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Sample records for crystal packing forces

  1. Determining the Molecular Packing Arrangements on Protein Crystal Faces by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Li, Huayu; Perozzo, Mary A.; Konnert, John H.; Nadarajan, Arunan; Pusey, Marc L.

    1998-01-01

    Periodic Bond Chain (PBC) analysis of the packing of tetragonal lysozyme crystals have revealed that there are two possible molecular packing arrangements for the crystal faces. The analysis also predicted that only one of these, involving the formation of helices about the 4(sub 3) axes, would prevail during crystal growth. In this study high resolution atomic force microscopy (AFM) was employed to verify these predictions for the (110) crystal face. A computer program was developed which constructs the expected AFM image for a given tip shape for each possible molecular packing arrangement. By comparing the actual AFM image with the predicted images the correct packing arrangement was determined. The prediction of an arrangement involving 4(sub 3) helices was confirmed in this manner,"while the alternate arrangement was not observed. The investigation also showed the protein molecules were packed slightly closer about the 4(sub 3) axes than in the crystallographic arrangement of the crystal interior. This study demonstrates a new approach for determining the molecular packing arrangements on protein crystal faces. It also shows the power of combining a theoretical PBC analysis with experimental high resolution AFM techniques in probing protein crystal growth processes at the molecular level.

  2. Crystallization force--a density functional theory concept for revealing intermolecular interactions and molecular packing in organic crystals.

    PubMed

    Li, Tonglei; Ayers, Paul W; Liu, Shubin; Swadley, Matthew J; Aubrey-Medendorp, Clare

    2009-01-01

    Organic molecules are prone to polymorphic formation in the solid state due to the rich diversity of functional groups that results in comparable intermolecular interactions, which can be greatly affected by the selection of solvent and other crystallization conditions. Intermolecular interactions are typically weak forces, such as van der Waals and stronger short-range ones including hydrogen bonding, that are believed to determine the packing of organic molecules during the crystal-growth process. A different packing of the same molecules leads to the formation of a new crystal structure. To disclose the underlying causes that drive the molecule to have various packing motifs in the solid state, an electronic concept or function within the framework of conceptual density functional theory has been developed, namely, crystallization force. The concept aims to describe the local change in electronic structure as a result of the self-assembly process of crystallization and may likely quantify the locality of intermolecular interactions that directs the molecular packing in a crystal. To assess the applicability of the concept, 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, so-called ROY, which is known to have the largest number of solved polymorphs, has been examined. Electronic calculations were conducted on the seven available crystal structures as well as on the single molecule. The electronic structures were analyzed and crystallization force values were obtained. The results indicate that the crystallization forces are able to reveal intermolecular interactions in the crystals, in particular, the close contacts that are formed between molecules. Strong correlations exist between the total crystallization force and lattice energy of a crystal structure, further suggesting the underlying connection between the crystallization force and molecular packing.

  3. Spontaneous Crystallization in Athermal Polymer Packings

    PubMed Central

    Karayiannis, Nikos Ch.; Foteinopoulou, Katerina; Laso, Manuel

    2013-01-01

    We review recent results from extensive simulations of the crystallization of athermal polymer packings. It is shown that above a certain packing density, and for sufficiently long simulations, all random assemblies of freely-jointed chains of tangent hard spheres of uniform size show a spontaneous transition into a crystalline phase. These polymer crystals adopt predominantly random hexagonal close packed morphologies. An analysis of the local environment around monomers based on the shape and size of the Voronoi polyhedra clearly shows that Voronoi cells become more spherical and more symmetric as the system transits to the ordered state. The change in the local environment leads to an increase in the monomer translational contribution to the entropy of the system, which acts as the driving force for the phase transition. A comparison of the crystallization of hard-sphere polymers and monomers highlights similarities and differences resulting from the constraints imposed by chain connectivity. PMID:23263666

  4. Toward the jamming threshold of sphere packings: Tunneled crystals

    NASA Astrophysics Data System (ADS)

    Torquato, S.; Stillinger, F. H.

    2007-11-01

    We have discovered a family of three-dimensional crystal sphere packings that are strictly jammed (i.e., mechanically stable) and yet possess an anomalously low density. This family constitutes an uncountably infinite number of crystal packings that are subpackings of the densest crystal packings and are characterized by a high concentration of self-avoiding "tunnels" (chains of vacancies) that permeate the structures. The fundamental geometric characteristics of these tunneled crystals command interest in their own right and are described here in some detail. These include the lattice vectors (that specify the packing configurations), coordination structure, Voronoi cells, and density fluctuations. The tunneled crystals are not only candidate structures for achieving the jamming threshold (lowest-density rigid packing), but may have substantially broader significance for condensed matter physics and materials science.

  5. Molecular structures and crystal packings of 2-styrylquinoxaline derivatives

    NASA Astrophysics Data System (ADS)

    Kuz'mina, L. G.; Sitin, A. G.; Gulakova, E. N.; Fedorova, O. A.; Lermontova, E. Kh.; Churakov, A. V.

    2012-01-01

    The crystal and molecular structures of 2-styrylquinoxaline derivatives with different substituents in the styryl fragment are determined. The degree of planarity of the molecules studied varies in a very wide range, from 1.7° to 33.5°. In the ethylene fragment, the double bond is essentially localized. The bicycle-pedal disordering of the ethylene fragment is found in the crystals of the methoxy and oxyacetyl derivatives of 2-styrylquinoxaline. None of the packings contains packing motifs favorable for the photocycloaddition (PCA) reaction with single crystal retention. The crystal packings of these compounds and that of 2-(4-methylstyryl)quinoxaline are characterized by a stacking motif of the head-to-head type, which eliminates the possibility of PCA taking place with single crystal retention but is suitable for this reaction in polycrystalline films. The crystal packing of 2-(3,4-dimethoxystyryl)quinoxaline does not contain elements with stacking interactions.

  6. How proteins pack into crystals: nuclei achieve translation symmetries by growing.

    PubMed

    Feng, Dan; Zeng, Zong-Hao

    2004-07-01

    How protein molecules pack into a crystal remains problematic. Packing units are direct materials for packing into crystals. The group generator method is introduced for automatically identifying the packing unit. By introducing deviations into the nucleation stage of crystallization, we proved that these deviations diminish in further packing. This process illustrates how translation symmetries are achieved by the growing of nuclei. Two effects, the size effect and the close up effect, are found to behave differently in this process.

  7. Dislocation dynamics in hexagonal close-packed crystals

    NASA Astrophysics Data System (ADS)

    Aubry, S.; Rhee, M.; Hommes, G.; Bulatov, V. V.; Arsenlis, A.

    2016-09-01

    Extensions of the dislocation dynamics methodology necessary to enable accurate simulations of crystal plasticity in hexagonal close-packed (HCP) metals are presented. They concern the introduction of dislocation motion in HCP crystals through linear and non-linear mobility laws, as well as the treatment of composite dislocation physics. Formation, stability and dissociation of < c + a > and other dislocations with large Burgers vectors defined as composite dislocations are examined and a new topological operation is proposed to enable their dissociation. The results of our simulations suggest that composite dislocations are omnipresent and may play important roles both in specific dislocation mechanisms and in bulk crystal plasticity in HCP materials. While fully microscopic, our bulk DD simulations provide wealth of data that can be used to develop and parameterize constitutive models of crystal plasticity at the mesoscale.

  8. Dislocation dynamics in hexagonal close-packed crystals

    DOE PAGESBeta

    Aubry, S.; Rhee, M.; Hommes, G.; Bulatov, V. V.; Arsenlis, A.

    2016-04-14

    Extensions of the dislocation dynamics methodology necessary to enable accurate simulations of crystal plasticity in hexagonal close-packed (HCP) metals are presented. They concern the introduction of dislocation motion in HCP crystals through linear and non-linear mobility laws, as well as the treatment of composite dislocation physics. Formation, stability and dissociation of and other dislocations with large Burgers vectors defined as composite dislocations are examined and a new topological operation is proposed to enable their dissociation. Furthermore, the results of our simulations suggest that composite dislocations are omnipresent and may play important roles both in specific dislocation mechanisms and in bulkmore » crystal plasticity in HCP materials. While fully microscopic, our bulk DD simulations provide wealth of data that can be used to develop and parameterize constitutive models of crystal plasticity at the mesoscale.« less

  9. Hydrogen Bonding: Between Strengthening the Crystal Packing and Improving Solubility of Three Haloperidol Derivatives.

    PubMed

    Saluja, Hardeep; Mehanna, Ahmed; Panicucci, Riccardo; Atef, Eman

    2016-01-01

    The purpose of this study is to confirm the impact of polar functional groups on inter and intra-molecular hydrogen bonding in haloperidol (HP) and droperidol (DP) and, hence, their effects on dissolution using a new approach. To confirm our theory, a new molecule: deshydroxy-haloperidol (DHP) was designed and its synthesis was requested from a contract laboratory. The molecule was then studied and compared to DP and HP. Unlike DHP, both the HP and DP molecules have hydrogen donor groups, therefore, DHP was used to confirm the relative effects of the hydrogen donor group on solubility and crystal packing. The solid dispersions of the three structurally related molecules: HP, DP, and DHP were prepared using PVPK30, and characterized using XRPD and IR. A comparative dissolution study was carried out in aqueous medium. The absence of a hydrogen bonding donor group in DHP resulted in an unexpected increase in its aqueous solubility and dissolution rate from solid dispersion, which is attributed to weaker crystal pack. The increased dissolution rate of HP and DP from solid dispersions is attributed to drug-polymer hydrogen bonding that interferes with the drug-drug intermolecular hydrogen bonding and provides thermodynamic stability of the dispersed drug molecules. The drug-drug intermolecular hydrogen bond is the driving force for precipitation and crystal packing. PMID:27258248

  10. Lateral Packing of Mineral Crystals in Bone Collagen

    SciTech Connect

    Burger, C.; Zhou, H; Wang, H; Sics, I; Hsiao, B; Chu, B; Graham, L; Glimcher, M

    2008-01-01

    Combined small-angle x-ray scattering and transmission electron microscopy studies of intramuscular fish bone (shad and herring) indicate that the lateral packing of nanoscale calcium-phosphate crystals in collagen fibrils can be represented by irregular stacks of platelet-shaped crystals, intercalated with organic layers of collagen molecules. The scattering intensity distribution in this system can be described by a modified Zernike-Prins model, taking preferred orientation effects into account. Using the model, the diffuse fan-shaped small-angle x-ray scattering intensity profile, dominating the equatorial region of the scattering pattern, could be quantitatively analyzed as a function of the degree of mineralization. The mineral platelets were found to be very thin (1.5nm{approx}2.0nm), having a narrow thickness distribution. The thickness of the organic layers between adjacent mineral platelets within a stack is more broadly distributed with the average value varying from 6nm to 10nm, depending on the extent of mineralization. The two-dimensional analytical scheme also leads to quantitative information about the preferred orientation of mineral stacks and the average height of crystals along the crystallographic c axis.

  11. Prediction of the crystal packing of di-tetrazine-tetroxide (DTTO) energetic material.

    PubMed

    Mendoza-Cortes, Jose L; An, Qi; Goddard, William A; Ye, Caichao; Zybin, Sergey

    2016-01-15

    Previous calculations suggested that di-tetrazine-tetroxide (DTTO), aka tetrazino-tetrazine-tetraoxide, might have a particularly large density (2.3 g/cm(3) ) and high energy release (8.8 kJ/kg), but it has not yet been synthesized successfully. We report here density functional theory (DFT) (M06, B3LYP, and PBE-ulg) on 20 possible isomers of DTTO. For the two most stable isomers, c1 and c2 we predict the best packings (i.e., polymorphs) among the 10 most common space groups for organic molecular crystal using the Universal force field and Dreiding force field with Monte Carlo sampling. This was followed by DFT calculations at the PBE-ulg level to optimize the crystal packing. We conclude that the c1 isomer has the P21 21 21 space group with a density of 1.96 g/cm(3) , while the c2 isomer has the Pbca space group with a density of 1.98 g/cm(3) . These densities are among the highest of current energetic materials, RDX (1.81 g/cm(3) ) and CL20 (2.01 g/cm(3) ). We observe that the stability of the polymorphs increases with the density while the planarity decreases. © 2015 Wiley Periodicals, Inc.

  12. Molecular interactions and crystal packing in nematogen: Computational thermodynamic approach

    NASA Astrophysics Data System (ADS)

    Lakshmi Praveen, P.; Ojha, Durga P.

    2011-10-01

    A computational thermodynamic approach of molecular interactions in a nematogen p-n-alkyl benzoic acid ( nBAC) molecule with an alkyl group butyl (4BAC) has been carried out with respect to translational and orientational motion. The atomic net charge and dipole moment at each atomic center were evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh-Schrödinger perturbation theory along with multicentered-multipole expansion method were employed to evaluate long-range intermolecular interactions, while a 6-exp potential function was assumed for short-range interactions. Various possible geometrical arrangements of molecular pairs with regard to different energy components were considered, and the energetically favorable configuration was found to understand the crystal packing picture. Furthermore, these interaction energy values are taken as input to calculate the configurational entropy at room temperature (300 K), nematic-isotropic transition temperature (386 K) and above transition temperature (450 K) during different modes of interactions. An attempt has been made to describe interactions in a nematogen at molecular level, through which one can simplify the system to make the model computationally feasible in understanding the delicate interplay between energy and entropy, that accounts for mesomorphism and there by to analyze the molecular structure of a nematogen.

  13. On plastic flow in notched hexagonal close packed single crystals

    NASA Astrophysics Data System (ADS)

    Selvarajou, Balaji; Kondori, Babak; Benzerga, A. Amine; Joshi, Shailendra P.

    2016-09-01

    The micromechanics of anisotropic plastic flow by combined slip and twinning is investigated computationally in single crystal notched specimens. Constitutive relations for hexagonal close packed materials are used which take into account elastic anisotropy, thirty potential deformation systems, various hardening mechanisms and rate-sensitivity. The specimens are loaded perpendicular to the c-axis but the presence of a notch generates three-dimensional triaxial stress states. The study is motivated by recent experiments on a polycrystalline magnesium alloy. To enable comparisons with these where appropriate, three sets of activation thresholds for the various deformation systems are used. For the conditions that most closely mimic the alloy material, attention is focused on the relative roles of pyramidal < c + a > and prismatic < a > slip, as well as on the emergence of {1012bar}[101bar1] extension twinning at sufficiently high triaxiality. In all cases, the spatial variations of stress triaxiality and plastic strain, inclusive of various system activities, are quantified along with their evolution upon straining. The implications of these findings in fundamental understanding of ductile failure of HCP alloys in general and Mg alloys in particular are discussed.

  14. Tailor-made force fields for crystal-structure prediction.

    PubMed

    Neumann, Marcus A

    2008-08-14

    A general procedure is presented to derive a complete set of force-field parameters for flexible molecules in the crystalline state on a case-by-case basis. The force-field parameters are fitted to the electrostatic potential as well as to accurate energies and forces generated by means of a hybrid method that combines solid-state density functional theory (DFT) calculations with an empirical van der Waals correction. All DFT calculations are carried out with the VASP program. The mathematical structure of the force field, the generation of reference data, the choice of the figure of merit, the optimization algorithm, and the parameter-refinement strategy are discussed in detail. The approach is applied to cyclohexane-1,4-dione, a small flexible ring. The tailor-made force field obtained for cyclohexane-1,4-dione is used to search for low-energy crystal packings in all 230 space groups with one molecule per asymmetric unit, and the most stable crystal structures are reoptimized in a second step with the hybrid method. The experimental crystal structure is found as the most stable predicted crystal structure both with the tailor-made force field and the hybrid method. The same methodology has also been applied successfully to the four compounds of the fourth CCDC blind test on crystal-structure prediction. For the five aforementioned compounds, the root-mean-square deviations between lattice energies calculated with the tailor-made force fields and the hybrid method range from 0.024 to 0.053 kcal/mol per atom around an average value of 0.034 kcal/mol per atom.

  15. Tailor-made force fields for crystal-structure prediction.

    PubMed

    Neumann, Marcus A

    2008-08-14

    A general procedure is presented to derive a complete set of force-field parameters for flexible molecules in the crystalline state on a case-by-case basis. The force-field parameters are fitted to the electrostatic potential as well as to accurate energies and forces generated by means of a hybrid method that combines solid-state density functional theory (DFT) calculations with an empirical van der Waals correction. All DFT calculations are carried out with the VASP program. The mathematical structure of the force field, the generation of reference data, the choice of the figure of merit, the optimization algorithm, and the parameter-refinement strategy are discussed in detail. The approach is applied to cyclohexane-1,4-dione, a small flexible ring. The tailor-made force field obtained for cyclohexane-1,4-dione is used to search for low-energy crystal packings in all 230 space groups with one molecule per asymmetric unit, and the most stable crystal structures are reoptimized in a second step with the hybrid method. The experimental crystal structure is found as the most stable predicted crystal structure both with the tailor-made force field and the hybrid method. The same methodology has also been applied successfully to the four compounds of the fourth CCDC blind test on crystal-structure prediction. For the five aforementioned compounds, the root-mean-square deviations between lattice energies calculated with the tailor-made force fields and the hybrid method range from 0.024 to 0.053 kcal/mol per atom around an average value of 0.034 kcal/mol per atom. PMID:18642947

  16. Molecular resolution imaging of macromolecular crystals by atomic force microscopy.

    PubMed Central

    Kuznetsov YuG; Malkin, A J; Land, T A; DeYoreo, J J; Barba, A P; Konnert, J; McPherson, A

    1997-01-01

    Atomic force microscopy (AFM) images at the molecular level have been obtained for a number of different protein and virus crystals. They can be utilized in some special cases to obtain information useful to crystal structure analyses by x-ray diffraction. In particular, questions of space group enantiomer, the packing of molecules within a unit cell, the number of molecules per asymmetric unit, and the dispositions of multiple molecules within the asymmetric unit may be resolved. In addition, because of the increasing sensitivity and resolution of the AFM technique, some molecular features of very large asymmetric units may be within reach. We describe here high-resolution studies, using AFM, to visualize individual molecules and viruses in their crystal lattices. These investigations included fungal lipase, lysozyme, thaumatin, canavalin, and satellite tobacco mosaic virus (STMV). Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 PMID:9129839

  17. Evolution of the force distributions in jammed packings of soft particles.

    PubMed

    Boberski, Jens; Shaebani, M Reza; Wolf, Dietrich E

    2013-12-01

    The evolution of the force distributions during the isotropic compression of two-dimensional packings of soft frictional particles is investigated numerically. Regardless of the applied deformation, the normal contact force distribution P(f(n)) can be fitted by the product of a power law, and a stretched exponential, while the tangential force distribution P(f(t)) is fitted well by a Gaussian. With increasing strain, the asymptotic behavior at large forces does not change, but both P(f(n)) and P(f(t)) exhibit a broadening, even though, when scaled with the average forces, their widths decrease. Furthermore, the distribution of friction mobilization P(η) is a decreasing function of η=|f(t)|/(μf(n)), except for an increased probability of fully mobilized contacts (η=1). The excess coordination number of the packings increases with the applied strain, indicating that the more a packing is compressed the more stable it becomes.

  18. From crystal to amorphous: A novel route to unjamming in soft disk packings.

    PubMed

    Potiguar, F Q

    2010-09-01

    Numerical studies on the unjamming packing fraction of bi- and polydisperse disk packings, which are generated through compression of a monodisperse crystal, are presented. In bidisperse systems, a fraction f(+) = 0.400 up to 0.800 of the total number of particles has their radii increased by [Formula: see text] R , while the rest has their radii decreased by the same amount. Polydisperse packings are prepared by changing all particle radii according to a uniform distribution in the range [-ΔR, ΔR] . The results indicate that the critical packing fraction is never larger than the value for the initial monodisperse crystal, Φ(o) = π/√12, and that the lowest value achieved is approximately the one for random close packing. These results are seen as a consequence of the interplay between the increase in small-small particle contacts and the local crystalline order provided by the large-large particle contacts.

  19. A comparison between bridges and force-chains in photoelastic disk packing.

    PubMed

    Zhang, Ling; Cai, Shuxiao; Hu, Zunpeng; Zhang, Jie

    2014-01-01

    In a dense granular material, force-chains form naturally as a backbone to support an external load. Due to the limitation of experimental techniques, the determination of the force-chain network in 3D packing is rather difficult, requiring a precise measurement of contact forces between particles. For 3D packing under gravity, it has long been proposed that bridges form as load-bearing structures. Identification of a bridge is relatively easy, requiring only the geometric information of particles. Although both concepts have existed for years, their relationship remains elusive. In this study, we aim towards resolving such a connection by comparing bridges and force-chains in packing of photoelastic disks. No direct correspondence between bridges and force-chains is observed. In addition, when a bridge grows longer, its probability of being a force-chain or part of the force-chain network decreases exponentially. Nonetheless, both are consistent in distinguishing certain properties of packing of strong hysteresis. To test the load-bearing assumption of bridges, stresses of particles in/out of bridges are analysed and compared and only minor differences are found.

  20. Random three-dimensional jammed packings of elastic shells acting as force sensors

    NASA Astrophysics Data System (ADS)

    Jose, Jissy; van Blaaderen, Alfons; Imhof, Arnout

    2016-06-01

    In a jammed solid of granular particles, the applied stress is in-homogeneously distributed within the packing. A full experimental characterization requires measurement of all the interparticle forces, but so far such measurements are limited to a few systems in two and even fewer in three dimensions. Particles with the topology of (elastic) shells are good local force sensors as relatively large deformations of the shells result from relatively small forces. We recently introduced such fluorescent shells as a model granular system in which force distributions can be determined in three dimensions using confocal microscopy and quantitative image analysis. An interesting aspect about these shells that differentiates them from other soft deformable particles is their buckling behavior at higher compression. This leads to deformations that do not conserve the inner volume of the particle. Here we use this system to accurately measure the contact forces in a three-dimensional packing of shells subjected to a static anisotropic compression and to shear. At small deformations forces are linear, however, for a buckled contact, the restoring force is related to the amount of deformation by a square root law, as follows from the theory of elasticity of shells. Near the unjamming-jamming transition (point J ), we found the probability distribution of the interparticle forces P (f ) to decay nearly exponentially at large forces, with little evidence of long-range force chains in the packings. As the packing density is increased, the tail of the distribution was found to crossover to a Gaussian, in line with other experimental and simulation studies. Under a small shear strain, up to 0.216, applied at an extremely low shear rate, we observed a shear-induced anisotropy in both the pair correlation function and contact force network; however, no appreciable change was seen in the number of contacts per particle.

  1. Random three-dimensional jammed packings of elastic shells acting as force sensors.

    PubMed

    Jose, Jissy; van Blaaderen, Alfons; Imhof, Arnout

    2016-06-01

    In a jammed solid of granular particles, the applied stress is in-homogeneously distributed within the packing. A full experimental characterization requires measurement of all the interparticle forces, but so far such measurements are limited to a few systems in two and even fewer in three dimensions. Particles with the topology of (elastic) shells are good local force sensors as relatively large deformations of the shells result from relatively small forces. We recently introduced such fluorescent shells as a model granular system in which force distributions can be determined in three dimensions using confocal microscopy and quantitative image analysis. An interesting aspect about these shells that differentiates them from other soft deformable particles is their buckling behavior at higher compression. This leads to deformations that do not conserve the inner volume of the particle. Here we use this system to accurately measure the contact forces in a three-dimensional packing of shells subjected to a static anisotropic compression and to shear. At small deformations forces are linear, however, for a buckled contact, the restoring force is related to the amount of deformation by a square root law, as follows from the theory of elasticity of shells. Near the unjamming-jamming transition (point J), we found the probability distribution of the interparticle forces P(f) to decay nearly exponentially at large forces, with little evidence of long-range force chains in the packings. As the packing density is increased, the tail of the distribution was found to crossover to a Gaussian, in line with other experimental and simulation studies. Under a small shear strain, up to 0.216, applied at an extremely low shear rate, we observed a shear-induced anisotropy in both the pair correlation function and contact force network; however, no appreciable change was seen in the number of contacts per particle. PMID:27415341

  2. Photoinduced shape changes of diarylethene single crystals: correlation between shape changes and molecular packing.

    PubMed

    Kuroki, Lumi; Takami, Shizuka; Yoza, Kenji; Morimoto, Masakazu; Irie, Masahiro

    2010-02-01

    Correlation between the photoinduced shape changes of diarylethene single crystals and their molecular packing in the crystals was studied. Crystals of 1,2-bis(5-ethyl-2-phenyl-4-thiazolyl)perfluorocyclopentene (3a) and 1,2-bis(2-isopropyl-5-phenyl-3-thienyl)perfluorocyclopentene (4a) showed similar photoinduced deformation from square to lozenge as that of 1,2-bis- (2-ethyl-5-phenyl-3-thienyl)perfluorocyclopentene (1a). Although these three diarylethenes have different electronic structures and exhibit different colours upon UV irradiation, the crystallographic structures and molecular packing of the crystals are very similar to each other. The result indicates that the deformation mode is determined by the packing mode of component molecules in the crystal. X-Ray crystallographic analysis of a micrometre-sized crystal 1a (20 x 15 x 8 microm) prepared by sublimation revealed that the small-size crystal, which shows photoinduced deformation, has the same crystal structure as that of the large bulk crystal. PMID:20126798

  3. Two-dimensional crystals of carboxysome shell proteins recapitulate the hexagonal packing of three-dimensional crystals

    PubMed Central

    Dryden, Kelly A; Crowley, Christopher S; Tanaka, Shiho; Yeates, Todd O; Yeager, Mark

    2009-01-01

    Bacterial microcompartments (BMCs) are large intracellular bodies that serve as simple organelles in many bacteria. They are proteinaceous structures composed of key enzymes encapsulated by a polyhedral protein shell. In previous studies, the organization of these large shells has been inferred from the conserved packing of the component shell proteins in two-dimensional (2D) layers within the context of three-dimensional (3D) crystals. Here, we show that well-ordered, 2D crystals of carboxysome shell proteins assemble spontaneously when His-tagged proteins bind to a monolayer of nickelated lipid molecules at an air–water interface. The molecular packing within the 2D crystals recapitulates the layered hexagonal sheets observed in 3D crystals. The results reinforce current models for the molecular design of BMC shells. PMID:19844993

  4. Modification of protein crystal packing by systematic mutations of surface residues: implications on biotemplating and crystal porosity.

    PubMed

    Wine, Yariv; Cohen-Hadar, Noa; Lamed, Raphael; Freeman, Amihay; Frolow, Felix

    2009-10-15

    Bioinspired nano-scale biotemplating for the development of novel composite materials has recently culminated in several demonstrations of nano-structured hybrid materials. Protein crystals, routinely prepared for the elucidation of protein 3D structures by X-ray crystallography, present an ordered and highly accurate 3D array of protein molecules. Inherent to the 3D arrangement of the protein "building blocks" in the crystal, a complementary 3D array of interconnected cavities--voids array, exhibiting highly ordered porosity is formed. The porous arrays of protein crystal may serve as a nano-structured, accurate biotemplate by a "filling" process. These cavities arrays are shaped by the mode of protein packing throughout the crystallization process. Here we propose and demonstrate feasibility of targeting site specific mutations to modify protein's surface to affect protein crystal packing, enabling the generation of a series of protein crystal "biotemplates" all originating from same parent protein. The selection of these modification sites was based on in silico analysis of protein-protein interface contact areas in the parent crystal. The model protein selected for this study was the N-terminal type II cohesin from the cellulosomal scaffold in ScaB subunit of Acetivibrio cellulolyticus and mutations were focused on lysine residues involved in protein packing as prime target. The impact of systematically mutating these lysine residues on protein packing and its resulting interconnected cavities array were found to be most significant when surface lysine residues were substituted to tryptophan residues. Our results demonstrate the feasibility of using pre-designed site directed mutations for the generation of a series of protein crystal biotemplates from a "parent" protein.

  5. Attractive particle interaction forces and packing density of fine glass powders

    PubMed Central

    Parteli, Eric J. R.; Schmidt, Jochen; Blümel, Christina; Wirth, Karl-Ernst; Peukert, Wolfgang; Pöschel, Thorsten

    2014-01-01

    We study the packing of fine glass powders of mean particle diameter in the range (4–52) μm both experimentally and by numerical DEM simulations. We obtain quantitative agreement between the experimental and numerical results, if both types of attractive forces of particle interaction, adhesion and non-bonded van der Waals forces are taken into account. Our results suggest that considering only viscoelastic and adhesive forces in DEM simulations may lead to incorrect numerical predictions of the behavior of fine powders. Based on the results from simulations and experiments, we propose a mathematical expression to estimate the packing fraction of fine polydisperse powders as a function of the average particle size. PMID:25178812

  6. Attractive particle interaction forces and packing density of fine glass powders.

    PubMed

    Parteli, Eric J R; Schmidt, Jochen; Blümel, Christina; Wirth, Karl-Ernst; Peukert, Wolfgang; Pöschel, Thorsten

    2014-09-02

    We study the packing of fine glass powders of mean particle diameter in the range (4-52) μm both experimentally and by numerical DEM simulations. We obtain quantitative agreement between the experimental and numerical results, if both types of attractive forces of particle interaction, adhesion and non-bonded van der Waals forces are taken into account. Our results suggest that considering only viscoelastic and adhesive forces in DEM simulations may lead to incorrect numerical predictions of the behavior of fine powders. Based on the results from simulations and experiments, we propose a mathematical expression to estimate the packing fraction of fine polydisperse powders as a function of the average particle size.

  7. Crystal packing of TCNQ anion pi-radicals governed by intermolecular covalent pi-pi bonding: DFT calculations and statistical analysis of crystal structures.

    PubMed

    Huang, Jingsong; Kingsbury, Stephanie; Kertesz, Miklos

    2008-05-21

    On the basis of a thorough Cambridge Structural Database survey, we present a statistical analysis of the packing of TCNQ anion pi-radicals in TCNQ charge transfer salts, which reveals three packing motifs between neighboring TCNQs: one with a zero longitudinal offset and an approximate 1 A transversal offset, another with an approximate 2 A longitudinal offset and zero transversal offset, and the third with a relatively long sigma-bond in the length of r = 1.6-1.7 A connecting two TCNQ fragments. Along with the statistical analysis of the crystal structures, we also present density functional theory calculations of the total energy, covalent pi-pi bonding interaction energy, and Coulombic repulsion energy for the [TCNQ](2)(2-)pi-dimers with various packing geometries. We find that the interactions between TCNQ anion pi-radicals include contributions from intermolecular covalent pi-pi bonding interaction and local dipole repulsions, in addition to Coulombic repulsion, van der Waals and the attractive electrostatic forces between counter-cations and TCNQ anions pointed out recently by other groups for TCNE anion radicals. We describe an approximate formula for intermolecular interaction energy, E(int) = E(coul) + E(bond) + E(vdW), for systems in vacuum, while in the solid state E(coul) is compensated by the attractive electrostatic forces between counter-cations and TCNQ anions. We conclude that the crystal packing of TCNQ molecules in their charge transfer salts is predominantly determined by the intermolecular covalent pi-pi bonding term, E(bond).

  8. Application of a force field algorithm for creating strongly correlated multiscale sphere packings

    NASA Astrophysics Data System (ADS)

    Zauner, Thomas

    2016-05-01

    This work presents a protocol driven force field algorithm, used to create multiscale correlated dense sphere packings. It was developed as part of a tool chain for the reconstruction of realistic multiscale porous rock samples. It overcomes limitations of Monte-Carlo or deposition based approaches, that are quite common in this field and were used previously. The new algorithm can create large, low porosity sphere packings with radius distributions covering two decades. Highly correlated structures that model pore clogging and sedimentation can be generated. To achieve this, an adequate force field and proper termination strategies are necessary. By changing the algorithm parameters in a controlled way during the simulation, a complex protocol driven process can be established. The implementation of the algorithm targets large parallel computer platforms to perform simulations with more than 10 million spheres. This article includes an application of the algorithm used to generate a highly polydisperse sphere packing with roughly 106 spheres and radii from 1 to 100 μm. The continuum description of this packing is discretized at resolutions from 0.25 to 1 μm and investigated using geometric and statistical characterizations and results from Lattice-Boltzmann flow simulations. These resolution dependent results affirm that reliable, predictive calculations for multiscale porous microstructures depend on the availability of large realistic continuum models. To obtain such models the algorithm presented herein can be used as a starting point.

  9. Synthesis, crystal packing, and ambipolar carrier transport property of twisted dibenzo[g,p]chrysenes.

    PubMed

    Ueda, Yasuyuki; Tsuji, Hayato; Tanaka, Hideyuki; Nakamura, Eiichi

    2014-06-01

    A versatile method for the synthesis of dibenzo[g,p]chrysene (DBC) derivatives based on regio- and stereoselective stannyllithiation to diarylacetylenes is described. This method affords a variety of DBCs possessing both electron-donating and electron-withdrawing functional groups. These twisted molecules take brickwork packing structures in single crystals. Thus, ambipolar carrier transport properties with mobility values of up to 10(-3)  cm(2)  V(-1)  s(-1) in the amorphous state were achieved. Functional groups on DBC frameworks are considered to increase carrier mobility through the enhancement of intermolecular interactions in the brickwork packing structures.

  10. Molecular structures and crystal packings of 2-styrylquinoline and its derivatives

    SciTech Connect

    Kuz'mina, L. G.; Sitin, A. G.; Gulakova, E. N.; Fedorova, O. A.; Lermontova, E. Kh.; Churakov, A. V.

    2011-07-15

    The crystal and molecular structures of five styrylheterocycles of the quinoline series are studied. All molecules are planar. The double bond in the ethylene fragment is essentially localized. In the molecule of 2-(4-methylstyryl)quinoline, the ethylene fragment is disordered by the bicycle-pedal pattern. In four of the five compounds, the crystal packings do not contain stacking dimers prearranged for the [2+2] photocycloaddition (PCA) reaction. In the crystal of 2-(3-nitrostyryl)quinoline, pairs of crystallographically independent molecules form stacking dimers. In a dimer, the ethylene fragments have a twist orientation, which is incompatible with the PCA reaction. An attempt to initiate a temperature-dependent process of bicyclepedal isomerization in the crystal and, as a consequence, the PCA reaction by means of simultaneous irradiation and heating of a single crystal is unsuccessful.

  11. Protein crystallization on liquid surfaces: Forced versus natural crystallization

    NASA Astrophysics Data System (ADS)

    Hirsa, A.

    2005-11-01

    Two-dimensional crystallization of proteins has recently been reported where streptavidin protein dissolved in the bulk liquid anchors to binding sites on a biotinylated lipid monolayer initially spread on the liquid surface. Thermodynamic aspects investigated include the effects of subphase buffer and pH, dilution of bulk protein and monolayer. Here, we investigate three possible avenues where flow can influence protein crystallization: i) change the initial state of monolayer, ii) advect dissolved protein to the interface, iii) apply direct hydrodynamic force on the crystals at the interface. The flow system consists of a stationary open cylinder driven by constant rotation of the floor, in the axisymmetric flow regime with inertia. Direct imaging of the interface illuminated by forward scattering of a laser was utilized to avoid labeling proteins for conventional fluorescence microscopy. These images provide greater detail than Brewster angle microscopy. Scientific motivation is to use flow to probe protein structure, and the application is to make designer protein thin-films, e.g. for biosensors.

  12. Protein crystals as scanned probes for recognition atomic force microscopy.

    PubMed

    Wickremasinghe, Nissanka S; Hafner, Jason H

    2005-12-01

    Lysozyme crystal growth has been localized at the tip of a conventional silicon nitride cantilever through seeded nucleation. After cross-linking with glutaraldehyde, lysozyme protein crystal tips image gold nanoparticles and grating standards with a resolution comparable to that of conventional tips. Force spectra between the lysozyme crystal tips and surfaces covered with antilysozyme reveal an adhesion force that drops significantly upon blocking with free lysozyme, thus confirming that lysozyme crystal tips can detect molecular recognition interactions.

  13. Effect of Crystal Packing on the Excitonic Properties of Rubrene Polymorphs

    NASA Astrophysics Data System (ADS)

    Wang, Xiaopeng; Garcia, Taylor; Monaco, Stephen; Schatschneider, Bohdan; Marom, Noa

    Singlet fission, the down-conversion of one singlet exciton into two triplet excitons, has been recently observed in molecular crystals of rubrene. The orthorhombic form of rubrene is the most stable in ambient conditions. However, rubrene has two additional known polymorphs, a triclinic form and a monoclinic form. To investigate the relative stability of the three polymorphs under different temperature and pressure conditions we use dispersion-inclusive density functional theory (DFT) with the pairwise Tkatchenko-Scheffler (TS) method and the many-body dispersion (MBD) method. Many-body perturbation theory is then employed to study the effect of crystal structure on the electronic and excitonic properties. Band structures are calculated within the GW approximation, where G is the one-particle Green's function and W is the screened Coulomb interaction, and optical properties are calculated by solving the Bethe-Salpeter equation (BSE). We find that crystal packing affects the band gaps, band dispersion, optical gaps, singlet-triplet gaps, and exciton localization in the three polymorphs of rubrene. Singlet fission efficiency may thus be improved by modulating the crystal packing.

  14. Preliminary investigations into mooring forces on a semisubmersible and a turret moored tanker in pack ice, current and waves

    SciTech Connect

    Murray, J.J.; Spencer, D.

    1996-12-01

    Physical model tests were carried out on a scale model of a semisubmersible and a monohull tanker in drifting pack ice. The tests covered a range of drift velocities, directions and ice concentrations. The models were tested in both a fully restrained and moored condition. Data from the experiments were used to develop a semi-empirical numerical model to predict maximum global loads on the mooring system. These results were compared with the maximum loads on the mooring system caused by hydrodynamic forces (waves and current) predicted from a linear numerical model for waves. Analysis results showed that the maximum mooring loads due to the pack ice on the semisubmersible were considerably higher than those caused by the hydrodynamic forces on the same vessel. Also, the maximum mooring loads due to pack ice on the tanker were close to the maximum mooring loads caused by the hydrodynamic forces. Maximum mooring loads related to pack ice forces were realized in ice concentrations of 10/10 coverage while for concentrations less than 6/10 coverage loads attributed to pack ice were negligible in comparison to the hydrodynamic forces. The paper also presents a number of recommendations, based on these findings, to improve the performance of both vessel types and to advance the general state-of-the-art for analysis procedures related to offshore vessel moored in pack ice.

  15. Crystal structure and packing analysis of nitrofurantoin N,N-dimethylformamide solvate

    NASA Astrophysics Data System (ADS)

    Cvetkovski, A.; Ferretti, V.

    2016-07-01

    The N, N'-dimethylformamide solvated crystal of the drug nitrofurantoin has been prepared and analysed by single-crystal X-ray diffraction. The two co-crystallized molecules, in the 1 : 1 stoichiometric ratio, are linked by a medium/strong N-H···O hydrogen bond (N···O is 2.759 (3) Å) and a weaker C-H···O interaction to form isolated supramolecular adducts, that in turn are packed into the lattice framework mainly through C-H···O hydrogen bonds. Two-dimensional fingerprint plots of Hirshfeld surfaces are used to visualize, analyze and compare intermolecular interactions found in the title compound and in similar structures.

  16. Close-packed polymer crystals from two-monomer-connected precursors

    NASA Astrophysics Data System (ADS)

    Lee, Hong-Joon; Jo, Yong-Ryun; Kumar, Santosh; Yoo, Seung Jo; Kim, Jin-Gyu; Kim, Youn-Joong; Kim, Bong-Joong; Lee, Jae-Suk

    2016-09-01

    The design of crystalline polymers is intellectually stimulating and synthetically challenging, especially when the polymerization of any monomer occurs in a linear dimension. Such linear growth often leads to entropically driven chain entanglements and thus is detrimental to attempts to realize the full potential of conjugated molecular structures. Here we report the polymerization of two-monomer-connected precursors (TMCPs) in which two pyrrole units are linked through a connector, yielding highly crystalline polymers. The simultaneous growth of the TMCP results in a close-packed crystal in polypyrrole (PPy) at the molecular scale with either a hexagonal close-packed or face-centred cubic structure, as confirmed by high-voltage electron microscopy, and the structure that formed could be controlled by simply changing the connector. The electrical conductivity of the TMCP-based PPy is almost 35 times that of single-monomer-based PPy, demonstrating its promise for application in diverse fields.

  17. Close-packed polymer crystals from two-monomer-connected precursors

    PubMed Central

    Lee, Hong-Joon; Jo, Yong-Ryun; Kumar, Santosh; Yoo, Seung Jo; Kim, Jin-Gyu; Kim, Youn-Joong; Kim, Bong-Joong; Lee, Jae-Suk

    2016-01-01

    The design of crystalline polymers is intellectually stimulating and synthetically challenging, especially when the polymerization of any monomer occurs in a linear dimension. Such linear growth often leads to entropically driven chain entanglements and thus is detrimental to attempts to realize the full potential of conjugated molecular structures. Here we report the polymerization of two-monomer-connected precursors (TMCPs) in which two pyrrole units are linked through a connector, yielding highly crystalline polymers. The simultaneous growth of the TMCP results in a close-packed crystal in polypyrrole (PPy) at the molecular scale with either a hexagonal close-packed or face-centred cubic structure, as confirmed by high-voltage electron microscopy, and the structure that formed could be controlled by simply changing the connector. The electrical conductivity of the TMCP-based PPy is almost 35 times that of single-monomer-based PPy, demonstrating its promise for application in diverse fields. PMID:27640812

  18. Close-packed polymer crystals from two-monomer-connected precursors.

    PubMed

    Lee, Hong-Joon; Jo, Yong-Ryun; Kumar, Santosh; Yoo, Seung Jo; Kim, Jin-Gyu; Kim, Youn-Joong; Kim, Bong-Joong; Lee, Jae-Suk

    2016-01-01

    The design of crystalline polymers is intellectually stimulating and synthetically challenging, especially when the polymerization of any monomer occurs in a linear dimension. Such linear growth often leads to entropically driven chain entanglements and thus is detrimental to attempts to realize the full potential of conjugated molecular structures. Here we report the polymerization of two-monomer-connected precursors (TMCPs) in which two pyrrole units are linked through a connector, yielding highly crystalline polymers. The simultaneous growth of the TMCP results in a close-packed crystal in polypyrrole (PPy) at the molecular scale with either a hexagonal close-packed or face-centred cubic structure, as confirmed by high-voltage electron microscopy, and the structure that formed could be controlled by simply changing the connector. The electrical conductivity of the TMCP-based PPy is almost 35 times that of single-monomer-based PPy, demonstrating its promise for application in diverse fields. PMID:27640812

  19. Hydrogen bonds in the crystal packings of mesalazine and mesalazine hydrochloride

    NASA Astrophysics Data System (ADS)

    Banić-Tomišić, Z.; Kojić-Prodić, B.; Širola, I.

    1997-10-01

    The crystal structures of pharmaceutical product mesalazine (marketed also under different proprietary names as Salofalk, Asacol, Asacolitin, and Claversal) and its hydrochloride are reported. In the crystal mesalazine is in zwitterion form as 5-ammoniosalicylate ( 1) whereas mesalazine hydrochloride crystallizes in an ionized form as 5-ammoniosalicylium chloride ( 2). Compound 1 (C 7H 7O 3N) crystallizes in the monoclinic space group {P2 1}/{n} with a = 3.769(1) Å, b = 7.353(2) Å, c = 23.475(5) Å, β = 94.38(2)°, V = 648.7(8) Å3, Z = 4, Dc = 1.568 g cm -3 and μ( MoKα) = 1.2 cm -1. Compound 2 (C 7H 8O 3NCl) crystallizes in the triclinic space group P 1¯ with a = 4.4839(2) Å, b = 5.7936(2) Å, c = 15.6819(5) Å, α = 81.329(3)°, β = 88.026(3)°, γ = 79.317(4)°, V = 395.74(3) Å3, Z = 2, Dc = 1.591 g cm -3 and μ(CuK α) = 40.8 cm -1. The crystal structures were solved by direct methods and refined to R = 0.041 for 1 and 0.028 for 2, using 607 and 1374 observed reflections, respectively. The configuration of both molecules, with the ortho hydroxyl to a carboxyl group, favours the intramolecular hydrogen bonds. Very complex systems of intermolecular hydrogen bonds were observed in both crystal packings. They are discussed in terms of graph-set notation. The mesalazine crystal structure is characterized by two-dimensional network of hydrogen bonds in the ab plane. The crystal structure pattern of mesalazine hydrochloride is a three-dimensional network significantly supported by N +H⋯Cl - interactions.

  20. Crystallization and Crystal-Packing Studies of Chlorella Virus Deoxyuridine Triphosphatase

    SciTech Connect

    Homma, K.; Moriyama, H

    2009-01-01

    The 141-amino-acid deoxyuridine triphosphatase (dUTPase) from the algal Chlorella virus IL-3A and its Glu81Ser/Thr84Arg-mutant derivative Mu-22 were crystallized using the hanging-drop vapor-diffusion method at 298 K with polyethylene glycol as the precipitant. An apo IL-3A dUTPase with an amino-terminal T7 epitope tag and a carboxy-terminal histidine tag yielded cubic P2{sub 1}3 crystals with unit-cell parameter a = 106.65 {angstrom}. In the presence of dUDP, the enzyme produced thin stacked orthorhombic P222 crystals with unit-cell parameters a = 81.0, b = 96.2, c = 132.8 {angstrom}. T7-histidine-tagged Mu-22 dUTPase formed thin stacked rectangular crystals. Amino-terminal histidine-tagged dUTPases did not crystallize but formed aggregates. Glycyl-seryl-tagged dUTPases yielded cubic P2{sub 1}3 IL-3A crystals with unit-cell parameter a = 105.68 {angstrom} and hexagonal P6{sub 3} Mu-22 crystals with unit-cell parameters a = 132.07, c = 53.45 {angstrom}, {gamma} = 120{sup o}. Owing to the Thr84Arg mutation, Mu-22 dUTPase had different monomer-to-monomer interactions to those of IL-3A dUTPase.

  1. Manipulation of an existing crystal form unexpectedly results in interwoven packing networks with pseudo-translational symmetry

    PubMed Central

    Reimer, Janice M.; Aloise, Martin N.; Powell, Harold R.; Schmeing, T. Martin

    2016-01-01

    Nonribosomal peptide synthetases (NRPSs) are multimodular enzymes that synthesize a myriad of diverse molecules. Tailoring domains have been co-opted into NRPSs to introduce further variety into nonribosomal peptide products. Linear gramicidin synthetase contains a unique formylation-tailoring domain in its initiation module (F-A-PCP). The structure of the F-A di-domain has previously been determined in a crystal form which had large solvent channels and no density for the minor Asub subdomain. An attempt was made to take advantage of this packing by removing the Asub subdomain from the construct (F-AΔsub) in order to produce a crystal that could accommodate the PCP domain. In the resulting crystal the original packing network was still present, but a second network with the same packing and almost no contact with the original network took the place of the solvent channels and changed the space group of the crystal. PMID:27710934

  2. Absolute configuration and crystal packing for three chiral drugs prone to spontaneous resolution: Guaifenesin, methocarbamol and mephenesin

    NASA Astrophysics Data System (ADS)

    Bredikhin, Alexander A.; Gubaidullin, Aidar T.; Bredikhina, Zemfira A.; Krivolapov, Dmitry B.; Pashagin, Alexander V.; Litvinov, Igor A.

    2009-02-01

    Popular chiral drugs, guaifenesin, methocarbamol, and mephenesin were investigated by single-crystal X-ray analysis both for enantiopure and racemic samples. The absolute configurations for all substances were established through Flack parameter method. The conglomerate-forming nature for the compounds was confirmed by equivalence of crystal characteristics of enantiopure and racemic samples. The molecular structures and crystal packing details were evaluated and compared with one another for all three investigated substances.

  3. Determining the Molecular Growth Mechanisms of Protein Crystal faces by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Li, Huayu; Nadarajah, Arunan; Pusey, Marc L.

    1998-01-01

    A high resolution atomic force microscopy (AFM) study had shown that the molecular packing on the tetragonal lysozyme (110) face corresponded to only one of two possible packing arrangements, suggesting that growth layers on this face were of bimolecular height (Li et al., 1998). Theoretical analyses of the packing had also indicated that growth of this face should proceed by the addition of growth units of at least tetramer size corresponding to the 43 helices in the crystal. In this study an AFM linescan technique was devised to measure the dimensions of individual growth units on protein crystal faces. The growth process of tetragonal lysozyme crystals was slowed down by employing very low supersaturations. As a result images of individual growth events on the (110) face were observed, shown by jump discontinuities in the growth step in the linescan images. The growth unit dimension in the scanned direction was obtained by suitably averaging these images. A large number of scans in two directions on the (110) face were performed and the distribution of lysozyme aggregate sizes were obtained. A variety of growth units, all of which were 43 helical lysozyme aggregates, were shown to participate in the growth process with a 43 tetramer being the minimum observed size. This technique represents a new application for AFM allowing time resolved studies of molecular process to be carried out.

  4. Determining the Molecular Growth Mechanisms of Protein Crystal Faces by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Nadarajah, Arunan; Li, Huayu; Pusey, Marc L.

    1999-01-01

    A high resolution atomic force microscopy (AFM) study had shown that the molecular packing on the tetragonal lysozyme (110) face corresponded to only one of two possible packing arrangements, suggesting that growth layers on this face were of bimolecular height. Theoretical analyses of the packing also indicated that growth of this face should proceed by the addition of growth units of at least tetramer size corresponding to the 43 helices in the crystal. In this study an AFM linescan technique was devised to measure the dimensions of individual growth units on protein crystal faces as they were being incorporated into the lattice. Images of individual growth events on the (110) face of tetragonal lysozyme crystals were observed, shown by jump discontinuities in the growth step in the linescan images as shown in the figure. The growth unit dimension in the scanned direction was obtained from these images. A large number of scans in two directions on the (110) face were performed and the distribution of lysozyme growth unit sizes were obtained. A variety of unit sizes corresponding to 43 helices, were shown to participate in the growth process, with the 43 tetramer being the minimum observed size. This technique represents a new application for AFM allowing time resolved studies of molecular process to be carried out.

  5. A method for fast safety screening of explosives in terms of crystal packing and molecular stability.

    PubMed

    Hu, Xiaohua; Chen, Nana; Li, Weichen

    2016-07-01

    Safety prediction is crucial to the molecular design or the material design of explosives, and the predictions based on any single factor alone will cause much inaccuracy, leading to a desire for a method on multi-bases. The presented proposes an improved method for fast screening explosive safety by combining a crystal packing factor and a molecular one, that is, steric hindrance against shear slide in crystal and molecular stability, denoted by intermolecular friction symbol (IFS) and bond dissociation energy (BDE) of trigger linkage respectively. Employing this BDE-IFS combined method, we understand the impact sensitivities of 24 existing explosives, and predict those of two energetic-energetic cocrystals of the observed CL-20/BTF and the supposed HMX/TATB. As a result, a better understanding is implemented by the combined method relative to molecular stability alone, verifying its improvement of more accurate predictions and the feasibility of IFS to graphically reflect molecular stacking in crystals. Also, this work verifies that the explosive safety is strongly related with its crystal stacking, which determines steric hindrance and influences shear slide. PMID:27365051

  6. A method for fast safety screening of explosives in terms of crystal packing and molecular stability.

    PubMed

    Hu, Xiaohua; Chen, Nana; Li, Weichen

    2016-07-01

    Safety prediction is crucial to the molecular design or the material design of explosives, and the predictions based on any single factor alone will cause much inaccuracy, leading to a desire for a method on multi-bases. The presented proposes an improved method for fast screening explosive safety by combining a crystal packing factor and a molecular one, that is, steric hindrance against shear slide in crystal and molecular stability, denoted by intermolecular friction symbol (IFS) and bond dissociation energy (BDE) of trigger linkage respectively. Employing this BDE-IFS combined method, we understand the impact sensitivities of 24 existing explosives, and predict those of two energetic-energetic cocrystals of the observed CL-20/BTF and the supposed HMX/TATB. As a result, a better understanding is implemented by the combined method relative to molecular stability alone, verifying its improvement of more accurate predictions and the feasibility of IFS to graphically reflect molecular stacking in crystals. Also, this work verifies that the explosive safety is strongly related with its crystal stacking, which determines steric hindrance and influences shear slide.

  7. Directed Self-Assembly of sub-10 nm Particles: Role of Driving Forces and Template Geometry in Packing and Ordering.

    PubMed

    Mehraeen, Shafigh; Asbahi, Mohamed; Fuke, Wang; Yang, Joel K W; Cao, Jianshu; Tan, Mei Chee

    2015-08-11

    By comparing the magnitude of forces, a directed self-assembly mechanism has been suggested previously in which immersion capillary is the only driving force responsible for packing and ordering of nanoparticles, which occur only after the meniscus recedes. However, this mechanism is insufficient to explain vacancies formed by directed self-assembly at low particle concentrations. Utilizing experiments, and Monte Carlo and Brownian dynamics simulations, we developed a theoretical model based on a new proposed mechanism. In our proposed mechanism, the competing driving forces controlling the packing and ordering of sub-10 nm particles are (1) the repulsive component of the pair potential and (2) the attractive capillary forces, both of which apply at the contact line. The repulsive force arises from the high particle concentration, and the attractive force is caused by the surface tension at the contact line. Our theoretical model also indicates that the major part of packing and ordering of nanoparticles occurs before the meniscus recedes. Furthermore, utilizing our model, we are able to predict the various self-assembly configurations of particles as their size increases. These results lay out the interplay between driving forces during directed self-assembly, motivating a better template design now that we know the importance and the dominating driving forces in each regime of particle size.

  8. Two-phase modelling of equiaxed crystal sedimentation and thermomechanic stress development in the sedimented packed bed

    NASA Astrophysics Data System (ADS)

    Ludwig, A.; Vakhrushev, A.; Holzmann, T.; Wu, M.; Kharicha, A.

    2015-06-01

    During many industrial solidification processes equiaxed crystals form, grow and move. When those crystals are small they are carried by the melt, whereas when getting larger they sediment. As long as the volume fraction of crystals is below the packing limit, they are able to move relatively free. Crystals being backed in a so called packed bed form a semi-solid slurry, which may behave like a visco-plastic material. In addition, cooling-induced density increase of both, liquid and solid phases might lead to shrinkage of the whole casting domain. So deformation happens and gaps between casting and mold occur. In the present work, a two-phase Eulerian-Eulerian volume averaging model for describing the motion of equiaxed crystals in the melt is combined with a similar two-phase model for describing the dynamic of the packed bed. As constitutive equation for the solid skeleton in the packed bed Norton-Hoff law is applied. Shrinkage induced by density changes in the liquid or the solid phase is explicitly taken into account and handled by remeshing the calculation domain accordantly.

  9. Nanostructured colloidal crystals from forced hydrolysis methods.

    PubMed

    Otal, Eugenio H; Granada, Mara; Troiani, Horacio E; Cánepa, Horacio; Walsöe de Reca, Noemí E

    2009-08-18

    In this work, an original route for ZnO nanostructured spherical colloids and their assembly into colloidal crystals are presented. The temporal evolution of crystal size and shape was followed by X-ray diffraction and the colloids size distribution by scanning electron microscopy. These spherical colloids showed a change in their size dispersion with aging time. Early stage suspensions, with a narrow size distribution, were settled to the bottom and dried with a slow evaporation rate to obtain colloidal crystals. This original route provides a new material for future applications in opalline photonic crystals, with a dielectric constant higher than that of classical materials (silica and latex). Moreover, this route means an improvement of previously reported data from the literature since it involves a one-pot strategy and room-temperature colloid assembly.

  10. Colloid-probe AFM studies of the interaction forces of proteins adsorbed on colloidal crystals.

    PubMed

    Singh, Gurvinder; Bremmell, Kristen E; Griesser, Hans J; Kingshott, Peter

    2015-04-28

    In recent years, colloid-probe AFM has been used to measure the direct interaction forces between colloidal particles of different size or surface functionality in aqueous media, as one can study different forces in symmerical systems (i.e., sphere-sphere geometry). The present study investigates the interaction between protein coatings on colloid probes and hydrophilic surfaces decorated with hexagonally close packed single particle layers that are either uncoated or coated with proteins. Controlled solvent evaporation from aqueous suspensions of colloidal particles (coated with or without lysozyme and albumin) produces single layers of close-packed colloidal crystals over large areas on a solid support. The measurements have been carried out in an aqueous medium at different salt concentrations and pH values. The results show changes in the interaction forces as the surface charge of the unmodified or modified particles, and ionic strength or pH of the solution is altered. At high ionic strength or pH, electrostatic interactions are screened, and a strong repulsive force at short separation below 5 nm dominates, suggesting structural changes in the absorbed protein layer on the particles. We also study the force of adhesion, which decreases with an increment in the salt concentration, and the interaction between two different proteins indicating a repulsive interaction on approach and adhesion on retraction. PMID:25758979

  11. General Schema for [001] Tilt Grain Boundaries in Dense Packing Cubic Crystals

    SciTech Connect

    Tong, Wen; Yang, Hao; Moeck, Peter; Nandasiri, Manjula I.; Browning, Nigel D.

    2013-03-16

    Atomic resolution Z-contrast images from a series of CeO2 [001] tilt grain boundaries at coincident site lattice (CSL) or near-CSL misorientations can all be explained within a structural unit model. These structural units (which cover all boundaries from 0-90 degrees) show striking similarities to comparable CSL boundaries observed in cubic crystal structures that are also derived from dense packing (fcc metal, rocksalt, perovskite etc). A general model for the structure of grain boundaries in such similarly structured materials systems has been developed that is based on the crystallography of the parent structures. Changes away from these predicted grain boundary symmetries can be interpreted as showing the frustration of symmetry caused by the incorporation of point defects (vacancies and impurities). This general model for grain boundary structures can, in principle, provide a means to infer the structure-property relationships in broad classes of materials.

  12. Charge Stabilized Crystalline Colloidal Arrays As Templates For Fabrication of Non-Close-Packed Inverted Photonic Crystals

    PubMed Central

    Bohn, Justin J.; Ben-Moshe, Matti; Tikhonov, Alexander; Qu, Dan; Lamont, Daniel N.

    2010-01-01

    We developed a straightforward method to form non close-packed highly ordered fcc direct and inverse opal silica photonic crystals. We utilize an electrostatically self assembled crystalline colloidal array (CCA) template formed by monodisperse, highly charged polystyrene particles. We then polymerize a hydrogel around the CCA (PCCA) and condense the silica to form a highly ordered silica impregnated (siPCCA) photonic crystal. Heating at 450 °C removes the organic polymer leaving a silica inverse opal structure. By altering the colloidal particle concentration we independently control the particle spacing and the wall thickness of the inverse opal photonic crystals. This allows us to control the optical dielectric constant modulation in order to optimize the diffraction; the dielectric constant modulation is controlled independently of the photonic crystal periodicity. These fcc photonic crystals are better ordered than typical close-packed photonic crystals because their self assembly utilizes soft electrostatic repulsive potentials. We show that colloidal particle size and charge polydispersity has modest impact on ordering, in contrast to that for close-packed crystals. PMID:20163800

  13. Dancing Crystals: A Dramatic Illustration of Intermolecular Forces

    ERIC Educational Resources Information Center

    Mundell, Donald W.

    2007-01-01

    Crystals of naphthalene form on the surface of an acetone solution and dance about in an animated fashion illustrating surface tension, crystallization, and intermolecular forces. Additional experiments reveal the properties of the solution. Flows within the solutions can be visualized by various means. Previous demonstrations of surface motion…

  14. Probing biomechanical properties with a centrifugal force quartz crystal microbalance

    NASA Astrophysics Data System (ADS)

    Webster, Aaron; Vollmer, Frank; Sato, Yuki

    2014-10-01

    Application of force on biomolecules has been instrumental in understanding biofunctional behaviour from single molecules to complex collections of cells. Current approaches, for example, those based on atomic force microscopy or magnetic or optical tweezers, are powerful but limited in their applicability as integrated biosensors. Here we describe a new force-based biosensing technique based on the quartz crystal microbalance. By applying centrifugal forces to a sample, we show it is possible to repeatedly and non-destructively interrogate its mechanical properties in situ and in real time. We employ this platform for the studies of micron-sized particles, viscoelastic monolayers of DNA and particles tethered to the quartz crystal microbalance surface by DNA. Our results indicate that, for certain types of samples on quartz crystal balances, application of centrifugal force both enhances sensitivity and reveals additional mechanical and viscoelastic properties.

  15. Modulating two-dimensional non-close-packed colloidal crystal arrays by deformable soft lithography.

    PubMed

    Li, Xiao; Wang, Tieqiang; Zhang, Junhu; Yan, Xin; Zhang, Xuemin; Zhu, Difu; Li, Wei; Zhang, Xun; Yang, Bai

    2010-02-16

    We report a simple method to fabricate two-dimensional (2D) periodic non-close-packed (ncp) arrays of colloidal microspheres with controllable lattice spacing, lattice structure, and pattern arrangement. This method combines soft lithography technique with controlled deformation of polydimethylsiloxane (PDMS) elastomer to convert 2D hexagonal close-packed (hcp) silica microsphere arrays into ncp ones. Self-assembled 2D hcp microsphere arrays were transferred onto the surface of PDMS stamps using the lift-up technique, and then their lattice spacing and lattice structure could be adjusted by solvent swelling or mechanical stretching of the PDMS stamps. Followed by a modified microcontact printing (microcp) technique, the as-prepared 2D ncp microsphere arrays were transferred onto a flat substrate coated with a thin film of poly(vinyl alcohol) (PVA). After removing the PVA film by calcination, the ncp arrays that fell on the substrate without being disturbed could be lifted up, deformed, and transferred again by another PDMS stamp; therefore, the lattice feature could be changed step by step. Combining isotropic solvent swelling and anisotropic mechanical stretching, it is possible to change hcp colloidal arrays into full dimensional ncp ones in all five 2D Bravais lattices. This deformable soft lithography-based lift-up process can also generate patterned ncp arrays of colloidal crystals, including one-dimensional (1D) microsphere arrays with designed structures. This method affords opportunities and spaces for fabrication of novel and complex structures of 1D and 2D ncp colloidal crystal arrays, and these as-prepared structures can be used as molds for colloidal lithography or prototype models for optical materials. PMID:19715332

  16. Modulating two-dimensional non-close-packed colloidal crystal arrays by deformable soft lithography.

    PubMed

    Li, Xiao; Wang, Tieqiang; Zhang, Junhu; Yan, Xin; Zhang, Xuemin; Zhu, Difu; Li, Wei; Zhang, Xun; Yang, Bai

    2010-02-16

    We report a simple method to fabricate two-dimensional (2D) periodic non-close-packed (ncp) arrays of colloidal microspheres with controllable lattice spacing, lattice structure, and pattern arrangement. This method combines soft lithography technique with controlled deformation of polydimethylsiloxane (PDMS) elastomer to convert 2D hexagonal close-packed (hcp) silica microsphere arrays into ncp ones. Self-assembled 2D hcp microsphere arrays were transferred onto the surface of PDMS stamps using the lift-up technique, and then their lattice spacing and lattice structure could be adjusted by solvent swelling or mechanical stretching of the PDMS stamps. Followed by a modified microcontact printing (microcp) technique, the as-prepared 2D ncp microsphere arrays were transferred onto a flat substrate coated with a thin film of poly(vinyl alcohol) (PVA). After removing the PVA film by calcination, the ncp arrays that fell on the substrate without being disturbed could be lifted up, deformed, and transferred again by another PDMS stamp; therefore, the lattice feature could be changed step by step. Combining isotropic solvent swelling and anisotropic mechanical stretching, it is possible to change hcp colloidal arrays into full dimensional ncp ones in all five 2D Bravais lattices. This deformable soft lithography-based lift-up process can also generate patterned ncp arrays of colloidal crystals, including one-dimensional (1D) microsphere arrays with designed structures. This method affords opportunities and spaces for fabrication of novel and complex structures of 1D and 2D ncp colloidal crystal arrays, and these as-prepared structures can be used as molds for colloidal lithography or prototype models for optical materials.

  17. Two-phase Computerized Planning of Cryosurgery Using Bubble-packing and Force-field Analogy

    PubMed Central

    Tanaka, Daigo; Shimada, Kenji; Rabin, Yoed

    2007-01-01

    Background: Cryosurgery is the destruction of undesired tissues by freezing, as in prostate cryosurgery, for example. Minimally-invasive cryosurgery is currently performed by means of an array of cryoprobes, each in the shape of a long hypodermic needle. The optimal arrangement of the cryoprobes, which is known to have a dramatic effect on the quality of the cryoprocedure, remains an art held by the cryosurgeon, based on the cryosurgeon's experience and “rules of thumb.” An automated computerized technique for cryosurgery planning is the subject matter of the current report, in an effort to improve the quality of cryosurgery. Method of Approach: A two-phase optimization method is proposed for this purpose, based on two previous and independent developments by this research team. Phase I is based on a bubble-packing method, previously used as an efficient method for finite elements meshing. Phase II is based on a force-field analogy method, which has proven to be robust at the expense of a typically long runtime. Results: As a proof-of-concept, results are demonstrated on a 2D case of a prostate cross-section. The major contribution of this study is to affirm that in many instances cryosurgery planning can be performed without extremely expensive simulations of bioheat transfer, achieved in Phase I. Conclusions: This new method of planning has proven to reduce planning runtime from hours to minutes, making automated planning practical in a clinical time frame. PMID:16532617

  18. Thermodynamic forces in single crystals with dislocations

    NASA Astrophysics Data System (ADS)

    Van Goethem, Nicolas

    2014-06-01

    A simple model for the evolution of macroscopic dislocation regions in a single crystal is presented. This model relies on maximal dissipation principle within Kröner's geometric description of the dislocated crystal. Mathematical methods and tools from shape optimization theory provide equilibrium relations at the dislocation front, similarly to previous work achieved on damage modelling (J Comput Phys 33(16):5010-5044, 2011). The deformation state variable is the incompatible strain as related to the dislocation density tensor by a relation involving the Ricci curvature of the crystal underlying elastic metric. The time evolution of the model variables follows from a novel interpretation of the Einstein-Hilbert flow in terms of dislocation microstructure energy. This flow is interpreted as the dissipation of non-conservative dislocations, due to the climb mechanism, modelled by an average effect of mesoscopic dislocations moving normal to their glide planes by adding or removing points defects. The model equations are a fourth-order tensor parabolic equation involving the operator "incompatibility," here appearing as a tensorial counterpart of the scalar Laplacian. This work encompasses and generalizes results previously announced (C R Acad Sci Paris Ser I 349:923-927, 2011), with in addition a series of physical interpretations to give a meaning to the newly introduced concepts.

  19. Effect of molecular structure and packing density of an azo self-assembled monolayer on liquid crystal alignment.

    PubMed

    Vengatesan, M R; Lee, Seung-Ho; Son, Jong-Ho; Lim, Jeong-Ku; Song, Jang Kun

    2013-10-01

    We studied the alignment of liquid crystals (LCs) on a photo-switchable azo-containing self-assembled monolayer (azo-SAM) with different packing densities and molecular structures. The packing density of the azo-SAM substrates was varied by changing the dipping time of the substrate in azosilane monomers solution (2mM in toluene). The thickness of the monolayer on the silicon substrate increased as the dipping time was increased. The relative surface packing density on the glass substrates was estimated from the surface energies of the azo-SAM. The photo-induced dynamics of liquid crystal alignment on the azo-SAM significantly varied according to the packing density of the azo-SAM and the structure of the azo-SAM molecules. The azo-SAM from long octyloxy chain-terminated azosilane (azo-S1) possessed stable homeotropic alignment even after photobuffing, while the azo-SAM from short methyl group-terminated azosilane monomer (azo-S2) showed photo-switchable homeotropic and planar alignments. However, when the packing density was increased to an excessive degree, even the azo-SAM from azo-S2 exhibited stable homeotropic alignment regardless of photobuffing.

  20. Effect of molecular structure and packing density of an azo self-assembled monolayer on liquid crystal alignment.

    PubMed

    Vengatesan, M R; Lee, Seung-Ho; Son, Jong-Ho; Lim, Jeong-Ku; Song, Jang Kun

    2013-10-01

    We studied the alignment of liquid crystals (LCs) on a photo-switchable azo-containing self-assembled monolayer (azo-SAM) with different packing densities and molecular structures. The packing density of the azo-SAM substrates was varied by changing the dipping time of the substrate in azosilane monomers solution (2mM in toluene). The thickness of the monolayer on the silicon substrate increased as the dipping time was increased. The relative surface packing density on the glass substrates was estimated from the surface energies of the azo-SAM. The photo-induced dynamics of liquid crystal alignment on the azo-SAM significantly varied according to the packing density of the azo-SAM and the structure of the azo-SAM molecules. The azo-SAM from long octyloxy chain-terminated azosilane (azo-S1) possessed stable homeotropic alignment even after photobuffing, while the azo-SAM from short methyl group-terminated azosilane monomer (azo-S2) showed photo-switchable homeotropic and planar alignments. However, when the packing density was increased to an excessive degree, even the azo-SAM from azo-S2 exhibited stable homeotropic alignment regardless of photobuffing. PMID:23871311

  1. Crystal-Packing Trends for a Series of 6,9,12,15,18-Pentaaryl-1-hydro[60]fullerenes

    SciTech Connect

    Kennedy, Robert D.; Halim, Merissa; Khan, Saeed I.; Schwartz, Benjamin J.; Tolbert, Sarah H.; Rubin, Yves

    2012-06-11

    The relationship between the size of the substituents of aryl groups in a series of fifteen 6,9,12,15,18-pentaaryl-1-hydro[60]fullerenes and the solid-state structures and packing motifs of these compounds has been analyzed. Pentaarylfullerenes have a characteristic “badminton shuttlecock” shape that causes several derivatives to crystallize into columnar stacks. However, many pentaarylfullerenes form non-stacked structures with, for example, dimeric, layered, diamondoid, or feather-in-cavity relationships between molecules. Computational modeling gave a qualitative estimate of the best shape match between the ball and socket surfaces of each pentaarylfullerene. The best match was for pentaarylfullerenes with large, spherically shaped para-substituents on the aryl groups. The series of pentaarylfullerenes was characterized by single-crystal X-ray diffraction. A total of 34 crystal structures were obtained as various solvates and were categorized by their packing motifs.

  2. A novel opal closest-packing photonic crystal for naked-eye glucose detection.

    PubMed

    Hong, Xiaodi; Peng, Yuan; Bai, Jialei; Ning, Baoan; Liu, Yuanyuan; Zhou, Zhijiang; Gao, Zhixian

    2014-04-01

    A novel opal closest-packing (OCP) photonic crystal (PC) is successfully prepared for naked-eye glucose detection. This PC is fabricated via a vertical convective self-assembly method with a new type of monodisperse microsphere polymerized by co-monomers, namely, methyl methacrylate (MMA), N-isopropylacrylamide (NIPA), and 3-acrylamidophenylboronic acid (AAPBA). The OCP PC has high stability and periodically-ordered structure, showing the desired structural color. The proposed PC material displays a red shift and reduced reflection intensity when detecting glucose molecules. The red-shift wavelength reaches 75 nm, which clearly changes the structural color from brilliant blue to emerald green. This visually distinguishable color change facilitates the detection of the glucose concentrations from 3 to 20 mm, which demonstrates the potential of the opal PC material for naked-eye detection. Thus, the novel PMMA–NIPA–AAPBA OCP PC is a simply prepared and sensitive material, which shows promising use in the diagnosis of diabetes mellitus and in real-time monitoring of diabetes. Different types of appropriated recognition groups are expected to be introduced into the 3D OCP PC to form new functional materials or chemical sensors, which will extensively broaden the PC material application. PMID:24829962

  3. A novel opal closest-packing photonic crystal for naked-eye glucose detection.

    PubMed

    Hong, Xiaodi; Peng, Yuan; Bai, Jialei; Ning, Baoan; Liu, Yuanyuan; Zhou, Zhijiang; Gao, Zhixian

    2014-04-01

    A novel opal closest-packing (OCP) photonic crystal (PC) is successfully prepared for naked-eye glucose detection. This PC is fabricated via a vertical convective self-assembly method with a new type of monodisperse microsphere polymerized by co-monomers, namely, methyl methacrylate (MMA), N-isopropylacrylamide (NIPA), and 3-acrylamidophenylboronic acid (AAPBA). The OCP PC has high stability and periodically-ordered structure, showing the desired structural color. The proposed PC material displays a red shift and reduced reflection intensity when detecting glucose molecules. The red-shift wavelength reaches 75 nm, which clearly changes the structural color from brilliant blue to emerald green. This visually distinguishable color change facilitates the detection of the glucose concentrations from 3 to 20 mm, which demonstrates the potential of the opal PC material for naked-eye detection. Thus, the novel PMMA–NIPA–AAPBA OCP PC is a simply prepared and sensitive material, which shows promising use in the diagnosis of diabetes mellitus and in real-time monitoring of diabetes. Different types of appropriated recognition groups are expected to be introduced into the 3D OCP PC to form new functional materials or chemical sensors, which will extensively broaden the PC material application.

  4. Cooling crystallization experiments observed by in situ scanning force microscopy

    NASA Astrophysics Data System (ADS)

    Kipp, S.; Lacmann, R.

    1996-03-01

    The change in surface morphology of potassium nitrate and potassium alum has been studied in situ by means of scanning force microscopy. The supersaturation and undersaturation were varied in a cooling crystallizer under flow conditions. To keep the crystal growth rate of potassium nitrate low, the specific additive DOW FAX 3B2 had been used in different concentrations. The crystal growth rate of both systems could be determined and the growth and dissolution surface morphologies of potassium alum exhibited structures similar to those of microscopic measurements.

  5. One more chiral drug prone to spontaneous resolution: Binary phase diagram, absolute configuration, and crystal packing of bevantolol hydrochloride

    NASA Astrophysics Data System (ADS)

    Bredikhina, Zemfira A.; Zakharychev, Dmitry V.; Gubaidullin, Aidar T.; Bredikhin, Alexander A.

    2009-11-01

    Spontaneous resolution of cardioselective β1-adrenergic blocker bevantolol hydrochloride1·HCl was established by IR spectroscopy, differential scanning calorimetry, and by single crystal X-ray analysis both for enantiopure and racemic samples. The absolute configuration of 1·HCl was evaluated through Flack parameter method. The molecular structure and crystal packing details were evaluated; the symmetry independent fragment of the P1 unit cell consists of two molecules which have almost identical spatial arrangement, but differ sufficiently in the nature of nitrogen atoms: quaternary form in one case and free amine form in the other.

  6. Energetics of the lattice: packing elements in crystals of four-stranded intercalated cytosine-rich DNA molecules

    NASA Technical Reports Server (NTRS)

    Berger, I.; Cai, L.; Chen, L.; Rich, A.

    1997-01-01

    Condensation of single molecules from solution into crystals represents a transition between distinct energetic states. In solution, the atomic interactions within the molecule dominate. In the crystalline state, however, a set of additional interactions are formed between molecules in close contact in the lattice--these are the packing interactions. The crystal structures of d(CCCT), d(TAACCC), d(CCCAAT), and d(AACCCC) have in common a four-stranded intercalated cytosine segment, built by stacked layers of cytosine.cytosine+ (C.C+) base pairs coming from two parallel duplexes that intercalate into each other with opposite polarity. The intercalated cytosine segments in these structures are similar in their geometry, even though the sequences crystallized in different space groups. In the crystals, adenine and thymine residues of the sequences are used to build the three-dimensional crystal lattice by elaborately interacting with symmetry-related molecules. The packing elements observed provide novel insight about the copious ways in which nucleic acid molecules can interact with each other--for example, when folded in more complicated higher order structures, such as mRNA and chromatin.

  7. Piconewton force measurement using a nanometric photonic crystal diaphragm.

    PubMed

    Jo, Wonuk; Digonnet, Michel J F

    2014-08-01

    A compact force fiber sensor capable of measuring forces at the piconewton level is reported. It consists of a miniature Fabry-Perot cavity fabricated at the tip a single-mode fiber, in which the external reflector is a compliant photonic-crystal diaphragm that deflects when subjected to a force. In the laboratory environment, this sensor was able to detect a force of only ∼4  pN generated by the radiation pressure of a laser beam. Its measured minimum detectable force (MDF) at 3 kHz was as weak as 1.3  pN/√Hz. In a quiet environment, the measured noise was ∼16 times lower, and the MDF predicted to be ∼76  fN/√Hz. PMID:25078221

  8. Crystal packing and melting temperatures of small oxalate esters: the role of C-H···O hydrogen bonding.

    PubMed

    Joseph, Sumy; Sathishkumar, Ranganathan; Mahapatra, Sudarshan; Desiraju, Gautam R

    2011-12-01

    The simple dialkyl oxalates are generally liquids at room temperature except for dimethyl and di-tert-butyl oxalate which melt at 327 and 343 K. The crystal structures of diethyl, di-iso-propyl, di-n-butyl, di-tert-butyl and methyl ethyl oxalates were determined. The liquid esters were crystallized using the cryocrystallization technique. A comparison of the intermolecular interactions and packing features in these crystal structures was carried out. The crystal structure of dimethyl oxalate was redetermined at various temperatures. The other compounds were also studied at several temperatures in order to assess the attractive nature of the hydrogen bonds therein. A number of moderate to well defined C-H···O interactions account for the higher melting points of the two solid esters. Additionally, a diminished entropic contribution ΔS(m) in di-tert-butyl oxalate possibly increases the melting point of this compound further.

  9. Self-assembly modes of glycyrrhetinic acid esters in view of the crystal packing of related triterpene molecules.

    PubMed

    Langer, Dominik; Wicher, Barbara; Szczołko, Wojciech; Gdaniec, Maria; Tykarska, Ewa

    2016-08-01

    The crystal structures of three ester derivatives of glycyrrhetinic acid (GE) are reported. X-ray crystallography revealed that despite differences in the size of the ester substituents (ethyl, isopropyl and 2-morpholinoethyl) the scheme of molecular self-assembly is similar in all three cases but differs significantly from that observed in other known GE esters. According to our analysis, the two basic patterns of self-assembly of GE esters observed in their unsolvated crystals correspond to two distinct orientations of the ester groups relative to the triterpene backbone. Moreover, comparison of the self-assembly modes of GE esters in their unsolvated forms with the supramolecular organization of GE and carbenoxolone in their solvated crystals revealed that ester substituents replace solvent molecules hydrogen bonded to the COOH group at the triterpene skeleton, resulting in similar packing arrangements of these compounds. PMID:27484379

  10. Effective refractive index of face-centered-cubic and hexagonal close-packed 250 nm-SiO2 based colloidal crystals

    NASA Astrophysics Data System (ADS)

    Salcedo-Reyes, Juan Carlos

    2012-01-01

    A quantitative kinematic analysis, of the refraction properties of face-centered-cubic and hexagonal close-packed 250 nm-SiO2-based colloidal crystals, was performed using the plane wave expansion method. The angle-dependent effective refractive index, for different frequencies, was calculated taking into account the continuity of the tangential component of the wave vector across the interface and the energy conservation principle as well. The results demonstrate that the unusual optical properties, of the close packed SiO2-based colloidal crystals, depend strongly on the sphere-packing symmetry rather than from the material itself.

  11. Mechanisms of protein and virus crystal growth: An atomic force microscopy study of Canavalin crystallization

    SciTech Connect

    Land, T.A.; De Yoreo, J.J.; Malkin, A.J.; Kutznesov, Y.G.; McPherson, A.

    1995-03-10

    The evolution of surface morphology and step dynamics during growth of single crystals of the protein Canavalin and of the cubic satellite tobacco mosaic virus crystals (STMV) have been investigated by in situ atomic force microscopy. These two crystals were observed to grow by very different mechanisms. Growth of Canavalin occurs on complex vicinal hillocks formed by multiple, independently acting screw dislocations. Small cluster were observed on the terraces. STMV on the other hand, was observed to grow by 2D nucleation of islands. No dislocations were found on the crystal. The results are used to determine the growth mechanisms and estimate fundamental materials parameters. The images also illustrate the important mechanism of defect incorporation and provide insight to the processes that limit the growth rate and uniformity of these crystals.

  12. The effect of ligand substituent on crystal packing: Structural and theoretical studies of two Ga(III) supramolecular compounds

    NASA Astrophysics Data System (ADS)

    Soleimannejad, Janet; Nazarnia, Esfandiar

    2016-07-01

    A new Ga(III) supramolecular compound (4,4‧-bipyH2)[Ga(hpydc)2]2·7H2O (2) (where H2hpydc = 4-hydroxy-pyridine-2,6-dicarboxylic acid and 4,4‧-bipy = 4,4‧-bipyridine) was synthesized using the proton transfer reaction. Compound 2 was structurally characterized using single crystal X-ray diffraction, and it was shown that its asymmetric unit consists of two independent anionic Ga(III) complexes, one fully protonated 4,4‧-bipyridine and seven uncoordinated water molecules. In order to understand the effect of pyridine OH substituent on supramolecular interactions and crystal packing, compound 2 was compared with (bipyH2)[Ga(pydc)2]·(H2pydc)·4H2O (1) (where H2pydc = pyridine-2,6-dicarboxylic acid), that does not have an OH group on the pyridine ligand. The Density Functional Theory (DFT) and Natural Bond Orbital (NBO) calculations and also Atoms in Molecules (AIM) analysis were used to analyze the non-covalent interactions in both complexes. The calculation of non-covalent interactions' energy provides a useful means to investigate their effects in the crystal packing.

  13. Collapse of homeotropic liquid-crystal alignment by increased molecular packing on comb-like polymer surfaces.

    PubMed

    Sohn, Eun-Ho; Kang, Hyo; Kim, Dong-Gyun; Song, Kigook; Lee, Jong-Chan

    2012-06-01

    We report an unusual alignment behavior of liquid crystals (LCs) on well-ordered comb-like poly(oxyethylene) surfaces. The homeotropic LC alignments that are observed on as-coated surfaces of the polymers are transformed to the random planar type after annealing treatment, even though the molecular structure of the polymer surface becomes more ordered and the surface energy decreases. Studies of the surface properties, such as molecular structure, morphology, and wettability, reveal that such an unexpected alteration of the LC alignment originates from the density of the alkyl side chains being enhanced by localized packing. PMID:22511283

  14. A master equation for the probability distribution functions of forces in soft particle packings.

    PubMed

    Saitoh, Kuniyasu; Magnanimo, Vanessa; Luding, Stefan

    2015-02-01

    We study the microscopic response of force-chain networks in jammed soft particles to quasi-static isotropic (de)compressions by molecular dynamics simulations. We show that not only contacts but also interparticle gaps between the nearest neighbors must be considered for the stochastic evolution of the probability distribution functions (PDFs) of forces, where the mutual exchange of contacts and interparticle gaps, i.e. opening and closing contacts, are also crucial to the incremental system behavior. By numerically determining the transition rates for all changes of contacts and gaps, we formulate a Master equation for the PDFs of forces, where the insight one gets from the transition rates is striking: the mean change of forces reflects non-affine system responses, while their fluctuations obey uncorrelated Gaussian statistics. In contrast, interparticle gaps react mostly affine in average, but imply multi-scale correlations according to a much wider stable distribution function.

  15. Closely packed Ge quantum dots in ITO matrix: influence of Ge crystallization on optical and electrical properties

    NASA Astrophysics Data System (ADS)

    Car, Tihomir; Nekić, Nikolina; Jerčinović, Marko; Salamon, Krešimir; Bogdanović-Radović, Iva; Delač Marion, Ida; Dasović, Jasna; Dražić, Goran; Ivanda, Mile; Bernstorff, Sigrid; Pivac, Branko; Kralj, Marko; Radić, Nikola; Buljan, Maja

    2016-06-01

    In the present work, a method for the low-temperature production of the material consisting of closely packed Ge QDs embedded in ITO matrix is described. The films are produced by magnetron sputtering deposition followed by thermal annealing. It is shown that the conductivity and optical properties of the films depend on the structure, Ge content in the ITO matrix as well as on the annealing conditions. The conductivity of the films changes up to seven orders of magnitude in dependence on the annealing conditions, and it shows transformation from semiconductor to metallic behavior. The optical properties are also strongly affected by the preparation and annealing conditions, so both conductivity and optical properties can be controllably manipulated. In addition, the crystallization of Ge is found to occur already at 300 °C, which is significantly lower than the crystallization temperature of Ge produced by the same method in silica and alumina matrices.

  16. Specific features of the crystal packing that enable styryl dyes of the pyridine series to undergo the solid-phase [2 + 2] photocycloaddition including the process with single crystal retention

    SciTech Connect

    Kuz'mina, L. G.; Vedernikov, A. I.; Sazonov, S. K.; Lobova, N. A.; Loginov, P. S.; Howard, J. A. K.; Alfimov, M. V.; Gromov, S. P.

    2008-05-15

    The crystal packing of a number of styryl dyes of the pyridine series is analyzed. The structures of three dyes and three [2 + 2] photocycloaddition (PCA) products, 1,2,3,4-tetrasubstituted cyclobutanes, obtained in single crystals are determined by X-ray diffraction. Stacks of planar organic cations are characteristic of styryl dye packings. The proceeding of the PCA reaction as a single crystal-to-single crystal transformation in the syn head-to-head stacks is in principle impossible. The syn head-to-tail stacking packings are favorable for the PCA reactions resulting in the centrosymmetric rctt isomers of cyclobutane. The stacking packings, in which molecules are related by the twofold axes (the anti arrangement of molecules), are also favorable for PCA in single crystals. In this case, the products are the rtct isomers of cyclobutane. The presence of the I{sup -} counterions in a packing is a factor impeding the PCA reaction, because the secondary I-H-C bonds increase the rigidity of the crystal lattice. The conditions necessary for proceeding the PCA reactions in styryl dyes as single crystal-to-single crystal processes are as follows: (1) the stacks split into pairs of organic cations (dimers) with the d distances within 4.2 A in a dimer and d exceeding 4.2 A between the dimers; and (2) the dimers are surrounded by flexible shells consisting of anions, solvate molecules, or flexible moieties of the organic cations themselves.

  17. Molecular packing and magnetic properties of lithium naphthalocyanine crystals: hollow channels enabling permeability and paramagnetic sensitivity to molecular oxygen.

    PubMed

    Pandian, Ramasamy P; Dolgos, Michelle; Marginean, Camelia; Woodward, Patrick M; Hammel, P Chris; Manoharan, Periakaruppan T; Kuppusamy, Periannan

    2009-01-01

    The synthesis, structural framework, magnetic and oxygen-sensing properties of a lithium naphthalocyanine (LiNc) radical probe are presented. LiNc was synthesized in the form of a microcrystalline powder using a chemical method and characterized by electron paramagnetic resonance (EPR) spectroscopy, magnetic susceptibility, powder X-ray diffraction analysis, and mass spectrometry. X-Ray powder diffraction studies revealed a structural framework that possesses long, hollow channels running parallel to the packing direction. The channels measured approximately 5.0 × 5.4 Å(2) in the two-dimensional plane perpendicular to the length of the channel, enabling diffusion of oxygen molecules (2.9 × 3.9 Å(2)) through the channel. The powdered LiNc exhibited a single, sharp EPR line under anoxic conditions, with a peak-to-peak linewidth of 630 mG at room temperature. The linewidth was sensitive to surrounding molecular oxygen, showing a linear increase in pO(2) with an oxygen sensitivity of 31.2 mG per mmHg. The LiNc microcrystals can be further prepared as nano-sized crystals without the loss of its high oxygen-sensing properties. The thermal variation of the magnetic properties of LiNc, such as the EPR linewidth, EPR intensity and magnetic susceptibility revealed the existence of two different temperature regimes of magnetic coupling and hence differing columnar packing, both being one-dimensional antiferromagnetic chains but with differing magnitudes of exchange coupling constants. At a temperature of ∼50 K, LiNc crystals undergo a reversible phase transition. The high degree of oxygen-sensitivity of micro- and nano-sized crystals of LiNc, combined with excellent stability, should enable precise and accurate measurements of oxygen concentration in biological systems using EPR spectroscopy.

  18. Six-membered metalla-coronands. synthesis and crystal packing: columns, compartments, and 3D-networks.

    PubMed

    Saalfrank, Rolf W; Deutscher, Christian; Sperner, Stefan; Nakajima, Takayuki; Ako, Ayuk M; Uller, Eveline; Hampel, Frank; Heinemann, Frank W

    2004-07-12

    Reaction of various N-substituted diethanolamines H(2)L(3) (4) with calcium hydride and iron(III) chloride leads to the self-assembly of six-membered ferric wheels [Fe(6)X(6)(L(3))(6)] (5). Principally, all the iron coronands are isostructural; however, they differ fundamentally with respect to their crystal packing. Exemplarily, this is discussed for selected members of the space groups R, P, P2(1)/c, P2(1)/n, C2/c, and P. Depending on the nature of their sidearms, the ferric wheels create various substructures. For instance, the ferric wheels 5a-i of space group R or P are piled in parallel in cylindrical columns, which are surrounded by six parallel columns alternately dislocated by (1)/(3)c and (2)/(3)c against the central one. Pronounced van der Waals interactions give rise to compartmentation and incarceration of guest molecules as seen for 5e,g. However, in 5h strong pi-pi interactions create a three-dimensional scaffold. The most significant difference of the ferric wheels 5j-p of space groups P2(1)/c, P2(1)/n, and C2/c is that these ferric wheels are arranged in parallel in two orientations. They differ mainly only by the included angle of the two groups of parallel wheels. In the case of 5l, molecular chains are formed in the crystal due to pi-pi interactions. The ferric wheels 5q-y of space group P are packed in the crystal most simply, with all the ferric wheels piled in parallel.

  19. Crystal structures of two bis-(iodo-meth-yl)benzene derivatives: similarities and differences in the crystal packing.

    PubMed

    McAdam, C John; Hanton, Lyall R; Moratti, Stephen C; Simpson, Jim

    2015-12-01

    The isomeric derivatives 1,2-bis-(iodo-meth-yl)benzene, (I), and 1,3-bis-(iodo-meth-yl)benzene (II), both C8H8I2, were prepared by metathesis from their di-bromo analogues. The ortho-derivative, (I), lies about a crystallographic twofold axis that bis-ects the C-C bond between the two iodo-methyl substituents. The packing in (I) relies solely on C-H⋯I hydrogen bonds supported by weak parallel slipped π-π stacking inter-actions [inter-centroid distance = 4.0569 (11) Å, inter-planar distance = 3.3789 (8) Å and slippage = 2.245 Å]. While C-H⋯I hydrogen bonds are also found in the packing of (II), type II, I⋯I halogen bonds [I⋯I = 3.8662 (2) Å] and C-H⋯π contacts feature prominently in stabilizing the three-dimensional structure. PMID:26870415

  20. Structure and stability of designed TPR protein superhelices: unusual crystal packing and implications for natural TPR proteins.

    PubMed

    Kajander, Tommi; Cortajarena, Aitziber L; Mochrie, Simon; Regan, Lynne

    2007-07-01

    The structure and stability of repeat proteins has been little studied in comparison to the properties of the more familiar globular proteins. Here, the structure and stability of designed tetratricopeptide-repeat (TPR) proteins is described. The TPR is a 34-amino-acid motif which adopts a helix-turn-helix structure and occurs as tandem repeats. The design of a consensus TPR motif (CTPR) has previously been described. Here, the crystal structures and stabilities of proteins that contain eight or 20 identical tandem repeats of the CTPR motif (CTPR8 and CTPR20) are presented. Both CTPR8 and CTPR20 adopt a superhelical overall structure. The structures of the different-length CTPR proteins are compared with each other and with the structures of natural TPR domains. Also, the unusual and perhaps unique crystal-packing interactions resulting in pseudo-infinite crystalline superhelices observed in the different crystal forms of CTPR8 and CTPR20 are discussed. Finally, it is shown that the thermodynamic behavior of CTPR8 and CTPR20 can be predicted from the behavior of other TPRs in this series using an Ising model-based analysis. The designed protein series CTPR2-CTPR20 covers the natural size repertoire of TPR domains and as such is an excellent model system for natural TPR proteins.

  1. Are proteins well-packed?

    PubMed

    Liang, J; Dill, K A

    2001-08-01

    The average packing density inside proteins is as high as in crystalline solids. Does this mean proteins are well-packed? We go beyond average densities, and look at the full distribution functions of free volumes inside proteins. Using a new and rigorous Delaunay triangulation method for parsing space into empty and filled regions, we introduce formal definitions of interior and surface packing densities. Although proteins look like organic crystals by the criterion of average density, they look more like liquids and glasses by the criterion of their free volume distributions. The distributions are broad, and the scalings of volume-to-surface, volume-to-cluster-radius, and numbers of void versus volume show that the interiors of proteins are more like randomly packed spheres near their percolation threshold than like jigsaw puzzles. We find that larger proteins are packed more loosely than smaller proteins. And we find that the enthalpies of folding (per amino acid) are independent of the packing density of a protein, indicating that van der Waals interactions are not a dominant component of the folding forces. PMID:11463623

  2. Transferability of coarse-grained force field for nCB liquid crystal systems.

    PubMed

    Zhang, Jianguo; Guo, Hongxia

    2014-05-01

    In this paper, the transferability of the coarse-grained (CG) force field originally developed for the liquid crystal (LC) molecule 5CB ( Zhang et al. J. Phys. Chem. B 2012 , 116 , 2075 - 2089 ) was investigated by its homologues 6CB and 8CB molecules. Note that, to construct the 5CB CG force field, we combined the structure-based and thermodynamic quantities-based methods and at the same time attempted to use several fragment molecular systems to derive the CG nonbonded interaction parameters. The resultant 5CB CG force field exhibits a good transferability to some extent. For example, not only the experimental densities, the local packing of atom groups, and the antiparallel arrangements of nearest neighboring molecules, but also the unique LC mesophases as well as the nematic-isotropic phase transition temperatures of 6CB and 8CB were reproduced. Meanwhile, the limitations of this 5CB CG force field were also observed, such as the phase transition from nematic to smectic was postponed to the lower temperature and the resulting smectic phase structure is single-layer-like instead of partially interdigitated bilayer-like as observed in underlying atomistic model. Apparently, more attention should be paid when applying a CG force field to the state point which is quite different from which the force field is explicitly parametrized for. The origin of the above limitations can be potentially traced back to the inherent simplifications and some approximations often adopted in the creation process of CG force field, for example, choosing symmetric CG potentials which do not explicitly include electrostatic interactions and are parametrized by reproducing the target properties of the specific nematic 5CB phase at 300 K and 1 atm, as well as using soft nonbonded potential and excluding torsion barriers. Moreover, although by construction this CG force field could inevitably incorporate both thermodynamic and local structural information on the nematic 5CB phase, the

  3. Transferability of coarse-grained force field for nCB liquid crystal systems.

    PubMed

    Zhang, Jianguo; Guo, Hongxia

    2014-05-01

    In this paper, the transferability of the coarse-grained (CG) force field originally developed for the liquid crystal (LC) molecule 5CB ( Zhang et al. J. Phys. Chem. B 2012 , 116 , 2075 - 2089 ) was investigated by its homologues 6CB and 8CB molecules. Note that, to construct the 5CB CG force field, we combined the structure-based and thermodynamic quantities-based methods and at the same time attempted to use several fragment molecular systems to derive the CG nonbonded interaction parameters. The resultant 5CB CG force field exhibits a good transferability to some extent. For example, not only the experimental densities, the local packing of atom groups, and the antiparallel arrangements of nearest neighboring molecules, but also the unique LC mesophases as well as the nematic-isotropic phase transition temperatures of 6CB and 8CB were reproduced. Meanwhile, the limitations of this 5CB CG force field were also observed, such as the phase transition from nematic to smectic was postponed to the lower temperature and the resulting smectic phase structure is single-layer-like instead of partially interdigitated bilayer-like as observed in underlying atomistic model. Apparently, more attention should be paid when applying a CG force field to the state point which is quite different from which the force field is explicitly parametrized for. The origin of the above limitations can be potentially traced back to the inherent simplifications and some approximations often adopted in the creation process of CG force field, for example, choosing symmetric CG potentials which do not explicitly include electrostatic interactions and are parametrized by reproducing the target properties of the specific nematic 5CB phase at 300 K and 1 atm, as well as using soft nonbonded potential and excluding torsion barriers. Moreover, although by construction this CG force field could inevitably incorporate both thermodynamic and local structural information on the nematic 5CB phase, the

  4. Role of hydrogen bonds in molecular packing of photoreactive crystals: templating photodimerization of protonated stilbazoles in crystalline state with a combination of water molecules and chloride ions.

    PubMed

    Mondal, Barnali; Zhang, Tingting; Prabhakar, Rajeev; Captain, Burjor; Ramamurthy, V

    2014-11-01

    A difference in photobehavior and molecular packing between hydrated and anhydrous crystals of protonated trans-stilbazoles has been identified. While stilbazoles are not photoreactive in the crystalline state, upon protonation with HCl in the solid state they dimerized to a single dimer (anti-head-tail) when exposed to UV light. In these photoreactive crystals the protonated stilbazole molecules are arranged in a ladder-like format with the rungs made up of water molecules and chloride ions. A combination of water and chloride ion holds the protonated trans-stilbazoles through either N-HO or N-HCl(-) interactions. Anhydrous protonated stilbazole crystals prepared by heating the 'wet' crystals under reduced pressure were inert upon exposure to UV light. As per X-ray crystal structure analyses these light stable crystals did not contain water molecules in their lattice. The current investigation has established that water molecules are essential for photodimerization of crystalline protonated trans-stilbazoles. To compare the reactivity of protonated trans-stilbazoles with that of protonated cis-stilbazoles, photoreactivity and packing arrangement of cis-4-iodo stilbazole·HCl salt was examined. This molecule in the crystalline state only isomerized to the trans isomer and did not dimerize. Thus, while the trans isomer dimerized and did not isomerize, the cis isomer only isomerized and did not dimerize in the crystalline state. To probe the role of cationπ interaction in the packing of protonated trans-stilbazoles, energies of various types of packing in the gas phase were estimated by MP-2 calculations and cationπ interaction was found to be unimportant in the packing of protonated trans-stilbazole crystals investigated here.

  5. Mesosized Crystal-like Structure of Hexagonally Packed Hollow Hoops by Solution Self-Assembly of Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Zhang, Lifeng; Bartels, Carl; Yu, Yisong; Shen, Hongwei; Eisenberg, Adi

    1997-12-01

    Mesosize crystal-like aggregates with an internal structure of hexagonally packed hollow hoops (HHH) in a polystyrene matrix have been prepared in solution by self-assembly of asymmetric polystyrene-b-poly(acrylic acid) diblock copolymers. Most of the aggregates are cylindrical or in the shape of truncated cones. The external surface of the aggregates and the internal surface of the hollow hoops are lines with short poly(acrylic acid) chains. The hoop morphology is imposed because the end-capping energy of a rod on this size scale is more important than the curvature energy. A strong interdependence between the external shape and the internal structure in these mesosize particles is demonstrated.

  6. Dislocation Dynamics Simulations of Junctions in Hexagonal Close-Packed Crystals

    SciTech Connect

    Wu, C; Aubry, S; Chung, P; Arsenlis, A

    2011-12-05

    The formation and strength of dislocations in the hexagonal closed packed material beryllium are studied through dislocation junctions and the critical stress required to break them. Dislocation dynamics calculations (using the code ParaDiS) of junction maps are compared to an analytical line tension approximation in order to validate our model. Results show that the two models agree very well. Also the critical shear stress necessary to break 30{sup o} - 30{sup o} and 30{sup o} - 90{sup o} dislocation junctions is computed numerically. Yield surfaces are mapped out for these junctions to describe their stability regions as function of resolved shear stresses on the glide planes. The example of two non-coplanar binary dislocation junctions with slip planes [2-1-10] (01-10) and [-12-10] (0001) corresponding to a prismatic and basal slip respectively is chosen to verify and validate our implementation.

  7. The dominant role of chalcogen bonding in the crystal packing of 2D/3D aromatics.

    PubMed

    Fanfrlík, Jindřich; Přáda, Adam; Padělková, Zdeňka; Pecina, Adam; Macháček, Jan; Lepšík, Martin; Holub, Josef; Růžička, Aleš; Hnyk, Drahomír; Hobza, Pavel

    2014-09-15

    The chalcogen bond is a nonclassical σ-hole-based noncovalent interaction with emerging applications in medicinal chemistry and material science. It is found in organic compounds, including 2D aromatics, but has so far never been observed in 3D aromatic inorganic boron hydrides. Thiaboranes, harboring a sulfur heteroatom in the icosahedral cage, are candidates for the formation of chalcogen bonds. The phenyl-substituted thiaborane, synthesized and crystalized in this study, forms sulfur⋅⋅⋅π type chalcogen bonds. Quantum chemical analysis revealed that these interactions are considerably stronger than both in their organic counterparts and in the known halogen bond. The reason is the existence of a highly positive σ-hole on the positively charged sulfur atom. This discovery expands the possibilities of applying substituted boron clusters in crystal engineering and drug design.

  8. Isostructural crystal packing and hydrogen bonding in alkylammonium tin(IV) chloride compounds.

    PubMed

    Lemmerer, Andreas; Billing, David G; Reisinger, Sandra A

    2007-03-01

    The three isostructural compounds butylammonium hexachloridotin(IV), pentylammonium hexachloridotin(IV) and hexylammonium hexachloridotin(IV), (C(n)H(2n+1)NH(3))(2)[SnCl(6)], with n = 4, 5 and 6, respectively, crystallize as inorganic-organic hybrids. As such, the structures consist of layers of [SnCl(6)](2-) octahedra, separated by hydrocarbon layers of interdigitated butylammonium, pentylammonium or hexylammonium cations. Corrugated layers of cations alternate with tin(IV) chloride layers. The asymmetric unit in each compound consists of an anionic component comprising one Sn and two Cl atoms on a mirror plane, and two Cl atoms in general positions; the two cations lie on another mirror plane. Application of the mirror symmetry generates octahedral coordination around the Sn atom. All compounds exhibit bifurcated and simple hydrogen-bonding interactions between the ammonium groups and the Cl atoms, with little variation in the hydrogen-bonding geometries. PMID:17339715

  9. Crystal packing in three related disaccharides: precursors to heparan sulfate oligosaccharides

    PubMed Central

    Gainsford, Graeme J.; Schwörer, Ralf; Tyler, Peter C.; Zubkova, Olga V.

    2015-01-01

    The three title compounds form part of a set of important precursor dissacharides which lead to novel therapeutics, in particular for Alzheimer’s disease. All three crystallize as poorly diffracting crystals with one independent mol­ecule in the asymmetric unit. Two of them are isostructural: 4-meth­oxy­phenyl 4-O-[6-O-acetyl-2-azido-3-O-benzyl-2-de­oxy-4-O-(9-fluor­en­yl­methyl­oxycarbon­yl)-α-d-gluco­pyranos­yl]-2-O-benzoyl-3-O-benzyl-6-O-chloro­acetyl-α-l-ido­pyran­oside, C59H56ClN3O16, (I), the ido-relative of a reported gluco-disaccharide [Gainsford et al., 2013 ▸). Acta Cryst. C69, 679–682] and 4-meth­oxy­phenyl 4-O-[6-O-acetyl-2-azido-3-O-benzyl-2-de­oxy-4-O-(9-fluorenyl­methyl­oxycarbon­yl)-α-d-gluco­pyranos­yl]-2-O-benzoyl-3-O-benzyl-6-O-meth­oxy­acetyl-α-l-ido­pyran­oside, C60H59N3O17, (II). Both exhibit similar conformational disorder of pendant groups. The third compound 4-meth­oxy­phenyl 4-O-[6-O-acetyl-2-azido-3,4-di-O-benzyl-2-de­oxy-α-d-gluco­pyranos­yl]-2-O-benzoyl-3-O-benzyl-6-O-meth­oxy­oacetyl-β-d-gluco­pyran­oside, C52H55N3O15, (III), illustrates that a slightly larger set of weak inter­molecular inter­actions can result in a less disordered mol­ecular arrangement. The mol­ecules are bound by weak C—H⋯O(ether) hydrogen bonds in (I) and (II), augmented by C—H⋯π inter­actions in (III). The absolute configurations were determined, although at varying levels of significance from the limited observed data. PMID:26090127

  10. Role of chloroform and dichloromethane solvent molecules in crystal packing: an interaction propensity study.

    PubMed

    Allen, Frank H; Wood, Peter A; Galek, Peter T A

    2013-08-01

    Using the Cambridge Structural Database (CSD), it is shown that the acidic C-H donors of chloroform and dichloromethane, respectively, form hydrogen bonds with N, O, S, halides or carbon-bound halogens in 82% and 77% of structures in which such interactions can occur. This hydrogen-bond potency is retained to a significant degree even in the presence of the more conventional O-H and N-H donors. The hydrogen-bond propensities exhibited by the C-H protons in CHCl3 and CH2Cl2 are similar to those of the acetylenic C-C≡C-H proton. However, involvement of the Cl atoms of CHCl3 and CH2Cl2 in non-bonded interactions is rather limited: the propensities for formation of (O or N)-H...Cl bonds are only 6% in both cases, while the propensities for the formation of halogen-halogen bonds is generally < 15%, with only Cl...Br interactions having slightly higher values. While C(phenyl)-H...Cl interactions are commonly observed, they are of low propensity and have distances at the upper end of the van der Waals limit. We conclude that the acidic C-H protons in chloroform and dichloromethane solvent molecules play a clear role in the involvement of these molecules in molecular aggregation in crystal structures, and this is exemplified by hydrogen-bond predictions made using the statistical propensity tool which is now part of the CSD system.

  11. The versatile role of the ethynyl group in crystal packing: an interaction propensity study.

    PubMed

    Allen, Frank H; Wood, Peter A; Galek, Peter T A

    2013-06-01

    It is well documented that the ethynyl group can act as a hydrogen-bond donor via its acidic C-H, and as a hydrogen-bond acceptor via the triple-bond π-density. Using the Cambridge Structural Database (CSD), it is shown that C-C≡C-H forms hydrogen bonds to N, O, S or halogens in 74% of structures in which these bonds can form. Additionally, the ethynyl group forms C-H···π interactions with itself or with phenyl groups in 23% of structures and accepts hydrogen bonds from O-H, N-H or C(aromatic)-H in 47% of structures where such bonds are possible. Overall, C-C≡C-H acts as a donor or acceptor in 87% of structures in which it occurs. These propensities for hydrogen-bond formation have been determined using quite tight geometrical constraints, and many more ethynyl groups form interactions with only slight relaxations of these constraints. We conclude that the ethynyl group makes crucial contributions to molecular aggregation in crystal structures, and this is exemplified by hydrogen-bond predictions for specific structures made using the statistical propensity tool now available in CSD system software.

  12. The versatile role of the ethynyl group in crystal packing: an interaction propensity study.

    PubMed

    Allen, Frank H; Wood, Peter A; Galek, Peter T A

    2013-06-01

    It is well documented that the ethynyl group can act as a hydrogen-bond donor via its acidic C-H, and as a hydrogen-bond acceptor via the triple-bond π-density. Using the Cambridge Structural Database (CSD), it is shown that C-C≡C-H forms hydrogen bonds to N, O, S or halogens in 74% of structures in which these bonds can form. Additionally, the ethynyl group forms C-H···π interactions with itself or with phenyl groups in 23% of structures and accepts hydrogen bonds from O-H, N-H or C(aromatic)-H in 47% of structures where such bonds are possible. Overall, C-C≡C-H acts as a donor or acceptor in 87% of structures in which it occurs. These propensities for hydrogen-bond formation have been determined using quite tight geometrical constraints, and many more ethynyl groups form interactions with only slight relaxations of these constraints. We conclude that the ethynyl group makes crucial contributions to molecular aggregation in crystal structures, and this is exemplified by hydrogen-bond predictions for specific structures made using the statistical propensity tool now available in CSD system software. PMID:23719472

  13. Role of chloroform and dichloromethane solvent molecules in crystal packing: an interaction propensity study.

    PubMed

    Allen, Frank H; Wood, Peter A; Galek, Peter T A

    2013-08-01

    Using the Cambridge Structural Database (CSD), it is shown that the acidic C-H donors of chloroform and dichloromethane, respectively, form hydrogen bonds with N, O, S, halides or carbon-bound halogens in 82% and 77% of structures in which such interactions can occur. This hydrogen-bond potency is retained to a significant degree even in the presence of the more conventional O-H and N-H donors. The hydrogen-bond propensities exhibited by the C-H protons in CHCl3 and CH2Cl2 are similar to those of the acetylenic C-C≡C-H proton. However, involvement of the Cl atoms of CHCl3 and CH2Cl2 in non-bonded interactions is rather limited: the propensities for formation of (O or N)-H...Cl bonds are only 6% in both cases, while the propensities for the formation of halogen-halogen bonds is generally < 15%, with only Cl...Br interactions having slightly higher values. While C(phenyl)-H...Cl interactions are commonly observed, they are of low propensity and have distances at the upper end of the van der Waals limit. We conclude that the acidic C-H protons in chloroform and dichloromethane solvent molecules play a clear role in the involvement of these molecules in molecular aggregation in crystal structures, and this is exemplified by hydrogen-bond predictions made using the statistical propensity tool which is now part of the CSD system. PMID:23873063

  14. Molecular imprinted opal closest-packing photonic crystals for the detection of trace 17β-estradiol in aqueous solution.

    PubMed

    Sai, Na; Wu, Yuntang; Sun, Zhong; Huang, Guowei; Gao, Zhixian

    2015-11-01

    A novel opal closest-packing (OCP) photonic crystal (PC) was prepared by the introduction of molecular imprinting technique into the OCP PC. This molecular imprinted (MI)-OCP PC was fabricated via a vertical convective self-assembly method using 17β-estradiol (E2) as template molecules for monitoring E2 in aqueous solution. Morphology characterization showed that the MI-OCP PC possessed a highly ordered three-dimensional (3D) periodically-ordered structure, showing the desired structural color. The proposed PC material displayed a reduced reflection intensity when detecting E2 in water environment, because the molecular imprinting recognition events make the optical characteristics of PC change. The Bragg diffraction intensity decreased by 19.864 a.u. with the increase of E2 concentration from 1.5 ng mL(-1) to 364.5 ng mL(-1) within 6 min, whereas there were no obvious peak intensity changes for estriol, estrone, cholesterol, testosterone and diethylstilbestrol, indicating that the MI-OCP PC had selective and rapid response for E2 molecules. The adsorption results showed that the OCP structure and homogeneous layers were created in the MI-OCP PC with higher adsorption capacity. Thus, it was learned the MI-OCP PC is a simple prepared, sensitive, selective, and easy operative material, which shows promising use in routine supervision for residue detection in food and environment. PMID:26452805

  15. Molecular imprinted opal closest-packing photonic crystals for the detection of trace 17β-estradiol in aqueous solution.

    PubMed

    Sai, Na; Wu, Yuntang; Sun, Zhong; Huang, Guowei; Gao, Zhixian

    2015-11-01

    A novel opal closest-packing (OCP) photonic crystal (PC) was prepared by the introduction of molecular imprinting technique into the OCP PC. This molecular imprinted (MI)-OCP PC was fabricated via a vertical convective self-assembly method using 17β-estradiol (E2) as template molecules for monitoring E2 in aqueous solution. Morphology characterization showed that the MI-OCP PC possessed a highly ordered three-dimensional (3D) periodically-ordered structure, showing the desired structural color. The proposed PC material displayed a reduced reflection intensity when detecting E2 in water environment, because the molecular imprinting recognition events make the optical characteristics of PC change. The Bragg diffraction intensity decreased by 19.864 a.u. with the increase of E2 concentration from 1.5 ng mL(-1) to 364.5 ng mL(-1) within 6 min, whereas there were no obvious peak intensity changes for estriol, estrone, cholesterol, testosterone and diethylstilbestrol, indicating that the MI-OCP PC had selective and rapid response for E2 molecules. The adsorption results showed that the OCP structure and homogeneous layers were created in the MI-OCP PC with higher adsorption capacity. Thus, it was learned the MI-OCP PC is a simple prepared, sensitive, selective, and easy operative material, which shows promising use in routine supervision for residue detection in food and environment.

  16. Analytical solutions and numerical tests of elastic and failure behaviors of close-packed lattice for brittle rocks and crystals

    NASA Astrophysics Data System (ADS)

    Liu, Chu; Pollard, David D.; Shi, Bin

    2013-01-01

    Analytical solutions of elastic properties and failure modes of a two-dimensional close-packed discrete element model are proposed. Based on the assumption of small deformation, the conversion formulas between five inter-particle parameters of the lattice model and rock mechanical properties were derived. Using the formulas, the inter-particle parameters can be determined by Young's modulus (E), Poisson's ratio (v), tensile strength (Tu), compressive strength (Cu), and coefficient of intrinsic friction (μi). The lattice defined by the parameters simulates the elastic and failure behaviors of rocks and crystals and therefore can be used to investigate the initiation and development of geological structures quantitatively. Furthermore, the solutions also provide a theoretical basis for the calibration of parameters of random discrete assemblies. The model of quartz was used as an example to validate the formulas and test the errors. The simulated results show that E and v converge to theoretical values when particle number increases. These elastic properties are almost constant when the magnitude of strain is lower than 10-3. The simulated Tu and Cu of a single three-element unit are also consistent with the formulas. However, due to the boundary effects and stress concentrations, Tu and Cu of lattices with multiple units are lower than the values predicted by the formulas. Therefore, greater Tu and Cu can be used in the formulas to counteract this effect. The model is applicable to the simulation of complicated structures that involve deformation and failure at different scales.

  17. Z-score biological significance of binding hot spots of protein interfaces by using crystal packing as the reference state.

    PubMed

    Liu, Qian; Wong, Limsoon; Li, Jinyan

    2012-12-01

    Characterization of binding hot spots of protein interfaces is a fundamental study in molecular biology. Many computational methods have been proposed to identify binding hot spots. However, there are few studies to assess the biological significance of binding hot spots. We introduce the notion of biological significance of a contact residue for capturing the probability of the residue occurring in or contributing to protein binding interfaces. We take a statistical Z-score approach to the assessment of the biological significance. The method has three main steps. First, the potential score of a residue is defined by using a knowledge-based potential function with relative accessible surface area calculations. A null distribution of this potential score is then generated from artifact crystal packing contacts. Finally, the Z-score significance of a contact residue with a specific potential score is determined according to this null distribution. We hypothesize that residues at binding hot spots have big absolute values of Z-score as they contribute greatly to binding free energy. Thus, we propose to use Z-score to predict whether a contact residue is a hot spot residue. Comparison with previously reported methods on two benchmark datasets shows that this Z-score method is mostly superior to earlier methods. This article is part of a Special Issue entitled: Computational Methods for Protein Interaction and Structural Prediction.

  18. The role of the "Casimir force analogue" at the microscopic processes of crystallization and melting

    NASA Astrophysics Data System (ADS)

    Chuvildeev, V. N.; Semenycheva, A. V.

    2016-10-01

    Melting (crystallization), a phase transition from a crystalline solid to a liquid state, is a common phenomenon in nature. We suggest a new factor, "the Casimir force analogue", to describe mechanisms of melting and crystallization. The Casimir force analogue is a force occurring between the surfaces of solid and liquid phases of metals caused by different energy density of phonons of these phases. It explains abrupt changes in geometry and thermodynamic parameters at a melting point. "The Casimir force analogue" helps to estimate latent melting heat and to gain an insight into a solid-liquid transition problem.

  19. Image forces on 3d dislocation structures in crystals of finite volume

    SciTech Connect

    El-Azab, A.

    1999-07-01

    The present work aims at studying the image stress and image Peach-Koehler force fields for three-dimensional dislocation configurations in a single crystal of finite volume. It is shown that the image stress field is significant within the entire crystal volume, and that the image Peach-Koehler force can be of the same order of magnitude as the direct interaction force calculated from the infinite domain solution. The results demonstrate that image stress gives rise to long-range interaction forces that are important in meso-scale dynamics of dislocation structures.

  20. Image Forces on 3-D Dislocation Structures in Crystals of Finite Volume

    SciTech Connect

    El-Azab, Anter ); V.V. Bulatov

    1999-01-01

    The present work aims at studying the image stress and image Peach-Koehler force fields for three-dimensional dislocation configurations in a single crystal of finite volume. It is shown that the image stress field is significant within the entire crystal volume, and that the image Peach-Koehler force can be of the same order of magnitude as the direct interaction force calculated from the infinite domain solution. The results demonstrate that image stress gives rise to long-range interaction forces that are important in meso-scale dynamics of dislocation structures.

  1. Supramolecular Fibers in Gels Can Be at Thermodynamic Equilibrium: A Simple Packing Model Reveals Preferential Fibril Formation versus Crystallization.

    PubMed

    Sasselli, Ivan Ramos; Halling, Peter J; Ulijn, Rein V; Tuttle, Tell

    2016-02-23

    Low molecular weight gelators are able to form nanostructures, typically fibers, which entangle to form gel-phase materials. These materials have wide-ranging applications in biomedicine and nanotechnology. While it is known that supramolecular gels often represent metastable structures due to the restricted molecular dynamics in the gel state, the thermodynamic nature of the nanofibrous structure is not well understood. Clearly, 3D extended structures will be able to form more interactions than 1D structures. However, self-assembling molecules are typically amphiphilic, thus giving rise to a combination of solvophobic and solvophilic moieties where a level of solvent exposure at the nanostructure surface is favorable. In this study, we introduce a simple packing model, based on prisms with faces of different nature (solvophobic and solvophilic) and variable interaction parameters, to represent amphiphile self-assembly. This model demonstrates that by tuning shape and "self" or "solvent" interaction parameters either the 1D fiber or 3D crystal may represent the thermodynamic minimum. The model depends on parameters that relate to features of experimentally known systems: the number of faces exposed to the solvent or buried in the fiber; the overall shape of the prism; and the free energy penalties associated with the interactions can be adjusted to match their chemical nature. The model is applied to describe the pH-dependent gelation/precipitation of well-known gelator Fmoc-FF. We conclude that, despite the fact that most experimentally produced gels probably represent metastable states, one-dimensional fibers can represent thermodynamic equilibrium. This conclusion has critical implications for the theoretical treatment of gels. PMID:26812130

  2. Supramolecular Fibers in Gels Can Be at Thermodynamic Equilibrium: A Simple Packing Model Reveals Preferential Fibril Formation versus Crystallization.

    PubMed

    Sasselli, Ivan Ramos; Halling, Peter J; Ulijn, Rein V; Tuttle, Tell

    2016-02-23

    Low molecular weight gelators are able to form nanostructures, typically fibers, which entangle to form gel-phase materials. These materials have wide-ranging applications in biomedicine and nanotechnology. While it is known that supramolecular gels often represent metastable structures due to the restricted molecular dynamics in the gel state, the thermodynamic nature of the nanofibrous structure is not well understood. Clearly, 3D extended structures will be able to form more interactions than 1D structures. However, self-assembling molecules are typically amphiphilic, thus giving rise to a combination of solvophobic and solvophilic moieties where a level of solvent exposure at the nanostructure surface is favorable. In this study, we introduce a simple packing model, based on prisms with faces of different nature (solvophobic and solvophilic) and variable interaction parameters, to represent amphiphile self-assembly. This model demonstrates that by tuning shape and "self" or "solvent" interaction parameters either the 1D fiber or 3D crystal may represent the thermodynamic minimum. The model depends on parameters that relate to features of experimentally known systems: the number of faces exposed to the solvent or buried in the fiber; the overall shape of the prism; and the free energy penalties associated with the interactions can be adjusted to match their chemical nature. The model is applied to describe the pH-dependent gelation/precipitation of well-known gelator Fmoc-FF. We conclude that, despite the fact that most experimentally produced gels probably represent metastable states, one-dimensional fibers can represent thermodynamic equilibrium. This conclusion has critical implications for the theoretical treatment of gels.

  3. Mechanisms of protein and virus crystal growth: An atomic force microscopy study of canavalin and STMV crystallization

    SciTech Connect

    Land, T.A.; De Yoreo, J.J.; Malkin, A.J.; Kutznesov, Yu.G.; McPherson, A.

    1996-05-01

    The evolution of surface morphology and step dynamics during growth of rhombohedral crystals of the protein canavalin and crystals of the cubic satellite tobacco mosaic virus (STMV) have been investigated for the first time by in situ atomic force microscopy. These two crystals were observed to grow by very different mechanisms. Growth of canavalin occurs on complex vicinal hillocks formed by multiple, independently acting screw dislocations. Small clusters were observed on the terraces. STMV on the other hand, was observed to grow by 2D nucleation of islands. No dislocations were found on the crystal. The results are used to determine the growth mechanisms and estimate the fundamental materials parameters. The images also illustrate the important mechanism of defect incorporation and provide insight to the processes that limit the growth rate and uniformity of these crystals.

  4. Sent packing: protein engineering generates a new crystal form of Pseudomonas aeruginosa DsbA1 with increased catalytic surface accessibility

    SciTech Connect

    McMahon, Roisin M. Coinçon, Mathieu; Tay, Stephanie; Heras, Begoña; Morton, Craig J.; Scanlon, Martin J.; Martin, Jennifer L.

    2015-11-26

    The crystal structure of a P. aeruginosa DsbA1 variant is more suitable for fragment-based lead discovery efforts to identify inhibitors of this antimicrobial drug target. In the reported structures the active site of the protein can simultaneously bind multiple ligands introduced in the crystallization solution or via soaking. Pseudomonas aeruginosa is an opportunistic human pathogen for which new antimicrobial drug options are urgently sought. P. aeruginosa disulfide-bond protein A1 (PaDsbA1) plays a pivotal role in catalyzing the oxidative folding of multiple virulence proteins and as such holds great promise as a drug target. As part of a fragment-based lead discovery approach to PaDsbA1 inhibitor development, the identification of a crystal form of PaDsbA1 that was more suitable for fragment-soaking experiments was sought. A previously identified crystallization condition for this protein was unsuitable, as in this crystal form of PaDsbA1 the active-site surface loops are engaged in the crystal packing, occluding access to the target site. A single residue involved in crystal-packing interactions was substituted with an amino acid commonly found at this position in closely related enzymes, and this variant was successfully used to generate a new crystal form of PaDsbA1 in which the active-site surface is more accessible for soaking experiments. The PaDsbA1 variant displays identical redox character and in vitro activity to wild-type PaDsbA1 and is structurally highly similar. Two crystal structures of the PaDsbA1 variant were determined in complex with small molecules bound to the protein active site. These small molecules (MES, glycerol and ethylene glycol) were derived from the crystallization or cryoprotectant solutions and provide a proof of principle that the reported crystal form will be amenable to co-crystallization and soaking with small molecules designed to target the protein active-site surface.

  5. Influence of quadrupolar interactions on the crystal packing of organic compounds: the pentafluorophenyl ester of a tricyclic α,β-unsaturated-γ-amino acid

    NASA Astrophysics Data System (ADS)

    Mann, Enrique; Mahía, José; Maestro, Miguel A.; Herradón, Bernardo

    2002-10-01

    The single crystal X-ray diffraction structure of (-)-pentafluorophenyl( Z, S, S)-2-(6-oxo-1,3,4,6,11,11a-hexahydro-2 H-pyrido[1,2- b]isoquinolin-11-yliden)acetate ( 1) is reported. We have found that the crystal packing of the α,β-unsaturated-γ-amino acid derivative 1 is mainly determined by the interaction between the two aromatic rings, namely the benzenic type and the pentafluorinated ring. The crystal packing of 1 shows a herringbone (zig-zag) structure, that is quite typical of aromatic compound with intermolecular arene-arene interactions. The benzenic and the fluorinated phenyl rings in 1 are in a matched face-to-face arrangement. The origin of this interaction can be ascribed to a favourably quadrupolar interaction between both types of aromatic ring. The results reported in the present paper indicate that the pentafluorophenyl ester functionality can be a useful building block in crystal engineering.

  6. Comparison of the simulations of cellulosic crystals with three carbohydrate force fields.

    PubMed

    Miyamoto, Hitomi; Schnupf, Udo; Crowley, Michael F; Brady, John W

    2016-03-01

    Three independently developed molecular mechanics force fields for carbohydrates have been used to simulate a suite of small molecule analogs of cellulose for which crystal structures have been reported, as a test to determine which might be best for simulations of cellulose itself. Such evaluation is necessary since the reported cellulose crystal structure is not stable in molecular dynamics simulations with any available force field. The present simulations found that all three resulted in small deviations from the reported crystal structures, but that all were reasonably accurate and none was clearly superior to the others for the entire suite of structures examined.

  7. Range of motion exercise of temporo-mandibular joint with hot pack increases occlusal force in patients with Duchenne muscular dystrophy.

    PubMed

    Nozaki, S; Kawai, M; Shimoyama, R; Futamura, N; Matsumura, T; Adachi, K; Kikuchi, Y

    2010-12-01

    The purpose of this study is to evaluate whether the range of motion exercise of the temporo-mandibular joint (jaw ROM exercise) with a hot pack and massage of the masseter muscle improve biting disorder in Duchenne muscular dystrophy (DMD). The subjects were 18 DMD patients (21.3+/- 4.1 years old). The jaw ROM exercise consisted of therapist-assisted training (2 times a week) and self-training (before each meal every day). The therapist-assisted training consisted of the application of a hot pack on the cheek of the masseter muscle region (15 minutes), the massage of the masseter (10 minutes), and jaw ROM exercise (5 minutes). The self-training involved jaw ROM exercise by opening the mouth to the maximum degree, ten times. These trainings continued for six months. Outcomes were evaluated by measuring the greatest occlusal force and the distance at the maximum degree of mouth opening between an incisor of the top and that of the bottom. Six months later, the greatest occlusal force had increased significantly compared with that at the start of jaw ROM exercise (intermediate values: from 73.8N to 97.3N) (p = 0.005) as determined by the Friedman test and Scheffi's nonparametric test. The patients' satisfaction with meals increased. However, the maximum degree of mouth opening did not change after six months of jaw ROM exercise. Jaw ROM exercise in DMD is effective for increasing the greatest occlusal force.

  8. Surface Polarity Of Beta-hmx Crystal And The Related Adhesive Forces With Estane Binder

    SciTech Connect

    Yang, Lu; Hanson, David E

    2008-01-01

    Here we present the results on the study of surface properties of {beta}-HMX crystal utilizing molecular simulations. The surface polarity of three principal crystal surfaces are investigated by measuring the water contact angles. The calculated contact angles agree excellently with the values measured by experiment and show that the surface polarity of three crystal surfaces are different. The free energies and forces of detaching an Estane chain with and without nitroplasticizer from the three principal crystal surfaces were calculated using umbrella sampling technique. We find that the detaching free energy/force increases with the increasing HMX surface polarity. In addition, our results also show that nitroplasticizer plays an important role in the adhesion forces between Estane and HMX surfaces.

  9. Dielectrophoretic and electrophoretic force analysis of colloidal fullerenes in a nematic liquid-crystal medium.

    PubMed

    Srivastava, Anoop Kumar; Kim, Miyoung; Kim, Sung Min; Kim, Mi-Kyung; Lee, Kyu; Lee, Young Hee; Lee, Myong-Hoon; Lee, Seung Hee

    2009-11-01

    This research focuses on the electrokinetic motion of fullerenes suspended in liquid crystal host medium, which are investigated in the homogeneously aligned nematic liquid crystal cells driven by in-plane field. We investigated the effect of electrophoretic and dielectrophoretic forces and related parameters of the colloidal fullerenes in liquid crystals. The electrophoretic mobility, zeta potential, and critical voltage have been evaluated. Fullerenes suspended in liquid crystal medium migrated toward the positive electrode, but were pulled back in the opposite direction when the polarity was reversed especially at low frequency range (<5 Hz) . At higher electric field and higher frequency ranges, the net displacement of fullerenes has been observed. We demonstrate that the dielectrophoretic force dominated the motion in the colloidal fullerenes by a proper analysis of different electrophoretic parameters. In addition, the electrodynamics of fullerenes was explained by applying the theory of the dielectrophoresis and Schwarz's formula. We propose a model to estimate the density of fullerenes suspended in liquid crystal medium.

  10. Chiral Asymmetric Structures in Aspartic Acid and Valine Crystals Assessed by Atomic Force Microscopy.

    PubMed

    Teschke, Omar; Soares, David Mendez

    2016-03-29

    Structures of crystallized deposits formed by the molecular self-assembly of aspartic acid and valine on silicon substrates were imaged by atomic force microscopy. Images of d- and l-aspartic acid crystal surfaces showing extended molecularly flat sheets or regions separated by single molecule thick steps are presented. Distinct orientation surfaces were imaged, which, combined with the single molecule step size, defines the geometry of the crystal. However, single molecule step growth also reveals the crystal chirality, i.e., growth orientations. The imaged ordered lattice of aspartic acid (asp) and valine (val) mostly revealed periodicities corresponding to bulk terminations, but a previously unreported molecular hexagonal lattice configuration was observed for both l-asp and l-val but not for d-asp or d-val. Atomic force microscopy can then be used to identify the different chiral forms of aspartic acid and valine crystals.

  11. Experimental analysis and computer simulation on stability margin and quench behaviour in a NbTi forced-flow cooled winding pack

    NASA Astrophysics Data System (ADS)

    Balsamo, E. P.; Bottura, L.; Cicchelli, O.; Gislon, P.; Ricci, M.; Spadoni, M.

    1994-07-01

    A significant amount (over 70 runs) of experimental data on stability margin and quench behavior in a two-dimensional, forced-flow cooled NbTi winding pack has been collected. The measurements performed over a wide range of operating conditions (operating current, field, and temperature) have been used as the experimental data-base for the comparison with the results of the simulations done using the quench analysis code SARUMAN. Here we present the results of the experimental and validation activities, which show that SARUMAN can successfully predict stability margin and quench propagation in a 3-D winding.

  12. Toward chaperone-assisted crystallography: Protein engineering enhancement of crystal packing and X-ray phasing capabilities of a camelid single-domain antibody (VHH) scaffold

    PubMed Central

    Tereshko, Valentina; Uysal, Serdar; Koide, Akiko; Margalef, Katrina; Koide, Shohei; Kossiakoff, Anthony A.

    2008-01-01

    A crystallization chaperone is an auxiliary protein that binds to a target of interest, enhances and modulates crystal packing, and provides high-quality phasing information. We critically evaluated the effectiveness of a camelid single-domain antibody (VHH) as a crystallization chaperone. By using a yeast surface display system for VHH, we successfully introduced additional Met residues in the core of the VHH scaffold. We identified a set of SeMet-labeled VHH variants that collectively produced six new crystal forms as the complex with the model antigen, RNase A. The crystals exhibited monoclinic, orthorhombic, triclinic, and tetragonal symmetry and have one or two complexes in the asymmetric unit, some of which diffracted to an atomic resolution. The phasing power of the Met-enriched VHH chaperone allowed for auto-building the entire complex using single-anomalous dispersion technique (SAD) without the need for introducing SeMet into the target protein. We show that phases produced by combining SAD and VHH model-based phases are accurate enough to easily solve structures of the size reported here, eliminating the need to collect multiple wavelength multiple-anomalous dispersion (MAD) data. Together with the presence of high-throughput selection systems (e.g., phage display libraries) for VHH, the enhanced VHH domain described here will be an excellent scaffold for producing effective crystallization chaperones. PMID:18445622

  13. Accurate force fields and methods for modelling organic molecular crystals at finite temperatures.

    PubMed

    Nyman, Jonas; Pundyke, Orla Sheehan; Day, Graeme M

    2016-06-21

    We present an assessment of the performance of several force fields for modelling intermolecular interactions in organic molecular crystals using the X23 benchmark set. The performance of the force fields is compared to several popular dispersion corrected density functional methods. In addition, we present our implementation of lattice vibrational free energy calculations in the quasi-harmonic approximation, using several methods to account for phonon dispersion. This allows us to also benchmark the force fields' reproduction of finite temperature crystal structures. The results demonstrate that anisotropic atom-atom multipole-based force fields can be as accurate as several popular DFT-D methods, but have errors 2-3 times larger than the current best DFT-D methods. The largest error in the examined force fields is a systematic underestimation of the (absolute) lattice energy.

  14. An optimized intermolecular force field for hydrogen-bonded organic molecular crystals using atomic multipole electrostatics

    PubMed Central

    Pyzer-Knapp, Edward O.; Thompson, Hugh P. G.; Day, Graeme M.

    2016-01-01

    We present a re-parameterization of a popular intermolecular force field for describing intermolecular interactions in the organic solid state. Specifically we optimize the performance of the exp-6 force field when used in conjunction with atomic multipole electrostatics. We also parameterize force fields that are optimized for use with multipoles derived from polarized molecular electron densities, to account for induction effects in molecular crystals. Parameterization is performed against a set of 186 experimentally determined, low-temperature crystal structures and 53 measured sublimation enthalpies of hydrogen-bonding organic molecules. The resulting force fields are tested on a validation set of 129 crystal structures and show improved reproduction of the structures and lattice energies of a range of organic molecular crystals compared with the original force field with atomic partial charge electrostatics. Unit-cell dimensions of the validation set are typically reproduced to within 3% with the re-parameterized force fields. Lattice energies, which were all included during parameterization, are systematically underestimated when compared with measured sublimation enthalpies, with mean absolute errors of between 7.4 and 9.0%. PMID:27484370

  15. An optimized intermolecular force field for hydrogen-bonded organic molecular crystals using atomic multipole electrostatics.

    PubMed

    Pyzer-Knapp, Edward O; Thompson, Hugh P G; Day, Graeme M

    2016-08-01

    We present a re-parameterization of a popular intermolecular force field for describing intermolecular interactions in the organic solid state. Specifically we optimize the performance of the exp-6 force field when used in conjunction with atomic multipole electrostatics. We also parameterize force fields that are optimized for use with multipoles derived from polarized molecular electron densities, to account for induction effects in molecular crystals. Parameterization is performed against a set of 186 experimentally determined, low-temperature crystal structures and 53 measured sublimation enthalpies of hydrogen-bonding organic molecules. The resulting force fields are tested on a validation set of 129 crystal structures and show improved reproduction of the structures and lattice energies of a range of organic molecular crystals compared with the original force field with atomic partial charge electrostatics. Unit-cell dimensions of the validation set are typically reproduced to within 3% with the re-parameterized force fields. Lattice energies, which were all included during parameterization, are systematically underestimated when compared with measured sublimation enthalpies, with mean absolute errors of between 7.4 and 9.0%. PMID:27484370

  16. Using Latex Balls and Acrylic Resin Plates to Investigate the Stacking Arrangement and Packing Efficiency of Metal Crystals

    ERIC Educational Resources Information Center

    Ohashi, Atsushi

    2015-01-01

    A high-school third-year or undergraduate first-semester general chemistry laboratory experiment introducing simple-cubic, face-centered cubic, body-centered cubic, and hexagonal closest packing unit cells is presented. Latex balls and acrylic resin plates are employed to make each atomic arrangement. The volume of the vacant space in each cell is…

  17. Molecular structure of 2-chloro-2'-deoxyadenosine an agent used in therapy for multiple sclerosis and its unusual crystal packing mode

    NASA Astrophysics Data System (ADS)

    Koellner, Gertraud; Kazimierczuk, Zygmunt; Steiner, Thomas; Kaminski, Jaroslaw

    1998-03-01

    The X-ray crystal structure of 2-chloro-2'-deoxyadenosine was determined at low temperature [space group orthorhombic P2 12 12, a = 7.493(6), b = 16.894(4), c = 9.065(4) → A, V = 1147.6(11) →A 3, 4097 unique reflections, R = 0.050]. The ribose unit is in 23T conformation, and the orientation around the Cl'-N glycosylic bond is syn with respect to the base. The 2-chloro-substitution leads to small but significant changes of the covalent geometry of the base at the substitution site, particularly to widening of the endocyclic angle at C2. The crystal packing is unusual foradenine nucleosides: molecules form stacks with parallel bases which are aligned by chains of short chlorine-chlorine contacts.

  18. Single-Crystal Diamond Nanowire Tips for Ultrasensitive Force Microscopy.

    PubMed

    Tao, Y; Degen, C L

    2015-12-01

    We report the fabrication, integration, and assessment of sharp diamond tips for ultrasensitive force microscopy experiments. Two types of tips, corresponding to the upper and lower halves of a diamond nanowire, were fabricated by top-down plasma etching from a single-crystalline substrate. The lower, surface-attached halves can be directly integrated into lithographically defined nanostructures, like cantilevers. The upper, detachable halves result in diamond nanowires with a tunable diameter (50-500 nm) and lengths of a few microns. Tip radii were around 10 nm and tip apex angles around 15°. We demonstrate the integration of diamond nanowires for use as scanning tips onto ultrasensitive pendulum-style silicon cantilevers. We find the noncontact friction and frequency jitter to be exceptionally low, with no degradation in the intrinsic mechanical quality factor (Q ≈ 130,000) down to tip-to-surface distances of about 10 nm. Our results are an encouraging step toward further improvement of the sensitivity and resolution of force-detected magnetic resonance imaging. PMID:26517172

  19. Tracking traction force changes of single cells on the liquid crystal surface.

    PubMed

    Soon, Chin Fhong; Tee, Kian Sek; Youseffi, Mansour; Denyer, Morgan C T

    2015-03-01

    Cell migration is a key contributor to wound repair. This study presents findings indicating that the liquid crystal based cell traction force transducer (LCTFT) system can be used in conjunction with a bespoke cell traction force mapping (CTFM) software to monitor cell/surface traction forces from quiescent state in real time. In this study, time-lapse photo microscopy allowed cell induced deformations in liquid crystal coated substrates to be monitored and analyzed. The results indicated that the system could be used to monitor the generation of cell/surface forces in an initially quiescent cell, as it migrated over the culture substrate, via multiple points of contact between the cell and the surface. Future application of this system is the real-time assaying of the pharmacological effects of cytokines on the mechanics of cell migration. PMID:25808839

  20. Tracking Traction Force Changes of Single Cells on the Liquid Crystal Surface

    PubMed Central

    Soon, Chin Fhong; Tee, Kian Sek; Youseffi, Mansour; Denyer, Morgan C. T.

    2015-01-01

    Cell migration is a key contributor to wound repair. This study presents findings indicating that the liquid crystal based cell traction force transducer (LCTFT) system can be used in conjunction with a bespoke cell traction force mapping (CTFM) software to monitor cell/surface traction forces from quiescent state in real time. In this study, time-lapse photo microscopy allowed cell induced deformations in liquid crystal coated substrates to be monitored and analyzed. The results indicated that the system could be used to monitor the generation of cell/surface forces in an initially quiescent cell, as it migrated over the culture substrate, via multiple points of contact between the cell and the surface. Future application of this system is the real-time assaying of the pharmacological effects of cytokines on the mechanics of cell migration. PMID:25808839

  1. Elasticity of two-dimensional crystals of polydisperse hard disks near close packing: Surprising behavior of the Poisson's ratio

    NASA Astrophysics Data System (ADS)

    Tretiakov, Konstantin V.; Wojciechowski, Krzysztof W.

    2012-05-01

    The equation of state, elastic constants, and Poisson's ratio of a crystalline two-dimensional polydisperse hard disk system were determined in the close packing limit. Monte Carlo simulations in the NpT ensemble with variable shape of the periodic box reveal that the pressure and elastic constants grow with increasing polydispersity. The equation of state and the bulk modulus are well described by the free volume approximation. The latter approximation fails, however, for the shear modulus. The simulations also show that the introduction of any amount of size polydispersity in the hard disk systems causes a discontinuous "jump" of the Poisson's ratio in the close packing limit from the value νδ=0 = 0.1308(22), obtained for equidiameter hard disks, to νδ>0 ≈ 1, estimated for the polydisperse disks.

  2. Kinetic Roughening and Energetics of Tetragonal Lysozyme Crystal Growth: A Preliminary Atomic Force Microscopy Investigation

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, Marc L.

    2004-01-01

    We examined particulars of crystal growth from measurements obtained at both microscopic and molecular levels. The crystal growth measurements performed at the microscopic level are well characterized by a model that balances the flux of macromolecules towards the crystal surface with the flux of the crystal surface. Numerical evaluation of model with measurements of crystal growth, in time, provided accurate estimates for the average growth velocities. Growth velocities thus obtained were also interpreted using well-established phenomenological theories. Moreover, we find that microscopic measurements of growth velocity measurements obtained as a function of temperature best characterizes changes in crystal growth modes, when present. We also examined the possibility of detecting a change in crystal growth modes at the molecular level using atomic force microscopy, AFM. From preliminary AFM measurements performed at various supersaturations, we find that magnitude of surface height fluctuations, h(x), increases with supersaturation. Further examination of surface height fluctuations using methods established for fluctuation spectroscopy also enabled the discovery of the existence of a characteristic length, c, which may possibly determine the mode of crystal growth. Although the results are preliminary, we establish the non- critical divergence of 5 and the root-mean-square (rms) magnitude of height-height fluctuations as the kinetic roughening transition temperatures are approached. Moreover, we also examine approximate models for interpreting the non-critical behavior of both 6 and rms magnitude of height-height fluctuations, as the solution supersaturation is increased towards the kinetic roughening supersaturation.

  3. Precise characterization of grain structures, stacking disorders, and lattice disorders of a close-packed colloidal crystal

    NASA Astrophysics Data System (ADS)

    Suzuki, Yoshihisa; Mori, Atsushi; Fujiwara, Takahisa; Tamura, Katsuhiro

    2011-05-01

    The perpendicular fracture surface of a dried colloidal crystal with pillar-like grains, obtained by centrifugation of a dispersion of polystyrene particles, was observed using a scanning electron microscope. Many grain boundaries on the fracture surface were observed at the particle level. Most of the particles on the surface showed a face-centered cubic (FCC) array. Although some grains were single FCC ones, other FCC grains contained some stacking disorders. Most of the surface was covered with such grains, and the grain boundaries formed a mosaic-like pattern. From these results, we confirmed that the colloidal crystals obtained by centrifugation formed a bundle structure of pillar-like FCC grains. A fracture surface adjacent to the side wall of the growth cell was also observed. The surface was composed of several layers. In the uppermost layer closest to the wall, numerous point defects and mismatches of triangular lattices between the neighboring two-dimensional islands were observed. These mismatches and point defects probably generated several lattice defects in the crystal. Similar generation of lattice defects probably occurred at the bottom of the container or the growth front of the crystals. Screw dislocations were also found in the layers, although they were not observed frequently. From these results, it was concluded that two-dimensional nucleation growth and spiral growth probably occurred on the crystal-dispersion interfaces of colloidal crystals as well as on the surface of atomic crystals.

  4. Enzymatic degradation of poly(L-lactide) film by proteinase K: quartz crystal microbalance and atomic force microscopy study.

    PubMed

    Yamashita, Koichi; Kikkawa, Yoshihiro; Kurokawa, Kenji; Doi, Yoshiharu

    2005-01-01

    Enzymatic degradation of the poly(L-lactide) (PLLA) amorphous film by proteinase K has been investigated by combination of the complementary techniques of quartz crystal microbalance and atomic force microscopy (AFM). The erosion rate increased with increasing enzyme concentrations and attained to be constant under the condition of [proteinase K] > 100 microg/mL. The amount of the enzyme molecules adsorbed to the film was quantitatively evaluated at various concentrations by AFM, and it revealed that the erosion rate is determined by the amount of adsorbed enzyme. Adsorption of proteinase K was irreversible despite lack of the binding domain, so that the enzyme molecules on the film surface could be observed directly by AFM. Transformation of the enzyme molecule caused by packing in high density on the surface was observed at higher enzyme concentrations. The "footprint" of the individual proteinase K molecule on the PLLA film after enzymatic degradation suggests that the enzyme moves on the surface to hydrolyze the film around it.

  5. Inducing forced and auto oscillations in one-dimensional photonic crystals with light

    NASA Astrophysics Data System (ADS)

    Lugo, J. E.; Doti, Rafael; Sanchez, Noemi; Faubert, Jocelyn

    2014-09-01

    We induced forced and auto oscillations in one-dimensional photonic crystals with localized defects when light impinges transversally to the defect layer. The photonic structure consists of a microcavity like structure formed of two onedimensional photonic crystals made of free-standing porous silicon, separated by variable air gap and the working wavelength is 633 nm. The force generation is made evident by driving a laser light by means of a chopper; the light hits the photonic structure and induces a vibration and the vibration is characterized by using a very sensitive vibrometer. Moreover we measured peak displacements and velocities ranging from 2 up to 35 microns and 0.4 up to 2.1 mm/s with a power of 13 mW. Recent evidence showed that giant resonant light forces could induce average velocity values of 0.45 mm/s in microspheres embedded in water with 43 mW light power.

  6. Theoretical and experimental study of electromagnetic forces induced in one-dimensional photonic crystals

    NASA Astrophysics Data System (ADS)

    Lugo, J. E.; Doti, Rafael; Faubert, Jocelyn; Sanchez, Noemi; Sanchez, Javier; Palomino, Martha A.; de la Mora, M. Beatriz; del Rio, J. Antonio

    2013-10-01

    We studied theoretically and experimentally the induction of electromagnetic forces in one-dimensional photonic crystals with localized defects when light impinges transversally to the defect layer. The theoretical calculations indicate that the electromagnetic forces increases at a certain frequency that coincide with a defect photonic state. The photonic structure consists of a microcavity like structure formed of two one-dimensional photonic crystals made of free-standing porous silicon, separated by variable air gap and the working wavelength is 633 nm. The force generation is made evident by driving a laser light by means of a chopper; the light hits the photonic structure and induces a vibration and the vibration is characterized by using a very sensitive vibrometer.

  7. Investigation of anchoring transition of liquid crystals on crown ether monolayers by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Dong, Xiao; Yang, Xiaomin; Zhu, Yangming; Lu, Zuhong; Wei, Yu

    1994-10-01

    The homeotropic and homogeneous alignment of a liquid crystal material, 4'-n-pentyl-4-cyanobiphenyl (5CB), were achieved by Langmuir monolayers of a double-armed crown ether liquid crystal, N,N-bis(4-(4-heptoxybenzoyloxy)benzo-yl)-1,10-diaza-4,7,13,16- tetracyclooxaotad ecane (CELC) . We found that when the monolayer was deposited before the phase transition during monolayer compression, it induced liquid crystal alignment homogeneously; when the monolayer was transferred after the transition, homeotropic liquid crystal alignment was produced. Atomic force microscopy was used to examine the morphology and microstructure of the alignment agent. The results show a conformational change of the alignment agent before and after the transition. The anchoring transition is interpreted as the result of orientational change of the CELC monolayer. We present strong evidence that the orientational change of dipoles in the alignment agent can induce an anchoring transition.

  8. Impact of molecular packing on electronic polarization in organic crystals: the case of pentacene vs TIPS-pentacene.

    PubMed

    Ryno, Sean M; Risko, Chad; Brédas, Jean-Luc

    2014-04-30

    Polarization energy corresponds to the stabilization of the cation or anion state of an atom or molecule when going from the gas phase to the solid state. The decrease in ionization energy and increase in electron affinity in the solid state are related to the (electronic and nuclear) polarization of the surrounding atoms and molecules in the presence of a charged entity. Here, through a combination of molecular mechanics and quantum mechanics calculations, we evaluate the polarization energies in two prototypical organic semiconductors, pentacene and 6,13-bis(2-(tri-isopropylsilyl)ethynyl)pentacene (TIPS-pentacene). Comparison of the results for the two systems reveals the critical role played by the molecular packing configurations in the determination of the polarization energies and provides physical insight into the experimental data reported by Lichtenberger and co-workers (J. Amer. Chem. Soc. 2010, 132, 580; J. Phys. Chem. C 2010, 114, 13838). Our results underline that the impact of packing configurations, well established in the case of the charge-transport properties, also extends to the polarization properties of π-conjugated materials. PMID:24725006

  9. Simulations of wave propagation and disorder in 3D non-close-packed colloidal photonic crystals with low refractive index contrast.

    PubMed

    Glushko, O; Meisels, R; Kuchar, F

    2010-03-29

    The plane-wave expansion method (PWEM), the multiple-scattering method (MSM) and the 3D finite-difference time-domain method (FDTD) are applied for simulations of propagation of electromagnetic waves through 3D colloidal photonic crystals. The system investigated is not a "usual" artificial opal with close-packed fcc lattice but a dilute bcc structure which occurs due to long-range repulsive interaction between electrically charged colloidal particles during the growth process. The basic optical properties of non-close-packed colloidal PhCs are explored by examining the band structure and reflection spectra for a bcc lattice of silica spheres in an aqueous medium. Finite size effects and correspondence between the Bragg model, band structure and reflection spectra are discussed. The effects of size, positional and missing-spheres disorder are investigated. In addition, by analyzing the results of experimental work we show that the fabricated structures have reduced plane-to-plane distance probably due to the effect of gravity during growth.

  10. Dielectrophoretic and electrophoretic force analysis of colloidal fullerenes in a nematic liquid-crystal medium

    NASA Astrophysics Data System (ADS)

    Srivastava, Anoop Kumar; Kim, Miyoung; Kim, Sung Min; Kim, Mi-Kyung; Lee, Kyu; Lee, Young Hee; Lee, Myong-Hoon; Lee, Seung Hee

    2009-11-01

    This research focuses on the electrokinetic motion of fullerenes suspended in liquid crystal host medium, which are investigated in the homogeneously aligned nematic liquid crystal cells driven by in-plane field. We investigated the effect of electrophoretic and dielectrophoretic forces and related parameters of the colloidal fullerenes in liquid crystals. The electrophoretic mobility, zeta potential, and critical voltage have been evaluated. Fullerenes suspended in liquid crystal medium migrated toward the positive electrode, but were pulled back in the opposite direction when the polarity was reversed especially at low frequency range (<5Hz) . At higher electric field and higher frequency ranges, the net displacement of fullerenes has been observed. We demonstrate that the dielectrophoretic force dominated the motion in the colloidal fullerenes by a proper analysis of different electrophoretic parameters. In addition, the electrodynamics of fullerenes was explained by applying the theory of the dielectrophoresis and Schwarz’s formula. We propose a model to estimate the density of fullerenes suspended in liquid crystal medium.

  11. Control of liquid crystal alignment by polyimide surface modification using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Pidduck, A. J.; Haslam, S. D.; Bryan-Brown, G. P.; Bannister, R.; Kitely, I. D.

    1997-11-01

    Atomic force microscopy (AFM) has been used to modify a polyimide surface to give controlled liquid crystal (LC) alignment, and to examine the modification produced. Strong LC azimuthal anchoring was observed typically for normal forces >300 nN and line densities >5 μm-1, and optically diffracting LC elements were fabricated by repeatedly overpatterning the same area along different directions. Atomic force microscopy images showed little sign of topographic modification such as grooving, whereas lateral force images showed locally increased friction. Estimated contact pressures, 0.08-0.3 GPa, suggest shear-yielding occurs within a surface layer, causing polymer chain alignment. The AFM micromechanical interaction is compared with that occurring during the conventional cloth-rubbing LC alignment process.

  12. Solid state synthesis, crystal growth, atomic packing and physicochemical studies of (E)-2-cyano-3-(3-hydroxyphenyl)acrylamide

    NASA Astrophysics Data System (ADS)

    Gupta, V. K.; Rai, R. N.; Inbanathan, S. S. R.; Fleck, M.

    2013-02-01

    The organic crystalline species (E)-2-cyano-3-(3-hydroxyphenyl)acrylamide has been synthesized by solid state reaction between 3-hydroxy benzaldehyde (HB) and 2-cyanoacetamide (CA). The molar ratio of HB and CA forming this new organic entity was found to be 1:1, established with the help of phase diagram study and single crystal XRD analysis. The phase diagram established between HB and CA shows the formation of a new compound surrounded by two eutectics on either side of the compound. Thermal properties such as heat of fusion, entropy of fusion, interfacial energy, and excess thermodynamic functions of the title compound and both eutectics are studied and reported, in addition to a DSC study to analyze the thermal behavior. A large and transparent single crystal with dimensions of 19×7×2 mm3 of this newly synthesized compound was grown from the saturated solution of a mixed solvent, employing the slow cooling technique. The single crystal X-ray diffraction analysis showed that the compound crystallizes in the monoclinic system (space group P21/n) with a=9.031(2) Å, b=5.178(2) Å, c=18.330(4) Å, and β=90.86(3)° and comprises dimers of symmetry-related molecules, connected to each other via strong OH···O bonds.

  13. Crystal growth of a layered silicate clay mineral as revealed by atomic force microscopy

    SciTech Connect

    Carrado, K.A.; Song, Kang; Zajac, G.W.

    1997-12-31

    Non-contact atomic force microscopy, commonly referred to as {open_quotes}tapping mode{close_quotes} AFM, has been used to scan primarily the morphological features of growing hectorite clay crystallites synthesized in the presence of organo-ammonium cations. The use of such cations allows larger crystals to form in this system, making study by AFM feasible. This is the first time that actual temporal {open_quotes}snapshots{close_quotes} of a clay`s nucleation and crystallization processes have been presented. The observed view does not support the perhaps predicted scene of small crystallites slowly ripening into larger and larger plates. Instead, larger and larger aggregates appear to coalesce from a larger number of small crystallites that are closely associated in globular networks similar in appearance to {open_quotes}strings of pearls{close_quotes} at the initial stages of crystallization.

  14. Nature of packs used in propellant modeling.

    PubMed

    Maggi, F; Stafford, S; Jackson, T L; Buckmaster, J

    2008-04-01

    In recent years we have constructed closely packed spheres using the Lubachevsky-Stillinger algorithm to generate morphological models of heterogeneous solid propellants. Improvements to the algorithm now allow us to create large polydisperse packs on a laptop computer, and to create monodisperse packs with packing fractions greater than 70% which display significant crystal order. The use of these models in the physical context motivates efforts to examine in some detail the nature of the packs, including certain statistical properties. We compare packing fractions for binary packs with long-known experimental data. Also, we discuss the near-neighbor number and the radial distribution function (RDF) for monodisperse packs and make comparisons with experimental data. We also briefly discuss the RDF for bidisperse packs. We also consider bounded monodisperse packs, and pay particular attention to the near-wall structure where we identify significant order.

  15. Understanding shape entropy through local dense packing.

    PubMed

    van Anders, Greg; Klotsa, Daphne; Ahmed, N Khalid; Engel, Michael; Glotzer, Sharon C

    2014-11-11

    Entropy drives the phase behavior of colloids ranging from dense suspensions of hard spheres or rods to dilute suspensions of hard spheres and depletants. Entropic ordering of anisotropic shapes into complex crystals, liquid crystals, and even quasicrystals was demonstrated recently in computer simulations and experiments. The ordering of shapes appears to arise from the emergence of directional entropic forces (DEFs) that align neighboring particles, but these forces have been neither rigorously defined nor quantified in generic systems. Here, we show quantitatively that shape drives the phase behavior of systems of anisotropic particles upon crowding through DEFs. We define DEFs in generic systems and compute them for several hard particle systems. We show they are on the order of a few times the thermal energy ([Formula: see text]) at the onset of ordering, placing DEFs on par with traditional depletion, van der Waals, and other intrinsic interactions. In experimental systems with these other interactions, we provide direct quantitative evidence that entropic effects of shape also contribute to self-assembly. We use DEFs to draw a distinction between self-assembly and packing behavior. We show that the mechanism that generates directional entropic forces is the maximization of entropy by optimizing local particle packing. We show that this mechanism occurs in a wide class of systems and we treat, in a unified way, the entropy-driven phase behavior of arbitrary shapes, incorporating the well-known works of Kirkwood, Onsager, and Asakura and Oosawa.

  16. Understanding shape entropy through local dense packing.

    PubMed

    van Anders, Greg; Klotsa, Daphne; Ahmed, N Khalid; Engel, Michael; Glotzer, Sharon C

    2014-11-11

    Entropy drives the phase behavior of colloids ranging from dense suspensions of hard spheres or rods to dilute suspensions of hard spheres and depletants. Entropic ordering of anisotropic shapes into complex crystals, liquid crystals, and even quasicrystals was demonstrated recently in computer simulations and experiments. The ordering of shapes appears to arise from the emergence of directional entropic forces (DEFs) that align neighboring particles, but these forces have been neither rigorously defined nor quantified in generic systems. Here, we show quantitatively that shape drives the phase behavior of systems of anisotropic particles upon crowding through DEFs. We define DEFs in generic systems and compute them for several hard particle systems. We show they are on the order of a few times the thermal energy ([Formula: see text]) at the onset of ordering, placing DEFs on par with traditional depletion, van der Waals, and other intrinsic interactions. In experimental systems with these other interactions, we provide direct quantitative evidence that entropic effects of shape also contribute to self-assembly. We use DEFs to draw a distinction between self-assembly and packing behavior. We show that the mechanism that generates directional entropic forces is the maximization of entropy by optimizing local particle packing. We show that this mechanism occurs in a wide class of systems and we treat, in a unified way, the entropy-driven phase behavior of arbitrary shapes, incorporating the well-known works of Kirkwood, Onsager, and Asakura and Oosawa. PMID:25344532

  17. Atomic force microscopy of crystalline insulins: the influence of sequence variation on crystallization and interfacial structure.

    PubMed Central

    Yip, C M; Brader, M L; DeFelippis, M R; Ward, M D

    1998-01-01

    The self-association of proteins is influenced by amino acid sequence, molecular conformation, and the presence of molecular additives. In the presence of phenolic additives, LysB28ProB29 insulin, in which the C-terminal prolyl and lysyl residues of wild-type human insulin have been inverted, can be crystallized into forms resembling those of wild-type insulins in which the protein exists as zinc-complexed hexamers organized into well-defined layers. We describe herein tapping-mode atomic force microscopy (TMAFM) studies of single crystals of rhombohedral (R3) LysB28ProB29 that reveal the influence of sequence variation on hexamer-hexamer association at the surface of actively growing crystals. Molecular scale lattice images of these crystals were acquired in situ under growth conditions, enabling simultaneous identification of the rhombohedral LysB28ProB29 crystal form, its orientation, and its dynamic growth characteristics. The ability to obtain crystallographic parameters on multiple crystal faces with TMAFM confirmed that bovine and porcine insulins grown under these conditions crystallized into the same space group as LysB28ProB29 (R3), enabling direct comparison of crystal growth behavior and the influence of sequence variation. Real-time TMAFM revealed hexamer vacancies on the (001) terraces of LysB28ProB29, and more rounded dislocation noses and larger terrace widths for actively growing screw dislocations compared to wild-type bovine and porcine insulin crystals under identical conditions. This behavior is consistent with weaker interhexamer attachment energies for LysB28ProB29 at active growth sites. Comparison of the single crystal x-ray structures of wild-type insulins and LysB28ProB29 suggests that differences in protein conformation at the hexamer-hexamer interface and accompanying changes in interhexamer bonding are responsible for this behavior. These studies demonstrate that subtle changes in molecular conformation due to a single sequence

  18. Layering, melting, and recrystallization of a close-packed micellar crystal under steady and large-amplitude oscillatory shear flows

    SciTech Connect

    López-Barrón, Carlos R.; Wagner, Norman J.; Porcar, Lionel

    2015-05-15

    The rheology and three-dimensional microstructure of a concentrated viscoelastic solution of the triblock copolymer poly(ethylene oxide){sub 106}-poly(propylene oxide){sub 68}-poly(ethylene oxide){sub 106} (Pluronic F127) in the protic ionic liquid ethylammonium nitrate are measured by small angle neutron scattering (SANS) under flow in three orthogonal planes. This solution's shear-thinning viscosity is due to the formation of two-dimensional hexagonal close-packed (HCP) sliding layer structure. Shear-melting of the crystalline structure is observed without disruption of the self-assembled micelles, resulting in a change in flow properties. Spatially resolved measurements in the 1–2 plane reveal that both shear-melting and sliding are not uniform across the Couette gap. Melting and recrystallization of the HCP layers occur cyclically during a single large amplitude oscillatory shear (LAOS) cycle, in agreement with the “stick-slip” flow mechanism proposed by Hamley et al. [Phys. Rev. E 58, 7620–7628 (1998)]. Analysis of 3D “structural” Lissajous curves show that the cyclic melting and sliding are direct functions of the strain rate amplitude and show perfect correlation with the cyclic stress response during LAOS. Both viscosity and structural order obey the Delaware–Rutgers rule. Combining rheology with in situ spatiotemporally resolved SANS is demonstrated to elucidate the structural origins of the nonlinear rheology of complex fluids.

  19. Simultaneous measurements of molecular forces and electro-optical properties of a confined 5CB liquid crystal film using a surface forces apparatus.

    PubMed

    Kristiansen, Kai; Zeng, Hongbo; Zappone, Bruno; Israelachvili, Jacob N

    2015-04-01

    Using a surface forces apparatus (SFA), we studied the forces associated with the reorientation of molecules of a common nematic thermotropic liquid crystal, 4'-n-pentyl-4-cyanobiphenyl (5CB), confined between two conducting (silver) surfaces and its optical behavior under the influence of electric fields with varying magnitudes and field directions. A transient attractive force was observed due to partial reorientations of the liquid crystal molecules and the flow of free ions, in addition to a stronger constant capacitance attraction between the silver surfaces. At the same time, the optical properties of the liquid crystals were observed perpendicular to the silver surfaces. Observations of shifts and fluctuations of the extraordinary wave of the (multiple beam) interference fringes measure the refractive index of the director component parallel to the surface, which is sensitive to tilt motion (or reorientation) of the liquid crystal molecules that provided details of the anisotropic orientations of the molecules and domains. Any lateral differential refractive index change is easily observed by optical microscopy. The optical microscope imaging showed that the changes in the optical properties are due to convective flow at domain boundaries of the liquid crystal molecules (and possible free ions) between the two charged surfaces. At low electric fields, propagation of domain boundaries was observed, while at higher electric fields, hexagonal patterns of flowing molecules were observed. The interplay of the force measurements and optical observations reveal a complex dynamic behavior of liquid crystals subjected to varying electric fields in confined spaces.

  20. Crystals in which some metal atoms are more equal than others: inequalities from crystal packing and their spectroscopic/magnetic consequences.

    PubMed

    Nippe, Michael; Wang, Jingfang; Bill, Eckhard; Hope, Håkon; Dalal, Naresh S; Berry, John F

    2010-10-13

    Crystal structures of the heterometallic compounds CrCrFe(dpa)(4)Cl(2) (1), CrCrMn(dpa)(4)Cl(2) (2), and MoMoMn(dpa)(4)Cl(2) (3) (dpa = 2,2'-dipyridylamide) show disorder in the metal atom positions such that the linear M(A)[quadruple bond]M(A)···M(B) array for a given molecule in the crystal is oriented in one of two opposing directions. Despite the fact that the direct coordination sphere of the metals in the two crystallographically independent orientations is identical, subtle differences in some metal-ligand bond distances are observed in 1 and 3 due to differences in the orientation of a solvent molecule of crystallization. The Fe(II) and Mn(II) ions serve as sensitive local spectroscopic probes that have been interrogated by Mössbauer spectroscopy and high-field EPR spectroscopy, respectively. The subtle differences in the two independent Fe and Mn sites in 1 and 3 unexpectedly give rise to unusually large differences in the measured Fe quadrupole splitting (ΔE(Q)) in 1 and Mn zero-field splitting (D) in 3. Variable-temperature/single-crystal EPR spectroscopy has allowed us to determine that the temperature-dependent D tensors in 3 are oriented along the metal-metal axis and that they show significantly different dynamic behavior with temperature. The differences in ΔE(Q) and D are reproduced by density functional calculations on truncated models for 1 and 3 that lack the quadruply bonded M(A)[quadruple bond]M(A) groups, though the magnitude of the calculated effect is not as large as that observed experimentally. We suggest that the large observed differences in ΔE(Q) and D for the individual sites could be due to the influence of the strong diamagnetic anisotropy of the quadruply bonded M[quadruple bond]M unit.

  1. Sub-nanometer resolution of an organic semiconductor crystal surface using friction force microscopy in water.

    PubMed

    Pimentel, Carlos; Varghese, Shinto; Yoon, Seong-Jun; Park, Soo Young; Gierschner, Johannes; Gnecco, Enrico; Pina, Carlos M

    2016-04-01

    Organic semiconductors (OSC) are attracting much interest for (opto)electronic applications, such as photovoltaics, LEDs, sensors or solid state lasers. In particular, crystals formed by small π-conjugated molecules have shown to be suitable for constructing OSC devices. However, the (opto)electronic properties are complex since they depend strongly on both the mutual orientation of molecules as well as the perfection of bulk crystal surfaces. Hence, there is an urgent need to control nano-topographic OSC features in real space. Here we show that friction force microscopy in water is a very suitable technique to image the free surface morphology of an OSC single crystal (TDDCS) with sub-nanometer resolution. We demonstrate the power of the method by direct correlation to the structural information extracted from combined single crystal (SC-) and specular (s-) XRD studies, which allows us to identify the pinning centers encountered in the stick-slip motion of the probing tip with the topmost methyl groups on the TDDCS surface.

  2. Sub-nanometer resolution of an organic semiconductor crystal surface using friction force microscopy in water.

    PubMed

    Pimentel, Carlos; Varghese, Shinto; Yoon, Seong-Jun; Park, Soo Young; Gierschner, Johannes; Gnecco, Enrico; Pina, Carlos M

    2016-04-01

    Organic semiconductors (OSC) are attracting much interest for (opto)electronic applications, such as photovoltaics, LEDs, sensors or solid state lasers. In particular, crystals formed by small π-conjugated molecules have shown to be suitable for constructing OSC devices. However, the (opto)electronic properties are complex since they depend strongly on both the mutual orientation of molecules as well as the perfection of bulk crystal surfaces. Hence, there is an urgent need to control nano-topographic OSC features in real space. Here we show that friction force microscopy in water is a very suitable technique to image the free surface morphology of an OSC single crystal (TDDCS) with sub-nanometer resolution. We demonstrate the power of the method by direct correlation to the structural information extracted from combined single crystal (SC-) and specular (s-) XRD studies, which allows us to identify the pinning centers encountered in the stick-slip motion of the probing tip with the topmost methyl groups on the TDDCS surface. PMID:26931487

  3. Cofacial Versus Coplanar Arrangement in Centrosymmetric Packing Dimers of Dipolar Small Molecules: Structural Effects on the Crystallization Behaviors and Optoelectronic Characteristics.

    PubMed

    Chou, Shu-Hua; Kang, Hao-Wei; Chang, Shu-Ting; Wu, Kuan-Yi; Bazan, Guillermo C; Wang, Chien-Lung; Lin, Hong-Lin; Chang, Jung-Hao; Lin, Hao-Wu; Huang, Yu-Ching; Tsao, Cheng-Si; Wong, Ken-Tsung

    2016-07-20

    Two D-π-A-A molecules (MIDTP and TIDTP) composed of an electron-rich ditolylamino group (D) and an electron-deficient 5-dicyanovinylenylpyrimidine (A-A) fragment bridged together with indeno[1,2-b]thiophene (IDT) were synthesized. These molecules provide an opportunity to examine in-depth the impact of side-chain variations (methyl vs p-tolyl) on the crystallization behaviors, solid-state morphology, physical properties, and optoelectronic characteristics relevant for practical applications. X-ray analyses on single-crystal structures indicate that methyl-substituted MIDTP forms "coplanar antiparallel dimers" via C-H···S interactions and organizes into an ordered slip-staircase arrays. In contrast, p-tolyl-bearing TIDTP shows "cofacial centrosymmetric dimers" via π-π interactions and packs into a less-ordered layered structures. The X-ray diffraction analyses upon thermal treatment are consistent with a superior crystallinity of MIDTP, as compared to that of TIDTP. This difference indicates a greater propensity to organization by introduction of the smaller methyl group versus the bulkier p-tolyl group. The increased propensity for order by MIDTP facilitates the crystallization of MIDTP in both solution-processed and vacuum-deposited thin films. MIDTP forms solution-processed single-crystal arrays that deliver OFET hole mobility of 6.56 × 10(-4) cm(2) V(-1) s(-1), whereas TIDTP only forms amorhpous films that gave lower hole mobility of 1.34 × 10(-5) cm(2) V(-1) s(-1). MIDTP and TIDTP were utilized to serve as donors together with C70 as acceptor in the fabrication of small-molecule organic solar cells (SMOSCs) with planar heterojunction (PHJ) or planar-mixed heterojunction (PMHJ) device architectures. OPV devices based on higher crystalline MIDTP delivered power conversion efficiencies (PCEs) of 2.5% and 4.3% for PHJ and PMHJ device, respectively, which are higher than those of TIDTP-based cells. The improved PCEs of MIDTP-based devices are attributed to

  4. Atomic force microscopy of AgBr crystals and adsorbed gelatin films

    SciTech Connect

    Haugstad, G.; Gladfelter, W.L.; Keyes, M.P.; Weberg, E.B.

    1993-06-01

    Atomic force microscopy of the (111) surface of macroscopic AgBr crystals revealed steps ranging in height from two atomic layers up to 10 nm, lying predominantly along the (110) and (112) families of crystal directions. Rods of elemental Ag, formed via photoreduction, were observed along the (110) family of directions. Images of adsorbed gelatin films revealed circular pores with diameters of order 10-100 nm, extending to the AgBr surface. The length of deposition time, the pH and concentration of the gelatin solution, and the presence of steps on the AgBr surface were observed to affect the size, number, and location of pores in the gelatin films. 12 refs., 7 figs.

  5. Single-crystal diamond pyramids: synthesis and application for atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Tuyakova, Feruza T.; Obraztsova, Ekaterina A.; Ismagilov, Rinat R.

    2016-03-01

    Here we present the results of investigations aimed at the development and testing of robust, chemically inert single-crystal diamond probes for atomic force microscopy (AFM). The probes were prepared by assembling common silicon probes with micrometer-sized pyramid-shaped single-crystal diamonds (SCD). The SCD were obtained by the selective thermal oxidation of the polycrystalline films grown by chemical vapor deposition. Electrostatic spray of adhesive coating onto silicon probes was used to attach individual SCD. Geometrical parameters of produced AFM SCD probes were revealed with transmission electron microscopy: the apex angle of the pyramidal diamond crystallite was ˜10 deg, and the curvature radius at the apex was ˜2 to 10 nm. The diamond AFM probes were used for surface imaging of deoxyribonucleic acid deposited on graphite substrate. Obtained results demonstrate high efficiency of the diamond AFM probes, allowing improvement of the image quality compared to standard silicon probes.

  6. Alignment Control of Liquid Crystals Using Conductive Atomic Force Microscopy Nanolithography

    NASA Astrophysics Data System (ADS)

    Lin, Tzu-Chieh; Chao, Chih-Yu

    2008-06-01

    Conductive atomic force microscopy (CAFM) nanolithography was used to modify a silicon surface. This approach generating the silicon oxide grating by CAFM gives a control of liquid crystal (LC) alignment in the micron or submicron region. It establishes a pixel with a smaller size to achieve high-resolution images. Compared with the conventional cloth rubbing and AFM scratching techniques, the CAFM nanolithography prevents scratching damage, dust contamination and residual static electricity problems. Furthermore, this inorganic alignment method can also avoid the damage caused by UV light exposure and high-temperature environment.

  7. Vitamin K 3 family members - Part II: Single crystal X-ray structures, temperature-induced packing polymorphism, magneto-structural correlations and probable anti-oncogenic candidature

    NASA Astrophysics Data System (ADS)

    Rane, Sandhya; Ahmed, Khursheed; Salunke-Gawali, Sunita; Zaware, Santosh B.; Srinivas, D.; Gonnade, Rajesh; Bhadbhade, Mohan

    2008-12-01

    Temperature-induced packing polymorphism is observed for vitamin K 3 (menadione, 3-methyl-1,4-naphthoquinone, 1). Form 1a crystallizes at 300 K and 1b at 277 K both in the same space group P2 1/ c. Form 1b contains one molecule per asymmetric unit, performing anisotropy in g-factor viz. g z = 2.0082, g y = 2.0055 and g x = 2.0025, whereas form 1a contains two molecules in its asymmetric unit. Vitamin K 3 family members 2, [2-hydroxy vitamin K 3] and 3, [2-hydroxy-1-oximino vitamin K 3] also perform intrinsic neutral active naphthosemiquinone valence tautomers even in dark having spin concentrations due to hydrogen bonding and aromatic stacking interactions which are compared to vitamin K 3. The significant lateral C-H⋯O and O-H⋯π bifurcated or π-π ∗ interactions are discussed for molecular associations and radical formations. X-ray structure of 3 revealed π-π ∗ stack dimers as radicals signatured in EPR as triplet with five hyperfine splits [ Ā( 14N) = 11.9 G]. The centrosymmetric biradicals in 3 show diamagnetism at high temperature but below 10 K it shows paramagnetism with μeff as 0.19 B.M. Vitamin K 3 and its family members inhibit biological activities of acid phosphatase ( APase), which are proportional to their spin concentrations. This may relate to their probable anti-oncogenic candidature in future.

  8. Study of flow in a smectic liquid crystal in the X-ray Surface Forces Apparatus

    SciTech Connect

    Idziak, S.H.J.; Koltover, I.; Israelachvilli, J.N.; Safinya, C.R.; Liang, K.S.

    1995-03-01

    We describe the newly invented X-ray Surface Forces Apparatus (X-SFA) which allows the simultaneous measurement of forces and collective structures of confined complex fluids under static and flow conditions. The structure of the smectic liquid crystal 8CB (4-cyano-4{prime}-octylbiphenyl) confined between two mica surfaces with separation ranging from 4000 to 20,000 {angstrom} was measured. At small gaps and no shear, the smectic layers take on distinct stable orientations, including the bulk forbidden {open_quotes}b{close_quotes} orientation, which persist under low shear ({dot {gamma}} {<=} 30 s{sup -1}). However, at higher shear rates ({dot {gamma}} = 360 s{sup -1}), the shear acts to dramatically order and align the smectic layers into a single {open_quotes}a{close_quotes} orientation.

  9. In-Situ Hot Stage Atomic Force Microscopy Study of Poly(E-Caprolactone) Crystal Growth in Ultrathin Films

    NASA Astrophysics Data System (ADS)

    Prud'Homme, Robert E.; Mareau, Vincent H.

    2005-03-01

    Morphologies, growth rates and melting of isothermally crystallized ultrathin (200 to 1 nm) poly(e-caprolactone) (PCL) films have been investigated in real-time by atomic force microscopy. The flat-on orientation of the lamellar crystals relative to the substrate was determined by electron diffraction. The truncated lozenge shape PCL crystals observed at low undercooling become distorted for films of thicknesses equal or thinner than the lamellar thickness, which depends on the crystallization temperature but not on the initial film thickness. The melting behavior of distorted crystals differs from that of undistorted ones, and their growth is slower and non-linear. The crystal growth rate decreases greatly with the film thickness. All these observations are discussed in terms of the diffusion of the polymer chains from the melt to the crystal growth front.

  10. Growth of semicarbazone of benzophenone single crystals

    NASA Astrophysics Data System (ADS)

    Vijayan, N.; Ramesh Babu, R.; Gopalakrishnan, R.; Dhanuskodi, S.; Ramasamy, P.

    2002-03-01

    Semicarbazone of benzophenone single crystals have been grown by slow evaporation solution growth technique. The grown crystals have been characterized using XRD, melting point, FT-IR and UV-Vis spectra analyses. The X-ray diffraction analysis reveals that the crystal belongs to the triclinic crystal system and space group P1. From FT-IR studies it is found that the compound possesses both free and hydrogen bonded N-H stretching modes. The hydrogen bonded N-H stretching mode is found to be the major driving force for packing of molecules in the crystals. The transparency of the grown crystals has been confirmed using UV-Vis spectra.

  11. Inducing forced and auto-oscillations in one-dimensional photonic crystals with light

    NASA Astrophysics Data System (ADS)

    Lugo, J. Eduardo; Doti, Rafael; Sanchez, Noemi; Faubert, Jocelyn

    2014-01-01

    We induced forced and auto-oscillations in one-dimensional photonic crystals (1-D-PCs) with localized defects when light impinges transversally to the defect layer. The photonic structure used consists of a microcavity-like structure formed of two 1-D-PCs made of free-standing porous silicon, separated by a variable air gap (the defect) and the working wavelength is 633 nm. The force generation was made evident by driving a laser light by means of a chopper; the light hit the photonic structure and induced a vibration and the vibration was characterized by using a very sensitive vibrometer. For example, we measured peak displacements and velocities ranging from 2 to 167 μm and 0.4 to 2.1 mm/s with a power light level from 2.6 to 13 mW. In comparison, recent evidence showed that giant resonant light forces could induce average velocity values of 0.45 mm/s in microspheres embedded in water with a 43-mW light power.

  12. Force.

    ERIC Educational Resources Information Center

    Gamble, Reed

    1989-01-01

    Discusses pupil misconceptions concerning forces. Summarizes some of Assessment of Performance Unit's findings on meaning of (1) force, (2) force and motion in one dimension and two dimensions, and (3) Newton's second law. (YP)

  13. The study on the nanomachining property and cutting model of single-crystal sapphire by atomic force microscopy.

    PubMed

    Huang, Jen-Ching; Weng, Yung-Jin

    2014-01-01

    This study focused on the nanomachining property and cutting model of single-crystal sapphire during nanomachining. The coated diamond probe is used to as a tool, and the atomic force microscopy (AFM) is as an experimental platform for nanomachining. To understand the effect of normal force on single-crystal sapphire machining, this study tested nano-line machining and nano-rectangular pattern machining at different normal force. In nano-line machining test, the experimental results showed that the normal force increased, the groove depth from nano-line machining also increased. And the trend is logarithmic type. In nano-rectangular pattern machining test, it is found when the normal force increases, the groove depth also increased, but rather the accumulation of small chips. This paper combined the blew by air blower, the cleaning by ultrasonic cleaning machine and using contact mode probe to scan the surface topology after nanomaching, and proposed the "criterion of nanomachining cutting model," in order to determine the cutting model of single-crystal sapphire in the nanomachining is ductile regime cutting model or brittle regime cutting model. After analysis, the single-crystal sapphire substrate is processed in small normal force during nano-linear machining; its cutting modes are ductile regime cutting model. In the nano-rectangular pattern machining, due to the impact of machined zones overlap, the cutting mode is converted into a brittle regime cutting model.

  14. Method for packing chromatographic beds

    DOEpatents

    Freeman, David H.; Angeles, Rosalie M.; Keller, Suzanne

    1991-01-01

    Column chromatography beds are packed through the application of static force. A slurry of the chromatography bed material and a non-viscous liquid is filled into the column plugged at one end, and allowed to settle. The column is transferred to a centrifuge, and centrifuged for a brief period of time to achieve a predetermined packing level, at a range generally of 100-5,000 gravities. Thereafter, the plug is removed, other fixtures may be secured, and the liquid is allowed to flow out through the bed. This results in an evenly packed bed, with no channeling or preferential flow characteristics.

  15. Development of a novel liquid crystal based cell traction force transducer system.

    PubMed

    Soon, C F; Youseffi, M; Berends, R F; Blagden, N; Denyer, M C T

    2013-01-15

    Keratinocyte traction forces play a crucial role in wound healing. The aim of this study was to develop a novel cell traction force (CTF) transducer system based on cholesteryl ester liquid crystals (LC). Keratinocytes cultured on LC induced linear and isolated deformation lines in the LC surface. As suggested by the fluorescence staining, the deformation lines appeared to correlate with the forces generated by the contraction of circumferential actin filaments which were transmitted to the LC surface via the focal adhesions. Due to the linear viscoelastic behavior of the LC, Hooke's equation was used to quantify the CTFs by associating Young's modulus of LC to the cell induced stresses and biaxial strain in forming the LC deformation. Young's modulus of the LC was profiled by using spherical indentation and determined at approximately 87.1±17.2kPa. A new technique involving cytochalasin-B treatment was used to disrupt the intracellular force generating actin fibers, and consequently the biaxial strain in the LC induced by the cells was determined. Due to the improved sensitivity and spatial resolution (∼1μm) of the LC based CTF transducer, a wide range of CTFs was determined (10-120nN). These were found to be linearly proportional to the length of the deformations. The linear relationship of CTF-deformations was then applied in a bespoke CTF mapping software to estimate CTFs and to map CTF fields. The generated CTF map highlighted distinct distributions and different magnitude of CTFs were revealed for polarized and non-polarized keratinocytes. PMID:22809522

  16. Development of a novel liquid crystal based cell traction force transducer system.

    PubMed

    Soon, C F; Youseffi, M; Berends, R F; Blagden, N; Denyer, M C T

    2013-01-15

    Keratinocyte traction forces play a crucial role in wound healing. The aim of this study was to develop a novel cell traction force (CTF) transducer system based on cholesteryl ester liquid crystals (LC). Keratinocytes cultured on LC induced linear and isolated deformation lines in the LC surface. As suggested by the fluorescence staining, the deformation lines appeared to correlate with the forces generated by the contraction of circumferential actin filaments which were transmitted to the LC surface via the focal adhesions. Due to the linear viscoelastic behavior of the LC, Hooke's equation was used to quantify the CTFs by associating Young's modulus of LC to the cell induced stresses and biaxial strain in forming the LC deformation. Young's modulus of the LC was profiled by using spherical indentation and determined at approximately 87.1±17.2kPa. A new technique involving cytochalasin-B treatment was used to disrupt the intracellular force generating actin fibers, and consequently the biaxial strain in the LC induced by the cells was determined. Due to the improved sensitivity and spatial resolution (∼1μm) of the LC based CTF transducer, a wide range of CTFs was determined (10-120nN). These were found to be linearly proportional to the length of the deformations. The linear relationship of CTF-deformations was then applied in a bespoke CTF mapping software to estimate CTFs and to map CTF fields. The generated CTF map highlighted distinct distributions and different magnitude of CTFs were revealed for polarized and non-polarized keratinocytes.

  17. Quantitative lateral and vertical piezoresponse force microscopy on a PbTiO3 single crystal

    NASA Astrophysics Data System (ADS)

    Lei, Shiming; Koo, Tae-Yeong; Cao, Wenwu; Eliseev, Eugene A.; Morozovska, Anna N.; Cheong, S.-W.; Gopalan, Venkatraman

    2016-09-01

    Piezoresponse force microscopy (PFM) has emerged as a powerful tool for research in ferroelectric and piezoelectric materials. While the vertical PFM (VPFM) mode is well understood and applied at a quantitative level, the lateral PFM (LPFM) mode is rarely quantified, mainly due to the lack of a practical calibration methodology. Here by PFM imaging on a LiNbO3 180° domain wall, we demonstrate a convenient way to achieve simultaneous VPFM and LPFM calibrations. Using these calibrations, we perform a full quantitative VPFM and LPFM measurement on a (001)-cut PbTiO3 single crystal. The measured effective piezoelectric coefficients d33 e f f and d35 e f f together naturally provide more information on a material's local tensorial electromechanical properties. The proposed approach can be applied to a wide variety of ferroelectric and piezoelectric systems.

  18. Separation-independent attractive force between like particles mediated by nematic-liquid-crystal distortions.

    PubMed

    Fukuda, Jun-Ichi; Yokoyama, Hiroshi

    2005-04-15

    We investigate numerically with the aid of the Landau-de Gennes continuum theory the interaction between two spherical particles carrying the same topological charges +1 mediated by the elastic distortion of a nematic liquid crystal. We consider the case where an escaped nontopological ring disclination is situated between the particles; the director is continuous everywhere and no counterdefects are present. We find that the interaction is attractive and its potential energy depends linearly on the interparticle distance D. This behavior yields the D-independent interaction force, which was observed experimentally by Poulin, Cabuil, and Weitz [Phys. Rev. Lett. 79, 4862 (1997)] in the presence of narrow strings of birefringent regions ("bubble-gum" configuration) between the particles. PMID:15904120

  19. A scanning force microscopy study on the drawing of solution crystallized UHMW-PE

    SciTech Connect

    MoEller, M.; Sheiko, S.; Kunz, M.

    1993-12-31

    Drawing of solution crystallized UHMW-PE has been monitored by scanning force microscopy (SFM). The work is focused on the transformation of lamellae to fibrilla crystals within the necking region ({lambda} = 1-10). SFM allows threedimensional visualization of the polymer surface in the range of Angstrom up to micrometers. No special treatment like staining an coating is necessary, and the experiments can be performed under ambient conditions. Thus, it was possible to reveal details of the structural transformation which could not be observed before. In order to recognize and eliminate artifacts, the probing tips were calibrated by means of a newly developed gauge and the results are compared with complimentary SEM and TEM (replica) studies. Two stages of the deformation could be distinguished: (i) sliding of the lamellae followed by (ii) transformation to 20-40 nm wide fibrils. These nanofibrils are already formed during the necking process and their diameter remains unchanged upon further drawing up to {lambda} = 70. The nanofibrils are identified as the basic building unit of the fibrillar structure. Their role regarding the improvement in strength upon drawing to large {lambda}-values will be discussed.

  20. Clean surface processing of rubrene single crystal immersed in ionic liquid by using frequency modulation atomic force microscopy

    SciTech Connect

    Yokota, Yasuyuki; Hara, Hisaya; Morino, Yusuke; Bando, Ken-ichi; Imanishi, Akihito; Fukui, Ken-ichi; Uemura, Takafumi; Takeya, Jun

    2014-06-30

    Surface processing of a rubrene single crystal immersed in ionic liquids is valuable for further development of low voltage transistors operated by an electric double layer. We performed a precise and clean surface processing based on the tip-induced dissolution of rubrene molecules at the ionic liquid/rubrene single crystal interfaces by using frequency modulation atomic force microscopy. Molecular resolution imaging revealed that the tip-induced dissolution proceeded via metastable low density states derived from the anisotropic intermolecular interactions within the crystal structure.

  1. Clean surface processing of rubrene single crystal immersed in ionic liquid by using frequency modulation atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Yokota, Yasuyuki; Hara, Hisaya; Morino, Yusuke; Bando, Ken-ichi; Imanishi, Akihito; Uemura, Takafumi; Takeya, Jun; Fukui, Ken-ichi

    2014-06-01

    Surface processing of a rubrene single crystal immersed in ionic liquids is valuable for further development of low voltage transistors operated by an electric double layer. We performed a precise and clean surface processing based on the tip-induced dissolution of rubrene molecules at the ionic liquid/rubrene single crystal interfaces by using frequency modulation atomic force microscopy. Molecular resolution imaging revealed that the tip-induced dissolution proceeded via metastable low density states derived from the anisotropic intermolecular interactions within the crystal structure.

  2. Analysis of anomalous slip in Ta single crystals using optical, atomic force, and orientation imaging microscopies

    SciTech Connect

    Stoelken, J.S.; King, W.E.; Schwartz, A.J.; Campbell, G.H.; Balooch, M.

    1999-07-01

    High purity Ta single crystals oriented for single slip were deformed in compression at 300K and 77K. The sample deformed at 300K exhibited wavy glide whereas the sample deformed at 77K exhibited anomalous slip. Sharp load drops were recorded in the stress-strain curve of the sample tested at 77K. Previous work attributes such unloading events to either the formation of large deformation twins or to the anomalous slip process itself. Orientation imaging microscopy was applied to probe lattice rotations occurring as a result of deformation in an effort to detect the presence of large deformation twins, none were found. Optical and atomic force microscopies were applied to map the slip traces appearing on the sample surface. Atomic force microscopy revealed that the fine structure within the rather coarse anomalous slip bands is comprised of atomistic scale slip lines organized into packets. These slip packets appear to account for the fine slip traces often observed within anomalous slip bands.

  3. Structural investigation of ionic liquid/rubrene single crystal interfaces by using frequency-modulation atomic force microscopy.

    PubMed

    Yokota, Yasuyuki; Hara, Hisaya; Harada, Tomohiro; Imanishi, Akihito; Uemura, Takafumi; Takeya, Jun; Fukui, Ken-ichi

    2013-11-21

    Frequency-modulation atomic force microscopy (FM-AFM) was employed to reveal the structural properties of a rubrene single crystal immersed in an ionic liquid. We found large vacancies formed by the anisotropic dissolution of rubrene molecules. Molecular resolution imaging revealed that structures of FM-AFM images deviated from the bulk-terminated structure. PMID:24091742

  4. Effect of direction of an external force on crystallization of colloidal particles in a V-shaped groove by sedimentation

    NASA Astrophysics Data System (ADS)

    Sato, Masahide

    2016-09-01

    We carried out Langevin dynamics simulations to study the effect of the direction of a uniform external force on the crystallization of colloidal particles in a V-shaped groove. When the inclination of the side walls of a groove was set to a suitable value and the external force bisected the angle, the face-centered-cubic (fcc) structure grew with a {100} growth interface. When the external force was inclined, the number of solidified particles decreased with increasing inclination, which is different from the growth in an inverted pyramidal container.

  5. Valve stem and packing assembly

    DOEpatents

    Wordin, John J.

    1991-01-01

    A valve stem and packing assembly is provided in which a rotatable valve stem includes a first tractrix surface for sliding contact with a stem packing and also includes a second tractrix surface for sliding contact with a bonnet. Force is applied by means of a spring, gland flange, and gland on the stem packing so the stem packing seals to the valve stem and bonnet. This configuration serves to create and maintain a reliable seal between the stem packing and the valve stem. The bonnet includes a second complementary tractrix surface for contacting the second sliding tractrix surface, the combination serving as a journal bearing for the entire valve stem and packing assembly. The journal bearing so configured is known as a Schiele's pivot. The Schiele's pivot also serves to maintain proper alignment of the valve stem with respect to the bonnet. Vertical wear between the surfaces of the Schiele's pivot is uniform at all points of contact between the second sliding tractrix surface and the second complementary tractrix surface of a bonnet. The valve stem is connected to a valve plug by means of a slip joint. The valve is opened and closed by rotating the valve stem. The slip joint compensates for wear on the Schiele's pivot and on the valve plug. A ledge is provided on the valve bonnet for the retaining nut to bear against. The ledge prevents overtightening of the retaining nut and the resulting excessive friction between stem and stem packing.

  6. Valve stem and packing assembly

    DOEpatents

    Wordin, J.J.

    1991-09-03

    A valve stem and packing assembly is provided in which a rotatable valve stem includes a first tractrix surface for sliding contact with a stem packing and also includes a second tractrix surface for sliding contact with a bonnet. Force is applied by means of a spring, gland flange, and gland on the stem packing so the stem packing seals to the valve stem and bonnet. This configuration serves to create and maintain a reliable seal between the stem packing and the valve stem. The bonnet includes a second complementary tractrix surface for contacting the second sliding tractrix surface, the combination serving as a journal bearing for the entire valve stem and packing assembly. The journal bearing so configured is known as a Schiele's pivot. The Schiele's pivot also serves to maintain proper alignment of the valve stem with respect to the bonnet. Vertical wear between the surfaces of the Schiele's pivot is uniform at all points of contact between the second sliding tractrix surface and the second complementary tractrix surface of a bonnet. The valve stem is connected to a valve plug by means of a slip joint. The valve is opened and closed by rotating the valve stem. The slip joint compensates for wear on the Schiele's pivot and on the valve plug. A ledge is provided on the valve bonnet for the retaining nut to bear against. The ledge prevents over tightening of the retaining nut and the resulting excessive friction between stem and stem packing. 2 figures.

  7. Anisotropic nanoparticles immersed in a nematic liquid crystal: Defect structures and potentials of mean force

    NASA Astrophysics Data System (ADS)

    Hung, Francisco R.; Guzmán, Orlando; Gettelfinger, Brian T.; Abbott, Nicholas L.; de Pablo, Juan J.

    2006-07-01

    We report results for the potential of mean force (PMF) and the defect structures that arise when spherocylindrical nanoparticles are immersed in a nematic liquid crystal. Using a dynamic field theory for the tensor order parameter Q of the liquid crystal, we analyzed configurations, including one, two, and three elongated particles, with strong homeotropic anchoring at their surfaces. For systems with one nanoparticle, the most stable configuration is achieved when the spherocylinder is placed with its long axis perpendicular to the far-field director, for which the defect structure consists of an elongated Saturn ring. For systems with two or three nanoparticles with their long axes placed perpendicular to the far-field director, at small separations the defect structures consist of incomplete Saturn rings fused with new disclination rings orthogonal to the original ones, in analogy to results previously observed for spherical nanoparticles. The shape of these orthogonal rings depends on the nanoparticles’ configuration, i.e., triangular, linear, or parallel with respect to their long axis. A comparison of the PMFs indicates that the latter configuration is the most stable. The stability of the different arrays depends on whether orthogonal disclination rings form or not, their size, and the curvature effects in the interparticle regions. Our results suggest that the one-elastic-constant approximation is valid for the considered systems; similar results were obtained when a three-constant expression is used to represent the elastic free energy. The attractive interactions between the elongated particles were compared to those observed for spheres of similar diameters. Similar interparticle energies were observed for linear arrays; in contrast, parallel and triangular arrays of spherocylinders yielded interactions that were up to 3.4 times stronger than those observed for spherical particles.

  8. Anisotropic nanoparticles immersed in a nematic liquid crystal: defect structures and potentials of mean force.

    PubMed

    Hung, Francisco R; Guzmán, Orlando; Gettelfinger, Brian T; Abbott, Nicholas L; de Pablo, Juan J

    2006-07-01

    We report results for the potential of mean force (PMF) and the defect structures that arise when spherocylindrical nanoparticles are immersed in a nematic liquid crystal. Using a dynamic field theory for the tensor order parameter Q of the liquid crystal, we analyzed configurations, including one, two, and three elongated particles, with strong homeotropic anchoring at their surfaces. For systems with one nanoparticle, the most stable configuration is achieved when the spherocylinder is placed with its long axis perpendicular to the far-field director, for which the defect structure consists of an elongated Saturn ring. For systems with two or three nanoparticles with their long axes placed perpendicular to the far-field director, at small separations the defect structures consist of incomplete Saturn rings fused with new disclination rings orthogonal to the original ones, in analogy to results previously observed for spherical nanoparticles. The shape of these orthogonal rings depends on the nanoparticles' configuration, i.e., triangular, linear, or parallel with respect to their long axis. A comparison of the PMFs indicates that the latter configuration is the most stable. The stability of the different arrays depends on whether orthogonal disclination rings form or not, their size, and the curvature effects in the interparticle regions. Our results suggest that the one-elastic-constant approximation is valid for the considered systems; similar results were obtained when a three-constant expression is used to represent the elastic free energy. The attractive interactions between the elongated particles were compared to those observed for spheres of similar diameters. Similar interparticle energies were observed for linear arrays; in contrast, parallel and triangular arrays of spherocylinders yielded interactions that were up to 3.4 times stronger than those observed for spherical particles.

  9. Exploring the folding pattern of a polymer chain in a single crystal by combining single-molecule force spectroscopy and steered molecular dynamics simulations.

    PubMed

    Song, Yu; Feng, Wei; Liu, Kai; Yang, Peng; Zhang, Wenke; Zhang, Xi

    2013-03-26

    Understanding the folding pattern of a single polymer chain within its single crystal will shed light on the mechanism of crystallization. Here, we use the combined techniques of atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) and steered molecular dynamics (SMD) simulations to study the folding pattern of a polyethylene oxide (PEO) chain in its single crystal. Our results show that the folding pattern of a PEO chain in the crystal formed in dilute solution follows the adjacent re-entry folding model. While in the crystal obtained from the melt, the nonadjacent folding with large and irregular loops contributes to big force fluctuations in the force-extension curves. The method established here can offer a novel strategy to directly unravel the chain-folding pattern of polymer single crystals at single-molecule level.

  10. Packed Bed Reactor Experiment

    NASA Video Gallery

    The purpose of the Packed Bed Reactor Experiment in low gravity is to determine how a mixture of gas and liquid flows through a packed bed in reduced gravity. A packed bed consists of a metal pipe ...

  11. Quasistatic packings of droplets in flat microfluidic channels

    NASA Astrophysics Data System (ADS)

    Kadivar, Erfan

    2016-02-01

    As observed in recent experiments, monodisperse droplets self-assemble spontaneously in different ordered packings. In this work, we present a numerical study of the droplet packings in the flat rectangular microfluidic channels. Employing the boundary element method, we numerically solve the Stokes equation in two-dimension and investigate the appearance of droplet packing and transition between one and two-row packings of monodisperse emulsion droplets. By calculating packing force applied on the droplet interface, we investigate the effect of flow rate, droplet size, and surface tension on the packing configurations of droplets and transition between different topological packings.

  12. Forced vibrations of SC-cut quartz crystal rectangular plates with partial electrodes by the Lee plate equations.

    PubMed

    Wu, Rongxing; Wang, Wenjun; Chen, Guijia; Du, Jianke; Ma, Tingfeng; Wang, Ji

    2016-02-01

    Lee plate equations for high frequency vibrations of piezoelectric plates have been established and perfected over decades with the sole objective of obtaining accurate predictions of frequency and mode shapes to aid the analysis and design of quartz crystal resonators. The latest improvement includes extra terms related to derivatives of the flexural displacement to provide much accurate solutions for vibrations of the thickness-shear mode, which is the functioning mode of resonators and has much higher frequency than the flexural mode. The improved Lee plate equations have been used in the analysis of high frequency vibrations of quartz crystal plates as an essential step for analysis of AT- and SC-cut quartz crystal resonators after validations with fully electrode quartz crystal piezoelectric plates. In this study, closed-form solutions of free and forced vibrations of SC-cut quartz plates with partial electrodes are obtained. A procedure has been established for the calculation of dispersion relations, frequency spectra, selected vibration modes, and capacitance ratios of forced vibrations. The vibration solutions obtained with the first-order Lee plate equations are proven to be close to solutions from the Mindlin plate equations. It is now clear that both the Mindlin and Lee plate equations can be used in the analysis and design of quartz crystal resonators.

  13. Viral capsomere structure, surface processes and growth kinetics in the crystallization of macromolecular crystals visualized by in situ atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Malkin, A. J.; Kuznetsov, Yu. G.; McPherson, A.

    2001-11-01

    In situ atomic force microscopy (AFM) was used to investigate surface evolution during the growth of single crystals of turnip yellow mosaic virus (TYMV), cucumber mosaic virus (CMV) and glucose isomerase. Growth of these crystals proceeded by two-dimensional (2D) nucleation. For glucose isomerase, from supersaturation dependencies of tangential step rates and critical step length, the kinetic coefficients of the steps and the surface free energy of the step edge were calculated for different crystallographic directions. The molecular structure of the step edges, the adsorption of individual virus particles and their aggregates, and the initial stages of formation of 2D nuclei on the surfaces of TYMV and CMV crystals were recorded. The surfaces of individual TYMV virions within crystals were visualized, and hexameric and pentameric capsomers of the T=3 capsids were clearly resolved. This, so far as we are aware, is the first direct visualization of the capsomere structure of a virus by AFM. In the course of recording the in situ development of the TYMV crystals, a profound restructuring of the surface arrangement was observed. This transformation was highly cooperative in nature, but the transitions were unambiguous and readily explicable in terms of an organized loss of classes of virus particles from specific lattice positions.

  14. A Phenomenological Model of Bulk Force in a Li-Ion Battery Pack and Its Application to State of Charge Estimation

    SciTech Connect

    Mohan, S; Kim, Y; Siegel, JB; Samad, NA; Stefanopoulou, AG

    2014-09-19

    A phenomenological model of the bulk force exerted by a lithium ion cell during various charge, discharge, and temperature operating conditions is developed. The measured and modeled force resembles the carbon expansion behavior associated with the phase changes during intercalation, as there are ranges of state of charge (SOC) with a gradual force increase and ranges of SOC with very small change in force. The model includes the influence of temperature on the observed force capturing the underlying thermal expansion phenomena. Moreover the model is capable of describing the changes in force during thermal transients, when internal battery heating due to high C-rates or rapid changes in the ambient temperature, which create a mismatch in the temperature of the cell and the holding fixture. It is finally shown that the bulk force model can be very useful for a more accurate and robust SOC estimation based on fusing information from voltage and force (or pressure) measurements. (C) The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email oa@electrochem.org. All rights reserved.

  15. Micro-gravity: Superconducting coils for crystal growth. Influence of the levitation force on natural convection in the fluid

    NASA Astrophysics Data System (ADS)

    Quettier, L.; Vincent-Viry, O.; Mailfert, A.; Juster, F. P.

    2003-04-01

    This paper presents a novel design of superconducting coils able to generate a micro-gravity environment for protein crystal growth in aqueous solution. The structures have been calculated thanks to a method for “inverse source synthesis problem" developed at the GREEN Choice of the angular offset between the directions of magnetic force field and magnetic field in the working area as well as convection phenomena are also studied.

  16. Scanning-force-microscopy study of MeV-atomic-ion-induced surface tracks in organic crystals

    SciTech Connect

    Kopniczky, J.; Reimann, C.T.; Hallen, A.; Sundqvist, B.U.R. ); Tengvall, P.; Erlandsson, R. )

    1994-01-01

    We present scanning force microscope images of craterlike defects induced by individual 78.2-MeV [sup 127]I ions incident on organic single-crystal [ital L]-valine surfaces. For grazing incidence ions, the craters are elongated along the ion azimuth of incidence and display a raised tail in the surface above the ion track. This permanent plastic deformation of the surface indicates that a hydrodynamic pressure-pulse phenomenon occurs in response to the electronically deposited energy.

  17. Stuffed Derivatives of Close-Packed Structures

    ERIC Educational Resources Information Center

    Douglas, Bodie E.

    2007-01-01

    Decades ago Buerger described and later Palmer reviewed stuffed silica crystal structures widely used by mineralogists. Many publications and books have discussed common crystal structures in terms of close-packing of one set of atoms or ions (P sites) with other atoms or ions in tetrahedral (T) or octahedral (O) sites. Douglas and Ho described…

  18. The short range anion-H interaction is the driving force for crystal formation of ions in water.

    PubMed

    Alejandre, José; Chapela, Gustavo A; Bresme, Fernando; Hansen, Jean-Pierre

    2009-05-01

    The crystal formation of NaCl in water is studied by extensive molecular dynamics simulations. Ionic solutions at room temperature and various concentrations are studied using the SPC/E and TIP4P/2005 water models and seven force fields of NaCl. Most force fields of pure NaCl fail to reproduce the experimental density of the crystal, and in solution some favor dissociation at saturated conditions, while others favor crystal formation at low concentration. A new force field of NaCl is proposed, which reproduces the experimental phase diagram in the solid, liquid, and vapor regions. This force field overestimates the solubility of NaCl in water at saturation conditions when used with standard Lorentz-Berthelot combining rules for the ion-water pair potentials. It is shown that precipitation of ions is driven by the short range interaction between Cl-H pairs, a term which is generally missing in the simulation of ionic solutions. The effects of intramolecular flexibility of water on the solubility of NaCl ions are analyzed and is found to be small compared to rigid models. A flexible water model, extending the rigid SPC/E, is proposed, which incorporates Lennard-Jones interactions centered on the hydrogen atoms. This force field gives liquid-vapor coexisting densities and surface tensions in better agreement with experimental data than the rigid SPC/E model. The Cl-H, Na-O, and Cl-O pair distribution functions of the rigid and flexible models agree well with experiment. The predicted concentration dependence of the electric conductivity is in fair agreement with available experimental data. PMID:19425788

  19. The short range anion-H interaction is the driving force for crystal formation of ions in water.

    PubMed

    Alejandre, José; Chapela, Gustavo A; Bresme, Fernando; Hansen, Jean-Pierre

    2009-05-01

    The crystal formation of NaCl in water is studied by extensive molecular dynamics simulations. Ionic solutions at room temperature and various concentrations are studied using the SPC/E and TIP4P/2005 water models and seven force fields of NaCl. Most force fields of pure NaCl fail to reproduce the experimental density of the crystal, and in solution some favor dissociation at saturated conditions, while others favor crystal formation at low concentration. A new force field of NaCl is proposed, which reproduces the experimental phase diagram in the solid, liquid, and vapor regions. This force field overestimates the solubility of NaCl in water at saturation conditions when used with standard Lorentz-Berthelot combining rules for the ion-water pair potentials. It is shown that precipitation of ions is driven by the short range interaction between Cl-H pairs, a term which is generally missing in the simulation of ionic solutions. The effects of intramolecular flexibility of water on the solubility of NaCl ions are analyzed and is found to be small compared to rigid models. A flexible water model, extending the rigid SPC/E, is proposed, which incorporates Lennard-Jones interactions centered on the hydrogen atoms. This force field gives liquid-vapor coexisting densities and surface tensions in better agreement with experimental data than the rigid SPC/E model. The Cl-H, Na-O, and Cl-O pair distribution functions of the rigid and flexible models agree well with experiment. The predicted concentration dependence of the electric conductivity is in fair agreement with available experimental data.

  20. Toward chaperone-assisted crystallography: Protein engineering enhancement of crystal packing and X-ray phasing capabilities of a camelid single-domain antibody (V[subscript H]H) scaffold

    SciTech Connect

    Tereshko, Valentina; Uysal, Serdar; Koide, Akiko; Margalef, Katrina; Koide, Shohei; Kossiakoff, Anthony A.

    2008-07-28

    A crystallization chaperone is an auxiliary protein that binds to a target of interest, enhances and modulates crystal packing, and provides high-quality phasing information. We critically evaluated the effectiveness of a camelid single-domain antibody (V{sub H}H) as a crystallization chaperone. By using a yeast surface display system for V{sub H}H, we successfully introduced additional Met residues in the core of the V{sub H}H scaffold. We identified a set of SeMet-labeled V{sub H}H variants that collectively produced six new crystal forms as the complex with the model antigen, RNase A. The crystals exhibited monoclinic, orthorhombic, triclinic, and tetragonal symmetry and have one or two complexes in the asymmetric unit, some of which diffracted to an atomic resolution. The phasing power of the Met-enriched V{sub H}H chaperone allowed for auto-building the entire complex using single-anomalous dispersion technique (SAD) without the need for introducing SeMet into the target protein. We show that phases produced by combining SAD and VHH model-based phases are accurate enough to easily solve structures of the size reported here, eliminating the need to collect multiple wavelength multiple-anomalous dispersion (MAD) data. Together with the presence of high-throughput selection systems (e.g., phage display libraries) for V{sub H}H, the enhanced V{sub H}H domain described here will be an excellent scaffold for producing effective crystallization chaperones.

  1. Molecularly clean ionic liquid/rubrene single-crystal interfaces revealed by frequency modulation atomic force microscopy.

    PubMed

    Yokota, Yasuyuki; Hara, Hisaya; Morino, Yusuke; Bando, Ken-ichi; Imanishi, Akihito; Uemura, Takafumi; Takeya, Jun; Fukui, Ken-ichi

    2015-03-14

    The structural properties of ionic liquid/rubrene single-crystal interfaces were investigated using frequency modulation atomic force microscopy. The spontaneous dissolution of rubrene molecules into the ionic liquid was triggered by surface defects such as rubrene oxide defects, and the dissolution rate strongly depended on the initial conditions of the rubrene surface. Dissolution of the second rubrene layer was slower due to the lower defect density, leading to the formation of a clean interface irrespective of the initial conditions. Molecular-resolution images were easily obtained at the interface, and their corrugation patterns changed with the applied force. Force curve measurements revealed that a few solvation layers of ionic liquid molecules formed at the interface, and the force needed to penetrate the solvation layers was an order of magnitude smaller than typical ionic liquid/inorganic solid interfaces. These specific properties are discussed with respect to electric double-layer transistors based on the ionic liquid/rubrene single-crystal interface. PMID:25669665

  2. Spheronization mechanism of pharmaceutical material crystals processed by extremely high shearing force using a mechanical powder processor.

    PubMed

    Kondo, Keita; Kido, Keisuke; Niwa, Toshiyuki

    2016-10-01

    We aimed to elucidate the mechanism of the spheronization of pharmaceutical material crystals through extremely high shearing force using a mechanical powder processor, which produces spherical crystals without a solvent. The spheronization of theophylline, acetaminophen, clarithromycin, ascorbic acid and lactose was investigated, and the relationship between the spheronization mechanism and material characteristics was also examined. Theophylline and ascorbic acid crystals were partially destroyed during mechanical processing, yielding large particles and dust, and the large fragments were then layered with powder to produce spheres with a core-shell structure. Acetaminophen crystals were completely fragmented under stress, yielding fine particles to which powder then agglomerated to produce spheres with a mosaic structure. Clarithromycin and lactose crystals were not spheronized. Our results showed that the fracture strength of intact material may be closely related to the size of intermediate fragments, determining spheronization mechanism. Furthermore, the results for powder cohesiveness suggest that the materials with moderate-to-high cohesiveness (theophylline, acetaminophen and ascorbic acid) are finally spheronized regardless of the degree of the strength, whereas those with low cohesiveness (clarithromycin and lactose) are not spheronized due to poor granulation. Hence, the cohesiveness of a material has a significant effect on the success of mechanical spheronization processes.

  3. Spheronization mechanism of pharmaceutical material crystals processed by extremely high shearing force using a mechanical powder processor.

    PubMed

    Kondo, Keita; Kido, Keisuke; Niwa, Toshiyuki

    2016-10-01

    We aimed to elucidate the mechanism of the spheronization of pharmaceutical material crystals through extremely high shearing force using a mechanical powder processor, which produces spherical crystals without a solvent. The spheronization of theophylline, acetaminophen, clarithromycin, ascorbic acid and lactose was investigated, and the relationship between the spheronization mechanism and material characteristics was also examined. Theophylline and ascorbic acid crystals were partially destroyed during mechanical processing, yielding large particles and dust, and the large fragments were then layered with powder to produce spheres with a core-shell structure. Acetaminophen crystals were completely fragmented under stress, yielding fine particles to which powder then agglomerated to produce spheres with a mosaic structure. Clarithromycin and lactose crystals were not spheronized. Our results showed that the fracture strength of intact material may be closely related to the size of intermediate fragments, determining spheronization mechanism. Furthermore, the results for powder cohesiveness suggest that the materials with moderate-to-high cohesiveness (theophylline, acetaminophen and ascorbic acid) are finally spheronized regardless of the degree of the strength, whereas those with low cohesiveness (clarithromycin and lactose) are not spheronized due to poor granulation. Hence, the cohesiveness of a material has a significant effect on the success of mechanical spheronization processes. PMID:27368746

  4. Structural and mechanical features of the order-disorder transition in experimental hard-sphere packings

    NASA Astrophysics Data System (ADS)

    Hanifpour, M.; Francois, N.; Robins, V.; Kingston, A.; Vaez Allaei, S. M.; Saadatfar, M.

    2015-06-01

    Here we present an experimental and numerical investigation on the grain-scale geometrical and mechanical properties of partially crystallized structures made of macroscopic frictional grains. Crystallization is inevitable in arrangements of monosized hard spheres with packing densities exceeding Bernal's limiting density ϕBernal≈0.64 . We study packings of monosized hard spheres whose density spans over a wide range (0.59 <ϕ <0.72 ) . These experiments harness x-ray computed tomography, three-dimensional image analysis, and numerical simulations to access precisely the geometry and the 3D structure of internal forces within the sphere packings. We show that clear geometrical transitions coincide with modifications of the mechanical backbone of the packing both at the grain and global scale. Notably, two transitions are identified at ϕBernal≈0.64 and ϕc≈0.68 . These results provide insights on how geometrical and mechanical features at the grain scale conspire to yield partially crystallized structures that are mechanically stable.

  5. Structural and mechanical features of the order-disorder transition in experimental hard-sphere packings.

    PubMed

    Hanifpour, M; Francois, N; Robins, V; Kingston, A; Allaei, S M Vaez; Saadatfar, M

    2015-06-01

    Here we present an experimental and numerical investigation on the grain-scale geometrical and mechanical properties of partially crystallized structures made of macroscopic frictional grains. Crystallization is inevitable in arrangements of monosized hard spheres with packing densities exceeding Bernal's limiting density ϕ(Bernal)≈0.64. We study packings of monosized hard spheres whose density spans over a wide range (0.59<ϕ<0.72). These experiments harness x-ray computed tomography, three-dimensional image analysis, and numerical simulations to access precisely the geometry and the 3D structure of internal forces within the sphere packings. We show that clear geometrical transitions coincide with modifications of the mechanical backbone of the packing both at the grain and global scale. Notably, two transitions are identified at ϕ(Bernal)≈0.64 and ϕ(c)≈0.68. These results provide insights on how geometrical and mechanical features at the grain scale conspire to yield partially crystallized structures that are mechanically stable. PMID:26172700

  6. Shock wave compression of hexagonal-close-packed metal single crystals: Time-dependent, anisotropic elastic-plastic response of beryllium

    SciTech Connect

    Winey, J. M.; Gupta, Y. M.

    2014-07-21

    Understanding and modeling the response of hcp metals to high stress impulsive loading is challenging because the lower crystal symmetry, compared to cubic metals, results in a significantly more complex material response. To gain insight into the inelastic deformation of hcp metals subjected to high dynamic stresses, shock wave compression of single crystals provides a useful approach because different inelastic deformation mechanisms can be examined selectively by shock compression along different crystal orientations. As a representative example, we report, here, on wave propagation simulations for beryllium (Be) single crystals shocked along the c-axis, a-axis, and several low-symmetry directions to peak stresses reaching 7 GPa. The simulations utilized a time-dependent, anisotropic material model that incorporated dislocation dynamics, deformation twinning, and shear cracking based descriptions of inelastic deformation. The simulation results showed good overall agreement with measured wave profiles for all the different crystal orientations examined [Pope and Johnson, J. Appl. Phys. 46, 720 (1975)], including features arising from wave mode coupling due to the highly anisotropic inelastic response of Be. This good agreement demonstrates that the measured profiles can be understood in terms of dislocation slip along basal, prismatic, and pyramidal planes, together with deformation twinning along (101{sup ¯}2) planes. Our results show that the response of shocked Be single crystals involves the simultaneous operation of multiple, distinct inelastic deformation mechanisms for all orientations except the c-axis. For shocked c-axis Be, the measured wave profiles do not provide good discrimination between pyramidal slip and other inelastic deformation mechanisms, such as shear cracking. The findings presented here provide insight into the complex inelastic deformation response of shocked Be single crystals and are expected to be useful for other hcp crystals

  7. Shock wave compression of hexagonal-close-packed metal single crystals: Time-dependent, anisotropic elastic-plastic response of beryllium

    NASA Astrophysics Data System (ADS)

    Winey, J. M.; Gupta, Y. M.

    2014-07-01

    Understanding and modeling the response of hcp metals to high stress impulsive loading is challenging because the lower crystal symmetry, compared to cubic metals, results in a significantly more complex material response. To gain insight into the inelastic deformation of hcp metals subjected to high dynamic stresses, shock wave compression of single crystals provides a useful approach because different inelastic deformation mechanisms can be examined selectively by shock compression along different crystal orientations. As a representative example, we report, here, on wave propagation simulations for beryllium (Be) single crystals shocked along the c-axis, a-axis, and several low-symmetry directions to peak stresses reaching 7 GPa. The simulations utilized a time-dependent, anisotropic material model that incorporated dislocation dynamics, deformation twinning, and shear cracking based descriptions of inelastic deformation. The simulation results showed good overall agreement with measured wave profiles for all the different crystal orientations examined [Pope and Johnson, J. Appl. Phys. 46, 720 (1975)], including features arising from wave mode coupling due to the highly anisotropic inelastic response of Be. This good agreement demonstrates that the measured profiles can be understood in terms of dislocation slip along basal, prismatic, and pyramidal planes, together with deformation twinning along { 10 1 ¯ 2 } planes. Our results show that the response of shocked Be single crystals involves the simultaneous operation of multiple, distinct inelastic deformation mechanisms for all orientations except the c-axis. For shocked c-axis Be, the measured wave profiles do not provide good discrimination between pyramidal slip and other inelastic deformation mechanisms, such as shear cracking. The findings presented here provide insight into the complex inelastic deformation response of shocked Be single crystals and are expected to be useful for other hcp crystals. More

  8. Formation of spatially patterned colloidal photonic crystals through the control of capillary forces and template recognition.

    PubMed

    Brozell, Adrian M; Muha, Michelle A; Parikh, Atul N

    2005-12-01

    We report the formation of microscopic patterns of substrate-supported, 3D planar colloidal crystals using physical confinement in conjunction with surfaces displaying predetermined binary patterns of hydropholicity. The formation process involves a primary self-assembly wherein nano- and microscale colloids order into a photonic fcc lattice via capillary interactions followed by a secondary template-induced crystal cleavage step. Following this method, arbitrary arrays of pattern elements, which preserve structural and orientational properties of the parent crystal, can be easily obtained.

  9. Vertical Magnetic Levitation Force Measurement on Single Crystal YBaCuO Bulk at Different Temperatures

    NASA Astrophysics Data System (ADS)

    Celik, Sukru; Guner, Sait Baris; Ozturk, Kemal; Ozturk, Ozgur

    Magnetic levitation force measurements of HTS samples are performed with the use of liquid nitrogen. It is both convenient and cheap. However, the temperature of the sample cannot be changed (77 K) and there is problem of frost. So, it is necessary to build another type of system to measure the levitation force high Tc superconductor at different temperatures. In this study, we fabricated YBaCuO superconducting by top-seeding-melting-growth (TSMG) technique and measured vertical forces of them at FC (Field Cooling) and ZFC (Zero Field Cooling) regimes by using our new designed magnetic levitation force measurement system. It was used to investigate the three-dimensional levitation force and lateral force in the levitation system consisting of a cylindrical magnet and a permanent cylindrical superconductor at different temperatures (37, 47, 57, 67 and 77 K).

  10. Transferable force field for crystal structure predictions, investigation of performance and exploration of different rescoring strategies using DFT-D methods.

    PubMed

    Broo, Anders; Nilsson Lill, Sten O

    2016-08-01

    A new force field, here called AZ-FF, aimed at being used for crystal structure predictions, has been developed. The force field is transferable to a new type of chemistry without additional training or modifications. This makes the force field very useful in the prediction of crystal structures of new drug molecules since the time-consuming step of developing a new force field for each new molecule is circumvented. The accuracy of the force field was tested on a set of 40 drug-like molecules and found to be very good where observed crystal structures are found at the top of the ranked list of tentative crystal structures. Re-ranking with dispersion-corrected density functional theory (DFT-D) methods further improves the scoring. After DFT-D geometry optimization the observed crystal structure is found at the leading top of the ranking list. DFT-D methods and force field methods have been evaluated for use in predicting properties such as phase transitions upon heating, mechanical properties or intrinsic crystalline solubility. The utility of using crystal structure predictions and the associated material properties in risk assessment in connection with form selection in the drug development process is discussed.

  11. Blocking force of a piezoelectric stack actuator made of single crystal layers (PMN-29PT)

    NASA Astrophysics Data System (ADS)

    Tran, K. S.; Phan, H. V.; Lee, H. Y.; Kim, Yongdae; Park, H. C.

    2016-09-01

    In this study, we fabricated and characterized a stack actuator made of forty layers of 1 mm thick PMN-29PT with a cross-sectional area of 10 × 10 mm2. From the measurement of actuation displacement, we confirmed that the piezoelectric strain constant in the direction of thickness of the material is 2000 pm V‑1, as suggested by the manufacturer. The blocking forces of the actuator are measured to be 230 N, 369 N, and 478 N for 100 V, 200 V, and 300 V, respectively. The measured blocking forces showed large discrepancies from the estimated blocking forces calculated using linear models, especially for a high voltage application. An empirical equation acquired by fitting the measured blocking forces indicates that the blocking force has a nonlinear relationship with the applied voltage. The measured hysteresis showed a slight nonlinear voltage-stroke relationship and small energy loss.

  12. Blocking force of a piezoelectric stack actuator made of single crystal layers (PMN-29PT)

    NASA Astrophysics Data System (ADS)

    Tran, K. S.; Phan, H. V.; Lee, H. Y.; Kim, Yongdae; Park, H. C.

    2016-09-01

    In this study, we fabricated and characterized a stack actuator made of forty layers of 1 mm thick PMN-29PT with a cross-sectional area of 10 × 10 mm2. From the measurement of actuation displacement, we confirmed that the piezoelectric strain constant in the direction of thickness of the material is 2000 pm V-1, as suggested by the manufacturer. The blocking forces of the actuator are measured to be 230 N, 369 N, and 478 N for 100 V, 200 V, and 300 V, respectively. The measured blocking forces showed large discrepancies from the estimated blocking forces calculated using linear models, especially for a high voltage application. An empirical equation acquired by fitting the measured blocking forces indicates that the blocking force has a nonlinear relationship with the applied voltage. The measured hysteresis showed a slight nonlinear voltage-stroke relationship and small energy loss.

  13. Cationic cobaltammine as anion receptor: Synthesis, characterization, single crystal X-ray structure and packing analysis of hexaamminecobalt(III) chloride ( R, R)-tartrate monohydrate

    NASA Astrophysics Data System (ADS)

    Bala, Ritu; Sharma, Raj Pal; Venugopalan, Paloth; Harrison, William T. A.

    2007-03-01

    In an effort to utilize the [Co(NH 3) 6] 3+ cation as a new anion receptor (binding agent) for dihydroxy dicarboxylate anion i.e., tartrate, orange single crystals of hexaamminecobalt(III) chloride ( R, R)-tartrate monohydrate, [Co(NH 3) 6]Cl(C 4H 4O 6)·H 2O, were obtained by reacting hexaamminecobalt(III) chloride with potassium-sodium tartrate tetrahydrate in a 1:1 molar ratio in hot water. The single crystal X-ray structure determination of [Co(NH 3) 6]Cl(C 4H 4O 6)·H 2O revealed that a distinctive network of hydrogen bonding interactions (N-H⋯O, N-H⋯Cl -, O-H⋯O) stabilize the crystal lattice. This is the first complex salt of hexaamminecobalt(III) with dihydroxy dicarboxylate anion i.e., tartrate.

  14. Enzymatic degradation processes of poly[(R)-3-hydroxybutyric acid] and poly[(R)-3-hydroxybutyric acid-co-(R)-3-hydroxyvaleric acid] single crystals revealed by atomic force microscopy: effects of molecular weight and second-monomer composition on erosion rates.

    PubMed

    Numata, Keiji; Kikkawa, Yoshihiro; Tsuge, Takeharu; Iwata, Tadahisa; Doi, Yoshiharu; Abe, Hideki

    2005-01-01

    Enzymatic degradation processes of poly[(R)-3-hydroxybutyric acid] (P(3HB)) and poly[(R)-3-hydroxybutyric acid-co-(R)-3-hydroxyvaleric acid] (P(3HB-co-3HV)) single crystals in the presence of PHB depolymerase from Ralstonia pickettii T1 were studied by real-time and static atomic force microscopy (AFM) observations. Fibril-like crystals were generated along the long axis of single crystals during the enzymatic degradation, and then the dimensions of fibril-like crystals were analyzed quantitatively. The morphologies and sizes of fibril-like crystals were dependent on the molecular weight and copolymer composition of polymers. For all samples, the crystalline thickness gradually decreased toward a tip from the root of a fibril-like crystal after enzymatic degradation for 1 h. The thinning of fibril-like crystals may be attributed to the destruction of chain-packing structure toward crystallographic c axis by the adsorption of enzyme. From the real-time AFM images, it was found that at the initial stage of degradation the enzymatic erosion started from the disordered chain-packing region in single crystals to form the grooves along the a axis. The generated fibril-like crystals deformed at a constant rate along the a axis with a constant rate after the induction time. The erosion rate at the grooves along the a axis increased with a decrease of molecular weight and with an increase of copolymer composition. On the other hand, the erosion rate along the a axis, at the tip of the fibril-like crystal, was dependent on only the copolymer composition, and the value increased with an increase in the copolymer composition. The morphologies and sizes of fibril-like crystals were governed by both the erosion rates along the a axis at the grooves and tip of fibril-like crystals. In addition, we were able to estimated the overall enzymatic erosion rate of single crystals by PHB depolymerase from the volumetric analysis.

  15. In situ atomic force microscopy of layer-by-layer crystal growth and key growth concepts

    NASA Astrophysics Data System (ADS)

    Rashkovich, L. N.; de Yoreo, J. J.; Orme, C. A.; Chernov, A. A.

    2006-12-01

    Contradictions that have been found recently between the representations of classical theory and experiments on crystal growth from solutions are considered. Experimental data show that the density of kinks is low in many cases as a result of the low rate of their fluctuation generation, the Gibbs-Thomson law is not always applicable in these cases, and there is inconsistency with the Cabrera-Vermilyea model. The theory of growth of non-Kossel crystals, which is to be developed, is illustrated by the analysis of the experimental dependence of the growth rate on the solution stoichiometry.

  16. Understanding the forces that govern packing: a density functional theory and structural investigation of anion-π-anion and nonclassical C-H···anion interactions.

    PubMed

    Brooker, Sally; White, Nicholas G; Bauzá, Antonio; Deyà, Pere M; Frontera, Antonio

    2012-10-01

    The ability of Ni(II) coordinated 4-pyrrolyl-3,5-di(2-pyridyl)-1,2,4-triazole (pldpt) to establish multiple anion-π interactions is analyzed. Experimentally, such complexes were previously shown to form strong anion-π interactions, including "π-pocket" and "π-sandwiched" motifs, in the crystal lattice. In the latter, the triazole ring is "sandwiched" by two anions forming a ternary anion-π-anion assembly (π-sandwich) which, surprisingly, gave about 0.2 Å shorter anion-π distances than in binary assemblies (where only one side of the triazole participates in the anion binding), indicating the possibility of cooperativity. In depth analysis, using dispersion-corrected density functional theory (DFT, BP86-D/def2-TZVP level of theory), shows that this ternary anion-π-anion interaction is slightly less energetically favorable than the binary anion-π interactions in isolation. Hence, the sandwich interaction is not cooperative (E(coop) is positive), but, as E(coop) contributes less than 1.5% of the total interaction energy (which is dominated by the strong electrostatic attraction of the anions to the highly π-acidic Ni(II)-coordinated triazole ring), the presence of nonclassical C-H···anion hydrogen bonds can offset this, making the short anion-π sandwich interactions the most favorable solid state conformation. PMID:22974250

  17. Torque and atomic forces for Cartesian tensor atomic multipoles with an application to crystal unit cell optimization.

    PubMed

    Elking, Dennis M

    2016-08-15

    New equations for torque and atomic force are derived for use in flexible molecule force fields with atomic multipoles. The expressions are based on Cartesian tensors with arbitrary multipole rank. The standard method for rotating Cartesian tensor multipoles and calculating torque is to first represent the tensor with n indexes and 3(n) redundant components. In this work, new expressions for directly rotating the unique (n + 1)(n + 2)/2 Cartesian tensor multipole components Θpqr are given by introducing Cartesian tensor rotation matrix elements X(R). A polynomial expression and a recursion relation for X(R) are derived. For comparison, the analogous rotation matrix for spherical tensor multipoles are the Wigner functions D(R). The expressions for X(R) are used to derive simple equations for torque and atomic force. The torque and atomic force equations are applied to the geometry optimization of small molecule crystal unit cells. In addition, a discussion of computational efficiency as a function of increasing multipole rank is given for Cartesian tensors. © 2016 Wiley Periodicals, Inc.

  18. Synthesis, crystal structure, vibrational spectral analysis and Z-scan studies of a new organic crystal N,N‧dimethylurea ninhydrin: A scaled quantum mechanical force field study

    NASA Astrophysics Data System (ADS)

    John, Jerin Susan; Sajan, D.; Umadevi, T.; Chaitanya, K.; Sankar, Pranitha; Philip, Reji

    2015-10-01

    A new organic material, N,N‧dimethylurea ninhydrin (3a,8a-dihydroxy-1,3-dimethyl-1,3,3a,8a-tetrahydroindeno[2,1-d]imidazole-2,8-dione) (NDUN) was synthesized. Structural details were obtained from single crystal X-ray diffraction (XRD) data. A detailed interpretation of the vibrational spectra is carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. TG/DTA and 1H NMR studies were carried out. Linear optical properties were studied from UV-Vis spectra. From the open aperture Z-scan data, it is found that the molecule shows third order nonlinear optical behaviour due to two photon absorption (2PA) mechanism.

  19. Charge transfer of single laser crystallized intrinsic and phosphorus-doped Si-nanocrystals visualized by Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Xu, Jie; Xu, Jun; Lu, Peng; Shan, Dan; Li, Wei; Chen, Kunji

    2014-10-01

    Isolated intrinsic and phosphorus doped (P-doped) Si-nanocrystals (Si-NCs) on n- and p-Si substrates are fabricated by excimer laser crystallization techniques. The formation of Si-NCs is confirmed by atomic force microscopy (AFM) and conductive AFM measurements. Kelvin probe force microscopy (KPFM) is then carried out to visualize the trapped charges in a single Si-NC dot which derives from the charge transfer between Si-NCs and Si substrates due to their different Fermi levels. The laser crystallized P-doped Si-NCs have a similar Fermi level around the mid-gap to the intrinsic counterparts, which might be caused by the inactivated impurity atoms or the surface states-related Fermi level pinning. A clear rise of the Fermi level in P-doped Si-NCs is observed after a short time thermal annealing treatment, indicating the activation of dopants in Si-NCs. Moreover, the surface charge quantity can be estimated using a simple parallel plate capacitor model for a quantitative understanding of the KPFM results at the nanoscale.

  20. Charge transfer of single laser crystallized intrinsic and phosphorus-doped Si-nanocrystals visualized by Kelvin probe force microscopy

    SciTech Connect

    Xu, Jie; Xu, Jun Lu, Peng; Shan, Dan; Li, Wei; Chen, Kunji

    2014-10-07

    Isolated intrinsic and phosphorus doped (P-doped) Si-nanocrystals (Si-NCs) on n- and p-Si substrates are fabricated by excimer laser crystallization techniques. The formation of Si-NCs is confirmed by atomic force microscopy (AFM) and conductive AFM measurements. Kelvin probe force microscopy (KPFM) is then carried out to visualize the trapped charges in a single Si-NC dot which derives from the charge transfer between Si-NCs and Si substrates due to their different Fermi levels. The laser crystallized P-doped Si-NCs have a similar Fermi level around the mid-gap to the intrinsic counterparts, which might be caused by the inactivated impurity atoms or the surface states-related Fermi level pinning. A clear rise of the Fermi level in P-doped Si-NCs is observed after a short time thermal annealing treatment, indicating the activation of dopants in Si-NCs. Moreover, the surface charge quantity can be estimated using a simple parallel plate capacitor model for a quantitative understanding of the KPFM results at the nanoscale.

  1. Importance of C-H-donor and C-H-anion contact interactions for the crystal packing, the lattice softness and the superconducting transition temperatures of organic conducting salts

    SciTech Connect

    Whangbo, M.-H.; Novoa, J.J.; Jung, D. . Dept. of Chemistry); Williams, J.M.; Kinj, A.M.; Wang, H.H.; Geiser, U.; Beno, M.A.; Carlson, K.D. )

    1990-01-01

    The organic donor molecule BEDT-TTF and its analogs 2--4 have yielded a number of ambient-pressure superconducting salts. What structural and electronic factors govern the magnitudes of their superconducting transition temperature {Tc} has been a topic of intense studies. Examination of the band electronic structures of closely related superconducting salts shows, that the magnitudes of their {Tc}'s are primarily determined by the softness of their crystal lattices. The crystal packing and the lattice softness of organic donor salts are strongly influenced by the donor{hor ellipsis}donor and donor{hor ellipsis}anion contact interactions involving the donor-molecule C-H bonds. In the present work, we briefly review the electronic structures of some representative organic salt superconductors and discuss the softness of their crytsal lattices on the basis of the interaction energies calculated for the C-H{hor ellipsis}donor and C-H{hor ellipsis}anion contact interactions. 34 refs., 14 figs., 8 tabs.

  2. Parallel packing of alpha-helices in crystals of the zervamicin IIA analog Boc-Trp-Ile-Ala-Aib-Ile-Val-Aib-Leu-Aib-Pro-OMe.2H2O.

    PubMed Central

    Karle, I L; Sukumar, M; Balaram, P

    1986-01-01

    An apolar synthetic analog of the first 10 residues at the NH2-terminal end of zervamicin IIA crystallizes in the triclinic space group P1 with cell dimensions a = 10.206 +/- 0.002 A, b = 12.244 +/- 0.002 A, c = 15.049 +/- 0.002 A, alpha = 93.94 +/- 0.01 degrees, beta = 95.10 +/- 0.01 degrees, gamma = 104.56 +/- 0.01 degrees, Z = 1, C60H97N11O13 X 2H2O. Despite the relatively few alpha-aminoisobutyric acid residues, the peptide maintains a helical form. The first intrahelical hydrogen bond is of the 3(10) type between N(3) and O(0), followed by five alpha-helix-type hydrogen bonds. Solution 1H NMR studies in chloroform also favor a helical conformation, with seven solvent-shielded NH groups. Continuous columns are formed by head-to-tail hydrogen bonds between the helical molecules along the helix axis. The absence of polar side chains precludes any lateral hydrogen bonds. Since the peptide crystallizes with one molecule in a triclinic space group, aggregation of the helical columns must necessarily be parallel rather than antiparallel. The packing of the columns is rather inefficient, as indicated by very few good van der Waals' contacts and the occurrence of voids between the molecules. Images PMID:2432594

  3. Stacking and twin faults in close-packed crystal structures: exact description of random faulting statistics for the full range of faulting probabilities.

    PubMed

    Estevez-Rams, E; Welzel, U; Pentón Madrigal, A; Mittemeijer, E J

    2008-09-01

    The classical model of independent random single deformation faults and twin faulting in face-centered-cubic and hexagonal close packing is revisited. The model is extended to account for the whole range of faulting probabilities. The faulting process resulting in the final stacking sequences is described by several equivalent computational models. The probability sequence tree is established. Random faulting is described as a finite-state automaton machine. An expression giving the percent of hexagonality from the faulting probabilities is derived. The average sizes of the cubic and hexagonal domains are given as a function of single deformation and twinning fault probabilities. An expression for the probability of finding a given sequence within the complete stacking arrangement is also derived. The probability P(0)(Delta) of finding two layers of the same type Delta layers apart is derived. It is shown that previous generalizations did not account for all terms in the final probability expressions. The different behaviors of the P(0)(Delta) functions are discussed.

  4. A Validation Study of the General Amber Force Field Applied to Energetic Molecular Crystals

    NASA Astrophysics Data System (ADS)

    Bergh, Magnus; Caleman, Carl

    2016-01-01

    Molecula dynamics is a well-established tool to computationally study molecules. However, to reach predictive capability at the level required for applied research and design, extensive validation of the available force fields is pertinent. Here we present a study of density, isothermal compressibility and coefficients of thermal expansion of four energetic materials (FOX-7, RDX, CL-20 and HMX) based on molecular dynamics simulations with the General Amber Force Field (GAFF), and compare the results to experimental measurements from the literature. Furthermore, we quantify the accuracy of the calculated properties through hydrocode simulation of a typical impact scenario. We find that molecular dynamics simulations with generic and computationally efficient force fields may be used to understand and estimate important physical properties of nitramine-like energetic materials.

  5. Forced diffusion via electrically induced crystallization for fabricating ZnO–Ti–Si structures

    SciTech Connect

    Chen, Yen-Ting; Hung, Fei-Yi

    2014-11-15

    Highlights: • ZnO–Ti–Si system is very important for the structural design. • The electrically induced crystallization method is useful to diffusion process. • Intermetallic compound characteristics have been presented using electrically induced crystallization. • Interface mechanism about diffusion of TZO–TiSi{sub x}–Si structure is presented. - Abstract: Electrically induced crystallization (EIC) is a recently developed process for material modification. This study is applied to EIC to fabricate ZnO–Ti–Si multi-layer structures of various thicknesses to dope Ti into ZnO thin film and to form TiSi{sub x} intermetallic compound (IMC) in a single step. The IMC layer was confirmed using transmission electron microscopy images. The Ti layer thickness was more than 40 nm, which enhanced electron transmission and decreased the total electrical resistance in the structure. Finally, the diffusion mechanisms of EIC and the annealing process were investigated. This study shows that the EIC process has potential for industrial applications.

  6. Patchy particle packing under electric fields.

    PubMed

    Song, Pengcheng; Wang, Yufeng; Wang, Yu; Hollingsworth, Andrew D; Weck, Marcus; Pine, David J; Ward, Michael D

    2015-03-01

    Colloidal particles equipped with two, three, or four negatively charged patches, which endow the particles with 2-fold, 3-fold, or tetrahedral symmetries, form 1D chains, 2D layers, and 3D packings when polarized by an AC electric field. Two-patch particles, with two patches on opposite sides of the particle (2-fold symmetry) pack into the cmm plane group and 3D packings with I4mm space group symmetry, in contrast to uncharged spherical or ellipsoidal colloids that typically crystallize into a face-centered ABC layer packing. Three-patch particles (3-fold symmetry) form chains having a 21 screw axis symmetry, but these chains pair in a manner such that each individual chain has one-fold symmetry but the pair has 21 screw axis symmetry, in an arrangement that aligns the patches that would favor Coulombic interactions along the chain. Surprisingly, some chain pairs form unanticipated double-helix regions that result from mutual twisting of the chains about each other, illustrating a kind of polymorphism that may be associated with nucleation from short chain pairs. Larger 2D domains of the three-patch particles crystallize in the p6m plane group with alignment (with respect to the field) and packing densities that suggest random disorder in the domains, whereas four-patch particles form 2D domains in which close-packed rows are aligned with the field.

  7. Patchy particle packing under electric fields.

    PubMed

    Song, Pengcheng; Wang, Yufeng; Wang, Yu; Hollingsworth, Andrew D; Weck, Marcus; Pine, David J; Ward, Michael D

    2015-03-01

    Colloidal particles equipped with two, three, or four negatively charged patches, which endow the particles with 2-fold, 3-fold, or tetrahedral symmetries, form 1D chains, 2D layers, and 3D packings when polarized by an AC electric field. Two-patch particles, with two patches on opposite sides of the particle (2-fold symmetry) pack into the cmm plane group and 3D packings with I4mm space group symmetry, in contrast to uncharged spherical or ellipsoidal colloids that typically crystallize into a face-centered ABC layer packing. Three-patch particles (3-fold symmetry) form chains having a 21 screw axis symmetry, but these chains pair in a manner such that each individual chain has one-fold symmetry but the pair has 21 screw axis symmetry, in an arrangement that aligns the patches that would favor Coulombic interactions along the chain. Surprisingly, some chain pairs form unanticipated double-helix regions that result from mutual twisting of the chains about each other, illustrating a kind of polymorphism that may be associated with nucleation from short chain pairs. Larger 2D domains of the three-patch particles crystallize in the p6m plane group with alignment (with respect to the field) and packing densities that suggest random disorder in the domains, whereas four-patch particles form 2D domains in which close-packed rows are aligned with the field. PMID:25692316

  8. Layered solids based on second-sphere coordination interactions: synthesis, spectroscopic characterization, crystal structure and packing of two copper(II) naphthalene-2-sulfonates

    NASA Astrophysics Data System (ADS)

    Sharma, Raj Pal; Sharma, Rajni; Bala, Ritu; Rychlewska, Urszula; Warżajtis, Beata

    2005-03-01

    [Cu(H 2O) 6](C 10H 7SO 3) 21 was obtained from reaction of CuCO 3·Cu(OH) 2 and naphthalene-2-sulphonic acid in aqueous medium in 1:4 molar ratio. It crystallizes in the monoclinic space group P2 1/ n with a=7.0582(3) Å, b=6.2666(3) Å, and c=27.1420(10) Å, β=92.678(4)°, Z=2. The structure was determined from 1986 observed reflections and refined to R=0.033. When ethylenediamine was added to hexaaquacopper(II) naphthalene-2-sulfonate dissolved in water, [Cu(en) 2(H 2O) 2](C 10H 7SO 3) 22 was obtained which crystallizes in the triclinic space group P1¯ with a=7.1491(5) Å, b=7.1949(5) Å, and c=14.6500(10) Å, α=99.025(6)°, β=98.976(6)°, and γ=104.262(6)°, Z=1. The structure was determined from 2296 observed reflections and refined to R=0.0313. X-ray structure determination of 1 revealed an ionic structure consisting of [Cu(H 2O) 6] +2 and two naphthalene-2-sulfonate anions while that of 2 contains [Cu(en) 2(H 2O) 2] 2+ cation and two naphthalene-2-sulfonate anions. Characteristic for the studied crystals is the alternated-layer arrangement of complex cations and naphthalene-2-sulfonate anions, linked together via hydrogen bonding, and the presence of a particularly robust R22(8) hydrogen-bonding motif that joins the complex cation with two oxygen atoms of the same sulfonate group. Elemental analyses, IR, UV/vis spectroscopic studies are consistent with the structures revealed by X-ray structure determination.

  9. Traceable atomic force microscopy of high-quality solvent-free crystals of [6,6]-phenyl-C61-butyric acid methyl ester

    NASA Astrophysics Data System (ADS)

    Lazzerini, Giovanni Mattia; Paternò, Giuseppe Maria; Tregnago, Giulia; Treat, Neil; Stingelin, Natalie; Yacoot, Andrew; Cacialli, Franco

    2016-02-01

    We report high-resolution, traceable atomic force microscopy measurements of high-quality, solvent-free single crystals of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). These were grown by drop-casting PCBM solutions onto the spectrosil substrates and by removing the residual solvent in a vacuum. A home-built atomic force microscope featuring a plane mirror differential optical interferometer, fiber-fed from a frequency-stabilized laser (emitting at 632.8 nm), was used to measure the crystals' height. The optical interferometer together with the stabilized laser provides traceability (via the laser wavelength) of the vertical measurements made with the atomic force microscope. We find that the crystals can conform to the surface topography, thanks to their height being significantly smaller compared to their lateral dimensions (namely, heights between about 50 nm and 140 nm, for the crystals analysed, vs. several tens of microns lateral dimensions). The vast majority of the crystals are flat, but an isolated, non-flat crystal provides insights into the growth mechanism and allows identification of "molecular terraces" whose height corresponds to one of the lattice constants of the single PCBM crystal (1.4 nm) as measured with X-ray diffraction.

  10. Monoclinic sphere packings. I. Invariant, univariant and bivariant lattice complexes.

    PubMed

    Sowa, Heidrun; Fischer, Werner

    2016-05-01

    All homogeneous sphere packings were derived that refer to the two invariant, the four univariant and the three bivariant lattice complexes belonging to the monoclinic crystal system. In total, sphere packings of 29 types have been found. Only for five types is the maximal inherent symmetry of their sphere packings monoclinic whereas the inherent symmetry is orthorhombic for nine types, tetragonal for five types, hexagonal for six types and cubic for four types. PMID:27126112

  11. Liquid crystal visualization and computer modeling of enhanced heat transfer on a flat plate in forced convection

    SciTech Connect

    Voegler, G.R.; Anderson, A.M.

    1996-12-31

    This paper presents the results of an experimental and computational study of heat transfer enhancement found in the vicinity of a three dimensional block placed on a constant heat flux plate in turbulent forced convection. The experiments used thermochromic liquid crystals to visualize temperature on the surface. Photographs were taken to establish temperature contour lines at a range of velocities and a variety of block sizes and configurations. The results show heat transfer enhancement exists upstream and downstream of the blocks. The enhancement is caused by a horse shoe vortex which stagnates on the front surface of the block and then wraps around the sides. Thin blocks (narrow in the flow direction) show the best enhancement. The computer simulations used the {kappa}-epsilon turbulence model and had reasonable qualitative agreement with the experiments.

  12. Chitinase activity on amorphous chitin thin films: a quartz crystal microbalance with dissipation monitoring and atomic force microscopy study.

    PubMed

    Wang, Chao; Kittle, Joshua D; Qian, Chen; Roman, Maren; Esker, Alan R

    2013-08-12

    Chitinases are widely distributed in nature and have wide-ranging pharmaceutical and biotechnological applications. This work highlights a real-time and label-free method to assay Chitinase activity via a quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). The chitin substrate was prepared by spincoating a trimethylsilyl chitin solution onto a silica substrate, followed by regeneration to amorphous chitin (RChi). The QCM-D and AFM results clearly showed that the hydrolysis rate of RChi films increased as Chitinase (from Streptomyces griseus) concentrations increased, and the optimal temperature and pH for Chitinase activity were around 37 °C and 6-8, respectively. The Chitinase showed greater activity on chitin substrates, having a high degree of acetylation, than on chitosan substrates, having a low degree of acetylation.

  13. Domain reversal and relaxation in LiNbO3 single crystals studied by piezoresponse force microscope

    NASA Astrophysics Data System (ADS)

    Kan, Yi; Lu, Xiaomei; Wu, Xiumei; Zhu, Jinsong

    2006-12-01

    The LiNbO3 crystal was polarized and characterized by the piezoresponse force mode of scanning probe microscope. By using the Kolmogorov-Avrami-Ishibashi [Izv. Akad. Nauk, USSR: Ser. Math. 3, 355 (1937); J. Chem. Phys. 8, 212 (1940); J. Phys. Soc. Jpn. 63, 1031 (1994); 63, 1601 (1994)] theory to analyze the relaxation process after domain switching, it was found that (1) the percent of final switched domains after poling increased with the enhancing poling voltage, (2) the nucleation time was a constant to a certain sample, (3) the dimension of domain growth decreased with the enhancing poling voltage, and (4) the relaxation time had a maximum at a medial voltage. The corresponding mechanism for domain switching was discussed, which is hopefully useful for domain engineering.

  14. Optimal packings of superballs

    NASA Astrophysics Data System (ADS)

    Jiao, Y.; Stillinger, F. H.; Torquato, S.

    2009-04-01

    Dense hard-particle packings are intimately related to the structure of low-temperature phases of matter and are useful models of heterogeneous materials and granular media. Most studies of the densest packings in three dimensions have considered spherical shapes, and it is only more recently that nonspherical shapes (e.g., ellipsoids) have been investigated. Superballs (whose shapes are defined by |x1|2p+|x2|2p+|x3|2p≤1 ) provide a versatile family of convex particles (p≥0.5) with both cubic-like and octahedral-like shapes as well as concave particles (0packings for all convex and concave cases. The candidate maximally dense packings are certain families of Bravais lattice packings (in which each particle has 12 contacting neighbors) possessing the global symmetries that are consistent with certain symmetries of a superball. We also provide strong evidence that our packings for convex superballs (p≥0.5) are most likely the optimal ones. The maximal packing density as a function of p is nonanalytic at the sphere point (p=1) and increases dramatically as p moves away from unity. Two more nontrivial nonanalytic behaviors occur at pc∗=1.1509… and po∗=ln3/ln4=0.7924… for “cubic” and “octahedral” superballs, respectively, where different Bravais lattice packings possess the same densities. The packing characteristics determined by the broken rotational symmetry of superballs are similar to but richer than their two-dimensional “superdisk” counterparts [Y. Jiao , Phys. Rev. Lett. 100, 245504 (2008)] and are distinctly different from that of ellipsoid packings. Our candidate optimal superball packings provide a starting point to quantify the equilibrium phase behavior of superball systems, which should deepen our understanding of the statistical thermodynamics of nonspherical-particle systems.

  15. Lubricant Supply from Crystal Boundaries of Perpendicular Magnetic Disk Evaluated by Lateral Modulation Friction Force Microscopy

    NASA Astrophysics Data System (ADS)

    Miyake, Shojiro; Takahashi, Yuuzi; Wang, Mei; Saitoh, Tadashi; Matsunuma, Satoshi

    2004-11-01

    The tribological behavior of perfluoropolyether (PFPE) films attached to perpendicular recording magnetic disks coated with diamondlike carbon (DLC) was studied in lateral vibration wear tests using lateral modulus friction force microscopy (LM-FFM). The viscoelastic and frictional properties of these PFPE films without heat cure were improved due to the lubricant supply by tip sliding. However, the PFPE films were easily removed with increasing load and lateral vibration amplitude following heat treatment since the free lubricants on the films solidified resulting in the lost of fluidity.

  16. A methodology to determine boundary conditions from forced convection experiments using liquid crystal thermography

    NASA Astrophysics Data System (ADS)

    Jakkareddy, Pradeep S.; Balaji, C.

    2016-05-01

    This paper reports the results of an experimental study to estimate the heat flux and convective heat transfer coefficient using liquid crystal thermography and Bayesian inference in a heat generating sphere, enclosed in a cubical Teflon block. The geometry considered for the experiments comprises a heater inserted in a hollow hemispherical aluminium ball, resulting in a volumetric heat generation source that is placed at the center of the Teflon block. Calibrated thermochromic liquid crystal sheets are used to capture the temperature distribution at the front face of the Teflon block. The forward model is the three dimensional conduction equation which is solved within the Teflon block to obtain steady state temperatures, using COMSOL. Match up experiments are carried out for various velocities by minimizing the residual between TLC and simulated temperatures for every assumed loss coefficient, to obtain a correlation of average Nusselt number against Reynolds number. This is used for prescribing the boundary condition for the solution to the forward model. A surrogate model obtained by artificial neural network built upon the data from COMSOL simulations is used to drive a Markov Chain Monte Carlo based Metropolis Hastings algorithm to generate the samples. Bayesian inference is adopted to solve the inverse problem for determination of heat flux and heat transfer coefficient from the measured temperature field. Point estimates of the posterior like the mean, maximum a posteriori and standard deviation of the retrieved heat flux and convective heat transfer coefficient are reported. Additionally the effect of number of samples on the performance of the estimation process has been investigated.

  17. Characterization of critically cleaned sapphire single-crystal substrates by atomic force microscopy, XPS and contact angle measurements

    NASA Astrophysics Data System (ADS)

    Zhang, Dan; Wang, You; Gan, Yang

    2013-06-01

    A contaminant-free surface of single-crystal α-Al2O3 (or sapphire) substrates is key to the experimental studies of its surface and interfacial properties at ambient conditions. Here we critically evaluated methods reported in the literature using comprehensive surface analysis techniques including atomic force microscopy, XPS and contact angle measurements. We found that reported methods did not perform well in terms of removing both organic and particulate contaminants from the (0 0 0 1) basal surface. After thoroughly examining the cleaning effect of various chemical solutions and UV light and plasma irradiation, and based on modified RCA cleaning protocols, we proposed a new wet-cleaning method showing outstanding cleaning performance. This new reliable method will be very useful for the next-step surface chemistry study of single-crystal α-Al2O3. It was also demonstrated that AFM, due to its high spatial resolution and sensitivity as a local probe technique, was an indispensable tool for surface contamination control studies.

  18. Flat Pack Toy Design

    ERIC Educational Resources Information Center

    Hutcheson, Brian

    2007-01-01

    In this article, the author introduces the concept of flat pack toys. Flat pack toys are designed using a template on a single sheet of letter-sized card stock paper. Before being cut out and built into a three-dimensional toy, they are scanned into the computer and uploaded to a website. With the template accessible from the website, anyone with…

  19. TLC Pack Unpacked

    ERIC Educational Resources Information Center

    Oberhofer, Margret; Colpaert, Jozef

    2015-01-01

    TLC Pack stands for Teaching Languages to Caregivers and is a course designed to support migrants working or hoping to work in the caregiving sector. The TLC Pack resources range from A2 to B2 level of the Common European Framework of Reference for Languages (CEFR), and will be made available online in the six project languages: Dutch, English,…

  20. Interactions of hyaluronan grafted on protein surfaces studied using a quartz crystal microbalance and a surface force balance.

    PubMed

    Jiang, Lei; Han, Juan; Yang, Limin; Ma, Hongchao; Huang, Bo

    2015-10-01

    Vocal folds are complex and multilayer-structured where the main layer is widely composed of hyaluronan (HA). The viscoelasticity of HA is key to voice production in the vocal fold as it affects the initiation and maintenance of phonation. In this study a simple layer-structured surface model was set up to mimic the structure of the vocal folds. The interactions between two opposing surfaces bearing HA were measured and characterised to analyse HA's response to the normal and shear compression at a stress level similar to that in the vocal fold. From the measurements of the quartz crystal microbalance, atomic force microscopy and the surface force balance, the osmotic pressure, normal interactions, elasticity change, volume fraction, refractive index and friction of both HA and the supporting protein layer were obtained. These findings may shed light on the physical mechanism of HA function in the vocal fold and the specific role of HA as an important component in the effective treatment of the vocal fold disease. PMID:26274046

  1. Interactions of hyaluronan grafted on protein surfaces studied using a quartz crystal microbalance and a surface force balance.

    PubMed

    Jiang, Lei; Han, Juan; Yang, Limin; Ma, Hongchao; Huang, Bo

    2015-10-01

    Vocal folds are complex and multilayer-structured where the main layer is widely composed of hyaluronan (HA). The viscoelasticity of HA is key to voice production in the vocal fold as it affects the initiation and maintenance of phonation. In this study a simple layer-structured surface model was set up to mimic the structure of the vocal folds. The interactions between two opposing surfaces bearing HA were measured and characterised to analyse HA's response to the normal and shear compression at a stress level similar to that in the vocal fold. From the measurements of the quartz crystal microbalance, atomic force microscopy and the surface force balance, the osmotic pressure, normal interactions, elasticity change, volume fraction, refractive index and friction of both HA and the supporting protein layer were obtained. These findings may shed light on the physical mechanism of HA function in the vocal fold and the specific role of HA as an important component in the effective treatment of the vocal fold disease.

  2. A new color of the synthetic chameleon methoxyallene: synthesis of trifluoromethyl-substituted pyridinol derivatives: an unusual reaction mechanism, a remarkable crystal packing, and first palladium-catalyzed coupling reactions.

    PubMed

    Flögel, Oliver; Dash, Jyotirmayee; Brüdgam, Irene; Hartl, Hans; Reissig, Hans-Ulrich

    2004-09-01

    Addition of lithiated methoxyallene to pivalonitrile afforded after aqueous workup the expected iminoallene 1 in excellent yield. Treatment of this intermediate with silver nitrate accomplished the desired cyclization to the electron-rich pyrrole derivative 2 in moderate yield. Surprisingly, trifluoroacetic acid converted iminoallene 1 to a mixture of enamide 3 and trifluoromethyl-substituted pyridinol 4 (together with its tautomer 5). A plausible mechanism proposed for this intriguing transformation involves addition of trifluoroacetate to the central allene carbon atom of an allenyl iminium intermediate as crucial step. Enamide 3 is converted to pyridinol 4 by an intramolecular aldol-type process. A practical direct synthesis of trifluoromethyl-substituted pyridinols 4, 10, 11, and 12 starting from typical nitriles and methoxyallene was established. Pyridinol 10 shows an interesting crystal packing with three molecules in the elementary cell and a remarkable helical supramolecular arrangement. Trifluoromethyl-substituted pyridinol 4 was converted to the corresponding pyridyl nonaflate 13, which is an excellent precursor for palladium-catalyzed reactions leading to pyridine derivatives 14-16 in good to excellent yields. The new synthesis of trifluoromethyl-substituted pyridines disclosed here demonstrates a novel reactivity pattern of lithiated methoxyallene which is incorporated into the products as the unusual tripolar synthon B. PMID:15352110

  3. A new color of the synthetic chameleon methoxyallene: synthesis of trifluoromethyl-substituted pyridinol derivatives: an unusual reaction mechanism, a remarkable crystal packing, and first palladium-catalyzed coupling reactions.

    PubMed

    Flögel, Oliver; Dash, Jyotirmayee; Brüdgam, Irene; Hartl, Hans; Reissig, Hans-Ulrich

    2004-09-01

    Addition of lithiated methoxyallene to pivalonitrile afforded after aqueous workup the expected iminoallene 1 in excellent yield. Treatment of this intermediate with silver nitrate accomplished the desired cyclization to the electron-rich pyrrole derivative 2 in moderate yield. Surprisingly, trifluoroacetic acid converted iminoallene 1 to a mixture of enamide 3 and trifluoromethyl-substituted pyridinol 4 (together with its tautomer 5). A plausible mechanism proposed for this intriguing transformation involves addition of trifluoroacetate to the central allene carbon atom of an allenyl iminium intermediate as crucial step. Enamide 3 is converted to pyridinol 4 by an intramolecular aldol-type process. A practical direct synthesis of trifluoromethyl-substituted pyridinols 4, 10, 11, and 12 starting from typical nitriles and methoxyallene was established. Pyridinol 10 shows an interesting crystal packing with three molecules in the elementary cell and a remarkable helical supramolecular arrangement. Trifluoromethyl-substituted pyridinol 4 was converted to the corresponding pyridyl nonaflate 13, which is an excellent precursor for palladium-catalyzed reactions leading to pyridine derivatives 14-16 in good to excellent yields. The new synthesis of trifluoromethyl-substituted pyridines disclosed here demonstrates a novel reactivity pattern of lithiated methoxyallene which is incorporated into the products as the unusual tripolar synthon B.

  4. α-amylase crystal growth investigated by in situ atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Astier, J. P.; Bokern, D.; Lapena, L.; Veesler, S.

    2001-06-01

    The growth behavior of porcine pancreatic α-amylase at defined supersaturation has been investigated by means of temperature controlled in situ atomic force microscopy (AFM). The step velocities measured by AFM were in overall agreement with the normal growth rates of an individual face measured by optical microscopy. In addition, highly local growth dynamics could be visualized. Imaging in tapping mode revealed crystalline amylase aggregates attached to the basal face and their subsequent incorporation into growing terraces producing a macrodefect. At high supersaturation ( β=1.6) 2-D nucleation was found to be the dominating growth mechanism, whereas at lower supersaturation ( β=1.3) the growth process appears to be defect controlled (spiral growth). The analysis of step heights on 2-D nucleation islands (monomolecular protein layers) and growth steps (two molecules in height) in combination with results from light scattering experiments suggest that a single protein molecule is the basic growth unit.

  5. Predictions of melting, crystallization, and local atomic arrangements of aluminum clusters using a reactive force field

    NASA Astrophysics Data System (ADS)

    Ojwang', J. G. O.; van Santen, Rutger; Kramer, Gert Jan; van Duin, Adri C. T.; Goddard, William A.

    2008-12-01

    A parametrized reactive force field model for aluminum ReaxFFAl has been developed based on density functional theory (DFT) data. A comparison has been made between DFT and ReaxFFAl outputs to ascertain whether ReaxFFAl is properly parametrized and to check if the output of the latter has correlation with DFT results. Further checks include comparing the equations of state of condensed phases of Al as calculated from DFT and ReaxFFAl. There is a good match between the two results, again showing that ReaxFFAl is correctly parametrized as per the DFT input. Simulated annealing has been performed on aluminum clusters Aln using ReaxFFAl to find the stable isomers of the clusters. A plot of stability function versus cluster size shows the existence of highly stable clusters (magic clusters). Quantum mechanically these magic clusters arise due to the complete filling of the orbital shells. However, since force fields do not care about electrons but work on the assumption of validity of Born-Oppenheimer approximation, the magic clusters are therefore correlated with high structural symmetry. There is a rapid decline in surface energy contribution due to the triangulated nature of the surface atoms leading to higher coordination number. The bulk binding energy is computed to be 76.8 kcal/mol. This gives confidence in the suitability of ReaxFF for studying and understanding the underlying dynamics in aluminum clusters. In the quantification of the growth of cluster it is seen that as the size of the clusters increase there is preference for the coexistence of fcc/hcp orders at the expense of simple icosahedral ordering, although there is some contribution from distorted icosahedral ordering. It is found that even for aluminum clusters with 512 atoms distorted icosahedral ordering exists. For clusters with N>=256 atoms fcc ordering dominates, which implies that at this point we are already on the threshold of bulklike bonding.

  6. Solidification (crystal growth) in the presence of gravitational forces. [indium antimonide melts at reduced gravity

    NASA Technical Reports Server (NTRS)

    Gatos, H. C.; Witt, A. F.

    1978-01-01

    The surface tension behavior of doped and undoped InSb melts was investigated as well as their temperature and composition dependence. Surface tension in InSb melts was determined using the sessile-drop technique covering the temperature range from 530 C to 880 C. A linear regression of the data obtained shows that the temperature dependence of sigma is 392- (T-530) x (7000) plus or minus 10 dyne/cm. The d sigma/d Tau for intrinsics InSb is less than that previously reported. On the basis of the surface tension data obtained, it is concluded that surface tension induced convective flow velocities in InSb under reduced gravity conditions range from zero to at most 1 cm/sec. Accordingly, no interference with dopant segregation can be expected during growth in space because the momentum boundary layer (at the crystal melt interface) associated with any Marangoni-type convective flows would, at the given growth rate, be significantly larger than the predicted diffusion boundary layer thickness.

  7. Use of Pom Pons to Illustrate Cubic Crystal Structures.

    ERIC Educational Resources Information Center

    Cady, Susan G.

    1997-01-01

    Describes a method that uses olefin pom pons to illustrate cubic crystal structure. Facilitates hands-on examination of different packing arrangements such as hexagonal close-packed and cubic close-packed structures. (JRH)

  8. Structural Evolution of a Granular Pack under Manual Tapping

    NASA Astrophysics Data System (ADS)

    Iikawa, Naoki; Bandi, Mahesh M.; Katsuragi, Hiroaki

    2015-09-01

    We experimentally study a two-dimensional (2D) granular pack of photoelastic disks subject to vertical manual tapping. Using bright- and dark-field images, we employ gradient-based image analysis methods to analyze various structural quantities. These include the packing fraction (ϕ), force per disk (Fd), and force chain segment length (l) as functions of the tapping number (τ). The increase in the packing fraction with the tapping number is found to exponentially approach an asymptotic value. An exponential distribution is observed for the cumulative numbers of both the force per disk Fd:Ncum(Fd) = AFexp ( - Fd/F0), and the force chain segment length l:Ncum(l) = Alexp ( - l/l0). Whereas the coefficient AF varies with τ for Fd, l shows no dependence on τ. The τ dependences of Fd and ϕ allow us to posit a linear relationship between the total force of the granular pack Ftot*(τ ) and ϕ(τ).

  9. Morphology Change of C60 Islands on Organic Crystals Observed by Atomic Force Microscopy.

    PubMed

    Freund, Sara; Hinaut, Antoine; Pawlak, Rémy; Liu, Shi-Xia; Decurtins, Silvio; Meyer, Ernst; Glatzel, Thilo

    2016-06-28

    Organic-organic heterojunctions are nowadays highly regarded materials for light-emitting diodes, field-effect transistors, and photovoltaic cells with the prospect of designing low-cost, flexible, and efficient electronic devices.1-3 However, the key parameter of optimized heterojunctions relies on the choice of the molecular compounds as well as on the morphology of the organic-organic interface,4 which thus requires fundamental studies. In this work, we investigated the deposition of C60 molecules at room temperature on an organic layer compound, the salt bis(benzylammonium)bis(oxalato)cupurate(II), by means of noncontact atomic force microscopy. Three-dimensional molecular islands of C60 having either triangular or hexagonal shapes are formed on the substrate following a "Volmer-Weber" type of growth. We demonstrate the dynamical reshaping of those C60 nanostructures under the local action of the AFM tip at room temperature. The dissipated energy is about 75 meV and can be interpreted as the activation energy required for this migration process.

  10. Morphology Change of C60 Islands on Organic Crystals Observed by Atomic Force Microscopy.

    PubMed

    Freund, Sara; Hinaut, Antoine; Pawlak, Rémy; Liu, Shi-Xia; Decurtins, Silvio; Meyer, Ernst; Glatzel, Thilo

    2016-06-28

    Organic-organic heterojunctions are nowadays highly regarded materials for light-emitting diodes, field-effect transistors, and photovoltaic cells with the prospect of designing low-cost, flexible, and efficient electronic devices.1-3 However, the key parameter of optimized heterojunctions relies on the choice of the molecular compounds as well as on the morphology of the organic-organic interface,4 which thus requires fundamental studies. In this work, we investigated the deposition of C60 molecules at room temperature on an organic layer compound, the salt bis(benzylammonium)bis(oxalato)cupurate(II), by means of noncontact atomic force microscopy. Three-dimensional molecular islands of C60 having either triangular or hexagonal shapes are formed on the substrate following a "Volmer-Weber" type of growth. We demonstrate the dynamical reshaping of those C60 nanostructures under the local action of the AFM tip at room temperature. The dissipated energy is about 75 meV and can be interpreted as the activation energy required for this migration process. PMID:27219352

  11. Graphitic packing removal tool

    SciTech Connect

    Meyers, K.E.; Kolsun, G.J.

    1996-12-31

    Graphitic packing removal tools are described for removal of the seal rings in one piece from valves and pumps. The packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal.

  12. Graphitic packing removal tool

    DOEpatents

    Meyers, K.E.; Kolsun, G.J.

    1997-11-11

    Graphitic packing removal tools for removal of the seal rings in one piece are disclosed. The packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal. 5 figs.

  13. Graphitic packing removal tool

    DOEpatents

    Meyers, Kurt Edward; Kolsun, George J.

    1997-01-01

    Graphitic packing removal tools for removal of the seal rings in one piece. he packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal.

  14. Packing frustration in dense confined fluids.

    PubMed

    Nygård, Kim; Sarman, Sten; Kjellander, Roland

    2014-09-01

    Packing frustration for confined fluids, i.e., the incompatibility between the preferred packing of the fluid particles and the packing constraints imposed by the confining surfaces, is studied for a dense hard-sphere fluid confined between planar hard surfaces at short separations. The detailed mechanism for the frustration is investigated via an analysis of the anisotropic pair distributions of the confined fluid, as obtained from integral equation theory for inhomogeneous fluids at pair correlation level within the anisotropic Percus-Yevick approximation. By examining the mean forces that arise from interparticle collisions around the periphery of each particle in the slit, we calculate the principal components of the mean force for the density profile--each component being the sum of collisional forces on a particle's hemisphere facing either surface. The variations of these components with the slit width give rise to rather intricate changes in the layer structure between the surfaces, but, as shown in this paper, the basis of these variations can be easily understood qualitatively and often also semi-quantitatively. It is found that the ordering of the fluid is in essence governed locally by the packing constraints at each single solid-fluid interface. A simple superposition of forces due to the presence of each surface gives surprisingly good estimates of the density profiles, but there remain nontrivial confinement effects that cannot be explained by superposition, most notably the magnitude of the excess adsorption of particles in the slit relative to bulk.

  15. Nasal packing and stenting

    PubMed Central

    Weber, Rainer K.

    2011-01-01

    Nasal packs are indispensable in ENT practice. This study reviews current indications, effectiveness and risks of nasal packs and stents. In endoscopic surgery, nasal packs should always have smooth surfaces to minimize mucosal damage, improve wound healing and increase patient comfort. Functional endoscopic endonasal sinus surgery allows the use of modern nasal packs, since pressure is no longer required. So called hemostatic/resorbable materials are a first step in this direction. However, they may lead to adhesions and foreign body reactions in mucosal membranes. Simple occlusion is an effective method for creating a moist milieu for improved wound healing and avoiding dryness. Stenting of the frontal sinus is recommended if surgery fails to produce a wide, physiologically shaped drainage path that is sufficiently covered by intact tissue. PMID:22073095

  16. Dense packings of polyhedra: Platonic and Archimedean solids.

    PubMed

    Torquato, S; Jiao, Y

    2009-10-01

    regarded to be the analog of Kepler's sphere conjecture for these solids.The truncated tetrahedron is the only nonchiral Archimedean solid that is not centrally symmetric [corrected], the densest known packing of which is a non-lattice packing with density at least as high as 23/24=0.958 333... . We discuss the validity of our conjecture to packings of superballs, prisms, and antiprisms as well as to high-dimensional analogs of the Platonic solids. In addition, we conjecture that the optimal packing of any convex, congruent polyhedron without central symmetry generally is not a lattice packing. Finally, we discuss the possible applications and generalizations of the ASC scheme in predicting the crystal structures of polyhedral nanoparticles and the study of random packings of hard polyhedra.

  17. Packing of elastic wires in flexible shells

    NASA Astrophysics Data System (ADS)

    Vetter, R.; Wittel, F. K.; Herrmann, H. J.

    2015-11-01

    The packing problem of long thin filaments that are injected into confined spaces is of fundamental interest for physicists and biologists alike. How linear threads pack and coil is well known only for the ideal case of rigid containers, though. Here, we force long elastic rods into flexible spatial confinement borne by an elastic shell to examine under which conditions recently acquired knowledge on wire packing in rigid spheres breaks down. We find that unlike in rigid cavities, friction plays a key role by giving rise to the emergence of two distinct packing patterns. At low friction, the wire densely coils into an ordered toroidal bundle with semi-ellipsoidal cross-section, while at high friction, it packs into a highly disordered, hierarchic structure. These two morphologies are shown to be separated by a continuous phase transition. Our findings demonstrate the dramatic impact of friction and confinement elasticity on filamentous packing and might drive future research on such systems in physics, biology and even medical technology toward including these mutually interacting effects.

  18. Microstructural characterization of random packings of cubic particles

    PubMed Central

    Malmir, Hessam; Sahimi, Muhammad; Tabar, M. Reza Rahimi

    2016-01-01

    Understanding the properties of random packings of solid objects is of critical importance to a wide variety of fundamental scientific and practical problems. The great majority of the previous works focused, however, on packings of spherical and sphere-like particles. We report the first detailed simulation and characterization of packings of non-overlapping cubic particles. Such packings arise in a variety of problems, ranging from biological materials, to colloids and fabrication of porous scaffolds using salt powders. In addition, packing of cubic salt crystals arise in various problems involving preservation of pavements, paintings, and historical monuments, mineral-fluid interactions, CO2 sequestration in rock, and intrusion of groundwater aquifers by saline water. Not much is known, however, about the structure and statistical descriptors of such packings. We have developed a version of the random sequential addition algorithm to generate such packings, and have computed a variety of microstructural descriptors, including the radial distribution function, two-point probability function, orientational correlation function, specific surface, and mean chord length, and have studied the effect of finite system size and porosity on such characteristics. The results indicate the existence of both spatial and orientational long-range order in the packing, which is more distinctive for higher packing densities. The maximum packing fraction is about 0.57. PMID:27725736

  19. Microstructural characterization of random packings of cubic particles

    NASA Astrophysics Data System (ADS)

    Malmir, Hessam; Sahimi, Muhammad; Tabar, M. Reza Rahimi

    2016-10-01

    Understanding the properties of random packings of solid objects is of critical importance to a wide variety of fundamental scientific and practical problems. The great majority of the previous works focused, however, on packings of spherical and sphere-like particles. We report the first detailed simulation and characterization of packings of non-overlapping cubic particles. Such packings arise in a variety of problems, ranging from biological materials, to colloids and fabrication of porous scaffolds using salt powders. In addition, packing of cubic salt crystals arise in various problems involving preservation of pavements, paintings, and historical monuments, mineral-fluid interactions, CO2 sequestration in rock, and intrusion of groundwater aquifers by saline water. Not much is known, however, about the structure and statistical descriptors of such packings. We have developed a version of the random sequential addition algorithm to generate such packings, and have computed a variety of microstructural descriptors, including the radial distribution function, two-point probability function, orientational correlation function, specific surface, and mean chord length, and have studied the effect of finite system size and porosity on such characteristics. The results indicate the existence of both spatial and orientational long-range order in the packing, which is more distinctive for higher packing densities. The maximum packing fraction is about 0.57.

  20. Surface-initiated dehydrogenative polymerization of monolignols: a quartz crystal microbalance with dissipation monitoring and atomic force microscopy study.

    PubMed

    Wang, Chao; Qian, Chen; Roman, Maren; Glasser, Wolfgang G; Esker, Alan R

    2013-11-11

    This work highlights a real-time and label-free method to monitor the dehydrogenative polymerization of monolignols initiated by horseradish peroxidase (HRP) physically immobilized on surfaces using a quartz crystal microbalance with dissipation monitoring (QCM-D). The dehydrogenative polymer (DHP) films are expected to provide good model substrates for studying ligninolytic enzymes. The HRP was adsorbed onto gold or silica surfaces or onto and within porous desulfated nanocrystalline cellulose films from an aqueous solution. Surface-immobilized HRP retained its activity and selectivity for monolignols as coniferyl and p-coumaryl alcohol underwent dehydrogenative polymerization in the presence of hydrogen peroxide, whereas sinapyl alcohol polymerization required the addition of a nucleophile. The morphologies of the DHP layers on the surfaces were investigated via atomic force microscopy (AFM). Data from QCM-D and AFM showed that the surface-immobilized HRP-initiated dehydrogenative polymerization of monolignols was greatly affected by the support surface, monolignol concentration, hydrogen peroxide concentration, and temperature.

  1. Modulation of Calcium Oxalate Crystallization by Proteins and Small Molecules Investigated by In Situ Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Qiu, R.; Orme, C.; Cody, A. M.; Wierzbicki, A.; Hoyer, J.; Nancollas, G.; de Yoreo, J.

    2002-12-01

    Understanding the physical mechanisms by which biological inhibitors control nucleation and growth of inorganic crystals is a major focus of biomineral research. Calcium oxalate monohydrate (COM), which plays a functional role in plant physiology, is also a source of pathogenesis in humans where it causes kidney stone disease. Although a great deal of research has been carried out on the modulation COM by proteins and small molecules, the basic mechanism has not yet been understood. However, because the proteins that play a role in COM growth have been identified and sequenced, COM provides an excellent model system for research into biomineral growth. In this study, in situ atomic force microscopy (AFM) was used to monitor the COM surface under controlled growth conditions both from pure solutions and those doped with citrate and osteopontin (OPN) in order to determine their effects on surface morphology and growth dynamics at the molecular level. As with other solution-grown crystals such as calcite, COM grows on complex dislocation hillocks. In pure solution, while growth on the (010) face is isotropic, hillocks on the (-101) face exhibit anisotropic step kinetics. Steps of [-10-1] and <120> orientation are clearly delineated with the [-10-1] being the fast growing direction. When citrate is added to the solution, both growth rate and morphology are drastically changed on (-101) face, especially along the [-10-1] direction. This results in isotropic disc-shaped hillocks a shape that is then reflected in the macroscopic growth habit. In contrast, no large growth changes were observed on the (010) facet. At the same time, molecular modeling predicts an excellent fit of the citrate ion into the (-101) plane and a poor fit to the (010) face. Here we propose a model that reconciles the step-specific interactions implied by the AFM results with the face-specific predictions of the calculations. Finally, we present the results of doping with aspartic acid as well as

  2. Pessimal shapes for packing

    NASA Astrophysics Data System (ADS)

    Kallus, Yoav

    2014-03-01

    The question of which convex shapes leave the most empty space in their densest packing is the subject of Reinhardt's conjecture in two dimensions and Ulam's conjecture in three dimensions. Such conjectures about pessimal packing shapes have proven notoriously difficult to make progress on. I show that the regular heptagon is a local pessimum among all convex shapes, and that the 3D ball is a local pessimum among origin-symmetric shapes. Any shape sufficiently close in the space of shapes to these local pessima can be packed at a greater efficiency than they. In two dimensions and in dimensions above three, the ball is not a local pessimum, so the situation in 3D is unusual and intriguing. I will discuss what conditions conspire to make the 3D ball a local pessimum and whether we can prove that it is also a global pessimum.

  3. The packing of particles

    SciTech Connect

    Cumberland, D.J.; Crawford, R.J.

    1987-01-01

    The wide range of information currently available on the packing of particles is brought together in this monograph. The authors' interest in the subject was initially aroused by the question of whether there is an optimum particle size distribution which would maximise the packing density of particles - a question which has attracted the interest of scientists and engineers for centuries. The densification of a powder mass is of relevance in a great many industries, among them the pharmaceutical, ceramic, powder metallurgy and civil engineering industries. In addition, the packing of regular - or irregular - shaped particles is also of relevance to a surprisingly large number of other industries and subject areas, i.e. the foundry industry, nuclear engineering, chemical engineering, crystallography, geology, biology, telecommunications, and so on. Accordingly, this book is written for a wide audience.

  4. Ex situ scanning force microscopic observation of growth and dissolution phenomena on {0 1 0} surfaces of potassium hydrogen phthalate crystals (KAP) caused by isomorphic exchange reactions

    NASA Astrophysics Data System (ADS)

    Woensdregt, Cornelis F.; Glikin, Arkady E.

    2005-10-01

    Ex situ scanning force microscopic observations reveal characteristic phenomena of growth and dissolution on {0 1 0} surfaces of potassium hydrogen phthalate crystals (KHC 8H 4O 4 or KAP) in contact with a saturated solution of rubidium hydrogen phthalate (RbHC 8H 4O 4 or RbAP) due to an isomorphic exchange reaction. An array of small torpedo-shaped inclusions elongated parallel to the crystallographic c-axis covers the initially smooth cleaved surfaces in less than 1 s. Even in such a short time, almost simultaneous very tiny acicular crystals crystallize parallel to the borders of the elongated etch pits. Moreover, protuberances on the step edges of these etch pits and isometric crystals on the surface are formed as well. When KAP {0 1 0} surfaces are wetted during 10 s with a saturated solution of RbAP, these phenomena are much better visible. After 15 s of wetting numerous elongated crystals cover the surface and the channels. After 30 s, the {0 1 0} surface becomes almost too rough for SFM observations since the etch pits are overgrown by precipitates. These phenomena of nearly simultaneous dissolution and consequent crystallization are the initial stages of the monocrystalline isomorphic exchange process on nanometric scale. It is a very fast process, which unfortunately could not be followed in situ. Our observations corroborate the importance of the volume effect on the isomorphic exchange reactions.

  5. Study of the mechanism of crystallization electromotive force during growth of congruent LiNbO 3 using a micro-pulling-down method

    NASA Astrophysics Data System (ADS)

    Koh, Shinji; Uda, Satoshi; Nishida, Masahiro; Huang, Xinming

    2006-12-01

    We have investigated the crystallization electromotive force (EMF) during the growth of congruent LiNbO 3 (LN) by exploiting the features of a micro-pulling-down ( μ-PD) method. The electric potential distribution around the growth interface that was measured in the μ-PD system was attributed to the Seebeck effect and several mV of crystallization EMF. The mechanism of the crystallization EMF during the growth of congruent LN from the melt was explained using a model wherein segregation of the ionic species in the melt formed a net ionic charge at the growth interface resulting in the development of an EMF. Redistribution of the net ionic charge, which was analyzed on the basis of a one-dimensional differential equation that included electric-field-driven transport in the melt, well reproduced the experimental data of the nonlinear dependence of crystallization EMF on the growth rate. We concluded that the crystallization EMF occurred during crystal growth of the congruent LN owing to the ionic-charge accumulation at the growth interface.

  6. Packing transition in alkali metallic clusters

    NASA Astrophysics Data System (ADS)

    Kawai, R.; Sung, Ming Wen; Weare, John H.

    1996-03-01

    Small metallic clusters form a local geometric configuration quite different from the bulk crystals. As the cluster size increases, several transitions in the local coordination take place before the bulk structure appears. These transitions involve change in the nature of chemical bonds. We have systematically investigated the structural transition of various alkali metal clusters including binary compounds using an ab initio molecular dynamics simulation. Among them, Li clusters exhibit unusual transition in their packing pattern. Small lithium clusters (N <= 21) form open structures based on a ``solvation shell''.(M. Sung, R. Kawai, and J. Weare, Phys. Rev. Lett. 73) (1994) 3552., which is quite different from other alkali metal clusters. The bonding of these small clusters is partially ionic. Above N=25, a close-packed structure is established. However, the local configuration still differ from that of the bulk crystal. As the size further increases, the ionic nature decreases and the system reaches another close-packed structure based on the Mackay icosahedron, which is similar to the bulk crystal structure.

  7. Sun Packs Double Punch

    NASA Video Gallery

    On August 3, the sun packed a double punch, emitting a M6.0-class flare at 9:43 am EDT. This video is of the second, slightly stronger M9.3-class flare at 11:41 pm EDT. Both flares had significant ...

  8. Packing Them In.

    ERIC Educational Resources Information Center

    Carter, Claudia

    1997-01-01

    This activity involves students investigating the mathematics of packaging and exploring various concepts in geometry, including area and the Pythagorean theorem. Mathematics comes out of the discussion of packaging cans into six-packs and focuses on the cost-effectiveness of the horizontal storage area used. Students learn how knowledge of…

  9. Nutrition Action Pack.

    ERIC Educational Resources Information Center

    Sockut, Joanne; Stumpe, Stephanie

    One of five McDonald's Action Packs, these instructional materials integrate elementary school-level nutrition education into other disciplines--biology, sociology, physiology, mathematics, and art. Contents include four units consisting of twelve activities. Unit 1, Why You Need Food, is a self-examination of what is needed for growth, health,…

  10. Economics Action Pack.

    ERIC Educational Resources Information Center

    McDonald's Corp., Oak Brook, IL.

    One of five McDonald's Action Packs, this learning package introduces intermediate grade students to basic economic concepts. The fourteen activities include the topics of consumption (4 activities), production (5), the market system (3), a pretest, and a posttest. Specific titles under consumption include The Wonderful Treasure Tree (introduction…

  11. AUTOmatic Message PACKing Facility

    2004-07-01

    AUTOPACK is a library that provides several useful features for programs using the Message Passing Interface (MPI). Features included are: 1. automatic message packing facility 2. management of send and receive requests. 3. management of message buffer memory. 4. determination of the number of anticipated messages from a set of arbitrary sends, and 5. deterministic message delivery for testing purposes.

  12. Fully ordered to disordered granular sphere packings with random deposition

    NASA Astrophysics Data System (ADS)

    Kudrolli, Arshad; Panaitescu, Andreea

    2013-03-01

    Granular packings are typically obtained by pouring grains into a container in a gravitational field as when sugar is poured into a jar, or grains into a silo. We deconstruct this method and study the impact on packing by simply varying the pour rate and energy of particles dropped randomly but spatially uniformly in a large container whose substrate can act as a template. We find that fully disordered packings are observed when large number of particles are added all at once but an ordered fcc crystal is observed when particles are added sequentially at random locations and allowed to come to rest before adding the next layer. By scanning the packings obtained by 3D X-ray tomography, we identify the positions of all the particles and the growth of order and defects. We present an analysis of the structures formed and compare and contrast it with packings obtained using other protocols including by cyclic shear.

  13. Softening of stressed granular packings with resonant sound waves.

    PubMed

    Reichhardt, C J Olson; Lopatina, L M; Jia, X; Johnson, P A

    2015-08-01

    We perform numerical simulations of a two-dimensional bidisperse granular packing subjected to both a static confining pressure and a sinusoidal dynamic forcing applied by a wall on one edge of the packing. We measure the response experienced by a wall on the opposite edge of the packing and obtain the resonant frequency of the packing as the static or dynamic pressures are varied. Under increasing static pressure, the resonant frequency increases, indicating a velocity increase of elastic waves propagating through the packing. In contrast, when the dynamic amplitude is increased for fixed static pressure, the resonant frequency decreases, indicating a decrease in the wave velocity. This occurs both for compressional and for shear dynamic forcing and is in agreement with experimental results. We find that the average contact number Zc at the resonant frequency decreases with increasing dynamic amplitude, indicating that the elastic softening of the packing is associated with a reduced number of grain-grain contacts through which the elastic waves can travel. We image the excitations created in the packing and show that there are localized disturbances or soft spots that become more prevalent with increasing dynamic amplitude. Our results are in agreement with experiments on glass bead packings and earth materials such as sandstone and granite and may be relevant to the decrease in elastic wave velocities that has been observed to occur near fault zones after strong earthquakes, in surficial sediments during strong ground motion, and in structures during earthquake excitation. PMID:26382390

  14. Softening of stressed granular packings with resonant sound waves.

    PubMed

    Reichhardt, C J Olson; Lopatina, L M; Jia, X; Johnson, P A

    2015-08-01

    We perform numerical simulations of a two-dimensional bidisperse granular packing subjected to both a static confining pressure and a sinusoidal dynamic forcing applied by a wall on one edge of the packing. We measure the response experienced by a wall on the opposite edge of the packing and obtain the resonant frequency of the packing as the static or dynamic pressures are varied. Under increasing static pressure, the resonant frequency increases, indicating a velocity increase of elastic waves propagating through the packing. In contrast, when the dynamic amplitude is increased for fixed static pressure, the resonant frequency decreases, indicating a decrease in the wave velocity. This occurs both for compressional and for shear dynamic forcing and is in agreement with experimental results. We find that the average contact number Zc at the resonant frequency decreases with increasing dynamic amplitude, indicating that the elastic softening of the packing is associated with a reduced number of grain-grain contacts through which the elastic waves can travel. We image the excitations created in the packing and show that there are localized disturbances or soft spots that become more prevalent with increasing dynamic amplitude. Our results are in agreement with experiments on glass bead packings and earth materials such as sandstone and granite and may be relevant to the decrease in elastic wave velocities that has been observed to occur near fault zones after strong earthquakes, in surficial sediments during strong ground motion, and in structures during earthquake excitation.

  15. Supramolecular complex formation and crystallization of isocitrate dehydrogenase from Thermus thermophilus HB8: preliminary studies with X-Ray crystallography and atomic force microscopy.

    PubMed

    Ishii, Noriyuki; Umemura, Kazuo; Miyazaki, Kentaro

    2008-09-01

    Atomic force microscopy (AFM) observation of a crystal surface of the thermostable isocitrate dehydrogenase (ICDH) from a thermophilic eubacterium, Thermus thermophilus HB8, suggested that the crystal consists of huge homo-complexed ellipsoidal bodies of the protein, with averaged long- and short-axis diameters of 18.6 nm and 10.9 nm respectively. Thick diamond-shaped crystals of about 0.4 mm on the longest axis were obtained by the vapor diffusion method from a solution of 100 mM sodium cacodylate, pH 6.6-8.4, containing 1.4 M sodium acetate as the precipitate, and diffracted X-rays at 3.7 A resolution. The crystals belonged to the monoclinic lattice type with space group C2 and had cell dimensions of a=495.5, b=189.2, c=336.2 A, and beta=126.4 degrees , indicating that an asymmetric unit contained more than 33 molecules with a molecular mass of 54.2 kDa. Calculations based on data obtained by the X-ray method showed good agreement with AFM observation. These results suggest the possibility that the residing T. thermophilus HB8 ICDH molecules are piled one on top another as a preformed supramolecular nano-architecture in the crystal lattice. The system appears suitable for further investigation using a bottom-up approach to the self-associated construction of nano-architectures with proteins.

  16. Random close packing in protein cores

    NASA Astrophysics Data System (ADS)

    Ohern, Corey

    Shortly after the determination of the first protein x-ray crystal structures, researchers analyzed their cores and reported packing fractions ϕ ~ 0 . 75 , a value that is similar to close packing equal-sized spheres. A limitation of these analyses was the use of `extended atom' models, rather than the more physically accurate `explicit hydrogen' model. The validity of using the explicit hydrogen model is proved by its ability to predict the side chain dihedral angle distributions observed in proteins. We employ the explicit hydrogen model to calculate the packing fraction of the cores of over 200 high resolution protein structures. We find that these protein cores have ϕ ~ 0 . 55 , which is comparable to random close-packing of non-spherical particles. This result provides a deeper understanding of the physical basis of protein structure that will enable predictions of the effects of amino acid mutations and design of new functional proteins. We gratefully acknowledge the support of the Raymond and Beverly Sackler Institute for Biological, Physical, and Engineering Sciences, National Library of Medicine training grant T15LM00705628 (J.C.G.), and National Science Foundation DMR-1307712 (L.R.).

  17. Impact of Molecular Orientation and Packing Density on Electronic Polarization in the Bulk and at Surfaces of Organic Semiconductors.

    PubMed

    Ryno, Sean M; Risko, Chad; Brédas, Jean-Luc

    2016-06-01

    The polarizable environment surrounding charge carriers in organic semiconductors impacts the efficiency of the charge transport process. Here, we consider two representative organic semiconductors, tetracene and rubrene, and evaluate their polarization energies in the bulk and at the organic-vacuum interface using a polarizable force field that accounts for induced-dipole and quadrupole interactions. Though both oligoacenes pack in a herringbone motif, the tetraphenyl substituents on the tetracene backbone of rubrene alter greatly the nature of the packing. The resulting change in relative orientations of neighboring molecules is found to reduce the bulk polarization energy of holes in rubrene by some 0.3 eV when compared to tetracene. The consideration of model organic-vacuum interfaces highlights the significant variation in the electrostatic environment for a charge carrier at a surface although the net change in polarization energy is small; interestingly, the environment of a charge even just one layer removed from the surface can be viewed already as representative of the bulk. Overall, it is found that in these herringbone-type layered crystals the polarization energy has a much stronger dependence on the intralayer packing density than interlayer packing density. PMID:27183361

  18. Impact of Molecular Orientation and Packing Density on Electronic Polarization in the Bulk and at Surfaces of Organic Semiconductors.

    PubMed

    Ryno, Sean M; Risko, Chad; Brédas, Jean-Luc

    2016-06-01

    The polarizable environment surrounding charge carriers in organic semiconductors impacts the efficiency of the charge transport process. Here, we consider two representative organic semiconductors, tetracene and rubrene, and evaluate their polarization energies in the bulk and at the organic-vacuum interface using a polarizable force field that accounts for induced-dipole and quadrupole interactions. Though both oligoacenes pack in a herringbone motif, the tetraphenyl substituents on the tetracene backbone of rubrene alter greatly the nature of the packing. The resulting change in relative orientations of neighboring molecules is found to reduce the bulk polarization energy of holes in rubrene by some 0.3 eV when compared to tetracene. The consideration of model organic-vacuum interfaces highlights the significant variation in the electrostatic environment for a charge carrier at a surface although the net change in polarization energy is small; interestingly, the environment of a charge even just one layer removed from the surface can be viewed already as representative of the bulk. Overall, it is found that in these herringbone-type layered crystals the polarization energy has a much stronger dependence on the intralayer packing density than interlayer packing density.

  19. Crystallization process

    DOEpatents

    Adler, Robert J.; Brown, William R.; Auyang, Lun; Liu, Yin-Chang; Cook, W. Jeffrey

    1986-01-01

    An improved crystallization process is disclosed for separating a crystallizable material and an excluded material which is at least partially excluded from the solid phase of the crystallizable material obtained upon freezing a liquid phase of the materials. The solid phase is more dense than the liquid phase, and it is separated therefrom by relative movement with the formation of a packed bed of solid phase. The packed bed is continuously formed adjacent its lower end and passed from the liquid phase into a countercurrent flow of backwash liquid. The packed bed extends through the level of the backwash liquid to provide a drained bed of solid phase adjacent its upper end which is melted by a condensing vapor.

  20. Condensation in Nanoporous Packed Beds.

    PubMed

    Ally, Javed; Molla, Shahnawaz; Mostowfi, Farshid

    2016-05-10

    In materials with tiny, nanometer-scale pores, liquid condensation is shifted from the bulk saturation pressure observed at larger scales. This effect is called capillary condensation and can block pores, which has major consequences in hydrocarbon production, as well as in fuel cells, catalysis, and powder adhesion. In this study, high pressure nanofluidic condensation studies are performed using propane and carbon dioxide in a colloidal crystal packed bed. Direct visualization allows the extent of condensation to be observed, as well as inference of the pore geometry from Bragg diffraction. We show experimentally that capillary condensation depends on pore geometry and wettability because these factors determine the shape of the menisci that coalesce when pore filling occurs, contrary to the typical assumption that all pore structures can be modeled as cylindrical and perfectly wetting. We also observe capillary condensation at higher pressures than has been done previously, which is important because many applications involving this phenomenon occur well above atmospheric pressure, and there is little, if any, experimental validation of capillary condensation at such pressures, particularly with direct visualization.

  1. Condensation in Nanoporous Packed Beds.

    PubMed

    Ally, Javed; Molla, Shahnawaz; Mostowfi, Farshid

    2016-05-10

    In materials with tiny, nanometer-scale pores, liquid condensation is shifted from the bulk saturation pressure observed at larger scales. This effect is called capillary condensation and can block pores, which has major consequences in hydrocarbon production, as well as in fuel cells, catalysis, and powder adhesion. In this study, high pressure nanofluidic condensation studies are performed using propane and carbon dioxide in a colloidal crystal packed bed. Direct visualization allows the extent of condensation to be observed, as well as inference of the pore geometry from Bragg diffraction. We show experimentally that capillary condensation depends on pore geometry and wettability because these factors determine the shape of the menisci that coalesce when pore filling occurs, contrary to the typical assumption that all pore structures can be modeled as cylindrical and perfectly wetting. We also observe capillary condensation at higher pressures than has been done previously, which is important because many applications involving this phenomenon occur well above atmospheric pressure, and there is little, if any, experimental validation of capillary condensation at such pressures, particularly with direct visualization. PMID:27115446

  2. Effect of homolog doping on surface morphology and mass-loss rates from PETN crystals. Studies using atomic force microscope and thermo-gravimetric analysis

    DOE PAGESBeta

    Bhattacharya, S. K.; Maiti, A; Gee, R. H.; Nunley, J.; Weeks, B. L.

    2012-08-28

    Pentaerythritol tetranitrate (PETN) is an important energetic material and its performance as a secondary explosive depends strongly on the density as well as flow porosity of powdered material, which in turn is governed by the size and surface properties of the PETN crystallite particles. Historically there has been evidence that the surface properties of PETN particles can be strongly influenced by the presence of homolog impurities of PETN, in particular, dipentaerythritol hexanitrate (diPEHN) and tripentaerythritol octanitrate (triPEON), although not many systematic studies characterizing such influence exist. In this work we employ thermogravimetric analysis (TGA) to measure mass-loss rates at elevatedmore » temperatures and show that doping with a small amount of diPEHN and triPEON can reduce the mass-loss rate from PETN single-crystal surfaces by as much as 35 % as compared to undoped crystals. Arrhenius plots of mass-loss rates as a function of temperature suggest that the reduction in evaporation is not due to the change in activation barrier of the molecular evaporation process, but perhaps due to the impedance to the receding motion of the steps by the immobile impurities on the surface. Removal of surface impurities through gentle washing with ethanol leads to enhanced mass-loss rate relative to pure PETN suggesting a roughened surface morphology. Some surface roughening in doped crystals is supported by Atomic force microscopy (AFM) images of growth layers that show evidences of growth layer stacking and rough edges. Furthermore, we find that a larger amount of impurity added to the original solution does not necessarily lead to a more highly doped crystal, which could perhaps be interpreted as PETN crystals being able to accommodate only up to a certain weight percent of homolog impurities.« less

  3. Effect of homolog doping on surface morphology and mass-loss rates from PETN crystals. Studies using atomic force microscope and thermo-gravimetric analysis

    SciTech Connect

    Bhattacharya, S. K.; Maiti, A; Gee, R. H.; Nunley, J.; Weeks, B. L.

    2012-08-28

    Pentaerythritol tetranitrate (PETN) is an important energetic material and its performance as a secondary explosive depends strongly on the density as well as flow porosity of powdered material, which in turn is governed by the size and surface properties of the PETN crystallite particles. Historically there has been evidence that the surface properties of PETN particles can be strongly influenced by the presence of homolog impurities of PETN, in particular, dipentaerythritol hexanitrate (diPEHN) and tripentaerythritol octanitrate (triPEON), although not many systematic studies characterizing such influence exist. In this work we employ thermogravimetric analysis (TGA) to measure mass-loss rates at elevated temperatures and show that doping with a small amount of diPEHN and triPEON can reduce the mass-loss rate from PETN single-crystal surfaces by as much as 35 % as compared to undoped crystals. Arrhenius plots of mass-loss rates as a function of temperature suggest that the reduction in evaporation is not due to the change in activation barrier of the molecular evaporation process, but perhaps due to the impedance to the receding motion of the steps by the immobile impurities on the surface. Removal of surface impurities through gentle washing with ethanol leads to enhanced mass-loss rate relative to pure PETN suggesting a roughened surface morphology. Some surface roughening in doped crystals is supported by Atomic force microscopy (AFM) images of growth layers that show evidences of growth layer stacking and rough edges. Furthermore, we find that a larger amount of impurity added to the original solution does not necessarily lead to a more highly doped crystal, which could perhaps be interpreted as PETN crystals being able to accommodate only up to a certain weight percent of homolog impurities.

  4. Two typical structure patterns in jammed monodisperse disk packings at high densities

    NASA Astrophysics Data System (ADS)

    Yuan, Ye; Jin, Weiwei; Liu, Lufeng; Li, Shuixiang

    2016-11-01

    We generate a large number of monodisperse disk packings in two dimensions via geometric-based packing algorithms including the relaxation algorithm and the Torquato-Jiao algorithm. Using the geometric-structure approach, a clear boundary of the geometrical feasible region in the order map is found which quite differs from that of the jammed region. For a certain packing density higher than 0.83, the crystalline degree varies in different packing samples. We find that the local hexatic order may increase in two fairly different ways as the system densifies. Therefore, two typical non-equilibrium jammed patterns, termed polycrystal and distorted crystal, are defined at high packing densities. Furthermore, their responses to isotropic compression are investigated using a compression-relaxation molecular dynamic protocol. The distorted crystal pattern is more stable than the polycrystal one with smaller displacements despite its low occurrence frequency. The results are helpful in understanding the structure and phase transition of disk packings.

  5. Epitaxial growth of ordered and disordered granular sphere packings.

    PubMed

    Panaitescu, Andreea; Kudrolli, Arshad

    2014-09-01

    We demonstrate that epitaxy can be used to obtain a wide range of ordered to disordered granular packings by simply changing the deposition flux. We show that a defect-free face-centered-cubic (fcc) monocrystal can be obtained by depositing athermal granular spheres randomly into a container with a templated surface in a gravitational field without direct manipulation. This packing corresponds to the maximum sphere packing fraction and is obtained when the substrate is templated corresponding to the (100) plane of a fcc crystal and the container side is an integer multiple of the sphere diameter. We find that the maximum sphere packing is obtained when the deposited grains come to rest, one at a time, without damaging the substrate. A transition to a disordered packing is observed when the flux is increased. Using micro x-ray computed tomography, we find that defects nucleate at the boundaries of the container in which the packing is grown as grains cooperatively come to rest above their local potential minimum. This leads to a transition from ordered to disordered loose packings that grow in the form of an inverted cone, with the apex located at the defect nucleation site. We capture the observed decrease in order using a minimal model in which a defect leads to growth of further defects in the neighboring sites in the layer above with a probability that increases with the deposition flux.

  6. Sound Packing DNA: packing open circular DNA with low-intensity ultrasound

    NASA Astrophysics Data System (ADS)

    Park, Donghee; Jung, Bong-Kwang; Park, Hyunjin; Lee, Hyungbeen; Lee, Gyudo; Park, Jingam; Shin, Unchul; Won, Jong Ho; Jo, Yong Jun; Chang, Jin Woo; Lee, Sangwoo; Yoon, Daesung; Seo, Jongbum; Kim, Chul-Woo

    2015-04-01

    Supercoiling DNA (folding DNA into a more compact molecule) from open circular forms requires significant bending energy. The double helix is coiled into a higher order helix form; thus it occupies a smaller footprint. Compact packing of DNA is essential to improve the efficiency of gene delivery, which has broad implications in biology and pharmaceutical research. Here we show that low-intensity pulsed ultrasound can pack open circular DNA into supercoil form. Plasmid DNA subjected to 5.4 mW/cm2 intensity ultrasound showed significant (p-values <0.001) supercoiling compared to DNA without exposure to ultrasound. Radiation force induced from ultrasound and dragging force from the fluid are believed to be the main factors that cause supercoiling. This study provides the first evidence to show that low-intensity ultrasound can directly alter DNA topology. We anticipate our results to be a starting point for improved non-viral gene delivery.

  7. Dynamics of ordered colloidal particle monolayers at nematic liquid crystal interfaces.

    PubMed

    Wei, Wei-Shao; Gharbi, Mohamed Amine; Lohr, Matthew A; Still, Tim; Gratale, Matthew D; Lubensky, T C; Stebe, Kathleen J; Yodh, A G

    2016-05-25

    We prepare two-dimensional crystalline packings of colloidal particles on surfaces of the nematic liquid crystal (NLC) 5CB, and we investigate the diffusion and vibrational phonon modes of these particles using video microscopy. Short-time particle diffusion at the air-NLC interface is well described by a Stokes-Einstein model with viscosity similar to that of 5CB. Crystal phonon modes, measured by particle displacement covariance techniques, are demonstrated to depend on the elastic constants of 5CB through interparticle forces produced by LC defects that extend from the interface into the underlying bulk material. The displacement correlations permit characterization of transverse and longitudinal sound velocities of the crystal packings, as well as the particle interactions produced by the LC defects. All behaviors are studied in the nematic phase as a function of increasing temperature up to the nematic-isotropic transition. PMID:27109759

  8. Switching adhesion forces by crossing the metal-insulator transition in Magnéli-type vanadium oxide crystals.

    PubMed

    Stegemann, Bert; Klemm, Matthias; Horn, Siegfried; Woydt, Mathias

    2011-01-01

    Magnéli-type vanadium oxides form the homologous series V(n)O(2) (n) (-1) and exhibit a temperature-induced, reversible metal-insulator first order phase transition (MIT). We studied the change of the adhesion force across the transition temperature between the cleavage planes of various vanadium oxide Magnéli phases (n = 3 … 7) and spherical titanium atomic force microscope (AFM) tips by systematic force-distance measurements with a variable-temperature AFM under ultrahigh vacuum conditions (UHV). The results show, for all investigated samples, that crossing the transition temperatures leads to a distinct change of the adhesion force. Low adhesion corresponds consistently to the metallic state. Accordingly, the ability to modify the electronic structure of the vanadium Magnéli phases while maintaining composition, stoichiometry and crystallographic integrity, allows for relating frictional and electronic material properties at the nano scale. This behavior makes the vanadium Magnéli phases interesting candidates for technology, e.g., as intelligent devices or coatings where switching of adhesion or friction is desired.

  9. On the perfect hexagonal packing of rods

    NASA Astrophysics Data System (ADS)

    Starostin, E. L.

    2006-04-01

    In most cases the hexagonal packing of fibrous structures or rods extremizes the energy of interaction between strands. If the strands are not straight, then it is still possible to form a perfect hexatic bundle. Conditions under which the perfect hexagonal packing of curved tubular structures may exist are formulated. Particular attention is given to closed or cycled arrangements of the rods like in the DNA toroids and spools. The closure or return constraints of the bundle result in an allowable group of automorphisms of the cross-sectional hexagonal lattice. The structure of this group is explored. Examples of open helical-like and closed toroidal-like bundles are presented. An expression for the elastic energy of a perfectly packed bundle of thin elastic rods is derived. The energy accounts for both the bending and torsional stiffnesses of the rods. It is shown that equilibria of the bundle correspond to solutions of a variational problem formulated for the curve representing the axis of the bundle. The functional involves a function of the squared curvature under the constraints on the total torsion and the length. The Euler-Lagrange equations are obtained in terms of curvature and torsion and due to the existence of the first integrals the problem is reduced to the quadrature. The three-dimensional shape of the bundle may be readily reconstructed by integration of the Ilyukhin-type equations in special cylindrical coordinates. The results are of universal nature and are applicable to various fibrous structures, in particular, to intramolecular liquid crystals formed by DNA condensed in toroids or packed inside the viral capsids. International Workshop on Biopolymers: Thermodynamics, Kinetics and Mechanics of DNA, RNA and Proteins, 30.05.2005-3.06.2005, The Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy.

  10. Packing Products: Polystyrene vs. Cornstarch

    ERIC Educational Resources Information Center

    Starr, Suzanne

    2009-01-01

    Packing materials such as polystyrene take thousands of years to decompose, whereas packing peanuts made from cornstarch, which some companies are now using, can serve the same purpose, but dissolve in water. The author illustrates this point to her class one rainy day using the sculptures students made from polystyrene and with the cornstarch…

  11. Direct preparation of spherically agglomerated salicylic acid crystals during crystallization.

    PubMed

    Kawashima, Y; Okumura, M; Takenaka, H; Kojima, A

    1984-11-01

    Needle-like salicylic acid crystals were transformed into a spherically shaped dense form during crystallization by the spherical crystallization technique. Agitation of a mixture of ethanol-water-chloroform containing salicylic acid yielded spherically agglomerated salicylic acid crystals. The crystallinity of the agglomerated salicylic acid the amount of ethanol in the solvent mixture was decreased. The wettability of the agglomerated crystals increased when the amount of ethanol in the solvent mixture was decreased, and this enhanced the dissolution rate of the crystals. The remarkable improvements in the flow and packing of the agglomerated crystals enabled the direct compression of the crystals.

  12. Packing developments improve valve availability

    SciTech Connect

    Aikin, J.

    1994-01-01

    Regulatory environment and clean air legislation demand improvements in valve stuffing box performance. In normally inaccessible or hazardous areas, the cost of valve maintenance and repair in terms of safety, radiation, and toxic gas exposure is very high. AECL Research`s Mechanical Equipment Development (MED) branch at Chalk River Laboratories (Chalk River, Ont.) has researched stem packing leakage problems since the early 1970s. Early research and development (R and D) significantly improved the understanding of operational characteristics of asbestos-based valve packing. Of note was the development of live loading, a stem packing method that reduces valve leakage to near zero under most operating conditions, and significantly prolongs packing life. This article describes how stem packing developments, including live loading techniques, are reducing valve fugitive emissions and leakage.

  13. 7 CFR 51.310 - Packing requirements.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... STANDARDS) United States Standards for Grades of Apples Packing Requirements § 51.310 Packing requirements. (a) Apples tray packed or cell packed in cartons shall be arranged according to approved and... that apples are of the proper size for molds or cell compartments in which they are packed, and...

  14. 7 CFR 51.310 - Packing requirements.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... STANDARDS) United States Standards for Grades of Apples Packing Requirements § 51.310 Packing requirements. (a) Apples tray packed or cell packed in cartons shall be arranged according to approved and... that apples are of the proper size for molds or cell compartments in which they are packed, and...

  15. 7 CFR 51.310 - Packing requirements.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... STANDARDS) United States Standards for Grades of Apples Packing Requirements § 51.310 Packing requirements. (a) Apples tray packed or cell packed in cartons shall be arranged according to approved and... that apples are of the proper size for molds or cell compartments in which they are packed, and...

  16. Probe with integrated heater and thermocouple pack

    DOEpatents

    McCulloch, Reginald W.; Dial, Ralph E.; Finnell, Wilber K. R.

    1988-01-01

    A probe for measuring heat includes an elongate rod fitted within a sheath, and a plurality of annular recesses are formed on the surface of the rod in a spaced-apart relationship to form annular chambers that are resistant to heat flow. A longitudinal bore extends axially into the rod and within the cylinders defined by the annular chambers, and an integrated heater and thermocouple pack is dimensioned to fit within the bore. In construction, the integrated pack includes a plurality of wires disposed in electrical insulation within a sheath and a heater cable. These wires include one common wire and a plurality of thermocouple wires. The common wire is constructed of one type of conductive material while the thermocouple wires are each constructed of two types of materials so that at least one thermocouple junction is formed therein. All of the wires extend the length of the integrated pack and are connected together at their ends. The thermocouple wires are constructed to form thermocouple junctions proximate to each annular chamber for producing electromotive forces corresponding to the temperature of the rod within the annular chambers relative to outside the chambers. In the preferred embodiment, each thermocouple wire forms two thermocouple junctions, one junction being disposed within an annular chamber and the second junction being disposed outside of, but proximate to, the same annular chamber. In one embodiment two thermocouple wires are configured to double the sensitivity of the probe in one region.

  17. Significant melting point depression of two-dimensional folded-chain crystals of isotactic poly(methyl methacrylate)s observed by high-resolution in situ atomic force microscopy.

    PubMed

    Takanashi, Yuma; Kumaki, Jiro

    2013-05-01

    The properties of polymer ultrathin films are a subject of intense study from both practical and academic viewpoints. Previously, we found that upon compression, an isotactic poly(methyl methacrylate) (it-PMMA) Langmuir monolayer crystallized to form a two-dimensional (2D) folded-chain crystal, and the molecular image of the crystal with chain folding and tie chains was clearly visualized by atomic force microscopy (AFM). In the present study, the melting behaviors of the it-PMMA 2D crystals were successfully observed in situ by high-temperature AFM at the molecular lever for the first time. The chain-chain distances (~1.2 nm) of the crystals were clearly resolved even at temperatures close to the melting temperatures (Tm) of the 2D crystals. We found that the Tm of the 2D crystals was at most 90 °C lower than the bulk crystals. The Tm depression strongly depended on the molecular weight, while the molecular weight dependence of the bulk Tm was negligible in the molecular weight regime studied. The Tm depression also depended on the substrates, a slightly larger depression being observed on a sapphire substrate compared to that on a mica. The large Tm depressions of the 2D crystals could not be explained by a simple Thomson-Gibbs argument, theoretical developments are necessary to understand the melting of the 2D crystals.

  18. Calcium carbonate crystal growth beneath Langmuir monolayers of acidic β-hairpin peptides.

    PubMed

    Gong, Haofei; Yang, Yi; Pluntke, Manuela; Marti, Othmar; Majer, Zsuzsa; Sewald, Norbert; Volkmer, Dirk

    2014-11-28

    Four amphiphilic peptides with designed hairpin structure were synthesized and their monolayers were employed as model systems to study biologically inspired calcium carbonate crystallization. Langmuir monolayers of hairpin peptides were investigated by surface pressure area isotherms, surface potential isotherms, Brewster angle microscopy (BAM), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. A β-hairpin conformation was found for all peptides at the air-water interface although their packing arrangements seem to be different. Crystallization of calcium carbonate under these peptide monolayers was investigated at different surface pressures and growth times both by in situ optical microscopy, BAM and ex situ investigations such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). An amorphous calcium carbonate precursor was found at the initial crystallization stage. The crystallization process occurred in three stages. It starts from the nucleation of amorphous particles being a kinetically controlled process. Crystal nuclei subsequently aggregate to large particles and vaterite crystals start to form inside the amorphous layer, with the monolayer fluidity exerting an important role. The third process includes the re-crystallization of vaterite to calcite, which is thermodynamically controlled by monolayer structural factors including the monolayer flexibility and packing arrangement of the polar headgroups. Thus, the kinetic factors, monolayer fluidity and flexibility as well as structure factors govern the crystal morphology and polymorph distribution simultaneously and synergistically.

  19. Simulation of granular packing of frictional cohesive particles with Gaussian size distribution

    NASA Astrophysics Data System (ADS)

    Jia, Tao; Gao, Di

    2016-09-01

    The granular packing of frictional cohesive particles with Gaussian distribution is investigated based on distinct element method. Different sliding frictional coefficients are considered in the simulation. Due to the inelastic collision between the particles, the agglomeration of the particles occurs and the packing structure is formed finally. The range of the diameter of the particle is between 50 and 100 μm, and the distribution of the particle diameter is Gaussian. The inelastic interaction is caused by the viscoelastic force and the frictional force. The internal structure of the granular matter is quantified by the coordination number, packing density, and the force distribution. It is found that the increase in the sliding frictional coefficient looses the packing structure, and the distribution range of the contact force is larger than that of the van der Waals force.

  20. Real-time atomic-resolution imaging of crystal growth process in water by phase modulation atomic force microscopy at one frame per second

    SciTech Connect

    Miyata, Kazuki; Asakawa, Hitoshi; Fukuma, Takeshi

    2013-11-11

    Recent advancement in dynamic-mode atomic force microscopy (AFM) has enabled its operation in liquid with atomic-scale resolution. However, its imaging speed has often been too slow to visualize atomic-scale dynamic processes. Here, we propose a method for making a significant improvement in the operation speed of dynamic-mode AFM. In this method, we use a wideband and low-latency phase detector with an improved algorithm for the signal complexification. We demonstrate atomic-scale imaging of a calcite crystal growth process in water at one frame per second. The significant improvement in the imaging speed should enable various studies on unexplored atomic-scale interfacial processes.

  1. Investigation of laser-fired point contacts on KOH structured laser-crystallized silicon by conductive atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Gref, Orman; Weizman, Moshe; Rhein, Holger; Gabriel, Onno; Gernert, Ulrich; Schlatmann, Rutger; Boit, Christian; Friedrich, Felice

    2016-06-01

    A conductive atomic force microscope is used to study the local topography and conductivity of laser-fired aluminum contacts on KOH-structured multicrystalline silicon surfaces. A significant increase in conductivity is observed in the laser-affected area. The area size and spatial uniformity of this enhanced conductivity depends on the laser energy fluence. The laser-affected area shows three ring-shaped regimes of different conductance depending on the local aluminum and oxygen concentration. Finally, it was found that the topographic surface structure determined by the silicon grain orientation does not significantly affect the laser-firing process.

  2. 7 CFR 982.11 - Pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and... Order Regulating Handling Definitions § 982.11 Pack. Pack means a specific commercial classification according to size, internal quality, and external appearance and condition of hazelnuts packed in...

  3. DHS Internship Summary-Crystal Assembly at Different Length Scales

    SciTech Connect

    Mishchenko, L

    2009-08-06

    . In particular, molecular crystals, which are typically dominated by ionic and covalent bonding, are an order of magnitude more strongly bonded than colloidal crystals. In molecular crystals, ordering is driven by the interaction potentials between molecules. By contrast, colloidal assembly is a competition between the repulsive electrostatic forces that prevent aggregation in solution (due to surface charge), and short-range van der Waals and entropic forces that leads to ordering. Understanding atomic crystallization is fundamentally important for fabrication of tailorable crystalline materials, for example for biological or chemical sensors. The transformation of brushite to OCP not only serves as a model system for atomic crystal growth (applicable to many other crystal growth processes), but is also important in bone cements. Colloidal crystals have unique optical properties which respond to chemical and mechanical stimuli, making them very important for sensing applications. The mechanism of colloidal crystal assembly is thus fundamentally important. Our in situ dissolution and regrowth experiments are one good method of analyzing how these crystals pack under different conditions and how defect sites are formed and filled. In these experiments, a silica additive was used to strengthen the colloidal crystal during initial assembly (ex situ) and to increase domain size and long range order. Reversible electrodeposition of colloids onto a conductive substrate (ITO in our case) is another system which can further our knowledge of colloidal assembly. This experiment holds promise of allowing in situ observation of colloidal crystal growth and the influence of certain additives on crystal order. The ultimate goal would be to achieve long range order in these crystals by changing the surface charge or the growth environment.

  4. Evolution of the dense packings of spherotetrahedral particles: from ideal tetrahedra to spheres.

    PubMed

    Jin, Weiwei; Lu, Peng; Li, Shuixiang

    2015-10-22

    Particle shape plays a crucial role in determining packing characteristics. Real particles in nature usually have rounded corners. In this work, we systematically investigate the rounded corner effect on the dense packings of spherotetrahedral particles. The evolution of dense packing structure as the particle shape continuously deforms from a regular tetrahedron to a sphere is investigated, starting both from the regular tetrahedron and the sphere packings. The dimer crystal and the quasicrystal approximant are used as initial configurations, as well as the two densest sphere packing structures. We characterize the evolution of spherotetrahedron packings from the ideal tetrahedron (s = 0) to the sphere (s = 1) via a single roundness parameter s. The evolution can be partitioned into seven regions according to the shape variation of the packing unit cell. Interestingly, a peak of the packing density Φ is first observed at s ≈ 0.16 in the Φ-s curves where the tetrahedra have small rounded corners. The maximum density of the deformed quasicrystal approximant family (Φ ≈ 0.8763) is slightly larger than that of the deformed dimer crystal family (Φ ≈ 0.8704), and both of them exceed the densest known packing of ideal tetrahedra (Φ ≈ 0.8563).

  5. Advanced Protein Crystallization Facility (APCF)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This section of the Life and Microgravity Spacelab (LMS) publication contains articles entitled: (1) Crystallization of EGFR-EGF; (2) Crystallization of Apocrustacyanin C1; (3) Crystallization and X-ray Analysis of 5S rRNA and the 5S rRNA Domain A; (4) Growth of Lysozyme Crystals at Low Nucleation Density; (5) Comparative Analysis of Aspartyl tRNA-synthetase and Thaumatin Crystals Grown on Earth and In Microgravity; (6) Lysosome Crystal Growth in the Advanced Protein Crystallization Facility Monitored via Mach-Zehnder Interferometry and CCD Video; (7) Analysis of Thaumatin Crystals Grown on Earth and in Microgravity; (8) Crystallization of the Nucleosome Core Particle; (9) Crystallization of Photosystem I; (10) Mechanism of Membrane Protein Crystal Growth: Bacteriorhodopsin-mixed Micelle Packing at the Consolution Boundary, Stabilized in Microgravity; (11) Crystallization in a Microgravity Environment of CcdB, a Protein Involved in the Control of Cell Death; and (12) Crystallization of Sulfolobus Solfataricus

  6. Hyperstaticity and loops in frictional granular packings

    NASA Astrophysics Data System (ADS)

    Tordesillas, Antoinette; Lam, Edward; Metzger, Philip T.

    2009-06-01

    The hyperstatic nature of granular packings of perfectly rigid disks is analyzed algebraically and through numerical simulation. The elementary loops of grains emerge as a fundamental element in addressing hyperstaticity. Loops consisting of an odd number of grains behave differently than those with an even number. For odd loops, the latent stresses are exterior and are characterized by the sum of frictional forces around each loop. For even loops, the latent stresses are interior and are characterized by the alternating sum of frictional forces around each loop. The statistics of these two types of loop sums are found to be Gibbsian with a "temperature" that is linear with the friction coefficient μ when μ<1.

  7. Solid-state 13C NMR study of banana liquid crystals - 3: Alkyl-tail-group packing environments of an acute-angle bent-core molecule in the hexagonal columnar and cubic phases

    NASA Astrophysics Data System (ADS)

    Kurosu, Hiromichi; Endo, Yumi; Kimura, Saori; Hashimoto, Tomoko; Harada, Motoi; Lee, Eun-Woo; Sone, Masato; Watanabe, Junji; Kang, Sungmin

    2016-02-01

    Solid-state 13C nuclear magnetic resonance (NMR) measurements were performed on the hexagonal columnar and cubic phases of an acute-angle banana-shaped molecule, N(1,7)-S30. In the hexagonal columnar phase, three peaks appear at the NMR chemical shifts assigned to the internal methylene carbons of alkyl tails, indicating that the two alkyl tails have different packing structures, and one of the tails has two different conformations within a single molecule. Combined cross-polarization/magic-angle spinning and pulse saturation transfer/magic-angle spinning measurements show that one of the alkyl chains is located inside and the other is located outside the columnar structure. In the cubic phase, pulse saturation transfer/magic-angle spinning measurement shows that only one peak appears at the NMR chemical shifts assigned to the internal methylene carbons of alkyl tails, indicating that both of the alkyl chains are located outside the cubic structure.

  8. Thermodynamics of sublimation, crystal lattice energies, and crystal structures of racemates and enantiomers: (+)- and (+/-)-ibuprofen.

    PubMed

    Perlovich, German L; Kurkov, Sergey V; Hansen, Lars Kr; Bauer-Brandl, Annette

    2004-03-01

    Thermodynamic differences between ibuprofen (IBP) racemate and the (+)-enantiomer were studied by X-ray diffraction, thermoanalysis, and crystal energy calculations. The thermodynamic functions of sublimation (as a measure of crystal lattice energy) were obtained by the transpiration method. The sublimation enthalpies (DeltaH(sub)) of (+/-)-IBP and (+)-IBP are 115.8 +/- 0.6 and 107.4 +/- 0.5 kJ. mol(-1), respectively. Using the temperature dependency of the saturated vapor pressure, the relative fractions of enthalpy and entropy of the sublimation process were calculated, and the sublimation process for both the racemate and the enantiomer was found to be enthalpy driven (62%). Two different force fields, Mayo et al. (M) and Gavezzotti (G), were used for comparative analysis of crystal lattice energies. Both force fields revealed that the van der Waals term contributes more to the packing energy in (+)-IBP than in (+/-)-IBP. The hydrogen bonding energy, however, contributes at 29.7 and 32.3% to the total crystal lattice energy in (+)-IBP and (+/-)-IBP (M), respectively. Furthermore, different structure fragments of the IBP molecule were analyzed with respect to their contribution to nonbonded van der Waals interactions. The effect of the C-H distance on the van der Waals term of the crystal lattice energy was also studied.

  9. Determining the sputter yields of molybdenum in low-index crystal planes via electron backscattered diffraction, focused ion beam and atomic force microscope

    SciTech Connect

    Huang, H.S.; Chiu, C.H.; Hong, I.T.; Tung, H.C.; Chien, F.S.-S.

    2013-09-15

    Previous literature has used several monocrystalline sputtering targets with various crystalline planes, respectively, to investigate the variations of the sputter yield of materials in different crystalline orientations. This study presents a method to measure the sputtered yields of Mo for the three low-index planes (100), (110), and (111), through using an easily made polycrystalline target. The procedure was firstly to use electron backscattered diffraction to identify the grain positions of the three crystalline planes, and then use a focused ion beam to perform the micro-milling of each identified grain, and finally the sputter yields were calculated from the removed volumes, which were measured by atomic force microscope. Experimental results showed that the sputter yield of the primary orientations for Mo varied as Y{sub (110)} > Y{sub (100)} > Y{sub (111)}, coincidental with the ranking of their planar atomic packing densities. The concept of transparency of ion in the crystalline substance was applied to elucidate these results. In addition, the result of (110) orientation exhibiting higher sputter yield is helpful for us to develop a Mo target with a higher deposition rate for use in industry. By changing the deformation process from straight rolling to cross rolling, the (110) texture intensity of the Mo target was significantly improved, and thus enhanced the deposition rate. - Highlights: • We used EBSD, FIB and AFM to measure the sputter yields of Mo in low-index planes. • The sputter yield of the primary orientations for Mo varied as Y{sub (110)} > Y{sub (100)} > Y{sub (111)}. • The transparency of ion was used to elucidate the differences in the sputter yield. • We improved the sputter rate of polycrystalline Mo target by adjusting its texture.

  10. Modulation of calcium oxalate crystallization by proteins and small molecules investigated by In Situ Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Qiu, S. R.; Orme, C. A.; Zepeda, S.; Cody, A. M.; Wierzbicki, A.; Hoyer, J. R.; Nancollas, G. H.; de Yoreo, J. J.

    2003-03-01

    Calcium oxalate monohydrate (COM) is known to be a source of pathogenesis in humans where it causes kidney stone disease. The basic modulation of COM by proteins and small molecules mechanism is not well understood. In situ atomic force microscopy (AFM) was used to monitor the COM surface morphology and growth dynamics under controlled growth conditions from pure solutions and those doped with citrate and osteopontin (OPN). AFM results show that OPN, like citrate, inhibits growth on the (-101) face through a step pinning mechanism, especially in the [-10-1] direction. We propose a model that reconciles the step-specific interactions implied by the AFM results with the face-specific predictions of the calculations. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

  11. Hard convex lens-shaped particles: Densest-known packings and phase behavior

    SciTech Connect

    Cinacchi, Giorgio; Torquato, Salvatore

    2015-12-14

    By using theoretical methods and Monte Carlo simulations, this work investigates dense ordered packings and equilibrium phase behavior (from the low-density isotropic fluid regime to the high-density crystalline solid regime) of monodisperse systems of hard convex lens-shaped particles as defined by the volume common to two intersecting congruent spheres. We show that, while the overall similarity of their shape to that of hard oblate ellipsoids is reflected in a qualitatively similar phase diagram, differences are more pronounced in the high-density crystal phase up to the densest-known packings determined here. In contrast to those non-(Bravais)-lattice two-particle basis crystals that are the densest-known packings of hard (oblate) ellipsoids, hard convex lens-shaped particles pack more densely in two types of degenerate crystalline structures: (i) non-(Bravais)-lattice two-particle basis body-centered-orthorhombic-like crystals and (ii) (Bravais) lattice monoclinic crystals. By stacking at will, regularly or irregularly, laminae of these two crystals, infinitely degenerate, generally non-periodic in the stacking direction, dense packings can be constructed that are consistent with recent organizing principles. While deferring the assessment of which of these dense ordered structures is thermodynamically stable in the high-density crystalline solid regime, the degeneracy of their densest-known packings strongly suggests that colloidal convex lens-shaped particles could be better glass formers than colloidal spheres because of the additional rotational degrees of freedom.

  12. Hard convex lens-shaped particles: Densest-known packings and phase behavior

    NASA Astrophysics Data System (ADS)

    Cinacchi, Giorgio; Torquato, Salvatore

    2015-12-01

    By using theoretical methods and Monte Carlo simulations, this work investigates dense ordered packings and equilibrium phase behavior (from the low-density isotropic fluid regime to the high-density crystalline solid regime) of monodisperse systems of hard convex lens-shaped particles as defined by the volume common to two intersecting congruent spheres. We show that, while the overall similarity of their shape to that of hard oblate ellipsoids is reflected in a qualitatively similar phase diagram, differences are more pronounced in the high-density crystal phase up to the densest-known packings determined here. In contrast to those non-(Bravais)-lattice two-particle basis crystals that are the densest-known packings of hard (oblate) ellipsoids, hard convex lens-shaped particles pack more densely in two types of degenerate crystalline structures: (i) non-(Bravais)-lattice two-particle basis body-centered-orthorhombic-like crystals and (ii) (Bravais) lattice monoclinic crystals. By stacking at will, regularly or irregularly, laminae of these two crystals, infinitely degenerate, generally non-periodic in the stacking direction, dense packings can be constructed that are consistent with recent organizing principles. While deferring the assessment of which of these dense ordered structures is thermodynamically stable in the high-density crystalline solid regime, the degeneracy of their densest-known packings strongly suggests that colloidal convex lens-shaped particles could be better glass formers than colloidal spheres because of the additional rotational degrees of freedom.

  13. Hard convex lens-shaped particles: Densest-known packings and phase behavior.

    PubMed

    Cinacchi, Giorgio; Torquato, Salvatore

    2015-12-14

    By using theoretical methods and Monte Carlo simulations, this work investigates dense ordered packings and equilibrium phase behavior (from the low-density isotropic fluid regime to the high-density crystalline solid regime) of monodisperse systems of hard convex lens-shaped particles as defined by the volume common to two intersecting congruent spheres. We show that, while the overall similarity of their shape to that of hard oblate ellipsoids is reflected in a qualitatively similar phase diagram, differences are more pronounced in the high-density crystal phase up to the densest-known packings determined here. In contrast to those non-(Bravais)-lattice two-particle basis crystals that are the densest-known packings of hard (oblate) ellipsoids, hard convex lens-shaped particles pack more densely in two types of degenerate crystalline structures: (i) non-(Bravais)-lattice two-particle basis body-centered-orthorhombic-like crystals and (ii) (Bravais) lattice monoclinic crystals. By stacking at will, regularly or irregularly, laminae of these two crystals, infinitely degenerate, generally non-periodic in the stacking direction, dense packings can be constructed that are consistent with recent organizing principles. While deferring the assessment of which of these dense ordered structures is thermodynamically stable in the high-density crystalline solid regime, the degeneracy of their densest-known packings strongly suggests that colloidal convex lens-shaped particles could be better glass formers than colloidal spheres because of the additional rotational degrees of freedom. PMID:26671389

  14. Effect of long-range repulsive Coulomb interactions on packing structure of adhesive particles.

    PubMed

    Chen, Sheng; Li, Shuiqing; Liu, Wenwei; Makse, Hernán A

    2016-02-14

    The packing of charged micron-sized particles is investigated using discrete element simulations based on adhesive contact dynamic model. The formation process and the final obtained structures of ballistic packings are studied to show the effect of interparticle Coulomb force. It is found that increasing the charge on particles causes a remarkable decrease of the packing volume fraction ϕ and the average coordination number 〈Z〉, indicating a looser and chainlike structure. Force-scaling analysis shows that the long-range Coulomb interaction changes packing structures through its influence on particle inertia before they are bonded into the force networks. Once contact networks are formed, the expansion effect caused by repulsive Coulomb forces are dominated by short-range adhesion. Based on abundant results from simulations, a dimensionless adhesion parameter Ad*, which combines the effects of the particle inertia, the short-range adhesion and the long-range Coulomb interaction, is proposed and successfully scales the packing results for micron-sized particles within the latest derived adhesive loose packing (ALP) regime. The structural properties of our packings follow well the recent theoretical prediction which is described by an ensemble approach based on a coarse-grained volume function, indicating some kind of universality in the low packing density regime of the phase diagram regardless of adhesion or particle charge. Based on the comprehensive consideration of the complicated inter-particle interactions, our findings provide insight into the roles of short-range adhesion and repulsive Coulomb force during packing formation and should be useful for further design of packings.

  15. Crystal structures and properties of nylon polymers from theory

    SciTech Connect

    Dasgupta, S.; Goddard, W.A. III; Hammond, W.B.

    1996-12-11

    A complete force field (MSXX) for simulation of all nylon polymers is derived from ab initio quantum calculations. Special emphasis is given to the accuracy of the hydrogen bond potential for the amide unit and the torsional potential between the peptide and alkane fragments. The MSXX force field was used to predict the structures, moduli, and detailed geometries of all nine nylons for which there are experimental crystal data plus one other. For nylon-(2n) with 2n = 6, the {alpha} crystal structure (with all-trans CH{sub 2} chains nearly coplanar with the hydrogen bonding plane) is more stable, while for 2n > 6, {gamma} (with the alkane plane twisted by 70{degree}) is more stable. This change results from the increased importance of methylene packing interactions over H bonds for larger 2n. We find the highest Young`s modulus for nylon-7. 51 refs., 6 figs., 7 tabs.

  16. Atomic force microscopy study of tooth surfaces.

    PubMed

    Farina, M; Schemmel, A; Weissmüller, G; Cruz, R; Kachar, B; Bisch, P M

    1999-03-01

    Atomic force microscopy (AFM) was used to study tooth surfaces in order to compare the pattern of particle distribution in the outermost layer of the tooth surfaces. Human teeth and teeth from a rodent (Golden hamster), from a fish (piranha), and from a grazing mollusk (chiton) with distinct feeding habits were analyzed in terms of particle arrangement, packing, and size distribution. Scanning electron microscopy and transmission electron microscopy were used for comparison. It was found that AFM gives high-contrast, high-resolution images and is an important tool as a source of complementary and/or new structural information. All teeth were cleaned and some were etched with acidic solutions before analysis. It was observed that human enamel (permanent teeth) presents particles tightly packed in the outer surface, whereas enamel from the hamster (continuously growing teeth) shows particles of less dense packing. The piranha teeth have a thin cuticle covering the long apatite crystals of the underlying enameloid. This cuticle has a rough surface of particles that have a globular appearance after the brief acidic treatment. The similar appearance of the in vivo naturally etched tooth surface suggests that the pattern of globule distribution may be due to the presence of an organic material. Elemental analysis of this cuticle indicated that calcium, phosphorus, and iron are the main components of the structure while electron microdiffraction of pulverized cuticle particles showed a pattern consistent with hydroxyapatite. The chiton mineralized tooth cusp had a smooth surface in an unabraded region and a very rough structure with the magnetite crystals (already known to make part of the structure) protruding from the surface. It was concluded that the structures analyzed are optimized for efficiency in feeding mechanism and life span of the teeth.

  17. Controlled graphene oxide assembly on silver nanocube monolayers for SERS detection: dependence on nanocube packing procedure

    PubMed Central

    Banchelli, Martina; Tiribilli, Bruno; Pini, Roberto; Dei, Luigi

    2016-01-01

    Summary Hybrid graphene oxide/silver nanocubes (GO/AgNCs) arrays for surface-enhanced Raman spectroscopy (SERS) applications were prepared by means of two procedures differing for the method used in the assembly of the silver nanocubes onto the surface: Langmuir–Blodgett (LB) transfer and direct sequential physisorption of silver nanocubes (AgNCs). Adsorption of graphene oxide (GO) flakes on the AgNC assemblies obtained with both procedures was monitored by quartz crystal microbalance (QCM) technique as a function of GO bulk concentration. The experiment provided values of the adsorbed GO mass on the AgNC array and the GO saturation limit as well as the thickness and the viscoelastic properties of the GO film. Atomic force microscopy (AFM) measurements of the resulting samples revealed that a similar surface coverage was achieved with both procedures but with a different distribution of silver nanoparticles. In the GO covered LB film, the AgNC distribution is characterized by densely packed regions alternating with empty surface areas. On the other hand, AgNCs are more homogeneously dispersed over the entire sensor surface when the nanocubes spontaneously adsorb from solution. In this case, the assembly results in less-packed silver nanostructures with higher inter-cube distance. For the two assembled substrates, AFM of silver nanocubes layers fully covered with GO revealed the presence of a homogeneous, flexible and smooth GO sheet folding over the silver nanocubes and extending onto the bare surface. Preliminary SERS experiments on adenine showed a higher SERS enhancement factor for GO on Langmuir–Blodgett films of AgNCs with respect to bare AgNC systems. Conversely, poor SERS enhancement for adenine resulted for GO-covered AgNCs obtained by spontaneous adsorption. This indicated that the assembly and packing of AgNCs obtained in this way, although more homogeneous over the substrate surface, is not as effective for SERS analysis. PMID:26925348

  18. COLLOIDS. Colloidal matter: Packing, geometry, and entropy.

    PubMed

    Manoharan, Vinothan N

    2015-08-28

    Colloidal particles with well-controlled shapes and interactions are an ideal experimental system for exploring how matter organizes itself. Like atoms and molecules, these particles form bulk phases such as liquids and crystals. But they are more than just crude analogs of atoms; they are a form of matter in their own right, with complex and interesting collective behavior not seen at the atomic scale. Their behavior is affected by geometrical or topological constraints, such as curved surfaces or the shapes of the particles. Because the interactions between the particles are often short-ranged, we can understand the effects of these constraints using geometrical concepts such as packing. The geometrical viewpoint gives us a window into how entropy affects not only the structure of matter, but also the dynamics of how it forms. PMID:26315444

  19. 7 CFR 51.1527 - Standard pack.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Standards for Grades of Fresh Plums and Prunes Standard Pack § 51.1527 Standard pack. (a) Packing. (1) All... plums or prunes in the top layer of any package shall be reasonably representative in quality and size of those in the remainder of the package. (3) “Well filled” means that the plums or prunes packed...

  20. 7 CFR 51.1527 - Standard pack.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Standards for Grades of Fresh Plums and Prunes Standard Pack § 51.1527 Standard pack. (a) Packing. (1) All... plums or prunes in the top layer of any package shall be reasonably representative in quality and size of those in the remainder of the package. (3) “Well filled” means that the plums or prunes packed...

  1. 7 CFR 51.310 - Packing requirements.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... (INSPECTION, CERTIFICATION, AND STANDARDS) United States Standards for Grades of Apples Packing Requirements § 51.310 Packing requirements. (a) Apples tray packed or cell packed in cartons shall be arranged.... 3 2 “Fairly tight” means that apples are of the proper size for molds or cell compartments in...

  2. 7 CFR 51.310 - Packing requirements.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... (INSPECTION, CERTIFICATION, AND STANDARDS) United States Standards for Grades of Apples Packing Requirements § 51.310 Packing requirements. (a) Apples tray packed or cell packed in cartons shall be arranged.... 3 2 “Fairly tight” means that apples are of the proper size for molds or cell compartments in...

  3. 7 CFR 51.1217 - Standard pack.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Peaches Standard Pack § 51.1217 Standard pack. (a) Each package shall be packed so that the peaches in the shown face shall be reasonably representative in size, color and quality of the contents of the package. (b) Peaches packed in U.S....

  4. 7 CFR 51.1217 - Standard pack.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Standards for Grades of Peaches Standard Pack § 51.1217 Standard pack. (a) Each package shall be packed so that the peaches in the shown face shall be reasonably representative in size, color and quality of the contents of the package. (b) Peaches packed in U.S. Standard bushel baskets, or half-bushel baskets,...

  5. 7 CFR 51.1217 - Standard pack.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Standards for Grades of Peaches Standard Pack § 51.1217 Standard pack. (a) Each package shall be packed so that the peaches in the shown face shall be reasonably representative in size, color and quality of the contents of the package. (b) Peaches packed in U.S. Standard bushel baskets, or half-bushel baskets,...

  6. 7 CFR 51.1217 - Standard pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Standards for Grades of Peaches Standard Pack § 51.1217 Standard pack. (a) Each package shall be packed so that the peaches in the shown face shall be reasonably representative in size, color and quality of the contents of the package. (b) Peaches packed in U.S. Standard bushel baskets, or half-bushel baskets,...

  7. 7 CFR 51.1217 - Standard pack.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Peaches Standard Pack § 51.1217 Standard pack. (a) Each package shall be packed so that the peaches in the shown face shall be reasonably representative in size, color and quality of the contents of the package. (b) Peaches packed in U.S....

  8. Disc pack cleaning table saves computer time

    NASA Technical Reports Server (NTRS)

    Guy, J. T., Sr.

    1970-01-01

    Disc pack holding table is support frame upon which computer disc pack is loaded and protective cover released. This combination permits manual off-line cleaning of disc pack storage units at any time without shutting down the computer, and eliminates on-line disc drive unit to hold pack during cleaning.

  9. Pseudo-fivefold diffraction symmetries in tetrahedral packing.

    PubMed

    Lee, Stephen; Henderson, Ryan; Kaminsky, Corey; Nelson, Zachary; Nguyen, Jeffers; Settje, Nick F; Schmidt, Joshua Teal; Feng, Ji

    2013-07-29

    We review the way in which atomic tetrahedra composed of metallic elements pack naturally into fused icosahedra. Orthorhombic, hexagonal, and cubic intermetallic crystals based on this packing are all shown to be united in having pseudo-fivefold rotational diffraction symmetry. A unified geometric model involving the 600-cell is presented: the model accounts for the observed pseudo-fivefold symmetries among the different Bravais lattice types. The model accounts for vertex-, edge-, polygon-, and cell-centered fused-icosahedral clusters. Vertex-centered and edge-centered types correspond to the well-known pseudo-fivefold symmetries in Ih and D5h quasicrystalline approximants. The concept of a tetrahedrally-packed reciprocal space cluster is introduced, the vectors between sites in this cluster corresponding to the principal diffraction peaks of fused-icosahedrally-packed crystals. This reciprocal-space cluster is a direct result of the pseudosymmetry and, just as the real-space clusters, can be rationalized by the 600-cell. The reciprocal space cluster provides insights for the Jones model of metal stability. For tetrahedrally-packed crystals, Jones zone faces prove to be pseudosymmetric with one another. Lower and upper electron per atom bounds calculated for this pseudosymmetry-based Jones model are shown to accord with the observed electron counts for a variety of Group 10-12 tetrahedrally-packed structures, among which are the four known Cu/Cd intermetallic compounds: CdCu2, Cd3Cu4, Cu5Cd8, and Cu3Cd10. The rationale behind the Jones lower and upper bounds is reviewed. The crystal structure of Zn11Au15Cd23, an example of a 1:1 MacKay cubic quasicrystalline approximant based solely on Groups 10-12 elements is presented. This compound crystallizes in Im3 (space group no. 204) with a = 13.842(2) Å. The structure was solved with R1 = 3.53 %, I > 2σ; = 5.33 %, all data with 1282/0/38 data/restraints/parameters.

  10. Bernal's road to random packing and the structure of liquids

    NASA Astrophysics Data System (ADS)

    Finney, John L.

    2013-11-01

    Until the 1960s, liquids were generally regarded as either dense gases or disordered solids, and theoretical attempts at understanding their structures and properties were largely based on those concepts. Bernal, himself a crystallographer, was unhappy with either approach, preferring to regard simple liquids as 'homogeneous, coherent and essentially irregular assemblages of molecules containing no crystalline regions'. He set about realizing this conceptual model through a detailed examination of the structures and properties of random packings of spheres. In order to test the relevance of the model to real liquids, ways had to be found to realize and characterize random packings. This was at a time when computing was slow and in its infancy, so he and his collaborators set about building models in the laboratory, and examining aspects of their structures in order to characterize them in ways which would enable comparison with the properties of real liquids. Some of the imaginative - often time consuming and frustrating - routes followed are described, as well the comparisons made with the properties of simple liquids. With the increase of the power of computers in the 1960s, computational approaches became increasingly exploited in random packing studies. This enabled the use of packing concepts, and the tools developed to characterize them, in understanding systems as diverse as metallic glasses, crystal-liquid interfaces, protein structures, enzyme-substrate interactions and the distribution of galaxies, as well as their exploitation in, for example, oil extraction, understanding chromatographic separation columns, and packed beds in industrial processes.

  11. Molecular packing in bone collagen fibrils prior to mineralization

    NASA Astrophysics Data System (ADS)

    Hsiao, Benjamin; Zhou, Hong-Wen; Burger, Christian; Chu, Benjamin; Glimcher, Melvin J.

    2012-02-01

    The three-dimensional packing of collagen molecules in bone collagen fibrils has been largely unknown because even in moderately mineralized bone tissues, the organic matrix structure is severely perturbed by the deposition of mineral crystals. During the past decades, the structure of tendon collagen (e.g. rat tail) --- a tissue that cannot mineralize in vivo, has been assumed to be representative for bone collagen fibrils. Small-angle X-ray diffraction analysis of the native, uncalcified intramuscular fish bone has revealed a new molecular packing scheme, significantly different from the quasi-hexagonal arrangement often found in tendons. The deduced structure in bone collagen fibrils indicates the presence of spatially discrete microfibrils, and an arrangement of intrafibrillar space to form ``channels'', which could accommodate crystals with dimensions typically found in bone apatite.

  12. Valve packings conquer fugitive emissions

    SciTech Connect

    1995-11-01

    In the early 1990s, when the US Environmental Protection Agency (EPA; Washington, D.C.) declared its intent to regulate fugitive emissions from valve-stem leakage, much of the chemical process industries (CPI) responded with fear and uncertainty. The biggest fear was that valve packing would not meet the required limits on leak rates and that expensive bellows seals may be required on many applications. The uncertainly was about how much it would cost. Today, for the most part, these concerns have been mitigated. It is estimated that about 80--90% of valves satisfy the emission requirements. The rest need some improvement in their packing systems to meet the regulations. Generally, these valves can be brought within compliance if the packing designers follow a few basic principles: Employ less-pliable outer rings and more-pliable inner rings; and don`t use excessive packing. While interest in valve packing remains high, mechanical seals continue to become more user-friendly. Many of those covered below are designed to run dry, and some can even tolerate high shaft-wobble without damage. Also look for improved flange gaskets and a host of seals to protect bearings. Twenty-one summaries are presented on new products and services.

  13. Sleeping distance in wild wolf packs

    USGS Publications Warehouse

    Knick, S.T.; Mech, L.D.

    1980-01-01

    Sleeping distances were observed among members of 13 wild wolf (Canis lupus) packs and 11 pairs in northeastern Minnesota to determine if the distances correlated with pack size and composition. The study utilized aerial radio-tracking and observation during winter. Pack size and number of adults per pack were inversely related to pack average sleeping distance and variability. No correlation between sleeping distance and microclimate was observed. Possible relationships between social bonding and our results are discussed.

  14. Dislocation nucleation in bcc Ta single crystals studied by nanoindentation

    SciTech Connect

    Biener, M M; Biener, J; Hodge, A M; Hamza, A V

    2007-08-08

    The study of dislocation nucleation in closed-packed metals by nanoindentation has recently attracted much interest. Here, we address the peculiarities of the incipient plasticity in body centered cubic (bcc) metals using low index Ta single-crystals as a model system. The combination of nanoindentation with high-resolution atomic force microscopy provides us with experimental atomic-scale information on the process of dislocation nucleation and multiplication. Our results reveal a unique deformation behavior of bcc Ta at the onset of plasticity which is distinctly different from that of closed-packed metals. Most noticeable, we observe only one rather than a sequence of discontinuities in the load-displacement curves. This and other differences are discussed in context of the characteristic plastic deformation behavior of bcc metals.

  15. Photovoltaic dryer with dual packed beds for drying medical herb

    SciTech Connect

    Abdel-Rehim, Z.S.; Fahmy, F.H.

    1998-03-01

    This work presents design and optimization of a cylindrical photovoltaic dryer with dual packed beds thermal energy storage for drying medical herb. The dryer is provided with electrical heater where the electrical energy is generated by using photovoltaic system. The electrical heater is designed and sized to realize continuous drying (day and night) to minimize the drying time. Two packed beds are used to fix the drying temperature in dryer during day and night. The main packed bed thermal energy storage is charged during the sunlight hours directly, to realize continued drying after sunset. An efficient PV dryer is devised to work under forced air created by air blower and heated by the electrical coils.

  16. Entanglement Theories: Packing vs. Percolation

    NASA Astrophysics Data System (ADS)

    Wool, Richard

    2007-03-01

    There are two emergent theories of polymer entanglements, the Packing Model (Fetters, Lohse, Graessley, Milner, Whitten, ˜'98) and the Percolation Model (Wool ˜'93). The Packing model suggests that the entanglement molecular weight Me is determined by Me = K p^3, where the packing length parameter p = V/R^2 in which V is the volume of the chain (V=M/ρNa), R is the end-to end vector of the chain, and K 357 ρNa, is an empirical constant. The Percolation model states that an entanglement network develops when the number of chains per unit area σ, intersecting any load bearing plane, is equal to 3 times the number of chain segments (1/a cross-section), such that when 3aσ =1 at the percolation threshold, Me 31 MjC∞, in which Mj is the step molecular weight and C∞ is the characteristic ratio. There are no fitting parameters in the Percolation model. The Packing model predicts that Me decreases rapidly with chain stiffness, as Me˜1/C∞^3, while the Percolation model predicts that Me increases with C∞, as Me˜C∞. The Percolation model was found to be the correct model based on computer simulations (M. Bulacu et al) and a re-analysis of the Packing model experimental data. The Packing model can be derived from the Percolation model, but not visa versa, and reveals a surprising accidental relation between C∞ and Mj in the front factor K. This result significantly impacts the interpretation of the dynamics of rheology and fracture of entangled polymers.

  17. Structural characterization of submerged granular packings

    NASA Astrophysics Data System (ADS)

    Jakšić, Z. M.; Šćepanović, J. R.; Lončarević, I.; Budinski-Petković, Lj.; Vrhovac, S. B.; Belić, A.

    2014-12-01

    We consider the impact of the effective gravitational acceleration on microstructural properties of granular packings through experimental studies of spherical granular materials saturated within fluids of varying density. We characterize the local organization of spheres in terms of contact connectivity, distribution of the Delaunay free volumes, and the shape factor (parameter of nonsphericity) of the Voronoï polygons. The shape factor gives a clear physical picture of the competition between less and more ordered domains of particles in experimentally obtained packings. As the effective gravity increases, the probability distribution of the shape factor becomes narrower and more localized around the lowest values of the shape factor corresponding to regular hexagon. It is found that curves of the pore distributions are asymmetric with a long tail on the right-hand side, which progressively reduces while the effective gravity gets stronger for lower densities of interstitial fluid. We show that the distribution of local areas (Voronoï cells) broadens with decreasing value of the effective gravity due to the formation of lose structures such as large pores and chainlike structures (arches or bridges). Our results should be particularly helpful in testing the newly developed simulation techniques involving liquid-related forces associated with immersed granular particles.

  18. [Electroflotation packing of mycelial wastes].

    PubMed

    Nikolaev, V B; Karpukhin, V F; Zav'ialova, E V; Faingol'd, Z L

    1989-04-01

    Data on testing a pilot plant for electroflotative packing of mycelial wastes are presented. Both the mycelial wastes and their mixtures were used. Concentration of dry substances raged from 3.5 to 131 g/l. The process was performed with varying flow density and consumption rate of the liquid supplied to the plant. Insoluble magnetite and ruthenium oxide anodes were used. The moister content in the packed phase was 81-97.5 per cent. The study provided specification of the process technological parameters and investigation of the flotator hydroulic characteristics.

  19. Cylinder valve packing nut studies

    SciTech Connect

    Blue, S.C.

    1991-12-31

    The design, manufacture, and use of cylinder valve packing nuts have been studied to improve their resistance to failure from stress corrosion cracking. Stress frozen photoelastic models have been analyzed to measure the stress concentrations at observed points of failure. The load effects induced by assembly torque and thermal expansion of stem packing were observed by strain gaging nuts. The effects of finishing operations and heat treatment were studied by the strain gage hole boring and X-ray methods. Modifications of manufacturing and operation practices are reducing the frequency of stress corrosion failures.

  20. Assembly of streptolysin O pores assessed by quartz crystal microbalance and atomic force microscopy provides evidence for the formation of anchored but incomplete oligomers.

    PubMed

    Stewart, Sarah E; D'Angelo, Michael E; Paintavigna, Stefania; Tabor, Rico F; Martin, Lisandra L; Bird, Phillip I

    2015-01-01

    Streptolysin O (SLO) is a bacterial pore forming protein that is part of the cholesterol dependent cytolysin (CDC) family. We have used quartz crystal microbalance with dissipation monitoring (QCM-D) to examine SLO membrane binding and pore formation. In this system, SLO binds tightly to cholesterol-containing membranes, and assembles into partial and complete pores confirmed by atomic force microscopy. SLO binds to the lipid bilayer at a single rate consistent with the Langmuir isotherm model of adsorption. Changes in dissipation illustrate that SLO alters the viscoelastic properties of the bilayer during pore formation, but there is no loss of material from the bilayer as reported for small membrane-penetrating peptides. SLO mutants were used to further dissect the assembly and insertion processes by QCM-D. This shows the signature of SLO in QCM-D changes when pore formation is inhibited, and that bound and inserted SLO forms can be distinguished. Furthermore a pre-pore locked SLO mutant binds reversibly to lipid, suggesting that the partially complete wtSLO forms observed by AFM are anchored to the membrane.

  1. Assessment of DNA binding to human Rad51 protein by using quartz crystal microbalance and atomic force microscopy: effects of ADP and BRC4-28 peptide inhibitor.

    PubMed

    Esnault, Charles; Renodon-Cornière, Axelle; Takahashi, Masayuki; Casse, Nathalie; Delorme, Nicolas; Louarn, Guy; Fleury, Fabrice; Pilard, Jean-François; Chénais, Benoît

    2014-12-01

    The interaction of human Rad51 protein (HsRad51) with single-stranded deoxyribonucleic acid (ssDNA) was investigated by using quartz crystal microbalance (QCM) monitoring and atomic force microscopy (AFM) visualization. Gold surfaces for QCM and AFM were modified by electrografting of the in situ generated aryldiazonium salt from the sulfanilic acid to obtain the organic layer Au-ArSO3 H. The Au-ArSO3 H layer was activated by using a solution of PCl5 in CH2 Cl2 to give a Au-ArSO2 Cl layer. The modified surface was then used to immobilize long ssDNA molecules. The results obtained showed that the presence of adenosine diphosphate promotes the protein autoassociation rather than nucleation around DNA. In addition, when the BRC4-28 peptide inhibitor was used, both QCM and AFM confirmed the inhibitory effect of BRC4-28 toward HsRad51 autoassociation. Altogether these results show the suitability of this modified surface to investigate the kinetics and structure of DNA-protein interactions and for the screening of inhibitors.

  2. Human immunoglobulin adsorption investigated by means of quartz crystal microbalance dissipation, atomic force microscopy, surface acoustic wave, and surface plasmon resonance techniques.

    PubMed

    Zhou, Cheng; Friedt, Jean-Michel; Angelova, Angelina; Choi, Kang-Hoon; Laureyn, Wim; Frederix, Filip; Francis, Laurent A; Campitelli, Andrew; Engelborghs, Yves; Borghs, Gustaaf

    2004-07-01

    Time-resolved adsorption behavior of a human immunoglobin G (hIgG) protein on a hydrophobized gold surface is investigated using multitechniques: quartz crystal microbalance/dissipation (QCM-D) technique; combined surface plasmon resonance (SPR) and Love mode surface acoustic wave (SAW) technique; combined QCM-D and atomic force microscopy (AFM) technique. The adsorbed hIgG forms interfacial structures varying in organization from a submonolayer to a multilayer. An "end-on" IgG orientation in the monolayer film, associated with the surface coverage results, does not corroborate with the effective protein thickness determined from SPR/SAW measurements. This inconsistence is interpreted by a deformation effect induced by conformation change. This conformation change is confirmed by QCM-D measurement. Combined SPR/SAW measurements suggest that the adsorbed protein barely contains water after extended contact with the hydrophobic surface. This limited interfacial hydration also contributed to a continuous conformation change in the adsorbed protein layer. The viscoelastic variation associated with interfacial conformation changes induces about 1.5 times overestimation of the mass uptake in the QCM-D measurements. The merit of combined multitechnique measurements is demonstrated.

  3. Computational crystallization.

    PubMed

    Altan, Irem; Charbonneau, Patrick; Snell, Edward H

    2016-07-15

    Crystallization is a key step in macromolecular structure determination by crystallography. While a robust theoretical treatment of the process is available, due to the complexity of the system, the experimental process is still largely one of trial and error. In this article, efforts in the field are discussed together with a theoretical underpinning using a solubility phase diagram. Prior knowledge has been used to develop tools that computationally predict the crystallization outcome and define mutational approaches that enhance the likelihood of crystallization. For the most part these tools are based on binary outcomes (crystal or no crystal), and the full information contained in an assembly of crystallization screening experiments is lost. The potential of this additional information is illustrated by examples where new biological knowledge can be obtained and where a target can be sub-categorized to predict which class of reagents provides the crystallization driving force. Computational analysis of crystallization requires complete and correctly formatted data. While massive crystallization screening efforts are under way, the data available from many of these studies are sparse. The potential for this data and the steps needed to realize this potential are discussed.

  4. Use of the Primitive Unit Cell in Understanding Subtle Features of the Cubic Closest-Packed Structure

    ERIC Educational Resources Information Center

    Hawkins, John A.; Rittenhouse, Jeffrey L.; Soper, Linda M.; Rittenhouse, Robert C.

    2008-01-01

    One of the most important crystal structures adopted by metals is characterized by the "abcabc"...stacking of close-packed layers. This structure is commonly referred to in textbooks as the cubic close-packed (ccp) or face-centered cubic (fcc) structure, since the entire lattice can be generated by replication of a face-centered cubic unit cell…

  5. Phase-separation-induced single-crystal morphology in poly(L-lactic acid) blended with poly(1,4-butylene adipate) at specific composition.

    PubMed

    Nurkhamidah, Siti; Woo, E M

    2011-11-17

    The single-crystal morphology of poly(L-lactic acid) (PLLA) in blending with poly(butylene adipate) (PBA) in PLLA/PBA blends was for the first time reported in melt crystallization. At crystallization temperature (T(c)) = 110 °C, by adding 30 wt % PBA into PLLA, the lamellae exhibit six-stalk dendrites with single-crystal packing. Phase separation and crystallization took place simultaneously at T(c) = 110 °C in PLLA/PBA (70/30) blend, leading to discrete PBA domains and continuous PLLA domains. For PLLA/PBA (70/30) blend, all PBA were rejected from the growth front of PLLA crystals, expelled, and crystallized at ambient temperature as ring-banded PBA spherulites inside the discrete domains only, resulting in a favorable environment for formation of PLLA single crystals in the continuous domain. Atomic force microscopy (AFM) observation on individual crystallites reveals that lozenge-shaped single crystals were packed with a clockwise spiral pattern, stacked in 1-3 layers, and these lozenge-shaped crystals are aligned six hexasected directions into hexastalk dendrites with occasional side branches that are also aligned at 60° to main branches. The monolamellar thickness of lozenge-shaped single crystals was measured to be about 13-34 nm, and the dimension is about 0.8-3 μm along the short axis and 1.6-5 μm along the long axis. Typically, three layers of single crystals are stacked one on another; the lozenge crystals on the bottom layer are about twice as large as those on the top layer, forming a pyramid shape in the depth direction. Formation mechanisms of single crystals in melt-crystallized PLLA/PBA blend from 700 nm film thickness are discussed in correlation with exact phase separation at 30 wt % PBA. PMID:21962158

  6. Protein Crystallization

    NASA Technical Reports Server (NTRS)

    Chernov, Alexander A.

    2005-01-01

    Nucleation, growth and perfection of protein crystals will be overviewed along with crystal mechanical properties. The knowledge is based on experiments using optical and force crystals behave similar to inorganic crystals, though with a difference in orders of magnitude in growing parameters. For example, the low incorporation rate of large biomolecules requires up to 100 times larger supersaturation to grow protein, rather than inorganic crystals. Nucleation is often poorly reproducible, partly because of turbulence accompanying the mixing of precipitant with protein solution. Light scattering reveals fluctuations of molecular cluster size, its growth, surface energies and increased clustering as protein ages. Growth most often occurs layer-by-layer resulting in faceted crystals. New molecular layer on crystal face is terminated by a step where molecular incorporation occurs. Quantitative data on the incorporation rate will be discussed. Rounded crystals with molecularly disordered interfaces will be explained. Defects in crystals compromise the x-ray diffraction resolution crucially needed to find the 3D atomic structure of biomolecules. The defects are immobile so that birth defects stay forever. All lattice defects known for inorganics are revealed in protein crystals. Contribution of molecular conformations to lattice disorder is important, but not studied. This contribution may be enhanced by stress field from other defects. Homologous impurities (e.g., dimers, acetylated molecules) are trapped more willingly by a growing crystal than foreign protein impurities. The trapped impurities induce internal stress eliminated in crystals exceeding a critical size (part of mni for ferritin, lysozyme). Lesser impurities are trapped from stagnant, as compared to the flowing, solution. Freezing may induce much more defects unless quickly amorphysizing intracrystalline water.

  7. Ecology and Energy Action Pack.

    ERIC Educational Resources Information Center

    McDonald's Corp., Oak Brook, IL.

    One of five McDonald's Action Packs, these elementary school-level instructional materials are for use as an introduction to existing units of study, supplements to a textbook, or a source of special projects for environmental education. Contents include these six units: Make Your Own Ecology Mini-spinner, Let's Look at a Food Chain, Drip the…

  8. Pack cementation coatings for alloys

    SciTech Connect

    He, Yi-Rong; Zheng, Minhui; Rapp, R.A.

    1996-08-01

    The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on a Cr-Cr{sub 2}Nb alloy in a single processing step. The morphology and composition of the coating depended both on the composition of the pack and on the composition and microstructure of the substrate. Higher Ge content in the pack suppressed the formation of CrSi{sub 2} and reduced the growth kinetics of the coating. Ge was not homogeneously distributed in the coatings. In cyclic and isothermal oxidation in air at 700 and 1050{degrees}C, the Ge-doped silicide coating protected the Cr-Nb alloys from significant oxidation by the formation of a Ge-doped silica film. The codeposition and diffusion of aluminum and chromium into low alloy steel have been achieved using elemental Al and Cr powders and a two-step pack cementation process. Sequential process treatments at 925{degrees}C and 1150{degrees}C yield dense and uniform ferrite coatings, whose compositions are close to either Fe{sub 3}Al or else FeAl plus a lower Cr content, when processed under different conditions. The higher content of Al in the coatings was predicted by thermodynamic calculations of equilibrium in the gas phase. The effect of the particle size of the metal powders on the surface composition of the coating has been studied for various combinations of Al and Cr powders.

  9. Wire and Packing Tape Sandwiches

    ERIC Educational Resources Information Center

    Rabinowitz, Sandy

    2009-01-01

    In this article, the author describes how students can combine craft wire with clear packing tape to create a two-dimensional design that can be bent and twisted to create a three-dimensional form. Students sandwich wire designs between two layers of tape. (Contains 1 online resource.)

  10. Inverse statistical mechanics, lattice packings, and glasses

    NASA Astrophysics Data System (ADS)

    Marcotte, Etienne

    Computer simulation methods enable the investigation of systems and properties that are intractable by purely analytical or experimental approaches. Each chapter of this dissertation contains an application of simulation methods to solve complex physical problems consisting of interacting many-particle or many-spin systems. The problems studied in this dissertation can be divided up into the following two broad categories: inverse and forward problems. The inverse problems considered are those in which we construct an interaction potential such that the corresponding ground state is a targeted configuration. In Chapters 2 and 3, we devise convex pair-potential functions that result in low-coordinated ground states. Chapter 2 describes targeted ground states that are the square and honeycomb crystals, while in Chapter 3 the targeted ground state is the diamond crystal. Chapter 4 applies similar techniques to explicitly enumerate all unique ground states up to a given system size, for spin configurations that interact according to generalized isotropic Ising potentials with finite range. We also consider forward statistical-mechanical problems. In Chapter 5, we adapt a linear programming algorithm to find the densest lattice packings across Euclidean space dimensions. In Chapter 6, we demonstrate that for two different glass models a signature of the glass transition is apparent well before the transition temperature is reached. In both models, this signature appears as nonequilibrium length scales that grow upon supercooling.

  11. Magnetic assembly of nonmagnetic particles into photonic crystal structures.

    PubMed

    He, Le; Hu, Yongxing; Kim, Hyoki; Ge, Jianping; Kwon, Sunghoon; Yin, Yadong

    2010-11-10

    We report the rapid formation of photonic crystal structures by assembly of uniform nonmagnetic colloidal particles in ferrofluids using external magnetic fields. Magnetic manipulation of nonmagnetic particles with size down to a few hundred nanometers, suitable building blocks for producing photonic crystals with band gaps located in the visible regime, has been difficult due to their weak magnetic dipole moment. Increasing the dipole moment of magnetic holes has been limited by the instability of ferrofluids toward aggregation at high concentration or under strong magnetic field. By taking advantage of the superior stability of highly surface-charged magnetite nanocrystal-based ferrofluids, in this paper we have been able to successfully assemble 185 nm nonmagnetic polymer beads into photonic crystal structures, from 1D chains to 3D assemblies as determined by the interplay of magnetic dipole force and packing force. In a strong magnetic field with large field gradient, 3D photonic crystals with high reflectance (83%) in the visible range can be rapidly produced within several minutes, making this general strategy promising for fast creation of large-area photonic crystals using nonmagnetic particles as building blocks.

  12. Packing tube assembly for pumping wells

    SciTech Connect

    Towner, G.F.; Carter, C.A.

    1987-09-22

    A packing tube assembly for replacing a conventional stuffing box is described. The packing tube assembly comprising: a packing tube; a rod adaptor adapted to be coupled between the polished rod and the sucker rod string and adapted to extend throughout the packing tube when positioned therein; compressible packing means on the rod adaptor adapted to provide a seal between the rod adaptor and the packing tube when the rod adaptor is in position within the packing tube; stabilizing means on the rod adaptor adapted to engage the packing tube to stabilize the rod adaptor within the packing tube during operation; and a mounting bushing connected to the top of the packing tube and adapted to be threaded into the pumping tee to secure the packing tube position within the production tubing string. A method of converting a conventional stuffing box-equipped pumping well to a packing tube-equipped well is described. It consists of: disconnecting the polished rod of the pumping well from the sucker rod string while suspending the sucker rod string within the well by the use of slips; unthreading the conventional stuffing box from the pumping tee of the well and removing the stuffing box; attaching the polished rod to the upper end of a rod adaptor of a packing tube assembly, inserting the rod adaptor with the polished rod attached into the packing tube of the packing tube assembly; aligning the packing tube assembly with the sucker rod string; connecting the lower end of the rod adaptor to the sucker rod string; removing the slips and lowering the packer tube assembly through the pumping tee; and connecting the upper end of the packing tube to the pumping tee.

  13. Scanning/friction force microscopy study of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} single crystals grown in BaZrO{sub 3} crucibles

    SciTech Connect

    Lang, H.P.; Jess, P.; Hubler, U.

    1996-12-01

    Very pure YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) single crystals grown in BaZrO{sub 3} crucibles are studied in the as-grown and the oxidized state by scanning force (SFM), friction force (FFM) and scanning tunneling microscopies (STM). The images show clean terraces with step-heights of one unit cell along YBCO(001), i.e. 1.2 nm. Only close to step edges is material contrast observed by FFM indicating traces of flux. Some crystal surfaces exhibit over-layer features, such as star-like, ribbon-like and checkerboard-like structures, which exhibit friction contrast implying the presence of different materials on the surface. Tunneling spectroscopy at 4-7 K in high vacuum reveals a superconducting energy gap of 2{Delta} {approx} 26 meV.

  14. 7 CFR 984.15 - Pack.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order Regulating Handling Definitions § 984.15 Pack. Pack means to bleach, clean, grade, shell or otherwise prepare walnuts for market as inshell or shelled walnuts....

  15. 7 CFR 984.15 - Pack.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order Regulating Handling Definitions § 984.15 Pack. Pack means to bleach, clean, grade, shell or otherwise prepare walnuts for market as inshell or shelled walnuts....

  16. 7 CFR 984.15 - Pack.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order Regulating Handling Definitions § 984.15 Pack. Pack means to bleach, clean, grade, shell or otherwise prepare walnuts for market as inshell or shelled walnuts....

  17. 7 CFR 984.15 - Pack.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order Regulating Handling Definitions § 984.15 Pack. Pack means to bleach, clean, grade, shell or otherwise prepare walnuts for market as inshell or shelled walnuts....

  18. 7 CFR 984.15 - Pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order Regulating Handling Definitions § 984.15 Pack. Pack means to bleach, clean, grade, shell or otherwise prepare walnuts for market as inshell or shelled walnuts....

  19. Designing gravel pack for uranium ISL wells

    NASA Astrophysics Data System (ADS)

    Ber, A. A.; Minaev, K. M.; Ber, L. M.; Isaev, Ye D.; Ulyanova, O. S.

    2016-09-01

    The paper describes the improvement of gravel packing technique applied for the production wells. The authors have suggested new design of gravel pack for gravel packing of productive formations. The issue is currently topical because gravel packing at drillhole ISL is less time- and money-consuming. The subject of the research is gravel pack design and content. The purpose defined by the authors is to design the gravel pack and to suggest the composition of gravel cement agent. As a result of the research, the authors have described different designs of the gravel pack, its optimal shape, as well as a choice and justification of cement agents, a hold cover of the gravel pack, and suggested the methods of experimental research.

  20. Structures of cyano-biphenyl liquid crystals

    NASA Technical Reports Server (NTRS)

    Chu, Yuan-Chao; Tsang, Tung; Rahimzadeh, E.; Yin, L.

    1989-01-01

    The structures of p-alkyl- p'-cyano- bicyclohexanes, C(n)H(2n+1) (C6H10)(C6H10) CN (n-CCH), and p-alkyl- p'-cyano- biphenyls, C(n)H(2n+1) (C6H4)(C6H4) CN (n-CBP), were studied. It is convenient to use an x ray image intensification device to search for symmetric x ray diffraction patterns. Despite the similarities in molecular structures of these compounds, very different crystal structures were found. For the smectic phase of 2CCH, the structure is close to rhombohedral with threefold symmetry. In contrast, the structure is close to hexagonal close-packed with two molecules per unit cell for 4CCH. Since intermolecular forces may be quite weak for these liquid crystals systems, it appears that crystal structures change considerably when the alkyl chain length is slightly altered. Different structures were also found in the crystalline phase of n-CBP for n = 6 to 9. For n = 7 to 9, the structures are close to monclinic. The structures are reminiscent of the smectic-A liquid crystal structures with the linear molecules slightly tilted away from the c-axis. In contrast, the structure is quite different for n = 6 with the molecules nearly perpendicular to the c-axis.

  1. Supramolecular Packing Controls H₂ Photocatalysis in Chromophore Amphiphile Hydrogels.

    PubMed

    Weingarten, Adam S; Kazantsev, Roman V; Palmer, Liam C; Fairfield, Daniel J; Koltonow, Andrew R; Stupp, Samuel I

    2015-12-01

    Light harvesting supramolecular assemblies are potentially useful structures as components of solar-to-fuel conversion materials. The development of these functional constructs requires an understanding of optimal packing modes for chromophores. We investigated here assembly in water and the photocatalytic function of perylene monoimide chromophore amphiphiles with different alkyl linker lengths separating their hydrophobic core and the hydrophilic carboxylate headgroup. We found that these chromophore amphiphiles (CAs) self-assemble into charged nanostructures of increasing aspect ratio as the linker length is increased. The addition of salt to screen the charged nanostructures induced the formation of hydrogels and led to internal crystallization within some of the nanostructures. For linker lengths up to seven methylenes, the CAs were found to pack into 2D crystalline unit cells within ribbon-shaped nanostructures, whereas the nine methylene CAs assembled into long nanofibers without crystalline molecular packing. At the same time, the different molecular packing arrangements after charge screening led to different absorbance spectra, despite the identical electronic properties of all PMI amphiphiles. While the crystalline CAs formed electronically coupled H-aggregates, only CAs with intermediate linker lengths showed evidence of high intermolecular orbital overlap. Photocatalytic hydrogen production using a nickel-based catalyst was observed in all hydrogels, with the highest turnovers observed for CA gels having intermediate linker lengths. We conclude that the improved photocatalytic performance of the hydrogels formed by supramolecular assemblies of the intermediate linker CA molecules likely arises from improved exciton splitting efficiencies due to their higher orbital overlap. PMID:26593389

  2. Protein packing interactions and polymorphy of chorismate lyase from E. Coli

    NASA Astrophysics Data System (ADS)

    Gallagher, Travis

    2001-11-01

    The enzyme chorismate lyase from E. coli crystallizes into three well characterized polymorphs in identical conditions. The Wild-type enzyme tends to aggregate, even in the presence of a reducing agent, and yields monoclinic crystals that grow in intricate clusters. Protein aggregation was largely eliminated by mutating the protein's two cysteines to serines. The double mutant retains full enzymatic activity and grows singly in two new forms: triclinic and orthorhombic. The triclinic crystals diffract to 0.9 Å resolution. A single-cysteine mutant that crystallizes in the orthorhombic form was used to determine the structure, enabling examination of the packing interactions at 2.0 Å resolution or better in all three forms. A novel system for labeling contacts is proposed, and relations between packing patterns and crystal properties are discussed. Diffraction resolution is found to correlate with coordination number and with the root-mean-square deviation from mean extent of the contacts. Implications for contact energies are considered.

  3. Power Plays: Proven Methods of Professional Learning Pack a Force

    ERIC Educational Resources Information Center

    Easton, Lois Brown

    2005-01-01

    Powerful professional learning is more than a one-shot workshop. It involves educators working collegially on a matter they care about with content arising directly from their classroom experiences. Educators know which strategies offer more powerful learning. Choosing the appropriate strategy requires answering just three questions.

  4. 7 CFR 51.1527 - Standard pack.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Fresh Plums and Prunes Standard Pack § 51... the approved and recognized methods. (2) The plums or prunes in the top layer of any package shall be...” means that the plums or prunes packed in loose or volume filled containers are packed within 1 inch...

  5. 7 CFR 51.1527 - Standard pack.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Fresh Plums and Prunes Standard Pack § 51... the approved and recognized methods. (2) The plums or prunes in the top layer of any package shall be...” means that the plums or prunes packed in loose or volume filled containers are packed within 1 inch...

  6. 7 CFR 966.11 - Pack.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE TOMATOES GROWN IN FLORIDA Order Regulating Handling Definitions § 966.11 Pack. Pack means any of the packs of tomatoes as defined and set forth in the United States Standards for Fresh Tomatoes issued by the United States Department of Agriculture (§§...

  7. 7 CFR 966.11 - Pack.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE TOMATOES GROWN IN FLORIDA Order Regulating Handling Definitions § 966.11 Pack. Pack means any of the packs of tomatoes as defined and set forth in the United States Standards for Fresh Tomatoes issued by the United States Department of Agriculture (§§...

  8. 7 CFR 966.11 - Pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TOMATOES GROWN IN FLORIDA Order Regulating Handling Definitions § 966.11 Pack. Pack means any of the packs of tomatoes as defined and set forth in the United States Standards for Fresh Tomatoes issued by the United States Department of Agriculture (§§...

  9. 7 CFR 966.11 - Pack.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TOMATOES GROWN IN FLORIDA Order Regulating Handling Definitions § 966.11 Pack. Pack means any of the packs of tomatoes as defined and set forth in the United States Standards for Fresh Tomatoes issued by the United States Department of Agriculture (§§...

  10. 7 CFR 966.11 - Pack.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TOMATOES GROWN IN FLORIDA Order Regulating Handling Definitions § 966.11 Pack. Pack means any of the packs of tomatoes as defined and set forth in the United States Standards for Fresh Tomatoes issued by the United States Department of Agriculture (§§...

  11. 7 CFR 51.1527 - Standard pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... package. The number of plums or prunes in California peach boxes or lug boxes shall not vary more than 4... Standards for Grades of Fresh Plums and Prunes Standard Pack § 51.1527 Standard pack. (a) Packing. (1) All... plums or prunes in the top layer of any package shall be reasonably representative in quality and...

  12. Marginal stability in jammed packings: Quasicontacts and weak contacts

    NASA Astrophysics Data System (ADS)

    Kallus, Yoav; Torquato, Salvatore

    2014-08-01

    Maximally random jammed (MRJ) sphere packing is a prototypical example of a system naturally poised at the margin between underconstraint and overconstraint. This marginal stability has traditionally been understood in terms of isostaticity, the equality of the number of mechanical contacts and the number of degrees of freedom. Quasicontacts, pairs of spheres on the verge of coming in contact, are irrelevant for static stability, but they come into play when considering dynamic stability, as does the distribution of contact forces. We show that the effects of marginal dynamic stability, as manifested in the distributions of quasicontacts and weak contacts, are consequential and nontrivial. We study these ideas first in the context of MRJ packing of d-dimensional spheres, where we show that the abundance of quasicontacts grows at a faster rate than that of contacts. We reexamine a calculation of Jin et al. [Phys. Rev. E 82, 051126 (2010), 10.1103/PhysRevE.82.051126], where quasicontacts were originally neglected, and we explore the effect of their inclusion in the calculation. This analysis yields an estimate of the asymptotic behavior of the packing density in high dimensions. We argue that this estimate should be reinterpreted as a lower bound. The latter part of the paper is devoted to Bravais lattice packings that possess the minimum number of contacts to maintain mechanical stability. We show that quasicontacts play an even more important role in these packings. We also show that jammed lattices are a useful setting for studying the Edwards ensemble, which weights each mechanically stable configuration equally and does not account for dynamics. This ansatz fails to predict the power-law distribution of near-zero contact forces, P(f )˜fθ.

  13. Marginal stability in jammed packings: quasicontacts and weak contacts.

    PubMed

    Kallus, Yoav; Torquato, Salvatore

    2014-08-01

    Maximally random jammed (MRJ) sphere packing is a prototypical example of a system naturally poised at the margin between underconstraint and overconstraint. This marginal stability has traditionally been understood in terms of isostaticity, the equality of the number of mechanical contacts and the number of degrees of freedom. Quasicontacts, pairs of spheres on the verge of coming in contact, are irrelevant for static stability, but they come into play when considering dynamic stability, as does the distribution of contact forces. We show that the effects of marginal dynamic stability, as manifested in the distributions of quasicontacts and weak contacts, are consequential and nontrivial. We study these ideas first in the context of MRJ packing of d-dimensional spheres, where we show that the abundance of quasicontacts grows at a faster rate than that of contacts. We reexamine a calculation of Jin et al. [Phys. Rev. E 82, 051126 (2010)], where quasicontacts were originally neglected, and we explore the effect of their inclusion in the calculation. This analysis yields an estimate of the asymptotic behavior of the packing density in high dimensions. We argue that this estimate should be reinterpreted as a lower bound. The latter part of the paper is devoted to Bravais lattice packings that possess the minimum number of contacts to maintain mechanical stability. We show that quasicontacts play an even more important role in these packings. We also show that jammed lattices are a useful setting for studying the Edwards ensemble, which weights each mechanically stable configuration equally and does not account for dynamics. This ansatz fails to predict the power-law distribution of near-zero contact forces, P(f)∼f(θ).

  14. Diffusion in Jammed Particle Packs.

    PubMed

    Bolintineanu, Dan S; Grest, Gary S; Lechman, Jeremy B; Silbert, Leonardo E

    2015-08-21

    Using random walk simulations we explore diffusive transport through monodisperse sphere packings over a range of packing fractions ϕ in the vicinity of the jamming transition at ϕ(c). Various diffusion properties are computed over several orders of magnitude in both time and packing pressure. Two well-separated regimes of normal "Fickian" diffusion, where the mean squared displacement is linear in time, are observed. The first corresponds to diffusion inside individual spheres, while the latter is the long-time bulk diffusion. The intermediate anomalous diffusion regime and the long-time value of the diffusion coefficient are both shown to be controlled by particle contacts, which in turn depend on proximity to ϕ(c). The time required to recover normal diffusion t* scales as (ϕ-ϕ(c))(-0.5) and the long-time diffusivity D(∞)∼(ϕ-ϕ(c))0.5, or D(∞)∼1/t*. It is shown that the distribution of mean first passage times associated with the escape of random walkers between neighboring particles controls both t* and D(∞) in the limit ϕ→ϕ(c).

  15. Polyolefin Blend Miscibility and Packing

    NASA Astrophysics Data System (ADS)

    Lohse, David J.

    2000-03-01

    Over the last several years data have been obtained on the miscibility of a wide range of polyolefins, covering some 200 blends involving about 75 different components. Despite the fact that there are no 'specific interactions' between these saturated hydrocarbon polymers, every kind of phase behavior has been observed, including UCST, LCST, and even negative values of the Flory interaction parameter. The key factor that determines how these polyolefins mix is the way that they pack. Very often, polyolefins mix regularly, that is, the interaction energy is determined by the cohesive energies of the pure components. When they do mix regularly, miscibility is achieved by a close match in the packing lengths of the components. Favorable irregular mixing appears to be the result of some specific packing arrangements. Recent data on the effects of pressure and temperature on the mixing of several polyolefin blends shows that the interaction energies depend only on density (and not on T and P independently) for UCST blends far from a critical point. As a result, the effects of pressure on miscibility can be predicted for such blends from knowledge of the effects of temperature on the interactions combined with PVT data. This remarkable simplification appears to be related to the van der Waals nature of the interactions between saturated hydrocarbons. Density dependence predicts the trends correctly for LCST polyolefin blends, but for these mixtures the interactions depend in a more complex way on T and P.

  16. Diffusion in Jammed Particle Packs.

    PubMed

    Bolintineanu, Dan S; Grest, Gary S; Lechman, Jeremy B; Silbert, Leonardo E

    2015-08-21

    Using random walk simulations we explore diffusive transport through monodisperse sphere packings over a range of packing fractions ϕ in the vicinity of the jamming transition at ϕ(c). Various diffusion properties are computed over several orders of magnitude in both time and packing pressure. Two well-separated regimes of normal "Fickian" diffusion, where the mean squared displacement is linear in time, are observed. The first corresponds to diffusion inside individual spheres, while the latter is the long-time bulk diffusion. The intermediate anomalous diffusion regime and the long-time value of the diffusion coefficient are both shown to be controlled by particle contacts, which in turn depend on proximity to ϕ(c). The time required to recover normal diffusion t* scales as (ϕ-ϕ(c))(-0.5) and the long-time diffusivity D(∞)∼(ϕ-ϕ(c))0.5, or D(∞)∼1/t*. It is shown that the distribution of mean first passage times associated with the escape of random walkers between neighboring particles controls both t* and D(∞) in the limit ϕ→ϕ(c). PMID:26340211

  17. Force production in the rugby union scrum.

    PubMed

    Quarrie, K L; Wilson, B D

    2000-04-01

    In this study, we examined the relationship between anthropometric, strength and power characteristics of rugby forwards, their body position when scrummaging, and their ability to apply force when scrummaging. Force applied to an instrumented scrum machine was measured for 56 players, both individually and as scrum packs. Measurements of body position for individuals were made by digitizing videotape records of the trials. Forty players subsequently had their anthropometry assessed and completed several strength and power tests. Body mass, each component of somatotype, maximal anaerobic power developed on a cycle ergometer, and isokinetic knee extension strength correlated significantly with individual scrummaging force. A regression model (P < 0.001) including body mass, mesomorphy, maximal anaerobic power and hip angle while in the scrummaging position accounted for 45% of the variance in individual scrummaging force. The packs that produced the largest scrummaging forces were, in general, characterized by a greater pack force to sum of individual force ratio than the packs producing lower forces. Our results emphasize the need for a scrum pack to develop technique and coordination as a unit to maximize scrummaging force. PMID:10824640

  18. The role of filament-packing dynamics in powering amoeboid cell motility

    PubMed Central

    Miao, Long; Vanderlinde, Orion; Liu, Jun; Grant, Richard P.; Wouterse, Alan; Shimabukuro, Katsuya; Philipse, Albert; Stewart, Murray; Roberts, Thomas M.

    2008-01-01

    Although several models have been proposed to account for how cytoskeleton polymerization drives protrusion in cell motility, the precise mechanism remains controversial. Here, we show that, in addition to force exerted directly against the membrane by growing filaments, the way elongating filaments pack also contributes to protrusion by generating an expansion of the cytoskeleton gel. Tomography shows that filament packing in the major sperm protein (MSP) -based nematode sperm-motility machinery resembles that observed with rigid rods. Maximum rod-packing density decreases dramatically as the rods lengthen. Therefore, as filaments elongate, the cytoskeleton gel expands to accommodate their packing less densely. This volume expansion combines with polymerization to drive protrusion. Consistent with this hypothesis, an engineered MSP mutant that generates shorter filaments shows higher filament-packing density and slower movement. PMID:18385381

  19. Solvent-Triggered Cis/Trans Isomerism in Cobalt Dioxolene Chemistry: Distinguishing Effects of Packing on Valence Tautomerism.

    PubMed

    Panja, Anangamohan; Jana, Narayan Ch; Bauzá, Antonio; Frontera, Antonio; Mathonière, Corine

    2016-09-01

    In this article, the synthesis and X-ray crystal structures of two cis/trans isomers of valence tautomeric (VT) cobalt dioxolene compounds are reported. The cis isomer (1) was isolated from the polar protic methanol solvent as a kinetic product, whereas the less polar nonprotic solvent acetone yielded the trans isomer (2). It should be noted that, although some coordination polymers involving cobalt bis(dioxolene) with the cis disposition are known for bridging ancillary ligands, such an arrangement is unprecedented for mononuclear compounds. A careful study of intermocular interactions revealed that the methanol solvent does not have much influence on the crystal growth in 1, whereas acetone forms strong halogen-bonding interactions that are crucial in the solid-state architecture of 2. This behavior can likely be used in crystal engineering to design new organic-inorganic hybrid materials. The energy difference between the two isomers was examined using DFT calculations, confirming that the trans form is in the thermodynamic state whereas the cis isomer is a kinetic product that can be converted into the trans isomer with time. Finally, both isomers exhibit solvent loss at elevated temperatures that is accompanied by a change in magnetic properties, associated with an irreversible valence tautomerism. Our results highlight the crucial role of the solvents for the isolation of cis/trans isomers in cobalt dioxolene chemistry, as well as the distinguishing effects of intermolecular forces and the solid-state packing on VT behavior. PMID:27557848

  20. Solvent-Triggered Cis/Trans Isomerism in Cobalt Dioxolene Chemistry: Distinguishing Effects of Packing on Valence Tautomerism.

    PubMed

    Panja, Anangamohan; Jana, Narayan Ch; Bauzá, Antonio; Frontera, Antonio; Mathonière, Corine

    2016-09-01

    In this article, the synthesis and X-ray crystal structures of two cis/trans isomers of valence tautomeric (VT) cobalt dioxolene compounds are reported. The cis isomer (1) was isolated from the polar protic methanol solvent as a kinetic product, whereas the less polar nonprotic solvent acetone yielded the trans isomer (2). It should be noted that, although some coordination polymers involving cobalt bis(dioxolene) with the cis disposition are known for bridging ancillary ligands, such an arrangement is unprecedented for mononuclear compounds. A careful study of intermocular interactions revealed that the methanol solvent does not have much influence on the crystal growth in 1, whereas acetone forms strong halogen-bonding interactions that are crucial in the solid-state architecture of 2. This behavior can likely be used in crystal engineering to design new organic-inorganic hybrid materials. The energy difference between the two isomers was examined using DFT calculations, confirming that the trans form is in the thermodynamic state whereas the cis isomer is a kinetic product that can be converted into the trans isomer with time. Finally, both isomers exhibit solvent loss at elevated temperatures that is accompanied by a change in magnetic properties, associated with an irreversible valence tautomerism. Our results highlight the crucial role of the solvents for the isolation of cis/trans isomers in cobalt dioxolene chemistry, as well as the distinguishing effects of intermolecular forces and the solid-state packing on VT behavior.

  1. Dynamics of particles and defects on spherical crystals

    NASA Astrophysics Data System (ADS)

    Guerra, Rodrigo; Kelleher, Colm; Chaikin, Paul

    Repulsive particles confined to two dimensions can form nearly perfect crystals that melt via the well-know Kosterlitz-Thouless two-step process. By contrast, when identical particles are confined to the surface of a sphere, the curvature and topology of the surface distorts the crystal lattice and forces it to accommodate point-like disclinations and chains of dislocations. Extensive numerical and theoretical investigation has shown that these extended scars are intrinsic to the ground-state-energy configuration of these packings, as they relieve some of the stress induced by the curvature of the surface. Nevertheless, the effect of these defects on the kinetics and phase behavior of spherical crystals is not at all well understood. Here we present results of computer simulations and experiments that suggest that these scars facilitate the motion of particles close to them and fundamentally alter the nature of the mobility and liquid-to-solid transition of packings of particles confined to spherical surfaces.

  2. Structural, crystal structure, Hirshfeld surface analysis and physicochemical studies of a new chlorocadmate template by 1-(2-hydroxyethyl)piperazine

    NASA Astrophysics Data System (ADS)

    Soudani, S.; Jeanneau, E.; Jelsch, C.; Lefebvre, F.; Ben Nasr, C.

    2016-11-01

    The synthesis, crystal structure and spectroscopic characterization of a new chlorocadmate template by the 1-(2-hydroxyethyl)piperazine ligand are reported. In the atomic arrangement, the CdCl5O entities are deployed in corrugated rows along the a-axis at y = 1/4 and y = 3/4 to form layers parallel to the (a,b) plane. In these crystals, piperazinediium cations are in a chair conformation and are inserted between these layers through Nsbnd H⋯Cl, Csbnd H⋯Cl, Osbnd H⋯Cl and Nsbnd H⋯O hydrogen bonds to form infinite three-dimensional network. Investigation of intermolecular interactions and crystal packing via Hirshfeld surface analysis reveals that H⋯Cl and Csbnd H⋯Hsbnd C intermolecular interactions are the most abundant contacts of the organic cation in the crystal packing. The crystal contacts enrichments reveals that, the Cd++ … Cl- salt bridges, the Cd⋯O complexation and Osbnd H⋯Cl- and Nsbnd H⋯Cl-strong H-bonds are the driving forces in the packing formation. The presence of twelve independent chloride anions and four organic cation in the asymmetric unit allowed comparing their contact propensities. The 13C and 15N CP-MAS NMR spectra are in agreement with the X-ray structure. Additional characterization of this compound has also been performed by IR spectroscopy.

  3. Adhesive loose packings of small dry particles

    NASA Astrophysics Data System (ADS)

    Liu, Wenwei; Li, Shuiqing; Baule, Adrian; Makse, Hernán A.

    We explore adhesive loose packings of dry small spherical particles of micrometer size using 3D discrete-element simulations with adhesive contact mechanics. A dimensionless adhesion parameter ($Ad$) successfully combines the effects of particle velocities, sizes and the work of adhesion, identifying a universal regime of adhesive packings for $Ad>1$. The structural properties of the packings in this regime are well described by an ensemble approach based on a coarse-grained volume function that includes correlations between bulk and contact spheres. Our theoretical and numerical results predict: (i) An equation of state for adhesive loose packings that appears as a continuation from the frictionless random close packing (RCP) point in the jamming phase diagram; (ii) The existence of a maximal loose packing point at the coordination number $Z=2$ and packing fraction $\\phi=1/2^{3}$. Our results highlight that adhesion leads to a universal packing regime at packing fractions much smaller than the random loose packing, which can be described within a statistical mechanical framework. We present a general phase diagram of jammed matter comprising frictionless, frictional, adhesive as well as non-spherical particles, providing a classification of packings in terms of their continuation from the spherical frictionless RCP.

  4. Kinetics of pack aluminization of nickel

    NASA Technical Reports Server (NTRS)

    Seigle, L. L.; Gupta, B. K.; Shankar, R.; Sarkhel, A. K.

    1978-01-01

    The kinetics of pack aluminization of unalloyed nickel in packs of varying aluminum activity with various halide activators were studied. Surface compositions of the coatings as functions of time, temperature, and pack composition were obtained in order to establish the boundary conditions for diffusion in the system. The structure of the packs was also examined in order to clarify the mechanism of aluminum transport. The results indicate that the kinetics of pack aluminization are controlled jointly by gas diffusion in the pack and solid diffusion in the coating. Levine and Caves' model for gas diffusion was combined with calculations of rates of diffusion in the solid to formulate a more complete theory for the kinetics of pack aluminization.

  5. Hydrodynamics of Packed Bed Reactor in Low Gravity

    NASA Technical Reports Server (NTRS)

    Motil, Brian J.; Nahra, Henry K.; Balakotaiah, Vemuri

    2005-01-01

    Packed bed reactors are well known for their vast and diverse applications in the chemical industry; from gas absorption, to stripping, to catalytic conversion. Use of this type of reactor in terrestrial applications has been rather extensive because of its simplicity and relative ease of operation. Developing similar reactors for use in microgravity is critical to many space-based advanced life support systems. However, the hydrodynamics of two-phase flow packed bed reactors in this new environment and the effects of one physiochemical process on another has not been adequately assessed. Surface tension or capillary forces play a much greater role which results in a shifting in flow regime transitions and pressure drop. Results from low gravity experiments related to flow regimes and two-phase pressure drop models are presented in this paper along with a description of plans for a flight experiment on the International Space Station (ISS). Understanding the packed bed hydrodynamics and its effects on mass transfer processes in microgravity is crucial for the design of packed bed chemical or biological reactors to be used for water reclamation and other life support processes involving water purification.

  6. Heterogeneity in the Small-Scale Deformation Behavior of Disordered Nanoparticle Packings.

    PubMed

    Lefever, Joel A; Jacobs, Tevis D B; Tam, Qizhan; Hor, Jyo Lyn; Huang, Yun-Ru; Lee, Daeyeon; Carpick, Robert W

    2016-04-13

    Atomic force microscopy-based nanoindentation is used to image and probe the local mechanical properties of thin disordered nanoparticle packings. The probed region is limited to the size of a few particles, and an individual particle can be loaded and displaced to a fraction of a single particle radius. The results demonstrate heterogeneous mechanical response that is location-dependent. The weak locations may be analogous to the "soft spots" previously predicted in glasses and other disordered packings. PMID:26977533

  7. Apparatus for mounting crystal

    DOEpatents

    Longeway, Paul A.

    1985-01-01

    A thickness monitor useful in deposition or etching reactor systems comprising a crystal-controlled oscillator in which the crystal is deposited or etched to change the frequency of the oscillator. The crystal rests within a thermally conductive metallic housing and arranged to be temperature controlled. Electrode contacts are made to the surface primarily by gravity force such that the crystal is substantially free of stress otherwise induced by high temperature.

  8. The glue that holds crystals together: a review

    NASA Astrophysics Data System (ADS)

    Karle, J.; Huang, L.

    2003-02-01

    The answer to the question as to what are the origin and nature of the forces that hold crystals together starts with the determination of the origin and nature of the forces that hold two molecules together. Attempts to answer this question began early in the last century before modern quantum mechanics was established. Soon after it was established, however, it played an important role in facilitating an understanding of the attraction of molecules for one another. It is still a problem to express this understanding in terms of accurate calculations of complex systems such as crystals, which has led to very clever empirical techniques. Both the status of some empirical methods and rigorous theoretical calculations will be discussed. The main topics to be described in some detail are the first attempts to account for the attraction between molecules, developments that have permitted the determination of packing energies for large numbers of organic molecules, the empirical investigation of the lattice energies associated with ionic crystals, and a discussion of an accurate quantum mechanical method for computing the interaction energy between two molecules and the possibility of this method having application to crystals in the future.

  9. Crystal structure analysis in solution-processed uniaxially oriented polycrystalline thin film of non-peripheral octahexyl phthalocyanine by grazing incidence wide-angle x-ray scattering techniques

    NASA Astrophysics Data System (ADS)

    Ohmori, Masashi; Uno, Takashi; Nakatani, Mitsuhiro; Nakano, Chika; Fujii, Akihiko; Ozaki, Masanori

    2016-10-01

    Uniaxially oriented thin films of metal-free non-peripherally octahexyl-substituted phthalocyanine (C6PcH2), which exhibits high carrier mobility, have been fabricated by the bar-coating technique, which is a simple solution process. The molecular orientation and molecular steps in the thin film were observed by the polarized spectroscopy and the atomic force microscopy, respectively. The three-dimensional molecular packing structure in the thin film was investigated by the grazing incidence wide-angle X-ray scattering technique with an in-plane sample rotation. The crystal orientation was clarified, and the three-dimensional molecular packing structure of the thin film was found to match the single crystal structure. Moreover, the X-ray diffraction patterns of the oriented thin films were simulated by using the lattice parameters of C6PcH2 single crystal to reproduce the observed X-ray diffraction patterns.

  10. Capillary and van der Waals interactions on CaF2 crystals from amplitude modulation AFM force reconstruction profiles under ambient conditions.

    PubMed

    Calò, Annalisa; Robles, Oriol Vidal; Santos, Sergio; Verdaguer, Albert

    2015-01-01

    There has been much interest in the past two decades to produce experimental force profiles characteristic of the interaction between nanoscale objects or a nanoscale object and a plane. Arguably, the advent of the atomic force microscope AFM was instrumental in driving such efforts because, in principle, force profiles could be recovered directly. Nevertheless, it has taken years before techniques have developed enough as to recover the attractive part of the force with relatively low noise and without missing information on critical ranges, particularly under ambient conditions where capillary interactions are believed to dominate. Thus a systematic study of the different profiles that may arise in such situations is still lacking. Here we employ the surfaces of CaF2, on which nanoscale water films form, to report on the range and force profiles that might originate by dynamic capillary interactions occurring between an AFM tip and nanoscale water patches. Three types of force profiles were observed under ambient conditions. One in which the force decay resembles the well-known inverse-square law typical of van der Waals interactions during the first 0.5-1 nm of decay, a second one in which the force decays almost linearly, in relatively good agreement with capillary force predicted by the constant chemical potential approximation, and a third one in which the attractive force is almost constant, i.e., forms a plateau, up to 3-4 nm above the surface when the formation of a capillary neck dominates the tip-sample interaction.

  11. USDC-based rapid penetrator of packed soil

    NASA Astrophysics Data System (ADS)

    Bao, X.; Bar-Cohen, Y.; Chang, Z.; Sherrit, S.; Badescu, M.; Du, S.; Song, T.; Peterson, T.

    2006-03-01

    Environment protection requires more testing and analysis tools. To detect buried chemical containers or other objects embedded in soil and avoid possible damage to them, a penetrator was developed for packed soil that requires low penetration force (the force needed to push rod probe into the soil). The design was based on the novel mechanism used by the ultrasonic/sonic driller/corer (USDC) that was developed jointly by scientists at the NDEAA lab at JPL and engineers at Cybersonics, Inc. [Bar-Cohen et al 2001, Bao et al 2003]. In the penetrator, a small free-flying mass is energized by a piezoelectric transducer and impacts a rod probe on its shoulder at frequencies of several hundred Hetz. The impacts help the probe to penetrate the packed soil with low pushing force. A large reduction of the penetration force was achieved. Preliminary tests show that the effects of the penetrator on plastic containers and other objectors are minimal. The details of the design of the prototype penetrator and the results of performance tests are presented.

  12. Diffusion in jammed particle packs

    NASA Astrophysics Data System (ADS)

    Bolintineanu, Dan S.; Silbert, Leonardo E.; Grest, Gary S.; Lechman, Jeremy B.

    2015-03-01

    Diffusive transport in jammed particle packs is of interest for a number of applications, as well as being a potential indicator of structural properties near the jamming point. To this end, we report stochastic simulations of equilibrium diffusion through monodisperse sphere packs near the jamming point in the limit of a perfectly insulating surrounding medium. The time dependence of various diffusion properties is resolved over several orders of magnitude. Two time regimes of expected Fickian diffusion are observed, separated by an intermediate regime of anomalous diffusion. This intermediate regime grows as the particle volume fraction approaches the critical jamming transition. The diffusion behavior is fully controlled by the extent of the contacts between neighboring particles, which in turn depend on proximity to the jamming point. In particular, the mean first passage time associated with the escape of random walkers between neighboring particles is shown to control both the time to recover Fickian diffusion and the long time diffusivity. Scaling laws are established that relate these quantities to the difference between the actual and critical jamming volume fractions. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under Contract DE- AC04-94AL85000.

  13. Protein crystal growth

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Atomic force microscopy uses laser technology to reveal a defect, a double-screw dislocation, on the surface of this crystal of canavalin, a major source of dietary protein for humans and domestic animals. When a crystal grows, attachment kinetics and transport kinetics are competing for control of the molecules. As a molecule gets close to the crystal surface, it has to attach properly for the crystal to be usable. NASA has funded investigators to look at those attachment kinetics from a theoretical standpoint and an experimental standpoint. Dr. Alex McPherson of the University of California, Irvine, is one of those investigators. He uses X-ray diffraction and atomic force microscopy in his laboratory to answer some of the many questions about how protein crystals grow. Atomic force microscopy provides a means of looking at how individual molecules are added to the surface of growing protein crystals. This helps McPherson understand the kinetics of protein crystal growth. McPherson asks, How fast do crystals grow? What are the forces involved? Investigators funded by NASA have clearly shown that such factors as the level of supersaturation and the rate of growth all affect the habit [characteristic arrangement of facets] of the crystal and the defects that occur in the crystal.

  14. Operation of Packed-Bed Reactors Studied in Microgravity

    NASA Technical Reports Server (NTRS)

    Motil, Brian J.; Balakotaiah, Vemuri

    2004-01-01

    The operation of a packed bed reactor (PBR) involves gas and liquid flowing simultaneously through a fixed-bed of solid particles. Depending on the application, the particles can be various shapes and sizes but are generally designed to force the two fluid phases through a tortuous route of narrow channels connecting the interstitial space. The PBR is the most common type of reactor in industry because it provides for intimate contact and high rates of transport between the phases needed to sustain chemical or biological reactions. The packing may also serve as either a catalyst or as a support for growing biological material. Furthermore, this type of reactor is relatively compact and requires minimal power to operate. This makes it an excellent candidate for unit operations in support of long-duration human space activities.

  15. Breather mechanism of the void ordering in crystals under irradiation

    NASA Astrophysics Data System (ADS)

    Dubinko, Vladimir

    2009-09-01

    The void ordering has been observed in very different radiation environments ranging from metals to ionic crystals. In the present paper the ordering phenomenon is considered as a consequence of the energy transfer along the close packed directions provided by self-focusing discrete breathers. The self-focusing breathers are energetic, mobile and highly localized lattice excitations that propagate great distances in atomic-chain directions in crystals. This points to the possibility of atoms being ejected from the void surface by the breather-induced mechanism, which is similar to the focuson-induced mechanism of vacancy emission from voids proposed in our previous paper. The main difference between focusons and breathers is that the latter are stable against thermal motion. There is evidence that breathers can occur in various crystals, with path lengths ranging from 104 to 107 unit cells. Since the breather propagating range can be larger than the void spacing, the voids can shield each other from breather fluxes along the close packed directions, which provides a driving force for the void ordering. Namely, the vacancy emission rate for "locally ordered" voids (which have more immediate neighbors along the close packed directions) is smaller than that for the "interstitial" ones, and so they have some advantage in growth. If the void number density is sufficiently high, the competition between them makes the "interstitial" voids shrink away resulting in the void lattice formation. The void ordering is intrinsically connected with a saturation of the void swelling, which is shown to be another important consequence of the breather-induced vacancy emission from voids.

  16. Second sphere coordination in anion binding: Synthesis and spectroscopic characterisation of [ trans-Co(en) 2Cl 2]X (X=SCN or N 3). Single crystal X-ray structure determination and packing of [ trans-Co(en) 2Cl 2]N 3

    NASA Astrophysics Data System (ADS)

    Sharma, Raj Pal; Sharma, Rajni; Bala, Ritu; Venugopalan, Paloth

    2006-04-01

    In an effort to explore [ trans-Co(en) 2Cl 2] + as anion receptor for linear thiocyanate and azide ions, green coloured microcrystalline [ trans-Co(en) 2Cl 2]SCN I and single crystals of [ trans-Co(en) 2Cl 2]N 3II have been obtained by slowly mixing the separately dissolved trans-dichlorobis(ethylenediamine)cobalt(III) chloride with ammonium thiocyanate and sodium azide respectively in aqueous medium in 1:1 molar ratio. The newly synthesised complex salts were characterised on the basis of elemental analysis and spectroscopic techniques (IR, UV/vis, 1H and 13C NMR). Single crystal X-ray structure determination of II revealed that it crystallizes in the triclinic space group P 1 with a=6.293(1) Å, b=6.696(1) Å, c=7.116(1) Å, α=94.02(1)°, β=111.42(1)°, γ=99.86(1)°, V=272.13(7) Å 3, Z=1, R=0.0183. Supramolecular hydrogen bonding networks between ionic groups: nitrogen atoms of azide group and NH groups of coordinated ethylenediamine molecules, i.e. N-H⋯N - interactions by second sphere coordination besides electrostatic forces of attraction have been observed which probably exist in case of thiocyanate also. This suggests that [ trans-Co(en) 2Cl 2] + is a promising anion receptor for the linear ions SCN - and N 3-. The solubility product measurements indicate that the affinity of cationic cobaltammine [ trans-Co(en) 2Cl 2] + is greater for azide ion than thiocyanate ion.

  17. The Packing of Granular Polymer Chains

    SciTech Connect

    Zou, Ling-Nan; Cheng, Xiang; Rivers, Mark L.; Jaeger, Heinrich M.; Nagel, Sidney R.; UC

    2009-12-01

    Rigid particles pack into structures, such as sand dunes on the beach, whose overall stability is determined by the average number of contacts between particles. However, when packing spatially extended objects with flexible shapes, additional concepts must be invoked to understand the stability of the resulting structure. Here, we examine the disordered packing of chains constructed out of flexibly connected hard spheres. Using x-ray tomography, we find that long chains pack into a low-density structure whose mechanical rigidity is mainly provided by the backbone. On compaction, randomly oriented, semi-rigid loops form along the chain, and the packing of chains can be understood as the jamming of these elements. Finally, we uncover close similarities between the packing of chains and the glass transition in polymers.

  18. Size-Topology Correlations and Crystallization in Tilings and Packings

    NASA Astrophysics Data System (ADS)

    Hilgenfeldt, Sascha

    2014-03-01

    Ever since its empirical formulation in 1928, Lewis`s law has intrigued scientists, postulating a linear correlation between the average in-plane area and the number of neighbors in a two-dimensional tiling. Many supporting and dissenting results have been reported in systems as diverse as foams, Voronoi tilings in glass models, and nanocrystals. A strong size-topology correlation is consistently observed, but it is often pronouncedly nonlinear. Recently, a variant of the granocentric model explained numerous cases of nonlinear correlations, but cannot account for the linear version of the law. We revisit Lewis's original work by conducting more extensive experiments on cucumber epidermis tissue. The data confirms the linear law, but also shows that the individual cells have a pronounced anisotropy, not present in systems with nonlinear correlation laws. We demonstrate how the granocentric model can be modified taking into account the cell anisotropy, and how this feature is capable of reproducing the linear Lewis law, as well as other characteristic differences in size-topology statistical quantities. The model should be generally applicable to jammed, plane-filling systems and identifies domain anisotropy as an important ingredient in their statistical description.

  19. Synthesis, electrochemical properties, and crystal packing of perfluororubrene.

    PubMed

    Zhang, Zhuoran; Ogden, William A; Young, Victor G; Douglas, Christopher J

    2016-06-21

    A synthesis of perfluorinated rubrene is reported. Electrochemical analysis revealed the significantly increased electron affinity of perfluororubrene compared with non-modified rubrene. Crystallographic investigation revealed two polymorphs and a solvate, each displaying twisted backbone conformations of perfluororubrene. Taken together, these results suggest perfluororubrene will find applications as a new n-type semiconductor.

  20. Synthesis, electrochemical properties, and crystal packing of perfluororubrene.

    PubMed

    Zhang, Zhuoran; Ogden, William A; Young, Victor G; Douglas, Christopher J

    2016-06-21

    A synthesis of perfluorinated rubrene is reported. Electrochemical analysis revealed the significantly increased electron affinity of perfluororubrene compared with non-modified rubrene. Crystallographic investigation revealed two polymorphs and a solvate, each displaying twisted backbone conformations of perfluororubrene. Taken together, these results suggest perfluororubrene will find applications as a new n-type semiconductor. PMID:27271849

  1. Capillary and van der Waals interactions on CaF2 crystals from amplitude modulation AFM force reconstruction profiles under ambient conditions

    PubMed Central

    Calò, Annalisa; Robles, Oriol Vidal; Santos, Sergio

    2015-01-01

    Summary There has been much interest in the past two decades to produce experimental force profiles characteristic of the interaction between nanoscale objects or a nanoscale object and a plane. Arguably, the advent of the atomic force microscope AFM was instrumental in driving such efforts because, in principle, force profiles could be recovered directly. Nevertheless, it has taken years before techniques have developed enough as to recover the attractive part of the force with relatively low noise and without missing information on critical ranges, particularly under ambient conditions where capillary interactions are believed to dominate. Thus a systematic study of the different profiles that may arise in such situations is still lacking. Here we employ the surfaces of CaF2, on which nanoscale water films form, to report on the range and force profiles that might originate by dynamic capillary interactions occurring between an AFM tip and nanoscale water patches. Three types of force profiles were observed under ambient conditions. One in which the force decay resembles the well-known inverse-square law typical of van der Waals interactions during the first 0.5–1 nm of decay, a second one in which the force decays almost linearly, in relatively good agreement with capillary force predicted by the constant chemical potential approximation, and a third one in which the attractive force is almost constant, i.e., forms a plateau, up to 3–4 nm above the surface when the formation of a capillary neck dominates the tip–sample interaction. PMID:25977852

  2. 7 CFR 982.11 - Pack.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON... according to size, internal quality, and external appearance and condition of hazelnuts packed in...

  3. 7 CFR 982.11 - Pack.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON... according to size, internal quality, and external appearance and condition of hazelnuts packed in...

  4. 7 CFR 982.11 - Pack.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON... according to size, internal quality, and external appearance and condition of hazelnuts packed in...

  5. 7 CFR 982.11 - Pack.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON... according to size, internal quality, and external appearance and condition of hazelnuts packed in...

  6. Random packing of spheres in Menger sponge.

    PubMed

    Cieśla, Michał; Barbasz, Jakub

    2013-06-01

    Random packing of spheres inside fractal collectors of dimension 2 < d < 3 is studied numerically using Random Sequential Adsorption (RSA) algorithm. The paper focuses mainly on the measurement of random packing saturation limit. Additionally, scaling properties of density autocorrelations in the obtained packing are analyzed. The RSA kinetics coefficients are also measured. Obtained results allow to test phenomenological relation between random packing saturation density and collector dimension. Additionally, performed simulations together with previously obtained results confirm that, in general, the known dimensional relations are obeyed by systems having non-integer dimension, at least for d < 3.

  7. A Constant-Force Resistive Exercise Unit

    NASA Technical Reports Server (NTRS)

    Colosky, Paul; Ruttley, Tara

    2010-01-01

    A constant-force resistive exercise unit (CFREU) has been invented for use in both normal gravitational and microgravitational environments. In comparison with a typical conventional exercise machine, this CFREU weighs less and is less bulky: Whereas weight plates and associated bulky supporting structures are used to generate resistive forces in typical conventional exercise machines, they are not used in this CFREU. Instead, resistive forces are generated in this CFREU by relatively compact, lightweight mechanisms based on constant-torque springs wound on drums. Each such mechanism is contained in a module, denoted a resistive pack, that includes a shaft for making a torque connection to a cable drum. During a stroke of resistive exercise, the cable is withdrawn from the cable drum against the torque exerted by the resistance pack. The CFREU includes a housing, within which can be mounted one or more resistive pack(s). The CFREU also includes mechanisms for engaging any combination of (1) one or more resistive pack(s) and (2) one or more spring(s) within each resistive pack to obtain a desired level of resistance.

  8. Inulin crystal initiation via a glucose-fructose cross-link of adjacent polymer chains: atomic force microscopy and static molecular modelling.

    PubMed

    Cooper, Peter D; Rajapaksha, K Harinda; Barclay, Thomas G; Ginic-Markovic, Milena; Gerson, Andrea R; Petrovsky, Nikolai

    2015-03-01

    Semi-crystalline microparticles of inulin (MPI) have clinical utility as potent human vaccine adjuvants but their relevant surface structure and crystal assembly remain undefined. We show inulin crystal surfaces to resemble multi-layered, discoid radial spherulites resulting from very rapid formation of complex tertiary structures, implying directed crystal initiation. Physical and in silico molecular modelling of unit cells confirm steric feasibility of initiation by hydrogen-bonded cross-linking of terminal glucose to a fructose of another chain, mimicking bonding in sucrose crystals. A strong, chelate-like dual H-bond is proposed to compel the known antiparallel alignment of inulin chains. Such cross-linking would require one extra fructose per chain in the native inulin crystal, as observed. Completion of five H-bonded internal ring-domains would 'lock in' each new 6-fructose structural unit of each antiparallel helix pair to create a new isoform. All known properties of inulin isoforms follow readily from these concepts.

  9. Inulin crystal initiation via a glucose-fructose cross-link of adjacent polymer chains: atomic force microscopy and static molecular modelling

    PubMed Central

    Cooper, Peter D.; Rajapaksha, K. Harinda; Barclay, Thomas G.; Ginic-Markovic, Milena; Gerson, Andrea R.; Petrovsky, Nikolai

    2014-01-01

    Semi-crystalline microparticles of inulin (MPI) have clinical utility as potent human vaccine adjuvants but their relevant surface structure and crystal assembly remain undefined. We show inulin crystal surfaces to resemble multi-layered, discoid radial spherulites resulting from very rapid formation of complex tertiary structures, implying directed crystal initiation. Physical and in silico molecular modelling of unit cells confirm steric feasibility of initiation by hydrogen-bonded cross-linking of terminal glucose to a fructose of another chain, mimicking bonding in sucrose crystals. A strong, chelate-like dual H-bond is proposed to compel the known antiparallel alignment of inulin chains. Such cross-linking would require one extra fructose per chain in the native inulin crystal, as observed. Completion of five H-bonded internal ring-domains would ‘lock in’ each new 6-fructose structural unit of each antiparallel helix pair to create a new isoform. All known properties of inulin isoforms follow readily from these concepts. PMID:25498723

  10. Inulin crystal initiation via a glucose-fructose cross-link of adjacent polymer chains: atomic force microscopy and static molecular modelling.

    PubMed

    Cooper, Peter D; Rajapaksha, K Harinda; Barclay, Thomas G; Ginic-Markovic, Milena; Gerson, Andrea R; Petrovsky, Nikolai

    2015-03-01

    Semi-crystalline microparticles of inulin (MPI) have clinical utility as potent human vaccine adjuvants but their relevant surface structure and crystal assembly remain undefined. We show inulin crystal surfaces to resemble multi-layered, discoid radial spherulites resulting from very rapid formation of complex tertiary structures, implying directed crystal initiation. Physical and in silico molecular modelling of unit cells confirm steric feasibility of initiation by hydrogen-bonded cross-linking of terminal glucose to a fructose of another chain, mimicking bonding in sucrose crystals. A strong, chelate-like dual H-bond is proposed to compel the known antiparallel alignment of inulin chains. Such cross-linking would require one extra fructose per chain in the native inulin crystal, as observed. Completion of five H-bonded internal ring-domains would 'lock in' each new 6-fructose structural unit of each antiparallel helix pair to create a new isoform. All known properties of inulin isoforms follow readily from these concepts. PMID:25498723

  11. Minimally packed phases in holography

    NASA Astrophysics Data System (ADS)

    Donos, Aristomenis; Gauntlett, Jerome P.

    2016-03-01

    We numerically construct asymptotically AdS black brane solutions of D = 4 Einstein-Maxwell theory coupled to a pseudoscalar. The solutions are holographically dual to d = 3 CFTs at finite chemical potential and in a constant magnetic field, which spontaneously break translation invariance leading to the spontaneous formation of abelian and momentum magnetisation currents flowing around the plaquettes of a periodic Bravais lattice. We analyse the three-dimensional moduli space of lattice solutions, which are generically oblique, and show, for a specific value of the magnetic field, that the free energy is minimised by the triangular lattice, associated with minimal packing of circles in the plane. We show that the average stress tensor for the thermodynamically preferred phase is that of a perfect fluid and that this result applies more generally to spontaneously generated periodic phases. The triangular structure persists at low temperatures indicating the existence of novel crystalline ground states.

  12. Chain packing in polycarbonate glasses

    NASA Astrophysics Data System (ADS)

    Stueber, Dirk; Yu, Tsyr-Yan; Hess, Berk; Kremer, Kurt; O'Connor, Robert D.; Schaefer, Jacob

    2010-03-01

    Chain packing in homogeneous blends of carbonate C13-labeled bisphenol A polycarbonate with either (i) CF3-labeled bisphenol A polycarbonate or (ii) ring-F-labeled bisphenol A polycarbonate has been characterized using C13{F19} rotational-echo double-resonance (REDOR) nuclear magnetic resonance. In both blends, the C13 observed spin was at high concentration, and the F19 dephasing or probe spin was at low concentration. In this situation, an analysis in terms of a distribution of isolated heteronuclear pairs of spins is valid. Nearest-neighbor separation of C13 and F19 labels was determined by accurately mapping the initial dipolar evolution using a shifted-pulse version of REDOR. Based on the results of this experiment, the average distance from a ring-fluorine to the nearest C13O is more than 1.2 Å greater than the corresponding CF3C13O distance. Next-nearest and more-distant-neighbor separations of labels were measured in a 416-rotor-cycle constant-time version of REDOR for both blends. Statistically significant local order was established for the nearest-neighbor labels in the methyl-labeled blend. These interchain packing results are in qualitative agreement with predictions based on coarse-grained simulations of a specially adapted model for bisphenol A polycarbonate. The model itself has been previously used to determine static and dynamic properties of polycarbonate with results in good agreement with those from rheological and neutron scattering experiments.

  13. Confined disordered strictly jammed binary sphere packings

    NASA Astrophysics Data System (ADS)

    Chen, D.; Torquato, S.

    2015-12-01

    Disordered jammed packings under confinement have received considerably less attention than their bulk counterparts and yet arise in a variety of practical situations. In this work, we study binary sphere packings that are confined between two parallel hard planes and generalize the Torquato-Jiao (TJ) sequential linear programming algorithm [Phys. Rev. E 82, 061302 (2010), 10.1103/PhysRevE.82.061302] to obtain putative maximally random jammed (MRJ) packings that are exactly isostatic with high fidelity over a large range of plane separation distances H , small to large sphere radius ratio α , and small sphere relative concentration x . We find that packing characteristics can be substantially different from their bulk analogs, which is due to what we term "confinement frustration." Rattlers in confined packings are generally more prevalent than those in their bulk counterparts. We observe that packing fraction, rattler fraction, and degree of disorder of MRJ packings generally increase with H , though exceptions exist. Discontinuities in the packing characteristics as H varies in the vicinity of certain values of H are due to associated discontinuous transitions between different jammed states. When the plane separation distance is on the order of two large-sphere diameters or less, the packings exhibit salient two-dimensional features; when the plane separation distance exceeds about 30 large-sphere diameters, the packings approach three-dimensional bulk packings. As the size contrast increases (as α decreases), the rattler fraction dramatically increases due to what we call "size-disparity" frustration. We find that at intermediate α and when x is about 0.5 (50-50 mixture), the disorder of packings is maximized, as measured by an order metric ψ that is based on the number density fluctuations in the direction perpendicular to the hard walls. We also apply the local volume-fraction variance στ2(R ) to characterize confined packings and find that these

  14. Nanoscale domains and preferred cracking planes in Pb(Zn1/3Nb2/3)O3-(6-7)% PbTiO3 single crystals studied by piezoresponse force microscopy and fractography

    NASA Astrophysics Data System (ADS)

    Wong, Meng Fei; Zeng, Kaiyang

    2010-06-01

    This paper presents recent studies on surface and cross-sectional domain structures of Pb(Zn1/3Nb2/3)O3-(6-7)%PbTiO3 (PZN-PT) single crystals using piezoresponse force microscopy and three-point bending technique. The surface domain structures for the rhombohedral-based single crystals in (001) orientation are found to be influenced by polishing process, whereas the surface domains on the (011)-oriented single crystals are aligned along [011¯] direction, unaffected by the polishing process. On the other hand, the domain structures on the cross-sectional fracture surface show preferential alignment which agrees reasonably with the rhombohedral dipoles on the {100} and {110} planes. The differences between the surface and cross-sectional domain structures could be attributed to stress compensation between the surface strain effect and the minimization of elastic energy. In addition, both surface and cross-sectional surface demonstrate nanoscale domains, about 100-200 nm in size. Further fractography observation suggests that the preferred cracking planes for the PZN-PT single crystals are {110} and {100} planes. The {110} planes may be the slip planes along which material pile up is observed upon indentation loading. The pile up results in tensile hoop stress, producing radial cracks along the {100} cleavage planes. To accommodate the localized stress change, new ferroelastic domains by mechanical stress are then formed without interrupting the out-of-plane piezoelectric response. Since the material pile up is thought to cause enhanced toughness along {110} planes, the PZN-PT single crystal in [011]-poled orientation exhibits more superior piezoelectric properties compared to that of the [001]-poled counterpart.

  15. Modular Approach for Continuous Cell-Level Balancing to Improve Performance of Large Battery Packs: Preprint

    SciTech Connect

    Muneed ur Rehman, M.; Evzelman, M.; Hathaway, K.; Zane, R.; Plett, G. L.; Smith, K.; Wood, E.; Maksimovic, D.

    2014-10-01

    Energy storage systems require battery cell balancing circuits to avoid divergence of cell state of charge (SOC). A modular approach based on distributed continuous cell-level control is presented that extends the balancing function to higher level pack performance objectives such as improving power capability and increasing pack lifetime. This is achieved by adding DC-DC converters in parallel with cells and using state estimation and control to autonomously bias individual cell SOC and SOC range, forcing healthier cells to be cycled deeper than weaker cells. The result is a pack with improved degradation characteristics and extended lifetime. The modular architecture and control concepts are developed and hardware results are demonstrated for a 91.2-Wh battery pack consisting of four series Li-ion battery cells and four dual active bridge (DAB) bypass DC-DC converters.

  16. Fluid-dynamic and mass-transfer behavior of static mixers and regular packings

    SciTech Connect

    Cavatorta, O.N.; Boehm, U.; Chiappori de del Giorgio, A.M.

    1999-05-01

    The fluid dynamics and liquid-to-wall mass transfer for spaced and stacked regular packings were studied for forced convection and fluidized beds. The behavior of these configurations in bubble columns and under natural convection conditions is also presented. Flow parameters characterizing structured packings, presented in the literature, were used in the evaluation of results. General equations to predict pressure drop and mass transfer are discussed, as well as the relationship between energy dissipation and mass transfer. In the presence of fluidized particles, single-phase flow or natural convection conditions, the mass-transfer behavior of a packing element stacked between other packs or separated from the neighboring elements by liquid layers is almost the same, but differs in bubble columns.

  17. Probe with integrated heater and thermocouple pack

    SciTech Connect

    McCulloch, R.W.; Dial, R.E.; Finnell, W.F.R.

    1988-02-16

    This patent describes a gamma thermometer probe for detecting heat produced within the thermometer probe. It comprises: an outer elongate thermometer sheath; an elongate rod; annular recesses; a longitudinal bore; and an integrated thermocouple pack. The thermocouple pack comprises: a first type wire, and second type wires. The second type wires comprises: an outer section; and an inner segment.

  18. Pack Density Limitations of Hybrid Parachutes

    NASA Technical Reports Server (NTRS)

    Zwicker, Matthew L.; Sinclair, Robert J.

    2013-01-01

    The development and testing of the Orion crew capsule parachute system has provided a unique opportunity to study dense parachute packing techniques and limits, in order to establish a new baseline for future programs. The density of parachute packs has a significant influence on vibration loads, retention system stresses, and parachute mortar performance. Material compositions and pack densities of existing designs for space capsule recovery were compared, using the pack density of the Apollo main parachutes as the current baseline. The composition of parachutes has changed since Apollo, incorporating new materials such as Kevlar , Vectran , Teflon and Spectra . These materials have different specific densities than Nylon, so the densities of hybrid parachute packs cannot be directly compared to Nylon parachutes for determination of feasibility or volume allocation. Six parachute packs were evaluated in terms of weighted average solid density in order to achieve a non-dimensional comparison of packing density. Means of mitigating damage due to packing pressure and mortar firing were examined in light of the Capsule Parachute Assembly System (CPAS) and Apollo experience. Parachute design improvements including incorporation of modern materials and manufacturing processes serves to make CPAS the new knowledge base on which future spacecraft parachute systems will be built.

  19. Kid's PACK: Population Awareness Campaign Kit.

    ERIC Educational Resources Information Center

    Zero Population Growth, Inc., Washington, DC.

    This fun and educational kit is designed specifically for elementary students. The "Kid's PACK" (Population Awareness Campaign Kit) entertains and informs children on the environment and human population growth through stories, games, and concrete ideas for making a difference. In three booklets, the "Kid's PACK" offers elementary students…

  20. Cluster and constraint analysis in tetrahedron packings.

    PubMed

    Jin, Weiwei; Lu, Peng; Liu, Lufeng; Li, Shuixiang

    2015-04-01

    The disordered packings of tetrahedra often show no obvious macroscopic orientational or positional order for a wide range of packing densities, and it has been found that the local order in particle clusters is the main order form of tetrahedron packings. Therefore, a cluster analysis is carried out to investigate the local structures and properties of tetrahedron packings in this work. We obtain a cluster distribution of differently sized clusters, and peaks are observed at two special clusters, i.e., dimer and wagon wheel. We then calculate the amounts of dimers and wagon wheels, which are observed to have linear or approximate linear correlations with packing density. Following our previous work, the amount of particles participating in dimers is used as an order metric to evaluate the order degree of the hierarchical packing structure of tetrahedra, and an order map is consequently depicted. Furthermore, a constraint analysis is performed to determine the isostatic or hyperstatic region in the order map. We employ a Monte Carlo algorithm to test jamming and then suggest a new maximally random jammed packing of hard tetrahedra from the order map with a packing density of 0.6337.

  1. Pack rats (Neotoma spp.): Keystone ecological engineers?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The potential role of two species of pack rats (Neotoma albigula and Neotoma micropus) as keystone ecological engineers was examined by estimating the species diversity of invertebrates living in the nest middens, and nitrogen mineralization rates in soils associated with the middens. Although pack-...

  2. 7 CFR 51.2338 - Standard pack.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... packed in containers with cell compartments, cardboard fillers or molded trays shall be of proper size for the cells, fillers, or molds in which they are packed, and conform to the marked count. (2) In... angles to a line from stem to blossom end. (f) In order to allow for variations incident to proper...

  3. 7 CFR 51.2338 - Standard pack.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... packed in containers with cell compartments, cardboard fillers or molded trays shall be of proper size for the cells, fillers, or molds in which they are packed, and conform to the marked count. (2) In... angles to a line from stem to blossom end. (f) In order to allow for variations incident to proper...

  4. 7 CFR 51.2338 - Standard pack.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    .... (c) Boxes, flats, lugs, or cartons: (1) Fruit packed in containers with cell compartments, cardboard fillers or molded trays shall be of proper size for the cells, fillers, or molds in which they are packed...” means the greatest dimension measured at right angles to a line from stem to blossom end. (f) In...

  5. 7 CFR 51.3152 - Standard pack.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...) Nectarines packed in containers equipped with cell compartments, cardboard fillers or molded trays shall be of the proper size for the cells, fillers, or molds in which they are packed, and the number of... angles to a line from stem to blossom end of the fruit. (h) Tolerances. In order to allow for...

  6. 7 CFR 51.2338 - Standard pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... packed in containers with cell compartments, cardboard fillers or molded trays shall be of proper size for the cells, fillers, or molds in which they are packed, and conform to the marked count. (2) In... angles to a line from stem to blossom end. (f) In order to allow for variations incident to proper...

  7. 7 CFR 51.3152 - Standard pack.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...) Nectarines packed in containers equipped with cell compartments, cardboard fillers or molded trays shall be of the proper size for the cells, fillers, or molds in which they are packed, and the number of... angles to a line from stem to blossom end of the fruit. (h) Tolerances. In order to allow for...

  8. 7 CFR 51.2338 - Standard pack.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    .... (c) Boxes, flats, lugs, or cartons: (1) Fruit packed in containers with cell compartments, cardboard fillers or molded trays shall be of proper size for the cells, fillers, or molds in which they are packed...” means the greatest dimension measured at right angles to a line from stem to blossom end. (f) In...

  9. Slimhole frac pack tools overcome erosion problems

    SciTech Connect

    Stout, G.; Matte, T.; Rogers, B.

    1997-04-01

    The application of frac pack technology for stimulation and sand control in the Gulf of Mexico`s unconsolidated formations has steadily increased during the past several years. In addition, re-entry drilling has been one of the fastest growing development techniques used by operators for optimizing reservoir productivity. As such, smaller casing sizes are becoming more common in oil and gas producing wells. Gravel pack tools were being used for frac packing in 7-in. casing sizes and larger, but no tools were available to frac pack in the smaller 5-in. and 5{1/2}-in. casing. The erosion problems operators were experiencing in 7-in. gravel pack tools heightened concerns about fracturing through 5-in. tools with even smaller flow areas. Flow cutting in the 7-in. tools was so severe that it caused fluid communication between the gravel pack ports and the return flow holes in the crossover tool. This allowed fluid and proppant to return to the annulus above the packer, which could cause possible early screen-out and sticking of the crossover tool. The flow cutting could also reduce the tool`s pressure and tensile ratings. Any one of these problems could jeopardize the success of the frac pack operation. Therefore, an erosion resistant crossover tool for slimhole casing was developed to address these problems and optimize frac pack success.

  10. 7 CFR 906.10 - Pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and... GRANDE VALLEY IN TEXAS Order Regulating Handling Definitions § 906.10 Pack. Pack means the specific grade, quality, size, or arrangement of fruit in a particular container or containers....

  11. Record high Wolf, Canis lupus, pack density

    USGS Publications Warehouse

    Mech, L.D.; Tracy, S.

    2004-01-01

    This report documents a year-around Wolf (Canis lupus) density of 18.2/100 km2 and a summer density of 30.8/100 km2, in a northeastern Minnesota Wolf pack. The previous record was a summer density of 14.1/100 km2, for a Wolf pack on Vancouver Island, British Columbia, Canada.

  12. Record high wolf, Canis lupus, pack density

    USGS Publications Warehouse

    Mech, L.D.; Tracy, S.

    2004-01-01

    This report documents a year-around wolf (Canis lupus) density of 18.2/100 m2 and summer density of 30.8/100 km2, in a northeastern Minnesota wolf pack. The previous record was a summer density of 14.1/100 km2, for a wolf pack on Vancouver Island, BC, Canada.

  13. Method of gravel packing a well

    SciTech Connect

    Almond, S. W.; Himes, R. E.

    1985-11-12

    The present invention relates to a thermally stable crosslinked gel gravel packing fluid for use in the treatment of highly deviated well bores penetrating a subterranean formation. The gravel packing fluid comprises an aqueous liquid, a gelling agent comprising a selected modified cellulose ether, a crosslinking agent, a breaker, a particulate agent and any additional additives that may be present.

  14. Does post septoplasty nasal packing reduce complications?

    PubMed

    Naghibzadeh, Bijan; Peyvandi, Ali Asghar; Naghibzadeh, Ghazal

    2011-01-01

    The main issues in nasal surgery are to stabilize the nose in the good position after surgery and preserve the cartilages and bones in the favorable situation and reduce the risk of deviation recurrence. Also it is necessary to avoid the synechia formation, nasal valve narrowing, hematoma and bleeding. Due to the above mentioned problems and in order to solve and minimize them nasal packing, nasal splint and nasal mold have been advised. Patients for whom the nasal packing used may faced to some problems like naso-pulmonary reflex, intractable pain, sleep disorder, post operation infection and very dangerous complication like toxic shock syndrome. We have two groups of patients and three surgeons (one of the surgeons used post operative nasal packing in his patients and the two others surgeons did not).Complications and morbidities were compared in these two groups. Comparing the two groups showed that the rate of complication and morbidities between these two groups were same and the differences were not valuable, except the pain and discomfort post operatively and at the time of its removal. Nasal packing has several risks for the patients while its effects are not studied. Septoplasty can be safely performed without postoperative nasal packing. Nasal packing had no main findings that compensated its usage. Septal suture is one of the procedures that can be used as alternative method to nasal packing. Therefore the nasal packing after septoplasty should be reserved for the patients with increased risk of bleeding. PMID:21425063

  15. Development of an effective valve packing program

    SciTech Connect

    Hart, K.A.

    1996-12-01

    Current data now shows that graphite valve packing installed within the guidance of a controlled program produces not only reliable stem sealing but predictable running loads. By utilizing recent technological developments in valve performance monitoring for both MOV`s and AOV`s, valve packing performance can be enhanced while reducing maintenance costs. Once known, values are established for acceptable valve packing loads, the measurement of actual valve running loads via the current MOV/AOV diagnostic techniques can provide indication of future valve stem sealing problems, improper valve packing installation or identify the opportunity for valve packing program improvements. At times the full benefit of these advances in material and predictive technology remain under utilized due to simple past misconceptions associated with valve packing. This paper will explore the basis for these misconceptions, provide general insight into the current understanding of valve packing and demonstrate how with this new understanding and current valve diagnostic equipment the key aspects required to develop an effective, quality valve packing program fit together. The cost and operational benefits provided by this approach can be significant impact by the: elimination of periodic valve repacking, reduction of maintenance costs, benefits of leak-free valve operation, justification for reduced Post Maintenance Test Requirements, reduced radiation exposure, improved plant appearance.

  16. 21 CFR 890.5700 - Cold pack.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Cold pack. 890.5700 Section 890.5700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5700 Cold pack. (a) Identification....

  17. 21 CFR 890.5700 - Cold pack.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cold pack. 890.5700 Section 890.5700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5700 Cold pack. (a) Identification....

  18. 21 CFR 890.5700 - Cold pack.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Cold pack. 890.5700 Section 890.5700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5700 Cold pack. (a) Identification....

  19. Soybean oil and methyl oleate adsorption onto a steel surface investigated using a quartz crystal microbalance with dissipation monitoring and atomic force microscopy**1

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The United States’ 2010 annual production of soybean oil exceeded 8 million metric tons, making a significant vegetable oil surplus available for new uses, particularly as a lubricant. Investigation of soybean oil and methyl oleate adsorption onto steel using a quartz crystal microbalance with diss...

  20. Coalescence preference in densely packed microbubbles

    SciTech Connect

    Kim, Yeseul; Lim, Su Jin; Gim, Bopil; Weon, Byung Mook

    2015-01-13

    A bubble merged from two parent bubbles with different size tends to be placed closer to the larger parent. This phenomenon is known as the coalescence preference. Here we demonstrate that the coalescence preference can be blocked inside a densely packed cluster of bubbles. We utilized high-speed high-resolution X-ray microscopy to clearly visualize individual coalescence events inside densely packed microbubbles with a local packing fraction of ~40%. Thus, the surface energy release theory predicts an exponent of 5 in a relation between the relative coalescence position and the parent size ratio, whereas our observation for coalescence in densely packed microbubbles shows a different exponent of 2. We believe that this result would be important to understand the reality of coalescence dynamics in a variety of packing situations of soft matter.

  1. Coalescence preference in densely packed microbubbles

    DOE PAGESBeta

    Kim, Yeseul; Lim, Su Jin; Gim, Bopil; Weon, Byung Mook

    2015-01-13

    A bubble merged from two parent bubbles with different size tends to be placed closer to the larger parent. This phenomenon is known as the coalescence preference. Here we demonstrate that the coalescence preference can be blocked inside a densely packed cluster of bubbles. We utilized high-speed high-resolution X-ray microscopy to clearly visualize individual coalescence events inside densely packed microbubbles with a local packing fraction of ~40%. Thus, the surface energy release theory predicts an exponent of 5 in a relation between the relative coalescence position and the parent size ratio, whereas our observation for coalescence in densely packed microbubblesmore » shows a different exponent of 2. We believe that this result would be important to understand the reality of coalescence dynamics in a variety of packing situations of soft matter.« less

  2. Fracture dimensions in frac&pack stimulation

    SciTech Connect

    Fan, Y.; Economides, M.J.

    1995-12-31

    A model is introduced to predict dynamic fracture dimensions in frac&pack stimulation. Design aspects of the two-in-one step treatment techniques, required by soft and high-permeability reservoirs are discussed. A pressure-dependent leakoff model, based on the transient flow of a non-Newtonian fluid displacing a reservoir fluid has been developed and incorporated with fracture mechanics concepts to simulate the entire process of frac&pack treatments including fracture propagation, inflation, proppant packing and closure. Results obtained in this study indicate the considerable difference between traditional fracturing and frac&pack treatments. In the latter, fracture length is much less important than fracture conductivity. This work shows how to terminate the fracture growth at the appropriate time, and how to design frac&packs resulting in fracture widths several times larger than those for traditional fracturing.

  3. Controlling Chirality of Entropic Crystals

    NASA Astrophysics Data System (ADS)

    Damasceno, Pablo F.; Karas, Andrew S.; Schultz, Benjamin A.; Engel, Michael; Glotzer, Sharon C.

    2015-10-01

    Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams.

  4. Controlling Chirality of Entropic Crystals.

    PubMed

    Damasceno, Pablo F; Karas, Andrew S; Schultz, Benjamin A; Engel, Michael; Glotzer, Sharon C

    2015-10-01

    Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams. PMID:26550757

  5. Spanning the scales of granular materials through microscopic force imaging

    NASA Astrophysics Data System (ADS)

    Brodu, Nicolas; Dijksman, Joshua A.; Behringer, Robert P.

    2015-03-01

    If you walk on sand, it supports your weight. How do the disordered forces between particles in sand organize, to keep you from sinking? This simple question is surprisingly difficult to answer experimentally: measuring forces in three dimensions, between deeply buried grains, is challenging. Here we describe experiments in which we have succeeded in measuring forces inside a granular packing subject to controlled deformations. We connect the measured micro-scale forces to the macro-scale packing force response with an averaging, mean field calculation. This calculation explains how the combination of packing structure and contact deformations produce the observed nontrivial mechanical response of the packing, revealing a surprising microscopic particle deformation enhancement mechanism.

  6. Spanning the scales of granular materials through microscopic force imaging

    PubMed Central

    Brodu, Nicolas; Dijksman, Joshua A.; Behringer, Robert P.

    2015-01-01

    If you walk on sand, it supports your weight. How do the disordered forces between particles in sand organize, to keep you from sinking? This simple question is surprisingly difficult to answer experimentally: measuring forces in three dimensions, between deeply buried grains, is challenging. Here we describe experiments in which we have succeeded in measuring forces inside a granular packing subject to controlled deformations. We connect the measured micro-scale forces to the macro-scale packing force response with an averaging, mean field calculation. This calculation explains how the combination of packing structure and contact deformations produce the observed nontrivial mechanical response of the packing, revealing a surprising microscopic particle deformation enhancement mechanism. PMID:25739968

  7. Connection between the packing efficiency of binary hard spheres and the glass-forming ability of bulk metallic glasses.

    PubMed

    Zhang, Kai; Smith, W Wendell; Wang, Minglei; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D; O'Hern, Corey S

    2014-09-01

    We perform molecular dynamics simulations to compress binary hard spheres into jammed packings as a function of the compression rate R, size ratio α, and number fraction x(S) of small particles to determine the connection between the glass-forming ability (GFA) and packing efficiency in bulk metallic glasses (BMGs). We define the GFA by measuring the critical compression rate R(c), below which jammed hard-sphere packings begin to form "random crystal" structures with defects. We find that for systems with α≳0.8 that do not demix, R(c) decreases strongly with Δϕ(J), as R(c)∼exp(-1/Δϕ(J)(2)), where Δϕ(J) is the difference between the average packing fraction of the amorphous packings and random crystal structures at R(c). Systems with α≲0.8 partially demix, which promotes crystallization, but we still find a strong correlation between R(c) and Δϕ(J). We show that known metal-metal BMGs occur in the regions of the α and x(S) parameter space with the lowest values of R(c) for binary hard spheres. Our results emphasize that maximizing GFA in binary systems involves two competing effects: minimizing α to increase packing efficiency, while maximizing α to prevent demixing.

  8. Crystallization of Self-Propelled Hard Discs.

    PubMed

    Briand, G; Dauchot, O

    2016-08-26

    We experimentally study the crystallization of a monolayer of vibrated discs with a built-in polar asymmetry, a model system of active liquids, and contrast it with that of vibrated isotropic discs. Increasing the packing fraction ϕ, the quasicontinuous crystallization reported for isotropic discs is replaced by a transition, or a crossover, towards a "self-melting" crystal. Starting from the liquid phase and increasing the packing fraction, clusters of dense hexagonal-ordered packed discs spontaneously form, melt, split, and merge, leading to a highly intermittent and heterogeneous dynamics. For a packing fraction larger than ϕ^{*}, a few large clusters span the system size. The cluster size distribution is monotonically decreasing for ϕ<ϕ^{*}, nonmonotonic for ϕ>ϕ^{*}, and is a power law at the transition. The system is, however, never dynamically arrested. The clusters permanently melt from place to place, forming droplets of an active liquid which rapidly propagate across the system. This self-melting crystalline state subsists up to the highest possible packing fraction, questioning the stability of the crystal for active discs unless it is at ordered close packing. PMID:27610889

  9. Crystallization of Self-Propelled Hard Discs

    NASA Astrophysics Data System (ADS)

    Briand, G.; Dauchot, O.

    2016-08-01

    We experimentally study the crystallization of a monolayer of vibrated discs with a built-in polar asymmetry, a model system of active liquids, and contrast it with that of vibrated isotropic discs. Increasing the packing fraction ϕ , the quasicontinuous crystallization reported for isotropic discs is replaced by a transition, or a crossover, towards a "self-melting" crystal. Starting from the liquid phase and increasing the packing fraction, clusters of dense hexagonal-ordered packed discs spontaneously form, melt, split, and merge, leading to a highly intermittent and heterogeneous dynamics. For a packing fraction larger than ϕ*, a few large clusters span the system size. The cluster size distribution is monotonically decreasing for ϕ <ϕ*, nonmonotonic for ϕ >ϕ*, and is a power law at the transition. The system is, however, never dynamically arrested. The clusters permanently melt from place to place, forming droplets of an active liquid which rapidly propagate across the system. This self-melting crystalline state subsists up to the highest possible packing fraction, questioning the stability of the crystal for active discs unless it is at ordered close packing.

  10. Understanding entangled polymers: What we can learn from athermal chain packings

    NASA Astrophysics Data System (ADS)

    Karayiannis, Nikos

    2012-02-01

    The study of random and ordered packings (from atoms and colloidal particles to sand grains) has been the focus of extensive research. This is not surprising since an understanding of the mechanisms that control morphology and packing is the key to the design and synthesis of novel ``smart'' materials and functionalities. In particular, the study of packings of chain molecules presents challenges but also insights which are absent in monatomic systems and further allows for a direction comparison with them. In this contribution we give an overview of our work on very dense and nearly jammed packings of athermal polymers. We show that chain molecules can be as efficiently and as densely packed as monatomic analogs up to the same maximally random jammed state. We also show that an exact correspondence can be established between the statistical-mechanical ensembles of packings of monatomic, and chain systems, which yields insights on the universality of jamming. By studying the effect of concentration on polymer size and on the underlying network of topological hindrances we precisely identify the distinct universal scaling regimes and the corresponding exponents. An unsuspected connection, valid from dilute up to very dense assemblies, is established between knots (of intermolecular origin) and entanglements (intermolecular constraints). We finally show that, against expectations, entropy-driven crystallization can occur in dense systems of athermal polymers once a critical volume fraction is reached. Such phase transition is driven by the increase in translational entropy: ordered sites exhibit enhanced mobility as their local free volume becomes more spherical and symmetric. Incipient nuclei develop well defined, stack-faulted layered crystal morphologies with a single stacking direction. The ordering transition and the resulting complex morphologies are analyzed, highlighting similarities and differences with respect to monatomic crystallization.

  11. Making Crystals from Crystals: A Solid-State Route to the Engineering of Crystalline Materials, Polymorphs, Solvates and Co-Crystals; Considerations on the Future of Crystal Engineering

    NASA Astrophysics Data System (ADS)

    Braga, Dario; Curzi, Marco; Dichiarante, Elena; Giaffreda, Stefano Luca; Grepioni, Fabrizia; Maini, Lucia; Palladino, Giuseppe; Pettersen, Anna; Polito, Marco

    Making crystals by design is the paradigm of crystal engineering. The main goal is that of obtaining and controlling the collective properties of a crystalline material from the convolution of the physical and chemical properties of the individual building blocks (whether molecules, ions, or metal atoms and ligands) with crystal periodicity and symmetry. Crystal engineering encompasses nowadays all traditional sectors of chemistry from organic to inorganic, organometallic, biological and pharmaceutical chemistry and nanotechnology. The investigation and characterization of the products of a crystal engineering experiment require the utilization of solid state techniques, including theoretical and advanced crystallography methods. Moreover, reactions between crystalline solids and/or between a crystalline solid and a vapour can be used to obtain crystalline materials, including new crystal forms, solvates and co-crystals. Indeed, crystal polymorphism, resulting from different packing arrangements of the same molecular or supramolecular entity in the crystal structure, represents a challenge to crystal makers.

  12. The unusual near-threshold FCG behavior of a single crystal superalloy and the resolved shear stress as the crack driving force

    NASA Technical Reports Server (NTRS)

    Telesman, Jack; Ghosn, Louis J.

    1989-01-01

    An investigation of the fatigue growth (FCG) behavior of PWA 1480 single crystal nickel base superalloy was conducted. Typical Paris region behavior was observed above a Delta-K of 8 MPa sq rt m. However, below that stress intensity range, the alloy exhibted highly unusual behavior. The behavior consisted of a region where the crack growth rate became essentially independent of the applied stress intensity. The transition in the FCG behavior was related to a change in the observed crack growth mechanisms.

  13. Optical trapping of colloidal particles and measurement of the defect line tension and colloidal forces in a thermotropic nematic liquid crystal

    SciTech Connect

    Smalyukh, I.I.; Kuzmin, A.N.; Kachynski, A.V.; Prasad, P.N.; Lavrentovich, O.D.

    2005-01-10

    We demonstrate optical trapping and manipulation of transparent microparticles suspended in a thermotropic nematic liquid crystal with low birefringence. We employ the particle manipulation to measure line tension of a topologically stable disclination line and to determine colloidal interaction of particles with perpendicular surface anchoring of the director. The three-dimensional director fields and positions of the particles manipulated by laser tweezers are visualized by fluorescence confocal polarizing microscopy.

  14. Domain structures and correlated out-of-plane and in-plane polarization reorientations in Pb(Zr0.96Ti0.04)O3 single crystal via piezoresponse force microscopy

    NASA Astrophysics Data System (ADS)

    Andreeva, N. V.; Pertsev, N. A.; Andronikova, D. A.; Filimonov, A. V.; Leontiev, N. G.; Leontyev, I. N.; Vakhrushev, S. B.

    2016-09-01

    Pb(Zr1-xTix)O3 single crystal with a low titanium content (x = 4%) was studied by the piezoresponse force microscopy (PFM) and X-ray diffraction (XRD). The XRD studies showed that the crystal faces are orthogonal to the principal cubic axes and confirmed the existence of an intermediate phase between the high-temperature paraelectric (PE) phase and the low-temperature antiferroelectric (AFE) one. A significant temperature hysteresis of phase transitions was observed by the XRD: On heating, the AFE state transforms into the intermediate one at about 373 K and the PE phase appears at 508 K, whereas on cooling the intermediate phase forms at 503 K and persists down to at least 313 K. The PFM investigation was focused on the intermediate phase and involved measurements of both out-of-plane and in-plane electromechanical responses of the (001)-oriented crystal face. The PFM images revealed the presence of polarization patterns switchable by an applied electric field, which confirms the ferroelectric character of the intermediate phase. Importantly, two types of regular domain structures were found, which differ by the spatial orientation of domain walls. The reconstruction of polarization configurations in the observed domain structures showed that one of them is a purely ferroelectric 180° structure with domain walls orthogonal to the crystal surface and parallel to one of the ⟨111⟩ pseudocubic directions. Another one is a ferroelectric-ferroelastic domain structure with the 71° walls parallel to the {101} or {011} crystallographic planes. Remarkably, this domain structure shows correlated out-of-plane and in-plane polarization reorientations after the poling with the aid of the microscope tip.

  15. Improved Taxation Rate for Bin Packing Games

    NASA Astrophysics Data System (ADS)

    Kern, Walter; Qiu, Xian

    A cooperative bin packing game is a N-person game, where the player set N consists of k bins of capacity 1 each and n items of sizes a 1, ⋯ ,a n . The value of a coalition of players is defined to be the maximum total size of items in the coalition that can be packed into the bins of the coalition. We present an alternative proof for the non-emptiness of the 1/3-core for all bin packing games and show how to improve this bound ɛ= 1/3 (slightly). We conjecture that the true best possible value is ɛ= 1/7.

  16. Leadership in wolf, Canis lupus, packs

    USGS Publications Warehouse

    Mech, L. David

    2000-01-01

    I examine leadership in Wolf (Canis lupus) packs based on published observations and data gathered during summers from 1986 to 1998 studying a free-ranging pack of Wolves on Ellesmere Island that were habituated to my presence. The breeding male tended to initiate activities associated with foraging and travel, and the breeding female to initiate, and predominate in, pup care and protection. However, there was considerable overlap and interaction during these activities such that leadership could be considered a joint function. In packs with multiple breeders, quantitative information about leadership is needed.

  17. Crystal sensor for microscopy applications

    SciTech Connect

    Peng Zhiqiang; West, Paul

    2005-01-03

    We report a force sensor based on a quartz crystal that is used for measuring nanoscale topographic images. The crystal is a length-extensional mode oscillator with a resonant frequency of about 650 kHz. Compared to 33 kHz tuning forks, such crystal sensors have a much higher resonance frequency, which allows for high force sensitivity and a fast response time. The crystal sensor is operated in the shear-force mode, with the probes vibrating parallel to the sample surface. The tip-sample interaction during operation is estimated to be less than 300 pN.

  18. 48-Pack low level waste storage facility

    SciTech Connect

    Bilik, T.J.

    1995-11-01

    ComEd has completed a design for a low level radioactive waste (LLW) storage facility, dubbed the {open_quotes}48-Pack{close_quotes}. The 48-Pack, so named because of its ability to hold 48 high integrity containers (HICs), is a modular, heavily shielded, concrete bunker. The facility was designed to serve as an effective means of augmenting the Company`s existing process waste storage capacity if and when the need arose. This paper identifies how ComEd addressed the potential need to supplement the storage capacity at its six nuclear stations through the development of the 48-Pack. Based on the criteria of meeting safety and regulatory requirements, low cost, short lead time for construction, universal design, and modularity, the 48-Pack concept was anticipated to meet and exceed the Company`s storage needs which were anticipated to end with the availability of a Central Midwest Compact (CMC) disposal facility.

  19. Packing and Entanglements in Polymer Melts

    NASA Astrophysics Data System (ADS)

    Ozisik, Rahmi; Sternstein, Sandy S.

    2004-03-01

    The idea of obtaining the properties of polymers simply from the chemical structure is a very attractive one. Recent work on entanglements and packing indicates that the entanglement molecular weight is related to packing length (= M/(ρ N_a), where M is the molecular weight, ρ is the density, R is the end-to-end vector, and Na is the Avogadro number). The exact relationship is given as follows: Me = 218 ρ p^3. This simple equation holds for a very large group of polymers and is temperature insensitive. In this study, we studied the packing and tried to obtain a scaling between packing and M_e, and extended the concept to cyclic polymers.

  20. Combination gravel packing device and method

    SciTech Connect

    Salerni, J. V.; Zachman, J. R.

    1985-09-17

    An apparatus for gravel packing a screen positioned adjacent the casing perforations of a subterranean well incorporates an annular sealing surface immediately above the gravel pack screen. A flapper valve is mounted for movement about a horizontal pivot axis into engagement with the annular valve seat. The flapper valve and the cooperating valve seat are both provided with spherical segment sealing surfaces so as to prevent leakage through the valve due to any misalignment of the pivot axis of the flapper valve with respect to the annular valve seat. With this apparatus, the withdrawal of the gravel packing apparatus at the completion of the gravel packing operations prevents the entry of undesired fluids and contaminates into the producing formation.

  1. Contact breaking in frictionless granular packings

    NASA Astrophysics Data System (ADS)

    Wu, Qikai; Bertrand, Thibault; O'Hern, Corey; Shattuck, Mark

    We numerically study the breaking of interparticle contact networks in static granular packings of frictionless bidisperse disks that are subjected to vibrations. The packings are created using an isotropic compression protocol at different values of the total potential energy per particle Ep. We first add displacements along a single vibrational mode i of the dynamical matrix to a given packing and calculate the minimum amplitude Ai of the perturbation at which the first interparticle contact breaks. We then identify the minimum amplitude Amin over all perturbations along each mode and study the distribution of Amin from an ensemble of packings at each Ep. We then study two-, three-, and multi-mode excitations and determine the dependence of Amin on the number of modes that are included in the perturbation. W. M. Keck Foundation Science and Engineering Grant.

  2. Groundwater well with reactive filter pack

    DOEpatents

    Gilmore, Tyler J.; Holdren, Jr., George R.; Kaplan, Daniel I.

    1998-01-01

    A method and apparatus for the remediation of contaminated soil and ground water wherein a reactive pack material is added to the annular fill material utilized in standard well construction techniques.

  3. Groundwater well with reactive filter pack

    DOEpatents

    Gilmore, T.J.; Holdren, G.R. Jr.; Kaplan, D.I.

    1998-09-08

    A method and apparatus are disclosed for the remediation of contaminated soil and ground water wherein a reactive pack material is added to the annular fill material utilized in standard well construction techniques. 3 figs.

  4. A Versatile, Automatic Chromatographic Column Packing Device

    ERIC Educational Resources Information Center

    Barry, Eugene F.; And Others

    1977-01-01

    Describes an inexpensive apparatus for packing liquid and gas chromatographic columns of high efficiency. Consists of stainless steel support struts, an Automat Getriebmotor, and an associated three-pulley system capable of 10, 30, and 300 rpm. (MLH)

  5. Simulation of the dynamic packing behavior of preparative chromatography columns via discrete particle modeling.

    PubMed

    Dorn, Martin; Hekmat, Dariusch

    2016-03-01

    Preparative packed-bed chromatography using polymer-based, compressible, porous resins is a powerful method for purification of macromolecular bioproducts. During operation, a complex, hysteretic, thus, history-dependent packed bed behavior is often observed but theoretical understanding of the causes is limited. Therefore, a rigorous modeling approach of the chromatography column on the particle scale has been made which takes into account interparticle micromechanics and fluid-particle interactions for the first time. A three-dimensional deterministic model was created by applying Computational Fluid Dynamics (CFD) coupled with the Discrete Element Method (DEM). The column packing behavior during either flow or mechanical compression was investigated in-silico and in laboratory experiments. A pronounced axial compression-relaxation profile was identified that differed for both compression strategies. Void spaces were clearly visible in the packed bed after compression. It was assumed that the observed bed inhomogeneity was because of a force-chain network at the particle scale. The simulation satisfactorily reproduced the measured behavior regarding packing compression as well as pressure-flow dependency. Furthermore, the particle Young's modulus and particle-wall friction as well as interparticle friction were identified as crucial parameters affecting packing dynamics. It was concluded that compaction of the chromatographic bed is rather because of particle rearrangement than particle deformation. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 32:363-371, 2016.

  6. Parametric reduced-order models of battery pack vibration including structural variation and prestress effects

    NASA Astrophysics Data System (ADS)

    Hong, Sung-Kwon; Epureanu, Bogdan I.; Castanier, Matthew P.

    2014-09-01

    The goal of this work is to develop a numerical model for the vibration of hybrid electric vehicle (HEV) battery packs to enable probabilistic forced response simulations for the effects of variations. There are two important types of variations that affect their structural response significantly: the prestress that is applied when joining the cells within a pack; and the small, random structural property discrepancies among the cells of a battery pack. The main contributions of this work are summarized as follows. In order to account for these two important variations, a new parametric reduced order model (PROM) formulation is derived by employing three key observations: (1) the stiffness matrix can be parameterized for different levels of prestress, (2) the mode shapes of a battery pack with cell-to-cell variation can be represented as a linear combination of the mode shapes of the nominal system, and (3) the frame holding each cell has vibratory motion. A numerical example of an academic battery pack with pouch cells is presented to demonstrate that the PROM captures the effects of both prestress and structural variation on battery packs. The PROM is validated numerically by comparing full-order finite element models (FEMs) of the same systems.

  7. Distillation of light hydrocarbons in packed columns

    SciTech Connect

    Strigle, R.F.

    1985-04-01

    Newly developed design procedures have led to a wider acceptance of packed columns for distillation operations, especially those operating at atmospheric or higher pressures. Based on these new design methods, modern IMTP packing has been used in a wide variety of services to revamp over 300 distillation columns previously equipped with trays. A few of these columns are listed. These revamps were justified by capacity increase and by greater product recovery. In addition, energy savings were realized from reduction of reflux ratio.

  8. Software For Nearly Optimal Packing Of Cargo

    NASA Technical Reports Server (NTRS)

    Fennel, Theron R.; Daughtrey, Rodney S.; Schwaab, Doug G.

    1994-01-01

    PACKMAN computer program used to find nearly optimal arrangements of cargo items in storage containers, subject to such multiple packing objectives as utilization of volumes of containers, utilization of containers up to limits on weights, and other considerations. Automatic packing algorithm employed attempts to find best positioning of cargo items in container, such that volume and weight capacity of container both utilized to maximum extent possible. Written in Common LISP.

  9. Gas-driven filter pressing: insights into melt segregation from crystal mushes

    NASA Astrophysics Data System (ADS)

    Pistone, Mattia; Arzilli, Fabio; Cordonnier, Benoit; Dobson, Katherine; Reusser, Eric; Ulmer, Peter; Marone, Federica; Whittington, Alan; Mancini, Lucia; Fife, Julie; Blundy, Jonathan

    2015-04-01

    Gas-driven filter pressing relieves the gas pressure developed through second boiling by expelling melt from a crystal mush. It is thought to play a major role in magma fractionation at shallow depths (< 10 km). We present new 4D (3D and time) experimental data that constrain conditions under which gas-driven filter pressing can occur. We performed in-situ high-temperature high-speed synchrotron X-ray tomography (500-800 °C, 3 μm/pixel, 8 seconds per full 3D dataset) to collect real time information on the behaviour of hydrous haplogranitic (2.1 wt.% H2O) and dacitic (4.2 wt.% H2O) crystal mushes with a wide range of crystal contents (34-80 vol.%). The data constrain how the crystal content affects the efficiency of gas-driven filter pressing of silicic melt out of the crystal mush framework, and show that gas-driven filter pressing operates below the maximum packing fraction of the suspended phases (bubbles + crystals) of ~74 vol.%. Above this value, the crystal mush is fated to fracture. These results provide essential constrain on the physical conditions under which gas-driven filter pressing can efficiently operate and force silicic melt out of the crystal framework. This also implies that, for effective gas-driven filter pressing, the crystal mush must inflate slowly relative to build-up of pressure and expulsion of melt. These observations suggest a possible explanation for the production of eruptible crystal-poor rhyolites in the Earth's crust.

  10. Bidispersed Sphere Packing on Spherical Surfaces

    NASA Astrophysics Data System (ADS)

    Atherton, Timothy; Mascioli, Andrew; Burke, Christopher

    Packing problems on spherical surfaces have a long history, originating in the classic Thompson problem of finding the ground state configuration of charges on a sphere. Such packings contain a minimal number of defects needed to accommodate the curvature; this is predictable using the Gauss-Bonnet theorem from knowledge of the topology of the surface and the local symmetry of the ordering. Famously, the packing of spherical particles on a sphere contains a 'scar' transition, where additional defects over those required by topology appear above a certain critical number of particles and self-organize into chains or scars. In this work, we study the packing of bidispersed packings on a sphere, and hence determine the interaction of bidispersity and curvature. The resultant configurations are nearly crystalline for low values of bidispersity and retain scar-like structures; these rapidly become disordered for intermediate values and approach a so-called Appollonian limit at the point where smaller particles can be entirely accommodated within the voids left by the larger particles. We connect our results with studies of bidispersed packings in the bulk and on flat surfaces from the literature on glassy systems and jamming. Supported by a Cottrell Award from the Research Corporation for Science Advancement.

  11. Pharyngeal Packing during Rhinoplasty: Advantages and Disadvantages

    PubMed Central

    Razavi, Majid; Taghavi Gilani, Mehryar; Bameshki, Ali Reza; Behdani, Reza; Khadivi, Ehsan; Bakhshaee, Mahdi

    2015-01-01

    Introduction: Controversy remains as to the advantages and disadvantages of pharyngeal packing during septorhinoplasty. Our study investigated the effect of pharyngeal packing on postoperative nausea and vomiting and sore throat following this type of surgery or septorhinoplasty. Materials and Methods: This clinical trial was performed on 90 American Society of Anesthesiologists (ASA) I or II patients who were candidates for septorhinoplasty. They were randomly divided into two groups. Patients in the study group had received pharyngeal packing while those in the control group had not. The incidence of nausea and vomiting and sore throat based on the visual analog scale (VAS) was evaluated postoperatively in the recovery room as well as at 2, 6 and 24 hours. Results: The incidence of postoperative nausea and vomiting (PONV) was 12.3%, with no significant difference between the study and control groups. Sore throat was reported in 50.5% of cases overall (56.8% on pack group and 44.4% on control). Although the severity of pain was higher in the study group at all times, the incidence in the two groups did not differ significantly. Conclusion: The use of pharyngeal packing has no effect in reducing the incidence of nausea and vomiting and sore throat after surgery. Given that induced hypotension is used as the routine method of anesthesia in septorhinoplasty surgery, with a low incidence of hemorrhage and a high risk of unintended retention of pharyngeal packing, its routine use is not recommended for this procedure. PMID:26788486

  12. Decontamination of pesticide packing using ionizing radiation

    NASA Astrophysics Data System (ADS)

    Duarte, C. L.; Mori, M. N.; Kodama, Yasko; Oikawa, H.; Sampa, M. H. O.

    2007-11-01

    The Brazilian agriculture activities have consumed about 288,000 tons of pesticides per year conditioned in about 107,000,000 packing with weight of approximately 23,000 tons. The discharge of empty plastic packing of pesticides can be an environmental concern causing problems to human health, animals, and plants if done without inspection and monitoring. The objective of this work is to study the ionizing radiation effect in the main pesticides used in Brazil for plastic packing decontamination. Among the commercial pesticides, chlorpyrifos has significant importance because of its wide distribution and extensive use and persistence. The radiation-induced degradation of chlorpyrifos in liquid samples and in polyethylene pack was studied by gamma radiolysis. Packing of high-density polyethylene (HDPE) three layer coextruded, named COEX, contaminated with chlorpyrifos, were irradiated using both a multipurpose Co-60 gamma irradiator and a gamma source with 5000 Ci total activity Gamma cell type. The chemical analysis of the chlorpyrifos was made using a gas chromatography associated to the Mass Spectrometry—GCMS from Shimadzu Model QP 5000. Gamma radiation was efficient for removing chlorpyrifos from the plastic packing, in all studied cases.

  13. Snow Pack and Lake Ice Pack Remote Sensing using Wideband Autocorrelation Radiometry

    NASA Astrophysics Data System (ADS)

    Mousavi, S.; De Roo, R. D.; Sarabandi, K.; England, A. W.

    2015-12-01

    A novel microwave radiometric technique, wideband autocorrelation radiometry (WiBAR), offers a deterministic method of remotely sensing the propagation time τdelay of microwaves through low loss layers at the bottom of the atmosphere. Terrestrial examples are the snow and lake ice packs. This technique is based on the Planck radiation from the surface beneath the pack which travels upwards through the pack towards the radiometer; such a signal we call a direct signal. On the other hand, part of this radiation reflects back from the pack's upper interface then from its lower interface, before traveling towards the radiometer's antenna. Thus, there are two signals received by the radiometer, the direct signal and a delayed copy of it. The microwave propagation time τdelay through the pack yields a measure of its vertical extent. We report a time series of measurements of the ice pack on Lake Superior from February to April 2014 to demonstrate this technique. The observations are done at frequencies from 7 to 10 GHz. At these frequencies, the volume and surface scattering are small in the ice pack. This technique is inherently low-power since there is no transmitter as opposed to active remote sensing techniques. The results of this paper is to present the WiBAR technique and show that the microwave travel time within a dry snow pack and lake ice pack can be deterministically measured for different thicknesses using this technique.

  14. Lorentz force velocimetry.

    PubMed

    Thess, A; Votyakov, E V; Kolesnikov, Y

    2006-04-28

    We describe a noncontact technique for velocity measurement in electrically conducting fluids. The technique, which we term Lorentz force velocimetry (LFV), is based on exposing the fluid to a magnetic field and measuring the drag force acting upon the magnetic field lines. Two series of measurements are reported, one in which the force is determined through the angular velocity of a rotary magnet system and one in which the force on a fixed magnet system is measured directly. Both experiments confirm that the measured signal is a linear function of the flow velocity. We then derive the scaling law that relates the force on a localized distribution of magnetized material to the velocity of an electrically conducting fluid. This law shows that LFV, if properly designed, has a wide range of potential applications in metallurgy, semiconductor crystal growth, and glass manufacturing. PMID:16712237

  15. Mathematical Simulation of the Structural Properties of Packed and Fluidized Beds

    NASA Astrophysics Data System (ADS)

    Fedorov, S. S.; Gubinskii, M. V.; Foris', S. N.

    2016-05-01

    Based on the algorithm of successive filling a given volume with single spheres, a mathematical model of random packing of a limited volume of a bed in the field of body forces has been developed. This model can be applied to electrothermal packed- and fluidized-bed furnaces and will make it possible to investigate the thermal and electrical conductivity of such beds. A check of the adequacy of the model showed its correspondence to the well-known experimental and calculated results, as well as the stability of the solutions obtained with its aid.

  16. Standard atomic volumes in double-stranded DNA and packing in protein--DNA interfaces.

    PubMed

    Nadassy, K; Tomás-Oliveira, I; Alberts, I; Janin, J; Wodak, S J

    2001-08-15

    Standard volumes for atoms in double-stranded B-DNA are derived using high resolution crystal structures from the Nucleic Acid Database (NDB) and compared with corresponding values derived from crystal structures of small organic compounds in the Cambridge Structural Database (CSD). Two different methods are used to compute these volumes: the classical Voronoi method, which does not depend on the size of atoms, and the related Radical Planes method which does. Results show that atomic groups buried in the interior of double-stranded DNA are, on average, more tightly packed than in related small molecules in the CSD. The packing efficiency of DNA atoms at the interfaces of 25 high resolution protein-DNA complexes is determined by computing the ratios between the volumes of interfacial DNA atoms and the corresponding standard volumes. These ratios are found to be close to unity, indicating that the DNA atoms at protein-DNA interfaces are as closely packed as in crystals of B-DNA. Analogous volume ratios, computed for buried protein atoms, are also near unity, confirming our earlier conclusions that the packing efficiency of these atoms is similar to that in the protein interior. In addition, we examine the number, volume and solvent occupation of cavities located at the protein-DNA interfaces and compared them with those in the protein interior. Cavities are found to be ubiquitous in the interfaces as well as inside the protein moieties. The frequency of solvent occupation of cavities is however higher in the interfaces, indicating that those are more hydrated than protein interiors. Lastly, we compare our results with those obtained using two different measures of shape complementarity of the analysed interfaces, and find that the correlation between our volume ratios and these measures, as well as between the measures themselves, is weak. Our results indicate that a tightly packed environment made up of DNA, protein and solvent atoms plays a significant role in

  17. Capillary Force Driven Self-Assembly of Anisotropic Hierarchical Structures Prepared by Femtosecond Laser 3D Printing and Their Applications in Crystallizing Microparticles.

    PubMed

    Lao, Zhaoxin; Hu, Yanlei; Zhang, Chenchu; Yang, Liang; Li, Jiawen; Chu, Jiaru; Wu, Dong

    2015-12-22

    The hierarchical structures are the derivation of various functionalities in the natural world and have inspired broad practical applications in chemical systhesis and biological manipulation. However, traditional top-down fabrication approaches suffered from low complexity. We propose a laser printing capillary-assisted self-assembly (LPCS) strategy for fabricating regular periodic structures. Microscale pillars are first produced by the localized femtosecond laser polymerization and are subsequently self-assembled into periodic hierarchical architectures with the assistance of controlled capillary force. Moreover, based on anisotropic assemblies of micropillars, the LPCS method is further developed for the preparation of more complicated and advanced functional microstructures. Pillars cross section, height, and spatial arrangement can be tuned to guide capillary force, and diverse assemblies with different configurations are thus achieved. Finally, we developed a strategy for growing micro/nanoparticles in designed spatial locations through solution-evaporation self-assembly induced by morphology. Due to the high flexibility of LPCS method, the special arrangements, sizes, and distribution density of the micro/nanoparticles can be controlled readily. Our method will be employed not only to fabricate anisotropic hierarchical structures but also to design and manufacture organic/inorganic microparticles.

  18. Photostability Can Be Significantly Modulated by Molecular Packing in Glasses.

    PubMed

    Qiu, Yue; Antony, Lucas W; de Pablo, Juan J; Ediger, M D

    2016-09-01

    While previous work has demonstrated that molecular packing in organic crystals can strongly influence photochemical stability, efforts to tune photostability in amorphous materials have shown much smaller effects. Here we show that physical vapor deposition can substantially improve the photostability of organic glasses. Disperse Orange 37 (DO37), an azobenzene derivative, is studied as a model system. Photostability is assessed through changes in the density and molecular orientation of glassy thin films during light irradiation. By optimizing the substrate temperature used for deposition, we can increase photostability by a factor of 50 relative to the liquid-cooled glass. Photostability correlates with glass density, with density increases of up to 1.3%. Coarse-grained molecular simulations, which mimic glass preparation and the photoisomerization reaction, also indicate that glasses with higher density have substantially increased photostability. These results provide insights that may assist in the design of organic photovoltaics and light-emission devices with longer lifetimes. PMID:27517130

  19. Anisotropic Packing of DNA-Mediated Colloidal Self-Assembly

    NASA Astrophysics Data System (ADS)

    Vo, Thi; Lu, Fang; Zhang, Yugang; Gang, Oleg; Kumar, Sanat

    The self-assembly of DNA-grafted nanoparticles has garnered considerable interest in recent years. However, many efforts focused on the usage of spherical nanoparticles, which limits us to the formation of only a handful of crystal lattices. Recent advances in the synthesis of non-spherical particles have directed attention towards the usage of these anisotropic particles for self-assembly. Here we combine experiments and theory on a series of DNA-grafted nanocubes. Our studies indicate that anisotropy not only directs where DNA linkers graft onto the particle but also affects how they pack and orient within a lattice, giving rise to both a preferential attachment effect and orientation-directed self-assembly. These results emphasize anisotropic self-assembly as a powerful new tool that allows for precise and directed control of nanoparticle self-assembly.

  20. 27 CFR 24.308 - Bottled or packed wine record.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Bottled or packed wine... BUREAU, DEPARTMENT OF THE TREASURY LIQUORS WINE Records and Reports § 24.308 Bottled or packed wine record. A proprietor who bottles, packs, or receives bottled or packed beverage wine in bond...

  1. 21 CFR 880.5760 - Chemical cold pack snakebite kit.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Chemical cold pack snakebite kit. 880.5760 Section... Therapeutic Devices § 880.5760 Chemical cold pack snakebite kit. (a) Identification. A chemical cold pack snakebit kit is a device consisting of a chemical cold pack and tourniquet used for first-aid treatment...

  2. 21 CFR 880.5760 - Chemical cold pack snakebite kit.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Chemical cold pack snakebite kit. 880.5760 Section... Therapeutic Devices § 880.5760 Chemical cold pack snakebite kit. (a) Identification. A chemical cold pack snakebit kit is a device consisting of a chemical cold pack and tourniquet used for first-aid treatment...

  3. 21 CFR 880.5760 - Chemical cold pack snakebite kit.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Chemical cold pack snakebite kit. 880.5760 Section... Therapeutic Devices § 880.5760 Chemical cold pack snakebite kit. (a) Identification. A chemical cold pack snakebit kit is a device consisting of a chemical cold pack and tourniquet used for first-aid treatment...

  4. 21 CFR 880.5760 - Chemical cold pack snakebite kit.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Chemical cold pack snakebite kit. 880.5760 Section... Therapeutic Devices § 880.5760 Chemical cold pack snakebite kit. (a) Identification. A chemical cold pack snakebit kit is a device consisting of a chemical cold pack and tourniquet used for first-aid treatment...

  5. 21 CFR 880.5760 - Chemical cold pack snakebite kit.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Chemical cold pack snakebite kit. 880.5760 Section... Therapeutic Devices § 880.5760 Chemical cold pack snakebite kit. (a) Identification. A chemical cold pack snakebit kit is a device consisting of a chemical cold pack and tourniquet used for first-aid treatment...

  6. Experimental evidence of icosahedral and decahedral packing in one-dimensional nanostructures.

    PubMed

    Velázquez-Salazar, J Jesús; Esparza, Rodrigo; Mejía-Rosales, Sergio Javier; Estrada-Salas, Rubén; Ponce, Arturo; Deepak, Francis Leonard; Castro-Guerrero, Carlos; José-Yacamán, Miguel

    2011-08-23

    The packing of spheres is a subject that has drawn the attention of mathematicians and philosophers for centuries and that currently attracts the interest of the scientific community in several fields. At the nanoscale, the packing of atoms affects the chemical and structural properties of the material and, hence, its potential applications. This report describes the experimental formation of 5-fold nanostructures by the packing of interpenetrated icosahedral and decahedral units. These nanowires, formed by the reaction of a mixture of metal salts (Au and Ag) in the presence of oleylamine, are obtained when the chemical composition is specifically Ag/Au = 3:1. The experimental images of the icosahedral nanowires have a high likelihood with simulated electron micrographs of structures formed by two or three Boerdijk-Coxeter-Bernal helices roped on a single structure, whereas for the decahedral wires, simulations using a model of adjacent decahedra match the experimental structures. To our knowledge, this is the first report of the synthesis of nanowires formed by the packing of structures with 5-fold symmetry. These icosahedral nanowire structures are similar to those of quasicrystals, which can only be formed if at least two atomic species are present and in which icosahedral and decahedral packing has been found for bulk crystals.

  7. Efficient linear programming algorithm to generate the densest lattice sphere packings.

    PubMed

    Marcotte, Étienne; Torquato, Salvatore

    2013-06-01

    Finding the densest sphere packing in d-dimensional Euclidean space R(d) is an outstanding fundamental problem with relevance in many fields, including the ground states of molecular systems, colloidal crystal structures, coding theory, discrete geometry, number theory, and biological systems. Numerically generating the densest sphere packings becomes very challenging in high dimensions due to an exponentially increasing number of possible sphere contacts and sphere configurations, even for the restricted problem of finding the densest lattice sphere packings. In this paper we apply the Torquato-Jiao packing algorithm, which is a method based on solving a sequence of linear programs, to robustly reproduce the densest known lattice sphere packings for dimensions 2 through 19. We show that the TJ algorithm is appreciably more efficient at solving these problems than previously published methods. Indeed, in some dimensions, the former procedure can be as much as three orders of magnitude faster at finding the optimal solutions than earlier ones. We also study the suboptimal local density-maxima solutions (inherent structures or "extreme" lattices) to gain insight about the nature of the topography of the "density" landscape. PMID:23848802

  8. Beef and pork packing industries.

    PubMed

    MacDonald, James M

    2003-07-01

    A remarkable transformation of the meatpacking industry occurred in the last 25 years. That transformation consolidated the industry into one that could deliver large volumes of meat at low costs. Slaughter plants grew much larger and realized economies of scale from their size, and operations within plants were rationalized to emphasize the delivery of a small set of consistent major products (boxed beef, cut-up pork, and by-products) to retailers, wholesalers, and other processors. Similar developments occurred in livestock feeding whereby the industry realized significant cost reductions by consolidating production in very large cattle feedlots and hog farms. Gains from scale have largely been met (absent the development of new technologies that are not yet on the horizon); therefore, we are unlikely to see similar shifts in plant sizes in the next 25 years. The major forces affecting meatpacking and livestock feeding in the near future are more likely to revolve around tighter coordination among livestock production, meatpacking, wholesaling, and retailing. Although much of the recent response to food safety concerns took the form of investments in equipment, testing, and training within meatpacking plants, packers and retailers are likely to focus more on assurance of livestock production quality and methods in the future. Such assurance can be met through vertical integration or through a greater reliance on tightly drawn contracts; producers who attempt to provide the assurance while still selling through cash markets will need to develop paper trails of testing and quality assurance that will move through the marketing chain with livestock. Similarly, because of likely increased future demand for meats of assured consumer qualities, such as organically grown products or branded meat products with very specific traits, producers will likely need to provide similar indicators of assurance throughout the marketing chain. Finally, the funding offered through

  9. [Research progress on the management of no packing after septoplasty].

    PubMed

    Lu, Sheng; Zhang, Longcheng; Li, Jieen

    2016-01-01

    Packing the nose after septoplasty is common practice. The use of postoperative packing has been proposed to reduce the dead space between the subperichondrial flaps and minimize postoperative complications such as hemorrhage, septal hematoma, and formation of synechiae. Additionally, postoperative packing is thought to stabilize the remaining cartilaginous septum and minimize persistence or recurrence of septal deviation. Despite these theoretic advantages, evidence to support the use of postoperative packing is lacking. Additionally, nasal packing is not an innocuous procedure. The use of nasal packing actually cause these complications such as postop- erative pain, mucosal injury, bleeding, worsening of breathing due to sleep disorders, and postoperative infections. Routine use of anterior nasal packing after septoplasty should be challenged for not presenting proven benefit. As alternatives to traditional packing, septal suturing, septal stapler and fibrin glue have been used recently. The purpose of this article is to summarize the progress of traditional packing to no packing after septoplasty. PMID:27197467

  10. Coalescence preference in dense packing of bubbles

    NASA Astrophysics Data System (ADS)

    Kim, Yeseul; Gim, Bopil; Gim, Bopil; Weon, Byung Mook

    2015-11-01

    Coalescence preference is the tendency that a merged bubble from the contact of two original bubbles (parent) tends to be near to the bigger parent. Here, we show that the coalescence preference can be blocked by densely packing of neighbor bubbles. We use high-speed high-resolution X-ray microscopy to clearly visualize individual coalescence phenomenon which occurs in micro scale seconds and inside dense packing of microbubbles with a local packing fraction of ~40%. Previous theory and experimental evidence predict a power of -5 between the relative coalescence position and the parent size. However, our new observation for coalescence preference in densely packed microbubbles shows a different power of -2. We believe that this result may be important to understand coalescence dynamics in dense packing of soft matter. This work (NRF-2013R1A22A04008115) was supported by Mid-career Researcher Program through NRF grant funded by the MEST and also was supported by Ministry of Science, ICT and Future Planning (2009-0082580) and by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry and Education, Science and Technology (NRF-2012R1A6A3A04039257).

  11. Computational strain gradient crystal plasticity

    NASA Astrophysics Data System (ADS)

    Niordson, Christian F.; Kysar, Jeffrey W.

    2014-01-01

    A numerical method for viscous strain gradient crystal plasticity theory is presented, which incorporates both energetic and dissipative gradient effects. The underlying minimum principles are discussed as well as convergence properties of the proposed finite element procedure. Three problems of plane crystal plasticity are studied: pure shear of a single crystal between rigid platens as well as plastic deformation around cylindrical voids in hexagonal close packed and face centered cubic crystals. Effective in-plane constitutive slip parameters for plane strain deformation of specifically oriented face centered cubic crystals are developed in terms of the crystallographic slip parameters. The effect on geometrically necessary dislocation structures introduced by plastic deformation is investigated as a function of the ratio of void radius to plasticity length scale.

  12. Fabrication of colloidal crystals with defined and complex structures via layer-by-layer transfer.

    PubMed

    Li, Wei; Yang, Bai; Wang, Dayang

    2008-12-01

    A new and versatile way--using poly(dimethylsiloxane) (PDMS) sheets to layer-by-layer (LbL) transfer hexagonal-close-packed particle monolayers from preformed colloidal crystals and stack them on substrates-has been demonstrated to create colloidal crystals. This approach allows LbL control of the thickness of the resulting crystals and especially of the size and the packing structure of the particles in each layer. Furthermore, it also allows fabrication of binary colloidal crystals over large areas by deformation of the PDMS sheets during LbL transfer. Two new binary crystals-one composed of identically sized particles but in different densities and the other of a nonclose-packed monolayer of large particles and a close-packed monolayer of small particles-were created, which are hard grown by other colloidal crystallization techniques developed thus far. PMID:18986179

  13. Deterioration of organic packing materials commonly used in air biofiltration: effect of VOC-packing interactions.

    PubMed

    Lebrero, Raquel; Estrada, José M; Muñoz, Raúl; Quijano, Guillermo

    2014-05-01

    The abiotic deterioration of three conventional organic packing materials used in biofiltration (compost, wood bark and Macadamia nutshells) caused by their interaction with toluene (used as a model volatile organic compound) was here studied. The deterioration of the materials was evaluated in terms of structural damage, release of co-substrates and increase of the packing biodegradability. After 21 days of exposure to toluene, all packing materials released co-substrates able to support microbial growth, which were not released by the control materials not exposed to toluene. Likewise, the exposure to toluene increased the packing material biodegradability by 26% in wood bark, 20% in compost and 17% in Macadamia nutshells. Finally, scanning electron microscopy analysis confirmed the deterioration in the structure of the packing materials evaluated due to the exposure to toluene, Macadamia nutshells being the material with the highest resistance to volatile organic compound attack.

  14. Deterioration of organic packing materials commonly used in air biofiltration: effect of VOC-packing interactions.

    PubMed

    Lebrero, Raquel; Estrada, José M; Muñoz, Raúl; Quijano, Guillermo

    2014-05-01

    The abiotic deterioration of three conventional organic packing materials used in biofiltration (compost, wood bark and Macadamia nutshells) caused by their interaction with toluene (used as a model volatile organic compound) was here studied. The deterioration of the materials was evaluated in terms of structural damage, release of co-substrates and increase of the packing biodegradability. After 21 days of exposure to toluene, all packing materials released co-substrates able to support microbial growth, which were not released by the control materials not exposed to toluene. Likewise, the exposure to toluene increased the packing material biodegradability by 26% in wood bark, 20% in compost and 17% in Macadamia nutshells. Finally, scanning electron microscopy analysis confirmed the deterioration in the structure of the packing materials evaluated due to the exposure to toluene, Macadamia nutshells being the material with the highest resistance to volatile organic compound attack. PMID:24603032

  15. Modeling of transient flow through a viscoelastic preparative chromatography packing.

    PubMed

    Hekmat, Dariusch; Kuhn, Michael; Meinhardt, Verena; Weuster-Botz, Dirk

    2013-01-01

    The common method for purification of macromolecular bioproducts is preparative packed-bed chromatography using polymer-based, compressible, viscoelastic resins. Because of a downstream processing bottleneck, the chromatography equipment is often operated at its hydrodynamic limit. In this case, the resins may exhibit a complex behavior which results in compression-relaxation hystereses. Up to now, no modeling approach of transient flow through a chromatography packing has been made considering the viscoelasticity of the resins. The aim of the present work was to develop a novel model and compare model calculations with experimental data of two agarose-based resins. Fluid flow and bed permeability were modeled by Darcy's law and the Kozeny-Carman equation, respectively. Fluid flow was coupled to solid matrix stress via an axial force balance and a continuity equation of a deformable packing. Viscoelasticity was considered according to a Kelvin-Voigt material. The coupled equations were solved with a finite difference scheme using a deformable mesh. The model boundary conditions were preset transient pressure drop functions which resemble simulated load/elution/equilibration cycles. Calculations using a homogeneous model (assuming constant variables along the column height) gave a fair agreement with experimental data with regard to predicted flow rate, bed height, and compression-relaxation hysteresis for symmetric as well as asymmetric pressure drop functions. Calculations using an inhomogeneous model gave profiles of the bed porosity as a function of the bed height. In addition, the influence of medium wall support and intraparticle porosity was illustrated. The inhomogeneous model provides insights that so far are not easily experimentally accessible.

  16. Maximum entropy and the stress distribution in soft disk packings above jamming.

    PubMed

    Wu, Yegang; Teitel, S

    2015-08-01

    We show that the maximum entropy hypothesis can successfully explain the distribution of stresses on compact clusters of particles within disordered mechanically stable packings of soft, isotropically stressed, frictionless disks above the jamming transition. We show that, in our two-dimensional case, it becomes necessary to consider not only the stress but also the Maxwell-Cremona force-tile area as a constraining variable that determines the stress distribution. The importance of the force-tile area had been suggested by earlier computations on an idealized force-network ensemble. PMID:26382394

  17. GraSPI (Graphical Structured Packing Interface)

    SciTech Connect

    Almedia, Valmor de

    2004-06-10

    GraSPI is a collection of macros (computer programs) written to work in concert with Fluent Inc. software GAMBIT and FLUENT for modeling and design of structured packing columns used in the chemical industry (the application focus is in distillation but other applications such as gas absorbers, and other chemical contactors can also be analyzed). GraSPI is an accessory to GAMBIT and FLUENT that drives the process of complex geometry creation, domain setup, and mesh generation. In addition, GraSPI manages automatic flow analysis in the aforementioned domain via either serial or parallel computing using FLUENT. A library of typical commercial structured packing elements is included in GraSPI, so is the capability for user-defined creation of new packings.

  18. Safety considerations for fabricating lithium battery packs

    NASA Technical Reports Server (NTRS)

    Ciesla, J. J.

    1986-01-01

    Lithium cell safety is a major issue with both manufacturers and end users. Most manufacturers have taken great strides to develop the safest cells possible while still maintaining performance characteristics. The combining of lithium cells for higher voltages, currents, and capacities requires the fabricator of lithium battery packs to be knowledgable about the specific electrochemical system being used. Relatively high rate, spirally wound (large surface area) sulfur oxychloride cells systems, such as Li/Thionyl or Sulfuryl chloride are considered. Prior to the start of a design of a battery pack, a review of the characterization studies for the cells should be conducted. The approach for fabricating a battery pack might vary with cell size.

  19. GraSPI (Graphical Structured Packing Interface)

    2004-06-10

    GraSPI is a collection of macros (computer programs) written to work in concert with Fluent Inc. software GAMBIT and FLUENT for modeling and design of structured packing columns used in the chemical industry (the application focus is in distillation but other applications such as gas absorbers, and other chemical contactors can also be analyzed). GraSPI is an accessory to GAMBIT and FLUENT that drives the process of complex geometry creation, domain setup, and mesh generation.more » In addition, GraSPI manages automatic flow analysis in the aforementioned domain via either serial or parallel computing using FLUENT. A library of typical commercial structured packing elements is included in GraSPI, so is the capability for user-defined creation of new packings.« less

  20. An integrated model of ring pack performance

    NASA Technical Reports Server (NTRS)

    Keribar, R.; Dursunkaya, Z.; Flemming, M. F.

    1991-01-01

    This paper describes an integrated model developed for the detailed characterization and simulation of piston ring pack behavior in internal combustion engines and the prediction of ring pack performance. The model includes comprehensive and coupled treatments of (1) ring-liner hydrodynamic and boundary lubrication and friction; (2) ring axial, radial, and (toroidal) twist dynamics; (3) inter-ring gas dynamics and blowby. The physics of each of these highly inter-related phenomena are represented by submodels, which are intimately coupled to form a design-oriented predictive tool aimed at the calculation of ring film thicknesses, ring motions, land pressures, engine friction, and blowby. The paper also describes the results of a series of analytical studies investigating effects of engine speed and load and ring pack design parameters, on ring motions, film thicknesses, and inter-ring pressures, as well as ring friction and blowby.

  1. Frustrated packing of spheres in a flat container under symmetry-breaking bias.

    PubMed

    Harth, K; Mauney, A; Stannarius, R

    2015-03-01

    We study statistical properties of packings of monodisperse spheres in a flat box. After "gravitational" filling and appropriate agitation, a nearly regular (in plane) but frustrated (normal to the plane) triangular lattice forms, where beads at individual sites touch either the front or back wall. It has striking analogies to order in antiferromagnetic Ising spin models. When tilting the container, Earth's gravitational field mimics external forces similar to magnetic fields in the spin systems. While packings in vertical containers adopt a frustrated state with statistical correlations between neighboring sites, the configurations continuously approach the predictions of a random Ising model when the cell tilt is increased. Our experiments offer insights into both the influence of geometrical constraints on random granular packing and a descriptive example of frustrated ordering.

  2. From Crystals to Disordered Crystals: A Hidden Order-Disorder Transition.

    PubMed

    Tong, Hua; Tan, Peng; Xu, Ning

    2015-10-20

    To distinguish between order and disorder is of fundamental importance to understanding solids. It becomes more significant with recent observations that solids with high structural order can behave like disordered solids, while properties of disordered solids can approach crystals under certain circumstance. It is then imperative to understand when and how disorder takes effect to deviate the properties of a solid from crystals and what the correct factors are to control the behaviours of solids. Here we answer these questions by reporting the finding of a hidden order-disorder transition from crystals to disordered crystals for static packings of frictionless spheres. While the geometric indicators are mostly blind to the transition, disordered crystals already exhibit properties apart from crystals. The transition approaches the close packing of hard spheres, giving rise to the singularity of the close packing point. We evidence that both the transition and properties of disordered crystals are jointly determined by the structural order and density. Near the transition, the elastic moduli and coordination number of disordered crystals show particular pressure dependence distinct from known behaviours of both crystals and jammed solids. The discovery of the transition therefore reveals some unknown aspects of solids.

  3. Damage of cells and battery packs due to ground impact

    NASA Astrophysics Data System (ADS)

    Xia, Yong; Wierzbicki, Tomasz; Sahraei, Elham; Zhang, Xiaowei

    2014-12-01

    The present paper documents a comprehensive study on the ground impact of lithium-ion battery packs in electric vehicles. With the purpose of developing generic methodology, a hypothetic global finite element model is adopted. The force-displacement response of indentation process simulated by the global FE model is cross-validated with the earlier analytical solutions. The punching process after the armor plate perforation, the ensuing crack propagation of the armor plate as well as the local deformation modes of individual battery cells are clearly predicted by the global modeling. A parametric study is carried out, and a few underlying rules are revealed, providing important clues on the design of protective structure of battery packs against ground impact. In the next step, detailed FE models at the level of a single battery cell and shell casing are developed and simulations are performed using boundaries and loading conditions taken from the global solution. In the detailed modeling the failure of individual components is taken into account, which is an important indicator of electric short circuit of a battery cell and possible thermal runaway. The damage modes and the deformation tolerances of components in the battery cell under various loading conditions are observed and compared.

  4. Packing density of rigid aggregates is independent of scale.

    PubMed

    Zangmeister, Christopher D; Radney, James G; Dockery, Lance T; Young, Jessica T; Ma, Xiaofei; You, Rian; Zachariah, Michael R

    2014-06-24

    Large planetary seedlings, comets, microscale pharmaceuticals, and nanoscale soot particles are made from rigid, aggregated subunits that are compacted under low compression into larger structures spanning over 10 orders of magnitude in dimensional space. Here, we demonstrate that the packing density (θf) of compacted rigid aggregates is independent of spatial scale for systems under weak compaction. The θf of rigid aggregated structures across six orders of magnitude were measured using nanoscale spherical soot aerosol composed of aggregates with ∼ 17-nm monomeric subunits and aggregates made from uniform monomeric 6-mm spherical subunits at the macroscale. We find θf = 0.36 ± 0.02 at both dimensions. These values are remarkably similar to θf observed for comet nuclei and measured values of other rigid aggregated systems across a wide variety of spatial and formative conditions. We present a packing model that incorporates the aggregate morphology and show that θf is independent of both monomer and aggregate size. These observations suggest that the θf of rigid aggregates subject to weak compaction forces is independent of spatial dimension across varied formative conditions. PMID:24927577

  5. Packing density of rigid aggregates is independent of scale

    PubMed Central

    Zangmeister, Christopher D.; Radney, James G.; Dockery, Lance T.; Young, Jessica T.; Ma, Xiaofei; You, Rian; Zachariah, Michael R.

    2014-01-01

    Large planetary seedlings, comets, microscale pharmaceuticals, and nanoscale soot particles are made from rigid, aggregated subunits that are compacted under low compression into larger structures spanning over 10 orders of magnitude in dimensional space. Here, we demonstrate that the packing density (θf) of compacted rigid aggregates is independent of spatial scale for systems under weak compaction. The θf of rigid aggregated structures across six orders of magnitude were measured using nanoscale spherical soot aerosol composed of aggregates with ∼17-nm monomeric subunits and aggregates made from uniform monomeric 6-mm spherical subunits at the macroscale. We find θf = 0.36 ± 0.02 at both dimensions. These values are remarkably similar to θf observed for comet nuclei and measured values of other rigid aggregated systems across a wide variety of spatial and formative conditions. We present a packing model that incorporates the aggregate morphology and show that θf is independent of both monomer and aggregate size. These observations suggest that the θf of rigid aggregates subject to weak compaction forces is independent of spatial dimension across varied formative conditions. PMID:24927577

  6. Prediction of packing of secondary structure.

    PubMed

    Nagano, K; Ponnuswamy, P K

    1984-01-01

    An improved method of picking up candidates for predicting the packing arrangement of beta-strands and alpha-helices of the alpha/beta type domains is described here. The method of judging whether the region of the protein would fold into the alpha/beta type or not is also described. The folding constraints of globular proteins are analysed and presented in this article for application to the prediction of packing of secondary structure. The analysis of the residue-fluctuations is also applicable for the purpose.

  7. Crystal structure of actinide metals at high compression

    SciTech Connect

    Fast, L.; Soederlind, P.

    1995-08-01

    The crystal structures of some light actinide metals are studied theoretically as a function of applied pressure. The first principles electronic structure theory is formulated in the framework of density functional theory, with the gradient corrected local density approximation of the exchange-correlation functional. The light actinide metals are shown to be well described as itinerant (metallic) f-electron metals and generally, they display a crystal structure which have, in agreement with previous theoretical suggestions, increasing degree of symmetry and closed-packing upon compression. The theoretical calculations agree well with available experimental data. At very high compression, the theory predicts closed-packed structures such as the fcc or the hcp structures or the nearly closed-packed bcc structure for the light actinide metals. A simple canonical band picture is presented to explain in which particular closed-packed form these metals will crystallize at ultra-high pressure.

  8. New AFM Techniques for Investigating Molecular Growth Mechanisms of Protein Crystals

    NASA Technical Reports Server (NTRS)

    Li, Huayu; Nadarajah, Arunan; Konnert, John H.; Pusey, Marc L.

    1998-01-01

    Atomic Force Microscopy (AFM) has emerged as a powerful technique for investigating protein crystal growth. Earlier AFM studies were among the first to demonstrate that these crystals grew by dislocation and 2D nucleation growth mechanisms [1]. These investigations were restricted to the micron range where only surface features, such as dislocation hillocks and 2D islands are visible. Most AFM instruments can scan at higher resolutions and have the potential to resolve individual protein molecules at nanometer ranges. Such scans are essential for determining the molecular packing arrangements on crystal faces and for probing the growth process at the molecular level. However, at this resolution the AFM tip influences the image produced, with the resulting image being a convolution of the tip shape and the surface morphology [2]. In most studies this problem is resolved by deconvoluting the image to obtain the true surface morphology. Although deconvolution routines work reasonably well for simple one- dimensional shapes, for complex surfaces this approach does not produce accurate results. In this study we devised a new approach which takes advantage of the precise molecular order of crystal surfaces, combined with the knowledge of individual molecular shapes from the crystallographic data of the protein and the AFM tip shape. This information is used to construct expected theoretical AFM images by convoluting the tip shape with the constructed crystal surface shape for a given surface packing arrangement. By comparing the images from actual AFM scans with the constructed ones for different possible surface packing arrangements, the correct packing arrangement can be conclusively determined. This approach was used in this study to determine the correct one from two possible packing arrangements on (I 10) faces of tetragonal lysozyme crystals. Another novel AFM technique was also devised to measure the dimension of individual growth units of the crystal faces

  9. Crystal structures and Hirshfeld surface analysis calculations of mercury(II) complexes with a diiminopyridine ligand

    NASA Astrophysics Data System (ADS)

    Hosseini, Seyed Ali; Mahmoudi, Ghodrat; Garczarek, Piotr; Hazendonk, Paul; Abedi, Marjan; Servati Gargari, Masoumeh

    2016-02-01

    The reaction of a diiminopyridine ligand, N,N‧-bis(phenyl(pyridin-2-yl)methylene)propane-1,3-diamine (L), with mercury(II) salts gave two complexes namely [Hg(L)Cl]·0.5[Hg2Cl6] (1) and [Hg(L)(μ-I)HgI3] (2), which were characterized by XRD, NMR and FTIR. The crystal structure of 1 consists of discrete units of [Hg(L)CI]+cations and [Hg2C16]2- anions in the ratio 2:1. The coordination of mercury in the cation is approximately square pyramidal (sp), the metal center is chelated in a tetradentate manner by the ligand and further coordinated by one chlorine atom. In 2 the packing can be described as units of μ-I-connected square pyramidal (sp) and tetrahedral Hg complexes. The sp coordination around the metal atom is defined by the N4 donor set of the ligand and one bridging iodide. The hydrogen-chlorine donor-accepter interactions in 1 stabilize an infinite 1-D chain; however, such interactions were not observed in 2. Analysis of their Hirshfeld surfaces indicates that the molecules in 1 and 2 are packed predominately by means of van der Waals forces, 'edge to face' aromatic ring packing and weak C-H··X donor-acceptor interactions.

  10. Unifying the crystallization behavior of hexagonal and square crystals with the phase-field-crystal model

    NASA Astrophysics Data System (ADS)

    Tao, Yang; Zheng, Chen; Jing, Zhang; Yongxin, Wang; Yanli, Lu

    2016-03-01

    By employing the phase-field-crystal models, the atomic crystallization process of hexagonal and square crystals is investigated with the emphasis on the growth mechanism and morphological change. A unified regime describing the crystallization behavior of both crystals is obtained with the thermodynamic driving force varying. By increasing the driving force, both crystals (in the steady-state) transform from a faceted polygon to an apex-bulged polygon, and then into a symmetric dendrite. For the faceted polygon, the interface advances by a layer-by-layer (LL) mode while for the apex-bulged polygonal and the dendritic crystals, it first adopts the LL mode and then transits into the multi-layer (ML) mode in the later stage. In particular, a shift of the nucleation sites from the face center to the area around the crystal tips is detected in the early growth stage of both crystals and is rationalized in terms of the relation between the crystal size and the driving force distribution. Finally, a parameter characterizing the complex shape change of square crystal is introduced. Project supported by the National Natural Science Foundation of China (Grant Nos. 54175378, 51474176, and 51274167), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2014JM7261), and the Doctoral Foundation Program of Ministry of China (Grant No. 20136102120021).

  11. Close packing of rods on spherical surfaces.

    PubMed

    Smallenburg, Frank; Löwen, Hartmut

    2016-04-28

    We study the optimal packing of short, hard spherocylinders confined to lie tangential to a spherical surface, using simulated annealing and molecular dynamics simulations. For clusters of up to twelve particles, we map out the changes in the geometry of the closest-packed configuration as a function of the aspect ratio L/D, where L is the cylinder length and D the diameter of the rods. We find a rich variety of cluster structures. For larger clusters, we find that the best-packed configurations up to around 100 particles are highly dependent on the exact number of particles and aspect ratio. For even larger clusters, we find largely disordered clusters for very short rods (L/D = 0.25), while slightly longer rods (L/D = 0.5 or 1) prefer a global baseball-like geometry of smectic-like domains, similar to the behavior of large-scale nematic shells. Intriguingly, we observe that when compared to their optimal flat-plane packing, short rods adapt to the spherical geometry more efficiently than both spheres and longer rods. Our results provide predictions for experimentally realizable systems of colloidal rods trapped at the interface of emulsion droplets.

  12. Close packing of rods on spherical surfaces

    NASA Astrophysics Data System (ADS)

    Smallenburg, Frank; Löwen, Hartmut

    2016-04-01

    We study the optimal packing of short, hard spherocylinders confined to lie tangential to a spherical surface, using simulated annealing and molecular dynamics simulations. For clusters of up to twelve particles, we map out the changes in the geometry of the closest-packed configuration as a function of the aspect ratio L/D, where L is the cylinder length and D the diameter of the rods. We find a rich variety of cluster structures. For larger clusters, we find that the best-packed configurations up to around 100 particles are highly dependent on the exact number of particles and aspect ratio. For even larger clusters, we find largely disordered clusters for very short rods (L/D = 0.25), while slightly longer rods (L/D = 0.5 or 1) prefer a global baseball-like geometry of smectic-like domains, similar to the behavior of large-scale nematic shells. Intriguingly, we observe that when compared to their optimal flat-plane packing, short rods adapt to the spherical geometry more efficiently than both spheres and longer rods. Our results provide predictions for experimentally realizable systems of colloidal rods trapped at the interface of emulsion droplets.

  13. Simple Cloud Chambers Using Gel Ice Packs

    ERIC Educational Resources Information Center

    Kamata, Masahiro; Kubota, Miki

    2012-01-01

    Although cloud chambers are highly regarded as teaching aids for radiation education, school teachers have difficulty in using cloud chambers because they have to prepare dry ice or liquid nitrogen before the experiment. We developed a very simple and inexpensive cloud chamber that uses the contents of gel ice packs which can substitute for dry…

  14. Monkey Baker in bio-pack

    NASA Technical Reports Server (NTRS)

    1959-01-01

    A squirrel monkey, Baker, in bio-pack couch being readied for Jupiter (AM-18 flight). Jupiter, AM-18 mission, also carried an American-born rhesus monkey, Able into suborbit. The flight was successful and both monkeys were recovered in good condition. AM-18 was launched on May 28, 1959.

  15. The benefits of using customized procedure packs.

    PubMed

    Baines, R; Colquhoun, G; Jones, N; Bateman, R

    2001-01-01

    Discrete item purchasing is the traditional approach for hospitals to obtain consumable supplies for theatre procedures. Although most items are relatively low cost, the management and co-ordination of the supply chain, raising orders, controlling stock, picking and delivering to each operating theatre can be complex and costly. Customized procedure packs provide a solution. PMID:11892113

  16. The General Heating Multi-Project Pack

    ERIC Educational Resources Information Center

    Cowking A.; And Others

    1978-01-01

    Describes a multi-project pack on central heating systems, developed into an educational game, used for teaching a variety of subjects in high school. The students examine the basic decision to install a central heating system, for a particular house, and the economics involved. (GA)

  17. 7 CFR 917.13 - Pack.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Pack. 917.13 Section 917.13 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE FRESH PEARS AND PEACHES GROWN IN...

  18. 7 CFR 917.13 - Pack.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Pack. 917.13 Section 917.13 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE FRESH PEARS AND PEACHES GROWN IN...

  19. 7 CFR 917.13 - Pack.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Pack. 917.13 Section 917.13 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING AGREEMENTS AND ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE FRESH PEARS AND PEACHES GROWN IN...

  20. 7 CFR 917.13 - Pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Pack. 917.13 Section 917.13 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE FRESH PEARS AND PEACHES GROWN IN...