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Sample records for structure-property relationship study

  1. Interactions of Indole Derivatives with β-Cyclodextrin: A Quantitative Structure-Property Relationship Study

    PubMed Central

    Šoškić, Milan; Porobić, Ivana

    2016-01-01

    Retention factors for 31 indole derivatives, most of them with auxin activity, were determined by high-performance liquid chromatography, using bonded β-cyclodextrin as a stationary phase. A three-parameter QSPR (quantitative structure-property relationship) model, based on physico-chemical and structural descriptors was derived, which accounted for about 98% variations in the retention factors. The model suggests that the indole nucleus occupies the relatively apolar cavity of β-cyclodextrin while the carboxyl group of the indole -3-carboxylic acids makes hydrogen bonds with the hydroxyl groups of β-cyclodextrin. The length and flexibility of the side chain containing carboxyl group strongly affect the binding of these compounds to β-cyclodextrin. Non-acidic derivatives, unlike the indole-3-carboxylic acids, are poorly retained on the column. A reasonably well correlation was found between the retention factors of the indole-3-acetic acids and their relative binding affinities for human serum albumin, a carrier protein in the blood plasma. A less satisfactory correlation was obtained when the retention factors of the indole derivatives were compared with their affinities for auxin-binding protein 1, a plant auxin receptor. PMID:27124734

  2. Structure Property Relationships of Carboxylic Acid Isosteres.

    PubMed

    Lassalas, Pierrik; Gay, Bryant; Lasfargeas, Caroline; James, Michael J; Tran, Van; Vijayendran, Krishna G; Brunden, Kurt R; Kozlowski, Marisa C; Thomas, Craig J; Smith, Amos B; Huryn, Donna M; Ballatore, Carlo

    2016-04-14

    The replacement of a carboxylic acid with a surrogate structure, or (bio)-isostere, is a classical strategy in medicinal chemistry. The general underlying principle is that by maintaining the features of the carboxylic acid critical for biological activity, but appropriately modifying the physicochemical properties, improved analogs may result. In this context, a systematic assessment of the physicochemical properties of carboxylic acid isosteres would be desirable to enable more informed decisions of potential replacements to be used for analog design. Herein we report the structure-property relationships (SPR) of 35 phenylpropionic acid derivatives, in which the carboxylic acid moiety is replaced with a series of known isosteres. The data set generated provides an assessment of the relative impact on the physicochemical properties that these replacements may have compared to the carboxylic acid analog. As such, this study presents a framework for how to rationally apply isosteric replacements of the carboxylic acid functional group.

  3. Quantitative structure-property relationship studies on amino acid conjugates of jasmonic acid as defense signaling molecules.

    PubMed

    Li, Zu-Guang; Chen, Ke-Xian; Xie, Hai-Ying; Gao, Jian-Rong

    2009-06-01

    Jasmonates and related compounds, including amino acid conjugates of jasmonic acid, have regulatory functions in the signaling pathway for plant developmental processes and responses to the complex equilibrium of biotic and abiotic stress. But the molecular details of the signaling mechanism are still poorly understood. Statistically significant quantitative structure-property relationship models (r(2) > 0.990) constructed by genetic function approximation and molecular field analysis were generated for the purpose of deriving structural requirements for lipophilicity of amino acid conjugates of jasmonic acid. The best models derived in the present study provide some valuable academic information in terms of the 2/3D-descriptors influencing the lipophilicity, which may contribute to further understanding the mechanism of exogenous application of jasmonates in their signaling pathway and designing novel analogs of jasmonic acid as ecological pesticides.

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

    PubMed

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

    2014-12-01

    A series of six structurally correlated donor-π 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 π 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 π-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.

  5. Selenium-Containing Fused Bicyclic Heterocycle Diselenolodiselenole: Field Effect Transistor Study and Structure-Property Relationship.

    PubMed

    Debnath, Sashi; Chithiravel, Sundaresan; Sharma, Sagar; Bedi, Anjan; Krishnamoorthy, Kothandam; Zade, Sanjio S

    2016-07-20

    The first application of the diselenolodiselenole (C4Se4) heterocycle as an active organic field effect transistor materials is demonstrated here. C4Se4 derivatives (2a-2d) were obtained by using a newly developed straightforward diselenocyclization protocol, which includes the reaction of diynes with selenium powder at elevated temperature. C4Se4 derivatives exhibit strong donor characteristics and planar structure (except 2d). The atomic force microscopic analysis and thin-film X-ray diffraction pattern of compounds 2a-2d indicated the formation of distinct crystalline films that contain large domains. A scanning electron microscopy study of compound 2b showed development of symmetrical grains with an average diameter of 150 nm. Interestingly, 2b exhibited superior hole mobility, approaching 0.027 cm(2) V(-1) s(-1) with a transconductance of 9.2 μS. This study correlate the effect of π-stacking, Se···Se intermolecular interaction, and planarity with the charge transport properties and performance in the field effect transistor devices. We have shown that the planarity in C4Se4 derivatives was achieved by varying the end groups attached to the C4Se4 core. In turn, optoelectronic properties can also be tuned for all these derivatives by end-group variation.

  6. Selenium-Containing Fused Bicyclic Heterocycle Diselenolodiselenole: Field Effect Transistor Study and Structure-Property Relationship.

    PubMed

    Debnath, Sashi; Chithiravel, Sundaresan; Sharma, Sagar; Bedi, Anjan; Krishnamoorthy, Kothandam; Zade, Sanjio S

    2016-07-20

    The first application of the diselenolodiselenole (C4Se4) heterocycle as an active organic field effect transistor materials is demonstrated here. C4Se4 derivatives (2a-2d) were obtained by using a newly developed straightforward diselenocyclization protocol, which includes the reaction of diynes with selenium powder at elevated temperature. C4Se4 derivatives exhibit strong donor characteristics and planar structure (except 2d). The atomic force microscopic analysis and thin-film X-ray diffraction pattern of compounds 2a-2d indicated the formation of distinct crystalline films that contain large domains. A scanning electron microscopy study of compound 2b showed development of symmetrical grains with an average diameter of 150 nm. Interestingly, 2b exhibited superior hole mobility, approaching 0.027 cm(2) V(-1) s(-1) with a transconductance of 9.2 μS. This study correlate the effect of π-stacking, Se···Se intermolecular interaction, and planarity with the charge transport properties and performance in the field effect transistor devices. We have shown that the planarity in C4Se4 derivatives was achieved by varying the end groups attached to the C4Se4 core. In turn, optoelectronic properties can also be tuned for all these derivatives by end-group variation. PMID:27353123

  7. Structure-property relationship in py-hexahydrocinchonidine diastereomers: ab initio and NMR study.

    PubMed

    Szöllösi, György; Chatterjee, Abhijit; Forgó, Péter; Bartók, Mihály; Mizukami, Fujio

    2005-02-10

    Two py-hexahydrocinchonidine diastereomers were selectively obtained in the heterogeneous catalytic hydrogenation of cinchonidine over supported Pt catalyst. The two isolated compounds when used as chiral base catalysts in the Michael addition of a beta-keto ester to methyl vinyl ketone gave products of opposite configuration in excess. To trace the reason of this behavior, in the present study, the structures of the two diastereomers were fully optimized by ab initio quantum chemical calculation. These results were then compared with several nuclear Overhauser enhancement spectroscopy (NOESY) signal intensities from the spectra of the two compounds. Further we performed a conformational search on all the optimized geometries independently for the two flexible torsional angles, which are linking the quinuclidine and tetrahydroquinoline moieties present in these molecules. This study allowed us to propose the configuration of the C(4)(') chiral center. Thus, the product mixture resulted in the hydrogenation of cinchonidine containing the 4'-(S)-diastereomer in excess (de = 20%). According to the computation results the 4'-(S)-diastereomer is more stable than the 4'-(R)-diastereomer. The 4'-(S)-conformer obtained by computation has lower electronic energy than the structures obtained for the 4'-(R)-diastereomer, which may explain the excess formation of the first one. The results of the Michael addition catalyzed by these diastereomers were interpreted on the basis of these conclusions.

  8. Study of Chemistry and Structure-Property Relationship on Tunable Plasmonic Nanostructures

    NASA Astrophysics Data System (ADS)

    Jing, Hao

    In this dissertation, the rational design and controllable fabrication of an array of novel plasmonic nanostructures with geometrically tunable optical properties are demonstrated, including metal-semiconductor hybrid hetero-nanoparticles, bimetallic noble metal nanoparticles and hollow nanostructures (nanobox and nanocage). Firstly, I have developed a robust wet chemistry approach to the geometry control of Ag-Cu2O core-shell nanoparticles through epitaxial growth of Cu2O nanoshells on the surfaces of various Ag nanostructures, such as quasi-spherical nanoparticles, nanocubes, and nanocuboids. Precise control over the core and the shell geometries enables me to develop detailed, quantitative understanding of how the Cu2O nanoshells introduce interesting modifications to the resonance frequencies and the extinction spectral line shapes of multiple plasmon modes of the Ag cores. Secondly, I present a detailed and systematic study of the controlled overgrowth of Pd on Au nanorods. The overgrowth of Pd nanoshells with fine-controlled dimensions and architectures on single-crystalline Au nanorods through seed-mediated growth protocol in the presence of various surfactants is investigated. Thirdly, I have demonstrated that creation of high-index facets on subwavelength metallic nanoparticles provides a unique approach to the integration of desired plasmonic and catalytic properties on the same nanoparticle. Through site-selective surface etching of metallic nanocuboids whose surfaces are dominated by low-index facets, I have controllably fabricated nanorice and nanodumbbell particles, which exhibit drastically enhanced catalytic activities arising from the catalytically active high index facets abundant on the particle surfaces. And the nanorice and nanodumbbell particles also possess appealing tunable plasmonic properties that allow us to gain quantitative insights into nanoparticle-catalyzed reactions with unprecedented sensitivity and detail through time

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

    PubMed

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

    2015-01-01

    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 π-σ* 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

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

    PubMed

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

    2014-08-01

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

  11. Structure Property Relationships of Biobased Epoxy Resins

    NASA Astrophysics Data System (ADS)

    Maiorana, Anthony Surraht

    The thesis is about the synthesis, characterization, development, and application of epoxy resins derived from sustainable feedstocks such as lingo-cellulose, plant oils, and other non-food feedstocks. The thesis can be divided into two main topics 1) the synthesis and structure property relationship investigation of new biobased epoxy resin families and 2) mixing epoxy resins with reactive diluents, nanoparticles, toughening agents, and understanding co-curing reactions, filler/matrix interactions, and cured epoxy resin thermomechanical, viscoelastic, and dielectric properties. The thesis seeks to bridge the gap between new epoxy resin development, application for composites and advanced materials, processing and manufacturing, and end of life of thermoset polymers. The structures of uncured epoxy resins are characterized through traditional small molecule techniques such as nuclear magnetic resonance, high resolution mass spectrometry, and infrared spectroscopy. The structure of epoxy resin monomers are further understood through the process of curing the resins and cured resins' properties through rheology, chemorheology, dynamic mechanical analysis, tensile testing, fracture toughness, differential scanning calorimetry, scanning electron microscopy, thermogravimetric analysis, and notched izod impact testing. It was found that diphenolate esters are viable alternatives to bisphenol A and that the structure of the ester side chain can have signifi-cant effects on monomer viscosity. The structure of the cured diphenolate based epoxy resins also influence glass transition temperature and dielectric properties. Incorporation of reactive diluents and flexible resins can lower viscosity, extend gel time, and enable processing of high filler content composites and increase fracture toughness. Incorpora-tion of high elastic modulus nanoparticles such as graphene can provide increases in physical properties such as elastic modulus and fracture toughness. The synthesis

  12. A novel approach to study the structure-property relationships and applications in living systems of modular Cu2+ fluorescent probes

    NASA Astrophysics Data System (ADS)

    She, Mengyao; Yang, Zheng; Hao, Likai; Wang, Zhaohui; Luo, Tianyou; Obst, Martin; Liu, Ping; Shen, Yehua; Zhang, Shengyong; Li, Jianli

    2016-08-01

    A series of Cu2+ probe which contains 9 probes have been synthesized and established. All the probes were synthesized using Rhodamine B as the fluorophore, conjugated to various differently substituted cinnamyl aldehyde with C=N Schiff base structural motif as their core moiety. The structure-property relationships of these probes have been investigated. The change of optical properties, caused by different electronic effect and steric effect of the recognition group, has been analyzed systematically. DFT calculation simulation of the Ring-Close and Ring-Open form of all the probes have been employed to illuminate, summarize and confirm these correlations between optical properties and molecular structures. In addition, biological experiment demonstrated that all the probes have a high potential for both sensitive and selective detection, mapping of adsorbed Cu2+ both in vivo and environmental microbial systems. This approach provides a significant strategy for studying structure-property relationships and guiding the synthesis of probes with various optical properties.

  13. Structure Property Relationships of Carboxylic Acid Isosteres

    PubMed Central

    2016-01-01

    The replacement of a carboxylic acid with a surrogate structure, or (bio)-isostere, is a classical strategy in medicinal chemistry. The general underlying principle is that by maintaining the features of the carboxylic acid critical for biological activity, but appropriately modifying the physicochemical properties, improved analogs may result. In this context, a systematic assessment of the physicochemical properties of carboxylic acid isosteres would be desirable to enable more informed decisions of potential replacements to be used for analog design. Herein we report the structure–property relationships (SPR) of 35 phenylpropionic acid derivatives, in which the carboxylic acid moiety is replaced with a series of known isosteres. The data set generated provides an assessment of the relative impact on the physicochemical properties that these replacements may have compared to the carboxylic acid analog. As such, this study presents a framework for how to rationally apply isosteric replacements of the carboxylic acid functional group. PMID:26967507

  14. Structure/property relationships in multipass GMA welding of beryllium.

    SciTech Connect

    Hochanadel, P. W.; Hults, W. L.; Thoma, D. J.; Dave, V. R.; Kelly, A. M.; Pappin, P. A.; Cola, M. J.; Burgardt, P.

    2001-01-01

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

  15. A novel approach to study the structure-property relationships and applications in living systems of modular Cu(2+) fluorescent probes.

    PubMed

    She, Mengyao; Yang, Zheng; Hao, Likai; Wang, Zhaohui; Luo, Tianyou; Obst, Martin; Liu, Ping; Shen, Yehua; Zhang, Shengyong; Li, Jianli

    2016-01-01

    A series of Cu(2+) probe which contains 9 probes have been synthesized and established. All the probes were synthesized using Rhodamine B as the fluorophore, conjugated to various differently substituted cinnamyl aldehyde with C=N Schiff base structural motif as their core moiety. The structure-property relationships of these probes have been investigated. The change of optical properties, caused by different electronic effect and steric effect of the recognition group, has been analyzed systematically. DFT calculation simulation of the Ring-Close and Ring-Open form of all the probes have been employed to illuminate, summarize and confirm these correlations between optical properties and molecular structures. In addition, biological experiment demonstrated that all the probes have a high potential for both sensitive and selective detection, mapping of adsorbed Cu(2+) both in vivo and environmental microbial systems. This approach provides a significant strategy for studying structure-property relationships and guiding the synthesis of probes with various optical properties. PMID:27485974

  16. A novel approach to study the structure-property relationships and applications in living systems of modular Cu2+ fluorescent probes

    PubMed Central

    She, Mengyao; Yang, Zheng; Hao, Likai; Wang, Zhaohui; Luo, Tianyou; Obst, Martin; Liu, Ping; Shen, Yehua; Zhang, Shengyong; Li, Jianli

    2016-01-01

    A series of Cu2+ probe which contains 9 probes have been synthesized and established. All the probes were synthesized using Rhodamine B as the fluorophore, conjugated to various differently substituted cinnamyl aldehyde with C=N Schiff base structural motif as their core moiety. The structure-property relationships of these probes have been investigated. The change of optical properties, caused by different electronic effect and steric effect of the recognition group, has been analyzed systematically. DFT calculation simulation of the Ring-Close and Ring-Open form of all the probes have been employed to illuminate, summarize and confirm these correlations between optical properties and molecular structures. In addition, biological experiment demonstrated that all the probes have a high potential for both sensitive and selective detection, mapping of adsorbed Cu2+ both in vivo and environmental microbial systems. This approach provides a significant strategy for studying structure-property relationships and guiding the synthesis of probes with various optical properties. PMID:27485974

  17. Structure-Property Relationships of Bismaleimides

    NASA Technical Reports Server (NTRS)

    Tenteris-Noebe, Anita D.

    1997-01-01

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

  18. Structure-property relationships of carbon aerogels

    SciTech Connect

    Pekala, R.W.; Alviso, C.T.; Kong, F.M.

    1993-12-01

    Of the organic reactions in sol-gel polymerizations, the most studied reaction is the aqueous polycondensation of resorcinol with formaldehyde; the resulting crosslinked gels are supercritically dried from CO{sub 2} to give resorcinol-formaldehyde (RF) aerogels. These aerogels can be pyrolyzed to form vitreous carbon monoliths with black color, high porosity, ultrafine cell/pore size, high surface area, and interconnected particles of the organic precursor. The structure and properties of the carbon aerogels depend on R/C (resorcinol/catalyst) ratio of starting solution, pyrolysis temperature, and chemical activation. Each variable is discussed. Carbon aerogels provide an almost ideal electrode material (in double-layer capacitors) owing to low electrical resistivity (<40 mohm-cm), controllable pore size distribution (5--500 {angstrom}), and high volumetric surface areas ({approximately}500 m{sup 2}/cm{sup 3}).

  19. Structure-Property Relationships of Solids in Pharmaceutical Processing

    NASA Astrophysics Data System (ADS)

    Chattoraj, Sayantan

    Pharmaceutical development and manufacturing of solid dosage forms is witnessing a seismic shift in the recent years. In contrast to the earlier days when drug development was empirical, now there is a significant emphasis on a more scientific and structured development process, primarily driven by the Quality-by-Design (QbD) initiatives of US Food and Drug Administration (US-FDA). Central to such an approach is the enhanced understanding of solid materials using the concept of Materials Science Tetrahedron (MST) that probes the interplay between four elements, viz., the structure, properties, processing, and performance of materials. In this thesis work, we have investigated the relationships between the structure and those properties of pharmaceutical solids that influence their processing behavior. In all cases, we have used material-sparing approaches to facilitate property assessment using very small sample size of materials, which is a pre-requisite in the early stages of drug development when the availability of materials, drugs in particular, is limited. The influence of solid structure, either at the molecular or bulk powder levels, on crystal plasticity and powder compaction, powder flow, and solid-state amorphization during milling, has been investigated in this study. Through such a systematic evaluation, we have captured the involvement of structure-property correlations within a wide spectrum of relevant processing behaviors of pharmaceutical solids. Such a holistic analysis will be beneficial for addressing both regulatory and scientific issues in drug development.

  20. Substituent effects on the structure-property relationship of unsymmetrical methyloxy and methoxycarbonyl phthalocyanines: DFT and TDDFT theoretical studies.

    PubMed

    Zhang, Lijuan; Qi, Dongdong; Zhao, Luyang; Bian, Yongzhong; Li, Wenjun

    2012-05-01

    Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were carried out to simulate the molecular and electronic structures together with the electronic absorption spectra of a series of peripheral methyloxy/methoxycarbonyl substituented phthalocyanines M[Pc(β-OMe)(2n)(β-COOMe)(8-2n)] (M=2H, Zn; n=0, 1, 2, 3, and 4). Fragment charge distribution and electrostatic potential analysis indicate that the presence of electron-withdrawing and -donation groups leads to the redistribution of charges and obvious polarization effects to the unsymmetrical phthalocyanine series. Peripheral methyloxy/methoxycarbonyl groups introduced onto phthalocyanine ring were revealed to destroy the degeneracy of LUMOs, resulting in significant Q-band splitting for the unsymmetrical phthalocyanine compounds. In addition, metal-free and zinc phthalocyanine compounds display similar electronic structures and absorptions due to the almost none contribution of the zinc atom or inner hydrogens to the frontier molecular orbitals. The microscopic mechanism of the UV-Vis spectra has been clarified on the basis of multi-band photon-induced electron transference. These theoretical studies would be helpful for the molecular design of novel unsymmetrical phthalocyanines.

  1. Bio-related noble metal nanoparticle structure property relationships

    NASA Astrophysics Data System (ADS)

    Leonard, Donovan Nicholas

    Structure property relationships of noble metal nanoparticles (NPs) can be drastically different than bulk properties of the same metals. This research study used state-of-the-art analytical electron microscopy and scanned probe microscopy to determine material properties on the nanoscale of bio-related Au and Pd NPs. Recently, it has been demonstrated the self-assembly of Au NPs on functionalized silica surfaces creates a conductive surface. Determination of the aggregate morphology responsible for electron conduction was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). In addition, changes in the electrical properties of the substrates after low temperature (<350°C) annealing was also studied. It was found that coalescence and densification of the Au NP aggregates disrupted the interconnected network which subsequently created a loss of conductivity. Investigation of bio-related Au/SiO2 core-shell NPs determined why published experimental results showed the sol-gel silica shell improved, by almost an order of magnitude, the detection efficiency of a DNA detection assay. Novel 360° rotation scanning TEM (STEM) imaging allowed study of individual NP surface morphology and internal structure. Electron energy loss spectroscopy (EELS) spectrum imaging determined optoelectronic properties and chemical composition of the silica shell used to encapsulate Au NPs. Results indicated the sol-gel deposited SiO2 had a band gap energy of ˜8.9eV, bulk plasmon-peak energy of ˜25.5eV and chemical composition of stoichiometric SiO2. Lastly, an attempt to elicit structure property relationships of novel RNA mediated Pd hexagon NPs was performed. Selected area electron diffraction (SAD), low voltage scanning transmission electron microscopy (LV-STEM), electron energy loss spectroscopy (EELS) and energy dispersive spectroscopy (EDS) were chosen for characterization of atomic ordering, chemical composition and optoelectronic properties of the novel

  2. Oxide Thermoelectric Materials: A Structure-Property Relationship

    NASA Astrophysics Data System (ADS)

    Nag, Abanti; Shubha, V.

    2014-04-01

    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.

  3. Structure property relationships of carbonaceous films grown under ion enhancement

    SciTech Connect

    Weissmantel, C.; Ackermann, E.; Bewilogua, K.; Hecht, G.; Kupfer, H.; Rau, B.

    1986-11-01

    Based on our own results and in comparison with data published by other groups the structure property relationships of carbon and carbon/metal films prepared by sputtering and deposition of partially ionized species are discussed. Films grown by ion beam sputtering are dark brownish and amorphous with a small fraction of microcrystals. However, a transition to transparent and insulating layers can be effected by ion bombardment. C/Me coatings, where Me stands for Ti or Sn, were obtained by magnetron sputtering of composite targets. The films proved to be amorphous up to metal concentrations of more than 10 at. %, but metal and carbide crystals grow upon annealing. Measurements of the hardness, the electrical conductivity, and the contact behavior in dependence on the composition provided interesting information. For carbon films prepared by deposition of partially ionized benzene species it has been found that the properties depend characteristically on the ion energy; typical ''diamondlike'' i-C films are obtained by applying a bias voltage from 1--3 keV. The thermal stability of the amorphous coatings is discussed in conjunction with their electrical conductivity. Summarizing extensive structure investigations, a structure model based on tetrahedrally interlinked carbon rings is proposed. Composites of the type i-C/Me (Me: Al, Ti, Cr), which were prepared by simultaneous metal evaporation, exhibit a wide range of structure property relations.

  4. Structure-property relationships in polymers for dielectric capacitors

    NASA Astrophysics Data System (ADS)

    Gupta, Sahil

    Effective energy storage is a key challenge of the 21st century that has fueled research in the area of energy storage devices. In this dissertation, structure-property relationships have been evaluated for polymers that might be suitable for storing energy in high-energy density, high-temperature capacitors. Firstly, hydroxyl-modified polypropylenes (PPOH) were synthesized by copolymerization of the propylene and undecenyloxytrimethylsilane monomers. The presence of H-bonding in PPOH copolymers increased their glass-transition temperature. Steric hindrance by the comonomer reduced the PP crystal growth rate and crystal size, resulting in a melting point depression. The comonomer was restricted outside the crystalline domains leaving the alpha-monoclinic crystal structure of PP unaffected, but increasing the fold-surface free energy. Crystallization was slower for PPOH copolymers than PP, but exhibited a skewed bell curve as a function of hydroxyl concentration. H-bonding persisted even at melt temperatures up to 250°C resulting in a higher elasticity and viscosity for PPOH copolymers. Secondly, sulfonated poly(ether ether ketone) (HSPEEK) was synthesized by sulfonating PEEK with sulfuric acid, and further neutralized with Zn to obtain ZnSPEEK. The thermal and dielectric properties of SPEEK were compared with PEEK. The glass-transition increased and melting point were high enough to enable the use of polymer at 180°C. The incorporation of sulfonic groups in PEEK increased the dielectric constant. HSPEEK had a higher dielectric constant than ZnSPEEK due to higher dipolar mobility, but the dielectric loss was also higher for HSPEEK due to electrode polarization and DC conduction. These results were consistent with our observations from sulfonated polystyrene (HSPS), which was used as a >model&lang' polymer. Lastly, commercial poly(4-methyl-1-pentene) (P4MP) was characterized to check its viability as a high-temperature polymer dielectric. Thermal stability up to

  5. Structure-property relationships in graphene/polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Iqbal, Muhammad Z.

    Graphene's unique combination of excellent electrical, thermal, and mechanical properties can provide multi-functional reinforcement for polymer nanocomposites. However, poor dispersion of graphene in non-polar polyolefins limits its applications as a universal filler. Thus, the overall goal of this thesis was to improve graphene's dispersion in graphene/polyolefin nanocomposites and develop processing-structure-property relationships. A new polymer matrix was synthesized by blending polyethylene (PE) with oxidized polyethylene (OPE). Inclusion of OPE in PE produced miscible blends, but the miscibility decreased with increasing OPE loading. Meanwhile, the Young's modulus of blends increased with increasing OPE concentration, attributed to decreased long period order in PE and increased crystallinity. In addition, the miscibility of OPE in PE substantially reduced the viscosity of blends. Using thermally reduced graphene (TRG) produced by simultaneous thermal exfoliation and reduction of graphite oxide, electrically conductive nanocomposites were manufactured by incorporating TRG in PE/OPE blends via solution blending. The rheological and electrical percolations decreased substantially to 0.3 and 0.13 vol% of TRG in PE/OPE/TRG nanocomposites compared to 1.0 and 0.3 vol% in PE/TRG nanocomposites. Improved dispersion of TRG in blends was attributed to increased TRG/polymer interactions, leading to high aspect ratio of the dispersed TRG. A universal Brownian dispersion mechanism for graphene was concluded similar to that of carbon nanotubes, following the Doi-Edwards theory. Furthermore, the improved dispersion of TRG correlated with the formation of surface fractals in PE/OPE/TRG nanocomposites, whereas the poor dispersion of TRG in PE led to the formation of only mass fractals. Moreover, graphene and carbon black (CB) were combined as a synergic filler for manufacturing electrically conductive PE nanocomposites. Smaller fractals were observed at lower CB

  6. Structure-property relationships of multiferroic materials: A nano perspective

    NASA Astrophysics Data System (ADS)

    Bai, Feiming

    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

  7. Structure-property relationships of flexible polyurethane foams

    NASA Astrophysics Data System (ADS)

    Aneja, Ashish

    This study examined several features of flexible polyurethane foams from a structure-property perspective. A major part of this dissertation addresses the issue of connectivity of the urea phase and its influence on mechanical and viscoelastic properties of flexible polyurethane foams and their plaque counterparts. Lithium salts (LiCl and LiBr) were used as additives to systematically alter the phase separation behavior, and hence the connectivity of the urea phase at different scale lengths. Macro connectivity, or the association of the large scale urea rich aggregates typically observed in flexible polyurethane foams was assessed using SAXS, TEM, and AFM. These techniques showed that including a lithium salt in the foam formulation suppressed the formation of the urea aggregates and thus led to a loss in the macro level connectivity of the urea phase. WAXS and FTIR were used to demonstrate that addition of LiCl or LiBr systematically disrupted the local ordering of the hard segments within the microdomains, i.e., it led to a reduction of micro level connectivity or the regularity in segmental packing of the urea phase. Based on these observations, the interaction of the lithium salt was thought to predominantly occur with the urea hard segments, and this hypothesis was confirmed using quantum mechanical calculations. Another feature of this research investigated model trisegmented polyurethanes based on monofunctional polyols, or "monos", with water-extended toluene diisocyanate (TDI) based hard segments. The formulations of the monol materials were maintained similar to those of flexible polyurethane foams with the exceptions that the conventional polyol was substituted by an oligomeric monofunctional polyether of ca. 1000 g/mol molecular weight. Plaques formed from these model systems were shown to be solid materials even at their relatively low molecular weights of 3000 g/mol and less, AFM phase images, for the first time, revealed the ability of the hard

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

    PubMed Central

    Liu, Fengping; Cao, Chenzhong; Cheng, Bin

    2011-01-01

    A quantitative structure–property relationship (QSPR) analysis of aliphatic alcohols is presented. Four physicochemical properties were studied: boiling point (BP), n-octanol–water partition coefficient (lg POW), water solubility (lg W) and the chromatographic retention indices (RI) on different polar stationary phases. In order to investigate the quantitative structure–property relationship of aliphatic alcohols, the molecular structure ROH is divided into two parts, R and OH to generate structural parameter. It was proposed that the property is affected by three main factors for aliphatic alcohols, alkyl group R, substituted group OH, and interaction between R and OH. On the basis of the polarizability effect index (PEI), previously developed by Cao, the novel molecular polarizability effect index (MPEI) combined with odd-even index (OEI), the sum eigenvalues of bond-connecting matrix (SX1CH) previously developed in our team, were used to predict the property of aliphatic alcohols. The sets of molecular descriptors were derived directly from the structure of the compounds based on graph theory. QSPR models were generated using only calculated descriptors and multiple linear regression techniques. These QSPR models showed high values of multiple correlation coefficient (R > 0.99) and Fisher-ratio statistics. The leave-one-out cross-validation demonstrated the final models to be statistically significant and reliable. PMID:21731451

  9. Structure-property relationships of electron-beam-irradiated monomeric and polymeric systems

    SciTech Connect

    Kim, Ha Chul.

    1989-01-01

    Structure-property relationships were investigated for electron beam (EB) irradiated monomeric and polymeric systems. The objectives were to study the feasibility of preparing systems of potential application, and to characterize these systems in terms of structure-property behavior. In this thesis, the basic theories on radiation chemistry were first reviewed. Next, five different studies on the application of EB radiation were discussed. In the first study on the surface modification of the methacyclic acid derivative of the glycidyl ether of bis-phenol A(bis-GMA) substrates, considerable changes in wetting characteristics were observed using functionalized poly(dimethyl siloxane) (PDMS) oligomers as surface modifiers. The second subject was utilized to cross-linked caprolactone-allyl glycidyl ether(CL-AGE) copolymers. EB radiation was utilized to crosslink these materials at various temperatures both above and below the crystalline melting point. In the third study, models of time-temperature-energy(TTE) diagrams in an idealized EB radiation curing system were developed to help provide a conceptual understanding of the TTE relationship. The fourth study focused on the effects of EB irradiation on the mechanical and thermal properties of poly(phenylene sulfide). In the fifth study, two systems(symmetric and asymmetric) based on the controlled distribution of bis-GMA within a crosslinked nitrile rubber(NBR) network were prepared utilizing EB irradiation.

  10. Structure-property study of keto-ether polyimides

    NASA Technical Reports Server (NTRS)

    Dezern, James F.; Croall, Catharine I.

    1991-01-01

    As part of an on-going effort to develop an understanding of how changes in the chemical structure affect polymer properties, an empirical study was performed on polyimides containing only ether and/or carbonyl connecting groups in the polymer backbone. During the past two decades the structure-property relationships in linear aromatic polyimides have been extensively investigated. More recently, work has been performed to study the effect of isomeric attachment of keto-ether polyimides on properties such as glass transition temperature and solubility. However, little work has been reported on the relation of polyimide structure to mechanical properties. The purpose of this study was to determine the effect of structural changes in the backbone of keto-ether polyimides on their mechanical properties, specifically, unoriented thin film tensile properties. This study was conducted in two stages. The purpose of the initial stage was to examine the physical and mechanical properties of a representative group (four) of polyimide systems to determine the optimum solvent and cure cycle requirements. These optimum conditions were then utilized in the second stage to prepare films of keto-ether polyimides which were evaluated for mechanical and physical properties. All of the polyimides were prepared using isomers of oxydianiline (ODA) and diaminobenzophenone (DABP) in combination with 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-oxydiphthalic anhydride (ODPA).

  11. Structure-Property-Function Relationship in Humic Substances to Explain the Biological Activity in Plants

    PubMed Central

    García, Andrés Calderín; de Souza, Luiz Gilberto Ambrosio; Pereira, Marcos Gervasio; Castro, Rosane Nora; García-Mina, José María; Zonta, Everaldo; Lisboa, Francy Junior Gonçalves; Berbara, Ricardo Luis Louro

    2016-01-01

    Knowledge of the structure-property-function relationship of humic substances (HSs) is key for understanding their role in soil. Despite progress, studies on this topic are still under discussion. We analyzed 37 humic fractions with respect to their isotopic composition, structural characteristics, and properties responsible for stimulating plant root parameters. We showed that regardless of the source of origin of the carbon (C3 or C4), soil-extracted HSs and humic acids (HAs) are structurally similar to each other. The more labile and functionalized HS fraction is responsible for root emission, whereas the more recalcitrant and less functionalized HA fraction is related to root growth. Labile structures promote root stimulation at lower concentrations, while recalcitrant structures require higher concentrations to promote a similar stimulus. These findings show that lability and recalcitrance, which are derived properties of humic fractions, are related to the type and intensity of their bioactivity. In summary, the comparison of humic fractions allowed a better understanding of the relationship between the source of origin of plant carbon and the structure, properties, and type and intensity of the bioactivity of HSs in plants. In this study, scientific concepts are unified and the basis for the agronomic use of HSs is established. PMID:26862010

  12. Structure-Property-Function Relationship in Humic Substances to Explain the Biological Activity in Plants

    NASA Astrophysics Data System (ADS)

    García, Andrés Calderín; de Souza, Luiz Gilberto Ambrosio; Pereira, Marcos Gervasio; Castro, Rosane Nora; García-Mina, José María; Zonta, Everaldo; Lisboa, Francy Junior Gonçalves; Berbara, Ricardo Luis Louro

    2016-02-01

    Knowledge of the structure-property-function relationship of humic substances (HSs) is key for understanding their role in soil. Despite progress, studies on this topic are still under discussion. We analyzed 37 humic fractions with respect to their isotopic composition, structural characteristics, and properties responsible for stimulating plant root parameters. We showed that regardless of the source of origin of the carbon (C3 or C4), soil-extracted HSs and humic acids (HAs) are structurally similar to each other. The more labile and functionalized HS fraction is responsible for root emission, whereas the more recalcitrant and less functionalized HA fraction is related to root growth. Labile structures promote root stimulation at lower concentrations, while recalcitrant structures require higher concentrations to promote a similar stimulus. These findings show that lability and recalcitrance, which are derived properties of humic fractions, are related to the type and intensity of their bioactivity. In summary, the comparison of humic fractions allowed a better understanding of the relationship between the source of origin of plant carbon and the structure, properties, and type and intensity of the bioactivity of HSs in plants. In this study, scientific concepts are unified and the basis for the agronomic use of HSs is established.

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

    SciTech Connect

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

    1993-05-01

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

  14. Structure-Property Relationship in Metal Carbides and Bimetallic Alloys

    SciTech Connect

    Chen, Jingguan

    2014-03-04

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

  15. Structure-Property Relationships in Sulfonated Pentablock Copolymers

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    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.

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

    SciTech Connect

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

    2011-12-31

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

  17. Application of quantitative structure-property relationship analysis to estimate the vapor pressure of pesticides.

    PubMed

    Goodarzi, Mohammad; Coelho, Leandro dos Santos; Honarparvar, Bahareh; Ortiz, Erlinda V; Duchowicz, Pablo R

    2016-06-01

    The application of molecular descriptors in describing Quantitative Structure Property Relationships (QSPR) for the estimation of vapor pressure (VP) of pesticides is of ongoing interest. In this study, QSPR models were developed using multiple linear regression (MLR) methods to predict the vapor pressure values of 162 pesticides. Several feature selection methods, namely the replacement method (RM), genetic algorithms (GA), stepwise regression (SR) and forward selection (FS), were used to select the most relevant molecular descriptors from a pool of variables. The optimum subset of molecular descriptors was used to build a QSPR model to estimate the vapor pressures of the selected pesticides. The Replacement Method improved the predictive ability of vapor pressures and was more reliable for the feature selection of these selected pesticides. The results provided satisfactory MLR models that had a satisfactory predictive ability, and will be important for predicting vapor pressure values for compounds with unknown values. This study may open new opportunities for designing and developing new pesticide.

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

    PubMed

    Khajeh, A; Modarress, H

    2014-01-01

    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

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

    PubMed

    Dearden, John C

    2003-08-01

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

  20. Structure-property relationships in major ampullate spider silk as deduced from polarized FTIR spectroscopy.

    PubMed

    Papadopoulos, P; Sölter, J; Kremer, F

    2007-10-01

    Polarized Fourier Transform Infrared (FTIR) spectroscopy is employed to study structure-property relationships in major ampullate spider silk being exposed to an external mechanical strain. From the measured infrared dichroism of aminoacid-residue - specific bands the molecular order parameter, the frequency width at half-maximum (FWHM) and the spectral position of the absorption maximum are determined in dependence on the external strain. For the highly ordered alanine-rich beta sheets a change in the vibrational potential is found for macroscopic strains as low as a few percent. It can be quantitatively described by a quantum-mechanical approach in which the mechanical strain is treated as a weak external perturbation. The immediate microscopic response to the external field proves that beta -sheeted crystals are tightly interconnected by pre-stretched chains as suggested recently (Y. Liu et al., Nat. Mater. 4, 901 (2005)).

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

    ERIC Educational Resources Information Center

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

    2013-01-01

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

  2. Density Functional Study of the structural properties in Tamoxifen

    NASA Astrophysics Data System (ADS)

    de Coss-Martinez, Romeo; Tapia, Jorge A.; Quijano-Quiñones, Ramiro F.; Canto, Gabriel I.

    2013-03-01

    Using the density functional theory, we have studied the structural properties of Tamoxifen. The calculations were performed with two methodological approaches, which were implemented in SIESTA and Spartan codes. For SIESTA, we considerate a linear combination of atomic orbitals method, using pseudopotentials and the van der Waals approximation for the exchange-correlation potential. Here we analyzed and compared the atomic structure between our results and other theoretical study. We found differences in the bond lengths between the results, that could be attributed to code approaches in each one. This work was supported under Grant FOMIX 2011-09 N: 170297 of Ph.D. A. Tapia.

  3. Structure-property relationships of anionic permselective membranes. [Fe/Cr redox storage batteries

    SciTech Connect

    Arnold, C. Jr.

    1983-01-01

    Anionic exchange membranes are used in Fe/Cr redox storage batteries to separate the anolyte from the catholyte and provide electrical continuity. Membranes with lower area resistivity, higher selectivity and reduced susceptibility toward fouling are required to improve the efficiency and lifetime of these batteries. In order to develop improved membrane, a better understanding of the relationships between these properties and such structural parameters as degree of crosslinking, ion exchange capacity and porosity were needed. The primary objective of this work was to define the structure-property relationships of anionic permselective membranes. A secondary goal was to develop empirical models which can be used to predict membrane performance. This kind of information should be useful for the development of improved membranes. To accomplish these goals a factorial study was carried out with model membranes. These membranes were designed in such a way that all three structural parameters could be varied independently. In this paper it will be shown how this approach not only provided models which could be used to predict membrane performance, but also how one of the model membrane exhibited better properties than state-of-the-art membranes.

  4. Development of quantitative structure property relationships for predicting the melting point of energetic materials.

    PubMed

    Morrill, Jason A; Byrd, Edward F C

    2015-11-01

    The accurate prediction of the melting temperature of organic compounds is a significant problem that has eluded researchers for many years. The most common approach used to develop predictive models entails the derivation of quantitative structure-property relationships (QSPRs), which are multivariate linear relationships between calculated quantities that are descriptors of molecular or electronic features and a property of interest. In this report the derivation of QSPRs to predict melting temperatures of energetic materials based on descriptors calculated using the AM1 semiempirical quantum mechanical method are described. In total, the melting points and experimental crystal structures of 148 energetic materials were analyzed. Principal components analysis was performed in order to assess the relative importance and roles of the descriptors in our QSPR models. Also described are the results of k means cluster analysis, performed in order to identify natural groupings within our study set of structures. The QSPR models resulting from these analyses gave training set R(2) values of 0.6085 (RMSE = ± 15.7 °C) and 0.7468 (RMSE = ± 13.2 °C). The test sets for these clusters had R(2) values of 0.9428 (RMSE = ± 7.0 °C) and 0.8974 (RMSE = ± 8.8 °C), respectively. These models are among the best melting point QSPRs yet published for energetic materials.

  5. Grain boundary plane orientation fundamental zones and structure-property relationships

    DOE PAGES

    Homer, Eric R.; Patala, Srikanth; Priedeman, Jonathan L.

    2015-10-26

    Grain boundary plane orientation is a profoundly important determinant of character in polycrystalline materials that is not well understood. This work demonstrates how boundary plane orientation fundamental zones, which capture the natural crystallographic symmetries of a grain boundary, can be used to establish structure-property relationships. Using the fundamental zone representation, trends in computed energy, excess volume at the grain boundary, and temperature-dependent mobility naturally emerge and show a strong dependence on the boundary plane orientation. Analysis of common misorientation axes even suggests broader trends of grain boundary energy as a function of misorientation angle and plane orientation. Due to themore » strong structure-property relationships that naturally emerge from this work, boundary plane fundamental zones are expected to simplify analysis of both computational and experimental data. This standardized representation has the potential to significantly accelerate research in the topologically complex and vast five-dimensional phase space of grain boundaries.« less

  6. Grain boundary plane orientation fundamental zones and structure-property relationships

    SciTech Connect

    Homer, Eric R.; Patala, Srikanth; Priedeman, Jonathan L.

    2015-10-26

    Grain boundary plane orientation is a profoundly important determinant of character in polycrystalline materials that is not well understood. This work demonstrates how boundary plane orientation fundamental zones, which capture the natural crystallographic symmetries of a grain boundary, can be used to establish structure-property relationships. Using the fundamental zone representation, trends in computed energy, excess volume at the grain boundary, and temperature-dependent mobility naturally emerge and show a strong dependence on the boundary plane orientation. Analysis of common misorientation axes even suggests broader trends of grain boundary energy as a function of misorientation angle and plane orientation. Due to the strong structure-property relationships that naturally emerge from this work, boundary plane fundamental zones are expected to simplify analysis of both computational and experimental data. This standardized representation has the potential to significantly accelerate research in the topologically complex and vast five-dimensional phase space of grain boundaries.

  7. Grain Boundary Plane Orientation Fundamental Zones and Structure-Property Relationships

    PubMed Central

    Homer, Eric R.; Patala, Srikanth; Priedeman, Jonathan L.

    2015-01-01

    Grain boundary plane orientation is a profoundly important determinant of character in polycrystalline materials that is not well understood. This work demonstrates how boundary plane orientation fundamental zones, which capture the natural crystallographic symmetries of a grain boundary, can be used to establish structure-property relationships. Using the fundamental zone representation, trends in computed energy, excess volume at the grain boundary, and temperature-dependent mobility naturally emerge and show a strong dependence on the boundary plane orientation. Analysis of common misorientation axes even suggests broader trends of grain boundary energy as a function of misorientation angle and plane orientation. Due to the strong structure-property relationships that naturally emerge from this work, boundary plane fundamental zones are expected to simplify analysis of both computational and experimental data. This standardized representation has the potential to significantly accelerate research in the topologically complex and vast five-dimensional phase space of grain boundaries. PMID:26498715

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

    NASA Astrophysics Data System (ADS)

    Vilayurganapathy, Subramanian

    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

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

    PubMed

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

    2014-04-15

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

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

    NASA Astrophysics Data System (ADS)

    Rodgers, Marianne Phelan

    The chemical and structural features of proton exchange membranes (PEMs) are related to their fuel cell relevant properties. The objective of this work is to understand structure-property relationships in PEMs through the fabrication and characterization of several classes of membranes. Incorporation of linear and angled monomers into the main chain of a polyimide permitted investigation of the effect of kinked versus linear polymers on membrane properties. The conductivity of angled sulfonated polyimide membranes is greater than those prepared from linear polymers, but water uptakes are lower. These differences are attributed to increased entanglements of angled polymers, which limit the degree of swelling and lead to increased proton concentration. Polyelectrolytes were incorporated into reinforcing materials to study the effect of incorporating and confining polyelectrolytes in the pores of reinforcing materials. The employment of reinforcing materials reduces conductivity, mobility, and permeance due to decreased ionomer content and connectivity of the ionomer. However, membranes are stronger and thinner, which compensates for these losses in terms of lower resistance and increased dimensional stability. Incorporating zirconium hydrogen phosphate (ZrP) and silicon dioxide (SiO2) into NafionRTM membranes permitted investigation of their effect on membrane properties. Data for NafionRTM/ZrP membranes support the theory that ZrP disrupts cohesive forces in Nafion RTM, causing it to absorb more water. The increased water content of the membranes does not result in increased conductivity because there is a concurrent decrease in proton concentration and mobility due to poorly conducting ZrP disrupting the conduction pathway and increased water content diluting protons and separating proton conduction sites. The decreasing density of the NafionRTM/SiO2 composite membranes with increasing SiO2 content and the increased dimensional stability of the membranes increasing

  11. Studies on structural properties of clay magnesium ferrite nano composite

    SciTech Connect

    Kaur, Manpreet Singh, Mandeep; Jeet, Kiran Kaur, Rajdeep

    2015-08-28

    Magnesium ferrite-bentonite clay composite was prepared by sol-gel combustion method employing citric acid as complexing agent and fuel. The effect of clay on the structural properties was studied with X-ray diffraction (XRD), Fourier transform infrared (FT-IR) Spectroscopy, Scanning electron microscopy (SEM), SEM- Energy dispersive Spectroscope (EDS) and BET surface area analyzer. Decrease in particle size and density was observed on addition of bentonite clay. The BET surface area of nano composite containing just 5 percent clay was 74.86 m{sup 2}/g. Whereas porosity increased from 40.5 per cent for the pure magnesium ferrite to 81.0 percent in the composite showing that nano-composite has potential application as an adsorbent.

  12. Structure-property relationships of photoresponsive inhibitors of the kinesin motor.

    PubMed

    Amrutha, Ammathnadu S; Kumar, K R Sunil; Matsuo, Kazuya; Tamaoki, Nobuyuki

    2016-07-26

    Recently we demonstrated the photoregulation of the activity of kinesin-1 using an azobenzene-tethered peptide (azo-peptide: Azo-Ile-Pro-Lys-Ala-Ile-Gln-Ala-Ser-His-Gly-Arg-OH). To understand the mechanism behind this photoswitchable inhibition, here we studied the structure-property relationships of a range of azo-peptides through systematic variations in the structures of the peptide and azobenzene units. The vital peptide sequence for kinesin inhibition-mediated through electrostatic, hydrophobic and C-Hπ interactions-was the same as that for the self-inhibition of kinesin. We also identified substituents on the azobenzene capable of enhancing the photoswitchability of inhibition. As a result, we developed a new inhibitor featuring a relatively short peptide unit (-Arg-Ile-Pro-Lys-Ala-Ile-Arg-OH) and an azobenzene unit bearing a para-OMe group. In the trans form of its azobenzene unit, this finely tuned inhibitor stopped the kinesin-driven gliding motility of microtubules completely at a relatively low concentration, yet allowed gliding motility with a relatively high velocity in the cis form obtained after UV irradiation. PMID:27270305

  13. Quantitative structure-property relationship modeling of remote liposome loading of drugs.

    PubMed

    Cern, Ahuva; Golbraikh, Alexander; Sedykh, Aleck; Tropsha, Alexander; Barenholz, Yechezkel; Goldblum, Amiram

    2012-06-10

    Remote loading of liposomes by trans-membrane gradients is used to achieve therapeutically efficacious intra-liposome concentrations of drugs. We have developed Quantitative Structure Property Relationship (QSPR) models of remote liposome loading for a data set including 60 drugs studied in 366 loading experiments internally or elsewhere. Both experimental conditions and computed chemical descriptors were employed as independent variables to predict the initial drug/lipid ratio (D/L) required to achieve high loading efficiency. Both binary (to distinguish high vs. low initial D/L) and continuous (to predict real D/L values) models were generated using advanced machine learning approaches and 5-fold external validation. The external prediction accuracy for binary models was as high as 91-96%; for continuous models the mean coefficient R(2) for regression between predicted versus observed values was 0.76-0.79. We conclude that QSPR models can be used to identify candidate drugs expected to have high remote loading capacity while simultaneously optimizing the design of formulation experiments.

  14. Relationships between physical and structural properties of intramuscular connective tissue and toughness of raw pork.

    PubMed

    Nishimura, Takanori; Fang, Suhong; Wakamatsu, Jun-ichi; Takahashi, Koui

    2009-02-01

    We studied the relationships between the shear-force value and physical and structural properties of the intramuscular connective tissue (IMCT) in six classes of porcine skeletal muscle to elucidate the contribution of IMCT to toughness of raw pork. The shear-force value of raw pork correlated significantly with that of the IMCT model prepared from each class of skeletal muscle (P < 0.05). The correlation suggested that the variable toughness of pork was caused by the mechanical strength of the endomysium and perimysium. The thickness of the secondary perimysium correlated significantly with the shear-force value of raw pork (P < 0.05) and with that of the IMCT model (P < 0.05). The shear-force value of raw pork correlated significantly with the total amount of collagen (P < 0.05) but not with the heat-solubility of collagen. We concluded therefore that the thickness of the secondary perimysium determines the mechanical strength of IMCT and contributes to toughness in raw pork.

  15. Quantitative structure-property relationship modeling of remote liposome loading of drugs.

    PubMed

    Cern, Ahuva; Golbraikh, Alexander; Sedykh, Aleck; Tropsha, Alexander; Barenholz, Yechezkel; Goldblum, Amiram

    2012-06-10

    Remote loading of liposomes by trans-membrane gradients is used to achieve therapeutically efficacious intra-liposome concentrations of drugs. We have developed Quantitative Structure Property Relationship (QSPR) models of remote liposome loading for a data set including 60 drugs studied in 366 loading experiments internally or elsewhere. Both experimental conditions and computed chemical descriptors were employed as independent variables to predict the initial drug/lipid ratio (D/L) required to achieve high loading efficiency. Both binary (to distinguish high vs. low initial D/L) and continuous (to predict real D/L values) models were generated using advanced machine learning approaches and 5-fold external validation. The external prediction accuracy for binary models was as high as 91-96%; for continuous models the mean coefficient R(2) for regression between predicted versus observed values was 0.76-0.79. We conclude that QSPR models can be used to identify candidate drugs expected to have high remote loading capacity while simultaneously optimizing the design of formulation experiments. PMID:22154932

  16. Processing-Structure-Property Relationships in Laser-Annealed PbSe Nanocrystal Thin Films.

    PubMed

    Treml, Benjamin E; Robbins, Andrew B; Whitham, Kevin; Smilgies, Detlef-M; Thompson, Michael O; Hanrath, Tobias

    2015-01-01

    As nanocrystal (NC) synthesis techniques and device architectures advance, it becomes increasingly apparent that new ways of connecting NCs with each other and their external environment are required to realize their considerable potential. Enhancing inter-NC coupling by thermal annealing has been a long-standing challenge. Conventional thermal annealing approaches are limited by the challenge of annealing the NC at sufficiently high temperatures to remove surface-bound ligands while at the same time limiting the thermal budget to prevent large-scale aggregation. Here we investigate nonequilibrium laser annealing of NC thin films that enables separation of the kinetic and thermodynamic aspects of nanocrystal fusion. We show that laser annealing of NC assemblies on nano- to microsecond time scales can transform initially isolated NCs in a thin film into an interconnected structure in which proximate dots "just touch". We investigate both pulsed laser annealing and laser spike annealing and show that both annealing methods can produce "confined-but-connected" nanocrystal films. We develop a thermal transport model to rationalize the differences in resulting film morphologies. Finally we show that the insights gained from study of nanocrystal mono- and bilayers can be extended to three-dimensional NC films. The basic processing-structure-property relationships established in this work provide guidance to future advances in creating functional thin films in which constituent NCs can purposefully interact.

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

    PubMed

    Luilo, G B; Cabaniss, S E

    2011-10-01

    Chlorinating water which contains dissolved organic matter (DOM) produces disinfection byproducts, the majority of unknown structure. Hence, the total organic halide (TOX) measurement is used as a surrogate for toxic disinfection byproducts. This work derives a robust quantitative structure-property relationship (QSPR) for predicting the TOX formation potential of model compounds. Literature data for 49 compounds were used to train the QSPR in moles of chlorine per mole of compound (Cp) (mol-Cl/mol-Cp). The resulting QSPR has four descriptors, calibration [Formula: see text] of 0.72 and standard deviation of estimation of 0.43 mol-Cl/mol-Cp. Internal and external validation indicate that the QSPR has good predictive power and low bias (‰<‰1%). Applying this QSPR to predict TOX formation by DOM surrogates - tannic acid, two model fulvic acids and two agent-based model assemblages - gave a predicted TOX range of 136-184 µg-Cl/mg-C, consistent with experimental data for DOM, which ranged from 78 to 192 µg-Cl/mg-C. However, the limited structural variation in the training data may limit QSPR applicability; studies of more sulfur-containing compounds, heterocyclic compounds and high molecular weight compounds could lead to a more widely applicable QSPR.

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

    NASA Astrophysics Data System (ADS)

    Luo, Sida

    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

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

    PubMed

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

    2014-07-01

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

  20. Boiling points of halogenated aliphatic compounds: a quantitative structure-property relationship for prediction and validation.

    PubMed

    Oberg, Tomas

    2004-01-01

    Halogenated aliphatic compounds have many technical uses, but substances within this group are also ubiquitous environmental pollutants that can affect the ozone layer and contribute to global warming. The establishment of quantitative structure-property relationships is of interest not only to fill in gaps in the available database but also to validate experimental data already acquired. The three-dimensional structures of 240 compounds were modeled with molecular mechanics prior to the generation of empirical descriptors. Two bilinear projection methods, principal component analysis (PCA) and partial-least-squares regression (PLSR), were used to identify outliers. PLSR was subsequently used to build a multivariate calibration model by extracting the latent variables that describe most of the covariation between the molecular structure and the boiling point. Boiling points were also estimated with an extension of the group contribution method of Stein and Brown.

  1. Processing-structure-property relationships in uni- and biaxially stretched binary and ternary blends

    NASA Astrophysics Data System (ADS)

    Zhou, Xixian

    Processing-structure-property relationships in uni and biaxially stretched PVDF/PMMA binary blends and PEN/PEI/PEEK ternary blends were investigated using a variety of characterization techniques that probe the structure at different levels. PVDF is a fast crystallizing polymer. It can form amorphous blends with PMMA which is fairly easy to process in their rubbery region. At the stretching temperature up to Tg + 10 ˜ 15sp°C, the blends with PVDF fraction more than 55 exhibit yielding due to the presence of the crystalline superstructure yet stress crystallizable films. The yielding and associated neck formation gradually disappear for the blends containing less than 55 wt%. The thickness uniformity and surface smoothness of the produced films are improved in these films upon stretching particularly when the influence of stress hardening is present. This causes self leveling in the films. At the lower stretch ratios (ca. lambdasbMD\\ ≤ 3x), 55/45 blend shows no crystallinity and crystalline orientation. Beyond this point, very highly oriented crystalline domains emerge. This is as a result of dilution effect at such compositions where the entanglement density of the PVDF chains is reduced thereby increasing efficiency of orientation that resembles crystallization from dilute solutions except in this case the solvent is the PMMA phase. Stretching converts the crystalline phase from alpha to beta in 85/15 and 70/30 wt% blends, while in 55/15 blend the crystalline regions are exclusively in beta form. A combination of four point diagrams with "lozenge" shape appears in SAXS patterns. A structure model has been proposed based on the three-phase morphology and SAXS theory. In this study, we concentrated on the biaxial stretching behavior of PEN rich and PEI rich crystallizable PEN/PEI/PEEK ternary blends. The main objective was to increase the glass transition temperature of the blends containing large fraction of PEN while maintaining strain induced

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

    PubMed

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

    2014-12-16

    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

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

    PubMed

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

    2014-12-16

    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

  4. Structure-property relationships in halogenbenzoic acids: Thermodynamics of sublimation, fusion, vaporization and solubility.

    PubMed

    Zherikova, Kseniya V; Svetlov, Aleksey A; Kuratieva, Natalia V; Verevkin, Sergey P

    2016-10-01

    Temperature dependences of vapor pressures for 2-, 3-, and 4-bromobenzoic acid, as well as for five isomeric bromo-methylbenzoic acids were studied by the transpiration method. Melting temperatures and enthalpies of fusion for all isomeric bromo-methylbenzoic acids and 4-bromobenzoic acid were measured with a DSC. The molar enthalpies of sublimation and vaporization were derived. These data together with results available in the literature were collected and checked for internal consistency using a group-additivity procedure and results from X-ray structural diffraction studies. Specific (hydrogen bonding) interactions in the liquid and in the crystal phase of halogenbenzoic acids were quantified based on experimental values of vaporization and sublimation enthalpies. Structure-property correlations of solubilities of halogenobenzoic acids with sublimation pressures and sublimation enthalpies were developed and solubilities of bromo-benzoic acids were estimated. These new results resolve much of the ambiguity in the available thermochemical and solubility data on bromobenzoic acids. The approach based on structure property correlations can be applied for the assessment of water solubility of sparingly soluble drugs. PMID:27424058

  5. TECHNIQUES FOR THE STUDY OF THE STRUCTURAL PROPERTIES.

    SciTech Connect

    FERNANDEZ-GARCIA, M.; RODRIGUEZ, J.A.; MARTINEZ-ARIAS, A.; HANSON, J.C.

    2006-06-30

    The evolution of our understanding of the behavior of oxide nanostructures depends heavily on the structural information obtained from a wide range of physical methods traditionally used in solid state physics, surface science and inorganic chemistry. In this chapter, we describe several techniques that are useful for the characterization of the structural properties of oxide nanostructures: X-ray diffraction (XRD) and scattering, X-ray absorption fine structure (XAFS), Raman spectroscopy, transmission electron microscopy (TEM), scanning tunneling microscopy (STM) and atomic force microscopy (AFM). The ultimate goal is to obtain information about the spatial arrangement of atoms in the nanostructures with precise interatomic distances and bond angles. This may not be possible for complex systems and one may get only partial information about the local geometry or morphology.

  6. New ganglio-tripod amphiphiles (TPAs) for membrane protein solubilization and stabilization: implications for detergent structure-property relationships.

    PubMed

    Chae, Pil Seok; Bae, Hyoung Eun; Ehsan, Muhammad; Hussain, Hazrat; Kim, Jin Woong

    2014-11-14

    Detergents are widely used for membrane protein research; however, membrane proteins encapsulated in micelles formed by conventional detergents tend to undergo structural degradation, necessitating the development of new agents with enhanced efficacy. Here we prepared several hydrophobic variants of ganglio-tripod amphiphiles (TPAs) derived from previously reported TPAs and evaluated for a multi-subunit, pigment protein superassembly. In this study, TPA-16 was found to be most efficient in protein solubilization while TPA-15 proved most favourable in long-term protein stability. The current study combined with previous TPA studies enabled us to elaborate on a few detergent structure-property relationships that could provide useful guidelines for novel amphiphile design.

  7. Structure/property relationships in polymer membranes for water purification and energy applications

    NASA Astrophysics Data System (ADS)

    Geise, Geoffrey

    Providing sustainable supplies of purified water and energy is a critical global challenge for the future, and polymer membranes will play a key role in addressing these clear and pressing global needs for water and energy. Polymer membrane-based processes dominate the desalination market, and polymer membranes are crucial components in several rapidly developing power generation and storage applications that rely on membranes to control rates of water and/or ion transport. Much remains unknown about the influence of polymer structure on intrinsic water and ion transport properties, and these relationships must be developed to design next generation polymer membrane materials. For desalination applications, polymers with simultaneously high water permeability and low salt permeability are desirable in order to prepare selective membranes that can efficiently desalinate water, and a tradeoff relationship between water/salt selectivity and water permeability suggests that attempts to prepare such materials should rely on approaches that do more than simply vary polymer free volume. One strategy is to functionalize hydrocarbon polymers with fixed charge groups that can ionize upon exposure to water, and the presence of charged groups in the polymer influences transport properties. Additionally, in many emerging energy applications, charged polymers are exposed to ions that are very different from sodium and chloride. Specific ion effects have been observed in charged polymers, and these effects must be understood to prepare charged polymers that will enable emerging energy technologies. This presentation discusses research aimed at further understanding fundamental structure/property relationships that govern water and ion transport in charged polymer films considered for desalination and electric potential field-driven applications that can help address global needs for clean water and energy.

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

    NASA Astrophysics Data System (ADS)

    Hule, Rohan A.

    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

  9. Structure-property relationships of small bandgap conjugated polymers for solar cells.

    PubMed

    Hellström, Stefan; Zhang, Fengling; Inganäs, Olle; Andersson, Mats R

    2009-12-01

    Conjugated polymers as electron donors in solar cells based on donor/acceptor combinations are of great interest, partly due to the possibility of converting solar light with a low materials budget. Six small bandgap polymers with optical bandgap ranging from 1.0-1.9 eV are presented in this paper. All polymers utilize an electron donor-acceptor-donor (DAD) segment in the polymer backbone, creating a partial charge-transfer, to decrease the bandgap. The design, synthesis and the optical characteristics as well as the solar cell characteristics of the polymers are discussed. The positions of the energy levels of the conjugated polymer relative to the electron acceptor are of significant importance and determine not only the driving force for exciton dissociation but also the maximum open-circuit voltage. This work also focuses on investigating the redox behavior of the described conjugated polymers and electron acceptors using square wave voltammetry. Comparing the electrochemical data gives important information of the structure-property relationships of the polymers.

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

    SciTech Connect

    Cummins, T.R.; Waddill, G.D.; Goodman, K.W.

    1997-04-01

    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.

  11. Determination of Quantitative Structure-Property Relationships of Solvent Resistance of Polycarbonate Copolymers Using a Resonant Multisensor System

    NASA Astrophysics Data System (ADS)

    Potyrailo, Radislav A.; Wroczynski, Ronald J.; McCloskey, Patrick J.; Morris, William G.

    In sensor and microfluidic applications, the need is to have an adequate solvent resistance of polymers to prevent degradation of the substrate surface upon deposition of sensor formilations, to prevent contamination of the solvent-containing sensor formulations or contamination of organic liquid reactions in microfluidic channels. Unfortunately, no comprehensive quantitative reference solubility data of unstressed copolymers is available to date. In this study, we evaluate solvent-resistance of several polycarbonate copolymers prepared from the reaction of hydroquinone (HQ), resorcinol (RS), and bisphenol A (BPA). Our high-throughput polymer evaluation approach permitted the construction of detailed solvent-resistance maps, the development of quantitative structure-property relationships for BPA-HQ-RS copolymers and provided new knowledge for the further development of the polymeric sensor and microfluidic components.

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

    NASA Astrophysics Data System (ADS)

    Cook, David James

    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

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

    NASA Astrophysics Data System (ADS)

    Stringer, Craig J.

    temperature (Tf) of ˜150°C. Static and in-situ transmission electron microscopy investigations of the BS-PMN-PT compositions demonstrated a frustrated microstructure of nanometer scale regions and were used to establish structure-property relationships with different electric field and thermal histories. A comparative study of the key relaxor parameters, EA, T f, and TD was tabulated with previously investigated relaxor ferroelectrics. These parameters were found to scale relative to other lead-based perovskite relaxor ferroelectric compounds and solid solutions, with the BS-PMN-PT ternary system exhibiting the highest temperature behavior. Finally, to demonstrate one possible application area for these materials, multilayer ceramic capacitor devices were designed for operation at 300°C and up to 10 kHz. The voltage saturation was found to be extremely encouraging at 300°C with observed changes in capacitance (˜3%) on the application of 10 kV/cm. The insulation resistivity followed an Arrhenius behavior and at 300°C was ˜1010 O-cm. Weibull statistics were used to estimate a characteristic breakdown field at 300°C for the BS-PMN-PT multilayer capacitors of ˜40 kV/cm. Current-voltage measurements were performed to voltages up to breakdown and exhibited Ohmic behavior, indicating intrinsically controlled conduction. Highly accelerated life time tests were performed on BS-PMN-PT capacitors. It was observed that silver migration from termination electrodes caused premature failure at elevated temperature.

  14. Empirical study on structural properties in temporal networks under different time scales

    NASA Astrophysics Data System (ADS)

    Chen, Duanbing

    2015-12-01

    Many network analyzing methods are usually based on static networks. However, temporal networks should be considered so as to investigate real complex systems deeply since some dynamics on these systems cannot be described by static networks accurately. In this paper, four structural properties in temporal networks are empirically studied, including degree, clustering coefficient, adjacent correlation, and connected component. Three real temporal networks with different time scales are analyzed in this paper, including short message, telephone, and router networks. Moreover, structural properties of these temporal networks are compared with that of corresponding static aggregation networks in the whole time window. Some essential differences of structural properties between temporal and static networks are achieved through empirical analysis. Finally, the effect of structural properties on spreading dynamics under different time scales is investigated. Some interesting results such as turning point of structure evolving time scale corresponding to certain spreading dynamics time scale from the point of view of infected scale are achieved.

  15. The Structure-property Relationships of D-π-A BODIPY Dyes for Dye-sensitized Solar Cells.

    PubMed

    Mao, Mao; Song, Qin-Hua

    2016-04-01

    BODIPY dyes have attracted considerable attention as potential photosensitizers in dye-sensitized solar cells (DSSCs) owing to their excellent optical properties and facile structural modification. This account focuses on recent advances in the molecular design of D-π-A BODIPY dyes for applications in DSSCs. Special attention has been paid to the structure-property relationships of D-π-A BODIPY dyes for DSSCs. The developmental process in the modified position at the BODIPY core with a donor/acceptor is described. The devices based on 2,6-modified BODIPY dyes exhibit better photovoltaic performance over other modified BODIPY dyes. Meanwhile, the research reveals the correlation of molecular structures (various donor chromophores, extended units, molecular frameworks, and long alkyl groups) with their photophysical and electrochemical properties and relates it to their performance in DSSCs. The structure-property relationships give valuable information and guidelines for designing new D-π-A BODIPY dyes for DSSCs. PMID:26846846

  16. The Structure-property Relationships of D-π-A BODIPY Dyes for Dye-sensitized Solar Cells.

    PubMed

    Mao, Mao; Song, Qin-Hua

    2016-04-01

    BODIPY dyes have attracted considerable attention as potential photosensitizers in dye-sensitized solar cells (DSSCs) owing to their excellent optical properties and facile structural modification. This account focuses on recent advances in the molecular design of D-π-A BODIPY dyes for applications in DSSCs. Special attention has been paid to the structure-property relationships of D-π-A BODIPY dyes for DSSCs. The developmental process in the modified position at the BODIPY core with a donor/acceptor is described. The devices based on 2,6-modified BODIPY dyes exhibit better photovoltaic performance over other modified BODIPY dyes. Meanwhile, the research reveals the correlation of molecular structures (various donor chromophores, extended units, molecular frameworks, and long alkyl groups) with their photophysical and electrochemical properties and relates it to their performance in DSSCs. The structure-property relationships give valuable information and guidelines for designing new D-π-A BODIPY dyes for DSSCs.

  17. Structure-Property Study of Piezoelectricity in Polyimides

    NASA Technical Reports Server (NTRS)

    Ounaies, Zoubeida; Park, Cheol; Harrison, Joycelyn S.; Smith, Joseph G.; Hinkley, Jeffrey

    1999-01-01

    High performance piezoelectric polymers are of interest to NASA as they may be useful for a variety of sensor applications. Over the past few years research on piezoelectric polymers has led to the development of promising high temperature piezoelectric responses in some novel polyimides. In this study, a series of polyimides have been studied with systematic variations in the diamine monomers that comprise the polyimide while holding the dianhydride constant. The effect of structural changes, including variations in the nature and concentration of dipolar groups, on the remanent polarization and piezoelectric coefficient is examined. Fundamental structure-piezoelectric property insight will enable the molecular design of polymers possessing distinct improvements over state-of-the-art piezoelectric polymers including enhanced polarization, polarization stability at elevated temperatures, and improved processability.

  18. A study of the mechanical and structural properties ofpolonium

    SciTech Connect

    Kraig, Robert E.; Roundy, David; Cohen, Marvin L.

    2003-05-15

    We have performed an ab initio study of the structure of polonium. By calculating total energies in a number of tetragonal lattice configurations, we have shown that the simple cubic structure is preferred by the system. The other two zero-stress structures, bcc and fcc, correspond to inflection points along this path. These calculations agree with experimental evidence that polonium is the only known element to assume the simple cubic structure at room temperature.

  19. Computational study of hydroxyapatite structures, properties and defects

    NASA Astrophysics Data System (ADS)

    Bystrov, V. S.; Coutinho, J.; Bystrova, A. V.; Dekhtyar, Yu D.; Pullar, R. C.; Poronin, A.; Palcevskis, E.; Dindune, A.; Alkan, B.; Durucan, C.; Paramonova, E. V.

    2015-03-01

    Hydroxyapatite (HAp) was studied from a first principle approach using the local density approximation (LDA) method in AIMPRO code, in combination with various quantum mechanical (QM) and molecular mechanical (MM) methods from HypemChem 7.5/8.0. The data obtained were used for studies of HAp structures, the physical properties of HAp (density of electronic states—DOS, bulk modulus etc) and defects in HAp. Computed data confirmed that HAp can co-exist in different phases—hexagonal and monoclinic. Ordered monoclinic structures, which could reveal piezoelectric properties, are of special interest. The data obtained allow us to characterize the properties of the following defects in HAp: O, H and OH vacancies; H and OH interstitials; substitutions of Ca by Mg, Sr, Mn or Se, and P by Si. These properties reveal the appearance of additional energy levels inside the forbidden zone, shifts of the top of the valence band or the bottom of the conduction band, and subsequent changes in the width of the forbidden zone. The data computed are compared with other known data, both calculated and experimental, such as alteration of the electron work functions under different influences of various defects and treatments, obtained by photoelectron emission. The obtained data are very useful, and there is an urgent need for such analysis of modified HAp interactions with living cells and tissues, improvement of implant techniques and development of new nanomedical applications.

  20. Studies on Structure Property Relations in Printed Polymer Semiconductors

    NASA Astrophysics Data System (ADS)

    Mahadevapuram, Nikhila; Ahmadi Vaselabadi, Saeed; Reza Shakarisaz, David; Strzalka, Joseph; Ruchhoeft, Paul; Stein, Gila

    2014-03-01

    Printed polymer semiconductors can be used in systems which require precise control on domain placements and for sequential casting like in sensors, multi color light-emitting diodes or tandem solar cells. Morphology in polymer semiconductors places an important role on carrier mobility. Polymer crystals help in charge transport. In this work, we used helium ion beam lithography to irradiate polymer films and study crystallinity and carrier mobility. Thin films of poly (3-hexylthiphene) P3HT were irradiated with helium ion beam and light absorption properties were measured using UV-Vis spectroscopy. Crystal orientations in irradiated P3HT films were investigated using grazing incidence wide angle X-ray scattering (GIWAXS). Degree of crystallinity in irradiated polymer films were estimated by constructing pole figures. Charge mobility was estimated from device measurements. It was observed that the light absorption properties were retained in irradiated polymer films. Irradiation can influence both crystal orientations and charge mobility as a function of exposure dose. In summary, polymer crystallinity can be independently varied using this technique and a better understanding of the charge transport and device function can be established.

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

    PubMed

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

    2013-01-01

    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.

  2. Processing-structure-property relationships in ultrafine grain and nanocrystalline materials

    NASA Astrophysics Data System (ADS)

    Koch, C. C.

    2009-01-01

    This paper will review selected aspects of the processingstructureproperty relationships in ultrafine grained (ufg- grain sizes 100 to 500 nm) and nanocrystalline (nc- grain sizes < 100 nm) materials. Of the various processing methods to obtain fine grain size materials, the two that have provided bulk artifactfree samples are electrodeposition and severe plastic deformation. The processing methods and important variables will be described for these techniques. Since the stability of the nanocrystalline microstructure is important for both processing (e.g. consolidation of powders) and elevated temperature mechanical property studies, the stability of nanocrystalline grain sizes as influenced by solute additions will be discussed. While hardness and strength usually increase with decreasing grain size, ductility is typically poor. There are now, however, a number of examples of nanocrystalline materials which combine high strength with good ductility. An example from the author's laboratory on nanocrystalline Cu with optimized mechanical properties will be presented.

  3. Key factors limiting carbon nanotube yarn strength: exploring processing-structure-property relationships.

    PubMed

    Beese, Allison M; Wei, Xiaoding; Sarkar, Sourangsu; Ramachandramoorthy, Rajaprakash; Roenbeck, Michael R; Moravsky, Alexander; Ford, Matthew; Yavari, Fazel; Keane, Denis T; Loutfy, Raouf O; Nguyen, SonBinh T; Espinosa, Horacio D

    2014-11-25

    Studies of carbon nanotube (CNT) based composites have been unable to translate the extraordinary load-bearing capabilities of individual CNTs to macroscale composites such as yarns. A key challenge lies in the lack of understanding of how properties of filaments and interfaces across yarn hierarchical levels govern the properties of macroscale yarns. To provide insight required to enable the development of superior CNT yarns, we investigate the fabrication-structure-mechanical property relationships among CNT yarns prepared by different techniques and employ a Monte Carlo based model to predict upper bounds on their mechanical properties. We study the correlations between different levels of alignment and porosity and yarn strengths up to 2.4 GPa. The uniqueness of this experimentally informed modeling approach is the model's ability to predict when filament rupture or interface sliding dominates yarn failure based on constituent mechanical properties and structural organization observed experimentally. By capturing this transition and predicting the yarn strengths that could be obtained under ideal fabrication conditions, the model provides critical insights to guide future efforts to improve the mechanical performance of CNT yarn systems. This multifaceted study provides a new perspective on CNT yarn design that can serve as a foundation for the development of future composites that effectively exploit the superior mechanical performance of CNTs. PMID:25353651

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

    PubMed

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

    2008-04-01

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

  5. Structure-Property Relationships of Polymer Brushes in Restricted Geometries and their Utilization as Ultra-Low Lubricants

    SciTech Connect

    Kuhl, Tonya Lynn; Faller, Roland

    2015-09-28

    Though polymer films are widely used to modify or tailor the physical, chemical and mechanical properties of interfaces in both solid and liquid systems, the rational design of interface- or surface-active polymer modifiers has been hampered by a lack of information about the behavior and structure-property relationships of this class of molecules. This is especially true for systems in which the role of the polymer is to modify the interaction between two solid surfaces in intimate contact and under load, to cause them to be mechanically coupled (e.g. to promote adhesion and wetting) or to minimize their interaction (e.g. lubrication, colloidal stabilization, etc.). Detailed structural information on these systems has largely been precluded by the many difficulties and challenges associated with direct experimental measurements of polymer structure in these geometries. As a result, many practitioners have been forced to employ indirect measurements or rely wholly on theoretical modeling. This has resulted in an incomplete understanding of the structure-property relationships, which are relied upon for the rational design of improved polymer modifiers. Over the course of this current research program, we made direct measurements of the structure of polymers at the interface between two solid surfaces under confinement and elucidated the fundamental physics behind these phenomena using atomistic and coarse grained simulations. The research has potential to lead to new lubricants and wear reducing agents to improve efficiency.

  6. Specific catalysis of asparaginyl deamidation by carboxylic acids: kinetic, thermodynamic, and quantitative structure-property relationship analyses.

    PubMed

    Connolly, Brian D; Tran, Benjamin; Moore, Jamie M R; Sharma, Vikas K; Kosky, Andrew

    2014-04-01

    Asparaginyl (Asn) deamidation could lead to altered potency, safety, and/or pharmacokinetics of therapeutic protein drugs. In this study, we investigated the effects of several different carboxylic acids on Asn deamidation rates using an IgG1 monoclonal antibody (mAb1*) and a model hexapeptide (peptide1) with the sequence YGKNGG. Thermodynamic analyses of the kinetics data revealed that higher deamidation rates are associated with predominantly more negative ΔS and, to a lesser extent, more positive ΔH. The observed differences in deamidation rates were attributed to the unique ability of each type of carboxylic acid to stabilize the energetically unfavorable transition-state conformations required for imide formation. Quantitative structure property relationship (QSPR) analysis using kinetic data demonstrated that molecular descriptors encoding for the geometric spatial distribution of atomic properties on various carboxylic acids are effective determinants for the deamidation reaction. Specifically, the number of O-O and O-H atom pairs on carboxyl and hydroxyl groups with interatomic distances of 4-5 Å on a carboxylic acid buffer appears to determine the rate of deamidation. Collectively, the results from structural and thermodynamic analyses indicate that carboxylic acids presumably form multiple hydrogen bonds and charge-charge interactions with the relevant deamidation site and provide alignment between the reactive atoms on the side chain and backbone. We propose that carboxylic acids catalyze deamidation by stabilizing a specific, energetically unfavorable transition-state conformation of l-asparaginyl intermediate II that readily facilitates bond formation between the γ-carbonyl carbon and the deprotonated backbone nitrogen for cyclic imide formation.

  7. Structure-Property Relationships in Atomic-Scale Junctions: Histograms and Beyond.

    PubMed

    Hybertsen, Mark S; Venkataraman, Latha

    2016-03-15

    are pulled apart has given complementary information such as the stiffness and rupture force of the molecule-metal link bond. Overall, while the BJ technique does not produce a single molecule circuit for practical applications, it has proved remarkably versatile for fundamental studies. Measured data and analysis have been combined with atomic-scale theory and calculations, typically performed for representative junction structures, to provide fundamental physical understanding of structure-function relationships. This Account integrates across an extensive series of our specific nanoscale junction studies which were carried out with the STM- and AFM-BJ techniques and supported by theoretical analysis and density functional theory based calculations, with emphasis on the physical characteristics of the measurement process and the rich data sets that emerge. Several examples illustrate the impact of measured trends based on the most probable values for key characteristics (obtained from ensembles of order 1000-10 000 individual junctions) to build a solid picture of conductance phenomena as well as attributes of the link bond chemistry. The key forward-looking question posed here is the extent to which the full data sets represented by the individual trajectories can be analyzed to address structure-function questions at the level of individual junctions. Initial progress toward physical modeling of conductance of individual junctions indicates trends consistent with physical junction structures. Analysis of junction mechanics reveals a scaling procedure that collapses existing data onto a universal force-extension curve. This research directed to understanding the distribution of structures and physical characteristics addresses fundamental questions concerning the interplay between chemical control and stochastically driven diversity. PMID:26938931

  8. Structure-Property Relationships in Atomic-Scale Junctions: Histograms and Beyond.

    PubMed

    Hybertsen, Mark S; Venkataraman, Latha

    2016-03-15

    are pulled apart has given complementary information such as the stiffness and rupture force of the molecule-metal link bond. Overall, while the BJ technique does not produce a single molecule circuit for practical applications, it has proved remarkably versatile for fundamental studies. Measured data and analysis have been combined with atomic-scale theory and calculations, typically performed for representative junction structures, to provide fundamental physical understanding of structure-function relationships. This Account integrates across an extensive series of our specific nanoscale junction studies which were carried out with the STM- and AFM-BJ techniques and supported by theoretical analysis and density functional theory based calculations, with emphasis on the physical characteristics of the measurement process and the rich data sets that emerge. Several examples illustrate the impact of measured trends based on the most probable values for key characteristics (obtained from ensembles of order 1000-10 000 individual junctions) to build a solid picture of conductance phenomena as well as attributes of the link bond chemistry. The key forward-looking question posed here is the extent to which the full data sets represented by the individual trajectories can be analyzed to address structure-function questions at the level of individual junctions. Initial progress toward physical modeling of conductance of individual junctions indicates trends consistent with physical junction structures. Analysis of junction mechanics reveals a scaling procedure that collapses existing data onto a universal force-extension curve. This research directed to understanding the distribution of structures and physical characteristics addresses fundamental questions concerning the interplay between chemical control and stochastically driven diversity.

  9. Quantitative Structure-Property Relationship (QSPR) Modeling of Drug-Loaded Polymeric Micelles via Genetic Function Approximation

    PubMed Central

    Lin, Wenjing; Chen, Quan; Guo, Xindong; Qian, Yu; Zhang, Lijuan

    2015-01-01

    Self-assembled nano-micelles of amphiphilic polymers represent a novel anticancer drug delivery system. However, their full clinical utilization remains challenging because the quantitative structure-property relationship (QSPR) between the polymer structure and the efficacy of micelles as a drug carrier is poorly understood. Here, we developed a series of QSPR models to account for the drug loading capacity of polymeric micelles using the genetic function approximation (GFA) algorithm. These models were further evaluated by internal and external validation and a Y-randomization test in terms of stability and generalization, yielding an optimization model that is applicable to an expanded materials regime. As confirmed by experimental data, the relationship between microstructure and drug loading capacity can be well-simulated, suggesting that our models are readily applicable to the quantitative evaluation of the drug-loading capacity of polymeric micelles. Our work may offer a pathway to the design of formulation experiments. PMID:25780923

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

    PubMed

    Munić Kos, Vesna; Koštrun, Sanja; Fajdetić, Andrea; Bosnar, Martina; Kelnerić, Željko; Stepanić, Višnja; Eraković Haber, Vesna

    2013-05-13

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

  11. Structure-property relationships of dissimilar friction stir welded aluminum alloys

    NASA Astrophysics Data System (ADS)

    Quinones, Rogie Irwin Rodriguez

    In this work, the relationship between microstructure and mechanical properties of dissimilar friction stir welded AA6061-to-AA7050 aluminum alloys were evaluated. Experimental results from this study revealed that static strength increased with the tool rotational speed and was correlated with the material intermixing. Fully-reversed low cycle fatigue experimental results showed an increase in the strain hardening properties as well as the number of cycles-to-failure as the tool rotational speed was increased. Furthermore, under both static and cyclic loading, fracture of the joint was dominated by the AA6061 alloy side of the weld. In addition, inspection of the fatigue surfaces revealed that cracks initiated from intermetallic particles located near the surface. In order to determine the corrosion resistance of the dissimilar joint, corrosion defects were produced on the crown surface of the weld by static immersion in 3.5% NaCl for various exposure times. Results revealed localized corrosion damage in the thermo-mechanically affected and heat affected zones. Results demonstrated a decrease in the fatigue life, with evidence of crack initiation at the corrosion defects; however, the fatigue life was nearly independent of the exposure time. This can be attributed to total fatigue life dominated by incubation time. Furthermore, two types of failure were observed: fatigue crack initiation in the AA6061 side at high strain amplitudes (>0.3%); and fatigue crack initiation in the AA7050 side at low strain amplitudes (<0.2%). Lastly, a microstructure-sensitive model based on a multi-stage fatigue damage concept was extended to the dissimilar friction stir welded joints in order to capture the crack initiation and propagation in as-welded and pre-corroded conditions. Good correlation between experimental fatigue results and the model was achieved based on the variation in the initial defect size, microstructure, and mechanical properties of the dissimilar friction stir

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

    NASA Astrophysics Data System (ADS)

    Kosilkin, Ilya V.

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

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

    NASA Astrophysics Data System (ADS)

    Khariwala, Devang

    Chapter 1. The effect of tie-layer thickness on delamination behavior of polypropylene/tie-layer/Nylon-6 multilayers is examined in this study. Various maleated polypropylene resins were compared for their effectiveness as tie-layers. Delamination failure occurred cohesively in all the multilayer systems. Two adhesion regimes were defined based on the change in slope of the linear relationship between the delamination toughness and the tie-layer thickness. The measured delamination toughness of the various tie-layers was quantitatively correlated to the damage zone length formed at the crack tip. In addition, the effect of tie-layer thickness on the multilayer tensile properties was correlated with the delamination behavior. The fracture strain of the multilayers decreased with decreasing tie-layer thickness. Examination of the prefracture damage mechanism of stretched multilayers revealed good correlation with the delamination toughness of the tie-layers. In thick tie-layers (>2microm) the delamination toughness of the tie-layers was large enough to prevent delamination of multilayers when they were stretched. In the thin tie-layers (<2microm) the delamination toughness of all the tie-layers is low and consequently delamination led to premature fracture in stretched multilayers. Chapter 2. The kinetics of interdiffusion in the layer multiplying coextrusion process was studied between the miscible Nylon-6 and EVOH pair. The interdiffusion was followed by studying multilayer films of alternating Nylon-6 and EVOH layers that were coextruded with increasing number of layers. The AFM confirmed that the layers interdiffused with increasing number of layers and were forced to a homogeneous blend after several multiplications. The oxygen permeability of Nylon-6/EVOH multilayers was strongly affected by the amount of interdiffusion. The symmetry of the multilayers made it possible to model the composition profile through the layer thickness by application of Fick's law of

  14. Synthesis, growth, vibrational spectral investigations and structure-property relationship of an organic NLO crystal: 3,4-Dimethoxy chalcone

    NASA Astrophysics Data System (ADS)

    Alen, S.; Sajan, D.; Joseph, Lynnette; Chaitanya, K.; Shettigar, Venkataraya; Jothy, V. Bena

    2015-09-01

    3,4-Dimethoxy chalcone, a nonlinear optical material, was synthesized and noncentro symmetric single crystals were grown in solution by slow evaporation technique. Thermal analysis such as DSC revealed a good thermal stability of 3,4-dimethoxy chalcone. The FT-IR and FT-Raman spectral studies were carried out to investigate the structural properties of the title compound. The molecular orbitals and natural bond analysis of this material were calculated by Density Functional Theory calculations. The second harmonic conversion efficiency was determined using the Kurtz powder technique, which is 8 times that of urea.

  15. Composition-structure-property relationships of commercial polyurethane foams for mattresses

    NASA Astrophysics Data System (ADS)

    Scarfato, P.; Di Maio, L.; D'Arienzo, L.; Rinaldi, S.; Incarnato, L.

    2015-12-01

    Three commercial flexible polyurethane foams used for mattress have been submitted to chemical-physical analyses, water vapor permeability and compression mechanical tests, in order to understand the relationships among their composition, structure, and some functional properties of interest for bedding applications. The results demonstrated that all the three foams have open cell morphology and similar cell structure, with average cell diameters ranging from 430 to 510 micron and wide cell size distribution. As a consequence, they also show comparable water vapor transport behavior. On the contrary, their mechanical response, in terms of hysteresis loss, surface firmness and resistance to bottoming out, was found strongly dependent on their chemical structure and molecular mobility, as inferred from infrared spectroscopy analysis.

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

    SciTech Connect

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

    2010-06-07

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

  17. Structure-Property Relationships in Lithium, Silver, and Cesium Uranyl Borates

    SciTech Connect

    Wang, Shuao; Alekseev, Evgeny V.; Stritzinger, Jared T.; Liu, Guokui; Depmeier, Wulf; Albrecht-Schmitt, Thomas E.

    2010-11-09

    Four new uranyl borates, Li[UO{sub 2}B{sub 5}O{sub 9}]·H{sub 2}O (LiUBO-1), Ag[(UO{sub 2})B{sub 5}O{sub 8}(OH){sub 2}] (AgUBO-1), α-Cs[(UO{sub 2}){sub 2}B{sub 11}O{sub 16}(OH){sub 6}] (CsUBO-1), and β-Cs[(UO{sub 2}){sub 2}B{sub 11}O{sub 16}(OH){sub 6}] (CsUBO-2) were synthesized via the reaction of uranyl nitrate with a large excess of molten boric acid in the presence of lithium, silver, or cesium nitrate. These compounds share a common structural motif consisting of a linear uranyl, UO{sub 2}{sup 2+}, cation surrounded by BO{sub 3} triangles and BO{sub 4} tetrahedra to create an UO{sub 8} hexagonal bipyramidal environment around uranium. The borate anions bridge between uranyl units to create sheets. Additional BO{sub 3} triangles extend from the polyborate layers, and are directed approximately perpendicular to the sheets. In Li[(UO{sub 2})B{sub 5}O{sub 9}]·H{sub 2}O, the additional BO{sub 3} triangles connect these sheets together to form a three-dimensional framework structure. Li[UO{sub 2})B{sub 5}O{sub 9}]·H{sub 2}O and β-Cs[(UO{sub 2}){sub 2}B{sub 11}O{sub 16}(OH){sub 6}] adopt noncentrosymmetric structures, while Ag[(UO{sub 2})B{sub 5}O{sub 8}(OH){sub 2}] and α-Cs[(UO{sub 2}){sub 2}B{sub 11}O{sub 16}(OH){sub 6}] are centrosymmetric. Li[(UO{sub 2})B{sub 5}O{sub 9}]·H{sub 2}O, which can be obtained as pure phase, displays second-harmonic generation of 532 nm light from 1064 nm light. Topological relationships of all actinyl borates are developed.

  18. Structure-property relationships in low-temperature adhesives. [for inflatable structures

    NASA Technical Reports Server (NTRS)

    Schoff, C. K.; Udipi, K.; Gillham, J. K.

    1977-01-01

    Adhesive materials of aliphatic polyester, linear hydroxyl end-capped polybutadienes, or SBS block copolymers are studied with the objective to replace conventional partially aromatic end-reactive polyester-isocyanate adhesives that have shown embrittlement

  19. Uniaxial Extensional Behavior of A--B--A Thermoplastic Elastomers: Structure-Properties Relationship and Modeling

    NASA Astrophysics Data System (ADS)

    Martinetti, Luca

    relation between the observed power-law exponent and molecular structure was established. The measured low-frequency response, originating from the incipient glass transition of the A domains, was exploited and extrapolated to lower frequencies via a sequential application of the fractional Maxwell model and the fractional Zener model. With only a few, physically meaningful material parameters a realistic description of the A--B--A self-similar relaxation was obtained over a frequency range much broader than the experimental window and not accessible via time-temperature superposition. The relationship between large-strain response and network structure of A--B--A triblocks was investigated, by examining (1) the effect of linear relaxation mechanisms on the tensile behavior, (2) the sources of elastic and viscoelastic nonlinearities, and (3) the strain rate dependence of the ultimate properties. For the first time in the literature, the complex high-dimensional rheological signature of chewing gum was analyzed, especially in response to nonlinear and unsteady deformations in both shear and extension. A unique rheological fingerprint was obtained that is sufficient to provide a new robust definition of chewing gum that is independent of specific molecular composition. (Abstract shortened by ProQuest.).

  20. Novel multiphase systems based on thermoplastic chitosan: Analysis of the structure-properties relationships

    NASA Astrophysics Data System (ADS)

    Avérous, Luc; Pollet, Eric

    2016-03-01

    In the last years, biopolymers have attracted great attention. It is for instance the case of chitosan, a linear polysaccharide. It is a deacetylated derivative of chitin, which is the second most abundant polysaccharide found in nature after cellulose. Chitosan has been found to be nontoxic, biodegradable, biofunctional, and biocompatible in addition to having antimicrobial and antifungal properties, and thus has a great potential for environmental (packaging,) or biomedical applications.For preparing chitosan-based materials, only solution casting or similar methods have been used in all the past studies. Solution casting have the disadvantage in low efficiency and difficulty in scaling-up towards industrial applications. Besides, a great amount of environmentally unfriendly chemical solvents are used and released to the environment in this method. The reason for not using a melt processing method like extrusion or kneading in the past studies is that chitosan, like many other polysaccharides such as starch, has very low thermal stability and degrade prior to melting. Therefore, even if the melt processing method is more convenient and highly preferred for industrial production, its adaptation for polysaccharide-based materials remains very difficult. However, our recently published studies has demonstrated the successful use of an innovative melt processing method (internal mixer, extrusion,) as an alternative route to solution casting, for preparing materials based on thermoplastic chitosan. These promising thermoplastic materials, obtained by melt processing, have been the main topic of recent international projects, with partners from different countries Multiphase systems based on various renewable plasticizers have been elaborated and studied. Besides, different blends, and nano-biocomposites based on nanoclays, have been elaborated and fully analyzed. The initial consortium of this vast project was based on an international consortium (Canada, Australia

  1. Quantitative Structure-Property Relationship Modeling of Electronic Properties of Graphene Using Atomic Radial Distribution Function Scores.

    PubMed

    Fernandez, Michael; Shi, Hongqing; Barnard, Amanda S

    2015-12-28

    The intrinsic relationships between nanoscale features and electronic properties of nanomaterials remain poorly investigated. In this work, electronic properties of 622 computationally optimized graphene structures were mapped to their structures using partial-least-squares regression and radial distributions function (RDF) scores. Quantitative structure-property relationship (QSPR) models were calibrated with 70% of a virtual data set of 622 passivated and nonpassivated graphenes, and we predicted the properties of the remaining 30% of the structures. The analysis of the optimum QSPR models revealed that the most relevant RDF scores appear at interatomic distances in the range of 2.0 to 10.0 Å for the energy of the Fermi level and the electron affinity, while the electronic band gap and the ionization potential correlate to RDF scores in a wider range from 3.0 to 30.0 Å. The predictions were more accurate for the energy of the Fermi level and the ionization potential, with more than 83% of explained data variance, while the electron affinity exhibits a value of ∼80% and the energy of the band gap a lower 70%. QSPR models have tremendous potential to rapidly identify hypothetical nanomaterials with desired electronic properties that could be experimentally prepared in the near future.

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

    PubMed

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

    2015-07-01

    We have synthesized TiO2 doped strontium borate glasses, 70B2O3-(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.

  3. Structure-property-glass transition relationships in non-isocyanate polyurethanes investigated by dynamic nanoindentation

    NASA Astrophysics Data System (ADS)

    Weyand, Stephan; Blattmann, Hannes; Schimpf, Vitalij; Mülhaupt, Rolf; Schwaiger, Ruth

    2016-07-01

    Newly developed green-chemistry approaches towards the synthesis of non-isocyanate polyurethane (NIPU) systems represent a promising alternative to polyurethanes (PU) eliminating the need for harmful ingredients. A series of NIPU systems were studied using different nanoindentation techniques in order to understand the influence of molecular parameters on the mechanical behavior. Nanoindentation revealed a unique characteristic feature of those materials, i.e. stiffening with increasing deformation. It is argued that the origin of this observed stiffening is a consequence of the thermodynamic state of the polymer network, the molecular characteristics of the chemical building blocks and resulting anisotropic elastic response of the network structure. Flat-punch nanoindentation was applied in order to characterize the constitutive viscoelastic nature of the materials. The complex modulus shows distinct changes as a function of the NIPU network topology illustrating the influence of the chemical building blocks. The reproducibility of the data indicates that the materials are homogeneous over the volumes sampled by nanoindentation. Our study demonstrates that nanoindentation is very well-suited to investigate the molecular characteristics of NIPU materials that cannot be quantified in conventional experiments. Moreover, the technique provides insight into the functional significance of complex molecular architectures thereby supporting the development of NIPU materials with tailored properties.

  4. Structure/property relationships of polymers containing hybrid nano-filler: Polyhedral oligomeric silsesquioxanes (POSS)

    NASA Astrophysics Data System (ADS)

    Geng, Haiping

    Polyhedral Oligomeric Silsesquioxane (POSS) is a three-dimensional structurally well-defined cage-like molecule represented by formula (RSiO 1.5)n (n = 6, 8, 10 or higher, R is an organic group). POSS macromers have an inorganic silica-like core, which is surrounded by organic groups, and the physical size of the POSS cage is about 1.5 nm. Because of their hybrid nature and nanometer-scale feature, as shown in this study, POSS macromers were dispersed in a molecular level into polymeric systems by blending, in effect achieved POSS/Polymer nano-blends. The POSS macromers used in this work were cubic-caged POSS macromers bearing different organic corner groups. Polystyrene (PS) and polydimethyl siloxane (PDMS) were used as model polymers. The investigations involved in this work include two parts. In the first part, the microstructures and thermal properties of the POSS macromers were investigated by using X-ray diffractometer, Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA). In the second part, the morphologies of POSS/Polymer blends were examined using Transmission Electronic Microscopy (TEM), and X-ray diffractometer. Their thermal and rheological properties were studied with DSC, TGA, and Rheometer. The results of this work showed that different corner groups on the POSS cage affected the morphological structures and properties of the POSS macromers. The higher the degree of the symmetry and regularity of the POSS macromers and the smaller the size of the corner groups, the more ordered the POSS macromers. The POSS macromers with functionalities, which may undergo chemical cross-linking reactions, possessed high thermal stabilities. The morphology studies of POSS/PS and POSS/PDMS blends showed that depending on the attached organic groups on the POSS cages, the structures of the polymer matrix and the composition of the blends, the morphologies of the POSS/polymer blends ranged from complete separation to homogeneous dispersion in

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

    SciTech Connect

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

    2006-09-27

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

  6. Structure-property relationships in thermomechanically treated beryllia dispersed nickel alloys

    NASA Technical Reports Server (NTRS)

    Grewal, M. S.; Sastri, S. A.; Grant, N. J.

    1975-01-01

    BeO dispersed nickel alloys, produced by powder metallurgy techniques, were studied extensively in stress rupture at 815, 982, and 1093 C (1088, 1255, and 1366 K) and by transmission electron microscopy. The alloys were subjected to a variety of thermomechanical treatments (TMT) to determine the benefits of TMT on properties. It is shown that the use of intermediate annealing treatments after 10 pct reduction steps is highly beneficial on both low and high temperature properties. It is indicated that the high temperature strength is not primarily dependent on the grain aspect ratio or texture but depends strongly on the dislocation density and distribution of dislocations in a stable substructure which is pinned by the fine oxide dispersion.

  7. Structure-Property relationship for H covered Fe3 O4 (001)

    NASA Astrophysics Data System (ADS)

    Liu, Fangyang; Kizilkaya, Orhan; Sprunger, Phillip; Kurtz, Richard; Jin, Rongying; Zhang, Jiandi; Plummer, Ward

    2015-03-01

    Magnetite (Fe3O4), the oldest permanent magnet, is still being studied, due to the fascinating surface properties. Clean B layer terminated Fe3O4(001) surface exhibits a (√2 × √2)R45 reconstruction, which as reported by LEED experiments can be removed by hydrogen adsorption at RT. However, the mechanism of this surface structural change is unknown. Combining HREELS, LEIS, ARXPS, UPS and XANES, we discovered a very unusual adsorption mechanism. Hydrogen appears to be bonded to the surface iron atoms not oxygen as expected. We observe H-Fe vibration mode with HREELS while no OH mode is present. Furthermore LEIS experiments confirmed H is on the iron atoms site. We will discuss the adsorption mechanism and electronic structure change with information provided by the core level photoemission techniques. This work was supported by Energy Frontier Research Center (EFRC) funded by the U.S. Department of Energy.

  8. Understanding nanocellulose chirality and structure-properties relationship at the single fibril level

    NASA Astrophysics Data System (ADS)

    Usov, Ivan; Nyström, Gustav; Adamcik, Jozef; Handschin, Stephan; Schütz, Christina; Fall, Andreas; Bergström, Lennart; Mezzenga, Raffaele

    2015-06-01

    Nanocellulose fibrils are ubiquitous in nature and nanotechnologies but their mesoscopic structural assembly is not yet fully understood. Here we study the structural features of rod-like cellulose nanoparticles on a single particle level, by applying statistical polymer physics concepts on electron and atomic force microscopy images, and we assess their physical properties via quantitative nanomechanical mapping. We show evidence of right-handed chirality, observed on both bundles and on single fibrils. Statistical analysis of contours from microscopy images shows a non-Gaussian kink angle distribution. This is inconsistent with a structure consisting of alternating amorphous and crystalline domains along the contour and supports process-induced kink formation. The intrinsic mechanical properties of nanocellulose are extracted from nanoindentation and persistence length method for transversal and longitudinal directions, respectively. The structural analysis is pushed to the level of single cellulose polymer chains, and their smallest associated unit with a proposed 2 × 2 chain-packing arrangement.

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

    NASA Astrophysics Data System (ADS)

    Neilson, James R.

    2011-12-01

    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

  10. Structure-property relationships of polystyrene/rubber bulk blends produced by compositional quenching

    NASA Astrophysics Data System (ADS)

    Mathur, Devesh

    1998-12-01

    Numerous continuum models exist that predict the behavior of copolymers in micelles or at interfaces. However, a comprehensive model for copolymers in melts which explains the equilibrium between the two with emphasis on surface saturation for blends has not been attempted. A scaling model is proposed for A-B diblock copolymers in homopolymer melts based on the minimization of free energy. Competition between the migration of block copolymer to the A and B homopolymer interface and the formation of micelles in the B phase has been modeled. Sample calculations done for polystyrene (PS), polybutadiene (PB), and PS-PB diblock copolymers supports experimental observation for the onset of micellization and for the aggregation number of a micelle. This model can be used as a predictive tool, once knowledge of the three scaling factors is obtained. This would allow a priori calculation of the block copolymer concentration needed for full coverage of the homopolymer interface. Billions of pounds of commercial high impact polystyrene (HIPS) are produced each year, yet the precise role of the rubber phase on toughening remains unknown. Strength is affected by the rubber phase volume, particle size and morphology, degree of crosslinking and adhesion to the matrix. Bulk blends were used to study the effectiveness of various PS-PB diblock and PS-PB-PS triblock copolymers in improving the impact strength of PS/PB blends. The blends were produced by compositional quenching and further ripened to control particle size and block copolymer concentration at the homopolymer interface. It was confirmed that a minimum rubber phase volume of 7% is required for significant impact modification. This volume fraction corresponds to an interparticle distance of one particle diameter. The increase in impact strength is attributed to stress field overlap. Atomic force microscopy studies performed on fracture surfaces showed that energy dissipation is not associated with the creation of surface

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

    PubMed

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

    2012-03-01

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

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

    SciTech Connect

    Joseph, E.; Wilkes, G.; Park, K.

    1981-10-01

    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 order was present in these systems during crosslinking in contrast to those crosslinked below the melting temperature.

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

    SciTech Connect

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

    2001-03-09

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

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

    NASA Astrophysics Data System (ADS)

    McConnell, Marla D.

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

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

    PubMed

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

    2014-11-18

    character through functionalization. This Account offers discussion of current state-of-the-art electronic structure approaches for prediction of structural, electronic, optical, and transport properties of materials, with illustration of these capabilities from a series of investigations involving curved aromatic materials. The class of curved aromatic materials offers the ability to investigate methodology across a wide range of materials complexity, including (a) molecules, (b) molecular crystals, (c) molecular adsorbates on metal surfaces, and (d) molecular nanojunctions. A reliable pallet of theoretical tools for such a wide array relies on expertise spanning multiple fields. Working together with experimental experts, advancements in the fundamental understanding of structural and dynamical properties are enabling focused design of functional materials. Most importantly, these studies provide an opportunity to compare experimental and theoretical capabilities and open the way for continual improvement of these capabilities.

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

    PubMed

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

    2014-11-18

    character through functionalization. This Account offers discussion of current state-of-the-art electronic structure approaches for prediction of structural, electronic, optical, and transport properties of materials, with illustration of these capabilities from a series of investigations involving curved aromatic materials. The class of curved aromatic materials offers the ability to investigate methodology across a wide range of materials complexity, including (a) molecules, (b) molecular crystals, (c) molecular adsorbates on metal surfaces, and (d) molecular nanojunctions. A reliable pallet of theoretical tools for such a wide array relies on expertise spanning multiple fields. Working together with experimental experts, advancements in the fundamental understanding of structural and dynamical properties are enabling focused design of functional materials. Most importantly, these studies provide an opportunity to compare experimental and theoretical capabilities and open the way for continual improvement of these capabilities. PMID:24933397

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

    PubMed

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

    2015-04-01

    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

  18. Predicting equilibrium vapour pressure isotope effects by using artificial neural networks or multi-linear regression - A quantitative structure property relationship approach.

    PubMed

    Parinet, Julien; Julien, Maxime; Nun, Pierrick; Robins, Richard J; Remaud, Gerald; Höhener, Patrick

    2015-09-01

    We aim at predicting the effect of structure and isotopic substitutions on the equilibrium vapour pressure isotope effect of various organic compounds (alcohols, acids, alkanes, alkenes and aromatics) at intermediate temperatures. We attempt to explore quantitative structure property relationships by using artificial neural networks (ANN); the multi-layer perceptron (MLP) and compare the performances of it with multi-linear regression (MLR). These approaches are based on the relationship between the molecular structure (organic chain, polar functions, type of functions, type of isotope involved) of the organic compounds, and their equilibrium vapour pressure. A data set of 130 equilibrium vapour pressure isotope effects was used: 112 were used in the training set and the remaining 18 were used for the test/validation dataset. Two sets of descriptors were tested, a set with all the descriptors: number of(12)C, (13)C, (16)O, (18)O, (1)H, (2)H, OH functions, OD functions, CO functions, Connolly Solvent Accessible Surface Area (CSA) and temperature and a reduced set of descriptors. The dependent variable (the output) is the natural logarithm of the ratios of vapour pressures (ln R), expressed as light/heavy as in classical literature. Since the database is rather small, the leave-one-out procedure was used to validate both models. Considering higher determination coefficients and lower error values, it is concluded that the multi-layer perceptron provided better results compared to multi-linear regression. The stepwise regression procedure is a useful tool to reduce the number of descriptors. To our knowledge, a Quantitative Structure Property Relationship (QSPR) approach for isotopic studies is novel.

  19. Predicting equilibrium vapour pressure isotope effects by using artificial neural networks or multi-linear regression - A quantitative structure property relationship approach.

    PubMed

    Parinet, Julien; Julien, Maxime; Nun, Pierrick; Robins, Richard J; Remaud, Gerald; Höhener, Patrick

    2015-09-01

    We aim at predicting the effect of structure and isotopic substitutions on the equilibrium vapour pressure isotope effect of various organic compounds (alcohols, acids, alkanes, alkenes and aromatics) at intermediate temperatures. We attempt to explore quantitative structure property relationships by using artificial neural networks (ANN); the multi-layer perceptron (MLP) and compare the performances of it with multi-linear regression (MLR). These approaches are based on the relationship between the molecular structure (organic chain, polar functions, type of functions, type of isotope involved) of the organic compounds, and their equilibrium vapour pressure. A data set of 130 equilibrium vapour pressure isotope effects was used: 112 were used in the training set and the remaining 18 were used for the test/validation dataset. Two sets of descriptors were tested, a set with all the descriptors: number of(12)C, (13)C, (16)O, (18)O, (1)H, (2)H, OH functions, OD functions, CO functions, Connolly Solvent Accessible Surface Area (CSA) and temperature and a reduced set of descriptors. The dependent variable (the output) is the natural logarithm of the ratios of vapour pressures (ln R), expressed as light/heavy as in classical literature. Since the database is rather small, the leave-one-out procedure was used to validate both models. Considering higher determination coefficients and lower error values, it is concluded that the multi-layer perceptron provided better results compared to multi-linear regression. The stepwise regression procedure is a useful tool to reduce the number of descriptors. To our knowledge, a Quantitative Structure Property Relationship (QSPR) approach for isotopic studies is novel. PMID:25559176

  20. Quantitative structure-property relationship analysis for the retention index of fragrance-like compounds on a polar stationary phase.

    PubMed

    Rojas, Cristian; Duchowicz, Pablo R; Tripaldi, Piercosimo; Pis Diez, Reinaldo

    2015-11-27

    A quantitative structure-property relationship (QSPR) was developed for modeling the retention index of 1184 flavor and fragrance compounds measured using a Carbowax 20M glass capillary gas chromatography column. The 4885 molecular descriptors were calculated using Dragon software, and then were simultaneously analyzed through multivariable linear regression analysis using the replacement method (RM) variable subset selection technique. We proceeded in three steps, the first one by considering all descriptor blocks, the second one by excluding conformational descriptor blocks, and the last one by analyzing only 3D-descriptor families. The models were validated through an external test set of compounds. Cross-validation methods such as leave-one-out and leave-many-out were applied, together with Y-randomization and applicability domain analysis. The developed model was used to estimate the I of a set of 22 molecules. The results clearly suggest that 3D-descriptors do not offer relevant information for modeling the retention index, while a topological index such as the Randić-like index from reciprocal squared distance matrix has a high relevance for this purpose. PMID:26521096

  1. Quantitative structure-property relationship analysis for the retention index of fragrance-like compounds on a polar stationary phase.

    PubMed

    Rojas, Cristian; Duchowicz, Pablo R; Tripaldi, Piercosimo; Pis Diez, Reinaldo

    2015-11-27

    A quantitative structure-property relationship (QSPR) was developed for modeling the retention index of 1184 flavor and fragrance compounds measured using a Carbowax 20M glass capillary gas chromatography column. The 4885 molecular descriptors were calculated using Dragon software, and then were simultaneously analyzed through multivariable linear regression analysis using the replacement method (RM) variable subset selection technique. We proceeded in three steps, the first one by considering all descriptor blocks, the second one by excluding conformational descriptor blocks, and the last one by analyzing only 3D-descriptor families. The models were validated through an external test set of compounds. Cross-validation methods such as leave-one-out and leave-many-out were applied, together with Y-randomization and applicability domain analysis. The developed model was used to estimate the I of a set of 22 molecules. The results clearly suggest that 3D-descriptors do not offer relevant information for modeling the retention index, while a topological index such as the Randić-like index from reciprocal squared distance matrix has a high relevance for this purpose.

  2. Chemical Modification of Graphene Oxide through Diazonium Chemistry and Its Influence on the Structure-Property Relationships of Graphene Oxide-Iron Oxide Nanocomposites.

    PubMed

    Rebuttini, Valentina; Fazio, Enza; Santangelo, Saveria; Neri, Fortunato; Caputo, Gianvito; Martin, Cédric; Brousse, Thierry; Favier, Frédéric; Pinna, Nicola

    2015-08-24

    4-Carboxyphenyl groups are covalently grafted onto graphene oxide via diazonium chemistry for studying their role on the adsorption of iron oxide nanoparticles. The nanoparticles are deposited via a novel phase-transfer approach involving specific interactions at the interface between two immiscible solvents. The increased density and the homogeneous distribution of surface carboxyl moieties enable the preparation of a nanocomposite with improved iron oxide distribution and loading. Structure-properties relationships are investigated by analysing the electrochemical properties of the nanocomposites, which are regarded as promising active materials for application in supercapacitors. It is demonstrated that the nature of the interactions between the components similarly affects the overall electrochemical performances of the nanocomposites and the structure of the materials.

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

    PubMed Central

    2012-01-01

    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

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

    ERIC Educational Resources Information Center

    Krein, Michael

    2011-01-01

    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…

  5. Design, synthesis, and characterization of new phosphazene related materials, and study the structure property correlations

    NASA Astrophysics Data System (ADS)

    Tian, Zhicheng

    The work described in this thesis is divided into three major parts, and all of which involve the exploration of the chemistry of polyphosphazenes. The first part (chapters 2 and 3) of my research is synthesis and study polyphoshazenes for biomedical applications, including polymer drug conjugates and injectable hydrogels for drug or biomolecule delivery. The second part (chapters 4 and 5) focuses on the synthesis of several organic/inorganic hybrid polymeric structures, such as diblock, star, brush and palm tree copolymers using living cationic polymerization and atom transfer radical polymerization techniques. The last part (chapters 6 and 7) is about exploratory synthesis of new polymeric structures with fluorinated side groups or cycloaliphatic side groups, and the study of new structure property relationships. Chapter 1 is an outline of the fundamental concepts for polymeric materials, as such the history, important definitions, and some introductory material for to polymer chemistry and physics. The chemistry and applications of phopshazenes is also briefly described. Chapter 2 is a description of the design, synthesis, and characterization of development of a new class of polymer drug conjugate materials based on biodegradable polyphosphazenes and antibiotics. Poly(dichlorophosphazene), synthesized by a thermal ring opening polymerization, was reacted with up to 25 mol% of ciprofloxacin or norfloxacin and three different amino acid esters (glycine, alanine, or phenylalanine) as cosubstituents via macromolecular substitutions. Nano/microfibers of several selected polymers were prepared by an electrospinning technique. Chapter 3 is concerned with the development of a class of injectable and biodegradable hydrogels based on water-soluble poly(organophosphazenes) containing oligo(ethylene glycol) methyl ethers and glycine ethyl esters. The hydrogels can be obtained by mixing alpha-cyclodextrin aqueous solution and poly(organophosphazenes) aqueous solution in

  6. Zn1-xCoxO nanoparticles: Synthesis and study of enhanced optical and structural properties

    NASA Astrophysics Data System (ADS)

    Ahad, Abdul; Majid, Suhail; Rahman, F.

    2016-05-01

    We have synthesized the Zn1-xCoxO (x= 0, 0.01, 0.03 and 0.05) using Sol-gel method. The structural properties were characterized using X-ray diffraction. Optical properties were characterized using UV-VIS and FT-IR spectroscopy. The lattice parameters were refined using Reitveld refinement which also reveals that all the peaks in XRD patterns were indexed in the wurtzite type hexagonal structure with space group P 63 mc. The FT-IR spectra confirmed the presence of functional groups and chemical bonding. The band gap of each sample was calculated by adopting Kubelka-Munk transformed reflectance spectra and effect of doping on band gap is also studied.

  7. Land-use and land-management change: relationships with earthworm and fungi communities and soil structural properties

    PubMed Central

    2013-01-01

    Background Change in land use and management can impact massively on soil ecosystems. Ecosystem engineers and other functional biodiversity in soils can be influenced directly by such change and this in turn can affect key soil functions. Here, we employ meta-analysis to provide a quantitative assessment of the effects of changes in land use and land management across a range of successional/extensification transitions (conventional arable → no or reduced tillage → grassland → wooded land) on community metrics for two functionally important soil taxa, earthworms and fungi. An analysis of the relationships between community change and soil structural properties was also included. Results Meta-analysis highlighted a consistent trend of increased earthworm and fungal community abundances and complexity following transitions to lower intensity and later successional land uses. The greatest changes were seen for early stage transitions, such as introduction of reduced tillage regimes and conversion to grassland from arable land. Not all changes, however, result in positive effects on the assessed community metrics. For example, whether woodland conversion positively or negatively affects community size and complexity depends on woodland type and, potentially, the changes in soil properties, such as pH, that may occur during conversion. Alterations in soil communities tended to facilitate subsequent changes in soil structure and hydrology. For example, increasing earthworm abundances and functional group composition were shown to be positively correlated with water infiltration rate (dependent on tillage regime and habitat characteristics); while positive changes in fungal biomass measures were positively associated with soil microaggregate stability. Conclusions These findings raise the potential to manage landscapes to increase ecosystem service provision from soil biota in relation to regulation of soil structure and water flow. PMID:24289220

  8. Structural properties of end-linked polymer networks: Monte Carlo simulation and neutron scattering studies

    NASA Astrophysics Data System (ADS)

    Gilra, Nisha

    2000-12-01

    In this work, computational and experimental approaches were taken to elucidate the structural behavior of end- linked polymer networks. Monte Carlo simulations with the bond fluctuation model were used to study the formation and structure of 10-, 20-, and 50-mer networks cured with various ratios of cross-link sites to chain ends, r. The simulations confirmed experimental results that optimum r values for structural properties are found at non- stoichiometric ratios, increase with increasing precursor polymer chain length, and increase with side reaction. The same structural properties were determined for 50-mer networks formed in the presence of a series of concentrations of 50-mer unreactive linear chain diluent. A slight maximum in the fraction of elastic material was observed at a small degree of dilution and was explained in terms of entanglement effects. The conformational behavior of a small fraction of 50-mer linear probe chains was studied in various polymer network mesh sizes, where mesh size is the number of monomers between cross- links. The radius of gyration, R g, of the probe chains decreased by less than 6% for all mesh sizes studied. Uniaxial network deformation was studied using constant pressure simulations. A new methodology to perform volume change moves was developed. The equation of state of 10- mer athermal network system was determined and found to be similar to the corresponding athermal linear polymer equation of state at high volume fractions, but approached a region of negative pressures at low volume fractions. The chain segment orientational correlation was determined for probe free chains trapped in isotropic and deformed networks. Increased correlation was observed at small distances, whereas no orientational preference was evident at larger distances. The study of probe free chains trapped in polymer networks was also performed using small-angle neutron scattering. The conformational behavior of 70K poly(dimethylsiloxane) (PDMS

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

    PubMed

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

    2014-09-01

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

  10. a Study of the Magnetic and Structural Properties of Small Iron and Cobalt Particles

    NASA Astrophysics Data System (ADS)

    Gangopadhyay, Sunita Bhardwaj

    The magnetic and structural properties of Fe and Co particles with different surface chemistries have been investigated in the size range of 50-400 A. The particles were prepared by vapor deposition in an inert environment. Particles with different surface chemistries were obtained: passivated with oxygen (Metal(Fe,Co)/FeO), sandwiched between two silver films (Metal(Fe,Co)/Ag), and surrounded by a Mg matrix (Metal(Fe,Co)/Mg). The effect of surface chemistry and particle size on the magnetic properties was studied. An attempt was made to explain the origin of high coercivity and reduced magnetization in small ferromagnetic particles by studying their microstructure, hysteresis, magnetization, exchange coupling and magnetic interactions. Magnetization, Mossbauer and structural data clearly show a "core-shell" morphology, where the core is metallic and the shell is polycrystalline Fe(Co)-oxide. The results indicate that the oxide shell controls both the magnitude and the temperature dependence of coercivity. The exchange coupling at the core-shell interface results in large anisotropy, which not only enhances the coercivity, but also causes larger switching field distributions. The surface oxide shell also contributes towards a reduction in magnetization of the small ferromagnetic particles by inducing strong pinning of the moments at the core-shell interface.

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

    PubMed

    Walker, Joseph R; Brown, Karen; Rohatagi, Shashank; Bathala, Mohinder S; Xu, Chao; Wickremasingha, Prachi K; Salazar, Daniel E; Mager, Donald E

    2009-10-01

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

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

    PubMed

    de Melo, Eduardo Borges

    2012-01-01

    A quantitative structure-property relationship (QSPR) study for predicting the logarithm of bioconcentration factors (LogBCF) of polychlorinated biphenyls (PCBs) is presented in this work. For this, the descriptors were obtained using only the Simplified Molecular Input Line Entry System (SMILES) strings in the free web server Parameter Client. The model was built using the Partial Least Squares (PLS) regression method. The best model presented five descriptors (one E-state index and four topological descriptors) and a high quality for fit, internal, and external predictions. The leave-N-out (LNO) cross validation and the y-randomization test showed the model is robust and has no shown chance correlation. With a second test set, the model was compared to other models and presented a root mean square error (RMSE) very close to the best model. The mechanistic interpretation was corroborated by other works in the literature and by the descriptors' theory. Thus, the results meet the five Organization for Economic Co-operation and Development (OECD) principles for validation of QSA(P)R models, and it is expected the model can effectively predict the BCF values in fishes of the PCB congeners without highly reliable experimental BCF. PMID:21959189

  13. Research on the relationship between the structural properties of bedding layer in spring mattress and sleep quality.

    PubMed

    Shen, Liming; Chen, Yu-xia; Guo, Yong; Zhong, ShiLu; Fang, Fei; Zhao, Jing; Hu, Tian-Yi

    2012-01-01

    Mattress, as a sleep platform, its types and physical properties has an important effect on sleep quality and rest efficiency. In this paper, by subjective evaluations, analysis of sleeping behaviors and tests of depth of sleep, the relationship between characteristics of the bedding materials, the structure of mattress, sleep quality and sleep behaviors were studied. The results showed that: (1) Characteristics of the bedding materials and structure of spring mattress had a remarkable effect on sleep behaviors and sleep quality. An optimum combination of the bedding materials, the structure of mattress and its core could improve the overall comfort of mattress, thereby improving the depth of sleep and sleep quality. (2) Sleep behaviors had a close relationship with sleeping postures and sleep habits. The characteristics of sleep behaviors vary from person to person.

  14. Supramolecular Dimerization and [2 + 2] Photocycloaddition Reactions of Crown Ether Styryl Dyes Containing a Tethered Ammonium Group: Structure-Property Relationships.

    PubMed

    Ushakov, Evgeny N; Vedernikov, Artem I; Lobova, Natalia A; Dmitrieva, Svetlana N; Kuz'mina, Lyudmila G; Moiseeva, Anna A; Howard, Judith A K; Alfimov, Michael V; Gromov, Sergey P

    2015-12-31

    Molecular self-assembly is an effective strategy for controlling the [2 + 2] photocycloaddition reaction of olefins. The geometrical properties of supramolecular assemblies are proven to have a critical effect on the efficiency and selectivity of this photoreaction both in the solid state and in solution, but the role of other factors remains poorly understood. Convenient supramolecular systems to study the structure-property relationships are pseudocyclic dimers spontaneously formed by styryl dyes containing a crown ether moiety and a remote ammonium group. New dyes of this type were synthesized to investigate the effects of structural and electronic factors on the quantitative characteristics of supramolecular dimerization and [2 + 2] photocycloaddition in solution. Variable structural parameters for the styryl dyes were the size and structure of macrocyclic moiety, the nature of heteroaromatic residue, and the length of the ammonioalkyl group attached to this residue. Quantum chemical calculations of the pseudocyclic dimers were performed in order to interpret the relationships between the structure of the ammonium dyes and the efficiency of the supramolecular photoreaction. One of the dimeric complexes was obtained in the crystalline state and studied by X-ray diffraction. The results obtained demonstrate that the photocycloaddition in the pseudocyclic dimers can be dramatically affected by the electronic structure of the styryl moieties, as dependent on the electron-donating ability of the substituents on the benzene ring, and by the conformational flexibility of the pseudocycle, which determines the mobility of the olefinic bonds. The significance of electronic factors is highlighted by the fact that the photocycloaddition quantum yield in geometrically similar dimeric structures varies from ≤10(-4) to 0.38. The latter value is unusually high for olefins in solution. PMID:26650887

  15. Supramolecular Dimerization and [2 + 2] Photocycloaddition Reactions of Crown Ether Styryl Dyes Containing a Tethered Ammonium Group: Structure-Property Relationships.

    PubMed

    Ushakov, Evgeny N; Vedernikov, Artem I; Lobova, Natalia A; Dmitrieva, Svetlana N; Kuz'mina, Lyudmila G; Moiseeva, Anna A; Howard, Judith A K; Alfimov, Michael V; Gromov, Sergey P

    2015-12-31

    Molecular self-assembly is an effective strategy for controlling the [2 + 2] photocycloaddition reaction of olefins. The geometrical properties of supramolecular assemblies are proven to have a critical effect on the efficiency and selectivity of this photoreaction both in the solid state and in solution, but the role of other factors remains poorly understood. Convenient supramolecular systems to study the structure-property relationships are pseudocyclic dimers spontaneously formed by styryl dyes containing a crown ether moiety and a remote ammonium group. New dyes of this type were synthesized to investigate the effects of structural and electronic factors on the quantitative characteristics of supramolecular dimerization and [2 + 2] photocycloaddition in solution. Variable structural parameters for the styryl dyes were the size and structure of macrocyclic moiety, the nature of heteroaromatic residue, and the length of the ammonioalkyl group attached to this residue. Quantum chemical calculations of the pseudocyclic dimers were performed in order to interpret the relationships between the structure of the ammonium dyes and the efficiency of the supramolecular photoreaction. One of the dimeric complexes was obtained in the crystalline state and studied by X-ray diffraction. The results obtained demonstrate that the photocycloaddition in the pseudocyclic dimers can be dramatically affected by the electronic structure of the styryl moieties, as dependent on the electron-donating ability of the substituents on the benzene ring, and by the conformational flexibility of the pseudocycle, which determines the mobility of the olefinic bonds. The significance of electronic factors is highlighted by the fact that the photocycloaddition quantum yield in geometrically similar dimeric structures varies from ≤10(-4) to 0.38. The latter value is unusually high for olefins in solution.

  16. High-throughput determination of quantitative structure-property relationships using a resonant multisensor system: solvent resistance of bisphenol a polycarbonate copolymers.

    PubMed

    Potyrailo, Radislav A; McCloskey, Patrick J; Wroczynski, Ronald J; Morris, William G

    2006-05-01

    Polymers are important materials for sensor, microfluidic, and other demanding applications. High-throughput screening methodology has been applied for the evaluation of the solvent resistance of a family of polycarbonate copolymers prepared from the reaction of bisphenol A (BPA), hydroquinone (HQ), and resorcinol (RS) in different solvents of practical importance, such as chloroform, tetrahydrofuran (THF), and methyl ethyl ketone (MEK). We employed a 24-channel acoustic-wave sensor system that provided previously unavailable capabilities for parallel evaluation of polymer solvent resistance. This high-throughput polymer evaluation approach assisted in construction of detailed solvent-resistance maps of polycarbonate copolymers and in determination of quantitative structure-property relationships. The best absolute solvent resistance of all studied copolymers was achieved in MEK, followed by chloroform and THF. A D-optimal mixture design was employed to explore the relationship between the copolymer compositions and their solvent resistance. The applied special cubic model for each solvent took into account the primary mixture terms such as BPA, HQ, and RS; binary interaction terms such as BPA-HQ, BPA-RS, and HQ-RS; and a ternary interaction term BPA-HQ-RS. A combination of the normal distribution of the model residuals and the very high values of adjusted R2 (0.97-0.99) demonstrated a good quality of the model. At a HQ concentration of 40 mol %, the solvent resistance was the highest for all tested solvents, and different concentrations of BPA (40 and 60 mol %) and RS (0 and 20 mol %) did not affect the solvent resistance. Without HQ, solvent resistance was decreasing with an increase of RS and decrease of BPA. Overall, with an increase of HQ concentration from 0 to 40 mol %, the solvent resistance of BPA-HQ-RS copolymers was improved by up to 3 times in THF, by 21 times in chloroform, and by 32 times in MEK.

  17. Structure-property relationships in an Al matrix Ca nanofilamentary composite conductor with potential application in high-voltage power transmission

    NASA Astrophysics Data System (ADS)

    Tian, Liang

    This study investigated the processing-structure-properties relationships in an Al/Ca composites using both experiments and modeling/simulation. A particular focus of the project was understanding how the strength and electrical conductivity of the composite are related to its microstructure in the hope that a conducting material with light weight, high strength, and high electrical conductivity can be developed to produce overhead high-voltage power transmission cables. The current power transmission cables (e.g., Aluminum Conductor Steel Reinforced (ACSR)) have acceptable performance for high-voltage AC transmission, but are less well suited for high-voltage DC transmission due to the poorly conducting core materials that support the cable weight. This Al/Ca composite was produced by powder metallurgy and severe plastic deformation by extrusion and swaging. The fine Ca metal powders have been produced by centrifugal atomization with rotating liquid oil quench bath, and a detailed study about the atomization process and powder characteristics has been conducted. The microstructure of Al/Ca composite was characterized by electron microscopy. Microstructure changes at elevated temperature were characterized by thermal analysis and indirect resistivity tests. The strength and electrical conductivity were measured by tensile tests and four-point probe resistivity tests. Predicting the strength and electrical conductivity of the composite was done by micro-mechanics-based analytical modeling. Microstructure evolution was studied by mesoscale-thermodynamics-based phase field modeling and a preliminary atomistic molecular dynamics simulation. The application prospects of this composite was studied by an economic analysis. This study suggests that the Al/Ca (20 vol. %) composite shows promise for use as overhead power transmission cables. Further studies are needed to measure the corrosion resistance, fatigue properties and energized field performance of this composite.

  18. Structures, properties, and functions of the stings of honey bees and paper wasps: a comparative study

    PubMed Central

    Zhao, Zi-Long; Zhao, Hong-Ping; Ma, Guo-Jun; Wu, Cheng-Wei; Yang, Kai; Feng, Xi-Qiao

    2015-01-01

    ABSTRACT Through natural selection, many animal organs with similar functions have evolved different macroscopic morphologies and microscopic structures. Here, we comparatively investigate the structures, properties and functions of honey bee stings and paper wasp stings. Their elegant structures were systematically observed. To examine their behaviors of penetrating into different materials, we performed penetration–extraction tests and slow motion analyses of their insertion process. In comparison, the barbed stings of honey bees are relatively difficult to be withdrawn from fibrous tissues (e.g. skin), while the removal of paper wasp stings is easier due to their different structures and insertion skills. The similarities and differences of the two kinds of stings are summarized on the basis of the experiments and observations. PMID:26002929

  19. Schematic Studies on the Structural Properties and Device Physics of All Small Molecule Ternary Photovoltaic Cells.

    PubMed

    Kim, Yu Jin; Hong, Jisu; Park, Chan Eon

    2015-09-30

    Although the field of ternary organic solar cells has seen much progress in terms of device performance in the past few years, limited understanding has restricted further development. For example, studies of the crystalline packing structure of ternary blends have rarely been reported in the solar cell field. Consequently, we chose two ternary blends of small molecules, two fullerene derivatives (small-molecule:PC71BM:PC61BM or small-molecule:PC71BM:ICBA), to investigate crystallization behavior and interactions among the three components. The crystalline structure of the ternary active blends was characterized using various techniques such as 2D-GIWAXS and AFM, and the relationship of the observed morphologies to device performance is discussed. Furthermore, the device physics associated with the charge generation, transport, and recombination dynamics of these ternary blend systems were investigated.

  20. Electronic and structural properties of nitrogen adsorbed Nb(100) surfaces: An ab initio study

    NASA Astrophysics Data System (ADS)

    Carvalho, P. A. S.; Miwa, R. H.

    2013-08-01

    We have performed an ab initio total energy investigation of the electronic and structural properties of nitrogen adsorbed Nb(100) surface, N/Nb(100). We find an energetic preference for the nitrogen adsorption on the hollow sites of the Nb(100) surface. Upon the presence of N adatoms, there is a reduction of the electronic density of states near the Fermi level. However, the metallic character of the Nb(100) surface has been maintained. The (occupied) electronic states of N adatoms are resonant within the valence band of Nb(100), mostly lying at 4 eV below the Fermi level. Further investigations reveal the formation of energetically stable N/Nb(100)-(n × 1) phase, being the (2 × 1), (5 × 1), and (10 × 1) the most likely ones. Those (n × 1) structures are composed by NbN stripes separated by N vacancy lines. Our scanning tunneling microscopy simulations indicate the formation of bright lines lying on the Nb atoms neighboring the (dark) N vacancy lines, giving rise to an anisotropic electronic structure on the N/Nb(100)-(n × 1) surface. That is, the metallic character of the surface has been strengthened along the vacancy-lines.

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

    NASA Astrophysics Data System (ADS)

    Krein, Michael

    After decades of development and use in a variety of application areas, Quantitative Structure Property Relationships (QSPRs) and related descriptor-based statistical learning methods have achieved a level of infamy due to their misuse. The field is rife with past examples of overtrained models, overoptimistic performance assessment, and outright cheating in the form of explicitly removing data to fit models. These actions do not serve the community well, nor are they beneficial to future predictions based on established models. In practice, in order to select combinations of descriptors and machine learning methods that might work best, one must consider the nature and size of the training and test datasets, be aware of existing hypotheses about the data, and resist the temptation to bias structure representation and modeling to explicitly fit the hypotheses. The definition and application of these best practices is important for obtaining actionable modeling outcomes, and for setting user expectations of modeling accuracy when predicting the endpoint values of unknowns. A wide variety of statistical learning approaches, descriptor types, and model validation strategies are explored herein, with the goals of helping end users understand the factors involved in creating and using QSPR models effectively, and to better understand relationships within the data, especially by looking at the problem space from multiple perspectives. Molecular relationships are commonly envisioned in a continuous high-dimensional space of numerical descriptors, referred to as chemistry space. Descriptor and similarity metric choice influence the partitioning of this space into regions corresponding to local structural similarity. These regions, known as domains of applicability, are most likely to be successfully modeled by a QSPR. In Chapter 2, the network topology and scaling relationships of several chemistry spaces are thoroughly investigated. Chemistry spaces studied include the

  2. Theoretical Studies on Structures, Properties and Dominant Debromination Pathways for Selected Polybrominated Diphenyl Ethers.

    PubMed

    Li, Lingyun; Hu, Jiwei; Shi, Xuedan; Ruan, Wenqian; Luo, Jin; Wei, Xionghui

    2016-01-01

    The B3LYP/6-311+G(d)-SDD method, which considers the relativistic effect of bromine, was adopted for the calculations of the selected polybrominated diphenyl ethers (PBDEs) in the present study, in which the B3LYP/6-311+G(d) method was also applied. The calculated values and experimental data for structural parameters of the selected PBDEs were compared to find the suitable theoretical methods for their structural optimization. The results show that the B3LYP/6-311+G(d) method can give the better results (with the root mean square errors (RMSEs) of 0.0268 for the C-Br bond and 0.0161 for the C-O bond) than the B3LYP/6-311+G(d)-SDD method. Then, the B3LYP/6-311+G(d) method was applied to predict the structures for the other selected PBDEs (both neutral and anionic species). The lowest unoccupied molecular orbital (LUMO) and the electron affinity are of a close relationship. The electron affinities (vertical electron affinity and adiabatic electron affinity) were discussed to study their electron capture abilities. To better estimate the conversion of configuration for PBDEs, the configuration transition states for BDE-5, BDE-22 and BDE-47 were calculated at the B3LYP/ 6-311+G(d) level in both gas phase and solution. The possible debromination pathway for BDE-22 were also studied, which have bromine substituents on two phenyl rings and the bromine on meta-position prefers to depart from the phenyl ring. The reaction profile of the electron-induced reductive debromination for BDE-22 were also shown in order to study its degradation mechanism. PMID:27322242

  3. Theoretical Studies on Structures, Properties and Dominant Debromination Pathways for Selected Polybrominated Diphenyl Ethers

    PubMed Central

    Li, Lingyun; Hu, Jiwei; Shi, Xuedan; Ruan, Wenqian; Luo, Jin; Wei, Xionghui

    2016-01-01

    The B3LYP/6-311+G(d)-SDD method, which considers the relativistic effect of bromine, was adopted for the calculations of the selected polybrominated diphenyl ethers (PBDEs) in the present study, in which the B3LYP/6-311+G(d) method was also applied. The calculated values and experimental data for structural parameters of the selected PBDEs were compared to find the suitable theoretical methods for their structural optimization. The results show that the B3LYP/6-311+G(d) method can give the better results (with the root mean square errors (RMSEs) of 0.0268 for the C–Br bond and 0.0161 for the C–O bond) than the B3LYP/6-311+G(d)-SDD method. Then, the B3LYP/6-311+G(d) method was applied to predict the structures for the other selected PBDEs (both neutral and anionic species). The lowest unoccupied molecular orbital (LUMO) and the electron affinity are of a close relationship. The electron affinities (vertical electron affinity and adiabatic electron affinity) were discussed to study their electron capture abilities. To better estimate the conversion of configuration for PBDEs, the configuration transition states for BDE-5, BDE-22 and BDE-47 were calculated at the B3LYP/ 6-311+G(d) level in both gas phase and solution. The possible debromination pathway for BDE-22 were also studied, which have bromine substituents on two phenyl rings and the bromine on meta-position prefers to depart from the phenyl ring. The reaction profile of the electron-induced reductive debromination for BDE-22 were also shown in order to study its degradation mechanism. PMID:27322242

  4. Structure-property correlation study through sum-over-state approach

    NASA Astrophysics Data System (ADS)

    Nandi, P. K.; Hatua, K.; Bansh, A. K.; Panja, N.; Ghanty, T. K.

    2015-01-01

    The use of Thomas Kuhn (TK) sum rule in the expanded sum-over-state (SOS) expression of hyperpolarizabilities leads to various relationships between different order of polarizabilities and ground state dipole moment etc.

  5. The effects of high energy electron beam irradiation in air on accelerated aging and on the structure property relationships of low density polyethylene

    NASA Astrophysics Data System (ADS)

    Murray, Kieran A.; Kennedy, James E.; McEvoy, Brian; Vrain, Olivier; Ryan, Damien; Cowman, Richard; Higginbotham, Clement L.

    2013-02-01

    The response of low density polyethylene (LDPE) to high energy electron beam irradiation in air (10 MeV) between 25 and 400 kGy was examined and compared to non-irradiated polyethylene in terms of the mechanical and structural properties. To quantify the degree of crosslinking, swelling studies were performed and from this it was observed that the crosslink density increased as the irradiation dose increased. Furthermore, a reduction was observed in the numerical data for molar mass between adjacent crosslinks and the number of monomeric units between adjacent crosslinks as the irradiation dose was conducted incrementally. Accelerated aging provided evidence that radicals became trapped in the polymer matrix of LDPE and this in turn initiated further reactions to transpire as time elapsed, leading to additional alteration in the structural properties. Fourier transform infrared spectroscopy (FTIR) was implemented to provide insight into this. This technique established that the aging process had increased the oxidative degradation products due to oxygen permeation into the polymer and double bonds within the material. Mechanical testing revealed an increase in the tensile strength and a decrease in the elongation at break. Accelerated aging caused additional modifications to occur in the mechanical properties which are further elucidated throughout this study. Dynamic frequency sweeps investigated the effects of irradiation on the structural properties of LDPE. The effect of varying the irradiation dose concentration was apparent as this controlled the level of crosslinking within the material. Maxwell and Kelvin or Voigt models were employed in this analytical technique to define the reaction procedure of the frequency sweep test with regards to non-crosslinked and crosslinked LDPE.

  6. Harnessing Structure-Property Relationships for Poly(alkyl thiophene)-Fullerene Derivative Thin Filmsto Optimize Performance in Photovoltaic Devices

    DOE PAGES

    Deb, Nabankur; Li, Bohao; Skoda, Maximilian; Rogers, Sarah; Sun, Yan; Gong, Xiong; Karim, Alamgir; Sumpter, Bobby G.; Bucknall, David G.

    2016-02-08

    Nanoscale bulk heterojunction (BHJ) systems, consisting of fullerenes dispersed in conjugated polymers as the active component, have been actively studied over the last decades in order to produce high performance organic photovoltaics (OPVs). A significant role in device efficiency is played by the active layer morphology, but despite considerable study, a full understanding of the exact role that morphology plays and therefore a definitive method to produce and control an ideal morphology is lacking. In order to understand the BHJ phase behavior and associated morphology in these devices, we have used neutron reflection, together with grazing incidence X-ray and neutronmore » scattering and X-ray photoelectron spectroscopy (XPS) to determine the morphology of the BHJ active layer in functional devices. We have studied nine model BHJ systems based on mixtures of three poly(3-alkyl thiophenes, P3AT) (A=butyl, hexyl, octyl) blended with three different fullerene derivatives, which provides variations in crystallinity and miscibility within the BHJ composite. In studying properties of functional devices, we show a direct correlation between the observed morphology within the BHJ layer and the device performance metrics, i.e., the short-circuit current (JSC), fill factor (FF), open-circuit voltage (VOC) and overall power conversion efficiency (PCE). Using these model systems, the effect of typical thermal annealing processes on the BHJ morphology through the film thickness as a function of the polythiophene-fullerene mixtures and different electron transport layer interfaces has been determined. It is shown that fullerene enrichment occurs at both the electrode interfaces after annealing. The degree of fullerene enrichment is found to strongly correlate with JSC and to a lesser degree with FF. Finally, based on these findings we demonstrate that by deliberately adding a fullerene layer at the electron transport layer interface, JSC can be increased by up to 20

  7. Structure-Property Relationship of CaO-MgO-SiO2 Slag: Quantitative Analysis of Raman Spectra

    NASA Astrophysics Data System (ADS)

    Park, Joo Hyun

    2013-08-01

    The quantitative structural information such as the relative abundance of silicate discrete anions (Q n units) and the concentration of three types of oxygens, viz. free-, bridging- and nonbridging oxygen can be obtained from micro-Raman spectra of the quenched CaO-SiO2-MgO glass samples. Various transport properties such as viscosity, density, and electrical conductivity can be expected as a simple linear function of "ln (Q3/Q2)," indicating that these physical properties are strongly dependent on a degree of polymerization of silicate melts. The methodology outlined in the current study can be extended to predict the physicochemical properties of silicate melts in ferrous and non-ferrous metallurgical processes.

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

    PubMed

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

    2014-04-01

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

  9. Structure-property relationships in non-epitaxial chalcogenide heterostructures: the role of interface density on charge exchange

    NASA Astrophysics Data System (ADS)

    Bauers, S. R.; Ditto, J.; Moore, D. B.; Johnson, D. C.

    2016-07-01

    A homologous series of quasi-2D ([PbSe]1+δ)m(TiSe2)m nanolayered heterostructures are prepared via self-assembly of designed precursors with 1 <= m <= 4 and their structures and properties investigated. All heterostructures have the same global composition but vary in their interface density. X-ray diffraction and electron microscopy studies show that the structures consist of rock salt structured PbSe layers alternating with TiSe2 layers, and that grain size increases with m. The compounds are all metallic with upturns in resistivity at low temperature suggesting electron localization, with room temperature resistivity of 1-3 10-5 Ω m, negative Hall coefficients and Seebeck coefficients between -50 and -100 μV K-1. A decrease in the mobile carrier concentration with temperature is observed for all m and the rate increases with increasing low-dimensionality. Decreasing the interface density also decreases the average carrier concentration while increasing the electron mobility. The Seebeck coefficients systematically increase in magnitude as m is increased, but the net effect to the power factor is small due to a compensating increase in resistivity. The observed transport behavior is not described by the simple rigid band models with charge transfer between constituents used previously. Charge exchange between constituents stabilizes the intergrowth, but also introduces mobile carriers and interfacial band bending that must play a role in the transport behavior of the heterostructures. As chemical potentials equilibrate in high m heterostructures there is a decrease in total coulombic stabilization as there are fewer interfaces, so m = 1 is likely to be most stable. This rationalizes why the structurally similar misfit layer compounds with m = 1 are often the only intergrowths that can be prepared. Charge transfer and band bending at interfaces should occur in other heterostructures with similar type II broken-gap band alignments and are important

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

    NASA Astrophysics Data System (ADS)

    Rathmell, Aaron R.

    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

  11. An in-situ analytical scanning and transmission electron microscopy investigation of structure-property relationships in electronic materials

    NASA Astrophysics Data System (ADS)

    Wagner, Andrew James

    As electronic and mechanical devices are scaled downward in size and upward in complexity, macroscopic principles no longer apply. Synthesis of three-dimensionally confined structures exhibit quantum confinement effects allowing, for example, silicon nanoparticles to luminesce. The reduction in size of classically brittle materials reveals a ductile-to-brittle transition. Such a transition, attributed to a reduction in defects, increases elasticity. In the case of silicon, elastic deformation can improve electronic carrier mobility by over 50%, a vital attribute of modern integrated circuits. The scalability of such principles and the changing atomistic processes which contribute to them presents a vitally important field of research. Beginning with the direct observation of dislocations and lattice planes in the 1950s, the transmission electron microscope has been a powerful tool in materials science. More recently, as nanoscale technologies have proliferated modern life, their unique ability to spatially resolve nano- and atomic-scale structures has become a critical component of materials research and characterization. Signals produced by an incident beam of high-energy electrons enables researchers to both image and chemically analyze materials at the atomic scale. Coherently and elastically-scattered electrons can be collected to produce atomic-scale images of a crystalline sample. New specimen stages have enabled routine investigation of samples heated up to 1000 °C and cooled to liquid nitrogen temperatures. MEMS-based transducers allow for sub-nm scale mechanical testing and ultrathin membranes allow study of liquids and gases. Investigation of a myriad of previously "unseeable" processes can now be observed within the TEM, and sometimes something new is found within the old. High-temperature annealing of pure a Si:H films leads to crystallization of the film. Such films provide higher carrier mobility compared to amorphous films, offering improved

  12. An in-situ analytical scanning and transmission electron microscopy investigation of structure-property relationships in electronic materials

    NASA Astrophysics Data System (ADS)

    Wagner, Andrew James

    As electronic and mechanical devices are scaled downward in size and upward in complexity, macroscopic principles no longer apply. Synthesis of three-dimensionally confined structures exhibit quantum confinement effects allowing, for example, silicon nanoparticles to luminesce. The reduction in size of classically brittle materials reveals a ductile-to-brittle transition. Such a transition, attributed to a reduction in defects, increases elasticity. In the case of silicon, elastic deformation can improve electronic carrier mobility by over 50%, a vital attribute of modern integrated circuits. The scalability of such principles and the changing atomistic processes which contribute to them presents a vitally important field of research. Beginning with the direct observation of dislocations and lattice planes in the 1950s, the transmission electron microscope has been a powerful tool in materials science. More recently, as nanoscale technologies have proliferated modern life, their unique ability to spatially resolve nano- and atomic-scale structures has become a critical component of materials research and characterization. Signals produced by an incident beam of high-energy electrons enables researchers to both image and chemically analyze materials at the atomic scale. Coherently and elastically-scattered electrons can be collected to produce atomic-scale images of a crystalline sample. New specimen stages have enabled routine investigation of samples heated up to 1000 °C and cooled to liquid nitrogen temperatures. MEMS-based transducers allow for sub-nm scale mechanical testing and ultrathin membranes allow study of liquids and gases. Investigation of a myriad of previously "unseeable" processes can now be observed within the TEM, and sometimes something new is found within the old. High-temperature annealing of pure a Si:H films leads to crystallization of the film. Such films provide higher carrier mobility compared to amorphous films, offering improved

  13. Structural properties of Al and TiAl3 metallic glasses — An embedded atom method study

    NASA Astrophysics Data System (ADS)

    Tahiri, M.; Trady, S.; Hasnaoui, A.; Mazroui, M.; Saadouni, K.; Sbiaai, K.

    2016-06-01

    In this paper, we investigated the structural properties of metallic glasses (MGs). We emphasized our study on monatomic Al and binary TiAl3 systems. The calculations are performed by using the molecular dynamics (MD) simulation based on semi-empirical many-body potentials derived from the embedded atom method. The structure is analyzed using the radial distribution function (RDF), the common neighbor analysis (CNA) and the coordination numbers (CNs). Our results demonstrated that it is possible to form MGs in both systems upon fast cooling from the liquid state. This is confirmed by the fact that the system energy and/or volume during the cooling stage decrease continuously with a slight change and by atomic scale analysis using the RDF, CNA and CN analyzing techniques. Furthermore, this specific study shows that under the same conditions, the icosahedral structures appeared in TiAl3 are more abundant than in pure Al. Implications of these findings are discussed.

  14. Silver nanowires electrodeposited into nanoporous templates: Study of the influence of sizes on crystallinity and structural properties

    NASA Astrophysics Data System (ADS)

    Dalchiele, E. A.; Marotti, R. E.; Cortes, A.; Riveros, G.; Gómez, H.; Martínez, L.; Romero, R.; Leinen, D.; Martin, F.; Ramos-Barrado, J. R.

    2007-03-01

    In this work, results on the study of the influence of silver nanowire dimensions on the crystallinity and structural properties are presented. Silver nanowire arrays with high aspect ratios were prepared in the hollow structures of nanoporous templates using potentiostatic electrodeposition. Two types of material were employed as a template: commercial porous anodic aluminum oxide (with a mean pore diameter of 180 nm) and track-etched polycarbonate membranes (with a mean pore diameter of 15, 30 and 80 nm). Characterization of the silver nanowires has been done by EDS, XRD, TEM and electron diffraction. The degree of preferred crystallographic orientation (along the (1 1 1), (2 0 0) or (2 2 0) crystallographic planes) and the crystallite size of the silver nanowires as a function of template pore diameter are given and discussed.

  15. Quantitative Structure-Property Relationship (QSPR) Models for a Local Quantum Descriptor: Investigation of the 4- and 3-Substituted-Cinnamic Acid Esterification.

    PubMed

    Rodrigues-Santos, Cláudio E; Echevarria, Aurea; Sant'Anna, Carlos M R; Bitencourt, Thiago B; Nascimento, Maria G; Bauerfeldt, Glauco F

    2015-09-22

    In this work, the theoretical description of the 4- and 3-substituted-cinnamic acid esterification with different electron donating and electron withdrawing groups was performed at the B3LYP and M06-2X levels, as a two-step process: the O-protonation and the nucleophile attack by ethanol. In parallel, an experimental work devoted to the synthesis and characterization of the substituted-cinnamate esters has also been performed. In order to quantify the substituents effects, quantitative structure-property relationship (QSPR) models based on the atomic charges, Fukui functions and the Frontier Effective-for-Reaction Molecular Orbitals (FERMO) energies were investigated. In fact, the Fukui functions, ƒ⁺C and ƒ(-)O, indicated poor correlations for each individual step, and in contrast with the general literature, the O-protonation step is affected both by the FERMO energies and the O-charges of the carbonyl group. Since the process was shown to not be totally described by either charge- or frontier-orbitals, it is proposed to be frontier-charge-miscere controlled. Moreover, the observed trend for the experimental reaction yields suggests that the electron withdrawing groups favor the reaction and the same was observed for Step 2, which can thus be pointed out as the determining step.

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

    PubMed

    Gawor, Anya; Wania, Frank

    2013-09-01

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

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

    PubMed

    Carbó-Dorca, Ramon

    2013-04-01

    A general algorithm implementing a useful variant of quantum quantitative structure-property relationships (QQSPR) theory is described. Based on quantum similarity framework and previous theoretical developments on the subject, the present QQSPR procedure relies on the possibility to perform geometrical origin shifts over molecular density function sets. In this way, molecular collections attached to known properties can be easily used over other quantum mechanically well-described molecular structures for the estimation of their unknown property values. The proposed procedure takes quantum mechanical expectation value as provider of causal relation background and overcomes the dimensionality paradox, which haunts classical descriptor space QSPR. Also, contrarily to classical procedures, which are also attached to heavy statistical gear, the present QQSPR approach might use a geometrical assessment only or just some simple statistical outline or both. From an applied point of view, several easily reachable computational levels can be set up. A Fortran 95 program: QQSPR-n is described with two versions, which might be downloaded from a dedicated web site. Various practical examples are provided, yielding excellent results. Finally, it is also shown that an equivalent molecular space classical QSPR formalism can be easily developed. PMID:23238931

  18. Synthesis and Structure-Property Relationships in (h6-Arene)Cr(CO)3 Chemistry: From Guided Experiments to Discovery Research

    NASA Astrophysics Data System (ADS)

    Hunter, Allen D.; Bianconi, Larry J.; Dimuzio, Steven J.; Braho, Dianne L.

    1998-07-01

    (h6-Arene)Cr(CO)3 complexes are only moderately air sensitive and can easily and inexpensively be prepared from most of the arenes already found in organic stockrooms. Since instructors can have each student prepare a different complex, they are ideal targets for student directed "discovery research" lab projects. Teams of students can compare how their syntheses and the physical, spectroscopic, and electrochemical properties of their products vary as a function of the arenes structures. The resulting empirical structure/property correlations can then be rationalized in terms of various bonding models. A discussion of (h6-arene)Cr(CO)3 chemistry suitable for student handouts is included along with suggestions for extending this experiment to create multi-step organic and inorganic synthesis projects. In addition, generic procedures for the syntheses using relatively simple glassware, example reaction procedures at both micro and conventional scales, practical hints for carrying out the syntheses, a discussion of substituent effects on arene suitability, lists of required equipment, and diagrams of the assembled glassware are included. Characterization data for over five dozen (h6-Arene)Cr(CO)3 complexes are tabulated. These data are particularly suitable for use as lecture, examination, and/or problem set examples in discussions of the relationships between structure, bonding, spectroscopy, electrochemistry, and reactivity in organometallic chemistry.

  19. Modeling of a short-path distillation process to remove persistent organic pollutants in fish oil based on process parameters and quantitative structure properties relationships.

    PubMed

    Oterhals, Age; Kvamme, Bjørn; Berntssen, Marc H G

    2010-06-01

    A factorial experimental design based on temperature, feed rate and addition of "working fluid" (WF; fatty acid ethyl esters) was used to model a short-path distillation process applied for removal of persistent organic pollutants (POPs) in fish oil. Decontamination effect was assessed by measuring the level of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (DL-PCBs) and polybrominated diphenylethers (PBDEs). The average reduction in chemical concentration of the individual PCDD, PCDF, DL-PCB and PBDE congeners was linearly dependent on the number of chlorine or bromine substitutions within each homologue group. DL-PCB and PBDE congeners could also be separated based on ortho-substitution. The quantitative structure properties relationships (QSPR) were combined with process parameters to establish response surface models for each homologue congener group based on partial least squares regression (PLSR). Cross validated predictive ability of the models was in the 4-9% range. Generally high temperature, low feed rate and WF addition improved the decontamination efficiency. The WHO-PCDD/F-PCB-TEQ level could be reduced by up to 98% based on the best experimental settings with residual concentration considerably below present maximum permitted levels in European food and feed legislations.

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

    NASA Astrophysics Data System (ADS)

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

    2008-05-01

    By performing both Z-scan and transient transmission measurements with 130 fs laser pulses in the near infrared region, we investigated structure-property relationships for χ(3) in acceptor-substituted 3,4,5-trimethoxy chalcone derivatives. We determined all nonlinear parameters, including two-photon absorption (2PA) cross section, 2PA-induced excited-state absorption (ESA) cross section, microscopic second-order hyperpolarizability, and lifetime of the excited state in these molecules. We found that the microscopic second-order hyperpolarizability γR and 2PA cross section σ2PA in chalcone derivatives increase as the acceptor strength of the molecules increases, which demonstrates an enhancement in optical nonlinearities by simple structural variations. We evaluated the one-photon, two-photon, and effective three-photon figures of merit for acetone solutions of chalcone derivatives at irradiance of 100 GW/cm2. Furthermore, we observed optical limiting behavior in these compounds, which result from both 2PA and 2PA-assisted ESA. These results indicated that chalcone derivatives are a promising candidate for applications on nonlinear photonic devices.

  1. X-ray studies on optical and structural properties of ZnO nanostructured thin films

    NASA Astrophysics Data System (ADS)

    Larcheri, S.; Armellini, C.; Rocca, F.; Kuzmin, A.; Kalendarev, R.; Dalba, G.; Graziola, R.; Purans, J.; Pailharey, D.; Jandard, F.

    2006-01-01

    X-ray absorption near-edge fine structure (XANES) studies have been carried out on nanostructured ZnO thin films prepared by atmospheric pressure chemical vapour deposition (APCVD). Films have been characterized by X-ray diffraction (XRD) and optical luminescence spectroscopy exciting with laser light (PL) or X-ray (XEOL). According to XRD measurements, all the APCVD samples reveal a highly (002) oriented crystalline structure. The samples have different thickness (less than 1 μm) and show significant shifts of the PL and XEOL bands in the visible region. Zn K-edge XANES spectra were recorded using synchrotron radiation at BM08 of ESRF (France), by detecting photoluminescence yield (PLY) and X-ray fluorescence yield (FLY). The differences between the PLY- and FLY-XANES confirm the possibility of studying the local environment in the luminescence centres and to correlate the structural and optical properties of ZnO nanostructured samples.

  2. Platinum Group Thiophenoxyimine Complexes: Syntheses,Crystallographic and Computational Studies of Structural Properties

    SciTech Connect

    Krinsky, Jamin L.; Arnold, John; Bergman, Robert G.

    2006-10-03

    Monomeric thiosalicylaldiminate complexes of rhodium(I) and iridium(I) were prepared by ligand transfer from the homoleptic zinc(II) species. In the presence of strongly donating ligands, the iridium complexes undergo insertion of the metal into the imine carbon-hydrogen bond. Thiophenoxyketimines were prepared by non-templated reaction of o-mercaptoacetophenone with anilines, and were complexed with rhodium(I), iridium(I), nickel(II) and platinum(II). X-ray crystallographic studies showed that while the thiosalicylaldiminate complexes display planar ligand conformations, those of the thiophenoxyketiminates are strongly distorted. Results of a computational study were consistent with a steric-strain interpretation of the difference in preferred ligand geometries.

  3. A review of the structure-property relationships in lead-free piezoelectric (1-x)Na0.5Bi0.5TiO3-(x)BaTiO3

    NASA Astrophysics Data System (ADS)

    McQuade, Ryan R.; Dolgos, Michelle R.

    2016-10-01

    Piezoelectric materials are increasingly being investigated for energy harvesting applications where (1-x)Na0.5Bi0.5TiO3-(x)BaTiO3 (NBT-BT) is an important lead-free piezoelectric material with potential to be used as an actuator in energy harvesting devices. Much effort has been put into modifying NBT-BT to tune the properties for specific applications, but there is currently no consensus regarding the structure-property relationships in this material, making targeted, rational design a major challenge. In this review, we will summarize the current body of knowledge of NBT-BT and discuss contradicting studies, unresolved problems, and future directions in the field.

  4. EXAFS study of the structural properties of In and In + C implanted Ge

    NASA Astrophysics Data System (ADS)

    Feng, R.; Kremer, F.; Sprouster, D. J.; Mirzaei, S.; Decoster, S.; Glover, C. J.; Medling, S. A.; Russo, S. P.; Ridgway, M. C.

    2016-05-01

    The structural configurations of In implanted Ge have been studied via x-ray absorption spectroscopy with and without the codoping of C. In the case of In singly implanted Ge, while the In atoms occupy an substitutional site in Ge (InGe4) at low In concentration (≤ 2 at. %), they precipitate into a metallic phase (In metal) and form complexes composed of one vacancy and three Ge atoms (InVGe3) at concentration ≥ 0.6 at. %. This behaviour can be suppressed by the addition of C leading to In-C pairing to form InCGe3 complexes. This cluster enables In atoms to recover a four-fold coordinated structure and has the potential to improve the electrical activation of In atoms in Ge.

  5. Structure, properties and animal study of a calcium phosphate/calcium sulfate composite cement.

    PubMed

    Chen, Wei-Luen; Chen, Chang-Keng; Lee, Jing-Wei; Lee, Yu-Ling; Ju, Chien-Ping; Lin, Jiin-Huey Chern

    2014-04-01

    In-vitro and in-vivo studies have been conducted on an in-house-developed tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA)/calcium sulfate hemihydrate (CSH)-derived composite cement. Unlike most commercial calcium-based cement pastes, the investigated cement paste can be directly injected into water and harden without dispersion. The viability value of cells incubated with a conditioned medium of cement extraction is >90% that of Al2O3 control and >80% that of blank medium. Histological examination reveals excellent bonding between host bone and cement without interposition of fibrous tissues. At 12 weeks-post implantation, significant remodeling activities are found and a new bone network is developed within the femoral defect. The 26-week samples show that the newly formed bone becomes more mature, while the interface between residual cement and the new bone appears less identifiable. Image analysis indicates that the resorption rate of the present cement is much higher than that of TTCP or TTCP/DCPA-derived cement under similar implantation conditions.

  6. Photometric and Structural Properties of NGC 6544: A Combined VVV-Hubble Space Telescope Study

    NASA Astrophysics Data System (ADS)

    Cohen, Roger E.; Mauro, Francesco; Geisler, Doug; Moni Bidin, Christian; Dotter, Aaron; Bonatto, Charles

    2014-07-01

    We combine archival Hubble Space Telescope imaging with wide-field near-infrared photometry to study the neglected metal-poor Galactic globular cluster NGC 6544. A high spatial resolution map of differential reddening over the inner portion of the cluster is constructed, revealing variations of up to half of the total reddening, and the resulting corrected color-magnitude diagrams reveal a sparse blue horizontal branch and centrally concentrated blue straggler population, verified via relative proper motions. Using the corrected photometry to investigate the cluster distance, reddening, and age via direct comparison to well-calibrated photometry of clusters with similar metallicities, we estimate (m - M)0 = 11.96, E(B - V) = 0.79, and an age coeval with M13 to within the relevant uncertainties. Although our data are insufficient to place tight constraints on the reddening law toward NGC 6544, we find no strong evidence that it is non-standard at optical or near-infrared wavelengths. We also provide near-infrared fiducial sequences extending nearly 2 mag below the cluster main sequence turnoff, generated from a statistically decontaminated sample of cluster stars. Lastly, we redetermine the cluster center and construct a radial number density profile which is well fit by an atypically flat power law with a slope of about 1.7. We discuss this result, together with a flattened main sequence luminosity function and inverted mass function, in the context of mass segregation and tidal stripping via interactions with Milky Way potential.

  7. Natural nanoparticle structure, properties and reactivity from X-ray studies

    SciTech Connect

    Waychunas, Glenn A.

    2009-10-01

    Synthetic analogs of naturally occurring nanoparticles have been studied by a range of X-ray techniques to determine their structure and chemistry, and relate these to their novel chemical properties and physical behavior. ZnS nanoparticles, formed in large concentrations naturally bymicrobial action, have an interesting core-shell structure with a highly distorted and strained outer layer. The strain propagates through the particles and produces unusual stiffness but can be relieved by changing the nature of the surface ligand binding. Weaker bound ligands allow high surface distortion, but strongly bound ligands relax this structure and reduce the overall strain. Only small amounts of ligand exchange causes transformations from the strained to the relaxed state. Most remarkably, minor point contacts between strained nanoparticles also relax the strain. Fe oxyhydroxide nanoparticles appear to go through structural transformations dependent on their size and formation conditions, and display a crystallographically oriented form of aggregation at the nanoscale that alters growth kinetics. At least one Fe oxyhydroxide mineral may only be stable on the nanoscale, and nonstoichiometry observed on the hematite surface suggests that for this phase and possibly other natural metal oxides, chemistry may be size dependent. Numerous questions exist on nanominerals formed in acid mine drainage sites and by reactions at interfaces.

  8. First-principles study of structural properties of SiO2 bilayers

    NASA Astrophysics Data System (ADS)

    Malashevich, Andrei; Ismail-Beigi, Sohrab; Altman, Eric I.

    Two dimensional (2D) materials draw a tremendous amount of interest because they exhibit unique physical properties due to reduced dimensionality. Recently, SiO2 2D bilayer systems were discovered. The structure of these bilayers is formed by two mirror-image planes of corner-sharing SiO4 tetrahedra and does not have a direct relation to bulk SiO2 systems. SiO2 bilayers may be obtained in crystalline or amorphous forms. In the crystalline form, the bilayers are constructed from six-membered rings of corner-sharing SiO4 tetrahedra. The amorphous form has rings of various sizes typically in the range from four to nine Si atoms in the ring. These structures may be of practical interest as atomically thin membranes and molecular sieves. In our work, we study the effect of strain and doping on the crystalline structure of SiO2 bilayers using density functional theory. We analyze the stability of structures depending on the ring size and establish strain and doping conditions that may render the structures with large ring sizes stable. This work is supported by the National Science Foundation through Grants MRSEC NSF DMR-1119826 and NSF DMR-1506800.

  9. Structural properties of iron-phosphate glasses: spectroscopic studies and ab initio simulations.

    PubMed

    Stoch, Pawel; Szczerba, Wojciech; Bodnar, Wiktor; Ciecinska, Malgorzata; Stoch, Agata; Burkel, Eberhard

    2014-10-01

    Vitrification is the most effective method for the immobilization of hazardous waste by incorporating toxic elements into a glass structure. Iron phosphate glasses are presently being considered as matrices for the storage of radioactive waste, even of those which cannot be vitrified using conventional borosilicate waste glass. In this study, a structural model of 60P2O5-40Fe2O3 glass is proposed. The model is based on the crystal structure of FePO4 which is composed of [FeO4][PO4] tetrahedral rings. The rings are optimized using the DFT method and the obtained theoretical FTIR and Raman spectra are being compared with their experimental counterparts. Moreover, the proposed model is in very good agreement with X-ray absorption fine structure spectroscopy (XANES/EXAFS) and Mössbauer spectroscopy measurements. According to the calculations the Fe(3+) is in tetrahedral and five-fold coordination. The maximal predicted load of waste constituents into the glass without rebuilding of the structure is 30 mol%. Below this content, waste constituents balance the charge of [FeO4](-) tetrahedra which leads to their strong bonding to the glass resulting in an increase of the chemical durability, transformation and melting temperatures and density. PMID:25115558

  10. Photometric and structural properties of NGC 6544: A combined VVV-Hubble space telescope study

    SciTech Connect

    Cohen, Roger E.; Mauro, Francesco; Geisler, Doug; Moni Bidin, Christian; Dotter, Aaron; Bonatto, Charles

    2014-07-01

    We combine archival Hubble Space Telescope imaging with wide-field near-infrared photometry to study the neglected metal-poor Galactic globular cluster NGC 6544. A high spatial resolution map of differential reddening over the inner portion of the cluster is constructed, revealing variations of up to half of the total reddening, and the resulting corrected color-magnitude diagrams reveal a sparse blue horizontal branch and centrally concentrated blue straggler population, verified via relative proper motions. Using the corrected photometry to investigate the cluster distance, reddening, and age via direct comparison to well-calibrated photometry of clusters with similar metallicities, we estimate (m – M){sub 0} = 11.96, E(B – V) = 0.79, and an age coeval with M13 to within the relevant uncertainties. Although our data are insufficient to place tight constraints on the reddening law toward NGC 6544, we find no strong evidence that it is non-standard at optical or near-infrared wavelengths. We also provide near-infrared fiducial sequences extending nearly 2 mag below the cluster main sequence turnoff, generated from a statistically decontaminated sample of cluster stars. Lastly, we redetermine the cluster center and construct a radial number density profile which is well fit by an atypically flat power law with a slope of about 1.7. We discuss this result, together with a flattened main sequence luminosity function and inverted mass function, in the context of mass segregation and tidal stripping via interactions with Milky Way potential.

  11. Theoretical studies of structure-property relations in graphene-based carbon nanostructures

    NASA Astrophysics Data System (ADS)

    Maroudas, Dimitrios

    2014-03-01

    This presentation focuses on establishing relations between atomic structure, electronic structure, and properties in graphene-based carbon nanostructures through first-principles density functional theory calculations and molecular-dynamics simulations. We have analyzed carbon nanostructure formation from twisted bilayer graphene, upon creation of interlayer covalent C-C bonds due to patterned hydrogenation or fluorination. For small twist angles and twist angles near 30 degrees, interlayer covalent bonding generates superlattices of diamond-like nanocrystals and of fullerene-like configurations, respectively, embedded within the graphene layers. The electronic band gaps of these superlattices can be tuned through selective chemical functionalization and creation of interlayer bonds, and range from a few meV to over 1.2 eV. The mechanical properties of these superstructures also can be precisely tuned by controlling the extent of chemical functionalization. Importantly, the shear modulus is shown to increase monotonically with the fraction of sp3-hybridized C-C bonds. We have also studied collective interactions of multiple defects such as random distributions of vacancies in single-layer graphene (SLG). We find that a crystalline-to-amorphous structural transition occurs at vacancy concentrations of 5-10% over a broad temperature range. The structure of our defect-induced amorphized graphene is in excellent agreement with experimental observations of SLG exposed to a high electron irradiation dose. Simulations of tensile tests on these irradiated graphene sheets identify trends for the ultimate tensile strength, failure strain, and toughness as a function of vacancy concentration. The vacancy-induced amorphization transition is accompanied by a brittle-to-ductile transition in the failure response of irradiated graphene sheets and even heavily damaged samples exhibit tensile strengths near 30 GPa, in significant excess of those typical of engineering materials.

  12. Fluorinated arene, imide and unsaturated pyrrolidinone based donor acceptor conjugated polymers: Synthesis, structure-property and device studies

    NASA Astrophysics Data System (ADS)

    Liyanage, Arawwawala Don Thilanga

    After the discovery of doped polyacetylene, organic semiconductor materials are widely studied as high impending active components in consumer electronics. They have received substantial consideration due to their potential for structural tailoring, low cost, large area and mechanically flexible alternatives to common inorganic semiconductors. To acquire maximum use of these materials, it is essential to get a strong idea about their chemical and physical nature. Material chemist has an enormous role to play in this novel area, including development of efficient synthetic methodologies and control the molecular self-assembly and (opto)-electronic properties. The body of this thesis mainly focuses on the substituent effects: how different substituents affect the (opto)-electronic properties of the donor-acceptor (D-A) conjugated polymers. The main priority goes to understand, how different alkyl substituent effect to the polymer solubility, crystallinity, thermal properties (e.g.: glass transition temperature) and morphological order. Three classes of D-A systems were extensively studied in this work. The second chapter mainly focuses on the synthesis and structure-property study of fluorinated arene (TFB) base polymers. Here we used commercially available 1,4-dibromo-2,3,5,6-tetrafluorobenzene (TFB) as the acceptor material and prepare several polymers using 3,3'-dialkyl(3,3'-R2T2) or 3,3'-dialkoxy bithiophene (3,3'-RO2T2) units as electron donors. A detail study was done using 3,3'-bithiophene donor units incorporating branched alkoxy-functionalities by systematic variation of branching position and chain length. The study allowed disentangling the branching effects on (i) aggregation tendency, intermolecular arrangement, (iii) solid state optical energy gaps, and (iv) electronic properties in an overall consistent picture, which might guide future polymer synthesis towards optimized materials for opto-electronic applications. The third chapter mainly focused on

  13. A study of structure-property correlation in vanadium pentoxide and titanium dioxide based thin films as functional materials

    NASA Astrophysics Data System (ADS)

    Thapa, Chandra

    The focus of this thesis is to study the structure-property correlation in thin films of V2O5 and TiO2 based transition metal oxides as functional materials. V2O5 is investigated as a cathode material for lithium ion battery and TiO2 as a high-k dielectric material. We studied V2O5 thin films prepared by spin coating using three different types of precursors, MOD precursor, sol-gel organic precursor and sol-gel inorganic precursor. On the basis of structural and electrochemical studies, we find that the capacity is dependent on the degree of non-stoichiometry. We have also studied the effect of addition of Ti. Although Ti doping enhances non-stoichiometry, the capacity was found to increase only in 5% Ti-doped sol-gel film. This means the optimal degree of non-stoichiometry is crucial to enhance the capacity. TiO2 is one of the possible high-k dielectric materials because of its very high dielectric constant. We studied leakage characteristics, the dielectric strength and frequency dependent behavior of dielectric constant of TiO2 thin films prepared by MOD, sputter deposition and annealed at different temperatures. We find dielectric constant increasing with the increase in annealing temperature and leakage current density improvement by almost one order of magnitude with each 100 °C increase in annealing temperature. Since TiO2 possess two distinct thermodynamic phases: anatase and rutile, which dramatically influences the values of dielectric constant and leakage current density, it is crucial to stabilize the phase of TiO2 by doping. We find that 20% Zr-doping completely stabilizes TiO2 phase in its anatase form. The dielectric constant of the films is independent of annealing temperature but the leakage current density improves by one order of magnitude with every 100 °C increase in annealing temperature.

  14. Synthesis of versatile chemical tools toward a structure/properties relationships study onto targeting colloids.

    PubMed

    Jolimaitre, Pascale; Poirier, Cécile; Richard, Antoine; Blanpain, Annick; Delord, Brigitte; Roux, Didier; Bourel-Bonnet, Line

    2007-01-01

    As part of a drug delivery project, four aldehydes of the type Pam-Lys(Pam)-spacer-CO-CHO were synthesized to be included in targeting colloids. Though amphiphilic, they were obtained within reasonable yields (18-55%) and with high RP-HPLC purity ( approximately 90%). Parallely, six complementary targeting peptides of the type H(2)N-NH-CH(2)-CO-spacer-YGRGDSP-NH(2) were prepared to be anchored onto colloids. Isolated yields are related to the spacer length and nature. To easily and rapidly modulate the distance between the peptide and the vesicle, every partners were elaborated on solid phase and the expected constructions were obtained by hydrazone ligation. One possible application is presented here with multilamellar vesicles targeting HUVEC cells. Preliminary results prove that the fine-tuning of the spacer length permits to optimize the recognition toward the target cells.

  15. Spectroscopic and structural properties of bisphthalonitriles with O/S/SO2 grafting: Comparative theoretical and experimental studies

    NASA Astrophysics Data System (ADS)

    Ekineker, Gülçin; Pilet, Guillaume; Berber, Savaş; Ahsen, Vefa; Dumoulin, Fabienne; Önal, Emel

    2016-11-01

    Three bisphthalonitriles with different grafting functions (O/S/SO2) have been selected for their future interest in the preparation of dimeric phthalocyanines with tailored properties. The bisphthalonitrile derivatives have been prepared and comparatively characterized. Their complete structural properties were investigated and their XRD-determined structures were compared with their DFT-optimized ones. Molecular orbital levels and energy gaps were also determined and analysed. The sulfonyl (SO2) function induces different behaviour compared to the S and O grafting which are more similar.

  16. Study of optical and structural properties of CZTS thin films grown by co-evaporation and spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Moreno, R.; Ramirez, E. A.; Gordillo Guzmán, G.

    2016-02-01

    Results regarding optical and structural properties of Cu2ZnSnS4 (CZTS) thin films prepared by co-evaporation using a novel procedure are compared with those obtained with CZTS films grown using a solution based route. The lattice strain ε and crystallite size D of CZTS films prepared by co-evaporation and by spray pyrolysis were estimated through X-ray diffraction (XRD) measurements using Williamson-Hall-isotropic strain model. The results of estimated average crystallite size of CZTS films by Scherrer and Williamson-Hall plot methods were compared with AFM (atomic force microscopy) measurements. It was found that the average crystallite size measured by Williamson-Hall plot methods agree quite well with AFM results. Further, information regarding the influence of preparation method on both, crystalline phases and the formation of structural defects was achieved through Raman and Urbach energy measurements.

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

    PubMed

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

    2013-06-01

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

  18. Molecular-Level Control of Ciclopirox Olamine Release from Poly(ethylene oxide)-Based Mucoadhesive Buccal Films: Exploration of Structure-Property Relationships with Solid-State NMR.

    PubMed

    Urbanova, Martina; Gajdosova, Marketa; Steinhart, Miloš; Vetchy, David; Brus, Jiri

    2016-05-01

    polymorphic form, Form I, which exhibited reduced dissolution kinetics. The bioavailability of CPX olamine formulated as PEO-based MBFs can thus be effectively controlled by inducing the complete dispersion and/or microsegregation and nanocrystallization of CPX olamine in the polymer matrix. Solid-state NMR spectroscopy is an efficient tool for exploring structure-property relationships in these complex pharmaceutical solids. PMID:27019088

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

    PubMed

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

    2015-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  1. Structure-Property Relations in Nonferrous Metals

    NASA Astrophysics Data System (ADS)

    Russell, Alan; Loong Lee, Kok

    2005-05-01

    A long-awaited text that fills the void in non-ferrous metallurgy literature While most undergraduate metallurgy textbooks focus on iron, the most commercially important metallic element, Structure-Property Relations in Nonferrous Metals is a comprehensive textbook covering the remaining eighty-two nonferrous metals. Designed to be readily accessible to materials engineering students at all academic levels, the text describes the relationships between the atomic-, crystal-, and micro-structures of nonferrous metals, and such physical behaviors as strength, ductility, electrical conductivity, and corrosion. In order to capture and retain students' interest, the authors maintain a strong focus on practical application. Each chapter supplements fundamental concepts with engaging examples from actual engineering case studies and industrial projects, directly relating content to real-world application. Part One describes the general concepts of crystal- and micro-structures and the implications of these structures for the mechanical, thermal, and electronic properties of nonferrous metals, intermetallic compounds, and metal matrix composites. Chapters focus on such relevant topics as: Point, line, and planar defects and their effects on a material's properties

  2. Dislocations and strengthening mechanisms Fracture and fatigue Strain rate effects and creep Deviations from classic crystallinity Processing methods Composites and intermetallic compounds Part Two builds on Part One by exploring how the concepts presented define the properties of a particular metallic element and its alloys, and how these properties contribute to the engineering uses of each nonferrous metal. An accompanying ftp site contains homework problems, appendices, bibliographies, and tables of data indicating the nations producing metallic elements and the quantities produced. Structure-Property Relations in Nonferrous Metals is a valuable reference for both students in

  3. Structure-Property Relationships in CO2-philic (Co)polymers: Phase Behavior, Self-Assembly, and Stabilization of Water/CO2 Emulsions.

    PubMed

    Girard, Etienne; Tassaing, Thierry; Marty, Jean-Daniel; Destarac, Mathias

    2016-04-13

    This Review provides comprehensive guidelines for the design of CO2-philic copolymers through an exhaustive and precise coverage of factors governing the solubility of different classes of polymers. Starting from computational calculations describing the interactions of CO2 with various functionalities, we describe the phase behavior in sc-CO2 of the main families of polymers reported in literature. The self-assembly of amphiphilic copolymers of controlled architecture in supercritical carbon dioxide and their use as stabilizers for water/carbon dioxide emulsions then are covered. The relationships between the structure of such materials and their behavior in solutions and at interfaces are systematically underlined throughout these sections.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.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

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

    PubMed

    Redmond, Haley; Thompson, Jonathan E

    2011-04-21

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

  6. Mossbauer Spectroscopic Study of Gamma Irradiation on the Structural Properties of Hematite, Magnetite and Limonite Concrete for Nuclear Reactor Shielding

    NASA Astrophysics Data System (ADS)

    Eissa, N. A.; Kany, M. S. I.; Mohamed, A. S.; Sallam, A. A.; El Fouly, M. H.

    1998-12-01

    This work investigate the effect of gamma irradiation on a heavy type of concrete, constructed for nuclear reactor shield. The effect of gamma irradiation was studied after annealing the concrete samples at 300°C for 24 hours in air.

  7. The electronic and structural properties of BN and BP nano-cages interacting with OCN-: A DFT study

    NASA Astrophysics Data System (ADS)

    Soltani, Alireza; Baei, Mohammad T.; Mirarab, Mehdi; Sheikhi, Masoome; Tazikeh Lemeski, E.

    2014-10-01

    The adsorption of OCN- (cyanato anion) on boron nitride (B12N12 and B16N16) and boron phosphide nano-cages (B12P12 and B16P16) in terms of energetic, geometric, and electronic properties are studied using density functional theory calculations. Our study results indicated that the first OCN- strongly prefers to be adsorbed from its N atom upon B atoms of the nano-cages than the O atoms of OCN-. These findings have been rationalized using frontier molecular orbitals and total electron density plots. The energy gap of the B12P12 is significantly reduced upon the adsorption of OCN- compared to B12N12, thus leading to the increase in electrical conductance of nano-cage.

  8. Abnormal Bone Mechanical and Structural Properties in Adolescent Idiopathic Scoliosis: A Study with Finite Element Analysis and Structural Model Index.

    PubMed

    Cheuk, K Y; Zhu, T Y; Yu, F W P; Hung, V W Y; Lee, K M; Qin, L; Cheng, J C Y; Lam, T P

    2015-10-01

    Previous studies found adolescent idiopathic scoliosis (AIS) is associated with low bone mineral density (BMD) and abnormal bone quality, whilst the association between AIS and their bone strength is unknown. From high-resolution peripheral quantitative computed tomography-generated images, bone mechanical properties can be evaluated with finite element analysis (FEA), and trabecular rod-plate configuration related to trabecular bone strength can be quantified by structure model index (SMI). This study aimed to compare trabecular configuration and bone mechanical properties between AIS and the controls. 95 AIS girls aged 12-14 years and 97 age- and gender-matched normal controls were recruited. Bilateral femoral necks and non-dominant distal radius were scanned by dual-energy X-ray absorptiometry for areal BMD and HR-pQCT for SMI and FEA, respectively. Subjects were further classified into osteopenic and non-osteopenic group based on their areal BMD. Bone mechanical properties (stiffness, failure load and apparent modulus) were calculated using FEA. Linear regression model was used for controlling age, physical activity and calcium intake. AIS was associated with lower failure load and apparent modulus after adjusting for age, whereas AIS was associated with lower apparent modulus after adjusting for all confounders. Osteopenic AIS was associated with more rod-like trabeculae when compared with non-osteopenic AIS, whereas no difference was detected between osteopenic and non-osteopenic controls. This might be the result of abnormal regulation and modulation of bone metabolism and bone modelling and remodelling in AIS which will warrant future studies with a longitudinal design to determine the significance of micro-architectural abnormalities in AIS.

  9. Novel amplex red oxidases based on noncanonical DNA structures: property studies and applications in microRNA detection.

    PubMed

    Wang, Shaoru; Fu, Boshi; Wang, Jiaqi; Long, Yuelin; Zhang, Xiaoe; Peng, Shuang; Guo, Pu; Tian, Tian; Zhou, Xiang

    2014-03-18

    G-triplex has recently been identified as a new secondary structure in G-rich sequences. However, its functions and biological roles remain largely unknown. This study first developed two kinds of Amplex Red oxidases, which were based on relatively new G-triplex structure and a common G-quadruplex one. A collection of DNA binding assays including circular dichroism (CD) spectroscopy, a CD melting assay, and a UV titration study were used to determine the G-triplex structure of G3 oligomer. The low intrinsic oxidative activity of hemin was significantly enhanced using G-triplex or G-quadruplex. Only one key guanine deletion from the G3 oligomer or G4 one could result in a much decreased Amplex Red oxidation activity. To the best of our knowledge, this is the first case reporting direct use of air as the oxidant for fluorescence generation based on DNAzyme strategies. Further mechanism studies demonstrated an involvement of on-site H2O2 generation from O2 and water and a following oxidation of Amplex Red to resorufin, causing a fluorescence enhancement. Furthermore, the newly developed oxidases have been effectively used in microRNA detection, using only one biotin-labeled probe and one small-molecule substrate. The conjugation of a target DNA to the G-triplex- or G-quadruplex-forming sequence enabled one to produce G-triplex or G-quadruplex by endonuclease in the presence of a slight amount of miRNA and amplify the signal of fluorescence from the oxidation of Amplex Red. Our findings of novel Amplex Red oxidases could potentially be used in a wide range of applications.

  10. Structural property investigations of 1-[2-(2-methoxyphenyl)ethyl]piperidinium chloride: An experimental and computational study

    NASA Astrophysics Data System (ADS)

    Kołodziejczak, Jerzy; Jezierska, Aneta; Panek, Jarosław J.; De Borggraeve, Wim M.; Kochel, Andrzej; Jose, Rani Alphonsa; Koll, Aleksander

    2008-11-01

    A phenethyl containing piperidinium compound was synthesized and the results of an X-ray crystallographic and computational analysis of this compound are reported. The compound, 1-[2-(2-methoxyphenyl)ethyl]piperidinium chloride, contains a C-H···O contact, which stabilizes the experimentally found conformation. Additionally, an ionic bond between N-H···Cl atoms is present as shown by the crystallographic measurements. The presence of these two contacts prompted us to perform further theoretical studies. The first part of the computational investigations was carried out on the basis of the Car-Parrinello molecular dynamics (CPMD) in the solid-state using experimental parameters and conditions as a starting point of the simulation. The time evolution of the interatomic distances of the atoms involved in the N-H···Cl interaction was investigated. Vibrational features of the compound were studied by predicted and power spectra. In addition, static models, based on density functional theory (DFT) and second-order Møller-Plesset perturbation calculus, were built to describe the geometric and electronic structure parameters. Finally, the details of the ionic bridge were analyzed using the natural bond orbitals (NBO) approach. The electron density topology was investigated by the atoms in molecules (AIM) theory. In summary, the ionic bridge modifies the spectroscopic properties of the bridge proton. The negative charge of the chloride anion is partially delocalized via the ammonium moiety to the organic subunit.

  11. Investigation into the structure-property relationship and technical properties of TPEs and TPVs derived from ethylene octene copolymer (EOC) and polydimethyl siloxane (PDMS) rubber blends

    NASA Astrophysics Data System (ADS)

    Padmanabhan, R.; Naskar, Kinsuk; Nando, Golok B.

    2015-10-01

    This work focuses on the study of thermoplastic vulcanizates based on ethylene octene copolymer (EOC) and poly dimethyl siloxane (PDMS) rubber prepared by melt mixing technique using dicumyl peroxide (DCP). It is found that the addition of peroxide causes crosslinking in both the phases. However, crosslinking without affecting the crystallinity of the EOC polymer leads to tremendous improvement in the mechanical properties, including the tensile strength which has improved by nearly 60%. For better understanding about the crosslinking characteristics of thermoplastic vulcanizates (TPVs), significant correlation has been made between the vulcanized network and the physico-mechanical properties. Further, the dynamic mechanical properties and creep behavior of these thermoplastic elastomers (TPEs) and TPVs have also been studied. It is inferred that the TPVs show a 19% decrease in the creep compliance, i.e. higher creep resistance compared to uncrosslinked blends. Subsequently, the morphology of the blends before and after vulcanization shows a decrease in the spherical PDMS domains from 0.8 μm to > 0.4 μm. Ageing and reprocessing studies of the prepared TPVs also show better physico-mechanical properties even after reprocessing twice. Thus, the prepared TPVs may have tremendous applications in automobile sectors.

  12. The study of the structural properties of very low viscosity sodium alginate by small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Badita, C. R.; Aranghel, D.; Radulescu, A.; Anitas, E. M.

    2016-03-01

    Sodium alginate is a linear polymer extract from brown algae and it is used in the biomedical, food, cosmetics and pharmaceutical industries as solution property modifiers and gelling agents. But despite the extensive studies of the alginate gelation process, still some fundamental questions remain unresolved. The fractal behavior of very low viscosity sodium alginate solutions and their influence on the critical gelation of alginate induced by Ca2+ ions were investigated using Small-Angle Neutron Scattering (SANS) measurements. SANS data are interpreted using both standard linear plots and the Beaucage model. The scattering intensity is dependent by alginate concentration and Ca2+ concentration. From a critical concentration of 1.0 % w/w our polymer swelled forming spherical structures with rough surfaces. Also the addition of the salt induces the collapse and the appearance of the aggregation and clusters formation.

  13. Study of optical and structural properties of CdSe quantum dot embedded in PVA polymer matrix

    NASA Astrophysics Data System (ADS)

    Tyagi, Chetna; Sharma, Ambika

    2015-08-01

    To enhance the properties and applicability of devices it is essential to incorporate semiconductor nanoparticles into polymer matrix. This introduces a new branch of science which includes device fabrications such as gas sensors, nonlinear optics, catalysis etc. Herein, we have synthesized CdSe/PVA nanocomposite (NC) material using wet chemical synthesis technique. The XRD studies revealed the formation of crystalline structure of CdSe nanoparticles (NP's) and PVA NC's with an average size of 100 nm and 5 nm respectively. Energy band gap is determined using UV-VIS Spectroscopy. A red shift in the absorption edge of CdSe/PVA NC is observed with respect to CdSe Np's, The photoluminescence spectra also show red shift for CdSe/PVA NC as compared to CdSe NP's Thus the use of CdSe/PVA for solar cell application would be more preferable than CdSe NP's.

  14. Vibrational and structural properties of amorphous n-butanol: A complementary Raman spectroscopy and X-ray diffraction study

    NASA Astrophysics Data System (ADS)

    Hédoux, Alain; Guinet, Yannick; Paccou, L.; Derollez, P.; Danède, F.

    2013-06-01

    Raman spectroscopy and X-ray diffraction experiments were performed in the liquid, undercooled liquid, and glassy states of n-butanol. Clear correlated signatures are obtained below the melting temperature, from both temperature dependences of the low-wavenumber vibrational excitations and the intermediate-range order characterized by a prepeak detected in the different amorphous states. It was found that these features are related to molecular associations via strong hydrogen bonds, which preferentially develop at low temperature, and which are not compatible with the long-range order of the crystal. This study provides information on structural heterogeneities developing in hydrogen-bonded liquids, associated to the undercooled regime and the inherent glass transition. The analysis of the isothermal abortive crystallization, 2 K above the glass transition temperature, has given the opportunity to analyze the early stages of the crystallization and to describe the origin of the frustration responsible for an uncompleted crystallization.

  15. Effect of substituents on redox, spectroscopic and structural properties of conjugated diaryltetrazines--a combined experimental and theoretical study.

    PubMed

    Kurach, Ewa; Djurado, David; Rimarčik, Jan; Kornet, Aleksandra; Wlostowski, Marek; Lukeš, Vladimir; Pécaut, Jacques; Zagorska, Malgorzata; Pron, Adam

    2011-02-21

    Two series of new soluble conjugated compounds containing tetrazine central ring have been synthesized. The three-ring compounds have been synthesized by the reaction of aryl cyanide (where aryl = thienyl, alkylthienyl, phenyl or pyridyl) with hydrazine followed by oxidation of the intermediate product with diethyl azodicarboxylate. The five-ring compounds have been prepared using two pathways: (i) reaction of 5-cyano-2,2'-bithiophene (or its alkyl derivative) with hydrazine; (ii) via Suzuki or Stille coupling of 3,6-bis(5-bromo-2-thienyl)-1,2,4,5-tetrazine with a stannyl or boronate derivative of alkylthiophene. UV-vis spectroscopic properties of the synthesized compounds are strongly dependent on the nature of the aryl group, the position of the solubilizing substituent and the length of the molecule, showing the highest bathochromic shift (λ(max) > 440 nm) for five-ring compounds with alkyl groups attached to C(α) carbon in the terminal thienyl ring. An excellent linear correlation has been found for spectroscopically determined and theoretically calculated (TD-B3LYP/6-31G*) excitation energies. With the exception of dipyridyl derivative, the calculated lowest unoccupied molecular orbital (LUMO) level of the investigated molecules changes within a narrow range (from -2.63 to -2.41 eV), in line with the electrochemical data, which show a reversible reduction process with the redox potential varying from -1.23 V to -1.33 V (vs. Fc/Fc(+)). The electrochemically determined positions of the LUMO levels are consistently lower by 0.9 to 1.2 eV with respect to the calculated ones. All molecules readily crystallize. Single crystal studies of 3,6-bis(2,2'-bithien-5-yl)-1,2,4,5-tetrazine show that it crystallizes in a P2(1)/c space group whose structural arrangement is not very favorable to the charge carriers flow within the crystal. Powder diffraction studies of other derivatives have shown that their structural organization is sensitive to the position of the

  16. Structure-property studies of thermoplastic and thermosetting polyurethanes using palm and soya oils-based polyols.

    PubMed

    Mohammed, Issam Ahmed; Al-Mulla, Emad Abbas Jaffar; Kadar, Nurul Khizien Abdul; Ibrahim, Mazlan

    2013-01-01

    Palm and soya oils were converted to monoglycerides via transesterification of triglycerides with glycerol by one step process to produce renewable polyols. Thermoplastic polyurethanes (TPPUs) were prepared from the reaction of the monoglycerides which act as polyol with 4,4'-methylenediphenyldiisocyanate (MDI) whereas, thermosetting polyurethanes (TSPUs) were prepared from the reaction of glycerol, MDI and monoglycerides in one pot. Characterization of the polyurethanes was carried out by FT-IR, (1)H NMR, and iodine value and sol-gel fraction. The TSPUs showed good thermal properties compared to TPPUs as well as TSPUs exhibits good properties in pencil hardness and adhesion, however poorer in flexural and impact strength compared to TPPUs. The higher percentage of cross linked fraction, the higher degree of cross linking occurred, which is due to the higher number of double bond presents in the TSPUs. These were reflected in iodine value test as the highest iodine value of the soya-based thermosetting polyurethanes confirmed the highest degree of cross linking. Polyurethanes based on soya oil showed better properties compared to palm oil. This study is a breakthrough development of polyurethane resins using palm and soya oils as one of the raw materials.

  17. Study of optical and structural properties of CdSe quantum dot embedded in PVA polymer matrix

    SciTech Connect

    Tyagi, Chetna Sharma, Ambika

    2015-08-28

    To enhance the properties and applicability of devices it is essential to incorporate semiconductor nanoparticles into polymer matrix. This introduces a new branch of science which includes device fabrications such as gas sensors, nonlinear optics, catalysis etc. Herein, we have synthesized CdSe/PVA nanocomposite (NC) material using wet chemical synthesis technique. The XRD studies revealed the formation of crystalline structure of CdSe nanoparticles (NP’s) and PVA NC’s with an average size of 100 nm and 5 nm respectively. Energy band gap is determined using UV-VIS Spectroscopy. A red shift in the absorption edge of CdSe/PVA NC is observed with respect to CdSe Np’s, The photoluminescence spectra also show red shift for CdSe/PVA NC as compared to CdSe NP’s Thus the use of CdSe/PVA for solar cell application would be more preferable than CdSe NP’s.

  18. Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Geon Joon; Sim, Geon Bo; Choi, Eun Ha; Kwon, Young-Wan; Kim, Jun Young; Jang, Siun; Kim, Seong Hwan

    2015-01-01

    To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.

  19. Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

    SciTech Connect

    Lee, Geon Joon Sim, Geon Bo; Choi, Eun Ha; Kim, Jun Young; Jang, Siun; Kim, Seong Hwan

    2015-01-14

    To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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 C-13 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.

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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.

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

    PubMed Central

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

    2014-01-01

    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. PMID:25524460

  2. glass chemistry: structure-property relationships

    NASA Astrophysics Data System (ADS)

    Smedskjaer, Morten M.; Youngman, Randall E.; Mauro, John C.

    2014-08-01

    Pyrex® glass was one of the first commercial boroaluminosilicate glass compositions, selected in 1915 from thousands of compositions due to its ability to sustain mechanical and thermal shock. While the microscopic structure of Pyrex® glass has recently been investigated, the microscopic origins of its macroscopic properties are not well understood, i.e., the atomic scale foundation of the original empirical invention of Pyrex® glass has yet to be established. In this work, we have tackled this problem by investigating the effects of varying Si/Al and Na/B ratios on the boron and aluminum speciation and a range of physical and rheological properties in the Pyrex® glass family. We show that the canonical Pyrex® boroaluminosilicate composition is indeed optimal for attaining relatively high values of glass transition temperature and elastic moduli and a low coefficient of thermal expansion, while simultaneously maintaining a high glass-forming ability.

  3. Structural properties of colloidal suspensions

    NASA Astrophysics Data System (ADS)

    Méndez-Alcaraz, J. M.; Chávez-Páez, M.; D'Aguanno, B.; Klein, R.

    1995-02-01

    Structural properties of three- and two-dimensional colloids composed by hard spheres and/or by Yukawa particles, which can have different diameters and charges, are studied by solving the Ornstein-Zernike equation, together with Percus-Yevick, hypernetted chain and Rogers-Young approximations. From the partial radial distribution functions gij( r) the partial structure factors Sij( k) are determined, and with them the compressibility structure factor Sx( k), the measured structure factor SM( k) and the Bhatia-Thornton structure factors SNN( k), SNQ( k) and SQQ( k). As an effect of diameter and/or charge polydispersity on the structure of binary mixtures, the position and height of the main peak of SM( k), and its value at k = 0, change non-monotonously with the composition. In the case of binary mixtures of hard and Yukawa spheres the structure is given by two different scales. A liquid-solid phase transition induced by a change in the dimensionality was found for monodisperse systems.

  4. Optimization of bulkheterojunction organic photovoltaics: Structure/property study with oxadiazole contained poly(p-phenylene)s [OXA-PPVs] and device system engineering

    NASA Astrophysics Data System (ADS)

    Ko, Changheui

    This thesis is focused on investigating organic semiconducting materials and photophysical phenomenon to build high efficient polymer light emitting diodes (PLEDs) and organic photovoltaic cells (OPVs) through material engineering and process engineering. We have synthesized and characterized three electroactive polymers of oxadiazole containing poly(p-phenylenevinylene)s [OXA-PPV3-1s] with different solubilizing alkoxy side chains. They have hybrid electronic characteristics of hole transporting and electron transporting properties in a molecule. By utilizing their novel properties we expect high PLED and OPV device performance. First, we seek to resolve the structure-property relationships by looking at the effects of side groups through photophysical studies such as UV/Vis spectroscopy, photoluminescence spectroscopy (PL) and also by morphological characterization with atomic force microscopy (AFM). High quantum efficiencies have been observed from solution OXA-PPVs. To investigate the electric field induced photogeneration characteristic in OXA-PPVs, we fabricated single layer PLEDs using three OXA-PPV3-1s as the active material. Balanced charge injection will be discussed based on device performances. At the same time, to investigate the photoactivated charge separation phenomenon in OXA-PPV3-1s, we prepared several bulkheterojunction OPVs. The active layer was formed from a solution mixture of OXA-PPV3-1s as an electron acceptor and well known semicrystalline poly(3-hexylthiophene) (P3HT) as an electron donor. As a pair, the well matched HOMO and LUMO levels, as well as significant oxidative stability in OXA-PPV3-1s and high carrier mobility in P3HT motivated our OPV study. When OXA-PPV3-1 is blended with P3HT and formed into films, significant photoluminescence quenching (PL quenching) is observed from the films using a wavelength that corresponds to the absorption maximum of OXA-PPV3-1s. Such PL quenching is evidence for the pre-requisite of photoactivated

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

    PubMed

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

    2014-08-18

    The creation of organic dyes with excellent high power conversion efficiency (PCE) is important for the further improvement of dye-sensitized solar cells. We wish to describe the rapid synthesis of a 112-membered donor-π-acceptor dye library by a one-pot procedure, evaluation of PCEs, and elucidation of structure-property relationships. No obvious correlations between ε, and the η were observed, whereas the HOMO and LUMO levels of the dyes were critical for η. The dyes with a more positive E(HOMO), and with an E(LUMO)<-0.80 V, exerted higher PCEs. The proper driving forces were crucial for a high J(sc), and it was the most important parameter for a high η. The above criteria of E(HOMO) and E(LUMO) should be useful for creating high PCE dyes; nevertheless, that was not sufficient for identifying the best combination of donor, π, and acceptor blocks. Combinatorial synthesis and evaluation was important for identifying the best dye.

  6. Semiconductor alloys - Structural property engineering

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  7. Finite Element Estimation of Meteorite Structural Properties

    NASA Technical Reports Server (NTRS)

    Hart, Kenneth Arthur

    2015-01-01

    The goal of the project titled Asteroid Threat Assessment at NASA Ames Research Center is to develop risk assessment tools. The expertise in atmospheric entry in the Entry Systems and Technology Division is being used to describe the complex physics of meteor breakup in the atmosphere. The breakup of a meteor is dependent on its structural properties, including homogeneity of the material. The present work describes an 11-week effort in which a literature survey was carried for structural properties of meteoritic material. In addition, the effect of scale on homogeneity isotropy was studied using a Monte Carlo approach in Nastran. The properties were then in a static structural response simulation of an irregularly-shape meteor (138-scale version of Asteroid Itokawa). Finally, an early plan was developed for doctoral research work at Georgia Tech. in the structural failure fragmentation of meteors.

  8. Structural properties of prokaryotic promoter regions correlate with functional features.

    PubMed

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

    2014-01-01

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

  9. Structural Properties of the Native Ligamentum Teres

    PubMed Central

    Philippon, Marc J.; Rasmussen, Matthew T.; Turnbull, Travis Lee; Trindade, Christiano A.C.; Hamming, Mark G.; Ellman, Michael B.; Harris, Matthew; LaPrade, Robert F.; Wijdicks, Coen A.

    2014-01-01

    Background: A majority of studies investigating the role of the ligamentum teres (LT) have focused primarily on anatomical and histological descriptions. To date, however, the structural properties of the LT have yet to be fully elucidated. Purpose: To investigate the structural properties of the native LT in a human cadaveric model. Study Design: Descriptive laboratory study. Methods: A total of 12 human cadaveric hemipelvises (mean age, 53.6 years; range, 34-63 years) were dissected free of all extra-articular soft tissues to isolate the LT and its acetabular and femoral attachments. A dynamic tensile testing machine distracted each femur in line with the fibers of the LT at a displacement-controlled rate of 0.5 mm/s. The anatomic dimensions, structural properties, and modes of failure were recorded. Results: The LT achieved a mean yield load of 75 N and ultimate failure load of 204 N. The LT had mean lengths of 38.0 and 53.0 mm at its yield and failure points, respectively. The most common (75% of specimens) mechanism of failure was tearing at the fovea capitis. On average, the LT had a linear stiffness of 16 N/mm and elastic modulus of 9.24 MPa. The mean initial length and cross-sectional area were 32 mm and 59 mm2, respectively. Conclusion: The human LT had a mean ultimate failure load of 204 N. Therefore, the results of this investigation, combined with recent biomechanical and outcomes studies, suggest that special consideration should be given to preserving the structural and corresponding biomechanical integrity of the LT during surgical intervention. Clinical Relevance: The LT may be more important as a static stabilizer of the hip joint than previously recognized. Further studies are recommended to investigate the appropriate indications to perform surgical repair or reconstruction of the LT for preservation of hip stability and function. PMID:26535290

  10. Orientation-dependent local structural properties of Zn(1-x)Mg(x)O nanorods studied by extended X-ray absorption fine structure.

    PubMed

    Jeong, E S; Park, Changin; Jin, Zhenlan; Yoo, Jinkyoung; Yi, Gyu-Chul; Han, S W

    2013-03-01

    The orientation-dependent structural properties of Zn(1-x)Mg(x)O nanorods with different Mg concentrations were investigated quantitatively using polarization-dependent extended X-ray absorption fine structure (EXAFS) measurements at the Zn K edge. Vertically-aligned Zn(1-x)Mg(x)O nanorods were synthesized on Si substrates using catalyst free metal organic chemical vapor deposition. Polarization-dependent EXAFS measurements showed that Mg ions mainly occupied the Zn sites of the nanorods. EXAFS revealed that the distance between Zn-Mg pairs in all directions is - 0.2 angstroms shorter than that of Zn-Zn pairs and that there is a substantial amount of disorder in the Mg sites of the nanorods, independent of Mg concentrations.

  11. Structural properties of small rhodium clusters

    NASA Astrophysics Data System (ADS)

    Soon, Yee Yeen; Lim, Thong Leng; Yoon, Tiem Leong

    2015-04-01

    We report a systematic study of the structural properties of rhodium clusters at the atomistic level. A novel global-minimum search algorithm, known as parallel tempering multicanonical basin hopping plus genetic algorithm (PTMBHGA), is used to obtain the geometrical structures with lowest minima at the semi-empirical level where Gupta potential is used to describe the atomic interaction among the rhodium atoms. These structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The structures are optimized for different spin multiplicities. The ones with lowest energies will be taken as ground-state structures. In most cases, we observe only minor changes in the geometry and bond length of the clusters as a result of DFT-level re-optimization. Only in some limited cases, the initial geometries obtained from the PTMBHGA are modified by the re-optimization. The variation of structural properties, such as ground-state geometry, symmetry and binding energy, with respect to the cluster size is studied and agreed well with other results available in the literature.

  12. Structural properties of small rhodium clusters

    SciTech Connect

    Soon, Yee Yeen; Yoon, Tiem Leong; Lim, Thong Leng

    2015-04-24

    We report a systematic study of the structural properties of rhodium clusters at the atomistic level. A novel global-minimum search algorithm, known as parallel tempering multicanonical basin hopping plus genetic algorithm (PTMBHGA), is used to obtain the geometrical structures with lowest minima at the semi-empirical level where Gupta potential is used to describe the atomic interaction among the rhodium atoms. These structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The structures are optimized for different spin multiplicities. The ones with lowest energies will be taken as ground-state structures. In most cases, we observe only minor changes in the geometry and bond length of the clusters as a result of DFT-level re-optimization. Only in some limited cases, the initial geometries obtained from the PTMBHGA are modified by the re-optimization. The variation of structural properties, such as ground-state geometry, symmetry and binding energy, with respect to the cluster size is studied and agreed well with other results available in the literature.

  13. Effective structural properties in polycrystalline graphene

    NASA Astrophysics Data System (ADS)

    Hossain, Zubaer

    This talk will discuss effective structural properties in polycrystalline graphene under the presence of atomic scale heterogeneity. Polycrystallinity is ubiquitous in solids, but theories describing their effective behavior remain limited, particularly when heterogeneity is present in the form of nonuniform deformation or composition. Over the decades, exploration of the effective transport and strength properties of heterogeneous systems has been carried out mostly with random distribution of grains or regular periodic structures under various approximations, in translating the underlying physics into a single representative volume element. Although heterogeneity can play a critical role in modulating the basic behavior of low-dimensional materials, it is difficult to capture the local characteristics accurately by these approximations. Taking polycrystalline graphene as an example material, we study the effective structural properties (such as Young's Modulus, Poisson's ratio and Toughness) by using a combination of density functional theory and molecular dynamic simulations. We identify the key mechanisms that govern their effective behavior and exploit the understanding to engineer the behavior by doping with a carefully selected choice of chemical elements.

  14. Mediterranean-style diet effect on the structural properties of the erythrocyte cell membrane of hypertensive patients: the Prevencion con Dieta Mediterranea Study.

    PubMed

    Barceló, Francisca; Perona, Javier S; Prades, Jesús; Funari, Sérgio S; Gomez-Gracia, Enrique; Conde, Manuel; Estruch, Ramon; Ruiz-Gutiérrez, Valentina

    2009-11-01

    A currently ongoing randomized trial has revealed that the Mediterranean diet, rich in virgin olive oil or nuts, reduces systolic blood pressure in high-risk cardiovascular patients. Here, we present a structural substudy to assess the effect of a Mediterranean-style diet supplemented with nuts or virgin olive oil on erythrocyte membrane properties in 36 hypertensive participants after 1 year of intervention. Erythrocyte membrane lipid composition, structural properties of reconstituted erythrocyte membranes, and serum concentrations of inflammatory markers are reported. After the intervention, the membrane cholesterol content decreased, whereas that of phospholipids increased in all of the dietary groups; the diminishing cholesterol:phospholipid ratio could be associated with an increase in the membrane fluidity. Moreover, reconstituted membranes from the nuts and virgin olive oil groups showed a higher propensity to form a nonlamellar inverted hexagonal phase structure that was related to an increase in phosphatidylethanolamine lipid class. These data suggest that the Mediterranean-style diet affects the lipid metabolism that is altered in hypertensive patients, influencing the structural membrane properties. The erythrocyte membrane modulation described provides insight in the structural bases underlying the beneficial effect of a Mediterranean-style diet in hypertensive subjects. PMID:19805640

  15. Structural properties, vibrational spectra and surface-enhanced Raman scattering of 2,4,6-trichloro- and tribromoanilines: A comparative study

    NASA Astrophysics Data System (ADS)

    Haruna, Kabiru; Saleh, Tawfik A.; Al Thagfi, Jameel; Al-Saadi, Abdulaziz A.

    2016-10-01

    A comparative electronic and spectroscopic analysis of 2,4,6-trichloroaniline (TCA) and 2,4,6-tribromoaniline (TBA) was carried out by theoretical and experimental techniques. The NH2 inversion barrier in TCA and TBA molecules was predicted to be three times less than that in aniline and 2,4,6-trifluoroaniline. The size of the halogen substituents in the ortho positions is shown by density functional theory to play an important role in determining the electronic and structural properties of the amino group in the investigated haloaniline derivatives. A thorough interpretation of the infrared and Raman spectra has been performed on the basis of the observed and calculated infrared and Raman spectra as well as calculated potential energy distribution values. In addition, the SERS spectra for both trihaloanilines were successfully collected up to a concentration of 10-6 M using aged hydroxylamine-reduced silver colloid as an active substrate for TCA and TBA. SERS intensities of several peaks were found to linearly change with concentration allowing quantitative analyses of TCA and TBA. A relatively stronger interaction in the case of TBA-silver colloids is predicted compared to the TCA analogue.

  16. Mediterranean-style diet effect on the structural properties of the erythrocyte cell membrane of hypertensive patients: the Prevencion con Dieta Mediterranea Study.

    PubMed

    Barceló, Francisca; Perona, Javier S; Prades, Jesús; Funari, Sérgio S; Gomez-Gracia, Enrique; Conde, Manuel; Estruch, Ramon; Ruiz-Gutiérrez, Valentina

    2009-11-01

    A currently ongoing randomized trial has revealed that the Mediterranean diet, rich in virgin olive oil or nuts, reduces systolic blood pressure in high-risk cardiovascular patients. Here, we present a structural substudy to assess the effect of a Mediterranean-style diet supplemented with nuts or virgin olive oil on erythrocyte membrane properties in 36 hypertensive participants after 1 year of intervention. Erythrocyte membrane lipid composition, structural properties of reconstituted erythrocyte membranes, and serum concentrations of inflammatory markers are reported. After the intervention, the membrane cholesterol content decreased, whereas that of phospholipids increased in all of the dietary groups; the diminishing cholesterol:phospholipid ratio could be associated with an increase in the membrane fluidity. Moreover, reconstituted membranes from the nuts and virgin olive oil groups showed a higher propensity to form a nonlamellar inverted hexagonal phase structure that was related to an increase in phosphatidylethanolamine lipid class. These data suggest that the Mediterranean-style diet affects the lipid metabolism that is altered in hypertensive patients, influencing the structural membrane properties. The erythrocyte membrane modulation described provides insight in the structural bases underlying the beneficial effect of a Mediterranean-style diet in hypertensive subjects.

  17. Molecular dynamics study of the transport and structural properties of the Cu 3Au and Ni 3Al (1 1 0) surface

    NASA Astrophysics Data System (ADS)

    Lekka, Ch. E.; Papageorgiou, D. G.; Evangelakis, G. A.

    2002-10-01

    We present molecular dynamics results concerning the transport and the structural properties of the Cu 3Au and Ni 3Al(1 1 0) surfaces in presence of adatoms and vacancies. In the Cu 3Au case we found that below 500 K the Cu adatom occupies preferably the so-called "dumb-bell" position, while the Au adatom penetrates into the second pure Cu layer via an exchange type mechanism inducing thereby local disorder. At higher temperatures the Cu adatom resides almost exclusively at fourfold positions, while spontaneous creation of adatom-vacancy pairs is also present. Vacancy diffusion processes induce surface disorder that starts by as much as 150 K below the bulk order-disorder temperature. In the case of Ni 3Al(1 1 0) surface, we found a new Al adatom position situated between two Ni surface atoms. It came out that this position plays an important role in the adatom's diffusive behavior. Above 800 K adatom-vacancy pairs are spontaneously created and in conjunction with exchange type diffusion mechanisms they affect seriously the surface order. In addition, we found that the Ni adatoms are more active than the Al adatoms, this difference in the adatom diffusivity being accentuated by exchange events, leading very quickly the surface in a disordered state. In conclusion, it comes out that the Cu 3Au and Ni 3Al(1 1 0) surfaces disorder well below the bulk transition temperature (663 K, Cu 3Au) and the melting point (1663 K, Ni 3Al) via diffusion processes of the adatoms and/or vacancies.

  18. A randomized school-based jumping intervention confers site and maturity-specific benefits on bone structural properties in girls: a hip structural analysis study.

    PubMed

    Petit, M A; McKay, H A; MacKelvie, K J; Heinonen, A; Khan, K M; Beck, T J

    2002-03-01

    We compared 7-month changes in bone structural properties in pre- and early-pubertal girls randomized to exercise intervention (10-minute, 3 times per week, jumping program) or control groups. Girls were classified as prepubertal (PRE; Tanner breast stage 1; n = 43 for intervention [I] and n = 25 for control [C]) or early-pubertal (EARLY; Tanner stages 2 and 3; n = 43 for I and n = 63 for C). Mean +/- SD age was 10.0 +/- 0.6 and 10.5 +/- 0.6 for the PRE and EARLY groups, respectively. Proximal femur scans were analyzed using a hip structural analysis (HSA) program to assess bone mineral density (BMD), subperiosteal width, and cross-sectional area and to estimate cortical thickness, endosteal diameter, and section modulus at the femoral neck (FN), intertrochanter (IT), and femoral shaft (FS) regions. There were no differences between intervention and control groups for baseline height, weight, calcium intake, or physical activity or for change over 7 months (p > 0.05). We used analysis of covariance (ANCOVA) to examine group differences in changes of bone structure, adjusting for baseline weight, height change, Tanner breast stage, and physical activity. There were no differences in change for bone structure in the PRE girls. The more mature girls (EARLY) in the intervention group showed significantly greater gains in FN (+2.6%, p = 0.03) and IT (+1.7%, p = 0.02) BMD. Underpinning these changes were increased bone cross-sectional area and reduced endosteal expansion. Changes in subperiosteal dimensions did not differ. Structural changes improved section modulus (bending strength) at the FN (+4.0%, p = 0.04), but not at the IT region. There were no differences at the primarily cortical FS. These data provide insight into geometric changes that underpin exercise-associated gain in bone strength in early-pubertal girls. PMID:11874228

  19. Study of hygrothermal effects and cure kinetics on the structure-property relations of epoxy-amine thermosets: Fundamental analysis and application

    NASA Astrophysics Data System (ADS)

    Choi, Sungwon

    2011-12-01

    For decades, epoxy systems have shown outstanding physical properties for various applications with numerous advantages over other thermoset resins such as lower cure shrinkage, lower residual stress, chemical resistance, and insulating properties. However, property degradation due to hygrothermal exposure is a critical issue in applications, in which their nature to absorb moisture results in a significant loss in glass transition temperature (T g), modulus, tensile strength, and adhesive strength. These detrimental effects often include some complex behavior in that both increase and decrease in Tg and/or modulus is observed during the course of exposure. In this study, to specifically describe the mechanism for this complex hygrothermal behavior, direct experimental measurement has been conducted employing thermodynamic analysis and spectroscopic measurements. Fourier transform near-infrared (FT-NIR) spectroscopic measurements showed that an increase in conversion was responsible for the increase in Tg, while plasticization occurred simultaneously, rendering the hygrothermal behavior to be complex. To evaluate those factors affecting this complex hygrothermal behavior separately, a relationship between Tg and conversion was constructed for the unexposed system and compared to the corresponding Tg values for the exposed system at the same point of each conversion value. For another part of this dissertation, the effect of water on cure kinetics was investigated with the hypothesis that water significantly accelerates the cure kinetics of epoxy-amine systems. The near FT-IR demonstrated that a small amount of water addition significantly accelerated the cure reaction in terms of epoxide conversion. A modified mechanistic model was successfully used to directly compare the effect of hydroxyl from water addition and that from auto-acceleration by the reaction. In the final section, in an effort to enhance the durability of bonding properties of an epoxy adhesive for

  20. Perspective: Composition-structure-property mapping in high-throughput experiments: Turning data into knowledge

    NASA Astrophysics Data System (ADS)

    Hattrick-Simpers, Jason R.; Gregoire, John M.; Kusne, A. Gilad

    2016-05-01

    With their ability to rapidly elucidate composition-structure-property relationships, high-throughput experimental studies have revolutionized how materials are discovered, optimized, and commercialized. It is now possible to synthesize and characterize high-throughput libraries that systematically address thousands of individual cuts of fabrication parameter space. An unresolved issue remains transforming structural characterization data into phase mappings. This difficulty is related to the complex information present in diffraction and spectroscopic data and its variation with composition and processing. We review the field of automated phase diagram attribution and discuss the impact that emerging computational approaches will have in the generation of phase diagrams and beyond.

  1. Structure Properties of Ternary Hydrides Ni3AlHx

    NASA Astrophysics Data System (ADS)

    Pan, Yi-wei; Zhang, Wen-qing; Chen, Nan-xian

    1996-09-01

    The structure properties of the ternary hydrides Ni3AlHx are studied by use of the interatomic pair potentials obtained from the first principles electronic structure calculation and Chen-Mobius 3-dimensional lattice inversion method. The heat of formation and volume expansion of the hydrogenized systems are investigated.

  2. Structural Properties of Mismatched Alloys

    NASA Astrophysics Data System (ADS)

    Mousseau, Normand

    The problem of understanding the local structure of disordered alloys has been around for a long time. In this thesis, I look more specifically at the effect of size-mismatch disorder in binary alloys under many forms: metallic and semiconductor alloys, bulk and surfaces, two and three dimensional systems. I have studied the limitations of a central-force model (CFM) and an embedded-atom potential (EAM) in describing the local structure of binary metallic alloys composed of Ag, Au, Cu, Ni, Pd, or Pt. Although an analytical model developed using the CFM explains qualitatively well the experimental and numerical results, in many cases, it is important to add electronic density effects through a more sophisticated potential like EAM in order to agree quantitatively with experiment. I have also looked at amorphous and crystalline silicon-germanium alloys. It turns out that the effect of size-mismatch is the same on a crystalline and an amorphous lattice. In the latter case, it can be seen as a perturbation of the much larger disorder due to the amorphisation process. However, the analytical predictions differ, for both the crystalline and amorphous alloys, from the experimental results. If one is to believe the data, there is only one possible explanation for this inconsistency: large amounts of hydrogen are present in the samples used for the measurements. Since the data analysis of EXAFS results is not always straightforward, I have proposed some experiments that could shed light on this problem. One of these experiments would be to look at the (111) surface of a Si-Ge alloy with a scanning tunneling microscope. I also present in this thesis the theoretical predictions for the height distribution at the surface as well as some more general structural information about the relaxation in the network as one goes away from the surface. Finally, I have studied the effect of size -mismatch in a purely two dimensional lattice, looking for mismatch-driven phase transitions

  3. Structural Properties of Green Tea Catechins.

    PubMed

    Botten, Dominic; Fugallo, Giorgia; Fraternali, Franca; Molteni, Carla

    2015-10-01

    Green tea catechins are polyphenols which are believed to provide health benefits; they are marketed as health supplements and are studied for their potential effects on a variety of medical conditions. However, their mechanisms of action and interaction with the environment at the molecular level are still not well-understood. Here, by means of atomistic simulations, we explore the structural properties of four green tea catechins, in the gas phase and water solution: specifically, (-)-epigallocatechin-3-gallate, which is the most abundant, (-)-epicatechin-3-gallate, (-)-epigallocatechin-3-O-(3-O-methyl)-gallate, and (-)-epigallocatechin. We characterize the free energy conformational landscapes of these catechins at ambient conditions, as a function of the torsional degrees of freedom of the pholyphenolic rings, determining the stable conformers and their connections. We show that these free energy landscapes are only subtly influenced by the interactions with the solvent and by the structural details of the polyphenolic rings. However, the number and position of the hydroxyl groups (or their sustituents) and the presence/absence of the galloyl moiety have significant impact on the selected catechin solvation shells and hydrogen bond capabilities, which are ultimately linked to their ability to interact with and affect the biological environment. PMID:26369298

  4. A first-principles study of the electronic and structural properties of Sb and F doped SnO{sub 2} nanocrystals

    SciTech Connect

    Kim, Minjung; Scott Bobbitt, N.; Marom, Noa; Chelikowsky, James R.

    2015-01-28

    We examine the electronic properties of Sb and F doped SnO{sub 2} nanocrystals up to 2.4 nm in diameter. A real-space pseudopotential implementation of density functional theory is employed within the local density approximation. We calculate electron binding energies and dopant formation energies as function of nanocrystal size, dopant concentration, and dopant species. Structural changes for different dopant species are also investigated. Our study should provide useful information for the design of transparent conducting oxides at the nanoscale.

  5. Structural properties of sodium-rich carbonate-silicate melts: An in-situ high-pressure EXAFS study on Y and Sr

    NASA Astrophysics Data System (ADS)

    Pohlenz, J.; Pascarelli, S.; Mathon, O.; Belin, S.; Shiryaev, A.; Safonov, O.; Veligzhanin, A.; Murzin, V.; Irifune, T.; Wilke, M.

    2016-05-01

    In-situ EXAFS combined with a Paris-Edinburgh press (PEP) is an outstanding tool to investigate the local environment of trace elements in melts at high pressure and temperature. A novel design of the pressure assembly ensures a highly stable experimental setup (reaching temperatures of up to 2000 K at 2.5 GPa) while permitting the necessary level of X- ray transmission. This study focuses on the structural incorporation of the geochemically important trace elements Y and Sr in sodium-rich silicate-carbonate melts. Y and Sr K edge EXAFS were collected in transmission mode of the melt (at ∼2.5 GPa, 1600 K) and its respective quench products. Distinct changes in the XANES region suggest a change in site symmetry during the cooling process.

  6. Structural Properties and UV-Visible Absorption Spectroscopy of Retinal-pyridyl-CN Re(I) Carbonyl Bipyridine Complex: A Theoretical Study.

    PubMed

    Eng, Julien; Daniel, Chantal

    2015-10-29

    The structural, electronic, and optical properties of the all-trans and five cis conformers of [Re(CO)3(bpy)(ret-pyr-CN)](+) (bpy = 2,2'-bipyridine; ret-pyr-CN = pyridyl-CN-3,7-dimethyl-9-(2,6,6-trimethylcyclohex-2-n)-none-(2,4,6,8-tetraen) were studied in solvent by means of density functional theory (DFT) and time-dependent DFT. The isolated retinal-like chromophore ret-pyr-CN was investigated as well for comparison. By coordination to the complex the two lowest intraligand (IL) states localized on the retinal group are slightly red-shifted from 627 to 690 nm and from 415 to 450 nm, respectively. Several isomerization pathways are open upon irradiation of the Re(I) complex by visible light (400-450 nm), especially to two cis conformers corresponding to the isomerization of the two double bonds of the retinal-like ligand close to the pyridyl group linked to the Re(I) fragment. The metal-to-ligand charge transfer states localized either on the retinal group or on the bpy ligand should play a minor role in the isomerization process itself but could improve its efficiency via ultra-fast intersystem crossing.

  7. Study of the magnetic and structural properties of Al-Cr codoped Y-type hexaferrite prepared via sol-gel auto-combustion method

    NASA Astrophysics Data System (ADS)

    Mirzaee, O.; Mohamady, R.; Ghasemi, A.; Farzin, Y. Alizad

    2015-04-01

    Nanostructure of Y-type hexaferrite with composition of Sr2Ni2Alx/2Crx/2Fe12-xO22 (where x are 0, 0.6, 1.2, 1.8, 2.4 and 3) were prepared by sol-gel auto-combustion method. The influence of Al and Cr doping on the structural and magnetic properties has been investigated. The X-ray diffraction (XRD) patterns confirm phase formation of Y-type hexaferrite. The microstructure and morphology of prepared samples were studied by high resolution field emission scanning electron microscope (FESEM) which shows the hexagonal shape for all of the samples. Magnetic properties were characterized using vibrating sample magnetometer (VSM). The magnetic results revealed that by increasing the Al and Cr to the structure, the coercivity was also increased from 840 Oe to 1160 Oe. Moreover it has been shown that with addition of dopants, saturation magnetization (Ms) and remnant magnetization (Mr) were decreased from 39.61 emu/g to 30.11 emu/g and from 17.51 emu/g to 14.62 emu/g, respectively, due to the entrance of nonmagnetic ions into Fe3+ sites.

  8. Structural properties of the putative fusion peptide of hepatitis B virus upon interaction with phospholipids. Circular dichroism and Fourier-transform infrared spectroscopy studies.

    PubMed

    Rodríguez-Crespo, I; Gómez-Gutiérrez, J; Encinar, J A; González-Ros, J M; Albar, J P; Peterson, D L; Gavilanes, F

    1996-12-01

    A peptide corresponding to the N-terminal sequence of the S protein from hepatitis B virus (Met-Glu-Asn-Ile-Thr-Ser-Gly-Phe-Leu-Gly-Pro-Leu-Leu-Val-Leu-Gln) has been previously shown to interact with phospholipids and promote vesicle aggregation, phospholipid mixing, and liposome leakage, as well as erythrocyte lysis [Rodríguez-Crespo, I., Núñez, E., Gómez-Gutiérrez, J., Yélamos, B., Albar, J. P., Peterson, D. L. & Gavilanes, F. (1995) J. Gen. Virol. 76, 301-308]. The conformation of this putative fusion peptide has been studied, both at low and high peptide concentrations, by means of circular dichroism and Fourier-transform infrared spectroscopy, respectively. When the peptide is dissolved in trifluoroethanol, a significant population of alpha-helical structure is found in spite of the proline residue at position 11. In contrast, this hydrophobic oligopeptide has a high tendency to form large beta-sheet aggregates in aqueous buffers. Most of these aggregates can be eliminated by centrifugation. The peptide remaining in the supernatant adopts a non-ordered conformation. The aggregates can be dissociated by the anionic detergent sodium cholate, but the peptide still maintains an extended conformation. In the presence of acidic phospholipid vesicles, the putative fusion peptide adopts a highly stable beta-sheet conformation. Thus, unlike the fusion peptides of other viruses, an extended conformation seems to be the preferred structure when interacting with phospholipids. Such a conformation should be responsible for its membrane destabilization properties.

  9. Comparative study of optical and structural properties of electrospun 1-dimensional CaYAl{sub 3}O{sub 7}:Eu{sup 3+} nanofibers and bulk phosphor

    SciTech Connect

    Yim, Chul Jin; Unithrattil, Sanjith; Chung, Woon Jin; Im, Won Bin

    2014-09-15

    We report the optical and structural studies of Eu{sup 3+}-doped 1-dimensional CaYAl{sub 3}O{sub 7} nano-fiber phosphor. CaYAl{sub 3}O{sub 7}:Eu{sup 3+} phosphors were synthesized by electrospinning technique and the pristine nano-fibers were annealed at 900 °C to form well crystallized uniform fibers. Under ultraviolet excitation, the CaYAl{sub 3}O{sub 7}:Eu{sup 3+} exhibited red emission, due to transitions in the 4f states of Eu{sup 3+}. In order to explore the difference between the quantum efficiency of nano-fiber and bulk CaYAl{sub 3}O{sub 7}:Eu{sup 3+} phosphor, detailed structural and optical analyses were carried out. The structural analysis of the CaYAl{sub 3}O{sub 7}:Eu{sup 3+} nano-fibers indicates that the structural environment surrounding the dopant Eu{sup 3+} ion was more unstable in nano-fiber when compared to a bulk sample. Decay curves for both the samples when fitted with double exponential decay model indicate that the nano-fiber has shorter decay time, arising from the larger contribution from the non-radiative decay, due to defect levels introduced in the host lattice. - Highlights: • Synthesis of red nano-phosphor through electrospinning • Luminescence properties of bulk and nano-phosphors are compared. • Inferior emission intensity of the nano-phosphor is analyzed using MEM. • Charge cloud around nano-phosphor was found to be oblique.

  10. Density measurements and structural properties of liquid and amorphous metals under high pressure studied by in situ X-ray scattering (Invited)

    NASA Astrophysics Data System (ADS)

    Morard, G.; Garbarino, G.; Andrault, D.; Antonangeli, D.; Guignot, N.; Siebert, J.; Roberge, M.; Boulard, E.; Lincot, A.; Denoeud, A.; Petitgirard, S.

    2013-12-01

    Density determination for crystalline materials under high pressure and high temperature is straightforward using X-ray diffraction. For liquid and amorphous materials, it is more complicated due to the absence of long-range order. Different high pressure techniques have been developed: in-situ X-ray absorption 1-4 or ex-situ sink/float method 5-8. However, these techniques suffer several limitations, such as the limited pressure range or the long exposure time required. We have implemented an in situ X-ray diffraction analysis method suitable for the determination of Pressure-Volume-Temperature equations of state (P-V-T EoS) in the critical case of liquid and amorphous materials over an extended thermodynamic range (T>2000 K and P> 40 GPa). This method is versatile, it can be applied to data obtained using various angle-dispersive X-ray diffraction high-pressure apparatus and, contrary to in situ X-ray absorption techniques, is independent from the sample geometry. Further advantage is the fast data acquisition (between 10 to 300 seconds integration time). Information on macroscopic bulk properties (density) and local atomic arrangement (pair distribution function g(r)) can be gathered in parallel. To illustrate the method, we present studies on liquid Fe-S alloys in Paris Edinburgh press and in laser-heated diamond anvil cell, and measurements on Ce glass in diamond anvil cell at room temperature. References 1 G. Shen, N. Sata, M. Newville et al., App. Phys. Lett. 81 (8), 1411 (2002). 2 C. Sanloup, F. Guyot, P. Gillet et al., Geophys. Res. Lett. 27 (6), 811 (2000). 3 Y. Katayama, K. Tsuji, O. Shimomura et al., J. Synch. Rad. 5, 1023 (1998). 4 T. Sato and N. Funamori, Phys. Rev. Lett. 101, 255502 (2008). 5 R. Knoche and R. W. Luth, Chem. Geol. 128, 229 (1996). 6 P.S. Balog, R.A. Secco, D.C. Rubie et al., J. Geophys. Res. 108 (B2), 2124 (2003). 7 C. B. Agee and D. Walker, J. Geophys. Res. 93 (B4), 3437 (1988). 8 E. Ohtani, A. Suzuki, and T. Kato, Proc. Jpn. Acad

  11. Relationship of Study Habits with Mathematics Achievement

    ERIC Educational Resources Information Center

    Odiri, Onoshakpokaiye E.

    2015-01-01

    The study examined the relationship of study habits of students and their achievement in mathematics. The method used for the study was correlation design. A sample of 500 students were randomly selected from 25 public secondary schools in Delta Central Senatorial District, Delta State, Nigeria. Questionnaires were drawn to gather data on…

  12. Theory of the electronic and structural properties of solid state oxides

    SciTech Connect

    Chelikowsky, J.R.

    1990-01-01

    Studies on electronic and structural properties of solid state oxides continued. This quarter, studies have concentrated on silica. Progress is discussed in the following sections: interatomic potentials and the structural properties of silica; chemical reactivity and covalent/metallic bonding on Si clusters; and surface and thermodynamic interatomic forces fields for silicon. 64 refs., 20 figs., 5 tabs. (CBS)

  13. Structure Property Studies for Additively Manufactured Parts

    SciTech Connect

    Milenski, Helen M; Schmalzer, Andrew Michael; Kelly, Daniel

    2015-08-17

    Since the invention of modern Additive Manufacturing (AM) processes engineers and designers have worked hard to capitalize on the unique building capabilities that AM allows. By being able to customize the interior fill of parts it is now possible to design components with a controlled density and customized internal structure. The creation of new polymers and polymer composites allow for even greater control over the mechanical properties of AM parts. One of the key reasons to explore AM, is to bring about a new paradigm in part design, where materials can be strategically optimized in a way that conventional subtractive methods cannot achieve. The two processes investigated in my research were the Fused Deposition Modeling (FDM) process and the Direct Ink Write (DIW) process. The objectives of the research were to determine the impact of in-fill density and morphology on the mechanical properties of FDM parts, and to determine if DIW printed samples could be produced where the filament diameter was varied while the overall density remained constant.

  14. Structure-property evolution during polymer crystallization

    NASA Astrophysics Data System (ADS)

    Arora, Deepak

    The main theme of this research is to understand the structure-property evolution during crystallization of a semicrystalline thermoplastic polymer. A combination of techniques including rheology, small angle light scattering, differential scanning calorimetry and optical microscopy are applied to follow the mechanical and optical properties along with crystallinity and the morphology. Isothermal crystallization experiments on isotactic poly-1-butene at early stages of spherulite growth provide quantitative information about nucleation density, volume fraction of spherulites and their crystallinity, and the mechanism of connecting into a sample spanning structure. Optical microscopy near the fluid-to-solid transition suggests that the transition, as determined by time-resolved mechanical spectroscopy, is not caused by packing/jamming of spherulites but by the formation of a percolating network structure. The effect of strain, Weissenberg number (We ) and specific mechanical work (w) on rate of crystallization (nucleation followed by growth) and on growth of anisotropy was studied for shear-induced crystallization of isotactic poly-1-butene. The samples were sheared for a finite strain at the beginning of the experiment and then crystallized without further flow (Janeschitz-Kriegl protocol). Strain requirements to attain steady state/leveling off of the rate of crystallization were found to be much larger than the strain needed to achieve steady state of flow. The large strain and We>1 criteria were also observed for morphological transition from spherulitic growth to oriented growth. An apparatus for small angle light scattering (SALS) and light transmission measurements under shear was built and tested at the University of Massachusetts Amherst. As a new development, the polarization direction can be rotated by a liquid crystal polarization rotator (LCPR) with a short response time of 20 ms. The experiments were controlled and analyzed with a LabVIEW(TM) based

  15. Are Sibling Relationships Protective? A Longitudinal Study

    ERIC Educational Resources Information Center

    Gass, Krista; Jenkins, Jennifer; Dunn, Judy

    2007-01-01

    Background: Although the protective effects of familial and parental support have been studied extensively in the child psychopathology literature, few studies have explored the protective quality of positive sibling relationships. Methods: A two-wave longitudinal design was used to examine the protective effect of positive sibling relationships…

  16. Answering the Questions of Whether and When Learning Occurs: Using Discrete-Time Survival Analysis to Investigate the Ways in Which College Chemistry Students' Ideas about Structure-Property Relationships Evolve

    ERIC Educational Resources Information Center

    Underwood, Sonia M.; Reyes-Gastelum, David; Cooper, Melanie M.

    2015-01-01

    Longitudinal studies can provide significant insights into how students develop competence in a topic or subject area over time. However, there are many barriers, such as retention of students in the study and the complexity of data analysis, that make these studies rare. Here, we present how a statistical framework, discrete-time survival…

  17. Structure - property relationship of permutite-like amorphous silicates, Nax+2yM3+xSi1-xO2+y(M3+= Al, Mn, Fe, Y), for ion-exchange reactions.

    SciTech Connect

    Pless, Jason D.; Nenoff, Tina Maria; Maxwell, Robert S.; Phillips, Mark L. F.; Axness, Marlene

    2005-03-01

    A series of amorphous silicate materials with the general formula Na{sub x+2y}M{sub x}{sup 3+}Si{sub 1-x}O{sub 2+y}(M{sup 3+} = Al, Mn, Fe, Y) were studied. Samples were synthesized by a precipitation reaction at room temperature. The results indicate that the ion-exchange capacity (IEC) decreases as follows: Al > Fe > Mn > Y. Additionally, the IEC increases with increasing aluminum concentration. Structural studies show that the relative amount of octahedrally coordinated aluminum increases with increasing Al content, as does the total amount of AlO{sub 4} species increases. The data suggest that the IEC value of these amorphous aluminosilicates is dependent on the tetrahedrally coordinated aluminum. Regeneration of the Al-silicate with acetic acid does not decrease the IEC significantly.

  18. Selective O 2 Sorption at Ambient Temperatures via Node Distortions in Sc-MIL-100 (The structure-property relationship of Sc-MIL-100 for O2 selectivity at high temperatures)

    DOE PAGES

    Sava Gallis, Dorina F.; Chapman, Karena W.; Rodriguez, Mark A.; Greathouse, Jeffery A.; Parkes, Marie V.; Nenoff, Tina M.

    2016-05-24

    In this study, oxygen selectivity in metal-organic frameworks (MOFs) at exceptionally high temperatures originally predicted by Density Functional Theory (DFT) and Grand Canonical Monte Carlo (GCMC) modeling is now confirmed by synthesis, sorption metal center access, in particular Sc and Fe. Based on DFT M-O2 binding energies, we chose the large pored MIL-100 framework for metal center access, in particular Sc and Fe. Both resulted in preferential O2 and N2 gas uptake at temperatures ranging from 77 K to ambient temperatures (258 K, 298 K and 313 K).

  19. 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

    NASA Astrophysics Data System (ADS)

    Yin, Shih-Chieh

    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

  20. Structure-property relationships based on Hammett constants in cyclometalated iridium(III) complexes: their application to the design of a fluorine-free FIrPic-like emitter.

    PubMed

    Frey, Julien; Curchod, Basile F E; Scopelliti, Rosario; Tavernelli, Ivano; Rothlisberger, Ursula; Nazeeruddin, Mohammad K; Baranoff, Etienne

    2014-04-21

    While phosphorescent cyclometalated iridium(iii) complexes have been widely studied, only correlations between oxidation potential EOX and Hammett constant σ, and between the redox gap (ΔEREDOX = EOX-ERED) and emission or absorption wavelength (λabs, λem) have been reported. We present now a quantitative model based on Hammett parameters that rationalizes the effect of the substituents on the properties of cyclometalated iridium(iii) complexes. This simple model allows predicting the apparent redox potentials as well as the electrochemical gap of homoleptic complexes based on phenylpyridine ligands with good accuracy. In particular, the model accounts for the unequal effect of the substituents on both the HOMO and the LUMO energy levels. Consequently, the model is used to anticipate the emission maxima of the corresponding complexes with improved reliability. We demonstrate in a series of phenylpyridine emitters that electron-donating groups can effectively replace electron-withdrawing substituents on the orthometallated phenyl to induce a blue shift of the emission. This result is in contrast with the common approach that uses fluorine to blue shift the emission maximum. Finally, as a proof of concept, we used electron-donating substituents to design a new fluorine-free complex, referred to as EB343, matching the various properties, namely oxidation and reduction potentials, electrochemical gap and emission profile, of the standard sky-blue emitter FIrPic. PMID:24345847

  1. Structure Property Relationships in Imidazole-based Deep Eutectic Mixtures

    NASA Astrophysics Data System (ADS)

    Terheggen, Logan; Cosby, Tyler; Sangoro, Joshua

    2015-03-01

    Deep eutectic mixtures of levulinic acid with a systematic series of imidazoles are measured by broadband dielectric spectroscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy to investigate the impact of steric interactions on charge transport and structural dynamics. An enhancement of dc conductivity is found in each of the imidazoles upon the addition of levulinic acid. However, the extent of increase is dependent upon the alkyl substitution on the imidazole ring. These results highlight the importance of molecular structure on hydrogen bonding and charge transport in deep eutectic mixtures.

  2. Processing-structure-properties relationships in PLA nanocomposite films

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  3. Structure-property-processing relationships in Kevlar fibers

    SciTech Connect

    Lacks, D.J.

    1996-12-31

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

  4. Structure property relationships for the nonlinear optical response of fullerenes

    NASA Astrophysics Data System (ADS)

    Rustagi, Kailash C.; Ramaniah, Lavanya M.; Nair, Selvakumar V.

    1994-11-01

    We present a phenomenological theory of nonlinear optical response of fullerenes. An empirical tight-binding model is used in conjunction with a classical electromagnetic picture for the screening. Since in bulk media such a picture of screening corresponds to the self- consistent field approach, the only additional approximation involved in our approach is the neglect of nonlocality. We obtain reliable estimates for the linear and nonlinear susceptibilities of C60, C70, C76 and other pure carbon fullerenes and also substituted fullerenes. The relatively large values of (beta) that we obtain for C76 and substituted fullerenes appear promising for the development of fullerene-based nonlinear optical materials. Our phenomenological picture of screening provides a good understanding of the linear absorption spectra of higher fullerenes and predicts that a comparison of the one-photon and multi-photon spectra will provide an insight into screening effects in these systems.

  5. Structure-Property Relationships of Architectural Coatings by Neutron Methods

    NASA Astrophysics Data System (ADS)

    Nakatani, Alan

    2015-03-01

    Architectural coatings formulations are multi-component mixtures containing latex polymer binder, pigment, rheology modifiers, surfactants, and colorants. In order to achieve the desired flow properties for these formulations, measures of the underlying structure of the components as a function of shear rate and the impact of formulation variables on the structure is necessary. We have conducted detailed measurements to understand the evolution under shear of local microstructure and larger scale mesostructure in model architectural coatings formulations by small angle neutron scattering (SANS) and ultra small angle neutron scattering (USANS), respectively. The SANS results show an adsorbed layer of rheology modifier molecules exist on the surface of the latex particles. However, the additional hydrodynamic volume occupied by the adsorbed surface layer is insufficient to account for the observed viscosity by standard hard sphere suspension models (Krieger-Dougherty). The USANS results show the presence of latex aggregates, which are fractal in nature. These fractal aggregates are the primary structures responsible for coatings formulation viscosity. Based on these results, a new model for the viscosity of coatings formulations has been developed, which is capable of reproducing the observed viscosity behavior.

  6. Cement-aggregate compatibility and structure property relationships including modelling

    SciTech Connect

    Jennings, H.M.; Xi, Y.

    1993-07-15

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

  7. Relationships between study skills and academic performance

    NASA Astrophysics Data System (ADS)

    Md Rahim, Nasrudin; Meon, Hasni

    2013-04-01

    Study skills play an important role in influencing academic performance of university students. These skills, which can be modified, can be used as an indicator on how a student would perform academically in his course of study. The purpose of the study is to determine the study skills profile among Universiti Selangor's (Unisel) students and to find the relationships of these skills with student's academic performance. A sample of seventy-eight (78) foundation studies and diploma students of Unisel were selected to participate in this study. Using Study Skills Inventory instrument, eight skills were measured. They are note taking; test taking; textbook study; concentration and memory; time management; analytical thinking and problem solving; nutrition; and vocabulary. Meanwhile, student's academic performance was measured through their current Grade Point Average (GPA). The result showed that vocabulary skill scored the highest mean with 3.01/4.00, followed by test taking (2.88), analytical thinking and problem solving (2.80), note taking (2.79), textbook study (2.58), concentration and memory (2.54), time management (2.25) and nutrition (2.21). Correlation analysis showed that test taking (r=0.286, p=0.011), note taking (r=0.224, p=0.048), and analytical thinking and problem solving (r=0.362, p=0.001) skills were positively correlated with GPA achievement.

  8. Experimental study of the relationship between local particle-size distributions and local ordering in random close packing.

    PubMed

    Kurita, Rei

    2015-12-01

    We experimentally study the structural properties of a sediment of size distributed colloids. By determining each particle size using a size estimation algorithm, we are able to investigate the relationship between local environment and local ordering. Our results show that ordered environments of particles tend to generate where the local particle-size distribution is within 5%. In addition, we show that particles whose size is close to the average size have 12 coordinate neighbors, which matches the coordination number of the fcc and hcp crystals. On the other hand, bcc structures are observed around larger particles. Our results represent experiments to show a size dependence of the specific ordering in colloidal systems.

  9. Understanding Structural Properties of Carbonate-Silicate Melts: An EXAFS Study on Y and Sr in the System Na2O-CaO-Al2O3-SiO2-CO2

    NASA Astrophysics Data System (ADS)

    Pohlenz, J.; Pascarelli, S.; Mathon, O.; Belin, S.; Shiryaev, A.; Safonov, O.; Murzin, V.; Shablinskaya, K.; Irifune, T.; Wilke, M.

    2014-12-01

    Carbonatite volcanism generally occurs in intra-plate settings associated with continental rifting. The only active carbonatitic volcano is the Oldoinyo Lengai, Tanzania, which generates sodium-rich carbonatites in close association with phonolites and nephelinites1. The processes of carbonatite genesis are still unresolved, however carbonate-bearing melts evidently play a crucial role during mantle melting, in diamond formation and as metasomatic agents. Carbonate melts show extraordinary properties, especially in regard to their low melt viscosities and densities, high surface tensions and electrical conductivities as well as distinct geochemical affinities to a wide range of trace elements2. Understanding the structural properties of carbonate-bearing melts is fundamental to explaining their chemical and physical behaviour as well as modeling processes operating in the deep Earth. Extended X-ray absorption fine structure (EXAFS) spectroscopy is a versatile tool for element specific investigation of the short to medium range structure of melts and glasses. This study focuses on unraveling the influence of carbonate concentration on the structural incorporation of the geochemically important trace elements Y and Sr in silicate and carbonate melts in the system Na2O-CaO-Al2O3-SiO2-CO2. First, we present structural data of silicate glasses with up to 10 wt% CO2, quenched from melts under high temperature and pressure, which indicate that the local structure of Y and Sr is not or only slightly affected by CO2. Melts with higher CO2 contents could not be quenched to glass, so far. Second, we show results of high pressure, high temperature experiments conducted in the Paris Edinburgh-Press, which provides in-situ insight into carbonate-silicate melts. All EXAFS measurements were performed at the synchrotron facility beamlines SAMBA (SOLEIL) and BM23 (ESRF). Information derived from the trace elements' local structure is used to develop a structural model for carbonate

  10. Thermodynamic and structural properties of Bi-based liquid alloys

    NASA Astrophysics Data System (ADS)

    Yadav, S. K.; Jha, L. N.; Adhikari, D.

    2015-10-01

    Thermodynamic and microscopic structural properties of two Bi-based liquid alloys, such as In-Bi at 900 K and Tl-Bi at 750 K have been studied employing the regular associated solution model. We have estimated the mole fractions of the complexes and the free monomers assuming the existence of complexes In2 Bi in In-Bi melt and TlBi in Tl-Bi melt. The thermodynamic properties have been studied by computing the Gibbs free energy of mixing, enthalpy of mixing, entropy of mixing and activities of the monomers. The compositional contributions of the heat associated with the formation of complexes and the heat of mixing of the monomers to the net enthalpy change has also been studied. The structural properties of the liquid alloys have been studied by computing concentration fluctuation in the long-wavelength limit, chemical short-range order parameter and the ratio of mutual to intrinsic diffusion coefficients. For both of the alloy systems, the theoretical as well as the experimental values of SCC (0) are found to be lower than the corresponding ideal values over the whole composition range, indicating the hetero-coordinating nature of Bi-In and Bi-Tl alloy melts. All the interaction energy parameters are found to be negative and temperature dependent, and both the alloy systems are found to be weakly interacting.

  11. High-pressure structural properties of tetramethylsilane

    NASA Astrophysics Data System (ADS)

    Zhen-Xing, Qin; Xiao-Jia, Chen

    2016-02-01

    High-pressure structural properties of tetramethylsilane are investigated by synchrotron powder x-ray diffraction at pressures up to 31.1 GPa and room temperature. A phase with the space group of Pnma is found to appear at 4.2 GPa. Upon compression, the compound transforms to two following phases: the phase with space groups of P21/c at 9.9 GPa and the phase with P2/m at 18.2 GPa successively via a transitional phase. The unique structural character of P21/c supports the phase stability of tetramethylsilane without possible decomposition upon heavy compression. The appearance of the P2/m phase suggests the possible realization of metallization for this material at higher pressure. Project supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project from Ministry of Education of China (Grant No. 708070), the Fundamental Research Funds for the Central Universities, South China University of Technology (Grant No. 2014ZZ0069), the National Natural Science Foundation of China (Grant No. 51502189), and the Doctoral Project of Taiyuan University of Science and Technology, China (Grant No. 20132010).

  12. Structural properties of impact ices accreted on aircraft structures

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  13. Parent-Child Relationships, Partner Relationships, and Emotional Adjustment: A Birth-to-Maturity Prospective Study

    ERIC Educational Resources Information Center

    Overbeek, Geertjan; Stattin, Hakan; Vermulst, Ad; Ha, Thao; Engels, Rutger C. M. E.

    2007-01-01

    This study examined whether detrimental childhood relationships with parents were related to partner relationship quality and emotional adjustment in adulthood. The authors tested a theoretical model in which (a) low-quality parent-child relationships were related to conflict and low-quality communication with parents in adolescence, (b)…

  14. Bulimia and Interpersonal Relationships: A Longitudinal Study.

    ERIC Educational Resources Information Center

    Thelen, Mark H.; And Others

    1990-01-01

    Assessed changes in bulimia in female college students (N=44) and in relation between bulimia and interpersonal relationships over time. Found (1) stable symptomology for normals and bulimics; (2) strong negative correlations between bulimia measures and interpersonal relationships with men; and (3) improvement in symptomology and relationships…

  15. Implicit Theories of Relationship: An Intergenerational Study.

    ERIC Educational Resources Information Center

    Rands, Marylyn; Levinger, George

    1979-01-01

    Explores generational differences in social relationships: college students and senior citizens two generations apart in age estimated the probabilities of each of 30 behaviors for each of 14 pairs of relationships varying in their closeness and in their sex composition. (CM)

  16. Structural properties of silver doped hydroxyapatite and their biocompatibility.

    PubMed

    Ciobanu, C S; Iconaru, S L; Pasuk, I; Vasile, B S; Lupu, A R; Hermenean, A; Dinischiotu, A; Predoi, D

    2013-04-01

    The aim of this study was to obtain a novel hydroxyapatite-based material with high biocompatibility. The structural properties of the samples were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The X-ray diffraction studies revealed the characteristic peaks of hydroxyapatite in each sample. Other phases or impurities were not observed. The scanning electron microscopy observations suggest that the doping components have no influence on the surface morphology of the samples, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O) and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) and X-ray Photoelectron Spectroscopy analyses. Nanocrystalline silver doped HAp stimulated viability and potentiated the activation of murine macrophages.

  17. Density Functional Theory and Electrochemical Studies: Structure-Efficiency Relationship on Corrosion Inhibition.

    PubMed

    Camacho-Mendoza, Rosa L; Gutiérrez-Moreno, Evelin; Guzmán-Percástegui, Edmundo; Aquino-Torres, Eliazar; Cruz-Borbolla, Julián; Rodríguez-Ávila, José A; Alvarado-Rodríguez, José G; Olvera-Neria, Oscar; Thangarasu, Pandiyan; Medina-Franco, José L

    2015-11-23

    The relationship between structure and corrosion inhibition of a series of 30 imidazol, benzimidazol, and pyridine derivatives has been established through the investigation of quantum descriptors calculated with PBE/6-311++G**. A quantitative structure-property relationship model was obtained by examination of these descriptors using a genetic functional approximation method based on a multiple linear regression analysis. Our results indicate that the efficiency of corrosion inhibitors is strongly associated with aromaticity, electron donor ability, and molecular volume descriptors. In order to calibrate and validate the proposed model, we performed electrochemical impedance spectroscopy (EIS) studies on imidazole, 2-methylimidazole, benzimidazole, 2-chloromethylbenzimidazole, pyridine, and 2-aminopyridine compounds. The experimental values for efficiency of corrosion inhibition are in good agreement with the estimated values obtained by our model, thus confirming that our approach represents a promising and suitable tool to predict the inhibition of corrosion attributes of nitrogen containing heterocyclic compounds. The adsorption behavior of imidazole or benzimidazole heterocyclic molecules on the Fe(110) surface was also studied to elucidate the inhibition mechanism; the aromaticity played an important role in the adsorbate-surface complex.

  18. Shared Relationship Efficacy of Dyad Can Increase Life Satisfaction in Close Relationships: Multilevel Study

    PubMed Central

    Ito, Kenichi; Yoshida, Toshikazu

    2016-01-01

    Characteristics of relationship itself play an important role in determining well-being of individuals who participate in the relationship. We used efficacy expectations mutually shared between close friends or romantic partners as a characteristic of relationship and investigated its impact on their life satisfaction. In Study 1, we conducted a cross-sectional study among 137 pairs of close same-sex friends to test whether the efficacy expectations shared between friends are associated with levels of life satisfaction. In Study 2, we conducted a longitudinal study among 114 heterosexual romantic couples to test predictive validity of the efficacy expectations shared between couples predict levels of life satisfaction 2 month later. In both studies we found a consistent result that as degrees of the efficacy expectations shared between individuals in a relationship increased, the degree of their life satisfaction also increased. Underlying mechanisms that explain how characteristics of relationship itself increase life satisfaction are discussed. PMID:27437946

  19. Structural properties of bismuth-bearing semiconductor alloys

    NASA Technical Reports Server (NTRS)

    Berding, M. A.; Sher, A.; Chen, A.-B.; Miller, W. E.

    1988-01-01

    The structural properties of bismuth-bearing III-V semiconductor alloys InPBi, InAsBi, and InSbBi were studied theoretically. Bond energies, bond lengths, and strain coefficients were calculated for pure AlBi, GaBi, and InBi compounds and their alloys, and predictions were made for the mixing enthalpies, miscibility gaps, and critical metastable-to-stable material transition temperatures. Miscibility calculations indicate that InSbBi will be the most miscible, and the InPBi will be the the most difficult to mix. However, calculations of the hardness of the Bi compounds indicate that, once formed, the InPBi alloy will be harder than the other Bi alloys and substantially harder than the currently favored narrow-gap semiconductor HgCdTe.

  20. Novel aliphatic lipid-based diesters for use in lubricant formulations: Structure property investigations

    NASA Astrophysics Data System (ADS)

    Raghunanan, Latchmi Cindy

    Structure-property relationships are increasingly valued for the identification of specifically engineered materials with properties optimized for targeted application(s). In this work, linear and branched diesters for use in lubricant formulations are prepared from lipid-based oleochemicals and their structure-property relationships reported. It is shown that the branched diesters possess exceptional physical property profiles, including suppression of crystallization, and are superior alternatives for use in lubricant formulations. For the linear aliphatic diesters, both high and low temperature properties were predictable functions of total chain length, and both were differently influenced by the fatty acid versus diol chain length. Symmetry did not influence either, although thermal stability decreased and thermal transition temperatures increased with increasing saturation. All of the linear diesters demonstrated Newtonian flow behaviour. Viscosity was also predictable as a function of total chain length; any microstructural features due to structural effects were superseded by mass effects.

  1. Condensed-phase effects on the structural properties of FCH2CN-BF3 and ClCH2CN-BF3: a matrix-isolation and computational study.

    PubMed

    Buchberger, Amanda R; Danforth, Samuel J; Bloomgren, Kaitlin M; Rohde, John A; Smith, Elizabeth L; Gardener, Colin C A; Phillips, James A

    2013-10-01

    We have measured several IR bands of FCH2CN-BF3 and ClCH2CN-BF3 in solid nitrogen, argon, and neon. These bands include the B-F asymmetric stretch (νBF(a)), the B-F symmetric stretch (νBF(s)), the BF3 symmetric deformation or "umbrella" mode (δBF(s)), and the CN stretch (νCN). For both complexes, the frequencies of these modes shift across the various media, particularly the B-F asymmetric stretching band, and thus they indicate that the inert gas matrix environments significantly alter the structural properties of FCH2CN-BF3 and ClCH2CN-BF3. Furthermore, the frequencies shift in a manner that parallels the dielectric constant of these media, which suggests a progressive contraction of the B-N distances in these systems and also that it parallels the ability of the medium to stabilize the increase in polarity that accompanies the bond contraction. We have also mapped the B-N distance potentials for FCH2CN-BF3 and ClCH2CN-BF3 using several density functional and post-Hartree-Fock methods, all of which reveal a flat, shelflike region that extends from the gas-phase minimum (near 2.4 Å) toward the inner wall (to about 1.7 Å). Furthermore, we were able to rationalize the medium effects on the structure by constructing hybrid bond potentials composed of the electrostatic component of the solvation free energy and the gas-phase electronic energy. These curves indicate that the solvation energies are greatest at short B-N distances (at which the complex is more polar), and ultimately, the potential minima shift inward as the dielectric constant of the medium increases.

  2. Social Anxiety and Close Relationships: A Hermeneutic Phenomenological Study

    ERIC Educational Resources Information Center

    Nielsen, Kate E. J.; Cairns, Sharon L.

    2009-01-01

    While only a few quantitative studies have looked at social anxiety and close relationships, this study uses the qualitative approach of hermeneutic phenomenology to explore the meaning of being in a close relationship for eight individuals with social anxiety. Participants completed a written questionnaire with open-ended questions about their…

  3. Effect of oxide nanoparticles on structural properties of multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Dhall, Shivani; Jaggi, Neena

    2016-03-01

    A simple chemical precipitation route is reported to partially decorate mutliwalled carbon nanotubes (MWCNTs) with oxide nanoparticles in the present study. X-ray diffraction (XRD), Raman spectroscopy and Scanning electron microscopy (SEM) are used to investigate the structural properties of MWCNTs composite with nickel, cuprous, zinc and tin oxides nanoparticles. Raman analysis confirms that, ZnO nanoparticles attached nanotubes show more ordering of graphene layers as compared to the others because of uniform dispersion of nanoparticles. It is investigated that, adopted route proved helpful to improve the structural properties of the nanotubes.

  4. Adolescents in Wilderness Therapy: A Qualitative Study of Attachment Relationships

    ERIC Educational Resources Information Center

    Bettmann, Joanna E.; Olson-Morrison, Debra; Jasperson, Rachael A.

    2011-01-01

    Characterized by acute changes in attachment relationships, adolescence is a time of balancing autonomy and attachment needs. For adolescents in wilderness therapy programs, the setting often challenges their understanding of their own attachment relationships. The current study evaluates the narratives of 13 adolescents in a wilderness therapy…

  5. Measuring Long-Distance Romantic Relationships: A Validity Study

    ERIC Educational Resources Information Center

    Pistole, M. Carole; Roberts, Amber

    2011-01-01

    This study investigated aspects of construct validity for the scores of a new long-distance romantic relationship measure. A single-factor structure of the long-distance romantic relationship index emerged, with convergent and discriminant evidence of external validity, high internal consistency reliability, and applied utility of the scores.…

  6. Experiences of Male Counselor Educators: A Study of Relationship Boundaries

    ERIC Educational Resources Information Center

    Ray, Dee C.; Huffman, David D.; Christian, David D.; Wilson, Brittany J.

    2016-01-01

    This study surveyed male counselor educators regarding the impact of being male upon their professional relationships. Participants (N = 163) were surveyed about their attitudes concerning the influence of gender on their relational behavior, as well as their relationship practices with students and colleagues. Mixed-methods analyses revealed a…

  7. University-Industry Research Relationships. Selected Studies.

    ERIC Educational Resources Information Center

    National Science Foundation, Washington, DC. National Science Board.

    The results of a study of university/industry research interactions are presented, along with four reports on collaboration, and an annotated bibliography. The study, "Current U.S University/Industry Research Connections" (Lois S. Peters, Herbert I. Fusfeld, and others), involved on-site interviews with 66 companies and 61 public and private…

  8. Stay vane and wicket gate relationship study

    SciTech Connect

    None, None

    2005-01-19

    This report evaluates potential environmental and performance gains that can be achieved in a Kaplan turbine through non-structural modifications to stay vane and wicket gate assemblies. This summary is based primarily on data and conclusions drawn from models and studies of Lower Granite Dam. Based on this investigation, the study recommends (1) a proof of concept at Lower Granite Dam to establish predicted improvements for the existing turbine and to further refine the stay vane wicket gate designs for fish passage; and (2) consideration of the stay vane wicket gate systems in any future turbine rehabilitation studies.

  9. Exploring the Structural Properties of the State Reading Policy Domain Using Network Visualization Techniques

    ERIC Educational Resources Information Center

    Song, Mengli; Miskel, Cecil G.

    2007-01-01

    Guided by the social network perspective, this study examined the structural properties of the state reading policy domain using network visualization tools: sociograms and multidimensional scaling scattergrams. The authors' graphic exploration of eight state reading policy networks produced rich insights about the density and the overall…

  10. Gogny HFB prediction of nuclear structure properties

    SciTech Connect

    Goriely, S.; Hilaire, S.; Girod, M.

    2011-10-28

    Large scale mean field calculations from proton to neutron drip lines have been performed using the Hartree-Fock-Bogoliubov method based on the Gogny nucleon-nucleon effective interaction. This extensive study has shown the ability of the method to reproduce bulk nuclear structure data available experimentally. This includes nuclear masses, radii, matter densities, deformations, moment of inertia as well as collective mode (low energy and giant resonances). In particular, the first mass table based on a Gogny-Hartree-Fock-Bogolyubov calculation including an explicit and coherent account of all the quadrupole correlation energies is presented. The rms deviation with respect to essentially all the available mass data is 798 keV. Nearly 8000 nuclei have been studied under the axial symmetry hypothesis and going beyond the mean-field approach.

  11. Stochastic simulation of structural properties of natively unfolded and denatured proteins.

    PubMed

    Curcó, David; Michaux, Catherine; Roussel, Guillaume; Tinti, Emmanuel; Perpète, Eric A; Alemán, Carlos

    2012-09-01

    A new simulation strategy based on a stochastic process has been developed and tested to study the structural properties of the unfolded state of proteins at the atomistic level. The procedure combines a generation algorithm to produce representative uncorrelated atomistic microstructures and an original relaxation method to minimize repulsive non-bonded interactions. Using this methodology, a set of 14 unfolded proteins, including seven natively unfolded proteins as well as seven "classical" proteins experimentally described in denaturation conditions, has been investigated. Comparisons between the calculated and available experimental values of several properties, at hydrodynamic and atomic level, used to describe the unfolded state, such as the radius of gyration, the maximum length, the hydrodynamic radius, the diffusion coefficient, the sedimentation coefficient, and the NMR chemical shifts, reflect a very good agreement. Furthermore, our results indicate that the relationship between the radius of gyration and the hydrodynamic radius deviates from the Zimm's theory of polymer dynamics for random coils, as was recently observed using single-molecule fluorescent methods. Simulations reveal that the interactions between atoms separated by three chemical bonds (1-4 interactions) play a crucial role in the generation process, suggesting that the unfolded state is essentially governed by bonding and short-range non-bonding interactions.

  12. Dielectric and structural properties of ferroelectric betaine arsenate films

    NASA Astrophysics Data System (ADS)

    Balashova, E. V.; Krichevtsov, B. B.; Zaitseva, N. V.; Yurko, E. I.; Svinarev, F. B.

    2014-12-01

    Ferroelectric films of betaine arsenate and partially deuterated betaine arsenate have been grown by evaporation on LiNbO3, α-Al2O3, and NdGaO3 substrates with a preliminarily deposited structure of interdigitated electrodes, as well as on the Al/glass substrate. This paper presents the results of the examination of the block structure of the films in a polarizing microscope, the X-ray diffraction analysis of their crystal structure, and the investigation of the dielectric properties in a measuring field oriented both parallel and perpendicular to the plane of the film. The transition of the films to the ferroelectric state at T = T c is accompanied by anomalies of the capacitance of the structure, an increase in the dielectric loss, and the appearance of dielectric hysteresis loops. The growth of the films from a solution of betaine arsenate in a heavy water leads to an increase in the ferroelectric transition temperature from T c = 119 K in the films without deuterium to T c = 149 K, which corresponds to the degree of deuteration of approximately 60-70%. The dielectric and structural properties of the films are compared with those of the betaine arsenate single crystals and the previously studied films of betaine phosphite and glycine phosphite.

  13. Structural properties of particle deposits at heterogeneous surfaces

    NASA Astrophysics Data System (ADS)

    Stojiljković, D.; Šćepanović, J. R.; Vrhovac, S. B.; Švrakić, N. M.

    2015-06-01

    The random sequential adsorption (RSA) approach is used to analyze adsorption of spherical particles of a fixed radius on nonuniform flat surfaces covered by rectangular cells. The configuration of the cells (heterogeneities) was produced by performing RSA simulations to a prescribed coverage fraction θ_0{(cell)} . Adsorption was assumed to occur if the particle (projected) center lies within a rectangular cell area, i.e. if sphere touches the cells. The jammed-state properties of the model were studied for different values of cell size α (comparable with the adsorbing particle size) and density θ_0{(cell)} . Numerical simulations were carried out to investigate adsorption kinetics, jamming coverage, and structure of coverings. Structural properties of the jammed-state coverings were analyzed in terms of the radial distribution function g(r) and distribution of the Delaunay ‘free’ volumes P(v). It was demonstrated that adsorption kinetics and the jamming coverage decreased significantly, at a fixed density θ_0{(cell)} , when the cell size α increased. The predictions following from our calculation suggest that the porosity (pore volumes) of deposited monolayer can be controlled by the size and shape of landing cells, and by anisotropy of the cell deposition procedure.

  14. Structural Properties of Finite MoS2 Nanowires

    NASA Astrophysics Data System (ADS)

    Clark, Shaylyn; Salgado, Andres; Fernandez-Seivane, Lucas; Lopez-Lozano, Xochitl

    2015-03-01

    Molybdenum disulfide (MoS2) has been one of the most important catalysts used in refineries worldwide for hydrodesulfurization over the past century. In the last decade, and with the advent of nanotechnology, there has been a special interest in MoS2 nanostructures due to their high potential as novel nanocatalysts. The study of the properties of these systems is of fundamental interest for the experimental design of their catalytic activity and efficiency. In this work, we have performed ab initio density-functional calculations (DFT) to investigate the structural properties of finite MoS2 nanostrutures. All the models here presented were based on newly experimentally observed morphologies in MoS2 industrial catalysts using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images. We simulated STEM images of the theoretical models to compare it with the experimental ones. In contrast with infinite models, the finite models prefer a rippled/twisted structure morphology over the planar or helical ones. The rippled/twisted models appear to be structurally more stable.

  15. [Studies on genetic relationship of Dioscorea].

    PubMed

    Huang, Han-han; Li, Xia; Gao, Wen-yuan; Xiao, Pei-gen

    2015-09-01

    Based on the results of the morphologic studies on genus Dioscorea, the paper summarized the entire chemical constituent that isolated from this genus and analyzed it with the methods of chemotaxonomy. The rules of the chemical constituent and pharmacodynamic effects were analyzed. Seventeen species which belong to Sect. Stenophora Uline of Dioscorea contain steroidal sapogenin. Other species with different main components such as polysaccharide and tannin have have different effects. This chemotaxonomic view point will conduce to establish a phylogeny of the genus Dioscorea.

  16. Electronic and structural properties of metallic microclusters

    SciTech Connect

    Maiti, A.

    1992-04-01

    The first part of this thesis presents a first-order pseudopotential calculation at T=O of the total energy of small sodium clusters of size N<800. The calculation is based on a local-pseudopotential scheme and local-density correlation and exchange. A temperature-size (T-N) phase-diagram is then derived using the T=O results and Lindemann`s criterion for melting. The phase-diagram contains three regions of stability: (1) a liquid (jellium) phase at temperatures above the melting line T{sub M}(N) where cluster-stability occurs at electronic magic numbers: (2) a phase related to complete geometrical shells of body-centered-cubic structure at temperatures below the melting line; and (3) a close-packed structure at very low temperatures and sufficiently large N. The melting line drops to T{sub M}(N)=O for N<65, where electronic magic numbers are stable even at T=O. The phase diagram reduces asymptotically to the known phases of sodium as N{yields}{infinity}, including the known martensitic transformation at T{approximately}5 K. The second and the last part of this thesis consists of a study of small-cluster many-body systems by means of an on-site ``local`` chemical potential which allows the continuous variation of local electron-density. This method yields a criterion to distinguish particular features of a small cluster that are likely to survive in the large-N thermodynamic limit from those discontinuities that arise only from finite-size effects.

  17. Electronic and structural properties of metallic microclusters

    SciTech Connect

    Maiti, A.

    1992-04-01

    The first part of this thesis presents a first-order pseudopotential calculation at T=O of the total energy of small sodium clusters of size N<800. The calculation is based on a local-pseudopotential scheme and local-density correlation and exchange. A temperature-size (T-N) phase-diagram is then derived using the T=O results and Lindemann's criterion for melting. The phase-diagram contains three regions of stability: (1) a liquid (jellium) phase at temperatures above the melting line T{sub M}(N) where cluster-stability occurs at electronic magic numbers: (2) a phase related to complete geometrical shells of body-centered-cubic structure at temperatures below the melting line; and (3) a close-packed structure at very low temperatures and sufficiently large N. The melting line drops to T{sub M}(N)=O for N<65, where electronic magic numbers are stable even at T=O. The phase diagram reduces asymptotically to the known phases of sodium as N{yields}{infinity}, including the known martensitic transformation at T{approximately}5 K. The second and the last part of this thesis consists of a study of small-cluster many-body systems by means of an on-site local'' chemical potential which allows the continuous variation of local electron-density. This method yields a criterion to distinguish particular features of a small cluster that are likely to survive in the large-N thermodynamic limit from those discontinuities that arise only from finite-size effects.

  18. A special relationship: Race, child study, and Rockefeller philanthropy.

    PubMed

    Milar, Katharine S

    2010-01-01

    In 1928, the Laura Spelman Rockefeller Memorial granted funds to the University of Cincinnati to establish a child study and parent education program for African Americans. This paper traces the origin of the idea for this program to a special relationship between the family of John D. Rockefeller, Sr., and Spelman College, an African American women's college in Atlanta, Georgia. This relationship embodied Rockefeller's interest in women and children, in Baptist charities, in higher education (especially in the South), and race. The case study of this relationship addresses the larger question: To what purpose was the African American woman to be educated?

  19. [Study of the relationship between human quality and reliability].

    PubMed

    Long, S; Wang, C; Wang, L i; Yuan, J; Liu, H; Jiao, X

    1997-02-01

    To clarify the relationship between human quality and reliability, 1925 experiments in 20 subjects were carried out to study the relationship between disposition character, digital memory, graphic memory, multi-reaction time and education level and simulated aircraft operation. Meanwhile, effects of task difficulty and enviromental factor on human reliability were also studied. The results showed that human quality can be predicted and evaluated through experimental methods. The better the human quality, the higher the human reliability. PMID:11539889

  20. Effect of wet grinding on structural properties of ball clay

    SciTech Connect

    Purohit, A. Chander, S.; Dhaka, M. S.; Hameed, A.; Singh, P.; Nehra, S. P.

    2015-05-15

    In this paper, the effect of wet grinding on structural properties of ball clay is undertaken. The wet grinding treatment was performed employing ball and vibro mills for different time spells of 2, 4, 8 and 16 hours. The structural properties were carried out using X-ray diffraction (XRD). The structure of ground samples is found to be simple cubic. The crystallographic parameters are calculated and slight change in lattice constant, inter planner spacing and particle size is observed with grinding treatment. The results are in agreement with the available literature.

  1. Structural properties and UV to NIR absorption spectra of metal-free phthalocyanine (H2Pc) thin films P. B. Thakor, P. N. Gajjar and A. R. Jani: Different reference systems in the study of structural properties of some simple liquid metals Shazia Bashir, M. S. Rafique, M. Khaleeq-ur-Rahman, Faizan-ul-Haq and B. R. Alvina: CO2 and Nd:YAG laser radiation induced damage in aluminium Smail Bougouffa: The study of atomic transitions by use of Numerov technique in schematic model

    NASA Astrophysics Data System (ADS)

    El-Nahass, M. M.; Farid, A. M.; Attia, A. A.; Ali, H. A. M.

    The structural properties and absorption spectra of H2Pc thin films have been studied. The films used in these studies were thermally evaporated on glass/quartz substrates with thickness ranging from 60 to 460 nm. The XRD studies of H2Pc thin films showed that the as-deposited films have a-form with monoclinic system. The mean crystallite size (L), the dislocation density (d) and the strain (x) were evaluated. The molecular structure of H2Pc thin films is confirmed by analysis of (FTIR) spectra. The surface morphology of H2Pc thin films was examined by scanning electron microscope. The absorption spectra of H2Pc recorded in the UV - VIS - IR region for the as-deposited and the annealed thin films of different thickness have been analyzed. The spectra showed two absorption bands namely the Q-band and the Soret (B)-band. The Q-band shows its characteristic splitting (Davydove splitting) with DQ = 0.21 eV. Values of some important optical parameters, namely optical absorption coefficient (a¢), molar extinction coefficient (emolar), half-band-width (Dl), electronic dipole strength (q2) and oscillator strength (f) were calculated. The fundamental and the onset of the indirect energy gaps were also determined as 2.47 and 1.4 eV, respectively.

  2. Morphological, luminescence and structural properties of nanocrystalline silicon thin films

    SciTech Connect

    Ali, Atif Mossad; Kobayashi, Hikaru; Inokuma, Takao; Al-Hajry, Ali

    2013-03-15

    Highlights: ► The PL spectra showed two stronger peaks and one weaker peak. ► The PL peak energies and optical band-gap values were found higher than 1.12 eV. ► The structural change from an amorphous to nanocrystalline with increasing [SiH{sub 4}]. - Abstract: Nanocrystalline silicon (nc-Si) thin films deposited by plasma-enhanced chemical vapor deposition at various silane flow rates ([SiH{sub 4}]) are studied. The characterization of these films by high-resolution transmission electron microscopy, Raman spectroscopy and X-ray diffraction reveals that no film and very thin film is deposited at [SiH{sub 4}] = 0.0 and 0.1 sccm, respectively. In addition, the structural change from an amorphous to a nanocrystalline phase occurs at around [SiH{sub 4}] = 0.2 sccm. In this study, the importance of arriving species at surfaces and precursors is clearly demonstrated by the effect of a small addition of SiH{sub 4} on the frequency and width of a Raman peak and the structure of the grown film. The infrared spectroscopic analysis shows no hydrogen incorporation in the nc-Si film deposited at the low value of [SiH{sub 4}]. However, the intensity of the peak around 2100 cm{sup −1} due to SiH decreases with increasing [SiH{sub 4}]. All fabricated films give photoluminescence in the range between 1.7 and 2.4 eV at room temperature, indicating enlargement of the band-gap energy. The presence of very small crystallites leads to the appearance of quantum confinement effects. The variations of the photoluminescence energy and spectral width are well correlated with the structural properties of the films such as crystallite size, crystalline volume fraction, and the density of Si-H bonds.

  3. Tyrosine Aminotransferase: Biochemical and Structural Properties and Molecular Dynamics Simulations

    SciTech Connect

    P Mehere; Q Han; J Lemkul; C Vavricka; H Robinson; D Bevan; J Li

    2011-12-31

    Tyrosine aminotransferase (TAT) catalyzes the transamination of tyrosine and other aromatic amino acids. The enzyme is thought to play a role in tyrosinemia type II, hepatitis and hepatic carcinoma recovery. The objective of this study is to investigate its biochemical and structural characteristics and substrate specificity in order to provide insight regarding its involvement in these diseases. Mouse TAT (mTAT) was cloned from a mouse cDNA library, and its recombinant protein was produced using Escherichia coli cells and purified using various chromatographic techniques. The recombinant mTAT is able to catalyze the transamination of tyrosine using {alpha}-ketoglutaric acid as an amino group acceptor at neutral pH. The enzyme also can use glutamate and phenylalanine as amino group donors and p-hydroxy-phenylpyruvate, phenylpyruvate and alpha-ketocaproic acid as amino group acceptors. Through macromolecular crystallography we have determined the mTAT crystal structure at 2.9 {angstrom} resolution. The crystal structure revealed the interaction between the pyridoxal-5'-phosphate cofactor and the enzyme, as well as the formation of a disulphide bond. The detection of disulphide bond provides some rational explanation regarding previously observed TAT inactivation under oxidative conditions and reactivation of the inactive TAT in the presence of a reducing agent. Molecular dynamics simulations using the crystal structures of Trypanosoma cruzi TAT and human TAT provided further insight regarding the substrate-enzyme interactions and substrate specificity. The biochemical and structural properties of TAT and the binding of its cofactor and the substrate may help in elucidation of the mechanism of TAT inhibition and activation.

  4. Tyrosine aminotransferase: biochemical and structural properties and molecular dynamics simulations

    SciTech Connect

    Mehere, P.; Robinson, H.; Han, Q.; Lemkul, J. A.; Vavricka, C. J.; Bevan, D. R.; Li, J.

    2010-11-01

    Tyrosine aminotransferase (TAT) catalyzes the transamination of tyrosine and other aromatic amino acids. The enzyme is thought to play a role in tyrosinemia type II, hepatitis and hepatic carcinoma recovery. The objective of this study is to investigate its biochemical and structural characteristics and substrate specificity in order to provide insight regarding its involvement in these diseases. Mouse TAT (mTAT) was cloned from a mouse cDNA library, and its recombinant protein was produced using Escherichia coli cells and purified using various chromatographic techniques. The recombinant mTAT is able to catalyze the transamination of tyrosine using {alpha}-ketoglutaric acid as an amino group acceptor at neutral pH. The enzyme also can use glutamate and phenylalanine as amino group donors and p-hydroxy-phenylpyruvate, phenylpyruvate and alpha-ketocaproic acid as amino group acceptors. Through macromolecular crystallography we have determined the mTAT crystal structure at 2.9 {angstrom} resolution. The crystal structure revealed the interaction between the pyridoxal-5'-phosphate cofactor and the enzyme, as well as the formation of a disulphide bond. The detection of disulphide bond provides some rational explanation regarding previously observed TAT inactivation under oxidative conditions and reactivation of the inactive TAT in the presence of a reducing agent. Molecular dynamics simulations using the crystal structures of Trypanosoma cruzi TAT and human TAT provided further insight regarding the substrate-enzyme interactions and substrate specificity. The biochemical and structural properties of TAT and the binding of its cofactor and the substrate may help in elucidation of the mechanism of TAT inhibition and activation.

  5. Biochemical and Structural Properties of Mouse Kynurenine Aminotransferase III

    SciTech Connect

    Han, Q.; Robinson, H; Cai, T; Tagle, D; Li, J

    2009-01-01

    Kynurenine aminotransferase III (KAT III) has been considered to be involved in the production of mammalian brain kynurenic acid (KYNA), which plays an important role in protecting neurons from overstimulation by excitatory neurotransmitters. The enzyme was identified based on its high sequence identity with mammalian KAT I, but its activity toward kynurenine and its structural characteristics have not been established. In this study, the biochemical and structural properties of mouse KAT III (mKAT III) were determined. Specifically, mKAT III cDNA was amplified from a mouse brain cDNA library, and its recombinant protein was expressed in an insect cell protein expression system. We established that mKAT III is able to efficiently catalyze the transamination of kynurenine to KYNA and has optimum activity at relatively basic conditions of around pH 9.0 and at relatively high temperatures of 50 to 60C. In addition, mKAT III is active toward a number of other amino acids. Its activity toward kynurenine is significantly decreased in the presence of methionine, histidine, glutamine, leucine, cysteine, and 3-hydroxykynurenine. Through macromolecular crystallography, we determined the mKAT III crystal structure and its structures in complex with kynurenine and glutamine. Structural analysis revealed the overall architecture of mKAT III and its cofactor binding site and active center residues. This is the first report concerning the biochemical characteristics and crystal structures of KAT III enzymes and provides a basis toward understanding the overall physiological role of mammalian KAT III in vivo and insight into regulating the levels of endogenous KYNA through modulation of the enzyme in the mouse brain.

  6. Tyrosine aminotransferase: biochemical and structural properties and molecular dynamics simulations.

    PubMed

    Mehere, Prajwalini; Han, Qian; Lemkul, Justin A; Vavricka, Christopher J; Robinson, Howard; Bevan, David R; Li, Jianyong

    2010-11-01

    Tyrosine aminotransferase (TAT) catalyzes the transamination of tyrosine and other aromatic amino acids. The enzyme is thought to play a role in tyrosinemia type II, hepatitis and hepatic carcinoma recovery. The objective of this study is to investigate its biochemical and structural characteristics and substrate specificity in order to provide insight regarding its involvement in these diseases. Mouse TAT (mTAT) was cloned from a mouse cDNA library, and its recombinant protein was produced using Escherichia coli cells and purified using various chromatographic techniques. The recombinant mTAT is able to catalyze the transamination of tyrosine using α-ketoglutaric acid as an amino group acceptor at neutral pH. The enzyme also can use glutamate and phenylalanine as amino group donors and p-hydroxy-phenylpyruvate, phenylpyruvate and alpha-ketocaproic acid as amino group acceptors. Through macromolecular crystallography we have determined the mTAT crystal structure at 2.9 Å resolution. The crystal structure revealed the interaction between the pyridoxal-5'-phosphate cofactor and the enzyme, as well as the formation of a disulphide bond. The detection of disulphide bond provides some rational explanation regarding previously observed TAT inactivation under oxidative conditions and reactivation of the inactive TAT in the presence of a reducing agent. Molecular dynamics simulations using the crystal structures of Trypanosoma cruzi TAT and human TAT provided further insight regarding the substrate-enzyme interactions and substrate specificity. The biochemical and structural properties of TAT and the binding of its cofactor and the substrate may help in elucidation of the mechanism of TAT inhibition and activation.

  7. Study of the CASAS Relationship to GED 2002. Research Brief

    ERIC Educational Resources Information Center

    CASAS - Comprehensive Adult Student Assessment Systems (NJ1), 2003

    2003-01-01

    CASAS, in cooperation with the CASAS National Consortium Policy Council, conducted a study to provide guidance to program and instructional staff regarding student readiness to take the GED Tests. The study looked at the relationship of CASAS reading and math scores to official 2002 GED test results from five states--California, Hawaii, Iowa,…

  8. The Relationship between College Students' Executive Functioning and Study Strategies

    ERIC Educational Resources Information Center

    Petersen, Rebecca; Lavelle, Ellen; Guarino, A. J.

    2006-01-01

    Working from a cognitive perspective, a range of studies have supported the relationship between study strategies and academic performance of college students (e.g., Peverly, Brobst, Graham, & Shaw, 2003). In particular, self-regulatory processes comprised of learner-directed activities geared toward promoting academic achievement have been linked…

  9. Structural properties and gas sensing behavior of sol-gel grown nanostructured zinc oxide

    NASA Astrophysics Data System (ADS)

    Rajyaguru, Bhargav; Gadani, Keval; Rathod, K. N.; Solanki, Sapana; Kansara, S. B.; Pandya, D. D.; Shah, N. A.; Solanki, P. S.

    2016-05-01

    In this communication, we report the results of the studies on structural properties and gas sensing behavior of nanostructured ZnO grown using acetone precursor based modified sol-gel technique. Final product of ZnO was sintered at different temperatures to vary the crystallite size while their structural properties have been studied using X-ray diffraction (XRD) measurement performed at room temperature. XRD results suggest the single phasic nature of all the samples and crystallite size increases from 11.53 to 20.96nm with increase in sintering temperature. Gas sensing behavior has been studied for acetone gas which indicates that lower sintered samples are more capable to sense the acetone gas and related mechanism has been discussed in the light of crystallite size, crystal boundary density, defect mechanism and possible chemical reaction between gas traces and various oxygen species.

  10. Structural properties of cyanase. Denaturation, renaturation, and role of sulfhydryls and oligomeric structure in catalytic activity.

    PubMed

    Little, R M; Anderson, P M

    1987-07-25

    Cyanase is an inducible enzyme in Escherichia coli that catalyzes bicarbonate-dependent decomposition of cyanate to give ammonia and bicarbonate. The enzyme is composed of 8-10 identical subunits (Mr = 17,008). The objective of this study was to clarify some of the structural properties of cyanase for the purpose of understanding the relationship between oligomeric structure and catalytic activity. Circular dichroism studies showed that cyanase has a significant amount of alpha-helix and beta-sheet structure. The one sulfhydryl group per subunit does not react with 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) unless cyanase is denatured. Denaturation is apparently complete in 10 M urea or 6 M guanidine hydrochloride, but is significantly reduced in 10 M urea by the presence of azide (analog of cyanate) and is incomplete in 8 M urea. Denatured cyanase could be renatured and reactivated (greater than 85%) by removal of denaturants. Reactivation was greatly facilitated by the presence of certain anions, particularly bicarbonate, and by high ionic strength and protein concentration. The catalytic activity of renatured cyanase was associated only with oligomer. Cyanase that had been denatured in the presence of DTNB to give a cyanase-DTNB derivative could also be renatured at 26 degrees C to give active cyanase-DTNB oligomer. The active oligomeric form of the cyanase-DTNB derivative could be converted reversibly to inactive dimer by lowering the temperature to 4 degrees C or by reduction of the ionic strength and removal of monoanions. These results provide evidence that free sulfhydryl groups are not required for catalytic activity and that catalytic activity may be dependent upon oligomeric structure.

  11. Doping effect on the structural properties of Cu1-x(Ni, Zn, Al and Fe)xO samples (0study

    NASA Astrophysics Data System (ADS)

    Amaral, J. B.; Araujo, R. M.; Pedra, P. P.; Meneses, C. T.; Duque, J. G. S.; dos S. Rezende, M. V.

    2016-09-01

    In this work, the effect of insertion of transition metal, TM (=Ni, Zn, Al and Fe), ions in Cu1-xTMxO samples (0studied through experimental and computational methods. The analyses of X-ray diffraction (XRD) patterns using Rietveld refinement show that i) at x=0, all samples present a monoclinic crystal system with space group C2/c and ii) for increasing the TM-doping, Ni and Zn-doped samples show a small amount of spurious phases for concentrations above x=0.05. Based on these results, a defect disorder study for using atomistic computational simulations which is based on the lattice energy minimization technique is employed to predict the location of the dopant ions in the structure. In agreement with XRD data, our computational results indicate that the trivalent (Al and Fe ions) are more favorable to be incorporated into CuO matrix than the divalent (Ni and Zn ions).

  12. Relationships

    ERIC Educational Resources Information Center

    Circle, David

    2006-01-01

    The author of this brief article asserts that one of the keys to being successful--whether one is a music teacher, a college professor, a business owner, a doctor, a lawyer, or in any other career--is his or her relationship with people. Music educators are in the people business. They do not make a tangible product. Instead, they provide a…

  13. Rheological and structural properties of differently acidified and renneted milk gels.

    PubMed

    Liu, X T; Zhang, H; Wang, F; Luo, J; Guo, H Y; Ren, F Z

    2014-01-01

    In this study we assessed the rheological and structural properties of differently acidified and renneted milk gels by controlling pH value and renneting extent. Skim milk were exactly renneted to 4 extents (20, 35, 55, and 74%) and then direct acidified to the desired pH (4.8, 5.0, 5.2, 5.5, 5.8, and 6.2), respectively. Rheological properties were assessed by dynamic rheological measurements, structural properties were studied by spontaneous whey separation and confocal laser scanning micrograph, and protein interactions were studied by dissociation test. Results showed that minimally renneted milk samples (20 and 35%) formed weak gels with low storage modulus, and the acidification range within which gels could form was narrow (pH ≤ 5.2). Highly renneted milk samples formed more gels with high storage modulus. The results of this study revealed that acidification determined the structural properties of highly renneted milk gels. As pH increased from 5.0 to 6.2, highly renneted milk gels had lower loss tangent, decreased spontaneous syneresis, and smaller pores. For both the low and high rennetings, divalent calcium bonds contributed less at low pH than at high pH. In conclusion, renneting increased the pH range suitable for gel formation; acidification determined the spontaneous syneresis and microstructure of highly renneted milk gels.

  14. A Special Relationship: Rockefeller, Child Study, and Race.

    ERIC Educational Resources Information Center

    Milar, Katherine S.

    In 1928, the Laura Spelman Rockefeller Memorial granted funds to the University of Cincinnati to establish a child study and parent education program for African-Americans. This paper traces the origin of the idea for this program to a special relationship between the family of John D. Rockefeller, Sr. and Spelman College, an African-American…

  15. Natural Mentoring Relationships among Adolescent Mothers: A Study of Resilience

    ERIC Educational Resources Information Center

    Hurd, Noelle M.; Zimmerman, Marc A.

    2010-01-01

    This study focused on natural mentoring relationships between nonparental adults and African American adolescent mothers. Data were collected from 93 adolescent mothers over 5 time points, starting in the adolescent mothers' senior year of high school and ending 5 years after high school. We found that having a natural mentor was related to fewer…

  16. A comprehensive study of ferromagnetic resonance and structural properties of iron-rich nickel ferrite (NixFe3-xO4, x≤1) films grown by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Pachauri, Neha; Khodadadi, Behrouz; Singh, Amit V.; Mohammadi, Jamileh Beik; Martens, Richard L.; LeClair, Patrick R.; Mewes, Claudia; Mewes, Tim; Gupta, Arunava

    2016-11-01

    We report a detailed study of the structural and ferromagnetic resonance properties of spinel nickel ferrite (NFO) films, grown on (100)-oriented cubic MgAl2O4 substrates by direct liquid injection chemical vapor deposition (DLI-CVD) technique. Three different compositions of NFO films (NixFe3-xO4 where x=1, 0.8, 0.6) deposited at optimized growth temperature of 600 °C are characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometry (VSM), and broadband ferromagnetic resonance (FMR) techniques. XRD confirms the growth of epitaxial, single crystalline NixFe3-xO4 films. The out-of-plane lattice constant (c) obtained for Ni0.8Fe2.2O4 film is slightly higher than the bulk value (0.833 nm), indicating only partial strain relaxation whereas for the other two compositions (x=1 and x=0.6) films exhibit complete relaxation. The in-plane and out-of-plane FMR linewidths measurements at 10 GHz give the lowest values of 458 Oe and 98 Oe, respectively, for Ni0.8Fe2.2O4 film as compared to the other two compositions. A comprehensive frequency (5-40 GHz) and temperature (10-300 K) dependent FMR study of the Ni0.8Fe2.2O4 sample for both in-lane and out-of-plane configurations reveals two magnon scattering (TMS) as the dominant in-plane relaxation mechanism. It is observed that the TMS contribution to the FMR linewidth scales with the saturation magnetization Ms. In-plane angle-dependent FMR measurements performed on the same sample show that the ferromagnetic resonance field (Hres) and the FMR linewidth (ΔH) have a four-fold symmetry that is consistent with the crystal symmetry of the spinel. SEM measurements show formation of pyramid-like microstructures at the surface of the Ni0.8Fe2.2O4 sample, which can explain the observed four-fold symmetry of the FMR linewidth.

  17. Structure-property relation and third order nonlinear optical absorption study of a new organic crystal: 1-(3,4-Dimethoxyphenyl)-3-(2-fluorophenyl) prop-2-en-1-one

    NASA Astrophysics Data System (ADS)

    Chidan Kumar, C. S.; Raghavendra, S.; Chia, Tze Shyang; Chandraju, Siddegowda; Dharmaprakash, S. M.; Fun, Hoong-Kun; Quah, Ching Kheng

    2015-11-01

    A new third order centrosymmetric organic crystal: 1-(3,4-dimethoxyphenyl)-3-(2-fluorophenyl) prop-2-en-1-one (2FRDP) belonging to chalcone family has been synthesized and characterized by FTIR, CHNS and UV-Visible spectroscopy. Single crystal X-ray diffraction reveals that compound crystallizes in C2/c monoclinic space group. The X-ray powder diffraction of the crystal was carried out and hkl values are indexed for the diffraction pattern using mercury software. UV-Visible spectrum showed that 2FRDP is transparent in the entire visible region. The thermal stability of the grown 2FRDP crystal was analyzed by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The dielectric study revealed that, 2FRDP possesses low dielectric constant and dielectric loss at high frequency. The third order nonlinear optical absorption and the optical limiting experiment were carried out using open aperture Z-scan data using an Nd:YAG laser operating at the wavelength 532 nm.

  18. Dose-response relationship of fibrous dusts in intraperitoneal studies.

    PubMed Central

    Roller, M; Pott, F; Kamino, K; Althoff, G H; Bellmann, B

    1997-01-01

    The relationship between the number of fibers injected intraperitoneally and the occurrence of peritoneal mesotheliomas in rats was investigated using data from a series of carcinogenicity studies with several fibrous dusts. Based on observed tumor incidences ranging between 10 and 90%, the hypothesis of a common slope of dose-response relationships (parallel probit lines in probit analysis) cannot be rejected. In general, parallelism of probit lines is considered an indication of a common mode of action. Analysis of the shape of the dose-response relationship, with one apparent exception, shows virtually linear or superlinear behavior, i.e., from these data, there is no indication of a decrease in carcinogenic potency of an elementary carcinogenic unit at lower doses. PMID:9400733

  19. Structural Properties of Gene Promoters Highlight More than Two Phenotypes of Diabetes

    PubMed Central

    Guja, Cristian

    2015-01-01

    Genome-wide association studies (GWAS) published in the last decade raised the number of loci associated with type 1 (T1D) and type 2 diabetes (T2D) to more than 50 for each of these diabetes phenotypes. The environmental factors seem to play an important role in the expression of these genes, acting through transcription factors that bind to promoters. Using the available databases we examined the promoters of various genes classically associated with the two main diabetes phenotypes. Our comparative analyses have revealed significant architectural differences between promoters of genes classically associated with T1D and T2D. Nevertheless, five gene promoters (about 16%) belonging to T1D and six gene promoters (over 19%) belonging to T2D have shown some intermediary structural properties, suggesting a direct relationship to either LADA (Latent Autoimmune Diabetes in Adults) phenotype or to non-autoimmune type 1 phenotype. The distribution of these promoters in at least three separate classes seems to indicate specific pathogenic pathways. The image-based patterns (DNA patterns) generated by promoters of genes associated with these three phenotypes support the clinical observation of a smooth link between specific cases of typical T1D and T2D. In addition, a global distribution of these DNA patterns suggests that promoters of genes associated with T1D appear to be evolutionary more conserved than those associated with T2D. Though, the image based patterns obtained by our method might be a new useful parameter for understanding the pathogenetic mechanism and the diabetogenic gene networks. PMID:26379145

  20. Structural Properties and Phase Behavior of Crosslinked Networks in Polymer Solutions

    PubMed Central

    Benmouna, Farida; Zemmour, Samira; Benmouna, Mustapha

    2016-01-01

    ABSTRACT Structural properties and phase behavior of crosslinked networks embedded in polymer solutions are theoretically investigated. The partial structure factor of the network is calculated using a matrix formulation of the random phase approximation and the forward scattering limit is correlated with the phase behavior. Swelling and deswelling processes are analyzed in terms of the polymer concentration, the mismatch of solvent quality with respect to polymer and network, the polymers incompatibility and their characteristic sizes. Most studies reported so far in the literature have focussed on the swelling of crosslinked networks and gels in pure solvents but the correlation of the structural properties with the phase behavior in the presence of high molecular weight polymers in solution has not been given sufficient attention. The present work is intended to fill this gap in view of the current efforts to develop novel drug encapsulating and targeted delivery devices. PMID:27134310

  1. Smartphone usage among ROTU and its relationship towards study performance

    NASA Astrophysics Data System (ADS)

    Redzuan, Muhammad Fazrul Ilahi Mohd; Roslan, Mohamad Amri; Rahman, Rosshairy Abd

    2015-12-01

    Reserve Officer Training Unit (ROTU) is a cooperation program between the Ministry of Defense and the Ministry of Higher Education for undergraduate students in public university. ROTU is known for its tight training schedule which might lead to limited learning time. The usage of smartphone with various applications might assist them in their learning activities. Therefore, this study aims to discover the rate of smartphone usage among ROTU and then analyze the relationship of smartphone usage towards their study performance. The result shows that most of the ROTU students use smartphone for five to eight hours a day. No significant correlation between relationship of smartphone and study performance of ROTU students with very small positive relationship was recorded. The result reflects that the frequent use of smartphone applications among ROTU students could not significantly help them in the study. However, further study need to be carried out since this paper does not specifically focus on each type of application. Therefore, for future research, usage rate for each application is also needed to be discovered so that the usage impact for ROTU study performance on each application can be seen clearly.

  2. Crystallization of Stretched Polyimides: A Structure-Property Study

    NASA Technical Reports Server (NTRS)

    Hinkley, Jeffrey A.; Dezern, James F.

    2002-01-01

    A simple rotational isomeric state model was used to detect the degree to which polyimide repeat units might align to give an extended crystal. It was found experimentally that the hallmarks of stretch-crystallization were more likely to occur in materials whose molecules could readily give extended, aligned conformations. A proposed screening criterion was 84% accurate in selecting crystallizing molecules.

  3. Structural properties of rutherfordium: An ab-initio study

    NASA Astrophysics Data System (ADS)

    Gyanchandani, Jyoti; Sikka, S. K.

    2012-01-01

    The structural and electronic properties of rutherfordium, the latest group IV B element, have been evaluated by first principles density functional theory in scalar relativistic formalism with and without spin-orbit coupling and compared with its 5d homologue Hf. It is found that Rf will crystallize in the hexagonal close packed structure as in Hf. However, under pressure, it will have different sequence of phase transitions than Hf: hcp→bcc instead of hcp→ω→bcc. An explanation is offered for this difference in terms of the competition between the band structure and the Ewald energy contributions.

  4. Processing-structure-property studies of: (I) submicron polymeric fibers produced by electrospinning and (II) films of linear low density polyethylenes as influenced by the short chain branch length in copolymers of ethylene/1-butene, ethylene/1-hexene and ethylene/1-octene synthesized by a single site metallocene catalyst

    NASA Astrophysics Data System (ADS)

    Gupta, Pankaj

    The overall theme of the research discussed in this dissertation has been to explore processing-structure-property relationships for submicron polymeric fibers produced by electrospinning (Part I) and to ascertain whether or not the length of the short chain branch has any effect on the physical properties of films of linear low-density polyethylenes (LLDPEs) (Part II). The research efforts discussed in Part I of this dissertation relate to some fundamental as well as more applied investigations involving electrospinning. These include investigating the effects of solution rheology on fiber formation and developing novel methodologies to fabricate polymeric mats comprising of high specific surface submicron fibers of more than one polymer, high chemical resistant substrates produced by in situ photo crosslinking during electrospinning, superparamagnetic flexible substrates by electrospinning a solution of an elastomeric polymer containing ferrite nanoparticles of Mn-Zn-Ni and substrates for filtration applications. Bicomponent electrospinning of poly(vinyl chloride)-polyurethane and poly(vinylidiene fluoride)-polyurethane was successfully performed. In addition, filtration properties of single and bicomponent electrospun mats of polyacrylonitrile and polystyrene were investigated. Results indicated lower aerosol penetration or higher filtration efficiencies of the filters based on submicron electrospun fibers in comparison to the conventional filter materials. In addition, Part II of this dissertation explores whether or not the length of the short chain branch affects the physical properties of blown and compression molded films of LLDPEs that were synthesized by a single site metallocene catalyst. Here, three resins based on copolymers of ethylene/1-butene, ethylene/1-hexene, and ethylene/1-octene were utilized that were very similar in terms of their molecular weight and distribution, melt rheology, density, crystallinity and short chain branching content and

  5. Reconstruction of explicit structural properties at the nanoscale via spectroscopic microscopy.

    PubMed

    Cherkezyan, Lusik; Zhang, Di; Subramanian, Hariharan; Taflove, Allen; Backman, Vadim

    2016-02-01

    The spectrum registered by a reflected-light bright-field spectroscopic microscope (SM) can quantify the microscopically indiscernible, deeply subdiffractional length scales within samples such as biological cells and tissues. Nevertheless, quantification of biological specimens via any optical measures most often reveals ambiguous information about the specific structural properties within the studied samples. Thus, optical quantification remains nonintuitive to users from the diverse fields of technique application. In this work, we demonstrate that the SM signal can be analyzed to reconstruct explicit physical measures of internal structure within label-free, weakly scattering samples: characteristic length scale and the amplitude of spatial refractive-index (RI) fluctuations. We present and validate the reconstruction algorithm via finite-difference time-domain solutions of Maxwell's equations on an example of exponential spatial correlation of RI. We apply the validated algorithm to experimentally measure structural properties within isolated cells from two genetic variants of HT29 colon cancer cell line as well as within a prostate tissue biopsy section. The presented methodology can lead to the development of novel biophotonics techniques that create two-dimensional maps of explicit structural properties within biomaterials: the characteristic size of macromolecular complexes and the variance of local mass density. PMID:26886803

  6. Reconstruction of explicit structural properties at the nanoscale via spectroscopic microscopy

    NASA Astrophysics Data System (ADS)

    Cherkezyan, Lusik; Zhang, Di; Subramanian, Hariharan; Taflove, Allen; Backman, Vadim

    2016-02-01

    The spectrum registered by a reflected-light bright-field spectroscopic microscope (SM) can quantify the microscopically indiscernible, deeply subdiffractional length scales within samples such as biological cells and tissues. Nevertheless, quantification of biological specimens via any optical measures most often reveals ambiguous information about the specific structural properties within the studied samples. Thus, optical quantification remains nonintuitive to users from the diverse fields of technique application. In this work, we demonstrate that the SM signal can be analyzed to reconstruct explicit physical measures of internal structure within label-free, weakly scattering samples: characteristic length scale and the amplitude of spatial refractive-index (RI) fluctuations. We present and validate the reconstruction algorithm via finite-difference time-domain solutions of Maxwell's equations on an example of exponential spatial correlation of RI. We apply the validated algorithm to experimentally measure structural properties within isolated cells from two genetic variants of HT29 colon cancer cell line as well as within a prostate tissue biopsy section. The presented methodology can lead to the development of novel biophotonics techniques that create two-dimensional maps of explicit structural properties within biomaterials: the characteristic size of macromolecular complexes and the variance of local mass density.

  7. Complementary study based on DFT to describe the structure and properties relationship of diblock copolymer based on PVK and PPV

    NASA Astrophysics Data System (ADS)

    Mbarek, M.; Abbassi, F.; Alimi, K.

    2016-09-01

    The structure-properties relationships of copolymer involving N-vinylcarbazole (PVK) and poly (p-phenylene-vinylene) (PPV) blocks, denoted PVK-PPV, was investigated by calculations based on density functional theory (DFT) and completed by experimental analyses. Thus, vibrational, optical and emission spectra of model compound have been simulated and compared to the experiments observations published recently. Ionization potentials (IPs), electron affinities (EAs) and energy gaps were determined. Furthermore, quantum yields, radiative and nonradiative exciton lifetime was highlighted.

  8. Structural properties of amorphous silicon produced by electron irradiation

    SciTech Connect

    Yamasaki, J.; Takeda, S.

    1999-07-01

    The structural properties of the amorphous Si (a-Si), which was created from crystalline silicon by 2 MeV electron irradiation at low temperatures about 25 K, are examined in detail by means of transmission electron microscopy and transmission electron diffraction. The peak positions in the radial distribution function (RDF) of the a-Si correspond well to those of a-Si fabricated by other techniques. The electron-irradiation-induced a-Si returns to crystalline Si after annealing at 550 C.

  9. Determination of HART I Blade Structural Properties by Laboratory Testing

    NASA Technical Reports Server (NTRS)

    Jung, Sung N.; Lau, Benton H.

    2012-01-01

    The structural properties of higher harmonic Aeroacoustic Rotor Test (HART I) blades were measured using the original set of blades tested in the German-dutch wind tunnel (DNW) in 1994. the measurements include bending and torsion stiffness, geometric offsets, and mass and inertia properties of the blade. the measured properties were compared to the estimated values obtained initially from the blade manufacturer. The previously estimated blade properties showed consistently higher stiffness, up to 30 percent for the flap bending in the blade inboard root section.

  10. RaptorX-Property: a web server for protein structure property prediction.

    PubMed

    Wang, Sheng; Li, Wei; Liu, Shiwang; Xu, Jinbo

    2016-07-01

    RaptorX Property (http://raptorx2.uchicago.edu/StructurePropertyPred/predict/) is a web server predicting structure property of a protein sequence without using any templates. It outperforms other servers, especially for proteins without close homologs in PDB or with very sparse sequence profile (i.e. carries little evolutionary information). This server employs a powerful in-house deep learning model DeepCNF (Deep Convolutional Neural Fields) to predict secondary structure (SS), solvent accessibility (ACC) and disorder regions (DISO). DeepCNF not only models complex sequence-structure relationship by a deep hierarchical architecture, but also interdependency between adjacent property labels. Our experimental results show that, tested on CASP10, CASP11 and the other benchmarks, this server can obtain ∼84% Q3 accuracy for 3-state SS, ∼72% Q8 accuracy for 8-state SS, ∼66% Q3 accuracy for 3-state solvent accessibility, and ∼0.89 area under the ROC curve (AUC) for disorder prediction.

  11. RaptorX-Property: a web server for protein structure property prediction

    PubMed Central

    Wang, Sheng; Li, Wei; Liu, Shiwang; Xu, Jinbo

    2016-01-01

    RaptorX Property (http://raptorx2.uchicago.edu/StructurePropertyPred/predict/) is a web server predicting structure property of a protein sequence without using any templates. It outperforms other servers, especially for proteins without close homologs in PDB or with very sparse sequence profile (i.e. carries little evolutionary information). This server employs a powerful in-house deep learning model DeepCNF (Deep Convolutional Neural Fields) to predict secondary structure (SS), solvent accessibility (ACC) and disorder regions (DISO). DeepCNF not only models complex sequence–structure relationship by a deep hierarchical architecture, but also interdependency between adjacent property labels. Our experimental results show that, tested on CASP10, CASP11 and the other benchmarks, this server can obtain ∼84% Q3 accuracy for 3-state SS, ∼72% Q8 accuracy for 8-state SS, ∼66% Q3 accuracy for 3-state solvent accessibility, and ∼0.89 area under the ROC curve (AUC) for disorder prediction. PMID:27112573

  12. RaptorX-Property: a web server for protein structure property prediction.

    PubMed

    Wang, Sheng; Li, Wei; Liu, Shiwang; Xu, Jinbo

    2016-07-01

    RaptorX Property (http://raptorx2.uchicago.edu/StructurePropertyPred/predict/) is a web server predicting structure property of a protein sequence without using any templates. It outperforms other servers, especially for proteins without close homologs in PDB or with very sparse sequence profile (i.e. carries little evolutionary information). This server employs a powerful in-house deep learning model DeepCNF (Deep Convolutional Neural Fields) to predict secondary structure (SS), solvent accessibility (ACC) and disorder regions (DISO). DeepCNF not only models complex sequence-structure relationship by a deep hierarchical architecture, but also interdependency between adjacent property labels. Our experimental results show that, tested on CASP10, CASP11 and the other benchmarks, this server can obtain ∼84% Q3 accuracy for 3-state SS, ∼72% Q8 accuracy for 8-state SS, ∼66% Q3 accuracy for 3-state solvent accessibility, and ∼0.89 area under the ROC curve (AUC) for disorder prediction. PMID:27112573

  13. A Study on the Relationship between Reflux Esophagitis and Periodontitis.

    PubMed

    Adachi, Kyoichi; Mishiro, Tomoko; Tanaka, Shino; Yoshikawa, Hiroo; Kinoshita, Yoshikazu

    2016-01-01

    Objective Metabolic syndrome and dental erosion have been demonstrated to correlate with gastroesophageal acid reflux disease (GERD), while periodontitis has been reported to have a positive relationship with metabolic syndrome. However, no correlation between periodontitis and GERD has yet been reported. We therefore investigated the relationship between periodontitis and GERD. Methods The subjects consisted of 280 individuals who visited the Health Center for a detailed medical checkup examination. Each underwent upper endoscopy and periodontitis examinations, with the latter performed by measuring the concentrations of lactate dehydrogenase and hemoglobin in saliva. The subjects were divided into those with positive and negative periodontitis findings, and the prevalence rates of endoscopically proven reflux esophagitis, dyslipidemia, hypertension, and hyperglycemia were compared. Results The number of subjects positive for periodontitis was 93, while 187 had negative findings. The prevalence of reflux esophagitis was not different between the positive and negative groups (8.6% vs. 8.0%). In addition, a multiple logistic regression analysis did not identify a positive relationship between the presence of periodontitis and reflux esophagitis. On the other hand, dyslipidemia and hypertension were more frequently observed in the subjects that were positive for periodontitis. Conclusion We did not find an association between periodontitis and reflux esophagitis in the present study. On the other hand, the presence of periodontitis was found to correlate with hypertension and dyslipidemia. PMID:27629943

  14. Structural properties of fluorozirconate-based glass ceramics doped with multivalent europium

    SciTech Connect

    PaBlick, C.; Müller, O.; Lützenkirchen-Hecht, D.; Frahm, R.; Johnson, J.A.; Schweizer, S.

    2012-10-10

    The structure/property relationships of fluorochlorozirconate glass ceramics as a function of divalent and trivalent europium (Eu) co-doping and thermal processing have been investigated; the influence of doping ratio on the formation of barium chloride (BaCl2) nanocrystals therein was elucidated. X-ray absorption near-edge structure spectroscopy shows that the post-thermal annealing changes the Eu valence of the as-poured glass slightly, but during the melting process Eu3+ is more strongly reduced to Eu2+, in particular, when doped as a chloride instead of fluoride compound. The Eu2+-to-Eu3+ doping ratio also plays a significant role in chemical equilibrium in the melt. X-ray diffraction measurements indicate that a higher Eu2+ fraction leads to a BaCl2 phase transition from hexagonal to orthorhombic structure at a lower temperature.

  15. Molecular structure-property correlations from optical nonlinearity and thermal-relaxation dynamics.

    PubMed

    Bhattacharyya, Indrajit; Priyadarshi, Shekhar; Goswami, Debabrata

    2009-02-01

    We apply ultrafast single beam Z-scan technique to measure saturation absorption coefficients and nonlinear-refraction coefficients of primary alcohols at 1560 nm. The nonlinear effects result from vibronic transitions and cubic nonlinear-refraction. To measure the pure total third-order nonlinear susceptibility, we removed thermal effects with a frequency optimized optical-chopper. Our measurements of thermal-relaxation dynamics of alcohols, from 1560 nm thermal lens pump and 780 nm probe experiments revealed faster and slower thermal-relaxation timescales, respectively, from conduction and convection. The faster timescale accurately predicts thermal-diffusivity, which decreases linearly with alcohol chain-lengths since thermal-relaxation is slower in heavier molecules. The relation between thermal-diffusivity and alcohol chain-length confirms structure-property relationship.

  16. Structural properties of fluorozirconate-based glass ceramics doped with multivalent europium

    SciTech Connect

    Passlick, C.; Mueller, O.; Luetzenkirchen-Hecht, D.; Frahm, R.; Johnson, J. A.; Schweizer, S.

    2011-12-01

    The structure/property relationships of fluorochlorozirconate glass ceramics as a function of divalent and trivalent europium (Eu) co-doping and thermal processing have been investigated; the influence of doping ratio on the formation of barium chloride (BaCl{sub 2}) nanocrystals therein was elucidated. X-ray absorption near-edge structure spectroscopy shows that the post-thermal annealing changes the Eu valence of the as-poured glass slightly, but during the melting process Eu{sup 3+} is more strongly reduced to Eu{sup 2+}, in particular, when doped as a chloride instead of fluoride compound. The Eu{sup 2+}-to-Eu{sup 3+} doping ratio also plays a significant role in chemical equilibrium in the melt. X-ray diffraction measurements indicate that a higher Eu{sup 2+} fraction leads to a BaCl{sub 2} phase transition from hexagonal to orthorhombic structure at a lower temperature.

  17. Electronic and structural properties of ultrathin tungsten nanowires and nanotubes by density functional theory calculation

    SciTech Connect

    Sun, Shih-Jye; Lin, Ken-Huang; Li, Jia-Yun; Ju, Shin-Pon

    2014-10-07

    The simulated annealing basin-hopping method incorporating the penalty function was used to predict the lowest-energy structures for ultrathin tungsten nanowires and nanotubes of different sizes. These predicted structures indicate that tungsten one-dimensional structures at this small scale do not possess B.C.C. configuration as in bulk tungsten material. In order to analyze the relationship between multi-shell geometries and electronic transfer, the electronic and structural properties of tungsten wires and tubes including partial density of state and band structures which were determined and analyzed by quantum chemistry calculations. In addition, in order to understand the application feasibility of these nanowires and tubes on nano-devices such as field emitters or chemical catalysts, the electronic stability of these ultrathin tungsten nanowires was also investigated by density functional theory calculations.

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

    PubMed Central

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

    2015-01-01

    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 π–σ* 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

  19. Vibrational and structural properties of tetramethyltin under pressure

    NASA Astrophysics Data System (ADS)

    Qin, Zhen-Xing; Chen, Xiao-Jia; Zhang, Chao; Tang, Ling-Yun; Zhong, Guo-Hua; Lin, Hai-Qing; Meng, Yue; Mao, Ho-Kwang

    2013-01-01

    The vibrational and structural properties of a hydrogen-rich group IVa hydride, Sn(CH3)4, have been investigated by combining Raman spectroscopy and synchrotron x-ray diffraction measurements at room temperature and at pressures up to 49.9 GPa. Both techniques allow the obtaining of complementary information on the high-pressure behaviors and yield consistent phase transitions at 0.9 GPa for the liquid to solid and 2.8, 10.4, 20.4, and 32.6 GPa for the solid to solid. The foregoing solid phases are identified to have the orthorhombic, tetragonal, monoclinic crystal structures with space groups of Pmmm for phase I, P4/mmm for phase II, P2/m for phase III, respectively. The phases IV and V coexist with phase III, resulting in complex analysis on the possible structures. These transitions suggest the variation in the inter- and intra-molecular bonding of this compound.

  20. Structural properties of composites of polyvinylidene fluoride and mechanically activated BaTiO3 particles

    NASA Astrophysics Data System (ADS)

    Pavlović, V. P.; Pavlović, V. B.; Vlahović, B.; Božanić, D. K.; Pajović, J. D.; Dojčilović, R.; Djoković, V.

    2013-11-01

    Nanocomposites of electroactive ceramics and ferroelectric polymers exploit favorable features of the matrix polymer and the nanostructured filler to produce new functional materials for pressure and IR sensors. In this study, the influence of mechanical activation of barium titanate (BaTiO3) particles on the structural properties of BaTiO3/polyvinylidene fluoride (PVDF) nanocomposites was investigated. Nanocomposite films were prepared by the solution casting method and characterized by scanning electron microscopy, x-ray diffraction and Raman spectroscopy. It was found that mechanically activated fillers promote the formation of a ferroelectric β-phase during crystallization of PVDF.

  1. Negative differential gain in quantum dot systems: Interplay of structural properties and many-body effects

    SciTech Connect

    Goldmann, E. Jahnke, F.; Lorke, M.; Frauenheim, T.

    2014-06-16

    The saturation behaviour of optical gain with increasing excitation density is an important factor for laser device performance. For active materials based on self-organized InGaAs/GaAs quantum dots, we study the interplay between structural properties of the quantum dots and many-body effects of excited carriers in the optical properties via a combination of tight-binding and quantum-kinetic calculations. We identify regimes where either phase-space filling or excitation-induced dephasing dominates the saturation behavior of the optical gain. The latter can lead to the emergence of a negative differential material gain.

  2. Interrelationship between structure-property-processings in injection molded polymeric products

    SciTech Connect

    Kim, Hyun Seog; Lee, Jae Wook

    1996-12-31

    Injection molding process is one of the major polymer processings for the polymeric products. This process is extensively used in the net-shaped production of plastic parts due to its capability to meet requirements of stringent dimensional accuracy and short cycle time. Specially the injection molding process consists of large, fast deformation and phase changes, which has much of processing parameters. Therefore it is important to optimize the injection molding conditions from the point of view of both productivity and product quality. In this study, we have investigated in the injection molding process for polymeric systems focusing on the understanding of structure-property-processing interrelationship and its utilization in the processing.

  3. Soil erosion-runoff relationships: insights from laboratory studies

    NASA Astrophysics Data System (ADS)

    Mamedov, Amrakh; Warrington, David; Levy, Guy

    2016-04-01

    Understanding the processes and mechanisms affecting runoff generation and subsequent soil erosion in semi-arid regions is essential for the development of improved soil and water conservation management practices. Using a drip type laboratory rain simulator, we studied runoff and soil erosion, and the relationships between them, in 60 semi-arid region soils varying in their intrinsic properties (e.g., texture, organic matter) under differing extrinsic conditions (e.g., rain properties, and conditions prevailing in the field soil). Both runoff and soil erosion were significantly affected by the intrinsic soil and rain properties, and soil conditions within agricultural fields or watersheds. The relationship between soil erosion and runoff was stronger when the rain kinetic energy was higher rather than lower, and could be expressed either as a linear or exponential function. Linear functions applied to certain limited cases associated with conditions that enhanced soil structure stability, (e.g., slow wetting, amending with soil stabilizers, minimum tillage in clay soils, and short duration exposure to rain). Exponential functions applied to most of the cases under conditions that tended to harm soil stability (e.g., fast wetting of soils, a wide range of antecedent soil water contents and rain kinetic energies, conventional tillage, following biosolid applications, irrigation with water of poor quality, consecutive rain simulations). The established relationships between runoff and soil erosion contributed to a better understanding of the mechanisms governing overland flow and soil loss, and could assist in (i) further development of soil erosion models and research techniques, and (ii) the design of more suitable management practices for soil and water conservation.

  4. Structure-Property Characterization of the Crinkle-Leaf Peach Wood Phenotype: A Future Model System for Wood Properties Research?

    NASA Astrophysics Data System (ADS)

    Wiedenhoeft, Alex C.; Arévalo, Rafael; Ledbetter, Craig; Jakes, Joseph E.

    2016-09-01

    Nearly 400 million years of evolution and field-testing by the natural world has given humans thousands of wood types, each with unique structure-property relationships to study, exploit, and ideally, to manipulate, but the slow growth of trees makes them a recalcitrant experimental system. Variations in wood features of two genotypes of peach ( Prunus persica L.) trees, wild-type and crinkle-leaf, were examined to elucidate the nature of weak wood in crinkle-leaf trees. Crinkle-leaf is a naturally-occurring mutation in which wood strength is altered in conjunction with an easily observed `crinkling' of the leaves' surface. Trees from three vigor classes (low growth rate, average growth rate, and high growth rate) of each genotype were sampled. No meaningful tendency of dissimilarities among the different vigor classes was found, nor any pattern in features in a genotype-by-vigor analysis. Wild-type trees exhibited longer vessels and fibers, wider rays, and slightly higher specific gravity. Neither cell wall mechanical properties measured with nanoindentation nor cell wall histochemical properties were statistically or observably different between crinkle-leaf and wild-type wood. The crinkle-leaf mutant has the potential to be a useful model system for wood properties investigation and manipulation if it can serve as a field-observable vegetative marker for altered wood properties.

  5. Structure-Property Characterization of the Crinkle-Leaf Peach Wood Phenotype: A Future Model System for Wood Properties Research?

    NASA Astrophysics Data System (ADS)

    Wiedenhoeft, Alex C.; Arévalo, Rafael; Ledbetter, Craig; Jakes, Joseph E.

    2016-08-01

    Nearly 400 million years of evolution and field-testing by the natural world has given humans thousands of wood types, each with unique structure-property relationships to study, exploit, and ideally, to manipulate, but the slow growth of trees makes them a recalcitrant experimental system. Variations in wood features of two genotypes of peach (Prunus persica L.) trees, wild-type and crinkle-leaf, were examined to elucidate the nature of weak wood in crinkle-leaf trees. Crinkle-leaf is a naturally-occurring mutation in which wood strength is altered in conjunction with an easily observed `crinkling' of the leaves' surface. Trees from three vigor classes (low growth rate, average growth rate, and high growth rate) of each genotype were sampled. No meaningful tendency of dissimilarities among the different vigor classes was found, nor any pattern in features in a genotype-by-vigor analysis. Wild-type trees exhibited longer vessels and fibers, wider rays, and slightly higher specific gravity. Neither cell wall mechanical properties measured with nanoindentation nor cell wall histochemical properties were statistically or observably different between crinkle-leaf and wild-type wood. The crinkle-leaf mutant has the potential to be a useful model system for wood properties investigation and manipulation if it can serve as a field-observable vegetative marker for altered wood properties.

  6. Personality and Adult Sibling Relationships: A Preliminary Study.

    ERIC Educational Resources Information Center

    Noberini, Mary Rose; And Others

    The limited research that exists about sibling relationships during adulthood has employed primarily sociological variables. Psychological aspects of the sibling relationship were explored in a sample of 35 women and 9 men with a mean age of 59. Subjects completed the California Psychological Inventory, the Scale of Sibling Relationships, and the…

  7. Response of Simulated Drinking Water Biofilm Mechanical and Structural Properties to Long-Term Disinfectant Exposure.

    PubMed

    Shen, Yun; Huang, Conghui; Monroy, Guillermo L; Janjaroen, Dao; Derlon, Nicolas; Lin, Jie; Espinosa-Marzal, Rosa; Morgenroth, Eberhard; Boppart, Stephen A; Ashbolt, Nicholas J; Liu, Wen-Tso; Nguyen, Thanh H

    2016-02-16

    Mechanical and structural properties of biofilms influence the accumulation and release of pathogens in drinking water distribution systems (DWDS). Thus, understanding how long-term residual disinfectants exposure affects biofilm mechanical and structural properties is a necessary aspect for pathogen risk assessment and control. In this study, elastic modulus and structure of groundwater biofilms was monitored by atomic force microscopy (AFM) and optical coherence tomography (OCT) during three months of exposure to monochloramine or free chlorine. After the first month of disinfectant exposure, the mean stiffness of monochloramine- or free-chlorine-treated biofilms was 4 to 9 times higher than those before treatment. Meanwhile, the biofilm thickness decreased from 120 ± 8 μm to 93 ± 6-107 ± 11 μm. The increased surface stiffness and decreased biofilm thickness within the first month of disinfectant exposure was presumably due to the consumption of biomass. However, by the second to third month during disinfectant exposure, the biofilm mean stiffness showed a 2- to 4-fold decrease, and the biofilm thickness increased to 110 ± 7-129 ± 8 μm, suggesting that the biofilms adapted to disinfectant exposure. After three months of the disinfectant exposure process, the disinfected biofilms showed 2-5 times higher mean stiffness (as determined by AFM) and 6-13-fold higher ratios of protein over polysaccharide, as determined by differential staining and confocal laser scanning microscopy (CLSM), than the nondisinfected groundwater biofilms. However, the disinfected biofilms and nondisinfected biofilms showed statistically similar thicknesses (t test, p > 0.05), suggesting that long-term disinfection may not significantly remove net biomass. This study showed how biofilm mechanical and structural properties vary in response to a complex DWDS environment, which will contribute to further research on the risk assessment and control of biofilm-associated-pathogens in DWDS.

  8. Using Bayesian Networks to Model Hierarchical Relationships in Epidemiological Studies

    PubMed Central

    2011-01-01

    OBJECTIVES To propose an alternative procedure, based on a Bayesian network (BN), for estimation and prediction, and to discuss its usefulness for taking into account the hierarchical relationships among covariates. METHODS The procedure is illustrated by modeling the risk of diarrhea infection for 2,740 children aged 0 to 59 months in Cameroon. We compare the procedure with a standard logistic regression and with a model based on multi-level logistic regression. RESULTS The standard logistic regression approach is inadequate, or at least incomplete, in that it does not attempt to account for potentially causal relationships between risk factors. The multi-level logistic regression does model the hierarchical structure, but does so in a piecewise manner; the resulting estimates and interpretations differ from those of the BN approach proposed here. An advantage of the BN approach is that it enables one to determine the probability that a risk factor (and/or the outcome) is in any specific state, given the states of the others. The currently available approaches can only predict the outcome (disease), given the states of the covariates. CONCLUSION A major advantage of BNs is that they can deal with more complex interrelationships between variables whereas competing approaches deal at best only with hierarchical ones. We propose that BN be considered as well as a worthwhile method for summarizing the data in epidemiological studies whose aim is understanding the determinants of diseases and quantifying their effects. PMID:21779534

  9. Rapid Changes in Soil Carbon and Structural Properties Due to Stover Removal from No-Till Corn Plots

    SciTech Connect

    Blanco-Canqui, H; Lal, Rattan; Post, W M.; Izaurralde, R Cesar C.; Owens, L B.

    2006-06-01

    Harvesting corn (Zea mays L.) stover for producing ethanol may be beneficial to palliate the dependence on fossil fuels and reduce CO2 emissions to the atmosphere, but stover harvesting may deplete soil organic carbon (SOC) and degrade soil structure. We investigated the impacts of variable rates of stover removal from no-till (NT) continuous corn systems on SOC and soil structural properties after 1 year of stover removal in three soils in Ohio: Rayne silt loam (fine-loamy, mixed, active, mesic Typic Hapludults) at Coshocton, Hoytville clay loam (fine, illitic, mesic Mollic Epiaqualfs) at Hoytville, and Celina silt loam (fine, mixed, active, mesic Aquic Hapludalfs) at South Charleston. This study also assessed relationships between SOC and soil structural properties as affected by stover management. Six stover treatments that consisted of removing 100, 75, 50, 25, and 0, and adding 100% of corn stover corresponding to 0 (T0), 1.25 (T1.25), 2.50 (T2.5), 3.75 (T3.75), 5.00 (T5), and 10.00 (T10) Mg haj1 of stover, respectively, were studied for their total SOC concentration, bulk density (>b), aggregate stability, and tensile strength (TS) of aggregates. Effects of stover removal on soil properties were rapid and significant in the 0- to 5-cm depth, although the magnitude of changes differed among soils after only 1 year of stover removal. The SOC concentration declined with increase in removal rates in silt loams but not in clay loam soils. It decreased by 39% at Coshocton and 30% at Charleston within 1 year of complete stover removal. At the same sites, macroaggregates contained 10% to 45% more SOC than microaggregates. Stover removal reduced 94.75-mm macroaggregates and increased microaggregates (P G 0.01). Mean weight diameter (MWD) and TS of aggregates in soils without stover (T0) were 1.7 and 3.3 times lower than those in soils with normal stover treatments (T5) across sites. The SOC concentration was negatively correlated with >b and positively with MWD and

  10. PREFACE: Symmetry and Structural Properties of Condensed Matter

    NASA Astrophysics Data System (ADS)

    Lulek, Tadeusz; Wal, Andrzej; Lulek, Barbara

    2008-03-01

    This volume comprises the proceedings of the Ninth Summer School on Theoretical Physics under the leading title `Symmetry and Structural Properties of Condensed Matter' (SSPCM 2007). The school, organised by Rzeszów University of Technology, Poland, together with AGH University of Science and Technology, Cracow, Poland, in 5-12 September 2007 in Myczkowce. The meeting aimed to continue the series of biannual SSPCM schools (since 1990), and focused on the promotion of some advanced mathematical methods within the physics of condensed matter, with an emphasis on quantum information aspects. The main topics of the SSPCM07 school were the following: Quantum information and computing Finite dimensional Hilbert spaces Generating functions and exactly soluble models The Proceedings are divided into three parts accordingly. These topics can be seen as a natural continuation of the previous SSPCM05 school, aimed at studying interrelations between solid state physics and quantum informatics, as well as an extension of earlier SSPCM meetings, devoted to mathematical tools of condensed matter theory. The school gathered together more than 60 participants from 11 countries and 7 scientific centres in Poland. Some of them were there for the first time, and some had attended nearly all previous meetings. We had advanced researchers as well as their young collaborators and students. Acknowledgements The Organizing Committee wishes to express our gratitude to all participants for several their activities at the school and for creating so friendly and inspiring an atmosphere that one can talk about the term: `SSPCM society'. Special thanks are due to all lecturers, for preparing and presenting their talks, and for several valuable discussions. We also give thanks to all those who prepared manuscripts, giving us thus an opportunity to share their ideas, to all referees who improved significantly the quality of this volume, to all members of our International Advisory Committee, and

  11. Close Relationships: A Study of Mobile Communication Records

    NASA Astrophysics Data System (ADS)

    Palchykov, Vasyl; Kertész, János; Dunbar, Robin; Kaski, Kimmo

    2013-05-01

    Mobile phone communication as digital service generates ever-increasing datasets of human communication actions, which in turn allow us to investigate the structure and evolution of social interactions and their networks. These datasets can be used to study the structuring of such egocentric networks with respect to the strength of the relationships by assuming direct dependence of the communication intensity on the strength of the social tie. Recently we have discovered that there are significant differences between the first and further "best friends" from the point of view of age and gender preferences. Here we introduce a control parameter p max based on the statistics of communication with the first and second "best friend" and use it to filter the data. We find that when p max is decreased the identification of the "best friend" becomes less ambiguous and the earlier observed effects get stronger, thus corroborating them.

  12. Studying the relationship between past people and their environments

    NASA Astrophysics Data System (ADS)

    Clift, Peter D.; Flad, Rowan; Fuller, Dorian Q.; Giosan, Liviu

    2011-06-01

    AGU Chapman Conference on Climates, Past Landscapes, and Civilizations; Santa Fe, New Mexico, 21-25 March 2011; The fortunes of human societies are intimately linked to the environments that sustain them. This has been true from the first emergence of human ancestors through to the present day. An AGU Chapman Conference was held to discuss the relationship between past people and their environments. Participants examined the state of the field, debated issues of contention, and formulated ways that such cross-disciplinary research can progress. Scientists' increasing ability to generate high-resolution climate records has proliferated studies that link the rise and fall of cultures to climate change. This meeting brought together scholars from across the divide between Earth sciences and archaeology to derive a deeper understanding of how humans have reacted to and shaped the changing environment.

  13. Magnitude of relationship between burnout and absenteeism: a preliminary study.

    PubMed

    Gil-Monte, Pedro R

    2008-04-01

    This study examined the influence of guilt related to a negative attitude toward patients and its relation with burnout and absenteeism. The sample consisted of 717 nursing professionals. Depersonalization was evaluated by the Maslach Burnout Inventory and Guilt was evaluated by one item. To estimate Absenteeism, participants were asked about the number of workdays they had missed in the past year. Hierarchical multiple regression analyses make it possible to conclude that guilt explains work absenteeism, and the interaction between depersonalization and guilt (Incr. R2 = .008, p < .05) indicates significant differences in the number of work days missed in the last year. Conclusions are limited, as these effects are quite weak: all variables together only explain about 4% of the shared variance in absenteeism. Researchers might assess whether feelings of guilt help explain the relationship between burnout and symptoms such as absenteeism.

  14. Intergenerational Transmission of Relationship Aggression: A Prospective Longitudinal Study

    PubMed Central

    Cui, Ming; Durtschi, Jared A.; Donnellan, M. Brent; Lorenz, Frederick O.; Conger, Rand D.

    2012-01-01

    The present study examined whether physical and verbal aggression in the family of origin were associated with similar patterns of aggression in young adult couples. Hypotheses were tested using a sample of 213 focal individuals who were followed from adolescence to adulthood. Results suggested that aggression in the family when focal participants were adolescents predicted aggression with romantic partners when participants were adults. The association between interparental aggression and later aggression in adult romantic unions was partially mediated through parents’ aggression to focal participants when they were adolescents. Both physical and verbal aggression revealed the same pattern of findings. All together, these findings are consistent with a developmental-interactional perspective (Capaldi & Gorman-Smith, 2003) concerning the developmental origins of aggression in intimate relationships. PMID:21171767

  15. Synthesis and Structural Activity Relationship Study of Antitubercular Carboxamides

    PubMed Central

    Ugwu, D. I.; Ezema, B. E.; Eze, F. U.; Ugwuja, D. I.

    2014-01-01

    The unusual structure and chemical composition of the mycobacterial cell wall, the tedious duration of therapy, and resistance developed by the microorganism have made the recurrence of the disease multidrug resistance and extensive or extreme drug resistance. The prevalence of tuberculosis in synergy with HIV/AIDS epidemic augments the risk of developing the disease by 100-fold. The need to synthesize new drugs that will shorten the total duration of effective treatment and/or significantly reduce the dosage taken under DOTS supervision, improve on the treatment of multidrug-resistant tuberculosis which defies the treatment with isoniazid and rifampicin, and provide effective treatment for latent TB infections which is essential for eliminating tuberculosis prompted this review. In this review, we considered the synthesis and structure activity relationship study of carboxamide derivatives with antitubercular potential. PMID:25610646

  16. Structure-activity relationship studies of pyrrolone antimalarial agents.

    PubMed

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

    2013-09-01

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

  17. Capsaicin and its analogues: structure-activity relationship study.

    PubMed

    Huang, X-F; Xue, J-Y; Jiang, A-Q; Zhu, H-L

    2013-01-01

    Capsaicin, the main ingredient responsible for the hot pungent taste of chilli peppers, is an alkaloid found in the Capsicum family. Capsaicin was traditionally used for muscular pain, headaches, to improve circulation and for its gastrointestinal protective effects. It was also commonly added to herbal formulations because it acts as a catalyst for other herbs and aids in their absorption. In addition, capsaicin and other capsaicinoid compounds showed strong evidence of having promising potential in the fight against many types of cancer. The mechanism of action of capsaicin has been extensively studied over the past decade. It has been established that capsaicin binds to the transient receptor potential vanilloid 1 receptor which was expressed predominantly by sensory neurons. And many analogues of capsaicin have been synthesized and evaluated for diverse bioactivities. In this review, we will attempt to summarize the biology and structure-activity relationship of capsaicinoids.

  18. A Molecular Dynamics Study of the Structure-Dynamics Relationships of Supercooled Liquids and Glasses

    NASA Astrophysics Data System (ADS)

    Soklaski, Ryan

    Central to the field of condensed matter physics is a decades old outstanding problem in the study of glasses -- namely explaining the extreme slowing of dynamics in a liquid as it is supercooled towards the so-called glass transition. Efforts to universally describe the stretched relaxation processes and heterogeneous dynamics that characteristically develop in supercooled liquids remain divided in both their approaches and successes. Towards this end, a consensus on the role that atomic and molecular structures play in the liquid is even more tenuous. However, mounting material science research efforts have culminated to reveal that the vast diversity of metallic glass species and their properties are rooted in an equally-broad set of structural archetypes. Herein lies the motivation of this dissertation: the detailed information available regarding the structure-property relationships of metallic glasses provides a new context in which one can study the evolution of a supercooled liquid by utilizing a structural motif that is known to dominate the glass. Cu64Zr36 is a binary alloy whose good glass-forming ability and simple composition makes it a canonical material to both empirical and numerical studies. Here, we perform classical molecular dynamics simulations and conduct a comprehensive analysis of the dynamical regimes of liquid Cu64Zr36, while focusing on the roles played by atomic icosahedral ordering -- a structural motif which ultimately percolates the glass' structure. Large data analysis techniques are leveraged to obtain uniquely detailed structural and dynamical information in this context. In doing so, we develop the first account of the origin of icosahedral order in this alloy, revealing deep connections between this incipient structural ordering, frustration-limited domain theory, and recent important empirical findings that are relevant to the nature of metallic liquids at large. Furthermore, important dynamical landmarks such as the breakdown

  19. Second vowel formant relationship to adduction: A preliminary study

    NASA Astrophysics Data System (ADS)

    Hanrahan, Kevin G.

    The relationship between the vocal tract and the larynx in the formation of vowels has been debated for decades. Vowels were first thought to have been formed in the larynx; then later it was believed that they were formed solely in the vocal tract. In the 1960s Fant formalized this belief into the Source-Filter Theory of Vowel Formation. The theory was interpreted by voice teachers to mean that the larynx had very little to do with the formation of vowels, and this interpretation has dominated voice teaching for decades. Recent research, however, is now suggesting that the larynx and the vocal tract are interactive with each other, meaning that a change of muscular function in the larynx will create a change of resonator function in the vocal tract, and vice versa. This conclusion is drawn mainly on the work of Titze, Story, Laukkanen, et.al. They have found that a relationship exists between laryngeal function and the first vowel formant (F1). When examining research on the second vowel formant (F2), this author discovered that there may be a relationship between F2 and adduction. Therefore, based on present evidence, it was hypothesized that an elevated frequency of F2 corresponded to an increase in adduction. The hypothesis was examined by comparing the resonance output and glottal closure between vowels where F2 was elevated and vowels without modification of F2. Subjects were asked to sing [i], [a], and [u] at a medium dynamic level on D4, G#4, and D5 for the female subjects and an octave below for the male subjects, once using a "generic" version of the vowel, meaning what they considered a "nice, easy, and generic" version of the vowel to be, and then again modifying the vowel to increase the frequency of the upper harmonics. Electroglottogram, pitch, intensity, and formant data were collected and compared. An increase in the frequency of F2 corresponded to an increase in the Closed Quotient (CQ), the length of time the vocal folds are closed, in a few

  20. Structural Properties of Amorphous Indium-Based Oxides

    NASA Astrophysics Data System (ADS)

    Khanal, Rabi; Medvedeva, Julia

    2014-03-01

    Amorphous transparent conducting and semiconducting oxides exhibit similar or even superior properties to those observed in their crystalline counterparts. To understand how the structural properties change upon amorphization and how chemical composition affects the local and long-range structure of the amorphous oxides, we employ first-principles molecular dynamics to generate amorphous In-X-O with X =Zn, Ga, Sn, Ge, Y, or Sc, and compare their local structure features to those obtained for amorphous and crystalline indium oxide. The results reveal that the short-range structure of the Metal-O polyhedra is generally preserved in the amorphous oxides; however, different metals (In and X) show quantitatively or qualitatively different behavior. Some of the metals retain their natural distances and/or coordination; while others allow for a highly distorted environment and thus favor ``defect'' formation under variable oxygen conditions. At the same time, we find that the presence of X increases both the average In-O coordination and the number of the 6-coordinated In atoms as compared to those in IO. The improved In coordination may be responsible for the observed reduction in the carrier concentration as the substitution level in In-X-O increases.

  1. Optical and structural properties of Al-ZnO nanocomposites.

    PubMed

    Lee, Geon Joon; Deshpande, Nishad Gopal; Lee, Young Pak; Cheong, Hyeonsik; Swami, Narasimha; Bhat, Jeddu Sadashiva

    2014-05-01

    The optical and structural properties of aluminium-doped zinc oxide (AZO) films were investigated by photoluminescence (PL) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy. Pure zinc oxide (ZnO) and AZO composite films were deposited using vacuum evaporation method. The films exhibited different morphologies and crystallinity depending on the Al-doping. The SEM micrographs showed that a granular and compact structure could be seen for the ZnO film, while a nanoleaf structure with relatively porous nature was observed for the AZO composite film. The XRD patterns indicated that the crystalline growth orientation would be significantly affected by addition of Al. Compared with pure ZnO, the XRD peak intensity of the AZO composite was stronger and the line-width was narrower. Two-probe resistivity measurements showed that the AZO composites could be used as transparent conducting materials. The PL spectra revealed that the PL intensities of the AZO composites were stronger than that of the pure ZnO. The PL enhancement might be ascribed to the surface plasmon resonance of metal nanoclusters within the composite. Another possible reason of the PL enhancement would be the metal-induced crystallization caused by doping Al to ZnO matrix.

  2. Nanostructured ferroelectrics: fabrication and structure-property relations.

    PubMed

    Han, Hee; Kim, Yunseok; Alexe, Marin; Hesse, Dietrich; Lee, Woo

    2011-10-25

    With the continued demand for ultrahigh density ferroelectric data storage applications, it is becoming increasingly important to scale the dimension of ferroelectrics down to the nanometer-scale region and to thoroughly understand the effects of miniaturization on the materials properties. Upon reduction of the physical dimension of the material, the change in physical properties associated with size reduction becomes extremely difficult to characterize and to understand because of a complicated interplay between structures, surface properties, strain effects from substrates, domain nucleation, and wall motions. In this Review, the recent progress in fabrication and structure-property relations of nanostructured ferroelectric oxides is summarized. Various fabrication approaches are reviewed, with special emphasis on a newly developed stencil-based method for fabricating ferroelectric nanocapacitors, and advantages and limitations of the processes are discussed. Stress-induced evolutions of domain structures upon reduction of the dimension of the material and their implications on the electrical properties are discussed in detail. Distinct domain nucleation, growth, and propagation behaviors in nanometer-scale ferroelectric capacitors are discussed and compared to those of micrometer-scale counterparts. The structural effect of ferroelectric nanocapacitors on the domain switching behavior and cross-talk between neighboring capacitors under external electric field is reviewed. PMID:21919083

  3. Structural properties of bismuth-bearing semiconductor alloys

    NASA Technical Reports Server (NTRS)

    Berding, M. A.; Sher, A.; Chen, A. B.

    1986-01-01

    The structural properties of bismuth-bearing III-V semiconductor alloys are addressed. Because the Bi compounds are not known to form zincblende structures, only the anion-substituted alloys InPBi, InAsBi, and InSbBi are considered candidates as narrow-gap semiconductors. Miscibility calculations indicate that InSbBi will be the most miscible, and InPBi, with the large lattice mismatch of the constituents, will be the most difficult to mix. Calculations of the hardness of the Bi compounds indicate that, once formed, the InPBi alloy will be harder than the other Bi alloys, and substantially harder than the currently favored narrow-gap semiconductor HgCdTe. Thus, although InSbBi may be an easier material to prepare, InPBi promises to be a harder material. Growth of the Bi compounds will require high effective growth temperatures, probably attainable only through the use of nonequilibrium energy-assisted epitaxial growth techniques.

  4. Structure-Property Correlations in Microwave Joining of Inconel 718

    NASA Astrophysics Data System (ADS)

    Bansal, Amit; Sharma, Apurbba Kumar; Kumar, Pradeep; Das, Shantanu

    2015-09-01

    The butt joining of Inconel 718 plates at 981°C solution treated and aged (981STA) condition was carried out using the microwave hybrid heating technique with Inconel 718 powder as a filler material. The developed joints were free from any microfissures (cracks) and were metallurgically bonded through complete melting of the powder particles. The as-welded joints were subjected to postweld heat treatments, including direct-aged, 981STA and 1080STA. The microstructural features of the welded joints were investigated using a field emission-scanning electron microscope equipped with x-ray elemental analysis. Microhardness and room-temperature tensile properties of the welded joints were evaluated. The postweld heat-treated specimens exhibited higher microhardness and tensile strength than the as-welded specimens due to the formation of strengthening precipitates in the microstructure after postweld heat treatments. The microhardness of the fusion zone of the joint in 1080STA condition was higher than all welded conditions due to the complete dissolution of Laves phase after 1080STA treatment. However, the tensile strength of the welded specimen in 981STA condition was higher than all welded conditions. The tensile strength in 1080STA condition was lower than that in 981STA condition because of the grain coarsening that took place after 1080STA condition. The fractography of the fractured surfaces was carried out to determine the structure-property-fracture correlation.

  5. Relationship between socioeconomic status and asthma: a longitudinal cohort study

    PubMed Central

    Hancox, R; Milne, B; Taylor, D; Greene, J; Cowan, J; Flannery, E; Herbison, G; McLachlan, C; Poulton, R; Sears, M

    2004-01-01

    Background: There is conflicting information about the relationship between asthma and socioeconomic status, with different studies reporting no, positive, or inverse associations. Most of these studies have been cross sectional in design and have relied on subjective markers of asthma such as symptoms of wheeze. Many have been unable to control adequately for potential confounding factors. Methods: We report a prospective cohort study of approximately 1000 individuals born in Dunedin, New Zealand in 1972–3. This sample has been assessed regularly throughout childhood and into adulthood, with detailed information collected on asthma symptoms, lung function, airway responsiveness, and atopy. The prevalence of these in relation to measures of socioeconomic status were analysed with and without controls for potential confounding influences including parental history of asthma, smoking, breast feeding, and birth order using cross sectional time series models. Results: No consistent association was found between childhood or adult socioeconomic status and asthma prevalence, lung function, or airway responsiveness at any age. Having asthma made no difference to educational attainment or socioeconomic status by age 26. There were trends to increased atopy in children from higher socioeconomic status families consistent with previous reports. Conclusions: Socioeconomic status in childhood had no significant impact on the prevalence of asthma in this New Zealand born cohort. Generalisation of these results to other societies should be done with caution, but our results suggest that the previously reported associations may be due to confounding. PMID:15115861

  6. Sexual Dimorphism and Population Differences in Structural Properties of Barn Swallow (Hirundo rustica) Wing and Tail Feathers.

    PubMed

    Pap, Péter L; Osváth, Gergely; Aparicio, José Miguel; Bărbos, Lőrinc; Matyjasiak, Piotr; Rubolini, Diego; Saino, Nicola; Vágási, Csongor I; Vincze, Orsolya; Møller, Anders Pape

    2015-01-01

    Sexual selection and aerodynamic forces affecting structural properties of the flight feathers of birds are poorly understood. Here, we compared the structural features of the innermost primary wing feather (P1) and the sexually dimorphic outermost (Ta6) and monomorphic second outermost (Ta5) tail feathers of barn swallows (Hirundo rustica) from a Romanian population to investigate how sexual selection and resistance to aerodynamic forces affect structural differences among these feathers. Furthermore, we compared structural properties of Ta6 of barn swallows from six European populations. Finally, we determined the relationship between feather growth bars width (GBW) and the structural properties of tail feathers. The structure of P1 indicates strong resistance against aerodynamic forces, while the narrow rachis, low vane density and low bending stiffness of tail feathers suggest reduced resistance against airflow. The highly elongated Ta6 is characterized by structural modifications such as large rachis width and increased barbule density in relation to the less elongated Ta5, which can be explained by increased length and/or high aerodynamic forces acting at the leading tail edge. However, these changes in Ta6 structure do not allow for full compensation of elongation, as reflected by the reduced bending stiffness of Ta6. Ta6 elongation in males resulted in feathers with reduced resistance, as shown by the low barb density and reduced bending stiffness compared to females. The inconsistency in sexual dimorphism and in change in quality traits of Ta6 among six European populations shows that multiple factors may contribute to shaping population differences. In general, the difference in quality traits between tail feathers cannot be explained by the GBW of feathers. Our results show that the material and structural properties of wing and tail feathers of barn swallows change as a result of aerodynamic forces and sexual selection, although the result of these

  7. Sexual Dimorphism and Population Differences in Structural Properties of Barn Swallow (Hirundo rustica) Wing and Tail Feathers

    PubMed Central

    Pap, Péter L.; Osváth, Gergely; Aparicio, José Miguel; Bărbos, Lőrinc; Matyjasiak, Piotr; Rubolini, Diego; Saino, Nicola; Vágási, Csongor I.; Vincze, Orsolya; Møller, Anders Pape

    2015-01-01

    Sexual selection and aerodynamic forces affecting structural properties of the flight feathers of birds are poorly understood. Here, we compared the structural features of the innermost primary wing feather (P1) and the sexually dimorphic outermost (Ta6) and monomorphic second outermost (Ta5) tail feathers of barn swallows (Hirundo rustica) from a Romanian population to investigate how sexual selection and resistance to aerodynamic forces affect structural differences among these feathers. Furthermore, we compared structural properties of Ta6 of barn swallows from six European populations. Finally, we determined the relationship between feather growth bars width (GBW) and the structural properties of tail feathers. The structure of P1 indicates strong resistance against aerodynamic forces, while the narrow rachis, low vane density and low bending stiffness of tail feathers suggest reduced resistance against airflow. The highly elongated Ta6 is characterized by structural modifications such as large rachis width and increased barbule density in relation to the less elongated Ta5, which can be explained by increased length and/or high aerodynamic forces acting at the leading tail edge. However, these changes in Ta6 structure do not allow for full compensation of elongation, as reflected by the reduced bending stiffness of Ta6. Ta6 elongation in males resulted in feathers with reduced resistance, as shown by the low barb density and reduced bending stiffness compared to females. The inconsistency in sexual dimorphism and in change in quality traits of Ta6 among six European populations shows that multiple factors may contribute to shaping population differences. In general, the difference in quality traits between tail feathers cannot be explained by the GBW of feathers. Our results show that the material and structural properties of wing and tail feathers of barn swallows change as a result of aerodynamic forces and sexual selection, although the result of these

  8. The Structural Properties and Stability of Monoclonal Antibodies at Freezing Conditions

    NASA Astrophysics Data System (ADS)

    Perevozchikova, Tatiana; Zarraga, Isidro; Scherer, Thomas; Wagner, Norman; Liu, Yun

    2013-03-01

    Monoclonal Antibodies (MAb) have become a crucial therapeutic agent in a number of anti-cancer treatments. Due to the inherent unstable nature of proteins in an aqueous formulation, a freeze-drying method has been developed to maintain long-term stability of biotherapeutics. The microstructural changes in Mabs during freezing, however, remain not fully described, and it was proposed that the formed morphology of freeze drying samples could affect the final product quality after reconstitution. Furthermore, it is well known that proteins tend to aggregate during the freezing process if a careful processing procedure is not formulated. Small Angle Neutron Scattering (SANS) is a powerful tool to investigate the structural properties and interactions of Mabs during various stages of lyophilization in situ. Here we present the SANS results of freeze-thaw studies on two MAbs at several different freezing temperatures. While the chosen proteins share a significant sequence homology, their freezing properties are found to be strikingly distinctive. We also show the effect of excipients, concentration and quenching speed on the final morphology of the frozen samples. These findings provide critical information for more effective lyophilization schemes for therapeutic proteins, as well as increase our understanding on structural properties of proteins under cryogenic conditions.

  9. Gender, Emotion Work, and Relationship Quality: A Daily Diary Study

    PubMed Central

    Curran, Melissa A.; McDaniel, Brandon T.; Pollitt, Amanda M.; Totenhagen, Casey J.

    2015-01-01

    We use the gender relations perspective from feminist theorizing to investigate how gender and daily emotion work predict daily relationship quality in 74 couples (148 individuals in dating, cohabiting, or married relationships) primarily from the southwest U.S. Emotion work is characterized by activities that enhance others’ emotional well-being. We examined emotion work two ways: trait (individuals’ average levels) and state (individuals’ daily fluctuations). We examined actor and partner effects of emotion work and tested for gender differences. As outcome variables, we included six types of daily relationship quality: love, commitment, satisfaction, closeness, ambivalence, and conflict. This approach allowed us to predict three aspects of relationship quality: average levels, daily fluctuations, and volatility (overall daily variability across a week). Three patterns emerged. First, emotion work predicted relationship quality in this diverse set of couples. Second, gender differences were minimal for fixed effects: Trait and state emotion work predicted higher average scores on, and positive daily increases in, individuals’ own positive relationship quality and lower average ambivalence. Third, gender differences were more robust for volatility: For partner effects, having a partner who reported higher average emotion work predicted lower volatility in love, satisfaction, and closeness for women versus greater volatility in love and commitment for men. Neither gender nor emotion work predicted average levels, daily fluctuations, or volatility in conflict. We discuss implications and future directions pertaining to the unique role of gender in understanding the associations between daily emotion work and volatility in daily relationship quality for relational partners. PMID:26508808

  10. Relationships between Students' Strategies for Influencing Their Study Environment and Their Strategic Approach to Studying

    ERIC Educational Resources Information Center

    Jungert, Tomas; Rosander, Michael

    2009-01-01

    The purpose of this study was to investigate the relationship between student influence, students' strategic approaches to studying and academic achievement, and to examine differences between students in a Master's programme in Engineering with conventional teaching and one based on problem-based learning in a sample of 268 students. A version of…

  11. Material and structural properties of fin whale (Balaenoptera physalus) Zwischensubstanz.

    PubMed

    Pinto, Sheldon J D; Shadwick, Robert E

    2013-08-01

    The oral anatomy of the fin whale (Balaenoptera physalus) consists of several major structures crucial to its engulfment method of feeding, such as stiff keratinized baleen plates, a large flaccid tongue, and a prominent vomer. One under-documented part of this anatomy is the cream white Zwischensubstanz that holds the baleen plates to the rostrum at their dorsal base. The mechanical and structural properties of Zwischensubstanz play a key role in baleen plate dynamics and, on the grand scale, contribute to baleen whales' filtration efficiency and attainment of large body size. Compression and tensile tests on the Zwischensubstanz sampled from an 18 m fin whale showed that this material unexpectedly exhibits linear isotropic behaviour with Elastic Modulus of 2.56 ± 0.60 MPa and hysteresis of 0.44 ± 0.02 in compression despite apparent unidirectional growth. Acting similar to a soft rubber, the Zwischensubstanz absorbs and dissipates the enormous forces acting on baleen plates during engulfment feeding while maintaining spacing between the plates to maximize filtration efficiency. Microscopic analysis provided images of connective tissue papillae penetrating the base of the Zwischensubstanz and developing within it to emerge as fully formed, keratinized baleen plates. The plates develop from the papillae and a connective tissue sheet within the 5-7 cm deep Zwischensubstanz. The Zwischensubstanz provides a keratin matrix of concentrically oriented fibers around each papilla forming the hard baleen plates and frayed fringes used for filter feeding. During this formation, the Zwischensubstanz remains unchanged and appears to slough away to allow the baleen plate to grow unhindered. PMID:23640788

  12. Structure-Activity Relationship Study of Hydroxycoumarins and Mushroom Tyrosinase.

    PubMed

    Asthana, Shailendra; Zucca, Paolo; Vargiu, Attilio V; Sanjust, Enrico; Ruggerone, Paolo; Rescigno, Antonio

    2015-08-19

    The structure-activity relationships of four hydroxycoumarins, two with the hydroxyl group on the aromatic ring of the molecule and two with the hydroxyl group replacing hydrogen of the pyrone ring, and their interactions with mushroom tyrosinase were studied. These compounds displayed different behaviors upon action of the enzyme. The two compounds, ar-hydroxylated 6-hydroxycoumarin and 7-hydroxycoumarin, were both weak substrates of the enzyme. Interestingly, in both cases, the product of the catalysis was the 6,7-hydroxycoumarin, although 5,6- and 7,8-isomers could also theoretically be formed. Additionally, both were able to reduce the formation of dopachrome when tyrosinase acted on its typical substrate, L-tyrosine. Although none of the compounds that contained a hydroxyl group on the pyrone ring were substrates of tyrosinase, the 3-hydroxycoumarin was a potent inhibitor of the enzyme, and the 4-hydroxycoumarin was not an inhibitor. These results were compared with those obtained by in silico molecular docking predictions to obtain potentially useful information for the synthesis of new coumarin-based inhibitors that resemble the structure of the 3-hydroxycoumarin.

  13. A Cross-National Study of the Relationship between Elderly Suicide Rates and Urbanization

    ERIC Educational Resources Information Center

    Shah, Ajit

    2008-01-01

    There is mixed evidence of a relationship between suicide rates in the general population and urbanization, and a paucity of studies examining this relationship in the elderly. A cross-national study with curve estimation regression model analysis, was undertaken to examine the a priori hypothesis that the relationship between elderly suicide…

  14. High School Football Players and Their Coaches: A Qualitative Study of Their Relationships

    ERIC Educational Resources Information Center

    Skaza, Robert J.

    2014-01-01

    This basic qualitative study of high school football coach-player relationships explores the players' perceptions of these relationships, specifically the perceptions the players have of how these relationships influenced their lives. This study allowed the researcher to examine the characteristics of high school football coaches as they relate to…

  15. Does Marriage and Relationship Education Work? A Meta-Analytic Study

    ERIC Educational Resources Information Center

    Hawkins, Alan J.; Blanchard, Victoria L.; Baldwin, Scott A.; Fawcett, Elizabeth B.

    2008-01-01

    In this meta-analytic study, the authors examined the efficacy of marriage and relationship education (MRE) on 2 common outcomes: relationship quality and communication skills. A thorough search produced 86 codable reports that yielded 117 studies and more than 500 effect sizes. The effect sizes for relationship quality for experimental studies…

  16. A multiple-plane approach to measure the structural properties of functionally active regions in the human cortex.

    PubMed

    Wang, Xin; Garfinkel, Sarah N; King, Anthony P; Angstadt, Mike; Dennis, Michael J; Xie, Hong; Welsh, Robert C; Tamburrino, Marijo B; Liberzon, Israel

    2010-02-15

    Advanced magnetic resonance imaging (MRI) techniques provide the means of studying both the structural and the functional properties of various brain regions, allowing us to address the relationship between the structural changes in human brain regions and the activity of these regions. However, analytical approaches combining functional (fMRI) and structural (sMRI) information are still far from optimal. In order to improve the accuracy of measurement of structural properties in active regions, the current study tested a new analytical approach that repeated a surface-based analysis at multiple planes crossing different depths of cortex. Twelve subjects underwent a fear conditioning study. During these tasks, fMRI and sMRI scans were acquired. The fMRI images were carefully registered to the sMRI images with an additional correction for cortical borders. The fMRI images were then analyzed with the new multiple-plane surface-based approach as compared to the volume-based approach, and the cortical thickness and volume of an active region were measured. The results suggested (1) using an additional correction for cortical borders and an intermediate template image produced an acceptable registration of fMRI and sMRI images; (2) surface-based analysis at multiple depths of cortex revealed more activity than the same analysis at any single depth; (3) projection of active surface vertices in a ribbon fashion improved active volume estimates; and (4) correction with gray matter segmentation removed non-cortical regions from the volumetric measurement of active regions. In conclusion, the new multiple-plane surface-based analysis approaches produce improved measurement of cortical thickness and volume of active brain regions. These results support the use of novel approaches for combined analysis of functional and structural neuroimaging. PMID:19922802

  17. Bridging Theory and Experiment to Address Structural Properties of Truncated Haemoglobins: Insights from Thermobifida fusca HbO.

    PubMed

    Howes, Barry D; Boechi, Leonardo; Boffi, Alberto; Estrin, Dario E; Smulevich, Giulietta

    2015-01-01

    In this chapter, we will discuss the paradigmatic case of Thermobifida fusca (Tf-trHb) HbO in its ferrous and ferric states and its behaviour towards a battery of possible ligands. This choice was dictated by the fact that it has been one of the most extensively studied truncated haemoglobins, both in terms of spectroscopic and molecular dynamics studies. Tf-trHb typifies the structural properties of group II trHbs, as the active site is characterized by a highly polar distal environment in which TrpG8, TyrCD1, and TyrB10 provide three potential H-bond donors in the distal cavity capable of stabilizing the incoming ligands. The role of these residues in key topological positions, and their interplay with the iron-bound ligands, has been addressed in studies carried out on the CO, F(-), OH(-), CN(-), and HS(-) adducts formed with the wild-type protein and a combinatorial set of mutants, in which the distal polar residues, TrpG8, TyrCD1, and TyrB10, have been singly, doubly, or triply replaced by a Phe residue. In this context, such a complete analysis provides an excellent benchmark for the investigation of the relationship between protein structure and function, allowing one to translate physicochemical properties of the active site into the observed functional behaviour. Tf-trHb will be compared with other members of the group II trHbs and, more generally, with members of the other trHb subgroups.

  18. TIGHT CORRELATIONS BETWEEN MASSIVE GALAXY STRUCTURAL PROPERTIES AND DYNAMICS: THE MASS FUNDAMENTAL PLANE WAS IN PLACE BY z ∼ 2

    SciTech Connect

    Bezanson, Rachel; Van Dokkum, Pieter G.; Leja, Joel; Van de Sande, Jesse; Franx, Marijn; Kriek, Mariska

    2013-12-20

    The fundamental plane (FP) is an empirical relation between the size, surface brightness, and velocity dispersion of early-type galaxies. This relation has been studied extensively for early-type galaxies in the local universe to constrain galaxy formation mechanisms. The evolution of the zero point of this plane has been extended to high redshifts to study the luminosity evolution of massive galaxies, under the assumption of structural homology. In this work, we assess this assumption by replacing surface brightness with stellar mass density and present the evolution of the ''mass FP'' for massive, quiescent galaxies since z ∼ 2. By accounting for stellar populations, we thereby isolate and trace structural and dynamical evolution. Despite the observed dramatic evolution in the sizes and morphologies of massive galaxies since z ∼ 3, we find that quiescent galaxies lie on the mass FP out to z ∼ 2. In contrast with ∼1.4 dex evolution in the luminosity FP, average residuals from the z ∼ 0 mass FP are less than ∼0.15 dex since z ∼ 2. Assuming the Hyde and Bernardi mass FP slope, we find that this minimal offset scales as (1 + z){sup –0.095} {sup ±} {sup 0.043}. This result lends credence to previous studies that derived luminosity evolution from the FP. Therefore, despite their compact sizes and suggestions that massive galaxies are more disk-like at z ∼ 2, the relationship between their dynamics and structural properties are consistent with local early-type galaxies. Finally, we find no strong evidence for a tilt of the mass FP relative to the virial plane, but emphasize the need for full models including selection biases to fully investigate this issue.

  19. Bridging Theory and Experiment to Address Structural Properties of Truncated Haemoglobins: Insights from Thermobifida fusca HbO.

    PubMed

    Howes, Barry D; Boechi, Leonardo; Boffi, Alberto; Estrin, Dario E; Smulevich, Giulietta

    2015-01-01

    In this chapter, we will discuss the paradigmatic case of Thermobifida fusca (Tf-trHb) HbO in its ferrous and ferric states and its behaviour towards a battery of possible ligands. This choice was dictated by the fact that it has been one of the most extensively studied truncated haemoglobins, both in terms of spectroscopic and molecular dynamics studies. Tf-trHb typifies the structural properties of group II trHbs, as the active site is characterized by a highly polar distal environment in which TrpG8, TyrCD1, and TyrB10 provide three potential H-bond donors in the distal cavity capable of stabilizing the incoming ligands. The role of these residues in key topological positions, and their interplay with the iron-bound ligands, has been addressed in studies carried out on the CO, F(-), OH(-), CN(-), and HS(-) adducts formed with the wild-type protein and a combinatorial set of mutants, in which the distal polar residues, TrpG8, TyrCD1, and TyrB10, have been singly, doubly, or triply replaced by a Phe residue. In this context, such a complete analysis provides an excellent benchmark for the investigation of the relationship between protein structure and function, allowing one to translate physicochemical properties of the active site into the observed functional behaviour. Tf-trHb will be compared with other members of the group II trHbs and, more generally, with members of the other trHb subgroups. PMID:26616516

  20. Adopting Quality Assurance Technology in Customer-Vendor Relationships: A Case Study of How Interorganizational Relationships Influence the Process

    NASA Astrophysics Data System (ADS)

    Heeager, Lise Tordrup; Tjørnehøj, Gitte

    Quality assurance technology is a formal control mechanism aiming at increasing the quality of the product exchanged between vendors and customers. Studies of the adoption of this technology in the field of system development rarely focus on the role of the relationship between the customer and vendor in the process. We have studied how the process of adopting quality assurance technology by a small Danish IT vendor developing pharmacy software for a customer in the public sector was influenced by the relationship with the customer. The case study showed that the adoption process was shaped to a high degree by the relationship and vice versa. The prior high level of trust and mutual knowledge helped the parties negotiate mutually feasible solutions throughout the adoption process. We thus advise enhancing trust-building processes to strengthen the relationships and to balance formal control and social control to increase the likelihood of a successful outcome of the adoption of quality assurance technology in a customer-vendor relationship.

  1. Structure-property relationships in Waspaloy via small angle scattering and electrical resistivity measurements

    SciTech Connect

    Whelchel, R.; Gerhardt, Dr. Rosario; Littrell, Ken

    2010-01-01

    The mechanical properties in superalloys are controlled by the distribution of the {gamma}{prime} precipitate phase. Electrical measurements have been shown to be sensitive to certain aspects of the precipitation process and show promise for predicting the evolving microstructural state in superalloys. Aging experiments were conducted on Waspaloy samples for temperatures between 600 and 950 C for times ranging from 2min to 500h. Particle size distributions were obtained by modeling of small angle scattering (SAS) data, whereas, small precipitate size information, strain, and lattice mismatch data were obtained from X-ray diffraction. The microstructural information was then used to create a figure of merit of electron scattering intended to correlate electrical properties to the precipitate microstructure. The proposed figure of merit shows an empirical correlation with the electrical resistivity data, demonstrating the sensitivity of the resistivity measurements to the precipitation process and coarsening behavior.

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

    SciTech Connect

    Prichard, P.D.

    1998-02-23

    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.

  3. New Synthetic Methods and Structure-Property Relationships in Neptunium, Plutonium, and Americium Borates. Final report

    SciTech Connect

    Albrecht-Schmitt, Thomas Edward

    2013-09-14

    The past three years of support by the Heavy Elements Chemistry Program have been highly productive in terms of advanced degrees awarded, currently supported graduate students, peer-reviewed publications, and presentations made at universities, national laboratories, and at international conferences. Ph.D. degrees were granted to Shuao Wang and Juan Diwu, who both went on to post-doctoral appointments at the Glenn T. Seaborg Center at Lawrence Berkeley National Laboratory with Jeff Long and Ken Raymond, respectively. Pius Adelani completed his Ph.D. with me and is now a post-doc with Peter C. Burns. Andrea Alsobrook finished her Ph.D. and is now a post-doc at Savannah River with Dave Hobbs. Anna Nelson completed her Ph.D. and is now a post-doc with Rod Ewing at the University of Michigan. As can be gleaned from this list, students supported by the Heavy Elements Chemistry grant have remained interested in actinide science after leaving my program. This follows in line with previous graduates in this program such as Richard E. Sykora, who did his post-doctoral work at Oak Ridge National Laboratory with R. G. Haire, and Amanda C. Bean, who is a staff scientist at Los Alamos National Laboratory, and Philip M. Almond and Thomas C. Shehee, who are both staff scientists at Savannah River National Laboratory, Gengbang Jin who is a staff scientist at Argonne National Lab, and Travis Bray who has been a post-doc at both LBNL and ANL. Clearly this program is serving as a pipe-line for students to enter into careers in the national laboratories. About half of my students depart the DOE complex for academia or industry. My undergraduate researchers also remain active in actinide chemistry after leaving my group. Dan Wells was a productive undergraduate of mine, and went on to pursue a Ph.D. on uranium and neptunium chalcogenides with Jim Ibers at Northwestern. After earning his Ph.D., he went directly into the nuclear industry.

  4. Investigating the Structure-Property Relationships of Aqueous Self-Assembled Materials

    NASA Astrophysics Data System (ADS)

    Krogstad, Daniel Vincent

    The components of all living organisms are formed through aqueous self-assembly of organic and inorganic materials through physical interactions including hydrophobic, electrostatic, and hydrogen bonding. In this dissertation, these physical interactions were exploited to develop nanostructured materials for a range of applications. Peptide amphiphiles (PAs) self-assemble into varying structures depending on the physical interactions of the peptides and tails. PA aggregation was investigated by cryo-TEM to provide insight on the effects of varying parameters, including the number and length of the lipid tails as well as the number, length, charge, hydrophobicity, and the hydrogen bonding ability of the peptides. It was determined that cylindrical micelles are most commonly formed, and that specific criteria must be met in order to form spherical micelles, nanoribbons, vesicles or less ordered aggregates. Controlling the aggregated structure is necessary for many applications---particularly in therapeutics. Additionally, two-headed PAs were designed to act as a catalyst and template for biomimetic mineralization to control the formation of inorganic nanomaterials. Finally, injectable hydrogels made from ABA triblock copolymers were synthesized with the A blocks being functionalized with either guanidinium or sulfonate groups. These oppositely charged polyelectrolyte endblocks formed complex coacervate domains, which served as physical crosslinks in the hydrogel network. The mechanical properties, the network structure, the nature of the coacervate domain and the kinetics of hydrogel formation were investigated as a function of polymer concentration, salt concentration, pH and stoichiometry with rheometry, SAXS and SANS. It was shown that the mechanical properties of the hydrogels was highly dependent on the structural organization of the coacervate domains and that the properties could be tuned with polymer and salt concentration. Polymer and salt concentration were also shown to play roles in determining the size and density of the coacervate domains. Additionally, 20 wt% hydrogels were shown to form through a nucleation and growth pathway, in which the coacervate domains formed within minutes, the BCC structure was predominant within 100 minutes, but the equilibrium structure was not achieved for months. Ultimately, the work presented in this dissertation has resulted in an improved understanding of the physical interactions that are needed for self-assembly and may eventually lead to smarter design of nanomaterials for therapeutic, electronic and mechanical applications.

  5. Quantitative structure-property relationships for chemical functional use and weight fractions in consumer articles

    EPA Science Inventory

    Chemical functional use -- the functional role a chemical plays in processes or products -- may be a useful heuristic for predicting human exposure potential in that it comprises information about the compound's likely physical properties and the product formulations or articles ...

  6. Structure-Property Relationships of Poly(lactide)-based Triblock and Multiblock Copolymers

    NASA Astrophysics Data System (ADS)

    Panthani, Tessie Rose

    Replacing petroleum-based plastics with alternatives that are degradable and synthesized from annually renewable feedstocks is a critical goal for the polymer industry. Achieving this goal requires the development of sustainable analogs to commodity plastics which have equivalent or superior properties (e.g. mechanical, thermal, optical etc.) compared to their petroleum-based counterparts. This work focuses on improving and modulating the properties of a specific sustainable polymer, poly(lactide) (PLA), by incorporating it into triblock and multiblock copolymer architectures. The multiblock copolymers in this work are synthesized directly from dihydroxy-terminated triblock copolymers by a simple step-growth approach: the triblock copolymer serves as a macromonomer and addition of stoichiometric quantities of either an acid chloride or diisocyanate results in a multiblock copolymer. This work shows that over wide range of compositions, PLA-based multiblock copolymers have superior mechanical properties compared to triblock copolymers with equivalent chemical compositions and morphologies. The connectivity of the blocks within the multiblock copolymers has other interesting consequences on properties. For example, when crystallizable poly(L-lactide)-based triblock and multiblock copolymers are investigated, it is found that the multiblock copolymers have much slower crystallization kinetics. Additionally, the total number of blocks connected together is found to effect the linear viscoelastic properties as well as the alignment of lamellar domains under uniaxial extension. Finally, the synthesis and characterization of pressure-sensitive adhesives based upon renewable PLA-containing triblock copolymers and a renewable tackifier is detailed. Together, the results give insight into the effect of chain architecture, composition, and morphology on the mechanical behavior, thermal properties, and rheological properties of PLA-based materials.

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

    SciTech Connect

    Heitfeld, Kevin A.; Schaefer, Dale W.

    2010-10-12

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

  8. Structure-property relationships of iron-hydroxyapatite ceramic matrix nanocomposite fabricated using mechanosynthesis method.

    PubMed

    Nordin, Jamillah Amer; Prajitno, Djoko Hadi; Saidin, Syafiqah; Nur, Hadi; Hermawan, Hendra

    2015-06-01

    Hydroxyapatite (HAp) is an attractive bioceramics due to its similar composition to bone mineral and its ability to promote bone-implant interaction. However, its low strength has limited its application as load bearing implants. This paper presented a work focusing on the improvement of HAp mechanical property by synthesizing iron (Fe)-reinforced bovine HAp nanocomposite powders via mechanosynthesis method. The synthesis process was performed using high energy milling at varied milling time (3, 6, 9, and 12h). The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM). Its mechanical properties were investigated by micro-Vicker's hardness and compression tests. Results showed that milling time directly influenced the characteristics of the nanocomposite powders. Amorphous BHAp was formed after 9 and 12h milling in the presence of HPO4(2-) ions. Continuous milling has improved the crystallinity of Fe without changing the HAp lattice structure. The nanocomposite powders were found in spherical shape, agglomerated and dense after longer milling time. The hardness and Young's modulus of the nanocomposites were also increased at 69% and 66%, respectively, as the milling time was prolonged from 3 to 12h. Therefore, the improvement of the mechanical properties of nanocomposite was attributed to high Fe crystallinity and homogenous, dense structure produced by mechanosynthesis. PMID:25842138

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

    PubMed

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

    2015-02-01

    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.

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

    PubMed

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

    2011-08-15

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

  11. Synthesis and Structure-Property Relationships of Poly(sulfone)s for Anion Exchange Membranes

    SciTech Connect

    Yan, JL; Moore, HD; Hibbs, MR; Hickner, MA

    2013-10-05

    Membranes based on cationic polymers that conduct anions are important for enabling alkaline membrane fuel cells and other solid-state electrochemical devices that operate at high pH. Anion exchange membranes with poly(arylene ether sulfone) backbones are demonstrated by two routes: chloromethylation of commercially available poly(sulfone)s or radical bromination of benzylmethyl moieties in poly(sulfone)s containing tetramethylbisphenol A monomer residues. Polymers with tethered trimethylbenzyl ammonium moieties resulted from conversion of the halomethyl groups by quaternization with trimethyl amine. The water uptake of the chloromethylated polymers was dependent on the type of poly(sulfone) backbone for a given IEC. Bisphenol A-based Udel (R) poly(sulfone) membranes swelled in water to a large extent while membranes from biphenol-based Radel (R) poly(sulfone), a stiffer backbone than Udel, only showed moderate water uptake. The water uptake of cationic poly(sulfone)s was further reduced by synthesizing tetramethylbisphenol A and 4,4-biphenol-containing poly(sulfone) copolymers where the ionic groups were clustered on the tetramethylbisphenol A residues. The conductivity of all samples scaled with the bulk water uptake. The hydration number of the membranes could be increased by casting membranes from the ionic form polymers versus converting the halomethyl form cast polymers to ionic form in the solid state. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1790-1798, 2013

  12. Structure-property relationships of iron-hydroxyapatite ceramic matrix nanocomposite fabricated using mechanosynthesis method.

    PubMed

    Nordin, Jamillah Amer; Prajitno, Djoko Hadi; Saidin, Syafiqah; Nur, Hadi; Hermawan, Hendra

    2015-06-01

    Hydroxyapatite (HAp) is an attractive bioceramics due to its similar composition to bone mineral and its ability to promote bone-implant interaction. However, its low strength has limited its application as load bearing implants. This paper presented a work focusing on the improvement of HAp mechanical property by synthesizing iron (Fe)-reinforced bovine HAp nanocomposite powders via mechanosynthesis method. The synthesis process was performed using high energy milling at varied milling time (3, 6, 9, and 12h). The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM). Its mechanical properties were investigated by micro-Vicker's hardness and compression tests. Results showed that milling time directly influenced the characteristics of the nanocomposite powders. Amorphous BHAp was formed after 9 and 12h milling in the presence of HPO4(2-) ions. Continuous milling has improved the crystallinity of Fe without changing the HAp lattice structure. The nanocomposite powders were found in spherical shape, agglomerated and dense after longer milling time. The hardness and Young's modulus of the nanocomposites were also increased at 69% and 66%, respectively, as the milling time was prolonged from 3 to 12h. Therefore, the improvement of the mechanical properties of nanocomposite was attributed to high Fe crystallinity and homogenous, dense structure produced by mechanosynthesis.

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

    ERIC Educational Resources Information Center

    Murphy, Peter M.

    2007-01-01

    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'…

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

    NASA Astrophysics Data System (ADS)

    Mehlem, Jeremy John

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

  15. Investigation of structure-property relationships in systematic series of novel polymers

    NASA Technical Reports Server (NTRS)

    Gillham, J. K.

    1976-01-01

    Solid state transitions in polymeric materials was associated with the onset of sub-molecular motions of the polymer chains. Although these were considered to be intramolecular in general, the local environment of the polymer molecule exerts a strong influence through, for example, the effects of crystallinity, polarity and diluents. The manner of specimen preparation and previous history also affect transitions. The transitions are considered to arise when sufficient free volume is available to permit the occurrence of these side chain and backbone reorientations. The glass transition is the principal transition of amorphous polymeric materials and is associated with the onset of long range segmental motion of the polymer backbone. The various types of shorter range motion occurring below the glass transition have been catalogued.

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

    SciTech Connect

    Dinesh; Kumar, Mukesh; Dalela, S.

    2014-04-24

    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.

  17. Structure-property relationships in hybrid dental nanocomposite resins containing monofunctional and multifunctional polyhedral oligomeric silsesquioxanes.

    PubMed

    Wang, Weiguo; Sun, Xiang; Huang, Li; Gao, Yu; Ban, Jinghao; Shen, Lijuan; Chen, Jihua

    2014-01-01

    Organic-inorganic hybrid materials, such as polyhedral oligomeric silsesquioxanes (POSS), have the potential to improve the mechanical properties of the methacrylate-based composites and resins used in dentistry. In this article, nanocomposites of methacryl isobutyl POSS (MI-POSS [bears only one methacrylate functional group]) and methacryl POSS (MA-POSS [bears eight methacrylate functional groups]) were investigated to determine the effect of structures on the properties of dental resin. The structures of the POSS-containing networks were determined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Monofunctional POSS showed a strong tendency toward aggregation and crystallization, while multifunctional POSS showed higher miscibility with the dimethacrylate monomer. The mechanical properties and wear resistance decreased with increasing amounts of MI-POSS, indicating that the MI-POSS agglomerates act as the mechanical weak point in the dental resins. The addition of small amounts of MA-POSS improved the mechanical and shrinkage properties. However, samples with a higher MA-POSS concentration showed lower flexural strength and flexural modulus, indicating that there is a limited range in which the reinforcement properties of MA-POSS can operate. This concentration dependence is attributed to phase separation at higher concentrations of POSS, which affects the structural integrity, and thus, the mechanical and shrinkage properties of the dental resin. Our results show that resin with 3% MA-POSS is a potential candidate for resin-based dental materials.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

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

    PubMed

    Lusvardi, G; Malavasi, G; Tarsitano, F; Menabue, L; Menziani, M C; Pedone, A

    2009-07-30

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

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

    PubMed Central

    Katz, J. Lawrence; Misra, Anil; Spencer, Paulette; Wang, Yong; Bumrerraj, Sauwanan; Nomura, Tsutomu; Eppell, Steven J.; Tabib-Azar, Massood

    2007-01-01

    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. PMID:18270549

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

    PubMed

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

    2015-03-30

    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 (η0, λ0, 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

  2. Structure-property relationships in ABA copolymer gels with A homopolymer additions

    NASA Astrophysics Data System (ADS)

    Seitz, Michelle; Rottsolk, Rebecca; Page, Kirt; Shull, Kenneth

    2009-03-01

    ABA acrylic triblock copolymers with poly(methyl methacrylate) endblocks and poly(butyl acrylate) midblocks transition from free flowing liquids to elastic solids with decreasing temperature in alcohol solvents. Homopolymer PMMA chains can be solubilized in the micelle cores if they are shorter than the endblocks. Indentation and compression tests were used to determine gel's modulus and large strain behavior. Gels with volume fractions of PMMA less than ˜0.2 are highly elastic and have moduli dictated by stretching of bridging midblocks. At higher PMMA contents, gels exhibit greater permanent deformation and moduli over an order of magnitude larger than would be expected from rubber elasticity alone. Small angle X-ray and neutron scattering and mean field simulations were used to correlate changes in gel structure and micelle morphology with the addition of homopolymer.

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

    NASA Astrophysics Data System (ADS)

    Donakowski, Martin Daniel

    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.

  4. Self-structuring properties of dominance hierarchies a new perspective.

    PubMed

    Chase, Ivan D; Seitz, Kristine

    2011-01-01

    Using aggressive behavior, animals of many species establish dominance hierarchies in both nature and the laboratory. Rank in these hierarchies influences many aspects of animals' lives including their health, physiology, weight gain, genetic expression, and ability to reproduce and raise viable offspring. In this chapter, we define dominance relationships and dominance hierarchies, discuss several model species used in dominance studies, and consider factors that predict the outcomes of dominance encounters in dyads and small groups of animals. Researchers have shown that individual differences in attributes, as well as in states (recent behavioral experiences), influence the outcomes of dominance encounters in dyads. Attributes include physical, physiological, and genetic characteristics while states include recent experiences such as winning or losing earlier contests. However, surprisingly, we marshal experimental and theoretical evidence to demonstrate that these differences have significantly less or no ability to predict the outcomes of dominance encounters for animals in groups as small as three or four individuals. Given these results, we pose an alternative research question: How do animals of so many species form hierarchies with characteristic linear structures despite the relatively low predictability based upon individual differences? In answer to this question, we review the evidence for an alternative approach suggesting that dominance hierarchies are self-structuring. That is, we suggest that linear forms of organization in hierarchies emerge from several kinds of behavioral processes, or sequences of interaction, that are common across many different species of animals from ants to chickens and fish and even some primates. This new approach inspires a variety of further questions for research.

  5. Thermal, dielectric and structural properties of Enceladus' leading face

    NASA Astrophysics Data System (ADS)

    Le Gall, Alice; Bonnefoy, Léa; Leyrat, Cedric; Janssen, Michael A.

    2016-10-01

    The Cassini RADAR was initially designed to examine the surface of Titan through the veil of its optically-opaque atmosphere. However, it is occasionally used to observe airless Saturn's moons from long range and, less frequently, during targeted flybys. In particular, the 16th targeted encounter of Enceladus (Nov. 6, 2011, flyby E16) was dedicated to the RADAR instrument which then acquired data for over 4 hours. This paper focuses on the mid-resolution (0.1-0.6REnceladus) and low-resolution polarized data (0.6-1.0REnceladus) collected during the E16 flyby in the radiometry mode of the RADAR, mainly on the leading side of the moon.In its passive mode, the RADAR records the thermal emission at 2-cm wavelength from, likely, the first meters of an icy surface. Ries and Janssen (2015) first analyzed the E16 mid-resolution radiometry observation and reported on a large-scale emissivity anomaly, possibly associated with the seemingly young tectonized Leading Hemisphere Terrain mapped by Crow-Willard and Pappalardo (2015). With the goal of further investigating the extension of the anomaly region and providing constrains on the thermal, dielectric and structural properties of Enceladus' near surface, we have re-examined this dataset as well as observations acquired in two orthogonal polarizations with the help of a thermal model. This thermal model accounts for both diurnal and seasonal variations of the incident flux, including eclipses which is of importance for the E16 observations partially occurred during a solar eclipse by Saturn.Preliminary results suggest that the average thermal inertia of the near surface of Enceladus' leading face is relatively low, as low as 40 Jm-2K-1s-1/2 . This value does not depart much from the one inferred from measurements in the IR suggesting that the surface of Enceladus is covered by a very porous regolith, at least a few meters thick. In agreement, with this interpretation, the degree of volume scattering (i.e., high

  6. The density, viscosity and structural properties of aqueous ethambutol hydrochloride solutions

    NASA Astrophysics Data System (ADS)

    Deosarkar, S. D.; Puyad, A. L.; Kalyankar, T. M.

    2012-05-01

    Ethambutol (EMB) is a bacteriostatic antimycobacterial drug prescribed to treat tuberculosis. It is bacteriostatic against actively growing TB bacilli. The density and viscosity of aqueous ethambutol hydrochloride solutions have been studied at 298.15, 301.15 and 304.15 K and at different concentrations (0.255, 0.168, 0.128, 0.087, 0.041, and 0.023 mol dm-3). The apparent molar volume of these solutions for different temperatures and concentrations was calculated from the density data. The relative viscosities of drug solutions have been analysed by Jones-Dole equation. The limiting apparent molar volumes have been evaluated for different temperatures. The different properties have been used to study structural properties, structure formation and breaking properties of drug and solute-solvent interactions in solutions.

  7. Digenean trematodes-marine mollusc relationships: a stable isotope study.

    PubMed

    Dubois, S Y; Savoye, N; Sauriau, P-G; Billy, I; Martinez, P; de Montaudouin, X

    2009-03-01

    The stable carbon and nitrogen isotopic composition of digenean trematode parasites and their marine mollusc hosts was investigated to describe the potential influence of parasites on their host and its different tissues, and to obtain further insight into their trophic relationships. Four parasite-host systems were studied: Labratrema minimus-Cerastoderma edule, Monorchis parvus-C. edule, Lepocreadiidae parasites-Nassarius reticulatus and Zoogonidae parasites-N. reticulatus. Among the 4 sampling occasions reported here and corresponding to the 4 parasite-host systems, isotopic shifts from pathologic (i.e. linked to disturbances in host metabolism) and mass-balance (i.e. linked to significant differences between host and parasite isotopic signatures) origins were observed only once. Both corresponded to delta 13C measurements of the L. minimus-C. edule system when the infestation load (percentage parasite dry weight compared to total flesh dry weight) was highest (9 to 25%, mean = 16%) over the sampling period. Overall, measurements indicate that digenean trematode parasitism induced low or no shifts in isotopic signatures of C. edule and N. reticulatus tissues. The 2 endoparasites L. minimus and M. parvus appeared to be slightly depleted in 13C compared to C. edule digestive gland and gonads, which were the most parasitized tissues. In contrast, no fractionation or low 15N trophic enrichments occurred in the parasites. These results highly contrast with the classical trophic enrichment reported in prey-predator systems but are in agreement with the scarce literature regarding other parasite-host systems. Our results indicate that (1) digenean trematodes mainly feed on digestive glands (the cockle tissue with which they are mainly associated) with a possible slight preference for lipids, and (2) fractionation due to parasite metabolism should be low due to abbreviated metabolic pathways and/or slight loss of materials through excretion, tegument diffusion and

  8. The effects of swift heavy ion irradiation on the structural properties of poly(lactide-co-glycolide)/clay nanocomposite

    NASA Astrophysics Data System (ADS)

    Kaur, Manpreet; Singh, Surinder; Mehta, Rajeev

    2016-05-01

    Radiation has been used as a processing technique to modify structural, chemical, physical and morphological properties of polymers and its nanocomposite and can thus be used as a method to control the rate of degradation. The swift heavy ions (SHI) irradiation effects on the structural properties of poly(lactide-co-glycolide) nanocomposites containing 5wt% organo-montmorillonite (OMMT) clay by irradiating with 50 MeV Li3+ and 180 MeV Ag8+ ions has been studied at different fluences. The structural responses of PLGA nanocomposite under the influence of SHI were studied using Fourier transform infrared (FTIR) spectroscopy. The presence of clay and irradiation by swift heavy ions (SHI) brings out interesting changes in structural properties of nanocomposite.

  9. College Student Mentors and Latino Youth: A Qualitative Study of the Mentoring Relationship

    ERIC Educational Resources Information Center

    Knoche, Lisa L.; Zamboanga, Byron L.

    2006-01-01

    This phenomenological study describes the meaning of mentoring relationships from the perspectives of six purposefully selected mentors involved in the Latino Achievement Mentoring Program (LAMP), and investigates underlying themes regarding the mentors' relationships. Clusters of themes pertaining to the mentors' relationship with the mentee, the…

  10. Exploring Familial Relationship Growth and Negotiation: A Case Study of Outward Bound Family Courses

    ERIC Educational Resources Information Center

    Overholt, Jillisa R.

    2013-01-01

    This study explored the phenomenon of father-child relationship development within the context of an Outward Bound (OB) family course, an environment that may both disrupt the ordinary aspects of an established relationship, and provide activities to purposefully encourage relationship development through a variety of aspects inherent to the…

  11. Study of the relationship between solar activity and terrestrial weather

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.; Brueckner, G. E.; Dickinson, R. E.; Fukuta, N.; Lanzerotti, L. J.; Lindzen, R. S.; Park, C. G.; Wilcox, J. M.

    1976-01-01

    Evidence for some connection between weather and solar related phenomena is presented. Historical data of world wide temperature variations with relationship to change in solar luminosity are examined. Several test methods for estimating the statistical significance of such phenomena are discussed in detail.

  12. Magnetic and structural properties of Ba M-type ferrite-composite powders

    NASA Astrophysics Data System (ADS)

    Paul, K. B.

    2007-01-01

    The goal of the work is to study the interparticle interactions, magnetic and structural properties of the M-type barium ferrite-composite powders BaFe8(Ti0.5Mn0.5)4O19 and BaFe8.5(Ti0.5Mn0.5)3.5O19 with packing densities ∼75%, embedded in synthetic rubber. The physical properties of the materials are investigated in a wide temperature range for their characterization and device adaptation down to a cryogenic environment. The development of the macromagnetic parameters, such as remanence, coercitivity, and squareness of the hysteresis loops, is observed upon change of the Fe composition. The interparticle interactions are estimated based on DC magnetic measurements. The dynamic magnetic properties of these composites are correlated to the dynamic characteristics of some disordered spin-glass-like materials.

  13. The effects of 7-dehydrocholesterol on the structural properties of membranes

    NASA Astrophysics Data System (ADS)

    Liu, Yingzhe; Chipot, Christophe; Shao, Xueguang; Cai, Wensheng

    2011-10-01

    Smith-Lemli-Opitz syndrome, a congenital and developmental malformation disease, is typified by abnormal accumulation of 7-dehydrocholesterol (7DHC), the immediate precursor of cholesterol (CHOL), and depletion thereof. Knowledge of the effect of 7DHC on the biological membrane is, however, still fragmentary. In this study, large-scale atomistic molecular dynamics simulations, employing two distinct force fields, have been conducted to elucidate differences in the structural properties of a hydrated dimyristoylphosphatidylcholine bilayer due to CHOL and 7DHC. The present series of results indicate that CHOL and 7DHC possess virtually the same ability to condense and order membranes. Furthermore, the condensing and ordering effects are shown to be strengthened at increasing sterol concentrations.

  14. Effect of Operating Temperature on Structure Properties of TICX Nanoparticle Coating Applied by Pacvd

    NASA Astrophysics Data System (ADS)

    Shanaghi, Ali; Sabour Rouhaghdam, Ali Reza; Ahangarani, Shahrokh; Moradi, Hadi; Mohammadi, Ali

    Titanium carbide (TiC) is a widely used hard coating to improve the wear resistance and lifetime of tools because of its outstanding properties such as high melting point, high hardness, corrosion resistance and abrasion resistance. These properties were drastically improved by using nanotechnology. So in this project, TiCx was applied on hot-working die steel (H11) by Plasma CVD (PACVD). The effect of operating temperatures on TiCx structure properties have been studies by typical and advanced analyses methods such as SEM, XRD, FTIR and Raman. The best properties of TiCx nanoparticle, such as nanostructure, mechanical properties and chemical properties, were obtained at 480 °C.

  15. Molecular and structural properties of polymer composites filled with activated charcoal particles

    NASA Astrophysics Data System (ADS)

    Tahir, Dahlang; Liong, Syarifuddin; Bakri, Fahrul

    2016-03-01

    We have studied the molecular properties, structural properties, and chemical composition of composites by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, and X-ray fluorescence (XRF) spectroscopy, respectively. FTIR spectra shows absorption band of hydroxyl group (-OH), methyl group (-CH3) and aromatic group (C-C). The absorption band for aromatic group (C-C) shows the formation of carbonaceous in composites. XRF shows chemical composition of composites, which the main chemicals are SO3, Cl, and ZnO. The loss on ignition value (LOI) of activated charcoal indicates high carbonaceous matter. The crystallite size for diffraction pattern from hydrogel polymer is about 17 nm and for activated charcoal are about 19 nm. The crystallite size of the polymer is lower than that of activated charcoal, which make possible of the particle from filler in contact with each other to form continuous conducting polymer through polymer matrix.

  16. Structural Properties and Estimation of Delay Systems. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Kwong, R. H. S.

    1975-01-01

    Two areas in the theory of delay systems were studied: structural properties and their applications to feedback control, and optimal linear and nonlinear estimation. The concepts of controllability, stabilizability, observability, and detectability were investigated. The property of pointwise degeneracy of linear time-invariant delay systems is considered. Necessary and sufficient conditions for three dimensional linear systems to be made pointwise degenerate by delay feedback were obtained, while sufficient conditions for this to be possible are given for higher dimensional linear systems. These results were applied to obtain solvability conditions for the minimum time output zeroing control problem by delay feedback. A representation theorem is given for conditional moment functionals of general nonlinear stochastic delay systems, and stochastic differential equations are derived for conditional moment functionals satisfying certain smoothness properties.

  17. Optical and structural properties of sulfur-doped ELOG InP on Si

    SciTech Connect

    Sun, Yan-Ting Junesand, Carl; Metaferia, Wondwosen; Kataria, Himanshu; Lourdudoss, Sebastian; Julian, Nick; Bowers, John; Pozina, Galia; Hultman, Lars

    2015-06-07

    Optical and structural properties of sulfur-doped epitaxial lateral overgrowth (ELOG) InP grown from nano-sized openings on Si are studied by room-temperature cathodoluminescence and cross-sectional transmission electron microscopy (XTEM). The dependence of luminescence intensity on opening orientation and dimension is reported. Impurity enhanced luminescence can be affected by the facet planes bounding the ELOG layer. Dark line defects formed along the [011] direction are identified as the facet planes intersected by the stacking faults in the ELOG layer. XTEM imaging in different diffraction conditions reveals that stacking faults in the seed InP layer can circumvent the SiO{sub 2} mask during ELOG and extend to the laterally grown layer over the mask. A model for Suzuki effect enhanced stacking fault propagation over the mask in sulfur-doped ELOG InP is constructed and in-situ thermal annealing process is proposed to eliminate the seeding stacking faults.

  18. Influence of consolidation method on structure/properties of rapidly solidified Type 304 SS powders

    SciTech Connect

    Flinn, J.E.; Korth, G.E.; Wright, R.N.

    1988-01-01

    The structure/properties of consolidated, centrifugally atomized (CA) Type 304 SS powders containing approx.8 appM helium entrapped during powder processing were evaluated. Three powder consolidation methods were used in the study: hot extrusion, hot isostatic pressing (HIPping), and dynamic (using explosives). In addition, cold-rolled 50% HIPped material was included in the evaluation. The four forms of consolidated powders were fully dense and possessed good bond strengths. The bond strength of the HIPped powders was the lowest. The consolidated materials were subjected to 1 h heat treatments and their grain growth, tensile, and creep behaviors were compared with those of wrought ingot metallurgy Type 304 SS materials. Grain growth of the CA Type 304 SS consolidated powders was substantially lower than for the wrought material. Similarly, significant strengthening was observed for the powder materials. The apparent microstructure stability and strengthening observed for the consolidated powder materials is attributed to the entrapped helium. 5 figs., 4 tabs.

  19. Melting curves and structural properties of tantalum from the modified-Z method

    NASA Astrophysics Data System (ADS)

    Liu, C. M.; Xu, C.; Cheng, Y.; Chen, X. R.; Cai, L. C.

    2015-12-01

    The melting curves and structural properties of tantalum (Ta) are investigated by molecular dynamics simulations combining with potential model developed by Ravelo et al. [Phys. Rev. B 88, 134101 (2013)]. Before calculations, five potentials are systematically compared with their abilities of producing reasonable compressional and equilibrium mechanical properties of Ta. We have improved the modified-Z method introduced by Wang et al. [J. Appl. Phys. 114, 163514 (2013)] by increasing the sizes in Lx and Ly of the rectangular parallelepiped box (Lx = Ly ≪ Lz). The influences of size and aspect ratio of the simulation box to melting curves are also fully tested. The structural differences between solid and liquid are detected by number density and local-order parameters Q6. Moreover, the atoms' diffusion with simulation time, defects, and vacancies formations in the sample are all studied by comparing situations in solid, solid-liquid coexistence, and liquid state.

  20. A review of bioactive glasses: Their structure, properties, fabrication and apatite formation.

    PubMed

    Kaur, Gurbinder; Pandey, Om P; Singh, Kulvir; Homa, Dan; Scott, Brian; Pickrell, Gary

    2014-01-01

    Bioactive glass and glass-ceramics are used in bone repair applications and are being developed for tissue engineering applications. Bioactive glasses/Bioglass are very attractive materials for producing scaffolds devoted to bone regeneration due to their versatile properties, which can be properly designed depending on their composition. An important feature of bioactive glasses, which enables them to work for applications in bone tissue engineering, is their ability to enhance revascularization, osteoblast adhesion, enzyme activity and differentiation of mesenchymal stem cells as well as osteoprogenitor cells. An extensive amount of research work has been carried out to develop silicate, borate/borosilicate bioactive glasses and phosphate glasses. Along with this, some metallic glasses have also been investigated for biomedical and technological applications in tissue engineering. Many trace elements have also been incorporated in the glass network to obtain the desired properties, which have beneficial effects on bone remodeling and/or associated angiogenesis. The motivation of this review is to provide an overview of the general requirements, composition, structure-property relationship with hydroxyapatite formation and future perspectives of bioglasses.Attention has also been given to developments of metallic glasses and doped bioglasses along with the techniques used for their fabrication.

  1. A NON-LINEAR STRUCTURE-PROPERTY MODEL FOR OCTANOL-WATER PARTITION COEFFICIENT

    PubMed Central

    Yerramsetty, Krishna M.; Neely, Brian J.; Gasem, Khaled A. M.

    2012-01-01

    Octanol-water partition coefficient (Kow) is an important thermodynamic property used to characterize the partitioning of solutes between an aqueous and organic phase and has importance in such areas as pharmacology, pharmacokinetics, pharmacodynamics, chemical production and environmental toxicology. We present a non-linear quantitative structure-property relationship model for determining Kow values of new molecules in silico. A total of 823 descriptors were generated for 11,308 molecules whose Kow values are reported in the PhysProp dataset by Syracuse Research. Optimum network architecture and its associated inputs were identified using a wrapper-based feature selection algorithm that combines differential evolution and artificial neural networks. A network architecture of 50-33-35-1 resulted in the least root-mean squared error (RMSE) in the training set. Further, to improve on single-network predictions, a neural network ensemble was developed by combining five networks that have the same architecture and inputs but differ in layer weights. The ensemble predicted the Kow values with RMSE of 0.28 and 0.38 for the training set and internal validation set, respectively. The ensemble performed reasonably well on an external dataset when compared with other popular Kow models in the literature. PMID:23185102

  2. [A study on the relationship between women's employment and fertility].

    PubMed

    Cho, A J; Kong, S K

    1988-07-01

    The Korean Family Life Cycle Survey data on women's employment are used to explore variations in women's employment patterns and the relationship between women's employment and fertility. In general, employment rates increase with women's age. Women in rural areas are more likely to work than those in urban areas. These patterns are clearly linked to different work opportunity structures. As a rule, the most educated and the least educated are more likely to work, whereas respondents in the middle educational categories were least likely. It has already been recognized that the employment period during the life course may be related to fertility in various ways. 1 is delay of marriage among women who work before they marry. The relatively better financial situation of unmarried working women contributes to the desire to extend single life compared with non-working women. In addition, particular types of work may provide exposure to ideas and norms that discourage early marriage. It may also be true that single working women who contribute to household income have some influence on women's decision to postpone marriage. The results show that women who work before marriage marry somewhat later than women who never work before marriage. For example, women who were in professional and clerical occupations married about 3 years later than women who had not worked before marriage. Among women who had been employed before marriage, age at marriage differed according to different occupations. For example, women with working experience in professional and clerical occupations had the highest mean age at marriage. An analysis of the relationship between women's employment and fertility shows that women in professional and clerical work bear somewhat fewer children on average than women with no recorded economic activity. In domestic household employee and agricultural work, however, no such relationship is observed. The relationship between occupation and fertility is

  3. Individual-Oriented Relationship Education: An Evaluation Study in Community-Based Settings.

    PubMed

    Visvanathan, Pallavi D; Richmond, Melissa; Winder, Chandra; Koenck, Cynthia Hoskins

    2015-12-01

    The effects of relationship education aimed at individuals, rather than couples, have not yet been widely investigated. However, increasingly, relationship education is provided to large and diverse groups of individuals who may be in varying stages of relationships. Several programs have been developed to strengthen relationship competencies among single individuals as well as among partnered individuals who, for a variety of reasons, seek relationship education without their partners. The current study is an exploratory evaluation study that examined self-reported outcomes for 706 single and partnered individuals who attended Within My Reach classes delivered in community-based agencies. Participants were from diverse backgrounds and exhibited many of the risk factors for poor relationship outcomes including unemployment, low income, and childhood experience of abuse or neglect. Pre-post analyses indicated that the program was beneficial for both singles and partnered individuals. Singles reported increased belief in ability to obtain healthy relationships. Partnered individuals reported increased relationship quality, relationship confidence, and reduced conflict. Regardless of relationship status, participants also reported improvement in general relationship and communication skill. Results support the utility of individual-oriented relationship education for singles and partnered individuals with diverse background characteristics.

  4. Structural properties of thermoresponsive poly(N-isopropylacrylamide)-poly(ethyleneglycol) microgels

    NASA Astrophysics Data System (ADS)

    Clara-Rahola, J.; Fernandez-Nieves, A.; Sierra-Martin, B.; South, A. B.; Lyon, L. A.; Kohlbrecher, J.; Fernandez Barbero, A.

    2012-06-01

    We present investigations of the structural properties of thermoresponsive poly(N-isopropylacrylamide) (PNiPAM) microgels dispersed in an aqueous solvent. In this particular work poly(ethyleneglycol) (PEG) units flanked with acrylate groups are employed as cross-linkers, providing an architecture designed to resist protein fouling. Dynamic light scattering (DLS), static light scattering (SLS), and small angle neutron scattering (SANS) are employed to study the microgels as a function of temperature over the range 10 °C ≤ T ≤ 40 °C. DLS and SLS measurements are simultaneously performed and, respectively, allow determination of the particle hydrodynamic radius, Rh, and radius of gyration, Rg, at each temperature. The thermal variation of these magnitudes reveals the microgel deswelling at the PNiPAM lower critical solution temperature (LCST). However, the hydrodynamic radius displays a second transition to larger radii at temperatures T ≤ 20 °C. This feature is atypical in standard PNiPAM microgels and suggests a structural reconfiguration within the polymer network at those temperatures. To better understand this behavior we perform neutron scattering measurements at different temperatures. In striking contrast to the scattering profile of soft sphere microgels, the SANS profiles for T ≤ LCST of our PNiPAM-PEG suspensions indicate that the particles exhibit structural properties characteristic of star polymer configurations. The star polymer radius of gyration and correlation length gradually decrease with increasing temperature despite maintenance of the star polymer configuration. At temperatures above the LCST, the scattered SANS intensity is typical of soft sphere systems.

  5. Finding a Balance: Fifteen Institutional Case Studies on the Relationship between Part-Time Work and Advanced Level Study. Report.

    ERIC Educational Resources Information Center

    Hodgson, Ann, Ed.; Spours, Ken, Ed.

    This document presents and discusses case studies that examined the relationship between part-time employment and advanced level study at 15 schools in Essex, England. "Foreword" (David Jones) provides a brief overview of the project. "Finding a Balance--Fifteen Institutional Case Studies on the Relationship between Part-time Work and Advanced…

  6. Rekindling Phlogiston: From Classroom Case Study to Interdisciplinary Relationships

    NASA Astrophysics Data System (ADS)

    Allchin, Douglas

    First, I show how to use the concept of phlogiston to teach oxidation and reduction reactions, based on the historical context of their discovery, while also teaching about the history and nature of science. Second, I discuss the project as an exemplar for integrating history, philosophy and sociology of science in teaching basic scientific concepts. Based on this successful classroom experience, I critique the application of common constructivist themes to teaching practice. Finally, this case shows, along with others, how the classroom is not merely a place for applying history, philosophy or sociology, but is also a site for active research in these areas. This potential is critical, I claim, for building a stable, permanent interdisciplinary relationships between these fields.

  7. Perceptions of Student-Teacher Relationships and GED Completion: A Correlational Study

    ERIC Educational Resources Information Center

    Hairston, Melissa Tynetta

    2013-01-01

    This study took an in depth look at student-teacher relationships as one institutional barrier affecting GED completion among adults. The purpose of this study was to examine the perceptions of student-instructor relationships, specifically Instructor Connectedness and Instructor Anxiety, and its effects on adults seeking GED completion. Data from…

  8. A Case Study on Two Advisor-Advisee Relationships in a Master's TESOL Program in Taiwan

    ERIC Educational Resources Information Center

    Chen, Cheryl Wei-yu

    2010-01-01

    Situated in an MA TESOL program in a large Taiwanese university, this study is a qualitative case study on two advising relationships. Three central issues were examined closely: (a) the nature of the advising relationships; (b) the challenges students encountered in the process of completing their theses; and (c) the advisors and advisee's…

  9. Fifth-Grade Teachers' Social Studies Knowledge and Beliefs and Their Relationship to Classroom Practices

    ERIC Educational Resources Information Center

    Harcarik, Michele

    2009-01-01

    This mixed methods study investigates the relationship between fifth-grade teachers' social studies knowledge and beliefs and their relationship to classroom practices. Quantitative data were collected through a beliefs and classroom practices survey and 60-item knowledge test covering the areas of American History, America and the World,…

  10. A Study of Social-Emotional Adjustment Levels of Preschool Children in Relation to Peer Relationships

    ERIC Educational Resources Information Center

    Gülay, Hülya; Önder, Alev

    2013-01-01

    The aim of this research is to study social--emotional adaptation levels of 5-to 6-year old preschool children in relation to peer relationships. One hundred and forty-four children aged between 5 and 6 joined in this relational survey study. According to the results of the research analysing the relationship between the social-emotional…

  11. An Exploratory Study of the Relationship between Attention-Deficit Hyperactivity Disorder and Youth Homelessness

    ERIC Educational Resources Information Center

    Harding, Blake

    2014-01-01

    A 1997 study by Lomas and Garside suggests a 62% prevalence rate of ADHD [Attention-Deficit Hyperactivity Disorder] amongst homeless, which prompts a need for further elucidation of this relationship. This study sought to examine the relationship between Attention-Deficit Hyperactivity Disorder and the homeless youth population aged 18-24. The…

  12. A Study of the Relationship between Historical Analysis and Student Achievement in Eighth Grade American History

    ERIC Educational Resources Information Center

    Stuart, Kevin

    2010-01-01

    The purpose of this action research project was to study the relationship between Historical Analysis and student performance on the California Standards Test (CSTs), both English Language Arts and History, as well as to study the relationship between Historical Analysis and Reading Comprehension. It was believed that Historical Analysis required…

  13. Novel thiosemicarbazone derivatives as potential antitumor agents: Synthesis, physicochemical and structural properties, DNA interactions and antiproliferative activity.

    PubMed

    Dilović, Ivica; Rubcić, Mirta; Vrdoljak, Visnja; Kraljević Pavelić, Sandra; Kralj, Marijeta; Piantanida, Ivo; Cindrić, Marina

    2008-05-01

    The paper describes synthesis of several novel thiosemicarbazone derivatives. Furthermore, crystal and molecular structure of 4-diethylamino-salicylaldehyde 4-phenylthiosemicarbazone revealed planarity of conjugated aromatic system, which suggested the possibility of DNA binding by intercalation, especially for here studied naphthalene derivatives. However, here presented DNA binding studies excluded this mode of action. Physicochemical and structural properties of novel derivatives were compared with previously studied analogues, taken as reference compounds, revealing distinctive differences. In addition, novel thiosemicarbazone derivatives (1, 2 and 5-8) clearly display stronger antiproliferative activity on five tumor cell lines than the reference compounds 3 and 4, which supports their further investigation as potential antitumor agents.

  14. Verb production in agrammatic aphasia: The influence of semantic class and argument structure properties on generalisation

    PubMed Central

    Schneider, Sandra L.; Thompson, Cynthia K.

    2011-01-01

    Background Some individuals with agrammatic aphasia have difficulty producing verbs when naming and generating sentences (Miceli, Silveri, Villa, & Caramazza, 1984; Saffran, Schwartz, & Marin, 1980; Zingeser & Berndt, 1990). And when verbs are produced there is an over-reliance on verbs requiring simple argument structure arrangements (Thompson, Lange, Schneider, & Shapiro, 1997; Thompson, Shapiro, Schneider, & Tait, 1994). Verbs, as argument-taking elements, show especially complex semantic and argument structure properties. This study investigated the role these properties have on verb production in individuals with agrammatic aphasia. Aim This treatment study examined the extent to which semantic class and argument structure properties of verbs influenced the ability of seven individuals with agrammatic Broca’s aphasia to retrieve verbs and then use them in correct sentence production. Verbs from two semantic classes and two argument structure categories were trained using either a semantic or an argument structure verb retrieval treatment. Specifically, acquisition and generalisation to trained and untrained verbs within and across semantic and argument structure categories was examined. In addition, the influence of verb production on each participant’s sentence production was also examined. Methods & Procedures Utilising a single-subject crossover design in combination with a multiple baseline design across subjects and behaviours, seven individuals with agrammatic aphasia were trained to retrieve verbs with specific argument structures from two semantic classes under two treatment conditions—semantic verb retrieval treatment and verb argument structure retrieval treatment. Treatment was provided on two-place and three-place motion or change of state verbs, counterbalanced across subjects and behaviours. A total of 102 verbs, depicted in black and white drawings, were utilised in the study, divided equally into motion and change of state verbs (semantic

  15. Verb production in agrammatic aphasia: The influence of semantic class and argument structure properties on generalisation.

    PubMed

    Schneider, Sandra L; Thompson, Cynthia K

    2003-01-01

    BACKGROUND: Some individuals with agrammatic aphasia have difficulty producing verbs when naming and generating sentences (Miceli, Silveri, Villa, & Caramazza, 1984; Saffran, Schwartz, & Marin, 1980; Zingeser & Berndt, 1990). And when verbs are produced there is an over-reliance on verbs requiring simple argument structure arrangements (Thompson, Lange, Schneider, & Shapiro, 1997; Thompson, Shapiro, Schneider, & Tait, 1994). Verbs, as argument-taking elements, show especially complex semantic and argument structure properties. This study investigated the role these properties have on verb production in individuals with agrammatic aphasia. AIM: This treatment study examined the extent to which semantic class and argument structure properties of verbs influenced the ability of seven individuals with agrammatic Broca's aphasia to retrieve verbs and then use them in correct sentence production. Verbs from two semantic classes and two argument structure categories were trained using either a semantic or an argument structure verb retrieval treatment. Specifically, acquisition and generalisation to trained and untrained verbs within and across semantic and argument structure categories was examined. In addition, the influence of verb production on each participant's sentence production was also examined. METHODS #ENTITYSTARTX00026; PROCEDURES: Utilising a single-subject crossover design in combination with a multiple baseline design across subjects and behaviours, seven individuals with agrammatic aphasia were trained to retrieve verbs with specific argument structures from two semantic classes under two treatment conditions-semantic verb retrieval treatment and verb argument structure retrieval treatment. Treatment was provided on two-place and three-place motion or change of state verbs, counterbalanced across subjects and behaviours. A total of 102 verbs, depicted in black and white drawings, were utilised in the study, divided equally into motion and change of state

  16. Multilocus Sequence Typing for Studying Genetic Relationships among Yersinia Species

    PubMed Central

    Kotetishvili, Mamuka; Kreger, Arnold; Wauters, Georges; Morris, J. Glenn; Sulakvelidze, Alexander; Stine, O. Colin

    2005-01-01

    The intra- and interspecies genetic relationships of 58 strains representing all currently known species of the genus Yersinia were examined by multilocus sequence typing (MLST), using sequence data from 16S RNA, glnA, gyrB, recA, and Y-HSP60 loci. Yersinia aldovae, Y. bercovieri, Y. intermedia, Y. pestis, Y. pseudotuberculosis, Y. rohdei, and Y. ruckeri were genetically more homogeneous than were Y. enterocolitica, Y. frederiksenii, Y. kristensenii, and Y. mollaretii. The MLST data concerning the genetic relatedness within and among various species of Yersinia support the idea that Y. pestis and Y. pseudotuberculosis are two lineages within the same species rather than two distinct species. Y. ruckeri is the genetically most distant species within the genus. There was evidence of O-antigen switching and genetic recombination within and among various species of Yersinia. The genetic relatedness data obtained by MLST of the four housekeeping genes and 16S RNA agreed in most, but not all, instances. MLST was better suited for determining genetic relatedness among yersiniae than was 16S RNA analysis. Some strains of Y. frederiksenii and Y. kristensenii are genetically less related to other strains within those species, compared to strains of all other species within the genus. The taxonomic standing of these strains should be further examined because they may represent currently unrecognized Yersinia species. PMID:15956383

  17. Multilocus sequence typing for studying genetic relationships among Yersinia species.

    PubMed

    Kotetishvili, Mamuka; Kreger, Arnold; Wauters, Georges; Morris, J Glenn; Sulakvelidze, Alexander; Stine, O Colin

    2005-06-01

    The intra- and interspecies genetic relationships of 58 strains representing all currently known species of the genus Yersinia were examined by multilocus sequence typing (MLST), using sequence data from 16S RNA, glnA, gyrB, recA, and Y-HSP60 loci. Yersinia aldovae, Y. bercovieri, Y. intermedia, Y. pestis, Y. pseudotuberculosis, Y. rohdei, and Y. ruckeri were genetically more homogeneous than were Y. enterocolitica, Y. frederiksenii, Y. kristensenii, and Y. mollaretii. The MLST data concerning the genetic relatedness within and among various species of Yersinia support the idea that Y. pestis and Y. pseudotuberculosis are two lineages within the same species rather than two distinct species. Y. ruckeri is the genetically most distant species within the genus. There was evidence of O-antigen switching and genetic recombination within and among various species of Yersinia. The genetic relatedness data obtained by MLST of the four housekeeping genes and 16S RNA agreed in most, but not all, instances. MLST was better suited for determining genetic relatedness among yersiniae than was 16S RNA analysis. Some strains of Y. frederiksenii and Y. kristensenii are genetically less related to other strains within those species, compared to strains of all other species within the genus. The taxonomic standing of these strains should be further examined because they may represent currently unrecognized Yersinia species.

  18. Structural properties of hexaphenyl powder under high pressure

    SciTech Connect

    Guha, S.; Graupner, W.; Resel, R.; Chandrasekhar, M.; Chandrasekhar, H.R.; Leising, G.

    1998-07-01

    The authors present X-ray and Raman studies of the conjugated oligomer, hexaphenyl, which forms polycrystalline layers. The Raman studies have been carried out under hydrostatic pressures up to 70 kbar. The relative intensity of the two modes at 1,220 cm{sup {minus}1} and 1,280 cm{sup {minus}1} shows the influence of planarization under hydrostatic pressure. These results are interpreted within the framework of theoretical calculations and compared with X-ray studies.

  19. Parent-infant relationship global assessment scale: a study of its predictive validity.

    PubMed

    Aoki, Yutaka; Zeanah, Charles H; Heller, Sherryl Scott; Bakshi, Sudha

    2002-10-01

    The Parent-Infant Relationship Global Assessment Scale (PIRGAS; Zero to Three, 1994) provides a continuously distributed scale of infant-parent relationship adaptation, raging from 'well-adapted' to 'dangerously impaired'. The present study examines the predictive validity of the PIRGAS in a high-risk sample by coding relationship adaptation level from a single sample of 10 min of unstructured free play between mothers and their 20-month-old infants and examining its relationship to subsequent interaction with mothers and behavior problems at 24 months. Relationship adaptation assessed reliably from observations of only 10 min of free play between mothers and their infants at 20 months of age using PIRGAS predicted subsequent mother- infant interaction in a laboratory based problem-solving paradigm (Crowell procedure) at 24 months and internalizing symptomatology of Child Behavior Checklist at age 24 months. These results contribute to the predictive validity of the PIRGAS as a measure of mother-infant relationship adaptation.

  20. Client-public health nurse relationships in child health care: a grounded theory study.

    PubMed

    Vehviläinen-Julkunen, K

    1992-08-01

    Client-public health nurse relationships are considered to be important in nursing literature. However, little research in nursing has touched this area. The purpose of this paper is to describe a study of the patterns of interaction in terms of relationships between clients (mother and child under 1 year of age) and public health nurses in child health care at Finnish health centres. The qualitative data were collected by observing client-public health nurse interactions during visits. In total, 1554 interactions were observed over 2 years from 20 visits to child health centres. The grounded theory method was used in this study. Various relationships were identified between child and mother, child and public health nurse and mother and public health nurse. The relationship between child and mother during the visit was called a tender, protective and persuasive relationship. The relationship between child and public health nurse was called a persuasive and entertainment relationship. The main relationship between mother and public health nurse was called relationship supporting self-confidence. Suggestions for nursing practice and further research are made. PMID:1506539

  1. Structural properties and energetics of diffuse 87Rb clusters in three-dimension.

    PubMed

    Debnath, Pankaj Kumar; Chakrabarti, Barnali; Das, Tapan Kumar; Canuto, Sylvio

    2012-07-01

    A correlated two-body basis function is used to describe the three-dimensional bosonic clusters interacting via two-body van der Waals potential. We calculate the ground state and the zero orbital angular momentum excited states for Rb(N) clusters with up to N = 40. We solve the many-particle Schrödinger equation by potential harmonics expansion method, which keeps all possible two-body correlations in the calculation and determines the lowest effective many-body potential. We study energetics and structural properties for such diffuse clusters both at dimer and tuned scattering length. The motivation of the present study is to investigate the possibility of formation of N-body clusters interacting through the van der Waals interaction. We also compare the system with the well studied He, Ne, and Ar clusters. We also calculate correlation properties and observe the generalised Tjon line for large cluster. We test the validity of the shape-independent potential in the calculation of the ground state energy of such diffuse cluster. These are the first such calculations reported for Rb clusters. PMID:22779642

  2. Gas-diffusion-layer structural properties under compression via X-ray tomography

    NASA Astrophysics Data System (ADS)

    Zenyuk, Iryna V.; Parkinson, Dilworth Y.; Connolly, Liam G.; Weber, Adam Z.

    2016-10-01

    There is a need to understand the structure properties of gas-diffusion layers (GDLs) in order to optimize their performance in various electrochemical devices. This information is important for mathematical modelers, experimentalists, and designers. In this article, a comprehensive study of a large set of commercially available GDLs' porosity, tortuosity, and pore-size distribution (PSD) under varying compression is presented in a single study using X-ray computed tomography (CT), which allows for a noninvasive measurement. Porosities and PSDs are directly obtained from reconstructed stacks of images, whereas tortuosity is computed with a finite-element simulation. Bimodal PSDs due to the presence of binder are observed for most of the GDLs, approaching unimodal distributions at high compressions. Sample to sample variability is conducted to show that morphological properties hold across various locations. Tortuosity values are the lowest for MRC and Freudenberg, highest for TGP, and in-between for SGL papers. The exponents for the MRC and Freudenberg tortuosity demonstrate a very small dependence on compression because the shapes of the pores are spherical indicating minimal heterogeneity. From the representative-elementary-volume studies it is shown that domains of 1 × 1 mm in-plane and full thickness in through-plane directions accurately represent GDL properties.

  3. PGS:Gelatin nanofibrous scaffolds with tunable mechanical and structural properties for engineering cardiac tissues.

    PubMed

    Kharaziha, Mahshid; Nikkhah, Mehdi; Shin, Su-Ryon; Annabi, Nasim; Masoumi, Nafiseh; Gaharwar, Akhilesh K; Camci-Unal, Gulden; Khademhosseini, Ali

    2013-09-01

    A significant challenge in cardiac tissue engineering is the development of biomimetic grafts that can potentially promote myocardial repair and regeneration. A number of approaches have used engineered scaffolds to mimic the architecture of the native myocardium tissue and precisely regulate cardiac cell functions. However, previous attempts have not been able to simultaneously recapitulate chemical, mechanical, and structural properties of the myocardial extracellular matrix (ECM). In this study, we utilized an electrospinning approach to fabricate elastomeric biodegradable poly(glycerol sebacate) (PGS):gelatin nanofibrous scaffolds with a wide range of chemical composition, stiffness and anisotropy. Our findings demonstrated that through incorporation of PGS, it is possible to create nanofibrous scaffolds with well-defined anisotropy that mimic the left ventricular myocardium architecture. Furthermore, we studied attachment, proliferation, differentiation and alignment of neonatal rat cardiac fibroblast cells (CFs) as well as protein expression, alignment, and contractile function of cardiomyocyte (CMs) on PGS:gelatin scaffolds with variable amount of PGS. Notably, aligned nanofibrous scaffold, consisting of 33 wt. % PGS, induced optimal synchronous contractions of CMs while significantly enhanced cellular alignment. Overall, our study suggests that the aligned nanofibrous PGS:gelatin scaffold support cardiac cell organization, phenotype and contraction and could potentially be used to develop clinically relevant constructs for cardiac tissue engineering.

  4. A Study of the Relationship between Students' Anxiety and Test Performance on State-Mandated Assessments

    ERIC Educational Resources Information Center

    Hernandez, Rosalinda; Menchaca, Velma; Huerta, Jeffery

    2011-01-01

    This study examined whether relationships exist between Hispanic fourth-grade students' anxiety and test performance on a state-mandated writing assessment. Quantitative methodologies were employed by using test performance and survey data from 291 participants. While no significantly direct relationship exists between students' levels of anxiety…

  5. Does Youth Relationship Education Continue to Work after a High School Class? A Longitudinal Study

    ERIC Educational Resources Information Center

    Gardner, Scott P.; Boellaard, Rila

    2007-01-01

    "Connections: Relationships and Marriage" ("Connections") is a high school marriage education curriculum designed to teach students how to develop healthy relationships and marriages. This study evaluated the effectiveness of this curriculum over 4-years postintervention with a matched set of 72 high school students who were in either the…

  6. Comparing Institutional Relationships with Academic Departments: A Study of Five Academic Fields

    ERIC Educational Resources Information Center

    Lee, Jenny J.

    2004-01-01

    Any effort to understand academic departments would be facilitated by a better understanding of its relationship between its two larger spheres: the institution and the discipline. This study particularly asks: How do the relationships between institutional culture and the culture of the academic department vary by disciplinary field? Using…

  7. Four Views of the Professional School Counselor-Principal Relationship: A Q-Methodology Study

    ERIC Educational Resources Information Center

    Janson, Christopher; Militello, Matthew; Kosine, Natalie

    2008-01-01

    This study in this article investigated how school counselors and principals perceive their professional relationship. Q methodology was used to develop 45 opinion statements about the relationship between school counselors and principals, and 39 professional school counselors and principals then sorted the statements. Four factors emerged…

  8. The Close Relationships of People with Intellectual Disabilities: A Qualitative Study

    ERIC Educational Resources Information Center

    Sullivan, Faye; Bowden, Keith; McKenzie, Karen; Quayle, Ethel

    2016-01-01

    Background: Positive interpersonal relationships have been found to enhance an individual's quality of life. However, people with intellectual disabilities (PWID) often have restricted social networks, and little is known about their views on close social relationships. The study aimed to explore how this group perceives and experiences close…

  9. Exploring Stakeholder Relationships in a University Internship Program: A Qualitative Study

    ERIC Educational Resources Information Center

    Hoyle, Jeffrey A.

    2013-01-01

    This study explores stakeholder relationships between the key stakeholders of a public university, private employers, and university students in a marketing undergraduate internship program. By exploring these relationships through the process of stakeholder analysis a deeper understanding of the power dynamics between key stakeholders emerged.…

  10. Shifts in Attachment Relationships: A Study of Adolescents in Wilderness Treatment

    ERIC Educational Resources Information Center

    Bettmann, Joanna E.; Tucker, Anita R.

    2011-01-01

    This study examined shifts in adolescents' attachment relationships with parents and peers during a 7-week wilderness therapy program. Ninety-six adolescents, aged 14-17, completed three quantitative measurements evaluating attachment relationships with mother, father and peers pre and post treatment. Adolescents reported improved attachment…

  11. Job Satisfaction and Teacher-Student Relationships across the Teaching Career: Four Case Studies

    ERIC Educational Resources Information Center

    Veldman, Ietje; van Tartwijk, Jan; Brekelmans, Mieke; Wubbels, Theo

    2013-01-01

    We studied the development of teacher-student relationships and teachers' job satisfaction throughout the careers of four veteran teachers who retained high job satisfaction. Teacher data gathered with the narrative-biographical method were compared with students' perceptions of the teacher-student relationships, using the Questionnaire on Teacher…

  12. Moral Orientation and Relationships in School and Adolescent Pro- and Antisocial Behaviors: A Multilevel Study

    ERIC Educational Resources Information Center

    Wissink, Inge B.; Dekovic, Maja; Stams, Geert-Jan; Asscher, Jessica J.; Rutten, Esther; Zijlstra, Bonne J. H.

    2014-01-01

    This multilevel study examined the relationships between moral climate factors and prosocial as well as antisocial behaviors inside and outside the school (school misconduct, delinquent behavior, and vandalism). The moral climate factors were punishment-and victim-based moral orientation, relationships among students, and teacher-student…

  13. Childhood Abuse and Neglect and Adult Intimate Relationships: A Prospective Study

    ERIC Educational Resources Information Center

    Colman, R.A.; Widom, C.S.

    2004-01-01

    Objective:: The present study extends prior research on childhood maltreatment and social functioning by examining the impact of early childhood physical abuse, sexual abuse, and neglect on rates of involvement in adult intimate relationships and relationship functioning. Method:: Substantiated cases of child abuse and neglect from 1967 to 1971…

  14. The Coach-Coachee Relationship in Executive Coaching: A Field Study

    ERIC Educational Resources Information Center

    Baron, Louis; Morin, Lucie

    2009-01-01

    Numerous authors have suggested that the working relationship between coach and coachee constitutes an essential condition to the success of executive coaching. This study empirically investigated the links between the coach-coachee relationship and the success of a coaching intervention in an organizational setting. Data were collected from two…

  15. The Study of Government-University Relationship in Malaysian Higher Education System

    ERIC Educational Resources Information Center

    Ahmad, Abd Rahman; Farley, Alan; Naidoo, Moonsamy

    2012-01-01

    Recently the Agency Theory is extensively used in the study of government-university relationship in higher education system. The theory expounds the main concept of information asymmetry and goal conflict in the relationship. In this paper these two concepts are used to explain efforts undertaken by the Malaysian Federal Government to improve the…

  16. Parent-Caregiver Relationships among Beginning Caregivers in Canada: A Quantitative Study

    ERIC Educational Resources Information Center

    Cantin, Gilles; Plante, Isabelle; Coutu, Sylvain; Brunson, Liesette

    2012-01-01

    Despite the importance of establishing meaningful parent-caregiver relationships, little is known about these dyadic relationships among beginning caregivers, who often feel insufficiently prepared to build successful alliances with parents. The present study examined the congruence between parents' and beginning caregivers' perceptions of their…

  17. The Relationship between Lesson Study and Self-Efficacy

    ERIC Educational Resources Information Center

    Sibbald, Tim

    2009-01-01

    This article addresses a gap in the literature by developing a theory that bridges lesson study and self-efficacy. Since self-efficacy has been linked to student achievement, the theory is important as an explanatory mechanism linking lesson study to student achievement. The theory was developed using grounded theory based on primary source data…

  18. Study made of relationship between growth and metabolism

    NASA Technical Reports Server (NTRS)

    Surrey, K.

    1967-01-01

    Study shows that the growth of X irradiated sunflower seeds is inversely related to the metabolism of the seeds. The actual magnitudes of the relation between the two differed for various ranges of X ray exposure. The results of the study suggested that the X rays affected the embryo.

  19. Home-School Relationships: A Qualitative Study with Diverse Families

    ERIC Educational Resources Information Center

    Cardona, Betty; Jain, Sachin; Canfield-Davis, Kathy

    2012-01-01

    This qualitative case study explored how families from diverse cultural backgrounds understood family involvement in the context of early childhood care and educational settings. Participants in the study included nine members from six families who had children enrolled in three early childhood care and education programs. The primary method of…

  20. The Symbiotic Relationship between Liberal Studies and Science

    ERIC Educational Resources Information Center

    Unah, Jim I.

    2008-01-01

    The Artistic and Humanistic studies (liberal studies) and the science and technology disciplines (science) constitute the two dominant cultures in a modern university. Subsumed in these cultures are the professional disciplines of law, architecture, engineering, medicine, accounting, administration and a few others. Essentially, the university…

  1. Fungal Polysaccharides: Biological Activity Beyond the Usual Structural Properties

    PubMed Central

    Rodrigues, Marcio L.; Nimrichter, Leonardo; Cordero, Radames J. B.; Casadevall, Arturo

    2011-01-01

    Studies on structure and function of polysaccharides in biological systems classically involve sequence and compositional analyses, anomeric configuration, type of glycosidic linkage, and presence of substituents. Recent studies, however, indicates that other structural parameters, so far little explored, can directly influence the biological activity of microbial polysaccharides. Among these parameters, we highlight the molecular dimensions of Cryptococcus neoformans polysaccharides, which appear to be inversely correlated with their immunobiological activity. These recent observations raise new concepts about the structure and function of polysaccharides, which stimulates the design of new experimental approaches and suggests previously unknown applications. PMID:21886639

  2. Equilibrium structural properties of two-dimensional nonideal systems

    NASA Astrophysics Data System (ADS)

    Vaulina, O. S.; Vasilieva, E. V.; Petrov, O. F.; Fortov, V. E.

    2011-12-01

    The pair correlation functions and the mean squared displacements of charged dust particles were studied experimentally for quasi-two-dimensional (2D) nonideal systems. The experiments were carried out in a plasma of a capacitive radio-frequency (RF-) discharge in argon for monolayers of monodispersed (melamine formaldehyde) spheres. A comparison with the existing theoretical and numerical data is presented.

  3. Acousto-Ultrasonics to Assess Material and Structural Properties

    NASA Astrophysics Data System (ADS)

    Kautz, Harold E.

    2002-10-01

    This report was created to serve as a manual for applying the Acousto-Ultrasonic NDE method, as practiced at NASA Glenn, to the study of materials and structures for a wide range of applications. Three state of the art acousto-ultrasonic (A-U) analysis parameters, ultrasonic decay (UD) rate, mean time (or skewing factor, "s"), and the centroid of the power spectrum, "fc," have been studied and applied at GRC for NDE interrogation of various materials and structures of aerospace interest. In addition to this, a unique application of Lamb wave analysis is shown. An appendix gives a brief overview of Lamb Wave analysis. This paper presents the analysis employed to calculate these parameters and the development and reasoning behind their use. It also discusses the planning of A-U measurements for materials and structures to be studied. Types of transducer coupling are discussed including contact and non-contact via laser and air. Experimental planning includes matching transducer frequency range to material and geometry of the specimen to be studied. The effect on results of initially zeroing the DC component of the ultrasonic waveform is compared with not doing so. A wide range of interrogation problems are addressed via the application of these analysis parameters to real specimens is shown for five cases: Case 1: Differences in density in 0 SiC/RBSN ceramic matrix composite. Case 2: Effect of tensile fatigue cycling in +/-45 SiC/SiC ceramic matrix composite. Case 3: Detecting creep life, and failure, in Udimet 520 Nickel-Based Super Alloy. Case 4: Detecting Surface Layer Formation in T-650-35/PMR-15 Polymer Matrix Composites Panels due to Thermal Aging. Case 5: Detecting Spin Test Degradation in PMC Flywheels. Among these cases a wide range of materials and geometries are studied.

  4. Acousto-ultrasonics to Assess Material and Structural Properties

    NASA Technical Reports Server (NTRS)

    Kautz, Harold E.

    2002-01-01

    This report was created to serve as a manual for applying the Acousto-Ultrasonic NDE method, as practiced at NASA Glenn, to the study of materials and structures for a wide range of applications. Three state of the art acousto-ultrasonic (A-U) analysis parameters, ultrasonic decay (UD) rate, mean time (or skewing factor, "s"), and the centroid of the power spectrum, "f(sub c)," have been studied and applied at GRC for NDE interrogation of various materials and structures of aerospace interest. In addition to this, a unique application of Lamb wave analysis is shown. An appendix gives a brief overview of Lamb Wave analysis. This paper presents the analysis employed to calculate these parameters and the development and reasoning behind their use. It also discusses the planning of A-U measurements for materials and structures to be studied. Types of transducer coupling are discussed including contact and non-contact via laser and air. Experimental planning includes matching transducer frequency range to material and geometry of the specimen to be studied. The effect on results of initially zeroing the DC component of the ultrasonic waveform is compared with not doing so. A wide range of interrogation problems are addressed via the application of these analysis parameters to real specimens is shown for five cases: Case 1: Differences in density in [0] SiC/RBSN ceramic matrix composite. Case 2: Effect of tensile fatigue cycling in [+/-45] SiC/SiC ceramic matrix composite. Case 3: Detecting creep life, and failure, in Udimet 520 Nickel-Based Super Alloy. Case 4: Detecting Surface Layer Formation in T-650-35/PMR-15 Polymer Matrix Composites Panels due to Thermal Aging. Case 5: Detecting Spin Test Degradation in PMC Flywheels. Among these cases a wide range of materials and geometries are studied.

  5. Domain-Specific Expertise of Chemistry Teachers on Context-Based Education about Macro-Micro Thinking in Structure-Property Relations

    ERIC Educational Resources Information Center

    Dolfing, Ria; Bulte, Astrid M. W.; Pilot, Albert; Vermunt, Jan D.

    2012-01-01

    This study aims to determine and describe the new domain-specific expertise of experienced chemistry teachers in teaching an innovative context-based unit about macro-micro thinking in structure-property relations. The construct of "teachers' domain-specific expertise" was used to analyse the new repertoire chemistry teachers need to acquire to…

  6. Structure-property correlation of Zr-base alloys

    NASA Astrophysics Data System (ADS)

    Wadekar, S. L.; Raman, V. V.; Banerjee, S.; Asundi, M. K.

    1988-01-01

    Zirconium alloys, because of their unique combination of high strength, good corrosion resistance in water and low capture cross-section for thermal neutrons, have become attractive for use as structural materials in the nuclear industry. Presently, Zircaloy-2 and Zircaloy-4 find wide application as fuel and pressure tube materials for water cooled power reactors. In order to understand how the various alloying elements of Zircaloy, namely Sn, Fe, Cr and Ni, affect the mechanical properties, a programme has been initiated to evolve a correlation between chemistry, microstructure and mechanical properties of Zr-alloy containing various amounts of Sn, Fe and Cr. In the present investigation, mechanical properties of Zr-alloys with various addition of Sn, Fe and Cr have been determined at 300 K and 573 K in various metallurgical conditions such as recrystallised annealed, β-quenched, tempered and α-annealed conditions. The study revealed that the reduced tin content dit not affect the mechanical properties as the reduced tin leads to formation of fine precipitates. The mechanical properties were also not altered drastically with the low level of iron and chromium concentrations studied. Cold work and α-annealing after β-quenching resulted in the growth and redistribution of second phase particles. Metallographie studies showed that particle distribution was not uniform. A TEM investigation of the alloys has also been undertaken to study the details of microstructure developed during various heat-treated conditions. It has been found that the β-quenched samples exhibit the most uniform microstructure consisting of acicular alpha phase with lath boundary enriched by solute element and fine intermetallic particle formation. The observed microstructural features together with the mechanical properties data have been compared with the available mechanical properties cum microstructure of Zircaloy.

  7. Etiological relationships in atopy: a review of twin studies.

    PubMed

    Thomsen, Simon Francis; Kyvik, Kirsten Ohm; Backer, Vibeke

    2008-04-01

    The genetics of asthma and atopy has been studied frequently in twin populations from various parts of the world. However, emphasis has been put on univariate analysis of questionnaire data, whereas clinical and intermediate traits only sporadically have been studied, especially in multivariate settings. This review focuses on multivariate twin studies of atopy and related traits. We conclude that the genetic liability to most atopic traits is significantly correlated but that trait-specific genes also play a role. Previous studies have estimated the genetic correlation between upper and lower respiratory allergic symptoms, that is, asthma and hay fever, to be between .47 and .95. Furthermore, atopic traits share a portion of their genetic determinants with other complex disorders like obesity and behavioral traits. A correlation of about .3 and .34 has been reported between genes associated with asthma and obesity, and between genes associated with asthma and depression, respectively. We emphasize that multivariate methods applied to twin studies, especially when genetic marker information is available, provide a valuable framework within which complex etiological mechanisms underlying atopy can be disentangled.

  8. Strontium substituted hydroxyapatites: Synthesis and determination of their structural properties, in vitro and in vivo performance.

    PubMed

    Kaygili, Omer; Keser, Serhat; Kom, Mustafa; Eroksuz, Yesari; Dorozhkin, Sergey V; Ates, Tankut; Ozercan, Ibrahim H; Tatar, Cengiz; Yakuphanoglu, Fahrettin

    2015-10-01

    The objective of this study is to present a detailed report related to the synthesis and characterization of strontium substituted hydroxyapatites. Based on this purpose, hydroxyapatite (HAp) bioceramics with different amounts of strontium (e.g., 0, 0.45, 0.90, 1.35, 1.80 and 2.25 at.%) were prepared using a sol-gel method. The effects of Sr substitution on the structural properties and biocompatibility of the samples were studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques, in vitro and in vivo tests. All the samples composed of the nanoparticles ranging from 21 to 27 nm. The presence of Sr at low levels influenced the crystal size, crystallinity degree, lattice parameters and volume of the unit cell of the HAp. Both in vitro conditions and soaking period in simulated body fluid (SBF) significantly affected these properties. Especially, the (Ca+Sr)/P molar ratio gradually decreases with increasing soaking period in SBF. Animal experiments revealed the bone formation and osseointegration for all samples, and as compared with other groups, more reasonable, were observed for the sample with the lowest Sr content.

  9. The chemical, physical and structural properties of estuarine ice in Great Bay, New Hampshire

    USGS Publications Warehouse

    Meese, D.A.; Gow, A.J.; Mayewski, P.A.; Ficklin, W.; Loder, T.C.

    1987-01-01

    The purpose of this study was to provide general information on the chemical, physical and structural properties of estuarine ice and show how it compares with sea ice found at higher latitudes in order to determine whether the ice in Great Bay can be used as an analog in the study of arctic sea ice. Ice cores and water samples were collected during the 1983-1984 winter season at Adams Point in Great Bay, New Hampshire. Concentrations of chloride, nitrogen (as nitrate and nitrite), bromide, phosphate, sulfate and silicate were determined for samples chosen on the basis of identifiable stratigraphic layers (i.e. bubble size and shape, sediment layers, etc.). Similarities between ice formation in Great Bay and those in the arctic regions include the nature of the freezing process and the ice types produced. In addition, the distribution and concentration of chemical constituents were found to be similar to those observed in arctic sea ice. Factors affecting the chemistry of the ice in Great Bay include rainfall during the freezing season, the presence of sediment layers in the ice cores, the nature of incorporation of brine into the crystal structure of the ice and the drainage of brine. ?? 1987.

  10. Textural and structural properties and surface acidity characterization of mesoporous silica-zirconia molecular sieves

    NASA Astrophysics Data System (ADS)

    Rodríguez-Castellón, E.; Jiménez-López, A.; Maireles-Torres, P.; Jones, D. J.; Rozière, J.; Trombetta, M.; Busca, G.; Lenarda, M.; Storaro, L.

    2003-11-01

    Homogeneous mesoporous zirconium-containing MCM-41 type silica were prepared by supramolecular templating and their textural and structural properties were studied using powder X-ray diffraction, N 2 porosimetry, atomic force microscopy, EXAFS, XPS, and UV-VIS-NIR diffuse reflectance spectroscopy. Their acid properties were also studied by using IR spectroscopy and by the use of catalytic tests such as the decomposition of isopropanol and the isomerization of 1-butene. The materials prepared show a good degree of crystallinity with a regular ordering of the pores into a hexagonal arrangement and high thermal stability. The specific surface area of the prepared materials decreases as the zirconium content rises. Zirconium atoms are in coordination 7 to 8 and located at the surface of the pores such that a high proportion of the oxygen atoms bonded to zirconium corresponds to surface non-condensed oxygen atoms. Both facts are responsible for the acid properties of the solids that show weak Brønsted and medium strong Lewis acidity.

  11. Optical and structural properties of InN grown by HPCVD

    NASA Astrophysics Data System (ADS)

    Buegler, M.; Alevli, M.; Atalay, R.; Durkaya, G.; Senevirathna, I.; Jamil, M.; Ferguson, I.; Dietz, N.

    2009-08-01

    The optical and structural properties of InN layers grown by 'High Pressure Chemical Vapor Deposition' (HPCVD) using a pulsed precursor approach have been studied. The study focuses on the effect of ammonia precursor exposure time and magnitude on the InN layer quality. The samples have been analyzed by X-ray diffraction, Raman scattering, infra red reflectance spectroscopy and photoluminescence spectroscopy. Raman measurements and X-ray diffraction showed the grown layers to be single phase InN of high crystalline quality. The E2(high) Raman mode showed FWHM's as small as 9.2 cm-1. The FWHM's of the InN(0002) X-ray Bragg reflex in the 2Θ-Ω- scans were around 350 arcsec, with rocking curve values as low as 1152 arcsec Photoluminescence features have been observed down to 0.7 eV, where the low energy cutoff might be due to the detector limitation. The analysis of the IR reflectance spectra shows that the free carrier concentrations are as low as as 3.3•1018 cm-3 for InN layers grown on sapphire substrates.

  12. Optical and structural properties of chalcone NLO single crystals

    NASA Astrophysics Data System (ADS)

    Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Manjunath, H. R.; Karegouda, Prakash; Crasta, Vincent; Sridhar, M. A.

    2011-11-01

    Organic compound (E)-1-(4-methoxyphenyl)-3-(2,3,5-trichlorophenyl)prop-2-en-1-one [MPTCPP] with molecular formula C 16H 11Cl 3O 2 was synthesized using Claisen-Schmidt condensation reaction method. 1H NMR spectra was recorded to identify the various functional groups present in the compound and confirm the chemical structure. The single crystals were grown using slow evaporation solution growth technique. The UV-Visible spectrum study reveals that the crystal is transparent in the entire visible region and the absorption is observed at 364 nm. The Kurtz powder second harmonic generation (SHG) test shows that the MPTCPP is NLO active and its SHG efficiency is three times that of urea. Single crystal XRD study shows that the compound crystallizes in the monoclinic system with a space group Cc. The corresponding lattice parameters of the crystal are a = 28.215(5) Å, b = 3.9740(4) Å, c = 16.178(3) Å and V = 1503.0(4) Å 3. The micro hardness test was carried out and the work hardening coefficient value ( n) of the crystal was found to be 1.48. This indicates that the crystal is hard and is suitable for device application. The thermal study reveals that the thermal stability of the crystal is good.

  13. Positive illusions in marital relationships: a 13-year longitudinal study.

    PubMed

    Miller, Paul J E; Niehuis, Sylvia; Huston, Ted L

    2006-12-01

    This study examined the long-term consequences of idealization in marriage, using both daily diary and questionnaire data collected from a sample of 168 newlywed couples who participated in a 4-wave, 13-year longitudinal study of marriage. Idealization was operationalized as the tendency for people to perceive their partner as more agreeable than would be expected based on their reports of their partner's agreeable and disagreeable behaviors. Spouses who idealized one another were more in love with each other as newlyweds. Longitudinal analyses suggested that spouses were less likely to suffer declines in love when they idealized one another as newlyweds. Newlywed levels of idealization did not predict divorce.

  14. Relationships between Student Cognitions and Their Effects on Study Strategies

    ERIC Educational Resources Information Center

    Ferla, Johan; Valcke, Martin; Schuyten, Gilberte

    2008-01-01

    Using Vermunt's model [Vermunt, J. D. (1998). "The regulation of constructive learning processes". "British Journal of Educational Psychology", 68, 149-171] of self-regulated learning as a conceptual framework, this study aims to contribute to the development of finer grained models of higher education students' learning by (1) investigating…

  15. A STUDY OF MATHEMATICAL ABILITY INVOLVING DIGIT RELATIONSHIPS. FINAL REPORT.

    ERIC Educational Resources Information Center

    KNAPP, ROBERT H.

    ATTITUDES OF STUDENTS TOWARD ARABIC NUMBERALS AND THEIR ASSOCIATIONS WITH THE NUMBERS FROM 1 TO 9 WERE INVESTIGATED IN A SERIES OF FIVE STUDIES ON (1) NONQUANTITATIVE ASSOCIATIONS TO NUMERALS AS A FUNCTION OF AGE, ABILITY LEVEL, AND SEX AMONG AMERICAN CHILDREN, (2) COLOR ASSOCIATIONS WITH NUMERALS AMONG MALE COLLEGE STUDENTS, (3) PERSONALITY…

  16. A Study: The Relationship of Personality Type to Vocabulary Development.

    ERIC Educational Resources Information Center

    Covner, Thelma Crockin

    To test the hypothesis that aspects of one's personality are associated with expansion of his or her vocabulary, a study focused on thirteen students of various ages who constituted a vocabulary development class. Students were taught techniques for discovering meaning through context or extracting meaning through word structure. Considerable time…

  17. Structural properties of silver nanowires from atomistic descriptions

    NASA Astrophysics Data System (ADS)

    Jia, Jianming; Shi, Daning; Zhao, Jijun; Wang, Baolin

    2007-10-01

    The structural formation process and physical properties of silver nanowires were investigated via an unbiased genetic algorithm search using empirical potential combined with density-functional theory calculations. Some unexpected structural behaviors resulting from the intrinsic properties of silver were revealed. Two kinds of atomic arrangements, i.e., normal and abnormal configurations, appear alternately during the growth of wire, from which a (111) facet-based formation mechanism was observed. The excellent agreements between theoretical results and experimental observations on the structural motif, Young’s modulus, and shell effects of Ag nanowires indicate the importance of objective and precise atomistic descriptions in the study of nanosystems.

  18. Structural Properties and Stability of Double Walled Armchair Silicon Nanotubes

    NASA Astrophysics Data System (ADS)

    Chen, Haoliang; Ray, Asok

    2012-02-01

    A systematic study of armchair double-walled Si nanotubes (DWNT) (n,n)@(m,m) (3 <= n <= 6 ; 7 <= m <= 12) using the finite cluster approximation is presented. The geometries of the tubes have been spin optimized with an all electron 3-21G* basis set and the B3LYP functional. The study indicates that the stabilities of the double-walled Si nanotubes are of the same order as those of single-walled Si nanotubes suggesting the possibilities of experimental synthesis of both single-walled and double-walled Si nanotubes. The binding energy per atom or the cohesive energy of the double-walled nanotubes depends not only on the number of atoms but also on the coupling of the constituent single-walled nanotubes. Some nanotubes with small interlayer separations do not hold the coaxial cylindrical structure after optimization. The NTS (n, n)@(n+3, n+3) are found to have large formation energies and binding energies per atom. For example, (3,3)@(6,6), (4,4)@(7,7), (5,5)@(8,8), and (6,6)@(9,9) all have large binding energies per atom, around 3.7eV/atom. All double-walled Si nanotubes are found to be semiconductors. However, the band gap, in general, is observed to decrease from single walled nanotubes to double walled nanotubes.

  19. Theoretical investigation of structural properties of CuCl, CuBr and CuI compounds under hydrostatic pressure

    SciTech Connect

    Louhibi-Fasla, S.; Djabri, H. Rekab; Achour, H.; Kefif, K.

    2013-12-16

    We have applied a recent version of the full potential linear muffin-tin orbitals method (FPLMTO) to study the structural properties of copper halides CuX (X=Cl, Br, I) under high pressure using the generalized gradient approximation (GGA) for the exchange and correlation potential by Perdew et al. Results are given for lattice parameters, bulk modulus and its first derivatives in the wurtzite(B4), zinc-blende (B3), CsCl (B2), rock-salt (B1), and PbO (B10) structures. The results of these calculations are compared with the available theoretical and experimental data.

  20. The influence of relationships on personhood in dementia care: a qualitative, hermeneutic study

    PubMed Central

    2013-01-01

    Background In dementia personhood can be understood as increasingly concealed rather than lost. The sense of being a person evolves in relationships with others. The aim of this study was to increase the understanding of the nature and quality of relationships between persons with dementia, family carers and professional caregivers and how these relationships influenced personhood in people with dementia. Methods This Norwegian study had a qualitative hermeneutical design based on ten cases. Each case consisted of a triad: the person with dementia, the family carer and the professional caregiver. Inclusion criteria for persons with dementia were (1) 67 years or older (2) diagnosed with dementia (3) Clinical Dementia Rating score 2 ie. moderate dementia (4) able to communicate verbally. A semi-structured interview guide was used in interviews with family carers and professional caregivers. Field notes were written after participant observation of interactions between persons with dementia and professional caregivers during morning care or activities at a day care centre. Data were analysed in two steps: (1) inductive analysis with an interpretive approach and (2) deductive analysis, applying a theoretical framework for person-centred care. Results Relationships that sustained personhood were close emotional bonds between family carers and persons with dementia and professional relationships between caregivers and persons with dementia. Relationships that diminished personhood were task-centred relationships and reluctant helping relationships between family carers and persons with dementia and unprofessional relationships between caregivers and persons with dementia. Conclusions A broad range of relationships was identified. Understanding the complex nature and quality of these relationships added insight as to how they influenced the provision of care and the personhood of persons with dementia. Personhood was not only bestowed upon them by family carers and

  1. The relationship between study strategies and academic performance

    PubMed Central

    Graham, Lori; West, Courtney

    2016-01-01

    Objectives To investigate if and to what extent the Learning and Study Strategy Inventory (LASSI) and the Self-Directed Learning Readiness Scale (SDLRS) yield academic performance predictors; To examine if LASSI findings are consistent with previous research. Methods Medical school students completed the LASSI and SDLRS before their first and second years (n = 168). Correlational and regression analyses were used to determine the predictive value of the LASSI and the SDLRS. Paired t-tests were used to test if the two measurement points differed. Bivariate correlations and R2s were compared with five other relevant studies. Results The SDLRS was moderately correlated with all LASSI subscales in both measures (r(152) =.255, p=.001) to (r(152) =.592, p =.000). The first SDLRS, nor the first LASSI, were predictive of academic performance. The second LASSI measure was a significant predictor of academic performance (R2(138) = 0.188, p = .003). Six prior LASSI studies yielded a range of R2s from 10-49%. Conclusions The SDLRS is moderately correlated with all LASSI subscales. However, the predictive value of the SDLRS and LASSI differ. The SDLRS does not appear to be directly related to academic performance, but LASSI subscales: Concentration, Motivation, Time Management, and Test Strategies tend to be correlated. The explained LASSI variance ranges from 10% to 49%, indicating a small to substantial effect. Utilizing the LASSI to provide medical school students with information about their strengths and weaknesses and implementing targeted support in specific study strategies may yield positive academic performance outcomes. PMID:27718497

  2. Luminescent and structural properties of ZnO-Ag films

    SciTech Connect

    Khomchenko, V. S. Kushnirenko, V. I. Papusha, V. P.; Savin, A. K.; Lytvyn, O. S.

    2010-05-15

    ZnO-Ag thin films were prepared by a two-stage method on glass and sapphire substrates. Ag doping was carried out by a method of close space sublimation at atmospheric pressure. The film thickness is varied from 0.6 to 7 {mu}m. The structural and radiative properties were explored by X-ray diffraction technique, atomic force microscopy, photoluminescence and cathodoluminescence spectroscopy. The influence of the fabricating conditions on the properties of ZnO-Ag films is studied. It is found that the Ag doping modifies the crystalline structure of the films and promotes the oriented growth of monocrystalline blocks with the size of 500-2000 nm in the [0002] direction. Improvement of the crystalline quality correlates with the change of the radiative characteristics of the films. The origin of emission centers is discussed.

  3. Phosphorylation of lamins determine their structural properties and signaling functions.

    PubMed

    Torvaldson, Elin; Kochin, Vitaly; Eriksson, John E

    2015-01-01

    Lamin A/C is part of the nuclear lamina, a meshwork of intermediate filaments underlying the inner nuclear membrane. The lamin network is anchoring a complex set of structural and linker proteins and is either directly or through partner proteins also associated or interacting with a number of signaling protein and transcription factors. During mitosis the nuclear lamina is dissociated by well established phosphorylation- dependent mechanisms. A-type lamins are, however, also phosphorylated during interphase. A recent study identified 20 interphase phosphorylation sites on lamin A/C and explored their functions related to lamin dynamics; movements, localization and solubility. Here we discuss these findings in the light of lamin functions in health and disease.

  4. Characterization of Magnetoacoustic Emission Related to Structural Properties of Ferromagnets

    NASA Technical Reports Server (NTRS)

    Namkung, M.; Wincheski, B.; Fulton, J. P.; Todhunter, R. G.

    1993-01-01

    An extensive study of magnetoacoustic emission (MAE) properties has been performed over the past several years. As a result, the dependence of the spectral characteristics of MAE on certain microstructural variations and uniaxially applied stress in a particular type of low carbon steel are now well known. The embrittlement-causing concentration of certain atomic species, e. g., tin, sulphur, phosphorous etc., at the grain boundaries of this steel creates strong potential barriers resisting the motion of non-180 domain walls which is the source of MAE. (Since the only type of non-180 domain walls in this material are 90 domain walls, the term 90 domain wall will be used throughout this paper in place of non-180 domain wall.) An MAE burst produced during one-half cycle of a hysteresis loop at a low AC magnetic field frequency (e. g., 0.7 Hz) shows two sub-peaks; the leading peak is usually sharp and short-lived, while the trailing peak is usually smooth and long-lasting. It has been shown that the enhanced domain wall-defect interaction, due to the strengthened potential barriers, causes an increase in the asymmetry of the MAE signal by suppressing the leading sub-peak and amplifying the trailing sub-peak. This phenomena is due to the delayed motion of the 90 domain walls. The effect of a tensile stress applied parallel to the external AC magnetic field is to diminish the MAE. On the other hand, the amplitude of the MAE burst has been shown to be a non-monotonic function of the stress amplitude. Recently, our study has concentrated on obtaining quantitative values for parameters computed from the MAE spectra averaged over a sufficient number of cycles to achieve statistical stability. Nevertheless, certain fundamental elements of the MAE characteristics remain unexplained.

  5. Relationship between Study Habits and Test Anxiety of Higher Secondary Students

    ERIC Educational Resources Information Center

    Lawrence, Arul A. S.

    2014-01-01

    The present study aims to probe the relationship between study habits and test anxiety of higher secondary students. In this normative study survey method was employed. The population for the present study consisted of higher secondary students studying in Tirunelveli district. The investigator used the simple random sampling technique. The sample…

  6. The characteristics of an effective physician-hospital working relationship: an exploratory study.

    PubMed

    Schramko, Tim D

    2007-06-01

    The working relationship between a private practice physician, whose medical practice was acquired by a health system, and the health system that sponsored the medical practices was studied using a dyadic perspective and drawing from agency theory to identify those characteristics that are present in an effective working relationship. In-depth interviews with currently employed physicians and those whose contracts were terminated within the last 3 years were used to identify why some working relationships failed and others succeeded. Hospital administrators and practice managers that provided the support services to the acquired medical practices were also interviewed for their assessment of the working relationship. As a result of the research, a model for developing an effective working relationship is presented to be considered as a framework for developing future working relationships. Based upon the data, this study posits that the physicians and the hospitals can have a more effective working relationship if specific characteristics are evident before, during, and after the contract is signed. Understanding the factors that contribute to an effective working relationship can help in designing contracts with physicians and better utilize resources at the physician private practice level, as well as at the hospital level. PMID:17628927

  7. Characteristics of natural mentoring relationships and adolescent adjustment: evidence from a national study.

    PubMed

    DuBois, David L; Silverthorn, Naida

    2005-03-01

    This research investigated characteristics of natural mentoring relationships (mentor role, frequency of contact, closeness, duration) as predictors of adjustment outcomes among older adolescents and young adults (N = 2,053) in the Add Health study. Outcomes were assessed in the domains of education/work, problem behavior, psychological well-being, and physical health. Mentoring relationships with persons in roles outside of the family predicted greater likelihood of favorable outcomes in all domains except psychological well-being, relative to mentoring relationships with family members. Greater reported closeness in relationships was predictive of several favorable outcomes, particularly those in the domain of psychological well-being. These findings indicate that strategies to promote mentoring of adolescents may be more effective if particular categories of adults are targeted and an effort is made to cultivate relationships with strong emotional bonds. Editors' Strategic Implications: These data suggest that the cultivation of natural (especially non-familial) mentoring relationships during adolescence may be a promising strategy for prevention and health promotion. This study is impressive due to its large, nationally representative sample, the examination of relationship characteristics and multiple mentors, and the links to a variety of outcomes (controlling for earlier functioning). School officials and mentoring programs must consider how to capitalize on - and promote - naturally occurring mentor relationships.

  8. Magnetic and Structural Properties of Ultra-Thin Cobalt Films

    NASA Astrophysics Data System (ADS)

    Wiedmann, Michael Helmut

    In situ polar Kerr effect measurements have been used to study the magnetic anisotropy of Au(111)/Co/X, Pd(111)/Co/X, Cu(111)/Co/X, and Pd(100)/Co/X sandwiches, where X is the nonmagnetic metal Ag, Au, Cu, Ir, and Pd or the insulator MgO. The films were grown by molecular beam epitaxy (MBE). For the metals, we found that the magnitude of the Co/X perpendicular interface anisotropy is strongly peaked at ~1 atomic layer (1.5-2.5 A) coverage. To investigate structural influences on the anisotropy, we have used reflection high energy diffraction (RHEED) and low energy electron diffraction (LEED) to measure changes resulting from overlayer coverage. Analysis of digitized RHEED images captured every ~ 1 A during metal overlayer coverage shows no abrupt change of the in-plane lattice constant. We have also investigated the out-of-plane lattice spacing as a function of nonmagnetic metal coverage by measuring LEED I-V curves along the (0,0) rod. In the case of Cu, where the LEED behavior is nearly kinematic, we see no evidence of any abrupt structural changes at ~1 atomic layer coverage. These results suggest the observed peak in magnetic anisotropy is not structural in origin. The influence of an insulating overlayer, MgO, on the perpendicular magnetic properties was also investigated.

  9. Harnessing the Unique Structural Properties of Isolated α-Helices*

    PubMed Central

    Swanson, Carter J.; Sivaramakrishnan, Sivaraj

    2014-01-01

    The α-helix is a ubiquitous secondary structural element that is almost exclusively observed in proteins when stabilized by tertiary or quaternary interactions. However, beginning with the unexpected observations of α-helix formation in the isolated C-peptide in ribonuclease A, there is growing evidence that a significant percentage (0.2%) of all proteins contain isolated stable single α-helical domains (SAH). These SAH domains provide unique structural features essential for normal protein function. A subset of SAH domains contain a characteristic ER/K motif, composed of a repeating sequence of ∼4 consecutive glutamic acids followed by ∼4 consecutive basic arginine or lysine (R/K) residues. The ER/K α-helix, also termed the ER/K linker, has been extensively characterized in the context of the myosin family of molecular motors and is emerging as a versatile structural element for protein and cellular engineering applications. Here, we review the structure and function of SAH domains, as well as the tools to identify them in natural proteins. We conclude with a discussion of recent studies that have successfully used the modular ER/K linker for engineering chimeric myosin proteins with altered mechanical properties, as well as synthetic polypeptides that can be used to monitor and systematically modulate protein interactions within cells. PMID:25059657

  10. Biological glass fibers: Correlation between optical and structural properties

    PubMed Central

    Aizenberg, Joanna; Sundar, Vikram C.; Yablon, Andrew D.; Weaver, James C.; Chen, Gang

    2004-01-01

    Biological systems have, through the course of time, evolved unique solutions for complex optical problems. These solutions are often achieved through a sophisticated control of fine structural features. Here we present a detailed study of the optical properties of basalia spicules from the glass sponge Euplectella aspergillum and reconcile them with structural characteristics. We show these biosilica fibers to have a distinctive layered design with specific compositional variations in the glass/organic composite and a corresponding nonuniform refractive index profile with a high-index core and a low-index cladding. The spicules can function as single-mode, few-mode, or multimode fibers, with spines serving as illumination points along the spicule shaft. The presence of a lens-like structure at the end of the fiber increases its light-collecting efficiency. Although free-space coupling experiments emphasize the similarity of these spicules to commercial optical fibers, the absence of any birefringence, the presence of technologically inaccessible dopants in the fibers, and their improved mechanical properties highlight the advantages of the low-temperature synthesis used by biology to construct these remarkable structures. PMID:14993612

  11. An Investigation of Magnetic, Electronic and Structural Properties of Metallofullerenes

    NASA Astrophysics Data System (ADS)

    Ong, S. Vincent; Qian, Meichun; Khanna, Shiv

    2008-03-01

    Gadolinium based endohedral metallofullerenes Gd3N@C80 functionalized with OH radicals have been found to enhance the relaxivity by orders of magnitude over conventional agents and are being sought as new contrast agents in magnetic resonance imaging (MRI). Using state of the art density functional theory (DFT) in the regime of the local density approximation with the on-site Coulomb interaction (LSDA+U), we have carried out theoretical studies to determine the electronic and magnetic properties of gadolinium-based and lutetium-based nitride fullerenes, namely Lu3-xGdxN@C80 (x = 1-2). While Gd3N@C80 has previously shown promising features as a contrast agent, the idea of replacing gadolinium atoms by lutetium has been proposed to result in a mixed-metal species for multi-modal imaging. Our results indicate that Lu2GdN@C80 is the most stable of all possible configurations with a binding energy 16.57 eV, can be considered for use as both an MRI contrast agent, due to gadolinium's high magnetic moment, and as a potential radioactive therapeutic or diagnostic agent, by neutron activation of a lutetium radioisotope. These results along with details of electronic structure will be presented.

  12. Composition-Structure-Property Relations of Compressed Borosilicate Glasses

    NASA Astrophysics Data System (ADS)

    Svenson, Mouritz N.; Bechgaard, Tobias K.; Fuglsang, Søren D.; Pedersen, Rune H.; Tjell, Anders Ø.; Østergaard, Martin B.; Youngman, Randall E.; Mauro, John C.; Rzoska, Sylwester J.; Bockowski, Michal; Smedskjaer, Morten M.

    2014-08-01

    Hot isostatic compression is an interesting method for modifying the structure and properties of bulk inorganic glasses. However, the structural and topological origins of the pressure-induced changes in macroscopic properties are not yet well understood. In this study, we report on the pressure and composition dependences of density and micromechanical properties (hardness, crack resistance, and brittleness) of five soda-lime borosilicate glasses with constant modifier content, covering the extremes from Na-Ca borate to Na-Ca silicate end members. Compression experiments are performed at pressures ≤1.0 GPa at the glass transition temperature in order to allow processing of large samples with relevance for industrial applications. In line with previous reports, we find an increasing fraction of tetrahedral boron, density, and hardness but a decreasing crack resistance and brittleness upon isostatic compression. Interestingly, a strong linear correlation between plastic (irreversible) compressibility and initial trigonal boron content is demonstrated, as the trigonal boron units are the ones most disposed for structural and topological rearrangements upon network compaction. A linear correlation is also found between plastic compressibility and the relative change in hardness with pressure, which could indicate that the overall network densification is responsible for the increase in hardness. Finally, we find that the micromechanical properties exhibit significantly different composition dependences before and after pressurization. The findings have important implications for tailoring microscopic and macroscopic structures of glassy materials and thus their properties through the hot isostatic compression method.

  13. Structure-property relations in amorphous carbon for photovoltaics

    SciTech Connect

    Risplendi, Francesca; Cicero, Giancarlo; Bernardi, Marco; Grossman, Jeffrey C.

    2014-07-28

    Carbon is emerging as a material with great potential for photovoltaics (PV). However, the amorphous form (a-C) has not been studied in detail as a PV material, even though it holds similarities with amorphous Silicon (a-Si) that is widely employed in efficient solar cells. In this work, we correlate the structure, bonding, stoichiometry, and hydrogen content of a-C with properties linked to PV performance such as the electronic structure and optical absorption. We employ first-principles molecular dynamics and density functional theory calculations to generate and analyze a set of a-C structures with a range of densities and hydrogen concentrations. We demonstrate that optical and electronic properties of interest in PV can be widely tuned by varying the density and hydrogen content. For example, sunlight absorption in a-C films can significantly exceed that of a same thickness of a-Si for a range of densities and H contents in a-C. Our results highlight promising features of a-C as the active layer material of thin-film solar cells.

  14. Structure, properties and applications of mussel-inspired polydopamine.

    PubMed

    Ho, Chia-Che; Ding, Shinn-Jyh

    2014-10-01

    Mussel-inspired polydopamine (PDA) has emerged as a promising molecule used for anchoring synthetic and biological substances or forming an adhesive layer onto various substrates for biomedical and nanotechnology applications because of its outstanding properties. This review article provides an overview of the recent progress in the PDA-based materials, including synthesis of nanoparticles, capsules, structure-mechanism, physicochemical and biological properties, and medical applications. Frist, to understand how PDA nanoparticles, capsules and films produce the unique properties is insight on the processing parameters. Next, we highlight what is known regarding the mechanism of self-polymerization and the structure features of dopamine (DA), which is based on the formation of covalent bond or through a combination mode between monomers. The inherent hydrophilicity and adhesive property of PDA with the coexistence of catechol and amine functionalities provide desirable surface characteristics without the need for further modification. Finally, successful applications, such as grafting substances, biomineralization, antifouling and antibacterial coatings, drug/gene delivery, and tissue engineering, reported to date involving PDA will be focused. The future study of PDA to develop novel materials with unique properties is emerging for specific nanomedicine applications.

  15. Optimization of compositional and structural properties in probiotic sausage production.

    PubMed

    Bağdatli, Aytunga; Kundakci, Akif

    2016-03-01

    In this study, the effects of different fat levels and different particle sizes on compositional and structural characteristics of probiotic fermented sausage were investigated. In order to obtain probiotic character, Lactobacillus casei CRL431 was added. The physicochemical, microbiological and sensory analysis were done. The effect of fat level x mincer hole diameter interaction on hardness values were statistically significant (p < 0.005). At the end of the fermentation-ripening period, L.casei CRL-431 count has reached to sufficient microbial count (10(6) cfu/g of probiotic bacteria) to demonstrate the character of probiotic food. A significant positive correlation was found between L.casei CRL431 count and surface appearance, texture and overall acceptability scores (r = 0.60, 0.52, 0.53). The values of TBARS number of probiotic sucuk samples increased during fermentation-ripening. A significant correlation between taste-aroma scores and fat level was detected (r = -0.61,p = 0.0008). Consiquently, the best sensorial quality was determined in L3 samples and the worst sensorial quality was determined in H8 samples.

  16. Optimization of compositional and structural properties in probiotic sausage production.

    PubMed

    Bağdatli, Aytunga; Kundakci, Akif

    2016-03-01

    In this study, the effects of different fat levels and different particle sizes on compositional and structural characteristics of probiotic fermented sausage were investigated. In order to obtain probiotic character, Lactobacillus casei CRL431 was added. The physicochemical, microbiological and sensory analysis were done. The effect of fat level x mincer hole diameter interaction on hardness values were statistically significant (p < 0.005). At the end of the fermentation-ripening period, L.casei CRL-431 count has reached to sufficient microbial count (10(6) cfu/g of probiotic bacteria) to demonstrate the character of probiotic food. A significant positive correlation was found between L.casei CRL431 count and surface appearance, texture and overall acceptability scores (r = 0.60, 0.52, 0.53). The values of TBARS number of probiotic sucuk samples increased during fermentation-ripening. A significant correlation between taste-aroma scores and fat level was detected (r = -0.61,p = 0.0008). Consiquently, the best sensorial quality was determined in L3 samples and the worst sensorial quality was determined in H8 samples. PMID:27570293

  17. Thermodynamic and structural properties of confined discrete-potential fluids

    NASA Astrophysics Data System (ADS)

    Benavides, A. L.; del Pino, L. A.; Gil-Villegas, A.; Sastre, F.

    2006-11-01

    The thermodynamic and structural behaviors of confined discrete-potential fluids are analyzed by computer simulations, studying in a systematic way the effects observed by varying the density, temperature, and parameters of the potentials that characterize the molecule-molecule interactions. The Gibbs ensemble simulation technique for confined fluids [A. Z. Panagiotopoulos, Mol. Phys. 62, 701 (1987)] is applied to a fluid confined between two parallel hard walls. Two different systems have been considered, both formed by spherical particles that differ by the interparticle pair potential: a square well plus square shoulder or a square shoulder plus square well interaction. These model interactions can describe in an effective way pair potentials of real molecular and colloidal systems. Results are compared with the simpler reference systems of square-shoulder and square-well fluids, both under confinement. From the adsorption characterization through the use of density profiles, it is possible to obtain specific values of the interparticle potential parameters that result in a positive to negative adsorption transition.

  18. A Study of the Relationship between Psychological Differentiation and Management Style

    ERIC Educational Resources Information Center

    Templer, Andrew J.

    1973-01-01

    The present study was designed to investigate the relationship between field dependence-independence as measured by the RFT (Rod and Frame Test) and management style as measured by a number of questionnaire and situational instruments. (Author/RK)

  19. Studies of relationships among outer solar system small bodies and related objects

    NASA Technical Reports Server (NTRS)

    Hartmann, William K.

    1991-01-01

    This program involves telescopic observations of colorimetry, spectroscopy, and photometry of small bodies of the solar system, emphasizing possible relationships among outer solar system asteroids, comets, and certain satellites. Earth approacher targets of opportunity and lab spectroscopic studies are included.

  20. A Study of the Relationship of Moral Development and Social Interest to Vocational Maturity of Adolescents.

    ERIC Educational Resources Information Center

    Krebs, Elfriede

    1983-01-01

    This study investigated the relationships among vocational, moral, and social development in ninth- and twelfth-grade students to clarify the psychological and psychosocial nature of vocational maturity. The effects of age differences and sex differences are discussed. (PP)

  1. Electronic and structural properties of extended-chain compounds and polymers

    SciTech Connect

    Springborg, M.

    2000-04-20

    Results of density functional calculations on infinite, periodic chains are reported. The method that is applied is based on linearized muffin-tin orbitals as basis functions, although the full potential and not only its muffin-tin part is included in the calculations. Special emphasis is put on analyzing the interatomic interactions by means of crystal-orbital overlap or Hamilton populations (COOP and COHP, respectively). As examples of conjugated polymers, trans-polyacetylene and polycarbonitrile are studied. Here, in particular, the existence of a bond length alternation is discussed. Subsequently, PtS{sub 2} (both without and with K counterions) and NbSe{sub 3} chains are considered. For the former, the single-chain calculations are supplemented with calculations on the crystalline compounds, and it is shown how single-chain effects are responsible for the structural properties whereas interchain effects have to be included in order to account for all the electronic properties. Parts of the results are explained through an analysis of the COOP and COHP. For NbSe{sub 3} the three different structures occurring in the crystalline material are considered, and the implications of the results for the existence of charge density waves as well as the importance of spin-orbit couplings are discussed. Finally, HF as an example of an extended hydrogen-bonded system is examined, and it is demonstrated how the electronic interactions change when the covalent and hydrogen bonds are interchanged as it occurs in charge transport via solitons.

  2. Electron momentum density, band structure, and structural properties of SrS

    SciTech Connect

    Sharma, G.; Munjal, N.; Vyas, V.; Kumar, R.; Sharma, B. K.; Joshi, K. B.

    2013-10-15

    The electron momentum density, the electronic band structure, and the structural properties of SrS are presented in this paper. The isotropic Compton profile, anisotropies in the directional Compton profiles, the electronic band structure and density of states are calculated using the ab initio periodic linear combination of atomic orbitals method with the CRYSTAL06 code. Structural parameters of SrS-lattice constants and bulk moduli in the B1 and B2 phases-are computed together with the transition pressure. The computed parameters are well in agreement with earlier investigations. To compare the calculated isotropic Compton profile, measurement on polycrystalline SrS is performed using 5Ci-{sup 241}Am Compton spectrometer. Additionally, charge transfer is studied by means of the Compton profiles computed from the ionic model. The nature of bonding in the isovalent SrS and SrO compounds is compared on the basis of equal-valenceelectron-density profiles and the bonding in SrS is found to be more covalent than in SrO.

  3. Electronic and structural properties at the interface between CuPc and graphene

    SciTech Connect

    Tao, Yongsheng; Mao, Hongying; He, Pimo

    2015-01-07

    The electronic and structural properties at Copper phthalocyanine (CuPc)/graphene have been studied using ultraviolet photoemission spectroscopy and first-principles density function theory calculation. The five emission features α, β, γ, δ, and ε originating from the CuPc molecules locate at 1.48, 3.66, 4.98, 6.90, and 9.04 eV, respectively. These features shift in binding energy with the increasing CuPc coverage. The feature α is mostly deriving from Cu 3d orbital with some contributions from C 2p orbital. Further theoretical calculation indicates that the adsorption of CuPc on a top site is the most favorable configuration, and the separation between the adsorbate and graphene is about 3.47 Å. According to the density of states before and after CuPc adsorption, the LUMO of CuPc is slightly occupied, while the Dirac point of graphene slightly shift towards higher energy, suggesting that a small amount of electron transfer from graphene to CuPc upon contact.

  4. Transport, electronic, and structural properties of nanocrystalline CuAlO2 delafossites

    NASA Astrophysics Data System (ADS)

    Durá, O. J.; Boada, R.; Rivera-Calzada, A.; León, C.; Bauer, E.; de la Torre, M. A. López; Chaboy, J.

    2011-01-01

    This work reports on the effect of grain size on the electrical, thermal, and structural properties of CuAlO2 samples obtained by solid-state reaction combined with ball milling. Electrical characterization made in microcrystalline and nanocrystalline samples shows that the electrical conductivity decreases several orders of magnitude for the nanocrystalline samples, and, in addition, there is a large discrepancy between the activation energies associated to thermoelectric power ES. The study of the Cu K-edge x-ray absorption spectra of the CuAlO2 samples shows that the local structure around Cu is preserved after the sintering process, indicating that the observed behavior of the electrical conductivity is of intrinsic origin. Complex conductivity measurements as a function of frequency allow us to discard grain-boundaries effects on the electrical transport. Thus, the changes in σ(T) and S(T) are interpreted in terms of charge localization in the framework of small polarons. This is in agreement with the analysis of the near-edge region of the absorption spectra, which indicates that sintering favors the Cu-O hybridization. As a consequence, oxygen atoms progressively lose their capability of trapping holes, and the electrical conductivity is also enhanced.

  5. Magnetic and structural properties of Co2FeAl thin films grown on Si substrate

    NASA Astrophysics Data System (ADS)

    Belmeguenai, Mohamed; Tuzcuoglu, Hanife; Gabor, Mihai; Petrisor, Traian; Tiusan, Coriolan; Berling, Dominique; Zighem, Fatih; Mourad Chérif, Salim

    2015-01-01

    The correlation between magnetic and structural properties of Co2FeAl (CFA) thin films of different thicknesses (10 nmstudied. x-ray diffraction (XRD) measurements revealed an (011) out-of-plane textured growth of the films. The deduced lattice parameter increases with the film thickness. Moreover, pole figures showed no in-plane preferential growth orientation. The magneto-optical Kerr effect hysteresis loops showed the presence of a weak in-plane uniaxial anisotropy with a random easy axis direction. The coercive field, measured with the applied field along the easy axis direction, and the uniaxial anisotropy field increase linearly with the inverse of the CFA thickness. The microstrip line ferromagnetic resonance measurements for in-plane and perpendicular applied magnetic fields revealed that the effective magnetization and the uniaxial in-plane anisotropy field follow a linear variation versus the inverse CFA thickness. This allows deriving a perpendicular surface anisotropy coefficient of -1.86 erg/cm2.

  6. Crystalline and structural properties of acid-modified lotus rhizome C-type starch.

    PubMed

    Cai, Jinwen; Cai, Canhui; Man, Jianmin; Yang, Yang; Zhang, Fengmin; Wei, Cunxu

    2014-02-15

    The crystalline and structural properties of acid-modified C-type starch from lotus rhizomes were investigated using a combination of techniques. The degradation of granule during hydrolysis began from the end distant from the hilum and then propagated into the center of granule, accompanied by loss of birefringence. The crystallinity changed from C-type to A-type via CA-type during hydrolysis. At the early stage of hydrolysis, the amylose content substantially reduced, the peak and conclusion gelatinization temperatures increased, and the enthalpy decreased. During hydrolysis, the double helix content gradually increased and the amorphous component decreased, the lamellar peak intensity firstly increased and then decreased accompanied by hydrolysis of amorphous and crystalline regions. This study elucidated that B-type allomorph was mainly arranged in the distal region of eccentric hilum, A-type allomorph was mainly located in the periphery of hilum end, and the center of granule was a mixed distribution of A- and B-type allomorphs. PMID:24507349

  7. Crystalline and structural properties of acid-modified lotus rhizome C-type starch.

    PubMed

    Cai, Jinwen; Cai, Canhui; Man, Jianmin; Yang, Yang; Zhang, Fengmin; Wei, Cunxu

    2014-02-15

    The crystalline and structural properties of acid-modified C-type starch from lotus rhizomes were investigated using a combination of techniques. The degradation of granule during hydrolysis began from the end distant from the hilum and then propagated into the center of granule, accompanied by loss of birefringence. The crystallinity changed from C-type to A-type via CA-type during hydrolysis. At the early stage of hydrolysis, the amylose content substantially reduced, the peak and conclusion gelatinization temperatures increased, and the enthalpy decreased. During hydrolysis, the double helix content gradually increased and the amorphous component decreased, the lamellar peak intensity firstly increased and then decreased accompanied by hydrolysis of amorphous and crystalline regions. This study elucidated that B-type allomorph was mainly arranged in the distal region of eccentric hilum, A-type allomorph was mainly located in the periphery of hilum end, and the center of granule was a mixed distribution of A- and B-type allomorphs.

  8. A Comparison of the Mechanical and Structural Properties of Fibrin Fibers with Other Protein Fibers

    PubMed Central

    Guthold, M.; Liu, W.; Sparks, E. A.; Jawerth, L. M.; Peng, L.; Falvo, M.; Superfine, R.; Hantgan, R. R.; Lord, S. T.

    2010-01-01

    In the past few years a great deal of progress has been made in studying the mechanical and structural properties of biological protein fibers. Here, we compare and review the stiffness (Young's modulus, E) and breaking strain (also called rupture strain or extensibility, εmax) of numerous biological protein fibers in light of the recently reported mechanical properties of fibrin fibers. Emphasis is also placed on the structural features and molecular mechanisms that endow biological protein fibers with their respective mechanical properties. Generally, stiff biological protein fibers have a Young's modulus on the order of a few Gigapascal and are not very extensible (εmax < 20%). They also display a very regular arrangement of their monomeric units. Soft biological protein fibers have a Young's modulus on the order of a few Megapascal and are very extensible (εmax > 100%). These soft, extensible fibers employ a variety of molecular mechanisms, such as extending amorphous regions or unfolding protein domains, to accommodate large strains. We conclude our review by proposing a novel model of how fibrin fibers might achieve their extremely large extensibility, despite the regular arrangement of the monomeric fibrin units within a fiber. We propose that fibrin fibers accommodate large strains by two major mechanisms: (1) an α-helix to β-strand conversion of the coiled coils; (2) a partial unfolding of the globular C-terminal domain of the γ-chain. PMID:17952642

  9. Magnetic and structural properties of Mn-doped Bi2Se3 topological insulators

    NASA Astrophysics Data System (ADS)

    Tarasenko, R.; Vališka, M.; Vondráček, M.; Horáková, K.; Tkáč, V.; Carva, K.; Baláž, P.; Holý, V.; Springholz, G.; Sechovský, V.; Honolka, J.

    2016-01-01

    A thorough investigation is presented of the magnetic and structural properties of Mn-doped Bi2Se3 topological insulators grown by molecular beam epitaxy on top of insulating BaF2 (111) substrates. The magnetic properties have been studied in the temperature range from 2 K to 300 K in magnetic fields up to 7 T. The systems were further characterized by means of high-resolution X-ray diffraction, electron-microprobe analysis, and X-ray photoemission spectroscopy. Samples with the atomic concentration of Mn up to about 0.06 exhibit an almost perfect crystalline structure while, for higher Mn concentrations, diffuse scattering from defects is observed. Photoemission results suggest a localized non-metallic Mn 3d5 ground state which is weakly or intermediately coupled to the Bi2Se3 environment. The exchange interaction between the Mn moments leads to a ferromagnetic phase at low temperatures with a roughly linear relation between the Curie temperature and the atomic concentration of Mn.

  10. Melting curves and structural properties of tantalum from the modified-Z method

    SciTech Connect

    Liu, C. M. E-mail: ycheng@scu.edu.cn; Xu, C.; Cheng, Y. E-mail: ycheng@scu.edu.cn; Chen, X. R.; Cai, L. C.

    2015-12-21

    The melting curves and structural properties of tantalum (Ta) are investigated by molecular dynamics simulations combining with potential model developed by Ravelo et al. [Phys. Rev. B 88, 134101 (2013)]. Before calculations, five potentials are systematically compared with their abilities of producing reasonable compressional and equilibrium mechanical properties of Ta. We have improved the modified-Z method introduced by Wang et al. [J. Appl. Phys. 114, 163514 (2013)] by increasing the sizes in L{sub x} and L{sub y} of the rectangular parallelepiped box (L{sub x} = L{sub y} ≪ L{sub z}). The influences of size and aspect ratio of the simulation box to melting curves are also fully tested. The structural differences between solid and liquid are detected by number density and local-order parameters Q{sub 6}. Moreover, the atoms' diffusion with simulation time, defects, and vacancies formations in the sample are all studied by comparing situations in solid, solid-liquid coexistence, and liquid state.

  11. Effect of alkali pretreatment on the structural properties and enzymatic hydrolysis of corn cob.

    PubMed

    Sahare, Padmavati; Singh, Rajkumar; Laxman, R Seeta; Rao, Mala

    2012-12-01

    An effective alkali pretreatment which affects the structural properties of cellulose (corn cob) has been studied. The pretreatment of corn cob was carried out with different combinations of alkali at varying temperatures. The most effective pretreatment of corn cob was achieved with 1 % alkali at 50 °C in 4 h. The crystallinity index (CrI) and specific surface area (SSA) of untreated corn cob was 39 % and 0.52 m(2)/g wherein after alkali pretreatment CrI decreased to 15 % and SSA increased to 3.32 m(2)/g. The fungal organism was identified as Penicillium pinophilum on the basis of ITS sequence. At 5 % substrate concentration using a complete cellulase from Penicillium pinophilum the hydrolysis of untreated corn cob with 5, 10 and 20 FPU/g enzyme loadings were 11 %, 13 % and 16 %, whereas after alkali treatment the hydrolysis increased to 78 %, 90 % and 100 %, respectively. Further hydrolytic potential of commercial cellulases viz. Accellerase™ 1,000, Palkofeel-30 and Palkocel-40 were investigated under similar conditions. PMID:22983744

  12. Structural properties and energetics of amorphous forms of carbon

    NASA Astrophysics Data System (ADS)

    Kelires, P. C.

    1993-01-01

    We have made a comparative theoretical study of the most common forms of unhydrogenated amorphous carbon (α-C), namely, of the dense, diamondlike phase and the low-density evaporated α-C (e-C). Emphasis is given to the connection among the structure, energetics, and stability of these phases. To make the simulations of the amorphous structures (formed by quenching the liquid) tractable, we used the Monte Carlo method, combined with the empirical-potential approach. Our analysis employs a powerful total-energy-partitioning scheme, which is proved very useful in treating the energetics of disordered systems. It is found that threefold sp2 sites are the energetically favorable geometries in e-C, and thus they are by far more numerous. The nonplanar character of sp2 sites and the absence of sixfold rings indicate that medium-range order is rather not significant in e-C. The increasing graphitic character of e-C, as the temperature is raised, is explained by resorting to the effective temperatures T*, at which the atoms freeze in their lattice positions. For diamondlike α-C, the simulations show that there exist two distinctly different dense structures. The ``as-quenched'' one (i-C) is mostly sp3 bonded, but it is metastable. Upon annealing, it converts into a second phase (i-C*), mostly sp2 bonded, with a significant energy gain. A specific mechanism is proposed for this transition. The insensitivity of density to annealing is explained if we use the concept of the ``glass transition temperature'' T*. Finally, by introducing an isotropic bulk modulus for the amorphous phase, it is found that e-C has a much lower compressibility than i-C*, enhancing the distinguishability among the two low-coordinated forms of α-C.

  13. Structural properties of ultrafine Ba-hexaferrite nanoparticles

    SciTech Connect

    Makovec, Darko; Primc, Darinka; Sturm, Saso; Kodre, Alojz; Hanzel, Darko; Drofenik, Miha

    2012-12-15

    Crystal structure of ultrafine Ba-hexaferrite (BaFe{sub 12}O{sub 19}) nanoparticles was studied using X-ray diffractometry (XRD), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDXS), X-ray absorption fine structure (XAFS), and Moessbauer spectroscopy (MS), to be compared to the structure of larger nanoparticles and the bulk. The nanoparticles were synthesized with hydrothermal treatment of an appropriate suspension of Ba and Fe hydroxides in the presence of a large excess of OH{sup -}. The ultrafine nanoparticles were formed in a discoid shape, {approx}10 nm wide and only {approx}3 nm thick, comparable to the size of the hexagonal unit cell in the c-direction. The HRTEM image analysis confirmed the hexaferrite structure, whereas EDXS showed the composition matching the BaFe{sub 12}O{sub 19} formula. XAFS and MS analyses showed considerable disorder of the structure, most probably responsible for the low magnetization. - Graphical abstract: Left: HREM image of an ultrafine Ba-hexaferrite nanoparticle (inset: TEM image of the nanoparticles); Right: the experimental HRTEM image is compared with calculated image and corresponding atomic model. Highlights: Black-Right-Pointing-Pointer Crystal structure of ultrafine Ba-hexaferrite (BaFe{sub 12}O{sub 19}) nanoparticles was compared to the structure of the bulk. Black-Right-Pointing-Pointer Thickness the discoid nanoparticles was comparable to the size of the hexagonal unit cell in the c-direction. Black-Right-Pointing-Pointer Considerable disorder of the nanoparticles' structure is most probably responsible for their low magnetization.

  14. Thermal and structural properties of low-fluence irradiated graphite

    NASA Astrophysics Data System (ADS)

    Lexa, Dusan; Dauke, Michael

    2009-02-01

    The release of Wigner energy from graphite irradiated by fast neutrons at a TRIGA Mark II research reactor has been studied by differential scanning calorimetry and simultaneous differential scanning calorimetry / synchrotron powder X-ray diffraction between 25 and 725 °C at a heating rate of 10 °C min -1. The graphite, having been subject to a fast-neutron fluence from 5.67 × 10 20 to 1.13 × 10 22 n m -2 at a fast-neutron flux ( E > 0.1 MeV) of 7.88 × 10 16 n m -2 s -1 and at temperatures not exceeding 100 °C, exhibits Wigner energies ranging from 1.2 to 21.8 J g -1 and a Wigner energy accumulation rate of 1.9 × 10 -21 J g -1 n -1 m 2. The differential-scanning-calorimeter curves exhibit, in addition to the well known peak at ˜200 °C, a pronounced fine structure consisting of additional peaks at ˜150, ˜230, and ˜280 °C. These peaks correspond to activation energies of 1.31, 1.47, 1.57, and 1.72 eV, respectively. Crystal structure of the samples is intact. The dependence of the c lattice parameter on temperature between 25 and 725 °C as determined by Rietveld refinement leads to the expected microscopic thermal expansion coefficient along the c axis of ˜26 × 10 -6 °C -1. At 200 °C, coinciding with the maximum in the differential-scanning-calorimeter curves, no measurable changes in the rate of thermal expansion have been detected - unlike its decrease previously seen in more highly irradiated graphite.

  15. Carbide cluster metallofullerenes: structure, properties, and possible origin.

    PubMed

    Lu, Xing; Akasaka, Takeshi; Nagase, Shigeru

    2013-07-16

    Endohedral metallofullerenes (EMFs) are hybrid molecules with different metallic species encapsulated inside the fullerene cages. In addition to conventional EMFs that contain only metal ions, researchers have constructed novel compounds that encapsulate metallic clusters of nitride, carbide, oxide, cyanide, and sulfide. Among these structures, carbide cluster metallofullerenes (CCMFs) are unique because their synthesis requires only graphite and the metal source. As a result the molecular structures of CCMFs are particularly difficult to characterize. Two carbon atoms are encapsulated inside the cage, but they do not participate in constructing the cage framework. Recent X-ray crystallographic studies of EMFs have allowed researchers to unambiguously identify CCMFs (MxC₂@C2n). Previously most of these structures had been described as conventional EMFs Mx@C2n+2. Most of these species are scandium-containing compounds such as Sc3C₂@Ih(7)-C₈₀ [not Sc₃@C3v(7)-C₈₂], Sc₂C₂@C2v(5)-C₈₀ [not Sc₂@C₈₂], Sc₂C₂@Cs(6)-C₈₂ [not Sc₂@Cs(10)-C₈₄], Sc₂C₂@C2v(9)-C₈₂ [not Sc₂@C2v(17)-C₈₄], Sc₂C₂@C3v(8)-C₈₂ [not Sc₂@D2d(23)-C₈₄], and Sc₂C₂@D2d(23)-C₈₄ [not Sc₂@C₈₆]. Additional examples of CCMFs include Gd₂C₂@D₃(85)-C₉₂, Sc₂C₂@C2v(6073)-C₆₈, Ti₂C₂@D3h(5)-C₇₈, M₂C₂@C3v(8)-C₈₂, M₂C₂@Cs(6)-C₈₂ (M = Y, Er, etc.), Y₂C₂@C₈₄, Y₂C₂@D₃(85)-C₉₂, Y₂C₂@D₅(450)-C₁₀₀, and Lu₃C₂@D₂(35)-C₈₈. The existence of so many CCMF species reminds us that the symbol '@' (which denotes the encapsulation status of EMFs) should be used with caution with species whose molecular structures have not been determined unambiguously. This Account presents a detailed summary of all aspects of CCMFs, including historically erroneous assignments and corrected structural characterizations, along with their intrinsic properties such as electrochemical and chemical

  16. Relationship Satisfaction Among Mothers of Children With Congenital Heart Defects: A Prospective Case-Cohort Study

    PubMed Central

    Solberg, Øivind; Holmstrøm, Henrik; Landolt, Markus A.; Eskedal, Leif T.; Vollrath, Margarete E.

    2013-01-01

    Objective To assess the level of partner relationship satisfaction among mothers of children with different severity of congenital heart defects (CHD) compared with mothers in the cohort. Methods Mothers of children with mild, moderate, or severe CHD (n = 182) and a cohort of mothers of children without CHD (n = 46,782) from the Norwegian Mother and Child Cohort Study were assessed at 5 time points from pregnancy to 36 months postpartum. A 5-item version of the Relationship Satisfaction scale was used, and relevant covariates were explored. Results The trajectories of relationship satisfaction among mothers of children with varying CHD severity did not differ from the trajectories in the cohort. All women in the cohort experienced decreasing relationship satisfaction from 18 months after delivery up to 36 months after delivery. Conclusions Having a child with CHD, regardless of severity, does not appear to exacerbate the decline in relationship satisfaction. PMID:23792348

  17. A STUDY OF RELATIONSHIP BETWEEN "GUERILLA HEAVY RAINFALL" AND DISASTER

    NASA Astrophysics Data System (ADS)

    Ushiyama, Motoyuki

    "Guerilla heavy rainfall" is a newly-coined word by mass media of Japan. The four major newspaper publishing companies began to use this word frequently from the beginning of August, 2008. The definition of "Guerilla heavy rainfall" is not clear. It was found from the result of newspaper article analysis from 2008 to 2009 that short-time very heavy rainfall events are called "Guerilla heavy rainfall". In this study, the rainfall event of 80mm or more of rainfalls of 1 hour and 149mm or less of rainfalls was defined as "Guerilla heavy rainfall". 104 events of "Guerilla heavy rainfall" were extracted from AMeDAS precipitation data from 1979 to 2008. There were two victims of these heavy rainfall events in total. They killed at basement or underpass. Although inundation above the floor level occurred in 38% of event, the damage of 100 or more buildings was 9%. We may say that "Guerilla heavy rainfall" does not cause large-scale damage. However, it is necessary to keep in mind that damage caused by "Guerilla heavy rainfall" is generated well in high-risk area of flood, such as basement, underpass, low land and river park.

  18. The Relationship Between Depression and Metabolic Syndrome: Systematic Review and Meta-Analysis Study

    PubMed Central

    Ghanei Gheshlagh, Reza; Parizad, Naser; Sayehmiri, Kourosh

    2016-01-01

    Context Several studies have been conducted on the relationship between depression and metabolic syndrome, which have had conflicting results. The purpose of this study was a meta-analysis of studies that have examined the relationship between these two variables. Evidence Acquisition This meta-analysis systematically reviewed the relationship between depression and metabolic syndrome. Scientific databases including IranMedex, SID, Magiran, Scopus, PubMed, Google Scholar, and Science Direct were searched and 17 articles were extracted from 2000 to 2014. Selected studies data were analyzed using meta-analysis and random effects model. Heterogeneity between the studies was examined using I2. Data were analyzed using STATA software version 12.1. Results Seventeen studies were analyzed with a sample size of 31880 people. Analysis by the type of studies showed that the relationship between the two variables in cross-sectional studies (OR = 1.51, CI 95% = 1.36 - 1.68) and cohort studies (OR = 1.6, CI 95% = 1.23 - 2.08) was significant. In general, the heterogeneity test results among the studies was not significant (P for heterogeneity = 0.08, I2 = 39.8%). Conclusions There is a relationship between depression and metabolic syndrome.

  19. The Relationship Between Depression and Metabolic Syndrome: Systematic Review and Meta-Analysis Study

    PubMed Central

    Ghanei Gheshlagh, Reza; Parizad, Naser; Sayehmiri, Kourosh

    2016-01-01

    Context Several studies have been conducted on the relationship between depression and metabolic syndrome, which have had conflicting results. The purpose of this study was a meta-analysis of studies that have examined the relationship between these two variables. Evidence Acquisition This meta-analysis systematically reviewed the relationship between depression and metabolic syndrome. Scientific databases including IranMedex, SID, Magiran, Scopus, PubMed, Google Scholar, and Science Direct were searched and 17 articles were extracted from 2000 to 2014. Selected studies data were analyzed using meta-analysis and random effects model. Heterogeneity between the studies was examined using I2. Data were analyzed using STATA software version 12.1. Results Seventeen studies were analyzed with a sample size of 31880 people. Analysis by the type of studies showed that the relationship between the two variables in cross-sectional studies (OR = 1.51, CI 95% = 1.36 - 1.68) and cohort studies (OR = 1.6, CI 95% = 1.23 - 2.08) was significant. In general, the heterogeneity test results among the studies was not significant (P for heterogeneity = 0.08, I2 = 39.8%). Conclusions There is a relationship between depression and metabolic syndrome. PMID:27621928

  20. A Case Study of a First Year Superintendent: The Relationship between Person and Context.

    ERIC Educational Resources Information Center

    Bogotch, Ira E.

    This paper presents findings of a case-study analysis of the first year of a superintendent, with a focus on the relationship between school-district context and individual characteristics. The case study was conducted as part of a larger, national study comprised of 13 case studies of the superintendency across the United States. The case study…