WorldWideScience

Sample records for adopt molecular properties

  1. Modeling of molecular properties

    CERN Document Server

    Comba, Peter

    2011-01-01

    Molecular modeling encompasses applied theoretical approaches and computational techniques to model structures and properties of molecular compounds and materials in order to predict and / or interpret their properties. The modeling covered in this book ranges from methods for small chemical to large biological molecules and materials. With its comprehensive coverage of important research fields in molecular and materials science, this is a must-have for all organic, inorganic and biochemists as well as materials scientists interested in applied theoretical and computational chemistry. The 28

  2. Innovation adoption processes for third party property management companies

    Energy Technology Data Exchange (ETDEWEB)

    Shockman, Chris; Piette, Mary Ann

    2000-07-01

    Innovation adoption studies have never been applied to third party property management companies. These companies manage buildings for a fee as their primary business. Property management companies are influential in the adoption process for new technologies because they act as gatekeepers for technical information. This study analyzes radical and routine adoption process that are found in large, professionally operated property management companies. The process is explicated. The technical managers, and their role as technology gate keepers, are described. The distinction to the technical managers between routine and radical technology is that routine technologies do something in a new way and radical technologies do something new. Observations concerning evaluation and adoption of information technologies are described. The findings suggest methods of successfully tailoring and introducing technologies to this market.

  3. Electrical properties of molecular crystals

    International Nuclear Information System (INIS)

    This literature survey summarizes the electrical properties of molecular crystals: molecular crystal structure, transport and excitation mechanisms of charge-carriers, and differences compared to inorganic semi-conductors. The main results concerning the electrical conductivity of the most-studied molecular crystals are presented, together with the optical and photo-electrical properties of these crystals. Finally the different types of electrical measurements used are reviewed, as well as the limits of each method. (author)

  4. Molecular Properties through Polarizable Embedding

    DEFF Research Database (Denmark)

    Olsen, Jógvan Magnus Haugaard; Kongsted, Jacob

    2011-01-01

    We review the theory related to the calculation of electric and magnetic molecular properties through polarizable embedding. In particular, we derive the expressions for the response functions up to the level of cubic response within the density functional theory-based polarizable embedding (PE...

  5. Transport properties of molecular junctions

    CERN Document Server

    Zimbovskaya, Natalya A

    2013-01-01

    A comprehensive overview of the physical mechanisms that control electron transport and the characteristics of metal-molecule-metal (MMM) junctions is presented. As far as possible, methods and formalisms presented elsewhere to analyze electron transport through molecules are avoided. This title introduces basic concepts—a description of the electron transport through molecular junctions—and briefly describes relevant experimental methods. Theoretical methods commonly used to analyze the electron transport through molecules are presented. Various effects that manifest in the electron transport through MMMs, as well as the basics of density-functional theory and its applications to electronic structure calculations in molecules are presented. Nanoelectronic applications of molecular junctions and similar systems are discussed as well. Molecular electronics is a diverse and rapidly growing field. Transport Properties of Molecular Junctions presents an up-to-date survey of the field suitable for researchers ...

  6. Adoption of Lean Principles in a High-Volume Molecular Diagnostic Microbiology Laboratory

    OpenAIRE

    Mitchell, P. Shawn; Mandrekar, Jayawant N.; Yao, Joseph D. C.

    2014-01-01

    Clinical laboratories are constantly facing challenges to do more with less, enhance quality, improve test turnaround time, and reduce operational expenses. Experience with adopting and applying lean concepts and tools used extensively in the manufacturing industry is described for a high-volume clinical molecular microbiology laboratory, illustrating how operational success and benefits can be achieved.

  7. Molecular Control of Macromolecular Properties

    Science.gov (United States)

    Holcombe, Thomas Wesley, III

    Molecular level control over macromolecules has been at the heart of human advancement, long before Hermann Staudinger coined the term Makromolekule. From the development of primitive pharmaceuticals to the advanced materials that sent Man into outer-space, We have been tinkering with God's paint since our inception. The work described herein primarily involves advances concerning poly-aromatic macromolecules for use in future electronic applications, particularly that of organic photovoltaics. There is a final chapter, however, that gives the reader a taste of how some molecular level changes can be directly visualized with modern microscopy techniques. Chapter 1 provides a very brief introduction to conjugated polymers and molecular level control over macromolecular properties. Chapters 2--4 introduces the concept of polymer substitution as a means by which to control and improve charge generation in organic photovoltaic devices. Chapters 5 and 6 show how these polymers can take on larger, defined structures, yet are still beholden to intrinsic molecular properties---such as regioregularity, a fancy word for the regularity of the position in which two aromatic rings are joined together. Chapter 7 re-examines the role of polymer substitution on photovoltaic performance, this time with an emphasis on homo-polymer packing rather than electron transfer at the donor/acceptor interface. Finally, Chapter 8 visualizes how controlling the environment about a single metal atom can lead directly to a cyclic polyolefin. Individually, these advances do not yield any breakthroughs noticeable to a general audience; collectively, they sit atop a mountain of human knowledge, waiting to provide a stepping stone for the next generation.

  8. Nanofriction properties of molecular deposition films

    Institute of Scientific and Technical Information of China (English)

    王强斌; 高芒来; 张嗣伟

    2000-01-01

    The nanofriction properties of Au substrate and monolayer molecular deposition film and multilayer molecular deposition films on Au substrate and the molecular deposition films modified with alkyl-terminal molecule have been investigated by using an atomic force microscope. It is concluded that ( i ) the deposition of molecular deposition films on Au substrate and the modification of alkyl-terminal molecule to the molecular deposition films can reduce the frictional force; (ii) the molecular deposition films with the same terminal exhibit similar nanofriction properties, which has nothing to do with the molecular chain-length and the layer number; (iii) the unstable nanofriction properties of molecular deposition films are contributed to the active terminal of the molecular deposition film, which can be eliminated by decorating the active molecular deposition film with alkyl-terminal molecule, moreover, the decoration of alkyl-terminal molecule can lower the frictional force conspicuously; (iv) the relat

  9. Molecularly resolved protein electromechanical properties.

    Science.gov (United States)

    Axford, Daniel; Davis, Jason J; Wang, Nan; Wang, Dongxu; Zhang, Tiantian; Zhao, Jianwei; Peters, Ben

    2007-08-01

    Previous work has shown that protein molecules can be trapped between the conductive surfaces presented by a metal-coated AFM probe and an underlying planar substrate where their molecule-specific conductance characteristics can be assayed. Herein, we demonstrate that transport across such a derived metal-protein-electrode junction falls within three, pressure-dependent, regimes and, further, that pressure-dependent conductance can be utilized in analyzing temporal variations of protein fold. Specifically, the electronic and mechanical properties of the metalloprotein azurin have been characterized under conditions of anisotropic vertical compression through the use of a conducting atomic force microscope (CP-AFM). By utilizing the ability of azurin to chemically self-assemble on the gold surface presented either by the apex of a suitably coated AFM probe or a planar metallic surface, molecular-level transport characteristics are assayable. Under conditions of low force, typically less than 2 nN, the weak physical and electronic coupling between the protein and the conducting contacts impedes tunneling and leads to charge buildup followed by dielectric breakdown. At slightly increased force, 3-5 nN, the copper protein exhibits temporal electron occupation with observable negative differential resistance, while the redox-inactive zinc mutant does not. At imposed loads greater than 5 nN, appreciable electron tunneling can be detected even at low bias for both the redox-active and -inactive species. Dynamic current-voltage characteristics have been recorded and are well-described by a modified Simmons tunneling model. Subsequent analyses enable the electron tunneling barrier height and barrier length to be determined under conditions of quantified vertical stress. The variance observed describes, in essence, the protein's mechanical properties within the confines of the tunnel junction. PMID:17628094

  10. Thermoelectric properties of molecular nanostructures

    OpenAIRE

    Ermakov, Vladimir N.; Kruchinin, Sergei P.; Kim, Hyun Taki; Pruschke, Thomas

    2011-01-01

    We use the concept of resonant tunneling to calculate the thermopower of molecular nanosystems. It turns out that the sign of the thermovoltage under resonant tunneling conditions depends sensitively on the participating molecular orbital, and one finds a sign change when the transport channel switches from the highest occupied molecular orbital to the lowest unoccupied molecular orbital. Comparing our results to recent experimental data obtained for a BDT molecule contacted with an STM tip, ...

  11. Molecular semiconductors photoelectrical properties and solar cells

    CERN Document Server

    Rees, Ch

    1985-01-01

    During the past thirty years considerable efforts have been made to design the synthesis and the study of molecular semiconductors. Molecular semiconductors - and more generally molecular materials - involve interactions between individual subunits which can be separately synthesized. Organic and metallo-organic derivatives are the basis of most of the molecular materials. A survey of the literature on molecular semiconductors leaves one rather confused. It does seem to be very difficult to correlate the molecular structure of these semiconductors with their experimental electrical properties. For inorganic materials a simple definition delimits a fairly homogeneous family. If an inorganic material has a conductivity intermediate between that of an 12 1 1 3 1 1 insulator « 10- n- cm- ) and that of a metal (> 10 n- cm- ), then it is a semiconductor and will exhibit the characteristic properties of this family, such as junction formation, photoconductivity, and the photovoltaic effect. For molecular compounds,...

  12. Nanofriction properties of molecular deposition films

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The nanofriction properties of Au substrate and monolayer molecular deposition film and multilayer molecular deposition films on Au substrate and the molecular deposition films modified with alkyl-terminal molecule have been investigated by using an atomic force microscope. It is concluded that (ⅰ) the deposition of molecular deposition films on Au substrate and the modification of alkyl-terminal molecule to the molecular deposition films can reduce the frictional force; (ⅱ) the molecular deposition films with the same terminal exhibit similar nanofriction properties, which has nothing to do with the molecular chain-length and the layer number; (ⅲ) the unstable nanofriction properties of molecular deposition films are contributed to the active terminal of the molecular deposition film, which can be eliminated by decorating the active molecular deposition film with alkyl-terminal molecule, moreover, the decoration of alkyl-terminal molecule can lower the frictional force conspicuously; (ⅳ) the relative humidity affects the frictional force; the higher the RH, the lower the frictional force.

  13. Fluctuation Solution Theory Properties from Molecular Simulation

    DEFF Research Database (Denmark)

    Abildskov, Jens; Wedberg, R.; O’Connell, John P.

    2013-01-01

    The thermodynamic properties obtained in the Fluctuation Solution Theory are based on spatial integrals of molecular TCFs between component pairs in the mixture. Molecular simulation, via either MD or MC calculations, can yield these correlation functions for model inter- and intramolecular...... potential functions. However, system-size limitations and statistical noise cause uncertainties in the functions at long range, and thus uncertainties or errors in the integrals. A number of methods such as truncation, distance shifting, long-range modeling, transforms, DCF matching, finite-size scaling...... and adaptive resolution, have been explored to overcome these problems. This chapter reviews the issues and published work associated with using molecular simulation to obtain FST properties. The results suggest that molecular simulation should now be more fully utilized for obtaining quantitative FST...

  14. Amino acid properties conserved in molecular evolution.

    Directory of Open Access Journals (Sweden)

    Witold R Rudnicki

    Full Text Available That amino acid properties are responsible for the way protein molecules evolve is natural and is also reasonably well supported both by the structure of the genetic code and, to a large extent, by the experimental measures of the amino acid similarity. Nevertheless, there remains a significant gap between observed similarity matrices and their reconstructions from amino acid properties. Therefore, we introduce a simple theoretical model of amino acid similarity matrices, which allows splitting the matrix into two parts - one that depends only on mutabilities of amino acids and another that depends on pairwise similarities between them. Then the new synthetic amino acid properties are derived from the pairwise similarities and used to reconstruct similarity matrices covering a wide range of information entropies. Our model allows us to explain up to 94% of the variability in the BLOSUM family of the amino acids similarity matrices in terms of amino acid properties. The new properties derived from amino acid similarity matrices correlate highly with properties known to be important for molecular evolution such as hydrophobicity, size, shape and charge of amino acids. This result closes the gap in our understanding of the influence of amino acids on evolution at the molecular level. The methods were applied to the single family of similarity matrices used often in general sequence homology searches, but it is general and can be used also for more specific matrices. The new synthetic properties can be used in analyzes of protein sequences in various biological applications.

  15. Molecular geometry and boiling related thermodynamic properties

    International Nuclear Information System (INIS)

    Highlights: ► Molecular geometric factors were found to be important determinants for boiling entropy and thus the boiling temperature. ► Only four molecular geometric factors were used in the study. ► A group contribution method was used to calculate enthalpy of boiling. ► The proposed method is simple and the estimations are in good agreement with experimental values. - Abstract: Boiling related thermodynamic properties are important parameters in research. In this study, a model integrating both additive groups and non-additive molecular geometric factors has been developed for the calculation of boiling enthalpy, entropy and temperature. The calculated values are in good agreement with the measured values of 470 compounds. This model provides a simple and accurate estimation of enthalpy of boiling, entropy of boiling and boiling temperatures with absolute average errors of 0.62 kJ/mol, 1.15 J/K · mol and 7.13 K respectively.

  16. Wetting properties of molecularly rough surfaces

    International Nuclear Information System (INIS)

    We employ molecular dynamics simulations to study the wettability of nanoscale rough surfaces in systems governed by Lennard-Jones (LJ) interactions. We consider both smooth and molecularly rough planar surfaces. Solid substrates are modeled as a static collection of LJ particles arranged in a face-centered cubic lattice with the (100) surface exposed to the LJ fluid. Molecularly rough solid surfaces are prepared by removing several strips of LJ atoms from the external layers of the substrate, i.e., forming parallel nanogrooves on the surface. We vary the solid-fluid interactions to investigate strongly and weakly wettable surfaces. We determine the wetting properties by measuring the equilibrium droplet profiles that are in turn used to evaluate the contact angles. Macroscopic arguments, such as those leading to Wenzel’s law, suggest that surface roughness always amplifies the wetting properties of a lyophilic surface. However, our results indicate the opposite effect from roughness for microscopically corrugated surfaces, i.e., surface roughness deteriorates the substrate wettability. Adding the roughness to a strongly wettable surface shrinks the surface area wet with the liquid, and it either increases or only marginally affects the contact angle, depending on the degree of liquid adsorption into the nanogrooves. For a weakly wettable surface, the roughness changes the surface character from lyophilic to lyophobic due to a weakening of the solid-fluid interactions by the presence of the nanogrooves and the weaker adsorption of the liquid into the nanogrooves

  17. Rheological properties of poly (vinylpiyrrolidone) as a function of average molecular weight and its applications

    DEFF Research Database (Denmark)

    Marani, Debora; Sudireddy, Bhaskar Reddy; Kiebach, Ragnar;

    formulation. Specifically, understanding the rheological properties is of paramount interest. Among the different factors that influence the rheological behavior, viscosity average molecular weight of the polymer is the most relevant. In this work, PVP polymers with various molecular weights have been...... characterized regarding their viscosimetric properties in ethanol. Average molecular weights (Mw, Mn, and Mz) have been determined by gel permeation chromatography (GPC), and then used in a numerical method to evaluate the viscosity average molecular weight (Mv) via the Mark-Houwink-Sakurada (MHS) equation. The...... MHS equation relates the intrinsic viscosity [η] of a polymer in a given solvent at fixed temperature to the molecular weight. The adopted method also enables for the evaluation of the two MHS equation parameters (a and K), and of the polydispersity correction factor (qMHS). The intrinsic viscosity...

  18. Prediction of Substrate-Enzyme-Product Interaction Based on Molecular Descriptors and Physicochemical Properties

    OpenAIRE

    Bing Niu; Guohua Huang; Linfeng Zheng; Xueyuan Wang; Fuxue Chen; Yuhui Zhang; Tao Huang

    2013-01-01

    It is important to correctly and efficiently predict the interaction of substrate-enzyme and to predict their product in metabolic pathway. In this work, a novel approach was introduced to encode substrate/product and enzyme molecules with molecular descriptors and physicochemical properties, respectively. Based on this encoding method, KNN was adopted to build the substrate-enzyme-product interaction network. After selecting the optimal features that are able to represent the main factors of...

  19. Molecular orbitals for properties and spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Robert, Vincent [Laboratoire de Chimie Quantique, Institut de Chimie, Université de Strasbourg, 1 rue Blaise Pascal 67000 Strasbourg-France (France); Domingo, Alex [Quantum Chemistry and Physical Chemistry Celestijnenlaan 200f, 3001 Heverlee - Belgium (Belgium); Braunstein, Pierre; Danopoulos, Andreas; Monakhov, Kirill [Laboratoire de Chimie de Coordination, Institut de Chimie, Université de Strasbourg, 4 rue Blaise Pascal 67081 Strasbourg-France (France)

    2015-12-31

    The description and clarification of spectroscopies and properties goes through ab initio calculations. Wave function based calculations (CASSCF/CASPT2) are particularly appealing since they offer spectroscopic accuracy and means of interpretation. we performed such calculations to elucidate the origin of unusual structural changes and intramolecular electron transfer phenomenon. Based on optimized molecular orbitals and a reading of the multireference wave function, it is suggested that intimate interactions are likely to considerably modify the standard pictures. A so-called PIMA (polarization-induced metalâĹŠarene) interaction similar to the more familiar anion-π interaction is responsible for a significant deviation from sp{sup 3} geometry and an energetic stabilization of 50 kJ/mol in Cr(II) benzyl organometallic complexes. In a similar fashion, it is proposed that the energetic profile of the IVCT (inter valence charge transfer) exhibits strong similarities to the Marcus’ theory, suggesting a response behaviour of the ensemble of electrons as electron transfer occurs in Fe{sup 2+}/Fe{sup 3+} bimetallic compound. The electronic reorganization induced by the IVCT process accounts for 11.8 eV, a very large effect that reduces the transfer energy down to 0.89 eV, in very good agreement with experiments.

  20. Molecular orbitals for properties and spectroscopies

    International Nuclear Information System (INIS)

    The description and clarification of spectroscopies and properties goes through ab initio calculations. Wave function based calculations (CASSCF/CASPT2) are particularly appealing since they offer spectroscopic accuracy and means of interpretation. we performed such calculations to elucidate the origin of unusual structural changes and intramolecular electron transfer phenomenon. Based on optimized molecular orbitals and a reading of the multireference wave function, it is suggested that intimate interactions are likely to considerably modify the standard pictures. A so-called PIMA (polarization-induced metalâĹŠarene) interaction similar to the more familiar anion-π interaction is responsible for a significant deviation from sp3 geometry and an energetic stabilization of 50 kJ/mol in Cr(II) benzyl organometallic complexes. In a similar fashion, it is proposed that the energetic profile of the IVCT (inter valence charge transfer) exhibits strong similarities to the Marcus’ theory, suggesting a response behaviour of the ensemble of electrons as electron transfer occurs in Fe2+/Fe3+ bimetallic compound. The electronic reorganization induced by the IVCT process accounts for 11.8 eV, a very large effect that reduces the transfer energy down to 0.89 eV, in very good agreement with experiments

  1. Molecular orbitals for properties and spectroscopies

    Science.gov (United States)

    Robert, Vincent; Domingo, Alex; Braunstein, Pierre; Danopoulos, Andreas; Monakhov, Kirill

    2015-12-01

    The description and clarification of spectroscopies and properties goes through ab initio calculations. Wave function based calculations (CASSCF/CASPT2) are particularly appealing since they offer spectroscopic accuracy and means of interpretation. we performed such calculations to elucidate the origin of unusual structural changes and intramolecular electron transfer phenomenon. Based on optimized molecular orbitals and a reading of the multireference wave function, it is suggested that intimate interactions are likely to considerably modify the standard pictures. A so-called PIMA (polarization-induced metalâĹŠarene) interaction similar to the more familiar anion-π interaction is responsible for a significant deviation from sp3 geometry and an energetic stabilization of 50 kJ/mol in Cr(II) benzyl organometallic complexes. In a similar fashion, it is proposed that the energetic profile of the IVCT (inter valence charge transfer) exhibits strong similarities to the Marcus' theory, suggesting a response behaviour of the ensemble of electrons as electron transfer occurs in Fe2+/Fe3+ bimetallic compound. The electronic reorganization induced by the IVCT process accounts for 11.8 eV, a very large effect that reduces the transfer energy down to 0.89 eV, in very good agreement with experiments.

  2. Modelling of Spectroscopic and Structural Properties using Molecular Dynamics

    OpenAIRE

    Francesco Muniz Miranda

    2013-01-01

    The following dissertation is about the study that I performed at the Chemistry Department of the University of Florence and at the European Laboratory for Non- Linear Spectroscopy (LENS) to recover and elucidate structural, dynamical, and spectroscopic molecular features adopting computer simulations. In particular, here ab initio molecular dynamics simulations and time-frequency analysis are the most employed “tools”, in order to have a better understanding of the origins ...

  3. Quantum Algorithm for Molecular Properties and Geometry Optimization

    OpenAIRE

    Kassal, Ivan; Aspuru-Guzik, Alan

    2009-01-01

    It is known that quantum computers, if available, would allow an exponential decrease in the computational cost of quantum simulations. We extend this result to show that the computation of molecular properties (energy derivatives) could also be sped up using quantum computers. We provide a quantum algorithm for the numerical evaluation of molecular properties, whose time cost is a constant multiple of the time needed to compute the molecular energy, regardless of the size of the system. Mole...

  4. Effect of Molecular Interactions between the Solid Wall and Liquid on the Flow Properties in Microtubes

    Institute of Scientific and Technical Information of China (English)

    BAO Fu-Bing; LIN Jian-Zhong

    2009-01-01

    The flow properties in microtubes, such as velocity profiles and pressure distributions, are different from those in macrotubes. We attribute this phenomenon to the molecular interactions between the solid wall and inner liquid. The apparent viscosity, which takes into consideration the molecular interactions, is introduced in the present study and the Navier-Stokes equations are solved. Water is adopted in the calculation. For the hydrophilic material wall, the water is more like to adhere to the wall. The velocity near the wall is smaller than that of conventional theory, while the centerline velocity and pressure gradients are much larger. Such a phenomenon becomes much more obvious with the decrease in tube diameter.

  5. Photonic properties of organic molecular assemblies

    Science.gov (United States)

    Huggins, Kevin Edward

    1997-12-01

    This work attempts to characterize various photonic properties of spontaneously created organic molecular objects. A novel diacetylene monomer was synthesized and found to polymerize forming two-dimensional supramolecular assemblies. The two-dimensional structure self assembles when UV light generates polydiacetylene comb polymers. The material forms blue solid thin films which have been characterized by x-ray diffraction, infrared spectroscopy and Raman scattering. The photopolymerization rate of the monomer was followed by Raman scattering and was shown to be of second order. A reaction rate threshold was observed between 300 and 400mW of incident 647.1nm laser radiation where the reaction rate increased substantially. The material generates high third order nonlinear optical signals and have remarkable photochemical stability to 1064nm radiation from a Q-switched Nd:YAG laser. Upon heating to 62oC, the material turns bright red reversibly while maintaining its two-dimensional structure, characterized by differential scanning calorimetry. Heating to 180oC results in an irreversible color change to bright orange characterized by UV-Vis-NIR spectrophotometry. Variable temperature sum frequency generation experiments show that the third harmonic generation signals retain much of their original intensity through the thermochromic transitions. A system of novel rodcoil materials self assembles into mushroom-shaped supramolecular objects. These nanophase separated aggregates form oblique-plane superlattices exhibiting long-range order. The superlattice is composed of isolated crystallized rod domains surrounded by amorphous coil which form from simple solvent casting techniques. Second harmonic generation was used to confirm the polar head-to-tail stacking of the aggregates and to determine the average physical tilt of (5/pm 5)o of the aggregates relative to the film plane. A novel chiral oligomer synthesized in our group gave rise to interesting phase behavior

  6. Influence of Molecular Conformations and Microstructure on the Optoelectronic Properties of Conjugated Polymers

    Directory of Open Access Journals (Sweden)

    Ioan Botiz

    2014-03-01

    Full Text Available It is increasingly obvious that the molecular conformations and the long-range arrangement that conjugated polymers can adopt under various experimental conditions in bulk, solutions or thin films, significantly impact their resulting optoelectronic properties. As a consequence, the functionalities and efficiencies of resulting organic devices, such as field-effect transistors, light-emitting diodes, or photovoltaic cells, also dramatically change due to the close structure/property relationship. A range of structure/optoelectronic properties relationships have been investigated over the last few years using various experimental and theoretical methods, and, further, interesting correlations are continuously revealed by the scientific community. In this review, we discuss the latest findings related to the structure/optoelectronic properties interrelationships that exist in organic devices fabricated with conjugated polymers in terms of charge mobility, absorption, photoluminescence, as well as photovoltaic properties.

  7. Influence of Molecular Conformations and Microstructure on the Optoelectronic Properties of Conjugated Polymers

    KAUST Repository

    Botiz, Ioan

    2014-03-19

    It is increasingly obvious that the molecular conformations and the long-range arrangement that conjugated polymers can adopt under various experimental conditions in bulk, solutions or thin films, significantly impact their resulting optoelectronic properties. As a consequence, the functionalities and efficiencies of resulting organic devices, such as field-effect transistors, light-emitting diodes, or photovoltaic cells, also dramatically change due to the close structure/property relationship. A range of structure/optoelectronic properties relationships have been investigated over the last few years using various experimental and theoretical methods, and, further, interesting correlations are continuously revealed by the scientific community. In this review, we discuss the latest findings related to the structure/optoelectronic properties interrelationships that exist in organic devices fabricated with conjugated polymers in terms of charge mobility, absorption, photoluminescence, as well as photovoltaic properties. © 2014 by the authors.

  8. Optical properties of disordered molecular aggregates : A numerical study

    NARCIS (Netherlands)

    Fidder, Henk; Knoester, Jasper; Wiersma, Douwe A.

    1991-01-01

    We present results of numerical simulations on optical properties of linear molecular aggregates with diagonal and off-diagonal disorder. In contrast to previous studies, we introduce off-diagonal disorder indirectly through Gaussian randomness in the molecular positions; this results in a strongly

  9. OPTICAL-PROPERTIES OF DISORDERED MOLECULAR AGGREGATES - A NUMERICAL STUDY

    NARCIS (Netherlands)

    FIDDER, H; KNOESTER, J; WIERSMA, DA

    1991-01-01

    We present results of numerical simulations on optical properties of linear molecular aggregates with diagonal and off-diagonal disorder. In contrast to previous studies, we introduce off-diagonal disorder indirectly through Gaussian randomness in the molecular positions; this results in a strongly

  10. Molecular Clouds: Internal Properties, Turbulence, Star Formation and Feedback

    OpenAIRE

    Tan, Jonathan C.; Shaske, Suzanne N.; Van Loo, Sven

    2012-01-01

    All stars are born in molecular clouds, and most in giant molecular clouds (GMCs), which thus set the star formation activity of galaxies. We first review their observed properties, including measures of mass surface density, Sigma, and thus mass, M. We discuss cloud dynamics, concluding most GMCs are gravitationally bound. Star formation is highly clustered within GMCs, but overall is very inefficient. We compare properties of star-forming clumps with those of young stellar clusters (YSCs). ...

  11. On nonadiabatic SCF calculations of molecular properties

    OpenAIRE

    Fernández, Francisco M.

    2009-01-01

    We argue that the dynamic extended molecular orbital (DEMO) method may be less accurate than expected because the motion of the center of mass was not properly removed prior to the SCF calculation. Under such conditions the virial theorem is a misleading indication of the accuracy of the wavefunction.

  12. Excited-State Properties of Molecular Solids from First Principles.

    Science.gov (United States)

    Kronik, Leeor; Neaton, Jeffrey B

    2016-05-27

    Molecular solids have attracted attention recently in the context of organic (opto)electronics. These materials exhibit unique charge carrier generation and transport phenomena that are distinct from those of conventional semiconductors. Understanding these phenomena is fundamental to optoelectronics and requires a detailed description of the excited-state properties of molecular solids. Recent advances in many-body perturbation theory (MBPT) and density functional theory (DFT) have made such description possible and have revealed many surprising electronic and optical properties of molecular crystals. Here, we review this progress. We summarize the salient aspects of MBPT and DFT as well as various properties that can be described by these methods. These properties include the fundamental gap and its renormalization, hybridization and band dispersion, singlet and triplet excitations, optical spectra, and excitonic properties. For each, we present concrete examples, a comparison to experiments, and a critical discussion. PMID:27090844

  13. Excited-State Properties of Molecular Solids from First Principles

    Science.gov (United States)

    Kronik, Leeor; Neaton, Jeffrey B.

    2016-05-01

    Molecular solids have attracted attention recently in the context of organic (opto)electronics. These materials exhibit unique charge carrier generation and transport phenomena that are distinct from those of conventional semiconductors. Understanding these phenomena is fundamental to optoelectronics and requires a detailed description of the excited-state properties of molecular solids. Recent advances in many-body perturbation theory (MBPT) and density functional theory (DFT) have made such description possible and have revealed many surprising electronic and optical properties of molecular crystals. Here, we review this progress. We summarize the salient aspects of MBPT and DFT as well as various properties that can be described by these methods. These properties include the fundamental gap and its renormalization, hybridization and band dispersion, singlet and triplet excitations, optical spectra, and excitonic properties. For each, we present concrete examples, a comparison to experiments, and a critical discussion.

  14. Many Molecular Properties from One Kernel in Chemical Space

    CERN Document Server

    Ramakrishnan, Raghunathan

    2015-01-01

    We introduce property-independent kernels for machine learning modeling of arbitrarily many molecular properties. The kernels encode molecular structures for training sets of varying size, as well as similarity measures sufficiently diffuse in chemical space to sample over all training molecules. Corresponding molecular reference properties provided, they enable the instantaneous generation of ML models which can systematically be improved through the addition of more data. This idea is exemplified for single kernel based modeling of internal energy, enthalpy, free energy, heat capacity, polarizability, electronic spread, zero-point vibrational energy, energies of frontier orbitals, HOMO-LUMO gap, and the highest fundamental vibrational wavenumber. Models of these properties are trained and tested using 112 kilo organic molecules of similar size. Resulting models are discussed as well as the kernels' use for generating and using other property models.

  15. Semiconductor nanostructure properties. Molecular Dynamic Simulations

    International Nuclear Information System (INIS)

    The need for research is based on the fact that development of non-planar semiconductor nanosystems and nanomaterials with controlled properties is an important scientific and industrial problem. So, final scientific and technological problem is the creation of adequate modern methods and software for growth and properties simulation and optimization of various III-V (GaAs, InAs, InP, InGaAs etc.) nanostructures (e.g. nanowires) with controlled surface morphology, crystal structure, optical, transport properties etc. Accordingly, now we are developing a specialized computer code for atomistic simulation of structural (distribution of atoms and impurities, elastic and force constants, strain distribution etc.) and thermodynamic (mixing energy, interaction energy, surface energy etc.) properties of the nanostructures. Some simulation results are shown too

  16. Estimation of mechanical properties of single wall carbon nanotubes using molecular mechanics approach

    Indian Academy of Sciences (India)

    P Subba Rao; Sunil Anandatheertha; G Narayana Naik; G Gopalakrishnan

    2015-06-01

    Molecular mechanics based finite element analysis is adopted in the current work to evaluate the mechanical properties of Zigzag, Armchair and Chiral Single wall Carbon Nanotubes (SWCNT) of different diameters and chiralities. Three different types of atomic bonds, that is Carbon–Carbon covalent bond and two types of Carbon–Carbon van der Waals bonds are considered in the carbon nanotube system. The stiffness values of these bonds are calculated using the molecular potentials, namely Morse potential function and Lennard-Jones interaction potential function respectively and these stiffness’s are assigned to spring elements in the finite element model of the CNT. The geometry of CNT is built using a macro that is developed for the finite element analysis software. The finite element model of the CNT is constructed, appropriate boundary conditions are applied and the behavior of mechanical properties of CNT is studied.

  17. Researches on molecular physical properties by radiation

    International Nuclear Information System (INIS)

    In this report, a part of the results of research on radiation-chemical initial processes in the low temperature condensating phase of high molecular materials and organic compounds is reviewed, together with the future prospect. The means to pursue the initial processes of interaction between radiation and material are roughly divided into two: a method of tracking the behaviour of the active nuclides generated after the irradiation with radiation pulses and a method to track those by reducing the reaction rate. Photo-deterioration mechanism of high molecular materials: The initial process of photo-deterioration was investigated by ESR (electron spin resonance). It was found in polyethylene and polypropylene that the transform reaction of acyl radical formed by decomposition due to heat and light occurred reversibly. The electronic structure and condensating status of radicals formed in irradiated organic substance studied by ESR: The identification and the analysis of behaviour were carried out for the radicals formed when polycarbonate, polypropylene and polyethylene used for the photo-deterioration study were irradiated at low temperature with high energy radiation such as electron beam or γ-ray, to investigate the difference from light irradiation. Mobile process of radicals: The radicals formed in the initial process of crosslinking reaction by irradiation, for example, in polyethylene, were investigated in detail for their mobile process by heat or light. Luminescence of irradiated organic substance: A part of the research on tunneling recombination luminescence at low temperature is introduced. (Wakatsuki, Y.)

  18. Molecular dynamic results on transport properties

    Energy Technology Data Exchange (ETDEWEB)

    Alder, B.J.; Alley, W.E.

    1978-06-01

    Following a broad discussion of generalized hydrodynamics, three examples are given to illustrate how useful this approach is in extending hydrodynamics to nearly the scale of molecular dimensions and the time between collisions, principally by including viscoelastic effects. The three examples concern the behavior of the velocity autocorrelation function, the decay of fluctuations in a resonating system, and the calculation of the dynamic structure factor obtained from neutron scattering. In the latter case the molecular dynamics results are also compared to the predictions of generalized kinetic theory. Finally it is shown how to implement generalized hydrodynamics both on a microscopic and macroscopic level. Hydrodynamics is unable to account for the long time tails in the velocity autocorrelation functions and the divergent Burnett coefficients observed for the Lorentz gas. Instead, the long time behavior of the Burnett coefficient and the distribution of displacements (the self part of the dynamic structure factor) can be accounted for by a random walk with a waiting time distribution which is chosen to give the correct velocity autocorrelation function. This random walk predicts, in agreement with the observations, that this displacement distribution is Gaussian at long times for the Lorentz gas, while for hard disks it has been found not to be so.

  19. Molecular dynamic results on transport properties

    International Nuclear Information System (INIS)

    Following a broad discussion of generalized hydrodynamics, three examples are given to illustrate how useful this approach is in extending hydrodynamics to nearly the scale of molecular dimensions and the time between collisions, principally by including viscoelastic effects. The three examples concern the behavior of the velocity autocorrelation function, the decay of fluctuations in a resonating system, and the calculation of the dynamic structure factor obtained from neutron scattering. In the latter case the molecular dynamics results are also compared to the predictions of generalized kinetic theory. Finally it is shown how to implement generalized hydrodynamics both on a microscopic and macroscopic level. Hydrodynamics is unable to account for the long time tails in the velocity autocorrelation functions and the divergent Burnett coefficients observed for the Lorentz gas. Instead, the long time behavior of the Burnett coefficient and the distribution of displacements (the self part of the dynamic structure factor) can be accounted for by a random walk with a waiting time distribution which is chosen to give the correct velocity autocorrelation function. This random walk predicts, in agreement with the observations, that this displacement distribution is Gaussian at long times for the Lorentz gas, while for hard disks it has been found not to be so

  20. Improving the morphological and magnetic properties of permalloy films by adopting ultra-low-pressure sputtering

    International Nuclear Information System (INIS)

    A series of permalloy (NiFe) thin films of fixed thickness were grown by DC-sputtering at different argon pressures and without buffer layers. When the pressure was lowered from 1.2 Pa to 0.004 Pa, the coercivity decreased remarkably form 1353.5 A/m to 119.4 A/m. In addition, the NiFe film fabricated at ultra-low-pressure showed low damping, and its zero-field linewidth approached zero. Based on ferromagnetic resonance (FMR) and atomic force microscopy (AFM) observations, we attribute the excellent magnetic properties of NiFe film fabricated under ultra-low pressure to its improved morphological and magnetic uniformity. - Highlights: • NiFe thin films deposited with ultralow-pressure. • The ultralow-pressure deposition NiFe films yielded excellent microstructure and magnetic properties. • The ultralow-pressure deposition is an effective way for tuning of magnetic and dynamic properties of NiFe film

  1. Physical and Molecular Properties of Lipid Polymorphs - A Review

    OpenAIRE

    Sato, K

    1987-01-01

    The physical and molecular properties of the polymorphism of stearic acid, oleic acid and SOS (1.3-distearoyl-2-oleoyl glycerol) are comparatively discussed. Temperature dependence of Gibbs energy (G-T relation) of three polymorphs of stearic acid; A, B and C, revealed close relationships to each other. The molecular structures subtly differed in these polymorphs. In contrast, three plymorphs of oleic acid, b , and y exhibited remarkably different characteristics. G-T relation showed more d...

  2. In Silico Study of Ceftaroline’s Molecular Properties

    Directory of Open Access Journals (Sweden)

    Elso Manuel Cruz Cruz

    2011-03-01

    Full Text Available Background: Ceftaroline is the latest developed cephalosporin. Its molecular modeling can help deepening the structural bases underpinning its pharmacological characteristics. Objective: to model structural and electronic properties of the ceftaroline. Method: a theoretical study using quantum mechanics methods was conducted in order to model the structure and electronic properties of the ceftaroline. Molecular geometry was optimized with semiempirical calculations according to parameterized model # 3. Molecular properties were calculated according to the Density Functional Theory. Densities of atomic charges and orbital borders were analyzed and compared to the ceftobiprole modeling. Results: the ceftaroline has a more compact and less elongated three-dimensional structure than the ceftobiprole. The positive charges densities on the carbonyl carbon are slightly lower than their equivalents in the ceftobiprole. Conclusions: an ethyl presence in the ceftaroline oxime group modifies its spatial configuration which makes it more compact and may influence its antibacterial action.

  3. Properties of the Molecular Gas in Starburst Galaxies and AGN

    CERN Document Server

    Mühle, S; Henkel, C

    2009-01-01

    There is growing evidence that the properties of the molecular gas in the nuclei of starburst galaxies and in AGN may be very different from those seen in Galactic star forming regions and that a high kinetic temperature in the molecular gas may lead to a non-standard initial mass function in the next generation of stars. Unfortunately, among the fundamental parameters derived from molecular line observations, the kinetic temperature of the molecular gas in external galaxies is often not well determined due to a lack of suitable tracer molecules. We discuss the diagnostic power of selected transition lines of formaldehyde (H_2CO), which can be used as a molecular thermometer as well as an excellent tracer of the molecular gas density. As a proof of concept, we present the results of our multi-transition line study of the H_2CO emission from the prototypical starburst galaxy M82. Using our large velocity gradient model, we tightly constrain the physical properties of the dense gas in the prominent molecular lo...

  4. Soy protein isolate molecular level contributions to bulk adhesive properties

    Science.gov (United States)

    Shera, Jeanne Norton

    Increasing environmental awareness and the recognized health hazards of formaldehyde-based resins has prompted a strong demand for environmentally-responsible adhesives for wood composites. Soy protein-based adhesives have been shown to be commercially viable with 90-day shelf stability and composite physical properties comparable to those of commercial formaldehyde-based particleboards. The main research focus is to isolate and characterize the molecular level features in soy protein isolate responsible for providing mechanical properties, storage stability, and water resistance during adhesive formulation, processing, and wood composite fabrication. Commercial composite board will be reviewed to enhance our understanding of the individual components and processes required for particleboard production. The levels of protein structure will be defined and an overview of current bio-based technology will be presented. In the process, the logic for utilizing soy protein as a sole binder in the adhesive will be reinforced. Variables such as adhesive components, pH, divalent ions, blend aging, protein molecular weight, formulation solids content, and soy protein functionalization will relate the bulk properties of soy protein adhesives to the molecular configuration of the soybean protein. This work has demonstrated that when intermolecular beta-sheet interactions and protein long-range order is disrupted, viscosity and mechanical properties decrease. Storage stability can be maintained through the stabilization of intermolecular beta-sheet interactions. When molecular weight is reduced through enzymatic digestion, long-range order is disrupted and viscosity and mechanical properties decrease accordingly. Processibility and physical properties must be balanced to increase solids while maintaining low viscosity, desirable mechanical properties, and adequate storage stability. The structure of the soybean protein must be related to the particleboard bulk mechanical

  5. Thermodynamic properties and phase transitions in CO2 molecular clusters

    Science.gov (United States)

    Etters, R. D.; Flurchick, K.; Pan, R. P.; Chandrasekharan, V.

    1981-01-01

    The thermodynamic properties of (CO2)N molecular aggregates of size N between 2 and 13 have been investigated. These crystallites exhibit well defined orientational order-disorder rotational transitions accompanied by a structural transition into a plastic crystallite phase. In addition, they exhibit melting and disassociation transitions. It is shown that the interpretation of experimental data, based upon dimer properties, depends crucially on these results. Equilibrium structures and orientations are also given.

  6. Adsorption properties of the SAPO-5 molecular sieve

    KAUST Repository

    Hu, Enping

    2010-09-09

    The adsorption properties of an aluminophosphate molecular sieve, SAPO-5, were measured for a number of gases and vapors, including N2, water, isopropanol, and xylenes. The data showed that SAPO-5 is quite hydrophobic and has a strong selectivity of o-xylene over its isomers m- and p-xylene. © 2010 American Chemical Society.

  7. Electrical properties of GaN-based heterostructures adopting InAlN/AlGaN bilayer barriers

    Science.gov (United States)

    Xu, Z. Y.; Xu, F. J.; Huang, C. C.; Wang, J. M.; Zhang, X.; Yang, Z. J.; Wang, X. Q.; Shen, B.

    2016-08-01

    Electrical properties of GaN-based heterostructures adopting InAlN/AlGaN bilayer barriers are investigated by Hall-effect and current-voltage measurements. It is found that this structure possesses both merits of high two-dimensional electron gas (2DEG) density and low gate leakage current density, while maintaining high 2DEG mobility. Furthermore, temperature dependence of the 2DEG density in this structure is verified to follow a combined tendency of InAlN/GaN (increase) and AlGaN/GaN (decrease) heterostructures with increasing temperature from 90 K to 400 K, which is mainly caused by superposition of the effects from carrier thermal activation induced by extrinsic factors in InAlN layer and the reduced conduction-band discontinuity.

  8. Molecular structure and elastic properties of thermotropic liquid crystals: Integrated molecular dynamics—Statistical mechanical theory vs molecular field approach

    Science.gov (United States)

    Capar, M. Ilk; Nar, A.; Ferrarini, A.; Frezza, E.; Greco, C.; Zakharov, A. V.; Vakulenko, A. A.

    2013-03-01

    The connection between the molecular structure of liquid crystals and their elastic properties, which control the director deformations relevant for electro-optic applications, remains a challenging objective for theories and computations. Here, we compare two methods that have been proposed to this purpose, both characterized by a detailed molecular level description. One is an integrated molecular dynamics-statistical mechanical approach, where the bulk elastic constants of nematics are calculated from the direct correlation function (DCFs) and the single molecule orientational distribution function [D. A. McQuarrie, Statistical Mechanics (Harper & Row, New York, 1973)]. The latter is obtained from atomistic molecular dynamics trajectories, together with the radial distribution function, from which the DCF is then determined by solving the Ornstein-Zernike equation. The other approach is based on a molecular field theory, where the potential of mean torque experienced by a mesogen in the liquid crystal phase is parameterized according to its molecular surface. In this case, the calculation of elastic constants is combined with the Monte Carlo sampling of single molecule conformations. Using these different approaches, but the same description, at the level of molecular geometry and torsional potentials, we have investigated the elastic properties of the nematic phase of two typical mesogens, 4'-n-pentyloxy-4-cyanobiphenyl and 4'-n-heptyloxy-4-cyanobiphenyl. Both methods yield K3(bend) >K1 (splay) >K2 (twist), although there are some discrepancies in the average elastic constants and in their anisotropy. These are interpreted in terms of the different approximations and the different ways of accounting for the structural properties of molecules in the two approaches. In general, the results point to the role of the molecular shape, which is modulated by the conformational freedom and cannot be fully accounted for by a single descriptor such as the aspect ratio.

  9. Molecular structure and elastic properties of thermotropic liquid crystals: integrated molecular dynamics--statistical mechanical theory vs molecular field approach.

    Science.gov (United States)

    Ilk Capar, M; Nar, A; Ferrarini, A; Frezza, E; Greco, C; Zakharov, A V; Vakulenko, A A

    2013-03-21

    The connection between the molecular structure of liquid crystals and their elastic properties, which control the director deformations relevant for electro-optic applications, remains a challenging objective for theories and computations. Here, we compare two methods that have been proposed to this purpose, both characterized by a detailed molecular level description. One is an integrated molecular dynamics-statistical mechanical approach, where the bulk elastic constants of nematics are calculated from the direct correlation function (DCFs) and the single molecule orientational distribution function [D. A. McQuarrie, Statistical Mechanics (Harper & Row, New York, 1973)]. The latter is obtained from atomistic molecular dynamics trajectories, together with the radial distribution function, from which the DCF is then determined by solving the Ornstein-Zernike equation. The other approach is based on a molecular field theory, where the potential of mean torque experienced by a mesogen in the liquid crystal phase is parameterized according to its molecular surface. In this case, the calculation of elastic constants is combined with the Monte Carlo sampling of single molecule conformations. Using these different approaches, but the same description, at the level of molecular geometry and torsional potentials, we have investigated the elastic properties of the nematic phase of two typical mesogens, 4'-n-pentyloxy-4-cyanobiphenyl and 4'-n-heptyloxy-4-cyanobiphenyl. Both methods yield K3(bend) >K1 (splay) >K2 (twist), although there are some discrepancies in the average elastic constants and in their anisotropy. These are interpreted in terms of the different approximations and the different ways of accounting for the structural properties of molecules in the two approaches. In general, the results point to the role of the molecular shape, which is modulated by the conformational freedom and cannot be fully accounted for by a single descriptor such as the aspect ratio

  10. Biased motion and molecular motor properties of bipedal spiders

    Science.gov (United States)

    Samii, Laleh; Linke, Heiner; Zuckermann, Martin J.; Forde, Nancy R.

    2010-02-01

    Molecular spiders are synthetic molecular motors featuring multiple legs that each can interact with a substrate through binding and cleavage. Experimental studies suggest the motion of the spider in a matrix is biased toward uncleaved substrates and that spider properties such as processivity can be altered by changing the binding strength of the legs to substrate [R. Pei, S. K. Taylor, D. Stefanovic, S. Rudchenko, T. E. Mitchell, and M. N. Stojanovic, J. Am. Chem. Soc. 128, 12693 (2006)]. We investigate the origin of biased motion and molecular motor properties of bipedal spiders using Monte Carlo simulations. Our simulations combine a realistic chemical kinetic model, hand-over-hand or inchworm modes of stepping, and the use of a one-dimensional track. We find that stronger binding to substrate, cleavage and spider detachment from the track are contributing mechanisms to population bias. We investigate the contributions of stepping mechanism to speed, randomness parameter, processivity, coupling, and efficiency, and comment on how these molecular motor properties can be altered by changing experimentally tunable kinetic parameters.

  11. Understanding the Synthesis and Properties of Molecular Silver Nanoparticles

    Science.gov (United States)

    Ashenfelter, Brian A.

    Molecular nanoparticles have emerged as an interesting class of materials whose atomically precise structures and discrete properties set them apart from their larger counterparts. Molecular silver nanoparticles are of particular interest because they provide a host of advantages as optical materials for possible use in sensing and imaging applications. However, relatively little is known about molecular silver nanoparticles including the details of their formation and their optical and mechanical properties. Size control remains a longstanding challenge in the production of glutathionate (SG) protected silver nanoparticles. Singular Ag:SG nanoparticle products have been difficult to obtain directly, but size focusing of larger distributions through attrition has been found to lead to useful isolation of particular species. Here, we present a methodology for controlling the size of Ag:SG molecular nanoparticles that leverages the stability of the most robust species. These results were then used to develop a facile approach for achieving two of the most stable species in the Ag:SG system. Molecular metal nanoparticles are known to be much more fluorescent than larger plasmonic nanoparticles, however the nature and origin of this fluorescence are not fully understood. Fluorescence can originate from either the quantum states within the metal core or mixed ligand states at the inorganic-organic interface. We have presented compelling evidence that fluorescence from molecular silver glutathionate nanoparticles has its origin in interfacial electronic states. Fluorescence spectra were found to be independent of size, with very similar wavelength and bandwidth, although the quantum yield was not. Excitation spectra indicated that the strongest fluorescence had its origin in that part of the spectrum that is dominated by ligand-related states. Further, excitations to strictly core states and to higher lying d-band states had little to no contribution to the fluorescence

  12. Understanding the high pressure properties of molecular solids and molecular surfaces deposited on hetrogeneous substrates

    Science.gov (United States)

    Etters, R. D.

    1985-01-01

    Work directed toward understanding the high pressure properties of molecular solids and molecular surfaces deposited on hetrogeneous substrates is reported. The motivation, apart from expanding our basic knowledge about these systems, was to understand and predict the properties of new materials synthesized at high pressure, including pressure induced metallic and superconducting states. As a consequence, information about the states of matter of the Jovian planets and their satellites, which are natural high pressure laboratories was also provided. The work on molecular surfaces and finite two and three dimensional clusters of atoms and molecules was connected with the composition and behavior of planetary atmospheres and on the processes involved in forming surface layers, which is vital to the development of composite materials and microcircuitry.

  13. Mixed 2D molecular systems: Mechanic, thermodynamic and dielectric properties

    Science.gov (United States)

    Beňo, Juraj; Weis, Martin; Dobročka, Edmund; Haško, Daniel

    2008-08-01

    Study of Langmuir monolayers consisting of stearic acid (SA) and dipalmitoylphosphatidylcholine (DPPC) molecules was done by surface pressure-area isotherms ( π- A), the Maxwell displacement current (MDC) measurement, X-ray reflectivity (XRR) and atomic force microscopy (AFM) to investigate the selected mechanic, thermodynamic and dielectric properties based on orientational structure of monolayers. On the base of π- A isotherms analysis we explain the creation of stable structures and found optimal monolayer composition. The dielectric properties represented by MDC generated monolayers were analyzed in terms of excess dipole moment, proposing the effect of dipole-dipole interaction. XRR and AFM results illustrate deposited film structure and molecular ordering.

  14. Mixed 2D molecular systems: Mechanic, thermodynamic and dielectric properties

    International Nuclear Information System (INIS)

    Study of Langmuir monolayers consisting of stearic acid (SA) and dipalmitoylphosphatidylcholine (DPPC) molecules was done by surface pressure-area isotherms (π-A), the Maxwell displacement current (MDC) measurement, X-ray reflectivity (XRR) and atomic force microscopy (AFM) to investigate the selected mechanic, thermodynamic and dielectric properties based on orientational structure of monolayers. On the base of π-A isotherms analysis we explain the creation of stable structures and found optimal monolayer composition. The dielectric properties represented by MDC generated monolayers were analyzed in terms of excess dipole moment, proposing the effect of dipole-dipole interaction. XRR and AFM results illustrate deposited film structure and molecular ordering

  15. Boron nitride ceramics from molecular precursors: synthesis, properties and applications.

    Science.gov (United States)

    Bernard, Samuel; Salameh, Chrystelle; Miele, Philippe

    2016-01-21

    Hexagonal boron nitride (h-BN) attracts considerable interest because its structure is similar to that of carbon graphite while it displays different properties which are of interest for environmental and green technologies. The polar nature of the B-N bond in sp(2)-bonded BN makes it a wide band gap insulator with different chemistry on its surface and particular physical and chemical properties such as a high thermal conductivity, a high temperature stability, a high resistance to corrosion and oxidation and a strong UV emission. It is chemically inert and nontoxic and has good environmental compatibility. h-BN also has enhanced physisorption properties due to the dipolar fields near its surface. Such properties are closely dependent on the processing method. Bottom-up approaches consist of transforming molecular precursors into non-oxide ceramics with retention of the structural units inherent to the precursor molecule. The purpose of the present review is to give an up-to-date overview on the most recent achievements in the preparation of h-BN from borazine-based molecular single-source precursors including borazine and 2,4,6-trichloroborazine through both vapor phase syntheses and methods in the liquid/solid state involving polymeric intermediates, called the Polymer-Derived Ceramics (PDCs) route. In particular, the effect of the chemistry, composition and architecture of the borazine-based precursors and derived polymers on the shaping ability as well as the properties of h-BN is particularly highlighted. PMID:26646607

  16. Density Functional Studies of Relativistic Effects on Molecular Properties

    OpenAIRE

    Wood, Hayley Marie

    2013-01-01

    Relativistic effects are extremely important for heavy atoms and heavy atom containing molecules. Therefore, a relativistic treatment is needed when calculating molecular properties of these species. The fully- relativistic Dirac treatment involves electronic and positronic wavefunctions and a very large basis set is required. This leads to calculations that are too costly and time-consuming for larger molecules. The Zeroth-Order Regular Approximation (ZORA) is an approximation to the Dirac a...

  17. Molecular Thermodynamic Modeling of Fluctuation Solution Theory Properties

    DEFF Research Database (Denmark)

    O’Connell, John P.; Abildskov, Jens

    2013-01-01

    Fluctuation Solution Theory provides relationships between integrals of the molecular pair total and direct correlation functions and the pressure derivative of solution density, partial molar volumes, and composition derivatives of activity coefficients. For dense fluids, the integrals follow a...... relatively simple corresponding-states behavior even for complex systems, show welldefined relationships for infinite dilution properties in complex and near-critical systems, allow estimation of mixed-solvent solubilities of gases and pharmaceuticals, and can be expressed by simple perturbation models for...

  18. Cold gas properties of the Herschel Reference Survey. II. Molecular and total gas scaling relations

    CERN Document Server

    Boselli, A; Boquien, M; Boissier, S; Catinella, B; Lagos, C; Saintonge, A

    2014-01-01

    We study the properties of the cold gas component of the interstellar medium of the Herschel Reference Survey, a complete volume-limited (15 10^10 Mo) from the COLD GASS survey down to stellar masses M* ~ 10^9 Mo. As scaling variables we use M*, the stellar surface density mu*, the specific star formation rate SSFR, and the metallicity of the target galaxies. By comparing molecular gas masses determined using a constant or a luminosity dependent conversion factor, we estimate the robustness of these scaling relations on the very uncertain assumptions used to transform CO line intensities into molecular gas masses. The molecular gas distribution of a K-band-selected sample is different from that of a far-infrared-selected sample since it includes a significantly smaller number of objects with M(H2) < 6 10^9 Mo. In spiral galaxies the molecular gas phase is only 25-30% of the atomic gas. The analysis also indicates that the slope of the main scaling relations depends on the adopted conversion factor. Among t...

  19. Adoption procedures

    OpenAIRE

    Marie Arendt

    1980-01-01

    In early Eastern Greek and Roman civilisations, a childless couple adopted a child to provide a direct heir or to perpetuate domestic ancestral worship, and in later centuries adoption was used to solve the problem of illegitimacy. Although the child often benefitted from adoption, it was used primarily as a means of giving a child to a family in the interests of the adults involved. Today, adoption is still used to smooth problems of rights and inheritance of the child, but it has also becom...

  20. Controllable molecular aggregation and fluorescence properties of 1,3,4-oxadiazole derivative

    KAUST Repository

    Li, Min

    2015-10-14

    The molecular self-assembly behaviour of 2,2’-Bis-(4-hexyloxyphenyl)-bi-1,3,4-oxadiazole (BOXD-6) in solution, on surfaces and in bulk crystals, and its photo-physical properties were studied via a combination of experimental techniques and theoretical calculations. It is found that BOXD-6 molecules self-assemble into both H- and J-aggregates at moderate concentration (~10-4 M) and then transit to exclusive J-aggregates at higher concentration (~10-3 M) in tetrahydrofuran. In H-aggregation (α polymorph), BOXD-6 adopts a linear conformation and forms a one- dimensional layered structure; in J-aggregation (β polymorph), it adopts a Z-shaped conformation and form a more ordered two-dimensional layered structure. A π-stacking structure is observed in both cases, and adjacent molecules in the J-aggregation show larger displacement along the molecular long axis direction than that in H-aggregation. Although J-aggregates are almost the only component in concentrated solutions (10-3 M), both H- and J-aggregates can be obtained if concentrated solution is transformed onto substrates through a simple drop-casting method. Such a phase transition during film formation can be easily avoided by adding water as precipitator; a film with pure J-aggregates is then obtained. In order to get more information on molecular self-assembly, intermolecular interaction potential energy surfaces (PES) were evaluated via theoretical calculations at the DFT level (M062x/6-31G**). The PES not only confirm the molecular stacking structures found in crystals but also predict some other likely structures, which will be the target of future experiments.

  1. ms2: A molecular simulation tool for thermodynamic properties

    Science.gov (United States)

    Deublein, Stephan; Eckl, Bernhard; Stoll, Jürgen; Lishchuk, Sergey V.; Guevara-Carrion, Gabriela; Glass, Colin W.; Merker, Thorsten; Bernreuther, Martin; Hasse, Hans; Vrabec, Jadran

    2011-11-01

    This work presents the molecular simulation program ms2 that is designed for the calculation of thermodynamic properties of bulk fluids in equilibrium consisting of small electro-neutral molecules. ms2 features the two main molecular simulation techniques, molecular dynamics (MD) and Monte-Carlo. It supports the calculation of vapor-liquid equilibria of pure fluids and multi-component mixtures described by rigid molecular models on the basis of the grand equilibrium method. Furthermore, it is capable of sampling various classical ensembles and yields numerous thermodynamic properties. To evaluate the chemical potential, Widom's test molecule method and gradual insertion are implemented. Transport properties are determined by equilibrium MD simulations following the Green-Kubo formalism. ms2 is designed to meet the requirements of academia and industry, particularly achieving short response times and straightforward handling. It is written in Fortran90 and optimized for a fast execution on a broad range of computer architectures, spanning from single processor PCs over PC-clusters and vector computers to high-end parallel machines. The standard Message Passing Interface (MPI) is used for parallelization and ms2 is therefore easily portable to different computing platforms. Feature tools facilitate the interaction with the code and the interpretation of input and output files. The accuracy and reliability of ms2 has been shown for a large variety of fluids in preceding work. Program summaryProgram title:ms2 Catalogue identifier: AEJF_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEJF_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Special Licence supplied by the authors No. of lines in distributed program, including test data, etc.: 82 794 No. of bytes in distributed program, including test data, etc.: 793 705 Distribution format: tar.gz Programming language: Fortran90 Computer: The

  2. Mechanical Properties of Gelatin Gels; Effect of Molecular Weight and Molecular Weight Distribution

    OpenAIRE

    Jonhard, Eysturskarð

    2010-01-01

    The goal of the gelatin manufacturer is to partial hydrolyze the covalent cross-linkages that organize the collagen molecules into a quarter staggered arrangement found in connective tissue, to minimize the hydrolysis of the peptide bonds and to obtain the appropriate molecular weigh distribution (MWD) for a specific application.The mechanical properties of the resulting gelatin are known to be influenced by the tissues and species from which it is produced as well as the pretreatment and ext...

  3. Unexpected Molecular Sieving Properties of Zeolitic Imidazolate Framework-8

    KAUST Repository

    Zhang, Chen

    2012-08-16

    We studied molecular sieving properties of zeolitic imidazolate framework-8 (ZIF-8) by estimating the thermodynamically corrected diffusivities of probe molecules at 35 °C. From helium (2.6 Å) to iso-C 4H 10 (5.0 Å), the corrected diffusivity drops 14 orders of magnitude. Our results further suggest that the effective aperture size of ZIF-8 for molecular sieving is in the range of 4.0 to 4.2 Å, which is significantly larger than the XRD-derived value (3.4 Å) and between the well-known aperture size of zeolite 4A (3.8 Å) and 5A (4.3 Å). Interestingly, because of aperture flexibility, the studied C 4 hydrocarbon molecules that are larger than this effective aperture size still adsorb in the micropores of ZIF-8 with kinetic selectivities for iso-C 4H 8/iso-C 4H 10 of 180 and n-C 4H 10/iso-C 4H 10 of 2.5 × 10 6. These unexpected molecular sieving properties open up new opportunities for ZIF materials for separations that cannot be economically achieved by traditional microporous adsorbents such as synthetic zeolites. © 2012 American Chemical Society.

  4. Molecular structure based property modeling: Development/ improvement of property models through a systematic property-data-model analysis

    DEFF Research Database (Denmark)

    Hukkerikar, Amol Shivajirao; Sarup, Bent; Sin, Gürkan;

    2013-01-01

    models. To make the property-data-model analysis fast and efficient, an approach based on the “molecular structure similarity criteria” to identify molecules (mono-functional, bi-functional, etc.) containing specified set of structural parameters (that is, groups) is employed. The method has been applied......The objective of this work is to develop a method for performing property-data-model analysis so that efficient use of knowledge of properties could be made in the development/improvement of property prediction models. The method includes: (i) analysis of property data and its consistency check...... to a wide range of properties of pure compounds. In this work, however, the application of the method is illustrated for the property modeling of normal melting point, enthalpy of fusion, enthalpy of formation, and critical temperature. For all the properties listed above, it has been possible to achieve...

  5. Liquid but Durable: Molecular Dynamics Simulations Explain the Unique Properties of Archaeal-Like Membranes

    Science.gov (United States)

    Chugunov, Anton O.; Volynsky, Pavel E.; Krylov, Nikolay A.; Boldyrev, Ivan A.; Efremov, Roman G.

    2014-12-01

    Archaeal plasma membranes appear to be extremely durable and almost impermeable to water and ions, in contrast to the membranes of Bacteria and Eucaryota. Additionally, they remain liquid within a temperature range of 0-100°C. These are the properties that have most likely determined the evolutionary fate of Archaea, and it may be possible for bionanotechnology to adopt these from nature. In this work, we use molecular dynamics simulations to assess at the atomistic level the structure and dynamics of a series of model archaeal membranes with lipids that have tetraether chemical nature and ``branched'' hydrophobic tails. We conclude that the branched structure defines dense packing and low water permeability of archaeal-like membranes, while at the same time ensuring a liquid-crystalline state, which is vital for living cells. This makes tetraether lipid systems promising in bionanotechnology and material science, namely for design of new and unique membrane nanosystems.

  6. Prediction of Substrate-Enzyme-Product Interaction Based on Molecular Descriptors and Physicochemical Properties

    Directory of Open Access Journals (Sweden)

    Bing Niu

    2013-01-01

    Full Text Available It is important to correctly and efficiently predict the interaction of substrate-enzyme and to predict their product in metabolic pathway. In this work, a novel approach was introduced to encode substrate/product and enzyme molecules with molecular descriptors and physicochemical properties, respectively. Based on this encoding method, KNN was adopted to build the substrate-enzyme-product interaction network. After selecting the optimal features that are able to represent the main factors of substrate-enzyme-product interaction in our prediction, totally 160 features out of 290 features were attained which can be clustered into ten categories: elemental analysis, geometry, chemistry, amino acid composition, predicted secondary structure, hydrophobicity, polarizability, solvent accessibility, normalized van der Waals volume, and polarity. As a result, our predicting model achieved an MCC of 0.423 and an overall prediction accuracy of 89.1% for 10-fold cross-validation test.

  7. Prediction of substrate-enzyme-product interaction based on molecular descriptors and physicochemical properties.

    Science.gov (United States)

    Niu, Bing; Huang, Guohua; Zheng, Linfeng; Wang, Xueyuan; Chen, Fuxue; Zhang, Yuhui; Huang, Tao

    2013-01-01

    It is important to correctly and efficiently predict the interaction of substrate-enzyme and to predict their product in metabolic pathway. In this work, a novel approach was introduced to encode substrate/product and enzyme molecules with molecular descriptors and physicochemical properties, respectively. Based on this encoding method, KNN was adopted to build the substrate-enzyme-product interaction network. After selecting the optimal features that are able to represent the main factors of substrate-enzyme-product interaction in our prediction, totally 160 features out of 290 features were attained which can be clustered into ten categories: elemental analysis, geometry, chemistry, amino acid composition, predicted secondary structure, hydrophobicity, polarizability, solvent accessibility, normalized van der Waals volume, and polarity. As a result, our predicting model achieved an MCC of 0.423 and an overall prediction accuracy of 89.1% for 10-fold cross-validation test. PMID:24455714

  8. Machine learning of molecular electronic properties in chemical compound space

    International Nuclear Information System (INIS)

    The combination of modern scientific computing with electronic structure theory can lead to an unprecedented amount of data amenable to intelligent data analysis for the identification of meaningful, novel and predictive structure–property relationships. Such relationships enable high-throughput screening for relevant properties in an exponentially growing pool of virtual compounds that are synthetically accessible. Here, we present a machine learning model, trained on a database of ab initio calculation results for thousands of organic molecules, that simultaneously predicts multiple electronic ground- and excited-state properties. The properties include atomization energy, polarizability, frontier orbital eigenvalues, ionization potential, electron affinity and excitation energies. The machine learning model is based on a deep multi-task artificial neural network, exploiting the underlying correlations between various molecular properties. The input is identical to ab initio methods, i.e. nuclear charges and Cartesian coordinates of all atoms. For small organic molecules, the accuracy of such a ‘quantum machine’ is similar, and sometimes superior, to modern quantum-chemical methods—at negligible computational cost. (paper)

  9. Adoption procedures

    Directory of Open Access Journals (Sweden)

    Marie Arendt

    1980-09-01

    Full Text Available In early Eastern Greek and Roman civilisations, a childless couple adopted a child to provide a direct heir or to perpetuate domestic ancestral worship, and in later centuries adoption was used to solve the problem of illegitimacy. Although the child often benefitted from adoption, it was used primarily as a means of giving a child to a family in the interests of the adults involved. Today, adoption is still used to smooth problems of rights and inheritance of the child, but it has also become, much more, a way of giving a family to a child who needs substitute parents from whom he can receive the love and nurture which are so necessary for his full development.

  10. Intercountry adoption

    OpenAIRE

    International Child Development Centre

    2007-01-01

    This Digest looks at intercountry adoption as one of a series of possible solutions for children unable to live with their families. Broadly accepted international instruments specify the conditions under which intercountry adoption should be undertaken if the rights and best interests of the children concerned are to be protected and fully respected. Although substantial efforts are being made to implement the standards and procedures set, current practices are often in violation of these no...

  11. Molecular properties,functions,and potential applications of NAD kinases

    Institute of Scientific and Technical Information of China (English)

    Feng Shi; Yongfu Li; Ye Li; Xiaoyuan Wang

    2009-01-01

    NAD kinase catalyzes the phosphorylation of NAD(H)to form NADP(H),using ATP as phosphoryl donor.It is the only key enzyme leading to the de novo NADP+/NADPH biosynthesis.Coenzymes such as NAD(H)and NADP(H)are known for their important functions.Recent studies have partially demonstrated that NAD kinase plays a crucial role in the regulation of NAD(H)/NADP(H)conversion.Here,the molecular properties,physiologic functions,and potential applications of NAD kinase are discussed.

  12. Nonlinear thermoelectric properties of molecular junctions with vibrational coupling

    DEFF Research Database (Denmark)

    Leijnse, Martin Christian; Wegewijs, M. R.; Flensberg, Karsten

    2010-01-01

    We present a detailed study of the nonlinear thermoelectric properties of a molecular junction, represented by a dissipative Anderson-Holstein model. A single-orbital level with strong Coulomb interaction is coupled to a localized vibrational mode and we account for both electron and phonon...... exchange with both electrodes, investigating how these contribute to the heat and charge transports. We calculate the efficiency and power output of the device operated as a heat to electric power converter in the regime of weak tunnel coupling and phonon exchange rate and identify the optimal operating...

  13. Three decades of structure- and property-based molecular design

    DEFF Research Database (Denmark)

    Müller, Klaus

    2014-01-01

    Roche has pioneered structure- and property-based molecular design to drug discovery. While this is an ongoing development, the past three decades feature key events that have revolutionized the way drug discovery is conducted in Big Pharma industry. It has been a great privilege to have been...... of bioinformatics. It describes the strategic shift to large compound libraries and high-throughput screening with the development of novel compound storage and ultra-high-throughput screening facilities, as well as the strategic return to focused screening of small motif-based compound libraries...

  14. Molecular Properties of Red Wine Compounds and Cardiometabolic Benefits

    Science.gov (United States)

    Markoski, Melissa M.; Garavaglia, Juliano; Oliveira, Aline; Olivaes, Jessica; Marcadenti, Aline

    2016-01-01

    Wine has been used since the dawn of human civilization. Despite many health benefits, there is still a lot of discussion about the real properties of its components and its actions on cells and molecular interactions. A large part of these issues permeate the fine line between the amount of alcohol that causes problems to organic systems and the amount that could be beneficial for the health. However, even after the process of fermentation, wine conserves different organic compounds from grapes, such as polysaccharides, acids, and phenolic compounds, such as flavonoids and nonflavonoids. These substances have known anti-inflammatory and antioxidant capacities, and are considered as regulatory agents in cardiometabolic process. In this study, the main chemical components present in the wine, its interaction with molecules and biological mechanisms, and their interference with intra- and extracellular signaling are reviewed. Finally, the properties of wine that may benefit cardiovascular system are also revised. PMID:27512338

  15. Properties of the molecular oxygen trimer from pairwise additive interactions

    International Nuclear Information System (INIS)

    Graphical abstract: The two lowest lying isomers of the molecular oxygen trimer. Diffusion Monte Carlo calculations indicate that the small potential barrier between them is surmountable when including zero-point energy. Highlights: ► Accurate calculation of the lowest isomers of the (O2)3 open-shell molecular trimer. ► Analysis of trimer structures in terms of dimer interactions. ► Analysis of vibrational ground state via accurate Diffusion Monte Carlo calculations. - Abstract: We report a theoretical study of the properties of the molecular oxygen trimer in its state of maximum spin multiplicity. The most stable structures for the complex were found using an accurate pair potential. Independent ab initio calculations on the trimer for selected geometries demonstrate the validity of this approximation and thus the small contribution of three-body effects. The three lowest structures found can be rationalized on the basis of the most stable dimer structures and possess C2, D3 and C2v point symmetries. The two lowest-lying structures are separated by only 0.6 meV and zero-point energy effects, which are sizable, reduce even further the gaps among the three structures studied. Diffusion Monte Carlo calculations indicate that the ground state vibrational wavefunction is mainly located around the C2 structure but also explores the D3 minimum, yielding a near oblate symmetric top with a binding energy of 32.1 meV.

  16. MICROSCOPIC HETEROGENEITY IN VISCOELASTIC PROPERTIES OF MOLECULAR ASSEMBLED SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Atsuomi Shundo; David P.Penaloza Jr; Keiji Tanaka

    2013-01-01

    An important step in understanding molecular assembled systems is to examine the structure and physical properties at various length scales and clarify the correlation between them.However,while the structures of these systems have been extensively studied from nanoscopic to macroscopic scales,their viscoelastic properties have been often limited to bulk rheological measurements.By using optical tweezers and particle tracking,we here show the local viscoelastic properties and their spatial distributions for the following systems:worm-like micelle solution,supramolecular hydrogel and lyotropic liquid crystal,which are formed by self-assembly of amphiphilic molecules in water.We found that all systems studied possessed a spatial heterogeneity in their viscoelastic properties and this was originated from the heterogeneous structures.It is interesting to note that there is the heterogeneity with the characteristic length scale of sub-micrometer or micrometer scale,thereby structures,although the systems are formed by molecules with nanometer size.The findings of these studies should lead to a better understanding of the dynamics of such systems.

  17. Mechanical Properties of Nanostructured Materials Determined Through Molecular Modeling Techniques

    Science.gov (United States)

    Clancy, Thomas C.; Gates, Thomas S.

    2005-01-01

    The potential for gains in material properties over conventional materials has motivated an effort to develop novel nanostructured materials for aerospace applications. These novel materials typically consist of a polymer matrix reinforced with particles on the nanometer length scale. In this study, molecular modeling is used to construct fully atomistic models of a carbon nanotube embedded in an epoxy polymer matrix. Functionalization of the nanotube which consists of the introduction of direct chemical bonding between the polymer matrix and the nanotube, hence providing a load transfer mechanism, is systematically varied. The relative effectiveness of functionalization in a nanostructured material may depend on a variety of factors related to the details of the chemical bonding and the polymer structure at the nanotube-polymer interface. The objective of this modeling is to determine what influence the details of functionalization of the carbon nanotube with the polymer matrix has on the resulting mechanical properties. By considering a range of degree of functionalization, the structure-property relationships of these materials is examined and mechanical properties of these models are calculated using standard techniques.

  18. Tuning the Electromechanical Properties of Single DNA Molecular Junctions.

    Science.gov (United States)

    Bruot, Christopher; Xiang, Limin; Palma, Julio L; Li, Yueqi; Tao, Nongjian

    2015-11-01

    Understanding the interplay between the electrical and mechanical properties of DNA molecules is important for the design and characterization of molecular electronic devices, as well as understanding the role of charge transport in biological functions. However, to date, force-induced melting has limited our ability to investigate the response of DNA molecular conductance to stretching. Here we present a new molecule-electrode linker based on a hairpin-like design, which prevents force-induced melting at the end of single DNA molecules during stretching by stretching both strands of the duplex evenly. We find that the new linker group gives larger conductance than previously measured DNA-electrode linkers, which attach to the end of one strand of the duplex. In addition to changing the conductance the new linker also stabilizes the molecule during stretching, increasing the length a single DNA molecule can be stretched before an abrupt decrease in conductance. Fitting these electromechanical properties to a spring model, we show that distortion is more evenly distributed across the single DNA molecule during stretching, and thus the electromechanical effects of the π-π coupling between neighboring bases is measured. PMID:26480049

  19. Structures and physicochemical properties of molecular aggregates of lipids

    International Nuclear Information System (INIS)

    Structures and physicochemical properties of lipids such as fatty acids, alcohols, acylglycerols and steroids in their two- or three-dimensional states were studied through the measurements of surface pressure (π), surface-molecular area (A), vapor-pressure osmosis, radioactivity (R), self-diffusion coefficient (D), density, viscosity, near-infrared spectroscopy (NIR), 13C-NMR spin-lattice relaxation time (T1), ESR, SEM, DSC, X-ray diffraction and small-angle neutron scattering (SANS). Following results are obtained: (1) π-A and R-A relationships indicate that the explanation, being widely believed, of the reaction occurred in the oleic acid or the trioleylglycerol monolayer on the aqueous KMnO4 solution is incorrect. (2) By using the LB film of 3H-labelled fatty acid, the upper limit of the neutrino mass was determined. In addition, by using the LB film of 14C-labelled fatty acid, a new type of crystal-transformation process was found, in which fatty-acid crystal transforms from its unstable state to its stable one by the transfer of the fatty acid molecules through the vapor phase. (3) Fatty acids always exist as their dimers in their liquid state and mostly in non-polar solvents; the dimers are the units of the molecular movements in the molten liquid and in solvents. T1 results clearly showed the internal molecular movements of the dimers. In addition, D and SANS results indicated that two different kinds of fatty acids in their binary mixture make only each homodimers. (4) Furthermore, the study on the liquid structure of fatty acids such as cis-6-, cis-9-, cis-11-, trans-9-octadecenoic acids and stearic acid indicated that these fatty-acid dimers construct the clusters resemble to the smectic-liquid crystal in the liquid state. The clusters determine the physicochemical properties of the liquid of the fatty acid. (author)

  20. Molecular mechanisms for maintenance of G-rich short tandem repeats capable of adopting G4 DNA structures

    International Nuclear Information System (INIS)

    Mammalian genomes contain several types of repetitive sequences. Some of these sequences are implicated in various specific cellular events, including meiotic recombination, chromosomal breaks and transcriptional regulation, and also in several human disorders. In this review, we document the formation of DNA secondary structures by the G-rich repetitive sequences that have been found in several minisatellites, telomeres and in various triplet repeats, and report their effects on in vitro DNA synthesis. d(GGCAG) repeats in the mouse minisatellite Pc-1 were demonstrated to form an intra-molecular folded-back quadruplex structure (also called a G4' structure) by NMR and CD spectrum analyses. d(TTAGGG) telomere repeats and d(CGG) triplet repeats were also shown to form G4' and other unspecified higher order structures, respectively. In vitro DNA synthesis was substantially arrested within the repeats, and this could be responsible for the preferential mutability of the G-rich repetitive sequences. Electrophoretic mobility shift assays using NIH3T3 cell extracts revealed heterogeneous nuclear ribonucleoprotein (hnRNP) A1 and A3, which were tightly and specifically bound to d(GGCAG) and d(TTAGGG) repeats with K d values in the order of nM. HnRNP A1 unfolded the G4' structure formed in the d(GGCAG) n and d(TTAGGG) n repeat regions, and also resolved the higher order structure formed by d(CGG) triplet repeats. Furthermore, DNA synthesis arrest at the secondary structures of d(GGCAG) repeats, telomeres and d(CGG) triplet repeats was efficiently repressed by the addition of hnRNP A1. High expression of hnRNPs may contribute to the maintenance of G-rich repetitive sequences, including telomere repeats, and may also participate in ensuring the stability of the genome in cells with enhanced proliferation. Transcriptional regulation of genes, such as c-myc and insulin, by G4 sequences found in the promoter regions could be an intriguing field of research and help further

  1. Synthesis of one-dimensional metal-containing insulated molecular wire with versatile properties directed toward molecular electronics materials.

    Science.gov (United States)

    Masai, Hiroshi; Terao, Jun; Seki, Shu; Nakashima, Shigeto; Kiguchi, Manabu; Okoshi, Kento; Fujihara, Tetsuaki; Tsuji, Yasushi

    2014-02-01

    We report, herein, the design, synthesis, and properties of new materials directed toward molecular electronics. A transition metal-containing insulated molecular wire was synthesized through the coordination polymerization of a Ru(II) porphyrin with an insulated bridging ligand of well-defined structure. The wire displayed not only high linearity and rigidity, but also high intramolecular charge mobility. Owing to the unique properties of the coordination bond, the interconversion between the monomer and polymer states was realized under a carbon monoxide atmosphere or UV irradiation. The results demonstrated a high potential of the metal-containing insulated molecular wire for applications in molecular electronics. PMID:24428791

  2. Property-optimized Gaussian basis sets for molecular response calculations

    Science.gov (United States)

    Rappoport, Dmitrij; Furche, Filipp

    2010-10-01

    With recent advances in electronic structure methods, first-principles calculations of electronic response properties, such as linear and nonlinear polarizabilities, have become possible for molecules with more than 100 atoms. Basis set incompleteness is typically the main source of error in such calculations since traditional diffuse augmented basis sets are too costly to use or suffer from near linear dependence. To address this problem, we construct the first comprehensive set of property-optimized augmented basis sets for elements H-Rn except lanthanides. The new basis sets build on the Karlsruhe segmented contracted basis sets of split-valence to quadruple-zeta valence quality and add a small number of moderately diffuse basis functions. The exponents are determined variationally by maximization of atomic Hartree-Fock polarizabilities using analytical derivative methods. The performance of the resulting basis sets is assessed using a set of 313 molecular static Hartree-Fock polarizabilities. The mean absolute basis set errors are 3.6%, 1.1%, and 0.3% for property-optimized basis sets of split-valence, triple-zeta, and quadruple-zeta valence quality, respectively. Density functional and second-order Møller-Plesset polarizabilities show similar basis set convergence. We demonstrate the efficiency of our basis sets by computing static polarizabilities of icosahedral fullerenes up to C720 using hybrid density functional theory.

  3. A molecular dynamics study on surface properties of supercooled water

    Institute of Scientific and Technical Information of China (English)

    L(U) Yongjun; WEI Bingbo

    2006-01-01

    Molecular dynamics simulations were performed to study the surface properties of water in a temperature range from 228 to 293 K by using the extended simple point charge (SPC/E) and four-site TIP4P potentials. The calculated surface tension increases with the decrease of temperature, and moreover the slopes of the surface tension-temperature curves show a weak rise below 273 K, whereas no obvious anomalies appear near 228 K, which accords with the previous experiments. Compared with the measured values, the SPC/E potential shows a good agreement, and the TIP4P potential scription of the surface structure of supercooled water for the SPC/E. When simulating the orientational distributions of water molecules near the surface, the SPC/E potential produces higher ordering and larger surface potentials than the TIP4P potential.

  4. Gd doped Au nanoclusters: Molecular magnets with novel properties

    KAUST Repository

    Mokkath, Junais Habeeb

    2014-01-01

    The structural, magnetic, and optical properties of subnanometer Au N and AuN-1Gd1 gas phase clusters (N = 2 to 8) are systematically investigated in the framework of (time-dependent) density functional theory, using the B3LYP hybrid exchange correlation functional. The size dependent evolution of the gap between the highest occupied and lowest unoccupied molecular orbitals, the magnetism, and the absorption spectra are studied. The simultaneous appearance of large magnetic moments, significant band gaps, and plasmon resonances in the visible spectral region leads to novel multi-functional nanomaterials for applications in drug delivery, magnetic resonance imaging, and photo-responsive agents. © 2013 Elsevier B.V. All rights reserved.

  5. Ferroelectricity in molecular solids: a review of electrodynamic properties.

    Science.gov (United States)

    Tomić, S; Dressel, M

    2015-09-01

    In conventional ferroelectrics the polarization is induced either by the relative displacement of positive and negative ions due to a lattice distortion or by the collective alignment of permanent electric dipoles. Strongly correlated materials with the inversion-symmetry-broken ground states feature electronic ferroelectricity, a phenomenon which has recently caught the attention of condensed matter physicists due to its great fundamental and technological importance. The discovery of electronic ferroelectricity in one and two-dimensional molecular solids is an exciting development because they show a rich variety of nonlinear properties and complex electrodynamics, including nontrivial emergent excitations. We summarize key experimental results, sketch the current theoretical understanding and outline promising prospects of this phenomenon which have great potential for future electronic devices. PMID:26214019

  6. Anisotropic mechanical properties of graphene: a molecular dynamics study

    Science.gov (United States)

    Yu, Ming; Zeng, Anna; Zeng, Kevin

    2014-03-01

    The anisotropic mechanical properties of monolayer graphene with different shapes have been studied using an efficient quantum mechanics molecular dynamics scheme based on a semi-empirical Hamiltonian (refereed as SCED-LCAO) [PRB 74, 15540; PHYSE 42, 1]. We have found the anisotropic nature of the membrane stress. The stresses along the armchair direction are slightly stronger than that along the zigzag direction, showing strong direction selectivity. The graphene with the rectangular shape could sustain strong load (i . e ., 20%) in both armchair and zigzag directions. The graphene with the rhombus shape show large difference in the strain direction: it will quickly crack after 18 % of strain in armchair the direction, but slowly destroyed after 20% in the zigzag direction. The obtained 2D Young's modulus at infinitesimal strain and the third-order (effective nonlinear) elastic modulus are in good consistent with the experimental observation.

  7. Properties of the molecular oxygen trimer from pairwise additive interactions

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Lamoneda, Ramon, E-mail: ramon@uaem.mx [Centro de Investigaciones Quimicas, Universidad Autonoma del Estado de Morelos, 62210 Cuernavaca, Mor. (Mexico); Perez-Rios, Jesus; Carmona-Novillo, Estela; Bartolomei, Massimiliano; Campos-Martinez, Jose [Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas (IFF-CSIC), Serrano 123, 28006 Madrid (Spain); Hernandez, Marta I., E-mail: marta@iff.csic.es [Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas (IFF-CSIC), Serrano 123, 28006 Madrid (Spain)

    2012-05-03

    Graphical abstract: The two lowest lying isomers of the molecular oxygen trimer. Diffusion Monte Carlo calculations indicate that the small potential barrier between them is surmountable when including zero-point energy. Highlights: Black-Right-Pointing-Pointer Accurate calculation of the lowest isomers of the (O{sub 2}){sub 3} open-shell molecular trimer. Black-Right-Pointing-Pointer Analysis of trimer structures in terms of dimer interactions. Black-Right-Pointing-Pointer Analysis of vibrational ground state via accurate Diffusion Monte Carlo calculations. - Abstract: We report a theoretical study of the properties of the molecular oxygen trimer in its state of maximum spin multiplicity. The most stable structures for the complex were found using an accurate pair potential. Independent ab initio calculations on the trimer for selected geometries demonstrate the validity of this approximation and thus the small contribution of three-body effects. The three lowest structures found can be rationalized on the basis of the most stable dimer structures and possess C{sub 2}, D{sub 3} and C{sub 2v} point symmetries. The two lowest-lying structures are separated by only 0.6 meV and zero-point energy effects, which are sizable, reduce even further the gaps among the three structures studied. Diffusion Monte Carlo calculations indicate that the ground state vibrational wavefunction is mainly located around the C{sub 2} structure but also explores the D{sub 3} minimum, yielding a near oblate symmetric top with a binding energy of 32.1 meV.

  8. Molecular mechanical properties of short-sequence peptide enzyme mimics.

    Science.gov (United States)

    Takahashi, Tsukasa; Vo Ngo, Bao C; Xiao, Leyang; Arya, Gaurav; Heller, Michael J

    2016-03-01

    While considerable attempts have been made to recreate the high turnover rates of enzymes using synthetic enzyme mimics, most have failed and only a few have produced minimal reaction rates that can barely be considered catalytic. One particular approach we have focused on is the use of short-sequence peptides that contain key catalytic groups in close proximity. In this study, we designed six different peptides and tested their ability to mimic the catalytic mechanism of the cysteine proteases. Acetylation and deacylation by Ellman's Reagent trapping experiments showed the importance of having phenylalanine groups surrounding the catalytic sites in order to provide greater proximity between the cysteine, histidine, and aspartate amino acid R-groups. We have also carried out all-atom molecular dynamics simulations to determine the distance between these catalytic groups and the overall mechanical flexibility of the peptides. We found strong correlations between the magnitude of fluctuations in the Cys-His distance, which determines the flexibility and interactions between the cysteine thiol and histidine imidazole groups, and the deacylation rate. We found that, in general, shorter Cys-His distance fluctuations led to a higher deacylation rate constant, implying that greater confinement of the two residues will allow a higher frequency of the acetyl exchange between the cysteine thiol and histidine imidazole R-groups. This may be the key to future design of peptide structures with molecular mechanical properties that lead to viable enzyme mimics. PMID:25921736

  9. Molecular structure and thermodynamic properties of scandium halides

    International Nuclear Information System (INIS)

    Experimental data on molecular constants of mono-, di- and trihalides of scandium, as well as di-scandium hexahalides of the composition ScXn and Sc2X6 (X = F - I; n = 1 - 3), have been analyzed. Specific features of the compounds molecule structure are considered. The values of molecular constants have been evaluated by the methods of statistical thermodynamics and thermodynamic properties of all scandium halides mentioned in the temperature range of 100 - 6000 K and 298.15 - 1000 K respectively for scandium monohalides and for di-, tri-, hexahalides have been calculated. The values of thermodynamic functions Cp Deg, Φ Deg (T), H Deg (T) - H Deg (0) at 298.15 K published for the first time equal respectively for ScF: 32.734; 192.186; 222.232; 8.958; for ScCl: 45.782; 203.351; 237.356; 10.138; for ScBr: 49.449; 215.090; 252.783; 11.238; for ScI: 42.605; 227.517; 265.635; 12.259

  10. Dust properties inside molecular clouds from coreshine modeling and observations

    CERN Document Server

    Lefèvre, Charlène; Juvela, Mika; Paladini, Roberta; Lallement, Rosine; Marshall, D J; Andersen, Morten; Bacmann, Aurore; Mcgee, Peregrine M; Montier, Ludovic; Noriega-Crespo, Alberto; Pelkonen, V -M; Ristorcelli, Isabelle; Steinacker, Jürgen

    2014-01-01

    Context. Using observations to deduce dust properties, grain size distribution, and physical conditions in molecular clouds is a highly degenerate problem. Aims. The coreshine phenomenon, a scattering process at 3.6 and 4.5 $\\mu$m that dominates absorption, has revealed its ability to explore the densest parts of clouds. We want to use this effect to constrain the dust parameters. The goal is to investigate to what extent grain growth (at constant dust mass) inside molecular clouds is able to explain the coreshine observations. We aim to find dust models that can explain a sample of Spitzer coreshine data. We also look at the consistency with near-infrared data we obtained for a few clouds. Methods. We selected four regions with a very high occurrence of coreshine cases: Taurus-Perseus, Cepheus, Chameleon and L183/L134. We built a grid of dust models and investigated the key parameters to reproduce the general trend of surface bright- nesses and intensity ratios of both coreshine and near-infrared observation...

  11. Magnetic and electronic properties of porphyrin-based molecular nanowires

    Directory of Open Access Journals (Sweden)

    Jia-Jia Zheng

    2016-01-01

    Full Text Available Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn. Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics.

  12. Magnetic and electronic properties of porphyrin-based molecular nanowires

    International Nuclear Information System (INIS)

    Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn). Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics

  13. Magnetic and electronic properties of porphyrin-based molecular nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Jia-Jia; Li, Qiao-Zhi; Dang, Jing-Shuang; Zhao, Xiang, E-mail: xzhao@mail.xjtu.edu.cn [Institute for Chemical Physics & Department of Chemistry, MOE Key Laboratory for Non-equilibrium Condensed Matter and Quantum Engineering, School of Science, Xi’an Jiaotong University, Xi’an 710049 (China); Wang, Wei-Wei [Research Center for Computational Science, Institute for Molecular Science, Okazaki, Aichi 444-8585 (Japan)

    2016-01-15

    Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn). Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics.

  14. Critical Assessment of the Performance of Density Functional Methods for Several Atomic and Molecular Properties

    OpenAIRE

    Riley, Kevin E.; Op’t Holt, Bryan T.; Merz, Kenneth M.

    2007-01-01

    The reliable prediction of molecular properties is a vital task of computational chemistry. In recent years, density functional theory (DFT) has become a popular method for calculating molecular properties for a vast array of systems varying in size from small organic molecules to large biological compounds such as proteins. In this work we assess the ability of many DFT methods to accurately determine atomic and molecular properties for small molecules containing elements commonly found in p...

  15. Structural and electronic properties of Diisopropylammonium bromide molecular ferroelectric crystal

    Science.gov (United States)

    Alsaad, A.; Qattan, I. A.; Ahmad, A. A.; Al-Aqtash, N.; Sabirianov, R. F.

    2015-10-01

    We report the results of ab-initio calculations based on Generalized Gradient Approximation (GGA) and hybrid functional (HSE06) of electronic band structure, density of states and partial density of states to get a deep insight into structural and electronic properties of P21 ferroelectric phase of Diisopropylammonium Bromide molecular crystal (DIPAB). We found that the optical band gap of the polar phase of DIPAB is ∼ 5 eV confirming it as a good dielectric. Examination of the density of states and partial density of states reveal that the valence band maximum is mainly composed of bromine 4p orbitals and the conduction band minimum is dominated by carbon 2p, carbon 2s, and nitrogen 2s orbitals. A unique aspect of P21 ferroelectric phase is the permanent dipole within the material. We found that P21 DIPAB has a spontaneous polarization of 22.64 consistent with recent findings which make it good candidate for the creation of ferroelectric tunneling junctions (FTJs) which have the potential to be used as memory devices.

  16. Characterization-Based Molecular Design of Bio-Fuel Additives Using Chemometric and Property Clustering Techniques

    OpenAIRE

    Subin eHada; Charles Conrad Solvason; Mario Richard Eden

    2014-01-01

    In this work, multivariate characterization data such as infrared spectroscopy was used as a source of descriptor data involving information on molecular architecture for designing structured molecules with tailored properties. Application of multivariate statistical techniques such as principal component analysis allowed capturing important features of the molecular architecture from enormous amount of complex data to build appropriate latent variable models. Combining the property clusterin...

  17. Study of effect of gamma radiation on molecular weight and mechanical properties of PHB and PHNV

    International Nuclear Information System (INIS)

    The effect of gamma radiation on molecular weight and mechanical properties (tensile and flexural) of PHB and PHBV samples was investigated. The values of stress and strain at the break point for both mechanical properties indicated that scission molecular reactions were predominant in PHB and PHBV samples submitted to gamma radiation. These results were confirmed by Size Exclusion Chromatography (SEC) analysis. (author)

  18. Cooperative effects enhance the transport properties of molecular spider teams

    CERN Document Server

    Rank, Matthias; Frey, Erwin

    2013-01-01

    Molecular spiders are synthetic molecular motors based on DNA nanotechnology. While natural molecular motors have evolved towards very high efficiency, it remains a major challenge to develop efficient designs for man-made molecular motors. Inspired by biological motor proteins like kinesin and myosin, molecular spiders comprise a body and several legs. The legs walk on a lattice that is coated with substrate which can be cleaved catalytically. We propose a novel molecular spider design in which n spiders form a team. Our theoretical considerations show that coupling several spiders together alters the dynamics of the resulting team significantly. Although spiders operate at a scale where diffusion is dominant, spider teams can be tuned to behave nearly ballistic, which results in fast and predictable motion. Based on the separation of time scales of substrate and product dwell times, we develop a theory which utilises equivalence classes to coarse-grain the micro-state space. In addition, we calculate diffus...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-12-31

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-11-01

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

  1. Computer modeling of properties of complex molecular systems

    International Nuclear Information System (INIS)

    Large molecular aggregates present important examples of strongly nonhomogeneous systems. We apply combined quantum mechanics / molecular mechanics approaches that assume treatment of a part of the system by quantum-based methods and the rest of the system with conventional force fields. Herein we illustrate these computational approaches by two different examples: (1) large-scale molecular systems mimicking natural photosynthetic centers, and (2) components of prospective solar cells containing titan dioxide and organic dye molecules. We demonstrate that modern computational tools are capable to predict structures and spectra of such complex molecular aggregates

  2. Properties of Molecular Gas in Star-Forming Galaxies at z˜1.4 with ALMA

    Science.gov (United States)

    Seko, A.; Ohta, K.; Hatsukade, B.; Yabe, K.

    2015-12-01

    We made CO(J=5-4) observations of 20 star-forming galaxies at z˜1.4 with ALMA to study properties of molecular gas with respect to the stellar mass and metallicity. Almost all of our sample galaxies are on the main sequence of star-forming galaxies at this redshift. Uniqueness of the sample is gas phase metallicity is known for each galaxy. The metallicities of our sample galaxies are derived from near-infrared spectroscopic observations with Subaru/FMOS. The ranges of metallicity (12+log(O/H)) and stellar mass are 8.2-8.9 and 4×10 9-4×1011 M⊙, respectively. The stellar mass range covers lower mass than that in previous studies. We detected CO emission lines from 11 galaxies. Molecular gas mass is derived by adopting metallicity-dependent CO-to-H2 conversion factor. The derived molecular gas masses of detected galaxies are (3-11)×1010 M⊙. The molecular gas mass fractions are 0.25-0.94, and the fraction is lower in a more massive galaxy or a galaxy with higher metallicity. However, it is difficult to conclude which of stellar mass and metallicity is a main cause for the relations. We try to constrain the inflow and outflow rate by using an analytic chemical evolution model.

  3. 知识产权纠纷的仲裁解决%Adoption of Arbitration in Intellectual Property Right Dispute

    Institute of Scientific and Technical Information of China (English)

    徐家力

    2012-01-01

    近年来知识产权纠纷越来越多,诉讼已经无法满足多元化解决纠纷的需求,仲裁、调解等纠纷解决方式大量涌现出来,对比以诉讼方式解决知识产权纠纷的不足,以仲裁方式解决知识产权纠纷有很多优点。但目前在我国,尽管仲裁机构得到一定发展,也以仲裁方式解决了一些知识产权纠纷,但诉讼依然是解决知识产权纠纷的主要方式。今后应创造更多条件,让仲裁、调解纠纷解决方式在解决知识产权纠纷中发挥越来越多的作用。%As the number of cases of intellectual property right dispute has become increasingly high in recent years,lawsuit can not meet the need of dispute solution,arbitration and mediation have emerged.In contrast with solution of lawsuit,the solution of arbitration has many advantages.Nevertheless,arbitration organization has improved and some intellectual property right cases have resolved with arbitration,lawsuit still is a main means of dispute solution.Arbitration and meditation should be encouraged from all aspects in solution of dispute of intellectual property right.

  4. Molecular Structural and Properties of 3-chloro-4 (dichloromethyl)-5-hydroxy-2 [5H] -furanone (MX)

    Institute of Scientific and Technical Information of China (English)

    李欣; 龙运前; 齐晶瑶; 王郁萍

    2004-01-01

    3 - chloro - 4 (dichloromethyl) - 5 - hydroxy - 2 [5H] - furanone (MX) formed during chlorination of water containing natural organic substances, is a very potent bacterial mutgen. Molecular mechanics calculations to evaluate the conformation of structure, and to determine structure relationship properties are put forward. The investigations allow the correlation of molecular structures of MX with its properties, such as mass,partial charges, steric energy, frontier molecular orbital. The VRML molecular models have been investigated using Virtual Reality software. The spectral simulation of MX is illustrated. The principal aim is to develop an efficient method which control of MX.

  5. Electronic properties of organic monolayers and molecular devices

    Indian Academy of Sciences (India)

    D Vuillaume; S Lenfant; D Guerin; C Delerue; C Petit; G Salace

    2006-07-01

    We review some of our recent experimental results on charge transport in organic nanostructures such as self-assembled monolayer and monolayers of organic semiconductors. We describe a molecular rectifying junction made from a sequential self-assembly on silicon. These devices exhibit a marked current–voltage rectification behavior due to resonant transport between the Si conduction band and the molecule highest occupied molecular orbital of the molecule. We discuss the role of metal Fermi level pinning in the current–voltage behavior of these molecular junctions. We also discuss some recent insights on the inelastic electron tunneling behavior of Si/alkyl chain/metal junctions.

  6. Preparation and Property Recognition of Nimodipine Molecularly Imprinted Polymer

    OpenAIRE

    Chen, Fei-Fei

    2015-01-01

    Objective: To explore the application of molecular imprinting technique in the separation and detection of nimodipine. Methods: Methacrylic acid as functional monomer, pentaerythritol triacrylate as cross-linking agent were used to prepare molecularly imprinted polymer (MIP) with the feature of specific recognition performance on imprinting molecule nimodipine under condition of template molecule nimodipine. The preparation conditions, recognition performance of MIP on nimodipine, different p...

  7. Improving the properties of GdBCO magnetic lenses by adopting a new design and resin impregnation

    International Nuclear Information System (INIS)

    High field concentration and magnetothermal stability are critical considerations when designing and fabricating magnetic lenses made from a stack of bulk high-temperature superconducting (HTS) material. In a previous study, we investigated a GdBCO magnetic lens for use as a compact high-field superconducting magnet, but it cracked due to a high flux jump. In the present study, we investigate the magnetic performance of an improved GdBCO lens. This new lens had almost the same dimensions as the previous one, but it was impregnated with epoxy resin to prevent it breaking. The impregnated lens exhibited superior stability and magnetic properties, making it promising for use in a compact magnet system. A maximum field of 13 T was obtained at 20 K with no flux jump. (paper)

  8. Delocalization error and "functional tuning" in Kohn-Sham calculations of molecular properties.

    Science.gov (United States)

    Autschbach, Jochen; Srebro, Monika

    2014-08-19

    Kohn-Sham theory (KST) is the "workhorse" of numerical quantum chemistry. This is particularly true for first-principles calculations of ground- and excited-state properties for larger systems, including electronic spectra, electronic dynamic and static linear and higher order response properties (including nonlinear optical (NLO) properties), conformational or dynamic averaging of spectra and response properties, or properties that are affected by the coupling of electron and nuclear motion. This Account explores the sometimes dramatic impact of the delocalization error (DE) and possible benefits from the use of long-range corrections (LC) and "tuning" of functionals in KST calculations of molecular ground-state and response properties. Tuning refers to a nonempirical molecule-specific determination of adjustable parameters in functionals to satisfy known exact conditions, for instance, that the energy of the highest occupied molecular orbital (HOMO) should be equal to the negative vertical ionization potential (IP) or that the energy as a function of fractional electron numbers should afford straight-line segments. The presentation is given from the viewpoint of a chemist interested in computations of a variety of molecular optical and spectroscopic properties and of a theoretician developing methods for computing such properties with KST. In recent years, the use of LC functionals, functional tuning, and quantifying the DE explicitly have provided valuable insight regarding the performance of KST for molecular properties. We discuss a number of different molecular properties, with examples from recent studies from our laboratory and related literature. The selected properties probe different aspects of molecular electronic structure. Electric field gradients and hyperfine coupling constants can be exquisitely sensitive to the DE because it affects the ground-state electron density and spin density distributions. For π-conjugated molecules, it is shown how the

  9. Time-dependent motor properties of multipedal molecular spiders

    Science.gov (United States)

    Samii, Laleh; Blab, Gerhard A.; Bromley, Elizabeth H. C.; Linke, Heiner; Curmi, Paul M. G.; Zuckermann, Martin J.; Forde, Nancy R.

    2011-09-01

    Molecular spiders are synthetic biomolecular walkers that use the asymmetry resulting from cleavage of their tracks to bias the direction of their stepping motion. Using Monte Carlo simulations that implement the Gillespie algorithm, we investigate the dependence of the biased motion of molecular spiders, along with binding time and processivity, on tunable experimental parameters, such as number of legs, span between the legs, and unbinding rate of a leg from a substrate site. We find that an increase in the number of legs increases the spiders’ processivity and binding time but not their mean velocity. However, we can increase the mean velocity of spiders with simultaneous tuning of the span and the unbinding rate of a spider leg from a substrate site. To study the efficiency of molecular spiders, we introduce a time-dependent expression for the thermodynamic efficiency of a molecular motor, allowing us to account for the behavior of spider populations as a function of time. Based on this definition, we find that spiders exhibit transient motor function over time scales of many hours and have a maximum efficiency on the order of 1%, weak compared to other types of molecular motors.

  10. Electron transport properties of single molecular junctions under mechanical modulations

    International Nuclear Information System (INIS)

    Electron transport behaviors of single molecular junctions are very sensitive to the atomic scale molecule-metal electrode contact interfaces, which have been difficult to control. We used a modified scanning probe microscope-break junction technique (SPM-BJT) to control the dynamics of the contacts and simultaneously monitor both the conductance and force. First, by fitting the measured data into a modified multiple tunneling barrier model, the static contact resistances, corresponding to the different contact conformations of single alkanedithiol and alkanediamine molecular junctions, were identified. Second, the changes of contact decay constant were measured under mechanical extensions of the molecular junctions, which helped to classify the different single molecular conductance sets into specific microscopic conformations of the molecule-electrode contacts. Third, by monitoring the changes of force and contact decay constant with the mechanical extensions, the changes of conductance were found to be caused by the changes of contact bond length and by the atomic reorganizations near the contact bond. This study provides a new insight into the understanding of the influences of contact conformations, especially the effect of changes of dynamic contact conformation on electron transport through single molecular junctions. (paper)

  11. Strengthening Adoption Practice, Listening to Adoptive Families

    Science.gov (United States)

    Atkinson, Anne; Gonet, Patricia

    2007-01-01

    In-depth interviews with 500 adoptive families who received postadoption services through Virginia's Adoptive Family Preservation (AFP) program paint a richly detailed picture of the challenges adoptive families face and what they need to sustain adoption for many years after finalization. Findings document the need for support in a variety of…

  12. Prediction of Transport Properties by Molecular Simulation: Methanol and Ethanol and their mixture

    OpenAIRE

    Guevara-Carrion, Gabriela; Nieto-Draghi, Carlos; Vrabec, Jadran; Hasse, Hans

    2009-01-01

    Transport properties of liquid methanol and ethanol are predicted by molecular dynamics simulation. The molecular models for the alcohols are rigid, non-polarizable and of united-atom type. They were developed in preceding work using experimental vapor-liquid equilibrium data only. Self- and Maxwell-Stefan diffusion coefficients as well as the shear viscosity of methanol, ethanol and their binary mixture are determined using equilibrium molecular dynamics and the Green-Kubo formalism. Non-equ...

  13. Cosmic rays as regulators of molecular cloud properties

    CERN Document Server

    Padovani, Marco; Galli, Daniele

    2014-01-01

    Cosmic rays are the main agents in controlling the chemical evolution and setting the ambipolar diffusion time of a molecular cloud. We summarise the processes causing the energy degradation of cosmic rays due to their interaction with molecular hydrogen, focusing on the magnetic effects that influence their propagation. Making use of magnetic field configurations generated by numerical simulations, we show that the increase of the field line density in the collapse region results in a reduction of the cosmic-ray ionisation rate. As a consequence the ionisation fraction decreases, facilitating the decoupling between the gas and the magnetic field.

  14. Elastic properties of surfactant monolayers at liquid-liquid interfaces: A molecular dynamics study

    DEFF Research Database (Denmark)

    Laradji, Mohamed; Mouritsen, Ole G.

    2000-01-01

    Using a simple molecular model based on the Lennard-Jones potential, we systematically study the elastic properties of liquid-liquid interfaces containing surfactant molecules by means of extensive and large-scale molecular dynamics simulations. The main elastic constants of the interface, corres...

  15. Optical properties and sensing in plexcitonic nanocavities: from simple molecular linkers to molecular aggregate layers

    International Nuclear Information System (INIS)

    We present a theoretical study of a metal–molecular aggregate hybrid system consisting of a strongly coupled dimer connected by molecules characterized by an excitonic transition. The plasmonic resonances of the metallic dimer interact with the molecular excitations giving rise to coupled plasmon–exciton states, so called plexcitons. We compare the differences in the optical response when the excitonic material is placed only as a linker in the plasmonic gap of the dimer and when the material is distributed as an aggregate layer covering the dimer entirely. We also explore the efficiency of plexcitons for localized surface plamon resonance (LSPR) sensing in both situations. The ordinary shift-based sensing is more efficient for dimers connected through molecular linkers, whereas intensity-based sensing is more effective when the molecular aggregate covers the entire nanostructure. These results can serve to design the chemistry of excitons around metallic nanoparticles. (paper)

  16. Statistical analysis of coding for molecular properties in the olfactory bulb

    Directory of Open Access Journals (Sweden)

    Benjamin eAuffarth

    2011-07-01

    Full Text Available The relationship between molecular properties of odorants and neural activities is arguably one of the most important issues in olfaction and the rules governing this relationship are still not clear. In the olfactory bulb (OB, glomeruli relay olfactory information to second-order neurons which in turn project to cortical areas. We investigate relevance of odorant properties, spatial localization of glomerular coding sites, and size of coding zones in a dataset of 2-deoxyglucose images of glomeruli over the entire OB of the rat. We relate molecular properties to activation of glomeruli in the OB using a nonparametric statistical test and a support-vector machine classification study. Our method permits to systematically map the topographic representation of various classes of odorants in the OB. Our results suggest many localized coding sites for particular molecular properties and some molecular properties that could form the basis for a spatial map of olfactory information. We found that alkynes, alkanes, alkenes, and amines affect activation maps very strongly as compared to other properties and that amines, sulfur-containing compounds, and alkynes have small zones and high relevance to activation changes, while aromatics, alkanes, and carboxylics acid recruit very big zones in the dataset. Results suggest a local spatial encoding for molecular properties.

  17. Electronic properties of single-molecule junction: Effect of the molecular distortion

    International Nuclear Information System (INIS)

    For a model system consisting of a benzenedithio (BDT) molecule sandwiched between two Au plates, the electronic properties as a function of different BDT geometry are investigated using density functional theory. The distorted BDT structures are got through stretching the electrode distance. The corresponding electronic properties, including the spatial distribution of the frontier orbits, the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital levels and density of states at the Fermi energy are determined. It reveals that the molecular distortion essentially determines electronic structures. The result should be beneficial to understand the stress-dependent or structure-dependent transport mechanism of electrons of the BDT junction.

  18. Transmission properties and molecular sensing application of CGPW.

    Science.gov (United States)

    Yang, Jianfeng; Yang, Jingjing; Deng, Wei; Mao, Fuchun; Huang, Ming

    2015-12-14

    In this paper, a cylindrical graphene plasmon waveguide (CGPW), which consists of two rolled graphene ribbons, a dielectric core and a dielectric interlayer is proposed, and its use for molecular sensing is investigated. First, an analytical model for the surface plasmon modes supported by this graphene geometry is presented and verified by finite element method simulations. Furthermore, we demonstrate a large tunability of the modes behavior by varying the Fermi level of the graphene, the coupling distance between the two sheets and the radius of the cylinder. Finally, a molecular sensing scheme based on the CGPW is proposed. Broadband spectroscopy of ethanol and toluene thin layers is realized by recording the changes in spectral intensity of the propagating mode. Due to the broadband localization capability of graphene plasmon mode which leads to a strong light-matter interaction in the midinfrared and terahertz regime, the proposed sensing scheme may provide an effective way for detecting nanometric-size molecules. PMID:26699019

  19. Local Correlation: Implementation and Application to Molecular Response Properties

    OpenAIRE

    Russ, Nicholas Joel

    2006-01-01

    One of the most promising methods for surmounting the high-degree polynomial scaling wall associated with electron correlating wave function methods is the local correlation technique of Pulay and Saebø. They have proposed using a set of localized occupied and virtual orbitals free of the canonical constraint commonly employed in quantum chemistry, resulting in a method that scales linearly (in the asymptotic limit) with molecular size. Pulay and Saeb$oslash; first applied their method...

  20. Molecular Dynamics Simulations of Poly(dimethylsiloxane) Properties

    Czech Academy of Sciences Publication Activity Database

    Fojtíková, J.; Kalvoda, L.; Sedlák, Petr

    2015-01-01

    Roč. 128, č. 4 (2015), s. 637-639. ISSN 0587-4246 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61388998 Keywords : molecular dynamics * poly(dimethylsiloxane) * dissipative particle dynamics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.530, year: 2014 http://przyrbwn.icm.edu.pl/APP/PDF/128/a128z4p40.pdf

  1. Molecular dynamics simulation of nanocrystalline nickel: structure and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Swygenhoven, H. van [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Caro, A. [Comision Nacional de Energia Atomica, San Carlos de Bariloche (Argentina). Centro Atomico Bariloche

    1997-09-01

    Molecular dynamics computer simulations of low temperature elastic and plastic deformation of Ni nanophase samples (3-7 nm) are performed. The samples are polycrystals nucleated from different seeds, with random locations and orientations. Bulk and Young`s modulus, onset of plastic deformation and mechanism responsible for the plastic behaviour are studied and compared with the behaviour of coarse grained samples. (author) 1 fig., 3 refs.

  2. Molecular properties of succinate dehydrogenase isolated from Micrococcus luteus (lysodeikticus).

    OpenAIRE

    Crowe, B A; Owen, P.(Imperial College London, London, United Kingdom)

    1983-01-01

    Succinate dehydrogenase (EC 1.3.99.1) of Micrococcus luteus was selectively precipitated from Triton X-100-solubilized membranes by using specific antiserum. The precipitated enzyme contained equimolar amounts of four polypeptides with apparent molecular weights of 72,000, 30,000, 17,000, and 15,000. The 72,000 polypeptide possessed a covalently bound flavin prosthetic group and appeared to be strongly antigenic as judged by immunoprinting experiments. Low-temperature absorption spectroscopy ...

  3. Radiation toxins: molecular mechanisms of action and radiomimetic properties .

    Science.gov (United States)

    Popov, Dmitri; Maliev, Vecheslav

    Introduction: Acute Radiation Disease (ARD) or Acute Radiation Syndromes (ARS) were defined as a toxic poisonous with development of the acute pathological processes in irradi-ated animals: systemic inflammatory response syndrome(SIRS), toxic multiple organ injury (TMOI), toxic multiple organ dysfunction syndromes (TMOD), toxic multiple organ failure (TMOF). However, the nature of radiation toxins, their mechanisms of formation, molecular structure, and mechanism of actions remain uncertain. Moderate and high doses of radiation induce apoptotic necrosis of radiosensitive cells with formation of Radiation Toxins and in-flammation development. Mild doses of radiation induce apoptosis or controlled programmed death of radiosensitive cells without Radiation Toxins formation and development of inflam-mation processes. Only radiation induced apoptotic necrosis initiates formation of Radiation Toxins(RT). Radiation Toxins are playing an important role as the trigger mechanisms for in-flammation development and cell lysis. The systemic inflammatory response syndrome after radiation involves an influence of various endogenous agents and mediators of inflammation such as bradykinin, histamine, serotonin and phospholipases activation, prostaglandins biosyn-thesis. Although, formation of non-specific toxins such as Reactive Oxygen Species (ROS) is an important pathological process at mild or high doses of radiation. Reactive Oxygen Species play an important role in molecules damage and development of peroxidation of lipids and pro-teins which are the structural parts of cell and mitochondrial membranes. ROS and bio-radicals induce damage of DNA and RNA and peroxidation of their molecules. But high doses of radia-tion, severe and extremely severe physiological stress, result in cells death by apoptotic necrosis and could be defined as the neuroimmune acute disease. Excitotoxicity is an important patho-logical mechanism which damages the central nervous system. We postulate that

  4. Synthesis and properties of ionic polyurethane dispersions: influence of polyol molecular weight

    International Nuclear Information System (INIS)

    A series of water dispersible polyurethanes containing carboxylate anion as the hydrophilic pendant group were prepared from toluene diisocyanate (TDI), 1,4- butanediol (1,4-BDO), dimethylol propionic acid and different molecular weight of polytetramethylene glycol . IR Spectroscopy was used to check the end of polymerization reaction and characterization of polymer. The effect of polytetramethylene glycol molecular weight was studied on the particle size distribution, contact angle, and mechanical and thermal properties of the emulsion-cast films. Average particle size of prepared polyurethane emulsions decreases with increasing the polytetramethylene glycol molecular weight. Tensile strength and hardness decrease and elongation-at-break and contact angle increase with increase of the polytetramethylene glycol molecular weight. Thermal property and thermal stability are also effected by variation of polytetramethylene glycol molecular weight. The thermal stability increases with increasing polytetramethylene glycol molecular weight. Glass transition temperature (Tg) moved toward the lower temperatures by increasing molecular weight of the polyol. Decrease in Tg and tensile properties are interpreted in terms of the decrease in hard segments and the increase in chain flexibility and phase separation in high molecular weight polytetramethylene glycol based polyurethane

  5. Aquifer vulnerability to pesticide pollution - Combining soil, land-use and aquifer properties with molecular descriptors

    Science.gov (United States)

    Worrall, F.; Kolpin, D.W.

    2004-01-01

    This study uses an extensive survey of herbicides in groundwater across the midwest United States to predict occurrences of a range of compounds across the region from a combination of their molecular properties and the properties of the catchment of a borehole. The study covers 100 boreholes and eight pesticides. For each of the boreholes its catchment the soil, land-use and aquifer properties were characterized. Discriminating boreholes where pollution occurred from those where no pollution occurred gave a model that was 74% correct with organic carbon content, percentage sand content and depth to the water table being significant properties of the borehole catchment. Molecular topological descriptors as well as Koc, solubility and half-life were used to characterize each compound included in the study. Inclusion of molecular properties makes it possible to discriminate between occurrence and non-occurrence of each compound in each well. The best-fit model combines: organic carbon content, percentage sand content and depth to the water table with molecular descriptors representing molecular size, molecular branching and functional group composition of the herbicides.

  6. A Quantitative Structure Property Relationship for Prediction of Flash Point of Alkanes Using Molecular Connectivity Indices

    Institute of Scientific and Technical Information of China (English)

    Morteza Atabati; Reza Emamalizadeh

    2013-01-01

    Many structure-property/activity studies use graph theoretical indices,which are based on the topological properties of a molecule viewed as a graph.Since topological indices can be derived directly from the molecular structure without any experimental effort,they provide a simple and straightforward method for property prediction.In this work the flash point of alkanes was modeled by a set of molecular connectivity indices (x),modified molecular connectivity indices (mx(1)h) and valance molecular connectivity indices (mxv),with mxv calculated using the hydrogen perturbation.A stepwise Multiple Linear Regression (MLR) method was used to select the best indices.The predicted flash points are in good agreement with the experimental data,with the average absolute deviation 4.3 K.

  7. Role of molecular properties of ulvans on their ability to elaborate antiadhesive surfaces.

    Science.gov (United States)

    Gadenne, Virginie; Lebrun, Laurent; Jouenne, Thierry; Thebault, Pascal

    2015-03-01

    Antiadhesive properties of polysaccharides (such ulvans) once immobilized on a surface are described in the literature but the parameters governing their antifouling properties are not yet well identified. In the present study, the relationship between molecular parameters of ulvans and the inhibition of bacterial adhesion was investigated. To this aim, various ulvans were grafted on silicon wafers under two different experimental immobilization conditions. Results showed that the experimental immobilization conditions and the polysaccharides molecular weight led to specific layer conformations which exhibited a key role in the surface antiadhesive properties. PMID:24890284

  8. Optical and transport properties of complex molecular systems

    OpenAIRE

    Díaz García, Elena

    2009-01-01

    Esta Tesis presenta el estudio de las propiedades ópticas y de transporte de sistemas de baja dimensionalidad a través de modelos de enlace fuerte. Nuestro trabajo se centra en dos tipos de sistemas: agregados moleculares lineales y moléculas de ADN.En los Capítulos 2, 3 y 4 se estudian las propiedades de localización de un Hamiltoniano de Frenkel desordenado unidimensional. El desorden se introduce en las energías de sitio y es correlacionado de largo alcance. Para correlaciones fuertes, se ...

  9. Molecular dynamics modelling of mechanical properties of polymers for adaptive aerospace structures

    Science.gov (United States)

    Papanikolaou, Michail; Drikakis, Dimitris; Asproulis, Nikolaos

    2015-02-01

    The features of adaptive structures depend on the properties of the supporting materials. For example, morphing wing structures require wing skin materials, such as rubbers that can withstand the forces imposed by the internal mechanism while maintaining the required aerodynamic properties of the aircraft. In this study, Molecular Dynamics and Minimization simulations are being used to establish well-equilibrated models of Ethylene-Propylene-Diene Monomer (EPDM) elastomer systems and investigate their mechanical properties.

  10. Prediction of molecular properties using graph-theoretical invariants

    International Nuclear Information System (INIS)

    study we intend to determine the biological action of certain alkylating agents, and to relate this data to one or more molecular descriptors. The compounds are ''similar'' in the sense that they each have a recognised mutagenic potency, and the employed molecular descriptors allow one to: (a) characterize the chemical structure quantitatively, (b) correlate the molecular descriptors with the determined mutagenic endpoints and (c) rank the chemical compounds and also reliably predict the action of other chemicals belonging to the same family, provided that data on the structure of these is available. (orig.)

  11. Anisotropic mechanical properties of graphene sheets from molecular dynamics

    International Nuclear Information System (INIS)

    Anisotropic mechanical properties are observed for a sheet of graphene along different load directions. The anisotropic mechanical properties are attributed to the hexagonal structure of the unit cells of the graphene. Under the same tensile loads, the edge bonds bear larger load in the longitudinal mode (LM) than in the transverse mode (TM), which causes fracture sooner in LM than in TM. The Young's modulus and the third order elastic modulus for the LM are slightly larger than that for the TM. Simulation also demonstrates that, for both LM and TM, the loading and unloading stress-strain response curves overlap as long as the graphene is unloaded before the fracture point. This confirms that graphene sustains complete elastic and reversible deformation in the elongation process.

  12. Calculating atomic and molecular properties using variational Monte Carlo methods

    International Nuclear Information System (INIS)

    The authors compute a number of properties for the 1 1S, 21S, and 23S states of helium as well as the ground states of H2 and H/+3 using Variational Monte Carlo. These are in good agreement with previous calculations (where available). Electric-response constants for the ground states of helium, H2 and H+3 are computed as derivatives of the total energy. The method used to calculate these quantities is discussed in detail

  13. Physical Properties and Galactic Distribution of Molecular Clouds identified in the Galactic Ring Survey

    CERN Document Server

    Roman-Duval, Julia; Heyer, Mark; Rathborne, Jill; Simon, Robert

    2010-01-01

    We derive the physical properties of 580 molecular clouds based on their 12CO and 13CO line emission detected in the University of Massachusetts-Stony Brook (UMSB) and Galactic Ring surveys. We provide a range of values of the physical properties of molecular clouds, and find a power-law correlation between their radii and masses, suggesting that the fractal dimension of the ISM is around 2.36. This relation, M = (228 +/- 18) R^{2.36+/-0.04}, allows us to derive masses for an additional 170 GRS molecular clouds not covered by the UMSB survey. We derive the Galactic surface mass density of molecular gas and examine its spatial variations throughout the Galaxy. We find that the azimuthally averaged Galactic surface density of molecular gas peaks between Galactocentric radii of 4 and 5 kpc. Although the Perseus arm is not detected in molecular gas, the Galactic surface density of molecular gas is enhanced along the positions of the Scutum-Crux and Sagittarius arms. This may indicate that molecular clouds form in...

  14. Accurate modeling of molecular optical properties by a combination of molecular dynamics and quantum chemistry

    Czech Academy of Sciences Publication Activity Database

    Andrushchenko, Valery; Bouř, Petr

    Katowice : University of Silesia, 2014. O6. [Chemistry towards Biology. Central Europe Conference /7./. 09.09.2014-12.09.2014, Katowice] R&D Projects: GA ČR(CZ) GA14-03564S Grant ostatní: AV ČR(CZ) M200550902 Institutional support: RVO:61388963 Keywords : molecular dynamics * quantum chemistry * multi-scale spectra Subject RIV: CF - Physical ; Theoretical Chemistry

  15. Tuning spin transport properties and molecular magnetoresistance through contact geometry

    Energy Technology Data Exchange (ETDEWEB)

    Ulman, Kanchan [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Narasimhan, Shobhana [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Sheikh Saqr Laboratory, ICMS, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064 (India); Delin, Anna [Department of Materials and Nanophysics, School of Information and Communication Technology, Electrum 229, Royal Institute of Technology (KTH), SE-16440 Kista (Sweden); Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); SeRC (Swedish e-Science Research Center), KTH, SE-10044 Stockholm (Sweden)

    2014-01-28

    Molecular spintronics seeks to unite the advantages of using organic molecules as nanoelectronic components, with the benefits of using spin as an additional degree of freedom. For technological applications, an important quantity is the molecular magnetoresistance. In this work, we show that this parameter is very sensitive to the contact geometry. To demonstrate this, we perform ab initio calculations, combining the non-equilibrium Green's function method with density functional theory, on a dithienylethene molecule placed between spin-polarized nickel leads of varying geometries. We find that, in general, the magnetoresistance is significantly higher when the contact is made to sharp tips than to flat surfaces. Interestingly, this holds true for both resonant and tunneling conduction regimes, i.e., when the molecule is in its “closed” and “open” conformations, respectively. We find that changing the lead geometry can increase the magnetoresistance by up to a factor of ∼5. We also introduce a simple model that, despite requiring minimal computational time, can recapture our ab initio results for the behavior of magnetoresistance as a function of bias voltage. This model requires as its input only the density of states on the anchoring atoms, at zero bias voltage. We also find that the non-resonant conductance in the open conformation of the molecule is significantly impacted by the lead geometry. As a result, the ratio of the current in the closed and open conformations can also be tuned by varying the geometry of the leads, and increased by ∼400%.

  16. Size dependency and potential field influence on deriving mechanical properties of carbon nanotubes using molecular dynamics

    Directory of Open Access Journals (Sweden)

    K.G.S. Dilrukshi

    2015-07-01

    Full Text Available A thorough understanding on the mechanical properties of carbon nanotube (CNT is essential in extending the advanced applications of CNT based systems. However, conducting experiments to estimate mechanical properties at this scale is extremely challenging. Therefore, development of mechanistic models to estimate the mechanical properties of CNTs along with the integration of existing continuum mechanics concepts is critically important. This paper presents a comprehensive molecular dynamics simulation study on the size dependency and potential function influence of mechanical properties of CNT. Commonly used reactive bond order (REBO and adaptive intermolecular reactive bond order (AIREBO potential functions were considered in this regard. Young’s modulus and shear modulus of CNTs are derived by integrating classical continuum mechanics concepts with molecular dynamics simulations. The results indicate that the potential function has a significant influence on the estimated mechanical properties of CNTs, and the influence of potential field is much higher when studying the torsional behaviour of CNTs than the tensile behaviour.

  17. Electronic and transport properties of a molecular junction with asymmetric contacts

    International Nuclear Information System (INIS)

    Asymmetric molecular junctions have been shown experimentally to exhibit a dual-conductance transport property with a pulse-like current-voltage characteristic, by Reed and co-workers. Using a recently developed first-principles integrated piecewise thermal equilibrium current calculation method and a gold-benzene-1-olate-4-thiolate-gold model molecular junction, this unusual transport property has been reproduced. Analysis of the electrostatics and the electronic structure reveals that the high-current state results from subtle bias induced charge transfer at the electrode-molecule contacts that raises molecular orbital energies and enhances the current-contributing molecular density of states and the probabilities of resonance tunneling of conduction electrons from one electrode to another.

  18. Prediction of Transport Properties by Molecular Simulation: Methanol and Ethanol and their mixture

    CERN Document Server

    Guevara-Carrion, Gabriela; Vrabec, Jadran; Hasse, Hans

    2009-01-01

    Transport properties of liquid methanol and ethanol are predicted by molecular dynamics simulation. The molecular models for the alcohols are rigid, non-polarizable and of united-atom type. They were developed in preceding work using experimental vapor-liquid equilibrium data only. Self- and Maxwell-Stefan diffusion coefficients as well as the shear viscosity of methanol, ethanol and their binary mixture are determined using equilibrium molecular dynamics and the Green-Kubo formalism. Non-equilibrium molecular dynamics is used for predicting the thermal conductivity of the two pure substances. The transport properties of the fluids are calculated over a wide temperature range at ambient pressure and compared with experimental and simulation data from the literature. Overall, a very good agreement with the experiment is found. For instance, the self-diffusion coefficient and the shear viscosity are predicted with average deviations of less 8% for the pure alcohols and 12% for the mixture. The predicted thermal...

  19. Electronic and magnetic properties of silicon supported organometallic molecular wires: a density functional theory (DFT) study

    Science.gov (United States)

    Liu, Xia; Tan, Yingzi; Li, Xiuling; Wu, Xiaojun; Pei, Yong

    2015-08-01

    The electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr and Mn) atom incorporated single and double one-dimensional (1D) styrene molecular wires confined on the hydrogen-terminated Si(100) surface are explored for the first time by means of spin-polarized density functional theory, denoted as Si-[TM(styrene)]. It is unveiled that TM atoms bind asymmetrically to the adjacent phenyl rings, which leads to novel electronic and magnetic properties in stark contrast to the well-studied gas phase TM-benzene molecular wires. Si-[Mn(styrene)]∞ and Si-[Cr(styrene)]∞ single molecular wires (SMWs) are a ferromagnetic semiconductor and half metal, respectively. Creation of H-atom defects on the silicon surface can introduce an impurity metallic band, which leads to novel half-metallic magnetism of a Si-[Mn(styrene)]∞ system. Moreover, double molecular wires (DMWs) containing two identical or hetero SMWs are theoretically designed. The [Mn(styrene)]∞-[Cr(styrene)]∞ DMW exhibits half-metallic magnetism where the spin-up and spin-down channels are contributed by two single molecular wires. Finally, we demonstrate that introducing a TM-defect may significantly affect the electronic structure and magnetic properties of molecular wires. These studies provide new insights into the structure and properties of surface supported 1-D sandwiched molecular wires and may inspire the future experimental synthesis of substrate confined organometallic sandwiched molecular wires.The electronic and magnetic properties of transition metal (TM = Sc, Ti, V, Cr and Mn) atom incorporated single and double one-dimensional (1D) styrene molecular wires confined on the hydrogen-terminated Si(100) surface are explored for the first time by means of spin-polarized density functional theory, denoted as Si-[TM(styrene)]. It is unveiled that TM atoms bind asymmetrically to the adjacent phenyl rings, which leads to novel electronic and magnetic properties in stark contrast to

  20. Calculation of the molecular properties of five cephalosporins: cephradine, cephalexin, cefadroxil, cefprozil and ceftobiprole

    Directory of Open Access Journals (Sweden)

    Elso Manuel Cruz Cruz

    2010-11-01

    Full Text Available Background: The side chains attached to the 7-amino cephalosporanic acid, the structural basis of cephalosporin, condition its molecular properties and cause differences in its pharmacological action. Molecular modeling contributes to further knowledge about this relationship. Objective: To calculate structural and electronic properties of five cephalosporins: cephradine, cephalexin, cefadroxil, cefprozil and ceftobiprole. Methods: A theoretical study using quantum mechanics methods to model the structure and electronic properties of the cephalosporins listed above was conducted. Molecular geometries were optimized with semi-empirical calculations, according to the parameterized number three model. The molecular properties were calculated following the density functional theory. The densities of atomic charges and the frontier orbitals were analyzed. Comparisons were established to measure the effect of substituents on the properties of the beta-lactam ring. All calculations were run on personal computers belonging to the Medical Sciences University of Las Tunas, from November 2009 to March 2010. Results: The structural parameters of the beta-lactam ring do not change as a result of changes in the side chains. The ring has a marked tendency to planarity. The ceftobiprole is different from the rest of the cephalosporins in the spatial disposition of the side chain, which facilitates access to the carbonyl carbon. There are no significant variations in the charge densities, especially in the positive charge of this carbon. Conclusions: The structure and electronic properties of the beta-lactam ring have no significant changes among modeled cephalosporins. The three dimensional structure of ceftobiprole favors a higher reactivity.

  1. Molecular metal-metal bonds compounds, synthesis, properties

    CERN Document Server

    Liddle, Stephen T

    2015-01-01

    Systematically covering all areas of the Periodic Table, this is a comprehensive and handy introduction to metal-metal bonding. The 15 chapters follow a uniform, coherent structure for a clear overview, allowing readers easy access to the information. The important molecules at the genesis of each area are mentioned but the focus lies principally on research published since 2005. Important topics such as synthesis, properties, structures,notable features, reactivity and examples of applications of the most important compounds in each group with metal-metal bonding throughout the periodic ta

  2. Molecular gas properties of the most isolated galaxies

    OpenAIRE

    Lisenfeld, Ute; Espada, D.; Verdes-Montenegro, L.; Kuno, N.; AMIGA (team)

    2009-01-01

    The AMIGA project: The role of nature vs. nurture for the properties and evolution of galaxies is still an open question. In order to find answers, it is crucial to have a well-selected sample of isolated galaxies as a baseline and comparison. We built, refined and analised such a sample in the project AMIGA ("Analysis of the Interstellar Medium of Isolated GAlaxies???, http://www.iaa.es/AMIGA.html). The sample is based on the Catalogue of Isolated Galaxies (CIG) by Karanchenseva ...

  3. In Silico Study of Ceftaroline’s Molecular Properties Estudio in silico de propiedades moleculares del ceftaroline

    Directory of Open Access Journals (Sweden)

    Elso Manuel Cruz Cruz

    2011-03-01

    Full Text Available Background: Ceftaroline is the latest developed cephalosporin. Its molecular modeling can help deepening the structural bases underpinning its pharmacological characteristics. Objective: to model structural and electronic properties of the ceftaroline. Method: a theoretical study using quantum mechanics methods was conducted in order to model the structure and electronic properties of the ceftaroline. Molecular geometry was optimized with semiempirical calculations according to parameterized model # 3. Molecular properties were calculated according to the Density Functional Theory. Densities of atomic charges and orbital borders were analyzed and compared to the ceftobiprole modeling. Results: the ceftaroline has a more compact and less elongated three-dimensional structure than the ceftobiprole. The positive charges densities on the carbonyl carbon are slightly lower than their equivalents in the ceftobiprole. Conclusions: an ethyl presence in the ceftaroline oxime group modifies its spatial configuration which makes it more compact and may influence its antibacterial action.Fundamento: El ceftaroline es la más novedosa cefalosporina que se ha desarrollado. Su modelación molecular permitirá profundizar en las bases estructurales que sustentan sus características farmacológicas. Objetivo: modelar propiedades estructurales y electrónicas del ceftaroline. Método: se realizó un estudio teórico con métodos de la mecánica cuántica para modelar la estructura y propiedades electrónicas del ceftaroline. Se optimizó la geometría molecular con cálculos semiempíricos, según el modelo parametrizado 3. Las propiedades moleculares se calcularon a partir de la teoría del funcional de la densidad. Se analizaron las densidades de cargas atómicas y los orbitales de frontera. Se comparó con la modelación del ceftobiprole. Resultados: el ceftaroline tiene una estructura

  4. Averaged Solvent Embedding Potential Parameters for Multiscale Modeling of Molecular Properties

    DEFF Research Database (Denmark)

    Beerepoot, Maarten; Steindal, Arnfinn Hykkerud; List, Nanna Holmgaard;

    2016-01-01

    We derive and validate averaged solvent parameters for embedding potentials to be used in polarizable embedding quantum mechanics/molecular mechanics (QM/MM) molecular property calculations of solutes in organic solvents. The parameters are solvent-specific atom-centered partial charges and isotr...... polarizable embedding multiscale modeling without compromising the accuracy. The results are promising for the development of general embedding parameters for biomolecules, where the reduction in computational cost can be considerable....

  5. Electronic transport properties of a molecular switch with carbon nanotube electrodes: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, P., E-mail: ss_zhaop@ujn.edu.c [School of Science, University of Jinan, Jinan 250022 (China); School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Wang, P.J.; Zhang, Z. [School of Science, University of Jinan, Jinan 250022 (China); Liu, D.S. [School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Department of Physics, Jining University, Qufu 273155 (China)

    2010-01-01

    We have studied the electronic transport properties of a new kind of optical molecular switch with two single-walled carbon nanotube (SWCNT) electrodes using first-principles transport calculations. It is shown that the enol form shows an overall higher conductance than the keto form at low-bias voltage, which is independent of the SWCNTs' chirality. Meantime, it is possible to tune the conductance of the molecular switch by changing the chirality of the SWCNTs.

  6. The influence of starch molecular mass on the properties of extruded thermoplastic starch

    OpenAIRE

    Vliegenthart, J. F. G.; van Soest, J.J.G.; Benes, K.; de Wit, D

    1996-01-01

    The mechanical properties of a low and a high molecular mass thermoplastic starch (TPS) were monitored at water contents in the range of 5–30% (w/w). The granular starches were plasticized by extrusion processing with glycerol and water. The low molecular mass starch was prepared by partial acid hydrolysis of potato starch. The extruded TPS materials were stored at 60% relative humidity for 12 months to level out differences in starch structure due to retrogradation. The water content was the...

  7. PIEZOELECTRIC PROPERTIES OF SINGLE-STRAND DNA MOLECULAR BRUSH BIOLAYERS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The paper is devoted to investigations on nanomechanical behaviors of biochips in label-free biodetections. The chip consists of Si-layer, Ti-layer, Au-layer and single-strand DNA (ssDNA) molecular brush biolayer immobilized by self-assembly technology of thiol group. Unlike previous viewpoints, such as force-bending, entropy-bending and curvature electricity effect, etc.,the piezoelectric effect of the biopolymer brush layer is viewed as the main factor that induces nanomechanical bending of biochips, and a classical macroscopic piezoelectric constitutive relation is used to describe the piezoelectric effect. A new laminated cantilever beam model with a piezoelectric biolayer in continuum mechanics, the linearized Poisson-Boltzmann equation in statistical mechanics and the scaling method in polyelectrolyte brush theory are combined to establish a relationship between the nanomechanical deflection of DNA chips and the factors such as nanoscopic structural features of ssDNA molecules, buffer salt concentration, macroscopic mechanical/piezoelectric parameters of DNA chips etc. Curve fitting of experimental data shows that the sign of the piezoelectric constant of the biolayer may control the deflection direction of DNA chips during the packaging process.

  8. Optically induced changes to the tunneling properties of molecular junctions

    Science.gov (United States)

    Zolotavin, Pavlo; Evans, Charlotte; Natelson, Douglas

    We report increased conductance under laser illumination in plasmonically active atomic scale gold junction in a cryogenic environment (substrate temperatures down to 4 K). Additionally, we observe changes in the bias dependence of differential conductance, which we attribute to local heating due to the illumination. We differentiate between plasmon and direct gold absorption by investigating the polarization dependence of the observed temperature change. The effect is quantified by measuring optically induced changes in the resistance of the metal nanowire and by the change in the magnitude of simultaneously measured Johnson-Nyquist noise. A combination of these techniques provides independent measurements of effective lattice and electronic temperatures. Unlike previous experiments at room temperature and 80 K, we report a substantially larger light-driven temperature increase of 80-120K for devices fabricated on SiO2/Si substrates held at substrate temperatures as low as 4 K. The implications of the observed behavior for electronic transport in single molecular junctions with plasmonically active nanowire leads will be discussed. ARO Award W911 NF-13-1-0476.

  9. LARGE-SCALE TOPOLOGICAL PROPERTIES OF MOLECULAR NETWORKS.

    Energy Technology Data Exchange (ETDEWEB)

    MASLOV,S.SNEPPEN,K.

    2003-11-17

    Bio-molecular networks lack the top-down design. Instead, selective forces of biological evolution shape them from raw material provided by random events such as gene duplications and single gene mutations. As a result individual connections in these networks are characterized by a large degree of randomness. One may wonder which connectivity patterns are indeed random, while which arose due to the network growth, evolution, and/or its fundamental design principles and limitations? Here we introduce a general method allowing one to construct a random null-model version of a given network while preserving the desired set of its low-level topological features, such as, e.g., the number of neighbors of individual nodes, the average level of modularity, preferential connections between particular groups of nodes, etc. Such a null-model network can then be used to detect and quantify the non-random topological patterns present in large networks. In particular, we measured correlations between degrees of interacting nodes in protein interaction and regulatory networks in yeast. It was found that in both these networks, links between highly connected proteins are systematically suppressed. This effect decreases the likelihood of cross-talk between different functional modules of the cell, and increases the overall robustness of a network by localizing effects of deleterious perturbations. It also teaches us about the overall computational architecture of such networks and points at the origin of large differences in the number of neighbors of individual nodes.

  10. Adoption & Foster Care

    Science.gov (United States)

    ... Children > Family Life > Family Dynamics > Adoption & Foster Care Adoption & Foster Care Article Body ​Each year, many children join families through adoption and foster care. These families may face unique ...

  11. Call to Adopt a Nominal Set of Astrophysical Parameters and Constants to Improve the Accuracy of Fundamental Physical Properties of Stars

    Science.gov (United States)

    Harmanec, Petr; Prša, Andrej

    2011-08-01

    The increasing precision of astronomical observations of stars and stellar systems is gradually getting to a level where the use of slightly different values of the solar mass, radius, and luminosity, as well as different values of fundamental physical constants, can lead to measurable systematic differences in the determination of basic physical properties. An equivalent issue with an inconsistent value of the speed of light was resolved by adopting a nominal value that is constant and has no error associated with it. Analogously, we suggest that the systematic error in stellar parameters may be eliminated by (1) replacing the solar radius Rsolar and luminosity Lsolar by the nominal values that are by definition exact and expressed in SI units: 1 R⊙^N =6.95508 × 108 m and 1 L⊙^N =3.846 × 1026 W (2) computing stellar masses in terms of Msolar by noting that the measurement error of the product GMsolar is 5 orders of magnitude smaller than the error in G; (3) computing stellar masses and temperatures in SI units by using the derived values M⊙2010 =1.988547 × 1030 kg and T⊙2010 =5779.57 K and (4) clearly stating the reference for the values of the fundamental physical constants used. We discuss the need and demonstrate the advantages of such a paradigm shift.

  12. Effect of molecular weight distribution on e-beam exposure properties of polystyrene

    International Nuclear Information System (INIS)

    Polystyrene is a negative electron beam resist whose exposure properties can be tuned simply by using different molecular weights (Mw). Most previous studies have used monodisperse polystyrene with a polydispersity index (PDI) of less than 1.1 in order to avoid any uncertainties. Here we show that despite the fact that polystyrene’s sensitivity is inversely proportional to its Mw, no noticeable effect of very broad molecular weight distribution on sensitivity, contrast and achievable resolution is observed. It is thus unnecessary to use the costly monodisperse polystyrene for electron beam lithography. Since the polydispersity is unknown for general purpose polystyrene, we simulated a high PDI polystyrene by mixing in a 1:1 weight ratio two polystyrene samples with Mw of 170 and 900 kg mol−1 for the high Mw range, and 2.5 and 13 kg mol−1 for the low Mw range. The exposure property of the mixture resembles that of a monodisperse polystyrene with similar number averaged molecular weight (Mn)-bar, which indicates that it is (Mn)-bar rather than (Mw)-bar (weight averaged molecular weight) that dominates the exposure properties of polystyrene resist. This also implies that polystyrene of a certain molecular weight can be simulated by a mixture of two polystyrenes having different molecular weights. (paper)

  13. Effect of molecular weight distribution on e-beam exposure properties of polystyrene

    Science.gov (United States)

    Dey, Ripon Kumar; Cui, Bo

    2013-06-01

    Polystyrene is a negative electron beam resist whose exposure properties can be tuned simply by using different molecular weights (Mw). Most previous studies have used monodisperse polystyrene with a polydispersity index (PDI) of less than 1.1 in order to avoid any uncertainties. Here we show that despite the fact that polystyrene’s sensitivity is inversely proportional to its Mw, no noticeable effect of very broad molecular weight distribution on sensitivity, contrast and achievable resolution is observed. It is thus unnecessary to use the costly monodisperse polystyrene for electron beam lithography. Since the polydispersity is unknown for general purpose polystyrene, we simulated a high PDI polystyrene by mixing in a 1:1 weight ratio two polystyrene samples with Mw of 170 and 900 kg mol-1 for the high Mw range, and 2.5 and 13 kg mol-1 for the low Mw range. The exposure property of the mixture resembles that of a monodisperse polystyrene with similar number averaged molecular weight \\overline{{Mn}}, which indicates that it is \\overline{{Mn}} rather than \\overline{{Mw}} (weight averaged molecular weight) that dominates the exposure properties of polystyrene resist. This also implies that polystyrene of a certain molecular weight can be simulated by a mixture of two polystyrenes having different molecular weights.

  14. Optical properties of polycarbonate/styrene-co-acrylonitrile blends: effects of molecular weight of the matrix.

    Science.gov (United States)

    Yi, Ping; Xiong, Ying; Guo, Shaoyun

    2015-12-01

    In this paper, the effects of the molecular weight of a polycarbonate (PC) matrix on the phase morphology and optical properties of a PC/styrene-co-acrylonitrile (SAN) blend were investigated. A scanning electron microscope is used to analyze the phase morphology of the blends, and Mie scattering theory is used to analyze the changing laws of the optical properties of PC/SAN blends with the increasing of PC molecular weight. Results show that the average particle diameter is not strongly changed with different PC molecular weight because the values of the viscosity ratios are very close to each other. But it is obvious that the number of large particles gradually reduced while small particles (especially dmolecular weight. And the increase in small particles will result in an increase in backward scattering so the transmittance of PC/SAN blends decreases with the increase of PC molecular weight. However, the balance of the scattering coefficients and the number concentration of particles eventually lead to the haze of the blends being very close, despite having different PC molecular weights. Meanwhile, the photographs of scattering patterns indicate that the PC/SAN blends whose component weight ratios are fixed at 70:30 have excellent antiglare properties, despite the changes in molecular weight of the PC matrix. PMID:26836652

  15. Molecular stacking character and charge transport properties of tetrabenzoheptacenes derivatives: the effects of nitrogen doping and phenyl substitution.

    Science.gov (United States)

    Guan, Lin; Wang, Wenliang; Shao, Rong; Liu, Fengyi; Yin, Shiwei

    2015-05-01

    The nitrogen doping and phenyl substitution effects on the geometries, molecular stacking character, electronic, and charge transport properties of tetrabenzoheptacene (TTBH) have been investigated by means of density functional theory (DFT) calculation and incoherent charge hopping model. Our results indicate that the nitrogen doping (TTH) at the 6,8,15,17 positions improves its stability in air and the ability of electron injection and in the meantime slightly changes the molecular stacking due to the C-H···N interaction. For both TTBH and TTH, large hole transport mobility (μh) and electron transport mobility (μe), which are on the same order of magnitude, are given rise by their dense displaced π-stacking in crystal. Comparatively, the phenyl substitution (Ph-TTBH) at the 6,8,15,17 positions adopts a non-planar conformation, adverse to close packing and therefore leads to smaller electron/hole transport mobility (μ) than those of TTBH and TTH. The calculations suggest TTBH and TTH are promising candidates for excellent ambipolar OFET materials. PMID:25910880

  16. Relationship between molecular structure and tribological properties of phosphazene lubricants

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Cyclotriphosphazene lubricants were synthesized and the relationship between theirstructures and tribological properties was investigated using an Optimol SRV oscillating frictionand wear tester and one-way reciprocating friction tester. It was found that aryloxyphosphazenewith polar substituent as a lubricant of steel/steel and steel/aluminum pair gave low wear, whilearyloxyphosphazene with nonpolar group on the phenyl pendant led to high wear. Phosphazeneprovides poor lubricity for steel/aluminum system under low load (0.5-3 N). The XPS analyticalresults of the antiwear films generated on the steel and aluminum surface indicate that phos-phazene reacted with steel or aluminum counterface and formed a surface protecting film consist-ing of fluoride and organic compounds containing O, C, F, N, P during friction. This contributes tcreduce the friction and wear of steel/aluminum system.

  17. (Pseudoamide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties

    Directory of Open Access Journals (Sweden)

    José L. Jiménez Blanco

    2010-02-01

    Full Text Available Oligosaccharides are currently recognised as having functions that influence the entire spectrum of cell activities. However, a distinct disadvantage of naturally occurring oligosaccharides is their metabolic instability in biological systems. Therefore, much effort has been spent in the past two decades on the development of feasible routes to carbohydrate mimetics which can compete with their O-glycosidic counterparts in cell surface adhesion, inhibit carbohydrate processing enzymes, and interfere in the biosynthesis of specific cell surface carbohydrates. Such oligosaccharide mimetics are potential therapeutic agents against HIV and other infections, against cancer, diabetes and other metabolic diseases. An efficient strategy to access this type of compounds is the replacement of the glycosidic linkage by amide or pseudoamide functions such as thiourea, urea and guanidine. In this review we summarise the advances over the last decade in the synthesis of oligosaccharide mimetics that possess amide and pseudoamide linkages, as well as studies focussing on their supramolecular and recognition properties.

  18. Physical Properties and Galactic Distribution of Molecular Clouds Identified in the Galactic Ring Survey

    Science.gov (United States)

    Roman-Duval, Julia; Jackson, James M.; Heyer, Mark; Rathborne, Jill; Simon, Robert

    2010-11-01

    We derive the physical properties of 580 molecular clouds based on their 12CO and 13CO line emission detected in the University of Massachusetts-Stony Brook (UMSB) and Galactic Ring surveys. We provide a range of values of the physical properties of molecular clouds, and find a power-law correlation between their radii and masses, suggesting that the fractal dimension of the interstellar medium is around 2.36. This relation, M = (228 ± 18) R 2.36 ± 0.04, allows us to derive masses for an additional 170 Galactic Ring Survey (GRS) molecular clouds not covered by the UMSB survey. We derive the Galactic surface mass density of molecular gas and examine its spatial variations throughout the Galaxy. We find that the azimuthally averaged Galactic surface density of molecular gas peaks between Galactocentric radii of 4 and 5 kpc. Although the Perseus arm is not detected in molecular gas, the Galactic surface density of molecular gas is enhanced along the positions of the Scutum-Crux and Sagittarius arms. This may indicate that molecular clouds form in spiral arms and are disrupted in the inter-arm space. Finally, we find that the CO excitation temperature of molecular clouds decreases away from the Galactic center, suggesting a possible decline in the star formation rate with Galactocentric radius. There is a marginally significant enhancement in the CO excitation temperature of molecular clouds at a Galactocentric radius of about 6 kpc, which in the longitude range of the GRS corresponds to the Sagittarius arm. This temperature increase could be associated with massive star formation in the Sagittarius spiral arm.

  19. Physical Properties and Galactic Distribution of Molecular Clouds identified in the Galactic Ring Survey

    OpenAIRE

    Roman-Duval, Julia; Jackson, James M.; Heyer, Mark; Rathborne, Jill; Simon, Robert

    2010-01-01

    We derive the physical properties of 580 molecular clouds based on their 12CO and 13CO line emission detected in the University of Massachusetts-Stony Brook (UMSB) and Galactic Ring surveys. We provide a range of values of the physical properties of molecular clouds, and find a power-law correlation between their radii and masses, suggesting that the fractal dimension of the ISM is around 2.36. This relation, M = (228 +/- 18) R^{2.36+/-0.04}, allows us to derive masses for an additional 170 G...

  20. Electronic absorption spectra and nonlinear optical properties of CO2 molecular aggregates: A quantum chemical study

    Indian Academy of Sciences (India)

    Tarun K Mandal; Sudipta Dutta; Swapan K Pati

    2009-09-01

    We have investigated the structural aspects of several carbon dioxide molecular aggregates and their spectroscopic and nonlinear optical properties within the quantum chemical theory framework. We find that, although the single carbon dioxide molecule prefers to be in a linear geometry, the puckering of angles occur in oligomers because of the intermolecular interactions. The resulting dipole moments reflect in the electronic excitation spectra of the molecular assemblies. The observation of significant nonlinear optical properties suggests the potential application of the dense carbon dioxide phases in opto-electronic devices.

  1. Molecular Origin of Properties of Organic-Inorganic Hybrid Perovskites: The Big Picture from Small Clusters.

    Science.gov (United States)

    Fang, Hong; Jena, Puru

    2016-04-21

    We show that the electronic properties, including the band gap, the gap deformation potential, and the exciton binding energy as well as the chemical stability of organic-inorganic hybrid perovskites can be traced back to their corresponding molecular motifs. This understanding allows one to quickly estimate the properties of the bulk semiconductors from their corresponding molecular building blocks. New hybrid perovskite admixtures are proposed by replacing halogens with superhalogens having compatible ionic radii. The mechanism of the boron-hydride based hybrid perovskite reacting with water is investigated by using a cluster model. PMID:27064550

  2. Effect of Molecular Weight on the Properties of Polyethyleneglycols Doped with Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Melnyk I.A.

    2015-08-01

    Full Text Available The aim of this study is to analyze the changes in the structure, thermal properties and electrophysical behavior of polyethylene glycol doped with multiwalled carbon nanotubes. The differential scanning calorimetry and electrical conductivity methods were used to study influence of doping multiwalled carbon NTs on the properties of polyethylene glycol of different molecular weights, Mw (PEG-400, PEG-1000, PEG-10000. Dependencies of the polymers degree of crystallinity and temperature behavior of conductivity on the concentration of NTs were researched. The obtained data indicates a strong influence of the molecular weight of PEG on the spatial distribution of NTs and electrical conductivity of researched systems.

  3. The Molecule Calculator: A web-server for fast quantum mechanics-based estimation of molecular properties

    OpenAIRE

    Jensen, Jan H.; Kromann, Jimmy C.

    2013-01-01

    A new web-server called The Molecule Calculator (MolCalc) is presented. The entry page is a molecular editor (JSmol) for interactive molecule building. The resulting structure can then be used to estimate molecular properties such as heats of formation and other thermodynamic properties, vibrational frequencies and vibrational modes, and molecular orbitals and orbital energies. These properties are computed using the GAMESS program at either the RHF/STO-3G (orbitals and orbital energies) or P...

  4. Molecularly Imprinted Polymer Theophylline Retention and Molecular Recognition Properties in Capillary Electrochromatography

    Institute of Scientific and Technical Information of China (English)

    Cai Ling-shuang; Wu Cai-ying; Mei Su-rong; Zeng Zao-rui

    2004-01-01

    Molecular imprinting of theophylline in poly (methacrylic acid- ethylene dimethacrylate) as CEC stationary phases was synthesized by an in situ photo-initiated polymerization reaction. The effect of electrolyte Ph on xanthine derivatives and the stability of MIP column performance were investigated, the relative standard deviation (DRs) of migration time of five consecutive runs on MIP column was in the range of 2. 2%-3. 1%. The reproducibility of migration time column to column of M(A) was in the range of 3.8%-4.9%.The highest column efficiency was more than 140000 plates per meter. The MIP capillaries had showed better selective for theophylline, which comparing with the reference column.The urine sample was separated by spiked 5×10-4 mol ·L-1 theophylline.

  5. Prediction of Physicochemical Properties of Indonesian Indica Rice Using Molecular Markers

    Directory of Open Access Journals (Sweden)

    PUJI LESTARI

    2014-06-01

    Full Text Available Physicochemical properties determine the palatability and cooking quality of rice, which must be determined efficiently in order to satisfy consumer demand. To date, little information exists on the use of molecular markers to predict physicochemical properties of the “indica” rice varieties found in Indonesia. The objective of this study was to investigate physicochemical properties and genetic variation of Indonesian rice varieties, and to formulate regression equations to analyze sets of DNA markers which could predict amylose content (AC, protein content (PC and pasting properties of the varieties. A total of 24 Indonesian indica rice varieties were chosen based on their genetic background and agricultural characteristics. We then measured selected physicochemical properties, and genotyped the varieties using 30 DNA markers. The chosen varieties showed favorable values for PC, AC, and six rapid viscosity analyzer (RVA pasting properties, which was supported by molecular data. As demonstrated by principal component analysis (PCA, markers could provide a complementary method for differentiating rice varieties, as an alternative to measuring physicochemical properties. PCA analysis also allowed us to establish marker sets using multiple regression analysis. We formulated eight model regression equations comprising data regarding 15 to 19 markers with high coefficients (R2=0.98-0.99. The formulas provided results that consistently correlated and therefore predicted the physicochemical properties of indica rice. Further validation of these marker sets may provide rapid and efficient means for predicting the physicochemical properties of Indonesian-bred indica rice in the future.

  6. Radiation toxins: molecular mechanisms of action and radiomimetic properties .

    Science.gov (United States)

    Popov, Dmitri; Maliev, Vecheslav

    Introduction: Acute Radiation Disease (ARD) or Acute Radiation Syndromes (ARS) were defined as a toxic poisonous with development of the acute pathological processes in irradi-ated animals: systemic inflammatory response syndrome(SIRS), toxic multiple organ injury (TMOI), toxic multiple organ dysfunction syndromes (TMOD), toxic multiple organ failure (TMOF). However, the nature of radiation toxins, their mechanisms of formation, molecular structure, and mechanism of actions remain uncertain. Moderate and high doses of radiation induce apoptotic necrosis of radiosensitive cells with formation of Radiation Toxins and in-flammation development. Mild doses of radiation induce apoptosis or controlled programmed death of radiosensitive cells without Radiation Toxins formation and development of inflam-mation processes. Only radiation induced apoptotic necrosis initiates formation of Radiation Toxins(RT). Radiation Toxins are playing an important role as the trigger mechanisms for in-flammation development and cell lysis. The systemic inflammatory response syndrome after radiation involves an influence of various endogenous agents and mediators of inflammation such as bradykinin, histamine, serotonin and phospholipases activation, prostaglandins biosyn-thesis. Although, formation of non-specific toxins such as Reactive Oxygen Species (ROS) is an important pathological process at mild or high doses of radiation. Reactive Oxygen Species play an important role in molecules damage and development of peroxidation of lipids and pro-teins which are the structural parts of cell and mitochondrial membranes. ROS and bio-radicals induce damage of DNA and RNA and peroxidation of their molecules. But high doses of radia-tion, severe and extremely severe physiological stress, result in cells death by apoptotic necrosis and could be defined as the neuroimmune acute disease. Excitotoxicity is an important patho-logical mechanism which damages the central nervous system. We postulate that

  7. Crystal Properties and Radiation Effects in Solid Molecular Hydrogens

    Energy Technology Data Exchange (ETDEWEB)

    Kozioiziemski, B

    2000-09-01

    The crystal lattice structure, growth shapes and helium generated by beta-decay of solid deuterium-tritium (D-T) mixtures have been studied. Understanding of these D-T properties is important for predicting and optimizing the target design of the National Ignition Facility (NIF). Raman spectroscopy showed the D-T crystal structure is hexagonal close packed, common to the non-tritiated isotopes. The isotopic mixtures of both tritiated and non-tritiated species broadens the rotational transitions, especially of the lighter species in the mixture. The vibrational frequencies of each isotope is shifted to higher energy in the mixture than the pure components. The J = 1-0 population decreases exponentially with a 1/e time constant which rapidly increases above 10.5 K for both D{sub 2} and T{sub 2} in D-T. The conversion rate is nearly constant from 5 K to 10 K for both D{sub 2} and T{sub 2} at 7.1 hours and 2.1 hours, respectively. The smoothing of D-T layers by beta decay heating is limited by the crystal surface energy. Deuterium and hydrogen-deuteride crystals were grown at a number of temperatures below the triple point to determine the surface energy and roughening transition. Several distinct crystal shapes were observed on a number of different substrates. The a facet roughens between 0.9 T{sub TP} and T{sub TP}, while the c facet persists up to the melting temperature. This is very different from the behavior of the other rare gas crystals which grow completely rounded above 0.8 T{sub TP}. Helium bubbles formed as a product of the beta decay were observed using optical microscopy and the diffusion of smaller bubbles measured with dynamic light scattering. Bubble diffusion coefficients as high as 2.0 x 10{sup -16} m{sup 2}/s were measured for 10-50 nm bubbles. The bubbles move in response to a thermal gradient, with speeds between 1 {micro}m/hour and 100 {micro}m/hour for thermal gradients and temperatures appropriate to NIF targets.

  8. The effect of the molecular properties of calcium channel blockers on their elimination route

    Directory of Open Access Journals (Sweden)

    Trbojević-Stanković Jasna B.

    2015-01-01

    Full Text Available Calcium channel blockers (CCBs are among the most widely used drugs in cardiovascular medicine. In this study, nine CCBs (amlodipine, felodipine, isradipine, nicardipine, nifedipine, nimodipine, nisoldipine, verapamil and diltiazem were investigated to assess the relationship between their molecular properties and elimination data obtained from literature. The descriptors of the molecular properties of CCBs were calculated using three software packages. The relationship between computed molecular properties and elimination data collected from relevant literature, initially investigated with simple linear regression analysis, showed poor correlation (R2 <0.25. Application of molecular weight or volume data as additional independent variable, multiple linear regression (MLR revealed better correlations (R2 ~ 0.38 between CCB renal and fecal elimination data and their lipophilicity. Excluding nimodipine from the calculations resulted in more acceptable correlations. The best correlations were established after computed lipophilicity descriptor and molecular weight were applied (R2 = 0.66 with acceptable probability value. [Projekat Ministarstva nauke Republike Srbije, br. TR34031

  9. Dielectric properties of crystalline organic molecular films in the limit of zero overlap

    Energy Technology Data Exchange (ETDEWEB)

    D’Avino, Gabriele, E-mail: gabriele.davino@gmail.com [Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, BE-7000 Mons, Belgium and Department of Physics, University of Liège, Allée du 6 Août 17, BE-4000 Liège (Belgium); Vanzo, Davide; Soos, Zoltán G., E-mail: soos@princeton.edu [Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States)

    2016-01-21

    We present the calculation of the static dielectric susceptibility tensor and dipole field sums in thin molecular films in the well-defined limit of zero intermolecular overlap. Microelectrostatic and charge redistribution approaches are applied to study the evolution of dielectric properties from one to a few molecular layers in films of different conjugated molecules with organic electronics applications. Because of the conditional convergence of dipolar interactions, dipole fields depend on the shape of the sample and different values are found in the middle layer of a thick film and in the bulk. The shape dependence is eliminated when depolarization is taken into account, and the dielectric tensor of molecular films converges to the bulk limit within a few molecular layers. We quantify the magnitude of surface effects and interpret general trends among different systems in terms of molecular properties, such as shape, polarizability anisotropy, and supramolecular organization. A connection between atomistic models for molecular dielectrics and simpler theories for polarizable atomic lattices is also provided.

  10. Dielectric properties of crystalline organic molecular films in the limit of zero overlap

    International Nuclear Information System (INIS)

    We present the calculation of the static dielectric susceptibility tensor and dipole field sums in thin molecular films in the well-defined limit of zero intermolecular overlap. Microelectrostatic and charge redistribution approaches are applied to study the evolution of dielectric properties from one to a few molecular layers in films of different conjugated molecules with organic electronics applications. Because of the conditional convergence of dipolar interactions, dipole fields depend on the shape of the sample and different values are found in the middle layer of a thick film and in the bulk. The shape dependence is eliminated when depolarization is taken into account, and the dielectric tensor of molecular films converges to the bulk limit within a few molecular layers. We quantify the magnitude of surface effects and interpret general trends among different systems in terms of molecular properties, such as shape, polarizability anisotropy, and supramolecular organization. A connection between atomistic models for molecular dielectrics and simpler theories for polarizable atomic lattices is also provided

  11. Effect of molecular characteristics of Konjac glucomannan on gelling and rheological properties of Tilapia myofibrillar protein.

    Science.gov (United States)

    Jian, Wenjie; Wu, Huayi; Wu, Lanlan; Wu, Yunhui; Jia, Lina; Pang, Jie; Sun, Yuan-Ming

    2016-10-01

    Konjac glucomannan (KGM) is an important gelling agent in composite gels. This study aimed to investigate the effects of KGM molecular characteristics (molecular weight, size and conformation) on gelling properties of Tilapia myofibrillar protein (TMP). In this work, TMP composite gels were prepared under neutral pH with varying KGM (native KGM, 10kGy-KGM, 20kGy-KGM, and 100kGy-KGM) of different molecular characteristics. Native KGM, 10kGy-KGM, and 20kGy-KGM exerted negative effect on gel strength or whiteness of TMP gels. Interestingly 100kGy-KGM improved gelling properties and whiteness of TMP gels. Such effects presented by varying KGM were attributed the physical filling behaviors and the interaction between KGM and TMP. These behaviors or interactions are resulted from different molecular size and conformation. Smaller molecular size (root-mean square radius, Rz 20.2nm) and approximated spherical conformation in 100kGy-KGM enhanced its interaction with TMP and maintained its compact and smooth structure, but the larger molecular size (Rz≥40.2nm) and random coil conformation in other KGMs inhibited part of actins from gelling and deteriorated the network structure. Our study provided principle knowledge to understand the structure-functions relationships of KGM-TMP composite gels. These results can be used to provide theoretical guidance for surimi gel processing. PMID:27312609

  12. Thermodynamic Properties of Selected Homologous Series of Ionic Liquids Calculated Using Molecular Dynamics.

    Science.gov (United States)

    Červinka, Ctirad; Pádua, Agilio A H; Fulem, Michal

    2016-03-10

    This work presents a molecular dynamics simulation study concerning the thermodynamic data of ionic liquids (ILs) including phase change enthalpies, liquid phase densities, radial and spatial distribution functions, and diffusive properties. Three homologous series of ILs were selected for this study, namely, 1-alkyl-3-methylimidazolium tetrafluoroborates, hexafluorophosphates, and 1,1,2,2-tetrafluoroethanesulfonates, so that properties of 36 ILs are calculated in total. The trends of calculated properties are compared to available experimental data and thoroughly discussed in context of the homologous series. The calculated trends of the vaporization enthalpies within the series are supported by analyzing the structural properties of the ILs. An excellent agreement of calculated structural properties (liquid phase density) with the experimental counterparts is reached. The calculated enthalpic properties are overestimated considerably; thus, further development of the force fields for ILs is required. PMID:26848831

  13. Looking beyond Lewis Structures: A General Chemistry Molecular Modeling Experiment Focusing on Physical Properties and Geometry

    Science.gov (United States)

    Linenberger, Kimberly J.; Cole, Renee S.; Sarkar, Somnath

    2011-01-01

    We present a guided-inquiry experiment using Spartan Student Version, ready to be adapted and implemented into a general chemistry laboratory course. The experiment provides students an experience with Spartan Molecular Modeling software while discovering the relationships between the structure and properties of molecules. Topics discussed within…

  14. Experiments for the Undergraduate Laboratory that Illustrate the Size-Exclusion Properties of Zeolite Molecular Sieves

    Science.gov (United States)

    Cooke, Jason; Henderson, Eric J.

    2009-01-01

    Experiments are presented that demonstrate the size-exclusion properties of zeolites and reveal the reason for naming zeolites "molecular sieves". If an IR spectrometer is available, the adsorption or exclusion of alcohols of varying sizes from dichloromethane or chloroform solutions can be readily demonstrated by monitoring changes in the…

  15. Transport properties of room temperature ionic liquids from classical molecular dynamics

    CERN Document Server

    Andreussi, Oliviero

    2012-01-01

    Room Temperature Ionic Liquids (RTILs) have attracted much of the attention of the scientific community in the past decade due the their novel and highly customizable properties. Nonetheless their high viscosities pose serious limitations to the use of RTILs in practical applications. To elucidate some of the physical aspects behind transport properties of RTILs, extensive classical molecular dynamics (MD) calculations are reported. Bulk viscosities and ionic conductivities of butyl-methyl-imidazole based RTILs are presented over a wide range of temperatures. The dependence of the properties of the liquids on simulation parameters, e.g. system size effects and choice of the interaction potential, is analyzed.

  16. Electronic Transport Properties of a Naphthopyran-Based Optical Molecular Switch:an ab initio Study

    Institute of Scientific and Technical Information of China (English)

    XIA Cai-Juan; LIU De-Sheng; ZHANG Ying-Tang

    2011-01-01

    The electronic transport properties of a. Naphthopyran-based molecular optical switch are investigated by using the nonequilibrium Green's Function formalism combined with first-principles density functional theory. The molecule that comprises the switch can convert between its open and closed forms upon photoexcitation. Theoretical results show that the current through the open form is significantly larger than that through the closed form, which is different from other optical switches based on ring-opening reactions of the molecular bridge. The maximum on-off ratio (about 90) can be obtained at 1.4 V. The physical origin of the switching behavior is interpreted based on the spatial distributions of molecular orbitals and the HOMO-LUMO gap. Our result shows that the naphthopyran-based molecule is a good candidate for optical molecular switches and will be useful in the near future.%@@ ronic transport properties of a naphthopyran-based molecular optical switch are investigated by using the nonequilibrium Green's function formalism combined with first-principles density functional theory.The molecule that comprises the switch can convert between its open and closed forms upon photoexcitation.Theoretical results show that the current through the open form is significantly larger than that through the closed form,which is different from other optical switches based on ring-opening reactions of the molecular bridge.The maximum on-off ratio(about 90)can be obtained at 1.4 V.The physical origin of the switching behavior is interpreted based on the spatial distributions of molecular orbitals and the HOMO-LUMO gap.Our result shows that the naphthopyran-based molecule is a good candidate for optical molecular switches and will be useful in the near future.

  17. Study of the Mechanical Properties and Vibration Isolation Performance of a Molecular Spring Isolator

    Directory of Open Access Journals (Sweden)

    Muchun Yu

    2016-01-01

    Full Text Available Molecular Spring Isolator (MSI is a novel passive vibration isolation technique, providing High-Static-Low-Dynamic (HSLD stiffness based on the use of molecular spring material. The molecular spring material is a solid-liquid mixture consisting of water and hydrophobic nanoporous materials. Under a certain level of external pressure, water molecules can intrude into the hydrophobic pores of nanoporous materials, developing an additional solid-liquid interface. Such interfaces are able to store, release, and transform mechanical energy, providing properties like mechanical spring. Having been only recently developed, the basic mechanic properties of a MSI have not been studied in depth. This paper focuses on the stiffness influence factors, the dynamic frequency response, and the vibration isolation performance of a MSI; these properties help engineers to design MSIs for different engineering applications. First, the working mechanism of a MSI is introduced from a three-dimensional general view of the water infiltration massive hydrophobic nanoporous pores. Next, a wide range of influence factors on the stiffness properties of MSI are studied. In addition, the frequency response functions (FRFs of the MSI vibration isolation system are studied utilizing the matching method based on equivalent piecewise linear (EPL system. Finally, the vibration isolation properties of MSI are evaluated by force transmissibility.

  18. The Properties of Bound and Unbound Molecular Cloud Populations Formed in Galactic Disc Simulations

    CERN Document Server

    Ward, Rachel L; Wadsley, James; Sills, Alison; Couchman, H M P

    2015-01-01

    We explore the effect of galactic environment on properties of molecular clouds. Using clouds formed in a large-scale galactic disc simulation, we measure the observable properties from synthetic column density maps. We confirm that a significant fraction of unbound clouds forms naturally in a galactic disc environment and that a mixed population of bound and unbound clouds can match observed scaling relations and distributions for extragalactic molecular clouds. By dividing the clouds into inner and outer disc populations, we compare their distributions of properties and test whether there are statistically significant differences between them. We find that clouds in the outer disc have lower masses, sizes, and velocity dispersions as compared to those in the inner disc for reasonable choices of the inner/outer boundary. We attribute the differences to the strong impact of galactic shear on the disc stability at large galactocentric radii. In particular, our Toomre analysis of the disc shows a narrowing enve...

  19. Molecular Structures and Mechanical Properties of Microbe Rapid Coagulation Natural Rubber

    Institute of Scientific and Technical Information of China (English)

    LIANG Yue; HUANG Mao-Fang; ZENG Zong-Qiang

    2011-01-01

    In this work,molecular structures,dynamic mechanical properties and glass transition temperatures of microbe coagulated natural rubber(NR) samples were analyzed by using pyrolysis gas chromatography-mass spectrometry(py-GC/MS),rubber process analyzer(RPA) and dynamic mechanical thermal analysis(DMA).And the cross-linked network structures and mechanical properties of the corresponding NR vulcanizates were further determined by using nuclear magnetic resonance(NMR) crosslink density spectrometer(XLDS-15) and universal testing machines.The results show that NR raw rubber produced by rapidly coagulated with microorganism exhibits a simple molecular structure composition and good dynamic mechanical properties,and the corresponding NR vulcanizates possess the aggregation structure of high cross-linked density,a high glass transition temperature of-61.5 ℃ and high mechanical properties(tensile strength reaches 25.2 MPa),as compared with that coagulated with acetic acid.

  20. Characterization-Based Molecular Design of Biofuel Additives Using Chemometric and Property Clustering Techniques

    Directory of Open Access Journals (Sweden)

    Subin eHada

    2014-06-01

    Full Text Available In this work, multivariate characterization data such as infrared (IR spectroscopy was used as a source of descriptor data involving information on molecular architecture for designing structured molecules with tailored properties. Application of multivariate statistical techniques such as principal component analysis (PCA allowed capturing important features of the molecular architecture from complex data to build appropriate latent variable models. Combining the property clustering techniques and group contribution methods (GCM based on characterization data in a reverse problem formulation enabled identifying candidate components by combining or mixing molecular fragments until the resulting properties match the targets. The developed methodology is demonstrated using molecular design of biodiesel additive which when mixed with off-spec biodiesel produces biodiesel that meets the desired fuel specifications. The contribution of this work is that the complex structures and orientations of the molecule can be included in the design, thereby allowing enumeration of all feasible candidate molecules that matched the identified target but were not part of original training set of molecules.

  1. THE INFLUENCE OF PEG MOLECULAR WEIGHT ON MORPHOLOGIES AND PROPERTIES OF PVDF ASYMMETRIC MEMBRANES

    Institute of Scientific and Technical Information of China (English)

    Dan-ying Zuo; You-yi Xu; Wei-lin Xu; Han-tao Zou

    2008-01-01

    The preparation and properties of asymmetric poly(vinyldiene fluoride) (PVDF) membranes are described in this study. Membranes were prepared from a casting solution of PVDF, N,N-dimethylacetamide (DMAc) solvent and water-soluble poly(ethylene glycol) (PEG) additives by immersing them in water as coagulant medium. Experiments showed that when PEG molecular weight increased, the changes in the resultant membranes" morphologies and properties showed a transition point at PEG6000. This indicated that PEG with a relatively low molecular weight was used as a pore-forming agent to enhance pure water flux and reduce solute rejection of membranes, but PEG was used as a pore-reducing agent with a further increment of PEG molecular weight to result in pure water flux decreasing and solute rejection increasing. Finally,combined with the precipitation rates of different membrane-forming systems, the membrane formation mechanism describing PEG mobility was discussed extensively basing on the length changes of PEG molecular chains and the affinity between PEG and casting solution. The results offered a better understanding of effects of PEG additives on membrane structure and properties.

  2. Using molecular mechanics to predict bulk material properties of fibronectin fibers.

    Directory of Open Access Journals (Sweden)

    Mark J Bradshaw

    Full Text Available The structural proteins of the extracellular matrix (ECM form fibers with finely tuned mechanical properties matched to the time scales of cell traction forces. Several proteins such as fibronectin (Fn and fibrin undergo molecular conformational changes that extend the proteins and are believed to be a major contributor to the extensibility of bulk fibers. The dynamics of these conformational changes have been thoroughly explored since the advent of single molecule force spectroscopy and molecular dynamics simulations but remarkably, these data have not been rigorously applied to the understanding of the time dependent mechanics of bulk ECM fibers. Using measurements of protein density within fibers, we have examined the influence of dynamic molecular conformational changes and the intermolecular arrangement of Fn within fibers on the bulk mechanical properties of Fn fibers. Fibers were simulated as molecular strands with architectures that promote either equal or disparate molecular loading under conditions of constant extension rate. Measurements of protein concentration within micron scale fibers using deep ultraviolet transmission microscopy allowed the simulations to be scaled appropriately for comparison to in vitro measurements of fiber mechanics as well as providing estimates of fiber porosity and water content, suggesting Fn fibers are approximately 75% solute. Comparing the properties predicted by single molecule measurements to in vitro measurements of Fn fibers showed that domain unfolding is sufficient to predict the high extensibility and nonlinear stiffness of Fn fibers with surprising accuracy, with disparately loaded fibers providing the best fit to experiment. This work shows the promise of this microstructural modeling approach for understanding Fn fiber properties, which is generally applicable to other ECM fibers, and could be further expanded to tissue scale by incorporating these simulated fibers into three dimensional

  3. Molecular dynamics simulations of silicate and borate glasses and melts : structure, diffusion dynamics and vibrational properties

    OpenAIRE

    Scherer, Christoph

    2015-01-01

    Molecular dynamics simulations of silicate and borate glasses and melts: Structure, diffusion dynamics and vibrational properties. In this work computer simulations of the model glass formers SiO2 and B2O3 are presented, using the techniques of classical molecular dynamics (MD) simulations and quantum mechanical calculations, based on density functional theory (DFT). The latter limits the system size to about 100−200 atoms. SiO2 and B2O3 are the two most important network formers for industri...

  4. Effect of molecular weight on the properties of polyethylene glycol doped by multiwalled carbon nanotubes

    International Nuclear Information System (INIS)

    The differential scanning calorimetry and electrical conductivity methods are used to study the influence of doping multiwalled carbon nanotubes (NTs) on the properties of polyethylene glycol (PEG) of different molecular weights, Mw (PEG-400, PEG-1000, PEG-10000). Dependences of the degree of crystallinity of polymers and the temperature behavior of conductivity on the concentration of NTs are researched. The obtained data indicate a strong influence of the molecular weight of PEG on the spatial distribution of NTs and the electrical conductivity of researched systems.

  5. The Molecule Calculator: A web-server for fast quantum mechanics-based estimation of molecular properties

    CERN Document Server

    Jensen, Jan H

    2013-01-01

    A new web-server called The Molecule Calculator (MolCalc) is presented. The entry page is a molecular editor (JSmol) for interactive molecule building. The resulting structure can then be used to estimate molecular properties such as heats of formation and other thermodynamic properties, vibrational frequencies and vibrational modes, and molecular orbitals and orbital energies. These properties are computed using the GAMESS program at either the RHF/STO-3G (orbitals and orbital energies) or PM3 level of theory (all other properties) in a matter of seconds or minutes depending on the size of the molecule. The results, though approximate, can help students develop a "chemical intuition" about how molecular structure affects molecular properties, without performing the underlying calculations by hand, a near impossible task for all but the simplest chemical systems.

  6. Molecular states in double quantum wells: nanochemistry for metatmaterials with new optical properties

    Science.gov (United States)

    Gutierrez, Rafael M.; Castañeda, Arcesio

    2009-08-01

    Quantum mechanics explains the existence and properties of the chemical bond responsible for the formation of molecules from isolated atoms. In this work we study quantum states of Double Quantum Wells, DQW, formed from isolated Single Quantum Wells, SQWs, that can be considered metamaterials. Using the quantum chemistry definition of the covalent bond, we discuss molecular states in DQW as a kind of nanochemistry of metamaterials with new properties, in particular new optical properties. An important particularity of such nanochemistry, is the possible experimental control of the geometrical parameters and effective masses characterizing the semiconductor heterostructures represented by the corresponding DQW. This implies a great potential for new applications of the controlled optical properties of the metamaterials. The use of ab initio methods of intensive numerical calculations permits to obtain macroscopic optical properties of the metamaterials from the fundamental components: the spatial distribution of the atoms and molecules constituting the semiconductor layers. The metamaterial new optical properties emerge from the coexistence of many body processes at atomic and molecular level and complex quantum phenomena such as covalent-like bonds at nanometric dimensions.

  7. Radiation protective property of water-soluble chitosan with low-molecular weight

    International Nuclear Information System (INIS)

    In order to investigate the radioprotection property of water-soluble chitosan with low-molecular weight, sodium hydroxide eluting and oxidation degradation of chitosan with H2O2 under HAc condition were used to prepare water-soluble low-molecular weight chitosan. MTT assay and flow cytometry (FCM) assay were performed to evaluate the cell survival rate, apoptosis and cell cycle alteration, respectively, after γ-rays irradiation. The results show that water-soluble low-molecular weight chitosan was successfully prepared, and the degree of deacetylation (D. D) of chitosan was increased from 79.3% to 94.1% while the molecular weight was decreased from 8.50 x 105 to 3.26 x 103 after treatment for 130 min. Low-molecular weight chitosan (LMWC) has good radio-protection effect to BRL cells from radiation damage induced by 4 Gy 60Co γ-rays in evidence of higher survival rate and lower SubG1 peek of the cells.After treatment with 50 μg/mL of LMWC, survival rate of BRL cells increased from 66.5%±0.19% to 87.5%±0.16% at 48 h (p60Co γ-irradiation (p<0.05). The results indicate that low molecular weight has excellent radio-protection effect to normal rat liver cell line (BRL). (authors)

  8. The Effects of Molecular Properties on Ready Biodegradation of Aromatic Compounds in the OECD 301B CO2 Evolution Test.

    Science.gov (United States)

    He, Mei; Mei, Cheng-Fang; Sun, Guo-Ping; Li, Hai-Bei; Liu, Lei; Xu, Mei-Ying

    2016-07-01

    Ready biodegradation is the primary biodegradability of a compound, which is used for discriminating whether a compound could be rapidly and readily biodegraded in the natural ecosystems in a short period and has been applied extensively in the environmental risk assessment of many chemicals. In this study, the effects of 24 molecular properties (including 2 physicochemical parameters, 10 geometrical parameters, 6 topological parameters, and 6 electronic parameters) on the ready biodegradation of 24 kinds of synthetic aromatic compounds were investigated using the OECD 301B CO2 Evolution test. The relationship between molecular properties and ready biodegradation of these aromatic compounds varied with molecular properties. A significant inverse correlation was found for the topological parameter TD, five geometrical parameters (Rad, CAA, CMA, CSEV, and N c), and the physicochemical parameter K ow, and a positive correlation for two topological parameters TC and TVC, whereas no significant correlation was observed for any of the electronic parameters. Based on the correlations between molecular properties and ready biodegradation of these aromatic compounds, the importance of molecular properties was demonstrated as follows: geometrical properties > topological properties > physicochemical properties > electronic properties. Our study first demonstrated the effects of molecular properties on ready biodegradation by a number of experiment data under the same experimental conditions, which should be taken into account to better guide the ready biodegradation tests and understand the mechanisms of the ready biodegradation of aromatic compounds. PMID:26498763

  9. Adoption in ancient times

    OpenAIRE

    Bisha Eugena

    2015-01-01

    Since in ancient times, in all human cultures, children transfered from biological parents to parents that want them to create family, for political alliances, for inheritance, for a future marriage, or to care for elderly parents. The practice of adoption was fairly common in different places and periods. Adoption is mention on Bible and Quran. Greeks, Romans, Egyptians and Babylonians had adoption systems.

  10. Single Parent Adoptive Homes.

    Science.gov (United States)

    Shireman, Joan F.

    1996-01-01

    Reviews research and reports on a longitudinal study of 15 single-parent adoptive homes over a 14-year period that demonstrated that these homes have the capacity to be successful adoptive placements. Identifies unique characteristics of single-parent adoptive homes, and notes the need for additional research to identify children for whom these…

  11. Torsional properties of hexagonal boron nitride nanotubes, carbon nanotubes and their hybrid structures: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Qi-lin, E-mail: xiongql@hust.edu.cn [Department of Mechanics, Huazhong University of Science & Technology, 1037 Luoyu Road, Wuhan 430074 (China); Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment, Luoyu Road 1037, Wuhan 430074 (China); Tian, Xiao Geng [State Key Laboratory for Mechanical Structure Strength and Vibration, Xi’an Jiaotong University, Xi’an 710049 (China)

    2015-10-15

    The torsional mechanical properties of hexagonal single-walled boron nitride nanotubes (SWBNNTs), single-walled carbon nanotubes (SWCNTs), and their hybrid structures (SWBN-CNTs) are investigated using molecular dynamics (MD) simulation. Two approaches - force approach and energy approach, are adopted to calculate the shear moduli of SWBNNTs and SWCNTs, the discrepancy between two approaches is analyzed. The results show that the shear moduli of single-walled nanotubes (SWNTs), including SWBNNTs and SWCNTs are dependent on the diameter, especially for armchair SWNTs. The armchair SWNTs show the better ability of resistance the twisting comparable to the zigzag SWNTs. The effects of diameter and length on the critical values of torque of SWNTs are obtained by comparing the torsional behaviors of SWNTs with different diameters and different lengths. It is observed that the MD results of the effect of diameter and length on the critical values of torque agrees well with the prediction of continuum shell model. The shear modulus of SWBN-CNT has a significant dependence on the percentages of SWCNT and the hybrid style has also an influence on shear modulus. The critical values of torque of SWBN-CNTs increase with the increase of the percentages of SWCNT. This phenomenon can be interpreted by the function relationship between the torque of different bonds (B-N-X, C-C-X, C-B-X, C-N-X) and the angles of bonds.

  12. Torsional properties of hexagonal boron nitride nanotubes, carbon nanotubes and their hybrid structures: A molecular dynamics study

    Directory of Open Access Journals (Sweden)

    Qi-lin Xiong

    2015-10-01

    Full Text Available The torsional mechanical properties of hexagonal single-walled boron nitride nanotubes (SWBNNTs, single-walled carbon nanotubes (SWCNTs, and their hybrid structures (SWBN-CNTs are investigated using molecular dynamics (MD simulation. Two approaches - force approach and energy approach, are adopted to calculate the shear moduli of SWBNNTs and SWCNTs, the discrepancy between two approaches is analyzed. The results show that the shear moduli of single-walled nanotubes (SWNTs, including SWBNNTs and SWCNTs are dependent on the diameter, especially for armchair SWNTs. The armchair SWNTs show the better ability of resistance the twisting comparable to the zigzag SWNTs. The effects of diameter and length on the critical values of torque of SWNTs are obtained by comparing the torsional behaviors of SWNTs with different diameters and different lengths. It is observed that the MD results of the effect of diameter and length on the critical values of torque agrees well with the prediction of continuum shell model. The shear modulus of SWBN-CNT has a significant dependence on the percentages of SWCNT and the hybrid style has also an influence on shear modulus. The critical values of torque of SWBN-CNTs increase with the increase of the percentages of SWCNT. This phenomenon can be interpreted by the function relationship between the torque of different bonds (B-N-X, C-C-X, C-B-X, C-N-X and the angles of bonds.

  13. Torsional properties of hexagonal boron nitride nanotubes, carbon nanotubes and their hybrid structures: A molecular dynamics study

    International Nuclear Information System (INIS)

    The torsional mechanical properties of hexagonal single-walled boron nitride nanotubes (SWBNNTs), single-walled carbon nanotubes (SWCNTs), and their hybrid structures (SWBN-CNTs) are investigated using molecular dynamics (MD) simulation. Two approaches - force approach and energy approach, are adopted to calculate the shear moduli of SWBNNTs and SWCNTs, the discrepancy between two approaches is analyzed. The results show that the shear moduli of single-walled nanotubes (SWNTs), including SWBNNTs and SWCNTs are dependent on the diameter, especially for armchair SWNTs. The armchair SWNTs show the better ability of resistance the twisting comparable to the zigzag SWNTs. The effects of diameter and length on the critical values of torque of SWNTs are obtained by comparing the torsional behaviors of SWNTs with different diameters and different lengths. It is observed that the MD results of the effect of diameter and length on the critical values of torque agrees well with the prediction of continuum shell model. The shear modulus of SWBN-CNT has a significant dependence on the percentages of SWCNT and the hybrid style has also an influence on shear modulus. The critical values of torque of SWBN-CNTs increase with the increase of the percentages of SWCNT. This phenomenon can be interpreted by the function relationship between the torque of different bonds (B-N-X, C-C-X, C-B-X, C-N-X) and the angles of bonds

  14. Semi-quantum approach to molecular dynamics simulation of thermal properties of low-dimensional nanostructures

    CERN Document Server

    Savin, Alexander V; Cantarero, Andres

    2011-01-01

    We present a detailed description of the semi-quantum approach to the molecular dynamics simulation of stochastic dynamics of a system of interacting particles. Within this approach, the dynamics of the system is described with the use of classical Newtonian equations of motion in which the quantum effects are introduced through random Langevin-like forces with a specific power spectral density (the color noise). The color noise describes the interaction of the molecular system with the thermostat. We apply this technique to the simulation of the thermal properties of different low-dimensional nanostructures. Within this approach, we simulate the specific heat and heat transport in carbon nanotubes, as well as the thermal transport in a molecular nanoribbon with rough edges and in a nanoribbon with a strongly anharmonic periodic interatomic potential. We show that the existence of rough edges and quantum statistics of phonons change drastically the thermal conductivity of the rough-edge nanoribbon in comparis...

  15. Comparison of Molecular Iodine Spectral Properties at 514.7 and 532 nm Wavelengths

    Directory of Open Access Journals (Sweden)

    Hrabina J.

    2014-08-01

    Full Text Available We present results of investigation and comparison of spectral properties of molecular iodine transitions in the spectral region of 514.7 nm that are suitable for laser frequency stabilization and metrology of length. Eight Doppler-broadened transitions that were not studied in detail before were investigated with the help of frequency doubled Yb-doped fiber laser, and three of the most promising lines were studied in detail with prospect of using them in frequency stabilization of new laser standards. The spectral properties of hyperfine components (linewidths, signal-to-noise ratio were compared with transitions that are well known and traditionally used for stabilization of frequency doubled Nd:YAG laser at the 532 nm region with the same molecular iodine absorption. The external frequency doubling arrangement with waveguide crystal and the Yb-doped fiber laser is also briefly described together with the observed effect of laser aging.

  16. Becoming an Adoptive Parent

    DEFF Research Database (Denmark)

    McIlvenny, Paul; Raudaskoski, Pirkko Liisa

    transnational adoption practice and representation. We present the results of our analysis of how the experiences of adoptive parents are (re)mediated in a Danish television documentary series following five prospective adoptive couples, not all of whom succeed in their 'quest' to adopt from abroad. Furthermore......, while crossing linguistic, sociocultural, kinship, racial, class and national boundaries in the process. By combining this qualitative approach with studies of governmentality we map out a set of analytical tools to examine the practices and micropolitics of adoptive parents and families, especially...

  17. First principles view on chemical compound space: Towards atomistic control of molecular properties

    CERN Document Server

    von Lilienfeld, O A

    2012-01-01

    A well-defined notion of chemical space is essential for gaining rigorous control of properties through variation of elemental composition and atomic configurations. Here, we revisit the atomistic first principles perspective on chemical compound space. First, we review chemical space in terms of conceptual density functional and molecular grand-canonical ensemble theory. Subsequently, compound-pairs, "alchemical" interpolation and reference compounds, and the relevance of property non-linearity are discussed. Thereafter, we will focus on recent contributions for accelerating atomistic simulations based on modern statistical data analysis methods (artificial intelligence). The crucial role of good descriptors for chemical compounds will be addressed.

  18. Structural and Dynamic Properties of Amorphous Silicon:Tight-Binding Molecular Dynamics Simulation

    Institute of Scientific and Technical Information of China (English)

    HUANG Shi-Ping; WANG Wen-Chuan

    2004-01-01

    @@ The tight-binding molecular dynamics simulation has been performed to study structural and dynamical properties of amorphous silicon. It is found that the radial distribution function and static structure factor are in good agreement with the experimental measurements. The bond order parameters Ql are sensitive to the structure change at different quenching rates. For the dynamical properties, we have calculated the vibration and electronic density of states. The simulation results show that the transverse acoustic is in good agreement with the experimental data, and the high frequency transverse optical (TO) peak shifts to the right of the experimental TO peak.

  19. Molecular design chemical structure generation from the properties of pure organic compounds

    CERN Document Server

    Horvath, AL

    1992-01-01

    This book is a systematic presentation of the methods that have been developed for the interpretation of molecular modeling to the design of new chemicals. The main feature of the compilation is the co-ordination of the various scientific disciplines required for the generation of new compounds. The five chapters deal with such areas as structure and properties of organic compounds, relationships between structure and properties, and models for structure generation. The subject is covered in sufficient depth to provide readers with the necessary background to understand the modeling

  20. Temperature Dependence of Elastic Properties for Amorphous SiO2 by Molecular Dynamics Simulation

    Institute of Scientific and Technical Information of China (English)

    LIU Bin; WANG Jing-Yang; ZHOU Yan-Chun; LI Fang-Zhi

    2008-01-01

    @@ Large-scale and long-time molecular-dynamics simulations are used to investigate the temperature dependences of elastic properties for amorphous SiO2. The elastic moduli increase in a temperature range up to 1600 K and decrease thereafter. The anomalous behaviour in elasticity is explained by analysing the changes of atomic-scale structure with respect to increment of temperature. The mechanism originates predominantly from distortion of the SiO4 tetrahedra network in low-temperature ranges. At an elevated temperature range, thermal-induced Si-O bond stretching dominates the process and leads to normal temperature dependence of elastic properties.

  1. High-Pressure Induced New Phases and Properties in Typical Molecular Systems

    Science.gov (United States)

    Cui, Tian

    2013-06-01

    High pressure introduces new phases by the rearrangement of atoms and reconfigurations of electronic states in materials, often with new physical and chemical phenomena. Study of the new phases in typical molecular systems under high pressure is an interesting subject, such as energy storage materials of solid hydrogen and polymeric nitrogen, hydrogen-rich compound with high-Tc superconductivity under high pressure, high pressure induced metallization of hydrogen, etc. High-pressure structures and pressure-induced phase transitions in the typical molecular solids, such as solid iodine, CHBr3, N2/CN, HBr/HCl, hydrogen-rich compounds (H2S, ZrH2, AsH3, BaReH9, etc.), and group IVA hydrides (Si2H6, Ge2H6, Sn2H6, etc.) are investigated extensively by means of first-principles density functional theory and extensive prediction strategies (molecular dynamics simulation, simulated annealing, soft mode phase transition, random structure-searching method and evolutionary methodology etc.). The new structures and new properties derived from pressure-induced phase transitions in these typical molecular systems have been observed. It is showed that high pressure provides a path for producing new materials with new properties.

  2. Prediction of transport properties by molecular simulation: methanol and ethanol and their mixture.

    Science.gov (United States)

    Guevara-Carrion, Gabriela; Nieto-Draghi, Carlos; Vrabec, Jadran; Hasse, Hans

    2008-12-25

    Transport properties of liquid methanol and ethanol are predicted by molecular dynamics simulation. The molecular models for the alcohols are rigid, nonpolarizable, and of united-atom type. They were developed in preceding work using experimental vapor-liquid equilibrium data only. Self- and Maxwell-Stefan diffusion coefficients as well as the shear viscosity of methanol, ethanol, and their binary mixture are determined using equilibrium molecular dynamics and the Green-Kubo formalism. Nonequilibrium molecular dynamics is used for predicting the thermal conductivity of the two pure substances. The transport properties of the fluids are calculated over a wide temperature range at ambient pressure and compared with experimental and simulation data from the literature. Overall, a very good agreement with the experiment is found. For instance, the self-diffusion coefficient and the shear viscosity are predicted with average deviations of less than 8% for the pure alcohols and 12% for the mixture. The predicted thermal conductivity agrees on average within 5% with the experimental data. Additionally, some velocity and shear viscosity autocorrelation functions are presented and discussed. Radial distribution functions for ethanol are also presented. The predicted excess volume, excess enthalpy, and the vapor-liquid equilibrium of the binary mixture methanol + ethanol are assessed and agree well with experimental data. PMID:19367909

  3. Molecular Gas and Star Formation Properties in the Central and Bar Regions of NGC 6946

    CERN Document Server

    Pan, Hsi-An; Koda, Jin; Hirota, Akihiko; Sorai, Kazuo; Kaneko, Hiroyuki

    2015-01-01

    In this work, we investigate the molecular gas and star formation properties in the barred spiral galaxy NGC 6946 using multiple molecular lines and star formation tracers. High-resolution image (100 pc) of $^{13}$CO (1-0) is created by single dish NRO45 and interferometer CARMA for the inner 2 kpc disk, which includes the central region (nuclear ring and bar) and the offset ridges of the primary bar. Single dish HCN (1-0) observations were also made to constrain the amount of dense gas. Physical properties of molecular gas are inferred by (1) the Large Velocity Gradient (LVG) calculations using our observations and archival $^{12}$CO (1-0), $^{12}$CO(2-1) data, (2) dense gas fraction suggested by HCN to $^{12}$CO (1-0) luminosity ratio, and (3) infrared color. The results show that the molecular gas in the central region is warmer and denser than that of the offset ridges. Dense gas fraction of the central region is similar with that of LIRGs/ULIRGs, while the offset ridges are close to the global average of...

  4. Investigation of coupling geometry and dimerization effects on thermoelectric properties of a C60 molecular transistor

    OpenAIRE

    Tagani, M. Bagheri; Golsanamlou, Z.; Izadi, S; Soleimani, H. Rahimpour

    2013-01-01

    Thermoelectric properties of a C60 molecular transistor are studied using Green function formalism in linear response regime. A tight-binding model is used to investigate the effect of the dimerization and coupling geometry on the electrical conductance, thermopower, and figure of merit. Increase of the connection points between the molecule and electrodes results in decrease of the number of the peaks of the electrical conductance owing to the interference effects. In addition, oscillation o...

  5. Beyond the Alphabet Soup: Molecular Properties of Aerosol Components Influence Optics. (Invited)

    Science.gov (United States)

    Thompson, J. E.

    2013-12-01

    Components within atmospheric aerosols exhibit almost every imaginable model of chemical bonding and physical diversity. The materials run the spectrum from crystalline to amorphous, covalent to ionic, and have varying viscosities, phase, and hygroscopicity. This seminar will focus on the molecular properties of materials that influence the optical behavior of aerosols. Special focus will be placed on the polarizability of materials, hygroscopic growth, and particle phase.

  6. Molecular Properties and Evaluation of Indion 234–Ondansetron Resinates

    OpenAIRE

    Shah, S; Pandya, S.; Bhalekar, MR

    2010-01-01

    Ondansetron is a serotonin 5HT3 antagonist; anti-emetic drug. Bitter taste of the ondansetron is a major problem in ensuring patient compliance. The study was designed to formulate tasteless complexes of ondansetron with ion exchange resin and evaluate molecular properties of drug complex. The drug-loading process was carried out using various resins and was optimized using different drug:resin ratio and pH. Resinates were characterized by infrared spectroscopy, thermal analysis, and X-ray po...

  7. Molecular properties of CD133+ glioblastoma stem cells derived from treatment-refractory recurrent brain tumors

    OpenAIRE

    Liu, Qinghai; Nguyen, David H.; DONG, QINGHUA; Shitaku, Peter; Chung, Kenneth; Liu, On Ying; Jonathan L Tso; Liu, Jason Y; Konkankit, Veerauo; Cloughesy, Timothy F.; Mischel, Paul S; Lane, Timothy F.; Liau, Linda M.; Stanley F Nelson; Tso, Cho-Lea

    2009-01-01

    Glioblastoma multiforme (GBM) remains refractory to conventional therapy. CD133+ GBM cells have been recently isolated and characterized as chemo-/radio-resistant tumor-initiating cells and are hypothesized to be responsible for post-treatment recurrence. In order to explore the molecular properties of tumorigenic CD133+ GBM cells that resist treatment, we isolated CD133+ GBM cells from tumors that are recurrent and have previously received chemo-/radio-therapy. We found that the purified CD1...

  8. Mass transport properties of Pu/DT mixtures from orbital free molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Kress, Joel David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ticknor, Christopher [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Collins, Lee A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-09-16

    Mass transport properties (shear viscosity and diffusion coefficients) for Pu/DT mixtures were calculated with Orbital Free Molecular Dynamics (OFMD). The results were fitted to simple functions of mass density (for ρ=10.4 to 62.4 g/cm3) and temperature (for T=100 up to 3,000 eV) for Pu/DT mixtures consisting of 100/0, 25/75, 50/50, and 75/25 by number.

  9. Photocatalytic Properties of Nb/MCM-41 Molecular Sieves: Effect of the Synthesis Conditions

    OpenAIRE

    Caterine Daza Gomez; J. E. Rodriguez-Paez

    2015-01-01

    The effect of synthesis conditions and niobium incorporation levels on the photocatalytic properties of Nb/MCM-41 molecular sieves was assessed. Niobium pentoxide supported on MCM-41 mesoporous silica was obtained using two methods: sol-gel and incipient impregnation, in each case also varying the percentage of niobium incorporation. The synthesized Nb-MCM-41 ceramic powders were characterized using the spectroscopic techniques of infrared spectroscopy (IR), Raman spectroscopy, X-ray diffract...

  10. The ab initio calculation of molecular electric, magnetic and geometric properties.

    Science.gov (United States)

    Bast, Radovan; Ekström, Ulf; Gao, Bin; Helgaker, Trygve; Ruud, Kenneth; Thorvaldsen, Andreas J

    2011-02-21

    We give an account of some recent advances in the development of ab initio methods for the calculation of molecular response properties, involving electric, magnetic, and geometric perturbations. Particular attention is given to properties in which the basis functions depend explicitly both on time and on the applied perturbations such as perturbations involving nuclear displacements or external magnetic fields when London atomic orbitals are used. We summarize a general framework based on the quasienergy for the calculation of arbitrary-order molecular properties using the elements of the density matrix in the atomic-orbital basis as the basic variables. We demonstrate that the necessary perturbed density matrices of arbitrary order can be determined from a set of linear equations that have the same formal structure as the set of linear equations encountered when determining the linear response equations (or time-dependent self-consistent-field equations). Additional components needed to calculate properties involving perturbation-dependent basis sets are flexible one- and two-electron integral techniques for geometric or magnetic-field differentiated integrals; in Kohn-Sham density-functional theory (KS-DFT), we also need to calculate derivatives of the exchange-correlation functional. We describe a recent proposal for evaluating these contributions based on automatic differentiation. Within this framework, it is now possible to calculate any molecular property for an arbitrary self-consistent-field reference state, including two- and four-component relativistic self-consistent-field wave functions. Examples of calculations that can be performed with this formulation are presented. PMID:21180690

  11. Companion animal adoption study.

    Science.gov (United States)

    Neidhart, Laura; Boyd, Renee

    2002-01-01

    To better understand the outcomes of companion animal adoptions, Bardsley & Neidhart Inc. conducted a series of 3 surveys over a 1-year period with dog and cat owners who had adopted their pet through either a (a) Luv-A-Pet location, (b) Adopt-a-thon, or (c) traditional shelter. This article suggests opportunities to improve owners' perceptions of their pets and the adoption process through (a) providing more information before adoption about pet health and behaviors, (b) providing counseling to potential adopters to place pets appropriately, and (c) educating adopters to promote companion animal health and retention. Results demonstrate that the pet's relationship to the family unit, such as where the pet sleeps and how much time is spent with the pet, is related to the amount of veterinary care the companion animal receives, and to long-term retention. Satisfaction and retention are attributed to the pet's personality, compatibility, and behavior, rather than demographic differences among adopters or between adoption settings. The age of the companion animal at adoption, the intended recipient, and presence of children in the home also play a role. Health problems were an issue initially for half of all adopted pets, but most were resolved within 12 months. Roughly one fourth of adopters who no longer have their companion animal said their pet died. Characteristics of pets that died support the contention that spaying and neutering profoundly affects a companion animal's life span. Although retention is similar for dogs and cats, mortality is higher among cats in the first year after adoption. PMID:12578739

  12. High-explosive properties from classical molecular dynamics simulations and quantum-chemical computations

    Energy Technology Data Exchange (ETDEWEB)

    Sewell, T. D. (Thomas D.); Gan, C. K. (Chee Kwan); Jaramillo, E. (Eugenio); Strachan, A. H. (Alejandro H.)

    2004-01-01

    We are using classical molecular dynamics and condensed phase electronic-structure methods to predict some of the thermophysical and mechanical properties that are needed as input to realistic mesoscale models for plastic-bonded explosives. The main materials studied to date are HMX, PETN, Estane copolymer, and bi(2,2-dinitropropyl) formal/acetal (BDNPF/A). Emphasis is placed on non-reactive properties and thermodynamic states relevant to cookoff and shock initiation phenomena. Both crystal and liquid-state properties are of interest. Typical simulation sizes and times are {approx}10{sup 2} molecules and 2-10 ns, respectively. The overarching goal is to develop internally consistent model thermodynamic and elastic mechanical descriptions for the materials. Prioritization among the set of properties amenable to atomistic simulation is made based on ongoing interactions with mesoscale modelers at Los Alamos and elsewhere. Recent work will be summarized and our view of profitable directions for future research will be discussed, including preliminary results for large-scale molecular dynamics simulations of shock response of crystalline HMX.

  13. Predicting the elastic properties of double-walled carbon nanotubes by molecular dynamics simulation

    International Nuclear Information System (INIS)

    Molecular dynamics simulation is performed on a double-walled carbon nanotube (DWCNT) to predict its elastic properties based on a double-walled shear deformable shell model. By direct buckling measurement, we present here a method for uniquely determining the effective wall thickness for the shell model. Accounting for two different kinds of DWCNTs by adding an inner or outer tube to a fiducial tube, the mechanical properties of DWCNTs are carefully investigated as compared with those of the fiducial tube. It is found that the predicted values of Young's and shear moduli depend strongly on the construction and helicity of DWCNTs, while the dependence on nanotube length is relatively small. The results also confirm that the temperature variation has a significant effect on the elastic properties of DWCNTs

  14. Mechanical properties of stanene under uniaxial and biaxial loading: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Mojumder, Satyajit [Department of Mechanical Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000 (Bangladesh); Amin, Abdullah Al [Department of Mechanical and Aerospace Engineering, Case western Reverse University, Cleveland, Ohio 44106 (United States); Islam, Md Mahbubul, E-mail: mmi122@psu.edu [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2015-09-28

    Stanene, a graphene like two dimensional honeycomb structure of tin has attractive features in electronics application. In this study, we performed molecular dynamics simulations using modified embedded atom method potential to investigate mechanical properties of stanene. We studied the effect of temperature and strain rate on mechanical properties of α-stanene for both uniaxial and biaxial loading conditions. Our study suggests that with the increasing temperature, both the fracture strength and strain of the stanene decrease. Uniaxial loading in zigzag direction shows higher fracture strength and strain compared to the armchair direction, while no noticeable variation in the mechanical properties is observed for biaxial loading. We also found at a higher loading rate, material exhibits higher fracture strength and strain. These results will aid further investigation of stanene as a potential nano-electronics substitute.

  15. Mechanical properties of defective {gamma}-graphyne using molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Ajori, S. [Department of Mechanical Engineering, University of Guilan, PO Box 3756, Rasht (Iran, Islamic Republic of); Ansari, R., E-mail: r_ansari@guilan.ac.ir [Department of Mechanical Engineering, University of Guilan, PO Box 3756, Rasht (Iran, Islamic Republic of); Mirnezhad, M. [Department of Mechanical Engineering, University of Guilan, PO Box 3756, Rasht (Iran, Islamic Republic of)

    2013-01-20

    This paper explores the mechanical properties of perfect and defective {gamma}-graphyne, a lattice of sp-sp{sup 2}-hybridized carbon atoms, as a graphene allotrope using the classical molecular dynamics simulations. These simulations are carried out on the basis of the Tersoff-Brenner potential function with the Nose-Hoover thermostat algorithm in canonical ensemble. In this examination, the influences of vacancy defects on mechanical properties of {gamma}-graphyne such as Young's modulus, ultimate stress and strain and Poisson's ratio are studied. The results demonstrated lower strength and stiffness of this new graphene allotrope than those of graphene. Also, it is observed that in comparison with the mapped vacancy defects, the random vacancy ones are more responsible for the change in the mechanical properties of {gamma}-graphyne. Furthermore, the fracture pattern of defective {gamma}-graphyne is considered.

  16. CheckDen, a program to compute quantum molecular properties on spatial grids.

    Science.gov (United States)

    Pacios, Luis F; Fernandez, Alberto

    2009-09-01

    CheckDen, a program to compute quantum molecular properties on a variety of spatial grids is presented. The program reads as unique input wavefunction files written by standard quantum packages and calculates the electron density rho(r), promolecule and density difference function, gradient of rho(r), Laplacian of rho(r), information entropy, electrostatic potential, kinetic energy densities G(r) and K(r), electron localization function (ELF), and localized orbital locator (LOL) function. These properties can be calculated on a wide range of one-, two-, and three-dimensional grids that can be processed by widely used graphics programs to render high-resolution images. CheckDen offers also other options as extracting separate atom contributions to the property computed, converting grid output data into CUBE and OpenDX volumetric data formats, and perform arithmetic combinations with grid files in all the recognized formats. PMID:19447056

  17. Preparation, tribological properties and biocompatibility of fluorinated graphene/ultrahigh molecular weight polyethylene composite materials

    Science.gov (United States)

    Xu, L.; Zheng, Y.; Yan, Z.; Zhang, W.; Shi, J.; Zhou, F.; Zhang, X.; Wang, J.; Zhang, J.; Liu, B.

    2016-05-01

    Fluorinated graphene (FG)/ultra-high molecular weight polyethylene (UHMWPE) composites were successfully prepared by ultrasonic dispersion and liquid thermoforming method. The mechanical and tribological properties of pure UHMWPE and FG/UHMWPE composites were investigated using micro-hardness tester and high-speed reciprocating friction tester. The results showed that: adding FG could not only increase the micro-hardness of the composites, but also decrease the wear volume of the composite significantly. The friction coefficients of the composites were also reduced with the increasing of FG content. In addition, the MC3T3-E1 cells adhered and grew well on the surface of the FG/UHMWPE composites as observed by SEM and fluorescence microscope, indicating the addition of FG did not affect the morphology and activity of the cells. The FG/UHMWPE composites exhibited excellent mechanical properties, tribological properties and biocompatibility, which could be used as the potential artificial joint replacement material.

  18. Mechanical properties of stanene under uniaxial and biaxial loading: A molecular dynamics study

    International Nuclear Information System (INIS)

    Stanene, a graphene like two dimensional honeycomb structure of tin has attractive features in electronics application. In this study, we performed molecular dynamics simulations using modified embedded atom method potential to investigate mechanical properties of stanene. We studied the effect of temperature and strain rate on mechanical properties of α-stanene for both uniaxial and biaxial loading conditions. Our study suggests that with the increasing temperature, both the fracture strength and strain of the stanene decrease. Uniaxial loading in zigzag direction shows higher fracture strength and strain compared to the armchair direction, while no noticeable variation in the mechanical properties is observed for biaxial loading. We also found at a higher loading rate, material exhibits higher fracture strength and strain. These results will aid further investigation of stanene as a potential nano-electronics substitute

  19. The Value of Adoption

    OpenAIRE

    Mary Eschelbach Hansen

    2006-01-01

    The human services cost of adoption is about half the cost of long-term foster care for children whose birth parents’ rights have been terminated. Because adoption is an effective intervention for improving a variety of outcomes for those exposed to adverse childhood experiences, the total savings to government in areas such as special education and criminal justice is of the same magnitude as the child welfare savings. The private benefit to adopted children in terms of additional income ear...

  20. The claim from adoption.

    Science.gov (United States)

    Petersen, Thomas Sobirk

    2002-08-01

    In this article several justifications of what I call 'the claim from adoption' are examined. The claim from adoption is that, instead of expending resources on bringing new children into the world using reproductive technology and then caring for these children, we ought to devote these resources to the adoption and care of existing destitute children. Arguments trading on the idea that resources should be directed to adoption instead of assisted reproduction because already existing people can benefit from such a use of resources whereas we cannot benefit individuals by bringing them into existence are rejected. It is then argued that a utilitarian argument proposed by Christian Munthe that supports the claim from adoption in some situations should be rejected because the support it offers does not extend to certain situations in which it seems morally obvious that resources should be expended on adoption rather than assisted reproduction. A version of the Priority View improves upon Munthe's utilitarianism by supporting the claim from adoption in the cases in which Munthe's argument failed. Some allegedly counterintuitive implications of the Priority View are then discussed, and it is concluded that the Priority View is more plausible than utilitarianism. In a concluding section on policy issues it is argued that, even though the claim from adoption can be justified in a variety of situations, it does not follow that, in these situations, governments should direct resources away from assisted reproduction and towards adoption. PMID:12956178

  1. Effect of the molecular structure of phenolic novolac precursor resins on the properties of phenolic fibers

    International Nuclear Information System (INIS)

    A series of phenolic resins with different weight-average molecular weights (Mw) and ortho/para (O/P) ratios were prepared. The effect of the phenolic precursor resin structure on the structure and properties of the resulting phenolic fibers was investigated. The structures of the resins and fibers were characterized by nuclear magnetic resonance spectroscopy, gel permeation chromatography, melt rheometry, dynamic mechanical analysis, and thermogravimetric analysis. The results show that the O/P ratio, unsubstituted ortho and para carbon ratio (Ou/Pu), and Mw of the phenolic resins play an important role in determining the properties of the phenolic fibers. The tensile strength of the phenolic fibers increases with increasing novolac precursor Ou/Pu ratios, corresponding to low O/P ratios, at comparable resin Mw values. Also, the tensile strength of the phenolic fibers increases with increasing novolac Mw values at comparable O/P ratios. Phenolic fibers with high tensile strength and good flame resistance characteristics were generated from a phenolic precursor resin, possessing a high weight-average molecular weight and a low O/P value. - Highlights: • Phenolic resins with different weight-average molecular weights and ortho/para ratios have been prepared. • The tensile strength of the phenolic fibers increases with reducing novolac O/P ratio. • The tensile strength of the phenolic fibers increases with increasing novolac Mw

  2. Machine learning predictions of molecular properties: Accurate many-body potentials and nonlocality in chemical space

    International Nuclear Information System (INIS)

    Simultaneously accurate and efficient prediction of molecular properties throughout chemical compound space is a critical ingredient toward rational compound design in chemical and pharmaceutical industries. Aiming toward this goal, we develop and apply a systematic hierarchy of efficient empirical methods to estimate atomization and total energies of molecules. These methods range from a simple sum over atoms, to addition of bond energies, to pairwise interatomic force fields, reaching to the more sophisticated machine learning approaches that are capable of describing collective interactions between many atoms or bonds. In the case of equilibrium molecular geometries, even simple pairwise force fields demonstrate prediction accuracy comparable to benchmark energies calculated using density functional theory with hybrid exchange-correlation functionals; however, accounting for the collective many-body interactions proves to be essential for approaching the 'holy grail' of chemical accuracy of 1 kcal/mol for both equilibrium and out-of-equilibrium geometries. This remarkable accuracy is achieved by a vectorized representation of molecules (so-called Bag of Bonds model) that exhibits strong nonlocality in chemical space. The same representation allows us to predict accurate electronic properties of molecules, such as their polarizability and molecular frontier orbital energies

  3. Molecular tailoring approach for exploring structures, energetics and properties of clusters

    Indian Academy of Sciences (India)

    Shridhar R Gadre; K V Jovan Jose; Anuja P Rahalkar

    2010-01-01

    Molecular Tailoring Approach (MTA) is a method developed for enabling ab initio calculations on prohibitively large molecules or atomic/molecular clusters. A brief review of MTA, a linear scaling technique based on set inclusion and exclusion principle, is provided. The Molecular Electrostatic Potential (MESP) of smaller clusters is exploited for building initial geometries for the larger ones, followed by MTA geometry optimization. The applications of MTA are illustrated with a few test cases such as (CO2) and Li clusters employing Density Functional theory (DFT) and a nanocluster of orthoboric acid at the Hartree-Fock (HF) level. Further, a discussion on the geometries and energetics of benzene tetramers and pentamers, treated at the Møller-Plesset second order (MP2) perturbation theory, is given. MTA model is employed for evaluating some cluster properties viz. adiabatic ionization potential, MESP, polarizability, Hessian matrix and infrared frequencies. These property evaluations are carried out on a series of test cases and are seen to offer quite good agreement with those computed by an actual calculation. These case studies highlight the advantages of MTA model calculations vis-à-vis the actual ones with reference to the CPU-time, memory requirements and accuracy.

  4. EFFECT OF MOLECULAR WEIGHT OF PDMS ON MORPHOLOGY AND MECHANICAL PROPERTIES OF PP/PDMS BLENDS

    Institute of Scientific and Technical Information of China (English)

    Ze-yong Zhao; Wei-wei Yap; Rong-ni Du; Qin Zhang; Qiang Fu; Ze-hao Qiu; Su-lan Yuan

    2009-01-01

    A series of polydimethylsiloxane (PDMS) with varied molecular weights (Mw = 3x106,1x106 and 0.5x106)were melt blended with PP to investigate the effect of PDMS molecular weight (MW) on the morphology and mechanical properties of PP/PDMS blends.Scanning electron microscopic (SEM) examination showed that the size of PDMS domains was dependent on the MW of PDMS.It was found that the lower the value of PDMS MW,the better dispersion of the PDMS domains in the PP matrix.Tensile and Izod impact tests revealed that the addition of PDMS with lower MW would lead to a more significant increase in impact strength of the blends compared with the blends with higher MW ones,while the influence of the molecular weight on tensile strengths of the blends was relatively small in the MW range studied.Differential scanning calorimetry (DSC) results also showed that the crystallization temperature of PP was increased with decreasing PDMS MW,indicating a better nucleation capability of lower MW of PDMS.Melting flow rate (MFR)measurements indicated that the processibility of PP could be enhanced by adding PDMS,and again the lower MW PDMS resulted in better data.Our work demonstrates that not only the processibility but also the mechanical properties of PP could be enhanced to a more significant degree by using low MW PDMS than the higher ones.

  5. Investigation of the Physical and Molecular Properties of Asphalt Binders Processed with Used Motor Oils

    Directory of Open Access Journals (Sweden)

    Mohyeldin Ragab

    2015-01-01

    Full Text Available In this work we investigated the performance aspects of addition of used motor oils (UMO to neat and crumb rubber modified asphalts (CRMA and related that to the change of molecular size distribution of modified asphalt’s fractions; asphaltenes, saturates, naphthene aromatics, and polar aromatics. Based on the results of temperature sweep viscoelastic tests, addition of crumb rubber modifier (CRM alone or with UMO results in the formation of internal network within the modified asphalt. Based on the results of short and long term aged asphalts, the utilization of combination of UMO and CRM enhanced the aging behavior of asphalt. Bending beam rheometer was utilized to investigate the low temperature behavior of UMO modified asphalts. Based on those tests, the utilization of the UMO and CRM enhanced the low temperature properties of asphalts. Based on the results of the asphalt separation tests and the Gel Permeation Chromatography (GPC analysis, it was found that saturates and naphthene aromatics are the two asphalt fractions that have similar molecular size fractions as those of UMO. However, UMO only shifts the molecular sizes of saturates after interaction with asphalt. Results also show that polar aromatics pose higher molecular size structures than UMO.

  6. Synchrotron based mass spectrometry to investigate the molecular properties of mineral-organic associations

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Suet Yi; Kleber, Markus; Takahashi, Lynelle K.; Nico, Peter; Keiluweit, Marco; Ahmed, Musahid

    2013-04-01

    Soil organic matter (OM) is important because its decay drives life processes in the biosphere. Analysis of organic compounds in geological systems is difficult because of their intimate association with mineral surfaces. To date there is no procedure capable of quantitatively separating organic from mineral phases without creating artifacts or mass loss. Therefore, analytical techniques that can (a) generate information about both organic and mineral phases simultaneously and (b) allow the examination of predetermined high-interest regions of the sample as opposed to conventional bulk analytical techniques are valuable. Laser Desorption Synchrotron Postionization (synchrotron-LDPI) mass spectrometry is introduced as a novel analytical tool to characterize the molecular properties of organic compounds in mineral-organic samples from terrestrial systems, and it is demonstrated that when combined with Secondary Ion Mass Spectrometry (SIMS), can provide complementary information on mineral composition. Mass spectrometry along a decomposition gradient in density fractions, verifies the consistency of our results with bulk analytical techniques. We further demonstrate that by changing laser and photoionization energies, variations in molecular stability of organic compounds associated with mineral surfaces can be determined. The combination of synchrotron-LDPI and SIMS shows that the energetic conditions involved in desorption and ionization of organic matter may be a greater determinant of mass spectral signatures than the inherent molecular structure of the organic compounds investigated. The latter has implications for molecular models of natural organic matter that are based on mass spectrometric information.

  7. Molecular Simulation of the Free Energy for the Accurate Determination of Phase Transition Properties of Molecular Solids

    Science.gov (United States)

    Sellers, Michael; Lisal, Martin; Brennan, John

    2015-06-01

    Investigating the ability of a molecular model to accurately represent a real material is crucial to model development and use. When the model simulates materials in extreme conditions, one such property worth evaluating is the phase transition point. However, phase transitions are often overlooked or approximated because of difficulty or inaccuracy when simulating them. Techniques such as super-heating or super-squeezing a material to induce a phase change suffer from inherent timescale limitations leading to ``over-driving,'' and dual-phase simulations require many long-time runs to seek out what frequently results in an inexact location of phase-coexistence. We present a compilation of methods for the determination of solid-solid and solid-liquid phase transition points through the accurate calculation of the chemical potential. The methods are applied to the Smith-Bharadwaj atomistic potential's representation of cyclotrimethylene trinitramine (RDX) to accurately determine its melting point (Tm) and the alpha to gamma solid phase transition pressure. We also determine Tm for a coarse-grain model of RDX, and compare its value to experiment and atomistic counterpart. All methods are employed via the LAMMPS simulator, resulting in 60-70 simulations that total 30-50 ns. Approved for public release. Distribution is unlimited.

  8. Functionality-oriented molecular gels: synthesis and properties of nitrobenzoxadiazole (NBD)-containing low-molecular mass gelators.

    Science.gov (United States)

    Yu, Hang; Lü, Yanchao; Chen, Xiangli; Liu, Kaiqiang; Fang, Yu

    2014-12-01

    Two nitrobenzoxadiazole (NBD)-containing cholesteryl (Chol) derivatives were prepared by introducing d/l-phenylalanine into the linkers between the NBD and Chol units. The compounds were denoted as and , respectively. The gelation behaviors of them were tested in 34 liquids. It was found that the chirality of the linkers shows a great effect on the gelation ability and the gel properties of the two compounds. SEM studies demonstrated that the gelator in the gel of /DMSO aggregated into uniform fibrous structures. FTIR, (1)H NMR and UV-Vis spectroscopy measurements revealed that intermolecular hydrogen bonding and π-π stacking are two main driving forces to promote the gel formation. Interestingly, the /DMSO gel exhibits rapid and reproducible gel-sol phase transition and fluorescence quenching upon introduction of ammonia. Furthermore, both the gel and the fluorescence emission could be fully recovered upon evaporation of the ammonia gas introduced. Spectroscopy and model system studies revealed the association of ammonia with the nitro group of the NBD unit of the compound, which is recognized as the main reason for the chemical responses of the gel system. On the basis of the discovery, an ammonia sensing film had been fabricated and made into a device. Furthermore, a device-based and conceptual "ammonia leaking" monitoring instrument was developed. A preliminary test demonstrated that the performance of the system is exceptionally good, a typical and persuasive example to show the important real-life applications of molecular gels. PMID:25318390

  9. Elastic Properties of UHMWPE-SWCNT Nanocomposites' Fiber: An Experimental, Theoretic, and Molecular Dynamics Evaluation

    Science.gov (United States)

    Khan, Mujibur R.; Mahfuz, Hassan; Adnan, Ashfaq; Shabib, Ishraq; Leventouri, Theodora

    2013-06-01

    Ultrahigh molecular weight polyethylene (PE) filaments were reinforced with 2 wt.% of single-walled carbon nanotubes (SWCNTs). The solution spinning method was used to produce both neat and reinforced PE filaments. Tensile tests and strain hardening through repeated loading-unloading cycles of the filaments revealed a spectacular contribution of the SWCNTs in enhancing the elastic properties, e.g., strength and modulus. The theoretic strength and modulus of the reinforced PE were predicted using the shear lag model and micromechanics-based model, respectively, and verifying with experimental results. It was observed that the predicted strength and modulus were comparable only with those obtained after strain hardening. In the next step, a molecular dynamic simulation was conducted by simulating a unit cell containing a SWCNT surrounded by PE matrix subjected to uniaxial tensile strain. The strength and modulus of the simulated structure showed an agreement, to certain extent, with experimental observations of strain-hardened nanocomposites.

  10. Small molecules make big differences: molecular doping effects on electronic and optical properties of phosphorene

    International Nuclear Information System (INIS)

    Systematical computations on the density functional theory were performed to investigate the adsorption of three typical organic molecules, tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE) and tetrathiafulvalene (TTF), on the surface of phosphorene monolayers and thicker layers. There exist considerable charge transfer and strong non-covalent interaction between these molecules and phosphorene. In particular, the band gap of phosphorene decreases dramatically due to the molecular modification and can be further tuned by applying an external electric field. Meanwhile, surface molecular modification has proven to be an effective way to enhance the light harvesting of phosphorene in different directions. Our results predict a flexible method toward modulating the electronic and optical properties of phosphorene and shed light on its experimental applications. (paper)

  11. Molecular structure in correlation with electrochemical properties of mixed-ligand cobalt(III complexes

    Directory of Open Access Journals (Sweden)

    K. BABIĆ-SAMARDZIJA

    2008-07-01

    Full Text Available Four mixed-ligand cobalt(III complexes (1–4 of the general formula [Co(Rdtccyclam](ClO42 and [Co(Raccyclam](ClO42 (cyclam = 1,4,8,11-tetraazacyclotetradecane; Rdtc = thiomorpholine-(Timdtc or 2-methylpiperidine-(2-Mepipdtc dithiocarbamates; Rac = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionato (Hfac or 2,2,6,6-tetramethyl-3,5-heptanedionato (Tmhd, respectively were electro­chemically examined on a glassy carbon and an iron electrode in perchloric acid solution. The obtained results showed the influence of these complexes on hydrogen evolution, the oxygen reduction reaction and iron dissolution. The exhibited effects of the complexes on these reactions depend on structure related to the bidentate dithiocarbamato or b-diketonato ligand. The electrochemical properties of the complexes were correlated with molecular structure and parameters derived from spectral analysis and molecular modeling.

  12. UManSysProp: an online facility for molecular property prediction and atmospheric aerosol calculations

    Science.gov (United States)

    Topping, D.; Barley, M. H.; Bane, M.; Higham, N.; Aumont, B.; McFiggans, G.

    2015-11-01

    In this paper we describe the development and application of a new web based facility, UManSysProp (manchester.ac.uk"target="_blank">http://umansysprop.seaes.manchester.ac.uk), for automating predictions of molecular and atmospheric aerosol properties. Current facilities include: pure component vapour pressures, critical properties and sub-cooled densities of organic molecules; activity coefficient predictions for mixed inorganic-organic liquid systems; hygroscopic growth factors and CCN activation potential of mixed inorganic/organic aerosol particles; absorptive partitioning calculations with/without a treatment of non-ideality. The aim of this new facility is to provide a single point of reference for all properties relevant to atmospheric aerosol that have been checked for applicability to atmospheric compounds where possible. The group contribution approach allows users to upload molecular information in the form of SMILES strings and UManSysProp will automatically extract the relevant information for calculations. Built using open source chemical informatics, and hosted at the University of Manchester, the facilities are provided via a browser and device-friendly web-interface, or can be accessed using the user's own code via a JSON API. In this paper we demonstrate its use with specific examples that can be simulated using the web-browser interface.

  13. Effects of overexpression of high molecular weight glutenin subunit 1Dy10 on wheat tortilla properties.

    Science.gov (United States)

    Pierucci, Valquíria R M; Tilley, Michael; Graybosch, Robert A; Blechl, Ann E; Bean, Scott R; Tilley, Katherine A

    2009-07-22

    Wheat (Triticum aestivum L.) flour properties necessary for optimal tortilla production have not been identified. Transgenic wheats (Triticum aestivum L.) overexpressing high molecular weight glutenin subunit (HMW-GS) 1Dy10 were used to make tortilla and their quality was evaluated. The level of HMW-GS 1Dy10 in flours derived from transgenic wheats was 2.5-5.8-fold greater than in controls. Polymeric proteins in the transgenic samples had a molecular weight distribution shifted toward larger polymers as indicated by increased levels of polymeric proteins present and greater M(w) averages of the largest fractions in the insoluble polymeric proteins. Dough derived from transgenic wheats had greater resistance to extension and lower extensibility than controls. Tortilla quality evaluation revealed that tortillas originated from transgenic wheats had decreased diameter, greater thickness and rupture force, and lower rollability scores and stretchability than controls. The presence of 1RS chromosomal translocations from rye (Secale cereale L.) in transgenic wheat decreased the negative effects of overexpression of HMW-GS 1Dy10, as tortillas made with this flour mostly exhibited quality properties similar to those made from control flour. Results suggested that the negative effects of overexpression of HMW-GS 1Dy10 on tortilla properties were derived from a nonideal gluten matrix formation. PMID:19537784

  14. The effects of zeolite molecular sieve based surface treatments on the properties of wool fabrics

    Science.gov (United States)

    Carran, Richard S.; Ghosh, Arun; Dyer, Jolon M.

    2013-12-01

    Wool is a natural composite fiber, with keratin and keratin-associated proteins as the key molecular components. The outermost surface of wool fibers comprises a hydrophobic lipid layer that can lead to unsatisfactory processing and properties of fabric products. In this study, molecular sieve 5A, a Na+ and Ca2+ exchanged type A zeolite with a 1:1 Si:Al ratio was integrated onto the surface of wool using 3-mercaptopropyl trimethoxy silane. The resultant surface morphology, hydrophilicity and mechanical performance of the treated wool fabrics were then evaluated. Notably, the surface hydrophilicity of wool was observed to increase dramatically. When wool was treated with a dispersion of 2 wt% acetic acid, 2.5 wt% zeolite and 0.3 wt% or more silane, the water contact angle was observed to decrease from an average value of 148° to 0° over a period of approximately 30 s. Scanning electron microscopic imaging indicated good coverage of the wool surface with zeolite particles, with infrared spectroscopic evaluation indicating strong bonding of the dealuminated zeolite to wool keratins. This application of zeolite showed no adverse effects on the tensile and other mechanical properties of the fabric. This study indicates that zeolite-based treatment is a potentially efficient approach to increasing the surface hydrophilicity and modifying other key surface properties of wool and wool fabrics.

  15. The effects of zeolite molecular sieve based surface treatments on the properties of wool fabrics

    International Nuclear Information System (INIS)

    Wool is a natural composite fiber, with keratin and keratin-associated proteins as the key molecular components. The outermost surface of wool fibers comprises a hydrophobic lipid layer that can lead to unsatisfactory processing and properties of fabric products. In this study, molecular sieve 5A, a Na+ and Ca2+ exchanged type A zeolite with a 1:1 Si:Al ratio was integrated onto the surface of wool using 3-mercaptopropyl trimethoxy silane. The resultant surface morphology, hydrophilicity and mechanical performance of the treated wool fabrics were then evaluated. Notably, the surface hydrophilicity of wool was observed to increase dramatically. When wool was treated with a dispersion of 2 wt% acetic acid, 2.5 wt% zeolite and 0.3 wt% or more silane, the water contact angle was observed to decrease from an average value of 148° to 0° over a period of approximately 30 s. Scanning electron microscopic imaging indicated good coverage of the wool surface with zeolite particles, with infrared spectroscopic evaluation indicating strong bonding of the dealuminated zeolite to wool keratins. This application of zeolite showed no adverse effects on the tensile and other mechanical properties of the fabric. This study indicates that zeolite-based treatment is a potentially efficient approach to increasing the surface hydrophilicity and modifying other key surface properties of wool and wool fabrics

  16. The effects of zeolite molecular sieve based surface treatments on the properties of wool fabrics

    Energy Technology Data Exchange (ETDEWEB)

    Carran, Richard S.; Ghosh, Arun, E-mail: Arun.Ghosh@agresearch.co.nz; Dyer, Jolon M.

    2013-12-15

    Wool is a natural composite fiber, with keratin and keratin-associated proteins as the key molecular components. The outermost surface of wool fibers comprises a hydrophobic lipid layer that can lead to unsatisfactory processing and properties of fabric products. In this study, molecular sieve 5A, a Na{sup +} and Ca{sup 2+} exchanged type A zeolite with a 1:1 Si:Al ratio was integrated onto the surface of wool using 3-mercaptopropyl trimethoxy silane. The resultant surface morphology, hydrophilicity and mechanical performance of the treated wool fabrics were then evaluated. Notably, the surface hydrophilicity of wool was observed to increase dramatically. When wool was treated with a dispersion of 2 wt% acetic acid, 2.5 wt% zeolite and 0.3 wt% or more silane, the water contact angle was observed to decrease from an average value of 148° to 0° over a period of approximately 30 s. Scanning electron microscopic imaging indicated good coverage of the wool surface with zeolite particles, with infrared spectroscopic evaluation indicating strong bonding of the dealuminated zeolite to wool keratins. This application of zeolite showed no adverse effects on the tensile and other mechanical properties of the fabric. This study indicates that zeolite-based treatment is a potentially efficient approach to increasing the surface hydrophilicity and modifying other key surface properties of wool and wool fabrics.

  17. The Danish Adoption Register

    DEFF Research Database (Denmark)

    Petersen, Liselotte; Sørensen, Thorkild I A

    2011-01-01

    The Danish Adoption Register was established in 1963-1964 to explore the genetic and environmental contribution to familial aggregation of schizophrenia.......The Danish Adoption Register was established in 1963-1964 to explore the genetic and environmental contribution to familial aggregation of schizophrenia....

  18. Single Parent Adoption.

    Science.gov (United States)

    Administration for Children, Youth, and Families (DHHS), Washington, DC.

    Presenting two views of the single-parent family, this pamphlet includes an article by two researchers (William Feigelman and Arnold R. Silverman) and a short statement by a single adoptive parent (Amanda Richards). The first paper summarizes earlier research on single-parent adoptions and discusses the results of a nationwide survey of 713…

  19. Very fast averaging of thermal properties of crystals by molecular simulation

    Science.gov (United States)

    Moustafa, Sabry G.; Schultz, Andrew J.; Kofke, David A.

    2015-10-01

    Knowledge of approximate harmonic behavior of crystals is introduced into a new "mapped averaging" framework to yield alternative expressions for the thermodynamic properties of crystalline systems. The expressions separate the known harmonic behavior from residual averages, which thus encapsulate anharmonic contributions to the properties. With harmonic contributions removed, direct measurement of these anharmonic contributions by molecular simulation can be accomplished without contamination by noise produced by the already-known harmonic behavior. We show with application to the Lennard-Jones model that first-derivative properties (pressure, energy) can be obtained to a given precision via this harmonically mapped averaging at least 10 times faster than by using conventional averaging, and second-derivative properties (e.g., heat capacity) are obtained at least 100 times faster; in more favorable cases, the speedup exceeds a millionfold. Free-energy calculations are accelerated by 50 to 1000 times. Data obtained using these formulations are rigorous and not subject to any added approximation, and in fact are less sensitive to inaccuracies relating to finite-size effects, potential truncation, equilibration, and similar considerations. Moreover, the approach does not require any alteration in how sampling is performed during the simulation, so it may be used with standard Monte Carlo or molecular dynamics methods. However, the mapped averages do require evaluation of first and second derivatives of the intermolecular potential, for evaluation of first and second thermodynamic-derivative properties, respectively. Apart from its usefulness to simulation, the formalism developed here may constitute a basis for new theoretical treatments of crystals.

  20. Effect of Molecular Weight on the Properties of Liquid Epoxidized Natural Rubber Acrylate (LENRA)/ Silica Hybrid Composites

    International Nuclear Information System (INIS)

    This paper reports on the effect of molecular weight on the morphological and mechanical properties of liquid epoxidized natural rubber acrylate (LENRA)/ silica hybrid composites prepared by sol-gel technique. The sol-gel reaction was conducted at different concentration of tetraethyl orthosilicate (TEOS), used as a precursor of silica. TEOS were introduced in 10, 20, 30, 40 and 50 parts per hundred rubber (phr) in the composites. Two different molecular weights of ENR were used to study the effect of molecular weight on the mechanical and morphological properties of the compounds. These compounds were cured by ultraviolet (UV) irradiation. The mechanical properties were studied through pendulum hardness and scratch tests. Higher molecular weight of ENR showed better mechanical properties than lower molecular weight. Transmission electron microscope was used to determine the silica size and to study the distribution and dispersion of the silica particles. High molecular weight showed greater distribution and dispersion of silica particles with diameter of 13 - 256 nm. Morphological and mechanical properties of LENRA/ silica hybrid composites were improved by using high molecular weight of ENR. (author)

  1. Confinement properties of 2D porous molecular networks on metal surfaces

    Science.gov (United States)

    Müller, Kathrin; Enache, Mihaela; Stöhr, Meike

    2016-04-01

    Quantum effects that arise from confinement of electronic states have been extensively studied for the surface states of noble metals. Utilizing small artificial structures for confinement allows tailoring of the surface properties and offers unique opportunities for applications. So far, examples of surface state confinement include thin films, artificial nanoscale structures, vacancy and adatom islands, self-assembled 1D chains, vicinal surfaces, quantum dots and quantum corrals. In this review we summarize recent achievements in changing the electronic structure of surfaces by adsorption of nanoporous networks whose design principles are based on the concepts of supramolecular chemistry. Already in 1993, it was shown that quantum corrals made from Fe atoms on a Cu(1 1 1) surface using single atom manipulation with a scanning tunnelling microscope confine the Shockley surface state. However, since the atom manipulation technique for the construction of corral structures is a relatively time consuming process, the fabrication of periodic two-dimensional (2D) corral structures is practically impossible. On the other side, by using molecular self-assembly extended 2D porous structures can be achieved in a parallel process, i.e. all pores are formed at the same time. The molecular building blocks are usually held together by non-covalent interactions like hydrogen bonding, metal coordination or dipolar coupling. Due to the reversibility of the bond formation defect-free and long-range ordered networks can be achieved. However, recently also examples of porous networks formed by covalent coupling on the surface have been reported. By the choice of the molecular building blocks, the dimensions of the network (pore size and pore to pore distance) can be controlled. In this way, the confinement properties of the individual pores can be tuned. In addition, the effect of the confined state on the hosting properties of the pores will be discussed in this review article.

  2. Confinement properties of 2D porous molecular networks on metal surfaces

    International Nuclear Information System (INIS)

    Quantum effects that arise from confinement of electronic states have been extensively studied for the surface states of noble metals. Utilizing small artificial structures for confinement allows tailoring of the surface properties and offers unique opportunities for applications. So far, examples of surface state confinement include thin films, artificial nanoscale structures, vacancy and adatom islands, self-assembled 1D chains, vicinal surfaces, quantum dots and quantum corrals. In this review we summarize recent achievements in changing the electronic structure of surfaces by adsorption of nanoporous networks whose design principles are based on the concepts of supramolecular chemistry. Already in 1993, it was shown that quantum corrals made from Fe atoms on a Cu(1 1 1) surface using single atom manipulation with a scanning tunnelling microscope confine the Shockley surface state. However, since the atom manipulation technique for the construction of corral structures is a relatively time consuming process, the fabrication of periodic two-dimensional (2D) corral structures is practically impossible. On the other side, by using molecular self-assembly extended 2D porous structures can be achieved in a parallel process, i.e. all pores are formed at the same time. The molecular building blocks are usually held together by non-covalent interactions like hydrogen bonding, metal coordination or dipolar coupling. Due to the reversibility of the bond formation defect-free and long-range ordered networks can be achieved. However, recently also examples of porous networks formed by covalent coupling on the surface have been reported. By the choice of the molecular building blocks, the dimensions of the network (pore size and pore to pore distance) can be controlled. In this way, the confinement properties of the individual pores can be tuned. In addition, the effect of the confined state on the hosting properties of the pores will be discussed in this review article

  3. Transport properties of carbon dioxide and methane from molecular dynamics simulations.

    Science.gov (United States)

    Aimoli, C G; Maginn, E J; Abreu, C R A

    2014-10-01

    Transport properties of carbon dioxide and methane are predicted for temperatures between (273.15 and 573.15) K and pressures up to 800 MPa by molecular dynamics simulations. Viscosities and thermal conductivities were obtained through the Green-Kubo formalism, whereas the Einstein relation was used to provide self-diffusion coefficient estimates. The differences in property predictions due to the force field nature and parametrization were investigated by the comparison of seven different CO2 models (two single-site models, three rigid three-site models, and two fully flexible three-site models) and three different CH4 models (two single-site models and one fully flexible five-site model). The simulation results show good agreement with experimental data, except for thermal conductivities at low densities. The molecular structure and force field parameters play an important role in the accuracy of the simulations, which is within the experimental deviations reported for viscosities and self-diffusion coefficients considering the most accurate CO2 and CH4 models studied. On the other hand, the molecular flexibility does not seem to improve accuracy, since the explicit account of vibrational and bending degrees of freedom in the CO2 flexible models leads to slightly less accurate results. Nonetheless, the use of a correctional term to account for vibrational modes in rigid models generally improves estimations of thermal conductivity values. At extreme densities, the caging effect observed with single-site representations of the molecules restrains mobility and leads to an unphysical overestimation of viscosities and, conversely, to the underestimation of self-diffusion coefficients. This result may help to better understand the limits of applicability of such force fields concerning structural and transport properties of dense systems. PMID:25296778

  4. Molecular dynamics simulations of the structural, vibrational, and electronic properties of amorphous silicon

    International Nuclear Information System (INIS)

    Amorphous silicon models have been computer-generated by melt-quenching and film deposition molecular dynamics simulations, employing classical interatomic Si-potentials. The structural, vibrational and electronic properties of these models is described. Dangling-bond gap states are well localized whereas, floating bonds gap states are considerably less localized with wavefunction amplitudes on the neighbors of the five-coordinated atom. In contrast to melt-quenched models, the a-Si films displayed voids, a 15-28% lower density than c-Si, and no five- coordinated atoms. A-Si:H models with 5 and 22% hydrogen, and both monohydride and dihydride species, have also been developed

  5. Synthesis and electrical properties of fullerene-based molecular junctions on silicon substrate

    OpenAIRE

    GUERIN,D; Lenfant, S.; Godey, S.; Vuillaume, D.

    2010-01-01

    We report the synthesis and the electrical properties of fullerene-based molecular junctions on silicon substrate in which the highly \\pi-conjugated molecule C60 (\\pi quantum well) is isolated from the electrodes by alkyl chains (\\sigma tunnel barriers). Initially, the Si/SiO2/\\sigmaC60 architecture was prepared either by sequential synthesis (3 different routes) or by direct grafting of the presynthesized C60-\\sigma-Si(OEt)3 molecule. We described the chemical synthesis of these routes and t...

  6. Investigation of thermodynamic properties of molten rare earth trichlorides by molecular dynamics method

    International Nuclear Information System (INIS)

    The physical and thermodynamic properties of molten rare earth trichlorides were investigated by the molecular dynamics (MD) technique. In addition to a fully ionic model, partially ionic models, in which covalency was considered in the nearest unlike ion pair (cation-chloride ion), was used in the present work. The liquid structure, shear viscosity and enthalpy of molten YCl3 and LaCl3 calculated from the MD simulation were compared with the experimental data. It is concluded that the partially ionic model can better represent the experimental data than the fully ionic model. (orig.)

  7. Comparison of oxidation properties of Nb and Sn in mesoporous molecular sieves

    Czech Academy of Sciences Publication Activity Database

    Nowak, I.; Feliczak, A.; Nekoksová, Iveta; Čejka, Jiří

    2007-01-01

    Roč. 321, č. 1 (2007), s. 40-48. ISSN 0926-860X R&D Projects: GA MPO FT-TA/040; GA AV ČR 1ET400400413 Grant ostatní: Ministry of Scientific Research and Information Technology(PL) N204 084 31/1965 Institutional research plan: CEZ:AV0Z40400503 Keywords : mesoporous molecular sieves * niobium * tin * synthesis * oxidation properties Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.166, year: 2007

  8. Measurements and equation-of-state modelling of thermodynamic properties of binary mixtures of 1-butyl-1-methylpyrrolidinium tetracyanoborate ionic liquid with molecular compounds

    International Nuclear Information System (INIS)

    Highlights: • Solubility data for 10 molecular solvents in [BMPYR][TCB] are reported. • Excess enthalpies for 7 molecular solvents in [BMPYR][TCB] are given. • Thermodynamic modelling with PC-SAFT equation of state is presented. - Abstract: This paper presents a comprehensive thermodynamic study of binary mixtures formed by 1-butyl-1-methylpyrrolidinium tetracyanoborate ionic liquid and hydrocarbons (n-heptane, benzene, toluene, ethylbenzene), thiophene and alcohols (methanol, ethanol, 1-propanol, 1-butanol, 1-hexanol, 1-octanol, 1-decanol and 1-dodecanol). An impact of chemical structure of molecular compounds on their solubility in the ionic liquid and excess enthalpies of mixing is discussed. Furthermore, modelling of the measured properties by using perturbed-chain statistical associating fluid theory (PC-SAFT) is presented. The theory is applied in both correlative and semi-predictive mode involving temperature-dependent binary corrections fitted to infinite dilution activity coefficients. Solubility curves and excess enthalpies are captured by the model with a reasonable accuracy, when semi-predictive strategy is adopted. Moreover, (liquid + liquid) equilibrium phase diagram in ternary system composed of the investigated ionic liquid, thiophene and n-heptane is predicted with PC-SAFT and then the calculations are confronted with available experimental data. The results indicate that the approach proposed can be perceived as an interesting tool for reproducing the thermodynamic behaviour disclosed by such complex systems as those based on ionic liquids

  9. An Orbital-free Molecular Dynamics Study of Static and Dynamic Properties of Liquid Sn

    Directory of Open Access Journals (Sweden)

    González D.J.

    2011-05-01

    Full Text Available The static and dynamic properties of liquid Sn at two different thermodynamic states have been studied from the Orbital Free Ab-Initio Molecular Dynamics (OFAIMD simulation method. This method is based on the density functional theory (DFT of Hohenberg and Kohn. The exchange and correlation interaction is described here with the local density approximation (LDA. We, in this study, have developed a pseudopotential model to describe the external non-Coulombic interaction acting on an electron; this is an essential ingredient of the theory. We have studied several static and dynamic properties of the system. The calculated results are found to be good in agreement with the available experimental data. They are also found to be of similar accuracy as those of other ab-initio studies.

  10. Molecular modeling of hydrogen bonding fluids: Vapor-liquid coexistence and interfacial properties

    CERN Document Server

    Horsch, Martin; Merker, Thorsten; Schnabel, Thorsten; Huang, Yow-Lin; Hasse, Hans; Vrabec, Jadran

    2010-01-01

    A major challenge for molecular modeling consists in optimizing the unlike interaction potentials. In many cases, combination rules are generally suboptimal when accurate predictions of properties like the mixture vapor pressure are needed. However, the well known Lorentz-Berthelot rule performs quite well and can be used as a starting point. If more accurate results are required, it is advisable to adjust the dispersive interaction energy parameter. In the present study, mixture properties are explored for binary systems containing hydrogen bonding components. Furthermore, vapor-liquid interface cluster criteria and contact angles are discussed and remarks on computational details are given. Finally, a sterically accurate generic model for benzyl alcohol is introduced and evaluated.

  11. Temperature-dependent mechanical properties of single-layer molybdenum disulphide: Molecular dynamics nanoindentation simulations

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Junhua, E-mail: junhua.zhao@uni-weimar.de [Jiangsu Province Key Laboratory of Advanced Manufacturing Equipment and Technology of Food, Jiangnan University, 214122 Wuxi (China); Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany); Jiang, Jin-Wu, E-mail: jwjiang5918@hotmail.com [Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany); Rabczuk, Timon, E-mail: timon.rabczuk@uni-weimar.de [Institute of Structural Mechanics, Bauhaus-University Weimar, 99423 Weimar (Germany); School of Civil, Environmental and Architectural Engineering, Korea University, 136-701 Seoul (Korea, Republic of)

    2013-12-02

    The temperature-dependent mechanical properties of single-layer molybdenum disulphide (MoS{sub 2}) are obtained using molecular dynamics (MD) nanoindentation simulations. The Young's moduli, maximum load stress, and maximum loading strain decrease with increasing temperature from 4.2 K to 500 K. The obtained Young's moduli are in good agreement with those using our MD uniaxial tension simulations and the available experimental results. The tendency of maximum loading strain with different temperature is opposite with that of metal materials due to the short range Stillinger-Weber potentials in MoS{sub 2}. Furthermore, the indenter tip radius and fitting strain effect on the mechanical properties are also discussed.

  12. Tribological properties of ultra-high molecular weight polyethylene at ultra-low temperature

    Science.gov (United States)

    Liu, Hongtao; Ji, Hongmin; Wang, Xuemei

    2013-12-01

    The hardness, compression properties, creep resistance and tribological properties of ultra-high molecular weight polyethylene at ultra-low temperature were researched in this paper, and the feasibility of its use in low temperature components was explored. Studies had shown that the UHMWPE sample at ultra-low temperature had a brittle tendency, and its compression curve was similar to the brittle material, for which the brittle fracture occurred in the 20% compression. Besides, the creep resistance of the sample at low temperature got worse, and its hardness showed an increasing tendency. With the increased experimental load, the friction coefficient varied seriously, and during the same load, the friction coefficient at low temperature was higher than that at room temperature. According to the worn morphology, the sample at low temperature showed a typical feature of fatigue wear and abrasive wear, while at room temperature it mainly for abrasive wear.

  13. Mechanical property of carbon nanotubes with intramolecular junctions: Molecular dynamics simulations

    International Nuclear Information System (INIS)

    Intramolecular junctions (IMJs) of carbon nanotubes hold a promise of potential applications in nano-electromechanical systems. However, their structure-property relation is still unclear. Using the revised second-generation Tersoff-Brenner potential, molecular dynamics simulations were performed to study the mechanical properties of single-walled to four-walled carbon nanotubes with IMJs under uniaxial tension. The dependence of deformation and failure behaviors of IMJs on the geometric parameters was examined. It was found that the rupture strength of a junction is close to that of its thinner carbon nanotube segment, and the rupture strain and Young's modulus show a significant dependence on its geometry. The simulations also revealed that the damage and rupture of multi-walled carbon nanotube junctions take place first in the innermost layer and then propagate consecutively to the outer layers. This study is helpful for optimal design and safety evaluation of IMJ-based nanoelectronics

  14. Structural properties of iron nitride on Cu(100): An ab-initio molecular dynamics study

    KAUST Repository

    Heryadi, Dodi

    2011-01-01

    Due to their potential applications in magnetic storage devices, iron nitrides have been a subject of numerous experimental and theoretical investigations. Thin films of iron nitride have been successfully grown on different substrates. To study the structural properties of a single monolayer film of FeN we have performed an ab-initio molecular dynamics simulation of its formation on a Cu(100) substrate. The iron nitride layer formed in our simulation shows a p4gm(2x2) reconstructed surface, in agreement with experimental results. In addition to its structural properties, we are also able to determine the magnetization of this thin film. Our results show that one monolayer of iron nitride on Cu(100) is ferromagnetic with a magnetic moment of 1.67 μ B. © 2011 Materials Research Society.

  15. NATO Advanced Research Workshop on Geometrical Derivatives of Energy Surfaces and Molecular Properties

    CERN Document Server

    Simons, Jack

    1986-01-01

    The development and computational implementation of analytical expres­ sions for the low-order derivatives of electronic energy surfaces and other molecular properties has undergone rapid growth in recent years. It is now fairly routine for chemists to make use of energy gradient information in locating and identifying stable geometries and transition states. The use of second analytical derivative (Hessian or curvature) expressions is not yet routine, and third and higher energy derivatives as well as property (e.g., dipole moment, polarizability) derivatives are just beginning to be applied to chemical problems. This NATO Advanced Research Workshop focused on analyzing the re­ lative merits of various strategies for deriving the requisite analyti­ cal expressions, for computing necessary integral derivatives and wave­ function parameter derivatives, and for efficiently coding these expres­ sions on conventional scalar machines and vector-oriented computers. The participant list contained many scientist...

  16. Evaluation of collective transport properties of ionic melts from molecular dynamics simulations

    Indian Academy of Sciences (India)

    Manish Agarwal; Charusita Chakravarty

    2009-09-01

    Molecular dynamics simulations of beryllium fluoride (BeF2) have been carried out in the canonical (NVT) ensemble using a rigid-ion potential model. The Green-Kubo formalism has been applied to compute viscosities and ionic conductivities of BeF2 melt. The computational parameters critical for reliably estimating these collective transport properties are shown to differ significantly for viscosity and ionic conductivity. In addition to the equilibrium values of these transport properties, structural relaxation times as well as high-frequency IR-active modes are computed from the pressure and charge-flux auto correlation functions (ACFs) respectively. It is shown that a network-forming ionic melt, such as BeF2, will display persistent oscillatory behaviour of the integral of the charge-flux ACF. By suitable Fourier transformation, one can show that these persistent oscillations correspond to highfrequency, infra-red active vibrations associated with local modes of the network.

  17. The effect of hot multistage drawing on molecular structure and optical properties of polyethylene terephthalate fibers

    Directory of Open Access Journals (Sweden)

    Aminoddin Haji

    2012-08-01

    Full Text Available In this work, mechanical and structural parameters related to the optical properties of polyethylene terephthalate (PET fibers drawn at hot multistage have been investigated. The changes in optical parameters upon changing draw ratio are used to obtain the mechanical orientation factors and , various orientation functions f2(θ, f4(θ and f6(θ, and amorphous and crystalline orientation functions (f a and f c. Also, the numbers of random links between the network junction points (N1, the average optical orientation (Fav, and the distribution function of segment ω(cos θ were calculated. In addition, an empirical formula was suggested to correlate changes in the birefringence with the draw ratio and its constants were determined. The study demonstrated change on the molecular orientation functions and structural parameters upon hot multistage drawing. Significant variations in the characteristic properties of the drawn PET fibers were due to reorientation of the molecules caused by applied heat and external tension.

  18. Electronic properties of liquid Hg-In alloys : Ab-initio molecular dynamics study

    Science.gov (United States)

    Sharma, Nalini; Thakur, Anil; Ahluwalia, P. K.

    2016-05-01

    Ab-initio molecular dynamics simulations are performed to study the structural properties of liquid Hg-In alloys. The interatomic interactions are described by ab-initio pseudopotentials given by Troullier and Martins. Three liquid Hg-In alloys (Hg10In90, Hg30In70,. Hg50In50, Hg70In30, and Hg90Pb10) at 299 K are considered. The calculated results for liquid Hg (l-Hg) and lead (l-In) are also drawn. Along with the calculated results of considered five liquid alloys of Hg-In alloy. The results obtained from electronic properties namely total density of state and partial density of states help to find the local arrangement of Hg and In atoms and the presence of liquid state in the considered five alloys.

  19. Thermophysical properties of liquid Ni around the melting temperature from molecular dynamics simulation

    Science.gov (United States)

    Rozas, R. E.; Demiraǧ, A. D.; Toledo, P. G.; Horbach, J.

    2016-08-01

    Thermophysical properties of liquid nickel (Ni) around the melting temperature are investigated by means of classical molecular dynamics (MD) simulation, using three different embedded atom method potentials to model the interactions between the Ni atoms. Melting temperature, enthalpy, static structure factor, self-diffusion coefficient, shear viscosity, and thermal diffusivity are compared to recent experimental results. Using ab initio MD simulation, we also determine the static structure factor and the mean-squared displacement at the experimental melting point. For most of the properties, excellent agreement is found between experiment and simulation, provided the comparison relative to the corresponding melting temperature. We discuss the validity of the Hansen-Verlet criterion for the static structure factor as well as the Stokes-Einstein relation between self-diffusion coefficient and shear viscosity. The thermal diffusivity is extracted from the autocorrelation function of a wavenumber-dependent temperature fluctuation variable.

  20. Correlation Between Pyrolysis Atmosphere and Carbon Molecular Sieve Membrane Performance Properties

    KAUST Repository

    Kiyono, Mayumi

    2011-01-01

    Carbon molecular sieve (CMS) membranes have attractive separation performance properties, greatly exceeding an "upper bound" trade-off curve of polymeric membrane performance. CMS membranes are prepared by pyrolyzing polymers, well above their glass transition temperatures. Multiple factors, such as polymer precursor and pyrolysis protocol, are known to affect the separation performance. In this study, a correlation observed between pyrolysis atmosphere and CMS separation performance properties is discussed. Specifically, oxygen exposure during the pyrolysis process is the focus. The theory and details of the oxygen exposure and development of a new CMS preparation method using oxygen as a "dopant" will be described with a strong correlation observed with separation performance for CMS membranes prepared with various polymer precursors. In addition, study of possible mass transfer limitations on the oxygen "doping" process will be described to clarify the basis for the equilibrium-based interpretation of doping data. The method is also explored by changing the pyrolysis temperature. © 2011 Elsevier B.V.

  1. Molecular dynamics study of structural and dynamical properties of amorphous Si-Ge alloys

    International Nuclear Information System (INIS)

    Structural and dynamical properties of amorphous silicon-germanium (a-Si1-xGex) alloys have been examined by molecular dynamics simulations using the Tersoff interatomic potential. Amorphous networks were generated by rapid quenching from liquid Si1-xGex alloys. Good agreement was obtained between the simulated and experimentally measured radial distribution functions and phonon densities of states, suggesting that the Tersoff potential is useful for analyzing the atomic configurations and vibrational properties of a-Si1-xGex alloys. Local atomistic structures, such as topological and chemical short-range order states, were also examined in detail, and we compared them with experimental and theoretical results reported previously. On the basis of the results obtained here, we proposed that the bond length and bond angle around Ge atoms have more distortion than those around Si atoms in a-Si1-xGex networks

  2. Electrical and optical properties of ZnO films grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Zinc oxide (ZnO) films have been grown on sapphire by molecular beam epitaxy (MBE), and it is found that the grain size of the ZnO films increased with increasing the growth temperature. Photoluminescence (PL) study shows that the intensity ratio of near-band-edge emission to deep-level-related emission (NBE/DL) of the ZnO is significantly enhanced with increasing the growth temperature, and the dependence of the carrier mobility on the growth temperature shows very similar trend, which implies that there is a community factor that determines the optical and electrical properties of ZnO, and this factor is suggested to be the grain boundary. The results obtained in this paper reveal that by reducing the grain boundaries, ZnO films with high optical and electrical properties may be acquired.

  3. Charge Transport in Molecular Junctions: A Study of Level-Alignment, Thermoelectric Properties, and Environmental Effects

    Science.gov (United States)

    Kotiuga, Michele

    Here, we use and develop first-principles methods based on density functional theory (DFT) and beyond to understand and predict charge transport phenomena in the novel class of nanostructured devices: molecular junctions. Molecular junctions, individual molecules contacted to two metallic leads, which can be systematically altered by modifying the chemistry of each component, serve as test beds for the study of transport at the nanoscale. To date, various experimental methods have been designed to reliably assemble and measure transport properties of molecular junctions. Furthermore, theoretical methods built on DFT designed to yield quantitative agreement with these experiments for certain classes of molecular junctions have been developed. In order to gain insight into a broader range of molecular junctions and environmental effects associated with the surrounding solution, this dissertation will employ, explore and extend first-principles DFT calculations coupled with approximate self-energy corrections known to yield quantitative agreement with experiments for certain classes of molecular junctions. To start we examine molecular junctions in which the molecule is strongly hybridized with the leads: a challenging limit for the existing methodology. Using a physically motivated tight-binding model, we find that the experimental trends observed for such molecules can be explained by the presence of a so-called "gateway" state associated with the chemical bond that bridges the molecule and the lead. We discuss the ingredients of a self-energy corrected DFT based approach to quantitatively predict conductance in the presence of these hybridization effects. We also develop and apply an approach to account for the surrounding environment on the conductance, which has been predominantly ignored in past transport calculations due to computational complexity. Many experiments are performed in a solution of non-conducting molecules; far from benign, this solution is known

  4. Equilibrium and Transport Properties of Primary, Secondary and Tertiary Amines by Molecular Simulation

    Directory of Open Access Journals (Sweden)

    Orozco Gustavo A.

    2014-09-01

    Full Text Available Using molecular simulation techniques such as Monte Carlo (MC and molecular dynamics (MD, we present several simulation results of thermodynamic and transport properties for primary, secondary and tertiary amines. These calculations are based on a recently proposed force field for amines that follows the Anisotropic United Atom approach (AUA. Different amine molecules have been studied, including n-ButylAmine, di-n-ButylAmine, tri-n-ButylAmine and 1,4-ButaneDiAmine for primary, secondary, tertiary and multi-functional amines respectively. For the transport properties, we have calculated the viscosity coefficients as a function of temperature using the isothermal-isobaric (NPT ensemble. In the case of the pure components, we have investigated different thermodynamic properties using NVT Gibbs ensemble simulations such as liquid-vapor phase equilibrium diagrams, vaporization enthalpies, vapor pressures, normal boiling points, critical temperatures and critical densities. We have also calculated the excess enthalpies for water-n-ButylAmine and n-heptane-n-ButylAmine mixtures using Monte Carlo simulations in the NPT ensemble. In addition, we present the calculation of liquid-vapor surface tensions of n-ButylAmine using a two-phase NVT simulation as well as the radial distribution functions. Finally, we have investigated the physical Henry constants of nitrous oxide (N2O and nitrogen (N2 in an aqueous solutions of n-ButylAmine. In general, we found a good agreement between the available experimental information and our simulation results for all the studied properties, ratifying the predictive capability of the AUA force field for amines.

  5. Properties and Microstructural Characteristic of Kaolin Geopolymer Ceramics with Addition of Ultra High Molecular Weight Polyethylene

    Science.gov (United States)

    Ahmad, Romisuhani; Bakri Abdullah, Mohd Mustafa Al; Hussin, Kamarudin; Sandu, Andrei Victor; Binhussain, Mohammed; Ain Jaya, Nur

    2016-06-01

    In this paper, the mechanical properties and microstructure of kaolin geopolymer ceramics with addition of Ultra High Molecular Weight Polyethylene were studied. Inorganic polymers based on alumina and silica polysialate units were synthesized at room temperature from kaolin and sodium silicate in a highly alkaline medium, followed by curing and drying at 80 °C. Alkaline activator was formed by mixing the 12 M NaOH solution with sodium silicate at a ratio of 0.24. Addition of Ultra High Molecular Weight Polyethylene to the kaolin geopolymer are fabricated with Ultra High Molecular Weight Polyethylene content of 2, 4, 6 and 8 (wt. %) by using powder metallurgy method. The samples were heated at 1200 °C and the strength and morphological were tested. It was found that the flexural strength for the kaolin geopolymer ceramics with addition of UHMWPE were improved and generally increased with the increasing of UHMWPE loading. The result revealed that the optimum flexural strength was obtained at UHMWPE loading of 4 wt. % (92.1 MPa) and the flexural strength started to decrease. Microstructural analysis showed the samples appeared to have more number of pores and connected of pores increased with the increasing of UHMWPE content.

  6. Structural parameters, molecular properties, and biological evaluation of some terpenes targeting Schistosoma mansoni parasite.

    Science.gov (United States)

    Mafud, Ana C; Silva, Marcos P N; Monteiro, Daniela C; Oliveira, Maria F; Resende, João G; Coelho, Mayara L; de Sousa, Damião P; Mendonça, Ronaldo Z; Pinto, Pedro L S; Freitas, Rivelilson M; Mascarenhas, Yvonne P; de Moraes, Josué

    2016-01-25

    The use of natural products has a long tradition in medicine, and they have proven to be an important source of lead compounds in the development of new drugs. Among the natural compounds, terpenoids present broad-spectrum activity against infective agents such as viruses, bacteria, fungi, protozoan and helminth parasites. In this study, we report a biological screening of 38 chemically characterized terpenes from different classes, which have a hydroxyl group connected by hydrophobic chain or an acceptor site, against the blood fluke Schistosoma mansoni, the parasite responsible for schistosomiasis mansoni. In vitro bioassays revealed that 3,7-dimethyl-1-octanol (dihydrocitronellol) (10) was the most active terpene (IC50 values of 13-52 μM) and, thus, we investigated its antischistosomal activity in greater detail. Confocal laser scanning microscopy revealed that compound 10 induced severe tegumental damage in adult schistosomes and a correlation between viability and tegumental changes was observed. Furthermore, we compared all the inactive compounds with dihydrocitronellol structurally by using shape and charge modeling. Lipophilicity (miLogP) and other molecular properties (e.g. molecular polar surface area, molecular electrostatic potential) were also calculated. From the 38 terpenes studied, compound 10 is the one with the greatest flexibility, with a sufficient apolar region by which it may interact in a hydrophobic active site. In conclusion, the integration of biological and chemical analysis indicates the potential of the terpene dihydrocitronellol as an antiparasitic agent. PMID:26697994

  7. Averaged Solvent Embedding Potential Parameters for Multiscale Modeling of Molecular Properties.

    Science.gov (United States)

    Beerepoot, Maarten T P; Steindal, Arnfinn Hykkerud; List, Nanna Holmgaard; Kongsted, Jacob; Olsen, Jógvan Magnus Haugaard

    2016-04-12

    We derive and validate averaged solvent parameters for embedding potentials to be used in polarizable embedding quantum mechanics/molecular mechanics (QM/MM) molecular property calculations of solutes in organic solvents. The parameters are solvent-specific atom-centered partial charges and isotropic polarizabilities averaged over a large number of geometries of solvent molecules. The use of averaged parameters reduces the computational cost to obtain the embedding potential, which can otherwise be a rate-limiting step in calculations involving large environments. The parameters are evaluated by analyzing the quality of the resulting molecular electrostatic potentials with respect to full QM potentials. We show that a combination of geometry-specific parameters for solvent molecules close to the QM region and averaged parameters for solvent molecules further away allows for efficient polarizable embedding multiscale modeling without compromising the accuracy. The results are promising for the development of general embedding parameters for biomolecules, where the reduction in computational cost can be considerable. PMID:26938368

  8. Contact geometry and electronic transport properties of Ag–benzene–Ag molecular junctions

    International Nuclear Information System (INIS)

    Highlights: ► We simulate Ag–benzene–Ag junctions with different contact geometries. ► Moderate benzene–Ag interactions can be realized for adsorptions through Ag adatoms. ► Molecular orbitals dominating the low-bias conductance match the contact symmetry. ► Three contact geometries deliver similar conductance consistent with the experiments. - Abstract: Contact geometry and the electronic transport properties of Ag–benzene–Ag molecular junctions have been investigated by using first-principles quantum transport simulations. Our calculations show that a moderate benzene–silver interaction can be achieved when benzene is adsorbed on the Ag(1 1 1) surface through adatoms. In this case three symmetric Ag–benzene–Ag junction models can be constructed, in which the molecule is connected to the electrodes through one or two Ag adatoms on each side. Although the contribution to the transmission around the Fermi level made by the benzene molecular orbitals depends on the number of Ag adatoms and the detailed binding configuration, the transmission coefficients at the Fermi level of the three junctions are calculated to be respectively 0.20, 0.18 and 0.16. These values are well consistent with the experimental ones of 0.24 ± 0.08. Our results thus demonstrate that the conductance of Ag–benzene–Ag junctions is rather stable regardless of the molecule/electrode contact geometry.

  9. Molecular adsorbates as probes of the local properties of doped graphene

    Science.gov (United States)

    Pham, Van Dong; Joucken, Frédéric; Repain, Vincent; Chacon, Cyril; Bellec, Amandine; Girard, Yann; Rousset, Sylvie; Sporken, Robert; Santos, Maria Cristina dos; Lagoute, Jérôme

    2016-01-01

    Graphene-based sensors are among the most promising of graphene’s applications. The ability to signal the presence of molecular species adsorbed on this atomically thin substrate has been explored from electric measurements to light scattering. Here we show that the adsorbed molecules can be used to sense graphene properties. The interaction of porphyrin molecules with nitrogen-doped graphene has been investigated using scanning tunneling microscopy and ab initio calculations. Molecular manipulation was used to reveal the surface below the adsorbed molecules allowing to achieve an atomic-scale measure of the interaction of molecules with doped graphene. The adsorbate’s frontier electronic states are downshifted in energy as the molecule approaches the doping site, with largest effect when the molecule sits over the nitrogen dopant. Theoretical calculations showed that, due to graphene’s high polarizability, the adsorption of porphyrin induces a charge rearrangement on the substrate similar to the image charges on a metal. This charge polarization is enhanced around nitrogen site, leading to an increased interaction of molecules with their image charges on graphene. Consequently, the molecular states are stabilized and shift to lower energies. These findings reveal the local variation of polarizability induced by nitrogen dopant opening new routes towards the electronic tuning of graphene. PMID:27097555

  10. Effect of molecular properties on the performance of polymer light-emitting diodes

    International Nuclear Information System (INIS)

    The performance of a single layer polymer light-emitting diode depends on several interdependent factors, although recombination between electrons and holes within the polymer layer is believed to play an important role. Our aim is to carry out computer experiments in which bipolar charge carriers are injected in polymer networks made of poly(p-phenylene vinylene) chains randomly oriented. In these simulations, we follow the charge evolution in time from some initial state to the steady state. The intra-molecular properties of the polymer molecules obtained from self-consistent quantum molecular dynamics calculations are used in the mesoscopic model. The purpose of the present work is to clarify the effects of intra-molecular charge mobility and energy disorder on recombination efficiency. In particular, we find that charge mobility along the polymer chains has a serious influence on recombination within the polymer layer. Our results also show that energy disorder due to differences in ionization potential and electron affinity of neighbouring molecules affects mainly recombinations that occur near the electrodes at polymer chains parallel to them

  11. (13)C NMR Studies, Molecular Order, and Mesophase Properties of Thiophene Mesogens.

    Science.gov (United States)

    Veeraprakash, B; Lobo, Nitin P; Narasimhaswamy, T

    2015-12-01

    Three-ring mesogens with a core comprising thiophene linked to one phenyl ring directly and to the other via flexible ester are synthesized with terminal alkoxy chains to probe the mesophase properties and find the molecular order. The phenyl thiophene link in the core offers a comparison of the mesophase features with the molecular shape of the mesogen. The synthesized mesogens display enantiotropic polymesomorphism and accordingly nematic, smectic A, smectic C and smectic B mesophases are perceived depending upon the terminal chain length. For some of the homologues, monotropic higher order smectic phases such as smectic F and crystal E are also witnessed. The existence of polymesomorphism are originally observed by HOPM and DSC and further confirmed by powder X-ray diffraction studies. For the C8 homologue, high resolution solid state (13)C NMR spectroscopy is employed to find the molecular structure in the liquid crystalline phase and using the 2D SLF technique, the (13)C-(1)H dipolar couplings are extracted to calculate the order parameter. By comparing the ratio of local order of thiophene as well as phenyl rings, we establish the bent-core shape of the mesogen. Importantly, for assigning the carbon chemical shifts of the core unit of aligned C8 mesogen, the (13)C NMR measured in mesophase of the synthetic intermediate is employed. Thus, the proposed approach addresses the key step in the spectral assignment of target mesogens with the use of (13)C NMR data of mesomorphic intermediate. PMID:26551439

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

    Directory of Open Access Journals (Sweden)

    Sorana-Daniela Bolboacă

    2007-03-01

    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.

  13. Multinuclear NMR spectroscopy for differentiation of molecular configurations and solvent properties between acetone and dimethyl sulfoxide

    Science.gov (United States)

    Wen, Yuan-Chun; Kuo, Hsiao-Ching; Jia, Hsi-Wei

    2016-04-01

    The differences in molecular configuration and solvent properties between acetone and dimethyl sulfoxide (DMSO) were investigated using the developed technique of 1H, 13C, 17O, and 1H self-diffusion liquid state nuclear magnetic resonance (NMR) spectroscopy. Acetone and DMSO samples in the forms of pure solution, ionic salt-added solution were used to deduce their active sites, relative dipole moments, dielectric constants, and charge separations. The NMR results suggest that acetone is a trigonal planar molecule with a polarized carbonyl double bond, whereas DMSO is a trigonal pyramidal-like molecule with a highly polarized S-O single bond. Both molecules use their oxygen atoms as the active sites to interact other molecules. These different molecular models explain the differences their physical and chemical properties between the two molecules and explain why DMSO is classified as an aprotic but highly dipolar solvent. The results are also in agreement with data obtained using X-ray diffraction, neutron diffraction, and theoretical calculations.

  14. Rectifying Properties of a Nitrogen/Boron-Doped Capped-Carbon-Nanotube-Based Molecular Junction

    Institute of Scientific and Technical Information of China (English)

    ZHAO Peng; LIU De-Sheng; ZHANG Ying; WANG Pei-Ji; ZHANG Zhong

    2011-01-01

    @@ Based on the non-equilibrium Green's function method and first-principles density functional theory calculations, we investigate the electronic transport properties of a nitrogen/boron-doped capped-single-walled carbonnanotube-based molecular junction.Obvious rectifying behavior is observed and it is strongly dependent on the doping site.The best rectifying performance can be carried out when the nitrogen/boron atom dopes at a carbon site in the second layer.Moreover, the rectifying performance can be further improved by adjusting the distance between the Cso nanotube caps.%Based on the non-equilibrium Green's function method and first-principles density functional theory calculations, we investigate the electronic transport properties of a nitrogen/boron-doped capped-single-walled carbon-nanotube-based molecular junction. Obvious rectifying behavior is observed and it is strongly dependent on the doping site. The best rectifying performance can be carried out when the nitrogen/boron atom dopes at a carbon site in the second layer. Moreover, the rectifying performance can be further improved by adjusting the distance between the C60 nanotube caps.

  15. Prediction of transport properties of new functional lanthanum-strontium cuprates based materials: molecular dynamics calculations

    International Nuclear Information System (INIS)

    Molecular dynamics method is used for the properties prediction of new lanthanum-strontium cuprates La2-xSrxCuO4-δ based functional materials. The most interesting phases have been synthesized, and electrophysical and thermomechanical properties have been investigated for the verification of acquired calculated data. High values of oxygen diffusion constants is demonstrated to be occurred in solid solutions La2-xSrxCuO4-δ with fine degree of substitution Sr→La (to x=1). Values of lattice parameters, thermal expansion coefficients and oxygen diffusion constants are agree with experimental data. Observed anisotropy of anion transport for all studied compositions is responsible for peculiarities of crystal structure of complex oxides. Applied molecular dynamics method permits to reveal the contribution of separate kinds of oxygen ions (equatorial and apical) in ionic transport at microscopic level, as well as really prove that the oxygen diffusion happens in the ordinary jump mechanism, mainly in (CuO2)-layers

  16. Li-Carboxylate Anode Structure-Property Relationships from Molecular Modeling

    KAUST Repository

    Burkhardt, Stephen E.

    2013-01-22

    The full realization of a renewable energy strategy hinges upon electrical energy storage (EES). EES devices play a key role in storing energy from renewable sources (which are inherently intermittent), to efficient transmission (e.g., grid load-leveling), and finally into the electrification of transportation. Organic materials represent a promising class of electrode active materials for Li-ion and post-Li-ion batteries. Organics consist of low-cost, lightweight, widely available materials, and their properties can be rationally tuned using the well-established principles of organic chemistry. Within the class of organic EES materials, carboxylates distinguish themselves for Li-ion anode materials based on their observed thermal stability, rate capability, and high cyclability. Further, many of the carboxylates studied to date can be synthesized from renewable or waste feedstocks. This report begins with a preliminary molecular density-functional theory (DFT) study, in which the calculated molecular properties of a set of 12 known Li-ion electrode materials based on carboxylate and carbonyl redox couples are compared to literature data. Based on the agreement between theoretical and experimental data, an expanded study was undertaken to identify promising materials and establish design principles for anodes based on Li-carboxylate salts. Predictive computational studies represent an important step forward for the identification of organic anode materials. © 2012 American Chemical Society.

  17. Structural analysis and investigation of molecular properties of Cefpodoxime acid, a third generation antibiotic

    Science.gov (United States)

    Suganthi, S.; Balu, P.; Sathyanarayanamoorthi, V.; Kannappan, V.; Kamil, M. G. Mohamed; Kumar, R.

    2016-03-01

    Extensive quantum mechanical studies are carried out on Cefpodoxime acid (CA), a new generation drug by Hartree-Fock (HF) and B3LYP methods to understand the structural and spectral characteristics of the molecule. The most stable geometry of the molecule was optimized and the bond parameters were reported. The spectroscopic properties of this pharmaceutically important compound were investigated by FT-IR, FT-Raman, UV and 1H NMR techniques. The scaled vibrational frequencies of CA in the ground state are calculated by HF and B3LYP methods with 6-311++G (d, p) basis set and compared with the observed FT-IR and FT-Raman spectra. The vibrational spectral analysis indicates the presence of two intra molecular hydrogen bonds in the molecule which is supported by theoretical study. 1H NMR chemical shifts (δ) were calculated for the CA molecule and compared with the experimental values. The theoretical electronic absorption spectral data in water and ethanol solvents were computed by TD-DFT method. UV-Vis absorption spectra of CA are recorded in these two solvents and compared with theoretical spectra. The spectral data and natural bond orbital (NBO) analysis confirm the occurrence of intra molecular interactions in CA. The electronic distribution, in conjunction with electrophilicity index of CA was used to establish the active site and type of interaction between CA and beta lactamases. Mulliken population analysis on atomic charges is also carried out and thermodynamic properties of the title compound are calculated.

  18. Prediction of Transport Properties of Liquid Ammonia and Its Binary Mixture with Methanol by Molecular Simulation

    Science.gov (United States)

    Guevara-Carrion, Gabriela; Vrabec, Jadran; Hasse, Hans

    2012-03-01

    Transport properties of ammonia and of the binary mixture ammonia + methanol are predicted for a broad range of liquid states by molecular dynamics (MD) simulation on the basis of rigid, non-polarizable molecular models of the united-atom type. These models were parameterized in preceding work using only experimental vapor-liquid equilibrium data. The self- and the Maxwell-Stefan (MS) diffusion coefficients as well as the shear viscosity are obtained by equilibrium MD and the Green-Kubo formalism. Non-equilibrium MD is used for the thermal conductivity. The transport properties of liquid ammonia are predicted for temperatures between 223 K and 473 K up to pressures of 200 MPa and are compared to experimental data and correlations thereof. Generally, good agreement is achieved. The predicted self-diffusion coefficient as well as the shear viscosity deviates on average by less than 15 % from the experiment and the thermal conductivity by less than 6 %. Furthermore, the self- and the MS transport diffusion coefficients as well as the shear viscosity of the liquid mixture ammonia + methanol are studied at different compositions and compared to the available experimental data.

  19. Role of surfactant molecular weight on morphology and properties of functionalized graphite oxide filled polypropylene nanocomposites

    Directory of Open Access Journals (Sweden)

    Y. Wang

    2014-12-01

    Full Text Available Various surfactants of different molecular weights, including alkylamine, poly(oxypropylene diamine (POP, and maleic anhydride grafted polypropylene (PPgMA oligomers, were used for simultaneous funtionalization and reduction of graphite oxide (fGO. In this study, the effect of molecular weight and compatibility of the surfactants on the morphology and properties of the nanocomposites are reported. Wide-angle X-ray diffraction (WAXD exhibited a definite interlayer thickness for GOA (alkylamine intercalated GO, however, the diffraction peaks were nearly suppressed for fGOs combining ODA with either POP (GOAP or PPgMA (GOAE. The uniform dispersion of the fGO flakes in the polypropylene matrix resulted in the significant increase in both the degradation temperature and the crystallization temperature. A single characteristic melting peak of monoclinic (α crystalline phase was observed from DSC traces, which was consistent with WAXD results. Dynamic mechanical analysis clearly indicated increase in both the storage modulus and the glass transition temperature of the nanocomposites due to the enhanced affinity between fGO and the polypropylene matrix. However, GOAP composite showed lower E' and Tg than GOAE because POP is less compatible with the matrix than PPgMA oligomer. Dielectric analysis also showed significant increase in both dielectric permittivity and dielectric loss at low frequency regimes with GOAE showing maximum dielectric properties. The finely dispersed GOAE and its compatibility with polymer matrix manifested the interfacial polarization, which gave rise to much greater ε' and ε" than other nanocomposites.

  20. Combined, solid-state molecular property and gamma spectrometers for CBRNE detection

    Science.gov (United States)

    Rogers, Ben; Grate, Jay; Pearson, Brett; Gallagher, Neal; Wise, Barry; Whitten, Ralph; Adams, Jesse

    2013-05-01

    Nevada Nanotech Systems, Inc. (Nevada Nano) has developed a multi-sensor solution to Chemical, Biological, Radiological, Nuclear and Explosives (CBRNE) detection that combines the Molecular Property Spectrometer™ (MPS™)—a micro-electro-mechanical chip-based technology capable of measuring a variety of thermodynamic and electrostatic molecular properties of sampled vapors and particles—and a compact, high-resolution, solid-state gamma spectrometer module for identifying radioactive materials, including isotopes used in dirty bombs and nuclear weapons. By conducting multiple measurements, the system can provide a more complete characterization of an unknown sample, leading to a more accurate identification. Positive identifications of threats are communicated using an integrated wireless module. Currently, system development is focused on detection of commercial, military and improvised explosives, radioactive materials, and chemical threats. The system can be configured for a variety of CBRNE applications, including handheld wands and swab-type threat detectors requiring short sample times, and ultra-high sensitivity detectors in which longer sampling times are used. Here we provide an overview of the system design and operation and present results from preliminary testing.

  1. Travelers' Health: International Adoption

    Science.gov (United States)

    ... any child with fever and bloody diarrhea. Unlike refugees, internationally adopted children are not treated for parasites ... disease is endemic throughout much of Mexico, Central America, and South America (Chapter 3, Trypanosomiasis, American (Chagas ...

  2. Adopt Your Watershed

    Data.gov (United States)

    U.S. Environmental Protection Agency — Adopt Your Watershed is a Website that encourages stewardship of the nation's water resources and serves as a national inventory of local watershed groups and...

  3. Effects of cross-linking molecular weights in a hyaluronic acid-poly(ethylene oxide) hydrogel network on its properties

    Energy Technology Data Exchange (ETDEWEB)

    Noh, Insup [Department of Chemical Engineering, Seoul National University of Technology, 172 Gongnung-dong, Nowon-gu, Seoul 139-743 (Korea, Republic of); Kim, Gun-Woo [Department of Chemical Engineering, Seoul National University of Technology, 172 Gongnung-dong, Nowon-gu, Seoul 139-743 (Korea, Republic of); Choi, Yoon-Jeong [Department of Chemical Engineering, Seoul National University of Technology, 172 Gongnung-dong, Nowon-gu, Seoul 139-743 (Korea, Republic of); Kim, Mi-Sook [Department of Chemical Engineering, Seoul National University of Technology, 172 Gongnung-dong, Nowon-gu, Seoul 139-743 (Korea, Republic of); Park, Yongdoo [Korea Artificial Organ Center, Korea University, Seoul 136-705 (Korea, Republic of); Lee, Kyu-Back [Korea Artificial Organ Center, Korea University, Seoul 136-705 (Korea, Republic of); Kim, In-Sook [Dental Research Institute, Seoul National University, Seoul 110-749 (Korea, Republic of); Hwang, Soon-Jung [Dental Research Institute, Seoul National University, Seoul 110-749 (Korea, Republic of); Tae, Giyoong [Department of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of)

    2006-09-15

    We examined the effects of cross-linking molecular weights on the properties of a hyaluronic acid (HA)-poly(ethylene oxide) (PEO) hydrogel. Swelling behaviors, mechanical strength and rheological behaviors of the HA-PEO hydrogel were evaluated by employing different cross-linking molecular weights (100 kDa and 1.63 mDa) of the HAs in the hydrogel networks. The low molecular weight of HA was obtained in advance by treating high molecular weight HA with a hydrogen chloride solution. Methacrylation of HA was obtained by grafting aminopropylmethacrylate to its caroboxylic acid functional groups. While reduction of the HA molecular weights was confirmed by gel permeation chromatography, the degree of methacrylate grafting to the HA was measured by {sup 1}H-nuclear magnetic resonance. Synthesis of the HA-PEO hydrogel was successfully achieved via the Michael-type addition reaction between the methacrylate arm groups in the HA and the six thiol groups in PEO. The hydrogel formation was not dependent upon the HA molecular weights and its gelation behaviors were markedly different. Compared to the properties of the high molecular weight HA-based PEO one, the low molecular weight HA-based hydrogel induced quicker hydrogelation, as observed from the behaviors of the elastic and viscous modulus. Furthermore, the low molecular weight HA-based hydrogel demonstrated stronger mechanical properties as measured with a texture analyzer, lower water absorption as measured with a microbalance and smaller pore sizes on its surface and cross section as observed with scanning electron microscopy. The information about the effects of the cross-linking molecular weights of the gel network on the properties of the HA-based PEO hydrogel may lead to better design of hydrogels, especially in tissue engineering applications.

  4. Effects of cross-linking molecular weights in a hyaluronic acid-poly(ethylene oxide) hydrogel network on its properties

    International Nuclear Information System (INIS)

    We examined the effects of cross-linking molecular weights on the properties of a hyaluronic acid (HA)-poly(ethylene oxide) (PEO) hydrogel. Swelling behaviors, mechanical strength and rheological behaviors of the HA-PEO hydrogel were evaluated by employing different cross-linking molecular weights (100 kDa and 1.63 mDa) of the HAs in the hydrogel networks. The low molecular weight of HA was obtained in advance by treating high molecular weight HA with a hydrogen chloride solution. Methacrylation of HA was obtained by grafting aminopropylmethacrylate to its caroboxylic acid functional groups. While reduction of the HA molecular weights was confirmed by gel permeation chromatography, the degree of methacrylate grafting to the HA was measured by 1H-nuclear magnetic resonance. Synthesis of the HA-PEO hydrogel was successfully achieved via the Michael-type addition reaction between the methacrylate arm groups in the HA and the six thiol groups in PEO. The hydrogel formation was not dependent upon the HA molecular weights and its gelation behaviors were markedly different. Compared to the properties of the high molecular weight HA-based PEO one, the low molecular weight HA-based hydrogel induced quicker hydrogelation, as observed from the behaviors of the elastic and viscous modulus. Furthermore, the low molecular weight HA-based hydrogel demonstrated stronger mechanical properties as measured with a texture analyzer, lower water absorption as measured with a microbalance and smaller pore sizes on its surface and cross section as observed with scanning electron microscopy. The information about the effects of the cross-linking molecular weights of the gel network on the properties of the HA-based PEO hydrogel may lead to better design of hydrogels, especially in tissue engineering applications

  5. Researching Multipath TCP Adoption

    OpenAIRE

    Warma, Henna; Hämmäinen, Heikki

    2010-01-01

    International audience The adoption process of a new Internet protocol or only a change to an existing one is anything but trivial. The classical diffusion theory does not apply as such for studying protocol adoption because the deployment of a protocol usually requires the involvement of multiple stakeholders with varying interests. Multipath TCP (MPTCP) is a new interesting change to the TCP/IP protocol suite which is an extension to regular TCP. MPTCP exploits the idea of resource pooli...

  6. The OER Adoption Pyramid

    OpenAIRE

    Trotter, Henry; Cox, Glenda

    2016-01-01

    This Pyramid was developed in the course of a research paper focusing on why South African academics adopt OER or not. We understood that numerous factors shaped their choices, but it became apparent that some factors were "essential" to OER activity while others were merely "influential". To clarify which factors were required for any type of OER activity, we developed the OER Adoption Pyramid, which consolidates the factors into six hierarchically related categories: acc...

  7. Molecular conformations, interactions, and properties associated with drug efficiency and clinical performance among VEGFR TK inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    McTigue, Michele [Pfizer Inc., San Diego, CA (United States); Murray, Brion William [Pfizer Inc., San Diego, CA (United States); Chen, Jeffrey H. [Pfizer Inc., San Diego, CA (United States); Deng, Ya-Li [Pfizer Inc., San Diego, CA (United States); Solowiej, James [Pfizer Inc., San Diego, CA (United States); Kania, Robert S. [Pfizer Inc., San Diego, CA (United States)

    2012-09-17

    We performed analyses of compounds in clinical development which have shown that ligand efficient-molecules with privileged physical properties and low dose are less likely to fail in the various stages of clinical testing, have fewer postapproval withdrawals, and are less likely to receive black box safety warnings. However, detailed side-by-side examination of molecular interactions and properties within single drug classes are lacking. As a class, VEGF receptor tyrosine kinase inhibitors (VEGFR TKIs) have changed the landscape of how cancer is treated, particularly in clear cell renal cell carcinoma, which is molecularly linked to the VEGF signaling axis. Despite the clear role of the molecular target, member molecules of this validated drug class exhibit distinct clinical efficacy and safety profiles in comparable renal cell carcinoma clinical studies. The first head-to-head randomized phase III comparative study between active VEGFR TKIs has confirmed significant differences in clinical performance [Rini BI, et al. (2011) Lancet 378:193–1939]. To elucidate how fundamental drug potency–efficiency is achieved and impacts differentiation within the VEGFR TKI class, we determined potencies, time dependence, selectivities, and X-ray structures of the drug–kinase complexes using a VEGFR2 TK construct inclusive of the important juxtamembrane domain. Collectively, the studies elucidate unique drug–kinase interactions that are dependent on distinct juxtamembrane domain conformations, resulting in significant potency and ligand efficiency differences. Finally, the identified structural trends are consistent with in vitro measurements, which translate well to clinical performance, underscoring a principle that may be broadly applicable to prospective drug design for optimal in vivo performance.

  8. Effect of the molecular structure of phenolic novolac precursor resins on the properties of phenolic fibers

    Energy Technology Data Exchange (ETDEWEB)

    Ying, Yong-Gang; Pan, Yan-Ping; Ren, Rui; Dang, Jiang-Min; Liu, Chun-Ling, E-mail: clliutt@snnu.edu.cn

    2013-12-16

    A series of phenolic resins with different weight-average molecular weights (M{sub w}) and ortho/para (O/P) ratios were prepared. The effect of the phenolic precursor resin structure on the structure and properties of the resulting phenolic fibers was investigated. The structures of the resins and fibers were characterized by nuclear magnetic resonance spectroscopy, gel permeation chromatography, melt rheometry, dynamic mechanical analysis, and thermogravimetric analysis. The results show that the O/P ratio, unsubstituted ortho and para carbon ratio (O{sub u}/P{sub u}), and M{sub w} of the phenolic resins play an important role in determining the properties of the phenolic fibers. The tensile strength of the phenolic fibers increases with increasing novolac precursor O{sub u}/P{sub u} ratios, corresponding to low O/P ratios, at comparable resin M{sub w} values. Also, the tensile strength of the phenolic fibers increases with increasing novolac M{sub w} values at comparable O/P ratios. Phenolic fibers with high tensile strength and good flame resistance characteristics were generated from a phenolic precursor resin, possessing a high weight-average molecular weight and a low O/P value. - Highlights: • Phenolic resins with different weight-average molecular weights and ortho/para ratios have been prepared. • The tensile strength of the phenolic fibers increases with reducing novolac O/P ratio. • The tensile strength of the phenolic fibers increases with increasing novolac M{sub w}.

  9. Synthesis and photophysical properties of a novel corrole–anthraquinone–corrole molecular system

    Energy Technology Data Exchange (ETDEWEB)

    Sudhakar, Kolanu [Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad-500007, Andhra Pradesh (India); Kanaparthi, Ravi Kumar [Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad-500007, Andhra Pradesh (India); Department of Chemistry, Central University of Kerala, Reverside Transit Campus, Padanakkad, Nileshwar Kasaragod District - 671 314 Kerala (India); Kumar, Challa Kiran [Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad-500007, Andhra Pradesh (India); Giribabu, Lingamallu, E-mail: giribabu@iict.res.in [Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad-500007, Andhra Pradesh (India)

    2014-09-15

    A novel molecular triad (AQ-(H{sub 3}){sub 2}) based on tritolylcorrole and anthraquinone having azomethine-bridge at the pyrrole-β position has been designed and synthesized by following a facile one step reaction. The molecular system, AQ-(H{sub 3}){sub 2} is characterized by elemental analysis, MALDI-MS, {sup 1}H-NMR, UV–Visible and fluorescence spectroscopy (steady-state and time-resolved) as well as electrochemical methods. In absorption spectra, prominent changes such as red-shift (∼7 nm) and broadening of the both Soret and Q-bands with respect to their monomer units were observed. The present study supported by density functional theory calculations manifest that there exists a negligible electronic communication in the ground state between the donor tritolylcorrole and acceptor anthraquinone of the triad. However, interestingly, in the triad AQ-(H{sub 3}){sub 2}, fluorescence emission of the tritolylcorrole quenched significantly (17–80%) compared to their monomeric units. The emission quenching is attributed to the excited state intramolecular photoinduced electron transfer from donor tritolylcorrole to acceptor anthraquinone and the electron transfer rates (k{sub ET}) are found in the range 4.1×10{sup 8} to 2.4×10{sup 9} s{sup −1} and are found to be solvent dependent. - Highlights: • Molecular triad based on corrole and anthraquinone having azomethine-bridge at pyrrole-β position. • Ground state properties showed that there exist minimum π–π interactions. • Excited state properties showed intramolecular photoinduced electron transfer from corrole to anthraquinone.

  10. Synthesis and photophysical properties of a novel corrole–anthraquinone–corrole molecular system

    International Nuclear Information System (INIS)

    A novel molecular triad (AQ-(H3)2) based on tritolylcorrole and anthraquinone having azomethine-bridge at the pyrrole-β position has been designed and synthesized by following a facile one step reaction. The molecular system, AQ-(H3)2 is characterized by elemental analysis, MALDI-MS, 1H-NMR, UV–Visible and fluorescence spectroscopy (steady-state and time-resolved) as well as electrochemical methods. In absorption spectra, prominent changes such as red-shift (∼7 nm) and broadening of the both Soret and Q-bands with respect to their monomer units were observed. The present study supported by density functional theory calculations manifest that there exists a negligible electronic communication in the ground state between the donor tritolylcorrole and acceptor anthraquinone of the triad. However, interestingly, in the triad AQ-(H3)2, fluorescence emission of the tritolylcorrole quenched significantly (17–80%) compared to their monomeric units. The emission quenching is attributed to the excited state intramolecular photoinduced electron transfer from donor tritolylcorrole to acceptor anthraquinone and the electron transfer rates (kET) are found in the range 4.1×108 to 2.4×109 s−1 and are found to be solvent dependent. - Highlights: • Molecular triad based on corrole and anthraquinone having azomethine-bridge at pyrrole-β position. • Ground state properties showed that there exist minimum π–π interactions. • Excited state properties showed intramolecular photoinduced electron transfer from corrole to anthraquinone

  11. Proton transport properties of poly(aspartic acid) with different average molecular weights

    International Nuclear Information System (INIS)

    Research highlights: → Seven polymers with different average molecular weights were synthesized. → The proton conductivity depended on the number-average degree of polymerization. → The difference of the proton conductivities was more than one order of magnitude. → The number-average molecular weight contributed to the stability of the polymer. - Abstract: We synthesized seven partially protonated poly(aspartic acids)/sodium polyaspartates (P-Asp) with different average molecular weights to study their proton transport properties. The number-average degree of polymerization (DP) for each P-Asp was 30 (P-Asp30), 115 (P-Asp115), 140 (P-Asp140), 160 (P-Asp160), 185 (P-Asp185), 205 (P-Asp205), and 250 (P-Asp250). The proton conductivity depended on the number-average DP. The maximum and minimum proton conductivities under a relative humidity of 70% and 298 K were 1.7 . 10-3 S cm-1 (P-Asp140) and 4.6 . 10-4 S cm-1 (P-Asp250), respectively. Differential thermogravimetric analysis (TG-DTA) was carried out for each P-Asp. The results were classified into two categories. One exhibited two endothermic peaks between t = (270 and 300) oC, the other exhibited only one peak. The P-Asp group with two endothermic peaks exhibited high proton conductivity. The high proton conductivity is related to the stability of the polymer. The number-average molecular weight also contributed to the stability of the polymer.

  12. Mixing and structural properties of model polymer solutions: Molecular theory and simulation

    Science.gov (United States)

    McDaniels, Brian S.

    1999-12-01

    Recent advances in new single-site catalysts continue to fuel an already growing polymer market. As the market increases, a better understanding of polymers becomes critical. The majority of this understanding has been acquired through experimentation. While important, experimentation may be expensive and time consuming. Thus, it is desirable to predict polymer properties from molecular level characteristics. While a large amount of work has been performed in the area of overall properties of pure and mixture fluids, little work has been done in the area of mixing properties. Our initial effort into this area includes investigating the ability of the compressible Flory, generalized Flory dimer, and interpolating equations of state to predict mixing properties of a model polymer system. In determining the accuracy of the equations, Monte Carlo simulations have been performed in the Gibbs ensemble. A problem in the simulation of these systems, limited access to sampling space, has occurred and an established remedy has been discussed. We have determined that the most effective solution to the problem is a combination of conventional moves and the established correction. Predictions of the overall pressure, osmotic pressure, activity coefficient and Flory Chi parameter have been compared with simulation results, good agreement occurs at high densities, long chain lengths, and high chain concentrations except for the compressible Flory equation of state which only provides qualitatively correct predictions for the mixing properties. The structure of the fluid also is discussed. An increase in the packing fraction results in chain contraction. The addition of a monomeric solvent causes solvation in low to medium packing fraction fluids. Because the addition of solvent increases the packing fraction, the chains also contract. The effect of increasing packing fraction is stronger than the addition of solvent. The monomeric solvent forms clusters over the range of

  13. Cold and warm atomic gas around the Perseus molecular cloud. I. Basic properties

    International Nuclear Information System (INIS)

    Using the Arecibo Observatory, we have obtained neutral hydrogen (HI) absorption and emission spectral pairs in the direction of 26 background radio continuum sources in the vicinity of the Perseus molecular cloud. Strong absorption lines were detected in all cases, allowing us to estimate spin temperature (Ts ) and optical depth for 107 individual Gaussian components along these lines of sight. Basic properties of individual H I clouds (spin temperature, optical depth, and the column density of the cold and warm neutral medium (CNM and WNM), respectively) in and around Perseus are very similar to those found for random interstellar lines of sight sampled by the Millennium H I survey. This suggests that the neutral gas found in and around molecular clouds is not atypical. However, lines of sight in the vicinity of Perseus have, on average, a higher total H I column density and the CNM fraction, suggesting an enhanced amount of cold H I relative to an average interstellar field. Our estimated optical depth and spin temperature are in stark contrast with the recent attempt at using Planck data to estimate properties of the optically thick H I. Only ∼15% of lines of sight in our study have a column density weighted average spin temperature lower than 50 K, in comparison with ≳ 85% of Planck's sky coverage. The observed CNM fraction is inversely proportional to the optical depth weighted average spin temperature, in excellent agreement with the recent numerical simulations by Kim et al. While the CNM fraction is, on average, higher around Perseus relative to a random interstellar field, it is generally low, between 10%-50%. This suggests that extended WNM envelopes around molecular clouds and/or significant mixing of CNM and WNM throughout molecular clouds are present and should be considered in the models of molecule and star formation. Our detailed comparison of H I absorption with CO emission spectra shows that only 3 of the 26 directions are clear

  14. Structural and Dynamical Properties of Polyethylene/Graphene Nanocomposites through Molecular Dynamics Simulations

    Directory of Open Access Journals (Sweden)

    Anastassia N. Rissanou

    2015-02-01

    Full Text Available Detailed atomistic (united atoms molecular dynamics simulations of several graphene based polymer (polyethylene, PE nanocomposite systems have been performed. Systems with graphene sheets of different sizes have been simulated at the same graphene concentration (~3%. In addition, a periodic graphene layer (“infinite sheet” has been studied. Results concerning structural and dynamical properties of PE chains are presented for the various systems and compared to data from a corresponding bulk system. The final properties of the material are the result of a complex effect of the graphene’s sheet size, mobility and fluctuations. A detailed investigation of density, structure and dynamics of the hybrid systems has been conducted. Particular emphasis has been given in spatial heterogeneities due to the PE/graphene interfaces, which were studied through a detailed analysis based on radial distances form the graphene’s center-of-mass. Chain segmental dynamics is found to be slower, compared to the bulk one, at the PE/graphene interface by a factor of 5 to 10. Furthermore, an analysis on the graphene sheets characteristics is presented in terms of conformational properties (i.e., wrinkling and mobility.

  15. Anomalous behaviour of thermophysical properties of stoichiometric uranium dioxide by molecular dynamics simulation

    International Nuclear Information System (INIS)

    We present a classical molecular dynamics simulation of uranium dioxide in the temperature range of 300-3000 K. Temperature dependences of thermal conductivity, heat capacity and ionic conductivity are investigated. Our study shows the rise of thermal conductivity of uranium dioxide at very high temperatures (above 2500 K), which is not predicted by the former anharmonic theories. Several pair potentials are used in the simulation, and they depict similar effects. Long range forces are accounted by Ewald sums. Static thermal properties are evaluated in NPT ensemble. It is shown that a high-temperature peak on heat capacity is present and is more legible in large systems. To ensure the best reliability, transport properties are evaluated using the theory of autocorrelation functions in NVE ensemble. In order to properly define thermal conductivity in ionic systems with charge fluxes, an expression which accounts the thermoelectric effect is derived from Onsager reciprocal relations. The rise on temperature dependence of thermal conductivity is accompanied by the peak on heat capacity and an anomalous rise of ionic conductivity. However, it is shown that there is no partial melting of the oxygen sublattice, which suggests that the system does not necessarily exhibit a superionic transition. Instead, kick-out diffusion in oxygen sublattice is proposed to be the origin of such anomalous behavior of thermophysical properties. (author)

  16. Attractive mechanical properties of a lightweight highly sensitive bi layer thermistor: polycarbonate/organic molecular conductor

    Science.gov (United States)

    Laukhina, E.; Lebedev, V.; Rovira, C.; Laukhin, V.; Veciana, J.

    2016-03-01

    The paper covers some of the basic mechanical characteristics of a recently developed bi layer thermistor: polycarbonate/(001) oriented layer of organic molecular conductor α’-(BEDT-TTF)2IxBr3-x, were BEDT-TTF=bis(ethylenedithio)tetrathiafulvalen. The nano and macro mechanical properties have been studied in order to use this flexible, low cost thermistor in sensing applications by proper way. The nano-mechanical properties of the temperature sensitive semiconducting layer of α’-(BEDT-TTF)2IxBr3-x were tested using nanoindentation method. The value of Young's modulus in direction being perpendicular to the layer plan was found as 9.0 ±1.4 GPa. The macro mechanical properties of the thermistor were studied using a 5848 MicroTester. The tensile tests showed that basic mechanical characteristics of the thermistor are close to those of polycarbonate films. This indicates a good mechanical strength of the developed sensor. Therefore, the thermistor can be used in technologies that need to be instrumented with highly robustness lightweight low cost temperature sensors. The paper also reports synthetic details on fabricating temperature sensing e-textile. As the temperature control is becoming more and more important in biomedical technologies like healthcare monitoring, this work strongly contributes on the ongoing research on engineering sensitive conducting materials for biomedical applications.

  17. On the spin separation of algebraic two-component relativistic Hamiltonians: Molecular properties

    International Nuclear Information System (INIS)

    The idea for separating the algebraic exact two-component (X2C) relativistic Hamiltonians into spin-free (sf) and spin-dependent terms [Z. Li, Y. Xiao, and W. Liu, J. Chem. Phys. 137, 154114 (2012)] is extended to both electric and magnetic molecular properties. Taking the spin-free terms (which are correct to infinite order in α ≈ 1/137) as zeroth order, the spin-dependent terms can be treated to any desired order via analytic derivative technique. This is further facilitated by unified Sylvester equations for the response of the decoupling and renormalization matrices to single or multiple perturbations. For practical purposes, explicit expressions of order α2 in spin are also given for electric and magnetic properties, as well as two-electron spin-orbit couplings. At this order, the response of the decoupling and renormalization matrices is not required, such that the expressions are very compact and completely parallel to those based on the Breit-Pauli (BP) Hamiltonian. However, the former employ sf-X2C wave functions, whereas the latter can only use nonrelativistic wave functions. As the sf-X2C terms can readily be interfaced with any nonrelativistic program, the implementation of the O(α2) spin-orbit corrections to sf-X2C properties requires only marginal revisions of the routines for evaluating the BP type of corrections

  18. Active microrheology reveals molecular-level variations in the viscoelastic properties of Chaetopterus mucus

    Science.gov (United States)

    Weigand, William; Messmore, Ashley; Anderson, Rae

    The sea annelid, Chaetopterus Variopedatus, secretes a bioluminescent mucus that also exhibits complex viscoelastic properties. The constituents of the mucus are relatively unknown but it does play an important role in the development of the worms' parchment-like housing tubes. In order to determine how and why this mucus can exhibit material properties ranging from fluidity to rigidity we perform microrheology experiments. We determine the microscale viscoelastic properties by using optical tweezers to produce small oscillations in the mucus which allow us to determine both the linear storage and loss moduli (G',G'') along with the viscosity of the fluid. By varying the size of the microspheres (2-10 µm) and oscillation amplitude (.5-10 µm) we are able to determine the dominant intrinsic length scales of the molecular mesh comprising the mucus. By varying the oscillation frequency (1-15Hz) we determine the crossover frequency at which G' surpasses G'', to quantify the longest relaxation time of the mesh network. Initial results show a strong dependence on bead size which indicate that the dominant entanglement lengthscale of the mucus mesh is ~5 um. Microspheres of this size exhibit a wide variety of stress responses in different regions of the mucus demonstrating the substantial microscale heterogeneity of the mucus. We carry out measurements on a population of worms of varying size and age to determine mucus variability between worms.

  19. A Molecular Dynamics Study of the Structural and Dynamical Properties of Putative Arsenic Substituted Lipid Bilayers

    Directory of Open Access Journals (Sweden)

    Ratna Juwita

    2013-04-01

    Full Text Available Cell membranes are composed mainly of phospholipids which are in turn, composed of five major chemical elements: carbon, hydrogen, nitrogen, oxygen, and phosphorus. Recent studies have suggested the possibility of sustaining life if the phosphorus is substituted by arsenic. Although this issue is still controversial, it is of interest to investigate the properties of arsenated-lipid bilayers to evaluate this possibility. In this study, we simulated arsenated-lipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-arsenocholine (POAC, lipid bilayers using all-atom molecular dynamics to understand basic structural and dynamical properties, in particular, the differences from analogous 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, (POPC lipid bilayers. Our simulations showed that POAC lipid bilayers have distinct structural and dynamical properties from those of native POPC lipid bilayers. Relative to POPC lipid bilayers, POAC lipid bilayers have a more compact structure with smaller lateral areas and greater order. The compact structure of POAC lipid bilayers is due to the fact that more inter-lipid salt bridges are formed with arsenate-choline compared to the phosphate-choline of POPC lipid bilayers. These inter-lipid salt bridges bind POAC lipids together and also slow down the head group rotation and lateral diffusion of POAC lipids. Thus, it would be anticipated that POAC and POPC lipid bilayers would have different biological implications.

  20. Biopolymer molecular weight control by radiation treatment for functional property improvement

    International Nuclear Information System (INIS)

    Radiation treatment was used to control molecular weight of chitosan in order to improve their functional properties including adherent capacity in shrimp feed and antimicrobial activity in fresh fruit coating. Solid-state radiation treatment of chitosan at dose 30-100 kGy significantly improved the water-stability of shrimp feed. Liquid-state radiation treatment, in comparison with solid-state irradiation at 100 kGy, required only dose of 4-6 kGy for similar MW and for the same improvement in adherent property. Gelatin also has been improved in adherent property by solid-state irradiation. Solid-state radiation treatment at 50-100 kGy enhanced antimicrobial activity of chitosan against bacteria, fungi, and yeast. The antimicrobial activity is regulated not only by MW but also by its distribution. Irradiated chitosan that has the largest width of MW distribution ( MW/Mn ) may possess the highest antimicrobial activity. The result from fractionation by using centrifugal filter devices showed that the 3-5 x 104 fraction has mainly contributed to the suppression of microbial growth. (Author)

  1. Beyond the adoption/ non-adoption dichotomy: the impact of innovation characteristics on potential adopters' transition through adoption process stages

    OpenAIRE

    Frambach, R T; Agarwal, M.K.; Nijssen, E.J.

    2002-01-01

    Research on innovation adoption has suffered from a bias towards understanding the factors that affect the dichotomous adoption/non-adoption decision. Much less attention is devoted to the question why potential adopters fail to progress to the adoption stage from earlier stages in the decision making process. Such knowledge is essential to understand what factors actually underlie the non-adoption of an innovation. As perceived innovation characteristics have been found to influence adoption...

  2. Defined-size DNA triple crossover construct for molecular electronics: modification, positioning and conductance properties

    International Nuclear Information System (INIS)

    We present a novel, defined-size, small and rigid DNA template, a so-called B-A-B complex, based on DNA triple crossover motifs (TX tiles), which can be utilized in molecular scale patterning for nanoelectronics, plasmonics and sensing applications. The feasibility of the designed construct is demonstrated by functionalizing the TX tiles with one biotin-triethylene glycol (TEG) and efficiently decorating them with streptavidin, and furthermore by positioning and anchoring single thiol-modified B-A-B complexes to certain locations on a chip via dielectrophoretic trapping. Finally, we characterize the conductance properties of the non-functionalized construct, first by measuring DC conductivity and second by utilizing AC impedance spectroscopy in order to describe the conductivity mechanism of a single B-A-B complex using a detailed equivalent circuit model. This analysis also reveals further information about the conductivity of DNA structures in general.

  3. Defined-size DNA triple crossover construct for molecular electronics: modification, positioning and conductance properties

    Energy Technology Data Exchange (ETDEWEB)

    Linko, Veikko; Paasonen, Seppo-Tapio; Jussi Toppari, J [Nanoscience Center, Department of Physics, University of Jyvaeskylae, PO Box 35, FIN-40014 (Finland); Leppiniemi, Jenni; Hytoenen, Vesa P, E-mail: veikko.linko@jyu.fi [Institute of Biomedical Technology, University of Tampere and Tampere University Hospital, FIN-33014 (Finland)

    2011-07-08

    We present a novel, defined-size, small and rigid DNA template, a so-called B-A-B complex, based on DNA triple crossover motifs (TX tiles), which can be utilized in molecular scale patterning for nanoelectronics, plasmonics and sensing applications. The feasibility of the designed construct is demonstrated by functionalizing the TX tiles with one biotin-triethylene glycol (TEG) and efficiently decorating them with streptavidin, and furthermore by positioning and anchoring single thiol-modified B-A-B complexes to certain locations on a chip via dielectrophoretic trapping. Finally, we characterize the conductance properties of the non-functionalized construct, first by measuring DC conductivity and second by utilizing AC impedance spectroscopy in order to describe the conductivity mechanism of a single B-A-B complex using a detailed equivalent circuit model. This analysis also reveals further information about the conductivity of DNA structures in general.

  4. Bond orientation properties in lipid molecules of membranes: molecular dynamics simulations

    International Nuclear Information System (INIS)

    Atomistic molecular dynamics simulations have been carried out for 16 different fully hydrated phosphatidylcholine lipid bilayers, having 16 or 18 carbon atoms in fully saturated sn − 1 chain and from 18 to 22 carbon atoms in sn − 2 chain with different degree of unsaturation, with the purpose to investigate the effect of unsaturation on physical properties of lipid bilayers. Special attention has been paid to profiles of C-C and C-H bond order parameters of lipid molecules and the orientational fluctuations of these bond vectors. It was shown that the study of anisotropy degree of bond orientations probability distributions allows distinguishing extended regions with different types of angular fluctuations of bonds in a membrane formed by lipid molecules with unsaturated chains.

  5. Molecular beam epitaxy growth and magnetic properties of Cr-Co-Ga Heusler alloy films

    International Nuclear Information System (INIS)

    We have re-investigated growth and magnetic properties of Cr2CoGa films using molecular beam epitaxy technique. Phase separation and precipitate formation were observed experimentally again in agreement with observation of multiple phases separation in sputtered Cr2CoGa films by M. Meinert et al. However, significant phase separation could be suppressed by proper control of growth conditions. We showed that Cr2CoGa Heusler phase, rather than Co2CrGa phase, constitutes the majority of the sample grown on GaAs(001) at 450 oC. The measured small spin moment of Cr2CoGa is in agreement with predicted HM-FCF nature; however, its Curie temperature is not as high as expected from the theoretical prediction probably due to the off-stoichiometry of Cr2CoGa and the existence of the disorders and phase separation

  6. Analytic nuclear forces and molecular properties from full configuration interaction quantum Monte Carlo

    CERN Document Server

    Thomas, Robert E; Overy, Catherine; Knowles, Peter J; Alavi, Ali; Booth, George H

    2015-01-01

    Unbiased stochastic sampling of the one- and two-body reduced density matrices is achieved in full configuration interaction quantum Monte Carlo with the introduction of a second, "replica" ensemble of walkers, whose population evolves in imaginary time independently from the first, and which entails only modest additional computational overheads. The matrices obtained from this approach are shown to be representative of full configuration-interaction quality, and hence provide a realistic opportunity to achieve high-quality results for a range of properties whose operators do not necessarily commute with the hamiltonian. A density-matrix formulated quasi-variational energy estimator having been already proposed and investigated, the present work extends the scope of the theory to take in studies of analytic nuclear forces, molecular dipole moments and polarisabilities, with extensive comparison to exact results where possible. These new results confirm the suitability of the sampling technique and, where suf...

  7. Structure and flow properties of micelle-nanoparticle solutions from Molecular Dynamics simulations

    Science.gov (United States)

    Sureshkumar, Radhakrishna; Dhakal, Subas; Sambasivam, Abhinanden

    2014-03-01

    In aqueous media, cationic surfactant molecules spontaneously self-assemble into diverse morphologies depending upon temperature, surfactant concentration and solution ionic strength. Spherical, cylindrical and long (~ microns) flexible wormlike structures with or without branches with distinct rheological properties are observed. Inclusion of nanoparticles (NPs) provides additional means to manipulate structure and create active ``nano-fluids'' that respond to optical, magnetic or electrical stimuli. We study self-assembly, dynamics and rheology of such fluids using coarse-grained Molecular Dynamics simulations in presence of explicit solvent and salt. Specifically, we will discuss the mechanisms underlying fascinating phenomenology observed experimentally such as the pronounced non-monotonic dependence of the zero shear viscosity on salt/NP concentration, shear-induced structure formation, and isotropic to nematic transitions. NSF grants 1049489, 1049454 for the financial support, and Pittsburg Super Computer Centre for providing HPC resources.

  8. Identification and properties of molecular systems of potential use in solar-pumped lasers

    Science.gov (United States)

    Micha, D. A.; Oehrn, N. Y.

    1985-01-01

    The concepts and computational tools of theortical chemistry are used to investigate molecular properties needed in direct solar-pumped lasers. Compounds of the type RR'CXY, with R and R' organic groups, and X and Y halide atoms were identified as likely candidates because of their highly enhanced absorption coefficients over compounds with a single halide atom. The use of a combination of vibrational excitation followed by electronic excitation to enhance quantum yields at certain wavelengths is indicated. A self-consistent eikonal approximation to state-to-state transitions was tested for CH3I and is useful for other problems involving electronic energy and charge transfer. An approach to calculate potential energy surfaces and transition dipoles was developed which is based on the generation of eigenstates of the nonrelativisitc Hamiltonian followed by incorporation of the spin-orbit coupling by configuration interaction.

  9. Gas-Transport-Property Performance of Hybrid Carbon Molecular Sieve−Polymer Materials

    KAUST Repository

    Das, Mita

    2010-10-06

    High-performance hybrid materials using carbon molecular sieve materials and 6FDA-6FpDA were produced. A detailed analysis of the effects of casting processes and the annealing temperature is reported. Two existing major obstacles, sieve agglomeration and residual stress, were addressed in this work, and subsequently a new membrane formation technique was developed to produce high-performing membranes. The successfully improved interfacial region of the hybrid membranes allows the sieves to increase the selectivity of the membranes above the neat polymer properties. Furthermore, an additional performance enhancement was seen with increased sieve loading in the hybrid membranes, leading to an actual performance above the upper bound for pure polymer membranes. The membranes were also tested under a mixed-gas environment, which further demonstrated promising results. © 2010 American Chemical Society.

  10. Thermodynamic properties of Li, Pb and Li17Pb83 with molecular dynamics simulations

    International Nuclear Information System (INIS)

    Graphical abstract: - Abstract: In this work, new EAM potentials for Li, Pb and Li–Pb alloy have been constructed. Based on these potentials, the structural, thermodynamic and diffusion properties of Li, Pb and Li17Pb83 have been studied with molecular dynamics simulations. The calculated radial distribution functions and static structure factors agree well with previous reported data. The partial radial distribution functions indicate that liquid Li17Pb83 shows a hetero-coordination tendency and the partial Bhatia–Thornton structure factor SCC(q) suggests the concentration fluctuation in Li17Pb83 is not large. As comparing to the self-diffusion coefficients, the component diffusion coefficients are much smaller for Li atoms, and almost the same for Pb atoms. Density, enthalpy, capacity, melting point, latent heat of fusion and surface tension are also in reasonable agreement with the literature data within the experimental error

  11. Photocatalytic Properties of Nb/MCM-41 Molecular Sieves: Effect of the Synthesis Conditions

    Directory of Open Access Journals (Sweden)

    Caterine Daza Gomez

    2015-08-01

    Full Text Available The effect of synthesis conditions and niobium incorporation levels on the photocatalytic properties of Nb/MCM-41 molecular sieves was assessed. Niobium pentoxide supported on MCM-41 mesoporous silica was obtained using two methods: sol-gel and incipient impregnation, in each case also varying the percentage of niobium incorporation. The synthesized Nb-MCM-41 ceramic powders were characterized using the spectroscopic techniques of infrared spectroscopy (IR, Raman spectroscopy, X-ray diffraction (XRD, and transmission electron microscopy (TEM. The photodegradation capacity of the powders was studied using the organic molecule, methylene blue. The effect of both the method of synthesis and the percentage of niobium present in the sample on the photodegradation action of the solids was determined. The mesoporous Nb-MCM-41 that produced the greatest photodegradation response was obtained using the sol-gel method and 20% niobium incorporation.

  12. Static and dynamic properties of confined, cold ion plasmas: MD (molecular dynamics) simulations

    Energy Technology Data Exchange (ETDEWEB)

    Schiffer, J.P.

    1989-01-01

    Some four years ago it was suggested that in the new generation of heavy ion accelerator storage rings for multiply charged ions, being planned in Europe, one may well attain internal temperatures that would correspond to very cold plasmas. Since that time, the techniques of electron or laser cooling of such beams has evolved and it may well be possible to reach temperatures corresponding to a plasma coupling parameter {Gamma} >> 100. I was fortunate to have had an opportunity to collaborate during 1986-87 with my former colleague Aneesur Rahman, of Molecular Dynamics fame, and we adapted the MD method to the calculation of the properties of cold confined plasmas. After Rahman's premature death two years ago I have continued the exploration of these systems and would like to summarize the results here. 9 refs., 10 figs.

  13. Effect of molecular weight reduction by gamma irradiation on chitosan film properties

    Energy Technology Data Exchange (ETDEWEB)

    García, Mario A., E-mail: marioifal@gmail.com [Pharmacy and Food Institute, University of Havana, St. 222 No. 2317, ZC 13600 Havana (Cuba); Pérez, Liliam [Pharmacy and Food Institute, University of Havana, St. 222 No. 2317, ZC 13600 Havana (Cuba); Paz, Nilia de la [Drugs Research and Development Center, Ave. 26 No. 1605, Havana (Cuba); González, Juan [Food Industry Research Institute, Carretera al Guatao km 3 1/2, Havana, CP 19200 (Cuba); Rapado, Manuel [Radiobiology Department, Center for Technological Applications and Nuclear Development, St. 30 No. 502, Playa, Havana (Cuba); Casariego, Alicia [Pharmacy and Food Institute, University of Havana, St. 222 No. 2317, ZC 13600 Havana (Cuba)

    2015-10-01

    The present work aimed the influence of molecular weight (MW) reduction by irradiation with {sup 60}Co and polymer concentration on some physical properties of chitosan films. Irradiation of chitosan with a MW of 275.221 kDa and 74.74% of deacetylation degree was performed using a {sup 60}Co source to provide doses of 5, 10, 20 and 50 kGy to obtain chitosans with molecular weights of 247.847, 221.563, 126.469 and 77.063 kDa, respectively. Films were prepared via the solution casting method. Film-forming solutions (FFS) of chitosan irradiated or not, were prepared at 1.5 and 2% (w/v) in a solution of lactic acid at 1% (v/v) and 0.1% (v/v) of Tween 80. The FFS were poured into glass plates of 400 cm{sup 2} and dried at 60 °C during 10 h without airflow. The decrease of MW and increase of chitosan concentration increased the tensil strength and water vapor permeability while decreased the elongation at break of the films. The chitosan MW did not significantly influence (p > 0.05) the water solubility of films within a same polymer concentration. There was a decrease in the films' brightness with the increase of concentration and a decrease of the MW of irradiated chitosan, while the b* values of films increased and there was an increasing tendency of their apparent opacity. - Highlights: • MW reduction by {sup 60}Co irradiation increased the tensil strength of chitosan films. • MW reduction increased the water vapor permeability of chitosan films. • MW did not affect the films' water solubility within a same chitosan concentration. • Films' brightness decreased with the chitosan molecular weight reduction.

  14. Effect of molecular weight reduction by gamma irradiation on chitosan film properties

    International Nuclear Information System (INIS)

    The present work aimed the influence of molecular weight (MW) reduction by irradiation with 60Co and polymer concentration on some physical properties of chitosan films. Irradiation of chitosan with a MW of 275.221 kDa and 74.74% of deacetylation degree was performed using a 60Co source to provide doses of 5, 10, 20 and 50 kGy to obtain chitosans with molecular weights of 247.847, 221.563, 126.469 and 77.063 kDa, respectively. Films were prepared via the solution casting method. Film-forming solutions (FFS) of chitosan irradiated or not, were prepared at 1.5 and 2% (w/v) in a solution of lactic acid at 1% (v/v) and 0.1% (v/v) of Tween 80. The FFS were poured into glass plates of 400 cm2 and dried at 60 °C during 10 h without airflow. The decrease of MW and increase of chitosan concentration increased the tensil strength and water vapor permeability while decreased the elongation at break of the films. The chitosan MW did not significantly influence (p > 0.05) the water solubility of films within a same polymer concentration. There was a decrease in the films' brightness with the increase of concentration and a decrease of the MW of irradiated chitosan, while the b* values of films increased and there was an increasing tendency of their apparent opacity. - Highlights: • MW reduction by 60Co irradiation increased the tensil strength of chitosan films. • MW reduction increased the water vapor permeability of chitosan films. • MW did not affect the films' water solubility within a same chitosan concentration. • Films' brightness decreased with the chitosan molecular weight reduction

  15. Size Effect on Transport Properties of Gaseous Argon: A Molecular Dynamics Simulation Study

    International Nuclear Information System (INIS)

    We have carried out a series of equilibrium molecular dynamics (EMD) simulations of gaseous argon at 273.15 K and 1.00 atm for the calculation of transport properties as a function of the number of argon molecules (N). While the diffusion coefficients (D) of gaseous argon approach to the experimental measure with increasing N, the viscosities (η) and thermal conductivities (λ) obtained for N = 432 are unreliable due to the high fluctuation of the time correlation functions and those for N = 1728 are rather acceptable. Increasing further to N = 6912 has improved the MD results a little closer to the experimental measures for η and λ. Both the EMD results for η and λ for N = 6912 underestimate the experimental measures and it is not expected that the more increasing N makes the closer results to the experimental measures. One possible explanation for the large disagreement between MD results and the experimental measures for η and λ may be due to the use of LJ parameters which were used for liquid argon. In a recent study, we have examined the Green-Kubo formula for the calculation of transport properties (diffusion coefficient, viscosity, and thermal conductivity) of noble gases (He, Ne, Ar, Kr, and Xe) by carrying out a series of equilibrium molecular dynamics (EMD) simulations for the system of N=1728 at 273.15 K and 1.00 atm.1 While the diffusion coefficients (D) of noble gases were obtained through the original Green-Kubo formula, the viscosities (η) and thermal conductivities (λ) were obtained by utilizing the revised Green-Kubo formulas. The structural and dynamic properties of gaseous argon are completely different from those of liquid argon at 94.4 K and 1.374 g/cm3. The results for transport properties (D, η, and λ) at 273.15 K and 1.00 atm obtained from our EMD simulations are in general agreement with the experimental data and superior to the rigorous results of the kinetic theory

  16. Cold and warm atomic gas around the Perseus molecular cloud I: Basic Properties

    CERN Document Server

    Stanimirovic, Snezana; Lee, Min-Young; Heiles, Carl; Miller, Jesse

    2014-01-01

    (Abridged) Using the Arecibo Observatory we have obtained neutral hydrogen (HI) absorption and emission spectral pairs in the direction of 26 background radio continuum sources in the vicinity of the Perseus molecular cloud. Strong absorption lines were detected in all cases allowing us to estimate spin temperature (T_s) and optical depth for 107 individual Gaussian components along these lines of sight. Basic properties of individual HI clouds (spin temperature, optical depth, and the column density of the cold and warm neutral medium, CNM and WNM) in and around Perseus are very similar to those found for random interstellar lines of sight sampled by the Millennium HI survey. This suggests that the neutral gas found in and around molecular clouds is not atypical. However, lines of sight in the vicinity of Perseus have on average a higher total HI column density and the CNM fraction, suggesting an enhanced amount of cold HI relative to an average interstellar field. Our estimated optical depth and spin temper...

  17. Wheat waxy proteins: polymorphism, molecular characterization and effects on starch properties.

    Science.gov (United States)

    Guzmán, Carlos; Alvarez, Juan B

    2016-01-01

    The starch fraction, comprising about 70% of the total dry matter in the wheat grain, can greatly affect the end-use quality of products made from wheat kernels, especially Asian noodles. Starch is associated with the shelf life and nutritional value (glycaemic index) of different wheat products. Starch quality is closely associated with the ratio of amylose to amylopectin, the two main macromolecules forming starch. In this review, we briefly summarise the discovery of waxy proteins-shown to be the sole enzymes responsible for amylose synthesis in wheat. The review particularly focuses on the different variants of these proteins, together with their molecular characterisation and evaluation of their effects on starch composition. There have been 19 different waxy protein variants described using protein electrophoresis; and at a molecular level 19, 15 and seven alleles described for Wx-A1, Wx-B1 and Wx-D1, respectively. This large variability, found in modern wheat and genetic resources such as wheat ancestors and wild relatives, is in some cases not properly ordered. The proper ordering of all the data generated is the key to enhancing use in breeding programmes of the current variability described, and thus generating wheat with novel starch properties to satisfy the demand of industry and consumers for novel high-quality processed food. PMID:26276148

  18. Properties of lipid electropores I: Molecular dynamics simulations of stabilized pores by constant charge imbalance.

    Science.gov (United States)

    Casciola, Maura; Kasimova, Marina A; Rems, Lea; Zullino, Sara; Apollonio, Francesca; Tarek, Mounir

    2016-06-01

    Molecular dynamics (MD) simulations have become a powerful tool to study electroporation (EP) in atomic detail. In the last decade, numerous MD studies have been conducted to model the effect of pulsed electric fields on membranes, providing molecular models of the EP process of lipid bilayers. Here we extend these investigations by modeling for the first time conditions comparable to experiments using long (μs-ms) low intensity (~kV/cm) pulses, by studying the characteristics of pores formed in lipid bilayers maintained at a constant surface tension and subject to constant charge imbalance. This enables the evaluation of structural (size) and electrical (conductance) properties of the pores formed, providing information hardly accessible directly by experiments. Extensive simulations of EP of simple phosphatidylcholine bilayers in 1M NaCl show that hydrophilic pores with stable radii (1-2.5nm) form under transmembrane voltages between 420 and 630mV, allowing for ionic conductance in the range of 6.4-29.5nS. We discuss in particular these findings and characterize both convergence and size effects in the MD simulations. We further extend these studies in a follow-up paper (Rems et al., Bioelectrochemistry, Submitted), by proposing an improved continuum model of pore conductance consistent with the results from the MD simulations. PMID:26883056

  19. Effects of ultrasound on molecular properties, structure, chain conformation and degradation kinetics of carboxylic curdlan.

    Science.gov (United States)

    Yan, Jing-Kun; Pei, Juan-Juan; Ma, Hai-Le; Wang, Zhen-Bin

    2015-05-01

    In this study, high-intensity ultrasound (20 kHz), a simple, effective and without any additive method, was used to the degradation of carboxylic curdlan (Cc) produced by 4-acetamido-TEMPO-mediated oxidation. The effects of ultrasound on molecular properties, structure and chain conformations of Cc were investigated by viscometry, size-exclusion chromatography with multiangle laser-light scattering (SEC-MALLS) analysis, as well as FTIR and NMR spectroscopies. The results indicated that the intrinsic viscosity [η] and the weight-average molecular weight (Mw) of Cc decreased obviously after ultrasound, and a uniform and narrow distribution of degradation product was obtained. The z-average radius of gyrations (Rg) firstly increased and then decreased as the sonication time prolonged. Ultrasound destroyed the hydrogen bonds resulting in the transition from compact random coil conformation to more flexible and even shorter extended chains. Ultrasonic treatment could not alter the primary chemical structure of Cc molecules according to the structural analysis by FTIR and NMR spectroscopies. Degradation kinetics based on Schmid model was applied to estimate the degradation rate constant k. It was found that the k value of Cc decreased with increasing the polymer concentration from 0.05 to 0.2% (w/v). PMID:25659672

  20. Structural properties of thermoelectric CoSb3 skutterudite thin films prepared by molecular beam deposition

    International Nuclear Information System (INIS)

    Highlights: • Different methods were used to deposit Co–Sb thin film by molecular beam deposition. • The phase formation is strongly dependent on the Sb content of the film. • The fabrication of high-quality single phase skutterudite thin films could be shown. • The grain size of the films is very sensitive to the used deposition parameters. • It was shown, that large deposition rates support the formation of parasitic phases. - Abstract: The research field of thermoelectricity was renewed by the progress made in nanostructuring approaches and by the investigation of new material groups as skutterudites, whose most promising representative is CoSb3. In this work Co–Sb thin films with a thickness of 30 nm were deposited by molecular beam deposition at different substrate temperatures as well as on non-heated substrates followed by a post-annealing step. An extended investigation of the phase formation in dependence of deposition method and parameters, film composition, and post-treatment is given. The presented results provide different routes to achieve high quality single phase films. It was also demonstrated that the grain size of the CoSb3 thin films is very sensitive to the used deposition method and especially on the substrate temperature during deposition. A controllable grain size by changing the deposition parameters could be a key feature for the optimization of the thermoelectric properties, since especially the thermal conductivity should strongly depend on the grain size due to enhanced grain boundary scattering of phonons

  1. Molecular dynamics study of mechanical properties of carbon nanotube reinforced aluminum composites

    Science.gov (United States)

    Srivastava, Ashish Kumar; Mokhalingam, A.; Singh, Akhileshwar; Kumar, Dinesh

    2016-05-01

    Atomistic simulations were conducted to estimate the effect of the carbon nanotube (CNT) reinforcement on the mechanical behavior of CNT-reinforced aluminum (Al) nanocomposite. The periodic system of CNT-Al nanocomposite was built and simulated using molecular dynamics (MD) software LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). The mechanical properties of the nanocomposite were investigated by the application of uniaxial load on one end of the representative volume element (RVE) and fixing the other end. The interactions between the atoms of Al were modeled using embedded atom method (EAM) potentials, whereas Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential was used for the interactions among carbon atoms and these pair potentials are coupled with the Lennard-Jones (LJ) potential. The results show that the incorporation of CNT into the Al matrix can increase the Young's modulus of the nanocomposite substantially. In the present case, i.e. for approximately 9 with % reinforcement of CNT can increase the axial Young's modulus of the Al matrix up to 77 % as compared to pure Al.

  2. Optimizing molecular properties using a relative index of thermodynamic stability and global optimization techniques

    Science.gov (United States)

    Fournier, René; Mohareb, Amir

    2016-01-01

    We devised a global optimization (GO) strategy for optimizing molecular properties with respect to both geometry and chemical composition. A relative index of thermodynamic stability (RITS) is introduced to allow meaningful energy comparisons between different chemical species. We use the RITS by itself, or in combination with another calculated property, to create an objective function F to be minimized. Including the RITS in the definition of F ensures that the solutions have some degree of thermodynamic stability. We illustrate how the GO strategy works with three test applications, with F calculated in the framework of Kohn-Sham Density Functional Theory (KS-DFT) with the Perdew-Burke-Ernzerhof exchange-correlation. First, we searched the composition and configuration space of CmHnNpOq (m = 0-4, n = 0-10, p = 0-2, q = 0-2, and 2 ≤ m + n + p + q ≤ 12) for stable molecules. The GO discovered familiar molecules like N2, CO2, acetic acid, acetonitrile, ethane, and many others, after a small number (5000) of KS-DFT energy evaluations. Second, we carried out a GO of the geometry of Cu m Snn + (m = 1, 2 and n = 9-12). A single GO run produced the same low-energy structures found in an earlier study where each Cu m S nn + species had been optimized separately. Finally, we searched bimetallic clusters AmBn (3 ≤ m + n ≤ 6, A,B= Li, Na, Al, Cu, Ag, In, Sn, Pb) for species and configurations having a low RITS and large highest occupied Molecular Orbital (MO) to lowest unoccupied MO energy gap (Eg). We found seven bimetallic clusters with Eg > 1.5 eV.

  3. Optimizing molecular properties using a relative index of thermodynamic stability and global optimization techniques.

    Science.gov (United States)

    Fournier, René; Mohareb, Amir

    2016-01-14

    We devised a global optimization (GO) strategy for optimizing molecular properties with respect to both geometry and chemical composition. A relative index of thermodynamic stability (RITS) is introduced to allow meaningful energy comparisons between different chemical species. We use the RITS by itself, or in combination with another calculated property, to create an objective function F to be minimized. Including the RITS in the definition of F ensures that the solutions have some degree of thermodynamic stability. We illustrate how the GO strategy works with three test applications, with F calculated in the framework of Kohn-Sham Density Functional Theory (KS-DFT) with the Perdew-Burke-Ernzerhof exchange-correlation. First, we searched the composition and configuration space of CmHnNpOq (m = 0-4, n = 0-10, p = 0-2, q = 0-2, and 2 ≤ m + n + p + q ≤ 12) for stable molecules. The GO discovered familiar molecules like N2, CO2, acetic acid, acetonitrile, ethane, and many others, after a small number (5000) of KS-DFT energy evaluations. Second, we carried out a GO of the geometry of CumSnn (+) (m = 1, 2 and n = 9-12). A single GO run produced the same low-energy structures found in an earlier study where each CumSnn (+) species had been optimized separately. Finally, we searched bimetallic clusters AmBn (3 ≤ m + n ≤ 6, A,B= Li, Na, Al, Cu, Ag, In, Sn, Pb) for species and configurations having a low RITS and large highest occupied Molecular Orbital (MO) to lowest unoccupied MO energy gap (Eg). We found seven bimetallic clusters with Eg > 1.5 eV. PMID:26772561

  4. Thermal and dynamic mechanical properties of vitamin E infused and blended ultra-high molecular weight polyethylenes

    OpenAIRE

    Puértolas, J. A.; Martínez-Morlanes, M. J.; Mariscal, M. D.; Medel, F. J.

    2011-01-01

    Vitamin E (or α-tocopherol) is an alternative via to thermal treatments to achieve oxidative stability of gamma or electron beam irradiated ultra-high molecular weight polyethylenes (UHMWPE) used in total joint replacements. Our aim was to study the effects of vitamin E on the molecular dynamics and microstructural properties of UHMWPE. We hypothesized that the antioxidant would plasticize UHMWPE. Vitamin E was incorporated into UHMWPE at different concentrations by diffusion and blending and...

  5. Adoption of Children With Disabilities: A Study With Adoptive Parents

    OpenAIRE

    Gisele De Mozzi; Adriano Henrique Nuernberg

    2016-01-01

    Abstract Taking into consideration the supremacy of a child's profile often chosen by adoptive parents, this study aimed to understand the adoption of children with disabilities from the perspective of adoptive parents who have experienced this practice. The participants were eleven adoptive families of disabled children, all of whom had knowledge about the health conditions of the adoptive children at the time of adoption. The instruments used were a semi-structured interview and a sociodemo...

  6. Questions about Adoption

    Science.gov (United States)

    ... Dynamics Adoption & Foster Care Communication & Discipline Types of Families Media Work & Play Getting Involved in Your Community Healthy Children > ... on. Find other words that everyone in your family is comfortable with. The terms birth mother and birth father are very common. Biological parents ...

  7. CERTS customer adoption model

    Energy Technology Data Exchange (ETDEWEB)

    Rubio, F. Javier; Siddiqui, Afzal S.; Marnay, Chris; Hamachi,Kristina S.

    2000-03-01

    This effort represents a contribution to the wider distributed energy resources (DER) research of the Consortium for Electric Reliability Technology Solutions (CERTS, http://certs.lbl.gov) that is intended to attack and, hopefully, resolve the technical barriers to DER adoption, particularly those that are unlikely to be of high priority to individual equipment vendors. The longer term goal of the Berkeley Lab effort is to guide the wider technical research towards the key technical problems by forecasting some likely patterns of DER adoption. In sharp contrast to traditional electricity utility planning, this work takes a customer-centric approach and focuses on DER adoption decision making at, what we currently think of as, the customer level. This study reports on Berkeley Lab's second year effort (completed in Federal fiscal year 2000, FY00) of a project aimed to anticipate patterns of customer adoption of distributed energy resources (DER). Marnay, et al., 2000 describes the earlier FY99 Berkeley Lab work. The results presented herein are not intended to represent definitive economic analyses of possible DER projects by any means. The paucity of data available and the importance of excluded factors, such as environmental implications, are simply too important to make such an analysis possible at this time. Rather, the work presented represents a demonstration of the current model and an indicator of the potential to conduct more relevant studies in the future.

  8. Associations between the molecular and optical properties of dissolved organic matter in the Florida Everglades, a model coastal wetland system

    Directory of Open Access Journals (Sweden)

    Sasha eWagner

    2015-11-01

    Full Text Available Optical properties are easy-to-measure proxies for dissolved organic matter (DOM composition, source and reactivity. However, the molecular signature of DOM associated with such optical parameters remains poorly defined. The Florida coastal Everglades is a subtropical wetland with diverse vegetation (e.g., sawgrass prairies, mangrove forests, seagrass meadows and DOM sources (e.g., terrestrial, microbial and marine. As such, the Everglades is an excellent model system from which to draw samples of diverse origin and composition to allow classically-defined optical properties to be linked to molecular properties of the DOM pool. We characterized a suite of seasonally- and spatially-collected DOM samples using optical measurements (EEM-PARAFAC, SUVA254, S275-295, S350-400, SR, FI, freshness index and HIX and ultrahigh resolution mass spectrometry (FTICR-MS. Spearman’s rank correlations between FTICR-MS signal intensities of individual molecular formulae and optical properties determined which molecular formulae were associated with each PARAFAC component and optical index. The molecular families that tracked with the optical indices were generally in agreement with conventional biogeochemical interpretations. Therefore, although they represent only a small portion of the bulk DOM pool, absorbance and fluorescence measurements appear to be appropriate proxies for the aquatic cycling of both optically-active and associated optically-inactive DOM in coastal wetlands.

  9. Coordination compounds for molecular electronics: Synthesis, characterization and electronic transport properties of copper rotaxanes and molecular complexes

    OpenAIRE

    Ponce González, Julia

    2014-01-01

    Esta tesis se centra en el estudio de compuestos de coordinación de interés en el campo de la electrónica molecular. Este campo tiene como objetivo la utilización de unidades moleculares como componentes activos en circuitos electrónicos. Los dispositivos unimoleculares presentan cualidades únicas, inherentes a la nanoescala, que no poseen equivalencia en los componentes convencionales, actualmente basados en el silicio. Además, la síntesis de moléculas dispone de un altísimo grado de control...

  10. Molecular Dynamics Simulation of Cross-Linked Epoxy Polymers: the Effect of Force Field on the Estimation of Properties

    Directory of Open Access Journals (Sweden)

    B. Arab

    2013-03-01

    Full Text Available In this paper, the molecular dynamics method was used to calculate the physical and mechanical properties of the cross-linked epoxy polymer composed of diglycidyl ether of bisphenol-A (DGEBA as resin and diethylenetriamine (DETA as curing agent. Calculation of the properties was performed using the constant-strain (static approach. A series of independent simulations were carried out based on four widely used force fields; COMPASS, PCFF, UFF and Dreiding. Proper comparisons between the results and also with experimental observations were made to find the most suitable force field for molecular dynamics simulation of polymer materials.

  11. Stearic acid based oleogels: a study on the molecular, thermal and mechanical properties.

    Science.gov (United States)

    Sagiri, S S; Singh, Vinay K; Pal, K; Banerjee, I; Basak, Piyali

    2015-03-01

    Stearic acid and its derivatives have been used as gelators in food and pharmaceutical gel formulations. However, the mechanism pertaining to the stearic acid based gelation has not been deciphered yet. Keeping that in mind, we investigated the role of stearic acid on physic-chemical properties of oleogel. For this purpose, two different oil (sesame oil and soy bean oil) formulations/oleogels were prepared. In depth analysis of gel kinetics, gel microstructure, molecular interactions, thermal and mechanical behaviors of the oleogels were done. The properties of the oleogels were dependent on the type of the vegetable oil used and the concentration of the stearic acid. Avrami analysis of DSC thermograms indicated that heterogeneous nucleation was coupled with the one-dimensional growth of gelator fibers as the key phenomenon in the formation of oleogels. Viscoelastic and pseudoplastic nature of the oleogels was analyzed in-depth by fitting the stress relaxation data in modified Peleg's model and rheological studies, respectively. Textural studies have revealed that the coexistence of hydrogen bond dissipation and formation of new bonds is possible under stress conditions in the physical oleogels. PMID:25579972

  12. Molecular dynamics simulation study of thermodynamic and mechanical properties of the Cu-Pd random alloy

    International Nuclear Information System (INIS)

    Molecular dynamics (MD) simulations have been performed to investigate the thermodynamic and mechanical properties of Cu-x% Pd (at%) random alloy, as well as those of the Cu3Pd and CuPd3 ordered alloys, in the temperature range from 200 K up to the melting point. The quantum Sutton-Chen (Q-SC) many-body interatomic potentials have been used to describe the energetics of the Cu and Pd pure metals, and a standard mixing rule has been employed to obtain the potential parameters for the mixed (alloy) states. We have computed the variation of the melting temperature with the concentration of Pd. Furthermore, the variation of the cohesive energy, the order parameter, the thermal expansion coefficient, the density, the isobaric heat capacity, the bulk modulus, and the elastic stiffness constants were also calculated at different temperatures and concentrations for these materials. The computed variations of the thermodynamic and mechanical properties with temperature are fitted to a polynomial function. Our computed results show good agreement with other computational simulations, as well as with the experimental results where they have been available.

  13. Relationship between processing and mechanical properties of injection molded high molecular mass polyethylene + hydroxyapatite composites

    Energy Technology Data Exchange (ETDEWEB)

    Reis, R.L.; Cunha, A.M.; Oliveira, M.J.; Campos, A.R. [Dept. of Polymer Engineering, University of Minho, Guimaraes (Portugal); Bevis, M.J. [Wolfson Center for Materials Processing, Brunel Univ., Uxbridge (United Kingdom)

    2001-04-01

    We apply a macromolecular-orientation approach to produce high molecular weight polyethylene (HMWPE) + hydroxyapatite (HA) ductile composites with the stiffness and strength within the range of human cortical bone. Our composites are produced with different amounts (10 to 50% by weight) of the reinforcement by two procedures: bi-axial rotating drum and twin screw extrusion (TSE). The processing is by conventional injection molding and by Scorim (shear controlled orientation in injection molding) under a wide range of processing windows. Tensile testing is performed and the corresponding performance related to the morphology evaluated by polarized light microscopy and scanning electron microscopy. The control of the processing parameters led to significant improvements of the tensile properties. Compounding by TSE and then processing by Scorim produces the maximum modulus of 7.4 GPa and the ductility as high as 19%, for the HA weight fraction of 30%. These mechanical properties match those of bone, and were obtained with much smaller amounts of HA reinforcement then has been previously reported in literature. Our PE + HA composites present the additional benefit of being ductile even for 50% HA amounts. The use Scorim is a unique way of inducing anisotropy to thick sections and to produce very stiff composites that may be used in biomedical applications with important mechanical loads. This fact, combined with the bioactive behavior of the HA phase, makes our composite usable for orthopedic load-bearing implants. (orig.)

  14. Molecular simulations of the effects of phospholipid and cholesterol peroxidation on lipid membrane properties.

    Science.gov (United States)

    Neto, Antenor J P; Cordeiro, Rodrigo M

    2016-09-01

    Non-enzymatic lipid peroxidation may change biomembrane structure and function. Here, we employed molecular dynamics simulations to study the effects of either phospholipid or cholesterol peroxidation individually, as well as the combined peroxidation of both components. When lipids were peroxidized, the generated OOH groups migrated to the membrane surface and engaged in H-bonds with each other and the phospholipid carbonyl ester groups. It caused the sn-2 acyl chains of phospholipid hydroperoxides to bend and the whole sterol backbone of cholesterol hydroperoxides to tilt. When phospholipids were kept intact, peroxidation of the sterol backbone led to a partial degradation of its condensing and ordering properties, independently of the position and isomerism of the OOH substitution. However, even in massively peroxidized membranes in which all phospholipids and cholesterol were peroxidized, the condensing and ordering properties of the sterol backbone were still significant. The possible implications for the formation of membrane lateral domains were discussed. Cholesterol peroxyl radicals were also investigated and we found that the OO groups did not migrate to the headgroups region. PMID:27349733

  15. Molecular dynamics investigation of structure and high-temperature mechanical properties of SiBCO ceramics

    International Nuclear Information System (INIS)

    Highlights: • The nano-domain structure of SiBCO is reproduced by large-scale atomistic simulations. • Calculated pair and angular distribution functions consist with experiments and DFT calculation. • Silicon atoms form mixed bonds tetrahedron with carbon and oxygen at domains interfaces. • Change in slope of temperature-dependent Young’s moduli indicates glass transition temperature. - Abstract: SiCO ceramics present excellent properties at high temperatures, the addition of boron for SiCO leads to enhanced performance on thermal stability and creep temperature. Investigating atomic structure and its influence on material property are essential for further study. In this study, large-scale molecular dynamics simulations were used to study amorphous SiBCO structures with different carbon contents. Phase separation and free carbon structures were successfully reproduced by melt-quench simulation. The calculated pair distribution functions of SiBCO are comparable to those of SiCO in experiments, the C–C–C angular distribution indicates strong sp2 carbon character together with a sp3 character. Si-centered tetrahedrons present in amorphous SiBCO and the most popular case is Si–C/O tetrahedron. Si3BC7O3 presents the largest Young’s modulus for all the temperatures due to the network structure of free carbon. A change in the slope of temperature-dependent Young’s moduli at 1300 K–1700 K for Si3BC3O3 indicates the glass transition temperature

  16. Fluorescent characteristics and metal binding properties of individual molecular weight fractions in municipal solid waste leachate

    International Nuclear Information System (INIS)

    Molecular weight (MW) is a fundamental property of dissolved organic matter (DOM), which potentially affects the binding behavior between DOM and metals. Here, a combined approach of ultrafiltration fractionation, fluorescence excitation-emission matrix quenching and parallel factor analysis (PARAFAC) was employed to elucidate fluorescent characteristics and metal binding properties of individual MW fractions of DOM in landfill leachate. Four humic-like and two protein-like components were identified by PARAFAC. Among them, a fulvic acid-like component was found to be responsible for Cd(II) binding while Cu(II) inclined to complex with humic-like components rather than protein-like ones. Apart from that, MW was found to exert less influence on metal binding than that of specific metals or components. Key components distributed within various fractions of DOM were the main influence on the impact of MW on metal binding. - Highlights: ► We examined binding behavior between heavy metal and individual MW fractions of DOM. ► MW was found to exert less influence on binding than that of metal or component. ► MW impact on binding was induced by key component distributed in various fractions. ► FA-like substance was found to be responsible for Cd(II) binding. ► Cu(II) tended to complex with HS (high MW) rather than protein substance (low MW). - Key components distributed within various fractions of DOM were the main influence on the impact of MW on metal binding.

  17. Translocation Properties of Primitive Molecular Machines and Their Relevance to the Structure of the Genetic Code

    CERN Document Server

    Aldana, M; Larralde, H; Martínez-Mekler, G; Aldana, Maximino; Cocho, Germinal; Larralde, Hernan; Martinez-Mekler, Gustavo

    2002-01-01

    We address the question, related with the origin of the genetic code, of why are there three bases per codon in the translation to protein process. As a followup to our previous work, we approach this problem by considering the translocation properties of primitive molecular machines, which capture basic features of ribosomal/messenger RNA interactions, while operating under prebiotic conditions. Our model consists of a short one-dimensional chain of charged particles(rRNA antecedent) interacting with a polymer (mRNA antecedent) via electrostatic forces. The chain is subject to external forcing that causes it to move along the polymer which is fixed in a quasi one dimensional geometry. Our numerical and analytic studies of statistical properties of random chain/polymer potentials suggest that, under very general conditions, a dynamics is attained in which the chain moves along the polymer in steps of three monomers. By adjusting the model in order to consider present day genetic sequences, we show that the ab...

  18. Amido analogs of mitoxantrone: physico-chemical properties, molecular modeling, cellular effects and antineoplastic potential.

    Science.gov (United States)

    Zagotto, G; Moro, S; Uriarte, E; Ferrazzi, E; Palù, G; Palumbo, M

    1997-03-01

    To assess the effects of amido substitution in the side-chains of the anticancer drug mitoxantrone (MX) two analogs were synthesized, having hydroxyethylaminoacetyl- and hydroxyethylaminopropionyl- substituents at the nitrogens located at positions 1, 4 of the anthracenedione ring system. The novel derivatives exhibit DNA-affinity and redox properties similar to the parent drug. However, unlike MX, they are not able to stimulate DNA cleavage, as shown by alkaline elution experiments. Molecular modeling studies using ab initio quantum mechanical methods show that, while the stereochemistry of the drug molecule is not appreciably affected when an amide group replaces the aromatic amino function, the reverse is true for the electrostatic properties. Indeed, overlapping of electron density of MX with its analogs is very poor. Moreover, a reversal in the direction of MX dipole moment occurs in the amido congeners. This may explain the lack of recognition of the cleavable topoisomerase II-DNA complex and loss of cleavage stimulation. However, the new derivatives exhibit pharmacological activity comparable to that found for MX, as they are remarkably cytotoxic and are active in vivo against P388 murine leukemia. Hence, amido substitution may lead to a different mechanism of cytotoxicity, not related to classical protein or free radical-mediated DNA damage, which points to a novel type of antineoplastic pharmacophore. PMID:9113065

  19. Anisotropic mechanical properties of hexagonal SiC sheet: a molecular dynamics study

    Science.gov (United States)

    Yu, Ming; Liu, Emily; Zhang, Congyan

    2015-03-01

    The anisotropic mechanical properties of hexagonal SiC sheet have been studied using an efficient quantum mechanics molecular dynamics scheme based on a robust semi-empirical Hamiltonian (refereed as SCED-LCAO) [PRB 74, 15540; PHYSE 42, 1]. It was found that the SiC sheet could sustain the heavy load up to about 20 %. In particular, it was found that the SiC sheet also shows large difference in the strain direction. It will quickly crack after 20 % of strain in armchair the direction, but it will be slowly destroyed after 30% in the zigzag direction, indicating the anisotropic nature of the mechanical properties of the SiC sheet. The nominal and 2D membrane stresses will be analyzed, from where we will obtain the 2D Young's modulus at infinitesimal strain and the third-order (effective nonlinear) elastic modulus for the SiC sheet. The detail results and discussions will be reported in the presentation.

  20. Structural and vibrational properties of amorphous GeO2: a molecular dynamics study

    International Nuclear Information System (INIS)

    We studied the structural and dynamical properties of amorphous germanium oxide (GeO2) by means of the molecular dynamics technique. The simulations were done in the microcanonical ensemble, with a system at a density of 3.7 g cm-3, using a pairwise potential. The resulting neutron static structure factor is compared to experimental results. The network topology of our system is analyzed through partial pair correlations, coordination number and angle distributions. A detailed analysis of the interatomic distances reveals that in the amorphous state there is a short range order dominated by a slightly distorted Ge(O1/2)4 tetrahedron. Beyond that, there is an intermediate range order composed of vertex-sharing tetrahedra. The vibrational properties were characterized by means of the density of states, obtained as a Fourier transform of the velocity autocorrelation function. The vibrational density of states has two bands, a low frequency one related to the inter-tetrahedron vibration and a high frequency band related to the intra-tetrahedron vibration

  1. Mechanical properties of self-assembled Fmoc-diphenylalanine molecular gels.

    Science.gov (United States)

    Dudukovic, Nikola A; Zukoski, Charles F

    2014-04-22

    We explore the phase diagram and mechanical properties of molecular gels produced from mixing water with a dimethyl sulfoxide (DMSO) solution of the aromatic dipeptide derivative fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF). Highly soluble in DMSO, Fmoc-FF assembles into fibrous networks that form gels upon addition of water. At high water concentrations, rigid gels can be formed at Fmoc-FF concentrations as low as 0.01 wt %. The conditions are established defining the Fmoc-FF and water concentrations at which gels are formed. Below the gel boundary, the solutions are clear and colorless and have long-term stability. Above the gel boundary, gels are formed with increasing rapidity with increasing water or Fmoc-FF concentrations. A systematic characterization of the effect of Fmoc-FF and water concentrations on the mechanical properties of the gels is presented, demonstrating that the elastic behavior of the gels follows a specific, robust scaling with Fmoc-FF volume fraction. Furthermore, we characterize the kinetics of gelation and demonstrate that these gels are reversible in the sense that they can be disrupted mechanically and rebuild strength over time. PMID:24684510

  2. Molecular mechanisms of radiative modification of electret properties of the polymers

    International Nuclear Information System (INIS)

    In this work the mechanism of density value change of electret charges of τe in corona-electrets from polythene films with high density of PEPV and isotactic polypropylene of PP are investigated, under preliminary influence of γ-radiation from Co60 in air. Influence of over molecular structure on orientation of modification processes of electret properties of these polymers is investigated at γ-modification. It is shown, that value of τe of the PEPV films increases up to doses of 40-55 Mrad, versus the D dose of a γ-radiation, and then decreases with increasing of the radiation dose. The dose for high tempered samples, in which is observed a maximal values of τe = (3-3.2)-10-4 C/m2, is about 55 Mrad, and for slowly cooled films is about 30-35 Mrad. At low doses of 5-6 Mrad, a non-significant extreme was observed at τe (D) dependence. The increase of τe in PE, at preliminary γ-radiation is due to formation of polymer and prevalence of formation processes with participation of oxygen. Effect of γ-radiation on polarized films comes to decrease of electret charges. A reason of change of the electret charges of polymers maybe two competing mechanisms; first - a formation of neutral traps of molecular or radical character, in polymer with energy of 0.5-4 eV having a positive affinity with electrons or holes. Second - a generation of charged particles and their stabilization in deep traps of a structural origin. The competition of mechanisms will define an orientation of change of the electret properties of polymers at γ-modification. In this work are discussed also the mechanisms, with participation of heminal pairs formation on distance up to 10-20 nm, and also holes of dielectric hollows both volumetric, and superficial origin. The opportunity of improvement of an electret properties of the PE and PP films by choice of crystallization regime and radiation condition of polymer are shown

  3. Molecular simulation of thermodynamic and transport properties for the H2O+NaCl system

    International Nuclear Information System (INIS)

    Molecular dynamics and Monte Carlo simulations have been carried out to obtain thermodynamic and transport properties of the binary mixture H2O+NaCl at temperatures from T = 298 to 473 K. In particular, vapor pressures, liquid densities, viscosities, and vapor-liquid interfacial tensions have been obtained as functions of pressure and salt concentration. Several previously proposed fixed-point-charge models that include either Lennard-Jones (LJ) 12-6 or exponential-6 (Exp6) functional forms to describe non-Coulombic interactions were studied. In particular, for water we used the SPC and SPC/E (LJ) models in their rigid forms, a semiflexible version of the SPC/E (LJ) model, and the Errington-Panagiotopoulos Exp6 model; for NaCl, we used the Smith-Dang and Joung-Cheatham (LJ) parameterizations as well as the Tosi-Fumi (Exp6) model. While none of the model combinations are able to reproduce simultaneously all target properties, vapor pressures are well represented using the SPC plus Joung-Cheathem model combination, and all LJ models do well for the liquid density, with the semiflexible SPC/E plus Joung-Cheatham combination being the most accurate. For viscosities, the combination of rigid SPC/E plus Smith-Dang is the best alternative. For interfacial tensions, the combination of the semiflexible SPC/E plus Smith-Dang or Joung-Cheatham gives the best results. Inclusion of water flexibility improves the mixture densities and interfacial tensions, at the cost of larger deviations for the vapor pressures and viscosities. The Exp6 water plus Tosi-Fumi salt model combination was found to perform poorly for most of the properties of interest, in particular being unable to describe the experimental trend for the vapor pressure as a function of salt concentration

  4. Molecular simulation of thermodynamic and transport properties for the H2O+NaCl system

    Science.gov (United States)

    Orozco, Gustavo A.; Moultos, Othonas A.; Jiang, Hao; Economou, Ioannis G.; Panagiotopoulos, Athanassios Z.

    2014-12-01

    Molecular dynamics and Monte Carlo simulations have been carried out to obtain thermodynamic and transport properties of the binary mixture H2O+NaCl at temperatures from T = 298 to 473 K. In particular, vapor pressures, liquid densities, viscosities, and vapor-liquid interfacial tensions have been obtained as functions of pressure and salt concentration. Several previously proposed fixed-point-charge models that include either Lennard-Jones (LJ) 12-6 or exponential-6 (Exp6) functional forms to describe non-Coulombic interactions were studied. In particular, for water we used the SPC and SPC/E (LJ) models in their rigid forms, a semiflexible version of the SPC/E (LJ) model, and the Errington-Panagiotopoulos Exp6 model; for NaCl, we used the Smith-Dang and Joung-Cheatham (LJ) parameterizations as well as the Tosi-Fumi (Exp6) model. While none of the model combinations are able to reproduce simultaneously all target properties, vapor pressures are well represented using the SPC plus Joung-Cheathem model combination, and all LJ models do well for the liquid density, with the semiflexible SPC/E plus Joung-Cheatham combination being the most accurate. For viscosities, the combination of rigid SPC/E plus Smith-Dang is the best alternative. For interfacial tensions, the combination of the semiflexible SPC/E plus Smith-Dang or Joung-Cheatham gives the best results. Inclusion of water flexibility improves the mixture densities and interfacial tensions, at the cost of larger deviations for the vapor pressures and viscosities. The Exp6 water plus Tosi-Fumi salt model combination was found to perform poorly for most of the properties of interest, in particular being unable to describe the experimental trend for the vapor pressure as a function of salt concentration.

  5. Molecular physics

    CERN Document Server

    Williams, Dudley

    2013-01-01

    Methods of Experimental Physics, Volume 3: Molecular Physics focuses on molecular theory, spectroscopy, resonance, molecular beams, and electric and thermodynamic properties. The manuscript first considers the origins of molecular theory, molecular physics, and molecular spectroscopy, as well as microwave spectroscopy, electronic spectra, and Raman effect. The text then ponders on diffraction methods of molecular structure determination and resonance studies. Topics include techniques of electron, neutron, and x-ray diffraction and nuclear magnetic, nuclear quadropole, and electron spin reson

  6. Molecular Dynamics Simulation of Cross-Linked Epoxy Polymers: the Effect of Force Field on the Estimation of Properties

    OpenAIRE

    B. Arab; A. Shokuhfar

    2013-01-01

    In this paper, the molecular dynamics method was used to calculate the physical and mechanical properties of the cross-linked epoxy polymer composed of diglycidyl ether of bisphenol-A (DGEBA) as resin and diethylenetriamine (DETA) as curing agent. Calculation of the properties was performed using the constant-strain (static) approach. A series of independent simulations were carried out based on four widely used force fields; COMPASS, PCFF, UFF and Dreiding. Proper comparisons between the res...

  7. Effect of surfactant structure on properties of oil/water interfaces : A coarse-grained molecular simulation study.

    OpenAIRE

    Rekvig, Live

    2004-01-01

    The elastic properties of oil/water/surfactant interfaces play an important role in the phase behaviour of microemulsions and for the stability of macroemulsions. The aim of this thesis is to obtain an understanding of the relationship between the structure of the surfactant molecules, the structure of the interface, and macroscopic interfacial properties. To achieve this aim, we performed molecular simulations of oil/water/surfactant systems. We made a quantitative comparison of various mo...

  8. Thermophysical properties of hydrogen-helium mixtures: Re-examination of the mixing rules via quantum molecular dynamics simulations

    OpenAIRE

    Wang, Cong; He, Xian-Tu; zhang, ping

    2013-01-01

    Thermophysical properties of hydrogen, helium, and hydrogen-helium mixtures have been investigated in the warm dense matter regime at electron number densities ranging from $6.02\\times10^{29}\\sim2.41\\times10^{30}$/m$^{3}$ and temperatures from 4000 to 20000 K via quantum molecular dynamics simulations. We focus on the dynamical properties such as the equation of states, diffusion coefficients, and viscosity. Mixing rules (density matching, pressure matching, and binary ionic mixing rules) hav...

  9. The precaution adoption process.

    Science.gov (United States)

    Weinstein, N D

    1988-01-01

    This article presents a critique of current models of preventive behavior. It discusses a variety of factors that are usually overlooked-including the appearance of costs and benefits over time, the role of cues to action, the problem of competing life demands, and the ways that actual decision behavior differs from the rational ideal implicit in expectancy-value and utility theories. Such considerations suggest that the adoption of new precautions should be viewed as a dynamic process with many determinants. The framework of a model that is able to accommodate these additional factors is described. This alternative model portrays the precaution adoption process as an orderly sequence of qualitatively different cognitive stages. Data illustrating a few of the suggestions made in the article are presented, and implications for prevention programs are discussed. PMID:3049068

  10. Hospitious Adoption: How Hospitality Empowers Children and Transforms Adoption

    Science.gov (United States)

    Gritter, James L.

    2009-01-01

    Building on previous books by the author, "Hospitious Adoption: How Hospitality Empowers Children and Transforms Adoption" examines the next step after open adoption. Gritter takes the approach that practicing goodwill, respect, and courage within the realm of adoption makes the process move smoother and enriches children's lives. Following a…

  11. Open Adoption: Adoptive Parents' Reactions Two Decades Later

    Science.gov (United States)

    Siegel, Deborah H.

    2013-01-01

    Unlike in the past, most adoption agencies today offer birth parents and adoptive parents the opportunity to share identifying information and have contact with each other. To understand the impacts of different open adoption arrangements, a qualitative descriptive study using a snowball sample of 44 adoptive parents throughout New England began…

  12. Adoption, nation, migration

    DEFF Research Database (Denmark)

    Müller, Anders Riel

    2013-01-01

    Som transnationalt adopteret vokser man ofte op med en fortælling om, at man er født i et fattigt land. Og at ens første forældre var fattige eller oplevede så store problemer, at de ikke så andre muligheder end at afgive en til adoption. Det er en historie, man bliver fortalt igen og igen. Og so...

  13. Microeconomics of Technology Adoption

    OpenAIRE

    Foster, Andrew D.; Rosenzweig, Mark R.

    2010-01-01

    There is an emerging consensus among macro-economists that differences in technology across countries accounts for the major differences in per-capita GDP and the wages of workers with similar skills across countries. Accounting for differences in technology levels across countries thus can go a long way towards understanding global inequality. One mechanism by which poorer countries can catch up with richer countries is through technological diffusion, the adoption by low-income countries of...

  14. Mobile Services Adoption Model

    OpenAIRE

    Abu Ghannam, Bashar

    2011-01-01

    This research presents an explanatory model for consumers' adoption of mobile services. This model uses the Unified Theory of Acceptance and Use of Technology presented by Venkatesh in 2003 as a baseline and integrates the Perceived Enjoyment, Mobile Affinity, Perceived Price of Service and the Frequency of Mobile Usage as to investigate the Attitude and the Intention to Use mobile services. The proposed model was empirically tested using data collected from a field survey where 1095 responde...

  15. Determination of structure and properties of molecular crystals from first principles.

    Science.gov (United States)

    Szalewicz, Krzysztof

    2014-11-18

    CONSPECTUS: Until recently, it had been impossible to predict structures of molecular crystals just from the knowledge of the chemical formula for the constituent molecule(s). A solution of this problem has been achieved using intermolecular force fields computed from first principles. These fields were developed by calculating interaction energies of molecular dimers and trimers using an ab initio method called symmetry-adapted perturbation theory (SAPT) based on density-functional theory (DFT) description of monomers [SAPT(DFT)]. For clusters containing up to a dozen or so atoms, interaction energies computed using SAPT(DFT) are comparable in accuracy to the results of the best wave function-based methods, whereas the former approach can be applied to systems an order of magnitude larger than the latter. In fact, for monomers with a couple dozen atoms, SAPT(DFT) is about equally time-consuming as the supermolecular DFT approach. To develop a force field, SAPT(DFT) calculations are performed for a large number of dimer and possibly also trimer configurations (grid points in intermolecular coordinates), and the interaction energies are then fitted by analytic functions. The resulting force fields can be used to determine crystal structures and properties by applying them in molecular packing, lattice energy minimization, and molecular dynamics calculations. In this way, some of the first successful determinations of crystal structures were achieved from first principles, with crystal densities and lattice parameters agreeing with experimental values to within about 1%. Crystal properties obtained using similar procedures but empirical force fields fitted to crystal data have typical errors of several percent due to low sensitivity of empirical fits to interactions beyond those of the nearest neighbors. The first-principles approach has additional advantages over the empirical approach for notional crystals and cocrystals since empirical force fields can only be

  16. Molecular Cloning and Pharmacological Properties of an Acidic PLA2 from Bothrops pauloensis Snake Venom

    Directory of Open Access Journals (Sweden)

    Francis Barbosa Ferreira

    2013-12-01

    Full Text Available In this work, we describe the molecular cloning and pharmacological properties of an acidic phospholipase A2 (PLA2 isolated from Bothrops pauloensis snake venom. This enzyme, denominated BpPLA2-TXI, was purified by four chromatographic steps and represents 2.4% of the total snake venom protein content. BpPLA2-TXI is a monomeric protein with a molecular mass of 13.6 kDa, as demonstrated by Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF analysis and its theoretical isoelectric point was 4.98. BpPLA2-TXI was catalytically active and showed some pharmacological effects such as inhibition of platelet aggregation induced by collagen or ADP and also induced edema and myotoxicity. BpPLA2-TXI displayed low cytotoxicity on TG-180 (CCRF S 180 II and Ovarian Carcinoma (OVCAR-3, whereas no cytotoxicity was found in regard to MEF (Mouse Embryonic Fibroblast and Sarcoma 180 (TIB-66. The N-terminal sequence of forty-eight amino acid residues was determined by Edman degradation. In addition, the complete primary structure of 122 amino acids was deduced by cDNA from the total RNA of the venom gland using specific primers, and it was significantly similar to other acidic D49 PLA2s. The phylogenetic analyses showed that BpPLA2-TXI forms a group with other acidic D49 PLA2s from the gender Bothrops, which are characterized by a catalytic activity associated with anti-platelet effects.

  17. Antimicrobial, antioxidant, cytotoxic and molecular docking properties of N-benzyl-2,2,2-trifluoroacetamide

    Science.gov (United States)

    Balachandran, C.; Kumar, P. Saravana; Arun, Y.; Duraipandiyan, V.; Sundaram, R. Lakshmi; Vijayakumar, A.; Balakrishna, K.; Ignacimuthu, S.; Al-Dhabi, N. A.; Perumal, P. T.

    2015-02-01

    N-Benzyl-2,2,2-trifluoroacetamide was obtained by acylation of benzylamine with trifluoroacetic anhydride using Friedel-Crafts acylation method. The synthesised compound was confirmed by spectroscopic and crystallographic techniques. N-Benzyl-2,2,2 -trifluoroacetamide was assessed for its antimicrobial, antioxidant, cytotoxic and molecular docking properties. It showed good antifungal activity against tested fungi and moderate antibacterial activity. The minimum inhibitory concentration values of N-benzyl-2,2,2 -trifluoroacetamide against fungi were 15.62 μg/mL against A. flavus, 31.25 μg/mL against B. Cinerea and 62.5 μg/mL against T. mentagrophytes, Scopulariopsis sp., C. albicans and M. pachydermatis. N-Benzyl-2,2,2-trifluoroacetamide showed 78.97 ± 2.24 of antioxidant activity at 1,000 μg/mL. Cupric ion reducing antioxidant capacity of N-benzyl-2,2,2-trifluoroacetamide was dependent on the concentration. Ferric reducing antioxidant power assay of N-benzyl-2,2,2-trifluoroacetamide showed (1.352 ± 0.04 mM Fe(II)/g) twofold higher value compared to the standard. N-Benzyl-2,2,2-trifluoroacetamide showed 75.3 % cytotoxic activity at the dose of 200 μg/mL with IC50 (54.7 %) value of 100 μg/mL. N-Benzyl-2,2,2-trifluoroacetamide was subjected to molecular docking studies for the inhibition AmpC beta-lactamase, Glucosamine-6-Phosphate Synthase and lanosterol 14 alpha-demethylase (CYP51) enzymes which are targets for antibacterial and antifungal drugs. Docking studies of N-benzyl-2,2,2-trifluoroacetamide showed low docking energy. N-Benzyl-2,2,2-trifluoroacetamide can be evaluated further for drug development.

  18. Conduct Problems in Adopted and Non-adopted Adolescents and Adoption Satisfaction as a Protective Factor

    OpenAIRE

    Nilsson, Renea; Rhee, Soo Hyun; Corley, Robin P.; Rhea, Sally-Ann; Wadsworth, Sally J.; DeFries, John C.

    2011-01-01

    The present study compared the level of conduct problems at age 17 in a large, non-clinical sample of adopted participants placed in infancy and children in non-adoptive families matched to the adoptive families on demographic characteristics. Higher levels of adolescent and parent adoption satisfaction were associated with lower levels of conduct problems. Gender by adoption status interactions were not significant. However, female adopted participants had higher levels of conduct problems t...

  19. Ab initio molecular dynamics with noisy forces: Validating the quantum Monte Carlo approach with benchmark calculations of molecular vibrational properties

    International Nuclear Information System (INIS)

    We present a systematic study of a recently developed ab initio simulation scheme based on molecular dynamics and quantum Monte Carlo. In this approach, a damped Langevin molecular dynamics is employed by using a statistical evaluation of the forces acting on each atom by means of quantum Monte Carlo. This allows the use of an highly correlated wave function parametrized by several variational parameters and describing quite accurately the Born-Oppenheimer energy surface, as long as these parameters are determined at the minimum energy condition. However, in a statistical method both the minimization method and the evaluation of the atomic forces are affected by the statistical noise. In this work, we study systematically the accuracy and reliability of this scheme by targeting the vibrational frequencies of simple molecules such as the water monomer, hydrogen sulfide, sulfur dioxide, ammonia, and phosphine. We show that all sources of systematic errors can be controlled and reliable frequencies can be obtained with a reasonable computational effort. This work provides convincing evidence that this molecular dynamics scheme can be safely applied also to realistic systems containing several atoms

  20. Ab initio molecular dynamics with noisy forces: Validating the quantum Monte Carlo approach with benchmark calculations of molecular vibrational properties

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Ye, E-mail: xw111luoye@gmail.com; Sorella, Sandro, E-mail: sorella@sissa.it [International School for Advanced Studies (SISSA), and CRS Democritos, CNR-INFM, Via Bonomea 265, I-34136 Trieste (Italy); Zen, Andrea, E-mail: zen.andrea.x@gmail.com [Dipartimento di Fisica, Università di Roma “La Sapienza,” Piazzale Aldo Moro 2, I-00185 Rome (Italy)

    2014-11-21

    We present a systematic study of a recently developed ab initio simulation scheme based on molecular dynamics and quantum Monte Carlo. In this approach, a damped Langevin molecular dynamics is employed by using a statistical evaluation of the forces acting on each atom by means of quantum Monte Carlo. This allows the use of an highly correlated wave function parametrized by several variational parameters and describing quite accurately the Born-Oppenheimer energy surface, as long as these parameters are determined at the minimum energy condition. However, in a statistical method both the minimization method and the evaluation of the atomic forces are affected by the statistical noise. In this work, we study systematically the accuracy and reliability of this scheme by targeting the vibrational frequencies of simple molecules such as the water monomer, hydrogen sulfide, sulfur dioxide, ammonia, and phosphine. We show that all sources of systematic errors can be controlled and reliable frequencies can be obtained with a reasonable computational effort. This work provides convincing evidence that this molecular dynamics scheme can be safely applied also to realistic systems containing several atoms.

  1. The Child Adoption Marketplace: Parental Preferences and Adoption Outcomes

    OpenAIRE

    Skidmore, Mark; Anderson, Gary; Eiswerth, Mark

    2011-01-01

    In the United States child adoption costs vary considerably, ranging from no out-of-pocket expense to $50,000 or more. What are the underlying causes for the variability in child adoption expenses? While cost variability is widely acknowledged, the sources of the differentials have not been systematically examined. This research considers the possibility that adoption cost differentials are determined by adoptive parent preferences for adoptive child characteristics. We administered a detaile...

  2. Biophysical exploration of protein-flavonol recognition: effects of molecular properties and conformational flexibility.

    Science.gov (United States)

    Ding, Fei; Peng, Wei; Peng, Yu-Kui

    2016-04-28

    The current work explores the biomolecular recognition of a series of flavonols by a protein and then uncovers the influences of the structural features of flavonols and the protein's own characteristics, e.g. the dynamics and flexibility, on the bioavailability of flavonols by using the pivotal biomacromolecule hemoglobin as a model. The experimental results revealed that flavonol may lead to a notable decrease in the steady-state fluorescence intensity of the β-37 Trp residue, and in the meantime the R-T transition of the protein transpired. Such noncovalent recognition forms the ground-state adduct, with an association intensity of 3.991 × 10(4) M(-1) in the reaction process, which has already been authenticated by the detailed analysis of time-resolved fluorescence and UV/vis absorption spectra. Furthermore, flavonol can form hydrogen bonds and π-conjugation effects with several amino acid residues on the polypeptide chain, for example, Trp-37, Arg-40, Asp-99 and Asn-102, and this event would induce self-regulation of the compact, regular conformation of the protein to a certain extent, which explicitly corroborates the results of circular dichroism. According to the study of molecular docking and structure-activity relationships, we could see that the recognition capacities of the protein-flavonols are inversely interrelated with the C log P values of the flavonol molecules. Moreover, the properties of the substituents in the structural B-ring unit of flavonols, i.e. polarity, position and number, will also prominently affect the degree of affinity and bioavailability of the protein-flavonol complexes. The analytical results of molecular dynamics (MD) simulation testified that the discussions of the structure-activity relationships are entirely logical, and the conformations of the amino acid residues forming noncovalent interactions tend to be stable in the MD simulation, as further elucidated from the dynamics data. Plainly, molecular recognition of

  3. A fast-moving copper-based molecular shuttle: synthesis and dynamic properties.

    Science.gov (United States)

    Durola, Fabien; Lux, Jacques; Sauvage, Jean-Pierre

    2009-01-01

    Fast-track changes: The synthesis of a new copper-based molecular shuttle is described, with a coordinating macrocycle based on a nonhindering but endocyclic ligand (see scheme), which makes the ligand exchange easier, and thus the motions of the ring along the thread faster.The present report deals with the synthesis of a two-station [2]rotaxane consisting of a dpbiiq-incorporating macrocycle (dpbiiq: 8,8'-diphenyl-3,3'-biisoquinoline) threaded by a coordinating fragment whose complexing units are a dpp and a terpy ligand (dpp: 2,9-diphenyl-1,10-phenanthroline; terpy: 2,2',6',2"-terpyridine). The [2]rotaxane was prepared in 11 steps from commercially available or easy-to-make molecules, without taking into account the preparation of the dpbiiq-containing 39-membered ring, which was available in our group. The ring-incorporated bidentate chelate is at the same time endocyclic and sterically nonhindering, which is a specific property of the dpbiiq-coordinating unit. This unique feature has a profound influence on the rate of the ring-and-copper translation motion between the two stations of the axle. Based on an analogous multistep strategy, a related molecular shuttle has also been prepared that contains exactly the same axle and stoppers as the first compound but whose threaded ring incorporates the sterically hindering dpp chelate. The translation motions of this other system are several orders of magnitude slower than the corresponding movements of the dpbiiq-based compound. The motion corresponding to the rearrangement of the unstable five-coordinate copper(I) form of the compounds is relatively fast for both shuttles; the half lifetime of the five-coordinate Cu(I) species being below 20 ms for the dpbiiq-containing system and below 1 s for the dpp-based molecule. The reverse motion corresponding to the rearrangement of the four-coordinate copper(II) complexes is much slower, especially for the dpp-based system. It is of the order of several hours for the dpp

  4. Molecular simulation of the role of interlayer water on the mechanical properties of montmorillonite

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Full text of publication follows: Montmorillonite - a swelling clay - is the main component of the clay fraction of the Callovo-Oxfordian argillite, which is considered as a possible host rock for radioactive waste disposal, and of the sealing bentonite plugs of storage tunnels. Montmorillonite layers have a great ability to adsorb water, resulting in the swelling of the clay. Montmorillonite consists of water molecules and sodium or calcium cations between negatively charged layers. Both the water content of the interlayer space and the nature of the charge-balancing cations are expected to have an effect on the mechanical properties of the clay layer. Computer simulations allow to reproduce the experimental swelling isotherms of the layers and to gain a deeper understanding of the physical mechanisms of the swelling process. They show how water is organized in discrete layers and how this process depends on the type of inter-layer cation. However, the effect of the swelling on the mechanical properties of the nano-scale have not been fully investigated. The objective of this work is to compute the elastic properties of a Na+- Montmorillonite and a Ca2+-Montmorillonite versus relative humidity at 300 K. The results of this work is the first step to build a macroscopic state equation of unsaturated clay-based materials. We use a simulation cell containing two Montmorillonite layers and sodium or calcium counterions. The partial charges of the atoms and the interatomic interaction parameters are given by the CLAYFF force field. Grand Canonical Monte-Carlo simulations are used to compute the adsorption/desorption isotherm. Each equilibrium configuration is then strained in all directions of space. Then, we perform Molecular Dynamics and compute the stress tensor and all the components of the elasticity tensor. We present the evolution of the elastic properties of the clay layers with the relative humidity. In

  5. QSPR models based on molecular mechanics and quantum chemical calculations. 2. Thermodynamic properties of alkanes, alcohols, polyols, and ethers

    DEFF Research Database (Denmark)

    Dyekjær, Jane Dannow; Jonsdottir, Svava Osk

    2003-01-01

    this work has been to include the most probable molecular conformers in the model development and thus account for the conformational flexibility of the molecules. The models cover the properties boiling points, melting points, enthalpies of vaporization, enthalpies of fusion, and liquid densities for...

  6. EFFECTS OF OVER-EXPRESSION OF HIGH MOLECULAR WEIGHT GLUTENIN SUBUNIT 1Dy10 ON WHEAT TORTILLA PROPERTIES

    Science.gov (United States)

    Wheat (Triticum aestivum L.) flour properties necessary for optimal tortilla production have not been identified. Transgenic wheats (Triticum aestivum L.) over-expressing high molecular weight glutenin subunit (HMW-GS) 1Dy10 were used to produce tortillas and their quality evaluated. The level of HM...

  7. Highly efficient molecular simulation methods for evaluation of thermodynamic properties of crystalline phases

    Science.gov (United States)

    Moustafa, Sabry Gad Al-Hak Mohammad

    Molecular simulation (MS) methods (e.g. Monte Carlo (MC) and molecular dynamics (MD)) provide a reliable tool (especially at extreme conditions) to measure solid properties. However, measuring them accurately and efficiently (smallest uncertainty for a given time) using MS can be a big challenge especially with ab initio-type models. In addition, comparing with experimental results through extrapolating properties from finite size to the thermodynamic limit can be a critical obstacle. We first estimate the free energy (FE) of crystalline system of simple discontinuous potential, hard-spheres (HS), at its melting condition. Several approaches are explored to determine the most efficient route. The comparison study shows a considerable improvement in efficiency over the standard MS methods that are known for solid phases. In addition, we were able to accurately extrapolate to the thermodynamic limit using relatively small system sizes. Although the method is applied to HS model, it is readily extended to more complex hard-body potentials, such as hard tetrahedra. The harmonic approximation of the potential energy surface is usually an accurate model (especially at low temperature and large density) to describe many realistic solid phases. In addition, since the analysis is done numerically the method is relatively cheap. Here, we apply lattice dynamics (LD) techniques to get the FE of clathrate hydrates structures. Rigid-bonds model is assumed to describe water molecules; this, however, requires additional orientation degree-of-freedom in order to specify each molecule. However, we were able to efficiently avoid using those degrees of freedom through a mathematical transformation that only uses the atomic coordinates of water molecules. In addition, the proton-disorder nature of hydrate water networks adds extra complexity to the problem, especially when extrapolating to the thermodynamic limit is needed. The finite-size effects of the proton disorder contribution is

  8. Adoption Research: Trends, Topics, Outcomes

    Science.gov (United States)

    Palacios, Jesus; Brodzinsky, David

    2010-01-01

    The current article provides a review of adoption research since its inception as a field of study. Three historical trends in adoption research are identified: the first focusing on risk in adoption and identifying adoptee-nonadoptee differences in adjustment; the second examining the capacity of adopted children to recover from early adversity;…

  9. Molecular dynamics modelling of nanocarbon cluster properties under conditions close to HE detonation

    Directory of Open Access Journals (Sweden)

    Sapozhnikov F.A.

    2011-01-01

    Full Text Available We use molecular dynamics for modelling properties of carbon nanoclusters. The size of modelled carbon nanoclusters is below 5 nm, which is typical of detonation diamond nanoclusters. We have found their structural changes at P = 0 to be as follows: Diamond → Diamond core + GL-surface → sandwich-type graphite → Graphite-like liquid. In smaller clusters the transformations start at a lower temperature. Adaptive Template Analysis (ATA was used to determine the structures. We studied evaporation properties at temperatures above 5000 K. For clusters of several thousands of atoms, the simple dependence kvap ∼ e−T0/T/N1/3 (T0 is constant is quite good. It has been found out that densities of saturated vapour for clusters containing from 4000 to 8000 atoms are very close at T = 5000 K. The structure of nanoclusters was studied at nonzero pressures set by an argon environment. Calculated results suggest that the patterns for different temperatures are qualitatively similar for three pressures under study (20, 25 and 30 GPa. At T = 1000–1500 K, the initial diamond core is preserved and a thin disordered GL layer is present on the surface. At T = 2000–5000 K, graphite grains form in the sample and a thin layer of liquid is present on its surface. The sample is amorphous at 5500 K and 6000 K. The prevalence of the graphite phase at these pressures seems to come from the absence of long-range interaction in REBO-2002.

  10. Molecular mechanics of DNA bricks: in situ structure, mechanical properties and ionic conductivity

    Science.gov (United States)

    Slone, Scott Michael; Li, Chen-Yu; Yoo, Jejoong; Aksimentiev, Aleksei

    2016-05-01

    The DNA bricks method exploits self-assembly of short DNA fragments to produce custom three-dimensional objects with subnanometer precision. In contrast to DNA origami, the DNA brick method permits a variety of different structures to be realized using the same library of DNA strands. As a consequence of their design, however, assembled DNA brick structures have fewer interhelical connections in comparison to equivalent DNA origami structures. Although the overall shape of the DNA brick objects has been characterized and found to conform to the features of the target designs, the microscopic properties of DNA brick objects remain yet to be determined. Here, we use the all-atom molecular dynamics method to directly compare the structure, mechanical properties and ionic conductivity of DNA brick and DNA origami structures different only by internal connectivity of their consistituent DNA strands. In comparison to equivalent DNA origami structures, the DNA brick structures are found to be less rigid and less dense and have a larger cross-section area normal to the DNA helix direction. At the microscopic level, the junction in the DNA brick structures are found to be right-handed, similar to the structure of individual Holliday junctions (HJ) in solution, which contrasts with the left-handed structure of HJ in DNA origami. Subject to external electric field, a DNA brick plate is more leaky to ions than an equivalent DNA origami plate because of its lower density and larger cross-section area. Overall, our results indicate that the structures produced by the DNA brick method are fairly similar in their overall appearance to those created by the DNA origami method but are more compliant when subject to external forces, which likely is a consequence of their single crossover design.

  11. Toward a QFT-based theory of atomic and molecular properties.

    Science.gov (United States)

    Aucar, Gustavo A

    2014-03-14

    The search for a QED-based (and then QFT-based) formalism that brings solid grounds to the whole area of relativistic quantum chemistry was just implicit in the first decades of the quantum theory. During the last few years it was shown that it is still unclear how to derive a well-defined N-electron relativistic Hamiltonian, and also the way negative-energy states may contribute to electron correlation. Furthermore, the relationship among electron correlation and radiative QED corrections is even more difficult to guess. These are few of the fundamental problems that need to be solved before such a program of research is finished within the wavefunction approach to quantum physics. The polarization propagator formalism was developed as an alternative approach to study atomic and molecular properties within both regimes, relativistic and nonrelativistic. In this article we expose how far away one can go today working with polarization propagators, until including QED (and afterwards QFT) effects. We will uncover its deepest formal origin, the path integral formalism, which explains why polarization propagators can be written formally the same in both regimes. This will also explain why the NR limit is obtained scaling the velocity of light to infinity. We shall introduce a few basic aspects of elementary propagators to show what they have in common with polarization propagators. Then we shall remark on the most important news that appears with the latter ones. Within the relativistic regime the contributions of negative energy orbitals to electron correlation are straightforwardly included. New insights on the relationship between spin and time-reversal operators are also given, together with an ansatz on how to consider both, QED and electron correlation effects on the same grounds. We focus here on the treatment of NMR spectroscopic parameters within such a formalism, that is still not broadly used by the quantum chemistry community. Most of the other response

  12. Dependence of surface morphology on molecular structure and its influence on the properties of OLEDs

    International Nuclear Information System (INIS)

    Most organic light-emitting diodes (OLEDs) have a multilayer structure composed of organic layers such as a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL) and an electron injection layer (EIL) sandwiched between two electrodes. The organic layers are thin solid films with a thickness from a few nano meters to a few tenths nano meter, respectively. Surface morphology of an organic thin solid film in OLEDs depends on the molecular structure of the organic material and has an affect on device performance. To analyze the effect of surface morphology of an organic thin solid film on fluorescence and electroluminescence (EL) properties, thin solid films of 4-(dicyanomethylene)-2-methyl-6-(julolidin-4-yl-vinyl)-4H-pyran (DCM2) and new red fluorophores, (2E,2'E)-3,3'-[4,4''-bis(dimethylamino)-1,1':4',1''-terphenyl-2',5'-diyl] bis[2= -(2-thienyl)acrylonitrile] (ABCV-Th) and (2Z,2'Z)-3,3'-[4,4''-bis(dimethylamino)-1,1':4',1''-terphenyl-2',5'-diyl] bis(2-phenylacrylonitrile) (ABCV-P) were investigated by atomic force microscopy (AFM). The samples for EL and AFM measurement were fabricated by the high-vacuum thermal deposition (8x10-7 Torr) of organic materials onto the surface of indium tin oxide (ITO)-coated glass substrate, in which the layer structures of samples for AFM measurement and those for EL measurement were ITO/NPB (40 nm)/red emitters (80 nm) and ITO/NPB (40 nm)/red emitters (80 nm)/BCP (30 nm)/Liq (2 nm)/Al (100 nm), respectively. The analysis based on AFM measurements well supported that the photoluminescence properties and the device performance were very much dependent upon surface morphology of an organic thin layer

  13. Impact of Associated Gases on Equilibrium and Transport Properties of a Stream: Molecular Simulation and Experimental Studies

    Science.gov (United States)

    Creton, Benoit; de Bruin, Theodorus; Le Roux, Dominique; Duchet-Suchaux, Pierre; Lachet, Véronique

    2014-02-01

    During the various carbon dioxide capture and storage (CCS) stages, an accurate knowledge of thermodynamic properties of streams is required for the correct sizing of plant units. The injected streams are not pure and often contain small amounts of associated gaseous components such as , , noble gases, etc. In this work, the thermodynamic behavior and transport properties of some -rich mixtures have been investigated using both experimental approaches and molecular simulation techniques such as Monte Carlo and molecular dynamics simulations. Using force fields available in the literature, we have validated the capability of molecular simulation techniques in predicting properties for pure compounds, binary mixtures, as well as multicomponent mixtures. These validations were performed on the basis of experimental data taken from the literature and the acquisition of new experimental data. As experimental data and simulation results were in good agreement, we proposed the use of simulation techniques to generate new pseudo-experimental data and to study the impact of associated gases on the properties of streams. For instance, for a mixture containing 92.0 mol% of , 4.0 mol% of , 3.7 mol% of Ar, and 0.3 mol% of , we have shown that the presence of associated gases leads to a decrease of 14 % and 21 % of the dense phase density and viscosity, respectively, as compared to pure properties.

  14. Broadband adoption by SMES

    OpenAIRE

    Oni, Oluwasola

    2007-01-01

    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. Because the benefits of broadband for businesses have been widely publicized, the UK government has tried to ensure that there is a wide and fast take-up of the technology. Initial figures showed that broadband adoption by SMEs was particularly slow and there has been little research on the use of broadband by businesses, particularly SMEs. An in-depth study into the roles and activities of t...

  15. Viscous-flow properties and viscosity-average molecular mass of orange peel pectin

    Institute of Scientific and Technical Information of China (English)

    周尽花; 吴宇雄; 沈志强

    2008-01-01

    The viscous-flow properties of pectin from the residue of orange peel after extraction of essential oil and flavonoid were studied and the viscosity-average molecular mass(Mv,ave) of this kind of pectin was determined.Experimental results show that Arrhenius viscous-flow equation can be applied to describing the effect of temperature on viscosity of this kind of orange peel pectin solutions with the average viscous-flow activation energy being 17.91 kJ/mol(depending on the concentration).Neither power equation,η =K1 cA1,nor exponential equation,η=K2exp(A2c) can describe the effect of concentration on viscosity of this kind of orange peel pectin solutions well.However,it seems that exponential equation model is more suitable to describe their relation due to its higher linear correlation coefficient.Schulz-Blaschke equation can be used to calculate the intrinsic viscosity of this kind of orange peel pectin.The Mv,ave of the orange peel pectin is 1.65×105 g/mol.

  16. Analytic nuclear forces and molecular properties from full configuration interaction quantum Monte Carlo

    International Nuclear Information System (INIS)

    Unbiased stochastic sampling of the one- and two-body reduced density matrices is achieved in full configuration interaction quantum Monte Carlo with the introduction of a second, “replica” ensemble of walkers, whose population evolves in imaginary time independently from the first and which entails only modest additional computational overheads. The matrices obtained from this approach are shown to be representative of full configuration-interaction quality and hence provide a realistic opportunity to achieve high-quality results for a range of properties whose operators do not necessarily commute with the Hamiltonian. A density-matrix formulated quasi-variational energy estimator having been already proposed and investigated, the present work extends the scope of the theory to take in studies of analytic nuclear forces, molecular dipole moments, and polarisabilities, with extensive comparison to exact results where possible. These new results confirm the suitability of the sampling technique and, where sufficiently large basis sets are available, achieve close agreement with experimental values, expanding the scope of the method to new areas of investigation

  17. Properties of interstellar filaments derived from Herschel, Planck, and molecular line observations

    Science.gov (United States)

    Arzoumanian, Doris

    2015-08-01

    The highly filamentary structure of the interstellar medium (ISM) is now impressively revealed by Herschel and Planck images. Previous observations have shown that clouds are filamentary, however, only recently the mapping capabilities of Herscheland Planck have discovered their ubiquity in the ISM. In particular, Herschel images, with their high spatial and intensity dynamic ranges, show that dense filaments are associated with the main sites of star formation, demonstrating their key role in the star formation process.The analysis of the column density profiles of filaments indicates that they all share a common central width of 0.1pc, while they span a wide range in length, column density, mass per unit length. The results derived from observations tracing cold dust and gas emission, in total and polarised intensity, suggest that filaments can be divided into two families: On the one hand, low column density, unbound, and quiescent filaments mostly aligned with the magnetic field orientation, and on the other hand, dense, self-gravitating filaments, which fragment into star forming cores.I will present the properties of the filamentary structures derived from Herschel, Planck, and molecular line observations, and I will discuss the observational constraints on the formation and evolution of interstellar filaments.

  18. Growth and properties of GdTiO3 films prepared by hybrid molecular beam epitaxy

    Science.gov (United States)

    Moetakef, Pouya; Ouellette, Daniel G.; Zhang, Jack Y.; Cain, Tyler A.; Allen, S. James; Stemmer, Susanne

    2012-09-01

    The paper reports on the thin film growth of a protoptype Mott insulator, ferrimagnetic GdTiO3, using shuttered molecular beam epitaxy. Substrates were (001) (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT), with and without epitaxial SrTiO3 buffer layers, respectively. It was found that on bare LSAT, the starting monolayer was crucial for stabilizing the GdTiO3 perovskite phase. The quality of the films was evaluated using structural, electric, optical and magnetic characterization. Structural characterization showed that the GdTiO3 layers were free of pyrochlore impurity phases and that the lattice parameter was close to what was expected for coherently strained, stoichiometric GdTiO3. The room temperature film resistivity was 7 Ωcm and increased with decreasing temperature, consistent with Mott insulating characteristics. The Curie temperature was 30 K and a small coercivity was observed at 2 K, in good agreement with bulk GdTiO3 properties reported in the literature.

  19. The Bolocam Galactic Plane Survey. XIII. Physical Properties and Mass Functions of Dense Molecular Cloud Structures

    CERN Document Server

    Ellsworth-Bowers, Timothy P; Riley, Allyssa; Rosolowsky, Erik; Ginsburg, Adam; Evans, Neal J; Bally, John; Battersby, Cara; Shirley, Yancy L; Merello, Manuel

    2015-01-01

    We use the distance probability density function (DPDF) formalism of Ellsworth-Bowers et al. (2013, 2015) to derive physical properties for the collection of 1,710 Bolocam Galactic Plane Survey (BGPS) version 2 sources with well-constrained distance estimates. To account for Malmquist bias, we estimate that the present sample of BGPS sources is 90% complete above 400 $M_\\odot$ and 50% complete above 70 $M_\\odot$. The mass distributions for the entire sample and astrophysically motivated subsets are generally fitted well by a lognormal function, with approximately power-law distributions at high mass. Power-law behavior emerges more clearly when the sample population is narrowed in heliocentric distance (power-law index $\\alpha = 2.0\\pm0.1$ for sources nearer than 6.5 kpc and $\\alpha = 1.9\\pm0.1$ for objects between 2 kpc and 10 kpc). The high-mass power-law indices are generally $1.85 \\leq \\alpha \\leq 2.05$ for various subsamples of sources, intermediate between that of giant molecular clouds and the stellar ...

  20. Molecular properties of Zic4 and Zic5 proteins: functional diversity within Zic family

    International Nuclear Information System (INIS)

    The Zic-family proteins control various developmental processes. Previous studies have shown that Zic1, Zic2, and Zic3 can act as transcriptional regulators, and that their functions are repressed by I-mfa, which has been identified as a repressor for basic helix-loop-helix-type transcriptional factors. Here, we investigated the molecular properties of the Zic4 and Zic5 proteins. Zic4/Zic5 showed DNA-binding activity to the Gli-binding sequence, similar to Zic1/Zic2/Zic3 proteins. However, Zic4/Zic5 did not exhibit any significant transcriptional activation ability nor they bind to I-mfa differently from Zic1/Zic2/Zic3. The nuclear localization of Zic4/Zic5 was not affected by the presence of the I-mfa protein, whereas the Zic1/Zic2/Zic3 proteins were translocated to the cytoplasmic compartment in the presence of I-mfa. The difference may be attributable to the dissimilarity of the N-terminal region between the Zic1/Zic2/Zic3 and Zic4/Zic5 proteins, since the binding of the Zic1/Zic2/Zic3 proteins to I-mfa occurs through their N-terminal regions

  1. A metal-ion-responsive adhesive material via switching of molecular recognition properties

    Science.gov (United States)

    Nakamura, Takashi; Takashima, Yoshinori; Hashidzume, Akihito; Yamaguchi, Hiroyasu; Harada, Akira

    2014-08-01

    Common adhesives stick to a wide range of materials immediately after they are applied to the surfaces. To prevent indiscriminate sticking, smart adhesive materials that adhere to a specific target surface only under particular conditions are desired. Here we report a polymer hydrogel modified with both β-cyclodextrin (βCD) and 2,2‧-bipyridyl (bpy) moieties (βCD-bpy gel) as a functional adhesive material responding to metal ions as chemical stimuli. The adhesive property of βCD-bpy gel based on interfacial molecular recognition is expressed by complexation of metal ions to bpy that controlled dissociation of supramolecular cross-linking of βCD-bpy. Moreover, adhesion of βCD-bpy gel exhibits selectivity on the kinds of metal ions, depending on the efficiency of metal-bpy complexes in cross-linking. Transduction of two independent chemical signals (metal ions and host-guest interactions) is achieved in this adhesion system, which leads to the development of highly orthogonal macroscopic joining of multiple objects.

  2. Theranostic properties of a survivin-directed molecular beacon in human melanoma cells.

    Directory of Open Access Journals (Sweden)

    Sara Carpi

    Full Text Available Survivin is an inhibitor of apoptosis overexpressed in different types of tumors and undetectable in most terminally differentiated normal tissues. In the current study, we sought to evaluate the in vitro theranostic properties of a molecular beacon-oligodeoxynucleotide (MB that targets survivin mRNA. We used laser scanning confocal microscopy to study MB delivery in living cells and real-time PCR and western blot to assess selective survivin-targeting in human malignant melanoma cells. We further assess the pro-apoptotic effect of MB by measuring internucleosomal DNA fragmentation, dissipation of mitochondrial membrane potential (MMP and changes in nuclear morphology. Transfection of MB into A375 and 501 Mel cells generated high signal intensity from the cytoplasm, while no signal was detected in the extracellular environment and in survivin-negative cells (i.e., human melanocytes and monocytes. MB time dependently decreased survivin mRNA and protein expression in melanoma cells with the maximum effect reached at 72 h. Treatment of melanoma cells with MB induced apoptosis by significant changes in MMP, accumulation of histone-complexed DNA fragments in the cytoplasm and nuclear condensation. MB also enhanced the pro-apoptotic effect of standard chemotherapeutic drugs tested at clinically relevant concentrations. The MB tested in the current study conjugates the ability of imaging with the pharmacological silencing activity against survivin mRNA in human melanoma cells and may represent an innovative approach for cancer diagnosis and treatment.

  3. Elastic properties of amorphous boron suboxide based solids studied using ab initio molecular dynamics

    International Nuclear Information System (INIS)

    We have studied the correlation between chemical composition, structure, chemical bonding and elastic properties of amorphous B6O based solids using ab initio molecular dynamics. These solids are of different chemical compositions, but the elasticity data appear to be a function of density. This is in agreement with previous experimental observations. As the density increases from 1.64 to 2.38 g cm-3, the elastic modulus increases from 74 to 253 GPa. This may be understood by analyzing the cohesive energy and the chemical bonding of these compounds. The cohesive energy decreases from -7.051 to -7.584 eV/atom in the elastic modulus range studied. On the basis of the electron density distributions, Mulliken analysis and radial distribution functions, icosahedral bonding is the dominating bonding type. C and N promote cross-linking of icosahedra and thus increase the density, while H hinders the cross-linking by forming OH groups. The presence of icosahedral bonding is independent of the density

  4. Graphene reinforced ultra high molecular weight polyethylene with improved tensile strength and creep resistance properties

    Directory of Open Access Journals (Sweden)

    A. Bhattacharyya

    2014-02-01

    Full Text Available Reduced graphene oxide or graphene was dispersed in ultra high molecular weight polyethylene (UHMWPE using two methods to prepare nanocomposite films. In pre-reduction method, graphite oxide (GO was exfoliated and dispersed in organic solvents and reduced to graphene before polymer was added, while reduction of graphene oxide was carried out after polymer addition for in situ reduction method. Raman spectroscopic study reveals that the second method results in better exfoliation of graphene but it has more amorphous content as evident from selected area electron diffraction (SAED pattern, wide angle X-ray and differential scanning calorimetry (DSC. The nanocomposite film produced by prereduction method possesses higher crystallinity (almost the same as that of the pure film as compared to the in situ method. It shows better modulus (increased from 864 to 1236 MPa, better strength (increased from 12.6 to 22.2 MPa, network hardening and creep resistance (creep strain reduced to 9% from 50% when 40% of maximum load was applied for 72 h than the pure film. These findings show that graphene can be used for reinforcement of UHMWPE to improve its tensile and creep resistance properties.

  5. Molecular beam epitaxy growth and magnetic properties of Cr-Co-Ga Heusler alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Wuwei, E-mail: wfeng@cugb.edu.cn; Wang, Weihua [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China); Zhao, Chenglong [Key Laboratory for Renewable Energy, Beijing Key Laboratory for New Energy Materials and Devices, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Van Quang, Nguyen; Cho, Sunglae, E-mail: slcho@ulsan.ac.kr [Department of Physics, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Dung, Dang Duc [Department of General Physics, School of Engineering Physics, Ha Noi University of Science and Technology, 1 Dai Co Viet Road, Ha Noi (Viet Nam)

    2015-11-15

    We have re-investigated growth and magnetic properties of Cr{sub 2}CoGa films using molecular beam epitaxy technique. Phase separation and precipitate formation were observed experimentally again in agreement with observation of multiple phases separation in sputtered Cr{sub 2}CoGa films by M. Meinert et al. However, significant phase separation could be suppressed by proper control of growth conditions. We showed that Cr{sub 2}CoGa Heusler phase, rather than Co{sub 2}CrGa phase, constitutes the majority of the sample grown on GaAs(001) at 450 {sup o}C. The measured small spin moment of Cr{sub 2}CoGa is in agreement with predicted HM-FCF nature; however, its Curie temperature is not as high as expected from the theoretical prediction probably due to the off-stoichiometry of Cr{sub 2}CoGa and the existence of the disorders and phase separation.

  6. Molecular dynamics simulation of the structural, elastic, and thermal properties of pyrochlores

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Liyuan; Li, Yuhong; Devanathan, Ram; Gao, Fei

    2016-04-28

    We present a comprehensive simulation study of the effect of composition on the structural, elastic and thermal properties of 25 different compounds from the pyrochlore family. We joined a repulsive potential to an existing interatomic potential to enable molecular dynamics simulations of conditions away from equilibrium. We systematically varied the chemistry of the pyrochlore by substituting different cations in the A and B sites of the A2B2O7 formula unit. The A cations varied from Lu3+ to La3+, and the B cations from Ti4+ to Ce4+. The lattice parameter increased steadily with increasing the radius of A or B cations, but the bulk modulus showed a decreasing trend with increasing cation radius. However, the specific heat capacity and thermal expansion coefficient remained almost unchanged with increasing the radii of A and B cations. It is of interest to note that Ce on the B site significantly reduces the specific heat capacity and thermal expansion coefficient, which could have implications for annealing of radiation damage in cerate pyrochlores. The present results are consistent with the experimental measurements, which validates these potentials for simulation of dynamical processes, such as radiation damage, in pyrochlores.

  7. The biophysical properties of ethanolamine plasmalogens revealed by atomistic molecular dynamics simulations.

    Science.gov (United States)

    Rog, Tomasz; Koivuniemi, Artturi

    2016-01-01

    Given the importance of plasmalogens in cellular membranes and neurodegenerative diseases, a better understanding of how plasmalogens affect the lipid membrane properties is needed. Here we carried out molecular dynamics simulations to study a lipid membrane comprised of ethanolamine plasmalogens (PE-plasmalogens). We compared the results to the PE-diacyl counterpart and palmitoyl-oleyl-phosphatidylcholine (POPC) bilayers. Results show that PE-plasmalogens form more compressed, thicker, and rigid lipid bilayers in comparison with the PE-diacyl and POPC membranes. The results also point out that the vinyl-ether linkage increases the ordering of sn-1 chain substantially and the ordering of the sn-2 chain to a minor extent. Further, the vinyl-ether linkage changes the orientation of the lipid head group, but it does not cause changes in the head group and glycerol backbone tilt angles with respect to the bilayer normal. The vinyl-ether linkage also packs the proximal regions of the sn-1 and sn-2 chains more closely together which also decreases the distance between the rest of the sn-1 and sn-2 chains. PMID:26522077

  8. Wettability, optical properties and molecular structure of plasma polymerized diethylene glycol dimethyl ether

    International Nuclear Information System (INIS)

    Modern industry has frequently employed ethylene glycol ethers as monomers in plasma polymerization process to produce different types of coatings. In this work we used a stainless steel plasma reactor to grow thin polymeric films from low pressure RF excited plasma of diethylene glycol dimethyl ether. Plasmas were generated at 5W RF power in the range of 16 Pa to 60 Pa. The molecular structure of plasma polymerized films and their optical properties were analyzed by Fourier Transform Infrared Spectroscopy (FTIR) and Ultraviolet-Visible Spectroscopy, respectively. The IR spectra show C-H stretching at 3000-2900 cm-1, C=O stretching at 1730-1650 cm-1, C-H bending at 1440-1380 cm-1, C-O and C-O-C stretching at 1200-1000 cm-1. The refraction index was around 1.5 and the optical gap calculated from absorption coefficient presented value near 3.8 eV. Water contact angle of the films ranged from 40 deg. to 35 deg. with corresponding surface energy from 66 to 73x10-7 J. Because of its favorable optical and hydrophilic characteristics these films can be used in ophthalmic industries as glass lenses coatings.

  9. EFFECTS OF MOLECULAR WEIGHT ON THERMAL RESPONSIVE PROPERTY OF PEGYLATED POLY-L-GLUTAMATES

    Institute of Scientific and Technical Information of China (English)

    Shusheng Zhang; Chongyi Chen; Zhibo Li

    2013-01-01

    We investigated the ring opening polymerization (ROP) of di-and tri-ethylene glycol monomethyl ether functionalized L-glutamate N-carboxyanhydrides (NCAs) using hexamethyldisilazane (HMDS) as primary initiator and 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD) as co-initiator.The binary initiator system afforded a living ROP for these pegylated NCAs,and a series of homopolypeptides with controlled molecular weight (MW) and low polydispersity were obtained.We then systematically studied the helical content and clouding point (CP) dependence on polypeptide MW using circular dichroism (CD) spectroscopy and turbidity measurements,respectively.We found that the helical content of both homopolypeptides increased with MW,but the triethylene glycol functionalized poly-L-glutamate (poly-L-EG3Glu) intended to form more stable α-helical structure than diethylene glycol functionalized counterpart (poly-L-EG2Glu) at similar MW.Accordingly,the CP of poly-L-EG2Glu with known end group has strong dependence on its helical content,which is essentially determined by MW.Our results suggested that the thermal responsive properties of these unique pegylated poly-L-glutamates not only rely on their chemical structure but also on their secondary structures,which is different from conventional thermal responsive polymers.

  10. Self-assembling of molecular nanowires for enhancing the conducting properties of discotic liquid crystals

    Science.gov (United States)

    Park, Ji Hyun; Kim, Kyung Ho; Takanishi, Yoichi; Yamamoto, Jun; Park, Yung Woo; Kim, Youn Sang; Scalia, Giusy

    2015-08-01

    The self-organization of discotic liquid crystal molecules in columns has enormous interest for soft nanoelectronic applications. A great advantage of discotic liquid crystal is that defects can be self-annealed in contrast to typical organic materials. Through the overlap of molecular orbitals, the aromatic cores assemble into long range ordered one-dimensional structures. Very thin structured films can be obtained by spin-coating from solution and the resulting morphologies are strongly dependent on the interaction between discotics and solvent molecules. Toluene produces films formed by very long nanowires, spontaneously aligned along a common direction and over fairly large areas. These nanostructured films are a result of the interplay between liquid crystal self-organization and solvent driven assembly. The ordered nanowire structures exhibit improvement in the electrical properties compared to misaligned structures and even to pristine HAT5, deposited without the aid of solvent. In this study we show that the toluene-based deposition of discotic liquid crystals is advantageous because it allows a uniform coverage of the substrate, unlike pristine HAT5 but also thanks to the type of induced structures exhibiting one order of magnitude higher conductivity, in the aligned nanowire films, compared to bare HAT5 ones.

  11. Adhesion and friction properties of molecularly thin perfluoropolyether liquid films on solid surface.

    Science.gov (United States)

    Tani, Hiroshi; Tagawa, Norio

    2012-02-28

    The adhesion and friction properties of molecularly thin perfluoropolyether (PFPE) lubricant films dip-coated on a diamond-like carbon (DLC) overcoat of magnetic disks were studied using a pin-on-disk-type micro-tribotester that we developed. The load and friction forces were simultaneously measured on a rotating disk surface under an increasing/decreasing load cycle and slow sliding conditions. Experiments were performed using two types of PFPE lubricants: Fomblin Z-tetraol2000S with functional end-groups and Fomblin Z-03 without any end-group. The curves of the friction force as a function of the applied load agree with the curves estimated using the Johnson-Kendall-Roberts (JKR) model. The friction forces on the Z-03 films having different thicknesses were not found to decrease drastically; however, the friction forces on the Z-tetraol film were found to decrease drastically when the film thickness is more than ~1.2 nm. This drastic change in the case of the Z-tetraol film is estimated to be affected by the coverage of the lubricant film. PMID:22292931

  12. Effects of pH and temperature on colloidal properties and molecular characteristics of Konjac glucomannan.

    Science.gov (United States)

    Jian, Wenjie; Siu, Ka-Chai; Wu, Jian-Yong

    2015-12-10

    The hydrocolloidal characteristics of Konjac glucomannan (KGM) are important for its application as a thickening and gelling agent for liquid foods. In this study, the rheological behavior and molecular properties such as molar mass, hydrodynamic radius and chain conformation of KGM in water were determined at various pH levels (4.0-10.0) during heating from 20 to 80 °C. Acidic and neutral conditions (pH 4.0-7.0) promoted the dispersion of KGM, and alkaline condition at pH 10 favored its aggregation in water, while KGM maintained a random coil conformation in the whole pH range. Associated with the pH effects were changes in the rheological behavior during heating from 20 to 80 °C. The significant differences in the colloidal and rheological characteristics were mainly attributed to alteration of intermolecular interaction (attractive or repulsive) rather than deacetylation at various pH levels. Deacetylation occurred in both acidic and alkaline condition. The second virial value was positive in acidic and negative in alkaline condition. The results showed that hydrocolloidal characteristics of KGM in water were significantly affected by pH. PMID:26428126

  13. Discovery and molecular and biocatalytic properties of hydroxynitrile lyase from an invasive millipede, Chamberlinius hualienensis.

    Science.gov (United States)

    Dadashipour, Mohammad; Ishida, Yuko; Yamamoto, Kazunori; Asano, Yasuhisa

    2015-08-25

    Hydroxynitrile lyase (HNL) catalyzes the degradation of cyanohydrins and causes the release of hydrogen cyanide (cyanogenesis). HNL can enantioselectively produce cyanohydrins, which are valuable building blocks for the synthesis of fine chemicals and pharmaceuticals, and is used as an important biocatalyst in industrial biotechnology. Currently, HNLs are isolated from plants and bacteria. Because industrial biotechnology requires more efficient and stable enzymes for sustainable development, we must continuously explore other potential enzyme sources for the desired HNLs. Despite the abundance of cyanogenic millipedes in the world, there has been no precise study of the HNLs from these arthropods. Here we report the isolation of HNL from the cyanide-emitting invasive millipede Chamberlinius hualienensis, along with its molecular properties and application in biocatalysis. The purified enzyme displays a very high specific activity in the synthesis of mandelonitrile. It is a glycosylated homodimer protein and shows no apparent sequence identity or homology with proteins in the known databases. It shows biocatalytic activity for the condensation of various aromatic aldehydes with potassium cyanide to produce cyanohydrins and has high stability over a wide range of temperatures and pH values. It catalyzes the synthesis of (R)-mandelonitrile from benzaldehyde with a 99% enantiomeric excess, without using any organic solvents. Arthropod fauna comprise 80% of terrestrial animals. We propose that these animals can be valuable resources for exploring not only HNLs but also diverse, efficient, and stable biocatalysts in industrial biotechnology. PMID:26261304

  14. Gas sorption and barrier properties of polymeric membranes from molecular dynamics and Monte Carlo simulations.

    Science.gov (United States)

    Cozmuta, Ioana; Blanco, Mario; Goddard, William A

    2007-03-29

    It is important for many industrial processes to design new materials with improved selective permeability properties. Besides diffusion, the molecule's solubility contributes largely to the overall permeation process. This study presents a method to calculate solubility coefficients of gases such as O2, H2O (vapor), N2, and CO2 in polymeric matrices from simulation methods (Molecular Dynamics and Monte Carlo) using first principle predictions. The generation and equilibration (annealing) of five polymer models (polypropylene, polyvinyl alcohol, polyvinyl dichloride, polyvinyl chloride-trifluoroethylene, and polyethylene terephtalate) are extensively described. For each polymer, the average density and Hansen solubilities over a set of ten samples compare well with experimental data. For polyethylene terephtalate, the average properties between a small (n = 10) and a large (n = 100) set are compared. Boltzmann averages and probability density distributions of binding and strain energies indicate that the smaller set is biased in sampling configurations with higher energies. However, the sample with the lowest cohesive energy density from the smaller set is representative of the average of the larger set. Density-wise, low molecular weight polymers tend to have on average lower densities. Infinite molecular weight samples do however provide a very good representation of the experimental density. Solubility constants calculated with two ensembles (grand canonical and Henry's constant) are equivalent within 20%. For each polymer sample, the solubility constant is then calculated using the faster (10x) Henry's constant ensemble (HCE) from 150 ps of NPT dynamics of the polymer matrix. The influence of various factors (bad contact fraction, number of iterations) on the accuracy of Henry's constant is discussed. To validate the calculations against experimental results, the solubilities of nitrogen and carbon dioxide in polypropylene are examined over a range of

  15. Thermophysical properties of hydrogen-helium mixtures: Re-examination of the mixing rules via quantum molecular dynamics simulations

    Science.gov (United States)

    Wang, Cong; He, Xian-Tu; Zhang, Ping

    2013-09-01

    Thermophysical properties of hydrogen, helium, and hydrogen-helium mixtures have been investigated in the warm dense matter regime at electron number densities ranging from 6.02×1029˜2.41×1030 m-3 and temperatures from 4000 to 20000 K via quantum molecular dynamics simulations. We focus on the dynamical properties such as the equation of states, diffusion coefficients, and viscosity. Mixing rules (density matching, pressure matching, and binary ionic mixing rules) have been validated by checking composite properties of pure species against that of the fully interacting mixture derived from quantum molecular dynamics simulations. These mixing rules reproduce pressures within 10% accuracy, while it is 75% and 50% for the diffusion and viscosity, respectively. The binary ionic mixing rule moves the results into better agreement. Predictions from one component plasma model are also provided and discussed.

  16. EHR adopters vs. non-adopters: Impacts of, barriers to, and federal initiatives for EHR adoption

    Science.gov (United States)

    Jamoom, Eric W.; Patel, Vaishali; Furukawa, Michael F.; King, Jennifer

    2016-01-01

    While adoption of electronic health record (EHR) systems has grown rapidly, little is known about physicians’ perspectives on its adoption and use. Nationally representative survey data from 2011 are used to compare the perspectives of physicians who have adopted EHRs with those that have yet to do so across three key areas: the impact of EHRs on clinical care, practice efficiency and operations; barriers to EHR adoption; and factors that influence physicians to adopt EHRs. Despite significant differences in perspectives between adopters and non-adopters, the majority of physicians perceive that EHR use yields overall clinical benefits, more efficient practices and financial benefits. Purchase cost and productivity loss are the greatest barriers to EHR adoption among both adopters and non-adopters; although non-adopters have significantly higher rates of reporting these as barriers. Financial incentives and penalties, technical assistance, and the capability for electronic health information exchange are factors with the greatest influence on EHR adoption among all physicians. However, a substantially higher proportion of non-adopters regard various national health IT policies, and in particular, financial incentives or penalties as a major influence in their decision to adopt an EHR system. Contrasting these perspectives provides a window into how national policies have shaped adoption thus far; and how these policies may shape adoption in the near future. PMID:26250087

  17. Process of adoption communication openness in adoptive families: adopters’ perspective

    Directory of Open Access Journals (Sweden)

    Maria Acciaiuoli Barbosa-Ducharne

    2016-01-01

    Full Text Available Abstract Communication about adoption is a family interaction process which is more than the simple exchange of information. Adoption communication can be characterized in terms of the level of openness of family conversations regarding the child’s past and the degree of the family’s adoption social disclosure. The objective of this study is to explore the process of adoption communication openness in Portuguese adoptive families by identifying the impact of variables related to the adoption process, the adoptive parenting and the adoptee. One hundred twenty five parents of children aged 3 to 15, who were adopted on average 4 years ago, participated in this study. Data was collected during home visits using the Parents Adoption Process Interview. A cluster analysis identified three different groups of families according to the level of adoption communication openness within the family and outside. The findings also showed that the process of the adoption communication openness started when parents decided to adopt, developed in parent-child interaction and was susceptible to change under professional intervention. The relevance of training given to prospective adopters and of professional practice based on scientific evidence is highlighted.

  18. Special topics in international adoption.

    Science.gov (United States)

    Jenista, Jerri Ann

    2005-10-01

    As international adoption has become more "mainstream," the issues recently addressed in domestic adoption have become more important in adoptions involving children originating in other countries. Certain groups of prospective adoptive parents, such as gay or lesbian couples, single parents, and parents with disabilities, have begun to apply to adopt in ever increasing numbers. Children who may have been considered unadoptable in the past are now routinely being offered to prospective adoptive parents. The numbers and ages of the children placed and the spacing between adoptions have come under scrutiny. The rates of adoption dissolutions and disruptions are being examined carefully by the receiving and sending countries. There is a pressing need for research into numerous social aspects of adoption. PMID:16154473

  19. Molecular clouds in the Carina arm - large-scale properties of molecular gas and comparison with H I

    Energy Technology Data Exchange (ETDEWEB)

    Grabelsky, D.A.; Cohen, R.S.; Bronfman, L.; Thaddeus, P.; May, J.

    1987-04-01

    Results from the first large-scale survey in the CO (J = 1 - 0) line of the Vela-Carina-Centaurus region of the southern Milky Way are reported. The results demonstrate that molecular clouds in the Galaxy are largely confined to the spiral arms and that CO is therefore an extremely good tracer of the large-scale structure of the system. The Carina arm is the dominant feature in the data. Its abrupt tangent at l of roughly 280 deg and characteristic loop in the (l, v) diagram are unmistakable evidence for CO spiral structure. When the emission is integrated over velocity and latitude, the height of the step seen in the tangent direction indicate that the arm-interarm contrast is at least 13:1. 44 references.

  20. Molecular clouds in the Carina arm - Large-scale properties of molecular gas and comparison with H I

    Science.gov (United States)

    Grabelsky, D. A.; Cohen, R. S.; Bronfman, L.; Thaddeus, P.; May, J.

    1987-01-01

    Results from the first large-scale survey in the CO (J = 1 - 0) line of the Vela-Carina-Centaurus region of the southern Milky Way are reported. The results demonstrate that molecular clouds in the Galaxy are largely confined to the spiral arms and that CO is therefore an extremely good tracer of the large-scale structure of the system. The Carina arm is the dominant feature in the data. Its abrupt tangent at l of roughly 280 deg and characteristic loop in the (l, v) diagram are unmistakable evidence for CO spiral structure. When the emission is integrated over velocity and latitude, the height of the step seen in the tangent direction indicate that the arm-interarm contrast is at least 13:1.

  1. A molecular dynamic model for analyzing concentrations of electrolytes: Fractional molar dependences of microstructure properties

    Science.gov (United States)

    Khalansky, D.; Popova, E.; Gladyshev, P.; Dushanov, E.; Kholmurodov, Kh.

    2014-12-01

    Aqueous electrolyte solutions play an important role in many electrophysical and chemical processes in aerospace technology and industrial applications. As noncovalent interactions, the interactions between ions are crucially important for biomolecular structures as well (protein structure folding, molecular level processes followed by ionic pair correlations, the formation of flexible hydrate shells, and so on). Specifically, ions (cations and anions with the same valence charges) can form stable pairs if their sizes match. The formation of ionic pairs can substantially affect the thermodynamic stabilities of proteins in the alkali salts physiologically present in the human body. Research aims and problems impose severe demands on readjustments of the ionic force fields and potential parameters developed to describe aqueous solutions and electrolytic systems. Ionic solutions and their interaction with biomolecules have been observed for over 100 years [1], but the behavior of such solutions remains poorly studied today. New data obtained in this work deals with parameterization strategies and adjustments for the ionic force fields of the alkali cations and halide anions that should be helpful in biomolecular research. Using molecular dynamics (MD) models, four electrolytic systems (HCl-H2O, LiCl-H2O, NaCl-H2O, and KCl-H2O) are investigated as binary mixtures of water and cations and anions, respectively. The intermolecular interaction parameters are varied for two of the four model electrolytes (HCl-H2O and NaCl-H2O) to simulate the possibility of different ionic shells forming during interaction with water. It is found that varying the potential parameters strongly affects the dynamic and structural characteristics of electrolyte systems. MD simulations are performed in the temperature range of 300 to 600 K with a step of 50 K. MD simulations for all electrolyte models (HCl-H2O, LiCl-H2O, NaCl-H2O, KCl-H2O) are also conducted for different molar fractions of

  2. Effect of electron beam radiation on the structure and mechanical properties of ultra high molecular weight polyethylene fibers

    International Nuclear Information System (INIS)

    Ultra high molecular weight polyethylene fibers have been crosslinked by electron beam. The structure and mechanical properties of them have been investigated in different irradiation atmospheres. The obtained results show that the gel content and crosslinking density increase with the increase of dose, the swelling ratio and average molecular weight of crosslinked net decrease with the increase of dose, the tensile strength and failure elongation decrease with the increase of dose, the tensile modulus increases with the increase of dose. When the samples are irradiated in air, vacuum and acetylene atmospheres, the effect of irradiation in acetylene atmosphere is best

  3. The emotional aftermath of adoption.

    Science.gov (United States)

    Nadelson, C C

    1976-09-01

    Adopted children are emotionally vulnerable. Adoptive parents must cope with more complex problems than biologic parents. The family physician can provide valuable counseling. Preadoption counseling focuses on motivation and ambivalence. After adoption, however, serious, sometimes predictable, issues arise, such as: how and when to tell the child he is adopted; the child's search for knowledge; the problem of subsequent divorce; the birth of a natural sibling, and the involvement of other family members. New concepts include "open adoption" and "single parent adoption." PMID:961560

  4. Parents' Feelings towards Their Adoptive and Non-Adoptive Children

    Science.gov (United States)

    Glover, Marshaun B.; Mullineaux, Paula Y.; Deater-Deckard, Kirby; Petrill, Stephen A.

    2010-01-01

    In the current study, we examined parent gender differences in feelings (negativity and positivity) and perceptions of child behavioural and emotional problems in adoptive and biological parent-child dyads. In a sample of 85 families, we used a novel within-family adoption design in which one child was adopted and one child was a biological child…

  5. Molecular dynamics studies of melting and liquid properties of ammonium dinitramide

    Science.gov (United States)

    Velardez, Gustavo F.; Alavi, Saman; Thompson, Donald L.

    2003-10-01

    The melting point and some liquid properties of ammonium dinitramide (ADN), NH4N(NO2)2, have been calculated using molecular dynamics calculations at various temperatures and pressures. The intramolecular potential for ADN was obtained from the AMBER 7 program and the intermolecular potential from Sorescu and Thompson [J. Phys. Chem. B 103, 6714 (1999)]. The simulations were performed for 3×2×4, 5×4×6, and 6×4×8 supercells of ADN. The 3×2×4 supercell was found to be adequate for predicting the melting point; however, the larger simulation cells were required to obtain converged results for the liquid properties. This model accurately predicts the temperature of the solid-to-liquid transition in ADN. The melting point of crystalline ADN has been determined by calculating the temperature dependence of the density, enthalpy, and radial distribution functions. The temperature dependence of the diffusion coefficient, calculated using equilibrium time-correlation functions, shows a discontinuity at the melting temperature and can also be used to determine the melting point. The value of the normal melting temperature of the perfect crystal calculated from the change in density is in the range 474-476 K, compared to the experimentally determined range 365-368 K. The difference is attributed to superheating of the perfect crystal. The superheating effect is eliminated by introducing voids in the crystal structure. Calculations of the temperature dependence of the density of a supercell with eight or more voids predict a melting temperature in the range 366-368 K, which is in excellent agreement with the experimental value. Melting temperatures have been calculated for pressures up to 0.8 GPa, which is the highest experimental pressure for ADN reported by Russell et al. [J. Phys. Chem. B 100, 3248 (1996)]. The computed dependence of the melting temperature on pressure is in excellent agreement with experiment. The temperature dependence of the diffusion and

  6. Biopolymer molecular weight control by radiation treatment for functional property improvement

    Energy Technology Data Exchange (ETDEWEB)

    Lam, Nguyen Duy; Diep, Tran Bang; Quynh, Tran Minh; Hung, Nguyen Manh [Vietnam Atomic Energy Commission, Institute for Nuclear Science and Techniques, Caugiay, Hanoi (Viet Nam); Nagasawa, Naotsugu; Kume, Tamikazu [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment

    2002-03-01

    Solid-state radiation treatment of chitosan an dose range of 30-100 kGy and of gelatin at dose range of 30-40 kGy significantly improved the water-stability of shrimp feed. In these dose ranges, the viscosity-average molecular weight (Mv) of bioadhesive was reduced from 552,000 to 250,000-130,000 and from 57,000 to 38,000-32,000 for chitosan and gelatin, respectively. Gelatin, which has been irradiated in liquid state, could not be used as bioadhesive due to the forming of higher macromolecules based on chaincrosslinks. Liquid-state radiation treatment, in comparison with solid-state irradiation at 100 kGy, required only dose of 4-6 kGy for similar MW and for the same optimal improvement of adhesive property. Radiation treatment with 60-100 kGy maximally enhanced the anti-microbial activity of chitosan. In addition, the optimal dose required for activity is depended on chitosan origin. Chitosan with initial MW of 830,000 required dose of 100 kGy to reduce to 120,000, while other kind of chitosan with initial MW of 550,000 required dose of 60-75 kGy to reduce to 170,000-150,000 for optimal enhancement. The antimicrobial activity is regulated by not only MW but also by its distribution. Irradiated chitosan that has largest width of MW distribution (Mw/Mn) may possesses highest antimicrobial activity. Result from fractionation by using centrifugal filter devices showed that fraction of 3-5 x 10{sup 4} has mainly contributed to the suppression of microbial growth. (author)

  7. Biopolymer molecular weight control by radiation treatment for functional property improvement

    International Nuclear Information System (INIS)

    Solid-state radiation treatment of chitosan an dose range of 30-100 kGy and of gelatin at dose range of 30-40 kGy significantly improved the water-stability of shrimp feed. In these dose ranges, the viscosity-average molecular weight (Mv) of bioadhesive was reduced from 552,000 to 250,000-130,000 and from 57,000 to 38,000-32,000 for chitosan and gelatin, respectively. Gelatin, which has been irradiated in liquid state, could not be used as bioadhesive due to the forming of higher macromolecules based on chaincrosslinks. Liquid-state radiation treatment, in comparison with solid-state irradiation at 100 kGy, required only dose of 4-6 kGy for similar MW and for the same optimal improvement of adhesive property. Radiation treatment with 60-100 kGy maximally enhanced the anti-microbial activity of chitosan. In addition, the optimal dose required for activity is depended on chitosan origin. Chitosan with initial MW of 830,000 required dose of 100 kGy to reduce to 120,000, while other kind of chitosan with initial MW of 550,000 required dose of 60-75 kGy to reduce to 170,000-150,000 for optimal enhancement. The antimicrobial activity is regulated by not only MW but also by its distribution. Irradiated chitosan that has largest width of MW distribution (Mw/Mn) may possesses highest antimicrobial activity. Result from fractionation by using centrifugal filter devices showed that fraction of 3-5 x 104 has mainly contributed to the suppression of microbial growth. (author)

  8. A DFT analysis of the molecular structure, vibrational spectra and other molecular properties of 5-nitrouracil and comparison with uracil

    Science.gov (United States)

    Kattan, D.; Alcolea Palafox, M.; Rathor, S. K.; Rastogi, V. K.

    2016-02-01

    The four unit cells found in the crystals of the biomolecule 5-Nitrouracil were simulated as tetramer forms by density functional calculations. Four tetramer forms were fully optimized. Specific scale factors and scaling equations deduced from uracil molecule were employed in the predicted wavenumbers of 5-nitrouracil. The experimental FT-Raman and FT-IR spectra were recorded in the solid state. Comprehensive interpretation of the experimental FT-IR and FT-Raman spectra of the compound under study in the solid state is based on potential energy distribution. A good reproduction of the experimental wavenumbers is obtained and the % error is very small in the majority of cases. A complete vibrational assignment in the isolated state was also carried out aided by the theoretical harmonic frequency analysis and the results compared with those reported in Ar matrix. The scaled wavenumbers were used in the reassignment of several experimental bands. A comparison between the molecular structure and charge distribution of 5-Nitrouracil with related 5-uracil derivatives was presented. The effect of the nitro substitution in the 5th position of the pyrimidine ring was evaluated.

  9. Structural, dynamic, and vibrational properties during heat transfer in Si/Ge superlattices: A Car-Parrinello molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Pengfei; Zhang, Yuwen, E-mail: zhangyu@missouri.edu [Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, Missouri 65211 (United States); Yang, Mo [College of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093 (China)

    2013-12-21

    The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective.

  10. Structural, dynamic, and vibrational properties during heat transfer in Si/Ge superlattices: A Car-Parrinello molecular dynamics study

    International Nuclear Information System (INIS)

    The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective

  11. Seeing the Forest Through the Trees: The Distribution and Properties of Dense Molecular Gas in the Milky Way Galaxy

    Science.gov (United States)

    Ellsworth-Bowers, Timothy P.

    The Milky Way Galaxy serves as a vast laboratory for studying the dynamics and evolution of the dense interstellar medium and the processes of and surrounding massive star formation. From our vantage point within the Galactic plane, however, it has been extremely difficult to construct a coherent picture of Galactic structure; we cannot see the forest for the trees. The principal difficulties in studying the structure of the Galactic disk have been obscuration by the ubiquitous dust and molecular gas and confusion between objects along a line of sight. Recent technological advances have led to large-scale blind surveys of the Galactic plane at (sub-)millimeter wavelengths, where Galactic dust is generally optically thin, and have opened a new avenue for studying the forest. The Bolocam Galactic Plane Survey (BGPS) observed over 190 deg 2 of the Galactic plane in dust continuum emission near lambda = 1.1 mm, producing a catalog of over 8,000 dense molecular cloud structures across a wide swath of the Galactic disk. Deriving the spatial distribution and physical properties of these objects requires knowledge of distance, a component lacking in the data themselves. This thesis presents a generalized Bayesian probabilistic distance estimation method for dense molecular cloud structures, and demonstrates it with the BGPS data set. Distance probability density functions (DPDFs) are computed from kinematic distance likelihoods (which may be double- peaked for objects in the inner Galaxy) and an expandable suite of prior information to produce a comprehensive tally of our knowledge (and ignorance) of the distances to dense molecular cloud structures. As part of the DPDF formalism, this thesis derives several prior DPDFs for resolving the kinematic distance ambiguity in the inner Galaxy. From the collection of posterior DPDFs, a set of objects with well-constrained distance estimates is produced for deriving Galactic structure and the physical properties of dense molecular

  12. International Adoption: A Way Forward

    OpenAIRE

    Bartholet, Elizabeth

    2011-01-01

    This is the introduction to a special issue of articles on international adoption, summing up their relevance to the debate in the field. International adoption is in turmoil, with a dramatic reduction in recent years in the number of children placed in adoptive homes. These articles provide important new support for international adoption as an appropriate way to advance children’s rights and interests. And they provide information about ways to address any problems of corruption and abus...

  13. Adoption Legislation Consultation - Discussion Paper

    OpenAIRE

    Department of Health

    2003-01-01

    Adoption Legislation Consultation РDiscussion Paper This discussion paper is part of a fundamental review of Irish adoption policy and practice referred to in the Minister for Children̢?Ts foreword. The purpose of the review is to give organisations and individuals with an interest in adoption law and practice an opportunity to contribute to the development of a modern adoption system characterised by clarity, consistency and fairness. Click here to download PDF 104kb

  14. Adoption of M-Commerce

    OpenAIRE

    Saljoughi, Farhad

    2002-01-01

    The development of ICT in recent years, and speed of this development is extremely rapid. ICT also spreads widely and influences deeply not only economic activities of business, households and governments but also various areas of people’s daily life. The adoption rate of mobile Internet was estimated by analogy to adoption pattern. This study examines patterns of mobile commerce adoption and usage in early adopters. One hundred and ninety mobile users were surveyed about their...

  15. Orbital free ab initio molecular dynamics simulation study of some static and dynamic properties of liquid noble metals

    Directory of Open Access Journals (Sweden)

    G.M. Bhuiyan

    2012-10-01

    Full Text Available Several static and dynamic properties of liquid Cu, Ag and Au at thermodynamic states near their respective melting points, have been evaluated by means of the orbital free ab-initio molecular dynamics simulation method. The calculated static structure shows good agreement with the available X-ray and neutron diffraction data. As for the dynamic properties, the calculated dynamic structure factors point to the existence of collective density excitations along with a positive dispersion for l-Cu and l-Ag. Several transport coefficients have been obtained which show a reasonable agreement with the available experimental data.

  16. Estimation and Uncertainty Analysis of Flammability Properties for Computer-aided molecular design of working fluids for thermodynamic cycles

    DEFF Research Database (Denmark)

    Frutiger, Jerome; Abildskov, Jens; Sin, Gürkan

    Computer Aided Molecular Design (CAMD) is an important tool to generate, test and evaluate promising chemical products. CAMD can be used in thermodynamic cycle for the design of pure component or mixture working fluids in order to improve the heat transfer capacity of the system. The safety...... analysis. In this case property prediction models like group contribution (GC) models can estimate flammability data. The estimation needs to be accurate, reliable and as less time consuming as possible [1]. However, GC property prediction methods frequently lack rigorous uncertainty analysis. Hence, there...

  17. Physicochemical properties of CuAlMCM-41 and CuNbMCM-41 mesoporous molecular sieves

    International Nuclear Information System (INIS)

    The texture and surface properties of copper-containing aluminosilica and niobiosilica mesoporous molecular sieves of MCM-41 type, in which all elements were introduced during the synthesis, have been studied by means of XRD, N2 adsorption, H2TPR, FTIR combined with pyridine and NO adsorption as well as the skeletal region, and the test reaction. The results were compared with those obtained earlier for Cu post synthesis exchanged AlMCM41 and NbMCM-41. All results and this comparison allow the suggestion that copper is partially located in the skeleton of both MCM-41 materials, which exhibit redox and acidic properties. (author)

  18. The effect of molecular geometry on the photovoltaic property of diketopyrrolopyrrole based non-fullerene acceptors

    DEFF Research Database (Denmark)

    Zhang, Fei; Brandt, Rasmus Guldbæk; Gu, Zhuowei;

    2015-01-01

    , Ph(DPP)2 and PhDMe(DPP)2 with similar chemical components but different molecular geometries. Due to its more twisted molecular conformation, PhDMe(DPP)2 shows more blue-shifted absorption bands, higher electron mobility, and better miscibility with the polymer donor poly(3-hexylthiophene) (P3HT...

  19. A Phenomenological Exploration of Adoption

    Science.gov (United States)

    Baltimore, Diana L.; Crase, Sedahlia Jasper

    2009-01-01

    This qualitative analysis explored children's and adults' experiences with adoption. We used phenomenological methodology and individually interviewed 25 participants and included adoptive mothers and fathers, and their children, each adopted before 18 months of age. Two research questions guided the data analysis: (a) What are children's and…

  20. Adoption Resources for Black Children

    Science.gov (United States)

    Gallagher, Ursula M.

    1971-01-01

    The growing number of adoptions in this country, including racially mixed adoptions, attest to the general acceptance of adoption as a way of bringing love to children in need of families of their own and the satisfactions of parenthood to childless couples, single men and women, and families who have room for one more. (Author/AJ)

  1. Dogmatism and Attitudes Toward Adoption

    Science.gov (United States)

    Dembroski, Betty G.; Johnson Dale L.

    1969-01-01

    Using Rokeach's Dogmatism Scale and an Adoption Attitude Scale administered to 113 college students study supports hypothesis that among males dogmatism and intolerance toward areas relating to adoption would be positively correlated. Negative correlation for females suggests that emphasis on maternal role makes adoption attitudes exception to…

  2. Structural, dynamical, electronic, and bonding properties of laser-heated silicon: An ab initio molecular-dynamics study

    OpenAIRE

    Silvestrelli, P.-L.; Alavi, A; Parrinello, M.; Frenkel, D

    1997-01-01

    The method of ab initio molecular dynamics, based on finite-temperature density-functional theory, is used to simulate laser heating of crystalline silicon. We found that a high concentration of excited electrons dramatically weakens the covalent bonding. As a result the system undergoes a melting transition to a metallic state. We studied several structural, dynamical, electronic, and bonding properties of this phase of silicon. In contrast to ordinary liquid silicon, this liquid is characte...

  3. Influence of Macromer Molecular Weight and Chemistry on Poly(β-amino ester) Network Properties and Initial Cell Interactions

    OpenAIRE

    Brey, Darren M.; Erickson, Isaac; Burdick, Jason A.

    2008-01-01

    A library of photocrosslinkable poly(β-amino ester)s (PBAEs) was recently synthesized to expand the number of degradable polymers that can be screened and developed for a variety of biological applications. In this work, the influence of variations in macromer chemistry and macromer molecular weight (MMW) on network reaction behavior, overall bulk properties, and cell interactions were investigated. The MMW was controlled through alterations in the initial diacrylate to amine ratio (≥1) durin...

  4. Structural, Dynamic, and Vibrational Properties during Heat Transfer in Si/Ge Superlattices: A Car-Parrinello Molecular Dynamics Study

    OpenAIRE

    Ji, Pengfei; Zhang, Yuwen; Yang, Mo

    2016-01-01

    The structural, dynamic, and vibrational properties during the heat transfer process in Si/Ge superlattices, are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) ar...

  5. Associations Between the Molecular and Optical Properties of Dissolved Organic Matter in the Florida Everglades, a Model Coastal Wetland System

    OpenAIRE

    Wagner, Sasha; Jaffé, Rudolf; Cawley, Kaelin; Dittmar, Thorsten; Stubbins, Aron

    2015-01-01

    Optical properties are easy-to-measure proxies for dissolved organic matter (DOM) composition, source, and reactivity. However, the molecular signature of DOM associated with such optical parameters remains poorly defined. The Florida coastal Everglades is a subtropical wetland with diverse vegetation (e.g., sawgrass prairies, mangrove forests, seagrass meadows) and DOM sources (e.g., terrestrial, microbial, and marine). As such, the Everglades is an excellent model system from which to draw ...

  6. Adsorption and switching properties of a N-benzylideneaniline based molecular switch on a Au(111) surface

    International Nuclear Information System (INIS)

    High resolution electron energy loss spectroscopy has been employed to analyze the adsorption geometry and the photoisomerization ability of the molecular switch carboxy-benzylideneaniline (CBA) adsorbed on Au(111). CBA on Au(111) adopts a planar (trans) configuration in the first monolayer (ML) as well as for higher coverages (up to 6 ML), in contrast to the strongly nonplanar geometry of the molecule in solution. Illumination with UV light of CBA in direct contact with the Au(111) surface (≤1 ML) caused no changes in the vibrational structure, whereas at higher coverages (>1 ML) pronounced modifications of vibrational features were observed, which we assign to a trans→cis isomerization. Thermal activation induced the back reaction to trans-CBA. We propose that the photoisomerization is driven by a direct (intramolecular) electronic excitation of the adsorbed CBA molecules in the second ML (and above) analogous to CBA in the liquid phase.

  7. Adoption of nuclear power generation

    International Nuclear Information System (INIS)

    This article develops a model of the innovation-adoption decision. The model allows the economic situation of a utility and its perception of uncertainty associated with an innovation to affect the probability of adopting it. This model is useful when uncertainties affecting decisions about adoption persist throughout the diffusion process, thereby making the usual adoption model implicit in rate-of-diffusion studies inappropriate. An empirical test of the model finds that firm size, power pool size, and selected aspects of uncertainty about the innovation are significant predictors of US utility companies' decisions on whether or not to adopt nuclear power generation. 17 references, 2 tables

  8. Technology Adoption: an Interaction Perspective

    Science.gov (United States)

    Sitorus, Hotna M.; Govindaraju, Rajesri; Wiratmadja, I. I.; Sudirman, Iman

    2016-02-01

    The success of a new technology depends on how well it is accepted by its intended users. Many technologies face the problem of low adoption rate, despite the benefits. An understanding of what makes people accept or reject a new technology can help speed up the adoption rate. This paper presents a framework for technology adoption based on an interactive perspective, resulting from a literature study on technology adoption. In studying technology adoption, it is necessary to consider the interactions among elements involved in the system, for these interactions may generate new characteristics or new relationships. The interactions among elements in a system adoption have not received sufficient consideration in previous studies of technology adoption. Based on the proposed interaction perspective, technology adoption is elaborated by examining interactions among the individual (i.e. the user or prospective user), the technology, the task and the environment. The framework is formulated by adopting several theories, including Perceived Characteristics of Innovating, Diffusion of Innovation Theory, Technology Acceptance Model, Task-Technology Fit and usability theory. The proposed framework is illustrated in the context of mobile banking adoption. It is aimed to offer a better understanding of determinants of technology adoption in various contexts, including technology in manufacturing systems.

  9. Insights into molecular properties of the human monocarboxylate transporter 8 by combining functional with structural information

    Directory of Open Access Journals (Sweden)

    Kleinau Gunnar

    2011-08-01

    Full Text Available Abstract Background The monocarboxylate transporter 8 (MCT8 is a member of the major facilitator superfamily (MFS and transports specificly iodothyronines. MCT8 mutations are the underlying cause of a syndrome of severe X-linked psychomotor retardation known as the Allan-Herndon-Dudley syndrome. This syndrome is characterized by abnormally high T3, low/normal T4 serum levels and slightly elevated serum TSH. To date, more than 25 pathogenic mutations in hMCT8 are known and they are valuable indicators of important regions for structural and functional MCT8 properties. Methods We designed a structural human MCT8 model and studied reported pathogenic missense mutations with focus on the estimation of those amino acid positions which are probably sensitive for substrate transport. Furthermore, assuming similarities between determinants of T3 binding observed in the published crystal structure of the thyroid hormone receptor beta occupied by its ligand T3 and the structural MCT8 model, we explore potential T3 binding sites in the MCT8 substrate channel cavity. Results We found that all known pathogenic missense mutations are located exclusively in the transmembrane helices and to a high degree at conserved residues among the MCT family. Furthermore, mutations either of or to prolines/glycines are located mainly at helices 9-12 and are expected to cause steric clashes or structural misfolding. In contrast, several other mutations are close to the potential substrate channel and affected amino acids are likely involved in the switching mechanism between different transporter conformations. Finally, three potential substrate binding sites are predicted for MCT8. Conclusions Naturally occurring mutations of MCT8 provide molecular insights into protein regions important for protein folding, substrate binding and the switching mechanism during substrate transport. Future studies guided by this information should help to clarify structure

  10. Molecular and Biochemical Analysis of the Estrogenic and Proliferative Properties of Vitamin E Compounds

    Science.gov (United States)

    Khallouki, Farid; de Medina, Philippe; Caze-Subra, Stéphanie; Bystricky, Kerstin; Balaguer, Patrick; Poirot, Marc; Silvente-Poirot, Sandrine

    2016-01-01

    Tocols are vitamin E compounds that include tocopherols (TPs) and tocotrienols (TTs). These lipophilic compounds are phenolic antioxidants and are reportedly able to modulate estrogen receptor β (ERβ). We investigated the molecular determinants that control their estrogenicity and effects on the proliferation of breast cancer cells. Docking experiments highlighted the importance of the tocol phenolic groups for their interaction with the ERs. Binding experiments confirmed that they directly interact with both ERα and ERβ with their isoforms showing potencies in the following order: δ-tocols > γ-tocols > α-tocols. We also found that tocols activated the transcription of an estrogen-responsive reporter gene that had been stably transfected into cells expressing either ERα or ERβ. The role of the phenolic group in tocol–ER interaction was further established using δ-tocopherylquinone, the oxidized form of δ-TP, which had no ER affinity and did not induce ER-dependent transcriptional modulation. Tocol activity also required the AF1 transactivation domain of ER. We found that both δ-TP and δ-TT stimulated the expression of endogenous ER-dependent genes. However, whereas δ-TP induced the proliferation of ER-positive breast cancer cells but not ER-negative breast cancer cells, δ-TT inhibited the proliferation of both ER-positive and ER-negative breast cancer cells. These effects of δ-TT were found to act through the down regulation of HMG-CoA reductase (HMGR) activity, establishing that ERs are not involved in this effect. Altogether, these data show that the reduced form of δ-TP has estrogenic properties which are lost when it is oxidized, highlighting the importance of the redox status in its estrogenicity. Moreover, we have shown that δ-TT has antiproliferative effects on breast cancer cells independently of their ER status through the inhibition of HMGR. These data clearly show that TPs can be discriminated from TTs according to their

  11. Intercountry versus Transracial Adoption: Analysis of Adoptive Parents' Motivations and Preferences in Adoption

    Science.gov (United States)

    Zhang, Yuanting; Lee, Gary R.

    2011-01-01

    The United States is one of the major baby-receiving countries in the world. Relatively little research has focused on why there is such a high demand for intercountry adoption. Using in-depth qualitative interviews with adoptive parents, the authors explored the reasons why Americans prefer to adopt foreign-born children instead of adopting…

  12. Wet-spinnability and crosslinked fibre properties of two collagen polypeptides with varied molecular weight

    CERN Document Server

    Tronci, Giuseppe; Arafat, M Tarik; Yin, Jie; Wood, David J; Russell, Stephen J

    2015-01-01

    The formation of naturally-derived materials with wet stable fibrous architectures is paramount in order to mimic the features of tissues at the molecular and microscopic scale. Here, we investigated the formation of wet-spun fibres based on collagen-derived polypeptides with comparable chemical composition and varied molecular weight. Gelatin and hydrolysed fish collagen (HFC) were selected as widely-available linear amino-acidic chains of high and low molecular weight, respectively, and functionalised in the wet-spun fibre state in order to preserve the material geometry in physiological conditions. Wet-spun fibre diameter and morphology were dramatically affected depending on the polypeptide molecular weight, wet-spinning solvent (i.e. 2,2,2-Trifluoroethanol and dimethyl sulfoxide) and coagulating medium (i.e. acetone and ethanol), resulting in either bulky or porous internal geometry. Dry-state tensile moduli were significantly enhanced in gelatin and HFC samples following covalent crosslinking with activ...

  13. Classical molecular dynamics simulation on the dynamical properties of H2 on silicene layer

    OpenAIRE

    Casuyac Miqueas; Bantaculo Rolando

    2016-01-01

    This study investigates the diffusion of hydrogen molecule physisorbed on the surface of silicene nanoribbon (SiNR)using the classical molecular dynamic (MD) simulation in LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). The interactions between silicon atoms are modeled using the modified Tersoff potential, the Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential for hydrogen – hydrogen interaction and the Lennard – Jones potential for the physisorbed H...

  14. Effects of ionizing radiation on the properties of ultra-high molecular weight polyethylene (PE-UHMW)

    International Nuclear Information System (INIS)

    Ultra high molecular weight polyethylene (PE-UHMW) is used in most artificial joint replacement devices. Prior to implantation in biological environment, radiatin sterilization by 60Co or electron beam is common. It is well known that polyethylene exposed to ionizing radiation of any sort undergo physical changes due to chain scission and/or crosslinking. PE-UHMW sheets, 8 mm thick, were either 60Co or electron beam irradiated, in the range of 10-150 kGy under air or nitrogen atmoshere. The crystallinity of the irradiated samples increases with the irradiation dose. The chain scission/crosslinking events ratio determine the network structure and the sol/gel ratio. The latter was found to depend on irradiation dose, radiation atmosphere and sample thickness. Moreover 60Co-irradiation is about 5 times more effective in forming PE-UHMW gel than electron-irradiation. Besides the degree of crosslinking, the molecular weight distribution is the main determinant of the structural properties of PE-UHMW. Low molecular weight fractions were also found. Using a dose of 30 kGy (60Co in air), the average molecular weight of the soluble part after extraction decreased from originally 2.3 million g/mol to 170.000 g/mol, corresponding to a factor of about 10. These changes in molecular weight have a strong influence on the mechanical properties of PE-UHMW. Crosslinking slightly increases the yield strength, while the elongation at break decreases. Long-term compressive creep is reduced if the material is irradiated. Obviously, increased crystallinity after oxidative chain scission affects a higher deformation resistance. Radiation crosslinked structures cause a significant increase in abrasion resistance. The above described structural changes occur even upon irradiation of very low doses as used during sterilization. This study will enable to reduce the radiation sterilization damage and thus to gain long term stability of PE-UHMW medical devices. (orig./BBR)

  15. Influence of alkyl chain length and temperature on thermophysical properties of ammonium-based ionic liquids with molecular solvent.

    Science.gov (United States)

    Kavitha, T; Attri, Pankaj; Venkatesu, Pannuru; Devi, R S Rama; Hofman, T

    2012-04-19

    Mixing of ionic liquids (ILs) with molecular solvent can expand the range of structural properties and the scope of molecular interactions between the molecules of the solvents. Exploiting of these phenomena essentially require a basic fundamental understanding of mixing behavior of ILs with molecular solvents. In this context, a series of protic ILs possessing tetra-alkyl ammonium cation [R(4)N](+) with commonly used anion hydroxide [OH](-) were synthesized and characterized by temperature dependent thermophysical properties. The ILs [R(4)N](+)[OH](-) are varying only in the length of alkyl chain (R is methyl, ethyl, propyl, or butyl) of tetra-alkyl ammonium on the cationic part. The ILs used for the present study included tetramethyl ammonium hydroxide [(CH(3))(4)N](+)[OH](-) (TMAH), tetraethyl ammonium hydroxide [(C(2)H(5))(4)N](+)[OH](-) (TEAH), tetrapropyl ammonium hydroxide [(C(3)H(7))(4)N](+)[OH](-) (TPAH) and tetrabutyl ammonium hydroxide [(C(4)H(9))(4)N](+)[OH](-) (TBAH). The alkyl chain length effect has been analyzed by precise measurements such as densities (ρ), ultrasonic sound velocity (u), and viscosity (η) of these ILs with polar solvent, N-methyl-2-pyrrolidone (NMP), over the full composition range as a function of temperature. The excess molar volume (V(E)), the deviation in isentropic compressibility (Δκ(s)) and deviation in viscosity (Δη) were predicted using these properties as a function of the concentration of ILs. Redlich-Kister polynomial was used to correlate the results. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding between ILs and NMP molecules. Later, the hydrogen bonding features between ILs and NMP were also analyzed using a molecular modeling program with the help of HyperChem 7. PMID:22443087

  16. Imparting super hydro/oleophobic properties to cotton fabric by means of molecular and nanoparticles vapor deposition methods

    International Nuclear Information System (INIS)

    Super hydro/oleophobic cotton fabrics were prepared using nanoparticle vapor deposition and molecular vapor deposition techniques. The surface was roughened by trimethylaluminum/water nanoparticles followed by functionalization with (tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane. This process imparted unique hydro/oleophobic properties (contact angle >160°). In contrast to wet chemistry processes, the chemicals used and the thickness of the coatings produced by this method could be controlled precisely, which allowed for the minimization of waste generation while preserving the original properties of the fabric. Dynamic contact angles were measured and the fabrics that were coated using this technique showed low-contact-angle hysteresis properties. Scanning electron microscopy and universal attenuated total reflectance Fourier transform infrared spectroscopy confirmed the formation of a nanostructure-roughened surface. Drop dynamics such as the force of droplet movement, work of adhesion, and surface free energy were also calculated.

  17. Molecular dynamic study of the mechanical properties of two-dimensional titanium carbides Tin+1Cn (MXenes)

    Science.gov (United States)

    Borysiuk, Vadym N.; Mochalin, Vadym N.; Gogotsi, Yury

    2015-07-01

    Two-dimensional materials beyond graphene are attracting much attention. Recently discovered 2D carbides and nitrides (MXenes) have shown very attractive electrical and electrochemical properties, but their mechanical properties have not been characterized yet. There are neither experimental measurements reported in the literature nor predictions of strength or fracture modes for single-layer MXenes. The mechanical properties of two-dimensional titanium carbides were investigated in this study using classical molecular dynamics. Young’s modulus was calculated from the linear part of strain-stress curves obtained under tensile deformation of the samples. Strain-rate effects were observed for all Tin+1Cn samples. From the radial distribution function, it is found that the structure of the simulated samples is preserved during the deformation process. Calculated values of the elastic constants are in good agreement with published DFT data.

  18. Molecular outflows driven by low-mass protostars. I. Correcting for underestimates when measuring outflow masses and dynamical properties

    Energy Technology Data Exchange (ETDEWEB)

    Dunham, Michael M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 78, Cambridge, MA 02138 (United States); Arce, Héctor G. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States); Mardones, Diego [Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago (Chile); Lee, Jeong-Eun [Department of Astronomy and Space Science, Kyung Hee University, Yongin, Gyeonggi 446-701 (Korea, Republic of); Matthews, Brenda C. [National Research Council of Canada, Herzberg Astronomy and Astrophysics, 5071 W. Saanich Road, Victoria, BC V9E 2E7 (Canada); Stutz, Amelia M. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); Williams, Jonathan P., E-mail: mdunham@cfa.harvard.edu [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States)

    2014-03-01

    We present a survey of 28 molecular outflows driven by low-mass protostars, all of which are sufficiently isolated spatially and/or kinematically to fully separate into individual outflows. Using a combination of new and archival data from several single-dish telescopes, 17 outflows are mapped in {sup 12}CO (2-1) and 17 are mapped in {sup 12}CO (3-2), with 6 mapped in both transitions. For each outflow, we calculate and tabulate the mass (M {sub flow}), momentum (P {sub flow}), kinetic energy (E {sub flow}), mechanical luminosity (L {sub flow}), and force (F {sub flow}) assuming optically thin emission in LTE at an excitation temperature, T {sub ex}, of 50 K. We show that all of the calculated properties are underestimated when calculated under these assumptions. Taken together, the effects of opacity, outflow emission at low velocities confused with ambient cloud emission, and emission below the sensitivities of the observations increase outflow masses and dynamical properties by an order of magnitude, on average, and factors of 50-90 in the most extreme cases. Different (and non-uniform) excitation temperatures, inclination effects, and dissociation of molecular gas will all work to further increase outflow properties. Molecular outflows are thus almost certainly more massive and energetic than commonly reported. Additionally, outflow properties are lower, on average, by almost an order of magnitude when calculated from the {sup 12}CO (3-2) maps compared to the {sup 12}CO (2-1) maps, even after accounting for different opacities, map sensitivities, and possible excitation temperature variations. It has recently been argued in the literature that the {sup 12}CO (3-2) line is subthermally excited in outflows, and our results support this finding.

  19. Detailed characterization of mechanical properties and molecular mobility within dry seed glasses: relevance to the physiology of dry biological systems.

    Science.gov (United States)

    Ballesteros, Daniel; Walters, Christina

    2011-11-01

    Slow movement of molecules in glassy matrices controls the kinetics of chemical and physical reactions in dry seeds. Variation in physiological activity among seeds suggests that there are differences in mobility among seed glasses. Testing this hypothesis is difficult because few tools are available to measure molecular mobility within dry seeds. Here, motional properties within dry pea cotyledons were assessed using dynamic mechanical analysis. The technique detected several molecular relaxations between -80 and +80°C and gave a more detailed description of water content-temperature effects on molecular motion than previously understood from studies of glass formation in seeds at glass transition (Tg). Diffusive movement is delimited by the α relaxation, which appears to be analogous to Tg. β and γ relaxations were also detected at temperatures lower than α relaxations, clearly demonstrating intramolecular motion within the glassy matrix of the pea cotyledon. Glass transitions, or the mechanical counterpart α relaxation, appear to be less relevant to seed aging during dry storage than previously thought. On the other hand, β relaxation occurs at temperature and moisture conditions typically used for seed storage and has established importance for physical aging of synthetic polymer glasses. Our data show that the nature and extent of molecular motion varies considerably with moisture and temperature, and that the hydrated conditions used for accelerated aging experiments and ultra-dry conditions sometimes recommended for seed storage give greater molecular mobility than more standard seed storage practices. We believe characterization of molecular mobility is critical for evaluating how dry seeds respond to the environment and persist through time. PMID:21831210

  20. TIME-DEPENDENT PROPERTIES OF LIQUID WATER: A COMPARISON OF CAR-PARRINELLO AND BORN-OPPENHIEMER MOLECULAR DYNAMICS SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, I W; Mundy, C; McGrath, M; Siepmann, J I

    2005-12-29

    A series of 30 ps first principles molecular dynamics simulations in the microcanonical ensemble were carried out to investigate transport and vibrational properties of liquid water. To allow for sufficient sampling, the thermodynamic constraints were set to an elevated temperature of around 423 K and a density of 0.71 g/cm{sup 3} corresponding to the saturated liquid density for the Becke-Lee-Yang-Parr (BLYP) representation of water. Four simulations using the Car-Parrinello molecular dynamics (CPMD) technique with varying values of the fictitious electronic mass ({mu}) and two simulations using the Born-Oppenheimer molecular dynamics (BOMD) technique are analyzed to yield structural and dynamical information. At the selected state point, the simulations are found to exhibit non-glassy dynamics and yield consistent results for the liquid structure and the self-diffusion coefficient, although the statistical uncertainties in the latter quantity are quite large. Consequently, it can be said that the CPMD and BOMD methods produce equivalent results for these properties on the time scales reported here. However, it was found that the choice of {mu} affects the frequency spectrum of the intramolecular modes, shifting them slightly to regions of lower frequency. Using a value of {mu} = 400 a.u. results in a significant drift in the electronic kinetic energy of the system over the course of 30 ps and a downward drift in the ionic temperature. Therefore, for long trajectories at elevated temperatures, lower values of this parameter are recommended for CPMD simulations of water.

  1. Coordination properties of a metal chelator clioquinol to Zn(2+) studied by static DFT and ab initio molecular dynamics.

    Science.gov (United States)

    Rodríguez-Santiago, Luis; Alí-Torres, Jorge; Vidossich, Pietro; Sodupe, Mariona

    2015-05-28

    Several lines of evidence supporting the role of metal ions in amyloid aggregation, one of the hallmarks of Alzheimer's disease (AD), have turned metal ion chelation into a promising therapeutic treatment. The design of efficient chelating ligands requires proper knowledge of the electronic and molecular structure of the complexes formed, including their hydration properties. Among various potential chelators, clioquinol (5-chloro-7-iodo-8-hydroxyquinoline, CQH) has been evaluated with relative success in in vitro experiments and even in phase 2 clinical trials. Clioquinol interacts with Zn(ii) to lead to a binary metal/ligand 1 : 2 stoichiometric complex in which the phenolic group of CQH is deprotonated, resulting in Zn(CQ)2 neutral complexes, to which additional water molecules may coordinate. In the present work, the coordinative properties of clioquinol in aqueous solution have been analyzed by means of static, minimal cluster based DFT calculations and explicit solvent ab initio molecular dynamics simulations. Results from static calculations accounting for solvent effects by means of polarized continuum models suggest that the preferred metal coordination environment is tetrahedral Zn(CQ)2, whereas ab initio molecular dynamics simulations point to quasi degenerate penta Zn(CQ)2(H2O) and hexa Zn(CQ)2(H2O)2 coordinated complexes. The possible reasons for these discrepant results are discussed. PMID:25939963

  2. Design rules for rational control of polymer glass formation behavior and mechanical properties with small molecular additives

    Science.gov (United States)

    Mangalara, Jayachandra Hari; Simmons, David

    Small molecule additives have long been employed to tune polymers' glass formation, mechanical and transport properties. For example, plasticizers are commonly employed to suppress polymer Tg and soften the glassy state, while antiplasticizers, which stiffen the glassy state of a polymer while suppressing its Tg, are employed to enhance protein and tissue preservation in sugar glasses. Recent literature indicates that additives can have a wide range of possible effects, but all of these have not been clearly understood and well appreciated. Here we employ molecular dynamics simulations to establish design rules for the selection of small molecule additives with size, molecular stiffness, and interaction energy chosen to achieve targeted effects on polymer properties. We furthermore find that a given additive's effect on a polymer's Tg can be predicted from its Debye-Waller factor via a function previously found to describe nanoconfinement effects on the glass transition. These results emphasize the potential for a new generation of targeted molecular additives to contribute to more targeted rational design of polymers. We acknowledge the Keck Foundation and the Ohio Supercomputing Center for financial and computational support of this effort, respectively.

  3. First principles investigations of electronic structure and transport properties of graphitic structures and single molecular junctions

    Science.gov (United States)

    Owens, Jonathan R.

    properties of the IV curves of single molecule nano-junctions. Specifically, these systems consist of a zinc-porphyrin molecule coupled between two gold electrodes, i.e., a nano-gap. The first observation we want to explain is the asymmetric nature of the experimental IV curve for this porphyrin system, where the IV curve is skewed heavily to the negative bias region. Using a plane-wave DFT calculation, we present the density of states of the porphyrin molecule (both in the presence and absence of the electrodes) and indeed see highly delocalized states (as confirmed by site-projection of the DOS) only in the negative bias region, meaning that the channels with high transmission probability reside there, in agreement with experimental observation. The next problem studied pertains to observed switching in an experimentally-measured IV curve, this time of a longer zinc porphyrin molecule, still within a gold nano-gap. The switching behavior is observed only at 300K, not at 4.2K. The temperature-dependance of this problem renders our previous toolset of DFT calculations void; DFT is a ground-state theory. Instead, we employ a density functional-based tight-binding (DFTB) approach in a molecular dynamics simulation. Basically, the structural configuration evaluated at each time step is based on a tight-binding electronic structure calculation, instead of a typical MD force field. Trajectories are presented at varying temperatures and electric field strengths. Indeed, we observe a conformation of the porphyrin molecule between two configurations of the dihedral angle of the central nitrogen ring, ±15. {o} at 300K, but not 4.2K. These confirmations are equally likely, i.e., the structure assumes these configurations an equal number of teams, meaning the average structure has an angle of 0. {o}. After computing the DOS of all three aforementioned configurations (0. {text{o}} and ±15. {text{o}}), we indeed see a difference between the DOS curves at ±15. {text{o}} (which are

  4. Adoption: a forgotten paediatric speciality

    OpenAIRE

    Mather, M.

    1999-01-01

    OBJECTIVE—To study the medical, emotional, and developmental profile of children being considered for permanent substitute care.
DESIGN—A retrospective analysis of 100 adoption/permanency medicals.
SETTING—All children considered by the adoption and permanency panel in Greenwich, south east London, between 1994 and 1998.
OUTCOME MEASURES—Analysis of medical reports completed using the British Agencies for Adoption and Fostering form C (under 5 years) or form D (over 5 yea...

  5. The JCMT nearby galaxies legacy survey - X. Environmental effects on the molecular gas and star formation properties of spiral galaxies

    Science.gov (United States)

    Mok, Angus; Wilson, C. D.; Golding, J.; Warren, B. E.; Israel, F. P.; Serjeant, S.; Knapen, J. H.; Sánchez-Gallego, J. R.; Barmby, P.; Bendo, G. J.; Rosolowsky, E.; van der Werf, P.

    2016-03-01

    We present a study of the molecular gas properties in a sample of 98 H I - flux selected spiral galaxies within ˜25 Mpc, using the CO J = 3 - 2 line observed with the James Clerk Maxwell Telescope. We use the technique of survival analysis to incorporate galaxies with CO upper limits into our results. Comparing the group and Virgo samples, we find a larger mean H2 mass in the Virgo galaxies, despite their lower mean H I mass. This leads to a significantly higher H2 to H I ratio for Virgo galaxies. Combining our data with complementary Hα star formation rate measurements, Virgo galaxies have longer molecular gas depletion times compared to group galaxies, due to their higher H2 masses and lower star formation rates. We suggest that the longer depletion times may be a result of heating processes in the cluster environment or differences in the turbulent pressure. From the full sample, we find that the molecular gas depletion time has a positive correlation with the stellar mass, indicative of differences in the star formation process between low- and high-mass galaxies, and a negative correlation between the molecular gas depletion time and the specific star formation rate.

  6. Implementation of a methodology for determining elastic properties of lipid assemblies from molecular dynamics simulations

    OpenAIRE

    Johner, Niklaus; Harries, Daniel; Khelashvili, George

    2016-01-01

    Background The importance of the material properties of membranes for diverse cellular processes is well established. Notably, the elastic properties of the membrane, which depend on its composition, can directly influence membrane reshaping and fusion processes as well as the organisation and function of membrane proteins. Determining these properties is therefore key for a mechanistic understanding of how the cell functions. Results We have developed a method to determine the bending rigidi...

  7. SCELib3.0: The new revision of SCELib, the parallel computational library of molecular properties in the Single Center Approach

    Science.gov (United States)

    Sanna, N.; Baccarelli, I.; Morelli, G.

    2009-12-01

    SCELib is a computer program which implements the Single Center Expansion (SCE) method to describe molecular electronic densities and the interaction potentials between a charged projectile (electron or positron) and a target molecular system. The first version (CPC Catalog identifier ADMG_v1_0) was submitted to the CPC Program Library in 2000, and version 2.0 (ADMG_v2_0) was submitted in 2004. We here announce the new release 3.0 which presents additional features with respect to the previous versions aiming at a significative enhance of its capabilities to deal with larger molecular systems. SCELib 3.0 allows for ab initio effective core potential (ECP) calculations of the molecular wavefunctions to be used in the SCE method in addition to the standard all-electron description of the molecule. The list of supported architectures has been updated and the code has been ported to platforms based on accelerating coprocessors, such as the NVIDIA GPGPU and the new parallel model adopted is able to efficiently run on a mixed many-core computing system. Program summaryProgram title: SCELib3.0 Catalogue identifier: ADMG_v3_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADMG_v3_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 2 018 862 No. of bytes in distributed program, including test data, etc.: 4 955 014 Distribution format: tar.gz Programming language: C Compilers used: xlc V8.x, Intel C V10.x, Portland Group V7.x, nvcc V2.x Computer: All SMP platforms based on AIX, Linux and SUNOS operating systems over SPARC, POWER, Intel Itanium2, X86, em64t and Opteron processors Operating system: SUNOS, IBM AIX, Linux RedHat (Enterprise), Linux SuSE (SLES) Has the code been vectorized or parallelized?: Yes. 1 to 32 (CPU or GPU) used RAM: Up to 32 GB depending on the molecular

  8. Adoption and Assisted Reproduction. Adoption and Ethics, Volume 4.

    Science.gov (United States)

    Freundlich, Madelyn

    The controversies in adoption have extended across a spectrum of policy and practice issues, and although the issues have become clear, resolution has not been achieved nor has consensus developed regarding a framework on which to improve the quality of adoption policy and practice. This book is the fourth in a series to use an ethics-based…

  9. Homosexuality and adoption in Brazil.

    Science.gov (United States)

    Uziel, A P

    2001-11-01

    Western societies are undergoing legal and policy changes in relation to laws governing the family, marital status, sexual orientation and the welfare of children, including in Brazil where, in the 1990s, the rights of homosexuals were incorporated into ongoing debates about what constitutes a family. This paper discusses the issue of adoption of children by homosexual men in Brazil, using information from court records from 1995-2000 in Rio de Janeiro, and from interviews with two judges, five psychologists and four social workers who evaluate those wishing to adopt. It uses the case records of one man's application to adopt, in which homosexuality became a central issue. Both the construction of masculinity in relation to parenting and concepts of the family were the parameters upon which the decision to allow him to adopt or not depended. Because the legislation does not specify what the sexual orientation of would-be adoptive parents should be, it is possible for single persons to adopt if they show they can be good parents. As more single people, alone or in couples, seek to adopt, it is important to clarify the criteria for judicial decisions on adoption applications. A dialogue is therefore needed on the meaning of family and whether and how it relates to sexual orientation. It is only on this basis that the courts can take a clear decision as to whether being homosexual is a relevant issue in regard to applications to adopt or not. PMID:11765396

  10. Changes in physical properties and molecular structure of butyl rubber during γ-irradiation

    International Nuclear Information System (INIS)

    Butyl rubber samples have been aged by γ-irradiation at 250C in air. The change in molecular structure due to chain scission and formation of oxygenated groups also change the number-average molecular weight, tensile strength and density of butyl rubber. The rubber predominantly undergoes chain scission upon γ-irradiation up to a dose of 50 Mrad, but there is also substantial chain crosslinking above 50 Mrad. The yield G(x) has been found, which provides an insight into the mechanism of the radiolytic degradation. Hydroperoxide is the major product and unsaturation is incorporated in the polymer back bone. The change in molecular structure due to recombination and chain scission are followed by the formation of a more ordered structure and hence an increase in density. (author)

  11. Molecular plating of thin lanthanide layers with improved material properties for nuclear applications

    International Nuclear Information System (INIS)

    This work describes experiments to gain an improved understanding of the processes associated with the electrochemical production of thin lanthanide layers for nuclear science investigations, i.e., nuclear targets. Nd, Sm, and Gd layers were prepared by means of the so-called molecular plating (MP) technique, where electrodeposition from an organic medium is usually performed in the constant current mode using two-electrode cells. The obtained results allowed the identification of optimized production conditions, which led to a significantly improved layer quality. Constant current density MP is a mass-transport controlled process. The applied current is maintained constant by constant fluxes of electroactive species towards the cathode - where the layer is grown - and the anode. The investigations showed the cell potentials of the electrodeposition systems to be always dominated by the ohmic drop produced by the resistance of the solutions used for the studies. This allowed to derive an expression relating cell potential with concentration of the electroactive species. This expression is able to explain the trends recorded with different electrolyte concentrations and it serves as a basis to get towards a full understanding of the reasons leading to the characteristic minima observed in the evolution of the cell potential curves with time. The minima were found to correspond to an almost complete depletion of the Nd ions obtained by dissolution of the model salt used for the investigations. Nd was confirmed to be deposited at the cathode as derivatives of Nd3+ - possibly as carboxylate, oxide or hydroxide. This fact was interpreted on the basis of the highly negative values of the standard redox potentials typical for lanthanide cations. Among the different electroactive species present in the complex MP solutions, the Nd3+ ions were found to contribute to less than 20% to the total current. Because of electrolysis, also the mixed solvent contributed to the

  12. Magnetic surfactants as molecular based-magnets with spin glass-like properties

    Science.gov (United States)

    Brown, Paul; Smith, Gregory N.; Padrón Hernández, Eduardo; James, Craig; Eastoe, Julian; Nunes, Wallace C.; Settens, Charles M.; Hatton, T. Alan; Baker, Peter J.

    2016-05-01

    This paper reports the use of muon spin relaxation spectroscopy to study how the aggregation behavior of magnetic surfactants containing lanthanide counterions may be exploited to create spin glass-like materials. Surfactants provide a unique approach to building in randomness, frustration and competing interactions into magnetic materials without requiring a lattice of ordered magnetic species or intervening ligands and elements. We demonstrate that this magnetic behavior may also be manipulated via formation of micelles rather than simple dilution, as well as via design of surfactant molecular architecture. This somewhat unexpected result indicates the potential of using novel magnetic surfactants for the generation and tuning of molecular magnets.

  13. The molecular properties of humic substances isolated from a UK upland peat system: a temporal investigation.

    Science.gov (United States)

    Scott, M J; Jones, M N; Woof, C; Simon, B; Tipping, E

    2001-12-01

    The study concerns the possible changes in the molecular characteristics of humic materials isolated from the same source as a function of time. A great deal of data has been reported concerning the contrast in molecular characteristics of humic substances isolated from different environments. This has primarily been an attempt to identify source-specific molecular characteristics. However, data presented in this paper suggests that humic substances isolated from a single catchment have significant changes in molecular characteristics over time. Two naturally occurring peat pools (X and Y) situated upon a small organic catchment on Great Dun Fell, Cumbria, UK were sampled monthly between November 1994 and November 1996. Dissolved organic matter (DOM) from the pool water samples was fractionated using macroporous nonionic resins (XAD8 and 4), and the humic, fulvic and hydrophilic acids were collected. These fractions were analysed for elemental composition (C, H and N), weight average molecular weight, functional group content and adsorption (340 nm) of a 1 g l(-1) solution measured in a 1-cm spectrophotometer cell. The molecular characteristics were compared to those of natural DOM described by Scott et al. (1998). Scott et al. reported that drought conditions and seasonal climatic changes could have appreciable effects upon molecular characteristics of natural DOM. Results showed that the atomic H/C ratio of the humic substances increased immediately after strong drought conditions experienced in the summer of 1995. This change was temporary with atomic H/C ratio decreasing gradually over the following months. A similar decrease was observed in the carboxyl group content of the isolated compounds. The data set suggested that atomic H/C ratio in the fulvic and hydrophilic fractions exhibited seasonal characteristics of higher ratios during the late summer/early autumn months. This was not observed in the humic fraction. Humic acids exhibited a seasonal pattern of

  14. Magnetic surfactants as molecular based-magnets with spin glass-like properties

    International Nuclear Information System (INIS)

    This paper reports the use of muon spin relaxation spectroscopy to study how the aggregation behavior of magnetic surfactants containing lanthanide counterions may be exploited to create spin glass-like materials. Surfactants provide a unique approach to building in randomness, frustration and competing interactions into magnetic materials without requiring a lattice of ordered magnetic species or intervening ligands and elements. We demonstrate that this magnetic behavior may also be manipulated via formation of micelles rather than simple dilution, as well as via design of surfactant molecular architecture. This somewhat unexpected result indicates the potential of using novel magnetic surfactants for the generation and tuning of molecular magnets. (paper)

  15. Structural, Dynamic, and Vibrational Properties during Heat Transfer in Si/Ge Superlattices: A Car-Parrinello Molecular Dynamics Study

    CERN Document Server

    Ji, Pengfei; Yang, Mo

    2016-01-01

    The structural, dynamic, and vibrational properties during the heat transfer process in Si/Ge superlattices, are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quant...

  16. Using molecular dynamics simulations and finite element method to study the mechanical properties of nanotube reinforced polyethylene and polyketone

    Science.gov (United States)

    Rouhi, S.; Alizadeh, Y.; Ansari, R.; Aryayi, M.

    2015-09-01

    Molecular dynamics simulations are used to study the mechanical behavior of single-walled carbon nanotube reinforced composites. Polyethylene and polyketone are selected as the polymer matrices. The effects of nanotube atomic structure and diameter on the mechanical properties of polymer matrix nanocomposites are investigated. It is shown that although adding nanotube to the polymer matrix raises the longitudinal elastic modulus significantly, the transverse tensile and shear moduli do not experience important change. As the previous finite element models could not be used for polymer matrices with the atom types other than carbon, molecular dynamics simulations are used to propose a finite element model which can be used for any polymer matrices. It is shown that this model can predict Young’s modulus with an acceptable accuracy.

  17. Molecular Arrangement, Electronic Structure and Transport Properties in Surfactant Gel- and Related Systems Studied by Soft X-ray and Dielectric Spectroscopy

    OpenAIRE

    Gråsjö, Johan

    2013-01-01

    This thesis concerns studies of aqueous soft matter systems, especially surfactant micelle systems. The aim has been to study the molecular arrangement and electronic structure of the constituents of, as well as transport properties in such a system. The molecular arrangement and electronic structure has been studied by means of X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray spectroscopy (RIXS). The transport properties have been investigated by low-frequency dielectric spec...

  18. Effect of molecular weight and testing rate on adhesion property of pressure-sensitive adhesives prepared from epoxidized natural rubber

    International Nuclear Information System (INIS)

    Research highlights: → Elucidation of adhesion property of epoxidized natural rubber (ENR 25). → Correlation of peel and shear strength with molecular weight and rate of testing. → Confirmation of miscibility of tackifier and ENR 25 by DSC and FTIR study. → Applicability of Fox equation in ENR 25/coumarone-indene resin system. -- Abstract: The dependence of peel strength and shear strength of epoxidized natural rubber (ENR 25)-based pressure-sensitive adhesive on molecular weight and rate of testing was investigated using coumarone-indene as the tackifying resin. Toluene and polyethylene terephthalate (PET) were used as the solvent and substrate respectively throughout the study. A SHEEN hand coater was used to coat the adhesive on the substrate at a coating thickness of 120 μm. All the adhesion properties were determined by a Llyod Adhesion Tester operating at different rates of testing. Result shows that peel strength and shear strength increases up to an optimum molecular weight of 6.5 x 104 of ENR 25. For peel strength, the observation is attributed to the combined effects of wettability and mechanical strength of rubber at the optimum molecular weight, whereas for the shear strength, it is ascribed to the increasing amount of adhesive present in the coating layer which enhances the shear resistance of the adhesive. Peel strength and shear strength also increases with increase in rate of testing, an observation which is associated to the viscoeslastic response of the adhesive. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) study confirms the miscibility of tackifier and the ENR 25.

  19. The effect of point mutations on structure and mechanical properties of collagen-like fibril: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Marlowe, Ashley E.; Singh, Abhishek; Yingling, Yaroslava G., E-mail: yara_yingling@ncsu.edu

    2012-12-01

    Understanding sequence dependent mechanical and structural properties of collagen fibrils is important for the development of artificial biomaterials for medical and nanotechnological applications. Moreover, point mutations are behind many collagen associated diseases, including Osteogenesis Imperfecta (OI). We conducted a combination of classical and steered atomistic molecular dynamics simulations to examine the effect of point mutations on structure and mechanical properties of short collagen fibrils which include mutations of glycine to alanine, aspartic acid, cysteine, and serine or mutations of hydroxyproline to arginine, asparagine, glutamine, and lysine. We found that all mutations disrupt structure and reduce strength of the collagen fibrils, which may affect the hierarchical packing of the fibrils. The glycine mutations were more detrimental to mechanical strength of the fibrils (WT > Ala > Ser > Cys > Asp) than that of hydroxyproline (WT > Arg > Gln > Asn > Lys). The clinical outcome for glycine mutations agrees well with the trend in reduction of fibril's tensile strength predicted by our simulations. Overall, our results suggest that the reduction in mechanical properties of collagen fibrils may be used to predict the clinical outcome of mutations. Highlights: Black-Right-Pointing-Pointer All mutations disrupt structure and bonding pattern and reduce strength of the collagen fibrils. Black-Right-Pointing-Pointer Gly based mutations are worst to mechanical integrity of fibrils than that of Hyp. Black-Right-Pointing-Pointer Lys and Arg mutations most dramatically destabilize collagen fibril properties. Black-Right-Pointing-Pointer Clinical outcome of mutations may be related to the reduced mechanical properties of fibrils.

  20. The effect of cross linking density on the mechanical properties and structure of the epoxy polymers: molecular dynamics simulation.

    Science.gov (United States)

    Shokuhfar, Ali; Arab, Behrouz

    2013-09-01

    Recently, great attention has been focused on using epoxy polymers in different fields such as aerospace, automotive, biotechnology, and electronics, owing to their superior properties. In this study, the classical molecular dynamics (MD) was used to simulate the cross linking of diglycidyl ether of bisphenol-A (DGEBA) with diethylenetriamine (DETA) curing agent, and to study the behavior of resulted epoxy polymer with different conversion rates. The constant-strain (static) approach was then applied to calculate the mechanical properties (Bulk, shear and Young's moduli, elastic stiffness constants, and Poisson's ratio) of the uncured and cross-linked systems. Estimated material properties were found to be in good agreement with experimental observations. Moreover, the dependency of mechanical properties on the cross linking density was investigated and revealed improvements in the mechanical properties with increasing the cross linking density. The radial distribution function (RDF) was also used to study the evolution of local structures of the simulated systems as a function of cross linking density. PMID:23793720

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

    Science.gov (United States)

    Murphy, Peter M.

    2007-01-01

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

  2. Investigation on the protein-binding properties of icotinib by spectroscopic and molecular modeling method.

    Science.gov (United States)

    Zhang, Hua-Xin; Xiong, Hang-Xing; Li, Li-Wei

    2016-05-15

    Icotinib is a highly-selective epidermal growth factor receptor tyrosine kinase inhibitor with preclinical and clinical activity in non-small cell lung cancer, which has been developed as a new targeted anti-tumor drug in China. In this work, the interaction of icotinib and human serum albumin (HSA) were studied by three-dimensional fluorescence spectra, ultraviolet spectra, circular dichroism (CD) spectra, molecular probe and molecular modeling methods. The results showed that icotinib binds to Sudlow's site I in subdomain IIA of HSA molecule, resulting in icotinib-HSA complexes formed at ground state. The number of binding sites, equilibrium constants, and thermodynamic parameters of the reaction were calculated at different temperatures. The negative enthalpy change (ΔH(θ)) and entropy change (ΔS(θ)) indicated that the structure of new complexes was stabilized by hydrogen bonds and van der Waals power. The distance between donor and acceptor was calculated according to Förster's non-radiation resonance energy transfer theory. The structural changes of HSA caused by icotinib binding were detected by synchronous spectra and circular dichroism (CD) spectra. Molecular modeling method was employed to unfold full details of the interaction at molecular level, most of which could be supported by experimental results. The study analyzed the probability that serum albumins act as carriers for this new anticarcinogen and provided fundamental information on the process of delivering icotinib to its target tissues, which might be helpful in understanding the mechanism of icotinib in cancer therapy. PMID:26963729

  3. Rheological properties of poly(vinylpiyrrolidone) as a function of molecular weight

    DEFF Research Database (Denmark)

    Marani, Debora; Sudireddy, Bhaskar Reddy; Kiebach, Wolff-Ragnar; Nielsen, Lotte; Ndoni, Sokol

    2014-01-01

    Different grades of poly (vinylpyrrolidone) (PVP) were studied as dispersant for gadolinium doped cerium oxide (CGO) in ethanol-based colloidal dispersions. The average molecular weights Mw, Mn, and Mz were determined by gel permeation chromatography (GPC), and then used in a numerical method to ...

  4. Molecular Design Properties of OxyVita Hemoglobin, a New Generation Therapeutic Oxygen Carrier: A Review

    Directory of Open Access Journals (Sweden)

    Hanna Wollocko

    2011-12-01

    Full Text Available OxyVita Hb is a new generation hemoglobin based oxygen carrier (HBOC produced through modification of a zero-linked polymerization mechanism using activators which incorporate cross-linked bovine tetramer hemoglobin into “super-polymeric” macromolecules (Average molecular weight = 17 MDa for the purpose of oxygen delivery when whole blood or packed red cells are not available. This molecular design approach was generated in order to address several fundamental biochemical and physiological weaknesses of previous generations of HBOCs. Observation during pre-clinical and clinical studies provided evidence that these early generation acellular HBOCs were directly associated with loss of retention within the circulatory system, extravasation across endothelial tissue membranes due to their small molecular size leading to arterial and venous vasoconstriction with coupled increases in mean arterial pressure (MAP. The inherent increase in molecular size and structural stability of the OxyVita Hb is a direct response to addressing these serious weaknesses that have occurred during the evolution of HBOC development within the past two decades. The nature of the zero-linked synthetic route eliminates any chemical linkers remaining in the product, eliminating side reaction concerns, such as reversibility and decomposition due to weak chemical bonds, dependency on temperature and pressure, and residual toxicity.

  5. Continuous far red irradiation controls molecular properties of delta-aminolevulinate dehydratase in Raphanus Sativus seedlings

    International Nuclear Information System (INIS)

    8-Aminolevulinate dehydratase (EC 4.2.1.24) (ALAD) is a phytochrome-dependent enzyme. Under continuous far red light (FR), the intracellular location of ALAD is modified: in young irradiated seedling cotyledons (48 h from sowing) it is localised in the cytoplasm, as for seedlings kept in continuous darkness or irradiated but treated with erythromycin (ERT). In seedlings kept 120 h under continuous FR light, ALAD is detected in cytoplasm too, but also in etioplasts. Studies from DEAE-cellulose chromatography show that, when ALAD is localised in the cytoplasm it has a stable charge, but an unstable molecular weight. If plastids are allowed to grow normally under continuous FR light, the enzyme can be purified from stroma of etioplasts from 72 h from sowing. The molecule is unstable, both in charge and in molecular weight. ALAD from etioplasts is further transformed into a species stable both in charge and in molecular weight. The relationship between the molecular modifications and physiological results observed previously are discussed. (author)

  6. Structure and properties of simple molecular systems at very high density

    International Nuclear Information System (INIS)

    The use of computer simulations in the study of molecular systems at very high density is reviewed. Applications to the thermodynamics of dense fluid nitrogen and phase transitions in solid oxygen are presented. The effects of changes in the atomic electronic structure on the equation of state of very dense helium are discussed. 19 refs., 2 figs

  7. Revealing structural and dynamical properties of high density lipoproteins through molecular simulations

    DEFF Research Database (Denmark)

    Koivuniemi, A.; Vattulainen, I.

    2012-01-01

    essentially atomistic considerations of HDL particles over microsecond time scales, thereby proving substantial added value to experimental research. In this article, we discuss recent highlights concerning the structure and dynamics of HDL particles as revealed by atomistic and coarse-grained molecular...

  8. Investigation on the protein-binding properties of icotinib by spectroscopic and molecular modeling method

    Science.gov (United States)

    Zhang, Hua-xin; Xiong, Hang-xing; Li, Li-wei

    2016-05-01

    Icotinib is a highly-selective epidermal growth factor receptor tyrosine kinase inhibitor with preclinical and clinical activity in non-small cell lung cancer, which has been developed as a new targeted anti-tumor drug in China. In this work, the interaction of icotinib and human serum albumin (HSA) were studied by three-dimensional fluorescence spectra, ultraviolet spectra, circular dichroism (CD) spectra, molecular probe and molecular modeling methods. The results showed that icotinib binds to Sudlow's site I in subdomain IIA of HSA molecule, resulting in icotinib-HSA complexes formed at ground state. The number of binding sites, equilibrium constants, and thermodynamic parameters of the reaction were calculated at different temperatures. The negative enthalpy change (ΔHθ) and entropy change (ΔSθ) indicated that the structure of new complexes was stabilized by hydrogen bonds and van der Waals power. The distance between donor and acceptor was calculated according to Förster's non-radiation resonance energy transfer theory. The structural changes of HSA caused by icotinib binding were detected by synchronous spectra and circular dichroism (CD) spectra. Molecular modeling method was employed to unfold full details of the interaction at molecular level, most of which could be supported by experimental results. The study analyzed the probability that serum albumins act as carriers for this new anticarcinogen and provided fundamental information on the process of delivering icotinib to its target tissues, which might be helpful in understanding the mechanism of icotinib in cancer therapy.

  9. Molecular characterisation of the thermostability and catalytic properties of enzymes from hyperthermophiles

    NARCIS (Netherlands)

    Lebbink, J.H.G.

    1999-01-01

    Hyperthermophilic organisms are able to survive and reproduce optimally between 80°C and 113°C. Most of them belong to the domain of the Archaea, although several hyperthermophilic Bacteria have been described. One of the major questions regarding hyperthermophiles concerns the molecular mechanisms

  10. Conformational and Molecular Structures of α,β-Unsaturated Acrylonitrile Derivatives: Photophysical Properties and Their Frontier Orbitals

    Directory of Open Access Journals (Sweden)

    María Judith Percino

    2016-03-01

    Full Text Available We report single crystal X-ray diffraction (hereafter, SCXRD analyses of derivatives featuring the electron-donor N-ethylcarbazole or the (4-diphenylaminophenyl moieties associated with a -CN group attached to a double bond. The compounds are (2Z-3-(4-(diphenylamino-phenyl-2-(pyridin-3-ylprop-2-enenitrile (I, (2Z-3-(4-(diphenylaminophenyl-2-(pyridin-4-yl-prop-2-enenitrile (II and (2Z-3-(9-ethyl-9H-carbazol-3-yl-2-(pyridin-2-ylenenitrile (III. SCXRD analyses reveal that I and III crystallize in the monoclinic space groups P2/c with Z’ = 2 and C2/c with Z’ = 1, respectively. Compound II crystallized in the orthorhombic space group Pbcn with Z’ = 1. The molecular packing analysis was conducted to examine the pyridine core effect, depending on the ortho, meta- and para-positions of the nitrogen atom, with respect to the optical properties and number of independent molecules (Z’. It is found that the double bond bearing a diphenylamino moiety introduced properties to exhibit a strong π-π-interaction in the solid state. The compounds were examined to evaluate the effects of solvent polarity, the role of the molecular structure, and the molecular interactions on their self-assembly behaviors. Compound I crystallized with a cell with two conformers, anti and syn, due to interaction with solvent. DFT calculations indicated the anti and syn structures of I are energetically stable (less than 1 eV. Also electrochemical and photophysical properties of the compounds were investigated, as well as the determination of optimization calculations in gas and different solvent (chloroform, cyclohexane, methanol, ethanol, tetrahydrofuran, dichloromethane and dimethyl sulfoxide in the Gaussian09 program. The effect of solvent by PCM method was also investigated. The frontier HOMO and LUMO energies and gap energies are reported.

  11. Solvent effect on molecular structure, IR spectra, thermodynamic properties and chemical stability of zoledronic acid: DFT study.

    Science.gov (United States)

    Liu, Qingzhu; Qiu, Ling; Wang, Yang; Lv, Gaochao; Liu, Guiqing; Wang, Shanshan; Lin, Jianguo

    2016-04-01

    Zoledronic acid (ZL) has been used widely for treating skeletal diseases because of its high potency in inhibiting bone resorption. A detailed understanding of its physicochemical characteristics may be of great significance in both medicinal chemistry and structural biology for the design of novel bisphosphonates with higher activity. In the present work, the monoclinic (IM) and triclinic (IT) polymorphs of ZL in the gas phase and the aqueous phase were studied by density functional theory (DFT) method at the B3LYP/6-311++G** level. The polarizable continuum model (PCM) was employed to study the solvent effect on structures and properties. The optimized IM and IT conformations in both phases are in reasonable agreement with the experimental structures with the overall mean absolute percent deviation (MAPD%) less than 3.1 %. The presence of intramolecular hydrogen bond within both conformations was identified in the solvent. The IR spectra were simulated and assigned in detail, which agreed well with the experimental data. The intramolecular hydrogen bonding interactions resulted in the shift of vibrational frequencies of hydroxyl to the low band by 12-22 cm(-1) and 24-26 cm(-1) for IM and IT conformations, respectively. Their thermodynamic properties were also calculated based on the harmonic vibrational analysis, including standard heat capacity (C(°)p,m), entropy (S(°)m), and enthalpy (H(°)m). The molecular stability, hydrogen bonding interaction and other electronic properties have been further analyzed by the natural bond orbital (NBO), atoms in molecules (AIM), molecular electrostatic potential (MEP) and frontier molecular orbital (FMO) analysis. PMID:26994018

  12. Molecular dynamics simulations of heat and mass transport properties of a simple binary mixture in micro/meso-pores

    International Nuclear Information System (INIS)

    Graphical abstract: Thermodiffusion factors relatively to the bulk value versus pore size for p∥∗=0.5 (full symbol) and p∥∗=1 (open symbol). The full circles correspond to the results for purely repulsive walls, the square to the moderately adsorbent walls and the down triangles to the highly adsorbent walls. Highlights: ► Molecular dynamics of heat and mass transport coefficients in micro/meso pores. ► Analysis of the influence of the pore width and fluid–solid interaction. ► Negligible effect for pore width larger than 10 molecular sizes. ► Thermodiffusion decreases noticeably for the thinnest pore. ► Trends on transport properties explained by changes in the average density. - Abstract: In this work, we have studied thermodiffusion of simple binary mixtures confined in a slit pore of nanometer width. To do so we have performed Non-Equilibrium Molecular Dynamics simulations of Lennard-Jones binary equimolar mixtures confined in structureless walls of three adsorbent natures, various widths (3–30 times the size of a molecule) and for two different thermodynamic states. The results showed that the width of the pore has a weak effect on the effective thermodiffusion factor, thermodiffusion coefficients and thermal conductivities for pore width larger than 10 times the size of the molecules. However, for narrower pore, all transport properties are noticeably affected and in particular thermodiffusion tends to decrease with the decrease of the pore width. These general trends on the transport properties in the smallest pores can be qualitatively explained by the impact of the confinement on the average density.

  13. The thickness-dependent dynamic magnetic property of Co2FeAl films grown by molecular beam epitaxy

    Science.gov (United States)

    Qiao, Shuang; Nie, Shuaihua; Zhao, Jianhua; Zhang, Xinhui

    2014-10-01

    Co2FeAl films with different thickness were prepared at different temperature by molecular beam epitaxy. Their dynamic magnetic property was studied by the time-resolved magneto-optical Kerr effect measurements. It is observed that the intrinsic damping factor of Co2FeAl for [100] orientation is not related to the film's thickness and magnetic anisotropy as well as temperature at high-field regime, but increases with structural disorder of Co2FeAl. The dominant contribution from the inhomogeneous magnetic anisotropy is revealed to be responsible for the observed extremely nonlinear and drastic field-dependent damping factors at low-field regime.

  14. Synthesis and Properties of Bis-Porphyrin Molecular Tweezers: Effects of Spacer Flexibility on Binding and Supramolecular Chirogenesis

    Directory of Open Access Journals (Sweden)

    Magnus Blom

    2015-12-01

    Full Text Available Ditopic binding of various dinitrogen compounds to three bisporphyrin molecular tweezers with spacers of varying conformational rigidity, incorporating the planar enediyne (1, the helical stiff stilbene (2, or the semi-rigid glycoluril motif fused to the porphyrins (3, are compared. Binding constants Ka = 104–106 M−1 reveal subtle differences between these tweezers, that are discussed in terms of porphyrin dislocation modes. Exciton coupled circular dichroism (ECCD of complexes with chiral dinitrogen guests provides experimental evidence for the conformational properties of the tweezers. The results are further supported and rationalized by conformational analysis.

  15. Effect of sliding speed and contact stress on tribological properties of ultra-high-molecular-weight polyethylene

    Science.gov (United States)

    Fusaro, R. L.

    1982-01-01

    A pin on disk apparatus was used to investigate the effect of sliding speed on the friction, wear, and transfer film characteristics of hemispherically tipped AISI 440C high temperature (HT) stainless steel riders sliding against ultrahigh molecular weight polyethylene (UHMWPE) disks. The surface morphology of the wear track was studied to determine possible wear mechanisms. Geometry effects were determined by comparing the results to those of others who used different specimen configurations. The results indicate that sliding speed, sliding distance, contact stress, and specimen geometry can all markedly influence the tribological properties of UHMWPE.

  16. The Effect of Alcohols on Red Blood Cell Mechanical Properties and Membrane Fluidity Depends on Their Molecular Size

    OpenAIRE

    Melda Sonmez; Huseyin Yavuz Ince; Ozlem Yalcin; Vladimir Ajdžanović; Ivan Spasojević; Meiselman, Herbert J.; Baskurt, Oguz K.

    2013-01-01

    The Effect of Alcohols on Red Blood Cell Mechanical Properties and Membrane Fluidity Depends on Their Molecular Size Melda Sonmez1, Huseyin Yavuz Ince1, Ozlem Yalcin1, Vladimir Ajdžanović2, Ivan Spasojević3, Herbert J. Meiselman4*, Oguz K. Baskurt1 1 Koc University, School of Medicine, Istanbul, Turkey, 2 University of Belgrade, Institute for Biological Research “Siniša Stanković”, Belgrade, Serbia, 3 University of Belgrade, Institute for Multidisciplinary Research, Belgrade...

  17. Faculty Adoption of Educational Technology

    Science.gov (United States)

    Moser, Franziska Zellweger

    2007-01-01

    Although faculty support has been identified as a critical factor in the success of educational-technology programs, many people involved in such efforts underestimate the complexities of integrating technology into teaching. In this article, the author proposes an adoption cycle to help tackle the complex issue of technology adoption for…

  18. Stories of Aboriginal Transracial Adoption

    Science.gov (United States)

    Nuttgens, Simon

    2013-01-01

    Despite the significant number of transracial Aboriginal adoptions that have taken place in Canada, little research is available that addresses the psychological and psychosocial ramifications for the children involved. The scant literature that does exist raises concerns about the psychological impact of this type of adoption. The present…

  19. Healthy Travel for International Adoptions

    Centers for Disease Control (CDC) Podcasts

    2007-10-22

    The number of international adoptions, many from developing countries, has doubled in the last 10 years. This podcast discusses ways adoptive families can protect their own health and the health of their new children.  Created: 10/22/2007 by National Center for the Prevention, Detection and Control of Infectious Diseases (NCPDCID).   Date Released: 10/24/2007.

  20. Characteristics of adopted juvenile delinquents.

    Science.gov (United States)

    Kim, W J; Zrull, J P; Davenport, C W; Weaver, M

    1992-05-01

    There have been many reports describing the uniqueness of adopted children and adolescents' delinquent behaviors in terms of both their delinquent characteristics and courts' treatment of them. A total of 43 adopted juveniles, 32 extrafamilial (1.0%) and 11 intrafamilial (0.3%) adoptions were initially identified out of 3,280 juvenile delinquents. The adopted subjects were then compared with the demographically matched and offense matched nonadopted subjects. The family variables, such as marital and employment status of parents, were significantly different. However, there were only a few discernible trends, and in general there were no significant differences between the adopted and nonadopted juveniles in terms of their offense characteristics and dispositions. PMID:1592787

  1. Molecular structure and charge transfer contributions to nonlinear optical property of 2-Methyl-4-nitroaniline: A DFT study

    Science.gov (United States)

    Jasmine, G. Femina; Amalanathan, M.; Roy, S. Dawn Dharma

    2016-05-01

    The Charge transfer contributions to the second-order nonlinear optical properties of 2-Methyl-4-nitroaniline have been performed by means of DFT computation. The vibrational contribution studies of 2-Methyl-4-nitroaniline have also been performed using FTIR, FT-Raman analysis. More support on the experimental findings were added from the quantum chemical studies performed with DFT (B3LYP) method using 6-311++G(d,p)basis sets. Natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction. The HOMO and LUMO analysis reveals the possibility of charge transfer within the molecule. The first order hyperpolarizability (α0) and related properties (β,α0 and Δα) of 2-Methyl-4-nitroaniline were calculated. In addition, molecular electrostatic potential (MEP), charge analysis also were investigated using theoretical calculations.

  2. The transport properties of the molecular-scale B{sub 2}C and BC{sub 3} electronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Li Guiqin, E-mail: ligqin@mail.tsinghua.edu.cn [Department of Physics, Tsinghua University, Beijing 100084 (China); Li Runqin [Inner Mongolia Radio and TV University, 010010 (China)

    2012-09-01

    The transport properties of the molecular-scale B{sub 2}C and BC{sub 3} electronic devices are investigated with an ab initio method combined with a nonequilibrium Green function technique. The effects of different BC graphenes and ribbon lengths on the transport properties of the devices are significant. The results show that the devices with different BC graphenes and sizes have unusual transmission coefficients, which leads to special current transport mechanisms for the devices. Notably, the current strength of the device with the shortest ribbon length is the largest in three B{sub 2}C devices, but the current strength of the device with the shortest ribbon length is the smallest for BC{sub 3} device.

  3. Transport properties of 2F F2 in a temperature gradient as studied by molecular dynamics simulations.

    Science.gov (United States)

    Xu, Jing; Kjelstrup, Signe; Bedeaux, Dick; Simon, Jean-Marc

    2007-02-28

    We calculate transport properties of a reacting mixture of F and F(2) from results of non-equilibrium molecular dynamics simulations. The reaction investigated is controlled by thermal diffusion and is close to local chemical equilibrium. The simulations show that a formulation of the transport problem in terms of classical non-equilibrium thermodynamics theory is sound. The chemical reaction has a large effect on the magnitude and temperature dependence of the thermal conductivity and the interdiffusion coefficient. The increase in the thermal conductivity in the presence of the chemical reaction, can be understood as a response to an imposed temperature gradient, which reduces the entropy production. The heat of transfer for the Soret stationary state was more than 100 kJ mol(-1), meaning that the Dufour and Soret effects are non-negligible in reacting mixtures. This sheds new light on the transport properties of reacting mixtures. PMID:17301887

  4. Mid-infrared to ultraviolet optical properties of InSb grown on GaAs by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    D' Costa, Vijay Richard, E-mail: elevrd@nus.edu.sg; Yeo, Yee-Chia, E-mail: eleyeoyc@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583 (Singapore); Tan, Kian Hua; Jia, Bo Wen; Yoon, Soon Fatt [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2015-06-14

    Spectroscopic ellipsometry was used to investigate the optical properties of an InSb film grown on a GaAs (100) substrate, and to compare the optical properties of InSb film with those of bulk InSb. The film was grown by molecular beam epitaxy under conditions intended to form 90° misfit dislocations at the InSb-GaAs interface. The complex dielectric function obtained in a wide spectroscopic range from 0.06–4.6 eV shows the critical point transitions E{sub 0}, E{sub 1}, E{sub 1} + Δ{sub 1}, E{sub 0}{sup ′}, and E{sub 2}. The amplitudes, energy transitions, broadenings, and phase angles have been determined using a derivative analysis. Comparing film and bulk critical point results reveal that the epitaxial film is nearly relaxed and has bulk-like optical characteristics.

  5. Thermal transport property of Ge34 and d-Ge investigated by molecular dynamics and the Slack's equation

    International Nuclear Information System (INIS)

    In this study, we evaluate the values of lattice thermal conductivity κL of type II Ge clathrate (Ge34) and diamond phase Ge crystal (d-Ge) with the equilibrium molecular dynamics (EMD) method and the Slack's equation. The key parameters of the Slack's equation are derived from the thermodynamic properties obtained from the lattice dynamics (LD) calculations. The empirical Tersoff's potential is used in both EMD and LD simulations. The thermal conductivities of d-Ge calculated by both methods are in accordance with the experimental values. The predictions of the Slack's equation are consistent with the EMD results above 250 K for both Ge34 and d-Ge. In a temperature range of 200–1000 K, the κL value of d-Ge is about several times larger than that of Ge34. (condensed matter: structure, thermal and mechanical properties)

  6. Influence of substrate quality on structural properties of AlGaN/GaN superlattices grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Short-period AlGaN/GaN superlattices were established as versatile test structures to investigate the structural properties of molecular beam epitaxy (MBE)-grown GaN and AlGaN layers and their dependence on the GaN substrate quality. X-ray diffractometry data of the investigated superlattices allow access to relevant structural parameters such as aluminum mole fraction and layer thicknesses. The occurrence of theoretically predicted intense high-order satellite peaks and pronounced interface fringes in the diffraction pattern reflects abrupt interfaces and perfect 2-dimensional growth resulting in smooth surfaces. The data unambiguously demonstrate that the structural quality of the MBE grown layers is limited by the structural properties of the GaN substrate

  7. Molecular Structure-Based Methods of Property Prediction in Application to Lipids: A Review and Refinement

    DEFF Research Database (Denmark)

    Cunico, Larissa; Hukkerikar, Amol; Ceriani, Roberta;

    2013-01-01

    dependent, have been developed. For mixtures, properties related to phase equilibria aremodeled with GE-based models (UNIQUAC, UNIFAC, NRTL, and combined UNIFAC-CI method). The col-lected phase equilibrium data for VLE and SLE have been tested for thermodynamic consistency togetherwith a performance...... purecomponent properties to develop simultaneously two parallel models, one based on group contribu-tion and another based on atom connectivity, for each property. The lipids present in the databaseare regarded as a separate class, for which special models for pure component properties, primary andtemperature...... evaluation of the GE-models. The paper also reviews the role of the databases andthe mathematical and thermodynamic consistency of the measured/estimated data and the predictivenature of the developed models....

  8. Statistical Properties of the Dense Hydrogen Plasma an ab initio Molecular Dynamics Investigation

    CERN Document Server

    Kohanoff, J J; Kohanoff, Jorge; Hansen, Jean-Pierre

    1996-01-01

    The metallic regime of the hydrogen plasma is studied by ab initio Molecular Dynamics simulations, for classical protons and fully degenerate electrons, in the strong coupling regime of the protons. The breakdown of linear screening observed for decreasing density gives rise to a surprisingly rich low-temperature phase diagram, showing in particular a dramatic drop of the melting temperature of the proton crystal. Extensive dynamical simulations reveal the remarkable persistence of a weakly damped high-frequency ion acoustic mode (plasmon-like), even under conditions of strong electron screening. This collective mode should disappear in the molecular phase, thus providing a probe for the metal-insulator transition in a region of parameters where experiment is difficult to achieve. Finite-size effects arising in the simulation of liquid metals are discussed. The status of the dense Hydrogen matter is extensively reviewed in the introduction.

  9. Molecular Dynamics Simulation of the Structure and Properties of Lithium Phosphate Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Liang, J-J; Cygan, R.T.; Alam, T.M.

    1999-07-09

    A new forcefield model was developed for the computer simulation of phosphate materials that have many important applications in the electronics and biomedical industries. The model provides a fundamental basis for the evaluation of phosphate glass structure and thermodynamics. Molecular dynamics simulations of a series of lithium phosphate glass compositions were performed using the forcefield model. A high concentration of three-membered rings (P{sub 3}O{sub 3}) occurs in the glass of intermediate composition (0.2 Li{sub 2}O {center_dot} 0.8P{sub 2}O{sub 5}) that corresponds to the minimum in the glass transition temperature curve for the compositional series. Molecular orbital calculations of various phosphate ring clusters indicate an increasing stabilization of the phosphate ring structure going from two- to four-membered rings.

  10. Effect of molecular structure on the thermal properties and water sorption of thin gelatin films

    International Nuclear Information System (INIS)

    The thin gelatin films, prepared by casting of gelatin solutions at different drying temperatures, had different molecular morphologies as monitored, using wide angle X-ray diffraction and differential scanning calorimetry techniques. It was revealed that gelatin films dried at lower temperatures showed markedly higher crystalline or helical structure with slightly higher Tg and lower ΔCp than those for the hot dried film with more coiled structure. These films exhibited different interactions with water, which were assessed, using dynamic vapour sorption experiments. The sorption capacity of these films increased with increasing the degree of molecular order. There was no difference between the diffusion coefficients obtained upon sorption and desorption steps for each gelatin samples. The diffusion coefficient did not show any significant dependence on water content

  11. MOLECULAR DESIGN OF FUNCTIONAL POLYMERS BASED ON UNIQUE PROPERTIES OF POLYMER CHAINS

    Institute of Scientific and Technical Information of China (English)

    Mikiharu Kamachi

    2000-01-01

    The inclusion complex formation of α-CD, β-CD, and γ-CD with various water-soluble polymers has been investigated, and the relationship between the chain cross-sectional areas of the polymers and the diameters of the cavities of cyclodextrins (molecular recognition) was found. Polyrotaxanes and tubular polymers were prepared on the basis of molecular recognition. Several kinds of polymers having tetraphenylporphyrin (TPP) and paramagnetic metallotetraphenylporphyrin (AgTPP, CuTPP, VOTPP or ZnTPP) have been prepared by radical polymerization of the corresponding monomers. Visible spectra of these polymers show hypochromism in the Soret bands of TPP moieties as compared with those of monomers. Polymer effects were observed in the magnetic behavior and oxygen adsorption of paramagnetic metallotetraphenylporphyrin moieties. Moreover, polymer effects on photophysical and photochemical behavior were found in the amphiphilic polymers covalently tethered with small amounts of zinc(Ⅱ)-tetraphenylporphyrin (ZnTPP).

  12. Classical molecular dynamics simulation on the dynamical properties of H2 on silicene layer

    Directory of Open Access Journals (Sweden)

    Casuyac Miqueas

    2016-01-01

    Full Text Available This study investigates the diffusion of hydrogen molecule physisorbed on the surface of silicene nanoribbon (SiNRusing the classical molecular dynamic (MD simulation in LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator. The interactions between silicon atoms are modeled using the modified Tersoff potential, the Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO potential for hydrogen – hydrogen interaction and the Lennard – Jones potential for the physisorbed H2 on SiNR. By varying the temperatures (60 K Δ 130 K, we observed that the Δxdisplacement of H2 on the surface SiNR shows a Brownian motion on a Lennard-Jones potential and a Gaussian probability distribution can be plotted describing the diffusion of H2. The calculated mean square displacement (MSD was approximately increasing in time and the activation energy barrier for diffusion has been found to be 43.23meV.

  13. ms2: A molecular simulation tool for thermodynamic properties, new version release

    CERN Document Server

    Glass, Colin W; Rutkai, Gábor; Deublein, Stephan; Köster, Andreas; Carrión, Gabriela Guevara; Wafai, Amer; Horsch, Martin; Bernreuther, Martin F; Windmann, Thorsten; Hasse, Hans; Vrabec, Jadran

    2015-01-01

    A new version release (2.0) of the molecular simulation tool ms2 [S. Deublein et al., Comput. Phys. Commun. 182 (2011) 2350] is presented. Version 2.0 of ms2 features a hybrid parallelization based on MPI and OpenMP for molecular dynamics simulation to achieve higher scalability. Furthermore, the formalism by Lustig [R. Lustig, Mol. Phys. 110 (2012) 3041] is implemented, allowing for a systematic sampling of Massieu potential derivatives in a single simulation run. Moreover, the Green-Kubo formalism is extended for the sampling of the electric conductivity and the residence time. To remove the restriction of the preceding version to electro-neutral molecules, Ewald summation is implemented to consider ionic long range interactions. Finally, the sampling of the radial distribution function is added.

  14. Dynamical properties of liquid Al near melting. An orbital-free molecular dynamics study

    OpenAIRE

    Gonzalez, David J; Gonzalez, Luis Enrique; Lopez, Jose Manuel; Stott, Malcolm J.

    2001-01-01

    The static and dynamic structure of liquid Al is studied using the orbital free ab-initio molecular dynamics method. Two thermodynamic states along the coexistence line are considered, namely T = 943 K and 1323 K for which X-ray and neutron scattering data are available. A new kinetic energy functional, which fulfills a number of physically relevant conditions is employed, along with a local first principles pseudopotential. In addition to a comparison with experiment, we also compare our ab-...

  15. Large-Scale Atomistic Simulations of Environmental Effects on the Formation and Properties of Molecular Junctions

    OpenAIRE

    French, William R.; Iacovella, Christopher R.; Cummings, Peter T.

    2012-01-01

    Using an updated simulation tool, we examine molecular junctions comprised of benzene-1,4-dithiolate bonded between gold nanotips, focusing on the importance of environmental factors and inter-electrode distance on the formation and structure of bridged molecules. We investigate the complex relationship between monolayer density and tip separation, finding that the formation of multi-molecule junctions is favored at low monolayer density, while single-molecule junctions are favored at high de...

  16. Molecular Dynamics Study on Mechanical Properties in the Structure of Self-Assembled Quantum Dot

    OpenAIRE

    Tatsuya Yamaguchi; Ken-ichi Saitoh

    2012-01-01

    Stress and strain in the structure of self-assembled quantum dots constructed in the Ge/Si(001) system is calculated by using molecular dynamics simulation. Pyramidal hut cluster composed of Ge crystal with {105} facets surfaces observed in the early growth stage are computationally modeled. We calculate atomic stress and strain in relaxed pyramidal structure. Atomic stress for triplet of atoms is approximately defined as an average value of pairwise (virial) quantity inside triplet, which is...

  17. Reaction Ensemble Molecular Dynamics: Direct Simulation of the Dynamic Equilibrium Properties of Chemically Reacting Mixtures

    Czech Academy of Sciences Publication Activity Database

    Brennan, J.K.; Lísal, Martin; Gubbins, K.E.; Rice, B.M.

    2004-01-01

    Roč. 70, č. 6 (2004), 0611031-0611034. ISSN 1063-651X R&D Projects: GA ČR GA203/03/1588 Grant ostatní: NSF(US) CTS-0211792 Institutional research plan: CEZ:AV0Z4072921 Keywords : reacting systems * simulation * molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.352, year: 2004

  18. Molecular dynamics studies of the bonding properties of amorphous silicon nitride coatings on crystalline silicon

    OpenAIRE

    Butler, K.T.; Lamers, M.P.W.E.; Weeber, A. W.; Harding, J. H.

    2011-01-01

    In this paper we present molecular dynamics simulations of silicon nitride, both in bulk and as an interface to crystalline silicon. We investigate, in particular, the bonding structure of the silicon nitride and analyze the simulations to search for de- fective geometries which have been identified as potential charge carrier traps when silicon nitride forms an interface with silicon semiconductors. The simulations reveal how the bonding patterns in silicon nitride are dependent upon the sto...

  19. Parallel variable selection of molecular dynamics clusters as a tool for calculation of spectroscopic properties

    Czech Academy of Sciences Publication Activity Database

    Kessler, Jiří; Dračínský, Martin; Bouř, Petr

    2013-01-01

    Roč. 34, č. 5 (2013), s. 366-371. ISSN 0192-8651 R&D Projects: GA ČR GAP208/11/0105; GA MŠk(CZ) LH11033 Grant ostatní: GA MŠk(CZ) LM2010005 Institutional support: RVO:61388963 Keywords : molecular dynamics * clusters * density functional theory * Raman optical activity * NMR Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.601, year: 2013

  20. Molecular characterisation of the thermostability and catalytic properties of enzymes from hyperthermophiles

    OpenAIRE

    Lebbink, J. H. G.

    1999-01-01

    Hyperthermophilic organisms are able to survive and reproduce optimally between 80°C and 113°C. Most of them belong to the domain of the Archaea, although several hyperthermophilic Bacteria have been described. One of the major questions regarding hyperthermophiles concerns the molecular mechanisms that determine the extreme stability of their macromolecules. In particular, enzymes on the one hand should be flexible in order to efficiently perform catalysis, while on the other hand they shoul...