local structural similarity. These regions, known as domains of applicability, are most likely to be successfully modeled by a QSPR. In Chapter 2, the network topology and scaling relationships of several chemistry spaces are thoroughly investigated. Chemistry spaces studied include the ZINC data set, a qHTS PubChem bioassay, as well as the protein binding sites from the PDB. The characteristics of these networks are compared and contrasted with those of the bioassay Structure Activity Landscape Index (SALI) subnetwork, which maps discontinuities or cliffs in the structure activity landscape. Mapping this newly generated information over underlying chemistry space networks generated using different descriptors demonstrates local modeling capacity and can guide the choice of better local representations of chemistry space. Chapter 2 introduces and demonstrates this novel concept, which also enables future work in visualization and interpretation of chemical spaces. Initially, it was discovered that there were no community-available tools to leverage best-practice ideas to comprehensively build, compare, and interpret QSPRs. The Yet Another Modeling System (YAMS) tool performs a series of balanced, rational decisions in dataset preprocessing and parameter/feature selection over a choice of modeling methods. To date, YAMS is the only community-available informatics tool that performs such decisions consistently between methods while also providing multiple model performance comparisons and detailed descriptor importance information. The focus of the tool is thus to convey rich information about model quality and predictions that help to "close the loop" between modeling and experimental efforts, for example, in tailoring nanocomposite properties. Polymer nanocomposites (PNC) are complex material systems encompassing many potential structures, chemistries, and self assembled morphologies that could significantly impact commercial and military applications. There is a strong desire to characterize and understand the tradespace of nanocomposites, to identify the important factors relating nanostructure to materials properties and determine an effective way to control materials properties at the manufacturing scale. Due to the complexity of the systems, existing design approaches rely heavily on trial-and-error learning. By leveraging existin

Krein, Michael

152

Quantitative structure-property relationship study on first reduction and oxidation potentials of donor-substituted phenylquinolinylethynes and phenylisoquinolinylethynes: Quantum chemical investigation  

Energy Technology Data Exchange (ETDEWEB)

The relationship between the chemical structure, first reduction and oxidation potentials of 30 Phenylquinolinylethyne (PhQE), and Phenylisoquinolinylethyne (PhIE) derivative compounds has been elucidated employing ab initio calculations. Quantum chemical calculations (HF/6-31G) were carried out to obtain: the optimized geometry, energy levels, quantum chemical indices, charges and dipole moments of these compounds. The quantitative structure-property relationship (QSPR) of PhQE and PhIE was studied for the first reduction (E{sub red}), and the first oxidation (E{sub ox}) potentials. The genetic algorithm (GA) was applied to select the variables that resulted in the best-fit models. After the variable selection, multiple linear regression (MLR) was utilized to construct linear QSPR models. The resulting QSPR equations indicated that the orbital energies, quantum chemical indices (i.e. electronegativity and softness) and localization of charge in molecules are important factors in the first oxidation and reduction potentials of PhQE and PhIE. The quantum-chemical calculations show that the HOMO and LUMO of both PhQE and PhIE derivatives are localized on the donor-substituted phenyl moiety, and the quinolinyl and isoquinolinyl acceptor moiety respectively. Thus, it was proposed that the first reduction and oxidation potentials can be ascribed to reduction at the quinolinyl acceptor moiety, and oxidation at the donor-substituted phenyl moiety.

Beheshti, Abolghasem [Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, P.O. Box 14155-6455, Tehran (Iran, Islamic Republic of); Riahi, Siavash [Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, P.O. Box 14155-6455, Tehran (Iran, Islamic Republic of); Institute of Petroleum Engineering, Faculty of Engineering, University of Tehran, P.O. Box 11365-4563, Tehran (Iran, Islamic Republic of)], E-mail: riahisv@khayam.ut.ac.ir; Ganjali, Mohammad Reza [Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, P.O. Box 14155-6455, Tehran (Iran, Islamic Republic of)

2009-09-30

153

Relationship between crystal structure and luminescent properties of novel red emissive BiVO{sub 4}:Eu{sup 3+} and its photocatalytic performance  

Energy Technology Data Exchange (ETDEWEB)

Crystalline BiVO{sub 4}:Eu{sup 3+} nanomaterials have been successfully synthesized by four different methods: co-precipitation, hydrothermal, solvothermal, and reverse micelles. The relationship between crystal structure and luminescent properties was studied by X-ray diffraction and steady-state fluorescence. The data indicate that Eu{sup 3+5}D{sub 0} {yields} {sup 7}F{sub 2} red luminescence at 618 nm can be excited by visible light at 466 nm in BiVO{sub 4} host. Furthermore, it has been found that the encapsulation of europium(III) in tetragonal phase (BiVO{sub 4}) results in enhanced luminescence intensities compared with monoclinic phase. Transmission electron microscopy showed rods with sizes ranging from nanometer to micrometer and nanospheres can be obtained under different experimental conditions.

Wang Qianming, E-mail: qmwang@scnu.edu.cn [School of Chemistry and Environment, South China Normal University, Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education (China); Li Yan [School of Chemistry and Environment, South China Normal University (China); Zeng Zhi [School of Chemistry and Environment, South China Normal University, Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education (China); Pang Shuting [School of Chemistry and Environment, South China Normal University (China)

2012-08-15

154

Relationship between oxide-ion conduction and dielectric properties of Gd2Zr2O7 having a fluorite-type structure  

International Nuclear Information System (INIS)

[en] The relationship between electrical conduction and dielectric properties was investigated for the oxide-ion conductor Gd2Zr2O7 having a fluorite-type structure. Computer simulation clarified that the anomalously large dielectric constant (?r') was successfully explained by the superposition of the Debye-type polarization and the electrolyte-electrode interfacial polarization. Two Debye-type relaxations were observed at 673 K and above. The lower-frequency relaxation was ascribed to the dopant-vacancy associate, (GdCe' - Vo··-GdCe'), and the higher one to the long range migration of oxide ions on the basis of the discussions of both the activation energies and the relaxation frequencies. The frequency dependences of both the ac conductivity (?ac) and the loss tangent (tan?) were also successfully explained using the dielectric parameters of the Debye-type dopant-vacancy associates. (author)

2008-01-01

155

Quantitative structure-property relationships modeling to predict in vitro and in vivo binding of drugs to the bile sequestrant, colesevelam (Welchol).  

UK PubMed Central (United Kingdom)

Quantitative structure-property relationship (QSPR) models were developed to correlate physicochemical properties of structurally unrelated drugs with extent of in vitro binding to colesevelam, and predicted values were compared with drug exposure changes in vivo following coadministration. The binding of 17 drugs to colesevelam was determined by an in vitro dissolution drug-binding assay. Data from several clinical studies in healthy volunteers to support administration of colesevelam in diabetic patients were also collected along with existing in vivo literature data and compared with in vitro results. Steric, electronic, and hydrophobic descriptors were calculated for test compounds, and univariate and partial least squares regression approaches were used to derive QSPR models to evaluate which of the molecular descriptors correlated best with in vitro binding. A quadrant analysis evaluated the correlation between predicted/actual in vitro binding results and the in vivo data. The in vitro binding assay exhibited high sensitivity, identifying those compounds with a low probability of producing relevant in vivo drug interactions. Drug lipophilicity was identified as the primary determinant of in vitro binding to colesevelam by the final univariate and partial least squares models (R(2) = 0.69 and 0.98; Q(2) = 0.48 and 0.59). The in vitro assay and in silico models represent predictive tools that may allow investigators to conduct only informative clinical drug interaction studies with colesevelam.

Walker JR; Brown K; Rohatagi S; Bathala MS; Xu C; Wickremasingha PK; Salazar DE; Mager DE

2009-10-01

156

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

International Nuclear Information System (INIS)

[en] 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

157

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.)

2008-01-01

158

Relationship Between Attitude Properties and Psychological Commitment  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of the study was to examine the relationship between attitude properties and psychological commitment to a sports team. In addition, this study attempted to examine whether there were gender differences in the relationship between attitude properties and psychological commitment to the team. A total of 453 questionnaires were distributed and returned from students at a large public university. Out of 453, twenty-nine were excluded because they were not applicable. 424 questionnaires were utilized for the data analysis. Data were analyzed with correlation analysis, Cron-bach’s ? coefficient, confirmatory factor analysis, and three structural models (total data, male data, and female data). Based on the results of the total data, direct experience, importance, certainty, and extremity directly contributed to psychological commitment to the team. The results also indicated that direct experience, importance, and extremity were significantly related to psychological commitment to the team for males, while for females, only importance was a significant predictor of psychological commitment to the team.

JAEHYUN HA; KEUNSU HAN; ETHAN STRIGAS

2011-01-01

159

Crystal structure of hyperthermophilic esterase EstE1 and the relationship between its dimerization and thermostability properties  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background EstE1 is a hyperthermophilic esterase belonging to the hormone-sensitive lipase family and was originally isolated by functional screening of a metagenomic library constructed from a thermal environmental sample. Dimers and oligomers may have been evolutionally selected in thermophiles because intersubunit interactions can confer thermostability on the proteins. The molecular mechanisms of thermostabilization of this extremely thermostable esterase are not well understood due to the lack of structural information. Results Here we report for the first time the 2.1-Å resolution crystal structure of EstE1. The three-dimensional structure of EstE1 exhibits a classic ?/? hydrolase fold with a central parallel-stranded beta sheet surrounded by alpha helices on both sides. The residues Ser154, Asp251, and His281 form the catalytic triad motif commonly found in other ?/? hydrolases. EstE1 exists as a dimer that is formed by hydrophobic interactions and salt bridges. Circular dichroism spectroscopy and heat inactivation kinetic analysis of EstE1 mutants, which were generated by structure-based site-directed mutagenesis of amino acid residues participating in EstE1 dimerization, revealed that hydrophobic interactions through Val274 and Phe276 on the ?8 strand of each monomer play a major role in the dimerization of EstE1. In contrast, the intermolecular salt bridges contribute less significantly to the dimerization and thermostability of EstE1. Conclusion Our results suggest that intermolecular hydrophobic interactions are essential for the hyperthermostability of EstE1. The molecular mechanism that allows EstE1 to endure high temperature will provide guideline for rational design of a thermostable esterase/lipase using the lipolytic enzymes showing structural similarity to EstE1.

Byun Jung-Sue; Rhee Jin-Kyu; Kim Nam; Yoon JeongHyeok; Kim Dong-Uk; Koh Eunhee; Oh Jong-Won; Cho Hyun-Soo

2007-01-01

160

Variable range hopping in single-wall carbon nanotube thin films: a processing-structure-property relationship study.  

UK PubMed Central (United Kingdom)

By varying the ultrasonication and ultracentrifugation conditions, single-walled carbon nanotube (SWCNT) dispersions with a broad range of SWCNT length and diameter (L = 342-3330 nm; d = 0.5-12 nm) were prepared and characterized by a preparative ultracentrifuge method (PUM) and dynamic light scattering (DLS) technique. The well-characterized dispersions were then fabricated into SWCNT thin films by spray coating. Combined optical, spectroscopic, and temperature-dependent electrical measurements were performed to study the effect of SWCNT structures on the charge transport behavior of SWCNT thin films. Regardless of SWCNT size in the dispersion and the thin film thickness, the three-dimensional variable range hopping (3D VRH) conduction model was found to be appropriate in explaining the temperature-dependent sheet resistance results for all SWCNT thin films prepared in this study. More importantly, with the SWCNT structural information determined by the PUM method, we were able to identify a strong correlation between the length of SWCNTs and the 3D VRH parameter T0, the Mott characteristic temperature. When the SWCNT length is less than ?700 nm, the T0 of SWCNT thin films shows a drastic increase, but when the length is greater than ~700 nm, T0 is only weakly dependent on the SWCNT length. Under the framework of traditional VRH, we further conclude that the electron localization length of SWCNT thin films shows a similar dependence on the SWCNT length.

Luo S; Liu T; Benjamin SM; Brooks JS

2013-07-01

 
 
 
 
161

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; Hossein Farahbakhsh; Nasrin Salehi

2012-01-01

162

Quantitative structure-property relationship (QSPR) for the adsorption of organic compounds onto activated carbon cloth: Comparison between multiple linear regression and neural network  

Energy Technology Data Exchange (ETDEWEB)

The adsorption of 55 organic compounds is carried out onto a recently discovered adsorbent, activated carbon cloth. Isotherms are modeled using the Freundlich classical model, and the large database generated allows qualitative assumptions about the adsorption mechanism. However, to confirm these assumptions, a quantitative structure-property relationship methodology is used to assess the correlations between an adsorbability parameter (expressed using the Freundlich parameter K) and topological indices related to the compounds molecular structure (molecular connectivity indices, MCI). This correlation is set up by mean of two different statistical tools, multiple linear regression (MLR) and neural network (NN). A principal component analysis is carried out to generate new and uncorrelated variables. It enables the relations between the MCI to be analyzed, but the multiple linear regression assessed using the principal components (PCs) has a poor statistical quality and introduces high order PCs, too inaccurate for an explanation of the adsorption mechanism. The correlations are thus set up using the original variables (MCI), and both statistical tools, multiple linear regression and neutral network, are compared from a descriptive and predictive point of view. To compare the predictive ability of both methods, a test database of 10 organic compounds is used.

Brasquet, C.; Bourges, B.; Le Cloirec, P.

1999-12-01

163

Ultrafast optical nonlinearities and figures of merit in acceptor-substituted 3,4,5-trimethoxy chalcone derivatives: Structure-property relationships  

Science.gov (United States)

By performing both Z-scan and transient transmission measurements with 130 fs laser pulses in the near infrared region, we investigated structure-property relationships for ?(3) in acceptor-substituted 3,4,5-trimethoxy chalcone derivatives. We determined all nonlinear parameters, including two-photon absorption (2PA) cross section, 2PA-induced excited-state absorption (ESA) cross section, microscopic second-order hyperpolarizability, and lifetime of the excited state in these molecules. We found that the microscopic second-order hyperpolarizability ?R and 2PA cross section ?2PA in chalcone derivatives increase as the acceptor strength of the molecules increases, which demonstrates an enhancement in optical nonlinearities by simple structural variations. We evaluated the one-photon, two-photon, and effective three-photon figures of merit for acetone solutions of chalcone derivatives at irradiance of 100 GW/cm2. Furthermore, we observed optical limiting behavior in these compounds, which result from both 2PA and 2PA-assisted ESA. These results indicated that chalcone derivatives are a promising candidate for applications on nonlinear photonic devices.

Gu, Bing; Ji, Wei; Patil, P. S.; Dharmaprakash, S. M.

2008-05-01

164

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

UK PubMed Central (United Kingdom)

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 was 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.

Franck T; Mouithys-Mickalad A; Robert T; Ghitti G; Deby-Dupont G; Neven P; Serteyn D

2013-09-01

165

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

International Nuclear Information System (INIS)

[en] 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.

2012-01-01

166

Structural properties and evolutionary relationships of PspA, a surface protein of Streptococcus pneumoniae, as revealed by sequence analysis.  

UK PubMed Central (United Kingdom)

Analysis of the sequence for the gene encoding PspA (pneumococcal surface protein A) of Streptococcus pneumoniae revealed the presence of four distinct domains in the mature protein. The structure of the N-terminal half of PspA was highly consistent with that of an alpha-helical coiled-coil protein. The alpha-helical domain was followed by a proline-rich domain (with two regions in which 18 of 43 and 5 of 11 of the residues are prolines) and a repeat domain consisting of 10 highly conserved 20-amino-acid repeats. A fourth domain consisting of a hydrophobic region too short to serve as a membrane anchor and a poorly charged region followed the repeats and preceded the translation stop codon. The C-terminal region of PspA did not possess features conserved among numerous other surface proteins, suggesting that PspA is attached to the cell by a mechanism unique among known surface proteins of gram-positive bacteria. The repeat domain of PspA was found to have significant homology with C-terminal repeat regions of proteins from Streptococcus mutans, Streptococcus downei, Clostridium difficile, and S. pneumoniae. Comparisons of these regions with respect to functions and homologies suggested that, through evolution, the repeat regions may have lost or gained a mechanism for attachment to the bacterial cell.

Yother J; Briles DE

1992-01-01

167

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

UK PubMed Central (United Kingdom)

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.

Amaral S; Mira L; Nogueira JM; da Silva AP; Helena Florêncio M

2009-03-01

168

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

2009-01-25

169

A new quantitative structure-property relationship model to predict bioconcentration factors of polychlorinated biphenyls (PCBs) in fishes using E-state index and topological descriptors.  

UK PubMed Central (United Kingdom)

A quantitative structure-property relationship (QSPR) study for predicting the logarithm of bioconcentration factors (LogBCF) of polychlorinated biphenyls (PCBs) is presented in this work. For this, the descriptors were obtained using only the Simplified Molecular Input Line Entry System (SMILES) strings in the free web server Parameter Client. The model was built using the Partial Least Squares (PLS) regression method. The best model presented five descriptors (one E-state index and four topological descriptors) and a high quality for fit, internal, and external predictions. The leave-N-out (LNO) cross validation and the y-randomization test showed the model is robust and has no shown chance correlation. With a second test set, the model was compared to other models and presented a root mean square error (RMSE) very close to the best model. The mechanistic interpretation was corroborated by other works in the literature and by the descriptors' theory. Thus, the results meet the five Organization for Economic Co-operation and Development (OECD) principles for validation of QSA(P)R models, and it is expected the model can effectively predict the BCF values in fishes of the PCB congeners without highly reliable experimental BCF.

de Melo EB

2012-01-01

170

Quantitative structure-(chromatographic) retention relationships.  

UK PubMed Central (United Kingdom)

Since the pioneering works of Kaliszan (R. Kaliszan, Quantitative Structure-Chromatographic Retention Relationships, Wiley, New York, 1987; and R. Kaliszan, Structure and Retention in Chromatography. A Chemometric Approach, Harwood Academic, Amsterdam, 1997) no comprehensive summary is available in the field. Present review covers the period of 1996-August 2006. The sources are grouped according to the special properties of kinds of chromatography: Quantitative structure-retention relationship in gas chromatography, in planar chromatography, in column liquid chromatography, in micellar liquid chromatography, affinity chromatography and quantitative structure enantioselective retention relationships. General tendencies, misleading practice and conclusions, validation of the models, suggestions for future works are summarized for each sub-field. Some straightforward applications are emphasized but standard ones. The sources and the model compounds, descriptors, predicted retention data, modeling methods and indicators of their performance, validation of models, and stationary phases are collected in the tables. Some important conclusions are: Not all physicochemical descriptors correlate with the retention data strongly; the heat of formation is not related to the chromatographic retention. It is not appropriate to give the errors of Kovats indices in percentages. The apparently low values (1-3%) can disorient the reviewers and readers. Contemporary mean interlaboratory reproducibility of Kovats indices are about 5-10 i.u. for standard non polar phases and 10-25 i.u. for standard polar phases. The predictive performance of QSRR models deteriorates as the polarity of GC stationary phase increases. The correlation coefficient alone is not a particularly good indicator for the model performance. Residuals are more useful than plots of measured and calculated values. There is no need to give the retention data in a form of an equation if the numbers of compounds are small. The domain of model applicability of models should be given in all cases.

Héberger K

2007-07-01

171

Lignin. Structural organisation and fractal properties  

International Nuclear Information System (INIS)

[en] The results of investigations of the topological and supramolecular structures of lignins are considered. The experimental data on the hydrodynamic and conformational properties of dilute solutions of hardwood and softwood lignins are generalised. The relationship between hydrodynamic and fractal properties of lignin macromolecules is analysed and the applicability of various fractal concepts is discussed. Good prospects of using the fractal approach for the study of amorphous polymers with complex topological and supramolecular structures are demonstrated.

2003-08-31

172

Lignin. Structural organisation and fractal properties  

Energy Technology Data Exchange (ETDEWEB)

The results of investigations of the topological and supramolecular structures of lignins are considered. The experimental data on the hydrodynamic and conformational properties of dilute solutions of hardwood and softwood lignins are generalised. The relationship between hydrodynamic and fractal properties of lignin macromolecules is analysed and the applicability of various fractal concepts is discussed. Good prospects of using the fractal approach for the study of amorphous polymers with complex topological and supramolecular structures are demonstrated.

Karmanov, Anatolii P [Institute of Chemistry of the Komi Scientific Centre, Urals Branch of the Russian Academy of Sciences (Russian Federation); Monakov, Yurii B [Institute of Organic Chemistry, Ufa Scientific Centre of the Russian Academy of Sciences, Ufa (Russian Federation)

2003-08-31

173

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

174

Spirooxazines: synthesis, structure, spectral and photochromic properties  

International Nuclear Information System (INIS)

The review surveys synthetic approaches to spiro[1,4]oxazines belonging to one of the most promising classes of organic photochromes. The relationships between the structures of spirooxazines and their spectral properties as well as characteristics of thermal and photoinduced processes are considered. The bibliography includes 201 references.

2002-11-30

175

Microstructure-property relationships in discontinuous fiber reinforced thermoplastic composites  

Energy Technology Data Exchange (ETDEWEB)

A novel Aligned Discontinuous Fiber (ADF) composite process has been developed to optimize performance and processability of discontinuous fiber thermoplastic composites. The principle feature of this process is the alignment of the fibers using electric fields in air. The successful control of the orientation state of the fibers using the ADF process led to the fabrication of micro-structure controlled discontinuous fiber composites and the subsequent investigation into the microstructure-property relationships of these materials.

Vyakarnam, M.N.; Drzal, L.T. [Michigan State Univ., East Lansing, MI (United States)

1996-12-31

176

Structure-property relationships in redox-gated single molecule junctions--a comparison of pyrrolo-tetrathiafulvalene and viologen redox groups.  

Science.gov (United States)

We demonstrate that the electrical "switching" behavior of single molecules connected between two electrode contacts can be controlled by altering their structure and electrochemical characteristics. The electrical properties of gold|molecule|gold single molecule junctions incorporating HS(CH2)6-X-(CH2)6SH, where X = viologen (4,4'-bipyridinium) or pyrrolotetrathiafulvalene, are determined using a scanning tunneling microscopy based technique. The switching behavior, controlled through a tuneable electrochemical gate, changes from an on-off response (viologen) to an off-on-off response (pyrrolotetrathiafulvalene) on changing the central redox group. In contrast, the electrical properties of junctions incorporating redox-inactive HS(CH2)6-1,4-C6H4-(CH2)6SH do not alter significantly as a function of applied potential. PMID:18722447

Leary, Edmund; Higgins, Simon J; van Zalinge, Harm; Haiss, Wolfgang; Nichols, Richard J; Nygaard, Sune; Jeppesen, Jan Oskar; Ulstrup, Jens

2008-08-23

177

Dislocations in single hemp fibres-investigations into the relationship of structural distortions and tensile properties at the cell wall level  

DEFF Research Database (Denmark)

The relationship between dislocations and mechanical properties of single hemp fibres (Cannabis sativa L. var. Felina) was studied using a microtensile testing setup in a 2-fold approach. In a first investigation the percentage of dislocations was quantified using polarized light microscopy (PLM) prior to microtensile testing of the fibres. In a second approach PLM was used to monitor the dislocations while straining single fibres. The first part of the study comprised 53 hemp fibres with up to 20% of their cell wall consisting of dislocations. For this data set the percentage of dislocations did not affect the mechanical properties. In the second part of the study it was found that dislocations disappeared during tensile testing, and that they did not reappear until several weeks after failure. A strain stiffening effect due to the straightening of the dislocations was not observed. It is possible that the former positions of the dislocations functioned as locations for crack initiation. However, the crack does not propagate transversely all the way trough the dislocation but results in a shear failure between the microfibrils. In rheological studies fibres were strained at constant stress levels, and dislocations that had disappeared did not reappear during that period.

Thygesen, Lisbeth Garbrecht; Eder, M.

2007-01-01

178

Relationship between composition, structure, properties, thermo mechanical processing, and ballistic performance of tungsten heavy alloys. Final report, Mar 86-Jul 91  

Energy Technology Data Exchange (ETDEWEB)

Traditional tungsten heavy alloys are tungsten--nickel--iron or tungsten--nickel--copper alloys containing 88 to 98% tungsten. Cobalt is also used in these alloys but to a lesser extent. These alloys are produced by blending the elemental powders, pressing billets from the blend and then liquid-phase sintering the billets. These alloys were first developed to provide high density materials that were easy to machine but were developed with little concern for mechanical properties. Initially W-Ni-Cu alloys were most common because the low melting point of copper made these alloys easier to sinter. As the demand for alloys with good mechanical properties increased, a shift occurred from the W-Ni-Cu alloys to the W-Ni-Fe alloys. Processing techniques to consistently produce high quality tungsten heavy alloys were developed. The purpose of this program was to do a thorough study of tungsten heavy alloys and the interrelationship between chemical composition, impurities, thermo-mechanical processing history, structure and ballistic properties. Ballistic testing was to include a wide range of types and sizes ranging from an in house 20mm range to full scale testing.

Spencer, J.R.; Mullendore, J.A.

1991-11-01

179

Evaluation of a quantitative structure-property relationship (QSPR) for predicting mid-visible refractive index of secondary organic aerosol (SOA).  

UK PubMed Central (United Kingdom)

In this work we describe and evaluate a simple scheme by which the refractive index (? = 589 nm) of non-absorbing components common to secondary organic aerosols (SOA) may be predicted from molecular formula and density (g cm(-3)). The QSPR approach described is based on three parameters linked to refractive index-molecular polarizability, the ratio of mass density to molecular weight, and degree of unsaturation. After computing these quantities for a training set of 111 compounds common to atmospheric aerosols, multi-linear regression analysis was conducted to establish a quantitative relationship between the parameters and accepted value of refractive index. The resulting quantitative relationship can often estimate refractive index to ±0.01 when averaged across a variety of compound classes. A notable exception is for alcohols for which the model consistently underestimates refractive index. Homogenous internal mixtures can conceivably be addressed through use of either the volume or mole fraction mixing rules commonly used in the aerosol community. Predicted refractive indices reconstructed from chemical composition data presented in the literature generally agree with previous reports of SOA refractive index. Additionally, the predicted refractive indices lie near measured values we report for ? = 532 nm for SOA generated from vapors of ?-pinene (R.I. 1.49-1.51) and toluene (R.I. 1.49-1.50). We envision the QSPR method may find use in reconstructing optical scattering of organic aerosols if mass composition data is known. Alternatively, the method described could be incorporated into in models of organic aerosol formation/phase partitioning to better constrain organic aerosol optical properties.

Redmond H; Thompson JE

2011-04-01

180

Polymeric materials: structure, properties, applications  

Energy Technology Data Exchange (ETDEWEB)

The following topics were dealt with: economic development, market review and predictions, characteristics of polymeric materials, thermoplastics, thermosets, elastomers, blends, molecular structure and synthesis, structure of polymeric materials, thermomechanical properties, mechanical behaviour, aging and stabilization, selected polymeric materials, guide values of the physical properties (WL)

Ehrenstein, G.W. [Erlangen-Nuernberg Univ., Erlangen (Germany). Lehrstuhl fuer Kunststofftechnik

2001-07-01

 
 
 
 
181

Vanadates: composition, synthesis, structure, properties  

International Nuclear Information System (INIS)

[en] Data on phase composition, phase equilibria, thermal, thermodynamic, structural and chemical properties of s-, d- and f- element oxides, containing pentavalent vanadium, are given. The synthesis, formation conditions and application fields of the vanadates are considered. Electron structure, magnetic properties, electrophysical and transport characteristics, the nature of ordering, thermostimulated luminescence of the vanadates, are discussed

1988-01-01

182

Divergent Structure-Activity Relationships of Structurally Similar Acetylcholinesterase Inhibitors.  

UK PubMed Central (United Kingdom)

The molecular interactions between the enzyme acetylcholinesterase (AChE) and two compound classes consisting of N-[2-(diethylamino)-ethyl]-benzenesulfonamides and N-[2-(diethylamino)-ethyl]-benzenemethanesulfonamides have been investigated using organic synthesis, enzymatic assays, X-ray crystallography, and thermodynamic profiling. The inhibitors' aromatic properties were varied to establish structure-activity relationships (SAR) between the inhibitors and the peripheral anionic site (PAS) of AChE. The two structurally similar compound classes proved to have distinctly divergent SARs in terms of their inhibition capacity of AChE. Eight X-ray structures revealed that the two sets have different conformations in PAS. Furthermore, thermodynamic profiles of the binding between compounds and AChE revealed class-dependent differences of the entropy/enthalpy contributions to the free energy of binding. Further development of the entropy-favored compound class resulted in the synthesis of the most potent inhibitor, and an extension beyond the established SARs. The divergent SARs will be utilized to develop reversible inhibitors of AChE into reactivators of nerve agent inhibited AChE.

Andersson CD; Forsgren N; Akfur C; Allgardsson A; Berg L; Engdahl C; Qian W; Ekström FJ; Linusson A

2013-08-01

183

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; ForoughRafii; RahmatollahKharazmirahimabadi

2012-01-01

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

Study of physicochemical interaction of aryloxyaminopropanol derivatives with teicoplanin and vancomycin phases in view of quantitative structure-property relationship studies.  

UK PubMed Central (United Kingdom)

The aim of this work was to study the physicochemical interactions between chiral stationary phases and chiral molecules and to elucidate which of the specific interactions are more or less important. The HPLC separation of 58 aryloxyaminopropanols was performed on two chiral stationary phases containing the macrocyclic antibiotics teicoplanin or vancomycin and using a methanol/acetonitrile/acetic acid/triethylamine mobile phase (volume ratios 45/55/0.3/0.2). The resolution of enantiomers (Rij) as the target variable was predicted for the mentioned kind of compounds by means of thoroughly selected descriptors provided by the applied Dragon software. The created QSPR models can be considered as a way to explore and discover new relationships or interactions between the quantitative structure and resolution of enantiomers. For calculation and validation of the QSPR models, different modelling methodologies were applied based on MLR (multiple linear regression) and ANN (artificial neural network) techniques. Both methods exhibit an ability for successful prediction of the enantioresolution characteristics of the studied molecules. The results seem to demonstrate that it is possible to predict resolution values of enantiomeric separations of related compounds on given chromatographic systems.

Boronová K; Lehotay J; Hrobo?ová K; Armstrong DW

2013-08-01

187

Relationship between time structure and procrastination.  

UK PubMed Central (United Kingdom)

The relationship between time structure and procrastination was investigated among 115 Irish undergraduate students. Significant negative zero-order correlations were found among scores for all five subscales of time structure and procrastination. A follow-up stepwise multiple regression indicated a significant multiple correlation (R = .61) between all five time structure subscale scores and procrastination. Significant predictors of procrastination were scores on the Time Structure subscales of Effective Organization followed by Sense of Purpose. These results suggest that strategies focusing on time management in conjunction with existential approaches of psychotherapy may be an effective intervention for reducing procrastination.

Vodanovich SJ; Seib HM

1997-02-01

188

Relationship between time structure and procrastination.  

Science.gov (United States)

The relationship between time structure and procrastination was investigated among 115 Irish undergraduate students. Significant negative zero-order correlations were found among scores for all five subscales of time structure and procrastination. A follow-up stepwise multiple regression indicated a significant multiple correlation (R = .61) between all five time structure subscale scores and procrastination. Significant predictors of procrastination were scores on the Time Structure subscales of Effective Organization followed by Sense of Purpose. These results suggest that strategies focusing on time management in conjunction with existential approaches of psychotherapy may be an effective intervention for reducing procrastination. PMID:9122329

Vodanovich, S J; Seib, H M

1997-02-01

189

Polysaccharide research: comparative studies on the structure/property relationship of cellulose and amylose derivatives. Final report; Polysaccharidforschung: Vergleichende Untersuchungen zur Struktur-Eigenschaftsrelation von Cellulose und Amylosederivaten. Schlussbericht  

Energy Technology Data Exchange (ETDEWEB)

The aim of the research project was to improve the basic knowledge and provide physicochemical data on the utilisation of polysaccharides as a vegetable raw material with a high yield. In particular, the relationships between the structure, dynamics and properties of solid cellulose and amylose derivatives were to be studied so as to permit predictions on the utility, quality and processability of films, fibres and solids. The set aims were reached. Indicious selection of samples, and, in particular, selective derivativisation yielded, on the one hand, practice-relevant data on derivatized vegetable raw materials and, on the other hand, revealed basic structure/property relationships. (orig.) [Deutsch] Die Zielsetzung des Forschungsvorhabens war die Verbesserung des Grundlagenwissens und die Bereitstellung von physikalisch-chemischen Daten zum Einsatz von Polysacchariden als nachwachsende Rohstoffe mit hoher Wertschoepfung. Insbesondere sollten die Zusammenhaenge zwischen Struktur, Dynamik und Eigenschaften von festen Cellulose- und Amylosederivaten aufgezeigt werden, um Vorhersagen ueber spezielle Verwertbarkeit, Guete und Verarbeitbarkeit von Filmen, Fasern und Feststoffen treffen zu koennen. Die gesteckten Ziele wurden erreicht. Durch eine sorgfaeltige Auswahl von Proben, insbesondere durch selektive Derivatisierung, konnten auf der einen Seite praxisrelevante Daten derivatisierter, nachwachsender Rohstoffe gewonnen, auf der anderen Seite allgemeine Zusammenhaenge zwischen Struktur und Eigenschaften aufgezeigt werden. (orig.)

Zugenmaier, P.; Henze-Wethkamp, H.

1993-06-01

190

Structure-property relationships in the R-type hexaferrites: cation distributions and magnetic susceptibilities of MX2Fe4O11  

International Nuclear Information System (INIS)

The strong, and heretofore unexplained, dependence of the magnetic properties of the R-type hexaferrites MX2Fe4O11 on heat treatment has been investigated by means of 57Fe and 119Sn Moessbauer spectroscopy at 297 K. 57Fe Moessbauer spectra of samples of BaTi2Fe4O11, BaSn2Fe4O11, and SrSn2Fe4O11 annealed at several temperatures consist of three partially resolved quadrupole doublet patterns. The pattern with the very large quadrupole splitting, i.e. 1.3 mm s-1 ? ?EQ ? 1.7 mm s-1, is readily assigned to the trigonal bipyramidal site, and exhibits no dependence of its parameters, including the relative intensity, on heat treatment. The remaining two patterns are assigned to Fe3+ ions on octahedral sites, and exhibit relative intensities that are strongly dependent on heat treatment. The 119Sn spectrum of BaSn2Fe4O11 is a broad, apparently single line that, with the exception of verifying the presence of tin as Sn4+, provides little insight into the details of the structure. The distributions of the cations over all the lattice sites have been deduced from the Moessbauer spectra and compared with the magnetic susceptibility data. It is concluded that the cation distributions of the Sn-containing phase are not strongly dependent on heat treatment, and the magnetic properties exhibit a similar insensitivity to heat treatment. The Ti analogs exhibit a strong dependence of cation distribution on heat treatment, which is reflected in widely varying magnetic ordering temperatures, a variation that is confirmed by the incipient magnetic hyperfine splitting despite the strong magnetic frustration in the R-type hexaferrites. (orig.).

1994-01-01

191

The synthesis, photophysical and photobiological properties and in vitro structure-activity relationships of a set of silicon phthalocyanine PDT photosensitizers.  

UK PubMed Central (United Kingdom)

Four silicon phthalocyanine photosensitizers have been prepared and studied in an effort to learn more about the structural features that a silicon phthalocyanine must have in order to be a good photodynamic therapy (PDT) photosensitizer. The compounds that have been studied are the known phthalocyanines HOSiPcOSi(CH3)2-(CH2)3N(CH3)2, Pc 4; and SiPc[OSi(CH3)2(CH2)3N(CH3)2]2, Pc 12; and the new photosensitizers HOSiPcOSi(CH3)2- (CH2)3N(CH2CH3)(CH2)2N(CH3)2, Pc 10; and SiPc[OSi (CH3)2(CH2)3N(CH2CH3)(CH2)2N(CH3)2]2, Pc 18. The triplet lifetimes of the four photosensitizers, their singlet oxygen quantum yields, their ability to photoenhance the generation of lipid peroxidation products in human erythrocyte ghosts, their ability to partition into V79 cells and their ability to photokill V79 and L5178Y-R cells have been determined. It is concluded that the presence of a small axial ligand (e.g. an OH ligand) is not necessary for efficient photosensitization, the presence of two aminosiloxy ligands generally provides at least as good photosensitization as one such ligand, and the presence of an elongated diaminosiloxy axial ligand rather than a short aminosiloxy ligand is less desirable. Further, it is concluded that the presence of structural features leading to improvement in the association between the photosensitizers and important cellular targets are more useful than those leading to improvements in their already acceptable photophysical and photochemical properties.

He J; Larkin HE; Li YS; Rihter D; Zaidi SI; Rodgers MA; Mukhtar H; Kenney ME; Oleinick NL

1997-03-01

192

The synthesis, photophysical and photobiological properties and in vitro structure-activity relationships of a set of silicon phthalocyanine PDT photosensitizers.  

Science.gov (United States)

Four silicon phthalocyanine photosensitizers have been prepared and studied in an effort to learn more about the structural features that a silicon phthalocyanine must have in order to be a good photodynamic therapy (PDT) photosensitizer. The compounds that have been studied are the known phthalocyanines HOSiPcOSi(CH3)2-(CH2)3N(CH3)2, Pc 4; and SiPc[OSi(CH3)2(CH2)3N(CH3)2]2, Pc 12; and the new photosensitizers HOSiPcOSi(CH3)2- (CH2)3N(CH2CH3)(CH2)2N(CH3)2, Pc 10; and SiPc[OSi (CH3)2(CH2)3N(CH2CH3)(CH2)2N(CH3)2]2, Pc 18. The triplet lifetimes of the four photosensitizers, their singlet oxygen quantum yields, their ability to photoenhance the generation of lipid peroxidation products in human erythrocyte ghosts, their ability to partition into V79 cells and their ability to photokill V79 and L5178Y-R cells have been determined. It is concluded that the presence of a small axial ligand (e.g. an OH ligand) is not necessary for efficient photosensitization, the presence of two aminosiloxy ligands generally provides at least as good photosensitization as one such ligand, and the presence of an elongated diaminosiloxy axial ligand rather than a short aminosiloxy ligand is less desirable. Further, it is concluded that the presence of structural features leading to improvement in the association between the photosensitizers and important cellular targets are more useful than those leading to improvements in their already acceptable photophysical and photochemical properties. PMID:9077144

He, J; Larkin, H E; Li, Y S; Rihter, D; Zaidi, S I; Rodgers, M A; Mukhtar, H; Kenney, M E; Oleinick, N L

1997-03-01

193

Using structural relationships for focused XML retrieval  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In focused XML retrieval, information retrieval systems have to find out which are the most appropriate retrieval units and return only these to the user, avoiding overlapping elements in the result lists. This paper studies structural relationships between elements and explains how they can be used...

Ramirez, G.; de Vries, A.; Westerveld, T.

194

Extremal Properties of Random Structures  

CERN Multimedia

The extremal characteristics of random structures, including trees, graphs, and networks, are discussed. A statistical physics approach is employed in which extremal properties are obtained through suitably defined rate equations. A variety of unusual time dependences and system-size dependences for basic extremal properties are obtained.

Ben-Naim, E; Redner, S

2004-01-01

195

Structure-function relationship of gonadotropins  

Energy Technology Data Exchange (ETDEWEB)

In this book, investigators highlight progress recently made in research on the structure-function relationship of gonadotropins. The contributors provide coverage of major breakthroughs such as the cloning of the ovarian receptor for lutropin and choriogonadotropin, the elucidation of the structure of this receptor, and the first crystallographic studies of human chorionic gonadotropin. The book also describes significant advances in the epitope mapping of gonadotropins, the immunochemical and biochemical study of their structure, the examination of regulatory processes involved in subunit association, and the elucidation of the complex mechanisms responsible for regulation and expression of gonadotropin genes.

Bellet, D.; Bidart, J.M.

1989-01-01

196

Structure-Function-Property-Design Interplay in Biopolymers: Spider Silk.  

UK PubMed Central (United Kingdom)

Spider silks have been a focus of research for almost two decades due to their outstanding mechanical and biophysical properties. Recent advances in genetic engineering have led to the synthesis of recombinant spider silks, thus helping to unravel a fundamental understanding of structure-function-property relationships. The relationships between molecular composition, secondary structures, and mechanical properties found in different types of spider silks are described, along with a discussion of artificial spinning of these proteins and their bioapplications, including the role of silks in biomineralization and fabrication of biomaterials with controlled properties.

Tokareva O; Jacobsen M; Buehler M; Wong J; Kaplan DL

2013-08-01

197

RELATIONSHIP BETWEEN BOARD STRUCTURE AND CONSERVATISM  

Directory of Open Access Journals (Sweden)

Full Text Available The rule of conservatism plays an important role for the. Corporate governance, data collection mechanism provides. Thereby to ensure that company assets are used efficiently. And improper distribution of assets to be managers and other groups prevent. In this paper, the relationship between board structure and conservatism has been studied. The sample includes 55 companies listed in Tehran Stock Exchange during the period 1385 to 1389.The period of investigation, gathering information about the study variables were the companies listed in Tehran Stock Exchange. The data in this study, both descriptive and inferential statistics using excel software and spss16 has been analyzed. The inferential statistics of Pearson correlation test and regression analysis, Thedescriptive statistics and data analysis using the mean and standard deviation are. The results indicate that test hypotheses, No relationship between board structure characteristics with the level of conservatism in the company are not listed in Tehran Stock Exchange.

Shahram Gilaninia; Reza Salimi Chena; Behnam Shadi Dizaj; Seyyed Javad Mousavian

2011-01-01

198

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

1987-01-01

199

The relationship of structural defect-redox property-catalytic performance of perovskites and their related compounds for CO and NO{sub x} removal  

Energy Technology Data Exchange (ETDEWEB)

Perovskite-type oxides La{sub 1-x}A{sub x}'Co{sub 1-y}Bi{sub y}O{sub 3-{delta}} (A{sub x}' = Ba{sub 0.2}, Sr{sub 0.4}; y=0, 0.2) and La{sub 1-x}Sr{sub x}MO{sub 3-{delta}} (M = Co{sub 0.77}Bi{sub 0.20}Pd{sub 0.03}, x=0, 0.2, 0.4) and perovskite-like oxides La{sub 1.867}Th{sub 0.100}CuO{sub 4-{delta}}, Nd{sub 2-x}A{sub x}'CuO{sub 4-{delta}} (A{sub x}' = Ba{sub 0.4}, Ce{sub 0.2}), and YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} have been investigated as catalysts for CO oxidation, NO removal, and N{sub 2}O decomposition, respectively. X-ray diffraction results revealed that (1) all of these materials were single phase, and (2) the crystal structures of La{sub 1-x}A{sub x}'Co{sub 1-y}Bi{sub y}O{sub 3-{delta}}, La{sub 1-x}Sr{sub x}MO{sub 3-{delta}}, La{sub 1.867}Th{sub 0.100}CuO{sub 4-{delta}}, Nd{sub 2-x}A{sub x}'CuO{sub 4-{delta}}, and YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} were cubic, orthorhombic, tetragonal (T structure), tetragonal (T' structure), and orthorhombic, respectively. The results of chemical analysis indicated that (1) there were Co{sup 4+}/Co{sup 3+} ions in La{sub 1-x}A{sub x}'CoO{sub 3-{delta}} (A{sub x}'= Ba{sub 0.2}, Sr{sub 0.4}), Co{sup 2+}/Co{sup 3+} and Bi{sup 5+}/Bi{sup 3+} ions in La{sub 1-x}A{sub x}'Co{sub 0.8}Bi{sub 0.2}O{sub 3-{delta}} (A{sub x}'= Ba{sub 0.2}, Sr{sub 0.4}) and La{sub 1-x}Sr{sub x}MO{sub 3-{delta}}, Cu{sup 2+}/Cu{sup 3+} ions in La{sub 1.867}Th{sub 0.100}CuO{sub 4-{delta}}, Nd{sub 2}CuO{sub 4-{delta}}, Nd{sub 1.6}Ba{sub 0.4}CuO{sub 4-{delta}}, and YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}; and (2) after pretreatments in H{sub 2} or helium at certain temperature, Cu{sup +}/Cu{sup 2+} ion couples appeared in these cuprate samples. Oxygen isotope exchange experiments indicated that the lattice oxygen mobility in the Bi-doped catalysts were much higher than that in the Bi-free ones. TPR results showed that lattice oxygen in the former samples could be reduced at temperatures lower than those in the latter samples. In the oxidation of CO, the Bi-incorporated catalysts performed much better than the corresponding Bi-free catalysts, the Sr-substituted perovskites showed higher catalytic activities than the Ba-substituted ones; among La{sub 1-x}Sr{sub x}MO{sub 3-{delta}}, La{sub 0.8}Sr{sub 0.2}MO{sub 2.90} exhibited the best catalytic activity. The improved catalytic performance due to the Sr (or Ba)- and Bi-doping is believed to be associated with the enhancements in oxygen vacancy density and Co{sup n+}/Co{sup (n+1)+} (n=2, 3) and Bi{sup 3+}/Bi{sup 5+} couple redox ability as well as in lattice oxygen mobility. In the elimination of NO over La{sub 1-x}Sr{sub x}MO{sub 3-{delta}}, La{sub 0.8}Sr{sub 0.2}MO{sub 2.90} performed the best. The 300C-reduced La{sub 1.867}Th{sub 0.100}CuO{sub 4-{delta}} catalyst that possessed dual cationic and anionic defects and Cu{sup +}/Cu{sup 2+} couple showed higher DeNO activity than the fresh one; the redox action between Cu{sup +} and Cu{sup 2+} is an essential process for NO decomposition. In the decomposition of N{sub 2}O, the 800C-treated Nd{sub 2-x}A{sub x}'CuO{sub 4-{delta}} (A{sub x}'= Ba{sub 0.4}, Ce{sub 0.2}) and YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} samples were superior in catalytic performance to their fresh counterparts; oxygen vacancies were favorable for the formation of the crucial N{sub 2}O{sub 2}{sup 2-} intermediate species in N{sub 2}O activation, and the redox Cu{sup p+}/Cu{sup (p+1)+} (p=1 and 2) couples involved in the N{sub 2}O decomposition processes. The DeN{sub 2}O activity over the Ce- or Ba-doped catalyst was much better than that over the undoped catalyst (Nd{sub 2}CuO{sub 4-{delta}}). This behavior is intimately related to the oxygen nonstoichiometry and copper ion redox properties. According to the outcome of our experiments, we conclude that there is a strong correlation either between the structural defect (mainly oxygen vacancies) and catalytic activity or between the redox [Co{sup n+}/Co{sup (n+1)+} (n=2, 3), Bi{sup 3+}/Bi{sup 5+}, and Cu{sup p+}/Cu{sup (p+1)+} (p=1 and 2) c

Dai, Hongxing; He, Hong; Li, Peiheng [Department of Applied Chemistry, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100022 (China); Gao, Lizhen [Department of Applied Chemistry, Shenzhen University, Shenzhen 518060 (China); Au, Chak-Tong [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong (Hong Kong)

2004-07-01

200

Foldamers structure, properties and applications  

CERN Multimedia

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

 
 
 
 
201

Coal devolatilisation relationship with coal structure  

Energy Technology Data Exchange (ETDEWEB)

Coal devolatilization is a complex chemical and physical process which directly depends on the chemical composition and structure of the parent coal as well as the operating condition. Recent research on the modelling of coal devolatilization has produced coal structure based models which aim to predict devolatilization behaviour for any coal under any operating conditions. Owing to the complexity of coal, determining the appropriate parameters, which can specify the coal structure and reflect the effects of coal structure on the devolatilization behaviour, has been a major concern in the modelling coal devolatilization. The development of advanced techniques such as {sup 13}C Nuclear Magnetic Resonance (NMR) spectroscopy and TG-FTIR has greatly increased the availability of coal structural data, and has promoted the development of devolatilization models. This paper examines the Chemical Percolation Devolatilization (CPD) model which uses five molecular structural parameters, which are directly derived from NMR data, to produce the initial coal micro-molecular configuration. Also included is an analysis of the relationship between the NMR data, the input structural parameters of the CPD model, and its predictions. The variation of the NMR parameters with coal rank is also detailed. (author).

Shan, G.; Tate, A.G.; Wall, T.F.; Kennedy, E. [Newcastle Univ., NSW (Australia). Dept. of Chemical Engineering

1997-04-01

202

Organisation Structurale et Texturale de Polymeres Traites Thermiquement, Relations Avec les Proprietes Mecaniques (Textural and Structural Organization of the Heat Treated Polymers: Mechanical Properties Relationships).  

Science.gov (United States)

The microstructure and the texture of ceramics obtained from organometallic polymer manufacturing are investigated. The interfaces and the bulk structure of the carbon fiber resin composite materials are studied. The transmission electron microscopy and x...

A. Oberlin M. Monthioux

1989-01-01

203

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%.

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

2013-01-01

204

Structure-phase morphology - Property relationship of a series of light-emitting alternating copolymers with distyrylbenzenes segments and oligo(ethylene oxide) spacers  

Energy Technology Data Exchange (ETDEWEB)

A series of light-emitting alternating copolymers: DSB-TEO, DSB-SEO, DSB-PEO{sub 1500} and dimethoxy(DM)DSB-SEO, consisting of 1,4-distyrylbenzene (DSB) and different length of ionic conducting oligomer ethylene oxide (OEO) spacers, were synthesized. The thermal stabilities, electrochemical behavior and photoluminescent properties of these polymers were studied systematically. It was found that with increasing OEO chain length, the solubility, film-forming property and relative fluorescence quantum yield were improved accordingly. The introduction of two methoxy groups as side chains into the DSB segment to form DMDSB not only enhanced the film-forming property, but also improved the quantum efficiency of the polymer. Phase contrast microscopy, polarized optical microscopy and atomic force microscopy (AFM) were employed to investigate the phase morphology of the thin films prepared from the pure polymer or polymer/LiCF{sub 3}SO{sub 3} blends. Results revealed that compared with pure polymer thin films, there was significant change in the phase morphology of the thin films prepared from polymer/LiCF{sub 3}SO{sub 3} blends. The reason could be attributed to the contrary roles of dissolved and undissolved lithium salt played in the polymer matrix, which was discussed in detail in the paper. Phase morphology study of DMDSB-SEO revealed that, compared with DSB-SEO, there was much less crystallization of OEO segments and the solubility of lithium salt had increased greatly. Furthermore, AFM was used to investigate the dependence of surface morphology on the spin-coat processing conditions, such as the solvents, substrates and rotation rate. A light-emitting electrochemical cell device of the copolymer was fabricated, and the brightness and maximum external quantum efficiency of the device were investigated.

Wang Haiqiao; Wang Huanfang [Key Laboratory for Nanomaterials, Ministry of Education, School of Materials Science and Technology, Beijing University of Chemical Technology, No. 15, Beisanhuan East Road, Beijing 100029 (China); Zhang Aiqing [Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, Hubei Province, South-Central University for Nationalities, Wuhan 430074 (China); Wen Fangdai; Song Na [Key Laboratory for Nanomaterials, Ministry of Education, School of Materials Science and Technology, Beijing University of Chemical Technology, No. 15, Beisanhuan East Road, Beijing 100029 (China); Li Xiaoyu [Key Laboratory for Nanomaterials, Ministry of Education, School of Materials Science and Technology, Beijing University of Chemical Technology, No. 15, Beisanhuan East Road, Beijing 100029 (China)], E-mail: Lixy@mail.buct.edu.cn

2008-08-15

205

Structure-phase morphology - Property relationship of a series of light-emitting alternating copolymers with distyrylbenzenes segments and oligo(ethylene oxide) spacers  

International Nuclear Information System (INIS)

A series of light-emitting alternating copolymers: DSB-TEO, DSB-SEO, DSB-PEO1500 and dimethoxy(DM)DSB-SEO, consisting of 1,4-distyrylbenzene (DSB) and different length of ionic conducting oligomer ethylene oxide (OEO) spacers, were synthesized. The thermal stabilities, electrochemical behavior and photoluminescent properties of these polymers were studied systematically. It was found that with increasing OEO chain length, the solubility, film-forming property and relative fluorescence quantum yield were improved accordingly. The introduction of two methoxy groups as side chains into the DSB segment to form DMDSB not only enhanced the film-forming property, but also improved the quantum efficiency of the polymer. Phase contrast microscopy, polarized optical microscopy and atomic force microscopy (AFM) were employed to investigate the phase morphology of the thin films prepared from the pure polymer or polymer/LiCF3SO3 blends. Results revealed that compared with pure polymer thin films, there was significant change in the phase morphology of the thin films prepared from polymer/LiCF3SO3 blends. The reason could be attributed to the contrary roles of dissolved and undissolved lithium salt played in the polymer matrix, which was discussed in detail in the paper. Phase morphology study of DMDSB-SEO revealed that, compared with DSB-SEO, there was much less crystallization of OEO segments and the solubility of lithium salt had increased greatly. Furthermore, AFM was used to investigate the dependence of surface morphology on the spin-coat processing conditions, such as the solvents, substrates and rotation rate. A light-emitting electrochemical cell device of the copolymer was fabricated, and the brightness and maximum external quantum efficiency of the device were investigated.

2008-01-01

206

Synthesis and structure-activity relationships of ring-opened 17-hydroxywortmannins: potent phosphoinositide 3-kinase inhibitors with improved properties and anticancer efficacy.  

Science.gov (United States)

The phosphoinositide 3-kinase (PI3K) signaling pathway is frequently up-regulated in human cancer and is a promising target for the treatment of cancer. Wortmannin and its analogues are potent inhibitors of PI3K but suffer from inherent defects such as instability, insolubility, and toxicity. Opening of the reactive furan ring of 17-hydroxywortmannin with amines gives compounds with improved properties such as greater stability and aqueous solubility and a larger therapeutic index. Ring-opened analogues such as compound 13 containing basic amine groups have significantly increased PI3K inhibitory potency and greater efficacy in nude mouse xenograft assays. PMID:18269228

Zask, Arie; Kaplan, Joshua; Toral-Barza, Lourdes; Hollander, Irwin; Young, Mairead; Tischler, Mark; Gaydos, Christine; Cinque, Michael; Lucas, Judy; Yu, Ker

2008-02-13

207

Structure-property correlations in strontium titanate  

International Nuclear Information System (INIS)

Being a model system for oxides with perovskite-type of structure, strontium titanate can be used to gain generalizable insights into the consequences of defects and to discuss resulting structure-property relationships. By employing different surface sensitive methods, an increased concentration of line defects is found at the surface that reduces on temperature treatment. The defect chemistry at elevated temperatures is used to simulate the electric conductivity depending on the oxygen partial pressure during annealing. Doping of the oxidic semiconductor depends on intrinsic defects, whereby oxygen vacancies form donor states and strontium vacancies have acceptor character. Beside the diffusion movement of these intrinsic defects at elevated temperatures, at low temperatures an electric field may cause their redistribution. Hence, the conductivity becomes dependent on external electric fields but also other properties can be altered in this way. Within this work, structural changes, valence changes and changing mechanical properties are shown to be switchable by the electric field. Finally, the dedicated usage of structural defects is demonstrated on memory cells that employ the switchable resistance of metal-SrTiO3 junctions. The applicability of the oxidic semiconductor as a resistive memory element is again based on the coupling between oxygen vacancies and the electric field.

2011-01-01

208

Controlled synthesis and relationship between luminescent properties and shape/crystal structure of Zn{sub 2}SiO{sub 4}:MN{sup 2+} phosphor  

Energy Technology Data Exchange (ETDEWEB)

Mn-doped Zn{sub 2}SiO{sub 4} phosphors with different morphology and crystal structure, which show different luminescence and photoluminescence intensity, were synthesized via a low-temperature hydrothermal route without further calcining treatment. As-synthesized zinc silicate nanostructures show green or yellow luminescence depending on their different crystal structure obtained under different preparation conditions. The yellow peak occurring at 575 nm comes from the {beta}-phase zinc silicate, while the green peak centering at 525 nm results from the usual {alpha}-phase zinc silicate. From photoluminescence spectra, it is found that Zn{sub 2}SiO{sub 4} nanorods have higher photoluminescence intensity than Zn{sub 2}SiO{sub 4} nanoparticles. It can be ascribed to reduced surface-damaged region and high crystallinity of nanorods.

Wan Junxi [Hefei National Laboratory for Physical Sciences at Microscale and Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026 (China)]. E-mail: wanjx@mail.ustc.edu.cn; Wang Zhenghua [Hefei National Laboratory for Physical Sciences at Microscale and Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026 (China); Chen Xiangying [Hefei National Laboratory for Physical Sciences at Microscale and Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026 (China); Mu Li [Hefei National Laboratory for Physical Sciences at Microscale and Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026 (China); Yu Weichao [Hefei National Laboratory for Physical Sciences at Microscale and Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026 (China); Qian Yitai [Hefei National Laboratory for Physical Sciences at Microscale and Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026 (China)]. E-mail: ytqian@ustc.edu.cn

2006-11-15

209

Ginkgolides and glycine receptors : a structure-activity relationship study  

DEFF Research Database (Denmark)

Ginkgolides from the Ginkgo biloba tree are diterpenes with a cage structure consisting of six five-membered rings and a unique tBu group. They exert a variety of biological properties. In addition to being antagonists of the platelet activating factor receptor (PAFR), it has recently been shown that native ginkgolides are potent and selective antagonists of the inhibitory glycine receptor. Forty new ginkgolide derivatives have been prepared in good to high yields on milligram scales and investigated for their antagonistic properties at homomeric alpha 1 glycine receptors, thus providing the first structure-activity relationship study of ginkgolides at glycine receptors. A high-throughput screening assay showed that native ginkgolide C was the most potent ligand, and that manipulation of any of the hydroxyl groups led to loss of activity at alpha 1 glycine receptors.

Jaracz, Stanislav; Nakanishi, Koji

2004-01-01

210

Structure-cytotoxicity relationship of tilivalline derivatives.  

Science.gov (United States)

Tilivalline (TV) possesses a pyrrolo[1,4]benzodiazepine nucleus and an indole substituent in its structure, and is cytotoxic toward mouse leukemia L1210 cells. In order to obtain more effective compounds, we have previously synthesized a variety of TV analogues. In this study, the cytotoxicity of these compounds has been evaluated. Among the compounds tested, the 11-beta-cyano compound, a TV analogue bearing the cyano group instead of the indole group, is approximately 100 times more cytotoxic than TV itself. The alpha-epimer of this cyano compound has about one-hundredth the cytotoxicity of the 11-beta-cyano compound. Structure-cytotoxicity relationships are discussed, including the effects of stereoisomers (alpha and beta) at the 11 position and substitution at the benzene moiety of TV. PMID:7710637

Shioiri, T; Aoyama, T; Yamagami, N; Shimizu, N; Mori, N; Kohda, K

1995-03-01

211

Structure-cytotoxicity relationship of tilivalline derivatives.  

UK PubMed Central (United Kingdom)

Tilivalline (TV) possesses a pyrrolo[1,4]benzodiazepine nucleus and an indole substituent in its structure, and is cytotoxic toward mouse leukemia L1210 cells. In order to obtain more effective compounds, we have previously synthesized a variety of TV analogues. In this study, the cytotoxicity of these compounds has been evaluated. Among the compounds tested, the 11-beta-cyano compound, a TV analogue bearing the cyano group instead of the indole group, is approximately 100 times more cytotoxic than TV itself. The alpha-epimer of this cyano compound has about one-hundredth the cytotoxicity of the 11-beta-cyano compound. Structure-cytotoxicity relationships are discussed, including the effects of stereoisomers (alpha and beta) at the 11 position and substitution at the benzene moiety of TV.

Shioiri T; Aoyama T; Yamagami N; Shimizu N; Mori N; Kohda K

1995-03-01

212

Structure-property relationships in self-assembled metalorganic chemical vapor deposition-grown CoFe{sub 2}O{sub 4-}-PbTiO{sub 3} multiferroic nanocomposites using three-dimensional characterization.  

Energy Technology Data Exchange (ETDEWEB)

Multiferroic nanocomposites, consisting of branched, ferrimagnetic CoFe{sub 2}O{sub 4} filaments and large protruding PbTiO{sub 3} particles embedded in a piezoelectric PbTiO{sub 3} matrix, have been fabricated by co-deposition using metalorganic chemical vapor deposition. Branched CoFe{sub 2}O{sub 4} filaments reduce the CoFe{sub 2}O{sub 4}/PbTiO{sub 3} interfacial strain and induce a perpendicular magnetic anisotropy. Three-dimensional characterizations reveal that in addition to the c-domain, grains with a second orientation in PbTiO{sub 3} particles contribute to an additional four apparent variants of polarization. In contrast, the PbTiO{sub 3} matrix exhibits only c-domain polarization with a smaller magnitude. The smaller piezoresponse results from the constraints imposed by the branched CoFe{sub 2}O{sub 4} filaments. Three-dimensional microstructure and property analysis provide a comprehensive insight on the structure-property relationship of multiferroic nanocomposites grown by metalorganic chemical vapor deposition.

Pan, M.; Liu, Y.; Bai, G.; Hong, S.; Dravid, V. P.; Petford-Long, A. K. (Center for Nanoscale Materials); ( MSD); (Northwestern Univ.)

2011-01-01

213

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

214

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

International Nuclear Information System (INIS)

[en] 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

215

Selection of a respiratory syncytial virus fusion inhibitor clinical candidate, part 1: improving the pharmacokinetic profile using the structure-property relationship.  

UK PubMed Central (United Kingdom)

We previously reported the discovery of substituted benzimidazole fusion inhibitors with nanomolar activity against respiratory syncytial virus (Andries, K.; et al. Antiviral Res. 2003, 60, 209-219). A lead compound of the series was selected for preclinical evaluation. This drug candidate, JNJ-2408068 (formerly R170591, 1), showed long tissue retention times in several species (rat, dog, and monkey), creating cause for concern. We herein describe the optimization program to develop compounds with improved properties in terms of tissue retention. We have identified the aminoethyl-piperidine moiety as being responsible for the long tissue retention time of 1. We have investigated the replacement or the modification of this group, and we suggest that the pKa of this part of the molecules influences both the antiviral activity and the pharmacokinetic profile. We were able to identify new respiratory syncytial virus inhibitors with shorter half-lives in lung tissue.

Bonfanti JF; Doublet F; Fortin J; Lacrampe J; Guillemont J; Muller P; Queguiner L; Arnoult E; Gevers T; Janssens P; Szel H; Willebrords R; Timmerman P; Wuyts K; Janssens F; Sommen C; Wigerinck P; Andries K

2007-09-01

216

Materials with a cluster structure. New properties, new possibilities  

International Nuclear Information System (INIS)

The author examines the structural special features, growth relationships and physical properties of a group of relatively new materials which includes quasicrystals, fullerites, aerogels, porous silicon. These materials are interesting because of their cluster structure. They include metallic alloys, semiconductor and molecular crystals, and disordered solidified gels. The nanocrystalline structure of the cluster materials determines their characteristic properties and unconventional properties, including those used in applied aspects. Special attention is given to the role of noise regarded as the statistical aspect in the formation of the cluster structure of the material in the aggregation condition, limited by diffusion during growth under highly non-equilibrium conditions. (author)

1998-01-01

217

Relationships between structure and superconducting properties in new ternary silicides of the systems: rare earths or thorium - transition metal (Rh or Ir) - silicon  

Energy Technology Data Exchange (ETDEWEB)

Nine families of ternary silices Msub(x) Tsub(y)Sisub(z) have been prepared in the rare earths of thorium (M) - transition metals (T = Th or Ir) - silicon systems: MT/sub 3/Si/sub 2/, MT/sub 2/Si/sub 2/ (two polymorphic forms), MTSi (TiNiSi and SrSi/sub 2/-type), M/sub 2/T/sub 3/Si/sub 5/, MTSi/sub 2/, MTSi/sub 3/ and M/sub 2/TSi/sub 3/. The occurence of superconductivity in these compounds has been related both to their crystal structure and composition.

Chevalier, S.; Lejay, P.; Lloret, B.; Wang-Xian-Zhong; Etourneau, J.; Hagenmuller, P. (Laboratoire de Chimie du Solide du CNRS, Universite de Bordeaux-1, 33 - Talence (France))

1984-01-01

218

Unveiling Structure Property Relationships in Sr2Fe1.5Mo0.5O6 , an Electrode Material for Symmetric Solid Oxide Fuel Cells  

Energy Technology Data Exchange (ETDEWEB)

We characterize experimentally and theoretically the promising new solid oxide fuel cell electrode material Sr2Fe1.5Mo0.5O6 (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 Sr2Fe1.5Mo0.5O5.90(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.

Hodges, Jason P [ORNL; Huq, Ashfia [ORNL; Bugaris, Daniel E [ORNL; Zur Loye, Hans-Conrad [ORNL; Muñoz-García, Ana B. [Princeton University; Pavone, Michele [Princeton University; Chen, Fenglin [University of South Carolina; Carter, Emily A. [Princeton University

2012-01-01

219

Relationships between structure and superconducting properties in new ternary silicides of the systems: rare earths or thorium - transition metal (Rh or Ir) - silicon  

International Nuclear Information System (INIS)

[en] Nine families of ternary silices Msub(x)Tsub(y)Sisub(z) have been prepared in the rare earths of thorium (M) - transition metals (T = Th or Ir) - silicon systems: MT3Si2, MT2Si2 (two polymorphic forms), MTSi (TiNiSi and SrSi2-type), M2T3Si5, MTSi2, MTSi3 and M2TSi3. The occurence of superconductivity in these compounds has been related both to their crystal structure and composition[fr] Neuf familles de siliciures ternaires Msub(x)Tsub(y)Sisub(z) ont ete preparees dans les systemes terre rares ou thorium (M) - metaux de transition (T=Rh ou Ir) - silicium: MT3Si2, MT2Si2 (deux varietes allotropiques), MTSi (type TiNiSi et SrSi2), M2T3Si5, MTSi2, MTSi3 et M2TSi3. L'apparition de la supraconductivite est correlee a la structure et a la composition de ces materiaux

1984-01-01

220

Structure-property relationship of extended ?-conjugation of ancillary ligands with and without an electron donor of heteroleptic Ru(II) bipyridyl complexes for high efficiency dye-sensitized solar cells.  

UK PubMed Central (United Kingdom)

Two new heteroleptic Ru(II) bipyridyl complexes MH06 and MH11 were designed, synthesized and characterized for DSSCs. While the ancillary ligand of MH06 was molecularly engineered with a strong electron donating group coupled with an extended ?-conjugated system, the ancillary ligand of MH11 contained a longer ?-conjugated system only. Molecular modeling, photophysical, and photovoltaic properties were compared under the same experimental conditions against the benchmark N719. In an effort to understand the structure-property relationship, their photovoltaic and photoelectrochemical properties including Jsc, Voc, ground and excited state oxidation potentials, UV-Vis absorption, and molar extinction coefficients were studied. The UV-Vis results showed intense MLCT absorption peaks of MH06 and MH11 in the visible region with a red shift of 12 and 18 nm, respectively, with significantly higher molar extinction coefficients compared to N719. Tetrabutylammonium (TBA) substituted MH11-TBA demonstrated the most efficient IPCE of over 90% in the plateau region covering the entire visible spectrum and extending into the near IR region (ca. 890 nm), which showed a solar-to-power conversion efficiency (?) of 10.06%, significantly higher than that of the benchmark N719 dye (9.32%). The superior performance in terms of the IPCE and Jsc of MH11 can be attributed to the bulky and highly hydrophobic nature of the pyrene-based ancillary ligand, which behaves as a shielding barrier for hole-transport recombination between TiO2 and the electrolyte. In addition, the IMPS results showed that the contribution of dyes to the conduction band shift of the TiO2 level is almost similar, regardless of different substitutions on the bipy-moiety. This implies that the open-circuit photovoltage (Voc) increases with reduced charge recombination in the presence of a thick layer of tetrabutyl ammonium ions (TBA) of the dye anchored on the surface of TiO2.

Hussain M; El-Shafei A; Islam A; Han L

2013-06-01

 
 
 
 
221

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

222

Cationic phospholipids: structure?transfection activity relationships  

Energy Technology Data Exchange (ETDEWEB)

Synthetic cationic lipids are presently the most widely used non-viral gene carriers. Examined here is a particularly attractive cationic lipid class, triester phosphatidylcholines (PCs) exhibiting low toxicities and good transfection efficiency. Similarly to other cationic lipids, they form stable complexes (lipoplexes) with the polyanionic nucleic acids. A summary of studies on a set of {approx}30 cationic PCs reveals the existence of a strong, systematic dependence of their transfection efficiency on the lipid hydrocarbon chain structure: transfection activity increases with increase of chain unsaturation from 0 to 2 double bonds per lipid and decreases with increase of chain length in the range {approx}30-50 total number of chain carbon atoms. Maximum transfection was observed for ethyl phosphate PCs (EPCs) with monounsaturated 14:1 chains (total of 2 double bonds and 30 chain carbon atoms). Lipid phase behavior is known to depend strongly on the chain molecular structure and the above relationships thus substantiate a view that cationic PC phase propensities are an important determinant of their activity. Indeed, X-ray structural studies show that the rate of DNA release from lipoplexes as well as transfection activity well correlate with non-lamellar phase progressions observed in cationic PC mixtures with membrane lipids. These findings appear to be of considerable interest because, according to current views, key processes in lipid-mediated transfection such as lipoplex disassembly and DNA release within the cells are believed to take place upon cationic lipid mixing with cellular lipids.

Koynova, Rumiana; Tenchov, Boris; (NWU)

2010-01-18

223

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.

Lorentz JÄNTSCHI; Sorana D. BOLBOACA

2011-01-01

224

Associative structure of integrated temporal relationships.  

UK PubMed Central (United Kingdom)

According to the temporal-coding hypothesis (TCH; Savastano & Miller, Behavioural Processes 44:147-162, 1998), acquired associations include temporal information concerning the interval between the associated elements. Moreover, the TCH posits that subjects can integrate two independently acquired associations that share a common element (e.g., S2-S1 and S1-US), which results in the creation of a third association with its own temporal relationship (S2-US). Some evidence has suggested that such temporal integration occurs at the time of testing (Molet, Miguez, Cham, & Miller, Journal of Experimental Psychology: Animal Behavior Processes 38:369-380, 2012). Here we report two fear-conditioning experiments with rats conducted to identify the associative structure of the integrated temporal relationship. The goal was to distinguish between two possible associative structures that could exist following an initial test on which temporal integration occurs: (1) Conditioned responding to S2 on subsequent tests could be the result of recurring successive activation of two independently learned temporal maps that remain independently stored in memory (i.e., S2-S1 plus S1-US). (2) Temporal integration at the moment of initial testing could result in the formation of a direct S2-US (or S2-response) temporal map. Integration was found to occur at test and to produce a new association that was independent of associations with the common element (S1). However, the associative status of S1 appeared to modulate whether or not the new association with S2 was US-specific (S2-US) or directly activated a fear response (S2-response).

Polack CW; Molet M; Miguez G; Miller RR

2013-08-01

225

[Structure and properties of pectin].  

UK PubMed Central (United Kingdom)

Pectin represents a very complex, heterogeneous family of plant cell wall polysaccharides that play a significant role in plant growth, morphology, development, and plant defense and also serves as a gelling and stabilizing polymer in diverse food and specialty products and has positive effects on human health. In this review functional and structural characteristic of pectin molecule elements and their interconnections are described. Attention is also given to process of commercial production of pectin with special emphasis on composition and physical properties of commercial pectin as a result of the acid extraction.

Wikiera A; Mika M

2013-01-01

226

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

227

Structure-property relationships in Discotic Mesogens  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Columnar liquid crystals have emerged as a promising class of materials for light emitting diodes, photovoltaic devices and field effect transistors. In addition to their practical importance, the ability of disc-shaped molecules to spontaneously form columnar nanostructures represents a striking ex...

Foster, Earl Johan

228

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; Yun Wang

2011-01-01

229

Relationship between RDX properties and sensitivity  

Energy Technology Data Exchange (ETDEWEB)

An interlaboratory comparison of seven lots of commercially available RDX was conducted to determine what properties of the nitramine particles can be used to assess whether the RDX has relatively high or relatively low sensitivity. The materials chosen for the study were selected to give a range of HMX content, manufacturing process and reported shock sensitivity. The results of two different shock sensitivity tests conducted on a PBX made with the RDX lots in the study showed that there are measurable differences in the shock sensitivity of the PBXs, but the impact sensitivity for all of the lots is essentially the same. Impact sensitivity is not a good predictor of shock sensitivity for these types of RDX. Although most RDX that exhibits RS has low HMX content, that characteristic alone is not sufficient to guarantee low sensitivity. A range of additional analytical chemistry tests were conducted on the material; two of these (HPLC and DSC) are discussed within. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

Doherty, Ruth M. [Research, Development, Test and Evaluation Directorate, Naval Surface Warfare Center Indian Head Division, Indian Head, MD 20640-5102 (United States); Watt, Duncan S. [Novare, Level 6 80 Petrie Terrace, Brisbane 4000 (Australia)

2008-02-15

230

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  

Directory of Open Access Journals (Sweden)

Full Text Available 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 fullerene cage. One class of electron-transfer molecules has introduced as [X-UT-Y][R-C60–M+](R=tert-Bu- & H–C?C-; M=Li & K). The supramolecular complexes [X-UT-Y] (1-9) and [R-C60–M+] (R=tert-Bu- & H–C?C-; M=Li & K) are shown to possess a previously unreported host-guest interaction for electron transfer processes. The unsaturated, thiocrown ethers (1-9, with cis-geometry) (described as [X-UT-Y], where X and Y indicate the numbers of carbon and sulfur atoms, respectively) are a group of crown ethers that display interesting physiochemical properties in light of their conformational restriction compared to a corresponding saturated system, as well as the sizes of their cavities. Topological indices have been successfully used to construct mathematical methods that relate the structural data to the various chemical and physical properties. To establish a good relationship between the structures of 1-9 with derivatives of alkynyldihydrofullerene (1-alkynyl-C60 carbanion) as [R-C60–M+] (R=tert-Bu- & H–C?C-; M=Li & K) in DMSO and THF solvents 12-38, an index (mcs) is utilized. This index is the ratio of the sum of the number of carbon atoms (nc) and the number of sulfur atoms (ns) with the product of these two numbers for 1-9. In this study, were investigated the relationships between this index and the first to third free energies of electron transfer (?Get(n); n=1-3, which is given by the Rehm-Weller equation) between 1-9 and [R-C60–M+] (R=tert-Bu- & H–C?C-; M=Li & K) as [X-UT-Y][R-C60–M+](R=tert-Bu- & H–C?C-; M=Li & K) supramolecular complexes in DMSO and THF solvents. The first to third free energies of electron transfer and the kinetic rate constants of the electron transfers, ?G#et(n) and ket (n=1-3), respectively, were also calculated for [X-UT-Y][R-C60–M+] (R=tert-Bu- & H–C?C-; M=Li & K) in DMSO and THF, in accordance with the Marcus theory.

Avat Arman Taherpour; Masomeh Tayebi-Suraki; Nosratollah Mahdizadeh

2012-01-01

231

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

232

Mixture designs to assess composition-structure-property relationships in SiO2-CaO-ZnO-La2O3-TiO2-MgO-SrO-Na2O glasses: Potential materials for embolization.  

UK PubMed Central (United Kingdom)

Embolization with micron-sized particulates is widely applied to treat uterine fibroids. The objective of this work was to develop mixture designs to predict materials composition-structure-property relationships for the SiO2-CaO-ZnO-La2O3-TiO2-MgO-SrO-Na2O glass system and compare its fundamental materials properties (density and cytocompatibility), against a state-of-the-art embolic agent (contour polyvinyl alcohol) to assess the potential of these materials for embolization therapies. The glass structures were evaluated using (29)Si MAS NMR to identify chemical shift and line width; the particulate densities were determined using helium pycnometry and the cell viabilities were assessed via MTT assay. (29)Si MAS NMR results indicated peak maxima for each glass in the range of -82.3?ppm to -89.9?ppm; associated with Q(2) to Q(3) units in silicate glasses. All experimental embolic compositions showed enhanced in vitro compatibility in comparison to Contour PVA with the exceptions of ORP9 and ORP11 (containing no TiO2). In this study, optimal compositions for cell viability were obtained for the following compositional ranges: 0.095-0.188?mole fraction ZnO; 0.068-0.159?mole fraction La2O3; 0.545-0.562?mole fraction SiO2 and 0.042-0.050?mole fraction TiO2. To ensure ease of producibility in obtaining good melts, a maximum loading of 0.068?mole fraction La2O3 is required. This is confirmed by the desirability approach, for which the only experimental composition (ORP5) of the materials evaluated was presented as an optimum composition; combining high cell viability with ease of production (0.188?mole fraction ZnO; 0.068?mole fraction La2O3; 0.562?mole fraction SiO2 and 0.042?mole fraction TiO2).

Kehoe S; Langman M; Werner-Zwanziger U; Abraham RJ; Boyd D

2013-09-01

233

Structure-property relationships in radical-cation (electron-donor molecule) and anion-based (including fullerides) organic superconductors and their use in the design of new materials  

Energy Technology Data Exchange (ETDEWEB)

The presently known structure-property relations that have been developed for organic superconductors based on the ET molecule (b- phases and k-phases), and the C{sub 60}-anion-based fullerides, and their use in the structural design of new superconducting materials are discussed. 12 refs, 11 figs, 4 tabs.

Williams, J.M.; Carlson, K.D.; Kini, A.M. [Argonne National Lab., IL (United States)

1993-08-01

234

Methods for applying the quantitative structure-activity relationship paradigm.  

UK PubMed Central (United Kingdom)

There are several Quantitative Structure-Activity Relationship (QSAR) methods to assist in the design of compounds for medicinal use. Owing to the different QSAR methodologies, deciding which QSAR method to use depends on the composition of system of interest and the desired results. The relationship between a compound's binding affinity/activity to its structural properties was first noted in the 1930s by Hammett and later refined by Hansch and Fujita in the mid-1960s. In 1988 Cramer and coworkers created Comparative Molecular Field Analysis (CoMFA) incorporating the three-dimensional (3D) aspects of the compounds, specifically the electrostatic fields of the compound, into the QSAR model. Hopfinger and coworkers included an additional dimension to 3D-QSAR methodology in 1997 that eliminated the question of "Which conformation to use in a QSAR study?", creating 4D-QSAR. In 1999 Chemical Computing Group Inc. (CCG) developed the Binary-QSAR methodology and added novel 3D-QSAR descriptors to the traditional QSAR model allowing the 3D properties of compounds to be incorporated into the traditional QSAR model. Recently CCG released Probabilistic Receptor Potentials to calculate the substrate's atomic preferences in the active site. These potentials are constructed by fitting analytical functions to experimental properties of the substrates using knowledge-based methods. An overview of these and other QSAR methods will be discussed along with an in-depth examination of the methodologies used to construct QSAR models. Also, included in this chapter is a case study of molecules used to create QSAR models utilizing different methodologies and QSAR programs.

Esposito EX; Hopfinger AJ; Madura JD

2004-01-01

235

TEACHING STRATEGY CONCERNING RELATIONSHIP STRUCTURE–BIODEGRADABILITY OF AGRO-ECOSYSTEMS SPECIFIC POLLUTANTS  

Directory of Open Access Journals (Sweden)

Full Text Available The general plan of the lesson based on classical presentation, dedicated to correlation of the structure with biodegradability of specific agro-ecosystems pollutants was realised. This teaching strategy is projected for third year students at the Environmental Chemistry section which follow the compulsory course: Relationships Structure-Properties–Toxicity of Industrial Pollutants.

Roxana Done; Iana Hutchins

2008-01-01

236

[Taxoids: structural and experimental properties].  

UK PubMed Central (United Kingdom)

Paclitaxel (Taxol) and docetaxel (Taxotere) are the first representatives of a new class of antitumor compounds. These two taxoids are clinically active against breast, ovarian and lung cancers. Taxoids are highly complex diterpenoids form natural origin. Preclinical and clinical developments have been made possible after a long and sustained chemical effort: paclitaxel is extracted from the barks of the Pacific yew tree Taxus brevifolia whereas docetaxel is prepared by hemisynthesis starting from 10-deacetyl-baccatin III, an inactive precursor found in the needles of the European yew tree Taxus baccata. These two drugs are active in various in vitro and in vivo preclinical models (cell lines, cloning of human tumor stem cells, murine grafted tumors, human xenografts). Taxoids constitute a new class of antimitotic agents different from vinca-alkaloids: on the one hand, paclitaxel and docetaxel can be considered as inhibitors of the reaction of depolymerization of microtubules into tubulin; on the other hand, vinca-alkaloids inhibit reaction of polymerization of tubulin into microtubules. An active program of medicine chemistry is done in various pharmaceutical and academic Institutions with two objectives: knowledge of structure-activity relationships and selection of new candidates for clinical trials.

Lavelle F; Combeau C; Commerçon A

1995-04-01

237

Protoglobin: structure and ligand-binding properties.  

Science.gov (United States)

Protoglobin is the first globin identified in Archaea; its biological role is still unknown, although it can bind O2, CO and NO reversibly in vitro. The X-ray structure of Methanosarcina acetivorans protoglobin revealed several peculiar structural features. Its tertiary structure can be considered as an expanded version of the canonical globin fold, characterised by the presence of a pre-A helix (named Z) and a 20-residue N-terminal extension. Other unusual trends are a large distortion of the haem moiety, and its complete burial in the protein matrix due to the extended CE and FG loops and the 20-residue N-terminal loop. Access of diatomic ligands to the haem has been proposed to be granted by two tunnels, which are mainly defined by helices B/G (tunnel 1) and B/E (tunnel 2), and whose spatial orientation and topology give rise to an almost orthogonal two-tunnel system unprecedented in other globins. At a quaternary level, protoglobin forms a tight dimer, mostly based on the inter-molecular four-helix bundle built by the G- and H-helices, similar to that found in globin-coupled sensor proteins, which share with protoglobin a common phylogenetic origin. Such unique structural properties, together with an unusually low O2 dissociation rate and a selectivity ratio for O2/CO binding that favours O2 ligation, make protoglobin a peculiar case for gaining insight into structure to function relationships within the globin superfamily. While recent structural and biochemical data have given answers to important questions, the functional issue is still unclear and it is expected to represent the major focus of future investigations. PMID:24054795

Pesce, Alessandra; Bolognesi, Martino; Nardini, Marco

2013-01-01

238

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

239

Interpretable correlation descriptors for quantitative structure-activity relationships.  

UK PubMed Central (United Kingdom)

BACKGROUND: The topological maximum cross correlation (TMACC) descriptors are alignment-independent 2D descriptors for the derivation of QSARs. TMACC descriptors are generated using atomic properties determined by molecular topology. Previous validation (J Chem Inf Model 2007, 47: 626-634) of the TMACC descriptor suggests it is competitive with the current state of the art. RESULTS: Here, we illustrate the interpretability of the TMACC descriptors, through the analysis of the QSARs of inhibitors of angiotensin converting enzyme (ACE) and dihydrofolate reductase (DHFR). In the case of the ACE inhibitors, the TMACC interpretation shows features specific to C-domain inhibition, which have not been explicitly identified in previous QSAR studies. CONCLUSIONS: The TMACC interpretation can provide new insight into the structure-activity relationships studied. Freely available, open source software for generating the TMACC descriptors can be downloaded from http://comp.chem.nottingham.ac.uk.

Spowage BM; Bruce CL; Hirst JD

2009-01-01

240

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

 
 
 
 
241

Structural Property Analysis of Petri Net  

Directory of Open Access Journals (Sweden)

Full Text Available 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 methods for individual properties.

Chuanliang Xia

2012-01-01

242

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

2013-09-02

243

[Quantitative structure-activity relationship of quinoline derivatives  

UK PubMed Central (United Kingdom)

Quantum-chemical computations using the Hückel method have been performed on quinoline derivatives that exhibit antibacterial activity against E. coli, in order to obtain quantitative structure-activity relationship and drug-receptor interaction data.

Gómez Contreras F; Yunta MJ

1985-08-01

244

Analysis of relationships between solid-state properties, counterion, and developability of pharmaceutical salts.  

UK PubMed Central (United Kingdom)

The solid-state properties of pharmaceutical salts, which are dependent on the counterion used to form the salt, are critical for successful development of a stable dosage form. In order to better understand the relationship between counterion and salt properties, 11 salts of procaine, which is a base, were synthesized and characterized using a variety of experimental and computational methods. Correlations between the various experimental and calculated physicochemical properties of the salts and counterions were probed. In addition to investigating the key factors affecting solubility, the hygroscopicity of the crystalline salts was studied to determine which solid-state and counterion properties might be responsible for enhancements in moisture uptake, thus providing the potential for adverse chemical stability. Multivariate principal components and partial least squares projection to latent structures analyses were performed in an attempt to establish predictive models capable of describing the relationships between these characteristics and both measured and calculated properties of the counterion and salt. Some success was achieved with respect to modeling crystalline salt solubility and the glass transition temperature of the amorphous salts. Through the modeling, insight into the relative importance of various descriptors on salt properties was achieved. The solid-state properties of crystalline and amorphous salts of procaine are highly dependent on the nature of the counterion. Important properties including aqueous solubility, melting point, hygroscopicity, and glass transition temperature were found to vary considerably between the different salts.

Guerrieri P; Rumondor AC; Li T; Taylor LS

2010-09-01

245

Structural volumes and collector properties of coal  

Energy Technology Data Exchange (ETDEWEB)

Studies gas permeation into interlaminar spaces of coal. Determines (with the help of X-ray crystallography) structural volumes of coal of various rank. Gives equations for calculating interlaminarspaces in structural units which enable determination of structural volume per 1 g of ash-free coal mass. Results obtained indicate that structural volume of coal polymer is the sole receptacle of gases occurring in coal mass. Establishes that there is a relationship between changes in structural volume of coal and its rank; unusual and sufficiently strong crystalline configuration has formed as a result of an association between gas and molecular and supermolecular structures of organic coal mass. 16 refs.

Batrakov, N.F.; Bineev, Eh.A.

1988-07-01

246

Transmission properties of frequency selective structures with air gaps  

Science.gov (United States)

The transmission properties of compound frequency selective structures with dielectric slab and air gaps were investigated by computation and experimentation. Mechanism analyses were also carried out. Results show that the air gaps have a distinct influence on the transmission properties. Resonant frequency of the structure would increase rapidly when the air gap appears. After the gap gets larger to a specific value, generally 1/5 wavelength corresponding to the resonant frequency, the transmission properties would change periodically with the gap thickness. The change of transmission properties in one period has a close relationship with the dielectric thickness. These results provide a new method for designing a bandpass radome of large incidence angle and low loss with the concept of stealth shield radome.

Meng, Zhi-Jun; Wang, Li-Feng; Lü, Ming-Yun; Wu, Zhe

2010-12-01

247

Structure-activity relationship of nerve-highlighting fluorophores.  

Science.gov (United States)

Nerve damage is a major morbidity associated with numerous surgical interventions. Yet, nerve visualization continues to challenge even the most experienced surgeons. A nerve-specific fluorescent contrast agent, especially one with near-infrared (NIR) absorption and emission, would be of immediate benefit to patients and surgeons. Currently, there are only three classes of small molecule organic fluorophores that penetrate the blood nerve barrier and bind to nerve tissue when administered systemically. Of these three classes, the distyrylbenzenes (DSBs) are particularly attractive for further study. Although not presently in the NIR range, DSB fluorophores highlight all nerve tissue in mice, rats, and pigs after intravenous administration. The purpose of the current study was to define the pharmacophore responsible for nerve-specific uptake and retention, which would enable future molecules to be optimized for NIR optical properties. Structural analogs of the DSB class of small molecules were synthesized using combinatorial solid phase synthesis and commercially available building blocks, which yielded more than 200 unique DSB fluorophores. The nerve-specific properties of all DSB analogs were quantified using an ex vivo nerve-specific fluorescence assay on pig and human sciatic nerve. Results were used to perform quantitative structure-activity relationship (QSAR) modeling and to define the nerve-specific pharmacophore. All DSB analogs with positive ex vivo fluorescence were tested for in vivo nerve specificity in mice to assess the effect of biodistribution and clearance on nerve fluorescence signal. Two new DSB fluorophores with the highest nerve to muscle ratio were tested in pigs to confirm scalability. PMID:24039960

Gibbs, Summer L; Xie, Yang; Goodwill, Haley L; Nasr, Khaled A; Ashitate, Yoshitomo; Madigan, Victoria J; Siclovan, Tiberiu M; Zavodszky, Maria; Tan Hehir, Cristina A; Frangioni, John V

2013-09-09

248

Structure-activity relationship of nerve-highlighting fluorophores.  

UK PubMed Central (United Kingdom)

Nerve damage is a major morbidity associated with numerous surgical interventions. Yet, nerve visualization continues to challenge even the most experienced surgeons. A nerve-specific fluorescent contrast agent, especially one with near-infrared (NIR) absorption and emission, would be of immediate benefit to patients and surgeons. Currently, there are only three classes of small molecule organic fluorophores that penetrate the blood nerve barrier and bind to nerve tissue when administered systemically. Of these three classes, the distyrylbenzenes (DSBs) are particularly attractive for further study. Although not presently in the NIR range, DSB fluorophores highlight all nerve tissue in mice, rats, and pigs after intravenous administration. The purpose of the current study was to define the pharmacophore responsible for nerve-specific uptake and retention, which would enable future molecules to be optimized for NIR optical properties. Structural analogs of the DSB class of small molecules were synthesized using combinatorial solid phase synthesis and commercially available building blocks, which yielded more than 200 unique DSB fluorophores. The nerve-specific properties of all DSB analogs were quantified using an ex vivo nerve-specific fluorescence assay on pig and human sciatic nerve. Results were used to perform quantitative structure-activity relationship (QSAR) modeling and to define the nerve-specific pharmacophore. All DSB analogs with positive ex vivo fluorescence were tested for in vivo nerve specificity in mice to assess the effect of biodistribution and clearance on nerve fluorescence signal. Two new DSB fluorophores with the highest nerve to muscle ratio were tested in pigs to confirm scalability.

Gibbs SL; Xie Y; Goodwill HL; Nasr KA; Ashitate Y; Madigan VJ; Siclovan TM; Zavodszky M; Tan Hehir CA; Frangioni JV

2013-01-01

249

Relationship between crystal chemistry and the local structure and electronic properties of Tl sub 2 Ba sub 2 Ca sub 2 Cu sub 3 O sub 10 superconductors determined by scanning tunneling microscopy and  

Energy Technology Data Exchange (ETDEWEB)

Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) have been used to characterize the local structure and electronic properties of Tl{sub 2}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} single crystals prepared from 4:1:3:6 and 4:1:3:10 stoichiometry melts. Magnetic-susceptibility, resistivity, x-ray-fluorescence, and x-ray-diffraction measurements indicate that samples prepared from the 4:1:3:6 melts (type 1) have a chemical inhomogeneity, while crystals obtained from the 4:1:3:10 melts (type 2) are high quality. STM studies of the type-1 crystals demonstrate that the inhomogeneities can be associated with distortions in the TlO layer atomic structure. STS measurements on the distorted TlO layer of the type-1 samples have shown that this layer is also metallic. STM and STS investigations of the type-2 samples have shown, however, that the TlO layer in these crystals is tetragonal and semiconducting. In addition, a superstructure that is localized over small regions of the TlO surface has been characterized in the type-1 crystals. These results demonstrate that single crystals of the same average structure and composition can exhibit substantial differences in the local-structure electronic states and superconducting properties.

Zhang, Z.; Chen, C.; Lieber, C.M. (Department of Chemistry and Division of Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)); Morosin, B.; Ginley, D.S.; Venturini, E.L. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States))

1992-01-01

250

Structure and properties of metals  

International Nuclear Information System (INIS)

Metals are one of the most widely used types of engineering materials. Some of their properties, e.g. elastic constants, can be directly related to the nature of the metallic bonds between the atoms. On the other hand macro- and microstructural features of metals , such as point defects, dislocations, grain boundaries, and second phase particles, control their yield, flow, and fracture stress. Images of microstructural elements can be obtained by modern imaging techniques. Modern computer aided methods can be further used to obtain a quantitative description of these microstructures. These methods take advantage of the progress made in recent years in the field of image processing, mathematical morphology and quantitative stereology. Quantitative description of the microstructures are used for modelling processes taking place under the action of applied load at a given temperature and test (service) environment. These model considerations can be illustrated on the example of an austenitic stainless steel, which is an important material for power generating and chemical industry. Reports recently published also show that properties of materials can be significantly modified by the effect of free surface. Examples of such situations include environmental effect on the mechanical properties of materials. Data for austenitic stainless steel is used to discuss contribution of the free surface to the mechanical properties of metals. (author)

1999-01-01

251

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

252

Relationship between the ratio of ligand to metal and the coordinating ability of anions. Synthesis and structural properties of AgX-bearing bis(4-pyridyl)dimethylsilane (X- = NO2-, NO3-, CF3SO3-, and PF6-).  

Science.gov (United States)

Studies of the anion effects on the molecular construction of a series of AgX complexes with bis(4-pyridyl)dimethylsilane (L) (X- = NO2-, NO3-, CF3SO3-, and PF6-) have been carried out. Formation of the skeletal bonds appears to be primarily associated with a suitable combination of bidentate N-donors of L and a variety of coordination geometries of Ag(I) ions. The L:Ag(I) ratios of the products are dependent on the nature of the polyatomic anions. The 1:1 adduct Ag(I)-L for NO2-, 3:4 adduct for NO3-, 2:3 adduct for CF3SO3-, and 1:2 adduct for PF6- have been obtained. A linear relationship between the ratio of ligand to metal and the coordinating ability of anions was observed. [Ag(NO2)(L)] has a unique sheet structure consisting of double helices, and [Ag3(L)4](NO3)3 is a 2 nm thick interwoven sheet structure consisting of nanotubes. The compound [Ag2(L)3](CF3SO3)2 affords a characteristic ladder-type channel structure, and [Ag(L)2](PF6) is a simple 2D grid structure. PMID:15847421

Lee, Jung Woon; Kim, Eun Ae; Kim, Yun Ju; Lee, Young-A; Pak, Youngshang; Jung, Ok-Sang

2005-05-01

253

Structure-function relationships in ?-galactosidase A  

Science.gov (United States)

With recent interest in the molecular mechanisms responsible for Fabry disease, the number of known mutations in the GLA gene which encodes ?-galactosidase A has expanded considerably. Combining a large database of Fabry disease-causing mutations with the recently determined crystal structure of human ?-galactosidase A allows for a new understanding of the atomic defects in the protein responsible for Fabry disease. We have conducted a systematic survey of the known Fabry disease-causing mutations and analyzed the mutations in the context of the ?-galactosidase A structure. We have applied quantitative methods for identifying the plausible effect of each mutation on the ?-galactosidase A protein. We present the analysis of 331 different defects in the GLA gene leading to non-native proteins in patients with Fabry disease. These mutations include 278 missense mutations, 49 nonsense mutations, and 4 single amino acid deletions. Conclusion Over half of the residues in the protein have been found to have changes in patients with Fabry disease. Most of these genetic mutations lead to the disruption of the hydrophobic core of the protein, thus Fabry disease is primarily a disease of protein folding. Further understanding of ?-galactosidase A, one of the best studied members of the lysosomal storage disease family, will lead to increased understanding of other lysosomal storage diseases and other protein folding diseases.

GARMAN, SCOTT C.

2011-01-01

254

Structure- and dose-absorption relationships of coffee polyphenols.  

UK PubMed Central (United Kingdom)

Chlorogenic acids (CGAs) from coffee have biological effects related to human health. Thus, specific data on their bioavailability in the upper gastrointestinal tract are of high interest, since some molecules are absorbed here and so are not metabolized by colonic microflora. Up to now, no data on structure-absorption relationships for CGAs have been published, despite this being the most consumed group of polyphenols in the western diet. To address this gap, we performed ex vivo absorption experiments with pig jejunal mucosa using the Ussing chamber model (a model simulating the mucosa and its luminal/apical side). The main coffee polyphenols, caffeoylquinic acid (CQA), feruloylquinic acid (FQA), caffeic acid (CA), dicaffeoylquinic acid (diCQA), and D-(-)-quinic acid (QA), were incubated in individual experiments equivalent to gut lumen physiologically achievable concentrations (0.2-3.5 mM). Identification and quantification were performed with HPLC-diode array detection and HPLC-MS/MS. Additionally, the presence of ABC-efflux transporters was determined by Western blot analysis. The percentages of initially applied CGAs that were absorbed through the jejunal pig mucosa were, in increasing order: diCQA, trace; CQA, ?1%; CA, ?1.5%; FQA, ?2%; and QA, ?4%. No differences were observed within the CGA subgroups. Dose-absorption experiments with 5-CQA suggested a passive diffusion (nonsaturable absorption and a linear dose-flux relationship) and its secretion was affected by NaN3 , indicating an active efflux. The ABC-efflux transporters MDR 1 and MRP 2 were identified in pig jejunal mucosa for the first time. We conclude that active efflux plays a significant role in CGA bioavailability and, further, that the mechanism of CGA absorption in the jejunum is governed by their physicochemical properties. © 2013 BioFactors, 2013.

Erk T; Hauser J; Williamson G; Renouf M; Steiling H; Dionisi F; Richling E

2013-03-01

255

Relationship between the structural stability with the types and land uses in southeastern Spain  

International Nuclear Information System (INIS)

Structural stability is one of the most important physical properties and is proposed as an indicator of quality. The aim of this study is to see the possible relationship between this property with soil types and uses of them. In this paper we have selected the Mazarron area based on their environmental characteristics and has taken forty-one topsoil samples, after analysis and study of the relationship between its structural stability with soil types and uses of same, we find a closer relationship in the case of uses that type, so that the natural soil as the percentage of stable aggregates close to 75%, while in soils anthropized this value reaches 44 %. (Author) 6 refs

2009-01-01

256

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

257

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...

Rudolf, Andreja; Sfiligoj-Smole, Majda

258

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

259

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

260

A Revisiting of Ownership Structures and Capital Structures Relationship: Evidence From East Asian Financial Crisis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Some previous research findings indicate that the relationship between ownership structure and company performance which is assumed it is influence by the relationship between managers and shareholder of the company. This relationship would have the potential to affect the decision making in an orga...

Warokka, Ari; Herrera, Juan Jose Duran

 
 
 
 
261

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.

262

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

263

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

264

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

265

Using theoretical descriptors in structure activity relationships: Validating toxicity predictions  

Energy Technology Data Exchange (ETDEWEB)

Quantitative Structure Activity Relationships (QSAR) and Linear Free Energy Relationships (LFER) are very useful for correlating toxicological data, and in characterizating trends in terms of structural and electronic effects. Several years ago, we developed a series of equations correlating a number of toxicity tests with theoretically determined descriptors. One of these tests was the Microtox test, using the degradation in light from Photobacteriurn phosphoreum. Recently, several new compounds have been tested in our laboratory using the Microtox test, and compared against the predicted values. The agreement between experimental and theoretical results will be discussed, as will reasons for {open_quotes}good{close_quotes} or {open_quotes}poor{close_quotes} predictions.

Famini, G.R.; Wilson, L.Y.; Chester, N.A.; Sterling, P.A. [Army Edgewood Research, Development and Engineering Center, Aberdeen Proving Ground, CA (United States)

1995-12-01

266

Data base on structural materials aging properties  

Energy Technology Data Exchange (ETDEWEB)

The US Nuclear Regulatory Commission has initiated a Structural Aging Program at the Oak Ridge National Laboratory to identify potential structural safety issues related to continued service of nuclear power plants and to establish criteria for evaluating and resolving these issues. One of the tasks in this program focuses on the establishment of a Structural Materials Information Center where long-term and environment-dependent properties of concretes and other structural materials are being collected and assembled into a data base. These properties will be used to evaluate the current condition of critical structural components in nuclear power plants and to estimate the future performance of these materials during the continued service period.

Oland, C.B.

1992-03-01

267

Data base on structural materials aging properties  

International Nuclear Information System (INIS)

The US Nuclear Regulatory Commission has initiated a Structural Aging Program at the Oak Ridge National Laboratory to identify potential structural safety issues related to continued service of nuclear power plants and to establish criteria for evaluating and resolving these issues. One of the tasks in this program focuses on the establishment of a Structural Materials Information Center where long-term and environment-dependent properties of concretes and other structural materials are being collected and assembled into a data base. These properties will be used to evaluate the current condition of critical structural components in nuclear power plants and to estimate the future performance of these materials during the continued service period

1992-01-01

268

Dihydroorotate dehydrogenase inhibitors: quantitative structure-activity relationship analysis.  

UK PubMed Central (United Kingdom)

PURPOSE: The main purpose of this study is to analyze the quantitative structure-activity relationship of two series of dihydroorotate dehydrogenase inhibitors (leflunomide and quinoline carboxylic acid analogues), and to determine the structural requirements for optimum activity of these analogues. METHODS: A new CQSAR program was used in deriving regression equations and calculating the octanol/water partition coefficient and the molar refractivity values. The molecular modeling was performed using the HyperChem program. RESULTS: Statistically significant correlations were obtained using a combination of 3-4 parameters. The structural requirements for optimum activity and critical regions for the inhibitory activity of dihydroorotate dehydrogenase were identified. CONCLUSIONS: The quantitative structure-activity relationship analysis demonstrated that two series of dihydroorotate dehydrogenase inhibitors may bind to different binding sites on the enzyme. These results provide a better understanding of dihydroorotate dehydrogenase inhibitor-enzyme interactions, and may be useful for further modification and improvement of inhibitors of this important enzyme.

Ren S; Wu SK; Lien EJ

1998-02-01

269

Visualization of protein structure relationships using constrained twin kernel embedding  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a recently proposed dimensional-ity reduction method called Twin Kernel Em-bedding (TKE) [10] is applied in 2-dimensional visualization of protein structure relationships. By matching the similarity measures of the input and the embedding spaces expressed by their respective kernels, TKE ensures that both local and global proximity information are preserved simultaneously. Experiments conducted on a subset of the Structural Classification Of Pro-tein (SCOP) database confirmed the effective-ness of TKE in preserving the original relation-ships among protein structures in the lower di-mensional embedding according to their simi-larities. This result is expected to benefit sub-sequent analyses of protein structures and their functions.

Yi Guo; Jun-Bin Gao; Paul Kwan; Xinsheng Hou

2008-01-01

270

Alternating and direct current field effects on the structure-property relationships in Na0.5Bi0.5TiO3-x%BaTiO3 textured ceramics  

Science.gov (United States)

The influence of alternating (ac) and direct current (dc) fields on the structural and dielectric properties of [001]PC textured Na0.5Bi0.5TiO3-7%BaTiO3 (NBT-7%BT) ceramics has been investigated. X-ray diffraction measurements revealed that the depolarization at temperature Td in poled samples resulted from a tetragonal --> pseudo-cubic transition on heating. Moderate ac drive and dc bias had opposite influences on Td: ac drive decreased the Td, whereas dc bias increased it. These investigations suggested an effective method to expand the working temperature range of NBT-x%BT textured ceramics to a high temperature.

Ge, Wenwei; Maurya, Deepam; Li, Jiefang; Priya, Shashank; Viehland, D.

2013-06-01

271

Capturing structure-activity relationships from chemogenomic spaces.  

UK PubMed Central (United Kingdom)

Modeling off-target effects is one major goal of chemical biology, particularly in its applications to drug discovery. Here, we describe a new approach that allows the extraction of structure-activity relationships from large chemogenomic spaces starting from a single chemical structure. Several public source databases, offering a vast amount of data on structure and activity for a large number of different targets, have been investigated for their usefulness in automated structure-activity relationships (SAR) extraction. SAR tables were constructed by assembling similar structures around each query structure that have an activity record for a particular target. Quantitative series enrichment analysis (QSEA) was applied to these SAR tables to identify trends and to transform these trends into topomer CoMFA models. Overall more than 1700 SAR tables with topomer CoMFA models have been obtained from the ChEMBL, PubChem, and ChemBank databases. These models were able to highlight the structural trends associated with various off-target effects of marketed drugs, including cases where other structural similarity metrics would not have detected an off-target effect. These results indicate the usefulness of the QSEA approach, particularly whenever applicable with public databases, in providing a new means, beyond a simple similarity between ligand structures, to capture SAR trends and thereby contribute to success in drug discovery.

Wendt B; Uhrig U; Bös F

2011-04-01

272

Capturing structure-activity relationships from chemogenomic spaces.  

Science.gov (United States)

Modeling off-target effects is one major goal of chemical biology, particularly in its applications to drug discovery. Here, we describe a new approach that allows the extraction of structure-activity relationships from large chemogenomic spaces starting from a single chemical structure. Several public source databases, offering a vast amount of data on structure and activity for a large number of different targets, have been investigated for their usefulness in automated structure-activity relationships (SAR) extraction. SAR tables were constructed by assembling similar structures around each query structure that have an activity record for a particular target. Quantitative series enrichment analysis (QSEA) was applied to these SAR tables to identify trends and to transform these trends into topomer CoMFA models. Overall more than 1700 SAR tables with topomer CoMFA models have been obtained from the ChEMBL, PubChem, and ChemBank databases. These models were able to highlight the structural trends associated with various off-target effects of marketed drugs, including cases where other structural similarity metrics would not have detected an off-target effect. These results indicate the usefulness of the QSEA approach, particularly whenever applicable with public databases, in providing a new means, beyond a simple similarity between ligand structures, to capture SAR trends and thereby contribute to success in drug discovery. PMID:21410249

Wendt, Bernd; Uhrig, Ulrike; Bös, Fabian

2011-03-16

273

[CONS-32: factor structure and psychometric properties].  

UK PubMed Central (United Kingdom)

CONS-32: Factor structure and psychometric properties. Risk prevention in the construction industry has a psychosocial etiology. This article studies the psychometric properties of a scale (CONS-32) created to detect personal prevention and job-related risks. The 336 participants in the present study are from the construction industry and reside in Catalonia. After exploratory factor analysis of the scale, the structure is shown to consist of four factors that involve job characteristics and individual behaviours. The results indicate adequate reliability. Therefore, the present scale may be ideal for identifying safety risks in the construction industry.

Boada Grau J; González Recio S; Vigil-Colet A; Mañas Rodríguez MA; Agulló Tomás E

2009-02-01

274

Electronic structure and magnetic properties of actinides  

International Nuclear Information System (INIS)

The study of the actinide series shows the change between transition metal behavior and lanthanide behavior, between constant weak paramagnetism for thorium and strong Curie-Weiss paramagnetism for curium. Curium is shown to be the first metal of the actinide series to be magnetically ordered, its Neel temperature being 52K. The magnetic properties of the actinides depending on all the peripheral electrons, their electronic structure was studied and an attempt was made to determine it by means of a phenomenological model. Attempts were also made to interrelate the different physical properties which depend on the outer electronic structure.

1975-01-01

275

Quantitative structure-activity relationships for fluoroelastomer/chlorofluorocarbon systems  

Energy Technology Data Exchange (ETDEWEB)

This paper reports on swell, tensile, and modulus data that were determined for a fluoroelastomer after exposure to a series of chlorofluorocarbon model fluids. Quantitative structure-activity relationships (QSAR) were developed for the swell as a function of the number of carbons and chlorines and for tensile strength as a function of carbon number and chlorine positions in the chlorofluorocarbons.

Paciorek, K.J.L.; Masuda, S.R.; Nakahara, J.H. (Ultrasystems, Inc., Irvine, CA (US)); Snyder, C.E. Jr.; Warner, W.M. (WRDC/Materials Lab., Wright-Patterson Air Force Base, OH (US))

1991-12-01

276

Review of Quantitative Structure - Activity Relationships for Acute Mammalian Toxicity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 a...

Ivanka Tsakovska; Iglika Lessigiarska; Tatiana Netzeva; Ilza Pajeva; Andrew Worth

277

Modeling of microstructure property relationships in titanium-aluminum-vanadium  

Science.gov (United States)

Fuzzy logic neural network models were developed to predict the room temperature tensile behavior of Ti-6Al-4V. This involved the development of a database relating microstructure to properties. This necessitated establishing heat treatment processes to develop microstructural features, mechanical testing of samples, creating rigorous stereology procedures, developing numerical models to predict mechanical behavior, and determining trends and inter-relationships relating microstructural features to mechanical properties. Microstructural features were developed using a Gleeble(TM) 1500 Thermal-mechanical simulator. Samples were obtained from mill annealed plate material and both alpha + beta forged and beta forged materials. A total of 72 samples were beta solutionized and heat treated using different heating and cooling conditions. Rigorous stereology procedures were developed to characterize the important microstructural features. The features included Widmanstatten alpha lath thickness, volume fraction of total alpha, volume fraction of Widmanstatten alpha, grain boundary alpha thickness, mean edge length, colony scale factor, and prior beta grain size factor. Chemical composition was also determined using standard chemical analysis and microscopy techniques. The samples were tested for yield strength, ultimate tensile strength, and elongation at room temperature. Results from the tests and the characterization were used to develop fuzzy logic neural network models to predict the mechanical behaviors and develop relationships between the microstructural features (using CubiCalc RTC(TM)). Results were compared to standard multi-variable regression models. The fuzzy logic neural network models were able to predict the yield, and ultimate tensile strength, within acceptable error ranges with a limited number of input data samples. The models also predicted the elongation values but with larger errors. Of particular importance, the models identified the importance of the Widmanstatten alpha lath widths, the mean edge length of the Widmanstatten alpha laths, the colony scale factor, and the prior beta grain size to the tensile behavior. The trends also identified the inter-relationship between the microstructural features. Chemical composition data for the primary alloying elements and interstitials was also determined to help explain the results in terms of traditional metallurgy.

Tiley, Jaimie Scott

278

Structures, physical properties, and chemistry of layered oxychalcogenides and oxypnictides.  

Science.gov (United States)

A series of layered oxychalcogenide and oxypnictide solids is described that contain oxide layers separated by distinct layers, which contain the softer chalcogenide (S, Se, Te) or pnictide (P, As, Sb, Bi) anions. The relationships between the crystal structures adopted by these compounds are described, and the physical and chemical properties of these materials are related to the structures and the properties of the elements. The properties exhibited by the oxychalcogenide materials include semiconductor properties, for example, in LaOCuCh (Ch = chalcogenide) and derivatives, unusual magnetic properties exhibited by the class Sr 2MO 2Cu 2-deltaS 2 (M = Mn, Co, Ni), and redox properties exhibited by the materials Sr 2MnO 2Cu 2 m-0.5 S m+1 ( m = 1-3) and Sr 4Mn 3O 7.5Cu 2Ch 2 (Ch = S, Se). Recent results in the oxychalcogenide area are reviewed, and some new results on the intriguing series of compounds Sr 2MO 2Cu 2-deltaS 2 (M = Mn, Co, Ni) are reported. Oxypnictides have received less recent attention, but this is changing: a new frenzy of research is underway following the discovery of high-temperature superconductivity (>40 K) in derivatives of the layered oxyarsenide LaOFeAs. The early results in this exciting new area will be reviewed. PMID:18821814

Clarke, Simon J; Adamson, Paul; Herkelrath, Sebastian J C; Rutt, Oliver J; Parker, Dinah R; Pitcher, Michael J; Smura, Catherine F

2008-10-01

279

Relationship between enzyme properties and disease progression in Canavan disease.  

Science.gov (United States)

Canavan disease (CD) is a fatal neurological disorder caused by defects in the gene that encodes for a critical metabolic enzyme. The enzyme aspartoacylase catalyzes the deacetylation of N-acetylaspartate to produce acetate required for fatty acid biosynthesis in the brain. The loss of aspartoacylase activity leads to the demyelination and disrupted brain development that is found in CD patients. Sixteen different clinical mutants of aspartoacylase have been cloned, expressed and purified to examine their properties and the relationship between enzyme properties and disease phenotype. In contrast to numerous cell culture studies that reported virtually complete loss of function, each of these purified mutant enzymes was found to have measureable catalytic activity. However, the activities of these mutants are diminished, by as little as three-fold to greater than 100-fold when compared to the native enzyme. Many of these mutated enzyme forms show decreased thermal stability and an increased propensity for denaturation upon exposure to urea, but only four of the 16 mutants examined showed both diminished thermal and diminished conformational stability. Significantly, each of these lower stability mutants are responsible for the more severe phenotypes of CD, while patients with milder forms of CD have aspartoacylase mutants with generally high catalytic activity and with either good thermal or good conformational stability. These results suggest that the loss of catalytic function and the accumulation of N-acetylaspartate in Canavan disease is at least partially a consequence of the decreased protein stability caused by these mutations. PMID:22850825

Zano, Stephen; Wijayasinghe, Yasanandana S; Malik, Radhika; Smith, Joshua; Viola, Ronald E

2012-08-01

280

Merocyanine dyes: synthesis, structure, properties and applications  

Energy Technology Data Exchange (ETDEWEB)

Key approaches to the synthesis of merocyanine dyes are summarised. The dependence of the dye properties on their chemical structure, the solvent nature and the aggregation type is analysed. The main methods of studying the electronic structure of merocyanines are considered. Attention is focused on polyene-polymethine electron transitions. The applications of merocyanines in modern research, including the design of new materials and technologies (non-linear optics, photovoltaics, holography, etc.) are presented.

Kulinich, A V; Ishchenko, Aleksandr A [Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kiev (Ukraine)

2009-02-28

 
 
 
 
281

Structure and physicochemical properties of irradiated ?-cellulose  

International Nuclear Information System (INIS)

Results of experimental study of the structure and physicochemical properties of ?-irradiated ?-cellulose are considered and generalized. Regularities in the change of dynamic viscosity and polymerization degree of ?-cellulose under the action of small irradiation doses are detected. Using X-ray diffraction analysis it is shown that the structure of ?-cellulose is preserved in the process of irradiation up to absorbed dose of 100 kGy.

1991-01-01

282

Strength properties of structural ceramics at elevated temperatures. ; Relationship between fracture toughness and fracture strength of smooth specimen. Kozoyo ceramics no koon kyodo tokusei. ; Hakai jinsei to heikatsuzai no kyodo no sokan  

Energy Technology Data Exchange (ETDEWEB)

Development of material with high toughness, the strength evaluation method (at high temperatures in particular) and accumulation of data are necessary for acceptance of ceramics as structural material. In this research, the strength of smooth speciments at room temperatures as well as high temperatures was measured using atmospheric sintered silicon nitride and silicon carbide and the fracture toughness was measured with Chevron-notched specimens and CSF specimens. Then the problematical points at the measurement of fracture toughness and the relationship between strength and fracture toughness of smooth specimens were studied fracture-dynamically. A part of the obtained results is as follows: The cause of fracture of a smooth silicon nitride specimen is mainly a defect of inclusion and the bonding power between inclusion and matrix declines as temperautre increases. The temperature dependencies of fracture toughness of both specimens are different depending upon the measuring methods used. When the fracture strength of a smooth silicon nitride specimen is evaluated by equivalent crack length of defect and fracture stress, the temperature dependency of the above strength at a high temperature zone agrees with the fracture toughness by the CSF method. 14 refs., 9 figs.

Koiso, N. (Tokyo Metropolitan Inst. of Technology, Tokyo (Japan))

1991-04-15

283

Polymers structure and properties introduction; Polymeres structure et proprietes introduction  

Energy Technology Data Exchange (ETDEWEB)

This introduction course to the Polymers science, show the relations that exist between the structure of these macro molecular materials and their properties. This presentation begins with the study of the smallest elements of this structure and it goes on considering bigger and bigger and more and more complex arrangements; Then, this book treats the mechanical behaviour of polymers, by establishing as much as possible, bonds with their macro molecular nature. Then, it ends with the analysis of thermal, optical and electrical properties. (N.C.)

Oudet, Ch. [Ecole Nationale Superieure des Mines, 75 - Paris (France)

1993-12-01

284

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

285

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

286

The structure and properties of water  

CERN Multimedia

The authors have correlated many experimental observations and theoretical discussions from the scientific literature on water. Topics covered include the water molecule and forces between water molecules, the thermodynamic properties of steam, the structures of the ices, hydrogen bonding in ice and water and much more.

Eisenberg, David S

2005-01-01

287

Chemical graphs, molecular matrices and topological indices in chemoinformatics and quantitative structure-activity relationships§.  

UK PubMed Central (United Kingdom)

Chemical and molecular graphs have fundamental applications in chemoinformatics, quantitative structureproperty relationships (QSPR), quantitative structure-activity relationships (QSAR), virtual screening of chemical libraries, and computational drug design. Chemoinformatics applications of graphs include chemical structure representation and coding, database search and retrieval, and physicochemical property prediction. QSPR, QSAR and virtual screening are based on the structure-property principle, which states that the physicochemical and biological properties of chemical compounds can be predicted from their chemical structure. Such structure-property correlations are usually developed from topological indices and fingerprints computed from the molecular graph and from molecular descriptors computed from the three-dimensional chemical structure. We present here a selection of the most important graph descriptors and topological indices, including molecular matrices, graph spectra, spectral moments, graph polynomials, and vertex topological indices. These graph descriptors are used to define several topological indices based on molecular connectivity, graph distance, reciprocal distance, distance-degree, distance-valency, spectra, polynomials, and information theory concepts. The molecular descriptors and topological indices can be developed with a more general approach, based on molecular graph operators, which define a family of graph indices related by a common formula. Graph descriptors and topological indices for molecules containing heteroatoms and multiple bonds are computed with weighting schemes based on atomic properties, such as the atomic number, covalent radius, or electronegativity. The correlation in QSPR and QSAR models can be improved by optimizing some parameters in the formula of topological indices, as demonstrated for structural descriptors based on atomic connectivity and graph distance.

Ivanciuc O

2013-06-01

288

Structure, chemistry, and properties of mineral nanoparticles  

Energy Technology Data Exchange (ETDEWEB)

Nanoparticle properties can depart markedly from their bulk analog materials, including large differences in chemical reactivity, molecular and electronic structure, and mechanical behavior. The greatest changes are expected at the smallest sizes, e.g. 10 nm and below, where surface effects are expected to dominate bonding, shape and energy considerations. The precise chemistry at nanoparticle interfaces can have a profound effect on structure, phase transformations, strain, and reactivity. Certain phases may exist only as nanoparticles, requiring transformations in chemistry, stoichiometry and structure with evolution to larger sizes. In general, mineralogical nanoparticles have been little studied.

Waychunas, G.A.; Zhang, H.; Gilbert, B.

2008-12-02

289

A New Structural Property of SAT  

CERN Document Server

We review a minimum set of notions from our previous paper on structural properties of SAT at arXiv:0802.1790 that will allow us to define and discuss the "complete internal independence" of a decision problem. This property is strictly stronger than the independence property that was called "strong internal independence" in cited paper. We show that SAT exhibits this property. We argue that this form of independence of a decision problem is the strongest possible for a problem. By relying upon this maximally strong form of internal independence, we reformulate in more strict terms the informal remarks on possible exponentiality of SAT that concluded our previous paper. The net result of that reformulation is a hint for a proof for SAT being exponential. We conjecture that a complete proof of that proposition can be obtained by strictly following the line of given hint of proof.

Di Zenzo, Silvano

2008-01-01

290

[Volunteer satisfaction: Internal structure and relationship with permanence in organizations].  

UK PubMed Central (United Kingdom)

Volunteer satisfaction: Internal structure and relationship with permanence in organizations. The concept of satisfaction is considered theoretically relevant in practically all the studies that have investigated the factors that influence the permanence of volunteer participation in organizations. However, the practical results are not conclusive, perhaps due to the wide range of ways in which the concept is understood and measured. The object of this study is: to analyse the internal structure of satisfaction and to verify its relationship with volunteer duration in organizations. The results of the factor analysis yield a three-factor structure: Satisfaction with the management of the organization, Satisfaction with the tasks, Satisfaction of motivations. The three factors allow us to differentiate between individuals who remain in the organization for a period of 12 consecutive months, and those who leave earlier. The results of structural equation model analysis show that the relationship between satisfaction and the length of time that volunteers stay with the organization is affected by the intention to remain.

Vecina Jiménez ML; Chacón Fuertes F; Sueiro Abad MJ

2009-02-01

291

Relationships between forest structure and vegetation indices in Atlantic Rainforest.  

UK PubMed Central (United Kingdom)

The alliance between remote sensing techniques and biophysical indicators can be valuable to studies on diagnosis and monitoring, especially in threatened habitats, such as the Atlantic Rainforest. This approach may improve monitoring through diagnosing forest fragments instead of quantifying only forest area reduction. This paper aims to evaluate relationships between forest structure and vegetation indices in Atlantic Rainforest fragments, in southeastern Brazil. Two Landsat 7 ETM+ images acquired in humid and dry seasons were used, and measurements of forest structure in nine forest fragments and in a continuous forest area in the Guapiaçú River Basin, in Rio de Janeiro State were taken. Three vegetation indices (normalized difference vegetation index (NDVI), moisture vegetation index using Landsat's band 5 (MVI5) and moisture vegetation index using Landsat's band 7 (MVI7)) were correlated with measurements of forest structure (frequency of multiple-stemmed trees, density of trees, mean and range of tree diameter, mean and range of tree height and average of basal area). Models describing the relationships between forest structure and vegetation indices using linear regression analysis were also developed. MVI5 and MVI7 showed the best performances in dense humid forests, whereas NDVI seems to be a good indicator of green biomass in deciduous and dry forests. Moreover, the saturation matter in vegetation indices and the transferability of relationships between biophysical characteristics and vegetation indices to other sites and times were discussed.

Freitas SR; Mello MCS; Cruz CBM

2005-10-01

292

Specialists meeting on properties of primary circuit structural materials including environmental effects  

International Nuclear Information System (INIS)

[en] The Specialists Meeting on Properties of Primary Circuit Structural Materials of LMFBRs covered the following topics: overview of materials program in different countries; mechanical properties of materials in air; fracture mechanics studies - component related activities; impact of environmental influences on mechanical properties; relationship of material properties and design methods. The purpose of the meeting was to provide a forum for exchange of information on structural materials behaviour in primary circuit of fast breeder reactors. Special emphasis was placed on environmental effects such as influence of sodium and irradiation on mechanical properties of reactor materials

1977-01-01

293

Silicon nitride ceramics – review of structure, processing and properties  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: The purpose of this review is to examine the development of silicon nitride and the related sialons and their processing into a range of high-grade structural ceramic materials.Design/methodology/approach: Silicon nitride is one of the major structural ceramics that possesses high flexural strength, good fracture resistance, good creep resistance and high hardness. These properties arise because of the processing route which involves liquid phase sintering and the development of microstructures in which high aspect ratio grains and intergranular glass phase lead to excellent fracture toughness and high strengthFindings: This review has examined the development of silicon nitride and the related sialons and their processing into a “family” of structural ceramic materials with high hardness, strength, fracture toughness, creeo resistance and wear resistance.Practical implications: The development of knowledge of microstructure–property relationships in silicon nitride materials is outlined, particularly recent advances in understanding of the effects of grain boundary chemistry and structure on mechanical properties.Originality/value: This review should be of interest to scientists and engineers concerned with the processing and use of ceramics for engineering applications.

S. Hampshire

2007-01-01

294

Nucleon structure and properties of dense matter  

International Nuclear Information System (INIS)

[en] We consider the properties of dense matter in a framework of the Skyrme soliton model and the chiral bag model. The influence of the nucleon structure on the equation of state of dense matter is emphasized. We find that in both models the energy per unit volume is proportional to n4/3, n being the baryon number density. We discuss the properties of neutron stars with a derived equation of state. The role of many-body effects is investigated. The effect of including higher order terms in the chiral lagrangian is examined. The phase transition to quark matter is studied. 29 refs., 6 figs. (author)

1988-01-01

295

Structural and rheological properties of meibomian lipid.  

UK PubMed Central (United Kingdom)

PURPOSE: We explore the unique rheological and structural properties of human and bovine meibomian lipids to provide insight into the physical behavior of the human tear-film lipid layer (TFLL). METHODS: Bulk rheological properties of pooled meibomian lipids were measured by a commercial stress-controlled rheometer; a home-built interfacial stress rheometer (ISR) probed the interfacial viscoelasticity of spread layers of meibomian lipids. Small- and wide-angle x-ray scattering detected the presence and melting of dispersed crystal structures. Microscope examination under cross polarizers provided confirmation of ordered crystals. A differential scanning calorimeter (DSC) analyzed phase transitions in bulk samples of bovine meibum. RESULTS: Bulk and interfacial rheology measurements show that meibum is extremely viscous and highly elastic. It is also a non-Newtonian, shear-thinning fluid. Small- and wide-angle x-ray diffraction (SAXS and WAXS), as well as differential scanning calorimetry (DSC) and polarizing microscopy, confirm the presence of suspended lamellar-crystal structures at physiologic temperature. CONCLUSIONS: We studied meibum architecture and its relation to bulk and interfacial rheology. Bovine and human meibomian lipids exhibit similar physical properties. From all structural probes utilized, we find a melt transition near eye temperature at which lamellar crystals liquefy. Our proposed structure for the tear-film lipid layer at physiologic temperature is a highly viscoelastic, shear-thinning liquid suspension consisting of lipid lamellar-crystallite particulates immersed in a continuous liquid phase with no long-range order. When spread over on-eye tear, the TFLL is a duplex film that exhibits bulk liquid properties and two separate interfaces, air/lipid and water/lipid, with aqueous protein and surfactantlike lipids adsorbed at the water/lipid surface.

Rosenfeld L; Cerretani C; Leiske DL; Toney MF; Radke CJ; Fuller GG

2013-04-01

296

Structure activity relationship studies of tricyclic bispyran sulfone ?-secretase inhibitors.  

UK PubMed Central (United Kingdom)

An investigation is detailed of the structure activity relationships (SAR) of two sulfone side chains of compound (-)-1a (SCH 900229), a potent, PS1-selective ?-secretase inhibitor and clinical candidate for the treatment of Alzheimer's disease. Specifically, 4-CF(3) and 4-Br substituted arylsulfone analogs, (-)-1b and (-)-1c, are equipotent to compound (-)-1a. On the right hand side chain, linker size and terminal substituents of the pendant sulfone group are also investigated.

Wu WL; Asberom T; Bara T; Bennett C; Burnett DA; Clader J; Domalski M; Greenlee WJ; Josien H; McBriar M; Rajagopalan M; Vicarel M; Xu R; Hyde LA; Del Vecchio RA; Cohen-Williams ME; Song L; Lee J; Terracina G; Zhang Q; Nomeir A; Parker EM; Zhang L

2013-02-01

297

A novel algorithm for QSAR (quantitative structure-activity relationships)  

Energy Technology Data Exchange (ETDEWEB)

A novel approach to quantitative structure-activity relationships (QSAR) is proposed. It is based on the molecular descriptor named the stereo-identification (SID) number. The applicability of this approach to QSAR studies is tested on aquatic toxicities of phenols against fathead minnows (Phimephales promelas). Our approach reproduced successfully the bioactivities of phenols and is superior to the Hall-Kier model based on Randic's connectivity index.

Carter, S. (Univ. of Reading (England)); Nikolic, S.; Trinajstic, N. (Rugjer Boskovic Institute, Croatia (Yugoslavia))

1989-01-01

298

(Quantitative structure-activity relationships in environmental toxicology)  

Energy Technology Data Exchange (ETDEWEB)

The traveler attended the Fourth International Workshop on QSAR (Quantitative Structure-Activity Relationships) in Environmental Toxicology. He was an author or co-author on one platform and two poster presentations. The subject of the workshop offers a framework for analyzing and predicting the fate of chemical pollutants in organisms and the environment. QSAR is highly relevant to the ORNL program on the physicochemical characterization of chemical pollutants for health protection.

Turner, J.E.

1990-10-04

299

Contenido de fenoles solubles e insolubles en las estructuras del grano de maíz y su relación con propiedades físicas/ Content of soluble and insoluble phenols in the structures of corn grain and their relationship with physical properties  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish El estudio de los compuestos fenólicos es importante por las funciones de algunos de ellos en los mecanismos de defensa de la planta contra el ataque de patógenos, así como por sus propiedades antioxidantes, antimutagénicas y anticancerígenas. Los objetivos de este trabajo fueron determinar el contenido de fenoles solubles (FS) e insolubles (FI) en el pericarpio, endospermo y germen del grano de maíz (Zea mays) y su correlación con las propiedades físicas del gran (more) o. Se trabajó con dos genotipos experimentales (HE y H-161) cultivados en diferentes localidades y tres maíces comerciales (Oso, Sable y Leopardo). Se analizaron los FS (libres, glucosilados y esterificados) y FI mediante el método de Folin-Ciocalteu. Las variables físicas del grano fueron: peso hectolítrico (PH), índice de flotación (IF), color de grano (CG) y peso de 100 granos (PCG). El contenido de FS fue más elevado en el germen, seguido del pericarpio y endospermo. Dentro de este tipo de fenoles, en las tres estructuras dominaron los fenoles libres. El mayor contenido de FI se presentó en el pericarpio, seguido del germen y endospermo. Existió diferencia estadística (p Abstract in english The study of phenolic compounds is important for the functions of some of them in plant defense mechanisms plant against pathogen attack and by its antioxidant, antimutagenic and anticarcinogenic properties. The objectives of this study were to determine soluble phenol content (FS) and insoluble (FI) in the pericarp, endosperm and germ of the corn grain (Zea mays) and its correlation with the physical properties of the grain. This work was done with two experimental genot (more) ypes (H and H-161) grown in different locations and three commercial maizes (Oso, Sable and Leopardo). The FS were analyzed (free, glycosylated and esterified) as well as FI using the method of Folin-Ciocalteu. The physical variables of the grain were: hectolitric weight (PH), flotation index (FI), grain color (CG) and weight of 100 grains (PCG). The content of FS was higher in the germ, followed by the pericarp and endosperm. Within this type of phenols, free phenols prevailed in the three structures. The highest content of FI was found in the pericarp, followed by the germ and endosperm. There was statistical difference (p

Cabrera-Soto, M. Luisa; Salinas-Moreno, Yolanda; Velázquez-Cardelas, Gustavo A.; Espinosa Trujillo, Edgar

2009-12-01

300

Relationship between molecular cloud structure and density PDFs  

CERN Document Server

Volume and column density PDFs in molecular clouds are important diagnostics for understanding their general structure. We developed a novel approach to trace the cloud structure by varying the lower PDF cut-off and exploring a suggested mass-density relationship with a power-law index $x^\\prime$. The correspondence of x' as a function of spatial scale to the slope of the high-density PDF tail is studied. To validate the proposed model, we use results from hydrodynamical simulations of a turbulent self-gravitating cloud and recent data on dust continuum emission from the Planck mission.

Stanchev, Orlin; Veltchev, Todor V; Shetty, Rahul

2013-01-01

 
 
 
 
301

Synthetic 2-methoxyestradiol derivatives: structure-activity relationships.  

UK PubMed Central (United Kingdom)

2-Methoxyestradiol (2ME2), a natural metabolite of estradiol which has no estrogenic activity, is a potent antitumor and anti-angiogenic compound, currently undergoing clinical trials for treatment of a variety of cancers. In the last two decades, an ever increasing number of synthetic 2-methoxyestradiol analogues have been reported. Structural changes include A/B/C/D-rings modification, homologation, aromatization, and introduction of various substituents on C-2 position along with substitution of alkyl and ethynyl groups for the 17-hydroxy function. In this review, an attempt has been made to compile the structure-activity relationships of various synthesized 2-methoxyestradiol analogues.

Peyrat JF; Brion JD; Alami M

2012-01-01

302

Applying quantitative structure-activity relationship approaches to nanotoxicology: Current status and future potential.  

UK PubMed Central (United Kingdom)

The potential (eco)toxicological hazard posed by engineered nanoparticles is a major scientific and societal concern since several industrial sectors (e.g. electronics, biomedicine, and cosmetics) are exploiting the innovative properties of nanostructures resulting in their large-scale production. Many consumer products contain nanomaterials and, given their complex life-cycle, it is essential to anticipate their (eco)toxicological properties in a fast and inexpensive way in order to mitigate adverse effects on human health and the environment. In this context, the application of the structure-toxicity paradigm to nanomaterials represents a promising approach. Indeed, according to this paradigm, it is possible to predict toxicological effects induced by chemicals on the basis of their structural similarity with chemicals for which toxicological endpoints have been previously measured. These structure-toxicity relationships can be quantitative or qualitative in nature and they can predict toxicological effects directly from the physicochemical properties of the entities (e.g. nanoparticles) of interest. Therefore, this approach can aid in prioritizing resources in toxicological investigations while reducing the ethical and monetary costs that are related to animal testing. The purpose of this review is to provide a summary of recent key advances in the field of QSAR modelling of nanomaterial toxicity, to identify the major gaps in research required to accelerate the use of quantitative structure-activity relationship (QSAR) methods, and to provide a roadmap for future research needed to achieve QSAR models useful for regulatory purposes.

Winkler DA; Mombelli E; Pietroiusti A; Tran L; Worth A; Fadeel B; McCall MJ

2012-11-01

303

Synthesis, characterization, and structure-property relationships in two new polar oxides: Zn2(MoO4)(SeO3) and Zn2(MoO4)(TeO3).  

UK PubMed Central (United Kingdom)

Two new noncentrosymmetric (NCS) polar oxide materials, Zn(2)(MoO(4))(AO(3)) (A = Se(4+) or Te(4+)), have been synthesized by hydrothermal and solid-state techniques. Their crystal structures have been determined, and characterization of their functional properties (second-harmonic generation, piezoelectricity, and polarization) has been performed. The isostructural materials exhibit a three-dimensional network consisting of ZnO(4), ZnO(6), MoO(4), and AO(3) polyhedra that share edges and corners. Powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicate the materials exhibit moderate SHG efficiencies of 100 × and 80 × ?-SiO(2) for Zn(2)(MoO(4))(SeO(3)) and Zn(2)(MoO(4))(TeO(3)), respectively. Particle size vs SHG efficiency measurements indicate the materials are type 1 non-phase-matchable. Converse piezoelectric measurements resulted in d(33) values of ?14 and ?30 pm/V for Zn(2)(MoO(4))(SeO(3)) and Zn(2)(MoO(4))(TeO(3)), respectively, whereas pyroelectric measurements revealed coefficients of -0.31 and -0.64 ?C/m(2) K at 55 °C for Zn(2)(MoO(4))(SeO(3)) and Zn(2)(MoO(4))(TeO(3)), respectively. Frequency-dependent polarization measurements confirmed that all of the materials are nonferroelectric; that is, the macroscopic polarization is not reversible, or "switchable". Infrared, UV-vis, thermogravimetric, and differential thermal analysis measurements were also performed. First-principles density functional theory (DFT) electronic structure calculations were also done. Crystal data: Zn(2)(MoO(4))(SeO(3)), monoclinic, space group P2(1) (No. 4), a = 5.1809(4) Å, b = 8.3238(7) Å, c = 7.1541(6) Å, ? = 99.413(1)°, V = 305.2(1) Å(3), Z = 2; Zn(2)(MoO(4))(TeO(3)), monoclinic, space group P2(1) (No. 4), a = 5.178(4) Å, b = 8.409(6) Å, c = 7.241(5) Å, ? = 99.351(8)°, V = 311.1(4) Å(3), Z = 2.

Nguyen SD; Kim SH; Halasyamani PS

2011-06-01

304

Synthesis, characterization, and structure-property relationships in two new polar oxides: Zn2(MoO4)(SeO3) and Zn2(MoO4)(TeO3).  

Science.gov (United States)

Two new noncentrosymmetric (NCS) polar oxide materials, Zn(2)(MoO(4))(AO(3)) (A = Se(4+) or Te(4+)), have been synthesized by hydrothermal and solid-state techniques. Their crystal structures have been determined, and characterization of their functional properties (second-harmonic generation, piezoelectricity, and polarization) has been performed. The isostructural materials exhibit a three-dimensional network consisting of ZnO(4), ZnO(6), MoO(4), and AO(3) polyhedra that share edges and corners. Powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicate the materials exhibit moderate SHG efficiencies of 100 × and 80 × ?-SiO(2) for Zn(2)(MoO(4))(SeO(3)) and Zn(2)(MoO(4))(TeO(3)), respectively. Particle size vs SHG efficiency measurements indicate the materials are type 1 non-phase-matchable. Converse piezoelectric measurements resulted in d(33) values of ?14 and ?30 pm/V for Zn(2)(MoO(4))(SeO(3)) and Zn(2)(MoO(4))(TeO(3)), respectively, whereas pyroelectric measurements revealed coefficients of -0.31 and -0.64 ?C/m(2) K at 55 °C for Zn(2)(MoO(4))(SeO(3)) and Zn(2)(MoO(4))(TeO(3)), respectively. Frequency-dependent polarization measurements confirmed that all of the materials are nonferroelectric; that is, the macroscopic polarization is not reversible, or "switchable". Infrared, UV-vis, thermogravimetric, and differential thermal analysis measurements were also performed. First-principles density functional theory (DFT) electronic structure calculations were also done. Crystal data: Zn(2)(MoO(4))(SeO(3)), monoclinic, space group P2(1) (No. 4), a = 5.1809(4) Å, b = 8.3238(7) Å, c = 7.1541(6) Å, ? = 99.413(1)°, V = 305.2(1) Å(3), Z = 2; Zn(2)(MoO(4))(TeO(3)), monoclinic, space group P2(1) (No. 4), a = 5.178(4) Å, b = 8.409(6) Å, c = 7.241(5) Å, ? = 99.351(8)°, V = 311.1(4) Å(3), Z = 2. PMID:21557565

Nguyen, Sau Doan; Kim, Sang-Hwan; Halasyamani, P Shiv

2011-05-10

305

Structure and properties of carbon fiber sorbents  

International Nuclear Information System (INIS)

Adsorption properties of fiber carbon materials, differing in initial raw material, preparation process, final treatment temperature, i. e. the factors responsible for the fiber structure, were studied. Conditions of surface activation, like oxidant nature, gas feed rate, oxidation temperature and duration were varied in a wide range of values to prepare adsorbents featuring prescribed parameters of porous structure. One type of carbon fiber was chosen and activation conditions, permitting development of the initial surface from 0.5 to 2000 m2/g without any loss of mechanical strength, were selected for it

2002-01-01

306

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

307

Bioisosterism of Urea-Based GCPII Inhibitors: Synthesis and Structure-Activity Relationships Studies  

Science.gov (United States)

We report a strategy based on bioisosterism to improve the physicochemical properties of existing hydrophilic, urea-based GCPII inhibitors. Comprehensive structure-activity relationship studies of the P1’ site of ZJ-43- and DCIBzL-based compounds identified several glutamate-free inhibitors with Ki values below 20 nM. Among them, compound 32d (Ki = 11 nM) exhibited selective uptake in GCPII-expressing tumors by SPECT-CT imaging in mice. A novel conformational change of amino acids in the S1’ pharmacophore pocket was observed in the X-ray crystal structure of GCPII complexed with 32d.

Wang, Haofan; Byun, Youngjoo; Barinka, Cyril; Pullambhatla, Mrudula; Bhang, Hyoeun C.; Fox, James J.; Lubkowski, Jacek; Mease, Ronnie C.; Pomper, Martin G.

2009-01-01

308

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.; Nasouri K.; Mousavi Shoushtari A.; Kaflou A.

2013-01-01

309

Spherulitic networks: from structure to rheological property.  

UK PubMed Central (United Kingdom)

A finite element method based on ABAQUS is employed to examine the correlation between the microstructure and the elastic response of planar Cayley treelike fiber networks. It is found that the elastic modulus of the fiber network decreases drastically with the fiber length, following the power law. The power law of elastic modulus G' vs the correlation length xi obtained from this simulation has an exponent of -1.71, which is close to the exponent of -1.5 for a single-domain network of agar gels. On the other hand, the experimental results from multidomain networks give rise to a power law index of -0.49. The difference between -1.5 and -0.49 can be attributed to the multidomain structure, which weakens the structure of the overall system and therefore suppresses the increase in G'. In addition, when the aspect ratio of the fiber is smaller than 20, the radius of the fiber cross-section has a great impact on the network elasticity, while, when the aspect ratio is larger than 20, it has almost no effect on the elastic property of the network. The stress distribution in the network is uniform due to the symmetrical network structure. This study provides a general understanding of the correlation between microscopic structure and the macroscopic properties of soft functional materials.

Shi JH; Liu XY; Li JL; Strom CS; Xu HY

2009-04-01

310

Spherulitic networks: from structure to rheological property.  

Science.gov (United States)

A finite element method based on ABAQUS is employed to examine the correlation between the microstructure and the elastic response of planar Cayley treelike fiber networks. It is found that the elastic modulus of the fiber network decreases drastically with the fiber length, following the power law. The power law of elastic modulus G' vs the correlation length xi obtained from this simulation has an exponent of -1.71, which is close to the exponent of -1.5 for a single-domain network of agar gels. On the other hand, the experimental results from multidomain networks give rise to a power law index of -0.49. The difference between -1.5 and -0.49 can be attributed to the multidomain structure, which weakens the structure of the overall system and therefore suppresses the increase in G'. In addition, when the aspect ratio of the fiber is smaller than 20, the radius of the fiber cross-section has a great impact on the network elasticity, while, when the aspect ratio is larger than 20, it has almost no effect on the elastic property of the network. The stress distribution in the network is uniform due to the symmetrical network structure. This study provides a general understanding of the correlation between microscopic structure and the macroscopic properties of soft functional materials. PMID:19292435

Shi, Jing Hua; Liu, Xiang Yang; Li, Jing Liang; Strom, Christina S; Xu, Hong Yao

2009-04-01

311

Quantitative structure-activity relationships for predicting mutagenicity and carcinogenicity.  

UK PubMed Central (United Kingdom)

Quantitative structure-activity relationships (QSARs) for predicting mutagenicity and carcinogenicity were reviewed. The QSARs for predicting mutagenicity and carcinogenicity have been mostly limited to specific classes of chemicals (e.g., aromatic amines and heteroaromatic nitro chemicals). The motivation to develop QSARs for predicting mutagenicity and carcinogenicity to screen inventories of chemicals has produced four major commercially available computerized systems that are able to predict these endpoints: Deductive estimation of risk from existing knowledge (DEREK) toxicity prediction by komputer assisted technology (TOPKAT), computer automated structure evaluation (CASE), and multiple computer automated structure evaluation (Multicase). A brief overview of these and some other expert systems for predicting mutagenicity and carcinogenicity is provided. The other expert systems for predicting mutagenicity and carcinogenicity include automatic data analysis using pattern recognition techniques (ADAPT), QSAR Expert System (QSAR-ES), OncoLogic computer optimized molecular parametric analysis of chemical toxicity system (COMPACT), and common reactivity pattern (COREPA).

Patlewicz G; Rodford R; Walker JD

2003-08-01

312

Structure-olfactive threshold relationships for pyrazine derivatives.  

UK PubMed Central (United Kingdom)

Structure-olfactive threshold relationships for 40 pyrazine derivatives have been studied by multivariate statistical analysis. Variable descriptors used to describe the molecules studied were obtained using molecular-mechanics software. A correlation coefficient of 0.82 was obtained when all the molecules were included in the model. When the model was established for closely related subsets of molecules, the correlation coefficients obtained were higher and the established models were bilinear. Such models allow the identification of optimal structures corresponding to low olfactive thresholds for the subsets studied. Surprisingly, we find that the optimum structures are included in the set of 40 molecules. The efficiency of the models was supported by the cross-validation technique, where the correlation coefficients were found to be good with respect to the precision of the values of the olfactive thresholds.

Zakarya D; Farhaoui L; Hamidi M; Bouachrine M

2006-09-01

313

Topological structure and relaxation properties of polymers  

International Nuclear Information System (INIS)

The experimental data and theoretical views on the relations between the relaxation properties and structure of polymers are generalised. The attention is focused on the topological structural level, in particular, characteristics including the molecular mass, the molecular mass distribution, the degree of branching, and the covalent and equilibrium network parameters. In relation to the discussion of the relaxation spectrometry concept, the physical meaning of the kinetic parameters of local transitions and the nature of ?-relaxation are considered. Methods of calculation of the continuous and discrete relaxation spectra from the results of relaxation and rheological experiments are described. Data establishing the relation between the relaxation spectrum and the topological structure of a polymer are analysed.

2005-10-31

314

EFFECT OF WEAVE STRUCTURE ON FABRIC PROPERTIES  

Directory of Open Access Journals (Sweden)

Full Text Available 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 characteristics of woven fabric. It is expected that the study will be helpful in (i) fixing cost of woven fabric more efficiently, (ii) generating a betterunderstanding about the weaving of fabrics having different weave structures, (iii) manufacturing fabric more efficiently from the technical and technological point of view and finally fashion designing of woven garments.

Md. Ruhul Amin; Md. Mahbubul Haque

2011-01-01

315

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

316

Structure-function relationships in a bacterial DING protein.  

UK PubMed Central (United Kingdom)

A recombinant DING protein from Pseudomonas fluorescens has been previously shown to have a phosphate-binding site, and to be mitogenic for human cells. Here we report the three-dimensional structure of the protein, confirming a close similarity to the "Venus flytrap" structure seen in other human and bacterial phosphate-binding proteins. Site-directed mutagenesis confirms the role of a key residue involved in phosphate binding, and that the mitogenic activity is not dependent on this property. Deletion of one of the two hinged domains that constitute the Venus flytrap also eliminates phosphate binding whilst enhancing mitogenic activity.

Ahn S; Moniot S; Elias M; Chabriere E; Kim D; Scott K

2007-07-01

317

Structure-function relationships in a bacterial DING protein.  

Science.gov (United States)

A recombinant DING protein from Pseudomonas fluorescens has been previously shown to have a phosphate-binding site, and to be mitogenic for human cells. Here we report the three-dimensional structure of the protein, confirming a close similarity to the "Venus flytrap" structure seen in other human and bacterial phosphate-binding proteins. Site-directed mutagenesis confirms the role of a key residue involved in phosphate binding, and that the mitogenic activity is not dependent on this property. Deletion of one of the two hinged domains that constitute the Venus flytrap also eliminates phosphate binding whilst enhancing mitogenic activity. PMID:17612529

Ahn, Soyeon; Moniot, Sebastien; Elias, Mikael; Chabriere, Eric; Kim, Donghyo; Scott, Ken

2007-06-27

318

The Relationship between Financial Flexibility and Capital Structure Decisions  

Directory of Open Access Journals (Sweden)

Full Text Available Making decisions about capital structure is one of the most challenging and problematic issues companies face and thereby it is the most crucial decisions companies have to make for their survival. The aim of this study was to investigate the relationship between financial flexibility and capital structure decisions in accepted companies in Tehran Stock Exchange with using Falkner and Wang Model. Results of testing hypothesis which are based on a sample- that is consisted of 82 firms for a period of five years from 2006 to 2011- using multivariate linear regression models as well as panel data method, implied that marginal value of cash is negative in terms of market, i.e. the market is not willing to raise funds and will not evaluate this increase to be positive in funds. Furthermore, findings represent that there is no significant relationship between marginal value of financial flexibility and capital structure decisions of firms and firms would not pay attention to financial flexibility level in their decisions regarding increasing or decreasing debts, which in long term would result in loosing financial flexibility as well as profitable investment opportunities.

Roya Darabi; Salah Mohamadi; Ahmad GHasemi; Shanaz Forozan

2013-01-01

319

Relationships between structure, density and strength of human trabecular bone.  

Science.gov (United States)

The article deals with the examination of the relationships between density, structure parameters and strength of human trabecular bone. The tests were carried out on the samples taken from osteoporotic and coxarthrotic human femoral heads. The samples cylindrical in shape had the diameters of 10 mm and the height of 8.5 mm. During the tests with microCT scanner the parameters of a sample structure were measured. Bone mineral density (BMD) was measured as well. The samples were subjected to compression in order to assess the ultimate compression strength sigma(c). The relationships between two-element combinations (BMD and one of the structure parameters) and the compression strength of the samples have been studied. The consistency of the results for multiple regression and response surface regression was estimated based on the correlation coefficient R. For the examined pairs of parameters, the value R increased in the range of 7-30% in comparison with the case where for the strength description only BMD was used. Additionally, the authors' own models of two-variable regression was calculated. The comparison of the results obtained for all models of regression based on the coefficient E proved the consistency of these results. PMID:20405816

Mazurkiewicz, Adam; Topoli?ski, Tomasz

2009-01-01

320

Electrochemically Deposited Nickel Membranes; Process-Microstructure-Property Relationships  

DEFF Research Database (Denmark)

This paper reports on the manufacturing, surface morphology, internal structure and mechanical properties of Ni-foils used as membranes in reference-microphones. Two types of foils, referred to as S-type and 0-type foils, were electrochemically deposited from a Watts-type electrolyte, with (S-type) or without (0-type) the use of the sulphur-containing additive sodium saccharin. Both types of Ni-foils appeared perfectly smooth when investigated with scanning electron microscopy (SEM), while atomic force microscopy (AFM) and transmission electron microscopy (TEM), revealed differences in the surface morphologies and a smaller grain-size in the S-type foils. X-ray diffraction showed a texture component in both types of Ni-foils, most pronounced for 0-type foils. A minor -texture component observed in both foil types was strongest in the S-type foils. Mechanically 0-type foils proved more ductile than S-type foils during thin film tensile testing, due to microstructural defects caused by sodium saccharin duringdeposition. Tensile strengths in the order of 700-1000 MPa were observed - highest for the more ductile 0-type foils. A hardness in the order of 6 GPa (590 HV) was found by nanoindentation. Keywords: Nickel; electrodeposition; microstructure; mechanical testing; thin films

Jensen, Jens Dahl; Pantleon, Karen

2003-01-01

 
 
 
 
321

Structural Properties of Silk Electro-Gels  

Science.gov (United States)

The interest in Bombyx Mori silk emerges from its biocompatibility and its structural superiority to synthetic polymers. Our particular interest lies in understanding the capabilities of silk electro-gels because of their reversibility and tunable adhesion. We create an electro-gel by applying a DC electric potential across a reconstituted silk fibroin solution derived directly from Bombyx Mori cocoons. This process leads to the intermolecular self-assembly of fibroin proteins into a weak gel. In this talk we will present our results on the effects of applied shear on electro-gels. We quantify the structural properties while dynamically imaging shear induced fiber formation; known as fibrillogenesis. It is observed that the mechanical properties and microstructure of these materials are highly dependent on shear history. We will also discuss the role of surface modification, through micro-patterning, on the observed gel structure. Our results provide an understanding of both the viscoelastiticity and microstucture of reconstituted silks that are being utilized as tissue scaffolds.

Tabatabai, A. P.; Urbach, J. S.; Blair, D. L.; Kaplan, D. L.

2013-03-01

322

Quantitative structure-activity relationships in amphotericin B derivatives.  

Science.gov (United States)

The quantitative structure-activity relationships studies of amphotericin B and its 16 semisynthetic derivatives obtained by modification at carboxyl and amino groups have been done. The results of five biological tests were subjected to principal component analysis, a numerical method useful in the investigation of large sets of data. For some compounds, also, interaction with lipidic vesicles was investigated by spectroscopic methods. The results obtained indicate that: (i) The presence of positively charged nitrogen atom (protonable or bearing fixed charge) is indispensable for biological activity and antibiotic-sterol interaction; (ii) The lack of free carboxyl group in the molecule favours the differentiation between cholesterol and ergosterol containing cells. PMID:3278711

Chéron, M; Cybulska, B; Mazerski, J; Grzybowska, J; Czerwi?ski, A; Borowski, E

1988-03-01

323

Perfluoroalkylated surfactants: relationships between structure and acute toxicity in mice.  

Science.gov (United States)

New single chain neutral, and single and double chain zwitterionic perfluoroalkylated surfactants or co-surfactants have been evaluated for in vivo applications. A study of the relationship between structure and acute toxicity in mice is presented. Acute toxicity evaluations i.v. in mice indicate the following trends (increasing tolerance): zwitterionic single-chain less than neutral single-chain less than zwitterionic double-chain and, where the polar head is concerned, single-chain compounds: phosphocholine less than phosphoramidate less than trehalose approximately sucrose less than maltose less than xylitol. PMID:1391421

Mahé, A M; Manoux, J; Valla, A; Follana, R; Zarif, L; Greiner, J; Vierling, P; Riess, J G

1992-01-01

324

Quantitative structure-mutagenic activity relationships of triazino indole derivatives.  

UK PubMed Central (United Kingdom)

The mutagenicity of 3-(4'-benzylidenamino)-5H-1,2,3-triazin[5,4-b]-indol-4-one derivatives, new compounds with considerable platelet antiaggregating activity, was assayed with the Ames test using the Salmonella typhimurium strains TA97, TA98, TA100 and TA102. The adaptive least-squares method (ALS method) was used to carry out a quantitative structure-activity relationship (QSAR) analysis. Three equations, based on 10 congeners, were found for strains TA97, TA98 and TA100. The results suggest that lipophilicity of the substituent decreases the mutagenicity of the series.

García E; Lopez-de-Cerain A; Martinez-Merino V; Monge A

1992-07-01

325

Relationship between chlorofluorocarbon chemical structure and their Salmonella mutagenicity.  

UK PubMed Central (United Kingdom)

This paper is a quantitative analysis of the relationship between the chemical structure and the Salmonella mutagenicity of a number of chlorofluorocarbons (CFC). The molecules were characterized by both molecular orbital and physical chemical parameters. The results of the analysis indicated that the CFC mutagenicity is correlated with two parameters: the free energy of binding to biological receptors, and the energy of the highest occupied molecular orbital (HOMO). Since these are the same factors that would favor the cytochrome P-450-catalyzed metabolism, it would appear that the CFC mutagenicity is determined more by the rate of initial activation than by the rate of DNA attack.

Benigni R; Cotta-Ramusino M; Andreoli C

1991-11-01

326

Relationships between milk coagulation property traits analyzed with different methodologies.  

UK PubMed Central (United Kingdom)

Milk coagulation properties (MCP) analysis is performed using a wide range of methodologies in different countries and laboratories, using different instruments, coagulant activity in the milk, and type of coagulant. This makes it difficult to compare results and data from different research. The aims of this study were to propose a method for the transformation of values of rennet coagulation time (RCT) and curd firmness (a(30)) and to predict the noncoagulation (NC) probability of milk samples analyzed using different methodologies. Individual milk samples were collected during the morning milking in October 2010 from each of 165 Holstein-Friesian dairy cows in 2 freestall barns in Italy, and sent to 3 laboratories for MCP analysis. For each laboratory, MCP analysis was performed using a different methodology: A, with a computerized renneting meter instrument using 0.051 international milk clotting units (IMCU)/mL of coagulant activity; B, with a Lattodinamografo (Foss-Italia, Padova, Italy) using 0.051 IMCU/mL of coagulant activity; and C, with an Optigraph (Ysebaert, Frépillon, France) using 0.120 IMCU/mL of coagulant activity. The relationships between MCP traits were analyzed with correlation and regression analyses for each pair of methodologies. For each MCP trait, 2 regression models were applied: model 1 was a single regression model, where the dependent and independent variables were the same MCP trait determined by 2 different methodologies; in model 2, both a(30) and RCT were included as independent variables. The NC probabilities for laboratories with the highest number of NC samples were predicted based on the RCT and a(30) values measured in the laboratories with lower number of NC samples using logistic regression and receiver operating characteristic analysis. The percentages of NC samples were 4.2, 11.5, and 0.6% for A, B, and C, respectively. The transformation of MCP traits was more precise with model 1 for RCT (R(2): 0.77-0.82) than for a(30) (R(2): 0.28-0.63). The application of model 2 was needed when the C measurements were transformed into the other scales. The analyses of NC probabilities of milk samples showed that NC samples from one methodology were well distinguishable (with an accuracy of 0.972-0.996) based on the rennet coagulation time measured with the other methodology. A standard definition for MCP traits analysis is needed to enable reliable comparisons between MCP traits recorded in different laboratories and in different animal populations and breeds.

Pretto D; Kaart T; Vallas M; Jõudu I; Henno M; Ancilotto L; Cassandro M; Pärna E

2011-09-01

327

Microstructure, process, and tensile property relationships in an investment cast near-?TiAl alloy  

International Nuclear Information System (INIS)

[en] The brittle nature of near-? TiAl alloys makes fabrication difficult. This paper reports on developing near-net shape technologies, such as investment casting, for these alloys which is one of the essential approached to their commercial introduction. The near-? TiAl alloy Ti-48Al-2Nb-2Cr (a%) is investment cast with two cooling rates. The effect of casting cooling rate on the fill and surface integrity was studied for complex shape thin walled components. Block and bar castings are hot isostatically pressed (HIP'd) and heat treated to produce duplex (lamellar + equiaxed) microstructures for mechanical property evaluation. The relationships between the casting conditions, microstructures, and tensile properties are studied. The strength and elongation below the ductile to brittle transition temperature are dependent on the casting cooling rate and section size. The tensile properties improved with faster cooling during the casting process as a result of microstructural refinement. Faster cooled castings are more fully transformed to a duplex structure during post-casting heat treatments. Above the ductile to brittle transition temperature the effect of casting cooling rate on tensile properties is less pronounced

1992-01-01

328

Identifying extended entity-relationship object structures in relational schemas  

Energy Technology Data Exchange (ETDEWEB)

One of the main goals of database design is to capture the structural semantics of information systems. This goal can be achieved by using an object-oriented data model for specifying the structure of an information system in terms of objects and object connections, and then translating such a specification into a relational database definition (schema). In previous papers the authors have investigated the problem of representing object structures using relational constructs in the context of an extended entity-relationship (EER) model. In this paper they address the reverse problem, namely of identifying EER object structures in relational schemas. They consider relational schemas consisting of relation-schemes, key dependencies, and key-based inclusion dependencies (referential integrity constraints). Schemas of this form are said to be EER-convertible if they can be associated with an EER schema. A procedure that determines whether a relational schema is EER-convertible if they can be associated with an EER schema. A procedure that determines whether a relational schema is EER-convertible is developed. They propose a normal form for relational schemas representing EER object structures. For EER-convertible relational schemas they present the corresponding normalization procedure. The procedures presented in this paper can be used for analyzing the semantics of existing relational databases, and for converting relational database schemas into object-oriented database schemas.

Markowitz, V.M. (Lawrence Berkeley Lab., Berkeley, CA (United States). Dept. of Computer Science Research); Makowsky, J.A. (Technion-Israel Inst. of Tech., Haifa (Israel). Dept. of Computer Science)

1990-08-01

329

A comprehensive analysis of the structure-function relationship in proteins based on local structure similarity.  

UK PubMed Central (United Kingdom)

BACKGROUND: Sequence similarity to characterized proteins provides testable functional hypotheses for less than 50% of the proteins identified by genome sequencing projects. With structural genomics it is believed that structural similarities may give functional hypotheses for many of the remaining proteins. METHODOLOGY/PRINCIPAL FINDINGS: We provide a systematic analysis of the structure-function relationship in proteins using the novel concept of local descriptors of protein structure. A local descriptor is a small substructure of a protein which includes both short- and long-range interactions. We employ a library of commonly reoccurring local descriptors general enough to assemble most existing protein structures. We then model the relationship between these local shapes and Gene Ontology using rule-based learning. Our IF-THEN rule model offers legible, high resolution descriptions that combine local substructures and is able to discriminate functions even for functionally versatile folds such as the frequently occurring TIM barrel and Rossmann fold. By evaluating the predictive performance of the model, we provide a comprehensive quantification of the structure-function relationship based only on local structure similarity. Our findings are, among others, that conserved structure is a stronger prerequisite for enzymatic activity than for binding specificity, and that structure-based predictions complement sequence-based predictions. The model is capable of generating correct hypotheses, as confirmed by a literature study, even when no significant sequence similarity to characterized proteins exists. CONCLUSIONS/SIGNIFICANCE: Our approach offers a new and complete description and quantification of the structure-function relationship in proteins. By demonstrating how our predictions offer higher sensitivity than using global structure, and complement the use of sequence, we show that the presented ideas could advance the development of meta-servers in function prediction.

Hvidsten TR; Laegreid A; Kryshtafovych A; Andersson G; Fidelis K; Komorowski J

2009-01-01

330

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

331

Electronic structure and optical properties of resin.  

UK PubMed Central (United Kingdom)

We used the density of functional theory (DFT) to study the electronic structure and density of states of resin by ab initio calculation. The results show the band gap of resin is 1.7 eV. The covalent bond is combined C/O atoms with H atoms. The O 2p orbital is the biggest effect near the Fermi level. The results of optical properties show the reflectivity is low, and the refractive index is 1.7 in visible light range. The highest absorption coefficient peak is in 490 nm and the value is 75,000.

Rao ZF; Zhou RF

2013-03-01

332

Multimode interference structuresproperties and applications  

Directory of Open Access Journals (Sweden)

Full Text Available 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, Mach–Zehnder interferometers (MZI) and phase shifters.

Marek Blahut; Damian Kasprzak

2004-01-01

333

Penoxsulam--structure-activity relationships of triazolopyrimidine sulfonamides.  

Science.gov (United States)

The discovery of the sulfonamide herbicides, which inhibit the enzyme acetolactate synthase (ALS), has resulted in many investigations to exploit their herbicidal activity. One area which proved particularly productive was the N-aryltriazolo[1,5-c]pyrimidine sulfonamides, providing three commercial herbicides, cloransulam-methyl, diclosulam and florasulam. Additional structure-activity investigations by reversing the sulfonamide linkage resulted in the discovery of triazolopyrimidine sulfonamides with cereal crop selectivity and high levels of grass and broadleaf weed control. Research efforts to exploit these high levels of weed activity ultimately led to the discovery of penoxsulam, a new herbicide developed for grass, sedge and broadleaf weed control in rice. Synthetic efforts and structure-activity relationships leading to the discovery of penoxsulam will be discussed. PMID:19464188

Johnson, Timothy C; Martin, Timothy P; Mann, Richard K; Pobanz, Mark A

2009-02-14

334

Penoxsulam--structure-activity relationships of triazolopyrimidine sulfonamides.  

UK PubMed Central (United Kingdom)

The discovery of the sulfonamide herbicides, which inhibit the enzyme acetolactate synthase (ALS), has resulted in many investigations to exploit their herbicidal activity. One area which proved particularly productive was the N-aryltriazolo[1,5-c]pyrimidine sulfonamides, providing three commercial herbicides, cloransulam-methyl, diclosulam and florasulam. Additional structure-activity investigations by reversing the sulfonamide linkage resulted in the discovery of triazolopyrimidine sulfonamides with cereal crop selectivity and high levels of grass and broadleaf weed control. Research efforts to exploit these high levels of weed activity ultimately led to the discovery of penoxsulam, a new herbicide developed for grass, sedge and broadleaf weed control in rice. Synthetic efforts and structure-activity relationships leading to the discovery of penoxsulam will be discussed.

Johnson TC; Martin TP; Mann RK; Pobanz MA

2009-06-01

335

TMACC: interpretable correlation descriptors for quantitative structure-activity relationships.  

UK PubMed Central (United Kingdom)

Highly predictive topological maximum cross correlation (TMACC) descriptors for the derivation of quantitative structure-activity relationships (QSARs) are presented, based on the widely used autocorrelation method. They require neither the calculation of three-dimensional conformations nor an alignment of structures. We have validated the TMACC descriptors across eight literature data sets, ranging in size from 66 to 361 molecules. In combination with partial least-squares regression, they perform competitively with a current state-of-the-art 2D QSAR methodology, hologram QSAR (HQSAR), yielding larger leave-one-out cross-validated coefficient of determination values (LOO q2) for five data sets. Like HQSAR, these descriptors are also interpretable but do not require hashing. The interpretation both enables the automated extraction of SARs and can give a description in qualitative agreement with more time-consuming 3D and 4D QSAR methods. Open source software for generating the TMACC descriptors is freely available from our Web site.

Melville JL; Hirst JD

2007-03-01

336

Structure-cardiac activity relationship of C19-diterpenoid alkaloids.  

UK PubMed Central (United Kingdom)

Thirty three C19-diterpenoid alkaloids, twenty-two prepared from known C19-diterpenoid alkaloids and eleven isolated from Aconitum and Delphinium spp. were evaluated for their cardiac activity in the isolated bullfrog heart assay. Among them, eleven compounds exhibited cardiac activity, with average rate of amplitude increase in the range of 16-118%. Compound 7, mesaconine (17), hypaconine (25), and beiwutinine (26) exhibited strong cardiac activities relative to the reference drug. The structure-activity relationship data acquired indicated that an alpha-hydroxyl group at C-15, a hydroxyl group at C-8, an alpha-methoxyl or hydroxyl group at C-1, and a secondary amine or N-methyl group in ring A are important structure features necessary for the cardiac activities of the aconitine-type C19-diterpenoid alkaloids without any ester groups. In addition, an alpha-hydroxyl group at C-3 is also helpful for the cardiac activity of these alkaloids.

Jian XX; Tang P; Liu XX; Chao RB; Chen QH; She XK; Chen DL; Wang FP

2012-06-01

337

Mechanical properties and the structure of magnetic composite materials  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: The purpose of the paper is to present the material and technological solution which makes possibleobtaining soft and hard magnetic composite materials: nanocrystalline material – polymer.Design/methodology/approach: The main base of the paper is to compare the structure and mechanicalproperties of chosen magnetic composite materials with polymer matrix reinforced with Nd-Fe-B or FINEMETparticles manufactured by one-sided uniaxal pressing. The complex relationships among the manufacturingtechnology of these materials, their microstructure, as well as their mechanical and physical properties wereevaluated.Findings: Modern magnetic materials have optimum technology of production with properties that allow forminiaturizing, simplification and lowering the costs of devicesPractical implications: The manufacturing of composite materials greatly expands the applicable possibilitiesof nanocrystalline powders of magnetically hard and soft materials however further examination obtainimproved properties of magnetic composite materials. The investigations of constructing of new machines anddevices with these materials elements are still needed.Originality/value: The paper shows the base of the material and technological solution which make possibleobtaining magnetic composite materials and their mechanical properties which are not commonly presented inother papers.

L.A. Dobrza?ski; B. Zi?bowicz; M. Drak

2006-01-01

338

Phase relationships, basic metallurgy and superconducting properties of Nb3Sn and related compounds  

International Nuclear Information System (INIS)

The phase relationships and the superconducting properties of Nb3Sn are compared with those of other high Tsub(c) compounds crystallizing in the A15 structure: Nb3Al, Nb3Ga, Nb3Ge, V3Si, V3Ga ... 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 Nb3Sn and V3Si 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 Nb3Sn, 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

339

???????????????? Regression Analysis on the Relationship between Water Consumption Structure and Industrial Structure in Fujian Province  

Directory of Open Access Journals (Sweden)

Full Text Available ??????????????????????????????????????????????????logratio??????????(PLS??)????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ? ???? ? ????? Prediction of water consumption structure on the basis of the relationship between water consumption structure and industrial structure is essential to the exploitation and utilization of water resources. Based on the symmetrical logratio transformation and partial least-squares regression, linear regression model for water consumption structure and industrial structure in FujianProvinceis developed in this study. Analysis on the model showed that the compositional data of water consumption structure and industrial structure inFujianProvincehad obvious linear relationship. This model fit the data very well with high accuracy and can be used to predict water consumption structure. Agricultural water was highly correlated with primary industry, and so was the industrial water with secondary industry. Agricultural water showed significantly negative correlation with secondary industry and tertiary industry. The variation of domestic water had an insignificant correlation with industrial structure. The capacity to explain water consumption structure of the industrial structure factors was in the order of primary industry > secondary industry > tertiary industry.

???; ???; ???; ??

2012-01-01

340

Structure and optical properties of tin oxide films  

Energy Technology Data Exchange (ETDEWEB)

In the study, we investigated the relationship between macroscopic and microscopic properties of tin oxide films. Three kinds of tin oxide films were evaluated: (1) Amorphous films deposited by thermal evaporation of SnO{sub 2} powder; (2) spray-deposited tin oxide films with poor crystallinity (DBDA films); and (3) spray-deposited tin oxide films with high crystallinity (MBTC films). Optical properties of these films were evaluated in terms of the macroscopic properties of TO. X-ray diffraction studies for morphologic investigation and FTIR spectra for bond properties were also evaluated to define the micro-macro properties relationship. (orig.).

Demiryont, H.; Nietering, K.E. (Ford Motor Co., Dearborn, MI (USA). Glass Div.)

1989-09-01

 
 
 
 
341

Structural properties of low density liquid selenium  

International Nuclear Information System (INIS)

We present extensive results of Reverse Monte Carlo (RMC) simulations of the static structural properties of liquid selenium from 573K to 1773K based on the diffraction data of Inui et al. (Inui M, Tamura K, Oh'ishi Y, Nakaso I, Funakoshi K and Utsumi W 1999 J. Non. - Cryst. Solids 250-252, 519). In all cases, the positions of 5000 atoms in a configuration box were altered until the resulting static structure factor S(q) was in agreement with the experimental one. Rom the simulations, we were able to extract information on the temperature dependence of the pair distribution function g(r), bond angle correlation b(cos ?) and coordination number distribution P(N). From our calculations, we deduce that with an increase in temperature, there is a decrease in the fraction of two fold coordinated atoms indicative of a destruction of the chain like structure of Se. Furthermore, our results indicate that the transition from a semiconducting to a metallic state with increasing temperature is accompanied by structural changes. (author)

2000-01-01

342

Structural properties of autoclaved aerated concrete masonry  

Energy Technology Data Exchange (ETDEWEB)

Autoclaved aerated concrete masonry units are manufactured from portland cement, quartz sand, water, lime, gypsum and a gas forming agent. The units are steam cured under pressure in an autoclave transforming the material into a hard calcium silicate. The autoclaved aerated concrete masonry units are large-size solid rectangular prisms which are laid using thin-bed mortar layers into masonry assemblages. The system and product are not new--patented in 1924 by Swedish architect Johan Eriksson. Over a period of 60 years this product has been used in all areas of residential and industrial construction and in virtually all climates. However, the principal locations of application have been generally outside the US Little information in the US is available on the structural properties of this product. Due to the interest in use of this product in the construction industry and the construction of production plants in the US, the Construction Research Center at the University of Texas at Arlington and Robert L. Nelson & Associates conducted a series of tests to determine some of the basic structural properties of this product. This paper presents the findings of those investigations.

Matthys, J.H.; Nelson, R.L.

1999-07-01

343

Structure and Properties of LENRA/ Silica Composite  

International Nuclear Information System (INIS)

The sol-gel reaction using tetra ethoxysilane (TEOS) was conducted for modified natural rubber (NR) matrix to obtain in situ generated NR/ silica composite. The present of acrylate group in the modified NR chain turns the composite into radiation-curable. The maximum amount of silica generated in the matrix was 50 p hr by weight. During the sol-gel process the inorganic mineral was deposited in the rubber matrix forming hydrogen bonding between organic and inorganic phases. The composites obtained were characterized by various techniques including thermogravimetric analysis and infrared spectrometry to study their molecular structure. The increase in mechanical properties was observed for low silica contents (30 p hr) where more silica were generated, agglomerations were observed at the expense of the mechanical properties. From the DMTA data, it shows an increase of the interaction between the rubber and silica phases up to 30 p hr TEOS. Structure and morphology of the heterogeneous system were analyzed by transmission electron microscopy. The average particle sizes of between 150 nm to 300 nm were achieved for the composites that contain less than 20 p hr of TEOS. (author)

2010-01-01

344

A compilation of structural property data for computer impact calculation (1/5)  

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 1 involve structural property data and data processing computer program. (author)

1988-01-01

345

A compilation of structural property data for computer impact calculation (3/5)  

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 3 involve structural property data of stainless steel. (author)

1988-01-01

346

A compilation of structural property data for computer impact calculation (2/5)  

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 2 involve structural property data of mild steel. (author)

1988-01-01

347

Water and water-like liquids: relationships between structure, entropy and mobility.  

Science.gov (United States)

Liquids with very diverse underlying interactions share the thermodynamic and transport anomalies of water, including metalloids, ionic melts and mesoscopic fluids. The generic feature that characterises such water-like liquids is a density-driven shift in the nature of local order in the condensed phases. The key semiquantitative relationships between structural order, thermodynamics and transport that are necessary in order to map out the consequences of this common qualitative feature for liquid-state properties and phase transformations of such systems are reviewed here. The application of these ideas to understand and model tetrahedral liquids, especially water, is discussed and possible extensions to other complex fluids are considered. PMID:23892732

Nayar, Divya; Chakravarty, Charusita

2013-07-29

348

Potential anticancer agents. XX. 2. Quantitative structure--activity relationships (QSAR) in aromatic nitrogen mustards area.  

UK PubMed Central (United Kingdom)

Quantitative structure--activity relationships have been fomulated for 27 aromatic nitrogen mustards derived from benzoic acids (9 monosubstituted and 18 disubstituted derivatives). Their toxicity (LD50) and antitumor activity against Jensen sarcoma were correlated with hydrolysis rate (log k66) lipophilicity constants (pi) and steric parameters (MDT). The chemical reactivity of the nitrogen mustard moiety (expressed as log k66) seems to be of main importance in determining the biological properties of these derivatives. The favorable effect of ortho-substitution was pointed out. Generally these results are in good agreement with those obtained by HANSCH et al. [7] on a different series of nitrogen mustards.

Niculescu-Duv?z I; Stihi G; Cr?escu T; Simon Z

1980-01-01

349

Potential anticancer agents. XX. 2. Quantitative structure--activity relationships (QSAR) in aromatic nitrogen mustards area.  

Science.gov (United States)

Quantitative structure--activity relationships have been fomulated for 27 aromatic nitrogen mustards derived from benzoic acids (9 monosubstituted and 18 disubstituted derivatives). Their toxicity (LD50) and antitumor activity against Jensen sarcoma were correlated with hydrolysis rate (log k66) lipophilicity constants (pi) and steric parameters (MDT). The chemical reactivity of the nitrogen mustard moiety (expressed as log k66) seems to be of main importance in determining the biological properties of these derivatives. The favorable effect of ortho-substitution was pointed out. Generally these results are in good agreement with those obtained by HANSCH et al. [7] on a different series of nitrogen mustards. PMID:7453847

Niculescu-Duv?z, I; Stihi, G; Cr?escu, T; Simon, Z

1980-01-01

350

The Measurement Properties of Mentoring Relationship Quality Scales for Mentoring Programs.  

UK PubMed Central (United Kingdom)

The measurement properties of two new scales designed to measure global and engagement mentoring relationship quality (Global Mentoring Relationship Quality Scale and Quality of Mentoring Relationship Engagement Scale) were examined among 272 mentors, 491 children, and 554 parents participating in Big Brothers Big Sisters community mentoring programs across Canada. Results demonstrated their unidimensionality, moderate convergent validity, good external validity, and weak-to-moderate reporter concordance. Longitudinal analyses demonstrated good predictive validity of mentor and parent mentoring relationship quality scales with respect to predicting mentoring relationship status.

Ferro A; Wells S; Speechley KN; Lipman E; Dewit D

2013-04-01

351

The Measurement Properties of Mentoring Relationship Quality Scales for Mentoring Programs.  

Science.gov (United States)

The measurement properties of two new scales designed to measure global and engagement mentoring relationship quality (Global Mentoring Relationship Quality Scale and Quality of Mentoring Relationship Engagement Scale) were examined among 272 mentors, 491 children, and 554 parents participating in Big Brothers Big Sisters community mentoring programs across Canada. Results demonstrated their unidimensionality, moderate convergent validity, good external validity, and weak-to-moderate reporter concordance. Longitudinal analyses demonstrated good predictive validity of mentor and parent mentoring relationship quality scales with respect to predicting mentoring relationship status. PMID:23605592

Ferro, Annalise; Wells, Samantha; Speechley, Kathy Nixon; Lipman, Ellen; Dewit, David

2013-04-23

352

Probing the Structure-Function Relationships of Microbial Systems  

Energy Technology Data Exchange (ETDEWEB)

The elucidation of microbial surface architecture and function is critical to determining mechanisms of pathogenesis, immune response, physicochemical properties, environmental resistance and development of countermeasures against bioterrorist agents. We have utilized high-resolution in vitro AFM for studies of structure, assembly, function and environmental dynamics of several microbial systems including bacteria and bacterial spores. Lateral resolutions of {approx}2.0 nm were achieved on pathogens, in vitro. We have demonstrated, using various species of Bacillus and Clostridium bacterial spores, that in vitro AFM can address spatially explicit spore coat protein interactions, structural dynamics in response to environmental changes, and the life cycle of pathogens at near-molecular resolution under physiological conditions. We found that strikingly different species-dependent crystalline structures of the spore coat appear to be a consequence of nucleation and crystallization mechanisms that regulate the assembly of the outer spore coat, and we proposed a unifying mechanism for outer spore coat self-assembly. Furthermore, we revealed molecular-scale transformations of the spore coat during the germination process, which include profound, previously unrecognized changes of the spore coat. We will present data on the direct visualization of stress-induced environmental response of metal-resistant Arthrobacter oxydans bacteria to Cr (VI) exposure, resulting in the formation of a supramolecular crystalline hexagonal structure on the cell surface. At higher Cr (VI) concentrations the formation of microbial extracellular polymers, which cover microbial colony was observed. High-resolution visualization of stress-induced structures on bacterial surfaces builds a foundation for real time in vitro molecular scale studies of structural dynamics of metal-resistant bacteria in response to environmental stimuli. In the case of the bacterium Chlamedia trachomatis, we were able to identify surface exposed proteins versus proteins embedded in the outer membrane. These studies establish in vitro AFM as a powerful new tool capable of revealing pathogen architecture, structural dynamics and variability at nanometer-to-micrometer scales.

Plomp, M; Leighton, T J; Holman, H; Malkin, A J

2005-11-03

353

Relationships between abiotic and biotic soil properties during fallow periods in the sudanian zone of Senegal  

UK PubMed Central (United Kingdom)

Relationships between soil characteristics, various forms of soil organic matter, microbial biomass and the structure ofphytoparasitic nematode populations were investigated in six fallow fields aged from 1 to 26 years in the West AfricanSavanna (WAS) belt in southern Senegal. Soil sampling was performed along two transects in each field. Herbaceous biomassand soil physical, chemical and biological characteristics were studied with principal component analysis (PCA) and therelationships between the parameters were extracted with co-inertia analysis.Soil properties (mainly calcium, magnesium and total carbon contents, and cation exchange capacity) slightly improved inthe upper soil layer (0--5 cm) during the succession of vegetation. In constrast, in the 0--10 cm soil layer, microbial biomassand total soil organic carbon content showed no clear pattern of change over time, while highest charcoal stocks were foundin older fallows where bush fires are frequent. In the 0--40 cm la...

Raphal J. Manlay; Patrice Cadet; Jean Thioulouse

354

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, VáclavG

355

Quantitative structure-activity relationships for organophosphates binding to acetylcholinesterase.  

UK PubMed Central (United Kingdom)

Organophosphates are a group of pesticides and chemical warfare nerve agents that inhibit acetylcholinesterase, the enzyme responsible for hydrolysis of the excitatory neurotransmitter acetylcholine. Numerous structural variants exist for this chemical class, and data regarding their toxicity can be difficult to obtain in a timely fashion. At the same time, their use as pesticides and military weapons is widespread, which presents a major concern and challenge in evaluating human toxicity. To address this concern, a quantitative structure-activity relationship (QSAR) was developed to predict pentavalent organophosphate oxon human acetylcholinesterase bimolecular rate constants. A database of 278 three-dimensional structures and their bimolecular rates was developed from 15 peer-reviewed publications. A database of simplified molecular input line entry notations and their respective acetylcholinesterase bimolecular rate constants are listed in Supplementary Material, Table I. The database was quite diverse, spanning 7 log units of activity. In order to describe their structure, 675 molecular descriptors were calculated using AMPAC 8.0 and CODESSA 2.7.10. Orthogonal projection to latent structures regression, bootstrap leave-random-many-out cross-validation and y-randomization were used to develop an externally validated consensus QSAR model. The domain of applicability was assessed by the William's plot. Six external compounds were outside the warning leverage indicating potential model extrapolation. A number of compounds had residuals >2 or <-2, indicating potential outliers or activity cliffs. The results show that the HOMO-LUMO energy gap contributed most significantly to the binding affinity. A mean training R (2) of 0.80, a mean test set R (2) of 0.76 and a consensus external test set R (2) of 0.66 were achieved using the QSAR. The training and external test set RMSE values were found to be 0.76 and 0.88. The results suggest that this QSAR model can be used in physiologically based pharmacokinetic/pharmacodynamic models of organophosphate toxicity to determine the rate of acetylcholinesterase inhibition.

Ruark CD; Hack CE; Robinson PJ; Anderson PE; Gearhart JM

2013-02-01

356

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)  

Directory of Open Access Journals (Sweden)

Full Text Available 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.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.

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

2005-01-01

357

Quantitative structure--activity relationship of double alkyl chain drugs.  

UK PubMed Central (United Kingdom)

The quantitative structure--activity relationship of double alkyl chain drugs, including alkanols, aliphatic esters, ketones, barbiturates, amphetamines, butyrylcholinesterase inhibitors, antimalarials, and rifamycin amides, is investigated. A series of double-chain homologues, CnH2n+1XCmH2m+1, in which n changes, keeping m constant, is classified into three types: in type IIL, n greater than m; in type IIE, n = m; in type IIS, n less than m. When a linear relationship, vis., log (1/C) = an + b, holds, the slope a depends on the type; aI greater than or equal to aIIL greater than aIIE greater than aIIS. Here aI means the slope for single-chain homologues. The same order is observed for the equation, log hydrophobicity = an + b, where the hydrophobicity of drug denotes the water solubility, the critical micelle concentration, and the partition coefficient for the 1-octanol--water phases. Therefore, decreased biological activity of a double-chain drug relative to that of a single-chain isomer can be explained by a decreased hydrophobicity of the double-chain drug, due to the intramolecular association of these chains in water. When a parabolic relationship between log (1/C) and n holds, the optimum n depends on the type: nopI less than nopIIL less than nopIIE. This order is also explicable on the basis of a decreased hydrophobicity of double-chain drug. The N-dealklation rate of amphetamines in vivo appears to be affected by the steric factor as well as the hydrophobic factor. A decreased hydrophobicity of double-chain compounds should be taken into consideration for estimating their partition coefficients.

Hada S; Neya S; Funasaki N

1983-05-01

358

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)

[en] 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

359

Cold adaptation of zinc metalloproteases in the thermolysin family from deep sea and arctic sea ice bacteria revealed by catalytic and structural properties and molecular dynamics: new insights into relationship between conformational flexibility and hydrogen bonding.  

UK PubMed Central (United Kingdom)

Increased conformational flexibility is the prevailing explanation for the high catalytic efficiency of cold-adapted enzymes at low temperatures. However, less is known about the structural determinants of flexibility. We reported two novel cold-adapted zinc metalloproteases in the thermolysin family, vibriolysin MCP-02 from a deep sea bacterium and vibriolysin E495 from an Arctic sea ice bacterium, and compared them with their mesophilic homolog, pseudolysin from a terrestrial bacterium. Their catalytic efficiencies, k(cat)/K(m) (10-40 degrees C), followed the order pseudolysin < MCP-02 < E495 with a ratio of approximately 1:2:4. MCP-02 and E495 have the same optimal temperature (T(opt), 57 degrees C, 5 degrees C lower than pseudolysin) and apparent melting temperature (T(m) = 64 degrees C, approximately 10 degrees C lower than pseudolysin). Structural analysis showed that the slightly lower stabilities resulted from a decrease in the number of salt bridges. Fluorescence quenching experiments and molecular dynamics simulations showed that the flexibilities of the proteins were pseudolysin < MCP-02 < E495, suggesting that optimization of flexibility is a strategy for cold adaptation. Molecular dynamics results showed that the ordinal increase in flexibility from pseudolysin to MCP-02 and E495, especially the increase from MCP-02 to E495, mainly resulted from the decrease of hydrogen-bond stability in the dynamic structure, which was due to the increase in asparagine, serine, and threonine residues. Finally, a model for the cold adaptation of MCP-02 and E495 was proposed. This is the first report of the optimization of hydrogen-bonding dynamics as a strategy for cold adaptation and provides new insights into the structural basis underlying conformational flexibility.

Xie BB; Bian F; Chen XL; He HL; Guo J; Gao X; Zeng YX; Chen B; Zhou BC; Zhang YZ

2009-04-01

360

Structure-activity relationship studies of pyrrolone antimalarial agents.  

Science.gov (United States)

Previously reported pyrrolones, such as TDR32570, exhibited potential as antimalarial agents; however, while these compounds have potent antimalarial activity, they suffer from poor aqueous solubility and metabolic instability. Here, further structure-activity relationship studies are described that aimed to solve the developability issues associated with this series of compounds. In particular, further modifications to the lead pyrrolone, involving replacement of a phenyl ring with a piperidine and removal of a potentially metabolically labile ester by a scaffold hop, gave rise to derivatives with improved in vitro antimalarial activities against Plasmodium falciparum K1, a chloroquine- and pyrimethamine-resistant parasite strain, with some derivatives exhibiting good selectivity for parasite over mammalian (L6) cells. Three representative compounds were selected for evaluation in a rodent model of malaria infection, and the best compound showed improved ability to decrease parasitaemia and a slight increase in survival. PMID:23918316

Murugesan, Dinakaran; Kaiser, Marcel; White, Karen L; Norval, Suzanne; Riley, Jennifer; Wyatt, Paul G; Charman, Susan A; Read, Kevin D; Yeates, Clive; Gilbert, Ian H

2013-08-05

 
 
 
 
361

Structure-biological activity relationship of synthetic trihydroxilated chalcones  

Directory of Open Access Journals (Sweden)

Full Text Available The bacteriostatic activity of 2?,4?,2-trihydroxychalcone; 2?,4?,3-trihydroxychalcone and 2?,4?,4-trihydroxychalcone, prepared by condensation of 2,4-dihydroxyacetophenone and benzaldehyde substituted, against Staphylococcus aureus ATCC 25923 was assayed by agar plate method. The three compounds presented important inhibition halos. In order to elucidate structure-activity relationships, the minimal inhibitory concentrations against S. aureus were determined by the broth dilution method and the results obtained were compared to that of 2',4'-dihydroxychalcone. The sequence observed was: MIC 2?,4?,3-(OH)3 > MIC 2?,4?-(OH)2 > MIC 2?,4?,4-(OH)3 > > MIC 2?,4?,2-(OH)3. These results showed that the introduction of an electron donating group (-OH) in the aromatic B-ring causes an increase in bioactivity, and that the intensity of action depends on the position of the OH substitute.

Devia Cristina M.; Pappano Nora B.; Debattista Nora B.

1998-01-01

362

Structure-activity relationship studies of pyrrolone antimalarial agents.  

UK PubMed Central (United Kingdom)

Previously reported pyrrolones, such as TDR32570, exhibited potential as antimalarial agents; however, while these compounds have potent antimalarial activity, they suffer from poor aqueous solubility and metabolic instability. Here, further structure-activity relationship studies are described that aimed to solve the developability issues associated with this series of compounds. In particular, further modifications to the lead pyrrolone, involving replacement of a phenyl ring with a piperidine and removal of a potentially metabolically labile ester by a scaffold hop, gave rise to derivatives with improved in vitro antimalarial activities against Plasmodium falciparum K1, a chloroquine- and pyrimethamine-resistant parasite strain, with some derivatives exhibiting good selectivity for parasite over mammalian (L6) cells. Three representative compounds were selected for evaluation in a rodent model of malaria infection, and the best compound showed improved ability to decrease parasitaemia and a slight increase in survival.

Murugesan D; Kaiser M; White KL; Norval S; Riley J; Wyatt PG; Charman SA; Read KD; Yeates C; Gilbert IH

2013-09-01

363

Structure and properties of ferroelectric polymers  

Energy Technology Data Exchange (ETDEWEB)

Copolymers of vinylidene fluoride with trifluoroethylene have been shown to be a ferroelectric polymer undergoing polarization reversal and the Curie transition. Besides ferroelectricity, they have an interesting character that annealing at a temperature in the paraelectric phase causes a remarkable increase in crystallinity as well as a growth of large crystalline lamellae. We have prepared the copolymer samples with well-defined higher order structures and examined their properties such as ferroelectric switching, non-linear dielectricity, piezoelectricity and pyroelectricity. For example, the samples annealed at just below the melting point are found to consist of crystallites thicker than 200nm and exhibit very sharp ferroelectric switching transients while those annealed at lower temperatures exhibit no or extremely broad switching transients. On the basis of these results, the microscopic mechanisms responsible for their ferroelectricity will be discussed.

Furukawa, T.; Takahashi, Y. [Science Univ. of Tokyo (Japan)

1995-12-01

364

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

365

Chitosan/halloysite nanotubes bionanocomposites: structure, mechanical properties and biocompatibility.  

UK PubMed Central (United Kingdom)

Incorporation of nanosized reinforcements into chitosan usually results in improved properties and changed microstructures. Naturally occurred halloysite nanotubes (HNTs) are incorporated into chitosan for forming bionanocomposite films via solution casting. The electrostatic attraction and hydrogen bonding interactions between HNTs and chitosan are confirmed. HNTs are uniformly dispersed in chitosan matrix. The tensile strength and Young's modulus of chitosan are enhanced by HNTs. The storage modulus and glass transition temperature of chitosan/HNTs films also increase significantly. Blending with HNTs induces changes in surface nanotopography and increase of roughness of chitosan films. In vitro fibroblasts response demonstrates that both chitosan and chitosan/HNTs nanocomposite films are cytocompatibility even when the loading of HNTs is 10%. In summary, these results provide insights into understanding of the structural relationships of chitosan/HNTs bionanocomposite films in potential applications, such as scaffold materials in tissue engineering.

Liu M; Zhang Y; Wu C; Xiong S; Zhou C

2012-11-01

366

Chitosan/halloysite nanotubes bionanocomposites: structure, mechanical properties and biocompatibility.  

Science.gov (United States)

Incorporation of nanosized reinforcements into chitosan usually results in improved properties and changed microstructures. Naturally occurred halloysite nanotubes (HNTs) are incorporated into chitosan for forming bionanocomposite films via solution casting. The electrostatic attraction and hydrogen bonding interactions between HNTs and chitosan are confirmed. HNTs are uniformly dispersed in chitosan matrix. The tensile strength and Young's modulus of chitosan are enhanced by HNTs. The storage modulus and glass transition temperature of chitosan/HNTs films also increase significantly. Blending with HNTs induces changes in surface nanotopography and increase of roughness of chitosan films. In vitro fibroblasts response demonstrates that both chitosan and chitosan/HNTs nanocomposite films are cytocompatibility even when the loading of HNTs is 10%. In summary, these results provide insights into understanding of the structural relationships of chitosan/HNTs bionanocomposite films in potential applications, such as scaffold materials in tissue engineering. PMID:22743347

Liu, Mingxian; Zhang, Yun; Wu, Chongchao; Xiong, Sheng; Zhou, Changren

2012-06-26

367

Mechanical properties and structure of austempered ductile iron -ADI  

Directory of Open Access Journals (Sweden)

Full Text Available The results of experimental study of austempered ductile iron are presented. The aim of the investigations was to look closer into the structure – mechanical properties relationships of this very attractive cast material. The experiment was carried out with 500 7 grade ductile iron, which was austempered using different parameters of heat treatment. The specimens were first solution treated 1 hour in 910oC and then isothermally quenched for different time in silicon oil bath of temperature 275, 325, 300 and 350oC. The mechanical properties heat treated specimens were tested in tensile to evaluate yield stress Re, 0.2, tensile strength Rm and elongation A10. Additionally hardness of heat treated samples was measured using Brinell-Rockwell hardness tester. Structure of the specimens was studied either with conventional metallography, scanning (SEM) and transmission (TEM) electron microscopy. It followed from the study that conventional grade ductile iron enabled to produce both low and high strength ADI, depend on heat treatment parameters. As expected the low temperature isothermal quenching produced higher strength ADI compare to the same ductile iron but austempered at 350oC. It was discovered however, that low yield strength ADI obtained for short time quenching at 275oC exhibited high strengthening effect while strained in tensile. So it was concluded that this had to by cause by large amount of untransformed austenite, which FCC lattice is characterized by high strengthening coefficient.

Kaczorowaki M.; Krzy?ska A.

2007-01-01

368

Free energies, kinetics, and photoelectron-transfer properties, and theoretical and quantitative structural relationship studies of [SWCNT(5,5)-armchair-C n H20][ R] ( R = ? 2-C m Pd(dppf), ? 2-C m Pd(dppr), and ? 2-C m Pd(dppcym)2, n = 20 to 300 and m = 60 and 70) nanostructure complexes  

Science.gov (United States)

Metal complexes containing one or several bis(triorganylphosphine)palladium fragments attached to the C60 core and coordinated in olefinic ? 2 mode have been previously described. The number of carbon atoms of the single-walled carbon nanotubes (SWCNTs) is the useful numerical and structural electrochemical properties contributing to the relationship between the structures of the ? 2_C m Pd(dppf), ? 2_C m Pd(dppr), and ? 2_C m Pd(dppcym)2 ( m = 60 and 70) ligands (A to E) and [SWCNT(5,5)-armchair-C n H20] ( n = 20 to 190) 1 to 18 and the production of the [SWCNT(5,5)-armchair-C n H20][ R] ( R = ? 2-C m Pd(dppf), ? 2-C m Pd(dppr), and ? 2-C m Pd(dppcym)2, n = 20 to 300 and m = 60 and 70) complexes 30 to 174. In this study, the relationship between the number of carbon atoms index and the first and second free energies of electron transfer ( ?G et( n), n = 1,2) using the Rehm-Weller equation based on the first and second oxidation potentials (ox E 1 and ox E 2) of A to E for the predicted complexes 30 to 174 between 1 and 29 with exohedral metallofullerenes A to E, as [SWCNT(5,5)-armchair-C n H20][ R] ( R = ? 2-C m Pd(dppf), ? 2-C m Pd(dppr), and ? 2-C m Pd(dppcym)2, n = 20 to 300 and m = 60 and 70) 30 to 174 was assessed. Here, the first and second free activation energies of electron transfer and the wavelengths of the electromagnetic photons in the photoelectron transfer process, ?G # et( n) and ? ( n) (nm), respectively, for 30 to 174 in accordance with the Marcus theory and Planck's equation were also calculated.

Taherpour, Avat Arman; Talebi-Haftadori, Zahra

2013-04-01

369

Relationship between Magnetic and Mechanical Properties of Cermet Tools  

International Nuclear Information System (INIS)

The commercial cermet cutting tools consist of multi-carbide and a binder metal of iron group, such as cobalt and nickel which are ferromagnetic. In this paper, a new approach to evaluate the mechanical properties of TiCN based cermet by magnetic properties were studied in relation to binder content and sintering conditions. The experimental cermet was prepared using commercial composition with the other binder contents by PM process. It was found that the magnetic properties of the sintered cermets remarkably depended on the microstructure and the total carbon content. The magnetic saturation was proportional to increment of coercive force. At high carbon content in sintered cermet, the magnetic saturation was increased by decreasing the concentration of solutes such as W, Mo, Ti in Co-Ni binder. As the coercive force increases, the hardness usually increases. The strength and toughness of the cermet also increased with increasing the magnetic saturation. The measurement of magnetic properties made it possible to evaluate the mechanical properties in the cermet cutting tools

2000-01-01

370

[Structure and properties of proprotein convertase inhibitors].  

Science.gov (United States)

This review is devoted to structure and properties of proprotein convertases (PCs), the intracellular Ca(2+)-dependent serine endoproteases of mammalia, that play the essential role in the processing of inactive protein precursors and their transforming into bioactive mature products. PCs are also implicated in development of a great variety of diseases including bacterial or viral infections and such pathologies as cancer, Alzheimer's disease, obesity and so on. Owing to these findings, PCs are considered as promising targets for design of their inhibitors and development of new potential therapeutic agents. Only several endogenous protein inhibitors are identified now for PCs: pro7B2 (Proprotein 7B2), the specific chaperon of PC2, granine-like precursor of neuroendocrine protein proSAAS, the selective ligand of PC1, and serpin Spn4A (Serine Proteinase Inhibitor) of Drosophila melanogaster that inhibits PC2 and furin. By the methods of site-directed mutagenesis, the bioengineered inhibitors of PCs were also designed. Structures and properties of protein or peptide fragments as inhibitors of PCs were also discussed. Particularly, the properties of polyarginines and small peptides containing pseudopeptide bond at the scissile site a suitable peptide substrate were described. The inhibitory activity of non-peptide compounds such as derivatives of andrographolid from Andrographis paniculata (K(i) = 2.6-200 microM against furin), certain complexes of pyridine analogs with ions of Cu2+ or Zn2+ inhibiting furin with IC50 = 5-10 microM, derivatives of 2,5-dideoxy-streptamine containing several guanidine groups (K(i) = 6-812 nM for furin) and also a number of dicoumarols (K(i) = 1-185 microM against furin) and some flavonoids (with K(i) = 5-230 microM for furin) were reflected in the article. The effects of enediynyl-amino acids derivatives or their peptides (K(i) = 40 nM against furin) were considered. Inhibition of PC2 by N-acylated bicyclic guanidines (K(i) = 3.3-10 microM) or derivatives of pyrrolidin bispyperazines (K(i) = 0.54-10 microM) are considered too. Some of synthesized derivatives may serve as lead compounds for design of the specific inhibitors for individual PCs. PMID:22642118

Kibirev, V K; Osadchuk, T V

371

[Structure and properties of proprotein convertase inhibitors].  

UK PubMed Central (United Kingdom)

This review is devoted to structure and properties of proprotein convertases (PCs), the intracellular Ca(2+)-dependent serine endoproteases of mammalia, that play the essential role in the processing of inactive protein precursors and their transforming into bioactive mature products. PCs are also implicated in development of a great variety of diseases including bacterial or viral infections and such pathologies as cancer, Alzheimer's disease, obesity and so on. Owing to these findings, PCs are considered as promising targets for design of their inhibitors and development of new potential therapeutic agents. Only several endogenous protein inhibitors are identified now for PCs: pro7B2 (Proprotein 7B2), the specific chaperon of PC2, granine-like precursor of neuroendocrine protein proSAAS, the selective ligand of PC1, and serpin Spn4A (Serine Proteinase Inhibitor) of Drosophila melanogaster that inhibits PC2 and furin. By the methods of site-directed mutagenesis, the bioengineered inhibitors of PCs were also designed. Structures and properties of protein or peptide fragments as inhibitors of PCs were also discussed. Particularly, the properties of polyarginines and small peptides containing pseudopeptide bond at the scissile site a suitable peptide substrate were described. The inhibitory activity of non-peptide compounds such as derivatives of andrographolid from Andrographis paniculata (K(i) = 2.6-200 microM against furin), certain complexes of pyridine analogs with ions of Cu2+ or Zn2+ inhibiting furin with IC50 = 5-10 microM, derivatives of 2,5-dideoxy-streptamine containing several guanidine groups (K(i) = 6-812 nM for furin) and also a number of dicoumarols (K(i) = 1-185 microM against furin) and some flavonoids (with K(i) = 5-230 microM for furin) were reflected in the article. The effects of enediynyl-amino acids derivatives or their peptides (K(i) = 40 nM against furin) were considered. Inhibition of PC2 by N-acylated bicyclic guanidines (K(i) = 3.3-10 microM) or derivatives of pyrrolidin bispyperazines (K(i) = 0.54-10 microM) are considered too. Some of synthesized derivatives may serve as lead compounds for design of the specific inhibitors for individual PCs.

Kibirev VK; Osadchuk TV

2012-03-01