WorldWideScience
1

Structure-Property Relationships of Bismaleimides  

Science.gov (United States)

The purpose of this research was to control and systematically vary the network topology of bismaleimides through cure temperature and chemistry (addition of various coreactants) and subsequently attempt to determine structure-mechanical property relationships. Characterization of the bismaleimide structures by dielectric, rheological, and thermal analyses, and density measurements was subsequently correlated with mechanical properties such as modulus, yield strength, fracture energy, and stress relaxation. The model material used in this investigation was 4,4'-BismaleiMidodIphenyl methane (BMI). BMI was coreacted with either 4,4'-Methylene Dianiline (MDA), o,o'-diallyl bisphenol A (DABA) from Ciba Geigy, or Diamino Diphenyl Sulfone (DDS). Three cure paths were employed: a low- temperature cure of 140 C where chain extension should predominate, a high-temperature cure of 220 C where both chain extension and crosslinking should occur simultaneously, and a low-temperature (140 C) cure followed immediately by a high-temperature (220 C) cure where the chain extension reaction or amine addition precedes BMI homopolymerization or crosslinking. Samples of cured and postcured PMR-15 were also tested to determine the effects of postcuring on the mechanical properties. The low-temperature cure condition of BMI/MDA exhibited the highest modulus values for a given mole fraction of BMI with the modulus decreasing with decreasing concentration of BMI. The higher elastic modulus is the result of steric hindrance by unreacted BMI molecules in the glassy state. The moduli values for the high- and low/high-temperature cure conditions of BMI/MDA decreased as the amount of diamine increased. All the moduli values mimic the yield strength and density trends. For the high-temperature cure condition, the room- temperature modulus remained constant with decreasing mole fraction of BMT for the BMI/DABA and BMI/DDS systems. Postcuring PMR-15 increases the modulus over that of the cured material even though density values of cured and postcured PMR were essentially the same. Preliminary results of a continuous and intermittent stress relaxation experiment for BMI:MDA in a 2:1 molar ratio indicate that crosslinking is occurring when the sample is in the undeformed state. Computer simulation of properties such as density, glass transition temperature, and modulus for the low- temperature cure conditions of BMI/MDA and BMI/DABA were completed. The computer modeling was used to help further understand and confirm the structure characterization results. The simulations correctly predicted the trends of these properties versus mole fraction BMI and were extended to other BMI/diamine systems.

Tenteris-Noebe, Anita D.

1997-01-01

2

Fundamental structure: Property relationships in luminescent materials  

Science.gov (United States)

The main body of this work consists of the development of a new model for describing the luminescence properties of Eusp{2+} in various host materials. Much of the emphasis has been in the area of Eusp{2+}-doped borates. As part of this work, the luminescence properties of the Eusp{2+}-doped hosts Basb2Mg(BOsb3)sb2,\\ Basb2Ca(BOsb3)sb2,\\ and\\ Srsb2Mg(BOsb3)sb2 were investigated. These materials exhibit emission in the red, green, and yellow, respectively. In addition, the structures and luminescent properties of another series of Eusp{2+}-doped borates have been examined. From this study, a simple structural relationship has been established that distinguishes violet and blue emitting compounds from those that emit at longer wavelengths (>500 nm). Emphasis is placed on the coordination environments of the O atoms in the host. Borates containing O atoms highly coordinated by heavy alkaline-earth metal atoms produce longer wavelength Eusp{2+} emission, while borates containing O atoms highly coordinated by B atoms produce short wavelength emission of Eusp{2+}. The basic ideas behind this model can be extended to other hosts. The luminescence properties of BaLiBsb9Osb{15}{:}Eusp{2+},\\ and\\ SrLiBsb9Osb{15}:Eusp{2+} were also investigated. Under photoexcitation at 4.2 K, these materials exhibit line emission from the sp6Psb{7/2}->\\ sp8Ssb{7/2} transition within the 4fsp7 configuration. In BaLiBsb9Osb{15}:Eusp{2+}, the line emission is present even at room temperature. By using the ratio of the integrated intensities of the line and band emissions, the differences in energy, DeltaE, between the 4fsp65dsp1 and sp6Psb{7/2} levels were calculated for SrLiBsb9Osb{15}:Eusp{2+}\\ and\\ BaLiBsb9Osb{15}:Eusp{2+}. The high energetic position of the Eusp{2+} 5d levels in these hosts is attributed to a weak nephelauxetic effect. The structure of the orthoborate Srsb3(BOsb3)sb2 has been refined by single crystal X-ray diffraction methods. It crystallizes in the trigonal space group R3c (No. 167). The structure consists of stacks of BOsb3 groups along the c axis with eight-coordinate Sr atoms in the channels. The O atoms in this material are highly coordinated by Sr atoms.

Diaz, Anthony Lee

3

Structure-property relationships in block copolymers  

Science.gov (United States)

Block copolymers are a class of relatively new materials which contain long sequences of two (or more) chemically different repeat units. Unlike random copolymers, each segment may retain some properties which are characteristic of its homopolymer. It is well known that most physical blends of two different homopolymers are incompatible on a macro-scale. By contrast most block copolymers display only a microphase (eg. 100-200 A domains) separation. Complete separation is restricted because of a loss in configurational entropy. The latter is due to presence of chemical bond(s) between the segments. Novel physical properties can be obtained because it is possible to prepare any desired combination of rubber-like, glassy, or crystalline blocks. The architecture and sequential arrangement of the segments can strongly influence mechanical behavior.

Mcgrath, J. E.

1976-01-01

4

Crosslinked flexible PVC: structure-property relationships  

International Nuclear Information System (INIS)

Samples of plasticized, filled PVC containing 10, 20, and 30 part hundred rubber (phr) mixture (67:33) of triallylcyanurate (TAC) and nitrile rubber (NBR) were exposed to ?radiation at room temperature. Experimental variables consisted of radiation dose and content of crosslinking co-agent mixture. Physico-mechanical and thermal properties have been analysed wherein significant changes have been observed, which in turn are dependent on total insolubles content and co-agent mixture loading. (author). 5 refs., 4 figs., 3 tabs

5

Teachers' Domain: Structure-Property Relationships  

Science.gov (United States)

This instructional module explores how molecular changes determine physical characteristics of materials. It opens with a short video clip that introduces atomic arrangement of solids by focusing on carbon in different forms. A second video discusses the structural changes to a water molecule that occur during phase change. Students then investigate differences among carbon forms through digital images of graphite and diamond structures. For gifted/talented learners, try the extension activity on buckyballs. Editor's Note: This lesson was developed for high school, but can easily be adapted for the middle school classroom by extending time allowed for group discussion. Teachers' Domain is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2011-08-19

6

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

7

Structure/property relationships in non-linear optical materials  

Energy Technology Data Exchange (ETDEWEB)

The application of neutrons to the study of structure/property relationships in organic non-linear optical materials (NLOs) is described. In particular, charge-transfer effects and intermolecular interactions are investigated. Charge-transfer effects are studied by charge-density analysis and an example of one such investigation is given. The study of intermolecular interactions concentrates on the effects of hydrogen-bonding and an example is given of two structurally similar molecules with very disparate NLO properties, as a result of different types of hydrogen-bonding. (author). 3 refs.

Cole, J.M. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)]|[Durham Univ. (United Kingdom); Howard, J.A.K. [Durham Univ. (United Kingdom); McIntyre, G.J. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

1997-04-01

8

Changing environments and structure--property relationships in marine biomaterials.  

Science.gov (United States)

Most marine organisms make functional biomolecular materials that extend to varying degrees 'beyond their skins'. These materials are very diverse and include shells, spines, frustules, tubes, mucus trails, egg capsules and byssal threads, to mention a few. Because they are devoid of cells, these materials lack the dynamic maintenance afforded intra-organismic tissues and thus are usually assumed to be inherently more durable than their internalized counterparts. Recent advances in nanomechanics and submicron spectroscopic imaging have enabled the characterization of structure-property relationships in a variety of extra-organismic materials and provided important new insights about their adaptive functions and stability. Some structure-property relationships in byssal threads are described to show how available analytical methods can reveal hitherto unappreciated interdependences between these materials and their prevailing chemical, physical and ecological environments. PMID:22357581

Waite, J Herbert; Broomell, Christopher C

2012-03-15

9

Processing-structure-property relationships in polyethylene blown films  

Science.gov (United States)

As part of a larger effort toward the fundamental understanding of processing-structure-property (P-S-P) relationships in polyolefin blown films, investigations were conducted on a variety of polyethylene (PE) blown films. The films chosen for the study were produced from different types of resins and under different processing conditions. The resins used include high-density polyethylene, low-density polyethylene, linear low-density polyethylene and metallocene linear low-density polyethylene. Model systems were composed for unambiguous study of the effect of key processing and/or material parameters. For each model system, the study focused either on one or a few factors. Comprehensive and detailed structural characterization of PE blown films was performed using transmission electron microscopy, infrared dichroism, small-angle X-ray scattering, X-ray pole figure analysis, differential scanning calorimetry, and solid-state nuclear magnetic resonance spectroscopy. The amount of crystalline and noncrystalline contents, the orientation in crystalline and amorphous phases, and the lamellar thickness distribution were studied in detail. A series of important morphological features have been revealed. Through model system studies, the results of the morphological investigations were used to comprehend the film mechanical behavior, the influence of processing conditions on film morphology, and the impact of PE molecular characteristics on the processing-structure relationship. Important mechanical properties considered include tear strength, dart impact resistance and tensile properties. Some fundamental correlations have been established between the morphological features and the mechanical properties of PE blown films. The effect of bubble stalk and heck height has been well understood through this study. This research has resulted in an improved understanding of the fundamental P-S-P relationships in PE blown films.

Lu, Jianjun

10

Oxide Thermoelectric Materials: A Structure-Property Relationship  

Science.gov (United States)

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

Nag, Abanti; Shubha, V.

2014-04-01

11

Processing-structure-property relationships in oriented polymers  

Science.gov (United States)

The Processing-Structure-Property (P-S-P) relationships in oriented polymers have been studied in this dissertation. Controlled polymer orientation has been achieved through the equal channel angular extrusion (ECAE) process. The structure of the ECAE-oriented polymers have been investigated from all dimensional levels, i.e., from spherulitical scale (micrometer scale), lamellar scale (nanometer scale) to crystallographic scale (angstrom scale). The results indicate that the polymer spherulites are deformed into macrofibrils after one ECAE process. Within the macrofibrils, a "V-type" lamellar orientation has been formed to accommodate the overall straining of spherulites. The molecular chains in the crystalline lamellae are found to be tilted at a small angle with respect to the lamellar surface. Whereas, the molecular chains between the macrofibrils and crystalline lamellae are highly stretched. Property characterization indicates that ECAE-induced microstructure is responsible for the improved physical and mechanical properties. The improved physical and mechanical properties include high tensile modulus, higher impact fracture toughness and better scratch resistance. This research has also clarified several controversies in the research of semicrystalline polymers. First, this research gives an unambiguous account on the lamellar evolution during large-scale plastic deformation. The crystalline lamellae in the ECAE-oriented samples have been found to be evolved from the original crystalline lamellae. Secondly, the shifting of the primary relaxation peak in ECAE-oriented PET has been found to be due to the increase in molecular orientation. Thirdly, the transmission electron microscopy (TEM) indicates that in low crystallinity semicrystalline polymers, the larger value of the two characteristic lengths from small angle X-ray scattering (SAXS) correlation function analysis should be assigned to the crystalline lamellar thickness.

Xia, Zhiyong

12

Mechanical properties of hybrid inorganic-organic framework materials: establishing fundamental structure-property relationships.  

OpenAIRE

The mechanical properties of hybrid framework materials, including both nanoporous metal-organic frameworks (MOFs) and dense inorganic-organic frameworks, are discussed in this critical review. Although there are relatively few studies of this kind in the literature, major recent advances in this area are beginning to shed light on the fundamental structure-mechanical property relationships. Indeed research into the mechanical behavior of this important new class of solid-state materials is c...

Tan, Jc; Cheetham, Ak

2011-01-01

13

Structure/property Relationships in Open Framework Nonlinear Optical Materials  

Science.gov (United States)

Potassium titanyl phosphate (KTP) is an extremely versatile nonlinear optical (NLO) material, and is the crystal of choice for the frequency doubling of the Nd:YAG laser line at 1.064 mum. The structure in which it crystallizes is very tolerant to isovalent substitution, and over four dozen compounds known to be KTP isostructures exist. While all current theories of optical nonlinearity in inorganic solids which have been applied to KTP concur that the distorted geometry of the TiO_6 octahedra are responsible for NLO behavior, none have resulted in a structure/property relationship which can be applied successfully to the entire KTP structure field. The facility with which potassium ions can be exchanged suggests that KTP should be treated as a host-guest system, in which the K^ {+} "guest" cations reside in channels formed by the titanyl phosphate "host" framework. Compounds are synthesized in which new metals replace Ti, and As replaces P, altering the characteristics of the host, and ion exchange yields new phases which test the effect of host-guest interactions on the NLO susceptibility, as measured by second harmonic generation (SHG) intensity. It is found that replacing Ti with main group metals results in less distorted MO_6 groups and drastically attenuated SHG intensity. When new cations replace potassium, the SHG intensity of the resulting phase depends on the strength of the bonding between the cation and the framework, though in no case are the Ti-O distances significantly altered. The cations thus play a significant role in defining SHG intensity in the KTP structure field, which is now accounted for in an extended version of the anionic group model. Other host-guest interactions studied in NLO materials include the p-nitroaniline-AlPO_4 -11 system, which results in SHG intensities an order of magnitude less than analogous NA:AlPO_4 -5 composites. Other systems investigated for use as host frameworks for studying such interactions include the gallophosphate sieve GaPO_4 -5 and the cesium zinc phosphate phase space.

Phillips, Mark Lincoln Freeman

1990-01-01

14

Transport properties of ribbon-shaped carbon fibers: Property-structure relationship  

Science.gov (United States)

Mesophase pitch-based carbon fibers are an ideal material for applications in which high rates of heat dissipation and low mass are required. Unfortunately, the high cost of current commercial high thermal conductivity mesophase pitch-based carbon fibers has limited their use in high volume applications. Understanding how the structure develops during the fiber formation process and how this structure relates to the final fiber properties is the way to optimizing the fiber properties while reducing the processing costs. Ribbon-shaped fibers have been developed at Clemson University and are being evaluated as a low-cost high thermal conductivity alternative fiber to traditional round-shaped fibers. However, the characterization of the thermal transport properties of carbon fibers is a difficult and time-consuming process. The objectives of this study were to evaluate the transport (both thermal and electronic) properties of ribbon-shaped fibers produced from an AR mesophase at different processing conditions, to characterize the structure of these fibers, to study their structure-property relationships, and to develop a model capable of estimating the thermal conductivity of carbon fibers based upon their structural parameters. For this purpose, several sets of ribbon fibers were produced from an AR mesophase at different spinning temperatures and shear rates and heat treated at a final temperature of 2400°C. The electrical resistivities, magnetoresistances and thermal conductivities of these fibers were measured and the structural parameters were determined with x-ray techniques. Two approaches (a short-fiber composite, and a periodic composite) were utilized to model the relationship between the structure of the fiber and its thermal conductivity. The results of this study confirmed that ribbon-shaped fibers develop excellent transport properties at lower graphitization temperatures than those used commercially for round-shaped fibers. Additionally, for the first time, two models that directly relate the structure of the carbon fiber to its thermal conductivity were developed.

Gallego, Nidia Constanza

15

Incoloy 908 database report: On process -- structure -- property relationship  

Energy Technology Data Exchange (ETDEWEB)

Incoloy 908 is a nickel-iron base superalloy with a coefficient of expansion (COE) and mechanical properties that have been optimized for use in Nb{sub 3}Sn superconducting magnets. It has been proposed for use as a conduit material for the International Thermonuclear Experimental Reactor (ITER) magnets. The relationship between manufacturing processes, microstructures and mechanical properties of Incoloy 908 are characterized in support of the magnet fabrication and quality control. This report presents microhardness, microstructure, and yield and ultimate tensile strengths as functions of thermomechanical process variables including heat treatment, annealing and cold work for laboratory prepared Incoloy 908 specimens. Empirical correlations have been developed for the microhardness at room temperature and tensile strength at room temperature and at 4K. These results may be used for manufacturing quality control or for design.

Toma, L.S.; Hwang, I.S.; Steeves, M.M.

1993-05-01

16

An Investigation of College Chemistry Students' Understanding of Structure-Property Relationships  

Science.gov (United States)

The connection between the molecular-level structure of a substance and its macroscopic properties is a fundamental concept in chemistry. Students in college-level general and organic chemistry courses were interviewed to investigate how they used structure-property relationships to predict properties such as melting and boiling points. Although…

Cooper, Melanie M.; Corley, Leah M.; Underwood, Sonia M.

2013-01-01

17

Structure-property relationships and biocompatibility of carbohydrate crosslinked polyurethanes.  

Science.gov (United States)

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

Solanki, Archana; Mehta, Jayen; Thakore, Sonal

2014-09-22

18

Development of Computational Tools for Use in Quantitative Structure-Activity and Structure-Property Relationships  

Science.gov (United States)

Computational tools are developed to relate theoretical aspects of molecular structure to experimental chemical behavior. The assumption that a causal relationship exists between molecular structure and chemical behavior is the fundamental premise that underlies the fields of quantitative structure-activity relationships (QSAR) and quantitative structure-property relationships (QSPR). Generation of a QSAR or QSPR involves the characterization of chemical structure in terms of numerical indices, and the development of mathematical models that correlate these indices with biological activities or physicochemical properties. Tools are developed in this thesis for use at three important stages of this process. A fast quantum mechanical molecular modeling technique based on a modified extended Huckel approach is developed for placing molecules in realistic energy-minimized conformations. The extended Huckel neglect-of-differential-overlap (EHNDO) method utilizes a one-electron approximation, semiempirical parameterization, and an efficient BFGS geometry optimization. The calculated molecular geometries from EHNDO are as accurate as those produced by the two-electron AM1 method, and the EHNDO geometry optimization is approximately three times faster. A new empirical method for calculating atomic charges is developed to characterize electronic structure. These charges are used in combination with the concepts of induction and resonance to arrive at an empirical model for pK _ a estimation in organic acids and bases. The PKACHG method generates partial atomic charges that yield accurate predictions of electric dipole moment, and the pK_ a model is accurate over wide ranges of acidity and basicity. Finally, nonlinear mathematical modeling techniques are investigated as a means of generating QSARs and QSPRs that contain stronger connections between calculated structure and experimental chemical behavior. A computational neural network program, QNET, is developed and outfitted with an efficient BFGS optimization for network training. A quadratic fitting routine, QUADFIT, is proposed as a fast alternative to neural networks. Both QNET and QUADFIT utilize external cross-validation during model development to prevent experimental data from being overfit. In a QSAR study of amine toxicity, QNET significantly outperforms conventional linear regression, and both QNET and QUADFIT yield post-model predictions that are considerably more accurate than those of linear regression.

Dixon, Steven L.

19

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

OpenAIRE

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

20

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.

2012-12-01

21

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

22

Structure-property relationships in a polymer memristor  

Science.gov (United States)

It has recently been shown that blends of semiconducting and ferroelectric polymers exhibit memristance, a property by which the resistance of a material can be reversibly switched between states purely as a function of its electrical history. While devices with relatively good memory retention times, cycle lifetimes, and on-off ratios have been made from poly-3-hexylthiophene (P3HT) blended with poly(vinylidene fluoride-ran-trifluoroethylene) (P(VDF-TrFE)), the morphology of such blends is composed of large, irregular domains of P3HT. These large domains represent a significant waste of material, as the memristive effect is believed to only arise at the interfaces of the domains, not in their cores. We show that, through the application of knowledge of how more conventional polymers interact in blends, we can control the morphology of these memristive devices through materials selection and potentially improve device performance as well as provide an additional means of optimization through morphological control. Through electrical characterization in a vacuum probe station and use of atomic force microscopy and differential scanning calorimetry, we show that we can smoothly alter morphology in a blended polymer memristor and that these memristors demonstrate switching with on-off current ratios of up to 100 and shelf lives of at least 18 months in atmosphere.

Jacobs, Andrew Robert

23

Structure-Property Relationships and Charge Transport Modeling of Organic Molecular Materials  

OpenAIRE

From the perspective of a new-generation opto-electronic technology based on organic semiconductors, a major objective is to achieve a deep and detailed knowledge of the structure-property relationships, in order to optimize the electronic, optical, and charge transport properties by tuning the chemical-physical characteristics of the compounds. The purpose of this dissertation is to contribute to such understanding, through suitable theoretical and computational studies. Precisely, the struc...

Di Motta, Simone

2012-01-01

24

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

25

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

26

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

27

Results from the Use of Molecular Descriptors Family on Structure Property/Activity Relationships  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of the paper is to present the results obtained by utilization of an originalapproach called Molecular Descriptors Family on Structure-Property (MDF-SPR andStructure-Activity Relationships (MDF-SAR applied on classes of chemical compoundsand its usefulness as precursors of models elaboration of new compounds with betterproperties and/or activities and low production costs. The MDF-SPR/MDF-SARmethodology integrates the complex information obtained from compound’s structure inunitary efficient models in order to explain properties/activities. The methodology has beenapplied on a number of thirty sets of chemical compounds. The best subsets of moleculardescriptors family members able to estimate and predict property/activity of interest wereidentified and were statistically and visually analyzed. The MDF-SPR/MDF-SAR modelswere validated through internal and/or external validation methods. The estimation andprediction abilities of the MDF-SPR/MDF-SAR models were compared with previousreported models by applying of correlated correlation analysis, which revealed that theMDF-SPR/MDF-SAR methodology is reliable. The MDF-SPR/MDF-SAR methodologyopens a new pathway in understanding the relationships between compound’s structure andproperty/activity, in property/activity prediction, and in discovery, investigation andcharacterization of new chemical compounds, more competitive as costs andproperty/activity, being a method less expensive comparative with experimental methods.

Sorana-Daniela Bolboacă

2007-03-01

28

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

29

Polydopamine and eumelanin: from structure-property relationships to a unified tailoring strategy.  

Science.gov (United States)

Conspectus Polydopamine (PDA), a black insoluble biopolymer produced by autoxidation of the catecholamine neurotransmitter dopamine (DA), and synthetic eumelanin polymers modeled to the black functional pigments of human skin, hair, and eyes have burst into the scene of materials science as versatile bioinspired functional systems for a very broad range of applications. PDA is characterized by extraordinary adhesion properties providing efficient and universal surface coating for diverse settings that include drug delivery, microfluidic systems, and water-treatment devices. Synthetic eumelanins from dopa or 5,6-dihydroxyindoles are the focus of increasing interest as UV-absorbing agents, antioxidants, free radical scavengers, and water-dependent hybrid electronic-ionic semiconductors. Because of their peculiar physicochemical properties, eumelanins and PDA hold considerable promise in nanomedicine and bioelectronics, as they are biocompatible, biodegradable, and exhibit suitable mechanical properties for integration with biological tissues. Despite considerable similarities, very few attempts have so far been made to provide an integrated unifying perspective of these two fields of technology-oriented chemical research, and progress toward application has been based more on empirical approaches than on a solid conceptual framework of structure-property relationships. The present Account is an attempt to fill this gap. Following a vis-à-vis of PDA and eumelanin chemistries, it provides an overall view of the various levels of chemical disorder in both systems and draws simple correlations with physicochemical properties based on experimental and computational approaches. The potential of large-scale simulations to capture the macroproperties of eumelanin-like materials and their hierarchical structures, to predict the physicochemical properties of new melanin-inspired materials, to understand the structure-property-function relationships of these materials from the bottom up, and to design and optimize materials to achieve desired properties is illustrated. The impact of synthetic conditions on melanin structure and physicochemical properties is systematically discussed for the first time. Rational tailoring strategies directed to critical control points of the synthetic pathways, such as dopaquinone, DAquinone, and dopachrome, are then proposed, with a view to translating basic chemical knowledge into practical guidelines for material manipulation and tailoring. This key concept is exemplified by the recent demonstration that varying DA concentration, or using Tris instead of phosphate as the buffer, results in PDA materials with quite different structural properties. Realizing that PDA and synthetic eumelanins belong to the same family of functional materials may foster unprecedented synergisms between research fields that have so far been apart in the pursuit of tailorable and marketable materials for energy, biomedical, and environmental applications. PMID:25340503

d'Ischia, Marco; Napolitano, Alessandra; Ball, Vincent; Chen, Chun-Teh; Buehler, Markus J

2014-12-16

30

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

International Nuclear Information System (INIS)

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

31

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

Directory of Open Access Journals (Sweden)

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

Antimo Gioiello

2013-08-01

32

Comparative Studies on Rigid ? Linker-Based Organic Dyes: Structure-Property Relationships and Photovoltaic Performance.  

Science.gov (United States)

A series of six structurally correlated donor-? bridge-acceptor organic dyes were designed, synthesized, and applied as sensitizers in dye-sensitized solar cells. Using the most widely studied donor (triarylamine) and cyclopenta[1,2-b:5,4-b']dithiophene or cyclopenta[1,2-b:5,4-b']dithiophene[2',1':4,5]thieno[2,3-d]thiophene as ? spacers, their structure-property relationships were investigated in depth by photophysical techniques and theoretical calculations. It was found that the photovoltaic performance of these dyes largely depends on their electronic structures, which requires synergistic interaction between donors and acceptors. Increasing the electron richness of the donor or the elongation of ?-conjugated bridges does not necessarily lead to higher performance. Rather, it is essential to rationally design the dyes by balancing their light-harvesting capability with achieving suitable energy levels to guarantee unimpeded charge separation and transport. PMID:25319943

Li, Hairong; Koh, Teck Ming; Hao, Yan; Zhou, Feng; Abe, Yuichiro; Su, Haibin; Hagfeldt, Anders; Grimsdale, Andrew C

2014-12-01

33

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

Science.gov (United States)

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

Rmaile, Hassan H.

34

Quantitative structure-property relationships for prediction of boiling point, vapor pressure, and melting point.  

Science.gov (United States)

Boiling point, vapor pressure, and melting point are important physicochemical properties in the modeling of the distribution and fate of chemicals in the environment. However, such data often are not available, and therefore must be estimated. Over the years, many attempts have been made to calculate boiling points, vapor pressures, and melting points by using quantitative structure-property relationships, and this review examines and discusses the work published in this area, and concentrates particularly on recent studies. A number of software programs are commercially available for the calculation of boiling point, vapor pressure, and melting point, and these have been tested for their predictive ability with a test set of 100 organic chemicals. PMID:12924571

Dearden, John C

2003-08-01

35

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

Directory of Open Access Journals (Sweden)

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

Grant Dubois

2012-04-01

36

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

Science.gov (United States)

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

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

2014-05-01

37

Elastomeric electron beam-cured coatings: structure-property relationships. I. Oligomer structure  

International Nuclear Information System (INIS)

Mechanical properties of electron beam-cured films were studied as a function of oligomer structure and monomer diluent. In films cast from polyester acrylourethane oligomers, increasing the chain length between the two acrylate groups on each end resulted in a decrease in breaking strength from 7000 psi to 1000 psi in Young's modulus from 200,000 psi to 700 psi, and in glass transition temperature from 50 to -250C, while the ultimate elongation increased from 20 to 210%. These properties were virtually independent of dose above 1 Mrad. The elongations were compared with literature values at equivalent degrees of crosslinking and found to fall within the range, but on the low elongation side of the distribution. It was speculated that the crosslinks' functionality would equal the average degree of polymerization of the double bond at each end of the oligomer, resulting in multirayed, star-shaped crosslinks with less flexibility than those with the usual functionality of 3 or 4, and methods for reducing this functionality were investigated. Addition of active monomers effected only minor change, but diethylaminoethyl acrylate was found to be very helpful in increasing the extensibility of these films considerably. This behavior can be explained by assuming that this monomer has a significant chain transfer constant, which should reduce the degree of polymerization of acrylic endgroups, producing a looser structure. 18 figures, 1 table8 figures, 1 table

38

Structure-property relationship and structural study of polyurethane-urea elastomers  

International Nuclear Information System (INIS)

The effect of structural chemistry of different soft segments on various structural properties of polyurethane-urea (PUU) elastomers was evaluated in this study. A series of PUU elastomers were prepared by the reaction of 4,4-diisocyanato dicylohexylmethane (H12MDI) with polycaprolactone (PCL), Polytetramethylene glycol (PTMG), Polyethylene glycol (PEG), Polybutylene adipate (PBA) and amine chain extender 4,4-methylenebis(2,6-diethylaniline) (MBDEA). Fourier transform infrared (FTIR) spectroscopy was used to study the synthesis of final PUU elastomers. Thermal behaviour of PUU elastomers was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. The surface properties and hardness of elastomers were characterized by measuring contact angle and hardness in shore A scale. The results showed highest thermal stability and hydrophobicity of PUPCL i.e., Polycaprolactone polyol based PUU elastomer. The proposed synthesis of PUU elastomers was confirmed by the appearance of NH peak at 3305-3315 cm-1 and disappearance of NCO peak at 2270 cm-1 in FTIR spectra. (author)

39

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

Directory of Open Access Journals (Sweden)

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

Trišovi? Nemanja

2011-10-01

40

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

2011-01-01

41

Linear and nonlinear quantitative structure-property relationship modelling of skin permeability.  

Science.gov (United States)

In this work, quantitative structure-property relationship (QSPR) models were developed to estimate skin permeability based on theoretically derived molecular descriptors and a diverse set of experimental data. The newly developed method combining modified particle swarm optimization (MPSO) and multiple linear regression (MLR) was used to select important descriptors and develop the linear model using a training set of 225 compounds. The adaptive neuro-fuzzy inference system (ANFIS) was used as an efficient nonlinear method to correlate the selected descriptors with experimental skin permeability data (log Kp). The linear and nonlinear models were assessed by internal and external validation. The obtained models with three descriptors show good predictive ability for the test set, with coefficients of determination for the MPSO-MLR and ANFIS models equal to 0.874 and 0.890, respectively. The QSPR study suggests that hydrophobicity (encoded as log P) is the most important factor in transdermal penetration. PMID:24090175

Khajeh, A; Modarress, H

2014-01-01

42

Quantitative structure property relationships on formation constants of radiometals for radiopharmaceuticals applications  

International Nuclear Information System (INIS)

Three (3D) and two dimensional (2D) quantitative structure-property relationships (QSPR) were established to model of the complexation formation of bifunctional coupling agents with 64Cu(II) and 67/68Ga(III) radiometal ions. The best model for 3D-QSPR has been obtained with R2 > 0.93 and Q2 > 0.75. Some simple 2D-QSAR models, able to correlate and predict the formation constants are developed. The final models satisfied a set of rigorous validation criteria and performed well in the prediction of an external test set. The information obtained could be very useful to design the most efficient ligands and find new matching chelators to radiometals for radiopharmaceuticals applications. (author)

43

Star-shaped molecules for organic photovoltaics: Synthesis and structure-property relationships  

Science.gov (United States)

In this thesis, the development and structure-property relationships of a novel class of two-dimensional star-shaped molecules synthesized for organic photovoltaics are presented. A promising approach towards low cost photovoltaics for power generation is fabrication of solar cells based on organic semiconductors. In addition to being a potentially reliable and environmentally friendly energy source, organic materials offer unique advantages such as low cost, lightweight, flexibility and high form factor. Though this field has witnessed tremendous progress over the last decade, power conversion efficiencies of the existing solar cells are still poor, prohibiting their wide spread commercial use. The available organic materials mainly suffer from low charge carrier mobilities and inefficient absorption in the bulk of the solar spectrum leading to low photocurrent generation. Charge transport in conjugated polymers is generally one-dimensional, while three-dimensional mobility is limited by the necessity for chain-to-chain activated hopping mechanism. Self-organization observed in conjugated crystalline small molecules and polymers favors strong intermolecular interactions in the pi-pi stacking distance and offers potential to improve charge carrier mobilities in organic materials. This motivated us to design and synthesize five different solution processible two-dimensional star-shaped molecules CN-X, THX-L, THX- S, THX-S=O and THX-D/A that offer interesting possibilities for improvement of charge mobilities and photophysical properties. The developed molecules self-organize in the form of pi-stacks and contain a tetra-substituted central phenyl ring with four phenylenevinylene or thiophene arms with conjugation through the arms and central phenyl core. The designed synthetic route is versatile, which enables facile incorporation of different electron rich and deficient moieties and solubilizing groups, thus facilitating systematic engineering of material properties like energy levels, bandgap, charge transport and solubility. The two-dimensional structural architecture with different functional groups led to molecules with small optical bandgaps in the range of 1.8-2.2 eV, absorbing in the bulk of the solar spectrum with band edges extending up to 700 nm and exhibiting strong intermolecular interactions in the pi-pi stacking distance of 3.5 A. A representative molecule, THX- L, from a set of four different oligothiophenes has shown field effect mobility of as high as 0.02 cm2V-1s-1 , which is amongst the best mobilities reported thus far for solution processible organics. In this thesis, the designed synthetic strategy, the fundamental structure-property relationships that govern the performance of the star molecules and their potential application mainly in solar cells and to some extent in light emitting diodes and field-effect transistors will be discussed. One relationship we have also investigated is whether the star architecture offers any fundamental advantages over linear molecules by comparing the properties of CN-X with its linear analog CN-L, which will be presented in the thesis.

Bhandari, Yashpal

44

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

45

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

Science.gov (United States)

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. PMID:23436749

Sarfraz Iqbal, M; Golsteijn, Laura; Öberg, Tomas; Sahlin, Ullrika; Papa, Ester; Kovarich, Simona; Huijbregts, Mark A J

2013-04-01

46

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

47

Hierarchical multiscale structure-property relationships of the red-bellied woodpecker (Melanerpes carolinus) beak.  

Science.gov (United States)

We experimentally studied beaks of the red-bellied woodpecker to elucidate the hierarchical multiscale structure-property relationships. At the macroscale, the beak comprises three structural layers: an outer rhamphotheca layer (keratin sheath), a middle foam layer and an inner bony layer. The area fraction of each layer changes along the length of the beak giving rise to a varying constitutive behaviour similar to functionally graded materials. At the microscale, the rhamphotheca comprises keratin scales that are placed in an overlapping pattern; the middle foam layer has a porous structure; and the bony layer has a big centre cavity. At the nanoscale, a wavy gap between the keratin scales similar to a suture line was evidenced in the rhamphotheca; the middle foam layer joins two dissimilar materials; and mineralized collagen fibres were revealed in the inner bony layer. The nano- and micro-indentation tests revealed that the hardness (associated with the strength, modulus and stiffness) of the rhamphotheca layer (approx. 470 MPa for nano and approx. 320 MPa for micro) was two to three times less than that of the bony layer (approx. 1200 MPa for nano and approx. 630 MPa for micro). When compared to other birds (chicken, finch and toucan), the woodpecker's beak has more elongated keratin scales that can slide over each other thus admitting dissipation via shearing; has much less porosity in the bony layer thus strengthening the beak and focusing the stress wave; and has a wavy suture that admits local shearing at the nanoscale. The analysis of the woodpeckers' beaks provides some understanding of biological structural materials' mechanisms for energy absorption. PMID:24812053

Lee, Nayeon; Horstemeyer, M F; Rhee, Hongjoo; Nabors, Ben; Liao, Jun; Williams, Lakiesha N

2014-07-01

48

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

Directory of Open Access Journals (Sweden)

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

Drago Skrtic

2009-11-01

49

Quantitative structure-property relationship (QSPR model for predicting acidities of ketones  

Directory of Open Access Journals (Sweden)

Full Text Available Ketones are one of the most common functional groups, and ketone-containing compounds are essential in both the nature and the chemical sciences. As such, the acidities (pKa of ketones provide valuable information for scientists to screen for biological activities, to determine physical properties or to study reaction mechanisms. Direct measurements of pKa of ketones are not readily available due to their extremely weak acidity. Hence, a quantitative structure-property relationship (QSPR model that can predict the acidities of ketones and their acidity order is highly desirable. The establishment of an acidity scale in dimethyl sulfoxide (DMSO solution by Bordwell et al. made such an effort possible. By utilizing the pKa values of forty-eight ketones determined in DMSO as the training set, a QSPR model for predicting acidities of ketones was built by stepwise multiple linear regression analysis. The established model showed statistical significance and predictive power (r2 = 0.91, q2 = 0.86, s = 1.42. Moreover, the QSPR model also gave reasonable acidity predictions for five ketones in an external prediction set that were not included in the model generation phase (r2 = 0.92, s = 1.618. Overall, the reported QSPR model for predicting acidities of ketones provides a useful tool for both biologists and chemists in understanding the biophysical properties and reaction rates of different classes of ketones.

Yan Zhang

2012-02-01

50

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

Science.gov (United States)

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

Luo, Sida

51

Crystal growth and structure-property relationships for ferroelectric strontium bismuth tantalate  

Science.gov (United States)

This thesis reports on the crystal growth of SrBi2Ta 2O9 ISBN, the measurements of intrinsic properties and the determination of structure-property relationships. Data are reported for the first time for the spontaneous polarization, dielectric anisotropy, electric resistivity, elastic coefficients, piezoelectric activity, heat capacity, and thermal expansion. Details are reported for the high-temperature solution growth of SBT from a Bi2O3 self-flux. Sizable single crystals (up to 6 x 2 x 1.7 mm3) were grown. High resolution TEM imaging verified the basic layer structure, and occasionally identified defects including stacking faults in the SBT structure. The crystal structure was determined by x-ray diffraction. The refinement was consistent with ion exchange between Bi and Sr sites. A theoretical value for the spontaneous polarization was calculated from ionic displacements in the refined structure, and found to be in excellent agreement with experimental data (17 muC/cm2). Well-saturated ferroelectric hysteresis loops were observed for the first time in this thesis for SBT single crystals, from which the spontaneous polarization was obtained. Dielectric constant values were determined along the three principal directions, and were at room temperature Ka = 300, Kb = 186, and Kc = 93. The temperature dependence of their anisotropy was also investigated, with a strong anomaly at a lower transition temperature of ˜300°C. In addition, the electrical resistivity was also determined for the three principal directions. The value along c (rhoc = 3.6 x 1014 ·CM) was more than an order of magnitude greater than along the other two principal directions (rhoa = 1.4 x 1013 ·cm and rhob = 2.2 x 1013 ·cm). The full tensors of elastic and piezoelectric coefficients were obtained by Brillouin scattering method. The piezoelectric coefficients for SBT are weak (e.g., d11˜24 pC/N), and should not give rise to any significant strain on switching PS. Two phase transformations were identified. The higher-temperature phase transformation (˜580°C) was attributed to a tetragonal-orthorhombic transformation on cooling (4/mmm?2mmm). The lower-temperature phase transformation (˜305°C) was identified to be within the same point group (2mm) and the same Aizu species. Raman spectroscopy as a function of temperature identified a soft mode with A1 symmetry which disappeared at the lower-transition temperature on heating. Raman data suggest a structural change with a lower transition from A21am to F2mm on heating. Thermal analysis indicated the latent heat of transformation was small. Thermal properties including thermal expansion coefficient and heat capacity were also determined. Discoveries in this thesis suggest that Sr and Bi exchange between the layers and compensated doping, and the weak piezoelectric properties, are the major mechanisms by which SBT shows excellent resistance to fatigue.

Lu, Xinliang

2000-10-01

52

Solid solution directionally solidified eutectics: Model systems for structure-property relationships in interfacial fracture  

Science.gov (United States)

The next generation of high temperature materials for application in aerospace and power generation systems will be required to withstand temperatures well in excess of 1200°C, often in oxidizing atmospheres. Oxide-oxide directionally solidified eutectics (DSE's) have shown promise as high temperature ceramic materials, only to be limited by their lack of fracture toughness at room temperature. In the case of DSE oxide materials, the interfacial fracture behavior has been blamed for the poor performance in the past and is the subject of interest in this work. In this thesis, the solid solution, directionally solidified quaternary eutectic (SS-DSE), Co1-xNixO/ZrO2(CaO), is developed as a model system for the study of interfacial fracture in oxide-oxide DSE's. A variety of structural and mechanical characterization techniques are applied to investigate structure-property relationships for interfacial fracture behavior. The optical floating zone technique was employed for growing both the eutectic crystals and their single crystal counterparts, Co1-x NixO. Co1-xNixO/ZrO2(CaO) was shown to possess the necessary structural elements to serve as a model system for interfacial fracture. Lamellar microstructures were observed for all compositions. The crystallographic relationships between phases evolved as a model solid solution. Interdiffusion of chemical species was minimal, allowing the layers to treated independently. The core of this thesis is dedicated to studying the nature of interfacial fracture behavior in oxide eutectics. This study is motivated by the novel observation of extensive interfacial delamination for the system CoO/ZrO 2(CaO). A transition from interfacial delamination to interfacial penetration is observed for compositions of Co1-xNixO/ZrO 2(CaO) with x > 0.2. The residual stress state in these materials was investigated using X-ray and neutron diffraction-based techniques. The role of plasticity in interfacial fracture was explored using a combination of indentation experiments, including spatially resolved nanoindentation testing. Constitutive laws for describing the elastoplastic behavior of the Co 1-xNixO phase were developed as a result of these measurements. These empirical laws are combined with dislocation theory to propose a dislocation-based mechanism for crack nucleation, which correctly describes the salient features of the interfacial fracture problem in this system.

Brewer, Luke Nathaniel

53

Structure-property-processing relationships and the effects of physical structure on the hygrothermal durability and mechanical response of polyimides  

Science.gov (United States)

Structure-property-processing interrelationships ate characterized for a variety of polyimide composite matrices used in advanced aerospace structural applications. The relationships between chemical/physical structure and (i) fabrication conditions, (ii) mechanical, thermal, and physical properties, and (iii) hydrolytic stability, are investigated. Major findings determined from this research are presented below. Carbon fiber/bismaleimide (BMI) cross-ply composite laminates are microcracked after standard cure and postcure procedures. Using a unique in-situ characterization of microcracking, it is demonstrated that extended cure times at low temperatures (177°C) prior to postcure can shift the microcracking threshold in these composites. Ultimately cute induced microcracking can be prevented under standard fabrication postcure temperatures as a result of a reduction in composite residual stress and an improved fiber/matrix interphase. Structure-property-processing characterization of BMI, polyetherimide (PEI), poly(4,4'-oxydiphenylene pyromellitimide) (POPPI), and a phenylethynyl terminated imide oligomer (PETI-5) demonstrates that deformation in thermoplastic polyimides is controlled primarily by free volume. In thermosets, deformation is controlled by network defects and free volume. Interestingly, PETI-5 was shown to crystallize under certain time-temperature cure cycles, which results in dramatic changes in neat resin mechanical properties. The observed crystallization behavior appears to be a result of liquid crystal-like ordering due to the phenylethynyl end groups. With respect to hygrothermal durability, thermoset polyimides prove to be more resistant to blistering and associated macroscopic damage than thermoplastics under hygrothermal excursions unless hydrolytic degradation induced chain scission has occurred. Accelerated hygrothermal exposure also demonstrated that the hydrolytic stability of polyimides is strongly dependent on the chemical nature of the polyimide and the end caps in thermosets. Phenylethynyl terminated imide oligomers displayed dramatically higher hydrolytic stability than norbornene terminated polyimides as a result of hydrolytic attack of the crosslinks associated with the Michael addition reaction. Compilation of the results presented provides insight into controlling the thermal, physical, and mechanical properties as well as the hydrolytic stability of polyimides based on chemical structure and processing conditions.

Lincoln, Jason E.

54

Structure-property relationships of meta-kerateine biomaterials derived from human hair.  

Science.gov (United States)

The structure-property relationships of kerateine materials were studied by separating crude hair extracts into two protein sub-fractions, referred to as ?- and ?-kerateines, followed by their de novo recombination into meta-kerateine hydrogels, sponges and films. The kerateine fractions were characterized using electrophoresis and mass spectrometry, which revealed that the ?-fraction contained complexes of type I and type II keratins and that the ?-fraction was primarily protein fragments of the ?-fraction along with three proteins of the KAP-1 family. Meta-kerateine materials with increased amounts of ?-kerateines showed diminished physical, mechanical and biological characteristics. Most notably, materials with higher ?-content formed less elastic and less solid-like hydrogels and sponges that were less hydrolytically stable. In addition, a model biological assay showed that meta-kerateine films with greater amounts of ?-kerateines were less supportive of hepatocyte attachment. Investigation into the mechanism of attachment revealed that hepatocyte adhesion to meta-kerateines is not mediated by the ?1 integrin subunit, despite the presence of LDV binding motifs within the type I ?-keratins. This work to define the role of protein composition on biomaterial function is essential for the optimization of keratin biomaterials for biomedical applications. PMID:21911088

Richter, Jillian R; de Guzman, Roche C; Greengauz-Roberts, Olga K; Van Dyke, Mark

2012-01-01

55

Teaching Structure-Property Relationships: Investigating Molecular Structure and Boiling Point  

Science.gov (United States)

A concise, well-organized table of the boiling points of 392 organic compounds has facilitated inquiry-based instruction in multiple scientific principles. Many individual or group learning activities can be derived from the tabulated data of molecular structure and boiling point based on the instructor's education objectives and the students'…

Murphy, Peter M.

2007-01-01

56

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

International Nuclear Information System (INIS)

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

57

Organic Materials for Electro-Optic and Optoelectronic Applications: Understanding Structure -- Property Relationships  

Science.gov (United States)

Organic materials are promising candidates for application to electro-optics (EO) due to such advantages as tunable properties, ease of processability and the possibility of chip-scale integration. To achieve EO activity on a bulk level, noncentrosymmetric alignment of chromophores is required. However, modern chromophores with high first-order molecular hyperpolarizability have large ground state dipole moments that oppose acentric order, diminishing EO performance. To address this, a better understanding of the relationship between molecular structure and bulk EO activity is required. In Chapter 2, the effects of functionalization of the benchmark chromophore YLD-124 on poling efficiency were studied. Substituents with different electronic nature and different sizes at the middle six-membered ring were explored. Attachment of a t-butylphenoxy group resulted in a 40% increase of the poling efficiency r33/Ep as well as significantly enhanced photostability. Unexpected optical properties of the functionalized chromophores in media with different polarities are explained in terms of electronic effects and aggregation. In Chapter 3, the synthesis of two chromophores with oblate shape is reported based on computational predictions that oblate spheroids with dipole moments formed short range linear stacks. These chromophores are potential candidates for application to a new type of nanophotonic device in which only several molecular layers of EO active material are required. An alternative approach for creating bulk acentricity upon crystallization is discussed in Chapter 4. A functionalization of two chromophores with acentric structure was performed in order to reduce the melting temperature of the parent materials. It was found that such a molecular arrangement is sensitive to the nature of the functionalization of the parent chromophores. Finally, the performance of novel polymerizable ionic liquids (PIL) as electrolytes for optoelectronic applications in polymeric light emitting electrochemical cells (LEC) is described in Chapter 5. The presented materials are organic salts and have allyl sulfonate as anion and trialkyl allyl/vinyl ammonium cation with varying length of alkyl groups; both anion and cation are capable of forming covalent bonds. LECs fabricated with these PILs demonstrated fixed junctions, improved film morphology and dramatically improved light output compared to the previously reported LEC with fixed junctions.

Kosilkin, Ilya V.

58

Understanding Structure-Property Relationships for Palladium-Gold Nanoparticles as Colloidal Catalysts  

Science.gov (United States)

Bimetallic palladium-gold (PdAu) nanoparticle (NP) catalysts have been demonstrated for the better catalytic performance than monometallic Pd catalysts in various reactions; however, the enhancement mechanism is not completely clear for most reactions. This thesis addresses the investigation of PdAu NP catalysts with emphasis on the structure-property relationships in water-phase reactions, using hydrodechlorination (HDC) of trichloroethene (TCE) as the model reaction. Catalyzed TCE HDC is a potential approach for water pollution control, in which colloidal Pd-decorated Au NPs (Pd/Au NPs) are known to be significantly better catalysts than monometallic Pd ones. X-ray absorption spectroscopy (XAS) of carbon-supported Pd/Au NPs with different surface Pd coverages verified their core-shell structure (Au-rich core and Pd-rich shell). Structure evolution was observed upon heat treatment, in which Pd was in the form of surface Pd ensembles at room temperature. The metals formed a surface PdAu alloy or a bulk PdAu alloy above 200°C, as determined from the average coordination environment. Results suggested a new way to promote Pd catalysis, namely, by impregnating supported Pd catalysts with gold salt followed by thermal annealing; such post-impregnation with different heat treatments could lead to >15-fold increase in TCE HDC activity. Pd ensembles on the Au NP surface were demonstrated to be major active sites for TCE HDC as the reaction rates correlated strongly with the size of Pd ensembles determined from XAS. The geometric effect, in which atomic ensembles act as active sites, appeared to dominate over the mixed metal site effect and the electronic effect. Au NPs could stabilize surface Pd atoms in the metallic form, possibly leading to a set of highly active sites that is not present in monometallic Pd NPs. The TCE HDC reaction with Pd/Au NPs and Pd NPs was conducted as a closed batch system. Mass transfer effects in this three-phase reaction were assessed and quantified by analyzing observed reaction rates as functions of stirring rates and initial catalyst charges. The largest effect on observed reaction rates came from gas-liquid mass transfer. TCE HDC was modeled as a Langmuir-Hinshelwood mechanism involving competitive chemisorption of dihydrogen and TCE molecules.

Fang, Yu-Lun

59

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

OpenAIRE

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

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

2012-01-01

60

The relationships between rheological properties and structural changes of chilled abalone meat  

Science.gov (United States)

The quantitative correlation between rheological properties and structural characteristic values of chilled abalone meat was studied. Structural changes were observed, and these values were enumerated using image processing and analysis technique. Structural changes in the myofibrils and collagen fibrils were the greatest in chilling for 24 h. After chilling for 48 h, similar structures of vertical and cross sections were observed. For chilling from 0h to 72 h, the instantaneous modulus E 0 of the both section meat decreases gradually with time, but no significant differences were observed after chilling for 48h. The relaxation time and viscosity of both sections attained the same values for the same chilling time, but increased gradually with increasing chilling time. Meanwhile, a negative correlation between the structural characteristic values (Dm, Am, Rvm), and rheological properties (E 1, ? 1, ? 1) clearly exists. Some logarithmic expressions have been obtained for these negative correlation. These results suggest that the difference in rheological properties between the cross and vertical sections was mainly due to the structural changes of myofibrils and collagen fibrils, and rheological properties are influenced quantitatively by the structural characteristics values for chilling from 0 h to 72 h.

Xin, Gao; Zhaohui, Zhang; Zhixu, Tang; Yuri, Tashiro; Hiroo, Ogawa

2003-10-01

61

Structure–morphology–mechanical properties relationship of some polypropylene/lignocellulosic composites  

International Nuclear Information System (INIS)

Natural lignocellulosic materials have an outstanding potential as thermoplastic reinforcement. Polypropylene composites were prepared using different types of lignocellulosic materials by melt blending of 70 wt% polypropylene (PP) and 30 wt% biomasses. The specimens were firstly evaluated for structural and morphological properties by infrared spectroscopy, X-ray diffraction, scanning electron and polarized optical microscopy. Depending on the biomass type, there were evidenced some particular shifts of the infrared bands and also crystallinity changes. An increase in crystallinity is explained by nucleating agent role of biomass. The morphological changes are directly related to variation in mechanical and rheological properties, an increase in Young modulus, melt viscosity and storage and loss moduli being recorded. - Highlights: • Composites based on polypropylene and different biomass filler were prepared by simple melting-mixing. • The specimens were evaluated for structural, morphological, mechanical and rheological properties. • The biomass filler act as a nucleation agent in the polymeric matrix

62

Relationship between structure and some properties of delta-Pu and ?-U alloys  

International Nuclear Information System (INIS)

Delta-plutonium, ?-uranium and alloys based on them have a number of anomalous properties not inherent in common metals and alloys. In addition to the properties known in the literature the paper discusses some other anomalous properties of these phases, in particular, an increase of the atomic volume as a result of cold working and prolonged room-temperature self-irradiation. A discussion is given as to the nature of the above phenomena. It is concluded that the anomalous properties of the phases considered result from the covalent component of the bond, that is due to the hybridization of the 5f and 6d levels and leads to a deviation of their structure from ideal fcc- and bcc-lattices. (Auth.)

63

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

64

Dicyanobenzene and dicyanopyrazine derived X-shaped charge-transfer chromophores: comparative and structure-property relationship study.  

Science.gov (United States)

A series of novel X-shaped push-pull compounds based on benzene-1,2-dicarbonitrile has been designed, synthesized and further investigated by X-ray analysis, electrochemistry, absorption and emission spectra, SHG experiment and quantum-chemical calculations. The obtained data were compared with those for isolobal 5,6-disubstituted pyrazine-2,3-dicarbonitriles. Structure-property relationships were elucidated. The extension, composition and planarization of the ?-linker used as well as the electron-withdrawing ability of both dicyano-substituted acceptor units affect the linear and nonlinear properties of the target charge-transfer chromophores most significantly. PMID:24948026

Dokládalová, L; Bureš, F; Kuznik, W; Kityk, I V; Wojciechowski, A; Mikysek, T; Almonasy, N; Ramaiyan, M; Pad?lková, Z; Kulhánek, J; Ludwig, M

2014-08-01

65

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

OpenAIRE

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

Shabani, Amin

2013-01-01

66

Structure-property relationships of curved aromatic materials from first principles.  

Science.gov (United States)

CONSPECTUS: Considerable effort in the past decade has been extended toward achieving computationally affordable theoretical methods for accurate prediction of the structure and properties of materials. Theoretical predictions of solids began decades ago, but only recently have solid-state quantum techniques become sufficiently reliable to be routinely chosen for investigation of solids as quantum chemistry techniques are for isolated molecules. Of great interest are ab initio predictive theories for solids that can provide atomic scale insights into properties of bulk materials, interfaces, and nanostructures. Adaption of the quantum chemical framework is challenging in that no single theory exists that provides prediction of all observables for every material type. However, through a combination of interdisciplinary efforts, a richly textured and substantive portfolio of methods is developing, which promise quantitative predictions of materials and device properties as well as associated performance analysis. Particularly relevant for device applications are organic semiconductors (OSC), with electrical conductivity between that of insulators and that of metals. Semiconducting small molecules, such as aromatic hydrocarbons, tend to have high polarizabilities, small band-gaps, and delocalized ? electrons that support mobile charge carriers. Most importantly, the special nature of optical excitations in the form of a bound electron-hole pairs (excitons) holds significant promise for use in devices, such as organic light emitting diodes (OLEDs), organic photovoltaics (OPVs), and molecular nanojunctions. Added morphological features, such as curvature in aromatic hydrocarbon structure, can further confine the electronic states in one or more directions leading to additional physical phenomena in materials. Such structures offer exploration of a wealth of phenomenology as a function of their environment, particularly due to the ability to tune their electronic character through functionalization. This Account offers discussion of current state-of-the-art electronic structure approaches for prediction of structural, electronic, optical, and transport properties of materials, with illustration of these capabilities from a series of investigations involving curved aromatic materials. The class of curved aromatic materials offers the ability to investigate methodology across a wide range of materials complexity, including (a) molecules, (b) molecular crystals, (c) molecular adsorbates on metal surfaces, and (d) molecular nanojunctions. A reliable pallet of theoretical tools for such a wide array relies on expertise spanning multiple fields. Working together with experimental experts, advancements in the fundamental understanding of structural and dynamical properties are enabling focused design of functional materials. Most importantly, these studies provide an opportunity to compare experimental and theoretical capabilities and open the way for continual improvement of these capabilities. PMID:24933397

Zoppi, Laura; Martin-Samos, Layla; Baldridge, Kim K

2014-11-18

67

Structure-dielectric properties relationships in copper-substituted magnesium ferrites  

Energy Technology Data Exchange (ETDEWEB)

Graphical abstract: - Highlights: • Synthesis of copper substituted magnesium ferrites materials is reported. • A shift from cubic to tetragonal structure starting with x = 0.84 was observed. • The dielectric properties are influenced by Cu-substitution. - Abstract: Nanocrystalline powders of copper-substituted magnesium ferrites with general formula Mg{sub 1?x}Cu{sub x}Fe{sub 2}O{sub 4} (x = 0.00, 0.17, 0.34, 0.50, 0.67, 0.84, 1.00) were prepared for the first time by sol–gel auto-combustion method, using glycine as fuel agent. Solid phase chemical reactions and the occurrence of spinel structure were monitored by using infrared spectroscopy. X-ray diffraction analysis confirmed the spinel single-phase formation. A shift from cubic structure to tetragonal structure starting with x = 0.84 was also observed. Microstructure of the samples was analyzed by scanning electron microscopy and particle size was estimated from the micrographs. Analysis of dielectric properties revealed very low values of dielectric loss at frequencies over 10 MHz.

Druc, A.C.; Borhan, A.I. [Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, Bulevardul Carol I, nr. 11, 700506 Iasi (Romania); Nedelcu, G.G.; Leontie, L. [Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Bulevardul Carol I, nr. 11, 700506 Iasi (Romania); Iordan, A.R. [Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, Bulevardul Carol I, nr. 11, 700506 Iasi (Romania); Palamaru, M.N., E-mail: palamaru@uaic.ro [Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, Bulevardul Carol I, nr. 11, 700506 Iasi (Romania)

2013-11-15

68

Structure-dielectric properties relationships in copper-substituted magnesium ferrites  

International Nuclear Information System (INIS)

Graphical abstract: - Highlights: • Synthesis of copper substituted magnesium ferrites materials is reported. • A shift from cubic to tetragonal structure starting with x = 0.84 was observed. • The dielectric properties are influenced by Cu-substitution. - Abstract: Nanocrystalline powders of copper-substituted magnesium ferrites with general formula Mg1?xCuxFe2O4 (x = 0.00, 0.17, 0.34, 0.50, 0.67, 0.84, 1.00) were prepared for the first time by sol–gel auto-combustion method, using glycine as fuel agent. Solid phase chemical reactions and the occurrence of spinel structure were monitored by using infrared spectroscopy. X-ray diffraction analysis confirmed the spinel single-phase formation. A shift from cubic structure to tetragonal structure starting with x = 0.84 was also observed. Microstructure of the samples was analyzed by scanning electron microscopy and particle size was estimated from the micrographs. Analysis of dielectric properties revealed very low values of dielectric loss at frequencies over 10 MHz

69

Further properties of causal relationship: causal structure stability, new criteria for isocausality and counterexamples  

International Nuclear Information System (INIS)

Recently (Garcia-Parrado and Senovilla 2003 Class. Quantum Grav. 20 625-64) the concept of causal mapping between spacetimes, essentially equivalent in this context to the chronological map defined in abstract chronological spaces, and the related notion of causal structure, have been introduced as new tools to study causality in Lorentzian geometry. In the present paper, these tools are further developed in several directions such as (i) causal mappings-and, thus, abstract chronological ones-do not preserve two levels of the standard hierarchy of causality conditions (however, they preserve the remaining levels as shown in the above reference), (ii) even though global hyperbolicity is a stable property (in the set of all time-oriented Lorentzian metrics on a fixed manifold), the causal structure of a globally hyperbolic spacetime can be unstable against perturbations; in fact, we show that the causal structures of Minkowski and Einstein static spacetimes remain stable, whereas that of de Sitter becomes unstable, (iii) general criteria allow us to discriminate different causal structures in some general spacetimes (e.g. globally hyperbolic, stationary standard); in particular, there are infinitely many different globally hyperbolic causal structures (and thus, different conformal ones) on R2 (iv) plane waves with the same number of positive eigenvalues in the frequency matrix share the same causal structure and, thus, they have equal causal extensions and cs, they have equal causal extensions and causal boundaries

70

Composition-structure-properties relationship of strontium borate glasses for medical applications.  

Science.gov (United States)

We have synthesized TiO2 doped strontium borate glasses, 70B2 O3 -(30-x)SrO-xTiO2 and 70B2 O3 -20SrO(10-x)Na2 O-xTiO2 . The composition dependence of glass structure, density, thermal properties, durability, and cytotoxicity of degradation products was studied. Digesting the glass in mineral acid and detecting the concentrations of various ions using an ICP provided the actual compositions that were 5-8% deviated from the theoretical values. The structure was investigated by means of (11) B magic angle spinning (MAS) NMR spectroscopy. DSC analyses provided the thermal properties and the degradation rates were measured by measuring the weight loss of glass disc-samples in phosphate buffered saline at 37°C in vitro. Finally, the MTT assay was used to analyze the cytotoxicity of the degradation products. The structural analysis revealed that replacing TiO2 for SrO or Na2 O increased the BO3 /BO4 ratio suggesting the network-forming role of TiO2 . Thermal properties, density, and degradation rates also followed the structural changes. Varying SrO content predominantly controlled the degradation rates, which in turn controlled the ion release kinetics. A reasonable control (2-25% mass loss in 21 days) over mass loss was achieved in current study. Even though, very high concentrations (up to 5500 ppm B, and 1200 ppm Sr) of ions were released from the ternary glass compositions that saturated the degradation media in 7 days, the degradation products from ternary glass system was found noncytotoxic. However, quaternary glasses demonstrated negative affect on cell viability due to very high (7000 ppm) Na ion concentration. All the glasses investigated in current study are deemed fast degrading with further control over degradation rates, release kinetics desirable. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2014. PMID:25366812

Hasan, Muhammad S; Werner-Zwanziger, Ulrike; Boyd, Daniel

2014-11-01

71

Structure-property relationships of an A36 steel alloy under dynamic loading conditions  

Science.gov (United States)

Structure-property quantification of an A36 steel alloy was the focus of this study in order to calibrate and validate a plasticity-damage model. The microstructural parameters included grain size, particle size, particle number density, particle nearest neighbor distances, and percent of ferrite and pearlite. The mechanical property data focused on stress-strain behavior under different applied strain rates (0.001/s, 0.1/s, and 1000/s), different temperatures (293 K and 573 K), and different stress states (compression, tension, and torsion). Notch tension tests were also conducted to validate the plasticity-damage model. Also, failure of an A36 I-beam was examined in cyclic loads, and the crack growth rates were quantified in terms of fatigue striation data. Dynamic strain aging was observed in the stress-strain behavior giving rise to an important point that there exists a critical temperature for such behavior.

Mayatt, Adam J.

72

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

Science.gov (United States)

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

Neilson, James R.

2011-12-01

73

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

International Nuclear Information System (INIS)

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

74

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

Directory of Open Access Journals (Sweden)

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

Bin Cheng

2011-04-01

75

A review of combined experimental and computational procedures for assessing biopolymer structure–process–property relationships  

Science.gov (United States)

Tailored biomaterials with tunable functional properties are desirable for many applications ranging from drug delivery to regenerative medicine. To improve the predictability of biopolymer materials functionality, multiple design parameters need to be considered, along with appropriate models. In this article we review the state of the art of synthesis and processing related to the design of biopolymers, with an emphasis on the integration of bottom-up computational modeling in the design process. We consider three prominent examples of well-studied biopolymer materials – elastin, silk, and collagen – and assess their hierarchical structure, intriguing functional properties and categorize existing approaches to study these materials. We find that an integrated design approach in which both experiments and computational modeling are used has rarely been applied for these materials due to difficulties in relating insights gained on different length- and time-scales. In this context, multiscale engineering offers a powerful means to accelerate the biomaterials design process for the development of tailored materials that suit the needs posed by the various applications. The combined use of experimental and computational tools has a very broad applicability not only in the field of biopolymers, but can be exploited to tailor the properties of other polymers and composite materials in general. PMID:22938765

Gronau, Greta; Krishnaji, Sreevidhya T.; Kinahan, Michelle E.; Giesa, Tristan; Wong, Joyce Y.; Kaplan, David L.; Buehler, Markus J.

2013-01-01

76

A review of combined experimental and computational procedures for assessing biopolymer structure-process-property relationships.  

Science.gov (United States)

Tailored biomaterials with tunable functional properties are desirable for many applications ranging from drug delivery to regenerative medicine. To improve the predictability of biopolymer materials functionality, multiple design parameters need to be considered, along with appropriate models. In this article we review the state of the art of synthesis and processing related to the design of biopolymers, with an emphasis on the integration of bottom-up computational modeling in the design process. We consider three prominent examples of well-studied biopolymer materials - elastin, silk, and collagen - and assess their hierarchical structure, intriguing functional properties and categorize existing approaches to study these materials. We find that an integrated design approach in which both experiments and computational modeling are used has rarely been applied for these materials due to difficulties in relating insights gained on different length- and time-scales. In this context, multiscale engineering offers a powerful means to accelerate the biomaterials design process for the development of tailored materials that suit the needs posed by the various applications. The combined use of experimental and computational tools has a very broad applicability not only in the field of biopolymers, but can be exploited to tailor the properties of other polymers and composite materials in general. PMID:22938765

Gronau, Greta; Krishnaji, Sreevidhya T; Kinahan, Michelle E; Giesa, Tristan; Wong, Joyce Y; Kaplan, David L; Buehler, Markus J

2012-11-01

77

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

Directory of Open Access Journals (Sweden)

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

Hmuda Sleem F.

2013-01-01

78

Fundamental study in FSW processing and FSW process-structure-property relationship for AA2024 and AA2524  

Science.gov (United States)

Friction stir welding (FSW) is a relatively new joining technique, copious data have been generated on the properties of FSWs in many alloys, but the factors governing the microstructure and properties of the nugget zone in precipitation hardenable aluminum alloy FSWs are still not fully understood. A series of FSW experiments and analyses were performed on precipitate hardening aluminum alloys AA2024-T351 and AA2524-T351 with an attempt to develop the process-structure-property correlation and characterize the processing and banding in these process and resultant joints. Results indicate that among the three control variables, rotation speed has the dominant effect on the nugget microstructure and property in AA2524 FSWs compared with welding speed and Fz force. For a given welding speed and z-axis force, there is an optimum rotation speed to produce a good combination of nugget ultimate tensile strength and elongation, higher rotation speed will cause overheating that results in grain boundary melting resulting in a big drop in elongation and ultimate tensile strength while having little inverse effect on the hardness and yield strength. The welding torque has a strong and good inverse proportional relationship with grain size, nugget hardness, yield strength and ultimate tensile strength. The effect of rotation speed, welding speed and z-axis force on the grain size, hardness and tensile properties can be rationalized based on their contribution to the welding torque. Results from processing and banding analysis show that there are well-defined periodic variations in the processing forces Fx and Fz during welding and periodic, semi-circular bands on the horizontal transverse cross-section for all the welds over a wide range of welding conditions. The measured band spacing is closely equal to the oscillation period of the Fx and Fz force of the welding tool, both are in good agreement with the FSW processing pitch. Different pin form tool may result in the difference between these banded structures, but could not change the relationship between processing and banding. The periodic banded structure in the nugget consists of alternating variation of grain size, particle distribution and micro-hardness variation, and would result in periodic variations of the measured strain response under loading. The direct and consistent relationship observed among periodicity in variation of Fx and Fz and the metallurgical and mechanical behavior indicate that the formation of banded structures in FSW joints is related to the periodic variation of welding parameters. (Abstract shortened by UMI.)

Yan, Junhui

79

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

CERN Document Server

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

Scientific Electronic Library Online (English)

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

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

81

Relationship between structure and creep properties of a predeformed austenitic steel  

International Nuclear Information System (INIS)

The effect that prior cold working with 7% and 14% deformation has upon the creep behaviour of AISI alloy 314 has been investigated at 9000C. For short-term testing the pretreated condition exhibits a beneficial effect in terms of creep and rupture strength, whereas the ductility is reduced. With increasing test times the strength and ductility of the material gradually approach those of the recrystallized condition. From structural analyses it is concluded that as long as the high dislocation density associated with the preformed condition remains, the strength is increased and the grain boundaries are sensitive to crack nucleation and growth. On the basis of the observation that the creep properties recover fully it is concluded that prior cold work at the applied level does not damage the material. (author)

82

New lanthanide-CB[6] coordination compounds: relationships between the crystal structure and luminescent properties.  

Science.gov (United States)

The reaction between cucurbit[6]uril (CB[6]) and lanthanide chlorides (Eu, Sm, Tb and Tm) in acidic aqueous media led to four new structures. The compounds obtained are isostructural with general formula [Ln2(H2O)12(H2O@CB[6])]Cl6(H2O)4 (Ln = Eu(3+) (1), Sm(3+) (2), Tb(3+) (3) and Tm(3+) (4)) and crystallize in the P21/c space group. For the complexes with Eu(3+), Sm(3+) and Tb(3+), the luminescent properties in the solid state and aqueous media were explored and all spectroscopic observations are in excellent agreement with the single crystal structure data. The excitation and emission spectra show the typical f-f transitions characteristic of the trivalent lanthanide ions. The transitions (7)FJ ? (5)D1 (J = 0,1,2) in the europium compound and (7)FJ ? (5)D4 (J = 0,1,2) in the terbium compound, not yet reported in lanthanide-CB[n] compounds, were also observed. PMID:24522452

da Silva, Fausthon F; de Oliveira, Carlos A F; Falcão, Eduardo H L; Chojnacki, Jaroslaw; Neves, Jorge L; Alves, S

2014-04-14

83

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

Energy Technology Data Exchange (ETDEWEB)

Thin films of various compositions in the Na{sub 2}O-SiO{sub 2}-P{sub 2}O{sub 5}-ZrO{sub 2} system were deposited in glassy form by reactive magnetron sputtering. An analysis by spectrophotometry showed an increase of the extinction coefficient (k) with the amount of Fe contamination. This contamination, originating from parasitic plasmas, was suppressed when convenient protections were used. Therefore, it was possible to produce optical clear films. A structural study by X-ray diffraction and Raman spectroscopy proved a reorganization in the amorphous state at low temperature and the appearance of a NASICON structure around 750 deg. C. The ionic conductivity, measured by impedance spectroscopy, and the optical properties were strongly affected by the thermal annealing process. The reorganization in the amorphous state and strong modifications of the ionic conductivity values and the refractive index (n) appeared in the same range of temperatures. This suggested a strong correlation between these different phenomena.

Horwat, D. [Laboratoire de Science et Genie des Surfaces (UMR 7570) - Ecole Nationale Superieure des Mines de Nancy - Parc de Saurupt - CS 14 234-54042 Nancy cedex (France)], E-mail: David.horwat@mines.inpl-nancy.fr; Pierson, J.F. [Laboratoire de Science et Genie des Surfaces (UMR 7570) - Ecole Nationale Superieure des Mines de Nancy - Parc de Saurupt - CS 14 234-54042 Nancy cedex (France); Billard, A. [Laboratoire d' Etudes et de Recherches sur les Materiaux, les Procedes et les Surfaces - Universite de Technologie de Belfort-Montbeliard - Site de Montbeliard - 90010 Belfort cedex (France)

2008-03-31

84

Structure–property relationships of synthetic organophosphorus flame retardant oligomers by thermal analysis  

Energy Technology Data Exchange (ETDEWEB)

Highlights: • Oligomers with different chemical components in molecular chains were synthesized. • FP-3 containing three IFR components possessed high thermal stability. • FP-3 possessed lowest flammability. • FP-3 exhibited a synergistic interaction between gas and condensed phase. - Abstract: A series of flame retardant oligomers with different chemical components in molecular chains, designated as FP-1, FP-2 and FP-3, respectively, were successfully synthesized using solution polycondensation and well characterized. The thermal properties and flammability of these oligomers were investigated by thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC). The results demonstrated that FP-3 had the lowest flammability in terms of the lowest maximum mass loss rate, and FP-1 possessed the highest thermal stability and char yield, due to its higher stable hexatomic ring structure of piperazine compared with the linear alkane chain structure of neopentyl glycol. The gases evolved during decomposition were analyzed using Fourier transform infrared coupled with the thermogravimetric analyzer (TG–IR) technique. The char residues of the flame retardant oligomers were investigated by scanning electron microscopy (SEM) and Raman spectroscopy. The results demonstrated that FP-3 exhibited a synergistic interaction between the gas phase and condensation phase, increasing its flame retardancy.

Bai, Zhiman [State Key Lab of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); USTC-CityU Joint Advanced Research Centre, Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, 166 Ren’ai Road Suzhou, Jiangsu 215123 (China); Wang, Xin; Tang, Gang; Song, Lei [State Key Lab of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Hu, Yuan, E-mail: yuanhu@ustc.edu.cn [State Key Lab of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); USTC-CityU Joint Advanced Research Centre, Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, 166 Ren’ai Road Suzhou, Jiangsu 215123 (China); Yuen, Richard K.K., E-mail: Richard.Yuen@cityu.edu.hk [USTC-CityU Joint Advanced Research Centre, Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute for Advanced Study, University of Science and Technology of China, 166 Ren’ai Road Suzhou, Jiangsu 215123 (China); Department of Building and Construction, City University of Hong Kong, Tat Chee Avenue Kowloon (Hong Kong)

2013-08-10

85

Structure–property relationships of synthetic organophosphorus flame retardant oligomers by thermal analysis  

International Nuclear Information System (INIS)

Highlights: • Oligomers with different chemical components in molecular chains were synthesized. • FP-3 containing three IFR components possessed high thermal stability. • FP-3 possessed lowest flammability. • FP-3 exhibited a synergistic interaction between gas and condensed phase. - Abstract: A series of flame retardant oligomers with different chemical components in molecular chains, designated as FP-1, FP-2 and FP-3, respectively, were successfully synthesized using solution polycondensation and well characterized. The thermal properties and flammability of these oligomers were investigated by thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC). The results demonstrated that FP-3 had the lowest flammability in terms of the lowest maximum mass loss rate, and FP-1 possessed the highest thermal stability and char yield, due to its higher stable hexatomic ring structure of piperazine compared with the linear alkane chain structure of neopentyl glycol. The gases evolved during decomposition were analyzed using Fourier transform infrared coupled with the thermogravimetric analyzer (TG–IR) technique. The char residues of the flame retardant oligomers were investigated by scanning electron microscopy (SEM) and Raman spectroscopy. The results demonstrated that FP-3 exhibited a synergistic interaction between the gas phase and condensation phase, increasing its flame retardancy

86

Relationship between crystal structure and mechanical properties of ranitidine hydrochloride polymorphs  

DEFF Research Database (Denmark)

Polymorphism plays a critical role during pharmaceutical development, as it helps in the selection of optimal solid form. In present study, mechanical properties of ranitidine hydrochloride polymorphs were studied using instrumented tablet press, to understand the effect of crystal packing on the compaction behaviour. Out-of-die compressibility plot and Heckel analysis confirmed greater plastic deformation of form II over form I. Detailed crystallographic examination revealed that form I has several weak C-H?O interactions across the 'proposed slip plane' parallel to (-2 0 2) that prevent slip under compaction pressure. On the other hand, crystal structure of form II was relatively more open and multiple slip were possible under compaction pressure. These crystallographic features offered increased compressibility and deformability to form II. In absence of an active slip plane system, closed crystal structure of form I resists deformation under compaction pressure and hence showed poor compressibility and higher mean yield pressure. However, form I showed greater tabletability at a given compaction pressure, by virtue of its greater bonding strength. © 2013 The Royal Society of Chemistry.

Upadhyay, Pratik Pankaj; Khomane, Kailas S.

2013-01-01

87

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

Science.gov (United States)

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

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

2014-01-21

88

Absorbability, Mechanism and Structure-Property Relationship of Three Phenolic Acids from the Flowers of Trollius chinensis  

Directory of Open Access Journals (Sweden)

Full Text Available The absorption properties, mechanism of action, and structure-property relationship of three phenolic acids isolated from the flowers of Trollius chinensis Bunge, namely, proglobeflowery acid (PA, globeflowery acid (GA and trolloside (TS, were investigated using the human Caco-2 cell monolayer model. The results showed that these three phenolic acids were transported across the Caco-2 cell monolayer in a time and concentration dependent manner at the Papp level of 10?5 cm/s, and their extent of absorption correlated with their polarity and molecular weight. In conclusion, all three of these compounds were easily absorbed through passive diffusion, which implied their high bioavailability and significant contribution to the effectiveness of T. chinensis.

Xiu-Wen Wu

2014-11-01

89

Structure-property relationships in block copolymer modified epoxy resins with novel morphologies  

Science.gov (United States)

Block copolymers self-assemble into ordered or micellar morphologies in cured epoxy depending on the block copolymer concentration in the blend. Curing retains these morphologies providing conditions leading to macroscopic phase separation are avoided. Structure-property investigations on the cured blends revealed that the self-assembled block copolymer morphology influences the fracture resistance improvement in these blends. Addition of block copolymer does not reduce the epoxy glass transition temperature and can even increase it in certain cases. However, the modulus decreased as the block copolymer concentration increased. Asymmetric block copolymers were examined in uncured and cured epoxy blends, where the shorter epoxy miscible block length results in vesicle or wormlike micelle formation in the dilute block copolymer limit. For an amine-cured epoxy, vesicles produced the highest increases in fracture resistance where these improvements correlate with the vesicle size and separation. Spherical micelles were shown to behave mechanically as small vesicles. Because of the success in toughening amine-cured epoxies, block copolymers were used to improve the fracture resistance of flame retardant epoxies. First, block copolymers were shown to self-assemble into ordered morphologies in blends containing a brominated epoxy, providing the block copolymer molecular weight was high enough to prevent phase separation. Then, well-dispersed vesicles, wormlike micelles, and spherical micelles were documented in the phenol novolac cured brominated (and nonbrominated) resins and the mechanical properties of these materials were investigated. Wormlike micelles increased the glass transition temperature of the phenol novolac cured brominated and non-brominated epoxies and produced a dramatic increase in the fracture resistance. In fact, the increase in fracture resistance of these blends correlates with the increase in the glass transition temperature. As an added benefit, the modulus of these materials did not decrease significantly. As the glass transition temperature and fracture resistance both increased, these materials contradict the assumption that an increase in toughness necessarily comes at the expense of the use temperature.

Dean, Jennifer Mary Elizabeth

90

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-01-01

91

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

Directory of Open Access Journals (Sweden)

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

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

Fernández-Golfín, J. I.

2003-06-01

92

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

Scientific Electronic Library Online (English)

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

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

2013-10-01

93

Quantitative structure-activity relationship models correctly predict the toxic and aneuploidizing properties of six halogenated methanes in Aspergillus nidulans.  

Science.gov (United States)

In a previous study, the relationships between the chemical structure and the ability of 35 chlorinated aliphatic hydrocarbons to induce aneuploidy and toxicity in Aspergillus nidulans were analyzed. Quantitative structure-activity relationships (QSAR) were defined for each of the biological activities under study: ARR (the dose able to block mitotic growth), D37 (the dose with 37% of survival) and LEC (the lowest efficient concentration in aneuploidy induction). In this study, these QSAR equations were used to predict the toxic and genetic activity of a further six chemicals, not included in the previous data base: bromotrichloromethane, bromoform, bromochloromethane, bromodichloromethane, dibromochloromethane and dibromochlorofluoromethane. Their ARR, D37 and LEC values were measured, and were in agreement with the predicted values, with correlation coefficients around 0.99. Furthermore, the QSAR model, which had previously been developed to discriminate between aneugenic and inactive halogenated hydrocarbons, correctly predicted the aneugenic activity of five out of six methanes. These correct predictions confirmed the validity of our QSAR model, according to which the induction of aneuploidy in A. nidulans depends on both the electrophilic and steric properties of the chemicals, whereas toxicity mainly depends on steric factors. PMID:8377647

Benigni, R; Andreoli, C; Conti, L; Tafani, P; Cotta-Ramusino, M; Carere, A; Crebelli, R

1993-07-01

94

Composition-structure-property relationships for non-classical ionomer cements formulated with zinc-boron germanium-based glasses.  

Science.gov (United States)

Non-classical ionomer glasses like those based on zinc-boron-germanium glasses are of special interest in a variety of medical applications owning to their unique combination of properties and potential therapeutic efficacy. These features may be of particular benefit with respect to the utilization of glass ionomer cements for minimally invasive dental applications such as the atruamatic restorative treatment, but also for expanded clinical applications in orthopedics and oral-maxillofacial surgery. A unique system of zinc-boron-germanium-based glasses (10 compositions in total) has been designed using a Design of Mixtures methodology. In the first instance, ionomer glasses were examined via differential thermal analysis, X-ray diffraction, and (11)B MAS NMR spectroscopy to establish fundamental composition - structure-property relationships for the unique system. Secondly, cements were synthesized based on each glass and handling characteristics (working time, Wt, and setting time, St) and compression strength were quantified to facilitate the development of both experimental and mathematical composition-structure-property relationships for the new ionomer cements. The novel glass ionomer cements were found to provide Wt, St, and compression strength in the range of 48-132?s, 206-602?s, and 16-36?MPa, respectively, depending on the ZnO/GeO2 mol fraction of the glass phase. A lower ZnO mol fraction in the glass phase provides higher glass transition temperature, higher N4 rate, and in combination with careful modulation of GeO2 mol fraction in the glass phase provides a unique approach to extending the Wt and St of glass ionomer cement without compromising (in fact enhancing) compression strength. The data presented in this work provide valuable information for the formulation of alternative glass ionomer cements for applications within and beyond the dental clinic, especially where conventional approaches to modulating working time and strength exhibit co-dependencies (i.e. the enhancement of one property comes at the expense of the other) and therefore limit development strategies. PMID:25391445

Zhang, Xiaofang; Werner-Zwanziger, Ulrike; Boyd, Daniel

2014-11-12

95

Atomically resolved tomography to directly inform simulations for structure–property relationships  

Science.gov (United States)

Microscopy encompasses a wide variety of forms and scales. So too does the array of simulation techniques developed that correlate to and build upon microstructural information. Nevertheless, a true nexus between microscopy and atomistic simulations is lacking. Atom probe has emerged as a potential means of achieving this goal. Atom probe generates three-dimensional atomistic images in a format almost identical to many atomistic simulations. However, this data is imperfect, preventing input into computational algorithms to predict material properties. Here we describe a methodology to overcome these limitations, based on a hybrid data format, blending atom probe and predictive Monte Carlo simulations. We create atomically complete and lattice-bound models of material specimens. This hybrid data can then be used as direct input into density functional theory simulations to calculate local energetics and elastic properties. This research demonstrates the role that atom probe combined with theoretical approaches can play in modern materials engineering.

Moody, Michael P.; Ceguerra, Anna V.; Breen, Andrew J.; Cui, Xiang Yuan; Gault, Baptiste; Stephenson, Leigh T.; Marceau, Ross K. W.; Powles, Rebecca C.; Ringer, Simon P.

2014-11-01

96

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

97

Does alkyl chain length really matter? Structure–property relationships in thermochemistry of ionic liquids  

International Nuclear Information System (INIS)

Graphical abstract: We have shown that enthalpies of formation, enthalpies of vaporization, and lattice potential energies of alkylsubstituted imidazolium, pyridinium, and pyrrolidinium based ionic liquids with Cl and Br anions are linearly dependant on the alkyl chain length. The thermochemical properties of ILs are generally obey the group additivity rules and the values of the additivity parameters for enthalpies of formation and vaporization are very close to those for molecular compounds. - Highlights: • Alkyl substituted imidazolium, pyridinium, and pyrrolidinium based ionic liquids with anions [Cl] and [Br] were studied using DSC and ab initio methods. • The thermochemical properties of ILs generally obey the group additivity rules. • A linear dependence on the chain length of the alkyl chain of cation was found. - Abstract: DSC was used for determination of reaction enthalpies of synthesis of ionic liquids [Cnmim][Cl]. A combination of DSC with quantum chemical calculations presents an indirect way to study thermodynamics of ionic liquids. The indirect procedure for vaporization enthalpy was validated with the direct experimental measurements by using thermogravimetry. First-principles calculations of the enthalpy of formation in the gaseous phase have been performed for the ionic species using the CBS-QB3 and G3 (MP2) theory. Experimental DSC data for homologous series of alkyl substituted imidazolium, pyridinium, and pyrrolidinium based ionic liquids with anions [Cl] and [Br] were collected from the literature. We have shown that enthalpies of formation, enthalpies of vaporization, and lattice potential energies are linearly dependant on the alkyl chain length. The thermochemical properties of ILs generally obey the group additivity rules and the values of the additivity parameters for enthalpies of formation and vaporization seem to be very close to those for molecular compounds

98

Investigations of the processing-structure-property relationships of selected semicrystalline polymers  

Science.gov (United States)

An investigation was carried out on a three stage method (extrusion/annealing/uniaxial-stretching) (MEAUS) utilized to produce semicrystalline polymeric microporous membranes. The two semicrystalline polymers studied were selected based on a set-of-prerequisites proposed for the formation of highly porous membranes via the method in question. The prerequisites included "fast" crystallization kinetics, presence of an alphac relaxation, ability to form a planar stacked lamellar morphology with a "good" crystalline orientation upon melt-extrusion, and rapid heat transfer of the film during extrusion. The first polymer was isotactic poly(4-methyl-1-pentene) (PMP), and the second was polyoxymethylene (POM). Three PMP resins were studied, which differed in weight average molecular weight. Three POM resins were also investigated where two of resins were characterized by relatively narrow molecular weight distributions (MWD) ca 2 while the third POM resin possessed a MWD ca 5.9. The melt-extruded film morphologies and orientation values were a consequence of the melt-relaxation times as a result of the resin characteristics and/or the melt-extrusion conditions. Following the extrusion stage, the effect of annealing (second stage) on film properties was investigated. The annealing variables investigated included the temperature, time, and level of extension applied during annealing. The annealed films were then subjected to the uniaxially stretching stage (third stage) consisting of a cold and hot step, respectively, where deformation was along the extrusion direction. The variables of interest included the cold and hot stretch temperature and extension level. It was found that starting precursor morphology and orientation, annealing conditions, and stretching variables impact the final film microporous morphology and permeability. Additionally, the proposed prerequisites were verified in both the PMP and POM film series. In addition to the MEAUS study, a comprehensive investigation was conducted of the optical properties of blown and cast films made from conventional Ziegler-Natta catalyzed linear low density polyethylene (LLDPE) as well as metallocene-catalyzed LLDPE resins. From this work, it was determined that in PE blown and cast films made using conventional processing conditions, the optical haze properties are adversely affected due to enhanced surface roughness caused by the formation of spherulitic-like superstructures in polymer melts that possess fast relaxing and low melt elasticity rheological characteristics. This optical property study was also published in J. Appl. Polym. Sci., 77(13), 2845, (2000).

Johnson, Matthew Brian

2000-10-01

99

Covalent attachment of nanoparticles to copolymer surfaces to control structure-property relationships  

Science.gov (United States)

Interest in functional nanoparticles has increased in recent years, because their small size gives them unique properties. Surface assembly of nanoparticles is particularly appealing, because it can create surfaces with tunable wetting and optical properties. This thesis presents a novel method for the covalent assembly of silica nanoparticles on random copolymer films via covalent bonding, and the subsequent analysis of the wetting and optical properties of these functionalized surfaces. First, the kinetics of the covalent attachment of amine-modified silica nanoparticles to poly(styrene-ran-acrylic acid) were investigated. The surface swelling of the copolymer films upon exposure to reaction solvents was studied with in situ AFM. The films' surface roughness controlled the nanoparticle attachment kinetics, as well as the final nanoparticle coverage. For particle diameters on the order of the roughness features, 70% surface coverage was achieved, while particles with diameters much larger than the surface features reached only 30% coverage. The wetting properties of the nanoparticle surfaces were investigated as a function of particle coverage and diameter. At low coverages of small particles, the surfaces exhibited Wenzel-type wetting behavior. At high particle coverages, the surfaces showed Cassie-type wetting. Finally, the particles were observed to sink into the polymer film with increasing reaction time. This sinking, as well as the magnitude of the contact angles achieved at high particle coverages, led to the hypothesis that polymer chains wet onto the surface of the silica particles. Core-shell Janus particles were prepared by electrostatic assembly of gold nanoparticles on the unprotected surfaces of the silica particles. The plasmon resonance absorption of the gold particles underwent a red shift upon formation of closely-packed networks on the silica particle surfaces. By applying gold, chromium, and gold:palladium coatings to the Janus particles and annealing at 350°C for 5s-24h, the wetting between the gold and silica was tuned to form shell morphologies from patchy coatings to hemispherical caps, with absorptions in the visible and near-IR, respectively.

McConnell, Marla D.

100

Structure-property relationship of regenerated spider silk protein nano/microfibrous scaffold fabricated by electrospinning.  

Science.gov (United States)

The regenerated Araneus ventricosus spider dragline silk protein fibrous scaffold with moderate strength and flexibility was fabricated by electrospinning and post treatment with 90 vol % acetone. The effect of collection method on the morphology of regenerated spider silk protein (RSSP) fibrous scaffold, the effects of the post treatment solvents and their concentrations on the molecular conformation, crystallinity and mechanical properties were studied. The results show that the morphology was affected by the solvent used in the coagulation bath. The molecular conformation, crystallinity and mechanical property of this scaffold were strongly affected by the kind of post treatment solvent and slightly influenced by its concentration when it was higher than 50 vol %. The degradation rate of this scaffold was very slow and resulting in little pH change of the degradation medium within 5 months. PC 12 cells were cultured on the electrospun RSSP fibrous scaffold and in its extraction fluid to examine the changes of PC 12 cells after different times of culture. The results show that the electrospun RSSP fibrous scaffold had good biocompatibility with PC 12 cells. PMID:24288266

Yu, Qiaozhen; Xu, Shuiling; Zhang, Hong; Gu, Li; Xu, Yepei; Ko, Frank

2014-11-01

101

Elucidation of the structure-property relationship of p-type organic semiconductors through rapid library construction via a one-pot, Suzuki-Miyaura coupling reaction.  

Science.gov (United States)

The elucidation of the structure-property relationship is an important issue in the development of organic electronics. Combinatorial synthesis and the evaluation of systematically modified compounds is a powerful tool in the work of elucidating structure-property relationships. In this manuscript, D-?-A structure, 32 p-type organic semiconductors were rapidly synthesized via a one-pot, Suzuki-Miyaura coupling with subsequent Knoevenagel condensation. Evaluation of the solubility and photovoltaic properties of the prepared compounds revealed that the measured solubility was strongly correlated with the solubility parameter (SP), as reported by Fedors. In addition, the SPs were correlated with the Jsc of thin-film organic solar cells prepared using synthesized compounds. Among the evaluated photovoltaic properties of the solar cells, Jsc and Voc had strong correlations with the photoconversion efficiency (PCE). PMID:25090049

Fuse, Shinichiro; Matsumura, Keisuke; Wakamiya, Atsushi; Masui, Hisashi; Tanaka, Hiroshi; Yoshikawa, Susumu; Takahashi, Takashi

2014-09-01

102

Structure-property relationships of carboxymethyl hydroxypropyl guar gum in water and a hyperentanglement parameter.  

Science.gov (United States)

The viscoelastic properties of carboxymethyl hydroxypropyl guar gum (CMHPG) in aqueous solution were determined as function of concentration and of molecular weight, using SEC/MALLS/dRI and viscometry. The chain is more rigid as in native guar as was deduced from the molecular parameter in dilute solution. Superstructures are formed in moderately concentrated solutions as is shown from the comparison of steady state shear and small amplitude oscillatory shear (SAOS) experiments. The shear rate dependent viscosity of CMHPG can satisfactorily be described by the Carreau-Yasuda model with the rheological parameters (?0, ?0, n, b) obtained from the evaluation of viscosity data. A quantitative hyperentanglement parameter is introduced to account for the differences in responses in shear and SAOS experiments. PMID:25563956

Szopinski, Daniel; Kulicke, Werner-Michael; Luinstra, Gerrit A

2015-03-30

103

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

104

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

Energy Technology Data Exchange (ETDEWEB)

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.

Heitfeld, Kevin A.; Schaefer, Dale W.

2010-10-12

105

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.

Fereshteh Shiri

2010-08-01

106

Influence of the chromium, molybdenum and carbon relationship on structure and properties of deposit metal in the Fe-Cr-Mo-C system  

International Nuclear Information System (INIS)

The Fe-Cr-Mo-C system components influence on structural-phase composition, tendency to cracks formation, heat-resistance and high-temperature hardness of metal deposited by electric arc and electric slag methods using flux-cored wire is considered. Optimal relationship between carbide-forming components and carbon is determined, at such relationship deposited method has sufficient properties level under hot press-dies operation conditions

107

Camel and bovine chymosin: the relationship between their structures and cheese-making properties.  

Science.gov (United States)

Bovine and camel chymosin are aspartic peptidases that are used industrially in cheese production. They cleave the Phe105-Met106 bond of the milk protein ?-casein, releasing its predominantly negatively charged C-terminus, which leads to the separation of the milk into curds and whey. Despite having 85% sequence identity, camel chymosin shows a 70% higher milk-clotting activity than bovine chymosin towards bovine milk. The activities, structures, thermal stabilities and glycosylation patterns of bovine and camel chymosin obtained by fermentation in Aspergillus niger have been examined. Different variants of the enzymes were isolated by hydrophobic interaction chromatography and showed variations in their glycosylation, N-terminal sequences and activities. Glycosylation at Asn291 and the loss of the first three residues of camel chymosin significantly decreased its activity. Thermal differential scanning calorimetry revealed a slightly higher thermal stability of camel chymosin compared with bovine chymosin. The crystal structure of a doubly glycosylated variant of camel chymosin was determined at a resolution of 1.6?Å and the crystal structure of unglycosylated bovine chymosin was redetermined at a slightly higher resolution (1.8?Å) than previously determined structures. Camel and bovine chymosin share the same overall fold, except for the antiparallel central ?-sheet that connects the N-terminal and C-terminal domains. In bovine chymosin the N-terminus forms one of the strands which is lacking in camel chymosin. This difference leads to an increase in the flexibility of the relative orientation of the two domains in the camel enzyme. Variations in the amino acids delineating the substrate-binding cleft suggest a greater flexibility in the ability to accommodate the substrate in camel chymosin. Both enzymes possess local positively charged patches on their surface that can play a role in interactions with the overall negatively charged C-terminus of ?-casein. Camel chymosin contains two additional positive patches that favour interaction with the substrate. The improved electrostatic interactions arising from variation in the surface charges and the greater malleability both in domain movements and substrate binding contribute to the better milk-clotting activity of camel chymosin towards bovine milk. PMID:23633601

Langholm Jensen, Jesper; Mølgaard, Anne; Navarro Poulsen, Jens Christian; Harboe, Marianne Kirsten; Simonsen, Jens Bæk; Lorentzen, Andrea Maria; Hjernø, Karin; van den Brink, Johannes M; Qvist, Karsten Bruun; Larsen, Sine

2013-05-01

108

Camel and bovine chymosin : the relationship between their structures and cheese-making properties  

DEFF Research Database (Denmark)

Bovine and camel chymosin are aspartic peptidases that are used industrially in cheese production. They cleave the Phe105-Met106 bond of the milk protein ?-casein, releasing its predominantly negatively charged C-terminus, which leads to the separation of the milk into curds and whey. Despite having 85% sequence identity, camel chymosin shows a 70% higher milk-clotting activity than bovine chymosin towards bovine milk. The activities, structures, thermal stabilities and glycosylation patterns of bovine and camel chymosin obtained by fermentation in Aspergillus niger have been examined. Different variants of the enzymes were isolated by hydrophobic interaction chromatography and showed variations in their glycosylation, N-terminal sequences and activities. Glycosylation at Asn291 and the loss of the first three residues of camel chymosin significantly decreased its activity. Thermal differential scanning calorimetry revealed a slightly higher thermal stability of camel chymosin compared with bovine chymosin. The crystal structure of a doubly glycosylated variant of camel chymosin was determined at a resolution of 1.6?Å and the crystal structure of unglycosylated bovine chymosin was redetermined at a slightly higher resolution (1.8?Å) than previously determined structures. Camel and bovine chymosin share the same overall fold, except for the antiparallel central ?-sheet that connects the N-terminal and C-terminal domains. In bovine chymosin the N-terminus forms one of the strands which is lacking in camel chymosin. This difference leads to an increase in the flexibility of the relative orientation of the two domains in the camel enzyme. Variations in the amino acids delineating the substrate-binding cleft suggest a greater flexibility in the ability to accommodate the substrate in camel chymosin. Both enzymes possess local positively charged patches on their surface that can play a role in interactions with the overall negatively charged C-terminus of ?-casein. Camel chymosin contains two additional positive patches that favour interaction with the substrate. The improved electrostatic interactions arising from variation in the surface charges and the greater malleability both in domain movements and substrate binding contribute to the better milk-clotting activity of camel chymosin towards bovine milk.

Jensen, Jesper Langholm; MØlgaard, Anne

2013-01-01

109

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

110

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

Energy Technology Data Exchange (ETDEWEB)

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.

Naebe, Minoo; Lin Tong; Wang Xungai [Centre for Material and Fibre Innovation, Deakin University, Geelong, VIC 3217 (Australia); Staiger, Mark P [Department of Mechanical Engineering, University of Canterbury, Christchurch (New Zealand); Dai Liming [Department of Chemical and Materials Engineering, University of Dayton, Dayton, OH 45469 (United States)], E-mail: tong.lin@deakin.edu.au

2008-07-30

111

Structure Property Relationship of Suspension Thermally Sprayed WC-Co Nanocomposite Coatings  

Science.gov (United States)

Tribomechanical properties of nanostructured coatings deposited by suspension high velocity oxy-fuel (S-HVOF) and conventional HVOF (Jet Kote) spraying were evaluated. Nanostructured S-HVOF coatings were obtained via ball milling of the agglomerated and sintered WC-12Co feedstock powder, which were deposited via an aqueous-based suspension using modified HVOF (TopGun) process. Microstructural evaluations of these hardmetal coatings included transmission electron microscopy, x-ray diffraction, and scanning electron microscopy equipped with energy dispersive x-ray spectroscopy. The nanohardness and modulus of the coated specimens were investigated using a diamond Berkovich nanoindenter. Sliding wear tests were conducted using a ball-on-flat test rig. Results indicated that low porosity coatings with nanostructured features were obtained. High carbon loss was observed, but coatings showed a high hardness up to 1000 HV2.9N. S-HVOF coatings also showed improved sliding wear and friction behavior, which were attributed to nanosized particles reducing ball wear in three-body abrasion and support of metal matrix due to uniform distribution of nanoparticles in the coating microstructure.

Ahmed, R.; Faisal, N. H.; Al-Anazi, Nayef M.; Al-Mutairi, S.; Toma, F.-L.; Berger, L.-M.; Potthoff, A.; Polychroniadis, E. K.; Sall, M.; Chaliampalias, D.; Goosen, M. F. A.

2014-11-01

112

Structure Property Relationship of Suspension Thermally Sprayed WC-Co Nanocomposite Coatings  

Science.gov (United States)

Tribomechanical properties of nanostructured coatings deposited by suspension high velocity oxy-fuel (S-HVOF) and conventional HVOF (Jet Kote) spraying were evaluated. Nanostructured S-HVOF coatings were obtained via ball milling of the agglomerated and sintered WC-12Co feedstock powder, which were deposited via an aqueous-based suspension using modified HVOF (TopGun) process. Microstructural evaluations of these hardmetal coatings included transmission electron microscopy, x-ray diffraction, and scanning electron microscopy equipped with energy dispersive x-ray spectroscopy. The nanohardness and modulus of the coated specimens were investigated using a diamond Berkovich nanoindenter. Sliding wear tests were conducted using a ball-on-flat test rig. Results indicated that low porosity coatings with nanostructured features were obtained. High carbon loss was observed, but coatings showed a high hardness up to 1000 HV2.9N. S-HVOF coatings also showed improved sliding wear and friction behavior, which were attributed to nanosized particles reducing ball wear in three-body abrasion and support of metal matrix due to uniform distribution of nanoparticles in the coating microstructure.

Ahmed, R.; Faisal, N. H.; Al-Anazi, Nayef M.; Al-Mutairi, S.; Toma, F.-L.; Berger, L.-M.; Potthoff, A.; Polychroniadis, E. K.; Sall, M.; Chaliampalias, D.; Goosen, M. F. A.

2015-02-01

113

The Structure-Property Relationship of Poly(amide-imide)/Organoclay Nanocomposites  

Science.gov (United States)

Surface treated montmorillonite (MMT) was used to prepare nanocomposites with poly(amide-imide) (PAI) 5 by solution intercalation technique with various percent of organoclay (5-15 mass %). Surface modification of the MMT was performed with Cloisite 20A for ample compatibilization with the PAI matrix. The PAI 5 chains were produced through polycondensation of 4,4-diamino diphenyl sulfone 4 with N-trimellitylimido-L-alanine 3 in a medium consisting of triphenyl phosphite, N-methyl-2-pyrolidone (NMP), pyridine and calcium chloride. The PAI-Nanocomposites morphology and clay dispersion were investigated by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The effect of clay dispersion and the interaction between clay and PAI chains on the properties of PAI-Nanocomposites films were investigated by using UV-Vis spectroscopy, thermogravimetric analysis (TGA) and water uptake measurements. Thermal stability of nanocomposites increased relative to the neat polyamide with increasing organoclay content but water uptake of these materials decreased as compared to the neat polyamide indicating reduced permeability.

Faghihi, Khalil; Soleimani, Masoumeh; Shabanian, Meisam; Abootalebi, Ashraf Sadateh

2011-06-01

114

Electrochemical property: Structure relationships in monoclinic Li(3-y)V2(PO4)3.  

Science.gov (United States)

Monoclinic lithium vanadium phosphate, alpha-Li(3)V(2)(PO(4))(3), is a highly promising material proposed as a cathode for lithium-ion batteries. It possesses both good ion mobility and high lithium capacity because of its ability to reversibly extract all three lithium ions from the lattice. Here, using a combination of neutron diffraction and (7)Li MAS NMR studies, we are able to correlate the structural features in the series of single-phase materials Li(3-y)V(2)(PO(4))(3) with the electrochemical voltage-composition profile. A combination of charge ordering on the vanadium sites and lithium ordering/disordering among lattice sites is responsible for the features in the electrochemical curve, including the observed hysteresis. Importantly, this work highlights the importance of ion-ion interactions in determining phase transitions in these materials. PMID:12926965

Yin, S-C; Grondey, H; Strobel, P; Anne, M; Nazar, L F

2003-08-27

115

Structure-property relationships in directionally solidified single crystal NiAl  

Science.gov (United States)

The ordered intermetallic alloy NiAl is being considered as a potential high temperature structural material, but lack of ductility at ambient temperatures, especially in polycrystalline form, is presently a major obstacle in achieving this goal. Even general agreement of the intrinsic ductility that can be achieved in monocrystals is in dispute. In order to understand this problem, two directionally solidified ingots of NiAl which displayed known differences in ductility were characterized in sufficient detail to identify the corresponding microstructural differences. It was found that the type and size of casting defects, i.e., porosity, present in the material were the major factors in controlling ductility of NiAl single crystals and could explain the order of magnitude variance in fracture strains reported in the literature.

Noebe, R. D.; Kim, J. T.; Gibala, R.

1987-01-01

116

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

117

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

International Nuclear Information System (INIS)

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

118

Barium titanate/polyester resin nanocomposites: Development, structure-properties relationship and energy storage capability  

Directory of Open Access Journals (Sweden)

Full Text Available Nanocomposite materials based on two different types of polyester matrix (a commercial type and a laboratory produced one with embedded barium titanate nano-particles were developed and characterized. Structural and morphological characteristics of the produced composite specimens were studied via X-ray diffraction, Fourier transformation infra red spectroscopy, and scanning electron microscopy. Thermal, mechanical and electrical performance was examined via differential scanning calorimetry, bending and shear strength tests, and broadband dielectric spectroscopy, respectively. Mechanical strength appears to reduce with the increase of filler content. Commercial polyester’s composites exhibit brittle behaviour, while laboratory polyester’s composites exhibit an elastomeric performance. Dielectric data reveal the presence of four relaxation processes, which are attributed to motion of small parts of the polymer chain (?-mode, re-arrangement of polar side groups (?-mode, glass to rubber transition of the polymer matrix (?-mode and Interfacial Polarization between the systems’ constituents. Finally, the energy storing efficiency of the systems was examined by calculating the density of energy.

I. A. Asimakopoulos

2014-09-01

119

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

International Nuclear Information System (INIS)

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

120

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

121

Quantitative structure-property relationships on direct photolysis of PCDD/Fs on surfaces of fly ash.  

Science.gov (United States)

Fly ash samples containing polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were generated by combustion of polyvinyl chloride, wood, high-density polyethylene and styrene. By partial least-squares (PLS) regression, quantitative structure-property relationship (QSPR) models were developed for photolysis half-lives (t(1/2)) of PCDD/Fs adsorbed on fly ash surfaces and irradiated by UV-B of simulated sunlight. Quantum chemical descriptors computed by PM3 hamiltonian were used as predictor variables. The cross validated value for the optimal QSPR model was 0.678, indicating robustness and good predictive abilities of the model. The QSPR results showed that the stability of the PCDD/F molecules increased with the increase of chlorine atoms in the parent molecules. Increasing the energy of the highest occupied molecular orbital (E(HOMO)), the energy of the lowest unoccupied molecular orbital (E(LUMO)), E(LUMO)+E(HOMO) and E(LUMO)-E(HOMO) values of the PCDD/Fs led to decrease of log t(1/2) values. Increasing the most negative atomic charge on the oxygen atom of PCDD/Fs led to elevated log t(1/2) values. The log t(1/2) values of PCDD/Fs increased with the decrease of the largest negative atomic charge on a carbon atom. PMID:15370417

Niu, J; Chen, J; Yu, G; Schramm, K-W

2004-08-01

122

Theoretical study of relationships between structural, optical, energetic, and magnetic properties and reactivity parameters of benzidine and its oxidized forms.  

Science.gov (United States)

Structural, topological, optical, energetic, and magnetic properties and reactivity parameters of benzidine, its radical cation, and its dication as well as molecular complexes of the benzidine dication with the F(-), Cl(-), Br(-), I(-), NO3(-), HSO4(-), and H2PO4(-) anions were calculated at the B3LYP/6-311++G(2d,2p) level of theory in the CH2Cl2 medium. The CAM-B3LYP functional (as the most reliable one) and the 6-311++G(3df,3pd) basis set were used for the UV-vis absorption spectra prediction. The obtained spectral results are in a good agreement with available experimental data. A number of the calculated global and local molecular properties, including several recently developed ones, (in general, more than 20 parameters), namely, ?max, the bond lengths and orders (l and LA,B), adiabatic ionization energy (IEad), global electrophilicity index (?), condensed electrophilic Fukui functions (f(+)) and dual descriptor (?fA), van der Waals molecular volume, nuclear independent chemical shifts (NICS) and QTAIM topological parameters were estimated in the critical points of the C(1)-C(1'), C(2)-C(3), and C(4)-N bonds as well as at the ring critical point. These quantities were found to be in a strong linear dependence (R(2) > 0.99 in most cases) with the number of detached electrons (Nel) from the benzidine molecule up to formation of the dication (Nel = 2). On one hand, a position of the long-wave absorption band (?CT) corresponding to the anion-to-cation charge transfer in the neutral complexes of the benzidine dication with anions, correlates with the Mulliken electronegativity of the anion (R(2) = 0.8646) and its adiabatic ionization energy (R(2) = 0.8054). On the other hand, the correlations with the anion charge in the complexes and the anion isotropic polarizability are rather poor (R(2) = 0.6392 and 0.3470, respectively). On the ground of the obtained strong relationships, one may recommend the calculated molecular properties as potentially preferable descriptors for the benzidine-based compounds in terms of the QSAR methodology. PMID:25188776

Bondarchuk, Sergey V; Minaev, Boris F

2014-09-25

123

Theoretical study of the structure-properties relationship in new class of 2,5-di(2-thienyl)pyrrole compounds  

Science.gov (United States)

Detailed studies of the structure-property relationships for conductive polymers are important for the proper understanding of the impact of morphological details on chemical and physical properties. This understanding is necessary for the development of realistic theoretical models. The particular cases of thienyl pyrroles are described. Ab initio methods based on Hartree-Fock (HF) and Density Functional Theory (DFT) calculations with the basis set of 6-31G(d) are performed to determine the molecular structural properties and to calculate FT-IR and NMR spectrum of the title molecule. Moreover, assignments of the vibrational modes are made on the basis of potential energy distribution (PED). Furthermore, the correlations between the observed and calculated frequencies are found to be in good agreement with each other as well as the correlation of the NMR data. A comparison of the experimental and theoretical calculations can be very useful in making correct assignment and understanding the properties and molecular structure relations.

Kart, Sevgi Özdemir; Ebru Tanbo?a, A.; Soyleyici, Hakan Can; Ak, Metin; Kart, Hasan Hüseyin

2015-02-01

124

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

Science.gov (United States)

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

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

1991-01-01

125

Investigating structure-property relationships in cathode materials via combined ex-situ and in-situ diffraction techniques  

International Nuclear Information System (INIS)

While anode and electrolyte materials continue to see significant advances, cathode materials remain underdeveloped in comparison. As a battery's performance is determined by its weakest component further improvements to cathode materials are essential. Given the complex chemical and structural changes which can take place in cathode materials on cycling, a range of advanced characterization techniques must be utilised in order to understand the properties well enough to then improve upon them. A combination and ex-situ type dialyses has been performed on the cathode material Li0.18Sr0.66Ti0.5BNb0.5O3. Ex-situ neutron diffraction experiments, following the chemical insertion of lithium enabled the location of lithium within the structure to be accurately determined through Rietveld refinement and calculation of Fourier difference maps. More significantly, the evolution of phases and structural change in this material has been followed utilizing both in-situ neutron and synchrotron diffraction experiments. Sequential Rietveld refinements have allowed the change in structure to be directly correlated with the observed electrochemical properties. Specifically, due to the real time collection of structure; data as a function of discharge. the rate of structural change was measured and directly correlated with electrochemical portfolio. This contribution will demonstrate how a combination of ex-situ diffraction of chemical and electrochemical insertion of lithium as well as in-situ diffraction of electrochemical insertion of lithium can provide a robust picture of how the structure influences properties.

126

Structure-property relationships of a class of carbamate-based Fatty Acid Amide Hydrolase (FAAH) inhibitors: chemical and biological stability  

OpenAIRE

Cyclohexylcarbamic acid aryl esters are a class of Fatty Acid Amide Hydrolase (FAAH) inhibitors, which includes the reference compound URB597. The reactivity of their carbamate fragment is involved in pharmacological activity and may affect pharmacokinetic and toxicological properties. We conducted in vitro stability experiments in chemical and biological environments to investigate the structure-stability relationships in this class of compounds. The results show that electrophilicity of the...

Vacondio, Federica; Silva, Claudia; Lodola, Alessio; Fioni, Alessandro; Rivara, Silvia; Duranti, Andrea; Tontini, Andrea; Sanchini, Silvano; Clapper, Jason; Piomelli, Daniele; Mor, Marco; Tarzia, Giorgio

2009-01-01

127

Shedding Light on Structure-Property Relationships for Conjugated Microporous Polymers: The Importance of Rings and Strain.  

Science.gov (United States)

The photophysical properties of insoluble porous pyrene networks, which are central to their function, differ strongly from those of analogous soluble linear and branched polymers and dendrimers. This can be rationalized by the presence of strained closed rings in the networks. A combined experimental and computational approach was used to obtain atomic scale insight into the structure of amorphous conjugated microporous polymers. The optical absorption and fluorescence spectra of a series of pyrene-based materials were compared with theoretical time-dependent density functional theory predictions for model clusters. Comparison of computation and experiment sheds light on the probable structural chromophores in the various materials. PMID:24159243

Zwijnenburg, Martijn A; Cheng, Ge; McDonald, Tom O; Jelfs, Kim E; Jiang, Jia-Xing; Ren, Shijie; Hasell, Tom; Blanc, Frédéric; Cooper, Andrew I; Adams, Dave J

2013-10-01

128

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

Directory of Open Access Journals (Sweden)

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

S. Y. Yang

2014-06-01

129

Study of the structure-properties-processing relationship of nanocomposites based on poly (lactic acid) (PLA) and o-MMT  

International Nuclear Information System (INIS)

In this work, the effect of processing and nanoclay content on the mechanical properties of thin sheets obtained by cast sheet extrusion from a commercial grade of PLA and organomodified nanoclay has been investigated. Microstructure was studied using Transmission Electron Microscopy (TEM) and Wide Angle X-ray Scattering (WAXS), revealing the development of structures intercalated, although exfoliated clay layers and agglomerates were observed also. The mechanical properties have been assessed by uniaxial tensile tests. Finally, a deaging thermal treatment was applied to all prepared samples, in order to study the materials under two different states: relaxed (after the thermal treatment) and aged (before treatment). The tensile behaviour is affected by processing only in the case of aged PLA samples, whereas the addition of nanoclay is only significant at 2,5 % w/w. The de-aging treatment causes a change in the brittle-ductile behaviour evidenced in a significant increase in ductilily

130

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, theance 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

131

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

International Nuclear Information System (INIS)

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 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

132

Theoretical study of the structure-properties relationship in new class of 2,5-di(2-thienyl)pyrrole compounds.  

Science.gov (United States)

Detailed studies of the structure-property relationships for conductive polymers are important for the proper understanding of the impact of morphological details on chemical and physical properties. This understanding is necessary for the development of realistic theoretical models. The particular cases of thienyl pyrroles are described. Ab initio methods based on Hartree-Fock (HF) and Density Functional Theory (DFT) calculations with the basis set of 6-31G(d) are performed to determine the molecular structural properties and to calculate FT-IR and NMR spectrum of the title molecule. Moreover, assignments of the vibrational modes are made on the basis of potential energy distribution (PED). Furthermore, the correlations between the observed and calculated frequencies are found to be in good agreement with each other as well as the correlation of the NMR data. A comparison of the experimental and theoretical calculations can be very useful in making correct assignment and understanding the properties and molecular structure relations. PMID:25305609

Kart, Sevgi Özdemir; Ebru Tanbo?a, A; Soyleyici, Hakan Can; Ak, Metin; Kart, Hasan Hüseyin

2015-02-25

133

DFT study on the bromination pattern dependence of electronic properties and their validity in quantitative structure-activity relationships of polybrominated diphenyl ethers.  

Science.gov (United States)

With quantum chemical computation of density functional theory (DFT), the electronic properties including the polarisabilities, polarisability anisotropies and quadrupole moments of a total of 209 congeners of polybrominated diphenyl ethers (PBDEs) were evaluated. The electronic properties were shown to be highly dependent on the bromination pattern, i.e. their values changed sensitively with the number and sites of bromination. Being similar to the 2,3,7,8-, 1,4,6,9-chlorination of dioxins, respectively, 3,3',4,4'-, 2,2',5,5'-bromination of PBDEs can impose relatively greater effects on the electronic properties. Some of electronic properties were found to be potent in explaining the variance of toxicity, and the potency was verified by the development of quantitative structure-activity relationships (QSARs). To further improve the stability and predictability of QSARs for toxicity, two-dimensional topological indices were introduced. In QSARs, polarisability anisotropy was more significant than other polarisability tensors, indicating the implicit occurrence of dispersion interaction between the ligand and aryl hydrocarbon receptor (AhR). For PBDEs, the quadrupole moment was as significant as shown previously for dioxins. As interesting descriptors with encoded information about dispersion and electronics, the electronic properties analysed herein are helpful in obtaining a better understanding of the congener-specific toxicities of PBDEs, and are applicable and may be extended to research into the toxicology of structurally similar compounds, such as halogenated aromatics. PMID:19544193

Gu, C G; Ju, X H; Jiang, X; Wang, F; Yang, S G; Sun, C

2009-01-01

134

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

135

Effect of tin on the relationship between composition, structure, and properties of soda-lime-silicate glasses  

Science.gov (United States)

The effect of tin on the properties of soda-lime-silicate glass was investigated using laboratory and commercial glasses. The commercial materials were float glasses, while the model glasses with nominal soda-lime-silicate commercial compositions were synthesized in the laboratory with tin concentrations ranging from 0--3 mol%. In one set of the modeled glasses, melt processing was used to drive the tin into the reduced state. Mossbauer spectroscopy was used to determine the presence and relative amounts of Sn2+ and Sn4+ in the glasses. The glasses were also examined using nuclear magnetic resonance (NMR) to gain insight into the effect of substituting tin for sodium on the number of silica Q4 species present in the glass structure. Dilatometry experiments revealed the effects of tin on the coefficient of thermal expansion, dilatometric softening temperature, and glass transition temperature. Beam-bending viscosity experiments were used to measure the viscosity as a function of tin, and from the viscosity curves, strain and annealing temperatures were determined. Sonic resonance, ultrasonic pulse, and nanoindentation experiments were performed to determine the role of tin on elastic modulus of the glass. The results of these experiments, along with the NMR and Mossbauer experiments, suggested that the substitution of tin for sodium results in an increase in the network connectivity of the glass structure. This increased network connectivity correlated with an increased in the ratio of Sn 4+/Sn2+ suggesting that Sn4+ plays a direct role in cross-linking the silicate structure.

Krohn, Matthew H.

136

Structure-activity relationships in 3-isothiazolones.  

Science.gov (United States)

The biological activity of a series of structurally diverse 3-isothiazolones (1) has been assessed by evaluating the minimum inhibitory concentration required to inhibit the growth of E. Coli. The structure and electronic properties of these derivatives have been calculated using both semi-empirical and ab initio molecular orbital methods. Multi-linear regression analysis shows no correlation between the experimental activity of the 3-isothiazolones and either the calculated geometries, electronic properties, or the frontier orbital energies of these derivatives, but a reasonable relationship is found with other parameters including their calculated solvation energies, suggesting that diffusion may play an important role in their mode of action. PMID:16211107

Morley, John O; Oliver Kapur, A Jayne; Charlton, Michael H

2005-10-21

137

Structure-Property Relationship of Cu-Al-Ni-Fe Shape Memory Alloys in Different Quenching Media  

Science.gov (United States)

This paper presents the effects of heat treatments using various quenching media on the phase transformation parameters and microstructure parameters. The effects of different quenching methods, step-quenched and up-quenched, in various media were evaluated by using differential scanning calorimetry, field emission electron microscopy, energy-dispersive spectrometry, atomic force microscopy, x-ray diffraction, and Vicker's hardness. The variations of the structure and properties of Cu-Al-Ni-Fe shape memory alloys were linked to the variations of morphology, type, and stabilization of the obtained phase. From the DSC results, the use of ice water as a quenching medium produced the highest transformation temperatures, while a brine solution-quenching medium resulted in the highest change of the entropy and enthalpy. Additionally, it was found that the best grain refinement was observed through the use of an oil-quenching medium, due to its high cooling rate.

Saud, Safaa N.; Hamzah, E.; Abubakar, T.; Farahany, S.

2014-01-01

138

Rational interface design of epoxy-organoclay nanocomposites: role of structure-property relationship for silane modifiers.  

Science.gov (United States)

Montmorillonite was modified by three silane surfactants with different functionalities to investigate the role of surfactant structure on the properties of a final epoxy-organoclay nanocomposite. N-aminopropyldimethylethoxysilane (APDMES), an aminated monofunctional silane, was chosen as a promising surfactant for several reasons: (1) it will bond to silica in montmorillonite, (2) it will bond to epoxide groups, and (3) to overcome difficulties found with trifunctional aminosilane bonding clay layers together and preventing exfoliation. A trifunctional and non-aminated version of APDMES, 3-aminopropyltriethoxysilane (APTES) and n-propyldimethylmethoxysilane (PDMMS), respectively, was also studied to provide comparison to this rationally chosen surfactant. APDMES and APTES were grafted onto montmorillonite in the same amount, while PDMMS was barely grafted (<1 wt%). The gallery spacing of APDMES organoclay was greater than APTES or PDMMS, but the final nanocomposite gallery spacing was not dependent on the surfactant used. Different concentrations of APDMES modified montmorillonite yielded different properties, as concentration decreased glass transition temperature increased, thermal stability increased, and the storage modulus decreased. Storage modulus, glass transition temperature, and thermal stability were more similar for epoxy-organoclay composites modified with the same concentration of silane surfactant, neat epoxy, and epoxy-montmorillonite nanocomposite. PMID:24491333

Bruce, Alex N; Lieber, Danielle; Hua, Inez; Howarter, John A

2014-04-01

139

Structural relationships within medical informatics.  

OpenAIRE

This study seeks to increase our understanding of the structure of Medical Informatics. In particular, it focuses on the relationships between information science and information technology on the one hand, and biomedical research, clinical practice, and medical education on the other, that have defined "medical informatics." Using indexing terms and MeSH tree structures assigned to medical informatics literature covered by MEDLINE, co-occurrence analysis provides a "map" of the field. Major ...

Morris, T. A.

2000-01-01

140

Dissolution of cellulose in 1-allyl-3-methylimizodalium carboxylates at room temperature: A structure-property relationship study.  

Science.gov (United States)

The development of highly efficient cellulose solvents is imperative to the effective utilization of cellulose. In this work, ionic liquids (ILs) with the same 1-allyl-3-methylimidazolium cation ([Amim](+)) but different carboxylate anions, such as formate ([HCOO](-)), acetate ([CH3COO](-)), propionate ([CH3CH2COO](-)), butyrate ([CH3CH2CH2COO](-)), glycollate ([HOCH2COO](-)), lactate ([CH3CHOHCOO](-)) and benzoate ([C6H5COO](-)) were synthesized, and their thermal properties and viscosities were determined. Then these ILs were used to investigate the effect of anion structure on solubility of cellulose in the ILs. It was shown that the viscosity and cellulose solubility depended strongly on the anion structure of the ILs. For example, at 30°C solubility of cellulose in [Amim][CH3CH2COO] was as high as 19.0%, whereas cellulose was not soluble in [Amim][HOCH2COO], [Amim][CH3CHOHCOO] and [Amim][C6H5COO]. In addition, solvatochromic UV/vis probe and (13)C NMR measurements were performed to demonstrate dissolution mechanism of cellulose in the ILs. The results suggested that although cations of the ILs have un-negligible contribution to the highly efficient dissolution of cellulose, hydrogen bonding interactions of anions of the ILs with cellulose is predominant. PMID:25498686

Zhang, Yajuan; Xu, Airong; Lu, Benlian; Li, Zhiyong; Wang, Jianji

2015-03-01

141

Structure-Property-Performance Relationships for Organic Photovoltaics and the Utilization of Photoconducting Atomic Force Microscopy for Characterizing Organic Thin Films  

Science.gov (United States)

Progress in the development of organic photovoltaics (OPVs) depends on a continually growing understanding of the effects of chemical composition or processing method on the optoelectronic and structural properties and, in turn, how those properties influence device performance. Unfortunately, no single characterization method can provide all of the necessary information to develop these structure-property-performance relationships. This thesis details examples of structure-property-performance studies in which multiple characterization methods are used to identify the root cause of limited device performance for a particular photovoltaic system. As a large part of this work, the refinement and utilization of a nanoscale characterization technique, namely photoconducting atomic force microscopy (pc-AFM) is presented, not as an alternative to other characterization methods, but as a unique approach to characterizing the nanoscale morphology and local optoelectronic properties of an organic thin film simultaneously. The goal of this work was to make pc-AFM as robust and reliable a characterization tool and as close an analog to bulk OPV performance testing as possible. The first sections of this thesis focus on the development of pc-AFM for the characterization of OPVs. The capabilities of pc-AFM at the time this research commenced are illustrated in a study of a multilayered p/i/n architecture OPV system comprising a thermoset small molecule donor, tetrabenzoporphyrin (BP) and one of two structurally similar soluble fullerene derivative acceptors. By investigating the nanoscale topography, dark current, and photocurrent in each layer of these multilayer devices, the differences in bulk device performance can be rationalized and the composition of specific morphological features can be identified. At the same time, this study demonstrates how interpretation of pc-AFM measurements was not straightforward and required knowledge of the bulk performance. This issue prompted efforts to improve the technique to increase reliability and applicability to OPVs. Subsequently, sensitivity studies of the experimental parameters such as contact force, illumination intensity and spot size, and film processing conditions were performed, further elucidating factors that must be taken into consideration when designing and interpreting a pc-AFM experiment. In order to better control and monitor the environmental conditions during a pc-AFM experiment, a custom glovebox was designed to house and interface with the pc-AFM. Realization of this glovebox allowed further improvements in reliability of pc-AFM measurements and enabled the use of low workfunction AFM probes that better mimic the low workfunction top electrode typically employed in bulk OPVs. The initial use of BP as a donor material in pc-AFM measurements led to the utilization of BP in other OPV systems due to its rare properties as a solution-processable, thermoset, small molecule electron donor. The latter sections of this thesis describe two structure-property-performance relationship studies utilizing BP as a donor material. In the first study, the use of BP enables the facile testing of solution processable bilayer OPV devices with perylene-based acceptors as alternatives to solubilized fullerene derivatives. The second study compares the optoelectronic and performance characteristics of BP to a Cu-metalized derivative, CuBP, which, despite the promise of this material due to its high charge carrier mobility measured in FETs, performs poorly in OPV devices. Altogether, this work demonstrates the importance of developing structure-property-performance relationships, provides insight to the continued improvement of OPV performance, and sets the groundwork for the reliable utilization of pc-AFM as a technique for characterizing organic thin films.

Guide, Michele Elyse

142

A relationship between structural and electronic order-disorder effects and optical properties in crystalline TiO2 nanomaterials.  

Science.gov (United States)

The focus of this paper is on the analysis of the structural and electronic order-disorder effects at long, medium and short ranges of titanium dioxide (TiO2) nanoparticles synthesized by the sol-gel process followed by the microwave-assisted solvothermal (MAS) method at low temperatures and short reaction times. X-ray diffraction (XRD), Rietveld refinement, micro-Raman (MR) spectroscopy, transmission electron microscopy (TEM) and X-ray spectroscopy (EDX) were used to characterize the TiO2 nanoparticles. Optical properties were investigated by ultraviolet-visible (UV-vis) and photoluminescence (PL) measurements performed at room temperature. XRD and Rietveld refinement confirmed the presence of the anatase and brookite phases; nonetheless anatase is the major phase. The X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of only Ti(4+) but the nonstoichiometry revealed that TiO2 NPs contain defects assigned to oxygen vacancies that lead to structural and electronic order-disorder effects observed by band gap narrowing and PL wide band emission. These intermediary energy levels (shallow and deep levels) created within the band gap act as acceptors/donors of electrons and recombination centers. The oxygen vacancies (VO(x), VO? and VO??) responsible by degree of structural order-disorder are related to distortions (tilts) on the [TiO6] octahedron and changes in the bond lengths and bond angles between oxygen and titanium atoms that gave rise to new species of cluster makers such as [TiO6]', [TiO5·VO(x)], [TiO5·VO?] and [TiO5·VO??]. This structural transformation is consistent with a redistribution of electron density from highly ordered [TiO6](x) clusters which form distorted [TiO6]' as well as complex [TiO5·VO(x)], [TiO5·VO?] and [TiO5·VO??] clusters assigned to oxygen vacancies which were understood as displacements in the oxygen atoms' position in the bond lengths (Ti-O). PMID:25579134

Silva Junior, E; La Porta, F A; Liu, M S; Andrés, J; Varela, J A; Longo, E

2015-02-01

143

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

144

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

International Nuclear Information System (INIS)

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 (Ered), and the first oxidation (Eox) 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.bstituted phenyl moiety.

145

Quantitative structure-property relationship studies for collision cross sections of 579 singly protonated peptides based on a novel descriptor as molecular graph fingerprint (MoGF)  

International Nuclear Information System (INIS)

Aiming at ion mobility spectrometry (IMS), computer-assisted ion mobility prediction (CAIMP) has been recently developed to simulate and predict diverse IMS behaviors in assistance of mathematics and computer science. Of that, quantitative structure-property relationship (QSPR) plays a vital role, dedicating to predict properties of unknown samples by creating statistical model based on known samples. In QSPR, the key lies in how to transform structural characteristics of target compounds into a group of numerical codes. In consideration that future IMS applications may mainly focus on intricate drug/biological systems, a novel molecular structural characterization method referring to molecular graphic fingerprint (MoGF) is proposed in this paper. In MoGF approach, radical distribution function is employed to map intrinsic interatomic correlations into a coordinate system according to a reasonable sampling interval, thus forming the characteristic graph curve which is rich in information on molecular structural characteristics, possessing of great merits in easy calculation, independent of experiments, large information contents, explicit structural meanings and intuitive expressions, etc. Consequently, MoGF is utilized to QSPR studies on 579 singly protonated peptide collision cross sections, and the constructed partial least square (PLS) regression model is confirmed to be robust and predictable by rigorous both internal and external validations, with statistics as external validations, with statistics as r2 = 0.991, q2 = 0.990, RMSEE = 5.526, RMSCV = 5.572, qext2=0.990, rext2=0.990, r0,ext2=0.990, r0,ext'2=0.990, k = 1.003, k' = 0.996 and RMSEP = 5.561, respectively

146

Structure-to-property Relationships in Addition Cured Polymers 2: Resin Tg Composite Initial Mechanical Properties of Norbornenyl Cured Polyimide Resins  

Science.gov (United States)

PRM (polymerization of monomeric reactants) methodology was used to prepare thirty different polyimide oligomeric resins. Monomeric composition as well as chain length between sites of crosslinks were varied to examine their effects on glass transition temperature (Tg) of the cured/postcured resins. An almost linear correlation of Tg versus molecular distance between the crosslinks was observed. An attempt was made to correlate Tg with initial mechanical properties (flexural strength and interlaminar shear strength) of unidirectional graphite fiber composites prepared with these resins. However, the scatter in mechanical strength data prevented obtaining as clear a correlation as was observed for the structural modification/crosslink distance versus Tg. Instead, only a range of composite mechanical properties was obtained at the test temperatures studied (room temperature, 288 and 316 C). Perhaps more importantly, what did become apparent during the attempted correlation study was: (1) that PMR methodology could be used to prepare composites from resins that contain a wide variety of monomer modifications, and (2) that these composites almost invariably provided satisfactory initial mechanical properties as long as the resins selected were melt processable.

Alston, W. B.

1986-01-01

147

Structure-to-property relationships in addition cured polymers. II - Resin Tg and composite initial mechanical properties of norbornenyl cured polyimide resins  

Science.gov (United States)

PRM (polymerization of monomeric reactants) methodology was used to prepare thirty different polyimide oligomeric resins. Monomeric composition as well as chain length between sites of crosslinks were varied to examine their effects on glass transition temperature (Tg) of the cured/postcured resins. An almost linear correlation of Tg versus molecular distance between the crosslinks was observed. An attempt was made to correlate Tg with initial mechanical properties (flexural strength and interlaminar shear strength) of unidirectional graphite fiber composites prepared with these resins. However, the scatter in mechanical strength data prevented obtaining as clear a correlation as was observed for the structural modification/crosslink distance versus Tg. Instead, only a range of composite mechanical properties was obtained at the test temperatures studied (room temperature, 288 and 316 C). Perhaps more importantly, what did become apparent during the attempted correlation study was: (1) that PMR methodology could be used to prepare composites from resins that contain a wide variety of monomer modifications, and (2) that these composites almost invariably provided satisfactory initial mechanical properties as long as the resins selected were melt processable.

Alston, William B.

1986-01-01

148

Structure-property relationships of a class of carbamate-based fatty acid amide hydrolase (FAAH) inhibitors: chemical and biological stability.  

Science.gov (United States)

Cyclohexylcarbamic acid aryl esters are a class of fatty acid amide hydrolase (FAAH) inhibitors, which includes the reference compound URB597. The reactivity of their carbamate fragment is involved in pharmacological activity and may affect their pharmacokinetic and toxicological properties. We conducted in vitro stability experiments in chemical and biological environments to investigate the structure-stability relationships in this class of compounds. The results show that electrophilicity of the carbamate influences chemical stability, as suggested by the relation between the rate constant of alkaline hydrolysis (log k(pH9)) and the energy of the lowest unoccupied molecular orbital (LUMO). Introduction of small electron-donor substituents at conjugated positions of the O-aryl moiety increased the overall hydrolytic stability of the carbamate group without affecting FAAH inhibitory potency, whereas peripheral non-conjugated hydrophilic groups, which favor FAAH recognition, helped decrease oxidative metabolism in the liver. PMID:19554599

Vacondio, Federica; Silva, Claudia; Lodola, Alessio; Fioni, Alessandro; Rivara, Silvia; Duranti, Andrea; Tontini, Andrea; Sanchini, Silvano; Clapper, Jason R; Piomelli, Daniele; Mor, Marco; Tarzia, Giorgio

2009-09-01

149

Relationship between crystal structure and luminescent properties of novel red emissive BiVO4:Eu3+ and its photocatalytic performance  

International Nuclear Information System (INIS)

Crystalline BiVO4:Eu3+ 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 Eu3+5D0 ? 7F2 red luminescence at 618 nm can be excited by visible light at 466 nm in BiVO4 host. Furthermore, it has been found that the encapsulation of europium(III) in tetragonal phase (BiVO4) 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.

150

Elucidating the structure-property relationships of donor-?-acceptor dyes for dye-sensitized solar cells (DSSCs) through rapid library synthesis by a one-pot procedure.  

Science.gov (United States)

The creation of organic dyes with excellent high power conversion efficiency (PCE) is important for the further improvement of dye-sensitized solar cells. We wish to describe the rapid synthesis of a 112-membered donor-?-acceptor dye library by a one-pot procedure, evaluation of PCEs, and elucidation of structure-property relationships. No obvious correlations between ?, and the ? were observed, whereas the HOMO and LUMO levels of the dyes were critical for ?. The dyes with a more positive E(HOMO), and with an E(LUMO)dyes; nevertheless, that was not sufficient for identifying the best combination of donor, ?, and acceptor blocks. Combinatorial synthesis and evaluation was important for identifying the best dye. PMID:24954633

Fuse, Shinichiro; Sugiyama, Sakae; Maitani, Masato M; Wada, Yuji; Ogomi, Yuhei; Hayase, Shuzi; Katoh, Ryuzi; Kaiho, Tatsuo; Takahashi, Takashi

2014-08-18

151

Quantitative Structure Pharmacokinetic Relationship Using Artificial Neural Network: A Review  

Directory of Open Access Journals (Sweden)

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

S. K. Singh

2009-10-01

152

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

Directory of Open Access Journals (Sweden)

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

Z. Bayat

2011-05-01

153

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

International Nuclear Information System (INIS)

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

154

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 t of uncoated stainless steel and CrB2-coated samples. (orig.)

155

A food polymer science approach to structure-property relationships in aqueous food systems: non-equilibrium behavior of carbohydrate-water systems.  

Science.gov (United States)

Descriptions of the functional significance of carbohydrates based on the familiar equilibrium thermodynamics of very dilute solutions fail for pragmatical time scales and conditions, which are far from equilibrium. This is not too surprising, since limiting partial-molar properties reflect the independent behavior of solute in the limit of infinite dilution where free volume is maximum at a given temperature, while Tg'-Wg' properties reflect the cooperative behavior of solute-plasticizer blends at the limiting minimum value of free volume to observe relaxation within experimental time scales. Carbohydrate-water systems, with well-characterized structure and MW above and below the entanglement limit, provide a unique framework for the investigation of non-equilibrium behavior. Thermal analysis by DSC reveals the central role of water as a plasticizer for carbohydrates and of the glass transition as a physicochemical parameter that governs their properties, processing, and stability. A classical polymer science approach is used to study structure-property relationships of carbohydrates as water-compatible food polymers, which are treated as homologous systems of polymers, oligomers, and monomers with their plasticizers and solvents. Mechanical relaxation behavior is described by a "transformation map" of the critical variables of moisture content, temperature, and time. The glass curve is a reference contour, which represents the limiting isogram for free volume, local viscosity, relaxation rates, and rotational and translational mobility. Map domains are discussed as aspects of "water dynamics," to dispel the myth of "bound water," and "glass dynamics," to relate to macroscopic structure and collapse phenomena. A particular glass with invariant composition and Tg (prepared by freeze-concentration) is identified as a pivotal and practical reference state. The Tg observed during DSC analysis is often an effective Tg, resulting from instantaneous relative relaxation rates and non-uniform distribution of total sample moisture. Non-equilibrium melting, annealing, and gelation/recrystallization of kinetically metastable, partially crystalline carbohydrate systems exhibit non-Arrhenius kinetics which depend on the magnitude of delta T above the appropriate Tg, as defined by WLF relaxation transformations. Thermally reversible aqueous gels (crystallized from an under-cooled, rubbery melt) are described by a "fringed micelle" structural model for a three-dimensional polymer network, composed of microcrystalline junction zones crosslinking plasticized amorphous regions of flexible-coiled, entangled chain segments. PMID:1746335

Slade, L; Levine, H

1991-01-01

156

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.

Koh Eunhee

2007-07-01

157

Ordered Structures and Thermoelectric Properties of MNiSn (M = Ti, Zr, Hf)-Based Half-Heusler Compounds Affected by Close Relationship with Heusler Compounds  

Science.gov (United States)

Half-Heusler compounds are excellent thermoelectric materials. A characteristic of the half-Heusler-type ordered structure is the vacancy site that occupies one-fourth of all the lattice points. Therefore, a half-Heusler ABX phase (where A and B are typically transition metal elements, such as Ti, Zr, and Hf, and X represents a half-metal element such as Sn or Sb) has a crystallographically close relationship with a Heusler AB2X phase in the sense that the vacancy site in the half-Heusler phase is filled with B atoms in the Heusler phase. The thermoelectric properties are improved or affected by point lattice defects related to the vacancy site and the B site, such as the antisite atom B in the vacancy site, vacancies in the B site, and vacancy-site occupancy by quaternary C atoms. A modulated-like nanostructure due to point defects regarding vacancies and Ni atoms is formed for an instance in ZrNiSn alloys even close to the stoichiometric composition. Ni-rich nanoclusters are locally formed by excessive Ni antisite atoms in the vacancy site, which work as precursors of Heusler precipitates (TiNi2Sn, ZrNi2Sn, and so forth). The vacancy-site occupation in ZrNiSn with Co and Ir results in the drastic conversion of thermoelectric properties from n type to p type, and the effective reduction of the lattice thermal conductivity.

Kimura, Yoshisato; Chai, Yaw-Wang

2015-01-01

158

Ordered Structures and Thermoelectric Properties of MNiSn (M = Ti, Zr, Hf)-Based Half-Heusler Compounds Affected by Close Relationship with Heusler Compounds  

Science.gov (United States)

Half-Heusler compounds are excellent thermoelectric materials. A characteristic of the half-Heusler-type ordered structure is the vacancy site that occupies one-fourth of all the lattice points. Therefore, a half-Heusler ABX phase (where A and B are typically transition metal elements, such as Ti, Zr, and Hf, and X represents a half-metal element such as Sn or Sb) has a crystallographically close relationship with a Heusler AB2X phase in the sense that the vacancy site in the half-Heusler phase is filled with B atoms in the Heusler phase. The thermoelectric properties are improved or affected by point lattice defects related to the vacancy site and the B site, such as the antisite atom B in the vacancy site, vacancies in the B site, and vacancy-site occupancy by quaternary C atoms. A modulated-like nanostructure due to point defects regarding vacancies and Ni atoms is formed for an instance in ZrNiSn alloys even close to the stoichiometric composition. Ni-rich nanoclusters are locally formed by excessive Ni antisite atoms in the vacancy site, which work as precursors of Heusler precipitates (TiNi2Sn, ZrNi2Sn, and so forth). The vacancy-site occupation in ZrNiSn with Co and Ir results in the drastic conversion of thermoelectric properties from n type to p type, and the effective reduction of the lattice thermal conductivity.

Kimura, Yoshisato; Chai, Yaw-Wang

2014-12-01

159

Metal Nanowires: Synthesis, Processing, and Structure-Property Relationships in the Context of Flexible Transparent Conducting Films  

Science.gov (United States)

The demand for flat-panel televisions, e-readers, smart-phones, and touch-screens has been increasing over the past few years and will continue to increase for the foreseeable future. Each of these devices contains a transparent conductor, which is usually indium tin oxide (ITO) because of its high transparency and low sheet resistance. ITO films, however, are brittle, expensive, and difficult to deposit, and because of these problems, alternative transparent electrodes are being studied. One cheap and flexible alternative to ITO is films of randomly oriented copper nanowires. We have developed a synthesis to make long, thin, and well-dispersed copper nanowires that can be suspended in an ink and coated onto a substrate to make flexible transparent films. These films are then made conductive by annealing in a hydrogen atmosphere or by a solution processing technique that can be done in air at room temperature. The resulting flexible transparent conducting films display transparencies and sheet resistance values comparable to ITO. Since it is well known that copper oxidizes, we also developed a synthesis to coat the copper nanowires with a layer of nickel in solution. Our measurements indicated that copper nanowires would double their sheet resistance in 3 months, but the sheet resistance of cupronickel nanowire films containing 20 mole% nickel will double in about 400 years. The addition of nickel to the copper nanowires also gave the film a more neutral grey appearance. The nickel coating can also be applied to the copper nanowires after the film is formed via an electroless plating method. To further optimize the properties of our transparent conductors we developed a framework to understand how the dimensions and area coverage of the nanowires affect the overall film properties. To quantify the effect of length on the sheet resistance and transmittance, wires with different lengths but the same diameter were synthesized to make transparent conducting films and finite-difference time-domain calculations were used to determine the effect of the nanowire diameter on the film's transmittance. The experimental data and calculations were then incorporated into random resistor network simulations that demonstrated that wires with an aspect ratio of 400 or higher are required to make a network that transmits >90% of visible light while maintaining a sheet resistance below 100 O/sq-1. These properties, and the fact that copper and nickel are 1000 times more abundant than indium or silver, make copper and cupronickel nanowire films a promising alternative for the sustainable, efficient production of transparent conductors.

Rathmell, Aaron R.

160

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

Science.gov (United States)

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

Li, Huixing; Chen, Maodu

2013-12-01

161

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

International Nuclear Information System (INIS)

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

162

Investigation of the structure/property relationship of spray-formed 7XXX series high-strength aluminum alloys and their metal matrix composites  

Science.gov (United States)

The purpose of this investigation was to identify the structure/property relationship of spray formed 7XXX series alloys. High solute, ultra-high strength 7XXX series aluminum alloys with solute contents close to equilibrium solid solubility limits of the Al-Zn-Mg-Cu system have been produced by rapid solidification using spray deposition. The process yields massive preforms directly from the liquid state. Various elements, including chromium, manganese, silver, zirconium and scandium, were incorporated to produce a variety of microstructures and mechanical properties. SiC particulate was added to these same alloy compositions to produce metal matrix composites (MMCs). The resulting extruded products in the T6 and T7 conditions were evaluated and compared. Under peak-aged conditions in the unreinforced materials, strengths in excess of 860 MPa were achieved, with one alloy exceeding 900 MPa. Apart from the elongation to failure, the mechanical properties of the composite materials were equal to or superior to those of their unreinforced counterparts. The superior strength properties of the spray formed alloys were attributed to two major substructures with different scale; nanometer sized eta ' metastable precipitates and slightly larger, but finely distributed dispersoids. The large volume fraction of plate-like eta' precipitates (average size 58A, ranging up to 73 A in diameter) were identified as having a hexagonal structure with lattice parameters a = 0.488 nm and c = 1.376. The remarkable strengthening is predominantly attributed to precipitation hardening. The enhanced mechanical properties of the MMC materials are attributed to the increased dislocation density, and thus, a higher concentration of structural particles compared to the unreinforced materials. Higher gas-to-metal ratios of 4.45, as opposed to lower gas-to-metal ratios of 1.95 produced a refined grain structure with an evenly distributed second phase. In both unreinforced and MMC materials, alloys with zinc contents over 12 wt. % attained the highest concentration of structural particles. One alloy displayed high strengths exceeding all others in the study. The superior strength properties were attributed to the addition of scandium, which produced a fine dispersion of the Al3Sc phase. This finely dispersed phase created additional strengthening through, coherency mismatch of Al3Sc and Al3(Sc,Zr) precipitates with the matrix, and ordered particle strengthening. The spray formed extrusions exhibited a loss in fracture resistance (K Q), compared to IM 7075 alloys. Characterization of the fracture surfaces indicated a predominantly intergranular decohesion, possibly facilitated by the presence of incoherent particles at the grain boundary regions and by the large strength differential between the matrix and precipitate zone. The MMC materials displayed a large increase in fatigue strength compared to commercial IM 7075-T6 and -T7 alloys. The enhanced fatigue performance of the spray formed alloys is attributed to low crack growth rates, which are a consequence of inhomogeneous slip. It is believed that the massive presence of coherent and semicoherent (GP zones and eta' phase) particles of reduced dimension in the spray formed alloys allowed a highly inhomogeneous slip behavior, where a slip reverse mechanism was operative.

Sharma-Judd, Malavika M.

2000-12-01

163

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

Science.gov (United States)

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. PMID:23751088

Luo, Sida; Liu, Tao; Benjamin, Shermane M; Brooks, James S

2013-07-01

164

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

Directory of Open Access Journals (Sweden)

Full Text Available

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

Mehdi Rahimi

2012-06-01

165

The development of comprehensive material models of the structure-property relationships for die-cast magnesium alloy AM60B  

Science.gov (United States)

The purpose of this study was to conduct experiments to determine the relevant microstructural features that influence mechanical properties of the high-pressure die-cast magnesium alloy AM60B. From these resulting experimental data, predictive capabilities of these relationships were developed. This work continues from a previous M.E.Sc. thesis [1]. Metallographic and indentation techniques were used to determine the skin thickness in regions of different solidification conditions throughout the die-casting. It was determined that the yield strength of AM6OB samples tested in uniaxial tension is described by a modified Hall-Petch relationship. These results were then used in FE (finite element) simulations to establish the predicted yield strength for uniaxial tensile samples given the average grain size. Medium- (˜8mum) and high-resolution (˜1mum) X-ray tomography testing were completed on several samples of AM60B, and one sample at several levels of loading during uniaxial tension, prior to fracture. The fracture location, strain and stress of the sample during uniaxial tensile testing were predicted using a critical strain model, previously presented in [1], and a new, modified failure model. FE simulations were used to simulate the fracture of uniaxial tensile samples with porosity. It was determined that the critical features leading to fracture of AM6OB samples are the area fraction of porosity, and the proximity of the centre of mass of the porosity to a free surface. With these two features, a mathematical model was formulated capable of predicting the fracture strain of six AM6OB samples tested in uniaxial tension within an error percentage of 6.8%. Multi-axial testing was completed on several samples of AM60B. Uniaxial compression, plane-strain compression, and shear testing were completed to fracture. FE simulations were found to accurately predict the deformation and true stress-true strain curves each of these loading states. An accurate yield surface was then established for the deformation of AM6OB in plane-stress up to 10% true effective strain. FE simulations were completed under plane-strain tension, balanced bi-axial tension, shear testing, and uniaxial tensile testing to determine a fracture surface for different area fractions of porosity for plane-stress loading. These fracture surfaces were validated using results from uniaxial tensile testing. Keywords: Finite element analysis simulations, high-resolution X-ray tomography, X-ray diffraction techniques, magnesium die-castings, failure modelling, multi-axial material testing, structure-property relationships.

Weiler, Jonathan P.

166

Processing-structure-property relationships of thermal barrier coatings deposited using the solution precursor plasma spray process  

Science.gov (United States)

This research is intended to develop a novel process, solution-precursor plasma-spray (SPPS), for the deposition of highly durable thermal barrier coatings (TBCs). In the SPPS process a solution precursor feedstock, that results in ZrO2-7 wt% Y2O3 ceramic, is injected into the plasma jet and the coating is deposited on a metal substrate. The formed coating has the following novel microstructural features: (i) ultra-fine splats, (ii) through-thickness cracks, (iii) micrometer and nanometer porosity, and (iv) interpass boundaries. The deposition mechanisms of the solution precursor droplets injected into the different regions of the plasma jet were found to be different due to large temperature variation across the plasma jet. The solution precursor droplets injected into the core of the plasma jet are deposited on the substrate as ultra-fine splats that account for around 65 volume% of the coating. The other 35 volume% of the coating includes porosity and deposits formed from the solution precursor droplets injected into other regions of the plasma jet. The optimum processing condition for highly durable TBCs was determined using Taguchi design of experiments. Meanwhile, the relationship of the microstructural features and processing parameters was revealed. During thermal cycling, the unmelted particles in the coating were observed to pyloyze and/or sinter, while no sign of sintering was observed for the ultra-fine splats. The spacing of through-thickness cracks remains in the range of 160 to 190 mum throughout the thermal cycling test. Three stages of oxidation of the bond coat were observed. Failure of the SPPS TBC starts with the crack nucleation along the unmelted particles in the top coat and the Ni, Cr, Co-rich oxides of large thickness. These cracks propagate and coalesce with thermal cycling. The extensive cracking of the rapidly formed Ni, Cr, Co-rich oxides resulting from the depletion of aluminum in the bond coat leads to the development of large separation between TBC and substrate. When a separation of sufficient size emerges, the TBC starts to separate from the metal substrate by large scale buckling as a result of the small strain energy stored in the strain tolerant SPPS TBCs.

Xie, Liangde

167

Structure-Property Relationship of Layered Metal Oxide Phosphonate/Chitosan Nanohybrids for Transducer in Biosensing Device  

Science.gov (United States)

A candid approach to analyze the performance characteristics of phenyl phosphonate-functionalized zirconium oxide and pure zirconium oxide (ZrO2) fillers reinforced chitosan nanocomposites and their suitability as a potential biomaterial for the development of transducer surface in biosensing device has been investigated in this communication. Functionalization of ZrO2 has been carried out using sulfophenylphosphonate which was confirmed using Fourier transform infrared spectrographs. The electrostatic intercalation of chitosan with filler particles was monitored using electrochemical impedance analyzer which exhibits lowest bulk resistance which is highly effective for ionic switching. Incorporation of zirconium sulfophenylphosphonate (ZrSP) the ionic conductivity of the chitosan film attained a value of 1.2 × 10-6 S/cm as compared to the unmodified one which is a prefeasibility work for the fabrication of biosensing platform. Variation in performance characteristics has been evaluated through morphological and thermal characterization. TGA and DSC analysis reveal that the thermal stability and decomposition temperature of the nanocomposites were improved by the addition of reinforcing filler particles. XRD and SEM and TEM results support the above assumption. The continuous alignment of the proton transfer channels of the nanocomposites was thoroughly investigated by AFM analysis which revealed phase morphology for improved enzyme entrapment. Further, surface functionalized nanofillers result considerable increment of mechanical properties in terms of elastic modulus and tensile stress.

De, Sriparna; Mohanty, Smita; Nayak, Sanjay Kumar

2014-11-01

168

Structure-Property Relationship of Layered Metal Oxide Phosphonate/Chitosan Nanohybrids for Transducer in Biosensing Device  

Science.gov (United States)

A candid approach to analyze the performance characteristics of phenyl phosphonate-functionalized zirconium oxide and pure zirconium oxide (ZrO2) fillers reinforced chitosan nanocomposites and their suitability as a potential biomaterial for the development of transducer surface in biosensing device has been investigated in this communication. Functionalization of ZrO2 has been carried out using sulfophenylphosphonate which was confirmed using Fourier transform infrared spectrographs. The electrostatic intercalation of chitosan with filler particles was monitored using electrochemical impedance analyzer which exhibits lowest bulk resistance which is highly effective for ionic switching. Incorporation of zirconium sulfophenylphosphonate (ZrSP) the ionic conductivity of the chitosan film attained a value of 1.2 × 10-6 S/cm as compared to the unmodified one which is a prefeasibility work for the fabrication of biosensing platform. Variation in performance characteristics has been evaluated through morphological and thermal characterization. TGA and DSC analysis reveal that the thermal stability and decomposition temperature of the nanocomposites were improved by the addition of reinforcing filler particles. XRD and SEM and TEM results support the above assumption. The continuous alignment of the proton transfer channels of the nanocomposites was thoroughly investigated by AFM analysis which revealed phase morphology for improved enzyme entrapment. Further, surface functionalized nanofillers result considerable increment of mechanical properties in terms of elastic modulus and tensile stress.

De, Sriparna; Mohanty, Smita; Nayak, Sanjay Kumar

2015-01-01

169

Chemical synthesis, structure-activity relationship, and properties of shepherin I: a fungicidal peptide enriched in glycine-glycine-histidine motifs.  

Science.gov (United States)

Although glycine-rich antimicrobial peptides (AMPs) are found in animals and plants, very little has been reported on their chemistry, structure activity-relationship, and properties. We investigated those topics for Shepherin I (Shep I), a glycine-rich AMP with the unique amino acid sequence G(1)YGGHGGHGGHGGHGGHGGHGHGGGGHG(28). Shep I and analogues were synthesized by the solid-phase method at 60 °C using conventional heating. Purification followed by chemical characterization confirmed the products' identities and high purity. Amino acid analysis provided their peptide contents. All peptides were active against the clinically important Candida species, but ineffective against bacteria and mycelia fungi. Truncation of the N- or C-terminal portion reduced Shep I antifungal activity, the latter being more pronounced. Carboxyamidation of Shep I did not affect the activity against C. albicans or C. tropicalis, but increased activity against S. cerevisiae. Carboxyamidated analogues Shep I (3-28)a and Shep I (6-28)a were equipotent to Shep I and Shep Ia against Candida species. As with most cationic AMPs, all peptides had their activity significantly reduced in high-salt concentrations, a disadvantage that is defeated if 10 µM ZnCl2 is present. At 100 µM, the peptides were practically not hemolytic. Shep Ia also killed C. albicans MDM8 and ATCC 90028 cells. Fluo-Shep Ia, an analogue labeled with 5(6)-carboxyfluorescein, was rapidly internalized by C. albicans MDM8 cells, a salt-sensitive process dependent on metabolic energy and temperature. Altogether, such results shed light on the chemistry, structural requirements for activity, and other properties of candidacidal glycine-rich peptides. Furthermore, they show that Shep Ia may have strong potential for use in topical application. PMID:25106507

Remuzgo, César; Oewel, Thaís S; Daffre, Sirlei; Lopes, Thiago R S; Dyszy, Fabio H; Schreier, Shirley; Machado-Santelli, Gláucia M; Teresa Machini, M

2014-11-01

170

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

International Nuclear Information System (INIS)

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

171

Molecular dynamics simulations of structure-property relationships of Tween 80 surfactants in water and at interfaces.  

Science.gov (United States)

We build a united atom model for Tween 80 (polyoxyethylene sorbitan oleates), based on the GROMOS53A6(OXY+D) force field, and apply it to two stereoisomers, three constitutional isomers, and three structures with one, two, and three tails, to represent components in the Tween 80 commercial mixture. In a preassembled micelle containing 60 molecules, the distribution of Tween tail and ethylene oxide head groups is found to be insensitive to stereoisomerization but sensitive to changes in relative lengths of the four polyoxyethylene head groups. At the air-water and oil-water interfaces, the interfacial tension is significantly lower for the constitutional isomer with a shorter W headgroup, which attaches the tail to the sorbitan ring, and for Tween 80 isomers with more than one tail group. The results indicate the possible scope for improvement in the design of polyoxyethylene sorbitan oleates with improved surface tension reduction or better spreading at the oil-water interface. We also report surfactant component distribution profiles within preassembled micelles and at interfaces that can be used for validating coarse-grained surfactant models needed for simulation of self-assembly of Tween 80 surfactant mixtures. PMID:25365212

Tang, Xueming; Huston, Kyle J; Larson, Ronald G

2014-11-13

172

Structure-property relationship of sol-gel electrospun ZnO nanofibers developed for ammonia gas sensing.  

Science.gov (United States)

Zinc oxide (ZnO) based nanomaterials have been used in various gas sensors due to the wide band gap (3.37eV), large exciton binding energy and high mobility of charge carriers of ZnO. In this work, nanocrystalline ZnO nanofiber mats were synthesized through combined sol-gel electrospinning techniques followed by calcination, in which poly(styrene-co-acrylonitrile) and zinc acetate were used as the binder and precursor, respectively. Average diameter of the ZnO nanofibers decreased from 400 to 60nm, while their grain size and crystallinity were enhanced by increasing the calcination temperature. Morphology and structure of the ZnO nanofiber mats were characterized by high resolution transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. ZnO nanofiber mats were found to be superhydrophilic (contact angle was close to 0°) by contact angle measurements. The sensitivity of these ZnO nanofibers in detecting gaseous ammonia was tested using an indigenous set up. Due to their high surface area and superhydrophility, these ZnO nanofiber mats were highly sensitive in sensing gaseous ammonia and the sensitivity of these mats increased as a function of their calcination temperatures. PMID:25086723

Senthil, T; Anandhan, S

2014-10-15

173

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-04-15

174

Similarity Matrices Quantitative Structure-Activity Relationships for Anticonvulsant Phenylacetanilides  

Directory of Open Access Journals (Sweden)

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

Ovidiu Ivanciuc

2004-07-01

175

Fluorescent J-aggregates of core-substituted perylene bisimides: studies on structure-property relationship, nucleation-elongation mechanism, and sergeants-and-soldiers principle.  

Science.gov (United States)

A series of highly soluble and fluorescent, at core tetraaryloxy-substituted and in imide positions hydrogen atom containing perylene bisimide (PBI) dyes 1a-e with varying peripheral side chains have been synthesized and thoroughly characterized. The self-assembly of these PBIs has been studied in detail by UV/vis, linear dichroism (LD) and circular dichroism (CD) spectroscopy, and scanning probe microscopy (AFM, STM). These studies revealed that the present PBIs self-assemble into extended double string cables, which consist of two hydrogen-bonded supramolecular polymeric chains of densely packed and strongly excitonically coupled PBI chromophores, providing highly fluorescent J-aggregates. The aggregation strength ("melting" temperature) and the fluorescence properties of these J-aggregates are dependent on the number and chain length of the peripheral alkoxy substituents, thus revealing a structure-property relationship. In contrast to previously reported assemblies of PBIs, for which the aggregation process is described by the isodesmic (or equal K) model, a cooperative nucleation-elongation mechanism applies for the aggregation of the present assemblies as revealed by concentration-dependent UV/vis absorption studies with the chiral PBI 1e, providing equilibrium constants for dimerization (= nucleation) of K(2) = 13 +/- 11 L mol(-1) and for elongation of K = 2.3 +/- 0.1 x 10(6) L mol(-1) in methylcyclohexane (MCH). LD spectroscopic measurements have been performed to analyze the orientation of the monomers within the aggregates. The nonlinearity of chiral amplification in PBI aggregates directed by sergeants-and-soldiers principle has been elucidated by coaggregation experiments of different PBI dyes using CD spectroscopy. The dimensions as well as the molecular arrangement of the monomeric units in assemblies have been explored by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). PMID:19388696

Kaiser, Theo E; Stepanenko, Vladimir; Würthner, Frank

2009-05-20

176

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

International Nuclear Information System (INIS)

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

177

Structure-property and composition-property relationships for poly(ethylene terephthalate) surfaces modified by helium plasma-based ion implantation  

International Nuclear Information System (INIS)

The surfaces of untreated and helium plasma-based ion implantation (He PBII) treated poly(ethylene terephthalate) (PET) samples were characterised by reflectance colorimetry, contact angle studies and measurements of surface electrical resistance. The results were related to the structural and compositional data obtained by the authors earlier on parallel samples by XPS and Raman spectroscopy. Inverse correlations between lightness and ID/IG ratio and between chroma and ID/IG ratio were obtained, suggesting that the PBII-treated PET samples darken and their colourfulness decreases with the increase of the portion of aromatic sp2 carbon rings in the chemical structure of the modified layer. Direct correlation between water contact angle and the ID/IG ratio and inverse correlations between surface energy and ID/IG ratio and between dispersive component of surface energy and ID/IG ratio were found, reflecting that surface wettability, surface energy and its dispersive component decrease with the formation of surface structure, characterised again by enhanced portion of aromatic sp2 carbon rings. The surface electrical resistance decreased with the increase of the surface C-content determined by XPS and also with the increase of the surface concentration of conjugated double bonds, reflected by the increase of the ? ? ?* shake-up satellitcrease of the ? ? ?* shake-up satellite of the C 1s peak.

178

Quasicrystals: Structure and properties  

International Nuclear Information System (INIS)

The structure and properties of quasicrystals are discussed. The short-and long-range atomic orders and the effect of these factors on the physical characteristics are considered. It is noted that investigations of the physical properties of quasicrystals at temperatures above room temperature should be performed. Promising applications are briefly outlined

179

Trichothecenes: structure-toxic activity relationships.  

Science.gov (United States)

Trichothecenes comprise a large family of structurally related toxins mainly produced by fungi belonging to the genus Fusarium. Among trichothecenes, type A and type B are of the most concern due to their broad and highly toxic nature. In order to address structure-activity relationships (SAR) of trichothecenes, relationships between structural features and biological effects of trichothecene mycotoxins in mammalian systems are summarized in this paper. The double bond between C-9-C-10 and the 12,13-epoxide ring are essential structural features for trichothecene toxicity. Removal of these groups results in a complete loss of toxicity. A hydroxyl group at C-3 enhances trichothecene toxicity, while this activity decreases gradually when C-3 is substituted with either hydrogen or an acetoxy group. The presence of a hydroxyl group at C-4 promotes slightly lower toxicity than an acetoxy group at the same position. The toxicity for type B trichothecenes decreases if the substituent at C-4 is changed from acetoxy to hydroxyl or hydrogen at C-4 position. The presence of hydroxyl and hydrogen groups on C-15 decreases the trichothecene toxicity in comparison with an acetoxy group attached to this carbon. Trichothecenes toxicity increases when a macrocyclic ring exists between the C-4 and C-15. At C-8 position, an oxygenated substitution at C-8 is essential for trichothecene toxicity, indicating a decrease in the toxicity if substituent change from isovaleryloxy through hydrogen to the hydroxyl group. The presence of a second epoxy ring at C-7-C-8 reduces the toxicity, whereas epoxidation at C-9-C-10 of some macrocyclic trichothecenes increases the activity. Conjugated trichothecenes could release their toxic precursors after hydrolysis in animals, and present an additional potential risk. The SAR study of trichothecenes should provide some crucial information for a better understanding of trichothecene chemical and biological properties in food contamination. PMID:23869809

Wu, Qinghua; Dohnal, Vlastimil; Kuca, Kamil; Yuan, Zonghui

2013-07-01

180

On exploring structure-activity relationships.  

Science.gov (United States)

Understanding structure-activity relationships (SARs) for a given set of molecules allows one to rationally explore chemical space and develop a chemical series optimizing multiple physicochemical and biological properties simultaneously, for instance, improving potency, reducing toxicity, and ensuring sufficient bioavailability. In silico methods allow rapid and efficient characterization of SARs and facilitate building a variety of models to capture and encode one or more SARs, which can then be used to predict activities for new molecules. By coupling these methods with in silico modifications of structures, one can easily prioritize large screening decks or even generate new compounds de novo and ascertain whether they belong to the SAR being studied. Computational methods can provide a guide for the experienced user by integrating and summarizing large amounts of preexisting data to suggest useful structural modifications. This chapter highlights the different types of SAR modeling methods and how they support the task of exploring chemical space to elucidate and optimize SARs in a drug discovery setting. In addition to considering modeling algorithms, I briefly discuss how to use databases as a source of SAR data to inform and enhance the exploration of SAR trends. I also review common modeling techniques that are used to encode SARs, recent work in the area of structure-activity landscapes, the role of SAR databases, and alternative approaches to exploring SAR data that do not involve explicit model development. PMID:23568465

Guha, Rajarshi

2013-01-01

181

Structural Antitumoral Activity Relationships of Synthetic Chalcones  

OpenAIRE

Relationships between the structural characteristic of synthetic chalcones and their antitumoral activity were studied. Treatment of HepG2 cells for 24 h with synthetic 2’-hydroxychalcones resulted in apoptosis induction and dose-dependent inhibition of cell proliferation. The calculated reactivity indexes and the adiabatic electron affinities using the DFT method including solvent effects, suggest a structure-activity relationship between the Chalcones structure and the apoptosi...

Cesar Echeverria; Juan Francisco Santibañez; Oscar Donoso-Tauda; Escobar, Carlos A.; Rodrigo Ramirez-Tagle

2009-01-01

182

The synthesis, characterization, and structure-property relationships of regioregular 4,4'-dialkyl-2,2'-bithiazole oligomers and polymers  

Science.gov (United States)

The 4,4'-dialkyl-2,2'-bithiazole moiety can be efficiently coupled to produce well-defined oligomers or block co-oligomers via Stille reactions of mono-bromo and tin substituted precursors. Dehalogenative polycondensations produce high molecular weight homo-polymers and Stille coupling of dibromo and di-tin monomers yields alternating copolymers. The symmetry of the bithiazole monomeric unit produces regioregular oligomers and polymers with the HH-TT dyad sequence. Model compound oligomers were synthesized and studied to explore the progression of structure property relationships with main chain extension. DSC measurements indicate the potential presence of at least three phases in solution cast thin films---the disordered isotropic melt, a stable low temperature morphology designated the alpha-phase, and a high temperature meta-stable morphology designated the beta-phase. Melt transition temperatures are inversely proportional to side alkyl chain length and directly proportional to main chain length and the interplay between the two effects greatly influences the observed thermochromism. Temperature dependent IR studies show an increase in the gauche conformations of the side chains at the low temperature alpha-beta phase transition and main chain twisting at the beta-isotropic transition. The onset of side chain and main chain motion at these phase transition temperatures was confirmed with variable temperature solid state NMR. Temperature dependent XRD results indicate the presence of a solid-to-solid crystal phase change at the low temperature transition followed by formation of preferred orientations of the beta and alpha ordered phases upon cooling from the isotropic melt. The solid-to-solid crystal phase transition is triggered by the increased motion of the side chains, and the magnitude of the intermolecular side chain packing forces dictate if the transitions occur cooperatively (observed isosbestic point) or as isolated events. Comparison with the 3-alkylthiophene series results have supported the proposal that alkyl chains of sufficient length begin to dominate and control the phase transition dynamics of these conjugated systems. Side chain and main chain packing forces lead to H-aggregation of the pi-stacked bithiazole structures and the observed UV/VIS spectra are interpreted within the exciton band model. The contributions of the excitonic/vibronic coupling and Davydov splitting of the electronic energy levels are evaluated and computational calculations aid and support the interpretation of experimental results.

Nanos, John I.

2005-12-01

183

Thermodynamics of the hydrogen bonding of nitrogen-containing cyclic and aromatic compounds with proton donors: The structure-property relationship  

Science.gov (United States)

Enthalpies of dissolution are measured at infinite dilution of nitrogen-containing cyclic (pyrrolidine, piperidine) and aromatic compounds (aniline, N-methylaniline, N,N-dimethylaniline, N-methylimidazole, pyridine, 2-, 3-, 4-methylpyridine, pyrrole, N-methylpyrrole) in chloroform and dichloromethane, and vice versa ( T = 298.15 K). The enthalpies of hydrogen bonds in the above systems are calculated. Relationships between resulting thermochemical data and the structure of nitrogen-containing cyclic and aromatic compounds are explored.

Rakipov, I. T.; Varfolomeev, M. A.; Kirgizov, A. Yu.; Solomonov, B. N.

2014-12-01

184

Structural Antitumoral Activity Relationships of Synthetic Chalcones  

Directory of Open Access Journals (Sweden)

Full Text Available Relationships between the structural characteristic of synthetic chalcones and their antitumoral activity were studied. Treatment of HepG2 cells for 24 h with synthetic 2’-hydroxychalcones resulted in apoptosis induction and dose-dependent inhibition of cell proliferation. The calculated reactivity indexes and the adiabatic electron affinities using the DFT method including solvent effects, suggest a structure-activity relationship between the Chalcones structure and the apoptosis in HepG2 cells. The absence of methoxy substituents in the B ring of synthetic 2’-hydroxychalcones, showed the mayor structure-activity pattern along the series.

Cesar Echeverria

2009-01-01

185

Structure-Property Relationships in Porous 3-D Nanostructures as a Function of Preparation Conditions: Isocyanate Cross-Linked Silica Aerogels  

Science.gov (United States)

Sol-gel derived silica aerogels are attractive candidates for many unique thermal, optical, catalytic, and chemical applications because of their low density and high mesoporosity. However, their inherent fragility has restricted use of aerogel monoliths to applications where they are not subject to any load. We have previously reported cross-linking the mesoporous silica structure of aerogels with di-isocyanates, styrenes or epoxies reacting with amine decorated silica surfaces. These approaches have been shown to significantly increase the strength of aerogels with only a small effect on density or porosity. Though density is a prime predictor of properties such as strength and thermal conductivity for aerogels, it is becoming clear from previous studies that varying the silica backbone and size of the polymer cross-link independently can give rise to combinations of properties which cannot be predicted from density alone. Herein, we examine the effects of four processing parameters for producing this type of polymer cross-linked aerogel on properties of the resulting monoliths. We focus on the results of 13C CP-MAS NMR which gives insight to the size and structure of polymer cross-link present in the monoliths, and relates the size of the cross-links to microstructure, mechanical properties and other characteristics of the materials obtained.

Meador, Mary Ann B.; Capadona, Lynn A.; McCorkle, Linda; Papadopoulos, Demetrios S.; Leventis, Nicholas

2007-01-01

186

Fluorination of Metal Phthalocyanines: Single-Crystal Growth, Efficient N-Channel Organic Field-Effect Transistors, and Structure-Property Relationships  

Science.gov (United States)

The fluorination of p-type metal phthalocyanines produces n-type semiconductors, allowing the design of organic electronic circuits that contain inexpensive heterojunctions made from chemically and thermally stable p- and n-type organic semiconductors. For the evaluation of close to intrinsic transport properties, high-quality centimeter-sized single crystals of F16CuPc, F16CoPc and F16ZnPc have been grown. New crystal structures of F16CuPc, F16CoPc and F16ZnPc have been determined. Organic single-crystal field-effect transistors have been fabricated to study the effects of the central metal atom on their charge transport properties. The F16ZnPc has the highest electron mobility (~1.1 cm2 V-1 s-1). Theoretical calculations indicate that the crystal structure and electronic structure of the central metal atom determine the transport properties of fluorinated metal phthalocyanines.

Jiang, Hui; Ye, Jun; Hu, Peng; Wei, Fengxia; Du, Kezhao; Wang, Ning; Ba, Te; Feng, Shuanglong; Kloc, Christian

2014-12-01

187

Fluorination of metal phthalocyanines: single-crystal growth, efficient N-channel organic field-effect transistors, and structure-property relationships.  

Science.gov (United States)

The fluorination of p-type metal phthalocyanines produces n-type semiconductors, allowing the design of organic electronic circuits that contain inexpensive heterojunctions made from chemically and thermally stable p- and n-type organic semiconductors. For the evaluation of close to intrinsic transport properties, high-quality centimeter-sized single crystals of F16CuPc, F16CoPc and F16ZnPc have been grown. New crystal structures of F16CuPc, F16CoPc and F16ZnPc have been determined. Organic single-crystal field-effect transistors have been fabricated to study the effects of the central metal atom on their charge transport properties. The F16ZnPc has the highest electron mobility (~1.1 cm(2) V(-1) s(-1)). Theoretical calculations indicate that the crystal structure and electronic structure of the central metal atom determine the transport properties of fluorinated metal phthalocyanines. PMID:25524460

Jiang, Hui; Ye, Jun; Hu, Peng; Wei, Fengxia; Du, Kezhao; Wang, Ning; Ba, Te; Feng, Shuanglong; Kloc, Christian

2014-01-01

188

Electromechanical actuation of buckypaper actuator: Material properties and performance relationships  

International Nuclear Information System (INIS)

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

189

Electromechanical actuation of buckypaper actuator: Material properties and performance relationships  

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-02-27

190

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

CERN Document Server

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

Ganesan, Aravindhan; Wang, Feng

2014-01-01

191

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

192

Critical laminar shear-temperature effects on the nano- and mesoscale structure of a model fat and its relationship to oil binding and rheological properties.  

Science.gov (United States)

This article reports on the effect of laminar shear on structural and mechanical properties of physical mixtures of fully hydrogenated soybean oil (FHSO) in soybean oil (SO). Blends were crystallized statically and under laminar shear rates of 30 and 240 s(-1) at different wall temperatures (-10, 0, 20 degrees C). The micro- and nanocrystalline structures were characterized using Polarized Light Microscopy (PLM), and Cryogenic Transmission Electron Microscopy (Cryo-TEM). Rheological analysis was used to determine changes in mechanical properties. Oil-binding capacity was analyzed through the measurement of the oil lost from the fat samples (OL). Shearing greatly affected the structure at the nano- and mesoscale. At low shear rates, blends displayed the largest increase in crystal size with an increase in wall temperature at both the nano- and mesoscale. On the other hand, at shear rates of 240 s(-1), the effect of crystallization temperature was observed only at the nanoscale since no changes in meso-crystal sizes were observed at different temperatures. Crystallization under laminar shear promoted the growth of spherical crystalline particles at the mesoscale, called here "solid-lipid meso-particles". Crystallization under higher shear rates led to the formation of a weak network with low oil-binding capacity and promoted the asymmetric growth of nanoplatelets. In statically crystallized blends, nanoplatelets had an aspect ratio of -2, while in sheared blends this value increased significantly. These results revealed the existence of critical shear rate values above which strong alterations in the structure of the solid crystalline network took place. Shearing also affected the material's strength. Laminar shear induced a decrease in elastic modulus and yield stress values which was more pronounced at higher shear rate-temperature combinations. Shear-temperature combinations were successfully used to structure fats at the nano and mesoscale. PMID:23234167

Acevedo, Nuria C; Block, Jane M; Marangoni, Alejandro G

2012-01-01

193

Microstructure property relationships of urethane magnetorheological elastomers  

Science.gov (United States)

Studies on the structure of urethane magnetorheological elastomers (MREs), with respect to their magnetic and mechanical properties, are reported. MREs were obtained from a mixture of polyurethane gel and carbonyl-iron particles cured in a magnetic field of 100 and 300 mT. Samples with different numbers of particles (1.5, 11.5 and 33 vol%) were produced. The microstructure and magnetic properties of the obtained MREs were studied. Also, the displacement of the samples in an external magnetic field was examined using a specially designed experimental set-up. The influences of the number of ferromagnetic particles and their arrangement in relation to the external magnetic field were investigated. It was found that the microstructure of the MREs depends on the number of ferrous particles and the fabrication conditions. The orientation of the iron particles into aligned chains is possible for a lower volume content of the ferromagnetic fillers. The high carbonyl-iron volume content in the matrix leads to the formation of more complex microstructures, similar to three-dimensional lattices. The magnetic measurements also confirmed the existence of the microstructure anisotropy for the MREs with 1.5 and 11.5 vol% of iron particles. The structural and magnetic anisotropy has not been found in the MREs with 33 vol% of Fe. To evaluate the effect of the external magnetic field on the magnetorheological properties, the displacement under magnetic field, the compressive strength, and the rheological properties were measured. The experiments showed that both the particle content and the field strength used during curing have a significant effect on the microstructure of the MREs and, in consequence, on their properties.

Boczkowska, Anna; Awietjan, Stefan F.; Wroblewski, Rafal

2007-10-01

194

Fluorination of Metal Phthalocyanines: Single-Crystal Growth, Efficient N-Channel Organic Field-Effect Transistors, and Structure-Property Relationships  

OpenAIRE

The fluorination of p-type metal phthalocyanines produces n-type semiconductors, allowing the design of organic electronic circuits that contain inexpensive heterojunctions made from chemically and thermally stable p- and n-type organic semiconductors. For the evaluation of close to intrinsic transport properties, high-quality centimeter-sized single crystals of F16CuPc, F16CoPc and F16ZnPc have been grown. New crystal structures of F16CuPc, F16CoPc and F16ZnPc have been determined. Organic s...

Jiang, Hui; Ye, Jun; Hu, Peng; Wei, Fengxia; Du, Kezhao; Wang, Ning; Ba, Te; Feng, Shuanglong; Kloc, Christian

2014-01-01

195

Complementary structure sensitive and insensitive catalytic relationships.  

Science.gov (United States)

The burgeoning field of nanoscience has stimulated an intense interest in properties that depend on particle size. For transition metal particles, one important property that depends on size is catalytic reactivity, in which bonds are broken or formed on the surface of the particles. Decreased particle size may increase, decrease, or have no effect on the reaction rates of a given catalytic system. This Account formulates a molecular theory of the structure sensitivity of catalytic reactions based on the computed activation energies of corresponding elementary reaction steps on transition metal surfaces. Recent progress in computational catalysis, surface science, and nanochemistry has significantly improved our theoretical understanding of particle-dependent reactivity changes in heterogeneous catalytic systems. Reactions that involve the cleavage or formation of molecular pi-bonds, as in CO or N(2), must be distinguished from reactions that involve the activation of sigma-bonds, such as CH bonds in methane. The activation of molecular pi-bonds requires a reaction center with a unique configuration of several metal atoms and step-edge sites, which can physically not be present on transition metal particles less than 2 nm. This is called class I surface sensitivity, and the rate of reaction will sharply decrease when particle size decreases below a critical size. The activation of sigma chemical bonds, in which the activation proceeds at a single metal atom, displays a markedly different size relationship. In this case, the dependence of reaction rate on coordinative unsaturation of reactive surface atoms is large in the forward direction of the reaction, but the activation energy of the reverse recombination reaction will not change. Dissociative adsorption with cleavage of a CH bond is strongly affected by the presence of surface atoms at the particle edges. This is class II surface sensitivity, and the rate will increase with decreasing particle size. Reverse reactions such as hydrogenation typically show particle-size-independent behavior. The rate-limiting step for these class III reactions is the recombination of an adsorbed hydrogen atom with the surface alkyl intermediate and the formation of a sigma-type bond. Herein is our molecular theory explaining the three classes of structure sensitivity. We describe how reactions with rates that are independent of particle size and reactions with a positive correlation between size and rate are in fact complementary phenomena. The elucidation of a complete theory explaining the size dependence of transition metal catalysts will assist in the rational design of new catalytic systems and accelerate the evolution of the field of nanotechnology. PMID:18986176

Van Santen, Rutger A

2009-01-20

196

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

OpenAIRE

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

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

2012-01-01

197

Discovering Relationships between Data Structures and Algorithms  

Directory of Open Access Journals (Sweden)

Full Text Available There are numerous of program code resources on the web which are solutions to programming problems on online judges. These program code resources are not organized for students to learn data structures and algorithms although they contain much knowledge of data structures and algorithms. For this reason, we propose an approach to organize the program code resources together with the programming problems systematically in terms of algorithms and data structures. This approach is based on the discovery of associate relationships between data structures and algorithms by applying ontology techniques. 1073 program codes on the web which are solutions to 480 problems distributed on online judges were mined in our experiment to discover the relationships between the data structures and algorithms used in the program codes. With the discovered relationships, the program codes and the corresponding problems were organized into learning materials in terms of algorithms and data structures. We believe that it would be useful for students to learn the programming knowledge.

Guojin Zhu

2013-07-01

198

Structure-property relationship of bifunctional MnO2 nanostructures: highly efficient, ultra-stable electrochemical water oxidation and oxygen reduction reaction catalysts identified in alkaline media.  

Science.gov (United States)

Manganese oxides of various structures (?-, ?-, and ?-MnO2 and amorphous) were synthesized by facile methods. The electrocatalytic properties of these materials were systematically investigated for catalyzing both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) in alkaline media. Extensive characterization was correlated with the activity study by investigating the crystal structures (XRD, HRTEM), morphologies (SEM), porosities (BET), surfaces (XPS, O2-TPD/MS), and electrochemical properties (Tafel analysis, Koutechy-Levich plots, and constant-current electrolysis). These combined results show that the electrocatalytic activities are strongly dependent on the crystallographic structures, and follow an order of ?-MnO2 > AMO > ?-MnO2 > ?-MnO2. Both OER studies and ORR studies reveal similar structure-determined activity trends in alkaline media. In the OER studies, ?-MnO2 displays an overpotential of 490 mV compared to 380 mV shown by an Ir/C catalyst in reaching 10 mA cm(-2). Meanwhile, ?-MnO2 also exhibits stability for 3 h when supplying a constant current density of 5 mA cm(-2). This was further improved by adding Ni(2+) dopants (ca. 8 h). The superior OER activity was attributed to several factors, including abundant di-?-oxo bridges existing in ?-MnO2 as the protonation sites, analogous to the OEC in PS-II of the natural water oxidation system; the mixed valencies (AOS = 3.7); and the lowest charge transfer resistances (91.8 ?, ? = 430 mV) as revealed from in situ electrochemical impedance spectroscopy (EIS). In the ORR studies, when reaching 3 mA cm(-2), ?-MnO2 shows 760 mV close to 860 mV for the best ORR catalyst (20% Pt/C). The outstanding ORR activity was due to the strongest O2 adsorption capability of ?-MnO2 suggested by temperature-programmed desorption. As a result, this discovery of the structure-related electrocatalytic activities could provide guidance in the further development of easily prepared, scalable, and low-cost catalysts based on metal oxides and their derivatives. PMID:25058174

Meng, Yongtao; Song, Wenqiao; Huang, Hui; Ren, Zheng; Chen, Sheng-Yu; Suib, Steven L

2014-08-13

199

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

Science.gov (United States)

This article reports on a comprehensive study of the two-photon absorption (2PA) properties of six novel push-pull octupolar triarylamine compounds as a function of the nature of the electron-withdrawing groups. These compounds present an octupolar structure consisting of a triarylamine core bearing two 3,3'-bis(trifluoromethyl)phenyl arms and a third group with varying electron-withdrawing strength (H GM for the lowest energy band and from 95 up to 270 GM for the highest energy band. The results were elucidated based on the large changes in the transition and permanent dipole moments and in terms of (i) EWG strength, (ii) degree of donor-acceptor charge transfer and (iii) electronic coupling between the arms. The 2PA results were eventually supported and confronted with theoretical DFT calculations of the two-photon transition oscillator strengths.

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

2014-03-01

200

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

Science.gov (United States)

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. PMID:23809846

Boronová, Katarína; Lehotay, Jozef; Hrobo?ová, Katarína; Armstrong, Daniel W

2013-08-01

201

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

Directory of Open Access Journals (Sweden)

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

Nadia A. Mohamed

2012-11-01

202

Novel self-dyed wholly aromatic polyamide-hydrazides covalently bonded with azo groups in their main chains: 1. Structure-property relationships.  

Science.gov (United States)

Twelve novel intrinsically colored wholly aromatic azopolyamide-hydrazides containing various proportions of para- and meta-phenylene units were successfully synthesized by a low temperature (-10 °C) solution polycondensation reaction of either 4-amino-3-hydroxybenzhydrazide (4A3HBH) or 3-amino-4-hydroxybenzhydrazide (3A4HBH) with an equimolar amount of either 4,4'-azodibenzoyl chloride (4,4'ADBC), 3,3'-azodibenzoyl chloride (3,3'ADBC), or mixtures of various molar ratios of 4,4'ADBC and 3,3'ADBC in anhydrous N,N-dimethyl acetamide (DMAc) containing 3% (wt/v) LiCl as a solvent. The structures of the polymers were proven by elemental analysis, FTIR, ¹H- and ¹³C-NMR spectroscopy. The polymers’ properties were strongly affected by their various structures. The intrinsic viscosities of the polymers were ranged from 0.7 to 4.75 dL g?¹ and increased with the para-phenylene units content. The polymers are partially soluble in DMAc, dimethyl formamide (DMF) and N-methyl-2-pyrrolidone (NMP). Their solubility increases with the introduction of meta-phenylene moieties into the polymer chains. The polymers exhibit a great affinity for water sorption. Their hydrophilicity increases as a function of the content of meta-phenylene rings incorporated into the polymer. Mechanical properties of the polymer films are improved markedly by substitution of para-phenylene units for meta-phenylene units. The completely para-oriented type polymer has the best thermal and thermo-oxidative stability relative to those of the other polymers. PMID:23183888

Mohamed, Nadia A; Sammour, Mohammad H; Elshafai, Ali M

2012-01-01

203

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

Science.gov (United States)

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

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

2014-03-28

204

Investigation of structure-property relationships of polyisobutylene-based biomaterials: Morphology, thermal, quasi-static tensile and long-term dynamic fatigue behavior.  

Science.gov (United States)

This study examines the morphology, thermal, quasi-static and long-term dynamic creep properties of one linear and three arborescent polyisobutylene-based block copolymers (L_SIBS31, D_IBS16, D_IBS27 and D_IBS33). Silicone rubber, a common biopolymer, was considered as a benchmark material for comparison. A unique hysteretic testing methodology of Stepwise Increasing Load Test (SILT) and Single Load Test (SLT) was used in this study to evaluate the long-term dynamic fatigue performance of these materials. Our experimental findings revealed that the molecular weight of polyisobutylene (PIB) and polystyrene (PS) arms [M(n)(PIB(arm)) and M(n)(PS(arm))], respectively had a profound influence on the nano-scaled phase separation, quasi-static tensile, thermal transition, and dynamic creep resistance behaviors of these PIB-based block copolymers. However, silicone rubber outperformed the PIB-based block copolymers in terms of dynamic creep properties due to its chemically crosslinked structure. This indicates a need for a material strategy to improve the dynamic fatigue and creep of this class of biopolymers to be considered as alternative to silicone rubber for biomedical devices. PMID:22520432

Götz, C; Lim, G T; Puskas, J E; Altstädt, V

2012-06-01

205

Structure-activity relationships and drug allergy.  

Science.gov (United States)

Structure-activity relationships (SARs) refer to the relation between chemical structure and pharmacologic activity for a series of compounds. Since the pioneering work of Crum-Brown and Fraser in 1868, they have been increasingly used in the pharmaceutical, chemical and cosmetic industries, especially for drug and chemical design purposes. Structure-activity relationships may be based on various techniques, ranging from considerations of similarity or diversity of molecules to mathematical relationships linking chemical structures to measured activities, the latter being referred to as quantitative SAR or QSAR. This review aims at briefly reviewing the history of SARs and highlighting their interest in delayed and immediate drug allergy using selected examples from the literature. Studies of SAR are commonly conducted in the area of contact dermatitis, a delayed hypersensitivity reaction, to determine the allergenic potential of a given compound without animal testing. In immediate, immunoglobulin E-mediated drug hypersensitivity, this kind of approach remains rather confidential. It has been mainly applied to neuromuscular blocking drugs (muscle relaxants) and betalactam antibiotics (penicillins, cephalosporins). This review shows that SARs can prove useful to (i) predict the allergenic potential of a chemical or a drug, (ii) help identify putative antigenic determinants for each patient or small group of patients sharing the same cross-reactivity pattern, and (iii) predict the likelihood of adverse reactions to related molecules and select safe alternatives. PMID:22299766

Hasdenteufel, Frederic; Luyasu, Samuel; Hougardy, Nicolas; Fisher, Malcolm; Boisbrun, Michel; Mertes, Paul-Michel; Kanny, Gisele

2012-02-01

206

Structure-property relationships of soluble poly(2,5-dibutoxyethoxy-1,4-phenylene-alt-2,5-thienylene) (PBuPT) for organic-optoelectronic devices  

Science.gov (United States)

In this work, we have analyzed the vibrational, optical and emission properties of soluble copolymer denoted poly(2,5-di-butoxyethoxy-1,4-phenylene-alt-2,5-thienylene) (PBuPT) by combining experimental and theoretical studies. Extrapolated Ionization Potentials (IPs), Electron Affinities (EAs) and energy gaps were determined employing Density Functional Theory (DFT) method. Theoretical analyses have been performed in order to understand deeply the interesting role played by the intra-molecular S⋯O interactions in determining the planarity of the copolymer. Further, an intra-molecular charge transfer for the copolymer has been proposed through the alternating donor-acceptor conjugated systems. In addition, vibrational, optical and emission spectra of three repeat units model compound have been simulated and compared to the experiments. Based on these results, we have described attentively the structure-property relationships of those samples which could be exploited as an active layer in organic optoelectronic devices.

Ayachi, S.; Ghomrasni, S.; Bouachrine, M.; Hamidi, M.; Alimi, K.

2013-03-01

207

RELATIONSHIP BETWEEN BOARD STRUCTURE AND CONSERVATISM  

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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

2011-10-01

208

Structure-activity relationships of the nikkomycins.  

Science.gov (United States)

The structure-activity relationships of different nikkomycins were studied to evaluate the structural requirements for a potent chitin synthase inhibitor. We investigated the transport of the nikkomycins via the peptide transport system of the yeast Yarrowia lipolytica and determined the kinetic parameters for nikkomycin Z uptake [Km = 24 microM, Vmax = 2.2 nmol min-1 (mg dry wt)-1]. We demonstrated that the beta-methyl group of the N-terminal amino acid of dipeptide nikkomycins protects the molecule against peptidase activity in crude cell-extracts of different fungi. Furthermore, the relationship between inhibition constants for chitin synthase, transport of the nikkomycins via the peptide transport system, susceptibility to degradation by cellular proteases and whole-cell activity of the nikkomycins are discussed. PMID:1955867

Decker, H; Zähner, H; Heitsch, H; König, W A; Fiedler, H P

1991-08-01

209

Porous Materials - Structure and Properties  

DEFF Research Database (Denmark)

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

Nielsen, Anders

1997-01-01

210

RELATIONSHIP BETWEEN BOARD STRUCTURE AND CONSERVATISM  

OpenAIRE

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...

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

2011-01-01

211

Structure-induction versus structure-toxicity relationships for polychlorinated biphenyls and related aromatic hydrocarbons.  

OpenAIRE

A comparison of the structure-induction (involving rat and mouse Ah receptor binding) and structure-toxicity (in vivo guinea pig toxicity) relationships suggests that two receptors with structurally distinct binding properties may be involved. This is supported by demonstration of potentiated toxicity through a mechanism believed to involve the Ah receptor as a site of loss with respect to toxicity. Theoretical and working models are proposed for these separate receptors to aid in the search ...

Mckinney, J. D.; Chae, K.; Mcconnell, E. E.; Birnbaum, L. S.

1985-01-01

212

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

Directory of Open Access Journals (Sweden)

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

Saldana D.A.

2013-06-01

213

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-05-15

214

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

Science.gov (United States)

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

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

2014-01-01

215

THE USE OF STRUCTURE-ACTIVITY RELATIONSHIPS IN INTEGRATING THE CHEMISTRY AND TOXICOLOGY OF ENDOCRINE DISRUPTING CHEMICALS  

Science.gov (United States)

Structure activity relationships (SARs) are based on the principle that structurally similar chemicals should have similar biological activity. SARs relate specifically-defined toxicological activity of chemicals to their molecular structure and physico-chemical properties. To de...

216

Structural relationships and vasorelaxant activity of monoterpenes  

Directory of Open Access Journals (Sweden)

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

Cardoso Lima Tamires

2012-09-01

217

Animal silks: their structures, properties and artificial production.  

Science.gov (United States)

This feature article reviews recent progress in the understanding of the hierarchically organized structures, the perfectly balanced mechanical properties and the structure-property relationship of the natural animal silk fibres, as well as the experimental attempts to fabricate man-made silk fibres by means of wet spinning, dry spinning, electrospinning and transgenosis. PMID:19865641

Fu, Chengjie; Shao, Zhengzhong; Fritz, Vollrath

2009-11-21

218

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

219

Structural Relationships and Vasorelaxant Activity of Monoterpenes  

Directory of Open Access Journals (Sweden)

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

Tamires Cardoso Lima

2012-09-01

220

Structure-cytotoxicity relationships for dietary flavonoids  

DEFF Research Database (Denmark)

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

Breinholt, V.; Dragsted, L.O.

1998-01-01

221

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

Science.gov (United States)

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

Alston, William B.

1992-01-01

222

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

Directory of Open Access Journals (Sweden)

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

Kevin Magniez

2013-08-01

223

[Structural activity relationship approaches for assessing genotoxicity].  

Science.gov (United States)

The focus of the latest legislative and governmental efforts is to establish simple screening tools for identifying those chemicals most likely to cause adverse effects without experimental testing of all chemicals of regulatory concern. The use of structure-activity relationship (SAR) models is a powerful in silico technique that should be considered for prioritizing chemicals for subsequent experimental verification. Because carcinogenicity and genotoxicity are among the toxicological endpoints that pose the highest concern for human health, efforts in SAR models for them have been much more pronounced than for any of the other human health end points. This review paper overviews the historical background of SAR models for predicting carcinogenicity and genotoxicity, the current status of capacity and usefulness of some in vitro genotoxicity SAR models, and their perspective. PMID:21381394

Honma, Masamitsu

2010-01-01

224

Structure-function-property-design interplay in biopolymers: spider silk.  

Science.gov (United States)

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. PMID:23962644

Tokareva, Olena; Jacobsen, Matthew; Buehler, Markus; Wong, Joyce; Kaplan, David L

2014-04-01

225

Solution processable benzooxadiazole and benzothiadiazole based D-A-D molecules with chalcogenophene: field effect transistor study and structure property relationship.  

Science.gov (United States)

We present here the physicochemical characterization of a series of D-A-D type molecules which comprise benzooxadiazole (BDO) and benzothiadiazole (BDT) core symmetrically linked to two aromatic-heterols (furan (F), thiophene (T) and selenophene (Se)) at 4 and 7-positions. The molecular structures of four compounds 2 (T-BDO-T), 3 (Se-BDO-Se), 5 (T-BDT-T), and 6 (Se-BDT-Se) were determined by single-crystal X-ray diffraction. The combination of chalcogen atoms of benzochalcogenadiazole and chalcogenophene in D-A-D molecules has significant impact on their molecular packing in crystal structures. Structural analyses and theoretical calculations showed that all the molecules are nearly planar. Crystal structures of 2, 3, 5, and 6 showed significant short range interactions such as ?···?, CH···?, S···?, Se···?, N···H, O···H, S···H, Se···H, S···O, and Se···N interactions, which influence crystal packing and orientation of the capped aromatic-heterol rings with respect to the central BDO or BDT unit. The ?-stacking interactions have been observed via intermolecular overlap of the donor with acceptor units of the adjacent molecules which facilitate the charge transport process. Good thermal stability and solubility in common organic solvents make them good candidate for flexible electronics. Interestingly, the molecules 2, 3, and 6 have the propensity to form ordered crystallites when sheared during the drying process in the thin films. Devices based on these solution processable all organic FETs demonstrated hole mobility as high as 0.08 cm(2) V(-1) s(-1) and Ion/Ioff ratio of 10(4). PMID:24237045

Pati, Palas Baran; Senanayak, Satyaprasad P; Narayan, K S; Zade, Sanjio S

2013-12-11

226

Relationship between the structure and the DNA binding properties of diazoniapolycyclic duplex- and triplex-DNA binders: efficiency, selectivity, and binding mode.  

Science.gov (United States)

The association of dicationic polycyclic ligands, namely, four diazoniapentaphene derivatives, three diazoniaanthra[1,2-a]anthracenes, diazoniahexaphene, and a partly saturated hydroxy-substituted diazoniapentaphene with double-stranded and triple-helical DNA, was investigated by spectrophotometric and viscosimetric titrations, CD and LD spectroscopy, DNA melting experiments, and molecular modeling studies. All experimental and theoretical data reveal an intercalative DNA-binding mode of the diazoniapentaphenes and diazoniaanthra[1,2-a]anthracenes; the latter have approximately 10-fold higher affinity for the DNA duplex. CD spectroscopic investigations and molecular modeling studies show that only one azonianaphthalene part of the ligand is intercalated between the DNA base pairs, whereas the remaining part of the ligand points outside the intercalation pocket. In contrast, the diazoniahexaphene is a DNA groove binder, which binds selectively to [poly(dAdT)]2. At low ligand-to-DNA ratios (r 0.2. Studies of the interaction of diazoniapolycyclic ions with triplex DNA reveal a preferential binding of both diazoniapentaphenes and diazoniaanthra[1,2-a]anthracenes to the triplex and stabilization thereof. These properties are more pronounced in the case of the hexacyclic diazoniaanthra[1,2-a]anthracenes; however, the diazoniahexaphene shows no preferential binding to the triplex. The DNA binding properties of the diazoniapentaphene derivatives remain essentially the same upon variation of the positions of nitrogen atoms or substitution with methyl groups. In contrast, the interactions of the diazoniaanthra[1,2-a]anthracence isomers with triplex DNA are slightly different. Notably, the 14a,16a-diazoniaanthra[1,2-a]anthracene is among the most efficient triplex stabilizers, with a 9-fold larger binding affinity for the triplex than for the DNA duplex. Moreover, the diazoniapentaphene and diazoniaanthra[1,2-a]anthracene derivatives represent the first examples of triplex-DNA binders that do not require additional aminoalkyl side chains for efficient triplex stabilization. PMID:17939688

Basili, Serena; Bergen, Anna; Dall'Acqua, Francesco; Faccio, Anita; Granzhan, Anton; Ihmels, Heiko; Moro, Stefano; Viola, Giampietro

2007-11-01

227

The Origin of Sulfur Tolerance in Supported Platinum Catalysts: The Relationship between Structural and Catalytic Properties in Acidic and Alkaline Pt/LTL.  

OpenAIRE

The reactivity, structure, and sulfur tolerance is compared for platinum supported on acidic and alkaline LTL zeolite. In the absence of sulfur, EXAFS spectroscopy indicates that small metallic platinum particles of approximately 6 to 14 atoms/cluster are present. The TOF for neopentane hydrogenolysis and isomerization is ca 100 times higher on the acidic LTL due to the metal-support interaction. Saturation of the platinum by H{2}S, results in the formation of surface Pt-S bonds with a bond l...

Koningsberger, D. C.; Miller, J. T.

1996-01-01

228

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-10-25

229

Structure-activity relationship studies: study of the analgesic properties of a series of synthesized esters of 3- (4-benzyl-1-piperazinyl) 1-phenylpropanols.  

Science.gov (United States)

Four previously stynthesized derivatives of 3- (4-benzyl-1-piperazinyl)-1-phenylpropanol were screened for analgesic activity in albino mice using a variation of the Eddy and Lambach hot plate method. The result showed that the most significant analgesic effect was elicited by the parent secondary 3-piperazinylpropanol, namely 3-(4-benzyl-1-piperazinyl)-1-phenylpropanol. Its esterification products with propanoyl, benzoyl and phenylacetyl chlorides exhibited reduced analgesic properties. The percent maximum protection against thermal pain produced by Aspirin (71.43%) was twice as high as that produced by the most active of the four derivatives (43.65%). The analgesic effect of the compounds was dose dependent. From acute toxicity studies in mice, the LD50 values were estimated to be in range of moderate toxicity (89.74 to 243 mg/kg). The most active of the compounds studied, namely, 3-(4-benzyl-1-piperazinyl-1-phenylpropanols, was also found to be the most toxic. The margin between its safe doses and its LD50 (89.74 mg/kg) was found to be very narrow. Esterification of the 3-(4-benzyl-1-piperazinyl)-1-phenylpropanol led to decrease in its analgesic activity and also a decrease in its toxicity. PMID:15200069

Osadebe, P O

2004-04-01

230

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.  

Science.gov (United States)

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. PMID:23629009

Hussain, Maqbool; El-Shafei, Ahmed; Islam, Ashraful; Han, Liyuan

2013-06-01

231

Quasicrystals - Discovery, Structure and Properties  

Directory of Open Access Journals (Sweden)

Full Text Available Quasicrystals are solid materials the structures of which can have crystallographically forbidden symmetries, e.g. of the fifth order, and do not have the translational invariance charactistic for classical crystals. Their properties are quite different from those of classical crystals. Although all being metals, they are poor conductors of heat and electricity and are hard and brittle. Their structures can be described as quasiperiodic. The mathematical description of quasiperiodicity predates the discovery of quasicrystals and has greatly facilitated the study and the interpretation of the quasicrystals’ structures and properties. This paper provides an overview of the most basic results of the study of quasicrystals and quasiperiodicity.

Stilinovi?, V.

2012-07-01

232

Relationships between structural and electrical properties in mixed conductors duplex materials in the ZrO2-Y2O3-TiO2 ternary system  

Science.gov (United States)

Duplex materials constituted by 0.50 mol titania-doped yttria-stabilized zirconia (YSZ) and 0.50 mol titania-doped yttria-tetragonal zirconia polycrystalline (YTZP) solid solutions in the ZrO2-Y2O3-TiO2 ternary system can be obtained using different processing strategies. In this study, different amounts of TiO2 dopant and different sintering times have been used for the preparation of the duplex materials: Doping YSZ with 10 mol% of TiO2 and sintering in air for 8 h (10Ti8h) and doping YSZ with 15 mol% of TiO2 and sintering in air for 2 h (15Ti2h) are both successful routes to obtain duplex materials. If we compare the field emission scanning electron microscopy-energy dispersive x-ray analyses of each cubic and each tetragonal solid solution of the two duplex materials, we conclude that the composition of each phase is different from each other, as was expected. The total ionic conductivity of both duplex samples is strongly reduced with respect to that of YSZ, and this reduction increases with the Ti content. In addition, the activation energy for ionic migration in 10Ti8h and 15Ti2h is lower than that for YSZ but higher than that for YTZP, as expected in terms of the relative amount of both YSZ and YTZP fractions in the materials. X-ray absorption spectroscopy (XAS) results, both x-ray absorption near-edge structure and extended x-ray absorption fine structure, show that Ti is sixfold coordinated in both the cubic and tetragonal phases of the duplex materials, departing from the eightfold coordination expected if a simple substitution at the Zr sites would take place. The XAS results also point out that the ability of Ti to trap oxygen vacancies in the cubic phase increases as Ti content does, in agreement with the electrical conductivity behavior, which cannot be accounted for in terms of a dilution effect.

Colomer, M. T.; Díaz-Moreno, S.; Boada, R.; Maczka, M.; Chaboy, J.

2014-03-01

233

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-03-15

234

Relationships between properties and functional targets of Chinese herbs  

Directory of Open Access Journals (Sweden)

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

Bin Xiao

2011-07-01

235

Relationship between structural characteristics and photoluminescent properties of (La{sub 1-x}Eu{sub x}){sub 2}M{sub 2}O{sub 7} (M=Zr, Hf, Sn) pyrochlores  

Energy Technology Data Exchange (ETDEWEB)

Eu-doped pyrochlores, La{sub 2}M{sub 2}O{sub 7} (M=Zr, Hf, Sn), were synthesized by solid-state reaction at a temperature range of 1473 and 1673 K, and their structures and optical properties were characterized by X-ray Rietveld analysis, field emission scanning electron microscope (FE-SEM), and photoluminescent spectroscopy. The Rietveld analysis indicated that the distortion of the (EuO{sub 8}){sup n-} scalenohedra increased with decreasing ionic radii of the M{sup 4+} ion, and the crystallinity increased with the sintering temperature. The splitting width of {sup 5}D{sub 0}-{sup 7}F{sub 1} transition of Eu{sup 3+} ions increased with the distortion of the (EuO{sub 8}){sup n-} scalenohedra. The luminescent intensity ratio of magnetic dipole transitions to electronic dipole transitions decreased with the crystallinity, and the chromaticity changed from deep-red to orange-red. The relationship between the chromaticity of phosphors and the crystallinity was clarified, and the control of crystallinity is an important factor that provides phosphors with required chromaticity.

Hirayama, Masaaki [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan); Sonoyama, Noriyuki [Graduate School of Engineering, Environmental Technology and Urban Planning, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, 466-8555 (Japan); Yamada, Atsuo [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan); Kanno, Ryoji [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)], E-mail: kanno@echem.titech.ac.jp

2008-11-15

236

Use of quantitative-structure property relationship (QSPR) and artificial neural network (ANN) based approaches for estimating the octanol-water partition coefficients of the 209 chlorinated trans-azobenzene congeners.  

Science.gov (United States)

Polychlorinated azobenzenes (PCABs) can be found as contaminant by products in 3,4-dichloroaniline and its derivatives and in the herbicides Diuron, Linuron, Methazole, Neburon, Propanil and SWEP. Trans congeners of PCABs are physically and chemically more stable and so are environmentally relevant, when compared to unstable cis congeners. In this study, to fulfill gaps on environmentally relevant partitioning properties of PCABs, the values of n-octanol/water partition coefficients (log K(OW)) have been determined for 209 congeners of chloro-trans-azobenzene (Ct-AB) by means of quantitative structure-property relationship (QSPR) approach and artificial neural networks (ANN) predictive ability. The QSPR methods used based on geometry optimalization and quantum-chemical structural descriptors, which were computed on the level of density functional theory (DFT) using B3LYP functional and 6-311++G basis set in Gaussian 03 and of the semi-empirical quantum chemistry method (PM6) of the molecular orbital package (MOPAC). Polychlorinated dibenzo-p-dioxins (PCDDs), -furans (PCDFs) and -biphenyls (PCBs), to which PCABs are related, were reference compounds in this study. An experimentally obtained data on physical and chemical properties of PCDD/Fs and PCBs were reference data for ANN predictions of log K(OW) values of Ct-ABs in this study. Both calculation methods gave similar results in term of absolute log K(OW) values, while the models generated by PM6 are considered highly efficient in time spent, when compared to these by DFT. The estimated log K(OW) values of 209 Ct-ABs varied between 5.22-5.57 and 5.45-5.60 for Mono-, 5.56-6.00 and 5.59-6.07 for Di-, 5.89-6.56 and 5.91-6.46 for Tri-, 6.10-7.05 and 6.13-6.80 for Tetra-, 6.43-7.39 and 6.48-7.14 for Penta-, 6.61-7.78 and 6.98-7.42 for Hexa-, 7.41-7.94 and 7.34-7.86 for Hepta-, 7.99-8.17 and 7.72-8.20 for Octa-, 8.35-8.42 and 8.10-8.62 for NonaCt-ABs, and 8.52-8.60 and 8.81-8.83 for DecaCt-AB. These log K(OW) values shows that Ct-ABs are compounds of relatively low environmental mobility (log K(OW) > 4.5) and of significant bioaccumulation potential. PMID:22251211

Wilczy?ska-Piliszek, Agata J; Piliszek, S?awomir; Falandysz, Jerzy

2012-01-01

237

Structural Analysis of Laplacian Spectral Properties in Complex Electric Grids  

CERN Document Server

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

Preciado, Victor M; Verghese, George C

2011-01-01

238

Some properties of galaxy structures  

OpenAIRE

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

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

2011-01-01

239

Structural properties of 3-dimensional carbon clusters  

International Nuclear Information System (INIS)

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

240

Relationship between the thermal properties and optical emission spectra of the KXeN polyatomic exciplexes  

Science.gov (United States)

The geometrical structures and optical emission spectra of the K(5S)XeN polyatomic exciplexes are calculated as functions of temperature in the range from 1 to 200 K. The relationships between the emission spectra and the thermal properties are investigated by use of the Metropolis Monte Carlo method. The peak energy values and the linewidths of the transition energy of the calculated emission light spectra of individual exciplexes reflect the structure and the thermal properties of each polyatomic exciplex. As the result of a detailed examination of relationships between the geometrical structure and the optical emission spectra of the KXe3, KXe7, KXe8, and KXe9 polyatomic exciplexes, a change in the structure of a given polyatomic exciplex, or the dissociation into a smaller cluster, can be detected by the discontinuities in the peak energy of the emission light and the linewidth as functions of temperature.

Fujisaki, Akihiro

2002-09-01

241

Structural changes in latosols of the cerrado region: I - relationships between soil physical properties and least limiting water range / Alterações estruturais de latossolos representativos da região do cerrado: I - relações entre propriedades físicas do solo e intervalo hídrico ótimo  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Apesar do elevado potencial agrícola dos Latossolos da região do Cerrado brasileiro, quando inseridos no processo produtivo sob sistemas de manejo inadequados, o seu espaço poroso pode ser seriamente alterado, levando à sua rápida degradação. Como consequência, tem-se observado aceleração do process [...] o erosivo e assoreamento dos mananciais associados na paisagem. Dessa forma, o presente trabalho teve por objetivo avaliar as alterações estruturais de Latossolos do município de Rio Verde, GO, por meio da caracterização do intervalo hídrico ótimo (IHO), e as relações entre IHO e demais propriedades físicas desses solos. O estudo foi conduzido utilizando-se amostras coletadas no horizonte Bw de cinco Latossolos oxídicos representativos da variabilidade textural observada nos Latossolos ocorrentes no bioma Cerrado. Foram determinados o IHO e os atributos físico-hídricos dos solos em diversos estados de compactação induzidos por compressão uniaxial. Os resultados indicaram que a compactação do solo resultou desde benefícios ao crescimento das plantas, relacionados ao aumento na retenção de água, até condições de severas restrições às suas funções edáficas, sendo observadas relações inversas entre o conteúdo de argila e os valores de densidade do solo (Ds) nas diversas condições estruturais. A Ds correspondente à macroporosidade crítica do solo (DscMAC) foi mais restritiva ao manejo sustentável dos Latossolos estudados que a Ds crítica correspondente ao IHO (DscIHO). A maior compactação permissível observada nesses Latossolos oxídicos deve-se à elevada porosidade de aeração conferida pela estrutura do tipo granular. Abstract in english The agricultural potential of Latosols of the Brazilian Cerrado region is high, but when intensively cultivated under inappropriate management systems, the porosity can be seriously reduced, leading to rapid soil degradation. Consequently, accelerated erosion and sedimentation of springs and creeks [...] have been observed. Therefore, the objective of this study was to evaluate structural changes of Latosols in Rio Verde, Goiás, based on the Least Limiting Water Range (LLWR), and relationships between LLWR and other physical properties. Soil samples were collected from the B horizons of five oxidic Latosols representing the textural variability of the Latosols of the Cerrado biome. LLWR and other soil physical properties were determined at various soil compaction degrees induced by uniaxial compression. Soil compaction caused effects varying from enhanced plant growth due to higher water retention, to severe restriction of edaphic functions. Also, inverse relationships were observed between clay content and bulk density values (Bd) under different structural conditions. Bd values corresponding to critical soil macroporosity (BdcMAC) were more restrictive to a sustainable use of the studied Latosols than the critical Bd corresponding to LLWR (BdcLLWR). The high tolerable compression potential of these oxidic Latosols was related to the high aeration porosity associated to the granular structure.

Eduardo da Costa, Severiano; Geraldo César de, Oliveira; Moacir de Souza, Dias Júnior; Katia Aparecida de Pinho, Costa; Fabiano Guimarães, Silva; Silvio Marcos, Ferreira Filho.

2011-06-01

242

Effective connectivity profile: a structural representation that evidences the relationship between protein structures and sequences.  

Science.gov (United States)

The complexity of protein structures calls for simplified representations of their topology. The simplest possible mathematical description of a protein structure is a one-dimensional profile representing, for instance, buriedness or secondary structure. This kind of representation has been introduced for studying the sequence to structure relationship, with applications to fold recognition. Here we define the effective connectivity profile (EC), a network theoretical profile that self-consistently represents the network structure of the protein contact matrix. The EC profile makes mathematically explicit the relationship between protein structure and protein sequence, because it allows predicting the average hydrophobicity profile (HP) and the distributions of amino acids at each site for families of homologous proteins sharing the same structure. In this sense, the EC provides an analytic solution to the statistical inverse folding problem, which consists in finding the statistical properties of the set of sequences compatible with a given structure. We tested these predictions with simulations of the structurally constrained neutral (SCN) model of protein evolution with structure conservation, for single- and multi-domain proteins, and for a wide range of mutation processes, the latter producing sequences with very different hydrophobicity profiles, finding that the EC-based predictions are accurate even when only one sequence of the family is known. The EC profile is very significantly correlated with the HP for sequence-structure pairs in the PDB as well. The EC profile generalizes the properties of previously introduced structural profiles to modular proteins such as multidomain chains, and its correlation with the sequence profile is substantially improved with respect to the previously defined profiles, particularly for long proteins. Furthermore, the EC profile has a dynamic interpretation, since the EC components are strongly inversely related with the temperature factors measured in X-ray experiments, meaning that positions with large EC component are more strongly constrained in their equilibrium dynamics. Last, the EC profile allows to define a natural measure of modularity that correlates with the number of domains composing the protein, suggesting its application for domain decomposition. Finally, we show that structurally similar proteins have similar EC profiles, so that the similarity between aligned EC profiles can be used as a structure similarity measure, a property that we have recently applied for protein structure alignment. The code for computing the EC profile is available upon request writing to ubastolla@cbm.uam.es, and the structural profiles discussed in this article can be downloaded from the SLOTH webserver http://www.fkp.tu-darmstadt.de/SLOTH/. PMID:18536008

Bastolla, Ugo; Ortíz, Angel R; Porto, Markus; Teichert, Florian

2008-12-01

243

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

244

Structure activity relationships of novel antiepileptic drugs.  

Science.gov (United States)

Despite notable success over years in the discovery and development of new antiepileptic drugs (AEDs), about 30-40% of the patients are resistant to drug treatment. There is a still significant need to develop novel AEDs that demonstrate superior efficacy, broad spectrum of activities and good safety profile. The synaptic vesicle glycoprotein 2A (SV2A), ?-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA-R) and voltage-gated potassium channels (KCNQ2/Q3) are clinically validated as new molecular targets for epilepsy. The discovery of SV2A as a target for levetiracetam, 2,3-benzodiazepine GYKI 52466 as a non-competitive AMPA-R antagonist and retigabine as a KCNQ2/Q3 channels activator provided a rational basis to develop novel AEDs. The optimization of SV2A binding affinity of levetiracetam led to the discovery of novel high affinity SV2A ligands that displayed superior efficacy and protective index in animal models of epilepsy. The high-throughput screening (HTS) and medicinal chemistry efforts yielded many non-competitive AMPA-R antagonists of which perampanel was recently approved as a first-in-a new class. The efficacy and lack of sub-type selectivity of retigabine prompted many research efforts to discover several potent and selective KCNQ2/Q3 channel activators of distinct chemical scaffolds that are at various stages of clinical development. Despite the known role of galanin and galanin receptor (Gal-R) in epilepsy over a decade, development of potent and brainpenetrant Gal-R agonists is very challenging. The discovery of selective Gal-R2 positive allosteric modulator, CYM 2503, offers a valuable and an alternative approach. The review focuses on the available structure-activity relationships and preclinical efficacy of novel antiepileptic compounds that are distinct from most of the approved AEDs, specifically SV2A ligands, non-competitive AMPA-R antagonists, KCNQ2/Q3 channels activators and Gal-R modulators. PMID:24251563

Mittapalli, G K; Roberts, E

2014-01-01

245

Distributing Correlation Coefficients of Linear Structure-Activity/Property Models  

Directory of Open Access Journals (Sweden)

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

Sorana D. BOLBOACA

2011-12-01

246

The structure-mechanical relationship of palm vascular tissue.  

Science.gov (United States)

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

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

2014-08-01

247

Native Cellulose: Structure, Characterization and Thermal Properties  

Directory of Open Access Journals (Sweden)

Full Text Available In this work, the relationship between cellulose crystallinity, the influence of extractive content on lignocellulosic fiber degradation, the correlation between chemical composition and the physical properties of ten types of natural fibers were investigated by FTIR spectroscopy, X-ray diffraction and thermogravimetry techniques. The results showed that higher extractive contents associated with lower crystallinity and lower cellulose crystallite size can accelerate the degradation process and reduce the thermal stability of the lignocellulosic fibers studied. On the other hand, the thermal decomposition of natural fibers is shifted to higher temperatures with increasing the cellulose crystallinity and crystallite size. These results indicated that the cellulose crystallite size affects the thermal degradation temperature of natural fibers. This study showed that through the methods used, previous information about the structure and properties of lignocellulosic fibers can be obtained before use in composite formulations.

Matheus Poletto

2014-08-01

248

Computational studies on tetrahydropyrimidine-2-one HIV-1 protease inhibitors: improving three-dimensional quantitative structure-activity relationship comparative molecular field analysis models by inclusion of calculated inhibitor- and receptor-based properties.  

Science.gov (United States)

A computational chemistry study has been performed on a series of tetrahydropyrimidine-2-ones (THPs) as HIV-1 protease (HIV-1 PR) inhibitors. The present investigation focuses on the correlation of inhibitor-enzyme complexation energies (E(compl)), inhibitor solvation energies E(solv)[I], and both polar and nonpolar buried surface areas (BSAs) with the observed values of the binding affinity (pK(I)). Various combinations of these specific inhibitor- and receptor-based properties were also evaluated as additional descriptors to three-dimensional quantitative structure-activity relationship (3D-QSAR) models constructed using comparative molecular field analysis (CoMFA). Linear regression of the observed pK(I) values with E(compl), E(solv)[I], and the BSAs yielded a strong correlation in terms of both self-consistency (r(2) approximately equal to 0.90) and internal predictive ability (r(cv)(2) > 0.50). The 3D-QSAR models obtained from CoMFA using standard partial least-squares (PLS) analysis also yielded a strong correlation between the CoMFA fields and the experimental pK(i) (r(2) = 0.96; r(cv)(2) = 0.58). Various "enhanced" 3D-QSAR models were constructed in which different combinations of the E(compl), E(solv)[I], and BSAs were added as additional descriptors to the default steric-electrostatic CoMFA fields. Inclusion of E(solv)[I] in particular yielded significant improvement in the predictive ability (r(cv)(2) approximately equal to 0.80) of the resultant 3D-QSAR model. PMID:11831910

Nair, Anil C; Jayatilleke, Philippa; Wang, Xia; Miertus, Stanislav; Welsh, William J

2002-02-14

249

Relationship between Static Stiffness and Modal Stiffness of Structures  

Directory of Open Access Journals (Sweden)

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

Tianjian Ji Tianjian Ji

2010-02-01

250

Properties-microstructure-processing relationships of monolithic fuel forms  

International Nuclear Information System (INIS)

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

251

Structural changes in latosols of the cerrado region: I - relationships between soil physical properties and least limiting water range Alterações estruturais de latossolos representativos da região do cerrado: I - relações entre propriedades físicas do solo e intervalo hídrico ótimo  

OpenAIRE

The agricultural potential of Latosols of the Brazilian Cerrado region is high, but when intensively cultivated under inappropriate management systems, the porosity can be seriously reduced, leading to rapid soil degradation. Consequently, accelerated erosion and sedimentation of springs and creeks have been observed. Therefore, the objective of this study was to evaluate structural changes of Latosols in Rio Verde, Goiás, based on the Least Limiting Water Range (LLWR), and relationships bet...

Eduardo da Costa Severiano; Geraldo César de Oliveira; Moacir de Souza Dias Júnior; Katia Aparecida de Pinho Costa; Fabiano Guimarães Silva; Silvio Marcos Ferreira Filho

2011-01-01

252

Quasicrystals Structure and Physical Properties  

CERN Document Server

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

Trebin, Hans-Rainer

2003-01-01

253

Some properties of galaxy structures  

CERN Document Server

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

254

A relationship between chemical structure and the critical temperature  

Science.gov (United States)

The present investigation is concerned with the effect of both molecular weight and chemical structure on the critical temperature. Using data from the comprehensive compilation of critical constants of Kudchadker et al. (1968), a simple relationship could be developed between the critical temperature and chemical structure. This relationship does not require experimental data such as the normal boiling point. It was found that the critical temperature (Tc) is given by an expression containing m and the sum of delta-i, where m is the total number of atoms in the molecule and delta-i is a number whose value is obtained from a table of additive atomic, group, and structural constants.

Fedors, R. F.

1982-01-01

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

256

Effect of processing on Polymer/Composite structure and properties  

Science.gov (United States)

Advances in the vitality and economic health of the field of polymer forecasting are discussed. A consistent and rational point of view which considers processing as a participant in the underlying triad of relationships which comprise materials science and engineering is outlined. This triad includes processing as it influences material structure, and ultimately properties. Methods in processing structure properties, polymer science and engineering, polymer chemistry and synthesis, structure and modification and optimization through processing, and methods of melt flow modeling in processing structure property relations of polymer were developed. Mechanical properties of composites are considered, and biomedical materials research to include polymer processing effects are studied. An analysis of the design technology of advances graphite/epoxy composites is also reported.

1982-01-01

257

The Relationship Communication Structure - Uncertainty Avoidance  

Directory of Open Access Journals (Sweden)

Full Text Available As today’s society heads towards digitalization, the virtual environment gains a growing importance. Shaping the e-environment in accordance to the real environment in order to favour the activities and processes going to take place there requires a thorough design. However, cultural attributes of reflected inherently by design play a core part in how the information displayed on websites is perceived. The present paper aims to bring a perspective about transposing the proper communication structure into the website design, from the cultural point of view and from genders point of view, as it resulted from a research of Romanian students from Bucharest Academy of Economic Studies

Doru Alexandru Ple?ea

2011-11-01

258

Introducing Spectral Structure Activity Relationship (S-SAR) Analysis. Application to Ecotoxicology  

OpenAIRE

A novel quantitative structure-activity (property) relationship model, namely Spectral-SAR, is presented in an exclusive algebraic way replacing the old-fashioned multi-regression one. The actual S-SAR method interprets structural descriptors as vectors in a generic data space that is further mapped into a full orthogonal space by means of the Gram-Schmidt algorithm. Then, by coordinated transformation between the data and orthogonal spaces, the S-SAR equation is given under simple determinan...

Ana-Maria Lacrămă; Putz, Mihai V.

2007-01-01

259

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

Science.gov (United States)

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

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

2013-11-14

260

The Relationship between Residential Property Development and Property Tax generation in Ibadan North, Oyo State  

Directory of Open Access Journals (Sweden)

Full Text Available This paper examined the relationship between residential property development and property tax generation in Ibadan North Local Government, Oyo State- Nigeria. Data on residential properties within the Local Government for an eleven year period (1999 – 2010 was obtained from the appropriate planning authority, while records of property taxes generated within the same eleven year period was sourced from the taxing authority within the local government. Regression analysis was used to examine the degree and nature of relationship that a change in the number of residential properties will have on the generation of property taxes. Results showed that the actual property tax paid in Ibadan North Local Government Council is being influenced by the number of residential buildings within the council at about 59.3% variation. This implies that a positive variation in the number of residential buildings within the council will lead to a positive variation in the actual property tax generated. Investigation further revealed that this revenue option is however not fully utilized as payments of these taxes are not fully enforced by the taxing authority. It is therefore paramount that the local government seeks for means of improving its tax base through effective property taxation, thus increasing funds available for community development projects such as electrification, road construction, drainages and other essential utilities.

Ajayi M. T. A.

2014-07-01

261

Preparation, structure and dielectric property of barium stannate titanate ceramics  

Energy Technology Data Exchange (ETDEWEB)

The processing route of barium stannate titanate ceramics were optimized to prepare full composition range solid solution sample. The phase structure, microscopic morphology and dielectric properties of barium stannate titanate ceramics were studied. X-ray diffraction patterns indicated that the samples are of single perovskite structure. Linear empirical relationship between crystal lattice and tin content was proposed. This relationship is valid covering the full composition range, which suggests that this solid solution system is ultimate mutual soluble. The phase transition behavior was studied and a phase diagram was obtained based on the dielectric measurements.

Wei Xiaoyong [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Xi' an Jiaotong Univesity, Xi' an 710049 (China)]. E-mail: wdy@mail.xjtu.edu.cn; Yao Xi [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Xi' an Jiaotong Univesity, Xi' an 710049 (China)

2007-02-25

262

Preparation, structure and dielectric property of barium stannate titanate ceramics  

International Nuclear Information System (INIS)

The processing route of barium stannate titanate ceramics were optimized to prepare full composition range solid solution sample. The phase structure, microscopic morphology and dielectric properties of barium stannate titanate ceramics were studied. X-ray diffraction patterns indicated that the samples are of single perovskite structure. Linear empirical relationship between crystal lattice and tin content was proposed. This relationship is valid covering the full composition range, which suggests that this solid solution system is ultimate mutual soluble. The phase transition behavior was studied and a phase diagram was obtained based on the dielectric measurements

263

The relationship between char morphology and its parental coal properties  

Energy Technology Data Exchange (ETDEWEB)

In this study five coals were investigated. Manual coal analyses were carried out to determine coal petrographic data, such as coal rank, vitrinite reflectance and maceral composition, etc. In addition, an automatic char image analysis technique has been employed to analyze coal chars obtained from a Drop-Tube furnace. Char morphological parameters, such as particle size, wall-thickness, char porosity, pore size and its distribution, etc., have been measured. All chars were, therefore, classified into eight char groups, tenuisphere, crassisphere, tenuinetwork, crassinetwork, mixed-porous, mixed-dense, inertoid and fusinoid/solid. The influence of coal rank, coal maceral composition and other coal properties on the formation and the proportion of those char groups was studied. It was found that coal rank, coal volatile content and coal petrographic composition have a strong link with the char type formed. Increasing vitrinite content leads to an increase in the proportion of spherical particles, increasing coal vitrinite reflectance leads to an increase in the proportion of thickwalled particles, while an increase in coal oxygen content may result in greater network particles and thick-walled particles. General empirical relationships between char morphology and its parent coal properties have been proposed. The relationships are promising for inclusion in a coal combustion model to improve the simulation of char reactivity and the accuracy of coal combustion modelling. 14 refs., 8 figs., 3 tabs.

T. Wu; M. Cloke; R. Barranco; E. Lester [University of Nottingham, Nottingham (United Kingdom). Nottingham Fuel and Energy Centre

2003-07-01

264

Flavonoids promoting HaCaT migration: I. Hologram quantitative structure-activity relationships.  

Science.gov (United States)

Cell migration plays an important role in multicellular development and preservation. Because wound healing requires cell migration, compounds promoting cell migration can be used for wound repair therapy. Several plant-derived polyphenols are known to promote cell migration, which improves wound healing. Previous studies of flavonoids on cell lines have focused on their inhibitory effects and not on wound healing. In addition, studies of flavonoids on wound healing have been performed using mixtures. In this study, individual flavonoids were used for cellular migration measurements. Relationships between the cell migration effects of flavonoids and their structural properties have never been reported. Here, we investigated the migration of keratinocytes caused by 100 flavonoids and examined their relationships using hologram quantitative structure-activity relationships. The structural conditions responsible for efficient cell migration on keratinocyte cell lines determined from the current study will facilitate the design of flavonoids with improved activity. PMID:24252338

Cho, Moonjae; Yoon, Hyuk; Park, Mijoo; Kim, Young Hwa; Lim, Yoongho

2014-03-15

265

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

266

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

Energy Technology Data Exchange (ETDEWEB)

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

Frick, Achim, E-mail: achim.frick@htw-aalen.de; Borm, Michael, E-mail: achim.frick@htw-aalen.de; Kaoud, Nouran, E-mail: achim.frick@htw-aalen.de; Kolodziej, Jan, E-mail: achim.frick@htw-aalen.de; Neudeck, Jens, E-mail: achim.frick@htw-aalen.de [Institute of Polymer Science and Processing (iPSP), HTW Aalen (Germany)

2014-05-15

267

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

International Nuclear Information System (INIS)

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

268

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

International Nuclear Information System (INIS)

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

269

Structural, Electronic, and Superconducting Properties of Solids.  

Science.gov (United States)

A first-principles pseudopotential method is used to calculate structural, electronic, and lattice vibrational properties for various types of solids. Applications of the pseudopotential method are extended to more complicated systems with superconducting states. Much of emphasis is placed on successful applications for calculating electron -phonon coupling parameters and predicting new superconducting states. A study of the relationship between soft phonon modes, structural phase transitions, and superconductivity is presented. The results are compared with available experimental data and the good agreements with experiments are found. Investigations of the phase stability for Si and Ge are given. New high pressure phases similar to those found in Si are predicted for Ge. For both crystals, the soft phonon modes are closely related to the phase transitions. High pressure phases for SiC, BeO, and MgO are also studied. Rhombohedral phase stability relative to simple cubic is investigated for the group-VA elements. This stability decreases with either increasing pressure or decreasing covalency. The electronic structures of CdS, BeO, and MgO are examined. Incorporating the Cd d state into the valence band improves substantially the main valence band width for CdS. The band structures for the hexagonal and cubic structures are compared. By studying the pressure variations of band gaps in semiconductors and insulators, it is demonstrated that although the local density approximation underestimates the band gaps, the pressure coefficients of band gaps are correctly estimated and are insensitive to the use of different functional forms for the exchange-correlation potential. The lattice dynamical properties such as the phonon frequency and the pressure dependence of the frequency are examined for AlAs. From the averaged electro-static potential, the longitudinal effective charges are estimated and satisfy the acoustic sum rule. Applying the pseudopotential method for calculating electron-phonon coupling parameters, superconducting solutions are found for the high pressure metallic phases of Si. The soft phonon modes near the structural phase transitions for Si and black phosphorus are found to significantly enhance the superconducting transition temperature. For metallic Si, Ge, and Sn, the following correlation is found: with increasing electron concentration, the phonon frequencies, force constants, phonon linewidths, and electron-phonon interactions increase. This calculation suggests that the Debye temperature dominates in determining the superconducting critical temperature.

Chang, Kee Joo

270

A genetic algorithm for structure-activity relationships: software implementation  

OpenAIRE

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 structu...

Jantschi, Lorentz

2009-01-01

271

Structural Diversity and Close Interracial Relationships in College  

Science.gov (United States)

Recent legal and political actions have challenged the use of race-conscious college admissions policies. Earlier research offers mixed evidence about the link between an institution's racial/ethnic composition (i.e., structural diversity) and the formation of close interracial relationships, so the present study examines this topic directly for…

Bowman, Nicholas A.

2012-01-01

272

Using Layer-Cake Geology to Illustrate Structural Topographic Relationships.  

Science.gov (United States)

Discusses some of the difficulties of visualizing underlying geologic structural patterns by using maps or wooden blocks. Suggests the use of a modified layer cake to show dipping beds, folds, faults and differential erosion, as well as the relationships of stream valleys to outcrop patterns. (TW)

Wagner, John Robert

1987-01-01

273

Structure and properties of nanocomposite polymer coatings  

Energy Technology Data Exchange (ETDEWEB)

We investigate the surface morphology and structure formations of nanocomposite polymer (polytetrafluoroethylene, polyurethane) coatings obtained by vacuum plasma method. We present data about the influence of coating composition and deposition conditions onto coating properties and structure.

Rogachev, A; Yarmolenko, M [Belarusian State University of Transport, 34 Kirov Street, Gomel, 246653 (Belarus); Rahachou, A V [Francisk Scorina Gomel State University, Sovetskaya Str. 104, Gomel, 246019 (Belarus); Tamulevicius, S; Prosycevas, I [Institute of Physical Electronics, Kaunas University of Technology, Savanoriu 271, LT-3009 Kaunas (Lithuania)], E-mail: rogachevav@mail.ru

2008-03-01

274

Relationship between mechanical and electrical properties in solarex semicrystalline silicon  

Science.gov (United States)

Four-point bending mechanical tests at 1100°C were performed on four different types of semicrystalline silicon: Solarex silicon grown by their standard growth method and by two different modifications to this method, and Wacker silicon. The bending tests showed that materials that produced inferior solar cells required roughly two times the applied stresses to initiate plastic deformation. These flow stresses reflect the deformation history of the material rather than the chemical make-up since the flow stresses are higher in samples without hardening agents. Room temperature, Vickers indentation hardness measurements correlate with the four-point bending results. The electrical properties of the as-grown materials were examined by both conventional low accelerating voltage electron-beam induced current (LAV-EBIC) and by EBIC using high accelerating voltages (HAV-EBIC). Solar cell efficiencies correlate better with currents measured by HAV-EBIC, which are representative of the bulk material behavior, than with LAV-EBIC, which primarily probes the junction depletion layer. These materials represent one of the few examples where there is a clear-cut relationship between the material microstructure and the electrical properties. Consequently, it may be possible to assess the quality of solar cell silicon directly from hardness measurements. Such a test might prove useful for in-line assessment of material quality and processing, resulting in more efficient and cost effective silicon solar cell production.

Hyland, S. L.; Perreault, G.; Wohlgemuth, J.; Ast, D. G.

1990-07-01

275

The textual idea and its relationship to discourse structure  

Directory of Open Access Journals (Sweden)

Full Text Available The textual idea could be characterized through a series of either detailing the current form of idea or continuing a previous form of it. Every element of the series has associated a span of the given text that carries it. If we are to relate different spans of text according to relationship between corresponding elements of the series, we will obtain a possible representation of discourse structure. In this paper we take a set of texts and represent their structure in the above manner. The purpose is to give researchers the possibility to asset our manner to represent discourse structure.

Cosmin D?nut BOC?NIAL?

2000-12-01

276

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

International Nuclear Information System (INIS)

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

277

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

278

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

International Nuclear Information System (INIS)

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

279

Structural and dynamical properties of Yukawa balls  

International Nuclear Information System (INIS)

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

280

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

Science.gov (United States)

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

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

2014-05-19

281

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

282

Structure and physical properties of silkworm cocoons  

OpenAIRE

Silkworm cocoons have evolved a wide range of different structures and combinations of physical and chemical properties in order to cope with different threats and environmental conditions. We present our observations and measurements on 25 diverse types of cocoons in a first attempt to correlate physical properties with the structure and morphology of the cocoons. These two architectural parameters appear to be far more important than the material properties of the silk fibres themselves. We...

Chen, Fujia; Porter, David; Vollrath, Fritz

2012-01-01

283

Quantitative structure-permeation relationship for iontophoretic transport across the skin  

OpenAIRE

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

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

2007-01-01

284

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

OpenAIRE

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

Mu Shuzhen; Hao Xiaojiang; Wang Ye; Chen Gang(Physics Department, School of Mathematics and Physics, China University of Geosciences, 430074 Wuhan, China); Sun Qianyun

2011-01-01

285

Structure, processing, and properties of potatoes  

Science.gov (United States)

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

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

1992-06-01

286

Cellulose Nanofibril Networks and Composites : Preparation, Structure and Properties  

OpenAIRE

The cellulose nanofibril from wood is an interesting new material constituent that can provide strong reinforcement in polymer nanocomposites due to the high stiffness of the cellulose crystals and the network formation characteristics of the nanofibrils. Cellulose nanofibrils can be used either in the form of low aspect ratio microcrystalline cellulose, MCC, or as high aspect ratio microfibrillated cellulose, MFC. The objective is to study structure-property relationships for cellulose nanof...

Henriksson, Marielle

2008-01-01

287

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

Directory of Open Access Journals (Sweden)

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

S.SeshaPhani

2013-01-01

288

Bank Image Structure: The Relationship to Consumer Behaviour  

Directory of Open Access Journals (Sweden)

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

Lukasova Ruzena

2014-03-01

289

Abnormal Structure–Function Relationship in Spasmodic Dysphonia  

OpenAIRE

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

Simonyan, Kristina; Ludlow, Christy L.

2011-01-01

290

Nematode-fungal interactions. Structure-function relationships.  

OpenAIRE

Nematophagous fungi can infect and digest nematodes and use the contents of the prey for development of fungal biomass. Generally, these organisms encounter the nematode host in two ways either by means of trapping devices formed on an extended mycelium (predatory or nematode-trapping fungi) or by means of conidia (endoparasitic fungi). Currently, the structure/ function relationships during the complex nematode/fungus interaction of the free-living bacteriovorous nematode Panagrellus rediviv...

Dijksterhuis, Jan

1993-01-01

291

THE RELATIONSHIP BETWEEN CORONAL DIMMING AND CORONAL MASS EJECTION PROPERTIES  

International Nuclear Information System (INIS)

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

292

Alternating and direct current field effects on the structure-property relationships in Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}-x%BaTiO{sub 3} textured ceramics  

Energy Technology Data Exchange (ETDEWEB)

The influence of alternating (ac) and direct current (dc) fields on the structural and dielectric properties of [001]{sub PC} textured Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}-7%BaTiO{sub 3} (NBT-7%BT) ceramics has been investigated. X-ray diffraction measurements revealed that the depolarization at temperature T{sub d} in poled samples resulted from a tetragonal {yields} pseudo-cubic transition on heating. Moderate ac drive and dc bias had opposite influences on T{sub d}: ac drive decreased the T{sub d}, 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; Li, Jiefang; Viehland, D. [Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Maurya, Deepam; Priya, Shashank [Center for Energy Harvesting Materials and Systems (CEHMS), Bio-Inspired Materials and Devices Laboratory (BMDL), Virginia Tech, Blacksburg, Virginia 24061 (United States)

2013-06-03

293

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

International Nuclear Information System (INIS)

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.

294

Structure and physical properties of silkworm cocoons.  

Science.gov (United States)

Silkworm cocoons have evolved a wide range of different structures and combinations of physical and chemical properties in order to cope with different threats and environmental conditions. We present our observations and measurements on 25 diverse types of cocoons in a first attempt to correlate physical properties with the structure and morphology of the cocoons. These two architectural parameters appear to be far more important than the material properties of the silk fibres themselves. We consider tensile and compressive mechanical properties and gas permeation of the cocoon walls, and in each case identify mechanisms or models that relate these properties to cocoon structure, usually based upon non-woven fibre composites. These properties are of relevance also for synthetic non-woven composite materials and our studies will help formulate bio-inspired design principles for new materials. PMID:22552916

Chen, Fujia; Porter, David; Vollrath, Fritz

2012-09-01

295

Structure-property relationships of novel microwave dielectric ceramics with low sintering temperatures: (Na(0.5x)Bi(0.5x)Ca(1-x))MoO(4).  

Science.gov (United States)

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

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

2014-08-21

296

Synthetic and structure-activity relationship of insecticidal bufadienolides.  

Science.gov (United States)

A new synthetic analog of bufadienolide, methyl isobryophyllinate A (1), and a known synthetic analog, methyl isobersaldegenate-1,3,5-orthoacetate (2), were obtained by methanolysis of bryophyllin A (3) and bersaldegenin-1,3,5-orthoacetate (5) in basic solution. Structure-insecticidal activity relationship studies revealed both orthoacetate and alpha-pyrone moieties seemed to be essential structural elements for exhibiting insecticidal activity, whereas oxygenated substituents in the C ring enhanced the insecticidal activity against the third instar larvae of silkworm (Bombyx mori). PMID:25230494

Hidayat, Ace Tatang; Zainuddin, Achmad; Dono, Danar; Hermawan, Wawan; Hayashi, Hideo; Supratman, Unang

2014-07-01

297

Structure-Activity Relationship of novel phenylacetic CXCR1 inhibitors.  

Science.gov (United States)

We reported recently the Structure-Activity Relationship (SAR) of a class of CXCL8 allosteric modulators. They invariably share a 2-arylpropionic moiety so far considered a key structural determinant of the biological activity. We show the results of recent SAR studies on a novel series of phenylacetic derivatives supported by a combined approach of mutagenesis experiments and conformational analysis. The results suggest novel insights on the fine role of the propionic/acetic chain in the modulation of CXCL8 receptors. PMID:19560921

Sablone, Manolo Rocco; Cesta, Maria Candida; Moriconi, Alessio; Aramini, Andrea; Bizzarri, Cinzia; Di Giacinto, Claudia; Di Bitondo, Rosa; Gloaguen, Isabelle; Aschi, Massimiliano; Crucianelli, Marcello; Bertini, Riccardo; Allegretti, Marcello

2009-08-01

298

Structural Properties of Ego Networks  

OpenAIRE

The structure of real-world social networks in large part determines the evolution of social phenomena, including opinion formation, diffusion of information and influence, and the spread of disease. Globally, network structure is characterized by features such as degree distribution, degree assortativity, and clustering coefficient. However, information about global structure is usually not available to each vertex. Instead, each vertex's knowledge is generally limited to t...

Gupta, Sidharth; Yan, Xiaoran; Lerman, Kristina

2014-01-01

299

Structure-property relationships of (C-O-H)-saturated silicate melt coexisting with silicate-saturated C-O-H fluid at high temperature and pressure and with variable redox conditions  

Science.gov (United States)

The solubility and solution mechanisms in silicate melts of C-O-H volatiles in silicate melts in equilibrium with silicate-saturated C-O-H fluids have been determined experimentally to upper mantle temperature and pressure conditions as a function of melt composition and redox conditions (hydrogen fugacity, fH2) in the range between magnetite-hematite + H2O [fH2 (MH)] and iron wustite + H2O buffer [fH2 (IW)]. Experiments have been carried out by examining both quenched materials with MAS NMR and vibrational spectroscopies as structural tools and in-situ with the sample at high temperature and pressure in a hydrothermal diamond anvil cell (HDAC) with vibrational spectroscopy as the structural tool. In fluid+melt-COH systems, volatiles are dissolved in molecular form (CO2, CH4, H2O, H2) and as complexes that form chemical bonding with the silicate network (CO3, CH3, OH). In silicate-OH systems molecular H2O and OH-groups coexist in silicate- and aluminosilicate-saturated fluids and water-saturated melts above with their OH/H2O-ratio positively correlated with temperature. The extent of hydrogen bonding in fluids and melts diminishes with temperature so that above ~ 400C it cannot be detected. Its ?H in aqueous fluid (22±1 kJ/mol) is about twice that of H2O dissolved in silicate melts (10±2 kJ/mol). Silicate speciation in silicate-saturated fluid and hydrous silicate melts comprises similar Q-species with ?H of the solution reactions in silicate-saturated fluid, water-saturated melt, and supercritical fluid ~400±50 kJ/mol. The increasing silicate content in aqueous fluids with temperature and pressure provides an explanation of positive temperature and pressure correlation of melt/fluid partitioning and Ti4+, P5+ and D/H ratio. It also explains why PVT properties of silicate-saturated aqueous fluid are significantly different from those of pure H2O under lower crustal and upper mantle temperature and pressure conditions. In oxidized [e.g., f H2(MH)] silicate-C-O-H systems the CO2 solubility is in the 1-4 wt% range between ~1 and 3 GPa and decreases the more felsic a melt. Its solution mechanism is, CO2+Qn=CO3+Qn+1. Methane solubility, CH4, in melts, in contrast, is 10-30% of that of CO2 at the same temperature, pressure and melt composition. From diamond cell (HDAC) experiments conducted in-situ to 800C and 1435 MPa, the dominant species in the fluid are CH4, H2, and H2O with the C(melt)/C(fluid) partition coefficient increasing from 0.01 to 0.08 between 400 and 800C (and pressure increasing from ~400 to ~1400 MPa). In coexisting melt, CH3 - groups linked to the silicate melt structure via Si-CH3 bonding coexist with molecular CH4 thus resulting in the solution mechanism, CH4+Qn=CH3+Qn-1. The fH2-dependent solution mechanisms of C-O-H volatile components in silicate melts result in fH2-dependent thermodynamic and transport properties of magmatic liquids in the interior of the Earth and terrestrial planets. These properties include mineral/melt minor and trace element partitioning, melt/fluid isotope fractionation, and transport and thermodynamic properties of melt saturated with variably-oxidized C-O-H volatile components.

Mysen, B. O.

2012-12-01

300

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)

301

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

International Nuclear Information System (INIS)

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

302

Relationship between mechanical and magnetic properties in cold rolled low carbon steel  

Science.gov (United States)

Structure-sensitive properties of minor hysteresis loops have been compared with Vickers hardness and ductile-brittle transition temperature (DBTT) obtained by Charpy impact test for cold rolled low carbon steel. Minor loops were measured with increasing magnetic field amplitude, step by step, and were analyzed in connection with the rolling reduction. We found that minor-loop coefficients deduced from relations between minor-loop parameters increase with increasing rolling reduction and have a simple relationship with both mechanical properties, Vickers hardness, and DBTT. We also found that these coefficients have a linear relation with coercive force obtained by the major loop. The present analysis method using minor loops is highly effective for nondestructive evaluation of ductile-brittle transition, in terms of the high sensitivity to lattice defects as well as low measurement field.

Takahashi, S.; Kobayashi, S.; Kikuchi, H.; Kamada, Y.

2006-12-01

303

Structure properties of even-even actinides  

CERN Document Server

Structure properties of fifty five even-even actinides have been calculated using the Gogny D1S force and the Hartree-Fock-Bogoliubov approach as well as the configuration mixing method. Theoretical results are compared with experimental data.

Delaroche, J P; Goutte, H; Libert, J

2006-01-01

304

Structure-activity relationship for the oxadiazole class of antibiotics.  

Science.gov (United States)

The structure-activity relationship (SAR) for the newly discovered oxadiazole class of antibiotics is described with evaluation of 120 derivatives of the lead structure. This class of antibiotics was discovered by in silico docking and scoring against the crystal structure of a penicillin-binding protein. They impair cell-wall biosynthesis and exhibit activities against the Gram-positive bacterium Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA) and vancomycin-resistant and linezolid-resistant S. aureus. 5-(1H-Indol-5-yl)-3-(4-(4-(trifluoromethyl)phenoxy)phenyl)-1,2,4-oxadiazole (antibiotic 75b) was efficacious in a mouse model of MRSA infection, exhibiting a long half-life, a high volume of distribution, and low clearance. This antibiotic is bactericidal and is orally bioavailable in mice. This class of antibiotics holds great promise in recourse against infections by MRSA. PMID:25590813

Spink, Edward; Ding, Derong; Peng, Zhihong; Boudreau, Marc A; Leemans, Erika; Lastochkin, Elena; Song, Wei; Lichtenwalter, Katerina; O'Daniel, Peter I; Testero, Sebastian A; Pi, Hualiang; Schroeder, Valerie A; Wolter, William R; Antunes, Nuno T; Suckow, Mark A; Vakulenko, Sergei; Chang, Mayland; Mobashery, Shahriar

2015-02-12

305

Structure-olfactive threshold relationships for pyrazine derivatives.  

Science.gov (United States)

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. PMID:16676210

Zakarya, Driss; Farhaoui, Lahbib; Hamidi, Mohammed; Bouachrine, Mohammed

2006-09-01

306

Structure and properties of commercial titanium alloys  

International Nuclear Information System (INIS)

The chemical composition, structure and properties of modern commercial titanium alloys and technical titanium (VT1-0, VT1-00, OT4, VT3-1, VT-6, VT14, VT16, VT-20, VT22, VT23, VT32) are considered. The effect of alloying elements, phase composition, heat treatment regimes, microstructure, experimental temperature on mechanical properties of the above alloys, is traced. Recommendation for processing alloy intermediate products to obtain optimum properties, are given

307

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

308

The relationships between electricity consumption and GDP in Asian countries, using hierarchical structure methods  

Science.gov (United States)

This study uses hierarchical structure methods (minimal spanning tree (MST) and hierarchical tree (HT)) to examine the relationship between energy consumption and economic growth in a sample of 30 Asian countries covering the period 1971-2008. These countries are categorized into four panels based on the World Bank income classification, namely high, upper middle, lower middle, and low income. In particular, we use the data of electricity consumption and real gross domestic product (GDP) per capita to detect the topological properties of the countries. We show a relationship between electricity consumption and economic growth by using the MST and HT. We also use the bootstrap technique to investigate a value of the statistical reliability to the links of the MST. Finally, we use a clustering linkage procedure in order to observe the cluster structure. The results of the structural topologies of these trees are as follows: (i) we identified different clusters of countries according to their geographical location and economic growth, (ii) we found a strong relationship between energy consumption and economic growth for all income groups considered in this study and (iii) the results are in good agreement with the causal relationship between electricity consumption and economic growth.

Kantar, Ersin; Keskin, Mustafa

2013-11-01

309

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.

Shanaz Forozan

2013-04-01

310

Structure-antioxidant relationship of flavonoids from fermented rooibos.  

Science.gov (United States)

Rooibos tea (Aspalathus linearis) contains different bioactive phenolic compounds such as dihydrochalcones, flavonols, flavanones, flavones, and flavanols. Flavonoids isolated from rooibos were subjected to different in vitro assays: Trolox equivalent antioxidant activity, LDL oxidation and Fremy's salt assays to determine the total antioxidant activity (TAA). Assay results were compared, and the structure-antioxidant relationship was investigated. A decoupled LDL oxidation test was established with the objective of having an assay adapted more to an in vivo situation. The different in vitro methods were coupled offline to HPLC-DAD. Results from these coupled offline methods were compared to the TAA to assess the usefulness of the coupling setup. PMID:19156714

Krafczyk, Nicole; Woyand, Franziska; Glomb, Marcus A

2009-05-01

311

Relationship structure-antioxidant activity of hindered phenolic compounds  

OpenAIRE

The relationship between the structure and the antioxidant activity of 21 hindered phenolic compounds was investigated by Rancimat and DPPH· tests. 3-tert-butyl-5-methylbenzene-1,2-diol is the strongest antioxidant in the Rancimat test but not in the DPPH· test because its two hydroxyl groups have very strong steric synergy. 2,6-Ditert-butyl-4-hydroxy-methylphenol exhibits a strong antioxidant activity as 2,6-ditertbutyl- 4-methoxyphenol does in lard. 2,6-Dite...

Weng, X. C.; Huang, Y.

2014-01-01

312

Structure and functional properties of colloidal systems  

CERN Document Server

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

313

Relationships between milk coagulation property traits analyzed with different methodologies.  

Science.gov (United States)

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. PMID:21854906

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

2011-09-01

314

Complex Fuzzy Structured Element and Its Properties  

Directory of Open Access Journals (Sweden)

Full Text Available The first part of this paper gives the definition about complex fuzzy structured element on the basis of one-dimensional fuzzy structured element and some of its property. The following part introduces its limit and continuity. All of this has opened up a vision for the research of fuzzy structured element, and also played an important role in promoting its progress.

Kaiqi ZOU

2010-01-01

315

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.

316

Property Relationship in Organosilanes and Nanotubes Filled Polypropylene Hybrid Composites  

Directory of Open Access Journals (Sweden)

Full Text Available Polypropylene composites with different filler contents were prepared by creating a masterbatch containing 3 wt%. filler. A variety of silanol groups were used to synthetized three compounds in different media trough a sol-gel process with acetic acid, formic acid and ammonium hydroxide as catalysts. Besides, four different nanotubular fillers were also used to analyze their behavior and compare it with the effect caused by the silanol groups. These tubular structures comprise: unmodified halloysite, carbon nanotubes and functionalized halloysite and carbon nanotubes. Morphological characterization in SEM and STEM/TEM showed dispersion in the polypropylene matrix. According to TGA and DSC measurements thermal behavior remain similar for all the composites. Mechanical test in tension demonstrate that modulus of the composites increases for all samples with a major impact for materials containing silanol groups synthetized in formic acid. Rheological measurements show a significantly increment in viscosity for samples containing unmodified and modified carbon nanotubes. No difference was found for samples containing silanol groups and halloysite when compared to neat polypropylene. Finally, the oxygen transmission rate increased for all samples showing high barrier properties only for samples containing natural and functionalized halloysite nanotubes.

Alejandra J. Monsiváis-Barrón

2014-10-01

317

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

318

Structure and properties of metals  

CERN Document Server

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 $9 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 $9 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, $9 mathematical morphology and quantitative stereology. Quantitative description of the microstructures are used for modeling processes taking place under the action of applied load at a given temperature and test (service) environment. $9 These model considerations can be illustrated on the example of an austenitic stainless...

Kurzydlowski, K J

1999-01-01

319

Structural properties of prokaryotic promoter regions correlate with functional features.  

Science.gov (United States)

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

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

2014-01-01

320

The structure?activity relationship in herbicidal monosubstituted sulfonylureas  

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-05-24

321

Propiedades microbiológicas, clasificación y relación estructura-actividad de cefalosporinas e importancia de las cefalosporinas de cuarta generación MICROBIOLOGICAL PROPERTIES, CLASSIFICATIONS AND STRUCTURE-ACTIVITY RELATIONSHIPS OF CEPHALOSPORINS AND THE IMPORTANCE OF FOURTH GENERATION CEPHALOSPORINS  

Directory of Open Access Journals (Sweden)

Full Text Available Las cefalosporinas son uno de los grupos de mayor importancia dentro de los ß-lactámicos. Existen diversas clasificaciones de estas moléculas, siendo la más utilizada aquella que agrupa a estos compuestos de acuerdo a propiedades estructurales, microbiológicas y desarrollo histórico: primera a cuarta generación. Las cefalosporinas de tercera generación han sido ampliamente utilizadas, pero la emergencia de resistencia bacteriana fundamentalmente derivada de la producción de ß-lactamasas tanto cromosomales como plasmidiales, ha limitado el uso de estos compuestos. Las cefalosporinas de cuarta generación se caracterizan por la presencia de un nitrógeno cuaternario en C3, además de mantener el grupo metoxi-imino aminotiazolil en C7. Presentan una elevada penetración intracelular a través de la membrana externa de bacilos Gram negativos y tienen una baja afinidad por enzimas que degradan cefalos-porinas de tercera generación. Cefepime, una cefalosporina de cuarta generación, demostró una mayor actividad inhibitoria sobre cepas chilenas de Klebsiella pneumoniae y Escherichia coli productoras de ß-lactamasas de espectro extendido, que cefotaxima y ceftazidimaThe cephalosporins are one of the most important types of ß-lactam antibiotics. There are various classifications of these molecules, but the most frecuently used classifies them according to their structures, microbiological properties and historical development: first to fourth generation cephalosporins. Third generation cephalosporins have been extensively used, but the emergence of bacterial resistance, mainly as a consecuence of chromosomal and plasmidial production of ß-lactamases has limited the use of these antibiotics. Fourth generation cephalosporins are characterized by the presence of a cuaternary nitrogen in C3; mantaining the methoxyimino aminothiazolyl in C7. Fourth generation cephalosporins display a high capacity of intracellular penetration through the external membranes of Gram negative rods and a low affinity to enzymes that degrade third generation cephalosporins. Cefepime, a fourth generation cephalosporin, has shown more inhibitory activity against chilean strains of Klebsiella pneumoniae and Escherichia coli that produce extended-spectrum ß-lactamases, than cefotaxime and ceftazidime

SERGIO MELLA M

2001-01-01

322

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

2009-06-15

323

The relationship between energy consumption structure, economic structure and energy intensity in China  

International Nuclear Information System (INIS)

This paper investigates the long-run equilibrium relationships, temporal dynamic relationships and causal relationships between energy consumption structure, economic structure and energy intensity in China. Time series variables over the periods from 1980 to 2006 are employed in empirical tests. Cointegration tests suggest that these three variables tend to move together in the long-run. In addition, Granger causality tests indicate that there is a unidirectional causality running from energy intensity to economic structure but not vice versa. Impulse response analysis provides reasonable evidences that one shock of the three variables will cause the periods of destabilized that followed. However, the impact of the energy consumption structure shock on energy intensity and the impact of the economic structure shock on energy consumption structure seem to be rather marginal. The findings have significant implications from the point of view of energy conservation and economic development. In order to decrease energy intensity, Chinese government must continue to reduce the proportion of coal in energy consumption, increase the utilization efficiency of coal and promote the upgrade of economic structure. Furthermore, a full analysis of factors that may relate to energy intensity (e.g. energy consumption structure, economic structure) should be conducted before making energy policies.

324

The relationship between energy consumption structure, economic structure and energy intensity in China  

Energy Technology Data Exchange (ETDEWEB)

This paper investigates the long-run equilibrium relationships, temporal dynamic relationships and causal relationships between energy consumption structure, economic structure and energy intensity in China. Time series variables over the periods from 1980 to 2006 are employed in empirical tests. Cointegration tests suggest that these three variables tend to move together in the long-run. In addition, Granger causality tests indicate that there is a unidirectional causality running from energy intensity to economic structure but not vice versa. Impulse response analysis provides reasonable evidences that one shock of the three variables will cause the periods of destabilized that followed. However, the impact of the energy consumption structure shock on energy intensity and the impact of the economic structure shock on energy consumption structure seem to be rather marginal. The findings have significant implications from the point of view of energy conservation and economic development. In order to decrease energy intensity, Chinese government must continue to reduce the proportion of coal in energy consumption, increase the utilization efficiency of coal and promote the upgrade of economic structure. Furthermore, a full analysis of factors that may relate to energy intensity (e.g. energy consumption structure, economic structure) should be conducted before making energy policies.

Feng Taiwen, E-mail: typhoonfeng@gmail.co [School of Management, Xi' an Jiaotong University, Xi' an (China); Key Laboratory of the Ministry of Education for Process Control and Efficiency Projects, Xi' an (China); School of Management, Xi' an Jiaotong University, Xi' an (China); Sun Linyan [School of Management, Xi' an Jiaotong University, Xi' an (China); Key Laboratory of the Ministry of Education for Process Control and Efficiency Projects, Xi' an (China); School of Management, Xi' an Jiaotong University, Xi' an (China); Zhang Ying [School of Management, Xi' an Jiaotong University, Xi' an (China); Key Laboratory of the Ministry of Education for Process Control and Efficiency Projects, Xi' an (China); State Key Lab for Manufacturing, Xi' an (China)

2009-12-15

325

The relationship between energy consumption structure, economic structure and energy intensity in China  

Energy Technology Data Exchange (ETDEWEB)

This paper investigates the long-run equilibrium relationships, temporal dynamic relationships and causal relationships between energy consumption structure, economic structure and energy intensity in China. Time series variables over the periods from 1980 to 2006 are employed in empirical tests. Cointegration tests suggest that these three variables tend to move together in the long-run. In addition, Granger causality tests indicate that there is a unidirectional causality running from energy intensity to economic structure but not vice versa. Impulse response analysis provides reasonable evidences that one shock of the three variables will cause the periods of destabilized that followed. However, the impact of the energy consumption structure shock on energy intensity and the impact of the economic structure shock on energy consumption structure seem to be rather marginal. The findings have significant implications from the point of view of energy conservation and economic development. In order to decrease energy intensity, Chinese government must continue to reduce the proportion of coal in energy consumption, increase the utilization efficiency of coal and promote the upgrade of economic structure. Furthermore, a full analysis of factors that may relate to energy intensity (e.g. energy consumption structure, economic structure) should be conducted before making energy policies. (author)

Feng, Taiwen; Sun, Linyan; Zhang, Ying [School of Management, Xi' an Jiaotong University, Xi' an (China); The Key Laboratory of the Ministry of Education for Process Control and Efficiency Projects, Xi' an (China); The State Key Lab for Manufacturing, Xi' an (China)

2009-12-15

326

Fractal Scaling of Particle Size Distribution and Relationships with Topsoil Properties Affected by Biological Soil Crusts  

Science.gov (United States)

Background Biological soil crusts are common components of desert ecosystem; they cover ground surface and interact with topsoil that contribute to desertification control and degraded land restoration in arid and semiarid regions. Methodology/Principal Findings To distinguish the changes in topsoil affected by biological soil crusts, we compared topsoil properties across three types of successional biological soil crusts (algae, lichens, and mosses crust), as well as the referenced sandland in the Mu Us Desert, Northern China. Relationships between fractal dimensions of soil particle size distribution and selected soil properties were discussed as well. The results indicated that biological soil crusts had significant positive effects on soil physical structure (P<0.05); and soil organic carbon and nutrients showed an upward trend across the successional stages of biological soil crusts. Fractal dimensions ranged from 2.1477 to 2.3032, and significantly linear correlated with selected soil properties (R2?=?0.494?0.955, P<0.01). Conclusions/Significance Biological soil crusts cause an important increase in soil fertility, and are beneficial to sand fixation, although the process is rather slow. Fractal dimension proves to be a sensitive and useful index for quantifying changes in soil properties that additionally implies desertification. This study will be essential to provide a firm basis for future policy-making on optimal solutions regarding desertification control and assessment, as well as degraded ecosystem restoration in arid and semiarid regions. PMID:24516668

Gao, Guang-Lei; Ding, Guo-Dong; Wu, Bin; Zhang, Yu-Qing; Qin, Shu-Gao; Zhao, Yuan-Yuan; Bao, Yan-Feng; Liu, Yun-Dong; Wan, Li; Deng, Ji-Feng

2014-01-01

327

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

328

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

329

Quantitative structure-activity relationship of sesquiterpene lactones with cytotoxic activity.  

Science.gov (United States)

Some sesquiterpene lactones (SLs) are the active compounds of a great number of traditionally medicinal plants from the Asteraceae family and possess considerable cytotoxic activity. Several studies in vitro have shown the inhibitory activity against cells derived from human carcinoma of the nasopharynx (KB). In this study, we investigated a set of 37 different sesquiterpene lactones, represented by 4 skeletons (14 germacranolides, 6 elemanolides, 9 guaianolides and nor-derivatives, and 8 pseudoguaianolides), in what it says respect of their cytotoxic properties. The experimental results were submitted to a QSAR study. A single model for the entire data set was described using 3D molecular descriptors and genetic algorithms establishing structure-activity relationships among the compounds. Important properties for the inhibition potency are discussed for the whole data set and for subsets of the different structural skeletons. PMID:17336532

Scotti, Marcus T; Fernandes, Mariane B; Ferreira, Marcelo J P; Emerenciano, Vicente P

2007-04-15

330

Synthesis and structure-activity relationships of potent thrombin inhibitors: piperazides of 3-amidinophenylalanine.  

Science.gov (United States)

Thrombin is the key enzyme in the blood coagulation system, and inhibitors of its proteolytic activity are of therapeutic interest since they are potential anticoagulants. The most potent inhibitor of the benzamidine type is N alpha-[(2-naphthylsulfonyl)glycyl]-4-amidinophenylalanylpiperid ide (NAPAP). However, NAPAP and other benzamidine derivatives do not show favorable pharmacological properties; above all, they have very low systemic bioavailability after oral administration. The goal of designing new compounds was to obtain potent inhibitors with improved pharmacokinetic properties. Piperazide derivatives of 3-amidinophenylalanine as the key building block were synthesized. The piperazine moiety opened the possibility to introduce quite different substituents on the second nitrogen using common synthetic procedures. Some of the newly synthesized compounds are potent inhibitors of thrombin and offer an approach to study structure-function relationships for inhibition of thrombin and related enzymes and for the improvement of their pharmacokinetic properties. PMID:9301673

Stürzebecher, J; Prasa, D; Hauptmann, J; Vieweg, H; Wikström, P

1997-09-12

331

Correlated structure-optical properties studies of plasmonic nanoparticles  

Science.gov (United States)

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

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

2014-06-01

332

Investigation of nanostructured oxides: synthesis, structure and properties.  

Science.gov (United States)

The process of forming three-component nanocrystalline fibers and powders of zirconia, yttria and alumina is studied depending on the component ratio and heat treatment temperature. It has been found that in the investigated system at 500-600 degrees C a nanocrystalline triple solid solution is formed, which exists up to 1200 degrees C. Beyond the above temperature, the triple solid solution decomposes into individual components. Specific regularities of changes in the crystalline structure and size of nanograins of oxides of triple solid solutions in the ZrO2(Y2O3)-Al2O3 system are established depending on the composition and thermal action. The structure--crystallite size--physical-chemical property relationship is also considered. The proposed synthesis method enables preparing nanocrystalline fibers and powders with a high degree of dispersion and reactive activity, whose use in composite materials and ceramics improves their service properties. PMID:21449356

Ulyanova, T M; Krut'ko, N P; Vityaz, P A; Titova, L V

2011-03-01

333

Propiedades microbiológicas, clasificación y relación estructura-actividad de cefalosporinas e importancia de las cefalosporinas de cuarta generación / MICROBIOLOGICAL PROPERTIES, CLASSIFICATIONS AND STRUCTURE-ACTIVITY RELATIONSHIPS OF CEPHALOSPORINS AND THE IMPORTANCE OF FOURTH GENERATION CEPHALOSPORINS  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish Las cefalosporinas son uno de los grupos de mayor importancia dentro de los ß-lactámicos. Existen diversas clasificaciones de estas moléculas, siendo la más utilizada aquella que agrupa a estos compuestos de acuerdo a propiedades estructurales, microbiológicas y desarrollo histórico: primera a cuart [...] a generación. Las cefalosporinas de tercera generación han sido ampliamente utilizadas, pero la emergencia de resistencia bacteriana fundamentalmente derivada de la producción de ß-lactamasas tanto cromosomales como plasmidiales, ha limitado el uso de estos compuestos. Las cefalosporinas de cuarta generación se caracterizan por la presencia de un nitrógeno cuaternario en C3, además de mantener el grupo metoxi-imino aminotiazolil en C7. Presentan una elevada penetración intracelular a través de la membrana externa de bacilos Gram negativos y tienen una baja afinidad por enzimas que degradan cefalos-porinas de tercera generación. Cefepime, una cefalosporina de cuarta generación, demostró una mayor actividad inhibitoria sobre cepas chilenas de Klebsiella pneumoniae y Escherichia coli productoras de ß-lactamasas de espectro extendido, que cefotaxima y ceftazidima Abstract in english The cephalosporins are one of the most important types of ß-lactam antibiotics. There are various classifications of these molecules, but the most frecuently used classifies them according to their structures, microbiological properties and historical development: first to fourth generation cephalos [...] porins. Third generation cephalosporins have been extensively used, but the emergence of bacterial resistance, mainly as a consecuence of chromosomal and plasmidial production of ß-lactamases has limited the use of these antibiotics. Fourth generation cephalosporins are characterized by the presence of a cuaternary nitrogen in C3; mantaining the methoxyimino aminothiazolyl in C7. Fourth generation cephalosporins display a high capacity of intracellular penetration through the external membranes of Gram negative rods and a low affinity to enzymes that degrade third generation cephalosporins. Cefepime, a fourth generation cephalosporin, has shown more inhibitory activity against chilean strains of Klebsiella pneumoniae and Escherichia coli that produce extended-spectrum ß-lactamases, than cefotaxime and ceftazidime

SERGIO, MELLA M; CLAUDIA, ZEMELMAN M; HELIA, BELLO T; MARIANA, DOMINGUEZ Y; GERARDO, GONZALEZ R; RAUL, ZEMELMAN Z.

334

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

???

2012-06-01

335

The properties of crystals with garnet structure  

International Nuclear Information System (INIS)

The results of investigations of the elastic and photoelastic properties of a number of garnets crystals obtained by Mandelshtam-Brillouin technique including the data of ultrasonic experiments are represented. The velocity of sound propagation, the character of elastic interaction between ions in the lattice, nature of photon-phonon interaction in garnets is revealed. The mechanical, thermal and acoustooptical properties of garnets are rated using measured elastic and photoelastic data. The obtained results allow to predict a number of important characteristics of crystals with garnet structure and promote the development of materials with given properties. (author)

336

Unimolecular and intramolecular dynamics. Relationship to potential energy surface properties  

International Nuclear Information System (INIS)

The relationship between potential energy surfaces and unimolecular reaction dynamics is surveyed. The specific topics discussed are the accuracy of the classical trajectory technique for treating unimolecular dynamics, intramolecular vibrational energy redistribution, and the sensitivity of experimental measurements to non-RRKM behavior. 102 references, 6 figures, 3 tables

337

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

International Nuclear Information System (INIS)

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

338

Unravelling the materials genome: Symmetry relationships in alloy properties  

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-07-25

339

Unravelling the materials genome: Symmetry relationships in alloy properties  

International Nuclear Information System (INIS)

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

340

Relationship of air sampling rates of semipermeable membrane devices with the properties of organochlorine pesticides.  

Science.gov (United States)

The organochlorine pesticides (OCP) in Eastern-Barvaria at Haidel 1160 m a.s.l. were monitored with a low volume active air sampler and semi-permeable membrane devices (SPMD). The air sampling rates (Rair) of SPMD for OCP were calculated. Quantitative structure-property relationship (QSPR) models of Rair of SPMD were developed for OCP with partial least square (PLS) regression. Quantum chemical descriptors computed by semi-empirical PM6 method were used as predictor variables. The cumulative variance of the dependent variable explained by the PLS components and determined by cross-validation (Q(2)cum), for the optimal models, is 0.637, indicating that the model has good predictive ability and robustness, and could be used to estimate Rair values of OCP. The main factors governing Rair of OCP are intermolecular interactions and the energy required for cave-forming in dissolution of OCP into triolein of SPMD. PMID:25084591

Zhu, Xiuhua; Ding, Guanghui; Levy, Walkiria; Jakobi, Gert; Schramm, Karl-Werner

2011-06-01

341

Structure and Antioxidant Activity Relationships of Isoflavonoids from Dalbergia parviflora  

Directory of Open Access Journals (Sweden)

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

Worrawat Promden

2014-02-01

342

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-(OH3 > MIC 2?,4?-(OH2 > MIC 2?,4?,4-(OH3 > > MIC 2?,4?,2-(OH3. 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.

1998-01-01

343

Defect structure and thermodynamic properties of nonstoichiometric vanadium monoxide  

International Nuclear Information System (INIS)

The relationship between the defect structure of oxides in the homogeneity region of VO and their thermodynamic properties has been established. The energy of the formation and interaction of defects responsible for the existence of VO has been determined. Possible ordering of the defect arrangement in VO in a wide temperature range has been elucidated. Seven zones of VO homogeneity have been considered according to the nature of ? anti Ssub o2)sup(0)/? anti H sub(o2)sup(0)/. The energy characteristics of the defects (kcal) have been determined on the basis of the found relationships for three temperature values in therange 1173-1373 deg K..It has been conluded that in the middle part of the homogeneity region of VO considerable attraction of opposite defects can lead to the formation of the complexes of the defects; at temperatures lower than considered an individual phase, similar in composition to VO, may be formed

344

Toxicity of aliphatic amines: structure-activity relationship.  

Science.gov (United States)

SARs may enable the evaluation of the toxic potential of chemicals by drawing conclusions from available data on structurally-related chemicals, thus reducing the need for further testing. The Advisory Committee on Existing Chemicals of Environmental Relevance (BUA) [1,2] of the German Chemical Society (Gesellschaft Deutscher Chemiker [GDCh]) has compiled data on the toxicity and ecological impact for several groups of chemicals [3, 4]. In the present review, some common toxicological properties for aliphatic amines were revealed after evaluation and comparison of the toxicity data. PMID:9569935

Greim, H; Bury, D; Klimisch, H J; Oeben-Negele, M; Ziegler-Skylakakis, K

1998-01-01

345

Analysis and Projection of the Relationship between Industrial Structure and Land Use Structure in China  

Directory of Open Access Journals (Sweden)

Full Text Available Based on the computable general equilibrium (CGE modelling method, this research analyzes the relationship between industrial structure and land use structure in China. The results show that our model is feasible, and the simulation results are of a certain stability. Under the scenario analysis and projection of the relationship between the industrial structure and land use structure of the thirty-one provinces in China from 2010 to 2020, the proportions of secondary and tertiary industry in each province have been increasing; correspondingly, the proportion of agriculture has been decreasing. This means that the industrial structure of China is changing. As for land use, in general, the trend is similar to the industrial structure changes. The transformation of the structure of industrial development and land use has driven economic structure changes in China. The economic structure has an inclination to transform from agriculture to both secondary and tertiary industry. Along with industrial transformation, the cultivated land in China shows a trend of continuous decline. Empirical analysis results indicate that a decrease of cultivated land is acceptable under the scenario of economic growth in the next ten years. This shows a possibility that the economic efficiency of land use for cultivation and business services will decline, and more attention ought to be paid to increasing the economic efficiency of land use.

Qin Jin

2014-12-01

346

The structure and properties of water  

CERN Document Server

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

347

Semiconducting clathrates: synthesis, structure and properties  

International Nuclear Information System (INIS)

The review surveys different aspects of chemical studies of semiconducting clathrates belonging to a unique family of inclusion compounds. The classification, crystal and electronic structures, properties and methods for the synthesis of semiconducting clathrates are considered on the basis of analysis of recent publications. The prospects for fundamental research and the construction of new-generation materials based on semiconducting clathrates are discussed.

348

Diamond nanowires: fabrication, structure, properties, and applications.  

Science.gov (United States)

C(sp(3) )?C-bonded diamond nanowires are wide band gap semiconductors that exhibit a combination of superior properties such as negative electron affinity, chemical inertness, high Young's modulus, the highest hardness, and room-temperature thermal conductivity. The creation of 1D diamond nanowires with their giant surface-to-volume ratio enhancements makes it possible to control and enhance the fundamental properties of diamond. Although theoretical comparisons with carbon nanotubes have shown that diamond nanowires are energetically and mechanically viable structures, reproducibly synthesizing the crystalline diamond nanowires has remained challenging. We present a comprehensive, up-to-date review of diamond nanowires, including a discussion of their synthesis along with their structures, properties, and applications. PMID:25376154

Yu, Yuan; Wu, Liangzhuan; Zhi, Jinfang

2014-12-22

349

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

350

Structure and properties of sintered solid alloys  

International Nuclear Information System (INIS)

The results of comparison investigation of structure and properties of alloys of the WC-Co Re system and TiC-steel of commercial composition and alloys, corresponding by composition and structure to binding phases are presented. It is shown that hardness of the TiC-steel alloys increases with the increase of carbon content within the investigated limits. The TiC-steel alloys with ferrite-pearlite bond, which is free of cementite secondary crystals in structure, have the optimum complex of properties. Investigation of WC alloys with cobalt-rhenium bond shows that they have a good wear resistance. Using of cobalt-rhenium bond permits to increase softening temperature of solid alloy, decrease adhesion with machined material and improve explitation characteristics at machining in WC base alloys

351

Unbalance Quantitative Structure Activity Relationship Problem Reduction in Drug Design  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: Activities of drug molecules can be predicted by Quantitative Structure Activity Relationship (QSAR models, which overcome the disadvantage of high cost and long cycle by employing traditional experimental methods. With the fact that number of drug molecules with positive activity is rather fewer than that with negatives, it is important to predict molecular activities considering such an unbalanced situation. Approach: Asymmetric bagging and feature selection was introduced into the problem and Asymmetric Bagging of Support Vector Machines (AB-SVM was proposed on predicting drug activities to treat unbalanced problem. At the same time, features extracted from structures of drug molecules affected prediction accuracy of QSAR models. Hybrid algorithm named SPRAG was proposed, which applied an embedded feature selection method to remove redundant and irrelevant features for AB-SVM. Results: Numerical experimental results on a data set of molecular activities showed that AB-SVM improved AUC and sensitivity values of molecular activities and SPRAG with feature selection further helps to improve prediction ability. Conclusion: Asymmetric bagging can help to improve prediction accuracy of activities of drug molecules, which could be furthermore improved by performing feature selection to select relevant features from the drug.

D. Pugazhenthi

2009-01-01

352

Electronic and structural properties of complex oxides  

Science.gov (United States)

This thesis focuses on oxides whose crystalline forms are isomorphic with silica (SiO2) in order to understand their electronic and structural properties. Silica is one of the most widely investigated oxides due to its important electronic, geophysical arid chemical properties. As many as 40 crystalline polymorphs along with amorphous and liquid forms have been described and studied in the literature. The alpha-quartz structure of silica exhibits interesting mechanical and pressure induced behavior. For example, when it is subjected to pressure, it will undergo a slow amorphization. There are many materials that are isostructural with SiO2. Isostructural materials should have similar properties and exhibit similar characteristics. Here we examine three materials: AlPO4, GaAsO4 and GeO 2. AlPO4 has attracted considerable attention owing to the potential technological importance of its high pressure behavior as a memory glass. GaAsO4 is another III-V analog compound, but shows no evidence of pressure induced amorphization as quartz does. GeO2, like silica, undergoes pressure induced amorphization in the alpha-quartz structure, but unlike silica, occurs only in two stable polymorphs. The objective of this thesis is to present a comprehensive picture of oxides that are isostructural with silica. We have computed a variety of properties of each material: (1) Equation of state in the form of volume versus pressure, (2) Structural properties as a function of pressure such as lattice constants and the internal coordinates describing the positions of constituent atoms within the cell, (3) Elastic properties such as the bulk modulus, (4) Electronic properties such as density of states, band structure, and charge density. Computations were performed using a quantum mechanical method based on "soft" ab initio pseudopotentials constructed within a local density approximation. The pseudopotentials required can be extracted from atomic structure calculations. A key element of the pseudopotential includes the elimination of chemically inert states, i.e., the core states. The resulting pseudopotential is weak and the wavefunctions can be described by simple basis sets such as plane waves. This approach is attractive for its reliability and its high predictive power.

Christie, Diane Marie

353

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

OpenAIRE

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

Saldana D.A.; Creton B.; Mougin P.; Jeuland N.; Rousseau B.; Starck L.

2013-01-01

354

Prediction and Derivation of the Higgs Boson from the Neutron and Properties of Hydrogen Demonstrating Relationships with Planck’s Time, the Down Quark, and the Fine Structure Constant  

OpenAIRE

A high accuracy Higgs boson, H0, is an important physical constant. The Higgs boson is associated with the property of mass related to broken symmetry in the Standard Model. The H0 mass cannot be derived by the Standard Model. The goal of this work is to derive and predict the mass of H0 from the subatomic data of the frequency equivalents of the neutron, electron, Bohr radius, and the ionization energy of hydrogen. H0’s close re...

Donald William Chakeres

2014-01-01

355

The Attitudes to Chocolate Questionnaire: psychometric properties and relationship to dimensions of eating.  

Science.gov (United States)

The aim of the present study was to evaluate the psychometric properties of the Attitudes to Chocolate Questionnaire (ACQ). We analyzed the factor structure of the ACQ by conducting exploratory and confirmatory factor analyses in a sample of healthy adults and a sample of dietician students. Further, the relationship between the resulting ACQ factors and dimensions of eating behavior, personality, emotionality, and tests of the pleasantness, sweetness, and intensity of sugar and chocolate was examined. The results yielded a clear two-factor structure of the ACQ: The first factor (guilt) was composed of items concerning negative consequences of chocolate eating including the feeling of guilt. The second factor (craving) comprised items related to craving and emotional chocolate eating. Guilt correlated significantly with "emotional eating", "restrained eating", and with neuroticism. Craving correlated significantly with "emotional eating" and "external eating", with neuroticism, and with the "difficulty identifying feelings" facet of the Toronto Alexithymia Scale; further, it correlated highly with the average reported chocolate consumption and with the ratings of the intensity of taste of sugar. In conclusion, results support the validity of the German version of the ACQ and showed a stable factor structure and a good internal consistency. PMID:18068267

Müller, Jochen; Dettmer, Dorothee; Macht, Michael

2008-01-01

356

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

Science.gov (United States)

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

Gupta, Mohit

357

["Structure-anti-arrhythmic activity" relationship of N-phenilacetamide derivatives and amides of aromatic carbonic acids].  

Science.gov (United States)

Using the computer system SARD-21 (Structure Activity Relationship & Design) structural features of high- and low-effective anti-arrhythmic agents have been recognized and the influence of these features on the anti-arrhythmic properties has been evaluated. This information has been used for generation of the model for prediction of anti-arrhythmic effectiveness of pharmaceutical preparations with the 82%-level of recognition by two methods. The recognized structural parameters may be successfully used for design of new highly effective anti-arrhythmic drugs, and also for modification of structures of known anti-arrhythmic drugs for the increase of effectiveness of their anti-arrhythmic action. PMID:21032897

Kha?rullina, V R; Tarasov, G P; Gerchikov, A Ia; Zarudy?, F S; Tiurina, L A

2010-01-01

358

Phylogenetic relationships and call structure in four African bufonid species  

Directory of Open Access Journals (Sweden)

Full Text Available ENGLISH ABSTRACT: Four species of toads of the genus Bufo. comprising three species endemic to southern Africa and one closely-related species, were examined electrophoretically to infer their phylogenetic relationships. The evolution of advertisement call structure in these species is discussed in relation to this phylogeny. Bufo rangeri and B. gutturalis, two species with very different call structures, are sister taxa. Two pairs of species with very similar call structures, B. pardalis and B. gutturalis, and B. rangeri and B. angusticeps, were only distantly related. Our results suggest that call parameters are poor characters to use in inferring phylogenies among congeneric species, probably because of selection for optimal audibility in different habitats, and because of the role that they play in premating isolation. The phylogeny derived from allozyme data agrees with evidence on albumin immunological distance, karyotype and morphology.***********AFRIKAANSE OPSOMMING: Vier spesies skurwepaddas van die genus Buto, bestaande uit drie wat endemies is in Suid-Afrika en een nou-verwante spesie, is elektroforeties ondersoek om hulle filogenetiese verwantskap af te lei. Die evolusie van die struktuur van die bekendstellingsroep by hierdie spesie word met betrekking tot hierdie filogenie bespreek. Buto rangeri en B. gutturalis, twee spesies met baie verskillende roepstrukture, is suster taksa. Twee pare van spesies met baie ooreenstemmende roepstrukture, B. pardalis en B. gutturalis, en B. rangeri en B. angusticeps, was slegs ver langs verwant. Ons resultate dui daarop dat roep-parameters swak kenmerke is om te gebruik by die aflei van filogenieë by verwante spesies, waarskynlik as gevolg van seleksie wat plaasvind vir optimale hoorbaarheid in verskillende habitatte, sowel as die rol wat hulle speel by die pre-paringsisolasie. Die filogenie wat van allosiemdata afgelei is, stem ooreen met getuienis oor albumien immunologiese afstand, kariotipe en morfologie .

W.S. Grant

2012-01-01

359

Third-generation and investigational cephalosporins: I. Structure-activity relationships and pharmacokinetic review.  

Science.gov (United States)

The structure-relationships and pharmacokinetic properties of the new second- and third-generation cephalosporins are reviewed. The new second-generation cephalosporins include ceforanide, cefotiam, and cefuroxime. The third-generation cephalosporins include cefmenoxime, cefoperazone, cefotaxime, cefsulodin, ceftazidime, ceftizoxime, ceftriaxone, and moxalactam. These new cephalosporins are semisynthetic analogs with different chemical substitutions on a 7-aminocephalosporanic nucleus. As a result of these chemical modifications, improvements in the antibacterial spectrum as well as pharmacokinetic properties have occurred. In general, the new cephalosporins have longer half-lives, higher and prolonged serum concentrations, and increased cerebrospinal fluid penetration. Selected cephalosporins also have increased biliary tract concentrations. A classification scheme for these new agents, based on generation and susceptibility to Pseudomonas aeruginosa, is presented. PMID:6347596

Garzone, P; Lyon, J; Yu, V L

1983-01-01

360

Synthesis and structure/antioxidant activity relationship of novel catecholic antioxidant structural analogues to hydroxytyrosol and its lipophilic esters.  

Science.gov (United States)

A large panel of novel catecholic antioxidants and their fatty acid or methyl carbonate esters has been synthesized in satisfactory to good yields through a 2-iodoxybenzoic acid (IBX)-mediated aromatic hydroxylation as the key step. The new catechols are structural analogues of naturally occurring hydroxytyrosol (3,4-DHE). To evaluate structure/activity relationships, the antioxidant properties of all catecholic compounds were evaluated in vitro by ABTS assay and on whole cells by DCF fluorometric assay and compared with that of the corresponding already known hydroxytyrosyl derivatives. Results outline that all of the new catechols show antioxidant capacity in vitro higher than that of the corresponding hydroxytyrosyl derivatives. Less evident positive effects have been detected in whole cells experiments. Cytotoxicity experiments, using MTT assay, on a representative set of compounds evidenced no influence in cell survival. PMID:22780104

Bernini, Roberta; Crisante, Fernanda; Barontini, Maurizio; Tofani, Daniela; Balducci, Valentina; Gambacorta, Augusto

2012-08-01

361

Nucleon structure and properties of dense matter  

International Nuclear Information System (INIS)

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)

362

Using structural equation modeling to investigate relationships among ecological variables  

Science.gov (United States)

Structural equation modeling is an advanced multivariate statistical process with which a researcher can construct theoretical concepts, test their measurement reliability, hypothesize and test a theory about their relationships, take into account measurement errors, and consider both direct and indirect effects of variables on one another. Latent variables are theoretical concepts that unite phenomena under a single term, e.g., ecosystem health, environmental condition, and pollution (Bollen, 1989). Latent variables are not measured directly but can be expressed in terms of one or more directly measurable variables called indicators. For some researchers, defining, constructing, and examining the validity of latent variables may be the end task of itself. For others, testing hypothesized relationships of latent variables may be of interest. We analyzed the correlation matrix of eleven environmental variables from the U.S. Environmental Protection Agency's (USEPA) Environmental Monitoring and Assessment Program for Estuaries (EMAP-E) using methods of structural equation modeling. We hypothesized and tested a conceptual model to characterize the interdependencies between four latent variables-sediment contamination, natural variability, biodiversity, and growth potential. In particular, we were interested in measuring the direct, indirect, and total effects of sediment contamination and natural variability on biodiversity and growth potential. The model fit the data well and accounted for 81% of the variability in biodiversity and 69% of the variability in growth potential. It revealed a positive total effect of natural variability on growth potential that otherwise would have been judged negative had we not considered indirect effects. That is, natural variability had a negative direct effect on growth potential of magnitude -0.3251 and a positive indirect effect mediated through biodiversity of magnitude 0.4509, yielding a net positive total effect of 0.1258. Natural variability had a positive direct effect on biodiversity of magnitude 0.5347 and a negative indirect effect mediated through growth potential of magnitude -0.1105 yielding a positive total effects of magnitude 0.4242. Sediment contamination had a negative direct effect on biodiversity of magnitude -0.1956 and a negative indirect effect on growth potential via biodiversity of magnitude -0.067. Biodiversity had a positive effect on growth potential of magnitude 0.8432, and growth potential had a positive effect on biodiversity of magnitude 0.3398. The correlation between biodiversity and growth potential was estimated at 0.7658 and that between sediment contamination and natural variability at -0.3769.

Malaeb, Z.A.; Kevin, Summers J.; Pugesek, B.H.

2000-01-01

363

Establishing collaborative structures and relationships: Teacher leaders' experiences  

Science.gov (United States)

The purpose of this study was to explore teacher leaders' experiences as they attempted to establish collaborative structures and relationships resulting in improved science instruction at their schools. Teacher leaders were middle school science facilitators, full-time classroom teachers who acted as liaisons between the science teachers at their schools and a change initiative funded by the National Science Foundation. This was a qualitative study, using interviews to create a case study. The researcher used a three-part interview design developed by Seidman (1991). Six research questions served as a framework for the data analysis. Participants identified the following as factors which contributed to their success: support from the principal, other science teachers, central staff personnel, and the district-wide group of science facilitators; professional development; and the successful completion of a scope and sequence for science instruction. Factors identified as hindering their success were: lack of support or conflict with the principal; resistance to change; time constraints; a district policy which limited meeting time; teacher and administrator turnover; tension between the middle school and junior high school models; and personal doubts. From descriptions of their understanding and exercising of leadership, the researcher concluded that teacher leaders had become empowered. The school culture was seen to have a great effect on teacher leaders. The contrasts between a school with a positive culture and another school in disarray were presented. Structures such as summer institutes and release time during the school day were identified as critical for giving teachers the time needed to establish more collaborative working relationships. Once greater trust and understanding were present, teachers were better able to examine their teaching practices more critically. Participants identified mentoring of new members, a continuing role for science facilitators, and central support as necessary for ensuring the sustainability of the changes made during the years of the grant initiative. The researcher concluded that teacher leaders can be a powerful force for bringing about change in schools when provided with training and time during the school day to work with colleagues.

Canizo, Thea Lynne

2002-04-01

364

Quantitative Structure-Activity Relationship Studies of 4-Imidazolyl- 1,4-dihydropyridines as Calcium Channel Blockers  

Science.gov (United States)

Objective(s): The structure- activity relationship of a series of 36 molecules, showing L-type calcium channel blocking was studied using a QSAR (quantitative structure–activity relationship) method. Materials and Methods: Structures were optimized by the semi-empirical AM1 quantum-chemical method which was also used to find structure-calcium channel blocking activity trends. Several types of descriptors, including electrotopological, structural and thermodynamics were used to derive a quantitative relationship between L-type calcium channel blocking activity and structural properties. The developed QSAR model contributed to a mechanistic understanding of the investigated biological effects. Results: Multiple linear regressions (MLR) was employed to model the relationships between molecular descriptors and biological activities of molecules using stepwise method and genetic algorithm as variable selection tools. The accuracy of the proposed MLR model was illustrated using cross-validation, and Y-randomisation -as the evaluation techniques. Conclusion: The predictive ability of the model was found to be satisfactory and could be used for designing a similar group of 1,4- dihydropyridines , based on a pyridine structure core which can block calcium channels. PMID:24106595

Hadizadeh, Farzin; Vahdani, Saadat; Jafarpour, Mehrnaz

2013-01-01

365

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

366

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

2005-03-01

367

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

International Nuclear Information System (INIS)

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

368

Structure and magnetic properties of powder HITPERM material  

Directory of Open Access Journals (Sweden)

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

J.E. Fr?ckowiak

2007-03-01

369

Relationships between supercontraction and mechanical properties of spider silk  

Science.gov (United States)

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

Liu, Yi; Shao, Zhengzhong; Vollrath, Fritz

2005-12-01

370

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

Science.gov (United States)

To elucidate the relationship between transport properties and phase transformations in mixed-conducting oxides, Sr 0.9Ca 0.1Co 0.89Fe 0.11O 3-? (SCCFO) and SrCoO 3-? (SCO) were chosen as the model materials and have been investigated in detail. Oxygen permeation measurements verified that both oxides are well permeable to oxygen at elevated temperatures, e.g., at 900 °C during a cooling procedure, oxygen permeation rates as large as 1.5 and 2.0 mL/min/cm 2 could be obtained with disk-shaped SCCFO and SCO membranes of thickness 1.5 mm, respectively. But when cooled to critical temperatures, the oxygen permeability of these kinds of oxides diminished sharply, which could be recovered by increasing the temperature again to certain values. Abrupt changes on electrical conductivity were also observed for both oxides around the same region of temperature as that of oxygen permeability. As indicated by high-temperature X-ray diffraction and thermal analysis, the SCCFO and SCO systems undergo phase transformation between a low-temperature orthorhombic brownmillerite structure (B) or a hexagonal 2H-type structure (H) and a high-temperature cubic perovskite structure (C), respectively. The present results suggest the observed abrupt changes in transport properties versus temperature are attributed to such phase transformation, which may be directly associated with the order-disorder transition of oxygen vacancies. Moreover, compared to the B/C transformation that mainly involves an order-disorder transition on the oxygen sublattice, the H/C one necessarily also involves the cooperative long-range reorganization on the cation sublattice. Therefore it occurs at a higher temperature and absorbs more heat quantity than those of B/C transformation.

Deng, Z. Q.; Yang, W. S.; Liu, W.; Chen, C. S.

2006-02-01

371

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

Science.gov (United States)

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

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

2012-03-01

372

Structural properties of dense hard sphere packings.  

Science.gov (United States)

We numerically study structural properties of mechanically stable packings of hard spheres (HS), in a wide range of packing fractions 0.53 ? ? ? 0.72. Detailed structural information is obtained from the analysis of orientational order parameters, which clearly reveals a disorder-order phase transition at the random close packing (RCP) density, ?c ? 0.64. Above ?c, the crystalline nuclei form 3D-like clusters, which upon further desification transform into alternating planar-like layers. We also find that particles with icosahedral symmetry survive only in a narrow density range in the vicinity of the RCP transition. PMID:25098389

Klumov, Boris A; Jin, Yuliang; Makse, Hernán A

2014-09-11

373

Structural and tunneling properties of Si nanowires  

KAUST Repository

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

Montes, E.

2013-12-06

374

Structural and energetic properties of sodium clusters  

Science.gov (United States)

In this work we present results from a theoretical study on the properties of sodium clusters. The structures of the global total-energy minima have been determined using two different methods. With the parameterized density-functional tight-binding method (DFTB) combined with a genetic-algorithm we investigated the properties of NaN clusters with cluster size up to 20 atoms, and with our own Aufbau/Abbau algorithm together with the embedded-atom method (EAM) up to 60 atoms. The two sets of results from the independent calculations are compared and a stability function is studied as function of the cluster size. Due to the electronic effects included in the DFTB method and the packing effects included in the EAM we have obtained different global-minima structures and different stability functions.

Tevekeliyska, V.; Dong, Y.; Springborg, M.; Grigoryan, V. G.

2007-07-01

375

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

Scientific Electronic Library Online (English)

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

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

2005-03-01

376

Molecular and Electronic Structure of Cyclic Trinuclear Gold(I) Carbeniate Complexes: Insights for Structure/Luminescence/Conductivity Relationships  

Energy Technology Data Exchange (ETDEWEB)

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