WorldWideScience
 
 
1

Teachers' Domain: Structure-Property Relationships  

Science.gov (United States)

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

2011-08-19

2

Structure property relationships in various filled polymers  

Science.gov (United States)

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

Yu, Jiong

3

Structure/property relationships for metal/metal interfaces  

International Nuclear Information System (INIS)

This volume contains the Proceedings of the Symposium on Structure/Property Relationships for Metal/Metal Interfaces held at the 1991 Spring Meeting of the Materials Research Society. The papers published here, address this topic by means of experimental and theoretical investigations on a variety of interfacial systems that are found or can be fabricated in metals. The central theme of the Symposium was the relationship between the physical properties of metallic materials containing interfaces and the detailed atomic structure of those interfaces. When categorized by an interest in interfacial structure, these fields include metal/vacuum surface physics and surface layer characterization, x-ray diffractometry of films and superlattices, TEM characterization of orientational relationships in superlattices, grain boundaries, and dissimilar metal interfaces, and analytical microscopy of grain boundaries and dissimilar metal interfaces. As categorized by an interest in properties, these fields include elastic and plastic properties of superlattices, grain boundaries, and generic interfaces, dislocation motion through interfaces, fracture, segregation, and precipitation at grain boundaries and at dissimilar metal interfaces, x-ray optical properties of multilayers, and magnetic properties of superlattices

4

Structure/property relationships in multipass GMA welding of beryllium.  

Energy Technology Data Exchange (ETDEWEB)

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

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

2001-01-01

5

Water Activated Carbon Organics Adsorption Structure - Property Relationships  

Directory of Open Access Journals (Sweden)

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

Lorentz JÄNTSCHI

2004-08-01

6

Structure-functional property relationships in thin film vanadium dioxide  

Science.gov (United States)

The metal-insulator transition (MIT) in VO2 induces a dramatic change in electric, dielectric and optical characteristics in the vicinity of room temperature. This fascinating phenomenon has attracted great attention from fundamental research to reveal its mechanisms relevant to the electronic correlation as well as from applications to exploit its effect in novel electronic and photonic devices. This dissertation includes detailed studies on the correlation among microstructure characteristics, functional electrical and dielectric properties, and chemical composition of VO2 thin films as well as the critical effects of synthesis conditions on them and their relationships on the basis of electrical transport measurements, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction analysis. We also demonstrated the novel post-deposition heat treatment method based on photon irradiation to modify MIT properties of VO2 thin films at temperature much lower than the synthesis temperature and showed the excellent stability of the MIT functionality of VO2 thin films through multiple cyclic transition experiments along with electric and structural property characterizations. Using experimental combination of temperature-variable Kelvin probe microscopy, electric property characterizations, and in-depth XPS profiling, we explored the discrepancy of MIT evolution on the film surface and inside bulk region of VO2 films in terms of work function, stoichiometry, and film conductivity. Further, we have introduced novel approaches to investigate MIT phenomena in nanoscale utilizing simple exploratory capacitor and metal-oxide-semiconductor structures based on VO2 thin layers.

Ko, Changhyun

7

Structure/Property Relationships in Polymer Light-emitting Diodes  

Science.gov (United States)

Since the first report of polymer light emitting diodes (PLED) in 1990, the search for new polymers with stable and efficient electroluminescent properties has increased, but a through understanding of the structure property relations in these polymers is still lacking. One of our primary goals is to develop a fundamental understanding of these structure/property relationships in conjugated polymers. Specifically, how do polydispersity in conjugation length, polymer architecture (1-dimensional versus 2-dimensional) and chain packing affect mobility and luminescence yield. We will report on recent results in these areas. By blending p-phenylenevinylene oligomers, that have different conjugation lengths, we have shown that long chains can act as traps and that polydispersity in conjugation significantly limits the performance of light-emitting diodes. We have also synthesized 2-dimensional phenylenevinylenes and will report on their performance versus the performance of the corresponding linear molecules. In combination, these results begin to form a more complete picture of how the structure of these polymers impacts performance.

Galvin, Mary

2002-03-01

8

Bio-related noble metal nanoparticle structure property relationships  

Science.gov (United States)

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 (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 nanostructures. Data from control experiments found the hexagons could be made without RNA and confirmed the presence of nanocrystalline Pd metal NPs in unpurified Pd2(DBA)3 reagent powder. Furthermore, the study determined the hexagon platelets to have a chemical composition of ˜90at% carbon and ˜10at% Pd and a lattice parameter corresponding to molecular crystals of Pd2(DBA)3 precursor, not Pd metal.* *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Windows MediaPlayer or RealPlayer.

Leonard, Donovan Nicholas

9

Modelling of the structure-property relationships in the ?-quartz structures  

Science.gov (United States)

The molecular mechanism has been employed to model the structure-property relationships of auxetic material with tetrahedral framework at the atomistic level. The germania ?-quartz subject uniaxial stress loading in z direction will be investigated. The strain-dependent structure and mechanical properties will be predicted from the force field based simulations, including the transformation from positive-to-negative Poisson's ratio behaviour and vice versa.

Yao, Yongtao; Alderson, Kim; Alderson, Andrew; Leng, Jinsong

2013-04-01

10

Relationships between structure and mechanical properties of Inconel 718  

International Nuclear Information System (INIS)

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

11

Structure-property relationships of multiferroic materials: A nano perspective  

Science.gov (United States)

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

Bai, Feiming

12

Quantitative Structure–Property Relationships for Aryldiazonia  

Directory of Open Access Journals (Sweden)

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

Oxana I. Zhelezko

2002-07-01

13

Structure-Property Relationships in Oxides Containing Tellurium  

Science.gov (United States)

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

Siritanon, Theeranun

14

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

Science.gov (United States)

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

A. C. Taylor, A. J. Kinloch

2006-01-01

15

Structure-Property-Function Relationships in Nanoscale Oxide Sensors : a Case Study Based on Zinc Oxide  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Chemical sensing on oxide sensors is a complex phenomenon involving catalytic activity as well as electronic properties. Thus, the properties of oxide sensors are highly sensitive towards structural changes. Effects like surface area, grain size, and, in addition, the occurrence of defects give separate contributions to the current. Structure property function relationships can be elucidated using a combination of state-of-the-art analytical techniques. It is shown, that impurity atoms in the...

Polarz, Sebastian; Roy, Abhijit; Lehmann, Michael; Driess, Matthias; Kruis, Frank E.; Hoffmann, Andreas; Zimmer, Patrick

2007-01-01

16

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of the paper is to present the results obtained by utilization of an original approach called Molecular Descriptors Family on Structure-Property (MDF-SPR) and Structure-Activity Relationships (MDF-SAR) applied on classes of chemical compounds and its usefulness as precursors of models elaboration of new compounds with better properties and/or activities and low production costs. The MDF-SPR/MDF-SAR methodology integrates the complex information obtained from compound’s structure in ...

Sorana-Daniela Bolboacă; Lorentz Jäntschi

2007-01-01

17

Multiscale relationships between fibronectin structure and functional properties.  

Science.gov (United States)

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

Bradshaw, M J; Smith, M L

2014-04-01

18

Structure-property-function relationships in triple helical collagen hydrogels  

CERN Document Server

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

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

2012-01-01

19

Neural networks as a method for elucidating structure-property relationships for organic compounds  

International Nuclear Information System (INIS)

The published data devoted to the use of the neural network approach in the simulation of structure-property relationships for organic compounds are reviewed. The basic principles of the neural network simulation are discussed along with the characteristic features of the neural network approach typical of the representation and classification of structural chemical data. Brief information on neural network models of spectral characteristics, reactivities, physicochemical properties and biological activities of organic compounds is presented.

20

Structure property relationships in polycarbonate/polydimethylsiloxane copolymers  

International Nuclear Information System (INIS)

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

 
 
 
 
21

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

Directory of Open Access Journals (Sweden)

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

Menezes Fabiano A. S.

2000-01-01

22

Structure-Properties Relationship of Hierarchically Ordered Large and Small Molecules Self-Assemblies.  

Science.gov (United States)

Membranes formed by mixing high molecular weight hyluronic acid (HA) and oppositely charged peptide amphiphiles (PAs) have been shown to have a unique hierarchically ordered structure which consists of three regions: an amorphous biopolymer layer, a narrow region of PA fibers parallel to the interface and a layer of fibers perpendicular to the interface. Understanding of the structure-property relationships in these self-assembling systems is a necessary step in designing these structures for specific applications. We have formed and characterized PA/polymer self-assembled membranes using different polyelectrolytes (alginate, ?-carrageenan, poly(acrylic acid) etc). SEM micrographs show that these assemblies have the same parallel/perpendicular fibers structure as the original HA/PA assembly. The mechanical properties and water permeability of these structures measured by membrane inflation techniques and osmotic swelling indicate that the polymer characteristics [i.e. Mw, charge density] are an important factor in determining structure formation, kinetics and final properties.

Bitton, Ronit; Carvajal, Daniel; Mantei, Jason; Velichko, Yuri; Shull, Kenneth; Stupp, Samuel

2010-03-01

23

Relationship of multifractal characteristics of fracture surface structures in molybdenum to its mechanical properties  

International Nuclear Information System (INIS)

A quantitative technique of material structure analysis based on interpretation of multifractal formalism is described. The technique also permits evaluating the uniformity and latent periodicity of structures under study. This new method was used to investigate relationships of multifractal characteristics of structure of static fracture surfaces in wires of commercial molybdenum and a low molybdenum alloy (Mo-0.1HfC-0.1HfN-0.03C) to mechanical properties of mentioned materials after various surface treatments (drawing, electropolishing, abrasive finishing). Relative changes of multifractal characteristics are shown to correlate well with values of relative changes in tensile properties and fatigue life. 26 refs.; 1 fig

24

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2006-07-14

25

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

Energy Technology Data Exchange (ETDEWEB)

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

Han, M.K.

2006-05-06

26

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

Energy Technology Data Exchange (ETDEWEB)

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

Mi-Kyung Han

2006-05-01

27

Experimental studies of the relationship between DNA structure and chemical modification, and its charge transport properties  

Science.gov (United States)

We experimentally investigate the influence of the physico-chemical properties of DNA molecules on its charge transport capabilities. By performing comparative rather than absolute charge transport measurements, we probe the effect of chemical modifications on the electronic properties of the molecule. Modifications include the introduction of phosphodiester bond breaks, and intercalation of metal cations, as probes to ascertain the relationship between DNA structure and electronic properties. Furthermore, we perform comparative measurements between double strand and single strand DNA molecules, to probe the importance of DNA duplex structure on its electronic properties. Our comparative current-voltage measurements yield distinct curves associated with specific modifications to the DNA molecule. We also investigate different lengths of lambda DNA. AFM images confirm the presence of DNA molecules between the lithographic measurement electrodes. (NSF DMR 0103034).

Soghomonian, V.; Davis, D. E.; Belak, A. A.; Dowd, J. F.; Heremans, J. J.

2007-03-01

28

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

Directory of Open Access Journals (Sweden)

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

Sorana-Daniela Bolboacă

2007-03-01

29

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

Science.gov (United States)

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

Hollowell, Kendall Birckhead

30

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

Directory of Open Access Journals (Sweden)

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

J. J. Schwab

2012-07-01

31

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

Science.gov (United States)

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

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

32

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2010-01-01

33

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

International Nuclear Information System (INIS)

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

34

Structure-property relationship of a spray formed Al-Y-Ni-Co alloy  

International Nuclear Information System (INIS)

The structure-property relationship of a spray formed Al-Y-Ni-Co alloy with two sets of processing conditions was investigated. Significant differences in tensile strength, yield strength, and high temperature ductility were observed with respect to the microstructural changes. Fracture toughness values were determined for both sets of specimens and found to be 7.5 and 5.8 MPa·m1/2, respectively. Three intermetallic phases were observed in the matrix and constitute a volume fraction of approximately 75%. It is believed that the specimens failed during fracture toughness testing by the mechanism of cleavage, observed in the Al3Y intermetallic particles

35

Synthesis and quantitative structure-property relationships of side chain-modified hyodeoxycholic acid derivatives.  

Science.gov (United States)

Bile acids have emerged as versatile signalling compounds of a complex network of nuclear and membrane receptors regulating various endocrine and paracrine functions. The elucidation of the interconnection between the biological pathways under the bile acid control and manifestations of hepatic and metabolic diseases have extended the scope of this class of steroids for in vivo investigations. In this framework, the design and synthesis of novel biliary derivatives able to modulate a specific receptor requires a deep understanding of both structure-activity and structure-property relationships of bile acids. In this paper, we report the preparation and the critical micellization concentration evaluation of a series of hyodeoxycholic acid derivatives characterized by a diverse side chain length and by the presence of a methyl group at the alpha position with respect to the terminal carboxylic acid moiety. The data collected are instrumental to extend on a quantitative basis, the knowledge of the current structure-property relationships of bile acids and will be fruitful, in combination with models of receptor activity, to design and prioritize the synthesis of novel pharmacokinetically suitable ligands useful in the validation of bile acid-responsive receptors as therapeutic targets. PMID:23999724

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

2013-01-01

36

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

Directory of Open Access Journals (Sweden)

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

Antimo Gioiello

2013-08-01

37

Quantitative structure property relationships for the adsorption of pharmaceuticals onto activated carbon.  

Science.gov (United States)

Isotherms were determined for the adsorption of five pharmaceutical residues, primidone, carbamazepine, ibuprofen, naproxen and diclofenac, to Calgon Filtrasorb 300 powdered activated carbon (PAC). The sorption behavior was examined in ultra-pure and wastewater effluent organic matter (EfOM) matrices, where more sorption was observed in the ultra-pure water for PAC doses greater than 10 mg/L suggesting the presence of EfOM hinders the sorption of the pharmaceuticals to the PAC. Adsorption behaviors were described by the Freundlich isotherm model. Quantitative structure property relationships (QSPRs) in the form of polyparameter linear solvation energy relationships were developed for simulating the Freundlich adsorption capacity in both ultra-pure and EfOM matrices. The significant 3D-based descriptors for the QSPRs were the molar volume, polarizability and hydrogen-bond donor parameters. PMID:21076212

Dickenson, E R V; Drewes, J E

2010-01-01

38

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 genera...

2011-01-01

39

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

Science.gov (United States)

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

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

2014-05-01

40

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

Science.gov (United States)

The structure activity relationship between the C??-C?? methylene double bond on the aglycone of steviol glycosides and the corresponding impact on their sweet taste has been reported here for the first time. It has been observed that converting stevioside and rebaudioside A to their corresponding ketones by switching the doubly bonded methylene on C-17 for a ketone group actually removes the sweet taste properties of these molecules completely. Regenerating the original molecules tends to restore the sweet taste of both the steviol glycosides. Thus this C??-C?? methylene double bond in rebaudioside A and stevioside can be regarded as a pharmacophore essential for the sweetness property of these molecules. PMID:22481539

Upreti, Mani; Dubois, Grant; Prakash, Indra

2012-01-01

 
 
 
 
41

Molecular basis of quantitative structure-properties relationships (QSPR): a quantum similarity approach.  

Science.gov (United States)

Since the dawn of quantitative structure-properties relationships (QSPR), empirical parameters related to structural, electronic and hydrophobic molecular properties have been used as molecular descriptors to determine such relationships. Among all these parameters, Hammett sigma constants and the logarithm of the octanol-water partition coefficient, log P, have been massively employed in QSPR studies. In the present paper, a new molecular descriptor, based on quantum similarity measures (QSM), is proposed as a general substitute of these empirical parameters. This work continues previous analyses related to the use of QSM to QSPR, introducing molecular quantum self-similarity measures (MQS-SM) as a single working parameter in some cases. The use of MQS-SM as a molecular descriptor is first confirmed from the correlation with the aforementioned empirical parameters. The Hammett equation has been examined using MQS-SM for a series of substituted carboxylic acids. Then, for a series of aliphatic alcohols and acetic acid esters, log P values have been correlated with the self-similarity measure between density functions in water and octanol of a given molecule. And finally, some examples and applications of MQS-SM to determine QSAR are presented. In all studied cases MQS-SM appeared to be excellent molecular descriptors usable in general QSPR applications of chemical interest. PMID:10216833

Ponec, R; Amat, L; Carbó-Dorca, R

1999-05-01

42

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Um modelo para a interação de bisamidinas aromáticas com o B-DNA foi estabelecido através de estudos de relações estruturas-propriedades derivadas dos cálculos de descritores tridimensionais WHIM-3D. Uma análise de componentes principais, PCA, dos descritores revelou três componentes principais sign [...] ificativas e agrupou as bisamidinas em diferentes conformações: estendida, semi-estendida e semifechada com interações tipo pi-pi e também por ligações de hidrogênio. O método SIMCA classificou as conformações de acordo com essas características. A interação das 29 bisamidinas estudadas com o B-DNA dá-se através de suas propriedades de forma, distribuição e dimensão. Abstract in english A proposed model for the interaction of bisamidine analogues with the B-DNA receptor is established by structure-property relationship studies derived from 3D-WHIM descriptor calculations. Three classes, each with relevant information about structural relationships, were determined by PCA and SIMCA [...] analyses for molecular conformations described by 3D-WHIM descriptors for a set of 29 bisamidines with antileishmaniasis and anti-PCP activities. Shape, distribution and dimension properties mostly govern the interaction of bisamidines with B-DNA through the minor groove AT rich regions.

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

2000-08-01

43

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

International Nuclear Information System (INIS)

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

44

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

Science.gov (United States)

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

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

2011-05-01

45

A study of structure-property relationships in layered copper oxides  

International Nuclear Information System (INIS)

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

46

Analysis of structure-Caco-2 permeability relationships using a property landscape approach.  

Science.gov (United States)

Understanding the relationship between the chemical structure of bioactive compounds and Caco-2 permeability is of major importance in modern drug discovery. The purpose of this work was to characterize systematically the Caco-2 permeability landscape of a benchmark dataset of 100 molecules using a novel approach based on the emerging concept of property landscape modeling. Pairwise comparisons of the Caco-2 permeability and chemical structures were calculated for all possible combinations in the dataset. To compare the chemical structures, two distinct manners to represent the molecules were employed, namely, continuous properties previously used to derive QSPR models and molecular fingerprints with different designs. We introduce the concept of "permeability cliffs" discussing cases of compounds with high molecular similarity but large permeability difference. All permeability cliffs were regarded as shallow cliffs, since no extreme difference in Caco-2 permeability (less than two log units) was identified in the dataset. A clear dependence of Caco-2 permeability landscape with molecular representation was observed. The current approach can be further extended to model other ADME relevant landscapes. PMID:24710715

Rojas-Aguirre, Yareli; Medina-Franco, José L

2014-08-01

47

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

Directory of Open Access Journals (Sweden)

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

Trišovi? Nemanja

2011-10-01

48

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

Science.gov (United States)

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

Khajeh, A; Modarress, H

2014-01-01

49

Quantitative structure-property relationship modeling: a valuable support in high-throughput screening quality control.  

Science.gov (United States)

Evaluation of important pharmacokinetic properties such as hydrophobicity by high-throughput screening (HTS) methods is a major issue in drug discovery. In this paper, we present measurements of the chromatographic hydrophobicity index (CHI) on a subset of the French chemical library Chimiothèque Nationale (CN). The data were used in quantitative structure-property relationship (QSPR) modeling in order to annotate the CN. An algorithm is proposed to detect problematic molecules with large prediction errors, called outliers. In order to find an explanation for these large discrepancies between predicted and experimental values, these compounds were reanalyzed experimentally. As the first selected outliers indeed had experimental problems, including hydrolysis or sheer absence of expected structure, we herewith propose the use of QSPR as a support tool for quality control of screening data and encourage cooperation between experimental and theoretical teams to improve results. The corrected data were used to produce a model, which is freely available on our web server at http://infochim.u-strasbg.fr/webserv/VSEngine.html . PMID:24479843

Ruggiu, Fiorella; Gizzi, Patrick; Galzi, Jean-Luc; Hibert, Marcel; Haiech, Jacques; Baskin, Igor; Horvath, Dragos; Marcou, Gilles; Varnek, Alexandre

2014-03-01

50

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

International Nuclear Information System (INIS)

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

51

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

Science.gov (United States)

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

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

2014-04-15

52

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

DEFF Research Database (Denmark)

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

Panpipat, Worawan; Dong, Mingdong

2013-01-01

53

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

DEFF Research Database (Denmark)

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

Ma, Zaifei; Sun, Wenjun

2014-01-01

54

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1997-04-01

55

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

Directory of Open Access Journals (Sweden)

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

Drago Skrtic

2009-11-01

56

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

Science.gov (United States)

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

Murphy, Peter M.

2007-01-01

57

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

International Nuclear Information System (INIS)

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

58

Quantitative structure-property relationships for longitudinal, transverse, and molecular static polarizabilities in polyynes.  

Science.gov (United States)

The present work reports for the first time quantitative structure-property relationships, derived at the benchmark CCSD(T)/cc-PVTZ level of theory that estimate the static longitudinal, transverse, and molecular polarizability in polyynes (C2nH2), as a function of their length (L). In the case of independent electron models, regardless of the form of the nuclei potential that the electrons experience, the polarizability increases strongly with system size, scaling as L(4). In contrast, the static longitudinal polarizability in polyynes have a considerably weaker length-dependence (L(1.64)). This is shown to predominantly arise from electron-electron repulsion rather than electron correlation by a systematic study of the polarizability length dependence in several simple quantum mechanical systems (e.g., particle-in-box, simple harmonic oscillator) and other molecular systems (e.g., H2, H2(+), polyynes). Decrease of the electron-electron repulsion term is suggested to be the key factor in enhancing nonlinear polarizability characteristics of linear oligomeric and polymeric materials. PMID:18528978

Zeinalipour-Yazdi, Constantinos D; Pullman, David P

2008-06-26

59

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

Science.gov (United States)

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

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

2009-09-21

60

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

International Nuclear Information System (INIS)

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

 
 
 
 
61

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

Energy Technology Data Exchange (ETDEWEB)

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

D' Archivio, Angelo Antonio, E-mail: angeloantonio.darchivio@univaq.it [Dipartimento di Chimica, Ingegneria Chimica e Materiali, Universita degli Studi dell' Aquila, Via Vetoio, 67010 Coppito, L' Aquila (Italy); Incani, Angela; Mazzeo, Pietro; Ruggieri, Fabrizio [Dipartimento di Chimica, Ingegneria Chimica e Materiali, Universita degli Studi dell' Aquila, Via Vetoio, 67010 Coppito, L' Aquila (Italy)

2009-09-21

62

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

Science.gov (United States)

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

Stringer, Craig J.

63

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

International Nuclear Information System (INIS)

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

64

Structure-property relationship in dielectric mixtures: application of the spectral density theory  

International Nuclear Information System (INIS)

This paper presents numerical simulations performed on dielectric properties of two-dimensional binary composites. The influence of structural differences and intrinsic electrical properties of constituents on the composite's overall electrical properties is investigated. The structural differences are resolved by fitting the dielectric data with an empirical formula and by the spectral density representation approach. At low concentrations of inclusions (concentrations lower than the percolation threshold), the spectral density functions are delta-sequences, which corresponds to the predictions of the general Maxwell-Garnett (MG) mixture formula. At high concentrations of inclusions (close to the percolation threshold) systems exhibit non-Debye-type dielectric dispersions, and the spectral density functions differ from each other and that predicted by the MG expression. The analysis of the dielectric dispersions with an empirical formula also brings out the structural differences between the considered geometries, however, the information is not qualitative. The empirical formula can only be used to compare structures. The spectral representation method on the other hand is a concrete way of characterizing the structures of the dielectric mixtures. Therefore, as in other spectroscopic techniques, a look-up table might be useful to classify/characterize structures of composite materials. This can be achieved by generating dielectric data for known structures by using ab initio calculations, as presented and emphasized in this study. The numerical technique presented here is not based on any a priori assumption methods

65

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-04-15

66

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2006-09-27

67

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

Science.gov (United States)

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

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

2014-08-01

68

Microstructure mechanical properties relationship in bainitic structures; Relacion microestructure-comportamiento mecanico en estructuras bainiticas  

Energy Technology Data Exchange (ETDEWEB)

In the present work, the microstructures and their mechanical properties have been studies in different bainitic structures. therefore, different bainitic morphologies have been produced by isothermal treatments carried out at different temperatures. For these steels, 400-450 degree centigree is the optimum range of temperatures in order to obtain bainitic structures. If the Temperature is higher, perlite is also formed and if it is lower, martensite is obtained during quenching. SEM and EBSD/OIM techniques were applied in order to study the microstructure. Tensile tests were carried out for mechanical characterization. (Author) 20 refs.

Altuna, M. A.; Gutierrez, I.

2005-07-01

69

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

1993-01-01

70

A study of structure-property relationships in layered copper oxides  

CERN Document Server

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

Hyatt, N

2000-01-01

71

Structure-dielectric properties relationships in copper-substituted magnesium ferrites  

International Nuclear Information System (INIS)

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

72

Analyzing structure-photophysical property relationships for isolated T8, T10, and T12 stilbenevinylsilsesquioxanes.  

Science.gov (United States)

Silsesquioxanes (SQs) are of considerable interest for hybrid electronic and photonic materials. However, to date, their photophysical properties have not been studied extensively, thus their potential remains conjecture. Here we describe the first known efforts to map structure-photophysical properties as a function of cage symmetry and size by comparing identically functionalized systems. Our focus here is on the solution photophysical properties of the title stilbenevinyl-SQs, which were characterized using single photon absorption, two-photon absorption, fluorescence emission, and fluorescence lifetime kinetics. We offer here the first detailed photophysical study of the larger pure T10 and T12 silsesquioxanes and show photophysical properties that differ as a function of size, especially in their fluorescence behavior, indicating that cage size and/or symmetry can strongly affect photophysical properties. We also find that they offer excitation-dependent emission (evidence of rare "red-edge" effects). The T10 stilbenevinyl-SQ offers up to a 10-fold increase in two-photon absorption cross section per chromophore over a free chromophore, signifying increased electronic coupling. The SQ cage compounds show "rise times" of 700-1000 fs and low anisotropy (~0.1) in fluorescence lifetime kinetic studies. These results indicate excited state energy transfer, unobserved for the free chromophores and unexpected for systems with "inert" silica cores and for 3-D hybrid molecular species. These findings provide the first detailed photophysical study of chromophore-functionalized T10 and T12 silsesquioxanes and show that SQs may be considered a separate class of compounds/materials with anticipated novel properties of value in developing new components for electronic and photonic applications. PMID:23875600

Furgal, Joseph C; Jung, Jae Hwan; Goodson, Theodore; Laine, Richard M

2013-08-21

73

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

Science.gov (United States)

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

Mayatt, Adam J.

74

Investigating the Structure-Property Relationships of Aqueous Self-Assembled Materials  

Science.gov (United States)

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.

Krogstad, Daniel Vincent

75

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

Science.gov (United States)

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

Neilson, James R.

76

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

Science.gov (United States)

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

Cook, David James

77

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-06-07

78

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

Directory of Open Access Journals (Sweden)

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

Bin Cheng

2011-04-01

79

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

Directory of Open Access Journals (Sweden)

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

???

2013-07-01

80

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

International Nuclear Information System (INIS)

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

 
 
 
 
81

Structure-property relationships in novel polymers and block copolymers from ring-opening metathesis polymerization  

Science.gov (United States)

The desire to tune macroscopic properties by controlling the underlying microscopic structure is a driving force in many different areas of scientific research, including polymer science. In living ring-opening metathesis polymerization (ROMP), the subject of this dissertation, there are a variety of different ways to alter the microscopic structure through synthesis. This is in part due to the presence of double bonds in the polymeric backbone, which can influence properties both through their isomeric structures (cis vs. trans) and through their removal by catalytic hydrogenation. Here, we demonstrate the ability to tune a variety of microstructural parameters of our ROMP polymers through synthesis, and investigate the resulting effects on macroscopic properties. ROMP and subsequent hydrogenation provide access to crystalline, glassy, and rubbery polymers, representing essentially the entire spectrum of polymer properties. These include hydrogenated polynorbornene (hPN), a highly crystalline polymer with Tm° = 156°C; hydrogenated poly(5-hexylnorbornene) (hPHN), a rubbery amorphous polymer with Tg = -22°C; and hydrogenated polymethyltetracyclododecene (hPMTD), a glassy polymer with Tg = 163°C. The microstructure of block copolymers of hPN, hPHN, and hPMTD can be controlled by varying block sequence, block lengths, and number of blocks. We used this control to design and synthesize thermoplastic elastomers (TPEs) containing both crystalline and glassy hard segments, with the aim of capturing the mechanical properties of conventional all-amorphous triblock TPEs, while forming the solid-state structure by crystallization from a single-phase melt. To accomplish this, we synthesized symmetric pentablock copolymers with the architecture crystalline-glassy-rubbery-glassy-crystalline. With this pentablock architecture and appropriate selection of block lengths, crystallization from a single-phase melt causes a layer rich in the glassy block to form around the crystallites, limiting their lateral growth and generating composite hard domains with both crystalline and glassy components. The pentablocks show the low initial modulus, strain-hardening behavior, and small permanent set desired for TPEs, while retaining an easily-processed single-phase melt. We found that the chain microstructure (cis/trans ratio) in the ROMP of norbornene and methyltetracyclododecene (MTD) using a so-called Schrock-type initiator to be a strong function of monomer concentration, providing a convenient means for tuning the average trans content in the resulting polymers. The results are explained based on a literature kinetic description for the behavior of this initiator, which allowed for the development of a quantitative model to describe the observed experimental data. In contrast, ROMP of MTD using the first-generation Grubbs initiator showed no dependence of the trans content on monomer concentration. hPN is unusual in that it is highly crystalline despite having an atactic placement of its backbone cyclopentylene rings. Furthermore, it has a crystal-crystal transition at elevated temperatures (˜110°C) where the crystal structure transforms from a conventional, three-dimensionally-ordered monoclinic lattice at lower temperatures to a high-temperature crystal polymorph that is rotationally disordered and shows a pseudo-hexagonal packing transverse to the chain axes. The tacticity of hPN, measured to first order as the ratio of meso to racemo dyads (m:r), was varied by altering the synthesis conditions, and was shown to have a direct correlation with the temperature at which the crystal-crystal transition occurs (T cc). Small changes in m:r (from 0.8 to 1.1) are sufficient to raise Tcc by nearly 20°C. When heated above Tcc, hPN crystals thicken at a rate much greater than conventional three-dimensionally-ordered crystals, but below the rates shown by the two-dimensional hexagonal (columnar) phase formed by some polymers. Finally, we report the synthesis of novel ROMP poly(5-phenylethylnorbornene), a polymer with pendant phenyl groups. Satura

Bishop, John Paul

82

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

CERN Document Server

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

Nasef, M M

2003-01-01

83

Relationships of structure to properties of various type RBa2Cu3Ox compounds  

International Nuclear Information System (INIS)

Verification of the structure of certain RBa2Cu3Ox type compounds is carried out using the neutron diffraction analysis of a powder at 298 K. The superconducting NdBa2Cu3O6.85, YBa2Cu3O6.91 and ErBa2Cu3O6.99 phases are shown to have the rhombic symmetry. In some rare-earth elements Cu-O short distance (? 0.185 nm) decreases with the growth of the rare-earth metal cation size, but the average Cu-O distance in extended chains remains practically constant. Verification of the structure of the YBa2Cu3O7-x phase has shown that transition to tetragonal modification of the YBa2Cu3O6 composition occurs without structure destruction. The latter phase possesses semiconducting properties and it is not a superconductor. On the basis is supposed that superconductivity in perovskites deficient by oxygen is caused by the presence of (-Cu-O-)n-chains. 5 refs.; 1 fig.; 4 tabs

84

On calibration of a nominal structure-property relationship model for chiral sculptured thin films by axial transmittance measurements  

Science.gov (United States)

A chiral sculptured thin film is fabricated from patinal titanium oxide using the serial bideposition technique. Axial transmittance spectrums are measured over a spectral region encompassing the Bragg regime for axial excitation. The same spectrums are calculated using a nominal structure-property relationship model and the parameter space of the model is explored for best fits of the calculated and measured transmittances. Ambiguity arising on calibrating the model against axial transmittance measurements is shown to be resolvable using non-axial transmittance measurements.

Sherwin, J. A.; Lakhtakia, A.; Hodgkinson, I. J.

2002-08-01

85

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

CERN Document Server

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

Santos, M C D

2000-01-01

86

Structure-Property Relationships in Solid AlF3 Lewis Acids  

International Nuclear Information System (INIS)

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

87

Relationship between structure and creep properties of a predeformed austenitic steel  

International Nuclear Information System (INIS)

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

88

Relationship between structure and antioxidative properties of some 3-formylchromone derivatives.  

Science.gov (United States)

Flavonoids, which generally exhibit very good antioxidant properties, contain the chromone unity. The work elucidates the relation between chemical structure of chromones and their ability to scavenge DPPH radicals. The work deals with antioxidative properties of some hydroxy derivatives of 3-formylchromones (without substituent, 6-hydroxy-, 7-hydroxy-, 7,8-dihydroxy-). It was found that the last two derivatives scavenge DPPH radicals, whereas the first two ones do not. It was demonstrated that the presence and location of hydroxyl groups play a crucial role for antioxidative activity of 3-formylchromones. The scavenging of DPPH radicals runs through H(+) abstraction from hydroxyl groups of formylchromones. The DPPH scavenging by 3-formylchromones with hydroxyl group in the 7th position is connected with the formation of more stable form of anion than in the case of 6-hydroxy-3-formylchromone. Calculation heats of formations of studied formylchromone anions confirmed this fact. All studied 3-formylchromones did not scavenge HO( ) radicals, what supports H(+) abstraction mechanism of DPPH scavenging. PMID:18673147

Sersen, F; Loos, D; Mezesová, L; Lácová, M

2008-07-01

89

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

Science.gov (United States)

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

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

2012-03-01

90

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

Directory of Open Access Journals (Sweden)

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

Ovidiu Ivanciuc

2002-09-01

91

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

Science.gov (United States)

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

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

2014-01-21

92

Inter-relationship between structure and dielectric properties of crystalline anodic zirconia  

International Nuclear Information System (INIS)

Crystalline anodic oxide films have been formed on sputter-deposited zirconium and Zr-Ti alloys in 0.1 mol dm-3 ammonium pentaborate electrolyte, with their structure, composition, dielectric properties and growth behaviour examined using X-ray diffraction, transmission electron microscopy, Rutherford backscattering spectroscopy, glow discharge optical emission spectroscopy and electrochemical impedance spectroscopy. The films formed on zirconium consist of a high-temperature stable ZrO2 phase (cubic or tetragonal) as well as monoclinic ZrO2, with the latter predominant with increasing formation voltage. The incorporation of titanium species into the films stabilizes the high-temperature phase up to high voltages. Associated with the change in the crystalline structure with the incorporation of titanium species, the permittivities of the oxides increase, in agreement with the higher permittivity of bulk cubic and tetragonal ZrO2 containing stabilizing cations compared with that of bulk monoclinic ZrO2. The transport number of cations during crystalline oxide growth is about 0.05, irrespective of titanium incorporation

93

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-03-31

94

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

Science.gov (United States)

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

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

2014-04-14

95

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-01-01

96

Structure-property relationship of highly ?-conjugated Schiff-base moiety in liquid crystal diepoxide polymerization and mesophases stabilization.  

Science.gov (United States)

A study of the structure-property relationship of the highly ?-conjugated Schiff-base moiety in polymerization of a liquid crystal (LC) diepoxide oligomer (PBMBA) and mesophases stabilization has been investigated. We first proposed two exothermic peaks distinctly observed in nonisothermal polymerization curves for thermal copolymerization of PBMBA monomer with a diamine comonomer that corresponded to two different reactions, namely, an epoxy-amine polymerization and anionic polymerization. For PBMBA, note that an unexpected homopolymerization accompanying an appearance of enantiotropic mesophase transitions had taken place in the absence of any initiators, evidencing the possibility of an anionic mechanism yielding a homopolymer. A novel Schiff-base model compound (SBM) was synthesized and used to induce the polymerization of different types of epoxies. Based on the structure-property relationship, we considered a specific role of highly ?-conjugated Schiff-base moieties in the anionic polymerization of PBMBA and hoped the mesophases could be stabilized using this mechanism, which may provide a key strategy for design of the polymer-dispersed liquid crystal (PDLC) materials via a chemical process. PMID:21604795

Liu, Huan; Fu, Zien; Xu, Kai; Cai, Hualun; Liu, Xin; Chen, Mingcai

2011-06-16

97

Structure and properties relationships of beta-Al2O3 electrolyte materials  

International Nuclear Information System (INIS)

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

98

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

Science.gov (United States)

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. PMID:25227873

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

2014-10-01

99

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

Directory of Open Access Journals (Sweden)

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

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

Fernández-Golfín, J. I.

2003-06-01

100

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

International Nuclear Information System (INIS)

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

 
 
 
 
101

Structure and properties relationships of beta-Al{sub 2}O{sub 3} electrolyte materials  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer The {beta}' phase of beta-Al{sub 2}O{sub 3} was stable in high temperature and the {beta}' phase content increased with the sintering temperature increasing by the addition of the stabilizers. Black-Right-Pointing-Pointer By using NMR, {delta}{sub Al(VI)} and {delta}{sub Al(IV)} of beta-Al{sub 2}O{sub 3} moved towards down field in different systems with different stabilizers. Li{sup +} and Mg{sup 2+} ions substituted the octahedron and tetrahedral Al{sup 3+} ions in the spinel blocks respectively, and Mg{sup 2+} stabilizer was more benefit to improve the symmetry of Al(VI) of the beta-Al{sub 2}O{sub 3} than Li{sup +} stabilizer. Black-Right-Pointing-Pointer The amounts ratio of octahedron and tetrahedron (A{sub Al(VI)}/A{sub Al(IV)}) of beta-Al{sub 2}O{sub 3} decreased with the {beta}' phase content increasing. - Abstract: Beta-Al{sub 2}O{sub 3} electrolyte materials were synthesized by solid-state reaction method in this paper. The effect of different stabilizers on the {beta}'-phase content of the beta-Al{sub 2}O{sub 3} electrolyte and the structures of aluminum-oxide polyhedron were investigated by X-ray diffraction technology (XRD) and {sup 27}Al MAS NMR, and the relationship between the {beta}' phase content and the amounts ratio of octahedron and tetrahedron (A{sub Al(VI)}/A{sub Al(IV)}) was summarized. The results showed that the {beta}' phase was stable at high temperatures and the {beta}' phase content increased with the temperature increasing by the addition of the stabilizers. Meanwhile, {delta}{sub Al(IV)} and {delta}{sub Al(VI)} moved towards down field, and A{sub Al(VI)}/A{sub Al(IV)} decreased with the {beta}' phase content increasing. The Mg{sup 2+} stabilizer was better to improve the symmetry of Al(VI) than the Li{sup +} stabilizer.

Zhu Chengfei, E-mail: zhucf@njut.edu.cn [College of Materials Science and Engineering, Nanjing University of Technology, Nanjing 210009 (China); Xue Jinhua [College of Materials Science and Engineering, Nanjing University of Technology, Nanjing 210009 (China)

2012-03-15

102

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

Scientific Electronic Library Online (English)

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

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

2013-10-01

103

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

Science.gov (United States)

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

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

2013-09-01

104

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

Science.gov (United States)

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

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

2014-06-23

105

Quantitative structure property relationship study of the electrophoretic mobilities of some benzoic acids derivatives in different carrier electrolyte compositions.  

Science.gov (United States)

Quantitative structure-properties relationship (QSPR) has been applied to modeling and predicting the electrophoretic mobilities of a series of benzoic acid derivatives in different carrier electrolyte composition. Descriptors that were selected by stepwise multiple linear regression (MLR) technique are radial distribution function-lag8 (RDF-8), unweighted R-maximal autocorrelation geometry, topology and atomic weight assembly-lag4 (R-GETAWAY-4), geometrical descriptor lag-26 (GEO-26), and the overall dielectric constant of the carrier electrolyte. These descriptors were used as inputs for generated 4-7-1 artificial neural network (ANN). The results obtained using ANN and MLR were compared as well as with the experimental values and showed the superiority of ANN over MLR model. Also the appearance of these descriptors in QSPR models reveals the role of electronic and steric interactions in solutes mobility in capillary electrophoresis due to the dielectric and hydrodynamic friction forces. PMID:16007694

Fatemi, Mohammad H; Goudarzi, Nasser

2005-08-01

106

Structure-property relationships in Waspaloy via small angle scattering and electrical resistivity measurements  

Energy Technology Data Exchange (ETDEWEB)

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.

Whelchel, R. [Georgia Institute of Technology; Gerhardt, Dr. Rosario [Georgia Institute of Technology; Littrell, Ken [ORNL

2010-01-01

107

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

Science.gov (United States)

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

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

2010-01-21

108

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Considering the pharmaceutical importance of hydantoins, a set of 25 derivatives of phenytoin, nirvanol and 5-methyl-5-phenylhydantoin, the lipophilicities of which were gradually increased by the introduction of different alkyl, cycloalkyl and alkenyl groups in position N3, was synthesized. Their properties under consideration were either estimated empirically, by UV/Vis spectroscopy, or calculated using established medicinal chemistry software. The UV absorption spectra o...

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

2011-01-01

109

Structure-Property Relationships of Oligothiophene-Isoindigo Polymers for Efficient Bulk-Heterojunction Solar Cells  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A series of alternating oligothiophene (nT)-isoindigo (I) copolymers (PnTI) were synthesized to investigate the influence of the oligothiophene block length on the photovoltaic (PV) properties of PnTI:PCBM bulk-heterojunction blends. Our study indicates that the number of thiophene rings (n) in the repeating unit alters both, polymer crystallinity and polymer-fullerene interfacial energetics, which results in a decreasing open-circuit voltage (Voc) of the solar cells with increasing n. The sh...

Ma, Zaifei; Sun, Wenjun; Himmelberger, Scott; Vandewal, Koen; Tang, Zheng; Bergqvist, Jonas; Salleo, Alberto; Wenzel Andreasen, Jens; Ingana?s, Olle; Andersson, Mats R.; Mu?ller, Christian; Zhang, Fengling; Wang, Ergang

2014-01-01

110

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

Science.gov (United States)

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

Tipton, John

111

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

Science.gov (United States)

The regenerated Araneus ventricosus spider dragline silk protein fibrous scaffold with moderate strength and flexibility was fabricated by electrospinning and post treatment with 90 vol % acetone. The effect of collection method on the morphology of regenerated spider silk protein (RSSP) fibrous scaffold, the effects of the post treatment solvents and their concentrations on the molecular conformation, crystallinity and mechanical properties were studied. The results show that the morphology was affected by the solvent used in the coagulation bath. The molecular conformation, crystallinity and mechanical property of this scaffold were strongly affected by the kind of post treatment solvent and slightly influenced by its concentration when it was higher than 50 vol %. The degradation rate of this scaffold was very slow and resulting in little pH change of the degradation medium within 5 months. PC 12 cells were cultured on the electrospun RSSP fibrous scaffold and in its extraction fluid to examine the changes of PC 12 cells after different times of culture. The results show that the electrospun RSSP fibrous scaffold had good biocompatibility with PC 12 cells. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3828-3837, 2014. PMID:24288266

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

2014-11-01

112

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

Science.gov (United States)

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

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

2010-05-01

113

Structure-properties relationship of poly(ethylene terephthalate) wool-type fibres  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Two PET wool-type fibres were studied for this research, i.e. a normal wool-type and a low-pilling modification. The structural morphology and crystalline orientation of the fibres were investigated by means of wide-angle x-ray scattering (WAXS), density measurements and infrared (IR) spectroscopy. The degree of crystallinity, crystallite orientation, apparent crystallite dimensions and micro-void system were determined by x-ray scattering. Birefringence measurements were used to study the av...

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

2012-01-01

114

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2004-07-01

115

Thermotropic resin systems. Relationships between formulation parameters, material structure and optical properties  

Energy Technology Data Exchange (ETDEWEB)

This paper focuses on a comprehensive characterization of various thermotropic resins under polymer physical aspects. Numerous thermotropic layers were produced under systematic variation of resin base, thermotropic additives and additive concentration. A detailed investigation of optical properties, switching temperature, switching process and residual transmittance was performed with a UV/Vis/NIR spectrophotometer. Switching temperatures are compared with thermal transitions in the material determined by Differential Scanning Calorimetry (DSC). Whereas the different film types show a direct solar transparency between 64 and 83% in the clear state, the direct solar transmittance decreases to values of about 27% to 80% above the switching temperature. In general the thermotropic resins are characterized by a steep and rapid switching process. The switching temperature can be adapted by varying the additives. The comparison of films thermal transitions with the switching performance reveals a good correlation. (orig.)

Resch, Katharina [Polymer Competence Center Leoben GmbH, Leoben (Austria); Wallner, Gernot M. [Univ. of Leoben (Austria)

2008-07-01

116

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

International Nuclear Information System (INIS)

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

117

Structure-property relationships in calcia and calcia + magnesia partially stabilised zirconias  

International Nuclear Information System (INIS)

Partially stabilised calcia-zirconia and calcia + magnesia zirconia ceramic alloys, fired in the single-phase cubic field and fast cooled, have been aged to various extents in order to develop specific two-phase microstructures. Optimum firing conditions have been determined for obtaining a ceramic with a high volume fraction of tetragonal phase in a cubic matrix. The development of the metastable tetragonal phase has been observed and studied by transmission electron microscopy and X-ray diffraction. A.C. conductivity measurements demonstrate that systematic changes in impedance spectra occur with ageing. These have been interpreted in terms of initial changes in composition, different electrical properties of the tetragonal and monoclinic precipitates and the cubic parent matrix, and the growth of grain boundary phases. The latter have been characterised by X-ray microanalysis, and their influence on strength and electrical conductivity is briefly discussed. (author)

118

Sputtered ITO for application in thin-film silicon solar cells: Relationship between structural and electrical properties  

Science.gov (United States)

Indium tin oxide (ITO) thin films for application in thin-film silicon solar cells with superior electrical and optical properties (resistivity ranging from 1.4 to 8.4 × 10-4 ? cm; transparency of >80%) have been investigated. ITO layers were deposited by radio-frequency (RF) magnetron sputtering process at different argon gas pressures and substrate temperatures ranging from room temperature to 280 °C. The main goal was to identify the relationship between structural and electrical properties. Generally, ITO layers were rather smooth with granular topography; electro-optically superior layers exhibited substantially different surface morphology of large, well-organized domain formations. Hall mobility of remarkably high value of 49 cm2/V s (resistivity of 2.6 × 10-4 ? cm) was achieved for the ITO layers, which were deposited at surprisingly low temperature of 125 °C. ITO process has been successfully applied, even at room temperature, to fabricate front contacts for microcrystalline silicon solar cells, exhibiting excellent performance on both rigid and flexible substrates.

Hotovy, J.; Hüpkes, J.; Böttler, W.; Marins, E.; Spiess, L.; Kups, T.; Smirnov, V.; Hotovy, I.; Ková?, J.

2013-03-01

119

Synthesis and Structure/property Relationships of Ring-Sulfonated Polyaniline.  

Science.gov (United States)

The main objectives of the present investigation were: (1) to synthesize self protonic doped conducting polyaniline by various methods, and find the best synthetic route; (2) to examine whether the solubility of polyaniline would be changed after parent polyaniline had been sulfonated; (3) to determine the thermal doping stability of the conducting forms and thermal stability of the insulating forms of parent and sulfonated polyaniline; (4) to use electronic spectra as a probe to elucidate the changes of the geometry and conformation of sulfonated polyaniline; (5) to develop a hypothesis to rationalize the charge transport properties of sulfonated polyaniline; (6) to compare electrochemical properties of parent polyaniline and sulfonated polyaniline. The most significant results and conclusions are as following: (1) Fuming sulfuric acid as a sulfonation agent gives the best sulfonation level and conductivity for the polymer. (2) The solubility of polyaniline is improved greatly by the presence of the -SO_sp {3}{-} groups, specifically, sulfonated polyaniline dissolves in basic aqueous solutions. (3) The conductivity of the polymer is independent of pH for pH less than 7; the sodium salt of sulfonated polyaniline, an insulator, can be converted into a conducting form by treating it with aqueous HCl. (4) The covalently bonded sulfonic groups on the polyaniline chain increase the doping stability for the conducting form and the stability of the backbone for the insulating form at high temperatures. (5) Sulfonation of the phenyl rings on the polyaniline backbone increases the torsional angle between adjacent rings to relieve the steric strain. (6) The transport studies slow that the charge is more localized in sulfonated polyaniline than in the polyaniline system. (7) The first redox process in cyclic voltammetry is dependent on pH for pH less than 7 due to the active protons on the polymer backbone.

Yue, Jiang

1991-05-01

120

Structure-property relationship in acetal-based chemically amplified three-component DUV resist  

Science.gov (United States)

AZ DX series are chemically amplified, three component resists based on a poly(4-hydroxystyrene-co-3-methyl-4-hydroxystyrene) matrix resin, a poly(N,O-acetal) dissolution inhibitor, and a bis(arylsulfonyl)diazomethane acid generator. The previously described AZ DX 46 is an environmentally and delay time stable, high performance resist capable of lineating structures down to 0.23 micrometers . The material contains a photoactive base to reduce the delay time effects. In this paper the influence of styrene units in the matrix resin, and some new polyacetals on the performance of the resist in comparison to the above mentioned standard formulation AZ DX 46.

Padmanaban, Munirathna; Kinoshita, Yoshiaki; Kudo, Takanori; Lynch, Thomas J.; Masuda, Seiya; Nozaki, Yuko; Okazaki, Hiroshi; Pawlowski, Georg; Przybilla, Klaus J.; Roeschert, Horst; Spiess, Walter; Suehiro, Natusmi; Wengenroth, Horst

1994-05-01

 
 
 
 
121

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

DEFF Research Database (Denmark)

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

Jensen, Jesper Langholm; MØlgaard, Anne

2013-01-01

122

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

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

Mehdi Jalali-Heravi

2002-08-01

123

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

Science.gov (United States)

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

Donakowski, Martin Daniel

124

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

International Nuclear Information System (INIS)

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

125

Elucidation of the Structure-Property Relationship of p-Type Organic Semiconductors through Rapid Library Construction via a One-Pot, Suzuki-Miyaura Coupling Reaction.  

Science.gov (United States)

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

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

2014-09-01

126

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

Directory of Open Access Journals (Sweden)

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

Pereira Fabiano V.

2006-01-01

127

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

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

Fereshteh Shiri

2010-08-01

128

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

International Nuclear Information System (INIS)

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

129

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

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

Virapong Prachayasittikul

2010-01-01

130

Benchmarking of linear and nonlinear approaches for quantitative structure-property relationship studies of metal complexation with ionophores.  

Science.gov (United States)

A benchmark of several popular methods, Associative Neural Networks (ANN), Support Vector Machines (SVM), k Nearest Neighbors (kNN), Maximal Margin Linear Programming (MMLP), Radial Basis Function Neural Network (RBFNN), and Multiple Linear Regression (MLR), is reported for quantitative-structure property relationships (QSPR) of stability constants logK1 for the 1:1 (M:L) and logbeta2 for 1:2 complexes of metal cations Ag+ and Eu3+ with diverse sets of organic molecules in water at 298 K and ionic strength 0.1 M. The methods were tested on three types of descriptors: molecular descriptors including E-state values, counts of atoms determined for E-state atom types, and substructural molecular fragments (SMF). Comparison of the models was performed using a 5-fold external cross-validation procedure. Robust statistical tests (bootstrap and Kolmogorov-Smirnov statistics) were employed to evaluate the significance of calculated models. The Wilcoxon signed-rank test was used to compare the performance of methods. Individual structure-complexation property models obtained with nonlinear methods demonstrated a significantly better performance than the models built using multilinear regression analysis (MLRA). However, the averaging of several MLRA models based on SMF descriptors provided as good of a prediction as the most efficient nonlinear techniques. Support Vector Machines and Associative Neural Networks contributed in the largest number of significant models. Models based on fragments (SMF descriptors and E-state counts) had higher prediction ability than those based on E-state indices. The use of SMF descriptors and E-state counts provided similar results, whereas E-state indices lead to less significant models. The current study illustrates the difficulties of quantitative comparison of different methods: conclusions based only on one data set without appropriate statistical tests could be wrong. PMID:16563012

Tetko, Igor V; Solov'ev, Vitaly P; Antonov, Alexey V; Yao, Xiaojun; Doucet, Jean Pierre; Fan, Botao; Hoonakker, Frank; Fourches, Denis; Jost, Piere; Lachiche, Nicolas; Varnek, Alexandre

2006-01-01

131

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

Science.gov (United States)

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 ?S and, to a lesser extent, more positive ?H. 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 ?-carbonyl carbon and the deprotonated backbone nitrogen for cyclic imide formation. PMID:24620787

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

2014-04-01

132

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

International Nuclear Information System (INIS)

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

133

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

International Nuclear Information System (INIS)

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

134

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-04-24

135

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

Directory of Open Access Journals (Sweden)

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

I. A. Asimakopoulos

2014-09-01

136

A density functional theory study of structure-property relationships for Pt-Ni alloy catalysts  

Science.gov (United States)

The ORR (Oxygen Reduction Reaction) is an important reaction in devices such as metal-air batteries and PEMFCs (Polymer Electrolyte Membrane fuel cells). Pure Pt is one of the most successful electrode catalysts for this key reaction. However, due to its expense, numerous efforts have been made to find a new catalysis system based on Pt bimetallic alloys, in which Pt is partially replaced by less expensive metals, such as Ni, Co and Fe. Experimental and theoretical works have shown that Pt3Ni alloys have a higher ORR activity than pure Pt. In order to investigate the enhanced catalytic activity, cluster expansions corresponding to a simplified 9-layer Pt-Ni slab model are built to accurately and quickly predict the energies of surfaces as a function of atomic order. With the help of this model, we can study systematically the atomic structure and the surface geometry of Pt3Ni surface system at a variety of temperature and chemical environments, and we can calculate the adsorption binding energies of O, OH and H on both equilibrium and non-equilibrium Pt-Ni(111) surfaces. Also, we can investigate the effects of off-stoichiometry on surface by searching for stable ground states under different concentrations.

Cao, Liang; Mueller, Tim

2013-03-01

137

Modelling the deformation mechanisms, structure-property relationships and applications of auxetic nanomaterials  

Science.gov (United States)

Analytical and Molecular Mechanics methods have been used to study the structure and deformation mechanisms acting at the molecular level in the auxetic polymorph of crystalline silica (-cristobalite). The Molecular Mechanics simulations indicate a stress-induced phase transition from -cristobalite to ordered -cristobalite occurs for uniaxial loading along the x3 direction. This is in reasonable agreement with the previous prediction from an analytical model assuming deformation is by concurrent dilation and cooperative rotation (about axes in the x1-x2 plane, passing through the midpoints of opposing edges - the a-axes) of the SiO4 tetrahedral molecular sub-units, previously shown to predict the Poisson's ratio for loading in the x3 direction. The analytical models have been extended to include cooperative rotation of each tetrahedron about its axis (the c-axis) mostly closely aligned with the principal unit-cell x3-axis. The new models enable significantly improved prediction of the Poisson's ratios of -cristobalite when loaded in one of the transverse (x1 or x2) directions. Parametric fitting of the analytical models indicate that the deformation mechanism for transverse uniaxial loading of -cristobalite is by concurrent dilation and cooperative rotation about the local a and c-axes of the SiO4 tetrahedra.

Alderson, A.; Alderson, K. L.; Evans, K. E.; Grima, J. N.; Williams, M. R.; Davies, P. J.

2005-03-01

138

Two-photon polarity probes built from octupolar fluorophores: synthesis, structure-properties relationships, and use in cellular imaging.  

Science.gov (United States)

A series of octupolar fluorophores built from a triphenylamine (TPA) core connected to electron-withdrawing (EW) peripheral groups through conjugated spacers has been synthesized. Their photoluminescence, solvatochromism, and two-photon absorption (2PA) properties were systematically investigated to derive structure-property relationships. All derivatives exhibit two 2PA bands in the 700-1000 nm region: a first band at low energy correlated with a core-to-periphery intramolecular charge transfer that leads to an intense 1PA in the blue-visible range, and a second more intense band at higher energy due to an efficient coupling of the branches through the TPA core. Increasing the strength of the EW end groups or the length of the conjugated spacers and replacing triple-bond linkers with double bonds induces both enhancement and broadening of the 2PA responses, thereby leading to cross-sections up to 2100 GM at peak and higher than 1000 GM over the whole 700-900 nm range. All derivatives exhibit intense photoluminescence (PL) in low- to medium-polarity environments (with quantum yields in the 0.5-0.9 range) and display a strong positive solvatochromic behavior (with Lippert-Mataga specific shifts ranging from 15,000 to 27,500 cm(-1)), triple bonds, and phenyl moieties in the conjugated spacers, thereby leading to larger sensitivities than those of double bonds and thienyl moieties. More hydrophilic derivatives were also shown to be biocompatible, to retain their 2PA and PL properties in biological conditions, and finally to be suitable as polarity sensors for multiphoton cell imaging. PMID:24019268

Le Droumaguet, Céline; Sourdon, Aude; Genin, Emilie; Mongin, Olivier; Blanchard-Desce, Mireille

2013-12-01

139

Structure-property relationships in main-chain liquid crystalline networks  

Science.gov (United States)

Main-chain liquid crystalline networks were prepared from mesogenic dienes using two different synthetic routes. First, main-chain liquid crystalline copolymers were synthesized by polymerizing a mesogen with a nonmesogenic comonomer using acyclic diene metathesis (ADMET) chemistry. The resulting polymers form nematic phases, with composition dictating the glass transition and isotropization temperatures. Free-radical crosslinking through the unsaturated bonds in the polymer was demonstrated for a selected composition to lead to an elastomeric network. This two step process was employed to control the polymer properties before crosslinking and serves as a viable route to tailored nematic networks for applications as anisotropic adhesives. Liquid crystalline elastomers (LCEs) were prepared using a second synthetic route that employed hydrosilylation chemistry to react the mesogens with hydrideterminated poly(dimethylsiloxane) and a vinyl crosslinker. The resulting LCEs formed a smectic-C phase with transition temperatures that depend on mesogen composition. The mesogens impart two distinct active behaviors to the elastomers. The first of these is actuation, the reversible extension and contraction of the polymer when cooled and heated, respectively, through the mesogen isotropization transition. Actuation is dependent on the crosslink density of the material and can cause the samples to elongate as much as 30% under tensile load. The second active behavior is shape memory, the ability to fix a temporary deformation and later recover the equilibrium shape by heating. The LCEs have excellent shape memory fixing and recovery ratios, both of which generally exceeded 95%. The ability of a soft network to fix strains above room temperature is unusual and was investigated using a combination of thermal analysis, mechanical testing, and wide angle x-ray scattering, where it was found that strain is fixed by freezing the mesogens within the smectic layers. The LCE's low modulus was exploited by reversible embossing, the localization of a temporary topography onto the LCE using shape memory. A microscale embossed topography was stable until erased by heating to recover the LCE's flat, permanent shape. Possible applications of these LCEs include artificial muscles, smart shear-based actuators, and active substrates.

Burke, Kelly Anne

140

Structure-composition-property relationships in 5xxx series aluminum alloys  

Science.gov (United States)

Al-Mg alloys are well suited for marine applications due to their low density, ease of fabrication, structural durability, and most notably resistance to corrosion. The purpose of this study is to investigate the effects of alloying additions, mechanical processing and heat treatments on the development of grain boundary phases that have an effect on intergranular corrosion (IGC). Cu, Zn, and Si modified compositions of AA5083 were produced that were subjected to a low and high degree of cold work and various heat treatments. ASTM G67 (NAMLT) intergranular corrosion testing and detailed microstructural characterization for various alloys was carried out. An optimal composition and processing condition that yielded the best intergranular corrosion resistant material was identified based on the ASTM G67 test screening. Further, the outstanding modified AA5083 was selected for further microstructural analysis. This particular alloy with has a magnesium level high enough to make it susceptible to intergranular corrosion is very resistant to IGC. It was found that development of the appropriate sub-structure with some Cu, Si and Zn resulted in a material very resistant to IGC. Formation of many sinks, provided by sub-boundaries, within microstructure is very beneficial since it produces a relatively uniform distribution of Mg in the grain interiors, and this can suppress sensitization of this alloy very successfully. This is a very promising rote for the production of high-strength, and corrosion resistant aluminum alloys. Additionally in this study, TEM sample preparation become very crucial step in grain boundary phase investigation. Focus Ion Beam (FIB) milling was used as a primary TEM sample preparation technique because it enables to extract the samples from desired and very specific locations without dissolving grain boundary phases as it was in conventional electropolishing method. However, other issues specifically relevant to FIB milling of aluminum alloys related to Ga accumulation were discovered, that produce significant microstructural artifacts. It is well known that liquid gallium can cause Liquid Metal Embitterment (LME) aluminum alloys, and gallium readily penetrates aluminum grain boundaries. Low energy Ar ion nanomilling is potentially quite effective at removing gallium from the external and internal surfaces of aluminum thin foils, but can still leave persistent artifacts. Al-Mg alloys can be also susceptible to localized corrosion such as pitting corrosion in the presence of chloride ions. In this study the phases responsible for this type of corrosion were identified. ASSET (ASTM G66) test was used to determine the influence of heat-treatment on pitting corrosion on various modified AA5083 alloys. Additionally, potentiodynamic polarization as well as potentiostatic measurements in conjunction with SEM analysis were carried out to obtain pitting potential (Epit) and to determine the location of metastable pit initiation, respectively.

Unocic, Kinga A.

 
 
 
 
141

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A influência da estrutura química dos grupos mesogênicos e do tamanho dos grupos espaçadores, no comportamento de fase de uma série de cristais líquidos poliméricos de cadeia lateral (SCLCP), foram estudados utilizando-se espalhamento de raios-X a Baixo Ângulo (SAXS) e Microscopia Ótica de Luz Polar [...] izada (POM). Análises do arranjo das mesofases em amostras não orientadas e orientadas por ação do campo magnético são descritas. O papel do tamanho do espaçador lateral no empacotamento local e na largura da camada esmética determinados nas mesofases SmA e SmC é elucidado. Os ângulos teta formados entre os grupos mesogênicos e a normal às camadas nas mesofases SmC foram determinados. Um estudo a respeito do grau de ordem em função da temperatura, para os polímeros esméticos foi possível através de medidas de SAXS. Uma ordenação particular em um dos SCLCPs estudados é relacionada com a coexistência de duas fases distintas. Abstract in english The influence of the chemical structure of the mesogenic groups and the length of the spacer groups on the phase behavior in a series of side-chain liquid crystalline polyacrylates (SCLCP) have been studied using Small Angle X-ray Scattering (SAXS) and Polarized Optical Microscopy (POM). Analyses of [...] the mesophase arrangement in unaligned and aligned samples by magnetic field are reported. The role of the spacer length on the local packing and on the thickness of the layers encountered in the SmA and SmC mesophases is elucidated. The tilt angles theta of the mesogenic cores related to the normal of the layers in the SmC mesophases are measured. A study about the degree of order as a function of temperature for the smectic polymers was possible using SAXS measurements. A particular arrangement in one of the studied SCLCPs is related to the coexistence of two different phases.

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

142

Structure-property relationship of amplified spontaneous emission in organic semiconductor materials: TPD, DPABP, and NPB.  

Science.gov (United States)

N,N'-Diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD) was demonstrated to be suitable for stimulated emission in doping and nondoping planar waveguide structure, but the mechanism for its lasing is of ambiguity. With the aim of providing a microsscopic picture for its lasing, we performed a combined experimental and theortical investigation of the absorption, photoluminescence (PL), and stimulated emission of TPD and other two similar molecules: 1,4-bis (diphenylamino)biphenyl (DPABP) and N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4?-diamine (NPB). It was found that DPABP shows the same amplified spontaneous emission (ASE) characteristics as TPD, but NPB did not. In theory, density functional theory (DFT) and Franck-Condon Principle were used to analyze the molecular geometry in the electronic ground state as well as the optically excited state and the vibrational levels in electronic ground state, respectively. The calculation results show that for TPD and DPABP, several strongly elongated high-frequency modes (1199-1664 cm(-1)) in the carbon rings contribute to the distinct first vibronic sideband in the PL spectra, which form an effective four-level system for lasing. For NPB, when the peripheral toluene or benzene is replaced with naphthyl, a number of strongly elongated low-frequency modes (11-689 cm(-1)) deriving from naphthyl leads to a series of energy sublevels, which destroys the four-level system. Our results provided a new insight and better understanding into the lasing of organic molecules. PMID:24032429

Wu, Zhaoxin; Ma, Lin; Liu, Peng; Zhou, Caihua; Ning, Shuya; El-Shafei, Ahmed; Zhao, Xiang; Hou, Xun

2013-10-24

143

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

Science.gov (United States)

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

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

2004-08-01

144

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-02-01

145

Structure-behavior-property relationship study of surfactants as foam stabilizers explored by experimental and molecular simulation approaches.  

Science.gov (United States)

A multiscale stability study of foams stabilized by sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), and sodium polyoxyethylene alkylether sulfate (AES) was conducted, to investigate the relationship of surfactant molecular behavior and interfacial monolayer configuration of foam film to the foam film properties. Molecular dynamic (MD) simulations using a full-atom model was utilized to explore the microscopic features of the air/liquid interface layer. Several parameters such as the distribution of surfactant head groups and the order degree of surfactant hydrophobic tails were used to describe the molecular adsorption behavior. The effect of molecular structure on the nature of the foam film and the impact on the dynamic stability of wet foam is discussed. In the experimental evaluation, the SDBS foam films manifest strong stiffness and low viscoelasticity as shown by the interfacial shear rheology determination as well as texture analyzer (TA) measurement results, which agree very well with the array behavior of SDBS molecules at the air/water interface as described by the simulation results and is identified to be the reason for the poor dynamic stability. Comparing the molecular structure of SDS, SDBS, and AES, the special contributions of the linking groups such as the O atom, the phenyl group, and the EO (oxyethyl) chain to the interfacial array behavior of surfactants were characterized. It is concluded that microhardness of the foam film enhanced by rigid linking groups favors static foam stability but decreases the dynamic foam stability, while viscoelasticity of the foam film enhanced by soft linking groups increases the dynamic foam stability. PMID:22136447

Hu, Xiaoying; Li, Ying; He, Xiujuan; Li, Chunxiu; Li, Zhengquan; Cao, Xulong; Xin, Xia; Somasundaran, P

2012-01-12

146

Theoretical Study of Relationships between Structural, Optical, Energetic, and Magnetic Properties and Reactivity Parameters of Benzidine and Its Oxidized Forms.  

Science.gov (United States)

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

Bondarchuk, Sergey V; Minaev, Boris F

2014-09-25

147

A systematic study of peripherally multiple aromatic ester-functionalized poly(benzyl ether) dendrons for the fabrication of organogels: structure-property relationships and thixotropic property.  

Science.gov (United States)

A new class of peripherally multiple aromatic ester-functionalized poly(benzyl ether) dendrons and/or dendrimers with different focal point substituents, surface groups, interior structures, as well as different generations have been synthesized and their structure-property relationships with respect to their gelation ability have been investigated systematically. Most of these dendrons are able to gel organic solvents over a wide polarity range. Evident dendritic effects were observed not only in gelation capability but also in thermotropic, morphological, and rheological characterizations. It was disclosed that subtle changes in peripheral ester functionalities and interior dendritic structures affected the gelation behavior of the dendrons significantly. Among all the dendrons studied, the second- and third-generation dendrons G0G2-Me and G0G3-Me with dimethyl isophthalates (DMIP) as peripheral groups exhibited the best capability in gelation, and stable gels were formed in more than 22 aromatic and polar organic solvents. The lowest critical gelation concentration (CGC) reached 2.0?mg?mL(-1), indicating that approximately 1.35×10(4) solvent molecules could be entrapped by one dendritic molecule. Further study on driving forces in gel formation was carried out by using a combination of single-crystal/powder X-ray diffraction (XRD) analysis and concentration-dependent (CD)/temperature-dependent (TD) (1)H?NMR spectroscopy. The results obtained from these experiments revealed that the multiple ?-? stacking of extended ?-systems due to the peripheral DMIP rings, cooperatively assisted by non-conventional hydrogen-bonding, is the key contributor in the formation of the highly ordered supramolecular and fibrillar network. In addition, these dendritic organogels exhibited unexpected thixotropic-responsive properties, which make them promising candidates with potential applications in the field of intelligent soft materials. PMID:24753161

Feng, Yu; Liu, Zhi-Xiong; Chen, Hui; Yan, Zhi-Chao; He, Yan-Mei; Liu, Chen-Yang; Fan, Qing-Hua

2014-06-01

148

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

Science.gov (United States)

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

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

2008-08-01

149

Geophysical Properties Within the San Andreas Fault Zone at the San Andreas Fault Observatory at Depth (SAFOD) and Their Relationships to Rock Properties and Fault Zone Structure  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We examine the relationships between borehole geophysical data and physical properties of fault?related rocks within the San Andreas Fault as determined from data from the San Andreas Fault Observatory at Depth borehole. Geophysical logs, cuttings data, and drilling data from the region 3? to 4?km measured depth of the borehole encompass the active part of the San Andreas Fault. The fault zone lies in a sequence of deformed sandstones, siltstone, shale, serpentinite?bearing block?in...

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

2010-01-01

150

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

Science.gov (United States)

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

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

2014-09-01

151

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

International Nuclear Information System (INIS)

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

152

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

International Nuclear Information System (INIS)

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

153

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-05-09

154

Structure-Activity Relationships of Novel Salicylaldehyde Isonicotinoyl Hydrazone (SIH) Analogs: Iron Chelation, Anti-Oxidant and Cytotoxic Properties.  

Science.gov (United States)

Salicylaldehyde isonicotinoyl hydrazone (SIH) is a lipophilic, tridentate iron chelator with marked anti-oxidant and modest cytotoxic activity against neoplastic cells. However, it has poor stability in an aqueous environment due to the rapid hydrolysis of its hydrazone bond. In this study, we synthesized a series of new SIH analogs (based on previously described aromatic ketones with improved hydrolytic stability). Their structure-activity relationships were assessed with respect to their stability in plasma, iron chelation efficacy, redox effects and cytotoxic activity against MCF-7 breast adenocarcinoma cells. Furthermore, studies assessed the cytotoxicity of these chelators and their ability to afford protection against hydrogen peroxide-induced oxidative injury in H9c2 cardiomyoblasts. The ligands with a reduced hydrazone bond, or the presence of bulky alkyl substituents near the hydrazone bond, showed severely limited biological activity. The introduction of a bromine substituent increased ligand-induced cytotoxicity to both cancer cells and H9c2 cardiomyoblasts. A similar effect was observed when the phenolic ring was exchanged with pyridine (i.e., changing the ligating site from O, N, O to N, N, O), which led to pro-oxidative effects. In contrast, compounds with long, flexible alkyl chains adjacent to the hydrazone bond exhibited specific cytotoxic effects against MCF-7 breast adenocarcinoma cells and low toxicity against H9c2 cardiomyoblasts. Hence, this study highlights important structure-activity relationships and provides insight into the further development of aroylhydrazone iron chelators with more potent and selective anti-neoplastic effects. PMID:25393531

Pot??ková, Eliška; Hrušková, Kate?ina; Bureš, Jan; Kova?íková, Petra; Spirková, Iva A; Pravdíková, Kate?ina; Kolbabová, Lucie; Hergeselová, Tereza; Hašková, Pavlína; Jansová, Hana; Machá?ek, Miloslav; Jirkovská, Anna; Richardson, Vera; Lane, Darius J R; Kalinowski, Danuta S; Richardson, Des R; Vávrová, Kate?ina; Sim?nek, Tomáš

2014-01-01

155

Structure-Activity Relationships of Novel Salicylaldehyde Isonicotinoyl Hydrazone (SIH) Analogs: Iron Chelation, Anti-Oxidant and Cytotoxic Properties  

Science.gov (United States)

Salicylaldehyde isonicotinoyl hydrazone (SIH) is a lipophilic, tridentate iron chelator with marked anti-oxidant and modest cytotoxic activity against neoplastic cells. However, it has poor stability in an aqueous environment due to the rapid hydrolysis of its hydrazone bond. In this study, we synthesized a series of new SIH analogs (based on previously described aromatic ketones with improved hydrolytic stability). Their structure-activity relationships were assessed with respect to their stability in plasma, iron chelation efficacy, redox effects and cytotoxic activity against MCF-7 breast adenocarcinoma cells. Furthermore, studies assessed the cytotoxicity of these chelators and their ability to afford protection against hydrogen peroxide-induced oxidative injury in H9c2 cardiomyoblasts. The ligands with a reduced hydrazone bond, or the presence of bulky alkyl substituents near the hydrazone bond, showed severely limited biological activity. The introduction of a bromine substituent increased ligand-induced cytotoxicity to both cancer cells and H9c2 cardiomyoblasts. A similar effect was observed when the phenolic ring was exchanged with pyridine (i.e., changing the ligating site from O, N, O to N, N, O), which led to pro-oxidative effects. In contrast, compounds with long, flexible alkyl chains adjacent to the hydrazone bond exhibited specific cytotoxic effects against MCF-7 breast adenocarcinoma cells and low toxicity against H9c2 cardiomyoblasts. Hence, this study highlights important structure-activity relationships and provides insight into the further development of aroylhydrazone iron chelators with more potent and selective anti-neoplastic effects. PMID:25393531

Pot??ková, Eliška; Hrušková, Kate?ina; Bureš, Jan; Kova?íková, Petra; Špirková, Iva A.; Pravdíková, Kate?ina; Kolbabová, Lucie; Hergeselová, Tereza; Hašková, Pavlína; Jansová, Hana; Machá?ek, Miloslav; Jirkovská, Anna; Richardson, Vera; Lane, Darius J. R.; Kalinowski, Danuta S.; Richardson, Des R.; Vávrová, Kate?ina; Šim?nek, Tomáš

2014-01-01

156

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

Energy Technology Data Exchange (ETDEWEB)

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

Janke, C.J.

1998-11-01

157

Effect of Fe(3)O(4) on the sedimentation and structure-property relationship of starch under different pHs.  

Science.gov (United States)

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

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

2014-06-01

158

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

International Nuclear Information System (INIS)

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

159

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

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

Jadwiga Borowiak

1988-12-01

160

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

Science.gov (United States)

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

Li, Yao-Wang; Li, Bo

2013-02-01

 
 
 
 
161

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

International Nuclear Information System (INIS)

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

162

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

Science.gov (United States)

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

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

2014-08-01

163

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

Science.gov (United States)

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

Carbó-Dorca, Ramon

2013-04-01

164

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

Energy Technology Data Exchange (ETDEWEB)

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

Yang Jiaxiang, E-mail: jxyang@ahu.edu.cn [Department of Chemistry, Anhui University, Hefei 230039 (China)] [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Wang Caixia; Li Lin [Department of Chemistry, Anhui University, Hefei 230039 (China); Lin Na; Tao Xutang [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Tian Yupeng [Department of Chemistry, Anhui University, Hefei 230039 (China); Zhao Xian; Jiang Minhua [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China)

2009-03-30

165

Derivation of Structure-Activity Relationships from the Anticancer Properties of Ruthenium(II) Arene Complexes with 2-Aryldiazole Ligands.  

Science.gov (United States)

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

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

2014-10-20

166

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

International Nuclear Information System (INIS)

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

167

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

Science.gov (United States)

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

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

2014-08-18

168

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

International Nuclear Information System (INIS)

Crystalline BiVO4:Eu3+ nanomaterials have been successfully synthesized by four different methods: co-precipitation, hydrothermal, solvothermal, and reverse micelles. The relationship between crystal structure and luminescent properties was studied by X-ray diffraction and steady-state fluorescence. The data indicate that Eu3+5D0 ? 7F2 red luminescence at 618 nm can be excited by visible light at 466 nm in BiVO4 host. Furthermore, it has been found that the encapsulation of europium(III) in tetragonal phase (BiVO4) results in enhanced luminescence intensities compared with monoclinic phase. Transmission electron microscopy showed rods with sizes ranging from nanometer to micrometer and nanospheres can be obtained under different experimental conditions.

169

Notes on quantitative structure-properties relationships (QSPR) (1): A discussion on a QSPR dimensionality paradox (QSPR DP) and its quantum resolution.  

Science.gov (United States)

Classical quantitative structure-properties relationship (QSPR) statistical techniques unavoidably present an inherent paradoxical computational context. They rely on the definition of a Gram matrix in descriptor spaces, which is used afterwards to reduce the original dimension via several possible kinds of algebraic manipulations. From there, effective models for the computation of unknown properties of known molecular structures are obtained. However, the reduced descriptor dimension causes linear dependence within the set of discrete vector molecular representations, leading to positive semi-definite Gram matrices in molecular spaces. To resolve this QSPR dimensionality paradox (QSPR DP) here is proposed to adopt as starting point the quantum QSPR (QQSPR) computational framework perspective, where density functions act as infinite dimensional descriptors. The fundamental QQSPR equation, deduced from employing quantum expectation value numerical evaluation, can be approximately solved in order to obtain models exempt of the QSPR DP. The substitution of the quantum similarity matrix by an empirical Gram matrix in molecular spaces, build up with the original non manipulated discrete molecular descriptor vectors, permits to obtain classical QSPR models with the same characteristics as in QQSPR, that is: possessing a certain degree of causality and explicitly independent of the descriptor dimension. PMID:18942738

Carbó-Dorca, Ramon; Gallegos, Ana; Sánchez, Angel J

2009-05-01

170

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

Science.gov (United States)

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

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

2008-07-01

171

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-12-05

172

The role of reactive silicates on the structure/property relationships and cell response evaluation in polyurethane nanocomposites.  

Science.gov (United States)

Precursors of polyurethane chains have been reacted by means of in situ polymerization with organically modified montmorillonite clay to obtain polyurethane nanocomposites containing from 1 to 4 wt % of nanoreinforcement. The effective final dispersion of inorganic component at nanometric scale was investigated by X-ray diffraction, atomic force microscopy, and transmission electron microscopy. In addition, the effect of the nanoreinforcement incorporation on thermal and mechanical behavior of polyurethane nanocomposites was evaluated. Nanocomposites showed similar mechanical properties to polyurethanes containing high-hard segment contents with higher tensile modulus and a decrease in elastomeric properties of polyurethane materials. Finally, biocompatibility studies using L-929 fibroblast have been carried out to examine in vitro cell response and cytotoxicity of the matrix and their nanocomposite materials. Results suggested that the organic modifier in the clay is unsuitable for biomedical devices in spite of the fact that the matrix is a good candidate for cell adhesion and proliferation. PMID:21495170

Rueda, Lorena; Garcia, Inaki; Palomares, Teodoro; Alonso-Varona, Ana; Mondragon, Inaki; Corcuera, Marian; Eceiza, Arantxa

2011-06-15

173

Relationship Between Attitude Properties and Psychological Commitment  

Directory of Open Access Journals (Sweden)

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

JAEHYUN HA

2011-01-01

174

Quantitative Structure Pharmacokinetic Relationship Using Artificial Neural Network: A Review  

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

S. K. Singh

2009-10-01

175

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

International Nuclear Information System (INIS)

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

176

Relationship between structural and magnetic properties in (Ti,Fe)O2 powders obtained by mechanical milling  

International Nuclear Information System (INIS)

Fe-doped TiO2 samples with different Fe content were prepared by mechanical alloying starting from TiO2 rutile and FeO. The samples were structurally and magnetically characterized by XRD, Mössbauer spectroscopy, X-ray absorption spectroscopy (XAS), AC-susceptibility and magnetization measurements. XAS results showed that Fe ions were incorporated into the rutile phase with oxygen coordination that was lower than that expected in this phase. The oxygen coordination number decreased with the increase of Fe2+ ions such as it was previously found in the milled samples of TiO2 doped with hematite. The RT Mössbauer spectra were reproduced using two paramagnetic interactions, one corresponding to Fe2+ (??0.87 mm/s) and the other to Fe3+ (??0.31 mm/s). Magnetometry measurements showed the presence of paramagnetic and ferromagnetic-like interactions at room temperature. Although saturation and coercivity of the ferromagnetic phase increased with iron, the effective magnetic moment per iron atom decreased, probably due to the precipitation of Fe rich antiferromagnetic structures.

177

Relationship between structural and magnetic properties in (Ti,Fe)O2 powders obtained by mechanical milling  

Science.gov (United States)

Fe-doped TiO2 samples with different Fe content were prepared by mechanical alloying starting from TiO2 rutile and FeO. The samples were structurally and magnetically characterized by XRD, Mössbauer spectroscopy, X-ray absorption spectroscopy (XAS), AC-susceptibility and magnetization measurements. XAS results showed that Fe ions were incorporated into the rutile phase with oxygen coordination that was lower than that expected in this phase. The oxygen coordination number decreased with the increase of Fe2+ ions such as it was previously found in the milled samples of TiO2 doped with hematite. The RT Mössbauer spectra were reproduced using two paramagnetic interactions, one corresponding to Fe2+ (??0.87 mm/s) and the other to Fe3+ (??0.31 mm/s). Magnetometry measurements showed the presence of paramagnetic and ferromagnetic-like interactions at room temperature. Although saturation and coercivity of the ferromagnetic phase increased with iron, the effective magnetic moment per iron atom decreased, probably due to the precipitation of Fe rich antiferromagnetic structures.

Mudarra Navarro, A. M.; Bilovol, V.; Cabrera, A. F.; Rodríguez Torres, C. E.

2012-08-01

178

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-08-15

179

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

Science.gov (United States)

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

Sharma-Judd, Malavika M.

180

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

Science.gov (United States)

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

Li, Huixing; Chen, Maodu

2013-12-01

 
 
 
 
181

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

Science.gov (United States)

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

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

2014-11-01

182

Structure-property relationships of symmetrical and asymmetrical azobenzene derivatives as gelators and their self-assemblies.  

Science.gov (United States)

Two different series of symmetrical and asymmetrical azobenzenes containing terminal cholesteryl/adamantyl derivatives (SAC/SAA and AAC) with varying spacer lengths (alkyl chains) have been developed. The gelation and aggregation of these derivatives were studied relative to structural motifs, spacer lengths, solvent affinity, temperatures and light conditions. Among these derivatives, the cholesteryl derivatives that have short alkyl chains (analysis. The reversibility of sol-gel transitions by light was studied with respect to solvent affinity. This study revealed that reversible transitions were only observed in the non-polar solvents, as supported by the FTIR analysis of the gelators in the various solvents. The thermal and mesomorphic behaviors of the gelators by DSC (Differential Scanning Calorimetry) and POM (Polarized Optical Microscopy) analyses revealed that the chiral nematic (N*) and cholesteric mesophase (Ch*) were exhibited by only the short and longer alkyl chain cholesteryl derivatives, respectively. However, the cholesteryl derivative without a spacer (AAC0) did not exhibit any liquid crystalline phase but acted as an efficient gelator relative to the other gelators in this study. PMID:25290740

Balamurugan, Rathinam; Kai-Ming, Wu; Chien, Chih-Chieh; Liu, Jui Hsiang

2014-10-23

183

Structure-property relationship for two-photon absorbing multiporphyrins: supramolecular assembly of highly-conjugated multiporphyrinic ladders and prisms.  

Science.gov (United States)

Two-photon absorption (TPA) phenomena of a series of single-strand as well as supramolecular self-assembled ladders and prisms of highly conjugated ethyne bridged multiporphyrin dimer, trimer, and star shaped pentamer have been investigated. The ligand mediated self-assembled supramolecular structures were characterized by UV-visible spectroscopy and small- and wide-angle X-ray scattering (SAXS/WAXS) analysis. The TPA cross section values of multiporphyrins increase nonlinearly from approximately 100 to approximately 18000 GM with an increased number of porphyrin units and elongated pi-conjugation length by virtue of charge transfer and excited-state cumulenic configurations. The observed opposite TPA behavior between their supramolecular ladder and prism configurations necessitates the importance of interstrand interactions between the multiporphyrinic units and the overall shape of the assembly. Furthermore, the diminished TPA cross section of the pentamer, despite the increased pi-conjugation resulting from duplex formation suggests that destabilizing the essential functional configurations at the cost of elongation of pi-delocalization pathway must cause unfavorable effects. We have also shown that one- and two-photon allowed energy-levels of linear multiporphyrins are nearly isoenergetic and the latter transition originates exclusively from the extent of pi-delocalization within the molecule. The identical TPA maximum position of the trimer and pentamer indicates that the TPA of the pentamer arises only from its basic trimer unit in spite of its extended two-dimensional pi-conjugation pathway involving five porphyrinic units. PMID:18588270

Easwaramoorthi, Shanmugam; Jang, So Young; Yoon, Zin Seok; Lim, Jong Min; Lee, Cheng-Wei; Mai, Chi-Lun; Liu, Yen-Chun; Yeh, Chen-Yu; Vura-Weis, Josh; Wasielewski, Michael R; Kim, Dongho

2008-07-24

184

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

Science.gov (United States)

We build a united atom model for Tween 80 (polyoxyethylene sorbitan oleates), based on the GROMOS53A6OXY+D force field, and apply it to two stereoisomers, three constitutional isomers, and three structures with one, two, and three tails, to represent components in the Tween 80 commercial mixture. In a preassembled micelle containing 60 molecules, the distribution of Tween tail and ethylene oxide head groups is found to be insensitive to stereoisomerization but sensitive to changes in relative lengths of the four polyoxyethylene head groups. At the air-water and oil-water interfaces, the interfacial tension is significantly lower for the constitutional isomer with a shorter W headgroup, which attaches the tail to the sorbitan ring, and for Tween 80 isomers with more than one tail group. The results indicate the possible scope for improvement in the design of polyoxyethylene sorbitan oleates with improved surface tension reduction or better spreading at the oil-water interface. We also report surfactant component distribution profiles within preassembled micelles and at interfaces that can be used for validating coarse-grained surfactant models needed for simulation of self-assembly of Tween 80 surfactant mixtures. PMID:25365212

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

2014-11-13

185

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

International Nuclear Information System (INIS)

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

186

Structure-Property Relationship for Two-Photon Absorbing Multiporphyrins: Supramolecular Assembly of Highly-Conjugated Multiporphyrinic Ladders and Prisms  

Energy Technology Data Exchange (ETDEWEB)

Two-photon absorption (TPA) phenomena of a series of single-strand as well as supramolecular self-assembled ladders and prisms of highly conjugated ethyne bridged multiporphyrin dimer, trimer, and star shaped pentamer have been investigated. The ligand mediated self-assembled supramolecular structures were characterized by UV-visible spectroscopy and small- and wide-angle X-ray scattering (SAXS/WAXS) analysis. The TPA cross section values of multiporphyrins increase nonlinearly from {approx}100 to {approx}18000 GM with an increased number of porphyrin units and elongated ?-conjugation length by virtue of charge transfer and excited-state cumulenic configurations. The observed opposite TPA behavior between their supramolecular ladder and prism configurations necessitates the importance of interstrand interactions between the multiporphyrinic units and the overall shape of the assembly. Furthermore, the diminished TPA cross section of the pentamer, despite the increased ?-conjugation resulting from duplex formation suggests that destabilizing the essential functional configurations at the cost of elongation of ?-delocalization pathway must cause unfavorable effects. We have also shown that one- and two-photon allowed energy-levels of linear multiporphyrins are nearly isoenergetic and the latter transition originates exclusively from the extent of ?-delocalization within the molecule. The identical TPA maximum position of the trimer and pentamer indicates that the TPA of the pentamer arises only from its basic trimer unit in spite of its extended two-dimensional {pi}-conjugation pathway involving five porphyrinic units.

Easwaramoorthi, Shanmugam; Jang, So Young; Yoon, Zin Seok; Lim, Jong Min; Lee, Cheng-Wei; Mai, Chi-Lun; Liu, Yen-Chun; Yeh, Chen-Yu; Vura-Weis, Josh; Wasielewski, Michael R.; Kim, Dongho (NWU); (Yonsei); (NSHU)

2008-10-03

187

The Structures and Properties of Carbon  

Science.gov (United States)

The four main forms of carbon--diamond, graphite, buckyballs, and CNTs--are an excellent vehicle for teaching fundamental principles of chemical bonding, material structure, and properties. Carbon atoms form a variety of structures that are intrinsically connected to the properties they exhibit. Educators can take advantage of this striking relationship between atomic structure and material properties to address several Physical Science Standards (9-12), including Structure of Atoms and Structure and Properties of Matter (NRC 1996, p. 178). This article discusses two new allotropes of carbon that are important for nanotechnology--buckyballs and CNTs--and related activities for the classroom.

Lisensky, George C.; Zenner, Greta M.; Ehrlich, Jennifer; Castellini, Olivia M.; Crone, Wendy C.

2006-12-01

188

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

Science.gov (United States)

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

de Melo, Eduardo Borges

2012-01-01

189

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

Science.gov (United States)

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

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

2014-03-01

190

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

International Nuclear Information System (INIS)

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

191

Similarity Matrices Quantitative Structure-Activity Relationships for Anticonvulsant Phenylacetanilides  

Directory of Open Access Journals (Sweden)

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

Ovidiu Ivanciuc

2004-07-01

192

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

Science.gov (United States)

The surfaces of untreated and helium plasma-based ion implantation (He PBII) treated poly(ethylene terephthalate) (PET) samples were characterised by reflectance colorimetry, contact angle studies and measurements of surface electrical resistance. The results were related to the structural and compositional data obtained by the authors earlier on parallel samples by XPS and Raman spectroscopy. Inverse correlations between lightness and ID/ IG ratio and between chroma and ID/ IG ratio were obtained, suggesting that the PBII-treated PET samples darken and their colourfulness decreases with the increase of the portion of aromatic sp 2 carbon rings in the chemical structure of the modified layer. Direct correlation between water contact angle and the ID/ IG ratio and inverse correlations between surface energy and ID/ IG ratio and between dispersive component of surface energy and ID/ IG ratio were found, reflecting that surface wettability, surface energy and its dispersive component decrease with the formation of surface structure, characterised again by enhanced portion of aromatic sp 2 carbon rings. The surface electrical resistance decreased with the increase of the surface C-content determined by XPS and also with the increase of the surface concentration of conjugated double bonds, reflected by the increase of the ? ? ?* shake-up satellite of the C 1s peak.

Tóth, A.; Veres, M.; Kereszturi, K.; Mohai, M.; Bertóti, I.; Szépvölgyi, J.

2011-10-01

193

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

Energy Technology Data Exchange (ETDEWEB)

The surfaces of untreated and helium plasma-based ion implantation (He PBII) treated poly(ethylene terephthalate) (PET) samples were characterised by reflectance colorimetry, contact angle studies and measurements of surface electrical resistance. The results were related to the structural and compositional data obtained by the authors earlier on parallel samples by XPS and Raman spectroscopy. Inverse correlations between lightness and I{sub D}/I{sub G} ratio and between chroma and I{sub D}/I{sub G} ratio were obtained, suggesting that the PBII-treated PET samples darken and their colourfulness decreases with the increase of the portion of aromatic sp{sup 2} carbon rings in the chemical structure of the modified layer. Direct correlation between water contact angle and the I{sub D}/I{sub G} ratio and inverse correlations between surface energy and I{sub D}/I{sub G} ratio and between dispersive component of surface energy and I{sub D}/I{sub G} ratio were found, reflecting that surface wettability, surface energy and its dispersive component decrease with the formation of surface structure, characterised again by enhanced portion of aromatic sp{sup 2} carbon rings. The surface electrical resistance decreased with the increase of the surface C-content determined by XPS and also with the increase of the surface concentration of conjugated double bonds, reflected by the increase of the {pi} {yields} {pi}* shake-up satellite of the C 1s peak.

Toth, A., E-mail: totha@chemres.hu [Institute of Materials and Environmental Chemistry, Chemical Research Center, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 17 (Hungary); Veres, M. [Research Institute for Solid State Physics and Optics of the Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 49 (Hungary); Kereszturi, K.; Mohai, M.; Bertoti, I.; Szepvoelgyi, J. [Institute of Materials and Environmental Chemistry, Chemical Research Center, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 17 (Hungary)

2011-10-01

194

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

Science.gov (United States)

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

Nanos, John I.

2005-12-01

195

Phase Transitions in the BiVO4- nPbO ( n = 1, 2) System: Structural-Electrical Properties Relationships  

Science.gov (United States)

In a general survey of nPbO-BiVO4 compounds, interesting phases corresponding to n = 1: PbBiVO5, and n = 2: Pb2BiVO6 are described. A phase transition has been unambiguously characterized for PbBiVO5. The crystal structures were solved from twinned crystals at room temperature (? phase, triclinic, S.G. P-1) and at 530°C (? phase, monoclinic, C2/ m). Powder neutron diffraction experiments confirmed these settings and both room-temperature (RT) and high-temperature (HT) refinements corroborated space group choices, clearing up a literature controversy about the centrosymmetry of the ? phase, and identifying structural modifications occurring under the ? ? ? transition. Cationic substitutions for V were tested and PbBi(V1- x M x )O5 (M = P) solid solutions identified. Pb2BiVO6 ( n = 2) is a compound showing several successive structural transitions, i.e., ? ? ? ? ?. Structures of ? and ? forms have been previously described from powder diffraction data (x-ray and neutron). In this work, we have refined these structures from single-crystal data, and the resolution of the intermediate ? form, so far unsolved, was possible through a stabilization thermal cycle; its complete structural understanding required a 4D formalism. Two new polymorphic phases, ?' and ?', were obtained by substituting Mn or P for V; their structures are closely related to, respectively, the ? phase at room temperature, and the ? phase at 680°C. Electrical conductivities of all structurally characterized compositions were investigated, and correlations were drawn between their conduction properties and structural characteristics. Conductivity properties measured under variable O2 partial pressures for Pb2Bi(V0.75P0.25)O6 were interpreted as a mixed ionic-electronic ( p-type) conduction mechanism.

Wignacourt, Jean-Pierre; Drache, Michel; Labidi, Olfa; Roussel, Pascal

2009-01-01

196

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

Science.gov (United States)

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

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

2007-01-01

197

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

Science.gov (United States)

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.

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

2013-02-01

198

Reversed- and normal-phase liquid chromatography in quantitative structure retention-property relationships of newly synthesized seco-androstene derivatives.  

Science.gov (United States)

The rational preselection of drug candidates includes also correlation between physico-chemical properties (lipophilicity, as the key one) and pharmacokinetic properties, as well as pharmacodynamic activity. Lipophilicity can be determined alternatively by chromatographic methods. Chromatographic behavior of nineteen newly synthesized derivatives of 16-cyano-16,17-seco-5-androstene has been studied by reversed-phase and normal-phase thin-layer chromatography (RP- and NP-TLC). Commercial plates RP-C18-HPTLC and water-dioxane and water-acetonitrile, as well as Lux(®) silica gel plates and toluene-dioxane and toluene-acetonitrile mixtures with different volume fractions of the solvents were used. Retention constants RM(0) and C0 for each compound were determined and correlated with (i) theoretical log P values and (ii) pharmacokinetic predictors determined in silico. Significant linear relationship was found between RP TLC retention constants, RM(0), and computational logP values as well as between NP TLC retention constants, C0, and logP. Lipophilicity values for the analytes, determined by RP TLC and NP TLC, were also correlated with computer calculated absorption constants, affinity for plasma proteins, volume of distribution and logarithm of blood-brain permeation. Significant linear relationships were obtained. These relations were further improved by introducing other regressors, as molecular size descriptors (molecular mass and/or volume) and a molecular polarity descriptor (total polar surface area). Retention parameters, RM(0) and C0, are recommended for lipophilicity expression of analyzed compounds. In silico pharmacokinetic descriptors for the analytes can be expressed as function of the lipophilicity determined by chromatographic methods, the size and the polarity of the molecules expressed as molecular mass/volume and total polar surface area. The analyzed seco-androstene derivatives have adequate lipophilicity which should provide druglikeness and good pharmacokinetic profiles and they can be recommended for further studies in which their biological activity would be examined. PMID:24216283

Miloševi?, Nataša P; Stojanovi?, Srdjan Z; Penov-Gaši, Katarina; Periši?-Janji?, Nada; Kaliszan, Roman

2014-01-01

199

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

CERN Document Server

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

Ganesan, Aravindhan; Wang, Feng

2014-01-01

200

Porous Materials - Structure and Properties  

DEFF Research Database (Denmark)

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

Nielsen, Anders

1997-01-01

 
 
 
 
201

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

DEFF Research Database (Denmark)

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

Nichols, Richard John; Nygaard, Sune

2008-01-01

202

Hypoxia-selective antitumor agents. 1. Relationships between structure, redox properties and hypoxia-selective cytotoxicity for 4-substituted derivatives of nitracrine.  

Science.gov (United States)

The nitroacridine derivative 9-[[3-(dimethylamino)propyl]amino]-1-nitroacridine (nitracrine) is selectively cytotoxic to hypoxic tumor cells in culture. However, the compound undergoes reductive metabolism too rapidly, with the reduction not being sufficiently inhibited by molecular oxygen in aerobic tissues, for it to demonstrate the same activity in vivo. In a search for derivatives with lower reduction potentials, we have synthesized and evaluated a series of derivatives bearing 4-substituents with a wide range of electronic properties. The one-electron reduction potentials (E(1] of these compounds, when compared under conditions of equivalent ionization, were highly correlated with sigma p values. However, at pH 7 the influence of substituent electronic properties was modified by prototrophic equilibria, with the basic nature of the acridine limiting the extent to which ring substituent electronic effects can be used to modulate reduction potential of the 1-nitro group. Nevertheless, comparison of the kinetics of the killing of AA8 cells under hypoxia suggests that some metabolic stabilization of the compounds can be achieved by the use of electron-donating substituents, with such compounds retaining the hypoxia-selective toxicity of nitracrine in cell culture. However, the 4-substituted nitracrines show no clear relationship between E(1) and cytotoxic potency, in distinct contrast to simpler nitroheterocycles such as nitroimidazoles. PMID:2909736

Wilson, W R; Anderson, R F; Denny, W A

1989-01-01

203

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

DEFF Research Database (Denmark)

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

Thygesen, Lisbeth Garbrecht

2007-01-01

204

Electromechanical actuation of buckypaper actuator: Material properties and performance relationships  

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-02-27

205

Electromechanical actuation of buckypaper actuator: Material properties and performance relationships  

International Nuclear Information System (INIS)

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

206

Structured Questionnaire To Measure Therapeutic Relationship  

Directory of Open Access Journals (Sweden)

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

FatemehKhoshnavafomani

2012-10-01

207

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

Science.gov (United States)

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

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

2008-04-01

208

Ionic conduction, bond valence analysis of structure–property relationships of NaHoP{sub 2}O{sub 7}  

Energy Technology Data Exchange (ETDEWEB)

Single crystals of NaHoP{sub 2}O{sub 7} diphosphate have been prepared by the flux method and its structural and physical properties have been investigated. It crystallizes in the monoclinic system with the space group P2{sub 1}/n and its parameters are: a=8.6796(4) Å, b=5.3677(2) Å, c=13.6904(6) Å, ?=106.120° (2), V=612.75 (5) Å{sup 3}, Z=4. The structure of NaHoP{sub 2}O{sub 7} consists of a three-dimensional framework of HoO{sub 6} octahedra, linked by P{sub 2}O{sub 7} diphosphate units, forming tunnels running parallel to [0 1 0], which are occupied by Na atoms. The infrared and Raman vibrational spectra have been investigated. Activation energy was obtained from Arrhenius plots (Ln ?T versus 1000/T) and found to be 1.27 eV. The coupling of the structural analysis with the BVS model for NaHoP{sub 2}O{sub 7} has better interpret the measurements of the ionic conductivity and the most probably transport pathway model was determined. - Graphical abstract: Schematic representation of the structural arrangement of NaHoP{sub 2}O{sub 7} shows the sodium conduction pathway along the [0 1 0] direction. Highlights: • Single crystals of NaHoP{sub 2}O{sub 7} were prepared by flux method and characterized by single-crystal X-ray data. • The conductivity and loss spectra were analysed in order explain the mechanism of conduction. • The most probably conduction pathway are determined.

Béjaoui, Anis, E-mail: bejaoui-anis@hotmail.fr; Horchani-Naifer, Karima; Férid, Mokhtar

2013-08-15

209

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

Directory of Open Access Journals (Sweden)

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

Nadia A. Mohamed

2012-11-01

210

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

Science.gov (United States)

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

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

2012-06-01

211

The Structures & Properties of Carbon  

Science.gov (United States)

The four main forms of carbon--diamond, graphite, buckyballs, and carbon nanotubes (CNTs)--are an excellent vehicle for teaching fundamental principles of chemical bonding, material structure, and properties. Carbon atoms form a variety of structures that are intrinsically connected to the properties they exhibit. Educators can take advantage of…

Castellini, Olivia M.; Lisensky, George C.; Ehrlich, Jennifer; Zenner, Greta M.; Crone, Wendy C.

2006-01-01

212

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

International Nuclear Information System (INIS)

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

213

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

Science.gov (United States)

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

Sethi, Guneet

214

Discovering Relationships between Data Structures and Algorithms  

Directory of Open Access Journals (Sweden)

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

Guojin Zhu

2013-07-01

215

Global description of structure-property relations  

International Nuclear Information System (INIS)

Over the last 50 years the Hume-Rothery rules have evolved in Quantum Structure Diagrams. QSD epitomize conveniently and accurately most of what is known by metallurgists and physicists about metallic bonding, and their history is fascinating. The most difficult technical problem was the one that everyone thought was solved-the issue of atomic size-which Villars finally resolved in 1983. In this paper, attention is focussed on successful rules for ternary structures and phase diagrams, and the relationship between structure and properties, such as ferroelecticity, superconductivity, and quasicrystallinity

216

Sharing chemical relationships does not reveal structures.  

Science.gov (United States)

In this study, we propose a new, secure method of sharing useful chemical information from small-molecule libraries, without revealing the structures of the libraries' molecules. Our method shares the relationship between molecules rather than structural descriptors. This is an important advance because, over the past few years, several groups have developed and published new methods of analyzing small-molecule screening data. These methods include advanced hit-picking protocols, promiscuous active filters, economic optimization algorithms, and screening visualizations, which can identify patterns in the data that might otherwise be overlooked. Application of these methods to private data requires finding strategies for sharing useful chemical data without revealing chemical structures. This problem has been examined in the context of ADME prediction models, with results from information theory suggesting it is impossible to share useful chemical information without revealing structures. In contrast, we present a new strategy for encoding the relationships between molecules instead of their structures, based on anonymized scaffold networks and trees, that safely shares enough chemical information to be useful in analyzing chemical data, while also sufficiently blinding structures from discovery. We present the details of this encoding, an analysis of the usefulness of the information it conveys, and the security of the structures it encodes. This approach makes it possible to share data across institutions, and may securely enable collaborative analysis that can yield insight into both specific projects and screening technology as a whole. PMID:24289228

Matlock, Matthew; Swamidass, S Joshua

2014-01-27

217

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

Directory of Open Access Journals (Sweden)

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

Saldana D.A.

2013-06-01

218

Relationship between the ligand structure and the luminescent properties of water-soluble lanthanide complexes containing bis(bipyridine) anionic arms.  

Science.gov (United States)

A series of six new ligands (L(1)-L(6)) suitable for the formation of luminescent lanthanide complexes in water is described. Ligands L(1)-L(4) are constructed from two 6'-carboxy-6-methylene-2,2'-bipyridine chromophoric arms bonded to the amino function of a 2-aminomethylene-6-carboxy-pyridine (L(1)), an N,N-diacetate-ethylene diamine (L(2)), a serine (L(3)), or an aminomalonic acid (L(4)). For ligands L(5) and L(6), the linking amino function is provided by a glutamic acid, and the anionic functions at the 6'-position of the bipyridyl arms are made of the sodium salts of monoethylphosphonic ester (L(5)) and phosphonic acid (L(6)). The synthesis and characterisation of the ligands are described, together with the study of the formation of lanthanide complexes with europium and terbium. In the case of L(3), the europium complex obtained in acidic conditions was crystallised and the X-ray crystal structure is depicted. Photophysical properties of the complexes were studied by means of UV-visible absorption, and steady-state and time-resolved luminescence spectroscopy. Excited-state luminescence lifetimes of the complexes were determined in water and deuterated water to gain insight into the number of water molecules directly coordinated in the first coordination sphere of the complexes. The coordination behaviour of the series of ligands is questioned in the light of the spectroscopic data and discussed in terms of protection of the cation towards water molecules and their impact on the luminescence efficiency. PMID:17009386

Charbonnière, Loïc J; Weibel, Nicolas; Retailleau, Pascal; Ziessel, Raymond

2007-01-01

219

RELATIONSHIP BETWEEN BOARD STRUCTURE AND CONSERVATISM  

Directory of Open Access Journals (Sweden)

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

Shahram Gilaninia

2011-10-01

220

Structural Properties of Ego Networks  

CERN Document Server

The structure of real-world social networks in large part determines the evolution of social phenomena, including opinion formation, diffusion of information and influence, and the spread of disease. Globally, network structure is characterized by features such as degree distribution, degree assortativity, and clustering coefficient. However, information about global structure is usually not available to each vertex. Instead, each vertex's knowledge is generally limited to the locally observable portion of the network consisting of the subgraph over its immediate neighbors. Such subgraphs, known as ego networks, have properties that can differ substantially from those of the global network. In this paper, we study the structural properties of ego networks and show how they relate to the global properties of networks from which they are derived. Through empirical comparisons and mathematical derivations, we show that structural features, similar to static attributes, suffer from paradoxes. We quantify the diff...

Gupta, Sidharth; Lerman, Kristina

2014-01-01

 
 
 
 
221

Structural relationships in high temperature superconductors  

International Nuclear Information System (INIS)

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

222

Quasicrystals - Discovery, Structure and Properties  

Directory of Open Access Journals (Sweden)

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

Stilinovi?, V.

2012-07-01

223

Structural tailoring of laminate properties  

Science.gov (United States)

In this study, structural synthesis techniques have been applied to tailor the composite laminate properties from the micromechanics to the laminate level for a desirable structural response. It is also demonstrated how to establish upper and lower bounds on design variables based on reliability considerations. The question of reliability arises in fiber composite analysis and design because of the inherent scatter that is observed in the constituent material properties in the experimental data. The symmetric composite laminates subject to mechanical loading are considered and no hygrothermal effects are taken into account in the present research. Application examples illustrate the effects of various ply and laminate parameters on the overall properties and structural response of composite laminates.

Thanedar, P. B.; Chamis, C. C.

1989-01-01

224

Constituent Property - Composite Property Relationships in Thermoset Matrices  

Science.gov (United States)

A procedure to effectively screen and evaluate resins for aerospace structures and advanced composites is described. The following conclusions were advanced: (1) laminate damage tolerance correlates positively with neat resin G sub IC; (2) TGDDM/DDS resins can be toughened; (3) using butadiene-nitrile rubbers, neat resin G sub IC and ultimate strain increase with increasing nitrile content, with the number of chemically reactive groups per molecule, and with increasing molecular weight; (4) better balance of properties combined with high G sub IC may be achieved by using tough glassy thermoplastics instead of rubbers to modify TGDDM/DDS resins; (5) both toughening mechanisms require good phase separation with an effective interphase; (6) the kind and the amount of thermoplastic modifier remain to be selected; and (7) presently only about a fourfold increase in G sub IC was achieved, whereas a forty fold increase is sought; modification of the matrix backbone and of crosslinking is required.

Diamant, J.; Moulton, R. J.

1984-01-01

225

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

Directory of Open Access Journals (Sweden)

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

Kevin Magniez

2013-08-01

226

Foldamers structure, properties and applications  

CERN Document Server

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

Hecht, Stefan

2007-01-01

227

Some properties of galaxy structures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2011-01-01

228

Quasicrystals - Discovery, Structure and Properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Quasicrystals are solid materials the structures of which can have crystallographically forbidden symmetries, e.g. of the fifth order, and do not have the translational invariance charactistic for classical crystals. Their properties are quite different from those of classical crystals. Although all being metals, they are poor conductors of heat and electricity and are hard and brittle. Their structures can be described as quasiperiodic. The mathematical description of quasiperiodicity predat...

Stilinovic?, V.; Bru?ckler, F. M.

2012-01-01

229

Ginkgolides and glycine receptors : a structure-activity relationship study  

DEFF Research Database (Denmark)

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

Jaracz, Stanislav; Nakanishi, Koji

2004-01-01

230

Structure-cytotoxicity relationships for dietary flavonoids  

DEFF Research Database (Denmark)

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

1998-01-01

231

Physical properties and structure of fine core-shell particles used as packing materials for chromatography relationships between particle characteristics and column performance  

Energy Technology Data Exchange (ETDEWEB)

The recent development of new brands of packing materials made of fine porous-shell particles, e.g., Halo and Kinetex, has brought great improvements in potential column efficiency, demanding considerable progress in the design of chromatographic instruments. Columns packed with Halo and Kinetex particles provide minimum values of their reduced plate heights of nearly 1.5 and 1.2, respectively. These packing materials have physical properties that set them apart from conventional porous particles. The kinetic performance of 4.6 mm I.D. columns packed with these two new materials is analyzed based on the results of a series of nine independent and complementary experiments: low-temperature nitrogen adsorption (LTNA), scanning electron microscopy (SEM), inverse size-exclusion chromatography (ISEC), Coulter counter particle size distributions, pycnometry, height equivalent to a theoretical plate (HETP), peak parking method (PP), total pore blocking method (TPB), and local electrochemical detection across the column exit section (LED). The results of this work establish links between the physical properties of these superficially porous particles and the excellent kinetic performance of columns packed with them. It clarifies the fundamental origin of the difference in the chromatographic performances of the Halo and the Kinetex columns.

Gritti, Fabrice [University of Tennessee, Knoxville (UTK); Guiochon, Georges A [ORNL

2010-01-01

232

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

Energy Technology Data Exchange (ETDEWEB)

We characterize experimentally and theoretically the promising new solid oxide fuel cell electrode material Sr2Fe1.5Mo0.5O6 (SFMO). Rietveld refinement of powder neutron diffraction data has determined that the crystal structure of this material is distorted from the ideal cubic simple perovskite, instead belonging to the orthorhombic space group Pnma. The refinement revealed the presence of oxygen vacancies in the as-synthesized material, resulting in a composition of Sr2Fe1.5Mo0.5O5.90(2) ( = 0.10(2)). DFT+U theory predicts essentially the same concentration of oxygen vacancies. Theoretical analysis of the electronic structure allows us to elucidate the origin of this nonstoichiometry and the attendant mixed ion electron conductor character so important for intermediate temperature fuel cell operation. The ease with which SFMO forms oxygen vacancies and allows for facile bulk oxide ion diffusivity is directly related to a strong hybridization of the Fe d and O p states, which is also responsible for its impressive electronic conductivity.

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

2012-01-01

233

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

Science.gov (United States)

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

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

2012-04-18

234

Relationship between the structure and luminescent properties for two crystal modifications of N-butyl-2-cyano-3-[4-(dimethylamino)phenyl]-2-propenamide  

International Nuclear Information System (INIS)

Two crystal modifications (1o and 1y) of N-butyl-2-cyano-3-[4-(dimethylamino)phenyl]-2-propenamide, which differ in the color of crystals and the color of luminescence, have been studied by X-ray diffraction and spectral-luminescence methods. The corresponding bond lengths and bond angles in the molecules of two crystal modifications are virtually identical. In both crystal structures, there are two systems of weak intermolecular interactions: ?-stacking interactions and -CN…H-N hydrogen bonds involving nitrile and NH groups. In the crystal structures, two hydrogen bonds connect pairs of molecules into centrosymmetric dimers. The N…H distances are 2.21 and 2.41 Å in 1o and 1y, respectively. The interplanar distances in the ?-stacked systems of 1o and 1y are 3.33 and 3.41 Å, respectively. Both types of weak interactions are stronger in 1o than in 1y, which accounts for a larger shift of absorption and luminescence bands for the former compound

235

The relationship between the crystal structure and electrical properties of K2NiF4-type (Ca2-xNdx)MnO4  

Science.gov (United States)

K2NiF4-type (Ca2-xNdx)MnO4 synthesized using a polymerized complex route crystallized in a tetragonal structure with space group I41/acd in the range of 0 ? x ? 0.2 and crystallized in an orthorhombic structure with space group Fmmm in the range of 0.3 ? x ? 0.4. The Mn-O(2) distance of the a- and b-axis directions increased with values of x. The samples were n-type semiconductors and exhibited hopping conduction in a small-polaron model at temperature greater than 393 K. At room temperature, the carrier concentration increased slightly, whereas mobility decreased by 20% with increasing x values. The absolute value of the Seebeck coefficient monotonously increased with temperature and abruptly decreased with increasing values of x at a given temperature. These results indicated that electrical conductivity was strongly affected by the antagonism of the electron transfer in the Mn4+-O-Mn3+ path and the overlap between the Mnt2g and Op? orbitals.

Taguchi, Hideki; Kido, Hiroyasu; Hirota, Ken

2013-11-01

236

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-10-25

237

Cationic phospholipids: structure?transfection activity relationships  

Energy Technology Data Exchange (ETDEWEB)

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

Koynova, Rumiana; Tenchov, Boris; (NWU)

2010-01-18

238

Structure-property correlations in strontium titanate  

International Nuclear Information System (INIS)

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

239

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

Science.gov (United States)

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

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

2014-03-01

240

Microstructure-Property Relationships in Cast Irons  

International Nuclear Information System (INIS)

Several cast irons, prepared with different chemical compositions and microstructures have been examined by extensive mechanical testing and optical and scanning electron microscopy (SEM). Properties arising from various microstructures are tabulated. Mechanical properties are shown to be a function of both the matrix and graphite (or carbide) forms. Changing the matrix from ferritic-pearlitic to bainitic-martensitic type results in effects similar to those experienced in steels containing these phases respectively. The influence of graphite (or carbides) on the final properties, however, is dictate by the respective shapes and distributions of these microstructural constituents. The coupled zone-eutectic region in gray cast iron is asymmetrical and inclined to the right-hand side in Fe-C equilibrium phase diagram. Consequently, hypereutectic compositions reveal dendrites of primary austenite. In white cast iron, the coupled zone symmetry is thought to arise from the high volume fraction of cementite which compensates for its growth rate anisotropy. (author)

 
 
 
 
241

Structural Analysis of Laplacian Spectral Properties in Complex Electric Grids  

CERN Document Server

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

Preciado, Victor M; Verghese, George C

2011-01-01

242

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1993-01-01

243

Structural properties of colloidal suspensions  

Science.gov (United States)

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.

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

1995-02-01

244

Native Cellulose: Structure, Characterization and Thermal Properties  

Directory of Open Access Journals (Sweden)

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

Matheus Poletto

2014-08-01

245

Distributing Correlation Coefficients of Linear Structure-Activity/Property Models  

Directory of Open Access Journals (Sweden)

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

Sorana D. BOLBOACA

2011-12-01

246

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

Science.gov (United States)

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

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

2012-01-01

247

Tribological Properties of Structural Ceramics  

Science.gov (United States)

Paper discusses tribological properties of structural ceramics. Function of tribological research is to bring about reduction in adhesion, friction, and wear of mechanical components; to prevent failures; and to provide long, reliable component life, through judicious selection of materials, operating parameters, and lubricants. Paper reviews adhesion, friction, wear, and lubrication of ceramics; anisotropic friction and wear behavior; and effects of surface films and interactions between ceramics and metals. Analogies with metals are made. Both oxide and nonoxide ceramics, including ceramics used as high temperature lubricants, are dicussed.

Buckley, Donald H.; Miyoshi, Kazuhisa

1987-01-01

248

Quasicrystals Structure and Physical Properties  

CERN Document Server

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

Trebin, Hans-Rainer

2003-01-01

249

Relationships between properties and functional targets of Chinese herbs  

Directory of Open Access Journals (Sweden)

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

Bin Xiao

2011-07-01

250

[Relationships between properties and functional targets of Chinese herbs].  

Science.gov (United States)

Functional targets are the objects that Chinese herbal medicines act directly upon. If the relationships between the properties of Chinese herbs and their functional targets were analyzed clearly, it would benefit the overall understanding of the holistic mechanisms of Chinese herbal treatments. In this paper, data regarding the properties of Chinese herbs and their functional targets were collected from the 2005 edition of The People's Republic of China Pharmacopoeia. After analyzing and assessing the data, the relationships were defined between the four qi, meridian entry and medicinal functional targets and between the four qi, five flavors and mode of function. Then the relationships between a single herbal medicine and a prescription were analyzed, and the results conformed with the traditional knowledge of Chinese herbal nature and efficacy. This demonstrated that the holistic mechanisms of the properties of Chinese herbs adhere to the findings, which may be beneficial for the development and compatibility of Chinese herbal medicines. PMID:21749831

Xiao, Bin; Tao, Ou; Luo, Ji; Wang, Yun

2011-07-01

251

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1993-12-31

252

Some properties of galaxy structures  

CERN Document Server

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

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

2011-01-01

253

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

Scientific Electronic Library Online (English)

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

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

254

Structure-charge transport relationship of 5,15-dialkylated porphyrins.  

Science.gov (United States)

5,15-Dialkyl-substituted porphyrins that are symmetrically capped with ethyl (C(2)-Por), butyl (C(4)-Por) and hexyl (C(6)-Por) were synthesized and characterized. Molecular structure versus physical property relationship has been established through the analysis of planar charge transport using thin film transistor (TFT) structure. PMID:22517491

Zhou, Li; Xu, Zong-Xiang; Zhou, Ye; Feng, Yan; Zhou, Xiang-Ge; Xiang, Hai-Feng; Roy, V A L

2012-05-25

255

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

Science.gov (United States)

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

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

2002-02-14

256

Structure activity relationships of novel antiepileptic drugs.  

Science.gov (United States)

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

Mittapalli, G K; Roberts, E

2014-01-01

257

Structural properties of zirconia nanoparticles  

Science.gov (United States)

Raman spectroscopy, X-ray diffraction and high resolution electron microscopy were used to investigate the structural properties of calcined ZrO2 nano powders having various sizes. For grain size of the order of a few nanometers, the Raman spectra and X-ray diffractograms are typical of an amorphous material. As the calcination temperature increases, the sizes of the grain increase and the corresponding spectra progressively evolve towards that of a crystallized sample. The coexistence of the different phases amorphous, monoclinic and metastable tetragonal is evidenced in a range of temperature lying approximately between 300°C and 600°C. Low frequency features are observed in the Raman spectra. Those bands correspond to the confined acoustical phonon and their frequencies are directly related to the size of the particles. Theoretically computed frequencies of the confined acoustical modes of a sphere agree reasonably with those determined experimentally by Raman spectroscopy.

Haro-Poniatowski, Emmanuel; Fuentes, Gustavo; Torres, Enelio; Hernandez-Tellez, Eva; Jouanne, Michel; Morhange, Jean-Francois; Kanehisa, Makoto

2001-03-01

258

Amphiphilic transdermal permeation enhancers: structure-activity relationships.  

Science.gov (United States)

Transdermal drug delivery offers numerous advantages over conventional routes of administration; however, poor permeation of most drugs across the skin barrier constitutes a serious limitation of this methodology. One of the approaches used to enlarge the number of transdermally-applicable drugs uses permeation enhancers. These compounds promote drug permeation through the skin by a reversible decrease of the barrier resistance. Enhancers can act on the stratum corneum intracellular keratin, influence desmosomes, modify the intercellular lipid domains or alter the solvent nature of the stratum corneum. Even though, hundreds of substances have been identified as permeation enhancers to date, yet our understanding of the structure-activity relationships is limited. In general, enhancers can be divided into two large groups: small polar solvents, e.g. ethanol, propylene glycol, dimethylsulfoxide and amphiphilic compounds containing a polar head and a hydrophobic chain, e.g. fatty acids and alcohols, 1-dodecylazepan-2-one (Azone), 2-nonyl-1,3-dioxolane (SEPA 009), and dodecyl-2-dimethylaminopropanoate (DDAIP). In this review we have focused on structure-activity relationships of amphiphilic permeation enhancers, including the properties of the hydrophobic chains, e.g. length, unsaturation, and branching, as well as the polar heads characteristics, e.g. hydrogen bonding ability, lipophilicity, and size. We present over 180 examples of enhancers with different polar head to illustrate the structural requirements and the possible role of the polar head. We have given an overview of the methods used for investigation of the mechanisms of permeation enhancement, namely differential scanning calorimetry (DSC), infrared (IR) and Raman spectroscopy, X-ray diffraction and future perspectives in this field. Furthermore, biodegradability and chirality of the enhancers are discussed. PMID:16178785

Vávrová, K; Zbytovská, J; Hrabálek, A

2005-01-01

259

Asymptotic Properties of Parameters for Linear Circular Functional Relationship Model  

Directory of Open Access Journals (Sweden)

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

A.G. Hussin

2008-01-01

260

Structure and properties of cell membranes. Volume 3: Methodology and properties of membranes  

International Nuclear Information System (INIS)

This book covers the topics: Quantum chemical approach to study the mechanisms of proton translocation across membranes through protein molecules; monomolecular films as biomembrane models; planar lipid bilayers in relation to biomembranes; relation of liposomes to cell membranes; reconstitution of membrane transport systems; structure-function relationships in cell membranes as revealed by X-ray techniques; structure-function relationships in cell membranes as revealed by spin labeling ESR; structure and dynamics of cell membranes as revealed by NMR techniques; the effect of dietary lipids on the composition and properties of biological membranes and index

 
 
 
 
261

Structure-activity relationship of cyanine tau aggregation inhibitors.  

Science.gov (United States)

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

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

2009-06-11

262

Sequence–structure relationships in yeast mRNAs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

It is generally accepted that functionally important RNA structure is more conserved than sequence due to compensatory mutations that may alter the sequence without disrupting the structure. For small RNA molecules sequence–structure relationships are relatively well understood. However, structural bioinformatics of mRNAs is still in its infancy due to a virtual absence of experimental data. This report presents the first quantitative assessment of sequence–structure divergence in the cod...

Chursov, Andrey; Walter, Mathias C.; Schmidt, Thorsten; Mironov, Andrei; Shneider, Alexander; Frishman, Dmitrij

2012-01-01

263

Preparation, structure and dielectric property of barium stannate titanate ceramics  

International Nuclear Information System (INIS)

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

264

Glucoamylase : structure/function relationships, and protein engineering  

DEFF Research Database (Denmark)

Glucoamylases are inverting exo-acting starch hydrolases releasing beta-glucose from the non-reducing ends of starch and related substrates. The majority of glucoamylases are multidomain enzymes consisting of a catalytic domain connected to a starch-binding domain by an O-glycosylated linker region. Three-dimensional structures have been determined of free and inhibitor complexed glucoamylases from Aspergillus awamori var. X100, Aspergillus niger, and Saccharomycopsis fibuligera. The catalytic domain folds as a twisted (alpha/alpha)(6)-barrel with a central funnel-shaped active site, while the starch-binding domain folds as an antiparallel beta-barrel and has two binding sites for starch or beta-cyclodextrin. Certain glucoamylases are widely applied industrially in the manufacture of glucose and fructose syrups. For more than a decade mutational investigations of glucoamylase have addressed fundamental structure/function relationships in the binding and catalytic mechanisms. In parallel, issues of relevance for application have been pursued using protein engineering to improve the industrial properties. The present review focuses on recent findings on the catalytic site, mechanism of action, substrate recognition, the linker region, the multidomain architecture, the engineering of specificity and stability, and roles of individual substrate binding subsites.

Sauer, J.; Sigurskjold, B. W.

2000-01-01

265

A structurally-based model of irradiated graphite properties  

International Nuclear Information System (INIS)

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

266

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

Science.gov (United States)

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

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

2013-11-14

267

Surface magnetic properties of ferromagnetic nickel thin films and multilayer structures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Xu, Tianhong

2008-01-01

268

Structural Property Analysis of Petri Net  

Directory of Open Access Journals (Sweden)

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

Chuanliang Xia

2012-01-01

269

A relationship between chemical structure and the critical temperature  

Science.gov (United States)

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

Fedors, R. F.

1982-01-01

270

A genetic algorithm for structure-activity relationships: software implementation  

CERN Document Server

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

Jantschi, Lorentz

2009-01-01

271

Structure- and dose-absorption relationships of coffee polyphenols.  

Science.gov (United States)

Chlorogenic acids (CGAs) from coffee have biological effects related to human health. Thus, specific data on their bioavailability in the upper gastrointestinal tract are of high interest, since some molecules are absorbed here and so are not metabolized by colonic microflora. Up to now, no data on structure-absorption relationships for CGAs have been published, despite this being the most consumed group of polyphenols in the western diet. To address this gap, we performed ex vivo absorption experiments with pig jejunal mucosa using the Ussing chamber model (a model simulating the mucosa and its luminal/apical side). The main coffee polyphenols, caffeoylquinic acid (CQA), feruloylquinic acid (FQA), caffeic acid (CA), dicaffeoylquinic acid (diCQA), and D-(-)-quinic acid (QA), were incubated in individual experiments equivalent to gut lumen physiologically achievable concentrations (0.2-3.5 mM). Identification and quantification were performed with HPLC-diode array detection and HPLC-MS/MS. Additionally, the presence of ABC-efflux transporters was determined by Western blot analysis. The percentages of initially applied CGAs that were absorbed through the jejunal pig mucosa were, in increasing order: diCQA, trace; CQA, ? 1%; CA, ? 1.5%; FQA, ? 2%; and QA, ? 4%. No differences were observed within the CGA subgroups. Dose-absorption experiments with 5-CQA suggested a passive diffusion (nonsaturable absorption and a linear dose-flux relationship) and its secretion was affected by NaN3 , indicating an active efflux. The ABC-efflux transporters MDR 1 and MRP 2 were identified in pig jejunal mucosa for the first time. We conclude that active efflux plays a significant role in CGA bioavailability and, further, that the mechanism of CGA absorption in the jejunum is governed by their physicochemical properties. PMID:23553742

Erk, Thomas; Hauser, Johanna; Williamson, Gary; Renouf, Mathieu; Steiling, Heike; Dionisi, Fabiola; Richling, Elke

2014-01-01

272

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

Directory of Open Access Journals (Sweden)

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

Ajayi M. T. A.

2014-07-01

273

Microstructural-electrical property relationships in high-conductivity zirconias  

International Nuclear Information System (INIS)

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

274

Membrane lipid polymorphism: relationship to bilayer properties and protein function.  

Science.gov (United States)

Bilayers are the most familiar arrangement of phospholipids. However, even as bilayers, phospholipids can arrange themselves in a variety of morphologies from essentially flat structures found in large liposomes or when adhered to a flat solid support, to the curved structures found in small liposomes or as bicontinuous cubic phases. Phospholipids can also arrange themselves as curved monolayers, such as in the hexagonal phase, and they can even form spherical or ellipsoid-shaped micelles. A number of factors will determine the final morphology of a lipid aggregate including the structure of the lipid, the nature of the lipid headgroup and its degree of hydration, and the temperature. In addition to being interesting in its own right, the property of lipid polymorphism can be applied to understand how fundamental intrinsic curvature properties of a membrane alter the physical properties of a membrane bilayer. This, in turn, will affect the functional characteristics of membrane proteins, with several possible mechanisms explaining the coupling of membrane properties with protein function. PMID:17951724

Epand, Richard M

2007-01-01

275

Cellulose Nanofibril Networks and Composites : Preparation, Structure and Properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Henriksson, Marielle

2008-01-01

276

Structure and properties of commercial titanium alloys  

International Nuclear Information System (INIS)

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

277

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

Science.gov (United States)

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

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

2014-03-15

278

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

International Nuclear Information System (INIS)

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

279

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-05-15

280

Structure-Biodegradation Relationship Study of Commercial Linear Alkylbenzene Sulfonates  

Directory of Open Access Journals (Sweden)

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

Li Li

2003-06-01

 
 
 
 
281

Interfacial structure, properties and design  

International Nuclear Information System (INIS)

These proceedings are organized in the order of presentation at the meeting, starting with the recent advances in structural characterization and analysis of internal interface and interphase boundaries. While the crystallographic theory of interfacial line defects had been established rigorously, its general applicability to mixed tilt and twist boundaries was questioned. The insights obtained from theoretical and experimental analyses of elasticity and localized deformation at interfaces relate directly to the intrinsic cohesive strength and intergranular fracture. Effects of processing on the grain boundary structure and chemistry of high Tc ceramic superconductors and the resulting changes in critical currents were established experimentally. A significant advancement was reported in processing and crystal growth techniques, which include the UHV diffusion bonding and MBE techniques for the controlled production of homo- and heterophase interfaces

282

A genetic algorithm for structure-activity relationships: software implementation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The design and the implementation of a genetic algorithm are described. The applicability domain is on structure-activity relationships expressed as multiple linear regressions and predictor variables are from families of structure-based molecular descriptors. An experiment to compare different selection and survival strategies was designed and realized. The genetic algorithm was run using the designed experiment on a set of 206 polychlorinated biphenyls searching on structu...

Jantschi, Lorentz

2009-01-01

283

Quantitative structure-activity relationship studies on nitrofuranyl antitubercular agents  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A series of nitrofuranylamide and related aromatic compounds displaying potent activity against M. tuberculosis has been investigated utilizing 3-Dimensional Quantitative Structure-Activity Relationship (3D-QSAR) techniques. Comparative Molecular Field Analysis (CoMFA) and Comparative Molecular Similarity Indices Analysis (CoMSIA) methods were used to produce 3D-QSAR models that correlated the Minimum Inhibitory Concentration (MIC) values against M. tuberculosis with the molecular structures ...

Hevener, Kirk E.; Ball, David M.; Buolamwini, John K.; Lee, Richard E.

2008-01-01

284

Structure and functional properties of colloidal systems  

CERN Document Server

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

Hidalgo-Alvarez, Roque

2009-01-01

285

Bacterial endotoxin: molecular relationships between structure and activity.  

Science.gov (United States)

The significance of endotoxins in bacterial infection and their role as bacterial surface antigens (O antigens) have stimulated investigations into their chemical nature and the mechanisms of their biologic action during the last few decades. This article summarizes some of the recent results and emphasizes structure-activity relationships. PMID:1723739

Rietschel, E T; Seydel, U; Zähringer, U; Schade, U F; Brade, L; Loppnow, H; Feist, W; Wang, M H; Ulmer, A J; Flad, H D

1991-12-01

286

Structure and Properties of Compressed Borate Glasses  

DEFF Research Database (Denmark)

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

Smedskjær, Morten Mattrup; Bauer, U.

287

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

International Nuclear Information System (INIS)

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

288

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

International Nuclear Information System (INIS)

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

289

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

Energy Technology Data Exchange (ETDEWEB)

The influence of alternating (ac) and direct current (dc) fields on the structural and dielectric properties of [001]{sub PC} textured Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}-7%BaTiO{sub 3} (NBT-7%BT) ceramics has been investigated. X-ray diffraction measurements revealed that the depolarization at temperature T{sub d} in poled samples resulted from a tetragonal {yields} pseudo-cubic transition on heating. Moderate ac drive and dc bias had opposite influences on T{sub d}: ac drive decreased the T{sub d}, whereas dc bias increased it. These investigations suggested an effective method to expand the working temperature range of NBT-x%BT textured ceramics to a high temperature.

Ge, Wenwei; Li, Jiefang; Viehland, D. [Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061 (United States); Maurya, Deepam; Priya, Shashank [Center for Energy Harvesting Materials and Systems (CEHMS), Bio-Inspired Materials and Devices Laboratory (BMDL), Virginia Tech, Blacksburg, Virginia 24061 (United States)

2013-06-03

290

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

International Nuclear Information System (INIS)

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

291

Mechanical properties relationships in V- and Ti-microalloyed steels  

Energy Technology Data Exchange (ETDEWEB)

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

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

2002-09-01

292

The textual idea and its relationship to discourse structure  

Directory of Open Access Journals (Sweden)

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

Cosmin D?nut BOC?NIAL?

2000-12-01

293

Molecular Structures and Functional Relationships in Clostridial Neurotoxins  

Energy Technology Data Exchange (ETDEWEB)

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

Swaminathan S.

2011-12-01

294

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

International Nuclear Information System (INIS)

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

295

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

International Nuclear Information System (INIS)

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

296

Data base on structural materials aging properties  

International Nuclear Information System (INIS)

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

297

Data base on structural materials aging properties  

Energy Technology Data Exchange (ETDEWEB)

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

Oland, C.B.

1992-03-01

298

Relationships between structures and performance of SOFC anodes  

DEFF Research Database (Denmark)

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

KlemensØ, Trine; Mogensen, Mogens Bjerg

2006-01-01

299

Structure and properties of small sodium clusters  

DEFF Research Database (Denmark)

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

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

2002-01-01

300

Examination of the Relationship Between Plot Scale Soil Properties and Catchment Scale Streamflow Recession Properties  

Science.gov (United States)

This work explores the empirical relationship between streamflow recession data from USGS stream gauges and high-resolution SSURGO soil data. The exploration of connections between streamflow recession and soil properties tests the general hypothesis that a relationship exists between plot scale soils data integrated across a catchment and catchment scale streamflow recession parameters. A dataset has been assembled using USGS HCDN watersheds for which SSURGO data is available across the continental United States. Tague and Grant (2004) have shown a linear relationship between streamflow recession parameters and a geologic classification based on the age of the underlying volcanic bedrock for Cascade streams in Oregon. Using a similar approach at a national scale, the research presented is aimed at improving the understanding of streamflow generation processes in different watersheds as well as the implications of using a priori parameters developed with high resolution soil data for distributed hydrologic modeling and prediction in ungauged basins. Watershed specific results elucidate the dominant factors controlling the hydrologic response in the different watersheds, such as geology (as a function of soil properties), slope/elevation, and soil properties identify landscape types. Overall results show that there is clustering of streamflow recession parameters based on regional climate and topography. References [1] Tague, C. and G.E. Grant, (2004), A Geological Framework for Interpreting the Low-Flow Regimes of Cascade Streams, Willamette River Basin, Oregon, Water Resources Research, 40(4)

Bandaragoda, C.; Tarboton, D.

2006-05-01

 
 
 
 
301

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2013-01-01

302

Quantitative Structure-Activity Relationships on Lipoxygenase Inhibitors  

Directory of Open Access Journals (Sweden)

Full Text Available The control of leukotrienes biosynthesis through the inhibition of the enzyme 5-lipoxygenase represents a potential new method of treating several diseases. Several quinonoid derivatives inhibiting 5-lipoxygenase were collected from the literature. For them a quantitative structure-activity relationship study was performed in order to provide a simple description of the physicochemical parameters which are involved in the lipoxygenasequinones site of action. The analysis was done by using the C-QSAR suite of programs (Biobyte. The evaluation of the quantitative structure-activity relationships (QSAR revealed that the primary physicochemical feature influencing the in vitro LOX inhibitory potencies of these compounds is the hydrophobicity of the molecule. A significant correlation was observed between the CMR of the studied molecules and the in vitro inhibitory activity. The QSAR study also demonstrated that the inhibitory activity is lowered by the presence of a carboxylic or a phenyl group.

Dimitra Hadjipavlou-Litina

2002-03-01

303

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

Directory of Open Access Journals (Sweden)

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

S.SeshaPhani

2013-01-01

304

Relationships between molecular properties and antimycobacterial activities of steroids.  

Science.gov (United States)

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

Rugutt, Joseph K; Rugutt, Kipngeno J

2002-04-01

305

Correlated structure-optical properties studies of plasmonic nanoparticles  

Science.gov (United States)

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

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

2014-06-01

306

Relationship between molecular cloud structure and density PDFs  

CERN Document Server

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

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

2013-01-01

307

Structural relationships in complex hydrides of the late transition metals  

International Nuclear Information System (INIS)

Literature data on complex hydrides of the late transition metals (groups 7-10), such as the hydrogen storage material Mg2NiH4, are reviewed with respect to order-disorder phase transitions and structural relationships. They are analysed in terms of crystallographic group-subgroup trees and their use in understanding the different crystal structures from a symmetry point of view is demonstrated. New data are presented on the low temperature behaviour of magnesium iridium hydrides and strontium rhodium hydrides studied by powder X-ray diffraction. (orig.)

308

Structural relationships in complex hydrides of the late transition metals  

Energy Technology Data Exchange (ETDEWEB)

Literature data on complex hydrides of the late transition metals (groups 7-10), such as the hydrogen storage material Mg{sub 2}NiH{sub 4}, are reviewed with respect to order-disorder phase transitions and structural relationships. They are analysed in terms of crystallographic group-subgroup trees and their use in understanding the different crystal structures from a symmetry point of view is demonstrated. New data are presented on the low temperature behaviour of magnesium iridium hydrides and strontium rhodium hydrides studied by powder X-ray diffraction. (orig.)

Kohlmann, Holger [Anorganische und Analytische Chemie und Radiochemie, Univ. des Saarlandes, Saarbruecken (Germany)

2009-07-01

309

Structure, chemistry, and properties of mineral nanoparticles  

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-12-02

310

Properties and structure of different rank anthracites  

Energy Technology Data Exchange (ETDEWEB)

The properties and structure of anthracitic coals through to meta-anthracites were examined using a variety of analytical methods. With increasing rank, the following increased as well: moisture content, carbon content, vitrinite reflectance, reflectance anisotropy, micro-hardness, real and apparent density, whereas volatile matter content, hydrogen content and calorific value decreased. Increasing rank effected an increase of the spatial ordering of organic matter of the anthracites, decrease of the interlayer distance, and increase in the crystallite dimensions. Also, the number of condensed aromatic rings in the basic structural unit of the anthracites, index of condensation and aromatization and total surface are and pore volume increased. The differences in the properties and structures of the anthracitic coals and meta-anthracites are described. 72 refs., 10 figs., 1 tab.

Bratek, K.; Bratek, W.; Gerus-Piasecka, I.; Jasienko, S.; Wilk, P. [Wroclaw University of Technology, Wroclaw (Poland). Inst. of Chemistry and Technology of Petroleum and Coal

2002-01-01

311

Structural and Magnetic Properties of Trigonal Iron  

CERN Document Server

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

Fox, S

1995-01-01

312

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

Science.gov (United States)

The potential (eco)toxicological hazard posed by engineered nanoparticles is a major scientific and societal concern since several industrial sectors (e.g. electronics, biomedicine, and cosmetics) are exploiting the innovative properties of nanostructures resulting in their large-scale production. Many consumer products contain nanomaterials and, given their complex life-cycle, it is essential to anticipate their (eco)toxicological properties in a fast and inexpensive way in order to mitigate adverse effects on human health and the environment. In this context, the application of the structure-toxicity paradigm to nanomaterials represents a promising approach. Indeed, according to this paradigm, it is possible to predict toxicological effects induced by chemicals on the basis of their structural similarity with chemicals for which toxicological endpoints have been previously measured. These structure-toxicity relationships can be quantitative or qualitative in nature and they can predict toxicological effects directly from the physicochemical properties of the entities (e.g. nanoparticles) of interest. Therefore, this approach can aid in prioritizing resources in toxicological investigations while reducing the ethical and monetary costs that are related to animal testing. The purpose of this review is to provide a summary of recent key advances in the field of QSAR modelling of nanomaterial toxicity, to identify the major gaps in research required to accelerate the use of quantitative structure-activity relationship (QSAR) methods, and to provide a roadmap for future research needed to achieve QSAR models useful for regulatory purposes. PMID:23165187

Winkler, David A; Mombelli, Enrico; Pietroiusti, Antonio; Tran, Lang; Worth, Andrew; Fadeel, Bengt; McCall, Maxine J

2013-11-01

313

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

Scientific Electronic Library Online (English)

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

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

314

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

International Nuclear Information System (INIS)

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

315

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

Directory of Open Access Journals (Sweden)

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

SERGIO MELLA M

2001-01-01

316

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

International Nuclear Information System (INIS)

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

317

Nucleon structure and properties of dense matter  

International Nuclear Information System (INIS)

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

318

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

Directory of Open Access Journals (Sweden)

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

Haji A.

2013-09-01

319

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

Science.gov (United States)

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

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

2006-12-01

320

The Relationship between Financial Flexibility and Capital Structure Decisions  

Directory of Open Access Journals (Sweden)

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

Shanaz Forozan

2013-04-01

 
 
 
 
321

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

Science.gov (United States)

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

Kantar, Ersin; Keskin, Mustafa

2013-11-01

322

The structural acoustic properties of stiffened shells  

DEFF Research Database (Denmark)

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

Luan, Yu

2008-01-01

323

Structural properties of dense hard sphere packings.  

Science.gov (United States)

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

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

2014-09-11

324

Structural and tunneling properties of Si nanowires  

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

Montes, E.

2013-12-06

325

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

Scientific Electronic Library Online (English)

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

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

326

Relationship between antimold activity and molecular structure of cinnamaldehyde analogues.  

Science.gov (United States)

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

Zhang, Yuanyuan; Li, Shujun; Kong, Xianchao

2013-03-01

327

Structure-antioxidant relationship of flavonoids from fermented rooibos.  

Science.gov (United States)

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

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

2009-05-01

328

Universal properties and structure of halo nuclei  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The universal properties and structure of halo nuclei composed of two neutrons (2n) and a core are investigated within an effective quantum mechanics framework. We construct an effective interaction potential that exploits the separation of scales in halo nuclei and treat the nucleus as an effective three-body system. The uncertainty from higher orders in the expansion is quantified through theoretical error bands. First, we investigate the possibility to observe excited Efi...

Canham, David L.; Hammer, H. -w

2008-01-01

329

Structure and properties of composite polyolefin materials  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Pryadilova, Olga

2006-01-01

330

Structure and Electronic Properties of Polycrystalline Dielectrics  

Energy Technology Data Exchange (ETDEWEB)

We present an overview of the theoretical approaches that can be employed to model polycrystalline oxides along with a discussion of their limitations and associated challenges. We then present results for two metal oxide materials, MgO and HfO2, where theory and experiment have come together to provide insight into the structure and electronic properties of grain boundaries. Finally, we conclude with a discussion and outlook.

Mckenna, Keith P.; Shluger, AL

2013-07-07

331

Electrochemically Deposited Nickel Membranes; Process-Microstructure-Property Relationships  

DEFF Research Database (Denmark)

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

Jensen, Jens Dahl; Pantleon, Karen

2003-01-01

332

Property Relationship in Organosilanes and Nanotubes Filled Polypropylene Hybrid Composites  

Directory of Open Access Journals (Sweden)

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

Alejandra J. Monsiváis-Barrón

2014-10-01

333

36 CFR 1210.37 - Property trust relationship.  

Science.gov (United States)

...1210.37 Parks, Forests, and Public Property NATIONAL ARCHIVES AND RECORDS ADMINISTRATION GENERAL RULES UNIFORM ADMINISTRATIVE...liens or other appropriate notices of record to indicate that personal or real property has been acquired or improved with...

2010-07-01

334

Structure and magnetic properties of powder HITPERM material  

Directory of Open Access Journals (Sweden)

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

J.E. Fr?ckowiak

2007-03-01

335

Numerical calculations of effective elastic properties of two cellular structures  

CERN Document Server

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

Tuncer, E

2004-01-01

336

Electronic and structural properties of functional nanostructures  

Science.gov (United States)

In this Thesis, I present a study of electronic and structural properties of functional nanostructures such as MoSxIy nanowires, self-assembled monolayer on top of metallic surfaces and structural changes induced in graphite by photo excitations. MoSxI y nanowires, which can be easily synthesized in one step, show many advantages over conventional carbon nanotubes in molecular electronics and many other applications. But how to self-assemble them into desired pattern for practical electronic network? Self-assembled monolayers of polymers on metallic surfaces may help to guide pattern formation of some nanomaterials such as MoSxIy nanowires. I have investigated the physical properties of these nanoscale wires and microscopic self-assembly mechanisms of patterns by total energy calculations combined with molecular dynamics simulations and structure optimization. First, I studied the stability of novel Molybdenum chaicohalide nanowires, a candidate for molecular electronics applications. Next, I investigated the self-assembly of nanoparticles into ordered arrays with the aid of a template. Such templates, I showed, can be formed by polymer adsorption on surfaces such as highly ordered pyrolytic graphite and Ag(111). Finally, I studied the physical origin of of structural changes induced in graphite by light in form of a femtosecond laser pulse.

Yang, Teng

337

Relationships between milk coagulation property traits analyzed with different methodologies.  

Science.gov (United States)

Milk coagulation properties (MCP) analysis is performed using a wide range of methodologies in different countries and laboratories, using different instruments, coagulant activity in the milk, and type of coagulant. This makes it difficult to compare results and data from different research. The aims of this study were to propose a method for the transformation of values of rennet coagulation time (RCT) and curd firmness (a(30)) and to predict the noncoagulation (NC) probability of milk samples analyzed using different methodologies. Individual milk samples were collected during the morning milking in October 2010 from each of 165 Holstein-Friesian dairy cows in 2 freestall barns in Italy, and sent to 3 laboratories for MCP analysis. For each laboratory, MCP analysis was performed using a different methodology: A, with a computerized renneting meter instrument using 0.051 international milk clotting units (IMCU)/mL of coagulant activity; B, with a Lattodinamografo (Foss-Italia, Padova, Italy) using 0.051 IMCU/mL of coagulant activity; and C, with an Optigraph (Ysebaert, Frépillon, France) using 0.120 IMCU/mL of coagulant activity. The relationships between MCP traits were analyzed with correlation and regression analyses for each pair of methodologies. For each MCP trait, 2 regression models were applied: model 1 was a single regression model, where the dependent and independent variables were the same MCP trait determined by 2 different methodologies; in model 2, both a(30) and RCT were included as independent variables. The NC probabilities for laboratories with the highest number of NC samples were predicted based on the RCT and a(30) values measured in the laboratories with lower number of NC samples using logistic regression and receiver operating characteristic analysis. The percentages of NC samples were 4.2, 11.5, and 0.6% for A, B, and C, respectively. The transformation of MCP traits was more precise with model 1 for RCT (R(2): 0.77-0.82) than for a(30) (R(2): 0.28-0.63). The application of model 2 was needed when the C measurements were transformed into the other scales. The analyses of NC probabilities of milk samples showed that NC samples from one methodology were well distinguishable (with an accuracy of 0.972-0.996) based on the rennet coagulation time measured with the other methodology. A standard definition for MCP traits analysis is needed to enable reliable comparisons between MCP traits recorded in different laboratories and in different animal populations and breeds. PMID:21854906

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

2011-09-01

338

Quantitative-Structure Activity Relationships on Thromboxane Receptor Antagonists  

Directory of Open Access Journals (Sweden)

Full Text Available TXA2 is an unstable metabolite of arachidonic acid and a potent inducer of platelet aggregation, vasoconstriction and bronchoconstriction. TXA2 receptor antagonists are effective for the treatment of circulatory disorders, angina and stroke. Some heptenoic acids synthesized as novel TXA2 receptor antagonists were collected from the literature. For them, quantitative structure-activity relationships study were determined in order to provide a simple description of the physicochemical parameters which are involved in the (±-(5Z-7-[3-endo-[(phenylsulfonylamino]bicyclo[2.2.1]hept-2-exo-yl]heptenoic acids TXA2 receptor site of action. The analysis was done by using the C-QSAR suite of programs (Biobyte. The evaluation of the quantitative structure-activity relationships (QSAR revealed that the primary physicochemical feature influencing the in vitro TXA2 receptor antagonists is the overall molar refractivity (CMR of the molecule. The Swain-Lupton factor F was found to be also significant. A significant parabolic correlation was observed between the CMR of the studied compounds and the in vitro inhibition of the aggregation of washed platelets. The QSAR study also demonstrated that the inhibitory activity is affected by the Sterimol minimum width B1.

Dimitra Hadjipavlou-Litina

2002-06-01

339

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

Directory of Open Access Journals (Sweden)

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

???

2012-06-01

340

Short range ordering and microstructure property relationship in amorphous alloys  

Energy Technology Data Exchange (ETDEWEB)

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

Shariq, A.

2006-07-01

 
 
 
 
341

Activity profile relationships between structurally similar promiscuous compounds.  

Science.gov (United States)

Compound promiscuity results from specific interactions of a small molecule with multiple biological targets and is an emerging concept in medicinal chemistry and drug discovery as it provides the basis for polypharmacology. Recent studies have assessed the degree of promiscuity among drugs and bioactive compounds. On the basis of currently available data, many drugs and bioactive compounds have been found to interact with more than one target. Herein, we further extend the study of promiscuity by focusing on structurally similar promiscuous compounds, comparing their activity profiles, and determining multi-target activity patterns. The analysis revealed that most structurally similar promiscuous compounds have identical or similar activity profiles but also detected different types of structure-activity pattern relationships. In addition, the propensity of activity cliff formation among promiscuous compounds was determined. Activity cliffs were formed at a high rate among promiscuous compounds indicating that many structurally similar promiscuous compounds have greatly varying activity against one or more targets they share. Taken together, these findings show that compound promiscuity and target selectivity are not mutually exclusive and further refine current views of promiscuity. PMID:24077530

Hu, Ye; Bajorath, Jürgen

2013-11-01

342

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

International Nuclear Information System (INIS)

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

343

Optical and structural properties of nanobiomaterials.  

Science.gov (United States)

In this review, the optical and structural properties of biomaterials are discussed. First, we demonstrate the optical and structural properties of natural and plasma-treated DNA, using UV-visible absorption, circular dichroism (CD), and Raman spectroscopy. Fluorescence and lasing action in the dye-doped DNA-surfactant complex are also explained. Additionally, nanomaterial-based DNA detection and DNA-templated nanomaterial growth are described. Next, we discuss protein folding studies utilizing fluorescence, CD, and nuclear magnetic resonance (NMR) spectroscopy. From the CD spectra of alpha-chymotrypsin (CT), we estimate the composition of a-helices and the beta-sheets, and random coils in the CT. 1H NMR spectroscopy is used to investigate the thermal effect on the refolding of CT in the presence of an ionic liquid. Finally, we explain the numerical simulation method used for studying the optical properties of biomaterials. Applications of the Monte-Carlo method in photodynamic therapy, skin tissue optics, and bioimaging are described. PMID:24730261

Lee, Geon Joon; Attri, Pankaj; Choi, Eun Ha; Kwon, Young-Wan; Krasnikov, Ilya; Seteikin, Alexey

2014-01-01

344

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

International Nuclear Information System (INIS)

The phase relationships and the superconducting properties of Nb3Sn are compared with those of other high Tsub(c) compounds crystallizing in the A15 structure: Nb3Al, Nb3Ga, Nb3Ge, V3Si, V3Ga ... Characteristic differences of these systems, i.e., the shape of the A15 phase field, the variation of Tsub(c) with composition or with atomic ordering, are discussed. Recent methods leading to the accurate determination of the phase relationships in these systems up to 2000 0C are reviewed. The discussion is extended to the low temperature relationships in Nb3Sn and V3Si with the corresponding tetragonal modifications. Methods for observing these low temperature details and recent results about their influence on Tsub(c) are presented. In the case of Nb3Sn, the factors influencing the formation of the low temperature tetragonal phase, such as hydrostatic pressure, precompression in multifilamentary wires, or hydrogen loading, are discussed. (orig.)

345

Structural evolution and electronic properties of n-type doped hydrogenated amorphous silicon thin films  

Science.gov (United States)

The relationship between structure and electronic properties of n-type doped hydrogenated amorphous silicon (a-Si:H) thin films was investigated. Samples with different features were prepared by plasma enhanced chemical vapor deposition (PECVD) at various substrate temperatures. Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy were used to evaluate the structural evolution, meanwhile, electronic-spin resonance (ESR) and optical measurement were applied to explore the electronic properties of P-doped a-Si:H thin films. Results reveal that the changes in materials structure affect directly the electronic properties and the doping efficiency of dopant.

He, Jian; Li, Wei; Xu, Rui; Qi, Kang-Cheng; Jiang, Ya-Dong

2011-12-01

346

Colloidal Platinum Nanoparticles: Synthesis, Structure and Properties.  

Science.gov (United States)

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

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

2006-03-01

347

Structural and magnetic properties in bidimensional manganites  

Science.gov (United States)

The Lny-xCa2-xMnO4 series, with a K2NiF4 structure, has been studied by neutron powder diffraction and electron microscopy in connection with the magnetic and transport properties. We report here the results of the structural and magnetic study of two compounds, Pr0.25Ca1.75MnO4 and Ho0.08Ca1.92MnO4, for which the Mn valency is 3.75 and 3.92 respectively and consequently that show different magnetic and transport behaviours. At room temperature (RT), the average structure of both compounds is orthorhombic with lattice parameters ap? , 12Å, ap? , and Cmca space group. With decreasing temperature, the Ho0.08Ca1.92MnO4 compound exhibits two magnetic phase transitions: antiferromagnetism appears at TN 165K and ferromagnetism at TC 75K. The two phases coexist below TC without any structural transition. The Pr0.25Ca1.75MnO4 compound exhibits charge ordering below TCO 275K, characterised by superlattice reflections clearly evidenced by electron diffraction. Neutron diffraction pattern refinements show a partial structural transition from Cmca (RT) to C2/c (low temperature) around the charge-ordering temperature and antiferromagnetism below TN 150K.

Autret, C.; André, G.; Bourée, F.; Martin, C.; Hervieu, M.; Maignan, A.; Retoux, R.; Raveau, B.

348

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

Science.gov (United States)

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

Feddern Donbaek, Dagmar; Elklit, Ask

2014-01-01

349

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

DEFF Research Database (Denmark)

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

Elklit, Ask; Feddern, Dagmar

2014-01-01

350

Structure and properties of lanthanide halides  

Science.gov (United States)

Lanthanum and cerium bromides and chlorides form isomorphous alloy systems with the UCl 3 type structure. These scintillating alloys exhibit high luminosity and proportional response, making them the first scintillators comparable to room temperature semiconductors for gamma spectroscopy; Ce(III) activated lanthanum bromide has recently enabled scintillating gamma ray spectrometers with < 3% FWHM energy resolutions at 662 keV. However brittle fracture of these materials impedes development of large volume crystals. Low fracture stress and perfect cleavage along prismatic planes cause material cracking during and after crystal growth. These and other properties pose challenges for material production and post processing; therefore, understanding mechanical behavior is key to fabricating large single crystals, and engineering of robust detectors and systems. Recent progress on basic structure and properties of the lanthanide halides is reported here, including thermomechanical and thermogravimetric analyses, hygroscopicity, yield strength, and fracture toughness. Observations including reversible hydrate formation under atmospheric pressure, loss of stoichiometry at high temperature, anisotropic thermal expansion, reactivity towards common crucible materials, and crack initiation and propagation under applied loads are reported. The fundamental physical and chemical properties of this system introduce challenges for material processing, scale-up, and detector fabrication. Analysis of the symmetry and crystal structure of this system suggests possible mechanisms for deformation and crack initiation under stress. The low c/a ratio and low symmetry relative to traditional scintillators indicate limited and highly anisotropic plasticity cause redistribution of residual process stress to cleavage planes, initiating fracture. This proposed failure mechanism and its implications for scale up to large diameter crystal growth are also discussed.

Doty, F. P.; McGregor, Douglas; Harrison, Mark; Findley, Kip; Polichar, Raulf

2007-09-01

351

Properties of metaphosphate depending on anion structure  

International Nuclear Information System (INIS)

A possibility of forecasting metaphosphate anion composition based on the analysis of data on crystal structure, physical and chemical properties of metaphosphates using computers is revealed. Frequencies of antisymmetric valent vibrations of different PO groups are most informatiVe signs depen-- dent on anion composition. There exist two non-overlapping regions of phosphate groupping in the plane [#betta#sub(as)pop-#betta#sub(as)po] for cyclophosphates with the number of phosphorus atoms in the cycle n=3 and 4 and long-chain phosphates. Data for 51 metaphosphates as well as for REE metaphosphates are given for illustration

352

Electronic band structure and properties of ?-U  

International Nuclear Information System (INIS)

We present some results of a detailed study of the electronic band structure and some physical properties of orthorhombic uranium using a relativistic version of the LAPW method. Total and projected (by orbital angular momentum) densities of states are used to discuss the photo-emission data of Veal and Lam. The Fermi surfaces of the dominant 6th and 7th bands are found to have high symmetry (and some nesting features) of interest to dHvA measurements being pursued by Arko and Schirber. The theoretical magnetic field induced neutron form factor is found to be in good agreement with the measurement of Maglic et al

353

Structure and properties of a beryllium dilayer  

International Nuclear Information System (INIS)

All-electron, density-functional calculations on an hcp Be dilayer find c/a at equilibrium to be 1.69 +- 0.03, a = 4.20 +- 0.02 a.u. (Kohn, Sham, Gaspar) or c/a = 1.69 +- 0.02, a = 4.10 +- 0.03 a.u. (Hedin and Lundqvist). In either case there is very weak interplanar bonding. While these structural properties are noticeably different from those of the bulk crystal, the dilayer work function (Hedin and Lundqvist) is essentially identical to the experimental bulk value

354

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

Science.gov (United States)

The quantitative structure--activity relationship of double alkyl chain drugs, including alkanols, aliphatic esters, ketones, barbiturates, amphetamines, butyrylcholinesterase inhibitors, antimalarials, and rifamycin amides, is investigated. A series of double-chain homologues, CnH2n+1XCmH2m+1, in which n changes, keeping m constant, is classified into three types: in type IIL, n greater than m; in type IIE, n = m; in type IIS, n less than m. When a linear relationship, vis., log (1/C) = an + b, holds, the slope a depends on the type; aI greater than or equal to aIIL greater than aIIE greater than aIIS. Here aI means the slope for single-chain homologues. The same order is observed for the equation, log hydrophobicity = an + b, where the hydrophobicity of drug denotes the water solubility, the critical micelle concentration, and the partition coefficient for the 1-octanol--water phases. Therefore, decreased biological activity of a double-chain drug relative to that of a single-chain isomer can be explained by a decreased hydrophobicity of the double-chain drug, due to the intramolecular association of these chains in water. When a parabolic relationship between log (1/C) and n holds, the optimum n depends on the type: nopI less than nopIIL less than nopIIE. This order is also explicable on the basis of a decreased hydrophobicity of double-chain drug. The N-dealklation rate of amphetamines in vivo appears to be affected by the steric factor as well as the hydrophobic factor. A decreased hydrophobicity of double-chain compounds should be taken into consideration for estimating their partition coefficients. PMID:6842509

Hada, S; Neya, S; Funasaki, N

1983-05-01

355

Electron density - structure relationships in some perovskite-type compounds  

International Nuclear Information System (INIS)

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

356

Unravelling the materials genome: Symmetry relationships in alloy properties  

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-07-25

357

Unravelling the materials genome: Symmetry relationships in alloy properties  

International Nuclear Information System (INIS)

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

358

Properties of multilayer nonuniform holographic structures  

International Nuclear Information System (INIS)

Experimental results and analysis of properties of multilayer nonuniform holographic structures formed in photopolymer materials are presented. The theoretical hypotheses is proved that the characteristics of angular selectivity for the considered structures have a set of local maxima, whose number and width are determined by the thicknesses of intermediate layers and deep holograms and that the envelope of the maxima coincides with the selectivity contour of a single holographic array. It is also experimentally shown that hologram nonuniformities substantially distort shapes of selectivity characteristics: they become asymmetric, the local maxima differ in size and the depths of local minima reduce. The modelling results are made similar to experimental data by appropriately choosing the nonuniformity parameters. (imaging and image processing. holography)

359

Structure-activity relationships for mono alkylated or halogenated phenols.  

Science.gov (United States)

The quantitative structure-activity relationships between toxicity (log BR), monitored as cell population growth, and two molecular descriptors, the log 1-octanol/water partition coefficient (log Kow) and the Hammett sigma constant (sigma) or the ionization parameter (pKa) for a series of 17 ortho-, meta- and para-substituted alkylated or halogenated phenols have been examined. The equation: log BR = 0.7998 (log Kow) + 1.2447 (sigma) - 1.5538; r2 = 0.897 s = 0.170 has been found to be an excellent planar model for these chemicals. This model uses the para-position sigma constant as the estimator of ortho-position electronic effects. A similar equation: log BR = 0.7845 (log Kow) - 0.3702 (pKa) + 2.1144; r2 = 0.860 s = 0.199 has been developed using pKa in place of sigma. PMID:3111016

Schultz, T W; Cajina-Quezada, M

1987-07-01

360

Capsaicin and its analogues: structure-activity relationship study.  

Science.gov (United States)

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. PMID:23627937

Huang, X-F; Xue, J-Y; Jiang, A-Q; Zhu, H-L

2013-01-01