WorldWideScience
1

Structure--properties relationships for manganese perovskites  

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-10-14

2

Structure-optical property relationships of porphyrins  

Science.gov (United States)

Porphyrins are attractive compounds for optical applications. We have been investigating the relationship between molecular structure and optical properties of a number of porphyrin compounds. Structural variations explored include insertion of metal ions, extension of conjugation, halogenation and alkylation either at the pyrrole position or the meso-aryl groups. The characterization of these chromophores includes measurement of UV/Vis, fluorescence and fluorescence lifetimes. Furthermore, we have investigated their nonlinear absorption, excitation dynamics. The significant factors influencing limiting behavior appear to be the heavy atom effect, electron donating and withdrawing substituents conformation distortion and changes in conjugation. Detailed understanding will be gained from measurements of photophysical parameters underlying limiting behavior.

Su, Weigie; Cooper, Thomas M.; Nguyen, Kiet; Brant, Mark C.; Brandelik, Donna M.; McLean, Daniel G.

1998-10-01

3

Molecular structure-property relationships for alkenes.  

Science.gov (United States)

Structure-property relationships were obtained for 11 physical and chemical properties (boiling points (bp), melting points (mp), molar refractions (MR), molar volumes (MV), heats of combustion (HCKJ), molar heats of vaporization (HVMOL), flashpoints (FLASHK), second virial coefficients (VIRC2), critical temperatures (Tc), critical pressures (Pc), and viscosities (VISC)) for a data set consisting of 162 C4-C9 monoalkenes. Both molecular connectivity indices and ad hoc descriptors were tested as structural descriptors, and both produced high-quality regression equations for most of the properties. As was observed in an earlier study of alkanes [J. Am. Chem. Soc. 110 (1988) 4186], mp were not well described by either descriptor set. For most properties, the mass/bulk of the molecule was found to be the most important structural feature determining the property, suggesting that dispersion forces play a dominant role in determining those properties influenced by intermolecular interactions. The amount of branching in the molecule and the nature of the double bond environment were also found to be influential features. PMID:11760001

Nelson, S D; Seybold, P G

2001-01-01

4

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 4,4sp'-bismaleimidodiphenyl methane (BMI). BMI was coreacted with either 4,4sp'-methylene dianiline (MDA), o,osp'-diallyl bisphenol A (DABA) from Ciba Geigy, or diamino diphenyl sulfone (DDS). Three cure paths were employed: a low-temperature cure of 140sp°C where chain extension should predominate, a high-temperature cure of 220sp°C where both chain extension and crosslinking should occur simultaneously, and a low-temperature (140sp°C) cure followed immediately by a high-temperature (220sp°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 BMI 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 Diane

5

Water Activated Carbon Organics Adsorption Structure - Property Relationships  

OpenAIRE

Investigation (determination) of chemical compounds properties need time and many resources when is performed by classical way, or experimentations. Nowadays a number of quantitative structure-property relationships (QSPRs) were developed in order to shorting the research and analysis time of chemical properties on classes of compounds. The ability of the molecular descriptor family (MDF) was used to produce QSPRs for estimating the adsorption onto activated carbon in water. A number of sixte...

Ja?ntschi, Lorentz

2004-01-01

6

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

7

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

8

Redox properties of structural Fe in clay minerals: 3. Relationships between smectite redox and structural properties.  

Science.gov (United States)

Structural Fe in clay minerals is an important redox-active species in many pristine and contaminated environments as well as in engineered systems. Understanding the extent and kinetics of redox reactions involving Fe-bearing clay minerals has been challenging due to the inability to relate structural Fe(2+)/Fe(total) fractions to fundamental redox properties, such as reduction potentials (EH). Here, we overcame this challenge by using mediated electrochemical reduction (MER) and oxidation (MEO) to characterize the fraction of redox-active structural Fe (Fe(2+)/Fe(total)) in smectites over a wide range of applied EH-values (-0.6 V to +0.6 V). We examined Fe(2+)/Fe(total )- EH relationships of four natural Fe-bearing smectites (SWy-2, SWa-1, NAu-1, NAu-2) in their native, reduced, and reoxidized states and compared our measurements with spectroscopic observations and a suite of mineralogical properties. All smectites exhibited unique Fe(2+)/Fe(total) - EH relationships, were redox active over wide EH ranges, and underwent irreversible electron transfer induced structural changes that were observable with X-ray absorption spectroscopy. Variations among the smectite Fe(2+)/Fe(total) - EH relationships correlated well with both bulk and molecular-scale properties, including Fe(total) content, layer charge, and quadrupole splitting values, suggesting that multiple structural parameters determined the redox properties of smectites. The Fe(2+)/Fe(total) - EH relationships developed for these four commonly studied clay minerals may be applied to future studies interested in relating the extent of structural Fe reduction or oxidation to EH-values. PMID:24219773

Gorski, Christopher A; Klüpfel, Laura E; Voegelin, Andreas; Sander, Michael; Hofstetter, Thomas B

2013-12-01

9

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

Science.gov (United States)

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

Kusoglu, Ahmet; Weber, Adam

2013-03-01

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

Predicting explosibility properties of chemicals from quantitative structure-property relationships  

OpenAIRE

Quantitative Structure-Property Relationship (QSPR) type methods have been up to now mainly devoted to biological, toxicological applications but their use to predict physico-chemical properties is a growing interest. In this context, an original approach associating QSPR methods and quantum chemical calculations for the prediction of chemicals explosibility properties is presented here. Indeed, the new European regulation of chemicals named REACH implies the new assessment of a tremendous nu...

Fayet, Guillaume; Rotureau, Patricia; Joubert, Laurent; Adamo, Carlo

2010-01-01

12

Structure-property relationships of multiferroic materials: A nano perspective  

Science.gov (United States)

The integration of sensors, actuators, and control systems is an ongoing process in a wide range of applications covering automotive, medical, military, and consumer electronic markets. Four major families of ceramic and metallic actuators are under development: piezoelectrics, electrostrictors, magnetostrictors, and shape-memory alloys. All of these materials undergo at least two phase transformations with coupled thermodynamic order parameters. These transformations lead to complex domain wall behaviors, which are driven by electric fields (ferroelectrics), magnetic fields (ferromagnetics), or mechanical stress (ferroelastics) as they transform from nonferroic to ferroic states, contributing to the sensing and actuating capabilities. This research focuses on two multiferroic crystals, Pb(Mg1/3Nb 2/3)O3-PbTiO3 and Fe-Ga, which are characterized by the co-existence and coupling of ferroelectric polarization and ferroelastic strain, or ferro-magnetization and ferroelastic strain. These materials break the conventional boundary between piezoelectric and electrostrictors, or magnetostrictors and shape-memory alloys. Upon applying field or in a poled condition, they yield not only a large strain but also a large strain over field ratio, which is desired and much benefits for advanced actuator and sensor applications. In this thesis, particular attention has been given to understand the structure-property relationships of these two types of materials from atomic to the nano/macro scale. X-ray and neutron diffraction were used to obtain the lattice structure and phase transformation characteristics. Piezoresponse and magnetic force microscopy were performed to establish the dependence of domain configurations on composition, thermal history and applied fields. It has been found that polar nano regions (PNRs) make significant contributions to the enhanced electromechanical properties of PMN-x%PT crystals via assisting intermediate phase transformation. With increasing PT concentration, an evolution of PNR?PND (polar nano domains)? micron-domains?macro-domains was found. In addition, a domain hierarchy was observed for the compositions near a morphotropic phase boundary (MPB) on various length scales ranging from nanometer to millimeter. The existence of a domain hierarchy down to the nm scale fulfills the requirement of low domain wall energy, which is necessary for polarization rotation. Thus, upon applying an E-field along direction(s) in a composition near the MPB, low symmetry phase transitions (monoclinic or orthorhombic) can easily be induced. For PMN-30%PT, a complete E-T (electric field vs temperature) diagram has been established. As for Fe-x at.% Ga alloys, short-range Ga-pairs serve as both magnetic and magnetoelastic defects, coupling magnetic domains with bulk elastic strain, and contributing to enhanced magnetostriction. Such short-range ordering was evidenced by a clear 2theta peak broadening on neutron scattering profiles near A2-DO3 phase boundary. In addition, a strong degree of preferred [100] orientation was found in the magnetic domains of Fe-12 at.%Ga and Fe-20 at.%Ga alloys with the A2 or A2+DO3 structures, which clearly indicates a deviation from cubic symmetry; however, no domain alignment was found in Fe-25 at.%Ga with the DO3 structure. Furthermore, an increasing degree of domain fluctuations was found during magnetization rotation, which may be related to short-range Ga-pairs cluster with a large local anisotropy constant, due to a lower-symmetry structure.

Bai, Feiming

13

Structure-Property Relationships in Sulfonated Pentablock Copolymers  

Science.gov (United States)

Membranes of pentablock copolymers consisting of poly(tert-butyl styrene) (TBS), hydrogenated polyisoprene (HI), and partially sulfonated poly(styrene-ran-styrene sulfonate) (SS) were studied using small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The TBS-HI-SS-HI-TBS pentablock copolymer in solution forms spherical micelles with a core of SS and a corona of solvated HI and TBS. The spherical micelles in solution compact as the solvent evaporates and some of SS cores merge to form interconnected SS microdomains without substantially changing their shape. The number of connections increases with the volume fraction of the SS block, which increases with sulfonation level. The structure does not have long-range order, because strong ionic interactions prevent extensive rearrangement. The morphologies of the sulfonated pentablock copolymers will be correlated with their transport properties.

Choi, Jae-Hong; Willis, Carl; Winey, Karen I.

2011-03-01

14

Material properties and structure-function relationships in the menisci.  

Science.gov (United States)

The menisci serve several important biomechanical functions in the knee. They distribute stresses over a broad area of articular cartilage, absorb shocks during dynamic loading, and probably assist in joint lubrication. These functions enhance the ability of articular cartilage to provide a smooth, near-frictionless articulation and to distribute loads evenly to the underlying bone of the femur and tibia. In addition, the menisci provide stability to the injured knee when the cruciate ligaments or other primary stabilizers are deficient. The ability to perform these mechanical functions is based on the intrinsic material properties of the menisci as well as their gross anatomic structure and attachments. The material properties of the menisci are determined by their biochemical composition and, perhaps more important, by the organization and interactions of the major tissue constituents: water, proteoglycan, and collagen. Interactions among the important constituents of the fibrocartilage matrix cause meniscal tissue to behave as a fiber-reinforced, porous, permeable composite material similar to articular cartilage, in which frictional drag caused by fluid flow governs its response to dynamic loading. The menisci are one-half as stiff in compression and dissipate more energy under dynamic loading than articular cartilage. Energy dissipation, or shock absorption, by the menisci is the result of high frictional drag caused by low permeability of the matrix, which is about one-sixth as permeable as articular cartilage. The dynamic shear modulus of meniscal tissue is only one-fourth to one-sixth as great as that of articular cartilage. The coarse, circumferential Type I collagen fiber bundles of the meniscus give the tissue great tensile stiffness (range, 100-300 megapascals) and strength. The highly oriented collagen ultrastructure of the menisci makes the tissue anisotropic in tension, compression, and shear and appears to dominate its behavior under all loading conditions. PMID:2406069

Fithian, D C; Kelly, M A; Mow, V C

1990-03-01

15

Multiscale relationships between fibronectin structure and functional properties.  

Science.gov (United States)

Cell behavior is tightly coupled to the properties of the extracellular matrix (ECM) to which they attach. Fibronectin (Fn) forms a supermolecular, fibrillar component of the ECM that is prominent during development, wound healing and the progression of numerous diseases. This indicates that Fn has an important function in controlling cell behavior during dynamic events in vivo. The multiscale architecture of Fn molecules assembled into these fibers determines the ligand density of cell adhesion sites on the surface of the Fn fiber, Fn fiber porosity for cell signaling molecules such as growth factors, the mechanical stiffness of the Fn matrix and the adhesivity of Fn for its numerous soluble ligands. These parameters are altered by mechanical strain applied to the ECM. Recent efforts have attempted to link the molecular properties of Fn with bulk properties of Fn matrix fibers. Studies of isolated Fn fibers have helped to characterize the fiber's material properties and, in combination with models of Fn molecular behavior in the fibers, have begun to provide insights into the Fn molecular arrangement and intermolecular adhesions within the fibers. A review of these studies allows the development of an understanding of the mechanobiological functions of Fn. PMID:23978411

Bradshaw, M J; Smith, M L

2014-04-01

16

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

17

Structure-property-function relationships in triple helical collagen hydrogels  

CERN Document Server

In order to establish defined biomimetic systems, type I collagen was functionalised with 1,3-Phenylenediacetic acid (Ph) as aromatic, bifunctional segment. Following investigation on molecular organization and macroscopic properties, material functionalities, i.e. degradability and bioactivity, were addressed, aiming at elucidating the potential of this collagen system as mineralization template. Functionalised collagen hydrogels demonstrated a preserved triple helix conformation. Decreased swelling ratio and increased thermo-mechanical properties were observed in comparison to state-of-the-art carbodiimide (EDC)-crosslinked collagen controls. Ph-crosslinked samples displayed no optical damage and only a slight mass decrease (~ 4 wt.-%) following 1-week incubation in simulated body fluid (SBF), while nearly 50 wt.-% degradation was observed in EDC-crosslinked collagen. SEM/EDS revealed amorphous mineral deposition, whereby increased calcium phosphate ratio was suggested in hydrogels with increased Ph content...

Tronci, Giuseppe; Russell, Stephen J; Wood, David J

2012-01-01

18

Processing-structure-properties relationships in PLA nanocomposite films  

Science.gov (United States)

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

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

2014-05-01

19

Structure property relationships in polycarbonate/polydimethylsiloxane copolymers  

International Nuclear Information System (INIS)

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

20

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

21

Relationship of solvent to the photopolymerization process, properties, and structure in model dentin adhesives  

OpenAIRE

The ratio of the double-bond content of monomer to polymer, i.e. degree of conversion (DC) has been used frequently as a convenient means of comparing the behavior and properties of dental composites and adhesives. The purpose of this investigation was to study the relationship of photopolymerization processes, bulk properties, and structure using model dentin adhesives cured in the presence of different ethanol content as an example. There was little difference in the DC of model BisGMA-base...

Ye, Qiang; Spencer, Paulette; Wang, Yong; Misra, Anil

2007-01-01

22

Relationship of the optical absorption and scattering properties with mechanical and structural properties of apple tissue  

Science.gov (United States)

Optical absorption and scattering properties of fruit change with the physiological and biochemical activities in the tissue during ripening and postharvest storage. But it has not been well understood on how these changes are related to the structural and mechanical properties of fruit. This resear...

23

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

24

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

25

Some reflections on relationships between structure, properties, and performance of engineering materials  

International Nuclear Information System (INIS)

The main object of materials science and technology is relationships between structure and properties. The practical use of engineering materials also involves consideration of things other than current theories for such relationships. Uncertainties of various kinds prompt reflections on the validity and applications of common practice based on experience. Among other things, this is true for decisions relating to reliability and safety. Hence, fundamental issues like determinism vs. probabilistics may become interesting to anyone who wants to deal efficiently with problems related to the use and performance of engineering materials

26

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

27

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

28

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

Science.gov (United States)

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

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

2010-09-01

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

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

OpenAIRE

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

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

2010-01-01

31

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

Directory of Open Access Journals (Sweden)

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

J. J. Schwab

2012-07-01

32

Comparative studies on rigid ? linker-based organic dyes: structure-property relationships and photovoltaic performance.  

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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  

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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

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

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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

35

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)

36

A study of structure-property relationships in layered copper oxides  

International Nuclear Information System (INIS)

In order to better understand the interplay between crystal structure and superconductivity in layered cuprate superconductors, a study of structure-property relationships in a number of layered cuprate materials has been undertaken. These studies are concerned, principally, with the investigation of such structure-property relationships in mercury-based cuprate superconductors. The crystal structure of HgBa2CuO4+? has been re-examined, on the basis of a conjoint powder X-ray and neutron diffraction study, as described in Chapter Three. This study has determined that, in this material, subtle atomic displacements occur in the neighbourhood of interstitial oxygen atoms. The synthesis, structure and superconducting properties of phases in the (Hg1-xRex)Sr2(Nd1-yCay)Cu2O6+? system is described in Chapter Four. The superconducting properties of this system may be controlled by judicious manipulation of the chemical stoichiometry. Samples of this system, prepared at room pressure, do not show the enhanced irreversibility field characteristics previously reported for similar materials prepared under high pressure. This difference in behaviour is rationalised in terms of (dis)order of the Hg and Re ions in the (Hg,Re)O? plane of this material. The compressibilities of several layered cuprate materials have been determined using high pressure X-ray diffraction methng high pressure X-ray diffraction methods, as described in Chapter Five. This investigation demonstrates that several intimate structure-compressibility relationships exist in these materials. Chapter Six continues the theme of high pressure crystallography, and examines, in detail, the crystal structure of HgBa2CuO4+? using high pressure neutron diffraction methods. This study indicates that the pressure induced increase in Tc observed in HgBa2CuO4+?, may be related to pressure induced relief of structural strain at the interface between the rock-salt and perovskite type layers of this material. Chapter Seven examines the crystal structure of Hg0.8Cr0.2Ba2CuO4+? under ambient and applied pressure. This study shows that significant distortions arise in the crystal structure of HgBa2CuO4+? when linear HgO2 units are substituted by tetrahedral CrO4 units. Finally, Chapter Eight describes a simple method for the fabrication of strontium-based mercurocuprate thin films, by pulsed laser ablation. This 'proof of concept' study demonstrates that superconducting, c-axis oriented, thin films of such materials may be fabricated by pulsed laser deposition of a mercury free precursor film, followed by ex-situ annealing of such thin films in the presence of a sacrifical mercury source. (author)

37

Property-structure relationship of nanoscale ionic materials based on multiwalled carbon nanotubes.  

Science.gov (United States)

Two categories of nanoscale ionic materials (NIMs) based on multiwalled carbon nanotubes (MWCNTs) were obtained. According to the nature of organic modifier and the type of interaction, these NIMs can be divided into two categories referred to as A-MWCNTs-Fs and I-MWCNTs-Fs, respectively. These MWCNT derivatives were virtually solvent-free and showed good flowability even at room temperature. The liquidlike manner of these MWCNT derivatives was from their relatively high organic content and continual departing-recombining motion of the large organic ions as suggested by the comparison of rheological response of the two categories of MWCNT-based NIMs. Thermal property and temperature-dependent and strain-dependent viscoelasticity of MWCNT derivatives were related to the microscopic structure of their coating layer and subsequently related to the configuration, chemistry, and molecular dimension of modifying molecules to establish the property-structure relationship of MWCNT-based NIMs, which could guide our future work on NIMs to appropriate and promising applications based on their tunable and controllable physical properties. PMID:20815401

Li, Qi; Dong, Lijie; Fang, Jingfei; Xiong, Chuanxi

2010-10-26

38

Structural similarity based kriging for quantitative structure activity and property relationship modeling.  

Science.gov (United States)

Structurally similar molecules tend to have similar properties, i.e. closer molecules in the molecular space are more likely to yield similar property values while distant molecules are more likely to yield different values. Based on this principle, we propose the use of a new method that takes into account the high dimensionality of the molecular space, predicting chemical, physical, or biological properties based on the most similar compounds with measured properties. This methodology uses ordinary kriging coupled with three different molecular similarity approaches (based on molecular descriptors, fingerprints, and atom matching) which creates an interpolation map over the molecular space that is capable of predicting properties/activities for diverse chemical data sets. The proposed method was tested in two data sets of diverse chemical compounds collected from the literature and preprocessed. One of the data sets contained dihydrofolate reductase inhibition activity data, and the second molecules for which aqueous solubility was known. The overall predictive results using kriging for both data sets comply with the results obtained in the literature using typical QSPR/QSAR approaches. However, the procedure did not involve any type of descriptor selection or even minimal information about each problem, suggesting that this approach is directly applicable to a large spectrum of problems in QSAR/QSPR. Furthermore, the predictive results improve significantly with the similarity threshold between the training and testing compounds, allowing the definition of a confidence threshold of similarity and error estimation for each case inferred. The use of kriging for interpolation over the molecular metric space is independent of the training data set size, and no reparametrizations are necessary when more compounds are added or removed from the set, and increasing the size of the database will consequentially improve the quality of the estimations. Finally it is shown that this model can be used for checking the consistency of measured data and for guiding an extension of the training set by determining the regions of the molecular space for which new experimental measurements could be used to maximize the model's predictive performance. PMID:24897621

Teixeira, Ana L; Falcao, Andre O

2014-07-28

39

Antioxidant properties of hydroxycinnamic acids: a review of structure- activity relationships.  

Science.gov (United States)

Hydroxycinnamic acids (HCAs) are important phytochemicals possessing significant biological properties. Several investigators have studied in vitro antioxidant activity of HCAs in detail. In this review, we have gathered the studies focused on the structure-activity relationships (SARs) of these compounds that have used medicinal chemistry to generate more potent antioxidant molecules. Most of the reports indicated that the presence of an unsaturated bond on the side chain of HCAs is vital to their activity. The structural features that were reported to be of importance to the antioxidant activity were categorized as follows: modifications of the aromatic ring, which include alterations in the number and position of hydroxy groups and insertion of electron donating or withdrawing moieties as well as modifications of the carboxylic function that include esterification and amidation process. Furthermore, reports that have addressed the influence of physicochemical properties including redox potential, lipid solubility and dissociation constant on the antioxidant activity were also summarized. Finally, the pro-oxidant effect of HCAs in some test systems was addressed. Most of the investigations concluded that the presence of ortho-dihydroxy phenyl group (catechol moiety) is of significant importance to the antioxidant activity, while, the presence of three hydroxy groups does not necessarily improve the activity. Optimization of the structure of molecular leads is an important task of modern medicinal chemistry and its accomplishment relies on the careful assessment of SARs. SAR studies on HCAs can identify the most successful antioxidants that could be useful for management of oxidative stress-related diseases. PMID:23834166

Razzaghi-Asl, N; Garrido, J; Khazraei, H; Borges, F; Firuzi, O

2013-01-01

40

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

41

Relationship between ultrasonic properties and structural changes in the mesophyll during leaf dehydration.  

Science.gov (United States)

The broad-band ultrasonic spectroscopy technique allows the determination of changes in the relative water content (RWC) of leaves with contrasting structural features. Specifically, the standardized frequency associated with the maximum transmittance (f/f(o)) is strongly related to the RWC. This relationship is characterized by the existence of two phases separated by an inflexion point (associated with the turgor loss point). To obtain a better understanding of the strong relationship found between RWC and f/f(o), this work has studied the structural changes experienced by Quercus muehlenbergii leaves during dehydration in terms of ultrasounds measurements, cell wall elasticity, leaf thickness, leaf density, and leaf structure. The results suggest that the decrease found in f/f(o) before the turgor loss point can be attributed to the occurrence of changes in the estimation of the macroscopic effective elastic constant of the leaf (c(33)), mainly associated with changes in the bulk modulus of elasticity of the cell wall (?). These changes are overriding or compensating for the thickness decreases recorded during this phase. On the other hand, the high degree of cell shrinkage and stretching found in the mesophyll cells during the second phase seem to explain the changes in the acoustic properties of the leaf beyond the turgor loss point. The formation of large intercellular spaces, which increased the irregularity in the acoustic pathway, may explain the increase of the attenuation coefficient of ultrasounds once the turgor loss point threshold is exceeded. The direct measurement of c(33) from ultrasonic measurements would allow a better knowledge of the overall biomechanical properties of the leaf further than those derived from the P-V analysis. PMID:21414961

Sancho-Knapik, Domingo; Alvarez-Arenas, Tomás Gómez; Peguero-Pina, José Javier; Fernández, Victoria; Gil-Pelegrín, Eustaquio

2011-06-01

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

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

44

Prediction of aqueous solubility of organic compounds using a quantitative structure-property relationship.  

Science.gov (United States)

A quantitative structure-property relationship (QSPR) was developed for predicting the aqueous solubility of drug-like compounds from their chemical structures. A set of 321 structurally diverse drugs or related compounds, with their intrinsic aqueous solubility collected from literature, was used in this analysis. The data were divided into a training set (n = 267) for building the model and a randomly chosen testing set (n = 54) for assessing the predictive ability of the model. A series of molecular descriptors was calculated directly from chemical structures and a set of eight descriptors, including dipole moment, surface area, volume, molecular weight, number of rotatable bonds/total bonds, number of hydrogen-bond acceptors, number of hydrogen-bond donors and density, was chosen for the final model. The eight-descriptor model generated by multiple linear regression was further optimized by a genetic algorithm guided selection method. The model has a correlation coefficient (r) of 0.95 and a root-mean-square (rms) error of 0.56 log unit. It predicts the solubility of testing set compounds with a reasonable degree of accuracy (r = 0.84 and rms = 0.86 log unit). The present model can serve as a tool for medicinal chemists to guide their early synthetic efforts in arriving at appropriate analogs. PMID:12115811

Chen, Xue-Qing; Cho, Sung Jin; Li, Yi; Venkatesh, Srini

2002-08-01

45

Structure-property relationship in core-shell rubber toughened epoxy nanocomposites  

Science.gov (United States)

The structure-property relationships of epoxy nanocomposites with inorganic layer-structure nanofillers have been studied to obtain the fundamental understanding of the role of nanofillers and the physics of polymer nanocomposites in this dissertation. Several polymer nanocomposite systems with modified montmorillonite (MMT) or alpha-zirconium phosphate (ZrP) nanofillers were prepared with epoxy matrices of different ductility and properties. The successful nanofiller's exfoliations were confirmed with X-ray diffraction and transmission electronic microscopy (TEM). Dynamic mechanical analysis (DMA) on the prepared epoxy nanocomposites revealed the significant increase in rubbery plateau moduli of the epoxy nanocomposite systems above Tg, as high as 4.5 times, and tensile test results showed improved modulus by the nanofiller addition, while the fracture toughness was not affected or slightly decreased by nanofillers. The brittle epoxy nanocomposite systems were toughened with core shell rubber (CSR) particles and showed remarkable increase in fracture toughness (KIC) value up to 270%. The CSR toughening is more effective at ductile matrices, and TEM observation indicates that major toughening mechanisms induced by the CSR addition involve a large scale CSR cavitation, followed by massive shear deformation of the matrix.

Gam, Ki Tak

46

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

47

Localized surface plasmon resonance induced structure-property relationships of metal nanostructures  

Science.gov (United States)

The confluence of nanotechnology and plasmonics has led to new and interesting phenomena. The industrial need for fast, efficient and miniature devices which constantly push the boundaries on device performance tap into the happy marriage between these diverse fields. Designing devices for real life application that give superior performance when compared with existing ones are enabled by a better understanding of their structure-property relationships. Among all the design constraints, without doubt, the shape and size of the nanostructure along with the dielectric medium surrounding it has the maximum influence on the response and thereby the performance of the device. Hence a careful study of the above mentioned parameters is of utmost importance in designing efficient devices. In this dissertation, we synthesize and study the optical properties of nanostructures of different shapes and size. In particular, we estimated the plasmonic near field enhancement via surface-enhanced Raman scattering (SERS) and 2-photon Photoemission electron microscopy (2P-PEEM). We synthesized the nanostructures using four different techniques. One synthesis technique, the thermal growth method was employed to grow interesting Ag and Au nanostructures on Si. The absence of toxic chemicals during nanostructure synthesis via the thermal growth technique opens up myriad possibilities for applications in the fields of biomedical science, bioengineering, drug delivery among others along with the huge advantage of being environment friendly. The other three synthesis techniques (ion implantation, Electrodeposition and FIB lithography) were chosen with the specific goal of designing novel plasmonic metal, metal hybrid nanostructures as photocathode materials in next generation light sources. The synthesis techniques for these novel nanostructures were dictated by the requirement of high quantum efficiency, robustness under constant irradiation and coherent unidirectional electron emission. Two designs, (i) partially exposed metal nanostructures in an oxide matrix (ii) metal nanorod arrays, couple with incoming light at particular wavelengths which leads to plasmonic near field enhancement from the nanostructures. This plasmonic response is expected to lead to enhanced photoemission and thereby enhanced quantum efficiency. Moreover, the plasmonic enhancement and the shape of the nanostructure enable coherent unidirectional electron emission. Such an in depth study of the structure-property relationship, particularly the near field enhancement of novel metal, metal-metal oxide nanostructures will lead to applications as photocathode materials in next generation light sources.

Vilayurganapathy, Subramanian

48

Structure–property relationships of oligothiophene–isoindigo polymers for efficient bulk-heterojunction solar cells  

DEFF Research Database (Denmark)

A series of alternating oligothiophene (nT)–isoindigo (I) copolymers (PnTI) were synthesized to investigate the influence of the oligothiophene block length on the photovoltaic (PV) properties of PnTI:PCBM bulk-heterojunction blends. Our study indicates that the number of thiophene rings (n) in the repeating unit alters both polymer crystallinity and polymer–fullerene interfacial energetics, which results in a decreasing open-circuit voltage (Voc) of the solar cells with increasing n. The short-circuit current density (Jsc) of P1TI:PCBM devices is limited by the absence of a significant driving force for electron transfer. Instead, blends based on P5TI and P6TI feature large polymer domains, which limit charge generation and thus Jsc. The best PV performance with a power conversion efficiency of up to 6.9% was achieved with devices based on P3TI, where a combination of a favorable morphology and an optimal interfacial energy level offset ensures efficient exciton separation and charge generation. The structure–property relationship demonstrated in this work would be a valuable guideline for the design of high performance polymers with small energy losses during the charge generation process, allowing for the fabrication of efficient solar cells that combine a minimal loss in Voc with a high Jsc.

Ma, Zaifei; Sun, Wenjun

2014-01-01

49

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

DEFF Research Database (Denmark)

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

Panpipat, Worawan; Dong, Mingdong

2013-01-01

50

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

51

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

Science.gov (United States)

A multivariate model to characterise nitroaromatics and related compounds based on molecular descriptors was calculated. Descriptors were collected from literature and through empirical, semi-empirical and density functional theory-based calculations. Principal components were used to describe the distribution of the compounds in a multidimensional space. Four components described 76% of the variation in the dataset. PC1 separated the compounds due to molecular weight, PC2 separated the different isomers, PC3 arranged the compounds according to different functional groups such as nitrobenzoic acids, nitrobenzenes, nitrotoluenes and nitroesters and PC4 differentiated the compounds containing chlorine from other compounds. Quantitative structure-property relationship models were calculated using partial least squares (PLS) projection to latent structures to predict gas chromatographic (GC) retention times and the distribution between the water phase and air using solid-phase microextraction (SPME). GC retention time was found to be dependent on the presence of polar amine groups, electronic descriptors including highest occupied molecular orbital, dipole moments and the melting point. The model of GC retention time was good, but the precision was not precise enough for practical use. An important environmental parameter was measured using SPME, the distribution between headspace (air) and the water phase. This parameter was mainly dependent on Henry's law constant, vapour pressure, logP, content of hydroxyl groups and atmospheric OH rate constant. The predictive capacity of the model substantially improved when recalculating a model using these five descriptors only. PMID:18573379

Jönsson, S; Eriksson, L A; van Bavel, B

2008-07-28

52

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

International Nuclear Information System (INIS)

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

53

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

Directory of Open Access Journals (Sweden)

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

Drago Skrtic

2009-11-01

54

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

Science.gov (United States)

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/re-mineralizing 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. PMID:21966588

O'Donnell, Justin N R; Schumacher, Gary E; Antonucci, Joseph M; Skrtic, Drago

2009-01-01

55

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

56

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

57

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1997-12-01

58

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

International Nuclear Information System (INIS)

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

59

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.

60

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

61

Adsorption of s-triazines onto polybenzimidazole: A quantitative structure-property relationship investigation  

International Nuclear Information System (INIS)

The adsorption of 25 symmetric triazines (s-triazines) on polybenzimidazole (PBI) beads is investigated under equilibrium (batch) conditions. The observed adsorption isotherms of the selected compounds are accurately described by the Freundlich model, while the agreement between the Langmuir model and the experimental data is moderately worse, which seems to reflect the heterogeneous meso- and micro-porosity of PBI and polydispersion in the interaction mechanism. Methylthio- and methoxytriazines exhibit a greater adsorption tendency as compared with chlorotriazines, moreover, progressive dealkylation of amino groups results in a progressive increase of triazine uptake on PBI. Based on these evidences, the adsorption mechanism seems to be governed by a combination of ?-? and hydrogen-bonding interactions. Genetic algorithm (GA) variable selection and multilinear regression (MLR) are combined in order to describe the effect of triazine structure on the extraction performance of PBI according to the quantitative structure-property relationship (QSPR) method. qmax, the amount of triazine adsorbed per weight unit of PBI assuming homogeneous monolayer (Langmuir) mechanism, exhibits a great variability within the set of investigated triazines and is the quantity here modelled by QSPR. On the other hand, the Freundlich constant, KF, which expresses the adsorption efficiency under multilayer heterogeneous conditions, even if markedly increases passing fns, even if markedly increases passing from chloro- to methylthio- or methoxytriazines, is less noticeably affected by the fine details of the adsorbate structure, as the number or nature of alkyl fragments bound to the amino groups. To quantitatively relate qmax with the triazine structure GA-MLR analysis is performed on the set of 1664 theoretical molecular descriptors provided by the software Dragon. Finally, a four-dimensional QSPR model is selected based on leave-one-out cross-validation and its prediction ability is further tested on four representative triazines excluded from model calibration. The four descriptors selected by GA-MLR, all belonging to the class of three-dimensional GETAWAY (GEometry, Topology, and Atom-Weights AssemblY) descriptors, adequately represent the structural factors influencing the affinity of triazines to PBI in the batch extraction process.

62

Adsorption of s-triazines onto polybenzimidazole: a quantitative structure-property relationship investigation.  

Science.gov (United States)

The adsorption of 25 symmetric triazines (s-triazines) on polybenzimidazole (PBI) beads is investigated under equilibrium (batch) conditions. The observed adsorption isotherms of the selected compounds are accurately described by the Freundlich model, while the agreement between the Langmuir model and the experimental data is moderately worse, which seems to reflect the heterogeneous meso- and micro-porosity of PBI and polydispersion in the interaction mechanism. Methylthio- and methoxytriazines exhibit a greater adsorption tendency as compared with chlorotriazines, moreover, progressive dealkylation of amino groups results in a progressive increase of triazine uptake on PBI. Based on these evidences, the adsorption mechanism seems to be governed by a combination of pi-pi and hydrogen-bonding interactions. Genetic algorithm (GA) variable selection and multilinear regression (MLR) are combined in order to describe the effect of triazine structure on the extraction performance of PBI according to the quantitative structure-property relationship (QSPR) method. q(max), the amount of triazine adsorbed per weight unit of PBI assuming homogeneous monolayer (Langmuir) mechanism, exhibits a great variability within the set of investigated triazines and is the quantity here modelled by QSPR. On the other hand, the Freundlich constant, KF, which expresses the adsorption efficiency under multilayer heterogeneous conditions, even if markedly increases passing from chloro- to methylthio- or methoxytriazines, is less noticeably affected by the fine details of the adsorbate structure, as the number or nature of alkyl fragments bound to the amino groups. To quantitatively relate q(max) with the triazine structure GA-MLR analysis is performed on the set of 1664 theoretical molecular descriptors provided by the software Dragon. Finally, a four-dimensional QSPR model is selected based on leave-one-out cross-validation and its prediction ability is further tested on four representative triazines excluded from model calibration. The four descriptors selected by GA-MLR, all belonging to the class of three-dimensional GETAWAY (GEometry, Topology, and Atom-Weights AssemblY) descriptors, adequately represent the structural factors influencing the affinity of triazines to PBI in the batch extraction process. PMID:19720189

D'Archivio, Angelo Antonio; Incani, Angela; Mazzeo, Pietro; Ruggieri, Fabrizio

2009-09-21

63

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

64

Prediction of Henry's Law Constants via group-specific quantitative structure property relationships.  

Science.gov (United States)

Henry's Law Constants (HLCs) for several hundred organic compounds in water at 25°C were predicted by Quantitative Structure Property Relationship (QSPR) models, with the division of organic compounds into specific classes to yield more accurate models than generalised ones. Both multiple linear regression (MLR) and artificial neural network (ANN) versions of models were produced for three general cases, encompassing the entire data set; one used the six best descriptors, as determined by maximising the correlation coefficient; another used the twelve best descriptors in a similar manner, whilst the third used the same twelve descriptors as English and Carroll (2001). These achieved, respectively, root-mean square errors (RMSEs) of 0.719, 0.52 and 0.607 log(Hcc) units for the MLR version and 0.601, 0.394 and 0.431 for the test set of the ANN models, where Hcc is the ratio of the compound's concentration in the vapour phase to that in the liquid phase. These were compared with models for six specific chemical classes: (i) alkanes, (ii) cyclic alkanes, (iii) alkenes, (iv) halogenated compounds, (v) aldehydes, ketones and esters grouped together, and (vi) monoaromatics. These group-specific models had RMSEs of 0.153, 0.141. 0.097, 0.168, 0.122 and 0.104 respectively for the MLR versions and 0.684, 0.719, 0.856, 0.784, 0.875 and 0.861 for the test set of the ANN models. It was found that the class-specific models achieved lower RMSEs than the general models, when using MLR models. The use of ANN was found to improve the predictive accuracy of the general models but failed to improve that for the class-specific models vis-à-vis MLR. PMID:25602194

O'Loughlin, Darragh R; English, Niall J

2015-05-01

65

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

66

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

International Nuclear Information System (INIS)

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

67

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

Science.gov (United States)

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

Hule, Rohan A.

68

SURFACE STRUCTURES OF OXIDES AND HALIDES AND THEIR RELATIONSHIPS TO CATALYTIC PROPERTIES  

OpenAIRE

In this review, the relationships between structure, morphology, and surface reactivity of microcrystals of oxides and halides are assessed. The investigated systems we discuss include alkali halides, alkaline earth oxides, NiO, CoO, NiO–MgO, CoO–MgO solid solutions, ZnO, spinels, cuprous oxide, chromia, ferric oxide, alumina, lanthana, perovskites, anatase, rutile, and chromia/silica. A combination of high-resolution transmission electron microscopy with vibrational spectroscopy of...

Zecchina, Adriano; Bordiga, Silvia; Scarano, Domenica; Spoto, Giuseppe; Lamberti, Carlo

2001-01-01

69

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

International Nuclear Information System (INIS)

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

70

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

Energy Technology Data Exchange (ETDEWEB)

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

Katz, J. Lawrence [School of Computing and Engineering, University of Missouri-Kansas City, Kansas City, MO (United States) and School of Dentistry, University of Missouri-Kansas City, Kansas City, MO (United States)]. E-mail: katzjl@umkc.edu; Misra, Anil [School of Computing and Engineering, University of Missouri-Kansas City, Kansas City, MO (United States); Spencer, Paulette [School of Dentistry, University of Missouri-Kansas City, Kansas City, MO (United States); Wang, Yong [School of Dentistry, University of Missouri-Kansas City, Kansas City, MO (United States); Bumrerraj, Sauwanan [School of Medicine, Khon Kaen University, Khon Kaen (Thailand); Nomura, Tsutomu [School of Dentistry, Niigata University, Niigata (Japan); Eppell, Steven J. [Case School of Engineering, Case Western Reserve University, Cleveland, OH (United States); Tabib-Azar, Massood [Case School of Engineering, Case Western Reserve University, Cleveland, OH (United States)

2007-04-15

71

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

72

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

OpenAIRE

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

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

1993-01-01

73

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

74

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

75

Processing-structure-property relationships in electron beam physical vapor deposited yttria stabilized zirconia coatings  

Energy Technology Data Exchange (ETDEWEB)

The physical and mechanical properties of yttria stabilized zirconia (YSZ) coatings deposited by the electron beam physical vapor deposition technique have been investigated by varying the key process variables such as vapor incidence angle and sample rotation speed. The tetragonal zirconia coatings formed under varying process conditions employed were found to have widely different surface and cross-sectional morphologies. The porosity, phase composition, planar orientation, hardness, adhesion, and surface residual stresses in the coated specimens were comprehensively evaluated to develop a correlation with the process variables. Under transverse scratch test conditions, the YSZ coatings exhibited two different crack formation modes, depending on the magnitude of residual stress. The influence of processing conditions on the coating deposition rate, column orientation angle, and adhesion strength has been established. Key relationships between porosity, hardness, and adhesion are also presented.

Rao, D. Srinivasa; Valleti, Krishna; Joshi, S. V.; Janardhan, G. Ranga [International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur (PO), Hyderabad 500 005 (India); Department of Mechanical Engineering, JNTUH College of Engineering, JNT University, Hyderabad 500 085 (India)

2011-05-15

76

Processing-structure-property relationships in electron beam physical vapor deposited yttria stabilized zirconia coatings  

International Nuclear Information System (INIS)

The physical and mechanical properties of yttria stabilized zirconia (YSZ) coatings deposited by the electron beam physical vapor deposition technique have been investigated by varying the key process variables such as vapor incidence angle and sample rotation speed. The tetragonal zirconia coatings formed under varying process conditions employed were found to have widely different surface and cross-sectional morphologies. The porosity, phase composition, planar orientation, hardness, adhesion, and surface residual stresses in the coated specimens were comprehensively evaluated to develop a correlation with the process variables. Under transverse scratch test conditions, the YSZ coatings exhibited two different crack formation modes, depending on the magnitude of residual stress. The influence of processing conditions on the coating deposition rate, column orientation angle, and adhesion strength has been established. Key relationships between porosity, hardness, and adhesion are also presented.

77

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

78

Processing, structure, property and performance relationships for the thermal spray of the internal surface of aluminum cylinders  

Science.gov (United States)

The increased need for automotive weight reduction has necessitated the use of aluminum for engine blocks. Conventional aluminum alloys cannot survive the constant wear from a piston ring reciprocating on the surface. However, a wear resistant thermal spray coating can be applied on the internal surface of the cylinder bore, which has significant advantages over other available options. Thermal spray is a well-established process for depositing molten, semi-molten, or solid particles onto a substrate to form a protective coating. For this application, the two main challenges were obtaining good wear resistance, and achieving good adhesion. To design a system capable of producing a well-adhered, wear resistant coating for this high volume application it is necessary to identify the overall processing, structure, properties, and performance relationships. The results will demonstrate that very important relationships exist among particle characteristics, substrate conditions, and the properties of the final coating. However, it is the scientific studies to understand some of the process physics in these relationships that allow recognition of the critical processing conditions that need to be controlled to ensure a consistent, reliable thermal spray coating. In this investigation, it will be shown that the critical microstructural aspect of the coating that produced the required tribological properties was the presence of wuestite (FeO). It was found that by using a low carbon steel material with compressed air atomizing gas, it was possible to create an Fe/FeO structure that exhibited excellent tribological properties. This study will also show that traditional thermal spray surface preparation techniques were not ideal for this application, therefore a novel alternative approach was developed. The application of a flux to the aluminum surface prior to thermal spray promotes excellent bond strengths to non-roughened aluminum. Analysis will show that this flux strips the oxide from the aluminum and allows for chemical bonding of the NiAl coating to the aluminum via the formation of intermetallics. By developing processing, structure, property, and performance relationships for the full process, it was possible to design a complete coating process to succeed in this application. The determination of these relationships and the underlying process physics improves reliability and instills confidence in the process.

Cook, David James

79

Relationship between structural composition and material properties of polymorphic hIAPP fibrils.  

Science.gov (United States)

Amyloid proteins are misfolded, denatured proteins that are responsible for causing several degenerative and neuro-degenerative diseases. Determining the mechanical stability of these amyloids is crucial for understanding the disease mechanisms, which will guide us in treatment. Furthermore, many research groups recognized amyloid proteins as functional biological materials that can be used in nanosensors, bacterial biofilms, coatings, etc. Many in vitro studies have been carried out to determine the characteristics of amyloid proteins via force spectroscopy methods, atomic force microscopy, and optical tweezers. However, computational methods (e.g. molecular dynamics and elastic network model) not only reveal the mechanical properties of the amyloid proteins, but also provide more in-depth information about the amyloids by presenting a visualization of their conformational changes. In this study, we evaluated the various material properties and behaviors of four different polymorphic structures of human islet amyloid polypeptide (hIAPP) by using steered molecular dynamics (SMD) simulations under tensile conditions. From our results, we examined how these mechanical properties may differ with respect to the structural formation of amyloid proteins. PMID:25682214

Lee, Myeongsang; Chang, Hyun Joon; Kim, Donghoi; Lee, Yongwoo; Suh, Heesu; Ahn, Namjo; Yoon, Gwonchan; Na, Sungsoo

2015-04-01

80

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

81

The relationship between microstructure and magnetic properties in high-energy permanent magnets characterized by polytwinned structures  

Science.gov (United States)

This report summarizes the results of a study of the relationship between microstructure and magnetic properties in a unique genre of ferromagnetic material characterized by a polysynthetically twinned structure which arises during solid state transformation. These results stem from the work over a period of approximately 27 months of a nominal 3 year grant period. The report also contains a proposal to extend the research project for an additional 3 years. The polytwinned structures produce an inhomogeneous magnetic medium in which the easy axis of magnetization varies quasi-periodically giving rise to special domain configurations which are expected to markedly influence the mechanism of magnetization reversal and hysteresis behavior of these materials in bulk or thin films. The extraordinary permanent magnet properties exhibited by the well-known Co-Pt alloys as well as the Fe-Pt and Fe-Pd systems near the equiatomic composition derive from the formation of a polytwinned microstructure.

82

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

83

Structure/property relationships in high hole mobility regioregular PT based copolymers  

Science.gov (United States)

The synthesis of novel solution processable conjugated polymers with high hole mobilites is an active field of study due to the potential to fabricate low cost, high though-put, lightweight organic field effect transistors (OFET). Two regioregular copolymers, based on cyclopenta[2,1-b:3,4-b']dithiophene (CDT) and pyridal[2,1,3]thiadiazole (PT) structural units, have been prepared by using polymerization reactions involving reactants specifically designed to avoid random orientation of the PT heterocycle. Compared to their regiorandom counterpart, the regioregular polymers exhibit a two orders of magnitude increase in hole mobility from 0.005 to 0.6 cm^2 V-1 s-1. Grazing incidence wide angle X-ray scattering (GIWAXS), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and transmission electron microscopy were carried out to obtain further insight into possible differences of structural order within the bulk and interfaces of the thin films. It was found that the backbone regioregularity leads to significant differences in the structural arrangement of the chains and indicates the importance of regioregularity for achieving optimal electronic properties.

Perez, Louis; Ying, Lei; Bazan, Guillermo; Kramer, Edward

2012-02-01

84

Water Transport Polymers -- Structure/Property Relationships of a Series of Phosphazene Polymers  

Energy Technology Data Exchange (ETDEWEB)

A study was undertaken to explore the water passing properties of a series of phosphazene polymers versus attached pendant group structure. Pendant groups containing different numbers ethyleneoxy groups were synthetically attached to the backbone of phosphazene polymers. Phosphazene polymers facilitate these types of studies because during their synthesis the polymer backbone is formed first and then the desired pendant groups are attached through nucleophilic substitution. For these studies, four polymer series were synthesized and tested for their water passing properties. The polymers contained different amounts of ethyleneoxy units. Two polymer families were synthesized and compared in this work. The critical difference in these two series is that one contained pendant groups with aromatic rings, in addition to the oligioethyleneoxy moieties, while the other does not. Polymers with phenyl group-containing pendant groups exhibited poor water permeability if they possessed fewer than six ethyleneoxy units. Polymers with more than six ethyleneoxy units inserted between the phenyl ring (tail) and the polymeric backbone, exhibited reasonable water permeability. Two additional series of mixed pendant group polymers were synthesized and the water passing properties of the phosphazenes varied in proportion to the hydrophilic to hydrophobic balance induced by each individual pendant group. A final study, polymers with shorter pendant groups, is shown to fully demonstrate the effect of pendant group on water permeability. These studies suggest that the polyphosphazenes may be tailored for specific water passing applications.

Christopher J. Orme; Eric S. Peterson; William F. Bauer; Frederick F. Stewart; Mason K. Harrup; Thomas A. Luther; John R. Klaehn; John E. Wey

2010-01-01

85

Investigation of multi-modal high-salt binding ion-exchange chromatography using quantitative structure-property relationship modeling.  

Science.gov (United States)

A quantitative structure-property relationship (QSPR) modeling approach was employed to correlate the physicochemical properties and structural components of multi-modal ion-exchange ligands with their ability to bind proteins under high-salt conditions. These ion-exchange ligands contain various substructures, which may contribute to secondary interactions that promote protein binding. A set of molecular descriptors was calculated based on the structures of these cation-exchange ligands. The molecular descriptors used to generate the QSPR models were used to characterize the ligand molecules and QSPR models were generated for predicting the elution conductivity of three test set proteins. The resulting models were able to predict the performance of test ligands not included in the generation of the models and the interpretation of the selected descriptors provided insight into the important physicochemical properties and structural characteristics required for protein binding under high-salt conditions. The results indicate that while the aromatic ring plays an important role in promoting protein binding under high-salt conditions, moieties associated with intermediate hydrophobicity (e.g. aliphatic side chain) or the presence of hydrogen bond donors (e.g. NH and OH) tended to suppress the binding. Further, regions of the ligands with negative partial charge also tended to promote protein binding at high-salt conditions in these multi-modal cation-exchange systems. This work demonstrates that ligand-based QSPR models may have utility for the a priori design of mixed mode chromatographic systems for protein separations. PMID:17991474

Yang, Ting; Breneman, Curt M; Cramer, Steven M

2007-12-14

86

Amino acid profiles and quantitative structure-property relationship models as markers for Merlot and Torrontés wines.  

Science.gov (United States)

Quantitative structure-property relationships (QSPRs) were applied to the aminograms obtained by HPLC in our laboratories for Torrontés and Merlot wines. Dragon theoretical descriptors were derived for a set of optimized amino acid structures with the purpose of establishing QSPR models. The statistical Replacement Method was used for designing the best multi-parametric linear regression models, which included structural features selected from a pool containing 1497 constitutional, topological, geometrical or electronic molecular descriptors. Predicted QSPR results were in good agreement with experimental amino acid profiles. The developed QSPR approach showed to be of practical value for distinguishing each wine varietal, and for calculating experimentally non-available amino acid concentrations of Torrontés and Merlot wines. It was also useful for assessing wine authenticity; the models were especially suitable for Merlot and Torrontés wines. PMID:23578635

Duchowicz, Pablo R; Giraudo, Miguel A; Castro, Eduardo A; Pomilio, Alicia B

2013-09-01

87

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)

88

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

CERN Document Server

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

Santos, M C D

2000-01-01

89

Silica-supported silver nanoparticles: Tailoring of structure-property relationships  

International Nuclear Information System (INIS)

Silica-supported silver nanoparticles were obtained by rf sputtering from Ar plasmas under soft synthesis conditions, with particular attention to the combined influence of rf power and total pressure on the system composition, nanostructure, morphology, and optical properties. In order to attain a thorough insight into the nucleation and growth phenomena of Ag nanoparticles on the silica substrate, several in situ and ex situ characterization techniques were used. In particular, a laser reflection interferometry system was employed for a real-time monitoring of the deposition process, providing useful and complementary information with respect to the other ex situ techniques (x-ray photoelectron spectroscopy and x-ray excited Auger electron spectroscopy, glancing incidence x-ray diffraction, atomic force microscopy, optical-absorption spectroscopy, and transmission electron microscopy). The above investigations evidenced the formation of silver-based nanosystems (average crystallite size ?10 nm), whose features (metal content, Ag particle size and shape, structure and optical properties) could be carefully tailored by moderate and controlled variations of the synthesis parameters

90

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

91

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

92

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

93

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

94

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

Energy Technology Data Exchange (ETDEWEB)

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

Prichard, P.D.

1998-02-23

95

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

Science.gov (United States)

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

Liyanage, Laalitha S. I.

96

Structure-property relationships in centrifugally cast IMI 550 (Ti4Al-4Mo-2Sn-0.5Si)  

International Nuclear Information System (INIS)

Centrifugal casting technology has been used to produce test pieces and hard-point bracket components for a determination of the structure-property relationships in the age-hardenable titanium alloy IMI 550. Tensile, high cycle fatigue, fracture toughness and elevated temperature creep results have shown that an attractive combination of property levels can be achieved in this alloy. It has been established that the tensile, fatigue and creep performance of cast plus Hot Isostatically Pressed (HIP) IMI 550 approaches that of conventionally wrought material while fracture toughness is superior. The improvement obtained in fracture toughness is a direct result of the presence of the highly acicular Widmanstatten or transformed beta microstructure produced by casting compared with the more traditional equiaxed alpha + beta structure exhibited by wrought products. HIP'ing has been shown to eliminate all traces of as cast internal shrinkage porosity and to thus yield a dramatic improvement in high cycle fatigue performance. HIP'ing was accompanied by general coarsening of the acicular alpha phases present in the micro-structure after casting. Macro and microstructural analysis of the castings indicated a refined and uniform beta grain size which it is believed is due to the presence of silicon in the alloy. 16 references

97

Polytellurophenes provide imaging contrast towards unravelling the structure–property–function relationships in semiconductor:insulator polymer blends  

KAUST Repository

Polymer blends are broadly important in chemical science and chemical engineering and have led to a wide range of commercial products, however their precise structure and phase morphology is often not well understood. Here we show for the first time that ?-conjugated polytellurophenes and high-density polyethylene form blends that can serve as active layers in field-effect transistor devices and can be characterized by a variety of element-specific imaging techniques such as STEM and EDX. Changing the hydrocarbon content and degree of branching on the polytellurophene side-chain leads to a variety of blend structures, and these variations can be readily visualized. Characterization by electron microscopy is complemented by topographic and X-ray methods to establish a nano- to micro-scale picture of these systems. We find that blends that possess microscale networks function best as electronic devices; however, contrary to previous notions a strong correlation between nanofiber formation and electrical performance is not observed. Our work demonstrates that use of organometallic polymers assists in clarifying relevant structure–property–function relationships in multicomponent systems such as semiconductor:insulator blends and sheds light on the structure development in polymer:polymer blends including crystallization, phase separation, and formation of supramolecular arrangements.

Yu, Liyang

2015-02-27

98

ZrN based Nanostructured Hard Coatings : Structure-Property Relationship  

OpenAIRE

Ever since the hard coatings have been introduced, there has been a constant push for better mechanical properties, which motivates for deeper understanding of the microstructure-mechanical properties correlation. The aim of this thesis is to extend the knowledge on how microstructural variation influences the deformation, fracture and wear behavior of ZrN based nanostructured coatings. Few microns thick, monolithic Zr-Si-N and multilayered Zr-Al-N coatings were deposited by reactive arc depo...

Yalamanchili, Phani Kumar

2014-01-01

99

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

100

Relationships of structure to properties in graphite fibers. III. Technical report  

Energy Technology Data Exchange (ETDEWEB)

Three-dimensional structural characterization of a variety of carbon fibers has been completed following determination of the axial and radial structures in the fibers studied. In addition the relation of fiber strength to three-dimensional structure has been developed. Fibers tend to fail in three separate ways depending on their moduli; failure mode changes from brittle fracture to fibril decoupling to plastic deformation as modulus increases. Strength in Orlon and Rayon base fibers follows the Griffith relation. Strength in Orlon and Courtelle base fibers above the maxima in the strength-modulus curve is controlled by flaws resulting from cool-down residual stresses as well as surface crystallization. (GRA)

Diefendorf, R.J.; Tokarsky, E.W.

1975-11-01

101

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

102

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.

Bradley University

2012-01-01

103

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

Science.gov (United States)

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

Tipton, John

104

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

OpenAIRE

Analysis of the crystal structures of the two milk-clotting enzymes bovine and camel chymosin has revealed that the better milk-clotting activity towards bovine milk of camel chymosin compared with bovine chymosin is related to variations in their surface charges and their substrate-binding clefts.

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

2013-01-01

105

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

106

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

International Nuclear Information System (INIS)

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

107

Electroformed iron as new biomaterial for degradable stents: development process and structure-properties relationship.  

Science.gov (United States)

An electroforming technique was developed for fabricating iron foils targeted for application as biodegradable cardiovascular stent material. The microstructure, mechanical properties and corrosion of electroformed iron (E-Fe) foils were evaluated and compared with those of pure iron made by casting and thermomechanical treatment (CTT-Fe), with 316L stainless steel (316L SS) and with other candidate metallic materials for biodegradable stents. Electron backscattered diffraction revealed an average grain size of 4 microm for E-Fe, resulting in a high yield (360 MPa) and ultimate tensile strength (423 MPa) being superior to those of other metallic biodegradable stent materials. Annealing at 550 degrees C was found to improve the ductility of the E-Fe from 8% to 18%. The corrosion rate of E-Fe in Hanks' solution, measured by potentiodynamic polarization, was higher than that of CTT-Fe, which had been found to have a slow in vivo degradation. The results showed that E-Fe possesses fine-grain microstructure, suitable mechanical properties and moderate corrosion rate as a degradable stent material. PMID:20085829

Moravej, M; Prima, F; Fiset, M; Mantovani, D

2010-05-01

108

Relationship between linear viscoelastic properties and molecular structure for linear and branched polymers  

OpenAIRE

The prediction of linear viscoelasticity (LVE) of a polymer melts from the knowledge of their structure has received tremendous attention in recent years. Quite accurate quantitative predictions are obtained for linear polymers, including inverse predictions of molecular weight distributions from knowledge of rheological response. The situation for branched polymers is much more complicated for at least two reasons. First, because of the incredible variety of architectures that can be, and ar...

Van Ruymbeke, Evelyne

2005-01-01

109

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

110

Excited States and Photodebromination of Selected Polybrominated Diphenyl Ethers: Computational and Quantitative Structure—Property Relationship Studies  

Science.gov (United States)

This paper presents a density functional theory (DFT)/time-dependent DFT (TD-DFT) study on the lowest lying singlet and triplet excited states of 20 selected polybrominateddiphenyl ether (PBDE) congeners, with the solvation effect included in the calculations using the polarized continuum model (PCM). The results obtained showed that for most of the brominated diphenyl ether (BDE) congeners, the lowest singlet excited state was initiated by the electron transfer from HOMO to LUMO, involving a ?–?* excitation. In triplet excited states, structure of the BDE congeners differed notably from that of the BDE ground states with one of the specific C–Br bonds bending off the aromatic plane. In addition, the partial least squares regression (PLSR), principal component analysis-multiple linear regression analysis (PCA-MLR), and back propagation artificial neural network (BP-ANN) approaches were employed for a quantitative structure-property relationship (QSPR) study. Based on the previously reported kinetic data for the debromination by ultraviolet (UV) and sunlight, obtained QSPR models exhibited a reasonable evaluation of the photodebromination reactivity even when the BDE congeners had same degree of bromination, albeit different patterns of bromination. PMID:25569092

Luo, Jin; Hu, Jiwei; Wei, Xionghui; Li, Lingyun; Huang, Xianfei

2015-01-01

111

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

112

Excited States and photodebromination of selected polybrominated diphenyl ethers: computational and quantitative structure--property relationship studies.  

Science.gov (United States)

This paper presents a density functional theory (DFT)/time-dependent DFT (TD-DFT) study on the lowest lying singlet and triplet excited states of 20 selected polybrominateddiphenyl ether (PBDE) congeners, with the solvation effect included in the calculations using the polarized continuum model (PCM). The results obtained showed that for most of the brominated diphenyl ether (BDE) congeners, the lowest singlet excited state was initiated by the electron transfer from HOMO to LUMO, involving a ?-?* excitation. In triplet excited states, structure of the BDE congeners differed notably from that of the BDE ground states with one of the specific C-Br bonds bending off the aromatic plane. In addition, the partial least squares regression (PLSR), principal component analysis-multiple linear regression analysis (PCA-MLR), and back propagation artificial neural network (BP-ANN) approaches were employed for a quantitative structure-property relationship (QSPR) study. Based on the previously reported kinetic data for the debromination by ultraviolet (UV) and sunlight, obtained QSPR models exhibited a reasonable evaluation of the photodebromination reactivity even when the BDE congeners had same degree of bromination, albeit different patterns of bromination. PMID:25569092

Luo, Jin; Hu, Jiwei; Wei, Xionghui; Li, Lingyun; Huang, Xianfei

2015-01-01

113

Excited States and Photodebromination of Selected Polybrominated Diphenyl Ethers: Computational and Quantitative Structure—Property Relationship Studies  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a density functional theory (DFT/time-dependent DFT (TD-DFT study on the lowest lying singlet and triplet excited states of 20 selected polybrominateddiphenyl ether (PBDE congeners, with the solvation effect included in the calculations using the polarized continuum model (PCM. The results obtained showed that for most of the brominated diphenyl ether (BDE congeners, the lowest singlet excited state was initiated by the electron transfer from HOMO to LUMO, involving a ?–?* excitation. In triplet excited states, structure of the BDE congeners differed notably from that of the BDE ground states with one of the specific C–Br bonds bending off the aromatic plane. In addition, the partial least squares regression (PLSR, principal component analysis-multiple linear regression analysis (PCA-MLR, and back propagation artificial neural network (BP-ANN approaches were employed for a quantitative structure-property relationship (QSPR study. Based on the previously reported kinetic data for the debromination by ultraviolet (UV and sunlight, obtained QSPR models exhibited a reasonable evaluation of the photodebromination reactivity even when the BDE congeners had same degree of bromination, albeit different patterns of bromination.

Jin Luo

2015-01-01

114

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

115

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

116

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

International Nuclear Information System (INIS)

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

117

Density functional theory based quantitative structure-property relationship studies on coumarin-based prodrugs.  

Science.gov (United States)

A coumarin-based prodrug system plays a significant role in preparing esterase-sensitive prodrugs of amines and peptides. The electronic structures of 27 coumarin-based prodrugs developed in our lab were calculated at a B3LYP/6-31+G (d,p) level with a Gaussian 03 program. The calculated structural parameters were taken as theoretical descriptors to establish five novel QSPR models. The SMLR linear model (q² = 0.427, r² = 0.516) and the PLS linear model (q² = 0.584, r² = 0.663) were developed with descriptors selected by an Unsupervised Forward Selection method. Another three nonlinear QSPR models were established by a Polynomial Neural Network (PNN) Simulation method (q² = 0.692, 0.675, 0.663; r² = 0.700, 0.688, 0.672). We suggest that the QSPR models derived here, especially the PNN models, can be used to predict the release kinetics of coumarin-based prodrugs as well as design new derivatives of coumarin-based prodrug candidates. PMID:23229116

Yang, Xinying; Hou, Xuben; Wang, Binghe; Li, Minyong; Fang, Hao

2012-10-01

118

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

119

Syntheses, Local Environments, and Structure-Property Relationships of Solid- State Vanadium Oxide-Fluorides  

Science.gov (United States)

Understanding the lateral heterogeneity of unconventional plays prior to hydraulic fracturing is important for hydrocarbon production and recovery. Lateral and vertical variability can be affected by composition and textural variation of the rock, which define the rock quality. To characterize the lateral and vertical heterogeneity of rock quality (composition) of the Montney Shale reservoir at Pouce Coupe, Alberta at different scales I conducted a multi-attribute analysis of wells logs integrated with post-stack and pre-stack inversion of a baseline multicomponent seismic survey. Cluster analysis was performed in four wells using the well logs that are most affected by composition. The cluster analysis provides more representative upscale input parameters for reservoir characterization that can be compared with seismic results. The result of this cluster analysis has indicated a lateral variation of composition of the unit C to the east side of the area, where six clusters were chosen and two of them have good petrophysical rock properties that were tied with core data. Post-stack and pre-stack inversions of the baseline of the multicomponent seismic data were performed using constrained sparse spike inversion (CSSI). Pre-stack results shows similar results for the P-impedance, however, there is an improvement in the accuracy of the estimated P-impedance from the pre-stack CSSI (compared to well log P-impedance). The results of P-impedance and S-impedance show the same strong change on the east side of the survey that was detected with the cluster analysis. Crossplots of elastic properties such as Lambda-rho and Mu-rho combined with the results of cluster analysis helped to identify the areas of better rock quality in the 3D seismic. The integration of this heterogeneity analysis with the production profile of the two horizontal wells in the area shows that the lithology has a major influence on the rock quality of the Montney interval. The combined interpretation of this work with an understanding of the natural fracture system and the stress state of the reservoir can provide a rock quality index (RQI). This RQI can aid in future exploration and operational development of the Montney play and other shale reservoirs worldwide.

Donakowski, Martin Daniel

120

Structure-property-composition relationships in doped zinc oxides: enhanced photocatalytic activity with rare Earth dopants.  

Science.gov (United States)

In this paper, we demonstrate the use of continuous hydrothermal flow synthesis (CHFS) technology to rapidly produce a library of 56 crystalline (doped) zinc oxide nanopowders and two undoped samples, each with different particle properties. Each sample was produced in series from the mixing of an aqueous stream of basic zinc nitrate (and dopant ion or modifier) solution with a flow of superheated water (at 450 °C and 24.1 MPa), whereupon a crystalline nanoparticle slurry was rapidly formed. Each composition was collected in series, cleaned, freeze-dried, and then characterized using analytical methods, including powder X-ray diffraction, transmission electron microscopy, Brunauer-Emmett-Teller surface area measurement, X-ray photoelectron spectroscopy, and UV-vis spectrophotometry. Photocatalytic activity of the samples toward the decolorization of methylene blue dye was assessed, and the results revealed that transition metal dopants tended to reduce the photoactivity while rare earth ions, in general, increased the photocatalytic activity. In general, low dopant concentrations were more beneficial to having greater photodecolorization in all cases. PMID:25602735

Goodall, Josephine B M; Illsley, Derek; Lines, Robert; Makwana, Neel M; Darr, Jawwad A

2015-02-01

121

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

122

Structure-property relationships of an electron beam cured model urethane prepolymer  

International Nuclear Information System (INIS)

A semicrystalline urethane prepolymer derived from polycaprolactone was crosslinked below and above the melt to different levels using electron beam radiation. Studies at room temperature on the systems crosslinked under ambient conditions, which is below the melting temperature, show that changes in mechanical properties which occur as the electron beam dose is increased are due principally to the increase in crosslink density and to the changes in the crosslinking mechanism. Specifically, crosslinking takes place mainly at the acrylate double bonds or may also occur along the polymer backbone. All systems, however, are semicrystalline and possess a spherulitic texture. Mechanical and rheo-optical testing above the melt on these same systems indicate that at extensions up to 125% classical rubber elasticity theory and photoelasticity theory is obeyed. Isothermal crystallization kinetics measurements show that the rate of crystallization decreases as the electron beam dose is raised. When the systems are crosslinked above the melt again a spherulitic texture results. Mechanical testing above the melting temperature on the prepolymer crosslinked up to 4 Mrad shows that at elongations up to 125% classical rubber elasticity theory is obeyed. At room temperature these latter crosslinked systems exhibited a lower modulus compared to the materials crosslinked below the melt. Polarizing optical microscopy carried out above the melting temperature strongly suggested that no og temperature strongly suggested that no order was present in these systems during crosslinking in contrast to those crosslinked below the melting temperature

123

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

124

Structure-property relationships in Sterculia urens/polyvinyl alcohol electrospun composite nanofibres.  

Science.gov (United States)

Sterculia urens (Gum Karaya) based polyvinyl alcohol (PVA) composite nanofibres have been successfully electrospun after chemical modification of S. urens to increase its solubility. The effect of deacetylated S. urens (DGK) on the morphology, structure, crystallization behaviour and thermal stability was studied for spuned fibres before and after spinning post treatment. An apparent increase in the PVA crystallinity were observed in the PVA-DGK composite nanofibres indicating S. urens induced crystallization of PVA. The pure PVA nanofibre and the nanofibres of PVA-DGK composites were introduced to post electrospinning heat treatment at 150°C for 15 min. The presence of sterculia gum reduced the fibre diameter and distribution of the nanofibres due to the increased stretching of the fibres during spinning. Switching of the thermal behaviour occurs due to post spinning heat treatments. PMID:25662689

Patra, Niranjan; Martinová, Lenka; Stuchlik, Martin; ?erník, Miroslav

2015-04-20

125

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

Science.gov (United States)

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

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

2013-01-01

126

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

Directory of Open Access Journals (Sweden)

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

Virapong Prachayasittikul

2010-01-01

127

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

Energy Technology Data Exchange (ETDEWEB)

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

Dinesh, E-mail: phy.dinesh.ap@gmail.com [Department of Physics, Govt. G.M. Science College, Jammu -180006 (India); Kumar, Mukesh [School of Physical Sciences, Banasthali University, Banasthali, Rajasthan -304022 (India); Dalela, S. [Department of Pure and Applied Physics, University of Kota, Kota, Rajasthan -324005 (India)

2014-04-24

128

Phase transition induced by pressure in TbCrO4 oxide: Relationship structure-properties  

International Nuclear Information System (INIS)

Terbium chromate TbCrO4, which has been described as belonging to the zircon-type structure showing tetragonal symmetry, space group I41/amd, has been prepared as a dimorphic compound. When the zircon-type TbCrO4 polymorph is treated at 40 kbar and 833 K takes place a phase transition to the tetragonal scheelite-type TbCrO4 polymorph, space group I41/a, with lattice parameters a = 5.0315(10) A and c = 11.3740(2) A. Magnetic susceptibility measurements reveal dramatic changes concerning the magnetic behavior of these two polymorphs. In this sense, the zircon-type TbCrO4 polymorph behaves as ferromagnetic with a Curie temperature of 22 K, while the scheelite-type TbCrO4 polymorph is antiferromagnetic with TN = 29 K. M vs. H plots at different temperatures show the presence of a metamagnetic transition for the scheelite-type TbCrO4 polymorph with a critical field of 2.6 T. The change of the sign of the magnetic interaction has been explained taking into account the differences found in the distances and bond angles of the superexchange Tb-O-Cr pathway through these interactions take place in both zircon and scheelite polymorphs.

129

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.

130

The Relationship Satisfaction scale – Psychometric properties  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study was to establish the psychometric properties of the new Relationship Satisfaction (RS scale. Two population based samples were used: The Norwegian Mother and Child Cohort Study (MoBa, N=117,178 and The Quality of Life study (N=347. Convergent and discriminant validity was investigated in relation to the Quality of Marriage Index (QMI, the Satisfaction With Life Scale (SWLS, Relationship Satisfaction of partner, Big Five personality traits (IPIP50 and future relationship dissolution. The full scale with ten items (RS10 and a short version with five items (RS5 showed good psychometric properties. The scale has high internal and test-retest reliability and high structural, convergent, and discriminant validity. Measurement invariance across gender was established. Additionally, predictive validity was evidenced by prediction of future relationship dissolution. We conclude that the RS scale is highly useful as a generic measure of global relationship satisfaction.

Espen Røysamb

2014-12-01

131

Structure-property relationships for n-alkyl-isocyanate-containing polymers  

Science.gov (United States)

Poly(n-hexyl isocyanate) (PHIC), poly(n-butyl-isocyanate) (PBIC), poly(n-butyl-co-cyclohexyl isocyanate) (PBCHIC), poly(n-hexyl isocyanate-b-isoprene) (HI), poly(n-butyl isocyanate-b-isoprene) (BI) and poly(n-hexyl isocyanate-b-isoprene- b-styrene) (MS) were synthesized and characterized with respect to composition, molecular Weight and polydispersity. PHIC, HI and HIS were found to be lyotropic liquid crystalline whereas PBIC, PBCHIC and BI were found to be non-lyotropic. A lyotropic-nematic liquid crystalline phase diagram was determined for the PHIC/xylene system. A novel and reversible electric-field-induced biphasic-paranematic phase transition was found for the PHIC/xylene system from the dynamics of topological defects. The electric-field-induced phase diagram for PHIC/xylene agreed with the theoretically predicted field-induced phase diagram of Khokhlov and Semenov for semiflexible-persistent polymers. The dielectric characteristics, steady-state electrically induced birefringence and steady-state electroheological (ER) activity of PHIC, PBIC and PBCHIC solutions were compared as a function of polymer concentration. The role of lyotropic liquid crystalline ordering in the functional ER mechanism of poly( n-hexyl isocyanate) solutions is presented. PBCHIC was found to thermally decompose by a first-order rate process which became slower with increasing cyclohexyl isocyanate content from thermal gravimetric analysis. Competition between monomer dissociation and degradative trimerization as well as a non-alternating sequence distribution were determined for PBCHIC from direct pyrolysis/mass spectrometry. The Arrhenius activation energy, pre-exponential factor and entropy for diffusion and evaporation of xylene from PHIC, were found to be functions of initial polymer concentration whereas the intrinsic diffusion coefficient of the solvent was found to be independent of initial polymer concentration. The cross polarized/magic angle spinning solid state 13C-NMR spectra of PBCHIC revealed perturbations to the helical polymer backbone structure. The wide angle x-ray diffraction pattern for the n-hexyl isocyanate containing polymers was found to be a function of DC electric field strength applied during isothermal crystallization from solution. The PHIC, backbone was protonated on a small percentage of monomer units by reaction with BF3 and H2O with no detectable chain scission but a loss of lyotropic liquid crystallinity. Methyl-N-(1,1-dimetboxyperfluroro- n-heptyl)carbamate was isolated from the reaction of perfluoro- n-heptyl isocyanate with excess methanol. 2,5-Dioxahexyl isocyanate and 2,5,8-trioxanonyl isocyanate were synthesized.

Aronson, Carl Lawrence

132

Structure-to-property relationships in fuel cell catalyst supports: Correlation of surface chemistry and morphology with oxidation resistance of carbon blacks  

Science.gov (United States)

Linking durability of carbon blacks, expressed as their oxidation resistance, used in PEMFCs as catalyst supports, with their chemistry and morphology is an important task towards designing carbon blacks with desired properties. Structure-to-property relationship between surface chemistry determined by X-ray photoelectron spectroscopy (XPS), morphological structure determined by digital image processing of scanning electron microscopy (SEM) images, physical properties, and electrochemical corrosion behavior determined in an air-breathing gas-diffusion electrode is studied for several un-altered and several modified carbon blacks. We are showing that surface chemistry, graphitic content and certain physical characteristics such as Brunauer-Emmett-Teller (BET) surface area and pore volume, determined by nitrogen adsorptions are not sufficient to explain high corrosion instability of types of carbon blacks. Inclusion of morphological characteristics, such as roughness, texture and shape parameters provide for more inclusive description and therefore more complete structure-to-property correlations of corrosion behavior of carbon blacks. This paper presents the first direct statistically-derived structure-to-property relationship, developed by multivariate analysis (MVA) that links chemical and physical structural properties of the carbon blacks to their critical properties as supports for PEMFC catalysts. We have found that balance between electrocatalytic activity and high resistance towards oxidation and corrosion is achieved by balance between amount of graphitic content and surface oxide coverage, smaller overall roughness and, finally, larger amount of big elongated and loose, and, hypothetically, more hydrophobic pores.

Artyushkova, Kateryna; Pylypenko, Svitlana; Dowlapalli, Madhu; Atanassov, Plamen

2012-09-01

133

Structure-property relationship of supramolecular ferroelectric [H-66dmbp][Hca] accompanied by high polarization, competing structural phases, and polymorphs.  

Science.gov (United States)

Three polymorphic forms of 6,6'-dimethyl-2,2'-bipyridinium chloranilate crystals were characterized to understand the origin of polarization properties and the thermal stability of ferroelectricity. According to the temperature-dependent permittivity, differential scanning calorimetry, and X-ray diffraction, structural phase transitions were found in all polymorphs. Notably, the ferroelectric ?-form crystal, which has the longest hydrogen bond (2.95?Å) among the organic acid/base-type supramolecular ferroelectrics, transformed from a polar structure (space group, P21) into an anti-polar structure (space group, P21/c) at 378?K. The non-ferroelectric ?- and ?-form crystals also exhibited structural rearrangements around hydrogen bonds. The hydrogen-bonded geometry and ferroelectric properties were compared with other supramolecular ferroelectrics. A positive relationship between the phase-transition temperature (TC ) and hydrogen-bond length () was observed, and was attributed to the potential barrier height for proton off-centering or order/disorder phenomena. The optimized spontaneous polarization (Ps ) agreed well with the results of the first-principles calculations, and could be amplified by separating the two equilibrium positions of protons with increasing . These data consistently demonstrated that stretching is a promising way to enhance the polarization performance and thermal stability of hydrogen-bonded organic ferroelectrics. PMID:25363720

Kobayashi, Kensuke; Horiuchi, Sachio; Ishibashi, Shoji; Kagawa, Fumitaka; Murakami, Youichi; Kumai, Reiji

2014-12-22

134

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

Science.gov (United States)

After decades of development and use in a variety of application areas, Quantitative Structure Property Relationships (QSPRs) and related descriptor-based statistical learning methods have achieved a level of infamy due to their misuse. The field is rife with past examples of overtrained models, overoptimistic performance assessment, and outright…

Krein, Michael

2011-01-01

135

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

136

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

137

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

OpenAIRE

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

Sarkhosh Maryam; Ghasemi Jahan B; Ayati Mahnaz

2012-01-01

138

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

Science.gov (United States)

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

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

2008-08-01

139

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

140

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

Directory of Open Access Journals (Sweden)

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

Agnaldo Arroio

2010-01-01

141

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

Scientific Electronic Library Online (English)

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

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

142

Relationship of binding specificity and structural property of the technetium-99m complexes for tumor hypoxia and tumor angiogenesis imaging  

International Nuclear Information System (INIS)

The growth of tumor requires nutrition and oxygen. Tumor cells will become hypoxic when the supply of oxygen is insufficient. Hypoxic tumor cells will not only resist radiation therapy and chemotherapy, but also induce angiogenesis for oxygen supply and for metastasis. Therefore, detection of tumor hypoxia and tumor angiogenesis with high sensitive radio labeled imaging agents is important. Hypoxic tumor cells may display some molecules as tumor markers for the specific binding with radiopharmaceuticals. Radiopharmaceuticals, unlike the non-radioactive drugs, are trace compounds in a given dosage. Due to the extreme low concentration, the non-specific accumulation of the radiotracers by blood cells and proteins, tissues, and organs can be even more serious compared to the non-radioactive drugs. The non-specific accumulation of the radiotracers can make the ratios of tumor/tissue (in terms of i.d.%/g) falling to the range of 2?7 [1-2]. Non-specific binding of radiopharmaceuticals is common, but detailed studies on it are poor documented. This presentation reports the study of the relationship of non-specific accumulation and the structural property of two type of 99mTC labeled compounds: (a) 99mTc-(amineoxime) containing either 2-nitroimidazole (2-NI, as hypoxia tumor cells specific agents), or 4-nitro- imidazole (4-NI, as control), or aniline (as reference) groups; (b) 99mTc-(arginine-glycine- aspartic acid, RGD, as tumor e-glycine- aspartic acid, RGD, as tumor angiogenesis specific agents) and 99mTc-(arginine-glycine- glutarmic acid, RGE, as control). The 99mTc-(amine-oxime) complexes, in addition to the 2-NI, 4-NI, and aniline groups, contain methyl-, ethyl-, propyl-, iso-butyl-, t-butyl-, phenyl-, and Benzyl- groups as well to make the radiotracers differing in structure and in lipophilicity , while the lipophilicity of a radiotracer plays an important role in non-specific cellular accumulation and protein binding, The results demonstrated that (1) the complex containing 2-NI showed specific accumulation to hypoxic cells, while those containing 4-NI and aniline did not; (2) among the 7 99mTc complexes containing 2-NI group, complex of greater lipophilicity showed higher level of non-specific cellular accumulation; (3) among the 99mTc complexes containing 2-NI, 4-NI, and aniline, the complexes with aniline group displayed greatest lipophilicity, greatest non-specific cellular uptake, and greatest serum protein binding. The 99mTc labeled RGD and RGE are similar in lipophilicity, but only the RGD has affinity to ?v?3 integrin proteins over expressing on tumor cells and exhibited 6 to 28 fold greater cellular accumulation than the RGE. However, the two labeled peptides, despite of the specific radioactivity, revealed identical accumulation in xenographed tumor, indicating non-specific uptake of the RGD in the tumor and non-specific binding to ?v?3 integrin proteins. These results implied that the non-specific accumulation and binding in vivo prevents a radiotracer reaching and binding to the target molecules of cancer cells. Therefore, besides binding specificity, non-specific effects of a compound is also an important aspect for consideration in designing effective radiopharmaceuticals for tumor imaging and therapy.

143

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

144

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

Science.gov (United States)

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

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

2014-09-01

145

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

146

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

147

A quantitative structure-property relationship analysis of soot-water partition coefficients for persistent organic pollutants.  

Science.gov (United States)

Geometrical optimization and electrostatic potential calculations have been performed at the HF/6-31G level of theory for investigated persistent organic pollutants (POPs). A number of statistically based parameters have been obtained. Relationship between soot-water partition coefficients (logK(SC)) of POPs and the structural descriptors has been established by the multiple linear regression method. The result shows that the quantities derived from electrostatic potential V(s)(-)¯ and V(s,max), together with molecular surface area (A(S)) and the energy of the highest occupied molecular orbital (E(HOMO)) can be well used to express the quantitative relationship between structure and logK(SC) (QSPR) of POPs. Predictive capability of the model has been demonstrated by leave-one-out cross-validation with the cross-validated correlation coefficient of 0.9797. Furthermore, the predictive power of this model was further examined for the external test set with the correlation coefficient of 0.9811 between observed and predicted logK(SC), validating the robustness and good predictive ability of our model. Furthermore, in order to further investigate the applicability of these parameters derived from electrostatic potential in prediction of soot-water partition coefficient for organic pollutants, eleven polycyclic aromatic hydrocarbons (PAHs), eleven polychlorinated biphenyls (PCBs) and nine phenyl urea herbicides (PUHs) from other source have also been studied. The QSPR models established may provide a new powerful method for predicting soot-water partition coefficients (logK(SC)) of organic pollutants. PMID:22377400

Xu, Hui-Ying; Zou, Jian-Wei; Min, Jian-Qing; Wang, Wei

2012-06-01

148

Ionic conduction, bond valence analysis of structure–property relationships of NaHoP2O7  

International Nuclear Information System (INIS)

Single crystals of NaHoP2O7 diphosphate have been prepared by the flux method and its structural and physical properties have been investigated. It crystallizes in the monoclinic system with the space group P21/n and its parameters are: a=8.6796(4) Å, b=5.3677(2) Å, c=13.6904(6) Å, ?=106.120° (2), V=612.75 (5) Å3, Z=4. The structure of NaHoP2O7 consists of a three-dimensional framework of HoO6 octahedra, linked by P2O7 diphosphate units, forming tunnels running parallel to [0 1 0], which are occupied by Na atoms. The infrared and Raman vibrational spectra have been investigated. Activation energy was obtained from Arrhenius plots (Ln ?T versus 1000/T) and found to be 1.27 eV. The coupling of the structural analysis with the BVS model for NaHoP2O7 has better interpret the measurements of the ionic conductivity and the most probably transport pathway model was determined. - Graphical abstract: Schematic representation of the structural arrangement of NaHoP2O7 shows the sodium conduction pathway along the [0 1 0] direction. Highlights: • Single crystals of NaHoP2O7 were prepared by flux method and characterized by single-crystal X-ray data. • The conductivity and loss spectra were analysed in order explain the mechanism of conduction. • The most probably conduction pathway are determined

149

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 (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

150

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

151

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

152

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

153

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

International Nuclear Information System (INIS)

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

154

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

Directory of Open Access Journals (Sweden)

Full Text Available Abstract A quantitative structure-property relationship (QSPR study is suggested for the prediction of retention times of volatile organic compounds. Various kinds of molecular descriptors were calculated to represent the molecular structure of compounds. Modeling of retention times of these compounds as a function of the theoretically derived descriptors was established by multiple linear regression (MLR and artificial neural network (ANN. The stepwise regression was used for the selection of the variables which gives the best-fitted models. After variable selection ANN, MLR methods were used with leave-one-out cross validation for building the regression models. The prediction results are in very good agreement with the experimental values. MLR as the linear regression method shows good ability in the prediction of the retention times of the prediction set. This provided a new and effective method for predicting the chromatography retention index for the volatile organic compounds.

Sarkhosh Maryam

2012-05-01

155

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

Science.gov (United States)

A quantitative structure-property relationship (QSPR) study is suggested for the prediction of retention times of volatile organic compounds. Various kinds of molecular descriptors were calculated to represent the molecular structure of compounds. Modeling of retention times of these compounds as a function of the theoretically derived descriptors was established by multiple linear regression (MLR) and artificial neural network (ANN). The stepwise regression was used for the selection of the variables which gives the best-fitted models. After variable selection ANN, MLR methods were used with leave-one-out cross validation for building the regression models. The prediction results are in very good agreement with the experimental values. MLR as the linear regression method shows good ability in the prediction of the retention times of the prediction set. This provided a new and effective method for predicting the chromatography retention index for the volatile organic compounds. PMID:22594439

Sarkhosh, Maryam; Ghasemi, Jahan B; Ayati, Mahnaz

2012-01-01

156

Revealing the structure-property relationship of covalent organic frameworks for CO? capture from postcombustion gas: a multi-scale computational study.  

Science.gov (United States)

With the aid of multi-scale computational methods, a diverse set of 46 covalent organic frameworks (COFs), covering the most typical COFs synthesized to date, were collected to study the structure-property relationship of COFs for CO2 capture. For this purpose, CO2 capture from postcombustion gas (CO2-N2 mixture) under industrial vacuum swing adsorption (VSA) conditions was considered as an example. This work shows that adsorption selectivity, CO2 working capacity and the sorbent selection parameter of COFs all exhibit strong correlation with the difference in the adsorbility of adsorbates (?AD), highlighting that realization of large ?AD can be regarded as an important starting point for designing COFs with improved separation performance. Furthermore, it was revealed that the separation performance of 2D-layered COFs can be greatly enhanced by generating "splint effects", which can be achieved through structural realignment to form slit-like pores with suitable size in the structures. Such "splint effects" in 2D-COFs can find their similar counterpart of "catenation effects" in 3D-COFs or MOFs. On the basis of these observations, a new design strategy was proposed to strengthen the separation performance of COFs. It could be expected that the information obtained in this work not only will enrich the knowledge of the structure-property relationship of COFs for separation, but also will largely facilitate their future applications to the fields related to energy and environmental science, such as natural gas purification, CO2, NO(x) and SO(x) capture, etc. PMID:24936781

Tong, Minman; Yang, Qingyuan; Xiao, Yuanlong; Zhong, Chongli

2014-08-01

157

Derivation of structure-activity relationships from the anticancer properties of ruthenium(II) arene complexes with 2-aryldiazole ligands.  

Science.gov (United States)

The ligands 2-pyridin-2-yl-1H-benzimidazole (HL(1)), 1-methyl-2-pyridin-2-ylbenzimidazole (HL(2)), and 2-(1H-imidazol-2-yl)pyridine (HL(3)) and the proligand 2-phenyl-1H-benzimidazole (HL(4)) have been used to prepare five different types of new ruthenium(II) arene compounds: (i) monocationic complexes with the general formula [(?(6)-arene)RuCl(?(2)-N,N-HL)]Y [HL = HL(1), HL(2), or HL(3); Y = Cl or BF4; arene = 2-phenoxyethanol (phoxet), benzene (bz), or p-cymene (p-cym)]; (ii) dicationic aqua complexes of the formula [(?(6)-arene)Ru(OH2)(?(2)-N,N-HL(1))](Y)2 (Y = Cl or TfO; arene = phoxet, bz, or p-cym); (iii) the nucleobase derivative [(?(6)-arene)Ru(9-MeG)(?(2)-N,N-HL(1))](PF6)2 (9-MeG = 9-methylguanine); (iv) neutral complexes consistent with the formulation [(?(6)-arene)RuCl(?(2)-N,N-L(1))] (arene = bz or p-cym); (v) the neutral cyclometalated complex [(?(6)-p-cym)RuCl(?(2)-N,C-L(4))]. The cytototoxic activity of the new ruthenium(II) arene compounds has been evaluated in several cell lines (MCR-5, MCF-7, A2780, and A2780cis) in order to establish structure-activity relationships. Three of the compounds with the general formula [(?(6)-arene)RuCl(?(2)-N,N-HL(1))]Cl differing in the arene moiety have been studied in depth in terms of thermodynamic dissociation constants, aquation kinetic constants, and DNA binding measurements. The biologically most active compound is the p-cym derivative, which strongly destabilizes the DNA double helix, whereas those with bz and phoxet have only a small effect on the stability of the DNA double helix. Moreover, the inhibitory activity of several compounds toward CDK1 has also been evaluated. The DNA binding ability of some of the studied compounds and their CDK1 inhibitory effect suggest a multitarget mechanism for their biological activity. PMID:25302401

Martínez-Alonso, Marta; Busto, Natalia; Jalón, Félix A; Manzano, Blanca R; Leal, José M; Rodríguez, Ana M; García, Begoña; Espino, Gustavo

2014-10-20

158

Design and prediction of new anticoagulants as a selective Factor IXa inhibitor via three-dimensional quantitative structure-property relationships of amidinobenzothiophene derivatives  

Science.gov (United States)

Factor IXa (FIXa), a blood coagulation factor, is specifically inhibited at the initiation stage of the coagulation cascade, promising an excellent approach for developing selective and safe anticoagulants. Eighty-four amidinobenzothiophene antithrombotic derivatives targeting FIXa were selected to establish three-dimensional quantitative structure–activity relationship (3D-QSAR) and three-dimensional quantitative structure–selectivity relationship (3D-QSSR) models using comparative molecular field analysis and comparative similarity indices analysis methods. Internal and external cross-validation techniques were investigated as well as region focusing and bootstrapping. The satisfactory q2 values of 0.753 and 0.770, and r2 values of 0.940 and 0.965 for 3D-QSAR and 3D-QSSR, respectively, indicated that the models are available to predict both the inhibitory activity and selectivity on FIXa against Factor Xa, the activated status of Factor X. This work revealed that the steric, hydrophobic, and H-bond factors should appropriately be taken into account in future rational design, especially the modifications at the 2?-position of the benzene and the 6-position of the benzothiophene in the R group, providing helpful clues to design more active and selective FIXa inhibitors for the treatment of thrombosis. On the basis of the three-dimensional quantitative structure–property relationships, 16 new potent molecules have been designed and are predicted to be more active and selective than Compound 33, which has the best activity as reported in the literature. PMID:25848211

Gao, Jia-Suo; Tong, Xu-Peng; Chang, Yi-Qun; He, Yu-Xuan; Mei, Yu-Dan; Tan, Pei-Hong; Guo, Jia-Liang; Liao, Guo-Chao; Xiao, Gao-Keng; Chen, Wei-Min; Zhou, Shu-Feng; Sun, Ping-Hua

2015-01-01

159

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

Science.gov (United States)

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

Nino, Juan C.

160

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

OpenAIRE

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

Coluccia, Salvatore; Viscardi, Guido; Barbero, Nadia; Park, Jinhyung; Quagliotto, Pierluigi; Barolo, Claudia

2012-01-01

161

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

162

Drug structure–transport relationships  

OpenAIRE

Malcolm Rowland has greatly facilitated an understanding of drug structure–pharmacokinetic relationships using a physiological perspective. His view points, covering a wide range of activities, have impacted on my own work and on my appreciation and understanding of our science. This overview summarises some of our parallel activities, beginning with Malcolm’s work on the pH control of amphetamine excretion, his work on the disposition of aspirin and on the application of clearance concep...

Roberts, Michael S.

2010-01-01

163

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-12-05

164

Synthesis-atomic structure-properties relationships in metallic nanoparticles by total scattering experiments and 3D computer simulations: case of Pt-Ru nanoalloy catalysts.  

Science.gov (United States)

An approach to determining the 3D atomic structure of metallic nanoparticles (NPs) in fine detail and using the unique knowledge obtained for rationalizing their synthesis and properties targeted for optimization is described and exemplified on Pt-Ru alloy NPs of importance to the development of devices for clean energy conversion such as fuel cells. In particular, PtxRu100-x alloy NPs, where x = 31, 49 and 75, are synthesized by wet chemistry and activated catalytically by a post-synthesis treatment involving heating under controlled N2-H2 atmosphere. So-activated NPs are evaluated as catalysts for gas-phase CO oxidation and ethanol electro-oxidation reactions taking place in fuel cells. Both as-synthesized and activated NPs are characterized structurally by total scattering experiments involving high-energy synchrotron X-ray diffraction coupled to atomic pair distribution functions (PDFs) analysis. 3D structure models both for as-synthesized and activated NPs are built by molecular dynamics simulations based on the archetypal for current theoretical modelling Sutton-Chen method. Models are refined against the experimental PDF data by reverse Monte Carlo simulations and analysed in terms of prime structural characteristics such as metal-to-metal bond lengths, bond angles and first coordination numbers for Pt and Ru atoms. Analysis indicates that, though of a similar type, the atomic structure of as-synthesized and respective activated NPs differ in several details of importance to NP catalytic properties. Structural characteristics of activated NPs and data for their catalytic activity are compared side by side and strong evidence found that electronic effects, indicated by significant changes in Pt-Pt and Ru-Ru metal bond lengths at NP surface, and practically unrecognized so far atomic ensemble effects, indicated by distinct stacking of atomic layers near NP surface and prevalence of particular configurations of Pt and Ru atoms in these layers, contribute to the observed enhancement of the catalytic activity of PtxRu100-x alloy NPs at x ? 50. Implications of so-established relationships between the atomic structure and catalytic activity of Pt-Ru alloy NPs on efforts aimed at improving further the latter by tuning-up the former are discussed and the usefulness of detailed NP structure studies to advancing science and technology of metallic NPs - exemplified. PMID:25874741

Prasai, Binay; Ren, Yang; Shan, Shiyao; Zhao, Yinguang; Cronk, Hannah; Luo, Jin; Zhong, Chuan-Jian; Petkov, Valeri

2015-04-24

165

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.)

166

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

167

Radiopharmaceuticals: structure-activity relationship  

International Nuclear Information System (INIS)

A collection of papers presented at a symposium held in Hartford Connecticut, March 21-23, 1980 is presented. The aim of the book is to review the influence of chemical structure on the biological distribution of radioactively labeled compounds with a view towards proposing a rational approach to the design of future radiopharmaceuticals. The material covers most of the known work that has been completed in this area. The book contains 38 chapters with 1,415 references arranged in five major sections: a) basic aspects of structure-activity relationship; b) metals and organometallic compounds; c) lipid soluble materials; d) analysis of structure-activity in major organs, and e) cyclotron-produced radionuclides, nutrients, and analogues. Each section can be read independent of the others

168

Highly emissive cyclometalated rhenium metallacycles: structure-luminescence relationship.  

Science.gov (United States)

We report on a series of new self-assembled cyclometalated dirhenium(I) metallacyclic complexes via an unprecedented rhenium-mediated C-H bond activation and the relationship between their structures and luminescence properties. PMID:20614862

Tseng, Yi-Hsiu; Bhattacharya, Dibyendu; Lin, Shih-Ming; Thanasekaran, P; Wu, Jing-Yun; Lee, Li-Wei; Sathiyendiran, M; Ho, Mei-Lin; Chung, Min-Wen; Hsu, Kung-Chung; Chou, Pi-Tai; Lu, Kuang-Lieh

2010-08-01

169

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

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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

170

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.

171

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

172

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

173

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

174

Causal structures and causal relationship  

CERN Document Server

Recently ({\\em Class. Quant. Grav.} {\\bf 20} 625-664) the concept of {\\em causal mapping} between spacetimes --which is stronger than the {\\em chronological map} one in abstract chronological spaces--, and the related notion of {\\em 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 Lorentz-Minkowski and Einstein static spacetimes remain stable, whereas that of de Sitter becomes unstable, (iii) ...

García-Parrado, A; Garc\\'{\\i}a-Parrado, Alfonso; S\\'anchez, Miguel

2005-01-01

175

Structure-property relationships and (1)O)2) photosensitisation in sterically encumbered diimine Pt(II) acetylide complexes.  

Science.gov (United States)

A series of sterically encumbered [Pt(L)(?-acetylide)2 ] complexes were prepared in which L, a dendritic polyaromatic diimine ligand, was held constant (L=1-(2,2'-bipyrid-6-yl)-2,3,4,5-tetrakis(4-tert-butylphenyl)benzene) and the cis ethynyl co-ligands were varied. The optical properties of the complexes were tuned by changing the electronic character, extent of ? conjugation and steric bulk of the ethynyl ligands. Replacing electron-withdrawing phenyl-CF3 substituents (4) with electron-donating pyrenes (5) resulted in a red shift of both the lowest-energy absorption (?E=3300?cm(-1) , 61?nm) and emission bands (?E=1930?cm(-1) , 64?nm). The emission, assigned in each case as phosphorescence on the basis of the excited-state lifetimes, switched from being (3) MMLL'CT-derived (mixed metal-ligand-to-ligand charge transfer) when phenyl/polyphenylene substituents (3, 4, 6) were present, to ligand-centred (3) ??* when the substituents were more conjugated aromatic platforms [pyrene (5) or hexa-peri-hexabenzocoronene (7)]. The novel Pt(II) acetylide complexes 5 and 7 absorb strongly in the visible region of the electromagnetic spectrum, which along with their long triplet excited-state lifetimes suggested they would be good candidates for use as singlet-oxygen photosensitisers. Determined by in situ photooxidation of 1,5-dihydroxynaphthalene (DHN), the photooxidation rate with pyrenyl-5 as sensitiser (kobs =39.3×10(-3) ?min(-1) ) was over half that of the known (1) O2 sensitiser tetraphenylporphyrin (kobs =78.6×10(-3) ?min(-1) ) under the same conditions. Measured (1) O2 quantum yields of complexes 5 and 7 were half and one-third, respectively, of that of TPP, and thus reveal an efficient triplet-triplet energy-transfer process in both cases. PMID:24108657

Nolan, Deanne; Gil, Belén; Wang, Longsheng; Zhao, Jianzhang; Draper, Sylvia M

2013-11-11

176

Phase transition induced by pressure in TbCrO{sub 4} oxide: Relationship structure-properties  

Energy Technology Data Exchange (ETDEWEB)

Terbium chromate TbCrO{sub 4}, which has been described as belonging to the zircon-type structure showing tetragonal symmetry, space group I4{sub 1}/amd, has been prepared as a dimorphic compound. When the zircon-type TbCrO{sub 4} polymorph is treated at 40 kbar and 833 K takes place a phase transition to the tetragonal scheelite-type TbCrO{sub 4} polymorph, space group I4{sub 1}/a, with lattice parameters a = 5.0315(10) A and c = 11.3740(2) A. Magnetic susceptibility measurements reveal dramatic changes concerning the magnetic behavior of these two polymorphs. In this sense, the zircon-type TbCrO{sub 4} polymorph behaves as ferromagnetic with a Curie temperature of 22 K, while the scheelite-type TbCrO{sub 4} polymorph is antiferromagnetic with T{sub N} = 29 K. M vs. H plots at different temperatures show the presence of a metamagnetic transition for the scheelite-type TbCrO{sub 4} polymorph with a critical field of 2.6 T. The change of the sign of the magnetic interaction has been explained taking into account the differences found in the distances and bond angles of the superexchange Tb-O-Cr pathway through these interactions take place in both zircon and scheelite polymorphs.

Climent, E.; Gallardo, J.M. [Dpto. Quimica Inorganica, Facultad Ciencias Quimicas, Universidad Complutense de Madrid, Ciudad Universitaria, E-28040 Madrid (Spain); Romero de Paz, J. [CAI Tecnicas Fisicas, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Taira, N. [Dpto. Quimica Inorganica, Facultad Ciencias Quimicas, Universidad Complutense de Madrid, Ciudad Universitaria, E-28040 Madrid (Spain); Saez Puche, R., E-mail: rsp92@quim.ucm.e [Dpto. Quimica Inorganica, Facultad Ciencias Quimicas, Universidad Complutense de Madrid, Ciudad Universitaria, E-28040 Madrid (Spain)

2009-12-04

177

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

Science.gov (United States)

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

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

2014-03-01

178

Improved quantitative structure property relationships for the prediction of dielectric constants for a set of diverse compounds by subsetting of the data set  

Science.gov (United States)

In a recent publication we explored the development of quantitative structure property relationships for the calculation of dielectric constants, which resulted in a general model for a wide range of compounds. Our current work explores the division of the set of compounds into eight more homogeneous subsets for which local models are developed. The full data set consists of 454 compounds with dielectric constants ranging from 1 to 40. A pool of up to 16 molecular descriptors is calculated for each of the eight data sets. The descriptors include dipole moment, polarizability, counts of elemental types or functional groups, charged partial surface area, and molecular connectivity. All possible 4-16 descriptor models are calculated for each of the eight data sets, and the best models are selected and compared to the results obtained from the best general model for all 454 compounds. Neural networks using the Broyden-Fletcher-Goldfarb-Shanno training algorithm are employed to build the models. The resulting combined mean test set error for the eight local models of 1.31 is significantly better than the mean test set error of 1.85 for the general model. PMID:11045821

Schweitzer; Morris

2000-09-01

179

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

Science.gov (United States)

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

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

2009-03-01

180

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

181

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

182

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

183

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

184

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

185

Comparative Study of Structure-Property Relationships in Polymer Networks Based on Bis-GMA, TEGDMA and Various Urethane-Dimethacrylates  

Directory of Open Access Journals (Sweden)

Full Text Available The effect of various dimethacrylates on the structure and properties of homo- and copolymer networks was studied. The 2,2-bis-[4-(2-hydroxy-3- methacryloyloxypropoxyphenyl]-propane (Bis-GMA, triethylene glycol dimethacrylate (TEGDMA and 1,6-bis-(methacryloyloxy-2-ethoxycarbonylamino-2,4,4-trimethylhexane (HEMA/TMDI, all popular in dentistry, as well as five urethane-dimethacrylate (UDMA alternatives of HEMA/TMDI were used as monomers. UDMAs were obtained from mono-, di- and tri(ethylene glycol monomethacrylates and various commercial diisocyanates. The chemical structure, degree of conversion (DC and scanning electron microscopy (SEM fracture morphology were related to the mechanical properties of the polymers: flexural strength and modulus, hardness, as well as impact strength. Impact resistance was widely discussed, being lower than expected in the case of poly(UDMAs. It was caused by the heterogeneous morphology of these polymers and only moderate strength of hydrogen bonds between urethane groups, which was not high enough to withstand high impact energy. Bis-GMA, despite having the highest polymer morphological heterogeneity, ensured fair impact resistance, due to having the strongest hydrogen bonds between hydroxyl groups. The TEGDMA homopolymer, despite being heterogeneous, produced the smoothest morphology, which resulted in the lowest brittleness. The UDMA monomer, having diethylene glycol monomethacrylate wings and the isophorone core, could be the most suitable HEMA/TMDI alternative. Its copolymer with Bis-GMA and TEGDMA had improved DC as well as all the mechanical properties.

Izabela Barszczewska-Rybarek

2015-03-01

186

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

187

Structure-Activity Relationships in Nitro-Aromatic Compounds  

Science.gov (United States)

Many nitro-aromatic compounds show mutagenic and carcinogenic properties, posing a potential human health risk. Despite this potential health hazard, nitro-aromatic compounds continue to be emitted into ambient air from municipal incinerators, motor vehicles, and industrial power plants. As a result, understanding the structural and electronic factors that influence mutagenicity in nitro-aromatic compounds has been a long standing objective. Progress toward this goal has accelerated over the years, in large part due to the synergistic efforts among toxicology, computational chemistry, and statistical modeling of toxicological data. The concerted influence of several structural and electronic factors in nitro-aromatic compounds makes the development of structure-activity relationships (SARs) a paramount challenge. Mathematical models that include a regression analysis show promise in predicting the mutagenic activity of nitro-aromatic compounds as well as in prioritizing compounds for which experimental data should be pursued. A major challenge of the structure-activity models developed thus far is their failure to apply beyond a subset of nitro-aromatic compounds. Most quantitative structure-activity relationship papers point to statistics as the most important confirmation of the validity of a model. However, the experimental evidence shows the importance of the chemical knowledge in the process of generating models with reasonable applicability. This chapter will concisely summarize the structural and electronic factors that influence the mutagenicity in nitro-aromatic compounds and the recent efforts to use quantitative structure-activity relationships to predict those physicochemical properties.

Vogt, R. A.; Rahman, S.; Crespo-Hernández, C. E.

188

Structural characterization, solution studies, and DFT calculations on a series of binuclear gold(III) oxo complexes: relationships to biological properties.  

Science.gov (United States)

A series of structurally related oxo-bridged binuclear gold(III) compounds, [Au2(mu-O)2(N;N)2](PF6)2, where N;N is 2,2'-bipyridine or a substituted 2,2'-bipyridine, have recently been shown to exhibit appreciable stability under physiological-like conditions and to manifest important antiproliferative effects toward selected human tumor cell lines (J. Med. Chem. 2006, 49, 5524). The crystal structures of four members of this series, namely, [Au2(mu-O)2(bipy)2](PF6)2, cis-[Au2(mu-O)2(6-Mebipy)2](PF6)2, trans-[Au2(mu-O)2(6-oXylbipy)2](PF6)2, and [Au2(mu-O)2(6,6'-Me2bipy)2](PF6)2, have been solved here and the respective structural parameters comparatively analyzed. Remarkably, all of the compounds contain a common structural motif consisting of a Au2O2 "diamond core" linked to two bipyridine ligands in a roughly planar arrangement. Interestingly, introduction of different kinds of alkyl or aryl substituents on the 6 (and 6') position(s) of the bipyridine ligand leads to small structural changes that nonetheless greatly affect the reactivity of the metal centers. The chemical behavior of these compounds in solution has been studied in detail, focusing in particular on the electrochemical properties. Some initial correlations among the structural parameters, the chemical behavior in solution, and the known cytotoxic effects of these compounds are proposed. Notably, we have found that the 6,6'-dimethyl-2,2'-bipyridine derivative, which showed the largest structural deviations with respect to the model compound [Au2(mu-O)2(bipy)2](PF6)2, also had the highest oxidizing power, the least thermal stability, and the greatest cytotoxic activity. The positive correlation that exists between the oxidizing power and the antiproliferative effects seems to be of particular interest. Moreover, the electronic structures of these compounds were extensively analyzed using DFT methods, and the effects of the various substituents on reactivity were predicted; overall, very good agreement between theoretical expectations and experimental data was achieved. In turn, theoretical predictions offer interesting hints for the design of new, more active binuclear gold(III) compounds. PMID:18314951

Gabbiani, Chiara; Casini, Angela; Messori, Luigi; Guerri, Annalisa; Cinellu, Maria Agostina; Minghetti, Giovanni; Corsini, Maddalena; Rosani, Claudia; Zanello, Piero; Arca, Massimiliano

2008-04-01

189

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

190

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

191

The Galaxy Structure-Redshift Relationship  

OpenAIRE

There exists a gradual, but persistent, evolutionary effect in the galaxy population such that galaxy structure and morphology change with redshift. This galaxy structure-redshift relationship is such that an increasingly large fraction of all bright and massive galaxies at redshifts 2 < z < 3 are morphologically peculiar at wavelengths from rest-frame ultraviolet to rest-frame optical. There are however examples of morphologically selected spirals and ellipticals at all red...

Conselice, Christopher

2004-01-01

192

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

193

Understanding the Relationships between Structural Features and Optical/Magnetic Properties When Designing Fe1-xMgxMoO4 as Piezochromic Compounds.  

Science.gov (United States)

Fe1-xMgxMoO4 compounds with x = 0, 0.25, 0.5, 0.75, and 1.0 were obtained after annealing under inert gas at T = 700 °C. All of the compounds exhibit a pressure-induced and/or temperature-induced phase transition between the two polymorphs adopted by AMoO4 compounds (A = Mn, Fe, Co, and Ni). For the FeMoO4 compound, for both the ? and the ? allotropic forms, the structural features have been correlated to the magnetic properties, the Mössbauer signals, and the optical absorption properties to gain a better understanding of the phenomena at the origin of the piezo(thermo)chromic behavior. The different contributions of the Mössbauer signals were attributed to the different Fe(2+) ions or Fe(3+) ions from the structural data (Wyckoff positions, bond distances and angles) and were quantified. Furthermore, the low Fe(3+) concentration (9 and 4 mol?%, respectively, in the ? and the ? allotropic forms) was also quantified based on the magnetic susceptibility measurements. The net increase in the Fe(3+) quantity in the ?-form in comparison to the ?-form, which is associated with the occurrence of Fe-Mo charge transfer, is at the origin of the important divergence of coloration of the two forms. To design new piezo(thermo)chromic oxides and to control the pressure (temperature) of this first-order phase transition, FeMoO4-MgMoO4 solid solutions were synthesized. The optical contrast between the two allotropic forms was increased due to magnesium incorporation, and the phase transition (? ? ?) pressure increased steadily with the Mg content. A new generation of nontoxic and chemically stable piezochromic compounds that are sensible to various pressures was proposed. PMID:25664488

Blanco-Gutierrez, Veronica; Demourgues, Alain; Toulemonde, Olivier; Wattiaux, Alain; Nguyen, Olivier; Gaudon, Manuel

2015-03-01

194

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

195

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

196

Structural graphite and its properties  

International Nuclear Information System (INIS)

Considered is the technology of the structural graphite production for the reactor equipment and its effect on the graphite properties. Shown is the effect of porosity, formed at different stages of graphite production, on its strength and elasticity properties, and also the effect of the processing temperature on the crystal lattice parameter and physical properties of graphite obtained. The analysis of the dependence of graphite physical properties on its structural characteristics shows that well-expressed anizotropy of graphite physico-mechanical properties is caused by its hexagonal, laminated structure, by the orientation of grains and inclusions, and by the direction of micro- and macrodefects, as well

197

Two new noncentrosymmetric (NCS) polar oxides: syntheses, characterization, and structure-property relationships in BaMTe2O7 (M = Mg2+ or Zn2+).  

Science.gov (United States)

Two new noncentrosymmetric (NCS) polar oxides, BaMgTe(2)O(7) and BaZnTe(2)O(7), have been synthesized and characterized, with their crystal structures determined by single crystal X-ray diffraction. The iso-structural materials exhibit structures consisting of layers of corner-shared MgO(5) or ZnO(5), Te(6+)O(6), and Te(4+)O(4) polyhedra that are separated by Ba(2+) cations. The Te(4+) cation is found in a highly asymmetric and polar coordination environment attributable to its stereoactive lone-pair. The alignment of the individual TeO(4) polar polyhedra results in macroscopic polarity for BaMgTe(2)O(7) and BaZnTe(2)O(7). Powder second-harmonic generation (SHG) measurements revealed a moderate SHG efficiency of approximately 5 × KDP (or 200 × ?-SiO(2)) for both materials. Piezoelectric charge constants of 70 and 57 pm/V, and pyroelectric coefficients of -18 and -10 ?C·m(-2)·K(-1) were obtained for BaMgTe(2)O(7) and BaZnTe(2)O(7), respectively. Although the materials are polar, frequency dependent polarization measurements indicated that the materials are not ferroelectric, that is, the observed macroscopic polarization cannot be reversed. Infrared, UV-vis diffuse spectroscopy, and thermal properties were also measured. Crystal data: BaMgTe(2)O(7), orthorhombic, space group Ama2 (No. 40), a = 5.558(2) Å, b = 15.215(6) Å, c = 7.307(3) Å, V = 617.9(4) Å(3), and Z = 4; BaZnTe(2)O(7), orthorhombic, space group Ama2 (No. 40), a = 5.5498(4) Å, b = 15.3161(11) Å, c = 7.3098(5) Å, V = 621.34(8) Å(3), and Z = 4. PMID:22296559

Yeon, Jeongho; Kim, Sang-Hwan; Nguyen, Sau Doan; Lee, Hana; Halasyamani, P Shiv

2012-02-20

198

Structure-activity relationship of cyanine tau aggregation inhibitors  

OpenAIRE

A structure-activity relationship for symmetrical cyanine inhibitors of human tau aggregation was elaborated using a filter trap assay. Antagonist activity depended on cyanine heterocycle, polymethine bridge length, and the nature of meso- and N-substituents. One potent member of the series, 3,3’-diethyl-9-methylthiacarbocyanine iodide (compound 11), retained submicromolar potency and had calculated physical properties consistent with blood-brain barrier and cell membrane penetration. Expos...

Chang, Edward; Congdon, Erin E.; Honson, Nicolette S.; Duff, Karen E.; Kuret, Jeff

2009-01-01

199

Analysis of protein sequence/structure similarity relationships.  

OpenAIRE

Current analyses of protein sequence/structure relationships have focused on expected similarity relationships for structurally similar proteins. To survey and explore the basis of these relationships, we present a general sequence/structure map that covers all combinations of similarity/dissimilarity relationships and provide novel energetic analyses of these relationships. To aid our analysis, we divide protein relationships into four categories: expected/unexpected similarity (S and S(?)) ...

Gan, Hin Hark; Perlow, Rebecca A.; Roy, Sharmili; Ko, Joy; Wu, Min; Huang, Jing; Yan, Shixiang; Nicoletta, Angelo; Vafai, Jonathan; Sun, Ding; Wang, Lihua; Noah, Joyce E.; Pasquali, Samuela; Schlick, Tamar

2002-01-01

200

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

201

Structure-properties relationships in triarylamine-based donor-acceptor molecules containing naphtyl groups as donor material for organic solar cells  

Science.gov (United States)

The effects of replacing the phenyl rings of triphenylamine (TPA) by naphtyl groups are analysed on a series of push-pull molecules containing a 2-thienyl-dicyanovinyl acceptor group. UV-Vis absorption spectroscopy and cyclic voltammetry show that the introduction of one or two naphtyl groups in the structure has limited effects on the optical properties and energy levels of the molecule. On the other hand, the evaluation of the compounds as donor material in bi-layer solar cells with C60 as acceptor shows that the number and mode of linkage of the naphtyl groups exert a marked influence on the power conversion efficiency (PCE) of the cell. Two naphtyl groups lead to a decrease of PCE with respect to TPA, while a single naphtyl group produces opposite effects depending on the linking mode. Compared to TPA, an alpha-naphtyl group leads to a small decrease of PCE while in contrast a beta-naphtyl leads to a ~35% increase of PCE due to improved short-circuit current density (Jsc) and fill-factor. The determination of the hole-mobility of these two donors by the space-charge-limited current method shows that these effects are correlated with the higher hole-mobility of the ?-naphtyl compound.

Mohamed, Salma; Demeter, Dora; Laffitte, Jean-Alex; Blanchard, Philippe; Roncali, Jean

2015-03-01

202

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

203

Structure-properties relationships in triarylamine-based donor-acceptor molecules containing naphtyl groups as donor material for organic solar cells  

Science.gov (United States)

The effects of replacing the phenyl rings of triphenylamine (TPA) by naphtyl groups are analysed on a series of push-pull molecules containing a 2-thienyl-dicyanovinyl acceptor group. UV-Vis absorption spectroscopy and cyclic voltammetry show that the introduction of one or two naphtyl groups in the structure has limited effects on the optical properties and energy levels of the molecule. On the other hand, the evaluation of the compounds as donor material in bi-layer solar cells with C60 as acceptor shows that the number and mode of linkage of the naphtyl groups exert a marked influence on the power conversion efficiency (PCE) of the cell. Two naphtyl groups lead to a decrease of PCE with respect to TPA, while a single naphtyl group produces opposite effects depending on the linking mode. Compared to TPA, an alpha-naphtyl group leads to a small decrease of PCE while in contrast a beta-naphtyl leads to a ~35% increase of PCE due to improved short-circuit current density (Jsc) and fill-factor. The determination of the hole-mobility of these two donors by the space-charge-limited current method shows that these effects are correlated with the higher hole-mobility of the ?-naphtyl compound. PMID:25761773

Mohamed, Salma; Demeter, Dora; Laffitte, Jean-Alex; Blanchard, Philippe; Roncali, Jean

2015-01-01

204

Structure-properties relationships in triarylamine-based donor-acceptor molecules containing naphtyl groups as donor material for organic solar cells.  

Science.gov (United States)

The effects of replacing the phenyl rings of triphenylamine (TPA) by naphtyl groups are analysed on a series of push-pull molecules containing a 2-thienyl-dicyanovinyl acceptor group. UV-Vis absorption spectroscopy and cyclic voltammetry show that the introduction of one or two naphtyl groups in the structure has limited effects on the optical properties and energy levels of the molecule. On the other hand, the evaluation of the compounds as donor material in bi-layer solar cells with C60 as acceptor shows that the number and mode of linkage of the naphtyl groups exert a marked influence on the power conversion efficiency (PCE) of the cell. Two naphtyl groups lead to a decrease of PCE with respect to TPA, while a single naphtyl group produces opposite effects depending on the linking mode. Compared to TPA, an alpha-naphtyl group leads to a small decrease of PCE while in contrast a beta-naphtyl leads to a ~35% increase of PCE due to improved short-circuit current density (Jsc) and fill-factor. The determination of the hole-mobility of these two donors by the space-charge-limited current method shows that these effects are correlated with the higher hole-mobility of the ?-naphtyl compound. PMID:25761773

Mohamed, Salma; Demeter, Dora; Laffitte, Jean-Alex; Blanchard, Philippe; Roncali, Jean

2015-01-01

205

RELATIONSHIP BETWEEN BOARD STRUCTURE AND CONSERVATISM  

Directory of Open Access Journals (Sweden)

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

Shahram Gilaninia

2011-10-01

206

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

207

Structural relationships in high temperature superconductors  

International Nuclear Information System (INIS)

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

208

The relationships between femoral cortex geometry and tissue mechanical properties.  

Science.gov (United States)

Bone tissue and geometry are constantly modified through modeling and remodeling at the periosteal, endosteal and intracortical envelopes. Results from several studies indicate that femoral bone geometry is a predictor of whole bone strength (e.g. femoral neck strength), however, it is not known whether there is a relationship between bone structural and material properties. Bone geometry can be determined from parameters based on plane X-ray radiogrammetry which are used to evaluate femoral bone quality for implant success. If there is a relationship between these parameters and tissue mechanical properties, this would have implications in the interpretation of such parameters for assessment of fracture risk and in further understanding of bone biology. Following measurement of radiogrammetric parameters from antero-posterior and medio-lateral X-rays (cortical thickness, bone diameter, bone area, moment of inertia, cortical index, Singh index), human femurs were machined into standard test specimens for assessment of tensile fracture toughness (GIc) of the tissue. Results indicated that tensile fracture toughness generally increased with increasing bone size. We also found that fracture toughness of the tissue was significantly related to radiogrammetric indices and that some of these indices explained a greater variability in toughness than porosity, age or gender. PMID:23454364

Yeni, Yener N; Brown, Christopher U; Gruen, Thomas A; Norman, Timothy L

2013-05-01

209

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

210

Structural Properties of Ego Networks  

CERN Document Server

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 the locally observable portion of the network consisting of the subgraph over its immediate neighbors. Such subgraphs, known as ego networks, have properties that can differ substantially from those of the global network. In this paper, we study the structural properties of ego networks and show how they relate to the global properties of networks from which they are derived. Through empirical comparisons and mathematical derivations, we show that structural features, similar to static attributes, suffer from paradoxes. We quantify the diff...

Gupta, Sidharth; Lerman, Kristina

2014-01-01

211

Spanish Version of the Savings Inventory-Revised: Adaptation, Psychometric Properties, and Relationship to Personality Variables  

Science.gov (United States)

The factor structure, psychometric properties, and relationship with personality variables of a Spanish version of the Savings Inventory-Revised (SI-R) are investigated in a sample of 381 undergraduate students. A maximum likelihood factor analysis suggests a three-factor structure, which is similar but not identical to that of the original…

Tortella-Feliu, Miquel; Fullana, Miquel A.; Caseras, Xavier; Andion, Oscar; Torrubia, Rafael; Mataix-Cols, David

2006-01-01

212

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

213

The physics and structure-property relationships of scintillator materials: effect of thermal history and chemistry on the light output of scintillating glasses  

Science.gov (United States)

The scintillation light output of a series of silicate glasses has been determined for a fixed electron energy deposition. The glasses are cerium-doped lithium-aluminosilicates. Scintillation light output measurements were made as a function of lithium and alumina concentration and of annealing history. In this system, the cerium outer electron cloud serves as a sensitive probe of the local glass structure. From these measurements, a sensitivity matrix relating the light output to the structure is developed and presented. A conceptual model for the behavior of the light output is also presented.

Bliss, M.; Craig, R. A.; Reeder, P. L.

1994-03-01

214

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

215

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  

Directory of Open Access Journals (Sweden)

Full Text Available 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.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 processo 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.

Eduardo da Costa Severiano

2011-06-01

216

Characterization of Enzyme Structure-Function Relationship of Adenylosuccinate Lyase  

Science.gov (United States)

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

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

2009-10-01

217

Antibacterial Barbituric Acid Analogues Inspired from Natural 3-Acyltetramic Acids; Synthesis, Tautomerism and Structure and Physicochemical Property-Antibacterial Activity Relationships  

Directory of Open Access Journals (Sweden)

Full Text Available The synthesis, tautomerism and antibacterial activity of novel barbiturates is reported. In particular, 3-acyl and 3-carboxamidobarbiturates exhibited antibacterial activity, against susceptible and some resistant Gram-positive strains of particular interest is that these systems possess amenable molecular weight, rotatable bonds and number of proton-donors/acceptors for drug design as well as less lipophilic character, with physicochemical properties and ionic states that are similar to current antibiotic agents for oral and injectable use. Unfortunately, the reduction of plasma protein affinity by the barbituric core is not sufficient to achieve activity in vivo. Further optimization to reduce plasma protein affinity and/or elevate antibiotic potency is therefore required, but we believe that these systems offer unusual opportunities for antibiotic drug discovery.

Yong-Chul Jeong

2015-02-01

218

Antibacterial barbituric Acid analogues inspired from natural 3-acyltetramic acids; synthesis, tautomerism and structure and physicochemical property-antibacterial activity relationships.  

Science.gov (United States)

The synthesis, tautomerism and antibacterial activity of novel barbiturates is reported. In particular, 3-acyl and 3-carboxamidobarbiturates exhibited antibacterial activity, against susceptible and some resistant Gram-positive strains of particular interest is that these systems possess amenable molecular weight, rotatable bonds and number of proton-donors/acceptors for drug design as well as less lipophilic character, with physicochemical properties and ionic states that are similar to current antibiotic agents for oral and injectable use. Unfortunately, the reduction of plasma protein affinity by the barbituric core is not sufficient to achieve activity in vivo. Further optimization to reduce plasma protein affinity and/or elevate antibiotic potency is therefore required, but we believe that these systems offer unusual opportunities for antibiotic drug discovery. PMID:25710842

Jeong, Yong-Chul; Moloney, Mark G

2015-01-01

219

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

220

Mixture designs to assess composition-structure-property relationships in SiO?-CaO-ZnO-La?O?-TiO?-MgO-SrO-Na?O glasses: potential materials for embolization.  

Science.gov (United States)

Embolization with micron-sized particulates is widely applied to treat uterine fibroids. The objective of this work was to develop mixture designs to predict materials composition-structure-property relationships for the SiO?-CaO-ZnO-La?O?-TiO?-MgO-SrO-Na?O glass system and compare its fundamental materials properties (density and cytocompatibility), against a state-of-the-art embolic agent (contour polyvinyl alcohol) to assess the potential of these materials for embolization therapies. The glass structures were evaluated using ²?Si MAS NMR to identify chemical shift and line width; the particulate densities were determined using helium pycnometry and the cell viabilities were assessed via MTT assay. ²?Si MAS NMR results indicated peak maxima for each glass in the range of -82.3?ppm to -89.9?ppm; associated with Q² to Q³ units in silicate glasses. All experimental embolic compositions showed enhanced in vitro compatibility in comparison to Contour PVA with the exceptions of ORP9 and ORP11 (containing no TiO?). In this study, optimal compositions for cell viability were obtained for the following compositional ranges: 0.095-0.188?mole fraction ZnO; 0.068-0.159?mole fraction La?O?; 0.545-0.562?mole fraction SiO? and 0.042-0.050?mole fraction TiO?. To ensure ease of producibility in obtaining good melts, a maximum loading of 0.068?mole fraction La?O? is required. This is confirmed by the desirability approach, for which the only experimental composition (ORP5) of the materials evaluated was presented as an optimum composition; combining high cell viability with ease of production (0.188?mole fraction ZnO; 0.068?mole fraction La?O?; 0.562?mole fraction SiO? and 0.042?mole fraction TiO?). PMID:22863846

Kehoe, Sharon; Langman, Maxine; Werner-Zwanziger, Ulli; Abraham, Robert J; Boyd, Daniel

2013-09-01

221

Thermotropic liquid crystals based on extended 2,5-disubstituted-1,3,4-oxadiazoles: structure-property relationships, variable-temperature powder X-ray diffraction, and small-angle X-ray scattering studies.  

Science.gov (United States)

A class of extended 2,5-disubstituted-1,3,4-oxadiazoles R1-C6H4-{OC2N2}-C6H4-R2 (R1 = R2 = C10H21O 1 a, p-C10H21O-C6H4-C[triple bond]C 3 a, p-CH3O-C6H4-C[triple bond]C 3 b; R1 = C10H21O, R2 = CH3O 1 b, (CH3)2N 1 c; F 1 d; R1 = C10H21O-C6H4-C[triple bond]C, R2 = C10H21O 2 a, CH3O 2 b, (CH3)2N 2 c, F 2 d) were prepared, and their liquid-crystalline properties were examined. In CH2Cl2 solution, these compounds displayed a room-temperature emission with lambda(max) at 340-471 nm and quantum yields of 0.73-0.97. Compounds 1 d, 2 a-2 d, and 3 a exhibited various thermotropic mesophases (monotropic, enantiotropic nematic/smectic), which were examined by polarized-light optical microscopy and differential scanning calorimetry. Structure determination by a direct-space approach using simulated annealing or parallel tempering of the powder X-ray diffraction data revealed distinctive crystal-packing arrangements for mesogenic molecules 2 b and 3 a, leading to different nematic mesophase behavior, with 2 b being monotropic and 3 a enantiotropic in the narrow temperature range of 200-210 degrees C. The structural transitions associated with these crystalline solids and their mesophases were studied by variable-temperature X-ray diffractometry. Nondestructive phase transitions (crystal-to-crystal, crystal-to-mesophase, mesophase-to-liquid) were observed in the diffractograms of 1 b, 1 d, 2 b, 2 d, and 3 a measured at 25-200 degrees C. Powder X-ray diffraction and small-angle X-ray scattering data revealed that the structure of the annealed solid residue 2 b reverted to its original crystal/molecular packing when the isotropic liquid was cooled to room temperature. Structure-property relationships within these mesomorphic solids are discussed in the context of their molecular structures and intermolecular interactions. PMID:17441124

Han, Jie; Chui, Stephen Sin-Yin; Che, Chi-Ming

2006-12-18

222

Semiconducting material property relationships: trends and their impact on design of radiation detection materials  

Science.gov (United States)

Materials properties important to the design and performance of semiconducting gamma detectors, such as band gap, density, mobility, and crystal cell anisotropy, can depend on similar underlying physics. The resulting property correlations limit the number of design variable and the place effective bounds on the range of physical properties available to gamma-detection materials However, trend correlations can also limit the dependence of error in structure-property relationships and information gaps when considering new candidate materials. Trend analysis complements property estimation via data regression techniques, increasing the generality and certainty of information-based conclusions.

Ferris, Kim F.; Webb-Robertson, Bobbie-Jo M.; Jones, Dumont M.

2009-08-01

223

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

224

Structure-interfacial properties relationship and quantification of the amphiphilicity of well-defined ionic and non-ionic surfactants using the PIT-slope method.  

Science.gov (United States)

The Phase Inversion Temperature of a reference C10E4/n-Octane/Water system exhibits a quasi-linear variation versus the mole fraction of a second surfactant S2 added in the mixture. This variation was recently proposed as a classification tool to quantify the Hydrophilic-Lipophilic Balance (HLB) of commercial surfactants. The feasibility of the so-called PIT-slope method for a wide range of well-defined non-ionic and ionic surfactants is investigated. The comparison of various surfactants having the same dodecyl chain tail allows to rank the polar head hydrophilicity as: SO3Na?SO4Na?NMe3Br>E2SO3Na?CO2Na?E1SO3Na?PhSO3Na>IsosorbideexoSO4Na?IsosorbideendoSO4Na?E8?NMe2O>E7>E6?Glucosyl>E5?Diglyceryl?E4>E3>E2?Isosorbideexo>Glyceryl>Isosorbideendo. The influence on the surfactant HLB of other structural parameters, i.e. hydrophobic chain length, unsaturation, replacement of Na(+) by K(+) counterion, and isomerism is also investigated. Finally, the method is successfully used to predict the optimal formulation of a new bio-based surfactant, 1-O-dodecyldiglycerol, when performing an oil scan at 25°C. PMID:25744856

Ontiveros, Jesús F; Pierlot, Christel; Catté, Marianne; Molinier, Valérie; Salager, Jean-Louis; Aubry, Jean-Marie

2015-06-15

225

Structure-property relationships in the crystals of the smallest amino acid: an incoherent inelastic neutron scattering study of the glycine polymorphs.  

Science.gov (United States)

Incoherent inelastic neutron scattering spectra for the three crystalline polymorphs (alpha- P2(1)/n, beta- P2(1), gamma- P3(1)) of glycine (C2H5NO2) at temperatures between 5 and 300 K (using the time-of-flight (ToF) spectrometer NEAT at HMI) and at pressures from ambient up to 1 GPa (using the ToF spectrometer IN6 at the ILL) were measured. Significant differences in the band positions and their relative intensities in the density of states (DoS) were observed for the three polymorphs, which can be related to the different intermolecular interactions. The mean-squared displacement, (T), dependence reveals a change in dynamic properties at about the same temperature (150 K) for all the three forms, which can be related to the reorientation of the NH3 group. Besides, a dynamic transition in beta-glycine at about 230-250 K on cooling was also observed, supporting previously obtained adiabatic calorimetry data. This behavior is similar to that already observed in amorphous solids, on approaching the glass transition temperatures, as well as in biological systems. It suggests the onset of degrees of freedom most likely related to transitions between slightly different conformational orientations. The DoS obtained as a function of pressure has confirmed the stability of the alpha-form with respect to pressure and also depicted a sign of the previously reported reversible beta-beta' glycine phase transition in between 0.6 and 0.8 GPa. Moreover, a remarkable kinetic effect in the pressure-induced phase transition in gamma-glycine was revealed. After the sample was kept at 0.8 GPa for an hour in the neutron beam, an irreversible transition into a high-pressure form (different from the beta'-form) occurred, although previously in X-Ray diffraction and Raman spectroscopy experiments a gamma- to delta-glycine phase transition was observed above 3.5 GPa only. PMID:18578525

Bordallo, Heloisa N; Boldyreva, Elena V; Buchsteiner, Alexandra; Koza, Michael Marek; Landsgesell, Sven

2008-07-24

226

Semiconductor alloys - Structural property engineering  

Science.gov (United States)

Semiconductor alloys have been used for years to tune band gaps and average bond lengths to specific applications. Other selection criteria for alloy composition, and a growth technique designed to modify their structural properties, are presently considered. The alloys Zn(1-y)Cd(y)Te and CdSe(y)Te(1-y) are treated as examples.

Sher, A.; Van Schilfgaarde, M.; Berding, M.; Chen, A.-B.

1987-01-01

227

Structure-function relationships in calpains.  

Science.gov (United States)

Calpains are a family of complex multi-domain intracellular enzymes that share a calcium-dependent cysteine protease core. These are not degradative enzymes, but instead carry out limited cleavage of target proteins in response to calcium signalling. Selective cutting of cytoskeletal proteins to facilitate cell migration is one such function. The two most abundant and extensively studied members of this family in mammals, calpains 1 and 2, are heterodimers of an isoform-specific 80 kDa large subunit and a common 28 kDa small subunit. Structures of calpain-2, both Ca2+-free and bound to calpastatin in the activated Ca2+-bound state, have provided a wealth of information about the enzyme's structure-function relationships and activation. The main association between the subunits is the pairing of their C-terminal penta-EF-hand domains through extensive intimate hydrophobic contacts. A lesser contact is made between the N-terminal anchor helix of the large subunit and the penta-EF-hand domain of the small subunit. Up to ten Ca2+ ions are co-operatively bound during activation. The anchor helix is released and individual domains change their positions relative to each other to properly align the active site. Because calpains 1 and 2 require ~30 and ~350 ?M Ca2+ ions for half-maximal activation respectively, it has long been argued that autoproteolysis, subunit dissociation, post-translational modifications or auxiliary proteins are needed to activate the enzymes in the cell, where Ca2+ levels are in the nanomolar range. In the absence of robust support for these mechanisms, it is possible that under normal conditions calpains are transiently activated by high Ca2+ concentrations in the microenvironment of a Ca2+ influx, and then return to an inactive state ready for reactivation. PMID:23035980

Campbell, Robert L; Davies, Peter L

2012-11-01

228

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

229

Magnetic properties of nanotube structures  

International Nuclear Information System (INIS)

With the discovery of carbon nanotube structures, a new class of materials with a reduced dimensionality has been introduced. Among various forms of carbon nanotubes, the single-walled nanotube has attracted much attention because of its unique structural and electrical properties. In this work, we have considered nanotube models of armchair (2,2) and zigzag (4,0) with one ? orbital per atom. We have studied the magnetic thermodynamic properties of these models using a single Hubbard model at half-filling. In these calculations we have used the grand canonical quantum Monte Carlo method. Our results show the temperature and field dependence of the magnetic susceptibility, subtracting the diamagnetic contribution, of the considered nanotube models in very good qualitative agreement with the experimental data for a mixture of nanotubes of different diameters

230

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

231

Grain boundary structure and properties  

International Nuclear Information System (INIS)

An attempt is made to distinguish those fundamental aspects of grain boundaries which should be relevant to the problem of the time dependent fracture of high temperature structural materials. These include the basic phenomena which are thought to be associated with cavitation and cracking at grain boundaries during service and with the more general microstructural changes which occur during both processing and service. A very brief discussion of the current state of our knowledge of these fundamentals is given. Included are the following: (1) structure of ideal perfect boundaries; (2) defect structure of grain boundaries; (3) diffusion at grain boundaries; (4) grain boundaries as sources/sinks for point defects; (5) grain boundary migration; (6) dislocation phenomena at grain boundaries; (7) atomic bonding and cohesion at grain boundaries; (8) non-equilibrium properties of grain boundaries; and (9) techniques for studying grain boundaries

232

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

233

Asymptotic Properties of Parameters for Linear Circular Functional Relationship Model  

Directory of Open Access Journals (Sweden)

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

A.G. Hussin

2008-01-01

234

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

235

Structure-Biodegradation Relationship Study of Commercial Linear Alkylbenzene Sulfonates  

OpenAIRE

Biodegradation (metabolism by microorganisms) is one of the most important processes determining the fate of organic chemicals in the environment. Structure-biodegradation relationships for linear alkylbenzene sulfonates (LAS) can be used to interpret the mechanism of LAS biodegradation and predict biodegradation rates by using theoretical descriptors computed from the chemical structure. Relationships between the electronic structure and biodegradability of commercial LAS are investigated by...

Li Li; Xiao Yi Zhang; Zheng Wu Wang; Gan Zuo Li

2003-01-01

236

[Structure and properties of pectin].  

Science.gov (United States)

Pectin represents a very complex, heterogeneous family of plant cell wall polysaccharides that play a significant role in plant growth, morphology, development, and plant defense and also serves as a gelling and stabilizing polymer in diverse food and specialty products and has positive effects on human health. In this review functional and structural characteristic of pectin molecule elements and their interconnections are described. Attention is also given to process of commercial production of pectin with special emphasis on composition and physical properties of commercial pectin as a result of the acid extraction. PMID:23821947

Wikiera, Agnieszka; Mika, Magdalena

2013-01-01

237

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)

238

Structure-activity relationship of cyanine tau aggregation inhibitors.  

Science.gov (United States)

A structure-activity relationship for symmetrical cyanine inhibitors of human tau aggregation was elaborated using a filter trap assay. Antagonist activity depended on cyanine heterocycle, polymethine bridge length, and the nature of meso- and N-substituents. One potent member of the series, 3,3'-diethyl-9-methylthiacarbocyanine iodide (compound 11), retained submicromolar potency and had calculated physical properties consistent with blood-brain barrier and cell membrane penetration. Exposure of organotypic slices prepared from JNPL3 transgenic mice (which express human tau harboring the aggregation prone P301L tauopathy mutation) to compound 11 for one week revealed a biphasic dose response relationship. Low nanomolar concentrations decreased insoluble tau aggregates to half those observed in slices treated with vehicle alone. In contrast, high concentrations (> or =300 nM) augmented tau aggregation and produced abnormalities in tissue tubulin levels. These data suggest that certain symmetrical carbocyanine dyes can modulate tau aggregation in the slice biological model at concentrations well below those associated with toxicity. PMID:19432420

Chang, Edward; Congdon, Erin E; Honson, Nicolette S; Duff, Karen E; Kuret, Jeff

2009-06-11

239

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

240

[Taxoids: structural and experimental properties].  

Science.gov (United States)

Paclitaxel (Taxol) and docetaxel (Taxotere) are the first representatives of a new class of antitumor compounds. These two taxoids are clinically active against breast, ovarian and lung cancers. Taxoids are highly complex diterpenoids form natural origin. Preclinical and clinical developments have been made possible after a long and sustained chemical effort: paclitaxel is extracted from the barks of the Pacific yew tree Taxus brevifolia whereas docetaxel is prepared by hemisynthesis starting from 10-deacetyl-baccatin III, an inactive precursor found in the needles of the European yew tree Taxus baccata. These two drugs are active in various in vitro and in vivo preclinical models (cell lines, cloning of human tumor stem cells, murine grafted tumors, human xenografts). Taxoids constitute a new class of antimitotic agents different from vinca-alkaloids: on the one hand, paclitaxel and docetaxel can be considered as inhibitors of the reaction of depolymerization of microtubules into tubulin; on the other hand, vinca-alkaloids inhibit reaction of polymerization of tubulin into microtubules. An active program of medicine chemistry is done in various pharmaceutical and academic Institutions with two objectives: knowledge of structure-activity relationships and selection of new candidates for clinical trials. PMID:10846536

Lavelle, F; Combeau, C; Commerçon, A

1995-04-01

241

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

Science.gov (United States)

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

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

242

Blends based on poly(lactic acid) : structure/rheology/processing relationship  

OpenAIRE

The ultimate aim of the present thesis focuses on the structure/processing/properties relationship of the PLA/PBAT materials. The latters are intended for food packaging in order to replace poly (ethylene terephthalate (PET). However, PLA has a limited processability in conventional technologies of plastics industry. The strengthening of its melt properties has been achieved through the incorporation of a multifunctional epoxide, able to react with the end chains of polyesters. Furthermore, P...

Al-itry, Racha

2012-01-01

243

Microstructural-electrical property relationships in high-conductivity zirconias  

International Nuclear Information System (INIS)

The relationship between electrical properties and microstructure has been examined for calcia and calcia + magnesia partially stabilized zirconia as a function of thermal history at a typical two-phase aging temperature and for yttria fully stabilized zirconia as a function of small additions of SiO2 and Al2O3. The evolution of the experimental complex resistivity plots has been correlated with grain-interior and grain-boundary microstructures as determined by optical, scanning, and transmission electron microscopy (at 100 and 1000 kV potentials), X-ray diffraction, and X-ray microanalysis

244

Relationships Between Magnetic Properties and Weathering Indices of Basaltic Rocks  

Science.gov (United States)

Performance of geophysical sensors is often hampered by soils and regolith with significant levels of magnetic susceptibility and viscosity, primarily dependent on the amount and form of ferrimagnetic iron oxide minerals present. In order to develop predictive models for the occurrence of such conditions, it is crucial to understand how the magnetic signal evolves during weathering from fresh rock to soil material. Rock weathering leads to destruction of primary minerals, formation of secondary minerals, and concomitant changes in magnetic properties and major-, minor-, and trace-element geochemistry. Previous work has examined relationships between magnetic properties (e.g., magnetic susceptibility) and single-element proxies for overall sample weathering state. In this contribution we study the relationships between bulk geochemical and magnetic characteristics of weathered basaltic rock, and regolith and soils with basaltic parent material. Four samples collected from a corestone formed by spheroidal weathering on the Kohala Peninsula on the Big Island of Hawaii represent the earliest stages of weathering; a series of samples from regolith to the B-horizon for a soil on Kaho'olawe Island represent later weathering stages. Our analysis includes X-Ray Fluorescence Spectroscopy of whole-sample geochemistry and magnetic measurements for a range of temperatures and frequencies. The extent of chemical weathering is assessed by use of a number of common (but Fe-free) major-element weathering indices. Progressive spheroidal weathering involves centripetal migration of a weathering front from joints and fractures into the interior of the joint blocks. As the weathering front passes through a volume of material, fresh or slightly weathered rock is transformed to a primary-mineral-depleted, clay-rich shell. The exfoliated shells farthest from the corestone were the first weathered; shells successively closer to the corestone were more recently transformed. In the Kohala corestone-shell complex, some chemical-weathering indices vary monotonically with total Fe (as Fe2O3), whereas other chemical-weathering indices vary monotonically with magnetic susceptibility. Thus, some Fe-free major-element chemical-weathering indices seem to scale more systematically with soil magnetic properties than others. For more strongly weathered soils from Kaho'olawe, there is a weak relationship between magnetic properties and total Fe. We hope that through the use of Fe-free major-element weathering indices an improved relationship can be developed. Such an improved correlation would benefit phenomenological understanding of geophysical sensor performance in areas with basaltic substrate.

van Dam, R. L.; Velbel, M. A.

2009-05-01

245

A Fast Retrieving Algorithm of Hierarchical Relationships Using Trie Structures.  

Science.gov (United States)

Presents a faster method for determining hierarchical relationships in information retrieval by using trie structures instead of a linear storage of a concept code. Highlights include case structures, a knowledge representation for natural-language understanding with semantic constraints; a compression algorithm of tries; and evaluation.…

Koyama, Masafumi; Morita, Kazuhiro; Fuketa, Masao; Aoe, Jun-Ichi

1998-01-01

246

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

247

Surface magnetic properties of ferromagnetic nickel thin films and multilayer structures  

OpenAIRE

Devices based on magnetic multilayer structures are widely used in the magnetic storage industry. The interfacial magnetic behaviour in these and related structures determines their spin-dependent electron transport properties. This thesis addresses the effects of the surface quality and magnetic properties of Ni thin films and multilayer structures to understand the relationship between the microscopic physical and magnetic structure and macroscopic transport properties. The effects of surfa...

Xu, Tianhong

2008-01-01

248

The Structure, Functions, and Mechanical Properties of Keratin  

Science.gov (United States)

Keratin is one of the most important structural proteins in nature and is widely found in the integument in vertebrates. It is classified into two types: ?-helices and ?-pleated sheets. Keratinized materials can be considered as fiber-reinforced composites consisting of crystalline intermediate filaments embedded in an amorphous protein matrix. They have a wide variety of morphologies and properties depending on different functions. Here, we review selected keratin-based materials, such as skin, hair, wool, quill, horn, hoof, feather, and beak, focusing on the structure-mechanical property-function relationships and finally give some insights on bioinspired composite design based on keratinized materials.

McKittrick, J.; Chen, P.-Y.; Bodde, S. G.; Yang, W.; Novitskaya, E. E.; Meyers, M. A.

2012-04-01

249

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

250

Structural and electronic properties of atomic chains  

International Nuclear Information System (INIS)

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

251

Pseudopotential calculations of structural properties of solids  

International Nuclear Information System (INIS)

Through the development of a total energy pseudopotential approach, it has become possible to compute structural, electronic, and vibrational properties of solids using only the atomic numbers and atomic masses of the constituent atoms as input. The method has been applied to semiconductors, insulators, and metals; and agreement with experiment for most properties is usually within a few percent. Applications include the determination of lattice constants for specific structural phases, properties of structural phase transitions, cohesive energies, bulk moduli, lattice vibrational spectra, electron-lattice interaction parameters, and electronic and superconducting properties. A recent example is the prediction of superconductivity in highly condensed hexagonal silicon which was subsequently found experimentally

252

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)

253

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

254

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

255

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

Science.gov (United States)

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

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

2014-05-01

256

Properties of meson structure function  

International Nuclear Information System (INIS)

Meson structure functions have been extracted from high transverse momentum pion production by various hadron beams. The agreement with structure functions obtained by leptonic probes is amazingly good. The scaling violations in the pion structure function are extracted, and are consistent with those expected from asymptotic freedom. No indication of higher twist power law corrections is found

257

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

258

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

International Nuclear Information System (INIS)

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

259

The Relationship between Financial Flexibility and Capital Structure Decisions  

OpenAIRE

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 pe...

Shanaz Forozan; Roya Darabi; Salah Mohamadi; Ahmad GHasemi

2013-01-01

260

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

261

Visualization of protein structure relationships using constrained twin kernel embedding  

OpenAIRE

In this paper, a recently proposed dimensional-ity reduction method called Twin Kernel Em-bedding (TKE) [10] is applied in 2-dimensional visualization of protein structure relationships. By matching the similarity measures of the input and the embedding spaces expressed by their respective kernels, TKE ensures that both local and global proximity information are preserved simultaneously. Experiments conducted on a subset of the Structural Classification Of Pro-tein (SCOP) database confirmed t...

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

2008-01-01

262

Synthesis and initial structure--activity relationships of modified salicylihalamides.  

Science.gov (United States)

[reaction:see text] The first stereoselective total synthesis of the potent antitumor compound (-)-salicylihalamide A is presented. The practicality of our approach provides for high material throughput and is highlighted by the rapid construction of a variety of modified congeners. Initial structure-activity relationships are derived from growth inhibition experiments with a human melanoma cancer cell line. PMID:11150209

Wu, Y; Seguil, O R; De Brabander, J K

2000-12-28

263

Fluency, Text Structure, and Retelling: A Complex Relationship  

Science.gov (United States)

This study examined the relationship between fluency and comprehension, specifically related to the text structures of narration and dialogue. Using descriptive statistics, this investigation first examined fluency and comprehension of three teacher educators and then through action research examined fluency and comprehension of five third grade…

Cohen, Lynn; Krustedt, Rosanne L.; May, Maria

2009-01-01

264

Structural relaxation: low temperature properties  

International Nuclear Information System (INIS)

We discuss the changes in transport and superconducting properties of amorphous Zr70Cu30, induced by thermal relaxation. The experimental results are used to investigate the relation between the microscopic parameters and the observed physical properties. It is shown that the density of eletronic states determines the shift Tc as well as the variation of the electrical resistivity. It is necessary to assume strong hybridization between s and d bands to understand the eletrodynamic response of the superconductor. (Author)

265

Mechanical properties relationships in V- and Ti-microalloyed steels  

Energy Technology Data Exchange (ETDEWEB)

Microalloyed steels are characterised by their mechanical properties. Nowadays, they are used in a wide range of applications. The convenience and simplicity of hardness tests permit to obtain economically and rapidly information on the structure of steels and control their treatments. This study has been carried out to derive equations for prediction of the mechanical properties of microalloyed steels by hardness measurement. With this objective, V- and Ti-microalloyed plain carbon steel bars were melted, hot rolled, heat treated and machined for the measurement of their mechanical properties and to reach a correlation between both ultimate tensile strength, yield strength and uniform elongation and Vickers hardness. The obtained data were treated using different mathematical fittings. They are mathematically treated as groups according to the heat treatment processes and as one group. The derived equations show good agreement with each other and with most of the little relations found in the literature. General equations for deducing mechanical properties values from the easily measured Vickers hardness values were derived. The equations derived from one group without regarding the treatment processes are more reliable. (orig.)

Eissa, M.; Mattar, T. [Steel and Ferroalloys Dept., Central Metallurgical Research and Development Inst. (CMRDI), Cairo (Egypt)

2002-09-01

266

Structural properties of semenogelin I.  

OpenAIRE

The zinc-binding protein semenogelin I is the major structural component of the gelatinous coagulum that is formed in freshly ejaculated semen. Semenogelin I is a rapidly evolving protein with a primary structure that consists of six repetitive units, each comprising approximately 60 amino acid residues. We studied the secondary and tertiary structure of semenogelin I by circular dichroism (CD) spectroscopy and Trp fluorescence emission spectroscopy. Fitting to the far-UV CD data indicated th...

Malm, Johan; Jonsson, Magnus; Frohm, Birgitta; Linse, Sara

2007-01-01

267

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

268

Structure-property correlations and microstructural design  

International Nuclear Information System (INIS)

Microstructures play an important role in alloy design. It is possible to control the properties of engineering structural materials by controlling their internal microstructures. It is now an accepted fact that the properties of metals and alloys can be tailored based on the knowledge of structure-property correlations. These studies are gaining importance in the design of alloys and in life prediction applications. The best combination of properties of alloys can be tailored during alloy design, based on economics, experience, knowledge and serendipity. Four different commercially available alloy systems used in nuclear industry are studied in this paper. (author). 23 refs., 6 figs., 4 tabs

269

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.

270

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

271

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)

272

Silicon nanowires: structure and properties  

International Nuclear Information System (INIS)

An attempt to grow silicon nanowires has been made by electron beam evaporation on highly oriented pyrolytic substrate. Needle-like objects are located along the normal to a substrate (density 2 x 1011 cm-2). For modeling quasi-one-dimensional objects calculations of nuclear structure and energy spectra have been accomplished. A fullerene-like structure Si24 is proposed as a basic atomic configuration of silicon nanowires

273

Nitridonickelates: Preparation, Structure and Properties  

OpenAIRE

Low valent nickel (less than +1) complexes are rare in nature, however they are regularly encountered in nitridonickelate chemistry. Ternary alkaline earth nitridonickelates exhibit a variety of interesting crystal structures with respect to their covalently bonded nitridonickelate anionic framework. The coordination geometry of low valent nickel in these compounds presents a unique structural feature with nickel being in linear coordination by nitrogen atoms. The nitridonickelate frameworks ...

Mehta, Akash

2005-01-01

274

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

275

Material properties of trabecular bone structures.  

Science.gov (United States)

The transplantation of human allograft for restoration and filling of cortical bone defects is well known. Our aim was an experimental investigation of the mechanical stability of the often used femoral head spongiosa depending on the caliber and extent of the allograft. To evaluate the orientation of the trabecular structures of the femoral head and relate this data to its mechanical properties, morphometric studies were combined with mechanical tests of cancellous bone specimens. The mechanical examination of the allograft was done following the compression test according to DIN 50106. We examined 36 human unfixed hip joint spongiosa cylinders with a height of 11 mm and a diameter of 24 mm. We took three specimens from each femoral head. We compressed the allograft at a constant velocity of 0.017 mm/sec. We calculated the maximum compression strength, the yield point and the Young's modulus. We also examined 12 parallelepipedic specimens with (17 x 17 x 51 mm) for morphometric analysis and loading in the direction of the primary compressive group (PCG), as well as perpendicular loading and at an angle of 45 degrees. We found divergent mechanical stabilities. None of the femoral heads showed comparable compressive strength. There was no position dependency of the strength of the samples. No relation between optical appearance and strength was found. We found a value for the lower compressive strength, which can be used for calculation as a basic value for safe constructions. Furthermore we tested the well known dependence of strength on the direction of the trabecular structure. We found a strong relationship between strength and load direction on the preferred direction of the trabecular structure. The sole recommendation resulting from our investigations is to rely on the lowest compressive strength for all preoperative planning. Relying on higher compressive strength by using the theoretical predicted areas of higher strength is hazardous since we found no correlation between position of sampling and strength. The size of our samples is important, because of the fact that different sizes of the samples might cause different failure mechanisms in the samples. The preparation of the femoral head spongiosa should be done according to the primary compressive group of the trabecular structure. PMID:11963622

Birnbaum, K; Sindelar, R; Gaertner, J R; Wirtz, D C

2001-01-01

276

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.

277

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

278

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

279

Relationships between molecular properties and antimycobacterial activities of steroids.  

Science.gov (United States)

Progesterone (1), cholesterol (2), stigmasterol (3), ergosterol endoperoxide (4), sitosterol (5), betulin (6), fusidic acid (7), chondrilasterol (8), and ergosterol (9) have been evaluated against Mycobacterium tuberculosis H37Rv. The maximum antimycobacterial activity seemed to depend on hydrophobicity and the type of substituents on the phytyl moiety on steroidal backbone. The variation in activity was rationalized using quantitative structure-activity relationship (QSAR) models based on several molecular descriptors including van der Waals surface area (VDW(A)), van der Waals volume (VDW(v)), polarizability, dipole moment, logP, and the differences between the Highest Occupied Molecular Orbital and the Lowest Unoccupied Molecular Orbital (HOMO-LUMO gap). The proposed QSAR models could be developed to predict the antimycobacterial activity of structurally similar steroids and to create a priority list for testing so that time, money, and effort can be focused on the potentially most promising steroids. The implications of QSAR data for the rational design of new antituberculosis agents are discussed. Because mycobacteria degrade steroids to progesterone-type compounds, unambiguous assignments of the high-field proton (1H) and carbon-13 (13C) NMR data of progesterone (1) were achieved through a combination of modern one- and two-dimensional (2D) NMR techniques. PMID:11990426

Rugutt, Joseph K; Rugutt, Kipngeno J

2002-04-01

280

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

281

Structural properties of semenogelin I.  

Science.gov (United States)

The zinc-binding protein semenogelin I is the major structural component of the gelatinous coagulum that is formed in freshly ejaculated semen. Semenogelin I is a rapidly evolving protein with a primary structure that consists of six repetitive units, each comprising approximately 60 amino acid residues. We studied the secondary and tertiary structure of semenogelin I by circular dichroism (CD) spectroscopy and Trp fluorescence emission spectroscopy. Fitting to the far-UV CD data indicated that the molecule comprises 5-10% alpha-helix and 20-30% beta-sheet formations. The far-UV spectrum of semenogelin I is clearly temperature dependent in the studied range 5-90 degrees C, and the signal at 222 nm increased with increasing temperature. The presence of Zn(2+) did not change the secondary structure revealed by the far-UV CD spectrum, whereas it did alter the near-UV CD spectrum, which implies that rearrangements occurred on the tertiary structure level. The conformational change induced in semenogelin I by the binding of Zn(2+) may contribute to the ability of this protein to form a gel. PMID:17680810

Malm, Johan; Jonsson, Magnus; Frohm, Birgitta; Linse, Sara

2007-09-01

282

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

283

Unbalance Quantitative Structure Activity Relationship Problem Reduction in Drug Design  

OpenAIRE

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 introduc...

Pugazhenthi, D.; Rajagopalan, S. P.

2009-01-01

284

Lattice Path Matroids: Structural Properties  

OpenAIRE

This paper studies structural aspects of lattice path matroids, a class of transversal matroids that is closed under taking minors and duals. Among the basic topics treated are direct sums, duals, minors, circuits, and connected flats. One of the main results is a characterization of lattice path matroids in terms of fundamental flats, which are special connected flats from which one can recover the paths that define the matroid. We examine some aspects related to key topics...

Bonin, Joseph; Mier Vinue?, Anna

2004-01-01

285

Native Cellulose: Structure, Characterization and Thermal Properties  

OpenAIRE

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 a...

Matheus Poletto; Heitor L.; Zattera, Ademir J.

2014-01-01

286

Relationship between molecular cloud structure and density PDFs  

OpenAIRE

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

Stanchev, Orlin; Donkov, Sava; Veltchev, Todor V.; Shetty, Rahul

2013-01-01

287

Relationship between molecular cloud structure and density PDFs  

CERN Document Server

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

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

2013-01-01

288

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

International Nuclear Information System (INIS)

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

289

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.

290

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

OpenAIRE

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

Rudolf, Andreja; Sfiligoj-smole, Majda

2012-01-01

291

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

Directory of Open Access Journals (Sweden)

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

Haji A.

2013-09-01

292

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

293

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

294

Structure and properties of small sodium clusters  

DEFF Research Database (Denmark)

We have investigated the structure and properties of small metal clusters using all-electron ab initio theoretical methods based on the Hartree-Fock approximation, density functional theory, and perturbation theory and compared the results of our calculations with the available experimental data and the results of other theoretical work. We have systematically calculated the optimized geometries of neutral and singly charged sodium clusters having up to 20 atoms, their multipole moments (dipole and quadrupole), static polarizabilities, binding energies per atom, ionization potentials, and frequencies of normal vibration modes. Our calculations demonstrate the important role of many-electron correlations in the formation of the electronic and ionic structure of small metal clusters and form a good basis for further detailed study of their dynamic properties, as well as the structure and properties of other atomic cluster systems.

Solov'yov, Ilia; Solov'yov, Andrey V.

2002-01-01

295

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

296

Determination of structural alloy equilibrium properties from quantum approximate methods  

International Nuclear Information System (INIS)

In this paper we address basic issues, not investigated previously, concerning the relationship between ab initio methods and the Bozzolo-Ferrante-Smith (BFS) method for alloys, and its ability to model the process of alloy formation and reproduce structural alloy properties near and at equilibrium. Based on perturbation theory, the method requires single element parameters and their binary combinations, even for multicomponent systems. A direct comparison of BFS predictions of equilibrium alloy properties against ab initio results, and the handling and influence of the parameterization on the accuracy with which the method reproduces the process of alloy formation are presented. Besides establishing a range of validity for the method in reference to first-principles results, a simple algorithm for the determination of equilibrium properties of ordered alloy systems is introduced and illustrated with applications to binary and higher order systems, maximizing the flow of information carried in the first-principles-based parameters

297

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)

298

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

Science.gov (United States)

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

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

2011-06-01

299

Structure and physicochemical properties of irradiated ?-cellulose  

International Nuclear Information System (INIS)

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

300

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

301

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

302

Atomic Scale Structure-Chemistry Relationships at Oxide Catalyst Surfaces and Interfaces  

Science.gov (United States)

Oxide catalysts are integral to chemical production, fuel refining, and the removal of environmental pollutants. However, the atomic-scale phenomena which lead to the useful reactive properties of catalyst materials are not sufficiently understood. In this work, the tools of surface and interface science and electronic structure theory are applied to investigate the structure and chemical properties of catalytically active particles and ultrathin films supported on oxide single crystals. These studies focus on structure-property relationships in vanadium oxide, tungsten oxide, and mixed V-W oxides on the surfaces of alpha-Al2O3 and alpha-Fe2O 3 (0001)-oriented single crystal substrates, two materials with nearly identical crystal structures but drastically different chemical properties. In situ synchrotron X-ray standing wave (XSW) measurements are sensitive to changes in the atomic-scale geometry of single crystal model catalyst surfaces through chemical reaction cycles, while X-ray photoelectron spectroscopy (XPS) reveals corresponding chemical changes. Experimental results agree with theoretical calculations of surface structures, allowing for detailed electronic structure investigations and predictions of surface chemical phenomena. The surface configurations and oxidation states of V and W are found to depend on the coverage of each, and reversible structural shifts accompany chemical state changes through reduction-oxidation cycles. Substrate-dependent effects suggest how the choice of oxide support material may affect catalytic behavior. Additionally, the structure and chemistry of W deposited on alpha-Fe 2O3 nanopowders is studied using X-ray absorption fine structure (XAFS) measurements in an attempt to bridge single crystal surface studies with real catalysts. These investigations of catalytically active material surfaces can inform the rational design of new catalysts for more efficient and sustainable chemistry.

McBriarty, Martin E.

303

Relationship Between Mechanical Properties of Lead-Free Solders and Their Heat Treatment Parameters  

Science.gov (United States)

The research was undertaken to establish mechanical properties of as-cast and heat-treated Sn-Zn-based alloys of binary and ternary systems as candidates for lead (Pb)-free solder materials for high-temperature applications. The heat treatment of as-cast alloys was made under different combinations of processing parameters (168 h/50 °C, 42 h/80 °C, and 24 h/110 °C). The systematic study of structure-property relationships in Sn-Zn, Sn-Zn-Ag, and Sn-Zn-Cu alloys containing the same amount of Zn (4.5, 9, 13.5 wt.%) and 1 wt.% of either Ag or Cu was conducted to identify the effects of chemical composition and heat treatment processing parameters on the alloy microstructure and mechanical behavior. Structural characterization was made using optical microscopy and scanning electron microscopy techniques coupled with EDS analysis. Mechanical properties (initial Young's modulus E, ultimate tensile strength UTS, elastic limit R 0.05, yield point R 0.2, elongation A 5, and necking Z) were determined by means of static tensile tests. All the examined Sn-Zn-based alloys have attractive combination of mechanical characteristics, especially tensile strength, having values higher than that of common leaded solders and their substitutes of Pb-free SAC family. The results obtained demonstrate that the Sn-Zn-based alloys present competitive Pb-free solder candidates for high-temperature applications.

Klasik, A.; Sobczak, N.; Pietrzak, K.; Makowska, K.; Wojciechowski, A.; Kudyba, A.; Sienicki, E.

2012-05-01

304

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

305

Assessing adult attachment across different contexts: validation of the Portuguese version of the experiences in Close Relationships-Relationship Structures questionnaire.  

Science.gov (United States)

The Experiences in Close Relationships-Relationship Structures questionnaire (ECR-RS) is one of the most recent measures of adult attachment. This instrument provides a contextual assessment of attachment-related anxiety and avoidance by measuring these dimensions in various close relationships (mother, father, partner, friend). To further explore its psychometric properties and cross-cultural adequacy, this study presents the validation of the ECR-RS in a sample of Portuguese community individuals (N = 236). The Portuguese version showed adequate reliability and construct validity. The original 2-factor structure was confirmed through confirmatory factor analysis. The ECR-RS is a psychometrically robust measure of attachment, representing an important advance in the measurement of adult attachment. PMID:25175516

Moreira, Helena; Martins, Teresa; Gouveia, Maria João; Canavarro, Maria Cristina

2015-01-01

306

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

International Nuclear Information System (INIS)

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

307

Structural stability properties of Friedman cosmology  

International Nuclear Information System (INIS)

A dynamical system with Robertson-Walker symmetries and the equation of the state p = ?epsilon, O <= ? <= 1, considered both as a conservative and nonconservative system, is studied with respect to its structural properties. Different cases are shown and analyzed on the phase space (x = Rsup(D), ? = (dx/dt)). (author)

308

Bioactive glasses-structure and properties.  

Science.gov (United States)

Bioactive glasses were the first synthetic materials to show bonding to bone, and they are successfully used for bone regeneration. They can degrade in the body at a rate matching that of bone formation, and through a combination of apatite crystallization on their surface and ion release they stimulate bone cell proliferation, which results in the formation of new bone. Despite their excellent properties and although they have been in clinical use for nearly thirty years, their current range of clinical applications is still small. Latest research focuses on developing new compositions to address clinical needs, including glasses for treating osteoporosis, with antibacterial properties, or for the sintering of scaffolds with improved mechanical stability. This Review discusses how the glass structure controls the properties, and shows how a structure-based design may pave the way towards new bioactive glass implants for bone regeneration. PMID:25765017

Brauer, Delia S

2015-03-27

309

The structure?activity relationship in herbicidal monosubstituted sulfonylureas  

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-05-24

310

Exploring the sequence-structure relationship for amyloid peptides.  

Science.gov (United States)

Amyloid fibril formation is associated with misfolding diseases, as well as fulfilling a functional role. The cross-? molecular architecture has been reported in increasing numbers of amyloid-like fibrillar systems. The Waltz algorithm is able to predict ordered self-assembly of amyloidogenic peptides by taking into account the residue type and position. This algorithm has expanded the amyloid sequence space, and in the present study we characterize the structures of amyloid-like fibrils formed by three peptides identified by Waltz that form fibrils but not crystals. The structural challenge is met by combining electron microscopy, linear dichroism, CD and X-ray fibre diffraction. We propose structures that reveal a cross-? conformation with 'steric-zipper' features, giving insights into the role for side chains in peptide packing and stability within fibrils. The amenity of these peptides to structural characterization makes them compelling model systems to use for understanding the relationship between sequence, self-assembly, stability and structure of amyloid fibrils. PMID:23252554

Morris, Kyle L; Rodger, Alison; Hicks, Matthew R; Debulpaep, Maya; Schymkowitz, Joost; Rousseau, Frederic; Serpell, Louise C

2013-03-01

311

Function-structure relationships of acetylated pea starches  

OpenAIRE

Starches from cowpea and chickpea seeds were isolated and their properties were compared with those of commercial yellow pea starch. Pullulanase digestion released two distinct populations from their amylopectins, representing short (DP 6-50) and long (DP 50-80) side chains. The higher gelatinization temperature, the greater pasting peak viscosity and a slight difference in crystalline structure found for cowpea starch compared to chickpea and yellow pea starches correlated with the larger pr...

Huang, J.

2006-01-01

312

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

313

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.

314

Silicon heteroepitaxy: interface structure and physical properties  

Science.gov (United States)

The interfaces in strained-layer Si mGe n superlattice (SLs) characterized by X-ray diffraction, Raman scattering and scanning tunneling microscopy are shown to deviate from the idealized form assumed in most calculations on electronic and optical properties. Electron microscopic investigations reveal that along the interfaces there exist thin regions of ordered alloys. In Si-rich SLs, the structure of these regions is dominated by growth-induced rhombohedral RS2 order, whereas with increasing Ge-content the fraction of RS1 domains becomes larger. The RS1 structure is found to be reversible, while the RS2 structure is not. Theoretical models, taking into account either growth kinetics or ground state properties, cannot explain all of the observed features.

von Känel, H.; Müller, E.; Nissen, H.-U.; Bacsa, W.; Ospelt, M.; Mäder, K. A.; Stalder, R.; Baldereschi, A.

1991-05-01

315

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

DEFF Research Database (Denmark)

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

Donbaek, Dagmar Feddern; Elklit, Ask

2014-01-01

316

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-12-31

317

???????????????? 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

318

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

319

Definition and properties of ideal amorphous structures  

International Nuclear Information System (INIS)

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

320

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

Science.gov (United States)

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

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

1983-01-01

321

Structural properties of the self-conjugate SU(3) tensor operators  

International Nuclear Information System (INIS)

Denominator functions for the set of self-conjugate SU(3) tensor operators are explicitly obtained and shown to be uniquely related to SU(3) -invariant structural properties. This relationship becomes manifest through the appearance of zeroes of the denominator functions which thereby express the fundamental null space properties of SU(3) tensor operators. It is demonstrated that there exist characteristic denominator functions whose zeroes, in position and multiplicity, possess the interesting, and unexpected, property of forming SU(3) weight space patterns

322

Structural properties of warm dense matter  

International Nuclear Information System (INIS)

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

323

Electronic structure and properties of lanthanum  

Science.gov (United States)

The total energy and electronic structure of lanthanum have been calculated in the bcc, fcc, hcp and dhcp structures for pressures up to 50 GPa. The full potential linearized-augmented-planewave method was used with both the local-density and general-gradient approximations. The correct phase ordering has been found, with lattice parameters and bulk moduli in good agreement with experimental data. The GGA method shows excellent agreement overall while the LDA results show larger discrepancies. The calculated strain energies for the fcc and bcc structures demonstrate the respective stable and unstable configurations at ambient conditions. The calculated superconductivity properties under pressure for the fcc structure are also found to agree well with measurements. Both LDA and GGA, with minor differences, reproduce well the experimental results for Tc.

Nixon, Lane; Papaconstantopoulos, Dimitrios

2008-03-01

324

Characterization of ion-exchange membrane materials: properties vs structure.  

Science.gov (United States)

This review focuses on the preparation, structure and applications of ion-exchange membranes formed from various materials and exhibiting various functions (electrodialytic, perfluorinated sulphocation-exchange and novel laboratory-tested membranes). A number of experimental techniques for measuring electrotransport properties as well as the general procedure for membrane testing are also described. The review emphasizes the relationships between membrane structures, physical and chemical properties and mechanisms of electrochemical processes that occur in charged membrane materials. The water content in membranes is considered to be a key factor in the ion and water transfer and in polarization processes in electromembrane systems. We suggest the theoretical approach, which makes it possible to model and characterize the electrochemical properties of heterogeneous membranes using several transport-structural parameters. These parameters are extracted from the experimental dependences of specific electroconductivity and diffusion permeability on concentration. The review covers the most significant experimental and theoretical research on ion-exchange membranes that have been carried out in the Membrane Materials Laboratory of the Kuban State University. These results have been discussed at the conferences "Membrane Electrochemistry", Krasnodar, Russia for many years and were published mainly in Russian scientific sources. PMID:18394577

Berezina, N P; Kononenko, N A; Dyomina, O A; Gnusin, N P

2008-06-22

325

Structure and Frictional Properties of Colloid Gel  

Directory of Open Access Journals (Sweden)

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

Masayuki Tokita

2014-03-01

326

Thinking in Terms of Structure-Activity-Relationships (T-SAR): A Tool to Better Understand Nanofiltration Membranes  

OpenAIRE

A frontier to be conquered in the field of membrane technology is related to the very limited scientific base for the rational and task-specific design of membranes. This is especially true for nanofiltration membranes with properties that are based on several solute-membrane interaction mechanisms. “Thinking in terms of Structure-Activity-Relationships” (T-SAR) is a methodology which applies a systematic analysis of a chemical entity based on its structural formula. However, the analysis...

Stefan Stolte; Jorg Thöming; Ferna?ndez, Jose? F.; Bernd Jastorff; Reinhold Störmann

2011-01-01

327

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

328

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

329

Structure and properties of atomic nanoclusters  

CERN Document Server

Atomic clusters are the bridge between molecules and the bulk matter. Following two key experiments - the observation of electronic shells in metallic clusters and the discovery of the C60 fullerence - the field of atomic clusters has experienced a rapid growth, and is now considered a mature field. The electrons of the cluster are confined to a small volume, hence, quantum effects are manifested on many properties of the clusters. Another interesting feature is that the properties often change in a non-smooth way as the number of atoms in the cluster increases. This book provides an updated overview of the field, and presents a detailed description of the structure and electronic properties of different types of clusters: Van der Waals clusters, metallic clusters, clusters of ionic materials and network clusters. The assembling of clusters is also considered, since specially stable clusters are expected to play a role in the future design and synthesis of new materials.

Alonso, Julio A

2005-01-01

330

The amyloid : structure, properties and application  

OpenAIRE

Protein aggregation, leading to the formation and depositions of amyloids, is a cause for a number of diseases such as Alzheimer’s and Creutzfeld-Jacob’s disease, systemic amyloidoses, type II diabetes and others . More than 20 proteins are associated with protein misfolding diseases and even a larger number of proteins can self-assemble into amyloid in vitro. Relating structural and functional properties of amyloid is of particular interest, as this will lead to the identification of the...

Malisauskas, Mantas

2007-01-01

331

Structure and properties of copper after large strain deformation  

Energy Technology Data Exchange (ETDEWEB)

Structure and properties of Cu in dependence on strain (from {epsilon}{proportional_to} 0.9 to {epsilon}{proportional_to} 15) during multi-axial compression processing at room temperature was investigated. The evolution of dislocation structure, misorientation distribution and crystallite size were observed by using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipment with electron back scattered diffraction (EBSD) facility. The mechanical properties of yield strength (YS), ultimate tensile strength (UTS) and uniform elongation was performed on MTS QTest/10 machine equipped with digital image correlation method (DIC). The structure-flow stress relationship of multi-axial compression processing material at strains {epsilon}{proportional_to} 3.5 and {epsilon}{proportional_to} 5.5 is discussed. It is found that processing does not produce any drastic changes in deformation structure and the microstructural refinement is slow. These results indicate that dynamic recrystallization plays an important role during multi-axial compression process in this range of deformation (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Rodak, Kinga; Molak, Rafal M.; Pakiela, Zbigniew

2010-05-15

332

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

333

Structural and reliability analysis of quality of relationship index in cancer patients.  

Science.gov (United States)

Among psychosocial factors affecting emotional adjustment and quality of life, social support is one of the most important and widely studied in cancer patients, but little is known about the perception of support in specific significant relationships in patients with cancer. This study examined the psychometric properties of the Quality of Relationship Inventory (QRI) by evaluating its factor structure and its convergent and discriminant validity in a sample of cancer patients. A total of 388 patients completed the QRI. Convergent validity was evaluated by testing the correlations between the QRI subscales and measures of general social support, anxiety and depression symptoms. Discriminant validity was examined by testing group comparison. The QRI's longitudinal invariance across time was also tested. Principal axis factor analysis with promax rotation identified three factors accounting for 42.99% of variance: perceived social support, depth, and interpersonal conflict. Estimates of reliability with McDonald's ? coefficient were satisfactory for all the QRI subscales (? ranging from 0.75 - 0.85). Satisfaction from general social support was negatively correlated with the interpersonal conflict subscale and positively with the depth subscale. The interpersonal conflict and social support scales were correlated with depression and anxiety scores. We also found a relative stability of QRI subscales (measured 3 months after the first evaluation) and differences between partner status and gender groups. The Quality of Relationship Inventory is a valid tool for assessing the quality of social support in a particular relationship with cancer patients. PMID:23514252

Cousson-Gélie, Florence; de Chalvron, Stéphanie; Zozaya, Carole; Lafaye, Anaïs

2013-01-01

334

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

335

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

336

Volumes and surface areas: geometries and scaling relationships between coarse- grained and atomic structures.  

Science.gov (United States)

Computing volumes and surface areas of molecular structures is generally considered to be a solved problem, however, comparisons presented in this review show that different ways of computing surface areas and volumes can yield dramatically different values. Volumes and surface areas are the most basic geometric properties of structures, and estimating these becomes especially important for large scale simulations when individual components are being assembled in protein complexes or drugs being fitted into proteins. Good approximations of volumes and surfaces are derived from Delaunay tessellations, but these values can differ significantly from those from the rolling ball approach of Lee and Richards (3V webserver). The origin of these differences lies in the extended parts and the less well packed parts of the proteins, which are ignored in some approaches. Even though surface areas and volumes from the two approaches differ significantly, their correlations are high. Atomic models have been compared, and the poorly packed regions of proteins are found to be most different between the two approaches. The Delaunay complexes have been explored for both fully atomic and for coarse-grained representations of proteins based on only C(?) atoms. The scaling relationships between the fully atomic models and the coarse-grained model representations of proteins are reported, and the lines fit yield simple relationships for the surface areas and volumes as a function of the number of protein residues and the number of heavy atoms. Further, the atomic and coarse-grained values are strongly correlated and simple relationships are reported. PMID:23713774

Flatow, Daniel; Leelananda, Sumudu P; Skliros, Aris; Kloczkowski, Andrzej; Jernigan, Robert L

2014-01-01

337

Psychometric properties of an Italian version of the Experiences in Close Relationships-Revised (ECR-R) Scale.  

Science.gov (United States)

This study examined the psychometric properties of a newly translated Italian version of the Experiences in Close Relationships-Revised (ECR-R) Scale. The sample comprised 1,363 adults (906 women, 456 men, 1 unreported sex; ages 18-64 yr., M = 33.4, SD = 8.9; 84.4% reported being engaged in a romantic relationship, 9.4% declared being single), all living in Italy and speaking Italian as their first language. Exploratory and confirmatory factor analyses showed the expected bi-factorial (anxiety/avoidance) structure and a close correspondence between factors and scales. Test-retest and internal consistency reliabilities were adequate. Correlations with the Relationship Questionnaire, a categorical measure of attachment, and with the Dyadic Adjustment Scale were consistent with the theoretical relations among the constructs. The findings confirm the transcultural validity of the ECR-R. PMID:25074302

Busonera, Alessandra; Martini, Pietro San; Zavattini, Giulio Cesare; Santona, Alessandra

2014-06-01

338

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

International Nuclear Information System (INIS)

The paper describes structural property data for computer impact calculations of nuclear fuel shipping casks. Four kinds of material data, mild steel, stainless steel, lead and wood are compiled. These materials are main structural elements of shipping casks. Structural data such as, the coefficient of thermal expansion, the modulus of longitudinal elasticity, the modulus of transverse elasticity, the Poisson's ratio and stress and strain relationships, have been tabulated against temperature or strain rate. This volume 2 involve structural property data of mild steel. (author)

339

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

International Nuclear Information System (INIS)

The paper describes structural property data for computer impact calculations of nuclear fuel shipping casks. Four kinds of material data, mild steel, stainless steel, lead and wood are compiled. These materials are main structural elements of shipping casks. Structural data such as, the coefficient of thermal expansion, the modulus of longitudinal elasticity, the modulus of transverse elasticity, the Poisson's ratio and stress and strain relationships, have been tabulated against temperature or strain rate. This volume 3 involve structural property data of stainless steel. (author)

340

Correlation of stability/rheology relationship with coal: Properties and chemical additives  

Energy Technology Data Exchange (ETDEWEB)

Coal-water slurries have the potential of a near term replacement for fuel oil. In order to gain the fundamental understanding of the preparation and handling of coal-water slurries, experiments were performed to identify the relationship between the coal content of a given coal-water slurry and its physical and chemical properties. The objectives of this program were: Investigate the relationship between the chemical and physical properties of coal and the rheology of coal-water slurry Define procedures for evaluating and preparing coal water slurries for a particular coal candidate, based on the characteristic coal properties Develop improved methods of screening surfactants used in coal-water slurry preparation Perform experiments designed to investigate the effect of characteristic coal properties on slurry quality, by examining the effect of the individual coal properties on slurry quality Develop a statistical formulation to predict the coal content of a given coal water slurry content based on the coal characteristic properties.

Ohene, F.

1992-02-19

341

Developing structure-activity relationships for the prediction of hepatotoxicity.  

Science.gov (United States)

Drug-induced liver injury is a major issue of concern and has led to the withdrawal of a significant number of marketed drugs. An understanding of structure-activity relationships (SARs) of chemicals can make a significant contribution to the identification of potential toxic effects early in the drug development process and aid in avoiding such problems. This process can be supported by the use of existing toxicity data and mechanistic understanding of the biological processes for related compounds. In the published literature, this information is often spread across diverse sources and can be varied and unstructured in quality and content. The current work has explored whether it is feasible to collect and use such data for the development of new SARs for the hepatotoxicity endpoint and expand upon the limited information currently available in this area. Reviews of hepatotoxicity data were used to build a structure-searchable database, which was analyzed to identify chemical classes associated with an adverse effect on the liver. Searches of the published literature were then undertaken to identify additional supporting evidence, and the resulting information was incorporated into the database. This collated information was evaluated and used to determine the scope of the SARs for each class identified. Data for over 1266 chemicals were collected, and SARs for 38 classes were developed. The SARs have been implemented as structural alerts using Derek for Windows (DfW), a knowledge-based expert system, to allow clearly supported and transparent predictions. An evaluation exercise performed using a customized DfW version 10 knowledge base demonstrated an overall concordance of 56% and specificity and sensitivity values of 73% and 46%, respectively. The approach taken demonstrates that SARs for complex endpoints can be derived from the published data for use in the in silico toxicity assessment of new compounds. PMID:20553011

Greene, Nigel; Fisk, Lilia; Naven, Russell T; Note, Reine R; Patel, Mukesh L; Pelletier, Dennis J

2010-07-19

342

Structure–Function Relationships in Highly Modified Shoots of Cactaceae  

Science.gov (United States)

• Background and Aims Cacti are extremely diverse structurally and ecologically, and so modified as to be intimidating to many biologists. Yet all have the same organization as most dicots, none differs fundamentally from Arabidopsis or other model plants. This review explains cactus shoot structure, discusses relationships between structure, ecology, development and evolution, and indicates areas where research on cacti is necessary to test general theories of morphogenesis. • Scope Cactus leaves are diverse; all cacti have foliage leaves; many intermediate stages in evolutionary reduction of leaves are still present; floral shoots often have large, complex leaves whereas vegetative shoots have microscopic leaves. Spines are modified bud scales, some secrete sugar as extra-floral nectaries. Many cacti have juvenile/adult phases in which the flowering adult phase (a cephalium) differs greatly from the juvenile; in some, one side of a shoot becomes adult, all other sides continue to grow as the juvenile phase. Flowers are inverted: the exterior of a cactus ‘flower’ is a hollow vegetative shoot with internodes, nodes, leaves and spines, whereas floral organs occur inside, with petals physically above stamens. Many cacti have cortical bundles vascularizing the cortex, however broad it evolves to be, thus keeping surface tissues alive. Great width results in great weight of weak parenchymatous shoots, correlated with reduced branching. Reduced numbers of shoot apices is compensated by great increases in number of meristematic cells within individual SAMs. Ribs and tubercles allow shoots to swell without tearing during wet seasons. Shoot epidermis and cortex cells live and function for decades then convert to cork cambium. Many modifications permit water storage within cactus wood itself, adjacent to vessels. PMID:16820405

MAUSETH, JAMES D.

2006-01-01

343

The Experiences in Close Relationships--Relationship Structures Questionnaire: A Method for Assessing Attachment Orientations across Relationships  

Science.gov (United States)

Most research on adult attachment is based on the assumption that working models are relatively general and trait-like. Recent research, however, suggests that people develop attachment representations that are relationship-specific, leading people to hold distinct working models in different relationships. The authors report a measure, the…

Fraley, R. Chris; Heffernan, Marie E.; Vicary, Amanda M.; Brumbaugh, Claudia Chloe

2011-01-01

344

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

345

Study of relationships between aerosol and cloud properties over the Amazon Basin using remote sensing retreievals  

Science.gov (United States)

Aerosols and clouds can exert radiative effects over Earth's climate, and contribute to significant uncertainties in climatic models. Aerosols can alter the thermodynamic conditions of cloud formation, as well as other aspects such as cloud fraction, droplet effective radius, and cloud optical depth. Radiative forcing by aerosols is commonly separated into two parts: the direct forcing stands for absorption and scattering of solar radiation by the aerosol itself, while the indirect effect accounts for radiative impacts due to varying cloud properties under the presence of aerosols. Remote sensing by satellites can provide information about atmospheric properties over a given location, as well as measured physical quantities required to evaluate the effects of variations in its structure on a greater picture. Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument retrievals of aerosol and cloud properties over the Amazon Basin were used in this work to study the indirect aerosol effect over clouds. Retrieved aerosol and cloud properties were analyzed within a time range of eleven years (2000-2010) in 2 x 2 ° boxes centered over two Amazon Basin research sites, located in the cities of Manaus (2° 35' 39.85'' S 60° 12' 33.28'' W, a predominantly forrested site) and Porto Velho (8° 41' 11.90'' S 63° 52' 0.01'', highly deforested site). As examples of our findings, Figure 1 show the relationship between cloud fraction and aerosol optical depth (AOD) for the whole Amazon Basin, for dry, wet and transition seasons. It shows different trends at about AOD ~ 0.3, which hint at distinct patterns for the indirect radiative forcing over the Amazon depending on aerosol loading. These results will be used in a simulation algorithm to study the shortwave radiative transfer over the 2 sites in Amazonia to assess the aerosol indirect radiative forcing.

Frigeri, F. F.; Correia, A. L.

2012-12-01

346

Scientific habits of mind: A reform of structure and relationships  

Science.gov (United States)

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

Mooney, Linda Beth

347

Structure-activity relationships of the cycloalkyl ring of phencyclidine.  

Science.gov (United States)

In order to investigate the structural requirements for a cycloalkyl moiety in the potent hallucinogen 1-(1-phenylcyclohexyl)piperidine (PCP, 1), a series of structural analogues was synthesized in which the size of the cycloalkyl ring was varied from three carbons to eight carbons. Biological activities of these compounds were assessed in an in vitro assay (phencyclidine binding assay) and an in vivo assay (discriminative stimulus assay). As the cycloalkyl ring size decreased from that of cyclohexane (PCP), PCP-like activity declined in both assays, but as the cycloalkyl ring size became larger than cyclohexane, a sharp decline in PCP-like activity was observed in the in vivo assay, while activity in the in vitro assay was only slightly less than that of PCP. 1-(1-Phenylcyclooctyl)piperidine (8) had potent competitive binding properties in the in vitro binding assay but produced no observable PCP-like effects in the in vivo assay. The importance of the cycloalkyl ring in the structure of PCP was demonstrated by testing benzylpiperidine (2), which had almost no measurable activity in either assay. PMID:7310819

McQuinn, R L; Cone, E J; Shannon, H E; Su, T P

1981-12-01

348

Relationships between low temperature properties of asphalt binders  

OpenAIRE

Cracking in asphalt mixes is highly influenced by binder properties. Current specifications for low temperature cracking resistance are based on empirical tests or tests involving linear viscoelasticity. Although these standard characteristics may work for conventional binders, they cannot be applied on all asphalts. Using the three points bending test (TPBT) on pre-notched asphalt beams appears to be a solution in that context. This paper presents a comparison between low temperature propert...

Babadopulos, Lucas Feitosa A. L.; Le Guern, Malo; Chailleux, Emmanuel; Dreessen, S.

2012-01-01

349

Structural material properties for fusion application  

International Nuclear Information System (INIS)

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

350

Morphology-mechanical Property Relationship of Polypropylene/starch Blends  

Directory of Open Access Journals (Sweden)

Full Text Available The influence of morphology on mechanical property of several polypropylene/starch (PP/starch blends of varying compositions was studied. The blends prepared were at wt%PP/wt%starch of 97.5/2.5, 95/5, 92.5/7.7, 90/10, 87.5/12.5 and 85/15. The morphology of the blends observed, using scanning electron microscopy showed them to be immiscible blends with distinct polymer-starch domains at high starch volume fractions (85%PP/15%starch-87.5%PP/12.5%starch, which gradually showed the morphology of well dispersed miscible blends at lower starch volume fractions (97.5%PP/2.5%starch,95%PP/5%starch,92.5%PP/7.7%starch, 90%PP/10%starch The starch domains exhibited characteristic voids which could be due to thermal degradation at the processing temperatures employed. The particle size of the starch domains increased with increase in volume fraction, probably due to the agglomeration and formation of aggregates of the starch granules. The mechanical properties of the blends and viscosity of the blends decrease with increase in starch volume fractions. The mechanical properties were explained using the blend morphologies at various volume fractions.

C. H. Azhari

2001-01-01

351

Presence of two distinct regions in the coiled-coil structure of the streptococcal Pep M5 protein: relationship to mammalian coiled-coil proteins and implications to its biological properties.  

OpenAIRE

The complete amino acid sequence of Pep M5, a biologically active 197-residue fragment comprising nearly half of the group A streptococcal M5 protein, has structural features characteristic of an alpha-helical coiled-coil protein. Fourier analyses of the nonpolar residues show strong periodicities based on repeats of 7 residues (7/2 and 7/3). Except for the nonhelical NH2-terminal 12-residue segment, the 7-residue periodicity in the distribution of nonpolar residues extends through the remain...

Manjula, B. N.; Trus, B. L.; Fischetti, V. A.

1985-01-01

352

Quantitative structure-activity relationships for organophosphates binding to acetylcholinesterase.  

Science.gov (United States)

Organophosphates are a group of pesticides and chemical warfare nerve agents that inhibit acetylcholinesterase, the enzyme responsible for hydrolysis of the excitatory neurotransmitter acetylcholine. Numerous structural variants exist for this chemical class, and data regarding their toxicity can be difficult to obtain in a timely fashion. At the same time, their use as pesticides and military weapons is widespread, which presents a major concern and challenge in evaluating human toxicity. To address this concern, a quantitative structure-activity relationship (QSAR) was developed to predict pentavalent organophosphate oxon human acetylcholinesterase bimolecular rate constants. A database of 278 three-dimensional structures and their bimolecular rates was developed from 15 peer-reviewed publications. A database of simplified molecular input line entry notations and their respective acetylcholinesterase bimolecular rate constants are listed in Supplementary Material, Table I. The database was quite diverse, spanning 7 log units of activity. In order to describe their structure, 675 molecular descriptors were calculated using AMPAC 8.0 and CODESSA 2.7.10. Orthogonal projection to latent structures regression, bootstrap leave-random-many-out cross-validation and y-randomization were used to develop an externally validated consensus QSAR model. The domain of applicability was assessed by the William's plot. Six external compounds were outside the warning leverage indicating potential model extrapolation. A number of compounds had residuals >2 or <-2, indicating potential outliers or activity cliffs. The results show that the HOMO-LUMO energy gap contributed most significantly to the binding affinity. A mean training R (2) of 0.80, a mean test set R (2) of 0.76 and a consensus external test set R (2) of 0.66 were achieved using the QSAR. The training and external test set RMSE values were found to be 0.76 and 0.88. The results suggest that this QSAR model can be used in physiologically based pharmacokinetic/pharmacodynamic models of organophosphate toxicity to determine the rate of acetylcholinesterase inhibition. PMID:22990135

Ruark, Christopher D; Hack, C Eric; Robinson, Peter J; Anderson, Paul E; Gearhart, Jeffery M

2013-02-01

353

Phase relationship, vaporization, and thermodynamic properties of neodymium hexaboride  

International Nuclear Information System (INIS)

The Nd-B system was studied between NdB441 and NdB868, and between 1700 and 2100 K by Langmuir and Knudsen techniques to determine the phase relationship, the chemical activity of the components, the vaporization rate, and the vapor composition. At 1900 K, the neodymium hexaboride phase exists bwtween NdB6008 and NdB92 with a congruently vaporizing composition at NdB6057. The Gibbs energy of formation at the low boron boundary is ?G/sub f/0 = 0.0323T - 131 (kcal/mol), with a more negative value at the high boron boundary. The value for the tetraboride is -58 kcal/mol (-243 kJ/mol) at its high boron boundary

354

Colloidal Platinum Nanoparticles: Synthesis, Structure and Properties.  

Science.gov (United States)

Interest in nanoparticles has risen in recent years as unique properties are being obtained from otherwise ordinary materials by reducing their sizes to molecular dimensions. We synthesized colloidal platinum nanoparticles with sizes of 1˜8 nm through four novel chemical methods and investigated their properties. These particles had an electrical resistivity of 1˜4 ?.m and also exhibited a ferromagnetic moment. When the particles were exposed to hydrogen we measured a 15% increase in their mass, indicating a high level of hydrogen absorption. The lattice constant was measured using HRTEM and was found to be the same as bulk Pt, even after H2 exposure, indicating no lattice distortion occurred. When dermal fibroblasts were exposed to the particles, the particles disrupted cellular actin, structure, and function. Practical applications include the use of Pt particles in semiconductor chips, hydrogen storage in fuel cells and particle chemotherapy targeted against cancer cells.

Katz, Daniel; Murali, Vikas; Isseroff, Rebecca; Sun, Yuan; Zhu, Yimei; Samuilov, Vladimir; Pernodet, Nadine; Rafailovich, Miriam; Sokolov, Jonathan

2006-03-01

355

Impact of variable [CO2] and temperature on water transport structure-function relationships in Eucalyptus.  

Science.gov (United States)

Nearly 30 years ago, Whitehead and Jarvis and Whitehead et al. postulated an elegant mechanistic explanation for the observed relationship between tree hydraulic structure and function, hypothesizing that structural adjustments promote physiological homeostasis. To date, this framework has been nearly completely overlooked with regard to varying atmospheric carbon dioxide ([CO(2)]). Here, we evaluated Whitehead's hypothesis of leaf water potential (?(l)) homeostasis in faster-growing (Eucalyptus saligna) and slower-growing (Eucalyptus sideroxylon) tree saplings grown under three [CO(2)] (pre-industrial, current and future) and two temperature (ambient and ambient + 4°C) treatments. We tested for relationships between physiological (stomatal conductance and ?(l)) and structural (leaf and sapwood areas (A(l), A(s)), height (h), xylem conductivity (k(s))) plant variables as a function of the [CO(2)] and temperature treatments to assess whether structural variables adjusted to maintain physiological homeostasis. Structural components (A(l), A(s), h) generally increased with [CO(2)] or temperature, while g(s) was negatively correlated with [CO(2)]. Contrary to Whitehead's hypothesis, ?(l) did not exhibit homeostasis in either species; elevated temperatures were associated with more negative ?(l) in faster-growing E. saligna, and less negative ?(l) in slower-growing E. sideroxylon. Moreover, individual structural variables were generally uncorrelated with ?(l). However, across both species, the integrated hydraulic property of leaf specific hydraulic conductance (K(l)) was positively correlated with an independent calculation of K(l) determined exclusively from leaf physiological variables. These results suggest that physiological homeostasis may not apply to saplings exposed to global change drivers including [CO(2)] and temperature. Nevertheless, Whitehead et al.'s formulation identified K(l) as a sensitive measure of plant structural-physiological co-variation across species. PMID:21712237

Phillips, Nathan G; Attard, Renee D; Ghannoum, Oula; Lewis, James D; Logan, Barry A; Tissue, David T

2011-09-01

356

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

Scientific Electronic Library Online (English)

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

Ricardo V. B., Oliveira; Creusa I., Ferreira; Luciano J. F., Peixoto; Otávio, Bianchi; Patricia A., Silva; Renan, Demori; Rodrigo P., Silva; Vinicius B., Veronese.

357

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, and optoelectronic properties of gold(I) carbeniates.

McDougaldJr, Roy N [University of North Texas; Chilukuri, Bhaskar [University of North Texas; Jia, Huiping [University of Texas at Dallas; Perez, Michael R [University of Texas at Dallas; Rabaa, Hassan [Ibn Tofail Univ, ESCTM, Morocco; Wang, Xiaoping [ORNL; Nesterov, Vladimir [University of North Texas; Cundari, Thomas R. [University of North Texas; Gnade, Bruce E [University of Texas at Dallas; Omary, Mohammad A [University of North Texas

2014-01-01

358

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

359

Relationship between the matrix effect and the physicochemical properties of analytes in gas chromatography.  

Science.gov (United States)

The phenomenon "matrix-induced chromatographic response enhancement" (matrix effect) causes quantitative errors in gas chromatography (GC) analyses. This effect varies according to the analyte nature, matrix type and concentration, and GC-system parameters. By focusing on the physicochemical properties of analytes, a predictive model was developed for the matrix effect using quantitative structure-property relationships. Experimental values of the matrix effect were determined for 58 compounds in a serum extract obtained from solid-phase extraction as the matrix. Eight molecular descriptors were selected, and the matrix-effect model was developed by multiple linear regression. The developed model predicted values for the matrix effect without any further experimental measurements. It also indicated that the molecular polarity (particularly H-bond donors) and volume of the analyte increase the matrix effect, while hydrophobicity and increasing number of nonpolar carbon atoms in the analyte decrease the matrix effect. The model was applied to the analysis of barbiturates. The predicted values indicated that N-methylation decreases the matrix effect, and the relative predicted values were effective for the selection of an internal standard. The obtained insight into the matrix effect and the prediction data will be helpful for developing quantitative analysis strategies. PMID:24173661

Saka, Kanju; Kudo, Keiko; Hayashida, Makiko; Kurisaki, Emiko; Niitsu, Hisae; Terada, Masaru; Yamaguchi, Koji; Yoshida, Ken-ichi

2013-12-01

360

Structure–property relationship of co-precipitated Cu-rich, Al2O3- or MgAl2O4-stabilized oxygen carriers for chemical looping with oxygen uncoupling (CLOU)  

International Nuclear Information System (INIS)

Highlights: • Development of a synthesis–performance relationship for co-precipitated materials. • CLOU reaction mechanism for Al2O3-stabilized oxygen carriers is proposed. • CuAl2O4 and CuAlO2 show, respectively, slow decomposition and oxidation kinetics. • MgAl2O4-stabilized CuO (80 wt.%) are identified as a suitable material for CLOU. - Abstract: Chemical looping with oxygen uncoupling (CLOU) is a novel combustion technology that utilizes the decomposition reaction of an oxygen storage material to combust solid (hydro-)carbonaceous fuels. CuO is an ideal candidate for CLOU owing to its high oxygen uncoupling capacity (?10 wt.%) and its ability to release oxygen at temperatures relevant for chemical looping combustion (CLC), i.e. 850–1000 °C. Here, we investigate the feasibility of Cu-rich, Al2O3 or MgAl2O4-stabilized oxygen carriers containing 70–90 wt.% CuO for the CLOU process. Al2O3- and MgAl2O4-stabilized oxygen carriers were synthesized using a co-precipitation technique and calcined either at 800 °C or 1000 °C. The CLOU performance of the oxygen carriers was evaluated at 950 °C in a fluidized bed reactor using a N2 atmosphere for the decomposition reaction and a mixture of 10.5 vol.% O2 and 89.5 vol.% N2 for the re-oxidation reaction. It was found that the calcination temperature and the surface area had no significant influence on the oxygen carrying capacity of the synthesized oxygen carriers. The oxygen uncoupling capacity of Al2O3-stabilized oxygen carriers was substantially below the theoretically expected values due to the formation of the mixed oxides CuAl2O4 and CuAlO2. Based on thermo-gravimetric measurements, a reaction pathway for the oxygen release and re-oxidation reactions of Al2O3-stabilized CuO was proposed. On the other hand, no interaction between MgAl2O4 and the active phase, i.e. CuO was observed. As a consequence, MgAl2O4-stabilized oxygen carriers possessed a high oxygen uncoupling capacity very close to the theoretical values. Owing to its stable and high oxygen release capacity, MgAl2O4-supported oxygen carriers containing 80 wt.% CuO were identified as a promising material for CLOU

361

Family Structure History: Links to Relationship Formation Behaviors in Young Adulthood  

OpenAIRE

Using data from three waves of the National Longitudinal Study of Adolescent Health (N=4,538), we examine the intergenerational link between parental family structure history and relationship formation in young adulthood. We investigate: (a) first, whether parental family structure history is associated with young adults' own relationship formation behaviors; (b) second, which dimensions of family structure history are most predictive of children's later relationship formation behaviors; and ...

Ryan, Suzanne; Franzetta, Kerry; Schelar, Erin; Manlove, Jennifer

2009-01-01

362

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

363

Exact relationship for third-order structure functions in helical flows  

Science.gov (United States)

An exact law for turbulent flows is written for third-order structure functions taking into account the invariance of helicity, a law akin to the so-called "4/5 law" of Kolmogorov. Here, the flow is assumed to be homogeneous, incompressible and isotropic but not invariant under reflectional symmetry. Our result is consistent with the derivation by O. Chkhetiani [JETP Lett. 10, 808, (1996)] of the von Karman-Howarth equation in the helical case, leading to a linear scaling relation for the third-order velocity correlation function. The alternative relation of the Kolmogorov type we derive here is written in terms of mixed structure functions involving combinations of differences of all components for both the velocity and vorticity fields. This relationship could prove to be a stringent test for the measuring of vorticity in the laboratory, and provide a supplementary tool for the study of the properties of helical flows. PMID:11031579

Gomez; Politano; Pouquet

2000-05-01

364

From Coherent Structures to Universal Properties  

OpenAIRE

Given a 2-category $\\twocat{K}$ admitting a calculus of bimodules, and a 2-monad T on it compatible with such calculus, we construct a 2-category $\\twocat{L}$ with a 2-monad S on it such that: (1)S has the adjoint-pseudo-algebra property. (2)The 2-categories of pseudo-algebras of S and T are equivalent. Thus, coherent structures (pseudo-T-algebras) are transformed into universally characterised ones (adjoint-pseudo-S-algebras). The 2-category $\\twocat{L}$ consists of lax alg...

Hermida, Claudio

2000-01-01

365

Understanding structure-property relationships in lithium metal phosphates and oxide electrode materials: X-ray/neutron diffraction and lithium-7 MAS-NMR coupled with lithium-ion electrochemistry  

Science.gov (United States)

Li-ion rechargeable battery has emerged as one of the most important portable energy carriers in the last decade. While LiCoO2 has been used as the cathode for a decade because of the good capacity and cycle retentions, tremendous efforts have been devoted to search other low cost and environmentally viable materials. Some of the promising materials such as LiFePO4, Li3V2(PO4)3, and LiNi1/3 Mn1/3Co1/3O2 were studied in this thesis. New lithium metal fluorophosphates were also discovered as potential cathode materials. The use of an aqueous solution synthesis route employing nanosized oxidized carbon black particles to inhibit LiFePO4 crystal growth was demonstrated. The resultant particle size of about 100 nm is reduced by 20 times compared to the solution synthesis method alone. Electron diffraction patterns and high resolution images from TEM experiments confirmed the single olivine phase nature of the material and the very small crystallite sizes. The 100 nm crystallites of LiFePO4-OCB showed vastly improved capacity (0.7 Li, 125mAh/g) compared to the 2mum particle. This improvement is due to contributions of decreased Li diffusion paths and improved contact with conductive carbon particles. Electrochemical PITT experiments coupled with ex-situ X-ray diffraction studies revealed the structural similarities of the delithiated monoclinic single phase compositions of LixV2(PO 4)3. (x = 2, 1, 0) From Le Bail refinements of XRD patterns, monoclinic Li3V2(PO4)3 shows only 7% volume variation upon delithiation which demonstrates its excellent intercalation characteristics. Structures of delithiated single phase compositions were further studied by both powder neutron diffraction and 7Li solid state NMR. From the structure solutions, each plateau in the V vs x curve corresponds to a two-phase transition involving the reorganization of electrons and Li ions within the lattice. The existence of charge ordering in Li2V2(PO4)3 demonstrates the electrons are pinned on both long and short time scales. The structures spanning the phase transition are energetically different, governed by the site potential of the Li+ ion, and interaction with the V"+ ions in the lattice. The solid solution regime on re-insertion (from x = 0 to x = 2.0) appears to be a consequence of the mixed V4+/V5+ state in V2(PO4)3 formed on complete emptying of the lattice, which does not display charge ordering. Therefore lithium insertion results in disorder until sufficient Li+ re-population and vanadium reduction occur. These findings explain the complex steps displayed in the voltage vs composition curves of LixV 2(PO4)3, and are also directly relevant to other materials. (Abstract shortened by UMI.)

Yin, Shih-Chieh

366

Morphology-mechanical Property Relationship of Polypropylene/starch Blends  

OpenAIRE

The influence of morphology on mechanical property of several polypropylene/starch (PP/starch) blends of varying compositions was studied. The blends prepared were at wt%PP/wt%starch of 97.5/2.5, 95/5, 92.5/7.7, 90/10, 87.5/12.5 and 85/15. The morphology of the blends observed, using scanning electron microscopy showed them to be immiscible blends with distinct polymer-starch domains at high starch volume fractions (85%PP/15%starch-87.5%PP/12.5%starch), which gradually showed the morphology o...

Azhari, C. H.; Wong, S. F.

2001-01-01

367

Relationships between fracture toughness and other material properties. Final report  

International Nuclear Information System (INIS)

The key experimental and analytical studies which have led to our present understanding of the mechanisms of ductile fracture are reviewed. It is concluded that insufficient progress has been made in the quantitative description of ductile separation mechanisms on a microscale to allow the realistic prediction of fracture toughness from material properties and microstructure. An experimental study of ductile fracture is underway which has the aim of determining the growth rate of voids in known plastic deformation fields as a function of triaxiality of stress and material work-hardening. Novel specimens of particularly well characterized microstructure are utilized

368

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

DEFF Research Database (Denmark)

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

Desrues, Oliver; Enemark, Heidi L.

2013-01-01

369

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

DEFF Research Database (Denmark)

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

Desrues, Olivier; Larsen Enemark, Heidi

370

Property Relationship in Organosilanes and Nanotubes Filled Polypropylene Hybrid Composites  

OpenAIRE

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 hal...

Monsiva?is-barro?n, Alejandra J.; Jaime Bonilla-Rios; Antonio Sánchez-Fernández

2014-01-01

371

Structure activity relationships to assess new chemicals under TSCA  

International Nuclear Information System (INIS)

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

372

Crystal Structure-Ionic Conductivity Relationships in Doped Ceria Systems  

DEFF Research Database (Denmark)

In the past, it has been suggested that the maximum ionic conductivity is achieved in ceria, when doped with an acceptor cation that causes minimum distortion in the cubic fluorite crystal lattice. In the present work, this hypothesis is tested by measuring both the ionic conductivity and elastic lattice strain of 10 mol% trivalent cation-doped ceria systems at the same temperatures. A consistent set of ionic conductivity data is developed, where the samples are synthesized under similar experimental conditions. On comparing the grain ionic conductivity, Nd0.10Ce0.90O2?? exhibits the highest ionic conductivity among other doped ceria systems. The grain ionic conductivity is around 17% higher than that of Gd0.10Ce0.90O2?? at 500°C, in air. X-ray diffraction profiles are collected on the sintered powder of all the compositions, from room temperature to 600°C, in air. From the lattice expansion data at high temperatures, the minimal elastic strain due to the presence of dopant is observed in Dy0.10Ce0.90O2??. Nd0.10Ce0.90O2?? exhibits larger elastic lattice strain than Dy0.10Ce0.90O2?? with better ionic conductivity at intermediate temperatures. Therefore, it is shown that the previously proposed crystal structure–ionic conductivity relationship based on minimum elastic strain is not sufficient to explain the ionic conductivity behavior in ceria-based system.

Omar, Shobit; Wachsman, Eric D.

2009-01-01

373

Structure activity relationships to assess new chemicals under TSCA  

Energy Technology Data Exchange (ETDEWEB)

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

Auletta, A.E. [Environmental Protection Agency, Washington, DC (United States)

1990-12-31

374

Structure activity relationships in PIPC-analogues against Pseudomonas aeruginosa.  

Science.gov (United States)

The relationship between the chemical structure and mode of action of piperacillin-analogues (PIPC-analogues) against Pseudomonas aeruginosa was investigated. The antibacterial activities of PIPC-analogues became stronger as the chain length of the alkyl group on the N-4 position in 2,3-dioxopiperazine when tested in constitutively beta-lactamase-producing strain, but not paralleled in wild and beta-lactamase-less strains. The outer membrane permeability was hardly affected by the chain length of the alkyl group at the N-4 position. The stability to beta-lactamase was stronger with the increase of the number of the carbon atoms of N-4 position. In the binding-affinities to the lethal penicillin-binding proteins (PBPs), compounds PIPC (C-2), C-3 and C-4 showed lower ID50 values than compounds C-1, C-6 and C-8. These results suggested that the stability to beta-lactamase was the governing part for the antibacterial activity in constitutively beta-lactamase-producing strain, and the binding affinity to lethal PBPs directly contributed to the antibacterial activity in wild and beta-lactamase-less strains. PMID:2498272

Mitsuyama, J; Hori, R; Ito, Y; Yotsuji, A; Yasuda, T; Saikawa, I

1989-04-01

375

Cytotoxic triosmium carbonyl clusters: a structure-activity relationship study.  

Science.gov (United States)

A structure-activity relationship (SAR) study of the triosmium carbonyl cluster Os3 (CO)10 (NCCH3 )2 was carried out with a series of clusters of the general formula Os3 (CO)12-n Ln , cationic osmium clusters and a hemi-labile maltolato-Os cluster. The SAR results showed that good solubility in DMSO and at least one vacant site are required for cytotoxicity. In vitro evaluation of these new compounds showed that some are selectively active against estrogen receptor (ER)-independent MDA-MB-231 breast cancer cell lines relative to ER-dependent MCF-7 breast cancer cells, suggesting that the compounds have a different biological target specific to MDA-MB-231 cells. In particular, the maltolato cluster exhibits strong antiproliferative activity, with an IC50 value of 3??M after only 24?h incubation. Additionally, biochemical assays conducted with the cationic cluster show that it induces apoptosis, although a biological target has not yet been identified. Further research to establish the molecular targets of these compounds and to develop improved organometallic clusters as potential breast cancer therapeutics is underway. PMID:24446332

Lee, Hui Zhi Shirley; Leong, Weng Kee; Top, Siden; Vessières, Anne

2014-07-01

376

Thermal and structural properties of ionic fluids  

CERN Document Server

The electrostatic interaction in ionic fluids is well-known to give rise to a characteristic phase behavior and structure. Sometimes its long range is proposed to single out the electrostatic potential over other interactions with shorter ranges. Here the importance of the range for the phase behavior and the structure of ionic fluids is investigated by means of grandcanonical Monte Carlo simulations of the lattice restricted primitive model (LRPM). The long-ranged electrostatic interaction is compared to various types of short-ranged potentials obtained by sharp and/or smooth cut-off schemes. Sharply cut off electrostatic potentials are found to lead to a strong dependence of the phase behavior and the structure on the cut-off radius. However, when combined with a suitable additional smooth cut-off, the short-ranged LRPM is found to exhibit quantitatively the same phase behavior and structure as the conventional long-ranged LRPM. Moreover, the Stillinger-Lovett perfect screening property, which is well-known...

Bartsch, Hendrik; Bier, Markus

2015-01-01

377

Structural properties of low density liquid selenium  

International Nuclear Information System (INIS)

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

378

Relationships among the physical properties of biodiesel and engine fuel system design requirement  

Energy Technology Data Exchange (ETDEWEB)

Biodiesel, an alternative fuel can be used in diesel engines as neat or blended with diesel. The physio-chemical properties of fuel are important in design of fuel system for compression ignition engines run on diesel, biodiesel or biodiesel blends. Biodiesel (B100) standards specify the limit values of these properties for blending with diesel. However, there are variations in the properties of biodiesel. The properties of biodiesel vary depending on the feedstock, vegetable oil processing, production methods and degree of purification. The objective of this study is to estimate the mathematical relationships between viscosity, density, heating values and flash point among various biodiesel samples. There is a high regression between various properties of biodiesel and the relationships between them are observed to be considerably regular.

Lakshmi Narayana Rao, G. [QIS Institute of Technology, Ongole, Andhra Pradesh (India); Ramadhas, A.S.; Sakthivel, P. [Indian Oil Corporation Ltd, Faridabad (India); Nallusamy, N. [Sri Venkateswara College of Engineering, Pennalur, Tamil Nadu (India)

2010-07-01

379

Property-porosity relationships for polymer-impregnated superconducting ceramic composite  

International Nuclear Information System (INIS)

A thermoplastic polymer, poly(methyl methacrylate) (PMMA), was used to improve the flexural properties of the high-temperature superconducting ceramic (YBa2Cu3O7-?). Ceramic specimens with different porosities were prepared by dry compacting 12.5-mm-diameter disk specimens at various uniaxial pressures. Density-pressure relationships have been developed for before- and after-sintering conditions. The PMMA polymer was impregnated into the porous ceramic at room temperature. The mechanical properties were evaluated by concentrically loading simply supported disk specimens. The load-displacement responses were analyzed using the finite-element method. Impregnation of PMMA polymer at room temperature increased the flexural strength and modulus of the superconducting ceramic without affecting its electrical properties. The flexural properties depended on the porosity of the ceramics, and, hence, linear and nonlinear property-porosity relationships have been used to characterize the behavior of superconducting ceramic with an without the polymer

380

Design, synthesis, and structure-activity relationship of novel aniline derivatives of chlorothalonil.  

Science.gov (United States)

Chlorothalonil with both low cost and low toxicity is a popularly used fungicide in the agrochemical field. The presence of nucleophilic groups on this compound allows further chemical modifications to obtain novel chlorothalonil derivatives. Fluazinam, another commercially available agent with a broad fungicidal spectrum, has a scaffold of diaryl amine structure. To mimic this backbone structure, a variety of (un)substituted phenyl amines was used as nucleophilic agents to react with chlorothalonil to obtain compounds with a diphenyl amine structure. Via an elegant design, two leads, 2,4,5-trichloro-6-(2,4-dichlorophenylamino)isophthalonitrile (7) and 2,4,5-trichloro-6-(2,4,6-trichlorophenylamino)isophthalonitrile (11), with potential fungicidal activity were discovered after a preliminary bioassay screen. These two leads were further modified to obtain final products by replacing the chlorine groups in the phenyl ring in phenyl amine with other functional groups. These functional groups with various electronic properties and spatial characteristics were considered to explore the relationship between structure and fungicidal activity. The results indicate that the electron-withdrawing group NO2 on the 4 position on the right phenyl ring plays a unique role on enhancing the fungicidal activity. The compounds were identified by proton nuclear magnetic resonance and elemental analysis. Bioassays demonstrated that some of the title compounds exhibited excellent fungicidal activities against cucumber downy mildew at 25 mg/L. Compound 20 has been shown as the optimal structure with 85% control against cucumber downy mildew at 6.25 mg/L concentration. The relationship between structure and fungicidal activity is reported. The present work demonstrates that chlorothalonil derivatives can be used as possible lead compounds for developing novel fungicides. PMID:24255942

Guan, Ai-Ying; Liu, Chang-Ling; Huang, Guang; Li, Hui-Chao; Hao, Shu-Lin; Xu, Ying; Li, Zhi-Nian

2013-12-11

381

Structure-activity relationship of immunostimulatory effects of phthalates  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Some chemicals, including some phthalate plasticizers, have been shown to have an adjuvant effect in mice. However, an adjuvant effect, defined as an inherent ability to stimulate the humoral immune response, was only observed after exposure to a limited number of the phthalates. An adjuvant effect may be due to the structure or physicochemical characteristics of the molecule. The scope of this study was to investigate which molecular characteristics that determine the observed adjuvant effect of the most widely used phthalate plasticizer, the di-(2-ethylhexyl phthalate (DEHP, which is documented as having a strong adjuvant effect. To do so, a series of nine lipophilic compounds with structural and physicochemical relations to DEHP were investigated. Results Adjuvant effect of phthalates and related compounds were restricted to the IgG1 antibody formation. No effect was seen on IgE. It appears that lipophilicity plays a crucial role, but lipophilicity does not per se cause an adjuvant effect. In addition to lipophilicity, a phthalate must also possess specific stereochemical characteristics in order for it to have adjuvant effect. Conclusion The adjuvant effect of phthalates are highly influenced by both stereochemical and physico-chemical properties. This knowledge may be used in the rational development of plasticizers without adjuvant effect as well as in the design of new immunological adjuvants.

Nielsen Gunnar D

2008-10-01